AIM2 inflammasome in infection, cancer, and autoimmunity: Role in DNA sensing, inflammation, and innate immunity

Relationship between serum NLRP3 along with its effector molecules and pregnancy outcomes in women with hyperglycemia

OBJECTIVE

The study aims to investigate the levels of serum NLRP3 along with its effector molecules (Caspase-1, IL-1β, and IL-18) in the mid-pregnancy in pregnant women with hyperglycemia, and explore the relationship between NLRP3, along with its effector molecules (Caspase-1, IL-1β, and IL-18) and insulin resistance, as well as pregnancy outcomes.

METHODS

The levels of serum NLRP3 along with its effector molecules (Caspase-1, IL-1β, and IL-18) in three groups of pregnant women with gestational diabetes mellitus (GDM), pregestational diabetes mellitus (PGDM) and normal glucose tolerance (NGT) were measured in mid-pregnancy, and their relationship with insulin resistance and pregnancy outcomes was analyzed. The ROC curve was also used to evaluate the predictive value of serum NLRP3 inflammasome and its effector molecules for pregnancy outcomes.

RESULTS

There were no statistical differences in the general clinical data of the three groups, and the concentrations of serum NLRP3 along with its effector molecules were higher in the GDM and PGDM groups than in the NGT group, and NLRP3 along with its effector molecules were positively correlated with fasting blood glucose, fasting insulin, and insulin resistance index in both groups (r > 0, p < .05). The incidence of preterm delivery, hypertensive disorders of pregnancy, premature rupture of membranes, neonatal hypoglycemia and macrosomia was significantly higher in both groups than in the NGT group (p < .05). The value of the combined serum NLRP3 and its effector molecules in mid-pregnancy to predict adverse pregnancy outcomes was highest, and the AUCs for the combined prediction of late hypertensive disorders of pregnancy, premature rupture of membranes, preterm delivery, neonatal hypoglycemia and macrosomia were 0.84 (95% CI 0.79-0.88, p < .001), 0.81 (95% CI 0.75-0.85, p < .001), 0.76 (95% CI 0.70-0.81, p < .001), 0.76 (95% CI 0.70-0.81, p < .001) and 0.72 (95% CI 0.63-0.81, p < .001), respectively.

CONCLUSIONS

Increased serum NLRP3 along with its effector molecules in pregnant women with hyperglycemia are associated with the levels of insulin resistance and the subsequent development of adverse pregnancy outcomes.

Mechanisms and emerging strategies for irinotecan-induced diarrhea

Irinotecan (also known as CPT-11) is a topoisomerase I inhibitor first approved for clinical use as an anticancer agent in 1996. Over the past more than two decades, it has been widely used for combination regimens to treat various malignancies, especially in gastrointestinal and lung cancers. However, severe dose-limiting toxicities, especially gastrointestinal toxicity such as late-onset diarrhea, were frequently observed in irinotecan-based therapy, thus largely limiting the clinical application of this agent. Current knowledge regarding the pathogenesis of irinotecan-induced diarrhea is characterized by the complicated metabolism of irinotecan to its active metabolite SN-38 and inactive metabolite SN-38G. A series of enzymes and transporters were involved in these metabolic processes, including UGT1A1 and CYP3A4. Genetic polymorphisms of these metabolizing enzymes were significantly associated with the occurrence of irinotecan-induced diarrhea. Recent discoveries and progress made on the detailed mechanisms enable the identification of potential biomarkers for predicting diarrhea and as such guiding the proper patient selection with a better range of tolerant dosages. In this review, we introduce the metabolic process of irinotecan and describe the pathogenic mechanisms underlying irinotecan-induced diarrhea. Based on the mechanisms, we further outline the potential biomarkers for predicting the severity of diarrhea. Finally, based on the current experimental evidence in preclinical and clinical studies, we discuss and prospect the current and emerging strategies for the prevention of irinotecan-induced diarrhea.

Importance of AIM2 as a serum marker for reflecting severity and predicting a poor outcome of human severe traumatic brain injury: A prospective longitudinal cohort study

BACKGROUND

Absent in melanoma 2 (AIM2) participates in neuroinflammation. Here, the prognostic significance of serum AIM2 was explored in severe traumatic brain injury (sTBI).

METHODS

A total of 135 sTBI patients and 80 healthy controls were recruited in this prospective cohort study. Serum C-reactive protein (CRP) and AIM2 levels were measured. Glasgow Coma Scale (GCS) and Rotterdam computed tomography (CT) classification were recorded as the severity indicators. Prognostic parameters were posttraumatic six-month extended Glasgow outcome scale (GOSE) scores and poor outcome (GOSE scores of 1-4).

RESULTS

As opposed to controls, there were significantly elevated serum AIM2 levels after sTBI. Serum AIM2 levels were independently correlated with serum CRP levels, GCS scores, Rotterdam CT scores, GOSE scores and poor outcome. Also, serum AIM2 levels were efficiently predictive of poor outcome under the receiver operating characteristic (ROC) curve. Under the restricted cubic spline, serum AIM2 levels were linearly correlated with risk of poor outcome. Using subgroup analysis, serum AIM2 levels did not significantly interact with other indices, such as age, gender, alcohol drinking, cigarette smoking, etc. Also, combination model, in which serum AIM2, GCS scores and Rotterdam CT scores were merged, was outlined using nomogram and performed well under calibration curve, ROC curve and decision curve.

CONCLUSIONS

Raised serum AIM2 levels after sTBI, in intimate correlation with systemic inflammation and trauma severity, are independently discriminative of posttraumatic six-month neurological outcome, substantializing serum AIM2 as an inflammatory prognostic biomarker of sTBI.

DNA sensing of dendritic cells in cancer immunotherapy

Dendritic cells (DCs) are involved in the initiation and maintenance of immune responses against malignant cells by recognizing conserved pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) through pattern recognition receptors (PRRs). According to recent studies, tumor cell-derived DNA molecules act as DAMPs and are recognized by DNA sensors in DCs. Once identified by sensors in DCs, these DNA molecules trigger multiple signaling cascades to promote various cytokines secretion, including type I IFN, and then to induce DCs mediated antitumor immunity. As one of the potential attractive strategies for cancer therapy, various agonists targeting DNA sensors are extensively explored including the combination with other cancer immunotherapies or the direct usage as major components of cancer vaccines. Moreover, this review highlights different mechanisms through which tumor-derived DNA initiates DCs activation and the mechanisms through which the tumor microenvironment regulates DNA sensing of DCs to promote tumor immune escape. The contributions of chemotherapy, radiotherapy, and checkpoint inhibitors in tumor therapy to the DNA sensing of DCs are also discussed. Finally, recent clinical progress in tumor therapy utilizing agonist-targeted DNA sensors is summarized. Indeed, understanding more about DNA sensing in DCs will help to understand more about tumor immunotherapy and improve the efficacy of DC-targeted treatment in cancer.

Longitudinal change of serum AIM2 levels after aneurysmal subarachnoid hemorrhage and its prognostic significance: a two-center prospective cohort study

Absent in melanoma 2 (AIM2) is implicated in neuroinflammation. Here, we explored the prognostic significance of serum AIM2 in human aneurysmal subarachnoid hemorrhage (aSAH). We conducted a consecutive enrollment of 127 patients, 56 of whom agreed with blood-drawings not only at admission but also at days 1, 2, 3, 5, 7 and 10 days after aSAH. Serum AIM2 levels of patients and 56 healthy controls were measured. Disease severity was assessed using the modified Fisher scale (mFisher) and World Federation of Neurological Surgeons Scale (WFNS). Neurological outcome at poststroke 90 days was evaluated via the modified Rankin Scale (mRS). Univariate analysis and multivariate analysis were sequentially done to ascertain relationship between serum AIM2 levels, severity, delayed cerebral ischemia (DCI) and 90-day poor prognosis (mRS scores of 3-6). Patients, in comparison to controls, had a significant elevation of serum AIM2 levels at admission and at days 1, 2, 3, 5, 7 and 10 days after aSAH, with the highest levels at days 1, 2, 3 and 5. AIM2 levels were independently correlated with WFNS scores and mFisher scores. Significantly higher serum AIM2 levels were detected in patients with a poor prognosis than in those with a good prognosis, as well as in patients with DCI than in those without DCI. Moreover, serum AIM2 levels independently predicted a poor prognosis and DCI, and were linearly correlated with their risks. Using subgroup analysis, there were no significant interactions between serum AIM2 levels and age, gender, hypertension and so on. There were substantially high predictive abilities of serum AIM2 for poor prognosis and DCI under the receiver operating characteristic curve. The combination models of DCI and poor prognosis, in which serum AIM2, WFNS scores and mFisher scores were incorporated, showed higher discriminatory efficiencies than anyone of the preceding three variables. Moreover, the models are delineated using the nomogram, and performed well under the calibration curve and decision curve. Serum AIM2 levels, with a substantial enhancement during early phase after aSAH, are closely related to bleeding severity, poor 90-day prognosis and DCI of patients, substantializing serum AIM2 as a potential prognostic biomarker of aSAH.

Benfotiamine improves dystrophic pathology and exercise capacity in mdx mice by reducing inflammation and fibrosis

Duchenne Muscular Dystrophy (DMD) is a progressive and fatal neuromuscular disease. Cycles of myofibre degeneration and regeneration are hallmarks of the disease where immune cells infiltrate to repair damaged skeletal muscle. Benfotiamine is a lipid soluble precursor to thiamine, shown clinically to reduce inflammation in diabetic related complications. We assessed whether benfotiamine administration could reduce inflammation related dystrophic pathology. Benfotiamine (10 mg/kg/day) was fed to male mdx mice (n = 7) for 15 weeks from 4 weeks of age. Treated mice had an increased growth weight (5-7 weeks) and myofibre size at treatment completion. Markers of dystrophic pathology (area of damaged necrotic tissue, central nuclei) were reduced in benfotiamine mdx quadriceps. Grip strength was increased and improved exercise capacity was found in mdx treated with benfotiamine for 12 weeks, before being placed into individual cages and allowed access to an exercise wheel for 3 weeks. Global gene expression profiling (RNAseq) in the gastrocnemius revealed benfotiamine regulated signalling pathways relevant to dystrophic pathology (Inflammatory Response, Myogenesis) and fibrotic gene markers (Col1a1, Col1a2, Col4a5, Col5a2, Col6a2, Col6a2, Col6a3, Lum) towards wildtype levels. In addition, we observed a reduction in gene expression of inflammatory gene markers in the quadriceps (Emr1, Cd163, Cd4, Cd8, Ifng). Overall, these data suggest that benfotiamine reduces dystrophic pathology by acting on inflammatory and fibrotic gene markers and signalling pathways. Given benfotiamine's excellent safety profile and current clinical use, it could be used in combination with glucocorticoids to treat DMD patients.

The role of IFI16 in regulating PANoptosis and implication in heart diseases

Interferon Gamma Inducible Protein 16 (IFI16) belongs to the HIN-200 protein family and is pivotal in immunological responses. Serving as a DNA sensor, IFI16 identifies viral and aberrant DNA, triggering immune and inflammatory responses. It is implicated in diverse cellular death mechanisms, such as pyroptosis, apoptosis, and necroptosis. Notably, these processes are integral to the emergent concept of PANoptosis, which encompasses cellular demise and inflammatory pathways. Current research implies a significant regulatory role for IFI16 in PANoptosis, particularly regarding cardiac pathologies. This review delves into the complex interplay between IFI16 and PANoptosis in heart diseases, including atherosclerosis, myocardial infarction, heart failure, and diabetic cardiomyopathy. It synthesizes evidence of IFI16's impact on PANoptosis, with the intention of providing novel insights for therapeutic strategies targeting heart diseases.

Herpes Simplex Virus ICP27 Protein Inhibits AIM 2-Dependent Inflammasome Influencing Pro-Inflammatory Cytokines Release in Human Pigment Epithelial Cells (hTert-RPE 1)

Although Herpes simplex virus type 1 (HSV-1) has been deeply studied, significant gaps remain in the fundamental understanding of HSV-host interactions: our work focused on studying the Infected Cell Protein 27 (ICP27) as an inhibitor of the Absent-in-melanoma-2 (AIM 2) inflammasome pathway, leading to reduced pro-inflammatory cytokines that influence the activation of a protective innate immune response to infection. To assess the inhibition of the inflammasome by the ICP27, hTert-immortalized Retinal Pigment Epithelial cells (hTert-RPE 1) infected with HSV-1 wild type were compared to HSV-1 lacking functional ICP27 (HSV-1∆ICP27) infected cells. The activation of the inflammasome by HSV-1∆ICP27 was demonstrated by quantifying the gene and protein expression of the inflammasome constituents using real-time PCR and Western blot. The detection of the cleavage of the pro-caspase-1 into the active form was performed by using a bioluminescent assay, while the quantification of interleukins 1β (IL-1β) and 18 (IL-18)released in the supernatant was quantified using an ELISA assay. The data showed that the presence of the ICP27 expressed by HSV-1 induces, in contrast to HSV-1∆ICP27 vector, a significant downregulation of AIM 2 inflammasome constituent proteins and, consequently, the release of pro-inflammatory interleukins into the extracellular environment reducing an effective response in counteracting infection.

Neutrophil extracellular traps promote acetaminophen-induced acute liver injury in mice via AIM2

Excessive acetaminophen (APAP) can induce neutrophil activation and hepatocyte death. Along with hepatocyte dysfunction and death, NETosis (a form of neutrophil-associated inflammation) plays a vital role in the progression of acute liver injury (ALI) induced by APAP overdose. It has been shown that activated neutrophils tend to migrate towards the site of injury and participate in inflammatory processes via formation of neutrophil extracellular traps (NETs). In this study we investigated whether NETs were involved in hepatocyte injury and contributed to APAP-induced ALI progression. ALI mouse model was established by injecting overdose (350 mg/kg) of APAP. After 24 h, blood and livers were harvested for analyses. We showed that excessive APAP induced multiple programmed cell deaths of hepatocytes including pyroptosis, apoptosis and necroptosis, accompanied by significantly increased NETs markers (MPO, citH3) in the liver tissue and serum. Preinjection of DNase1 (10 U, i.p.) for two consecutive days significantly inhibited NETs formation, reduced PANoptosis and consequently alleviated excessive APAP-induced ALI. In order to clarify the communication between hepatocytes and neutrophils, we induced NETs formation in isolated neutrophils, and treated HepaRG cells with NETs. We found that NETs treatment markedly increased the activation of GSDMD, caspase-3 and MLKL, while pre-treatment with DNase1 down-regulated the expression of these proteins. Knockdown of AIM2 (a cytosolic innate immune receptor) abolished NETs-induced PANoptosis in HepaRG cells. Furthermore, excessive APAP-associated ALI was significantly attenuated in AIM2KO mice, and PANoptosis occurred less frequently. Upon restoring AIM2 expression in AIM2KO mice using AAV9 virus, both hepatic injury and PANoptosis was aggravated. In addition, we demonstrated that excessive APAP stimulated mtROS production and mitochondrial DNA (mtDNA) leakage, and mtDNA activated the TLR9 pathway to promote NETs formation. Our results uncover a novel mechanism of NETs and PANoptosis in APAP-associated ALI, which might serve as a therapeutic target.

The interaction of inflammasomes and gut microbiota: novel therapeutic insights

Inflammasomes are complex platforms for the cleavage and release of inactivated IL-1β and IL-18 cytokines that trigger inflammatory responses against damage-associated molecular patterns (DAMPs) or pathogen-associated molecular patterns (PAMPs). Gut microbiota plays a pivotal role in maintaining gut homeostasis. Inflammasome activation needs to be tightly regulated to limit aberrant activation and bystander damage to the host cells. Several types of inflammasomes, including Node-like receptor protein family (e.g., NLRP1, NLRP3, NLRP6, NLRP12, NLRC4), PYHIN family, and pyrin inflammasomes, interact with gut microbiota to maintain gut homeostasis. This review discusses the current understanding of how inflammasomes and microbiota interact, and how this interaction impacts human health. Additionally, we introduce novel biologics and antagonists, such as inhibitors of IL-1β and inflammasomes, as therapeutic strategies for treating gastrointestinal disorders when inflammasomes are dysregulated or the composition of gut microbiota changes.

A Variety of Mouse PYHIN Proteins Restrict Murine and Human Retroviruses

PYHIN proteins are only found in mammals and play key roles in the defense against bacterial and viral pathogens. The corresponding gene locus shows variable deletion and expansion ranging from 0 genes in bats, over 1 in cows, and 4 in humans to a maximum of 13 in mice. While initially thought to act as cytosolic immune sensors that recognize foreign DNA, increasing evidence suggests that PYHIN proteins also inhibit viral pathogens by more direct mechanisms. Here, we examined the ability of all 13 murine PYHIN proteins to inhibit HIV-1 and murine leukemia virus (MLV). We show that overexpression of p203, p204, p205, p208, p209, p210, p211, and p212 strongly inhibits production of infectious HIV-1; p202, p207, and p213 had no significant effects, while p206 and p214 showed intermediate phenotypes. The inhibitory effects on infectious HIV-1 production correlated significantly with the suppression of reporter gene expression by a proviral Moloney MLV-eGFP construct and HIV-1 and Friend MLV LTR luciferase reporter constructs. Altogether, our data show that the antiretroviral activity of PYHIN proteins is conserved between men and mice and further support the key role of nuclear PYHIN proteins in innate antiviral immunity.

AIM2 regulates autophagy to mitigate oxidative stress in aged mice with acute liver injury

The cytoplasmic pattern recognition receptor, absent in melanoma 2 (AIM2), detects cytosolic DNA, activating the inflammasome and resulting in pro-inflammatory cytokine production and pyroptotic cell death. Recent research has illuminated AIM2's contributions to PANoptosis and host defense. However, the role of AIM2 in acetaminophen (APAP)-induced hepatoxicity remains enigmatic. In this study, we unveil AIM2's novel function as a negative regulator in the pathogenesis of APAP-induced liver damage in aged mice, independently of inflammasome activation. AIM2-deficient aged mice exhibited heightened lipid accumulation and hepatic triglycerides in comparison to their wild-type counterparts. Strikingly, AIM2 knockout mice subjected to APAP overdose demonstrated intensified liver injury, compromised mitochondrial stability, exacerbated glutathione depletion, diminished autophagy, and elevated levels of phosphorylated c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK). Furthermore, our investigation revealed AIM2's mitochondrial localization; its overexpression in mouse hepatocytes amplified autophagy while dampening JNK phosphorylation. Notably, induction of autophagy through rapamycin administration mitigated serum alanine aminotransferase levels and reduced the necrotic liver area in AIM2-deficient aged mice following APAP overdose. Mechanistically, AIM2 deficiency exacerbated APAP-induced acute liver damage and inflammation in aged mice by intensifying oxidative stress and augmenting the phosphorylation of JNK and ERK. Given its regulatory role in autophagy and lipid peroxidation, AIM2 emerges as a promising therapeutic target for age-related acute liver damage treatment.

Correlation between double-stranded DNA and acute urticaria

BACKGROUND

Acute urticaria is a prevalent inflammatory dermatosis characterized by fulminant wheals, often accompanied by severe pruritis. It may also cause nausea, vomiting, and abdominal pain. Numerous studies have substantiated the pivotal involvement of double-stranded DNA (dsDNA) in autoimmunity. However, the role of dsDNA in the pathogenesis of acute urticaria is unclear.

METHODS

We measured serum dsDNA levels in patients and controls. The relationship between dsDNA levels and environmental exposures (temperature, ultraviolet [UV] index, and season) was investigated by correlating disease onset dates with archived meteorological data. Finally, we used quantitative PCR to determine the expressions of genes encoding dsDNA receptors, single-stranded RNA (ssRNA) receptors, exosome formation, and type I interferon in the peripheral blood of patients and controls.

RESULTS

Serum dsDNA levels were significantly higher in patients with acute urticaria compared with controls (mean values 1.38 and 0.94 ng/ml, respectively, P < 0.001). dsDNA levels were higher in patients exposed to higher environmental temperatures and UV indices and were higher during the summer months. We also found that the expressions of genes encoding dsDNA receptors, ssRNA receptors, absent in melanoma factor 2 (AIM2)-related inflammatory factors, and interferon alpha were up-regulated in patients.

CONCLUSIONS

We demonstrated that serum dsDNA levels are elevated in acute urticaria and are influenced by climatic factors such as temperature, ultraviolet index, and season. We also found that elevated dsDNA promotes the expression of AIM2-related factors and type I interferons. This study generates new hypotheses regarding the pathogenesis of acute urticaria and suggests novel therapeutic targets.

The BK Channel Limits the Pro-Inflammatory Activity of Macrophages

Macrophages play a crucial role in the innate immune response, serving as key effector cells in the defense against pathogens. Although the role of the large-conductance voltage and calcium-activated potassium channel, also known as the KCa1.1 or BK channel, in regulating neurotransmitter release and smooth muscle contraction is well known, its potential involvement in immune regulation remains unclear. We employed BK-knockout macrophages and noted that the absence of a BK channel promotes the polarization of macrophages towards a pro-inflammatory phenotype known as M1 macrophages. Specifically, the absence of the BK channel resulted in a significant increase in the secretion of the pro-inflammatory cytokine IL-6 and enhanced the activity of extracellular signal-regulated kinases 1 and 2 (Erk1/2 kinases), Ca2+/calmodulin-dependent protein kinase II (CaMKII), and the transcription factor ATF-1 within M1 macrophages. Additionally, the lack of the BK channel promoted the activation of the AIM2 inflammasome without affecting the activation of the NLRC4 and NLRP3 inflammasomes. To further investigate the role of the BK channel in regulating AIM2 inflammasome activation, we utilized BK channel inhibitors, such as paxilline and iberiotoxin, along with the BK channel activator NS-11021. Pharmacological inactivation of the BK channel increased, and its stimulation inhibited IL-1β production following AIM2 inflammasome activation in wild-type macrophages. Moreover, wild-type macrophages displayed increased calcium influx when activated with the AIM2 inflammasome, whereas BK-knockout macrophages did not due to the impaired extracellular calcium influx upon activation. Furthermore, under conditions of a calcium-free medium, IL-1β production following AIM2 inflammasome activation was increased in both wild-type and BK-knockout macrophages. This suggests that the BK channel is required for the influx of extracellular calcium in macrophages, thus limiting AIM2 inflammasome activation. In summary, our study reveals a regulatory role of the BK channel in macrophages under inflammatory conditions.

Non-apoptotic cell death programs in cervical cancer with an emphasis on ferroptosis

BACKGROUND

Cervical cancer, a pernicious gynecological malignancy, causes the mortality of hundreds of thousands of females worldwide. Despite a considerable decline in mortality, the surging incidence rate among younger women has raised serious concerns. Immortality is the most important characteristic of tumor cells, hence the carcinogenesis of cervical cancer cells pivotally requires compromising with cell death mechanisms.

METHODS

The current study comprehensively reviewed the mechanisms of non-apoptotic cell death programs to provide possible disease management strategies.

RESULTS

Comprehensive evidence has stated that focusing on necroptosis, pyroptosis, and autophagy for disease management is associated with significant limitations such as insufficient understanding, contradictory functions, dependence on disease stage, and complexity of intracellular pathways. However, ferroptosis represents a predictable role in cervix carcinogenesis, and ferroptosis-related genes demonstrate a remarkable correlation with patient survival and clinical outcomes.

CONCLUSION

Ferroptosis may be an appropriate option for disease management strategies from predicting prognosis to treatment.

New insights into nucleic acid sensor AIM2: The potential benefit in targeted therapy for cancer

The AIM2 inflammasome represents a multifaceted oligomeric protein complex within the innate immune system, with the capacity to perceive double-stranded DNA (dsDNA) and engage in diverse physiological reactions and disease contexts, including cancer. While originally conceived as a discerning DNA sensor, AIM2 has demonstrated its capability to discern various nucleic acid variations, encompassing RNA and DNA-RNA hybrids. Through its interaction with nucleic acids, AIM2 orchestrates the assembly of a complex involving multiple proteins, aptly named the AIM2 inflammasome, which facilitates the enzymatic cleavage of proinflammatory cytokines, namely pro-IL-1β and pro-IL-18. This process, in turn, underpins its pivotal biological role. In this review, we provide a systematic summary and discussion of the latest advancements in AIM2 sensing various types of nucleic acids. Additionally, we discuss the modulation of AIM2 activation, which can cause cell death, including pyroptosis, apoptosis, and autophagic cell death. Finally, we fully illustrate the evidence for the dual role of AIM2 in different cancer types, including both anti-tumorigenic and pro-tumorigenic functions. Considering the above information, we uncover the therapeutic promise of modulating the AIM2 inflammasome in cancer treatment.

cGAS-STING, inflammasomes and pyroptosis: an overview of crosstalk mechanism of activation and regulation

BACKGROUND

Intracellular DNA-sensing pathway cGAS-STING, inflammasomes and pyroptosis act as critical natural immune signaling axes for microbial infection, chronic inflammation, cancer progression and organ degeneration, but the mechanism and regulation of the crosstalk network remain unclear. Cellular stress disrupts mitochondrial homeostasis, facilitates the opening of mitochondrial permeability transition pore and the leakage of mitochondrial DNA to cell membrane, triggers inflammatory responses by activating cGAS-STING signaling, and subsequently induces inflammasomes activation and the onset of pyroptosis. Meanwhile, the inflammasome-associated protein caspase-1, Gasdermin D, the CARD domain of ASC and the potassium channel are involved in regulating cGAS-STING pathway. Importantly, this crosstalk network has a cascade amplification effect that exacerbates the immuno-inflammatory response, worsening the pathological process of inflammatory and autoimmune diseases. Given the importance of this crosstalk network of cGAS-STING, inflammasomes and pyroptosis in the regulation of innate immunity, it is emerging as a new avenue to explore the mechanisms of multiple disease pathogenesis. Therefore, efforts to define strategies to selectively modulate cGAS-STING, inflammasomes and pyroptosis in different disease settings have been or are ongoing. In this review, we will describe how this mechanistic understanding is driving possible therapeutics targeting this crosstalk network, focusing on the interacting or regulatory proteins, pathways, and a regulatory mitochondrial hub between cGAS-STING, inflammasomes, and pyroptosis.

SHORT CONCLUSION

This review aims to provide insight into the critical roles and regulatory mechanisms of the crosstalk network of cGAS-STING, inflammasomes and pyroptosis, and to highlight some promising directions for future research and intervention.

Exploring the role of the inflammasomes on prostate cancer: Interplay with obesity

Obesity is a weight-related disorder characterized by excessive adipose tissue growth and dysfunction which leads to the onset of a systemic chronic low-grade inflammatory state. Likewise, inflammation is considered a classic cancer hallmark affecting several steps of carcinogenesis and tumor progression. In this regard, novel molecular complexes termed inflammasomes have been identified which are able to react to a wide spectrum of insults, impacting several metabolic-related disorders, but their contribution to cancer biology remains unclear. In this context, prostate cancer (PCa) has a markedly inflammatory component, and patients frequently are elderly individuals who exhibit weight-related disorders, being obesity the most prevalent condition. Therefore, inflammation, and specifically, inflammasome complexes, could be crucial players in the interplay between PCa and metabolic disorders. In this review, we will: 1) discuss the potential role of each inflammasome component (sensor, molecular adaptor, and targets) in PCa pathophysiology, placing special emphasis on IL-1β/NF-kB pathway and ROS and hypoxia influence; 2) explore the association between inflammasomes and obesity, and how these molecular complexes could act as the cornerstone between the obesity and PCa; and, 3) compile current clinical trials regarding inflammasome targeting, providing some insights about their potential use in the clinical practice.

Pyroptosis in neurodegenerative diseases: from bench to bedside

The central nervous system regulates all aspects of physiology to some extent. Neurodegenerative diseases (NDDs) lead to the progressive loss and dysfunction of neurons, which are particularly evident in Alzheimer's disease, Parkinson's disease, and many other conditions. NDDs are multifactorial diseases with complex pathogeneses, and there has been a rapid increase in the prevalence of NDDs. However, none of these diseases can be cured, making the development of novel treatment strategies an urgent necessity. Numerous studies have indicated how pyroptosis induces inflammation and affects many aspects of NDD. Therefore, components related to pyroptosis are potential therapeutic candidates and are attracting increasing attention. Here, we review the role of pyroptosis in the pathogenesis of NDDs and potential treatment options. Additionally, several of the current drugs and relevant inhibitors are discussed. Through this article, we provide theoretical support for exploring new therapeutic targets and updating clinical treatment strategies for NDDs. Notably, pyroptosis, a recently widely studied mode of cell death, is still under-researched compared to other traditional forms of cell death. Moreover, the focus of research has been on the onset and progression of NDDs, and the lack of organ-specific target discovery and drug development is a common problem for many basic studies. This urgent problem requires scientists and companies worldwide to collaborate in order to develop more effective drugs against NDDs.

Innate immune inflammatory cell death: PANoptosis and PANoptosomes in host defense and disease

Regulated cell death (RCD) triggered by innate immune activation is an important strategy for host survival during pathogen invasion and perturbations of cellular homeostasis. There are two main categories of RCD, including nonlytic and lytic pathways. Apoptosis is the most well-characterized nonlytic RCD, and the inflammatory pyroptosis and necroptosis pathways are among the best known lytic forms. While these were historically viewed as independent RCD pathways, extensive evidence of cross-talk among their molecular components created a knowledge gap in our mechanistic understanding of RCD and innate immune pathway components, which led to the identification of PANoptosis. PANoptosis is a unique innate immune inflammatory RCD pathway that is regulated by PANoptosome complexes upon sensing pathogens, pathogen-associated molecular patterns (PAMPs), damage-associated molecular patterns (DAMPs) or the cytokines produced downstream. Cytosolic innate immune sensors and regulators, such as ZBP1, AIM2 and RIPK1, promote the assembly of PANoptosomes to drive PANoptosis. In this review, we discuss the molecular components of the known PANoptosomes and highlight the mechanisms of PANoptosome assembly, activation and regulation identified to date. We also discuss how PANoptosomes and mutations in PANoptosome components are linked to diseases. Given the impact of RCD, and PANoptosis specifically, across the disease spectrum, improved understanding of PANoptosomes and their regulation will be critical for identifying new therapeutic targets and strategies.

The role of pyroptosis in incomplete immune reconstitution among people living with HIV：Potential therapeutic targets

Globally, HIV infection causes significant morbidity and mortality, and is a major public health problem. Despite the fact that widespread use of antiretroviral therapy (ART) has substantially altered the natural history of HIV infection from originally being a universally lethal disease to now being a chronic medical condition for those taking appropriate treatment, approximately 10-40% of people living with HIV (PLWH) who take effective ART and maintain long-term viral suppression fail to achieve normalization of CD4 + T-cell counts. This phenomenon is referred to as incomplete immune reconstitution or immunological non-response. Although the precise mechanisms underlying this outcome have not been elucidated, recent evidence indicates that excessive pyroptosis may play a crucial role in the development of incomplete immune reconstitution. Pyroptosis is characterized by the formation of pores in the cell membrane, cell rupture, and secretion of intracellular contents and pro-inflammatory cytokines, including IL-1β and IL-18. This excessive inflammation-induced programmed cell death leads to a massive loss of CD4 + T-cells, and inflammatory consequences that may promote and sustain incomplete immune reconstitution. Herein, we review the possible pathways activated in HIV infection by inflammasomes that act as switches of pyroptosis, and the role of pyroptosis in HIV, as well as the relevance of CD4 + T-cells in incomplete immune reconstitution. We also highlight the possible mechanisms of pyroptosis involved in incomplete immune reconstitution, thus paving the way for the development of potential targets for the treatment of incomplete immune reconstitution.

Inflammasome: structure, biological functions, and therapeutic targets

Inflammasomes are a group of protein complex located in cytoplasm and assemble in response to a wide variety of pathogen-associated molecule patterns, damage-associated molecule patterns, and cellular stress. Generally, the activation of inflammasomes will lead to maturation of proinflammatory cytokines and pyroptotic cell death, both associated with inflammatory cascade amplification. A sensor protein, an adaptor, and a procaspase protein interact through their functional domains and compose one subunit of inflammasome complex. Under physiological conditions, inflammasome functions against pathogen infection and endogenous dangers including mtROS, mtDNA, and so on, while dysregulation of its activation can lead to unwanted results. In recent years, advances have been made to clarify the mechanisms of inflammasome activation, the structural details of them and their functions (negative/positive) in multiple disease models in both animal models and human. The wide range of the stimuli makes the function of inflammasome diverse and complex. Here, we review the structure, biological functions, and therapeutic targets of inflammasomes, while highlight NLRP3, NLRC4, and AIM2 inflammasomes, which are the most well studied. In conclusion, this review focuses on the activation process, biological functions, and structure of the most well-studied inflammasomes, summarizing and predicting approaches for disease treatment and prevention with inflammasome as a target. We aim to provide fresh insight into new solutions to the challenges in this field.

Clustering predicted structures at the scale of the known protein universe

Proteins are key to all cellular processes and their structure is important in understanding their function and evolution. Sequence-based predictions of protein structures have increased in accuracy1, and over 214 million predicted structures are available in the AlphaFold database2. However, studying protein structures at this scale requires highly efficient methods. Here, we developed a structural-alignment-based clustering algorithm-Foldseek cluster-that can cluster hundreds of millions of structures. Using this method, we have clustered all of the structures in the AlphaFold database, identifying 2.30 million non-singleton structural clusters, of which 31% lack annotations representing probable previously undescribed structures. Clusters without annotation tend to have few representatives covering only 4% of all proteins in the AlphaFold database. Evolutionary analysis suggests that most clusters are ancient in origin but 4% seem to be species specific, representing lower-quality predictions or examples of de novo gene birth. We also show how structural comparisons can be used to predict domain families and their relationships, identifying examples of remote structural similarity. On the basis of these analyses, we identify several examples of human immune-related proteins with putative remote homology in prokaryotic species, illustrating the value of this resource for studying protein function and evolution across the tree of life.

Leishmania braziliensis exosomes activate human macrophages to produce proinflammatory mediators

Exosomes, organelles measuring 30-200nm, are secreted by various cell types. Leishmania exosomes consist of many proteins, including heat shock proteins, annexins, Glycoprotein 63, proteins exerting signaling activity and those containing mRNA and miRNA. Studies have demonstrated that Leishmania donovani exosomes downregulate IFN-γ and inhibit the expression of microbicidal molecules, such as TNF and nitric oxide, thus creating a microenvironment favoring parasite proliferation. Despite lacking immunological memory, data in the literature suggest that, following initial stimulation, mononuclear phagocytes may become "trained" to respond more effectively to subsequent stimuli. Here we characterized the effects of macrophage sensitization using L. braziliensis exosomes prior to infection by the same pathogen. Human macrophages were stimulated with L. braziliensis exosomes and then infected with L. braziliensis. Higher levels of IL-1β and IL-6 were detected in cultures sensitized prior to infection compared to unstimulated infected cells. Moreover, stimulation with L. braziliensis exosomes induced macrophage production of IL-1β, IL-6, IL-10 and TNF. Inhibition of exosome secretion by L. braziliensis prior to macrophage infection reduced cytokine production and produced lower infection rates than untreated infected cells. Exosome stimulation also induced the consumption/regulation of NLRP3 inflammasome components in macrophages, while the blockade of NLRP3 resulted in lower levels of IL-6 and IL-1β. Our results suggest that L. braziliensis exosomes stimulate macrophages, leading to an exacerbated inflammatory state that may be NLRP3-dependent.

Effects of AIM2 and IFI16 on Infectious Diseases and Inflammation

Both absent in melanoma 2 (AIM2) and interferon-inducible protein 16 (IFI16) are intracellular innate immune receptors that recognize double-stranded DNA released during pathogenic infection, leading to the assembly of the inflammasome. The assembly of the inflammasome results in the secretion of bioactive interleukin (IL)-1β and IL-18 and induces cell death through an inflammatory process called pyroptosis. Although the AIM2 inflammasome is generally harmful in the context of some aseptic inflammatory illnesses, it plays a protective role in infectious diseases. During inflammatory processes, there is competition between IFI16 and AIM2. In this review, we explore the impacts of IFI16 and AIM2 in infectious disease and aseptic inflammation, respectively, and how they compete.

Tocilizumab suppresses NF-kappa B activation via toll-like receptor 9 signaling by reducing cell-free DNA in rheumatoid arthritis

Endogenous DNA is released into the bloodstream as cell-free DNA (cfDNA) following cell death and is associated with various pathological conditions. However, their association with therapeutic drugs against rheumatoid arthritis (RA) remains unknown. Therefore, we investigated the significance of cfDNA in RA treated with tocilizumab and tumour necrosis factor inhibitor (TNF-I). Biological DMARDs (bDMARDs), including tocilizumab and TNF-I, were administered to 77 and 59 RA patients, respectively. Plasma cfDNA levels were measured at weeks 0, 4, and 12 by quantitative polymerase chain reaction. Disease activity was evaluated at the same time point using DAS28ESR. cfDNA levels from RA synovial cells treated with tocilizumab or etanercept for 24 h were measured. Human toll-like receptor 9 (hTLR9)-expressing HEK293 cells, which release secreted embryonic alkaline phosphatase (SEAP) upon NF-κB activation, were stimulated by cfDNA from RA patients, and subsequently, SEAP levels were determined. NF-κB translocation was evaluated by immunofluorescence staining with or without tocilizumab. The DAS28ESR significantly improved in both bDMARD groups at week 12. However, plasma cfDNA levels significantly decreased in the tocilizumab group at week 12 compared to that in week 0. cfDNA levels correlated with DAS28ESR in biological treatment-naïve patients administered tocilizumab. cfDNA levels in synovial cells were significantly suppressed by tocilizumab treatment and unaltered with etanercept. HEK293 cells released SEAP upon cfDNA stimulation, and the observed NF-κB nuclear translocation was suppressed by tocilizumab. Tocilizumab suppressed inflammation via the TLR9 pathway by decreasing cfDNA levels. Regulation of cfDNA may be a therapeutic target for RA.

Intracellular DNA sensing by neutrophils and amplification of the innate immune response

As the first responders, neutrophils lead the innate immune response to infectious pathogens and inflammation inducing agents. The well-established pathogen neutralizing strategies employed by neutrophils are phagocytosis, the action of microbicide granules, the production of ROS, and the secretion of neutrophil extracellular traps (NETs). Only recently, the ability of neutrophils to sense and respond to pathogen-associated molecular patterns is being appreciated. This review brings together the current information about the intracellular recognition of DNA by neutrophils and proposes models of signal amplification in immune response. Finally, the clinical relevance of DNA sensing by neutrophils in infectious and non-infectious diseases including malignancy are also discussed.

Inflammasomes: Mechanisms of Action and Involvement in Human Diseases

Inflammasome complexes and their integral receptor proteins have essential roles in regulating the innate immune response and inflammation at the post-translational level. Yet despite their protective role, aberrant activation of inflammasome proteins and gain of function mutations in inflammasome component genes seem to contribute to the development and progression of human autoimmune and autoinflammatory diseases. In the past decade, our understanding of inflammasome biology and activation mechanisms has greatly progressed. We therefore provide an up-to-date overview of the various inflammasomes and their known mechanisms of action. In addition, we highlight the involvement of various inflammasomes and their pathogenic mechanisms in common autoinflammatory, autoimmune and neurodegenerative diseases, including atherosclerosis, rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease, Alzheimer's disease, Parkinson's disease, and multiple sclerosis. We conclude by speculating on the future avenues of research needed to better understand the roles of inflammasomes in health and disease.

Regulatory Cues in Pulmonary Fibrosis-With Emphasis on the AIM2 Inflammasome

Pulmonary fibrosis (PF) is a chronic lung disorder characterized by the presence of scarred and thickened lung tissues. Although the Food and Drug Administration approved two antifibrotic drugs, pirfenidone, and nintedanib, that are currently utilized for treating idiopathic PF (IPF), the clinical therapeutic efficacy remains unsatisfactory. It is crucial to develop new drugs or treatment schemes that combine pirfenidone or nintedanib to achieve more effective outcomes for PF patients. Understanding the complex mechanisms underlying PF could potentially facilitate drug discovery. Previous studies have found that the activation of inflammasomes, including nucleotide-binding and oligomerization domain (NOD)-like receptor protein (NLRP)1, NLRP3, NOD-like receptor C4, and absent in melanoma (AIM)2, contributes to lung inflammation and fibrosis. This article aims to summarize the cellular and molecular regulatory cues that contribute to PF with a particular emphasis on the role of AIM2 inflammasome in mediating pathophysiologic events during PF development. The insights gained from this research may pave the way for the development of more effective strategies for the prevention and treatment of PF.

Targeting Inflammasome Activation in Viral Infection: A Therapeutic Solution?

Inflammasome activation is exclusively involved in sensing activation of innate immunity and inflammatory response during viral infection. Accumulating evidence suggests that the manipulation of inflammasome assembly or its interaction with viral proteins are critical factors in viral pathogenesis. Results from pilot clinical trials show encouraging results of NLRP3 inflammasome suppression in reducing mortality and morbidity in SARS-CoV-2-infected patients. In this article, we summarize the up-to-date understanding of inflammasomes, including NLRP3, AIM2, NLRP1, NLRP6, and NLRC4 in various viral infections, with particular focus on RNA viruses such as SARS-CoV-2, HIV, IAV, and Zika virus and DNA viruses such as herpes simplex virus 1. We also discuss the current achievement of the mechanisms involved in viral infection-induced inflammatory response, host defense, and possible therapeutic solutions.

Inflammasomes and Atherosclerosis: a Mixed Picture

The CANTOS (Canakinumab Anti-inflammatory Thrombosis Outcome Study) and colchicine trials suggest an important role of inflammasomes and their major product IL-1β (interleukin 1β) in human atherosclerotic cardiovascular disease. Moreover, studies in mouse models indicate a causal role of inflammasomes and IL-1β in atherosclerosis. However, recent studies have led to a more granular view of the role of inflammasomes in atherosclerosis. Studies in hyperlipidemic mouse models suggest that prominent activation of the NLRP3 inflammasome requires a second hit such as defective cholesterol efflux, defective DNA repair, clonal hematopoiesis or diabetes. Similarly in humans some mutations promoting clonal hematopoiesis increase coronary artery disease risk in part by promoting inflammasome activation. Recent studies in mice and humans point to a wider role of the AIM2 (absent in melanoma 2) inflammasome in promoting cardiovascular disease including in some forms of clonal hematopoiesis and diabetes. These developments suggest a precision medicine approach in which treatments targeting inflammasomes or IL-1β might be best employed in clinical settings involving increased inflammasome activation.

Pyroptosis and its role in cancer

Programmed cell death (PCD) is mediated by specific genes that encode signals. It can balance cell survival and death. Pyroptosis is a type of inflammatory, caspase-dependent PCD mediated by gasdermin proteins, which function in pore formation, cell expansion, and plasma membrane rupture, followed by the release of intracellular contents. Pyroptosis is mediated by caspase-1/3/4/5/11 and is primarily divided into the classical pathway, which is dependent on caspase-1, and the non-classical pathway, which is dependent on caspase-4/5/11. Inflammasomes play a vital role in these processes. The various components of the pyroptosis pathway are related to the occurrence, invasion, and metastasis of tumors. Research on pyroptosis has revealed new options for tumor treatment. This article summarizes the recent research progress on the molecular mechanism of pyroptosis, the relationship between the various components of the pyroptosis pathway and cancer, and the applications and prospects of pyroptosis in anticancer therapy.

Filament assembly underpins the double-stranded DNA specificity of AIM2-like receptors

Upon sensing cytosolic- and/or viral double-stranded (ds)DNA, absent-in-melanoma-2 (AIM2)-like-receptors (ALRs) assemble into filamentous signaling platforms to initiate inflammatory responses. The versatile yet critical roles of ALRs in host innate defense are increasingly appreciated; however, the mechanisms by which AIM2 and its related IFI16 specifically recognize dsDNA over other nucleic acids remain poorly understood (i.e. single-stranded (ss)DNA, dsRNA, ssRNA and DNA:RNA hybrid). Here, we find that although AIM2 can interact with various nucleic acids, it preferentially binds to and assembles filaments faster on dsDNA in a duplex length-dependent manner. Moreover, AIM2 oligomers assembled on nucleic acids other than dsDNA not only display less ordered filamentous structures, but also fail to induce the polymerization of downstream ASC. Likewise, although showing broader nucleic acid selectivity than AIM2, IFI16 binds to and oligomerizes most readily on dsDNA in a duplex length-dependent manner. Nevertheless, IFI16 fails to form filaments on single-stranded nucleic acids and does not accelerate the polymerization of ASC regardless of bound nucleic acids. Together, we reveal that filament assembly is integral to nucleic acid distinction by ALRs.

The regulation of self-tolerance and the role of inflammasome molecules

Inflammasome molecules make up a family of receptors that typically function to initiate a proinflammatory response upon infection by microbial pathogens. Dysregulation of inflammasome activity has been linked to unwanted chronic inflammation, which has also been implicated in certain autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, type 1 diabetes, systemic lupus erythematosus, and related animal models. Classical inflammasome activation-dependent events have intrinsic and extrinsic effects on both innate and adaptive immune effectors, as well as resident cells in the target tissue, which all can contribute to an autoimmune response. Recently, inflammasome molecules have also been found to regulate the differentiation and function of immune effector cells independent of classical inflammasome-activated inflammation. These alternative functions for inflammasome molecules shape the nature of the adaptive immune response, that in turn can either promote or suppress the progression of autoimmunity. In this review we will summarize the roles of inflammasome molecules in regulating self-tolerance and the development of autoimmunity.

Inflammation and DNA damage: cause, effect or both

Inflammation is a biological response involving immune cells, blood vessels and mediators induced by endogenous and exogenous stimuli, such as pathogens, damaged cells or chemicals. Unresolved (chronic) inflammation is characterized by the secretion of cytokines that maintain inflammation and redox stress. Mitochondrial or nuclear redox imbalance induces DNA damage, which triggers the DNA damage response (DDR) that is orchestrated by ATM and ATR kinases, which modify gene expression and metabolism and, eventually, establish the senescent phenotype. DDR-mediated senescence is induced by the signalling proteins p53, p16 and p21, which arrest the cell cycle in G1 or G2 and promote cytokine secretion, producing the senescence-associated secretory phenotype. Senescence and inflammation phenotypes are intimately associated, but highly heterogeneous because they vary according to the cell type that is involved. The vicious cycle of inflammation, DNA damage and DDR-mediated senescence, along with the constitutive activation of the immune system, is the core of an evolutionarily conserved circuitry, which arrests the cell cycle to reduce the accumulation of mutations generated by DNA replication during redox stress caused by infection or inflammation. Evidence suggests that specific organ dysfunctions in apparently unrelated diseases of autoimmune, rheumatic, degenerative and vascular origins are caused by inflammation resulting from DNA damage-induced senescence.

The role of long non-coding RNA in abdominal aortic aneurysm

The abdominal aortic aneurysm (AAA) is characterized by segmental expansion of the abdominal aorta and a high mortality rate. The characteristics of AAA suggest that apoptosis of smooth muscle cells, the production of reactive oxygen species, and inflammation are potential pathways for the formation and development of AAA. Long non-coding RNA (lncRNA) is becoming a new and essential regulator of gene expression. Researchers and physicians are focusing on these lncRNAs to use them as clinical biomarkers and new treatment targets for AAAs. LncRNA studies are beginning to emerge, suggesting that they may play a significant but yet unidentified role in vascular physiology and disease. This review examines the role of lncRNA and their target genes in AAA to increase our understanding of the disease’s onset and progression, which is crucial for developing potential AAA therapies.

IFN-Induced PARPs—Sensors of Foreign Nucleic Acids?

Cells have developed different strategies to cope with viral infections. Key to initiating a defense response against viruses is the ability to distinguish foreign molecules from their own. One central mechanism is the perception of foreign nucleic acids by host proteins which, in turn, initiate an efficient immune response. Nucleic acid sensing pattern recognition receptors have evolved, each targeting specific features to discriminate viral from host RNA. These are complemented by several RNA-binding proteins that assist in sensing of foreign RNAs. There is increasing evidence that the interferon-inducible ADP-ribosyltransferases (ARTs; PARP9—PARP15) contribute to immune defense and attenuation of viruses. However, their activation, subsequent targets, and precise mechanisms of interference with viruses and their propagation are still largely unknown. Best known for its antiviral activities and its role as RNA sensor is PARP13. In addition, PARP9 has been recently described as sensor for viral RNA. Here we will discuss recent findings suggesting that some PARPs function in antiviral innate immunity. We expand on these findings and integrate this information into a concept that outlines how the different PARPs might function as sensors of foreign RNA. We speculate about possible consequences of RNA binding with regard to the catalytic activities of PARPs, substrate specificity and signaling, which together result in antiviral activities.

Role of the inflammasome in insulin resistance and type 2 diabetes mellitus

The inflammasome is a protein complex composed of a variety of proteins in cells and which participates in the innate immune response of the body. It can be activated by upstream signal regulation and plays an important role in pyroptosis, apoptosis, inflammation, tumor regulation, etc. In recent years, the number of metabolic syndrome patients with insulin resistance (IR) has increased year by year, and the inflammasome is closely related to the occurrence and development of metabolic diseases. The inflammasome can directly or indirectly affect conduction of the insulin signaling pathway, involvement the occurrence of IR and type 2 diabetes mellitus (T2DM). Moreover, various therapeutic agents also work through the inflammasome to treat with diabetes. This review focuses on the role of inflammasome on IR and T2DM, pointing out the association and utility value. Briefly, we have discussed the main inflammasomes, including NLRP1, NLRP3, NLRC4, NLRP6 and AIM2, as well as their structure, activation and regulation in IR were described in detail. Finally, we discussed the current therapeutic options-associated with inflammasome for the treatment of T2DM. Specially, the NLRP3-related therapeutic agents and options are widely developed. In summary, this article reviews the role of and research progress on the inflammasome in IR and T2DM.

Pyroptosis and airway homeostasis regulation

Pyroptosis is a form of cell death associated with inflammation. In the maintenance of airway homeostasis, pyroptosis goes through activation and assembly of Inflammasome. The pyroptosis pathway is mediated by caspase which activates the pore-forming effect of substrate gasdermin family members. It eventually leads to lysis and release of the cell contents and then induces an inflammatory response. In this process, it participates in airway homeostasis regulation by affecting airway immunity, airway epithelial structure and airway microbiota. Therefore, we discussed the correlation between airway immunity, airway epithelial structure, airway microbiota and the mechanism of pyroptosis to describe the role of pyroptosis in airway homeostasis regulation which is of great significance for understanding the occurrence and treatment of airway inflammatory diseases.

Deciphering the Role of Pyroptosis Impact on Cardiovascular Diseases

Pyroptosis has become a noteworthy area of focus in recent years due to its association with inflammatory diseases. Pyroptosis is a type of programmed cell death accompanied by an inflammatory response, and the discovery of the gasdermin family has expanded the study of pyroptosis. The primary characteristics of pyroptosis include cell expansion, membrane penetration, and the ejection of cell contents. In healthy physiology, pyroptosis is an essential part of the host's defence against pathogen infection. Excessive Pyroptosis, however, can lead to unchecked and persistent inflammatory responses, including the emergence of inflammatory diseases. More precisely, gasdermin family members have a role in the creation of membrane holes during pyroptosis, which leads to cell lysis. It is also related to how pro-inflammatory intracellular substances, including IL-1, IL-18, and High mobility group box 1 (HMGB1), are used. Two different signalling pathways, one of which is regulated by caspase-1 and the other by caspase-4/5/11, are the primary causes of pyroptosis. Cardiovascular diseases are often associated with cell death and acute or chronic inflammation, making this area of research particularly relevant. In this review, we first systematically summarize recent findings related to Pyroptosis, exploring its characteristics and the signalling pathway mechanisms, as well as various treatment strategies based on its modulation that has emerged from the studies. Some of these strategies are currently undergoing clinical trials. Additionally, the article elaborates on the scientific evidence indicating the role of Pyroptosis in various cardiovascular diseases. As a whole, this should shed insight into future paths and present innovative ideas for employing Pyroptosis as a strong disease-fighting weapon.

Canonical Inflammasomes

The innate immune response represents the first line of host defense, and it is able to detect pathogen- and damage-associated molecular patterns (PAMPs and DAMPs, respectively) through a variety of pattern recognition receptors (PRRs). Among these PRRs, certain cytosolic receptors of the NLRs family (specifically NLRP1, NLRP3, NLRC4, and NAIP) or those containing at least a pyrin domain (PYD) such as pyrin and AIM2, activate the multimeric complex known as inflammasome, and its effector enzyme caspase-1. The caspase-1 induces the proteolytic maturation of the pro-inflammatory cytokines IL-1ß and IL-18, as well as the pore-forming protein gasdermin D (GSDMD). GSDMD is responsible for the release of the two cytokines and the induction of lytic and inflammatory cell death known as pyroptosis. Each inflammasome receptor detects specific stimuli, either directly or indirectly, thereby enhancing the cell's ability to sense infections or homeostatic disturbances. In this chapter, we present the activation mechanism of the so-called "canonical" inflammasomes.

Significance of pyroptosis-related gene in the diagnosis and classification of rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA), a chronic autoimmune inflammatory disease, is often characterized by persistent morning stiffness, joint pain, and swelling. Early diagnosis and timely treatment of RA can effectively delay the progression of the condition and significantly reduce the incidence of disability. In the study, we explored the function of pyroptosis-related genes (PRGs) in the diagnosis and classification of rheumatoid arthritis based on Gene Expression Omnibus (GEO) datasets.

METHOD

We downloaded the GSE93272 dataset from the GEO database, which contains 35 healthy controls and 67 RA patients. Firstly, the GSE93272 was normalized by the R software "limma" package. Then, we screened PRGs by SVM-RFE, LASSO, and RF algorithms. To further investigate the prevalence of RA, we established a nomogram model. Besides, we grouped gene expression profiles into two clusters and explored their relationship with infiltrating immune cells. Finally, we analyzed the relationship between the two clusters and the cytokines.

RESULT

CHMP3, TP53, AIM2, NLRP1, and PLCG1 were identified as PRGs. The nomogram model revealed that decision-making based on established model might be beneficial for RA patients, and the predictive power of the nomogram model was significant. In addition, we identified two different pyroptosis patterns (pyroptosis clusters A and B) based on the 5 PRGs. We found that eosinophil, gamma delta T cell, macrophage, natural killer cell, regulatory T cell, type 17 T helper cell, and type 2 T helper cell were significant high expressed in cluster B. And, we identified gene clusters A and B based on 56 differentially expressed genes (DEGs) between pyroptosis cluster A and B. And we calculated the pyroptosis score for each sample to quantify the different patterns. The patients in pyroptosis cluster B or gene cluster B had higher pyroptosis scores than those in pyroptosis cluster A or gene cluster A.

CONCLUSION

In summary, PRGs play vital roles in the development and occurrence of RA. Our findings might provide novel views for the immunotherapy strategies with RA.

NLRC4-mediated activation of CD1c+ DC contributes to perpetuation of synovitis in rheumatoid arthritis

The individual contribution of specific myeloid subsets such as CD1c+ conventional DC (cDC) to perpetuation of rheumatoid arthritis (RA) pathology remains unclear. In addition, the specific innate sensors driving pathogenic activation of CD1c+ cDC in patients with RA and their functional implications have not been characterized. Here, we assessed phenotypical, transcriptional, and functional characteristics of CD1c+ and CD141+ cDC and monocytes from the blood and synovial fluid of patients with RA. Increased levels of CCR2 and the IgG receptor CD64 on circulating CD1c+ cDC was associated with the presence of this DC subset in the synovial membrane in patients with RA. Moreover, synovial CD1c+ cDC are characterized by increased expression of proinflammatory cytokines and high abilities to induce pathogenic IFN-γ+IL-17+CD4+ T cells in vitro. Finally, we identified the crosstalk between Fcγ receptors and NLRC4 as a potential molecular mechanism mediating pathogenic activation, CD64 upregulation, and functional specialization of CD1c+ cDC in response to dsDNA-IgG in patients with RA.

The strategies of NLRP3 inflammasome to combat Toxoplasma gondii

Infection with the protozoan parasite Toxoplasma gondii (T. gondii) results in the activation of nucleotide-binding domain leucine-rich repeat containing receptors (NLRs), which in turn leads to inflammasome assembly and the subsequent activation of caspase-1, secretion of proinflammatory cytokines, and pyroptotic cell death. Several recent studies have addressed the role of the NLRP3 inflammasome in T. gondii infection without reaching a consensus on its roles. Moreover, the mechanisms of NLRP3 inflammasome activation in different cell types remain unknown. Here we review current research on the activation and specific role of the NLRP3 inflammasome in T. gondii infection.

Heterogeneity of T cells and macrophages in chlorine-induced acute lung injury in mice using single-cell RNA sequencing

OBJECTIVE

Chlorine (Cl₂), as an asphyxiant toxicant, induced poisoning incidents and acute lung injury (ALI) occur frequently. The specific pathogenesis of Cl₂-induced ALI remains unclear. Immune cells play an important role in the process of lung damage. We used single-cell RNA sequencing (scRNA-seq) technology to explore T cells and macrophages molecular mechanism.

METHODS

Female BALB/c mice were exposed to 400 ppm Cl₂ for 15 min. scRNA-seq technology was used to observe the heterogeneity of T cells and macrophages. Hematoxylin-eosin (H&E) staining was used to evaluate the degree of lung injury. Immunofluorescence was used to verify the highly expressed genes of our interest.

RESULTS

A total of 5316 to 7742 cells were classified into eight different cell types. Several new highly expressed anti-inflammatory and pro-inflammatory genes were found in T cells and macrophages, which were further verified in vitro. Through the pseudotime analysis of macrophages, it was found that the expression of pro-inflammatory and anti-inflammatory genes showed opposite trends in the development of Cl₂-induced ALI. This study also mapped T cells-macrophage communication and identified the development of several important receptor-ligand complexes in Cl₂-induced ALI.

CONCLUSIONS

These findings are worthy of further exploration and provide new resources and directions for the study of Cl₂-induced ALI in mice, especially in immune and inflammation mechanisms.

Mitochondrial VDAC1: A Potential Therapeutic Target of Inflammation-Related Diseases and Clinical Opportunities

The multifunctional protein, voltage-dependent anion channel 1 (VDAC1), is located on the mitochondrial outer membrane. It is a pivotal protein that maintains mitochondrial function to power cellular bioactivities via energy generation. VDAC1 is involved in regulating energy production, mitochondrial oxidase stress, Ca²⁺ transportation, substance metabolism, apoptosis, mitochondrial autophagy (mitophagy), and many other functions. VDAC1 malfunction is associated with mitochondrial disorders that affect inflammatory responses, resulting in an up-regulation of the body’s defensive response to stress stimulation. Overresponses to inflammation may cause chronic diseases. Mitochondrial DNA (mtDNA) acts as a danger signal that can further trigger native immune system activities after its secretion. VDAC1 mediates the release of mtDNA into the cytoplasm to enhance cytokine levels by activating immune responses. VDAC1 regulates mitochondrial Ca²⁺ transportation, lipid metabolism and mitophagy, which are involved in inflammation-related disease pathogenesis. Many scientists have suggested approaches to deal with inflammation overresponse issues via specific targeting therapies. Due to the broad functionality of VDAC1, it may become a useful target for therapy in inflammation-related diseases. The mechanisms of VDAC1 and its role in inflammation require further exploration. We comprehensively and systematically summarized the role of VDAC1 in the inflammatory response, and hope that our research will lead to novel therapeutic strategies that target VDAC1 in order to treat inflammation-related disorders.

Pyroptosis and pyroptosis-inducing cancer drugs

Pyroptosis, an inflammatory form of lytic cell death, is a type of cell death mediated by the gasdermin (GSDM) protein family. Upon recognizing exogenous or endogenous signals, cells undergo inflammasome assembly, GSDM cleavage, the release of proinflammatory cytokines and other cellular contents, eventually leading to inflammatory cell death. In this review, we discuss the roles of the GSDM family for anti-cancer functions and various antitumor drugs that could activate the pyroptosis pathways.

Pyroptosis in development, inflammation and disease

In the early 2000s, caspase-1, an important molecule that has been shown to be involved in the regulation of inflammation, cell survival and diseases, was given a new function: regulating a new mode of cell death that was later defined as pyroptosis. Since then, the inflammasome, the inflammatory caspases (caspase-4/5/11) and their substrate gasdermins (gasdermin A, B, C, D, E and DFNB59) has also been reported to be involved in the pyroptotic pathway, and this pathway is closely related to the development of various diseases. In addition, important apoptotic effectors caspase-3/8 and granzymes have also been reported to b involved in the induction of pyroptosis. In our article, we summarize findings that help define the roles of inflammasomes, inflammatory caspases, gasdermins, and other mediators of pyroptosis, and how they determine cell fate and regulate disease progression.

Roles of AIM2 Gene and AIM2 Inflammasome in the Pathogenesis and Treatment of Psoriasis

Psoriasis is an immune-mediated chronic inflammatory skin disease caused by a combination of environmental incentives, polygenic genetic control, and immune regulation. The inflammation-related gene absent in melanoma 2 (AIM2) was identified as a susceptibility gene for psoriasis. AIM2 inflammasome formed from the combination of AIM2, PYD-linked apoptosis-associated speck-like protein (ASC) and Caspase-1 promotes the maturation and release of inflammatory cytokines such as IL-1β and IL-18, and triggers an inflammatory response. Studies showed the genetic and epigenetic associations between AIM2 gene and psoriasis. AIM2 gene has an essential role in the occurrence and development of psoriasis, and the inhibitors of AIM2 inflammasome will be new therapeutic targets for psoriasis. In this review, we summarized the roles of the AIM2 gene and AIM2 inflammasome in pathogenesis and treatment of psoriasis, hopefully providing a better understanding and new insight into the roles of AIM2 gene and AIM2 inflammasome in psoriasis.

Neuro-Inflammaging and Psychopathological Distress

Inflammaging is a low degree of chronic and systemic tissue inflammation associated with aging, and is intimately linked to pro-inflammatory mediators. These substances are involved in the pathogenesis of chronic inflammatory diseases and related psychopathological symptoms. When inflammation and aging affect the brain, we use the term neuro-inflammaging. In this review, we focused on the neuro-inflammatory process typical of advanced ages and the related psychopathological symptoms, with particular attention to understanding the immune-pathogenetic mechanisms involved and the potential use of immunomodulatory drugs in the control of clinical psychological signs. Inflammation and CNS were demonstrated being intimately linked in the neuro-inflammatory loop. IL-1, IL-6, TNF-a, COX and PGE are only partially responsible. BBB permeability and the consequent oxidative stress resulting from tissue damage make the rest. Some authors elaborated the “theory of cytokine-induced depression”. Inflammation has a crucial role in the onset symptoms of psychopathological diseases as it is capable of altering the metabolism of biogenic monoamines involved in their pathogenesis. In recent years, NSAIDs as an adjunct therapy in the treatment of relevant psychopathological disorders associated with chronic inflammatory conditions demonstrated their efficacy. Additionally, novel molecules have been studied, such as adalimumab, infliximab, and etanercept showing antidepressant and anxiolytic promising results. However, we are only at the beginning of a new era characterized by the use of biological drugs for the treatment of inflammatory and autoimmune diseases, and this paper aims to stimulate future studies in such a direction.