Effects And Mechanism Study Of Kiwifruit On Pb-induced Learning And Memory Deficit In Rats

Kiwifruit has been praised as’the king of fruits’based on its remarkable abundance of nutrition and considerable antioxidant effect. Environmental pollution is a serious threat to human health. Lead (Pb) is a widely existed environmental toxicant and impairs the ability of cognition. Oxidative stress has been demonstrated as one of the crucial mechanisms of neurotoxicity of Pb. Previous studies showed Pb act as initiator that induced ROS generation, meanwhile, Pb repressed antioxidant enzyme (SOD) activity. However, the effect and molecular basis of kiwifruit improvement learning and memory damage induced by Pb exposure still remains unclear.Objective:To explore the different of antioxidative component in different cultivars kiwifruits; To explore the effect of kiwifruit on scavenging oxygen free radicals and Pb-induced oxidative damage; To explore the effect of kiwifruit on hippocampal neuron dendritic spine morphology and spatial memory in SD rats and the possible molecular mechanism especially focusing on microglia cell.Methods:1. We tested the main bioactive components, vitamin C and polyphenol, by HPLC and Folin-Ciocalteu respectively.2. To determined the best antioxidant of kiwifruit cultivars by 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assay, and through MTT to determined the concentration of Pb, DCFH-DA was used to observe the generation of ROS intervened by kiwifruit following Pb exposure in PC 12 cell. Sprague-Dawley (SD) rats were feed on 250 ppm lead acetate solution. The pups treated with vitamin C or kiwifruit powder received a daily intragastric. Y maze and Morris water maze experiments were performed at 10weeks. Golgi-cox staining method was used to observe the dendritic spine morphology. Testing SOD and GSH-Px activity by test kits. Western blotting method was employed to determine and quantify microglia related proteins. PCR method was used to quantify SOD2, GSH-Px and pro-inflammatory.Results:1. The content of vitamin C and polyphenol in different kiwifruit were species-dependent, Qinmei kiwi and Jinkui kiwi had the higher level of antioxidant components in our study.2. Qinmei kiwi showed strong scavenging ability towards DPPH free radicals and FRAP antioxidation. In conclusion, only the kiwifruit of Qinmei was used in further studies because it showed the best antioxidant effect than other cultivars of kiwifruits in above studies.3. In vivo, kiwifruit improves learning and memroy deficits induced by Pb exposure, and increased spine density at 10.7%. And significantly increased the activity and mRNA levels of SOD and GSH-Px, accompanied by down-regulation of Ibal expression and TNF-α, EL-1β mRNA levels.Conclusion:Qinmei kiwi is a most excellent antioxidant among five cultivars that we investigated. The kiwifruit is suggested to relieve the oxidative stress, and then quench the activation of microglia, thus reduce the release pro-inflammatory cytokine, protect against Pb-induced learning and memory impairment These results may provide new evidence regarding the effects of kiwifruit on adjuvant therapy for Pb exposure.