[HTD4010 attenuates myocardial injury in mice with septic cardiomyopathy by promoting autophagy via the AMPK/mTOR signaling pathway].

OBJECTIVE: To investigate the protective effects of HTD4010 against lipopolysaccharide (LPS)-induced septic cardiomyopathy (SCM) in mice and explore the mechanisms mediating its effect. METHODS: Forty-five male ICR mice were randomized equally into control group, LPS (10 mg/kg) group, and LPS+HTD4010 group (in which 2.5 mg/kg HTD4010 was injected subcutaneously at 1 h and 6 h after LPS injection). Cardiac function of the mice was evaluated by ultrasound, and pathological changes in the myocardial tissues were observed with HE staining. The levels of IL-6 and TNF-α in serum and myocardial tissues were detected using ELISA, and apoptosis of the cardiomyocytes was detected with TUNEL staining. The expression levels of the key proteins associated with apoptosis, autophagy and the AMPK/mTOR pathway in the myocardial tissues were detected using Western blotting. The ultrastructural changes of cardiac myocardial mitochondria was observed with transmission electron microscopy. RESULTS: LPS exposure caused severe myocardial damage in mice, characterized by myocardial fiber rupture, structural disorder, inflammatory cell infiltration, and mitochondrial damage. The LPS-treated mice exhibited significantly decreased cardiac LVEF and FS values, elevated IL-6 and TNF-αlevels in serum and myocardial tissue, and an increased myocardial cell apoptosis rate with enhanced expressions of Bax, p-62 and p-mTOR and lowered expressions of Bcl-2, LC3 II/I, Beclin-1 and p-AMPK (P < 0.05 or 0.01). Treatment of the septic mice with HTD4010 significantly alleviated myocardial damage, increased LVEF and FS values, reduced IL-6 and TNF-α levels in serum and myocardial tissue, decreased cardiomyocyte apoptosis, lowered myocardial expressions of Bax, p-62 and p-mTOR, and increased Bcl-2, LC3 II/I, Beclin-1 and p-AMPK expressions (P < 0.05 or 0.01). CONCLUSION: HTD4010 can attenuate myocardial injury in SCM mice possibly by promoting autophagy via modulating the AMPK/mTOR signaling pathway.

Rat Model of Isoproterenol-Induced Myocardial Injury.

Isoproterenol (ISO) administration produces significant biochemical and histological changes including oxidative stress, reactive oxygen species (ROS) overproduction, and inflammation that leads to aggravation of myocardial injury. Subcutaneous or intraperitoneal ISO injection into rats can replicate several features of human heart disease, making it a useful tool for comprehending the underlying mechanisms and evaluating potential therapeutic strategies. In the present chapter, we elaborate on how depending on the precise experimental goals and the intended level of severity, different dosages and regimens are employed to induce myocardial injury.

ptx3a+ fibroblast/epicardial cells provide a transient macrophage niche to promote heart regeneration.

Macrophages conduct critical roles in heart repair, but the niche required to nurture and anchor them is poorly studied. Here, we investigated the macrophage niche in the regenerating heart. We analyzed cell-cell interactions through published single-cell RNA sequencing datasets and identified a strong interaction between fibroblast/epicardial (Fb/Epi) cells and macrophages. We further visualized the association of macrophages with Fb/Epi cells and the blockage of macrophage response without Fb/Epi cells in the regenerating zebrafish heart. Moreover, we found that ptx3a+ epicardial cells associate with reparative macrophages, and their depletion resulted in fewer reparative macrophages. Further, we identified csf1a expression in ptx3a+ cells and determined that pharmacological inhibition of the csf1a pathway or csf1a knockout blocked the reparative macrophage response. Moreover, we found that genetic overexpression of csf1a enhanced the reparative macrophage response with or without heart injury. Altogether, our studies illuminate a cardiac Fb/Epi niche, which mediates a beneficial macrophage response after heart injury.

Arglabin: A mediator of inflammasome modulated and independent myocardial injury (PARA-AMI study).

BACKGROUND: Arglabin is a plant alkaloid (sesquiterpene lactone) that is used as an anticancer drug. It has potential anti-diabetic and anti-atherogenic effects. PURPOSE: Arglabin has drawn particular attention because of its therapeutic effects as an anti-inflammatory agent in multiple diseases. Since arglabin inhibits Epidermal Growth Factor Receptor (EGFR) tyrosine kinase, concerns for cardiotoxic effects are valid. The present study was designed to investigate the protective effects of arglabin on the myocardium. STUDY DESIGN: This study was designed to evaluate the effect of arglabin on the myocardium in an experimental model of myocardial necrosis in rats. Different doses of arglabin (2.5, 5, and 10 µg/kg) were investigated as pre-treatment for 21 days in the isoproterenol (ISO) model of myocardial necrosis groups and per se groups. METHODS: On the 22nd day, hemodynamic, histopathological, electron microscopy, oxidative stress markers, inflammatory mediators, apoptotic markers, inflammasome mediators, and Western blot analysis were performed to evaluate the effects of arglabin. RESULTS: Arglabin pre-treatment showed improvement in hemodynamic parameters and histopathological findings at low doses in isoproterenol-induced myocardial necrosis model of rats. Arglabin administration altered myocardial structure and modulated myocardial function via activation of NFκB/MAPK pathway that led to myocardial injury with an increase in dose. CONCLUSION: Arglabin imparted partial cardio-protection via an inflammasome-dependent pathway and mediated injury through the inflammasome-independent pathway.

Extracellular vesicle mediated targeting delivery of growth differentiation factor-15 improves myocardial repair by reprogramming macrophages post myocardial injury.

OBJECTIVE: Extracellular vesicles (EVs) have garnered considerable attention among researchers as candidates for natural drug delivery systems. This study aimed to investigate whether extracellular vesicle mediated targeting delivery of growth differentiation factor-15 (GDF15) improves myocardial repair by reprogramming macrophages post myocardial injury. METHODS: EVs were isolated from macrophages transfected with GDF15 (EXO-GDF15) and control macrophages (EXO-NC). In vitro and vivo experiments, we compared their reprogram ability of macrophages and regeneration activity. Furthermore, proteomic analysis were employed to determine the specific mechanism by which GDF15 repairs the myocardium. RESULTS: Compared with EXO-NC, EXO-GDF15 significantly regulated macrophage phenotypic shift, inhibited cardiomyocyte apoptosis, and enhanced endothelial cell angiogenesis. Moreover, EXO-GDF15 also significantly regulated macrophage heterogeneity and inflammatory cytokines, reduced fibrotic area, and enhanced cardiac function in infarcted rats. Proteomic analysis revealed a decrease in fatty acid-binding protein 4 (FABP4) protein expression following treatment with EXO-GDF15. Mechanistically, the reprogramming of macrophages by EXO-GDF15 is accomplished through the activation of Smad2/3 phosphorylation, which subsequently inhibits the production of FABP4. CONCLUSIONS: Extracellular vesicle mediated targeting delivery of growth differentiation factor-15 improves myocardial repair by reprogramming macrophages post myocardial injury via down-regulating the expression of FABP4. EXO-GDF15 may serve as a promising approach of immunotherapy.

Cardiac injury activates STING signaling via upregulating SIRT6 in macrophages after myocardial infarction.

AIMS: This work sought to investigate the mechanism underlying the STING signaling pathway during myocardial infarction (MI), and explore the involvement and the role of SIRT6 in the process. MAIN METHODS: Mice underwent the surgery of permanent left anterior descending (LAD) artery constriction. Primary cardiomyocytes (CMs) and fibroblasts were subjected to hypoxia to mimic MI in vitro. STING expression was assessed in the infarct heart, and the effect of STING inhibition on cardiac fibrosis was explored. This study also evaluated the regulatory effect of STING by SIRT6 in macrophages. KEY FINDINGS: STING protein was increased in the infarct heart tissue, highlighting its involvement in the post-MI inflammatory response. Hypoxia-induced death of CMs and fibroblasts contributed to the upregulation of STING in macrophages, establishing the involvement of STING in the intercellular signaling during MI. Inhibition of STING resulted in a significant reduction of cardiac fibrosis at day 14 after MI. Additionally, this study identified SIRT6 as a key regulator of STING via influencing its acetylation and ubiquitination in macrophages, providing novel insights into the posttranscriptional modification and expression of STING at the acute phase after myocardial infarction. SIGNIFICANCE: This work shows the key role of SIRT6/STING signaling in the pathogenesis of cardiac injury after MI, suggesting that targeting this regulatory pathway could be a promising strategy to attenuate cardiac fibrosis after MI.

Ivabradine Alleviates Experimental Autoimmune Myocarditis-Mediated Myocardial Injury.

Ivabradine (IVA) reduces heart rate by inhibiting hyperpolarization-activated cyclic nucleotide-gated channels (HCNs), which play a role in the promotion of pacemaker activity in cardiac sinoatrial node cells. HCNs are highly expressed in neural and myocardial tissues and are involved in the modulation of inflammatory neuropathic pain. However, whether IVA exerts any effect on myocardial inflammation in the pathogenesis of heart failure is unclear. We employed single-cell RNA sequencing (scRNA-seq) in porcine cardiac myosin-induced experimental autoimmune myocarditis rat model to determine the effects and mechanisms of IVA. Lewis rats (n = 32) were randomly divided into the normal, control, high-dose-IVA, and low-dose-IVA groups. Heart rate and blood pressure were measured on days 0 and 21, respectively. Echocardiography was performed on day 22, and inflammation of the myocardium was evaluated via histopathological examination. Western blot was employed to detect the expression of HCN1-4, MinK-related protein 1 (MiRP1), matrix metalloproteinase 2 (MMP-2), MMP-9, and transforming growth factor-ß (TGF-ß). Furthermore, enzyme-linked immunosorbent assay was performed to measure serum IL-1, IL-6, and TNF-α. The relative mRNA levels of collagen I, collagen III, and α-smooth muscle actin (α-SMA) were determined via qRT-PCR. We found that IVA reduced the total number of cells infiltrated into the myocardium, particularly in the subset of fibroblasts, endocardia, and monocytes. IVA administration ameliorated cardiac inflammation and reduced collagen production. Results of the echocardiography indicated that left ventricular internal diameter at end-systole LVIDs increased whereas left ventricular ejection fraction and left ventricular fractional shortening decreased in the control group. IVA improved cardiac performance. The expression of HCN4 and MiRP1 protein and the level of serum IL-1, IL-6, and TNF-α were decreased by IVA treatment. In conclusion, HCNs and the helper proteins were increased in the profile of myocardial inflammation. HCNs may be involved in the regulation of myocardial inflammation by inhibiting immune cell infiltration. Our findings can contribute to the development of IVA-based combination therapies for the future treatment of cardiac inflammation and heart failure.

Versican Promotes Cardiomyocyte Proliferation and Cardiac Repair.

BACKGROUND: The adult mammalian heart is incapable of regeneration, whereas a transient regenerative capacity is maintained in the neonatal heart, primarily through the proliferation of preexisting cardiomyocytes. Neonatal heart regeneration after myocardial injury is accompanied by an expansion of cardiac fibroblasts and compositional changes in the extracellular matrix. Whether and how these changes influence cardiomyocyte proliferation and heart regeneration remains to be investigated. METHODS: We used apical resection and myocardial infarction surgical models in neonatal and adult mice to investigate extracellular matrix components involved in heart regeneration after injury. Single-cell RNA sequencing and liquid chromatography-mass spectrometry analyses were used for versican identification. Cardiac fibroblast-specific Vcan deletion was achieved using the mouse strains Col1a2-2A-CreER and Vcanfl/fl. Molecular signaling pathways related to the effects of versican were assessed through Western blot, immunostaining, and quantitative reverse transcription polymerase chain reaction. Cardiac fibrosis and heart function were evaluated by Masson trichrome staining and echocardiography, respectively. RESULTS: Versican, a cardiac fibroblast-derived extracellular matrix component, was upregulated after neonatal myocardial injury and promoted cardiomyocyte proliferation. Conditional knockout of Vcan in cardiac fibroblasts decreased cardiomyocyte proliferation and impaired neonatal heart regeneration. In adult mice, intramyocardial injection of versican after myocardial infarction enhanced cardiomyocyte proliferation, reduced fibrosis, and improved cardiac function. Furthermore, versican augmented the proliferation of human induced pluripotent stem cell-derived cardiomyocytes. Mechanistically, versican activated integrin ß1 and downstream signaling molecules, including ERK1/2 and Akt, thereby promoting cardiomyocyte proliferation and cardiac repair. CONCLUSIONS: Our study identifies versican as a cardiac fibroblast-derived pro-proliferative proteoglycan and clarifies the role of versican in promoting adult cardiac repair. These findings highlight its potential as a therapeutic factor for ischemic heart diseases.

Bioinformatics and experimental studies jointly reveal that Sacubitril Valsartan improves myocardial oxidative stress and inflammation by regulating the MAPK signaling pathway to treat chemotherapy related cardiotoxicity.

BACKGROUND: CRC is a common but serious complication or sequela of tumor treatment, and new coping strategies are urgently needed. SV is a classic clinical cardiovascular protective drug, which has been widely used in the treatment of heart failure, hypertension and other diseases. It has good therapeutic effect in other cardiovascular diseases such as diabetes cardiomyopathy, ischemic cardiomyopathy and vascular disease, but it has not been proved by research that SV can prevent and treat CRC. METHOD: In this study, DOX was used to induce a rat CRC model and evaluate the therapeutic effect of SV on it. Subsequently, R software was applied to analyze the control group, SV group, and DOX group in databases GSE207283 and GSE22369, and to screen for common differentially expressed genes. Use the DAVID website for enrichment analysis and visualization. Use STRING website to analyze and visualize protein interaction networks of key genes. Finally, experimental verification was conducted on key genes. RESULT: Our research results show that SV has a protective effect on DOX induced myocardial injury by alleviating Weight loss, increasing Ejection fraction, and reducing the level of biomarkers of myocardial injury. Meanwhile, SV can effectively alleviate the above abnormalities. Bioinformatics and KEGG pathway analysis showed significant enrichment of metabolic and MAPK signaling pathways, suggesting that they may be the main regulatory pathway for SV treatment of CRC. Subsequent studies have also confirmed that SV can inhibit DOX induced myocardial injury through the MAPK signaling pathway, and alleviate DOX induced oxidative stress and inflammatory states. CONCLUSION: Our research indicates that SV is a potential drug for treating CRC and preliminarily elucidates its molecular mechanism of regulating the MAPK pathway to improve oxidative stress and inflammation.

Epicardial placement of human placental membrane protects from heart injury in a swine model of myocardial infarction.

Cardiac ischemic reperfusion injury (IRI) is paradoxically instigated by reestablishing blood-flow to ischemic myocardium typically from a myocardial infarction (MI). Although revascularization following MI remains the standard of care, effective strategies remain limited to prevent or attenuate IRI. We hypothesized that epicardial placement of human placental amnion/chorion (HPAC) grafts will protect against IRI. Using a clinically relevant model of IRI, swine were subjected to 45 min percutaneous ischemia followed with (MI + HPAC, n = 3) or without (MI only, n = 3) HPAC. Cardiac function was assessed by echocardiography, and regional punch biopsies were collected 14 days post-operatively. A deep phenotyping approach was implemented by using histological interrogation and incorporating global proteomics and transcriptomics in nonischemic, ischemic, and border zone biopsies. Our results established HPAC limited the extent of cardiac injury by 50% (11.0 ± 2.0% vs. 22.0 ± 3.0%, p = 0.039) and preserved ejection fraction in HPAC-treated swine (46.8 ± 2.7% vs. 35.8 ± 4.5%, p = 0.014). We present comprehensive transcriptome and proteome profiles of infarct (IZ), border (BZ), and remote (RZ) zone punch biopsies from swine myocardium during the proliferative cardiac repair phase 14 days post-MI. Both HPAC-treated and untreated tissues showed regional dynamic responses, whereas only HPAC-treated IZ revealed active immune and extracellular matrix remodeling. Decreased endoplasmic reticulum (ER)-dependent protein secretion and increased antiapoptotic and anti-inflammatory responses were measured in HPAC-treated biopsies. We provide quantitative evidence HPAC reduced cardiac injury from MI in a preclinical swine model, establishing a potential new therapeutic strategy for IRI. Minimizing the impact of MI remains a central clinical challenge. We present a new strategy to attenuate post-MI cardiac injury using HPAC in a swine model of IRI. Placement of HPAC membrane on the heart following MI minimizes ischemic damage, preserves cardiac function, and promotes anti-inflammatory signaling pathways.

[Cardiac progenitor cells-derived exosomes alleviate myocardial injury by regulating Treg cell differentiation through the mTOR pathway in mice with myocardial infarction].

OBJECTIVE: To investigate the effect of cardiac progenitor cells-derived exosomes (CPCs-Exo) on Treg differentiation in mice with myocardial infarction (MI). METHODS: Mouse models of MI established by ligation of the left anterior descending coronary artery (LAD) were treated with CPCs-Exos, and naive CD4+T cells were isolated from the spleen of the mice and divided into control group, CD4+T cell activation group (CD3+CD28), CPCs-Exos stimulation group (CD3+CD28+CPCs-Exos), mTOR activator group (CD3+CD28+CPCs-Exos+mTOR activator) and mTOR inhibitor group (CD3+CD28+CPCs-Exos+mTOR inhibitor). Western blotting was used to detect the expression levels of mTOR and p-mTOR in the treated cells. Flow cytometry was used to analyze the percentages of Treg and CD4+IL-10+T cells. The infarct size of the mice were measured with 2, 3, 5-triphenyltetrazole chloride (TTC) staining, and serum levels of LDH and CK-MB were detected using an automatic biochemical analyzer. RESULTS: Compared with the control group, the mouse models of MI showed significantly increased release of LDH (P<0.001) and CK-MB (P=0.0002) and increased percentages of Treg and CD4+IL-10+T cells. Treatment with CPC-Exos effectively reduced the MI area and lowered serum levels of LDH (P=0.003) and CK-MB (P=0.003) and the percentages of Tregs (P=0.001) and CD4+IL-10+T cells (P=0.004) in the MI mouse models. In the isolated CD4+T cells, CPCsExos treatment significantly up-regulated the percentages of Treg (P=0.01) and CD4+IL-10+ T cells (P=0.004) and increased the expression of mTOR (P=0.009) and p-mTOR (P=0.009), and these effects could be further enhanced by the mTOR activator but obviously attenuated by the mTOR inhibitor. CONCLUSION: CPCs-Exos promotes the differentiation of Treg in mice with MI by modulating the mTOR signaling pathway.

Pachymic Acid Prevents Hemorrhagic Shock-Induced Cardiac Injury by Suppressing M1 Macrophage Polarization and NF-[Formula: see text]B Signaling Pathway.

Hemorrhagic shock (HS) is the leading cause of death in trauma patients. Inflammation following HS can lead to cardiac damage. Pachymic acid (PA), a triterpenoid extracted from Poria cocos, has been found to possess various biological activities, including anti-inflammatory and anti-apoptotic properties. Our research aims to investigate the protective effects of PA against HS-induced heart damage and the underlying mechanisms involved. Male Sprague-Dawley rats were intraperitoneally injected with PA (7.5 or 15[Formula: see text]mg/kg) daily for three days. Subsequently, we created a rat model of HS by drawing blood through a catheter inserted into the femoral artery followed by resuscitation. The results revealed that HS led to abnormalities in hemodynamics, serum cardiac enzyme levels, and cardiac structure, as well as induced cardiac apoptosis. However, pretreatment with PA effectively alleviated these effects. PA-pretreatment also suppressed mRNA and protein levels of interleukin (IL)-1[Formula: see text], IL-6, and tumor necrosis factor [Formula: see text] (TNF-[Formula: see text]) in the heart tissues of HS rats. Additionally, PA-pretreatment reduced inflammatory cell infiltration and M1 macrophage polarization while exaggerating M2 polarization in HS rat hearts. The study observed a decreased proportion of the expression of of M1 macrophages (CD86[Formula: see text]) and their marker (iNOS), along with an increased proportion of the expression of M2 macrophages (CD206[Formula: see text]) and their marker (Arg-1). Notably, PA-pretreatment suppressed NF-[Formula: see text]B pathway activation via inhibiting NF-[Formula: see text]B p65 phosphorylation and its nuclear translocation. In conclusion, PA-pretreatment ameliorates HS-induced cardiac injury, potentially through its inhibition of the NF-[Formula: see text]B pathway. Therefore, PA treatment holds promise as a strategy for mitigating cardiac damage in HS.

ANNEXIN A2 FACILITATES NEOVASCULARIZATION TO PROTECT AGAINST MYOCARDIAL INFARCTION INJURY VIA INTERACTING WITH MACROPHAGE YAP AND ENDOTHELIAL INTEGRIN Β3.

ABSTRACT: Cardiac macrophages with different polarization phenotypes regulate ventricular remodeling and neovascularization after myocardial infarction (MI). Annexin A2 (ANXA2) promotes macrophage polarization to the repair phenotype and regulates neovascularization. However, whether ANXA2 plays any role in post-MI remodeling and its underlying mechanism remains obscure. In this study, we observed that expression levels of ANXA2 were dynamically altered in mouse hearts upon MI and peaked on the second day post-MI. Using adeno-associated virus vector-mediated overexpression or silencing of ANXA2 in the heart, we also found that elevation of ANXA2 in the infarcted myocardium significantly improved cardiac function, reduced cardiac fibrosis, and promoted peri-infarct angiogenesis, compared with controls. By contrast, reduction of cardiac ANXA2 exhibited opposite effects. Furthermore, using in vitro coculture system, we found that ANXA2-engineered macrophages promoted cardiac microvascular endothelial cell (CMEC) proliferation, migration, and neovascularization. Mechanistically, we identified that ANXA2 interacted with yes-associated protein (YAP) in macrophages and skewed them toward pro-angiogenic phenotype by inhibiting YAP activity. In addition, ANXA2 directly interacted with integrin ß3 in CMECs and enhanced their growth, migration, and tubule formation. Our results indicate that increased expression of ANXA2 could confer protection against MI-induced injury by promoting neovascularization in the infarcted area, partly through the inhibition of YAP in macrophages and activation of integrin ß3 in endothelial cells. Our study provides new therapeutic strategies for the treatment of MI injury.

Circulating GDF11 exacerbates myocardial injury in mice and associates with increased infarct size in humans.

AIMS: The heart rejuvenating effects of circulating growth differentiation factor 11 (GDF11), a transforming growth factor-ß superfamily member that shares 90% homology with myostatin (MSTN), remains controversial. Here, we aimed to probe the role of GDF11 in acute myocardial infarction (MI), a frequent cause of heart failure and premature death during ageing. METHODS AND RESULTS: In contrast to endogenous Mstn, myocardial Gdf11 declined during the course of ageing and was particularly reduced following ischaemia/reperfusion (I/R) injury, suggesting a therapeutic potential of GDF11 signalling in MI. Unexpectedly, boosting systemic Gdf11 by recombinant GDF11 delivery (0.1 mg/kg body weight over 30 days) prior to myocardial I/R augmented myocardial infarct size in C57BL/6 mice irrespective of their age, predominantly by accelerating pro-apoptotic signalling. While intrinsic cardioprotective signalling pathways remained unaffected by high circulating GDF11, targeted transcriptomics and immunomapping studies focusing on GDF11-associated downstream targets revealed attenuated Nkx2-5 expression confined to CD105-expressing cells, with pro-apoptotic activity, as assessed by caspase-3 levels, being particularly pronounced in adjacent cells, suggesting an indirect effect. By harnessing a highly specific and validated liquid chromatography-tandem mass spectrometry-based assay, we show that in prospectively recruited patients with MI circulating GDF11 but not MSTN levels incline with age. Moreover, GDF11 levels were particularly elevated in those at high risk for adverse outcomes following the acute event, with circulating GDF11 emerging as an independent predictor of myocardial infarct size, as estimated by standardized peak creatine kinase-MB levels. CONCLUSION: Our data challenge the initially reported heart rejuvenating effects of circulating GDF11 and suggest that high levels of systemic GDF11 exacerbate myocardial injury in mice and humans alike. Persistently high GDF11 levels during ageing may contribute to the age-dependent loss of cardioprotective mechanisms and thus poor outcomes of elderly patients following acute MI.

Bradykinin receptor participates in doxorubicin-induced cardiotoxicity by modulating iNOS signal pathway.

Doxorubicin (DOX), an effective and broad-spectrum anthracycline antibiotic, is widely used in the treatment of numerous malignancies. However, dose-dependent cardiotoxicity limits the clinical application of DOX, and the molecular mechanisms are still unknown. In this study, we used the BK receptor B1/B2 double-knockout (B1B2 -/- ) mice to observe the role of BK receptor in cardiotoxicity induced by DOX and the underlying mechanisms. DOX induced myocardial injury with increased serum levels of AST, CK, and LDH, upregulated tissue expression of bradykinin B1/B2 receptor, FABP4 and iNOS, and downregulated expression of eNOS. However, these altered releases of myocardial enzyme and the expression level of iNOS were significantly prevented in the B1B2-/- mice. We concluded that the activation of both B1 and B2 receptors of BK were involved in the DOX-induced acute myocardial injury, possibly mediated through iNOS signaling pathways.

Musings on intrinsic cardiomyocyte cell cycle activity and myocardial regeneration.

Although the myocardial renewal rate in the adult mammalian heart is quite low, recent studies have identified genetic variants which can impact the degree of cardiomyocyte cell cycle reentry. Here we use the compound interest law to model the level of regenerative growth over time in mice exhibiting different rates of cardiomyocyte cell cycle reentry following myocardial injury. The modeling suggests that the limited ability of S-phase adult cardiomyocytes to progress through cytokinesis, rather than the ability to reenter the cell cycle per se, is a major contributor to the low levels of intrinsic regenerative growth in the adult myocardium.

[Protective effect and mechanism of AKAP1 on myocardial injury induced by highland hypobaric hypoxia].

Objective: To investigate the protective effect and its possible mechanism of A-kinase anchored protein 1 (AKAP1) on the myocardial injury induced by highland hypobaric hypoxia. Methods: From January 2021 to May 2022, male C57BL/6 SPF grade mice were divided into wild type control (WT) group and highland hypobaric hypoxia (HH) group with 6 mice in each group. HH group simulated 6000 m altitude with low pressure oxygen chamber for 4 weeks to build the model. Primary myocardial cells of SD rats were divided into normoxia control group and hypoxia experimental group (n=3). Cell models were constructed in a three-gas hypoxia incubator with 1% oxygen concentration for 24 h. AKAP1 protein and mRNA expression in myocardial tissue and cells were detected by western blotting, immunohistochemistry and quantitative real-time polymerase chain reaction (qPCR). After myocardial point injection of the AKAP1 or the control adenovirus, the mice were divided into 3 groups (n=6) : WT group, highland hypobaric hypoxia overexpression control group (HH+Ad-Ctrl group) and highland hypobaric hypoxia overexpression experimental group (HH+Ad-AKAP1 group). The cardiac function of mice was detected by noninvasive M-type ultrasonic cardiomotive, myocardial fibrosis was detected by Masson and Sirius Red staining, and cardiomyocyte hypertrophy was detected by wheat germ agglutinin. After the expression of AKAP1 in primary cardiomyocytes was downregulated by siRNA and upregulated by adenovirus, the cells were divided into three groups (n=3) : normoxia control group, hypoxia interference control group (hypoxia+siCtrl group), hypoxia AKAP1 knockdown group (hypoxia+siAKAP1 group) ; normoxia control group, hypoxia overexpression control group (hypoxia+Ad-Ctrl group), hypoxia AKAP1 overexpression group (hypoxia+Ad-AKAP1 group). Apoptosis was detected by flow cytometry, AKAP1, apoptosis-related protein and mRNA expression levels were detected by western blotting and qPCR, mitochondrial membrane potential was detected by JC-1 staining, and mitochondrial reactive oxygen specie (ROS) level was detected by MitoSOX. Results: The expression of AKAP1 in cardiac muscle of HH group was lower than that in the WT group, and the expression of AKAP1 in hypoxia experimental group was lower than that in normoxia control group (P<0.01). Compared with WT group, the left ventricular ejection fraction and fraction shortening of left ventricle in HH+Ad-Ctrl group were decreased (P<0.01), myocardial fibrosis and hypertrophy were aggravated (P<0.01), and the expression of B-cell lymphoma-2 (BCL-2) was decreased, the expressions of BCL-2-associated X protein (BAX), Caspase 3 and Caspase 9 were increased (P<0.01). After AKAP1 overexpression, compared with HH+Ad-Ctrl group, the left ventricular ejection fraction and left ventricular fraction shortening were increased in HH+Ad-AKAP1 group (P<0.01), myocardial fibrosis and hypertrophy were reduced (P<0.01), and the expression of BCL-2 was increased, the expressions of BAX, Caspase 3 and Caspase 9 were decreased (P<0.01). Compared with normoxia control group, the expression of BCL-2 in hypoxia+siCtrl group was decreased, the expressions of BAX, Caspase 3, Caspase 9 were increased, the apoptosis level was increased (P<0.01), the mitochondrial membrane potential was decreased and the production of ROS was increased (P<0.01). After AKAP1 knockdown, compared with hypoxia+siCtrl group, the expression of BCL-2 in hypoxia+siAKAP1 group was decreased, the expressions of BAX, Caspase 3, Caspase 9 were increased, the apoptosis level was increased (P<0.01), mitochondrial membrane potential was decreased, and the production of ROS was increased (P<0.01). After AKAP1 overexpression, compared with hypoxia+Ad-Ctrl group, the expression of BCL-2 in hypoxia+Ad-AKAP1 group was increased, the expressions of BAX, Caspase 3 and Caspase 9 were decreased (P<0.05), the apoptosis level was decreased (P<0.01), and the mitochondrial membrane potential was enhanced, and the production of ROS was decreased (P<0.01) . Conclusion: The downregulation of AKAP1 in cardiomyocytes under highland hypobaric hypoxia may lead to the decrease of mitochondrial membrane potential and the increase of ROS generation, leading to the apoptosis of cardiomyocytes, and thus aggravating the myocardial injury at highland hypobaric hypoxia.

Dapagliflozin ameliorates sepsis-induced heart injury by inhibiting cardiomyocyte apoptosis and electrical remodeling through the PI3K/Akt pathway.

BACKGROUND: Sepsis-induced heart injury is one of the leading causes of circulation disorders worldwide. Dapagliflozin, a sodium-glucose cotransporter 2 inhibitor mainly used for controlling blood glucose, has been shown to exert a protective effect on cardiomyocytes. However, the protective effect of dapagliflozin against sepsis-induced cardiac injury and the underlying mechanism needs to be studied. AIM: This study aims to investigate the effect of dapagliflozin on sepsis-induced cardiomyopathy and the potential mechanisms involved. METHODS: The rat model of sepsis was constructed by intraperitoneal injection of lipopolysaccharide. Echocardiography and electrophysiological studies were performed to detect changes in cardiac function and electrical activity. Cardiac pathological alternation and cardiomyocyte apoptosis were measured by H&E staining, serological analysis, immunohistochemical, immunofluorescence, and TUNEL assays. Western blot and qRT-PCR were performed to elucidate the underlying mechanism of dapagliflozin. Additionally, corresponding experiments in H9c2 cells were performed to further validate the mechanisms in vitro. RESULTS: Dapagliflozin improved cardiac dysfunction and reduced the susceptibility to ventricular arrhythmias in sepsis rats by ameliorating cardiac inflammation, suppressing cardiomyocyte apoptosis, and alleviating ventricular electrical remodeling. The PI3K/Akt signaling pathway inhibitor inhibited the anti-apoptotic effect of dapagliflozin, indicating that the protective effect was related to the activation of the PI3K/Akt pathway. CONCLUSION: Dapagliflozin ameliorated sepsis-induced cardiac injury by suppressing electrical remodeling and cardiomyocyte apoptosis, which could be attributed to the PI3K/Akt pathway.

Dibutyl phthalate causes heart damage by disrupting Ca2+ transfer from endoplasmic reticulum to mitochondria and triggering subsequent pyroptosis.

Dibutyl phthalate (DBP) is a typical plasticizer and is widely used in industrial manufacturing. DBP has been reported to be cardiotoxic, manifested by oxidative stress and inflammatory damage. However, the potential mechanism of heart damage caused by DBP remains unclear. By in vivo and in vitro experiments, first, this study demonstrated that DBP induced endoplasmic reticulum (ER) stress, mitochondrial damage, and pyroptosis in cardiomyocytes; second, it was confirmed that the ER stress increased mitochondrial-associated ER membrane (MAM), which led to mitochondrial damage by abnormalizing Ca2+ transfer within MAMs; finally, it was confirmed that mitochondrial reactive oxygen species (mtROS) production was increased after mitochondrial damage, which activated NLRP3 inflammasome and pyroptosis in cardiomyocytes. In summary, ER stress is the initiation of DBP cardiotoxicity, which leads to mitochondrial damage by disrupting Ca2+ transfer from ER to mitochondria. Subsequently, released mtROS promotes the activation of NLRP3 inflammasome and pyroptosis, eventually leading to heart damage.

Cardiomyocyte Ploidy, Metabolic Reprogramming and Heart Repair.

The adult heart is made up of cardiomyocytes (CMs) that maintain pump function but are unable to divide and form new myocytes in response to myocardial injury. In contrast, the developmental cardiac tissue is made up of proliferative CMs that regenerate injured myocardium. In mammals, CMs during development are diploid and mononucleated. In response to cardiac maturation, CMs undergo polyploidization and binucleation associated with CM functional changes. The transition from mononucleation to binucleation coincides with unique metabolic changes and shift in energy generation. Recent studies provide evidence that metabolic reprogramming promotes CM cell cycle reentry and changes in ploidy and nucleation state in the heart that together enhances cardiac structure and function after injury. This review summarizes current literature regarding changes in CM ploidy and nucleation during development, maturation and in response to cardiac injury. Importantly, how metabolism affects CM fate transition between mononucleation and binucleation and its impact on cell cycle progression, proliferation and ability to regenerate the heart will be discussed.