Rho-kinase signaling regulates pulmonary infiltration of neutrophils in abdominal sepsis via attenuation of CXC chemokine formation and Mac-1 expression on neutrophils

Excessive neutrophil infiltration is a major component in septic lung injury, although the signaling mechanisms behind pulmonary recruitment of neutrophils in polymicrobial sepsis remain elusive. Herein, we hypothesized that Rho-kinase activity may play a significant role in pulmonary neutrophil recruitment and tissue damage in abdominal sepsis. Male C57BL/6 mice were treated with the Rho-kinase inhibitor Y-27632 (0.5 or 5 mg/kg) before cecal ligation and puncture (CLP). Bronchoalveolar lavage fluid and lung tissue were harvested for analysis of neutrophil infiltration, as well as edema and CXC chemokine formation. Blood was collected for analysis of Mac-1 on neutrophils and CD40L on platelets as well as soluble CD40L and matrix metalloproteinase 9 (MMP-9) in plasma. Cecal ligation and puncture triggered significant pulmonary damage characterized by neutrophil infiltration, increased levels of CXC chemokines, and edema formation in the lung. Furthermore, CLP upregulated Mac-1 expression on neutrophils, decreased CD40L on platelets, and increased soluble CD40L and MMP-9 in the circulation. Interestingly, inhibition of Rho-kinase dose-dependently decreased CLP-induced neutrophil expression of Mac-1, formation of CXC chemokines and edema, as well as neutrophil infiltration and tissue damage in the lung. Moreover, Rho-kinase inhibition significantly reduced sepsis-provoked gene expression of CXC chemokines in alveolar macrophages. In contrast, Rho-kinase inhibition had no effect on platelet shedding of CD40L or plasma levels of MMP-9 in septic mice. In conclusion, these data demonstrate that the Rho-kinase signaling pathway plays a key role in regulating pulmonary infiltration of neutrophils and tissue injury via regulation of CXC chemokine production in the lung and Mac-1 expression on neutrophils in abdominal sepsis.