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.

Noncoding RNAs (ncRNAs), such as microRNA (miRNA), long ncRNA (lncRNA), and circular RNA (circRNA), are regulators of important biological functions. Therefore, understanding their crosstalk and regulatory patterns can provide treatment for diseases. In this study, differentially expressed RNA transcripts were obtained by RNA sequencing in bleomycin-induced pulmonary fibrosis in mice. Four miRNAs, 10 lncRNAs, and two circRNAs were tested to validate the sequencing. There were differentially expressed 585 mRNAs, 236 miRNAs, 272 lncRNAs, and 74 circRNAs in pulmonary fibrosis. Their location on chromosome, length varieties, interaction, and host genes were analyzed. lnc949, circ949, and circ057 were chosen to explore the detailed crosstalk and regulatory pattern, which were measured by using RNA-FISH, dual-luciferase reporter assay, real-time cell analysis and rescue experiment, co-localization analysis, RNA immunoprecipitation, and RNA pull down. The data showed that the three ncRNAs were predominant in the cytoplasm, and their regulatory patterns were focused on post-transcription. The fibrotic function of lnc949 depended on its host gene FKBP5. circ949 and circ057 formed a regulatory network with lnc865 and lnc556 to simultaneously regulate miR-29b-2-5p targeting STAT3 phosphorylation. Collectively, different RNAs can crosstalk with each other to regulate pulmonary fibrosis through different regulatory patterns. We hope these data can provide a full concept of RNA transcripts, leading to a new treatment for pulmonary fibrosis.

The role of long non-coding RNA (lncRNA) in idiopathic pulmonary fibrosis (IPF) is poorly understood. We found a novel lncRNA-ITPF that was upregulated in IPF. Bioinformatics and in vitro translation verified that lncITPF is an actual lncRNA, and its conservation is in evolution. Northern blot and rapid amplification of complementary DNA ends were used to analyze the full-length sequence of lncITPF. RNA fluorescence in situ hybridization and nucleocytoplasmic separation demonstrated that lncITPF was mainly located in the nucleus. RNA sequencing, chromatin immunoprecipitation (ChIP)-qPCR, CRISPR-Cas9 technology, and promoter activity analysis showed that the fibrotic function of lncITPF depends on its host gene integrin b-like 1 (ITGBL1), but they did not share the same promoter and were not co-transcribed. Luciferase activity, pathway inhibitors, and ChIP-qPCR showed that smad2/3 binds to the lncITPF promoter, and TGF-b1-smad2/3 was the upstream inducer of the fibrotic pathway. Furthermore, RNA-protein pull-down, liquid chromatography-mass spectrometry (LC-MS), and protein-RNA immunoprecipitation showed that lncITPF regulated H3 and H4 histone acetylation in the ITGBL1 promoter by targeting heterogeneous nuclear ribonucleoprotein L. Finally, sh-lncITPF was used to evaluate the therapeutic effect of lncITPF. Clinical analysis showed that lncITPF is associated with the clinicopathological features of IPF patients. Our findings provide a therapeutic target or diagnostic biomarker for IPF.