Design And Synthesis Of Nitroxide Derivatives With Long-Chain And Their Protective Effects On Brain Injury Induced By High Altitude Hypoxia

China's plateau is vast,accounting for about one-sixth of the country's total area.When the plain people rush into the plateau,they are highly susceptible to low-pressure and low-oxygen in the plateau,which causes serious harm to the body.The brain,as one of the organs with the largest oxygen consumption in the body,is highly vulnerable to hypoxia.Brain tissue damage has a rapid onset and high mortality.Its molecular mechanism,drug prevention and treatment are among the problems that need to be solved urgently.Our team first found that nitronyl nitroxide HPN is a good free radical scavenger,which performed a good protective effect on high altitude hypoxia injury,but it lacks the targeting of brain tissue.In this experiment,a series of nitroxide long-chain derivatives were designed and synthesized with HPN as the lead compound,in order to obtain target compounds with higher brain targeting and stronger anti-hypoxia activity.Mainly completed the following work:1.The nitroxide long-chain derivatives were obtained by substituting the nitroxide HPN with a bromoalkane of different lengths.The target compounds were confirmed by IR,EPR and HR-MS,and their purity were verified by HPLC.The best anti-hypoxia activity compound and the optimal drug concentration were screened by mouse normobaric hypoxia test.2.Establishment of a plateau hypoxia injury model.Eight healthy Blab/c male mice were randomly divided into normal group?Normal?,hypobaric hypoxia group?HH?,hypobaric hypoxia HPN group?HH+HPN?,and hypobaric hypoxia C₆-HPN?HH+C₆-HPN?.Among them,the Normal group did not do any treatment,the other three groups of mice were placed in a large hypobaric hypoxia chamber at a simulated altitude of 8000m and anoxic exposure for 12h,after the completion of hypoxia,the brain tissues were taken.By HE staining,TUNEL staining,the oxidative stress related index,the energy metabolism related index,NO related index,inflammatory factors,apoptosis-related index.The preliminary mechanism of C₆-HPN prevention and treatment of plateau brain injury in mice was discussed.The above results indicate that:1.The synthesized compounds are confirmed by IR,EPR and HR-MS analysis,which are consistent with the structure of the target compound,and the purity of compounds are hign using HPLC detection.The results of normobaric hypoxia experiments show that the anti-hypoxia activity of HPN can be enhanced by introducing hydrophobic long-chain alkanes into HPN molecules.The activitys are significantly enhanced with the increase of carbon chain length.When the carbon chain length is longer than C₆,its activitys are enhanced,but the change is not large.When the carbon chain length is greater than C₁₄,the activitys decrease.The compound with the best anti-hypoxia activity is finally determined:C₆-HPN,and the optimal concentration is 100 mg/kg.2.Acute high altitude hypoxia experiment results can be seen,C₆-HPN can significantly increase the following index:the activity of CAT,SOD,GSH-Px,P-AKT/AKT ratio,ATP,Na⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase activity,cytoplasmic NF?B protein expression,and decrease the following index:the apoptosis rate,the content of H₂O₂,MDA and LDH,the expression of HIF-1?and VEGF protein,the concentration of IL-1?,IL-6 and TNF-?,NF?B protein expression in nuclear,cleaved-caspase-3 protein expression,the production of NO and the protein expression of nNOS.Thus,C₆-HPN protects high aititude induced brain injury by improving pathological,alleviating oxidative stress levels,improving glycolysis and aerobic respiration pathway,alleviating inflammatory reaction,attenuating the apoptotic reaction as well as regulating NO neurophysiological activityThrough the above research,the following conclusions can be drawn:1.The brain targeting and anti-hypoxia activity of HPN can be significantly improve by appropriately adding a certain length of fatty chain to improve the liposol.2.C₆-HPN shows better effect than HPN on prevention and treatment of brain damage in mice.The possible mechanism of action is to improve pathological changes and energy metabolism pathways,reduce the incidence of apoptosis,and alleviate oxidative stress and inflammatory responseas well as improve the neurophysiological activities involved in NO.