The Protective Effects And Mechanisms Of Hypericum Perforatum Extract On The Aluminum Chloride-Exposed Hippocampus Of Rats

Al,a cumulative neurotoxin,caused cognitive dysfunction in human and other animal models through altering oxidative stress,inflammation,amyloid ?-protein?A??production and dendritic spine density.And there is no effective and safe drug available for clinic use to prevent or treat Al associated neurodegenerative diseases.Hypericum perforatum extract?HP?is a natural phytochemicals that possesses multi physiological functions,including antioxidant,anti-inflammatory,inhibiting A? overexpression and maintaining dendritic spine stability.Thus,it is feasible that HP can be used,through these multi functions,against hippocampus injury induced by AlCl₃.To investigate the protective effect and mechanism of HP on rat hippocampus injury induced by AlCl₃,120 male Wistar rats?8 weeks old?were randomly divided into four groups,control group was orally administered the vehicle,AlCl₃ group was orally treated with AlCl₃ at 150 mg/kg for 90 d,AlCl₃+ HP group was orally administered AlCl₃ at 150 mg/kg for 90 d and HP at 300 mg/kg for 60 d,as well HP group was orally administrated with HP at 300 mg/kg for 60 d.We investigated the effect of HP on learning and memory in AlCl₃-exposed rats through Morris Water Maze and open field behavior test;ultrastructure of hippocampus,the level of ROS,GSH,MDA,8-OHd G and carbonyl,SOD activity,total protein and nuclear protein expression of Nrf2 as well as mRNA expressions of OH-1,GCLC and NQO1 were detected for investigating the effects of HP on oxidative stress and Nrf2 signaling in hippocampus of rats exposed to AlCl₃;the mRNA expressions of MHC II,GFAP,IL-6 and TNF-?,as well as nuclear protein and total protein of NF-?B were measured for investigating the effects of HP on inflammation and NF-?B signaling in hippocampus of rats exposed to AlCl₃;the formation of amyloid plaques,content of A?42,as well as mRNA expressions of APP,ADAM9,ADAM10,ADAM17,BACE1,PS1 and PS2 for investigating the effects of HP on A? and amyloid plaque generation in the hippocampus of rats exposed to AlCl₃;dendritic spine density,protein ratio of F-actin/G-actin,and BDNF protein expression were texted for exploring the effect of HP on dendritic spine density and its regulatory factors in the hippocampus of rats exposed to AlCl₃.The results were shown as follows:?1?For the body weights and brain index,there were no significant differences among the groups?p>0.05?.?2?In Morris Water Maze test,the acquisition trial showed the escape latency of Al group was longer than that of control group?p<0.01?,and the escape latency of Al+HP group was shorter than that of AlCl₃ group in fourth and fifth days?p<0.01?.For the probe trial,the time spent in the target quadrant and the number of crossing the platform position in Al group were longer than these in control group?p<0.01?,and the time spent in the target quadrant and the number of crossing the platform position in Al group were shorter by Al+HP group than that these in Al group?p<0.01?.In open field test,Al group showed significant reductions in crossing and rearing relative to control group?p<0.01?,while the numbers of crossing and rearings in AlCl₃+150SJW group and Al+HP group was more than these in Al group?p<0.05?.These results suggest that HP administration attenuates AlCl₃-induced behavioral abnormality.?3?AlCl₃ significantly increased the level of ROS,8-OHd G,carbonyl and MDA?p<0.01?,whereas significantly inhibited GSH content and SOD activity?p<0.01?as compared to the control group;however,HP significantly relieved AlCl₃-induced augment of ROS,8-OHd G,carbonyl and MDA,as well as decreased GSH content and SOD activity?p<0.05?.Besides,under electron microscope,nuclear membrane cleavage,mitochondrial vacuolization,swollen and fused were observed in the hippocampus of rats exposed to AlCl₃,while there was no significant lesions in the HP+Al group,indicating that HP could effectively alleviate AlCl₃-induced oxidative stress in rat hippocampus.The total protein and nuclear protein expressions of Nrf2,and OH-1,GCLC and NQO1 mRNA expressions were significantly increased in Al group and HP+Al group compared with control group?p<0.05?,and they were significantly elevated in the HP+Al group as compared to the Al group?p<0.01?,illustrating that HP could alleviate AlCl₃-induced oxidative stress through activating Nrf2 signal in rat hippocampus.?4?The protein expressions of MHC II and GFAP,as well as the content of IL-6 and TNF-?were significantly raised in Al group compared with control group?p<0.05?,whereas they were significantly inhibited in the HP+Al group compared with the Al group?P < 0.01?,indicating that HP could mitigate inflammatory reaction in the hippocampus of rats exposed to AlCl₃.The total and nuclear protein expressions of NF-?B,and mRNA expression of IL-6 and TNF-? mRNA expression were significantly increased in Al group compared with control group?p<0.01?,while they were significantly inhibited in the HP+Al group compared with the Al group?P < 0.05?,illustrating that HP could mitigate AlCl₃-induced inflammation through inactivating NF-?B signal in rat hippocampus.?5?AlCl₃ treatment significantly increased APP,BACE1,PS1 and PS2 mRNA expression and A?42 content,while significantly decreased ADAM9,ADAM10 and ADAM17 mRNA expression as compared to control group?p<0.01?,whereas HP co-treated with AlCl₃ significantly inhibited APP,BACE1,PS1 and PS2 mRNA expressions and A?42 content?p<0.01?,and elevated ADAM9,ADAM10 and ADAM17 mRNA expressions compared with Al group?p<0.05?.In addition,under optical microscope,there were lots of amyloid plaques accumulated in hippocampus of rat exposedto AlCl₃,while there was few amyloid plaques accumulation in hippocampus of rat from HP+Al group,indicating that HP could alleviate AlCl₃-induced A? and amyloid plaques generation through regulating the expression of APP hydrolase.?6?The dendritic spine densities of CA1,CA3 and DG in Al group was significantly decreased as compared to control group?p<0.05?,whereas they were significantly increased in HP+Al group compared with Al group?p<0.05?.Besides,the protein expression of BDNF and the protein ratio of F-actin/G-actin were significantly decreased in Al group as compared to control group?p<0.01?,while they were significantly increased in HP+Al group compared with Al group?p<0.05?.There results proved that HP could mitigate AlCl₃-induced dendritic spine density reduction through increasing BDNF protein expression and the protein ratio of F-actin/G-actin.In summary,HP could protect rat from AlCl₃-induced hippocampus injury through alleviating oxidative stress,inflammation,A? overproduction and dendritic spine loss.