Pathophysiologic role of myocardial apoptosis in post-infarction left ventricular remodeling

Mitochondrial outer membrane protein Samm50 protects against hypoxia-induced cardiac injury by interacting with Shmt2

Cardiac remodeling is a critical process following myocardial infarction (MI), potentially leading to heart failure if untreated. The significance of mitochondrial homeostasis in MI remains insufficiently understood. Samm50 is an essential component of mitochondria. Our study aimed to investigate its role in hypoxia-induced cardiac injury and the underlying mechanisms. First, we observed that Samm50 was dynamically downregulated in mice with MI compared to the control mice. In vitro, Samm50 was also downregulated in oxygen-glucose-deprived neonatal rat cardiomyocytes and fibroblasts. Overexpression and knockdown of Samm50 mitigated and exacerbated cardiac apoptosis and fibrosis, while also improving and worsening mitochondrial homeostasis, respectively. Protein interactions with Samm50 during the protective process were identified via immune-coprecipitation/mass spectroscopy. Mechanistically, serine hydroxymethyltransferase 2 (Shmt2) interacted with Samm50, acting as a crucial element in the protective process by hindering the transfer of Bax from the cytoplasm to the mitochondria and subsequent activation of caspase-3. Inhibition of Shmt2 diminished the protective effect of Samm50 overexpression against cardiac injury. Finally, Samm50 overexpression in vivo mitigated cardiac remodeling and enhanced cardiac function in both acute and chronic MI. In conclusion, Samm50 overexpression mitigated hypoxia-induced cardiac remodeling by inhibiting apoptosis and fibrosis, with Shmt2 acting as a key regulator in this protective process. The Samm50/Shmt2 axis represents a newly discovered mitochondria-related pathway for mitigating hypoxia-induced cardiac injury.

Platelets Induce Cell Apoptosis of Cardiac Cells via FasL after Acute Myocardial Infarction

Acute myocardial infarction (AMI) is one of the leading causes of death worldwide. Cell apoptosis in the myocardium plays an important role in ischemia and reperfusion (I/R) injury, leading to cardiac damage and dysfunction. Platelets are major players in hemostasis and play a crucial role in vessel occlusion, inflammation, and cardiac remodeling after I/R. Here, we studied the impact of platelets on cell apoptosis in the myocardium using a close-chest mouse model of AMI. We found caspase-3-positive resident cardiac cells, while leukocytes were negative for caspase-3. Using two different mouse models of thrombocytopenia, we detected a significant reduction in caspase-3 positive cells in the infarct border zone after I/R injury. Further, we identified platelet FasL to induce cell apoptosis via the extrinsic pathway of Fas receptor activation of target cells. Mechanistically, hypoxia triggers platelet adhesion to FasR, suggesting that platelet-induced apoptosis is elevated after I/R. Platelet-specific FasL knock-out mice showed reduced Bax and Bcl2 expression, suggesting that platelets modulate the intrinsic and extrinsic pathways of apoptosis, leading to reduced infarct size after myocardial I/R injury. Thus, a new mechanism for how platelets contribute to tissue homeostasis after AMI was identified that should be validated in patients soon.

Apoptosis and heart failure: The role of non-coding RNAs and exosomal non-coding RNAs

Heart failure is a condition that affects the cardio vascular system and occurs if the heart cannot adequately pump the oxygen and blood to the body. Myocardial infarction, reperfusion injury, and this disease is the only a few examples of the numerous cardiovascular illnesses that are impacted by the closely controlled cell deletion process known as apoptosis. Attention has been paid to the creation of alternative diagnostic and treatment modalities for the condition. Recent evidences have shown that some non-coding RNAs (ncRNAs) influence the stability of proteins, control of transcription factors, and HF apoptosis through a variety of methods. Exosomes make a significant paracrine contribution to the regulation of illnesses as well as to the communication between nearby and distant organs. However, it has not yet been determined whether exosomes regulate the cardiomyocyte-tumor cell interaction in ischemia HF to limit the vulnerability of malignancy to ferroptosis. Here, we list the numerous ncRNAs in HF that are connected to apoptosis. In addition, we emphasize the significance of exosomal ncRNAs in the HF.

Peri-event plasma PCSK9 and hsCRP after an acute myocardial infarction correlate with early deterioration of left ventricular ejection fraction: a cohort study

Background

It is important to identify patients at increased risk of worsening of left ventricular ejection fraction (LVEF) after a myocardial infarction (MI). We aimed to identify the association of various potential biomarkers with LVEF impairment after an MI in South American patients.

Methods

We studied adult patients admitted to a University Hospital and diagnosed with an acute MI. Plasma concentrations of high-sensitivity C-reactive protein (hsCRP), proprotein convertase subtilisin/kexin type 9 (PCSK9), N-terminal prohormone of brain natriuretic peptide (NT-proBNP) and heart-type fatty-acid-binding protein (FABP3) were determined in samples drawn shortly after the event. Participants had a follow-up visit at least 45 days after the event. The primary endpoint was defined as any decline in LVEF at follow-up relative to baseline.

Results

The study included 106 patients (77.4% men, 22.6% women), mean age was 64.1, mean baseline LVEF was 56.6, 19% had a prior MI. We obtained a follow-up evaluation in 100 (94.4%) of participants, mean follow-up time was 163 days. There was a significant correlation between baseline PCSK9 and hsCRP (r = 0.39, p < 0.001). Baseline hsCRP concentrations were higher in patients who developed the endpoint than in those who did not (32.1 versus 21.2 mg/L, p = 0.066). After multivariate adjustment, baseline PCSK9, male sex and age were significantly associated with impairment in LVEF. The absolute change in LVEF was inversely correlated with baseline hsCRP (standardized coefficient = − 0.246, p = 0.004).

Conclusion

High plasma levels of PCSK9 and hsCRP were associated with early decreases in LVEF after an MI in Latin American patients.

Inhibition of GSDMD Activates Poly(ADP-ribosyl)ation and Promotes Myocardial Ischemia-Reperfusion Injury

The precise control of cardiomyocyte viability is imperative to combat myocardial ischemia-reperfusion injury (I/R), in which apoptosis and pyroptosis putatively contribute to the process. Recent researches indicated that GSDMD is involved in I/R as an executive protein of pyroptosis. However, its effect on other forms of cell death is unclear. We identified that GSDMD and GSDMD-N levels were significantly upregulated in the I/R myocardium of mice. Knockout of GSDMD conferred the resistance of the hearts to reperfusion injury in the acute phase of I/R but aggravated reperfusion injury in the chronic phase of I/R. Mechanistically, GSDMD deficiency induced the activation of PARylation and the consumption of NAD+ and ATP, leading to cardiomyocyte apoptosis. Moreover, PJ34, a putative PARP-1 inhibitor, reduced the myocardial injury caused by GSDMD deficiency. Our results reveal a novel action modality of GSDMD in the regulation of cardiomyocyte death; inhibition of GSDMD activates PARylation, suggesting the multidirectional role of GSDMD in I/R and providing a new theory for clinical treatment.

A Novel Anderson-Evans Polyoxometalate-based Metal-organic Framework Composite for the Highly Selective Isolation and Purification of Cytochrome C from Porcine Heart

Anderson-Evans type polyoxometalate group (Na₆[TeW₆O₂₄]·22 H₂O, TeW₆) was combined with porous metal-organic framework ZIF-8 by electrostatic interaction to obtain a novel Anderson-Evans polyoxometalate-based metal-organic framework composite, TeW₆ @ZIF-8. FT-IR, Raman, XRD, TG, DSC, SEM, and TEM were used to characterize the composite. It was proved that the Anderson-Evans type polyoxometalate group TeW₆ was successfully hybridized with metal-organic framework ZIF-8, and the composite possesses good stability. Based on the potential interaction between TeW₆ and proteins and the coordination between imidazole groups in ZIF-8 and proteins with a porphyrin ring structure, the adsorption selectivity towards different proteins on the TeW₆ @ZIF-8 composite was studied in this work. The experiment results showed that the TeW₆ @ZIF-8 composite was selectively adsorbed to cytochrome C. At pH 11.0, the adsorption efficiency of 94.01% was obtained for processing 1.0 mL 100 μg mL^-1 cytochrome C with 3.0 mg TeW₆ @ZIF-8 composite. The adsorption behavior of cytochrome C fits well with the Langmuir adsorption model, corresponding to a theoretical adsorption capacity of 232.56 mg g^-1. The retained cytochrome C could be readily recovered by 1% SDS (m/m), giving rise to a recovery of 65.6%. Circular dichroism spectra indicate no conformational change for cytochrome C after the adsorption and desorption processes, demonstrating the favorable biocompatibility of TeW₆ @ZIF-8 composite. In applying practical samples, SDS-PAGE results showed that cytochrome C was successfully isolated and purified by TeW₆ @ZIF-8 composite from porcine heart protein extract, which is further identified with LC-MS/MS. Thus, a new strategy for separating and purifying cytochrome C from the porcine heart using TeW₆ @ZIF-8 composite as an adsorbent was established.

Immediate Renal Denervation After Acute Myocardial Infarction Mitigates the Progression of Heart Failure via the Modulation of IL-33/ST2 Signaling

Objective: Previous studies have demonstrated the protective effects of renal denervation (RDN) in pre-existing heart failure, but the effects of immediate RDN after acute myocardial infarction (AMI) on subsequent cardiac remodeling have not been reported. This study aimed to investigate the cardioprotective effects of immediate RDN after AMI and its underlying mechanism.

Methods: AMI was induced by intracoronary gelatin sponge embolization in 14 Shanghai white pigs that were randomized to undergo either renal angiography (AMI+sham group) or RDN (AMI+RDN group) after 1 h of hemodynamic monitoring. Cardiac function of the two groups was measured at baseline, 1 h post-AMI and at the 1 month follow-up (1M-FU) by transthoracic echocardiography (TTE). Plasma NT-proBNP, soluble ST2 (sST2), norepinephrine (NE), and renin-angiotensin-aldosterone system activity were detected simultaneously. The renal cortex was harvested for NE measurement after the 1M-FU, and the renal arteries were stained with tyrosine hydroxylase for the evaluation of sympathetic activity. Heart tissues in the non-ischemic areas were collected to assess histological and molecular left ventricular (LV) remodeling by pathological staining, RT-PCR, and western blotting.

Results: There was no difference in the hemodynamic stability or cardiac function between the two groups at baseline and 1 h post-AMI. Six pigs from each of the two groups completed the 1M-FU. TTE analysis revealed the improved cardiac function of immediate RDN in the AMI+RDN group and circulating NT-proBNP levels were lower than those in the AMI+sham group. Further analysis showed significantly less interstitial fibrosis in the remote non-ischemic myocardium after immediate RDN, together with decreased cardiomyocyte hypertrophy and inflammatory cell infiltration. sST2 levels in circulating and myocardial tissues of animals in the AMI+RDN group were significantly higher than those in the AMI+sham group, accompanied by corresponding alterations in IL-33/ST2 and downstream signaling.

Conclusions: Immediate RDN can improve cardiac function and myocardial remodeling after AMI via modulation of IL-33/ST2 and downstream signaling.

Advances in Nanomaterials for Injured Heart Repair

Atherosclerotic cardiovascular disease (ASCVD) is one of the leading causes of mortality worldwide. Because of the limited regenerative capacity of adult myocardium to compensate for the loss of heart tissue after ischemic infarction, scientists have been exploring the possible mechanisms involved in the pathological process of ASCVD and searching for alternative means to regenerate infarcted cardiac tissue. Although numerous studies have pursued innovative solutions for reversing the pathological process of ASCVD and improving the effectiveness of delivering therapeutics, the translation of those advances into downstream clinical applications remains unsatisfactory because of poor safety and low efficacy. Recently, nanomaterials (NMs) have emerged as a promising new strategy to strengthen both the efficacy and safety of ASCVD therapy. Thus, a comprehensive review of NMs used in ASCVD treatment will be useful. This paper presents an overview of the pathophysiological mechanisms of ASCVD and the multifunctional mechanisms of NM-based therapy, including antioxidative, anti-inflammation and antiapoptosis mechanisms. The technological improvements of NM delivery are summarized and the clinical transformations concerning the use of NMs to treat ASCVD are examined. Finally, this paper discusses the challenges and future perspectives of NMs in cardiac regeneration to provide insightful information for health professionals on the latest advancements in nanotechnologies for ASCVD treatment.

Role of IL-37- and IL-37-Treated Dendritic Cells in Acute Coronary Syndrome

As a chronic inflammatory disease, atherosclerosis is a leading cause of morbidity and mortality in most countries. Inflammation is responsible for plaque instability and the subsequent onset of acute coronary syndrome (ACS), which is one of the leading causes of hospitalization. Therefore, exploring the potential mechanism underlying ACS is of considerable concern, and searching for alternative therapeutic targets is very urgent. Interleukin-37 (IL-37) inhibits the production of proinflammatory chemokines and cytokines and acts as a natural inhibitor of innate and adaptive immunity. Interestingly, our previous study with murine models showed that IL-37 alleviated cardiac remodeling and myocardial ischemia/reperfusion injury. Of note, our clinical study revealed that IL-37 is elevated and plays a beneficial role in patients with ACS. Moreover, dendritic cells (DCs) orchestrate both immunity and tolerance, and tolerogenic DCs (tDCs) are characterized by more secretion of immunosuppressive cytokines. As expected, IL-37-treated DCs are tolerogenic. Hence, we speculate that IL-37- or IL-37-treated DCs is a novel therapeutic possibility for ACS, and the precise mechanism of IL-37 requires further study.

Nobiletin Attenuates Pathological Cardiac Remodeling after Myocardial Infarction via Activating PPARγ and PGC1α

Materials and Methods

C57BL/6 mice were treated with coronary artery ligation to generate an MI model, followed by treatment for 3 weeks with NOB (50 mg/kg/d) or vehicle (50 mg/kg/d), with or without the peroxisome proliferator-activated receptor gamma (PPARγ) inhibitor T0070907 (1 mg/kg/d). Cardiac function (echocardiography, survival rate, Evans blue, and triphenyl tetrazolium chloride staining), fibrosis (Masson's trichrome staining, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot (WB)), hypertrophy (haematoxylin-eosin staining, wheat germ agglutinin staining, and qRT-PCR), and apoptosis (WB and terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) staining) were evaluated. Hypoxia-induced apoptosis (TUNEL, WB) and phenylephrine- (PE-) induced pathological hypertrophy (immunofluorescence staining, qRT-PCR) models were established in primary neonatal rat ventricular myocytes (NRVMs). The effects of NOB with or without T0070907 were examined for the expression of PPARγ and PPARγ coactivator 1α (PGC1α) by WB in mice and NRVMs. The potential downstream effectors of PPARγ were further analyzed by WB in mice.

Results

Following MI in mice, NOB intervention enhanced cardiac function across three predominant dimensions of pathological cardiac remodeling, which reflected in decreasing cardiac fibrosis, apoptosis, and hypertrophy decompensation. NOB intervention also alleviated apoptosis and hypertrophy in NRVMs. NOB intervention upregulated PPARγ and PGC1α in vivo and in vitro. Furthermore, the PPARγ inhibitor abolished the protective effects of NOB against pathological cardiac remodeling during the progression from MI to CHF. The potential downstream effectors of PPARγ were nuclear factor erythroid 2-related factor 2 (Nrf-2) and heme oxygenase 1 (HO-1).

Conclusions

Our findings suggested that NOB alleviates pathological cardiac remodeling after MI via PPARγ and PGC1α upregulation.

lncRNA NONHSAT069381 and NONHSAT140844 Increase in Aging Human Blood, Regulating Cardiomyocyte Apoptosis

Aging augments postischemic apoptosis via incomplete mechanisms. Our previous animal study suggests that in addition to proapoptotic effects, lncRNAs also exert antiapoptotic effects in cardiomyocytes. However, whether this unexpected phenomenon exists in humans is unknown. In the present study, we investigated the relationship between aging and apoptosis regulation in human blood samples and confirmed their role by utilizing the cardiomyocyte lines (AC16 cells). Human blood samples were collected from 20 pairs of older adult and young volunteers. Age-different apoptotic regulatory lncRNAs and miRNAs were identified by microarray and bioinformatics analysis. The results indicated that lncRNA (NONHSAT069381 and NONHSAT140844) and miRNA (hsa-miR-124-5p and hsa-miR-6507-5p) were increased in aging human blood, confirmed by both bioinformatics analysis and polymerase chain reaction (PCR). Overexpression of NONHSAT069381 in AC16 cells increased caspase-3 levels and increased cardiomyocyte apoptotic cell death (determined by TUNEL staining and caspase activity assays) after hypoxia/reoxygenation (H/R), while overexpression of NONHSAT140844 increased X-chromosome-linked inhibitor of apoptosis protein (XIAP) content and decreased the myocardial apoptotic cell death. Furthermore, luciferase reporter assay revealed that hsa-miR-124-5p might be a mediator between NONHSAT069381 and mCASP3 and hsa-miR-6507-5p might be a mediator between NONHSAT140844 and mXIAP. Overexpression of hsa-miR-124-5p decreased caspase-3 levels and overexpression of hsa-miR-6507-5p decreased XIAP content in AC16 cells. We have found evidence that lncRNAs are important regulatory molecules in aging-mediated effects upon apoptosis. More interestingly, besides apoptosis-promoting effects, aging also inhibits myocardial apoptosis after H/R. This phenomenon also exists in the human cardiomyocyte line.

The cardioprotective effect and mechanism of bioactive glass on myocardial reperfusion injury

Myocardial reperfusion treatment for ischemic infarction may cause lethal injury of cardiomyocytes, which is known as ischemia/reperfusion (I/R) injury. As a kind of prospective biomaterial with superior properties, the application of bioactive glasses (BGs) in myocardial tissue engineering have received great interests. In this study, the cardioprotective effect and relevant mechanism of BG on myocardial reperfusion injury were investigatedin vitro. H9c2 cardiomyocytes were pretreated with BG extracts and then cultured in hypoxic environment for 30 min followed by reoxygenation for 1 h. The activity of released lactate dehydrogenase (LDH) and the content of malondialdehyde (MDA) in H9c2 cells were tested by assay kits. Cell viability was analyzed by Live/Dead staining assay and the number of living cells was detected by Cell Counting Kit-8 (CCK-8) assay. The cytoskeletal protein F-actin was stained and observed under inverted fluorescence microscope. Mitochondrial membrane potential (MMP) level, reactive oxygen species (ROS) production and apoptosis ratio were evaluated by fluorescent observation and flow cytometry simultaneously. The gene expressions relevant to apoptosis were detected by quantitative real time polymerase chain reaction (qRT-PCR) analysis. The results showed that BG extracts effectively inhibited hypoxia/reoxygenation (H/R)-induced cell injury by suppressing oxidative stress and mitochondrial permeability transition (MPT) within H9c2 cells. Meanwhile, apoptosis caused by H/R injury was alleviated and three classic apoptotic signaling pathways were proved to be regulated by BG extracts. Further analysis showed that phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway was up-regulated in H/R-induced H9c2 cells by BG extracts, leading to relieved cellular apoptosis. These results indicated that BG might exert cardioprotective effect in reperfusion injury when applied in myocardial tissue regeneration and repair.

Therapies Targeted at Non-Coding RNAs in Prevention and Limitation of Myocardial Infarction and Subsequent Cardiac Remodeling-Current Experience and Perspectives

Myocardial infarction is one of the major causes of mortality worldwide and is a main cause of heart failure. This disease appears as a final point of atherosclerotic plaque progression, destabilization, and rupture. As a consequence of cardiomyocytes death during the infarction, the heart undergoes unfavorable cardiac remodeling, which results in its failure. Therefore, therapies aimed to limit the processes of atherosclerotic plaque progression, cardiac damage during the infarction, and subsequent remodeling are urgently warranted. A hopeful therapeutic option for the future medicine is targeting and regulating non-coding RNA (ncRNA), like microRNA, circular RNA (circRNA), or long non-coding RNA (lncRNA). In this review, the approaches targeted at ncRNAs participating in the aforementioned pathophysiological processes involved in myocardial infarction and their outcomes in preclinical studies have been concisely presented.

Nuanxin capsule enhances cardiac function by inhibiting oxidative stress-induced mitochondrial dependent apoptosis through AMPK/JNK signaling pathway

OBJECTIVE

Oxidative stress and apoptosis play critical roles in the pathogenesis of heart failure (HF).Nuanxin capsule (NX) is a Chinese medicine that has outstanding protective effects on HF. The present study aimed to elucidate whether NX could protect HF against oxidative stress-induced apoptosis through intrinsic mitochondrial pathway.

METHODS

In vivo, HF was induced by transverse aortic constriction. NX and Compound C (Comp C) were administered to C57BL/6 J mice for over a 4-week period. Cardiac function was assessed with echocardiography. In vitro, H9c2 cells were exposed to H2O2 in the presence or absence of NX and Compound C. Cell viability, cytotoxicity, reactive oxygen species (ROS) production, apoptosis, mitochondrial membrane potential (ΔΨm) and mitochondrial function by oxygen consumption rate (OCR) were detected. The expressions of cytochrome c, BAX, Bcl-2, cleaved caspase-3, AMPK and JNK were evaluated by western blotting.

RESULTS

The results indicated that NX significantly improved cardiac function and enhanced the cell viability, ΔΨm and mitochondrial respiration. Also NX treatment reduced cell cytotoxicity and ROS production. Moreover, NX inhibited mitochondrial-mediated apoptosis by upregulating AMPK and downregulating JNK both in vivo and in vitro. The protective effects of NX on cardiac function by reducing oxidative stress-induced mitochondrial dependent apoptosis were reversed by Compound C treatment.

CONCLUSIONS

These findings demonstrated that NX effectively improved cardiac function in TAC mice by reducing oxidative stress-induced mitochondrial dependent apoptosis by activating AMPK/JNK signaling pathway.

PGAM1 deficiency ameliorates myocardial infarction remodeling by targeting TGF-β via the suppression of inflammation, apoptosis and fibrosis

Myocardial ischemia-reperfusion (MIR) represents critical challenge for the treatment of acute myocardial infarction diseases. Presently, identifying the molecular basis revealing MIR progression is scientifically essential and may provide effective therapeutic strategies. Phosphoglycerate mutase 1 (PGAM1) is a key aerobic glycolysis enzyme, and exhibits critical role in mediating several biological events, such as energy production and inflammation. However, whether PGAM1 can affect MIR is unknown. Here we showed that PGAM1 levels were increased in murine ischemic hearts. Mice with cardiac knockout of PGAM1 were resistant to MIR-induced heart injury, evidenced by the markedly reduced infarct volume, improved cardiac function and histological alterations in cardiac sections. In addition, inflammatory response, apoptosis and fibrosis in hearts of mice with MIR operation were significantly alleviated by the cardiac deletion of PGAM1. Mechanistically, the activation of nuclear transcription factor κB (NF-κB), p38, c-Jun NH2-terminal kinase (JNK) and transforming growth factor β (TGF-β) signaling pathways were effectively abrogated in MI-operated mice with specific knockout of PGAM1 in hearts. The potential of PGAM1 suppression to inhibit inflammatory response, apoptosis and fibrosis were verified in the isolated cardiomyocytes and fibroblasts treated with oxygen-glucose deprivation reperfusion (OGDR) and TGF-β, respectively. Importantly, PGAM1 directly interacted with TGF-β to subsequently mediate inflammation, apoptosis and collagen accumulation, thereby achieving its anti-MIR action. Collectively, these findings demonstrated that PGAM1 was a positive regulator of myocardial infarction remodeling due to its promotional modulation of TGF-β signaling, indicating that PGAM1 may be a promising therapeutic target for MIR treatment.

Targeted Injection of a Truncated Form of Tissue Inhibitor of Metalloproteinase 3 Alters Post-Myocardial Infarction Remodeling

Infarct expansion can occur after myocardial infarction (MI), which leads to adverse left ventricular (LV) remodeling and failure. An imbalance between matrix metalloproteinase (MMP) induction and tissue inhibitors of MMPs (TIMPs) can accelerate this process. Past studies have shown different biologic effects of TIMP-3, which may depend upon specific domains within the TIMP-3 molecule. This study tested the hypothesis that differential effects of direct myocardial injections of either a full-length recombinant TIMP-3 (F-TIMP-3) or a truncated form encompassing the N-terminal region (N-TIMP-3) could be identified post-MI. MI was induced in pigs that were randomized for MI injections (30 mg) and received targeted injections within the MI region of F-TIMP-3 (n = 8), N-TIMP-3 (n = 9), or saline injection (MI-only, n = 11). At 14 days post-MI, LV ejection fraction fell post-MI but remained higher in both TIMP-3 groups. Tumor necrosis factor and interleukin-10 mRNA increased by over 10-fold in the MI-only and N-TIMP-3 groups but were reduced with F-TIMP-3 at this post-MI time point. Direct MI injection of either a full-length or truncated form of TIMP-3 is sufficient to favorably alter the course of post-MI remodeling. The functional and differential relevance of TIMP-3 domains has been established in vivo since the TIMP-3 constructs demonstrated different MMP/cytokine expression profiles. These translational studies identify a unique and more specific therapeutic strategy to alter the course of LV remodeling and dysfunction after MI. SIGNIFICANCE STATEMENT: Using different formulations of tissue inhibitor of matrix metalloproteinase-3 (TIMP-3), when injected into the myocardial infarction (MI) region, slowed the progression of indices of left ventricular (LV) failure, suggesting that the N terminus of TIMP-3 is sufficient to attenuate early adverse functional events post-MI. Injections of full-length recombinant TIMP-3, but not of the N-terminal region of TIMP-3, reduced relative indices of inflammation at the mRNA level, suggesting that the C-terminal region affects other biological pathways. These unique proof-of-concept studies demonstrate the feasibility of using recombinant small molecules to selectively interrupt adverse LV remodeling post-MI.

Identification of key genes and pathways affected in epicardial adipose tissue from patients with coronary artery disease by integrated bioinformatics analysis

Background

Coronary artery disease (CAD) is a common disease with high cost and mortality. Here, we studied the differentially expressed genes (DEGs) between epicardial adipose tissue (EAT) and subcutaneous adipose tissue (SAT) from patients with CAD to explore the possible pathways and mechanisms through which EAT participates in the CAD pathological process.

Methods

Microarray data for EAT and SAT were obtained from the Gene Expression Omnibus database, including three separate expression datasets: GSE24425, GSE64554 and GSE120774. The DEGs between EAT samples and SAT control samples were screened out using the limma package in the R language. Next, we conducted bioinformatic analysis of gene ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways to discover the enriched gene sets and pathways associated with DEGs. Simultaneously, gene set enrichment analysis was carried out to discover enriched gene functions and pathways from all expression data rather than DEGs. The PPI network was constructed to reveal the possible protein interactions consistent with CAD. Mcode and Cytohubba in Cytoscape revealed the possible key CAD genes. In the next step, the corresponding predicted microRNAs (miRNAs) were analysed using miRNA Data Integration Portal. RT-PCR was used to validate the bioinformatic results.

Results

The three datasets had a total of 89 DEGs (FC log2 > 1 and P value < 0.05). By comparing EAT and SAT, ten common key genes (HOXA5, HOXB5, HOXC6, HOXC8, HOXB7, COL1A1, CCND1, CCL2, HP and TWIST1) were identified. In enrichment analysis, pro-inflammatory and immunological genes and pathways were up-regulated. This could help elucidate the molecular expression mechanism underlying the involvement of EAT in CAD development. Several miRNAs were predicted to regulate these DEGs. In particular, hsa-miR-196a-5p and hsa-miR-196b-5p may be more reliably associated with CAD. Finally, RT-PCR validated the significant difference of OXA5, HOXC6, HOXC8, HOXB7, COL1A1, CCL2 between EAT and SAT (P value < 0.05).

Conclusions

Between EAT and SAT in CAD patients, a total of 89 DEGs, and 10 key genes, including HOXA5, HOXB5, HOXC6, HOXC8, HOXB7, COL1A1, CCND1, CCL2, HP and TWIST1, and miRNAs hsa-miR-196a-5p and hsa-miR-196b-5p were predicted to play essential roles in CAD pathogenesis. Pro-inflammatory and immunological pathways could act as key EAT regulators by participating in the CAD pathological process.

Small Extracellular Microvesicles Mediated Pathological Communications Between Dysfunctional Adipocytes and Cardiomyocytes as a Novel Mechanism Exacerbating Ischemia/Reperfusion Injury in Diabetic Mice

BACKGROUND

Diabetes mellitus exacerbates myocardial ischemia/reperfusion (MI/R) injury by incompletely understood mechanisms. Adipocyte dysfunction contributes to remote organ injury. However, the molecular mechanisms linking dysfunctional adipocytes to increased MI/R injury remain unidentified. The current study attempted to clarify whether and how small extracellular vesicles (sEV) may mediate pathological communication between diabetic adipocytes and cardiomyocytes, exacerbating MI/R injury.

METHODS

Adult male mice were fed a normal or a high-fat diet for 12 weeks. sEV (from diabetic serum, diabetic adipocytes, or high glucose/high lipid-challenged nondiabetic adipocytes) were injected intramyocardially distal of coronary ligation. Animals were subjected to MI/R 48 hours after injection.

RESULTS

Intramyocardial injection of diabetic serum sEV in the nondiabetic heart significantly exacerbated MI/R injury, as evidenced by poorer cardiac function recovery, larger infarct size, and greater cardiomyocyte apoptosis. Similarly, intramyocardial or systemic administration of diabetic adipocyte sEV or high glucose/high lipid-challenged nondiabetic adipocyte sEV significantly exacerbated MI/R injury. Diabetic epididymal fat transplantation significantly increased MI/R injury in nondiabetic mice, whereas administration of a sEV biogenesis inhibitor significantly mitigated MI/R injury in diabetic mice. A mechanistic investigation identified that miR-130b-3p is a common molecule significantly increased in diabetic serum sEV, diabetic adipocyte sEV, and high glucose/high lipid-challenged nondiabetic adipocyte sEV. Mature (but not primary) miR-130b-3p was significantly increased in the diabetic and nondiabetic heart subjected to diabetic sEV injection. Whereas intramyocardial injection of a miR-130b-3p mimic significantly exacerbated MI/R injury in nondiabetic mice, miR-130b-3p inhibitors significantly attenuated MI/R injury in diabetic mice. Molecular studies identified AMPKα1/α2, Birc6, and Ucp3 as direct downstream targets of miR-130b-3p. Overexpression of these molecules (particularly AMPKα2) reversed miR-130b-3p induced proapoptotic/cardiac harmful effect. Finally, miR-130b-3p levels were significantly increased in plasma sEV from patients with type 2 diabetes mellitus. Incubation of cardiomyocytes with diabetic patient sEV significantly exacerbated ischemic injury, an effect blocked by miR-130b-3p inhibitor.

CONCLUSIONS

We demonstrate for the first time that miR-130b-3p enrichment in dysfunctional adipocyte-derived sEV, and its suppression of multiple antiapoptotic/cardioprotective molecules in cardiomyocytes, is a novel mechanism exacerbating MI/R injury in the diabetic heart. Targeting miR-130b-3p mediated pathological communication between dysfunctional adipocytes and cardiomyocytes may be a novel strategy attenuating diabetic exacerbation of MI/R injury.

Apoptosis and autophagy in polycystic kidney disease (PKD)

Apoptosis in the cystic epithelium is observed in most rodent models of polycystic kidney disease (PKD) and in human autosomal dominant PKD (ADPKD). Apoptosis inhibition decreases cyst growth, whereas induction of apoptosis in the kidney of Bcl-2 deficient mice increases proliferation of the tubular epithelium and subsequent cyst formation. However, alternative evidence indicates that both induction of apoptosis as well as increased overall rates of apoptosis are associated with decreased cyst growth. Autophagic flux is suppressed in cell, zebra fish and mouse models of PKD and suppressed autophagy is known to be associated with increased apoptosis. There may be a link between apoptosis and autophagy in PKD. The mammalian target of rapamycin (mTOR), B-cell lymphoma 2 (Bcl-2) and caspase pathways that are known to be dysregulated in PKD, are also known to regulate both autophagy and apoptosis. Induction of autophagy in cell and zebrafish models of PKD results in suppression of apoptosis and reduced cyst growth supporting the hypothesis autophagy induction may have a therapeutic role in decreasing cyst growth, perhaps by decreasing apoptosis and proliferation in PKD. Future research is needed to evaluate the effects of direct autophagy inducers on apoptosis in rodent PKD models, as well as the cause and effect relationship between autophagy, apoptosis and cyst growth in PKD.

Rapamycin regulates the balance between cardiomyocyte apoptosis and autophagy in chronic heart failure by inhibiting mTOR signaling

The progressive loss of cardiomyocytes caused by cell death leads to cardiac dysfunction and heart failure (HF). Rapamycin has been shown to be cardioprotective in pressure-overloaded and ischemic heart diseases by regulating the mechanistic target of rapamycin (mTOR) signaling network. However, the impact of rapamycin on cardiomyocyte death in chronic HF remains undetermined. Therefore, in the current study we addressed this issue using a rat myocardial infarction (MI)-induced chronic HF model induced by ligating the coronary artery. Following surgery, rats were randomly divided into six groups, including the sham-, vehicle- and rapamycin-operated groups, at 8 or 12 weeks post-MI. A period of 4 weeks after MI induction, the rats were treated with rapamycin (1.4 mg-kg-day) or vehicle for 4 weeks. Cardiac function was determined using echocardiography, the rats were subsequently euthanized and myocardial tissues were harvested for histological and biochemical analyses. In the cell culture experiments with H9c2 rat cardiomyocytes, apoptosis was induced using angiotensin II (100 nM; 24 h). Cardiomyocyte apoptosis and autophagy were assessed via measuring apoptosis- and autophagy-associated proteins. The activities of mTOR complex 1 (mTORC1) and mTORC2 were evaluated using the phosphorylation states of ribosomal S6 protein and Akt, respectively. The activity of the endoplasmic reticulum (ER) stress pathway was determined using the levels of GRP78, caspase-12, phospho-JNK and DDIT3. Echocardiographic and histological measurements indicated that rapamycin treatment improved cardiac function and inhibited cardiac remodeling at 8 weeks post-MI. Additionally, rapamycin prevented cardiomyocyte apoptosis and promoted autophagy at 8 weeks post-MI. Rapamycin treatment for 4 weeks inhibited the mTOR and ER stress pathways. Furthermore, rapamycin prevented angiotensin II-induced H9c2 cell apoptosis and promoted autophagy by inhibiting the mTORC1 and ER stress pathways. These results demonstrated that rapamycin reduced cardiomyocyte apoptosis and promoted cardiomyocyte autophagy, by regulating the crosstalk between the mTOR and ER stress pathways in chronic HF.

First-in-Man Study of a Cardiac Extracellular Matrix Hydrogel in Early and Late Myocardial Infarction Patients

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A first-in-man clinical trial was completed with VentriGel, an extracellular matrix hydrogel derived from decellularized porcine myocardium, in post–MI patients.

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Results from the trial support the safety and feasibility of transendocardial injection of VentriGel in post–MI patients with left ventricular dysfunction.

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Although the study was not designed to evaluate efficacy, there were suggestions of improvements including increases in 6-min walk test distance and decreases in New York Heart Association functional class across the entire cohort of patients.

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Improvements in left ventricular remodeling were mainly observed in patients who were treated >1-year post–MI as opposed to <1 year.

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Results from the trial warrant further evaluation in larger randomized, controlled clinical trials.

This study evaluated the safety and feasibility of transendocardial injections of VentriGel, a cardiac extracellular matrix hydrogel, in early and late post–myocardial infarction (MI) patients with left ventricular (LV) dysfunction. VentriGel was delivered in 15 patients with moderate LV dysfunction (25% ≤ LV ejection fraction ≤ 45%) who were between 60 days to 3 years post-MI and were revascularized by percutaneous coronary intervention. The primary endpoints were incidence of adverse events and abnormal clinical laboratory results. This first-in-man study established the safety and feasibility of delivering VentriGel in post-MI patients, thus warranting further evaluation in larger, randomized clinical trials.

Cathepsin K-deficiency impairs mouse cardiac function after myocardial infarction

BACKGROUND

Extracellular matrix metabolism and cardiac cell death participate centrally in myocardial infarction (MI). This study tested the roles of collagenolytic cathepsin K (CatK) in post-MI left ventricular remodeling.

METHODS AND RESULTS

Patients with acute MI had higher plasma CatK levels (20.49 ± 7.07 pmol/L, n = 26) than those in subjects with stable angina pectoris (8.34 ± 1.66 pmol/L, n = 28, P = .01) or those without coronary heart disease (6.63 ± 0.84 pmol/L, n = 93, P = .01). CatK protein expression increases in mouse hearts at 7 and 28 days post-MI. Immunofluorescent staining localized CatK expression in cardiomyocytes, endothelial cells, fibroblasts, macrophages, and CD4⁺ T cells in infarcted mouse hearts at 7 days post-MI. To probe the direct participation of CatK in MI, we produced experimental MI in CatK-deficient mice (Ctsk^-/-) and their wild-type (Ctsk^+/+) littermates. CatK-deficiency yielded worsened cardiac function at 7 and 28 days post-MI, compared to Ctsk^+/+ littermates (fractional shortening percentage: 5.01 ± 0.68 vs. 8.62 ± 1.04, P < .01, 7 days post-MI; 4.32 ± 0.52 vs. 7.60 ± 0.82, P < .01, 28 days post-MI). At 7 days post-MI, hearts from Ctsk^-/- mice contained less CatK-specific type-I collagen fragments (10.37 ± 1.91 vs. 4.60 ± 0.49 ng/mg tissue extract, P = .003) and more fibrosis (1.67 ± 0.93 vs. 0.69 ± 0.20 type-III collagen positive area percentage, P = .01; 14.25 ± 4.12 vs. 6.59 ± 0.79 α-smooth muscle actin-positive area percentage, P = .016; and 0.82 ± 0.06 vs. 0.31 ± 0.08 CD90-positive area percentage, P = .008) than those of Ctsk^+/+ mice. Immunostaining demonstrated that CatK-deficiency yielded elevated cardiac cell death but reduced cardiac cell proliferation. In vitro studies supported a role of CatK in cardiomyocyte survival.

CONCLUSION

Plasma CatK levels are increased in MI patients. Heart CatK expression is also elevated post-MI, but CatK-deficiency impairs post-MI cardiac function in mice by increasing myocardial fibrosis and cardiomyocyte death.

Update on the Protective Role of Regulatory T Cells in Myocardial Infarction: A Promising Therapy to Repair the Heart

Myocardial infarction (MI) remains one of the leading causes of heart failure development and death worldwide. To date, interventional and pharmacological therapies are effective in reducing the onset of heart failure and promoting survival. However, progressive maladaptive remodeling post-MI persists in a large fraction of patients resulting in poor prognosis. Immune cell responses and an inflammatory environment largely contribute to adverse cardiac remodeling post-MI. CD4FOXP3 regulatory T cells (Tregs) are known for their immunosuppressive capacity and have been successfully implemented in multiple preclinical studies of permanent and ischemia-reperfusion MI. In this review, we highlight the important cardioprotective role of Tregs at the cardiac tissue, cellular, and molecular level, as well as the most prominent pharmacological venues that could be used to exploit Tregs as a novel therapeutic intervention to lessen myocardial injury post-MI.

Role of MicroRNA-93 I in Pathogenesis of Left Ventricular Remodeling via Targeting Cyclin-D1

Background

The objective of this study was to identify the pathway responsible for ventricular remodeling.

Material/Methods

We collected remodeling myocardium tissue (n=18) and control myocardium tissue (n=22), and detected the expression of 4 miRNAs in these 2 groups using real-time PCR. We then searched the miRNA database online to find the candidate genes of miR-93. Real-time PCR and Western blot analysis were used to confirm the regulatory relationship.

Results

We found that only miR-93 was decreased in remodeling myocardium tissue, and validated CCND1 to be the direct target gene of miR-93, with the “seed sequence” located within the 3′-UTR of the target gene via luciferase reporter assay system. Furthermore, we established the negative regulatory relationship between miR-93 and CCND1 by determining the relative luciferase activity of cells transfected with wild-type or mutant 3′-UTR of CCND1. We also found that The CCND1 protein and mRNA expression level of HL-1 cells treated with 50 nM miR-93 mimics were apparently lower than the scramble control, and those of the cells treated with 100 nM miR-93 mimics and CCND1 siRNA (100 nM) were even lower than those in the 50 nM treatment group. Meanwhile, cells transfected with miR-93 mimics (50 nM) showed evidently downregulated viability when compared with the scramble controls, while cells transfected with (100 nM) and CCND1 siRNA (100nM) showed even lower viability.

Conclusions

We showed that CCND1 is a direct target of miR-93, and the dysregulation of the miR-93/CCND1 signaling pathway is responsible for the development of ventricular remodeling.

MicroRNA-98 negatively regulates myocardial infarction-induced apoptosis by down-regulating Fas and caspase-3

Acute myocardial infarction (MI) is the leading cause of sudden death worldwide. MicroRNAs (miRs) is a novel class of regulators of cardiovascular diseases such as MI. This study aimed to explore the role of miR-98 in MI and its underlying mechanisms. We found that miR-98 was downregulated both in infarcted and ischemic myocardium of MI mice as well as H₂O₂-treated neonatal rat ventricular myocytes (NRVCs). miR-98 overexpression remarkably increased cell viability and inhibited apoptosis of H₂O₂-treated NRVCs. Meanwhile, overexpression of miR-98 reversed H₂O₂-induced Bcl-2 downregulation and Bax elevation and significantly reduced JC-1 monomeric cells. Meanwhile, miR-98 overexpression attenuated the upregulation of Fas and caspase-3 in H₂O₂-treated cardiomyocytes at the mRNA and protein levels. Dual-luciferase reporter assay showed that miR-98 directly targeted to Fas 3'-UTR. Furthermore, MI mice injected with miR-98-agomir had a significant reduction of apoptotic cells, the serum LDH levels, myocardial caspase-3 activity, Fas and caspase-3 expression in heart tissues. Administration of miR-98-agomir also showed decreased infarct size and improved cardiac function. Collectively, miR-98 is downregulated in the MI heart and NRVCs in response to H₂O₂ stress, and miR-98 overexpression protects cardiomyocytes against apoptosis. Anti-apoptotic effects of miR-98 are associated with regulation of Fas/Caspase-3 apoptotic signal pathway.

ZYZ-772 Prevents Cardiomyocyte Injury by Suppressing Nox4-Derived ROS Production and Apoptosis

Nox-dependent signaling plays critical roles in the development of heart failure, cardiac hypertrophy, and myocardial infarction. NADPH oxidase 4 (Nox4) as a major source of oxidative stress in the heart offers a new therapeutic target in cardiovascular disease. In the present work, a novel flavonoid was isolated from Zanthoxylum bungeanum. Its structure was elucidated as Quercetin-3-O-(6′′-O-α-l-rhamnopyransoyl)-β-d-glucopyranoside-7-O-β-d-glucopyranoside (ZYZ-772) for the first time. ZYZ-772 exhibited significant cardio-protective property against CoCl₂ induced H9c2 cardiomyocyte cells injury. In CoCl₂ stimulated cardiomyocyte injury, ZYZ-772 inhibited expression of Nox4, and alleviated ROS overproduction. Importantly, ROS triggered MAPKs phosphorylation and P53 signaling mediated apoptosis were restored by ZYZ-772. Our findings present the first piece of evidence for the therapeutic properties of ZYZ-772 in preventing cardiomyocyte injury, which could be attributed to the suppression of Nox4/MAPKs/P53 axis. This will offer a novel therapeutic strategy for the treatment of cardiac ischemia disease.

trans-Polydatin protects the mouse heart against ischemia/reperfusion injury via inhibition of the renin–angiotensin system (RAS) and Rho kinase (ROCK) activity

Background: Recent studies highlighted the protective benefits of a Chinese herb extract frompolygonum cuspidatum,trans-polydatin, on cardiac disease.

Interleukin-37 and Dendritic Cells Treated With Interleukin-37 Plus Troponin I Ameliorate Cardiac Remodeling After Myocardial Infarction

BACKGROUND

Excessive immune-mediated inflammatory reactions play a deleterious role in postinfarction ventricular remodeling. Interleukin-37 (IL-37) emerges as an inhibitor of both innate and adaptive immunity. However, the exact role of IL-37 and IL-37 plus troponin I (TnI)-treated dendritic cells (DCs) in ventricular remodeling after myocardial infarction (MI) remains elusive.

METHODS AND RESULTS

MI was induced by permanent ligation of the left anterior descending artery. Our results showed that treatment with recombinant human IL-37 significantly ameliorated ventricular remodeling after MI, as demonstrated by decreased infarct size, better cardiac function, lower mortality, restricted inflammatory responses, decreased myocardial fibrosis, and inhibited cardiomyocyte apoptosis. In vitro, we examined the phenotype of IL-37 plus TnI-conditioned DCs of male C57BL/6 mice and their capacity to influence the number of regulatory T cells. Our results revealed that IL-37 plus TnI-conditioned DCs obtained the characteristics of tolerogenic DCs (tDCs) and expanded the number of regulatory T cells when co-cultured with splenic CD4+ T cells. Interestingly, we also found that adoptive transfer of these antigen-loaded tDCs markedly increased the number of regulatory T cells in the spleen, attenuated the infiltration of inflammatory cells in the infarct hearts, decreased myocardial fibrosis, and improved cardiac function.

CONCLUSIONS

Our results reveal a beneficial role of IL-37 or tDCs treated with IL-37 plus TnI in post-MI remodeling that is possibly mediated by reestablishing a tolerogenic immune response, indicating that IL-37 or adoptive transfer of IL-37 plus TnI-treated tDCs may be a novel therapeutic strategy for ventricular remodeling after MI.

Mitochondrial phosphatase PGAM5 regulates Keap1-mediated Bcl-xL degradation and controls cardiomyocyte apoptosis driven by myocardial ischemia/reperfusion injury

Phosphoglycerate mutase 5 (PGAM5) is a mitochondrial membrane protein that plays crucial roles in necroptosis and apoptosis. Though PGAM5 is known to be required for inducing intrinsic apoptosis through interacting with BCL2 associated X protein (Bax) and dynamin-related protein 1 (Drp1), the expression and role of PGAM5 in cardiomyocyte apoptosis driven by myocardial ischemia/reperfusion injury(MIRI) has not been studied. The present study shows that PGAM5 expression decreased after MIRI in vivo, positively correlated with Bcl-xL expression, negatively correlated with Kelch-ECH associating protein 1 (Keap1) expression. Furthermore, PGAM5 expression also decreased in cardiomyocytes after hypoxia/reoxygenation (H/R) treatment in vitro. PGAM5 silence promoted cardiomyocyte apoptosis and inhibited Bcl-xL expression, but with no effect on Keap1 expression. Accordingly, Keap1 overexpression further inhibited Bcl-xL and PGAM5 expression. Additionally, PGAM5-Bcl-xL-Keap1 interaction was identified, suggesting that PGAM5 might participate in the degradation of Bcl-xL mediated by Keap1. In summary, PGAM5 controls cardiomyocyte apoptosis induced by MIRI through regulating Keap1-mediated Bcl-xL degradation, which may supply a novel molecular target for acute myocardial infarction (AMI) therapy. Graphical abstract ᅟ.

Sex-related differences in intrinsic myocardial properties influence cardiac function in middle-aged rats during infarction-induced left ventricular remodeling

We previously determined that residual left ventricular (LV) myocardium of middle-aged rats had sex-related differences in regional tissue properties 4 weeks after a large myocardial infarction (MI). However, the impact of such differences on cardiac performance remained unclear. Therefore, our current study aimed to elucidate whether sex-related changes in MI-induced myocardial remodeling can influence cardiac function. A similar-sized MI was induced in 12-month-old male (M-MI) and female (F-MI) Sprague-Dawley rats by ligation of the left coronary artery. The cardiac function was monitored for 2 months after MI and then various LV parameters were compared between sexes. We found that although two sex groups had a similar pattern of MI-induced decline in LV function, F-MI rats had greater cardiac performance compared to M-MI rats, considering the higher values of EF (39.9 ± 3.4% vs. 26.7 ± 7.7%, P < 0.05), SW index (40.4 ± 2.1 mmHg • mL/kg vs. 20.2 ± 3.3 mmHg • mL/kg, P < 0.001), and CI (139.2 ± 7.9 mL/min/kg vs. 74.9 ± 14.7 mL/min/kg, P < 0.01). The poorer pumping capacity in M-MI hearts was associated with markedly reduced LV compliance and prolonged relaxation. On the tissue level, F-MI rats revealed a higher, than in M-MI rats, density of cardiac myocytes in the LV free wall (2383.8 ± 242.6 cells/mm(2) vs. 1785.7 ± 55.9 cells/mm(2), P < 0.05). The latter finding correlated with a lower density of apoptotic cardiac myocytes in residual LV myocardium of F-MI rats (0.18 ± 0.08 cells/mm(2) vs. 0.91 ± 0.30 cells/mm(2) in males, P < 0.01). Thus, our data suggested that F-MI rats had markedly attenuated decline in cardiac performance compared to males due to ability of female rats to better retain functionally favorable intrinsic myocardial properties.

Increased mortality and aggravation of heart failure in liver X receptor-α knockout mice after myocardial infarction

Liver X receptors, LXRα (NR1H3) and LXRβ (NR1H2), are best known as nuclear oxysterol receptors and physiological master regulators of lipid and cholesterol metabolism. LXRα play a protective role in acute myocardial ischemia/reperfusion (MI/R) injury, but its role in myocardial infarction (MI) is unknown. The present study was undertaken to determine the effect of LXRα knockout on survival and development of chronic heart failure after MI. Wild-type (WT) and LXRα(-/-) mice were subjected to MI followed by serial echocardiographic and histological assessments. Greater myocyte apoptosis and inflammation within the infarcted zones were found in LXRα(-/-) group at 3 days after MI. At 4 weeks post-MI, LXRα(-/-) MI murine hearts demonstrated significantly increased infarct size, reduced ejection fraction (LXRα(-/-) 29.4 % versus WT 34.4 %), aggravated left ventricular (LV) chamber dilation, enhanced fibrosis and reduced angiogenesis. In addition, LXRα(-/-) mice had increased mortality compared with WT mice. LXRα deficiency increases mortality, aggravates pathological injury and LV remodeling induced by MI. Drugs specifically targeting LXRα may be promising in the treatment of MI.

Left Ventricular Remodelling: A Problem in Search of Solutions

Cardiac remodelling (REM) is a generally unfavourable process that leads to left ventricular dilation in response to cardiac injury, predominantly acute myocardial infarction (AMI). REM occurs in around 30 % of anterior infarcts despite timely primary coronary intervention and the use of drugs, i.e. angiotensin-converting enzyme inhibitors (ACEI) or angiotensin II receptor blockers (ARBs), beta-blockers, aldosterone inhibitors and statins. In order to diagnose REM, many imaging modalities (echocardiography, cardiac magnetic resonance, scintigraphy) are employed together with an increasing number of serum biomarkers including microRNAs. The most widely used definition of REM is a >20 % increase in left ventricular end-diastolic volume (LVEDV). There is also evidence that regression of REM can occur, i.e. reverse REM. The latter is defined as a ≥10 % decrease in left ventricular end-systolic volume (LVESV) and confers a more favourable outcome. Many therapeutic agents may be used during primary intervention and over the long term; however, few have demonstrated significant benefits. Revascularisation, anti-REM surgery and, where indicated, cardiac resynchronisation therapy can be of benefit. Gene therapy by sarcoplasmic reticulum Ca²⁺ ATPase 2 (SERCA-2a) transfer has been investigated but data from the Calcium upregulation by percutaneous administration of gene therapy in patients with cardiac disease (CUPID 2) trial were disappointing. Progenitor cell therapy shows promise. In conclusion, therapy for REM remains inadequate.

Deficiency of ataxia telangiectasia mutated kinase delays inflammatory response in the heart following myocardial infarction

Background

Ataxia‐telangiectasia results from mutations in ataxia telangiectasia mutated kinase (ATM) gene. We recently reported that ATM deficiency attenuates left ventricular (LV) dysfunction and dilatation 7 days after myocardial infarction (MI) with increased apoptosis and fibrosis. Here we investigated the role of ATM in the induction of inflammatory response, and activation of survival signaling molecules in the heart acute post‐MI.

Methods and Results

LV structure, function, inflammatory response, and biochemical parameters were measured in wild‐type (WT) and ATM heterozygous knockout (hKO) mice 1 and 3 days post‐MI. ATM deficiency had no effect on infarct size. MI‐induced decline in heart function, as measured by changes in percent fractional shortening, ejection fraction and LV end systolic and diastolic volumes, was lower in hKO‐MI versus WT‐MI (n=10 to 12). The number of neutrophils and macrophages was significantly lower in the infarct LV region of hKO versus WT 1 day post‐MI. Fibrosis and expression of α‐smooth muscle actin (myofibroblast marker) were higher in hKO‐MI, while active TGF‐β1 levels were higher in the WT‐MI 3 days post‐MI. Myocyte cross‐sectional area was higher in hKO‐sham with no difference between the two MI groups. MMP‐9 protein levels were similarly increased in the infarct LV region of both MI groups. Apoptosis was significantly higher in the infarct LV region of hKO at both time points. Akt activation was lower, while Bax expression was higher in hKO‐MI infarct.

Conclusion

ATM deficiency results in decreased dilative remodeling and delays inflammatory response acute post‐MI. However, it associates with increased fibrosis and apoptosis.

NF45 inhibits cardiomyocyte apoptosis following myocardial ischemia-reperfusion injury

Cardiomyocyte apoptosis, which occurs during ischemia and reperfusion injury, can cause irreversible damage to cardiac function. There is accumulating evidence that nuclear factor 45 (NF45) and regulatory pathways are important in understanding reparative processes in the myocardium. NF45 is a multifunctional regulator of gene expression that participates in the regulation of DNA break repair. Recently, NF45 has been proved to be associated with tumor cell apoptosis in various human malignancies. However, the underlying mechanism of NF45 regulating myocardial ischemia-reperfusion (I/R) injury remains unclear. In this study, western blot showed that NF45 expression decreased after myocardial I/R in vivo. Double immunofluorescent staining revealed that NF45, located in the nucleus of cardiomyocyes, was correlated with cardiomyocyte apoptosis. Furthermore, NF45 expression decreased in H9c2 cells after hypoxia-reoxygenation (H/R) treatment in vitro, which was in line with the results in vivo. Overexpression of NF45 in H9c2 cells reduced cell apoptosis, as evidenced by increased Bcl-2 level, as well as decreased cleaved caspase-3, p53 and p21 expression. The expression of NF45 was reduced by LY294002 (a PI3K/Akt inhibitor), but not SB203580 (a p38 inhibitor), suggesting that NF45 prevented H/R-induced H9c2 cell apoptosis via PI3K/Akt pathway. Our data may supply a novel molecular target for acute myocardial infarction (AMI) therapy.

HSP70 inhibits stress-induced cardiomyocyte apoptosis by competitively binding to FAF1

Stress-induced cardiomyocyte apoptosis plays an important role in the pathogenesis of a variety of cardiovascular diseases. Our early studies showed that HSP70 effectively inhibited apoptosis, but the underlying mechanism remained unclear. Fas-associated factor 1 (FAF1) is a member of the Fas death-inducing signaling complex (Fas-DISC) that acts upstream of caspase-8. We investigated the interactions among FAF1, HSP70, and FAS in stressed cardiomyocytes to elucidate the protective mechanism of HSP70. FAS and caspase-3/8 activity was higher in cardiomyocytes undergoing stress-induced apoptosis in restraint-stressed rats compared with cardiomyocytes in non-stressed rats, which indicated that the Fas signaling pathway was activated after restraint stress. Geranylgeranylacetone (GGA) induced an increase in HSP70 expression, which reduced stress-induced apoptosis. Additionally, overexpression of HSP70 via transfection with the pEGFP-rHSP70 plasmid attenuated norepinephrine (NE)-induced apoptosis. FAF1 expression increased during stress-induced apoptosis, and overexpression of FAF1 exacerbated NE-induced apoptosis. We also found that HSP70 interacted with FAF1. Overexpression of HSP70 inhibited the binding of FAF1 to FAS in H9C2 cells, which indicated that HSP70 suppressed NE-induced apoptosis by competitively binding to FAF1. An N-terminal deletion mutant of HSP70 (HSP70-△N) was unable to interact with FAF1. After HSP70-△N was transfected into H9C2 cells, the cells were unable to attenuate the NE-induced increases in caspase-8 and apoptosis. These results indicate that the 1-120 sequence of HSP70 binds to FAF1, which alters the interactions between FAS and FAF1 and inhibits the activation of the Fas signaling pathway and apoptosis.

The different role of sex hormones on female cardiovascular physiology and function: not only oestrogens

Human response to different physiologic stimuli and cardiovascular (CV) adaptation to various pathologies seem to be gender specific. Sex-steroid hormones have been postulated as the major contributors towards these sex-related differences. This review will discuss current evidence on gender differences in CV function and remodelling, and will present the different role of the principal sex-steroid hormones on female heart. Starting from a review of sex hormones synthesis, receptors and CV signalling, we will summarize the current knowledge concerning the role of sex hormones on the regulation of our daily activities throughout the life, via the modulation of autonomic nervous system, excitation-contraction coupling pathway and ion channels activity. Many unresolved questions remain even if oestrogen effects on myocardial remodelling and function have been extensively studied. So this work will focus attention also on the controversial and complex relationship existing between androgens, progesterone and female heart.

The inflammasome in myocardial injury and cardiac remodeling

SIGNIFICANCE

An inflammatory response follows an injury of any nature, and while such a response is an attempt to promote healing, it may, itself, result in further injury.

RECENT ADVANCES

The inflammasome is a macromolecular structure recently recognized as a central mediator in the acute inflammatory response. The inflammasome senses the injury and it amplifies the response by leading to the release of powerful pro-inflammatory cytokines, interleukin-1β (IL-1β) and IL-18.

CRITICAL ISSUES

The activation of the inflammasome in the heart during ischemic and nonischemic injury represents an exaggerated response to sterile injury and promotes adverse cardiac remodeling and failure.

FUTURE DIRECTIONS

Pilot clinical trials have explored blockade of the inflammasome-derived IL-1β and have shown beneficial effects on cardiac function. Additional clinical studies testing this approach are warranted. Moreover, specific inflammasome inhibitors that are ready for clinical use are currently lacking.

Cardioprotective role of growth/differentiation factor 1 in post-infarction left ventricular remodelling and dysfunction

Growth/differentiation factor 1 (GDF1) is a secreted glycoprotein of the transforming growth factor-β (TGF-β) superfamily that mediates cell differentiation events during embryonic development. GDF1 is expressed in several tissues, including the heart. However, the functional role of GDF1 in myocardial infarction (MI)-induced cardiac remodelling and dysfunction is not known. Here, we performed gain-of-function and loss-of-function studies using cardiac-specific GDF1 transgenic (TG) and knockout (KO) mice to determine the role of GDF1 in the pathogenesis of functional and architectural cardiac remodelling after MI, which was induced by surgical left anterior descending coronary artery ligation. Our results demonstrate that overexpression of GDF1 in the heart causes a significant decrease in MI-derived mortality post-MI and leads to attenuated infarct size expansion, left ventricular (LV) dilatation, and cardiac dysfunction at 1 week and 4 weeks after MI injury. Compared with control animals, cardiomyocyte apoptosis, inflammation, hypertrophy, and interstitial fibrosis were all remarkably reduced in the GDF1-TG mice following MI. In contrast, GDF1 deficiency greatly exacerbated the pathological cardiac remodelling response after infarction. Further analysis of the in vitro and in vivo signalling events indicated that the beneficial role of GDF1 in MI-induced cardiac dysfunction and LV remodelling was associated with the inhibition of non-canonical (MEK-ERK1/2) and canonical (Smad) signalling cascades. Overall, our data reveal that GDF1 in the heart is a novel mediator that protects against the development of post-infarction cardiac remodelling via negative regulation of the MEK-ERK1/2 and Smad signalling pathways. Thus, GDF1 may serve as a valuable therapeutic target for the treatment of MI.

Co-expression of POU4F2/Brn-3b with p53 may be important for controlling expression of pro-apoptotic genes in cardiomyocytes following ischaemic/hypoxic insults

Cardiomyocyte death following ischaemic/hypoxic injury causes irreversible damage to cardiac function and contributes to chronic diseases such as heart failure. Understanding the mechanisms associated with myocyte loss under these conditions can help to identify strategies to minimise/abrogate such detrimental effects. The p53 protein can induce apoptosis or cell cycle arrest, but effects on cell fate depend on interactions with other regulators such as POU4F2/Brn-3b (Brn-3b), which co-operates with p53 to increase the expression of pro-apoptotic genes. In contrast, the related POU4F1/Brn-3a (Brn-3a) blocks p53-mediated apoptosis but co-operates with p53 to enhance cell cycle arrest. In this study, we showed that permanent coronary artery ligation in mouse hearts, which induced apoptotic markers, activated caspase-3 and -8 and necroptosis markers; RIP-1 and -3 also increased Brn-3b and Brn-3a expression. However, Brn-3a was only detected in uninjured myocardium but not at the site of injury, whereas Brn-3b showed generalised increase, including within the infarct zone. Conversely, p53 was detected in the infarct zone and in some cells adjacent to the site of injury but not in uninjured myocardium. Co-localisation studies showed Brn-3a co-expression with p53 in cardiomyocytes adjacent to the infarct zone, whereas Brn-3b was co-localised with p53 in the infarct zone only. Increased Brn-3b and p53 correlated with elevated expression of pro-apoptotic target genes, Bax, Noxa and PUMA, whereas cleaved caspase-3 confirmed the presence of apoptotic cells within this region of the injured heart. Similarly, simulated ischaemia/reoxygenation (sI/R) injury in neonatal rat ventricular cardiomyocytes (NRVM) and heart derived H9c2 myoblasts increased Brn-3b, p53 as well as apoptotic genes, and this was associated with enhanced apoptosis. Furthermore, targeted reduction of Brn-3b using shRNA caused reduction in pro-apoptotic Bax and Noxa proteins, even though p53 expression remained intact, suggesting that Brn-3b is important for controlling the fate of the myocardium in the injured heart.

Anti-inflammatory strategies for ventricular remodeling following ST-segment elevation acute myocardial infarction

Acute myocardial infarction (AMI) leads to molecular, structural, geometric, and functional changes in the heart in a process known as ventricular remodeling. An intense organized inflammatory response is triggered after myocardial ischemia and necrosis and involves all components of the innate immunity, affecting both cardiomyocytes and noncardiomyocyte cells. Inflammation is triggered by tissue injury; it mediates wound healing and scar formation and affects ventricular remodeling. Many therapeutic attempts aimed at reducing inflammation in AMI during the past 3 decades presented issues of impaired healing or increased risk of cardiac rupture or failed to show any additional benefit in addition to standard therapies. More recent strategies aimed at selectively blocking one of the key factors upstream rather than globally suppressing the response downstream have shown some promising results in pilot trials. We herein review the pathophysiological mechanisms of inflammation and ventricular remodeling after AMI and the results of clinical trials with anti-inflammatory strategies.

Prevention of remodeling in congestive heart failure due to myocardial infarction by blockade of the renin–angiotensin system

Ventricular remodeling subsequent to myocardial infarction (MI) is a complex process and is considered to be a major determinant of the clinical course of congestive heart failure (CHF). Emerging evidence suggests that activation of the renin-angiotensin system (RAS) plays an important role in post-MI ventricular remodeling; however, it is becoming clear that this is one of several neurohumoral systems that are activated in CHF. Blockade of RAS by angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor antagonists attenuates the ventricular dysfunction, but the effects of individual drugs in reducing the morbidity and mortality in CHF patients are variable. Furthermore, there is a difference of opinion as to the time of initiation of therapy with RAS blockers after the onset of MI. Since blockade of RAS partially improves cardiac function, it is suggested that a combination therapy involving RAS blockers (angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor antagonists) and agents that affect other neurohumoral systems may prove useful for improved treatment of CHF. Although activation of RAS has been shown to promote oxidative stress in experimental studies, the use of antioxidant therapy in CHF patients is controversial. Recent experimental studies have shown that ventricular remodeling in CHF is associated with remodeling of subcellular organelles such as sarcolemma, sarcoplasmic reticulum, myofibrils and extracellular matrix in terms of their molecular structure and composition. Since attenuation of remodeling in one and/or more subcellular organelles by different agents may prevent the progression of CHF, it is a challenge to develop specific drugs affecting molecular mechanisms associated with subcellular remodeling for the improved therapy of CHF.

Protective effects of hydrogen sulfide against chronic alcohol intake-induced left ventricular remodeling in rats

PURPOSE

To investigate the protective effects of hydrogen sulfide (H(2)S) against chronic alcohol intake-induced left ventricular remodeling and explore the potential mechanisms involved.

METHODS

Rats were randomly divided into 4 groups: alcohol group, NaHS group, alcohol + NaHS group, and control group. The echocardiographic and morphometric studies were performed to assess left ventricular remodeling. Oxidative stress was evaluated by detecting MDA, GSH-Px, Tot-SOD, CuZn-SOD and Mn-SOD in the supernatant. Cardiomyocyte apoptotic rate was determined by flow cytometry with Annexin V/PI staining. Western blotting was conducted to detect the expression of Bcl-2 family of apoptosis regulator proteins.

RESULTS

The echocardiographic and morphometric data indicated that H(2)S has protective effects against chronic alcohol intake-induced left ventricular remodeling. Our findings showed a significant increase in MDA level and decreases in GSH-Px, Tot-SOD, CuZn-SOD and Mn-SOD activities in the alcohol group compared to the control group, while in the alcohol + NaHS group, a significant decrease in MDA level and increases in GSH-Px, Tot-SOD, CuZn-SOD and Mn-SOD activities were found compared to the alcohol group. The apoptotic rate in the alcohol group was significantly higher than in the control group, whereas apoptotic rate in the alcohol + NaHS group was significantly lower than in the alcohol group. In addition, Bcl-2 and Bcl-xL expression was upregulated and Bax expression was downregulated in the alcohol + NaHS group compared to the alcohol group.

CONCLUSIONS

Our study demonstrates that H(2)S protects against chronic alcohol intake-induced left ventricular remodeling via attenuating oxidative stress and apoptosis.

Decreased autophagy contributes to myocardial dysfunction in rats subjected to nonlethal mechanical trauma

Autophagy is important in cells for removing damaged organelles, such as mitochondria. Insufficient autophagy plays a critical role in tissue injury and organ dysfunction under a variety of pathological conditions. However, the role of autophagy in nonlethal traumatic cardiac damage remains unclear. The aims of the present study were to investigate whether nonlethal mechanical trauma may result in the change of cardiomyocyte autophagy, and if so, to determine whether the changed myocardial autophagy may contribute to delayed cardiac dysfunction. Male adult rats were subjected to nonlethal traumatic injury, and cardiomyocyte autophagy, cardiac mitochondrial function, and cardiac function in isolated perfused hearts were detected. Direct mechanical traumatic injury was not observed in the heart within 24 h after trauma. However, cardiomyocyte autophagy gradually decreased and reached a minimal level 6 h after trauma. Cardiac mitochondrial dysfunction was observed by cardiac radionuclide imaging 6 h after trauma, and cardiac dysfunction was observed 24 h after trauma in the isolated perfused heart. These were reversed when autophagy was induced by administration of the autophagy inducer rapamycin 30 min before trauma. Our present study demonstrated for the first time that nonlethal traumatic injury caused decreased autophagy, and decreased autophagy may contribute to post-traumatic organ dysfunction. Though our study has some limitations, it strongly suggests that cardiac damage induced by nonlethal mechanical trauma can be detected by noninvasive radionuclide imaging, and induction of autophagy may be a novel strategy for reducing posttrauma multiple organ failure.

Effect of wenxin granule on ventricular remodeling and myocardial apoptosis in rats with myocardial infarction

Aim. To determine the effect of a Chinese herbal compound named Wenxin Granule on ventricular remodeling and myocardial apoptosis in rats with myocardial infarction (MI). Methods. Male Sprague-Dawley (SD) rats were randomly divided into four groups: the control group, the model group, the metoprolol group, and the Wenxin Granule group (WXKL group) with sample size (n) of 7 rats in each group. An MI model was established in all rats by occlusion of the left anterior descending coronary artery (the control group was without occlusion). Wenxin Granule (1.35 g/kg/day), metoprolol (12 mg/kg/day), and distilled water (5 mL/kg/day for the control and model groups) were administered orally for 4 weeks. Ultrasonic echocardiography was used to examine cardiac structural and functional parameters. Myocardial histopathological changes were observed using haematoxylin and eosin (H&E) dyeing. Myocardial apoptosis was detected by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) staining. Serum angiotensin II (Ang II) concentration was measured using the enzyme-linked immunosorbent assay (ELISA). Results. It was found that Wenxin Granule could partially reverse ventricular remodeling, improve heart function, alleviate the histopathological damage, inhibit myocardial apoptosis, and reduce Ang II concentration in rats with MI. Conclusions. The results of the current study suggest that Wenxin Granule may be a potential alternative and complementary medicine for the treatment of MI.