miRNA-302e attenuates inflammation in infantile pneumonia though the RelA/BRD4/NF-κB signaling pathway

Granulocyte-macrophage colony-stimulating factor suppresses induction of type I interferon in infants with severe pneumonia

BACKGROUND

The underlying mechanisms for infantile bronchopneumonia development remain unknown.

METHODS

Peripheral blood mononuclear cell (PBMCs) and serum derived from severe and mild infantile bronchopneumonia were obtained, and the expression of various molecules was detected with enzyme-linked immunosorbent assay and quantitative PCR. Such molecules were also detected in granulocyte-macrophage colony-stimulating factor (GM-CSF)-induced bone marrow-derived NFκB2^-/- dendritic cells (DCs) or NIK SMI1 (NF-κB-inducing kinase inhibitor) administrated DCs.

RESULTS

The relative mRNA expression levels of type I interferons (IFNs) (IFN-α4, IFN-β), Th17 cell-associated markers (interleukin-17A, retinoic-acid-receptor-related orphan nuclear receptor gamma, and GM-CSF), and non-canonical NF-κB member (NFκB2) were significantly up-regulated in PBMCs and DCs derived from infantile bronchopneumonia compared with healthy controls. However, compared with Th17 cell-associated markers and non-canonical NF-κB molecules, the expression of IFN-α4 and IFN-β was significantly inhibited in severe infantile bronchopneumonia compared with mild infantile bronchopneumonia. The relative protein expression of the above molecules also showed a similar expression pattern in the PBMCs or serum. NF-κB2 knockout or NIK SMI1 administration could reverse the diminished expression of IFN-β in GM-CSF-induced bone marrow-derived DCs.

CONCLUSIONS

GM-CSF-dependent non-canonical NF-κB pathway-mediated inhibition of type I IFNs production in DCs contributes to the development of severe bronchopneumonia in infant.

IMPACT

Granulocyte-macrophage colony-stimulating factor-dependent non-canonical NF-κB pathway-mediated inhibition of type I IFNs production in dendritic cells is critical for the development of infantile bronchopneumonia. Our findings reveal a possible mechanism underlying the development of severe infantile bronchopneumonia. The results could provide therapeutic molecular target for the treatment of such disease.

Sphingosine Kinase-1 (SPHK1) promotes inflammation in infantile pneumonia by regulating NLRP3 inflammasome and SIRT1 expression

BACKGROUND

Infantile pneumonia is an acute inflammatory disorder of the lung caused by mycoplasma pneumonia. SPHK1 (sphingosine kinase-1) signaling pathway is involved in the process of inflammatory diseases. However, whether SphK1 regulates inflammatory responses in infantile pneumonia remains unclear. In this study, we investigated the role of SPHK1 in infantile pneumonia and its underlying mechanisms.

METHODS

Serum samples of 12 patients with infantile pneumonia and healthy controls were obtained from Hunan Children's Hospital. To induce pneumonia, mice were administrated with LPS (lipopolysaccharide) into the lung. RAW264.7 cells were used as an in vitro macrophage model stimulated with LPS or PBS for 4 h.

RESULTS

SPHK1 mRNA level and protein level in the LPS-treated mice and patients with infantile pneumonia were significantly increased. SPHK1 promoted inflammation and lung injury in mice with infantile pneumonia. The knockdown of SPHK1 expression inhibited inflammation and restrained lung injury in mice with infantile pneumonia. SPHK1 overexpression also exacerbated inflammation in RAW264.7 cells stimulated by LPS, and SPHK1 silencing reduced inflammatory responses. We further showed that SPHK1 induced NLRP3 (NLR Family Pyrin Domain Containing 3) activity by inhibiting SIRT1 expression.

CONCLUSION

Our study demonstrated that SPHK1 promotes inflammation of infantile pneumonia by modulating NLRP3 inflammasome via the regulation of SIRT1 expression and mitochondrial permeability transition.

Hepatic BRD4 Is Upregulated in Liver Fibrosis of Various Etiologies and Positively Correlated to Fibrotic Severity

Bromodomain-containing protein 4 (BRD4) has been implicated to play a regulatory role in fibrogenic gene expression in animal models of liver fibrosis. The potential role of BRD4 in liver fibrosis in humans remains unclear. We sought to investigate the expression and cellular localization of BRD4 in fibrotic liver tissues. Human liver tissues were collected from healthy individuals and patients with liver fibrosis of various etiologies. RNA-seq showed that hepatic BRD4 mRNA was elevated in patients with liver fibrosis compared with that in healthy controls. Subsequent multiple manipulations such as western blotting, real-time quantitative polymerase chain reaction, and dual immunofluorescence analysis confirmed the abnormal elevation of the BRD4 expression in liver fibrosis of various etiologies compared to healthy controls. BRD4 expression was positively correlated with the severity of liver fibrosis, and also correlated with the serum levels of aspartate aminotransferase and total bilirubin. Moreover, the expression of C-X-C motif chemokine ligand 6 (CXCL6), a factor interplayed with BRD4, was increased in hepatic tissues of the patients with liver fibrosis. Its expression level was positively correlated with BRD4 level. BRD4 is up-regulated in liver fibrosis, regardless of etiology, and its increased expression is positively correlated with higher degrees of liver fibrosis. Our data indicate that BRD4 play a critical role in the progress of liver fibrosis, and it holds promise as a potential target for intervention of liver fibrosis.

Pharmacological Modulation of BET Family in Sepsis

The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis 3.0) recommended defining sepsis as a life-threatening organ dysfunction caused by the host's uncontrolled response to infection. The bromodomain and extra-terminal (BET) protein family (such as BRD2, BRD3, and BRD4), an epigenetic regulator of gene transcription, has recently been recognized as a significant septic regulator of inflammation and immune response, including cytokine and chemokine production. Mechanistically, the two N-terminal conserved tandem bromodomains (namely the first bromodomain [BD1] and the second bromodomain [BD2]) favor the binding of BETs to acetylated histones or transcription factors, thereby initiating gene transcription machinery after CycT1 and CDK9 (also known as P-TEFb) are recruited to gene promoters to phosphorylate RNA pol II. Notably, BD1 and BD2 are not functionally redundant because they have different target genes in innate immune cells. Small-molecule BET inhibitors (BETis) for different BDs, such as I-BET, JQ1, I-BET151, apabetalone, RVX-297, and dBET1 have shown promising therapeutic effects in experimental sepsis models. This mini-review summarizes the emerging roles of BETs and the applications of BETis in sepsis, discusses the existing shortcomings of BETis, and introduces possible future research directions in this area.

JQ1 as a BRD4 Inhibitor Blocks Inflammatory Pyroptosis-Related Acute Colon Injury Induced by LPS

Endotoxemia is a severe inflammation response induced by infection especially bacterial endotoxin translocation, which severely increases mortality in combination with acute colon injury. Bromodomain-containing protein 4 (BRD4) is an important Bromo and Extra-Terminal (BET) protein to participate in inflammatory responses. However, it is still unknown about the specific connection between BRD4 and inflammation-related pyroptosis in endotoxemia colon. Here, through evaluating the mucous morphology and the expression of tight junction proteins such as occludin and ZO1, we found the upregulation of BRD4 in damaged colon with poor tight junction in an endotoxemia mouse model induced by lipopolysaccharides (LPS). Firstly, the BRD4 inhibitor JQ1 was used to effectively protect colon tight junction in endotoxemia. As detected, high levels of pro-inflammation cytokines IL6, IL1β and IL18 in endotoxemia colon were reversed by JQ1 pretreatment. In addition, JQ1 injection reduced endotoxemia-induced elevation of the phosphorylated NF κB and NLRP3/ASC/caspase 1 inflammasome complex in colon injury. Furthermore, activated pyroptosis markers gasdermins in endotoxemia colon were also blocked by JQ1 pretreatment. Together, our data indicate that BRD4 plays a critical role in regulating pyroptosis-related colon injury induced by LPS, and JQ1 as a BRD4 inhibitors can effectively protect colon from endotoxemia-induced inflammation injury.

The BET family in immunity and disease

Innate immunity serves as the rapid and first-line defense against invading pathogens, and this process can be regulated at various levels, including epigenetic mechanisms. The bromodomain and extraterminal domain (BET) family of proteins consists of four conserved mammalian members (BRD2, BRD3, BRD4, and BRDT) that regulate the expression of many immunity-associated genes and pathways. In particular, in response to infection and sterile inflammation, abnormally expressed or dysfunctional BETs are involved in the activation of pattern recognition receptor (e.g., TLR, NLR, and CGAS) pathways, thereby linking chromatin machinery to innate immunity under disease or pathological conditions. Mechanistically, the BET family controls the transcription of a wide range of proinflammatory and immunoregulatory genes by recognizing acetylated histones (mainly H3 and H4) and recruiting transcription factors (e.g., RELA) and transcription elongation complex (e.g., P-TEFb) to the chromatin, thereby promoting the phosphorylation of RNA polymerase II and subsequent transcription initiation and elongation. This review covers the accumulating data about the roles of the BET family in innate immunity, and discusses the attractive prospect of manipulating the BET family as a new treatment for disease.

MicroRNA-127-5p attenuates severe pneumonia via tumor necrosis factor receptor-associated factor 1

Pneumonia is a persistent and pervasive disease, the effects of which can be severe. MicroRNA (miR)-127-5p has been utilized as a novel biomarker for the diagnosis of severe pneumonia. The present study aimed to investigate the function of miR-127-5p during severe pneumonia. An in vitro model of severe pneumonia in Ana-1 murine macrophages was established using lipopolysaccharide (LPS). Subsequently, reverse transcription-quantitative PCR and ELISA were performed to detect the mRNA and protein expression levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α. Western blotting was also performed to measure the activity of AKT and NF-κB. The results indicated that compared with the control group, LPS treatment increased TNF receptor-associated factor 1 (TRAF1) expression levels and reduced miR-127-5p expression levels. Furthermore, the results revealed that the 3'-untranslated region of TRAF1 was targeted by miR-127-5p. miR-127-5p mimic reduced LPS-induced increases in IL-1β, IL-6 and TNF-α expression by targeting TRAF1, which was potentially mediated by inactivation of the AKT and NF-κB signaling pathways. Collectively, the results demonstrated that miR-127-5p may attenuate severe pneumonia by reducing LPS-induced inflammatory cytokine production, and inactivating the AKT and NF-κB signaling pathways by targeting TRAF1.