A role for long chain myosin light chain kinase (MLCK-210) in microvascular hyperpermeability during severe burns

• Published in: Shock (Augusta, Ga.) Ga.), 2007-11, Vol.28 (5), p.589-595
• Main Authors: Reynoso, Rashell, Perrin, Rachel M, Breslin, Jerome W, Daines, Dayle A, Watson, Katherine D, Watterson, D Martin, Wu, Mack H, Yuan, Sarah
• Format: Article
• Language: English
• Subjects: Animals; Burns - enzymology; Burns - genetics; Burns - pathology; Burns - therapy; Capillary Permeability; Edema - enzymology; Edema - genetics; Edema - pathology; Edema - therapy; Endothelium, Vascular - enzymology; Endothelium, Vascular - pathology; Isoenzymes - genetics; Isoenzymes - metabolism; Male; Mice; Mice, Knockout; Myosin-Light-Chain Kinase - genetics; Myosin-Light-Chain Kinase - metabolism; Splanchnic Circulation
• ISSN: 1073-2322
• DOI: 10.1097/SHK.0b013e31804d415f

Microvascular leakage has been implicated in the pathogenesis of multiple organ dysfunction during trauma. Previous studies suggest the involvement of myosin light chain (MLC) phosphorylation-triggered endothelial contraction in the development of microvascular hyperpermeability. Myosin light chain kinase (MLCK) plays a key role in the control of MLC-phosphorylation status; thus, it is thought to modulate barrier function through its regulation of intracellular contractile machinery. The aim of this study was to further investigate the endothelial mechanism of MLC-dependent barrier injury in burns, focusing on the long isoform of MLCK (MLCK-210) that has recently been identified as the predominant isoform expressed in vascular endothelial cells. An MLCK-210 knockout mouse model was subjected to third-degree scald burn covering 25% total body surface area. The mesenteric microcirculation was observed using intravital microscopy, and the microvascular permeability was assessed by measuring the transvenular flux of fluorescein isothiocyanate-albumin. In a separate experiment, in vivo mesenteric hydraulic conductivity (Lp) was measured using the modified Landis technique. The injury caused a profound microvascular leakage, as indicated by a 2-fold increase in albumin flux and 4-fold increase in Lp at the early stages, which was associated with a high mortality within the 24-h period. Compared with wild-type control, the MLCK-210-deficient mice displayed a significantly improved survival with a greatly attenuated microvascular hyperpermeability response to albumin and fluid. These results provide direct evidence for a role of MLCK-210 in mediating burn-induced microvascular barrier injury and validate MLCK-210 as a potential therapeutic target in the treatment of burn edema.