DNA sensors in metabolic and cardiovascular diseases: Molecular mechanisms and therapeutic prospects

Ferroptosis-activating metabolite acrolein antagonizes necroptosis and anti-cancer therapeutics

Dysregulated cell death leading to uncontrolled cell proliferation is a hallmark of cancer. Chemotherapy-induced cell death is critical for the success of cancer treatment but this process is impaired by metabolic byproducts. How these byproducts interfere with anti-cancer therapy is unclear. Here, we show that the metabolic byproduct acrolein derived from polyamines, tobacco smoke or fuel combustion, induces ferroptosis independently of ZBP1, while suppressing necroptosis in cancer cells by inhibiting the oligomerization of the necroptosis effector MLKL. Loss of the enzyme SAT1, which contributes to intracellular acrolein production, sensitizes cells to necroptosis. In mice, administration of an acrolein-trapping agent relieves necroptosis blockade and enhances the anti-tumor efficacy of the chemotherapeutic drug cyclophosphamide. Human patients with cancer coupled with a higher cell death activity but a lower expression of genes controlling polyamine metabolism exhibit improved survival. These findings highlight that the removal of metabolic byproducts improves the success of certain chemotherapies.

The immune system in cardiovascular diseases: from basic mechanisms to therapeutic implications

Immune system plays a crucial role in the physiological and pathological regulation of the cardiovascular system. The exploration history and milestones of immune system in cardiovascular diseases (CVDs) have evolved from the initial discovery of chronic inflammation in atherosclerosis to large-scale clinical studies confirming the importance of anti-inflammatory therapy in treating CVDs. This progress has been facilitated by advancements in various technological approaches, including multi-omics analysis (single-cell sequencing, spatial transcriptome et al.) and significant improvements in immunotherapy techniques such as chimeric antigen receptor (CAR)-T cell therapy. Both innate and adaptive immunity holds a pivotal role in CVDs, involving Toll-like receptor (TLR) signaling pathway, nucleotide-binding oligomerization domain-containing proteins 1 and 2 (NOD1/2) signaling pathway, inflammasome signaling pathway, RNA and DNA sensing signaling pathway, as well as antibody-mediated and complement-dependent systems. Meanwhile, immune responses are simultaneously regulated by multi-level regulations in CVDs, including epigenetics (DNA, RNA, protein) and other key signaling pathways in CVDs, interactions among immune cells, and interactions between immune and cardiac or vascular cells. Remarkably, based on the progress in basic research on immune responses in the cardiovascular system, significant advancements have also been made in pre-clinical and clinical studies of immunotherapy. This review provides an overview of the role of immune system in the cardiovascular system, providing in-depth insights into the physiological and pathological regulation of immune responses in various CVDs, highlighting the impact of multi-level regulation of immune responses in CVDs. Finally, we also discuss pre-clinical and clinical strategies targeting the immune system and translational implications in CVDs.

A short history of the atrial NLRP3 inflammasome and its distinct role in atrial fibrillation

Inflammasomes are multiprotein complexes of the innate immune system that mediate inflammatory responses to infection and to local and systemic stress and tissue injury. The principal function is to facilitate caspase-1 auto-activation and subsequently maturation and release of the effectors interleukin (IL)-1β and IL-18. The atrial-specific NLRP3 inflammasome is a unifying causal feature of atrial fibrillation (AF) development, progression and recurrence after ablation. Many AF-associated risk factors and co-morbidities converge mechanistically on the activation of this central inflammatory signaling platform. This review presents the historical conceptual development of a distinct atrial inflammasome and its potential causal involvement in AF. We follow the early observations linking systemic and local inflammation with AF, to the emergence of an atrial-intrinsic NLRP3 inflammasome operating within not just immune cells but also in resident atrial fibroblasts and cardiomyocytes. We outline the key developments in understanding how the atrial NLRP3 inflammasome and its effector IL-1β contribute causally to cellular and tissue-level arrhythmogenesis in different pathological settings, and outline candidate therapeutic concepts verified in preclinical models of atrial cardiomyopathy and AF.

Mitochondrial damage mediates STING activation driving obesity-mediated atrial fibrillation

AIMS

Obesity is a significant risk factor for atrial fibrillation (AF), but the mechanisms by which obesity contributes to AF are not fully understood. Recent studies have indicated that the Stimulator of Interferon Genes (STING) signalling, mediated by mitochondrial damage, plays a crucial role in cardiac remodelling in various metabolic and cardiovascular diseases. This study aims to explore the role of STING in obesity-mediated AF and its potential mechanisms.

METHODS AND RESULTS

In this study, rats were divided into four groups: two groups received tail vein injections of AAV9-cTnT-STING siRNA and were fed either a normal diet or a high-fat diet (HFD) for 12 weeks; the other two groups received injections of AAV9-cTnT-NC siRNA and were similarly fed either a normal diet or a HFD. The atrial STING signalling, AF vulnerability, electrical remodelling, and substrate remodelling were assessed in all groups. Results showed that the induction of AF was increased in obese rats, accompanied by severe mitochondrial damage and upregulation of the STING inflammatory signalling cascade. STING activation was associated with atrial fibrosis, cardiomyocyte apoptosis, and substrate remodelling, including alterations in the gap junction protein CX40 and ion channels. Additionally, STING was linked to excessive calcium transfer from the endoplasmic reticulum to the mitochondria. Knockdown of STING prevented AF vulnerability and both electrical and substrate remodelling in obese rats.

CONCLUSION

Mitochondrial damage-mediated activation of the STING signalling pathway promotes obesity-induced atrial remodelling and the occurrence of AF.

Cytosolic nucleic acid sensing as driver of critical illness: mechanisms and advances in therapy

Nucleic acids from both self- and non-self-sources act as vital danger signals that trigger immune responses. Critical illnesses such as acute respiratory distress syndrome, sepsis, trauma and ischemia lead to the aberrant cytosolic accumulation and massive release of nucleic acids that are detected by antiviral innate immune receptors in the endosome or cytosol. Activation of receptors for deoxyribonucleic acids and ribonucleic acids triggers inflammation, a major contributor to morbidity and mortality in critically ill patients. In the past decade, there has been growing recognition of the therapeutic potential of targeting nucleic acid sensing in critical care. This review summarizes current knowledge of nucleic acid sensing in acute respiratory distress syndrome, sepsis, trauma and ischemia. Given the extensive research on nucleic acid sensing in common pathological conditions like cancer, autoimmune disorders, metabolic disorders and aging, we provide a comprehensive summary of nucleic acid sensing beyond critical illness to offer insights that may inform its role in critical conditions. Additionally, we discuss potential therapeutic strategies that specifically target nucleic acid sensing. By examining nucleic acid sources, sensor activation and function, as well as the impact of regulating these pathways across various acute diseases, we highlight the driving role of nucleic acid sensing in critical illness.

U-shaped association between plasma cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) levels and myocardial infarction

BACKGROUND

The cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes (cGAS-STING) signaling pathway is closely associated with myocardial infarction (MI). Cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) is a key component of this pathway; however, there is currently a lack of clinical evidence linking plasma cGAMP levels to MI.

METHODS

This study utilized clinical data from 270 patients diagnosed with coronary heart disease (CHD) at the Second Xiangya Hospital of Central South University. The outcomes included ST-segment elevation and non-ST-segment elevation MI. Univariate and multivariate logistic regression models were used to explore the relationships between plasma cGAMP levels and MI, while restricted cubic spline (RCS) using logistic regression to explore the dose-response relationship.

RESULTS

Among the 270 patients, the mean plasma cGAMP level was 1352.58 ± 106.02 ng/L and 89 (32.96%) patients were diagnosed with MI. The RCS curves indicated a U-shape association between the cGAMP levels and MI; the risk of MI was negatively correlated with the cGAMP until it hit bottoms at 1352 ng/L. When the cGAMP level exceeded 1352 ng/L, the risk of MI increased significantly (adjusted OR, 1.02; 95% CI: 1.01-1.03). When considering cGAMP as a categorical variable, patients in Tertile 1 and Tertile 3 had a 167% (adjusted OR: 2.67, 95% CI: 1.23-5.78) and 155% (adjusted OR: 2.55, 95% CI: 1.17-5.55) higher risk of MI compared to those in Tertile 2, respectively. These results were consistent across subgroup analyses, notably, a significant interaction by age category was observed in patients with cGAMP ≥ 1352 ng/L, where the positive association was pronounced in the elderly.

CONCLUSIONS

A U-shaped association exists between cGAMP and MI in the CHD population, with a cutoff point at the cGAMP of 1352 ng/L. Both excessively high and low cGAMP levels are associated with an increased risk of MI, particularly among the elderly with cGAMP ≥ 1352 ng/L. This is the first clinical evidence of the cGAS-cGAMP-STING pathway in metabolic cardiovascular diseases.

CLINICALTRIALS

GOV IDENTIFIER

NCT03363035 (Registration date: 2018-01-15).