Emerging roles of absent in melanoma 2 in cardiovascular diseases

The Role of Inflammasomes in Heart Failure

Heart failure (HF) poses a significant world health challenge due to the increase in the aging population and advancements in cardiac care. In the pathophysiology of HF, the inflammasome has been correlated with the development, progression, and complications of HF disease. Discovering biomarkers linked to inflammasomes enhances understanding of HF diagnosis and prognosis. Directing inflammasome signaling emerges as an innovative therapeutic strategy for managing HF. The present review aims to delve into this inflammatory cascade, understanding its role in the development of HF, its potential role as biomarker, as well as the prospects of modulating inflammasomes as a therapeutic approach for HF.

The Role of Inflammasome in Abdominal Aortic Aneurysm and Its Potential Drugs

Abdominal aortic aneurysm (AAA) has been recognized as a serious chronic inflammatory degenerative aortic disease in recent years. At present, there is no other effective intervention except surgical treatment for AAA. With the aging of the human population, its incidence is increasing year by year, posing a serious threat to human health. Modern studies suggest that vascular chronic inflammatory response is the core process in AAA occurrence and development. Inflammasome, a multiprotein complex located in the cytoplasm, mediates the expression of various inflammatory cytokines like interleukin (IL)-1β and IL-18, and thus plays a pivotal role in inflammation regulation. Therefore, inflammasome may exert a crucial influence on the progression of AAA. This article reviews some mechanism studies to investigate the role of inflammasome in AAA and then summarizes several potential drugs targeting inflammasome for the treatment of AAA, aiming to provide new ideas for the clinical prevention and treatment of AAA beyond surgical methods.

A High-Protein Diet Promotes Atrial Arrhythmogenesis via Absent-in-Melanoma 2 Inflammasome

High-protein diets (HPDs) offer health benefits, such as weight management and improved metabolic profiles. The effects of HPD on cardiac arrhythmogenesis remain unclear. Atrial fibrillation (AF), the most common arrhythmia, is associated with inflammasome activation. The role of the Absent-in-Melanoma 2 (AIM2) inflammasome in AF pathogenesis remains unexplored. In this study, we discovered that HPD increased susceptibility to AF. To demonstrate the involvement of AIM2 signaling in the pathogenesis of HPD-induced AF, wildtype (WT) and Aim2-/- mice were fed normal-chow (NC) and HPD, respectively. Four weeks later, inflammasome activity was upregulated in the atria of WT-HPD mice, but not in the Aim2-/--HPD mice. The increased AF vulnerability in WT-HPD mice was associated with abnormal sarcoplasmic reticulum (SR) Ca2+-release events in atrial myocytes. HPD increased the cytoplasmic double-strand (ds) DNA level, causing AIM2 activation. Genetic inhibition of AIM2 in Aim2-/- mice reduced susceptibility to AF, cytoplasmic dsDNA level, mitochondrial ROS production, and abnormal SR Ca2+-release in atrial myocytes. These data suggest that HPD creates a substrate conducive to AF development by activating the AIM2-inflammasome, which is associated with mitochondrial oxidative stress along with proarrhythmic SR Ca2+-release. Our data imply that targeting the AIM2 inflammasome might constitute a novel anti-AF strategy in certain patient subpopulations.

Epigallocatechin gallate prevents cardiomyocytes from pyroptosis through lncRNA MEG3/TAF15/AIM2 axis in myocardial infarction

BACKGROUND

( -)-Epigallocatechin-3-gallate (EGCG), a bioactive polyphenol isolated from green tea, has recently garnered attention for its potential protective role against acute myocardial infarction (MI) via inhibiting inflammation. Herein, we tested whether EGCG participates in modulating cardiac ischemia reperfusion-induced injury and elucidate its potential mechanisms.

METHODS

To induce MI in mice, we employed coronary artery ligation, while cell models utilized oxygen glucose deprivation/re-oxygenation (OGD/R)-treated HL-1 cells. TTC, HE and Massion staining evaluated the pathological changes of heart tissues. Besides, RNA-pull down and RIP assays analyzed the interactions of MEG3/TAF15 and AIM2 mRNA/TAF15. FISH associated with immunofiuorescence (IF) double staining was conducted to measure the co-localization of MEG3 and TAF15.

RESULTS

In vitro and in vivo evidence supported that EGCG treatment improved cardiomyocytes viability while inhibiting the expressions of AIM2, C-caspase-1, ASC, GSDMD-N, IL-18 and IL-1β. Knockdown of MEG3 intensified EGCG's therapeutic effects both in vitro and in vivo. LncRNA MEG3 and AIM2 mRNA interacted with TAF15, and MEG3, in turn, promoted the stability of AIM2 mRNA through regulating TAF15. Overexpression of TAF15 reversed the promoting effect of EGCG and MEG3 knockdown on cell viability, and the inhibiting effect on cell pyroptosis.

CONCLUSION

EGCG protected cardiomyocytes from pyroptosis by the MEG3/TAF15/AIM2 axis, indicating EGCG as a potential novel therapeutic strategy for managing MI.

Novel Therapeutic Avenues for Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a complicated, heterogeneous genetic condition that causes left ventricular hypertrophy, fibrosis, hypercontractility, and decreased compliance. Despite the advances made over the past 3 decades in understanding the molecular and cellular mechanisms aggravating HCM, the relationship between pathophysiological stress stimuli and distinctive myocyte growth profiles is still imprecise. Currently, mavacamten, a selective and reversible inhibitor of cardiac myosin ATPase, is the only drug approved by the US FDA for the treatment of HCM. Thus, there is an unmet need for developing novel disease-specific therapeutic approaches. This article provides an overview of emerging therapeutic targets for the treatment of HCM based on various molecular pathways and novel developments that are hopefully soon to enter the clinical study. These newly discovered targets include the dual specificity tyrosine-phosphorylation-regulated kinase 1B, the absence of the melanoma 1 inflammasome, the leucine-rich repeat kinase 2 enzyme, and the cluster of differentiation 147.

The Association of Serum AIM2 Level with the Prediction and Short-Term Prognosis of Coronary Artery Disease

Objective. Coronary artery disease (CAD), one of the commonest cardiovascular diseases, has high morbidity and mortality. Absent in melanoma 2 (AIM2) is involved in atherosclerosis, and no clinical trials have explored the association between AIM2 and CAD. Therefore, this study was aimed at evaluating the predictive and short-term prognostic value of AIM2 for CAD. Methods. 279 patients who underwent coronary angiography were enrolled in this study. The AIM2 level was detected from the serum of collected artery blood samples. The association of serum AIM2 level with the prediction and short-term prognosis of CAD was further assessed. Results. The serum AIM2 level of the CAD group was significantly higher than the control group ( $5.5\pm 2.1$ vs. $3.7\pm 1.7$ ; $p<0.001$ ). AIM2 was demonstrated to be the risk factor of CAD [odds ratio, 1.589; 95% confidence interval (CI), 1.346-1.876; $p<0.001$ ]. The area under the receiver operating characteristic (ROC) curve of 0.738 showed the diagnostic value of AIM2 in CAD. Additionally, AIM2 was an independent predictor of major adverse cardiovascular events (hazard ratio, 1.453; 95% CI, 1.086-1.945; $p=0.012$ ), and CAD patients with high AIM2 levels (>4.9 ng/mL) had a markedly lower survival rate (log-rank $p=0.040$ ). Conclusions. The serum AIM2 $\text{level}>4.9$  ng/mL can predict CAD to a certain extent. AIM2 might be an independent predictor of its short-term poor prognosis.

Emerging Roles of Inflammasomes in Cardiovascular Diseases

Cardiovascular diseases are known as the leading cause of morbidity and mortality worldwide. As an innate immune signaling complex, inflammasomes can be activated by various cardiovascular risk factors and regulate the activation of caspase-1 and the production and secretion of proinflammatory cytokines such as IL-1β and IL-18. Accumulating evidence supports that inflammasomes play a pivotal role in the progression of atherosclerosis, myocardial infarction, and heart failure. The best-known inflammasomes are NLRP1, NLRP3, NLRC4, and AIM2 inflammasomes, among which NLRP3 inflammasome is the most widely studied in the immune response and disease development. This review focuses on the activation and regulation mechanism of inflammasomes, the role of inflammasomes in cardiovascular diseases, and the research progress of targeting NLRP3 inflammasome and IL-1β for related disease intervention.

Contribution of the innate and adaptive immune systems to aortic dilation in murine mucopolysaccharidosis type I

BACKGROUND

Adult immunocompetent male C57Bl/6 mucopolysaccharidosis, type I (MPSI) mice develop aortic insufficiency (AI), dilated ascending aortas and decreased cardiac function, findings not observed in immune incompetent adult male NSG MPSI mice. We sought to determine why.

METHODS

Cardiac ultrasound measurements of ascending aorta and left ventricular dimensions and Doppler interrogation for AI were performed in 6-month-old male B6 MPSI (N = 12), WT (N = 6), NSG MPSI (N = 8), NSG (N = 6) mice. Urinary glycosaminoglycans, RNA sequencing with quantitative PCR were performed and aortic pathology assessed by routine and immunohistochemical staining on subsets of murine aortas.

RESULTS

Ascending aortic diameters were significantly greater, left ventricular function significantly decreased, and AI significantly more frequent in B6 MPSI mice compared to NSG MPSI mice (p < 0.0001, p = 0.008 and p = 0.02, respectively); NSG and B6 WT mice showed no changes. Urinary glycosaminoglycans were significantly greater in B6 and NSG MPSI mice and both were significantly elevated compared to WT controls (p = 0.003 and p < 0.0001, respectively). By RNA sequencing, all 11 components of the inflammasome pathway were upregulated in B6 MUT, but only Aim2 and Ctsb in NSG MUT mice and none in WT controls. Both B6 and NSG MUT mice demonstrated variably-severe intramural inflammation, vacuolated cells, elastin fragmentation and disarray, and intense glycosaminoglycans on histological staining. B6 MPSI mice demonstrated numerous medial MAC2+ macrophages and adventitial CD3+ T-cells while MAC2+ macrophages were sparse and CD3+ T-cells absent in NSG MPSI mice.

CONCLUSIONS

Aortic dilation, AI and decreased cardiac function occur in immunocompetent B6 MPSI male mice but not in immune incompetent NSG MPSI mice, unrelated to GAG excretion, upregulation of Ctsb, or routine histologic appearance. Upregulation of all components of the inflammasome pathway in B6 MUT, but not NSG MUT mice, and abundant medial MAC2 and adventitial CD3 infiltrates in B6, but not NSG, MPSI aortas differentiated the two strains. These results suggest that the innate and adaptive immune systems play a role in these cardiac findings which may be relevant to human MPSI.

Pyroptosis and Its Regulation in Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DbCM) is a prevalent disease, characterized by contractile dysfunction and left ventricular hypertrophy. Patients with DbCM have high morbidity and mortality worldwide. Recent studies have identified that pyroptosis, a kind of cell death, could be induced by hyperglycemia involved in the formation of DbCM. This review summarizes the regulatory mechanisms of pyroptosis in DbCM, including NOD-like receptor3, AIM2 inflammasome, long non-coding RNAs, microRNAs, circular RNA, autophagy, and some drugs.

Novel Insights Into the Pathogenesis of Diabetic Cardiomyopathy and Pharmacological Strategies

Diabetic cardiomyopathy (DCM) is a severe complication of diabetes developed mainly in poorly controlled patients. In DCM, several clinical manifestations as well as cellular and molecular mechanisms contribute to its phenotype. The production of reactive oxygen species (ROS), chronic low-grade inflammation, mitochondrial dysfunction, autophagic flux inhibition, altered metabolism, dysfunctional insulin signaling, cardiomyocyte hypertrophy, cardiac fibrosis, and increased myocardial cell death are described as the cardinal features involved in the genesis and development of DCM. However, many of these features can be associated with broader cellular processes such as inflammatory signaling, mitochondrial alterations, and autophagic flux inhibition. In this review, these mechanisms are critically discussed, highlighting the latest evidence and their contribution to the pathogenesis of DCM and their potential as pharmacological targets.

AIM2 inhibits the proliferation, invasion and migration, and promotes the apoptosis of osteosarcoma cells by inactivating the PI3K/AKT/mTOR signaling pathway

Osteosarcoma is a primary bone tumor that mainly occurs in children and adolescents. Absent in melanoma 2 (AIM2) has been demonstrated to be involved in regulating the occurrence and development of cancer, exerting oncogenic and pro-cancer effects; however, its role in osteosarcoma is poorly understood. The present study aimed to explore the function and molecular mechanism of AIM2 in the progression of osteosarcoma. In the present study, AIM2 expression was predicted using the Cancer Cell Line Encyclopedia database and examined in several osteosarcoma cell lines using reverse transcription-quantitative PCR and western blotting. Following AIM2 overexpression, cell proliferation and apoptosis were examined using Cell Counting Kit-8, colony formation and TUNEL staining assays. The expression levels of proteins related to apoptosis, epithelial-mesenchymal transition (EMT) and the PI3K/AKT/mTOR signaling pathway were determined by western blotting. Additionally, cell invasion and migration were assessed using Transwell and wound healing assays. After addition of the PI3K/AKT/mTOR signaling pathway inhibitor LY294002 or activator 740Y-P, cell function analysis was performed. The results demonstrated that AIM2 was expressed at low levels in osteosarcoma cell lines. AIM2 overexpression inhibited proliferation, invasion, migration and EMT, and promoted apoptosis in osteosarcoma cells. Furthermore, the levels of phosphorylated (p)-PI3K, p-AKT and p-mTOR were markedly downregulated following AIM2 overexpression. Furthermore, LY294002 treatment had the same effects as AIM2 upregulation on osteosarcoma cell proliferation, apoptosis, invasion, migration and EMT. By contrast, 740Y-P reversed the effects of AIM2 overexpression on the behavior of osteosarcoma cells. Overall, the findings of the present study demonstrated that AIM2 may inhibit the progression of osteosarcoma by inactivating the PI3K/AKT/mTOR signaling pathway, and suggested that AIM2 may be a promising marker for the treatment of osteosarcoma.

The Role of the Inflammasome in Heart Failure

Inflammation promotes the development of heart failure (HF). The inflammasome is a multimeric protein complex that plays an essential role in the innate immune response by triggering the cleavage and activation of the proinflammatory cytokines interleukins (IL)-1β and IL-18. Blocking IL-1β with the monoclonal antibody canakinumab reduced hospitalizations and mortality in HF patients, suggesting that the inflammasome is involved in HF pathogenesis. The inflammasome is activated under various pathologic conditions that contribute to the progression of HF, including pressure overload, acute or chronic overactivation of the sympathetic system, myocardial infarction, and diabetic cardiomyopathy. Inflammasome activation is responsible for cardiac hypertrophy, fibrosis, and pyroptosis. Besides inflammatory cells, the inflammasome in other cardiac cells initiates local inflammation through intercellular communication. Some inflammasome inhibitors are currently being investigated in clinical trials in patients with HF. The current evidence suggests that the inflammasome is a critical mediator of cardiac inflammation during HF and a promising therapeutic target. The present review summarizes the recent advances in both basic and clinical research on the role of the inflammasome in HF.