Iloprost inhibits superoxide formation and gp91phox expression induced by the thromboxane A2 analogue U46619 8-isoprostane F2α prostaglandin F2α cytokines and endotoxin in the pig pulmonary artery

摘要

class="enumerated" style="list-style-type:decimal">Since the roles of thromboxane A2 (TXA2), prostacyclin (PGI2) and 8-isoprostane F2α in mediating vascular O2^•− formation and its relation to adult respiratory distress syndrome (ARDS) is unknown, the effects of these eicosanoids on the expression of gp91^phox (catalytic subunit of NADPH oxidase) and O2^•− release from cultured pig pulmonary artery (PA) segments, PA vascular smooth muscle cells (PAVSMCs) and PA endothelial cells (PAECs) were investigated.PA segments, PAVSMCs and PAECs were incubated with the TXA2 analogue, U46619, (±LPS, tumour necrosing factor-alpha (TNF-α) or IL-1α), 8-isoprostane F2α and±iloprost (a stable PGI2 analogue) for 16 h. The formation of superoxide dismutase-inhibitable O2^•− was then measured spectrophotometrically and gp91^phox expression assessed using Western blotting. In parallel experiments, whole PA segments were treated with LPS, TNF-α and IL-α after which time TXA2, PGI2, PGF2α and 8-isoprostane F2α formation was measured using enzyme-linked immunoassays.U46619, PGF2α and 8-isoprostane F2α promoted the formation of O₂^•− in PA segments, PAVSMCs and PAECs, an effect inhibited by diphenyleneiodonium and apocynin (both NADPH oxidase inhibitors) and upregulated the expression of gp91^phox in PAECs and PAVSMCs. These effects were augmented by LPS, TNF-α and IL-1α but inhibited by iloprost. Under identical incubation conditions, IL-1α, LPS and TNF-α all induced an increase in the formation of TXA₂, PGF_2α and 8-isoprostane F_2α but reduced the concomitant formation of PGI₂.These data demonstrate that LPS and cytokines influence the relative balance of TXA₂, PGI₂, PGF_2α and 8-isoprostane F_2α in pig PA, which in turn alter NADPH oxidase expression and O₂^•− formation. These novel findings have implications in devising effective strategies for treating ARDS.