Dephosphorylated Polymerase I and Transcript Release Factor Prevents Allergic Asthma Exacerbations by Limiting IL-33 Release

METTL3 mediates SOX5 m6A methylation in bronchial epithelial cells to attenuate Th2 cell differentiation in T2 asthma

Objective

Asthma, a chronic inflammatory disease in which type 2 T helper cells (Th2) play a causative role in the development of T2 asthma. N6-methyladenosine (m6A) modification, an mRNA modification, and methyltransferase-like 3 (METTL3) is involved in the development of T2 asthma by inhibiting Th2 cell differentiation. Sex determining region Y-box protein 5 (SOX5) is involved in regulating T cell differentiation, but its role in T2 asthma was unclear. The objective of this study was to explore the role of METTL3 and SOX5 in T2 asthma and whether there is an interaction between the two.

Materials and methods

Adults diagnosed with T2 asthma (n = 14) underwent clinical information collection and pulmonary function tests. In vivo and in vitro T2 asthma models were established using female C57BL/6 mice and human bronchial epithelial cells (HBE). The expressions of METTL3 and SOX5 were detected by Western blot and qRT-PCR and Western blot. Th2 cell differentiation was determined by flow cytometry and IL-4 level was detected by ELISA. m6A methylation level was determined by m6A quantitative assay. The relationship between METTL3 expression and clinical parameters was determined by Spearman rank correlation analysis. The function of METTL3 and SOX5 genes in asthma was investigated in vitro and in vivo. The RNA immunoprecipitation assay detected the specific interaction between METTL3 and SOX5.

Results

Patients with T2 asthma displayed lower METTL3 levels compared to healthy controls. Within this group, a negative correlation was observed between METTL3 and Th2 cells, while a positive correlation was noted between METTL3 and clinical parameters as well as Th1 cells. In both in vitro and in vivo models representing T2 asthma, METTL3 levels decreased significantly, while SOX5 levels showed the opposite trend. Overexpression of METTL3 gene in HBE cells significantly inhibited Th2 cell differentiation and increased m6A methylation activity. From a mechanism perspective, low METTL3 negatively regulates SOX5 expression through m6A modification dependence, while high SOX5 expression is positively associated with T2 asthma severity. Cell transfection experiments confirmed that METTL3 regulates Th2 cell differentiation and IL-4 release through SOX5.

Conclusions

Overall, our results indicate that METTL3 alleviates Th2 cell differentiation in T2 asthma by modulating the m6A methylation activity of SOX5 in bronchial epithelial cells. This mechanism could potentially serve as a target for the prevention and management of T2 asthma.

PTRF-IL33-ZBP1 signaling mediating macrophage necroptosis contributes to HDM-induced airway inflammation

Polymerase 1 and transcript release factor (PTRF, encoding by Cavin-1) regulates interleukin 33 (IL-33) release, which is implicated in asthma development. Z-DNA binding protein 1 (ZBP1)-sensing Z-RNAs induces necroptosis which causes inflammatory diseases. House dust mite (HDM) is the major source of allergen in house dust and is strongly associated with the development of asthma. Whether PTRF via IL-33 and ZBP1 mediates HDM-induced macrophage necroptosis and airway inflammation remains unclear. Here, we found that deficiency of PTRF could reduce lung IL-33, ZBP1, phosphor-receptor-interacting protein kinase 3 (p-RIPK3), and phosphor-mixed lineage kinase domain-like (p-MLKL) (necroptosis executioner), and airway inflammation in an HDM-induced asthma mouse model. In HDM-treated macrophages, ZBP1, p-RIPK3, and p-MLKL levels were markedly increased, and these changes were reversed by deletion of Cavin-1. Deletion of Il33 also reduced expression of ZBP1, p-RIPK3, and p-MLKL in HDM-challenged lungs. Moreover, IL-33 synergizing with HDM boosted expression of ZBP1, p-RIPK3, and p-MLKL in macrophages. In bronchial epithelial cells rather than macrophages and vascular endothelial cells, PTRF positively regulates IL-33 expression. Therefore, we conclude that PTRF mediates HDM-induced macrophage ZBP1/necroptosis and airway inflammation, and this effect could be boosted by bronchial epithelial cell-derived IL-33. Our findings suggest that PTRF-IL33-ZBP1 signaling pathway might be a promising target for dampening airway inflammation.

MBD2 mediates Th17 cell differentiation by regulating MINK1 in Th17-dominant asthma

Objectives: .Asthma is a highly heterogeneous disease, and T-helper cell type 17 (Th17) cells play a pathogenic role in the development of non-T2 severe asthma. Misshapen like kinase 1 (MINK1) is involved in the regulation of Th17 cell differentiation, but its effect on severe asthma remains unclear. Our previous studies showed that methyl-CpG binding domain protein 2 (MBD2) expression was significantly increased in patients with Th17 severe asthma and could regulate Th17 cell differentiation. The aim of this study was to investigate how MBD2 interacts with MINK1 to regulate Th17 cell differentiation in Th17-dominant asthma.

Materials and methods: Female C57BL/6 mice and bronchial epithelial cells (BECs) were used to establish mouse and cell models of Th17-dominant asthma, respectively. Flow cytometry was used to detect Th17 cell differentiation, and the level of IL-17 was detected by enzyme-linked immunosorbent assay (ELISA). Western blot and quantitative real-time PCR (qRT-PCR) were used to detect MBD2 and MINK1 expression. To investigate the role of MBD2 and MINK1 in Th17 cell differentiation in Th17-dominant asthma, the MBD2 and MINK1 genes were silenced or overexpressed by small interfering RNA and plasmid transfection.

Results: Mouse and BEC models of Th17-dominant asthma were established successfully. The main manifestations were increased neutrophils in BALF, airway hyperresponsiveness (AHR), activated Th17 cell differentiation, and high IL-17 levels. The expression of MBD2 in lung tissues and BECs from the Th17-dominant asthma group was significantly increased, while the corresponding expression of MINK1 was significantly impaired. Through overexpression or silencing of MBD2 and MINK1 genes, we have concluded that MBD2 and MINK1 regulate Th17 cell differentiation and IL-17 release. Interestingly, MBD2 was also found to negatively regulate the expression of MINK1.

Conclusion: Our findings have revealed new roles for MBD2 and MINK1, and provide new insights into epigenetic regulation of Th17-dominant asthma, which is dominated by neutrophils and Th17 cells. This study could lead to new therapeutic targets for patients with Th17-dominant asthma.

PTRF/Cavin-1 as a Novel RNA-Binding Protein Expedites the NF-κB/PD-L1 Axis by Stabilizing lncRNA NEAT1, Contributing to Tumorigenesis and Immune Evasion in Glioblastoma

Background

Immunotherapy, especially checkpoint inhibitors targeting PD-1 or PD-L1, has revolutionized cancer therapy. However, PD-1/PD-L1 inhibitors have not been investigated thoroughly in glioblastoma (GBM). Studies have shown that polymerase 1 and transcript release factor (PTRF/Cavin-1) has an immune-suppressive function in GBM. Thus, the relationship between PTRF and PD-L1 and their role in immune suppression requires further investigation in GBM.

Methods

We used public databases and bioinformatics analysis to investigate the relationship between PTRF and PD-L1. We next confirmed the predicted relationship between PTRF and PD-L1 in primary GBM cell lines by using different experimental approaches. RIP-Seq, RIP, ChIP, and qRT-PCR were conducted to explore the molecular mechanism of PTRF in immunosuppression.

Results

We found that PTRF stabilizes lncRNA NEAT1 to induce NF-κB and PD-L1 and promotes immune evasion in GBM. PTRF was found to correlate with immunosuppression in the public GBM databases. PTRF increased the level of PD-L1 in primary cell lines from GBM patients. We carried out RIP-Seq of GBM cells and found that PTRF interacts with lncRNA NEAT1 and stabilizes its mRNA. PTRF also promoted the activity of NF-κB by suppressing UBXN1 expression via NEAT1 and enhanced the transcription of PD-L1 through NF-κB activation. Finally, PTRF promoted immune evasion in GBM cells by regulating PD-1 binding and PD-L1 mediated T cell cytotoxicity.

Conclusions

In summary, our study identified the PTRF-NEAT1-PD-L1 axis as a novel immune therapeutic target in GBM.

USP4 is pathogenic in allergic airway inflammation by inhibiting regulatory T cell response

AIMS

Asthma is characterized by chronic inflammation and airway hyperresponsiveness (AHR). It is controllable, but not curable. Ubiquitin-specific peptidase 4 (USP4) has been verified as a regulator of regulatory T (Treg) cells and Th17 cells in vitro. In this study, we aim to investigate whether USP4 could serve as a therapeutic target for asthma.

MAIN METHODS

Age-matched USP4 wild-type and knockout mice received an intraperitoneal injection of 100 μg ovalbumin (OVA) mixed in 2 mg aluminum hydroxide in 1 × PBS on days 0, 7 and 14. On days 21 to 27, the mice were challenged with aerosolized 1% OVA in 1 × PBS for 30 min. Tissue histology, ELISA and flow cytometry were applied 24 h after the last OVA challenge.

KEY FINDINGS

USP4 deficiency protected mice from OVA-induced AHR and decreased the production of several inflammatory cytokines in T cells in vivo. Compared to the lung cells isolated from WT mice, Usp4^-/- lung cells decreased secretion of IL-4, IL-13 and IL-17A upon stimulation in vitro. Meanwhile, the percentage of CD4⁺Foxp3⁺ Treg cells was elevated, with more CCR6⁺Foxp3⁺ Treg cells accumulating in the lungs of OVA-challenged USP4 deficient mice than in their wild-type counterparts. Treatment with the USP4 inhibitor, Vialinin A, reduced inflammatory cell infiltration in the lungs of OVA-challenged mice in vivo.

SIGNIFICANCE

We found USP4 deficiency contributes to attenuated airway inflammation and AHR in allergen-induced murine asthma, and Vialinin A treatment alleviates asthma pathogenesis and may serve as a promising therapeutic target for asthma.

PTRF/cavin-1 remodels phospholipid metabolism to promote tumor proliferation and suppress immune responses in glioblastoma by stabilizing cPLA2

BACKGROUND

Metabolism remodeling is a hallmark of glioblastoma (GBM) that regulates tumor proliferation and the immune microenvironment. Previous studies have reported that increased polymerase 1 and transcript release factor (PTRF) levels are associated with a worse prognosis in glioma patients. However, the biological role and the molecular mechanism of PTRF in GBM metabolism remain unclear.

METHODS

The relationship between PTRF and lipid metabolism in GBM was detected by nontargeted metabolomics profiling and subsequent lipidomics analysis. Western blotting, quantitative real-time PCR, and immunoprecipitation were conducted to explore the molecular mechanism of PTRF in lipid metabolism. A sequence of in vitro and in vivo experiments (both xenograft tumor and intracranial tumor mouse models) were used to detect the tumor-specific impacts of PTRF.

RESULTS

Here, we show that PTRF triggers a cytoplasmic phospholipase A2 (cPLA2)-mediated phospholipid remodeling pathway that promotes GBM tumor proliferation and suppresses tumor immune responses. Research in primary cell lines from GBM patients revealed that cells overexpressing PTRF show increased cPLA2 activity-resulting from increased protein stability-and exhibit remodeled phospholipid composition. Subsequent experiments revealed that PTRF overexpression alters the endocytosis capacity and energy metabolism of GBM cells. Finally, in GBM xenograft and intracranial tumor mouse models, we showed that inhibiting cPLA2 activity blocks tumor proliferation and prevents PTRF-induced reduction in CD8+ tumor-infiltrating lymphocytes.

CONCLUSIONS

The PTRF-cPLA2 lipid remodeling pathway promotes tumor proliferation and suppresses immune responses in GBM. In addition, our findings highlight multiple new therapeutic targets for GBM.

Mas receptor activation attenuates allergic airway inflammation via inhibiting JNK/CCL2-induced macrophage recruitment

BACKGROUND

Defective absorption of acute allergic airway inflammation is involved in the initiation and development of chronic asthma. After allergen exposure, there is a rapid recruitment of macrophages around the airways, which promote acute inflammatory responses. The Ang-(1-7)/Mas receptor axis reportedly plays protective roles in various tissue inflammation and remodeling processes in vivo. However, the exact role of Mas receptor and their underlying mechanisms during the pathology of acute allergic airway inflammation remains unclear.

OBJECTIVE

We investigated the role of Mas receptor in acute allergic asthma and explored its underlying mechanisms in vitro, aiming to find critical molecules and signal pathways.

METHODS

Mas receptor expression was assessed in ovalbumin (OVA)-induced acute asthmatic murine model. Then we estimated the anti-inflammatory role of Mas receptor in vivo and explored expressions of several known inflammatory cytokines as well as phosphorylation levels of MAPK pathways. Mas receptor functions and underlying mechanisms were studied further in the human bronchial epithelial cell line (16HBE).

RESULTS

Mas receptor expression decreased in acute allergic airway inflammation. Multiplex immunofluorescence co-localized Mas receptor and EpCAM, indicated that Mas receptor may function in the bronchial epithelium. Activating Mas receptor through AVE0991 significantly alleviated macrophage infiltration in airway inflammation, accompanied with down-regulation of CCL2 and phosphorylation levels of MAPK pathways. Further studies in 16HBE showed that AVE0991 pre-treatment inhibited LPS-induced or anisomycin-induced CCL2 increase and THP-1 macrophages migration via JNK pathways.

CONCLUSION

Our findings suggested that Mas receptor activation significantly attenuated CCL2 dependent macrophage recruitments in acute allergic airway inflammation through JNK pathways, which indicated that Mas receptor, CCL2 and phospho-JNK could be potential targets against allergic airway inflammation.

Caveola-forming proteins and prostate cancer

Caveolae are specialised and dynamic plasma membrane subdomains, involved in many cellular functions including endocytosis, signal transduction, mechanosensing and lipid storage, trafficking, and metabolism. Two protein families are indispensable for caveola formation and function, namely caveolins and cavins. Mutations of genes encoding these caveolar proteins cause serious pathological conditions such as cardiomyopathies, skeletal muscle diseases, and lipodystrophies. Deregulation of caveola-forming protein expression is associated with many types of cancers including prostate cancer. The distinct function of secretion of the prostatic fluid, and the unique metabolic phenotype of prostate cells relying on lipid metabolism as a main bioenergetic pathway further suggest a significant role of caveolae and caveolar proteins in prostate malignancy. Accumulating in vitro, in vivo, and clinical evidence showed the association of caveolin-1 with prostate cancer grade, stage, metastasis, and drug resistance. In contrast, cavin-1 was found to exhibit tumour suppressive roles. Studies on prostate cancer were the first to show the distinct function of the caveolar proteins depending on their localisation within the caveolar compartment or as cytoplasmic or secreted proteins. In this review, we summarise the roles of caveola-forming proteins in prostate cancer and the potential of exploiting them as therapeutic targets or biological markers.