p300 promotes differentiation of Th17 cells via positive regulation of the nuclear transcription factor RORγt in acute respiratory distress syndrome

Interleukin-17-A multifaceted cytokine in viral infections

Viral infections are a major threat to the human population due to the lack of selective therapeutic measures. The morbidity and mortality reported worldwide are very alarming against viral pathogens. The proinflammatory environment is required for viral inhibition by initiating the host immune response. The host immune response fights these pathogens by secreting different cytokines. Interleukin-17 (IL-17) a proinflammatory cytokine mainly produced by T helper type 17 cells, plays a vital role in the regulation of host immune response against various pathogens, including viruses. However, dysregulated production of IL-17 induces chronic inflammation, autoimmune disorders, and may lead to cancer. Recent studies suggest that IL-17 is not only involved in the antiviral immune response but also promotes virus-mediated illnesses. In this review, we discuss the protective and pathogenic role of IL-17 against various viral infections. A detailed understanding of IL-17 during viral infections could contribute to improve therapeutic measures and enable the development of an efficient and safe IL-17 based immunotherapy.

Depression of lncRNA MINCR antagonizes LPS-evoked acute injury and inflammatory response via miR-146b-5p and the TRAF6-NFkB signaling

BACKGROUND

Inflammation plays an important role in the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). The long non-coding RNA (lncRNA) MINCR is closely related to inflammation injury. This study was performed to explore the protective effects and mechanisms of MINCR in lipopolysaccharide (LPS)-induced lung injury and inflammation.

METHODS

The expression levels of MINCR and miR-146b-5p in lung tissue status were detected by using quantitative real-time polymerase chain reaction (qRT-PCR), hematoxylin and eosin staining, immunohistochemical staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Enzyme-linked immunosorbent assay and Western blotting analysis were used to detect the expression of inflammatory factors such as tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 in lung tissue. The relationship between MINCR, miR-146b-5p, and TRAF6 was explored using bioinformatics analysis and luciferase assay.

RESULTS

The expression levels of MINCR were increased in a mouse model of LPS-induced ALI and small airway epithelial cells (SAECs). shMINCR resulted in increased cell viability and decreased apoptosis, which protected against LPS-induced cell damage. shMINCR can inhibit the formation of neutrophil extracellular traps, neutrophil numbers, myeloperoxidase activity, and the production of inflammatory cytokines IL-6, IL-1β, and TNF-α induced by LPS. The silencing of miR-146b-5p reversed the effects of MINCR on LPS-induced lung damage. Sh-MINCR decreased the expression levels of TRAF6 and p-P65 in LPS-induced SAECs and lung tissues. Co-transfection of sh-MINCR with miR-146b-5p inhibitor reversed the effect of sh-MINCR on the expression of TRAF6 and p-P65.

CONCLUSIONS

MINCR may induce alveolar epithelial cell injury and inflammation and aggravate the progression of ALI/ARDS through miR-146b-5p and TRAF6/NF-κB pathways, which would provide a promising target for the treatment of ALI/ARDS.

MiR-141-3p and miR-200a-3p are involved in Th17 cell differentiation by negatively regulating RARB expression

Among T helper (Th) lineages differentiated from naïve CD4⁺ T cells, interleukin (IL)-17-producing Th17 cells are highly correlated with the pathogenesis of autoimmune disorders. This study aimed to clarify the involvement of miR-141-3p and miR-200a-3p in Th17 cell differentiation as well as explore their potential target genes involved. For this purpose, human naïve CD4⁺ T cells were cultured under Th17 cell polarizing condition. The differentiation process was confirmed through measurement of IL-17 secretion using the ELISA method and assessment of Th17 cell-defining genes expression during the differentiation period. MiR-141-3p and miR-200a-3p downstream genes were identified via consensus and integration in silico approach and their expression pattern and alterations were evaluated by quantitative real-time PCR. Finally, direct interaction between both microRNAs (miRNAs) and their common predicted target sequences was approved by dual-luciferase reporter assay. Highly increased IL-17 secretion and Th17 lineage-specific genes expression confirmed Th17 cell differentiation. Our results have demonstrated that miR-141-3p and miR-200a-3p are Th17 cell-associated miRNAs and their expression level is upregulated significantly during Th17 cell induction. We have also found that retinoic acid receptor beta (RARB) gene, whose product has been reported as a negative regulator of Th17 cell generation, is a direct target of both miRNAs and its downregulation can affect the transcriptional level of JAK/STAT pathway genes. Overall, our results have identified two novel Th17 lineage-associated miRNAs and have provided evidence for the RARB-dependent mechanism of miR-141-3p and miR-200a-3p-induced Th17 cell differentiation and hence Th17-mediated autoimmunity.

JQ1, a bromodomain inhibitor, suppresses Th17 effectors by blocking p300-mediated acetylation of RORγt

BACKGROUND AND PURPOSE

Th17 cells play critical roles in chronic inflammation, including fibrosis. Histone acetyltransferase p300, a bromodomain-containing protein, acetylates RORγt and promotes Th17 cell development. The bromodomain inhibitor JQ1 was shown to alleviate Th17-mediated pathologies, but the underlying mechanism remains unclear. We hypothesized that JQ1 suppresses the response of Th17 cells by impairing p300-mediated acetylation of RORγt.

EXPERIMENTAL APPROACH

The effect of JQ1 on p300-mediated acetylation of RORγt was investigated in HEK293T (overexpressing Flag-p300 and Myc-RORγt) and human Th17 cells through immunoprecipitation and western blotting. To determine the regions of p300 responsible for JQ1-mediated suppression of HAT activity, we performed HAT assays on recombinant p300 fragments with/without the bromodomain, after exposure to JQ1. Additionally, the effect of JQ1 on p300-mediated acetylation of RORγt and Th17 cell function was verified in vivo, using murine Schistosoma-induced fibrosis models. Liver injury was assessed by histopathological examination and measurement of serum enzyme levels. Expression of Th17 effectors was detected by qRT-PCR, whereas IL-17- and RORγt-positive granuloma cells were detected by FACS.

KEY RESULTS

JQ1 impaired p300-mediated RORγt acetylation in human Th17 and HEK293T cells. JQ1 failed to suppress the acetyltransferase activity of p300 fragments lacking the bromodomain. JQ1 treatment attenuated Schistosoma-induced fibrosis in mice, by inhibiting RORγt acetylation and IL-17 expression.

CONCLUSIONS AND IMPLICATIONS

JQ1 impairs p300-mediated RORγt acetylation, thus reducing the expression of RORγt target genes, including Th17-specific cytokines. JQ1-mediated inhibition of p300 acetylase activity requires the p300 bromodomain. Strategies targeting p300 may provide new therapeutic approaches for controlling Th17-related diseases.

Kcnq1ot1/miR-381-3p/ETS2 Axis Regulates Inflammation in Mouse Models of Acute Respiratory Distress Syndrome

Inflammatory mediators play a key role in the pathogenesis of acute respiratory distress syndrome (ARDS). In this study, we aimed to explore the involvement of the Kcnq1 opposite strand/antisense transcript 1 (Kcnq1ot1)/miR-381-3p/E26 transformation-specific proto-oncogene 2 (ETS2) axis in inflammation of lipopolysaccharide (LPS)-induced ARDS. Microarray analysis revealed ETS2 as an upregulated gene in ARDS. Then, a LPS-induced ARDS mouse model was constructed, with a series of gain- or loss-of-function experiments conducted to evaluate the lung function and neutrophil extracellular trap (NET) formation in lung tissue and determine the neutrophil number, myeloperoxidase (MPO) activity, and inflammatory factor levels in bronchoalveolar lavage fluid (BALF). As the results revealed, downregulated expression of ETS2 resulted in improved lung function, decreased NETs, MPO activity, and levels of interleukin (IL)-6 and tumor necrosis factor alpha (TNF-α), as well as increased IL-10 level. Then, the assays of dual-luciferase reporter, RNA-binding protein immunoprecipitation (RIP), and RNA pull-down were performed to validate that Kcnq1ot1 promoted ETS2 expression by competitively binding to miR-381-3p. Meanwhile, it was also found that Kcnq1ot1 silencing reversed the promotive effect of EST2 on ARDS. Our results provide evidence that Kcnq1ot1 silencing may reduce the inflammatory response in LPS-induced ARDS via inhibition of miR-381-30-dependent ETS2, thereby presenting new molecular understanding for the development of ARDS.

Epigenetics in Sepsis: Understanding Its Role in Endothelial Dysfunction, Immunosuppression, and Potential Therapeutics

Sepsis has a complex pathophysiology in which both excessive and refractory inflammatory responses are hallmark features. Pro-inflammatory cytokine responses during the early stages are responsible for significant endothelial dysfunction, loss of endothelial integrity, and organ failure. In addition, it is now well-established that a substantial number of sepsis survivors experience ongoing immunological derangement and immunosuppression following a septic episode. The underpinning mechanisms of these phenomena are incompletely understood yet they contribute to a significant proportion of sepsis-associated mortality. Epigenetic mechanisms including DNA methylation, histone modifications, and non-coding RNAs, have an increasingly clear role in modulating inflammatory and other immunological processes. Recent evidence suggests epigenetic mechanisms are extensively perturbed as sepsis progresses, and particularly play a role in endothelial dysfunction and immunosuppression. Whilst therapeutic modulation of the epigenome is still in its infancy, there is substantial evidence from animal models that this approach could reap benefits. In this review, we summarize research elucidating the role of these mechanisms in several aspects of sepsis pathophysiology including tissue injury and immunosuppression. We also evaluate pre-clinical evidence for the use of "epi-therapies" in the treatment of poly-microbial sepsis.