A Role for Long Chain Myosin Light Chain Kinase (Mlck-210) in Microvascular Hyperpermeability During Severe Burns

Abstract

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.

STIM1 Controls Endothelial Barrier Function Independently of Orai1 and Ca 2+ Entry

“…Introduction of constitutively active MLCK into coronary venular endothelial cells increased phosphorylation of MLC and increased transendothelial flux of albumin across endothelial monolayers (58). Mice with an endothelial-specific knockout of MLCK (MLCK210) have reduced microvascular hyperpermeability in models of atherosclerosis or in response to severe burns (61, 62). However, another study with endothelial-specific MLCK-knockout mice found that the increase of microvascular endothelial permeability in response to lipopolysaccharides was not dependent on MLCK(63), in agreement with our study here.…”

Internalization of eNOS and NO delivery to subcellular targets determine agonist-induced hyperpermeability

“…The mechanisms by which eNOS internalization and NO production, possibly via soluble guanylyl cyclase, modify junctional proteins to induce hyperpermeability to proteins remain unresolved. It is plausible that NO production in the cytosol may influence cytoskeletal proteins; thus, promoting EC contraction and hyperpermeability (20)(21)(22). One may alternatively speculate that NO-driven S-nitrosylation of proteins may induce changes in trafficking and permeability.…”

Nonmuscle Myosin Light Chain Kinase: A Key Player in Intermittent Hypoxia‐Induced Vascular Alterations

“…In endothelial cells, this retraction is linked to endothelial permeability enhancement and vascular leakage under proinflammatory conditions. In this context, an activation of the nmMLCK has been linked to several pathophysiological conditions, such as vascular inflammation and atherosclerosis,18 acute lung injury,19 endotoxic shock,20 and severe burns 21…”