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7β‐hydroxysterol is cytotoxic to neonatal rat astrocytes in primary culture when cAMP levels are increased
Author(s) -
Bochelen D.,
Langley K.,
Adamczyk M.,
Kupferberg A.,
Hor F.,
Vincendon G.,
Mersel M.
Publication year - 2000
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/1097-4547(20001001)62:1<99::aid-jnr11>3.0.co;2-2
Subject(s) - glial fibrillary acidic protein , forskolin , astrocyte , protein kinase a , cytotoxic t cell , astrogliosis , biology , cytotoxicity , ibmx , medicine , endocrinology , microbiology and biotechnology , in vitro , kinase , chemistry , biochemistry , immunology , immunohistochemistry , central nervous system
We have shown previously that 7β‐hydroxycholesterol (7βOHCH) and 7β‐hydroxycholesteryl‐3‐oleate (7βOHCH‐ 3‐OL) are potent inhibitors of lesion‐induced astrogliosis in the rat cortex or spinal cord; these substances reduce reactive astrocyte proliferation and hypertrophy. In this study, we employed cultured newborn rat astrocytes with increased cAMP levels as an in vitro model of reactive astrocytes. Treatment with either dibutyryl‐cAMP (dbcAMP) or isoproterenol resulted in morphologic differentiation of astrocytes which became fibrous. Concomitant incubation with 30 μM 7βOHCH and dbcAMP (or isoproterenol) provoked the cells to retract and was cytotoxic. When the β‐adrenergic receptor‐mediated cAMP increase was abolished by propranolol, the 7βOHCH cytotoxicity was inhibited. Immunocytochemical labelling for glial fibrillary acidic protein (GFAP) and β‐tubulin and electron microscopy suggested that intermediate filament and microtubular organizations were modified by 7βOHCH. Analysis of the activity of cAMP‐dependent protein kinase (PKA) in astrocytes treated with dbcAMP and 7βOHCH showed a rapid and marked inhibition of the phosphotransferase activity which lasted for 24 hr. We suggest that this culture system provides an experimental system to study the molecular mechanisms involved in the effect of oxysterols on astrocytic hypertrophy. The cytotoxicity of 7βOHCH seems to be mediated by inhibition of PKA, which phosphorylates intermediate filaments and the transcription factor cyclic AMP responsive element binding. J. Neurosci. Res. 62:99–111, 2000. © 2000 Wiley‐Liss, Inc.