ERK1/2 and JNKs, but not p38 kinase, are involved in reactive oxygen species‐mediated induction of osteopontin gene expression by angiotensin II and interleukin‐1β in adult rat cardiac fibroblasts

Abstract

Osteopontin (OPN), also called cytokine Eta‐1, expressed in the myocardium co‐incident with heart failure plays an important role in post myocardial infarction (MI) remodeling by promoting collagen synthesis and accumulation. Angiotensin II (Ang II) and inflammatory cytokines are increased in the heart following MI. We studied the involvement of mitogen‐activated protein kinases (ERK1/2, JNKs, p38 kinase) and reactive oxygen species (ROS) in Ang II‐ and cytokine‐induced OPN gene expression in adult rat cardiac fibroblasts. Ang II alone increased OPN mRNA (3.3 ± 0.3‐folds; P < 0.05; n = 7), while interleukin‐1β (IL‐1β), tumor necrosis factor (TNF‐α), and interferon‐γ (IFN‐γ) had no effect. A combination of Ang II with IL‐1β or TNF‐α, not IFN‐γ, increased OPN mRNA more than Ang II alone. Nitric oxide donor, S‐nitrosoacetylpenicillamine (SNAP), alone or in combination with Ang II had no effect. Diphenylene iodonium (DPI), inhibitor of NAD(P)H oxidase, and tiron, superoxide scavenger, inhibited Ang II‐ and Ang II+ IL‐1β‐stimulated increases in OPN mRNA. Ang II activated ERK1/2 within 5 min of treatment, not JNKs. IL‐1β activated ERK1/2 and JNKs within 15 min of treatment. A combination of Ang II and IL‐1β activated ERK1/2 within 5 min of treatment. None of these stimuli activated p38 kinase. DPI almost completely inhibited Ang II + IL‐1β‐stimulated activation of ERK1/2, while partially inhibiting JNKs. PD98059, ERK1/2 pathway inhibitor, and SP600125, JNKs inhibitor, partially inhibited Ang II + IL‐1β‐stimulated increases in OPN mRNA. A combination of PD98059 and SP600125 almost completely inhibited Ang II + IL‐1β‐stimulated increases in OPN mRNA. Thus, Ang II alone increases OPN expression, while IL‐1β and TNF‐α act synergistically with Ang II to increase OPN mRNA possibly via NO independent mechanisms. The synergistic increase in OPN mRNA involves ROS‐mediated activation of ERK1/2 and JNKs, not P38 kinase, pathways in cardiac fibroblasts. J. Cell. Physiol. 198: 399–407, 2004