Abstract:

Objective To investigate the role and mechanism of miR21⁃5p regulating transcriptional acti⁃ vator protein STAT3 in hyperoxia ⁃induced acute lung injury（HALI）. Methods Forty C57BL/6J mice were ran⁃ domly divided into normoxia group，hyperoxia group，hyperoxia+miR21⁃5p group，hyperoxia+empty carrier group， and the HALI mouse model was established by inhaling more than 90% oxygen concentration. The normoxia group was raised in normal air；the hyperoxia+miR21⁃5p group and the hyperoxia+empty vector group were instilled with miR21⁃5p AAV6 or empty vector through the tracheal tube，respectively，and the HALI mouse model was estab⁃ lished after three weeks of feeding. After 48 hours of hyperoxia exposure，lung tissue was collected，and ELISA kits were used to detect the levels of inflammatory factors（TNF ⁃α，IL ⁃6，IL ⁃1β）and oxidative stress markers （SOD，MDA，ROS）；the lung water content was calculated；Morphological changes were observed by HE staining and pathological scoring；Tunel method to detect apoptosis rate of lung tissue cells；RT⁃PCR was used to detect the expression level of miR21⁃5p；Western blotting was used to detect the relative expression levels of STAT3， p⁃STAT3，Bax and Bcl⁃2. Results Compared with the normox group，the pathological score，lung water content and apoptosis rate of lung tissue cells in the hyperoxia group were increase（P < 0.05），and the inflammatory factor TNF ⁃α，IL ⁃6 and IL ⁃1 β The level of MDA and ROS increased（P < 0.05），the level of SOD decreased （P < 0.05），the expression of STAT3，p⁃STAT3 and Bax protein increased（P < 0.05），and the expression of Bcl⁃2 protein decreased（P < 0.05）；Compared with the hyperoxia group，the pathological score，lung water content and apoptosis rate of lung tissue cells in the hyperoxia + miR21⁃5p group were reduced（P < 0.05），and the inflamma⁃ tory factor TNF⁃ α、IL⁃6 and IL⁃1 β The level of MDA and ROS decreased（P < 0.05），the level of SOD increased （P < 0.05），the expression of STAT3，p⁃STAT3 and Bax decreased（P < 0.05），and the expression of high Bcl⁃2 protein increased（P < 0.05）. HE staining in the hyperoxia group showed disordered alveolar structure，septal thickening，extensive infiltration of inflammatory cells，formation of transparent membrane，and alveolar collapse. HE staining results in hyperoxia + miR21 ⁃ 5p group showed a significant reduction of lung injury. Conclusion miR21 ⁃ 5p targets transcriptional activator protein STAT3 activity to inhibit inflammatory response and apoptosis and maintain redox balance to alleviate HALI.

Key words:

microRNA?21?5p, hyperoxia?induced acute lung injury, STAT3, acute respiratory dis? tress syndrome, apoptosis ,