American journal of physiology. Lung cellular and molecular physiology
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Am. J. Physiol. Lung Cell Mol. Physiol. · Nov 2011
Cinaciguat, a soluble guanylate cyclase activator, augments cGMP after oxidative stress and causes pulmonary vasodilation in neonatal pulmonary hypertension.
Although inhaled NO (iNO) therapy is often effective in treating infants with persistent pulmonary hypertension of the newborn (PPHN), up to 40% of patients fail to respond, which may be partly due to abnormal expression and function of soluble guanylate cyclase (sGC). To determine whether altered sGC expression or activity due to oxidized sGC contributes to high pulmonary vascular resistance (PVR) and poor NO responsiveness, we studied the effects of cinaciguat (BAY 58-2667), an sGC activator, on pulmonary artery smooth muscle cells (PASMC) from normal fetal sheep and sheep exposed to chronic intrauterine pulmonary hypertension (i.e., PPHN). We found increased sGC α(1)- and β(1)-subunit protein expression but lower basal cGMP levels in PPHN PASMC compared with normal PASMC. ⋯ After birth, cinaciguat caused a significantly greater fall in PVR than either 100% oxygen, iNO, or ACh. We conclude that cinaciguat causes more potent pulmonary vasodilation than iNO in experimental PPHN. We speculate that increased NO-insensitive sGC may contribute to the pathogenesis of PPHN, and cinaciguat may provide a novel treatment of severe pulmonary hypertension.
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Am. J. Physiol. Lung Cell Mol. Physiol. · Nov 2011
Rho-kinase inhibition alleviates pulmonary hypertension in transgenic mice expressing a dominant-negative type II bone morphogenetic protein receptor gene.
Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by a sustained elevation in the pulmonary artery pressure and subsequent right heart failure. The activation of Rho/Rho-kinase activity and the beneficial effect of Rho-kinase inhibition have been demonstrated in several experimental models of pulmonary hypertension. However, it remains unclear whether Rho-kinase inhibitors can also be used against pulmonary hypertension associated with mutations in the type II bone morphogenetic protein receptor (BMPRII) gene. ⋯ Fasudil, a Rho-kinase inhibitor, significantly decreased RVSP, alleviated RV hypertrophy and muscularization of small pulmonary arteries, and improved blood flow in SM22-tet-BMPR2(R899X) mice, although it did not alter Smad signaling. Our study demonstrates that Rho/Rho-kinase signaling is activated via a Smad-independent pathway in an animal model of pulmonary hypertension with a BMPRII mutation in the cytoplasmic tail domain. Rho-kinase inhibition is therefore a possible therapeutic approach for the treatment of PAH associated with genetic mutation.
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Am. J. Physiol. Lung Cell Mol. Physiol. · Nov 2011
Positive end-expiratory pressure and surfactant decrease lung injury during initiation of ventilation in fetal sheep.
The initiation of ventilation in preterm, surfactant-deficient sheep without positive end-expiratory pressure (PEEP) causes airway injury and lung inflammation. We hypothesized that PEEP and surfactant treatment would decrease the lung injury from initiation of ventilation with high tidal volumes. Fetal sheep at 128-day gestational age were randomized to ventilation with: 1) no PEEP, no surfactant; 2) 8-cmH(2)O PEEP, no surfactant; 3) no PEEP + surfactant; 4) 8-cmH(2)O PEEP + surfactant; or 5) control (2-cmH(2)O continuous positive airway pressure) (n = 6-7/group). ⋯ Surfactant administration further decreased some cytokine mRNAs and changed the distribution of early growth response protein-1 expression. The use of PEEP during initiation of ventilation at birth decreased early mediators of lung injury. Surfactant administration changed the distribution of injury and had a moderate additive protective effect.
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Am. J. Physiol. Lung Cell Mol. Physiol. · Oct 2011
Regulatory domain phosphorylation to distinguish the mechanistic basis underlying acute CFTR modulators.
Modulator compounds intended to overcome disease-causing mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) show significant promise in clinical testing for cystic fibrosis. However, the mechanism(s) of action underlying these compounds are not fully understood. Activation of CFTR ion transport requires PKA-regulated phosphorylation of the regulatory domain (R-D) and dimerization of the nucleotide binding domains. ⋯ In contrast, VRT-532 moderately activated CFTR short-circuit current and strongly potentiated forskolin-mediated current. Combined with the result that UC(CF)-152, but not VRT-532 or VX-770, acts by increasing CFTR R-D phosphorylation, these findings indicate that potentiation of endogenous cAMP-mediated activation of mutant CFTR is not due to a pathway involving augmented R-D phosphorylation. This study presents an assay useful to distinguish preclinical compounds by a crucial mechanism underlying CFTR activation, delineates two types of compound able to acutely augment CFTR activity (e.g., activators and potentiators), and demonstrates that a number of different mechanisms can be successfully employed to activate mutant CFTR.
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Am. J. Physiol. Lung Cell Mol. Physiol. · Oct 2011
Caveolin-1 in cytokine-induced enhancement of intracellular Ca(2+) in human airway smooth muscle.
Diseases such as asthma are characterized by airway hyperresponsiveness. Enhanced airway smooth muscle (ASM) intracellular Ca(2+) ([Ca(2+)](i)) response to agonist stimulation leading to increased airway constriction has been suggested to contribute to airway hyperresponsiveness. Caveolae are flask-shaped plasma membrane invaginations that express the scaffolding protein caveolin and contain multiple proteins important in [Ca(2+)](i) signaling (e.g., agonist receptors, ion channels). ⋯ However, disruption of caveolae using caveolin-1 suppression via small-interfering RNA resulted in significant blunting of agonist-induced [Ca(2+)](i) responses of vehicle and TNF-α-exposed cells. These functional data were correlated to the presence of TNFR(1) receptor (but not the IL-4/IL-13 receptor) within caveolae. Overall, these results indicate that caveolin-1 plays an important role in airway inflammation by modulating the effect of specific cytokines on [Ca(2+)](i).