Mitogen-Activated Protein Kinases Regulate Susceptibility to Ventilator-Induced Lung Injury

Background: Mechanical ventilation causes ventilator-induced lung injury in animals and humans. Mitogen-activated protein kinases have been implicated in ventilator-induced lung injury though their functional significance remains incomplete. We characterize the role of p38 mitogen-activated protein kinase/mitogen activated protein kinase kinase-3 and c-jun-NH2-terminal kinase-1 in ventilator-induced lung injury and investigate novel independent mechanisms contributing to lung injury during mechanical ventilation. Methodology and Principle Findings: C57/BL6 wild-type mice and mice genetically deleted for mitogen-activated protein kinase kinase-3 (mkk-3-/-) or c-Jun-NH2-terminal kinase-1 (jnk1-/-) were ventilated, and lung injury parameters were assessed. We demonstrate that mkk3-/- or jnk1-/- mice displayed significantly reduced inflammatory lung injury and apoptosis relative to wild-type mice. Since jnk1-/- mice were highly resistant to ventilator-induced lung injury, we performed comprehensive gene expression profiling of ventilated wild-type or jnk1-/- mice to identify novel candidate genes which may play critical roles in the pathogenesis of ventilator-induced lung injury. Microarray analysis revealed many novel genes differentially expressed by ventilation including matrix metalloproteinase-8 (MMP8) and GAFF45α. Functional characterization of MMP8 revealed that mmp8-/- mice were sensitized to ventilator-induced lung injury with increased lung vascular permeability. Conclusion: We demonstrate that mitogen-activated protein kinase pathways mediate inflammatory lung injury during ventilator-induced lung injury. C-Jun-NH2-terminal kinase was also involved in alveolo-capillary leakage and edema formation, whereas MMP8 inhibited alveolo-capillary protein leakage. © 2008 Dolinay et al

Platelet Function and Coronary Microvascular Dysfunction

The ability of platelets to activate and aggregate to form blood clots in response to endothelial injury is well established. They are therefore critical contributors to ischaemia in atherothrombosis [1]. However, their role in cardiovascular disease is not limited to end-stage thrombosis in large vessels [2]. Abundant experimental evidence has established that activated platelets are also important mediators of microvascular thrombosis and promote the inflammatory response during ischaemia-reperfusion (IR) injury [3–5]. While platelets do not physically interact with the healthy endothelium, they can bind to the wall of hypoxic microvessels and release a plethora of inflammatory mediators that further enhance the activation of the endothelial monolayer and the recruitment of circulating leukocytes (monocytes, neutrophils, T-cells) [2]. In addition, deposition of platelets to the dysfunctional endothelium can lead to vasoconstriction which accelerates microvascular occlusion, thereby impairing tissue perfusion [3]. In this chapter, we discuss the role of platelets in promoting microvascular dysfunction and inflammation during IR injury. Focus is placed on the cross-talk between platelets and other cell types (endothelial cells [ECs] and leukocytes) via platelet adhesion receptors and platelet-derived proinflammatory mediators. We also consider new paradoxical functionalities of platelets promoting cardiac recovery after myocardial infarction (MI)