Role of Non‐muscle Myosin Light Chain Kinase in Neutrophil‐mediated Intestinal Barrier Dysfunction During Thermal Injury

Abstract

Neutrophils and non‐muscle myosin light chain kinase (nmMLCK) have been implicated in intestinal microvascular leakage and mucosal hyperpermeability in inflammation and trauma. The aim of the study was to characterize the role of nmMLCK in neutrophil‐dependent gut barrier dysfunction following thermal injury. Histopathological examination revealed that severe burns led to intestinal mucosa inflammation characterized by neutrophil infiltration, epithelial contraction, and narrow villi with blunt brush boarders and loss of goblet cells. These abnormalities were diminished in nmMLCK−/− mice. Intravital microscopic studies showed significant leukocyte adhesion in intestinal microvessels post‐burn, a response blunted in the absence of nmMLCK. Functionally, thermal injury significantly increased the gut lumen‐to‐blood transport of FITC‐dextran, which was attenuated by either neutrophil depletion or nmMLCK deficiency. Stimulation of Caco‐2 cells with activated neutrophils caused a decrease in transcellular electric resistance coupled with MLC phosphorylation, actomyosin ring condensation, and claudin‐1 internalization. The responses were prevented by MLCK inhibition. Taken together, the results suggest that nmMLCK plays an important role in neutrophil‐dependent intestinal barrier dysfunction during inflammatory injury. Supported by NIH RO1 HL‐96640, HL‐61507 and HL‐70752.