Sestrin 1 ameliorates cardiac hypertrophy via autophagy activation

Effects of electrolyte balance on intestinal barrier, amino acid metabolism, and mTORC1 signaling pathway in piglets fed low-protein diets

A proper dietary electrolyte balance (dEB) is essential to ensure optimal growth performance of piglets. In the low-protein diet, this balance may be affected by the reduction of soybean meal and the inclusion of high levels of synthetic amino acids. The objective of this experiment was to evaluate the optimal dEB of low-protein diets and its impact on the growth performance of piglets. A total of 108 piglets (initial age of 35 d) were randomly divided into 3 groups with 6 replicates of 6 pigs each as follows: low electrolyte diet (LE group; dEB = 150 milliequivalents [mEq]/kg); medium electrolyte diet (ME group; dEB = 250 mEq/kg); high electrolyte diet (HE group; dEB = 350 mEq/kg). Results indicated that the LE and HE diet significantly decreased the average daily gain, average daily feed intake, and crude protein digestibility (P < 0.05) in piglets. Meanwhile, LE diets disrupted the structural integrity of the piglets' intestines and decreased jejunal tight junction protein (occludin and claudin-1) expression (P < 0.05). Additionally, the pH and HCO3- in the arterial blood of piglets in the LE group were lower than those in the ME and HE groups (P < 0.05). Interestingly, the LE diet significantly increased lysine content in piglet serum (P < 0.05), decreased the levels of arginine, leucine, glutamic acid, and alanine (P < 0.05), and inhibited the mammalian target of rapamycin complex 1 (mTORC1) pathway by decreasing the phosphorylation abundance of key proteins. In summary, the dietary electrolyte imbalance could inhibit the activation of the mTORC1 signaling pathway, which might be a key factor in the influence of the dEB on piglet growth performance and intestinal health. Moreover, second-order polynomial (quadratic) regression analysis showed that the optimal dEB of piglets in the low-protein diet was 250 to 265 mEq/kg.

Gallic acid as a Sestrin (SESN2) activator and potential obesity therapeutic agent: A molecular docking study

Sestrins (SESNs) are a family of evolutionarily conserved proteins among mammals. They have several body homeostatic functions such as antioxidant, metabolic, and anti-aging, and are required to regenerate hyperoxidized forms of peroxiredoxins and reactive oxygen species. Sestrin 2 has been studied as a therapeutic agent in obesity treatment. Gallic acid (GA) is a triphenolic compound with beneficial biological activities including anti-inflammatory, antidiabetic, antihypertensive, and antioxidant effects. Recent studies demonstrated the GA's ability to reduce body weight gain and improve glycemic parameters. In this sense, the present study aims to investigate the GA activating potential of Sestrin using the molecular docking method. The 3D structure of gallic acid was retrieved from the NCBI PubChem database and the chemical structure of the Sestrin2 protein from the RCSB Protein Data Bank (5DJ4). The docking calculus was performed via UCSF Chimera and AutoDock Vinaprograms. The results showed that amino acids Arg390, Glu451, Trp444, Thr386, Arg448, Thr374, Tyr375, Asn376, Thr377, Leu389, His454, Ser450, His86, and Val455 are very important for GA stabilization, resembling the interactions that permit Leucine to activate SESN2. In this context, the obesity therapeutic property of GA can be understood from a Sestrin activating process through amino acid metabolism.

Muscular Sestrins: Roles in Exercise Physiology and Stress Resistance

Sestrins are a family of stress-inducible proteins that are critical for stress adaptation and the maintenance of metabolic homeostasis. High expression of Sestrins is observed in skeletal and cardiac muscle tissues, suggesting their significance in the physiological homeostasis of these organs. Furthermore, expression of Sestrins is dynamically controlled in the tissues, based on the level of physical activity and the presence or absence of stress insults. Genetic studies in model organisms have shown that muscular Sestrin expression is critical for metabolic homeostasis, exercise adaptation, stress resistance, and repair and may mediate the beneficial effects of some available therapeutics. The current minireview summarizes and discusses recent findings that shed light on the role of Sestrins in regulating muscle physiology and homeostasis.

SESN1 attenuates the Ox‑LDL‑induced inflammation, apoptosis and endothelial‑mesenchymal transition of human umbilical vein endothelial cells by regulating AMPK/SIRT1/LOX1 signaling

Endothelial cells are an important component of the heart and vasculature and form a crucial link between the cardiovascular system and the immune system. Sestrin 1 (SESN1) has an important role in atherosclerosis by inhibiting NOD-like receptor family pyrin domain containing 3 inflammasome activation. However, whether SESN1 is involved in human umbilical vein endothelial cell (HUVEC) injury caused by atherosclerosis has remained to be elucidated. The present study aimed to investigate the functions of SESN1 in the inflammatory response, apoptosis and endothelial-mesenchymal transition (EndMT) of HUVECs following stimulation with oxidized low-density lipoprotein (Ox-LDL). SESN1 expression at the mRNA and protein levels was detected using reverse transcription-quantitative PCR (RT-qPCR) and western blot analysis. Following SESN1 overexpression in Ox-LDL-stimulated HUVECs, cell viability was determined using a Cell Counting Kit-8 assay. Terminal deoxynucleotidyl transferase-mediated nick-end labeling staining was employed to detect cell apoptosis and western blot analysis was used to determine the levels of apoptosis-related proteins. RT-qPCR, ELISA and western blot were utilized to determine the levels of inflammatory factors. Immunofluorescence staining, RT-qPCR and western blot analysis were employed to assess the EndMT of Ox-LDL-stimulated HUVECs. The results revealed that SESN1 exhibited a low expression in HUVECs following Ox-LDL stimulation. SESN1 overexpression suppressed inflammation, apoptosis and EndMT in Ox-LDL-induced HUVECs. In addition, SESN1 stimulated adenosine monophosphate-activated protein kinase catalytic subunit α1/sirtuin 1 signaling to suppress Ox-LDL receptor-1 expression. An AMPK and SIRT1 inhibitor reversed the effects of SESN1 overexpression on the inflammatory response, apoptosis and EndMT of HUVECs exposed to Ox-LDL. Taken together, the present study demonstrated that SENS1 exerts a suppressive effect on Ox-LDL-induced inflammation, apoptosis and EndMT of HUVECs, suggesting that SENS1 may be used as a novel biomarker for endothelial injury-related disorders.

Decreased Sestrin levels in patients with type 2 diabetes and dyslipidemia and their association with the severity of atherogenic index

PURPOSE

We earlier reported that Sestrin2 regulates monocyte activation and atherogenic events through AMPK-mTOR nexus under high-glucose and dyslipidemic conditions. However, the statuses of Sestrins in diabetes and dyslipidemia are not known. We report here on the status of Sestrins and their association with diabetic dyslipidemia and atherosclerosis.

METHODS

Individuals with normal glucose tolerance (NGT) (n = 46), dyslipidemia (n = 42), and patients with Type 2 diabetes with (n = 41) and without dyslipidemia (n = 40) were recruited from a tertiary diabetes centre, Chennai, India to study the mRNA expression levels of Sestrins (1, 2, and 3) in monocytes by RT-qPCR. Serum levels of Sestrins were measured using ELISA. Atherogenic index of plasma was calculated as log (triglyceride/HDL).

RESULTS

mRNA expressions of Sestrin1 and Sestrin3 were significantly reduced in monocytes under dyslipidemic conditions but not in diabetes condition. Interestingly, Sestrin2 mRNA expression was significantly reduced in all disease conditions including dyslipidemia, and diabetes with and without dyslipidemia. Sestrin2 mRNA levels were negatively correlated with glycemic and lipid parameters and plasma atherogenic index. Furthermore, circulatory Sestrin2 was also found to be significantly decreased in dyslipidemia (415.2 ± 44.7 pg/ml), diabetes (375 ± 45 pg/ml), and diabetes with dyslipidemia (319.2 ± 26.3 pg/ml) compared to NGT (706.3 ± 77 pg/ml) and negatively correlated with glycemic, lipid parameters, and plasma atherogenic index.

CONCLUSION

We report for the first time that Sestrins levels are significantly decreased in diabetes and dyslipidemic conditions. More strikingly, Sestrin2 had a strong association with atherogenic risk factors and severity of atherogenic index and we suggest that Sestrin2 may be used as a biomarker for assessing atherogenesis.

Sestrins as modulators of aging processes and diseases related to age

Sestrins are highly conserved proteins that regulate cell growth, metabolism, survival and proliferation under oxidative stress, genotoxic stress, hypoxia or endoplasmic reticulum stress. Sestrins affect cell signaling by inhibiting the production of reactive oxygen species, activating the AMP-activated protein kinase (AMPK), inhibiting the mTOR pathway and acting as a positive regulator of autophagy. Therefore, their protective role against cancer, metabolic disorders, cardiovascular diseases and neurodegeneration is increasingly being postulated. The article describes the mechanisms of action of sestrins and their meaning in aging and age-related diseases. The latest studies indicating their physiological significance and role in key signaling pathways controlling the cell metabolism and survival under stress conditions were also discussed.

Baicalein attenuates cardiac hypertrophy in mice via suppressing oxidative stress and activating autophagy in cardiomyocytes

Baicalein is a natural flavonoid extracted from the root of Scutellaria baicalensis that exhibits a variety of pharmacological activities. In this study, we investigated the molecular mechanisms underlying the protective effect of baicalein against cardiac hypertrophy in vivo and in vitro. Cardiac hypertrophy was induced in mice by injection of isoproterenol (ISO, 30 mg·kg-1·d-1) for 15 days. The mice received caudal vein injection of baicalein (25 mg/kg) on 3rd, 6th, 9th, 12th, and 15th days. We showed that baicalein administration significantly attenuated ISO-induced cardiac hypertrophy and restored cardiac function. The protective effect of baicalein against cardiac hypertrophy was also observed in neonatal rat cardiomyocytes treated with ISO (10 μM). In cardiomyocytes, ISO treatment markedly increased reactive oxygen species (ROS) and inhibited autophagy, which were greatly alleviated by pretreatment with baicalein (30 μM). We found that baicalein pretreatment increased the expression of catalase and the mitophagy receptor FUN14 domain containing 1 (FUNDC1) to clear ROS and promote autophagy, thus attenuated ISO-induced cardiac hypertrophy. Furthermore, we revealed that baicalein bound to the transcription factor FOXO3a directly, promoting its transcription activity, and transactivated catalase and FUNDC1. In summary, our data provide new evidence for baicalein and FOXO3a in the regulation of ISO-induced cardiac hypertrophy. Baicalein has great potential for the treatment of cardiac hypertrophy.

Inhibition of sestrin 1 alleviates polycystic ovary syndrome by decreasing autophagy

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of reproductive age, accounting for 50-70% of anovulatory infertility cases. However, the etiology of PCOS at the molecular level remains unclear. Here, bioinformatics analysis was performed to identify differentially expressed genes (DEGs) between adipose tissue of PCOS patients and matched tissues from non-hyperandrogenic women. RT-qPCR, western blot, cell counting kit-8 (CCK-8), EdU (5-Ethynyl-2'-deoxyuridine) staining, LC3 staining, ROS (reactive oxygen species) detection, and apoptosis assays were conducted to explore the effects of sestrin 1 on KGN human granulosa-like tumor cells. Bioinformatics analysis indicated that DEGs in adipose tissue from PCOS patients were enriched in the p53 signaling pathway. Moreover, sestrin 1 was identified as a major target of the p53 gene. Downregulation of sestrin 1 inhibited proliferation of KGN cells by inhibiting autophagy. Additionally, sestrin 1 downregulation increased ROS generation and promoted apoptosis in KGN cells. By contrast, overexpression of sestrin 1 increased cell viability by increasing autophagy in KGN cells. Together, these results suggest that downregulation of sestrin 1 may be a potential novel treatment strategy for PCOS.

Activation of P53 Via Nutlin-3a Reveals Role for P53 In ROS Signaling During Cardiac Differentiation of hiPSCs

Activation of the transcription factor P53 within cancer cells is a well-characterized pathway, whereas the effects of P53 activation during development remain largely unexplored. Previous research has indicated that increased levels of P53 protein during key murine developmental stages cause defects in multiple embryonic tissues, including the heart. These findings were confirmed in several different mouse models of congenital heart defects, but P53 activation in a human system of cardiovascular development is not available. Utilizing human induced pluripotent stem cells (hiPSCs), we characterized the normal levels of P53 during cardiac differentiation and showed that levels of P53 are high in hiPSCs and decrease upon cardiac lineage commitment. We also observed P53 localization changed from mainly cytoplasmic in iPS colonies to the nucleus in the Nkx2-5 + cardiac progenitor stage. Pharmacological-mediated increase of P53 protein levels with the Mdm2 inhibitor Nutlin-3a during early (mesoderm to cardiac mesoderm) stages of cardiogenesis resulted in a sizeable loss of cardiomyocytes due to increased apoptosis and cell cycle arrest. Interestingly, increasing P53 levels did not result in apoptosis at later (cardiac progenitor to beating cardiomyocytes) stages of the cardiac differentiation. These results illustrate the temporal sensitivity to increased P53 levels during cardiogenesis. We conducted RNA-Seq on these cells with or without Nutlin-3a to ascertain transcriptional differences due to increased P53 at the different stages during the differentiation. Our results from the RNA-Seq revealed up-regulation of Sestrins after Nutlin-3a treatment suggesting a new role for P53 in the metabolism of cardiac regeneration.

Pharmacokinetic Analysis of Carnosic Acid and Carnosol in Standardized Rosemary Extract and the Effect on the Disease Activity Index of DSS-Induced Colitis

Rosemary extract (RE) is an approved food preservative in the European Union and contains dietary phytochemicals that are beneficial for gastrointestinal health. This study investigated the effects of RE on dextran sodium sulfate (DSS)-induced colitis and also determined the pharmacokinetics of dietary phytochemicals administered to mice via oral gavage. Individual components of rosemary extract were separated and identified by LC–MS/MS. The pharmacokinetics of two major diterpenes from RE, carnosic acid (CA) and carnosol (CL), administered to mice via oral gavage were determined. Then, the effect of RE pre-treatment on the disease activity index (DAI) of DSS-induced colitis in mice was investigated. The study determined that 100 mg/kg RE significantly improved DAI in DSS-induced colitis compared to negative control. Sestrin 2 protein expression, which increased with DSS exposure, was reduced with RE treatment. Intestinal barrier integrity was also shown to improve via fluorescein isothiocyanate (FITC)–dextran administration and Western blot of zonula occludens-1 (ZO-1), a tight junction protein. Rosemary extract was able to improve the DAI of DSS-induced colitis in mice at a daily dose of 100 mg/kg and showed improvement in the intestinal barrier integrity. This study suggests that RE can be an effective preventative agent against IBD.

Ghrelin inhibited pressure overload-induced cardiac hypertrophy by promoting autophagy via CaMKK/AMPK signaling pathway

Ghrelin, a novel gut hormone, has been shown to exert protective effects on cardiac dysfunction and remodeling. However, the underlying mechanisms of its protective effects remain unclear. Here, we investigated the effects of ghrelin on cardiac hypertrophy and explored the mechanisms involved. Ghrelin (30 μg.kg^-1. day^-1) was systemically administered to rats with cardiac hypertrophy induced by abdominal aortic constriction (AAC) by a mini-osmotic pump the next day after surgery continuously for 4 weeks. The AAC treated rats without ghrelin infusion showed decreased ghrelin content and expression of its receptors in the hearts. Exogenous ghrelin greatly attenuated cardiac hypertrophy as shown by heart weight to tibial length (HW/TL), hemodynamics, echocardiography, histological analyses, and expression of hypertrophic markers induced by AAC. This corresponded with decreased cardiac fibrosis and inflammation in the hearts of AAC rats treated with ghrelin. Moreover, ghrelin significantly increased the myocardial expression of autophagy markers, which was further confirmed in cultured cardiomyocytes. Concurrently, cardiomyocyte apoptosis in vivo and in vitro was ameliorated by ghrelin, which was reversed by inhibition of autophagy. The enhancement of autophagy and inhibition of apoptosis by ghrelin were eliminated on pretreatment with compound C, an AMP-activated protein kinase (AMPK) inhibitor. Furthermore, inhibition of Ca²⁺/Calmodulin-dependent protein kinase kinase (CaMKK), an upstream kinase of AMPK, made ghrelin fail to activate AMPK and simultaneously reversed ghrelin's promotion of autophagy. In conclusion, ghrelin could exert its cardioprotective effects on cardiac hypertrophy by promoting autophagy, possibly via CaMKK/AMPK signaling pathway.

Cardiac Shock Wave Therapy Alleviates Hypoxia/Reoxygenation-Induced Myocardial Necroptosis by Modulating Autophagy

Regulated necrosis (necroptosis) is crucially involved in cardiac ischaemia-reperfusion injury (MIRI). The aim of our study is to investigate whether shock wave therapy (SWT) is capable of exerting protective effects by inhibiting necroptosis during myocardial ischaemia-reperfusion (I/R) injury and the possible role of autophagy in this process. We established a hypoxia/reoxygenation (H/R) model in vitro using HL-1 cells to simulate MIRI. MTS assays and LDH cytotoxicity assay were performed to measure cell viability and cell damage. Annexin V/PI staining was used to determine apoptosis and necrosis. Western blotting was performed to assess the changes in cell signaling pathways associated with autophagy, necroptosis, and apoptosis. Reactive oxygen species (ROS) production was detected using DHE staining. Autophagosome generation and degradation (autophagic flux) were analysed using GFP and RFP tandemly tagged LC3 (tfLC3). HL-1 cells were then transfected with p62/SQSTM1 siRNA in order to analyse its role in cardioprotection. Our results revealed that SWT increased cell viability in the H/R model and decreased receptor-interacting serine/threonine-protein kinase 1 (RIPK1) and RIPK3 expression. ROS production was also inhibited by SWT. Moreover, SWT decreased Beclin1 expression and the ratio of LC3-II/LC3-I following H/R. Simultaneously, in the tfLC3 assay, the SWT provoked a decrease in the cumulative autophagosome abundance. siRNA-mediated knockdown of p62 attenuated H/R-induced necroptosis, and SWT did not exert additive effects. Taken together, SWT ameliorated H/R injury by inhibiting necroptosis. SWT also relieved the blockade of autophagic flux in response to H/R injury. The restoration of autophagic flux by SWT might contribute to its cardioprotective effect on necroptosis following H/R injury.

miR-133a-3p attenuates cardiomyocyte hypertrophy through inhibiting pyroptosis activation by targeting IKKε

OBJECTIVE

Cardiac hypertrophy is an adaptive response to physiological and pathological stimuli, the latter of which frequently progresses to valvulopathy, heart failure and sudden death. Recent reports revealed that pyroptosis is involved in regulating multiple cardiovascular diseases progression, including cardiac hypertrophy. However, the underlying mechanisms remain poorly understood. This study aims to extensively investigate the regulation of miR-133a-3p on pyroptosis in angiotensin II (Ang II)-induced cardiac hypertrophyin vitro.

METHODS

The in vitro model of cardiac hypertrophy was induced by Ang II, which was validated by qPCR combined with measurement of cell surface area by immunofluorescence assay. CCK-8 assay and Hochest33342/PI staining was performed to assess pyroptosis. Dual luciferase reporter system was used to verify the direct interaction between miR-133a-3p and IKKε. The effects of miR-133a-3p/IKKε on pyroptosis activation and cardiac hypertrophy markers (Caspase-1, NLRP3, IL-1β, IL-18, GSDMD, ASC, ANP, BNP and β-MHC) were evaluated by western blot, ELISA and qPCR.

RESULTS

Ang II treatment could induce cardiomyocyte hypertrophy and pyroptosis. The expression of miR-133a-3p was repressed in Ang II-treated HCM cells, and its overexpression could attenuate both pyroptosis and cardiac hypertrophyin vitro. Additionally, IKKε expression was significantly up-regulated in Ang II-induced HCM cells. Dual luciferase reporter system and qPCR validated that miR-133a-3p directly targeted the 3'-UTR of IKKε and suppressed its expression. Moreover, IKKε overexpression impaired the protective function of miR-133a-3p in cardiomyocyte hypertrophy.

CONCLUSION

Collectively, miR-133a-3p attenuates Ang II induced cardiomyocyte hypertrophy via inhibition of pyroptosis by targeting IKKε. Therefore, miR-133a-3p up-regulation may be a promising strategy for cardiac hypertrophy treatment.

Hispidulin Attenuates Cardiac Hypertrophy by Improving Mitochondrial Dysfunction

Cardiac hypertrophy is a pathophysiological response to harmful stimuli. The continued presence of cardiac hypertrophy will ultimately develop into heart failure. The mitochondrion is the primary organelle of energy production, and its dysfunction plays a crucial role in the progressive development of heart failure from cardiac hypertrophy. Hispidulin, a natural flavonoid, has been substantiated to improve energy metabolism and inhibit oxidative stress. However, how hispidulin regulates cardiac hypertrophy and its underlying mechanism remains unknown. We found that hispidulin significantly inhibited pressure overload-induced cardiac hypertrophy and improved cardiac function in vivo and blocked phenylephrine (PE)-induced cardiomyocyte hypertrophy in vitro. We further proved that hispidulin remarkably improved mitochondrial function, manifested by increased electron transport chain (ETC) subunits expression, elevated ATP production, increased oxygen consumption rates (OCR), normalized mitochondrial morphology, and reduced oxidative stress. Furthermore, we discovered that Sirt1, a well-recognized regulator of mitochondrial function, might be a target of hispidulin, as evidenced by its upregulation after hispidulin treatment. Cotreatment with EX527 (a Sirt1-specific inhibitor) and hispidulin nearly completely abolished the antihypertrophic and protective effects of hispidulin on mitochondrial function, providing further evidence that Sirt1 could be the pivotal downstream effector of hispidulin in regulating cardiac hypertrophy.

Sestrins in Physiological Stress Responses

Sestrins are a family of proteins that respond to a variety of environmental stresses, including genotoxic, oxidative, and nutritional stresses. Sestrins affect multiple signaling pathways: AMP-activated protein kinase, mammalian target of rapamycin complexes, insulin-AKT, and redox signaling pathways. By regulating these pathways, Sestrins are thought to help adapt to stressful environments and subsequently restore cell and tissue homeostasis. In this review, we describe how Sestrins mediate physiological stress responses in the context of nutritional and chemical stresses (liver), physical movement and exercise (skeletal muscle), and chemical, physical, and inflammatory injuries (heart). These findings also support the idea that Sestrins are a molecular mediator of hormesis, a paradoxical beneficial effect of low- or moderate-level stresses in living organisms.

Corosolic acid ameliorates cardiac hypertrophy via regulating autophagy

Aim: In this work, we explored the role of corosolic acid (CRA) during pressure overload-induced cardiac hypertrophy. Methods and results: Cardiac hypertrophy was induced in mice by aortic banding. Four weeks post-surgery, CRA-treated mice developed blunted cardiac hypertrophy, fibrosis, and dysfunction, and showed increased LC3 II and p-AMPK expression. In line with the in vivo studies, CRA also inhibited the hypertrophic response induced by PE stimulation accompanying with increased LC3 II and p-AMPK expression. It was also found that CRA blunted cardiomyocyte hypertrophy and promoted autophagy in Angiotensin II (Ang II)-treated H9c2 cells. Moreover, to further verify whether CRA inhibits cardiac hypertrophy by the activation of autophagy, blockade of autophagy was achieved by CQ (an inhibitor of the fusion between autophagosomes and lysosomes) or 3-MA (an inhibitor of autophagosome formation). It was found that autophagy inhibition counteracts the protective effect of CRA on cardiac hypertrophy. Interestingly, AMPK knockdown with AMPKα2 siRNA-counteracted LC3 II expression increase and the hypertrophic response inhibition caused by CRA in PE-treated H9c2 cells. Conclusion: These results suggest that CRA may protect against cardiac hypertrophy through regulating AMPK-dependent autophagy.

Substrate metabolism regulated by Sestrin2-mTORC1 alleviates pressure overload-induced cardiac hypertrophy in aged heart

Sestrin2 (Sesn2) is a stress sensor for the mammalian target of rapamycin complex 1 (mTORC1) pathway. Aging impairs cardiac mTORC1 activation, thereby sensitizing the heart to hypertrophy. C57BL/6 J young wild-type (young WT; 4-6 months), aged WT (24-26 months), and young Sestrin2 knockout mice (Y-Sesn2 KO; 4-6 months) underwent transverse aortic constriction (TAC) for pressure overload. Cardiac expression of Sesn2 decreased with age. At 4 weeks after TAC, aged WT and Y-Sesn2 KO exhibited larger hearts and impaired cardiac function, compared with young WT mice. Augmented phosphorylation of mTOR and downstream effectors; damaged mitochondria and elevated redox markers, as well as and impaired glucose and fatty acid oxidation were observed in aged WT and Y-Sesn2 KO hearts. A pressure overload-induced interaction between Sesn2 and GTPase-activating protein activity toward Rags 2 (GATOR2), which positively regulates mTORC1, was impaired in aged WT hearts. Adeno-associated virus 9-Sesn2 treatment rescued Sesn2 expression, attenuated mTORC1 activation, and increased pressure overload tolerance in aged WT and Y-Sesn2 KO hearts. These results indicated that cardiac Sesn2 acts as a pressure overload sensor for mTORC1. Furthermore, Sesn2 deficiency may cause increased sensitivity to hypertrophy in elderly individuals.

Overexpression of FNTB and the activation of Ras induce hypertrophy and promote apoptosis and autophagic cell death in cardiomyocytes

Farnesyltransferase (FTase) is an important enzyme that catalyses the modification of protein isoprene downstream of the mevalonate pathway. Previous studies have shown that the tissue of the heart in the suprarenal abdominal aortic coarctation (AAC) group showed overexpression of FTaseβ (FNTB) and the activation of the downstream protein Ras was enhanced. FTase inhibitor (FTI) can alleviate myocardial fibrosis and partly improve cardiac remodelling in spontaneously hypertensive rats. However, the exact role and mechanism of FTase in myocardial hypertrophy and remodelling are not fully understood. Here, we used recombinant adenovirus to transfect neonatal rat ventricular cardiomyocytes to study the effect of FNTB overexpression on myocardial remodelling and explore potential mechanisms. The results showed that overexpression of FNTB induces neonatal rat ventricular myocyte hypertrophy and reduces the survival rate of cardiomyocytes. FNTB overexpression induced a decrease in mitochondrial membrane potential and increased apoptosis in cardiomyocytes. FNTB overexpression also promotes autophagosome formation and the accumulation of autophagy substrate protein, LC3II. Transmission electron microscopy (TEM) and mCherry‐GFP tandem fluorescent‐tagged LC3 (tfLC3) showed that FNTB overexpression can activate autophagy flux by enhancing autophagosome conversion to autophagolysosome. Overactivated autophagy flux can be blocked by bafilomycin A1. In addition, salirasib (a Ras farnesylcysteine mimetic) can alleviate the hypertrophic phenotype of cardiomyocytes and inhibit the up‐regulation of apoptosis and autophagy flux induced by FNTB overexpression. These results suggest that FTase may have a potential role in future treatment strategies to limit the adverse consequences of cardiac hypertrophy, cardiac dysfunction and heart failure.

Sophocarpine ameliorates cardiac hypertrophy through activation of autophagic responses

Mounting evidences indicate that autophagy is an essential homeostatic mechanism to maintain the global cardiac structure function. Sophocarpine (SOP), a major bioactive compound derived from the natural plant Sophora flavescens. However, the role of SOP in cardiac hypertrophy remain to be fully elucidated. In the present study, we tested the hypothesis that SOP protects against Ang II-induced cardiac hypertrophy by mediating the regulation of autophagy. The results demonstrated that SOP attenuated the Ang II-induced cardiac hypertrophy, as assessed by measurements of echocardiography parameters, the ratios of heart weight/body weight and left ventricle weight/body weight, histopathological staining, cross-sectional cardiomyocyte area, and the expression levels of cardiac hypertrophic markers. The anti-hypertrophic effect of SOP was mediated by activating autophagy-related pathway, as revealed by reversal of the increased autophagy marker protein expression. These findings reveal a novel mechanism of SOP attenuating cardiac hypertrophy via activating autophagy-related signaling pathways.

Circulating Sestrin Levels Are Increased in Hypertension Patients

Background

Sestrins (Sesns), a group of oxidative stress-related proteins, have been reported to be involved in various cardiovascular diseases, including aortic dissection and chronic heart failure. This study is aimed at investigating the level of circulating Sesn1, Sesn2, and Sesn3 in hypertension patients.

Methods

Plasma levels of Sesn1, Sesn2, and Sesn3 in 400 hypertensive patients and 100 normotensive subjects were detected using enzyme-linked immunosorbent assay (ELISA) kits. The hypertension patients were divided into groups with grade I (n = 140), grade II (n = 180), and grade III (n = 80) hypertension.

Results

Compared with the normotensive subjects, Sesn1, Sesn2, and Sesn3 levels were increased in patients with hypertension, with a gradual increase between the groups with grade I, grade II, and grade III hypertension. Elevated Sesn1, Sesn2, and Sesn3 levels were positively correlated with both the systolic blood pressure (SBP) and diastolic blood pressure (DBP). Moreover, Sesn1, Sesn2, and Sesn3 levels were elevated in patients with dipper hypertension and further increased in patients with nondipper hypertension. In addition, smokers, as well as patients with higher levels of angiotensin II (Ang II) and carotid atherosclerotic plaque (CAP), exhibited increased Sesn1, Sesn2, and Sesn3 levels when compared with patients without these clinical characteristics. Furthermore, plasma levels of Sesn1, Sesn2, and Sesn3 were negatively correlated with the presence of CAP.

Conclusions

Circulating Sesn levels are increased in patients with hypertension and may be a target for the prevention and treatment of clinical hypertension.

Sestrin proteins in cardiovascular disease

Cardiovascular diseases are the main cause of mortality and morbidity worldwide. Cardiovascular diseases such as AMI, AS, cardiac hypertrophy and cardiac fibrosis can be alleviated by controlling the inflammatory response, cellular proliferation, production of ROS and secretion of cytokines. Sestrins are considered to be protective proteins which can prevent age-related diseases. A potential mechanism is an inhibitory effect on mTORC, which depends on the sestrin-AMPK-mTORC pathway. Sestrins regulate the M1/M2 macrophage balance, level of ROS and certain cytokines during stress and cardiovascular diseases through the above pathway. Sestrins exert different functions in diverse organs and tissue. According to existing studies, the main functions of sestrins are strongly associated with the pathological features of cardiovascular disease and exert protective roles in cardiovascular disease. Based on the current evidence, we present a mini-review on the physiological functions and mechanism of sestrins in cardiology. The purpose of this review is to summarize the functions and mechanism of sestrins in common cardiovascular diseases, to raise awareness in clinicians that sestrins may be an important potential target for controlling progression of disease.

Polyphyllin I attenuates pressure over-load induced cardiac hypertrophy via inhibition of Wnt/β-catenin signaling pathway

AIMS

Cardiac hypertrophy is one of most important risk factors for cardiovascular mortality. Activation of Wnt/β-catenin signaling pathway is acknowledged to be an important mechanism for pathogenesis of cardiac hypertrophy. Polyphyllin I (PPI), a component in the traditional Chinese medicinal herb, has shown anticancer effect partially via interruption of Wnt/β-catenin signaling pathway. Our aim was to test whether PPI attenuates cardiac hypertrophy.

MATERIALS AND METHODS

Adult male C57BL/6J mice were subjected to either pressure overload generated by transverse aortic constriction (TAC) or sham surgery (control group). Angiotensin-II (Ang-II) was used to induce cardiomyocyte hypertrophy in vitro. PPI was intraperitoneally administrated daily for 4 weeks after TAC surgery and then cardiac function was determined by echocardiography and histological analysis was performed.

KEY FINDINGS

PPI significantly ameliorated cardiac dysfunction of mice subjected to TAC. Meanwhile, PPI attenuated TAC induced cardiac hypertrophy indicated by blunted increase in heart mass, cross section area of cardiomyocyte, cardiac fibrosis and expression of hypertrophic biomarkers ANP, BNP and β-MHC. In addition, PPI also ameliorated Ang-II induced cardiomyocyte hypertrophy in vitro. Importantly, PPI decreased protein expression of active β-catenin/total β-catenin, phosphorylation of GSK3β and Wnt target genes c-myc, c-jun, c-fos and cyclin D1 and its anti-hypertrophic effect was blunted by supplementation of Wnt 3a.

SIGNIFICANCE

Our results suggest that PPI attenuates cardiac dysfunction and attenuate development of pressure over-load induced cardiac hypertrophic via suppressing Wnt/β-catenin signaling pathway. PPI might be a candidate drug for treatment of cardiac hypertrophy.

Inhibiting SLC26A4 reverses cardiac hypertrophy in H9C2 cells and in rats

Background

It has been confirmed that mutations in solute carrier family 26 member 4 (SLC26A4) contribute to pendred syndrome. However, the role of SLC26A4 in cardiac hypertrophy and the signaling pathways remain unclear.

Methods

Cardiomyocytes were treated by 200 µM phenylephrine (PE) to induce cardiac hypertrophy. Also, the expression of SLC26A4, GSK3, cardiac hypertrophy markers including atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) was detected through real-time quantitative polymerase chain reaction (RT-qPCR). Flow cytometry assay was used to test the apoptosis of PE-induced cardiomyocytes transfected by small interfere RNA (siRNA)-SLC26A4. Furthermore, we detected the expression of autophagy-related markers including light chain 3 (LC3) and P62. Finally, we established a rat model of abdominal aortic constriction (AAC)-induced cardiac hypertrophy in vivo.

Results

RT-qPCR results showed that the mRNA expression of SLC26A4 was significantly up-regulated in PE-induced cardiac hypertrophy. After inhibiting SLC26A4, the release of ANP and BNP was significantly decreased and GSK3β was elevated in vivo and in vitro. Furthermore, inhibiting SLC26A4 promoted apoptosis of cardiac hypertrophy cells. In addition, LC3 was down-regulated and P62 was enhanced after transfection of siRNA-SLC26A4.

Conclusion

Our findings revealed that SLC26A4 increases cardiac hypertrophy, and inhibiting SLC26A4 could decrease the release of ANP/BNP and promote the expression of GSK-3β in vitro and in vivo. Moreover, SLC26A4 silencing inhibits autophagy of cardiomyocytes and induces apoptosis of cardiomyocytes. Therefore, SLC26A4 possesses potential value to be a therapeutic target of cardiac hypertrophy, and our study provides new insights into the mechanisms of cardiac hypertrophy.

Sestrin2: Its Potential Role and Regulatory Mechanism in Host Immune Response in Diseases

Sestrin2 (SESN2), a highly evolutionarily conserved protein, is critically involved in cellular responses to various stresses. SESN2 has a protective effect on physiological and pathological states mainly via regulating oxidative stress, endoplasmic reticulum stress, autophagy, metabolism, and inflammation. In recent years, breakthrough investigations with regard to the regulation and signaling mechanisms of SESN2 have markedly deepened our understanding of its potential role as well as its significance in host response. However, the functions of SESN2 in the immune system and inflammation remain elusive. It has been documented that many immune cells positively express SESN2 and, in turn, that SESN2 might modulate cellular activities. This review incorporates recent progress and aims to provide novel insight into the protective role and regulatory pathway of SESN2, which acts as a potential biomarker and therapeutic target in the context of various diseases.

PKD deletion promotes autophagy and inhibits hypertrophy in cardiomyocyte

Protein kinase D (PKD) plays an important role in the development of cardiac hypertrophy induced by pressure overload. However, the mechanism involved is unclear. This study, using primary cardiomyocyte culture, PKD knockdown and overexpression, and other molecular techniques, tested our hypothesis that PKD pathway mediates cardiac hypertrophy by negatively regulating autophagy in cardiomyocyte. Neonatal cardiomyocytes were isolated from Wistar rats and cell hypertrophy was induced by norepinephrine treatment (PE, 10^-4 mol/L), and divided into the following groups: (1) Vehicle; (2) PE; (3) PE + control siRNA; (4) PE + Rapamycin (100 nM); (5) PE + PKD-siRNA (2 × 10⁸ U/0.1 ml); (6) PE + PKD siRNA + 3 MA (10 mM). The results showed that PE treatment induced cardiomyocyte hypertrophy, which were confirmed by cell size and biomarkers of cardiomyocyte hypertrophy including increased ANP and BNP mRNA. PKD knockdown or Rapamycin significantly inhibited PE-induced cardiomyocyte hypertrophy. In addition, PKD siRNA increased autophagy activity determined by electron microscopy, increased biomarkers of autophagy by Western blot, accompanied by down-regulated AKT/mTOR/S6K pathway. All the effects of PKD knockout were inhibited by co-treatment with 3-MA, an autophagy inhibitor. Oppositely, the autophagy in cardiomyocytes was inhibited by PKD overexpression. These results suggest that PKD participates in the development of cardiac hypertrophy by regulating autophagy via AKT/mTOR/S6K pathway.

Transcribed Ultraconserved Regions, Uc.323, Ameliorates Cardiac Hypertrophy by Regulating the Transcription of CPT1b (Carnitine Palmitoyl transferase 1b)

Transcribed ultraconserved regions (T-UCRs) are a novel class of long noncoding RNAs transcribed from UCRs, which exhibit 100% DNA sequence conservation among humans, mice, and rats. However, whether T-UCRs regulate cardiac hypertrophy remains unclear. We aimed to explore the effects of T-UCRs on cardiac hypertrophy. First, we performed long noncoding RNA microarray analysis on hearts of mice subjected to sham surgery or aortic banding and found that the T-UCR uc.323 was decreased significantly in mice with aortic banding-induced cardiac hypertrophy. In vitro loss- and gain-of-function experiments demonstrated that uc.323 protected cardiomyocytes against hypertrophy induced by phenylephrine. Additionally, we discovered that mammalian target of rapamycin 1 contributed to phenylephrine-induced uc.323 downregulation and uc.323-mediated cardiomyocyte hypertrophy. We further mapped the possible target genes of uc.323 through global microarray mRNA expression analysis after uc.323 knockdown and found that uc.323 regulated the expression of cardiac hypertrophy-related genes such as CPT1b (Carnitine Palmitoyl transferase 1b). Then, chromatin immunoprecipitation proved that EZH2 (enhancer of zeste homolog 2) bound to the promoter of CPT1b via H3K27me3 (trimethylation of lysine 27 of histone H3) to induce CPT1b downregulation. And overexpression of CPT1b could block uc.323-mediated cardiomyocyte hypertrophy. Finally, we found that uc.323 deficiency induced cardiac hypertrophy. Our results reveal that uc.323 is a conserved T-UCR that inhibits cardiac hypertrophy, potentially by regulating the transcription of CPT1b via interaction with EZH2.

Maf1 ameliorates cardiac hypertrophy by inhibiting RNA polymerase III through ERK1/2

Rationale: An imbalance between protein synthesis and degradation is one of the mechanisms of cardiac hypertrophy. Increased transcription in cardiomyocytes can lead to excessive protein synthesis and cardiac hypertrophy. Maf1 is an RNA polymerase III (RNA pol III) inhibitor that plays a pivotal role in regulating transcription. However, whether Maf1 regulates of cardiac hypertrophy remains unclear.

Methods: Cardiac hypertrophy was induced in vivo by thoracic aortic banding (AB) surgery. Both the in vivo and in vitro gain- and loss-of-function experiments by Maf1 knockout (KO) mice and adenoviral transfection were used to verify the role of Maf1 in cardiac hypertrophy. RNA pol III and ERK1/2 inhibitor were utilized to identify the effects of RNA pol III and ERK1/2. The possible interaction between Maf1 and ERK1/2 was clarified by immunoprecipitation (IP) analysis.

Results: Four weeks after surgery, Maf1 KO mice exhibited significantly exacerbated AB-induced cardiac hypertrophy characterized by increased heart size, cardiomyocyte surface area, and atrial natriuretic peptide (ANP) expression and by exacerbated pulmonary edema. Also, the deficiency of Maf1 causes more severe cardiac dilation and dysfunction than wild type (WT) mice after pressure overload. In contrast, compared with adenoviral-GFP injected mice, mice injected with adenoviral-Maf1 showed significantly ameliorated AB-induced cardiac hypertrophy. In vitro study has demonstrated that Maf1 could significantly block phenylephrine (PE)-induced cardiomyocyte hypertrophy by inhibiting RNA pol III transcription. However, application of an RNA pol III inhibitor markedly improved Maf1 knockdown-promoted cardiac hypertrophy. Moreover, ERK1/2 was identified as a regulator of RNA pol III, and ERK1/2 inhibition by U0126 significantly repressed Maf1 knockdown-promoted cardiac hypertrophy accompanied by suppressed RNA pol III transcription. Additionally, IP analysis demonstrated that Maf1 could directly bind ERK1/2, suggesting Maf1 could interact with ERK1/2 and then inhibit RNA pol III transcription so as to attenuate the development of cardiac hypertrophy.

Conclusions: Maf1 ameliorates PE- and AB-induced cardiac hypertrophy by inhibiting RNA pol III transcription via ERK1/2 signaling suppression.

Aldehyde Dehydrogenase 2 and Heart Failure

Heart failure (HF) is a structural or functional cardiac abnormal syndrome characterized with series of symptoms and signs such as breathlessness, fatigue, pulmonary crackles, and peripheral edema. Being a terminal phase of most myocardial lesions, HF has become a leading cause of mobility and mortality worldwide, associated with heavy clinical burden and economic costs affecting over 23 million people [14]. There is an increase to 5.5% with systolic dysfunction and an increase to 36.0% with diastolic dysfunction in people 60 years or older [85]. The costs accompanied with heart failure stand 2-3% of the total healthcare system expenditure in high-income countries and are expected to increase >2-fold in the next 2 decades [34].

The role of angiopoietin-like protein 4 in phenylephrine-induced cardiomyocyte hypertrophy

Angiopoietin-like protein 4 (ANGPTL4) is a multifunctional secreted protein that can be induced by fasting, hypoxia and glucocorticoids. ANGPTL4 has been associated with a variety of diseases; however, the role of ANGPTL4 in cardiac hypertrophy remains poorly understood. In our study, we aimed to explore the effect of ANGPTL4 on phenylephrine-induced cardiomyocyte hypertrophy. Our results showed that knockdown of ANGPTL4 expression significantly exacerbated cardiomyocyte hypertrophy, as demonstrated by increased hypertrophic marker expression, including ANP and cell surface area. Moreover, significantly reduced fatty acid oxidation, as featured by decreased CPT-1 levels, was observed in hypertrophic cardiomyocytes following ANGPTL4 down-regulation. Furthermore, knockdown of ANGPLT4 led to down-regulated expression of peroxisome proliferator-activated receptor α (PPARα), which is the key regulator of cardiac fatty acid oxidation. In addition, ANGPTL4 silencing promoted the activation of JNK1/2, and JNK1/2 signaling blockade could restore the level of PPARα and significantly ameliorate the ANGPTL4 knockdown-induced cardiomyocyte hypertrophy. Therefore, our study demonstrated that ANGPTL4 regulates PPARα through JNK1/2 signaling and is required for the inhibition of cardiomyocyte hypertrophy.

Cardioprotective roles of sestrin 1 and sestrin 2 against doxorubicin cardiotoxicity

Doxorubicin is a chemotherapy medication widely used to treat a variety of cancers. Even though it offers one of the most effective anti-cancer treatments, its clinical use is limited because of its strong cardiotoxicity that can lead to fatal conditions. Here, we show that sestrin 1 and sestrin 2, members of the sestrin family of proteins that are stress-inducible regulators of metabolism, are critical for suppressing doxorubicin cardiotoxicity and coordinating the AMPK-mammalian target of rapamycin complex 1 (mTORC1) autophagy signaling network for cardioprotection. Expression of both sestrin 1 and sestrin 2 was highly increased in the mouse heart after doxorubicin injection. Genetic ablation of sestrin 1 and sestrin 2 rendered mice more vulnerable to doxorubicin and exacerbated doxorubicin-induced cardiac pathologies including cardiomyocyte apoptosis and cardiac dysfunction. These pathologies were associated with strong dysregulation of the cardiac signaling network, including suppression of the AMPK pathway and activation of the mTORC1 pathway. Consistent with AMPK downregulation and mTORC1 upregulation, autophagic activity of heart tissue was diminished, leading to prominent accumulation of autophagy substrate, p62/SQSTM1. Taken together, our results indicate that sestrin 1 and sestrin 2 are important cardioprotective proteins that coordinate metabolic signaling pathways and autophagy to minimize cardiac damage in response to doxorubicin insult. Augmenting this protective mechanism could provide a novel therapeutic rationale for prevention and treatment of doxorubicin cardiotoxicity. NEW & NOTEWORTHY Doxorubicin is a highly efficient chemotherapeutic medicine; however, its use is limited because of its strong cardiotoxicity. Here, we show that sestrin 1 and sestrin 2 are critical protectors of cardiomyocytes from doxorubicin damage. By upregulating AMPK and autophagic activities and suppressing mammalian target of rapamycin complex 1 and oxidative stress, sestrins counteract detrimental effects of doxorubicin on cardiomyocytes. Correspondingly, loss of sestrin 1 and sestrin 2 produced remarkable dysregulation of these pathways, leading to prominent cardiac cell death and deterioration of heart function.

Soluble epoxide hydrolase inhibitor, TUPS, attenuates isoproterenol/angiotensin II-induced cardiac hypertrophy through mammalian target of rapamycin-mediated autophagy inhibition

OBJECTIVES

To investigate the potential role and mechanism of TUPS, a soluble epoxide hydrolase inhibitor, in cardiac hypertrophy.

METHODS

Rat and H9C2 cell models of cardiac hypertrophy were induced by isoproterenol and angiotensin II, respectively, followed by TUPS treatment. The expression of hypertrophic markers, ANP and BNP, was determined by quantitative real-time PCR. The abundance of Beclin-1, LC3, p-AMPK and phosphorylated-mammalian target of rapamycin (p-mTOR) proteins was analysed by Western blot and immunohistocytology. Cell morphology and viability were evaluated by F-actin staining and MTS. H9C2 cells were transfected with GFP-LC3 to evaluate autophagy flux.

KEY FINDINGS

TUPS significantly inhibited rat heart size, heart weight-to-body weight ratio, heart wall thickness, hypertrophic H9C2 cell swelling and viability suppression as well as the expression of ANP and BNP genes in hypertrophic models. In addition, autophagic markers Beclin-1 and LC3 were elevated in both cellular and animal models, which were suppressed by TUPS, with corresponding changes of autophagy flux. The abundance of p-AMPK was increased, while p-mTOR was decreased in hypertrophic cells, which were abolished by TUPS. Rapamycin decreased p-mTOR level, increased Beclin-1 and LC3 expression and induced cell size enlargement and cell viability inhibition in hypertrophic H9C2 cells treated with TUPS.

CONCLUSIONS

TUPS inhibits cardiac hypertrophy by regulating mTOR/autophagy axis.

Pentamethylquercetin protects against cardiac remodeling via activation of Sestrin2

Oxidative stress is widely involved in pathophysiological processes of cardiac remodeling. Molecules associated with antioxidant functions may be ideal targets for reversing cardiac remodeling. Sestrin2 is the important component of endogenous antioxidant defense, while there is little information on the pathophysiological roles of it in cardiac remodeling. The aim of this study was to investigate whether Sestrin2 is closely involved in cardiac remodeling, and whether the protective effect of pentamethylquercetin (PMQ) on cardiac remodeling is related to upregulation of the Sestrin2 endogenous antioxidant system. We generated a transverse aorta constriction (TAC)-induced pressure-overload cardiac-remodeling model in mice, and also established an isoproterenol (ISO)-induced neonatal rat cardiomyocyte (NRCM) hypertrophy model. The data showed Sestrin2 expression was downregulated significantly, and Nrf2 and HO-1 expression was also reduced in myocardial tissue or NRCM of model group, whereas keap1 expression was upregulated. PMQ significantly ameliorated cardiac remodeling and rectified the abnormal expression of Sestrin2/Nrf2/keap1. Sestrin2 small interfering RNA (SiRNA) reduced the protective effect of PMQ on NRCMs, as well as abolished its regulating effect on the Nrf2/keap1 pathway. In conclusion, Sestrin2 may be an important target in the anti-myocardial remodeling of PMQ.

Autophagy: A Lysosome-Dependent Process with Implications in Cellular Redox Homeostasis and Human Disease

SIGNIFICANCE

Autophagy, a lysosome-dependent homeostatic process inherent to cells and tissues, has emerging significance in the pathogenesis of human disease. This process enables the degradation and turnover of cytoplasmic substrates via membrane-dependent sequestration in autophagic vesicles (autophagosomes) and subsequent lysosomal delivery of cargo. Recent Advances: Selective forms of autophagy can target specific substrates (e.g., organelles, protein aggregates, and lipids) for processing. Autophagy is highly regulated by oxidative stress, including exposure to altered oxygen tension, by direct and indirect mechanisms, and contributes to inducible defenses against oxidative stress. Mitochondrial autophagy (mitophagy) plays a critical role in the oxidative stress response, through maintenance of mitochondrial integrity.

CRITICAL ISSUES

Autophagy can impact a number of vital cellular processes including inflammation and adaptive immunity, host defense, lipid metabolism and storage, mitochondrial homeostasis, and clearance of aggregated proteins, all which may be of significance in human disease. Autophagy can exert both maladaptive and adaptive roles in disease pathogenesis, which may also be influenced by autophagy impairment. This review highlights the essential roles of autophagy in human diseases, with a focus on diseases in which oxidative stress or inflammation play key roles, including human lung, liver, kidney and heart diseases, metabolic diseases, and diseases of the cardiovascular and neural systems.

FUTURE DIRECTIONS

Investigations that further elucidate the complex role of autophagy in the pathogenesis of disease will facilitate targeting this pathway for therapies in specific diseases.

p53 and metabolism: from mechanism to therapeutics

The tumor cell changes itself and its microenvironment to adapt to different situations, including action of drugs and other agents targeting tumor control. Therefore, metabolism plays an important role in the activation of survival mechanisms to keep the cell proliferative potential. The Warburg effect directs the cellular metabolism towards an aerobic glycolytic pathway, despite the fact that it generates less adenosine triphosphate than oxidative phosphorylation; because it creates the building blocks necessary for cell proliferation. The transcription factor p53 is the master tumor suppressor; it binds to more than 4,000 sites in the genome and regulates the expression of more than 500 genes. Among these genes are important regulators of metabolism, affecting glucose, lipids and amino acids metabolism, oxidative phosphorylation, reactive oxygen species (ROS) generation and growth factors signaling. Wild-type and mutant p53 may have opposing effects in the expression of these metabolic genes. Therefore, depending on the p53 status of the cell, drugs that target metabolism may have different outcomes and metabolism may modulate drug resistance. Conversely, induction of p53 expression may regulate differently the tumor cell metabolism, inducing senescence, autophagy and apoptosis, which are dependent on the regulation of the PI3K/AKT/mTOR pathway and/or ROS induction. The interplay between p53 and metabolism is essential in the decision of cell fate and for cancer therapeutics.

Macroautophagy and Chaperone-Mediated Autophagy in Heart Failure: The Known and the Unknown

Cardiac diseases including hypertrophic and ischemic cardiomyopathies are increasingly being reported to accumulate misfolded proteins and damaged organelles. These findings have led to an increasing interest in protein degradation pathways, like autophagy, which are essential not only for normal protein turnover but also in the removal of misfolded and damaged proteins. Emerging evidence suggests a previously unprecedented role for autophagic processes in cardiac physiology and pathology. This review focuses on the major types of autophagic processes, the genes and protein complexes involved, and their regulation. It discusses the key similarities and differences between macroautophagy, chaperone-mediated autophagy, and selective mitophagy structures and functions. The genetic models available to study loss and gain of macroautophagy, mitophagy, and CMA are discussed. It defines the markers of autophagic processes, methods for measuring autophagic activities, and their interpretations. This review then summarizes the major studies of autophagy in the heart and their contribution to cardiac pathology. Some reports suggest macroautophagy imparts cardioprotection from heart failure pathology. Meanwhile, other studies find macroautophagy activation may be detrimental in cardiac pathology. An improved understanding of autophagic processes and their regulation may lead to a new genre of treatments for cardiac diseases.

Sestrin2 as a Novel Biomarker and Therapeutic Target for Various Diseases

Sestrin2 (SESN2), a highly conserved stress-inducible metabolic protein, is known to repress reactive oxygen species (ROS) and provide cytoprotection against various noxious stimuli including genotoxic and oxidative stress, endoplasmic reticulum (ER) stress, and hypoxia. Studies demonstrate that the upregulation of Sestrin2 under conditions of oxidative stress augments autophagy-directed degradation of Kelch-like ECH-associated protein 1 (Keap1), which targets and breaks down nuclear erythroid-related factor 2 (Nrf2), a key regulator of various antioxidant genes. Moreover, ER stress and hypoxia are shown to induce Sestrins, which ultimately reduce cellular ROS levels. Sestrin2 also plays a pivotal role in metabolic regulation through activation of the key energy sensor AMP-dependent protein kinase (AMPK) and inhibition of mammalian target of rapamycin complex 1 (mTORC1). Other downstream effects of Sestrins include autophagy activation, antiapoptotic effects in normal cells, and proapoptotic effects in cancer cells. As perturbations in the aforementioned pathways are well documented in multiple diseases, Sestrin2 might serve as a potential therapeutic target for various diseases. Thus, the aim of this review is to discuss the upstream regulators and the downstream effectors of Sestrins and to highlight the significance of Sestrin2 as a biomarker and a therapeutic target in diseases such as metabolic disorders, cardiovascular and neurodegenerative diseases, and cancer.