Protective Effect Of Naringin On Intestinal Barrier Function And Its Mechanism

Naringin is a kind of polymethoxy-flavonoid,which has antioxidant,anti-inflammatory and antibacterial activities and can relieve colitis.However,the effect and mechanism of naringin on intestinal barrier destruction induced by LPS have not been reported.The aim of this study was to investigate the effect of naringin on LPS induced intestinal barrier function injury and its mechanism.In this study,Balb/c mice were first selected as research objects to explore the alleviating effect of naringin on LPS induced intestinal morphology,inflammatory cytokine secretion,antioxidant capacity and tight junction protein related genes expression in mice.On this basis,cell experiments were designed to study whether naringin can alleviate the damage caused by LPS to intestinal epithelial cells.To further explore whether naringin alleviates LPS-induced intestinal barrier function damage by inhibiting p38 MAPK pathway.The main research contents and results are as follows:Test 1.Effects of Naringin on the intestinal barrier function injury induced by LPS in miceForty-five 3-week-old healthy male Balb/c mice with similar body weight were randomly divided into control group,LPS group,LPS + naringin group,with 15 mice in each treatment group.The mice were intraperitonealy injected with the same dose of saline or LPS(10 mg/kg BW)at 43 d.Our results showed that LPS treatment group significantly increased the serum diamine oxidase(DAO)activity and d-lactate(D-LA)and malondialdehyde(MDA)content,and also increased the MDA content in jejunum,while decreased the activities of total superoxide dismutase(T-SOD),glutathione peroxidase(Gpx)and catalase(CAT)in jejunum,as well as an increase in the crypt depth,a decrease in the villus height and the ratio of villus height to crypt depth(V/C)of the jejunum.In addition,LPS treatment significantly increased the m RNA expression levels of jejunal proinflammatory cytokines related genes and the key genes of p38 MAPK signaling pathway,while decreased the tight junction related genes m RNA expression in jejunum.However,naringin treatment mitigated these effects induced by LPS.Taken together,our findings suggested that naringin attenuates LPS-induced intestinal barrier damage by inhibiting inflammatory factors and improves intestinal morphology,antioxidant function and tight junction protein expression,and this effect may be mediated by the p38 MAPK signaling pathway.Test 2.Naringin attenuated LPS-induced intestinal barrier dysfunction via p38 MAPK signaling pathwayIn this study,IEC-6 cells were first treated with LPS(1,2.5,5,10 and 20 μg/m L),and the optimal LPS concentration was selected according to the change of cell viability.Then,the cells were co-treated with LPS and naringin(10,20,40,60μmol/L),to study the effects of naringin on LPS-induced intestinal epithelial barrier function injury.Finally,the p38 MAPK inhibitor SB203580 was added to inhibit p38 MAPK signaling to investigate whether naringin alleviates LPS-induced intestinal epithelial barrier function damage through p38 MAPK signaling pathway.The results showed that 5 μg/m L LPS could affect cell morphology and cause a significant decrease in IEC-6 cell viability,the m RNA expression of tight junction and antioxidant-related genes and antioxidant enzyme activity,while increased the m RNA expression of inflammatory-related genes and the content of inflammatory factors and MDA.However,naringin supplementation with different concentrations can alleviate LPS-induced intestinal epithelial barrier function injury.In addition,after SB203580 was used to inhibit the activity of p38 MAPK,naringin had a stronger alleviating effect on the LPS-induced decline of tight junction and antioxidation-related gene m RNA expression and the increase of inflammation-related gene m RNA expression and inflammatory factor content.In summary,this study confirmed in vitro and in vivo that naringin reduces inflammatory response,enhances antioxidant capacity and maintains intestinal barrier integrity by inhibiting p38 MAPK signaling,thus alleviating LPS-induced intestinal barrier function injury.