1 Acute respiratory distress syndrome (ARDS) is associated with increased superoxide (O 2 K À ) formation in the pulmonary vasculature and negation of the bioavailability of nitric oxide (NO). Since NO inhibits NADPH oxidase expression through a cyclic GMP-mediated mechanism, sildenafil, a type V phosphodiesterase inhibitor, may be therapeutically effective in ARDS through an augmentation of NO-mediated inhibition of NADPH oxidase. Therefore, the effect of sildenafil citrate and NO-donating sildenafil (NCX 911) on O 2 K À formation and gp91 phox (active catalytic subunit of NADPH oxidase) expression was investigated in cultured porcine pulmonary artery endothelial cells (PAECs). 2 PAECs were incubated with 10 nM TXA 2 analogue, 9,11-dideoxy-9a,11a-methanoepoxy-prostaglandin F 2a (U46619) (7sildenafil or NCX 911), for 16 h and O 2 K À formation measured spectrophometrically and gp91 phox using Western blotting. The role of the NO-cGMP axis was studied using morpholinosydnonimine hydrochloride (SIN-1), the diethylamine/NO complex (DETA-NONOate), the guanylyl cyclase inhibitor, 1H-{1,2,4}oxadiazolo{4,3-a}quinoxalin-1-one (ODQ), and the protein kinase G inhibitor, 8-bromoguanosine-3 0 ,5 0 -cyclic monophosphorothioate, Rp-isomer (Rp-8-BrcGMPS). NO release was studied using a fluorescence assay and O 2 K À -NO interactions by measuring nitrites.3 After a 16-h incubation with 10 nM U46619, both NCX 911 and sildenafil elicited a concentrationdependent inhibition of O 2 K À formation and gp91 phox expression, NCX 911 being more potent (IC 50 ; 0.26 nM) than sildenafil citrate (IC 50 ; 1.85 nM). These inhibitory effects were reversed by 1 mM ODQ and 10 mM Rp-8-Br-cGMPS. NCX 911 stimulated the formation of cGMP in PAECs and generated NO in a cell-free system to a greater degree than sildenafil citrate. The inhibitory effect of sildenafil was augmented by 1 mM SIN-1 and blocked partially by the eNOS inhibitor 10 mM N 5 -(1-iminoethyl)-ornithine (L-NIO). Acutely, sildenafil and NCX 911 also inhibited O 2 K À formation, again blocked by 1 mM ODQ. NCX 911 reacted with O 2 K À generated by xanthine oxidase, an effect that was inhibited by superoxide dismutase (500 U ml À1 ). 4 Since O 2 K À formation plays contributory role in ARDS, both sildenafil citrate and NCX 911 may be indicated for treating ARDS through suppression of NADPH oxidase expression and therefore of O 2 K À formation and preservation of NO bioavailability.

Obese mice have increased responses to acute ozone (O 3) exposure. T-cadherin is a binding protein for the high-molecular weight isoforms of adiponectin, an anti-inflammatory hormone that declines in obesity. The objective of the present study was to determine whether adiponectin affects pulmonary responses to O 3 , and whether these effects are mediated through T-cadherin. We performed bronchoalveolar lavage (BAL) and measured pulmonary responsiveness to methacholine after acute air or O 3 exposure (2 ppm for 3 h) in adiponectin-deficient (Adipo 2/2) or T-cadherindeficient (T-Cad 2/2) mice. O 3 increased pulmonary responses to methacholine and increased BAL neutrophils and protein to a greater extent in wild-type than in Adipo 2/2 mice, whereas T-cadherin deficiency had no effect. O 3-induced increases in BAL IL-6 and keratinocyte-derived chemokine (KC), which contribute to O 3induced pulmonary neutrophilia, were also greater in wild-type than in Adipo 2/2 mice. In contrast, responses to O 3 were not altered by transgenic overexpression of adiponectin. To determine which adiponectin isoforms are present in the lung, Western blotting was performed. The hexameric isoform of adiponectin dominated in serum, whereas BAL was dominated by the high-molecular weight isoform of adiponectin. Interestingly, serum adiponectin was greater in T-Cad 2/2 versus wild-type mice, whereas BAL adiponectin was lower in T-Cad 2/2 versus wild-type mice, suggesting that T-cadherin may be important for transit of high-molecular weight adiponectin from the blood to the lung. Our results indicate that adiponectin deficiency inhibits pulmonary inflammation induced by acute O 3 exposure, and that T-cadherin does not mediate the effects of adiponectin responsible for these events.

No abstract

No abstract