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Steroid effects on cell membrane structure: Implications for depressive illness
Abstracts
mOL PSYCHIATRY 1996;39:500-666
hypotheses regarding eNS rnonoaminerglc systems in depression: (a) that absolute concentratlons of the inforrnational substances norepinephrine (NE) and S·hydroxyimloleacet!c acid (5-H1AA) arc altered in the eNS of depressed patients (b) that abnormal rhythms of NE andlor 5-HIAA exist in the eNS of depressed patients, and (c) that the relationship between the CNS serotonin (5HT) and NE systems is disrupted in depressed patients. This last theory was originally advanced by Sulser as the "serotonin-norcplnephrinc link" hypnthesis of depressian. Using continuous sampling at the rate of 0,I mllmin vla an indwelling spinal canal catheter we obtained detailed, 6-h concentration time series of NE and 5·HlAA in the CSF of 10 patients with major depressive disorderand 10 normal volunteer controls. The subarachnoid catheter had been placed 3 h prior to the commencement of CSF sampling. CSF S-HIAA and CSF NE concentrations and rhythms Were similar in normal volunteers and depressed patients. However. a. highly slgniflcant, negative linear relationship was observed between mean concentrations of 5HIAA and NE in the CSF of the normal volunteers (r -0.916 [r = 0.839}, df 9, p 0; 0.0002). In contrast, depressed patients showed no such relationship (r = +0.094 [r 0.008771. df 9, P ::: 0.80). These data support the idea that a disturbance in the internction between the serotonergic and noradrenergic systems can exist in depressive illness, in the absenceof any simple5HT or NE deficitor surplus. Furthermore. taken together with our additional finding of abnormal CSF conlcotropln-releaslng hormone (CRH) concentrations in these same patients (JCEM 1992 and unpublished data). our data arc supportive of Sulser's more recent "SHT-NE-gillcocorticoid link" hypothesis of major depression.
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292. STEROID EFFECTS ON CELL
MEMBRANE STRUCTURE: IMPLICATIONS FOR DEPRESSIVE ILLNESS R.P. Mason, G.A. Golden, P,E. Mason, & R.T. Rubin Neurosciences Research Center, Allegheny Campus. Medical College of Pennsylvania and Hahnernann Univcn;ity. Pittsburgh, PA 15212 Cortisol and estradiol arc lipophilic steroids which internet with the cell plasma membrane, in addition to binding to cytosolic receptors, To explorethe imeractlons of thesesteroidswith phospholipid rnultilamellar vesicles, we determined their membrane- based partition coefficients and their time-averaged locations within the phospholipid bilayer. In the absence of cholesterol, the (Kplrncml) values for cortisol and estradiol were 250 and 5.000, respectively. In the presence of Q physlologlcal concentratlon of cholesterol (0.4:I cholestcroVphospholipid mole ratio), the Kp[mcml valuesfor bothcortisoland estradiol werereduced by 50%. In washout experiments, the dissociation of cortisol from the membrane was significantly greater than that of estradiol (>50% vs, <5%), One-dimensional electron densitypmlilesgenerated by small-angle x-ray diffraction (13A resolution) indicated thatthese steroids occupy discrete, time-averaged locations in the lipidbilayer. Estradiol, a nonpolar steroid. was concentrated near the center of the membrane hydrocarbon core, the region with the grentest molecular volume. In contrast, cortisol, a more polar steroid, was concentrated near the phospholipid headgrcups, u charged region of high molecular density. Studies with ROC cell membranes arc yielding very similar results. These lindings support a model of steroid partitioning to discrete locations in the cell plasma membrane. The membrane interactions of these steroids 1)nrcinfluenced by membrane lipid composition, particuln.rly cholesterol content, 2) may be responsible for someof the very rapid physiologlc effectsof sterolds, 3) may influence the structure-activity characteristlcs of membranebound proteins, and 4) may modulate theability of steroids 10 bind 10 and activate their specific intracellular receptors, These findings may have
585
particular relevance for the postulated tissue resistance to elevated cortisol in major depression. as well as 10 the reduced lymphocyte function in this illness in spite of normal lymphocyte cytosollc glucocortlcoid receptor number and affinity.
293_ AMESERGIDE PRE-TREATMENT OF m-CPP IN NORMAL CONTROLS C.M. Wong, E. Hollander, & C. Decaria Mount Sinai School of Medicine. New York. NY 10029 We attempted to determine whether pre-treatment with the 5·HT2C antagonist amesergltle effectively blocks the neuroendocrine effects of tlle partial S-HT agonist m·CPP in normal controls. Seven normal controls wererandomized todcuble-blind challenges of plecebo/pleccbo, amesergide (50mg)/plncebo, placebolm.CPP (0.5 mglkg). and amescrgidc/m.CPP. Prolactin, cortisol. and m·epp levels were drawn, andthe analogue affeci scale,visual analogue affectscaleand acutepanic inventory were administered at regular Intervals, There was a marked increase in prolactin release (peak dl!lta=16.76 ::!: 15.26) following placebo/m-CPP, whereas the peak change in prolactin was low in the placebo/placebo group (peak delta= 1.14 ± 1.3). Of particular interest, following nmesergidc/m-CPP, there was minimal prolactin release (peak delta::: 1.57 ± 1.45), indicating that this S-HT2C antagonist effectively blocked prolactin response to rn-Cl'P, Analysis of variance was signiflcant (F=4,456, p=O.038), with post-hoc t-tests demonstrating 1I trend towards a. significant difference in prolactin levels after placebo/m·epP challenge compared to both placebo/placebo (1""2.28, p=O.084) and ameserglde/m-Cl'P (t=2.21. p=O,090). Placebo/m-CPP led to a marked increase in cortisol release (peak della.= 12,06 :t 2.75). In contrast, peak change in cortisol was low after placebo/placebo (peak della=- 1.1 ± 2.13), and llmesergidl!/m-CPP (peak delta=6.96 ± 4,36). Analyses of variance was significant (F= 10.912, p=0.OO7); post-hoc t-testsdemonstrating n significant difference between cortisol Icvcls after placebo/mCPP challenge vs placebo/placebo (t=5.73, p=O.OO5), but not with placebo/amescrgldc (I = 1.11, p=O.175). There was a trend toward signilicancc via ANOVA (F=2.6, p=-O.09), with less increase in anxiety afternmcsergidc/pla.cebo than after the other challenges, These findings suggest that nmesergide may have someanxiolylie properties, Ourresults indicate that II SO rng dose of ameserglde is able to block proInctin response. suggestingthatprolactin response 10 m·CPPis mediated by the S·HT2C receptor.
294. EXPRESSION OF MEF2C BY SUBSETS OF NEOCORTICAL AND HIPPOCAMPAL NEURONS Y.L. Li & D. Leifer Yale University School of Medicine, New Haven,
cr 06520
MEF2C belongs to the MADS family of transcription factors and is
expressed in muscle lind in the brain. In situ hybridizution and immunehlsrochcmlstry indic:ltl: that It is found ut high levels in post-mltotle neurons in the cerebralcortex. We have now performed double-labeling Immunohistochemical experiments on samples of human neocortex and hippocampus resected from palienl<; during surgery (or epilepsy. We used
mOL PSYCHIATRY 1996;39:500-666
hypotheses regarding eNS rnonoaminerglc systems in depression: (a) that absolute concentratlons of the inforrnational substances norepinephrine (NE) and S·hydroxyimloleacet!c acid (5-H1AA) arc altered in the eNS of depressed patients (b) that abnormal rhythms of NE andlor 5-HIAA exist in the eNS of depressed patients, and (c) that the relationship between the CNS serotonin (5HT) and NE systems is disrupted in depressed patients. This last theory was originally advanced by Sulser as the "serotonin-norcplnephrinc link" hypnthesis of depressian. Using continuous sampling at the rate of 0,I mllmin vla an indwelling spinal canal catheter we obtained detailed, 6-h concentration time series of NE and 5·HlAA in the CSF of 10 patients with major depressive disorderand 10 normal volunteer controls. The subarachnoid catheter had been placed 3 h prior to the commencement of CSF sampling. CSF S-HIAA and CSF NE concentrations and rhythms Were similar in normal volunteers and depressed patients. However. a. highly slgniflcant, negative linear relationship was observed between mean concentrations of 5HIAA and NE in the CSF of the normal volunteers (r -0.916 [r = 0.839}, df 9, p 0; 0.0002). In contrast, depressed patients showed no such relationship (r = +0.094 [r 0.008771. df 9, P ::: 0.80). These data support the idea that a disturbance in the internction between the serotonergic and noradrenergic systems can exist in depressive illness, in the absenceof any simple5HT or NE deficitor surplus. Furthermore. taken together with our additional finding of abnormal CSF conlcotropln-releaslng hormone (CRH) concentrations in these same patients (JCEM 1992 and unpublished data). our data arc supportive of Sulser's more recent "SHT-NE-gillcocorticoid link" hypothesis of major depression.
=
=
=
=
292. STEROID EFFECTS ON CELL
MEMBRANE STRUCTURE: IMPLICATIONS FOR DEPRESSIVE ILLNESS R.P. Mason, G.A. Golden, P,E. Mason, & R.T. Rubin Neurosciences Research Center, Allegheny Campus. Medical College of Pennsylvania and Hahnernann Univcn;ity. Pittsburgh, PA 15212 Cortisol and estradiol arc lipophilic steroids which internet with the cell plasma membrane, in addition to binding to cytosolic receptors, To explorethe imeractlons of thesesteroidswith phospholipid rnultilamellar vesicles, we determined their membrane- based partition coefficients and their time-averaged locations within the phospholipid bilayer. In the absence of cholesterol, the (Kplrncml) values for cortisol and estradiol were 250 and 5.000, respectively. In the presence of Q physlologlcal concentratlon of cholesterol (0.4:I cholestcroVphospholipid mole ratio), the Kp[mcml valuesfor bothcortisoland estradiol werereduced by 50%. In washout experiments, the dissociation of cortisol from the membrane was significantly greater than that of estradiol (>50% vs, <5%), One-dimensional electron densitypmlilesgenerated by small-angle x-ray diffraction (13A resolution) indicated thatthese steroids occupy discrete, time-averaged locations in the lipidbilayer. Estradiol, a nonpolar steroid. was concentrated near the center of the membrane hydrocarbon core, the region with the grentest molecular volume. In contrast, cortisol, a more polar steroid, was concentrated near the phospholipid headgrcups, u charged region of high molecular density. Studies with ROC cell membranes arc yielding very similar results. These lindings support a model of steroid partitioning to discrete locations in the cell plasma membrane. The membrane interactions of these steroids 1)nrcinfluenced by membrane lipid composition, particuln.rly cholesterol content, 2) may be responsible for someof the very rapid physiologlc effectsof sterolds, 3) may influence the structure-activity characteristlcs of membranebound proteins, and 4) may modulate theability of steroids 10 bind 10 and activate their specific intracellular receptors, These findings may have
585
particular relevance for the postulated tissue resistance to elevated cortisol in major depression. as well as 10 the reduced lymphocyte function in this illness in spite of normal lymphocyte cytosollc glucocortlcoid receptor number and affinity.
293_ AMESERGIDE PRE-TREATMENT OF m-CPP IN NORMAL CONTROLS C.M. Wong, E. Hollander, & C. Decaria Mount Sinai School of Medicine. New York. NY 10029 We attempted to determine whether pre-treatment with the 5·HT2C antagonist amesergltle effectively blocks the neuroendocrine effects of tlle partial S-HT agonist m·CPP in normal controls. Seven normal controls wererandomized todcuble-blind challenges of plecebo/pleccbo, amesergide (50mg)/plncebo, placebolm.CPP (0.5 mglkg). and amescrgidc/m.CPP. Prolactin, cortisol. and m·epp levels were drawn, andthe analogue affeci scale,visual analogue affectscaleand acutepanic inventory were administered at regular Intervals, There was a marked increase in prolactin release (peak dl!lta=16.76 ::!: 15.26) following placebo/m-CPP, whereas the peak change in prolactin was low in the placebo/placebo group (peak delta= 1.14 ± 1.3). Of particular interest, following nmesergidc/m-CPP, there was minimal prolactin release (peak delta::: 1.57 ± 1.45), indicating that this S-HT2C antagonist effectively blocked prolactin response to rn-Cl'P, Analysis of variance was signiflcant (F=4,456, p=O.038), with post-hoc t-tests demonstrating 1I trend towards a. significant difference in prolactin levels after placebo/m·epP challenge compared to both placebo/placebo (1""2.28, p=O.084) and ameserglde/m-Cl'P (t=2.21. p=O,090). Placebo/m-CPP led to a marked increase in cortisol release (peak della.= 12,06 :t 2.75). In contrast, peak change in cortisol was low after placebo/placebo (peak della=- 1.1 ± 2.13), and llmesergidl!/m-CPP (peak delta=6.96 ± 4,36). Analyses of variance was significant (F= 10.912, p=0.OO7); post-hoc t-testsdemonstrating n significant difference between cortisol Icvcls after placebo/mCPP challenge vs placebo/placebo (t=5.73, p=O.OO5), but not with placebo/amescrgldc (I = 1.11, p=O.175). There was a trend toward signilicancc via ANOVA (F=2.6, p=-O.09), with less increase in anxiety afternmcsergidc/pla.cebo than after the other challenges, These findings suggest that nmesergide may have someanxiolylie properties, Ourresults indicate that II SO rng dose of ameserglde is able to block proInctin response. suggestingthatprolactin response 10 m·CPPis mediated by the S·HT2C receptor.
294. EXPRESSION OF MEF2C BY SUBSETS OF NEOCORTICAL AND HIPPOCAMPAL NEURONS Y.L. Li & D. Leifer Yale University School of Medicine, New Haven,
cr 06520
MEF2C belongs to the MADS family of transcription factors and is
expressed in muscle lind in the brain. In situ hybridizution and immunehlsrochcmlstry indic:ltl: that It is found ut high levels in post-mltotle neurons in the cerebralcortex. We have now performed double-labeling Immunohistochemical experiments on samples of human neocortex and hippocampus resected from palienl<; during surgery (or epilepsy. We used