Ogg1-Dependent DNA Repair Regulates NLRP3 Inflammasome and Prevents Atherosclerosis

m6A-methylated Lonp1 drives mitochondrial proteostasis stress to induce testicular pyroptosis upon environmental cadmium exposure

Cadmium (Cd) is a widely distributed typical environmental pollutant and one of the most toxic heavy metals. It is well-known that environmental Cd causes testicular damage by inducing classic types of cell death such as cell apoptosis and necrosis. However, as a new type of cell death, the role and mechanism of pyroptosis in Cd-induced testicular injury remain unclear. In the current study, we used environmental Cd to generate a murine model with testicular injury and AIM2-dependent pyroptosis. Based on the model, we found that increased cytoplasmic mitochondrial DNA (mtDNA), activated mitochondrial proteostasis stress occurred in Cd-exposed testes. We used ethidium bromide to generate mtDNA-deficient testicular germ cells and further confirmed that increased cytoplasmic mtDNA promoted AIM2-dependent pyroptosis in Cd-exposed cells. Uracil-DNA glycosylase UNG1 overexpression indicated that environmental Cd blocked UNG-dependent repairment of damaged mtDNA to drive the process in which mtDNA releases to cytoplasm in the cells. Interestingly, we found that environmental Cd activated mitochondrial proteostasis stress by up-regulating protein expression of LONP1 in testes. Testicular specific LONP1-knockdown significantly reversed Cd-induced UNG1 protein degradation and AIM2-dependent pyroptosis in mouse testes. In addition, environmental Cd significantly enhanced the m6A modification of Lonp1 mRNA and its stability in testicular germ cells. Knockdown of IGF2BP1, a reader of m6A modification, reversed Cd-induced upregulation of LONP1 protein expression and pyroptosis activation in testicular germ cells. Collectively, environmental Cd induces m6A modification of Lonp1 mRNA to activate mitochondrial proteostasis stress, increase cytoplasmic mtDNA content, and trigger AIM2-dependent pyroptosis in mouse testes. These findings suggest that mitochondrial proteostasis stress is a potential target for the prevention of testicular injury.

Role of 8-hydroxyguanine DNA glycosidase 1 deficiency in exacerbating diabetic cardiomyopathy through the regulation of insulin resistance

Diabetic cardiomyopathy (DCM) is a heart failure syndrome, and is one of the major causes of morbidity and mortality in diabetes. DCM is mainly characterized by ventricular dilation, myocardial hypertrophy, myocardial fibrosis and cardiac dysfunction. Clinical studies have found that insulin resistance is an independent risk factor for DCM. However, its specific mechanism of DCM remains unclear. 8-hydroxyguanine DNA glycosylase 1(OGG1)is involved in DNA base repair and the regulation of inflammatory genes. In this study, we show that OGG1 was associated with the occurrence of DCM. for the first time. The expression of OGG1 was increased in the heart tissue of DCM mice, and OGG1 deficiency aggravated the cardiac dysfunction of DCM mice. Metabolomics show that OGG1 deficiency resulted in obstruction of glycolytic pathway. At the molecular level, OGG1 regulated glucose uptake and insulin resistance by interacting with PPAR-γ in vitro. In order to explore the protective effect of exogenous OGG1 on DCM, OGG1 adeno-associated virus was injected into DCM mice through tail vein in the middle stage of the disease. We found that the overexpression of OGG1 could improve cardiac dysfunction of DCM mice, indicating that OGG1 had a certain therapeutic effect on DCM. These results demonstrate that OGG1 is a new molecular target for the treatment of DCM and has certain clinical significance.

The role of DNA and RNA guanosine oxidation in cardiovascular diseases

Cardiovascular diseases (CVD) persist as a prominent cause of mortality worldwide, with oxidative stress constituting a pivotal contributory element. The oxidative modification of guanosine, specifically 8-oxoguanine, has emerged as a crucial biomarker for oxidative stress, providing novel insights into the molecular underpinnings of CVD. 8-Oxoguanine can be directly generated at the DNA (8-oxo-dG) and RNA (8-oxo-G) levels, as well as at the free nucleotide level (8-oxo-dGTP or 8-oxo-GTP), which are produced and can be integrated through DNA replication or RNA transcription. When exposed to oxidative stress, guanine is more readily produced in RNA than in DNA. A burgeoning body of research surrounds 8-oxoguanine, exhibits its accumulation playing a pivotal role in the development of CVD. Therapeutic approaches targeting oxidative 8-Oxoguanine damage to DNA and RNA, encompassing the modulation of repair enzymes and the development of small molecule inhibitors, are anticipated to enhance CVD management. In conclusion, we explore the noteworthy elevation of 8-oxoguanine levels in patients with various cardiac conditions and deliberate upon the formation and regulation of 8-oxo-dG and 8-oxo-G under oxidative stress, as well as their function in CVD.

Release of damaged mitochondrial DNA: A novel factor in stimulating inflammatory response

Mitochondrial DNA (mtDNA) is a circular double-stranded genome that exists independently of the nucleus. In recent years, research on mtDNA has significantly increased, leading to a gradual increase in understanding of its physiological and pathological characteristics. Reactive oxygen species (ROS) and other factors can damage mtDNA. This damaged mtDNA can escape from the mitochondria to the cytoplasm or extracellular space, subsequently activating immune signaling pathways, such as NLR family pyrin domain protein 3 (NLRP3), and triggering inflammatory responses. Numerous studies have demonstrated the involvement of mtDNA damage and leakage in the pathological mechanisms underlying various diseases including infectious diseases, metabolic inflammation, and immune disorders. Consequently, comprehensive investigation of mtDNA can elucidate the pathological mechanisms underlying numerous diseases. The prevention of mtDNA damage and leakage has emerged as a novel approach to disease treatment, and mtDNA has emerged as a promising target for drug development. This article provides a comprehensive review of the mechanisms underlying mtDNA-induced inflammation, its association with various diseases, and the methods used for its detection.

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.

Research progress on the role of reactive oxygen species in the initiation, development and treatment of breast cancer

According to international cancer data, breast cancer (BC) is the leading type of cancer in women. Although significant progress has been made in treating BC, metastasis and drug resistance continue to be the primary causes of mortality for many patients. Reactive oxygen species (ROS) play a dual role in vivo: normal levels can maintain the body's normal physiological function; however, high levels of ROS below the toxicity threshold can lead to mtDNA damage, activation of proto-oncogenes, and inhibition of tumor suppressor genes, which are important causes of BC. Differences in the production and regulation of ROS in different BC subtypes have important implications for the development and treatment of BC. ROS can also serve as an important intracellular signal transduction factor by affecting the antioxidant system, activating MAPK and PI3K/AKT, and other signal pathways to regulate cell cycle and change the relationship between cells and the activity of metalloproteinases, which significantly impacts the metastasis of BC. Hypoxia in the BC microenvironment increases ROS production levels, thereby inducing the expression of hypoxia inducible factor-1α (HIF-1α) and forming "ROS- HIF-1α-ROS" cycle that exacerbates BC development. Many anti-BC therapies generate sufficient toxic ROS to promote cancer cell apoptosis, but because the basal level of ROS in BC cells exceeds that of normal cells, this leads to up-regulation of the antioxidant system, drug efflux, and apoptosis inhibition, rendering BC cells resistant to the drug. ROS crosstalks with tumor vessels and stromal cells in the microenvironment, increasing invasiveness and drug resistance in BC.

Construction of single-molecule counting-based biosensors for DNA-modifying enzymes: A review

DNA-modifying enzymes act as critical regulators in a wide range of genetic functions (e.g., DNA damage & repair, DNA replication), and their aberrant expression may interfere with regular genetic functions and induce various malignant diseases including cancers. DNA-modifying enzymes have emerged as the potential biomarkers in early diagnosis of diseases and new therapeutic targets in genomic research. Consequently, the development of highly specific and sensitive biosensors for the detection of DNA-modifying enzymes is of great importance for basic biomedical research, disease diagnosis, and drug discovery. Single-molecule fluorescence detection has been widely implemented in the field of molecular diagnosis due to its simplicity, high sensitivity, visualization capability, and low sample consumption. In this paper, we summarize the recent advances in single-molecule counting-based biosensors for DNA-modifying enzyme (i.e, alkaline phosphatase, DNA methyltransferase, DNA glycosylase, flap endonuclease 1, and telomerase) assays in the past four years (2019 - 2023). We highlight the principles and applications of these biosensors, and give new insight into the future challenges and perspectives in the development of single-molecule counting-based biosensors.

Advances in the study of S100A9 in cardiovascular diseases

Cardiovascular disease (CVD) is a group of diseases that primarily affect the heart or blood vessels, with high disability and mortality rates, posing a serious threat to human health. The causative factors, pathogenesis, and characteristics of common CVD differ, but they all involve common pathological processes such as inflammation, oxidative stress, and fibrosis. S100A9 belongs to the S100 family of calcium-binding proteins, which are mainly secreted by myeloid cells and bind to the Toll-like receptor 4 and receptor for advanced glycation end products and is involved in regulating pathological processes such as inflammatory response, fibrosis, vascular calcification, and endothelial barrier function in CVD. The latest research has found that S100A9 is a key biomarker for diagnosing and predicting various CVD. Therefore, this article reviews the latest research progress on the diagnostic and predictive, and therapeutic value of S100A9 in inflammatory-related CVD such as atherosclerosis, myocardial infarction, and arterial aneurysm and summarizes its molecular mechanisms in the progression of CVD, aiming to explore new predictive methods and to identify potential intervention targets for CVD in clinical practice.

Pyroptosis in Osteoarthritis: Molecular Mechanisms and Therapeutic Implications

Osteoarthritis (OA) is a chronic disease that causes pain and functional impairment by affecting joint tissue. Its global impact is noteworthy, causing significant economic losses and property damage. Despite extensive research, the underlying pathogenesis of OA remain an area of ongoing investigation. It has recently been discovered that the OA progression is significantly influenced by pyroptosis. Pyroptosis is a complex process that involves three pathways culminating in the assembly of Gasdermin-D (GSDMD)-N-terminal (GSDMD-NT) into pores through aggregation on the plasma membrane. The aggregation of GSDMD-NT proteins stimulates the release of inflammatory mediators, such as Interleukin-1β (IL-1β), Interleukin-18 (IL-18), and Matrix Metallopeptidase 13 (MMP13), ultimately leading to cellular lysis. The pyroptosis process in specific cells, including synovial macrophages, fibroblast-like synoviocytes (FLS), chondrocytes, and subchondral osteoblasts, contributs factor to the development of OA. Currently, the specific cells that undergo pyroptosis first are not yet fully understood, and it remains unknown whether pyroptosis in one cell can trigger the same process in other cells. Therefore, targeting pyroptosis could potentially offer a novel treatment approach for OA patients. We present a comprehensive analysis of the molecular mechanisms and key features of pyroptosis. We also outline the current research progress on various aspects, including synovial tissue, articular cartilage, extracellular matrix (ECM), and subchondral bone, with a focus on pyroptosis. The aim is to provide theoretical references for the effective management of OA.

Crosstalk between inflammasome sensors and DNA damage response pathways

Eukaryotic cells encounter diverse threats jeopardizing their integrity, prompting the development of defense mechanisms against these stressors. Among these mechanisms, inflammasomes are well-known for their roles in coordinating the inflammatory response against infections. Extensive research has unveiled their multifaceted involvement in cellular processes beyond inflammation. Recent studies emphasize the intricate relationship between the inflammasome and the DNA damage response (DDR). They highlight how the DDR participates in inflammasome activation and the reciprocal impact of inflammasome on DDR and genome integrity preservation. Moreover, novel functions of inflammasome sensors in DDR pathways have emerged, broadening our understanding of their roles. Finally, this review delves into identifying common signals that drive the activation of inflammasome sensors alongside activation cues for the DNA damage response, offering potential insights into shared regulatory pathways between these critical cellular processes.

Research progress on mitochondria regulating tumor immunity

Tumor cells adapt their metabolism to meet the demands for energy and biosynthesis. Mitochondria, pivotal organelles in the metabolic reprogramming of tumor cells, contribute to tumorigenesis and cancer progression significantly through various dysfunctions in both tumor and immune cells. Alterations in mitochondrial dynamics and metabolic signaling pathways exert crucial regulatory influence on the activation, proliferation, and differentiation of immune cells. The tumor microenvironment orchestrates the activation and functionality of tumor-infiltrating immune cells by reprogramming mitochondrial metabolism and inducing shifts in mitochondrial dynamics, thereby facilitating the establishment of a tumor immunosuppressive microenvironment. Stress-induced leakage of mitochondrial DNA contributes multifaceted regulatory effects on anti-tumor immune responses and the immunosuppressive microenvironment by activating multiple natural immune signals, including cGAS-STING, TLR9, and NLRP3. Moreover, mitochondrial DNA-mediated immunogenic cell death emerges as a promising avenue for anti-tumor immunotherapy. Additionally, mitochondrial reactive oxygen species, a crucial factor in tumorigenesis, drives the formation of tumor immunosuppressive microenvironment by changing the composition of immune cells within the tumor microenvironment. This review focuses on the intrinsic relationship between mitochondrial biology and anti-tumor immune responses from multiple angles. We explore the core role of mitochondria in the dynamic interplay between the tumor and the host to facilitate the development of targeted mitochondrial strategies for anti-tumor immunotherapy.

Mitochondrial DNA is a key driver in cigarette smoke extract-induced IL-6 expression

Smoking is an independent risk factor for atherosclerosis, the primary pathogenesis of which is inflammation. We recently reported that cigarette smoke extract (CSE) causes cytosolic and extracellular accumulation of both nuclear (n) and mitochondrial (mt) DNA, which leads to inflammation in human umbilical vein endothelial cells (HUVECs). In this study, we examined whether inflammation induction depends more on cytosolic nDNA or mtDNA, and which chemical constituents of CSE are involved. Acrolein (ACR), methyl vinyl ketone (MVK), and 2-cyclopenten-1-one (CPO) were used in the experiments, as these are the major cytotoxic factors in CSE in various cell types. Stimulation with ACR, MVK, or CPO alone resulted in the accumulation of DNA double-strand breaks (DSBs), but not oxidative DNA damage, accumulation of cytosolic DNA, or increased expression of inflammatory cytokines. Simultaneous administration of all three constituents (ALL) resulted in oxidative DNA damage in both the nucleus and mitochondria, accumulation of DSBs, reduced mitochondrial membrane potential, induction of minority mitochondrial outer membrane permeabilization, accumulation of cytosolic free DNA, and increased expression of inflammatory cytokines such as IL-6 and IL-1α. Treatment with N-acetyl-L-cysteine, a reactive oxygen species scavenger, suppressed oxidative DNA damage and the increased expression of IL-6 and IL-1α induced by ALL or CSE. The ALL- or CSE-induced increase in IL-6 expression, but not that of IL-1α, was suppressed by mtDNA depletion. In conclusion, ACR, MVK, and CPO may strongly contribute to CSE-induced inflammation. More importantly, cytosolic free mtDNA is thought to play an important role in IL-6 expression, a central mediator of inflammation.

OGG1 prevents atherosclerosis-induced vascular endothelial cell injury through mediating DNA damage repair

OBJECTIVE

This study was designed to investigate the role of 8-oxoguanine DNA glycosylase 1 (OGG1) in preventing atherosclerosis-induced vascular EC injury, thereby providing a theoretical basis for the exploration of drug targets and treatment methods for atherosclerosis.

METHODS

Human umbilical vein cell line (EA.hy926) was treated with ox-LDL to construct an in vitro atherosclerotic cell model. pcDNA3.1-OGG1 was transfected into EA.hy926 cells to overexpress OGG1. qRT-PCR, CCK-8 assay, flow cytometry, oil red O staining, ELISA, comet assay and western blot were used to evaluate the OGG1 expression, viability, apoptosis level, lipid droplet content, 8-OHdG level and DNA damage of cells in each group.

RESULTS

Compared with the Control group, ox-LDL stimulation of endothelial cells significantly decreased cell viability, promoted apoptosis and DNA damage, and increased intracellular levels of 8-OHdG and γH2AX, while decreasing protein levels of PPARγ, FASN, FABP4, RAD51 and POLB. However, overexpression of OGG1 can significantly inhibit ox-LDL damage to endothelial cells, promote lipid metabolism, decrease lipid droplet content, and improve DNA repair function.

CONCLUSION

Over-expression of OGG1 improves DNA repair. Briefly, OGG1 over-expression enhances the DNA damage repair of ECs by regulating the expression levels of γH2AX, RAD51 and POLB, thereby enhancing cell viability and reducing apoptosis.

Vincamine as an agonist of G-protein-coupled receptor 40 effectively ameliorates diabetic peripheral neuropathy in mice

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes, which has yet no curable medication. Neuroinflammation and mitochondrial dysfunction are tightly linked to DPN pathology. G-protein-coupled receptor 40 (GPR40) is predominantly expressed in pancreatic β-cells, but also in spinal dorsal horn and dorsal root ganglion (DRG) neurons, regulating neuropathic pain. We previously have reported that vincamine (Vin), a monoterpenoid indole alkaloid extracted from Madagascar periwinkle, is a GPR40 agonist. In this study, we evaluated the therapeutic potential of Vin in ameliorating the DPN-like pathology in diabetic mice. Both STZ-induced type 1 (T1DM) and db/db type 2 diabetic (T2DM) mice were used to establish late-stage DPN model (DPN mice), which were administered Vin (30 mg·kg-1·d-1, i.p.) for 4 weeks. We showed that Vin administration did not lower blood glucose levels, but significantly ameliorated neurological dysfunctions in DPN mice. Vin administration improved the blood flow velocities and blood perfusion areas of foot pads and sciatic nerve tissues in DPN mice. We demonstrated that Vin administration protected against sciatic nerve myelin sheath injury and ameliorated foot skin intraepidermal nerve fiber (IENF) density impairment in DPN mice. Moreover, Vin suppressed NLRP3 inflammasome activation through either β-Arrestin2 or β-Arrestin2/IκBα/NF-κB signaling, improved mitochondrial dysfunction through CaMKKβ/AMPK/SIRT1/PGC-1α signaling and alleviated oxidative stress through Nrf2 signaling in the sciatic nerve tissues of DPN mice and LPS/ATP-treated RSC96 cells. All the above-mentioned beneficial effects of Vin were abolished by GPR40-specific knockdown in dorsal root ganglia and sciatic nerve tissues. Together, these results support that pharmacological activation of GPR40 as a promising therapeutic strategy for DPN and highlight the potential of Vin in the treatment of this disease.

DNA damage response, a double-edged sword for vascular aging

Vascular aging is a major risk factor for age-related cardiovascular diseases, which have high rates of morbidity and mortality. It is characterized by changes in the blood vessels, such as macroscopically increased vascular diameter and intima-medial thickness, chronic inflammation, vascular calcification, arterial stiffening, and atherosclerosis. DNA damage and the subsequent various DNA damage response (DDR) pathways are important causative factors of vascular aging. Deficient DDR, which may result in the accumulation of unrepaired damaged DNA or mutations, can lead to vascular aging. On the other hand, over-activation of some DDR proteins, such as poly (ADP ribose) polymerase (PARP) and ataxia telangiectasia mutated (ATM), also can enhance the process of vascular aging, suggesting that DDR can have both positive and negative effects on vascular aging. Despite the evidence reviewed in this paper, the role of DDR in vascular aging and potential therapeutic targets remain poorly understood and require further investigation.

Contribution of membrane raft redox signalling to visfatin-induced inflammasome activation and podocyte injury

Recently we have shown that adipokine visfatin-induced NLRP3 inflammasome activation contributes to podocyte injury. However, the molecular mechanisms of how visfatin-induces the Nlrp3 inflammasome activation and podocyte damage is still unknown. The present study tested whether membrane raft (MR) redox signalling pathway plays a central role in visfatin-induced NLRP3 inflammasomes formation and activation in podocytes. Upon visfatin stimulation an aggregation of NADPH oxidase subunits, gp91phox and p47phox was observed in the membrane raft (MR) clusters, forming a MR redox signalling platform in podocytes. The formation of this signalling platform was blocked by prior treatment with MR disruptor MCD or NADPH oxidase inhibitor DPI. In addition, visfatin stimulation significantly increased the colocalization of Nlrp3 with Asc or Nlrp3 with caspase-1, IL-β production, cell permeability in podocytes compared to control cells. Pretreatment with MCD, DPI, WEHD significantly abolished the visfatin-induced colocalization of NLRP3 with Asc or NLRP3 with caspase-1, IL-1β production and cell permeability in podocytes. Furthermore, Immunofluorescence analysis demonstrated that visfatin treatment significantly decreased the podocin and nephrin expression (podocyte damage) and prior treatments with DPI, WEHD, MCD attenuated this visfatin-induced podocin and nephrin reduction. In conclusion, our results suggest that visfatin stimulates membrane raft clustering in the membrane of podocytes to form redox signaling platforms by aggregation and activation of NADPH oxidase subunits enhancing O2·- production and leading to NLRP3 inflammasome activation in podocytes and ultimate podocyte injury.

Mitochondrial quality control in health and cardiovascular diseases

Cardiovascular diseases (CVDs) are one of the primary causes of mortality worldwide. An optimal mitochondrial function is central to supplying tissues with high energy demand, such as the cardiovascular system. In addition to producing ATP as a power source, mitochondria are also heavily involved in adaptation to environmental stress and fine-tuning tissue functions. Mitochondrial quality control (MQC) through fission, fusion, mitophagy, and biogenesis ensures the clearance of dysfunctional mitochondria and preserves mitochondrial homeostasis in cardiovascular tissues. Furthermore, mitochondria generate reactive oxygen species (ROS), which trigger the production of pro-inflammatory cytokines and regulate cell survival. Mitochondrial dysfunction has been implicated in multiple CVDs, including ischemia-reperfusion (I/R), atherosclerosis, heart failure, cardiac hypertrophy, hypertension, diabetic and genetic cardiomyopathies, and Kawasaki Disease (KD). Thus, MQC is pivotal in promoting cardiovascular health. Here, we outline the mechanisms of MQC and discuss the current literature on mitochondrial adaptation in CVDs.

Mitochondrial Dysfunction-Associated Mechanisms in the Development of Chronic Liver Diseases

The liver is a major metabolic organ that performs many essential biological functions such as detoxification and the synthesis of proteins and biochemicals necessary for digestion and growth. Any disruption in normal liver function can lead to the development of more severe liver disorders. Overall, about 3 million Americans have some type of liver disease and 5.5 million people have progressive liver disease or cirrhosis, in which scar tissue replaces the healthy liver tissue. An estimated 20% to 30% of adults have excess fat in their livers, a condition called steatosis. The most common etiologies for steatosis development are (1) high caloric intake that causes non-alcoholic fatty liver disease (NAFLD) and (2) excessive alcohol consumption, which results in alcohol-associated liver disease (ALD). NAFLD is now termed "metabolic-dysfunction-associated steatotic liver disease" (MASLD), which reflects its association with the metabolic syndrome and conditions including diabetes, high blood pressure, high cholesterol and obesity. ALD represents a spectrum of liver injury that ranges from hepatic steatosis to more advanced liver pathologies, including alcoholic hepatitis (AH), alcohol-associated cirrhosis (AC) and acute AH, presenting as acute-on-chronic liver failure. The predominant liver cells, hepatocytes, comprise more than 70% of the total liver mass in human adults and are the basic metabolic cells. Mitochondria are intracellular organelles that are the principal sources of energy in hepatocytes and play a major role in oxidative metabolism and sustaining liver cell energy needs. In addition to regulating cellular energy homeostasis, mitochondria perform other key physiologic and metabolic activities, including ion homeostasis, reactive oxygen species (ROS) generation, redox signaling and participation in cell injury/death. Here, we discuss the main mechanism of mitochondrial dysfunction in chronic liver disease and some treatment strategies available for targeting mitochondria.

A possible role for proinflammatory activation via cGAS-STING pathway in atherosclerosis induced by accumulation of DNA double-strand breaks

DNA damage contributes to atherosclerosis. However, causative links between DNA double-strand breaks (DSBs) and atherosclerosis have yet to be established. Here, we investigated the role of DSBs in atherosclerosis using mice and vascular cells deficient in Ku80, a DSB repair protein. After 4 weeks of a high-fat diet, Ku80-deficient apolipoprotein E knockout mice (Ku80+/-ApoE-/-) displayed increased plaque size and DSBs in the aorta compared to those of ApoE-/- control. In the preatherosclerotic stages (two-week high-fat diet), the plaque size was similar in both the Ku80+/-ApoE-/- and ApoE-/- control mice, but the number of DSBs and mRNA levels of inflammatory cytokines such as IL-6 and MCP-1 were significantly increased in the Ku80+/-ApoE-/- aortas. We further investigated molecular links between DSBs and inflammatory responses using vascular smooth muscle cells isolated from Ku80 wild-type and Ku80+/- mice. The Ku80+/- cells displayed senescent features and elevated levels of inflammatory cytokine mRNAs. Moreover, the cytosolic DNA-sensing cGAS-STING pathway was activated in the Ku80+/- cells. Inhibiting the cGAS-STING pathway reduced IL-6 mRNA level. Notably, interferon regulatory factor 3 (IRF3), a downstream effector of the cGAS-STING pathway, was activated, and the depletion of IRF3 also reduced IL-6 mRNA levels in the Ku80+/- cells. Finally, DSBs accumulation in normal cells also activated the cGAS-STING-IRF3 pathway. In addition, cGAS inhibition attenuated DNA damage-induced IL-6 expression and cellular senescence in these cells. These results suggest that DSBs accumulation promoted atherosclerosis by upregulating proinflammatory responses and cellular senescence via the cGAS-STING (-IRF3) pathway.

Immunometabolism and immune response regulate macrophage function in atherosclerosis

Macrophages are crucial in the progression of atherosclerotic cardiovascular disease (ASCVD). In the atherosclerotic lesions, macrophages play a central role in maintaining inflammatory response, promoting plaque development, and facilitating thrombosis. Increasing studies indicate that metabolic reprogramming and immune response mediate macrophage functional changes in all stages of atherosclerosis. In this review article, we explain how metabolic changes in glycolysis, oxidative phosphorylation, the tricarboxylic acid cycle, fatty acid synthesis, fatty acid oxidation, and cholesterol metabolism regulate macrophage function in atherosclerosis. We discuss how immune response to oxidized lipids regulate macrophage function in atherosclerosis. Additionally, we explore how abnormal metabolism leads to macrophage mitochondrial dysfunction in atherosclerosis.

Restraint stress promotes monobenzone-induced depigmentation in mice via the activation of glucocorticoid receptor/macrophage migration inhibitory factor signaling pathway

Psychological stress triggers onset and development of vitiligo in humans. However, the mechanism of psychological stress on vitiligo remains unclear. The study aims to investigate whether psychological stress promotes vitiligo and explore the underlying mechanism. A depigmentation mouse model induced by applying a skin-bleaching reagent monobenzone to dorsal skin and an in vitro HaCaT keratinocyte death model induced by monobenzone were employed to explore the effect of restraint stress, which mimics psychological stress, on depigmentation. The results indicated that restraint stress promoted vitiligo-related depigmentation, vacuolisation, spongiosis, CD8+ T lymphocyte infiltration, and loss of melanocytes in the skin. Restraint stress activated cutaneous NLR family containing pyrin domain protein 3 (NLRP3) inflammasome. In addition, restraint stress aggravated anxiety-like behaviors and increased levels of macrophage migration inhibitory factor (MIF) and corticosterone in the circulation, accompanied with decreasing the expression of cutaneous 8-oxoguanine DNA glycosylase (OGG1) in depigmentation mice. In vitro experiments demonstrated that activation of glucocorticoid receptor (GR) by cortisol upregulated NLRP3 expression dependent on MIF, and directly decreased the transcription of OGG1. Blockade of MIF reversed the NLRP3 signal in restraint stress-induced depigmentation mice. In conclusion, restraint stress promotes vitiligo-related depigmentation in mice via the activation of GR/MIF signaling pathway. The findings provide a theoretical basis for prevention and treatments of vitiligo with therapies of targeting GR, MIF, and OGG1.

Regulation of inflammation and immunity in sepsis by E3 ligases

Sepsis is a life-threatening organ dysfunction caused by an abnormal infection-induced immune response. Despite significant advances in supportive care, sepsis remains a considerable therapeutic challenge and is the leading cause of death in the intensive care unit (ICU). Sepsis is characterized by initial hyper-inflammation and late immunosuppression. Therefore, immune-modulatory therapies have great potential for novel sepsis therapies. Ubiquitination is an essential post-translational protein modification, which has been known to be intimately involved in innate and adaptive immune responses. Several E3 ubiquitin ligases have been implicated in innate immune signaling and T-cell activation and differentiation. In this article, we review the current literature and discuss the role of E3 ligases in the regulation of immune response and their effects on the course of sepsis to provide insights into the prevention and therapy for sepsis.

Hematopoietic NLRP3 and AIM2 Inflammasomes Promote Diabetes-Accelerated Atherosclerosis, but Increased Necrosis Is Independent of Pyroptosis

Serum apolipoprotein C3 (APOC3) predicts incident cardiovascular events in people with type 1 diabetes, and silencing of APOC3 prevents both lesion initiation and advanced lesion necrotic core expansion in a mouse model of type 1 diabetes. APOC3 acts by slowing the clearance of triglyceride-rich lipoproteins, but lipid-free APOC3 has recently been reported to activate an inflammasome pathway in monocytes. We therefore investigated the contribution of hematopoietic inflammasome pathways to atherosclerosis in mouse models of type 1 diabetes. LDL receptor-deficient diabetes mouse models were transplanted with bone marrow from donors deficient in NOD, LRR and pyrin domain-containing protein 3 (NLRP3), absent in melanoma 2 (AIM2) or gasdermin D (GSDMD), an inflammasome-induced executor of pyroptotic cell death. Mice with diabetes exhibited inflammasome activation and consistently, increased plasma interleukin-1β (IL-1β) and IL-18. Hematopoietic deletions of NLRP3, AIM2, or GSDMD caused smaller atherosclerotic lesions in diabetic mice. The increased lesion necrotic core size in diabetic mice was independent of macrophage pyroptosis because hematopoietic GSDMD deficiency failed to prevent necrotic core expansion in advanced lesions. Our findings demonstrate that AIM2 and NLRP3 inflammasomes contribute to atherogenesis in diabetes and suggest that necrotic core expansion is independent of macrophage pyroptosis.

ARTICLE HIGHLIGHTS

The contribution of hematopoietic cell inflammasome activation to atherosclerosis associated with type 1 diabetes is unknown. The goal of this study was to address whether hematopoietic NOD, LRR, and pyrin domain-containing protein 3 (NLRP3), absent in melanoma 2 (AIM2) inflammasomes, or the pyroptosis executioner gasdermin D (GSDMD) contributes to atherosclerosis in mouse models of type 1 diabetes. Diabetic mice exhibited increased inflammasome activation, with hematopoietic deletions of NLRP3, AIM2, or GSDMD causing smaller atherosclerotic lesions in diabetic mice, but the increased lesion necrotic core size in diabetic mice was independent of macrophage pyroptosis. Further studies on whether inflammasome activation contributes to cardiovascular complications in people with type 1 diabetes are warranted.

Hexokinase dissociation from mitochondria promotes oligomerization of VDAC that facilitates NLRP3 inflammasome assembly and activation

NLRP3 inflammasome activation is a highly regulated process for controlling secretion of the potent inflammatory cytokines IL-1β and IL-18 that are essential during bacterial infection, sterile inflammation, and disease, including colitis, diabetes, Alzheimer's disease, and atherosclerosis. Diverse stimuli activate the NLRP3 inflammasome, and unifying upstream signals has been challenging to identify. Here, we report that a common upstream step in NLRP3 inflammasome activation is the dissociation of the glycolytic enzyme hexokinase 2 from the voltage-dependent anion channel (VDAC) in the outer membrane of mitochondria. Hexokinase 2 dissociation from VDAC triggers activation of inositol triphosphate receptors, leading to release of calcium from the ER, which is taken up by mitochondria. This influx of calcium into mitochondria leads to oligomerization of VDAC, which is known to form a macromolecule-sized pore in the outer membranes of mitochondria that allows proteins and mitochondrial DNA (mtDNA), often associated with apoptosis and inflammation, respectively, to exit the mitochondria. We observe that VDAC oligomers aggregate with NLRP3 during initial assembly of the multiprotein oligomeric NLRP3 inflammasome complex. We also find that mtDNA is necessary for NLRP3 association with VDAC oligomers. These data, together with other recent work, help to paint a more complete picture of the pathway leading to NLRP3 inflammasome activation.

Mitochondrial DNA Release in Innate Immune Signaling

According to the endosymbiotic theory, most of the DNA of the original bacterial endosymbiont has been lost or transferred to the nucleus, leaving a much smaller (∼16 kb in mammals), circular molecule that is the present-day mitochondrial DNA (mtDNA). The ability of mtDNA to escape mitochondria and integrate into the nuclear genome was discovered in budding yeast, along with genes that regulate this process. Mitochondria have emerged as key regulators of innate immunity, and it is now recognized that mtDNA released into the cytoplasm, outside of the cell, or into circulation activates multiple innate immune signaling pathways. Here, we first review the mechanisms through which mtDNA is released into the cytoplasm, including several inducible mitochondrial pores and defective mitophagy or autophagy. Next, we cover how the different forms of released mtDNA activate specific innate immune nucleic acid sensors and inflammasomes. Finally, we discuss how intracellular and extracellular mtDNA release, including circulating cell-free mtDNA that promotes systemic inflammation, are implicated in human diseases, bacterial and viral infections, senescence and aging.

Effect of 8-Hydroxyguanine DNA Glycosylase 1 on the Function of Immune Cells

Excess reactive oxygen species (ROS) can cause an imbalance between oxidation and anti-oxidation, leading to the occurrence of oxidative stress in the body. The most common product of ROS-induced base damage is 8-hydroxyguanine (8-oxoG). Failure to promptly remove 8-oxoG often causes mutations during DNA replication. 8-oxoG is cleared from cells by the 8-oxoG DNA glycosylase 1 (OGG1)-mediated oxidative damage base excision repair pathway so as to prevent cells from suffering dysfunction due to oxidative stress. Physiological immune homeostasis and, in particular, immune cell function are vulnerable to oxidative stress. Evidence suggests that inflammation, aging, cancer, and other diseases are related to an imbalance in immune homeostasis caused by oxidative stress. However, the role of the OGG1-mediated oxidative damage repair pathway in the activation and maintenance of immune cell function is unknown. This review summarizes the current understanding of the effect of OGG1 on immune cell function.

Polydatin protects against atherosclerosis by activating autophagy and inhibiting pyroptosis mediated by the NLRP3 inflammasome

ETHNOPHARMACOLOGICAL RELEVANCE

Polydatin is a bioactive ingredient extracted from the roots of the Reynoutria japonica Houtt, and it is a natural precursor of resveratrol. Polydatin is a useful inhibitor of inflammation and acts as a regulator of lipid metabolism. However, the specific mechanisms of action of polydatin in atherosclerosis (AS) remains poorly explained.

AIM OF THE STUDY

The aim of this study was to assess the efficacy of polydatin on inflammation induced by the inflammatory cell death and autophagy in AS.

MATERIALS AND METHODS

Apolipoprotein E knockout (ApoE^-/-) mice were fed with a high-fat diet (HFD) for 12 weeks to induce the formation of atherosclerotic lesions. The ApoE^-/- mice were then randomly divided into the following six groups: (1) model group, (2) simvastatin group, (3) MCC950 group, (4) low dose polydatin group (Polydatin-L), (5) medium dose polydatin group (Polydatin-M), (6) and high dose polydatin group (Polydatin-H). The C57BL/6J mice were treated as controls and administered a standard chow diet. All mice were gavaged once daily for 8 weeks. The distribution of aortic plaques was observed by En Oil-red-O staining and hematoxylin and eosin staining (H&E). Oil-red-O staining was used to observe lipid content in the aortic sinus plaque; Masson trichrome staining was used to gauge collagen content in the plaque; and immunohistochemistry was used to evaluate smooth muscle actin (α-SMA) and CD68 macrophages marker expression levels in the plaque, which were used to assess the vulnerability index of the plaque. The lipid levels were measured using an enzymatic assay with an automatic biochemical analyzer. The level of inflammation was detected by enzyme-linked-immunosorbent assay (ELISA). Autophagosomes were detected by transmission electron microscopy (TEM). Pyroptosis was detected by terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL)/caspase-1 and other proteins related to the expression levels of autophagy and pyroptosis were detected by Western blot analysis.

RESULTS

Nucleotide oligomerization (NOD)-like receptor (NLR) family pyrin domain-containing protein 3 (NLRP3) inflammasome activation leads to pyroptosis, including the cleavage of caspase-1, interleukin (IL)-1β and IL-18 production, and the co-expression of TUNEL/caspase-1-all of these are inhibited by polydatin, whose inhibitory effect is similar to that of MCC950, a specific inhibitor of NLRP3. Further, polydatin decreased the protein expression of NLRP3 and the phosphorylated mammalian target of rapamycin (p-mTOR), and increased the number of autophagosomes as well as the increased the cytoplasmic microtubule-associated protein light chain 3 (LC3)/autophagosome membrane-type LC3 ratio. Moreover, the protein expression levels of p62 decreased, suggesting that polydatin can increase autophagy.

CONCLUSIONS

Polydatin can inhibit the activation of the NLRP3 inflammasome and cleavage of caspase-1, thereby inhibiting pyroptosis and secretion of inflammatory cytokines, and promoting autophagy through NLRP3/mTOR pathway in AS.

Mitochondrial control of innate immune responses

Mitochondria are versatile organelles and essential components of numerous biological processes such as energy metabolism, signal transduction, and cell fate determination. In recent years, their critical roles in innate immunity have come to the forefront, highlighting impacts on pathogenic defense, tissue homeostasis, and degenerative diseases. This review offers an in-depth and comprehensive examination of the multifaceted mechanisms underlying the interactions between mitochondria and innate immune responses. We will delve into the roles of healthy mitochondria as platforms for signalosome assembly, the release of mitochondrial components as signaling messengers, and the regulation of signaling via mitophagy, particularly to cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling and inflammasomes. Furthermore, the review will explore the impacts of mitochondrial proteins and metabolites on modulating innate immune responses, the polarization of innate immune cells, and their implications on infectious and inflammatory diseases.

Inflammasomes and Atherosclerosis: a Mixed Picture

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

Exploring the effect of Er miao San-containing serum on macrophage polarization through miR-33/NLRP3 pathway

HEADINGS ETHNOPHARMACOLOGICAL RELEVANCE

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease. Er miao San (EMS) has been shown to have good anti-inflammatory effects and is widely used in the clinical treatment of RA. However, the exact mechanism is not completely understood.

AIM OF THE STUDY

The aim of this study was to explore that EMS-containing serum affects M1/M2 polarization of macrophages and may be mediated through the microRNA (miRNA)-33/NLRP3 pathway, thereby elucidating the molecular mechanism of EMS treatment of RA.

MATERIALS AND METHODS

We screened for safe concentrations of EMS-containing serum by using CCK-8 measurement. RAW264.7 cells were cultured with lipopolysaccharide (LPS) (100 ng/mL) and interferon-γ (20 ng/mL) for 24 h to induce M1-type macrophages. Adenosine triphosphate (ATP) (5 mM) was added in the last 30 min to activate NLRP3. The content of miR-33 was detected by RT‒qPCR after transfection of the miRNA-33 mimic. The protein expression levels of NLRP3, ASC, caspase-1, Inducible Nitric Oxide Synthase (iNOS) and Arginase-1 (Arg-1) were detected by Western blot. The contents of IL-1β, IL-10, TNF-α, TGF-β and IL-18 in serum and cell supernatant were determined by ELISA. The fluorescence intensity of CD86 and CD206 was detected by immunofluorescence.

RESULTS

The results showed that EMS-containing serum promoted the protein expression level of Arg-1 and the secretion levels of TGF-β and IL-10, inhibited the levels of iNOS, IL-1β and TNF-α, and regulated the balance of pro-inflammatory factors and anti-inflammatory factors. RT‒qPCR results showed that EMS-containing serum could reduce the level of miRNA-33. EMS-containing serum could reduce the expression of NLRP3 inflammasome-related proteins and downregulate the expression levels of IL-1β and IL-18. These results suggest that EMS exerts its effect on macrophage polarization through the miRNA-33/NLRP3 pathway.

CONCLUSION

EMS-containing serum inhibits the activation of the NLRP3 inflammasome by downregulating miRNA-33, thus preventing the polarization of M1-type macrophages.

Oxidized mitochondrial DNA: a protective signal gone awry

Despite the emergence of mitochondria as key regulators of innate immunity, the mechanisms underlying the generation and release of immunostimulatory alarmins by stressed mitochondria remains nebulous. We propose that the major mitochondrial alarmin in myeloid cells is oxidized mitochondrial DNA (Ox-mtDNA). Fragmented Ox-mtDNA enters the cytosol where it activates the NLRP3 inflammasome and generates IL-1β, IL-18, and cGAS-STING to induce type I interferons and interferon-stimulated genes. Inflammasome activation further enables the circulatory release of Ox-mtDNA by opening gasdermin D pores. We summarize new data showing that, in addition to being an autoimmune disease biomarker, Ox-mtDNA converts beneficial transient inflammation into long-lasting immunopathology. We discuss how Ox-mtDNA induces short- and long-term immune activation, and highlight its homeostatic and immunopathogenic functions.

Cigarette smoke induces mitochondrial DNA damage and activates cGAS-STING pathway: application to a biomarker for atherosclerosis

Cigarette smoking is a major risk factor for atherosclerosis. We previously reported that DNA damage was accumulated in atherosclerotic plaque, and was increased in human mononuclear cells by smoking. As vascular endothelial cells are known to modulate inflammation, we investigated the mechanism by which smoking activates innate immunity in endothelial cells focusing on DNA damage. Furthermore, we sought to characterize the plasma level of cell-free DNA (cfDNA), a result of mitochondrial and/or genomic DNA damage, as a biomarker for atherosclerosis. Cigarette smoke extract (CSE) increased DNA damage in the nucleus and mitochondria in human endothelial cells. Mitochondrial damage induced minority mitochondrial outer membrane permeabilization, which was insufficient for cell death but instead led to nuclear DNA damage. DNA fragments, derived from the nucleus and mitochondria, were accumulated in the cytosol, and caused a persistent increase in IL-6 mRNA expression via the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway. cfDNA, quantified with quantitative PCR in culture medium was increased by CSE. Consistent with in vitro results, plasma mitochondrial cfDNA (mt-cfDNA) and nuclear cfDNA (n-cfDNA) were increased in young healthy smokers compared with age-matched nonsmokers. Additionally, both mt-cfDNA and n-cfDNA were significantly increased in patients with atherosclerosis compared with the normal controls. Our multivariate analysis revealed that only mt-cfDNA predicted the risk of atherosclerosis. In conclusion, accumulated cytosolic DNA caused by cigarette smoke and the resultant activation of the cGAS-STING pathway may be a mechanism of atherosclerosis development. The plasma level of mt-cfDNA, possibly as a result of DNA damage, may be a useful biomarker for atherosclerosis.

Next-Generation Sequencing in the Assessment of the Transcriptomic Landscape of DNA Damage Repair Genes in Abdominal Aortic Aneurysm, Chronic Venous Disease and Lower Extremity Artery Disease

Vascular diseases are one of the most common causes of death and morbidity. Lower extremity artery disease (LEAD), abdominal aortic aneurysm (AAA) and chronic venous disease (CVD) belong to this group of conditions and exhibit various presentations and courses; thus, there is an urgent need for revealing new biomarkers for monitoring and potential treatment. Next-generation sequencing of mRNA allows rapid and detailed transcriptome analysis, allowing us to pinpoint the most pronounced differences between the mRNA expression profiles of vascular disease patients. Comparison of expression data of 519 DNA-repair-related genes obtained from mRNA next-generation sequencing revealed significant transcriptomic marks characterizing AAA, CVD and LEAD. Statistical, gene set enrichment analysis (GSEA), gene ontology (GO) and literature analyses were applied and highlighted many DNA repair and accompanying processes, such as cohesin functions, oxidative stress, homologous recombination, ubiquitin turnover, chromatin remodelling and DNA double-strand break repair. Surprisingly, obtained data suggest the contribution of genes engaged in the regulatory function of DNA repair as a key component that could be used to distinguish between analyzed conditions. DNA repair-related genes depicted in the presented study as dysregulated in AAA, CVD and LEAD could be utilized in the design of new biomarkers or therapies associated with these diseases.

Oxidative Stress-Mediated Programmed Cell Death: a Potential Therapy Target for Atherosclerosis

Nowadays, as a type of orderly and active death determined by genes, programmed cell death (PCD), including apoptosis, pyroptosis, ferroptosis, and necroptosis, has attracted much attention owing to its participation in numerous chronic cardiovascular diseases, especially atherosclerosis (AS), a canonical chronic inflammatory disease featured by lipid metabolism disturbance. Abundant researches have reported that PCD under distinct internal conditions fulfills different roles of atherosclerotic pathological processes, including lipid core expansion, leukocyte adhesion, and infiltration. Noteworthy, emerging evidence recently has also suggested that oxidative stress (OS), an imbalance of antioxidants and oxygen free radicals, has the potential to mediate PCD occurrence via multiple ways, including oxidization and deubiquitination. Interestingly, more recently, several studies have proposed that the mediating mechanisms could effect on the atherosclerotic initiation and progression significantly from variable aspects, so it is of great clinical importance to clarify how OS-mediated PCD and AS interact. Herein, with the aim of summarizing potential and sufficient atherosclerotic therapy targets, we seek to provide extensive analysis of the specific regulatory mechanisms of PCD mediated by OS and their multifaceted effects on the entire pathological atherosclerotic progression.

Smooth muscle cell fate decisions decipher a high-resolution heterogeneity within atherosclerosis molecular subtypes

BACKGROUND

Mounting evidence has revealed the dynamic variations in the cellular status and phenotype of the smooth muscle cell (SMC) are vital for shaping the atherosclerotic plaque microenvironment and ultimately mapping onto heterogeneous clinical outcomes in coronary artery disease. Currently, the underlying clinical significance of SMC evolutions remains unexplored in atherosclerosis.

METHODS

The dissociated cells from diseased segments within the right coronary artery of four cardiac transplant recipients and 1070 bulk samples with atherosclerosis from six bulk cohorts were retrieved. Following the SMC fate trajectory reconstruction, the MOVICS algorithm integrating the nearest template prediction was used to develop a stable and robust molecular classification. Subsequently, multi-dimensional potential biological implications, molecular features, and cell landscape heterogeneity among distinct clusters were decoded.

RESULTS

We proposed an SMC cell fate decision signature (SCFDS)-based atherosclerosis stratification system and identified three SCFDS subtypes (C1-C3) with distinguishing features: (i) C1 (DNA-damage repair type), elevated base excision repair (BER), DNA replication, as well as oxidative phosphorylation status. (ii) C2 (immune-activated type), stronger immune activation, hyper-inflammatory state, the complex as well as varied lesion microenvironment, advanced stage, the most severe degree of coronary stenosis severity. (iii) C3 (stromal-rich type), abundant fibrous content, stronger ECM metabolism, immune-suppressed microenvironment.

CONCLUSIONS

This study uncovered atherosclerosis complex cellular heterogeneity and a differentiated hierarchy of cell populations underlying SMC. The novel high-resolution stratification system could improve clinical outcomes and facilitate individualized management.

Effect of Er Miao San on peritoneal macrophage polarisation through the miRNA-33/NLRP3 signalling pathway in a rat model of adjuvant arthritis

CONTEXT

Er Miao San (EMS) is a formulation that contains Atractylodis Rhizoma and Phellodendri Cortex in 1:1 ratio, and is commonly used to treat rheumatoid arthritis (RA) and other inflammatory diseases.

OBJECTIVE

We investigated the mechanism of action and effects of EMS on peritoneal macrophage differentiation in a rat model of adjuvant arthritis (AA).

MATERIALS AND METHODS

EMS (3, 1.5 and 0.75 g/kg; once daily) and methotrexate (0.5 mg/kg; once every 3 days) were administered orally from days 21 to 35 after immunisation. Paw swelling and arthritis index were measured; pathological changes in the ankle joint were observed using x-ray and haematoxylin eosin staining. The ratio of CD86/CD206 in macrophages was detected by flow cytometry. Examination of the miRNA-33/NLRP3 signalling pathway was examined by RT-qPCR and western blotting. The levels of cytokines in the serum and cell supernatants were tested by ELISA.

RESULTS

EMS significantly reduced the AA index in rats (from 11.0 to 9.3) and pathological changes in the ankle joint (from 3.8 to 1.4). The ratio of CD86/CD206 was reduced, and polarisation to M1 improved (from 0.9 to 0.6) in macrophages of EMS-treated rats. EMS downregulated the miRNA-33/NLRP3 pathway. Furthermore, EMS treatment increased IL-10 and TGF-β levels in the serum and supernatant of macrophages of AA rats and simultaneously decreased the levels of IL-1β and TNF-α.

DISCUSSION AND CONCLUSIONS

Our results suggest that EMS may reduce macrophage polarisation to the M1 inflammatory phenotype by downregulating the miRNA-33/NLRP3 pathway in AA rats. These findings may provide new insights into the treatment of RA.

Brown adipose tissue-derived Nrg4 alleviates endothelial inflammation and atherosclerosis in male mice

Brown adipose tissue (BAT) activity contributes to cardiovascular health by its energy-dissipating capacity but how BAT modulates vascular function and atherosclerosis through endocrine mechanisms remains poorly understood. Here we show that BAT-derived neuregulin-4 (Nrg4) ameliorates atherosclerosis in mice. BAT-specific Nrg4 deficiency accelerates vascular inflammation and adhesion responses, endothelial dysfunction and apoptosis and atherosclerosis in male mice. BAT-specific Nrg4 restoration alleviates vascular inflammation and adhesion responses, attenuates leukocyte homing and reduces endothelial injury and atherosclerosis in male mice. In endothelial cells, Nrg4 decreases apoptosis, inflammation and adhesion responses induced by oxidized low-density lipoprotein. Mechanistically, protein kinase B (Akt)-nuclear factor-κB signaling is involved in the beneficial effects of Nrg4 on the endothelium. Taken together, the results reveal Nrg4 as a potential cross-talk factor between BAT and arteries that may serve as a target for atherosclerosis.

NLRP3 inflammasome: The rising star in cardiovascular diseases

Cardiovascular diseases (CVDs) are the prevalent cause of mortality around the world. Activation of inflammasome contributes to the pathological progression of cardiovascular diseases, including atherosclerosis, abdominal aortic aneurysm, myocardial infarction, dilated cardiomyopathy, diabetic cardiomyopathy, heart failure, and calcific aortic valve disease. The nucleotide oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasome plays a critical role in the innate immune response, requiring priming and activation signals to provoke the inflammation. Evidence shows that NLRP3 inflammasome not only boosts the cleavage and release of IL-1 family cytokines, but also leads to a distinct cell programmed death: pyroptosis. The significance of NLRP3 inflammasome in the CVDs-related inflammation has been extensively explored. In this review, we summarized current understandings of the function of NLRP3 inflammasome in CVDs and discussed possible therapeutic options targeting the NLRP3 inflammasome.

DNA damage, inflammation and aging: Insights from mice

Persistent DNA lesions build up with aging triggering inflammation, the body’s first line of immune defense strategy against foreign pathogens and irritants. Once established, DNA damage-driven inflammation takes on a momentum of its own, due to the amplification and feedback loops of the immune system leading to cellular malfunction, tissue degenerative changes and metabolic complications. Here, we discuss the use of murine models with inborn defects in genome maintenance and the DNA damage response for understanding how irreparable DNA lesions are functionally linked to innate immune signaling highlighting their relevance for developing novel therapeutic strategies against the premature onset of aging-associated diseases.

The landscape of aging

Aging is characterized by a progressive deterioration of physiological integrity, leading to impaired functional ability and ultimately increased susceptibility to death. It is a major risk factor for chronic human diseases, including cardiovascular disease, diabetes, neurological degeneration, and cancer. Therefore, the growing emphasis on “healthy aging” raises a series of important questions in life and social sciences. In recent years, there has been unprecedented progress in aging research, particularly the discovery that the rate of aging is at least partly controlled by evolutionarily conserved genetic pathways and biological processes. In an attempt to bring full-fledged understanding to both the aging process and age-associated diseases, we review the descriptive, conceptual, and interventive aspects of the landscape of aging composed of a number of layers at the cellular, tissue, organ, organ system, and organismal levels.

Oxidized DNA fragments exit mitochondria via mPTP- and VDAC-dependent channels to activate NLRP3 inflammasome and interferon signaling

Mitochondrial DNA (mtDNA) escaping stressed mitochondria provokes inflammation via cGAS-STING pathway activation and, when oxidized (Ox-mtDNA), it binds cytosolic NLRP3, thereby triggering inflammasome activation. However, it is unknown how and in which form Ox-mtDNA exits stressed mitochondria in non-apoptotic macrophages. We found that diverse NLRP3 inflammasome activators rapidly stimulated uniporter-mediated calcium uptake to open mitochondrial permeability transition pores (mPTP) and trigger VDAC oligomerization. This occurred independently of mtDNA or reactive oxygen species, which induce Ox-mtDNA generation. Within mitochondria, Ox-mtDNA was either repaired by DNA glycosylase OGG1 or cleaved by the endonuclease FEN1 to 500-650 bp fragments that exited mitochondria via mPTP- and VDAC-dependent channels to initiate cytosolic NLRP3 inflammasome activation. Ox-mtDNA fragments also activated cGAS-STING signaling and gave rise to pro-inflammatory extracellular DNA. Understanding this process will advance the development of potential treatments for chronic inflammatory diseases, exemplified by FEN1 inhibitors that suppressed interleukin-1β (IL-1β) production and mtDNA release in mice.

New insights into macrophage subsets in atherosclerosis

Macrophages in atherosclerotic patients are notably plastic and heterogeneous. Single-cell RNA sequencing (Sc RNA-seq) can provide information about all the RNAs in individual cells, and it is used to identify cell subpopulations in atherosclerosis (AS) and reveal the heterogeneity of these cells. Recently, some findings from Sc RNA-seq experiments have suggested the existence of multiple macrophage subsets in atherosclerotic plaque lesions, and these subsets exhibit significant differences in their gene expression levels and functions. These cells affect various aspects of plaque lesion development, stabilization, and regression, as well as plaque rupture. This article aims to review the content and results of current studies that used RNA-seq to explore the different types of macrophages in AS and the related molecular mechanisms as well as to identify the potential roles of these macrophage types in the pathogenesis of atherosclerotic plaques. Also, this review listed some new therapeutic targets for delaying atherosclerotic lesion progression and treatment based on the experimental results.

Relationship between Brain Metabolic Disorders and Cognitive Impairment: LDL Receptor Defect

The low-density-lipoprotein receptor (LDLr) removes low-density lipoprotein (LDL), an endovascular transporter that carries cholesterol from the bloodstream to peripheral tissues. The maintenance of cholesterol content in the brain, which is important to protect brain function, is affected by LDLr. LDLr co-localizes with the insulin receptor and complements the internalization of LDL. In LDLr deficiency, LDL blood levels and insulin resistance increase, leading to abnormal cholesterol control and cognitive deficits in atherosclerosis. Defects in brain cholesterol metabolism lead to neuroinflammation and blood–brain-barrier (BBB) degradation. Moreover, interactions between endoplasmic reticulum stress (ER stress) and mitochondria are induced by ox-LDL accumulation, apolipoprotein E (ApoE) regulates the levels of amyloid beta (Aβ) in the brain, and hypoxia is induced by apoptosis induced by the LDLr defect. This review summarizes the association between neurodegenerative brain disease and typical cognitive deficits.

HSF1 Protects Sepsis-Induced Acute Lung Injury by Inhibiting NLRP3 Inflammasome Activation

As an important transcription factor, heat shock factor 1 (HSF1) plays an endogenous anti-inflammation role in the body and can alleviate multiple organ dysfunction caused by sepsis, which contributes to an uncontrolled inflammatory response. The NLRP3 inflammasome is a supramolecular complex that plays key roles in immune surveillance. Inflammation is accomplished by NLRP3 inflammasome activation, which leads to the proteolytic maturation of IL-1β and pyroptosis. However, whether HSF1 is involved in the activation of the NLRP3 inflammasome in septic acute lung injury (ALI) has not been reported. Here, we show that HSF1 suppresses NLRP3 inflammasome activation in transcriptional and post-translational modification levels. HSF1 can repress NLRP3 expression via inhibiting NF-κB phosphorylation. HSF1 can inhibit caspase-1 activation and IL-1β maturation via promoting NLRP3 ubiquitination. Our finding not only elucidates a novel mechanism for HSF1-mediated protection of septic ALI but also identifies new therapeutic targets for septic ALI and related diseases.

DNA double-strand break repair and nucleic acid-related immunity

DNA damage repair and innate immunity are two conserved mechanisms that both function in cellular stress responses. Recently, an increasing amount of evidence has uncovered the close relationship between these two ancient biological processes. Here, we review the classical function of factors involved in DNA repair, and especially double-strand break repair, in innate immunity; more importantly, we discuss the novel roles of DNA repair factors in regulating innate immunity and vice versa. In addition, we also review the roles of DNA repair, innate immunity and their crosstalk in human diseases, which suggest that these two pathways may be compelling targets for disease prevention and treatment.

Nur77 Deficiency Exacerbates Macrophage NLRP3 Inflammasome-Mediated Inflammation and Accelerates Atherosclerosis

Purpose

Activation of NLR (nucleotide-binding and leucine-rich repeat immune receptor) family pyrin domain containing 3 (NLRP3) inflammasome mediating interleukin- (IL-) 1β secretion has emerged as an important component of inflammatory processes in atherogenesis. The nuclear receptor Nur77 is highly expressed in human atherosclerotic lesions; however, its functional role in macrophage NLRP3 inflammasome activation has not yet been clarified. Methods, Materials, and Results. Eight-week-old apolipoprotein E (ApoE)−/− and ApoE−/− Nur77−/− mice that were fed a Western diet underwent partial ligation of the left common carotid artery (LCCA) and left renal artery (LRA) to induce atherogenesis. Four weeks later, severe plaque burden associated with increased lipid deposition, reduced smooth muscle cells, macrophage infiltration, and decreased collagen expression was identified in ApoE−/− Nur77−/− mice compared with those in ApoE−/− mice. ApoE−/− Nur77−/− mice showed increased macrophage inflammatory responses in carotid atherosclerotic lesions. In vitro studies demonstrated that oxidized low-density lipoprotein cholesterol (ox-LDL) increased the release of lactate dehydrogenase (LDH) and upregulated the expressions of cleaved caspase-1, cleaved IL-1β and gasdermin D (GSMD) in WT peritoneal macrophages (PMs) in a NLRP3-dependent manner. Nur77−/− PMs exhibited a further increased level of NLRP3 inflammasome-mediated inflammation under ox-LDL treatment compared with WT PMs. Mechanistically, Nur77 could bind to the promoter of NLRP3 and inhibit its transcriptional activity.

Conclusions

This study demonstrated that Nur77 deletion promotes atherogenesis by exacerbating NLRP3 inflammasome-mediated inflammation.