SIRT1 regulates macrophage self-renewal

Inhibition of SIRT1 relieves hepatocarcinogenesis via alleviating autophagy and inflammation

Imbalanced Sirtuin 1 (SIRT1) levels may lead to liver diseases through abnormal regulation of autophagy, but the roles of SIRT1-regulated autophagy in hepatocellular carcinoma are still controversial. In this study, we found that SIRT1 mRNA and protein levels were upregulated in hepatocellular carcinoma, and high SIRT1 expression hinted an advanced stage and a poor prognosis. The differentially expressed proteins were significantly elevated in autophagy, cellular response to stress, and immune signaling pathways. In a thioacetamide-induced hepatocellular carcinoma mouse model, we found that SIRT1 expression was highly increased with increased autophagy and excessive macrophage inflammatory response. Next, we established a Hepa 1-6 cells and macrophage co-culture system in vitro to model the alteration of tumor microenvironment, and found that the medium from CCl4-treated or SIRT1-overexpressing Hepa 1-6 cells triggered the polarization of macrophage M1, and the culture medium derived from M1 macrophage promoted Hepa 1-6 cells growth and intracellular oxidative stress. The progression of liver fibrosis in the CCl4-induced liver fibrosis mouse model showed that inhibition of SIRT1 alleviated inflammatory response and ameliorated liver fibrosis. These findings suggest that SIRT1-regulated autophagy and inflammation are oncogenic in hepatocarcinogenesis.

Tissue-resident C1q + macrophages exert anti-aging potential through the Sirt1 pathway

OBJECTIVE

Resident immune cells are at the forefront of sensory organ-specific signals, and changes in these cells are closely related to the aging process. The Sirt pathway can regulate NAD + metabolism during aging, thereby affecting the accumulation of ROS. However, the role of the Sirt pathway in resident immune cells in aged tissues is currently unclear.

METHODS

We investigated Sirt1 signalling in resident immune cells during chronic inflammation in an aged mouse model. Integrated single-cell RNA sequencing data from young and aged mice were used to refine the characterization of immune cells in aged tissues RESULTS: We found that C1q + macrophages could affect chronic inflammation during aging. C1q + macrophages acted in an opposing manner to Il1b + macrophages and were responsible for anti-inflammatory effects during aging. Sirt1 agonists inhibited the decrease in C1qb in macrophages during aging, and anti-aging drugs could affect the expression of C1qb in macrophages via the Sirt1 pathway.

CONCLUSIONS

In this study, we first identified the relevance of C1q + macrophages in chronic inflammation during aging. The potential anti-aging effect of C1q + macrophages was mediated by the Sirt1 pathway, suggesting new strategies for aging immunotherapy.

Wogonin alleviates sepsis-induced acute lung injury by modulating macrophage polarization through the SIRT1-FOXO1 pathways

Sepsis-induced acute lung injury is a common and severe complication of sepsis, for which effective treatments are currently lacking. Previous studies have demonstrated the influence of wogonin in treating acute lung injury (ALI). However, its precise mechanism of action remains unclear. To delve deeper into the mechanisms underlying wogonin's impacts in sepsis-induced acute lung injury, we established a mouse sepsis model through cecal ligation and puncture and conducted further cell experiments using lipopolysaccharide-treated MH-S and MLE-12 cells to explore wogonin's potential mechanisms of action in treating ALI. Our results revealed that wogonin significantly increased the survival rate of mice, alleviated pulmonary pathological damage and inflammatory cell infiltration, and activated the SIRT1-FOXO1 pathway. Additionally, wogonin suppressed the release of pro-inflammatory factors by M1 macrophages and induced the activation of M2 anti-inflammatory factors. Further in vitro studies confirmed that wogonin effectively inhibited M1 macrophage polarization through the activation of the SIRT1-FOXO1 pathway, thereby mitigating lung pathological changes caused by ALI. In summary, our study demonstrated that wogonin regulated macrophage M1/M2 polarization through the activation of the SIRT1-FOXO1 pathway, thereby attenuating the inflammatory response and improving pulmonary pathological changes induced by sepsis-induced ALI. This discovery provided a solid mechanistic foundation for the therapeutic use of wogonin in sepsis-induced ALI, shedding new light on potential strategies for the treatment of sepsis-induced ALI.

Conserved role of hnRNPL in alternative splicing of epigenetic modifiers enables B cell activation

The multifunctional RNA-binding protein hnRNPL is implicated in antibody class switching but its broader function in B cells is unknown. Here, we show that hnRNPL is essential for B cell activation, germinal center formation, and antibody responses. Upon activation, hnRNPL-deficient B cells show proliferation defects and increased apoptosis. Comparative analysis of RNA-seq data from activated B cells and another eight hnRNPL-depleted cell types reveals common effects on MYC and E2F transcriptional programs required for proliferation. Notably, while individual gene expression changes are cell type specific, several alternative splicing events affecting histone modifiers like KDM6A and SIRT1, are conserved across cell types. Moreover, hnRNPL-deficient B cells show global changes in H3K27me3 and H3K9ac. Epigenetic dysregulation after hnRNPL loss could underlie differential gene expression and upregulation of lncRNAs, and explain common and cell type-specific phenotypes, such as dysfunctional mitochondria and ROS overproduction in mouse B cells. Thus, hnRNPL is essential for the resting-to-activated B cell transition by regulating transcriptional programs and metabolism, at least in part through the alternative splicing of several histone modifiers.

Gut microbial GABAergic signaling improves stress-associated innate immunity to respiratory viral infection

INTRODUCTION

Epidemiological evidences reveal that populations with psychological stress have an increased likelihood of respiratory viral infection involving influenza A virus (IAV) and SARS-CoV-2.

OBJECTIVES

This study aims to explore the potential correlation between psychological stress and increased susceptibility to respiratory viral infections and how this may contribute to a more severe disease progression.

METHODS

A chronic restraint stress (CRS) mouse model was used to infect IAV and estimate lung inflammation. Alveolar macrophages (AMs) were observed in the numbers, function and metabolic-epigenetic properties. To confirm the central importance of the gut microbiome in stress-exacerbated viral pneumonia, mice were conducted through microbiome depletion and gut microbiome transplantation.

RESULTS

Stress exposure induced a decline in Lactobacillaceae abundance and hence γ-aminobutyric acid (GABA) level in mice. Microbial-derived GABA was released in the peripheral and sensed by AMs via GABAAR, leading to enhanced mitochondrial metabolism and α-ketoglutarate (αKG) generation. The metabolic intermediator in turn served as the cofactor for the epigenetic regulator Tet2 to catalyze DNA hydroxymethylation and promoted the PPARγ-centered gene program underpinning survival, self-renewing, and immunoregulation of AMs. Thus, we uncover an unappreciated GABA/Tet2/PPARγ regulatory circuitry initiated by the gut microbiome to instruct distant immune cells through a metabolic-epigenetic program. Accordingly, reconstitution with GABA-producing probiotics, adoptive transferring of GABA-conditioned AMs, or resumption of pulmonary αKG level remarkably improved AMs homeostasis and alleviated severe pneumonia in stressed mice.

CONCLUSION

Together, our study identifies microbiome-derived tonic signaling tuned by psychological stress to imprint resident immune cells and defensive response in the lungs. Further studies are warranted to translate these findings, basically from murine models, into the individuals with psychiatric stress during respiratory viral infection.

RNA methylation patterns, immune characteristics, and autophagy-related mechanisms mediated by N6-methyladenosine (m6A) regulatory factors in venous thromboembolism

Recent studies have found a link between deep vein thrombosis and inflammatory reactions. N6-methyladenosine (m6A), a crucial element in immunological regulation, is believed to contribute to the pathophysiology of venous thromboembolism (VTE). However, how the m6A-modified immune microenvironment is involved in VTE remains unclear. In the present study, we identified a relationship between VTE and the expression of several m6A regulatory elements by analyzing peripheral blood samples from 177 patients with VTE and 88 healthy controls from public GEO databases GSE19151 and GSE48000. We used machine learning to identify essential genes and constructed a diagnostic model for VTE using multivariate logistic regression. Unsupervised cluster analysis revealed a marked difference between m6A modification patterns in terms of immune cell infiltration, inflammatory reactivity, and autophagy. We identified two m6A-related autophagy genes (i.e., CHMP2B and SIRT1) and the crucial m6A regulator YTHDF3 using bioinformatics. We also examined two potential mechanisms through which YTHDF3 may affect VTE. m6A modification, immunity, and autophagy are closely linked in VTE, offering novel mechanistic and therapeutic insights.

Melatonin ameliorates retinal ganglion cell senescence and apoptosis in a SIRT1-dependent manner in an optic nerve injury model

Melatonin is involved in exerting protective effects in aged-related and neurodegenerative diseases through a silent information regulator type 1 (SIRT1)-dependent pathway. However, little was known about the impact of melatonin on retinal ganglion cell (RGC) senescence and apoptosis following optic nerve crush (ONC). Thus, this study aimed to examine the effects of melatonin on RGC senescence and apoptosis after ONC and investigate the involvement of SIRT1 in this process. To study this, an ONC model was established. EX-527, an inhibitor of SIRT1, was injected intraperitoneally into mice. And melatonin was administrated abdominally into mice after ONC every day. Hematoxylin & eosin staining, retina flat-mounts and optical coherence tomography were used to evaluate the loss of retina cells/neurons. Pattern electroretinogram (p-ERG) was performed to evaluate the function of RGCs. Immunofluorescence and western blot were used to evaluate protein expression. SA-β-gal staining was employed to detect senescent cells. The results demonstrated that melatonin partially rescued the expression of SIRT1 in RGC 3 days after ONC. Additionally, melatonin administration partly rescued the decreased RGC number and ganglion cell complex thickness observed 14 days after ONC. Melatonin also suppressed ONC-induced senescence and apoptosis index. Furthermore, p-ERG showed that melatonin improved the amplitude of P50, N95 and N95/P50 following ONC. Importantly, the protective effects of melatonin were reversed when EX-527 was administered. In summary, this study revealed that melatonin attenuated RGC senescence and apoptosis through a SIRT1-dependent pathway after ONC. These findings provide valuable insights for the treatment of RGC senescence and apoptosis.

Roles of Sirt1 and its modulators in diabetic microangiopathy: A review

Diabetic vascular complications include diabetic macroangiopathy and diabetic microangiopathy. Diabetic microangiopathy is characterised by impaired microvascular endothelial function, basement membrane thickening, and microthrombosis, which may promote renal, ocular, cardiac, and peripheral system damage in diabetic patients. Therefore, new preventive and therapeutic strategies are urgently required. Sirt1, a member of the nicotinamide adenine dinucleotide-dependent histone deacetylase class III family, regulates different organ growth and development, oxidative stress, mitochondrial function, metabolism, inflammation, and aging. Sirt1 is downregulated in vascular injury and microangiopathy. Moreover, its expression and distribution in different organs correlate with age and play critical regulatory roles in oxidative stress and inflammation. This review introduces the background of diabetic microangiopathy and the main functions of Sirt1. Then, the relationship between Sirt1 and different diabetic microangiopathies and the regulatory roles mediated by different cells are described. Finally, we summarize the modulators that target Sirt1 to ameliorate diabetic microangiopathy as an essential preventive and therapeutic measure for diabetic microangiopathy. In conclusion, targeting Sirt1 may be a new therapeutic strategy for diabetic microangiopathy.

Antagomir of miR-31-5p modulates macrophage polarization via the AMPK/SIRT1/NLRP3 signaling pathway to protect against DSS-induced colitis in mice

Macrophage-driven immune dysfunction of the intestinal mucosa is involved in the pathophysiology of ulcerative colitis (UC). Emerging evidence indicates that there is an elevation in miR-31-5p levels in UC, which is accompanied by a downregulation of adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) expression. Nevertheless, the precise influence of miR-31-5p on macrophage polarization and the integrity of the intestinal epithelial barrier in UC remains to be fully elucidated. This study explored the role of miR-31-5p and AMPK in UC through a bioinformatics investigation. It investigated the potential of miR-31-5p antagomir to shift macrophages from pro-inflammatory M1 phenotype to anti-inflammatory M2 phenotype and enhance the intestinal mucosal barrier in DSS-induced UC mice. Additionally, RAW264.7 cells stimulated with LPS were employed to confirm the reversal of miR-31-5p antagomir's therapeutic effect under AMPK inhibition. The findings demonstrated that miR-31-5p antagomir penetrated colonic tissues and ameliorated DSS-induced experimental colitis. Transformation of spleen and mesenteric lymph node macrophages from M1 to M2 type was seen in the DSS+miR-31-5p antagomir group. AMPK/Sirt1 expression increased while NLRP3 expression decreased. Expression of M2-related genes and proteins was enhanced and that of the M1 phenotype suppressed. Tight junction proteins, ZO-1 and occludin, were increased. The therapeutic effects of miR-31-5p antagomir transfection into RAW264.7 cells were repressed when AMPK expression was inhibited. Therefore, our results suggest that suppression of miR-31-5p expression transformed macrophages from M1 to M2, ameliorated inflammation and repaired the intestinal epithelium to alleviate DSS-induced colitis. AMPK/Sirt1/NLRP3 was involved.

SIRT1 safeguards adipogenic differentiation by orchestrating anti-oxidative responses and suppressing cellular senescence

Adipose tissue is an important endocrine organ that regulates metabolism, immune response and aging in mammals. Healthy adipocytes promote tissue homeostasis and longevity. SIRT1, a conserved NAD+-dependent deacetylase, negatively regulates adipogenic differentiation by deacetylating and inhibiting PPAR-γ. However, knocking out SIRT1 in mesenchymal stem cells (MSCs) in mice not only causes defects in osteogenesis, but also results in the loss of adipose tissues, suggesting that SIRT1 is also important for adipogenic differentiation.Here, we report that severe impairment of SIRT1 function in MSCs caused significant defects and cellular senescence during adipogenic differentiation. These were observed only when inhibiting SIRT1 during adipogenesis, not when SIRT1 inhibition was imposed before or after adipogenic differentiation. Cells generate high levels of reactive oxygen species (ROS) during adipogenic differentiation. Inhibiting SIRT1 during differentiation resulted in impaired oxidative stress response. Increased oxidative stress with H2O2 or SOD2 knockdown phenocopied SIRT1 inhibition. Consistent with these observations, we found increased p16 levels and senescence associated β-galactosidase activities in the inguinal adipose tissue of MSC-specific SIRT1 knockout mice. Furthermore, previously identified SIRT1 targets involved in oxidative stress response, FOXO3 and SUV39H1 were both required for healthy adipocyte formation during differentiation. Finally, senescent adipocytes produced by SIRT1 inhibition showed decreased Akt phosphorylation in response to insulin, a lack of response to adipocytes browning signals, and increased survival for cancer cells under chemotherapy drug treatments. These findings suggest a novel safeguard function for SIRT1 in regulating MSC adipogenic differentiation, distinct from its roles in suppressing adipogenic differentiation.

The SIRT1/Nrf2 signaling pathway mediates the anti-pulmonary fibrosis effect of liquiritigenin

BACKGROUND

At present, the treatment options available for idiopathic pulmonary fibrosis are both limited and often come with severe side effects, emphasizing the pressing requirement for innovative therapeutic alternatives. Myofibroblasts, which hold a central role in pulmonary fibrosis, have a close association with the Smad signaling pathway induced by transforming growth factor-β1 (TGF-β1) and the transformation of myofibroblasts driven by oxidative stress. Liquiritigenin, an active compound extracted from the traditional Chinese herb licorice, boasts a wide array of biomedical properties, such as anti-fibrosis and anti-oxidation. The primary objective of this study was to examine the impact of liquiritigenin on bleomycin-induced pulmonary fibrosis in mice and the underlying mechanisms.

METHODS

The anti-pulmonary fibrosis and anti-oxidant effects of liquiritigenin in vivo were tested by HE staining, Masson staining, DHE staining and bio-chemical methods. In vitro, primary mouse lung fibroblasts were treated with TGF-β1 with or without liquiritigenin, the effects of liquiritigenin in inhibiting differentiation of myofibroblasts and facilitating the translocation of Nrf2 were valued using Quantitative real-time polymerase chain reaction (Q-PCR), western blotting and immunofluorescence. Nrf2 siRNA and SIRT1 siRNA were used to investigate the mechanism underlies liquiritigenin's effect in inhibiting myofibroblast differentiation.

RESULTS

Liquiritigenin displayed a dose-dependent reduction effect in bleomycin-induced fibrosis. In laboratory experiments, it was evident that liquiritigenin possessed the ability to enhance and activate sirtuin1 (SIRT1), thereby facilitating the nuclear translocation of Nrf2 and mitigating the oxidative stress-induced differentiation of primary mouse myofibroblasts. Moreover, our investigation unveiled that SIRT1 not only regulated myofibroblast differentiation via Nrf2-mediated antioxidant responses against oxidative stress but also revealed liquiritigenin's activation of SIRT1, enabling direct binding to Smad. This led to decreased phosphorylation of the Smad complex, constrained nuclear translocation, and suppressed acetylation of the Smad complex, ultimately curtailing the transcription of fibrotic factors. Validation in live subjects provided substantial evidence for the anti-fibrotic efficacy of liquiritigenin through the SIRT1/Nrf2 signaling pathway.

CONCLUSIONS

Our findings imply that targeting myofibroblast differentiation via the SIRT1/Nrf2 signaling pathway may constitute a pivotal strategy for liquiritigenin-based therapy against pulmonary fibrosis.

Sirtuins in macrophage immune metabolism: A novel target for cardiovascular disorders

Sirtuins (SIRT1-SIRT7), as a family of NAD+-dependent protein modifying enzymes, have various catalytic functions, such as deacetylases, dealkalylases, and deribonucleases. The Sirtuins family is directly or indirectly involved in pathophysiological processes such as glucolipid metabolism, oxidative stress, DNA repair and inflammatory response through various pathways and assumes an important role in several cardiovascular diseases such as atherosclerosis, myocardial infarction, hypertension and heart failure. A growing number of studies supports that metabolic and bioenergetic reprogramming directs the sequential process of inflammation. Failure of homeostatic restoration leads to many inflammatory diseases, and that macrophages are the central cells involving the inflammatory response and are the main source of inflammatory cytokines. Regulation of cellular metabolism has emerged as a fundamental process controlling macrophage function, but its exact signaling mechanisms remain to be revealed. Understanding the precise molecular basis of metabolic control of macrophage inflammatory processes may provide new approaches for targeting immune metabolism and inflammation. Here, we provide an update of studies in cardiovascular disease on the function and role of sirtuins in macrophage inflammation and metabolism, as well as drug candidates that may interfere with sirtuins, pointing to future prospects in this field.

Isolation, Ex Vivo Expansion, and Lentiviral Transduction of Alveolar Macrophages

Alveolar macrophages (AM) are resident macrophages of the lung and play important roles in the maintenance of tissue homeostasis as well as host defense. Here, we describe how they can be harvested from murine lungs, expanded in vitro, and transduced with lentiviral vectors.

Microglial Senescence and Activation in Healthy Aging and Alzheimer's Disease: Systematic Review and Neuropathological Scoring

The greatest risk factor for neurodegeneration is the aging of the multiple cell types of human CNS, among which microglia are important because they are the "sentinels" of internal and external perturbations and have long lifespans. We aim to emphasize microglial signatures in physiologic brain aging and Alzheimer's disease (AD). A systematic literature search of all published articles about microglial senescence in human healthy aging and AD was performed, searching for PubMed and Scopus online databases. Among 1947 articles screened, a total of 289 articles were assessed for full-text eligibility. Microglial transcriptomic, phenotypic, and neuropathological profiles were analyzed comprising healthy aging and AD. Our review highlights that studies on animal models only partially clarify what happens in humans. Human and mice microglia are hugely heterogeneous. Like a two-sided coin, microglia can be protective or harmful, depending on the context. Brain health depends upon a balance between the actions and reactions of microglia maintaining brain homeostasis in cooperation with other cell types (especially astrocytes and oligodendrocytes). During aging, accumulating oxidative stress and mitochondrial dysfunction weaken microglia leading to dystrophic/senescent, otherwise over-reactive, phenotype-enhancing neurodegenerative phenomena. Microglia are crucial for managing Aβ, pTAU, and damaged synapses, being pivotal in AD pathogenesis.

Proliferation of monocytes and macrophages in homeostasis, infection, injury, and disease

Monocytes (Mo) and macrophages (Mφ) play important roles in the function of tissues, organs, and systems of all animals during homeostasis, infection, injury, and disease. For decades, conventional wisdom has dictated that Mo and Mφ are end-stage cells that do not proliferate and that Mφ accumulation in tissues is the result of infiltration of Mo from the blood and subsequent differentiation to Mφ. However, reports from the early 1900s to the present describe evidence of Mo and Mφ proliferation in different tissues and contexts. The purpose of this review is to summarize both historical and current evidence for the contribution of Mφ proliferation to their accumulation in different tissues during homeostasis, infection, injury, and disease. Mφ proliferate in different organs and tissues, including skin, peritoneum, lung, heart, aorta, kidney, liver, pancreas, brain, spinal cord, eye, adipose tissue, and uterus, and in different species including mouse, rat, rabbit, and human. Mφ can proliferate at different stages of differentiation with infiltrating Mo-like cells proliferating in certain inflammatory contexts (e.g. skin wounding, kidney injury, bladder and liver infection) and mature resident Mφ proliferating in other inflammatory contexts (e.g. nematode infection, acetaminophen liver injury) and during homeostasis. The pathways involved in stimulating Mφ proliferation also may be context dependent, with different cytokines and transcription factors implicated in different studies. Although Mφ are known to proliferate in health, injury, and disease, much remains to be learned about the regulation of Mφ proliferation in different contexts and its impact on the homeostasis, injury, and repair of different organs and tissues.

Electroacupuncture ameliorates AOM/DSS-induced mice colorectal cancer by inhibiting inflammation and promoting autophagy via the SIRT1/miR-215/Atg14 axis

Colorectal cancer (CRC) is one of the most common tumors of the digestive tract, with the third-highest incidence and the second-highest mortality rate among all malignant tumors worldwide. However, treatment options for CRC remain limited. As a complementary therapy, acupuncture or electro-acupuncture (EA) has been widely applied in the treatment of various inflammation-related diseases, such as obesity, ulcerative colitis and tumors. Although numerous pre-clinical and clinical studies have investigated the beneficial effects of acupuncture on CRC, the mechanism underlying the therapeutic action of EA is largely unknown. Evidence from previous studies has revealed that SIRT1 participates in CRC progression by activating autophagy-related miRNAs. Using azoxymethane/dextran sulfate sodium- (AOM/DSS-) induced colorectal cancer model in mice, we explored whether EA treatment can inhibit inflammation and promote autophagy via the SIRT1/miR-215/Atg14 axis. Our results showed that EA notably alleviated the CRC in mice, by decreasing the tumor number and DAI scores, inflammation, and increasing body weight of mice. Besides, EA increased the expression of SIRT1 and autophagy. Further experiments showed that SIRT1 overexpression downregulated miR-215, and promoted the expression of Atg14, whereas SIRT1 knockdown induced opposite results. In conclusion, EA can ameliorate AOM/DSS-induced CRC through regulating the SIRT1-mediated miR-215/Atg14 axis by suppressing inflammation and promoting autophagy in mice. These findings reveal a potential molecular mechanism underlying the anti-CRC effect of EA indicating that EA is a promising therapeutic candidate for CRC.

SIRT1 Asn346 sugar chain promoting collagen deacetylation protective effect on osteoblasts under stress

Silencing type information regulator homolog 1 (SIRT1) is a class of nicotinamide adenine dinucleotide (NAD+) dependent deacetylases, which is the convergence point of important physiological processes in vivo, namely, osteoblast aging, energy metabolism, and bone remodeling. To verify whether the O-acetylglucosamine (O-GlcNAc) modification of SIRT1 in the nucleus of osteoblasts enhances its deacetylase activity under stress and protects osteoblasts through the RANK/RANKL signaling pathway by collagen deacetylation. The R language and online data research identified SIRT1 as being involved in bone metabolism. Enrichment analysis showed that SIRT1 is involved in osteoblast transcription, apoptosis, and deacetylation pathways. Interactive Immuno-blotting and immunofluorescence experiments revealed that SIRT1 and O-glycosylation catalytic enzyme (OGT) were localized in the nucleus. Mass Spectrometry analysis showed that O-glycosylation occurred on the asparagine at the 346th position of SIRT1, and N346th was located in the central domain of SIRT1. Furthermore, the protein structure analysis of PyMol also proved that the OGT binding region was in the central domain of SIRT1. Under physiological conditions, both wtSIRT1 and SIRT1N346R can inhibit RANKL-mediated transcriptional activation. The RT-PCR detection results showed that wtSIRT1 reduced RANKL transcription under the conditions of apoptotic agent treatment. The finding that SIRT1 can regulate the physiological process of bone remodeling through the RANK/RANKL signaling pathway in osteoblasts under stress. The O-glycosylation and deacetylation activity of SIRT1 significantly increased, regulating the balance between osteoblast survival and apoptosis by deacetylation of key proteins such as RANKL.

Insufficient SIRT1 in macrophages promotes oxidative stress and inflammation during scarring

Macrophage is a critical regulator in wound healing and scar formation, and SIRT1 is related to macrophage activation and polarization, while the specific mechanism is still unclear. To explore the specific effects of SIRT1 in scarring, we established a skin incision mouse model and LPS-induced inflammation cell model. The expression of SIRT1 in tissue and macrophage was detected, and the level of SIRT1 was changed to observe the downstream effects. LPS-induced macrophages with or without SIRT1 deficiency were used for TMT-based quantitative proteomic analysis. SIRT1 was suppressed in scar while increased in macrophages of scar tissue. And macrophages were proven to be necessary for wound healing. In the early stage of wound healing, knockout of SIRT1 in macrophage could greatly strengthen inflammation and finally promote scarring. NADH-related activities and oxidoreductase activities were differentially expressed in TMT-based quantitative proteomic analysis. We confirmed that ROS production and NOX2 level were elevated after LPS stimulation while the Nrf2 pathway and the downstream proteins, such as Nqo-1 and HO-1, were suppressed. In contrast, the suppression of SIRT1 strengthened this trend. The NF-κB pathway was remarkably activated compared with the control group. Insufficient increase of SIRT1 in macrophage leads to over activated oxidative stress and activates NF-κB pathways, which then promotes inflammation in wound healing and scarring. Further increasing SIRT1 in macrophages could be a promising method to alleviate scarring. KEY MESSAGES: SIRT1 was suppressed in scar while increased in macrophages of scar tissue. Inhibition of SIRT1 in macrophage leads to further activated oxidative stress. SIRT1 is negatively related to oxidative stress in macrophage. The elevation of SIRT1 in macrophage is insufficient during scarring.

BET proteins inhibitor JQ1 impairs GM-CSF-promoted peritoneal macrophage self-renewal and IL-4-induced alternative polarization

Peritoneal macrophages (PMs), which resided in peritoneal cavity, are crucial to maintain tissue homeostasis and immunity. Macrophage self-renewal and polarization states are critical for PM population homeostasis and function. However, the underlying molecular mechanism that regulates self-renewal and polarization of PMs is still unclear and needs to be explored. Here, we demonstrated that PMs self-renewal was stimulated by granulocyte macrophage colony-stimulating factor (GM-CSF), but not by macrophage colony-stimulating factor (M-CSF). Pharmacological inhibition of Bromodomain & Extraterminal (BET) Proteins by either JQ1 or ARV-825 significantly reduced GM-CSF-dependent peritoneal macrophage self-renewal by abrogating cell proliferation and decreasing self-renewal-related gene expression, such as MYC and Klf4, at transcriptional and protein levels. In addition, transcriptomic analysis showed that JQ1 blocked alternative PMs polarization by downregulating key transcriptional factor IRF4 expression, but not the activation of AKT or STAT6 in PMs. These findings illustrated that the significance of BET family proteins in GM-CSF-induced PMs self-renewal and IL-4-induced alternative polarization.

Research Progress on Natural Small-Molecule Compounds for the Prevention and Treatment of Sepsis

Sepsis is a serious disease with high mortality and has been a hot research topic in medical research in recent years. With the continuous reporting of in-depth research on the pathological mechanisms of sepsis, various compounds have been developed to prevent and treat sepsis. Natural small-molecule compounds play vital roles in the prevention and treatment of sepsis; for example, compounds such as resveratrol, emodin, salidroside, ginsenoside, and others can modulate signaling through the NF-κB, STAT3, STAT1, PI3K, and other pathways to relieve the inflammatory response, immunosuppression, and organ failure caused by sepsis. Here, we discuss the functions and mechanisms of natural small-molecule compounds in preventing and treating sepsis. This review will lay the theoretical foundation for discovering new natural small-molecule compounds that can potentially prevent and treat sepsis.

AIF1 + CSF1R + MSCs, induced by TNF-α, act to generate an inflammatory microenvironment and promote hepatocarcinogenesis

BACKGROUND AND AIMS

Increasing evidence suggests that mesenchymal stem cells (MSCs) home to injured local tissues and the tumor microenvironment in the liver. Chronic inflammation is regarded as the major trait of primary liver cancer. However, the characteristics of endogenous MSCs in the inflammatory environment and their role in the occurrence of liver cancer remain obscure.

APPROACH AND RESULTS

Using single-cell RNA sequencing, we identified a distinct inflammation-associated subset of MSCs, namely AIF1 + CSF1R + MSCs, which existed in the microenvironment before the occurrence of liver cancer. Furthermore, we found that this MSC subgroup is likely to be induced by TNF-α stimulation through the TNFR1/SIRT1 (sirtuin 1) pathway. In a rat primary liver cancer model, we showed that MSCs with high SIRT1 expression (Ad-Sirt1-MSCs) promoted macrophage recruitment and synergistically facilitated liver cancer occurrence by secreting C-C motif chemokine ligand (CCL) 5. Interestingly, depletion of macrophages or knockdown of CCL5 expression in Ad-Sirt1-MSCs attenuated the promotive effect of Ad-Sirt1-MSCs on liver inflammation and hepatocarcinogenesis (HCG). Finally, we demonstrated that SIRT1 up-regulated CCL5 expression through activation of the AKT/HIF1α signaling axis in MSCs.

CONCLUSIONS

Together, our results show that MSCs, which are mobilized to the injured site, can be educated by macrophages. In turn, the educated MSCs are involved in generating a chronic inflammatory microenvironment and promoting HCG.

Epigenomics Analysis of the Suppression Role of SIRT1 via H3K9 Deacetylation in Preadipocyte Differentiation

Sirtuin 1 (SIRT1) overexpression significantly inhibits lipid deposition during yak intramuscular preadipocyte (YIMA) differentiation; however, the regulatory mechanism remains unknown. We elucidated the role of SIRT1 in YIMA differentiation using lentivirus-mediated downregulation technology and conducted mRNA-seq and ChIP-seq assays using H3K9ac antibodies after SIRT1 overexpression in order to reveal SIRT1 targets during YIMA adipogenesis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed in order to identify the functional annotation of common genes. In addition, a potential target of SIRT1 was selected to verify its effects on the differentiation and proliferation of YIMAs. SIRT1 interfered with lipid deposition and promoted YIMA differentiation. In total, 143,518 specific peaks were identified after SIRT1 overexpression, where genes associated with downregulation peaks were enriched in transcription, gene expression, lipid-related processes, and classical lipid-related pathways. The H3K9ac signal in the whole genome promoter region (2 kb upstream and downstream of the transcription start site (TSS)) was weakened, and the peaks were distributed across all gene functional regions. Genes that lost signals in their TSS region or gene body region were enriched in both biological processes and pathways associated with lipogenesis. The ChIP-seq results revealed 714 common differential genes in mRNA-seq, which were enriched in "MAPK signaling", "lipid and atherosclerosis", "mTOR signaling", and "FoxO signaling" pathways. A total of 445 genes were downregulated in both their H3K9ac signals and mRNA expression, and one of their most significantly enriched pathways was FoxO signaling. Nine genes (FBP2, FPGT, HSD17B11, KCNJ15, MAP3K20, SLC5A3, TRIM23, ZCCHC10, and ZMYM1) lost the H3K9ac signal in their TSS regions and had low mRNA expression, and three genes (KCNJ15, TGM3, and TRIM54) had low expression but lost their H3K9ac signal in the gene body region. The interference of TRIM23 significantly inhibited fat deposition during preadipocyte differentiation and promoted cell proliferation by increasing S-phase cell numbers. The present study provides new insights into the molecular mechanism of intramuscular fat content deposition and the epigenetic role of SIRT1 in adipocyte differentiation.

The SWI/SNF chromatin-remodeling subunit DPF2 facilitates NRF2-dependent antiinflammatory and antioxidant gene expression

During emergency hematopoiesis, hematopoietic stem cells (HSCs) rapidly proliferate to produce myeloid and lymphoid effector cells, a response that is critical against infection or tissue injury. If unresolved, this process leads to sustained inflammation, which can cause life-threatening diseases and cancer. Here, we identify a role of double PHD fingers 2 (DPF2) in modulating inflammation. DPF2 is a defining subunit of the hematopoiesis-specific BAF (SWI/SNF) chromatin-remodeling complex, and it is mutated in multiple cancers and neurological disorders. We uncovered that hematopoiesis-specific Dpf2-KO mice developed leukopenia, severe anemia, and lethal systemic inflammation characterized by histiocytic and fibrotic tissue infiltration resembling a clinical hyperinflammatory state. Dpf2 loss impaired the polarization of macrophages responsible for tissue repair, induced the unrestrained activation of Th cells, and generated an emergency-like state of HSC hyperproliferation and myeloid cell-biased differentiation. Mechanistically, Dpf2 deficiency resulted in the loss of the BAF catalytic subunit BRG1 from nuclear factor erythroid 2-like 2-controlled (NRF2-controlled) enhancers, impairing the antioxidant and antiinflammatory transcriptional response needed to modulate inflammation. Finally, pharmacological reactivation of NRF2 suppressed the inflammation-mediated phenotypes and lethality of Dpf2Δ/Δ mice. Our work establishes an essential role of the DPF2-BAF complex in licensing NRF2-dependent gene expression in HSCs and immune effector cells to prevent chronic inflammation.

The Role of Sirtuin 1 (SIRT1) in Neurodegeneration

Sirtuins (SIRT) are a class of histone deacetylases that regulate important metabolic pathways and play a role in several disease processes. Of the seven mammalian homologs currently identified, sirtuin 1 (SIRT1) is the best understood and most studied. It has been associated with several neurodegenerative diseases and cancers. As such, it has been further investigated as a therapeutic target in the treatment of disorders such as Parkinson's disease (PD), Huntington's disease (HD), and Alzheimer's disease (AD). SIRT1 deacetylates histones such as H1 lysine 26, H3 lysine 9, H3 lysine 56, and H4 lysine 16 to regulate chromatin remodeling and gene transcription. The homolog has also been observed to express contradictory responses to tumor suppression and tumor promotion. Studies have shown that SIRT1 may have anti-inflammatory properties by inhibiting the effects of NF-κB, as well as stimulating upregulation of autophagy. The SIRT1 activators resveratrol and cilostazol have been shown to improve Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) scores in AD patients. In this review, we aim to explore the various roles of SIRT1 with regard to neuroprotection and neurodegeneration.

Therapeutic potential of natural molecules against Alzheimer's disease via SIRT1 modulation

Alzheimer's disease (AD) is a neurodegenerative disease mainly characterized by progressive cognitive dysfunction and memory impairment. Recent studies have shown that regulating silent information regulator 1 (SIRT1) expression has a significant neuroprotective effect, and SIRT1 may become a new therapeutic target for AD. Natural molecules are an important source of drug development for use in AD therapy and may regulate a wide range of biological events by regulating SIRT1 as well as other SIRT1-mediated signaling pathways. This review aims to summarize the correlation between SIRT1 and AD and to identify in vivo and in vitro studies investigating the anti-AD properties of natural molecules as modulators of SIRT1 and SIRT1-mediated signaling pathways. A literature search was conducted for studies published between January 2000 and October 2022 using various literature databases, including Web of Science, PubMed, Google Scholar, Science Direct, and EMBASE. Natural molecules, such as resveratrol, quercetin, icariin, bisdemethoxycurcumin, dihydromyricetin, salidroside, patchouli, sesamin, rhein, ligustilide, tetramethoxyflavanone, 1-theanine, schisandrin, curcumin, betaine, pterostilbene, ampelopsin, schisanhenol, and eriodictyol, have the potential to modulate SIRT1 and SIRT1 signaling pathways, thereby combating AD. The natural molecules modulating SIRT1 discussed in this review provide a potentially novel multi-mechanistic therapeutic strategy for AD. However, future clinical trials need to be conducted to further investigate their beneficial properties and to determine the safety and efficacy of SIRT1 natural activators against AD.

Cordycepin Enhances SIRT1 Expression and Maintains Stemness of Human Mesenchymal Stem Cells

BACKGROUND/AIM

Mesenchymal stem cells (MSCs) have been employed for therapeutic applications of various degenerative diseases. However, the major concern is MSC aging during the in vitro cultivation. Thus, the approach to delay MSC aging was examined in this research by focusing on the expression of Sirtuin 1 (SIRT1), a key anti-aging marker.

MATERIALS AND METHODS

Cordycepin, a bioactive compound derived from Cordyceps militaris, was used to up-regulate SIRT1 and maintain stemness of MSCs. Upon treatment with cordycepin, MSCs were investigated for cell viability, doubling time, key gene/protein expression, galactosidase-associated senescence assay, relative telomere length, and telomerase expression.

RESULTS

Cordycepin significantly increased the expression of SIRT1 in MSCs by activating the adenosine monophosphate activated protein kinase (AMPK)-SIRT1 signalling pathway. Moreover, cordycepin maintained the stemness of MSCs by deacetylating SRY-box transcription factor 2 (SOX2) via SIRT1, and cordycepin delayed cellular senescence and aging of MSCs by enhancing autophagy, inhibiting the activity of senescence-associated-galactosidase, maintaining proliferation rate, and increasing telomere activity.

CONCLUSION

Cordycepin could be used to increase SIRT1 expression in MSCs for anti-aging applications.

PBX1-SIRT1 Positive Feedback Loop Attenuates ROS-Mediated HF-MSC Senescence and Apoptosis

Stem cell senescence and depletion are major causes of aging and aging-related diseases. The NAD (Nicotinamide adenine dinucleotide) - SIRT1 (Silent Information Regulator 1) - PARP1 (Poly (ADP-ribose) polymerase-1) axis has gained interest owing to its significant role in regulating stem cell senescence and organismal aging. A recent study from our lab showed that pre-B-cell leukemia transcription factor1 (PBX1) overexpression attenuates hair follicle-derived mesenchymal stem cells (HF-MSCs) senescence and apoptosis by regulating ROS-mediated DNA damage via PARP1 downregulation; thus, suggesting that PARP1 downregulation is a common manifestation of the roles of both PBX1 and SIRT1 in HF-MSCs senescence attenuation, and implying a potential link between PBX1 and SIRT1. To this end, HF-MSCs overexpressing PBX1, overexpressing both PBX1 and PARP1, downregulating SIRT1, and overexpressing PBX1 as well as downregulating SIRT1 were generated, and senescence, apoptosis, DNA damage, and repair biomarkers were analyzed. Our results showed that (1) PBX1 overexpression alleviated HF-MSCs senescence and apoptosis accompanied by SIRT1 upregulation, PARP1 downregulation, and increased intracellular NAD and ATP levels. (2) SIRT1 knockdown enhanced cellular senescence and apoptosis, accompanied by increased ROS accumulation, DNA damage aggravation, and decreased intracellular NAD and ATP levels. (3) PBX1 overexpression rescued HF-MSCs senescence and apoptosis induced by SIRT1 knockdown. (4) PBX1 rescued PARP1 overexpression-mediated ATP and NAD depletion, accompanied by increased SIRT1 expression. Collectively, our results revealed that a positive interaction feedback loop exists between PBX1 and SIRT1. To the best of our knowledge we are the first to report that there is a PBX1-SIRT1-PARP1 axis that plays a critical role in alleviating HF-MSCs senescence and apoptosis. We provide a new perspective on the mechanisms underlying stem cell senescence as well as age-related disease prevention and treatment.

Tanshinone IIA ameliorates Aβ transendothelial transportation through SIRT1-mediated endoplasmic reticulum stress

BACKGROUND

The disruption of blood-brain barrier (BBB), predominantly made up by brain microvascular endothelial cells (BMECs), is one of the characteristics of Alzheimer's disease (AD). Thus, improving BMEC function may be beneficial for AD treatment. Tanshinone IIA (Tan IIA) has been proved to ameliorate the cognitive dysfunction of AD. Herein, we explored how Tan IIA affected the function of BMECs in AD.

METHODS

Aβ_1-42-treated brain-derived endothelium cells.3 (bEnd.3 cells) was employed for in vitro experiments. And we performed molecular docking and qPCR to determine the targeting molecule of Tan IIA on Sirtuins family. The APP^swe/PS^dE9 (APP/PS1) mice were applied to perform the in vivo experiments. Following the behavioral tests, protein expression was determined through western blot and immunofluorescence. The activities of oxidative stress-related enzymes were analyzed by biochemically kits. Nissl staining and thioflavin T staining were conducted to reflect the neurodegeneration and Aβ deposition respectively.

RESULTS

Molecular docking and qPCR results showed that Tan IIA mainly acted on Sirtuin1 (SIRT1) in Sirtuins family. The inhibitor of SIRT1 (EX527) was employed to further substantiate that Tan IIA could attenuate SIRT1-mediated endoplasmic reticulum stress (ER stress) in BMECs. Behavioral tests suggested that Tan IIA could improve the cognitive deficits in APP/PS1 mice. Tan IIA administration increased SIRT1 expression and alleviated ER stress in APP/PS1 mice. In addition, LRP1 expression was increased and RAGE expression was decreased after Tan IIA administration in both animals and cells.

CONCLUSION

Tan IIA could promote Aβ transportation by alleviating SIRT1-mediated ER stress in BMECs, which ameliorated cognitive deficits in APP/PS1 mice.

Role of Sirtuins in the Pathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune and inflammatory disease leading to joint destruction. The causes of RA are not fully known. Most likely, the development of the disease depends on the coexistence of many factors, such as hereditary factors, immune system defects, gender, infectious agents, nicotine, and stress. Various epigenetic changes have been identified and correlated with the aggressive phenotype of RA, including the involvement of sirtuins, which are enzymes found in all living organisms. Their high content in the human body can slow down the aging processes, reduce cell death, counteract the appearance of inflammation, and regulate metabolic processes. Sirtuins can participate in several steps of RA pathogenesis. This narrative review presents, collects, and discusses the role of all sirtuins (1-7) in the pathogenesis of rheumatoid arthritis.

Mitophagy in ototoxicity

Mitochondrial dysfunction is associated with ototoxicity, which is caused by external factors. Mitophagy plays a key role in maintaining mitochondrial homeostasis and function and is regulated by a series of key mitophagy regulatory proteins and signaling pathways. The results of ototoxicity models indicate the importance of this process in the etiology of ototoxicity. A number of recent investigations of the control of cell fate by mitophagy have enhanced our understanding of the mechanisms by which mitophagy regulates ototoxicity and other hearing-related diseases, providing opportunities for targeting mitochondria to treat ototoxicity.

Novel Role of the SIRT1 in Endocrine and Metabolic Diseases

Silent information regulator 1 (SIRT1), a highly conserved NAD⁺-dependent deacetylase, is a cellular regulator that has received extensive attention in recent years and regarded as a sensor of cellular energy and metabolism. The accumulated evidence suggests that SIRT1 is involved in the development of endocrine and metabolic diseases. In a variety of organisms, SIRT1 regulates gene expression through the deacetylation of histone, transcription factors, and lysine residues of other modified proteins including several metabolic and endocrine signal transcription factors, thereby enhancing the therapeutic effects of endocrine and metabolic diseases. These evidences indicate that targeting SIRT1 has promising applications in the treatment of endocrine and metabolic diseases. This review focuses on the role of SIRT1 in endocrine and metabolic diseases. First, we describe the background and structure of SIRT1. Then, we outline the role of SIRT1 in endocrine and metabolic diseases such as hyperuricemia, diabetes, hypertension, hyperlipidemia, osteoporosis, and polycystic ovarian syndrome. Subsequently, the SIRT1 agonists and inhibitors in the above diseases are summarized and future research directions are proposed. Overall, the information presents here may highlight the potential of SIRT1 as a future biomarker and therapeutic target for endocrine and metabolic diseases.

The sirtuin family in health and disease

Sirtuins (SIRTs) are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes, and are involved in numerous biological processes. Currently, seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified. Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions. Notably, this protein family plays a variety of important roles in cellular biology such as inflammation, metabolism, oxidative stress, and apoptosis, etc., thus, it is considered a potential therapeutic target for different kinds of pathologies including cancer, cardiovascular disease, respiratory disease, and other conditions. Moreover, identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules, which can modify SIRT activity. Furthermore, several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples, and supplementation of SIRT modulators might have diverse impact on physiological function in different participants. In this review, we introduce the history and structure of the SIRT protein family, discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family, elaborate on the regulatory roles of SIRTs in human disease, summarize SIRT inhibitors and activators, and review related clinical studies.

Involvement of LARP7 in Activation of SIRT1 to Inhibit NF-κB Signaling Protects Microglia from Acrylamide-Induced Neuroinflammation

Acrylamide (AM) is a potent neurotoxin and carcinogen that is mainly formed by the Maillard reaction of asparagine with starch at high temperatures. However, the toxicity mechanism underlying AM has not been investigated from a proteomic perspective, and the regulation of protein expression by AM remains poorly understood. This research was the first to utilize proteomics to explore the mechanism of AM exposure-induced neuroinflammation. Target proteins were obtained by differential protein analysis, functional annotation, and enrichment analysis of proteomics. Then, molecular biology methods, including Western blot, qPCR, and immunofluorescence, were used to verify the results and explore possible mechanisms. We identified 100 key differential metabolites by proteomic analysis, which was involved in the occurrence of various biological functions. Among them, the KEGG pathway enrichment analysis showed that the differential proteins were enriched in the P53 pathway, sulfur metabolism pathway, and ferroptosis. Finally, the differential target protein we locked was LARP7. Molecular biological verification found that AM exposure inhibited the expression of LARP7 and induced the burst of inflammation, while SRT1720 agonist treatment showed no effect on LARP7, but significant changes in inflammatory factors and NF-κB. Taken together, these findings suggested that AM may activate NF-κB to induce neuroinflammation by inhibiting the LARP7-SIRT1 pathway. And our study provided a direction for AM-induced neurotoxicity through proteomics and multiple biological analysis methods.

Self-Renewal of Macrophages: Tumor-Released Factors and Signaling Pathways

Macrophages are the most abundant immune cells of the tumor microenvironment (TME) and have multiple important functions in cancer. During tumor growth, both tissue-resident macrophages and newly recruited monocyte-derived macrophages can give rise to tumor-associated macrophages (TAMs), which have been associated with poor prognosis in most cancers. Compelling evidence indicate that the high degree of plasticity of macrophages and their ability to self-renew majorly impact tumor progression and resistance to therapy. In addition, the microenvironmental factors largely affect the metabolism of macrophages and may have a major influence on TAMs proliferation and subsets functions. Thus, understanding the signaling pathways regulating TAMs self-renewal capacity may help to identify promising targets for the development of novel anticancer agents. In this review, we focus on the environmental factors that promote the capacity of macrophages to self-renew and the molecular mechanisms that govern TAMs proliferation. We also highlight the impact of tumor-derived factors on macrophages metabolism and how distinct metabolic pathways affect macrophage self-renewal.

Sirtuins as novel pharmacological targets in podocyte injury and related glomerular diseases

Podocyte injury is a major cause of proteinuria in kidney diseases, and persistent loss of podocytes leads to rapid irreversible progression of kidney disease. Sirtuins, a class of nicotinamide adenine dinucleotide-dependent deacetylases, can promote DNA repair, modify transcription factors, and regulate the cell cycle. Additionally, sirtuins play a critical role in renoprotection, particularly against podocyte injury. They also have pleiotropic protective effects on podocyte injury-related glomerular diseases, such as improving the immune inflammatory status and oxidative stress levels, maintaining mitochondrial homeostasis, enhancing autophagy, and regulating lipid metabolism. Sirtuins deficiency causes podocyte injury in different glomerular diseases. Studies using podocyte sirtuin-specific knockout and transgenic models corroborate this conclusion. Of note, sirtuin activators have protective effects in different podocyte injury-related glomerular diseases, including diabetic kidney disease, focal segmental glomerulosclerosis, membranous nephropathy, IgA nephropathy, and lupus nephritis. These findings suggest that sirtuins are promising therapeutic targets for preventing podocyte injury. This review provides an overview of recent advances in the role of sirtuins in kidney diseases, especially their role in podocyte injury, and summarizes the possible rationale for sirtuins as targets for pharmacological intervention in podocyte injury-related glomerular diseases.

Alzheimer’s Amyloid-β Accelerates Cell Senescence and Suppresses the SIRT1/NRF2 Pathway in Human Microglial Cells

Microglia play important roles in maintenance of brain homeostasis, while due to some pathological stimuli in aging-related neurodegenerative diseases including Alzheimer's disease, they are malfunctioning. Here, we demonstrated that amyloid-β (Aβ) accelerated cell senescence characterized by the upregulation of p21 and PAI-1 as well as senescence-associated beta-galactosidase (SA-β-gal) in human microglial cells. Consistently, Aβ induced the senescence-associated mitochondrial dysfunctions such as repression of ATP production, oxygen consumption rate (OCR), and mitochondrial membrane potential and enhancement of ROS production. Furthermore, Aβ was found to significantly suppress mRNA expression and protein level of Sirtuin-1 (SIRT1), a key regulator of senescence, and inhibit mRNA expression and translocation of NRF2, a critical transcription factor in inflammatory responses, leading to impairment of phagocytosis. Rescue of SIRT1, as expected, could counteract the pathological effects of Aβ. In summary, our findings revealed that Aβ accelerates human microglial senescence mainly through its suppression of the SIRT1/NRF2 pathway and suggested that genetic and pharmaceutical rescue of SIRT1 may provide a potential alternative treatment.

The Essential Role of FoxO1 in the Regulation of Macrophage Function

Macrophages are widely distributed in various tissues and organs. They not only participate in the regulation of innate and adaptive immune response, but also play an important role in tissue homeostasis. Dysregulation of macrophage function is closely related to the initiation, development and prognosis of multiple diseases, including infection and tumorigenesis. Forkhead box transcription factor O1 (FoxO1) is an important member among the forkhead box transcription factor family. Through directly binding to the promoter regions of downstream target genes, FoxO1 is implicated in cell proliferation, apoptosis, metabolic activities and other biological processes. In this review, we summarized the regulatory role of FoxO1 in macrophage phagocytosis, migration, differentiation and inflammatory activation. We also emphasized that macrophage reciprocally modulated FoxO1 activity via a post-translational modification (PTM) dominant manner.

SIRT1 ameliorated septic associated-lung injury and macrophages apoptosis via inhibiting endoplasmic reticulum stress

BACKGROUND

The inappropriate apoptosis of macrophages plays an important role in the pathogenesis of sepsis-induced acute lung injury, however, the detailed regulatory mechanisms remain largely unknown. As an endogenous apoptosis pathway, endoplasmic reticulum (ER) stress plays an important role in cell damage in patients with sepsis. Clarifying the ER stress response and its effect on macrophages during the development of sepsis is helpful to explore new strategies for the prevention and treatment of ALI in sepsis.

METHODS

The mouse model and the RAW264.7 inflammation model were stimulated with LPS to establish in vivo and in vitro. We explored the effects of different expression levels of silent information regulator factor 2-related enzyme 1 (SIRT1) on the ER stress response and apoptosis of macrophages in the sepsis-related injury model.

RESULTS

Our studies found that the increased expression of SIRT1 can significantly improve sepsis-related lung injury and relieve lung inflammation. SRT1720, a SIRT1 activator, can significantly inhibit the ER stress response of lung tissue and macrophages, inhibit the expression of pro-apoptotic proteins, promote the expression of anti-apoptotic proteins, and reduce macrophages of apoptosis. While the EX527, an inhibitor of SIRT1, had the opposite effect.

CONCLUSION

SIRT1 can significantly improve sepsis-associated lung injury and LPS-induced macrophage apoptosis. This protective effect is closely related to its inhibition of the ER stress response via the PERK/eIF2-α/ATF4/CHOP pathway.

Daming capsule protects against myocardial infarction by promoting mitophagy via the SIRT1/AMPK signaling pathway

Myocardial infarction (MI) is a myocardial injury caused by coronary thrombosis or persistent ischemia and hypoxia. Due to its high morbidity and mortality, a safer and more effective treatment strategy is urgently needed. Daming capsule (DMC), a hypolipidemic drug, reportedly exerts cardioprotective effects in clinical and basic research, although its protective mechanism remains unknown. To investigate the mechanism underlying DMC-mediated improvement of cardiac function post-MI, C57/BL6 mice subjected to coronary artery ligation were administered DMC for 4 weeks. Our data demonstrated that DMC significantly improved cardiac structure and function compared to the saline group. Moreover, DMC inhibited inflammatory response and oxidative stress and improved mitochondrial structure and function in MI mice and hypoxia-stressed cardiomyocytes. Next, our research proved that DMC increased the expression of mitophagy receptor NLRX1. Interestingly, with the administration of DMC and siNLRX1, NLRX1 expression, mitochondria and lysosome colocalization, and mitochondrial membrane potential decreased, while mitochondrial ROS accumulation increased, suggesting that DMC promoted mitophagy to improve mitochondrial function via NLRX1 regulation. Further analysis showed that DMC activated the SIRT1/AMPK signaling pathway in vivo and in vitro. Our data showed that SIRT1 knockdown downregulated NLRX1 expression, leading to structural damage and functional impairment in mitochondria, as well as increased oxidative stress, inflammatory response, and decreased cardiac function in MI mice. Collectively, our findings reveal that DMC improves cardiac function post-MI by increasing mitophagy and inhibiting oxidative stress and inflammotory response in cardiomyocytes through the SIRT1/AMPK signaling pathway.

Sirtuin1 attenuates acute liver failure by reducing reactive oxygen species via hypoxia inducible factor 1α

BACKGROUND

The occurrence and development of acute liver failure (ALF) is closely related to a series of inflammatory reactions, such as the production of reactive oxygen species (ROS). Hypoxia inducible factor 1α (HIF-1α) is a key factor that regulates oxygen homeostasis and redox, and the stability of HIF-1α is related to the ROS level regulated by Sirtuin (Sirt) family. The activation of Sirt1 will lead to a powerful antioxidant defense system and therapeutic effects in liver disease. However, little is known about the relationship between HIF-1α and Sirt1 in the process of ALF and the molecular mechanism.

AIM

To investigate whether HIF-1α may be a target of Sirt1 deacetylation and what the effects on ALF are.

METHODS

Mice were administrated lipopolysaccharide (LPS)/D-gal and exposed to hypoxic conditions as animal model, and resveratrol was used as an activator of Sirt1. The cellular model was established with L02 cells stimulated by LPS. N-acetyl-L-cysteine was used to remove ROS, and the expression of Sirt1 was inhibited by nicotinamide. Western blotting was used to detect Sirt1 and HIF-1α activity and related protein expression. The possible signaling pathways involved were analyzed by immunofluorescent staining, co-immunoprecipitation, dihydroethidium staining, and Western blotting.

RESULTS

Compared with mice stimulated with LPS alone, the expression of Sirt1 decreased, the level of HIF-1α acetylation increased in hypoxic mice, and the levels of carbonic anhydrase 9 and Bcl-2-adenovirus E1B interacting protein 3 increased significantly, which was regulated by HIF-1α, indicating an increase of HIF-1α activity. Under hypoxia, the down-regulation of Sirt1 activated and acetylated HIF-1α in L02 cells. The inhibition of Sirt1 significantly aggravated this effect and the massive production of ROS. The regulation of ROS was partly through peroxisome proliferator-activated receptor alpha or AMP-activated protein kinase. Resveratrol, a Sirt1 activator, effectively relieved ALF aggravated by hypoxia, the production of ROS, and cell apoptosis. It also induced the deacetylation of HIF-1α and inhibited the activity of HIF-1α.

CONCLUSION

Sirt1 may have a protective effect on ALF by inducing HIF-1α deacetylation to reduce ROS.

Regulation of SIRT1 and Its Roles in Inflammation

The silent information regulator sirtuin 1 (SIRT1) protein, a highly conserved NAD⁺-dependent deacetylase belonging to the sirtuin family, is a post-translational regulator that plays a role in modulating inflammation. SIRT1 affects multiple biological processes by deacetylating a variety of proteins including histones and non-histone proteins. Recent studies have revealed intimate links between SIRT1 and inflammation, while alterations to SIRT1 expression and activity have been linked to inflammatory diseases. In this review, we summarize the mechanisms that regulate SIRT1 expression, including upstream activators and suppressors that operate on the transcriptional and post-transcriptional levels. We also summarize factors that influence SIRT1 activity including the NAD⁺/NADH ratio, SIRT1 binding partners, and post-translational modifications. Furthermore, we underscore the role of SIRT1 in the development of inflammation by commenting on the proteins that are targeted for deacetylation by SIRT1. Finally, we highlight the potential for SIRT1-based therapeutics for inflammatory diseases.

SIRT1-SIRT7 Expression in Patients with Lymphoproliferative Disorders Undergoing Hematopoietic Stem Cell Mobilization

Sirtuins are involved in the fate of hematopoietic stem cells (HSCs), including their metabolism, stress response, differentiation, migration, and apoptosis. The aim of this study was to explore SIRT1-7 expression during HSC mobilization. The study included 50 patients with lymphoproliferative disorders (39 multiple myeloma, 11 lymphoma). Samples were taken before mobilization (day 0) and on the day of first apheresis (day A). The sirtuin expression was evaluated by the Droplet Digital PCR (ddPCR) method. A significant increase of the SIRT1, SIRT2, SIRT3, SIRT5, SIRT6, and SIRT7 levels measured at day A as compared to baseline was observed. The study revealed a positive correlation between SIRT5, SIRT6, and SIRT7 expression and the CD34+ peak value in peripheral blood and the number of CD34+ cells collected on day A. Patients from the SIRT7 “high expressors” group collected more CD34+ cells on day A than “low expressors”. Upregulated expressions of SIRT3 and SIRT7 on the day of first apheresis were observed in patients in complete remission status (CR) as compared to the non-CR group. Our results suggest that the investigated sirtuins may influence the HSC migration and hematopoietic landscape during mobilization. SIRT5, SIRT6, and SIRT7 may be associated with the efficacy of HSC mobilization.

Long-term culture-expanded alveolar macrophages restore their full epigenetic identity after transfer in vivo

Alveolar macrophages (AMs) are lung tissue-resident macrophages that can be expanded in culture, but it is unknown to what extent culture affects their in vivo identity. Here we show that mouse long-term ex vivo expanded AMs (exAMs) maintained a core AM gene expression program, but showed culture adaptations related to adhesion, metabolism and proliferation. Upon transplantation into the lung, exAMs reacquired full transcriptional and epigenetic AM identity, even after several months in culture and could self-maintain long-term in the alveolar niche. Changes in open chromatin regions observed in culture were fully reversible in transplanted exAMs and resulted in a gene expression profile indistinguishable from resident AMs. Our results indicate that long-term proliferation of AMs in culture did not compromise cellular identity in vivo. The robustness of exAM identity provides new opportunities for mechanistic analysis and highlights the therapeutic potential of exAMs.

The impact of the lung environment on macrophage development, activation and function: diversity in the face of adversity

The last decade has been somewhat of a renaissance period for the field of macrophage biology. This renewed interest, combined with the advent of new technologies and development of novel model systems to assess different facets of macrophage biology, has led to major advances in our understanding of the diverse roles macrophages play in health, inflammation, infection and repair, and the dominance of tissue environments in influencing all of these areas. Here, we discuss recent developments in our understanding of lung macrophage heterogeneity, ontogeny, metabolism and function in the context of health and disease, and highlight core conceptual advances and key unanswered questions that we believe should be focus of work in the coming years.

Pinocembrin ameliorates acute liver failure via activating the Sirt1/PPARα pathway in vitro and in vivo

Acute liver failure (ALF) is a life-threatening disease and affects multiple organ systems. Pro-inflammatory factors derived from macrophage plays a key role in septicemia. Pinocembrin is a natural favonoid compound, which can be extracted from honey, propolis and several other plants. Recent investigations demonstrate that Pinocembrin has a variety of pharmacological activities, including anti-inflammatory and antioxidant. To investigate the effects of Pinocembrin on ALF, we explored its possible molecular mechanisms through the experiments in vivo and in vitro. Pre-treatment with Pinocembrin attenuated LPS-induced hepatocyte dysfunction and reduced levels of pro-inflammatory factors and macrophages infiltration. Pinocembrin inhibited the hepatocyte apoptosis and pro-inflammatory reaction of peritoneal macrophages by reducing reactive oxygen species (ROS) via the Sirt1/PPARα signaling pathway. Our study suggests that Pinocembrin might represent a novel therapeutic drug and offers a new method for the treatment of ALF.

Low Expression of YTH Domain-Containing 1 Promotes Microglial M1 Polarization by Reducing the Stability of Sirtuin 1 mRNA

The N6-methyladenosine (m6A) modification is the most abundant posttranscriptional mRNA modification in mammalian cells and is dynamically modulated by a series of "writers," "erasers," and "readers." Studies have shown that m6A affects RNA metabolism in terms of RNA processing, nuclear export, translation, and decay. However, the role of the m6A modification in retinal microglial activation remains unclear. Here, we analyzed the single-cell RNA sequencing data of retinal cells from mice with uveitis and found that the m6A-binding protein YTH domain-containing 1 (YTHDC1) was significantly downregulated in retinal microglia in the context of uveitis. Further studies showed that YTHDC1 deficiency resulted in M1 microglial polarization, an increased inflammatory response and the promotion of microglial migration. Mechanistically, YTHDC1 maintained sirtuin 1 (SIRT1) mRNA stability, which reduced signal transducer and activator of transcription 3 (STAT3) phosphorylation, thus inhibiting microglial M1 polarization. Collectively, our data show that YTHDC1 is critical for microglial inflammatory response regulation and can serve as a target for the development of therapeutics for autogenic immune diseases.

TangShenWeiNing Formula Prevents Diabetic Nephropathy by Protecting Podocytes Through the SIRT1/HIF-1α Pathway

BACKGROUND

Diabetic nephropathy (DN) represents a major complication of diabetes, and podocyte injury has a critical function in DN development. TangShenWeiNing formula (TSWN) has been demonstrated to efficiently decrease proteinuria and protect podocytes in DN. This work aimed to explore the mechanism by which TSWN alleviates DN and protects podocytes.

METHODS

The major bioactive components of TSWN were detected by mass spectrometry (MS) and pharmacological databases. Eight-week-old male C57BLKS/J db/m and db/db mice were provided pure water, valsartan, low dose TSWN, middle dose TSWN and high dose TSWN by gavage for 12 weeks, respectively.

RESULTS

MS and network pharmacology analyses suggested that TSWN might prevent DN through the sirtuin (SIRT)1/hypoxia-inducible factor (HIF)-1α pathway. Diabetic mice showed elevated urinary albumin in comparison with non-diabetic mice, and TSWN decreased urinary albumin in diabetic mice. Histological injury increased in the kidney in diabetic mice, which could be improved by TSWN. Fibrosis and collagen I expression were induced in the diabetic mouse kidney in comparison with the non-diabetic mouse kidney; TSWN alleviated these effects. Apoptosis and cleaved caspase-3 were induced in the diabetic mouse kidney in comparison with the non-diabetic mouse kidney, and TSWN blunted these effects. Podocytes were damaged in the diabetic mouse kidney, which was improved by TSWN. Podocin and nephrin amounts were decreased in the diabetic mouse kidney in comparison with the non-diabetic mouse kidney, and podocalyxin was increased in urine of diabetic animals in comparison with non-diabetic counterparts. After TSWN treatment, podocin and nephrin were raised in the diabetic mouse kidney, and urinary podocalyxin was depressed in diabetic animals. Diabetic mice had lower SIRT1 and higher HIF-1α amounts in kidney specimens in comparison with non-diabetic mice, and TSWN promoted SIRT1 and inhibited HIF-1α in the diabetic mouse kidney. Moreover, co-staining of SIRT1 and podocin revealed that SIRT1 decreased in podocytes from diabetic mice in comparison with those from non-diabetic mice, and TSWN elevated SIRT1 in podocytes.

CONCLUSIONS

This study indicated that TSWN alleviates DN by improving podocyte injury through the SIRT1/HIF-1α pathway in diabetic mouse kidneys.

Sirt1 Promotes the Restoration of Hepatic Progenitor Cell (HPC)-Mediated Liver Fatty Injury in NAFLD Through Activating the Wnt/β-Catenin Signal Pathway

Non-alcoholic fatty liver disease (NAFLD) has developed into the world's largest chronic epidemic. In NAFLD, hepatic steatosis causes hepatocytes dysfunction and even apoptosis. The liver has a strong restoration or regeneration ability after an injury, however, it is unclear through which pattern fatty liver injury in NAFLD is repaired and what the repair mechanism is. Here, we found that in the high-fat diet (HFD)-induced NAFLD mice model, fatty liver injury caused the significant ductular reaction (DR), which is a marker to promote the repair of liver injury. SOX9⁺ and HNF4α⁺ biphenotype also suggested that hepatic progenitor cells (HPCs) were activated by fatty liver injury in the HFD-elicited NAFLD mice model. Concurrently, fatty liver injury also activated the Wnt/β-catenin signal pathway, which is a necessary process for HPC differentiation into mature hepatocytes. However, Sirt1 knockdown weakened HPC activation and Wnt/β-catenin signal in Sirt1^+/− mice with HFD feeding. In rat-derived WB-F344 hepatic stem cell line, Sirt1 overexpression (OE) or Sirt1 activator–Resveratrol promoted HPC differentiation via activating Wnt/β-catenin signal pathway. Glycogen PAS staining demonstrated that Sirt1 OE promoted WB-F344 cells to differentiate into mature hepatocytes with glycogen synthesis ability, while Sirt1 inhibitor EX527 or Wnt/β-catenin pathway inhibitor HF535 decreased glycogen positive cells. Together, our data suggested that Sirt1 plays a vital role in activating HPCs to repair fatty liver injury or promote liver regeneration through the Wnt/β-catenin signal pathway in NAFLD, which might provide a new strategy for fatty liver injury or NAFLD therapy.