Cardiac Atrophy Research Articles

Abstract 15784: Left Ventricular Structural Remodeling and Cardiomyopathy in Duchenne Muscular Dystrophy Carriers

Introduction: Duchenne muscular dystrophy (DMD) is an X-linked neuromuscular disorder. DMD-associated cardiomyopathy is the primary mode of premature death in the majority of male DMD patients, but the prevalence of cardiomyopathy and its clinical significance in female DMD carriers is less well characterized. Hypothesis: We hypothesized that a significant proportion of DMD carriers develop maladaptive left ventricular (LV) structural remodeling and cardiomyopathy over time. Methods: A cross-sectional study was undertaken comparing cardiac magnetic resonance imaging (cMRI) and cardiopulmonary stress test (CPX) parameters between DMD carriers and healthy age- and sex-matched controls from the Dallas Heart Study (DHS). Demographic data, cMRI parameters, and CPX parameters were collected retrospectively on 30 consecutive DMD carriers and 26 control DHS subjects. Results: Overall, DMD carriers had a significantly lower LVEF compared to DHS controls (58+8% vs 70+7%, p< 0.0001). The overall prevalence of reduced LVEF in DMD carriers (defined as LVEF <60%) was 63% compared to 8% in DHS controls. The volumetric variables indexed to body surface area (LVEDVi and LVESVi) were significantly higher in DMD carriers compared to control subjects (72+14 ml/m 2 vs 58+7, p< 0.0001; 31+10 ml/m 2 vs 17+5, p< 0.0001; respectively). LV concentricity was also significantly lower among all DMD carriers compared to DHS controls (3.10+0.65 g/mL 0.67 vs 3.73+0.79, p =0.002). LV concentricity was significantly lower in DMD carriers with reduced EF compared to controls (3.09+0.51 g/mL 0.67 vs 3.73+0.79, p = 0.012), while DMD carriers with preserved EF also had reduced concentricity compared to controls (3.12+0.86 vs 3.73+0.79, p = 0.054). Finally, peak VO 2 was lower in DMD carriers compared to DHS controls (23+6 ml/kg/min vs 25+4, p =0.076), though this difference did not reach statistical significance. Conclusions: Collectively, the data suggest that middle-aged female DMD carriers are at greater risk of developing left ventricular systolic dysfunction and cardiomyopathy associated with decreased exercise capacity. A possible mechanism driving the development of this cardiomyopathy is progressive, maladaptive left ventricular dilatation and cardiac atrophy.

Abstract 15153: Functional Cardiac Adaptation to 60 Days Strict Head-Down-Tilt Bedrest

Background: Reduced physical activity increases the risk for heart failure. Myocardial strain measurements capture subtle abnormalities in myocardial function. We tested the hypothesis that bedrest deconditioning produces cardiac dysfunction in healthy persons. Methods: In the AGBRESA study, which assessed artificial gravity through centrifugation as potential countermeasure for space travel, 24 healthy persons (8 women) were submitted to 60 days strict -6°-head-down-tilt bedrest. 8 subjects each were included in a control group or groups subjected to continuous artificial gravity training on a short-arm centrifuge [30 minutes/day] or intermittent centrifugation [6x5 min/day]. We assessed cardiac morphology, function, strain and hemodynamics by cardiac-MRI (baseline, end of bedrest, recovery) and echocardiography (baseline, end of bedrest). Before and after bedrest, we assessed orthostatic heart rate responses as measure of cardiovascular deconditioning. Results: We conducted a pooled analysis because cardiovascular responses to bedrest did not differ between groups. Supine heart rate (baseline: 64±9.6bpm; bedrest: 72.3±10.5bpm; recovery: 69.6±10.5bpm, p <0.0001) and diastolic blood-pressure (69.6±7.3mmHg; bedrest: 78.5±6.9mmHg; recovery: 70.3±6.3mmHg, p <0.0001) increased with bedrest. With head-up tilt, heart rate increased 22.8±10.5bpm before and 45.9±213bpm at the end of bedrest ( p <0.0001) consistent with cardiovascular deconditioning. Cardiac-output decreased from 6.6±0.9l/min to 6±1l/min at end of bedrest (recovery: 6.8±1.2l/min, p =0.0096). Left ventricular ejection fraction and mass-index did not change. Echocardiographic global longitudinal strain (baseline: -19.90±2.1%; bedrest: -18.1±2.1%, p <0.0001) decreased, whereas global circumferential strain in MRI tended to increase (baseline: -18.6±1.7%; bedrest: -19.1±1.6%, p =0.0843). After four days of recovery MRI measurements had returned to baseline. Conclusion: In healthy persons, cardiovascular deconditioning through 60 days head-down-tilt bedrest does not lead to cardiac atrophy or sustained reductions in cardiac performance. The transient nature of cardiac strain changes suggests functional rather than structural changes in the heart.

Beneficial Cardiac Structural and Functional Adaptations After Lumbosacral Spinal Cord Epidural Stimulation and Task-Specific Interventions: A Pilot Study.

Cardiac myocyte atrophy and the resulting decreases to the left ventricular mass and dimensions are well documented in spinal cord injury. Therapeutic interventions that increase preload can increase the chamber size and improve the diastolic filling ratios; however, there are no data describing cardiac adaptation to chronic afterload increases. Research from our center has demonstrated that spinal cord epidural stimulation (scES) can normalize arterial blood pressure, so we decided to investigate the effects of scES on cardiac function using echocardiography. Four individuals with chronic, motor-complete cervical spinal cord injury were implanted with a stimulator over the lumbosacral enlargement. We assessed the cardiac structure and function at the following time points: (a) prior to implantation; (b) after scES targeted to increase systolic blood pressure; (c) after the addition of scES targeted to facilitate voluntary (i.e., with intent) movement of the trunk and lower extremities; and (d) after the addition of scES targeted to facilitate independent, overground standing. We found significant improvements to the cardiac structure (left ventricular mass = 10 ± 2 g, p < 0.001; internal dimension during diastole = 0.1 ± 0.04 cm, p < 0.05; internal dimension during systole = 0.06 ± 0.03 cm, p < 0.05; interventricular septum dimension = 0.04 ± 0.02 cm, p < 0.05), systolic function (ejection fraction = 1 ± 0.4%, p < 0.05; velocity time integral = 2 ± 0.4 cm, p < 0.001; stroke volume = 4.4 ± 1.5 ml, p < 0.01), and diastolic function (mitral valve deceleration time = -32 ± 11 ms, p < 0.05; mitral valve deceleration slope = 50 ± 25 cm s–1, p < 0.05; isovolumic relaxation time = −6 ± 1.9 ms, p < 0.05) with each subsequent scES intervention. Despite the pilot nature of this study, statistically significant improvements to the cardiac structure, systolic function, and diastolic function demonstrate that scES combined with task-specific interventions led to beneficial cardiac remodeling, which can reverse atrophic changes that result from spinal cord injury. Long-term improvements to cardiac function have implications for increased quality of life and improved cardiovascular health in individuals with spinal cord injury, decreasing the risk of cardiovascular morbidity and mortality.

Combined administration of lauric acid and glucose improved cancer-derived cardiac atrophy in a mouse cachexia model.

Cancer‐derived myocardial damage is an important cause of death in cancer patients. However, the development of dietary interventions for treating such damage has not been advanced. Here, we investigated the effect of dietary intervention with lauric acid (LAA) and glucose, which was effective against skeletal muscle sarcopenia in a mouse cachexia model, on myocardial damage. Treatment of H9c2 rat cardiomyoblasts with lauric acid promoted mitochondrial respiration and increased ATP production by Seahorse flux analysis, but did not increase oxidative stress. Glycolysis was also promoted by LAA. In contrast, mitochondrial respiration and ATP production were suppressed, and oxidative stress was increased in an in vitro cachexia model in which cardiomyoblasts were treated with mouse cachexia ascites. Ascites‐treated H9c2 cells with concurrent treatment with LAA and high glucose showed that mitochondrial respiration and glycolysis were promoted more than that of the control, and ATP was restored to the level of the control. Oxidative stress was also reduced by the combined treatment. In the mouse cachexia model, myocardiac atrophy and decreased levels of a marker of muscle maturity, SDS‐soluble MYL1, were observed. When LAA in CE‐2 diet was orally administered alone, no significant rescue was observed in the cancer‐derived myocardial disorder. In contrast, combined oral administration of LAA and glucose recovered myocardial atrophy and MYL1 to levels observed in the control without increase in the cancer weight. Therefore, it is suggested that dietary intervention using a combination of LAA and glucose for cancer cachexia might improve cancer‐derived myocardial damage.

Exercise training delays cardiac remodeling in a mouse model of cancer cachexia

AimsWe aimed to investigate the impact of cancer cachexia and previous aerobic exercise training (AET) on cardiac function and structure in tumor bearing mice. Main methodsColon adenocarcinoma cells 26 (CT26) were subcutaneously injected in BALB/c mice to establish robust cancer cachexia model. AET was performed on a treadmill during 45 days, 60 min/5 days per week. Cardiac function was evaluated by echocardiography and cardiac morphology was assessed by light microscopy. The protein expression levels of mitochondrial complex were analyzed by Western blotting. The mRNA levels of genes related to cardiac remodeling and autophagy were analyzed by quantitative Real-Time PCR. Key findingsOur data confirms CT26 tumor bearing mice as a well-characterized and robust model of cancer cachexia. CT26 mice exhibited cardiac remodeling and dysfunction characterized by cardiac atrophy and impaired left ventricle ejection fraction paralleled by cardiac necrosis, inflammation and fibrosis. AET partially reversed the left ventricle ejection fraction and led to significant anti-cardiac remodeling effect associated reduced necrosis, inflammation and cardiac collagen deposition in CT26 mice. Reduced TGF-β1 mRNA levels, increased mitochondrial complex IV protein levels and partial recovery of BNIP3 mRNA levels in cardiac tissue were associated with the cardiac effects of AET in CT26 mice. Thus, we suggest AET as a powerful regulator of key pathways involved in cardiac tissue homeostasis in cancer cachexia. SignificanceOur study provides a robust model of cancer cachexia, as well as highlights the potential and integrative effects of AET as a preventive strategy for reducing cardiac damage in cancer cachexia.

Cancer-induced Cardiac Atrophy Adversely Affects Myocardial Redox State and Mitochondrial Oxidative Characteristics.

Determine how cancer-induced cardiac atrophy alters mitochondrial turnover, mitochondrial mRNA translation machinery and in-vitro oxidative characteristics. Lewis lung carcinoma (LLC) tumors were implanted in C57BL6/J mice and grown for 28days to induce cardiac atrophy. Endogenous metabolic species, and markers of mitochondrial function were assessed. H9c2 cardiomyocytes were cultured in LLC-conditioned media with(out) the antioxidant MitoTempo. Cells were analyzed for ROS, oxidative capacity, and hypoxic resistance. LLC heart weights were ~10% lower than controls. LLC hearts demonstrated ~15% lower optical redox ratio (FAD/FAD+NADH) compared to PBS controls. When compared to PBS, LLC hearts showed ~50% greater COX-IV and VDAC, attributed to ~50% lower mitophagy markers. mt-mRNA translation machinery was elevated similarly to markers of mitochondrial content. mitochondrial DNA-encoded Cytb was ~30% lower in LLC hearts. ROS scavengers GPx-3 and GPx-7 were ~50% lower in LLC hearts. Treatment of cardiomyocytes with LLC-conditioned media resulted in higher ROS (25%), lower oxygen consumption rates (10% at basal, 75% at maximal), and greater susceptibility to hypoxia (~25%) -- which was reversed by MitoTempo. These results substantiate metabolic cardiotoxic effects attributable to tumor-associated factors and provide insight into interactions between mitochondrial mRNA translation, ROS mitigation, oxidative capacity and hypoxia resistance.

Abstract 465: A 3D Bioprinted Human Cardiac Cell Platform to Model the Pathophysiology of Diabetes

Type-II diabetes (T2D) patients affected by underlying hyperglycemic (high glucose/blood sugar) conditions often suffer from cardiac atrophy, resulting in tissue mass reduction and debilitating cardiac health. To understand pathophysiological mechanisms during progression of cardiac atrophy, a 3D bioprinted organoid platform was developed from a mixture of hydrogels containing human cardiac cells, including cardiomyocytes (CM), fibroblasts (CF) and endothelial cells (EC), to mimic the functionality of the in-vivo tissue. The organoids were cultured using normoglycemic- or hyperglycemic-conditions. The expression of essential biomarkers in these organoids, for myocardin (Myocd), troponin-I (TRP-I), fibroblast protein-1 (FSP-1) and endothelin-1 (ET-1) was confirmed. To assess the physiological cellular connections during hyperglycemia, the presence of Connexin-43 (CX-43) was assessed in the presence of a CX-43 blocker, gap26. Epigenomic tools were used to simultaneously interrogate histone-modifications by histone 3 lysine 9 mono-methylation (H3K9me1) along with the co-regulation of inflammatory mediators, such as the high mobility group box 1 (HMGB1) and toll like receptor 4 (TLR4) in the cardiac organoids cultured using normal versus hyperglycemic conditions. Organoids exposed to high glucose showed an increased expression of H3K9me1 as well as inflammatory mediators HMGB1 and TLR4. Hyperglycemia also exhibited alterations in expression of Myocd and FSP-1 in the organoids, compared to normoglycemic conditions. Treatment with gap26 affected the CX-43 expression significantly, in organoids cultured under hyperglycemia suggesting that high glucose conditions associated with prolonged diabetes may lead to compromised CM-CF coupling, essential for maintenance of cardiac functionality. Increased levels of H3K9me1 suggest decreased expression of Myocd, which may lead to CM degeneration. Epigenetic modifications including alterations in histone methylation in regulation of the myocardial genes and gap junction proteins under hyperglycemic conditions, may lead to cardiac atrophy. We expect to establish an actual T2D patient iPSC cell derived cardiac platform, to offer new therapeutic opportunities within the field.

Abstract MP131: The CDK2-FOXO1 Axis Mediates Doxorubicin-induced Cardiomyocyte Apoptosis and Atrophy

Recent clinical investigations indicate that anthracycline-based chemotherapy induces early declines in heart mass in cancer patients. A decline in heart mass can be caused by a decrease in cardiac cell number due to exaggerated cell death, and/or a reduction in cell size via atrophy. Our previous study reveals that the anthracycline doxorubicin (DOX) induces apoptotic death of cardiomyocytes through activation of cyclin-dependent kinase 2 (CDK2). However, the signaling pathway downstream of CDK2 remains to be characterized. In addition, it is unclear whether the same pathway also mediates cardiac atrophy. Here we demonstrated that DOX exposure induced CDK2-dependent phosphorylation of forkhead box O1 (FOXO1) at S249, leading to transcription of its pro-apoptotic target gene Bim. In cultured cardiomyocytes, treatment with the small molecule FOXO1 inhibitor AS1842856, or transfection with FOXO1-specific siRNAs protected against DOX-induced apoptosis and mitochondrial damage. Oral administration of AS1842856 in mice hindered apoptosis and prevented DOX-induced decline in left ventricular systolic function. Intriguingly, pharmacologic inhibition of FOXO1 also attenuated DOX-induced cardiac atrophy, likely due to repression of MuRF1, a pro-atrophic FOXO1 target gene. In conclusion, DOX exposure induces CDK2-dependent FOXO1 activation, resulting in cardiomyocyte apoptosis and atrophy. Our results identify FOXO1 as a promising drug target for DOX-induced cardiotoxicity. FOXO1 inhibitors may represent a novel class of therapeutics for cardioprotection during chemotherapy.

ALDH2 contributes to melatonin-induced protection against APP/PS1 mutation-prompted cardiac anomalies through cGAS-STING-TBK1-mediated regulation of mitophagy

Ample clinical evidence suggests a high incidence of cardiovascular events in Alzheimer’s disease (AD), although neither precise etiology nor effective treatment is available. This study was designed to evaluate cardiac function in AD patients and APP/PS1 mutant mice, along with circulating levels of melatonin, mitochondrial aldehyde dehydrogenase (ALDH2) and autophagy. AD patients and APP/PS1 mice displayed cognitive and myocardial deficits, low levels of circulating melatonin, ALDH2 activity, and autophagy, ultrastructural, geometric (cardiac atrophy and interstitial fibrosis) and functional (reduced fractional shortening and cardiomyocyte contraction) anomalies, mitochondrial injury, cytosolic mtDNA buildup, apoptosis, and suppressed autophagy and mitophagy. APP/PS1 mutation downregulated cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) levels and TBK1 phosphorylation, while promoting Aβ accumulation. Treatment with melatonin overtly ameliorated unfavorable APP/PS1-induced changes in cardiac geometry and function, apoptosis, mitochondrial integrity, cytosolic mtDNA accumulation (using both immunocytochemistry and qPCR), mitophagy, and cGAS-STING-TBK1 signaling, although these benefits were absent in APP/PS1/ALDH2−/− mice. In vitro evidence indicated that melatonin attenuated APP/PS1-induced suppression of mitophagy and cardiomyocyte function, and the effect was negated by the nonselective melatonin receptor blocker luzindole, inhibitors or RNA interference of cGAS, STING, TBK1, and autophagy. Our data collectively established a correlation among cardiac dysfunction, low levels of melatonin, ALDH2 activity, and autophagy in AD patients, with compelling support in APP/PS1 mice, in which melatonin rescued myopathic changes by promoting cGAS-STING-TBK1 signaling and mitophagy via an ALDH2-dependent mechanism.

Resistance Training Attenuates Cancer Cachexia-induced Cardiac Remodeling

Scott Baumel1, Eric Bredahl1, Jacob Siedlik1, Joan Eckerson FACSM1, Kristen Drescher2 1Department of Exercise Science and Pre-Health Professions, Creighton University 2Department of Medical Microbiology and Immunology, Creighton University Cancer-induced cachexia is a state of ill health characterized by cardiac and skeletal muscle atrophy that has profound impacts on cardiovascular function and quality of life. Resistance training (RT) during treatment has been shown to improve cardiac function via cardiac hypertrophy. PURPOSE: To assess the capacity for RT to minimize cachexia-induced cardiac remodeling. METHODS: All procedures were done in accordance with an IACUC approved protocol. Male-Wistar rats (n=48) were randomly assigned to a sedentary (SED), RT, SED+cancer, and RT+cancer group. Animals assigned to RT groups trained for a total of 13 wk using an elevated food model to simulate low intensity RT. SED animals were placed in standard animal housing for an equivalent amount of time. At week 10, animals were injected with Walker-256-mammarycarcinoma cells (106 cells) or an equivalent amount of 0.9% saline. Left ventricular morphology was measured using echocardiography prior to injection and at the end of the 13 wk experiment. Differences in cardiac morphology (i.e. thickness and diameter) between groups were analyzed using a one-way ANOVA (p < 0.05). RESULTS: There was a significant (p < 0.05) differance in posterior wall thickness during systole of SED animals (0.30±0.04 cm) compared to of RT (0.34±0.05 cm). Posterior wall thickness during diastole was significantly (p < 0.05) increased in RT+cancer (0.21±0.03 cm) animals compared to SED+cancer (0.18±0.04 cm). SED+cancer animals had a significantly larger left ventricular diameter (LV) (0.72±0.04 cm) than SED controls (0.67±0.06 cm). The combination of RT+cancer significantly attenuated the increase in LV diameter (0.67±0.034 cm). CONCLUSIONS: The results suggest that the posterior wall is susceptible to cachexia induced remodeling. however, RT attenuated the degree of cardiac remodeling.

Angiotensin-II receptor type Ia does not contribute to cardiac atrophy following high-thoracic spinal cord injury in mice.

What is the central question of this study? What is the role of the renin-angiotensin system with angiotensin II acting via its receptor AT1a in spinal cord injury-induced cardiac atrophy? What is the main finding and its importance? Knockout of AT1a did not protect mice that had undergone thoracic level 4 transection from cardiac atrophy. There were no histopathological signs but there was reduced load-dependent left ventricular function (lower stroke volume and cardiac output) with preserved ejection fraction. Spinal cord injury (SCI) leads to cardiac atrophy often accompanied by functional deficits. The renin-angiotensin system (RAS) with angiotensin II (AngII) signalling via its receptor AT1a might contribute to cardiac atrophy post-SCI. We performed spinal cord transection at thoracic level T4 (T4-Tx) or sham-operation in female wild-type mice (WT, n=27) and mice deficient in AT1a (Agtr1a-/- , n=27). Echocardiography (0, 7, 21 and 28days post-SCI) and histology and gene expression analyses at 1 and 2months post-SCI were performed. We found cardiac atrophy post-SCI: reduced heart weight, reduced estimated left ventricular mass in Agtr1a-/- , and reduced cardiomyocyte diameter in WT mice. Although, the latter as well as stroke volume (SV) and cardiac output (CO) were reduced in Agtr1a-/- mice already at baseline, cardiomyocyte diameter was even smaller in injured Agtr1a-/- mice compared to injured WT mice. SV and CO were reduced in WT mice post-SCI. Ejection fraction and fractional shortening were preserved post-SCI in both genotypes. There were no histological signs of fibrosis and pathology in the cardiac sections of either genotype post-SCI. Gene expression of Agtr1a showed a trend for up-regulation at 2months post-SCI; angiotensinogen was up-regulated at 2month post-SCI in both genotypes. AngII receptor type 2 (Agtr2) was up- and down-regulated at 1 and 2months post-SCI in WT mice, respectively, and Ang-(1-7) receptor (Mas) at 1 and 2months post-SCI. Atrogin-1/MAFbx and MuRF1, atrophy markers, were not significantly up-regulated post-SCI. Our data show that lack of AT1a does not protect from cardiac atrophy post-SCI.

Long-term spaceflight and the cardiovascular system.

While early investigations into the physiological effects of spaceflight suggest the body's ability to reversibly adapt, the corresponding effects of long-term spaceflight (>6 months) are much less conclusive. Prolonged exposure to microgravity and radiation yields profound effects on the cardiovascular system, including a massive cephalad fluid translocation and altered arterial pressure, which attenuate blood pressure regulatory mechanisms and increase cardiac output. Also, central venous pressure decreases as a result of the loss of venous compression. The stimulation of baroreceptors by the cephalad shift results in an approximately 10%–15% reduction in plasma volume, with fluid translocating from the vascular lumen to the interstitium. Despite possible increases in cardiac workload, myocyte atrophy and notable, yet unexplained, alterations in hematocrit have been observed. Atrophy is postulated to result from shunting of protein synthesis from the endoplasmic reticulum to the mitochondria via mortalin-mediated action. While data are scarce regarding their causative agents, arrhythmias have been frequently reported, albeit sublethal, during both Russian and American expeditions, with QT interval prolongation observed in long, but not short duration, spaceflight. Exposure of the heart to the proton and heavy ion radiation of deep space has also been shown to result in coronary artery degeneration, aortic stiffness, carotid intima thickening via collagen-mediated action, accelerated atherosclerosis, and induction of a pro-inflammatory state. Upon return, long-term spaceflight frequently results in orthostatic intolerance and altered sympathetic responses, which can prove hazardous should any rapid mobilization or evacuation be required, and indicates that these cardiac risks should be especially monitored for future missions.

Dilated cardiomyopathy-linked heat shock protein family D member 1 mutations cause up-regulation of reactive oxygen species and autophagy through mitochondrial dysfunction.

During heart failure, the levels of circulatory heat shock protein family D member 1 (HSP60) increase. However, its underlying mechanism is still unknown. The apical domain of heat shock protein family D member 1 (HSPD1) is conserved throughout evolution. We found a point mutation in HSPD1 in a familial dilated cardiomyopathy (DCM) patient. A similar point mutation in HSPD1 in the zebrafish mutant, nbl, led to loss of its regenerative capacity and development of pericardial oedema under heat stress condition. In this study, we aimed to determine the direct involvement of HSPD1 in the development of DCM. By Sanger method, we found a point mutation (Thr320Ala) in the apical domain of HSPD1, in one familial DCM patient, which was four amino acids away from the point mutation (Val324Glu) in the nbl mutant zebrafish. The nbl mutants showed atrio-ventricular block and sudden death at 8-month post-fertilization. Histological and microscopic analysis of the nbl mutant hearts showed decreased ventricular wall thickness, elevated level of reactive oxygen species (ROS), increased fibrosis, mitochondrial damage, and increased autophagosomes. mRNA and protein expression of autophagy-related genes significantly increased in nbl mutants. We established HEK293 stable cell lines of wild-type, nbl-type, and DCM-type HSPD1, with tetracycline-dependent expression. Compared to wild-type, both nbl- and DCM-type cells showed decreased cell growth, increased expression of ROS and autophagy-related genes, inhibition of the activity of mitochondrial electron transport chain complexes III and IV, and decreased mitochondrial fission and fusion. Mutations in HSPD1 caused mitochondrial dysfunction and induced mitophagy. Mitochondrial dysfunction caused increased ROS and cardiac atrophy.

Inflammation due to Chronic Alcohol Exposure Promotes Cardiac Atrophy and Dysfunction Resulting from Impaired Fibroblast‐Myocyte Crosstalk

Alcoholic cardiomyopathy (ACM) is a cardiac disease caused by chronic heavy alcohol abuse. ACM is most notably a type of dilated cardiomyopathy (DCM), accounting for approximately 21–50% of all idiopathic non‐ischemic DCM cases in Western countries. ACM is typically characterized by left ventricular dilation and LV muscle wasting (atrophy), with diastolic and systolic dysfunction (ejection fraction &lt; 40%) occurring in later stages. Previous studies in our lab have shown that chronic alcohol exposure prevents compensatory hypertrophy in both volume‐ and pressure‐overload models of heart failure. However, the mechanisms of alcohol‐induced cardiac atrophy and dysfunction are not clear. The purpose of this study was to investigate mechanisms of chronic alcohol‐induced cardiac remodeling and dysfunction. We also sought to determine the role of cardiac fibroblasts, which play a dynamic role in cardiac remodeling, in mediating these effects.Adult male Wistar rats were exposed to ethanol (EtOH) vapor inhalation for 16 weeks. Echocardiography was performed to assess terminal cardiac structure and function. Cardiac fibroblasts were isolated from the left ventricle (LV) for both ex vivo and in vitro analysis. Gene expression was determined by real‐time PCR and flow cytometry. Protein expression was determined via Western blot analysis. EtOH led to cardiac wall thinning and impaired systolic function, as evident by decreased LV wall thickness at diastole (LVPWd) and fractional shortening, respectively, Additionally, EtOH decreased mRNA levels of various contractile proteins including Acta1, Actc1, and Myh7. EtOH also increased mRNA and protein levels of LV inflammatory markers, TNF‐α and NF‐κB. Furthermore, EtOH induced increased activation of JNK and decreased mTOR activation, suggestive of decreased hypertrophic signaling and atrophy. EtOH led to myofibroblast activation as assessed by flow cytometry and led to ECM remodeling (increased collagen III content). EtOH increased Tnf and Il6 mRNA in cardiac fibroblasts ex vivo, and increased mRNA levels of several pro‐inflammatory cytokines and chemokines in vitro. Administration of conditioned media from EtOH‐treated fibroblasts decreased contractile protein mRNA levels and impaired Akt and mTOR signaling in differentiated H9C2 cardiomyocytes.Our results indicate that EtOH‐induced cardiac atrophy and dysfunction is associated with activation of inflammatory pathways. Furthermore, EtOH may induce a pro‐inflammatory cardiac fibroblast phenotype, leading to aberrant fibroblast‐myocyte cross‐talk.Support or Funding InformationFunding provided by the NIH/NIAAA 1R21AA022690 (JDG) and the Saving tiny Hearts Society (JDG).

Doxorubicin Cardiotoxicity in Young Tumor‐Bearing Mice

BackgroundChildhood cancer survivors have about 15‐times higher risk of heart failure than their siblings mainly due to the cardiotoxicity of chemotherapy. Nearly 50% of pediatric cancer patients receive doxorubicin (DOX) which is known to be cardiotoxic. DOX‐induced cardiotoxicity had been extensively studied in tumor‐free mouse models. The objective of the current study is to characterize a juvenile tumor‐bearing immunocompetent mouse model of DOX‐induced cardiotoxicity.MethodsJuvenile five‐week old male C57Bl/6 mice were injected subcutaneously with EL4 lymphoma cells (5X104 cells/mouse) in the flank region suspended in sterile PBS, while tumorfree mice were only injected with sterile PBS. One week after tumor implantation, both tumorfree and tumor‐bearing mice were injected intraperitoneally with either a clinically relevant dose of DOX (4 mg/kg/week) or saline for 3 weeks. One week after the last DOX injection, mice were euthanized and the hearts and tumors were harvested and weighed. Gene expression of molecular markers of cardiotoxicity and inflammation was quantified using real‐time PCR.ResultsDOX 4 mg/kg/week for 3 weeks significantly reduced tumor weights in EL4 tumor‐bearing mice. DOX administration caused significant cardiac atrophy in tumor‐free and tumor‐bearing mice. Moreover, tumor itself caused a significant reduction in heart weight compared to tumor‐free mice. Additionally, DOX administration induced the expression of markers of cardiotoxicity, ANP and BNP, in both tumor‐free and tumor‐bearing mice. Saline‐treated tumor‐bearing mice demonstrated higher expression of TNF‐alpha, an inflammatory marker, compared to tumor‐free mice.ConclusionWe have established a juvenile tumor‐bearing immunocompetent mouse model to investigate DOX‐induced cardiotoxicity. Our tumor‐bearing mouse model will optimize our understanding of the interplay between tumor and DOX‐induced cardiotoxicity. Additionally, this clinically relevant model will be used for investigation of cardioprotective strategies that mitigate DOX cardiotoxicity without compromising its chemotherapeutic efficacy before translating to the clinical settings.Support or Funding InformationResearch was supported by the National Institutes of Health’s National Center for Advancing Translational Sciences, grant UL1TR002494, and by a grant from the St. Baldrick’s Foundation [B.N.Z.]. B.N.Z. is a Masonic Cancer Center Women’s Health Scholar, sponsored by the Masonic Cancer Center, and administered by the University of Minnesota Women’s Health Research Program.

Reductions in Cardiac Structure and Function 24 Months After Spinal Cord Injury

Smaller heart structures and reduced cardiac function are documented in cross‐sectional comparisons of individuals with spinal cord injury (SCI) and age/weight matched able bodied controls. The smaller heart structures and reduced function may result from progressive cardiac atrophy similar to that observed with diminished physical activity, extended periods of bed rest, and space flight. It is unknown if there is progressive cardiac atrophy in the months following SCI. Additionally, slightly larger hearts and greater retention of function are found in individuals with thoracic compared to cervical injuries, suggesting that the level of spinal injury may differentially affect reductions in heart structure and function after SCI. Therefore, the purpose of this research was to 1) quantify cardiac structure and function of individuals within the first 24 months after injury, 2) identify the relationship between cardiac structure and function and time since injury, and 3) examine injury level’s effect on heart structure/function and time since injury. A cross‐sectional assessment of cardiac structure and function was made using transthoracic echocardiography (Vivid‐Q; GE Healthcare) on twenty‐nine (4F) volunteers who were 3‐ to 24‐months post‐injury. Myocardial structure and function were assessed using 2D, speckle‐tracking, and tissue Doppler in accordance with contemporary clinical echocardiographic guidelines. Heart rate and blood pressures were assessed simultaneously using a combination of a standard lead II electrocardiogram (ECG) and brachial oscillometric blood pressure monitor (Dash 5000 patient monitor, GE). The relationship between cardiac structure/function and time since injury were analyzed using linear regression. Neurological and sensory level of injury were entered into the model as covariates to determine whether or not the relationships differed with time since injury. Time since injury was most strongly associated with a reduction in left ventricular end‐diastolic volume (Δ= −2.07±0.70 ml·mo−1, r2=0.266, p=0.007), end‐systolic volume (Δ= −1.05±0.38 ml·mo−1, r2=0.237, p=0.012), and left ventricular mass (Δ= −3.0 ± 1.2 g·mo−1, r2=0.192, p=0.018). These changes in left ventricular structure were paralleled by a reduced stroke volume (Δ= −1.03±0.50 ml·mo−1, r2=0.154 p=0.048) and cardiac output (Δ= −0.12±0.04 L·min−1·mo−1, r2=0.322, p=0.002). There were no significant associations of blood pressures, wall thickness, or measures of diastolic function with time since injury (p&gt;0.050). The reductions in left ventricular structure and systolic function were not differentially affected by neurological or sensory level of injury (p= 0.412–0.973). These results suggest there are gradual reductions in left ventricular structure and systolic function over the 24 months following spinal cord injury which are not affected by the neurological or sensory level of injury. Although there is loss of left ventricular structure and function, blood pressure appears maintained suggesting peripheral compensatory adjustments. This information indicates that cardiac rehabilitation interventions should occur relatively soon after spinal cord injury to mitigate cardiac atrophy.Support or Funding InformationFunded by NIH Grant (R01‐HL‐117037) and The Spaulding Research Institute Leadership Catalyst

Neurohypophyseal hormones and skeletal muscle: a tale of two faces.

The neurohypophyseal hormones vasopressin and oxytocin were invested, in recent years, with novel functions upon striated muscle, regulating its differentiation, trophism, and homeostasis. Recent studies highlight that these hormones not only target skeletal muscle but represent novel myokines. We discuss the possibility of exploiting the muscle hypertrophying activity of oxytocin to revert muscle atrophy, including cancer cachexia muscle wasting. Furthermore, the role of oxytocin in cardiac homeostasis and the possible role of cardiac atrophy as a concause of death in cachectic patients is discussed.

Long-Term Outcome of LVAD in Duchenne Population with End Stage Cardiomyopathy

The aim of this study was to report the effect of long-term use of VAD in patients affected by Duchenne Muscular Distrophy and end stage cardiomyopathy. We collected data of DMD patients with end-stage cardiomyopathy implanted with LVAD in our center (group 1) and the ones in regular follow-up not eligible for LVAD implantation (group 2). Each patient of group 1 underwent extensive pre-operative assessment, in-hospital treatment and was enrolled in a dedicated DMD HF (heart failure) clinic during the post-discharge period. Patients of group 2 were followed in a dedicated DMD HF clinic or as inpatient in case of need of inotropic support. During long-term follow-up all data were recorded including echocardiography, ECG examination, laboratory blood tests, and respiratory function. Survival was represented by Kaplan Meier analysis and compared by log rank. A total of 8 DMD patients (group 1) were implanted with LVAD and treated at our center during the period from 2011 until 2018 (mean age at implantation was 16.9 ± 2.9 years)¸ whilst 4 patients (group 2) were not eligible for LVAD implantation. At the time of the last follow-up, 4 out of 8 patients were alive and 2 out of 8 patients did not have post-operative complications. The principal causes of 3 deaths at the median follow-up of 22 months were sepsis, tracheal bleeding, and cerebral hemorrhage. After 1 year from implantation we noticed a significant decrease in heart rate (p=0.002), in LV volumes and diameters (LVEDD p=0.03, LVESD p=0.02, EDV p=0.01 and ESV p=0.02) and significant increase in ejection fraction (p=0.0036). However, relative wall thickness did not change over time, showing an eccentric remodeling pattern before and after LVADs. Analysis on short and long-term follow-up showed significant improvement of survival in DMD patients treated with LVAD compared to the group that was not implanted (log rank&lt0.001), with a 5-year increase in life expectancy. Our data showed that cardiac atrophy is persistent in Duchenne cardiomyopathy despite the improvement of EF due to a significant ventricular unloading coupled with chronic therapy. LVAD improved outcomes in patients with LVAD when compared to those without. An integration of outpatient DMD HF clinic and patient-centered palliative care will most likely increase the quality of life and delivery of care for this population.

Angiotensin-(1-7) Receptor Mas Deficiency Does Not Exacerbate Cardiac Atrophy Following High-Level Spinal Cord Injury in Mice.

Experimental spinal cord injury (SCI) causes a morphological and functional deterioration of the heart, in which the renin–angiotensin system (RAS) might play a role. The recently discovered non-canonical axis of RAS with angiotensin-(1–7) and its receptor Mas, which is associated with cardioprotection could be essential to prevent damage to the heart following SCI. We investigated the cardiac consequences of SCI and the role of Mas in female wild-type (WT, n = 22) and mice deficient of Mas (Mas–/–, n = 25) which underwent spinal cord transection at thoracic level T4 (T4-Tx) or sham-operation by echocardiography (0, 7, 21, and 28 days post-SCI), histology and gene expression analysis at 1 or 2 months post-SCI. We found left ventricular mass reduction with preserved ejection fraction (EF) and fractional shortening in WT as well as Mas–/– mice. Cardiac output was reduced in Mas–/– mice, whereas stroke volume (SV) was reduced in WT T4-Tx mice. Echocardiographic indices did not differ between the genotypes. Smaller heart weight (HW) and smaller cardiomyocyte diameter at 1 month post-SCI compared to sham mice was independent of genotype. The muscle-specific E3 ubiquitin ligases Atrogin-1/MAFbx and MuRF1 were upregulated or showed a trend for upregulation in WT mice at 2 months post-SCI, respectively. Angiotensinogen gene expression was upregulated at 1 month post-SCI and angiotensin II receptor type 2 downregulated at 2 month post-SCI in Mas–/– mice. Mas was downregulated post-SCI. Cardiac atrophy following SCI, not exacerbated by lack of Mas, is a physiological reaction as there were no signs of cardiac pathology and dysfunction.

Doxorubicin induces cardiomyocyte apoptosis and atrophy through cyclin-dependent kinase 2–mediated activation of forkhead box O1

Recent clinical investigations indicate that anthracycline-based chemotherapies induce early decline in heart mass in cancer patients. Heart mass decline may be caused by a decrease in cardiac cell number because of increased cell death or by a reduction in cell size because of atrophy. We previously reported that an anthracycline, doxorubicin (DOX), induces apoptotic death of cardiomyocytes by activating cyclin-dependent kinase 2 (CDK2). However, the signaling pathway downstream of CDK2 remains to be characterized, and it is also unclear whether the same pathway mediates cardiac atrophy. Here we demonstrate that DOX exposure induces CDK2-dependent phosphorylation of the transcription factor forkhead box O1 (FOXO1) at Ser-249, leading to transcription of its proapoptotic target gene, Bcl-2-interacting mediator of cell death (Bim). In cultured cardiomyocytes, treatment with the FOXO1 inhibitor AS1842856 or transfection with FOXO1-specific siRNAs protected against DOX-induced apoptosis and mitochondrial damage. Oral administration of AS1842856 in mice abrogated apoptosis and prevented DOX-induced cardiac dysfunction. Intriguingly, pharmacological FOXO1 inhibition also attenuated DOX-induced cardiac atrophy, likely because of repression of muscle RING finger 1 (MuRF1), a proatrophic FOXO1 target gene. In conclusion, DOX exposure induces CDK2-dependent FOXO1 activation, resulting in cardiomyocyte apoptosis and atrophy. Our results identify FOXO1 as a promising drug target for managing DOX-induced cardiotoxicity. We propose that FOXO1 inhibitors may have potential as cardioprotective therapeutic agents during cancer chemotherapy.