ET-1 stimulates pulmonary arterial smooth muscle cell proliferation via induction of reactive oxygen species

Recent studies implicate reactive oxygen species (ROS) such as superoxide a nions and H2O2 in the proliferation of systemic vascular smooth muscle cell s (SMCs). However, the role of ROS in SMC proliferation within the pulmonar y circulation remains unclear. We investigated the effects of endothelin-1 (ET-1), a potential SMC mitogen, on ROS production and proliferation of fet al pulmonary artery SMCs (FPASMCs). Exposure to ET-1 resulted in increases in superoxide production and viable FPASMCs after 72 h. These increases wer e prevented by pretreatment with PD-156707. Treatment with pertussis toxin blocked the effects of ET-1, whereas cholera toxin stimulated superoxide pr oduction and increased viable cell numbers even in the absence of ET-1. Wor tmannin, LY-294002, diphenyleneiodonium (DPI), 4-(2-aminoethyl) benzenesulf onyl fluoride, and apocynin also prevented the ET-1-mediated increases in s uperoxide production and viable cell numbers. Exposure to H2O2 or diethyldi thiocarbamate increased viable cell number by 37% and 50%, respectively. Co nversely, ascorbic acid and DPI decreased viable cell number, which appeare d to be due to an increase in programmed cell death. Our data suggest that ET-1 exerts a mitogenic effect on FPASMCs via an increase in ROS production and that antioxidants can block this effect via induction of apoptosis. An tioxidant treatment may therefore represent a potential therapy for pulmona ry vascular diseases.