INTERFERON-ALFA AND INTERFERON-GAMMA INHIBIT PROLIFERATION AND COLLAGEN-SYNTHESIS OF HUMAN ITO CELLS IN CULTURE

During the course of ongoing liver fibrogenesis, Ito cells acquire myo fibroblastic features, proliferate, and synthesize increased amounts o f extracellular matrix components. Interferon (IFN) alfa and IFN gamma have been shown to elicit antiproliferative and/or antifibrogenic eff ects in various cell cultures of mesenchymal origin. The aim of this s tudy was to investigate the effects of IFN-alpha and IFN-gamma on cult ured human myofibroblastic Ito cells (MFBIC) proliferation and collage n synthesis and secretion. Serum-stimulated incorporation of [H-3]thym idine into DNA of MFBIC was dose-dependently decreased by both cytokin es. IFN-alpha (10(4) U/mL) and IFN-gamma (10(3) U/mL) decreased DNA sy nthesis by 69% and 66%, respectively. Inhibition of cell proliferation was confirmed by cell counting. Similar results were observed when ce ll growth was stimulated with platelet-derived growth factor (PDGF-BB, PDGF-AA) or transforming growth factor (TGF)-beta 1. Collagen secreti on per cell was inhibited by both cytokines, as assessed by [H-3]hydro xyproline incorporation. After a 6-day treatment, IFN-gamma showed a g reater potency than IFN-alpha in inhibiting secretion of newly synthet ized collagen (41% and 48% of control in the presence of 10(2) U/mL of IFN-gamma and 10(4) U/mL of IFN-alpha, respectively). Both IFN-alpha and IFN-gamma concurrently decreased steady-state expression of type I and type III procollagen messenger RNAs (mRNAs) in quiescent MFBIC. V iability assays ruled out cytotoxic effects of the two molecules. Fina lly, both IFNs decreased smooth muscle alpha-actin (SM alpha-actin) ex pression, whether assayed by immunobloting or by Northern blot analysi s. We conclude that IFN-alpha and IFN-gamma inhibit proliferation as w ell as collagen synthesis in human MFBIC.