MicroRNA-216a Inhibits NF-κB-Mediated Inflammatory Cytokine Production in Teleost Fish by Modulating p65

The Inducible microRNA-21 Negatively Modulates the Inflammatory Response in Teleost Fish via Targeting IRAK4

Eradication of bacterial infection requires timely and appropriate immune and inflammatory responses, but excessive induction of inflammatory cytokines can cause acute or chronic inflammatory disorders. Thus, various layers of negative regulators and mechanisms are needed to ensure maintenance of the homeostasis for the immune system. miRNAs are a family of small non-coding RNAs that emerged as significant and versatile regulators involved in regulation of immune responses. Recently, the molecular mechanisms of miRNA in host-pathogen interaction networks have been extensively studied in mammals, whereas the underlying regulatory mechanisms in fish are still poorly understood. In this study, we identify miR-21 as a negative regulator of the teleost inflammatory response. We found that lipopolysaccharide and Vibrio anguillarum significantly upregulated the expression of fish miR-21. Upregulated miR-21 suppresses LPS-induced inflammatory cytokine expression by targeting IL-1 receptor-associated kinase 4 (IRAK4), thereby avoiding excessive inflammatory responses. Furthermore, we demonstrated that miR-21 regulates inflammatory responses through NF-κB signaling pathways. The collective findings indicate that miR-21 plays a regulatory role in host-pathogen interactions through IRAK4-mediated NF-κB signaling pathway.

MicroRNA-155 promotes pro-inflammatory functions and augments apoptosis of monocytes/macrophages during Vibrio anguillarum infection in ayu, Plecoglossus altivelis

Upon recognition of pathogen-associated molecular patterns by pattern-recognition receptors, immune cells are recruited, and multiple antibacterial/viral signaling pathways are activated, leading to the production of immune-related cytokines, chemokines, and interferons along with further activation of the adaptive immune response. MicroRNAs (miRs) play essential roles in regulating such immune signaling pathways, as well as the biological activities of immune cells; however, knowledge regarding the roles of miRs in the immune-related function of monocytes/macrophages (MO/MΦ) remains limited in teleosts. In the present study, we addressed the effects of miR-155 on Vibrio anguillarum-infected MO/MΦ. Our results showed that miR-155 augmented MO/MΦ expression of proinflammatory cytokines and attenuated the expression of anti-inflammatory cytokines. Additionally, the phagocytosis and bacteria-killing abilities of these cells were boosted by miR-155 administration, which also promoted M1-type polarization but inhibited M2-type polarization. Furthermore, the V. anguillarum-infection-induced apoptosis was also enhanced by miR-155 mimic transfection, which might have been due to excessive inflammation or the accumulation of reactive oxygen species. These results represent the first report providing a detailed account of the regulatory roles of miR-155 on MO/MΦ functions in teleosts and offer insight into the evolutionary history of miR-155-mediated regulation of host immune responses.

Non-coding RNAs Function as Immune Regulators in Teleost Fish

Non-coding RNAs (ncRNAs) are functional RNA molecules that are transcribed from DNA but not translated into proteins. ncRNAs function as key regulators of gene expression and chromatin modification. Recently, the functional role of ncRNAs in teleost fish has been extensively studied. Teleost fish are a highly diverse group among the vertebrate lineage. Fish are also important in terms of aquatic ecosystem, food production and human life, being the source of animal proteins worldwide and models of biomedical research. However, teleost fish always suffer from the invasion of infectious pathogens including viruses and bacteria, which has resulted in a tremendous economic loss to the fishing industry worldwide. Emerging evidence suggests that ncRNAs, especially miRNAs and lncRNAs, may serve as important regulators in cytokine and chemokine signaling, antigen presentation, complement and coagulation cascades, and T cell response in teleost fish. In this review, we summarize current knowledge and understanding of the roles of both miRNAs and lncRNAs in immune regulation in teleost fish. Molecular mechanism insights into the function of ncRNAs in fish immune response may contribute to the development of potential biomarkers and therapeutic targets for the prevention and treatment of fish diseases.

MiR-216a-5p protects 16HBE cells from H2O2-induced oxidative stress through targeting HMGB1/NF-kB pathway

Asthma is a complex, chronic inflammatory disorder of the bronchial tree, and can affect patients of all ages including children. High mobility group box 1 (HMGB1) has been proved as a therapeutic target in children with asthma, and was predicted to be the target gene of microRNA-216a-5p (miR-216a-5p). The present study aimed to investigate the function of miR-216a-5p in asthma by creating a human bronchial epithelial cell (16HBE) injury model using H₂O₂. A significantly elevation of HMGB1 protein expression and a reduction of miR-216a-5p expression were observed in children with asthma as well as in H₂O₂ stimulated 16HBE cells. Dual luciferase reporter assays confirmed the target reaction between HMGB1 and miR-216a-5p. MiR-216a-5p repressed HMGB1 protein expression in H₂O₂ induced 16HBE cells. Moreover, miR-216a-5p inhibited H₂O₂ induced cell injury by elevating cell proliferation and decreasing cell apoptosis in 16HBE cells. Furthermore, miR-216a-5p repressed NF-kB pathway activation in H₂O₂ induced 16HBE cells. In conclusion, these results suggested that miR-216a-5p functions as a negative regulator of H₂O₂ induced 16HBE cell injury through targeting HMGB1/NF-kB pathway, provided a potential therapeutic target for asthma.