Cardiac Mitochondrial Dynamics Research Articles

Muscarinic and nicotinic receptors stimulation by vagus nerve stimulation ameliorates trastuzumab-induced cardiotoxicity via reducing programmed cell death in rats

Despite its efficacy in human epidermal growth factor receptor 2 positive cancer treatment, trastuzumab-induced cardiotoxicity (TIC) has become a growing concern. Due to the lack of cardiomyocyte regeneration and proliferation in adult heart, cell death significantly contributes to cardiovascular diseases. Cardiac autonomic modulation by vagus nerve stimulation (VNS) has shown cardioprotective effects in several heart disease models, while the effects of VNS and its underlying mechanisms against TIC have not been found. Forty adult male Wistar rats were divided into 5 groups: (i) control without VNS (CSham) group, (ii) trastuzumab (4 mg/kg/day, i.p.) without VNS (TSham) group, (iii) trastuzumab + VNS (TVNS) group, (iv) trastuzumab + VNS + mAChR blocker (atropine; 1 mg/kg/day, ip, TVNS + Atro) group, and (v) trastuzumab + VNS + nAChR blocker (mecamylamine; 7.5 mg/kg/day, ip, TVNS + Mec) group. Our results showed that trastuzumab induced cardiac dysfunction by increasing autonomic dysfunction, mitochondrial dysfunction/dynamics imbalance, and cardiomyocyte death including apoptosis, autophagic deficiency, pyroptosis, and ferroptosis, which were notably alleviated by VNS. However, mAChR and nAChR blockers significantly inhibited the beneficial effects of VNS on cardiac autonomic dysfunction, mitochondrial dysfunction, cardiomyocyte apoptosis, pyroptosis, and ferroptosis. Only nAChR could counteract the protective effects of VNS on cardiac mitochondrial dynamics imbalance and autophagy insufficiency. Therefore, VNS prevented TIC by rebalancing autonomic activity, ameliorating mitochondrial dysfunction and cardiomyocyte death through mAChR and nAChR activation. The current study provides a novel perspective elucidating the potential treatment of VNS, thus also offering other pharmacological therapeutic promises in TIC patients.

Fenofibrate reduces cardiac remodeling by mitochondrial dynamics preservation in a renovascular model of cardiac hypertrophy

Fenofibrate, a PPAR-α agonist clinically used to lower serum lipid levels, reduces cardiac remodeling and improves cardiac function. However, its mechanism of action is not completely elucidated. In this study we examined the effect of fenofibrate on mitochondria in a rat model of renovascular hypertension, focusing on mediators controlling mitochondrial dynamics and autophagy.Rats with two-kidney one-clip (2K1C) hypertension were treated with fenofibrate 150 mg/kg/day (2K1C-FFB) or vehicle (2K1C-VEH) for 8 weeks. Systolic blood pressure and cardiac functional were in-vivo assessed, while cardiomyocyte size and protein expression of mediators of cardiac hypertrophy and mitochondrial dynamics were ex-vivo examined by histological and Western blot analyses.Fenofibrate treatment counteracted the development of hypertension and the increase of left ventricular mass, relative wall thickness and cross-sectional area of cardiomyocytes. Furthermore, fenofibrate re-balanced the expression Mfn2, Drp1 and Parkin, regulators of fusion, fission, mitophagy respectively. Regarding autophagy, the LC3-II/LC3-I ratio was increased in 2K1C-VEH and 2K1C-FFB, whereas the autophagy was increased only in 2K1C-FFB.In cultured H9C2 cardiomyoblasts, fenofibrate reversed the Ang II-induced mRNA up-regulation of hypertrophy markers Nppa and Myh7, accumulation of reactive oxygen species and depolarization of the mitochondrial membrane exerting protection mediated by up-regulation of the Uncoupling protein 2.Our results indicate that fenofibrate acts directly on cardiomyocytes and counteracts the pressure overload-induced cardiac maladaptive remodeling. This study reveals a so far hidden mechanism involving mitochondrial dynamics in the beneficial effects of fenofibrate, support its repurposing for the treatment of cardiac hypertrophy and provide new potential targets for its pharmacological function.

Exosomal miR-9-5p derived from iPSC-MSCs ameliorates doxorubicin-induced cardiomyopathy by inhibiting cardiomyocyte senescence

Doxorubicin (DOX) is a chemotherapeutic agent widely used for tumor treatment. Nonetheless its clinical application is heavily limited by its cardiotoxicity. There is accumulated evidence that transplantation of mesenchymal stem cell-derived exosomes (MSC-EXOs) can protect against Dox-induced cardiomyopathy (DIC). This study aimed to examine the cardioprotective effects of EXOs isolated from human induced pluripotent stem cell-derived MSCs (iPSC-MSCs) against DIC and explore the potential mechanisms. EXOs were isolated from the cultural supernatant of human BM-MSCs (BM-MSC-EXOs) and iPSC-MSCs (iPSC-MSC-EXOs) by ultracentrifugation. A mouse model of DIC was induced by intraperitoneal injection of Dox followed by tail vein injection of PBS, BM-MSC-EXOs, or iPSC-MSC-EXOs. Cardiac function, cardiomyocyte senescence and mitochondrial dynamics in each group were assessed. In vitro, neonatal mouse cardiomyocytes (NMCMs) were subjected to Dox and treated with BM-MSC-EXOs or iPSC-MSC-EXOs. The mitochondrial morphology and cellular senescence of NMCMs were examined by Mitotracker staining and senescence-associated-β-galactosidase assay, respectively. Compared with BM-MSC-EXOs, mice treated with iPSC-MSC-EXOs displayed improved cardiac function and decreased cardiomyocyte mitochondrial fragmentation and senescence. In vitro, iPSC-MSC-EXOs were superior to BM-MSC-EXOs in attenuation of cardiomyocyte mitochondrial fragmentation and senescence caused by DOX. MicroRNA sequencing revealed a higher level of miR-9-5p in iPSC-MSC-EXOs than BM-MSC-EXOs. Mechanistically, iPSC-MSC-EXOs transported miR-9-5p into DOX-treated cardiomyocytes, thereby suppressing cardiomyocyte mitochondrial fragmentation and senescence via regulation of the VPO1/ERK signal pathway. These protective effects and cardioprotection against DIC were largely reversed by knockdown of miR-9-5p in iPSC-MSC-EXOs. Our results showed that miR-9-5p transferred by iPSC-MSC-EXOs protected against DIC by alleviating cardiomyocyte senescence via inhibition of the VPO1/ERK pathway. This study offers new insight into the application of iPSC-MSC-EXOs as a novel therapeutic strategy for DIC treatment.Graphical

Guanxin V alleviates ventricular remodeling after acute myocardial infarction with circadian disruption by regulating mitochondrial dynamics.

Circadian disruption has been a common issue due to modern lifestyles. Ventricular remodeling (VR) is a pivotal progressive pathologic change after acute myocardial infarction (AMI) andcircadian disruption may have anegative influence on VR according to thelatest research. Whether or notGuanxin V (GXV) has a positive effect on VR after AMI with circadian disruption drew our interest. Rats were randomly divided into asham group, anAMI group, anAMI with circadian disruption group, and anAMI with circadian disruption treated with the GXV group according to a random number table. RNA sequencing (RNA-Seq) was utilized to confirm the different expressed genes regulated by circadian disruption. Cardiac function, inflammation factors, pathological evaluation, and mitochondrial dynamics after the intervention were conducted to reveal the mechanism by which GXV regulated VR after AMI with circadian disruption. RNA-Seq demonstrated that NF-κB was up-regulated by circadian disruption in rats with AMI. Functional and pathological evaluation indicated that compared with the AMI group, circadian disruption was associcataed withdeteriorated cardiac function, expanded infarcted size, and exacerbated fibrosis and cardiomyocyte apoptosis. Further investigation demonstrated that mitochondrial dynamics imbalance was induced by circadian disruption. GXV intervention reversed the inflammatory status including down-regulation of NF-κB. Reserved cardiac function, limited infarct size, and ameliorated fibrosis and apoptosis were also observed in the GXV treated group. GXV maintained mitochondrial fission/fusion imbalance through suppressed expression of mitochondrial fission-associated proteins. The study findings suggestthat identified mitochondrial dysfunctions may underlie the link between circadian disruption and VR. GXV may exert cardioprotection after AMI with circadian disruption through regulating mitochondrial dynamics.

The interplay between sex, time of day, fasting status, and their impact on cardiac mitochondrial structure, function, and dynamics

Mitochondria morphology and function, and their quality control by mitophagy, are essential for heart function. We investigated whether these are influenced by time of the day (TOD), sex, and fed or fasting status, using transmission electron microscopy (EM), mitochondrial electron transport chain (ETC) activity, and mito-QC reporter mice. We observed peak mitochondrial number at ZT8 in the fed state, which was dependent on the intrinsic cardiac circadian clock, as hearts from cardiomyocyte-specific BMAL1 knockout (CBK) mice exhibit different TOD responses. In contrast to mitochondrial number, mitochondrial ETC activities do not fluctuate across TOD, but decrease immediately and significantly in response to fasting. Concurrent with the loss of ETC activities, ETC proteins were decreased with fasting, simultaneous with significant increases of mitophagy, mitochondrial antioxidant protein SOD2, and the fission protein DRP1. Fasting-induced mitophagy was lost in CBK mice, indicating a direct role of BMAL1 in regulating mitophagy. This is the first of its kind report to demonstrate the interactions between sex, fasting, and TOD on cardiac mitochondrial structure, function and mitophagy. These studies provide a foundation for future investigations of mitochondrial functional perturbation in aging and heart diseases.

The Chinese herbal medicine Fufang Zhenzhu Tiaozhi ameliorates diabetic cardiomyopathy by regulating cardiac abnormal lipid metabolism and mitochondrial dynamics in diabetic mice

Diabetic cardiomyopathy (DCM) is an important complication leading to the death of patients with diabetes, but there is no effective strategy for clinical treatments. Fufang Zhenzhu Tiaozhi (FTZ) is a patent medicine that is a traditional Chinese medicine compound preparation with comprehensive effects for the prevention and treatment of glycolipid metabolic diseases under the guidance of “modulating liver, starting pivot and cleaning turbidity”. FTZ was proposed by Professor Guo Jiao and is used for the clinical treatment of hyperlipidemia. This study was designed to explore the regulatory mechanisms of FTZ on heart lipid metabolism dysfunction and mitochondrial dynamics disorder in mice with DCM, and it provides a theoretical basis for the myocardial protective effect of FTZ in diabetes. In this study, we demonstrated that FTZ protected heart function in DCM mice and downregulated the overexpression of free fatty acids (FFAs) uptake-related proteins cluster of differentiation 36 (CD36), fatty acid binding protein 3 (FABP3) and carnitine palmitoyl transferase 1 (CPT1). Moreover, FTZ treatment showed a regulatory effect on mitochondrial dynamics by inhibiting mitochondrial fission and promoting mitochondrial fusion. We also identified in vitro that FTZ could restore lipid metabolism-related proteins, mitochondrial dynamics-related proteins and mitochondrial energy metabolism in PA-treated cardiomyocytes. Our study indicated that FTZ improves the cardiac function of diabetic mice by attenuating the increase in fasting blood glucose levels, inhibiting the decrease in body weight, alleviating disordered lipid metabolism, and restoring mitochondrial dynamics and myocardial apoptosis in diabetic mouse hearts.

Regulation of PM2.5 on mitochondrial damage in H9c2 cells through miR-421/SIRT3 pathway and protective effect of miR-421 inhibitor and resveratrol

Fine particulate matter (PM2.5) exposure is associated with cardiovascular disease (CVD) morbidity and mortality. Mitochondria are sensitive targets of PM2.5, and mitochondrial dysfunction is closely related to the occurrence of CVD. The epigenetic mechanism of PM2.5-triggered mitochondrial injury of cardiomyocytes is unclear. This study focused on the miR-421/SIRT3 signaling pathway to investigate the regulatory mechanism in cardiac mitochondrial dynamics imbalance in rat H9c2 cells induced by PM2.5. Results illustrated that PM2.5 impaired mitochondrial function and caused dynamics homeostasis imbalance. Besides, PM2.5 up-regulated miR-421 and down-regulated SIRT3 gene expression, along with decreasing p-FOXO3a (SIRT3 downstream target gene) and p-Parkin expression and triggering abnormal expression of fusion gene OPA1 and fission gene Drp1. Further, miR-421 inhibitor (miR-421i) and resveratrol significantly elevated the SIRT3 levels in H9c2 cells after PM2.5 exposure and mediated the expression of SOD2, OPA1 and Drp1, restoring the mitochondrial morphology and function. It suggests that miR-421/SIRT3 pathway plays an epigenetic regulatory role in mitochondrial damage induced by PM2.5 and that miR-421i and resveratrol exert protective effects against PM2.5-incurred cardiotoxicity.

Chronic exposure to polluted urban air aggravates myocardial infarction by impaired cardiac mitochondrial function and dynamics

Chronic exposure to polluted urban air aggravates myocardial infarction by impaired cardiac mitochondrial function and dynamics

Melatonin and metformin ameliorated trastuzumab-induced cardiotoxicity through the modulation of mitochondrial function and dynamics without reducing its anticancer efficacy

Trastuzumab has an impressive level of efficacy as regards antineoplasticity, however it can cause serious cardiotoxic side effects manifested by impaired cardiac contractile function. Although several pharmacological interventions, including melatonin and metformin, have been reported to protect against various cardiovascular diseases, their potential roles in trastuzumab-induced cardiotoxicity remain elusive. We hypothesized that either melatonin or metformin co-treatment effectively attenuates trastuzumab-mediated cardiotoxicity through attenuating the impaired mitochondrial function and mitochondrial dynamics. Male Wistar rats were divided into control (normal saline, n = 8) and trastuzumab group (4 mg/kg/day for 7 days, n = 24). Rats in the trastuzumab group were subdivided into 3 interventional groups (n = 8/group), and normal saline, or melatonin (10 mg/kg/day), or metformin (250 mg/kg/day) were orally administered for 7 consecutive days. Cardiac parameters were determined, and biochemical investigations were carried out on blood and heart tissues. Trastuzumab induced left ventricular (LV) dysfunction by increasing oxidative stress, inflammation, and apoptosis. It also impaired cardiac mitochondrial function, dynamics, and autophagy. Treatment with either melatonin or metformin equally attenuated trastuzumab-induced cardiac injury, indicated by a marked reduction in inflammation, oxidative damage, cardiac mitochondrial injury, mitochondrial dynamic imbalance, autophagy dysregulation, and apoptosis, leading to improved LV function, as demonstrated by increased LV ejection fraction. Melatonin and metformin conferred equal levels of cardioprotection against trastuzumab-induced cardiotoxicity, which may provide novel and promising approaches for management of cardiotoxicity induced by trastuzumab.

Chronic insulin resistance deteriorates cardiac mitochondrial quality control in a mouse model of SEC-NAFLD-IR

Abstract Background Insulin resistance and nonalcoholic fatty liver disease (NAFLD) both relate to cardiovascular mortality. Using a mouse model of chronic lipid overload and secondary-NAFLD-induced insulin resistance (SEC-NAFLD-IR), we recently deciphered that SEC-NAFLD-IR already at young age provoked myocardial lipotoxicity with reduced mitochondrial efficiency and increased vulnerability to cardiac ischemia. However, long-term consequences of SEC-NAFLD-IR remain elusive. Purpose Here we aimed to elucidate the impact of long-term SEC-NAFLD-IR on multiple mitochondrial quality control (mQC) mechanisms in the heart and its consequences for cardiac function. Methods We studied 36 SEC-NAFLD-IR mice (72-week-old). For mechanistic experiments, we applied palmitate-induced insulin resistant murine HL-1 cells. Cardiac mitochondrial dynamics were measured via quantification of mitochondrial morphology and expression of mitochondrial fusion and fission factors (Opa1, Drp1, Fis1, Mfn 1 & 2). Mitophagy level was evaluated via immunofluorescence and protein expression of key mitophagy-related genes (Parkin, NIX, LC3). Mitochondrial biogenesis and mass were examined via quantitation of PGC-1α expression, mtDNA and citrate synthase activity. Results 72-week-old SEC-NAFLD-IR mice exhibited 21% (p=0.001) and 32% (p<0.001) higher body weight and heart weight compared with controls. Along with elevated oxidative stress, hepatic lipid accumulation and inflammation, 6h-fasted SEC-NAFLD-IR mice were characterized by increased plasma glucose, insulin and cholesterol. SEC-NAFLD-IR mice displayed a cardiac phenotype with 21% higher left ventricular mass (normalized to body weight, p<0.001) and 6% lower ejection fraction compared to controls (73.5% SEM 0.90 vs 69.4% SEM 1.65, p=0.04). We found several advantageous mQC mechanisms suppressed in aged SEC-NAFLD-IR mice including long form OPA1-mediated mitochondrial fusion, Parkin- and NIX-mediated mitophagy. Likewise, mitochondrial biogenesis was suppressed in the aged insulin-resistant heart, which was connected to a 65% downregulation of PGC-1α1 expression (p=0.01). Interestingly, downregulation of cardiac PGC-1α1 in aged SEC-NAFLD-IR mice coincided with upregulation of PARIS, indicating the crucial participation of the Parkin/PARIS pathway in mQC of the insulin-resistant heart. In addition, induction of insulin resistance in murine HL-1 cardiomyocytes also led to increased mitochondrial fragmentation and decreased PGC-1α1 expression. Conclusion This study demonstrated that regulation of mitochondrial network and turnover is hampered by SEC-NAFLD-IR in the hearts of aged mice, which may contribute to hypertrophy and cardiac dysfunction in insulin resistance. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Collaborative Research Centre 1116 (German Research Foundation)

Myeloid differentiation factor 2 inhibitor and N-acetyl cysteine synergistically reduced left ventricular dysfunction in rats with cardiac ischemia/reperfusion injury

Abstract Background Myeloid differentiation factor 2 inhibitor (MD2i) is a novel anti-inflammatory agent that exerts favorable outcomes in various diseases including cardiac ischemia/reperfusion (I/R) injury. However, whether a potent antioxidant N-acetyl cysteine (NAC) can augment the beneficial effects of MD2i in rats with cardiac I/R injury have never been investigated. Purpose We tested the hypothesis that NAC increases the beneficial effects of MD2i against cardiac I/R injury in rats. Methods Rats were divided into either a sham (n=6) or cardiac I/R group (n=72). Rats in the I/R group received one of the following 6 treatments (n=12 each) at the onset of reperfusion: vehicle, MD2i at 20 and 40 mg/kg, NAC at 75 and 150 mg/kg, and combined MD2i 20 mg/kg with NAC 150 mg/kg. Left ventricular (LV) function, infarct size, arrhythmia score, and cardiac mitochondrial function and dynamics were determined. Results Myocardial infarction, LV dysfunction, and cardiac arrhythmias were observed in rats with cardiac I/R injury, along with mitochondrial dysfunction (Fig. 1). Treatment with MD2i at either 20 or 40 mg/kg effectively reduced LV dysfunction but failed to reduce the infarct size (Fig. 1). NAC at 150 mg/kg, but not at 75 mg/kg, significantly decreased both LV dysfunction and infarct size following cardiac I/R injury (Fig. 1). However, combined treatment exerted even greater efficacy in reducing cardiac I/R injury than monotherapy, through a greater reduction of cardiac mitochondrial dysfunction and mitochondrial fission (Fig. 1). However, no benefit on reducing the arrhythmia score in all groups. Conclusion Combined MD2i and NAC treatment exerted a superior cardioprotective effect against cardiac I/R injury than either monotherapy regimen via an improved cardiac mitochondrial function. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): 1. NSTDA Research Chair Grant from the National Science and Technology Development Agency Thailand2. National Research Council of Thailand

Empagliflozin prohibits high-fructose diet-induced cardiac dysfunction in rats via attenuation of mitochondria-driven oxidative stress

SGLT2 inhibitors show promising cardio-protection in the diabetic populace. However, the defending effect of SGLT2 inhibition in diabetes-associated cardiac complications and the molecular mechanism behind this effect are not thoroughly studied. Therefore, we aimed to investigate the effect of Empagliflozin, an SGLT2 inhibitor, in type-2 diabetic rat hearts.We induced type-2 diabetes in SD rats by giving a high-fructose diet for 20 weeks. We administered Empagliflozin (10 mg/kg p.o.) daily from the 12th week to the 20th week, along with high-fructose diet. We weighed the cardiac structure and function by echocardiography, electrocardiography, and blood pressure in diabetic rats. Other parameters like cardiac fibrosis, oxidative stress, and mitochondrial dynamics by protein expression were measured. To simulate a similar in-vivo condition, we persuaded insulin resistance in H9c2 cells by palmitic acid (PA) treatment. We then examined glucose uptake, cellular ROS, mitochondrial ROS and membrane potential in the presence and absence of Empagliflozin treatment.We saw a significant perturbation of the majority of the parameters associated with cardiac structure and function in high-fructose diet-induced diabetic rats. We found that administration of Empagliflozin improved all the perturbed parameters by attenuating insulin resistance, oxidative stress, and cardiac fibrosis and also by promoting cardiac mitochondrial fusion in high-fructose diet-induced type-2 diabetic rats. Empagliflozin also reduced palmitate-induced insulin resistance, total cellular ROS, and mitochondrial ROS in H9c2 cells.Our study concluded that SGLT2 inhibition with Empagliflozin prevented the high-fructose diet-insulted cardiac function by suppressing insulin resistance and oxidative stress and promoting mitochondrial fusion.

Chronic exposure to polluted urban air aggravates myocardial infarction by impaired cardiac mitochondrial function and dynamics

Air pollution exposure positively correlates with increased cardiovascular morbidity and mortality rates, mainly due to myocardial infarction (MI). Herein, we aimed to study the metabolic mechanisms underlying this association, focusing on the evaluation of cardiac mitochondrial function and dynamics, together with its impact over MI progression. An initial time course study was performed in BALB/c mice breathing filtered air (FA) or urban air (UA) in whole-body exposure chambers located in Buenos Aires City downtown for up to 16 weeks (n = 8 per group and time point). After 12 weeks, lung inflammatory cell recruitment was evident in UA-exposed mice. Interestingly, impaired redox metabolism, characterized by decreased lung SOD activity and increased GSSG levels and NOX activity, precede local inflammation in this group. At this selected time point, additional mice were exposed to FA or UA (n = 12 per group) and alveolar macrophage PM uptake and nitric oxide (NO) production was observed in UA-exposed mice, together with increased pro-inflammatory cytokine levels (TNF-α and IL-6) in BAL and plasma. Consequently, impaired heart tissue oxygen metabolism and altered mitochondrial ultrastructure and function were observed in UA-exposed mice after 12 weeks, characterized by decreased active state respiration and ATP production rates, and enhanced mitochondrial H2O2 production. Moreover, disturbed cardiac mitochondrial dynamics was detected in this group. This scenario led to a significant increase in the area of infarcted tissue following myocardial ischemia reperfusion injury in vivo, from 43 ± 3% of the area at risk in mice breathing FA to 66 ± 4% in UA-exposed mice (n = 6 per group, p < 0.01), together with a sustained increase in LVEDP during myocardial reperfusion. Taken together, our data unravel cardiac mitochondrial mechanisms that contribute to the understanding of the adverse health effects of urban air pollution exposure, and ultimately highlight the importance of considering environmental factors in the development of cardiovascular diseases.

Altered cardiac mitochondrial dynamics and biogenesis in rat after short-term cocaine administration

Abuse of the potent psychostimulant cocaine is widely established to have cardiovascular consequences. The cardiotoxicity of cocaine is mainly associated with oxidative stress and mitochondrial dysfunction. Mitochondrial dynamics and biogenesis, as well as the mitochondrial unfolded protein response (UPRmt), guarantee cardiac mitochondrial homeostasis. Collectively, these mechanisms act to protect against stress, injury, and the detrimental effects of chemicals on mitochondria. In this study, we examined the effects of cocaine on cardiac mitochondrial dynamics, biogenesis, and UPRmt in vivo. Rats administered cocaine via the tail vein at a dose of 20 mg/kg/day for 7 days showed no structural changes in the myocardium, but electron microscopy revealed a significant increase in the number of cardiac mitochondria. Correspondingly, the expressions of the mitochondrial fission gene and mitochondrial biogenesis were increased after cocaine administration. Significant increase in the expression and nuclear translocation of activating transcription factor 5, the major active regulator of UPRmt, were observed after cocaine administration. Accordingly, our findings show that before any structural changes are observable in the myocardium, cocaine alters mitochondrial dynamics, elevates mitochondrial biogenesis, and induces the activation of UPRmt. These alterations might reflect cardiac mitochondrial compensation to protect against the cardiotoxicity of cocaine.

A chronic exposure to urban polluted air hampers cardiac mitochondrial dynamics in mice

A chronic exposure to urban polluted air hampers cardiac mitochondrial dynamics in mice

Abstract 9373: Cinnamamide Derivative Reduces Left Ventricular Dysfunction by Modulating Mitochondrial Dynamics in Prediabetic Rats

Introduction: Chronic high-fat diet (HFD) consumption induces prediabetes via increased systemic inflammation by activating myeloid differentiation factor 2 (MD2)/toll-like receptor 4 pathway, resulting in left ventricular (LV) dysfunction. Cinnamamide derivative was shown previously to reduce inflammation in lipopolysaccharide-induced septic mice by targeting MD2. However, the effects of cinnamamide derivative, 2i-10, on the LV function in prediabetes are not known. Hypothesis: 2i-10 improves LV function in prediabetic rats by reducing cardiac inflammation, mitochondrial dysfunction, and mitochondrial dynamics imbalance. Methods: Prediabetic rats were induced by feeding HFD for 12 weeks, and were divided into 3 groups; vehicle, 2i-10 (40 mg/kg), or metformin (300 mg/kg). Normal diet fed rats received vehicle. Rats orally received their assigned treatment for 4 weeks. Then, LV function, cardiac inflammation, and mitochondrial function and dynamics were examined. Results: Prediabetic rats had impaired LV function, as shown by reduced %LV ejection fraction. Moreover, impaired mitochondrial function and dynamics were observed, as shown by increased reactive oxygen species (ROS), mitochondrial depolarization, swelling, increased mitochondrial fission (p-Drp1/Drp1) and decreased mitochondrial fusion (OPA1). NF-κB phosphorylation was increased in these rats, indicating inflammation. Treatment with 2i-10 significantly reduced cardiac inflammation, mitochondrial dysfunction, mitochondrial dynamic imbalance, and improved LV function in prediabetic rats (Fig 1). Similar benefits were observed in metformin-treated rats. Conclusions: Chronic treatment with 2i-10, effectively suppressed cardiac inflammation, mitochondrial dysfunction and mitochondrial dynamics imbalance, leading to improved LV function in prediabetic rats. These findings suggest that targeting MD2 could be a novel treatment to protect the heart in prediabetes.

Abstract 12199: Sirtuin1 Mediates Pressure Overload-Induced Cardiac Pathological Hypertrophy Through Regulating Mitochondrial Dynamics

Introduction: Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide-dependent histone deacetylase. We revealed that the pressure-overload-induced SIRT1 can exacerbate cardiac systolic dysfunction. But the mechanisms by which SIRT1 undermines cardiac function under pathological conditions remain unclear. Hypothesis: SIRT1 induced by pathological hypotrophy disturbs mitochondrial dynamics homeostasis resulting in an exacerbated cardiac dysfunction. Methods: Wild-type littermates SIRT1 f/f (3-5 months) and inducible cardiomyocyte-specific SIRT1 knockout (icSIRT1 -/- ) (3-5 months) C57BL/6J mice were subjected to transverse aortic constriction (TAC) surgery for six weeks. Echocardiography assessed cardiac functions and CODA tail-cuff system measured blood pressure. The mitochondrial dynamics were examined by immunoblotting and transmission electron microscopy (TEM). Results: The echocardiography showed that there were significant reductions in ejection fraction (EF) and fractional shortening (FS) of the SIRT1 f/f mice after 6-weeks of TAC-induced pressure overload. The diastolic and systolic blood pressure were increased in SIRT1 f/f mice during TAC surgery. Intriguingly, icSIRT1 -/- versus SIRT1 f/f demonstrated significant resistance to pathological hypertrophy caused by TAC-induced pressure overload as determined with echocardiography and blood pressure measurements. The immunoblotting revealed that the six weeks of TAC surgery caused significantly higher levels of the mitochondrial fusion protein, mitofusin 2 (MFN2), in SIRT1 f/f versus icSIRT1 -/- hearts. In addition, TEM data showed more elongated mitochondria in SIRT1 f/f versus icSIRT1 -/- hearts, indicating a critical role of SIRT1 in maintaining mitochondrial dynamic homeostasis under pathological stress conditions. Metabolomics and proteomics showed that SIRT1 regulates carnitine palmitoyltransferase-1 and long-chain acyl CoA dehydrogenase to modulate fatty acid metabolism in response to TAC-induced stress. Conclusions: Cardiomyocyte SIRT1 plays a key role in cardiac mitochondrial dynamics during pathological stress conditions. Inhibition of SIRT1 activity could be a good strategy to ameliorate pressure overload-induced hypertrophy.

Abstract 15178: Mitochondrial Dynamic Modulators Mitigates Mitochondrial Dynamic Index, Biogenesis and Metabolic Impairments in Prediabetic Rats With Cardiac Ischemia-reperfusion Injury

Introduction: Long-term exposure to high-fat diet (HFD) caused obesity, which not only was positively associated with cardiovascular disorders but also had a negative impact on the outcome of acute myocardial ischemia-reperfusion (I/R) injury. Uncontrolled fission and diminished fusion of cardiac mitochondria augment the impairment of mitochondrial biogenesis and metabolism which have been implicated in metabolic diseases and I/R injury pathology. Since cardioprotective efficacy of acute administration of mitochondrial fission inhibitor (Mdivi-1) and fusion promoter (M1) have previously been reported, the effects of chronic treatment with both modulators on cardiac mitochondrial dynamics, biogenesis and lipid metabolism in prediabetic rats subjected to cardiac I/R injury have never been elucidated. Hypothesis: Chronic treatment of Mdivi-1 and M1 after acute myocardial I/R improve mitochondrial dynamic index, biogenesis and metabolic pathway in prediabetic rats. Methods: Male Wistar rats (n=18) were fed with HFD. After 12 weeks, all rats were randomly divided into: 1) HFV (Vehicle, 0.1% DMSO), 2) HFMd (Mdivi-1, 1.2 mg/kg), and 3) HFM1 (M1, 2 mg/kg) with intraperitoneal injection for 14 days. Then, all rats underwent 30 minutes of left anterior descending coronary artery occlusion followed by reperfusion for 120 minutes. The expression of mitochondrial dynamics (p-Drp1 ser616 per Mfn2 ratio or dynamic index), biogenesis (PGC1- α) and lipid metabolism (CPT1) proteins from ischemic area of heart were determined. Results: Chronic treatment of Mdivi-1 and M1 similarly improved cardiac mitochondrial dynamic index (p-Drp1 ser616 per Mfn2 ratio), increased PGC1-α and CPT1 expression levels, when compared to HFV (Fig). Conclusions: Modulating mitochondrial dynamics by chronic treatment of Mdivi-1 and M1 improved cardiac mitochondrial dynamic index, biogenesis and metabolic pathway in prediabetic rats following acute myocardial I/R injury.

Abstract 14148: Local Aldosterone Production via StAR in PAH and in Human IPS Cell-derived Cardiomyocytes: Efficacy of Spironolactone in Cardiac Remodeling and Mitochondrial Dynamics Under Hypoxic Stress

Objective: Pulmonary arterial hypertension (PAH) is a progressive disease that frequently leads to right ventricular (RV) remodeling. Increased plasma aldosterone levels have been reported in patients with PAH. The aim of this study was to examine the expression of steroidogenic acute regulatory protein (StAR) in patients and animal model of PAH, and in the human iPS cell-derived cardiomyocytes (hiPSC-CMs). Furthermore, we evaluated therapeutic effects of mineralocorticoid receptor (MR) antagonist, spironolactone (SPL) on mitochondrial dynamics in the RV myocardium. Methods: Autopsied heart samples (n=20) were obtained from patients with or without PAH. PAH model rats (n=46) were injected with Sugen5416 (20 mg/kg) and then exposed to hypoxia and reoxygenation for 4 weeks with/without treatment with SPL (25 mg/kg/day). Human umbilical vein endothelial cells (HUVECs) and hiPSC-CMs were cultured under hypoxic conditions (37 °C, 1% O 2 , 5% CO 2 ) with/without treatment with SPL (10 μM). In addition, we applied the Clustered Regularly Interspaced Short Palindromic Repeats interference (CRISPRi) technology and repressed StAR gene expression in hiPSC-CMs under hypoxic conditions. Results: In PAH patients, the expression of StAR and MR was significantly increased in cardiomyocytes and endothelial cells in the RV myocardium. In PAH rats, RV systolic pressure elevated over 60 mm Hg with deteriorated RV function. Under electron microscopy, severe degeneration of mitochondria and capillaries with myofibrillar lysis in the RV myocardium were observed, which were compatible with those findings in PAH patients. Hypoxic stress significantly increased the StAR and phosphorylated JNK, ERK-1/2, and NF-kB proteins in hiPSC-CMs as well as in HUVECs. Furthermore, we established the CRISPRi-hiPSC cell lines where StAR gene was successfully knockdown. Treatment with SPL decreased the phosphorylation of JNK, ERK-1/2, NF-kB, and Smad3 in HUVECs and hiPSC-CMs. Strikingly, SPL attenuated mitochondrial degeneration and increased mitophagy, suppressing the RV remodeling under hypoxic stress. Conclusion: SPL might regulate mitochondrial dynamics and attenuates RV remodeling in PAH via StAR/JNK signaling pathway.

Acetylcholinesterase inhibitor protects against cardiac ischaemia/reperfusion injury via enhancing mitophagy and rebalancing mitochondrial dynamics

Abstract Background Ischaemic heart disease is the most common cause of death globally. Although reperfusion therapy is essential to restore myocardial blood flow, it can also damage heart tissues, this process is known as ischaemia/reperfusion (I/R) injury. Cardiac autonomic imbalance including sympathetic overactivity and diminished parasympathetic activity plays an important role in cardiac I/R injury, resulting in left ventricular (LV) dysfunction. Increased vagus nerve activity by an electrical stimulation from an implantable medical device has been shown to be cardioprotective in cardiac I/R injury. However, the role of pharmacological intervention that increases parasympathetic activity on the heart during I/R is not clear. Purpose We investigated the effects of a parasympathomimetic drug, donepezil, on the heart with I/R injury. We hypothesized that donepezil exerts cardioprotective effects in rats with cardiac I/R injury by attenuating the impairment of cardiac mitochondrial function, mitochondrial dynamics and mitophagy, resulting in improved LV function. Methods Forty male Wistar rats were randomly divided into sham and I/R groups. In I/R group, rats were subjected to acute cardiac I/R injury by ligating left anterior descending coronary artery (LAD) for 30 mins followed by reperfusion for 120 mins, while sham group had similar operation but did not have LAD ligation. Moreover, rats in the I/R group were randomly assigned to be treated with either saline (vehicle group) or donepezil 3 mg/kg by intravenous injection. In donepezil-treated rats, they were divided into 3 subgroups to receive the drug at one of the following time-points; before ischaemia, or during ischaemia, or at the onset of reperfusion. During I/R protocol, LV function was recorded. At the end of protocol, the heart was removed to determine infarct size, cardiac mitochondrial function, mitochondrial dynamics, and mitophagy. Results Rats with cardiac I/R injury showed increased infarct size when compared to sham group (Fig. 1A). Rats in all donepezil-treated groups showed reduction of infarct size compared to the vehicle group. This accounts for ∼63%, ∼47%, and ∼44% reduction for the treatment before ischaemia, during ischaemia and onset of reperfusion, respectively. In addition, all donepezil-treated rats had improved LV function by attenuating the reduction of LV ejection fraction (Fig. 1B). The reduction in cardiac mitochondrial ROS production (Fig. 1C), increased mitophagy as indicated by increased PINK-1 expression (Fig. 1D), and rebalancing mitochondrial dynamics were also found in all donepezil-treated rats. Conclusion Donepezil protects against cardiac I/R injury by reducing mitochondrial ROS production, enhancing mitophagy, and improving mitochondrial dynamics, leading to decreased infarct size and improved cardiac function. Figure 1. The effects of donepezil in cardiac I/R Funding Acknowledgement Type of funding source: Public Institution(s). Main funding source(s): Thailand Research Fund grants TRF-Royal Golden Jubilee Program (TK and NC), RTA6180003 (SCC), RSA6180056 (SP); The NSTDA Research Chair grant from the National Science and Technology Development Agency Thailand (NC)