Myocardial Mitochondria Research Articles

Effect and interaction of PINK1 genetic polymorphisms and environmental factors on blood pressure in COEs-exposed workers

ABSTRACT Coke oven emissions (COEs) contain a variety of polycyclic aromatic hydrocarbons (PAHs), which can cause damage to the human cardiovascular system. In addition, myocardial mitochondria are susceptible to damage in hypertensive patients. However, it is not clear whether genetic variation, in single nucleotide polymorphisms (SNPs) in PINK1 affects COEs exposure-induced abnormal blood pressure. We surveyed and tested 518 workers exposed to COEs and statistically analyzed them with SPSS 21.0 software. SBP was greater in the high-exposure group than in the low-exposure group. Generalized linear model analysis showed that the interaction of PINK1 rs3738136 (GA+AA) and COEs had an effect on SBP [β(95%CI) = -6.537(−12.072, −1.002), p = 0.021] and DBP [β(95%CI) = -4.811(−8.567, −1.056), p = 0.012]. This study is the first to identify the role of PINK1 rs3738136 in COE- induced abnormal blood pressure, and to prove that the abnormal blood pressure of workers is the result of environmental and genetic factors.

Alcohol exposure during pregnancy induces cardiac mitochondrial damage in offspring mice.

Prenatal alcohol exposure (PAE) has been linked to congenital heart disease and fetal alcohol syndrome. The heart primarily relies on mitochondria to generate energy, so impaired mitochondrial function due to alcohol exposure can significantly affect cardiac development and function. Our study aimed to investigate the impact of PAE on myocardial and mitochondrial functions in offspring mice. We administered 30% alcohol (3 g/kg) to pregnant C57BL/6 mice during the second trimester. We assessed cardiac function by transthoracic echocardiography, observed myocardial structure and fibrosis through staining tests and electron transmission microscopy, and detected cardiomyocyte apoptosis with dUTP nick end labeling assay and real-time quantitative PCR. Additionally, we measured the reactive oxygen species content, ATP level, and mitochondrial DNA copy number in myocardial mitochondria. Mitochondrial damage was evaluated by assessing the level of mitochondrial membrane potential and the opening degree of mitochondrial permeability transition pores. Our findings revealed that PAE caused cardiac systolic dysfunction, ventricular enlargement, thinned ventricular wall, cardiac fibrosis in the myocardium, scattered loss of cardiomyocytes, and disordered arrangement of myocardial myotomes in the offspring. Furthermore, we observed a significant increase in mitochondrial reactive oxygen species content, a decrease in mitochondrial membrane potential, ATP level, and mitochondrial DNA copy number, and sustained opening of mitochondrial permeability transition pores in the heart tissues of the offspring. These results indicated that PAE had adverse effects on the cardiac structure and function of the newborn mice and could trigger oxidative stress in their myocardia and contribute to mitochondrial dysfunction.

Mitochondrial Kinase Signaling for Cardioprotection.

Myocardial ischemia/reperfusion injury is reduced by cardioprotective adaptations such as local or remote ischemic conditioning. The cardioprotective stimuli activate signaling cascades, which converge on mitochondria and maintain the function of the organelles, which is critical for cell survival. The signaling cascades include not only extracellular molecules that activate sarcolemmal receptor-dependent or -independent protein kinases that signal at the plasma membrane or in the cytosol, but also involve kinases, which are located to or within mitochondria, phosphorylate mitochondrial target proteins, and thereby modify, e.g., respiration, the generation of reactive oxygen species, calcium handling, mitochondrial dynamics, mitophagy, or apoptosis. In the present review, we give a personal and opinionated overview of selected protein kinases, localized to/within myocardial mitochondria, and summarize the available data on their role in myocardial ischemia/reperfusion injury and protection from it. We highlight the regulation of mitochondrial function by these mitochondrial protein kinases.

Improving lysosomal ferroptosis with NMN administration protects against heart failure.

Myocardial mitochondria are primary sites of myocardial energy metabolism. Mitochondrial disorders are associated with various cardiac diseases. We previously showed that mice with cardiomyocyte-specific knockout of the mitochondrial translation factor p32 developed heart failure from dilated cardiomyopathy. Mitochondrial translation defects cause not only mitochondrial dysfunction but also decreased nicotinamide adenine dinucleotide (NAD+) levels, leading to impaired lysosomal acidification and autophagy. In this study, we investigated whether nicotinamide mononucleotide (NMN) administration, which compensates for decreased NAD+ levels, improves heart failure because of mitochondrial dysfunction. NMN administration reduced damaged lysosomes and improved autophagy, thereby reducing heart failure and extending the lifespan in p32cKO mice. We found that lysosomal damage due to mitochondrial dysfunction induced ferroptosis, involving the accumulation of iron in lysosomes and lipid peroxide. The ameliorative effects of NMN supplementation were found to strongly affect lysosomal function rather than mitochondrial function, particularly lysosome-mediated ferroptosis. NMN supplementation can improve lysosomal, rather than mitochondrial, function and prevent chronic heart failure.

Irisin deficiency exacerbates diet-induced insulin resistance and cardiac dysfunction in type II diabetes in mice.

Irisin is involved in the regulation of a variety of physiological conditions, metabolism, and survival. We and others have demonstrated that irisin contributes critically to modulation of insulin resistance and the improvement of cardiac function. However, whether the deletion of irisin will regulate cardiac function and insulin sensitivity in type II diabetes remains unclear. We utilized the CRISPR/Cas-9 genome-editing system to delete irisin globally in mice and high-fat diet (HFD)-induced type II diabetes model. We found that irisin deficiency did not result in developmental abnormality during the adult stage, which illustrates normal cardiac function and insulin sensitivity assessed by glucose tolerance test in the absence of stress. The ultrastructural analysis of the transmission electronic microscope (TEM) indicated that deletion of irisin did not change the morphology of mitochondria in myocardium. Gene expression profiling showed that several key signaling pathways related to integrin signaling, extracellular matrix, and insulin-like growth factors signaling were coordinately downregulated by deletion of irisin. However, when mice were fed a high-fat diet and chow food for 16 wk, ablation of irisin in mice exposed to HFD resulted in much more severe insulin resistance, metabolic derangements, profound cardiac dysfunction, and hypertrophic response and remodeling as compared with wild-type control mice. Taken together, our results indicate that the loss of irisin exacerbates insulin resistance, metabolic disorders, and cardiac dysfunction in response to HFD and promotes myocardial remodeling and hypertrophic response. This evidence reveals the molecular evidence and the critical role of irisin in modulating insulin resistance and cardiac function in type II diabetes.NEW & NOTEWORTHY By utilizing the CRISPR/Cas-9 genome-editing system and high-fat diet (HFD)-induced type II diabetes model, our results provide direct evidence showing that the loss of irisin exacerbates cardiac dysfunction and insulin resistance while promoting myocardial remodeling and a hypertrophic response in HFD-induced diabetes. This study provides new insight into understanding the molecular evidence and the critical role of irisin in modulating insulin resistance and cardiac function in type II diabetes.

Rational Engineering of a Mitochondrial‐Mimetic Therapy for Targeted Treatment of Dilated Cardiomyopathy by Precisely Regulating Mitochondrial Homeostasis

AbstractDilated cardiomyopathy (DCM) is a leading cause of heart failure and the most common indication for heart transplantation. Currently, there is still an unmet clinical need in effective therapies for DCM. Herein a mitochondrial‐mimetic therapy capable of efficiently targeting the heart, cardiomyocytes, and myocardial mitochondria as well as effectively regulating mitochondrial homeostasis for targeted treatment of DCM is reported. A bioactive conjugate TPT is first synthesized by integrating three functional moieties onto a scaffold, which can assemble into small‐size nanomicelles (i.e., TPTN). Intravenously delivered TPTN efficiently accumulates in the heart and mainly localizes in cardiomyocytes and myocardial mitochondria of DCM mice, thereby alleviating DCM. Mechanistically, TPTN inhibits intracellular oxidative stress, alleviates mitochondrial injury, improves mitochondrial dynamics, regulates mitochondrial oxidative phosphorylation, and reduces calpain‐1 and NLRP3 inflammasome activation, thus restoring mitochondrial homeostasis and inhibiting adverse cardiac remodeling. By packaging TPTN into outer mitochondrial membrane‐derived vesicles, a mitochondrial‐mimetic therapy is engineered, which displays significantly enhanced three‐level targeting capability to the heart, cardiac cells, and myocardial mitochondria, thereby affording notably potentiated therapeutic effects in DCM mice. Accordingly, the three‐level targeting mimetics is promising for targeted treatment of DCM. The findings provide new insight into rational design of precision therapies for mitochondrial dysfunction‐associated diseases.

Effects and mechanism of perinatal nonylphenol exposure on cardiac function and myocardial mitochondria in neonatal rats

BackgroundNonylphenol (NP) is a common environmental endocrine disruptor that is associated with the development of cardiovascular disease. However, the toxic effect of NP on mitochondria in the heart of offspring to exposed individuals remains exclusive. ObjectiveTo investigate whether perinatal NP exposure causes mitochondrial damage in the hearts of offspring of exposed individuals and determine its mechanism of action through both animal and cell experiments. Methods and resultsFor the in vivo experiment, pregnant rats were randomly divided into four groups: the control group (corn oil, C), low dose group (2.5 mg/kg/day, L-NP group), medium dose group (50 mg/kg/day, M-NP group), and high dose group (100 mg/kg/day, H-NP group), with 12 rats in each group. The NP concentration in the hearts of offspring at PND21 and PND90 increased with the increase of the NP dose. Perinatal NP exposure induced a gradual increase in systolic blood pressure in offspring at PND90. In the H-NP group, there was a high degree of inflammatory cell infiltration, myofibril breaks, inconspicuous or absent nuclei, and pink collagen deposition. At PND90, the membrane integrity of mitochondria in the H-NP group was disrupted, the cristae disorder was aggravated, and there was internal lysis with vacuolation. Compared to the control group, the mitochondrial membrane potential of offspring at PND21 and PND90 was decreased in each of the NP exposure groups. NP exposure decreased the activity of mitochondrial respiratory enzyme complex I (CI) and increased the activity of mitochondrial respiratory enzyme complex IV (CIV) in the offspring. At PND21 and PND90, the mRNA and protein expression levels of cardiac mitochondrial PGC-1α, NRF-1, and TFAM decreased with increasing NP dose in a dose-dependent manner. In the in vitro experiment, H9C2 cells were divided into the following four groups: the blank group, RSV group (15 μg/ml), RSV + NP group (15 μg/ml RSV + 120 mmol/L NP), and NP group (120 mmol/L). With increasing NP concentration, the cell survival rate gradually decreased. Compared to the control, the membrane potential was significantly decreased in the NP group; the protein expression levels of SIRT1, PGC-1α, NRF-1, and TFAM in the NP group were significantly lower. ConclusionPerinatal NP exposure caused mitochondrial damage and dysfunction in the offspring of exposed individuals in a dose-dependent manner. This toxic effect may be related to NP-induced mitochondrial pathology in the offspring and the inhibition of both gene and protein expression involved in the PGC-1α/NRF-1/TFAM mitochondrial biogenesis signaling pathway following NP exposure.

Sodium Glucose Cotransporter 2 (SGLT2) Inhibitor Ameliorate Metabolic Disorder and Obesity Induced Cardiomyocyte Injury and Mitochondrial Remodeling.

Sodium-glucose transporter 2 inhibitors (SGLT2is) exert significant cardiovascular and heart failure benefits in type 2 diabetes mellitus (DM) patients and can help reduce cardiac arrhythmia incidence in clinical practice. However, its effect on regulating cardiomyocyte mitochondria remain unclear. To evaluate its effect on myocardial mitochondria, C57BL/6J mice were divided into four groups, including: (1) control, (2) high fat diet (HFD)-induced metabolic disorder and obesity (MDO), (3) MDO with empagliflozin (EMPA) treatment, and (4) MDO with glibenclamide (GLI) treatment. All mice were sacrificed after 16 weeks of feeding and the epicardial fat secretome was collected. H9c2 cells were treated with the different secretomes for 18 h. ROS production, Ca2+ distribution, and associated proteins expression in mitochondria were investigated to reveal the underlying mechanisms of SGLT2is on cardiomyocytes. We found that lipotoxicity, mitochondrial ROS production, mitochondrial Ca2+ overload, and the levels of the associated protein, SOD1, were significantly lower in the EMPA group than in the MDO group, accompanied with increased ATP production in the EMPA-treated group. The expression of mfn2, SIRT1, and SERCA were also found to be lower after EMPA-secretome treatment. EMPA-induced epicardial fat secretome in mice preserved a better cardiomyocyte mitochondrial biogenesis function than the MDO group. In addition to reducing ROS production in mitochondria, it also ameliorated mitochondrial Ca2+ overload caused by MDO-secretome. These findings provide evidence and potential mechanisms for the benefit of SGLT2i in heart failure and arrhythmias.

Abstract 3209: Metabolic characterization of radiation-induced cardiotoxicity

Abstract Background: Approximately 50% of all cancer patients receive radiation therapy as a component of their cancer care. While radiation therapy has demonstrable benefit in improving survival in patients, radiation-induced heart disease (RIHD) is a major contributor to morbidity and mortality in cancer survivors with history of thoracic radiation. Understanding metabolic changes underlying RIHD may enable development of novel diagnostic and therapeutic approaches for early detection and treatment of RIHD. The high energetic demands of the heart require properly functioning mitochondria to meet the ATP production needs. Fatty acids are the primary metabolic substrates for energy production in a healthy heart. However, under conditions of stress, the cardiac metabolism shifts towards increased glucose utilization. In this study, we characterize the impact of radiation of cardiac substrate utilization and energy production. Methods: Pre-clinical RIHD models were established by administering whole heart radiation (8Gy x 5) in mice and rats followed by structural and biochemical characterization. Transmission electron microscopy and western blot analyses were used to characterize structural and biochemical changes in the heart in response to radiation. Spectrophotometric assays and Western blot analyses were used to characterize changes in pyruvate dehydrogenase (PDH) activity and function in the heart in response to radiation. Results: Our studies identified myocardial mitochondrial dysfunction as an early event following exposure of heart to radiation. Cardiac irradiation resulted in increased mitochondrial fusion and higher expression of MFN1, a key protein that mediates mitochondrial fusion. The pathological structural and biochemical changes in the myocardial mitochondria are associated with reduced glucose metabolism due to impaired PDH activity. This decline was mediated by increased phosphorylation of PDH in irradiated hearts, which inhibits its activity. Conclusion: Cardiac irradiation results in early metabolic dysregulation, especially in glucose metabolism, which may be exploited for early detection and mitigation of radiation-induced cardiotoxicity. Citation Format: Sarah C. Elliott, Jayesh Sharma, Elizabeth R. Zhang-Velten, Abdallah Elnwasany, Chantal Vidal, Luke Szweda, Prasanna Alluri. Metabolic characterization of radiation-induced cardiotoxicity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3209.

Resveratrol Reestablishes Mitochondrial Quality Control in Myocardial Ischemia/Reperfusion Injury through Sirt1/Sirt3-Mfn2-Parkin-PGC-1α Pathway.

Resveratrol is a natural polyphenol found in various plants. It has been widely studied on cardiovascular disorders. It is known that resveratrol can activate Sirtuin proteins and participate in cellular energy metabolism through a Sirtuin-dependent pathway. Here, we hypothesized that resveratrol may protect against myocardial ischemia/reperfusion injury (MIRI) through the target of Sirt1/Sirt3 on mitochondrial dynamics, cardiac autophagy, bioenergetics and oxidative damage in hypoxia/reoxygenation (H/R)-induced neonatal rat cardiomyocytes. We observed that resveratrol could activate the Sirt1/Sirt3-FoxO pathway on myocardial mitochondria in H/R cardiomyocytes. Subsequently, we found that resveratrol repaired the fission–fusion balance, autophagic flux and mitochondrial biosynthesis compared by H/R group. These changes were followed by increased functional mitochondrial number, mitochondrial bioenergetics and a better mitochondrial antioxidant enzyme system. Meanwhile, these effects were antagonized by co-treatment with Selisistat (Ex527), a Sirtuin inhibitor. Together, our findings uncover the potential contribution of resveratrol in reestablishing a mitochondrial quality control network with Parkin, Mfn2 and PGC-1α as the key nodes.

Harm of circadian misalignment to the hearts of the adolescent wistar rats

PurposeThe purpose of this study was to observe the harm of circadian misalignment (CM), caused by an inverted photoperiod (IP), on the hearts of the adolescent Wistar rats, and to explore the mechanisms leading to harm.MethodsAn IP was used to create a CM model. A total of 174 Wistar rats were randomly divided into circadian alignment (CA) and CM groups (87 rats per group). The different activity rhythms of the two groups of rats were adjusted through different light/dark cycles for 90 days. We recorded the rhythmic activity trajectory and sleep time of the rats. After 90 days of modeling, we performed various analyses (i.e., blood pressure, weight, cardiac ultrasound tests, serological tests, cardiac tissue immunofluorescence, immunohistochemistry, transmission electron microscopy on myocardial mitochondria, western blotting, and quantitative polymerase chain reactions).Results(1) The IP protocol caused CM in rats. (2) CM rats showed significantly higher blood pressure during the day (resting phase). They also showed significantly higher serum levels of angiotensin II and epinephrine during the day compared to the CA rats. (3) CM caused up-regulation of gene expression of adrenergic receptors α1 (α1-AR) and β1 (β1-AR) and down-regulation of the glucocorticoid receptor (Gr) gene expression in rat hearts. It also caused downregulation of Bmal1 expression. In addition, the changes in Bmal1 and Per2 correlated with the changes in β1-AR and α1-AR. (4) CM had adverse effects on multiple molecular proteins of the heart. (5) CM increased the collagen fibers in the rat heart and increased the destruction of mitochondria. (6) Eventually, CM caused a decrease in the pumping function of the heart and decreased the coronary blood flow rate.Conclusions(1) CM significantly affected the cardiac structure and function in the adolescent rats through a variety of mechanisms. (2) CM can regulate the expression of myocardial clock genes, and it is likely to have an impact on the heart through this pathway.

Abstract P2073: Rbx2-CRL5 Mediates Mitochondrial Ubiquitination And Mitophagy To Maintain Myocardial Homeostasis Independent Of Parkin

The ubiquitin (Ub) ligase Parkin has been recognized as a central player in mitophagy. In contrast to its presumed importance in the heart, ablation of Parkin fails to impact homeostatic mitophagy and cardiac function in both young and aging mice, suggesting compensation from other mitochondrial Ub ligases. However, the identities of such additional mitochondrial Ub ligases, as well as their physiological significance in the heart, remain unclear. Here, we demonstrate that Cullin-RING Ub ligase 5 (CRL5) plays a key role in the control of mitochondrial homeostasis in cardiomyocytes. CRL5 belongs to the family of Cullin-RING Ub ligases (CRLs) and consists of the RING box protein RBX2, scaffold protein Cullin 5 (Cul5), and one of 38 substrate receptor proteins. Analysis of the mitochondrial outer membrane-interacting proteome revealed a robust association of CRLs with mitochondria. Pharmacological and genetic perturbations of CRLs inhibited mitochondrial ubiquitination and mitophagy. Subcellular fractionation, live-cell imaging and immunogold electron microscopy further revealed that RBX2 and Cul5, two core components of CRL5, are quickly recruited to mitochondria upon mitochondrial depolarization. Depletion of RBX2 or Cul5 inhibited mitochondrial ubiquitination and turnover, impaired mitochondrial function, and increased cell death in cardiomyocytes. Importantly, RBX2 deficiency did not alter Parkin expression, had a more robust inhibitory effect on mitochondrial ubiquitination compared to Parkin deficiency, and remained effective in the absence of Parkin. Moreover, loss of RBX2 attenuated Parkin-mediated ubiquitination, suggesting its dominant, Parkin-independent actions in mitochondria. In vivo , deletion of RBX2 in adult mouse hearts suppressed mitophagic activity and provoked accumulation of damaged mitochondria in myocardium, leading to rapid development of dilated cardiomyopathy and heart failure. Finally, RBX2 was upregulated in pressure overloaded mouse hearts but downregulated in human failing hearts, further supporting its protective role in the heart. Taken together, our data allow us to propose RBX2-CRL5 as a mitochondrial Ub ligase and a physiological regulator of mitochondrial and cardiac integrity.

Abstract 3659: Early in vivo detection of radiation-induced cardiotoxicity

Abstract Background: Radiation-Induced Heart Disease (RIHD) is a major source of morbidity and mortality in patients receiving thoracic radiation, which is a common treatment for malignancies like lung cancer. There is currently no standardized program for follow-up of RIHD in cancer survivors. Therefore, there is an acute need for developing detection of RIHD at a stage that offers potential for early intervention and reversibility. The gold standard for detection of global cardiac dysfunction is echocardiography. However, this current paradigm detects cardiac changes in metrics such as Left Ventricular Ejection Fraction (LVEF), which are relatively late manifestations in the pathology of cardiotoxicity, decreasing the possibility of reversing such damage. We sought to assess radiation-induced changes significantly earlier than the current standard of care by measuring the efficiency of the tricarboxylic acid cycle in cardiac mitochondria; we hypothesized that radiation leads to impaired mitochondrial function, causing increased conversion of pyruvate to lactate in the cytosol and decreased conversion in the mitochondria. In order to non-invasively measure this impairment, we utilized Magnetic Resonance Spectroscopy (MRS) to track the fate of hyperpolarized (HP) C-13 pyruvate. Methods: Sprague-Dawley rats underwent baseline and post treatment echocardiography and HP C-13 pyruvate MRS at multiple timepoints. Half of the animals underwent image-guided cardiac radiation with cone-beam CT, to a total dose of 40 Gy in 5 fractions, a paradigm similar to a common dose given to lung cancer patients. Results: In the cardiac radiation group, C-13 pyruvate MRS demonstrated a statistically significant decrease in cardiac function (determined by bicarbonate-to-lactate ratio in myocardial mitochondria) compared to pre-radiation baseline (p=0.02, one-tailed paired t-test) as early as 1 week post treatment. No significant decrease in this ratio was observed in the non-irradiated, age matched controls (p=0.95). Comparatively, no significant changes in LVEF or global longitudinal strain were observed in either the cardiac irradiation or control group of rats until 2 months post treatment. Conclusion: Radiation-induced myocardial mitochondrial dysfunction is an early event that can be characterized and detected in vivo by hyperpolarized C-13 pyruvate MRS within 1 week after radiation prior to onset of echocardiographic changes. For the first time, we have demonstrated feasibility of employing HP C-13 pyruvate MRS for detecting radiation-induced myocardial mitochondrial metabolic changes in a pre-clinical rat model. This technology has the potential to serve as a platform for building radiation-focused cardio-oncology programs for early detection and mitigation of radiation-induced cardiac injury in hundreds of thousands of patients receiving thoracic radiation annually. Citation Format: Jayesh Sharma, Elizabeth Zhang, Xuliang Wang, Junjie Ma, Jun Chen, Gabriele Schiattarella, Joseph Hill, Jaemo Park, Craig Malloy, Vlad Zaha, Prasanna Alluri. Early in vivo detection of radiation-induced cardiotoxicity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3659.

Effects of HIF-1α overexpression on mitochondrial function in aged mice with myocardial ischemia-reperfusion

To evaluate the effects of HIF-1α overexpression on mitochondrial function in aged mice with myocardial ischemia-reperfusion (I/R). Mice were divided into 1) Blank (Sham) group; 2) Ischemia-reperfusion (I/R) group; 3) I/R+2ME2 group (I/R+HIF-1α blocker 2ME2. Compared with Sham group, in I/R group and I/R+2ME2 group, HR slowed down, LVDP and +dp/dtmax decreased, LVEDP, myocardial infarction area, and ROS generation rate was significantly increased; whereas the mitochondrial respiratory function (State3, RCR) and mitochondrial respiratory enzyme activity (NADH-OX, Cytc-OX and SUC-OX) were significantly reduced. Compared with the I/R group, the respiratory function of myocardial mtochondria (State3, RCR) and respiratory enzyme activity of myocardial (NADH-OX, Cytc-OX and SUC-OX) were significantly reduced in the I/R+2ME2 group; and the levels of p-HIF-1α and p-VEGF in the I/R+2ME2 group were significantly decreased. HIF-1α pathway upregulate the respiratory enzyme activity of myocardial and respiratory function of I/R myocardial mitochondria.

Radiation‑induced dysfunction of energy metabolism in the heart results in the fibrosis of cardiac tissues.

Thoracic radiotherapy increases the risk of radiation-induced heart damage (RIHD); however, the molecular mechanisms underlying these changes are not fully understood. The aim of the present study was to investigate the effects of radiation on the mouse heart using high-throughput proteomics. Male C57BL/6J mice were used to establish a model of RIHD by exposing the entire heart to 16 Gy high-energy X-rays, and cardiac injuries were verified using a cardiac echocardiogram, as well as by measuring serum brain natriuretic peptide levels and conducting H&E and Masson staining 5 months after irradiation. Proteomics experiments were performed using the heart apex of 5-month irradiated mice and control mice that underwent sham-irradiation. The most significantly differentially expressed proteins were enriched in ‘cardiac fibrosis’ and ‘energy metabolism’. Next, the cardiac fibrosis and changes to energy metabolism were confirmed using immunohistochemistry staining and western blotting. Extracellular matrix proteins, such as collagen type 1 α 1 chain, collagen type III α 1 chain, vimentin and CCCTC-binding factor, along with metabolism-related proteins, such as fatty acid synthase and solute carrier family 25 member 1, exhibited upregulated expression following exposure to ionizing radiation. Additionally, the myocardial mitochondria inner membranes were injured, along with a decrease in ATP levels and the accumulation of lactic acid in the irradiated heart tissues. These results suggest that the high doses of ionizing radiation used lead to structural remodeling, functional injury and fibrotic alterations in the mouse heart. Radiation-induced mitochondrial damage and metabolic alterations of the cardiac tissue may thus be a pathogenic mechanism of RIHD.

Abstract P321: Chronic Central Nervous System Leptin Infusion Increases Cardiomyocyte Mitochondrial Function And Biogenesis And Improves Cardiac Function After Ischemia-reperfusion Injury.

Mitochondrial (MT) dysfunction plays an important role in the pathophysiology of myocardial ischemia/reperfusion injury (I/R). We recently showed that leptin, via its actions in the central nervous system (CNS), improves left ventricular (LV) function in a model of heart failure induced by permanent ligation of the left anterior descending coronary artery (LAD). In the present study, we examined if the CNS effects of leptin protect against myocardial ischemia/reperfusion (I/R) injury, and whether chronic intracerebroventricular (ICV) leptin infusion increases MT function and biogenesis in the non-infarcted area of the LV that is at risk but still viable. Male Wistar rats were instrumented with an ICV cannula in the brain lateral ventricle. After recovery and baseline assessment of cardiac function by echocardiography (ECHO), myocardial I/R was induced by temporary (60 min) ligation of the LAD. Vehicle (saline, 0.5 μL/hr) or leptin (0.62 μg/day) was infused chronically for 28 days starting 20 min after reperfusion using osmotic minipumps connected to the ICV cannula. ECHO assessment of cardiac function was performed every week. At the end of week 4, +dP/dt max and Tau were accessed by LV catheterization. Hearts were then collected for evaluation of MT function in isolated cardiac fibers using Oroboros oxygraphy-2k respirometer. ICV leptin treatment improved systolic and diastolic function as evidenced by increased ejection fraction 4 weeks after I/R (46±3 vs. 26±3 %), stroke volume (353±19 vs. 193±27 μL), +dP/dt max (10387±1686 vs. 5022±442 mmHg/s) and reduced Tau (6.5±0.3 vs. 8±0.3 ms) when compared with vehicle-treated rats. In addition, ICV leptin infusion significantly increased ATP-linked respiration (55±3 vs. 39±1 %), reduced proton leak (45±3 vs. 61±1 %), and improved MT reserve capacity (42±5 vs. 27±2 %). Improved MT function was associated with increased MT Complex I- mediated respiration (47±6 vs. 26±1 pmolO 2 /s - mg). ICV leptin treatment also increased PGC1 α protein expression and COX3 gene expression, indicating enhanced MT biogenesis. These results demonstrate that chronic ICV leptin infusion improves cardiac function following I/R injury and suggests that leptin’s CNS-mediated cardioprotective effects may involve improved myocardial MT function and biogenesis.

A Change in the Content of Endogenous Energy Substrates in Rabbit Myocardium Mitochondria Depending upon Frequency and Duration of Vibration

A Change in the Content of Endogenous Energy Substrates in Rabbit Myocardium Mitochondria Depending upon Frequency and Duration of Vibration

The Protective Effect of 1,25(OH)2D3 on Myocardial Function is Mediated via Sirtuin 3-Regulated Fatty Acid Metabolism.

Energy substrate imbalance is a major cause of cardiac dysfunction. Vitamin D/vitamin D receptor (VD/VDR) deficiency is involved in the pathogenesis of various cardiac diseases; however, the exact underlying mechanism remains unclear. The aim of this study was to investigate whether vitamin D modulates mitochondrial fatty acid oxidase via sirtuin 3 signaling to protect the myocardium. 1-Alpha-hydroxylase-defficient mice exhibited a high metabolic rate and lower myocardial contractility than wild-type mice. Sirtuin 3 upregulation was detected in high-fat diet-fed mice receiving vitamin D3 compared with that in high-fat diet-fed mice. Both sirtuin 3 blockade and knockout inhibited the VD/VDR-induced downregulation of fatty acid oxidase in myocardial mitochondria. VD/VDR suppressed fatty acid metabolism by upregulating sirtuin 3 and lowering mitochondrial fat uptake, thereby improving myocardial function and balancing energy substrates, rather than by altering fat endocytosis and exocytosis.

Effects of Zoniporide and BMA-1321 Compound on the Rate of Oxygen Absorption by Cardiomyocyte Mitochondria in Rats with Experimental Chronic Heart Failure.

Uncoupling of respiration and ATP production by myocardial mitochondria was observed in rats with chronic isoproterenol intoxication (L-isoproterenol subcutaneously, 1 mg/kg, for 10 days) in comparison with controls (injected with the solvent). Inhibitors of NHE-1 zoniporide (1 mg/kg intraperitoneally, 13 days) and BMA-1321 compound (0.92 mg/kg intraperitoneally, 13 days) improved the mitochondrial function in rats with isoproterenol-induced cardiac failure: respiratory control coefficients increased, more so for the respiratory chain complex II, the main source of ROS in heart failure. The effect of BMA-1321 was more manifest (53%; p<0.05) in comparison with zoniporide (35%; p<0.05).

Targeted inhibition of calpain in mitochondria alleviates oxidative stress-induced myocardial injury.

The protein levels and activities of calpain-1 and calpain-2 are increased in cardiac mitochondria under pathological conditions including ischemia, diabetes, and sepsis, and transgenic overexpression of mitochondrial-targeted calpain-1 induces dilated heart failure, which underscores an important role of increased calpain in mitochondria in mediating myocardial injury. However, it remains to be determined whether selective inhibition of calpain in mitochondria protects the heart under pathological conditions. In this study, we generated transgenic mice overexpressing mitochondrial-targeted calpastatin in cardiomyocytes. Their hearts were isolated and subjected to global ischemia/reperfusion. Hyperglycemia was induced in the transgenic mice by injections of STZ. We showed that transgenic calpastatin was expressed exclusively in mitochondria isolated from their hearts but not from other organs including skeletal muscle and lung tissues. Transgenic overexpression of mitochondrial-targeted calpastatin significantly attenuated mitochondrial oxidative stress and cell death induced by global ischemia/reperfusion in isolated hearts, and ameliorated mitochondrial oxidative stress, cell death, myocardial remodeling and dysfunction in STZ-treated transgenic mice. The protective effects of mitochondrial-targeted calpastatin were correlated with increased ATP5A1 protein expression and ATP synthase activity in isolated hearts subjected to global ischemia/reperfusion and hearts of STZ-treated transgenic mice. In cultured rat myoblast H9c2 cells, overexpression of mitochondrial-targeted calpastatin maintained the protein levels of ATP5A1 and ATP synthase activity, prevented mitochondrial ROS production and decreased cell death following hypoxia/reoxygenation, whereas upregulation of ATP5A1 or scavenging of mitochondrial ROS by mito-TEMPO abrogated mitochondrial ROS production and decreased cell death. These results confirm the role of calpain in myocardial injury, suggesting that selective inhibition of calpain in myocardial mitochondria by mitochondrial-targeted calpastatin is an effective strategy for alleviating myocardial injury and dysfunction in cardiac pathologies.