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.

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.

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.

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.

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.

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.

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.

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.

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.

Left bundle branch area pacing is superior to right ventricular septum pacing concerning depolarization-repolarization reserve.

INTRODUCTION: Left bundle branch area pacing (LBBAP) has recently been reported to be a new physiological pacing strategy with clinical feasibility and safety. The present study aims to investigate depolarization-repolarization measures including QT interval, QT dispersion (QTD), and Tpeak-end interval (Tp Te ) in this novel LBBAP strategy. METHODS AND RESULTS: A total of 131 pacing-indicated patients were prospectively enrolled and randomized to the LBBAP group (n = 66) and right ventricular septum pacing (RVSP) group (n = 65). LBBAP was successfully achieved in 61 subjects with stable lead performance and comparable complications (ie, pocket hematoma, lead perforation, and dislodgement) compared with RVSP. Of the 61 patients with successful LBBAP, the mean LV peak activation time was 67.89 ± 6.80 ms, with the LBB potential mapped in 46 cases (75.4%). Electrocardiogram (ECG) indices were compared between these two groups before and after implantation. As a result, LBBAP yielded a narrower paced QRS duration (121.49 ± 9.87 ms vs 145.62 ± 8.89 ms; P < .001), shorter QT interval (434.16 ± 32.70 ms vs 462.66 ± 32.04 ms; P < .001), and QTc interval (472.44 ± 33.30 ms vs 499.65 ± 31.35 ms; P < .001), lower QTD (40.10 ± 8.68 ms vs 46.11 ± 10.85 ms; P = .001), and QTc D (43.57 ± 8.78 ms vs 49.86 ± 11.98 ms; P = .001), and shorter Tp Te (96.59 ± 10.76 ms vs 103.77 ± 10.16 ms; P < .001) than RVSP. However, Tp Te /QT ratio did not differ between these two groups (0.223 ± 0.026 vs 0.225 ± 0.022; P = .733). Furthermore, LBBAP displayed less increased QRS duration, QTc interval, QTD, QTc D, and a more shortened QT interval compared with RVSP (all P < .05). CONCLUSION: LBBAP proves to be a feasible and safe pacing procedure with better depolarization-repolarization reserve, which may predict lower risk of ventricular arrhythmia and sudden cardiac death.

The mechanical effects of CRT promoting autophagy via mitochondrial calcium uniporter down-regulation and mitochondrial dynamics alteration.

The mechanism of cardiac resynchronization therapy (CRT) remains unclear. In this study, mitochondria calcium uniporter (MCU), dynamin-related protein-1 (DNM1L/Drp1) and their relationship with autophagy in heart failure (HF) and CRT are investigated. Thirteen male beagle's dogs were divided into three groups (sham, HF, CRT). Animals received left bundle branch (LBB) ablation followed by either 8-week rapid atrial pacing or 4-week rapid atrial pacing and 4-week biventricular pacing. Cardiac function was evaluated by echocardiography. Differentially expressed genes (DEGs) were detected by microarray analysis. General morphological changes, mitochondrial ultrastructure, autophagosomes and mitophagosomes were investigated. The cardiomyocyte stretching was adopted to imitate the mechanical effect of CRT. Cells were divided into three groups (control, angiotensin-II and angiotensin-II + stretching). MCU, DNM1L/Drp1 and autophagy markers were detected by western blots or immunofluorescence. In the present study, CRT could correct cardiac dysfunction, decrease cardiomyocyte's size, alleviate cardiac fibrosis, promote the formation of autophagosome and mitigate mitochondrial injury. CRT significantly influenced gene expression profile, especially down-regulating MCU and up-regulating DNM1L/Drp1. Cell stretching reversed the angiotensin-II induced changes of MCU and DNM1L/Drp1 and partly restored autophagy. CRT's mechanical effects down-regulated MCU, up-regulated DNM1L/Drp1 and subsequently enhanced autophagy. Besides, the mechanical stretching prevented the angiotensin-II-induced cellular enlargement.

FTY720 alleviates coxsackievirus B3-induced myocarditis and inhibits viral replication through regulating sphingosine 1-phosphate receptors and AKT/caspase-3 pathways.

Fingolimod (FTY720) after phosphorylation, as the ligand of sphingosine 1-phosphate receptors (S1PRs), plays an important role in cell proliferation and differentiation. In this article, FTY720 in the treatment of coxsackievirus B3 (CVB3)-induced viral myocarditis was closely related to apoptosis and AKT/caspase-3 apoptotic pathways. We found that CVB3 inhibited myocardial apoptosis at the early stage with upregulating p-AKT level and downregulating activated caspase-3 level for replication of virus progeny, whereas it promoted apoptosis at a late stage with downregulating p-AKT and upregulating activated caspase-3 for releasing the newly synthesized virus to spread. Interestingly, FTY720 could reverse this trend; it promoted apoptosis at an early stage and inhibited apoptosis at the late stage in vivo and vitro, which proved the antiviral effect. We also found that S1PR1, S1PR4, and S1PR5, rather than S1PR2 and S1PR3, were regulated by FTY720 in this process. The results confirmed that FTY720 alleviates CVB3-induced myocarditis and inhibits viral replication through regulating S1PRs and AKT/caspase-3 pathways with a bidirectional regulation of apoptosis.

Increased calpain-1 in mitochondria induces dilated heart failure in mice: role of mitochondrial superoxide anion.

We and others have reported that calpain-1 was increased in myocardial mitochondria from various animal models of heart disease. This study investigated whether constitutive up-regulation of calpain-1 restricted to mitochondria induced myocardial injury and heart failure and, if so, whether these phenotypes could be rescued by selective inhibition of mitochondrial superoxide production. Transgenic mice with human CAPN1 up-regulation restricted to mitochondria in cardiomyocytes (Tg-mtCapn1/tTA) were generated and characterized with low and high over-expression of transgenic human CAPN1 restricted to mitochondria, respectively. Transgenic up-regulation of mitochondria-targeted CAPN1 dose-dependently induced cardiac cell death, adverse myocardial remodeling, heart failure, and early death in mice, the changes of which were associated with mitochondrial dysfunction and mitochondrial superoxide generation. Importantly, a daily injection of mitochondria-targeted superoxide dismutase mimetics mito-TEMPO for 1 month starting from age 2 months attenuated cardiac cell death, adverse myocardial remodeling and heart failure, and reduced mortality in Tg-mtCapn1/tTA mice. In contrast, administration of TEMPO did not achieve similar cardiac protection in transgenic mice. Furthermore, transgenic up-regulation of mitochondria-targeted CAPN1 induced a reduction of ATP5A1 protein and ATP synthase activity in hearts. In cultured cardiomyocytes, increased calpain-1 in mitochondria promoted mitochondrial permeability transition pore (mPTP) opening and induced cell death, which were prevented by over-expression of ATP5A1, mito-TEMPO or cyclosporin A, an inhibitor of mPTP opening. In conclusion, this study has provided direct evidence demonstrating that increased mitochondrial calpain-1 is an important mechanism contributing to myocardial injury and heart failure by disrupting ATP synthase, and promoting mitochondrial superoxide generation and mPTP opening.

LAP+ Treg is a better biomarker than total Treg in viral myocarditis.

Latency associated peptide (LAP) is a protein expressed on the membrane of some regulatory T cells (Treg). LAP+ Treg have a greater immunomodulatory effect than that of their negative counterparts. In this study, we presented the data on the proportion of LAP+ Treg out of CD4+ cells in mice with viral myocarditis, which we believed was more sensitive and specific than that of the ratio of total Treg in CD4+ cells. Comparing with the previously recognized total Treg, LAP+ Treg was a better biomarker on myocardial inflammation.

microRNA-34a aggravates coxsackievirus B3-induced apoptosis of cardiomyocytes through the SIRT1-p53 pathway.

Viral myocarditis is inflammation of the myocardium mainly caused by a viral infection, and coxsackievirus B3 (CVB3) infection is one of the most common. It is well known that cardiomyocyte apoptosis is involved in the pathogenesis of viral myocarditis. microRNAs (miRNAs, miRs) are endogenous noncoding oligoribonucleotides involved in various pathological conditions, and miR-34a is one of the miRNAs causing apoptosis. Whether miR-34a participates in cardiomyocyte apoptosis during CVB3 infection and the underlying mechanisms is still unclear. In this in vitro study, we found that miR-34a expression increased in cardiomyocytes after CVB3 infection. Furthermore, we found that CVB3 infection augmented histone deacetylase 1 (HDAC1) and Bax expression while inhibiting sirtuin 1 (SIRT1) and Bcl-2 expression, along with the acetylated p53 (Ac-p53) upregulation in cardiomyocytes. The above-mentioned phenomenon was reversed by a miR-34a inhibitor after CVB3 infection. In addition, the Ac-p53 amount increased in CVB3-infected cardiomyocytes, and SRT1720 and trichostatin A (TSA) pretreatment decreased Ac-p53 levels. After pifithrin-α pretreatment of CVB3-infected cardiomyocytes, the protein expression level of HDAC1 decreased while that of SIRT1 increased. Moreover, miR-34a expression and CVB3-induced apoptosis of cardiomyocytes were attenuated by pretreatment with SRT1720, TSA, or pifithrin-α, accompanied with Bax downregulation and Bcl-2 upregulation. In summary, these data indicate that miR-34a induces cardiomyocyte apoptosis by downregulating SIRT1, and the activation of the SIRT1-p53 pathway contributes to CVB3-induced apoptosis of cardiomyocytes. Thus, miR-34a might serve as a potential therapeutic target because it promotes cardiomyocyte apoptosis through the SIRT1-p53 signaling pathway.

Electrocardiographic parameters effectively predict ventricular tachycardia/fibrillation in acute phase and abnormal cardiac function in chronic phase of ST-segment elevation myocardial infarction.

BACKGROUND: Abnormal cardiac repolarization is closely associated with ventricular tachycardia/ventricular fibrillation (VT/VF). Myocardial ischemia and infarction aggravate cardiac repolarization dispersion, and VT/VF could be lethal in the early stage of ST-segment elevation myocardial infarction (STEMI). Unfortunately, VT/VF cannot be effectively predicted in current clinical practice. The present study aimed to assess electrocardiographic parameters of the sinus rhythmic complex in relation to cardiac repolarization, e.g., QT interval and T-peak to T-end interval (TpTe), to independently predict VT/VF in acute STEMI. Additionally, we hypothesized that QT and TpTe of PVC would be also valuable to predict VT/VF in STEMI. METHODS AND RESULTS: A total of 198 cases diagnosed as STEMI with PVC on admission by electrography were included. During hospitalization, VT/VF values were recorded. Logistic analysis was performed between patients with and without VT/VF to validate independent electrocardiographic predictors. QTcPVC interval > 520 ms (OR = 3.2; P = 0.027), TpTe interval > 100 ms (OR = 3.1; P = 0.04), TpTePVC  > 101 ms (OR = 3.6; P = 0.029), TpTe/QT > 0.258 (OR = 5.7; P = 0.003), and TpTe/QTPVC  > 0.253 (OR = 3; P = 0.048). However, QRS duration, QTc interval, coupling interval, and QRSPVC duration did not predict VT/VF. Besides, QRSPVC duration >140 ms (OR = 2.6; P = 0.001) independently predicted LVEF decrease after 1 year or more. CONCLUSIONS: QTcPVC interval, TpTe interval, TpTePVC interval, TpTe/QT ratio, and TpTe/QTPVC ratio are risk factors for ECG independent from other confounding factors in predicting VT/VF in the acute phase of STEMI. In addition, PVC characteristics as risk factors for VT/VF in acute phase and LVEF decrease in chronic phase were firstly reported.

Sphingosine 1-phosphate alleviates Coxsackievirus B3-induced myocarditis by increasing invariant natural killer T cells.

Sphingosine 1-phosphate (S1P), via binding to its specific receptors of S1PR1, participates in the regulation of both innate and adaptive immunity. Recent reports have identified S1P as a messenger mediating inflammation. However, roles of S1P in Coxsackievirus B3 (CVB3)-induced myocarditis were largely unknown. Here, we investigated the effect of S1P treatment on CVB3-induced myocarditis in vivo. We found that CVB3 infection downregulated S1PR1 expression in spleen and decreased the proportion of invariant natural killer T cells (iNKT) in CD3 positive T cells both in spleen and in blood from left ventricle, which accompanied by severe inflammation lesions and more virus capsid protein (VP1) expression in heart tissue. In comparison, S1P supply upregulated iNKT in the spleen and in blood from left ventricle, which represented the strengthening of anti-inflammatory effects. Indeed, inflammation infiltration, VP1 expression and apoptosis in the myocardium was all downregulated. These results demonstrated that S1P supplement could alleviate CVB3-induced myocarditis.

Integrative and quantitive evaluation of the efficacy of his bundle related pacing in comparison with conventional right ventricular pacing: a meta-analysis.

BACKGROUND: Long-term RVP could bring adverse problems to cardiac electro-mechanics and result in inter- and intra-ventricular asynchrony, impaired labor force, and aggravation of cardiac function. HBRP including direct His bundle pacing and para-His bundle pacing was regarded as a novel physiological pacing pattern to avoid devastating cardiac function. This synthetic study was conducted to integratively and quantitatively evaluate the efficacy of His bundle related pacing (HBRP) in comparison with conventional right ventricular pacing (RVP). METHODS: Published studies on comparison of left ventricular ejection fraction (LVEF), left ventricular end diastolic volume (LVEDV), left ventricular end systolic volume (LVESV), New York Heart Association (NYHA) class, inter-ventricular asynchrony, and QRS duration, etc. between HBRP and RVP were collected and for meta-analysis. RESULTS: HBRP showed higher LVEF (WMD = 3.9%, 95% CI: 1.6% - 6.1%), lower NYHA class (WMD = -0.5, 95% CI: -0.7 - -0.3), WMD of LVESV = -0.1 ml, 95% CI: -3.0 - 2.8 ml), less inter-ventricular asynchrony (WMD = -13.2 ms, 95% CI: -16.4 - -10.0 ms), and shorter QRS duration for long-term (WMD = -36.9 ms, 95% CI: -40.0 - -33.8 ms), however, no significant difference of ventricular volume (WMDLVEDV = -2.4 ml, 95% CI: -5.0 - 0.2 ml; WMDLVESV = -0.1 ml, 95% CI: -3.0 - 2.8 ml) compared to RVP. CONCLUSIONS: The efficacy of HBRP was firstly verified by meta-analysis to date. Compared with RVP, HBRP markedly preserve LVEF, NYHA class, and QRS duration. However, it seemed to have less effect on ventricular volume.

Inhibition of MicroRNA 195 Prevents Apoptosis and Multiple-Organ Injury in Mouse Models of Sepsis.

BACKGROUND: MicroRNAs (miRs) are a class of short RNA molecules, which negatively regulate gene expression. The levels of circulating miR-15 family members are elevated in septic patients and may be associated with septic death. This study investigated whether inhibition of miR-195, a member of the miR-15 family, provided beneficial effects in sepsis. METHODS AND RESULTS: Sepsis was induced by injection of feces into the peritoneum in mice. miR-195 was upregulated in the lung and liver of septic mice. Silencing of miR-195 increased the protein levels of BCL-2, Sirt1, and Pim-1; prevented apoptosis; reduced liver and lung injury; and improved the survival in septic mice. Silencing of miR-195 provided similar protection in lipopolysaccharide-induced endotoxemic mice. In endothelial cells, upregulation of miR-195 induced apoptosis, and inhibition of miR-195 prevented lipopolysaccharide-induced apoptosis. miR-195 repressed expression of its protein targets, BCL-2, Sirt1, and Pim-1. Furthermore, overexpression of Pim-1 prevented apoptosis induced by lipopolysaccharide and miR-195 mimic. Inhibition of Pim-1 attenuated the protective effects of miR-195 silencing in septic mice. CONCLUSIONS: Silencing of miR-195 reduced multiple-organ injury and improved the survival in sepsis, and the protective effects of miR-195 inhibition were associated with upregulation of Bcl-2, Sirt1, and Pim-1. Thus, inhibition of miR-195 may represent a new therapeutic approach for sepsis.

MicroRNA-19b Downregulates Gap Junction Protein Alpha1 and Synergizes with MicroRNA-1 in Viral Myocarditis.

Viral myocarditis (VMC) is a life-threatening disease that leads to heart failure or cardiac arrhythmia. A large number of researches have revealed that mircroRNAs (miRNAs) participate in the pathological processes of VMC. We previously reported that miR-1 repressed the expression of gap junction protein α1 (GJA1) in VMC. In this study, miR-19b was found to be significantly upregulated using the microarray analysis in a mouse model of VMC, and overexpression of miR-19b led to irregular beating pattern in human cardiomyocytes derived from the induced pluripotent stem cells (hiPSCs-CMs). The upregulation of miR-19b was associated with decreased GJA1 in vivo. Furthermore, a miR-19b inhibitor increased, while its mimics suppressed the expression of GJA1 in HL-1 cells. When GJA1 was overexpressed, the miR-19b mimics-mediated irregular beating was reversed in hiPSCs-CMs. In addition, the effect of miR-19b on GJA1 was enhanced by miR-1 in a dose-dependent manner. These data suggest miR-19b contributes to irregular beating through regulation of GJA1 by cooperating with miR-1. Based on the present and our previous studies, it could be indicated that miR-19b and miR-1 might be critically involved in cardiac arrhythmia associated with VMC.