Abstract. Cytochrome P450 epoxygenase-derived epoxyeicosatrienoic acids (EETs) have multiple biological functions in cardiovascular homeostasis. The anti-inflammatory, anti-migratory and pro-proliferative effects of EETs suggest a possible beneficial role for EETs in the apoptosis, proliferation and migration of pulmonary vascular cells. In this study, we investigated the effects of exogenous EETs and cytochrome P450 2J2 (CYP2J2) overexpression on tumor necrosis factor-α (TNF-α)-induced pulmonary artery endothelial cell (PAEC) apoptosis, and transforming growth factor-β1 (TGF-β1)-induced pulmonary artery smooth muscle cell (PASMC) proliferation and migration. PAECs and PASMCs were cultured from porcine pulmonary arteries. Our findings indicated that EETs or CYP2J2 overexpression significantly protected the PAECs from TNF-α-induced apoptosis, as evaluated by cell viability and flow cytometry. Two mechanisms were found to be involved in these important protective effects: firstly, EETs and CYP2J2 overexpression inhibited the decrease in the expression of the antiapoptotic proteins, Bcl-2 and Bcl-xL, as well as the increase in the expression of the pro-apoptotic protein, Bax, mediated by TNF-α; secondly, they activated the phosphoinositide 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK) signaling pathways. We also found that 11,12-EET and 14,15-EET significantly inhibited TGF-β1-stimulated PASMC migration. However, EETs did not suppress TGF-β1-induced PASMC proliferation in vitro. These data may represent a novel approach to mitigate pulmonary vascular remodeling in diseases, such as pulmonary arterial hypertension.
IntroductionPulmonary vascular remodeling is one of the most important pathological changes in patients with pulmonary arterial hypertension (PAH). Endothelial cells are recognized as major regulators of vascular function. The balance between endothelial cell survival and death is critical in various processes, such as the regulation of vasoconstriction and vasodilation, smooth muscle cell growth and migration, thrombotic formation, intravascular inflammation and vascular remodeling (1,2). Inflammation is one of the main features of PAH, and circulating levels of cytokines, including tumor necrosis factor-α (TNF-α), are elevated in patients with PAH (3,4). During the early stages of vascular remodeling, inflammatory infiltration directly participates in the apoptosis of endothelial cells. Considerable experimental evidence suggests that the apoptosis of endothelial cells induces the release of mediators, in particular, transforming growth factor-β1 (TGF-β1), which induces the proliferation and migration of vascular smooth muscle cells (5,6). Sturrock et al (7) demonstrated that TGF-β1 is abundantly expressed in patients with pulmonary hypertension, and promotes pulmonary artery smooth muscle cell (PASMC) proliferation in low serum medium. The inhibition of TGF-β1 signaling has been demonstrated to attenuate pulmonary vascular remodeling and increase right ventricular pressure in anim...