- Email: [email protected]
Abnormal IL-1β cytokine expression in the cerebellum of the ataxic mutant mice staggerer and Lurcher
Molecular Brain Research 62 Ž1998. 224–227
Short communication
Abnormal IL-1b cytokine expression in the cerebellum of the ataxic mutant mice staggerer and Lurcher Beatrice Vernet-der Garabedian ) , Yolande Lemaigre-Dubreuil, Nicole Delhaye-Bouchaud, ´ Jean Mariani Laboratoire de Neurobiologie du DeÕeloppement, Institut des Neurosciences (CNRS UMR 7624), UniÕersite´ Pierre et Marie Curie, 9 quai Saint Bernard, ´ 75005 Paris, France Accepted 22 September 1998
Abstract To assess the extent to which interleukin-1b ŽIL-1b . may contribute to the development andror progression of neurodegenerative processes, we have examined the levels of IL-1b in the brain of two types of neurological mutant mice, staggerer and Lurcher. Using a quantitative immunological method Ženzyme-linked immunosorbent assay, ELISA., we measured IL-1b in the cerebellum, hippocampus and cerebral cortex of mutant mice at baseline and after peripheral LPS treatment. Two types of IL-1b expression abnormalities were found in the mutant cerebella: higher basal level in Lurcher and a response to peripheral administration of LPS in staggerer. The association of IL-1b expression abnormalities with the only brain structure where a massive neurodegeneration occurs supports the role of proinflammatory cytokines in this process. q 1998 Elsevier Science B.V. All rights reserved. Keywords: Lurcher mutant mouse; staggerer mutant mouse; Neurodegeneration; Cerebellum; Inflammation; Proinflammatory cytokine; IL-1b; ELISA
Interleukin-1b ŽIL-1b . is primarily an inflammatory cytokine responsible for many of the effects associated with peripheral inflammation such as fever, sleep, behavioral changes and stimulation of the hypothalamic–pituitary–adrenal axis. IL-1b might work as a mediator in neural pathways and might be synthesized in the central nervous system w4x. IL-1b immunoreactivity and mRNA transcripts have been described in different brain areas and neural cell subtypes. This central IL-1b expression has been demonstrated to be modulated by an acute systemic inflammation or peripheral lipopolysaccharide treatment w9,18x. Beside its normal biological activity as part of the host defense, IL-1b may have deleterious effects. Inappropriate expression of proinflammatory cytokines is associated with a variety of neurodegenerative diseases w14x. The place and the extent to which cytokines may contribute to the development and progression of the neurodegenerative process are largely unknown.
) Corresponding author. Fax: q33-1-44-07-15-85; [email protected]
E-mail:
We have attempted to address these issues in the ataxic mutant mice staggerer and Lurcher which both perinatally develop a severe degeneration of Purkinje, olivary and granule neurons w8,19,22,23x. In both mutants, this neurodegeneration is associated with immunological disturbances in the periphery such as a delayed thymic development, undersized spleen w20x and abnormal macrophage production of proinflammatory cytokines w10,11x. We have recently demonstrated higher levels of IL-1b and IL-6 mRNAs in the cerebellum of staggerer compared to an unaffected brain region or to the wild type w12x. As mRNAs are not always translated into protein w5x, it was important to assess the protein levels of cytokines in the pathological cerebellum of the staggerer and Lurcher mice. In the present study, we have quantified IL-1b in different brain regions of homozygous staggerer and heterozygous Lurcher mice using an immuno-enzymatic method and investigated their response to a peripheral stimulation by LPS. The staggerer mutation was bred on C57BLr6J background and the Lurcher mutation on C57BLr6J= CBA ŽB6rCBA.. Mutants were identified by their ataxic behavior around postnatal day 15 in litters from qrsg= qrsg
0169-328Xr98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 9 - 3 2 8 X Ž 9 8 . 0 0 2 6 8 - X
B. Vernet-der Garabedian et al.r Molecular Brain Research 62 (1998) 224–227
and qrLc= qrq matings. All animals were maintained and experiments were performed in strict compliance with the relevant welfare guidelines adopted by the European Community. Ten 30-day old female sgrsg, five 4-month old female qrLc and age-matched C57BLr6J and B6rCBA received one intraperitoneal Ži.p.. or subcutaneous injection of LPS Ž0.5 mgrg b.wt. from Escherichia coli Ž0127-B8. in RPMI as vehicle or RPMI. Mice were sacrificed by cervical dislocation 1 to 24 h later. Spleen, cerebellum, hippocampus and cerebral cortex were rapidly dissected on ice, immediately frozen in liquid nitrogen and stored at y808C. Pooled samples were prepared as previously described w7x. IL-1b concentrations were measured using a sandwich enzyme-linked immunosorbent assay ŽELISA. performed with the Duoset ELISA Development System ŽGenzyme. according to the supplier’s recommended procedure. Blanks Žsample buffer. were deduced. The sensitivity threshold was defined as the mean absorbance value of 10 sample buffer determinations plus 2 S.D. IL-1b concentrations were determined in the linear part Žfrom 75 to 500 pgrml. of the standard curve. The differences of IL-1b level between samples were assessed by statistical analysis ŽMann–Whitney’s U-test.. Protein concentrations were determined using the DC protein assay ŽBio-Rad.. The optimal conditions of LPS stimulation on peripheral and central IL-1b expression were determined in preliminary assays by kinetic studies differing in the way of administration and the purity of LPS. While no change of IL-1b level was observed in the cerebellum for 24 h after LPS stimulation, we choose to sacrifice the mice 2 h after a single i.p. injection of purified LPS at the peak of spleen stimulation. The IL-1b basal levels were generally barely over the sensitivity threshold in all the studied brain structures of wild type and mutant mice ŽFig. 1.. The IL-1b basal levels of mutant cerebral cortex and hippocampus were not sig-
Fig. 1. The IL-1b basal levels in cerebellum Žsolid bars., cortex Žstippled bars. and hippocampus Žopen bars. of staggerer Žsgrsg. and Lurcher ŽqrLc. mutants and of the corresponding wild type C57BLr6J and B6rCBA mice. Values are means"S.E.M. Ž). Significantly different from the B6rCBA cerebellum Ž p- 0.05..
225
Fig. 2. The modulation of brain IL-1b by a peripheral LPS stimulation. IL-1b levels in the cerebellum of staggerer Žsgrsg. and Lurcher ŽqrLc. mutants and of the corresponding wild type C57BLr6J and B6rCBA mice 2 h after an i.p. RPMI Žsolid bars. and LPS Žstriped bars. injection. Values are means"S.E.M. Ž). Significantly different from RPMI-treated mice Ž ps 0.05..
nificantly different from those of the corresponding wild strains. On the contrary, in the cerebellum of Lurcher and staggerer, basal IL-1b concentrations were, respectively 2.7- and 2.5-fold higher than in wild type mice. Differences were significant for Lurcher Ž p s 0.006. but not for staggerer Ž p s 0.53.. After LPS stimulation, a robust increase Ž16.2-fold above basal level. was induced in spleens indicating that mice were efficiently stimulated. In the brain, the only altered IL-1b level was observed in the cerebellum of staggerer. IL-1b concentrations increased 3-fold compared to basal levels ŽFig. 2., the difference being significant Ž p s 0.05.. The results of this study provide further evidence that IL-1b plays a role in neurodegenerative processes within the brain. In the two ataxic mutants, IL-1b expression abnormalities were found to be exclusively associated with the cerebellum, the only brain region where a massive neurodegeneration occurs. Abnormalities were of two types: higher basal levels compared to wild type in Lurcher and a response to peripheral administration of LPS in staggerer. No IL-1b increase was induced in any normal mouse brain structure examined, nor in Lurcher. Modulation of brain IL-1b by peripheral LPS administration is widely debated, especially regarding localization of IL-1b reactivity w3,15,17,21,24x. The differences may be due to differences in stimulation by LPS Žorigin, doses.. High doses Ž2.5 to 5 mgrkg b.wt., have been reported to induce IL-1b changes throughout the brain at the mRNA or protein levels, whereas lower doses only affected meninges and brain regions with fenestered endothelial capillaries such as the circumventricular organs and choroid plexus w3,21x. LPS is a complex glycolipid which pleiotropically stimulates the cells implicated in the inflammatory response. Injected at high doses, it could modify blood–brain barrier permeability, cross the cerebral
226
B. Vernet-der Garabedian et al.r Molecular Brain Research 62 (1998) 224–227
endothelium and directly stimulate the resident brain monocyte lineage cells w1,13x. In the present study, we were interested in the reaction in the brain to a peripheral inflammation, thus LPS was used at low dose Ž0.5 mgrkg b.wt. efficient for stimulating splenic macrophages and for inducing behavioral changes in mice. In this condition, modulation of brain IL-1b was observed in normal mice at the mRNA level w12x but, in contrast with previous results w7x, remained undetectable at the protein level using the ELISA technique. It must be noted that mouse strain, purity of LPS and ELISA kit used in the two laboratories were different.The dose of LPS we used likely restricted alterations to the most responsive structures inside or surrounding the brain Žthe choroid plexus and the meninges.. The significant increase of cerebellum IL-1b levels we observed in the systemic LPS-treated staggerer may thus be due to the peripheral inflammatory abnormalities which affect this mutant w11x. Indeed, the meninges, which are external to the blood–brain barrier, were not removed from brain tissues during dissection, and the structural and functional integrity of the mutant blood–brain barrier is preserved wRiva-Depaty et al., unpublished datax. The IL-1b abnormalities have also been described in Lurcher macrophages w11x. The unexpected absence of response in the Lurcher cerebellum may be related to glucocorticoids as it has been shown that they can suppress IL-1b production in the brain w16x. We have recently reported that plasmatic corticosterone and ACTH increases were much greater in Lurcher than in wild type mice after LPS injection w6x. This difference could mask a possible increase of IL-1b responsiveness in the Lurcher brain. The cell categories responsible for IL-1b abnormalities in the two mutants are not yet identified. However, an important astrogliosis has been described in staggerer cerebellum as well as an hyperinducibility for IL-1b of microglial cells in vitro w2x. In conclusion, the association of IL-1b expression abnormalities with the only brain structure where a massive neurodegeneration occurs supports the role of proinflammatory cytokines in this process. High basal level of IL-1b may reflect altered parenchymal IL-1b expression within the cerebellum. Peripheral inflammation could contribute to additive or synergistic effects on local neurodegeneration even if the blood–brain barrier integrity is not perturbed. In this context, the Lurcher and staggerer mutants appear to be valuable model to study the relationship between immune system and neurodegeneration.
Acknowledgements We are grateful to Dr. Robert Dantzer and Chantal Combe for their help in establishing the ELISA assay for IL-1b detection. We wish to thank Colette Chianale for the breeding of the mice. This work was supported by a grant
from the European Community Žgrant BIOMED, Cybrainet no. PL 962492.. References w1x N.J. Abbott, P.A. Revest, Control of brain endothelial permeability, Cerebrovasc. Brain Metab. Rev. 3 Ž1991. 39–72. w2x B. Brugg, Y. Lemaigre-Dubreuil, G. Huber, B. Kopmels, N. Delhaye-Bouchaud, E. Wollman, J. Mariani, Neuronal death, proinflammatory cytokines and amyloid precursor protein: studies on staggerer mutant mice, in: K.S. Kosik, Y. Christen, D.J. Selkoe ŽEds.., Alzheimer’s Disease: Lessons from Cell Biology, Foundation Ipsen, Springer, Berlin, 1995, pp. 202–216. w3x M. Buttini, H. Boddeke, Peripheral lipopolysaccharide stimulation induces interleukin-1beta messenger RNA in rat brain microglial cells, Neuroscience 65 Ž1995. 523–530. w4x B.W. Coltman, C.F. Ide, Temporal characterization of microglia, IL-1 beta-like immunoreactivity and astrocytes in the dentate gyrus of hippocampal organotypic slice cultures, Int. J. Dev. Neurosci. 14 Ž1996. 707–719. w5x J.P. Corradi, C. Yang, J.C. Darnell, J. Dalmau, R.B. Darnell, A post-transcriptional regulatory mechanism restricts expression of the paraneoplastic cerebellar degeneration antigen cdr2 to immune privileged tissues, J. Neurosci. 17 Ž1997. 1406–1415. w6x F. Frederic, T. Chautard, R. Brochard, C. Chianale, E. Wollman, C. Oliver, N. Delhaye-Bouchaud, J. Mariani, Enhanced endocrine response to novel environment stress and endotoxin in lurcher mutant mice, Neuroendocrinology 66 Ž1997. 341–347. w7x E. Goujon, P. Parnet, S. Laye, ´ C. Combe, R. Dantzer, Adrenalectomy enhances pro-inflammatory cytokines gene expression, in the spleen, pituitary and brain of mice response to lipopolysaccharide, Mol. Brain Res. 36 Ž1996. 53–62. w8x K. Herrup, R.J. Mullen, Regional variation and absence of large neurons in the cerebellum of the staggerer mouse, Brain Res. 172 Ž1979. 1–12. w9x S.J. Hopkins, N.J. Rothwell, Cytokines and the nervous system: I. Expression and recognition, TINS 18 Ž1995. 83–88. w10x B. Kopmels, J. Mariani, V. Taupin, N. Delhaye-Bouchaud, E.E. Wollman, Differential IL-6 mRNA expression by stimulated peripheral macrophages of staggerer and lurcher cerebellar mutant mice, Eur. Cytokine Netw. 2 Ž1991. 345–353. w11x B. Kopmels, E. Wollman, J.M. Guastavino, N. Delhaye-Bouchaud, D. Fradelizi, J. Mariani, Interleukin-1 hyperproduction by in vitro activated peripheral macrophages from cerebellar mutant mice, J. Neurochem. 55 Ž1990. 1980–1985. w12x Y. Lemaigre-Dubreuil, B. Brugg, C. Chianale, N. DelhayeBouchaud, J. Mariani, Over-expression of interleukin-1beta-converting enzyme mRNA in staggerer cerebellum, NeuroReport 7 Ž1996. 1777–1780. w13x W.A. Lynn, D.T. Golenbock, Lipopolysaccharide antagonists, Immunology Today 13 Ž1992. 271–276. w14x J.E. Merrill, G.M. Jonakait, Interactions of the nervous and immune systems in development, normal brain, homeostasis and disease, FASEB J. 9 Ž1995. 611–661. w15x T. Nakamori, A. Morimoto, K. Yamaguchi, T. Watanabe, N. Murakami, Interleukin-1beta production in the rabbit brain during endotoxin-induced fever, J. Physiol. 476.1 Ž1994. 177–186. w16x K.T. Nguyen, T. Deak, S.M. Owens, T. Kohno, M. Fleshner, L.R. Watkins, S.F. Maier, Exposure to acute stress induces brain interleukin-1b protein in the rat, J. Neurosci. 18 Ž1998. 2239–2246. w17x N. Quan, S. Sundar, J. Weiss, Induction of interleukin-1 in various brain regions after peripheral and central injections of lipopolysaccharide, J. Neuroimmunol. 49 Ž1994. 125–134. w18x N.J. Rothwell, S.J. Hopkins, Cytokines and the nervous system: II. Actions and mechanisms of action, Trends Neurosci. 18 Ž1995. 130–136.
B. Vernet-der Garabedian et al.r Molecular Brain Research 62 (1998) 224–227 w19x H. Shojaeian, N. Delhaye-Bouchaud, J. Mariani, Decreased number of cells in the inferior olivary nucleus of the developing staggerer mouse, Dev. Brain Res. 21 Ž1985. 141–146. w20x E. Trenkner, M.K. Hoffmann, Defective development of the thymus and immunological abnormalities in the neurological mutation staggerer, J. Neurosci. 6 Ž1986. 1733–1737. w21x A.-M. van Dam, M. Brouns, S. Louisse, F. Berkenbosch, Appearance of interleukin-1 in macrophages and in ramified microglia in the brain of endotoxin-treated rats: a pathway for the induction of non-specific symptoms of sickness?, Brain Res. 588 Ž1992. 291–296.
227
w22x R. Wetts, K. Herrup, Interaction of granule, Purkinje and olivary neurons in lurcher chimeric mice: I. Qualitative studies, J. Embryol. Exp. Morphol. 68 Ž1982. 87–98. w23x R. Wetts, K. Herrup, Interaction of granule, Purkinje and olivary neurons in lurcher chimeric mice: II. Granule cell death, Brain Res. 250 Ž1982. 358–362. w24x M.-L. Wong, P.B. Bongiorno, A. Al-Shekhlee, A. Esposito, P. Khatri, J. Licinio, IL-1beta, IL-1 receptor type I and iNOS gene expression in rat brain vasculature and perivascular areas, NeuroReport 7 Ž1996. 2445–2448.
Short communication
Abnormal IL-1b cytokine expression in the cerebellum of the ataxic mutant mice staggerer and Lurcher Beatrice Vernet-der Garabedian ) , Yolande Lemaigre-Dubreuil, Nicole Delhaye-Bouchaud, ´ Jean Mariani Laboratoire de Neurobiologie du DeÕeloppement, Institut des Neurosciences (CNRS UMR 7624), UniÕersite´ Pierre et Marie Curie, 9 quai Saint Bernard, ´ 75005 Paris, France Accepted 22 September 1998
Abstract To assess the extent to which interleukin-1b ŽIL-1b . may contribute to the development andror progression of neurodegenerative processes, we have examined the levels of IL-1b in the brain of two types of neurological mutant mice, staggerer and Lurcher. Using a quantitative immunological method Ženzyme-linked immunosorbent assay, ELISA., we measured IL-1b in the cerebellum, hippocampus and cerebral cortex of mutant mice at baseline and after peripheral LPS treatment. Two types of IL-1b expression abnormalities were found in the mutant cerebella: higher basal level in Lurcher and a response to peripheral administration of LPS in staggerer. The association of IL-1b expression abnormalities with the only brain structure where a massive neurodegeneration occurs supports the role of proinflammatory cytokines in this process. q 1998 Elsevier Science B.V. All rights reserved. Keywords: Lurcher mutant mouse; staggerer mutant mouse; Neurodegeneration; Cerebellum; Inflammation; Proinflammatory cytokine; IL-1b; ELISA
Interleukin-1b ŽIL-1b . is primarily an inflammatory cytokine responsible for many of the effects associated with peripheral inflammation such as fever, sleep, behavioral changes and stimulation of the hypothalamic–pituitary–adrenal axis. IL-1b might work as a mediator in neural pathways and might be synthesized in the central nervous system w4x. IL-1b immunoreactivity and mRNA transcripts have been described in different brain areas and neural cell subtypes. This central IL-1b expression has been demonstrated to be modulated by an acute systemic inflammation or peripheral lipopolysaccharide treatment w9,18x. Beside its normal biological activity as part of the host defense, IL-1b may have deleterious effects. Inappropriate expression of proinflammatory cytokines is associated with a variety of neurodegenerative diseases w14x. The place and the extent to which cytokines may contribute to the development and progression of the neurodegenerative process are largely unknown.
) Corresponding author. Fax: q33-1-44-07-15-85; [email protected]
E-mail:
We have attempted to address these issues in the ataxic mutant mice staggerer and Lurcher which both perinatally develop a severe degeneration of Purkinje, olivary and granule neurons w8,19,22,23x. In both mutants, this neurodegeneration is associated with immunological disturbances in the periphery such as a delayed thymic development, undersized spleen w20x and abnormal macrophage production of proinflammatory cytokines w10,11x. We have recently demonstrated higher levels of IL-1b and IL-6 mRNAs in the cerebellum of staggerer compared to an unaffected brain region or to the wild type w12x. As mRNAs are not always translated into protein w5x, it was important to assess the protein levels of cytokines in the pathological cerebellum of the staggerer and Lurcher mice. In the present study, we have quantified IL-1b in different brain regions of homozygous staggerer and heterozygous Lurcher mice using an immuno-enzymatic method and investigated their response to a peripheral stimulation by LPS. The staggerer mutation was bred on C57BLr6J background and the Lurcher mutation on C57BLr6J= CBA ŽB6rCBA.. Mutants were identified by their ataxic behavior around postnatal day 15 in litters from qrsg= qrsg
0169-328Xr98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 9 - 3 2 8 X Ž 9 8 . 0 0 2 6 8 - X
B. Vernet-der Garabedian et al.r Molecular Brain Research 62 (1998) 224–227
and qrLc= qrq matings. All animals were maintained and experiments were performed in strict compliance with the relevant welfare guidelines adopted by the European Community. Ten 30-day old female sgrsg, five 4-month old female qrLc and age-matched C57BLr6J and B6rCBA received one intraperitoneal Ži.p.. or subcutaneous injection of LPS Ž0.5 mgrg b.wt. from Escherichia coli Ž0127-B8. in RPMI as vehicle or RPMI. Mice were sacrificed by cervical dislocation 1 to 24 h later. Spleen, cerebellum, hippocampus and cerebral cortex were rapidly dissected on ice, immediately frozen in liquid nitrogen and stored at y808C. Pooled samples were prepared as previously described w7x. IL-1b concentrations were measured using a sandwich enzyme-linked immunosorbent assay ŽELISA. performed with the Duoset ELISA Development System ŽGenzyme. according to the supplier’s recommended procedure. Blanks Žsample buffer. were deduced. The sensitivity threshold was defined as the mean absorbance value of 10 sample buffer determinations plus 2 S.D. IL-1b concentrations were determined in the linear part Žfrom 75 to 500 pgrml. of the standard curve. The differences of IL-1b level between samples were assessed by statistical analysis ŽMann–Whitney’s U-test.. Protein concentrations were determined using the DC protein assay ŽBio-Rad.. The optimal conditions of LPS stimulation on peripheral and central IL-1b expression were determined in preliminary assays by kinetic studies differing in the way of administration and the purity of LPS. While no change of IL-1b level was observed in the cerebellum for 24 h after LPS stimulation, we choose to sacrifice the mice 2 h after a single i.p. injection of purified LPS at the peak of spleen stimulation. The IL-1b basal levels were generally barely over the sensitivity threshold in all the studied brain structures of wild type and mutant mice ŽFig. 1.. The IL-1b basal levels of mutant cerebral cortex and hippocampus were not sig-
Fig. 1. The IL-1b basal levels in cerebellum Žsolid bars., cortex Žstippled bars. and hippocampus Žopen bars. of staggerer Žsgrsg. and Lurcher ŽqrLc. mutants and of the corresponding wild type C57BLr6J and B6rCBA mice. Values are means"S.E.M. Ž). Significantly different from the B6rCBA cerebellum Ž p- 0.05..
225
Fig. 2. The modulation of brain IL-1b by a peripheral LPS stimulation. IL-1b levels in the cerebellum of staggerer Žsgrsg. and Lurcher ŽqrLc. mutants and of the corresponding wild type C57BLr6J and B6rCBA mice 2 h after an i.p. RPMI Žsolid bars. and LPS Žstriped bars. injection. Values are means"S.E.M. Ž). Significantly different from RPMI-treated mice Ž ps 0.05..
nificantly different from those of the corresponding wild strains. On the contrary, in the cerebellum of Lurcher and staggerer, basal IL-1b concentrations were, respectively 2.7- and 2.5-fold higher than in wild type mice. Differences were significant for Lurcher Ž p s 0.006. but not for staggerer Ž p s 0.53.. After LPS stimulation, a robust increase Ž16.2-fold above basal level. was induced in spleens indicating that mice were efficiently stimulated. In the brain, the only altered IL-1b level was observed in the cerebellum of staggerer. IL-1b concentrations increased 3-fold compared to basal levels ŽFig. 2., the difference being significant Ž p s 0.05.. The results of this study provide further evidence that IL-1b plays a role in neurodegenerative processes within the brain. In the two ataxic mutants, IL-1b expression abnormalities were found to be exclusively associated with the cerebellum, the only brain region where a massive neurodegeneration occurs. Abnormalities were of two types: higher basal levels compared to wild type in Lurcher and a response to peripheral administration of LPS in staggerer. No IL-1b increase was induced in any normal mouse brain structure examined, nor in Lurcher. Modulation of brain IL-1b by peripheral LPS administration is widely debated, especially regarding localization of IL-1b reactivity w3,15,17,21,24x. The differences may be due to differences in stimulation by LPS Žorigin, doses.. High doses Ž2.5 to 5 mgrkg b.wt., have been reported to induce IL-1b changes throughout the brain at the mRNA or protein levels, whereas lower doses only affected meninges and brain regions with fenestered endothelial capillaries such as the circumventricular organs and choroid plexus w3,21x. LPS is a complex glycolipid which pleiotropically stimulates the cells implicated in the inflammatory response. Injected at high doses, it could modify blood–brain barrier permeability, cross the cerebral
226
B. Vernet-der Garabedian et al.r Molecular Brain Research 62 (1998) 224–227
endothelium and directly stimulate the resident brain monocyte lineage cells w1,13x. In the present study, we were interested in the reaction in the brain to a peripheral inflammation, thus LPS was used at low dose Ž0.5 mgrkg b.wt. efficient for stimulating splenic macrophages and for inducing behavioral changes in mice. In this condition, modulation of brain IL-1b was observed in normal mice at the mRNA level w12x but, in contrast with previous results w7x, remained undetectable at the protein level using the ELISA technique. It must be noted that mouse strain, purity of LPS and ELISA kit used in the two laboratories were different.The dose of LPS we used likely restricted alterations to the most responsive structures inside or surrounding the brain Žthe choroid plexus and the meninges.. The significant increase of cerebellum IL-1b levels we observed in the systemic LPS-treated staggerer may thus be due to the peripheral inflammatory abnormalities which affect this mutant w11x. Indeed, the meninges, which are external to the blood–brain barrier, were not removed from brain tissues during dissection, and the structural and functional integrity of the mutant blood–brain barrier is preserved wRiva-Depaty et al., unpublished datax. The IL-1b abnormalities have also been described in Lurcher macrophages w11x. The unexpected absence of response in the Lurcher cerebellum may be related to glucocorticoids as it has been shown that they can suppress IL-1b production in the brain w16x. We have recently reported that plasmatic corticosterone and ACTH increases were much greater in Lurcher than in wild type mice after LPS injection w6x. This difference could mask a possible increase of IL-1b responsiveness in the Lurcher brain. The cell categories responsible for IL-1b abnormalities in the two mutants are not yet identified. However, an important astrogliosis has been described in staggerer cerebellum as well as an hyperinducibility for IL-1b of microglial cells in vitro w2x. In conclusion, the association of IL-1b expression abnormalities with the only brain structure where a massive neurodegeneration occurs supports the role of proinflammatory cytokines in this process. High basal level of IL-1b may reflect altered parenchymal IL-1b expression within the cerebellum. Peripheral inflammation could contribute to additive or synergistic effects on local neurodegeneration even if the blood–brain barrier integrity is not perturbed. In this context, the Lurcher and staggerer mutants appear to be valuable model to study the relationship between immune system and neurodegeneration.
Acknowledgements We are grateful to Dr. Robert Dantzer and Chantal Combe for their help in establishing the ELISA assay for IL-1b detection. We wish to thank Colette Chianale for the breeding of the mice. This work was supported by a grant
from the European Community Žgrant BIOMED, Cybrainet no. PL 962492.. References w1x N.J. Abbott, P.A. Revest, Control of brain endothelial permeability, Cerebrovasc. Brain Metab. Rev. 3 Ž1991. 39–72. w2x B. Brugg, Y. Lemaigre-Dubreuil, G. Huber, B. Kopmels, N. Delhaye-Bouchaud, E. Wollman, J. Mariani, Neuronal death, proinflammatory cytokines and amyloid precursor protein: studies on staggerer mutant mice, in: K.S. Kosik, Y. Christen, D.J. Selkoe ŽEds.., Alzheimer’s Disease: Lessons from Cell Biology, Foundation Ipsen, Springer, Berlin, 1995, pp. 202–216. w3x M. Buttini, H. Boddeke, Peripheral lipopolysaccharide stimulation induces interleukin-1beta messenger RNA in rat brain microglial cells, Neuroscience 65 Ž1995. 523–530. w4x B.W. Coltman, C.F. Ide, Temporal characterization of microglia, IL-1 beta-like immunoreactivity and astrocytes in the dentate gyrus of hippocampal organotypic slice cultures, Int. J. Dev. Neurosci. 14 Ž1996. 707–719. w5x J.P. Corradi, C. Yang, J.C. Darnell, J. Dalmau, R.B. Darnell, A post-transcriptional regulatory mechanism restricts expression of the paraneoplastic cerebellar degeneration antigen cdr2 to immune privileged tissues, J. Neurosci. 17 Ž1997. 1406–1415. w6x F. Frederic, T. Chautard, R. Brochard, C. Chianale, E. Wollman, C. Oliver, N. Delhaye-Bouchaud, J. Mariani, Enhanced endocrine response to novel environment stress and endotoxin in lurcher mutant mice, Neuroendocrinology 66 Ž1997. 341–347. w7x E. Goujon, P. Parnet, S. Laye, ´ C. Combe, R. Dantzer, Adrenalectomy enhances pro-inflammatory cytokines gene expression, in the spleen, pituitary and brain of mice response to lipopolysaccharide, Mol. Brain Res. 36 Ž1996. 53–62. w8x K. Herrup, R.J. Mullen, Regional variation and absence of large neurons in the cerebellum of the staggerer mouse, Brain Res. 172 Ž1979. 1–12. w9x S.J. Hopkins, N.J. Rothwell, Cytokines and the nervous system: I. Expression and recognition, TINS 18 Ž1995. 83–88. w10x B. Kopmels, J. Mariani, V. Taupin, N. Delhaye-Bouchaud, E.E. Wollman, Differential IL-6 mRNA expression by stimulated peripheral macrophages of staggerer and lurcher cerebellar mutant mice, Eur. Cytokine Netw. 2 Ž1991. 345–353. w11x B. Kopmels, E. Wollman, J.M. Guastavino, N. Delhaye-Bouchaud, D. Fradelizi, J. Mariani, Interleukin-1 hyperproduction by in vitro activated peripheral macrophages from cerebellar mutant mice, J. Neurochem. 55 Ž1990. 1980–1985. w12x Y. Lemaigre-Dubreuil, B. Brugg, C. Chianale, N. DelhayeBouchaud, J. Mariani, Over-expression of interleukin-1beta-converting enzyme mRNA in staggerer cerebellum, NeuroReport 7 Ž1996. 1777–1780. w13x W.A. Lynn, D.T. Golenbock, Lipopolysaccharide antagonists, Immunology Today 13 Ž1992. 271–276. w14x J.E. Merrill, G.M. Jonakait, Interactions of the nervous and immune systems in development, normal brain, homeostasis and disease, FASEB J. 9 Ž1995. 611–661. w15x T. Nakamori, A. Morimoto, K. Yamaguchi, T. Watanabe, N. Murakami, Interleukin-1beta production in the rabbit brain during endotoxin-induced fever, J. Physiol. 476.1 Ž1994. 177–186. w16x K.T. Nguyen, T. Deak, S.M. Owens, T. Kohno, M. Fleshner, L.R. Watkins, S.F. Maier, Exposure to acute stress induces brain interleukin-1b protein in the rat, J. Neurosci. 18 Ž1998. 2239–2246. w17x N. Quan, S. Sundar, J. Weiss, Induction of interleukin-1 in various brain regions after peripheral and central injections of lipopolysaccharide, J. Neuroimmunol. 49 Ž1994. 125–134. w18x N.J. Rothwell, S.J. Hopkins, Cytokines and the nervous system: II. Actions and mechanisms of action, Trends Neurosci. 18 Ž1995. 130–136.
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