Chignalia, Andréia Z.

Accumulating evidence indicates that the lungs are active participants in the pathogenesis of heart failure (HF). Increases in left ventricular end diastolic pressure (LVEDP) leads to elevated pulmonary capillary pressure (PCP) that causes fluid filtration resulting in dyspnea and, ultimately, frank pulmonary edema (PE). However, the severity of dyspnea does not directly relate to the increase in PCP indicating that the clinical manifestation of HF cannot be solely explained by changes in Starling forces. Acute increases in PCP activate glycocalyx‐dependent signaling (endothelial mechanotransduction) that result in oxidative stress, eNOS activation and endothelial hyper‐permeability. Herein we sought to investigate if glypican‐1, a component of the glycocalyx, contributes to pressure‐dependent hyper‐permeability and PE in a model of acute HF. The isolated perfused lung preparation was used to simulate acute HF in male CD‐1 (wild type, WT) and glypican‐1 knockout (Gpc‐1 KO) mice (6 weeks old). Briefly, mice were anesthetized with isoflurane, tracheostomized and mechanically ventilated. Pulmonary artery and left atria were cannulated and in‐line pressure transducers recorded arterial and left atrial pressure; lungs were perfused at 2 mL/min with a Krebs‐Ringer 3% BSA buffer. Control experiments were done setting left atria pressure (P LA ) at 3 cm H2O for 10 minutes; acute heart failure was simulated by setting P LA at 10 cm H2O for 10 minutes. Lung edema was assessed by lung wet‐to‐dry ratio; reactive oxygen species (ROS) production and eNOS activation were assessed as indices of mechanotransduction activation by lucigenin enhanced chemiluminescence and immunoblotting, respectively. NADPH oxidase activity was measured by dihydroethidium fluorescence in isolated membrane‐fracions. WT and Gpc‐1 KO mice had similar increase in pulmonary artery pressure (from 8 to 10 mmHg). Deletion of glypican‐1 protected mice from pressure‐induced PE (wet‐to dry ratio [high and low pressure, respectfully] in WT: 7.3±0.3 vs 4.9±0.3 and in Gpc‐1 KO: 4.8±0.3 vs 4.8±0.2), prevented pressure‐dependen increase in NADPH oxidase activity (15% increase in WT) and in ROS production (80% increase in WT). Moreover, while WT mice showed increased eNOS activation (2‐fold) during acute HF, Gpc‐1 KO mice showed reduced eNOS activation (0.5 fold) indicating that Gpc‐1 is a determinant for mechanotransduction signaling. Taken together, these results suggest that Gpc‐1 activation by pressure leads to endothelial hyper‐permeability due to ROS and NO‐dependent pathways and contributes to PE in an in situ model of acute HF. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Aims: Acute increases in left ventricular end diastolic pressure (LVEDP) can induce pulmonary edema (PE). The mechanism(s) for this rapid onset edema may involve more than just increased fluid filtration. Lung endothelial cell permeability is regulated by pressure-dependent activation of nitric oxide synthase (NOS). Herein, we demonstrate that pressure-dependent NOS activation contributes to vascular failure and PE in a model of acute heart failure (AHF) caused by hypertension. Methods and results: Male Sprague–Dawley rats were anesthetized and mechanically ventilated. Acute hypertension was induced by norepinephrine (NE) infusion and resulted in an increase in LVEDP and pulmonary artery pressure (Ppa) that were associated with a rapid fall in PaO2, and increases in lung wet/dry ratio and injury scores. Heart failure (HF) lungs showed increased nitrotyrosine content and ROS levels. L-NAME pretreatment mitigated the development of PE and reduced lung ROS concentrations to sham levels. Apocynin (Apo) pretreatment inhibited PE. Addition of tetrahydrobiopterin (BH4) to AHF rats lung lysates and pretreatment of AHF rats with folic acid (FA) prevented ROS production indicating endothelial NOS (eNOS) uncoupling. Conclusion: Pressure-dependent NOS activation leads to acute endothelial hyperpermeability and rapid PE by an increase in NO and ROS in a model of AHF. Acute increases in pulmonary vascular pressure, without NOS activation, was insufficient to cause significant PE. These results suggest a clinically relevant role of endothelial mechanotransduction in the pathogenesis of AHF and further highlights the concept of active barrier failure in AHF. Therapies targetting the prevention or reversal of endothelial hyperpermeability may be a novel therapeutic strategy in AHF.