Rho proteins are involved in the regulation of several cellular functions. Data from in vitro studies suggest that RhoA could be involved in the inflammatory response. We investigated the role of RhoA and its downstream effector Rho kinase in intestinal inflammation.

Activation of RhoA was assessed by pull-down assays. A specific inhibitor of Rho kinase, Y-27632, was used to examine the role of Rho kinase in inflammatory response in vivo and in vitro by molecular biology and by immunological and biochemical approaches.

Increased activation of RhoA was found in inflamed intestinal mucosa of patients with Crohn’s disease and of rats with 2,4,6-trinitrobenzene sulfonic acid-induced colitis. Oral administration of Y-27632 in rats significantly reduced the colonic inflammation. In vitro, activation of RhoA alone was sufficient to induce tumor necrosis factor production. Y-27632 inhibited production of tumor necrosis factor-α and interleukin-1β by lamina propria and peripheral blood mononuclear cells. Rho kinase inhibition prevented nuclear factor κB activation and I-κB phosphorylation and degradation. We showed that Rho kinase associates with and activates I-κB kinase α and that Y-27632 prevents I-κB kinase activation.

Our study provides the first evidence that Rho kinase activates I-κB kinase and, thus, nuclear factor κB, suggesting a key role of Rho kinase in inflammatory responses and intestinal inflammation. Specific inhibition of Rho kinase may be a promising approach for the treatment of patients with Crohn’s disease.