Role of Rho kinase and actin filament in the increased vascular permeability of skin venules in rats after scalding

Objective: To investigate the role of the Small GTPase Rho and endothelial cytoskeleton in the increased vascular permeability of rat skin after scalding. Methods: Rats were subjected to scalding local ventral skin and a venule was isolated from scalded skin and cannulated by micropipette. The venular permeability was measured with a fluorescence ratio technique and expressed with the permeability coefficient to albumin (Pa). The venular F-actin filaments were observed by staining with rhodamine phalloidin and laser confocal scanning microscopy. A specific Rho kinase inhibitor Y-27632 was added into vessel bathing solution or preincubated with vessels to evaluate the role of Rho kinase in regulating of vascular barrier function. Results: Scalding increased Pa value of skin venule about threefold compared to normal skin venules (P<0.01) and was maintained for 120 min. Inhibition of Rho kinase with Y-27632 (30 μmol/l in low-concentration group; 60 μmol/l in high-concentration group) significantly attenuated the hyperpermeability responses to scalding in a dose dependent fashion. A prominent peripheral actin rim (PAR) existed at the outer area of endothelial cells and apparently delineated the cell-to-cell borders. In the control group, the PARs were arranged smoothly and fairly continuously. However, occasionally PARs did show focal interruption with focal fluorescein isothiocyanate (FITC)-albumin leakage. In the burned group, PARs were less organized and accompanied by a large amount of FITC-albumin leakage. Inhibition of Rho kinase with Y-27632 dramatically reduced Pa value with recovery of actin filament arrangement in venule after scalding. Conclusion: Burn leads to dermal venular permeability increase with endothelial cytoskeleton depolymerization and disruption. Rho signal transduction pathway is involved in these responses.