Involvement of cytokines in acute neurodegeneration in the CNS

NeurosctenceandBtobehavloralReviews,Vol 17, pp. 217-227, 1993

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Involvement of Cytokines in Acute Neurodegeneration in the CNS N A N C Y J. R O T H W E L L l A N D J A N E K. R E L T O N

Department o f Physiological Sciences, University o f Manchester, Oxford Road, Manchester, M13 9 P T UK Received 17 F e b r u a r y 1992 ROTHWELL, N. J. AND J. K. RELTON. Involvement of cytokines tn acute neurodegeneration m the CNS. NEUROSCI BIOBEHAV REV 17(2) 217-227, 1993-Cytokmes, (particularly interleukins and growth factors) are synthesised m the brain, and induced by brain damage. Interleulin-I appears to directly mediate ischaemic and excitotoxic brain damage, whereas growth factors (e.g., bFGF, NGF), and the phosphohpld binding protein lipocortin-I exhibit neuroprotective actions. Central administration of recombinant interleukin-I receptor antagonist markedly attenuates damage induced by focal cerebral ischaemia, or pharmacological activauon of NMDA receptors in the rat brain. The mechanisms of action of these cytokmes on neurodegeneratlon are unknown, but indirect evidence has implicated cortlcotrophin releasing factor, arachidonic acid, and nitric oxide. In vitro effects of interleukin-1, growth factors, and lipocortin-1 have been reported on mtracellular calcmm homeostasis, which is critically important in neurodegeneration. Pharmacological modulation of the expression and/or actions of cytokmes in the brain may be of considerable therapeutic benefit in the treatment of acute neurodegenerat~on. Interleukm-I

Ltpocortin-I

Growth factors

Stroke

Brain injury

ogy including epilepsy, Parkinson's, and Alzheimer's diseases, and infections such as HIV and cytomegalus virus (102,116). NMDA receptor antagonists have been shown to significantly inhibit acute neurodegeneration in experimental animals (115,116), and thus offer considerable therapeutic potential for the treatment of a variety of neurological disorders. However, given the importance of EAA's in normal physiological processes (e.g., synaptic plasticity and neuronal development), inhibition of their actions may affect normal brain function. Although the role of excitatory amino acids in neurodegeneration is undisputed, it is apparent that mechanisms of neuronal death, or damage in the CNS also depend on complex interactions between neurotransmitters, neuropeptides, and inflammatory molecules that alter survival and repair, not only by direct actions on neuronal function, but also by influencing vascular function, activity of glial cells, and invasion of inflammatory and immune cells. This highly complex picture has been further extended by recent demonstrations that the cytokines, classically associated with peripheral immune function and inflammation, play important roles in acute neurodegeneration and repair in the brain.

DAMAGE, and ultimate death of brain neurons occurs as a result of several forms of brain insult including traumatic injury, ischaemia, and hyperexcitability (e.g., seizures). Although periods of complete anoxia or direct injury will lead to rapid and irreversible cell death, much of the neuronal damage incurred by these insults is secondary to, and outside the primary focus of damage. Thus, in cerebral ischaemia, for example, a "penumbral" region has been identified in which neuronal death appears to be susceptible to therapeutic intervention (7,117). In addition, delayed and chronic neuronal death may ensue over periods of days or months after the initial damage, including regions receiving projections from primary areas of infarct. Neurodegeneration has been ascribed to the release of endogenous, excitatory amino acids (EAA's) such as glutamate and aspartate, acting predominantly on N-methyl-D-aspartate (NMDA) receptors (see 30,31,115,116,146 for detailed reviews). EAA's serve important physiological functions in synaptic plasticity and memory, but excessive release, or impaired reuptake of EAA's leads to neuronal damage, and ultimate death. These excitotoxic actions, that are dependent on a fatal increase in intracellular calcium concentration, have been directly implicated in many forms of acute neuronal damage, such as that resulting from cerebral ischaemia, induced by either haemorrhage or thromboembolism, or mechanical injury (30,120). There is also evidence to implicate EAA's in a number of chronic neurodegenerative states of diverse aetiol-

CYTOKINES IN THE BRAIN The cytokines are a large group of polypeptides that includes the interleukins, interferons, growth and cell stimulating factors, and tumour necrosis factors. Cytokines are syn-

t To whom requests for reprints should be addressed 217

ROTHWELL AND RELTON

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thesized predominantly by peripheral immune cells (e.g., macrophages, lymphocytes, and fibroblasts), although numerous cell types rroduce specific cytokines, including neurons and glia (see below). Constitutive expression of cytokines is generally low, but is probably induced by invading pathogens, and by various forms of tissue damage. Until recently, the brain has been considered an "immune privileged site" that is largely protected from the peripheral immune system by the blood-brain barrier. However, after exogenous or erdogenous damage, invasion of peripheral immune cells (e.g., macrophages or neutrophils) may contribute to the progression of neurodegeneration or recovery of neuronal function (66). In addition, many of the processes and molecules associated with the peripheral immune system appeared to have close parallels within the brmn, where antigen presenting, antibody producing and phagocytic cells, complement system, and cytokines synthesis have been identified 07,86,95,170,173,180). Several )nterleukins (IL-I, 2, 3 and 6) have been identified in the CNS, where they act directly to influence many aspects of the acute phase response such as fever, behaviour, neuroendocrine and immune function (75,94,95,148). Interleukin-1 (IL-1) was probably the first cytokine shown to exert direct actions on the brain when it was identified as "endogenous pyrogen" (23,42,94). It was originally proposed that IL-1 enters the brain from the peripheral circulation, possibly by entering at sites which lack a functional blood-brain barrier such as the organum vasculosum of the lamina terminalis (OVLT) (23). A transport system for IL-1 from circulation into the brain has recently been reported in rodents (11). However less than 1% of circulating IL-1 enters the CNS by this transport system (11), and while this might explain effects of peripherally administered IL-I on CNS function, it is unlikely to be a physiologically important source of endogenous IL-I in the brain. Circulating concentrations of IL-1 in nonlethal conditions rarely exceed 1 ng/ml, even during severe infection or fever (42,94,148), while ng quantities of recombinant IL-1 injected in the brain are usually required to elicit maximal changes in fever, behaviour, or neuroendocrine function (94,148). After brain damage, peripheral circulating macrophages (a rich source of IL-I and TNFc0 may enter the brain, thus providing a potential cell source of cytokines (130). However, analysis of mRNA for cytokines by in situ hybridization, Northern blot, or PCR analysis indicate that a number of cytokines are synthesised directly within the CNS. For example, expression of IL-1/$ and its mRNA is very low in normal brain, but it is markedly increased in response to local inflammation (17), injury (68,69,175), convulsants (124), focal cerebral ischaemia (125), or local or peripheral injection of endotoxin 00,34,56,84) in experimental animals. Increased IL-1 activity has also been reported in brain or cerebrospinai fluid (CSF) from head injured patients (113), or those suffering various infections including HIV, inflammation, or Alzheimer's disease (17,63,74,86,118,162,168-171). The primary source of IL-1 in the brain appears to be microglia (67,83, 130), although both neurons and astrocytes appear to synthesize IL-1 (25,51,95). There is now evidence for direct synthesis of numerous other interleukins and their receptors in the brain (see Table 1), Including IL-1 (9,10,37,51,52,166), IL-2 (4,87, 129), IL-3 (52,58), and IL-6 (60,61). INTERLEUKINS AND NEURODEGENERATION

Administration of IL-1 into the brain of experimental animals, or to cultured neurons or glia in vitro elicits glial activa-

TABLE 1 CYTOKINES SYNTHESIZED IN T H E BRAIN

Interleukins-1, 2, 3, 6 Interferon -ct, -¢ Tumour necros,s factor c~ Nerve growth factor Brain derived nerve growth factor Platelet denved growth factor Transforming growth factor Flbroblast growth factor

(NGF) (BDGF) (PDGF) (I'GF) (FGF)

tion and proliferation, neuronal sprouting, scar formation, and neovascularization (65,66,99). B:cause these are all characteristic responses to brain injury, it has been proposed that IL-I plays a physiological role in wound healing and repair after neuronal damage (65,66). These effects of IL-1 have generally been considered beneficial, acting to promote repair and regeneration, and some support for this hypothesis derives from the observations that low doses of IL-I augment GABA transmission, and, therefore, inhibit seizure activity (121), and Chat IL-1 inhibits long term potentiation (LTP) (92), which is an NMDA receptor dependent process (36). However, direct evidence that endogenous IL-1 exerts a physiological role in responses to brain damage has been absent. Recent studies on cerebral ischaemia m the rat indicate that endogenous IL-1 directly mediates acute neuronal death. Infarct volume, determined 24 h after focal ischaemia (middle cerebral artery occlusion, MCAO) was markedly reduced (by 5007o) in animals injected centrally (ICV) with recombinant interleukin-1 receptor antagonist (IL-lra), 30 min before, and I0 min after ischaemia (139) (Fig. 1). I L - l r a is an endogenous protein (48,78), present in normal rat brain (101), that binds predominantly to the rodent Type I receptor (44). IL-lra inhibits many biological actions of exogenous and endogenous IL-1, and significantly attenuates morbidity and mortality induced by sepsis or inflammation of laboratory rodents (43). In view of the short half life of IL-lra in vivo, it is possible that higher doses, or sustained administration may offer greater neuroprotection against ischaemic damage. Nevertheless, these data (139) indicate that endogenous IL-I, that is rapidly induced m the brain following cerebral ischaemia (125), is directly involved in the development of neuronal death. The cel,alar source of IL-I in the brain after injury is unclear, but depletion of peripheral macrophages by injection of liposome encapsulated toxin (DMDP) does not modify ischaemic damage (Relton & Rothwell, unpublished data), suggesting that invading macrophages are not a major source of IL-1, at least within 24 h of cerebral ischaemia. Now, we have also demonstrated that mtracerebral injection of the ILIra potently inhibits striatal damage induced by NMDA receptor activation (infusion of cis-2,4-methanoglutamate) in the rat (139). This latter observation implies that endogenous IL-I could be involved m other forms of brain damage that are related to NMDA receptor activation (e.g., mechanical injury or epilepsy), and that the IL-lra may be of therapeutic value in these conditions. The mechanisms of neuroprotection offered by I L - l r a are unknown. In view of the critical importance of brain temperature in neuronal survival after ischaemia (27), and the action of IL-I as an endogenous pyrogen within the CNS (94,148),

CYTOKINES AND NEURODEGENERATION

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FIG. 1. Effect of central injection (10ttg icv) of interleukin-I receptor antagonist (IL-lra, Synergen, USA) on infarct volume, determined histologically24 hours after focal, permanent cerebral ischaemia (middle cerebral artery occlusion) in the rat. Upper graph shows mean infarct areas (n = 10, + SEM) of coronal brain slices taken at predetermined stereotaxic coordinates (shown on the abscissa) for animals injected with vehicle (0.9% saline open circles) or IL-lra (closed circles) l0 min before and 30 rain after ischaemia. Lower graph shows infarct volumes computed by integration of areas under the curves for data from each animal shown in the upper graph. *p < 0.05 vs vehicle treated rats.

neuroprotective actions of the IL-lra may be related to hypothermic actions. Stroke patients, and those with head injuries do show elevated body temperature (8,35,85,180). However, rats subjected to permanent MCAO do not show increased body temperatures (Relton & Rothwell, unpublished data), and recent reports have shown that modulation of brain temperature has no effect on neurological outcome following permanent MCAO (127,140). In addition, administration of a cyclooxygenase inhibitor at antipyretic doses fails to modify ischaemic damage (97 and Relton & Rothwell, unpublished data). Furthermore, central administration of the IL-lra does not modulate body temperature following MCAO (139), or prevent the fever induced by central injection of IL-I# which may be dependent on a Type II IL-I receptor (149). Thus, it is unlikely that neuroprotection offered by the IL-lra is due to modification of body temperature. Receptors for IL-1, predominantly the Type I (80kDa) receptor, have been identified in the brain, with the greatest

density in hippocampus (9,37,51,166), a region particularly st.sceptible to excitotoxic damage. It is likely that neurotoxic effects of IL-I involve interaction with the Type I receptor, because we have failed to observe neuroprotection after central injection of a monoclonal antibody to the Type Il (68ka) IL-I receptor after MCAO in the rat (LeFeuvre, Ghiara, and Rothwell, unpublished data). However, recent data obtained from PCR analysis on the rat indicate that IL-I receptor(s) in the brain do not conform to the sequence of the identified Type I IL-1 receptor (10). IL-1 is a potent inducer of arachidonic acid release (42, 108), which is a precursor for the proinflammatory eicosanoids, and can lead to free radical formation. Arachidonic acid can also act independently of eicosanoid synthesis to mediate glutamate actions at the NMDA receptor (122), and as a retrograde messenger to modify presynaptic glutamate release (105). IL-1 also stimulates production of nitric oxide (14), which has been implicated in excitotoxic death in cultured neurones and cerebral ischaemia (15,39,132). Additional actions of IL-I on neuronal excitability, intracellular calcium concentrations, and release or actions of neurotrophic factors, may also be important in ischaemic or excitotoxic change, because IL-1 antagonises effects of several growth factors such as fibroblast growth factor (FGF) (103), and causes increases in intracellular calcium concentrations in cultured neurones (41). However, IL-1 has been implicated in cholinergic sprouting (50), and induces expression of growth factors such as NGF (161), which maybe potentially beneficial. It is not yet known if IL-I can directly cause neuronal death, or if it acts only in the presence of other insults. However, IL-1 has been reported to inhibit survival of cultured hippocampal neurones under certain conditions (5), to cause breakdown of the blood-brain barrier and meningitis (137), and at high doses can induce cerebral oedema (73). IL-I could also influence neuronal survwal in vivo via indirect effects on microglia. Exposure of cultured neurones to activated microglia results in rapid cell death (136), which appears to be due to release of EAA from the microglia (136). Because IL-1 is a potent activator of microglia (65,68), its effects on neuronal survival might be due to glial release of EAA's. IL-I, therefore, appears to exert a variety of complex actions in the brain, some of which may promote repair of damaged neurones, while others could exacerbate, or directly induce cell death (Table 2). These seemingly contradictory effects probably reflect different sites of action, or involvement of different receptors. However, results of studies in which endogenous IL-I action is inhibited (see above) indicate that the overall

TABLE 2 EFFECTS OF IL-l WHICH MAY INFLUENCEBRAIN DAMAGE Detrimental Fever Arachidonic acid release Nitric oxide synthesis CRF synthesis Glucocortlcoid release Inhibition of FGF action Induction of oedema Increased calcium

Benefioal Ghali proliferation Neovascularisation Induction of NGF Enhancement of GABA action

220

ROTHWELL AND RELTON

effect of this cytokine, at least on acute responses to ischaemic or excitotoxic brain damage in the rat, are severely detrimental. Very few data exist on the effects of other interleukins on neuronal damage, although increased synthesis of IL-2 and IL-6 in the brain has been reported in various neurological disorders including CNS infection (60,61,118, l 19,17 I), injury (129,175), multiple sclerosis (87,118,126,141), HIV infection (118,126,169), and Alzheimer's disease (163,170). Interleukin 6 mediates many effects of IL-I (42,82,148), and is produced by astrocytes and microglia in response to IL-1 and TNFc~ (60,141). IL-6 has been reported to improve survival of cholinergic neurones (77), both IL-2 and IL-3 have been suggested to exert neurotrophic actions (91), and IL-3 may stimulate growth o f cholinergic neurones (91). TUMOUR NECROSIS FACTOR ct Tumour necrosis factor-ix (TNFtx) is present in the brain, where it is synthesized mainly by glial cells, and is increased in response to a variety of experimental or clinical insults (33,61, 72,87,118,126,141). Central injection of T N F a in experimental animals mimics several actions of IL-1, such as induction of fever, hypophagia, and activation of the pituitary adrenal axis (32,148). Elevated concentrations of T N F a have been reported in patients with head injury (72), and in stroke-prone rats (76), and increased TNFc~ synthesis by glial cells occurs in response to inflammatory stimuli (33). TNFtx, and TNFB (lymphotoxin) are both toxic to oligodendrocytes, and could indirectly lead to nerve demylination (157,158). Furthermore TNFct induces astrocyte proliferation (13,99,156), increases "peripheral-type" benzodiazepine binding sites in the brain in vivo (24) and in cultured astrocytes (133), activates neutrophils to produce free radicals (165), and potentiates actions of IL-1 on damage to the blood-brain barrier (137). Thus, considerable circumstantial evidence indicates that TNFcz may participate in neuronal damage and/or repair either directly, or by potentiation of the effects of other actions cytokines such as IL-I. But the effects of endogenous TNFcz remain to be examined. INTERFERONS Interferons (IFN) c~, B and 3' have been identified in the CSF of patients with brain infections or inflammation, and in cells located around plaques in multiple sclerosis brain (118, 126). IFN-3' has been reported to induce reactive gliosis (118,179), to increase expression of major histocompatabflity complex antigens by astrocyes and microglia (59,80), and inhibit LTP (38). From data currently available, it is difficult to determine the overall reverse "effects of the actions" of IFN-3" on glial and neuronal function, particularly during the acute phase after brain insults. The precise time course of early glial activation and proliferation after specific forms of brain damage has not been well characterized. Increased glial activity may offer some benefits for neuronal survival, for example by phagocyocisis of dead or damaged cells or reuptake of toxic molecules such as excitatory amino acids. But glia can also act as a source of toxic agents (see above), and formation of a glial scar may limit regeneration of neurones. NEUROTROPHIC FACTORS Nerve growth factor (NGF) was the f r s t growth factor shown to exert neurotrophic actions on peripheral nerves and central cholinergic neurones during development, and following injury (62,81,98,103,174). Several other brain-derived neu-

rotrophic factors have subsequently been shown to influence neuronal growth or repair (12,29,110,126,176). Interest in these peptides has focused mainly on their chronic actions, and their relationship to neurodegenerative conditions such as Alzheimer's disease. However, recent studies (see below) have suggested that neurotrophic growth factors may be rapidly induced after brain damage, and could participate in acute neuronal degeneration and repair. Increased expression of NGF, basic fibroblast growth factor (bFGF), transforming growth factor/3 (TGF/~), brain derived neurotrophic factor (BDNF), platelet derived growth factor (PDGF), or their messenger RNAs has been reported in the brains of experimental animals after injury (16,46, 53,54,134), ischaemia (16,54,134), hypoglycaemic brain damage (16,134), limbic seizures (16,142), administration of neurotoxins such as glutamate (110) or MPTP (104), and in infections associated with neurological defects (126,172). This suggests that some general mechanism related to damage of brain cells results in increased synthesis of numerous growth factors. Evidence derived from both in vivo and vitro studies suggests that growth factors (particularly NGF and FGF) can protect neurones from acute damage and degeneration (81,110-112). Basic FGF markedly inhibits thalamic degeneration after focal cerebral ischaemia in the rat (176), and hippocampal neuronal death induced by global ischaemia (19). Furthermore, NGF, bFGF and insulin-like growth factor inhibit the rise in intracellular calcium and neuronal death induced by hypoglycaemia in rat hippocampal and human cortical neurones in vitro, while epidermal growth is ineffective (29). F G F inhibits glutamate toxicity in cultured hippocampal neurones, and increases the threshold for glutamate toxicity (57,110). Mattson and Rychlik (111) have reported that protective effects of glia against excitotoxic damage may be due to the release of FGF. It has been proposed that bFGF protects neurones against excitotoxic damage by limiting the rise in intracellular calcium, possibly by increasing sodium-dependent calcium extrusion (29). Transforming growth factor/3 is important in the regulation of neuronal development (143), and in tissue repair after injury (103,126). Increased expression of TGFfl (protein and mRNA) is observed after experimental mechanical injury in rodents (A Logan personal communication), and in HIV infected brains (126,172), and is probably derived from both invading macrophages and resident glia. Recent studies on the role of TGFfl in repair after mechanical brain damage in the rat have shown that administration of recombinant TGFfl significantly delays wound healing, causing increased scar formation, while administration of neutralizing anti TGFfl antibody dramatically improves wound healing (A Logan personal communication). Similar effects of TGF/~ or TGFfl antibody have been reported on healing of peripheral wounds (159). TGFfl induces astrocyte chemotaxis (thereby recrmting inflammatory cells to the site of injury), and can enhance the production of cytokines such as TNFc~ (126). These observations have led to the proposal that endogenous TGF/3 is directly involved in neuronal damage, or death induced by mechanical injury or infection such as with HIV virus (126). Thus, several growth factors are expressed after neuronal damage, and apparently offer protection against insults, suggesting that they act as endogenous neuroprotective agents. However, direct evidence for a physiological role of these proteins (for example, by assessing effects of inhibiting their actions on neuronal damage) is lacking in many cases, with the notable exception of TGFB.

CYTOKINES AND NEURODEGENERATION RELATIONSHIP OF CYTOKINES TO OTHER NEUROPEPTIDES Numerous neuropeptide systems have been implicated in the acute neurodegeneration that follows brain injury or infection, including hypothalamic releasing factors, such as thyrotrophin releasing hormone (TRH), corticotrophin releasing factor (CRF), opioids such as/3 endorphin, enkephalin, and proopiomelanocortin products (ACTH and ACTH fragments), vasoactive intestinal polypeptide, substance P and neuropeptide Y (49). In view of the diverse and numerous actions of cytokines in the CNS, which have already been identified, interactions with one or more of these neuropeptides may be responsible for reported effects of specific cytokines. A close relationship has already been identified between IL-I, IL-6, and CRF. Both cytokines are potent inducers of CRF expression in the brain (18,95,153), and cause release of CRF from isolated hypothalami (167). Studies using neutralizing antibodies, or receptor antagonist to CRF, have revealed that the central effects of IL-1/5 on fever, pituitary- adrenal activation, and behaviour are all dependent on the release and action of CRF (45,147). CRF has been proposed to act within the brain as a mediator of host responses to stress (45,147). It exerts potent actions on body temperature, behaviour, cardiovascular responses, and the peripheral immune system (45), and has been implicated in neurodegenerative diseases (40). A recent study by Lyons et al. (106) revealed that central administration of a CRF receptor antagonist (t~ helical CRF9-41) caused potent and dose-dependent inhibition of hippocampal neuronal death measured seven days after global ischaemia in the gerbil. We have subsequently showed that an ICV injection of this antagonist results in a 50% reduction in infarct volume measured 24 h after MCAO in the rat, and also significantly inhibits (by 70%) neuronal damage induced by striatal infusion of an NMDA agonist (Relton, Strijbos and Rothwell, unpublished data). Lyons et al. (106) proposed that endogenous CRF is an important mediator of ischaemic damage, and postulated that this action may be due to either release of glucocorticoids, or to direct neuronal actions of CRF. Glucocorticoids exacerbate several forms of neurodegeneration, including ischaemic damage (97,153), but administration of a Type II glucocorticoid receptor antagonist (RU486) does not modify damage induced by MCAO (Relton & Rothwell, unpublished data). The possibility remains that Type I glucocorticoid receptors may be important in neurodegeneration, but this seems unlikely in view of their very low density in the areas of infarct associated with MCAO. A further proposal (106) is that CRF may exacerbate damage via its potent effects on body temperature and metabolic rate (26,100). However, perhaps the most likely mechanism of action is hyperexcitability, because CRF increases excitability of brain neurons, and at high doses, induces seizures (3,47,107,160), possibly by inhibiting neuronal glucose uptake (88). These data indicate that neurotoxic effects of endogenous cytokines, particularly IL-1, may be due, at least in part, to release of CRF, although this relationship remains to be tested directly. CYTOKINES AND /~ AMYLOID /5 amyloid deposition in the brain is a classical feature of Alzheimer's disease and Down Syndrome (70,109), and it now seems likely that increased expression, and/or altered processing of/5 amyloid precursor protein (~APP) is a causal factor in the neurodegeneration and dementia which characterize

221 Alzheimer's disease (79). Although the mechanisms underlying the chronic and complex pattern of neurological damage seen in Alzheimer brain is beyond the scope of this review, recent data have revealed that flAPP expression occurs rapidly after many forms of brain insult in animals or humans (1,93, 128,144,151), its synthesis can be induced by cytokines such as IL-I (71), and/5 amyloid protein can induce acute neurotoxicity in vivo, and in vitro (114,177). Thus, interactions between cytokines and/SAPP and/or/5amyloid synthesis may be directly involved in the pathogenesis of acute neuronal death in the brain. /5 amyloid protein is neurotrophic to undifferentiated neutones, but neurotoxic to mature neurones (177,178), and increases the vulnerability of cultured cortical neurones to excitotoxic damage (96). These actions of/5 amyloid have been ascribed to a specific portion of the molecule (amino acids 2535), which is homologous to the tachykinin neuropeptide family (177). Effects of/3 amyloid on neuronal survival are mimicked by tachykinins (e.g., substance P), and inhibited by tackykinin antagonists (177). /5 amyloid is also neurotoxic when infused into the susceptible brain regions of rats and primates (114,177,178). The relevance of these observations to neuropathology of Alzheimer's disease is uncertain, particularly as/5 amyloid deposits are rarely associated with regions of neuronal damage. However, rapid increases (24 h) in expression of/SPP have been reported in experimental animals after infusion of excitotoxic agents (128) or focal cerebral ischaemia (1,151), and in patients who have died within days of a head injury (144). Synthesis of cytokines in the brain is also increased in each of these conditions (see above), and IL-I/5 potently induces synthesis of/5APP in vivo and in vitro (17,71). In the rat, expression of/SAPP, 24 h after focal cerebral ischaemia is markedly inhibited by central injection of recombinant IL-1 receptor antagonist, which also inhibits neuronal death (151). Thus, /SAPP (and/or/5 amyloid) may be directly involved in acute neurotoxic effects of IL-1. A further relationship between these molecules in the chronic neurodegenerative processes associated with Alzheimer's disease is implied from the observation that expression of both IL-I (74) and IL-6 (163) is increased in the brains of Alzheimer patients. ENDOGENOUS INHIBITORSOF CYTOKINE ACTION Circulating binding proteins, soluble receptors, and endogenous antagonists have been identified for a number of cytokines (42,48,154), and although these molecules are potential inhibitors of cytokine action, their biological importance, particularly in the brain, remains unknown, mRNA for the endogenous IL-lra has been reported in the rat hippocampus (101), but as yet no information is available on its synthesis, release, or actions. Central effects of cytokines on fever and related functions are potently inhibited by t~-melanocyte stimulating hormone, or arginine vasopressin (94), which may, therefore, influence neurodegeneration. Similarly, glucocorticoids inhibit numerous effects of cytokines, including direct actions on the brain such as fever and thermogenesis (2,28,123). However, while glucocorticoids may offer some benefit in limiting cerebral oedema, their direct actions on neurons appear to he detrimental (152). We have identified an endogenous inhibitor of cytokineinduced fever, and thermogenesis in the r a t - t h e calcium and phospholipid binding protein, lipocortin-I (annexin-l; 55). Central injection of a biologically active recombinant frag-

ROTHWELL AND RELTON

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FIG. 2. Effect of central injection (l/~g ICV) of a recombinant fragment (l-188aa) of human hpocortm-I on lschaemic infarct volume determined histologically, 24 h after middle cerebral artery occlusion in the rat. The open bar (100%) represents infarct volume in vehicle treated rats equivalent to 80mm3 (n = 10) injected with lipocortin-1 fragment at different times relanve to induction of ischaemia. *p < 0.05, **p < 0.01 vs respective vehicle treated groups.

ment of lipocortin-I potently inhibits pyrogenic actions of IL-I/3, IL-6, and CRF (150), while inhibition of the actions of endogenous lipocortin-I reverses the antipyretic actions of glucocorticoids (28). Lipocortin-1 is a member of the annexin family of proteins that exhibit diverse actions on coagulation, inhibition of arachidonic acid release (and hence on eicosanoid synthesis), exocytosis, and receptor phosphorylation (21,55,145). Lipocortin-1 is widely distributed in mammalian brain in neurones and glial cells (90, 164). Johnson et ai. (90) observed dense lipocortin-I immunoreactivity in human brain, in reactive astrocytes around sites of infarct associated with stroke, haemorrhage, and traumatic injury, in plaques of AIzheimer's patients and brain tumours. In the rat, lipocortin-1 staining is markedly increased after focal ischaemia or excitotoxic damage in cells surrounding the infarct within 24 h and is still present at least seven days later (Relton, Roberts & Rothwell, unpublished data). Central injection of a recombinant fragment of lipocortin-I markedly inhibits (by up to 70%) infarct volume caused by MCAO in the rat (138). Neuroprotection is observed even when lipocortin fragment is injected 30-60 min after induction of ischaemia (Fig 2). Local infusion of this lipocortin-1 fragment also inhibits neuronal damage induced by striatal mfusion of an NMDA receptor agonist in the rat (20), and attenuates cerebral oedema induced by ischaemia (138). In contrast, central injection of neutralizing antibody to lipocortin-I enhances ischaemic or excitotoxic brain damage in the rat (20,138). These data provide evidence that lipocortin-I acts as an endogenous neuroprotective agent against ischaemic or excitotoxic damage. In view of the direct inhibitory effects of lipocortin-1 on fever and thermogenesis induced by IL-1 or IL-6 (28, 150), it seems plausable that neuroprotective actions of this molecule

may also be due to inhibition of effects of endogenous cytokines. Arachidonic acid has been strongly implicated in many forms of neurodegeneration, and arachidonic acid release is stimulated by cytokines (see above), but potently inhibited by lipocortin-I (55). However, lipocortin-1 exhibits several other actions that may influence neuronal survival such as calcium binding (64), vesicle aggregation and membrane fusion (21), and inhibition of neutrophil migration (135), and acts as a substrate for phosphorylation by growth factors such as FGF (22), and the epidermal growth factor receptor (89), which are both present in the brain (103,126,131). CONCLUSIONS Recent observations on the expression and actions of cytokines in the brain after damage indicate that a fundamental revision of our current unde;standing of mechanisms underlying neurodegeneration and repair in the CNS may be necessary, and provide an important example of the direct interactions between the brain and immune system which are now being revealed. However, these exciting findings must be tempered with some caution, because, in many cases, the quantitative importance of the endogenous peptide remains unknown. Increased expression of cytokines in the brain after damage does not necessarily imply a functional importance of these molecules, nor does it indicate whether their actions are beneficial or detrimental. Reported effects of recombinant cytokines in vivo and in vitro may represent pharmacological rather than physiological actions. However, as inhibitors (e.g., neutralizing antibodies or receptor antagonists) for many cytokines are becoming increasingly available, it should be possible to answer these questions by direct experimental intervention. Evidence for cytokine involvement in neurodegeneration derives from experimental and clinical observations on a wide range of brain insults, with varied actiologies and severities. The effects of a specific cytokine identified in one form of neurodegeneration may not be directly applicable to other conditions. For example, it is important to distinguish between the very early phase of cell death after brain insults, and the subsequent period of delayed neurodegeneration, which is often accompanied by active repair processes. It is likely that cytokines may exert opposing actions in each of these phases. At present very little is known of the mechanisms of action of cytokines in neurodegeneratlon, but present data indicate that these include direct neuronal effects on release, and actions of EAA's and their mediators, alterations in glial function, and invasion of peripheral immune cells. Thus, we have only scratched the surface of this topic, but it is likely that further understanding of the actions of cytokines in the brain may be of direct therapeutic beneHt ta several neurological conditions.

REFERENCES 1 Abe, K.; Tanzi, R. E.; Kogure, K. Selectivereduction of Kunitztype protease inhibitor domain contaanmg amyloid precursor protein mRNA after perslstant focal lschaemia in rat cerebral cortex. NeuroscienceLett. 125: 172-174; 1991. 2. Abul, H.; Davidson, J.; Milton, A. S.; Rotondo, D. Dexamethasone pretreatment is antipyretic toward polyinosmlc:polycyhdylic acid, lipopolysacchande and interleukin-1/endogenous pyrogen. Naunyn Schmiedeberg'sArch. Pharmacol. 335: 305-309; 1987. 3. Aldenhoff, J. B.; Gruol, D. L.; Ravler, J.; Vale, W.; Siggms,

G. R. CorUcotropin releasing factor decreases postburst hyperpolarizations and excites hippocampal neurons. Science. 221: 875-877; 1983. 4. Araujo, D. M.; Lapchalk, P A.; Collier, B.; Quirion, R. Locaiisation of interleukin-2 immunoreactwity and interleukin-2 receptors in rat brain: Interaction with the cholinergic system. Brmn Res 498: 257-266; 1989. 5. Araujo, D. M.; Cotman, C. W. Transient neurotropic effects of interleukins on hippocampal neurons in vitro. Third IBRO World conference on Neuroscience243; 1991.

CYTOKINES AND NEURODEGENERATION 6. Armanini, M. P.; Hutchins, C.; Stem, B. A.; Sapolsky R. M. Glucocorticoid endangerment of hlppocampai neurons is NMDA-receptor dependent Brain Res. 532:7-12; 1990. 7. Astrup, J.; Siesjo, B. K.; Symon, L. The thresholds in cerebral ischameia-The ischaemic penumbra. Stroke 12:723-725; 1981. 8. Auhck, L. H.; Wilmore, D. W. Hypermetabohsm in trauma. In: Girardier, L.; Stock, M. J., eds. Mammahan thermogenesis. London:Chapman & Hall; 1993:259-304. 9. Ban, E.; Milon, G.; Prudhomme, N.; Filhon, G.; Haour, F. Receptors for interleukin 1 (ct and fl) in mouse brain mapping and neuronal localization in hippocampus. Neurosci. 43:21-30; 1991. 10. Ban E.; Haour, F.; Leinstra, R. Brain interleukin 1 gene expression reduced by peripheral lipopolysaccharide admimstratmn. Cytokine 4:48-54; 1992. 11. Banks, W. A.; Oritz, L.; Plotkin, S. R.; Kastin, A. J. Human interleukin (IL-)lc~, murme IL-lc~ and routine IL-l are transported from blood to brain in the mouse by a shared saturable mechanism. J. Pharmacol. Exp. Therap 259:988-996; 1991. 12. Barde, Y.-A. What, if anything, is a neurotrophic factor? Trends m Neurosclence 11:343-346; 1988. 13. Barna, B. P.; Estes, M. L.; Jacobs, B. S.; Hudson, S.; Ranscohoff, R. M. Human astrocytes proliferate in response to tumour necrosis factor alpha. J. Neuroimmunol. 30:239-243; 1990. 14. Beasley, D.; Schwartz, J. H.; Brenner, B. M. Interleukin-l induces prolonged L-argimne-dependent cyclic guanosine monophosphate and nitrite production in rat vascular smooth muscle cells. J. Clin. Invest. 87:602-608; 1991. 15. Beckman, J. S. The double edged role of nitric oxade m brain function and superoxlde-mediated injury. J. Dev. Physiol. 15: 53-59; 1991. 16. Bengzon, J.; Kokala, Z.; Ernfors, P.; Smith, M. L.; Ekman, R.; Siesjo, B. K.; Persson, H.; Lindvall, O. Ischaemia, hypoglycaemia and kindling increase brain levels of mRNA's for neurotrophlc factors. Soc. Neurosci. 17:183; 1991. 17. Berkenbosch, F; Robakis, N; Blum, M. Interleukin-l in the central nervous system: A role in the acute phase response and in brain injury, brain development, and the pathogenesis of Alzheimer's disease. In: Frederickson, R. C. A.; McGaugh, J. L.; Felten, D. L. eds., Peripheral signalhng of the brain. Toronto: Hogrefe & Huber; 1991 : 131-145. 18. Berkenbosch, F.; van Oers, J.; del Rey, A.; Tdders, F.; Besedovsky, H. Corticotrophin releasing factor neurons in the rat are activated by lnterleukin-1. Science 238:524-526; 1987. 19. Berlove, D. J.; Canday, C. G.; Moskovltz, M. A., Flnklestein, S. P. Basic fibroblast growth factor (bFGF) protects against lschaemic neuronal death m VlVO. Soc. NeuroscL 17:1267; 1991. 20. Black, M.; Carey, F.; Crossman, A. R.; Relton, J. K.; Rothwell, N. J. Lipocortin-I inhibits NMDA receptor medmted neuronal damage m the striatum of the rat. Brain Res. 585:i35-140; 1992. 21. Blackwood, R. A.; Ernst, J. D. Characterization of Ca 2÷ - d e pendent phosphohpid binding, vesicle aggregation and membrane fusion by annexins. Bmchem. J. 266:195-200; 1990. 22. Blanquet, P. R.; Paillerd, S.; Courtois, Y. Influence of fibroblast growth factor on phosphorylation and activity of a 34kDa lipocortm-hke protein in bovine epithehal lens cells. FEBS Lett, 229, 183-187; 1988. 23 Blatte~s, C. M. Neuronal mechanisms in the pyrogemc and acute phase responses to interleukin-l. Int. J. Neurosci. 38:223-232; 1988 24. Bourdiol, F.; Toulmond, S.; Serrano, A.; Benavides, J.; Scatton, B. Increase in w3 (peripheral type benzodmzepine) binding sites in the rat cortex and striatum after local injection of mterleukin-l, tumour necros~s factor ct and lipopolysaccharide. Brain Res. 543:194-200; 1991 25. Breder, C. D.; Dinarello, C A.; Saper, C B. Interleukm-I lmmunoreactive innervation of the human hypothalamus. Scsence 240:321-324; 1988. 26. Brown, M. R.; Fisher, A.; Durer, J.; Spelss, J.; Rivier, C.; Vale, W. Corticotropin releasing factor: Effects on the sympathetic

223

27. 28.

29. 30. 31. 32. 33. 34.

35. 36. 37.

38. 39

40. 41.

42. 43. 44.

45. 46.

47.

nervous system and oxygen consumption. Life Sci. 30:207-210; 1982. Busto, R.; Dietrich, M. Y. T.; Globus, I.; Ginsberg, M. D. The importance of brain temperature in cerebral ischaemic injury. Stroke 20:1113-1120; 1989. Carey, F.; Forder, R.; Edge, M. D.; Greene, A. R.; Horan, M. A.; Stnjbos, P. J. L. M.; Rothwell, N. J. Lipocortin I fragment modifies the pyrogenic actions of cytokines in the rat. Am. J. Physiol. 259:R266-R269; 1990. Cheng, B.; Mattson, M. P. NGF, bFGF and IGFs protect rat hippocampai and human cortical neurons against calcium mechated hypoglycaemic damage. Soc. Neurosci. 17:220; 1991. Chol, D. W. Calcium mediated neurotoxiclty: RelaUonship to specific channel types and role In ischaemic damage. Trends in Neurosciences 11:465-469; 1988. Chin, D. W.; Rothman, S. M. The role of glutamate neurotox~clty in hypoyac-ischaemic neuronal death. Ann. Rev. NeuroscL 13:171-182; 1990. Chomab, S.; Brandellec, D.; Buurman, W. More insights into the complex physiology of TNF. Immunol. Today 12:141-142; 1991. Chung, I. L.; Beneviste, E. N. Tumor necrosis factor-c~ production by astrocytes: Induction by lipopolysaccharide, IFN--r, and IL-lfl. J. Immunol. 144:2999-3007; 1990. Clark, B. D.; Bedrosian, I.; Schindler, R.; Gominelli, F.; Cannon, J. G.; Shaw, A. R.; Dinarello, C A. Detection of interleukin lc~ and Ifl in rabbit tissues during endotoxaemia using sensitive radioimm unoassays. J. Appl. Physiol. 71:2412-2418; 1991. Clitton, G. L.; Robertson, C. S.; Kyper, K.; Taylor, A. A.; Dhekne, R D.; Grossman, R. G. The metabohc response to severe head injury. J. Neurosurg. 60:687-696; 1984. Collingndge, G. L.; Singer, W. Excitatory amino acid receptors and synaptic plasticity. Trends in Pharmacol. Sciences I 1:290296; 1990. Cunningham, E. T., Jr.; Wada, E.; Carter, D. B.; Tracey, D. E.; Battey, J. F.; DeSouza, E. B. Localization of mterleukin-1 receptor messenger RNA in murine luppocampus. Endocrinol. 128:2666-2668; 1991. D'Arcangelo, G.; Grassi, F.; Raggozmo, D.; Santoni, A.; Tancredl, V.; Eusebi, F. Interferon inhibits synaptic potentiation in rat hippocampus. Brmn Res. 564:245-248; 1991. Dawson, V. L.; Dawson, T. M.; London, E. D.; Bredt, D. S.; Snyder, S. H. Nitric oxide medmtes glutamate neurotoxicity in primary cortical cultures. Proc. Natl. Acad. Sci. 88:6368-6377; 1991. DeSouza, E. B. Role of corticotrophin releasing factor in neuropsychiatric disorders and neurodegenerative diseases. Ann. Rep. Med. Chem. 25:215-224; 1990. Di Julio, N.; Urrutia, A.; Gruol, D. L. Interleukm-1 beta increases intracellular calcium and alters the electrophysiology of cultured cerehellar purkmje neurones. Soc. Neurosci 17:1197; 1991. Dinarello, C. A. Interleukin-l and interleukin-l antagomsm. Blood 77:1627-1652; 1991. Dinarello, C. A.; Thompson, R. C. Blocking IL-I: Interleukin-I receptor antagonist in vivo and in vitro. Immunol. Today 12: 404-410; 1991. Dripps, D. J.; Brandhuber, B. J.; Thompson, R. C.; Eisenberg, S. P. Interleukin-i (IL-1) receptor antagonist binds to the 80kDa IL-1 receptor, but does not initiate IL-I s~gnal transdnction. J. Biol. Chem. 266:10331-10336; 1991. Dunn, A. J ; Berridge, C. W. Physiological and hehavioural responses to corticotrophin releasing factor: Is CRF a mediator of anxiety or stress responses? Brain Res. Rev. 15:71-100; 1990. Eclancher, F.; Perraud, F ; Faltin, J.; Labourdette, G.; Sensenbrenner, M. Reactive astrocytes after basic fibroblast growth factor (bFGF) injectmn in injured neonatal brmn. Glia 3:502509; 1990. Ehlers, C. L.; Henriksen, S. J.; Wang, M.; Riwer, J.; Vale, W.; Bloom, F. E. Cortlcotrophin releasing factor produces increases in brain excitability and convulsive seizures in rats. Brain Res. 278:332-336; 1983.

224 48. Eisenberg, S. P ; Evans, R. J.; Arend, N. P.; Verderber, E.; Brewer, M. T.; Hannum, C. T.; Thompson, R. C. Primary structure and functional expression from complimentary DNA of a known mterleukm-1 receptor antagonist. Nature 343:341346; 1990. 49. Faden, A. I. Neuropeptides and stroke: current status and potential application. Stroke 14:169-172; 1983. 50. Fagan, A. M.; Gage, F. H. Cholinergic sprouting m the hlppocampus: A proposed role for IL-1. Exp. Neurol., 110:105-120; 1990. 51. Farrar, W. L.; Kilian, P. L.; Ruff, M. R.; Hill, J. M.; Pert, C. B. Visuahsatlon and charactensation of interleukin-l receptors in brain. J. Immunol. 139:459-463; 1987. 52. Farrar, W. L.; Vinocour, M.; Hill, J. M. In situ histochemical localisation of interleukin-3 mRNA in mouse brain. Blood 73: 137-140; 1989. 53. Finklestein, S. P.; Apostolides, P. J.; Cadey, C. G.; Prosser, J.; Phillps, M. F.; Klagsbrun, M. Increased basic fibroblast growth factor 0aFGF) immunoreactivity at the site of local brain wounds. Brain Res. 460:253-259; 1988. 54. Finklestem, S. P.; Caday, C. G.; Kano, M.; Berlove, D. J.; Hsu, C. Y.; Moskowltz, M.; Klagsbrun, M. Growth factor expression after stroke. Stroke 21:122-124; 1990. 55. Flower, R. J. Llpocortin and the mechanisms of action of the glucocorticoids. Br. J. Pharmacol. 94:987-1015; 1988. 56. Fontana, A.; Weber, E.; Dayer, J.-M. Synthesis of interleukin-l/endogenous pyrogen in the brain of endotoyan-treated mice: A step in fever induction? J. Exp. Med., 133:1696-1698; 1984. 57 Freese, A.; Finklestein, S P.; Difiglia, M. Basic fibroblast growth factor protects striatal neurones In vitro from NMDAreceptor mediated excitotoxicity. Brain Res., 575:351-355; 1992. 58. Frei, K.; Bodmer, S.; Schwerdel, C.; Fontana, A. Astrocytes of the brain synthesise interleukin-3 like factors. J. Immunol. 135: 4044--4047; 1985. 59. Frel, K.; Siepl, C.; Groscurth, P.; Bodmer, S.; Schwerdel, C.; Fontana, A. Antigen presentation and tumor cytotoxicity by interferon-treated microglial cells. Eur. J. Immunol. 17:12711278; 1987. 60. Frel, K.; Mahpiedro, U. V.; Leist, T. P.; Zinkernagel, R. M.; Schwab, M. E.; Fontana, A. On the cellular source and function of interleukin-6 produced in the central nervous system in viral diseases. Eur. J. Immunol. 19:689-694; 1989. 61. Frel, K.; Nadal, D.; Fontana, A. Intracerebral synthesis of turnout necrosis factor-alpha and interleukin-6 m infectious meningitis Ann. NY Acad. Sci. 594:326-35; 1990. 62. Furukawa, S.; Furukawa, Y. Nerve growth factor synthesis and its regulatory mechanisms: An approach to therapeutic induction of nerve growth. Cerebrovasc. & Brain Metab. Rev. 2:328344; 1990. 63. Gallo, P.; Frei, K.; Rordorf, C.; Lazdins, J.; Tavolato, B.; Fontana, A. Human immuno deficiency virus type 1 (HIV-I) infection of the central nervous system: an evaluation of cytokmes in cerebrospmal fluid. J. Neuroimmunol. 23:109-116; 1989 64. Giesow, M J. Common domain structure of calcium and lipid binding proteins. FEBS Lett 203:99-103; i 986. 65. Gxulian, D.; Lachman, L. B. Interleukin-I stimulation of astrogial proliferation after brain injury. Science 228:497-499; 1985. 66. Giulian, D.; Tapscott, M. Immunoregulatlon of cells within the central nervous system. Brain Behav. Immun. 2:352-358; 1988. 67. Gmhan, D.; Baker, T. J.; Shih, N.; Lachman, L. B. Interleukml of the central nervous system is produced by amoeboid mlcroglia. J. Exp. Med. 164:594-604, 1986. 68. Giulian, D.; Woodward, J.; Young, D.; Krebs, J. F.; Lachman, L. B. Interleukm-I injected in to mammalian brain stimulates astroghosis and neovascularization. J. Neuroscl. 8:2485-2490; 1989. 69. Glulian, D.; Chen, J.; Ingeman, J. E ; George, J. K.; Noponen, M. The role of mononuclear phagocytes in wound healing after traumatic injury to adult mammalian brain. J. Neurosci., 9: 4416-4429 1989.

ROTHWELL

AND RELTON

70. Glenner, G. G.; Wong, C. W. Alzheimer's disease: Initial report of the purification and characterization of novel cerebrovascular amyloid protein. Biochem. Blophys. Res. Commun. 120:885890; 1984. 71. Goldgaber, D.; Harris, H. W.; Hla, T.; Maciagi, T.; Donnelly, R. J.; Jacobsen, J. S.; Vitek, M. P.; Gajdusek, D. C. Interleukin 1 regulates synthesis of amylold -protein precursor mRNA in human endothelial cells. Proc. Natl. Acad. 86:7606-7610; 1989. 72. Goodman J. C.; Robertson, C. S ; Grossman, R. G.; Narayan, R. K. Elevation of tumour necrosis factor m head injury. J. Neuroimmunol. 30:213-217; 1990. 73. Gordon, C. R.; Merchant, R. S.; Marmarou, A.; Rice, C.D.; Young, H. F. Effect of murine mterleukln-I on brain oedema in the rat. Acta Neurochlurgica Suppl. 51:268-270; 1990. 74. Griffin, W. S. T.; Stanley, L. C.; Ling, C.; White, L.; MacLeod, V.; Perrot, L. J.; White, C. L.; Araoz, C. Brain interleukin-I and S-100 immunoreactivity are elevated m Down's Syndrome and Alzheimer's disease. Proc. Natl. Acad. Sci. USA, 86: 7611-7622; 1989. 75. Hail, A. K.; Rao, M S. Cytokines and neurokines: Related hgands and related receptors. Trends in Neuroscience 15:35-37; 1992. 76. Hallenbeck, J. M.; Dutka, A. J.; Vogel, S. N.; Heldman, E.; Doran, D. A.; Feuerstein, G. Lipopolysaccharide-induced production of tumour necrosis factor activity in rats with and without risk factors for stroke. Brain Res. 541' 115-120; 1991. 77. Hama, T.; Kushima, Y.; Mlyamoto, M.; Kubota, M.; Takei, N.; Hatanaka, H. Interleukin-6 improves the survival of mesencephalic catecholaminerglc and septal chohnerglc neurones from two-week-old rats in culture. Neurosci. 40:445-452; 1991. 78. Hannum, C. H.; Wilcox, C. J.; Arend, W. P.; Joslin, F. G.; Dripps, D. J.; Heimdal, P. M.; Armes, L. G.; Sommer, A.; Eisenberg, S. P.; Thompson, R. C. Primary structure and functional expression from complementary DNA of a human interleukin-1 receptor antagonist. Nature, 343:336-340; 1990. 79. Hardy, J.; Allsop, D. Amyloid deposition as the central event in the aetiology of Alzhelmer's disease. Trends in Pharmacol. Sciences 12:383-388; 1991. 80. Hartung, H.-P.; Schlafer, B.; van der Meide, P. H.; Fierz, W.; Heininger, K ; Toyka, K. V. The role of interferon-gamma m the pathogenesis of experimental autoimmune disease of the peripheral nervous system. Ann. Neurol. 27:247-257; 1990. 81. Hefti, F. Nerve growth factor promotes survival of septai cholinergic neurones after fimbriai transectlons. J. Nerosci. 6:21552162; 1986. 82. Helle, M.; Brakenhoff, J. P. J.; DeGroot, E. R.; Aarden, L. A. Interleukin 6 involved in interleukm-I induced activities. Eur. J. Immunol. 18:957-959; 1988. 83. Hetier, E.; Ayala, J. Denefle, P., Brousseau, A.; Rouget, P.; Mallet, M.; Prochiantz, A. Brain macrophages synthesize interleukin-1 and interleukm-I mRNA's in vitro. J. Neuroscience Res. 21:391-397; 1988. 84. Hlggins, G. A.; Olschowka, J. A. Induction of mterleukin-I/3 mRNA in adult rat brain. Mol. Brmn Res. 9:143-148; 1991. 85. Hindfelt, B. The prognostic significance of subfebrility and fever in ischaemic cerebral infarctmn. Acta Neurol. Scand. 53:7279; 1976. 86. Hofman, F. M. Cytokines in central nervous system dtsease. In: Goetz, E. J.; Spector, N. H. eds., Neuroimmune Networks" Physiology of Diseases. Alan R.Liss Inc.; 1989:65-71. 87. Hofman, F. M.; Hanwehr, R. I.; Dinarello, C. A.; Mizel, S. B.; Hinton, D.; Merrill, J. E. Immunoregulatory molecules and IL-2 receptors identified in multiple sclerosis brain. J. Immunol., 136:3239-3245; 1986. 88. Hornet, H.; Packan, D. R.; Sapolsky, R. M. Glucocorticoids inhibit glucose transport in cultured hippocampal neurons and gila. Neuroendocrinol. 52:57-64; 1990. 89. Huang, K.; Wallner, B. P.; Mattahano, R.; Tizard, R.; Burne, C.; Frey, A.; Hession, C.; McGrey, P.; Sinclair, L.; Chow, P.; Browning, J. L.; Ramachandran, K.; Tang, J.; Smart, J.; Pepinsky, R. B. Two human 35kD mhibitors of phospholipase

CYTOKINES AND NEURODEGENERATION

90.

91.

92.

93. 94. 95. 96. 97. 98. 99. 100.

101. 102. 103. 104.

105.

106. 107. 108. 109.

110. 111.

112.

A2 are related to pp60v-src and of the epidermal growth factor receptor/kinase. Cell 46:191-199; 1986. Johnson, M. D.; Kamso-Pratt, J. M.; Whetsell, W. O.; Pepinsky, R. B. Lipocortin-I immunoreactiwty in the normal human central nervous system and lesions with astrocytos~s. Am. J. Clin. Pathol. 92:424-429; 1989. Kamegai, M.; Niijima, K.; Kumishlta, T.; Nishlzawa, M.; Ogawa, M.; Araki, M.; Ueki, A.; Konishi, Y.; Tabira, T. Interleukin 3 as a trophic factor for central cholinergic neurons in vitro and in vivo. Neuron 2:249-254; 1990. Katsukl, H.; Nakai, S.; Hiral, Y.; Akaji, K.; Kiso, Y.; Satoh, M. Interleukin-1 inhibits long term potentiation in the CA3 region of mouse hippocampal slices. Eur. J. Pharmacol. 181:323326; 1990. Kawarabayashi, T.; Shoji, M.; Harigaya, Y.; Yamaguchi, H.; Hirai, S. Expression of APP in the early stage of brain damage. Brain Res., 563:334-338; 1991. Kluger, M. J. Fever: Role of pyrogens and cryogens. Physiol. Rev. 71:93-127; 1991. Koemg, J. T. Presence of cytokmes in the hypothlamic-pitmtary axis. Prog. Neuro. Endocrinlmmunol. 4:143-153; 1991. Koh, J.; Yang, L. L.; Cotman, C. W. B amyloid protein increases the vulnerability of cultured cortical neurones to excitotoxic damage. Brain Res. 533:315-320; 1990. Koide, T.; Wieloch, T.; Siesjo, B. Chronic dexamethasone pretreatment aggravates ~schaemic neuronal necros~s. J. Cereb. Blood Flow Metab. 6:395-406; 1986. Kromar, L. F. Nerve growth factor treatment after brain injury prevents neuronal death. Science 235:214-216; 1987. Lachman, L. B.; Brown, D. C.; Dinarello, C. A. Growth promotmg effect of recombinant IL-1 and TNF for human astrocyte cell line. J. Immunol. 138:2913-2916, 1987. LeFeuvre, R. A.; RothweU, N. J.; Stock, M. J. ActivaUon of brown fat thermogenesis in response to central rejection of corticotropin releasing hormone in the rat. Neuropharmacol. 26: 1217-1221; 1987. Licinio, J.; Wong, M. L.; Gold, P. W. Locahsation of interleukin-I receptor antagonist mRNA on rat brain. Endocrinol. 129: 562-564; 1991. Lipton, S. A. Models of neuronal injury in AIDS: Another role for the NMDA receptor? Trends Neurosci. 15:75-79; 1992. Logan, A. CNS growth factors. Br. J. Hosp. Med. 43:428-437; 1990. Logel, J.; Luthman, D.; Luthman, J.; Hall, M.; Hoffer, B.; Leonard, S. Endogenous expression of acidic and basic fibroblast growth factors in 2-methyl-4-phenyl-l,2,3,5,-tetrahydropyridme (MPTP) lesioned mouse brain. Soc. Neurosci. 17:44; 1991. Lynch, M. A.; Voss, K. L. Arach~donic acid increases inositol phospholipid metabolism and glutamate release in synaptosomes prepared from hippocampal tissue. J. Neurochem 55:215-221; 1990. Lyons, M. K.; Anderson, R. E; Meyer, F. B. Corticotrophin releasing factor antagonist reduces ischaemic hippocampai neuronai injury. Brain Res. 545:339-342; 1991. Marrosu, F.; Fratta, W.; Carcangm, P.; Gmgheddu, M.; Gessa, G. L. Localized epileptiform activity induced by murme CRF in rats. Epflepsia 29:369-373; 1988. Martin, M.; Resch, K. Interleukin-1: more than a medmtor between leukocytes. Trends Pharmacol. Sci. 9:171-177; 1988. Masters, C. L.; Simmins, G.; Weinman, N. A.; Multhaup, G.; McDonald, L. A.; Beyreuther, K. Amyloid plaque core protein in Alzheimer's disease and Down's syndrome. Proc. Natl. Acad. Sci. 82:4245-4249; 1985. Mattson, M. P. Excitatory amino acids, growth factors and calcium:a teeter-totter model for neural plasticity and degeneration. Adv. Exp. Med. Biol. 268:211-220, 1990. Mattson, M. P.; Rychlik, B. Glia protect hlppocampal neurons against excitatory amino acid-induced degeneration: Involvement of fibroblast growth factor. Int. J. Dev. Neurosci. 8:399415; 1990. Mattson, M. P.; Murrain, M.; Guthrie, P. B.; Kater, S. B. F~broblast growth factor and glutamate:opposing roles in the

225

113. 114. 115. 116. ! 17. 118. 119.

120. 121. 122. 123. 124.

125. 126. 127.

128.

129. 130. 131.

132.

133.

generation and degeneration of hippocampal architecture. J. Neurosci. 9:3728-3740; 1989. McClain, C. J.; Cohen, D.; Ott, L.; Dmarello, C. A.; Young, B. Ventricular fluid interleukm-1 activity in pauents with head injury. J. Lab. Clin. Med. 15:48-54:1987. McKee, A. C.; Kowall, N. W.; Beal, M. F.; Schumacher, J.; Yankner, B. A. Effects of beta amylmd III: The primate brain. Soc. Neuroscience 17:1294; 1991. Meldrum, B. Protection against ischaemic neuronal damage by drugs acting on excitatory neurotransmiss~on. Cerebrovasc. Brain Metab. Rev. 1:27-57; 1990. Meidrum, B.; Garthwaite, J. Excitatory amino acid neurotoxicity and neurodegenerative disease. Trends Pharmacol. Sci. 11: 379-387; 1990. Memezawa, H.; Minamisawa, H.; Smith, M.-L.; Siesjo, B. K. Ischaemic penumbra in a model of reversible middle cerebral artery occlusion in the rat. Exp. Brain Res. 89:67-78; 1992. Merrill, J. E.; Chen, I. S. HIV-I, macrophages, glial cells, and cytokines m AIDS nervous system disease. FASEB J 5:2391-7; 1991. Merrill, J. E.; Kong, D. A.; Clayton, J.; Ando, D. G.; Hinton, D. R.; Hofman, F. M. Inflammatory leukocytes and cytokmes m peptide induced d~sease of experimental allergic encephalomyelitis m SJC and BIO. PL trace. Proc. Natl. Acad. So. 89:574578; 1992. Meyer, F. B. Caic~um, neuronal excitability and lschaemlc injury. Brain Res. Rev. 14:227-243; 1989. Miller, L. G.; Galpern, W. R.; Dunlap, K.; Dmarello, C. A.; Turner, T. J. Interleukin-I augments 7-amino butyric acidA receptor function in brain Mol. Pharmacol. 39:105-108; 1990. Miller, B.; Sarantis, M.; Traynelis, S. F.; Atwell, D. Potentmtion of NMDA receptor currents by arachidonic acid. Nature 355:722-725; 1992. Milton, A. S. Prostaglandin in fever and the mode of action of antipyretics. In: Milton A. S. ed., Pyretlc and Antipyreucs. Heidelberg:Springer-Verlag; 1982:257-297. Mmami, M.; Kuraishi, Y.; Yamaguchi, T.; Nakah S.; Hirai, Y.; Sato, M. Convulsants reduce mterleukm-1 messenger RNA m rat brain. Biochem. Biophys. Res. Commun. 171:832-837; 1990. Minami, M.; Kuraishi, Y.; Yabuuchi, K.; Yamazaki, A.; Sato, M. Induction of mterleukm-lB mRNA in rat brain after transient fore brmn ischaemla. J. Neurochem. 58:390-392; 1992. Morganti-Kossmann, M. C.; Kossman, T.; Wahl, S. M. Cytokme mediated neuropathology. Trends Pharmacol. Sci. 13:286291; 1992. Morikawa, E.; Gmsberg, M. D.; Dietrich, W. D.; Duncan, R. C.; Kraydieh, S.; Globus, M.Y.-T.; Busto, R. The significance of brain temperature in focal cerebral lschaemia: Histopathological consequences of middle cerebral artery occlusion in the rat. J. Cereb. Bood Flow Metab. 12:380-389; 1992. Nakamura, Y.; Takeda, M.; Nilgawa, H.; Hariguchi, S.; Nishimura, T. Amyloid/S-protein precursor deposits in rat hippocampus lesioned by ibotenic acid rejection. Neurosci. Lett. 136:9598; 1992. Nletro-Sampedro, M.; Chandry, K. M. Interleukin-2-1ike activIty in injured rat brain. Neurochem. Res. 12:723-727; 1987. Nietro-Sampedro, M.; Berman, M. A. Interleukm-l-like activity in rat brain: Sources, targets, and effects of injury. J. Neurosci. 17:214-219; 1987. Nietro-Sampedro, M.; Gomez-Pinilla, F.; Knauer, D. J.; Broderick, J. T. Epidermal growth factor receptor immuno-reactivlty in rat brain astrocytes: Response to injury. Neurosci. Lett. 91: 276-282; 1988. Nowicki, J. P.; Poignet, H.; Carreau, A.; Scatton, B. Potent neuroprotective acuvity of nitroarg~nlne in a model of irreversible focal cerebral ischaemia in the mouse. IBC Conference on Nitric Oxide (London); 1991. Oh, Y. J.; Francis, J. W.; Markelonis, G. J.; Oh, T. H. Interleukin-l-B and tumor necrosis factor-a increase peripheral-type bezodiazepine binding sites in cultured polygonal astrocytes. J. Neurochem. 58:2131-2138; 1992.

226 134. Patterson, S. L.; Grover, L. M.; Bothwell, M.; Schwartzkrom, P. A. Actiwty dependent changes m neurotrophm expression in rat hlppocampal slices. Soc. Neuroscl. 17:220; 1991. 135. Perretti, M.; Parente, L.; Browning, J. L.; Flower, R. J. Human lipocortin-I inhibits interleukin-l induced neutrophil migration in the mouse air pouch model. Br. J. Pharmacol. 104:44P; 1992. 136. Piani, D.; Frei, K.; Do, K.; Cuerod, M.; Fontana, A. Murme macrophages induce NMDA receptor mediated toxicity by secreting glutamate. Neurosci. Lett. 133:159-162; 1991. 137. Quagliarello, V. J.; Wispelwey, B.; Long, W. J., Jr.; Scheld. W. M. Recombinant human mterleukin-l induces meningitis and bloodvbram barrier injury in the rat. J. Clin. Invest. 87:13601366; 1991. 138. Relton, J. K.; Strijbos, P. J.; O'Shaugnessy, C. T.; Carey, F.; Forder, R. A.; Tdders, F. J.; Rothwell, N. J. Llpocortm-1 is an endogenous inhibitor of ischaermc damage in the rat brain. J. Exp. Med. 174; 305-310; 1991. 139. Relton, J. K.; Rothwell, N. J. Interleukm-1 receptor antagonist inhibits neuronal damage induced by cerebral ischaemia or NMDA-receptor activation in the rat. Brain Res. Bull. 585: 135-160; 1992. 140. Radenour, T. R.; Warner, D. S.; Todd, M. M.; McAllister, A. C. Mild hypothermia reduces infarct size resulting from temporary but not permanent focal ischaemia in the rat. Stroke. 23: 733-738; 1992. 141. Righi, M.; Mori, L.; DeLibero, G.; Sironi, M.; Blondi, A.; Mantovani, A.; Donini, S. D.; Ricciardi-Castagnoli, P. Monokine production by mlcroghai cell clones. Eur. J. Immunol. 19: 1443-1444; 1989. 142. Rlva, M. A.; Gale, K.; Graham, J.; Pazos, A.; Mocchetti, I. Llmbic seizures increase basic fibroblast growth factor (bFGF) gene expression in hippocampus and entorhinal cortex. Soc. Neurosci. 17:44; 1991. 143. Roberts, A. B.; Flanders, K. C.; Heine, U. I.; Jackowlew, S.; Kondaiah, P.; Kim, S. J.; Sporn, M. B. Transforming growth factor-beta: Multifunctional regulator of differentmtionand development. Philos. Trans. R. Soc. Lond. 327:145-54; 1990. 144. Roberts, G. N.; Gentleman, S. M.; Lynch, A.; Graham, D. I. Head trauma triggers B/A4 amyloid protein deposmon in the brain. Lancet 337:1342v1343; 1991. 145. Romisch, J.; Schorlemmer, U.; Fickenscher, K.; Paques, E. P.; Heimburger, N. Anucoagulant properties of placenta protein 4 (annexin V). Thromb. Res. 60(5):355-366; 1990. 146. Rothman, S. M.; Olney, J. W. Excitotoxicity and the NMDA receptor. Trends Neurosci. 10:299-302; 1987. 147. Rothwell, N. J. Central effects of CRF on metabolism and energy balance. NeuroscL Biobehav. Rev. 14:263-271; 1990. 148. Rothwell, N. J. Functions and mechanisms of mterleukin-1 in the brain. Trends Pharmacol. Sci. 12:430-436. 1991. 149. Rothwell, N. J.; Hardwick, A. J. Effect of lnterleukin-I receptor antagonist on fever and thermogenesis induced by interleukin-1 m the rat. J. Physiol. 452:125P; 1992. 150. Rothwell, N. J.; Stnjbos, P. J. L. M.; Hardwick, A. J.; Relton, J. K.; Carey, F. Inhibmon of cytokine action by lipocortln-I (anneyan-1): Implications for mechanisms of action. Br. J. Pharm. 104:316P; 1991. 151. Royston, M. C.; Rothwell, N. J.; Roberts, G. W. Alzheimer's disease: From molecular biology to treatment. Trends Pharmacol. Sci. 13:131-133; 1992. 152. Sapolsky, R. A mechamsm for glucocorticoid toxicity in the hippocampus: Increased neuronal viability to metabolic insults. J. Neurosci. 5:1228-1232; 1985. 153. Sapolsky, R.; Rivier, C.; Yamamoto, G.; Plotsky, P.; Vale, W. Interleukin-1 stimulates the secretion of hypothalamic corticotrophin releasing factor. Science 238:522-524; 1987. 154. Seckmger, P.; Isaaz, S.; Dayer, J.-M. A human inhibitor of tumour necrosis factor c¢. J. Exp. Med. 167:1511-1516; 1988. 156. Selmaj, K. W.; Farooq, M.; Norton, W. T.; Raine, S.; Brosnan, C. F. Proliferation of astrocytes in vitro in response to cytokines: A primary role for tumor necrosis factor. J. Immunol. 144:129-135; 1990.

ROTHWELL

AND RELTON

157. Selmaj, K. W.; Rmne, C. S. Tumour necrosis factor mediates myelin and ollgodendrocyte damage in vitro. Ann. Neurol. 23: 339-346; 1988. 158. Selmaj, K.; Ratine, C. S.; Farooq, M.; Norton, W. T.; Brosnan, C. F. Cytokine cytoxicity against oligodendrocytes. Apoptosis induced by lymphotoxm. J. Immunol. 147:1522-9; 1991. 159. Shah, M.; Foreman, D. M.; Ferguson, M. W J. Control of scarring in adult wounds by neutralizing antibody to transforming agrowth factor B- Lancet 339:213-214; 1992. 160. Siggins, G. R.; Gruol, D.; Aldenhoff, J.; Pittmann, Q. Electrophysiological actions of CRF in the CNS. Fed. Proc. 44:237242; 1985. 161. Spranger, M.; Lindholm, D.; Bandtlow, C.; Heimann, G.; Naher-Noe, M.; Thoenen, H. Regulauon of nerve growth factor (NGF) synthesis in the rat central nervous system: Comparison between the effects of interleukm-I and various growth factors in astrocyte culture and in vivo. Eur. J. Neurosci. 2:6976; 1990. 162. Stanley, L C.; Mrak, R. E.; Perrot, L. J.; Griffin, W. S. T. IL-lct and IL-I/3 are elevated m brain cells of AIDS patients. Soc. Neurosci. 17:1273; 1991. 163. Strauss, S.; Bauer, J.; Ganter, U.; Jones, U.; Berger, M.; Volk, B. Detection of mterleukin-6 and ct2 macroglobuhn lmmunoreactivity on cortex and hippocampus of Alzheimer's disease patients. Lab. Invest. 66:223-230; 1992. 164. Strijbos, P. J. L. M.; Tilders, F. J. H.; Carey, F.; Forder, R.; Rothwell, N. J. Locahsation of immunoreactive lipocortin-1 in the brmn and pituitary gland of the rat. Effects of adrenalectomy, dexamethasone and colchicine treatment. Brain. Res. 553: 249-260; 1991. 165. Sullivan G. W.; Carper, H. T.; Sullivan, J.; Murata, T.; Mandell, G. Both recombinant interleukin-1 (beta) and purified human monocyte interleukin-l prime human neutrophils for increased oradative activity and promote neutrophd spreading. J. Leukocyte Biol. 45:389-395; 1989. 166. Takao, T.; Tracey, D. E.; Mitchell, W. M.; DeSouza, E. B. Interleukin-1 receptors m mouse brain: Characterization and neuronal localization. Endocrinol. 127:3070-3078; 1990. 167. Tsagakaris, S.; Gillies, G.; Rees, L. H.; Besser, M.; Grossman, M.; Interleukin-I directly stimulates the release of corticotrophin releasing factor from rat hypothalamus. Neuroendocrinology 49:98-101; 1989. 168. Tsukada, N.; Mijagi, K.; Matsuda, M.; Yanagisawa, N.; Yone K. Turnout necrosis factor and interleukin in the CSF and sera of pauents with multiple sclerosis. J. Neurolog. Sci. 102:230234; 1991. 169. Tyor. W R.; Glass, J. D.; Griffin, J. W.; Becker, P. S.; McArthur, J. C.; Bezman, L.; Griffin, D. E. Cytokine expression in the brain during the aquired immunodeficiency syndrome. Ann. Neurol. 31:349-360; 1992. 170. Vandenabeele, P.; Fiefs, W. Is amyloidogenesis during Alzheireef's disease due to an IL-1/I L-6-mediated acute phase response in the brain? Immunol. Today 12:207-219; 1991. 171. Waage, A.; Halstensen, A.; Shalaby, R.; Brantzaeg, P.; Kierulf, P.; Espewk, T. Local production of tumour necrosis factor c~, interleukin-l and mterleukin-6 in meningococcal meningitus. J. Exp. Med. 170:1859-1867; 1989. 172 Wahl, S. M.; Allen, J. B.; McCarthy-Francis, N.; MorgantiKossman, M. C.; Kossman, T.; Ellingsworth, L.; Mai, U. E.; Mergenhagen, S. E.; Orenstein, J. M. Macrophage- and astrocyte-derived transforming growth factor beta as a mediator of central nervous system dysfunction in acquired immune deficiency syndrome. J. Exp. Med. 173:981-91; 1991. 173. Wekerle, H.; Linigton, C.; Lassmann, H.; Meyermann, R. Cellular ~mmune reactivity in the CNS. Trends NeuroscL 9:271277; 1986. 174. Williams, L. R.; Varon, S.; Peterson, G. M.; Wictorin, K.; Fischer, W.; Bjorklund, A.; Gage, F. H. Continuous infusion of nerve growth factor prevents basal forebram neuronal death after fimbria formx transection. Proc. Natl. Acad. Sci. 83:92319235; 1986. 175. Woodroofe, M. N.; Sarna, G. S ; Wawda, M.; Hayes, G. M.;

CYTOKINES AND NEURODEGENERATION Loughlin, A. J.; Tinker, A.; Cuzner, M. L. Detection of interleukm-1 and interleukin-6 in adult rat brain following mechanical injury by in vivo microdialysls: Evidence of a role for microglia in cytokme production. J. Immunol. 33:227-236; 1991. 176. Yamada, K.; Kinoshita, A.; Kohmura, E.; Sakaguchi, T.; Taguch~, J.; Kataoka, K.; Hayakawa, T. Basic fibroblast growth factor prevents thalam~c degeneration after cortical infarction. J. Cereb. Blood Flow Metab. 11:472-478; 1991. 177. Yankner, B.; York, D. A. Neurotrophic and neurotoxic effects of amyloid fl protein: Reversal by tachykinin neuropept~des. Science 250:279-282; 1990

227 178. Yankner. B. A.; Dawes, L. R.; Fisher, S.; Villa-Komeroff, L; Oster-Granite, M. L.; Neve, R. L. Neurotoxioty of a fragment of the amyloid precursor associated with Alzheimer's d~sease. Science 245:417-420; 1989. 179. Yong, V. W.; Moumdjian, R.; Young, F. P; Ruijus, T. G.; Feedmen, M. S.; Cashman, N.; Antel, J. P. 3' Interferon promotes proliferation of adult human astrocytes m v~tro and reactive gliosis m the adult mouse brain in vivo. Proc. Natl. Acad. Sci. 88:7016-7020; 1991. 180. Young, A. B.; Ott, L. G.;Beard, D.; Dempsey, R. J.; Tibbs, P. A.; McClaln, C. J.; The acute phase response of the braininjured patient. J. Neurosurg 69:375-380; 1988.