Soluble guanylyl cyclase contributes to ventilator-induced lung injury in mice

Abstract

(HV T) ventilation causes pulmonary endothelial barrier dysfunction. HV T ventilation also increases lung nitric oxide (NO) and cGMP. NO contributes to HV T lung injury, but the role of cGMP is unknown. In the current study, ventilation of isolated C57BL/6 mouse lungs increased perfusate cGMP as a function of V T. Ventilation with 20 ml/kg V T for 80 min increased the filtration coefficient (K f), an index of vascular permeability. The increased cGMP and Kf caused by HVT were attenuated by nitric oxide synthase (NOS) inhibition and in lungs from endothelial NOS knockout mice. Inhibition of soluble guanylyl cyclase (sGC) in wild-type lungs (10 M ODQ) also blocked cGMP generation and inhibited the increase in K f, suggesting an injurious role for sGC-derived cGMP. sGC inhibition also attenuated lung Evans blue dye albumin extravasation and wetto-dry weight ratio in an anesthetized mouse model of HV T injury. Additional activation of sGC (1.5 M BAY 41-2272) in isolated lungs at 40 min increased cGMP production and K f in lungs ventilated with 15 ml/kg V T. HVT endothelial barrier dysfunction was attenuated with a nonspecific phosphodiesterase (PDE) inhibitor (100 M IBMX) as well as an inhibitor (10 M BAY 60-7550) specific for the cGMPstimulated PDE2A. Concordantly, we found a V T-dependent increase in lung cAMP hydrolytic activity and PDE2A protein expression with a decrease in lung cAMP concentration that was blocked by BAY 60-7550. We conclude that HV T-induced endothelial barrier dysfunction resulted from a simultaneous increase in NO/sGC-derived cGMP and PDE2A expression causing decreased cAMP. nitric oxide; guanosine 3Ј,5Ј-cyclic monophosphate; phosphodiesterase 2A; adenosine 3Ј,5Ј-cyclic monophosphate; atrial natriuretic peptide; endothelial permeability MECHANICAL VENTILATION is necessary to support patients with the acute respiratory distress syndrome. However, mechanical ventilation also contributes to lung injury by a mechanism that directly correlates with tidal volume (V T ) (39). High V T (HV T ) ventilation causes pulmonary endothelial barrier dysfunction and edema, leading to ventilator-induced lung injury (VILI) (42). The mechanisms behind this injury are complex, but it is evident that HV T -induced changes in intracellular signaling play a significant role (12).Recent evidence from animal models of VILI implicates nitric oxide (NO) in the pathogenesis of HV T endothelial barrier dysfunction (4,6,29). NO is synthesized by three isoforms of nitric oxide synthase (NOS): endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS. Ventilatory lung stretch stimulates pulmonary microvascular NO production by an increase in eNOS expression (6), phosphorylation of eNOS by phosphatidylinositol 3-kinase-induced protein kinase B activation (22), or induction of iNOS expression (13,29). Once produced by NOS, NO reacts with reactive oxygen species (ROS) to generate peroxynitrite, a toxic free radical that contributes to VILI (29). NO can also stimulate endothelial soluble guanylyl cyclase (sGC) to generat...

Knockdown of lung phosphodiesterase 2A attenuates alveolar inflammation and protein leak in a two-hit mouse model of acute lung injury

“…More recently, increased lung PDE2A expression was found in a murine model of pneumococcal pneumonia (52). In both studies, pharmacological PDE2A inhibition attenuated the associated ALI (39,52).…”

“…More recently, increased lung PDE2A expression was found in a murine model of pneumococcal pneumonia (52). In both studies, pharmacological PDE2A inhibition attenuated the associated ALI (39,52).On the basis of these observations, we hypothesized that IT LPS would potently increase lung PDE2A expression. Because of our observation regarding VILI-induced PDE2A upregulation (39), we wondered whether the combination of IT LPS and high tidal volume (HV T ) ventilation would produce a more severe injury through an increase in lung PDE2A expression.…”

“…LPS, through Toll-like receptor-4 signaling, was shown to cause increased NO from phosphorylated endothelial (eNOS) (11) and inducible nitric oxide synthase (iNOS) (24,31) in alveolar macrophages, neutrophils, epithelium, and endothelium. NO from both eNOS and iNOS was found to play a major pathogenic role in ALI from LPS (24,31,42) and in ventilator-induced lung injury (VILI) (33,39). These injurious effects of endogenous NO have been attributed to a reaction with superoxide to generate peroxynitrite (31,33).…”

“…These injurious effects of endogenous NO have been attributed to a reaction with superoxide to generate peroxynitrite (31,33). In both LPS-induced ALI (47) and VILI (39), however, NO also activates soluble guanylyl cyclase (sGC), increasing production of cGMP in multiple cell types including endothelium (39), epithelium (9,17), and macrophages (3).…”

“…The effects of cGMP signaling in ALI are complex, depending on cell type, intracellular compartmentalization, and the downstream cGMP targets (39). These targets include cyclic nucleotide-gated cation channels, cGMP-sensitive phosphodiesterases (PDEs), and the cGMP-dependent protein kinase (PKG) (20).…”