Alcohol and cigarette smoke components activate human pancreatic stellate cells: implications for the progression of chronic pancreatitis.

BACKGROUND: Chronic pancreatitis, a known complication of alcohol abuse, is characterized histopathologically by prominent fibrosis. Pancreatic stellate cells (PSCs) are responsible for producing this fibrous tissue in chronic pancreatitis and are activated by alcohol. Progression of alcoholic chronic pancreatitis (as assessed by calcification and fibrosis) is thought to be facilitated by concurrent smoking, but the mechanisms are unknown. This study aimed to (a) determine whether human PSCs (hPSCs) and rat PSCs express nicotinic acetylcholine receptors (nAChRs), which are known to bind 2 important components of cigarette smoke, namely nicotine and nicotine-derived nitrosamine ketone (NNK), and (b) examine the effects of cigarette smoke components in the presence and absence of alcohol on PSC activation in vitro. METHODS: Western blotting was used to detect the presence of nAChRs in primary cultures of PSCs. Clinically relevant concentrations of cigarette smoke components (either cigarette smoke extract [CSE], NNK, or nicotine) ± ethanol (EtOH) were used to treat primary cultures of PSCs, and stellate cell activation was assessed by cell migration, proliferation, collagen production, and apoptosis. RESULTS: We demonstrate, for the first time, that PSCs express nAChRs (isoforms α3, α7, ß, ε) and that the expression of the α7 isoform in hPSCs is induced by CSE + EtOH. We also provide novel findings that PSCs are activated by CSE and NNK (both alone and in combination with EtOH) as evidenced by an increase in cell migration and/or proliferation. Further, we demonstrate that activation of PSCs by CSE + EtOH and NNK + EtOH may be mediated via nAChRs on the cells. CONCLUSIONS: PSCs are activated by clinically relevant concentrations of cigarette smoke components (CSE and NNK), alone and in combination with EtOH. Thus, in alcoholics who smoke, progression of pancreatic fibrosis may be facilitated by the combined effects of alcohol and cigarette smoke components on hPSC behavior.

The role of the hepatocyte growth factor/c-MET pathway in pancreatic stellate cell-endothelial cell interactions: antiangiogenic implications in pancreatic cancer.

Activated cancer-associated human pancreatic stellate cells (CAhPSCs, which produce the collagenous stroma of pancreatic cancer [PC]) are known to play a major role in PC progression. Apart from inducing cancer cell proliferation and migration, CAhPSCs have also been implicated in neoangiogenesis in PC. However, the mechanisms mediating the observed angiogenic effects of CAhPSCs are unknown. A candidate pathway that may be involved in this process is the hepatocyte growth factor (HGF)/c-MET pathway and its helper molecule, urokinase-type plasminogen activator (uPA). This study investigated the effects of CAhPSC secretions on endothelial cell function in the presence and absence of HGF, c-MET and uPA inhibitors. HGF levels in CAhPSC secretions were quantified using ELISA. CAhPSC secretions were then incubated with human microvascular endothelial cells (HMEC-1) and angiogenesis assessed by quantifying HMEC-1 tube formation and proliferation. CAhPSC-secreted HGF significantly increased HMEC-1 tube formation and proliferation; notably, these effects were downregulated by inhibition of HGF, its receptor c-MET and uPA. Phosphorylation of p38 mitogen-activated protein kinase was downregulated during inhibition of the HGF/c-MET pathway, whereas phosphatidylinositol-3 kinase and ERK1/2 remained unaffected. Our studies have shown for the first time that CAhPSCs induce proliferation and tube formation of HMEC-1 and that the HGF/c-MET pathway plays a major role in this induction. Given that standard antiangiogenic treatment targeting vascular endothelial growth factor has had limited success in the clinical setting, the findings of the current study provide strong support for a novel, alternative antiangiogenic approach targeting the HGF/c-MET and uPA pathways in PC.