Activation of Endothelial Pro-resolving Anti-Inflammatory Pathways by Circulating Microvesicles from Non-muscular Myosin Light Chain Kinase-Deficient Mice.

Abderahim Gaceb,Luisa Vergori,M C Martinez,Ramaroson Andriantsitohaina

doi:10.3389/fphar.2016.00322

Abstract

Microvesicles, small membrane vesicles released from cells, have beneficial and/or deleterious effects in sepsis. We previously reported that non-muscle myosin light chain kinase (nmMLCK) deletion protects mice against endotoxic shock by reducing inflammation. Here, we have evaluated the consequences of nmMLCK deletion on microvesicle phenotypes and their effects on mouse aortic endothelial cells in association with vascular inflammation and endothelial dysfunction during endotoxic shock induced by lipopolysaccharide in mice. Treatment with lipopolysaccharide induced an increase in levels of circulating microvesicles in wild type but not in nmMLCK-deficient mice. Microvesicles from nmMLCK-deficient mice (MVsnmMLCK-/-) prevented the inflammatory effects of lipopolysaccharide with concomitant increase of anti- inflammatory and reduction of pro-inflammatory secretome in mouse aortic endothelial cells. In addition, MVsnmMLCK-/- reduced the efficacy of lipopolysaccharide to increase aortic oxidative and nitrosative stresses as well as macrophage infiltration in the aorta. Moreover, MVsnmMLCK-/- prevented ex vivo endothelial dysfunction, vascular hyporeactivity, and in vivo overproduction of nitric oxide in heart and liver in response to lipopolysaccharide. Altogether, these findings provide evidence that nmMLCK deletion generates circulating microvesicles displaying protective effects by activating endothelial pro-resolving anti-inflammatory pathways allowing the effective down-regulation of oxidative and nitrative stresses associated with endotoxic shock. Thus, nmMLCK plays a pivotal role in susceptibility to sepsis via the control of cellular activation and release of circulating microvesicles.

Highlights

Sepsis is defined as a clinical syndrome characterized by a systemic inflammatory response to infection that leads to microvascular thrombosis, vascular hyporeactivity, and endothelial dysfunction resulting in multiple organ dysfunction (Annane et al, 2005; Schouten et al, 2008)
Treatment with LPS induced an increase in levels of circulating MVs in wild type mice especially those derived from platelets, endothelial cells, erythrocytes, and leukocytes without affecting procoagulant MVs (Figures 1A–F)
The increase in levels of platelet, endothelial, and leukocyte-derived MVs was less pronounced in non-muscle myosin light chain kinase (nmMLCK)−/− mice, whereas no changes were observed in TER+-derived MVs

Summary

Introduction

Sepsis is defined as a clinical syndrome characterized by a systemic inflammatory response to infection that leads to microvascular thrombosis, vascular hyporeactivity, and endothelial dysfunction resulting in multiple organ dysfunction (Annane et al, 2005; Schouten et al, 2008). Among the potential new targets for sepsis therapy, a new protein has been found to play an important role during endotoxic shock in different experimental models of sepsis (Ralay Ranaivo et al, 2007) This protein, the nmMLCK, belongs to a family of protein kinases whose main function is to phosphorylate the 20 kDa regulatory MLC-2 at Ser-19 for ATPase driven actin-myosin contraction. Soriano et al (2005) have shown that elevated levels of circulating MVs negatively correlated with sequential organ failure assessment score and with survival of septic patients. These reports suggest that, in sepsis, MVs are effectors that participate in the pathogenesis and outcome of the disease

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Conclusion