Asthma is defined by airway inflammation and hyperresponsiveness, and contributes to morbidity and mortality worldwide. Although bronchodilation is a cornerstone of treatment, current bronchodilators become ineffective with worsening asthma severity. We investigated an alternative pathway that involves activating the airway smooth muscle enzyme, soluble guanylate cyclase (sGC). Activating sGC by its natural stimulant nitric oxide (NO), or by pharmacologic sGC agonists BAY 41-2272 and BAY 60-2770, triggered bronchodilation in normal human lung slices and in mouse airways. Both BAY 41-2272 and BAY 60-2770 reversed airway hyperresponsiveness in mice with allergic asthma and restored normal lung function. The sGC from mouse asthmatic lungs displayed three hallmarks of oxidative damage that render it NO-insensitive, and identical changes to sGC occurred in human lung slices or in human airway smooth muscle cells when given chronic NO exposure to mimic the high NO in asthmatic lung. Our findings show how allergic inflammation in asthma may impede NO-based bronchodilation, and reveal that pharmacologic sGC agonists can achieve bronchodilation despite this loss.A sthma is an inflammatory disease that causes airway hyperreactivity (AHR) and bronchoconstriction, which impedes daily life activities and, when severe, can cause death. It is the most common chronic disease of childhood, accounts for one in three emergency department visits daily, and asthma diagnoses are increasing worldwide (1). The leading treatment for relief and acute care is bronchodilation, which relies heavily on the β-adrenergic receptor-cAMP pathway. Nearly 70% of patients, however, develop resistance or tachyphylaxis to the existing β-agonist therapy (2), underscoring a need for new bronchodilators that can act through a different pharmacologic principle.The nitric oxide-soluble guanylate cyclase-cGMP pathway (NO-sGC-cGMP) is the primary signal transduction pathway for relaxing vascular smooth muscle (3). In contrast, a role for the NO-sGC-cGMP pathway in relaxing airway smooth muscle is less clear (4, 5), and bronchodilation was instead suggested to depend on glutathione nitrosothiol levels in the lung (6, 7). However, recent studies have shown that inflammation can desensitize sGC toward its natural activator, NO (8), and new drugs have become available that directly activate sGC, independent of NO (9). These developments encouraged us to re-examine the NO-sGC-cGMP pathway regarding its role in bronchodilation, its becoming damaged in inflammatory asthma, and its potential for alternative bronchodilator development under this circumstance. ResultsThe NO-sGC-cGMP Pathway Bronchodilates Human Lung. We first tested if stimulating the NO-sGC-cGMP pathway would dilate preconstricted small airways in human precision-cut lung slices (PCLS) obtained from healthy donor lungs (Fig. 1A and Table S1). Graded doses of the slow-release NO donor DETA/NO [3,3-Bis(aminoethyl)-1-hydroxy-2-oxo-1-triazene] produced bronchodilation in human PCLS similar to what was ...

Summary. Background: The nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signaling cascade is involved in the precise regulation of platelet responses. NO released from the endothelium is known to activate NO-sensitive guanylyl cyclase (NO-GC) in platelets. By the generation of cGMP and subsequent activation of cGMP-dependent protein kinase (PKG), NO-GC mediates the reduction of the intracellular calcium and inhibits platelet adhesion and aggregation. However, NO has been postulated to influence these platelet functions also via cGMP-independent mechanisms. Objective: We studied the effect of NO on platelets lacking NO-sensitive guanylyl cyclase with regards to aggregation, adhesion, calcium mobilization and bleeding time. Methods and results: Here, we show that NO signaling leading to inhibition of agonist-induced platelet aggregation is totally abrogated in platelets from mice deficient in NO-GC (GCKO). Even at millimolar concentrations none of the several different NO donors inhibited collagen-induced aggregation of GCKO platelets. In addition, NO neither affected adenosine 5¢-diphosphate (ADP)-induced adhesion nor thrombin-induced calcium release in GCKO platelets. Although the NO-induced cGMP signal transduction was totally abrogated cyclic adenosine monophosphate (cAMP) signaling was still functional; however, cGMP/cAMP crosstalk was disturbed on the level of phosphodiesterase type 3 (PDE3). These in vitro data are completed by a reduced bleeding time indicating the lack of NO effect in vivo. Conclusions: We conclude that NO-GC is the only NO receptor in murine platelets mediating the inhibition of calcium release, adhesion and aggregation: lack of the enzyme leads to disturbance of primary hemostasis.

No abstract

No abstract