Increased cardiac microvascular permeability and activation of cardiac endothelial nitric oxide synthase in high tidal volume ventilation-induced lung injury

Abstract

Abstract Background: Positive pressure ventilation with large tidal volumes has been shown to cause lung injury via the serine/threonine kinase-protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS)-pathways. However, the effects of high tidal volume (VT) ventilation on the heart are unclear. Objectives: Evaluate the effect of VT ventilation on the cardiac vascular permeability and intracellular Akt and eNOS signaling pathway. Methods: C57BL/6 and Akt knock-out (heterozygotes, +/−) mice were exposed to high VT (30 mL/kg) mechanical ventilation with room air for one and/or five hours. Results: High VT ventilation increased cardiac microvascular permeability and eNOS phosphorylation in a timedependent manner. Serum cardiac troponin I was increased after one hour of high VT ventilation. Cardiac Akt phosphorylation was accentuated after one hour and attenuated after five hours of high VT ventilation. Pharmacological inhibition of Akt with LY294002 and high VT ventilation of Akt+/− mice attenuated cardiac Akt phosphorylation, but not eNOS phosphorylation. Conclusion: High VT ventilation increased cardiac myocardial injury, microvascular permeability, and eNOS phosphorylation. Involvement of cardiac Akt in high VT ventilation was transient.