Hyperoxia Increases Elastic Modulus of Alveolar Epithelial Cells Through Rho Kinase

Abstract

Patients with acute lung injury are administered high concentrations of oxygen during mechanical ventilation, and both hyperoxia and mechanical ventilation can independently cause injury. However, the precise mechanisms that lead to epithelial injury are not well understood. We hypothesized that alveolar epithelial cells may be more susceptible to injury caused by mechanical ventilation because hyperoxia causes cells to be more stiff due to increased f‐action formation via activation of the GTPase RhoA and its downstream effecter Rho kinase (ROCK). We used fluorescence microscopy to examine cytoskeletal structures in murine lung alveolar epithelial cells. We measured cell elasticity (E) using atomic force microscopy in the indenter mode. Hyperoxia caused increased f‐actin stress fibers formation, and cells became stiffer (higher E). Treatment with an inhibitor of ROCK significantly decreased E and prevented the cytoskeletal changes. Pre‐exposure of cells to hyperoxia promoted detachment when cells were subsequently stretched using the Flexercell device, but the ROCK inhibitor prevented this effect. Loss of cell adhesion would result in decreased barrier function. In summary, hyperoxia caused cytoskeletal remodeling that resulted in increased cell stiffness and promoted cell detachment during stretch. These effects were ameliorated by inhibition of ROCK. Supported by NIH grant HL094366 (CMW).