Proinflammatory cytokines inhibit secretion in rat bile duct epithelium

Background & Aims: Cholestatic disorders often are associated with portal i nflammation, but whether or how inflammation contributes to cholestasis is unknown. Thus we studied the effects of proinflammatory cytokines on bile d uct epithelia secretory mechanisms. Methods: Isolated bile duct units (IBDU s) were cultured with interleukin (IL)-6, interferon gamma, tumor necrosis factor (TNF)-alpha, and IL-1 alone or in combination. Ductular secretion wa s measured using video-optical planimetry. Bicarbonate and Cl- transport we re assessed microfluorimetric measuring pH, (BCECF) and [Cl-](i) transients (MEQ). Expression of Cl-/HCO3- exchanger (AE-2), cystic fibrosis transmemb rane conductance regulator (CFTR), and the secretin receptor (SR) were asse ssed by ribonuclease protection assay. Cellular cyclic adenosine monophosph ate (cAMP) levels were studied by enzymatic immunoassay. Paracellular perme ability was assessed using fluorescein-labeled dextrans (FD) in cholangiocy te monolayers (NRC-1). Results: Although not effective when given alone, ea ch combination of IL-6, interferon gamma, IL-1, and TNF-alpha inhibited sec retion in IBDU. Cytokines inhibited cAMP formation, AE-2 activity, and cycl ic AMP-dependent Cl- efflux, but not that induced by purinergic agonists. A E-2 gene expression was unaffected by proinflammatory cytokines, whereas CF TR and SR expression was increased. In addition, paracellular transit of FD across NRC-1 monolayers was increased. Conclusions: Inflammatory cytokines inhibit cAMP-dependent fluid secretion in cholangiocytes and impair the ba rrier functions of biliary epithelia. These changes may represent the molec ular mechanisms by which inflammation leads to ductular cholestasis in vivo .