The
hypoxia-induced proliferation of pulmonary artery smooth muscle cells (PASMCs) is the main cause of
pulmonary arterial hypertension (PAH), in which oxidative stress,
cyclooxygenase (COX)-2 and
hydrogen sulfide (H(2)S) all play an important role. In the present study, we aimed to examine the effects of H(2)S on the
hypoxia-induced proliferation of human PASMCs (HPASMCs) and to elucidate the underlying mechanisms. The HPASMCs were treated with
cobalt chloride (
CoCl(2)), a
hypoxia-mimicking agent, to establish a cellular model of hypoxic PAH. Prior to treatment with
CoCl(2), the cells were pre-conditioned with
sodium hydrosulfide (
NaHS), a donor of H(2)S. Cell proliferation,
reactive oxygen species (ROS) production, COX-2 expression,
prostacyclin (also known as
prostaglandin I2 or PGI(2)) secretion and H(2)S levels were detected in the cells. The exposure of the HPASMCs to
CoCl(2) markedly increased cell proliferation, accompanied by a decrease in COX-2 expression, PGI(2) secretion and H(2)S levels; however, the levels of ROS were not altered. Although the exogenous ROS donor, H(2)O(2), triggered similar degrees of proliferation to
CoCl(2), the ROS scavenger,
N-acetyl-L-cysteine (NAC), markedly abolished the H(2)O(2)‑induced cell proliferation, as opposed to the CoCl(2)-induced proliferation. The CoCl(2)-induced proliferation of HPASMCs was suppressed by exogenously applied PGI(2). The addition of H(2)S (
NaHS) attenuated the CoCl(2)-induced cell proliferation through the increase in the intercellular content of H(2)S. Importantly, the exposure of the cells to H(2)S suppressed the CoCl(2)-induced downregulation in COX-2 expression and PGI(2) secretion from the HPASMCs. In conclusion, the results from the current study suggest that H(2)S enhances
hypoxia-induced cell proliferation through the upregulation of COX-2/PGI(2), as opposed to ROS.