A gain-of-function NLRP3 3'-UTR polymorphism causes miR-146a-mediated suppression of NLRP3 expression and confers protection against sepsis progression

The 3'UTR Polymorphisms in the NLRP3 Gene Associated with the Risk of COPD and Their Putative Effects on the microRNA Mechanism

Aims: Evaluating the association between a single nucleotide polymorphism in the 3' untranslated region (3'UTR) of the miRNA binding site of the NLRP3 gene and the occurrence and development of chronic obstructive pulmonary disease (COPD) and providing information to aid in the early detection and treatment of COPD. Materials and Methods: The regulatory single nuclear polymorphisms (SNPs) located in NLRP3 3'UTR were searched by using the dbSNP database and miRNA binding site prediction database. Meanwhile, samples from COPD patients and healthy controls in the same period were used for verification. The clinical baseline information of all subjects was collected, and the transcription level and protein expression level of NLRP3 and the expression level of inflammatory factors downstream of NLRP3 were detected. The effects of SNPs' single nucleotide changes on the transcription and expression of inflammatory factors were analyzed. Results: The study included 418 participants (249 in the COPD group and 169 in the control group). NLRP3 SNPs with miRNA binding sites include rs10754558 (G > C), rs1664774076 (ATAT > del), and rs1664775106 (C > G). Furthermore, two genotypes, GCG and GCA, were discovered to have a linkage mutation at 3'UTR 459-461. COPD susceptibility is tightly associated with the expression of the rs1664774076 del/del genotype, and the risk of COPD increased by 2.770 times (p = 0.003). Type 459-461 GCA was substantially related to the likelihood of developing COPD at various stages (p < 0.05). Except for rs10754558, all homozygous mutants increased NLRP3 mRNA and protein levels. NLRP3 had the greatest area under the receiver operating characteristic (ROC) curve for predicting the development and diagnosis of COPD when compared with its downstream inflammatory variables (AUC = 0.9291). Conclusions: The NLRP3 rs1664774076 del/del genotype is a COPD susceptibility gene, and the GCA genotype at 459-461 can be used as an early predictor of COPD exacerbation. The NLRP3 3'UTR polymorphism may alter the loss of miRNA binding sites, leading to an increase in NLRP3 expression. In the development of COPD, NLRP3 has a better diagnostic value than traditional inflammatory factors. The Clinical Trials Registration number Z: protocol KY01-2020-11-06.

Exosomal microRNA/miRNA Dysregulation in Respiratory Diseases: From Mycoplasma-Induced Respiratory Disease to COVID-19 and Beyond

Respiratory diseases represent a significant economic and health burden worldwide, affecting millions of individuals each year in both human and animal populations. MicroRNAs (miRNAs) play crucial roles in gene expression regulation and are involved in various physiological and pathological processes. Exosomal miRNAs and cellular miRNAs have been identified as key regulators of several immune respiratory diseases, such as chronic respiratory diseases (CRD) caused by Mycoplasma gallisepticum (MG), Mycoplasma pneumoniae pneumonia (MMP) caused by the bacterium Mycoplasma pneumoniae, coronavirus disease 2019 (COVID-19), chronic obstructive pulmonary disease (COPD), asthma, and acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Consequently, miRNAs seem to have the potential to serve as diagnostic biomarkers and therapeutic targets in respiratory diseases. In this review, we summarize the current understanding of the functional roles of miRNAs in the above several respiratory diseases and discuss the potential use of miRNAs as stable diagnostic biomarkers and therapeutic targets for several immune respiratory diseases, focusing on the identification of differentially expressed miRNAs and their targeting of various signaling pathways implicated in disease pathogenesis. Despite the progress made, unanswered questions and future research directions are discussed to facilitate personalized and targeted therapies for patients with these debilitating conditions.

The NLRP3 inflammasome rs35829419 C>A polymorphism is associated with type 2 diabetes mellitus in Saudi Arabia

OBJECTIVES

To investigate the frequency of NLRP3 gene rs35829419 C>A single-nucleotide polymorphism (SNP) in a Saudi Arabian population from Jazan (Southwest Saudi Arabia) and test its potential association with type 2 diabetes mellitus (T2DM).

METHODS

This case-control study included 546 volunteers (271 patients with T2DM and 275 healthy controls) recruited from outpatient clinics at Jazan University Hospital and King Fahad Central Hospital in Jazan, Saudi Arabia, between December 2021 and July 2022. Genomic DNA was extracted from all samples and genotyped for the NLRP3 rs35829419 C>A SNP using TaqMan technology. The association between the NLRP3 rs35829419 polymorphism and T2DM was examined using logistic regression analysis.

RESULTS

Overall genotype distributions were 90.5% (CC), 9.3% (CA), and 0.2% (AA). The heterozygous CA genotype was more frequent in T2DM group (12.2%) compared to the control group (6.5%) and logistic regression analysis showed a statically significant association with T2DM risk under codominant (CA versus CC; odds ratio [OR]=1.99; 95% confidence interval [CI]= [1.11-3.61]; p=0.0270), and dominant (CA+AA versus CC; OR=2.05; CI=[1.16-3.75]; p=0.019) models of inheritance.

CONCLUSION

This study revealed the frequency of NLRP3 rs35829419 C>A polymorphism in our population and showed a direct correlation between having the minor allele for A and having a higher risk of developing T2DM. This study highlights the significance of NLRP3 rs35829419 C>A polymorphism in the pathophysiology of T2DM.

The double sides of NLRP3 inflammasome activation in sepsis

Sepsis is defined as a life-threatening organ dysfunction induced by a dysregulated host immune response to infection. Immune response induced by sepsis is complex and dynamic. It is schematically described as an early dysregulated systemic inflammatory response leading to organ failures and early deaths, followed by the development of persistent immune alterations affecting both the innate and adaptive immune responses associated with increased risk of secondary infections, viral reactivations, and late mortality. In this review, we will focus on the role of NACHT, leucin-rich repeat and pyrin-containing protein 3 (NLRP3) inflammasome in the pathophysiology of sepsis. NLRP3 inflammasome is a multiproteic intracellular complex activated by infectious pathogens through a two-step process resulting in the release of the pro-inflammatory cytokines IL-1β and IL-18 and the formation of membrane pores by gasdermin D, inducing a pro-inflammatory form of cell death called pyroptosis. The role of NLRP3 inflammasome in the pathophysiology of sepsis can be ambivalent. Indeed, although it might protect against sepsis when moderately activated after initial infection, excessive NLRP3 inflammasome activation can induce dysregulated inflammation leading to multiple organ failure and death during the acute phase of the disease. Moreover, this activation might become exhausted and contribute to post-septic immunosuppression, driving impaired functions of innate and adaptive immune cells. Targeting the NLRP3 inflammasome could thus be an attractive option in sepsis either through IL-1β and IL-18 antagonists or through inhibition of NLRP3 inflammasome pathway downstream components. Available treatments and results of first clinical trials will be discussed.

Molecular mechanisms and functions of pyroptosis in sepsis and sepsis-associated organ dysfunction

Sepsis, a life-threatening organ dysfunction caused by a dysregulated host response to infection, is a leading cause of death in intensive care units. The development of sepsis-associated organ dysfunction (SAOD) poses a threat to the survival of patients with sepsis. Unfortunately, the pathogenesis of sepsis and SAOD is complicated, multifactorial, and has not been completely clarified. Recently, numerous studies have demonstrated that pyroptosis, which is characterized by inflammasome and caspase activation and cell membrane pore formation, is involved in sepsis. Unlike apoptosis, pyroptosis is a pro-inflammatory form of programmed cell death that participates in the regulation of immunity and inflammation. Related studies have shown that in sepsis, moderate pyroptosis promotes the clearance of pathogens, whereas the excessive activation of pyroptosis leads to host immune response disorders and SAOD. Additionally, transcription factors, non-coding RNAs, epigenetic modifications and post-translational modifications can directly or indirectly regulate pyroptosis-related molecules. Pyroptosis also interacts with autophagy, apoptosis, NETosis, and necroptosis. This review summarizes the roles and regulatory mechanisms of pyroptosis in sepsis and SAOD. As our understanding of the functions of pyroptosis improves, the development of new diagnostic biomarkers and targeted therapies associated with pyroptosis to improve clinical outcomes appears promising in the future.

Staphylococcus aureus adaptive evolution: Recent insights on how immune evasion, immunometabolic subversion and host genetics impact vaccine development

Despite meritorious attempts, a S. aureus vaccine that prevents infection or mitigates severity has not yet achieved efficacy endpoints in prospective, randomized clinical trials. This experience underscores the complexity of host-S. aureus interactions, which appear to be greater than many other bacterial pathogens against which successful vaccines have been developed. It is increasingly evident that S. aureus employs strategic countermeasures to evade or exploit human immune responses. From entering host cells to persist in stealthy intracellular reservoirs, to sensing the environmental milieu and leveraging bacterial or host metabolic products to reprogram host immune responses, S. aureus poses considerable challenges for the development of effective vaccines. The fact that this pathogen causes distinct types of infections and can undergo transient genetic, transcriptional or metabolic adaptations in vivo that do not occur in vitro compounds challenges in vaccine development. Notably, the metabolic versatility of both bacterial and host immune cells as they compete for available substrates within specific tissues inevitably impacts the variable repertoire of gene products that may or may not be vaccine antigens. In this respect, S. aureus has chameleon phenotypes that have alluded vaccine strategies thus far. Nonetheless, a number of recent studies have also revealed important new insights into pathogenesis vulnerabilities of S. aureus. A more detailed understanding of host protective immune defenses versus S. aureus adaptive immune evasion mechanisms may offer breakthroughs in the development of effective vaccines, but at present this goal remains a very high bar. Coupled with the recent advances in human genetics and epigenetics, newer vaccine technologies may enable such a goal. If so, future vaccines that protect against or mitigate the severity of S. aureus infections are likely to emerge at the intersection of precision and personalized medicine. For now, the development of S. aureus vaccines or alternative therapies that reduce mortality and morbidity must continue to be pursued.

Investigation of Association of Complement 5 Genetic Polymorphisms with Sepsis and Sepsis-Induced Inflammatory Responses

Background

Complement 5 (C5) and C5a production play a pivotal role in the pathophysiology of sepsis. Strong evidence demonstrates an association of C5 gene polymorphisms with various inflammatory diseases. However, no current studies have explored the clinical relevance of C5 polymorphisms in sepsis.

Methods

Two C5 gene polymorphisms, rs17611 and rs2269067, were identified by genotyping in 636 sepsis patients and 753 controls in a Han Chinese population. C5 gene expression was detected via quantitative real-time PCR. C5a and proinflammatory cytokine production was measured by enzyme-linked immunosorbent assay. An Annexin V apoptosis assay was performed to assess cell apoptosis.

Results

Our results showed significantly lower frequencies of rs2269067 GC/CC genotypes or C allele in sepsis patients than healthy controls. The frequencies of rs17611 CC/CT genotypes or C allele were significantly overrepresented in both the septic shock and non-survivor subgroups. Patients with this sepsis-associated high-risk rs17611 C allele exhibited a significant increase in C5a, TNF-α and IL-6 production. However, no significant difference in C5a and downstream proinflammatory cytokine production was observed among patients with different rs2269067 genotypes. In addition, in vitro experiments showed an effect of recombinant C5a on enhancing LPS-stimulated IL-1β, IL-6 and TNF-α production and cell apoptosis in THP-1 monocytes.

Conclusion

The rs2269067 polymorphism conferred protection against sepsis susceptibility. The rs17611 polymorphism was associated with increased C5a production, which ultimately potentiated the secretion of downstream proinflammatory cytokines and conferred susceptibility to sepsis progression and poor prognosis.

The Impact of NLRP3 Activation on Hematopoietic Stem Cell Transplantation

NLR family pyrin domain-containing 3 (NLRP3) is an intracellular protein that after recognizing a broad spectrum of stressors, such as microbial motifs and endogenous danger signals, promotes the activation and release of the pro-inflammatory cytokines IL-1β and IL-18, thus playing an essential role in the innate immune response. Several blood cell types, including macrophages, dendritic cells, and hematopoietic stem and progenitor cells (HSPCs), express NLRP3, where it has been implicated in various physiological and pathological processes. For example, NLRP3 participates in the development and expansion of HSPCs, and their release from bone marrow into the peripheral blood has been implicated in certain hematological disorders including various types of leukemia. In addition, accumulating evidence indicates that activation of NLRP3 plays a pivotal role in the development of transplant complications in patients receiving hematopoietic stem cell transplantation (HSCT) including graft versus host disease, severe infections, and transplant-related mortality. The majority of these complications are triggered by the severe tissue damage derived from the conditioning regimens utilized in HSCT which, in turn, activates NLRP3 and, ultimately, promotes the release of proinflammatory cytokines such as IL-1β and IL-18. Here, we summarize the implications of NLRP3 in HSCT with an emphasis on the involvement of this inflammasome component in transplant complications.

Bacteria and Sepsis: Microbiome to the Rescue?

The microbiome is the metagenome of all microbes that live on and within every individual, and evidence for its role in the pathogenesis of a variety of diseases has been increasing over the past several decades. While there are various causes of sepsis, defined as the abnormal host response to infection, the host microbiome may provide a unifying explanation for discrepancies that are seen in septic patient survival based on age, sex, and other confounding factors. As has been the case for other human diseases, evidence exists for the microbiome to control patient outcomes after sepsis. In this review, associative data for the microbiome and sepsis survival are presented with causative mechanisms that may be at play. Finally, clinical trials to manipulate the microbiome in order to improve patient outcomes after sepsis are presented as well as areas of potential future research in order to aid in the clinical treatment of these patients.