Effects of hydrogen-rich saline on hippocampal mammalian target of rapamycin/tau pathway after operation in aged rats

Objective To investigate the effects of hydrogen-rich saline on hippocampal mammalian target of rapamycin(mTOR)/tau pathway after operation in aged rats. Methods One hundred fifty healthy male Sprague Dawley rats, aged 18 months, weighing 400–540 g, were randomly divided into 5 groups(n=30 each)using a random number table: control group(group C); sham operation group(group S); operation group(group O); hydrogen-rich saline treatment group(group HS); normal saline group(group NS). Splenectomy was performed in group O. Hydrogen-rich saline 1 ml/100 g was injected intraperitoneally at 5 min before splenectomy in group HS.Normal saline 1 ml/100g was injected intraperitoneally at 5 min before splenectomy in group NS.Morris water maze test was performed at 1, 3 and 7 days after surgery, and the escape latency and swimming distance were recorded.After the end of the test, the rats were sacrificed, and the brains were removed for examination of the pathological changes in the hippocampal CA3 region(under light microscope), and for determination of the expression of mTOR mRNA and tau mRNA(using reverse transcriptase polymerase chain reaction)and mTOR and pS396 tau(by Western blot). Results Compared with C and S groups, the escape latency and swimming distance were significantly prolonged, and the expression of mTOR protein and mRNA, tau mRNA and pS396 tau was up-regulated in O, HS and NS groups(P<0.05). Compared with O and NS groups, the escape latency and swimming distance were significantly shortened, and the expression of mTOR protein and mRNA, tau mRNA and pS396 tau was down-regulated in group HS(P<0.05). The pathological changes of the hippocampal tissues were mitigated in group HS when compared with group O. Conclusion The mechanism by which hydrogen-rich saline mitigates postoperative cognitive dysfunction may be associated with inhibited activation of hippocampal mTOR/tau pathway in aged rats. Key words: Hydrogen; Aged; Receptor-interacting protein serine-threonine kinases; tau proteins; Cognition disorders; Postoperative complications