Fellowship for Emily Huffman: Piezo1 Channels in Hyperoxia-Induced Lung Injury

PROJECT SUMMARY/ABSTRACT Over 1.5 million Americans with cardiovascular disease currently receive supplemental oxygen (hyperoxia) to improve blood oxygenation. As their respiratory function declines, mechanical ventilation sometimes becomes necessary. However, mechanical ventilation, while life-saving, can also lead to ventilator-induced lung injury (VILI). VILI can occur when mechanical ventilation causes further damage to already compromised lungs, particularly with tidal volumes that overdistend lung tissue. This injury manifests as alveolar barrier dysfunction, pulmonary edema, and inflammation. It is well recognized that long-term exposure to hyperoxia alone causes injury to the lungs. Importantly, work from our group suggests that acute exposure to hyperoxia prior to mechanical ventilation increases the severity of lung injury more than either treatment alone. Despite extensive research into the mechanisms of VILI, it remains unclear how hyperoxia influences alveolar barrier integrity to contribute to the progression of lung injury during mechanical ventilation. Understanding this interaction is crucial for improving treatment strategies and patient outcomes. We previously reported that hyperoxia promotes f-actin formation in alveolar epithelial cells, leading to stiffer cells that are resistant to stretch and more likely to develop injury during cyclic stretch, as experienced during mechanical ventilation. Studies from outside our lab demonstrate that endothelial cells also exhibit this increase in actin stress fibers in response to hyperoxia. This change in stiffness may be detected by Piezo1, a well-characterized mechanosensitive cation channel. In preliminary studies, using our clinically relevant in vivo and in vitro cyclic stretch models of VILI, we observed an increase in expression of Piezo1 which correlated with the development of pulmonary edema in vivo. We propose that activation of Piezo1 by hyperoxia and cyclic stretch may explain the severity of VILI that we observe during hyperoxic mechanical ventilation. Inhibiting Piezo1 could therefore prevent the acceleration of lung injury associated with mechanical ventilation. Piezo1 has been implicated as a mediator of lung vascular hyperpermeability, specifically through the activation of calpain, a calcium-activated protease that can contribute to the degradation of junctional proteins. Importantly, Piezo1 has been implicated in the development of VILI; however, the contribution of hyperoxia to the acceleration of injury has not been studied. While there has been extensive investigation of the signaling pathways that lead to lung injury after days of exposure to hyperoxia, the possibility that hyperoxia promotes Piezo1-mediated barrier disruption has not been explored. Using in vitro, in vivo, and ex vivo models of VILI, this project will (1) identify the role of Piezo1 in hyperoxia-induced endothelial barrier dysfunction and (2) demonstrate that the combination of hyperoxia and cyclic stretch accelerates lung injury through Piezo1-mediated endothelial barrier dysfunction. These experiments will test the central hypothesis that hyperoxia increases Piezo1 activity to promote endothelial barrier dysfunction and lung injury. This proposal will employ innovative imaging techniques to assess barrier disruption in stretched cells and will leverage our lab’s unique in vitro model of VILI to investigate these questions. Successful completion of this project will define the role of Piezo1 in the pathogenesis of ventilator-induced lung injury accelerated by hyperoxia pre-exposure.