Oxidative stress is an important molecular mechanism underlying lung fibrosis. The mitochondrion is a major organelle for oxidative stress in cells. Therefore, blocking the mitochondrial signalling pathway may be the best therapeutic manoeuver to ameliorate lung fibrosis. Astaxanthin (AST) is an excellent antioxidant, but no study has addressed the pathway of AST against pulmonary oxidative stress and free radicals by the mitochondrion-mediated signalling pathway. In this study, we investigated the antioxidative effects of AST against H2O2- or bleomycin (BLM)-induced mitochondrial dysfunction and reactive oxygen species (ROS) production in alveolar epithelial cells type II (AECs-II) in vivo and in vitro. Our data show that AST blocks H2O2- or BLM-induced ROS generation and dose-dependent apoptosis in AECs-II, as characterized by changes in cell and mitochondria morphology, translocation of apoptotic proteins, inhibition of cytochrome c (Cyt c) release, and the activation of caspase-9, caspase-3, Nrf-2 and other cytoprotective genes. These data suggest that AST inhibits apoptosis in AECs-II cells through the ROS-dependent mitochondrial signalling pathway and may be of potential therapeutic value in lung fibrosis treatment.
Emerging evidence suggests that microRNA (miRNA) and long noncoding RNA (lncRNA) play important roles in disease development. However, the mechanism underlying mRNA interaction with miRNA and lncRNA in idiopathic pulmonary fibrosis (IPF) remains unknown. This study presents a novel lnc-PCF that promotes the proliferation of TGF-β1-activated epithelial cells through the regulation of map3k11 by directly targeting miR-344a-5p during pulmonary fibrogenesis. Bioinformatics and in vitro translation assay were performed to confirm whether or not lnc-PCF is an actual lncRNA. RNA fluorescent in situ hybridization (FISH) and nucleocytoplasmic separation showed that lnc-PCF is mainly expressed in the cytoplasm. Knockdown and knockin of lnc-PCF indicated that lnc-PCF could promote fibrogenesis by regulating the proliferation of epithelial cells activated by TGF-β1 according to the results of xCELLigence real-time cell analysis system, flow cytometry, and western blot analysis. Computational analysis and a dual-luciferase reporter system were used to identify the target gene of miR-344a-5p, whereas RNA pull down, anti-AGO2 RNA immunoprecipitation, and rescue experiments were conducted to confirm the identity of this direct target. Further experiments verified that lnc-PCF promotes the proliferation of activated epithelial cells that were dependent on miR-344a-5p, which exerted its regulatory functions through its target gene map3k11. Finally, adenovirus packaging sh-lnc-PCF was sprayed into rat lung tissues to evaluate the therapeutic effect of lnc-PCF. These findings revealed that lnc-PCF can accelerate pulmonary fibrogenesis by directly targeting miR-344a-5p to regulate map3k11, which may be a potential therapeutic target in IPF.
Promotion of myofibroblast apoptosis is a potential therapeutic strategy for pulmonary fibrosis. This study investigated the antifibrotic effect of astaxanthin on the promotion of myofibroblast apoptosis based on dynamin-related protein-1 (Drp1)-mediated mitochondrial fission in vivo and in vitro. Results showed that astaxanthin can inhibit lung parenchymal distortion and collagen deposition, as well as promote myofibroblast apoptosis. Astaxanthin demonstrated pro-apoptotic function in myofibroblasts by contributing to mitochondrial fission, thereby leading to apoptosis by increasing the Drp1 expression and enhancing Drp1 translocation into the mitochondria. Two specific siRNAs were used to demonstrate that Drp1 is necessary to promote astaxanthin-induced mitochondrial fission and apoptosis in myofibroblasts. Drp1-associated genes, such as Bcl-2-associated X protein, cytochrome c, tumour suppressor gene p53 and p53-up-regulated modulator of apoptosis, were highly up-regulated in the astaxanthin group compared with those in the sham group. This study revealed that astaxanthin can prevent pulmonary fibrosis by promoting myofibroblast apoptosis through a Drp1-dependent molecular pathway. Furthermore, astaxanthin provides a potential therapeutic value in pulmonary fibrosis treatment.
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