Figure 6.

Mechanical ventilator-induced lung injury (VILI) in mice and humans is characterized by reduced expression of VE-Cad. (A) Long-term mechanical ventilation increases pulmonary transvascular albumin permeability in mice (see Methods). Time course of lung vascular permeability in C57BL/6J mice subjected to 2 or 4 hours of HVMV (see Methods) and followed by monitoring lung vascular permeability up to 72 hours. Mean ± SEM; n = 3. *P < 0.05 and **P < 0.01 by ANOVA. (B) Expression of VE-Cad is significantly reduced in C57BL/6J mice exposed to 4 hours of HVMV. Western blot analysis was performed in freshly isolated lung ECs from these mice. (C) Expression of VE-Cad is reduced in Piezo1^iEC−/− mice exposed to 2 hours of HVMV. (D) Pharmacological activation of calpain with A23187 prevents downregulation of both Piezo1 and VE-Cad induced by 4 hours of HVMV. Western blot analysis of VE-Cad, CD31, and GAPDH (as loading control). (E) Human lung tissue samples were collected from patients undergoing short-term mechanical ventilation (SMV) for lobectomy or from organ donors who had undergone long-term mechanical ventilation (LMV). Western blot analysis of Piezo1, VE-Cad, CD31, and GAPDH (loading control) was performed. (F) Model of endothelial Piezo1-mediated stabilization of AJs. Alveolar CS adaptively activates Piezo1 and its downstream target calpain via Ca²⁺ influx. Calpain, in turn, cleaves Src, reducing Src-dependent VE-Cad phosphorylation and stabilizing AJs.