TGF-β1/FGF-2 signaling mediates the 15-HETE-induced differentiation of adventitial fibroblasts into myofibroblasts

Background: Pulmonary adventitial fibroblasts (PAFs) are activated under stress stimuli leading to their differentiation into myofibroblasts, which is involved in vessel remodeling. 15-HETE is known as an important factor in vessel remodeling under hypoxia; however, the role of 15-HETE in PAF phenotypic alteration is not clear. Results: The effect of 15-HETE on PAF phenotypic alterations was investigated in the present study. PAFs were treated with 15-HETE (0.5 mu M) for 24 h, and the myofibroblast marker alpha-smooth muscle actin (alpha-SMA) was analyzed. The 15-HETE induced alpha-SMA expression and cell morphology. 15-HETE upregulated FGF-2 levels in PAFs, and knockdown FGF-2 by siRNAs blocked the enhanced alpha-SMA expression induced by 15-HETE. p38 kinase was activated, and blocked depressed 15-HETE-induced FGF-2 expression. The downstream of p38 pathway, Egr-1 activation, was also raised by 15-HETE treatment, and silenced Egr-1 suppressed the 15-HETE-induced upregulation of FGF-2. TGF-beta 1 was upregulated with FGF-2 treatment, and a-SMA expression induced by FGF-2 was inhibited after the cell was transferred with TGF-beta 1 siRNA. Meanwhile, FGF-2 increased alpha-SMA expression and improved proliferation, which was associated with p27(kip1) and cyclin E variation. Conclusions: The above results suggest that p38/Egr-1 pathway-mediated FGF-2 is involved in 15-HETE-induced differentiation of PAFs into myofibroblasts and cell proliferation.