Stromal Cell-SLIT3/Cardiomyocyte-ROBO1 Axis Regulates Pressure Overload-Induced Cardiac Hypertrophy.

BACKGROUND: Recently shown to regulate cardiac development, the secreted axon guidance molecule SLIT3 maintains its expression in the postnatal heart. Despite its known expression in the cardiovascular system after birth, SLIT3's relevance to cardiovascular function in the postnatal state remains unknown. As such, the objectives of this study were to determine the postnatal myocardial sources of SLIT3 and to evaluate its functional role in regulating the cardiac response to pressure overload stress. METHODS: We performed in vitro studies on cardiomyocytes and myocardial tissue samples from patients and performed in vivo investigation with SLIT3 and ROBO1 (roundabout homolog 1) mutant mice undergoing transverse aortic constriction to establish the role of SLIT3-ROBO1 in adverse cardiac remodeling. RESULTS: We first found that SLIT3 transcription was increased in myocardial tissue obtained from patients with congenital heart defects that caused ventricular pressure overload. Immunostaining of hearts from WT (wild-type) and reporter mice revealed that SLIT3 is secreted by cardiac stromal cells, namely fibroblasts and vascular mural cells, within the heart. Conditioned media from cardiac fibroblasts and vascular mural cells both stimulated cardiomyocyte hypertrophy in vitro, an effect that was partially inhibited by an anti-SLIT3 antibody. Also, the N-terminal, but not the C-terminal, fragment of SLIT3 and the forced overexpression of SLIT3 stimulated cardiomyocyte hypertrophy and the transcription of hypertrophy-related genes. We next determined that ROBO1 was the most highly expressed roundabout receptor in cardiomyocytes and that ROBO1 mediated SLIT3's hypertrophic effects in vitro. In vivo, Tcf21+ fibroblast and Tbx18+ vascular mural cell-specific knockout of SLIT3 in mice resulted in decreased left ventricular hypertrophy and cardiac fibrosis after transverse aortic constriction. Furthermore, α-MHC+ cardiomyocyte-specific deletion of ROBO1 also preserved left ventricular function and abrogated hypertrophy, but not fibrosis, after transverse aortic constriction. CONCLUSIONS: Collectively, these results indicate a novel role for the SLIT3-ROBO1-signaling axis in regulating postnatal cardiomyocyte hypertrophy induced by pressure overload.

A pilot study of S100A4, S100A8/A9, and S100A12 in dilated cardiomyopathy: novel biomarkers for diagnosis or prognosis?

AIMS: Circulating biomarkers can provide important information for the diagnosis and prognosis of dilated cardiomyopathy (DCM). We explored novel biomarkers for the diagnosis and prognosis of DCM to improve clinical decision-making. METHODS AND RESULTS: A total of 238 DCM patients and 65 control were consecutively enrolled at Zhongshan Hospital between January 2017 and January 2019. In the screening set, four DCM patients and four controls underwent measurements of serum proteomic analysis. Seventy-six differentially expressed circulating proteins were screened by data-independent acquisition proteomics, and three of these proteins (S100A4, S100A8/A9, and S100A12) were validated by multiple-reaction monitoring-mass spectrometry. In the validation set, subsequently, a total of 234 DCM patients and 61 control subjects were evaluated by enzyme-linked immunosorbent assay. Circulating S100A4, S100A8/A9, and S100A12 were significantly increased in DCM patients (P < 0.001). These three proteins were significant positively correlated with other parameters, such as Lg (NT-proBNP), IL-1ß, TGF-ß, CRP, left ventricular end-diastolic diameter, and left ventricular end-systolic diameter, whereas they were negatively correlated with left ventricular ejection fraction, respectively (P < 0.05). The receiver operator characteristic curve showed the combination of S100A4, S100A8/A9, and S100A12 [area under curve (AUC) 0.88, 95% confidence interval (CI) 0.84-0.93] was better than single S100A4 (AUC 0.74, 95% CI 0.68-0.81), S100A8/A9 (AUC 0.82, 95% CI 0.77-0.88), or S100A12 (AUC 0.80, 95% CI 0.72-0.88) in the diagnosis of DCM (P < 0.01). After a median follow-up period of 33.5 months, 110 patients (47.01%) experienced major adverse cardiac events (MACEs), including 46 who had cardiac deaths and 64 who had heart failure rehospitalizations. Kaplan-Meier analysis indicated that the DCM patients with ≥75th percentile level of S100A4 had a significantly higher incidence of MACEs than those with <75th percentile level of S100A4 (61.40% vs. 42.37%, P < 0.05). There were no significant differences of MACE rate among DCM patients with different concentrations of S100A8/A9 and S100A12 (P > 0.05). Cox proportional hazards regression analysis revealed that S100A4 [≥75th percentile vs. <75th percentile: hazard ratio (HR) 1.65; 95% CI 1.11-2.45] remained significant independent predictors for MACEs (P < 0.05); however, S100A8/A9 and S100A12 were not independent factors for predicting MACE (P ≥ 0.05). CONCLUSIONS: S100A4, S100A8/A9, and S100A12 may be additional diagnostic tools for human DCM recognition, and the combination of these three indicators helped to improve the accuracy of a single index to diagnose DCM. Additionally, S100A4 was identified as a significant predictor of prognosis in patients with DCM.

Causal associations between thyroid cancer and IgA nephropathy: a Mendelian randomization study.

BACKGROUND: The incidence of kidney disease caused by thyroid cancer is rising worldwide. Observational studies cannot recognize whether thyroid cancer is independently associated with kidney disease. We performed the Mendelian randomization (MR) approach to genetically investigate the causality of thyroid cancer on immunoglobulin A nephropathy (IgAN). METHODS AND RESULTS: We explored the causal effect of thyroid cancer on IgAN by MR analysis. Fifty-two genetic loci and single nucleotide polymorphisms were related to thyroid cancer. The primary approach in this MR analysis was the inverse variance weighted (IVW) method, and MR‒Egger was the secondary method. Weighted mode and penalized weighted median were used to analyze the sensitivity. In this study, the random-effect IVW models showed the causal impact of genetically predicted thyroid cancer across the IgAN risk (OR, 1.191; 95% CI, 1.131-1.253, P < 0.001). Similar results were also obtained in the weighted mode method (OR, 1.048; 95% CI, 0.980-1.120, P = 0.179) and penalized weighted median (OR, 1.185; 95% CI, 1.110-1.264, P < 0.001). However, the MR‒Egger method revealed that thyroid cancer decreased the risk of IgAN, but this difference was not significant (OR, 0.948; 95% CI, 0.855-1.051, P = 0.316). The leave-one-out sensitivity analysis did not reveal the driving influence of any individual SNP on the association between thyroid cancer and IgAN. CONCLUSION: The IVW model indicated a significant causality of thyroid cancer with IgAN. However, MR‒Egger had a point estimation in the opposite direction. According to the MR principle, the evidence of this study did not support a stable significant causal association between thyroid cancer and IgAN. The results still need to be confirmed by future studies.

Macrophage CAPN4 regulates CVB3-induced cardiac inflammation and injury by promoting NLRP3 inflammasome activation and phenotypic transformation to the inflammatory subtype.

Exploring the immune mechanism of coxsackievirus B3 (CVB3)-induced myocarditis may provide a promising therapeutic strategy. Here, we investigated the regulatory role of macrophage CAPN4 in the phenotypic transformation of macrophages and NOD-like receptor protein 3 (NLRP3) inflammasome activation. We found that CAPN4 was the most upregulated subtype of the calpain family in CVB3-infected bone marrow-derived macrophages (BMDMs) and Raw 264.7 cells after CVB3 infection and was upregulated in cardiac macrophages from CVB3-infected mice. Conditional knockout of CAPN4 (CAPN4flox/flox; LYZ2-Cre, CAPN4-cKO mice) ameliorated inflammation and myocardial injury and improved cardiac function and survival after CVB3 infection. Enrichment analysis revealed that macrophage differentiation and the interleukin signaling pathway were the most predominant biological processes in macrophages after CVB3 infection. We further found that CVB3 infection and the overexpression of CAPN4 promoted macrophage M1 polarization and NLRP3 inflammasome activation, while CAPN4 knockdown reversed these changes. Correspondingly, CAPN4-cKO alleviated CVB3-induced M1 macrophage transformation and NLRP3 expression and moderately increased M2 transformation in vivo. The culture supernatant of CAPN4-overexpressing or CVB3-infected macrophages impaired cardiac fibroblast function and viability. Moreover, macrophage CAPN4 could upregulate C/EBP-homologous protein (chop) expression, which increased proinflammatory cytokine release by activating the phosphorylation of transducer of activator of transcription 1 (STAT1) and 3 (STAT3). Overall, these results suggest that CAPN4 increases M1-type and inhibits M2-type macrophage polarization through the chop-STAT1/STAT3 signaling pathway to mediate CVB3-induced myocardial inflammation and injury. CAPN4 may be a novel target for viral myocarditis treatment.

Myeloid-specific deletion of Capns1 attenuates myocardial infarction injury via restoring mitochondrial function and inhibiting inflammasome activation.

BACKGROUND: Mitochondrial dysfunction of macrophage-mediated inflammatory response plays a key pathophysiological process in myocardial infarction (MI). Calpains are a well-known family of calcium-dependent cysteine proteases that regulate a variety of processes, including cell adhesion, proliferation, and migration, as well as mitochondrial function and inflammation. CAPNS1, the common regulatory subunit of calpain-1 and 2, is essential for the stabilization and activity of the catalytic subunit. Emerging studies suggest that calpains may serve as key mediators in mitochondria and NLRP3 inflammasome. This study investigated the role of myeloid cell calpains in MI. METHODS: MI models were constructed using myeloid-specific Capns1 knockout mice. Cardiac function, cardiac fibrosis, and inflammatory infiltration were investigated. In vitro, bone marrow-derived macrophages (BMDMs) were isolated from mice. Mitochondrial function and NLRP3 activation were assessed in BMDMs under LPS stimulation. ATP5A1 knockdown and Capns1 knock-out mice were subjected to MI to investigate their roles in MI injury. RESULTS: Ablation of calpain activities by Capns1 deletion improved the cardiac function, reduced infarct size, and alleviated cardiac fibrosis in mice subjected to MI. Mechanistically, Capns1 knockout reduced the cleavage of ATP5A1 and restored the mitochondria function thus inhibiting the inflammasome activation. ATP5A1 knockdown antagonized the protective effect of Capns1 mKO and aggravated MI injury. CONCLUSION: This study demonstrated that Capns1 depletion in macrophages mitigates MI injury via maintaining mitochondrial homeostasis and inactivating the NLRP3 inflammasome signaling pathway. This study may offer novel insights into MI injury treatment.

Trimetazidine Affects Mitochondrial Calcium Uniporter Expression to Restore Ischemic Heart Function via Reactive Oxygen Species/NFκB Pathway Inhibition.

ABSTRACT: Studies have demonstrated the roles of trimetazidine beyond being an antianginal agent in ischemic heart disease (IHD) treatment associated with mechanisms of calcium regulation. Our recent studies revealed that mitochondrial calcium uniporter (MCU, the pore-forming unit responsible for mitochondrial calcium entrance) inhibition provided cardioprotective effects for failing hearts. Because trimetazidine and MCU are associated with calcium homeostasis, we hypothesized that trimetazidine may affect MCU to restore the failing heart function. In the present study, we tested this hypothesis in the context of cardiac ischemia in vivo and in vitro. The IHD model was established in male C57BL/6 mice followed by trimetazidine administration intraperitoneally at 20 mg/kg q.o.d for 8 weeks. In vitro studies were performed in a hypoxia model using primary rat neonate cardiomyocytes. The mice survival outcomes and heart function, pathohistologic, and biological changes were analyzed. The results demonstrated that trimetazidine treatment resulted in longer life spans and heart function improvement accompanied by restoration of mitochondrial calcium levels and increase in ATP production via MCU down-regulation. Studies in vitro further showed that trimetazidine treatment and MCU inhibition decreased reactive oxygen species (ROS) production, inhibited the NFκB pathway, and protected the cardiomyocytes from hypoxic injury, and vice versa. Thus, the present study unveils a unique mechanism in which trimetazidine is involved in ameliorating the ischemic failing heart via MCU down-regulation and the following mitochondrial calcium homeostasis restoration, ROS reduction, and cardiomyocyte protection through NFκB pathway inhibition. This mechanism provides a novel explanation for the treatment effects of trimetazidine on IHD.

GAS-STING signaling plays an essential pathogenetic role in Doxorubicin-Induced Cardiotoxicity.

BACKGROUND: The severe unfavorable effects of doxorubicin on the heart restrict its clinical usage. Numerous investigations document that cyclic GMP-AMP synthase (cGAS) activator of interferon genes (STING) cascade influences inflammation along with the immune response in a variety of diseases. The pathophysiological function of the cGAS-STING cascade in Doxorubicin-induced cardiomyopathy (DIC) is, nevertheless, unknown. METHODS: In vivo, cardiotoxicity was triggered by a single dose of intra-peritoneal inoculation of doxorubicin (15 mg/kg) in wild-type C57BL/6J mice and STING knockdown animals. Adeno-associated virus 9 (AAV9) was utilized to silence STING. qPCR along with Western blotting were adopted to assess alterations in the cGAS/STING cascade. To assess cardiac function, we employed echocardiography coupled with histology, as well as molecular phenotyping. In vitro, HL-1 cardiomyocytes were introduced as test models. RESULTS: In wild type mice, doxorubicin stimulation significantly activated the cGAS/STING pathway. STING silencing increased rate of survival along with heart function in mice, as well as diminished myocardial inflammatory cytokines along with apoptosis. These observations were also confirmed by utilizing siRNA of STING in vitro studies. CONCLUSION: This research premise established that STING inhibition could alleviate Dox-triggered cardiotoxicity in mice. As a result, preventing DIC by repressing STING in cardiomyocytes might be a possible treatment approach.

Experimental diabetes exacerbates autophagic flux impairment during myocardial I/R injury through calpain-mediated cleavage of Atg5/LAMP2.

To explore the role of autophagic flux in the increased susceptibility of the experimental diabetic heart to ischaemia-reperfusion (I/R) injury, we established STZ-induced diabetic mice and performed I/R. In vitro, neonatal mouse cardiomyocytes were subjected to high glucose and hypoxia/reoxygenation challenge to mimic diabetic I/R injury. We found that experimental diabetes aggravated I/R-induced injury than compared with nondiabetic mice. Autophagic flux was impaired in I/R hearts, and the impairment was exacerbated in diabetic mice subjected to I/R with defective autophagosome formation and clearance. Calpains, calcium-dependent thiol proteases, were upregulated and highly activated after I/R of diabetes, while calpain inhibition attenuated cardiac function and cell death and partially restored autophagic flux. The expression levels of Atg5 and LAMP2, two crucial autophagy-related proteins, were significantly degraded in diabetic I/R hearts, alterations that were associated with calpain activation and could be reversed by calpain inhibition. Co-overexpression of Atg5 and LAMP2 reduced myocardial injury and normalized autophagic flux. In conclusion, experimental diabetes exacerbates autophagic flux impairment of cardiomyocytes under I/R stress, resulting in worse I/R-induced injury. Calpain activation and cleavage of Atg5 and LAMP2 at least partially account for the deterioration of autophagic flux impairment.

Mitochondrial calpain-1 activates NLRP3 inflammasome by cleaving ATP5A1 and inducing mitochondrial ROS in CVB3-induced myocarditis.

Treatment options for myocarditis are currently limited. Inhibition of calpains has been shown to prevent Coxsackievirus B3 (CVB3)-induced cardiac injuries, but the underlying mechanism of action of calpains has not been elucidated. We investigated whether NOD-, LRR-, and pyrin domain-containing 3 (NLRP3) inflammasome participated in CVB3-induced myocarditis, and investigated the effects of calpain-1 on CVB3-induced cardiac injury. NLRP3 inflammasome was activated in CVB3-infected hearts, evidenced by elevated protein levels of NLRP3, N-terminal domain of Gasdermin D, and cleaved caspase-1, and the increased co-localization of NLRP3 and apoptosis-associated speck-like protein. The intraperitoneal administration of MCC950, a selective inhibitor of the NLRP3 inflammasome, led to decreased levels of serum creatine kinase-MB, cardiac troponin I, lactate dehydrogenase, interleukin-18, interleukin-1ß, prevention of the infiltration of inflammatory cells, and improvement of cardiac function under CVB3 infection. Transgenic mice overexpressing the endogenous calpain inhibitor calpastatin (Tg-CAST mice) exhibited not only decreased apoptosis, inflammation, fibrosis, and enhanced cardiac function but also inhibition of NLRP3 inflammasome and pyroptosis. The selective inhibition of calpain-1 using PD151746 protected cardiomyocytes in vitro from CVB3 infection by downregulating NLRP3 inflammasome and, thus, preserved cell viability. Mechanistically, we showed that mitochondrial dysfunction preceded inflammatory response after CVB3 treatment and elimination of mitochondrial reactive oxygen species (ROS) using mitochondria-targeted antioxidants (mito-TEMPO) recapitalized the phenotype observed in Tg-CAST mice. Furthermore, the promotion or inhibition of calpain-1 activation in vitro regulated the mitochondrial respiration chain. Mito-TEMPO reversed calpain-1-mediated NLRP3 inflammation activation and cell death. We also found that mitochondrial calpain-1, which was increased after CVB3 stimulation, activated the NLRP3 inflammasome and resulted in cell death. Furthermore, ATP synthase-α (ATP5A1) was revealed to be the cleaving target of calpain-1 after CVB3 treatment. Downregulating ATP5A1 using ATP5A1-small interfering RNA impaired mitochondrial function, decreased cell viability, and induced NLRP3 inflammasome activation. In conclusion, CVB3 infection induced calpain-1 accumulation in mitochondria, and led to subsequent ATP5A1 cleavage, mitochondrial ROS overproduction, and impaired mitochondrial function, eventually causing NLRP3 inflammasome activation and inducing pyroptosis. Therefore, our findings established the role of calpain in viral myocarditis and unveiled its underlying mechanism of its action. Calpain appears as a promising target for the treatment of viral myocarditis.

Translocation of gasdermin D induced mitochondrial injury and mitophagy mediated quality control in lipopolysaccharide related cardiomyocyte injury.

BACKGROUNDS: Inflammation underlies the mechanism of different kinds of heart disease. Cytoplasmic membrane localized N-terminal fragment of gasdermin-D (GSDMD-N) could induce inflammatory injury to cardiomyocyte. However, effects and dynamic changes of GSDMD during the process of lipopolysaccharide (LPS) related inflammatory stress induced cardiomyocyte injury are barely elucidated to date. In this study, LPS related cardiomyocyte injury was investigated based on potential interaction of GSDMD-N induced mitochondrial injury and mitophagy mediated mitochondria quality control. METHODS: HL-1 cardiomyocytes were treated with LPS and Nigericin to induce inflammatory stress. The dual-fluorescence-labelled GSDMD expressed HL-1 cardiomyocytes were constructed to study the translocation of GSDMD. The mitochondrial membrane potential (MMP) was measured by JC-1 staining. Mitophagy and autophagic flux were recorded by transmission electron microscopy and fluorescent image. RESULTS: GSDMD-N showed a time-dependent pattern of translocation from mitochondria to cytoplasmic membrane under LPS and Nigericin induced inflammatory stress in HL-1 cardiomyocytes. GSDMD-N preferred to localize to mitochondria to permeablize its membrane and dissipate the MMP. This effect couldn't be reversed by cyclosporine-A (mPTP inhibitor), indicating GSDMD-N pores as alternative mechanism underlying MMP regulation, in addition to mitochondrial permeability transition pore (mPTP). Moreover, the combination between GSDMD-N and autophagy related Microtubule Associated Protein 1 Light Chain 3 Beta (LC3B) was verified by co-immunoprecipitation. Besides, mitophagy alleviating GSDMD-N induced mitochondrial injury was proved by pre-treatment of autophagy antagonist or agonist in GSDMD-knock out or GSDMD-overexpression cells. A time-dependent pattern of GSDMD translocation and mitochondrial GSDMD targeted mitophagy were verified. CONCLUSION: Herein, our study confirmed a crosstalk between GSDMD-N induced mitochondrial injury and mitophagy mediated mitochondria quality control during LPS related inflammation induced cardiomyocyte injury, which potentially facilitating the development of therapeutic target to myocardial inflammatory disease. Our findings support pharmaceutical intervention on enhancing autophagy or inhibiting GSDMD as potential target for inflammatory heart disease treatment.

Role of the Gut Microbiota in Glucose Metabolism During Heart Failure.

Background: Blood glucose disorders are prevalent in heart failure, while the influence of the gut microbiota on this process remains unclear. Here, we used heart failure model mice and fecal microbiota transplantation (FMT) mice to evaluate the effect of the gut microbiota on the regulation of blood glucose during heart failure. Methods: Thoracic aortic constriction (TAC) surgery was performed in a heart failure model, while an antibiotic cocktail was used to eliminate the microbiota to establish a germ-free (GF) model. Blood glucose, insulin, and glucagon levels were measured, and an intraperitoneal glucose tolerance test (IPGTT) was performed. 16S rRNA sequencing and metabolomics were used to evaluate the changes in gut microbiota structure and metabolism induced by TAC. Another group of FMT mice was established to observe the effect of the gut microbiota on host metabolism. Results: After microbiota clearance, the glucagon concentration, the homeostasis model assessment for insulin resistance (HOMA-IR), and the area under the curve (AUC) of the IPGTT were decreased significantly in the TAC germ-free (TAC-GF) group in the third month as compared to the other groups. 16S rRNA sequencing indicated that TAC surgery affected the gut microbiota structure, and fecal metabolomics suggested that noradrenaline and adrenaline levels were higher in the TAC group than in the sham group. The FMT mice transplanted with the feces of the TAC (FMT-TAC) mice displayed a higher AUC of IPGTT, accompanied by a higher glucagon level, insulin level, and HOMA-IR than those of the mice in the other groups. The serum metabolomics of the FMT-TAC group showed that noradrenaline levels were significantly higher than those of the FMT-sham group. Conclusion: The gut microbiota and its metabolism were altered during heart failure, which increased blood glucose and glucagon in the host.

Myeloid cell-specific deletion of Capns1 prevents macrophage polarization toward the M1 phenotype and reduces interstitial lung disease in the bleomycin model of systemic sclerosis.

BACKGROUND: Calpains are a family of calcium-dependent thiol proteases that participate in a wide variety of biological activities. In our recent study, calpain is increased in the sera of scleroderma or systemic sclerosis (SSc). However, the role of calpain in interstitial lung disease (ILD) has not been reported. ILD is a severe complication of SSc, which is the leading cause of death in SSc. The pathogenesis of SSc-related ILD remains incompletely understood. This study investigated the role of myeloid cell calpain in SSc-related ILD. METHODS: A novel line of mice with myeloid cell-specific deletion of Capns1 (Capns1-ko) was created. SSc-related ILD was induced in Capns1-ko mice and their wild-type littermates by injection 0.l mL of bleomycin (0.4 mg/mL) for 4 weeks. In a separate experiment, a pharmacological inhibitor of calpain PD150606 (Biomol, USA, 3 mg/kg/day, i.p.) daily for 30 days was given to mice after bleomycin injection on daily basis. At the end of the experiment, the animals were killed, skin and lung tissues were collected for the following analysis. Inflammation, fibrosis and calpain activity and cytokines were assessed by histological examinations and ELISA, and immunohistochemical analyses, western blot analysis and Flow cytometry analysis. RESULTS: Calpain activities increased in SSc-mouse lungs. Both deletion of Capns1 and administration of PD150606 attenuated dermal sclerosis as evidenced by a reduction of skin thickness and reduced interstitial fibrosis and inflammation in bleomycin model of SSc mice. These effects of reduced calpain expression or activity were associated with prevention of macrophage polarization toward M1 phenotype and consequent reduced production of pro-inflammatory cytokines including TNF-α, IL-12 and IL-23 in lung tissues of Capns1-ko mice with bleomycin model of SSc. Furthermore, inhibition of calpain correlated with an increase in the protein levels of PI3K and phosphorylated AKT1 in lung tissues of the bleomycin model of SSc mice. CONCLUSIONS: This study for the first time demonstrates that the role of myeloid cell calpain may be promotion of macrophage M1 polarization and pro-inflammatory responses related PI3K/AKT1 signaling. Thus, myeloid cell calpain may be a potential therapeutic target for bleomycin model of SSc-related ILD.

Risk factors of pacing dependence and cardiac dysfunction in patients with permanent pacemaker implantation.

AIMS: Right ventricular pacing (RVP) dependence could impair left ventricular ejection fraction (LVEF). This study aimed to illuminate the relationship between RVP proportion and LVEF, as well as disclosing independent predictors of RVP dependence. METHODS AND RESULTS: Patients indicated for permanent pacemaker implantation were included (2016-2020). The ventricular pacing lead was placed in right ventricular apex or septum. Pacing mode programming followed universal standard. Electrocardiographic, echocardiographic, and serological parameters were collected. RVP dependence was defined according to its influence on LVEF. This study was of case-control design. Included patients were matched by potentially confounding factors through propensity score matching. A total of 1183 patients were included, and the mean duration of follow-up was 24 months. Percentage of RVP < 80% hardly influenced LVEF; however, LVEF tended to decrease with higher RVP proportion. High degree/complete atrioventricular block (AVB) [odds ratio (OR) = 5.71, 95% confidence interval (CI): 3.66-8.85], atrial fibrillation (AF) (OR = 2.04, 95% CI: 1.47-2.82), percutaneous coronary intervention (PCI) (OR = 2.89, 95% CI: 1.24-6.76), maximum heart rate (HRmax ) < 110 b.p.m. (OR = 2.74, 95% CI: 1.58-4.76), QRS duration > 120 ms (OR = 2.46, 95% CI: 1.42-4.27), QTc interval > 470 ms (OR = 2.01, 95% CI: 1.33-3.05), and pulmonary artery systolic pressure (PASP) > 40 mmHg (OR = 1.93, 95% CI: 1.46-2.56) were proved to predict RVP dependence. CONCLUSIONS: High RVP percentage (>80%) indicating RVP dependence significantly correlates with poor prognosis of cardiac function. High degree/complete AVB, AF, ischaemic aetiology, PCI history, HRmax  < 110 b.p.m., QRS duration > 120 ms, QTc interval > 470 ms, and PASP > 40 mmHg were verified as independent risk factors of RVP dependence.

Inhibition of calpain reduces cell apoptosis by suppressing mitochondrial fission in acute viral myocarditis.

Cardiomyocyte apoptosis is critical for the development of viral myocarditis (VMC), which is one of the leading causes of cardiac sudden death in young adults. Our previous studies have demonstrated that elevated calpain activity is involved in the pathogenesis of VMC. This study aimed to further explore the underlying mechanisms. Neonatal rat cardiomyocytes (NRCMs) and transgenic mice overexpressing calpastatin were infected with coxsackievirus B3 (CVB3) to establish a VMC model. Apoptosis was detected with flow cytometry, TUNEL staining, and western blotting. Cardiac function was measured using echocardiography. Mitochondrial function was measured using ATP assays, JC-1, and MitoSOX. Mitochondrial morphology was observed using MitoTracker staining and transmission electron microscopy. Colocalization of dynamin-related protein 1 (Drp-1) in mitochondria was examined using immunofluorescence. Phosphorylation levels of Drp-1 at Ser637 site were determined using western blotting analysis. We found that CVB3 infection impaired mitochondrial function as evidenced by increased mitochondrial ROS production, decreased ATP production and mitochondrial membrane potential, induced myocardial apoptosis and damage, and decreased myocardial function. These effects of CVB3 infection were attenuated by inhibition of calpain both by PD150606 treatment and calpastatin overexpression. Furthermore, CVB3-induced mitochondrial dysfunction was associated with the accumulation of Drp-1 in the outer membrane of mitochondria and subsequent increase in mitochondrial fission. Mechanistically, calpain cleaved and activated calcineurin A, which dephosphorylated Drp-1 at Ser637 site and promoted its accumulation in the mitochondria, leading to mitochondrial fission and dysfunction. In summary, calpain inhibition attenuated CVB3-induced myocarditis by reducing mitochondrial fission, thereby inhibiting cardiomyocyte apoptosis. Calpain is activated by CVB3 infection. Activated calpain cleaves calcineurin A and converts it to active form which could dephosphorylate Drp-1 at Ser637 site. Then, the active Drp-1 translocates from the cytoplasm to mitochondria and triggers excessive mitochondrial fission. Eventually, the balance of mitochondrial dynamics is broken, and apoptosis occurs.

Oxidized LDL but not angiotensin II induces cardiomyocyte hypertrophic responses through the interaction between LOX-1 and AT1 receptors.

It is well known that lectin-like oxidized low-density lipoprotein (ox-LDL) and its receptor LOX-1, angiotensin II (AngII) and its type 1 receptor (AT1-R) play an important role in the development of cardiac hypertrophy. However, the molecular mechanism is not clear. In this study, we found that ox-LDL-induced cardiac hypertrophy was suppressed by inhibition of LOX-1 or AT1-R but not by AngII inhibition. These results suggest that the receptors LOX-1 and AT1-R, rather than AngII, play a key role in the role of ox-LDL. The same results were obtained in mice lacking endogenous AngII and their isolated cardiomyocytes. Ox-LDL but not AngII could induce the binding of LOX-1 and AT1-R; inhibition of LOX-1 or AT1-R but not AngII could abolish the binding of these two receptors. Overexpression of wild type LOX-1 with AT1-R enhanced ox-LDL-induced binding of two receptors and phosphorylation of ERKs, however, transfection of LOX-1 dominant negative mutant (lys266ala / lys267ala) or an AT1-R mutant (glu257ala) not only reduced the binding of two receptors but also inhibited the ERKs phosphorylation. Phosphorylation of ERKs induced by ox-LDL in LOX-1 and AT1-R-overexpression cells was abrogated by an inhibitor of Gq protein rather than Jak2, Rac1 or RhoA. Genetically, an AT1-R mutant lacking Gq protein coupling ability inhibited ox-LDL induced ERKs phosphorylation. Furthermore, through bimolecular fluorescence complementation analysis, we confirmed that ox-LDL rather than AngII stimulation induced the direct binding of LOX-1 and AT1-R. We conclude that direct binding of LOX-1 and AT1-R and the activation of downstream Gq protein are important mechanisms of ox-LDL-induced cardiomyocyte hypertrophy.

Inhibition of Calpain Alleviates Apoptosis in Coxsackievirus B3-induced Acute Virus Myocarditis Through Suppressing Endoplasmic Reticulum Stress.

Virus myocarditis (VMC) is a common cardiovascular disease and a major cause of sudden death in young adults. However, there is still a lack of effective treatments. Our previous studies found that calpain activation was involved in VMC pathogenesis. This study aims to explore the underlying mechanisms further. Neonatal rat cardiomyocytes (NRCMs) and transgenic mice overexpressing calpastatin (Tg-CAST), the endogenous calpain inhibitor, were used to establish VMC model. Hematoxylin and eosin and Masson staining revealed inflammatory cell infiltration and fibrosis. An ELISA array detected myocardial injury. Cardiac function was measured using echocardiography. CVB3 replication was assessed by capsid protein VP1. Apoptosis was measured by TUNEL staining, flow cytometry, and western blot. The endoplasmic reticulum (ER) stress-related proteins were detected by western blot. Our data showed that CVB3 infection resulted in cardiac injury, as evidenced by increased inflammatory responses and fibrosis, which induced myocardial apoptosis. Inhibiting calpain, both by PD150606 and calpastatin overexpression, could attenuate these effects. Furthermore, ER stress was activated during CVB3 infection. However, calpain inhibition could downregulate some ER stress-associated protein levels such as GRP78, pancreatic ER kinase-like ER kinase (PERK), and inositol-requiring enzyme-1α (IRE-1α), and ER stress-related apoptotic factors, during CVB3 infection. In conclusion, calpain inhibition attenuated CVB3-induced myocarditis by suppressing ER stress, thereby inhibiting cardiomyocyte apoptosis.

Cardiomyocyte-restricted high-mobility group box 1 (HMGB1) deletion leads to small heart and glycolipid metabolic disorder through GR/PGC-1α signalling.

Cardiac growth and remodelling are key biological processes influencing the physiological performance of the heart, and a previous study showed a critical role for intracellular HMGB1 in vitro. However, the in vivo study, which used conditional Hmgb1 ablation, did not show a significant effect on cellular or organic function. We have demonstrated the extracellular effect of HMGB1 as a pro-inflammatory molecule on cardiac remodelling. In this study, we found that HMGB1 deletion by cTnT-Cre in mouse hearts altered glucocorticoid receptor (GR) function and glycolipid metabolism, eventually leading to growth retardation, small heart and heart failure. The subcellular morphology did not show a significant change caused by HMGB1 knockout. The heart showed significant elevation of glycolysis, free fatty acid deposition and related enzyme changes. Transcriptomic analysis revealed a list of differentially expressed genes that coincide with glucocorticoid receptor function in neonatal mice and a significant increase in inflammatory genes in adult mice. Cardiac HMGB1 knockout led to a series of changes in PGC-1α, UCP3 and GyK, which were the cause of metabolic changes and further impacted cardiac function. Ckmm-Cre Hmgb1fl/fl mice did not show a specific phenotype, which was consistent with the reported negative result of cardiomyocyte-specific Hmgb1 deletion via MHC-Cre. We concluded that HMGB1 plays essential roles in maintaining normal cardiac growth, and different phenotype from cardiac-specific HMGB1-deficient mice may be caused by the cross with mice of different Cre strains.

NLRP3 inflammasome, an immune-inflammatory target in pathogenesis and treatment of cardiovascular diseases.

Inflammation is an important process involved in several cardiovascular diseases (CVDs), and nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is a vital player in innate immunity and inflammation. In this review, we aim to provide a comprehensive summary of the current knowledge on the role and involvement of NLRP3 inflammasome in the pathogenesis and treatment of CVDs. NLRP3 inflammasome functions as a molecular platform, and triggers the activation of caspase-1 and cleavage of pro-IL-1ß, pro-IL-18, and gasdermin D (GSDMD). Cleaved NT-GSDMD forms pores in the cell membrane and initiates pyroptosis, inducing cell death and release of many intracellular pro-inflammatory molecules. NLRP3 inflammasome activation is triggered via inter-related pathways downstream of K+ efflux, lysosomal disruption, and mitochondrial dysfunction. In addition, the Golgi apparatus and noncoding RNAs are gradually being recognized to play important roles in NLRP3 inflammasome activation. Many investigations have revealed the association between NLRP3 inflammasome and CVDs, including atherosclerosis, ischemia/reperfusion (I/R) injury and heart failure induced by pressure overload or cardiomyopathy. Some existing medications, including orthodox and natural medicines, used for CVD treatment have been newly discovered to act via NLRP3 inflammasome. In addition, NLRP3 inflammasome pathway components such as NLRP3, caspase-1, and IL-1ß may be considered as novel therapeutic targets for CVDs. Thus, NLRP3 inflammasome is a key molecule involved in the pathogenesis of CVDs, and further research focused on development of NLRP3 inflammasome-based targeted therapies for CVDs and the clinical evaluation of these therapies is essential.

Inhibition of calpain alleviates coxsackievirus B3-induced myocarditis through suppressing the canonical NLRP3 inflammasome/caspase-1-mediated and noncanonical caspase-11-mediated pyroptosis pathways.

This study aimed to verify the effects of calpain on coxsackievirus B3 (CVB3)-induced myocarditis and to further explore the underlying mechanisms. Transgenic mice overexpressing calpastatin, the endogenous calpain inhibitor, were introduced in the present study. The murine model of viral myocarditis (VMC) was established by intraperitoneal injection of CVB3 into transgenic and wild-type mice. Myocardial injury was measured by H&E staining and ELISA for cTnI. CVB3 replication was assessed via capsid protein VP1 detection and virus titration. The fibrotic factors collagen and TGF-ß1 were evaluated by Masson staining and real-time PCR analysis, respectively. Moreover, the levels of NLRP3, AIM2, ASC, cleaved caspase-1, cleaved caspase-11 and the pyroptosis indicators GSDMD p30, IL-1ß and HMGB1 were determined by real-time PCR, western blot or immunohistochemical analysis. In addition, peripheral IL-1ß and HMGB1 were evaluated by ELISA. We observed that CVB3-infected transgenic mice had lower pathological scores, peripheral cTnI levels, viral loads and expression levels of collagen and TGF-ß1 in the heart than CVB3-infected wild-type mice. Furthermore, we found decreased levels of NLRP3, ASC, cleaved caspase-1 and cleaved caspase-11 in the hearts of CVB3-infected transgenic mice. However, after CVB3 infection, the levels of AIM2 in transgenic mice and wild-type mice did not differ significantly. Additionally, calpastatin overexpression significantly reduced the levels of GSDMD p30, IL-1ß and HMGB1 in the myocardium as well as peripheral IL-1ß and HMGB1. Taken together, these findings indicate that calpain inhibition attenuates CVB3-induced myocarditis by suppressing the canonical NLRP3 inflammasome/caspase-1-mediated and noncanonical caspase-11-mediated pyroptosis pathways.

Left ventricular response in the transition from hypertrophy to failure recapitulates distinct roles of Akt, ß-arrestin-2, and CaMKII in mice with aortic regurgitation.

BACKGROUND: Although aortic regurgitation (AR) is a clinically important condition that is becoming increasingly common, few relevant murine models and mechanistic studies exist for this condition. In this study, we attempted to delineate the pathological and molecular changes and address the roles of some potentially relevant molecules in an animal model of surgically induced AR. METHODS: AR was induced by puncturing the aortic valve leaflets in C57BL/6J mice under echocardiographic guidance. RESULTS: As early as 1 week following AR, the left ventricles (LV) displayed marked impairments in diastolic function and coronary flow reserve (CFR), as well as cardiac hypertrophy and chamber dilatation at both end-systole and end-diastole. LV free wall thickening and cardiomyocyte hypertrophy in LV were observed 2 weeks following of AR while a decline in ejection fraction was not seen until after 4 weeks. Nppa (natriuretic peptide A) and Nppb (natriuretic peptide B) increased over time, in conjunction with prominent Akt activation as well as slight CaMKII (Ca2+/calmodulin-dependent protein kinase II) activation and biphasic changes in ß-arrestin-2 expression. Treatment of AR mice with Akt inhibition exacerbated the eccentric hypertrophy, while neither inhibition of CaMKII nor ß-arrestin-2 overexpression influenced the response to AR. CONCLUSIONS: Our structural, functional, molecular and therapeutic analyses reveal that Akt, but not CaMKII or ß-arrestin-2, plays a regulatory role in the development of LV remodeling after AR in Mice. These results may shed important light on therapeutic targets for volume overloaded cardiomyopathy.