The Inhibitory Effect Of Carnosine On Inflammatory Cytokines Release In LPS-induced Astrocytes And Its Mechanisms

ObjectiveTo investigate the effect of carnosine on inflammatory cytokine release in astrocytes（AS）induced by lipopolysaccharide（LPS）and its mechanisms.MethodsIn vivo model of type II diabetes was prepared by high-sugar and high-fat feeding and STZ injection.After successful modeling,the rats were randomly divided into diabetic model group,low-dose group,medium-dose high-dose group.Rats in the low,medium and high doses of carnosine were given 100,300 and 900 mg·kg^-1carnosine by gavage,respectively.The expression of glial fibrous acidic protein（GFAP）in hippocampus CA1 region of rats in each group was observed by immunohistochemical staining.The neonatal rat cerebral cortex AS were cultured and purified in vitro.They were randomly divided into Control group,LPS group and LPS+CAR group(10,30,90 mmol·L^-1carnosine).The cells in control group were only cultured with complete medium;the cells in LPS group were stimulated in vitro with 1 mg·L^-1LPS and then continued to culture for 24 h to construct the inflammatory injury model;the cells in low-dose,medium-dose and high-dose carnosine groups was preloaded with 10,30 and90 mmol·L^-1carnosine,respectively,in complete medium for 1 h,then treated with LPS with a final concentration of 1 mg·L^-1for 24 h.The survival rates of AS in various groups were determined by MTT assay.The levels of IL-1βand TNF-αin AS culture medium were detected by ELISA.DCFH-DA fluorescence probe was used to detect the ROS levels in AS in various groups;Hoechst33258 fluorescent staining was used to detect the apoptotic rates of AS in various groups;The expression level of p-NF-κB p65 in AS was determined by immunofluorescence staining;The protein expression levels of P-NF-кB p65 in AS in various groups were detected by western blotting method.ResultsAt the whole level,compared with the control group,the number of GFAP positive cells in the hippocampus of the diabetic model group was significantly increased（P<0.05）.At the cellular level,compared with control group,the survival rate of AS in LPS group was significantly decreased（P<0.05）,the levels of IL-1βand TNF-αwere increased（P<0.05）,the ROS level was significantly increased（P<0.05）,the apoptotic rates and the number of P-NF-кB p65 positive AS was increased significantly（P<0.05）.The ratio of P-NF-кB p65/NF-кB p65was increased（P<0.05）.At the overall level,compared with the diabetic model group,the number of GFAP positive cells in the hippocampal tissues of the carnosine group(100,300,900 mg·kg^-1carnosine)was significantly decreased（P<0.05）.At the cellular level,compared with the LPS group,the survival rates of AS in LPS+CAR groups were significantly increased（P<0.05）,the levels of IL-1βand TNF-αwere decreased（P<0.05）,the ROS levels were decreased（P<0.05）,and the apoptotic rates and the number of P-NF-кB p65 positive AS was decreased significantly（P<0.05）.The ratio of P-NF-кB p65/NF-кB p65 was decreased（P<0.05）.ConclusionsCarnosine can effectively improve the over-activation of central nervous system AS in diabetic rats,thereby inhibiting the occurrence of neuroinflammation.This may be related to reducing ROS in activated AS and inhibiting the phosphorylation of NF-κB p65 into the nucleus,thereby reducing the expression of IL-1βand TNF-α.