Antidepressant drugs activate SREBP and up-regulate cholesterol and fatty acid biosynthesis in human glial cells.

Dysfunction of glial lipid metabolism and abnormal myelination has recently been reported in both schizophrenia and bipolar disorder. Cholesterol is a major component of myelin, and glia-produced cholesterol serves as a glial growth factor in synaptogenesis. We have recently demonstrated that antipsychotic drugs activate the sterol regulatory element-binding protein (SREBP) transcription factors in human and rat glial cells, with subsequent up-regulation of numerous downstream genes involved in cholesterol and fatty acid biosynthesis. Since this stimulation of cellular lipogenesis could represent a new mechanism of action of psychotropic drugs, we investigated whether antidepressants and mood-stabilizers were able to induce a similar activation of SREBP-controlled lipid biosynthesis. Cultured human glioma cells (GaMg) were exposed to the antidepressant drugs imipramine, amitriptyline, clomipramine, citalopram, fluoxetine, mirtazapine and bupropion and the mood-stabilizers/antiepileptics lithium, valproate and carbamazepine. All antidepressant drugs activated the SREBP system with subsequent up-regulation of the downstream lipogenesis-related genes, although to a markedly different extent. The mood-stabilizers did not affect the SREBPs or the downstream genes. These results link antidepressant drugs, but not mood-stabilizers, to SREBP-mediated activation of cellular lipogenesis, and demonstrate a functional similarity between antipsychotic and antidepressant molecular drug action.