An Acetylation Switch of the NLRP3 Inflammasome Regulates Aging-Associated Chronic Inflammation and Insulin Resistance

Regulation of Stem Cell Function by NAD. Physiology (Bethesda) 2025;40:0. [PMID: 39907078 DOI: 10.1152/physiol.00052.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Nicotinamide adenine dinucleotide (NAD+), a coenzyme in cellular metabolism, has never ceased to capture the fascination of scientists since its discovery in 1906. The expansion of NAD+'s function from cellular metabolism to DNA repair, gene regulation, cell signaling, and aging reflects the central role of cellular metabolism in orchestrating the diverse cellular pathways. In the past decade, NAD+ has emerged as a key regulator of stem cells, opening the door to potential approaches for regenerative medicine. Here we reflect on how the field of NAD+ regulation of stem cells has evolved since a decade ago, when sirtuins, NAD+-dependent enzymes, were shown to be critical regulators of stem cells. We review the recent development on how NAD+ is regulated in stem cells to influence fate decision. We discuss the difference in NAD+ regulation of normal and cancer stem cells. Finally, we consider the consequences of NAD+ regulation of stem cells for health and diseases.

Discovery of novel Bis-amide analogue ST12 for the treatment of inflammatory bowel diseases (IBD) by inhibiting NLRP3 inflammasome activation

Herein, we designed and synthesized a series of novel bis-amide small molecule anti-inflammatory agents, among them, compound ST12 showed most potent anti-inflammatory activity. ST12 effectively inhibited the production of nitric oxide (NO) (inhibition rate of 52.67 ± 0.03 % at 10 μM) and downregulated the mRNA levels of proinflammatory cytokines iNOS, IL-6, IL-1β and TNF-α in lipopolysaccharide (LPS) induced RAW264.7 cells. Furthermore, mechanism studies suggest that compound ST12 exerted anti-inflammatory effects by inhibiting the activation of the NLRP3 inflammasome. Importantly, ST12 effectively ameliorated DSS-induced colitis in vivo. Taken together, ST12 is worthy of further investigation as a small molecule anti-inflammatory agent for treatment of inflammatory bowel diseases (IBD).

Hydrogen sulfide preserves the function of senescent endothelium through SIRT2 mediated inflammatory inhibition

Endothelial aging is an independent risk factor of cardiovascular diseases, and this study aims to explore the mechanism of endothelial aging. We first applied two animal aging models and two cellular aging models to observe the characteristics of senescent endothelium at the morphological, functional, and molecular levels. It was confirmed that the aging of endothelial cells was accompanied by activation of Nod like receptor protein 3 (NLRP3) inflammasome pathway, reduced levels of hydrogen sulfide (H2S) and sirtuin2 (SIRT2) activity. Endothelial specific knockout of cystathionine-γ-lyase (CSE) led to premature aging of blood vessels, and excessive activation of the SIRT2/NLRP3 inflammasome. Finally, H2S supplementation improved vascular and endothelial cell function, normalized inflammatory cytokine levels, and thereby reversed endothelial aging through SIRT2/NLRP3 mediated pathway. In this study, we found that the decrease in SIRT2 activity in aging endothelial cells increased the level of NLRP3 inflammasome and H2S inhibited inflammation to improve endothelial aging through the SIRT2/NLRP3 pathway. This provided H2S could be a new target for improving endothelial aging, and offered new strategies for defending human aging.

Global Analysis of the Lysine Acetylome in Macrophages from Salt-sensitive Hypertensive Rats

Research indicates that patients with salt-sensitive (SS) hypertension experience higher morbidity and target organ damage than in patients with non-SS hypertension. Dysregulated macrophage activation has been implicated in SS hypertension development, with lysine acetylation playing a role in modulating macrophage function. However, the role of macrophage acetylation patterns in SS hypertension remains unclear. This study aimed to investigate how acetylation regulates macrophage function and its role in the pathogenesis of SS hypertension. We employed quantitative acetylation proteomics to characterize the acetylome of bone marrow-derived macrophages in Dahl SS hypertensive rats fed either a high-salt or a low-salt diet. We identified 94 hyperacetylated and 49 hypoacetylated sites on 79 and 45 proteins, respectively, in the high-salt group. Notably, acetylation levels increased at lysine 20 (K20) and K46 on histone H2B, at K56 on H3, and at K77 and K79 on H4c2. We also identified conserved acetylation motifs, analyzed their Gene Ontology terms and pathways, and explored the protein-protein interactions of these differentially acetylated proteins using bioinformatics analyses. Finally, we validated the altered acetylation of H2, H3, H4, and several metabolic proteins using immunoprecipitation and western blotting. Overall, these findings offer insights into the role of lysine acetylation in macrophages from SS hypertensive rats, revealing potential therapeutic targets.

NLRP3 Inflammasome-mediated pyroptosis in acute lung injury: Roles of main lung cell types and therapeutic perspectives

The NLRP3 inflammasome plays a pivotal role in the pathogenesis of acute lung injury (ALI) by regulating pyroptosis, a highly inflammatory form of programmed cell death. NLRP3-mediated pyroptosis leads to alveolar epithelial cell injury, increased pulmonary microvascular endothelial permeability, excessive alveolar macrophage activation, and neutrophil dysfunction, collectively driving ALI progression. In addition to the classical NLRP3-dependent pathway, the non-canonical pyroptosis pathway (caspase-4/5/11) also contributes to ALI by inducing pyroptotic cell death in AECs and ECs, further amplifying NLRP3 activation through damage-associated molecular patterns (DAMP) release. Moreover, neutrophils (NE) pyroptosis exhibits dual roles in ALI, as it enhances pathogen clearance but also exacerbates excessive inflammation and tissue damage, highlighting the complexity of its regulation. Targeting the NLRP3 inflammasome and pyroptotic pathways has emerged as a promising therapeutic strategy for ALI. Various NLRP3 inhibitors (e.g., MCC950, CY-09, OLT1177) and pyroptosis inhibitors have demonstrated significant anti-inflammatory and tissue-protective effects in preclinical models. However, the clinical translation of NLRP3-targeted therapies remains challenging due to off-target effects, potential immunosuppression, lack of patient stratification strategies, and compensatory activation of alternative inflammasomes (e.g., AIM2, NLRC4). Future studies should focus on optimizing the selectivity of NLRP3 inhibitors, developing personalized therapeutic approaches, and exploring combination strategies to enhance their clinical applicability in ALI.

Itaconate: A Potential Therapeutic Strategy for Autoimmune Disease

Itaconate is a metabolite of the Krebs cycle, and endogenous itaconate is driven by a variety of innate signals that inhibit the production of inflammatory cytokines. The key mechanism of action of itaconate was initially found to be the competitive inhibition of succinate dehydrogenase (SDH), which inhibits the production of inflammatory factors, as well as its antioxidant effects. With increasing research, it was discovered that it modifies cysteine residues of related proteins through the Michael addition, such as modifying the Kelch-like ECH-associated protein 1 (KEAP1) protein and activating the nuclear factor erythroid 2-related factor 2 (NRF2) signalling pathway, as well as glycolytic enzymes and cellular pathway-associated factors that attenuate inflammatory responses and oxidative stress. It also acts on a variety of immune cells, affecting their function and activity, and has been increasingly shown to play a therapeutic role in a variety of inflammatory and autoimmune diseases through a combination of these mechanisms. In conclusion, there has been a great breakthrough in the research of itaconate, from the initial industrial application to the redefinition of the biological functions of itaconate. However, with the deepening of the research, we also found that there are more questions: the mechanism of action of itaconate, more functions of itaconate, clinical application of itaconate, and the use of itaconate still needs to be solved.

The Role of NAD+ Metabolism in Cardiovascular Diseases: Mechanisms and Prospects

Nicotinamide adenine dinucleotide (NAD+) is a promising anti-aging molecule that plays a role in cellular energy metabolism and maintains redox homeostasis. Additionally, NAD+ is involved in regulating deacetylases, DNA repair enzymes, inflammation, and epigenetics, making it indispensable in maintaining the basic functions of cells. Research on NAD+ has become a hotspot, particularly regarding its potential in cardiovascular disease (CVD). Many studies have demonstrated that NAD+ plays a crucial role in the occurrence and development of CVD. This review summarizes the biosynthesis and consumption of NAD+, along with its precursors and their effects on raising NAD+ levels. We also discuss new mechanisms of NAD+ regulation in cardiovascular risk factors and its effects of NAD+ on atherosclerosis, aortic aneurysm, heart failure, hypertension, myocardial ischemia-reperfusion injury, diabetic cardiomyopathy, and dilated cardiomyopathy, elucidating different mechanisms and potential treatments. NAD+-centered therapy holds promising advantages and prospects in the field of CVD.

Metformin activates SIRT2 to improve insulin resistance and promote granulosa cell glycolysis in a rat model of polycystic ovary syndrome

RESEARCH QUESTION

What is the mechanism by which metformin enhances insulin sensitivity, improves granulosa cell glycolysis and induces ovulation in a rat model of polycystic ovary syndrome (PCOS)?

DESIGN

Analysis of the GSE168404 gene expression profile in the Gene Expression Omnibus database revealed increased levels of IGF1 and decreased levels of glycolytic enzymes (HK2, LDHA, PKM2) in the granulosa cells of PCOS patients. To explore the effects of metformin on the imbalance in glycolysis induced by insulin resistance (IR), experiments were conducted using Sprague-Dawley rats and KGN cells (human ovarian granulosa cells). Oestrous cycles were monitored in control, PCOS model (induced by letrozole and a high-fat diet) and metformin-treated PCOS groups. Analyses of body weight, hormone concentrations and biochemical, histopathological, immunohistochemical and glycolytic pathways were performed. KGN cells were used to model insulin resistance with insulin, and AGK2 was used specifically to inhibit sirtuin 2 (SIRT2), while metformin was applied.

RESULTS

Metformin significantly improved insulin resistance in PCOS rats, reduced insulin-like growth factor 1 (IGF1) protein and mRNA expression (all P ≤ 0.0348) and increased IGF1 receptor (IGF1R) impression (all P ≤ 0.0361). Insulin inhibited glycolytic activity in KGN cells, but metformin attenuated this effect (all P ≤ 0.0255). Metformin reversed the inhibition of SIRT2 in PCOS rat ovaries (all P ≤ 0.0483) and restored glycolysis in KGN cells treated by AGK2 (all P ≤ 0.0369).

CONCLUSION

Metformin enhances insulin sensitivity and restores glycolysis by regulating SIRT2, which may improve follicular development and reduce ovarian damage in PCOS rats, offering a potential clinical treatment strategy for PCOS.

Updated insights into the molecular networks for NLRP3 inflammasome activation

Over the past decade, significant advances have been made in our understanding of how NACHT-, leucine-rich-repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasomes are activated. These findings provide detailed insights into the transcriptional and posttranslational regulatory processes, the structural-functional relationship of the activation processes, and the spatiotemporal dynamics of NLRP3 activation. Notably, the multifaceted mechanisms underlying the licensing of NLRP3 inflammasome activation constitute a focal point of intense research. Extensive research has revealed the interactions of NLRP3 and its inflammasome components with partner molecules in terms of positive and negative regulation. In this Review, we provide the current understanding of the complex molecular networks that play pivotal roles in regulating NLRP3 inflammasome priming, licensing and assembly. In addition, we highlight the intricate and interconnected mechanisms involved in the activation of the NLRP3 inflammasome and the associated regulatory pathways. Furthermore, we discuss recent advances in the development of therapeutic strategies targeting the NLRP3 inflammasome to identify potential therapeutics for NLRP3-associated inflammatory diseases. As research continues to uncover the intricacies of the molecular networks governing NLRP3 activation, novel approaches for therapeutic interventions against NLRP3-related pathologies are emerging.

SIRT2 suppresses aging-associated cGAS activation and protects aged mice from severe COVID-19

Aging-associated vulnerability to coronavirus disease 2019 (COVID-19) remains poorly understood. Here, we show that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected aged mice lacking SIRT2, a cytosolic NAD+-dependent deacetylase, develop more severe disease and show increased mortality, while treatment with an NAD+ booster, 78c, protects aged mice from lethal infection. Mechanistically, we demonstrate that SIRT2 modulates the acetylation of cyclic GMP-AMP synthase (cGAS), an immune sensor for cytosolic DNA, and suppresses aging-associated cGAS activation and inflammation. Furthermore, we show that SARS-CoV-2 infection-induced inflammation is mediated at least in part by ORF3a, which triggers mtDNA release and cGAS activation. Collectively, our study reveals a molecular basis for aging-associated susceptibility to COVID-19 and suggests therapeutic approaches to protect aged populations from severe SARS-CoV-2 infection.

Exosomes secreted from adipose-derived stem cells inhibit M1 macrophage polarization ameliorate chronic endometritis by regulating SIRT2/NLRP3

Chronic endometritis (CE) is a key factor in adverse pregnancy outcomes such as miscarriage and infertility. Macrophages are an important immune cell type that secrete pro-inflammatory and anti-inflammatory cytokines that are essential for maintaining endometrial function. This study aimed to investigate the key mechanisms by which exosomes derived from adipose-derived mesenchymal stem cells (ADSCs) regulate macrophage polarization through the sirtuin 2 (SIRT2)/NOD-like receptor pyrin containing 3 (NLRP3) axis and exert a protective effect on CE. Exosomes were obtained from ADSCs (ADSCs-exo) using the classical ultracentrifugation method and characterized using transmission electron microscopy, nanoparticle tracking analysis, and western blotting. ADSCs-exo protective effects on CE mice and RAW 264.7 cells and its related molecular mechanisms were investigated using real-time quantitative polymerase chain reaction, western blotting, enzyme-linked immunosorbent assay, flow cytometry, immunofluorescence, immunoprecipitation, hematoxylin and eosin staining, and immunohistochemistry. ADSCs-exo significantly inhibited M1 macrophage polarization, as evidenced by a 54% reduction in tumor necrosis factor alfa (TNF-α), a 46% reduction in interleukin 1β (IL-1β), and a 36% reduction in interleukin 6 (IL-6) levels in LPS-induced RAW264.7 cells. In vivo, ADSCs-exo treatment reduced the expression of TNF-α by 50%, IL-1β by 58%, and IL-6 by 49% in the uterine tissues of CE mice. Moreover, ADSCs-exo upregulated the expression of SIRT2, promoted the deacetylation modification of NLRP3 to inhibit NLRP3 inflammasome activation, and further suppressed M1 macrophage polarization. However, these trends were reversed after SIRT2 silencing. Our experimental results demonstrate that ADSCs-exo alleviate CE by regulating the SIRT2/NLRP3 axis to inhibit M1 macrophage polarization. This provides a potential theoretical basis for the therapeutic role of stem cells in CE.

Sirt2 deficiency aggravates intramuscular adipose tissue infiltration and impairs myogenesis with aging in male mice

Sarcopenia, closely associated with other diseases such as diabetes, metabolic syndrome, and osteoporosis, significantly impacts aging populations. It is characterized by muscle atrophy, increased intramuscular adipose tissue, impaired myogenesis, chronic low-grade inflammation, and reduced muscle function. The mechanisms behind aging muscle remain incompletely understood. This study aims to elucidate the role of Sirt2 in the aging process of skeletal muscles and enhance our understanding of the underlying mechanisms. Sirt2 expression was reduced in aging muscle of male mice by 40%, compared to young muscle. Aged male Sirt2 knockout mice exhibit increased intramuscular adipose tissue infiltration by 8.5-fold changes. Furthermore, the deletion of Sirt2 exacerbated myogenesis impairment in aged muscle by decreasing the expression of Pax7 (50%) and NogoA (80%), compared to age- and sex- matched counterparts, emphasizing the role of Sirt2 in pathology of aging muscle. Additionally, long-term Sirt2 deletion affected other Sirtuin subfamily members, with decreased expressions of Sirt1 (65%), Sirt4 (94%), and Sirt5 (71%), and increased expressions of Sirt6 (4.6-fold) and Sirt7 (2.8-fold) in old male Sirt2 knockout mice, while there was no difference of these gene expression in young male mice. This study underscores the critical need for a deeper investigation into Sirt2, promising new insights that could lead to targeted therapies for sarcopenia, ultimately improving the quality of life in the elderly.

Lipoprotein profile as a predictor of type 2 diabetes with sarcopenia: a cross-sectional study

PURPOSE

This study investigated the relationship between lipoprotein profiles and sarcopenia in patients with type 2 diabetes mellitus (T2DM). The objective is to provide a solid theoretical foundation and treatment strategies for clinical prevention and management of diabetes, particularly in individuals with concurrent sarcopenia.

METHODS

In this study, we selected inpatients aged over 60 years diagnosed with T2DM who were admitted to the Department of Geriatrics at Qinghai University Affiliated Hospital from July 2023 to June 2024 as research subjects. We collected general patient data, including gender, age, ethnicity, height, weight, and calculated body mass index (BMI). Key indices measured included glycated hemoglobin (HbA1c), triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apolipoproteins A and B (ApoA and ApoB), phospholipids, lipoprotein(a) [Lp(a)], very low-density lipoprotein (VLDL), and free fatty acids (FFA). Additionally, we assessed limb skeletal muscle mass, grip strength, walking speed, and calculated the appendicular skeletal muscle mass index (ASMI). Based on Asian diagnostic criteria for sarcopenia, patients were categorized into a non-sarcopenic group or a group with T2DM combined with sarcopenia. Baseline laboratory data along with ASMI measurements, grip strength assessments, and walking speeds were statistically analyzed for both groups.

RESULTS

Compared with T2DM patients without sarcopenia, the levels of HbA1c, Lp(a), FFA, serum albumin, TC, TG, HDL-C, ApoA and VLDL in type 2 diabetic patients with sarcopenia were statistically significant (all P < 0.05). When multivariate adjustments were made for these clinical features, age (OR = 1.18, 95%CI: 1.11-1.25, P < 0.001), BMI (OR = 0.81, 95%CI: 0.72-0.92, P < 0.001), ApoA (OR = 0.03, 95%CI: 0.00-0.90, P = 0.043), Lp(a) > = 15.5 mg/dL (OR = 3.14, 95%CI: 1.51-6.54, P = 0.002) and FFA > = 0.48 g/L (OR = 4.11, 95%CI: 1.97-8.57, P < 0.001) were independent predictors of diabetes mellitus with sarcopenia. ROC curve analysis showed that free fatty acids (AUC = 0.721, 95%CI: 0.660-0.782, P < 0.001) in T2DM with sarcopenia has good predictive value judgment.

CONCLUSION

Age, BMI, ApoA, Lp(a), and FFA were independent predictors of T2DM with sarcopenia. Serum free fatty acids have a good predictive value in the judgment of T2DM complicated with sarcopenia.

NLRP3 inflammasome in neuroinflammation and central nervous system diseases

Neuroinflammation plays an important role in the pathogenesis of various central nervous system (CNS) diseases. The NLRP3 inflammasome is an important intracellular multiprotein complex composed of the innate immune receptor NLRP3, the adaptor protein ASC, and the protease caspase-1. The activation of the NLRP3 inflammasome can induce pyroptosis and the release of the proinflammatory cytokines IL-1β and IL-18, thus playing a central role in immune and inflammatory responses. Recent studies have revealed that the NLRP3 inflammasome is activated in the brain to induce neuroinflammation, leading to further neuronal damage and functional impairment, and contributes to the pathological process of various neurological diseases, such as multiple sclerosis, Parkinson's disease, Alzheimer's disease, and stroke. In this review, we summarize the important role of the NLRP3 inflammasome in the pathogenesis of neuroinflammation and the pathological course of CNS diseases and discuss potential approaches to target the NLRP3 inflammasome for the treatment of CNS diseases.

Estimated Glucose Disposal Rate Associated With Risk of Frailty and Likelihood of Reversion

BACKGROUND

Estimated glucose disposal rate (eGDR) is a simple and effective measure for insulin resistance, which is associated with higher risk of frailty. We aim to analyse the associations of eGDR with frailty risk and its reversibility.

METHODS

A population-based longitudinal study was conducted of 11 670 participants from the China Health and Retirement Longitudinal Study and 19 355 participants from the Health and Retirement Study. Frailty was assessed by the frailty index and reversibility was measured by transitions from frailty at baseline to non-frailty during follow-up. The eGDR was divided into Q1, Q2, Q3 and Q4 according to the quartiles. Multi-state Markov model was performed to evaluate the effects of eGDR on transitions among non-frailty, frailty and death. Cox regression model was used to estimate eGDR associated with the risk of frailty and the likelihood of reversion.

RESULTS

In Chinese population characterized by a median age of 60 years (IQR: 54-66) with 6119 women (52.43%), compared with the Q1 level of eGDR, participants exposure to Q3 and Q4 level decreased the probability of transitioning from non-frailty to frailty by 22% (HR = 0.78, 95% CI: 0.69-0.88) and 25% (HR = 0.75, 95% CI: 0.66-0.86), respectively. But its Q2, Q3 and Q4 levels increased the probability of transitioning from frailty to non-frailty by 24% (HR = 1.24, 95% CI: 1.06-1.44), 39% (HR = 1.39, 95% CI: 1.19-1.64) and 33% (HR = 1.33, 95% CI: 1.13-1.58). In American population with a median age of 63 years (IQR: 56-72) and 11 189 women (57.81%), its Q2, Q3 and Q4 levels decreased the probability of transitioning from non-frailty to frailty by 17% (HR = 0.83, 95% CI: 0.77-0.89), 24% (HR = 0.76, 95% CI: 0.70-0.82) and 46% (HR = 0.54, 95% CI: 0.49-0.59), respectively. The probability of revising frailty increased by 25% (HR = 1.25, 95% CI: 1.13-1.38), 36% (HR = 1.36, 95% CI: 1.22-1.51) and 48% (HR = 1.48, 95% CI: 1.30-1.69) for levels Q2, Q3 and Q4. As shown in the prospective analysis, increased eGDR levels from Q2 to Q4 were associated with decreased frailty risk and higher likelihood of reversion, as evidenced by the dose-response relationship revealed by restricted cubic spline analysis.

CONCLUSIONS

Higher levels of eGDR were associated with a reduced risk of frailty, delayed transition from non-frailty to frailty and an increased likelihood of reversion. eGDR emerges as a promising predictor for early frailty detection, prognosis assessment and a potential therapeutic target for intervention strategies.

Systemic aging and aging-related diseases

Aging is a biological process along with systemic and multiple organ dysfunction. It is more and more recognized that aging is a systemic disease instead of a single-organ functional disorder. Systemic aging plays a profound role in multiple diseases including neurodegenerative diseases, cardiovascular diseases, and malignant diseases. Aged organs communicate with other organs and accelerate aging. Skeletal muscle, heart, bone marrow, skin, and liver communicate with each other through organ-organ crosstalk. The crosstalk can be mediated by metabolites including lipids, glucose, short-chain fatty acids (SCFA), inflammatory cytokines, and exosomes. Metabolic disorders including hyperglycemia, hyperinsulinemia, and hypercholesterolemia caused by chronic diseases accelerate hallmarks of aging. Systemic aging leads to the destruction of systemic hemostasis, causes the release of inflammatory cytokines, senescence-associated secretory phenotype (SASP), and the imbalance of microbiota composition. Released inflammatory factors further aggregate senescence, which promotes the aging of multiple solid organs. Targeting senescence or delaying aging is emerging as a critical health strategy for solving age-related diseases, especially in the old population. In the current review, we will delineate the mechanisms of organ crosstalk in systemic aging and age-related diseases to provide therapeutic targets for delaying aging.

A cis-regulatory element controls expression of histone deacetylase 9 to fine-tune inflammasome-dependent chronic inflammation in atherosclerosis

Common genetic variants in a conserved cis-regulatory element (CRE) at histone deacetylase (HDAC)9 are a major risk factor for cardiovascular disease, including stroke and coronary artery disease. Given the consistency of this association and its proinflammatory properties, we examined the mechanisms whereby HDAC9 regulates vascular inflammation. HDAC9 bound and mediated deacetylation of NLRP3 in the NACHT and LRR domains leading to inflammasome activation and lytic cell death. Targeted deletion of the critical CRE in mice increased Hdac9 expression in myeloid cells to exacerbate inflammasome-dependent chronic inflammation. In human carotid endarterectomy samples, increased HDAC9 expression was associated with atheroprogression and clinical plaque instability. Incorporation of TMP195, a class IIa HDAC inhibitor, into lipoprotein-based nanoparticles to target HDAC9 at the site of myeloid-driven vascular inflammation stabilized atherosclerotic plaques, implying a lower risk of plaque rupture and cardiovascular events. Our findings link HDAC9 to atherogenic inflammation and provide a paradigm for anti-inflammatory therapeutics for atherosclerosis.

Relationship Between Metabolic Age Determined by Bioimpedance and Insulin Resistance Risk Scales in Spanish Workers

Introduction: Metabolic age (MA) is the difference between an individual's actual age and the age of their body based on physiological and biological factors. It is an indicator that reflects a person's physical and biological state, regardless of chronological age. Insulin resistance (IR) is a health disorder in which tissues exhibit a reduced response to the circulating glucose uptake stimulated by insulin. Objective: The aim of this study is to evaluate the association between MA, determined through bioelectrical impedance analysis, and the risk of IR, assessed using validated scales, in a cohort of Spanish workers. Methodology: A descriptive cross-sectional study was conducted on 8590 Spanish workers to assess the association between MA and a set of sociodemographic variables, health habits, and IR risk scales such as the Triglyceride-Glucose Index (TyG Index), Metabolic Score for Insulin Resistance (METS-IR), and Single Point Insulin Sensitivity Estimator (SPISE). Results: All analyzed variables were associated with MA values, with the strongest associations observed for IR risk scale values (OR 4.88 [95% CI 4.12-5.65] for METS-IR, 4.42 [95% CI 3.70-5.15] for SPISE, and 3.42 [95% CI 2.97-3.87] for the TyG Index) and physical activity. Conclusions: Metabolic age is influenced by sociodemographic variables such as age, sex, and social class; health habits such as smoking, physical activity, and adherence to the Mediterranean diet; and by IR risk scale values.

Polysaccharides with Arabinose: Key Players in Reducing Chronic Inflammation and Enhancing Immune Health in Aging

Aging is associated with a decline in physiological performance leading to increased inflammation and impaired immune function. Polysaccharides (PLs) found in plants, fruits, and fungi are emerging as potential targets for therapeutic intervention, but little is known about their effects on chronic inflammation and aging. This review aims to highlight the current advances related to the use of PLs, with the presence of arabinose, to attenuate oxidative stress and chronic and acute inflammation, and their immunomodulatory effects associated with antioxidant status in monocytes, macrophages, and neutrophil infiltration, and leukocyte rolling adhesion in neutrophils. In addition, recent studies have shown the importance of investigating the 'major' monosaccharide, such as arabinose, present in several of these polysaccharides, and with described effects on gut microbiome, glucose, inflammation, allergy, cancer cell proliferation, neuromodulation, and metabolic stress. Perspectives and opportunities for further investigation are provided. By promoting a balanced immune response and reducing inflammation, PLs with arabinose or even arabinose per se may alleviate the immune dysregulation and inflammation seen in the elderly, therefore providing a promising strategy to mitigate a variety of diseases.

NLRP3 inflammasome promotes functional repair after spinal cord injury in mice by regulating autophagy and its mechanism

BACKGROUND

Inflammation at the injury site exacerbates tissue cell death following a spinal cord injury (SCI). Studies show that NLRP3 inflammasomes are crucial in the inflammation following Spinal Cord Injury, and NLRP3 inflammasomes have been shown to promote cells to undergo excessive autophagy in other diseases. Moreover, excessive autophagy levels could hinder functional repair post-SCI. In this regard, we hypothesized that inhibiting NLRP3 inflammasomes could reduce autophagy levels at the injury site, thus promoting functional repair post-SCI.

METHODS

Herein, a mouse SCI model was used for in vivo experiments, and an in vitro neuroinflammatory model created using LPS-activated BV2 cells was used for in vitro experiments. Histopathological staining was used to assess tissue repair. Western Blot (WB) and quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) were used to detect changes in relevant autophagy molecules, macrophage polarization-related markers and downstream inflammatory factors, and Immunofluorescence (IF) was used to detect changes in macrophage polarization.

RESULTS

Following SCI, the inhibition of NLRP3 inflammasomes resulting from intraperitoneal injection of MCC950 significantly reduced autophagy levels at the injury site, resulting in both histological and behavioral improvements. In addition, the phosphorylation of mTOR during inhibition of NLRP3 inflammasomes to reduce autophagy levels further improved the immune microenvironment at the injury site, and M2-type macrophages were significantly upregulated M2-type macrophages. Moreover, in vitro experiments yielded results consistent with those of in vivo experiments regarding changes in autophagy-related indexes and polarization-related markers.

CONCLUSIONS

Inhibition of NLRP3 inflammasomes can reduce autophagy level at the injury site to promote functional recovery and play a neuroprotective role. Moreover, phosphorylation of mTOR during the process of inhibition of NLRP3 inflammasomes to reduce autophagy, leading to reduced autophagy levels, could improve the immune microenvironment at the injury site, thus promoting functional recovery and histopathological repair post-SCI.

HDAC4-AS1/CTCF Transcriptionally Represses HDAC4 Under Stress, Whereas HDAC4 Inhibits Stress-Induced Syncytiotrophoblast Cellular Pyroptosis by Deacetylating NLRP3 and GSDMD

Our previous study reported that histone deacetylase 4 (HDAC4) expression is significantly downregulated in placental tissues of pre-eclampsia (PE) pregnancies. Cellular pyroptosis is a key event in the pathogenesis of PE that induces the release of factors into the maternal circulation. The aim of this study is to analyze the role and related molecular mechanisms of HDAC4 in PE trophoblast cell pyroptosis. Hypoxia and lipopolysaccharide (LPS)/ATP-treated immortalized human placental villous trophoblast cells HTR-8/SVneo were utilized to mimic the placental trophoblast cell state in PE. Both hypoxia and LPS/ATP treatments induced significant HTR-8/SVneo cell pyroptosis, whereas HDAC4 overexpression inhibited the induced cell pyroptosis. HDAC4 could bind to NLRP3 and GSDMD proteins, and lead to a decrease in acetylated NLRP3 and GSDMD proteins, thereby inhibiting cell pyroptosis. Hypoxia and LPS/ATP treatment significantly upregulated HDAC4-AS1 levels in HRT-8/SVneo cells. HDAC4-AS1 could bind to HDAC4 gene promoter sequences as well as CTCF protein. HDAC4-AS1 overexpression recruited the enrichment of CTCF on HDAC4 promoter sequences and further repressed HDAC4 transcription and expression. Targeting the transcriptional regulatory mechanism of HDAC4-AS1/HDAC4 may be able to ameliorate the clinical symptoms of PE maternal by inhibiting cellular pyroptosis in syncytiotrophoblast cells under stress.

Sirtuins as therapeutic targets in diabetes

INTRODUCTION

Sirtuins (SIRTs) are NAD+-dependent deacetylases that mediate post-translational modifications of proteins. Seven members of the SIRT family have been identified in mammals. Importantly, SIRTs interact with numerous metabolic and inflammatory pathways. Thus, researchers have investigated their role in metabolic and inflammatory disorders.

AREAS COVERED

In this review, we comprehensively discuss the involvement of SIRTs in the processes of pancreatic β-cell dysfunction, glucose tolerance, insulin secretion, lipid metabolism, and adipocyte functions. In addition, we describe the current evidence regarding modulation of the expression and activity of SIRTs in diabetes, diabetic complications, and obesity.

EXPERT OPINION

The development of specific SIRT activators and inhibitors that exhibit high selectivity toward specific SIRT isoforms remains a major challenge. This involves the need to elucidate the physiological pathways involving SIRTs, as well as their important role in the development of metabolic disorders. Molecular modeling techniques will be helpful to develop new compounds that modulate the activity of SIRTs, which may contribute to the preparation of new drugs that selectively target specific SIRTs. SIRTs hold promise as potential targets in metabolic disease, but there is much to learn about specific modulators and the final answers will await clinical trials.

Vinegar-processed Schisandra chinensis polysaccharide ameliorates type 2 diabetes via modulation serum metabolic profiles, gut microbiota, and fecal SCFAs

Numerous studies indicate that Schisandra chinensis (Turcz.) Baill (SC) has anti-type 2 diabetes mellitus (T2DM) effects, and its processed products are commonly used in clinical practice. However, limited reports exist on the mechanisms of polysaccharides from its vinegar products and their role in T2DM. We purified a novel polysaccharide from vinegar-processed Schisandra chinensis (VSC) and used intestinal microbiota 16S rRNA analysis and metabolomics to study changes in T2DM mice after vinegar-processed Schisandra chinensis polysaccharide (VSP) intervention, aiming to elucidate how VSP alleviates T2DM. VSP has shown significant therapeutic effects in T2DM mice, which can regulate the imbalance of glucose and lipid metabolism, alleviate pancreatic and liver damage, restore the integrity of the intestinal barrier, and inhibit the inflammatory response. Serum metabolomics and microbiological analysis showed that VSP could significantly regulate 104 endogenous metabolites and rectify gut microbiota disorders in T2DM mice. Additionally, VSP enhanced the levels of short-chain fatty acids (SCFAs) and the expression of GPR41/43 in the colon of T2DM mice. Correlation analysis revealed significant correlations among specific gut microbiota, serum metabolites, and fecal SCFAs. Overall, these findings will provide a basis for further VSP development.

Context-dependent role of sirtuin 2 in inflammation

Sirtuin 2 is a member of the sirtuin family nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases, known for its regulatory role in different processes, including inflammation. In this context, sirtuin 2 has been involved in the modulation of key inflammatory signaling pathways and transcription factors by deacetylating specific targets, such as nuclear factor κB and nucleotide-binding oligomerization domain-leucine-rich-repeat and pyrin domain-containing protein 3 (NLRP3). However, whether sirtuin 2-mediated pathways induce a pro- or an anti-inflammatory response remains controversial. Sirtuin 2 has been implicated in promoting inflammation in conditions such as asthma and neurodegenerative diseases, suggesting that its inhibition in these conditions could be a potential therapeutic strategy. Conversely, arthritis and type 2 diabetes mellitus studies suggest that sirtuin 2 is essential at the peripheral level and, thus, its inhibition in these pathologies would not be recommended. Overall, the precise role of sirtuin 2 in inflammation appears to be context-dependent, and further investigation is needed to determine the specific molecular mechanisms and downstream targets through which sirtuin 2 influences inflammatory processes in various tissues and pathological conditions. The present review explores the involvement of sirtuin 2 in the inflammation associated with different pathologies to elucidate whether its pharmacological modulation could serve as an effective strategy for treating this prevalent symptom across various diseases.

Exploring the Plasma Proteome: Identifying Hub Proteins linking Aging, Homeostasis, and Organ Function

As effectors of interactions between genes and the environment, plasma proteins can monitor homeostasis and reflect the aging state of an organism. However, biomarkers of aging that are associated with homeostasis are still unclear. This study investigates the phenotype-related plasma proteome profiles of healthy individuals and to identify proteins that are specifically related to aging and physiological indices and their expression patterns across the lifespan. From September 2020 to March 2021, 71 participants aged over 20 to 100 years were enrolled in this cross-sectional study. Data were analyzed from April 2021 to December 2023. The plasma proteome was analyzed to identify proteins that are specifically related to aging and their expression patterns across the lifespan. Then, hub proteins were screened through correlation of aging proteins with physiological and biochemical phenotypes. Based on levels of plasma proteins, physiological indices are associated with age. Additionally, these differences in protein expression correlate with age and physiological indices. Finally, we identified 20 hub proteins that correlate with both physiological indices and age, and these proteins are involved in oxidative stress, inflammation and metabolism. Bibliometric analysis confirmed that 8 hub proteins (CD44, CD14, IGF2, CFD, LBP, IGFBP3, EFEMP1, and AHSG) associated with age affect organ function by mediating homeostasis. Plasma proteins associated with both age and physiological indices are involved in oxidative stress, inflammation, and metabolism. This is the first investigation to link aging and homeostasis based on plasma proteins.

Moxibustion Alleviates Inflammation via SIRT5-mediated Post-translational Modification and Macrophage Polarization

Macrophage polarisation is influenced by Sirtuin5 (SIRT5), which is crucial for regulating anti-inflammatory processes. Moxibustion, a traditional Chinese medicine therapy, exerts anti-inflammatory effects by altering the succinate/α-ketoglutarate (α-KG) ratio, an indicator of the M1 to M2 macrophage shift. Glutamate dehydrogenase 1 (GLUD1), a key enzyme involved in α-KG production, is desuccinylated by SIRT5. Currently, the potential influence of moxibustion on SIRT5-GLUD1-α-KG-mediated macrophage polarization in inflammatory diseases remains unexplored. C57BL/6 J and Sirt5 knockout mice were used as complete Freund's adjuvant (CFA)-induced adjuvant arthritis models. Moxibustion and acupoint injections of MC3482 were administered. Paw capacity asssays and ELISA were performed to quantify inflammatory effects and the expression of succinate, and α-KG expressions. Flow cytometry (FCM) and immunofluorescence were used to assesss the expression of M1- and M2-like macrophages. LC-MS/MS-based proteomic analysis was performed, and GLUD1 was identified desuccinylated protein associated with SIRT5. Western blotting and immunoprecipitation (IP) were used to detect SIRT5, GLUD1, and succinylated GLUD1expressions. Moxibustion and the SIRT5-mediated desuccinylation inhibitor MC3482 decreased inflammation by increasing the number of M2 macrophages and reducing the number of M1 macrophage in the CFA model. The potential mechanism may be related to the effects of moxibustion and SIRT5 inhibition, which inverted succinate and α-KG levels in the CFA group, resulting in low succinate, high α-KG, and increased GLUD1 succinylation after treatment. These findings suggest that the anti-inflammatory effects moxibustion are related to the impact of macrophage conversion after SIRT5-mediated post-translational modification.

VANGL2 alleviates inflammatory bowel disease by recruiting the ubiquitin ligase MARCH8 to limit NLRP3 inflammasome activation through OPTN-mediated selective autophagy

Inflammatory bowel disease (IBD) is a chronic and potentially life-threatening inflammatory disease of gastroenteric tissue characterized by episodes of intestinal inflammation, but the underlying mechanisms remain elusive. Here, we explore the role and precise mechanism of Van-Gogh-like 2 (VANGL2) during the pathogenesis of IBD. VANGL2 decreases in IBD patients and dextran sulfate sodium (DSS)-induced colitis in mice. Myeloid VANGL2 deficiency exacerbates the progression of DSS-induced colitis in mice and specifically enhances the activation of NLRP3 inflammasome in macrophages. NLRP3-specific inhibitor MCC950 effectively alleviates DSS-induced colitis in VANGL2 deficient mice. Mechanistically, VANGL2 interacts with NLRP3 and promotes the autophagic degradation of NLRP3 through enhancing the K27-linked polyubiquitination at lysine 823 of NLRP3 by recruiting E3 ligase MARCH8, leading to optineurin (OPTN)-mediated selective autophagy. Notably, decreased VANGL2 in the peripheral blood mononuclear cells from IBD patients results in overt NLRP3 inflammasome activation and sustained inflammation. Taken together, this study demonstrates that VANGL2 acts as a repressor of IBD progression by inhibiting NLRP3 inflammasome activation and provides insights into the crosstalk between inflammation and autophagy in preventing IBD.

NAD World 3.0: the importance of the NMN transporter and eNAMPT in mammalian aging and longevity control

Over the past five years, systemic NAD+ (nicotinamide adenine dinucleotide) decline has been accepted to be a key driving force of aging in the field of aging research. The original version of the NAD World concept was proposed in 2009, providing an integrated view of the NAD+-centric, systemic regulatory network for mammalian aging and longevity control. The reformulated version of the concept, the NAD World 2.0, was then proposed in 2016, emphasizing the importance of the inter-tissue communications between the hypothalamus and peripheral tissues including adipose tissue and skeletal muscle. There has been significant progress in our understanding of the importance of nicotinamide mononucleotide (NMN), a key NAD+ intermediate, and nicotinamide phosphoribosyltransferase (NAMPT), particularly extracellular NAMPT (eNAMPT). With these exciting developments, the further reformulated version of the concept, the NAD World 3.0, is now proposed, featuring multi-layered feedback loops mediated by NMN and eNAMPT for mammalian aging and longevity control.

Antioxidants in Age-Related Macular Degeneration: Lights and Shadows

Age-related macular degeneration (AMD) is a leading cause of vision impairment worldwide, primarily driven by oxidative stress and inflammation. This review examines the role of antioxidants in mitigating oxidative damage, emphasizing both their therapeutic potential and limitations in AMD management. Key findings underscore the efficacy of specific antioxidants, including vitamins C and E, lutein, zeaxanthin, and Coenzyme Q10, in slowing AMD progression. Landmark studies such as AREDS and AREDS2 have shaped current antioxidant formulations, although challenges persist, including patient variability and long-term safety concerns. Emerging therapies, such as mitochondrial-targeted antioxidants and novel compounds like saffron and resveratrol, offer promising avenues for AMD treatment. Complementary lifestyle interventions, including antioxidant-rich diets and physical activity, further support holistic management approaches. This review highlights the critical role of antioxidants in AMD therapy, advocating for personalized strategies to optimize patient outcomes.

Sirtuin 2 exacerbates renal tubule injury and inflammation in diabetic mice via deacetylation of c-Jun/c-Fos

Diabetic nephropathy (DN) is a serious complication of diabetes, and inflammation plays a crucial role. Sirtuin 2 (SIRT2), a NAD+-dependent deacetylase, which is involved in the regulation of cell metabolism, proliferation and longevity through deacetylation. Our previous research showed a positive correlation between urinary SIRT2 levels and renal injury markers in DN patients. Therefore, this study explored the specific role of SIRT2 in DN and its regulatory relationship with inflammatory response. Increased expression of SIRT2 was observed in kidney tissues of DN mice and in HK2 cells induced by HG/PA. SIRT2 knockout mice alleviated microalbuminuria, inflammatory responses, and kidney damage induced by HFD/STZ. In HK2 cells, reducing SIRT2 expression or inhibiting its acetylase activity alleviated the inflammatory response induced by HG/PA, whereas overexpression of SIRT2 exacerbated this response. Further investigation revealed that SIRT2 directly interacts with c-Jun/c-Fos, promoting their deacetylation. And inhibitors of c-Jun/c-Fos partially reversed the upregulation of inflammatory factors caused by SIRT2 overexpression. Meanwhile, disrupting SIRT2 reduced the binding activity between AP-1 and the MCP-1 promoter, while overexpressing SIRT2 further increased their binding activity in HK2 cells. Interestingly, SIRT2 increased its phosphorylation while deacetylating c-Jun, leading to nuclear accumulation of p-c-Jun. In conclusion, SIRT2 knockout can alleviate kidney injury and inflammatory response in HFD/STZ mice. The mechanism is related to the increased acetylation of c-Jun/c-Fos in renal tubular epithelial cells, accompanied by crosstalk between c-Jun phosphorylation and acetylation. Blocking SIRT2 could therefore be a potential therapeutic target for DN.

NLRP3 Inflammasome-Mediated Osteoarthritis: The Role of Epigenetics

The prevalence of osteoarthritis (OA) notably surges with age and weight gain. The most common clinical therapeutic drugs are painkillers, yet they cannot impede the deteriorating course of OA. Thus, understanding OA's pathogenesis and devising effective therapies is crucial. It is generally recognized that inflammation, pyroptosis, and OA progression are tightly linked. The activation of NLRP3 inflammasome can lead to the discharge of the pro-inflammatory cytokines Interleukin-1β and IL-18, intensifying subsequent inflammatory reactions and promoting OA development. Conversely, the imbalance caused by deacetylase-regulated NLRP3 inflammasome underlies the chronic mild inflammation related to degenerative diseases. Therefore, this article expounds on the mechanism of OA pathogenesis and the role of histone deacetylases (HDACs) in NLRP3 inflammasome-triggered OA, and illustrates the application of HDAC inhibitors in OA, striving to provide more insights into novel OA treatment approaches.

Exploring the health benefits of food bioactive compounds from a perspective of NLRP3 inflammasome activation: an insight review

The food industry has been focusing on food bioactive compounds with multiple physiological and immunological properties that benefit human health. These bioactive compounds, including polyphenols, flavonoids, and terpenoids, have great potential to limit inflammatory responses especially NLRP3 inflammasome activation, which is a key innate immune platform for inflammation. Current studies have revealed numerous food bioactive compounds with promising activities for unraveling immune metabolic disorders and excessive inflammatory responses by directly and indirectly regulating the NLRP3 inflammasome activation. This review explores the food hazards, including microbial and abiotic factors, that may trigger NLRP3-mediated illnesses and inflammation. It also highlights bioactive compounds in food that can suppress NLRP3 inflammasome activation through various mechanisms, linking its activation and inhibition to different pathways. Especially, this review provided further insight into NLRP3-related targets where food bioactive compounds can interact to block the NLRP3 inflammasome activation process, as well as mechanisms on how these compounds facilitate inactivation processes.

Total saponins from Panax japonicus mediate the paracrine interaction between adipocytes and macrophages to promote lipolysis in the adipose tissue during aging via the NLRP3 inflammasome/GDF3/ATGL axis

Adipocytic lipolysis is strongly related to the increase of visceral fat, decrease of exercise capacity, and various other metabolic syndromes during aging. It is significantly influenced by the paracrine relationship between adipocytes and the adipose tissue macrophages (ATMs), and the cytokines secreted by ATMs have endocrine effects on adjacent tissues. We previously reported that the total saponins from Panax japonicus (TSPJs) can enhance lipid metabolism. In this work, we for the first time proved that TSPJs promoted adipocytic lipolysis by preventing NLRP3 activation in ATMs to inhibit the expression of GDF3. The decrease of GDF3 by TSPJs restored the expression of the adipose triglyceride lipase (ATGL) and phosphorylated hormone-sensitive lipase (p-HSL), both of which are known to decrease with aging. Thus, the NLRP3 inflammasome/GDF3/ATGL axis may be a worthy target in developing future clinical solutions for aging-related obesity.

Gene-Activating Framework Nucleic Acid-Targeted Upregulating Sirtuin-1 to Modulate Osteoimmune Microenvironment for Diabetic Osteoporosis Therapeutics

Diabetic osteoporosis, a prevalent chronic complication of diabetes, is marked by reduced bone mass, increased bone fragility, and susceptibility to fractures. A significant cause of this condition is the disruption of osteoblastic homeostasis due to prolonged hyperglycemia, which impedes bone regeneration and remodeling. Despite its prevalence, no effective treatments specifically target diabetic osteoporosis. Recently, small-activating RNA (saRNA) therapy has attracted attention for its targeting capacity, high efficacy, and minimal side effects. However, RNA's inherent properties, such as structural instability, susceptibility to degradation, and poor penetration, limit its applications. To address these limitations, a gene-activating tetrahedral framework nucleic acid (tFNA) with sirtuin-1 (SIRT1) gene activation function is developed, termed Tsa. Tsa exhibits an RNA-protecting effect and can effectively penetrate cell membranes to upregulate SIRT1 gene expression. At the histological level, Tsa treatment alleviates diabetic osteoporosis by increasing bone trabecular density and promoting new bone formation. At the cellular level, it switches macrophage polarization toward the anti-inflammatory M2 phenotype while inhibiting the inflammatory M1 phenotype, creating a favorable bone immune microenvironment for osteoblasts. At the genetic level, Tsa activates SIRT1 expression, which deacetylates Acetyl-p65 to block the NF-κB pathway and restore the osteoimmune environment. Overall, this research demonstrates a nanodrug "Tsa", capable of activating SIRT1 and modulating the bone immune environment, thereby showcasing its immense potential for diabetic osteoporosis treatment.

Transmembrane Amino Acid Transporters in Shaping the Metabolic Profile of Breast Cancer Cell Lines: The Focus on Molecular Biological Subtype

Amino acid metabolism in breast cancer cells is unique for each molecular biological subtype of breast cancer. In this review, the features of breast cancer cell metabolism are considered in terms of changes in the amino acid composition due to the activity of transmembrane amino acid transporters. In addition to the main signaling pathway PI3K/Akt/mTOR, the activity of the oncogene c-Myc, HIF, p53, GATA2, NF-kB and MAT2A have a direct effect on the amino acid metabolism of cancer cells, their growth and proliferation, as well as the maintenance of homeostatic equilibrium. A distinctive feature of luminal subtypes of breast cancer from TNBC is the ability to perform gluconeogenesis. Breast cancers with a positive expression of the HER2 receptor, in contrast to TNBC and luminal A subtype, have a distinctive active synthesis and consumption of fatty acids. It is interesting to note that amino acid transporters exhibit their activity depending on the pH level inside the cell. In the most aggressive forms of breast cancer or with the gradual progression of the disease, pH will also change, which will directly affect the metabolism of amino acids. Using the cell lines presented in this review, we can trace the characteristic features inherent in each of the molecular biological subtypes of breast cancer and develop the most optimal therapeutic targets.

Decoding NAD+ Metabolism in COVID-19: Implications for Immune Modulation and Therapy

The persistent threat of COVID-19, particularly with the emergence of new variants, underscores the urgency for innovative therapeutic strategies beyond conventional antiviral treatments. Current immunotherapies, including IL-6/IL-6R monoclonal antibodies and JAK inhibitors, exhibit suboptimal efficacy, necessitating alternative approaches. Our review delves into the significance of NAD+ metabolism in COVID-19 pathology, marked by decreased NAD+ levels and upregulated NAD+-consuming enzymes such as CD38 and poly (ADP-ribose) polymerases (PARPs). Recognizing NAD+'s pivotal role in energy metabolism and immune modulation, we propose modulating NAD+ homeostasis could bolster the host's defensive capabilities against the virus. The article reviews the scientific rationale behind targeting NAD+ pathways for therapeutic benefit, utilizing strategies such as NAD+ precursor supplementation and enzyme inhibition to modulate immune function. While preliminary data are encouraging, the challenge lies in optimizing these interventions for clinical use. Future research should aim to unravel the intricate roles of key metabolites and enzymes in NAD+ metabolism and to elucidate their specific mechanisms of action. This will be essential for developing targeted NAD+ therapies, potentially transforming the management of COVID-19 and setting a precedent for addressing other infectious diseases.

HDAC10 switches NLRP3 modification from acetylation to ubiquitination and attenuates acute inflammatory diseases

BACKGROUND

The NOD-like receptor protein (NLRP)3 inflammasome is at the signaling hub center to instigate inflammation in response to pathogen infection or oxidative stress, and its tight control is pivotal for immune defense against infection while avoiding parallel intensive inflammatory tissue injury. Acetylation of NLRP3 is critical for the full activation of NLRP3 inflammasome, while the precise regulation of the acetylation and deacetylation circuit of NLRP3 protein remained to be fully understood.

METHODS

The interaction between histone deacetylase 10 (HDAC10) and NLRP3 was detected by immunoprecipitation and western blot in the HDAC10 and NLRP3 overexpressing cells. The role of HDAC10 in NLRP3 inflammasome activation was measured by immunofluorescence, real-time PCR and immunoblotting assay in peritoneal macrophages and bone marrow-derived macrophages after the stimulation with LPS and ATP. To investigate the role of HDAC10 in NLRP3-involved inflammatory diseases, the Hdac10 knockout (Hdac10-/-) mice were used to construct the LPS-induced acute endotoxemia model and folic acid-induced acute tubular necrosis model. Tissue injury level was analyzed by hematoxylin and eosin staining, and the serum level of IL-1β was measured by enzyme-linked immunosorbent assay (ELISA). The conservative analysis and immunoprecipitation assay were performed to screen the precise catalytic site regulated by HDAC10 responsible for the switching from the acetylation to ubiquitination of NLRP3.

RESULTS

Here we demonstrated that HDAC10 directly interacted with NLRP3 and induced the deacetylation of NLRP3, thus leading to the inhibition of NLRP3 inflammasome and alleviation of NLRP3 inflammasome-mediated acute inflammatory injury. Further investigation demonstrated that HDAC10 directly induced the deacetylation of NLRP3 at K496 residue, thus switching NLRP3 acetylation to the ubiquitination modification, resulting in the proteasomal degradation of NLRP3 protein. Thus, this study identified HDAC10 as a new eraser for NLRP3 acetylation, and HDAC10 attenuated NLRP3 inflammasome involved acute inflammation via directly deacetylating NLRP3.

CONCLUSIONS

This study indicated that HDAC10 switched NLRP3 modification from acetylation to ubiquitination and attenuated acute inflammatory diseases, thus it provided a potential therapeutic strategy for NLRP3 inflammasome-associated diseases by targeting HDAC10.

Targeting purine metabolism-related enzymes for therapeutic intervention: A review from molecular mechanism to therapeutic breakthrough

Purines are ancient metabolites with established and emerging metabolic and non-metabolic signaling attributes. The expression of purine metabolism-related genes is frequently activated in human malignancies, correlating with increased cancer aggressiveness and chemoresistance. Importantly, under certain stimulating conditions, the purine biosynthetic enzymes can assemble into a metabolon called "purinosomes" to enhance purine flux. Current evidence suggests that purine flux is regulated by a complex circuit that encompasses transcriptional, post-translational, metabolic, and association-dependent regulatory mechanisms. Furthermore, purines within the tumor microenvironment modulate cancer immunity through signaling mediated by purinergic receptors. The deregulation of purine metabolism has significant metabolic consequences, particularly hyperuricemia. Herbal-based therapeutics have emerged as valuable pharmacological interventions for the treatment of hyperuricemia by inhibiting the activity of hepatic XOD, modulating the expression of renal urate transporters, and suppressing inflammatory responses. This review summarizes recent advancements in the understanding of purine metabolism in clinically relevant malignancies and metabolic disorders. Additionally, we discuss the role of herbal interventions and the interaction between the host and gut microbiota in the regulation of purine homeostasis. This information will fuel the innovation of therapeutic strategies that target the disease-associated rewiring of purine metabolism for therapeutic applications.

Hydrogen sulfide mitigates mitochondrial dysfunction and cellular senescence in diabetic patients: Potential therapeutic applications

Diabetes induces a pro-aging state characterized by an increased abundance of senescent cells in various tissues, heightened chronic inflammation, reduced substance and energy metabolism, and a significant increase in intracellular reactive oxygen species (ROS) levels. This condition leads to mitochondrial dysfunction, including elevated oxidative stress, the accumulation of mitochondrial DNA (mtDNA) damage, mitophagy defects, dysregulation of mitochondrial dynamics, and abnormal energy metabolism. These dysfunctions result in intracellular calcium ion (Ca2+) homeostasis disorders, telomere shortening, immune cell damage, and exacerbated inflammation, accelerating the aging of diabetic cells or tissues. Hydrogen sulfide (H2S), a novel gaseous signaling molecule, plays a crucial role in maintaining mitochondrial function and mitigating the aging process in diabetic cells. This article systematically explores the specific mechanisms by which H2S regulates diabetes-induced mitochondrial dysfunction to delay cellular senescence, offering a promising new strategy for improving diabetes and its complications.

Decoding senescence of aging single cells at the nexus of biomaterials, microfluidics, and spatial omics

Aging has profound effects on the body, most notably an increase in the prevalence of several diseases. An important aging hallmark is the presence of senescent cells that no longer multiply nor die off properly. Another characteristic is an altered immune system that fails to properly self-surveil. In this multi-player aging process, cellular senescence induces a change in the secretory phenotype, known as senescence-associated secretory phenotype (SASP), of many cells with the intention of recruiting immune cells to accelerate the clearance of these damaged senescent cells. However, the SASP phenotype results in inducing secondary senescence of nearby cells, resulting in those cells becoming senescent, and improper immune activation resulting in a state of chronic inflammation, called inflammaging, in many diseases. Senescence in immune cells, termed immunosenescence, results in further dysregulation of the immune system. An interdisciplinary approach is needed to physiologically assess aging changes of the immune system at the cellular and tissue level. Thus, the intersection of biomaterials, microfluidics, and spatial omics has great potential to collectively model aging and immunosenescence. Each of these approaches mimics unique aspects of the body undergoes as a part of aging. This perspective highlights the key aspects of how biomaterials provide non-cellular cues to cell aging, microfluidics recapitulate flow-induced and multi-cellular dynamics, and spatial omics analyses dissect the coordination of several biomarkers of senescence as a function of cell interactions in distinct tissue environments. An overview of how senescence and immune dysregulation play a role in organ aging, cancer, wound healing, Alzheimer's, and osteoporosis is included. To illuminate the societal impact of aging, an increasing trend in anti-senescence and anti-aging interventions, including pharmacological interventions, medical procedures, and lifestyle changes is discussed, including further context of senescence.

Nicotinamide mononucleotide improves the ovarian reserve of POI by inhibiting NLRP3-mediated pyroptosis of ovarian granulosa cells

BACKGROUND

Premature ovarian insufficiency (POI) is a common clinical problem, but there is currently no effective treatment. NLRP3 inflammasome-induced pyroptosis is thought to be a possible mechanism of POI. Nicotinamide mononucleotide (NMN) has a certain anti-inflammatory effect, providing a promising approach for the treatment of POI.

METHODS

Thirty female Sprague Dawley rats were randomly divided into a control group (n = 10) and a POI group (n = 20). Cyclophosphamide (CTX) was administered for 2 weeks to induce POI. Then the POI group was divided into two groups: the CTX-POI group (n = 10), which was given saline; and the CTX-POI + NMN group (n = 10), which was given NMN at a dose of 500 mg/kg/day for 21 consecutive days. At the end of the study, the serum hormone concentrations of each group were determined, and each group was subjected to biochemical, histopathological, and immunohistochemical analyses. In the in vitro experiment, cell pyroptosis was simulated by using lipopolysaccharide (LPS) and nigricin (Nig), and then KGN cells were treated with NMN, MCC950, and AGK2, and the levels of Nicotinamide adenine dinucleotide (NAD+) and inflammatory factors Interleukin-18(IL-18) and Interleukin-1β(IL-1β) in the cell supernatants were detected, and the levels of pyroptosis-related factors in the cells were determined.

RESULTS

In POI rats, NMN treatments can improve blood hormone levels and partially improve the number of follicles, enhance ovarian reserve function and ovarian index.The evidence is that the increase in NAD+ levels and the activation of SIRT2 expression can reduce the expression of NLRP3, Gasdermin D (GSDMD), Caspase-1, IL-18, and IL-1β in the ovary.

CONCLUSION

NMN improves CTX-induced POI by inhibiting NLRP3-mediated pyroptosis, providing a new therapeutic strategy and drug target for clinical POI patients.

Nampt/SIRT2/LDHA pathway-mediated lactate production regulates follicular dysplasia in polycystic ovary syndrome

Decreased nicotinamide adenine dinucleotide (NAD+) content has been shown to contribute to metabolic dysfunction during aging, including polycystic ovary syndrome (PCOS). However, the effect of NAD+ on ovulatory dysfunction in PCOS by regulating glycolysis has not been reported. Based on the observations of granulosa cells (GCs) transcriptome data from the Gene Expression Omnibus (GEO) database, the signal pathways including glycolysis and nicotinate-nicotinamide metabolism were significantly enriched, and most genes of the above pathway like LDHA and SIRT2 were down-regulated in PCOS patients. Therefore, the PCOS rat model was established by combining letrozole with a high-fat diet (HFD), we demonstrate that in vivo supplementation of nicotinamide mononucleotide (NMN) significantly improves the ovulatory dysfunction by facilitating the follicular development, promoting luteal formation, as well the fertility in PCOS rats. Furthermore, target energy metabolomics and transcriptome results showed that NMN supplementation ameliorates the lactate production by activating glycolytic process in the ovary. In vitro, when NAD+ synthesis and SIRT2 expression were inhibited, lactate content in KGN cells was decreased and LDHA expression was significantly inhibited. We confirmed that FK866 can enhance the acetylation of LDHA on 293T cells by Co-immunoprecipitation (Co-IP) assay. We also observed that inhibition of NAD+ synthesis can reduce the activity and increase the apoptosis of KGN cells. Overall, these benefits of NMN were elucidated and the Nampt/SIRT2/LDHA pathway mediated lactate production in granulosa cells played an important role in the improvement of follicular development disorders in PCOS. This study will provide experimental evidence for the clinical application of NMN in the treatment of PCOS in the future.

Functional identification of soluble uric acid as an endogenous inhibitor of CD38

Excessive elevation or reduction of soluble uric acid (sUA) levels has been linked to some of pathological states, raising another subject that sUA at physiological levels may be essential for the maintenance of health. Yet, the fundamental physiological functions and molecular targets of sUA remain largely unknown. Using enzyme assays and in vitro and in vivo metabolic assays, we demonstrate that sUA directly inhibits the hydrolase and cyclase activities of CD38 via a reversible non-competitive mechanism, thereby limiting nicotinamide adenine dinucleotide (NAD+) degradation. CD38 inhibition is restricted to sUA in purine metabolism, and a structural comparison using methyl analogs of sUA such as caffeine metabolites shows that 1,3-dihydroimidazol-2-one is the main functional group. Moreover, sUA at physiological levels prevents crude lipopolysaccharide (cLPS)-induced systemic inflammation and monosodium urate (MSU) crystal-induced peritonitis in mice by interacting with CD38. Together, this study unveils an unexpected physiological role for sUA in controlling NAD+ availability and innate immunity through CD38 inhibition, providing a new perspective on sUA homeostasis and purine metabolism.

BubR1 and SIRT2: Insights into aneuploidy, aging, and cancer

Aging is a significant risk factor for cancer which is due, in part, to heightened genomic instability. Mitotic surveillance proteins such as BubR1 play a pivotal role in ensuring accurate chromosomal segregation and preventing aneuploidy. BubR1 levels have been shown to naturally decline with age and its loss is associated with various age-related pathologies. Sirtuins, a class of NAD+-dependent deacylases, are implicated in cancer and genomic instability. Among them, SIRT2 acts as an upstream regulator of BubR1, offering a critical pathway that can potentially mitigate age-related diseases, including cancer. In this review, we explore BubR1 as a key regulator of cellular processes crucial for aging-related phenotypes. We delve into the intricate mechanisms through which BubR1 influences genomic stability and cellular senescence. Moreover, we highlight the role of NAD+ and SIRT2 in modulating BubR1 expression and function, emphasizing its potential as a therapeutic target. The interaction between BubR1 and SIRT2 not only serves as a fundamental regulatory pathway in cellular homeostasis but also represents a promising avenue for developing targeted therapies against age-related diseases, particularly cancer.

The role of NLRP3 inflammasome-mediated neuroinflammation in chronic noise-induced impairment of learning and memory ability

BACKGROUND

Noise pollution pervades daily working and living environment, becoming a serious public health problem. In addition to causing auditory impairment, noise independently contributes to cognitive decline as a risk factor. Though neuroinflammation plays an important role in noise-induced cognitive deficits, the mechanisms underlying noise-induced neuroinflammation in the hippocampus are still poorly understood. Glial hyperactivation of the NLRP3 inflammasome contributes to various neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). However, whether the NLRP3 inflammasome plays a role in noise-induced cognitive impairment remains to be further investigated.

METHODS

Adult male Wistar rats were exposed to 100 dB white noise (4 h/day) for 30 days with or without injection of the NLRP3 inhibitor MCC950 (10 mg/kg/day). The Morris water maze (MWM) test and the open field test (OFT) were performed to evaluate learning and memory ability of rats. HE staining was used to explore hippocampal pathological changes, while immunohistochemical staining was employed to evaluate the number and morphology of microglia and astrocytes. The mRNA levels of the NLRP3 inflammasome in the hippocampus were examined by Real-time PCR. The protein levels of NLRP3 inflammasome, inflammatory cytokines, p-Tau-S396, and amyloid-β (Aβ) 42 in the hippocampus were examined by Western blot. Immunofluorescence was used to observe the distribution of NLRP3 in glial cells and neurons, and the assembly of the NLRP3 inflammasome.

RESULTS

We found that noise exposure induced learning and memory impairment in rats, mainly related to the activation of microglia and astrocytes in hippocampus region. Noise exposure increased the protein levels of p-Tau-S396, Aβ42, ionized calcium binding adapter molecule 1 (Iba-1), glial fibrillary acidic protein (GFAP), interleukin (IL)-1β, IL-18, and tumor necrosis factor-α (TNF-α) in hippocampus. Furthermore, the hippocampus of noise-exposed rats showed elevated protein levels of NLRP3, ASC and cleaved caspase-1. The co-labeled immunofluorescence levels of Iba-1 or GFAP with NLRP3 significantly increased in the dentate gyrus (DG) region of the hippocampus. NLRP3 inhibitor MCC950 intervention reversed chronic noise-induced activation of NLRP3 inflammasome, AD-like pathologies and impairment of learning and memory in rats.

CONCLUSIONS

The NLRP3 inflammasome-mediated neuroinflammation played an essential role in chronic noise-induced cognitive dysfunction. These results provide novel strategies for the prevention and treatment of cognitive deficits caused by chronic noise.

The regulation of pyroptosis by post-translational modifications: molecular mechanisms and therapeutic targets

Pyroptosis, a type of programmed cell death mediated by gasdermin family proteins, releases a large amount of immune stimulatory substances, which further contribute to inflammation and elicit an adaptive immune response against tumours and pathogens. And it occurs through multiple pathways that involve the activation of specific caspases and the cleavage of gasdermins. Post-translational modifications (PTMs) could influence the chemical properties of the modified residues and neighbouring regions, ultimately affecting the activity, stability, and functions of proteins to regulate pyroptosis. Many studies have been conducted to explore the influence of PTMs on the regulation of pyroptosis. In this review, we provide a comprehensive summary of different types of PTMs that influence pyroptosis, along with their corresponding modifying enzymes. Moreover, it elaborates on the specific contributions of different PTMs to pyroptosis and delves into how the regulation of these modifications can be leveraged for therapeutic interventions in cancer and inflammatory diseases.

Novel post-translational modifications of protein by metabolites with immune responses and immune-related molecules in cancer immunotherapy

Tumour immunotherapy is an effective and essential treatment for cancer. However, the heterogeneity of tumours and the complex and changeable tumour immune microenvironment (TME) creates many uncertainties in the clinical application of immunotherapy, such as different responses to tumour immunotherapy and significant differences in individual efficacy. It makes anti-tumour immunotherapy face many challenges. Immunometabolism is a critical determinant of immune cell response to specific immune effector molecules, significantly affecting the effects of tumour immunotherapy. It is attributed mainly to the fact that metabolites can regulate the function of immune cells and immune-related molecules through the protein post-translational modifications (PTMs) pathway. This study systematically summarizes a variety of novel protein PTMs including acetylation, propionylation, butyrylation, succinylation, crotonylation, malonylation, glutarylation, 2-hydroxyisobutyrylation, β-hydroxybutyrylation, benzoylation, lactylation and isonicotinylation in the field of tumour immune regulation and immunotherapy. In particular, we elaborate on how different PTMs in the TME can affect the function of immune cells and lead to immune evasion in cancer. Lastly, we highlight the potential treatment with the combined application of target-inhibited protein modification and immune checkpoint inhibitors (ICIs) for improved immunotherapeutic outcomes.

An NAD+-dependent metabolic checkpoint regulates hematopoietic stem cell activation and aging

How hematopoietic stem cells (HSCs) maintain metabolic homeostasis to support tissue repair and regeneration throughout the lifespan is elusive. Here, we show that CD38, an NAD+-dependent metabolic enzyme, promotes HSC proliferation by inducing mitochondrial Ca2+ influx and mitochondrial metabolism in young mice. Conversely, aberrant CD38 upregulation during aging is a driver of HSC deterioration in aged mice due to dysregulated NAD+ metabolism and compromised mitochondrial stress management. The mitochondrial calcium uniporter, a mediator of mitochondrial Ca2+ influx, also supports HSC proliferation in young mice yet drives HSC decline in aged mice. Pharmacological inactivation of CD38 reverses HSC aging and the pathophysiological changes of the aging hematopoietic system in aged mice. Together, our study highlights an NAD+ metabolic checkpoint that balances mitochondrial activation to support HSC proliferation and mitochondrial stress management to enhance HSC self-renewal throughout the lifespan, and links aberrant Ca2+ signaling to HSC aging.

Review on the role of nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome pathway in diabetes: mechanistic insights and therapeutic implications

This review explores the pivotal role of the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome in the pathogenesis of diabetes and its complications, highlighting the therapeutic potential of various oral hypoglycemic drugs targeting this pathway. NLRP3 inflammasome activation, triggered by metabolic stressors like hyperglycemia, hyperlipidemia, and free fatty acids (FFAs), leads to the release of pro-inflammatory cytokines interleukin-1β and interleukin-18, driving insulin resistance, pancreatic β-cell dysfunction, and systemic inflammation. These processes contribute to diabetic complications such as nephropathy, neuropathy, retinopathy, and cardiovascular diseases (CVD). Here we discuss the various transcriptional, epigenetic, and gut microbiome mediated regulation of NLRP3 activation in diabetes. Different classes of oral hypoglycemic drugs modulate NLRP3 inflammasome activity through various mechanisms: sulfonylureas inhibit NLRP3 activation and reduce inflammatory cytokine levels; sodium-glucose co-transporter 2 inhibitors (SGLT2i) suppress inflammasome activity by reducing oxidative stress and modulating intracellular signaling pathways; dipeptidyl peptidase-4 inhibitors mitigate inflammasome activation, protecting against renal and vascular complications; glucagon-like peptide-1 receptor agonists attenuate NLRP3 activity, reducing inflammation and improving metabolic outcomes; alpha-glucosidase inhibitors and thiazolidinediones exhibit anti-inflammatory properties by directly inhibiting NLRP3 activation. Agents that specifically target NLRP3 and inhibit their activation have been identified recently such as MCC950, Anakinra, CY-09, and many more. Targeting the NLRP3 inflammasome, thus, presents a promising strategy for managing diabetes and its complications, with oral hypoglycemic drugs offering dual benefits of glycemic control and inflammation reduction. Further research into the specific mechanisms and long-term effects of these drugs on NLRP3 inflammasome activity is warranted.