BACKGROUND/AIMS: Hepatic myofibroblasts are central in liver fibrogenesis associated with chronic liver diseases. We previously showed that heme-oxygenase-1 (HO-1) displays antifibrogenic properties in human hepatic myofibroblasts. Here, we further investigated the mechanisms regulating HO-1 expression. METHODS: Expression of HO-1 was assayed in cultured human hepatic myofibroblasts by Northern and Western blot. Functional studies were also performed in cultured human hepatic myofibroblasts. RESULTS: 15-Deoxy-Delta(12,14)-prostaglandin J2 (15-d-PGJ2) elicited inhibition of proliferation and of alpha1(I) collagen mRNA expression. These effects were reproduced by the glutathione depletor diethyl maleate and blunted by the glutathione precursor N-acetyl cysteine, indicating the involvement of oxidative stress. Two consecutive events mediated inhibition of proliferation and of alpha1(I) collagen mRNA expression by 15-d-PGJ2: (i) mild oxidative stress characterized by a transient GSH decrease and (ii) activation of p38 MAPK, resulting in increased HO-1 mRNA stability. CONCLUSIONS: Our results provide new insights into the regulatory mechanisms governing HO-1 expression in human hepatic myofibroblasts and identify mild oxidative stress and p38 MAPK as two consecutive early signals promoting HO-1 induction that are crucial for its antifibrogenic properties, namely inhibition of growth and extracellular matrix gene expression.
BACKGROUND/AIMS: Hepatic myofibroblasts are central in liver fibrogenesis associated with chronic liver diseases. We previously showed that heme-oxygenase-1 (HO-1) displays antifibrogenic properties in human hepatic myofibroblasts. Here, we further investigated the mechanisms regulating HO-1 expression. METHODS: Expression of HO-1 was assayed in cultured human hepatic myofibroblasts by Northern and Western blot. Functional studies were also performed in cultured human hepatic myofibroblasts. RESULTS:15-Deoxy-Delta(12,14)-prostaglandin J2 (15-d-PGJ2) elicited inhibition of proliferation and of alpha1(I) collagen mRNA expression. These effects were reproduced by the glutathione depletor diethyl maleate and blunted by the glutathione precursor N-acetyl cysteine, indicating the involvement of oxidative stress. Two consecutive events mediated inhibition of proliferation and of alpha1(I) collagen mRNA expression by 15-d-PGJ2: (i) mild oxidative stress characterized by a transient GSH decrease and (ii) activation of p38 MAPK, resulting in increased HO-1 mRNA stability. CONCLUSIONS: Our results provide new insights into the regulatory mechanisms governing HO-1 expression in human hepatic myofibroblasts and identify mild oxidative stress and p38 MAPK as two consecutive early signals promoting HO-1 induction that are crucial for its antifibrogenic properties, namely inhibition of growth and extracellular matrix gene expression.
Authors: J J O'Brien; C J Baglole; T M Garcia-Bates; N Blumberg; C W Francis; R P Phipps Journal: J Thromb Haemost Date: 2008-10-10 Impact factor: 5.824
Authors: Karen E Iles; Marcienne M Wright; Marsha P Cole; Nathan E Welty; Lorraine B Ware; Michael A Matthay; Francisco J Schopfer; Paul R S Baker; Anupam Agarwal; Bruce A Freeman Journal: Free Radic Biol Med Date: 2008-12-14 Impact factor: 7.376