title: A new approach on valproic acid induced hepatotoxicity: involvement of lysosomal membrane leakiness and cellular proteolysis.
abstract: Although valproic acid (VPA) a proven anticonvulsant agent thought to have relatively few side-effects VPA has been referred as the third most common xenobiotic suspected of causing death due to liver injury. In this study the cellular pathways involved in VPA hepatotoxicity were investigated in isolated rat hepatocytes. Accelerated cytotoxicity mechanism screening (ACMS) techniques using fluorescent probes including, ortho-phthalaldehyde, rhodamine 123 and acridine orange were applied for measurement of ROS formation, glutathione depletion, mitochondrial membrane potential and Lysosomal membrane damage, respectively. Our results showed that cytotoxic action of VPA is mediated by lysosomal membrane leakiness along with reactive oxygen species (ROS) formation and decline of mitochondrial membrane potential before cell lysis ensued. Incubation of hepatocytes with VPA also caused rapid hepatocyte glutathione (GSH) depletion which is another marker of cellular oxidative stress. Most of the VPA induced GSH depletion could be attributed to the expulsion of GSSG. Our results also showed that CYP2EI is involved in the mechanism of VPA cytotoxicity. We finally concluded that VPA hepatotoxicity is a result of metabolic activation by CYP2E1 and ROS formation, leading to lysosomal labialization, mitochondrial/lysosomal toxic cross-talk and finally general cellular proteolysis in the rat hepatocytes.
authors.affiliation: Faculty of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran 14155-6153, Iran. j.pourahmadjaktaji@utoronto.ca
authors.forename: Jalal
authors.initials: J
authors.lastname: Pourahmad
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Eskandari
authors.forename: Amineh
authors.initials: A
authors.lastname: Kaghazi
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Shaki
authors.forename: Jafar
authors.initials: J
authors.lastname: Shahraki
authors.forename: Javad Khalili
authors.initials: JK
authors.lastname: Fard
mesh_terms: D000818:Animals; D000927:Anticonvulsants / Q000633:toxicity*; D000975:Antioxidants / Q000494:pharmacology; D002478:Cells, Cultured; D056486:Chemical and Drug Induced Liver Injury / Q000378:metabolism*; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism; D065691:Cytochrome P-450 CYP2E1 Inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects / Q000502:physiology; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D014635:Valproic Acid / Q000633:toxicity*
chemical_list: D000927:Anticonvulsants; D000975:Antioxidants; D065691:Cytochrome P-450 CYP2E1 Inhibitors; D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D014635:Valproic Acid; D019392:Cytochrome P-450 CYP2E1; D005978:Glutathione