Study On The Effect And Mechanism Of Emodin On Liver Damage In Immune Stressed Piglets

The purpose of this experiment was to investigate the effects of emodin(ED)supplementation in diets on serum biochemical indicators,inflammatory cytokines,and antioxidant capacity,liver histomorphological damage,and liver anti-inflammatory and antioxidant capacity in immune stressed piglets induced by lipopolysaccharide(LPS),as well as their molecular mechanisms.In the experiment,a total of 24 three-way crossbred weaned piglets(weaned at 28 days old,Duroc × [Landrace × Yorkshire])with similar birth times and good health were randomly divided into 4 groups with 6replicates in each group.Control group(CON): fed with a basic diet and injected sterile physiological saline intraperitoneally before slaughter.Emodin test group(ED): fed with a basal diet of+300 mg/kg ED,and injected with sterile physiological saline intraperitoneally before slaughter.LPS stress group(LPS): fed with a basal diet,100μg/kg LPS was injected intraperitoneally before slaughter.The emodin+ LPS test group(ED-LPS)was fed with a 300 mg/kg ED basal diet,and 100 μg/kg LPS was injected intraperitoneally before slaughter.The trial period was 21 days,and the animals were slaughtered on the 21 st day.The test results are as follows:Compared with CON group,serum creatinine(CRE)content,alkaline phosphatase(ALP)activity,and interleukin-6(IL-6)level in LPS group were significantly increased(P<0.05),while catalase(CAT),glutathione peroxidase(GSH-Px)activity,and trace reduced glutathione(GSH)content were significantly decreased(P<0.05).Compared with LPS group,serum ALP activity and IL-6 level in ED-LPS group were significantly decreased(P<0.05),while CAT activity,GSH content,and total antioxidant capacity(T-AOC)were significantly increased(P<0.05).Compared with CON,the piglets in LPS group exhibited significant histopathological changes,with structural disorder of liver lobules,loose arrangement,increased volume,and swelling of hepatocytes.In addition,there was vacuolation in the cytoplasm of hepatocytes,accompanied by parenchymal tissue lysis.The liver ALT level in LPS group was significantly lower than that in ED group(P<0.05).The total fluorescence intensity of TUNEL positive liver sections in LPS group was significantly higher than that in CON group(P<0.05),and LPS induced significantly increased m RNA expression levels of liver B-cell lymphoma-2(Bcl-2),cytochrome C(Cyt-C),and cysteinyl aspartate specific proteinase-3(caspase-3)in piglets(P<0.05).Compared with the LPS group,the liver tissue structure and morphology of piglets in the ED-LPS group were improved,with only local cellular loosening,swelling,and vacuolization.The total fluorescence intensity of TUNEL positive liver sections of piglets in the EDLPS group was significantly lower than that in the LPS group(P<0.05),and the expression level of caspase-3 m RNA in the liver was significantly reduced(P<0.05),while the expression level of Bcl-2 m RNA showed a downward trend.Compared with CON group,the levels of IL-1β,IL-6,and tumor necrosis factor-α(TNF-α)in the liver of piglets in LPS group were significantly increased(P<0.05),the expression of IL-10 m RNA was significantly decreased(P<0.05),and the expression of TNF-α m RNA was significantly increased(P<0.05).LPS significantly upregulated the m RNA expression levels of liver Toll-like receptor 4(TLR4)and myeloid differentiation marker 88(My D88),as well as the protein expression level of cyclooxygenase-2(COX-2)(P<0.05),and upregulated liver phosphorylation nuclear factor-κB p65(p-NF-κB p65)protein expression level.Compared with LPS group,the content of IL-1β and IL-6 in liver of piglets in ED-LPS group significantly decreased(P<0.05),while the content of TNF-α showed a downward trend.The expression of IL-10 m RNA was significantly increased(P<0.05),while the expression of TNF m RNA was significantly decreased in ED-LPS group(P<0.05).At the same time,the addition of ED significantly downregulated the high expression level of COX-2 protein in the liver caused by LPS(P<0.05),and alleviated the effect of LPS on the expression level of p-NF-κB p65 protein.Compared with the CON group,the liver GSH content,CAT activity,and T-AOC in LPS group significantly decreased(P<0.05),while the expression of superoxide dismutase 1(SOD1),SOD2,and GSH-Px m RNA in LPS group significantly decreased(P<0.05).LPS significantly upregulated the m RNA expression level of heme oxygenase-1(HO-1)in the liver(P<0.05),significantly downregulated the protein expression levels of HO-1 and NAD(P)H quinone oxidoreductase 1(NQO1)in the liver(P<0.05),and downregulated the protein expression level of nuclear factor E2 related factor 2(Nrf2)in the liver.Compared with the LPS group,the liver GSH content,CAT,and GSH-Px activity in the ED-LPS group significantly increased(P<0.05),while the malondialdehyde(MDA)content significantly decreased(P<0.05).In addition,the m RNA expression levels of SOD1 and GSH-Px were significantly increased(P<0.05),the protein expression levels of Nrf2,HO-1,and NQO1 were significantly increased(P<0.05),and the m RNA expression level of HO-1 showed a downward trend.In summary,LPS stress leads to histological and functional damage to the liver tissue of piglets,and may lead to cell apoptosis.LPS stress induces liver inflammation and oxidative stress in piglets.Adding 300 mg/kg of ED to the diet of piglets can alleviate liver damage induced by LPS in immune stress piglets and improve liver cell apoptosis by inhibiting the activation of NF-κB pathway by LPS,activating Nrf2/the antioxidant response element(ARE)pathway,improving the antioxidant capacity of piglets’ liver.