[Sulfasalazine relieves cholestatic liver injury by activating peroxisome proliferator-activated receptor-α]

Objective: To investigate the efficacy and potential mechanism of sulfasalazine (SASP) therapy for intrahepatic cholestasis. Methods: Forty SD rats were randomly divided into a normal group (carboxymethylcellulose sodium 0.5%), a model group (carboxymethylcellulose sodium 0.5%), a SASP group (sulfasalazine 150 mg/kg), and an ursodeoxycholic acid (UDCA 100 mg/kg) group, with ten rats in each group. The cholestatic liver injury model was induced using α-naphthylisothiocyanate. Blood samples were collected to detect liver biochemistry and cholestasis indexes. Rat liver tissue was collected for hematoxylin-eosin staining and Mason staining. Liver tissue was analyzed using transcriptome sequencing, real-time reverse transcription quantitative polymerase chain reaction, Western blotting and flow cytometry. Simultaneously, the level of inflammatory factors, total cholesterol, and total bile acids were measured in liver tissue. A t-test or a nonparametric test was selected based on the distribution and variance characteristics of the data. Results: The serum levels of alanine aminotransferase [(386.88±155.77) U/L], aspartate aminotransferase [(593.13±251.44) U/L], alkaline phosphatase [(561.25±167.54) U/L], total bilirubin [(38.00±29.75) mol/L] and total bile acids [(191.31±91.48) mol/L] were significantly lower in the SASP than the model groups [(778.75±313.59) U/L, (1 159.38±274.62) U/L, (801.25±161.28) U/L, (86.63±27.83) mol/L, (432.63±151.54) mol/L,P<0.05]. Liver histopathology showed that the inflammatory cells in the manifold area, the bile duct proliferation and dilation, and the collagen deposition in the manifold area were significantly improved under the pathological state of cholestasis in the SASP group. The results of transcriptome sequencing demonstrated that SASP activated the peroxisome proliferator actived receptor α (PPARα) and inhibited Th17 cell differentiation. The PPARα mRNA level in the liver tissue of rats was significantly increased in the SASP group compared with that in the model group [(0.41±0.28) vs. (0.16±0.04), P<0.05], and the expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase was decreased compared with that in the model group [(3.09±1.16) vs. (8.19±2.19), P<0.05], which was also verified at the protein level. The concentrations of total cholesterol [(0.31±0.34) mmol/g] and total bile acids [(2.58±0.99) μmol/g] were lower than the model group [(0.83±0.62) mmol/g and (4.07±0.91) μmol/g] (P<0.05), and at the same time it was accompanied by lower levels of inflammatory factors (P<0.05). SASP treatment decreased the expression of retinoic acid receptor-related orphan receptor γt gene (P<0.05) and the proportion of Th17 (P<0.05). Conclusion: SASP can improve cholestatic liver injury, and its mechanism is related to the activation of peroxisome proliferator-activated receptor α and the inhibition of Th17 cell differentiation.