LncRNA MALAT1 to Enhance Pyroptosis in Viral Myocarditis Through UPF1-Mediated SIRT6 mRNA Decay and Wnt-ß-Catenin Signal Pathway.

Viral myocarditis (VMC) is an inflammatory disease of the myocardium caused by cardioviral infection, especially coxsackievirus B3 (CVB3), and is a major contributor to acute heart failure and sudden cardiac death in children and adolescents. LncRNA MALAT1 knockdown reportedly inhibits the differentiation of Th17 cells to attenuate CVB3-induced VMC in mice. Moreover, long non-coding RNAs (lncRNAs) interact with RNA-binding proteins (RBPs) to regulate UPF1-mediated mRNA decay. However, it remains unclear whether MALAT1 can bind to UPF1 to mediate the mRNA decay of its target genes in VMC. Herein, we aimed to explore the effect of lncRNA MALAT1 on UPF1-mediated SIRT6 mRNA decay in VMC using in vivo and in vitro experiments. CVB3-infected BABL/C mice were used as VMC models, and MALAT1 interfering adenovirus was injected to achieve MALAT1 knockdown. The heart function of the VMC mice was assessed using echocardiography. Pathological changes in myocardial tissues were assessed after hematoxylin-eosin staining. Myocardial injury and inflammation were evaluated by measuring creatine kinase isoenzyme B, cardiac troponin T, interleukin (IL)-1ß, and IL-18. TUNEL staining was performed to assess apoptosis in myocardial tissues. In vitro experiments were performed using H9c2 cells after transfection and CVB3 infection. The lactic dehydrogenase release, caspase-1 activity, and IL-1ß and IL-18 levels in the cellular supernatant were detected. Western blotting was performed to determine the expression of pyroptosis-related proteins (GSDMD-N, NLRP3, ASC, and Cleaved-Caspase-1) and Wnt/ß-catenin signal pathway-related proteins (Wnt1, ß-catenin, and p-GSK-3ß). RNA immunoprecipitation and RNA stability assays assessed the relationship between MALAT1, UPF1, and SIRT6. CVB3-infected mice and H9c2 cells exhibited elevated MALAT1 and reduced SIRT6 expression. MALAT1 knockdown or SIRT6 overexpression suppressed inflammation and pyroptosis and inhibited the activation of the Wnt/ß-catenin signal pathway in myocardial tissues and cells. MALAT1 enhanced the enrichment of SIRT6 mRNA by UPF1 and disturbed the stability of SIRT6 mRNA to promote the development of VMC. MALAT1 can bind UPF1 to mediate SIRT6 mRNA decay and activate the Wnt/ß-catenin signal pathway in VMC.

LncRNA TUG1 regulates mir-34a-5p / SIRT6 to participate in benzene-induced hematotoxicity through PI3K / AKT /mTOR signaling pathway.

LncRNA TUG1 plays pivotal roles in various diseases. However, its exact roles in benzene - induced hematotoxicity remain unclear. Herein, we aimed to investigate the role and mechanism of TUG1 in hematoxic injuries caused by benzene. In the current study, TUG1 was found dramatically decreased in WBCs of benzene exposure workers and negatively correlated with benzene exposure duration and urine SPMA. In vitro assays demonstrated that TUG1 overexpression attenuated 1,4-BQ-caused suppression of cell viability and proliferation, and promotion of ROS generation and apoptosis via PI3K/AKT/mTOR pathway. Bioinformatic prediction and molecular assay validated miR-34a-5p was negatively regulated by TUG1. The miR-34a-5p was upregulated in 1,4-BQ treated cells and downregulated in TUG1 overexpression cells. Moreover, miR-34a-5p upregulation partially reversed the protective effects of TUG1 overexpression on 1,4-BQ - caused cytotoxicity. Furthermore, SIRT6 was a downstream target gene of miR-34a-5p, whose expression was reduced in miR-34a-5p upregulation cells and elevated in TUG1 overexpression cells. Upregulated SIRT6 could counteract accelerated cytotoxicity mediated by miR-34a-5p upregulation after 1,4-BQ treatment. Taken together, our study revealed that the critical role of the TUG1/miR-34a-5p/SIRT6 axis in benzene-caused hematotoxicity, and provided scientific basis for further understanding the epigenetic regulatory mechanisms underlying benzene hematotoxicity.

Sirt6 ameliorates high glucose-induced podocyte cytoskeleton remodeling via the PI3K/AKT signaling pathway.

BACKGROUND: Podocyte injury plays an important role in the occurrence and progression of diabetic kidney disease (DKD), which leads to albuminuria. Cytoskeletal remodeling is an early manifestation of podocyte injury in DKD. However, the underlying mechanism of cytoskeletal remodeling has not been clarified. Histone deacetylase sirtuin6 (Sirt6) has been found to play a key role in DKD progression, and the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB/AKT) pathway directly regulates the cytoskeletal structure of podocytes. Whereas, the relationship between Sirt6, the PI3K/AKT pathway and DKD progression remains unclear. METHODS: Renal injury of db/db mice was observed by PAS staining and transmission electron microscope. Expression of Sirt6 in the glomeruli of db/db mice was detected by immunofluorescence. UBCS039, a Sirt6 activator, was used to explore the renal effects of Sirt6 activation on diabetic mouse kidneys. We also downregulating Sirt6 expression in podocytes using the Sirt6 inhibitor, OSS_128167, and induced upregulation of Sirt6 using a recombinant plasmid, after which the effects of Sirt6 on high glucose (HG)-induced podocyte damage were assessed in vitro. Podocyte cytoskeletal structures were observed by phalloidin staining. The podocyte apoptotic rate was assessed by flow cytometry, and PI3K/AKT signaling activation was measured by Western blotting. RESULTS: Db/db mice exhibited renal damage including elevated urine albumin-to-creatinine ratio (ACR), increased mesangial matrix, fused podocyte foot processes, and thickened glomerular basement membrane. The expression of Sirt6 and PI3K/AKT pathway components was decreased in db/db mice. UBCS039 increased the expressions of Sirt6 and PI3K/AKT pathway components and ameliorated renal damage in db/db mice. We also observed consistent Sirt6 expression was in HG-induced podocytes in vitro. Activation of the PI3K/AKT pathway via a Sirt6 recombinant plasmid ameliorated podocyte cytoskeletal remodeling and apoptosis in HG-treated immortalized human podocytes in vitro, whereas Sirt6 inhibition by OSS_128167 accelerated HG-induced podocyte damage in vitro. CONCLUSIONS: Sirt6 protects podocytes against HG-induced cytoskeletal remodeling and apoptosis through activation of the PI3K/AKT signaling pathway. These findings provide evidence supporting the potential efficacy of Sirt6 activation as a promising therapeutic strategy for addressing podocyte injury in DKD.

A Novel Prognostic Model of Hepatocellular Carcinoma per Two NAD+ Metabolic Synthesis-Associated Genes.

Hepatocellular carcinoma (HCC) is a formidable challenge to global human health, while recent years have witnessed the important role of NAD+ in tumorigenesis and progression. However, the expression pattern and prognostic value of NAD+ in HCC still remain elusive. Gene expression files and corresponding clinical pathological files associated with HCC were obtained from the Cancer Genome Atlas (TCGA) database, and genes associated with NAD+ were retrieved from the GSEA and differentially analyzed in tumor and normal tissues. A consensus clustering analysis was conducted by breaking down TCGA patients into four distinct groups, while Kaplan-Meier curves were generated to investigate the disparity in clinical pathology and endurance between clusters. A prognostic model based on NAD+-associated genes was established and assessed by combining LASSO-Cox regression, uni- and multi-variate Cox regression, and ROC curve analyses. Investigations were conducted to determine the expression of distinct mRNAs and proteins in both HCC and non-tumor tissues. A novel two-gene signature including poly (ADP-Ribose) polymerase 2 (PARP2) and sirtuin 6 (SIRT6) was obtained through LASSO-Cox regression and was identified to have favorable prognostic performance in HCC patients from TCGA. Analyses of both single and multiple variables showed that the prognostic model was a distinct prognostic factor in the endurance of liver cancer patients in both the training and trial groups. The nomogram also exhibited clinical significance in the prognosis of HCC patients. Immunohistochemistry, qRT-PCR, and Western blotting revealed that HCC samples exhibited higher PARP2 and SIRT6 expression levels than those of normal controls. This study identified a robust prognostic model comprising two NAD+-associated genes using bioinformatic methods, which is accurate in predicting the survival outcome of HCC patients. This model might benefit the early diagnosis of HCC and further facilitate the management of individualized medical service and clinical decision-making.

Investigating the influence of the SIRT6 gene and alternative splicing on canine longevity: an in-depth bioinformatics analysis and experimental confirmation via NGS-based targeted sequencing.

Sirtuin 6 (SIRT6) has many functions, but its most notable contribution lies in the intricate regulation of cell senescence and lifespan. The effect of the SIRT6 gene on body size and longevity in dogs has not been extensively studied, particularly with regard to alternative splicing mechanisms. To address this gap, the present study used a comprehensive approach that integrated bioinformatics analysis, DNA sequence analysis, and next-generation sequencing-based targeted sequencing analyses. Our results show that, according to the reference genomes of different dog breeds, the canine SIRT6 gene exhibits different variants according to the dog breed. Except for the exonic variant g.55,146,051C > T (rs851065050) detected in the Boxer breed, all variants obtained from other genomes were determined to be intronic variants. The g.56,075,604 G > T (rs3343377774) intronic variant previously detected in the Labrador Retriever breed was only detected in the small breed group in our study. As a result of in silico analysis, the g.56,075,604 G > T variant has an exonic splicing enhancer (ESE) site; this variant has created the motif of the binding site for the splicing factor ESE_SRp55. The g.55.146,051C > T variant was associated with a change in the ratio of exonic splicing silencer/ESE binding motifs. This change indicates an increased probability of exon skipping for the mutant allele. Thus, as with the intronic variant g.56,075,604 G > T, the mis-splicing induced by the exonic variant g.55,146,051C > T could potentially be associated with an altered distribution of regulatory splicing factors of the canine SIRT6 gene.

Modulation of SIRT6 Related Signaling Pathways of p-AKT/mTOR and NRF2/HO-1 by Memantine Contributes to Curbing the Progression of Tamoxifen/HFD-Induced MASH in Rats.

Metabolic dysfunction-associated steatohepatitis (MASH) is a chronic liver disorder marked by hepatic fat accumulation and inflammatory infiltrates which may evolve to cirrhosis. Clinical studies have demonstrated the higher risk of MASH development after tamoxifen (TAM) therapy, especially in obese patients. Therefore, we aimed to evaluate MASH induction by TAM combined with high fat diet (HFD) and the potential interference of memantine (MEMA) with MASH progression via modulation of SIRT6 and its related signaling pathways. MASH was induced in female Wistar rats by co-administration of TAM (25 mg/kg/day, p.o.) and HFD for 5 weeks. Liver function biomarkers, tissue triglyceride and cholesterol, MASH scoring, SIRT6 and its related signals, and lipid synthesis/oxidation markers were estimated. By comparison to MASH group, MEMA improved liver function indices (ALT, AST, ALP, albumin) and reduced the progression of MASH, evidenced by decreased accumulation of lipids in hepatic tissue, improved histological features, and reduced MASH scoring. MEMA enhanced hepatic SIRT6 and downregulated p-AKT/mTOR signaling, that subsequently reduced expressions of the lipid synthesis biomarkers (SREBP1c, CPT1), while elevating the lipid oxidation markers (PPAR-α, SCD). Moreover, MEMA enhanced NRF2/HO-1 signaling, with subsequently improved antioxidant defense and pro-inflammatory/anti-inflammatory cytokines balance. Analysis of SIRT6 correlations with p-AKT/mTOR, NRF2/HO-1, SREBP1c, and PPAR-α further confirmed our results. Consequently, we conclude that MEMA could interfere with MASH progression, at least in part, via enhanced SIRT6 expression and modulation of its related p-AKT/mTOR and NRF2/HO-1 signaling pathways, eventually reducing liver steatosis and inflammation. That could be a promising therapeutic modality for curbing MASH progression.

Expression of SIRT6 and VNN1 in children with primary nephrotic syndrome and their correlation with acute kidney injury.

OBJECTIVE: To explore the diagnostic and prognostic values of Sirtuin 6 (SIRT6) and Vanin-1 (VNN1) in peripheral blood monocytes of children with primary nephrotic syndrome (PNS) and their correlation with acute kidney injury (AKI). METHODS: A retrospective analysis was conducted on 101 children (observation group) diagnosed with PNS and treated at the Shanxi University of Traditional Chinese Medicine Affiliated Hospital from December 2021 to December 2023. These children were categorized into two groups: the AKI group (n=35) and the non-AKI group (n=66), based on the presence of AKI. Additionally, 101 healthy children who underwent physical examinations during the same period served as the control group. Western blotting and RT-PCR were employed to measure the protein and mRNA levels of SIRT6 and VNN1 in monocytes across the three groups. The correlation between SIRT6 and VNN1 mRNA levels and clinical data, as well as kidney function indicators, was analyzed. The diagnostic value of SIRT6 and VNN1 mRNA levels for AKI in PNS was assessed using ROC curves. Multivariate logistic regression identified independent factors influencing AKI in PNS. The mRNA levels of SIRT6 and VNN1 were also compared before and after treatment in children with PNS. RESULTS: The AKI group exhibited lower SIRT6 protein and mRNA levels, and higher VNN1 protein and mRNA levels in monocytes compared to the other groups (all P<0.05). Correlation analysis revealed that SIRT6 mRNA levels were positively correlated with serum creatinine (Scr), uric acid (UA), blood urea nitrogen (BUN), 24-hour urine protein (24h UP), cystatin C (Cys-C), and ß2-microglobulin (ß2-MG), but negatively correlated with albumin (ALB) and estimated glomerular filtration rate (eGFR) (all P<0.05). In contrast, VNN1 levels showed the opposite correlations (P<0.05). ROC curve analysis showed that the AUC for SIRT6 or VNN1 mRNA alone in diagnosing AKI was above 0.8, with a combined diagnostic AUC exceeding 0.9. Logistic regression indicated that eGFR, ß2-MG, Cys-C, and the mRNA levels of SIRT6 and VNN1 were independent risk factors for AKI in PNS (all P<0.05). After treatment, SIRT6 mRNA levels significantly decreased, while VNN1 mRNA levels increased in children with PNS (both P<0.05). CONCLUSION: SIRT6 and VNN1 are closely associated with AKI in children with PNS and may serve as valuable biomarkers for the diagnosis of AKI.

Sirt6 Mono-ADP-Ribosylates YY1 to Promote Dystrophin Expression for Neuromuscular Transmission.

The degeneration of the neuromuscular junction (NMJ) and the decline in motor function are common features of aging, but the underlying mechanisms have remained largely unclear. This study reveals that Sirt6 is reduced in aged mouse muscles. Ablation of Sirt6 in skeletal muscle causes a reduction of Dystrophin levels, resulting in premature NMJ degeneration, compromised neuromuscular transmission, and a deterioration in motor performance. Mechanistic studies show that Sirt6 negatively regulates the stability of the Dystrophin repressor YY1 (Yin Yang 1). Specifically, Sirt6 mono-ADP-ribosylates YY1, causing its disassociation from the Dystrophin promoter and allowing YY1 to bind to the SMURF2 E3 ligase, leading to its degradation. Importantly, supplementation with nicotinamide mononucleotide (NMN) enhances the mono-ADP-ribosylation of YY1 and effectively delays NMJ degeneration and the decline in motor function in elderly mice. These findings provide valuable insights into the intricate mechanisms underlying NMJ degeneration during aging. Targeting Sirt6 could be a potential therapeutic approach to mitigate the detrimental effects on NMJ degeneration and improve motor function in the elderly population.

The nitration of SIRT6 aggravates neuronal damage during cerebral ischemia-reperfusion in rat.

Ischemic stroke is a major cause of death and disability. The activation of neuronal nitric oxide synthase (nNOS) and the resulting production of nitric oxide (NO) via NMDA receptor-mediated calcium influx play an exacerbating role in cerebral ischemia reperfusion injury. The NO rapidly reacts with superoxide (O2-) to form peroxynitrite (ONOO-), a toxic molecule may modify proteins through tyrosine residue nitration, ultimately worsening neuronal damage. SIRT6 has been proven to be crucial in regulating cell proliferation, death, and aging in various pathological settings. We have previous reported that human SIRT6 tyrosine nitration decreased its intrinsic catalytic activity in vitro. However, the exact role of SIRT6 function in the process of cerebral ischemia reperfusion injury is not yet fully elucidated. Herein, we demonstrated that an increase in the nitration of SIRT6 led to reduce its enzymatic activity and aggravated hippocampal neuronal damage in a rat model of four-artery cerebral ischemia reperfusion. In addition, reducing SIRT6 nitration resulted in increase the activity of SIRT6, alleviating hippocampal neuronal damage. Moreover, SIRT6 nitration affected its downstream molecule activity such as PARP1 and GCN5, promoting the process of neuronal ischemic injury in rat hippocampus. Additionally, treatment with NMDA receptor antagonist MK801, or nNOS inhibitor 7-NI, and resveratrol (an antioxidant) diminished SIRT6 nitration and the catalytic activity of downstream molecules like PARP1 and GCN5, thereby reducing neuronal damage. Finally, in the biochemical regulation of SIRT6 activity, tyrosine 257 was essential for its activity and susceptibility to nitration. Replacing tyrosine 257 with phenylalanine in rat SIRT6 attenuated the death of SH-SY5Y neurocytes under oxygen-glucose deprivation (OGD) conditions. These results may offer further understanding of SIRT6 function in the pathogenesis of cerebral ischemic diseases.

ADSCs encapsulated in Gelatin methacrylate substrate promotes the repair of peripheral nerve injury by SIRT6/PGC-1α pathway.

Peripheral nerve injury is a prevalent disease but the spontaneous recovery of nerve function is protracted and incomplete. Given the damaging of stem cells and fragile of intra-neural structures in the course of stem cell transplantation, our study tried to investigate whether encapsulating adipose derived mesenchymal stem cells (ADSCs) with GelMA could achieve better repair in peripheral nerve injury. PC-12 cells were cultured on the surface of GelMA encapsulating ADSCs and 3D co-culture system was constructed. CCK-8, Real-Time PCR, ELISA, Immunofluorescent Assay and Western Blot were used to evaluate the functionality of this system. Ultimately, nerve conduit containing the 3D co-culture system was linked between the two ends of an injured nerve. ADSCs encapsulated in 5% GeIMA had a better activity than 10% GeIMA. Furthermore, the viability of PC-12 cells was also better in this 3D co-culture system than in co-culture system with ADSCs without GeIMA. The expression of SIRT6 and PGC-1α in PC-12 cells were prominently promoted, and the entry to nuclear of PGC-1α was more obvious in this 3D co-culture system. After silencing of SIRT6, the protein expression level of PGC-1α was inhibited, and the activity of PC-12 cells was significantly reduced, suggesting that ADSCs encapsulated in GelMA upregulated the expression of SIRT6 to induce the level of PGC-1α protein, thereby achieving an impact on the activity of PC-12 cells. In vivo, nerve conduit containing the 3D co-culture system significantly promoted the repair of damaged peripheral nerves. In conclusion, our study demonstrated that 5% GelMA enhanced ADSCs activity, thereby promoting the activity of nerve cells and repair of damaged peripheral nerves by SIRT6/PGC-1α pathway.

Oral administration of astilbin mitigates acetaminophen-induced acute liver injury in mice by modulating the gut microbiota.

Acetaminophen (APAP) overdose-induced acute liver injury (ALI) is characterized by extensive oxidative stress, and the clinical interventions for this adverse effect remain limited. Astilbin is an active compound found in the rhizome of Smilax glabra Roxb. with anti-inflammatory and antioxidant activities. Due to its low oral bioavailability, astilbin can accumulate in the intestine, which provides a basis for the interaction between astilbin and gut microbiota (GM). In the present study we investigated the protective effects of astilbin against APAP-induced ALI by focusing on the interaction between astilbin and GM. Mice were treated with astilbin (50 mg·kg-1·d-1, i.g.) for 7 days. After the last administration of astilbin for 2 h, the mice received APAP (300 mg/kg, i.g.) to induce ALI. We showed that oral administration of astilbin significantly alleviated APAP-induced ALI by altering the composition of GM and enriching beneficial metabolites including hydroxytyrosol (HT). GM depletion using an "antibiotics cocktail" or paraoral administration of astilbin abolished the hepatoprotective effects of astilbin. On the other hand, administration of HT (10 mg/kg, i.g.) caused similar protective effects in APAP-induced ALI mice. Transcriptomic analysis of the liver tissue revealed that HT inhibited reactive oxygen species and inflammation-related signaling in APAP-induced ALI; HT promoted activation of the Nrf2 signaling pathway to combat oxidative stress following APAP challenge in a sirtuin-6-dependent manner. These results highlight that oral astilbin ameliorates APAP-induced ALI by manipulating the GM and metabolites towards a more favorable profile, and provide an alternative therapeutic strategy for alleviating APAP-induced ALI.

Deacetylation by SIRT6 increases the stability of GILZ to suppress NSCLC cell migration and invasion.

Glucocorticoid-induced leucine zipper (GILZ) plays a role in cancer cell proliferation in several tumor types. However, in our present study, GILZ was demonstrated to be a metastasis regulator but not a proliferation regulator in non-small cell lung cancer (NSCLC). The overexpression of GILZ had no significant effect on the proliferation of NSCLC cells but inhibited their metastasis by targeting the epithelial-mesenchymal transition pathway. The deacetylase SIRT6, a key regulator of protein stability, can enhance the stability of the GILZ protein by mediating its deacetylation, which prevents ubiquitination and degradation. This process ultimately enhances the inhibitory effect of GILZ on the migration and invasion of NSCLC cells. Thus, GILZ may be a promising new therapeutic target for tumor metastasis.

Melatonin alleviates LPS-induced depression-like behavior in mice by inhibiting ferroptosis by regulating RNA methylation-mediated SIRT6/Nrf2/HO-1 pathway.

PURPOSE: The objective of this study is to investigate the impact of ferroptosis on depression and elucidate the molecular mechanism underlying melatonin's inhibitory effect on ferroptosis in the treatment of depression. METHODS: In this study, a depression-like behavior model was induced in mice using LPS, and the effect of melatonin on depression-like behavior was evaluated through behavioral experiments (such as forced swimming test (FST) and sucrose preference test (SPT)). Additionally, molecular biological techniques (including real-time fluorescence quantitative PCR, Western blotting, immunoprecipitation) were employed to detect the expression levels and interactions of METTL3, SIRT6 and ferroptosis-related genes in mouse brain tissue. Furthermore, both in vitro and in vivo experiments were conducted to verify the regulatory effect of melatonin on Nrf2/HO-1 pathway and explore its potential molecular mechanism for regulating ferroptosis. RESULTS: Melatonin was found to significantly ameliorate depression-like behavior in mice, as evidenced by reduced immobility time in the forced swimming test and increased sucrose intake in the sucrose preference test. Subsequent investigations revealed that melatonin modulated SIRT6 stability through METTL3-mediated ubiquitination of SIRT6, leading to its degradation. As a deacetylase, SIRT6 plays a pivotal role in cellular metabolism regulation and antioxidative stress response. This study elucidated potential signaling pathways involving Nrf2/HO-1 through which SIRT6 may exert its effects. CONCLUSION: The findings suggest that melatonin can improve depressive behavior by suppressing ferroptosis and protecting neurons through its antioxidant properties. Additionally, targeting the Nrf2/HO-1 pathway via METTL3 and NEDD4 regulation may be a potential therapeutic approach for depression.

SIRT6 modulates lesion microenvironment in LPC induced demyelination by targeting astrocytic CHI3L1.

Demyelination occurs widely in the central nervous system (CNS) neurodegenerative diseases, especially the multiple sclerosis (MS), which with a complex and inflammatory lesion microenvironment inhibiting remyelination. Sirtuin6 (SIRT6), a histone/protein deacetylase is of interest for its promising effect in transcriptional regulation, cell cycling, inflammation, metabolism and longevity. Here we show that SIRT6 participates in the remyelination process in mice subjected to LPC-induced demyelination. Using pharmacological SIRT6 inhibitor or activator, we found that SIRT6 modulated LPC-induced damage in motor or cognitive function. Inhibition of SIRT6 impaired myelin regeneration, exacerbated neurological deficits, and decreased oligodendrocyte precursor cells (OPCs) proliferation and differentiation, whereas activation of SIRT6 reversed behavioral performance in mice, demonstrating a beneficial effect of SIRT6. Importantly, based on RNA sequencing analysis of the corpus callosum tissues, it was further revealed that SIRT6 took charge in regulation of glial activation during remyelination, and significant alterations in CHI3L1 were obtained, a glycoprotein specifically secreted by astrocytes. Impaired proliferation and differentiation of OPCs could be induced in vitro using supernatants from reactive astrocyte, especially when SIRT6 was inhibited. Mechanistically, SIRT6 regulates the secretion of CHI3L1 from reactive astrocytes by histone-H3-lysine-9 acetylation (H3K9Ac). Adeno-associated virus-overexpression of SIRT6 (AAV-SIRT6-OE) in astrocytes improved remyelination and functional recovery after LPC-induced demyelination, whereas together with AAV-CHI3L1-OE inhibits this therapeutic effect. Collectively, our data elucidate the role of SIRT6 in remyelination and further reveal astrocytic SIRT6/CHI3L1 as the key regulator for improving the remyelination environment, which may be a potential target for MS therapy.

On the interface of aging, cancer, and neurodegeneration with SIRT6 and L1 retrotransposon protein interaction network.

Roles of the sirtuins in aging and longevity appear related to their evolutionarily conserved functions as retroviral-restriction factors. Retrotransposons also promote the aging process, which can be reversed by the inhibition of their activity. SIRT6 can functionally limit the mutation activity of LINE-1 (L1), a retrotransposon causing cancerogenesis-linked mutations accumulating during aging. Here, an overview of the molecular mechanisms of the controlling effects was created by the pathway enrichment and gene function prediction analysis of a protein interaction network of SIRT6 and L1 retrotransposon proteins L1 ORF1p, and L1 ORF2p. The L1-SIRT6 interaction network is enriched in pathways and nodes associated with RNA quality control, DNA damage response, tumor-related and retrotransposon activity-suppressing functions. The analysis also highlighted sumoylation, which controls protein-protein interactions, subcellular localization, and other post-translational modifications; DNA IR Damage and Cellular Response via ATR, and Hallmark Myc Targets V1, which scores are a measure of tumor aggressiveness. The protein node prioritization analysis emphasized the functions of tumor suppressors p53, PARP1, BRCA1, and BRCA2 having L1 retrotransposon limiting activity; tumor promoters EIF4A3, HNRNPA1, HNRNPH1, DDX5; and antiviral innate immunity regulators DDX39A and DDX23. The outline of the regulatory mechanisms involved in L1 retrotransposition with a focus on the prioritized nodes is here demonstrated in detail. Furthermore, a model establishing functional links between HIV infection, L1 retrotransposition, SIRT6, and cancer development is also presented. Finally, L1-SIRT6 subnetwork SIRT6-PARP1-BRCA1/BRCA2-TRIM28-PIN1-p53 was constructed, where all nodes possess L1 retrotransposon activity-limiting activity and together represent candidates for multitarget control.

SIRT6 alleviates senescence induced by Porphyromonas gingivalis in human gingival fibroblasts.

OBJECTIVE: Bidirectional influences between senescence and inflammation are newly discovered. This study aimed to clarify the roles and mechanism of Porphyromonas gingivalis (P. gingivalis) in exacerbating senescence in human gingival fibroblasts (HGFs). DESIGN: Subgingival plaque and gingivae were collected from twenty-four periodontitis patients and eighteen periodontally healthy subjects. Quantities of P. gingivalis in subgingival plaque were explored using real-time PCR and the expressions of p53, p21 and SIRT6 in gingivae were detected by IHC. Moreover, senescence in HGFs was induced by P. gingivalis lipopolysaccharide (LPS) and the expressions of senescence-related ß-galactosidase (SA-ß-gal), p53, p21 and senescence-associated secretory phenotype (IL-6 and IL-8) with or without treatment by SIRT6 activator UBCS039 were explored by IHC, western blot and ELISA, respectively. In addition, the levels of SIRT6, Nrf2, HO-1 and reactive oxygen species (ROS) were examined by western blot and flow cytometry. RESULTS: Quantities of P. gingivalis in subgingival plaque and semi-quantitative scores of p53 and p21 in gingivae of periodontitis patients were increased compared with healthy controls (p < 0.05), while SIRT6 score in periodontitis patients was decreased (p < 0.001). Quantities of P. gingivalis were positively correlated with p53 and p21 scores (0.6 < r < 0.9, p < 0.01), and negatively correlated with SIRT6 score (-0.9 < r<-0.6, p < 0.01). Moreover, P. gingivalis LPS increased the levels of SA-ß-gal, p53, p21, IL-6, IL-8 and ROS and decreased the levels of SIRT6, Nrf2 and HO-1 in HGFs, which was rescued by UBCS039 (p < 0.05). CONCLUSIONS: P. gingivalis LPS could induce senescence of HGFs, which could be reversed by SIRT6 via Nrf2-HO-1 signaling pathway.

MitoAMPK inhibits the Warburg effect by MZF1-SIRT6 with glycosis related genes in NSCLC.

MitoAMPK was proved to inhibit the Warburg effect, but the specific mechanisms on non-small-cell lung cancer remain unclear. Here, we selected SIRT6 and MZF1 to clarify the mechanism. By western blotting, quantitative polymerase chain reaction, the CCK-8 assay, and immunohistochemistry assays, we found SIRT6 expression was lower in NSCLC tissues and cell lines than normal tissues and cells. Moreover, SIRT6 could inhibit the Warburg effect by regulating glycolysis-related genes of SLC2A2, SLC2A4 and PKM2. Finally, we demonstrated the interaction between SIRT6 and MZF1 using ChIP-qPCR. In conclusion, mitoAMPK inhibits the Warburg effect by regulating the expression of the MZF1-SIRT6 complex.

Decoding the Role of Nuclear Sirtuins in Parkinson's Pathogenesis.

Parkinson's disease (PD) is the second most prevailing degenerative disease that deals with dopaminergic neuronal loss and deficiency of dopamine in SNpc and striatum. Manifestations primarily include motor symptoms like tremor, rigidity, and akinesia/dyskinesia along with some nonmotor symptoms like GI and olfactory dysfunction. α-Synuclein pathogenesis is the major cause behind progression of PD; however there are many underlying molecular mechanisms behind the pathophysiology of PD. Sirtuins are small molecular deacetylases that have an imperative role in pathology of such neurodegenerative disorders like PD. Sirtuins are majorly classified according to their location; nuclear (SIRT1,7,6), mitochondrial sirtuins (SIRT3-5), and cytosolic (SIRT2). These actively take part in pathological development and possess independent actions. In this review, the role of nuclear sirtuins is individualistically explored for better understanding of PD pathology and development of advanced therapeutics targeting sirtuins.

Baicalein Inhibits Cerebral Ischemia-Reperfusion Injury through SIRT6-Mediated FOXA2 Deacetylation to Promote SLC7A11 Expression.

Ischemic stroke (IS) poses a serious threat to patient survival. The inhibition of ferroptosis can effectively alleviate ischemia-reperfusion (I/R) injury, suggesting potential targets in the ferroptosis pathway for the treatment of IS. In this study, MCAO/R mice and OGD/R-induced HT22 cell were constructed. It was found that baicalein decreased ROS, MDA, and Fe2+ levels, upregulated GSH levels, and enhanced the expression of ferroptosis-related proteins (GPX4 and SLC7A11), downregulated the expression of proapoptotic proteins (Bax, cytochrome c, and cleaved caspase-3), and upregulated the expression of an antiapoptotic protein (Bcl-2), ameliorating cerebral I/R injury. In animal and cell models, Sirtuin6 (SIRT6) is downregulated, and Forkhead boxA2 (FOXA2) expression and acetylation levels are abnormally upregulated. SIRT6 inhibited FOXA2 expression and acetylation. Baicalein promoted FOXA2 deacetylation by upregulating SIRT6 expression. FOXA2 transcriptionally inhibits SLC7A11 expression. In conclusion, baicalein inhibited apoptosis and partially suppressed the role of ferroptosis to alleviate cerebral I/R injury via SIRT6-mediated FOXA2 deacetylation to promote SLC7A11 expression.

SIRT6 loss causes intervertebral disc degeneration in mice by promoting senescence and SASP status.

Intervertebral disc degeneration is a major risk factor contributing to chronic low back and neck pain. While the etiological factors for disc degeneration vary, age is still one of the most important risk factors. Recent studies have shown the promising role of SIRT6 in mammalian aging and skeletal tissue health, however its role in the intervertebral disc health remains unexplored. We investigated the contribution of SIRT6 to disc health by studying the age-dependent spinal phenotype of mice with conditional deletion of Sirt6 in the disc (Acan CreERT2 ; Sirt6 fl/fl ). Histological studies showed a degenerative phenotype in knockout mice compared to Sirt6 fl/fl control mice at 12 months which became pronounced at 24 months. RNA-Seq analysis of NP and AF tissues, quantitative histone analysis, and in vitro multiomics employing RNA-seq with ATAC-seq revealed that SIRT6-loss resulted in changes in acetylation and methylation status of specific Histone 3 lysine residues, thereby affecting DNA accessibility and transcriptomic landscape. A decrease in autophagy and an increase in DNA damage were also noted in Sirt6-deficient cells. Further mechanistic insights revealed that loss of SIRT6 increased senescence and SASP burden in the disc characterized by increased p21, γH2AX, IL-6, and TGF-ß abundance. Taken together our study highlights the contribution of SIRT6 in modulating DNA damage, autophagy and cell senescence, and its importance in maintaining disc health during aging thereby underscoring it as a potential therapeutic target to treat intervertebral disc degeneration.