title: Valproic acid induces caspase 3-mediated apoptosis in microglial cells.
abstract: Valproic acid is widely used for the treatment of epilepsy and mood disorders, but its mode of action is unclear. Treatment of neuronal cells with valproic acid promotes neurite sprouting, is neuroprotective and drives neurogenesis; however its effects on non-neuronal brain cells are less clear. We report that valproic acid induces apoptosis in the mouse microglial cell line, BV-2, at concentrations within the therapeutic range. When BV-2 cells were incubated for 24 h with 500-1000 microM valproic acid we observed a reduction in cell number, the appearance of apoptotic morphology and increased caspase 3 cleavage. Exposure of a macrophage cell line (RAW 264.7) to similar concentrations of valproic acid also led to reduced cell number but no caspase 3 cleavage, suggesting these cells responded to valproic acid with reduced proliferation rather than apoptosis. This was confirmed using bromodeoxyuridine incorporation studies. Similar concentrations of valproic acid added to Neuro-2a, SK-N-SH and C6 cell lines as well as human NTera-2 astrocytes did not evoke cell death. The caspase 3 inhibitor DEVD-CHO inhibited valproic acid-induced apoptosis in BV-2 cells whereas the MEK inhibitor U0126 potentiated valproic acid-mediated apoptosis. These results demonstrate that valproic acid selectively induces apoptosis in BV-2 cells by way of a caspase 3-mediated action. As activated microglia secrete neurotoxins in neurodegenerative diseases such as Alzheimer's, Parkinson's, and HIV dementia, valproic acid may alleviate these diseases by selectively killing microglia.
authors.affiliation: Department of Pharmacology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand. m.dragunow@auckland.ac.nz
authors.forename: M
authors.initials: M
authors.lastname: Dragunow
authors.forename: J M
authors.initials: JM
authors.lastname: Greenwood
authors.forename: R E
authors.initials: RE
authors.lastname: Cameron
authors.forename: P J
authors.initials: PJ
authors.lastname: Narayan
authors.forename: S J
authors.initials: SJ
authors.lastname: O'Carroll
authors.forename: A G
authors.initials: AG
authors.lastname: Pearson
authors.forename: H M
authors.initials: HM
authors.lastname: Gibbons
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D053148:Caspase 3; D020169:Caspases / Q000096:biosynthesis*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects / Q000502:physiology; D006801:Humans; D051379:Mice; D017628:Microglia / Q000187:drug effects* / Q000201:enzymology; D014635:Valproic Acid / Q000494:pharmacology*
chemical_list: D014635:Valproic Acid; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases