Protective Effects Of Aloe Polysaccharide On Oxidative Stress Of HepG2 Cells And Acute Liver Injury In Mice

When the organism is affected by external factors,free radicals such as reactive oxygen species and active nitrogen in the cell accumulate excessively to exceed its regulatory capacity,and the body’s antioxidant defense system is unbalanced,which is manifested as oxidative stress.The search for natural active substances without side effects to protect the body from oxidative damage is the focus of current research.Polysaccharide in aloe leaf gel have many pharmacological effects such as enhancing immunity,promoting autophagy of cancer cells,anti-inflammatory,and so on.There are mature extraction,separation,and purification processes.Studies showed that aloe polysaccharide can scavenge free radicals and prevent alcoholic liver injury in vitro.It has potential application in the prevention of oxidative stress-induced injury.In this study,the protective effect of aloe polysaccharide on D-galactose（D-gal）-induced oxidative damage model of Hep G2 cells and CCl₄-induced acute liver injury model in mice were studied,to investigate the effect of aloe polysaccharide on the signal pathway of Hep G2 cells and mouse liver tissue in the process of antioxidation and liver injury reduction.The research contents and results are as follows:1.The oxidative damage model of Hep G2 cells was established by D-gal.The survival rate of Hep G2 cells was determined by CCK-8 method.The content of malondialdehyde（MDA）and total antioxidant capacity（T-AOC）in cells was determined by enzyme-linked immunosorbent assay（ELISA）.The activities of superoxide dismutase（SOD）,catalase（CAT）and glutathione peroxidase（GPx）in cells were detected by the biochemical method.The results showed that Aloe polysaccharide had no toxic effect on Hep G2 cells in the range of12.5-200μg/m L.Aloe polysaccharide at three concentrations of 25,50 and 100μg/m L could increase the survival rate of oxidative damaged cells,reduce the production of MDA,increase the activity of SOD,CAT and GPx,and enhance the total antioxidant capacity of cells.2.The m RNA expression levels of Keap1,Nrf2,HO-1 and NQO1 in Hep G2 cells were determined by real-time fluorescence quantitative PCR（q PCR）.The protein expression levels of Keap1/Nrf2/HO-1 and PI3K/Akt signaling pathway were determined by Western Blot.The results showed that aloe polysaccharide could up-regulate the expression levels of Nrf2,HO-1,NQO1 genes and proteins in oxidatively damaged cells in a concentration-dependent manner,reduce the expression levels of Keap1 genes and proteins,activate the Keap1/Nrf2/HO-1signaling pathway,and increase the protein phosphorylation levels in the PI3K/Akt signaling pathway.3.The acute liver injury model of mice was established by CCl₄.The activities of alanine aminotransferase（ALT）,aspartate aminotransferase（AST）and alkaline phosphatase（ALP）in serum and the content of reduced glutathione（GSH）,the activities of SOD,CAT and GPx in liver tissue were determined by the biochemical method.The contents of serum total bilirubin（TBIL）and liver tissue MDA and T-AOC were determined by ELISA.The results showed that 50 mg/（kg.bw）,100 mg/（kg.bw）and 200 mg/（kg.bw）Aloe polysaccharide could down-regulate the liver index of mice to varying degrees,reduce the activity of ALT,AST,ALP and TBIL in serum of mice,reduce the production of MDA in liver tissue of mice,increase the content of GSH and the activity of SOD,CAT and GPx in liver tissue,enhance the total antioxidant capacity of liver tissue,and alleviate the oxidative stress injury of the liver in mice.4.The expression levels of the Keap1/Nrf2/HO-1 signaling pathway and downstream GCLC genes and proteins in liver tissues of mice with acute liver injury were determined by q PCR and Western Blot,to explore the effect of aloe polysaccharide on the signal pathway of liver tissue in mice when it was played the role of antioxidation and liver protection in vivo.The results showed that aloe polysaccharide could up-regulate the expression levels of Nrf2,HO-1,GCLC genes and proteins in mice liver tissue in a concentration-dependent manner and reduce the expression levels of Keap1 genes and proteins,improve the ability of mouse liver to resist oxidative damage and achieve liver protection.The results showed that aloe polysaccharide had a protective effect on oxidative stress in Hep G2 cells and liver injury in mice,which may be related to the activation and cascade regulation of Keap1/Nrf2/HO-1 and PI3K/Akt signaling pathway.It has a certain significance for the further development and utilization of aloe polysaccharide.