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A2963 - Characterization and Functional Significance of Lung Extracellular Vesicles in the Presence of Noxious Stimuli
Author Block: H. Lee, D. Zhang, Y. Jin; Boston University, Boston, MA, United States.
Background and significance: Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are clinical syndromes of the lung inflammation triggered by both direct and indirect inciting events. Hyperoxia and acid exposure are well-known elements involved in the pathogenesis of ALI/ARDS. Despite decades of research, the detailed mechanisms of those elements-induced ALI/ARDS still remain unclear, especially mechanisms of the intercellular crosstalk. Recent evidence suggests that extracellular vesicles (EV) play an essential role in cell to cell communication. EVs are generally classified as microvesicles (MVs), exosomes (Exos) and apoptotic bodies (ABs). However, their generation and functional significance in the acute lung injury are still not fully understood. Methods: Hyperoxia-induced oxidative stress and Intratracheal instillation of acid (0.1N HCl) were applied to generate ALI mouse model. Sequential centrifugation was performed to obtain ABs, MVs, and Exos from bronchoalveolar lavage fluid (BALF). Size distribution of the isolated EVs were measured using dynamic light scattering and nanoparticle tracking analysis. Western blot analysis and flow cytometry were applied to analyze the EVs. Differential inflammatory cell counting in BALF was conducted using cytospin preparations. Pro-inflammatory cytokines in BALF were measured using ELISA. Result: We first confirmed that hyperoxia and acid exposure trigger recruitment of inflammatory cells into the lung, and significantly induce generation of BALF-EVs. Notably, we found that MVs are main types of EVs in BALF, and predominantly derived from lung epithelial cells after lung injury. Next, we demonstrated that hyperoxia- or acid-induced MVs are responsible for triggering macrophage recruitment into the lung. Moreover, the BALF-MVs isolated from the injured condition, significantly upregulated gene expression of pro-inflammatory cytokines in macrophages in vivo. We further demonstrated that the cytokine secretions are increased by both hyperoxia- and acid-MVs in vivo. Summary: We demonstrated that MVs are generated from the lung and their secretions are strongly induced by hyperoxia and acid exposure. Importantly, the hyperoxia- and acid-induced MVs are critical for triggering macrophage recruitment and producing pro-inflammatory cytokines. Taken together, our data shows that MVs are important factor in the lung inflammation and might be a novel therapeutic target in ALI.