Post-myocardial Infarction Rats Research Articles

Chronic mitochondrial dynamic-targeted therapy alleviates left ventricular dysfunction by reducing multiple programmed cell death in post-myocardial infarction rats

Mitochondrial dysfunction and the activation of multiple programmed cell death (PCD) have been shown to aggravate the severity and mortality associated with the progression of myocardial infarction (MI). Although pharmacological modulation of mitochondrial dynamics, including treatment with the fusion promoter (M1) and the fission inhibitor (Mdivi-1), exerted cardioprotection against several cardiac complications, their roles in the post-MI model have never been investigated. Using a MI rat model instigated by permanent left-anterior descending (LAD) coronary artery occlusion, post-MI rats were randomly assigned to receive one of 4 treatments (n = 10/group): vehicle (DMSO 3%V/V), enalapril (10 mg/kg), Mdivi-1 (1.2 mg/kg) and M1 (2 mg/kg), while a control group of sham operated rats underwent surgery without LAD occlusion (n = 10). After 32-day treatment, cardiac and mitochondrial function, and histopathological morphology were investigated and molecular analysis was performed. Treatment with enalapril, Mdivi-1, and M1 significantly mitigated cardiac pathological remodeling, reduced myocardial injury, and improved left ventricular (LV) function in post-MI rats. Importantly, all interventions also attenuated mitochondrial dynamic imbalance and mitigated activation of apoptosis, necroptosis, and pyroptosis after MI. This investigation demonstrated for the first time that chronic mitochondrial dynamic-targeted therapy mitigated mitochondrial dysfunction and activation of PCD, leading to improved LV function in post-MI rats.

Therapeutic potential of pharmacological inhibition of programmed apoptosis, necroptosis, and ferroptosis in improving left ventricular function in post-myocardial infarction rats

Abstract Background Heart failure (HF) is considered the most fatal complicating sequelae after myocardial infarction (MI). Various types of programmed cell deaths (PCDs), including apoptosis, necroptosis, and ferroptosis, have been documented as the pathological progression following MI. Although novel pharmacologically specific cell death inhibitors of apoptosis, necroptosis, and ferroptosis have been shown to exert cardioprotection against acute MI and reperfusion injury, their beneficial effects have never been investigated in a post-MI-induced HF model. Purpose To investigate the therapeutic efficacy and potential underlying mechanisms of inhibitors of apoptosis, necroptosis, and ferroptosis in post-MI rats. Methods Adult male Wistar rats were assigned to the sham (n = 6) and the MI groups (n = 30) via a permanent LAD occlusion. After 1-week LAD ligation, MI rats were divided into 5 subgroups: 1) vehicle (3% DMSO/day, IP, CON, n = 6), 2) enalapril (10 mg/kg/day, PO, ENA, n = 6), 3) apoptosis inhibitor zVAD-FMK (1 mg/kg/day, IP, zVAD, n = 6), 4) necroptosis inhibitor Necrostatin-1 (1.65 mg/kg/day, IP, Nec-1, n = 6), or 5) ferroptosis inhibitor Ferrostatin-1 (2 mg/kg/day, IP, Fer-1, n = 6) for 4 weeks. Then, echocardiography for LV function was performed, and the hearts were removed to determine pertinent apoptosis, necroptosis, and ferroptosis proteins by immunoblotting assays. Malondialdehyde (MDA) levels for myocardial oxidative stress were quantified. Results Post-MI rats exhibited worsening LV dysfunction, as indicated by a markedly reduced %LV ejection fraction (LVEF) (Fig. 1A). Post-MI rats showed higher MDA levels in cardiac tissue, indicating myocardial oxidative stress (Fig. 1B). Furthermore, post-MI rats had elevated expressions of proteins related to apoptosis (Cleaved caspase3/Caspase 3) and necroptosis (pMLKL/tMLKL), but not ferroptosis (ACSL4/GAPDH) (Fig. 1C-E). As a standard treatment for MI, enalapril reduced not only myocardial oxidative stress, but also apoptosis and necroptosis activation, thereby enhancing %LVEF after MI (Fig 1A-D). Notably, treatment of post-MI rats with the apoptosis inhibitor zVAD-FMK, necroptosis inhibitor Necrostatin-1, and ferroptosis inhibitor Ferroptosin-1 ameliorated LV dysfunction and myocardial oxidative stress upregulation (Fig A-B). Interestingly, treatment with zVAD, Nec-1, and Fer-1 effectively attenuated both myocardial apoptosis and necroptosis activation after MI (Fig 1C-D). Conclusion Post-MI increased myocardial oxidative stress and activated multiple PCDs, including apoptosis and necroptosis but not ferroptosis, thus leading to LV dysfunction. Apoptosis and necroptosis inhibitors effectively mitigated oxidative stress and myocardial death, resulting in improved LV function in post-MI rats. These findings highlight the therapeutic potential of inhibiting apoptosis and necroptosis as promising pharmacological interventions to improve clinical outcomes for post-MI patients.

Dengzhan Shengmai capsule attenuates cardiac fibrosis in post-myocardial infarction rats by regulating LTBP2 and TGF-β1/Smad3 pathway

BackgroundCardiac fibrosis contributes to myocardial remodeling after myocardial infarction (MI), which may facilitate the progression to end-stage heart failure. Dengzhan Shengmai capsule (DZSMC), a traditional Chinese formula derived from Shen-mai powder, has shown remarkable therapeutic effects against cardiovascular diseases. However, the effect of DZSMC on cardiac fibrosis and its potential mechanism are ill-defined. PurposeTo evaluate the effects of DZSMC on cardiac fibrosis after myocardial infarction (MI) and investigate its underlying mechanism. MethodIn vivo, MI rat models were established by permanently ligation of left anterior descending coronary arteries (LAD) and then were intragastrically treated with DZSMC or captopril for 5 weeks. Ex vivo, an everted intestinal sac model was used to study the intestinal absorption components of DZSMC, which were further identified through an ultra-performance liquid chromatography tandem mass spectrometry (UHPLC-MS) method. In vitro, a myocardium fibrotic model was constructed by stimulating primary cardiac fibroblasts (CFs) with 1 μM Ang II. Subsequently, the absorbent solution of DZSMC from the intestinal sac was performed on the cell models to further elucidate its anti-fibrotic effects and underling mechanism. ResultsIn vivo results showed that DZSMC significantly improved cardiac function and inhibited pathological myocardial fibrosis in post-MI rats in a dose dependent manner. Histological analysis and western blot results demonstrated that DZSMC treatment significantly reduced the expression of extracellular matrix (ECM)-related proteins, including LTBP2, TGF-βR1, Smad3 and pSmad3, in myocardial tissue of MI rats. Ex vivo results showed that 18 absorbed components were identified, mainly consisting of phenolic acids, flavonoids and lignans, which may be responsible for the anti-fibrotic effects. Further in vitro results validated that DZSMC attenuated myocardial fibrosis by suppressing the expression of LTBP2, TGF-β1 and pSmad3. ConclusionDZSMC ameliorates cardiac function and alleviates cardiac fibrosis, which may be mediated by inhibition of CFs activation and reduction of excessive ECM deposition via LTBP2 and TGF-β1/Smad3 pathways.

Modified Linggui Zhugan Decoction protects against ventricular remodeling through ameliorating mitochondrial damage in post-myocardial infarction rats.

Modified Linggui Zhugan Decoction (MLZD) is a Traditional Chinese Medicine prescription developed from Linggui Zhugan Decoction (LZD) that has been used for the clinical treatment of ischemic cardiovascular diseases. However, the cardioprotective mechanism of MLZD against post-myocardial infarction (MI) ventricular remodeling remains unclear. We explored the effects of MLZD on ventricular remodeling and their underlying mechanisms, respectively, in SD rats with MI models and in H9c2 cardiomyocytes with oxygen-glucose deprivation (OGD) models. The cardiac structure and function of rats were measured by echocardiography, HE staining, and Masson staining. Apoptosis, inflammation, mitochondrial structure and function, and sirtuin 3 (SIRT3) expression were additionally examined. MLZD treatment significantly ameliorated cardiac structure and function, and thus reversed ventricular remodeling, compared with the control. Further research showed that MLZD ameliorated mitochondrial structural disruption, protected against mitochondrial dynamics disorder, restored impaired mitochondrial function, inhibited inflammation, and thus inhibited apoptosis. Moreover, the decreased expression level of SIRT3 was enhanced after MLZD treatment. The protective effects of MLZD on SIRT3 and mitochondria, nevertheless, were blocked by 3-TYP, a selective inhibitor of SIRT3. These findings together revealed that MLZD could improve the ventricular remodeling of MI rats by ameliorating mitochondrial damage and its associated apoptosis, which might exert protective effects by targeting SIRT3.

Cardiac sympathetic afferent denervation reduces matrix metalloproteinase expression and improves cardiac remodeling in rats post myocardial infarction

Abstract In a previous study from our laboratory, we demonstrated that chronic and selective cardiac sympathetic afferent (spinal) denervation at the time of myocardial infarction (MI) using epicardial application of resiniferatoxin (RTX), a neuronal toxin capable of inducing rapid degeneration of transient receptor potential vanilloid 1 (TRPV1)-expressing afferent neurons and fibers, markedly reduced the cardiac remodeling process 9–11 weeks post-MI in rats. This included reduced cardiac hypertrophy, fibrosis and apoptosis. Here, we further investigated the effect of epicardial application of RTX at the time of MI on cardiac extracellular matrix (ECM) and remodeling post-MI. Echocardiographic and morphologic data demonstrated that, compared to MI+vehicle, MI+RTX exhibited a significantly slower LV chamber dilation (6-week echocardiographic data: left ventricular end-diastolic diameter, 10.7±0.2 vs. 9.6±0.3 mm; left ventricular end-systolic diameter: 8.8±0.2 vs. 7.8±0.3 mm; MI+vehicle vs. MI+RTX, n=18, p<0.05; mean±SE). Scanning electron microscopy showed that RTX reduced collagen deposition in the peri-infarct area in post-MI rats. Western blot and zymography were used to further evaluate the effect of RTX application on matrix metalloproteinase (MMP) expression and activity, which is responsible for degrading ECM and contributing to cardiac dilation post MI. Our data suggest time-dependent increases in MMP expression in infarcted hearts post MI. RTX application largely prevented the increase in MMP9 but not MMP2, 4 weeks post-MI. RTX prevented both increased MMP2 and MMP9 activities in the peri-infarct myocardium at 8–10 weeks post-MI. We further investigated the effect of RTX application on MI-induced cardiac inflammation, which has been reported as an upstream mechanism triggering MMP activation post-MI. The data show that RTX largely abolished MI-induced plasma extravasation and reduced macrophage infiltration and cardiac cytokine content in the peri-infarct or remote myocardium of post-MI rats. These data suggest that cardiac sympathetic afferent denervation at the time of MI exerts a local anti-inflammatory effect and reduces ECM remodeling by preventing excessive MMP activation in post-MI rats. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Institutes of Health Grant HL126796

Influence of the SGLT2 inhibitor empagliflozin on post myocardial infarction rat hearts

Abstract Studies have shown that inhibition of the sodium glucose transporter protein 2 (SGLT2) reduces cardiovascular death in patients with heart failure and reduced ejection fraction. However, the mechanisms involved in the benefits of SGLT2 inhibitors are poorly understood. Objective To evaluate the effects of empagliflozin (EMP) on normal and post-myocardial infarction (MI) rat hearts. Methods Male Wistar rats (n=80) were assigned into four groups: Sham; Sham treated with EMP (Sham-EMP); myocardial infarction (MI); and MI treated with EMP (MI-EMP). EMP added to rat chow (5 mg/kg/day) was initiated 10 days after MI induction and maintained for 12 weeks. Echocardiogram was performed at the end of the experimental period. Markers of oxidative stress, energy metabolism, and respiratory complex activity were analyzed in left ventricular myocardium. Statistical analysis: ANOVA. Results Histological evaluation showed that EMP did not change infarct size. Cardiac structural and functional parameters did not differ between MI-EMP and MI groups. Myocardial oxidative stress, evaluated by lipid hydroperoxide concentration, was lower in MI-EMP than MI group (Sham 143±26; Sham-EMP 123±20; MI 183±29; MI-EMP 137±11 nmol/g tissue). Glutathione peroxidase was lower in the infarcted groups and did not differ between MI-EMP and MI (Sham 37.6±6.14; Sham-EMP 40.8±10.1; MI 27.7±6.61; MI-EMP 26.5±6.80 μmol/g tissue). Activity of the energy metabolism enzymes lactate dehydrogenase (Sham 45.2±6.65; Sham-EMP 41.1±9.33; MI 58.4±14.4; MI-EMP 55.7±10.1 nmol/mg protein) and citrate synthase (Sham 30.4±4.25; Sham-EMP 37.2±4.85; MI 45.8±8.47; MI-EMP 46.5±9.95 nmol/mg protein) was higher, and β-hydroxyacyl-CoA dehydrogenase (Sham 24.0±3.12; Sham-EMP 20.4±4.84; MI 16.9±4.81; MI-EMP 14.4±4.58 nmol/mg protein) lower in the infarcted groups with no differences between MI-EMP and MI. Respiratory complexes I and II, and ATP synthase did not differ between the infarcted groups. Conclusion Empagliflozin reduces myocardial oxidative stress independent of changes in antioxidant enzymes activity, energy metabolism, and respiratory complex activity in the myocardium of infarcted rats. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Fapesp, CNPq

Effect of TLR4/MyD88/NF-kB axis in paraventricular nucleus on ventricular arrhythmias induced by sympathetic hyperexcitation in post-myocardial infarction rats.

Sympathetic activation after myocardial infarction (MI) leads to ventricular arrhythmias (VAs), which can result in sudden cardiac death (SCD). The toll‐like receptor 4 (TLR4)/myeloid differentiation primary response 88 (MyD88)/nuclear factor‐kappa B (NF‐kB) axis within the hypothalamic paraventricular nucleus (PVN), a cardiac‐neural sympathetic nerve centre, plays an important role in causing VAs. An MI rat model and a PVN‐TLR4 knockdown model were constructed. The levels of protein were detected by Western blotting and immunofluorescence, and localizations were visualized by multiple immunofluorescence staining. Central and peripheral sympathetic activation was visualized by immunohistochemistry for c‐fos protein, renal sympathetic nerve activity (RSNA) measurement, heart rate variability (HRV) analysis and norepinephrine (NE) level detection in serum and myocardial tissue measured by ELISA. The arrhythmia scores were measured by programmed electrical stimulation (PES), and cardiac function was detected by the pressure–volume loop (P‐V loop). The levels of TLR4 and MyD88 and the nuclear translocation of NF‐kB within the PVN were increased after MI, while sympathetic activation and arrhythmia scores were increased and cardiac function was decreased. However, inhibition of TLR4 significantly reversed these conditions. PVN‐mediated sympathetic activation via the TLR4/MyD88/NF‐kB axis ultimately leads to the development of VAs after MI.

Abstract 10978: Ecklonia Stolonifera Okamura Extract Suppresses Cardiac Hypertrophy and Systolic Dysfunction Through P300-HAT Inhibition

Introduction: Heart failure is the leading cause of death in the world. Cardiomyocyte hypertrophy is observed during the development of heart failure, suggesting that its inhibition is a potential target for the prevention and treatment of heart failure. In this study, we screened a natural compound library using cultured cardiomyocytes and found that Ecklonia stolonifera Okamura extract (ESE) suppressed cardiomyocyte hypertrophy. Hypothesis: ESE, a perennial brown alga, has been reported to have various bioactive effects, such as antioxidant and anti-inflammatory activity, but its effect on heart failure is still unclear. Therefore, we investigated whether ESE has an inhibitory effect on cardiomyocyte hypertrophic response and on the progression of heart failure in post-myocardial infarction (MI) rats. Methods and Results: First, primary cultured cardiomyocytes from neonatal rats were treated with ESE and then stimulated with phenylephrine (PE) for 48 hours. ESE (1000 μg/mL) significantly suppressed PE-induced increases in cardiomyocyte surface area, hypertrophic response gene transcription, and acetylation of histone H3K9. An in vitro p300-HAT assay indicated that ESE directly inhibited p300-HAT activity (IC50: 505 μg/mL). Next, one week after the ligation of the left anterior descending artery, rats with moderate MI (left ventricular fractioning shorting (LVFS) <40%) were randomly assigned to three groups: vehicle (saline) (n=9), ESE (0.3 g/kg) (n=10), or ESE (1 g/kg) (n=10). Daily oral administration was repeated for 8 weeks. After treatment, LVFS was significantly higher in the ESE (1 g/kg) group (23.3 ± 0.7%, p<0.05) than in the vehicle group (16.6 ± 1.3%). ESE treatment significantly suppressed MI-induced increases both in myocardial cell diameter and in the mRNA levels of hypertrophic response genes. ESE also inhibited MI-induced perivascular fibrosis and the acetylation of histone H3K9. Conclusion: These results suggest that ESE suppresses both hypertrophic responses in cardiomyocytes and the development of heart failure by inhibiting p300-HAT activity. Further studies are needed to clarify the effectiveness of ESE for heart failure therapy.

Abstract P381: Ecklonia Stolonifera Okamura Extract Suppresses Hypertrophic Responses In Cardiomyocytes And Development Of Heart Failure By Inhibiting P300-HAT Activity

Introduction: Heart failure is the leading cause of death in the world. Cardiomyocyte hypertrophy is observed during the development of heart failure, suggesting that its inhibition is a potential target for the prevention and treatment of heart failure. In this study, we screened a natural compound library using cultured cardiomyocytes and found that Ecklonia stolonifera Okamura extract (ESE) suppressed cardiomyocyte hypertrophy. ESE, a perennial brown alga, has been reported to have various bioactive effects, such as antioxidant and anti-inflammatory activity, but its effect on heart failure is still unclear. Therefore, we investigated whether ESE has an inhibitory effect on cardiomyocyte hypertrophic response and on the progression of heart failure in post-myocardial infarction (MI) rats. Methods and Results: First, primary cultured cardiomyocytes from neonatal rats were treated with ESE and then stimulated with phenylephrine (PE) for 48 hours. ESE (1000 μg/mL) significantly suppressed PE-induced increases in cardiomyocyte surface area, hypertrophic response gene transcription, and acetylation of histone H3K9. An in vitro p300-HAT assay indicated that ESE directly inhibited p300-HAT activity (IC50: 505 μg/mL). Next, one week after the ligation of the left anterior descending artery, rats with moderate MI (left ventricular fractioning shorting (LVFS) <40%) were randomly assigned to three groups: vehicle (saline) (n=9), ESE (0.3 g/kg) (n=10), or ESE (1 g/kg) (n=10). Daily oral administration was repeated for 8 weeks. After treatment, LVFS was significantly higher in the ESE (1 g/kg) group (23.3 ± 0.7%, p<0.05) than in the vehicle group (16.6 ± 1.3%). Next, the hearts were isolated and histological analysis, evaluation of gene transcription, and measurement of histone H3K9 acetylation. were performed. ESE treatment significantly suppressed MI-induced increases both in myocardial cell diameter and in the mRNA levels of hypertrophic response genes. ESE also inhibited MI-induced perivascular fibrosis and the acetylation of histone H3K9. Conclusion: These results suggest that ESE suppresses both hypertrophic responses in cardiomyocytes and the development of heart failure by inhibiting p300-HAT activity. Further studies are needed to clarify the effectiveness of ESE for heart failure therapy.

Ghrelin attenuates depressive-like behavior, heart failure, and neuroinflammation in postmyocardial infarction rat model

Depression after myocardial infarction (MI) and chronic heart failure (CHF) is a common condition that is resistant to anti-depressive drugs. Ghrelin (a peptide hormone) shows dual protective effects on heart and brain. Whether ghrelin treatment attenuated depression after MI was investigated. Coronary artery occlusion was performed to induce MI and subsequent CHF in rats. Ghrelin (100 μg/kg in 0.5 ml of saline) or vehicle (0.5 ml of saline) was injected subcutaneously twice a day for 4 weeks. At week 5, all the animals underwent behavioral assessments including sucrose preference test (SPT), elevated plus maze test (EPM), and open field test (OFT). After cardiac function analysis, brain tissues were processed to determine inflammatory cytokines and microglial activations in hippocampus. Results showed that ghrelin substantially improved cardiac dysfunction, infarction size, and cardiac remodeling and modulated the release of inflammatory cytokines and the increase of Iba-1 positive microglia and glial fibrillary acidic protein-positive astrocytes in the CA1 area of hippocampus. Behavioral tests revealed that this treatment remarkably increased sucrose preference and mobile times and numbers. These findings provided evidence that peripheral ghrelin administration inhibits depression-like behavior and neuroinflammation and thus could be a new approach for the treatment of CHF-associated depression.

BRAIN-PENETRATING AMINOPEPTIDASE A INHIBITORS FOR NEW TREATMENT OF HYPERTENSION AND HEART FAILURE

Objective: Brain renin-angiotensin system (RAS) hyperactivity is involved in the pathophysiology of hypertension and heart failure (HF). Angiotensin III/(AngIII), one of the main effector peptides of the brain RAS, exerts tonic stimulatory control over blood pressure/(BP) in hypertensive rats and plays a pivotal role in sympathetic hyperactivity and left ventricular/(LV) dysfunction in rats post-myocardial infarction/(MI). Thus, aminopeptidase A/(APA), the enzyme generating brain AngIII represents a potential therapeutic target for the treatment of these pathologies. Our aim was to evaluate the mode of action of firibastat, a brain-penetrating prodrug of the APA inhibitor, EC33, to reduce BP in hypertensive rats and prevent LV dysfunction in mice post-MI. Design and method: Firibastat and MLN4760, an angiotensin-converting enzyme2/(ACE2) inhibitor were administered by central route in hypertensive DOCA-salt rats and mean arterial BP (MABP) was recorded following insertion of a catheter into the femoral artery. Brain APA and ACE2 activities were measured 30 min post-treatment. Two days post-MI induced by the left anterior descending artery ligation, mice were randomized to receive during 4–8 weeks oral treatment with vehicle, firibastat (150 mg/kg) or the ACE inhibitor, enalapril (1 mg/kg). Cardiac function was evaluated by echocardiography Results: 1-Firibastat, when given centrally in hypertensive rats, is immediately cleaved by brain reductases, generating EC33 which inhibits brain APA activity, blocks brain AngIII formation and decreases BP. At the same time, firibastat treatment increases the activity of brain ACE2, majoring the conversion of AngII to Ang1-7, which by acting on the Mas-receptor, participate to the firibastat-induced BP decrease. 2-Chronic firibastat treatment in mice post-MI normalizes brain APA activity (normalizing brain RAS activity) and prevents sympathetic hyperactivity. It reduced LV end-diastolic pressure, LV end-systolic diameter and volume, and increased LV ejection fraction. It decreased the expression of HF and fibrosis biomarkers. Firibastat treatment prevents cardiac dysfunction and attenuates cardiac hypertrophy and fibrosis. Conclusions: Following these data, firibastat was selected for clinical development. Phase IIa/IIb clinical trials provided pharmacological proof-of-principle of firibastat efficacy for decreasing BP in hypertensive patients. The ongoing phase II study/QUORUM will determine if firibastat treatment may constitute a new therapeutic approach for preventing HF post-MI.

Effects of exercise on BDNF-TrkB signaling in the paraventricular nucleus and rostral ventrolateral medulla in rats post myocardial infarction

Brain-derived neurotrophic factor (BDNF)-tropomyosin-related kinase B (TrkB) signaling in the paraventricular nucleus (PVN) and rostral ventrolateral medulla (RVLM) is associated with cardiovascular regulation. Exercise increases plasma BDNF and attenuates activation of central pathways in the PVN and RVLM post myocardial infarction (MI). The present study assessed whether MI alters BDNF-TrkB signaling and intracellular factors Ca2+/calmodulin-dependent protein kinase II (CaMKII) and Akt in the PVN and RVLM of male Wistar rats with or without exercise or treatment with the TrkB blocker ANA-12. A 4-week period of treadmill exercise training was performed in MI rats. A separate experiment was conducted with 2.5 mg/kg ANA-12 in sedentary MI rats. At 5 weeks post MI, in both the PVN and RVLM, the ratio of full-length TrkB (TrkB.FL) and truncated TrkB (TrkB.T1) was decreased. 0.5 mg/kg ANA-12 did not affect BDNF-TrkB signaling and cardiac function post MI, but 2.5 mg/kg ANA-12 further decreased ejection fraction (EF). Exercise increased mature BDNF (mBDNF) and decreased Akt activity in the PVN, whereas in the RVLM, exercise did not affect mBDNF but lowered p-CaMKIIβ. ANA-12 prevented the exercise-induced increase in mBDNF in the PVN and decrease in p-CaMKIIβ in the RVLM. In conclusion, exercise decreases Akt activity in the PVN and decreases p-CaMKIIβ in the RVLM post MI. BDNF-TrkB signaling only mediates the decrease in p-CaMKIIβ in the RVLM. The exercise-induced decreases in Akt activity in the PVN and p-CaMKIIβ in the RVLM may contribute to the attenuation of the decrease in EF and sympathetic hyperactivity post MI.

Comparison of renal impairment post-myocardial infarction with reduced and preserved left ventricular function in rats with normal renal function

This study aimed to compare the renal impairments in post-myocardial infarction (MI) rats with normal renal biochemical parameters at baseline with versus without cardiac dysfunction and explore the potential mechanisms involved in these differences. Sprague–Dawley rats with permanent ligation of coronary artery were used as MI models. Renal function, histological and molecular changes were compared between the reduced ejection fraction (EF) (EF < 40%) group and the preserved EF (EF ≥ 40%) group 3 or 9 weeks post-MI. The results revealed that blood cystatin C increased significantly at 9 but not 3 weeks, but it was not associated with cardiac dysfunction. Renal fibrosis and inflammatory cell infiltrations increased significantly in the reduced EF group than in the preserved EF group at 3 and 9 weeks. Glomerular podocyte injury, identified by increased immunostaining for desmin and decreased immunostaining for Wilms’ tumor-1, was more significant in the reduced EF group than in the preserved EF group at 9, but not 3 weeks. The number of p16ink4a-positive and 8-hydroxy-2′-deoxyguanosine-positive podocytes was greater in the reduced EF group than in the preserved EF group at both time points. These changes were associated with increased expression of angiotensin II type 1/2 receptors at both time points. In conclusion, our study demonstrated that cardiac dysfunction accounted for substantially severity in renal parenchymal impairment in a partially time-dependent manner, and local activation of angiotensin II receptors, increased cell senescence and oxidative stress, and enhanced inflammatory reaction may be potential modulators participated in the deterioration of renal parenchymal injury.

Tongguan capsule derived-herb ameliorates remodeling at infarcted border zone and reduces ventricular arrhythmias in rats after myocardial infarction

ObjectiveTongguan Capsule, a traditional Chinese medicine, is safe to use and is efficient in treating ischemic heart diseases. The present study aimed to investigate whether Tongguan capsule derived-herb (TGD) can mitigate left ventricular remodeling and dysfunction in post myocardial infarction (MI) rats as well as reduce arrhythmias. Design and methodsMI was induced by a ligation of the left anterior descending coronary artery. TGD was administered to the post-MI rats over a period of 4 weeks. TGD treatment significantly attenuated tachyarrhythmia inducibility and cardiac dysfunction in post-MI heart. Echocardiogram showed that TGD significantly reduced the development of ventricular remodeling. Histological study revealed that TGD significantly reduced myocardial interstitial collagen deposition, myocyte area and α-smooth muscle actin (α-SMA) expression, and increased connexin 43 expression in the infarcted border zone (IBZ). Western blotting results revealed that TGD treatment significantly down-regulated the protein expression levels of type I and III collagen, α-SMA, and up-regulated connexin 43. RT-qPCR results showed that TGD decreased the levels of ANP and BNP. ConclusionsThese findings provided strong evidences that TGD intervention ameliorated interstitial fibrosis, myocyte hypertrophy and gap junction expression in the IBZ, attenuated left ventricular remodeling and dysfunction, and reduced vulnerability to tachyarrhythmia. TGD inhibited IBZ remodeling by its inhibition effect on myofibroblasts differentiation.

Danqi soft capsule prevents infarct border zone remodelling and reduces susceptibility to ventricular arrhythmias in post-myocardial infarction rats.

Danqi soft capsule (DQ) is a traditional Chinese medicine containing Salvia miltiorrhiza and Panax notoginseng; it is safe and efficient in treating ischaemic heart diseases. The purpose of the present study was to assess whether DQ could prevent infarct border zone (IBZ) remodelling and decrease ventricular arrhythmias occurrence in post‐myocardial infarction (MI) stage. MI was induced by a ligation of the left anterior descending coronary artery. DQ was administered to the post‐MI rats started from 1 week after MI surgery for 4 weeks. The results showed that DQ treatment significantly attenuated tachyarrhythmia induction rates and arrhythmia score in post‐MI rats. In echocardiography, DQ improved left ventricular (LV) systolic and diastolic function. Histological assessment revealed that DQ significantly reduced fibrotic areas and myocyte areas, and increased connexin (Cx) 43 positive areas in IBZ. Western blot revealed that DQ treatment significantly reduced the protein expression levels of type I and III collagens, α‐smooth muscle actin (α‐SMA), transforming growth factor‐β1 (TGF‐β1) and Smad3 phosphorylation, while increasing Cx43 amounts. Overall, these findings mainly indicated that DQ intervention regulates interstitial fibrosis, Cx43 expression and myocyte hypertrophy by TGF‐β1/Smad3 pathway in IBZ, inhibits LV remodelling and reduces vulnerability to tachyarrhythmias after MI. This study presents a proof of concept for novel antiarrhythmic strategies in preventing IBZ remodelling, modifying the healed arrhythmogenic substrate and thus reducing susceptibility to ventricular arrhythmias in the late post‐MI period.

Inhibition of inflammation by minocycline improves heart failure and depression-like behaviour in rats after myocardial infarction.

RationalePatients with heart failure have an increased incidence of depression. Central and peripheral inflammation play a major role in the pathophysiology of both heart failure and depression.AimMinocycline is an antibiotic that inhibits microglia activation and release of pro-inflammatory cytokines. We assessed effects of minocycline on extent of heart failure and depression at 2 and 8 weeks post myocardial infarction.Methods/ResultsMale Wistar rats were randomly divided into 3 groups: (i) sham + vehicle; (ii) MI + vehicle; and (iii) MI + minocycline with n/group of 8, 9 and 9 at 2 weeks, and 10, 16, 8 at weeks, respectively. Oral minocycline (50 mg/kg/day) or vehicle started 2 days before surgery. Depression-like behaviour was assessed with sucrose preference and forced swim tests, and cardiac function with echo and hemodynamics. After myocardial infarction, microglia activation and plasma/brain pro-inflammatory cytokines increased, which were mostly prevented by minocycline. At 8 weeks, cardiac dysfunction was attenuated by minocycline: infarct size (MI + Vehicle 29±1, MI + Min 23±1%), ejection fraction (Sham 80±1, MI + Vehicle 48±2, MI + Min 58±2%) and end diastolic pressure (Sham 3.2±0.3, MI + Vehicle 18.2±1.1, MI + Min 8.5±0.9 mm Hg). Depression-like behaviour was significantly improved by minocycline in sucrose preference test (% Sucrose Intake: Sham 96±1, MI + Vehicle 78±2, MI + Min 87±2) and forced swim test (% Immobile: Sham 40±4, MI + Vehicle 61±3, MI + Min 37±6).ConclusionRats post myocardial infarction develop systemic inflammation, heart failure and depression-like behaviour that are all attenuated by minocycline. Targeting (neuro) inflammation may represent new therapeutic strategy for patients with heart failure and depression.

Malonyl CoA Decarboxylase Inhibition Improves Cardiac Function Post-Myocardial Infarction

Alterations in cardiac energy metabolism after a myocardial infarction contribute to the severity of heart failure (HF). Although fatty acid oxidation can be impaired in HF, it is unclear if stimulating fatty acid oxidation is a desirable approach to treat HF. Both immediate and chronic malonyl coenzyme A decarboxylase inhibition, whichdecreases fatty acid oxidation, improved cardiac function through enhancing cardiac efficiency in a post-myocardial infarction rat that underwent permanent left anterior descending coronary artery ligation. The beneficial effects of MCD inhibition were attributed to a decrease in proton production due to an improved coupling between glycolysis and glucose oxidation.

Chitosan/Calcium Silicate Cardiac Patch Stimulates Cardiomyocyte Activity and Myocardial Performance after Infarction by Synergistic Effect of Bioactive Ions and Aligned Nanostructure.

Cardiac tissue engineering (CTE) remains a great challenge to construct a cell-inductive scaffold that has positive effects on cardiac cell behaviors and cardiac tissue repair. In this study, we for the first time demonstrated that Si ions evidently stimulated the expression of cardiac-specific genes and proliferation of neonatal rat cardiomyocytes (NRCMs) at concentration ranges of 0.13-10.78 ppm. Accordingly, the optimized concentrations of calcium silicate (CS) were incorporated into the controllable aligned chitosan electrospun nanofibers, constructing the composite cardiac patch scaffolds. These scaffolds showed synergistic effect of bioactive chemical and structural signals on both cardiomyocytes and endothelial cells with aligned cell morphology and enhanced viability and function characterized by upregulated expressions of cardiac and angiogenic specific markers, improved myofilament structure, and better Ca2+ transients of NRCMs as compared to the scaffolds free of CS component or with disordered structures. The in vivo studies further demonstrated that the NRCM-seeded aligned CS/chitosan cardiac patch evidently improved cardiac function via limiting the scar area and promoting angiogenesis in postmyocardial infarction rats. Conclusively, our study highlights the potential application of bioactive ions and nanostructured biomaterials in CTE, and the CS/chitosan composite cardiac patch may be a promising scaffold for repair of infarcted myocardium.

Effects of exercise training and TrkB blockade on cardiac function and BDNF-TrkB signaling postmyocardial infarction in rats.

Exercise training is beneficial for preserving cardiac function postmyocardial infarction (post-MI), but the underlying mechanisms are not well understood. We investigated one possible mechanism, brain-derived neurotrophic factor (BDNF)-tropomyosin-related kinase B (TrkB) signaling, with the TrkB blocker ANA-12 (0.5 mg·kg-1·day-1). Male Wistar rats underwent sham surgery or ligation of the left descending coronary artery. The surviving MI rats were allocated as follows: sedentary MI rats treated with vehicle, exercise-trained MI rats treated with vehicle, and exercise-trained MI rats treated with ANA-12. Exercise training was done 5 days/wk for 4 wk on a motor-driven treadmill. At the end, left ventricular (LV) function was evaluated by echocardiography and a Millar catheter. Mature BDNF and downstream effectors of BDNF-TrkB signaling, Ca2+/calmodulin-dependent protein kinase II (CaMKII), Akt, and AMP-activated protein kinase (AMPK), were assessed in the noninfarct area of the LV by Western blot analysis. Exercise training increased stroke volume and cardiac index and attenuated the decrease in ejection fraction (EF) and increase in LV end-diastolic pressure post-MI. ANA-12 blocked the improvement of EF and attenuated the increases in stroke volume and cardiac index but did not affect LV end-diastolic pressure. Exercise training post-MI prevented decreases in mature BDNF, phosphorylated (p-)CaMKII, p-Akt, and p-AMPKα expression. These effects were all blocked by ANA-12 except for p-AMPKα. In conclusion, the exercise-induced improvement of EF is mediated by the BDNF-TrkB axis and the downstream effectors CaMKII and Akt. BDNF-TrkB signaling appears to contribute to the improvement in systolic function by exercise training. NEW & NOTEWORTHY Exercise training improves ejection fraction and left ventricular end-diastolic pressure (LVEDP) and increases stroke volume and cardiac index in rats postmyocardial infarction (post-MI). The improvement of EF but not LVEDP is mediated by activation of the brain-derived neurotrophic factor (BDNF)-tropomyosin-related kinase B (TrkB) axis and downstream effectors Ca2+/calmodulin-dependent protein kinase II (CaMKII) and Akt. This suggests that activation of BDNF-TrkB signaling and CaMKII and Akt is a promising target to attenuate progressive cardiac dysfunction post-MI.

PO-163 Aerobic exercise activates myocardial FGF21/FGFR1/PI3K-AKT signaling pathway and inhibits cardiomyocyte apoptosis in post-myocardial infarction rats

Objective To investigate the effect of aerobic exercise on the expression of fibroblast growth factor 21 (FGF21) and cardiomyocyte apoptosis in Myocardial Infarction (MI) rats.&#x0D; Methods male SD rats were randomly divided into three groups：the sham operation (S), sedentary MI group (MI) and MI with aerobic exercise group (ME). The MI model was established by ligation of the left anterior descending branch of the left coronary artery. ME group were trained four weeks after the operation. LVSP, LVEDP and ±dp/dtmax were used to evaluate cardiac function. H9C2 cardiomyocytes were stimulated by 400 μmol/L H2O2 for 4h to simulate myocardial apoptosis mode. AMPK agonist AICAR and FGF21 receptor inhibitor PD166866 were used to interfere with H9C2. Myocardial collagen volume fraction was calculated by Masson staining and myocardium FGF21, FGFR1, Bax, Bcl-2 and PI3K-AKT pathway by western blotting or RT-Qpcr. Cardiomyocytes apoptosis was evaluated by TUNEL.&#x0D; Results Compared with S, the expression of FGF21, FGFR1, Bax, Bcl-2 and PI3K, AKT increased significantly in MI group, the apoptotic cardiomyocytes and collagen fibers increased significantly, but the cardiac function decreased. Compared to MI, myocardium FGF21, FGFR1 and PI3K, AKT were further increased in ME group, the Bax/Bcl-2 and the apoptotic cardiomyocytes decreased significantly. The percentage of collagen fibers decreased and the cardiac function was improved. Myocardium FGF21 was positively correlated with the inhibition of cardiomyocyte apoptosis and the improvement of cardiac function. Furthermore, the expression of Bax/Bcl-2, TNF-α/IL-10 and the apoptotic cardiomyocytes was significantly increased by PD166866, but PI3K-AKT pathway decreased significantly by PD166866. However, AICAR single intervention or PD166866 simultaneous intervention also can reverse this adverse effects.&#x0D; Conclusions Exercise can increase myocardial FGF21/FGFR1 with MI. The one of the mechanisms is to activate PI3K-AKT pathway to inhibit cardiaomyocyte apoptosis and inflammatory. It indicates that FGF21/FGFR1/PI3K-AKT signaling pathway plays an important role in inhibiting myocardial apoptosis and improving cardiac function.