Preconditioning exercise reduces hippocampal neuronal damage via increasing Klotho expression in ischemic rats

Abstract

Considerable amounts of oxidants are produced in cerebral ischemia, where oxidative stress plays a key role in neuronal damage after ischemia. Klotho, an anti-aging protein, alleviates oxidative stress by activating the transcription of an important antioxidant enzyme, manganese superoxide dismutase (MnSOD), in the nervous system. Thus, increased Klotho expression level could lead to a reduction in neuronal damages after brain ischemia via lowering oxidative stress. It is known that physical activity increases Klotho expressions. In this study, we assessed neuroprotective effects of preconditioning exercise in rats (treadmill running at a speed of 20 m/min,30 min/day, six days/week, for3 weeks) on hippocampal Klotho and MnSOD expression in the brain using an animal model of stroke, middle cerebral artery occlusion (MCAO). Our study revealed a reduction in hippocampal Klotho and MnSOD expression as well as CA1 neuronal activity in MCAO compared to the sham group. Exercise prevented the ischemia-induced decline in Klotho and MnSOD expression levels as well as CA1 neuronal activity in Exercise + MCAO compared to the MCAO group. Also, exercise significantly improved the neurological scores and reduced brain infarction area in Exercise + MCAO in comparison to MCAO group. There was a post-ischemia deficit in the working memory, as measured by spontaneous alternation percentage using Y-maze test, in MCAO compared to the sham group. The latter effect was not observed in the Exercise + MCAO group, which could be related to an increase in the antioxidant capacity as exhibited by Klotho and MnSOD up-regulation. The results were confirmed with a positive correlation between Klotho expression and MnSOD expression which allows proposing Klotho as a potential neuroprotective protein in ischemic stroke with respect to antioxidant defense. In general, the present study suggested that preconditioning exercise induced upregulation of Klotho and MnSOD, as well as attenuated the post-ischemic injuries. The upregulation of Klotho might be an underlying mechanism by which preconditioning exercise plays as a neuroprotective factor against post-ischemic neural injuries in ischemic rats.