Nicotine-dependent activation of the Ca2+/IP3/ERK 1/2 intracellular signaling pathway
Background Epidemiological studies have indicated smoking to be a risk factor for the progression of liver diseases. Nicotine is the chief addictive substance in cigarette smoke and has powerful biological properties throughout the body. Nicotine has been implicated in a number of disease processes, including increased cell proliferation and fibrosis in several organ systems.
AIMS: The aim of this study was to evaluate the effects of chronic administration of nicotine on biliary proliferation and fibrosis in normal rats.
METHODS: In vivo, rats were treated with nicotine by osmotic minipumps for two weeks. Proliferation, α7-nicotinic receptor and profibrotic expression were evaluated in liver tissue, cholangiocytes and a polarized cholangiocyte cell line (normal rat intrahepatic cholangiocyte). Nicotine-dependent activation of the Ca2+/IP3/ERK 1/2 intracellular signalling pathway was also evaluated in normal rat intrahepatic cholangiocyte.Results: Cholangiocytes express α7-nicotinic receptor. Chronic administration of nicotine to normal rats stimulated biliary proliferation and profibrotic gene and protein expression such as alpha-smooth muscle actin and fibronectin 1. Activation of α7-nicotinic receptor stimulated Ca2+/ERK1/2-dependent cholangiocyte proliferation.
CONCLUSION: Chronic exposure to nicotine contributes to biliary fibrosis by activation of cholangiocyte proliferation and expression of profibrotic genes. Modulation of α7-nicotinic receptor signalling axis may be useful for the management of biliary proliferation and fibrosis during cholangiopathies.
Dig Liver Dis. 2013 Sep;45(9):754-61.