Rac mediates actin remodeling and permeability during alveolar epithelial stretch

Abstract

Alveolar epithelial cells (AECs) maintain integrity of the blood‐gas barrier via gasket‐like transcellular tight junction proteins bound to the actin cytoskeleton. AEC monolayers stretched biaxially undergo rapid actin cytoskeletal remodeling. We hypothesize that Rac1 and downstream effectors LIMK½, cofilin, Akt, and SSH1L are activated in stretched AECs. Furthermore we hypothesize that Rac1 pathway inhibition will attenuate actin remodeling and preserve paracellular permeability during AEC stretch. Primary AEC monolayers were stretched biaxially to create a change in surface area of 37% at ¼ Hz for 10 or 60 min. Additional monolayers were pretreated with Rac1 pathway inhibitors wortmannin, EHT‐1864, or IPA‐3 and stretched. Unstretched treated and untreated AECs served as two control groups. Without treatments, biaxial stretch rapidly increased Rac1, Akt, LIMK½, and cofilin activity, and resulted in rapid actin remodeling and increased monolayer permeability. Compared to stretched vehicle control monolayers, Rac1 pathway inhibitors reduced Rac1, Akt, LIMK½, and cofilin activity, attenuated actin remodeling, and preserved monolayer permeability in stretched monolayers. This study provides a foundation for developing treatment strategies aimed at reducing cellular injury during high magnitude biaxial deformation. NIH R01 HL057204