Inflammation and apoptosis play important roles in the initiation and progression of acute lung injury (ALI). Our previous study has shown that progranulin (PGRN) exerts lung protective effects during LPS-induced ALI. Here, we have investigated the potential roles of PGRN-targeting microRNAs (miRNAs) in regulating inflammation and apoptosis in ALI and have highlighted the important role of PGRN. LPS-induced lung injury and the protective roles of PGRN in ALI were first confirmed. The function of miR-34b-5p in ALI was determined by transfection of a miR-34b-5p mimic or inhibitor in intro and in vivo. The PGRN level gradually increased and subsequently significantly decreased, reaching its lowest value by 24 hr; PGRN was still elevated compared to the control. The change was accompanied by a release of inflammatory mediators and accumulation of inflammatory cells in the lungs. Using bioinformatics analysis and RT-PCR, we demonstrated that, among 12 putative miRNAs, the kinetics of the miR-34b-5p levels were closely associated with PGRN expression in the lung homogenates. The gain- and loss-of-function analysis, dual-luciferase reporter assays, and rescue experiments confirmed that PGRN was the functional target of miR-34b-5p. Intravenous injection of miR-34b-5p antagomir in vivo significantly inhibited miR-34b-5p up-regulation, reduced inflammatory cytokine release, decreased alveolar epithelial cell apoptosis, attenuated lung inflammation, and improved survival by targeting PGRN during ALI. miR-34b-5p knockdown attenuates lung inflammation and apoptosis in an LPS-induced ALI mouse model by targeting PGRN. This study shows that miR-34b-5p and PGRN may be potential targets for ALI treatments.
Keywords: acute lung injury; apoptosis; inflammation; miR-34b-5p; progranulin.
© 2017 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals Inc.