Cytoskeletal and integrin-mediated mechanobiology of the alveolar epithelium

Abstract

Ventilator-associated lung injury (VALI) describes the process by which mechanical ventilation of the lungs causes systemic injury. Cyclic Mechanical Strain (CMS) of alveolar epithelial cells induces cytokine release, suggesting that mechanotransduction of force into injurious biological signaling occurs in the alveolar epithelium. The work in this thesis investigated the role of integrin and cytoskeletal signalling in CMS-induced cytokine release in these cells. Specifically, the roles of RhoA-Rho associated protein kinase (ROCK) signaling and the integrin-associated protein, CD98hc, were assessed. Inhibition of ROCK and non-muscle myosin II (NMII), and knockdown of CD98hc abrogated CMS-induced IL-8 release. Preliminary data obtained using FRET probes indicated that CD98hc knockdown reduced baseline RhoA activity. To investigate these pathways upon CMS-induced injury in intact human lung, and to generate translational data, we established a model of CMS using precision-cut lung slices (PCLS). CMS induced cytokine release in both murine and human PCLS and there was also an indication that cells spatially correlating with ATII proliferated in response to CMS. These data suggest a key role for the RhoA-ROCK-NMII axis in the mechanotransduction of CMS in the alveolar epithelium. CD98hc may modulate baseline RhoA expression and CMS-induced injurious signalling by affecting baseline cellular pre-stress. PCLS respond to CMS thereby enabling mechanotransduction studies in human tissue with near physiological conditions. This will potentially facilitate future translational research in VALI.