SIRT4 Suppresses Doxorubicin-Induced Cardiotoxicity by Regulating the AKT/mTOR/Autophagy Pathway

Protein Kinase C Epsilon Overexpression Protects the Heart Against Doxorubicin-Induced Cardiotoxicity Via Activating SIRT1

Doxorubicin (DOX)-induced cardiotoxicity (DIC) is known to be associated with reduction of cardiac protein kinase C epsilon (PKC-ε). PKC-ε promotes cell survival and protects hearts against various stresses. However, it is unclear whether or not the reduction in cardiac PKC-ε expression plays a causal role in DIC and in particular the potential underlying mechanism whereby PKC-ε may protect against DIC. C57BL/6 mice (8-10-week-old) were either treated with DOX administered intraperitoneally for a duration of 4 weeks to produce cardiotoxicity, or untreated in which mice received the same volume of saline. In vitro, neonatal rat ventricle cardiomyocytes were exposed to DOX for 24 h in the absence or presence of adenovirus overexpressing PKC-ε. Cardiomyocytes in a subgroup were treated with sirtuin-1 (SIRT1) selective inhibitor Ex527. Four weeks after DOX, cardiac contractile function was decreased concomitant with increased serum CK-MB and LDH levels as well as increases in Bax-to-Bcl-2 ratio and Cleaved Caspase 3 proteins expression, while PKC-ε and Sirt1 protein expressions were significantly decreased. In vitro, DOX reduced cardiomyocyte PKC-ε and SIRT1 protein expression, decreased cardiomyocyte viability, and increased LDH release with concomitant increases in oxidative stress and apoptosis. These changes were attenuated by overexpression of PKC-ε. IP study showed that PKC-ε could directly or indirectly bind SIRT1 in cardiomyocytes, and the protect effects of PKC-ε were further canceled by SIRT1 inhibition. In conclusion, activating SIRT1 may represent a major mechanism whereby PKC-ε protects the heart against DOX-induced cell apoptosis and oxidative stress.

Pathophysiology of Doxorubicin-Mediated Cardiotoxicity

Doxorubicin (DOX) is used for the treatment of various malignancies, including leukemias, lymphomas, sarcomas, and bladder, breast, and gynecological cancers in adults, adolescents, and children. However, DOX causes severe side effects in patients, such as cardiotoxicity, which encompasses heart failure, arrhythmia, and myocardial infarction. DOX-induced cardiotoxicity (DIC) is based on the combination of nuclear-mediated cardiomyocyte death and mitochondrial-mediated death. Oxidative stress, altered autophagy, inflammation, and apoptosis/ferroptosis represent the main pathogenetic mechanisms responsible for DIC. In addition, in vitro and in vivo models of DIC sirtuins (SIRT), and especially, SIRT 1 are reduced, and this event contributes to cardiac damage. In fact, SIRT 1 inhibits reactive oxygen species and NF-kB activation, thus improving myocardial oxidative stress and cardiac remodeling. Therefore, the recovery of SIRT 1 during DIC may represent a therapeutic strategy to limit DIC progression. Natural products, i.e., polyphenols, as well as nano formulations of DOX and iron chelators, are other potential compounds experimented with in models of DIC. At present, few clinical trials are available to confirm the efficacy of these products in DIC. The aim of this review is the description of the pathophysiology of DIC as well as potential drug targets to alleviate DIC.

The Role of mTOR in the Doxorubicin-Induced Cardiotoxicity: A Systematic Review

Doxorubicin (DOX) is a chemotherapy drug known to induce metabolic changes in the heart, leading to potential heart toxicity. These changes impact various cellular functions and pathways such as disrupting the mechanistic target of rapamycin (mTOR) signaling pathway. The study aimed to investigate the effect of DOX on the mTOR pathway through an in vivo systematic review. Databases were searched on September 11, 2023. We finally included 30 in vivo studies that examined the mTOR expression in cardiac tissue samples. The present study has shown that the PI3K/AKT/mTOR, the AMPK/mTOR, the p53/mTOR signaling, the mTOR/TFEB pathway, the p38 MAPK/mTOR, the sestrins/mTOR, and the KLF15/eNOS/mTORC1 signaling pathways play a crucial role in the development of DOX-induced cardiotoxicity. Inhibition or dysregulation of these pathways can lead to increased oxidative stress, apoptosis, and other adverse effects on the heart. Strategies that target and modulate the mTOR pathways, such as the use of mTOR inhibitors like rapamycin, have the potential to enhance the anticancer effects of DOX while also mitigating its cardiotoxic side effects.

Activation and inhibition of sirtuins: From bench to bedside

The sirtuin family comprises seven NAD+-dependent enzymes which catalyze protein lysine deacylation and mono ADP-ribosylation. Sirtuins act as central regulators of genomic stability and gene expression and control key processes, including energetic metabolism, cell cycle, differentiation, apoptosis, and aging. As a result, all sirtuins play critical roles in cellular homeostasis and organism wellness, and their dysregulation has been linked to metabolic, cardiovascular, and neurological diseases. Furthermore, sirtuins have shown dichotomous roles in cancer, acting as context-dependent tumor suppressors or promoters. Given their central role in different cellular processes, sirtuins have attracted increasing research interest aimed at developing both activators and inhibitors. Indeed, sirtuin modulation may have therapeutic effects in many age-related diseases, including diabetes, cardiovascular and neurodegenerative disorders, and cancer. Moreover, isoform selective modulators may increase our knowledge of sirtuin biology and aid to develop better therapies. Through this review, we provide critical insights into sirtuin pharmacology and illustrate their enzymatic activities and biological functions. Furthermore, we outline the most relevant sirtuin modulators in terms of their modes of action, structure-activity relationships, pharmacological effects, and clinical applications.

The dual function of autophagy in doxorubicin-induced cardiotoxicity: Mechanism and natural products

Doxorubicin (DOX) is an anthracycline antitumor drug discovered in 1969, which can care for leukemia, breast cancer, lymphoma, and sarcoma. However, cardiotoxicity induced by DOX seriously limits its clinical value. The etiopathogenesis and therapeutic strategies are not unified. Autophagy is a critical mechanism in the progression of DOX-induced cardiotoxicity (DIC), autophagy intervention is a potential therapeutic strategy for DIC. Natural product has been considered as a complementary and alternative approach to treat cardiovascular disease. In this review, we summarize the pathology of autophagy in DIC and the natural products for DIC therapy.

Thiolutin Alleviates Cardiotoxic Effects of Doxorubicin by Suppressing NLRP3 Inflammasome in the Mouse Model

Doxorubicin (DOX) has a limitation in clinical oncology due to its dose-dependent cardiotoxicity. Thiolutin (THL) can undermine DOX-induced cardiomyocyte injury by inhibiting the NLRP3 inflammasome activation, yet the efficacy of THL in DOX-induced cardiotoxicity (DOXIC) needs to be validated in animal models. DOX-induced mice were treated with THL to evaluate the efficacy of THL. Relative NLRP3 mRNA levels were determined by quantitative PCR. Blood samples were collected from diffuse large B-cell lymphoma (DLBCL) patients with or without DOXIC to validate serum levels of cTnT, IL-1β, CRP, BNP, and IL-18 by enzyme-linked immunosorbent assay. Apoptosis and pyroptosis-related protein levels were analyzed by western blot. Cardiac function and histopathological changes were determined by echocardiography, HE, Masson's, and wheat germ agglutinin staining. In clinical samples, NLRP3 mRNA and/or protein levels were also markedly heightened in peripheral blood mononuclear cells and serum samples from DOXIC patients, along with higher concentrations of IL-18, cTnT, and IL-1β. Importantly, cTnT possessed a positive correlation with NLRP3 mRNA, IL-1β, and IL-18. Moreover, cTnT possessed a positive correlation with NLRP3 mRNA, IL-1β, and IL-18 levels, suggesting a potential link between DOXIC and NLRP3 inflammasome. The outcomes demonstrated that THL reduced LVEF and LVFS, as well as elevated LVESD and LVEDD in DOX-challenged mice, accompanied by elevated serum concentrations of cTnT, CRP, and BNP. In addition, THL attenuated DOX-induced myocardial hypertrophy and cardiac fibrosis in mice, in conjunction with attenuation of DOX-induced upregulation of C-caspase3, Bax, NLRP3, C-caspase-1/Pro-caspase, GSDMD-N/GSDMD, IL-1β, and IL-18 in heart or serum samples. In conclusion, our data supported that THL alleviates the cardiotoxic effects of DOX and suppresses NLRP3 inflammasome in the mouse model, suggesting that THL as a potential drug for DOXIC.

Early detection of anthracycline-induced cardiotoxicity

Although anthracyclines are important anticancer agents, their use is limited due to various adverse effects, particularly cardiac toxicity. Mechanisms underlying anthracycline-induced cardiotoxicity (AIC) are complex. Given the irreplaceable role of anthracyclines in treatment of malignancies and other serious diseases, early monitoring of AIC is paramount. In recent years, multiple studies have investigated various biomarkers for early detection of AIC. Currently, the two most common are cardiac troponin and B-type natriuretic peptide. In addition, a range of other molecules, including RNAs, myeloperoxidase (MPO), C-reactive protein (CRP), various genes, and others, also play roles in AIC prediction. Unfortunately, current research indicates a need to validate their sensitivity and specificity of these biomarkers especially in large study populations. In this review, we summarize the mechanisms and potential biomarkers of AIC, although some remain preliminary.

Doxorubicin inhibits SIRT2 and NF-kB p65 phosphorylation in Brest cell-line cancer

Doxorubicin (DOXO) is a widely used anti-cancer agent, yet the precise mechanism underlying the induction of tumor cell death remains unclear. This study aimed to elucidate new mechanisms by which doxorubicin induces apoptosis in the EMT6 mouse breast carcinoma cell line. The role of doxorubicin was assessed using the XTT assay. The assessment of oxidative stress markers, alongside the analysis of SIRT2 and NF-κB p65 (RelA) phosphorylation inhibition, was conducted. In silico studies, including density functional theory (DFT) calculations and molecular docking simulations, were employed to characterize the molecular interactions between doxorubicin and SIRT2. Additionally, doxorubicin was assessed for its capacity to modulate gene expression and associated pathways using multiple bioinformatics tools and web-based platforms. Our finding indicates that Doxorubicin induced apoptosis in EMT6 cells with an IC50 of 8,32 μM. At lower concentrations, doxorubicin enhances the oxidative balance and promotes cell viability. At high concentrations, doxorubicin inhibits SIRT2. Furthermore, an experimental investigation revealed that doxorubicin inhibits RelA phosphorylation. The results also showed that doxorubicin modulated the expression of 19 genes involved in different pathways and several transcription factors. The results of implementing the gene set with SIRT2 and RELA consolidated the experimental results. In conclusion, Doxorubicin was observed to induce EMT6 apoptosis through the inhibition of SIRT2 and RelA proteins. The outcomes of both experimental and bioinformatic studies provide a novel perspective on the biological effects of doxorubicin and underscore the potential of inhibiting the SIRT2-RelA axis as a promising biological target for cancer therapy.

P62-autophagic pathway degrades SLC7A11 to regulate ferroptosis in doxorubicin-induced cardiotoxicity

Doxorubicin-induced cardiotoxicity (DIC) poses a significant challenge, impeding its widespread application. Emerging evidence suggests the involvement of ferroptosis in the DIC. While the downregulation of SLC7A11 expression has been linked to the promotion of ferroptosis, the precise regulatory mechanism remains unclear. Recent studies, including our own, have highlighted abnormal levels of autophagy adapter protein P62 and autophagy in DIC development. Thus, our study aimed to further investigate the role of autophagy and ferroptosis in DIC, elucidating underlying molecular mechanisms across molecular, cellular, and whole-organ levels utilizing gene knockdown, immunoprecipitation, and mass spectrometry techniques. The results of our findings unveiled cardiomyocyte damage, heightened autophagy levels, and ferroptosis in DOX-treated mouse hearts. Notably, inhibition of autophagy levels attenuated DOX-induced ferroptosis. Mechanistically, we discovered that the autophagy adaptor protein P62 mediates the entry of SLC7A11 into the autophagic pathway for degradation. Furthermore, the addition of autophagy inhibitors (CQ or BAF) could elevate SLC7A11 and GPX4 protein expression, reduce the accumulation of Fe2+ and ROS in cardiomyocytes, and thus mitigate DOX-induced ferroptosis. In summary, our findings underscore the pivotal role of the P62-autophagy pathway in SLC7A11 degradation, modulating ferroptosis to exacerbate DIC. This finding offers significant insights into the underlying molecular mechanisms of DOX-induced ferroptosis and identifies new targets for reversing DIC.

The role of Klotho and sirtuins in sleep-related cardiovascular diseases: a review study

The prevalence of sleep disorders has been reported from 1.6% to 56.0%, worldwide. Sleep deprivation causes cardiovascular diseases (CVDs) including atherosclerosis, vascular aging, hypertension, heart dysfunction, reduced heart rate variability, and cardiac arrhythmia. Reduced tissue oxygen causes various CVDs by activating pro-inflammatory factors and increasing oxidative stress. Sleep disorders are more important and prevalent in older people and cause more severe cardiovascular complications. On the other hand, the reduction of Klotho level, an age-dependent protein whose expression decreases with age, is associated with age-related diseases. Sirtuins, class III histone deacetylases, also are among the essential factors in postponing cellular aging and increasing the lifespan of organisms, and they do this by regulating different pathways in the cell. Sirtuins and Klotho play an important role in the pathophysiology of CVDS and both have anti-oxidative stress and anti-inflammatory activity. Studies have shown that the levels of Klotho and sirtuins are altered in sleep disorders. In this article, alterations of Klotho and sirtuins in sleep disorders and in the development of sleep-related CVDs were reviewed and the possible signaling pathways were discussed. The inclusion criteria were studies with keywords of different types of sleep disorders and CVDs, klotho, SIRT1-7, and sirtuins in PubMed, Scopus, Embase، Science Direct، Web of Sciences and Google Scholar by the end of 2023. The studies revealed there is a bidirectional relationship between sleep disorders and the serum and tissue levels of Klotho and sirtuins and sleep related-CVDs.

Epigenetic regulation of diverse regulated cell death modalities in cardiovascular disease: Insights into necroptosis, pyroptosis, ferroptosis, and cuproptosis

Cell death constitutes a critical component of the pathophysiology of cardiovascular diseases. A growing array of non-apoptotic forms of regulated cell death (RCD)-such as necroptosis, ferroptosis, pyroptosis, and cuproptosis-has been identified and is intimately linked to various cardiovascular conditions. These forms of RCD are governed by genetically programmed mechanisms within the cell, with epigenetic modifications being a common and crucial regulatory method. Such modifications include DNA methylation, RNA methylation, histone methylation, histone acetylation, and non-coding RNAs. This review recaps the roles of DNA methylation, RNA methylation, histone modifications, and non-coding RNAs in cardiovascular diseases, as well as the mechanisms by which epigenetic modifications regulate key proteins involved in cell death. Furthermore, we systematically catalog the existing epigenetic pharmacological agents targeting novel forms of RCD and their mechanisms of action in cardiovascular diseases. This article aims to underscore the pivotal role of epigenetic modifications in precisely regulating specific pathways of novel RCD in cardiovascular diseases, thus offering potential new therapeutic avenues that may prove more effective and safer than traditional treatments.

The mechanism and therapeutic strategies in doxorubicin-induced cardiotoxicity: Role of programmed cell death

Doxorubicin (DOX) is the most commonly used anthracycline anticancer agent, while its clinical utility is limited by harmful side effects like cardiotoxicity. Numerous studies have elucidated that programmed cell death plays a significant role in DOX-induced cardiotoxicity (DIC). This review summarizes several kinds of programmed cell death, including apoptosis, pyroptosis, necroptosis, autophagy, and ferroptosis. Furthermore, oxidative stress, inflammation, and mitochondrial dysfunction are also important factors in the molecular mechanisms of DIC. Besides, a comprehensive understanding of specific signal pathways of DIC can be helpful to its treatment. Therefore, the related signal pathways are elucidated in this review, including sirtuin deacetylase (silent information regulator 2 [Sir2]) 1 (SIRT1)/nuclear factor erythroid 2-related factor 2, SIRT1/Klotho, SIRT1/Recombinant Sestrin 2, adenosine monophosphate-activated protein kinase, AKT, and peroxisome proliferator-activated receptor. Heat shock proteins function as chaperones, which play an important role in various stressful situations, especially in the heart. Thus, some of heat shock proteins involved in DIC are also included. Hence, the last part of this review focuses on the therapeutic research based on the mechanisms above.

Identification of autophagy-related signatures in doxorubicin-induced cardiotoxicity

PURPOSE

Doxorubicin is an antibiotic drug used clinically to treat infectious diseases and tumors. Unfortunately, it is cardiotoxic. Autophagy is a cellular self-decomposition process that is essential for maintaining homeostasis in the internal environment. Accordingly, the present study was proposed to characterize the autophagy-related signatures of doxorubicin-induced cardiotoxicity.

METHODS

Datasets related to doxorubicin-induced cardiotoxicity were retrieved by searching the GEO database and differentially expressed genes (DEGs) were identified. DEGs were taken to intersect with autophagy-related genes to obtain autophagy-related signatures, and Gene Ontology (GO)/Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis and protein-protein interaction (PPI) network were performed on them. Further, construction of miRNA-hub gene networks and identification of target drugs to reveal potential molecular mechanisms and therapeutic strategies. Animal models of doxorubicin-induced cardiotoxicity were constructed to validate differences in gene expression for autophagy-related signatures.

RESULTS

PBMC and heart samples from the GSE37260 dataset were selected for analysis. There were 995 and 2357 DEGs in PBMC and heart samples, respectively, and they had 23 intersecting genes with autophagy-related genes. RT-qPCR confirmed the differential expression of 23 intersecting genes in doxorubicin-induced cardiotoxicity animal models in general agreement with the bioinformatics results. An autophagy-related signatures consisting of 23 intersecting genes is involved in mediating processes and pathways such as autophagy, oxidative stress, apoptosis, protein ubiquitination and phosphorylation. Moreover, Akt1, Hif1a and Mapk3 are hub genes in autophagy-associated signatures and their upstream miRNAs are mainly rno-miR-1188-5p, rno-miR-150-3p and rno-miR-326-3p, and their drugs are mainly CHEMBL55802, Carboxyamidotriazole and 3-methyladenine.

CONCLUSION

This study identifies for the first-time autophagy-related signatures in doxorubicin's cardiotoxicity, which could provide potential molecular mechanisms and therapeutic strategies for doxorubicin-induced cardiotoxicity.

Research progress on the role and mechanism of Sirtuin family in doxorubicin cardiotoxicity

BACKGROUND

Doxorubicin (DOX) is a widely utilized anthracycline chemotherapy drug in cancer treatment, yet its efficacy is hindered by both short-term and long-term cardiotoxicity. Although oxidative stress, inflammation and mitochondrial dysfunction are established factors in DOX-induced cardiotoxicity, the precise molecular pathways remain elusive. Further exploration of the pathogenesis and identification of novel molecular targets are imperative. Recent studies have implicated the Sirtuins family in various physiological and pathological processes, suggesting their potential in ameliorating DOX-induced cardiotoxicity. Moreover, research on Sirtuins has discovered small-molecule compounds or medicinal plants with regulatory effects, representing a notable advancement in preventing and treating DOX-induced cardiac injury.

PURPOSE

In this review, we delve into the pathogenesis of DOX-induced cardiotoxicity and explore the therapeutic effects of Sirtuins in mitigating this condition, along with the associated molecular mechanisms. Furthermore, we delineate the roles and mechanisms of small-molecule regulators of Sirtuins in the prevention and treatment of DOX-induced cardiotoxicity.

STUDY-DESIGN/METHODS

Data for this review were sourced from various scientific databases (such as Web of Science, PubMed and Science Direct) up to March 2024. Search terms included "Sirtuins," "DOX-induced cardiotoxicity," "DOX," "Sirtuins regulators," "histone deacetylation," among others, as well as several combinations thereof.

RESULTS

Members of the Sirtuins family regulate both the onset and progression of DOX-induced cardiotoxicity through anti-inflammatory, antioxidative stress and anti-apoptotic mechanisms, as well as by maintaining mitochondrial stability. Moreover, natural plant-derived active compounds such as Resveratrol (RES), curcumin, berberine, along with synthetic small-molecule compounds like EX527, modulate the expression and activity of Sirtuins.

CONCLUSION

The therapeutic role of the Sirtuins family in mitigating DOX-induced cardiotoxicity represents a potential molecular target. However, further research is urgently needed to elucidate the relevant molecular mechanisms and to assess the safety and biological activity of Sirtuins regulators. This review offers an in-depth understanding of the therapeutic role of the Sirtuins family in mitigating DOX-induced cardiotoxicity, providing a preliminary basis for the clinical application of Sirtuins regulators in this condition.

Eupatilin attenuates doxorubicin-induced cardiotoxicity by activating the PI3K-AKT signaling pathway in mice

Eupatilin is a pharmacologically active flavonoid with a variety of biological activities, such as anticancer, anti-inflammatory, antioxidant, neuroprotective, anti-allergic and cardioprotective effects. However, whether eupatilin has protective effects on doxorubicin-induced cardiotoxicity remains unknown. Thus, this study aimed to investigate the role of eupatilin in doxorubicin-induced cardiotoxicity. Mice were exposed to a single dose of doxorubicin (15 mg/kg) to generate doxorubicin-induced cardiotoxicity or normal saline as a control. To explore the protective effects, mice were intraperitoneally injected with eupatilin daily for 7 days. Then, we examined the changes in cardiac function, inflammation, apoptosis, and oxidative stress to evaluate the effects of eupatilin on doxorubicin-induced cardiotoxicity. Additionally, RNA-seq analysis was introduced to explore the potential molecular mechanisms. Eupatilin ameliorated doxorubicin-induced cardiotoxicity by attenuating inflammation, oxidative stress, and cardiomyocyte apoptosis and ameliorated doxorubicin-induced cardiac dysfunction. Mechanistically, eupatilin activated the PI3K-AKT signaling pathway, as evidenced by RNA-seq analysis and Western blot analysis. This study provides the first evidence that eupatilin ameliorates doxorubicin-induced cardiotoxicity by attenuating inflammation, oxidative stress, and apoptosis. Pharmacotherapy with eupatilin provides a novel therapeutic regimen for doxorubicin-induced cardiotoxicity.

Molecular mechanisms involved in doxorubicin-induced cardiotoxicity: A bibliometrics analysis by VOSviewer

Doxorubicin is a potent chemotherapeutic agent that can cause cardiotoxicity. Many documents (more than 14,000) have been published in the area of doxorubicin-induced cardiotoxicity (DIC) since 1970. A comprehensive bibliographic analysis of author keywords was used to describe better and understand the molecular mechanisms involved in DIC. The objective was to consider the state of the author keywords of research on the molecular mechanisms involved in DIC based on a bibliometrics study of articles published over the past fifty years. A bibliometrics analysis was conducted using VOSviewer with data collected from the Web of Science Core Collection database of over 14,000 documents (from 1970 to July 19, 2023). Using scientific publications retrieved about DIC, author keywords were assessed at the scientific field level. The current study showed that the annual number of DIC-related publications has increased over the past 50 years. The Journal of Clinical Oncology is the leading journal in this field. The top cited DIC document was published in 2004. The top keywords with high frequency were "doxorubicin," "cardiotoxicity," and "adriamycin." According to the results of this study, the most common mechanisms involved in DIC were as follows oxidative stress, apoptosis, inflammation, autophagy, mitophagy, endoplasmic reticulum stress, pyroptosis, and ferroptosis. The highest occurrences of regulators-related author keywords were "AKT," "Sirt1," and "AMPK." Based on the findings, oxidative stress, apoptosis, inflammation, autophagy, mitophagy, endoplasmic reticulum stress, pyroptosis, and ferroptosis were hot research mechanisms of DIC from 1970 to July 19, 2023.

Sirtuins Affect Cancer Stem Cells via Epigenetic Regulation of Autophagy

Sirtuins (SIRTs) are stress-responsive proteins that regulate several post-translational modifications, partly by acetylation, deacetylation, and affecting DNA methylation. As a result, they significantly regulate several cellular processes. In essence, they prolong lifespan and control the occurrence of spontaneous tumor growth. Members of the SIRT family have the ability to govern embryonic, hematopoietic, and other adult stem cells in certain tissues and cell types in distinct ways. Likewise, they can have both pro-tumor and anti-tumor effects on cancer stem cells, contingent upon the specific tissue from which they originate. The impact of autophagy on cancer stem cells, which varies depending on the specific circumstances, is a very intricate phenomenon that has significant significance for clinical and therapeutic purposes. SIRTs exert an impact on the autophagy process, whereas autophagy reciprocally affects the activity of certain SIRTs. The mechanism behind this connection in cancer stem cells remains poorly understood. This review presents the latest findings that position SIRTs at the point where cancer cells and autophagy interact. Our objective is to highlight the various roles of distinct SIRTs in cancer stem cell-related functions through autophagy. This would demonstrate their significance in the genesis and recurrence of cancer and offer a more precise understanding of their treatment possibilities in relation to autophagy.

Regulatory factor X7 Represses Ox-LDL-Induced Proliferation and Migration of VSMCs via SIRT4-Mediated Inactivation of JAK2/STAT3 Pathway

The regulatory factor X7 (RFX7) is a vital mediator in atherosclerosis. This study aims to discuss the effect and underlying mechanism of RFX7 on the regulation of oxidized low-density lipoprotein (ox-LDL) -induced proliferation and migration of vascular smooth muscle cells (VSMCs).Ox-LDL was used to construct atherosclerosis in vitro model. The mRNA and protein levels of RFX7 and Sirtuin 4 (SIRT4) were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot assays. The cellular functions were measured via 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT), EdU, flow cytometry, and wound healing assay assays. The interaction between RFX7 and SIRT4 promoter was validated using chromatin immunoprecipitation and dual-luciferase reporter assays.The stimulation with ox-LDL elevated the viability of VSMCs and decreased the mRNA and protein levels of RFX7 and SIRT4 in VSMCs in a dose-dependent manner. Functionally, RFX7 overexpression restrained the VSMC viability, proliferation, and migration induced by ox-LDL, but facilitated VSMC apoptosis. RFX7 elevated SIRT4 expression via binding to its promoter. Furthermore, overexpressing either SIRT4 or RFX7 inactivated JAK2/STAT3 signaling, causing a decrease in VSMC proliferation and migration and an increase in VSMC apoptosis when exposed to ox-LDL. The impact of RFX7 overexpression on JAK2/STAT3 signaling and cellular function following ox-LDL exposure was abrogated by SIRT4 silencing.The heightened RFX7 expression restrained the proliferation and migration of ox-LDL-stimulated VSMCs via SIRT4-mediated inactivation of JAK2/STAT3 pathway.

Sirtuins and autophagy in lipid metabolism

Sirtuins are a family of NAD+ -dependent deacetylases that regulate some important biological processes, including lipid metabolism and autophagy, through their deacetylase function. Autophagy is a new discovery in the field of lipid metabolism, which may provide a new idea for the regulation of lipid metabolism. There are many tandem parts in the regulation process of lipid metabolism and autophagy of sirtuins protein family. This paper summarized these tandem parts and proposed the possibility of sirtuins regulating lipid autophagy, as well as the interaction and synergy between sirtuins protein family. Currently, some natural drugs have been reported to affect metabolism by regulating sirtuins, some of which regulate autophagy by targeting sirtuins.

Doxorubicin-mediated cardiac dysfunction: Revisiting molecular interactions, pharmacological compounds and (nano)theranostic platforms

Although chemotherapy drugs are extensively utilized in cancer therapy, their administration for treatment of patients has faced problems that regardless of chemoresistance, increasing evidence has shown concentration-related toxicity of drugs. Doxorubicin (DOX) is a drug used in treatment of solid and hematological tumors, and its function is based on topoisomerase suppression to impair cancer progression. However, DOX can also affect the other organs of body and after chemotherapy, life quality of cancer patients decreases due to the side effects. Heart is one of the vital organs of body that is significantly affected by DOX during cancer chemotherapy, and this can lead to cardiac dysfunction and predispose to development of cardiovascular diseases and atherosclerosis, among others. The exposure to DOX can stimulate apoptosis and sometimes, pro-survival autophagy stimulation can ameliorate this condition. Moreover, DOX-mediated ferroptosis impairs proper function of heart and by increasing oxidative stress and inflammation, DOX causes cardiac dysfunction. The function of DOX in mediating cardiac toxicity is mediated by several pathways that some of them demonstrate protective function including Nrf2. Therefore, if expression level of such protective mechanisms increases, they can alleviate DOX-mediated cardiac toxicity. For this purpose, pharmacological compounds and therapeutic drugs in preventing DOX-mediated cardiotoxicity have been utilized and they can reduce side effects of DOX to prevent development of cardiovascular diseases in patients underwent chemotherapy. Furthermore, (nano)platforms are used comprehensively in treatment of cardiovascular diseases and using them for DOX delivery can reduce side effects by decreasing concentration of drug. Moreover, when DOX is loaded on nanoparticles, it is delivered into cells in a targeted way and its accumulation in healthy organs is prevented to diminish its adverse impacts. Hence, current paper provides a comprehensive discussion of DOX-mediated toxicity and subsequent alleviation by drugs and nanotherapeutics in treatment of cardiovascular diseases.

Targeting Mitochondrial Sirtuins in Age-Related Neurodegenerative Diseases and Fibrosis

Aging is a natural and complex biological process that is associated with widespread functional declines in numerous physiological processes, terminally affecting multiple organs and tissues. Fibrosis and neurodegenerative diseases (NDs) often occur with aging, imposing large burdens on public health worldwide, and there are currently no effective treatment strategies for these diseases. Mitochondrial sirtuins (SIRT3-5), which are members of the sirtuin family of NAD+-dependent deacylases and ADP-ribosyltransferases, are capable of regulating mitochondrial function by modifying mitochondrial proteins that participate in the regulation of cell survival under various physiological and pathological conditions. A growing body of evidence has revealed that SIRT3-5 exert protective effects against fibrosis in multiple organs and tissues, including the heart, liver, and kidney. SIRT3-5 are also involved in multiple age-related NDs, including Alzheimer's disease, Parkinson's disease, and Huntington's disease. Furthermore, SIRT3-5 have been noted as promising targets for antifibrotic therapies and the treatment of NDs. This review systematically highlights recent advances in knowledge regarding the role of SIRT3-5 in fibrosis and NDs and discusses SIRT3-5 as therapeutic targets for NDs and fibrosis.

Protective effect of vitamin B6 against doxorubicin-induced cardiotoxicity by modulating NHE1 expression

Doxorubicin (DOX) has been used to treat various types of cancer, but its application is limited due to its heart toxicity as well as other drawbacks. Chronic inhibition of Na+ /H+ exchanger (NHE1) reduces heart failure and reduces the production of reactive oxygen species (ROS); vitamin B6 (VitB6 ) has been demonstrated to have a crucial role in antioxidant mechanism. So, this study was designed to explore the effect of VitB6 supplement on the DOX-induced cardiotoxicity and to imply whether NHE1 is involved. Ultrasonic cardiogram analysis revealed that VitB6 supplement could alleviate DOX-induced cardiotoxicity; hematoxylin and eosin (HE) and Masson's staining further confirmed this effect. Furthermore, VitB6 supplement exhibited significant antioxidative stress and antiapoptosis effect, which was evidenced by decreased serum malondialdehyde (MDA) content and increased serum superoxide dismutase (SOD) content, and decreased Bcl-2-associated X protein/B-cell lymphoma-2 ratio, respectively. Collectively, VitB6 supplement may exert antioxidative and antiapoptosis effects to improve cardiac function by decreasing NHE1 expression and improve DOX-induced cardiotoxicity.

The Current State of Research on Sirtuin-Mediated Autophagy in Cardiovascular Diseases

Sirtuins belong to the class III histone deacetylases and possess nicotinamide adenine dinucleotide-dependent deacetylase activity. They are involved in the regulation of multiple signaling pathways implicated in cardiovascular diseases. Autophagy is a crucial adaptive cellular response to stress stimuli. Mounting evidence suggests a strong correlation between Sirtuins and autophagy, potentially involving cross-regulation and crosstalk. Sirtuin-mediated autophagy plays a crucial regulatory role in some cardiovascular diseases, including atherosclerosis, ischemia/reperfusion injury, hypertension, heart failure, diabetic cardiomyopathy, and drug-induced myocardial damage. In this context, we summarize the research advancements pertaining to various Sirtuins involved in autophagy and the molecular mechanisms regulating autophagy. We also elucidate the biological function of Sirtuins across diverse cardiovascular diseases and further discuss the development of novel drugs that regulate Sirtuin-mediated autophagy.

The autophagy-NAD axis in longevity and disease

Autophagy is an intracellular degradation pathway that recycles subcellular components to maintain metabolic homeostasis. NAD is an essential metabolite that participates in energy metabolism and serves as a substrate for a series of NAD+-consuming enzymes (NADases), including PARPs and SIRTs. Declining levels of autophagic activity and NAD represent features of cellular ageing, and consequently enhancing either significantly extends health/lifespan in animals and normalises metabolic activity in cells. Mechanistically, it has been shown that NADases can directly regulate autophagy and mitochondrial quality control. Conversely, autophagy has been shown to preserve NAD levels by modulating cellular stress. In this review we highlight the mechanisms underlying this bidirectional relationship between NAD and autophagy, and the potential therapeutic targets it provides for combatting age-related disease and promoting longevity.

SIRT4 is an independent prognostic factor in bladder cancer and inhibits bladder cancer growth by suppressing autophagy

BACKGROUND

Nucleosome-localized sirtuin 4 (SIRT4) was found to function as an oncogene and tumor suppressor gene in different tumors. However, the clinical significance of SIRT4 in bladder urothelial carcinoma (BLCA) has not been assessed, nor has the function of SIRT4 in BLCA been analyzed.

METHODS

In this study, we assessed the levels of SIRT4 protein in BLCA tissues and its association with clinicopathological parameters and overall survival time of BLCA patients by immunohistochemical staining of tissue microarrays containing 59 BLCA patients. Then, we constructed BLCA cell lines (T24) with overexpression or interference of SIRT4 by lentiviral infection. The effects of SIRT4 on the proliferation, migration and invasive ability of T24 cells were investigated using cell counting kit-8 (CCK-8) assays, wound healing assays, and migration and invasion assays. Moreover, we also investigated the effect of SIRT4 on the cell cycle and apoptosis of T24 cells. Mechanistically, we explored the relationship between SIRT4 and autophagy and its role in the inhibition of BLCA.

RESULTS

We found by immunohistochemistry that SIRT4 protein levels were reduced in BLCA and that lower SIRT4 levels were associated with larger tumor volumes, later T-staging and later AJCC staging in BLCA patients and were an independent prognostic factor in BLCA patients. Overexpression of SIRT4 significantly inhibited the proliferative viability, scratch healing capacity, migratory capacity, and invasive capacity of T24 cells, while interference with SIRT4 had the opposite effect. Moreover, overexpression of SIRT4 significantly inhibited the cell cycle and increased the apoptosis rate of T24 cells. Mechanistically, SIRT4 inhibits BLCA growth by suppressing autophagic flow.

CONCLUSIONS

Our study suggests that SIRT4 is an independent prognostic factor for BLCA and that SIRT4 plays a tumor suppressor role in BLCA. This suggests a potential target for SIRT4 in the diagnosis and treatment of BLCA.

SIRT4 in ageing

Ageing is a phenomenon in which cells, tissues and organs undergo systemic pathological changes as individuals age, leading to the occurrence of ageing-related diseases and the end of life. It is associated with many phenotypes known as ageing characteristics, such as genomic instability, nutritional imbalance, mitochondrial dysfunction, cell senescence, stem cell depletion, and an altered microenvironment. The sirtuin family (SIRT), known as longevity proteins, is thought to delay ageing and prolong life, and mammals, including humans, have seven family members (SIRT1-7). SIRT4 has been studied less among the sirtuin family thus far, but it has been reported that it has important physiological functions in organisms, such as promoting DNA damage repair, participating in the energy metabolism of three substances, inhibiting inflammatory reactions and apoptosis, and regulating mitochondrial function. Recently, some studies have demonstrated the involvement of SIRT4 in age-related processes, but knowledge in this field is still scarce. Therefore, this review aims to analyse the relationship between SIRT4 and ageing characteristics as well as some age-related diseases (e.g., cardiovascular diseases, metabolic diseases, neurodegenerative diseases and cancer).

Activation of the sirtuin silent information regulator 1 pathway inhibits pathological myocardial remodeling

Myocardial remodeling refers to structural and functional disorders of the heart caused by molecular biological changes in the cardiac myocytes in response to neurological and humoral factors. A variety of heart diseases, such as hypertension, coronary artery disease, arrhythmia, and valvular heart disease, can cause myocardial remodeling and eventually lead to heart failure. Therefore, counteracting myocardial remodeling is essential for the prevention and treatment of heart failure. Sirt1 is a nicotinamide adenine dinucleotide⁺-dependent deacetylase that plays a wide range of roles in transcriptional regulation, energy metabolism regulation, cell survival, DNA repair, inflammation, and circadian regulation. It positively or negatively regulates myocardial remodeling by participating in oxidative stress, apoptosis, autophagy, inflammation, and other processes. Taking into account the close relationship between myocardial remodeling and heart failure and the involvement of SIRT1 in the development of the former, the role of SIRT1 in the prevention of heart failure via inhibition of myocardial remodeling has received considerable attention. Recently, multiple studies have been conducted to provide a better understanding of how SIRT1 regulates these phenomena. This review presents the progress of research involving SIRT1 pathway involvement in the pathophysiological mechanisms of myocardial remodeling and heart failure.

Sirtuin 4 activates autophagy and inhibits tumorigenesis by upregulating the p53 signaling pathway

The role of autophagy in cancer is context-dependent. In the present study, we aimed to investigate the regulator and underlying mechanism of autophagy. We found that a sirtuin (SIRT) family member, SIRT4, was significantly associated autophagy pathway in pancreatic ductal adenocarcinoma (PDAC). Specifically, in vitro cell culture experiments and in vivo transgenic and xenografted animal models revealed that SIRT4 could inhibit tumor growth and promote autophagy in PDAC. In terms of the mechanism, we demonstrated that SIRT4 activated the phosphorylation of p53 protein by suppressing glutamine metabolism, which was crucial in SIRT4-induced autophagy. AMPKα was implicated in the regulation of autophagy and phosphorylation of p53 mediated by SIRT4, contributing to the suppression of pancreatic tumorigenesis. Notably, the clinical significance of the SIRT4/AMPKα/p53/autophagy axis was demonstrated in human PDAC specimens. Collectively, these findings suggested that SIRT4-induced autophagy further inhibited tumorigenesis and progression of PDAC, highlighting the potential of SIRT4 as a therapeutic target for cancer.

Protective role of cezanne in doxorubicin-induced cardiotoxicity by inhibiting autophagy, apoptosis and oxidative stress

Doxorubicin (DOX) is frequently used in clinical practice for its broad-spectrum effects. However, its benefit is limited by a series of complications, including excessive apoptosis and autophagy of cardiomyocytes, overproduction of reactive oxygen species (ROS) and high level of oxidative stress. As a new protein, OTU domain-containing 7B (OTUD7B), also called Cezanne, has been reported to regulate many pathological processes. However, whether it plays a role in DOX-induced cardiotoxicity is still unclear. We discovered that the Cezanne level was significantly increased in DOX-treated neonatal rat cardiomyocytes (NRCMs) and C57BL/6 J mice hearts. In vitro, the knockdown of Cezanne with adenovirus in NRCMs significantly worsened DOX-induced apoptosis, autophagy and oxidative stress, while Cezanne overexpression showed opposite results. In vivo, the overexpression of Cezanne using cardiomyocyte-targeted adeno-associated virus 9 (AAV9) significantly reduced cardiomyocyte apoptosis, autophagy and oxidative stress level when C57BL/6 J mice were subjected to DOX. Mechanistically, the overexpression of Cezanne significantly reversed the in-activation of the PI3K/AKT/mTOR pathway induced by DOX, while the inhibitors of this pathway abolished the effect of Cezanne, suggesting that the PI3K/AKT/mTOR pathway plays a role in the protective function of Cezanne. These findings indicate that Cezanne could ameliorate DOX-induced cardiotoxicity by attenuating the apoptosis and autophagy of cardiomyocytes and decreasing the level of oxidative stress.

Why Is Longevity Still a Scientific Mystery? Sirtuins-Past, Present and Future

The sirtuin system consists of seven highly conserved regulatory enzymes responsible for metabolism, antioxidant protection, and cell cycle regulation. The great interest in sirtuins is associated with the potential impact on life extension. This article summarizes the latest research on the activity of sirtuins and their role in the aging process. The effects of compounds that modulate the activity of sirtuins were discussed, and in numerous studies, their effectiveness was demonstrated. Attention was paid to the role of a caloric restriction and the risks associated with the influence of careless sirtuin modulation on the organism. It has been shown that low modulators' bioavailability/retention time is a crucial problem for optimal regulation of the studied pathways. Therefore, a detailed understanding of the modulator structure and potential reactivity with sirtuins in silico studies should precede in vitro and in vivo experiments. The latest achievements in nanobiotechnology make it possible to create promising molecules, but many of them remain in the sphere of plans and concepts. It seems that solving the mystery of longevity will have to wait for new scientific discoveries.

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.

Puerarin activates adaptive autophagy and protects the myocardium against doxorubicin-induced cardiotoxicity via the 14–3-3γ/PKCε pathway

Doxorubicin (Dox)-induced cardiotoxicity (DIC) seriously threatens the health of related patients. Studies have confirmed that 14-3-3γ and protein kinase C epsilon (PKCε) are the endogenous protective proteins. Puerarin (Pue) is a bioactive ingredient isolated from the root of Pueraria lobata. It possesses many pharmacological properties, which have been widely used in treating and adjuvant therapy of cardiovascular diseases. In the study, we intended to explore the effects and mechanism of Pue pretreatment to protect the myocardium against DIC injury. Adult mice and H9c2 cells were pretreated with Pue, and the injury model was made with Dox. Results showed that Pue pretreatment alleviated DIC injury, as revealed by increased cell viability, decreased LDH activity and apoptosis, inhibited excess oxidative stress, maintained mitochondrial function and energy metabolism, and improved myocardial function. Furthermore, Pue pretreatment upregulated 14-3-3γ expression, interacted with PKCε, phosphorylated and impelled migration to mitochondria, activated adaptive autophagy, and protected the myocardium. However, pAD/14-3-3γ-shRNA or εV1-2 (a PKCε activity inhibitor) or 3-methyladenine (an autophagy inhibitor) could weaken the above effects of Pue pretreatment. Together, Pue pretreatment could activate adaptive autophagy by the 14-3-3γ/PKCε pathway and protect the myocardium against DIC injury.

Induction of P-glycoprotein expression by dandelion in tumor and heart tissues: Impact on the anti-tumor activity and cardiotoxicity of doxorubicin

BACKGROUND

Previously, we have investigated the anti-tumor activity and mechanism through which dandelion acts against triple-negative breast cancer (TNBC). However, traditional Chinese medicine is mostly accepted as an adjunct therapy during chemotherapy in clinical practice. So far, little is known about the effects of dandelion in conjunction with chemotherapeutic drugs.

PURPOSE

To investigate the effects of dandelion on the anti-tumor activity and cardiotoxicity of doxorubicin (DOX), and to further explore the molecular mechanisms through which these effects occur.

STUDY DESIGN

At the beginning of this study, dandelion was observed to alleviate DOX-induced cardiotoxicity and reduce the anti-tumor activity of DOX. Subsequently, we investigated whether the resistance to DOX mediated by P-glycoprotein was involved in the above effects.

METHODS

The cardioprotective effect of dandelion was investigated on DOX-treated mice by histological analysis, myocardial enzyme assays, and an untargeted metabolomics study based on LC-Q-TOF/MS. TNBC cell lines and 4T1 tumor-bearing mice were employed to investigate the combined anti-tumor activity. Laser scanning confocal microscope and a flow cytometry analysis were employed to measure the intracellular accumulation of DOX. A specific, sensitive, and rapid LC-MS/MS method was developed to detect the efflux of DOX from cells. Expression of P-glycoprotein in mouse tumor and heart tissues was detected via Western blotting analysis.

RESULTS

Dandelion was found to significantly alleviate DOX-induced cardiotoxicity, as was evidenced by improved cardiomyocyte morphology, decreased LDH and CK-MB release, and adjusted metabolic biomarker levels. However, in vitro and in vivo studies showed that dandelion could reduce the anti-tumor activity of DOX. This counteraction was achieved by activating of the drug efflux transporter P-glycoprotein, thereby promoting the efflux of DOX from cells and reducing the intracellular accumulation of DOX. Moreover, the activation of P-glycoprotein by dandelion in mouse heart tissue was also observed, thus suggesting that the decrease of cardiac DOX accumulation plays an important role in the cardioprotective effect of dandelion.

CONCLUSION

Dandelion can activate the P-glycoprotein in heart and tumor tissues, which ameliorates DOX-induced cardiotoxicity but attenuates DOX cytotoxicity toward TNBC. Our findings have important implications for the correct clinical use of dandelion.

Autophagy in Rat Müller Glial Cells Is Modulated by the Sirtuin 4/AMPK/mTOR Pathway and Induces Apoptosis under Oxidative Stress

Müller glial cells (MGCs) are a group of glial cells in the retina that provide essential support to retinal neurons; however, the understanding of MGC apoptosis and autophagy remains limited. This study was aimed at investigating the role of autophagy in MGCs under normal and oxidative conditions, and identifying the underlying mechanisms. In addition, the sirtuin 4 (SIRT4)-mediated signaling pathway was observed to regulate the autophagic process in MGCs. To assess the effect of autophagy on MGC mitochondrial function and survival, we treated rMC-1 cells—rat-derived Müller glial cells—with rapamycin and 3-methyladenine (3-MA), and found that MGC death was not induced by such treatment, while autophagic dysfunction could increase MGC apoptosis under oxidative stress, as reflected by the expression level of cleaved caspase 3 and PI staining. In addition, the downregulation of autophagy by 3-MA could influence the morphology of the mitochondrial network structure, the mitochondrial membrane potential, and generation of reactive oxygen species (ROS) under oxidative stress. Moreover, SIRT4 depletion enhanced autophagosome formation, as verified by an increase in the LC3 II/I ratio and a decrease in the expression of SQSTM1/p62, and vice versa. The inhibition of AMPK phosphorylation by compound C could reverse these changes in LC3 II/I and SQSTM1/p62 caused by SIRT4 knockdown. Our research concludes that MGCs can endure autophagic dysfunction in the absence of oxidative stress, while the downregulation of autophagy can cause MGCs to become more sensitized to oxidative stress. Simultaneous exposure to oxidative stress and autophagic dysfunction in MGCs can result in a pronounced impairment of cell survival. Mechanically, SIRT4 depletion can activate the autophagic process in MGCs by regulating the AMPK–mTOR signaling pathway.