The biochemically defined super relaxed state of myosin-A paradox.

The biochemical SRX (super-relaxed) state of myosin has been defined as a low ATPase activity state. This state can conserve energy when the myosin is not recruited for muscle contraction. The SRX state has been correlated with a structurally defined ordered (versus disordered) state of muscle thick filaments. The two states may be linked via a common interacting head motif (IHM) where the two heads of heavy meromyosin (HMM), or myosin, fold back onto each other and form additional contacts with S2 and the thick filament. Experimental observations of the SRX, IHM, and the ordered form of thick filaments, however, do not always agree, and result in a series of unresolved paradoxes. To address these paradoxes, we have reexamined the biochemical measurements of the SRX state for porcine cardiac HMM. In our hands, the commonly employed mantATP displacement assay was unable to quantify the population of the SRX state with all data fitting very well by a single exponential. We further show that mavacamten inhibits the basal ATPases of both porcine ventricle HMM and S1 (Ki, 0.32 and 1.76 µM respectively) while dATP activates HMM cooperatively without any evidence of an SRX state. A combination of our experimental observations and theories suggests that the displacement of mantATP in purified proteins is not a reliable assay to quantify the SRX population. This means that while the structurally defined IHM and ordered thick filaments clearly exist, great care must be employed when using the mantATP displacement assay.

Non-Uniform Bioaccumulation of Lead and Arsenic in Two Remote Regions of the Human Heart's Left Ventricle: A Post-Mortem Study.

The extent of heavy-metal-induced cardiotoxicity is proportional to the levels of metal bioaccumulation, and it was previously assumed that heavy metals accumulate uniformly in the myocardium. Therefore, the aim of this study was to investigate concentrations of metals and metalloids in two distant regions of the left ventricle (LV), the base of the LV, and apex of the LV using inductively coupled plasma mass spectrometry (ICP-MS). We also examined the potential correlation between metal levels and the thickness of the interventricular septum in twenty LV specimens (ten from the base of LV and ten from the apex of LV) from 10 individuals (mean age 75 ± 6 years). We found significantly higher concentrations of arsenic and lead in the LV apex compared to the base of the LV. We also found a positive correlation between the concentrations of arsenic in the myocardium of LV and the thickness of the interventricular septum. Our results indicate that arsenic and lead accumulate to a higher extent in the apex of the LV compared to the base of the LV. Therefore, future studies designed to measure levels of metals in heart muscle should consider non-uniform accumulation of metals in the myocardium.

[Impact of interventional therapy on top of standard drug therapy on left ventricular structure and function in HFrEF patients complicating with middle aortic syndrome caused by Takayasu arteritis].

Objective: To evaluate the impact of interventional therapy on top of drug therapy on cardiac function and structure in heart failure with reduced ejection fraction (HFrEF) patients complicating with middle aortic syndrome caused by Takayasu arteritis (TA-MAS). Methods: It was a retrospective longitudinal study. The data of patients with TA-MAS and HFrEF, who received interventional therapy on top of drug therapy in Fuwai Hospital from January 2010 to September 2020, were collected and analyzed. Baseline clinical data (including demographic data, basic treatment, etc.) were collected through the electronic medical record system. Changes of indexes such as New York Heart Association (NYHA) classification, N-terminal pro-brain natriuretic peptide (NT-proBNP), left ventricular end diastolic diameter (LVEDD), left ventricular ejection fraction (LVEF), left ventricular mass index (LVMI) before and after therapy were analyzed. Results: A total of 10 patients were collected. There were 8 females in this patient cohort, age was (18.4±5.0) years and onset age was (15.3±5.0) years. All 10 patients received standard heart failure medication therapy in addition to hormone and/or immunosuppressive anti-inflammatory therapy, but cardiac function was not improved, so aortic balloon dilatation and/or aortic stenting were performed in these patients. The median follow-up was 3.3(1.3, 5.6) years. On the third day after interventional therapy, the clinical symptoms of the 10 patients were significantly improved, NYHA classfication was restored from preoperative Ⅲ/Ⅳ to Ⅱ at 6 months post intervention(P<0.05). Compared with preoperation, NT-proBNP (P=0.028), LVEDD (P=0.011) and LVMI (P=0.019) were significantly decreased, LVEF was significantly increased (P<0.001) at 6 months after operation. Compared with preoperation, NT-proBNP (P=0.016), LVEDD (P=0.023) and LVMI (P=0.043) remained decreased, LVEF remained increased (P<0.001) at 1 year after operation. Conclusion: Results from short and medium term follow-up show that interventional therapy on top of heart failure drug therpay can effectively improve left cardiac function and attenuate cardiac remodeling in patients with TA-MAS comorbid with HFrEF.

Effects of oxymatrine and matrine on left ventricular contractility using pressure-volume relationship analysis in anesthetized rats.

The purpose of this study was to investigate the effects of oxymatrine and matrine on integrated cardiac function in rats using pressure-volume loop analysis. A pressure-volume loop catheter was advanced into the left ventricle in anesthetized rats. Steady-state hemodynamic and load-independent parameters were recorded before and after oxymatrine or matrine injection. Oxymatrine (200 mg/kg) and matrine (50, 100 mg/kg) significantly increased the preload recruitable stroke work, slope of maximal systolic pressure increase (dP/dtmax) - end-diastolic volume relationship, end-systolic elastance and volume axis intercept (V0), which are load-independent parameters. Furthermore, the observed increased cardiac efficiency, along with the decreased ventricular arterial coupling, pressure volume area and potential energy, reflect improved mechanoenergetics in oxymatrine (200 mg/kg) and matrine (25, 50 or 100 mg/kg) treated rats respectively. In addition, matrine (25, 50 mg/kg) decreased end-systolic volume and end-diastolic volume, and increased ejection fraction; matrine at 100 mg/kg further decreased end-systolic volume, end-diastolic volume, stroke volume and stroke work, shortened the time constant of left ventricular pressure decay, and increased dP/dtmax, and heart rate. These results suggest that both oxymatrine and matrine enhance left ventricular contractility and improve cardiac mechanical function. As the dose of matrine was much lower than that of oxymatrine, the effect of matrine on myocardial contractility was stronger than that of oxymatrine.

Pterostilbene Reduces Experimental Myocardial Infarction-Induced Oxidative Stress in Lung and Right Ventricle. / Pterostilbeno Reduz o Estresse Oxidativo no Pulmão e no Ventrículo Direito Induzido por Infarto do Miocárdio Experimental.

BACKGROUND: Pterostilbene (PS), a natural and antioxidant polyphenolic compound emerges as a promising intervention in improving the myocardial infarction (MI) damages. OBJETIVES: This study aimed to evaluate PS actions in promoting redox homeostasis in lungs and right ventricle (RV) of infarcted animals. METHODS: Male Wistar rats (60 day-old) were randomized into three groups: SHAM, MI (infarcted), and MI+PS (MI+pterostilbene). Seven days after MI procedure, rats were treated with PS (100 mg/kg/day) via gavage for eight days. Animals were euthanized and the lungs and RV were harvested for analyses of redox balance (Differences were considered significant when p<0.05). RESULTS: Our results show that MI triggers a redox disruption scenario in RV and lungs, which can contribute to MI-induced damage on these organs. Consistently, PS mitigated oxidative stress and restored antioxidant defenses (GSH in lungs: SHAM= 0.79±0.07; MI=0.67±0.05; MI+PS=0.86±0.14; p<0.05), indicating its protective role in this scenario. CONCLUSIONS: Our work evidences the PS potential use as an adjuvant therapeutic approach after MI focusing on protecting pulmonary and right-sided heart tissues.

FUNDAMENTO: O pterostilbeno (PS), um composto polifenólico natural e antioxidante, surge como uma intervenção promissora para minimizar danos do infarto agudo do miocárdio (IAM). OBJETIVO: Este estudo teve como objetivo avaliar o desempenho do PS na promoção da homeostase redox nos pulmões e no ventrículo direito (VD) de animais infartados. MÉTODOS: Ratos Wistar machos (60 dias de idade) foram randomizados em três grupos: SHAM, IAM (infarto) e IAM+PS (IAM + pterostilbeno). Sete dias após o procedimento de IAM, os ratos foram tratados com PS (100 mg/kg/dia) por gavagem por oito dias. Os animais foram depois sacrificados e os pulmões e VD foram coletados para análise do balanço redox (diferenças foram consideradas significativas quando p<0,05). RESULTADOS: Nossos resultados mostram que o IAM desencadeia a interrupção redox no VD e nos pulmões, o que pode contribuir para danos induzido pelo IAM nesses órgãos. Consistentemente, o PS mitigou o estresse oxidativo e restaurou as defesas antioxidantes (Glutationa ­ GSH nos pulmões: SHAM = 0,79 ± 0,07; IAM = 0,67 ± 0,05; IAM + PS = 0,86 ± 0,14; p<0,05), indicando seu papel protetor neste cenário. CONCLUSÃO: Nosso trabalho evidencia o potencial do uso de PS como abordagem terapêutica adjuvante após IAM para proteção dos tecidos pulmonares e cardíacos direitos.

Endothelial cell ferroptosis mediates monocrotaline-induced pulmonary hypertension in rats by modulating NLRP3 inflammasome activation.

Inflammation triggers pulmonary vascular remodelling. Ferroptosis, a nonapoptotic form of cell death that is triggered by iron-dependent lipid peroxidation and contributes to the pathogenesis of several inflammation-related diseases, but its role in pulmonary hypertension (PH) has not been studied. We examined endothelial cell ferroptosis in PH and the potential mechanisms. Pulmonary artery endothelial cells (PAECs) and lung tissues from monocrotaline (MCT)-induced PH rats were analysed for ferroptosis markers, including lipid peroxidation, the labile iron pool (LIP) and the protein expression of glutathione peroxidase 4 (GPX4), ferritin heavy chain 1 (FTH1) and NADPH oxidase-4 (NOX4). The effects of the ferroptosis inhibitor ferrostatin-1 (Fer-1) on endothelial cell ferroptosis and pulmonary vascular remodelling in MCT-induced rats were studied in vitro and in vivo. Ferroptosis was observed in PAECs from MCT-induced PH rats in vitro and in vivo and was characterized by a decline in cell viability accompanied by increases in the LIP and lipid peroxidation, the downregulation of GPX4 and FTH1 expression and the upregulation of NOX4 expression. High-mobility group box 1 (HMGB1)/Toll-like receptor 4 (TLR4)/NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome signalling was measured by western blotting. These changes were significantly blocked by Fer-1 administration in vitro and in vivo. These results suggest that Fer-1 plays a role in inhibiting ferroptosis-mediated PAEC loss during the progression of PH. The ferroptosis-induced inflammatory response depended on the activation of HMGB1/TLR4 signalling, which activated the NLRP3 inflammasome in vivo. We are the first to suggest that pulmonary artery endothelial ferroptosis triggers inflammatory responses via the HMGB1/TLR4/NLRP3 inflammasome signalling pathway in MCT-induced rats. Treating PH with a ferroptosis inhibitor and exploring new treatments based on ferroptosis regulation might be promising therapeutic strategies for PH.

MSC Pretreatment for Improved Transplantation Viability Results in Improved Ventricular Function in Infarcted Hearts.

Many clinical studies utilizing MSCs (mesenchymal stem cells, mesenchymal stromal cells, or multipotential stromal cells) are underway in multiple clinical settings; however, the ideal approach to prepare these cells in vitro and to deliver them to injury sites in vivo with maximal effectiveness remains a challenge. Here, pretreating MSCs with agents that block the apoptotic pathways were compared with untreated MSCs. The treatment effects were evaluated in the myocardial infarct setting following direct injection, and physiological parameters were examined at 4 weeks post-infarct in a rat permanent ligation model. The prosurvival treated MSCs were detected in the hearts in greater abundance at 1 week and 4 weeks than the untreated MSCs. The untreated MSCs improved ejection fraction in infarcted hearts from 61% to 77% and the prosurvival treated MSCs further improved ejection fraction to 83% of normal. The untreated MSCs improved fractional shortening in the infarcted heart from 52% to 68%, and the prosurvival treated MSCs further improved fractional shortening to 77% of normal. Further improvements in survival of the MSC dose seems possible. Thus, pretreating MSCs for improved in vivo survival has implications for MSC-based cardiac therapies and in other indications where improved cell survival may improve effectiveness.

Sildenafil protects against pulmonary hypertension induced by hypoxia in neonatal rats via activation of PPARγ­mediated downregulation of TRPC.

Persistent pulmonary hypertension of the newborn (PPHN) is a common pulmonary vascular disease during the neonatal period, and it is associated with a high clinical mortality rate and a poor prognosis. At present, the treatment of PPHN is based mainly on inhaled nitric oxide (iNO), high­frequency ventilation, and pulmonary vasodilators. Sildenafil has gradually begun to be used in recent years for the treatment of PPHN and has exhibited some success; however, its detailed mechanism of action requires further elucidation. An animal model of neonatal pulmonary hypertension (neonatal rats, 48 h after birth, 10% O2, 14 days) as well as a cell model [human pulmonary artery smooth muscle cells (PASMCs), 4% O2, 60 h] were established. The effects of sildenafil on pulmonary hypertension in neonatal rats were evaluated by hematoxylin and eosin staining, immunofluorescence analysis, western blotting and PCR, and the changes in peroxisome proliferator­activated receptor Î³ (PPARγ), transient receptor potential canonical (TRPC)1, TRPC6 and Ki67 expression levels were detected under hypoxic conditions. The results revealed that sildenafil reversed the increases in the right ventricular mean pressure and right ventricular hypertrophy index induced by hypoxia, and attenuated pulmonary arterial remodeling as well as PASMC proliferation. The inhibitory effects of sildenafil on TRPC expression and PASMC proliferation were attenuated by GW9662 and PPARγ small interfering RNA. In conclusion, sildenafil protects against hypoxia­induced pulmonary hypertension and right ventricular hypertrophy in neonatal rats by upregulating PPARγ expression and downregulating TRPC1 and TRPC6 expression.

Rationale and design of the effects of EMpagliflozin on left ventricular DIAstolic function in diabetes (EmDia) study.

BACKGROUND: Data of the EMPA-REG OUTCOME study have demonstrated a beneficial effect of the sodium-glucose cotransporter 2 inhibitor empagliflozin on cardiovascular outcome in patients with type 2 diabetes. The reduction in cardiovascular mortality and hospitalization due to heart failure might be in part explained by the direct effects of empagliflozin on cardiac diastolic function. The EmDia trial investigates the short-term effects of empagliflozin compared to placebo on the left ventricular E/E' ratio as a surrogate of left ventricular diastolic function. METHODS: EmDia is a single-center, randomized, double-blind, two-arm, placebo-controlled, parallel group study of phase IV. Individuals with diabetes mellitus type 2 (T2DM) are randomized 1:1 to receive empagliflozin 10 mg per day or a placebo for 12 weeks. The main inclusion criteria are diagnosed as T2DM with stable glucose-lowering and/or dietary treatment, elevated HbA1c level (6.5-10.0% if receiving glucose-lowering therapy, or 6.5-9.0% if drug-naïve), and diastolic cardiac dysfunction with left ventricular E/E'≥8. The primary end point is the difference of the change in the E/E' ratio by treatment groups after 12 weeks. Secondary end points include assessment of the effect of empagliflozin on left ventricular systolic function, measures of vascular structure and function, as well as humoral cardiovascular biomarkers (i.e. brain natriuretic peptide, troponin, C-reactive protein). In addition, the multidimensional biodatabase enables explorative analyses of molecular biomarkers to gain insights into possible mechanisms of the effects of empagliflozin on human health in a systems medicine-oriented, multiomics approach. CONCLUSION: By evaluating the short-term effect of empagliflozin with a comprehensive biobanking program, the EmDia Study offers an opportunity to primarily assess the effects on diastolic function but also to examine effects on clinical and molecular cardiovascular traits. TRIAL REGISTRATION: ClinicalTrials.gov; NCT02932436. Registration date, 2016/10/13.

Inflammatory Glycoprotein 130 Signaling Links Changes in Microtubules and Junctophilin-2 to Altered Mitochondrial Metabolism and Right Ventricular Contractility.

BACKGROUND: Right ventricular dysfunction (RVD) is the leading cause of death in pulmonary arterial hypertension (PAH), but no RV-specific therapy exists. We showed microtubule-mediated junctophilin-2 dysregulation (MT-JPH2 pathway) causes t-tubule disruption and RVD in rodent PAH, but the druggable regulators of this critical pathway are unknown. GP130 (glycoprotein 130) activation induces cardiomyocyte microtubule remodeling in vitro; however, the effects of GP130 signaling on the MT-JPH2 pathway and RVD resulting from PAH are undefined. METHODS: Immunoblots quantified protein abundance, quantitative proteomics defined RV microtubule-interacting proteins (MT-interactome), metabolomics evaluated the RV metabolic signature, and transmission electron microscopy assessed RV cardiomyocyte mitochondrial morphology in control, monocrotaline, and monocrotaline-SC-144 (GP130 antagonist) rats. Echocardiography and pressure-volume loops defined the effects of SC-144 on RV-pulmonary artery coupling in monocrotaline rats (8-16 rats per group). In 73 patients with PAH, the relationship between interleukin-6, a GP130 ligand, and RVD was evaluated. RESULTS: SC-144 decreased GP130 activation, which normalized MT-JPH2 protein expression and t-tubule structure in the monocrotaline RV. Proteomics analysis revealed SC-144 restored RV MT-interactome regulation. Ingenuity pathway analysis of dysregulated MT-interacting proteins identified a link between microtubules and mitochondrial function. Specifically, SC-144 prevented dysregulation of electron transport chain, Krebs cycle, and the fatty acid oxidation pathway proteins. Metabolomics profiling suggested SC-144 reduced glycolytic dependence, glutaminolysis induction, and enhanced fatty acid metabolism. Transmission electron microscopy and immunoblots indicated increased mitochondrial fission in the monocrotaline RV, which SC-144 mitigated. GP130 antagonism reduced RV hypertrophy and fibrosis and augmented RV-pulmonary artery coupling without altering PAH severity. In patients with PAH, higher interleukin-6 levels were associated with more severe RVD (RV fractional area change 23±12% versus 30±10%, P=0.002). CONCLUSIONS: GP130 antagonism reduces MT-JPH2 dysregulation, corrects metabolic derangements in the RV, and improves RVD in monocrotaline rats.

Chrysosplenol-C Increases Contraction by Augmentation of Sarcoplasmic Reticulum Ca2+ Loading and Release via Protein Kinase C in Rat Ventricular Myocytes.

Naturally found chrysosplenol-C (4',5,6-trihydroxy-3,3',7-trimethoxyflavone) increases the contractility of cardiac myocytes independent of ß-adrenergic signaling. We investigated the cellular mechanism for chrysosplenol-C-induced positive inotropy. Global and local Ca2+ signals, L-type Ca2+ current (ICa), and contraction were measured from adult rat ventricular myocytes using two-dimensional confocal Ca2+ imaging, the whole-cell patch-clamp technique, and video-edge detection, respectively. Application of chrysosplenol-C reversibly increased Ca2+ transient magnitude with a maximal increase of ∼55% within 2- to 3-minute exposures (EC50 ≅ 21 µM). This chemical did not alter ICa and slightly increased diastolic Ca2+ level. The frequency and size of resting Ca2+ sparks were increased by chrysosplenol-C. Chrysosplenol-C significantly increased sarcoplasmic reticulum (SR) Ca2+ content but not fractional release. Pretreatment of protein kinase C (PKC) inhibitor but not Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibitor abolished the stimulatory effects of chrysosplenol-C on Ca2+ transients and Ca2+ sparks. Chrysosplenol-C-induced positive inotropy was removed by the inhibition of PKC but not CaMKII or phospholipase C. Western blotting assessment revealed that PKC-δ protein level in the membrane fractions significantly increase within 2 minutes after chrysosplenol-C exposure with a delayed (5-minute) increase in PKC-α levels in insoluble membrane. These results suggest that chrysosplenol-C enhances contractility via PKC (most likely PKC-δ)-dependent enhancement of SR Ca2+ releases in ventricular myocytes. SIGNIFICANCE STATEMENT: Study shows that chrysosplenol-C, a natural flavone showing a positive inotropic effect, increases SR Ca2+ releases on depolarizations and Ca2+ sparks with an increase of SR Ca2+ loading but not L-type Ca2+ current in ventricular myocytes. Chrysosplenol-C-induced enhancement in contraction is eliminated by PKC inhibition, and it is associated with redistributions of PKC to the membrane. These indicate that chrysosplenol-C enhances contraction via PKC-dependent augmentations of SR Ca2+ release and Ca2+ loading during action potentials.

Impact of interventional therapy on top of standard drug therapy on left ventricular structure and function in HFrEF patients complicating with middle aortic syndrome caused by Takayasu arteritis / 中华心血管病杂志

Objective: To evaluate the impact of interventional therapy on top of drug therapy on cardiac function and structure in heart failure with reduced ejection fraction (HFrEF) patients complicating with middle aortic syndrome caused by Takayasu arteritis (TA-MAS). Methods: It was a retrospective longitudinal study. The data of patients with TA-MAS and HFrEF, who received interventional therapy on top of drug therapy in Fuwai Hospital from January 2010 to September 2020, were collected and analyzed. Baseline clinical data (including demographic data, basic treatment, etc.) were collected through the electronic medical record system. Changes of indexes such as New York Heart Association (NYHA) classification, N-terminal pro-brain natriuretic peptide (NT-proBNP), left ventricular end diastolic diameter (LVEDD), left ventricular ejection fraction (LVEF), left ventricular mass index (LVMI) before and after therapy were analyzed. Results: A total of 10 patients were collected. There were 8 females in this patient cohort, age was (18.4±5.0) years and onset age was (15.3±5.0) years. All 10 patients received standard heart failure medication therapy in addition to hormone and/or immunosuppressive anti-inflammatory therapy, but cardiac function was not improved, so aortic balloon dilatation and/or aortic stenting were performed in these patients. The median follow-up was 3.3(1.3, 5.6) years. On the third day after interventional therapy, the clinical symptoms of the 10 patients were significantly improved, NYHA classfication was restored from preoperative Ⅲ/Ⅳ to Ⅱ at 6 months post intervention(P<0.05). Compared with preoperation, NT-proBNP (P=0.028), LVEDD (P=0.011) and LVMI (P=0.019) were significantly decreased, LVEF was significantly increased (P<0.001) at 6 months after operation. Compared with preoperation, NT-proBNP (P=0.016), LVEDD (P=0.023) and LVMI (P=0.043) remained decreased, LVEF remained increased (P<0.001) at 1 year after operation. Conclusion: Results from short and medium term follow-up show that interventional therapy on top of heart failure drug therpay can effectively improve left cardiac function and attenuate cardiac remodeling in patients with TA-MAS comorbid with HFrEF.

Pterostilbeno Reduz o Estresse Oxidativo no Pulmão e no Ventrículo Direito Induzido por Infarto do Miocárdio Experimental / Pterostilbene Reduces Experimental Myocardial Infarction-Induced Oxidative Stress in Lung and Right Ventricle

Resumo Fundamento O pterostilbeno (PS), um composto polifenólico natural e antioxidante, surge como uma intervenção promissora para minimizar danos do infarto agudo do miocárdio (IAM). Objetivo Este estudo teve como objetivo avaliar o desempenho do PS na promoção da homeostase redox nos pulmões e no ventrículo direito (VD) de animais infartados. Métodos Ratos Wistar machos (60 dias de idade) foram randomizados em três grupos: SHAM, IAM (infarto) e IAM+PS (IAM + pterostilbeno). Sete dias após o procedimento de IAM, os ratos foram tratados com PS (100 mg/kg/dia) por gavagem por oito dias. Os animais foram depois sacrificados e os pulmões e VD foram coletados para análise do balanço redox (diferenças foram consideradas significativas quando p<0,05). Resultados Nossos resultados mostram que o IAM desencadeia a interrupção redox no VD e nos pulmões, o que pode contribuir para danos induzido pelo IAM nesses órgãos. Consistentemente, o PS mitigou o estresse oxidativo e restaurou as defesas antioxidantes (Glutationa - GSH nos pulmões: SHAM = 0,79 ± 0,07; IAM = 0,67 ± 0,05; IAM + PS = 0,86 ± 0,14; p<0,05), indicando seu papel protetor neste cenário. Conclusão Nosso trabalho evidencia o potencial do uso de PS como abordagem terapêutica adjuvante após IAM para proteção dos tecidos pulmonares e cardíacos direitos.

Abstract Background Pterostilbene (PS), a natural and antioxidant polyphenolic compound emerges as a promising intervention in improving the myocardial infarction (MI) damages. Objetives This study aimed to evaluate PS actions in promoting redox homeostasis in lungs and right ventricle (RV) of infarcted animals. Methods Male Wistar rats (60 day-old) were randomized into three groups: SHAM, MI (infarcted), and MI+PS (MI+pterostilbene). Seven days after MI procedure, rats were treated with PS (100 mg/kg/day) via gavage for eight days. Animals were euthanized and the lungs and RV were harvested for analyses of redox balance (Differences were considered significant when p<0.05). Results Our results show that MI triggers a redox disruption scenario in RV and lungs, which can contribute to MI-induced damage on these organs. Consistently, PS mitigated oxidative stress and restored antioxidant defenses (GSH in lungs: SHAM= 0.79±0.07; MI=0.67±0.05; MI+PS=0.86±0.14; p<0.05), indicating its protective role in this scenario. Conclusions Our work evidences the PS potential use as an adjuvant therapeutic approach after MI focusing on protecting pulmonary and right-sided heart tissues.

Mitigation of doxorubicin-induced cardiotoxicity by dichloroacetate: potential roles of restoration of PGC-1α/SIRT3 signaling and suppression of oxidative stress and apoptosis.

OBJECTIVE: Doxorubicin (DOX) is an effective chemotherapeutic agent used in the treatment of various neoplasms. Nevertheless, its therapeutic efficacy is hampered by life-threatening heart failure. Therefore, the current study was undertaken to investigate whether dichloroacetate (DCA), a metabolic and mitochondrial modulator, when administered at a therapeutically feasible dose could potentially reverse acute DOX cardiotoxicity. Furthermore, the possible underlying mechanisms of cardioprotection were also assessed. MATERIALS AND METHODS: Different techniques were performed to assess cardiac injury like echocardiography, histopathology, transmission electron microscope, biomarkers of cardiac injury, and oxidative stress markers. Further, the expression levels of mRNA and protein were quantified by PCR and immunohistochemistry, respectively. RESULTS: Echocardiography showed that mice that received DOX/DCA combination were protected against heart failure. Additionally, histopathology and transmission electron microscopy revealed structural damage alleviation by DOX/DCA combination, which was confirmed biochemically via significant suppression of elevated CK-MB and AST levels. Mechanistically, DOX dysregulated the expression of PGC-1α and SIRT-3 genes which are key to normal mitochondrial functioning. Of note, co-treatment with DCA effectively restored PGC-1α/SIRT-3 signaling and normalized the mitochondrial DNA index. Moreover, events downstream of DOX-triggered mitochondrial dysfunction such as oxidative stress and p53-dependent apoptosis were all abrogated by combination with DCA. CONCLUSIONS: The present study is the first to provide in vivo evidence that DCA is effective in protecting against acute DOX cardiotoxicity. Additionally, the study highlights the potential of administering metabolic modulators to safeguard against DOX cardiotoxicity.

The short-chain fatty acid propionate improved ventricular electrical remodeling in a rat model with myocardial infarction.

The short-chain fatty acid (SCFA) propionate (C3), a microorganism metabolite produced by gut microbial fermentation, has parasympathetic-activation effects. The cardiac autonomic rebalancing strategy is considered as an important therapeutic approach to myocardial infarction (MI)-produced ventricular arrhythmias (VAs). Thus, our research was designed to clarify the potential functions of the SCFA propionate in VAs and cardiac electrophysiology in MI rats. A hundred adult Sprague-Dawley rats were allocated to four groups: the sham group (200 mM sodium chloride), the sham + C3 group (200 mM propionate), the MI group (200 mM sodium chloride) and the MI + C3 group (200 mM propionate). In comparison with the sham group, propionate significantly increased the parasympathetic components heart rate variability (HRV) and acetylcholine levels, prolonged cardiac repolarization, induced STAT3 phosphorylation and up-regulated the c-fos expression in nodose ganglia and solitary nucleus. Propionate intake reduced the susceptibility to VAs. MI induced by coronary ligation caused a significant increase in the sympathetic components HRV, abnormal repolarization, global repolarization dispersion, norepinephrine and inflammatory cytokines, reduction and redistribution of Connexin 43 in the infarcted border zone, and activation of NFκB, which were attenuated in the MI + C3 group. Oral propionate supplementation, as a nutritional intervention, protected the heart against MI-induced VAs and cardiac electrophysiology instability partly by parasympathetic activation based on the gut-brain axis.

Betulinic Acid Improves Cardiac-Renal Dysfunction Caused by Hypertrophy through Calcineurin-NFATc3 Signaling.

Cardiac hypertrophy can lead to congestive heart failure and is a leading cause of morbidity and mortality worldwide. In recent years, it has been essential to find the treatment and prevention of cardiac hypertrophy. Betulinic acid (BA), the main active ingredient in many natural products, is known to have various physiological effects. However, as the potential effect of BA on cardiac hypertrophy and consequent renal dysfunction is unknown, we investigated the effect of BA on isoprenaline (ISO)-induced cardiac hypertrophy and related signaling. ISO was known to induce left ventricular hypertrophy by stimulating the ß2-adrenergic receptor (ß2AR). ISO was injected into Sprague Dawley rats (SD rats) by intraperitoneal injection once a day for 28 days to induce cardiac hypertrophy. From the 14th day onwards, the BA (10 or 30 mg/kg/day) and propranolol (10 mg/kg/day) were administered orally. The study was conducted in a total of 5 groups, as follows: C, control; Is, ISO (10 mg/kg/day); Pr, positive-control, ISO + propranolol (10 mg/kg/day); Bl, ISO + BA (10 mg/kg/day); Bh, ISO + BA (30 mg/kg/day). As a result, the total cardiac tissue and left ventricular tissue weights of the ISO group increased compared to the control group and were significantly reduced by BA treatment. In addition, as a result of echocardiography, the effect of BA on improving cardiac function, deteriorated by ISO, was confirmed. Cardiac hypertrophy biomarkers such as ß-MHC, ANP, BNP, LDH, and CK-MB, which were increased by ISO, were significantly decreased by BA treatment. Also, the cardiac function improvement effect of BA was confirmed to improve cardiac function by inhibiting calcineurin/NFATc3 signaling. Renal dysfunction is a typical complication caused by cardiac hypertrophy. Therefore, the study of renal function indicators, creatinine clearance (Ccr) and osmolality (BUN) was aggravated by ISO treatment but was significantly restored by BA treatment. Therefore, it is thought that BA in cardiac hypertrophy can be used as valuable data to develop as a functional material effective in improving cardiac-renal dysfunction.

Inflammation-induced left ventricular fibrosis is partially mediated by tumor necrosis factor-α.

OBJECTIVE: To determine the mechanisms of inflammation-induced left ventricular (LV) remodeling and effects of blocking circulating tumor necrosis factor alpha (TNF-α) in a model of systemic inflammation. METHODS: Seventy Sprague-Dawley rats were divided into three groups: the control group, the collagen-induced arthritis (CIA) group, and the anti-TNF-α group. Inflammation was induced in the CIA and anti-TNF-α groups. Following the onset of arthritis, the anti-TNF-α group received the TNF-α inhibitor, etanercept, for 6 weeks. LV geometry and function were assessed with echocardiography. Circulating inflammatory markers were measured by ELISA and LV gene expression was assessed by comparative TaqMan® polymerase chain reaction. RESULTS: The LV relative gene expression of pro-fibrotic genes, transforming growth factor ß (TGFß) (p = 0.03), collagen I (Col1) (p < 0.0001), and lysyl oxidase (LOX) (p = 0.002), was increased in the CIA group compared with controls, consistent with increased relative wall thickness (p = 0.0009). Col1 and LOX expression in the anti-TNF-α group were similar to controls (both, p > 0.05) and tended to be lower compared to the CIA group (p = 0.06 and p = 0.08, respectively), and may, in part, contribute to the decreased relative wall thickness in the anti-TNF-α group compared to the CIA group (p = 0.03). In the CIA group, the relative gene expression of matrix metalloproteinase 2 (MMP2) and MMP9 was increased compared to control (p = 0.04) and anti-TNF-α (p < 0.0001) groups, respectively. CONCLUSION: Chronic systemic inflammation induces fibrosis and dysregulated LV extracellular matrix remodeling by increasing local cardiac pro-fibrotic gene expression, which is partially mediated by TNF-α. Inflammation-induced LV diastolic dysfunction is likely independent of myocardial fibrosis.

Characterization and functional role of rapid- and slow-activating delayed rectifier K+ currents in atrioventricular node cells of guinea pigs.

The atrioventricular (AV) node is the only conduction pathway where electrical impulse can pass from atria to ventricles and exhibits spontaneous automaticity. This study examined the function of the rapid- and slow-activating delayed rectifier K+ currents (IKr and IKs) in the regulation of AV node automaticity. Isolated AV node cells from guinea pigs were current- and voltage-clamped to record the action potentials and the IKr and IKs current. The expression of IKr or IKs was confirmed in the AV node cells by immunocytochemistry, and the positive signals of both channels were localized mainly on the cell membrane. The basal spontaneous automaticity was equally reduced by E4031 and HMR-1556, selective blockers of IKr and IKs, respectively. The nonselective ß-adrenoceptor agonist isoproterenol markedly increased the firing rate of action potentials. In the presence of isoproterenol, the firing rate of action potentials was more effectively reduced by the IKs inhibitor HMR-1556 than by the IKr inhibitor E4031. Both E4031 and HMR-1556 prolonged the action potential duration and depolarized the maximum diastolic potential under basal and ß-adrenoceptor-stimulated conditions. IKr was not significantly influenced by ß-adrenoceptor stimulation, but IKs was concentration-dependently enhanced by isoproterenol (EC50: 15 nM), with a significant negative voltage shift in the channel activation. These findings suggest that both the IKr and IKs channels might exert similar effects on regulating the repolarization process of AV node action potentials under basal conditions; however, when the ß-adrenoceptor is activated, IKs modulation may become more important.

Application of plasma polymerized pyrrole nanoparticles to prevent or reduce de-differentiation of adult rat ventricular cardiomyocytes.

Cardiovascular diseases are the leading cause of death in the world, cell therapies have been shown to recover cardiac function in animal models. Biomaterials used as scaffolds can solve some of the problems that cell therapies currently have, plasma polymerized pyrrole (PPPy) is a biomaterial that has been shown to promote cell adhesion and survival. The present research aimed to study PPPy nanoparticles (PPPyN) interaction with adult rat ventricular cardiomyocytes (ARVC), to explore whether PPPyN could be employed as a nanoscaffold and develop cardiac microtissues. PPPyN with a mean diameter of 330 nm were obtained, the infrared spectrum showed that some pyrrole rings are fragmented and that some fragments of the ring can be dehydrogenated during plasma synthesis, it also showed the presence of amino groups in the structure of PPPyN. PPPyN had a significant impact on the ARVC´s shape, delaying dedifferentiation, necrosis, and apoptosis processes, moreover, the cardiomyocytes formed cell aggregates up to 1.12 mm2 with some aligned cardiomyocytes and generated fibers on its surface similar to cardiac extracellular matrix. PPPyN served as a scaffold for adult ARVC. Our results indicate that PPPyN-scaffold is a biomaterial that could have potential application in cardiac cell therapy (CCT).

The Short-Chain Fatty Acid Butyrate Attenuates Pulmonary Vascular Remodeling and Inflammation in Hypoxia-Induced Pulmonary Hypertension.

Pulmonary hypertension (PH) is a progressive cardiovascular disorder in which local vascular inflammation leads to increased pulmonary vascular remodeling and ultimately to right heart failure. The HDAC inhibitor butyrate, a product of microbial fermentation, is protective in inflammatory intestinal diseases, but little is known regarding its effect on extraintestinal diseases, such as PH. In this study, we tested the hypothesis that butyrate is protective in a Sprague-Dawley (SD) rat model of hypoxic PH. Treatment with butyrate (220 mg/kg intake) prevented hypoxia-induced right ventricular hypertrophy (RVH), hypoxia-induced increases in right ventricular systolic pressure (RVSP), pulmonary vascular remodeling, and permeability. A reversal effect of butyrate (2200 mg/kg intake) was observed on elevated RVH. Butyrate treatment also increased the acetylation of histone H3, 25-34 kDa, and 34-50 kDa proteins in the total lung lysates of butyrate-treated animals. In addition, butyrate decreased hypoxia-induced accumulation of alveolar (mostly CD68+) and interstitial (CD68+ and CD163+) lung macrophages. Analysis of cytokine profiles in lung tissue lysates showed a hypoxia-induced upregulation of TIMP-1, CINC-1, and Fractalkine and downregulation of soluble ICAM (sICAM). The expression of Fractalkine and VEGFα, but not CINC-1, TIMP-1, and sICAM was downregulated by butyrate. In rat microvascular endothelial cells (RMVEC), butyrate (1 mM, 2 and 24 h) exhibited a protective effect against TNFα- and LPS-induced barrier disruption. Butyrate (1 mM, 24 h) also upregulated tight junctional proteins (occludin, cingulin, claudin-1) and increased the acetylation of histone H3 but not α-tubulin. These findings provide evidence of the protective effect of butyrate on hypoxic PH and suggest its potential use as a complementary treatment for PH and other cardiovascular diseases.