Pathologic Mechanical Stress and Endotoxin Exposure Increases Lung Endothelial Microparticle Shedding

Abstract

Acute lung injury (ALI) results from infectious challenges and from pathologic lung distention produced by excessive tidal volume delivered during mechanical ventilation (ventilator-induced lung injury [VILI]) and is characterized by extensive alveolar and vascular dysfunction. Identification of novel ALI therapies is hampered by the lack of effective ALI/VILI biomarkers. We explored endothelial cell (EC)-derived microparticles (EMPs) (0.1-1 mm) as potentially important markers and potential mediators of lung vascular injury in preclinical models of ALI and VILI. We characterized EMPs (annexin V and CD31 immunoreactivity) produced from human lung ECs exposed to physiologic or pathologic mechanical stress (5 or 18% cyclic stretch [CS]) or to endotoxin (LPS). EC exposure to 18% CS or to LPS resulted in increased EMP shedding compared with static cells (z 4-fold and z 2.5-fold increases, respectively). Proteomic analysis revealed unique 18% CS-derived (n = 10) and LPS-derived EMP proteins (n = 43). VILI-challenged mice (40 ml/kg, 4 h) exhibited increased plasma and bronchoalveolar lavage CD62E (E-selectin)-positive MPs compared with control mice. Finally, mice receiving intratracheal instillation of 18% CS-derived EMPs displayed significant lung inflammation and injury. These findings indicate that ALI/VILI-producing stimuli induce significant shedding of distinct EMP populations that may serve as potential ALI biomarkers and contribute to the severity of lung injury.Keywords: microparticles; ventilator-induced lung injury; cyclic stretch; LPS; proteomics Clinical RelevanceAcute lung injury (ALI) results from infectious challenges and pathologic lung distention produced by excessive tidal volume delivered during mechanical ventilation (ventilator-induced lung injury [VILI]) and is characterized by extensive alveolar and vascular dysfunction. Identification of novel ALI therapies is hampered by the lack of effective ALI/VILI biomarkers. We explored endothelial cell (EC)-derived microparticles (EMPs) (0.1-1 mm) as potentially important markers and potential mediators of lung vascular injury in preclinical models of ALI and VILI. Our findings indicate that ALI/VILIproducing stimuli induce significant shedding of distinct EMP populations that may serve as potential ALI biomarkers and contribute to the severity of lung injury.

Extracellular vesicles in lung microenvironment and pathogenesis

“…In the airway microenvironment, various environmental stressors, such as proteomic and miRNA profiles (which can be associated with disease pathogenesis), can modify the EV composition. It has been reported that EV secretion from lung endothelial cells is enhanced by physiologic mechanical stress, endotoxin, and cigarette smoke [40][41][42]. This finding shows that these vesicles are primarily generated by an apoptosisdependent mechanism that is triggered by pulmonary endothelial damage during stress exposure.…”

“…Many researchers have assumed that the cigarette smoke-induced paracrine factors that are secreted by lung epithelial cells are primarily responsible for COPD pathogenesis through aberrant activation of the EMTU; however, the detailed molecular functions of lung epithelial cell-derived EVs in EMTU activation for COPD pathogenesis are not yet fully understood. It has been reported that various stress triggers promote the secretion of circulating lung endothelial cell-derived EVs [40][41][42]. The EVs may predict the degree of lung endothelial injury in COPD.…”

The pulmonary endothelium in acute respiratory distress syndrome: insights and therapeutic opportunities

“…30), particularly in the context of mechanical stretch. Hence, EMP levels were elevated in human macrovascular endothelial cells and animals exposed to pathological mechanical stress as well as endotoxin 31 32…”

Alveolar macrophage-derived microvesicles mediate acute lung injury

“…Despite this emerging interest, there is a paucity of literature investigating the role of MVs in ARDS (or any other respiratory pathology), and in particular their bioactivity within the intra-alveolar space. The presence of MVs of various cell origins including endothelial, epithelial or platelet-derived MVs within bronchoalveolar lavage fluid (BALF) has been confirmed in patients with established ARDS12 13 and a preclinical model of ventilator-induced lung injury 14. However, whether these are merely present as markers of cellular damage or key components of the pathophysiological process in ARDS is yet to be determined.…”