Search

BACKGROUND: The parasympathetic nervous system (PNS), via neurotransmitter Acetylcholine (ACh), modulates fibrogenesis in animal models. However, the role of ACh in human hepatic fibrogenesis is unclear. AIMS: We aimed to determine the fibrogenic responses of human hepatic stellate cells (hHSC) to ACh and the relevance of the PNS in hepatic fibrosis in patients with non-alcoholic steatohepatitis (NASH). METHODS: Primary hHSC were analysed for synthesis of endogenous ACh and acetylcholinesterase (AChE), and gene expression of choline acetyltransferase (ChAT) and muscarinic acetylcholine receptors (mAChR). Cell proliferation and fibrogenic markers were analysed in hHSC exposed to ACh, Atropine (Atrop), Mecamylamine (Mec), methoctramine and 4-Diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP). MAChR expression was analysed in human NASH scored for fibrosis. RESULTS: We observed that hHSC synthesise ACh and AChE, and express ChAT and M1-M5 mAChR. We also show that M2 was increased during NASH progression, while both M2 and M3 were found upregulated in activated hHSC. Furthermore, endogenous ACh is required for hHSC basal growth. Exogenous ACh resulted in hHSC hyperproliferation via mAChR and PI-3 K and MEK signalling pathways, as well as increased fibrogenic markers. CONCLUSION: We show that ACh regulates hHSC activation via M2 and M3 mAChR involving the PI-3 K and MEK pathways in vitro. Finally, we provide evidence that the PNS may be involved in human NASH fibrosis.

Background & aims Obesity induced, non-alcoholic fatty liver disease (NAFLD), is now the major cause in affluent countries, of the spectrum of steatosis-to-cirrhosis. Obesity and NAFLD rates in reproductive age women, and adolescents, are rising worldwide. Our hypothesis was that maternal obesity and lactation transmit to the offspring a pre-disposition to dysmetabolism, obesity and NAFLD. Methods Female mice were fed standard or obesogenic chow, before, throughout pregnancy, and during lactation. The critical developmental period was studied by cross-fostering offspring of lean and obese dams. Offspring were then weaned onto standard chow and studied at 3months. Read-outs included markers of metabolic dysfunction, biochemical and histological indicators of NAFLD, induction of liver fibrogenesis, and activation of pro-fibrotic pathways. Mechanisms involved in programming a dysmetabolic and NAFLD phenotype were investigated by assaying breast milk components. Results Offspring of obese dams had a dysmetabolic, insulin resistant and NAFLD phenotype compared to offspring of lean dams. Offspring of lean dams that were suckled by obese dams showed an exaggerated dysmetabolic and NAFLD phenotype, with increased body weight, as well as increased levels of insulin, leptin, aspartate transaminase, interleukin-6, tumour necrosis factor-alpha, liver triglycerides, steatosis, hepatic fibrogenesis, renal norepinephrine, and liver alpha1-D plus beta1-adrenoceptors, indicative of sympathetic nervous system activation. Obese dams also had raised breast milk leptin levels compared to lean dams. Conclusions Maternal obesity programs development of a dysmetabolic and NAFLD phenotype, which is critically dependent on the early postnatal period and possibly involving alteration of hypothalamic appetite nuclei signalling by maternal breast milk and neonatal adipose tissue derived, leptin.

Amphiregulin (AR) involvement in liver fibrogenesis and hepatic stellate cells (HSC) regulation is under study. Non-alcoholic fatty liver disease (NAFLD) and its more severe form non-alcoholic steatohepatitis (NASH) may progress to cirrhosis and hepatocellular cancer (HCC). Our aim was to investigate ex vivo the effect of AR on human primary HSC (hHSC) and verify in vivo the relevance of AR in NAFLD fibrogenesis. hHSC isolated from healthy liver segments were analyzed for expression of AR and its activator, TNF-α converting enzyme (TACE). AR induction of hHSC proliferation and matrix production was estimated in the presence of antagonists. AR involvement in fibrogenesis was also assessed in a mouse model of NASH and in humans with NASH. hHSC time dependently expressed AR and TACE. AR increased hHSC proliferation through several mitogenic signaling pathways such as EGFR, PI3K and p38. AR also induced marked upregulation of hHSC fibrogenic markers and reduced hHSC death. AR expression was enhanced in the HSC of a murine model of NASH and of severe human NASH. In conclusion, AR induces hHSC fibrogenic activity via multiple mitogenic signaling pathways and is upregulated in murine and human NASH, suggesting that AR antagonists may be clinically useful anti-fibrotics in NAFLD.

Background Sympathetic nervous system (SNS) signalling regulates murine hepatic fibrogenesis through effects on hepatic stellate cells (HSC), and obesity-related hypertension with SNS activation accelerates progression of non-alcoholic fatty liver disease (NAFLD), the commonest cause of chronic liver disease. NAFLD may lead to cirrhosis. The effects of the SNS neurotransmitters norepinephrine (NE), epinephrine (EPI) and neuropeptide Y (NPY) on human primary HSC (hHSC) function and in NAFLD pathogenesis are poorly understood. Aims to determine the mechanistic effects of NE/EPI/NPY on phenotypic changes in cultured hHSC, and to study SNS signalling in human NAFLD livers. Methods Freshly isolated hHSC were assessed for expression of cathecholamine/neuropeptide Y receptors and for the synthesis of NE/EPI. The effects of NE/EPI/NPY and adrenoceptor antagonists prazosin (PRZ)/propranolol (PRL) on hHSC fibrogenic functions and the involved kinases and interleukin pathways were examined. Human livers with proven NAFLD were then assessed for upregulation of SNS signalling components. Results Activated hHSC express functional α/β-adrenoceptors and NPY receptors, which are upregulated in the livers of patients with cirrhotic NAFLD. hHSC in culture synthesize and release NE/EPI, required for their optimal basal growth and survival. Exogenous NE/EPI and NPY dose-dependently induced hHSC proliferation, mediated via p38 MAP, PI3K and MEK signalling. NE and EPI but not NPY increased expression of collagen-1α2 via TGF-β without involvement of the pro-fibrogenic cytokines leptin, IL-4 and IL-13 or the anti-fibrotic cytokine IL-10. Conclusions hHSC synthesize and require cathecholamines for optimal survival and fibrogenic functionality. Activated hHSC express directly fibrogenic α/β-adrenoceptors and NPY receptors, upregulated in human cirrhotic NAFLD. Adrenoceptor and NPY antagonists may be novel anti-fibrotic agents in human NAFLD.