Adult skeletal muscles are comprised of multinuclear muscle cells called myofibers. During skeletal muscle development and regeneration, mononuclear progenitor cells (myoblasts) fuse to form multinuclear myotubes, which mature and become myofibers. The molecular events mediating myoblast fusion are not fully understood. Here we report that Shisa2, an endoplasmic reticulum (ER) localized protein, regulates the fusion of muscle satellite cell-derived primary myoblasts. Shisa2 expression is repressed by Notch signaling, elevated in activated compared to quiescent satellite cells, and further upregulated during myogenic differentiation. Knockdown of Shisa2 inhibits the fusion of myoblasts without affecting proliferation. Conversely, Shisa2 overexpression in proliferating myoblasts inhibits their proliferation but promotes premature fusion. Interestingly, Shisa2-overexpressing nascent myotubes actively recruit myoblasts to fuse with. At the molecular level, Rac1/Cdc42-mediated cytoskeletal F-actin remodeling is required for Shisa2 to promote myoblast fusion. These results provide a novel mechanism through which an ER protein regulates myogenesis.

The progressive decline of physiological function and the increased risk of age-related diseases challenge healthy aging. Multiple anti-aging manipulations, such as senolytics, have proven beneficial for health; however, the biomarkers that label in vivo senescence at systemic levels are lacking, thus hindering anti-aging applications. In this study, we generate a Glb1+/m‒Glb1-2A-mCherry (GAC) reporter allele at the Glb1 gene locus, which encodes lysosomal β-galactosidase-an enzyme elevated in tissues of old mice. A linear correlation between GAC signal and chronological age is established in a cohort of middle-aged (9 to 13 months) Glb1+/m mice. The high GAC signal is closely associated with cardiac hypertrophy and a shortened lifespan. Moreover, the GAC signal is exponentially increased in pathological senescence induced by bleomycin in the lung. Senolytic dasatinib and quercetin (D + Q) reduce GAC signal in bleomycin treated mice. Thus, the Glb1-2A-mCherry reporter mice monitors systemic aging and function decline, predicts lifespan, and may facilitate the understanding of aging mechanisms and help in the development of anti-aging interventions.

Background: Recent studies have revealed that a novel selective sodium-glucose cotransporter 1 (SGLT1) inhibiton has shown beneficial effects in cardiovascular diseases. However, the question of whether SGLT1 inhibition influences diabetic cardiomyopathy (DCM) remains unanswered. In this study, we investigated the influence and underlying mechanism of SGLTI inhibition on DCM. Methods: SGLT1 levels were measured in diabetic patients with similar conditions who visited our hospital from January to December 2019. Wistar male rats (n = 50) were divided into five groups: control, diabetes induced by streptozotocin infusion, and diabetes treated with 0.5, 1.0, or 1.5 mg/kg mizagliflozin via stomach gavage for 12 weeks. H9C2 cardiomyocytes were treated with mizagliflozin and then exposed to a high glucose concentration (30 mmol/L). TUNEL assays were performed, and bcl2, bax, p-p38, p-Erk, p-JNK and caspase-3 levels were measured. We used siRNA and an SGLT1 overexpression plasmid to detect the effects of SGLT1. Results: SGLT1 levels were significantly elevated in DCM patients, and receiver operating characteristic (ROC) curve analysis identified SGLT1 as influencing DCM. The area under the curve (AUC) was 0.705 (p < 0.05), with 65.8% sensitivity, and 62.2% specificity. SGLT1 inhibition appeared to attenuate apoptosis in DCM via the JNK and p38 pathway. Conclusion: SGLT1 can be used as a marker for the diagnosis of DCM, and SGLT1 inhibition can attenuate apoptosis, thereby suppressing DCM development via the JNK and p38 pathway.

The gamma-type phospholipase A2 inhibitor (PLIγ) is a natural protein commonly found in snake serum, which can neutralize pathophysiological effects of snake venom phospholipases A2. Therefore, this protein is a potential candidate to the development of a novel antivenom. To the best of our knowledge, there is no antibody currently available for PLIγ identification and characterization.

Cancer stem cell (CSC)-dictated intratumor heterogeneity accounts for the majority of drug-resistance and distant metastases of breast cancers. Here, we identify a SIRT1-PRRX1-KLF4-ALDH1 circuitry, which couples CSCs, chemo-resistance, metastasis and aging. Pro-longevity protein SIRT1 deacetylates and stabilizes the epithelial-to-mesenchymal-transition (EMT) inducer PRRX1, which inhibits the transcription of core stemness factor KLF4. Loss of SIRT1 destabilizes PRRX1, disinhibits KLF4, and activates the transcription of ALDH1, which induces and functionally marks CSCs, resulting in chemo-resistance and metastatic relapse. Clinically, the level of PRRX1 is positively linked to SIRT1, whereas KLF4 is reversely correlated. Importantly, KLF4 inhibitor Kenpaullone sensitizes breast cancer cells and xenograft tumors to Paclitaxel and improves therapeutic effects. Our findings delineate a SIRT1-centered circuitry that regulates CSC origination, and targeting this pathway might be a promising therapeutic strategy.

Hair follicle stem cells (HFSCs) are maintained in a quiescent state until activated to grow, but the mechanisms that reactivate the quiescent HFSC reservoir are unclear. Here, we find that loss of Sirt7 in mice impedes hair follicle life-cycle transition from telogen to anagen phase, resulting in delay of hair growth. Conversely, Sirt7 overexpression during telogen phase facilitated HSFC anagen entry and accelerated hair growth. Mechanistically, Sirt7 is upregulated in HFSCs during the telogen-to-anagen transition, and HFSC-specific Sirt7 knockout mice (Sirt7f/f ;K15-Cre) exhibit a similar hair growth delay. At the molecular level, Sirt7 interacts with and deacetylates the transcriptional regulator Nfatc1 at K612, causing PA28γ-dependent proteasomal degradation to terminate Nfatc1-mediated telogen quiescence and boost anagen entry. Cyclosporin A, a potent calcineurin inhibitor, suppresses nuclear retention of Nfatc1, abrogates hair follicle cycle delay, and promotes hair growth in Sirt7-/- mice. Furthermore, Sirt7 is downregulated in aged HFSCs, and exogenous Sirt7 overexpression promotes hair growth in aged animals. These data reveal that Sirt7 activates HFSCs by destabilizing Nfatc1 to ensure hair follicle cycle initiation.

17β-hydroxysteroid dehydrogenase-13 is a hepatocyte-specific, lipid droplet-associated protein. A common loss-of-function variant of HSD17B13 (rs72613567: TA) protects patients against non-alcoholic fatty liver disease with underlying mechanism incompletely understood. In the present study, we identify the serine 33 of 17β-HSD13 as an evolutionally conserved PKA target site and its phosphorylation facilitates lipolysis by promoting its interaction with ATGL on lipid droplets. Targeted mutation of Ser33 to Ala (S33A) decreases ATGL-dependent lipolysis in cultured hepatocytes by reducing CGI-58-mediated ATGL activation. Importantly, a transgenic knock-in mouse strain carrying the HSD17B13 S33A mutation (HSD17B1333A/A) spontaneously develops hepatic steatosis with reduced lipolysis and increased inflammation. Moreover, Hsd17B1333A/A mice are more susceptible to high-fat diet-induced nonalcoholic steatohepatitis. Finally, we find reproterol, a potential 17β-HSD13 modulator and FDA-approved drug, confers a protection against nonalcoholic steatohepatitis via PKA-mediated Ser33 phosphorylation of 17β-HSD13. Therefore, targeting the Ser33 phosphorylation site could represent a potential approach to treat NASH.

Doxorubicin (DOX) has a wide antitumor spectrum, but its adverse cardiotoxicity may lead to heart failure. Urotensin II (UII) is the most potent vasoconstrictor in mammals. It plays a role by activating the UII receptor (UT), the orphan G protein-coupled receptor (GPR14), collectively referred to as the UII/UT system. In the new version of "Chinese expert consensus on cardiac rehabilitation of chronic heart failure," it is pointed out that exercise rehabilitation is the cornerstone of cardiac rehabilitation. In this study, in vitro and in vivo assessments were performed using DOX-treated H9C2 cells and rats. It was found that the UT antagonist Urantide and exercise training improved DOX-induced cardiac insufficiency, reduced DOX-induced cardiomyocyte apoptosis, improved the structural disorder of myocardial fibers, and inhibited DOX-induced myocardial fibrosis. Further studies showed that Urantide alleviated DOX-induced cardiotoxicity by downregulating the expression levels of the p38 mitogen-activated protein kinase signaling pathway.

Cutaneous wound healing, an integral part for protection of skin barrier, is a complex biological process and intimately associated with keratinocyte migration. However, mechanisms regulating keratinocyte migration in the process of cutaneous wound repair remain largely unknown. Here, we found that N-acetyltransferase 10 (NAT10) is essential for cutaneous wound repair in an in vivo skin wound healing model-a significant delay of wound repair in Nat10 haploinsufficient mice and a remarkable inhibition of keratinocyte migration by NAT10 knockdown in an in vitro keratinocyte migration model. We further demonstrate that loss of NAT10 expression attenuates the wound-induced IL-6/IL-8 expression through inhibiting NF-κB/p65 activity in keratinocytes. By deeply digging, silencing NAT10 compromises the level of nuclear p65 by facilitating its poly-ubiquitination, thus accelerates its degradation in the nucleus. Notably, we detected a strong positive correlation between the expression of NAT10 and relevant NF-kB/p65-IL6 signaling activity in mouse wound skin tissues. Overall, our study reveals an important role of NAT10 on cutaneous wound repair by potentiating NF-κB/p65-IL-6/8-STAT3 signaling. Targeting NAT10 might be a potential strategy for the treatment of skin wound dysfunctions and related diseases.

The tumor necrosis factor (TNF) superfamily consists of a wide variety of inflammatory cytokine, including cell-bound and secreted proteins. These TNFs function through binding and activation of the TNF receptors for modulating TNF-associated intracellular signals. A set of mammalian TNF receptor-associated factors (TRAFs) that have emerged as the major signal transducers for the TNF receptor superfamily, play an important role in both adaptive and innate immunity. However, the existence of TRAFs and their biological functions in planarian are still unknown. In this study, a new member of TRAFs, DjTRAF2, was identified in planarian Dugesia japonica. Phylogenetic analysis revealed that DjTRAF2 could be a new member of the invertebrate TRAF2 family. Sequence analysis showed that the open reading frame of DjTRAF2 had 1353 bp in length and encoded a putative protein of 450 amino acids with a predicted molecular mass of ~51.8 kDa and an isoelectric point of 7.052. Whole-mount in situ hybridization showed that DjTRAF2 was predominantly expressed in adult and regenerative pharynx, which is an important immune organ of planarian. Quantitative real-time PCR revealed that the transcriptional level of DjTRAF2 was significantly up-regulated after induced by pathogen-associated molecular patterns (polyinosinic-polycytidylic acid, lipopolysaccharide, peptidoglycan and β-glucan), suggesting that DjTRAF2 is involved in the immune response against pathogen invasion. Collectively, these results demonstrated that DjTRAF2 might play important roles in the innate immunity of planarian.

Circadian clock relies on a transcription and translation feedback loop (TTFL). Two transcription factors, i.e. Bmal1 and Clock, activate the transcription of Period (Per) and Cryptochrome (Cry), which inhibit their own transcription when accumulated to a critical concentration. NAD+-dependent deacylase Sirt1 deacetylates Bmal1 and Per2 to regulate circadian rhythms. Sirt6 interacts with Bmal1 to regulate clock-controlled gene (CCG) expression by local chromatin remodeling. Whether Sirt6 directly modify clock components is elusive. Here, we found that loss of Sirt6 jeopardizes circadian phase. At molecular level, Sirt6 interacts with and deacetylates Per2, thus preventing its proteasomal degradation. These data highlight an important function of Sirt6 in the direct regulation of TTFL and circadian rhythms.

Snake venom is a complex cocktail of toxins which induces a series of clinical and pathophysiological manifestations in victims, including severe local tissue damage and systemic alterations. Deinagkistrodon acutus (D. acutus) ranks among the "big four" life-threatening venomous species in China, whose venom possesses strong myotoxicity and hematotoxicity that often lead to permanent disability or muscle atrophy. Varespladib, an inhibitor of mammalian phospholipase A₂ (PLA₂), has been recently reproposed as an effective antidote against snakebite envenomation. The present study aimed at evaluating the protective role of varespladib on muscle regeneration in envenomed mice. Mice were grouped and subjected to inoculation with D. acutus venom or a mixture of venom and varespladib or control vehicle in the gastrocnemius muscle. Local injuries including hemorrhage, myonecrosis, ulceration, and systemic damages including general dysfunction, visceral failure, and inflammatory responses were observed at 1, 3, 7, 14, and 21 days. The results indicated that most of the muscle myonecrosis and hemorrhage were alleviated by varespladib. Besides, the pretreated mice recovered rapidly with lesser atrophy and muscle fibrosis. In conclusion, the findings of the present study suggested that varespladib is an effective antidote that could neutralize D. acutus venom and allow for earlier and improved rehabilitation outcome.

Distant metastasis is the main cause of breast cancer-related death; however, effective therapeutic strategies targeting metastasis are still scarce. This is largely attributable to the spatiotemporal intratumor heterogeneity during metastasis. Here we show that protein deacetylase SIRT7 is significantly downregulated in breast cancer lung metastases in human and mice, and predicts metastasis-free survival. SIRT7 deficiency promotes breast cancer cell metastasis, while temporal expression of Sirt7 inhibits metastasis in polyomavirus middle T antigen breast cancer model. Mechanistically, SIRT7 deacetylates and promotes SMAD4 degradation mediated by β-TrCP1, and SIRT7 deficiency activates transforming growth factor-β signaling and enhances epithelial-to-mesenchymal transition. Significantly, resveratrol activates SIRT7 deacetylase activity, inhibits breast cancer lung metastases, and increases survival. Our data highlight SIRT7 as a modulator of transforming growth factor-β signaling and suppressor of breast cancer metastasis, meanwhile providing an effective anti-metastatic therapeutic strategy.Metastatic disease is the major reason for breast cancer-related deaths; therefore, a better understanding of this process and its players is needed. Here the authors report the role of SIRT7 in inhibiting SMAD4-mediated breast cancer metastasis providing a possible therapeutic avenue.

Chronic endoplasmic reticulum stress (ERS) plays a crucial role in cardiovascular diseases. Thus, it can be considered a therapeutic target for these diseases. In this study, poly (D,L-lactic acid) (PDLLA) nanoparticle-eluting stents loaded with tauroursodeoxycholic acid (TUDCA), an ER stress inhibitor, was fabricated to assess their ability to reduce endothelial cell apoptosis and promote re-endothelialization after stent implantation.

Vascular dysfunction is a typical characteristic of aging, but its contributing roles to systemic aging and the therapeutic potential are lacking experimental evidence. Here, we generated a knock-in mouse model with the causative Hutchinson-Gilford progeria syndrome (HGPS) LmnaG609G mutation, called progerin. The Lmnaf/f ;TC mice with progerin expression induced by Tie2-Cre exhibit defective microvasculature and neovascularization, accelerated aging, and shortened life span. Single-cell transcriptomic analysis of murine lung endothelial cells revealed a substantial up-regulation of inflammatory response. Molecularly, progerin interacts and destabilizes deacylase Sirt7; ectopic expression of Sirt7 alleviates the inflammatory response caused by progerin in endothelial cells. Vascular endothelium-targeted Sirt7 gene therapy, driven by an ICAM2 promoter, improves neovascularization, ameliorates aging features, and extends life span in Lmnaf/f ;TC mice. These data support endothelial dysfunction as a primary trigger of systemic aging and highlight gene therapy as a potential strategy for the clinical treatment of HGPS and age-related vascular dysfunction.

The stem cell theory of aging dictates that a decline in the number and/or function of stem cells causes tissue degeneration and aging; however, it still lacks unequivocal experimental support. Here, using lineage tracing and single-cell transcriptomics, we identify a population of CD133+ bone marrow-derived endothelial-like cells (ELCs) as potential endothelial progenitor cells, which contribute to tubular structures in vitro and neovascularization in vivo. We demonstrate that supplementation with wild-type and young ELCs respectively restores neovascularization and extends lifespan in progeric and naturally aged mice. Mechanistically, we identify an upregulation of farnesyl diphosphate synthase (FDPS) in aged CD133+ ELCs-a key enzyme in isoprenoid biosynthesis. Overexpression of FDPS compromises the neovascularization capacity of CD133+ ELCs, whereas FDPS inhibition by pamidronate enhances neovascularization, improves health measures and extends lifespan in aged mice. These findings highlight stem cell-based strategies for the treatment of progeria and age-related pathologies.

NAD+-dependent SIRT7 deacylase plays essential roles in ribosome biogenesis, stress response, genome integrity, metabolism and aging, while how it is transcriptionally regulated is still largely unclear. TGF-β signaling is highly conserved in multicellular organisms, regulating cell growth, cancer stemness, migration and invasion. Here, we demonstrate that histone deacetylase HDAC8 forms complex with SMAD3/4 heterotrimer and occupies SIRT7 promoter, wherein it deacetylates H4 and thus suppresses SIRT7 transcription. Treatment with HDAC8 inhibitor compromises TGF-β signaling via SIRT7-SMAD4 axis and consequently, inhibits lung metastasis and improves chemotherapy efficacy in breast cancer. Our data establish a regulatory feedback loop of TGF-β signaling, wherein HDAC8 as a novel cofactor of SMAD3/4 complex, transcriptionally suppresses SIRT7 via local chromatin remodeling and thus further activates TGF-β signaling. Targeting HDAC8 exhibits therapeutic potential for TGF-β signaling related diseases.

Dietary interventions such as intermittent fasting (IF) have emerged as an attractive strategy for cancer therapies; therefore, understanding the underlying molecular mechanisms is pivotal. Here, we find SIRT7 decline markedly attenuates the anti-tumor effect of IF. Mechanistically, AMP-activated protein kinase (AMPK) phosphorylating SIRT7 at T263 triggers further phosphorylation at T255/S259 by glycogen synthase kinase 3β (GSK3β), which stabilizes SIRT7 by decoupling E3 ligase UBR5. SIRT7 hyperphosphorylation achieves anti-tumor activity by disrupting the SKP2-SCF E3 ligase, thus preventing SKP2-mediated K63-linked AKT polyubiquitination and subsequent activation. In contrast, GSK3β-SIRT7 axis is inhibited by EGF/ERK2 signaling, with ERK2 inactivating GSK3β, thus accelerating SIRT7 degradation. Unfavorably, glucose deprivation or chemotherapy hijacks the GSK3β-SIRT7 axis via ERK2, thus activating AKT and ensuring survival. Notably, Trametinib, an FDA-approved MEK inhibitor, enhances the efficacy of combination therapy with doxorubicin and IF. Overall, we have revealed the GSK3β-SIRT7 axis that must be fine-tuned in the face of the energetic and oncogenic stresses in malignancy.

Progerin accumulation disrupts nuclear lamina integrity and causes nuclear structure abnormalities, leading to premature aging, that is, Hutchinson-Gilford progeria syndrome (HGPS). The roles of nuclear subcompartments, such as PML nuclear bodies (PML NBs), in HGPS pathogenesis, are unclear. Here, we show that classical dot-like PML NBs are reorganized into thread-like structures in HGPS patient fibroblasts and their presence is associated with late stage of senescence. By co-immunoprecipitation analysis, we show that farnesylated Progerin interacts with human PML2, which accounts for the formation of thread-like PML NBs. Specifically, human PML2 but not PML1 overexpression in HGPS cells promotes PML thread development and accelerates senescence. Further immunofluorescence microscopy, immuno-TRAP, and deep sequencing data suggest that these irregular PML NBs might promote senescence by perturbing NB-associated DNA repair and gene expression in HGPS cells. These data identify irregular structures of PML NBs in senescent HGPS cells and support that the thread-like PML NBs might be a novel, morphological, and functional biomarker of late senescence.

Defective nuclear lamina protein lamin A is associated with premature aging. Casein kinase 2 (CK2) binds the nuclear lamina, and inhibiting CK2 activity induces cellular senescence in cancer cells. Thus, it is feasible that lamin A and CK2 may cooperate in the aging process. Nuclear CK2 localization relies on lamin A and the lamin A carboxyl terminus physically interacts with the CK2α catalytic core and inhibits its kinase activity. Loss of lamin A in Lmna-knockout mouse embryonic fibroblasts (MEFs) confers increased CK2 activity. Conversely, prelamin A that accumulates in Zmpste24-deficent MEFs exhibits a high CK2α binding affinity and concomitantly reduces CK2 kinase activity. Permidine treatment activates CK2 by releasing the interaction between lamin A and CK2, promoting DNA damage repair and ameliorating progeroid features. These data reveal a previously unidentified function for nuclear lamin A and highlight an essential role for CK2 in regulating senescence and aging.