ROCK insufficiency attenuates ozone-induced airway hyperresponsiveness in mice

Abstract

Ozone causes airway hyperresponsiveness (AHR) and pulmonary inflammation. Rho kinase (ROCK) is a key regulator of smooth muscle cell contraction and inflammatory cell migration. To determine the contribution of the two ROCK isoforms ROCK1 and ROCK2 to ozone-induced AHR, we exposed wild-type, ROCK1(+/-), and ROCK2(+/-) mice to air or ozone (2 ppm for 3 h) and evaluated mice 24 h later. ROCK1 or ROCK2 haploinsufficiency did not affect airway responsiveness in air-exposed mice but significantly reduced ozone-induced AHR, with a greater reduction in ROCK2(+/-) mice despite increased bronchoalveolar lavage (BAL) inflammatory cells in ROCK2(+/-) mice. Compared with wild-type mice, ozone-induced increases in BAL hyaluronan, a matrix protein implicated in ozone-induced AHR, were lower in ROCK1(+/-) but not ROCK2(+/-) mice. Ozone-induced increases in other inflammatory moieties reported to contribute to ozone-induced AHR (IL-17A, osteopontin, TNFα) were not different in wild-type vs. ROCK1(+/-) or ROCK2(+/-) mice. We also observed a dose-dependent reduction in ozone-induced AHR after treatment with the ROCK1/ROCK2 inhibitor fasudil, even though fasudil was administered after induction of inflammation. Ozone increased pulmonary expression of ROCK2 but not ROCK1 or RhoA. A ROCK2 inhibitor, SR3677, reduced contractile forces in primary human airway smooth muscle cells, confirming a role for ROCK2 in airway smooth muscle contraction. Our results demonstrate that ozone-induced AHR requires ROCK. Whereas ROCK1-dependent changes in hyaluronan may contribute to ROCK1's role in O3-induced AHR, the role of ROCK2 is downstream of inflammation, likely at the level of airway smooth muscle contraction.

Ozone-induced airway hyperresponsiveness: roles of ROCK isoforms

“…They reported that insufficiency of either ROCK1 or ROCK2 resulted in a reduction in AHR without having an effect on inflammation. The article reviewed herein (14) extends these findings and sheds additional light into the mechanism of O 3 -induced AHR.…”

Kinases as Novel Therapeutic Targets in Asthma and Chronic Obstructive Pulmonary Disease

“…This drug inhibits AHR, bronchoconstriction, and eosinophilic inflammation in a mouse model of acute allergic inflammation (Henry et al, 2005). Another ROCK inhibitor, fasudil, reduces airway inflammation and AHR induced by ozone exposure in mice (Kasahara et al, 2015). There is growing evidence that ROCK inhibitors inhibit fibrosis and so may reduce airway remodeling in airway diseases (Knipe et al, 2015).…”

The Next Generation of Risk Assessment Multi-Year Study—Highlights of Findings, Applications to Risk Assessment, and Future Directions

“…Evidence for a causal relationship between a specific AOP and adverse effects includes pharmacologic intervention to block identified pathway changes, use of knock-in and knock-out models, or identification of pathway polymorphisms and concomitant amelioration of severity or incidence of the specified adverse outcomes (U.S. EPA 2014; French et al 2015; Hatzimichael and Crook 2013; Kasahara et al 2015; McCullough et al 2014; McHale et al 2012; Smith 2010; Thomas R et al 2014; Wu et al 2015). …”