Endurance Training and Exogenous Adenosine Infusion Mitigate Hippocampal Inflammation and Cell Death in a Rat Model of Cerebral Ischemia/Reperfusion Injury

Abstract

Background: Cerebral ischemia can cause irreversible structural and functional damages to the brain, especially to the hippocampus. Preconditioning with endurance training and endogenous adenosine infusion may reduce ischemia-associated damages. Objectives: This study aimed to evaluate the effect of preconditioning with endurance training and endogenous adenosine infusion on cell death in the hippocampal CA1 region following ischemia/reperfusion injuries in a rat model. Methods: Male Wistar rats were divided into five groups: (1) control (n = 8); (2) ischemia (n = 12); (3) endurance training + ischemia (n = 12); (4) adenosine infusion + ischemia (n = 12); and (5) endurance training + adenosine infusion + ischemia (n = 12). The rats in the training groups ran on a treadmill five days per week for eight weeks. In the adenosine infusion groups, the rats were injected 0.1 mg/mL/kg of adenosine intraperitoneally. Also, in the ischemic groups, both common carotid arteries were clamped for 45 minutes. Cresyl violet staining and real-time polymerase chain reaction (PCR) assay were used to evaluate cell death and cytokine gene expression, respectively. Results: Based on the present results, treatments, including endurance training + ischemia, adenosine infusion + ischemia, and endurance training + adenosine infusion + ischemia reduced the level of interleukin-6 (IL-6) and glutamate gene expression, respectively, compared to the group of ischemia only. In contrast, the expression of nerve growth factor (NGF) and adenosine receptor (A2A) genes increased by seven, four, and two folds in the endurance training + ischemia, adenosine infusion + ischemia, and endurance training + adenosine infusion + ischemia groups, respectively, compared to the group of ischemia only. Conclusions: Endurance training on a treadmill and exogenous adenosine infusion synergistically diminished cell death and reduced the expression of pro-inflammatory cytokines, while promoting the neurotrophic factor expression. When endurance training and adenosine infusion were used as stimulants before the induction of cerebral ischemia, they significantly reduced cell death.