Inhibition of ER stress using tauroursodeoxycholic acid rescues obesity-evoked cardiac remodeling and contractile anomalies through regulation of ferroptosis.

Interrupted ER homeostasis contributes to the etiology of obesity cardiomyopathy although it remains elusive how ER stress evokes cardiac anomalies in obesity. Our study evaluated the impact of ER stress inhibition on cardiac anomalies in obesity. Lean and ob/ob obese mice received chemical ER chaperone tauroursodeoxycholic acid (TUDCA, 50 mg/kg/d, p.o.) for 35 days prior to evaluation of glucose sensitivity, echocardiographic, myocardial geometric, cardiomyocyte mechanical and subcellular Ca2+ property, mitochondrial integrity, oxidative stress, apoptosis, and ferroptosis. Intracellular Ca2+ governing domains including sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) were monitored by45Ca2+uptake and immunoblotting. Our results noted that TUDCA alleviated myocardial remodeling (fibrosis, hypertrophy, enlarged LVESD), echocardiographic anomalies (compromised fractional shortening and ejection fraction), cardiomyocyte contractile dysfunction (amplitude and velocity of cell shortening, relengthening time) and intracellular Ca2+ anomalies (compromised subcellular Ca2+ release, clearance and SERCA function), mitochondrial damage (collapsed membrane potential, downregulated mitochondrial elements and ultrastructural alteration), ER stress (GRP78, eIF2α and ATF4), oxidative stress, apoptosis and ferroptosis [downregulated SLC7A11, GPx4 and upregulated transferrin receptor (TFRC)] without affecting global glucose sensitivity and serum Fe2+ in obese mice. Obesity-evoked change in HSP90, phospholamban and Na+-Ca2+ exchanger was spared by the chemical ER chaperone. Moreover, in vitro results noted that TUDCA, PERK inhibitor GSK2606414, TFRC neutralizing antibody and ferroptosis inhibitor LIP1 mitigated palmitic acid-elicited changes in lipid peroxidation and mechanical function. Our findings favored a role for ferroptosis in obesity cardiomyopathy downstream of ER stress.

Cardiomyocyte-specific deletion of endothelin receptor A (ETA) obliterates cardiac aging through regulation of mitophagy and ferroptosis.

Advanced aging evokes unfavorable changes in the heart including cardiac remodeling and contractile dysfunction although the underlying mechanism remains elusive. This study was conducted to evaluate the role of endothelin-1 (ET-1) in the pathogenesis of cardiac aging and mechanism involved. Echocardiographic and cardiomyocyte mechanical properties were determined in young (5-6 mo) and aged (26-28 mo) wild-type (WT) and cardiomyocyte-specific ETA receptor knockout (ETAKO) mice. GSEA enrichment identified differentially expressed genes associated with mitochondrial respiration, mitochondrial protein processing and mitochondrial depolarization in cardiac aging. Aging elevated plasma levels of ET-1, Ang II and suppressed serum Fe2+, evoked cardiac remodeling (hypertrophy and interstitial fibrosis), contractile defects (fractional shortening, ejection fraction, cardiomyocyte peak shortening, maximal velocity of shortening/relengthening and prolonged relengthening) and intracellular Ca2+ mishandling (dampened intracellular Ca2+ release and prolonged decay), the effects with the exception of plasma AngII, ET-1 and Fe2+ were mitigated by ETAKO. Advanced age facilitated O2- production, carbonyl protein damage, cardiac hypertrophy (GATA4, ANP, NFATc3), ER stress, ferroptosis, compromised autophagy (LC3B, Beclin-1, Atg7, Atg5 and p62) and mitophagy (parkin and FUNDC1), and deranged intracellular Ca2+ proteins (SERCA2a and phospholamban), the effects of which were reversed by ETA ablation. ET-1 provoked ferroptosis in vitro, the response was nullified by the ETA receptor antagonist BQ123 and mitophagy inducer CsA. ETA but not ETB receptor antagonism reconciled cardiac aging, which was abrogated by inhibition of mitophagy and ferroptosis. These findings collectively denote promises of targeting ETA, mitophagy and ferroptosis in the management of aging-associated cardiac remodeling and contractile defect.

Selective inhibition of the NLRP3 inflammasome protects against acute ethanol-induced cardiotoxicity in an FBXL2-dependent manner.

Binge drinking exerts cardiac toxicity through various mechanisms, including oxidative stress and inflammation. NLRP3 inflammasomes possess both pro- and anti-inflammatory properties, although the role of NLRP3 in ethanol-induced cardiotoxicity remains unknown. This study is designed to examine the role of NLRP3 inflammasome in acute ethanol cardiotoxicity and the underlying mechanisms of action. Nine- to twelve-week-old adult male C57BL/6 mice are administered with ethanol (1.5 g/kg, twice daily, i.p.) for 3 days. A cohort of control and ethanol-challenged mice are treated with the NLRP3 inhibitor MCC950 (10 mg/kg/day, i.p., days 1 and 3). Myocardial geometry and function are monitored using echocardiography and cardiomyocyte edge-detection techniques. Levels of NLRP3 inflammasome, mitophagy and apoptosis are evaluated by western blot analysis and immunofluorescence techniques. Acute ethanol challenge results in abnormally higher cardiac systolic function, in conjunction with deteriorated cardiac diastolic function and cardiomyocyte contractile function. Levels of NLRP3 inflammasome and apoptosis are elevated, and mitophagy flux is blocked (elevated Pink1-Parkin and LC3B along with diminished p62 and Rab7) in mice receiving acute ethanol challenge. Although MCC950 does not elicit a notable effect on myocardial function, apoptosis or inflammasome activation in the absence of ethanol exposure, it effectively rescues acute ethanol cardiotoxicity, as manifested by restored myocardial and cardiomyocyte functional homeostasis, suppressed NLRP3 inflammasome activation and apoptosis, and improved mitophagy flux. Our data further suggest that FBXL2, an E3 ubiquitin ligase associated with mitochondrial homeostasis and mitophagy, is destabilized due to proteasomal degradation of caspase-1 by ethanol-induced hyperactivation of NLRP3-caspase-1 inflammasome signaling, resulting in mitochondrial injury and apoptosis. These findings denote a role for NLRP3 inflammasome in acute ethanol exposure-induced cardiotoxicity in an FBXL2-dependent manner and the therapeutic promise of targeting NLRP3 inflammasome for acute ethanol cardiotoxicity.

A dual-acting aldose reductase inhibitor impedes oxidative and carbonyl stress in tissues of fructose- and streptozotocin-induced rats: comparison with antioxidant stobadine.

Inhibiting aldose reductase (ALR2, AR) as well as maintaining a concomitant antioxidant (AO) activity via dual-acting agents may be a rational approach to prevent cellular glucotoxicity and at least delay the progression of diabetes mellitus (DM). This study was aimed at evaluating the dual-acting AR inhibitor (ARI) cemtirestat (CMTI) on tissue oxidative stress (OS) and carbonyl stress (CS) biomarkers in rats exposed to fructose alone (F) or fructose plus streptozotocin (D; type-2 diabetic). D and F rats were either untreated or treated daily with low- or high-dose CMTI, ARI drug epalrestat (EPA) or antioxidant stobadine (STB) for 14 weeks. Malondialdehyde (MDA), glutathione S-transferase (GST), nitric oxide synthase (NOS), and catalase (CAT) were increased in the sciatic nerve of F and D. These increases were attenuated by low doses of CMTI and STB in D, but exacerbated by low-dose EPA and high-dose CMTI in F. STB and CMTI and to a lesser extent EPA improved MDA, protein-carbonyl, GST and CAT in the hearts and lungs of F and D. CMTI and STB were more effective than EPA in improving the increased MDA and protein-carbonyl levels in the kidneys of F and especially D. CMTI ameliorated renal GST inhibition in D. In the lungs, hearts, and kidneys of F and D, the GSH to GSSG ratio decreased and caspase-3 activity increased, but partially resolved with treatments. In conclusion, CMTI with ARI/AO activity may be advantageous in overcoming OS, CS, and their undesirable consequences, with low dose efficacy and limited toxicity, compared to ARI or antioxidant alone.

Cemtirestat, an aldose reductase inhibitor and antioxidant compound, induces ocular defense against oxidative and inflammatory stress in rat models for glycotoxicity.

Fructose, endogenously produced as a consequence of activation of the polyol pathway under hyperglycemic conditions, contribute to formation of advanced glycoxidation end products (AGEs) and carbonyl stress. Oxidative stress is increased in diabetes (DM) due to AGEs formation and the utilization of NADPH by aldo-keto reductase, AKR1B1(AR), the first enzyme in polyol pathway. Since inhibition of AR is an attractive approach for the management of diabetic eye diseases, we aimed to compare the effects of a novel AR inhibitor (ARI)/antioxidant (AO) compound cemtirestat on eye tissues with the effects of ARI drug epalrestat and AO agent stobadine in rat model for glycotoxicity. One group of rats was fed high fructose (10% drinking water; 14 weeks), while type-2 DM was induced in the other group of rats with fructose plus streptozotocin (40 mg/kg-bw/day). Diabetic (D) and nondiabetic fructose-fed rats (F) were either untreated or treated with two different doses of cemtirestat (2.5 and 7.5 mg/kg-bw/day), epalrestat (25 and 50 mg/kg-bw/day), or stobadine (25 and 50 mg/kg-bw/day) for 14 weeks. Cemtirestat, epalrestat, and stobadine elaviate the increase in TNF-α, IL-1ß, NF-ƙB, and caspase-3 in retina, lens, cornea, and sclera of F and D rats. Both glycotoxicity models resulted in a decrease in GSH to GSSG ratio and a change in glutathione S-transferase activity in eye tissues, but these alterations were improved especially with cemtirestat and stobadine. Lens D-sorbitol of D rats increased more than that of F rats, this increase was only attenuated by cemtirestat and epalrestat. Epalrestat was more effective than cemtirestat and stobadine in inhibiting the increase of vascular endothelial growth factor (VEGF) in the retina of F and D rats. Cemtirestat and stobadine but not epalrestat decreased high level of Nε-(carboxymethyl)lysine in the lens and retina of F and D rats. Cemtirestat is a potential therapeutic in protecting the rat eye against glycotoxicity insults.

Parkin Insufficiency Accentuates High-Fat Diet-Induced Cardiac Remodeling and Contractile Dysfunction Through VDAC1-Mediated Mitochondrial Ca2+ Overload.

Mitochondrial Ca2+ overload contributes to obesity cardiomyopathy, yet mechanisms that directly regulate it remain elusive. The authors investigated the role of Parkin on obesity-induced cardiac remodeling and dysfunction in human hearts and a mouse model of 24-week high-fat diet (HFD) feeding. Parkin knockout aggravated HFD-induced cardiac remodeling and dysfunction, mitochondrial Ca2+ overload, and apoptosis without affecting global metabolism, blood pressure, and aortic stiffness. Parkin deficiency unmasked HFD-induced decline in voltage-dependent anion channel (VDAC) type 1 degradation through the ubiquitin-proteasome system but not other VDAC isoforms or mitochondrial Ca2+ uniporter complex. These data suggest that Parkin-mediated proteolysis of VDAC type 1 is a promising therapeutic target for obesity cardiomyopathy.

Deficiency in Beclin1 attenuates alcohol-induced cardiac dysfunction via inhibition of ferroptosis.

BACKGROUND: Binge drinking leads to compromised mitochondrial integrity and contractile function in the heart although little effective remedy is readily available. Given the possible derangement of autophagy in ethanol-induced cardiac anomalies, this study was designed to examine involvement of Beclin1 in acute ethanol-induced cardiac contractile dysfunction, in any, and the impact of Beclin1 haploinsufficiency on ethanol cardiotoxicity with a focus on autophagy-related ferroptosis. METHODS: WT and Beclin1 haploinsufficiency (BECN+/-) mice were challenged with ethanol for one week (2 g/kg, i.p. on day 1, 3 and 7) prior to assessment of cardiac injury markers (LDH, CK-MB), cardiac geometry, contractile and mitochondrial integrity, oxidative stress, lipid peroxidation, apoptosis and ferroptosis. RESULTS: Ethanol exposure compromised cardiac geometry and contractile function accompanied with upregulated Beclin1 and autophagy, mitochondrial injury, oxidative stress, lipid peroxidation and apoptosis, and ferroptosis (GPx4, SLC7A11, NCOA4). Although Beclin1 deficiency did not affect cardiac function in the absence of ethanol challenge, it alleviated ethanol-induced changes in cardiac injury biomarkers, cardiomyocyte area, interstitial fibrosis, echocardiographic and cardiomyocyte mechanical properties along with mitochondrial integrity, oxidative stress, lipid peroxidation, apoptosis and ferroptosis. Ethanol challenge evoked pronounced ferroptosis (downregulated GPx4, SLC7A11 and elevated NCOA4, lipid peroxidation), the effect was alleviated by Beclin1 haploinsufficiency. Inhibition of ferroptosis using LIP-1 rescued ethanol-induced cardiac mechanical anomalies. In vitro study noted that ferroptosis induction using erastin abrogated Beclin1 haploinsufficiency-induced response against ethanol. CONCLUSIONS: In sum, our data suggest that Beclin1 haploinsufficiency benefits acute ethanol challenge-induced myocardial remodeling and contractile dysfunction through ferroptosis-mediated manner.

Beclin1 haploinsufficiency compromises mesenchymal stem cell-offered cardioprotection against myocardial infarction.

Mesenchymal stem cells (MSCs)-based therapy has displayed some promises in ischemia heart diseases although its efficacy may be affected by changes in surrounding environments. This study evaluated the role of autophagy insufficiency using Beclin1 haploinsufficiency (BECN+/-) on intra-myocardial MSC transplantation-evoked effect against myocardial infarction. Donor MSCs from C57BL/6 mice were labelled with cell-tracker CM Dil and were delivered into LV free wall adjacent to infarct region in wild-type (WT) and BECN+/- recipient mice following ligation of left main coronary artery (MI-MSCs). Ten days following MI, myocardial function was assessed using echocardiography. Cardiomyocyte contractility and intracellular Ca2+ were monitored using cardiomyocytes from the area-at-risk adjacent to infarct. CM-Dil labeled cells were tracked in MSCs recipient mice using fluorescence microscopy. Lectin, Masson trichrome staining and Western blot analysis were employed to determine cardiomyocyte area, scar fibrosis, apoptosis and inflammation. MI insult triggered scar fibrosis, LV chamber dilation, decreased fractional shortening, ejection fraction, cardiomyocyte shortening, maximal velocity of shortening and relengthening as well as prolonged relengthening, which were abrogated or attenuated by MSCs therapy in WT but not BECN+/- mice. MI decreased intracellular Ca2+ rise and decay in response to electrical stimuli without affecting resting intracellular Ca2+, which were reconciled by MSCs in WT but not BECN+/- mice. MSCs further attenuated MI-induced mitochondrial ultrastructural injury, apoptosis, inflammation and autophagy defects in peri-infarct area in WT but not BECN+/- mice. Collectively, our results suggested that autophagy insufficiency dampened in MSCs-elicited cardioprotection associated with dampened apoptosis and inflammation.

Protective Effects of Novel Substituted Triazinoindole Inhibitors of Aldose Reductase and Epalrestat in Neuron-like PC12 Cells and BV2 Rodent Microglial Cells Exposed to Toxic Models of Oxidative Stress: Comparison with the Pyridoindole Antioxidant Stobadine.

Aldose reductase (AR) catalyzes the conversion of glucose to sorbitol in a NADPH-dependent reaction, thereby increasing the production of reactive oxygen species (ROS). Since AR activation is linked to redox dysregulation and cell damage in neurodegenerative diseases, AR inhibitors (ARIs) constitute promising therapeutic tools for the treatment of these disorders. Among these compounds, the novel substituted triazinoindole derivatives cemtirestat (CMTI) and COTI, as well as the clinically employed epalrestat (EPA) and the pyridoindole-antioxidant stobadine (STB), were tested in both PC12 cells and BV2 microglia exposed to four different neurotoxic models. These include (1) oxidative stress with hydrogen peroxide (H2O2), (2) mitochondrial complex IV inhibition with NaN3, (3) endoplasmic reticulum-stress and lipotoxicity induced by palmitic acid/bovine serum albumin (PAM/BSA), and (4) advanced carbonyl compound lipotoxicity by 4-hydroxynonenal (4-HNE). All toxic compounds decreased cell viability and increased ROS formation in both PC12 and BV2 cells in a concentration-dependent manner (1-1000 µM; NaN3 < H2O2≈PAM/BSA < 4-HNE). In PC12 cells, EPA increased cell viability in all toxic models only at 1 µM, whereas CMTI restored baseline viability in all toxic models. COTI afforded protection against lipotoxicity, while STB only prevented H2O2-induced toxicity. Except for the 4-HNE model, EPA prevented ROS generation in all other toxic models, whereas CMTI, COTI, and STB prevented ROS production in all toxic models. In BV2 cells, EPA and CMTI restored baseline cell viability in all toxic models tested, while COTI and STB did not prevent the loss of viability in the NaN3 model. All ARIs and STB efficiently prevented ROS formation in all toxic models in a concentration-independent manner. The differential protective effects evoked by the novel ARIs and STB on the toxic models tested herein provide novel and relevant comparative evidence for the design of specific therapeutic strategies against neurodegenerative events associated with neurological disorders.

Parkin deficiency accentuates chronic alcohol intake-induced tissue injury and autophagy defects in brain, liver and skeletal muscle.

Alcoholism leads to organ injury including mitochondrial defect and apoptosis with evidence favoring a role for autophagy dysregulation in alcoholic damage. Parkin represents an autosomal recessive inherited gene for Parkinson's disease and an important member of selective autophagy for mitochondria. The association between Parkinson's disease and alcoholic injury remains elusive. This study aimed to examine the effect of parkin deficiency on chronic alcohol intake-induced organ injury in brain, liver and skeletal muscle (rectus femoris muscle). Adult parkin-knockout (PRK-/-) and wild-type mice were placed on Liber-De Carli alcohol liquid diet (4%) for 12 weeks prior to assessment of liver enzymes, intraperitoneal glucose tolerance, protein carbonyl content, apoptosis, hematoxylin and eosin morphological staining, and mitochondrial respiration (cytochrome c oxidase, NADH:cytochrome c reductase and succinate:cytochrome c reductase). Autophagy protein markers were monitored by western blot analysis. Our data revealed that chronic alcohol intake imposed liver injury as evidenced by elevated aspartate aminotransferase and alanine transaminase, glucose intolerance, elevated protein carbonyl formation, apoptosis, focal inflammation, necrosis, microvesiculation, autophagy/mitophagy failure and dampened mitochondrial respiration (complex IV, complexes I and III, and complexes II and III) in the brain, liver and rectus femoris skeletal muscle. Although parkin ablation itself did not generate any notable effects on liver enzymes, insulin sensitivity, tissue carbonyl damage, apoptosis, tissue morphology, autophagy or mitochondrial respiration, it accentuated alcohol intake-induced tissue damage, apoptosis, morphological change, autophagy/mitophagy failure and mitochondrial injury without affecting insulin sensitivity. These data suggest that parkin plays an integral role in the preservation against alcohol-induced organ injury, apoptosis and mitochondrial damage.

Mitophagy inhibitor liensinine suppresses doxorubicin-induced cardiotoxicity through inhibition of Drp1-mediated maladaptive mitochondrial fission.

Doxorubicin (DOX) is one of the most effective antineoplastic drugs. However, its clinical application has been greatly limited due to the development of cardiotoxicity with DOX utilization. A number of theories have been postulated for DOX-induced cardiotoxicity with a pivotal contribution from unchecked (excess) mitophagy and mitochondrial fission. Liensinine (LIEN), a newly identified mitophagy inhibitor, strengthens the antineoplastic efficacy of DOX although its action on hearts remains elusive. This study was designed to examine the effect of LIEN on DOX-induced cardiotoxicity and the underlying mechanisms involved with a focus on mitochondrial dynamics. Our data revealed that LIEN alleviated DOX-induced cardiac dysfunction and apoptosis through inhibition of dynamin-related protein 1 (Drp1)-mediated excess (unchecked) mitochondrial fission. LIEN treatment decreased Drp1 phosphorylation at Ser616 site, inhibited mitochondrial fragmentation, mitophagy (assessed by TOM20 and TIM23), oxidative stress, cytochrome C leakage, cardiomyocyte apoptosis, as well as improved mitochondrial function and cardiomyocyte contractile function in DOX-induced cardiac injury. In DOX-challenged neonatal mouse ventricular myocytes (NMVMs), LIEN-suppressed Drp1 phosphorylation, mitochondrial fragmentation, and apoptosis were blunted by Rab7 overexpression, the effect of which was reversed by the ERK inhibitor U0126. Moreover, activation of ERK or Drp1 abolished the protective effects of LIEN on cardiomyocyte mechanical anomalies. These data shed some lights towards understanding the role of LIEN as a new protective agent against DOX-associated cardiotoxicity without compromising its anti-tumor effects.

Cardiomyocyte-specific knockout of endothelin receptor a attenuates obesity cardiomyopathy.

Endothelin (ET)-1 is implicated in the pathophysiology of cardiovascular diseases although its role in obesity anomalies has not been fully elucidated. This study was designed to examine the impact of ET-1 receptor A (ETA) ablation on obesity-induced changes in cardiac geometry and contractile function, as well as the mechanisms involved with a focus on autophagy. Cardiomyocyte-specific ETA receptor knockout (ETAKO) and WT mice were fed either low-fat (10% calorie from fat) or high-fat (45% calorie from fat) diet for 24 weeks. Glucose tolerance test was examined to confirm insulin resistance. High-fat diet intake compromised myocardial geometry (enlarged left ventricular diameters in systole and diastole), morphology (cardiac hypertrophy, increased wall thickness and interstitial fibrosis), contractile function (reduced fractional shortening, ejection fraction and cardiomyocyte shortening) and intracellular Ca2+ handling, the effect of which was significantly attenuated by ETAKO. TUNEL staining revealed overt apoptosis in high-fat-fed group, the effect was reverted by ETAKO. Western blot analysis noted that high-fat intake downregulated leptin receptor and PPARγ, insulin signaling (elevated basal/dampened insulin-stimulated phosphorylation of Akt and IRS1), phosphorylation of AMPK, ACC, upregulated GATA-4, ANP, NFATc3, PPARα, m-TOR/p70s6k signaling, which were attenuated by ETAKO with the exception of AMPK/ACC. Furthermore, high-fat intake suppressed cardiac autophagy, which was abrogated by ETAKO. In cultured murine cardiomyocytes, palmitic acid challenged mimicked high-fat diet-induced hypertrophic and autophagic responses, the effect of which were abolished by the ETA receptor antagonist BQ123 or mTOR inhibitor rapamycin. These results suggest that inhibition of ETA rescues high-fat intake-induced cardiac anomalies possibly through autophagy regulation.

Sodium Glucose Co-Transporter 2 Inhibitors: Beyond Glucose Lowering.

Diabetes is an important cause of morbidity and mortality worldwide. Management of blood glucose is critical for diabetic patients since diabetes carries a risk for many diseases and disorders. Although there are several antidiabetic agents in the markets for a long time, some of the agents have dose-limiting side effects, such as hypoglycemia and weight gain which limits their ability to reduce cardiovascular complications. Sodium-glucose co-transporter 2 (SGLT2) inhibitors are a new class of antidiabetic agents which exerts their effects insulin-independent mechanism, therefore, they do not cause hypoglycemia in the diabetic patients. Due to the unique class-dependent mechanism, they can be adjunct to the standard therapy of the diabetic patients. Recent studies have speculated that SGLT2 inhibitors have some beneficial effects other than hypoglycemic effects in diabetic patients like lowering body weight, reducing blood pressure and hyperuricemia. This review aims to discuss the pleiotropic effects of SGLT2 inhibitors and gives an avenue for new research ideas.

Akt2 ablation prolongs life span and improves myocardial contractile function with adaptive cardiac remodeling: role of Sirt1-mediated autophagy regulation.

Aging is accompanied with unfavorable geometric and functional changes in the heart involving dysregulation of Akt and autophagy. This study examined the impact of Akt2 ablation on life span and cardiac aging as well as the mechanisms involved with a focus on autophagy and mitochondrial integrity. Cardiac geometry, contractile, and intracellular Ca2+ properties were evaluated using echocardiography, IonOptix® edge-detection and fura-2 techniques. Levels of Sirt1, mitochondrial integrity, autophagy, and mitophagy markers were evaluated using Western blot. Our results revealed that Akt2 ablation prolonged life span (by 9.1%) and alleviated aging (24 months)-induced unfavorable changes in myocardial function and intracellular Ca2+ handling (SERCA2a oxidation) albeit with more pronounced cardiac hypertrophy (58.1%, 47.8%, and 14.5% rises in heart weight, wall thickness, and cardiomyocyte cross-sectional area). Aging downregulated levels of Sirt1, increased phosphorylation of Akt, and the nuclear transcriptional factor Foxo1, as well as facilitated acetylation of Foxo1, the effects of which (except Sirt1 and Foxo1 acetylation) were significantly attenuated or negated by Akt2 ablation. Advanced aging disturbed autophagy, mitophagy, and mitochondrial integrity as evidenced by increased p62, decreased levels of beclin-1, Atg7, LC3B, BNIP3, PTEN-induced putative kinase 1 (PINK1), Parkin, UCP-2, PGC-1α, and aconitase activity, the effects of which were reversed by Akt2 ablation. Aging-induced cardiomyocyte contractile dysfunction and loss of mitophagy were improved by rapamycin and the Sirt1 activator SRT1720. Activation of Akt using insulin or Parkin deficiency prevented SRT1720-induced beneficial effects against aging. In conclusion, our data indicate that Akt2 ablation protects against cardiac aging through restored Foxo1-related autophagy and mitochondrial integrity.

Mitochondrial aldehyde dehydrogenase protects against doxorubicin cardiotoxicity through a transient receptor potential channel vanilloid 1-mediated mechanism.

Cardiotoxicity is one of the major life-threatening effects encountered in cancer chemotherapy with doxorubicin and other anthracyclines. Mitochondrial aldehyde dehydrogenase (ALDH2) may alleviate doxorubicin toxicity although the mechanism remains elusive. This study was designed to evaluate the impact of ALDH2 overexpression on doxorubicin-induced myocardial damage with a focus on mitochondrial injury. Wild-type (WT) and transgenic mice overexpressing ALDH2 driven by chicken ß-actin promoter were challenged with doxorubicin (15mg/kg, single i.p. injection, for 6days) and cardiac mechanical function was assessed using the echocardiographic and IonOptix systems. Western blot analysis was used to evaluate intracellular Ca(2+) regulatory and mitochondrial proteins, PKA and its downstream signal eNOS. Doxorubicin challenge altered cardiac geometry and function evidenced by enlarged left ventricular end systolic and diastolic diameters, decreased factional shortening, cell shortening and intracellular Ca(2+) rise, prolonged relengthening and intracellular Ca(2+) decay, the effects of which were attenuated by ALDH2. Doxorubicin challenge compromised mitochondrial integrity and upregulated 4-HNE and UCP-2 levels while downregulating levels of TRPV1, SERCA2a and PGC-1α, the effects of which were alleviated by ALDH2. Doxorubicin-induced cardiac functional defect and apoptosis were reversed by the TRPV1 agonist SA13353 and the ALDH-2 agonist Alda-1 whereas the TRPV1 antagonist capsazepine nullified ALDH2/Alda-1-induced protection. Doxorubicin suppressed phosphorylation of PKA and eNOS, the effect of which was reversed by ALDH2. Moreover, 4-HNE mimicked doxorubicin-induced cardiomyocyte anomalies, the effect of which was ablated by SA13353. Taken together, our results suggested that ALDH2 may rescue against doxorubicin cardiac toxicity possibly through a TRPV1-mediated protection of mitochondrial integrity.