Melatonin and circadian rhythms in liver diseases: Functional roles and potential therapies.

Circadian rhythms and clock gene expressions are regulated by the suprachiasmatic nucleus in the hypothalamus, and melatonin is produced in the pineal gland. Although the brain detects the light through retinas and regulates rhythms and melatonin secretion throughout the body, the liver has independent circadian rhythms and expressions as well as melatonin production. Previous studies indicate the association between circadian rhythms with various liver diseases, and disruption of rhythms or clock gene expression may promote liver steatosis, inflammation, or cancer development. It is well known that melatonin has strong antioxidant effects. Alcohol drinking or excess fatty acid accumulation produces reactive oxygen species and oxidative stress in the liver leading to liver injuries. Melatonin administration protects these oxidative stress-induced liver damage and improves liver conditions. Recent studies have demonstrated that melatonin administration is not limited to antioxidant effects and it has various other effects contributing to the management of liver conditions. Accumulating evidence suggests that restoring circadian rhythms or expressions as well as melatonin supplementation may be promising therapeutic strategies for liver diseases. This review summarizes recent findings for the functional roles and therapeutic potentials of circadian rhythms and melatonin in liver diseases.

Gonadotropin-releasing hormone stimulates biliary proliferation by paracrine/autocrine mechanisms.

During cholestatic liver disease, there is dysregulation in the balance between biliary growth and loss in bile duct-ligated (BDL) rats modulated by neuroendocrine peptides via autocrine/paracrine pathways. Gonadotropin-releasing hormone (GnRH) is a trophic peptide hormone that modulates reproductive function and proliferation in many cell types. We evaluated the autocrine role of GnRH in the regulation of cholangiocyte proliferation. The expression of GnRH receptors was assessed in a normal mouse cholangiocyte cell line (NMC), sham, and BDL rats. The effect of GnRH administration was evaluated in normal rats and in NMC. GnRH-induced biliary proliferation was evaluated by changes in intrahepatic bile duct mass and the expression of proliferation and function markers. The expression and secretion of GnRH in NMC and isolated cholangiocytes was assessed. GnRH receptor subtypes GnRHR1 and GnRHR2 were expressed in cholangiocytes. Treatment with GnRH increased intrahepatic bile duct mass as well as proliferation and function markers in cholangiocytes. Transient knockdown and pharmacologic inhibition of GnRHR1 in NMC decreased proliferation. BDL cholangiocytes had increased expression of GnRH compared with normal rats, accompanied by increased GnRH secretion. In vivo and in vitro knockdown of GnRH decreased intrahepatic bile duct mass/cholangiocyte proliferation and fibrosis. GnRH secreted by cholangiocytes promotes biliary proliferation via an autocrine pathway. Disruption of GnRH/GnRHR signaling may be important for the management of cholestatic liver diseases.

Chelidonium majus is not hepatotoxic in Wistar rats, in a 4 weeks feeding experiment.

AIM OF THE STUDY: Aerial parts of Chelidonium majus L. (Papaveraceae family) are traditionally used in the treatment of gallstones and dyspepsia, however several cases of hepatotoxicity are reported. In this work we evaluated the effects on liver function of a C. majus extract, obtained from the herbal material responsible for one case of hepatotoxicity. MATERIALS AND METHODS: Experiments were performed in Wistar rats, after oral administration of doses corresponding to 1.5 and 3g/(kg day) of herbal drug, for 2 or 4 weeks. Blood samples were collected to perform biochemical analysis, whereas liver samples were used for histomorphological and immunohistochemical examination along with the determination of oxidative stress parameters. RESULTS: No significant modification in animal body weight, food consumption, enzyme activities, hepatic histomorphology and MDA formation, at either time or dosage level. Conversely, C. majus induced a slight but significant decrease of GSH levels and SOD activity, especially at the high dose. CONCLUSIONS: Our study suggests that C. majus, at doses about 50 and 100 times higher than those generally used in humans, does not alter hepatic function. However, the reduction in GSH levels and SOD activity suggests particular attention in use of C. majus or its preparations in situations (pharmacological treatments, physio-pathological conditions, etc.) that can compromise liver function.