Melatonin inhibits bile acids-initiated Cxcl2 expression through JNK/c-Jun signalling pathway

To investigate the underlying molecular mechanism by which melatonin suppresses bile acids (BAs)-initiated expression of chemokine C-X-C motif chemokine ligand 2 (Cxcl2).

Mice were fed a 1% cholic acid (CA)-supplemented diet for 2 weeks to establish a model of cholestatic disease, and were given an intraperitoneal injection of melatonin (100 mg/kg) once a day for 2 weeks. Then, the liver tissues were collected for HE staining, and the liver histology was scored using the Scheuer scoring system. Effects of melatonin on the expression of Cxcl2, Cxcr2, myeloperoxidase (Mpo) and c-Jun in the liver tissues at mRNA and protein levels were detected by real-time qPCR and Western blotting. The expression of c-Jun in the liver tissues was measured by immunohistochemical assay. Primary mouse hepatocytes were isolated and cultured, and then treated with taurine-conjugated bile acid, taurocholic acid (TCA) and melatonin in order to explore the mechanism of melatonin reducing BAs-initiated Cxcl2 expression. Furthermore, these primarily cultured cells were treated with anisomycin (JNK agonist) and melatonin to further detect the expression of Cxcl2.

Melatonin treatment significantly ameliorated cholestasis-induced inflammatory liver injury (P<0.05), and reduced the elevated expression of Cxcl2, Cxcr2, Mpo (a biomarker of neutrophils) and the transcription factor c-Jun in the livers of cholestatic disease mice (P<0.05). In addition, melatonin suppressed TCA-stimulated Cxcl2 in primary mouse hepatocytes (P<0.05). Anisomycin reversed melatonin-inhibited Cxcl2 (P<0.05).

Melatonin treatment can decrease BAs-initiated expression of Cxcl2 via inhibition of JNK/c-Jun signaling pathway in mouse hepatocytes.