Endothelial Caveolin‐1 Positive Microvesicles and Apoptotic Bodies as Early Biomarkers of Acute Lung Injury and Possible Mediators of TGF‐β‐mediated Repair/Remodeling

Abstract

Endothelial cell injury is a hallmark of Acute Lung Injury and Acute Respiratory Distress Syndrome (ALI/ARDS). We and others have shown endothelial cell caveolin‐1 (Cav‐1) expression is critical for maintaining vascular homeostasis. The aim of this study was to determine how Cav‐1 is depleted during ALI/ARDS and how this may lead to defective vascular repair. ALI was induced in C57BL6 WT mice (male; 2.5–3 months old) by nebulized Escherichia coli lipopolysaccharide (LPS; 10 mg over 1 hr daily for 1 or 4 days). Lung pathology and Cav‐1+ EVs in platelet‐free plasma were assessed by immunohistochemistry, quantification of immune cell number in bronchoalveolar lavage fluid, and western blot. In vitro, human pulmonary artery endothelial cells (HPAECs) and isolated bone marrow‐derived macrophages (BMDMs) were treated with LPS or EVs from control or LPS‐treated animals. At 24 hs, LPS‐induced ALI increased the total number of EVs in murine plasma by 50%. Characterization of isolated EVs indicated Cav‐1 is abundantly expressed in large microvesicles and apoptotic bodies when compared with smaller vesicles, suggesting Cav1+ EVs may be an endothelial cell damage‐associated factor. By western blot, we observed EV‐Cav‐1 expression was increased by 38% after 24 hrs of LPS exposure (0.61 ± 0.05 to 0.98 ± 0.16 a.u.) in control and LPS‐treated mice, respectively (n= 8–10 mice; P<0.05) and decreased below basal level after 96 hrs indicating endothelial Cav‐1 depletion may be partially due to release Cav‐1+ EVs into the circulation. In vitro, LPS‐treated HPAECs released Cav1+ EVs in a concentration‐dependent manner and EVs‐derived from LPS‐treated mice induced TGF‐β release from BMDMs. Thus, EC‐Cav‐1 depletion may be due in part to EV shedding as a result of EC damage which in vivo may be a mechanism of macrophage‐dependent TGF‐β‐induced vascular repair/remodeling. These novel observations may provide an important link to new ways of preventing the onset or progression of ALI/ARDS.Support or Funding InformationCNPq Fellowship‐CsF/Brazil (SDO) and HL125356 and DOD W911NF‐15‐R‐002 (RDM, MGB).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.