A. J. Kandathiparampil1, X. Wang1, F. J. Bohanon1, C. Rastellini1, J. Zhou2, R. S. Radhakrishnan1 1University Of Texas Medical Branch,Surgery,Galveston, TX, USA 2University Of Texas Medical Branch,Pharmacology And Toxicology,Galveston, TX, USA
Introduction: Luteolin is an important member of the flavonoid family and is present in fruits, vegetables, and plant-derived beverages. Luteolin is known to have anti-tumorigenic, anti-oxidant, and anti-inflammatory properties. A recent study revealed the therapeutic effect of luteolin on a mouse model of liver fibrosis. However, its molecular mechanisms of action remains unclear. In the present study, we investigated the effect of luteolin on activated hepatic stellate cells (HSC), the major source for excessive extracellular matrix (ECM) deposition in hepatic fibrosis.
Methods: Alamar Blue assay was used for proliferation analysis of human activated HSC cell line LX-2. Cellular proteins were measured by immunoblot and immunofluorescence. Apoptosis was determined with the staining of Yo-Pro-1 and propidium iodide. Cell cycle was assessed by Flow Cytometry.
Results: Luteolin treatment induced LX-2 cells apoptosis and potent growth inhibition in a time-dependent fashion. Luteolin induced G1 and S phases cell cycle arrest, and correlated with increased p53 activity, and decreased expression of cyclinB1, cyclinD1, cyclinE2, CDK2, CDK9, and mini-chromosome maintenance 2 (MCM2). In addition, the HSC activation marker α-smooth muscle actin, as well as major ECM proteins collagen type I and fibronectin were markedly down-regulated by luteolin in a time-and dose-dependent manner (Fig. 1A). TGF-β is a potent profibrogenic cytokine. Our data showed that pretreatment with luteolin blocked TGF-β-induced fibronectin, collagen type I, collagen type III and phospho-Smad2/3 expression (Fig. 1B).
Conclusion: Luteolin treatment inhibited HSC proliferation, suppressed endogenous and TGF-β-induced ECMs expression, while impairing cell cycle and TGF-β signaling in LX-2 cells. Luteolin may be a promising agent for reducing liver fibrosis.
