Rho‐kinase inhibitors protect against neonatal hyperoxia‐induced airway hyperreactivity in a rat pup model: Role of prostaglandin F_2α

Abstract

Background Oxygen therapy in preterm neonates is associated with airway hyperreactivity. The role of Rho/Rho‐kinase smooth muscle signaling in hyperoxia‐induced airway hyperreactivity remains understudied. We hypothesized that inhibition of Rho‐kinase will attenuate airway hyperreactivity induced by neonatal hyperoxia. Methods Newborn rats were raised in hyperoxia (>95% O2) or ambient air (AA) for 7 days. Subgroups were injected with a Rho‐kinase inhibitor: Y‐27632 (10 mg·kg−1·day−1) or fasudil (10 mg·kg−1·day−1), or a FP receptor antagonist ‐ AS604872 (30 mg·kg−1·day−1). After exposures, tracheal cylinders were prepared for in vitro wire myography. Contraction to methacholine or PGF2α was measured in the presence or absence of tissue‐bath Y‐27632, fasudil, or AS604872. Lung PGF2α levels, Rho‐kinase protein level and Rho‐kinase 1 activity were measured by ELISA. Results Tracheal smooth muscle contraction was significantly greater in hyperoxic compared to AA groups. Both, Y‐27632 and fasudil significantly decreased contractility to MCh or PGF2α in hyperoxic groups versus hyperoxic controls (p < 0.001), but did not alter AA group responses. Inhibition of FP receptors attenuated responses to PGF2α. Hyperoxia significantly increased lung PGF2α compared to AA (p < 0.01), but Rho‐kinase inhibition did not influence PGF2α level. Rho‐kinase protein level (p < 0.001) and activity (p < 0.01), were increased by hyperoxia, but blockade of FP receptor reduced the Rho‐kinase 1 activity (p < 0.05) under hyperoxic condition. Conclusions This study demonstrates an active role of Rho/Rho‐kinase signaling on hyperoxia‐induced airway hyperreactivity. These findings suggest that Rho‐kinase inhibitors might serve as an effective therapy for hyperoxia‐induced airway hyperreactivity.

Quercetin supplementation attenuates airway hyperreactivity and restores airway relaxation in rat pups exposed to hyperoxia

“…14 Another study revealed that quercetin reduces myocardial Rho-kinase activity in rats, while in previous study we found that hyperoxia increases Rho-kinase expression and activity, and the administration of Rho-kinase inhibitors was protective against hyperoxia-induced airway hyperreactivity. 4,26 However, future studies are needed to undertake to clarify the involvement of quercetin on Rho/Rho-kinase signaling in its protective effect under hyperoxic conditions.…”

“…Rings of 3 mm length were isolated from the mid-trachea and transferred into a tissue-organ bath containing KH buffer (10 mL) at 37°C, for in vitro force contraction measurements, as previously described. 4…”

“…Rings of 3 mm length were isolated from the mid-trachea and transferred into a tissue-organ bath containing KH buffer (10 mL) at 37°C, for in vitro force contraction measurements, as previously described. 4 Tracheal rings were suspended between a stainless-steel wire triangle at the bottom of the tissue bath and a forcedisplacement transducer. TSM tension was measured by the four-channel organ bath system (DMT-750TOBS, Danish Myo Technology, Denmark) connected to Power Lab/8SP (AD Instruments Inc., CO, USA) and interfaced with computer-monitored recordings (Chart 8.0 software).…”

“…3 Exposure of newborn rodents to hyperoxia represents an established model that reproduces the BPD phenotype including airway hyperreactivity and alveolar simplification, and also induces inflammation. [4][5][6][7] Previously, we have shown that hyperoxia decreases relaxant responses due to reduced nitric oxide (NO) production, a major component of bronchodilation. 5,8 Reduced relaxant responses of ASM in an experimental model of BPD were associated with increased contractile responses which involved upregulation of Ca 2+ sensitization signaling.…”

“…5,8 Reduced relaxant responses of ASM in an experimental model of BPD were associated with increased contractile responses which involved upregulation of Ca 2+ sensitization signaling. 4 Moreover, neonatal hyperoxia induces upregulation of proinflammatory cytokines…”