Coronary Artery Ligation Model Research Articles

Reprogramming the myocardial infarction microenvironment with melanin-based composite nanomedicines in mice

Myocardial infarction (MI) has a 5-year mortality rate of more than 50% due to the lack of effective treatments. Interactions between cardiomyocytes and the MI microenvironment (MIM) can determine the progression and fate of infarcted myocardial tissue. Here, a specially designed Melanin-based composite nanomedicines (MCN) is developed to effectively treat MI by reprogramming the MIM. MCN is a nanocomposite composed of polydopamine (P), Prussian blue (PB) and cerium oxide (CexOy) with a Mayuan-like structure, which reprogramming the MIM by the efficient conversion of detrimental substances (H+, reactive oxygen species, and hypoxia) into beneficial status (O2 and H2O). In coronary artery ligation and ischemia reperfusion models of male mice, intravenously injecting MCN specifically targets the damaged area, resulting in restoration of cardiac function. With its promising therapeutic effects, MCN constitutes a new agent for MI treatment and demonstrates potential for clinical application.

Edoxaban treatment in a post-infarction experimental model

BackgroundThe sequelae of myocardial infarction (MI) require specific pharmacological therapy to minimise the post-MI remodelling, which in many cases evolves into cardiovascular complications. The aim of this study was to analyse the effect of edoxaban, an oral anticoagulant, on cardiac recovery in a rat model of permanent coronary artery ligation. MethodsAn experimental method to assess the post-MI remodelling in rats for 4 weeks, based on cardiac magnetic resonance imaging (MRI) and final histological analysis of the hearts was performed. The influence of daily oral treatment with edoxaban (20 mg/kg/day) for 28 days post-MI was analysed in comparison to vehicle. ResultsIn our model, edoxaban was shown to be safe and bleeding was observed in 1 of 10 animals. General physical recovery of the treated animals was shown by higher body weight recovery compared with non-treated animals (38.6 ± 2.9 vs. 29.9 ± 3.1 g, respectively, after 28 days). There was not a pronounced effect of edoxaban in post-MI cardiac remodelling, but mitigated fibrosis was observed by the reduced expression of vascular endothelial growth factor and tumour growth factor β1 in the peri-infarct zone. ConclusionsOur analysis provided the experimental basis to support the feasibility of MRI to study cardiac function and characterise myocardial scarring in a rat model. Overall data suggested the safety of edoxaban in the model, and compared to placebo, it showed a better post-MI recovery, probably by reducing fibrosis of the heart. Further research on mid-term cardiac recovery with edoxaban after MI is justified.

Effect and mechanism of Jiming Powder on myocardial fibrosis in mice with myocardial infarction

Jiming Powder is a traditional ancient prescription with good therapeutic effect in the treatment of heart failure, but its mechanism lacks further exploration. In this study, a mouse model of coronary artery ligation was used to evaluate the effect and mechanism of Jiming Powder on myocardial fibrosis in mice with myocardial infarction. The study constructed a mouse model of heart failure after myocardial infarction using the method of left anterior descending coronary artery ligation. The efficacy of Jiming Powder was evaluated from multiple angles, including ultrasound imaging, hematoxylin-eosin(HE) staining, Masson staining, Sirius Red staining, and serum myocardial enzyme spectrum detection. Western blot analysis was performed to detect key proteins involved in ventricular remodeling, including transforming growth factor-β1(TGF-β1), α-smooth muscle actin(α-SMA), wingless-type MMTV integration site family member 3a(Wnt3a), β-catenin, matrix metallopeptidase 2(MMP2), matrix metallopeptidase 3(MMP3), TIMP metallopeptidase inhibitor 1(TIMP1), and TIMP metallopeptidase inhibitor 2(TIMP2). The results showed that compared with the model group, the high and low-dose Jiming Powder significantly reduced the left ventricular internal diameter in systole(LVID;s) and diastole(LVID;d), increased the left ventricular ejection fraction(LVEF) and left ventricular fractional shortening(LVFS), effectively improved cardiac function in mice after myocardial infarction, and effectively reduced the levels of myocardial injury markers such as creatine kinase(CK), creatine kinase isoenzyme(CK-MB), and lactic dehydrogenase(LDH), thus protecting ischemic myocardium. HE staining showed that Jiming Powder could attenuate myocardial inflammatory cell infiltration after myocardial infarction. Masson and Sirius Red staining demonstrated that Jiming Powder effectively inhibited myocardial fibrosis, reduced the collagen Ⅰ/Ⅲ ratio in myocardial tissues, and improved collagen remodeling after myocardial infarction. Western blot results showed that Jiming Powder reduced the expression of TGF-β1, α-SMA, Wnt3a, and β-catenin, decreased the levels of MMP2, MMP3, and TIMP2, and increased the level of TIMP1, suggesting its role in inhibiting cardiac fibroblast transformation, reducing extracellular matrix metabolism in myocardial cells, and lowering collagen Ⅰ and α-SMA content, thus exerting an anti-myocardial fibrosis effect after myocardial infarction. This study revealed the role of Jiming Powder in improving ventricular remodeling and treating myocardial infarction, laying the foundation for further research on the pharmacological effect of Jiming Powder.

S100A8∕A9 is a valuable biomarker and treatment target to detect and modulate neutrophil involvement in myocardial infarction.

Myocardial infarction (MI) leads to irreversible ischemic damage of the heart muscle and is the leading cause of heart failure. The ischemic cardiac injury triggers a potent local and systemic immune response. In the acute phase post-MI, neutrophils infiltrate the myocardium in large numbers and induce further cardiomyocyte death, expanding the infarcted area. The alarmin S100A8∕A9 is a proinflammatory mediator primarily produced by myeloid cells, with an emerging role in MI. We previously demonstrated that short-term inhibition of S100A8∕A9 during the inflammatory phase of the immune response to MI improves long-term cardiac function. In the present study, we investigated the effects of S100A8∕A9 blockade on myocardial inflammation and post-ischemic myocardial injury in a mouse model of coronary artery ligation. Immunohistochemical (IHC) staining revealed that the presence of S100A9 is strongly correlated with neutrophil infiltration in the myocardium on days 1 and 3 post-MI. A 3-day treatment with the S100A8∕A9 blocker ABR-238901 starting immediately after MI decreased the number of neutrophils and S100A9 presence in the myocardium and had a positive impact on cardiac damage, reducing infarction size. These findings promote S100A9 as an IHC biomarker of neutrophil infiltration and a promising immunomodulatory target to regulate neutrophil recruitment, reduce ischemic injury and promote long-term beneficial cardiac recovery after MI.

Involvement of HIF1α/Reg protein in the regulation of HMGB3 in myocardial infarction

AimsMyocardial ischemia and infarction are the number one cause of cardiovascular disease associated mortality. Cardiomyocyte death during ischemia leads to the loss of cardiac tissue and initiates a signaling cascade between the infarct zone and the area at risk of the myocardium. Here, we sought to determine the involvement of one of the damage-associated molecular patterns HMGB3 in myocardial ischemia and infarction. Methods and resultsWe used the left anterior descending coronary artery ligation model to study the involvement of HMGB3 in myocardial ischemia and infarction. Our results indicated the presence of HMGB3 at a low level under normal conditions, while myocardial injury caused a robust increase in HMGB3 levels in the heart. Further, intra-cardiac injection of mabHMGB3 had improved cardiac function at day 3 by downregulating HMGB3 levels. In contrast, injection of recombinant rat HMGB3 for 7 days during the adaptation phase of myocardial ischemia improved cardiac functional parameters by increasing regenerative protein family expression. Further, to mimic the disease condition, neonatal rat ventricle cardiomyocytes and fibroblasts were exposed to hypoxia; we observed a significant upregulation in the HMGB3, HIF1α, and Reg1α levels. Endothelial cells exposed to recombinant HMGB3 increased the tubule length. Further, the mitochondrial oxygen consumption rate was reduced with the acute induction of recombinant HMGB3 on cardiomyocytes and fibroblasts. ConclusionHMGB3 plays a dual role during the progression of myocardial ischemia and infarction. Clinically, post-myocardial infarction HMGB3-induced sterile inflammation needs to be tightly controlled, as it plays both a pro-inflammatory role and improves cardiac function during the cardiac remodeling phase.

Glutamine metabolism improves cardiac function after myocardial infarction independent of macrophage polarization

During myocardial infarction (MI), macrophages (MØ) infiltrate the ischemic left ventricle (LV) and mediate cardiac remodeling and healing. Metabolic shifts in the LV and infiltrating MØs is a hallmark of the response to injury. Glutamine is a major metabolic fuel for cardiac muscle and MØs. However, the role of GLN metabolism in the remodeling heart after MI is not well understood. We used a model of permanent coronary artery ligation in adult male C57BL/6J mice to assess GLN metabolism in extracted cardiac MØs at post-MI days (D) 1, 3, and 7. Using untargeted metabolomics, we found time-dependent changes in metabolites related to GLN and glutamate (GLU) metabolism in cardiac MØs (p=6E-4). GLN levels were significantly increased at day 3, while GLU was decreased at day 7, and the GLN/GLU ratio was higher at both D3 and 7 compared to D1 post-MI. Using Seahorse extracellular flux analysis, GLN consumption in MØs was increased on D1 and 3. In the remote area of the heart (RA), genes for GLN-metabolizing enzymes (Glud1, Got1, Gpt1) were decreased at D3 and 7, indicating a loss of GLN metabolism. We then administered GLN (1 g/kg body weight, i.p.) daily post-MI for up to D3 or 7. Compared to vehicle, GLN administration increased ejection fraction at D3 (1.2-fold increase) and 7 post-MI (1.6-fold increase), and attenuated anterior and posterior wall thinning at D7 by 1.6-fold and 1.3-fold, respectively. GLN also restored expression of genes associated with GLN metabolism (Gls1, Glul, Got1, Gpt1, Glud1) in the RA, as well as glucose oxidation (Pdha1). GLN also restored Myh6 expression and attenuated Myh7 expression, indicating favorable expression of myosin heavy chains. However, GLN did not affect cardiac MØ phenotype, as assessed by flow cytometry and cytokine mRNA levels (Il1b, Tnf, Il6, Ccl2, Il18, and Il10). We then blocked GLN metabolism by administering BPTES (12.5 mg/kg daily i.p. in corn oil) to mice for 3 days post-MI. BPTES exacerbated anterior wall thinning (1.4-fold decrease) and further decreased EF (1.4-fold) after MI, and also increased expression of Myh7 in the RA. However, BPTES did not affect MØ phenotypes. In conclusion, dysregulation of GLN metabolism is a hallmark of post-MI cardiac remodeling, and enhancing GLN metabolism may improve cardiac function, but may not be effective for reducing MØ-mediated inflammation post-MI. Funding: NIDDK 1R01121411, P20GM104357, U54GM115428, AHA856365 This is the full abstract presented at the American Physiology Summit 2023 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 key mediators involved in myocardial endoplasmic reticulum stress induced by ischaemia reperfusion injury in rats

Objective: Endoplasmic reticulum stress (ERS) occurs throughout the pathological process of myocardial ischaemia reperfusion injury (MIRI); however, the key mediators involved in the biological processes of ERS or that can influence the outcomes of ischaemia reperfusion injury (IRI) are unclear. To identify the differentially expressed genes (DEGs) encoding promising mediators in rat hearts in the context of MIRI, gene profiles were mined through transcriptome analysis. Methods: By searching the Gene Expression Omnibus (GEO) database, a suitable GEO dataset was identified in the context of MIRI with 24 h reperfusion after 45 min ischaemia in rats. DEGs were extracted and analysed with R studio, and the properties of those DEGs were elucidated by utilizing protein‒protein-interaction (PPI), Cytoscape, GO and KEGG bioinformatics techniques. The potential hub genes in the first cluster of the DEG dataset were retrieved and verified by basal experiments. Results: By searching the target dataset GSE122020, 1647 mRNAs, including 790 upregulated and 857 downregulated genes, were found in the datasets with criteria of | fold change ≥ 1.2 and p value <0.05. The upregulated and downregulated genes were primarily involved in the “positive regulation of cytokine production”, “regulation of inflammatory response” and “response to pheromone” biological processes. Most of them were mainly correlated with the MAPK, Ras and calcium signalling pathways. In particular, 15 DEGs were found to be involved in the ERS signalling pathways, including Bfar, Itpr1, Srpx, Hspa1b, Usp25, Jun, Casp12, Eif2ak2, Casp4, Trim25, Ifng, Atf3, Hspa1a, Ppp1r15a, and Creb3. Through analysis with the MCODE plugin in Cytoscape, six genes, Atf3, Ppp1r15a, Casp12, Eif2ak2, Ifng, and Hspa1a, were identified as hub genes by the K-means algorithm from Cluster 1. In the in vivo MIRI model, the six genes mentioned above exhibited significant mRNA overexpression in the left anterior descending coronary artery ligation (LAD) model in rats. Conclusions: Altogether, the present study identified six potential DEGs involved in ERS induced by MIRI, which could be therapeutic targets in dealing with IRI-related ERS.

Galectin-3 Is Associated with Cardiac Fibrosis and an Increased Risk of Sudden Death.

Myocardial fibrosis is a common postmortem finding among individuals with Sudden Cardiac Death (SCD). Numerous in vivo and in vitro studies have shown that increased galectin-3 (gal3) expression into the myocardium is associated with higher incidence of fibrosis. Although elevated gal3 expression is linked with myocardial fibrosis, its role in predicting the risk of SCD is unknown. We reviewed the clinical datasets and post-mortem examination of 221 subjects who had died suddenly. We examined myocardial pathology including the extent of cardiac hypertrophy, fibrosis, and the degree of coronary atherosclerosis in these subjects. In a select group of SCD subjects, we studied myocardial gal3 and periostin expression using immunohistochemistry. To further examine if a higher level of circulating gal3 can be detected preceding sudden death, we measured serum gal3 in a porcine model of subtotal coronary artery ligation which shows an increased tendency to develop lethal cardiac arrhythmias, including ventricular tachycardia or fibrillation. Of the total 1314 human subjects screened, 12.7% had SCD. Comparison of age-matched SCD with non-SCD subjects showed that SCD groups had excessive myocardial fibrosis involving both the left ventricular free wall and interventricular septum. In pigs with subtotal coronary artery ligation and SCD, we detected significantly elevated circulating gal3 levels approximately 10 days preceding the SCD event. Immunohistochemistry showed increased myocardial gal3 and periostin expression in pigs that died suddenly, compared to the controls. Our study shows that increased gal3 is associated with a higher risk of myocardial fibrosis and the risk of SCD. This supports the importance of larger translational studies to target gal3 to prevent cardiac fibrosis and attenuate the risk of SCD.

XCR1+ conventional dendritic cell-induced CD4+ T helper 1 cell activation exacerbates cardiac remodeling after ischemic myocardial injury

Cardiac remodeling has no established therapies targeting inflammation. CD4+ T-cell subsets have been reported to play significant roles in healing process after ischemic myocardial injury, but their detailed mechanisms of activation remain unknown. To explore immune reactions during cardiac remodeling, we applied a non-surgical model of coronary heart disease (CHD) induced by a high-fat diet (HFD-CHD) in SR-BI−/−/ApoeR61h/h mice. Flow cytometry analyses throughout the period of progressive cardiac dysfunction revealed that CD4+ T Helper 1 (Th1) cells were predominantly activated in T-cell subsets. Probucol was reported to attenuate cardiac dysfunction after coronary artery ligation model (ligation-MI) in rats. To determine whether probucol suppress cardiac remodeling after HFD-CHD, we treated SR-BI−/−/ApoeR61h/h mice with probucol. We found treatment with probucol in HFD-CHD mice reduced cardiac dysfunction, with attenuated activation of Th1 cells. RNA-seq analyses revealed that probucol suppressed the expression of CXCR3, a Th1-related chemokine receptor, in the heart. XCR1+ cDC1 cells, which highly expresses the CXCR3 ligands CXCL9 and CXCL10, were predominantly activated after HFD-CHD. XCR1+ cDC1 lineage skewing of pre-DC progenitors was observed in bone marrow, with subsequent systemic expansion of XCR1+ cDC1 cells after HFD-CHD. Activation of CXCR3+ Th1 cell and XCR1+ cDC1 cells was also observed in ligation-MI. Notably, post-MI depletion of XCR1+ cDC1 cells suppressed CXCR3+ Th1 cell activation and prevented cardiac dysfunction. In patient autopsy samples, CXCR3+ Th1 and XCR1+ cDC1 cells infiltrated the infarcted area. In this study, we identified a critical role of XCR1+ cDC1-activated CXCR3+ Th1 cells in ischemic cardiac remodeling.

Investigation of Cardioprotective Effect of 2, 4-thiazolidinedione Derivative Using HFD-STZ Fed Rats

Abstract: Background: Myocardial infarction is a 2nd most important origin of universal death and after coronary revascularization, cardiovascular events occurs further a lot in subjects through DM: 3.5- as well as 2-fold fatality ranks correspondingly behind percutaneous coronary intervention or coronary bypass graft surgery. Objectives: The aim of an attendance research was to discover usefulness of 2, 4- thiazolidinedione derivatives lying on diabetic MI and HFD-STZ diabetic rats. Materials and Methods: In in-vivo investigation, Type-2 diabetes was elicited by higher fatty meal plus little dosage for streptozotocin and MI was provoked by LAD Coronary artery ligation model. The rats were divided into a variety of groups, including treatment groups (Composite An epalrestat, Composite B pioglitazone). And after 15 days of treatment a variety of factors were evaluated, i.e. serum glucose, total cholesterol, serum triglycerides, lipid profile antioxidant enzymes, ECG analysis, and Histopathological examination of heart were done. Results: In in-vivo investigation, levels of serum glucose, triglycerides, LDL level, LDH level, CK-MB, Troponin I, malondialdehyde (MDA), total cholesterol, infarct area, were considerably decreased in composite A and B treated animals. Whereas the HDL level, antioxidant enzymes, had drastically risen in composite, treated animals balanced to disease control rats. In ECG analysis ST elevation was restored in drug treated animals. Composite treated heart indicated mild congestion and inflammation in histopathological examination. Homogenate of drug treated animals indicated less apoptotic signals and nearer to normal animals. Conclusion: The treatment with Composite A and Composite B notably ameliorated the alterations in MI in a dose dependant manner. Keywords: 2, 4-Thiazolidinedione, Myocardial infarction, Diabetic MI, Type-2 diabetes, LAD, Macrovascular complication.

Recombinant Klotho Protein Ameliorates Myocardial Ischemia/Reperfusion Injury by Attenuating Sterile Inflammation

Currently, no effective therapy and potential target have been elucidated for preventing myocardial ischemia and reperfusion injury (I/R). We hypothesized that the administration of recombinant klotho (rKL) protein could attenuate the sterile inflammation in peri-infarct regions by inhibiting the extracellular release of high mobility group box-1 (HMGB1). This hypothesis was examined using a rat coronary artery ligation model. Rats were divided into sham, sham+ rKL, I/R, and I/R+ rKL groups (n = 5/group). Administration of rKL protein reduced infarct volume and attenuated extracellular release of HMGB1 from peri-infarct tissue after myocardial I/R injury. The administration of rKL protein inhibited the expression of pro-inflammatory cytokines in the peri-infarct regions and significantly attenuated apoptosis and production of intracellular reactive oxygen species by myocardial I/R injury. Klotho treatment significantly reduced the increase in the levels of circulating HMGB1 in blood at 4 h after myocardial ischemia. rKL regulated the levels of inflammation-related proteins. This is the first study to suggest that exogenous administration of rKL exerts myocardial protection effects after I/R injury and provides new mechanistic insights into rKL that can provide the theoretical basis for clinical application of new adjunctive modality for critical care of acute myocardial infarction.

Single-Cell RNA Sequencing Reveals the Temporal Diversity and Dynamics of Cardiac Immunity after Myocardial Infarction.

Myocardial infarction (MI) is strongly associated with the temporal regulation of cardiac immunity. However, a variety of current clinical trials have failed because of the lack of post-MI immunomodulating/anti-inflammatory targets. Single-cell RNA sequencing analysis of the cardiac Cd45+ immune cell at 0, 3, 7, and 14 d after injury in a mouse left anterior descending coronary artery ligation model is performed. Major immune cell populations, distinct subsets, and dynamic changes are identified. Macrophages (Mø) are most abundant, peaking at 3 d after infarction. Mø-5 and Mø-6 are the predominant infiltrated subsets at this time point, with strong expression of inflammatory factors. Further analysis demonstrates that suppressing these sets attenuated pathological MI progression by preventing subsequent leukocyte extravasation and adverse remodeling. Abundant apoptotic neutrophils and a profibrotic macrophage subset on days 7 and 14, respectively, are also detected. These results provide a basis for developing cell type- and time-specific interventions in MI.

Positron Emission Tomography (PET) with 18F-FGA for Diagnosis of Myocardial Infarction in a Coronary Artery Ligation Model.

Location and extent of necrosis are valuable information in the management of myocardial infarction (MI). Methods. We investigated 2-deoxy-2-18F-fluoro glucaric acid (FGA), a novel infarct-avid agent, for positron emission tomography (PET) of MI. We synthesized FGA from commercially available 18F-fluoro-2-deoxy-2-D-glucose (FDG). MI was induced in mice by permanently occluding the left anterior descending coronary artery. Biodistribution of FGA was assessed 1 h after FGA injection (11 MBq). PET/CT was conducted 1 h, 6 h, 1 d, 3 d, and 4 d after MI. Subcellular compartment of FGA accumulation in necrosis was studied by tracing the uptake of biotin-labeled glucaric acid with streptavidin-HRP in H2O2-treated H9c2 cardiomyoblasts. Streptavidin-reactive protein bands were identified by LC-MS/MS. Results. We obtained a quantitative yield of FGA from FDG within 7 min (radiochemical purity > 99%). Cardiac uptake of FGA was significantly higher in MI mice than that in control mice. Imaging after 1 h of FGA injection delineated MI for 3 days after MI induction, with negligible background signal from surrounding tissues. Myocardial injury was verified by tetrazolium staining and plasma troponin (47.63 pg/mL control versus 311.77 pg/mL MI). In necrotic H9c2 myoblasts, biotinylated glucaric acid accumulated in nuclear fraction. LC-MS/MS primarily identified fibronectin in necrotic cells as a putative high fidelity target of glucaric acid. Conclusion. FGA/PET detects infarct early after onset of MI and FGA accumulation in infarct persists for 3 days. Its retention in necrotic cells appears to be a result of interaction with fibronectin that is known to accumulate in injured cardiac tissue.

Carbonic anhydrase IX and hypoxia-inducible factor 1 attenuate cardiac dysfunction after myocardial infarction.

Myocardial infarction (MI) is one of the leading causes of death worldwide. Prognosis and mortality rate are directly related to infarct size and post-infarction pathological heart remodeling, which can lead to heart failure. Hypoxic MI-affected areas increase the expression of hypoxia-inducible factor (HIF-1), inducing infarct size reduction and improving cardiac function. Hypoxia translocates HIF-1 to the nucleus, activating carbonic anhydrase IX (CAIX) transcription. CAIX regulates myocardial intracellular pH, critical for heart performance. Our objective was to investigate CAIX participation and relation with sodium bicarbonate transporters 1 (NBC1) and HIF-1 in cardiac remodeling after MI. We analyzed this pathway in an "in vivo" rat coronary artery ligation model and isolated cardiomyocytes maintained under hypoxia. Immunohistochemical studies revealed an increase in HIF-1 levels after 2 h of infarction. Similar results were observed in 2-h infarcted cardiac tissue (immunoblotting) and in hypoxic cardiomyocytes with a nuclear distribution (confocal microscopy). Immunohistochemical studies showed an increase CAIX in the infarcted area at 2 h, mainly distributed throughout the cell and localized in the plasma membrane at 24 h. Similar results were observed in 2 h in infarcted cardiac tissue (immunoblotting) and in hypoxic cardiomyocytes (confocal microscopy). NBC1 expression increased in cardiac tissue after 2 h of infarction (immunoblotting). CAIX and NBC1 interaction increases in cardiac tissue subjected to MI for 2h when CAIX is present (immunoprecipitation). These results suggest that CAIX interacts with NBC1 in our infarct model as a mechanism to prevent acidic damage in hypoxic tissue, making it a promising therapeutic target.

Targeted temperature management at 33°C or 36℃ induces equivalent myocardial protection by inhibiting HMGB1 release in myocardial ischemia/reperfusion injury.

Acute myocardial infarction (AMI) is lethal and causes myocardial necrosis via time-dependent ischemia due to prolonged occlusion of the infarct-related artery. No effective therapy or potential therapeutic targets can prevent myocardial ischemia/reperfusion (I/R) injury. Targeted temperature management (TTM) may reduce peri-infarct regions by inhibiting the extracellular release of high mobility group box-1 (HMGB1) as a primary mediator of the innate immune response. We used a rat left anterior descending (LAD) coronary artery ligation model to determine if TTM at 33°C and 36°C had similar myocardial protective effects. Rats were divided into sham, LAD I/R+37°C normothermia, LAD I/R+33°C TTM, and LAD I/R+36°C TTM groups (n = 5 per group). To verify the cardioprotective effect of TTM by specifically inhibiting HMGB1, rats were assigned to sham, LAD I/R, and LAD I/R after pre-treatment with glycyrrhizin (known as a pharmacological inhibitor of HMGB1) groups (n = 5 per group). Different target temperatures of 33°C and 36°C caused equivalent reductions in infarct volume after myocardial I/R, inhibited the extracellular release of HMGB1 from infarct tissue, and suppressed the expression of inflammatory cytokines from peri-infarct regions. TTM at 33°C and 36°C significantly attenuated the elevation of cardiac troponin, a sensitive and specific marker of heart muscle damage, after injury. Similarly, glycyrrhizin alleviated myocardial damage by suppressing the extracellular release of HMGB1. TTM at 33°C and 36°C had equivalent myocardial protective effects by similar inhibiting HMGB1 release against myocardial I/R injury. This is the first study to suggest that a target core temperature of 36°C is applicable for cardioprotection.

Commercial 4-dimensional echocardiography for murine heart volumetric evaluation after myocardial infarction

BackgroundTraditional preclinical echocardiography (ECHO) modalities, including 1-dimensional motion-mode (M-Mode) and 2-dimensional long axis (2D-US), rely on geometric and temporal assumptions about the heart for volumetric measurements. Surgical animal models, such as the mouse coronary artery ligation (CAL) model of myocardial infarction, result in morphologic changes that do not fit these geometric assumptions. New ECHO technology, including 4-dimensional ultrasound (4D-US), improves on these traditional models. This paper aims to compare commercially available 4D-US to M-mode and 2D-US in a mouse model of CAL.Methods37 mice underwent CAL surgery, of which 32 survived to a 4 week post-operative time point. ECHO was completed at baseline, 1 week, and 4 weeks after CAL. M-mode, 2D-US, and 4D-US were taken at each time point and evaluated by two separate echocardiographers. At 4 weeks, a subset (n = 12) of mice underwent cardiac magnetic resonance (CMR) imaging to serve as a reference standard. End systolic volume (ESV), end diastolic volume (EDV), and ejection fraction (EF) were compared among imaging modalities. Hearts were also collected for histologic evaluation of scar size (n = 16) and compared to ECHO-derived wall motion severity index (WMSI) and global longitudinal strain as well as gadolinium-enhanced CMR to compare scar assessment modalities.Results4D-US provides close agreement of ESV (Bias: -2.55%, LOA: − 61.55 to 66.66) and EF (US Bias: 11.23%, LOA − 43.10 to 102.8) 4 weeks after CAL when compared to CMR, outperforming 2D-US and M-mode estimations. 4D-US has lower inter-user variability as measured by intraclass correlation (ICC) in the evaluation of EDV (0.91) and ESV (0.93) when compared to other modalities. 4D-US also allows for rapid assessment of WMSI, which correlates strongly with infarct size by histology (r = 0.77).Conclusion4D-US outperforms M-Mode and 2D-US for volumetric analysis 4 weeks after CAL and has higher inter-user reliability. 4D-US allows for rapid calculation of WMSI, which correlates well with histologic scar size.

The role of Nrf2 in astragaloside IV-mediated antioxidative protection on heart failure

Context Heart failure is one of the most serious diseases worldwide. Astragaloside IV (ASI) is widely used in the treatment of cardiovascular diseases. Objective To elucidate the antioxidative mechanism of ASI in a rat model of left coronary artery ligation. Materials and methods Left coronary artery of Sprague–Dawley rats was ligated to establish the model of heart failure, and then vehicle (saline) or ASI (1 mg/kg/day) was orally administered to the rats (n = 15) for 6 weeks. Echocardiography was used to evaluate the cardiac function. Myocardial infarct size was measured by triphenyltetrazolium chloride staining. Oxidative stress in the ventricular myocardium was determined. Molecular mechanisms were investigated by Western blot and chromatin immunoprecipitation. Results ASI improved the cardiac function, especially ejection fraction (75.27 ± 5.75% vs. 36.26 ± 4.14%) and fractional shortening (45.39 ± 3.66% vs. 17.88 ± 1.32%), and reduced the infarct size of left ventricle (20.69 ± 2.98% vs. 39.11 ± 3.97%). ASI maintained the levels of glutathione, catalase and superoxide dismutase and prevented the leakage of creatine kinase. In addition, ASI induced the protein expression of Nrf2 (1.97-fold) and HO-1 (2.79-fold), while reduced that of Keap-1 (0.77-fold) in the ventricular myocardium. In H9c2 cells, a rat cardiomyocyte cell line, ASI induced the translocation of Nrf2 from cytoplasm to nucleus, followed by transcriptional activation of NQO-1 (8.27-fold), SOD-2 (3.27-fold) and Txn-1 (9.83-fold) genes. Discussion and conclusions ASI prevented heart failure by counteracting oxidative stress through the Nrf2/HO-1 pathway. Application in clinical practice warrants further investigation.

Development of a Novel Sodium-Hydrogen Exchanger Inhibitor for Heart Failure

This study was designed to determine the potential therapeutic effects of a new sodium-hydrogen exchanger (NHE-1) inhibitor in the rat coronary artery ligation model of chronic heart failure. After the induction of acute myocardial infarction, rats were entered into a randomly designed pilot dose study from 0.3 mg/kg, 1.0 mg/kg, and 3.0 mg/kg. Solid state micrometer hemodynamics, echocardiographic, and pressure-volume relationships were measured after 6 weeks of treatment. Treatment with this NHE-¬1 inhibitor at 3 mg/kg increased (P<0.05) ejection fraction from 23±3% (N=6) to 33±2% (N=13), while the 1 mg/kg dose decreased (P<0.05) the infarct size in CHF rats from 21.7±1.4% (N=7) to 15.9±0.7% (N=3) and prevented (P<0.05) dilata¬tion of the left ventricle in CHF rats in diastole (1.0±0.1 cm, N=6) to 0.9±0.1 cm, N=10) and in systole (0.9±0.1 cm, N=6) to 0.8±0.1, N=10). These study results suggest that this new NHE-1 inhibitor may be potentially useful in treating CHF with an improvement in maladaptive left ventricle remodeling. Because the mechanism of action of this agent is entirely different than the currently applied approach in treating CHF that focuses on aggressive neuro-hormonal blockade and because this agent does not adversely affect important hemodynamic variables, further investigations with this agent may be warranted.

Endoplasmic Reticulum Stress-Induced NLRP1 Inflammasome Activation Contributes to Myocardial Ischemia/Reperfusion Injury

Studies have shown that Nod-like receptor protein (NLRP) 3 inflammasome activation contributes to myocardial ischemia/reperfusion (I/R) injury. However, the role and mechanism of NLRP1 inflammasome in myocardial I/R injury remain unknown. Endoplasmic reticulum (ER) stress is involved in the development of myocardial I/R injury. The relationship between ER stress and NLRP1 inflammasome in myocardial I/R injury needs further study. NLRP1 inflammasome activation and ER stress were investigated in hypoxia/reoxygenation (H/R)-treated primary mouse cardiomyocytes and left anterior descending coronary artery ligation and reperfusion mouse models. Downregulation of NLRP1 expression with NLRP1 small interfering RNA (siRNA) was used to evaluate the role of NLRP1 inflammasome in H/R-stimulated cardiomyocyte injury. 4-phenylbutyric acid (4-PBA), an ER stress inhibitor, was used to pretreat cardiomyocytes before H/R treatment, the cardiomyocyte injury and NLRP1 inflammasome activation were determined. Also, nuclear factor (NF)-κB signaling activity was measured. Additionally, pyrrolidine dithiocar bamate (PDTC), an NF-κB inhibitor, was used to treat cardiomyocytes before H/R stimulation and NLRP1 inflammasome activation was examined. We found the levels of ER stress markers GRP78, p-PERK, p-eIF2α and CHOP as well as NLRP1 inflammasome activation were significantly elevated both in vivo and in vitro. NLRP1 siRNA notably increased cell viability inhibited by H/R, suppressed H/R-induced cell apoptosis, lactate dehydrogenase release, and creatine kinase activity. 4-PBA reduced H/R-stimulated cardiomyocyte injury via NLRP1 inflammasome inactivation, and it also suppressed NF-κB signaling activity. NLRP1 inflammasome activation induced by H/R was also suppressed by PDTC. In conclusion, NLRP1 inflammasome activation promotes myocardial I/R injury. ER stress can activate NLRP1 inflammasome via activating the NF-κB signaling pathway.

The Clock Mechanism Influences Neurobiology and Adaptations to Heart Failure in Clock\u220619/\u220619 Mice With Implications for Circadian Medicine

In this study we investigated the role of the circadian mechanism on cognition-relevant brain regions and neurobiological impairments associated with heart failure (HF), using murine models. We found that the circadian mechanism is an important regulator of healthy cognitive system neurobiology. Normal Clock∆19/∆19 mice had neurons with smaller apical dendrite trees in the medial prefrontal cortex (mPFC), and hippocampus, showed impaired visual-spatial memory, and exhibited lower cerebrovascular myogenic tone, versus wild types (WT). We then used the left anterior descending coronary artery ligation model to investigate adaptations in response to HF. Intriguingly, adaptations to neuron morphology, memory, and cerebrovascular tone occurred in differing magnitude and direction between Clock∆19/∆19 and WT mice, ultimately converging in HF. To investigate this dichotomous response, we performed microarrays and found genes crucial for growth and stress pathways that were altered in Clock∆19/∆19 mPFC and hippocampus. Thus these data demonstrate for the first time that (i) the circadian mechanism plays a role in neuron morphology and function; (ii) there are changes in neuron morphology and function in HF; (iii) CLOCK influences neurobiological gene adaptations to HF at a cellular level. These findings have clinical relevance as patients with HF often present with concurrent neurocognitive impairments. There is no cure for HF, and new understanding is needed to reduce morbidity and improve the quality of life for HF patients.