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

I Since the roles of thromboxane A(2) (TXA(2)), prostacyclin (PGI(2)) and 8-isoprostane F-2alpha in mediating vascular O-2(circle-) 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 O-2(circle-) release from cultured pig pulmonary artery (PA) segments, PA vascular smooth muscle cells (PAVSMCs) and PA endothelial cells (PAECs) were investigated. 2 PA segments, PAVSMCs and PAECs were incubated with the TXA(2) analogue, U46619, (+/-LPS, tumour necrosing factor-alpha (TNF-alpha) or IL-1alpha), 8-isoprostane F-2alpha and +/- iloprost (a stable PGI(2) analogue) for 16 It. The formation of superoxide dismutase-inhibitable O-2(circle-) was then measured spectrophotometrically and gp91(phox) expression assessed using Western blotting. In parallel experiments, whole PA segments were treated with LPS, TNF-alpha and IL-alpha after which time TXA(2), PGI(2), PGF(2alpha) and 8-isoprostane F-2alpha formation was measured using enzyme-linked immunoassays. 3 U46619, PGF(2alpha) and 8-isoprostane F-2alpha promoted the formation of O-2(circle-) 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-alpha and IL-1alpha but inhibited by iloprost. Under identical incubation conditions, IL-1alpha, LPS and TNF-alpha all induced an increase in the formation of TXA(2), PGF(2alpha) and 8-isoprostane F-2alpha but reduced the concomitant formation of PGI(2). 4 These data demonstrate that LPS and cytokines influence the relative balance of TXA(2), PGI(2), PGF(2alpha) and 8-isoprostane F-2alpha in pig PA, which in turn alter NADPH oxidase expression and O-2(circle-) formation. These novel findings have implications in devising effective strategies for treating ARDS.