Molecular Mechanism Of Betulinic Acid Inhibits Oxidative Damage Of Lymphocytes In Mice Via JNK-P38MAPK Signaling Pathway

Betulinic acid(BA),a naturally occurring pentacyclic triterpene,exhibits a variety of biological activities,including anti-oxidative stress,immunomodulatory,antitumor,antimicrobial,anti-parasitic,anti-inflammatory,anti-ulcer,and antimalarial.In our previous research,we discovered that BA possess protective capability against dexamethasone(Dex)induced cell death by reducing oxidative stress via mitochondrial mediated signal pathway.Thus it can enhance the immune system and improve anti-oxidative stress activities.However,there is barely research on the JNK-P38 MAPK signal transduction pathway of BA against oxidative stress.In this project,the protective effects of BA on oxidative stress and its molecular mechanism were investigated using in vivo animal model.It would shed light on the theoretic research and scientific application of oxidative stress.Objective: To investigate the protective effect and molecular mechanism of BA against oxidative damage induced by Dex.To provide a scientific basis for further research and development of BA.Methods: A total of 64 male Kunming mice were randomly divided into 8 groups after feeding one week: normal control group,Dex group,0.25 mg/kg,0.5 mg/kg and 1.0 mg/kg BA with or without Dex groups.Mice in control group and Dex group were orally administered 1% starch solution and the other groups were orally administered different doses of BA for 14 days.Except normal control group,0.25 mg/kg BA group,0.5 mg/kg BA group and 1.0 mg/kg BA group,mice in the other groups were intraperitoneal injected Dex at dosage of 25 mg/kg to set up oxidative damage model.After fasting 15 hours(with access to water),the mice were sacrificed,and serum,liver,spleen and thymus were collected for analysis.The biochemical parameters in serum were determinated by using the automated blood analyzer.The antioxidant capacity were determinated by reagent kits in serum,liver,spleen and thymus.Lymphoid organ related genes and proteins expression were determinated by RTPCR and Western blot.Results: 1)BA alone had no significant effects on the serum biochemical parameters and antioxidative capacity.BA pretreatment significantly reduced the activities of ALP and hydroxyl free radical capacity,and the contents of TC,TG,T-Bil,and MDA,while increased the level of Ca2+,the activities of SOD and T-AOC in serum of mice induced by Dex.2)BA pretreatment enhanced the T-AOC,hydroxyl free radical capacity and the activity of POD in liver,spleen and thymus of mice induced by Dex.3)BA pretreatment decreased the m RNA expression of ASK1,JNK and P38 in spleen and thymus by RT-PCR,and reduced the protein expression of ASK1,JNK and P38 by Western blot in spleen of Dex treated mice.Conclusions: BA can effectively attenuate Dex-induced oxidative damage via JNK-P38 MAPK signal transduction pathway and maintain the normal physiology of the cells.