Effects of Rho‐kinase inactivation on eosinophilia and hyper‐reactivity in murine airways by allergen challenges

Abstract

Background A small GTPase, Rho, and its target molecule, Rho‐kinase, play an important role in the cell functions, including contractility, chemotaxis, adhesion, and migration. It is generally considered that eosinophilic inflammation and hyper‐reactivity to methacholine in airways are fundamental to the pathophysiology of bronchial asthma. Objective This study was designed to determine whether the Rho/Rho‐kinase pathways are involved in the eosinophil recruitment and airway hyper‐reactivity. We investigated inhibitory effects of fasudil, a specific inhibitor of Rho‐kinase, on acute allergic inflammation in mice. Methods BALB/c mice were sensitized and challenged with ovalbumin (OVA). OVA‐challenged mice were treated orally with fasudil (3, 10, 30 mg/kg) or saline before each OVA challenge. Total cell counts, differential cell counts, cytokines, and chemokines levels were measured in bronchoalveolar lavage (BAL), and lungs were examined histologically. Moreover, respiratory resistance in response to methacholine was measured. Results When fasudil was administrated to OVA‐challenged mice, increased cell numbers of total cells and eosinophils were significantly attenuated in a dose‐dependent manner. However, inflammatory cells other than eosinophils were not affected by fasudil. Fasudil caused a dose‐dependent inhibition in increased levels of IL‐5, IL‐13, and eotaxin in BAL fluid by OVA challenges. Histological analysis of the airways revealed that both infiltration of inflammatory cells and goblet cell hyperplasia were significantly suppressed in fasudil treatment. Furthermore, fasudil significantly suppressed the augmented responsiveness to methacholine induced by OVA challenges. Conclusion Oral administration of fasudil inhibits eosinophil recruitment, goblet cell hyperplasia and airway hyper‐reactivity by allergen challenges. These effects of this agent may be mediated by suppressing a chemokine and cytokines related to the pathophysiology of bronchial asthma such as eotaxin, IL‐5, and IL‐13. Our findings provide evidence that inhibition of the Rho/Rho‐kinase pathway may be beneficial for bronchial asthma.