Soluble guanylate cyclase modulators blunt hyperoxia effects on calcium responses of developing human airway smooth muscle

Exposure to moderate hyperoxia in prematurity contributes to subsequent airway dysfunction and increases the risk of developing recurrent wheeze and asthma. The nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic GMP (cGMP) axis modulates airway tone by regulating airway smooth muscle (ASM) intracellular Ca²⁺ ([Ca²⁺]_i) and contractility. However, the effects of hyperoxia on this axis in the context of Ca²⁺/ contractility are not known. In developing human ASM, we explored the effects of novel drugs that activate sGC independent of NO on alleviating hyperoxia (50% oxygen)-induced enhancement of Ca²⁺ responses to bronchoconstrictor agonists. Treatment with BAY 41– 2272 (sGC stimulator) and BAY 60-2770 (sGC activator) increased cGMP levels during exposure to 50% O₂. Although 50% O₂ did not alter sGCα1 or sGCβ1 expression, BAY 60-2770 did increase sGCβ1 expression. BAY 41-2272 and BAY 60-2770 blunted Ca²⁺ responses to histamine in cells exposed to 50% O₂. The effects of BAY 41-2272 and BAY 60-2770 were reversed by protein kinase G inhibition. These novel data demonstrate that BAY 41-2272 and BAY 60-2770 stimulate production of cGMP and blunt hyperoxia-induced increases in Ca²⁺ responses in developing ASM. Accordingly, sGC stimulators/ activators may be a useful therapeutic strategy in improving bronchodilation in preterm infants.