Melatonin attenuates cholestatic liver injury by improving bile acid metabolism in mice

To explore the mechanism of melatonin (Mel) alleviating cholestatic liver injury in a mouse cholestasis model induced by cholic acid (CA) feeding.

A total of 15 8-week-old male C57BL/6J mice were randomly divided into control group, 1%CA group, and 1%CA+Mel group, with 5 animals in each group. The control group was fed with normal chow diet, and the other 2 groups were fed with a diet containing 1%CA for 14 d to construct a model of cholestasis, and intraperitoneal injection with 100 mg/kg Mel was given to the mice from the 1%CA+Mel group. Immunohistochemical assay of α-SMA was applied for the liver tissues in the 1%CA group and the 1%CA+Mel group. The mRNA expression levels of fibrosis-related indicators in mouse liver tissue were examined by RT-qPCR. Liquid chromatography tandem mass spectrometry (LC-MS/MS) and automated biochemical analyzer were used to detect the contents of bile acids in the liver tissues and the serum of mouse, respectively. Then real-time qPCR and Western blotting were applied to detect the expression of bile acid synthesis and liver detoxification enzymes related indicators at mRNA and protein levels, respectively, to further investigate the mechanism of bile acid metabolism.

Compared with the 1%CA group, the mRNA levels of liver fibrosis indicators (such as Tgfβ1, ColⅠa1, ColⅡa1 and α-SMA) were significantly reduced (P<0.05), and activation of stellate cells was obviously weakened displayed by immunohistochemical staining in the 1%CA+Mel group. The 1%CA+Mel group had notably decreased contents of bile acids in the serum and liver tissues, especially taurocholic acid and reduced mRNA levels of cholesterol 7α-hydroxylase (Cyp7a1) and Cyp8b1, while enhanced mRNA levels of hepatic detoxification enzymes Cyp2b10 and udp-glucuronosyltransferase (Ugt1a1) as well as protein levels of Cyp2b10 and sulfotransferase family 2A member 1 (Sult2a1/2) when compared with the 1%CA group (P<0.05).

Mel exerts its therapeutic effect on cholestasis by decreasing bile acid synthesis and increasing hepatic detoxification enzymes.