Hyperoside Attenuated Hypoxia-induced Memory Impairment And Mechanism Of Resisting To Oxidative Stress Injury

Objective:The objective of the study is to determine the effects of Hyperoside(Hyp) on the memory impairment induced by hypobaric hypoxia and its antioxidation mechanism. On the basic, we will provide the new siginificant theory and drug target to prevent memory impairment induced by hypobaric hypoxia.Method:1. Sprague Dawley(SD) rats were exposed to normoxia and hypoxia. Rats exposed to normoxia were divide into control group and three groups treated with Hyp(10、20、40 mg/kg). Rats exposed in hypobaric hypoxia also were divide into four group as normoxia. Rats under hypoxia were exposed in hypobaric hypoxia chamber which simulated 6100 m high altitude for 7 days to induce memory impairment. Morris maze was applied to determine the effects of Hyp on memory in hypobaric chamber. The nerve cells in hippocaml CA1 region was observed by HE stain.2. The activities of SOD and CAT and levels of GSH and MDA in rat hippocampus were measured by assay kit. The expression level of m RNA and protein of Nrf2 and HO-1 in rat hippocampus were determined by q RT-PCR and Western blot.3. PC12 cells were exposed to normoxia and hypoxia. The PC12 cells were exposed to hypoxia by using hypoxic incubator with 1%O2 or Co Cl2(200 μM). PC12 cells which exposed to normoxia by using cell incubator 20% O2. PC12 cells exposed to hypoxia and normoxia were divide into one control group and three treatment groups which cells were pre-treated with Hyp(25, 50, 100 μM) in the same time. PC12 cells were treated with hyperoside at 25, 50, 100 μM for 24 h prior to the exposure of hypoxia(1%O2) for 24 h or Co Cl2(200 μM) for 6 h. The cell viability was determined by the CCK-8 assay. The effects of Hyp on MDA level and the activity of SOD and HO-1 were measured by ELISA kit. The levels of m RNA of Nrf2 and HO-1 in PC12 cells were determined by q RT-PCR. The effect of Hyp on protein level of Nrf2 in PC12 cells was quantified by Western blot.Result :1. In target quadrant, the time and path and the frequency to cross platform were reduced under hypobaric hypoxia as compared with normoxia group(P<0.05). Administration of Hyp significantly attenuated the hypoxia-induced the memory impairment responses(P<0.05 or P<0.01). As compared to normoxia control, it was observed that the number of nerve cells in hippocampal CA1 region decreased and the configuration of the cell became abnormal. The presence of Hyp significantly improved it.2. The activities of SOD and CAT in rats hippocampus exposed to hypobaric hypoxia were significantly improved in the presence of Hyp as compared with the absence of Hyp(P<0.05 or P<0.01), so did GSH level(P<0.05 or P<0.01). Significant decrease of MDA levels was observed in the hippocampus under hypobaric hypoxia exposure with Hyp pre-treatment as compared with without Hyp. The presence of Hyp significantly up-regulated the m RNA and protein level of Nrf2 and HO-1 under hypoxia or normoxia(P<0.05 or P<0.01).3. In PC12 cells, Hyp significantly increased cell viability under hypoxia exposure in a concentration dependent manner. MDA level was significantly increased in the hypoxia groups as compared with normoxia group. Pre-treatment of of Hyp decreased the level of MDA under hypoxia exposure(p <0.05 or p <0.01). Hypoxia significantlydecreased the activity of SOD. Under hypoxia, the SOD activity were increased in the presence of 50 μM or 100 μM Hyp as compared to absence of Hyp(p<0.05). Besides, HO-1 activity was significantly increased by Hyp 50 and 100μM under hypoxia exposure(p<0.05), it was also increased by 100 μM Hyp under normoxia(p<0.05). As compare to normoxia group, hypoxia up-regulated Nrf2 and HO-1 m RNA level(p<0.05). Hyp(25, 50 and 100 μM) treatment further up-regulated it under hypoxia exposure(p<0.05 or p<0.01). It is interesting that 50 or 100 μM Hyp significantly increased the m RNA levels of Nrf2 and HO-1 in PC12 cells under Normoxia(p<0.05). No matter under normoxia or hypoxia exposure, Hyp(25, 50 or 100 μM) dramatically up-regulated the protein level of Nrf2(p<0.05 or p<0.01).Conclusion:Hyp attenuated memory impairment induced by hypobaric hypoxia. The effect was attributed to Hyp-induced up-regulation of m RNA expression of Nrf2 which reduced oxidative stress injury by promoting expression of antioxidant protein such as HO-1 and SOD in rats hippocampus and PC12 cells.