Effect of the NADPH oxidase inhibitor apocynin on ischemia-reperfusion hippocampus injury in rat brain.

Blockage along with sudden restoration of blood following ischemia, results in several cascading events, such as a massive ROS production which plays an important role in the pathophysiology of ischemia. NADPH oxidase complex in mitochondria complex is believed to be the major source for ROS production. The present study explores the therapeutic potential of apocynin, an NADPH oxidase inhibitor in attenuating the ROS production, and the resultant neuroinflammation and mitochondrial injury during cerebral ischemia in rats. Bilateral common carotid artery occlusion (BCCAO) model was chosen for the study where intracellular ROS and NO levels as well as the NADPH oxidase activity were found to be increased significantly post 7th day of ischemic injury. Enhanced glial activation was observed and an upregulated expression of GFAP and Iba-1 in hippocampus along with that of the transcription factor NFκB and inflammatory markers iNOS, IL-1α, IL-1β and TNF-α.The activity of mitochondrial electron transport chain (ETC) complexes I, II, IV and V were significantly decreased following ischemia. Consequently, there was a decrease in mitochondrial membrane potential (MMP) while an increased release of cytochrome c and upregulated apoptotic markers Bax, caspase-3 and 9 initiated the programmed neuronal death which was also reflected by the marked increase in TUNEL positive cells in the hippocampal region. The physiological functional alterations have been observed following ischemic injury i.e memory and motor deficits. The apocynin supplementation significantly reduced the NADPH oxidase activity and resulted in declined ROS production which in-turn prevented the glial activation and downregulated the inflammatory and pro-apoptotic markers. Apocynin also restored the MMP (Δψm ) and mitochondrial enzymes via inhibition of ROS vicious and relationship between NADPH oxidase and mitochondrial complexes. Apocynin treatment was also successfully reduced the behavioural deficits in ischemic animals. In conclusion, inhibiting the NADPH oxidase complex presumably attenuated the mitochondrial injury, neuroinflammation and apoptosis following ischemic injury in rat brain.