IRF3 and type I interferons fuel a fatal response to myocardial infarction

Synergistically targeting synovium STING pathway for rheumatoid arthritis treatment

Rheumatoid arthritis (RA) is a common autoimmune disease leading to pain, disability, and even death. Although studies have revealed that aberrant activation of STING was implicated in various autoimmune diseases, the role of STING in RA remains unclear. In the current study, we demonstrated that STING activation was pivotal in RA pathogenesis. As the accumulation of dsDNA, a specific stimulus for STING, is a feature of RA, we developed a spherical polyethyleneimine-coated mesoporous polydopamine nanoparticles loaded with STING antagonist C-176 (PEI-PDA@C-176 NPs) for treating RA. The fabricated NPs with biocompatibility had high DNA adsorption ability and could effectively inhibit the STING pathway and inflammation in macrophages. Intra-articular administration of PEI-PDA@C-176 NPs could effectively reduce joint damage in mice models of dsDNA-induced arthritis and collagen-induced arthritis by inhibiting STING pathway. We concluded that materials with synergistic effects of STING inhibition might be an efficacious strategy to treat RA.

cGAMP the travelling messenger

2'3'-cGAMP is a key molecule in the cGAS-STING pathway. This cyclic dinucleotide is produced by the cytosolic DNA sensor cGAS in response to the presence of aberrant dsDNA in the cytoplasm which is associated with microbial invasion or cellular damage. 2'3'-cGAMP acts as a second messenger and activates STING, the central hub of DNA sensing, to induce type-I interferons and pro-inflammatory cytokines necessary for responses against infection, cancer or cellular stress. Classically, detection of pathogens or danger by pattern recognition receptors (PRR) was thought to signal and induce the production of interferon and pro-inflammatory cytokines in the cell where sensing occurred. These interferon and cytokines then signal in both an autocrine and paracrine manner to induce responses in neighboring cells. Deviating from this dogma, recent studies have identified multiple mechanisms by which 2'3'-cGAMP can travel to neighboring cells where it activates STING independent of DNA sensing by cGAS. This observation is of great importance, as the cGAS-STING pathway is involved in immune responses against microbial invaders and cancer while its dysregulation drives the pathology of a wide range of inflammatory diseases to which antagonists have been elusive. In this review, we describe the fast-paced discoveries of the mechanisms by which 2'3'-cGAMP can be transported. We further highlight the diseases where they are important and detail how this change in perspective can be applied to vaccine design, cancer immunotherapies and treatment of cGAS-STING associated disease.

Single cell transcriptomics of bone marrow derived macrophages reveals Ccl5 as a biomarker of direct IFNAR-independent responses to DNA sensing

Introduction

The type I interferon (IFN) response is an innate immune program that mediates anti-viral, anti-cancer, auto-immune, auto-inflammatory, and sterile injury responses. Bone marrow derived macrophages (BMDMs) are commonly used to model macrophage type I IFN responses, but the use of bulk measurement techniques obscures underlying cellular heterogeneity. This is particularly important for the IFN response to immune stimulatory double-stranded DNA (dsDNA) because it elicits overlapping direct and indirect responses, the latter of which depend on type I IFN cytokines signaling via the IFN alpha receptor (IFNAR) to upregulate expression of interferon stimulated genes (ISGs). Single cell transcriptomics has emerged as a powerful tool for revealing functional variability within cell populations.

Methods

Here, we use single cell RNA-Seq to examine BMDM heterogeneity at steady state and after immune-stimulatory DNA stimulation, with or without IFNAR-dependent amplification.

Results

We find that many macrophages express ISGs after DNA stimulation. We also find that a subset of macrophages express ISGs even if IFNAR is inhibited, suggesting that they are direct responders. Analysis of this subset reveals Ccl5 to be an IFNAR-independent marker gene of direct DNA sensing cells.

Discussion

Our studies provide a method for studying direct responders to IFN-inducing stimuli and demonstrate the importance of characterizing BMDM models of innate immune responses with single cell resolution.

Dynamics of monocyte-derived macrophage diversity in experimental myocardial infarction

AIMS

Macrophages have a critical and dual role in post-ischaemic cardiac repair, as they can foster both tissue healing and damage. Multiple subsets of tissue resident and monocyte-derived macrophages coexist in the infarcted heart, but their precise identity, temporal dynamics, and the mechanisms regulating their acquisition of discrete states are not fully understood. To address this, we used multi-modal single-cell immune profiling, combined with targeted cell depletion and macrophage fate mapping, to precisely map monocyte/macrophage transitions after experimental myocardial infarction.

METHODS AND RESULTS

We performed single-cell transcriptomic and cell-surface marker profiling of circulating and cardiac immune cells in mice challenged with acute myocardial infarction, and integrated single-cell transcriptomes obtained before and at 1, 3, 5, 7, and 11 days after infarction. Using complementary strategies of CCR2+ monocyte depletion and fate mapping of tissue resident macrophages, we determined the origin of cardiac macrophage populations. The macrophage landscape of the infarcted heart was dominated by monocyte-derived cells comprising two pro-inflammatory populations defined as Isg15hi and MHCII+Il1b+, alongside non-inflammatory Trem2hi cells. Trem2hi macrophages were observed in the ischaemic area, but not in the remote viable myocardium, and comprised two subpopulations sequentially populating the heart defined as Trem2hiSpp1hi monocyte-to-macrophage intermediates, and fully differentiated Trem2hiGdf15hi macrophages. Cardiac Trem2hi macrophages showed similarities to 'lipid-associated macrophages' found in mouse models of metabolic diseases and were observed in the human heart, indicating conserved features of this macrophage state across diseases and species. Ischaemic injury induced a shift of circulating Ly6Chi monocytes towards a Chil3hi state with granulocyte-like features, but the acquisition of the Trem2hi macrophage signature occurred in the ischaemic tissue. In vitro, macrophages acquired features of the Trem2hi signature following apoptotic-cell efferocytosis.

CONCLUSION

Our work provides a comprehensive map of monocyte/macrophage transitions in the ischaemic heart, constituting a valuable resource for further investigating how these cells may be harnessed and modulated to promote post-ischaemic heart repair.

Role of cGAS-Sting Signaling in Alzheimer's Disease

There is mounting evidence that the development of Alzheimer's disease (AD) interacts extensively with immunological processes in the brain and extends beyond the neuronal compartment. Accumulation of misfolded proteins can activate an innate immune response that releases inflammatory mediators and increases the severity and course of the disease. It is widely known that type-I interferon-driven neuroinflammation in the central nervous system (CNS) accelerates the development of numerous acute and chronic CNS diseases. It is becoming better understood how the cyclic GMP-AMP synthase (cGAS) and its adaptor protein Stimulator of Interferon Genes (STING) triggers type-I IFN-mediated neuroinflammation. We discuss the principal elements of the cGAS-STING signaling pathway and the mechanisms underlying the association between cGAS-STING activity and various AD pathologies. The current understanding of beneficial and harmful cGAS-STING activity in AD and the current treatment pathways being explored will be discussed in this review. The cGAS-STING regulation offers a novel therapeutic opportunity to modulate inflammation in the CNS because it is an upstream regulator of type-I IFNs.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

A DUSP6 inhibitor suppresses inflammatory cardiac remodeling and improves heart function after myocardial infarction

Acute myocardial infarction (MI) results in loss of cardiomyocytes and abnormal cardiac remodeling with severe inflammation and fibrosis. However, how cardiac repair can be achieved by timely resolution of inflammation and cardiac fibrosis remains incompletely understood. Our previous findings have shown that dual-specificity phosphatase 6 (DUSP6) is a regeneration repressor from zebrafish to rats. In this study, we found that intravenous administration of the DUSP6 inhibitor (E)-2-benzylidene-3-(cyclohexylamino)-2,3-dihydro-1H-inden-1-one (BCI) improved heart function and reduced cardiac fibrosis in MI rats. Mechanistic analysis revealed that BCI attenuated macrophage inflammation through NF-κB and p38 signaling, independent of DUSP6 inhibition, leading to the downregulation of various cytokines and chemokines. In addition, BCI suppressed differentiation-related signaling pathways and decreased bone-marrow cell differentiation into macrophages through inhibiting DUSP6. Furthermore, intramyocardial injection of poly (D, L-lactic-co-glycolic acid)-loaded BCI after MI had a notable effect on cardiac repair. In summary, BCI improves heart function and reduces abnormal cardiac remodeling by inhibiting macrophage formation and inflammation post-MI, thus providing a promising pro-drug candidate for the treatment of MI and related heart diseases. This article has an associated First Person interview with the first author of the paper.

Role of antimicrobial peptide cathelicidin in thrombosis and thromboinflammation

Thrombosis is a frequent cause of cardiovascular mortality and hospitalization. Current antithrombotic strategies, however, target both thrombosis and physiological hemostasis and thereby increase bleeding risk. In recent years the pathophysiological understanding of thrombus formation has significantly advanced and inflammation has become a crucial element. Neutrophils as most frequent immune cells in the blood and their released mediators play a key role herein. Neutrophil-derived cathelicidin next to its strong antimicrobial properties has also shown to modulates thrombosis and thus presents a potential therapeutic target. In this article we review direct and indirect (immune- and endothelial cell-mediated) effects of cathelicidin on platelets and the coagulation system. Further we discuss its implications for large vessel thrombosis and consecutive thromboinflammation as well as immunothrombosis in sepsis and COVID-19 and give an outlook for potential therapeutic prospects.

Scutellarin ameliorates ischemia/reperfusion injury‑induced cardiomyocyte apoptosis and cardiac dysfunction via inhibition of the cGAS‑STING pathway

Ischemic heart disease is a common cardiovascular disease. Scutellarin (SCU) exhibits protective effects in ischemic cardiomyocytes; however, to the best of our knowledge, the protective mechanism of SCU remains unclear. The present study was performed to investigate the protective effect of SCU on cardiomyocytes after ischemia/reperfusion (I/R) injury and the underlying mechanism. Mice were intraperitoneally injected with SCU (20 mg/kg) for 7 days before establishing the heart I/R injury model. Cardiac function was detected using small animal echocardiography, apoptotic cells were visualized using TUNEL staining, the myocardial infarct area was assessed by 2,3,5-triphenyltetrazolium chloride staining, and the protein levels of cyclic GMP-AMP synthase (cGAS), stimulator of interferon genes (STING), Bcl-2, Bax and cleaved Caspase-3 were detected by western blotting. In in vitro experiments, H9c2 cells were pretreated with SCU, RU.521 (cGAS inhibitor) and H-151 (STING inhibitor), before cell hypoxia/reoxygenation (H/R) injury. The viability of H9c2 cells was detected using a Cell Counting Kit-8 assay, the rate of apoptosis was determined by flow cytometry, and the protein expression levels of cGAS, STING, Bcl-2, Bax and cleaved Caspase-3 were detected by western blotting. It was revealed that SCU ameliorated cardiac dysfunction and apoptosis, and inhibited the activation of the cGAS-STING and Bcl-2/Bax/Caspase-3 signaling pathways in I/R-injured mice. It was also observed that SCU significantly increased cell viability and decreased apoptosis in H/R-induced H9c2 cells. Furthermore, H/R increased the expression levels of cGAS, STING and cleaved Caspase-3, and decreased the ratio of Bcl-2/Bax, which could be reversed by treatment with SCU, RU.521 and H-151. The present study demonstrated that the cGAS-STING signaling pathway may be involved in the regulation of the activation of the Bcl-2/Bax/Caspase-3 signaling pathway to mediate I/R-induced cardiomyocyte apoptosis and cardiac dysfunction, which could be ameliorated by SCU treatment.

The STING inhibitor C-176 attenuates osteoclast-related osteolytic diseases by inhibiting osteoclast differentiation

Inflammatory osteolysis occurs primarily in the context of osteoarthritis, aseptic inflammation, prosthesis loosening, and other conditions. An excessive immune inflammatory response causes excessive activation of osteoclasts, leading to bone loss and bone destruction. The signaling protein stimulator of interferon gene (STING) can regulate the immune response of osteoclasts. C-176 is a furan derivative that can inhibit activation of the STING pathway and exert anti-inflammatory effects. The effect of C-176 on osteoclast differentiation is not yet clear. In this study, we found that C-176 could inhibit STING activation in osteoclast precursor cells and inhibit osteoclast activation induced by nuclear factor κB ligand receptor activator in a dose-dependent manner. After treatment with C-176, the expression of the osteoclast differentiation marker genes nuclear factor of activated T-cells c1(NFATc1), cathepsin K, calcitonin receptor, and V-ATPase a3 decreased. In addition, C-176 reduced actin loop formation and bone resorption capacity. The WB results showed that C-176 downregulated the expression of the osteoclast marker protein NFATc1 and inhibited activation of the STING-mediated NF-κB pathway. We also found that C-176 could inhibit the phosphorylation of mitogen-activated protein kinase signaling pathway factors induced by RANKL. Moreover, we verified that C-176 could reduce LPS-induced bone absorption in mice, reduce joint destruction in knee arthritis induced by meniscal instability, and protect against cartilage matrix loss in ankle arthritis induced by collagen immunity. In summary, our findings demonstrated that C-176 could inhibit the formation and activation of osteoclasts and could be used as a potential therapeutic agent for inflammatory osteolytic diseases.

Potential Therapeutic Value of the STING Inhibitors

The stimulator of interferon genes (STING) is a critical protein in the activation of the immune system in response to DNA. It can participate the inflammatory response process by modulating the inflammation-preferred translation program through the STING-PKR-like endoplasmic reticulum kinase (PERK)-eIF2α pathway or by inducing the secretion of type I interferons (IFNs) and a variety of proinflammatory factors through the recruitment of TANK-binding kinase 1 (TBK1) and interferon regulatory factor 3 (IRF3) or the regulation of the nuclear factor kappa-B (NF-κB) pathway. Based on the structure, location, function, genotype, and regulatory mechanism of STING, this review summarizes the potential value of STING inhibitors in the prevention and treatment of infectious diseases, psoriasis, systemic lupus erythematosus, non-alcoholic fatty liver disease, and other inflammatory and autoimmune diseases.

STING contributes to trauma-induced heterotopic ossification through NLRP3-dependent macrophage pyroptosis

Trauma-induced heterotopic ossification (HO) is featured by aberrant bone formation at extra-skeletal site. STING is a master adaptor protein linking cellular damage to immune responses, while its role in HO remains elusive. A murine burn/tenotomy model was used to mimic trauma-induced HO in vivo. We demonstrated elevated STING expression in macrophages in inflammatory stage after burn/tenotomy, and STING inhibition significantly alleviated HO formation. Activated NLRP3-dependent macrophage pyroptosis was also found in inflammatory stage after burn/tenotomy. Either STING or NLRP3 suppression reduced mature HO by weakening macrophage pyroptotic inflammation, while protective effects of STING were abolished by NLRP3 overexpression. Further, in vitro, we also found a prominent STING level in pyroptotic BMDMs. STING suppression relieved macrophage pyroptotic inflammation, while abolished by NLRP3 overexpression. Our results reveal that STING poses regulatory effects on trauma-induced HO formation, via modulating NLRP3-dependent macrophage pyroptosis. Targeting STING-NLRP3 axis represents an attractive approach for trauma-induced HO prevention.

Single-cell transcriptomes in the heart: when every epigenome counts

The response of an organ to stimuli emerges from the actions of individual cells. Recent cardiac single-cell RNA-sequencing studies of development, injury, and reprogramming have uncovered heterogeneous populations even among previously well-defined cell types, raising questions about what level of experimental resolution corresponds to disease-relevant, tissue-level phenotypes. In this review, we explore the biological meaning behind this cellular heterogeneity by undertaking an exhaustive analysis of single-cell transcriptomics in the heart (including a comprehensive, annotated compendium of studies published to date) and evaluating new models for the cardiac function that have emerged from these studies (including discussion and schematics that depict new hypotheses in the field). We evaluate the evidence to support the biological actions of newly identified cell populations and debate questions related to the role of cell-to-cell variability in development and disease. Finally, we present emerging epigenomic approaches that, when combined with single-cell RNA-sequencing, can resolve basic mechanisms of gene regulation and variability in cell phenotype.

Innate immune signaling drives late cardiac toxicity following DNA-damaging cancer therapies

Late cardiac toxicity is a potentially lethal complication of cancer therapy, yet the pathogenic mechanism remains largely unknown, and few treatment options exist. Here we report DNA-damaging agents such as radiation and anthracycline chemotherapies inducing delayed cardiac inflammation following therapy due to activation of cGAS- and STING-dependent type I interferon signaling. Genetic ablation of cGAS-STING signaling in mice inhibits DNA damage-induced cardiac inflammation, rescues late cardiac functional decline, and prevents death from cardiac events. Treatment with a STING antagonist suppresses cardiac interferon signaling following DNA-damaging therapies and effectively mitigates cardiac toxicity. These results identify a therapeutically targetable, pathogenic mechanism for one of the most vexing treatment-related toxicities in cancer survivors.

Mitochondrial control of inflammation

Numerous mitochondrial constituents and metabolic products can function as damage-associated molecular patterns (DAMPs) and promote inflammation when released into the cytosol or extracellular milieu. Several safeguards are normally in place to prevent mitochondria from eliciting detrimental inflammatory reactions, including the autophagic disposal of permeabilized mitochondria. However, when the homeostatic capacity of such systems is exceeded or when such systems are defective, inflammatory reactions elicited by mitochondria can become pathogenic and contribute to the aetiology of human disorders linked to autoreactivity. In addition, inefficient inflammatory pathways induced by mitochondrial DAMPs can be pathogenic as they enable the establishment or progression of infectious and neoplastic disorders. Here we discuss the molecular mechanisms through which mitochondria control inflammatory responses, the cellular pathways that are in place to control mitochondria-driven inflammation and the pathological consequences of dysregulated inflammatory reactions elicited by mitochondrial DAMPs.

Transcriptomic profiling of cardiac tissues from SARS-CoV-2 patients identifies DNA damage

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is known to present with pulmonary and extra-pulmonary organ complications. In comparison with the 2009 pandemic (pH1N1), SARS-CoV-2 infection is likely to lead to more severe disease, with multi-organ effects, including cardiovascular disease. SARS-CoV-2 has been associated with acute and long-term cardiovascular disease, but the molecular changes that govern this remain unknown. In this study, we investigated the host transcriptome landscape of cardiac tissues collected at rapid autopsy from seven SARS-CoV-2, two pH1N1, and six control patients using targeted spatial transcriptomics approaches. Although SARS-CoV-2 was not detected in cardiac tissue, host transcriptomics showed upregulation of genes associated with DNA damage and repair, heat shock, and M1-like macrophage infiltration in the cardiac tissues of COVID-19 patients. The DNA damage present in the SARS-CoV-2 patient samples, were further confirmed by γ-H2Ax immunohistochemistry. In comparison, pH1N1 showed upregulation of interferon-stimulated genes, in particular interferon and complement pathways, when compared with COVID-19 patients. These data demonstrate the emergence of distinct transcriptomic profiles in cardiac tissues of SARS-CoV-2 and pH1N1 influenza infection supporting the need for a greater understanding of the effects on extra-pulmonary organs, including the cardiovascular system of COVID-19 patients, to delineate the immunopathobiology of SARS-CoV-2 infection, and long term impact on health.

Targeting immunoregulation for cardiac regeneration

Inducing endogenous cardiomyocyte proliferation and heart regeneration is a promising strategy to treat ischemic heart failure. The immune response has recently been considered critical in cardiac regeneration. Thus, targeting the immune response is a potent strategy to improve cardiac regeneration and repair after myocardial infarction. Here we reviewed the characteristics of the relationship between the postinjury immune response and heart regenerative capacity and summarized the latest studies focusing on inflammation and heart regeneration to identify potent targets of the immune response and strategies in the immune response to promote cardiac regeneration.

The Role of cGAS-STING in Age-Related Diseases from Mechanisms to Therapies

With aging, the incidence of age-related diseases increases. Hence, age-related diseases are inevitable. However, the mechanisms by which aging leads to the onset and progression of age-related diseases remain unclear. It has been reported that inflammation is closely associated with age-related diseases and that the cGAS-STING signaling pathway, which can sense the aberrant presence of cytosolic DNA during aging and induce an inflammatory response, is an important mediator of inflammation in age-related diseases. With a better understanding of the structure and molecular biology of the cGAS-STING signaling axis, numerous selective inhibitors and agonists targeting the cGAS-STING pathway in human age-related diseases have been developed to modulate inflammatory responses. Here, we provide a narrative review of the activity of the cGAS- STING pathway in age-related diseases and discuss its general mechanisms in the onset and progression of age-related diseases. In addition, we outline treatments targeting the cGAS-STING pathway, which may constitute a potential therapeutic alternative for age-related diseases.

Mitochondria Dysfunction at the Heart of Viral Myocarditis: Mechanistic Insights and Therapeutic Implications

The myocardium/heart is the most mitochondria-rich tissue in the human body with mitochondria comprising approximately 30% of total cardiomyocyte volume. As the resident "powerhouse" of cells, mitochondria help to fuel the high energy demands of a continuously beating myocardium. It is no surprise that mitochondrial dysfunction underscores the pathogenesis of many cardiovascular ailments, including those of viral origin such as virus-induced myocarditis. Enteroviruses have been especially linked to injuries of the myocardium and its sequelae dilated cardiomyopathy for which no effective therapies currently exist. Intriguingly, recent mechanistic insights have demonstrated viral infections to directly damage mitochondria, impair the mitochondrial quality control processes of the cell, such as disrupting mitochondrial antiviral innate immune signaling, and promoting mitochondrial-dependent pathological inflammation of the infected myocardium. In this review, we briefly highlight recent insights on the virus-mitochondria crosstalk and discuss the therapeutic implications of targeting mitochondria to preserve heart function and ultimately combat viral myocarditis.

TREM2hi resident macrophages protect the septic heart by maintaining cardiomyocyte homeostasis

Sepsis-induced cardiomyopathy (SICM) is common in septic patients with a high mortality and is characterized by an abnormal immune response. Owing to cellular heterogeneity, understanding the roles of immune cell subsets in SICM has been challenging. Here we identify a unique subpopulation of cardiac-resident macrophages termed CD163⁺RETNLA⁺ (Mac1), which undergoes self-renewal during sepsis and can be targeted to prevent SICM. By combining single-cell RNA sequencing with fate mapping in a mouse model of sepsis, we demonstrate that the Mac1 subpopulation has distinct transcriptomic signatures enriched in endocytosis and displays high expression of TREM2 (TREM2^hi). TREM2^hi Mac1 cells actively scavenge cardiomyocyte-ejected dysfunctional mitochondria. Trem2 deficiency in macrophages impairs the self-renewal capability of the Mac1 subpopulation and consequently results in defective elimination of damaged mitochondria, excessive inflammatory response in cardiac tissue, exacerbated cardiac dysfunction and decreased survival. Notably, intrapericardial administration of TREM2^hi Mac1 cells prevents SICM. Our findings suggest that the modulation of TREM2^hi Mac1 cells could serve as a therapeutic strategy for SICM.

Identification of biomarkers, pathways, and potential therapeutic targets for heart failure using next-generation sequencing data and bioinformatics analysis

BACKGROUND

Heart failure (HF) is the most common cardiovascular diseases and the leading cause of cardiovascular diseases related deaths. Increasing molecular targets have been discovered for HF prognosis and therapy. However, there is still an urgent need to identify novel biomarkers. Therefore, we evaluated biomarkers that might aid the diagnosis and treatment of HF.

METHODS

We searched next-generation sequencing (NGS) dataset (GSE161472) and identified differentially expressed genes (DEGs) by comparing 47 HF samples and 37 normal control samples using limma in R package. Gene ontology (GO) and pathway enrichment analyses of the DEGs were performed using the g: Profiler database. The protein-protein interaction (PPI) network was plotted with Human Integrated Protein-Protein Interaction rEference (HiPPIE) and visualized using Cytoscape. Module analysis of the PPI network was done using PEWCC1. Then, miRNA-hub gene regulatory network and TF-hub gene regulatory network were constructed by Cytoscape software. Finally, we performed receiver operating characteristic (ROC) curve analysis to predict the diagnostic effectiveness of the hub genes.

RESULTS

A total of 930 DEGs, 464 upregulated genes and 466 downregulated genes, were identified in HF. GO and REACTOME pathway enrichment results showed that DEGs mainly enriched in localization, small molecule metabolic process, SARS-CoV infections, and the citric acid tricarboxylic acid (TCA) cycle and respiratory electron transport. After combining the results of the PPI network miRNA-hub gene regulatory network and TF-hub gene regulatory network, 10 hub genes were selected, including heat shock protein 90 alpha family class A member 1 (HSP90AA1), arrestin beta 2 (ARRB2), myosin heavy chain 9 (MYH9), heat shock protein 90 alpha family class B member 1 (HSP90AB1), filamin A (FLNA), epidermal growth factor receptor (EGFR), phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1), cullin 4A (CUL4A), YEATS domain containing 4 (YEATS4), and lysine acetyltransferase 2B (KAT2B).

CONCLUSIONS

This discovery-driven study might be useful to provide a novel insight into the diagnosis and treatment of HF. However, more experiments are needed in the future to investigate the functional roles of these genes in HF.

The role of macrophage subsets in and around the heart in modulating cardiac homeostasis and pathophysiology

Cardiac and pericardial macrophages contribute to both homeostatic and pathophysiological processes. Recent advances have identified a vast repertoire of these macrophage populations in and around the heart - broadly categorized into a CCR2⁺/CCR2^- dichotomy. While these unique populations can be further distinguished by origin, localization, and other cell surface markers, further exploration into the role of cardiac and pericardial macrophage subpopulations in disease contributes an additional layer of complexity. As such, novel transgenic models and exogenous targeting techniques have been employed to evaluate these macrophages. In this review, we highlight known cardiac and pericardial macrophage populations, their functions, and the experimental tools used to bolster our knowledge of these cells in the cardiac context.

Inhibition of Stimulator of Interferon Genes Protects Against Myocardial Ischemia-Reperfusion Injury in Diabetic Mice

Background: Although the past decade has witnessed substantial scientific progress with the advent of cardioprotective pharmacological agents, most have failed to protect against myocardial ischemia/reperfusion (I/R) injury in diabetic hearts. This study was aimed at investigating the role of stimulator of interferon genes (STING) in I/R injury in diabetic mice and further exploring the underlying mechanisms.

Methods: Type 2 diabetic mice were subjected to I/R or sham operation to investigate the role of STING. STING knockout mice were subjected to 30 minutes of ischemia followed by reperfusion for 24 hours. Finally, myocardial injury, cardiac function, and inflammation levels were assessed.

Results: STING pathway activation was observed in diabetic I/R hearts, as evidenced by increased p-TBK and p-IRF3 expression. STING knockout significantly decreased the ischemic area and improved cardiac function after I/R in diabetic mice. STING knockout also elicited cardio-protective effects by decreasing serum cardiac troponin T and lactate dehydrogenase levels, thus diminishing the inflammatory response in the heart after I/R in diabetic mice. In vitro, STING inhibition decreased the expression of hypoxia-re-oxygenation-induced inflammatory cytokines.

Conclusions: Targeting STING inhibits inflammation and prevents I/R injury in diabetic mice. Thus, STING may be a potential novel therapeutic target against myocardial I/R injury in diabetes.

Red light-green light: T-cell trafficking in cardiac and vascular inflammation

Extravasation of T cells from the bloodstream into inflamed tissues requires interactions between T cells and vascular endothelial cells, a necessary step that allows T cells to exert their effector function during the immune response to pathogens and to sterile insults. This cellular cross talk involves adhesion molecules on both the vascular endothelium and the T cells themselves that function as receptor-ligand pairs to slow down circulating T cells. These will eventually extravasate into sites of inflammation when they receive the correct chemokine signals. Accumulation of T cells within the vascular wall can lead to vessel thickening and vascular disease, whereas T-cell extravasation into the myocardium often leads to cardiac chronic inflammation and adverse cardiac remodeling, hallmarks of heart failure. On the flip side, T-cell trafficking is required for pathogen clearance and to promote tissue repair after injury resulting from cardiac ischemia. Thus, a better understanding of the central players mediating these interactions may help develop novel therapeutics to modulate vascular and cardiac inflammation. Here, we review the most recent literature on pathways that regulate T-cell transendothelial migration, the last step leading to T-cell infiltration into tissues and organs in the context of vascular and cardiac inflammation. We discuss new potential avenues to therapeutically modulate these pathways to enhance or prevent immune cell infiltration in cardiovascular disease.

Multifaceted functions of STING in human health and disease: from molecular mechanism to targeted strategy

Since the discovery of Stimulator of Interferon Genes (STING) as an important pivot for cytosolic DNA sensation and interferon (IFN) induction, intensive efforts have been endeavored to clarify the molecular mechanism of its activation, its physiological function as a ubiquitously expressed protein, and to explore its potential as a therapeutic target in a wide range of immune-related diseases. With its orthodox ligand 2'3'-cyclic GMP-AMP (2'3'-cGAMP) and the upstream sensor 2'3'-cGAMP synthase (cGAS) to be found, STING acquires its central functionality in the best-studied signaling cascade, namely the cGAS-STING-IFN pathway. However, recently updated research through structural research, genetic screening, and biochemical assay greatly extends the current knowledge of STING biology. A second ligand pocket was recently discovered in the transmembrane domain for a synthetic agonist. On its downstream outputs, accumulating studies sketch primordial and multifaceted roles of STING beyond its cytokine-inducing function, such as autophagy, cell death, metabolic modulation, endoplasmic reticulum (ER) stress, and RNA virus restriction. Furthermore, with the expansion of the STING interactome, the details of STING trafficking also get clearer. After retrospecting the brief history of viral interference and the milestone events since the discovery of STING, we present a vivid panorama of STING biology taking into account the details of the biochemical assay and structural information, especially its versatile outputs and functions beyond IFN induction. We also summarize the roles of STING in the pathogenesis of various diseases and highlight the development of small-molecular compounds targeting STING for disease treatment in combination with the latest research. Finally, we discuss the open questions imperative to answer.

cGAS in nucleus: The link between immune response and DNA damage repair

As the first barrier of host defense, innate immunity sets up the parclose to keep out external microbial or virus attacks. Depending on the type of pathogens, several cytoplasm pattern recognition receptors exist to sense the attacks from either foreign or host origins, triggering the immune response to battle with the infections. Among them, cGAS-STING is the major pathway that mainly responds to microbial DNA, DNA virus infections, or self-DNA, which mainly comes from genome instability by-product or released DNA from the mitochondria. cGAS was initially found functional in the cytoplasm, although intriguing evidence indicates that cGAS exists in the nucleus where it is involved in the DNA damage repair process. Because the close connection between DNA damage response and immune response and cGAS recognizes DNA in length-dependent but DNA sequence-independent manners, it is urgent to clear the function balance of cGAS in the nucleus versus cytoplasm and how it is shielded from recognizing the host origin DNA. Here, we outline the current conception of immune response and the regulation mechanism of cGAS in the nucleus. Furthermore, we will shed light on the potential mechanisms that are restricted to be taken away from self-DNA recognition, especially how post-translational modification regulates cGAS functions.

Global Characteristics and Dynamics of Single Immune Cells After Myocardial Infarction

Background Myocardial infarction (MI) is characterized by the emergence of dead or dying cardiomyocytes and excessive immune cell infiltration after coronary vessel occlusion. However, the complex transcriptional profile, pathways, cellular interactome, and transcriptional regulators of immune subpopulations after MI remain elusive. Methods and Results Here, male C57BL/6 mice were subjected to MI surgery and monitored for 1 day and 7 days, or sham surgery for 7 days, then cardiac CD45-positive immune cells were collected for single-cell RNA sequencing to determine immune heterogeneity. A total of 30 135 CD45⁺ immune cells were partitioned into macrophages, monocytes, neutrophils, dendritic cells, and T or B cells for further analysis. We showed that macrophages enriched for Olr1 and differentially expressed Gpnmb represented 2 crucial ischemia-associated macrophages with distinct proinflammatory and prophagocytic capabilities. In contrast to the proinflammatory subset of macrophages enriched for Olr1, Gpnmb-positive macrophages exhibited higher phagocytosis and fatty acid oxidation preference, which could be abolished by etomoxir treatment. In addition to macrophages, MI triggered prompt recruitment of neutrophils into murine hearts, which constituted the sequential cell-fate from naïve S100a4-positive, to activated Sell-high, to aging Icam1-high neutrophils. In silico tools predicted that the excessively expanded neutrophils at 1 day were attributed to chemokine C-C motif ligand/chemokine C-X-C motif ligand pathways, whereas CD80/inducible T-cell costimulator (ICOS) signaling was responsible for the immunosuppressive response at day 7 after MI. Finally, the Fos/AP-1 (activator protein 1) regulon was identified as the critical regulator of proinflammatory responses, which was significantly activated in patients with dilated cardiomyopathy and ischemic cardiomyopathy. We showed the enriched Fos/AP-1 target gene loci in genome-wide association study signals for coronary artery diseases and MI. Targeting Fos/AP-1 with the selective inhibitor T5224 blunted leukocyte infiltration and alleviated cardiac dysfunction in the preclinical murine MI model. Conclusions Taken together, this single-cell RNA sequencing data lay the groundwork for the understanding of immune cell heterogeneity and dynamics in murine ischemic hearts. Moreover, Fos/AP-1 inhibition mitigates inflammatory responses and cardiac dysfunction, which might provide potential therapeutic benefits for heart failure intervention after MI.

Quo Vadis? Immunodynamics of Myeloid Cells after Myocardial Infarction

Myocardial infarction (MI), a major contributor to worldwide morbidity and mortality, is caused by a lack of blood flow to the heart. Affected heart tissue becomes ischemic due to deficiency of blood perfusion and oxygen delivery. In case sufficient blood flow cannot be timely restored, cardiac injury with necrosis occurs. The ischemic/necrotic area induces a systemic inflammatory response and hundreds of thousands of leukocytes are recruited from the blood to the injured heart. The blood pool of leukocytes is rapidly depleted and urgent re-supply of these cells is needed. Myeloid cells are generated in the bone marrow (BM) and spleen, released into the blood, travel to sites of need, extravasate and accumulate inside tissues to accomplish various functions. In this review we focus on the "leukocyte supply chain" and will separately evaluate different myeloid cell compartments (BM, spleen, blood, heart) in steady state and after MI. Moreover, we highlight the local and systemic kinetics of extracellular factors, chemokines and danger signals involved in the regulation of production/generation, release, transportation, uptake, and activation of myeloid cells during the inflammatory phase of MI.

Alternative pathways driven by STING: From innate immunity to lipid metabolism

The Stimulator of Interferon Genes (STING) is a major adaptor protein that is central to the initiation of type I interferon responses and proinflammatory signalling. STING-dependent signalling is triggered by the presence of cytosolic nucleic acids that are generated following pathogen infection or cellular stress. Beyond this central role in controlling immune responses through the production of cytokines and chemokines, recent reports have uncovered inflammation-independent STING functions. Amongst these, a rapidly growing body of evidence demonstrates a key role of STING in controlling metabolic pathways at several levels. Since immunity and metabolic homeostasis are tightly interconnected, these findings deepen our understanding of the involvement of STING in human pathologies. Here, we discuss these findings and reflect on their impact on our current understanding of how nucleic acid immunity controls homeostasis and promotes pathological outcomes.

Genetic Ablation of the DNA Damage Response Pathway Attenuates Lamin-Associated Dilated Cardiomyopathy in Mice

Hereditary dilated cardiomyopathy (DCM) is a primary disease of cardiac myocytes caused by mutations in genes encoding proteins with a diverse array of functions. Mutations in the LMNA gene, encoding the nuclear envelope protein lamin A/C, are the second most common causes of DCM. The phenotype is characterized by progressive cardiac dysfunction, leading to refractory heart failure, myocardial fibrosis, cardiac arrhythmias, and sudden cardiac death. The molecular pathogenesis of DCM caused by the LMNA mutations is not well known. The LMNA protein is involved in nuclear membrane stability. It is also a guardian of the genome involved in the processing of the topoisomerases at the transcriptionally active domain and the repair of double-stranded DNA breaks (DSBs). Deletion of the mouse Lmna gene in cardiac myocytes leads to premature death, DCM, myocardial fibrosis, and apoptosis. The phenotype is associated with increased expression of the cytosolic DNA sensor cyclic GMP-AMP synthase (CGAS) and activation of the DNA damage response (DDR) pathway. Genetic blockade of the DDR pathway, upon knockout of the Mb21d1 gene encoding CGAS, prolonged survival, improved cardiac function, partially restored levels of molecular markers of heart failure, and attenuated myocardial apoptosis and fibrosis in the LMNA-deficient mice. The findings indicate that targeting the CGAS/DDR pathway might be beneficial in the treatment of DCM caused by mutations in the LMNA gene.

Myocardial Protection and Current Cancer Therapy: Two Opposite Targets with Inevitable Cost

Myocardial protection against ischemia/reperfusion injury (IRI) is mediated by various ligands, activating different cellular signaling cascades. These include classical cytosolic mediators such as cyclic-GMP (c-GMP), various kinases such as Phosphatydilinositol-3- (PI3K), Protein Kinase B (Akt), Mitogen-Activated-Protein- (MAPK) and AMP-activated (AMPK) kinases, transcription factors such as signal transducer and activator of transcription 3 (STAT3) and bioactive molecules such as vascular endothelial growth factor (VEGF). Most of the aforementioned signaling molecules constitute targets of anticancer therapy; as they are also involved in carcinogenesis, most of the current anti-neoplastic drugs lead to concomitant weakening or even complete abrogation of myocardial cell tolerance to ischemic or oxidative stress. Furthermore, many anti-neoplastic drugs may directly induce cardiotoxicity via their pharmacological effects, or indirectly via their cardiovascular side effects. The combination of direct drug cardiotoxicity, indirect cardiovascular side effects and neutralization of the cardioprotective defense mechanisms of the heart by prolonged cancer treatment may induce long-term ventricular dysfunction, or even clinically manifested heart failure. We present a narrative review of three therapeutic interventions, namely VEGF, proteasome and Immune Checkpoint inhibitors, having opposing effects on the same intracellular signal cascades thereby affecting the heart. Moreover, we herein comment on the current guidelines for managing cardiotoxicity in the clinical setting and on the role of cardiovascular confounders in cardiotoxicity.

Single-cell and spatial transcriptomics of the infarcted heart define the dynamic onset of the border zone in response to mechanical destabilization

The border zone (BZ) of the infarcted heart is a geographically complex and biologically enigmatic interface separating poorly perfused infarct zones (IZs) from remote zones (RZs). The cellular and molecular mechanisms of myocardial BZs are not well understood because microdissection inevitably combines them with uncontrolled amounts of RZs and IZs. Here, we use single-cell/nucleus RNA sequencing, spatial transcriptomics and multiplexed RNA fluorescence in situ hybridization to redefine the BZ based on cardiomyocyte transcriptomes. BZ1 (Nppa + Xirp2 -) forms a hundreds-of-micrometer-thick layer of morphologically intact cells adjacent to RZs that are detectable within an hour of injury. Meanwhile, BZ2 (Nppa + Xirp2 +) forms a near-single-cell-thick layer of morphologically distorted cardiomyocytes at the IZ edge that colocalize with matricellular protein-expressing myofibroblasts and express predominantly mechanotransduction genes. Surprisingly, mechanical injury alone is sufficient to induce BZ genes. We propose a 'loss of neighbor' hypothesis to explain how ischemic cell death mechanically destabilizes the BZ to induce its transcriptional response.

Hematopoietic Stem Cells in Wound Healing Response

Significance: Emerging evidence has shown a link between the status of hematopoietic stem cells (HSCs) and wound healing responses. Thus, better understanding HSCs will contribute to further advances in wound healing research. Recent Advances: Myeloid cells such as neutrophils and monocyte-derived macrophages are critical players in the process of wound healing. HSCs actively respond to wound injury and other tissue insults, including infection and produce the effector myeloid cells, and a failing of the HSC response can result in impaired wound healing. Technological advances such as transcriptome at single-cell resolution, epigenetics, three-dimensional imaging, transgenic animals, and animal models, have provided novel concepts of myeloid generation (myelopoiesis) from HSCs, and have revealed cell-intrinsic and -extrinsic mechanisms that can impact HSC functions in the context of health conditions. Critical Issues: The newer concepts include-the programmed cellular fate at a differentiation stage that is used to be considered as the multilineage, the signaling pathways that can activate HSCs directly and indirectly, the mechanisms that can deteriorate HSCs, the roles and remodeling of the surrounding environment for HSCs and their progenitors (the niche). Future Directions: The researches on HSCs, which produce blood cells, should contribute to the development of blood biomarkers predicting a risk of chronic wounds, which may transform clinical practice of wound care with precision medicine for patients at high risk of poor healing.

Macrophage-specific inhibition of the histone demethylase JMJD3 decreases STING and pathologic inflammation in diabetic wound repair

Macrophage plasticity is critical for normal tissue repair following injury. In pathologic states such as diabetes, macrophage plasticity is impaired, and macrophages remain in a persistent proinflammatory state; however, the reasons for this are unknown. Here, using single-cell RNA sequencing of human diabetic wounds, we identified increased JMJD3 in diabetic wound macrophages, resulting in increased inflammatory gene expression. Mechanistically, we report that in wound healing, JMJD3 directs early macrophage-mediated inflammation via JAK1,3/STAT3 signaling. However, in the diabetic state, we found that IL-6, a cytokine increased in diabetic wound tissue at later time points post-injury, regulates JMJD3 expression in diabetic wound macrophages via the JAK1,3/STAT3 pathway and that this late increase in JMJD3 induces NFκB-mediated inflammatory gene transcription in wound macrophages via an H3K27me3 mechanism. Interestingly, RNA sequencing of wound macrophages isolated from mice with JMJD3-deficient myeloid cells (Jmjd3f/fLyz2Cre+) identified that the STING gene (Tmem173) is regulated by JMJD3 in wound macrophages. STING limits inflammatory cytokine production by wound macrophages during healing. However, in diabetic mice, its role changes to limit wound repair and enhance inflammation. This finding is important since STING is associated with chronic inflammation, and we found STING to be elevated in human and murine diabetic wound macrophages at late time points. Finally, we demonstrate that macrophage-specific, nanoparticle inhibition of JMJD3 in diabetic wounds significantly improves diabetic wound repair by decreasing inflammatory cytokines and STING. Taken together, this work highlights the central role of JMJD3 in tissue repair and identifies cell-specific targeting as a viable therapeutic strategy for nonhealing diabetic wounds.

Heart failure and cancer: From active exposure to passive adaption

The human body seems like a "balance integrator." On the one hand, the body constantly actively receives various outside stimuli and signals to induce changes. On the other hand, several internal regulations would be initiated to adapt to these changes. In most cases, the body could keep the balance in vitro and in vivo to reach a healthy body. However, in some cases, the body can only get to a pathological balance. Actively exposed to unhealthy lifestyles and passively adapting to individual primary diseases lead to a similarly inner environment for both heart failure and cancer. To cope with these stimuli, the body must activate the system regulation mechanism and face the mutual interference. This review summarized the association between heart failure and cancer from active exposure to passive adaption. Moreover, we hope to inspire researchers to contemplate these two diseases from the angle of overall body consideration.

LPS-Induced Activation of the cGAS-STING Pathway is Regulated by Mitochondrial Dysfunction and Mitochondrial DNA Leakage in Endometritis

Introduction

Chronic endometritis is a common disease in women of childbearing age and can cause pelvic inflammatory disease. The cGAS-STING pathway plays an important role in many inflammatory diseases.

Purpose

The aim of this study was to investigate the relationship between the cGAS-STING pathway and endometritis.

Methods

We collected endometrium samples from patients with endometritis to detect changes in the cGAS-STING pathway. In vitro, human endometrial stromal cells (HESC) were stimulated with lipopolysaccharide (LPS), and a mouse STING gene-knockout model was established by CRISPR/cas9 for STING to further explore the mechanism underlying its effects in endometritis. We used Western blotting (WB) and immunohistochemical staining to detect the variations in protein levels and real-time PCR to study the variations in gene expression.

Results

We observed the activation of the cGAS-STING pathway and an increase in the expression of cytokine-encoding genes, including IL-8, IL-6, IL-1β, and IFN-β1, in endometrial tissues of patients with endometritis. Stimulation of HESCs using LPS demonstrated increase in the expression of proteins involved the cGAS-STING pathway and the gene expression of inflammatory cytokines. STING-knockdown experiments demonstrated a decrease in the gene expression levels of inflammatory cytokines. Moreover, we also identified the translocation of IRF3 and STING after LPS stimulation. Regarding mitochondrial function, LPS led to an increase in reactive oxygen species levels and a reduction in mitochondrial membrane potential. However, we observed that the mitochondrial DNA (mtDNA) leaked into the cytoplasm, upregulating the levels of proteins involved in the cGAS-STING pathway upon LPS stimulation. Furthermore, our results showed that LPS induced hyperemia, inflammatory factor production, and expression of Pho-TBK1 in wild-type mice compared with the levels in control mice, and STING gene-knockdown alleviated these effects.

Conclusion

LPS induces mitochondrial dysfunction in endometrial stromal cells, resulting in mtDNA leakage and promoting endometritis by stimulating the cGAS-STING pathway.

Macrophages in myocardial infarction

The heart contains a population of resident macrophages that markedly expands following injury through recruitment of monocytes and through proliferation of macrophages. In myocardial infarction, macrophages have been implicated in both injurious and reparative responses. In coronary atherosclerotic lesions, macrophages have been implicated in disease progression and in the pathogenesis of plaque rupture. Following myocardial infarction, resident macrophages contribute to initiation and regulation of the inflammatory response. Phagocytosis and efferocytosis are major functions of macrophages during the inflammatory phase of infarct healing, and mediate phenotypic changes, leading to acquisition of an anti-inflammatory macrophage phenotype. Infarct macrophages respond to changes in the cytokine content and extracellular matrix composition of their environment and secrete fibrogenic and angiogenic mediators, playing a central role in repair of the infarcted heart. Macrophages may also play a role in scar maturation and may contribute to chronic adverse remodeling of noninfarcted segments. Single cell studies have revealed a remarkable heterogeneity of macrophage populations in infarcted hearts; however, the relations between transcriptomic profiles and functional properties remain poorly defined. This review manuscript discusses the fate, mechanisms of expansion and activation, and role of macrophages in the infarcted heart. Considering their critical role in injury, repair, and remodeling, macrophages are important, but challenging, targets for therapeutic interventions in myocardial infarction.

Palmitic acid promotes endothelial-to-mesenchymal transition via activation of the cytosolic DNA-sensing cGAS-STING pathway

Elevated levels of plasma free fatty acids (FFAs) lead to endothelial dysfunction, a process that is involved in the pathogenesis of atherosclerosis. Endothelial-to-mesenchymal transformation (EndMT) has been reported to accelerate endothelial dysfunction during the process of atherosclerosis. However, the underlying mechanisms of EndMT remain poorly understood. The present study aimed to investigate the role of the cytosolic DNA-sensing cyclic GMP-AMP synthase-stimulator interferon gene (cGAS-STING) pathway in palmitic acid (PA)-induced EndMT. Human aortic endothelial cells (HAECs) were exposed to different concentrations of PA, and subsequently its effects on EndMT and the cGAS-STING pathway were assessed. To investigate the role of cGAS-STING pathway on PA-induced EndMT, RNA interference was used to knockdown the expression of cGAS in HAECs prior to their exposure to PA. First, it was observed that PA reduced cell viability and intracellular nitric oxide production, and increased migratory capacity of the HAECs as well as the cellular oxidative stress response, leading to EndMT. Moreover, it was observed that the cGAS-STING pathway was activated in PA-exposed primary HAECs. Activating cGAS-STING pathway via mtDNA directing lead to EndMT in HAECs. Interestingly, cGAS knockdown by RNA interference attenuated PA-induced inflammation, oxidative stress and EndMT in HAECs. Taken together, the results of the present study suggested that the cytosolic DNA-sensing cGAS-STING pathway may have important roles in PA-induced EndMT in endothelial cells.

Post-Translational Modifications of cGAS-STING: A Critical Switch for Immune Regulation

Innate immune mechanisms initiate immune responses via pattern-recognition receptors (PRRs). Cyclic GMP-AMP synthase (cGAS), a member of the PRRs, senses diverse pathogenic or endogenous DNA and activates innate immune signaling pathways, including the expression of stimulator of interferon genes (STING), type I interferon, and other inflammatory cytokines, which, in turn, instructs the adaptive immune response development. This groundbreaking discovery has rapidly advanced research on host defense, cancer biology, and autoimmune disorders. Since cGAS/STING has enormous potential in eliciting an innate immune response, understanding its functional regulation is critical. As the most widespread and efficient regulatory mode of the cGAS-STING pathway, post-translational modifications (PTMs), such as the covalent linkage of functional groups to amino acid chains, are generally considered a regulatory mechanism for protein destruction or renewal. In this review, we discuss cGAS-STING signaling transduction and its mechanism in related diseases and focus on the current different regulatory modalities of PTMs in the control of the cGAS-STING-triggered innate immune and inflammatory responses.

Resident cardiac macrophages: Heterogeneity and function in health and disease

Understanding tissue macrophage biology has become challenging in recent years due the ever-increasing complexity in macrophage-subset identification and functional characterization. This is particularly important within the myocardium, as we have come to understand that macrophages play multifaceted roles in cardiac health and disease, and heart disease remains the leading cause of death worldwide. Here, we review recent progress in the field, focusing on resident cardiac macrophage heterogeneity, origins, and functions at steady state and after injury. We stratify resident cardiac macrophage functions by the ability of macrophages to either directly influence cardiac physiology or indirectly influence cardiac physiology through orchestrating multi-cellular communication with cardiomyocytes and stromal and immune populations.

Role of the cGAS-STING pathway in systemic and organ-specific diseases

Cells are equipped with numerous sensors that recognize nucleic acids, which probably evolved for defence against viruses. Once triggered, these sensors stimulate the production of type I interferons and other cytokines that activate immune cells and promote an antiviral state. The evolutionary conserved enzyme cyclic GMP-AMP synthase (cGAS) is one of the most recently identified DNA sensors. Upon ligand engagement, cGAS dimerizes and synthesizes the dinucleotide second messenger 2',3'-cyclic GMP-AMP (cGAMP), which binds to the endoplasmic reticulum protein stimulator of interferon genes (STING) with high affinity, thereby unleashing an inflammatory response. cGAS-binding DNA is not restricted by sequence and must only be >45 nucleotides in length; therefore, cGAS can also be stimulated by self genomic or mitochondrial DNA. This broad specificity probably explains why the cGAS-STING pathway has been implicated in a number of autoinflammatory, autoimmune and neurodegenerative diseases; this pathway might also be activated during acute and chronic kidney injury. Therapeutic manipulation of the cGAS-STING pathway, using synthetic cyclic dinucleotides or inhibitors of cGAMP metabolism, promises to enhance immune responses in cancer or viral infections. By contrast, inhibitors of cGAS or STING might be useful in diseases in which this pro-inflammatory pathway is chronically activated.

Link between sterile inflammation and cardiovascular diseases: Focus on cGAS-STING pathway in the pathogenesis and therapeutic prospect

Sterile inflammation characterized by unresolved chronic inflammation is well established to promote the progression of multiple autoimmune diseases, metabolic disorders, neurodegenerative diseases, and cardiovascular diseases, collectively termed as sterile inflammatory diseases. In recent years, substantial evidence has revealed that the inflammatory response is closely related to cardiovascular diseases. Cyclic guanosine monophosphate–adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway which is activated by cytoplasmic DNA promotes the activation of interferon regulatory factor 3 (IRF3) or nuclear factor-κB (NF-κB), thus leading to upregulation of the levels of inflammatory factors and interferons (IFNs). Therefore, studying the role of inflammation caused by cGAS-STING pathway in cardiovascular diseases could provide a new therapeutic target for cardiovascular diseases. This review focuses on that cGAS-STING-mediated inflammatory response in the progression of cardiovascular diseases and the prospects of cGAS or STING inhibitors for treatment of cardiovascular diseases.

Transcription-independent regulation of STING activation and innate immune responses by IRF8 in monocytes

Sensing of cytosolic DNA of microbial or cellular/mitochondrial origin by cGAS initiates innate immune responses via the adaptor protein STING. It remains unresolved how the activity of STING is balanced between a productive innate immune response and induction of autoimmunity. Here we show that interferon regulatory factor 8 (IRF8) is essential for efficient activation of STING-mediated innate immune responses in monocytes. This function of IRF8 is independent of its transcriptional role in monocyte differentiation. In uninfected cells, IRF8 remains inactive via sequestration of its IRF-associated domain by its N- and C-terminal tails, which reduces its association with STING. Upon triggering the DNA sensing pathway, IRF8 is phosphorylated at Serine 151 to allow its association with STING via the IRF-associated domain. This is essential for STING polymerization and TBK1-mediated STING and IRF3 phosphorylation. Consistently, IRF8-deficiency impairs host defense against the DNA virus HSV-1, and blocks DNA damage-induced cellular senescence. Bone marrow-derived mononuclear cells which have an autoimmune phenotype due to deficiency of Trex1, respond to IRF-8 deletion with reduced pro-inflammatory cytokine production. Peripheral blood mononuclear cells from systemic lupus erythematosus patients are characterized by elevated phosphorylation of IRF8 at the same Serine residue we find to be important in STING activation, and in these cells STING is hyper-active. Taken together, the transcription-independent function of IRF8 we describe here appears to mediate STING activation and represents an important regulatory step in the cGAS/STING innate immune pathway in monocytes.

The transcription factor IRF8 has been shown to regulate monocyte differentiation via its DNA-binding activity. Here authors show that IRF8 is also involved in cytosolic DNA sensing via its phosphorylation-dependent association to the adaptor protein STING, thus representing an important checkpoint between immune response and autoimmunity in monocytes.

Spatiotemporal dynamics of macrophage heterogeneity and a potential function of Trem2hi macrophages in infarcted hearts

Heart failure (HF) is a frequent consequence of myocardial infarction (MI). Identification of the precise, time-dependent composition of inflammatory cells may provide clues for the establishment of new biomarkers and therapeutic approaches targeting post-MI HF. Here, we investigate the spatiotemporal dynamics of MI-associated immune cells in a mouse model of MI using spatial transcriptomics and single-cell RNA-sequencing (scRNA-seq). We identify twelve major immune cell populations; their proportions dynamically change after MI. Macrophages are the most abundant population at all-time points (>60%), except for day 1 post-MI. Trajectory inference analysis shows upregulation of Trem2 expression in macrophages during the late phase post-MI. In vivo injection of soluble Trem2 leads to significant functional and structural improvements in infarcted hearts. Our data contribute to a better understanding of MI-driven immune responses and further investigation to determine the regulatory factors of the Trem2 signaling pathway will aid the development of novel therapeutic strategies for post-MI HF.

Advances in molecular pathogenesis of hidradenitis suppurativa: Dysregulated keratins and ECM signaling

Hidradenitis suppurativa (HS) is characterized by deep-seated, highly inflamed, and painful lumps/abscesses, fistulae, and sinus tracts that grow extensively deep in the dermis and are highly immunogenic in nature. In about one-third of the HS patients there is strong evidence for the role of γ-secretase mutations along with dysregulated Notch signaling. However, the contribution of dysregulated Notch signaling in HS pathogenesis in relation to hair follicle alterations and hyper-activation of the immune system remains undefined. A genome-wide association study (GWAS), proteomic data and functional investigations of identified sequence variants in HS pathology are not fully revealing. The disease initiation or progression may involve bacterial infection besides intrinsic functional defects in keratinocytes, which may be key to further exacerbate immune cell infiltration and cytokine production in and around the lesional tissue. The absence of a suitable animal model that could fully recapitulate the pathogenesis of HS is a major impediment for proper understanding the underlying mechanisms and development of effective treatments. The presence of extracellular matrix (ECM) degradation products along with dysregulation in keratinocytes and, dermal fibroblasts ultimately affect immune regulation and are various components of HS pathogenesis. Bacterial infection further exacerbates the complexity of the disease progression. While anti-TNFα therapy shows partial efficacy, treatment to cure HS is absent. Multiple clinical trials targeting various cytokines, complement C5a and ECM products are in progress. This review provides state-of-the-art information on these aspects with a focus on dysregulated keratinocyte and immune cells; and role of ECM, and Keratin functions in this regard.