Possible Involvement of Oxidative Stress and Inflammatory Mediators in the Protective Effects of the Early Preconditioning Window Against Transient Global Ischemia in Rats

Ischemic preconditioning (IPC), comprising exposure to sub-lethal short term ischemic events, has been shown to exert adaptive responses in many organs including the brain, thus guarding against exacerbations of ischemia reperfusion (IR). However, the mechanisms involved in the early phase of such a protection remain elusive; hence, the present study aimed to investigate the modulatory effect of preconditioning against IR induced injury on infarct size, free radicals, inflammatory/antiinflammatory markers, caspase-3 and heat shock protein (HSP)70 in the rat hippocampus. To this end, male Wistar rats were divided into 3 groups, (1) sham operated (SO) control; (2) IPC, animals were subject to 3 episodes of ischemia (5 min) followed by reperfusion (10 min), afterwards rats underwent ischemia (15 min) followed by reperfusion (60 min); (3) IR animals were subjected to 15 min global ischemia followed by 60 min reperfusion. IR produced cerebral infarction accompanied by an imbalance in the hippocampal redox status, neutrophil infiltration, elevation in tumor necrosis factor (TNF)-alpha and prostaglandin (PG)E-2, besides reduction in interleukin (IL)-10 and nitric oxide (NO) levels. IPC reverted all changes except for PGE(2); however, neither HSP70 nor caspase-3 expression was altered following IR or IPC. The current study points thus towards the activation of the antioxidant system, anti-inflammatory pathway, as well as NO in the early phase of preconditioning protection.