Type 17 mucosal-associated invariant T cells contribute to neutrophilic inflammation in patients with nasal polyps

Mucosal-Associated Invariant T (MAIT) Cell-Mediated Immune Mechanisms of Peritoneal Dialysis-Induced Peritoneal Fibrosis and Therapeutic Targeting

Key Points

Background

Peritoneal fibrosis is a serious complication of long-term peritoneal dialysis (PD) and abdominal surgeries, yet effective treatments remain elusive. Given the known roles of mucosal-associated invariant T (MAIT) cells in immune responses and fibrotic diseases, we investigated their involvement in PD-induced peritoneal fibrosis to identify potential therapeutic targets.

Methods

We used single-cell RNA sequencing and flow cytometry to characterize the activation and function of peritoneal MAIT cells in patients undergoing long-term PD. Our investigation focused on the molecular pathways activated by these cells, particularly the MHC class 1–related protein 1 (MR1)-mediated interaction with mesothelial cells and subsequent activation of the mTOR complex 1 signaling pathway. We further assessed the effect of inhibiting MAIT cells on fibrogenesis using both in vitro models and Mr1 knockout mice.

Results

Our study revealed that long-term PD significantly enhanced the activation of MAIT cells, particularly the proinflammatory MAIT17 subtype. These activated cells contributed to peritoneal fibrogenesis by binding to the MR1 receptor on mesothelial cells, which triggered hyperglycolysis through the mTOR complex 1 pathway, ultimately leading to fibrogenesis. Notably, we demonstrated that blocking the MR1–MAIT interaction, either through genetic knockout or pharmacological inhibition with acetyl-6-formylpterin, effectively mitigated fibrosis.

Conclusions

This study identified MAIT cells as crucial drivers of PD-induced peritoneal fibrosis.

Revisiting T Cells in Chronic Rhinosinusitis

A variety of immune cells in the nasal tissue are involved in the immunopathogenesis of chronic rhinosinusitis (CRS), a chronic inflammatory disease affecting the nasal cavity and paranasal sinuses. T cells play a pivotal role in orchestrating immune dysregulation in CRS by producing key cytokines. Recent studies have expanded the understanding of T cell biology across the inflammatory endotypes of CRS. This review summarizes current knowledge on the multifaceted roles of T cells in the pathophysiology of CRS. Particularly, we highlight the alterations in phenotypes and functions of various T cell subsets in CRS. Additionally, as functional studies of effector and regulatory T cell populations have revealed potential translational targets, we suggest perspectives for future research into T cell-oriented therapeutic strategies for CRS.

Genetic correlation between chronic sinusitis and autoimmune diseases

Objective

The association between autoimmune diseases and chronic rhinosinusitis in observational studies remains unclear. This study aimed to explore the genetic correlation between chronic rhinosinusitis and autoimmune diseases.

Methods

We employed Mendelian randomization (MR) analysis and linkage disequilibrium score regression (LDSC) to investigate causal relationships and genetic correlations between autoimmune phenotypes and chronic rhinosinusitis. Additionally, transcriptome-wide association (TWAS) analysis was conducted to identify the shared genes between the two conditions to demonstrate their relationship. The CRS GWAS (genome-wide association study) data and other autoimmune diseases were retrieved from ieuOpenGWAS (https://gwas.mrcieu.ac.uk/), the FinnGen alliance (https://r8.finngen.fi/), the UK Biobank (https://www.ukbiobank.ac.uk/), and the EBI database (https://www.ebi.ac.uk/).

Results

Utilizing a bivariate two-sample Mendelian randomization approach, our findings suggest a significant association of chronic rhinosinusitis with various autoimmune diseases, including allergic rhinitis (p = 9.55E-10, Odds Ratio [OR] = 2,711.019, 95% confidence interval [CI] = 261.83391-28,069.8), asthma (p = 1.81E-23, OR = 33.99643, 95%CI = 17.52439-65.95137), rheumatoid arthritis (p = 9.55E-10, OR = 1.115526, 95%CI = 1.0799484-1.1522758), hypothyroidism (p = 2.08828E-2, OR = 4.849254, 95%CI = 1.7154455-13.707962), and type 1 diabetes (p = 2.08828E-2, OR = 01.04849, 95%CI = 1.0162932-1.0817062). LDSC analysis revealed a genetic correlation between the positive autoimmune phenotypes mentioned above and chronic rhinosinusitis: AR (rg = 0.344724754, p = 3.94E-8), asthma (rg = 0.43703672, p = 1.86E-10), rheumatoid arthritis (rg = 0.27834931, p = 3.5376E-2), and hypothyroidism (rg = -0.213201473, p = 3.83093E-4). Utilizing the Transcriptome-Wide Association Studies (TWAS) approach, we identified several genes commonly associated with both chronic rhinosinusitis and autoimmune diseases. Genes such as TSLP/WDR36 (Chromosome 5, top SNP: rs1837253), ORMDL3 (Chromosome 13, top SNP: rs11557467), and IL1RL1/IL18R1 (Chromosome 2, top SNP: rs12905) exhibited a higher degree of consistency in their shared involvement across atopic dermatitis (AT), allergic rhinitis (AR), and chronic rhinosinusitis (CRS).

Conclusion

Current evidence suggests a genetic correlation between chronic rhinosinusitis and autoimmune diseases like allergic rhinitis, asthma, rheumatoid arthritis, hypothyroidism, and type 1 diabetes. Further research is required to elucidate the mechanisms underlying these associations.

Identification of hub genes associated with neutrophils in chronic rhinosinusitis with nasal polyps

Neutrophil infiltration plays a key role in the pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP). However, pertinent mechanisms remain poorly elucidated. Here, we obtained the data from gene expression omnibus (GEO) and gene set enrichment analysis (GSEA) to identify and validate neutrophil-associated hub genes in CRSwNP. We found that four neutrophil-associated hub genes, namely ICAM1, IL-1β, TYROBP, and BCL2A1, were markedly upregulated and positively correlated with neutrophil infiltration levels in patients with CRSwNP. Subsequently, this was confirmed by real-time quantitative PCR. In conclusion, we identified the role of neutrophil infiltration in the pathophysiology of CRSwNP, which may be the potential targets for the diagnosis and treatment of CRSwNP.

Differentiation of Type 17 Mucosal-Associated Invariant T Cells in Circulation Contributes to the Severity of Sepsis

Mucosal-associated invariant T (MAIT) cells are essential in defending against infection. Sepsis is a systemic inflammatory response to infection and a leading cause of death. The relationship between the overall competency of the host immune response and disease severity is not fully elucidated. This study identified a higher proportion of circulating MAIT17 with expression of IL-17A and retinoic acid receptor-related orphan receptor γt in patients with sepsis. The proportion of MAIT17 was correlated with the severity of sepsis. Single-cell RNA-sequencing analysis revealed an enhanced expression of lactate dehydrogenase A (LDHA) in MAIT17 in patients with sepsis. Cell-culture experiments demonstrated that phosphoinositide 3-kinase-LDHA signaling was required for retinoic acid receptor-related orphan receptor γt expression in MAIT17. Finally, the elevated levels of plasma IL-18 promoted the differentiation of circulating MAIT17 cells in sepsis. In summary, this study reveals a new role of circulating MAIT17 in promoting sepsis severity and suggests the phosphoinositide 3-kinase-LDHA signaling as a driving force in MAIT17 responses.

Metabolic heterogeneity in tumor microenvironment - A novel landmark for immunotherapy

The surrounding non-cancer cells and tumor cells that make up the tumor microenvironment (TME) have various metabolic rhythms. TME metabolic heterogeneity is influenced by the intricate network of metabolic control within and between cells. DNA, protein, transport, and microbial levels are important regulators of TME metabolic homeostasis. The effectiveness of immunotherapy is also closely correlated with alterations in TME metabolism. The response of a tumor patient to immunotherapy is influenced by a variety of variables, including intracellular metabolic reprogramming, metabolic interaction between cells, ecological changes within and between tumors, and general dietary preferences. Although immunotherapy and targeted therapy have made great strides, their use in the accurate identification and treatment of tumors still has several limitations. The function of TME metabolic heterogeneity in tumor immunotherapy is summarized in this article. It focuses on how metabolic heterogeneity develops and is regulated as a tumor progresses, the precise molecular mechanisms and potential clinical significance of imbalances in intracellular metabolic homeostasis and intercellular metabolic coupling and interaction, as well as the benefits and drawbacks of targeted metabolism used in conjunction with immunotherapy. This offers insightful knowledge and important implications for individualized tumor patient diagnosis and treatment plans in the future.

MAIT cells in bacterial infectious diseases: heroes, villains, or both?

Due to the aggravation of bacterial drug resistance and the lag in the development of new antibiotics, it is crucial to develop novel therapeutic regimens for bacterial infectious diseases. Currently, immunotherapy is a promising regimen for the treatment of infectious diseases. Mucosal-associated invariant T (MAIT) cells, a subpopulation of innate-like T cells, are abundant in humans and can mount a rapid immune response to pathogens, thus becoming a potential target of immunotherapy for infectious diseases. At the site of infection, activated MAIT cells perform complex biological functions by secreting a variety of cytokines and cytotoxic substances. Many studies have shown that MAIT cells have immunoprotective effects because they can bridge innate and adaptive immune responses, leading to bacterial clearance, tissue repair, and homeostasis maintenance. MAIT cells also participate in cytokine storm generation, tissue fibrosis, and cancer progression, indicating that they play a role in immunopathology. In this article, we review recent studies of MAIT cells, discuss their dual roles in bacterial infectious diseases and provide some promising MAIT cell-targeting strategies for the treatment of bacterial infectious diseases.