Ichthyotoxic Cochlodinium polykrikoides Induces Mitochondrial Mediated Oxidative Stress and Apoptosis in Rat Liver Hepatocytes

In this research, we investigated the cytotoxic mechanisms of Cochlodinium polykrikoidescell lysate on isolated rat liver hepatocytes.This micro algae is responsible for a severe and widespread harmful algal bloom in the Persian Gulf and Gulf of Oman (2008-2009). Isolated hepatocytes were obtained by collagenase perfusion of Sprague-Dawley rat liver.According to our results, incubation of algal lysate with isolated rat hepatocytescaused hepatocyte membrane lysis, reactive oxygen species (ROS) formation, glutathione depletion, collapse of mitochondrial membrane potential,ATP depletion and increase in ADP/ATP ratio, cytochrome c release in to the hepatocyte cytosol,activation of caspase-3 (final mediator of apoptosis) and appearance of apoptosis phenotype. On the other hand, pretreatment of antioxidants (α-tocopherol succinate and BHT), hydroxyl radical scavengers (mannitol and DMSO), mitochondrial permeability transition (MPT) pore sealing agents (cyclosporine A, carnitine and trifluoperazine), NADPH P450 reductase inhibitor (Diphenyliodonium chloride), CYP2E1 inhibitors (Phenylimidazole and 4-Methylpyrazole) andATP generators (L-glutamine, Fructose and Xylitol)inhibited caspase-3 activation and cell death in algal lysate treated hepatocytes.Our data also confirmed that algal lysate activates apoptosis signaling via oxidative stress and mitochondrial pathway. Thus, ROS formation caused by the lysate exposure could directly be involved in mitochondrial MPT pore opening and activation of caspase-3 leading to C.polykrikoides lysateinduced apoptosis on rat hepatocytes. These findings contribute to a better understanding of C.polykrikoides-toxic effects on mammalian liver cells.