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Am J Physiol Gastrointest Liver Physiol. 2017 Nov 1;313(5):G410-G418. doi: 10.1152/ajpgi.00421.2016. Epub 2017 Jul 27.

Melatonin inhibits hypothalamic gonadotropin-releasing hormone release and reduces biliary hyperplasia and fibrosis in cholestatic rats.

McMillin M1,2,3, DeMorrow S1,2,3, Glaser S1,2,3, Venter J2,3, Kyritsi K2,3, Zhou T1,3, Grant S2,3, Giang T1,2,3, Greene JF Jr4, Wu N2,3, Jefferson B2,3, Meng F1,2,3,5, Alpini G6,2,3.

Author information

1
Research, Central Texas Veterans Health Care System, Temple, Texas.
2
Digestive Disease Research Center, Baylor Scott & White Health, Temple, Texas.
3
Department of Medicine, Division Gastroenterology, Texas A&M University Health Science Center and Baylor Scott & White Health, Temple, Texas.
4
Department of Pathology, Baylor Scott & White Health, Temple, Texas; and.
5
Research Foundation, Baylor Scott & White Health, Temple, Texas.
6
Research, Central Texas Veterans Health Care System, Temple, Texas; galpini@tamu.edu.

Abstract

Melatonin is a hormone produced by the pineal gland with increased circulating levels shown to inhibit biliary hyperplasia and fibrosis during cholestatic liver injury. Melatonin also has the capability to suppress the release of hypothalamic gonadotropin-releasing hormone (GnRH), a hormone that promotes cholangiocyte proliferation when serum levels are elevated. However, the interplay and contribution of neural melatonin and GnRH to cholangiocyte proliferation and fibrosis in bile duct-ligated (BDL) rats have not been investigated. To test this, cranial levels of melatonin were increased by implanting osmotic minipumps that performed an intracerebroventricular (ICV) infusion of melatonin or saline for 7 days starting at the time of BDL. Hypothalamic GnRH mRNA and cholangiocyte secretion of GnRH and melatonin were assessed. Cholangiocyte proliferation and fibrosis were measured. Primary human hepatic stellate cells (HSCs) were treated with cholangiocyte supernatants, GnRH, or the GnRH receptor antagonist cetrorelix acetate, and cell proliferation and fibrosis gene expression were assessed. Melatonin infusion reduced hypothalamic GnRH mRNA expression and led to decreased GnRH and increased melatonin secretion from cholangiocytes. Infusion of melatonin was found to reduce hepatic injury, cholangiocyte proliferation, and fibrosis during BDL-induced liver injury. HSCs supplemented with BDL cholangiocyte supernatant had increased proliferation, and this increase was reversed when HSCs were supplemented with supernatants from melatonin-infused rats. GnRH stimulated fibrosis gene expression in HSCs, and this was reversed by cetrorelix acetate cotreatment. Increasing bioavailability of melatonin in the brain may improve outcomes during cholestatic liver disease.NEW & NOTEWORTHY We have previously demonstrated that GnRH is expressed in cholangiocytes and promotes their proliferation during cholestasis. In addition, dark therapy, which increases melatonin, reduced cholangiocyte proliferation and fibrosis during cholestasis. This study expands these findings by investigating neural GnRH regulation by melatonin during BDL-induced cholestasis by infusing melatonin into the brain. Melatonin infusion reduced cholangiocyte proliferation and fibrosis, and these effects are due to GNRH receptor 1-dependent paracrine signaling between cholangiocytes and hepatic stellate cells.

KEYWORDS:

bile duct ligation; cholangiocyte; endocrine; hepatic stellate cells

PMID:
28751425
PMCID:
PMC5792219
DOI:
10.1152/ajpgi.00421.2016
[Indexed for MEDLINE]
Free PMC Article

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