post-MI Rats Research Articles

Sodium-glucose cotransporter 2 inhibitor attenuates left ventricular dysfunction in post-myocardial infarction in rats via reducing cardiac mitochondrial impairment

Abstract Background Sodium-glucose cotransporter 2 inhibitor (SGLT2i) is a class of antidiabetic drugs that has demonstrated cardiovascular benefits in heart failure patients, regardless of diabetic status. Although current evidence regarding the role of SGLT2i in myocardial infarction (MI) is still limited, a recent randomized study reported the favorable effects of dapagliflozin on cardiometabolic outcomes in post-MI patients. Nevertheless, the evidence of the underlying mechanism of SGLT2i in post-MI is still unclear. Purpose We aimed to investigate the cardioprotective effects and cellular mechanisms of SGLT2i in post-MI rats. Methods 72 male Wistar rats were divided into two groups: the MI group, which underwent surgery involving permanent ligation of the left anterior descending coronary artery to induce MI (n=58), and the sham group, which underwent a sham operation (n=14). One-week post-surgery, echocardiography was performed. For inclusion in the MI group, only rats exhibiting anterior wall akinesia and a left ventricular ejection fraction (LVEF) < 50% were considered. Subsequently, MI rats were stratified into three groups to receive different interventions: 1) MI+VEH (distilled water, PO, n=13), 2) MI+DAPA (dapagliflozin, 1 mg/kg, PO, n=11), and 3) MI+ENA (enalapril, 10 mg/kg, PO, n=14). After 8 weeks of treatment, echocardiography was performed again. Then, the rats were sacrificed, and heart tissues were used to determine mitochondrial function and protein expressions. Results After 8 weeks of treatment, the MI+VEH group exhibited a decrease in LVEF compared to the sham group (Fig. 1A). The MI+VEH group was associated with cardiac mitochondrial dysfunction, as indicated by increased mitochondrial oxidative stress, mitochondrial membrane depolarization, and mitochondrial swelling, and impaired mitochondrial biogenesis, as indicated by decreasing peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) expressions (Fig. 1B-F). Treatment with dapagliflozin and enalapril effectively attenuated left ventricular (LV) systolic dysfunction, reversed mitochondrial dysfunction, and restored mitochondrial biogenesis induced by MI (Fig. 1A-F). Conclusion SGLT2i could attenuate LV dysfunction and restore mitochondrial dysfunction in post-MI rats. These findings demonstrate SGLT2i as a novel cardioprotection against post-MI complications.

BA6b9, a novel sk4 K + channel blocker, attenuates atrial fibrillation substrate in rats with reduced ejection fraction

Abstract Background Atrial fibrillation (AF), the most common cardiac arrhythmia, is strongly associated with several comorbidities including heart failure (HF). AF in general, and specifically in the context of HF, is progressive in nature and associated with poor clinical outcomes. Current therapies for AF are limited in number and efficacy and do not target the underlying causes of atrial remodeling such as inflammation or fibrosis. We previously identified the calcium-activated SK4 K+ channels, which are preferentially expressed in the atria relative to the ventricles in both rat and human hearts, as novel druggable targets for efforts to treat AF. Methods and Findings We examined the ability of BA6b9, a novel allosteric inhibitor of SK4 channels that targets the specific calmodulin-PIP2 binding domain, to alter AF susceptibility and atrial remodeling in a systolic HF rat post-myocardial infarction (post-MI) model. Daily BA6b9 injection (20 mg/kg/day) for 3 weeks starting 1-week post-MI prolonged the atrial effective refractory period, reduced AF induction and duration, and dramatically prevented atrial structural remodeling. In the post-MI left atrium (LA), pronounced upregulation of the SK4 K+ channel was observed, with corresponding increases in collagen deposition, α-SMA levels, and NLRP3 inflammasome expression. Strikingly, BA6b9 treatment reversed these changes while also significantly reducing the lateralization of the atrial connexin Cx43 in the LA of post-MI rats. Interpretation Our findings indicate that the blockade of SK4 K+ channels using BA6b9 not only favors rhythm control but also remarkably reduces atrial structural remodeling, a property that is highly desirable for novel AF therapies, particularly in patients with comorbid HF.

Qingxin Jieyu Granule alleviates myocardial infarction through inhibiting neutrophil extracellular traps via activating ANXA1/FPR2 axis

BackgroundMyocardial infarction (MI), representing the most severe manifestation of coronary artery disease (CAD), stands as a primary concern in the prevention and management of cardiovascular diseases. Clinical evidence demonstrates that Qingxin Jieyu Granule (QXJYG) is efficacious in treatment of MI patients. However, the mechanisms underlying its therapeutic effects remain to be elucidated. PurposeThis study aimed to evaluate the effects of QXJYG on MI and investigate its underlying mechanisms. Materials and methodsThe MI model in rats was developed through ligating the left anterior descending (LAD) artery. The effect of QXJYG on cardiac function impairment in MI rats was assessed by echocardiography, while the improvement of cardiomyocyte morphology and myocardial fibrosis after treatment with QXJYG was evaluated through hematoxylin-eosin (H&E) staining and Masson staining. The chemical constituents of QXJYG in blood were identified by using the UPLC-Q-TOF/MS technique. Furthermore, the molecular mechanism underlying the QXJYG therapeutic effect in MI was postulated based on the disease gene-drug target network analysis. Other technical methods such as ELISA, immunohistochemical staining, Western Blot analysis and application of pharmacological inhibitors were employed to verify the effectiveness of QXJYG in treating MI and explore its potential molecular targets. ResultsThe cardiac function in experimental rats post-MI was significantly impaired, as evidenced by an enlarged infarction area, disordered arrangement of cardiomyocytes, and aggravated myocardial fibrosis. QXJYG treatment significantly enhanced the cardiac function and reduced the pathological damage of the cardiac tissue in MI rats. Through the network pharmacology analysis, we identified that FPR2 might be a potential target of QXJYG in its cardiac protection role. QXJYG markedly downregulated the level of neutrophil extracellular traps (NETs) in MI rats, specifically manifested as a significant reduction in the Histone-DNA level and expression of myeloperoxidase (MPO) and citrullinated histone H3 (CitH3) proteins. Furthermore, QXJYG upregulated the levels of ANXA1 and FPR2 proteins in MI rats. The level of FPR2 was markedly reduced in MI rats upon administration of WRW4, a specific inhibitor of FPR2, which was associated with exacerbated MI injury and an elevated level of NETs. When WRW4 was co-administered with QXJYG, the cardioprotective effects of QXJYG on MI were significantly diminished. However, the addition of DNase I did not result in significant changes of the outcomes in MI rats after QXJYG intervention. ConclusionQXJYG treatment alleviates cardiac tissue injury in MI rats by inhibiting NETs through activating the ANXA1/FPR2 axis. The findings extend our understanding of the therapeutic effectiveness of QXJYG and offer a scientific foundation for the clinical utilization of QXJYG.

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.

Effects of MicroRNA-24 on Myocardial Fibrosis in Rats After Myocardial Infarction by Targeting Wnt Family Member 4/Dvl-1/β-Catenin Signaling Pathway

In this study, we investigated the impact of miR-24 on myocardial fibrosis severity in rats following myocardial infarction (MI) and explored its underlying mechanisms. We established an MI-induced myocardial fibrosis rat model and assessed cardiac function via echocardiography. We employed Western blotting and RT-qPCR to examine the effects of agomiR-24 on key fibrotic markers, including COL1A1, COL3A1, and α-SMA. Microarray analysis, pathway enrichment, and proteinprotein interaction network analysis revealed the signaling pathways and genes influenced by agomiR-24. Primary rat cardiac fibroblasts (CFs) were isolated, and miR-24’s direct target was confirmed using luciferase reporter assays. We modulated miR-24 expression in CFs and assessed cell proliferation and invasion through CCK-8 and Transwell assays, respectively. Furthermore, we investigated the impact of miR-24 on the Wnt4/Dvl-1/β-catenin signaling pathway by Western blotting. Finally, we examined mRNA expression levels of key genes (Cyclin D1, p27, p21, MMP-3, and MMP-9) through RT-qPCR. Our findings demonstrated that agomiR-24 improved cardiac function and reduced fibrotic marker expression in rat myocardial tissues. MiR-24 inhibited CF proliferation and invasion, potentially by targeting Wnt4/Dvl-1/β- catenin signaling. It also regulated mRNA expression of genes associated with cell proliferation and matrix remodeling. Overall, our study suggests that miR-24 may attenuate myocardial fibrosis in post-MI rats by suppressing the Wnt4/Dvl- 1/β-catenin pathway.

Myocardial CD34+ Stromal Cells/Telocytes Demonstrate a Dynamic Pattern of Interactions with CD68+ Macrophages During Post-Myocardial Infarction Healing

Introduction: Myocardial CD34-positive (+) stromal cells/telocytes (SC/TCs) have been recently recognized as a novel type of resident cells involved in post-myocardial infarction (MI) repair. Alternatively, CD68-positive (+) macrophages are well-known constituents in this process. However, the relationship between these two cell populations remains mostly obscure. Therefore, this study was aimed to determine whether resident CD34+ SC/TCs and phagocytic CD68+ macrophages have any evident pattern of interactions during the inflammatory and proliferative phases of post-MI scar formation. Methods: A large transmural MI was induced in middle-aged male Sprague-Dawley rats (n = 15) under ketamine and xylazine anesthesia by permanent ligation of the left anterior descending coronary artery. The post-MI rats were infused with BrdU (5-bromo-2'-deoxyuridine) in a dose of 12.5 mg/kg/day for 72 hours via intraperitoneal osmotic minipumps on day 0, 4, or 11 after surgery. The rats were euthanized on day 3, 7 and 14 after MI, and their hearts were processed for histology and immunostaining. Results: On the third day after MI, CD34+ SC/TCs and CD68+ macrophages were absent within the core of the necrotic tissue, whereas both types of cells were juxtaposed in the space surrounding the area of coagulative necrosis. Furthermore, the presence of BrdU labeling in the nuclei of numerous CD34+ SC/TCs suggests their proliferation in the region of the active macrophage clearing. On the seventh day after MI, CD68+ macrophages were observed to have had advanced toward the center of the necrotic region leaving behind the area occupied primarily with acellular basement membranes from the resorbed CMs, whereas most of CD34+ SC/TCs trailed slightly behind. In part, such delay in centripetal progression of CD34+ SC/TCs through the areas of resorption could be attributed to the fact that these cells, in contrast to macrophages, often migrated along the acellular basement membranes left from the dead CMs that required phagocytic removal of necrotic debris to occur first. On the fourteenth day after MI, the population of CD68+ cells appeared notably reduced and demonstrated a patchy distribution predominantly along the remnants of the necrotic tissue. Meanwhile, the substantially expanded population of CD34+ SC/TCs were observed throughout the entire transmural scar, excluding the areas containing dead “mummified” CMs, aggregates of myofibroblasts and the fibroelastic thickening in subepicardial and subendocardial regions. Conclusion: Our findings, for the first time, demonstrate that populations of resident CD34+ SC/TCs and phagocytic CD68+ macrophages exhibit a dynamic pattern of interactions during early phases of post-MI scar formation, suggesting their importance in the process of post-ischemic myocardial healing. Supported by Camden Health Research Initiative. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The SK4 channel allosteric blocker, BA6b9, reduces atrial fibrillation substrate in rats with reduced ejection fraction.

Atrial fibrillation (AF), the most common cardiac arrhythmia, is strongly associated with several comorbidities including heart failure (HF). AF in general, and specifically in the context of HF, is progressive in nature and associated with poor clinical outcomes. Current therapies for AF are limited in number and efficacy and do not target the underlying causes of atrial remodeling such as inflammation or fibrosis. We previously identified the calcium-activated SK4 K+ channels, which are preferentially expressed in the atria relative to the ventricles in both rat and human hearts, as attractive druggable target for AF treatment. Here, we examined the ability of BA6b9, a novel allosteric inhibitor of SK4 channels that targets the specific calmodulin-PIP2 binding domain, to alter AF susceptibility and atrial remodeling in a systolic HF rat postmyocardial infarction (post-MI) model. Daily BA6b9 injection (20 mg/kg/day) for 3 weeks starting 1-week post-MI prolonged the atrial effective refractory period, reduced AF induction and duration, and dramatically prevented atrial structural remodeling. In the post-MI left atrium (LA), pronounced upregulation of the SK4 K+ channel was observed, with corresponding increases in collagen deposition, α-SMA levels, and NLRP3 inflammasome expression. Strikingly, BA6b9 treatment reversed these changes while also significantly reducing the lateralization of the atrial connexin Cx43 in the LA of post-MI rats. Our findings indicate that the blockade of SK4 K+ channels using BA6b9 not only favors rhythm control but also remarkably reduces atrial structural remodeling, a property that is highly desirable for novel AF therapies, particularly in patients with comorbid HF.

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.

Sotagliflozin attenuates cardiac dysfunction and remodeling in myocardial infarction rats

ObjectiveSotagliflozin is a dual sodium-glucose co-transporter-1 and 2 (SGLT1/2) inhibitor with selectivity towards SGLT2. Previous studies showed that SGLT2 inhibitors can improve cardiac function and reduce myocardial infarction size in animal models of myocardial infarction (MI). However, it remains unknown whether the dual inhibition of SGLT1/2 by sotagliflozin has beneficial effects in this context. In this study, we investigated the potential cardioprotective effects of sotagliflozin in an animal model of MI. MethodsSprague Dawley (SD) rats underwent left anterior descending coronary artery ligation or sham ligation then were randomly assigned to receive either sotagliflozin (10 mg/kg) or vehicle via intraperitoneal injection. Fourteen days post-MI, we assessed cardiac function using echocardiography and evaluated histological and molecular markers of cardiac remodeling and inflammation in the left ventricle. ResultsOur findings indicate that sotagliflozin treatment resulted in improved cardiac function and reduced infarct size compared with the vehicle-treated group. Additionally, sotagliflozin improved cardiac remodeling as shown by the decreased cardiac hypertrophy and cardiac apoptosis in the post-MI heart. Mechanistically, an apparent reduction in the cardiac inflammatory response in sotagliflozin-treated hearts was observed in the post-MI rats. ConclusionOverall, our results suggest that sotagliflozin may have cardioprotective effects against myocardial infarction.

Celastrol relieves myocardial infarction-induced cardiac fibrosis by inhibiting NLRP3 inflammasomes in rats.

Myocardial infarction (MI) triggers a strong inflammatory response mediating by NLRP3 inflammasome which is associated with cardiac fibrosis. The key players in this response are Interleukin (IL)-1 and IL-18, which are regulated by NLRP3 inflammasomes. Celastrol, a traditional Chinese medicine with strong anti-inflammatory activity, has recently reported as a cardioprotective agent. However, the mechanisms by which celastrol is cardioprotective in MI remain elusive. We hypothesized that Celastrol could reduce IL-1β and IL-18 expression and ameliorate myocardial fibrosis after myocardial infarction in rats, improve poor heart remodeling, and preserve heart function. Myocardial infarction (MI) was caused by ligating the left anterior descending of male SD rats. Celastrol (1mg/kg) or saline was administered every other day for 4weeks. Heart function and fibrosis were assessed. Inflammatory and fibrotic markers in the myocardia were evaluated with immunohistochemistry, western blot, and ELISA. Molecular docking was employed to predict Celastrol's binding to NLRP3 protein. The effects of Celastrol on the expression of NLRP3 inflammasome and myocardial fibrosis genes were then examined in vitro. Celastrol maintained the left ventricular fractional shortening (FS) and ejection fraction (EF). Fibrosis was significantly reduced in animals treated with 1mg/kg Celastrol (15.17±1.82%) relative to controls (29.88±4.28%). Celastrol also significantly reduced the NLRP3, IL-18, and IL-1β levels, together with macrophage and neutrophil infiltration in the myocardium. Molecular docking predicted that NLRP3 would bind tightly to Celastrol [Docking energy: -8.9 (kcal/mol)]. In vitro experiments showed reduced NLRP3 inflammasome and myocardial fibrosis-associated proteins expression in neonatal rat cardiac fibroblasts treated with Celastrol. In post-MI rats, Celastrol, a naturally occurring active ingredient, was able to reduce myocardial fibrosis and improve cardiac function, according to our study. These effects may result from inhibiting the NLRP3 inflammasome and attenuating the early inflammatory storm after MI, suggesting that Celastrol may be useful in treating acute MI.

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.

Rapamycin treatment unmasks a sex-specific pattern of scar expansion of the infarcted rat heart: The relationship between mTOR and KATP channel.

Inhibition of the mammalian target of rapamycin (mTOR) with the macrolide rapamycin or pharmacological suppression of KATP channel opening translated to scar expansion of the myocardial infarcted (MI) adult female rodent heart. The present study tested the hypotheses that rapamycin-mediated scar expansion was sex-specific and that mTOR signaling directly influenced KATP channel subunit expression/activity. Scar size was significantly larger in post-MI male rats as compared to the previous data reported in post-MI female rats. The reported scar expansion of rapamycin-treated post-MI female rats was not observed following the administration of the macrolide to post-MI male rats. Protein levels of the KATP channel subunits Kir6.2 and SUR2A and phosphorylation of the serine2448 residue of mTOR were similar in the normal heart of adult male and female rats. By contrast, greater tuberin inactivation characterized by the increased phosphorylation of the threonine1462 residue and reduced raptor protein levels were identified in the normal heart of adult female rats. Rapamycin pretreatment of phorbol 12,13-dibutyrate (PDBu)-treated neonatal rat ventricular cardiomyocytes (NNVMs) suppressed hypertrophy, inhibited p70S6K phosphorylation, and attenuated SUR2A protein upregulation. In the presence of low ATP levels, KATP channel activity detected in untreated NNVMs was significantly attenuated in PDBu-induced hypertrophied NNVMs via a rapamycin-independent pathway. Thus, rapamycin administration to post-MI rats unmasked a sex-specific pattern of scar expansion and mTOR signaling in PDBu-induced hypertrophied NNVMs significantly increased SUR2A protein levels. However, the biological advantage associated with SUR2A protein upregulation was partially offset by an mTOR-independent pathway that attenuated KATP channel activity in PDBu-induced hypertrophied NNVMs.

GSDMD-mediated pyroptosis dominantly promotes left ventricular remodeling and dysfunction in post-myocardial infarction: a comparison across modes of programmed cell death and mitochondrial involvement

BackgroundMyocardial infarction (MI) has recently accounted for more than one-third of global mortality. Multiple molecular pathological pathways, such as oxidative stress, inflammation, and mitochondrial dysfunction, have been recognized as possible mechanisms in the development of MI. Furthermore, different phases of ischemic injury following the progression of MI were also associated with multiple types of programmed cell death (PCDs), including apoptosis, necroptosis, ferroptosis, and pyroptosis. However, it remains unknown whether which types of PCDs play the most dominant role in post-myocardial infarction (post-MI).MethodIn this study, we used a preclinical rat model of MI induced by permanent left anterior descending coronary artery (LAD) ligation (n = 6) or a sham operated rat model (n = 6). After a 5-week experiment, cardiac function and morphology, mitochondrial studies, and molecular signaling analysis of PCDs were determined.ResultsHerein, we demonstrated that post-MI rats had considerably impaired cardiac geometry, increased oxidative stress, myocardial injuries, and subsequently contractile dysfunction. They also exhibited worsened cardiac mitochondrial function and dynamic imbalance. More importantly, we found that post-MI mediated abundant myocardial cell death through multiple PCDs, including apoptosis, necroptosis, and pyroptosis, but not ferroptosis.ConclusionIn this study, we provide the first insights into the mechanism of PCDs by pyroptosis, which is leveraged as the most dominant mode of cell death after MI.

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

PM2.5 Exposure Lowers Mitochondrial Endurance During Cardiac Recovery in a Rat Model of Myocardial Infarction.

Many studies have reported the negative effect of PM2.5exposure on heart function which is likely to impair postcardiac surgery rehabilitation that is involved in recovery and wound healing, yet the direct effects ofPM2.5from diesel exhaust (DPM)on cardiac recovery is unknown.To study the impact ofDPM on cardiac recovery and repair, we utilized isoproterenol induced myocardial infarction (MI) model where female rats were exposed to DPM prior and after MI induction. The experimental groups comprise of normal, ISO control, DPM control (42days of exposure), DPM exposed prior (21days) and after (21days) MI induction (D + I + D) and DPM exposed (21days) after MI (I + D). Post-MI rat hearts from D + I + D group exhibited higher fibrosis, elevated cardiac injury and altered electrophysiology, where this pathology was also observed in I + D group animals which was mild.Loss of mitochondrial quality was evidentin DPM exposed animals with and without MI, where severe mitochondrial damage persisted in D + I + D group. In addition, these animals showed strikingdecline in ETC enzyme activity, ATP levels, mitochondrial copy number and down regulation of PGC1-α, TFAM and POLGalong with thegenes involved in mitophagy and mitofusion. Besides, the MI associated inactivation of cardio protective signalling pathways like PI3K and Akt were persistent in D + I + D group. In fact, I + D group animals also showed a similar pattern of change, but in a mild form. Taken together, exposure to PM2.5increases the risk, frequency or progression of MI by impairing the recovery potential of the myocardium.

Association of Valproic Acid Use With Post-Myocardial Infarction Heart Failure Development: A Meta-Analysis of Two Retrospective Case-Control Studies.

Despite advances in treatments, myocardial infarction (MI) remains a significant cause of morbidity and mortality worldwide. Our team has previously shown that valproic acid (VPA) is cardio-protective when administered to rats post-MI. The aim of this study was to investigate the association of VPA use with post-MI heart failure (HF) development in humans. This study was a random effects meta-analysis of two retrospective case-control studies collected from electronic health record (Michigan Medicine) and claims data (OptumInsight). Cases with an active prescription for VPA at the time of their MI were matched 1:4 to controls not taking VPA at the time of their MI by multiple demographic and clinical characteristics. The primary outcome, time-to-HF development, was analyzed using the Fine-Gray competing risks model of any VPA prescription versus no VPA prescription. An exploratory analysis was conducted to evaluate the association of different VPA doses (≥1000 mg/day vs <1000 mg/day vs 0 mg/day VPA). In total, the datasets included 1313 patients (249 cases and 1064 controls). In the meta-analysis, any dose of VPA during an MI tended to be protective against incident HF post-MI (HR = 0.87; 95% CI = 0.72-1.01). However, when stratified by dose, high-dose VPA (≥1000 mg/day) significantly associated with 30% reduction in risk for HF post-MI (HR = 0.70; 95% CI = 0.49-0.91), whereas low-dose VPA (<1000 mg/day) did not (HR = 0.95; 95% CI = 0.78-1.13). VPA doses ≥1000 mg/day may provide post-MI cardio-protection resulting in a reduced incidence of HF.

Vena cava presents endothelial dysfunction prior to thoracic aorta in heart failure: the pivotal role of nNOS uncoupling/oxidative stress.

Arterial endothelial dysfunction has been extensively studied in heart failure (HF). However, little is known about the adjustments shown by the venous system in this condition. Considering that inferior vena cava (VC) tone could influence cardiac performance and HF prognosis, the aim of the present study was to assess the VC and thoracic aorta (TA) endothelial function of HF-post-myocardial infarction (MI) rats, comparing both endothelial responses and signaling pathways developed. Vascular reactivity of TA and VC from HF post-MI and sham operated (SO) rats was assessed with a wire myograph, 4 weeks after coronary artery occlusion surgery. Nitric oxide (NO), H2O2 production and oxidative stress were evaluated in situ with fluorescent probes, while protein expression and dimer/monomer ratio was assessed by Western blot. VC from HF rats presented endothelial dysfunction, while TA exhibited higher acetylcholine (ACh)-induced vasodilation when compared with vessels from SO rats. TA exhibited increased ACh-induced NO production due to a higher coupling of endothelial and neuronal NO synthases isoforms (eNOS, nNOS), and enhanced expression of antioxidant enzymes. These adjustments, however, were absent in VC of HF post-MI rats, which exhibited uncoupled nNOS, oxidative stress and higher H2O2 bioavailability. Altogether, the present study suggests a differential regulation of endothelial function between VC and TA of HF post-MI rats, most likely due to nNOS uncoupling and compromised antioxidant defense.

Heart Repair Induced by Cardiac Progenitor Cell Delivery within Polypyrrole-Loaded Cardiogel Post-ischemia

Myocardial infarction (MI) irreversibly injures the heart tissue. Cardiovascular tissue engineering has been developed as a promising therapeutic approach for post-MI repair. Previously, we discovered the ability of a polypyrrole (PPy)-incorporated cardiogel (CG) for improvement of maturity and functional synchrony of rat neonatal cardiomyocytes. Here, we used the cross-linked form of PPy-incorporated CG (CG-PPy), in order to improve electromechanical properties of scaffold, for application in cardiac progenitor cell (CPC) transplantation on post-MI rat hearts. Improved mechanical property and electrical conductivity (sixfold) were evident in the cross-linked CG-PPy (P1) compared to cross-linked CG (C1) scaffolds. Transplantation of CPC-loaded P1 (P1-CPC) resulted in substantial improvement of cardiac functional properties. Furthermore, lower fibrotic tissue and higher CPC retention were observed. The grafted cells showed cardiomyocyte characteristics when stained with human cardiac troponin T and connexin43 antibodies, while neovessel formation was similarly prominent. These findings highlight the therapeutic promise of the P1 scaffold as a CPC carrier for functional restoration of the heart post-MI.

Role of endoplasmic reticulum stress in renal damage after myocardial infarction.

Myocardial infarction (MI) is associated with renal alterations resulting in poor outcomes in patients with MI. Renal fibrosis is a potent predictor of progression in patients and is often accompanied by inflammation and oxidative stress; however, the mechanisms involved in these alterations are not well established. Endoplasmic reticulum (ER) plays a central role in protein processing and folding. An accumulation of unfolded proteins leads to ER dysfunction, termed ER stress. Since the kidney is the organ with highest protein synthesis fractional rate, we herein investigated the effects of MI on ER stress at renal level, as well as the possible role of ER stress on renal alterations after MI. Patients and MI male Wistar rats showed an increase in the kidney injury marker neutrophil gelatinase-associated lipocalin (NGAL) at circulating level or renal level respectively. Four weeks post-MI rats presented renal fibrosis, oxidative stress and inflammation accompanied by ER stress activation characterized by enhanced immunoglobin binding protein (BiP), protein disulfide-isomerase A6 (PDIA6) and activating transcription factor 6-alpha (ATF6α) protein levels. In renal fibroblasts, palmitic acid (PA; 50-200 µM) and angiotensin II (Ang II; 10-8 to 10-6M) promoted extracellular matrix, superoxide anion production and inflammatory markers up-regulation. The presence of the ER stress inhibitor, 4-phenylbutyric acid (4-PBA; 4 µM), was able to prevent all of these modifications in renal cells. Therefore, the data show that ER stress mediates the deleterious effects of PA and Ang II in renal cells and support the potential role of ER stress on renal alterations associated with MI.

Ivabradine is as effective as metoprolol in the prevention of ventricular arrhythmias in acute non-reperfused myocardial infarction in the rat

Ventricular arrhythmias are a major source of early mortality in acute myocardial infarction (MI) and remain a major therapeutic challenge. Thus we investigated effects of ivabradine, a presumably specific bradycardic agent versus metoprolol, a β-blocker, at doses offering the same heart rate (HR) reduction, on ventricular arrhythmias in the acute non-reperfused MI in the rat. Immediately after MI induction a single dose of ivabradine/ metoprolol was given. ECG was continuously recorded and ventricular arrhythmias were analyzed. After 6 h epicardial monophasic action potentials (MAPs) were recorded and cardiomyocyte Ca2+ handling was assessed. Both ivabradine and metoprolol reduced HR by 17% and arrhythmic mortality (14% and 19%, respectively, versus 33% in MI, p < 0.05) and ventricular arrhythmias in post-MI rats. Both drugs reduced QTc prolongation and decreased sensitivity of ryanodine receptors in isolated cardiomyocytes, but otherwise had no effect on Ca2+ handling, velocity of conduction or repolarization. We did not find any effects of potential IKr inhibition by ivabradine in this setting. Thus Ivabradine is an equally effective antiarrhythmic agent as metoprolol in early MI in the rat. It could be potentially tested as an alternative antiarrhythmic agent in acute MI when β-blockers are contraindicated.