0398: Role of non-muscular myosin light chain kinase (nmMLCK) in the inflammation associated with intermittent hypoxia

Intermittent hypoxia (IH) alters endothelial function favoring inflammation and could accelerate atherosclerosis-induced cardiovascular diseases. A protein that may play a role in this process is the non-muscular myosin light chain kinase (nmMLCK). The deficiency of this kinase protects mice from death in septic choc models and prevents the atherosclerosis in mice fed with a high fat dietary. The aim of this study was to analyze the implication of nmMLCK in the vascular effects and the inflammation induced by IH. Human aortic endothelial cells (HAoECs) and endothelial cells isolated from wild type or deficient nmMLCK mice were exposed to 6 h of IH, which include 30 min of hypoxia (O2 5%) followed by 30 min of normoxia (O2 21%), in the absence or the presence of ML-7 (5 μM), a nmMLCK inhibitor. After the stimulation, we evaluated the production of the superoxide anion, nitric oxide (NO), the pro-inflammatory cytokine IL-6, and also the activation of the NF-κB pathway. IH treatment increased superoxide, NO and IL-6 production in HAoECs. However, while the nmMLCK inhibitor ML-7 had no effect on the IH-induced superoxide anion increase, it decreased both NO and IL-6 production. Furthermore, p65-NF-κB pathway was activated by IH in a ML-7-insensitive manner in HAoECs. By using aortic endothelial cells from nmMLCK deficient mice, we showed that nmMLCK deletion abolished the increase of superoxide anion induced by IH indicating that the presence and not the kinase activity of nmMLCK is crucial to regulate oxidative stress induced by IH. In conclusion, IH induced oxidative and nitrative stresses as well as changes in inflammatory secretome of human endothelial cells. In this experimental model of IH, both nitrative and pro-inflammatory cytokine secretion are sensitive to inhibition of the activity of nmMLCK and oxidative stress require its presence. These results suggest strength the notion that nmMLCK participates to the IH-induced inflammatory process in endothelial cells.