Myosin Light Chain Kinase Deletion Worsens Lung Permeability and Increases Mortality in Pneumonia-Induced Sepsis

Abstract

Increased epithelial permeability in sepsis is mediated via disruptions in tight junctions, which are closely associated with the perijunctional actin-myosin ring. Genetic deletion of myosin light chain kinase (MLCK) reverses sepsis-induced intestinal hyperpermeability and improves survival in a murine model of intra-abdominal sepsis. In an attempt to determine the generalizability of these findings, this study measured the impact of MLCK deletion on survival and potential associated mechanisms following pneumonia-induced sepsis. MLCK −/− and wild-type mice underwent intratracheal injection of Pseudomonas aeruginosa. Unexpectedly, survival was significantly worse in MLCK −/− mice than wild-type mice. This was associated with increased permeability to Evans blue dye in bronchoalveolar lavage fluid but not in tissue homogenate, suggesting increased alveolar epithelial leak. In addition, bacterial burden was increased in bronchoalveolar lavage fluid. Cytokine array using whole-lung homogenate demonstrated increases in multiple proinflammatory and anti-inflammatory cytokines in knockout mice. These local pulmonary changes were associated with systemic inflammation with increased serum levels of IL-6 and IL-10 and a marked increase in bacteremia in MLCK −/− mice. Increased numbers of both bulk and memory CD4 + T cells were identified in the spleens of knockout mice, with increased early and late activation. These results demonstrate that genetic deletion of MLCK unexpectedly increases mortality in pulmonary sepsis, associated with worsened alveolar epithelial leak and both local and systemic inflammation. This suggests that caution is required in targeting MLCK for therapeutic gain in sepsis.

Association between intracellular adenosine triphosphate content of CD4+ T lymphocytes and mortality in sepsis patients: A prospective observational study

“…The immune system plays a crucial role in sepsis, and mounting evidence suggests the occurrence of both hyperinflammatory and immunosuppressive responses in septic patients. 5 , 6 , 7 Apart from the initial hyperinflammatory response, a considerable number of sepsis patients develop sepsis‐associated immunosuppression, which has been implicated in disease progression and adverse outcomes, 6 , 8 , 9 this immunosuppression is characterized by dysfunctional T cell responses, including apoptosis, 10 exhaustion, 11 and impaired effector function, 12 further exacerbating the disease's severity. Several biomarkers, including lymphocyte counts, CD4 + cell counts, monocyte human leukocyte antigen DR (mHLA‐DR), programmed death receptor‐1 (PD‐1), B and T lymphocyte attenuator (BTLA), neutrophil chemotaxis activity, and endogenous cytokines, have been proposed to monitor immune status and predict outcomes in sepsis.…”

“…The immune system plays a crucial role in sepsis, and mounting evidence suggests the occurrence of both hyperinflammatory and immunosuppressive responses in septic patients 5‐7 . Apart from the initial hyperinflammatory response, a considerable number of sepsis patients develop sepsis‐associated immunosuppression, which has been implicated in disease progression and adverse outcomes, 6,8,9 this immunosuppression is characterized by dysfunctional T cell responses, including apoptosis, 10 exhaustion, 11 and impaired effector function, 12 further exacerbating the disease's severity.…”