Hasan Kulaksiz

Alcohol metabolism-mediated oxidative stress down-regulates hepcidin transcription and leads to increased duodenal iron transporter expression.

Patients with alcoholic liver disease frequently exhibit iron overload in association with increased hepatic fibrosis. Even moderate alcohol consumption elevates body iron stores; however, the underlying molecular mechanisms are unknown. Hepcidin, a circulatory peptide synthesized in the liver, is a key mediator of iron metabolism. Ethanol metabolism significantly down-regulated both in vitro and in vivo hepcidin mRNA and protein expression. 4-Methylpyrazole, a specific inhibitor of the alcohol-metabolizing enzymes, abolished the effects of ethanol on hepcidin. However, ethanol did not alter the expression of transferrin receptor1 and ferritin or the activation of iron regulatory RNA-binding proteins, IRP1 and IRP2. Mice maintained on 10-20% ethanol for 7 days displayed down-regulation of liver hepcidin expression without changes in liver triglycerides or histology. This was accompanied by elevated duodenal divalent metal transporter1 and ferroportin protein expression. Injection of hepcidin peptide negated the effect of ethanol on duodenal iron transporters. Ethanol down-regulated hepcidin promoter activity and the DNA binding activity of CCAAT/enhancer-binding protein α (C/EBPα) but not β. Interestingly, the antioxidants vitamin E and N-acetylcysteine abolished both the alcohol-mediated down-regulation of C/EBPα binding activity and hepcidin expression in the liver and the up-regulation of duodenal divalent metal transporter 1. Collectively, these findings indicate that alcohol metabolism-mediated oxidative stress regulates hepcidin transcription via C/EBPα, which in turn leads to increased duodenal iron transport.

Influence of dominant bile duct stenoses and biliary infections on outcome in primary sclerosing cholangitis

BACKGROUND/AIMSnIn primary sclerosing cholangitis (PSC) dominant stenoses are frequently associated with bacterial, and in part, also fungal infections of the bile ducts. In the present study, the influence of dominant stenoses and of biliary infections on the long-term outcome was studied.nnnMETHODSnIn a prospective study, 171 patients were followed up for 20 years. All patients were treated with ursodeoxycholic acid. Dominant stenoses were treated endoscopically and during endoscopic procedures, bile was obtained for microbiologic analysis.nnnRESULTSnOf the 171 patients, 97 had or developed major bile duct stenoses and 96/97 were treated endoscopically. In the 55/97 patients with dominant stenosis, bile samples were obtained and of these, 41/55 had bacteria, five had also Candida and 2/55 had only Candida in their bile. Survival free of liver transplantation in patients without dominant stenosis at 18 years was 73.1% and of patients with dominant stenosis was 25.0% (p=0.011). Bacteria in bile had no effect on survival whereas Candida in bile was associated with reduced survival (p=0.025).nnnCONCLUSIONSnIn patients with dominant stenosis, survival free of liver transplantation is reduced. Bacteria in bile do not worsen the outcome if dominant stenoses are opened endoscopically and infection is adequately treated with antibiotics. Candida in bile is associated with a poor prognosis and these patients need liver transplantation relatively soon.

In PSC with dominant bile duct stenosis, IBD is associated with an increase of carcinomas and reduced survival

BACKGROUND & AIMSnIn patients with primary sclerosing cholangitis (PSC) treated with ursodeoxycholic acid (UDCA), dominant stenoses are associated with reduced survival free of liver transplantation and the role of inflammatory bowel disease (IBD) in such patients is unclear. In the present study the influence of IBD on the outcome in patients with and without dominant stenosis has been evaluated.nnnMETHODSnIn a prospective study, 171 patients were followed for up to 20 years. All patients were treated with ursodeoxycholic acid; patients with dominant stenosis in addition were treated endoscopically.nnnRESULTSnA total of 97 out of 171 patients had or developed dominant bile duct stenoses and 96 out of 97 were treated endoscopically. In patients with dominant stenosis without IBD, no carcinoma was found whereas all six bile duct and two gallbladder carcinomas and 6/7 colo-rectal carcinomas were found in patients with dominant stenosis with IBD (p=0.012). In patients without dominant stenosis but with IBD, 1 out of 7 had colo-rectal carcinoma. In patients with dominant stenosis without IBD (n=30), actuarial survival free of liver transplantation at 18 years was 77.8% and in those with dominant stenosis and inflammatory bowel disease (n=67) it was 23.0% (p=0.045). In PSC patients without dominant stenosis and without IBD (n=21), actuarial survival free of liver transplantation at 18 years was 68.2% and in those with inflammatory bowel disease (n=53) it was 78.4% (n.s.).nnnCONCLUSIONSnIn patients without dominant stenosis, IBD had no effect on the incidence of carcinomas and survival. Only patients with dominant stenosis with additional IBD had an increased carcinoma rate. This may contribute to the reduced survival free of liver transplantation in such patients.

Regulation of hepcidin in HepG2 and RINm5F cells

Despite the high impact of the antimicrobial peptide hepcidin in iron homeostasis, the regulation of this hormone is still not completely understood. Studies concerning hepcidin regulation are performed at the mRNA level. For the first time we analyzed the regulation of hepcidin not only at mRNA, but also at protein level in a hepatoma and a pancreatic beta cell line using quantitative RT-PCR and immunoblot analysis. Our data show, that hepcidin is present in HepG2 and RINm5F cells. A significant up-regulation of hepcidin was observed in both cell lines by the inflammatory cytokine interleukin-6, lipopolysaccharide, and a slight upregulation by deferoxamine. A down-regulation was detected after stimulation with erythropoietin. Hepcidin was regulated by iron in a dose dependent manner: low doses up to 3 microM increased hepcidin expression, high doses of iron (65 microM) revealed a switch-over to down-regulation of hepcidin expression. Regulation of hepcidin in HepG2 and RINm5F cells at mRNA and protein level by these substances indicates its involvement in inflammation and iron metabolism.

Guanylin and Functional Coupling Proteins in the Human Salivary Glands and Gland Tumors : Expression, Cellular Localization, and Target Membrane Domains

Cystic fibrosis transmembrane conductance regulator (CFTR)-mediated secretion of an electrolyte-rich fluid is a major but incompletely understood function of the salivary glands. We provide molecular evidence that guanylin, a bioactive intestinal peptide involved in the CFTR-regulated secretion of electrolyte/water in the gut epithelium, is highly expressed in the human parotid and submandibular glands and in respective clinically most relevant tumors. Moreover, in the same organs we identified expression of the major components of the guanylin signaling pathway, ie, guanylin-receptor guanylate cyclase-C, cGKII, and CFTR, as well as of the epithelial Cl(-)/HCO(3)(-) anion exchanger type 2 (AE2). At the cellular level, guanylin is localized to epithelial cells of the ductal system that, based on its presence in the saliva, is obviously released into the salivary gland ducts. The guanylin-receptor guanylate cyclase-C, cGKII, CFTR, and AE2 are all confined exclusively to the apical membrane of the same duct cells. These findings implicate guanylin as intrinsic regulator of electrolyte secretion in the salivary glands. We assume that duct epithelial cells synthesize and release guanylin into the saliva to regulate electrolyte secretion in the ductal system by an intraductal luminocrine signaling pathway. Moreover, the high expression of guanylin in pleomorphic adenoma and Warthin tumors (cystadenolymphoma), the most common neoplasms of salivary glands, predicts guanylin as a significant marker in tumor pathology.