Abstract P185: Periostin Increases Inducible Nitric Oxide Synthase Expression in Right Ventricular Fibroblasts From Pulmonary Arterial Hypertension Rats

Abstract

Background: Pulmonary arterial hypertension (PAH) leads to a lethal right heart failure (RHF), effective treatment for which has not been established. Inducible nitric oxide synthase (iNOS) is thought to be associated with the pathogenesis of heart failure. Inflammatory cytokines, which are increased in RHF, are known to induce iNOS expression in cardiac fibroblasts. We previously demonstrated that the mRNA expression of periostin, a matricellular protein, was upregulated in right ventricles (RVs) of monocrotaline (MCT)-induced PAH model rats. In the present study, we investigated the effects of periostin on iNOS expression in right ventricular fibroblasts isolated from PAH model rats. Methods: MCT (60 mg/kg) was injected intraperitoneally to 4-week-old male Wistar rats. Two weeks after the MCT-injection, cardiac fibroblasts were enzymatically isolated from RVs using a modified Langendorff apparatus. A soluble form of recombinant rat periostin protein was produced by Escherichia coli . The right ventricular fibroblasts (RVFs) were stimulated with a recombinant rat periostin (10-1000 ng/ml, 30 min-24 h). The expression of iNOS and activation of extracellular signal-regulated kinase (ERK) 1/2 and c-jun N-terminal kinase (JNK) were investigated by Western blotting. Results: Periostin (1000 ng/ml, 24 h) significantly increased iNOS (3.9 ± 0.6-fold, P <0.01, n=4) but not eNOS in RVFs. Periostin (1000 ng/ml, 30 min) increased phosphorylation of ERK1/2 (4.0 ± 2.3-fold, n=3) and JNK (13.2 ± 2.7-fold, P <0.05, n=3) in RVFs. An ERK pathway inhibitor, PD98059 (10 μM) or JNK inhibitor, SP600125 (30 μM) almost completely suppressed the periostin-induced iNOS expression (PD98059, P <0.01; SP600125, P <0.05, n=3). Conclusion: We for the first time demonstrated that periostin increases iNOS expression via the activation of ERK and JNK in RVFs isolated from PAH model rats. It is suggested that inflammatory reaction mediated by periostin might be a novel target for treatment of PAH-induced RHF.