Apoptotic cardiomyocyte death in fatal myocarditis

Targeting cardiomyocyte cell cycle regulation in heart failure

Heart failure continues to be a significant global health concern, causing substantial morbidity and mortality. The limited ability of the adult heart to regenerate has posed challenges in finding effective treatments for cardiac pathologies. While various medications and surgical interventions have been used to improve cardiac function, they are not able to address the extensive loss of functioning cardiomyocytes that occurs during cardiac injury. As a result, there is growing interest in understanding how the cell cycle is regulated and exploring the potential for stimulating cardiomyocyte proliferation as a means of promoting heart regeneration. This review aims to provide an overview of current knowledge on cell cycle regulation and mechanisms underlying cardiomyocyte proliferation in cases of heart failure, while also highlighting established and novel therapeutic strategies targeting this area for treatment purposes.

Health position paper and redox perspectives on reactive oxygen species as signals and targets of cardioprotection

The present review summarizes the beneficial and detrimental roles of reactive oxygen species in myocardial ischemia/reperfusion injury and cardioprotection. In the first part, the continued need for cardioprotection beyond that by rapid reperfusion of acute myocardial infarction is emphasized. Then, pathomechanisms of myocardial ischemia/reperfusion to the myocardium and the coronary circulation and the different modes of cell death in myocardial infarction are characterized. Different mechanical and pharmacological interventions to protect the ischemic/reperfused myocardium in elective percutaneous coronary interventions and coronary artery bypass grafting, in acute myocardial infarction and in cardiotoxicity from cancer therapy are detailed. The second part keeps the focus on ROS providing a comprehensive overview of molecular and cellular mechanisms involved in ischemia/reperfusion injury. Starting from mitochondria as the main sources and targets of ROS in ischemic/reperfused myocardium, a complex network of cellular and extracellular processes is discussed, including relationships with Ca2+ homeostasis, thiol group redox balance, hydrogen sulfide modulation, cross-talk with NAPDH oxidases, exosomes, cytokines and growth factors. While mechanistic insights are needed to improve our current therapeutic approaches, advancements in knowledge of ROS-mediated processes indicate that detrimental facets of oxidative stress are opposed by ROS requirement for physiological and protective reactions. This inevitable contrast is likely to underlie unsuccessful clinical trials and limits the development of novel cardioprotective interventions simply based upon ROS removal.

Modulation of TLR4/NFκB Pathways in Autoimmune Myocarditis

Myocarditis is an inflammatory and oxidative disorder characterized by immune cell recruitment in the damaged tissue and organ dysfunction. In this paper, we evaluated the molecular pathways involved in myocarditis using a natural compound, Coriolus versicolor, in an experimental model of autoimmune myocarditis (EAM). Animals were immunized with an emulsion of pig cardiac myosin and complete Freund's adjuvant supplemented with mycobacterium tuberculosis; thereafter, Coriolus versicolor (200 mg/Kg) was orally administered for 21 days. At the end of the experiment, blood pressure and heart rate measurements were recorded and the body and heart weights as well. From the molecular point of view, the Coriolus versicolor administration reduced the activation of the TLR4/NF-κB pathway and the levels of pro-inflammatory cytokines (INF-γ, TNF-α, IL-6, IL-17, and IL-2) and restored the levels of anti-inflammatory cytokines (IL-10). These anti-inflammatory effects were accompanied with a reduced lipid peroxidation and nitrite levels and restored the antioxidant enzyme activities (SOD and CAT) and GSH levels. Additionally, it reduced the histological injury and the immune cell recruitment (CD4+ and CD68+ cells). Moreover, we observed an antiapoptotic activity in both intrinsic (Fas/FasL/caspase-3) and extrinsic (Bax/Bcl-2) pathways. Overall, our data showed that Coriolus versicolor administration modulates the TLR4/NF-κB signaling in EAM.

Regulation of endogenous cardiomyocyte proliferation: The known unknowns

Myocardial regeneration in patients with cardiac damage is a long-sought goal of clinical medicine. In animal species in which regeneration occurs spontaneously, as well as in neonatal mammals, regeneration occurs through the proliferation of differentiated cardiomyocytes, which re-enter the cell cycle and proliferate. Hence, the reprogramming of the replicative potential of cardiomyocytes is an achievable goal, provided that the mechanisms that regulate this process are understood. Cardiomyocyte proliferation is under the control of a series of signal transduction pathways that connect extracellular cues to the activation of specific gene transcriptional programmes, eventually leading to the activation of the cell cycle. Both coding and non-coding RNAs (in particular, microRNAs) are involved in this regulation. The available information can be exploited for therapeutic purposes, provided that a series of conceptual and technical barriers are overcome. A major obstacle remains the delivery of pro-regenerative factors specifically to the heart. Improvements in the design of AAV vectors to enhance their cardiotropism and efficacy or, alternatively, the development of non-viral methods for nucleic acid delivery in cardiomyocytes are among the challenges ahead to progress cardiac regenerative therapies towards clinical application.

A common oral pathogen Porphyromonas gingivalis induces myocarditis in rats

AIM

To evaluate whether Porphyromonas gingivalis (P. gingivalis) inoculation could induce cardiac remodelling in rats.

MATERIALS AND METHODS

The study was conducted on 33 Wistar rats, which were distributed in the following experimental groups: not inoculated; inoculated with 1 × 10⁸ CFU/ml of bacteria; inoculated with 3 × 10⁸ CFU/ml of bacteria. The animals were inoculated at baseline and on the 15th day of follow-up. Blood collection was performed at baseline and 60 min after each inoculation. At 29 days, the animals were subjected to echocardiography and at 30 days to haemodynamic studies before sacrificing them.

RESULTS

Impact of the bacteria was more evident in rats that received higher P. gingivalis concentration. Thus, 3 × 10⁸ CFU/ml of bacteria increased the rectal temperature and water content in the lung as well as myocardial necrosis and fibrosis. P. gingivalis induced the intensification of DNA fragmentation and increased the levels of malondialdehyde, oxidized proteins, and macrophage expression in the myocardium. These findings were associated with lower LV isovolumetric relaxation time, +dP/dt, -dP/dt, and higher end-diastolic pressure.

CONCLUSIONS

P. gingivalis bacteraemia is significantly associated with adverse cardiac remodelling and may play a biological role in the genesis of heart failure.

STAT3 Suppresses Cardiomyocytes Apoptosis in CVB3-Induced Myocarditis Via Survivin

Background: Viral myocarditis (VMC) is a common inflammatory cardiovascular disease with unclear mechanisms, which mainly affects children and adolescents. Apoptosis is the key to CVB3-induced myocarditis, and blocking this process may be beneficial to the therapy of VMC. Hence, this study aimed to explore the protective function of STAT3 on cardiomyocyte apoptosis of VMC and its underlying mechanisms.

Methods and Results: In this research, we confirmed that STAT3 was significantly activated in both animal and cell models of VMC. To further clarify what role did STAT3 play in VMC, AG490, an inhibitor of STAT3, was used to suppress p-STAT3. Our results demonstrated that decreased expression of p-STAT3 caused by AG490 significantly aggravated severity of VMC with elevated myocardial inflammation, deteriorative ventricular systolic function and increased mortality. It suggested that STAT3 plays a protective role in VMC. To further identify the anti-apoptosis impact that activated STAT3 made, we constructed lentivirus to regulate the expression of STAT3 in NMCs. We found that up-regulated activated STAT3 attenuated cardiomyocyte apoptosis, but down-regulated one aggravated that, which verified activated STAT3 played an anti-apoptosis role in VMC. Following that, we explored what elements are involved in the anti-apoptotic mechanism of activated STAT3 by using survivin inhibitor YM155. The result showed the anti-apoptotic effect of activated STAT3 does not work in the case of survivin inhibition.

Conclusion: Our findings demonstrated STAT3 by targeting survivin alleviated cardiomyocyte apoptosis in CVB3-induced myocarditis.

Cardiac apoptosis caused by elevated cholesterol level in experimental autoimmune myocarditis

It has been reported that cholesterol-lowing agents can ameliorate severity of myocarditis. However, the beneficial effect of the agents has been claimed to be independent of cholesterol reduction as there is no significant change in the plasma cholesterol level in myocarditis. In the present study, using experimental autoimmune myocarditis (EAM) rats as an animal model, we demonstrated that EAM induced elevation of cholesterol level and impaired cholesterol efflux capacity in the cardiac tissue. Moreover, serum high-density lipoprotein (HDL) content was reduced and HDL function associated protein Paraoxonase 1 (PON1) activity was decreased. Besides, the major structural protein within HDL, Apolipoprotein A1 (ApoA1) expression in the cardiac tissues was significantly reduced while the level of serum ApoA1 was not significantly altered. Importantly, cholesterol depleting agent methyl-β-cyclodextrin (MβCD) alleviated the development of EAM, as monitored by decreased ratio of heart weight to body weight (HW/BW), decreased infiltration of inflammatory cells and collagen deposition, improved cardiac function, reduced expression of apoptosis-related protein Bax, Fas, FasL and caspase-3 and increased level of anti-apoptotic protein Bcl-2. These results suggest that reduction of cholesterol level in cardiac tissue could suppress EAM-induced cardiac apoptosis through both intrinsic and extrinsic apoptotic pathways.

The protection effects of survivin in the cell model of CVB3-induced viral myocarditis

Viral myocarditis (VMC) is a widely studied but poorly understood inflammatory cardiomyopathy which mainly affects children and young adults and results in adverse outcomes. Cardiomyocyte apoptosis was reported important in the progress of coxsackievirus B3 (CVB3)-induced VMC and the blocking of this process may contribute to the therapeutic effect towards VMC. Therefore, this study was designed to explore whether survivin, one of the strongest antiapoptotic proteins, can protect cardiomyocytes from apoptosis in VMC and to discover its related mechanisms. Here, the cultured neonatal mouse cardiomyocytes (NMCs) were exposed to CVB3 to establish the cell model of VMC and the results of Western Blot showed that the protein expression of survivin in CVB3-infected NMCs varied at different post-infection time. Lentivirus was next used to examine the function of survivin in CVB3-infected NMCs. TUNEL assay demonstrated that the overexpression of survivin interrupted CVB3-induced apoptosis. It was next examined whether caspase-3 and -9 were involved in the antiapoptotic pathway initiated by survivin via Western Blot. The results showed a reverse relationship between the protein expression of survivin and that of cleaved caspase-3 and cleaved caspase-9, suggesting that survivin may attenuate apoptosis through restraining the activity of caspase-3 and -9. Moreover, the supernatant fluid of cultured NMCs was extracted to detect the quantitation of released lactate dehydrogenase (LDH) and a sharp decrease was discovered in the survivin-overexpressed group compared to the CVB3-infected group, indicating a protective role of survivin in the cell model of CVB3-induced myocarditis. This study demonstrated that survivin was triggered by CVB3 infection in NMCs and survivin executed its antiapoptotic effects via caspase-3- and caspase-9-dependent signaling pathway.

MG-132 attenuates cardiac deterioration of viral myocarditis via AMPK pathway

BACKGROUND

Coxsackievirus B3 (CVB3) is the primary cause of infectious myocarditis. Aggressive immunological activation and apoptosis of myocytes contributes to progressive dysfunction of cardiac contraction and poor prognosis. MG-132, a proteasome inhibitor, regulates mitochondrial-mediated intrinsic myocardial apoptosis and downregulates NF-κB-mediated inflammation. Here, we determined whether AMPK pathway participates in MG-132-mediated myocardial protection in viral-induced myocarditis.

METHODS AND RESULTS

Acute viral myocarditis models were established by intraperitoneal inoculation of CVB3 in male BALB/c mice. Myocarditis and age-matched control mice were administered MG-132 and/or BML-275 dihydrochloride (BML) (AMPK antagonist) intraperitoneally daily from the day following CVB3 inoculation. MG-132 improved hemodynamics and inhibited the structural remodeling of the ventricle in mice with myocarditis, while BML largely blunted these effects. TUNEL staining and immunochemistry suggested that MG-132 exerts anti-apoptotic and anti-inflammatory effects against CVB3-induced myocardial injuries. BML attenuated the effects of MG-132 on anti-apoptosis and anti-inflammation.

CONCLUSION

MG-132 modulated apoptosis and inflammation, improved hemodynamics, and inhibited the structural remodeling of ventricles in a myocarditis mouse model via regulation of the AMPK signal pathway.

Enterovirus 71 targets the cardiopulmonary system in a robust oral infection mouse model

Severe infection with the re-emerging enterovirus 71 (EV71 or EV-A71) can cause cardiopulmonary failure. However, in patients' heart and lung, viral protein has not been detected. In mouse models, heart disease has not been reported. EV71-infected brainstem is generally believed to be responsible for the cardiopulmonary collapse. One major limitation in EV71 research is the lack of an efficient oral infection system using non-mouse-adapted clinical isolates. In a robust oral infection NOD/SCID mouse model, we detected EV71 protein at multiple organs, including heart and lung, in 100% of moribund mice with limb paralysis. Infiltrating leukocytes were always detected in heart and muscle, and VP1-positive M2 macrophages were abundant in the lung. Functional dissection on the pathogenesis mechanism revealed severe apoptosis, inflammatory cytokines, and abnormal electrocardiogram (EKG) in orally infected hearts. Therefore, cardiopulmonary disease could be one plausible cause of death in this mouse model. Inoculation of EV71 through an oral route resulted in viral infection in the intestine, viremia, and EV71 appeared to spread to peripheral tissues via blood circulation. Infectious virus was no longer detected in the blood on day 5 post-infection by the plaque formation assay. We demonstrated that both EV71 clinical isolate and cloned virus can target the cardiopulmonary system via a natural infection-like oral route.

Inhibitory effect of melatonin on Mst1 ameliorates myocarditis through attenuating ER stress and mitochondrial dysfunction

Viral myocarditis has been found to be one of the leading causes of sudden death in young adults. However, no effective drugs have been developed to intervene the progression of myocarditis. Accordingly, the present study is carried out to explore the protective role played by melatonin in the setting of viral myocarditis with a focus on Mst1-Hippo pathway, mitochondrial dysfunction and ER stress. Cardiac function was determined via echocardiographic examination. Mitochondrial function and ER stress were detected via ELISA, western blots, and immunofluorescence. Our data demonstrated that virus injection induced cardiac dysfunction as evidenced by reduced contractile function in myocardium. Besides, LDH release assay and western blotting analysis demonstrated that cardiomyocyte death was activated by virus injection. Interestingly, melatonin treatment improved cardiac function and repressed virus-mediated cardiomyocyte apoptosis. At the molecular levels, mitochondrial dysfunction was induced by virus infection, as indicated by mitochondrial membrane potential reduction, mPTP opening rate elevation and caspase-9-related apoptosis activation. Besides, ER stress parameters were also elevated in virus-treated cardiomyocytes. Interestingly, melatonin treatment maintained mitochondrial dysfunction and repressed ER stress. To the end, we found that Mst1 was upregulated by virus infection; this effect was attenuated through supplementation with melatonin. However, Mst1 overexpression reduced the beneficial impact exerted by melatonin on cardiomyocyte viability, mitochondrial function and ER homeostasis. Our study illustrated that melatonin treatment attenuated viral myocarditis via sustaining cardiomyocyte viability, repressing mitochondrial dysfunction and inhibiting ER stress in a manner dependent on Mst1 inhibition.

Hydrogen sulfide-mediated regulation of cell death signaling ameliorates adverse cardiac remodeling and diabetic cardiomyopathy

The death of cardiomyocytes is a precursor for the cascade of hypertrophic and fibrotic remodeling that leads to cardiomyopathy. In diabetes mellitus (DM), the metabolic environment of hyperglycemia, hyperlipidemia, and oxidative stress causes cardiomyocyte cell death, leading to diabetic cardiomyopathy (DMCM), an independent cause of heart failure. Understanding the roles of the cell death signaling pathways involved in the development of cardiomyopathies is crucial to the discovery of novel targeted therapeutics and biomarkers for DMCM. Recent evidence suggests that hydrogen sulfide (H2S), an endogenous gaseous molecule, has cardioprotective effects against cell death. However, very little is known about signaling by which H2S and its downstream targets regulate myocardial cell death in the DM heart. This review focuses on H2S in the signaling of apoptotic, autophagic, necroptotic, and pyroptotic cell death in DMCM and other cardiomyopathies, abnormalities in H2S synthesis in DM, and potential H2S-based therapeutic strategies to mitigate myocardial cell death to ameliorate DMCM.

Astragalus mongholicus (Fisch.) Bge Improves Peripheral Treg Cell Immunity Imbalance in the Children With Viral Myocarditis by Reducing the Levels of miR-146b and miR-155

Viral myocarditis (VMC) is a common cardiac disease, however, there still lacks an effective therapeutic strategy for VMC. Astragalus mongholicus (Fisch.) Bge (AB), a Chinese herb with some functional metabolites, may have some pharmacological effects on VMC. AB ingredients were measured by a full-scan LCQ mass spectrum. We aimed to explore the effects of AB on the VMC children by investigating peripheral Treg cell homeostasis. A total of 68 VMC children were random and evenly assigned into an AG group (received 10-mL AB oral liquid daily), and a CG group (received placebo daily). Peripheral blood mononuclear cells (PBMC) were obtained from peripheral blood and Treg cells were isolated. The levels of miR-146b, miR-155, Treg immunity activity and myocarditis biomarkers were measured in Treg cells. There were four main components (sucrose, calycosin, Astragaloside IV and calycosin-7-glucoside) in AB. The cases sinus tachycardia, frequent premature ventricular contractions, and supraventricular tachycardia were significantly reduced in the AG group (P < 0.05). Meanwhile, the myocardial enzymes and cardiac function indexes were improved in the AG group when compared with the CG group (P < 0.05). The time of electrocardiogram recovery, symptom duration and hospital stay was shorter in the AG group than in the CG group (P < 0.05). The levels of miR-146b and miR-155 were higher in the CG group than in the AG group (P < 0.05). The levels of ROR-γt (retinoic acid receptor-related orphan nuclear receptor gamma), FoxP3 (forkhead transcription factor), IL-10 (interleukin-11) and TGF-β (transforming growth factor beta) were lower in the CG group than in the AG group (P < 0.05). In contrast, the levels of IL-17, IL-21, CK-MB (creatine kinase-MB), cTnI (cardiac troponin I), GrB (granzyme B), sFasL (soluble fas ligand) and caspase-3 were higher in the CG group than in the AG group (P < 0.05). Furthermore, the levels of ROR-γt, FoxP3, IL-10, and TGF-β were positively, whereas the levels of IL-17, IL-21, CK-MB, cTnI, GrB, sFasL and caspase-3 were negatively, associated with the levels of miR-146b and miR-155 (P < 0.05). AB treatment improved cardiac functions, peripheral Treg cell immunity imbalance in the children with VMC by reducing the levels of miR-146b and miR-155.

Gestational hyperglycemia reprograms cardiac gene expression in rat offspring

BackgroundRat fetuses with maternal pregestational hyperglycemia develop cardiac dysfunction, and their cardiac gene expression differs from that of healthy control fetuses near term. We hypothesized that cardiac gene expression and morphologic abnormalities of rat fetuses with maternal pregestational hyperglycemia become normal after birth.MethodsNine rats were preconceptually injected with streptozotocin to induce maternal hyperglycemia and nine rats served as controls. The hyperglycemia group comprised 82 mice and the control group 74 offspring fed by euglycemic dams. Hearts of the offspring were collected on postnatal days 0, 7, and 14, and processed for histologic and gene expression analyses.ResultsOn day 0, heart weight was increased, and expression of cardiac genes involved in contractility, growth, and metabolism was decreased in the hyperglycemia group. On day 7, although cardiomyocyte apoptosis was enhanced, most of the changes in gene expression had normalized in the hyperglycemia group. By day 14, the expression of genes important for myocardial growth, function, and metabolism was again abnormal in the hyperglycemia group.ConclusionMost cardiac gene expression abnormalities become transiently normal during the first week of life of offspring to hyperglycemic rats. However, by day 14, cardiac expressions of genes involved in growth, function, and metabolism are again abnormal in relation to control offspring.

Effect of PKC inhibitor on experimental autoimmune myocarditis in Lewis rats

Myocarditis is a major cause of sudden, unexpected death in young people. However, it is still one of the most challenging diseases to treat in cardiology. In the present study, we showed that both expression level and activity of PKC-α were up-regulated in the rat heart of experimental autoimmune myocarditis (EAM). Intraperitoneal administration of PKC inhibitor (Ro-32-0432) at the end of the most severe inflammation period of EAM still significantly reduced the EAM induced expression of failure biomarkers. Furthermore, Ro-32-0432 reduced the ratio of Bax/Bcl-2 and suppressed the expression of cleaved caspase-3, both of which were increased in the heart of the EAM rats, suggesting an anti-apoptotic role of Ro-32-0432. Besides, Ro-32-0432 suppressed EAM-induced cardiac fibrosis and release of pro-inflammatory cytokines IL-1β and IL-17. These results suggest that inhibition of PKC may serve as a potential therapeutic strategy for the treatment of myocarditis.

Inhibition of Drp1 attenuates mitochondrial damage and myocardial injury in Coxsackievirus B3 induced myocarditis

Viral myocarditis (VMC) is closely related to apoptosis, oxidative stress, innate immunity, and energy metabolism, which are all linked to mitochondrial dysfunction. A close nexus between mitochondrial dynamics and cardiovascular disease with mitochondrial dysfunction has been deeply researched, but there is still no relevant report in viral myocarditis. In this study, we aimed to explore the role of Dynamin-related protein 1 (Drp1)-linked mitochondrial fission in VMC. Mice were inoculated with the Coxsackievirus B3 (CVB3) and treated with mdivi1 (a Drp1 inhibitor). Protein expression of Drp1 was increased in mitochondria while decreased in cytoplasm and accompanied by excessive mitochondrial fission in VMC mice. In addition, midivi1 treatment attenuate inflammatory cells infiltration in myocardium of the mice, serum Cardiac troponin I (CTnI) and Creatine kinase-MB (CK-MB) level. Mdivi1 also could improved the survival rate of mice and mitochondrial dysfunction reflected as the up-regulated mitochondrial marker enzymatic activities of succinate dehydrogenase (SDH), cytochrome c oxidase (COX) and mitochondrial membrane potential (MMP). At the same time, mdivi1 rescued the body weight loss, myocardial injury and apoptosis of cardiomyocyte. Furthermore, decease in LVEDs and increase in EF and FS were detected by echocardiogram, which indicated the improved myocardial function. Thus, Drp1-linked excessive mitochondrial fission contributed to VMC and midivi1 may be a potential therapeutic approach.

Gene expression analysis during recovery process indicates the mechanism for innate immune injury and repair from Coxsackievirus B3-induced myocarditis

To investigate the innate immune injury and repair mechanism during recovery from Coxsackievirus B3 (CVB3) induced myocarditis, we established an acute viral myocarditis recovery model by infecting BALB/c mice with CVB3. Histopathological examination of cardiac tissues after infection showed a gradual increase of myocardial injury to the maximum degree at 8 dpi (days post infection), followed by a recovery process with reduced viral replication. We also measured expression changes of innate immune genes in heart after 4, 8 and 12 days of infection using innate immune real-time PCR array. The results showed expression alterations in many Pattern Recognition Receptors (PRRs) genes upon CVB3 infection, which activated multiple important signaling pathways during recovery process. The expression of TLRs, RLRs, PKR and cytokines were strongly induced and reached the peak at 4 dpi in early myocarditis stage, followed by a gradual reduction in recovery stage, during which the levels were even lower than normal at 12 dpi. The strong correlation between cardiac histopathology score and chemokine expression level suggested that the chemokines might play a role in pathological changes during early myocarditis stage. In addition, we also found that both cell survival signaling pathways (AKT1, p38MAPK) and antiviral signaling pathways (IKKα/β/ε) were activated and promoted the recovery during late myocarditis stage. Altogether, our observations improved the understanding of formation and progression of the pathological lesions, as well as the repair mechanism for acute viral myocarditis.

Inhibition of Histone Deacetylase Activity Aggravates Coxsackievirus B3-Induced Myocarditis by Promoting Viral Replication and Myocardial Apoptosis

Viral myocarditis, which is most prevalently caused by coxsackievirus B3 (CVB3), is a serious clinical condition characterized by excessive myocardial inflammation. Recent studies suggest that regulation of protein acetylation levels by inhibiting histone deacetylase (HDAC) activity modulates inflammatory response and shows promise as a therapy for several inflammatory diseases. However, the role of HDAC activity in viral myocarditis is still not fully understood. Here, we aim to investigate the role of HDAC activity in viral myocarditis and its underlying mechanism. CVB3-infected BALB/c mice were treated with the HDAC inhibitor (HDACI) suberoylanilide hydroxamic acid (SAHA) or trichostatin A (TSA). We found inhibition of HDAC activity aggravated rather than ameliorated the severity of CVB3-induced myocarditis, which was contrary to our expectations. The aggravated myocarditis by HDACI treatment seemed not to be caused by an elevated inflammatory response but by the increased CVB3 replication. Further, it was revealed that the increased CVB3 replication was closely associated with the HDACI-enhanced autophagosome formation. Inhibition of autophagosome formation by wortmannin or ATG5 short hairpin RNA dramatically suppressed the HDACI-increased CVB3 replication. The increased viral replication subsequently elevated CVB3-induced myocardial apoptosis. Conversely, inhibition of CVB3 replication and ensuing myocardial apoptosis by the antiviral drug ribavirin significantly reversed the HDACI-aggravated viral myocarditis. In conclusion, we elucidate that the inhibition of HDAC activity increases CVB3 replication and ensuing myocardial apoptosis, resulting in aggravated viral myocarditis. Possible adverse consequences of administering HDACI should be considered in patients infected (or coinfected) with CVB3.

IMPORTANCE Viral myocarditis, which is most prevalently caused by CVB3, is characterized by excessive myocardial inflammation. Inhibition of HDAC activity was originally identified as a powerful anti-cancer therapeutic strategy and was recently found to be implicated in the regulation of inflammatory response. HDACI has been demonstrated to be efficacious in animal models of several inflammatory diseases. Thus, we hypothesize that inhibition of HDAC activity also protects against CVB3-induced viral myocarditis. Surprisingly, we found inhibition of HDAC activity enhanced myocardial autophagosome formation, which led to the elevated CVB3 viral replication and ensuing increased myocardial apoptosis. Viral myocarditis was eventually aggravated rather than ameliorated by HDAC inhibition. In conclusion, we elucidate the role of HDAC activity in viral myocarditis. Moreover, given the importance of HDACI in preclinical and clinical treatments, the possible unfavorable effect of HDACI should be carefully evaluated in patients infected with viruses, including CVB3.

Antiviral and myocyte protective effects of IL-28A in coxsackievirus B3-induced myocarditis

OBJECTIVE

This study aimed to investigate whether interleukin-28A (IL-28A) plays a role in murine myocarditis induced by coxsackievirus B3 (CVB3), and to explore its possible mechanism involved.

METHODS

Male BALB/c mice both infected and not infected by CVB3 were randomly divided into four groups (n=40), untreated or treated with different doses of IL-28A for 4 days, and then sacrificed on days 4 and 7 post-infection. The heart samples were collected for histopathologic examination. Cardiac viral load was determined by a plaque assay. Additionally, immunoblot analysis, TUNEL assay, and immunohistochemistry were performed to examine the expression of signal transducer, activator of transcription 1 and 2 (STAT1 and STAT2), CVB3-induced apoptosis and the expression of Bcl-2, BAX and Caspase-3.

RESULTS

Compared to uninfected mice, the CVB3 infected mice exhibited higher mortality rate (p<0.001), apparent inflammation and myocardial lesion (p<0.01), and higher cardiac viral load (p<0.01). After CVB3 infection, IL-28A treated mice presented no death (p<0.001), reduced inflammation and myocardial lesion (p<0.01), and lower viral load (p<0.01) compared to untreated mice. Besides, treatment with IL-28A markedly increased the expressions of STAT1 and STAT2, and inhibited CVB3-induced apoptosis in myocardial cells with increased ratio of Bcl-2/BAX.

CONCLUSION

The antiviral and myocyte protective effects of IL-28A in CVB3-induced myocarditis are regulated by STAT1 and STAT2.

Myocardial apoptosis and SIDS

Apoptosis mediates cardiac damage in severe forms of myocarditis. In fatal myocarditis, large amounts of cardiomyocytes show apoptotic DNA fragmentation, while in human controls, few apoptotic cardiomyocytes are found. In the present study the frequency of apoptosis in 88 SIDS cases (category 1b according to the San Diego Classification) and 15 control cases was investigated. In every case myocardial samples from 8 standard locations were collected. Detection of apoptotic cardiomyocytes was performed by TUNEL method. Furthermore the myocardial tissue was stained with HE and immunohistochemical methods (LCA, CD68, CD45-R0). More than 90% of the slides did not contain apoptotic cardiomyocytes at all. The detection rate of apoptotic cardiomyocytes was almost equal in control group (26.7%) and SIDS group (23.86%). A quantification of apoptotic cardiomyocytes per mm(2) revealed no significant difference between both groups either. Altogether there is no evidence for a higher rate of apoptosis in SIDS.

Mouse models of heart failure: cell signaling and cell survival

Heart failure is one of the paramount global causes of morbidity and mortality. Despite this pandemic need, the available clinical counter-measures have not altered substantially in recent decades, most notably in the context of pharmacological interventions. Cell death plays a causal role in heart failure, and its inhibition poses a promising approach that has not been thoroughly explored. In previous approaches to target discovery, clinical failures have reflected a deficiency in mechanistic understanding, and in some instances, failure to systematically translate laboratory findings toward the clinic. Here, we review diverse mouse models of heart failure, with an emphasis on those that identify potential targets for pharmacological inhibition of cell death, and on how their translation into effective therapies might be improved in the future.

Maternal hyperglycemia leads to fetal cardiac hyperplasia and dysfunction in a rat model

Accelerated fetal myocardial growth with altered cardiac function is a well-documented complication of human diabetic pregnancy, but its pathophysiology is still largely unknown. Our aim was to explore the mechanisms of fetal cardiac remodeling and cardiovascular hemodynamics in a rat model of maternal pregestational streptozotocin-induced hyperglycemia. The hyperglycemic group comprised 107 fetuses (10 dams) and the control group 219 fetuses (20 dams). Fetal cardiac function was assessed serially by Doppler ultrasonography. Fetal cardiac to thoracic area ratio, newborn heart weight, myocardial cell proliferative and apoptotic activities, and cardiac gene expression patterns were determined. Maternal hyperglycemia was associated with increased cardiac size, proliferative, apoptotic and mitotic activities, upregulation of genes encoding A- and B-type natriuretic peptides, myosin heavy chain types 2 and 3, uncoupling proteins 2 and 3, and the angiogenetic tumor necrosis factor receptor superfamily member 12A. The genes encoding Kv channel-interacting protein 2, a regulator of electrical cardiac phenotype, and the insulin-regulated glucose transporter 4 were downregulated. The heart rate was lower in fetuses of hyperglycemic dams. At 13-14 gestational days, 98% of fetuses of hyperglycemic dams had holosystolic atrioventricular valve regurgitation and decreased outflow mean velocity, indicating diminished cardiac output. Maternal hyperglycemia may lead to accelerated fetal myocardial growth by cardiomyocyte hyperplasia. In fetuses of hyperglycemic dams, expression of key genes that control and regulate cardiomyocyte electrophysiological properties, contractility, and metabolism are altered and may lead to major functional and clinical implications on the fetal heart.

Cardiac-specific overexpression of melanoma differentiation-associated gene-5 protects mice from lethal viral myocarditis

BACKGROUND

Viral myocarditis is among the most common causes of heart failure in children and young adults. The RNA helicase melanoma differentiation-associated gene-5 (MDA5) is critical for host antiviral responses against members of the Picornaviridae family, such as encephalomyocarditis virus (EMCV). MDA5-knockout mice are highly susceptible to EMCV infection and develop significant myocardial injury and left ventricular dysfunction. However, the mechanisms by which MDA5 signaling within cardiac myocytes contributes to the host response against viral infection have not been defined.

METHODS AND RESULTS

We generated cardiac-specific MDA5 transgenic (alpha-myosin heavy chain [αMHC]-MDA5) mice. These mice showed increased baseline cardiac expression of antiviral cytokines and increased cellular infiltration but no alterations in cardiac function and structure. αMHC-MDA5 mice were less susceptible to EMCV infection and had a significantly lower cardiac viral load compared with littermate control mice. The severity of myocarditis, prevalence of cardiac myocyte apoptosis, and cleavage of caspase 3 after EMCV infection were attenuated in αMHC-MDA5 mice. Furthermore, αMHC-MDA5 mice were protected against EMCV-induced myocardial dysfunction.

CONCLUSIONS

Our data suggest that myocardial MDA5 may be a key molecule in protecting the heart from direct viral injury and myocardial dysfunction.

Induction of caspase cascade as a nonspecific response to myocardial damage

In three experimental series, acute hemodynamic overload of the left ventricle, focal ischemia of the left ventricle, and diphtheritic intoxication were modeled in rabbits. On days 1, 3, and 5 of the experiments, activity of myocardial caspase-3 and caspase-8 were measured separately in the left and right ventricles. In the left ventricle, caspase-3 activity increased in all 3 modeled pathological processes, while in the right ventricle this parameter increased during acute overload and ischemic injury to the left ventricle. Caspase-8 activity increased only in the left ventricle during its hemodynamic overload and remained unchanged in other cases. It was concluded that induction of the caspase cascade can be considered as a nonspecific response to myocardial damage. In this case, specific mechanisms responsible for generation and transmission of apoptotic stimuli in cardiomyocytes have unique features.

Myocarditis as a precipitating factor for heart failure: evaluation and 1-year follow-up using cardiovascular magnetic resonance and endomyocardial biopsy

AIMS

The aim of this study was to evaluate myocarditis as a precipitating factor for heart failure using cardiovascular magnetic resonance (CMR) and endomyocardial biopsy.

METHODS AND RESULTS

Eighty-five patients with suspected myocarditis and 20 controls were evaluated. Seventy-one patients with positive CMR were referred for endomyocardial biopsy and re-evaluation after 1 year. Cardiovascular magnetic resonance was performed using STIR T2-weighted (T2W), early T1-weighted (EGE), and late gadolinium-enhanced (LGE) images. Immunohistological and polymerase chain reaction (PCR) analysis of myocardial specimens was employed. In patients with myocarditis, T2 and EGE were increased compared with controls (2.6 ± 0.9 vs. 1.57 ± 0.13, P < 0.001 and 7.9 ± 5.5 vs. 3.59 ± 0.08, P < 0.001, respectively). Late gadolinium enhancement was found in all myocarditis patients. Endomyocardial biopsy performed in 50 of 71 patients with positive CMR showed positive immunohistology in 48% and presence of infectious genomes in 80% (mainly Chlamydia, Herpes, and Parvovirus B19). Left ventricular ejection fraction (LVEF) was significantly decreased compared with controls (47.7 ± 19.2 vs. 64 ± 0.2, P < 0.001). After 1 year, CMR showed normalization of T2 and EGE, and decreased LGE. Left ventricular ejection fraction increased in 36.5% of patients, remained stable in 56.5% and decreased in 7% of patients, in whom biopsy showed persistence of the initial infective agents. A negative correlation was identified between EGE, LGE, and LVEF. Patients with positive biopsies had lower LVEFs.

CONCLUSION

In a Greek population with myocarditis, Chlamydia with viruses was a common finding. Cardiovascular magnetic resonance and PCR proved useful for the detection of myocarditis; EGE and LGE had the best correlation for the development of heart failure. Persistence of the initially detected infective agents was identified in patients who deteriorated further.

Evaluation of myocarditis in a pediatric population using cardiovascular magnetic resonance and endomyocardial biopsy

OBJECTIVES

To evaluate myocarditis in a pediatric population using cardiovascular magnetic resonance (CMR) and endomyocardial biopsy.

METHODS

Twenty suspected for myocarditis patients aged 8-16 years and 20 controls were evaluated. CMR was performed using STIR T2-weighted (T2W), early T1-weighted (EGE) and late gadolinium-enhanced images (LGE). Immunohistologic and polymerase chain reaction (PCR) analysis of myocardial specimens were employed in 8/16, who fulfilled the criteria for myocarditis according to clinical and CMR findings.

RESULTS

Typical clinical, ECG and echocardiographic presentation were identified in 10/16. Troponine I was positive only in 3/16 patients. T2 and EGE in myocarditis were increased compared to controls (2.35 ± 0.5 vs. 1.57 ± 0.13, p<0.001 and 8.5 ± 3 vs. 3.59 ± 0.08, p<0.001, respectively). LGE was found only in 10/16 patients. Endomyocardial biopsy, performed in 8/16 patients with positive CMR, showed positive immunohistology in 2/8 and presence of viral genomes in 6/8 (Herpes, Parvo B19 and Epstein-Barr). Left ventricular ejection fraction (LVEF) was significantly decreased compared to controls (49.6 ± 14.8 vs. 64 ± 0.2, p<0.001). After 6 months, CMR showed normalization of T2, EGE and decreased/or absent LGE. LVEF was normal in all, except two, who remained with low LVEF but in a stable clinical condition.

CONCLUSIONS

In a small Greek pediatric population with myocarditis, CMR proved useful for the detection of myocarditis, especially in those with negative troponine and mild clinical presentation.

Atorvastatin prevents left ventricular remodeling in spontaneously hypertensive rats

Statins improve left ventricular (LV) remodeling in spontaneously hypertensive rats (SHRs). This study was designed to investigate the effects of atorvastatin administered in the early stage on LV remodeling in SHRs, and to explore the underlying mechanisms.Sixteen male 8-week-old SHRs were randomized to receive distilled water (SHR-DW) or atorvastatin (SHR-ATV) for 12 weeks. Age-matched male Wistar-Kyoto (WKY) rats gavaged with distilled water served as controls. LV remodeling was evaluated, myocardial CTGF expression levels were detected using Western blotting, and cardiomyocyte apoptosis was detected with the TUNEL method.Compared with WKY and SHR-DW, atorvastatin treatment significantly decreased systolic blood pressure in SHRs; atorvastatin significantly inhibited LV remodeling, as indicated by the reduced LV weight/body weight ratio (SHR-ATV: 4.0 ± 0.4 versus SHR-DW: 4.7 ± 0.4 mg/g, P < 0.05), cardiomyocyte diameter (SHR-ATV: 16.2 ± 2.8 versus SHR-DW: 19.0 ± 1.0 µm, P < 0.05), and interstitial fibrosis (SHR-ATV: 3.3 ± 2.1 versus SHR-DW: 4.5 ± 1.8%, P < 0.05). Compared with WKY, myocardial CTGF expression was significantly increased and cardiomyocyte apoptosis decreased in SHRs. Compared with the SHR-DW group, atorvastatin treatment significantly inhibited myocardial CTGF expression (SHR-ATV: 0.69 ± 0.21 versus SHR-DW: 1.12 ± 0.27, P < 0.05) and induced cardiomyocyte apoptosis in SHRs (SHR-ATV: 5.2 ± 0.6 versus SHR-DW: 1.9 ± 0.3%, P < 0.05).The results indicate that early-stage administration of atorvastatin effectively prevented LV remodeling in SHRs, and that inhibition of myocardial CTGF expression and induction of cardiomyocyte apoptosis may be the underlying mechanisms.

Exacerbation of acute viral myocarditis by tobacco smoke is associated with increased viral load and cardiac apoptosis

Exposure to tobacco smoke is known to have deleterious cardiovascular effects. In this study, we tested whether exposure to tobacco smoke exacerbates the severity of viral myocarditis in mice. Viral myocarditis was generated in 4-week-old male BALB/c mice by injection of Encephalomyocarditis virus (EMCV). Four groups were studied: (1) control (C, no smoke and no virus); (2) smoke only (S, exposure to cigarette smoke for 90 min/day for 15 days); (3) virus only (V); and (4) exposure to smoke for 5 days before plus 10 days following virus injection (S+V). We found that viral inoculation preceded by smoke exposure increased mortality more than twofold compared with virus inoculation alone. In addition, the mRNA level of atrial natriuretic factor was significantly higher in S+V than among any of the other 3 groups. Virus injection significantly decreased cardiac function compared with controls, with further deterioration observed in the S+V group. We also observed a significantly increased rate of apoptosis, with an increased activation of apoptosis-inducing factor in hearts exposed to S+V compared with those exposed to V alone. Our results suggest that preexposure to smoke significantly exacerbates the severity of viral myocarditis, likely through increased viral load and increased cardiomyocyte cell death.

Oral levosimendan prevents postinfarct heart failure and cardiac remodeling in diabetic Goto-Kakizaki rats

BACKGROUND

Diabetes increases the risk for fatal myocardial infarction and development of heart failure. Levosimendan, an inodilator acting both via calcium sensitization and opening of ATP-dependent potassium channels, is used intravenously for acute decompensated heart failure. The long-term effects of oral levosimendan on postinfarct heart failure are largely unknown.

OBJECTIVE

To examine whether oral treatment with levosimendan could improve cardiac functions and prevent cardiac remodeling after myocardial infarction in a rodent model of type 2 diabetes, the Goto-Kakizaki rat.

METHODS

Myocardial infarction (MI) was induced to diabetic Goto-Kakizaki and nondiabetic Wistar rats by coronary ligation. Twenty-four hours after surgery, Goto-Kakizaki and Wistar rats were randomized into four groups: MI group without treatment, MI group with levosimendan for 12 weeks (1 mg/kg per day), sham-operated group, sham-operated group with levosimendan. Blood pressure, cardiac functions as wells as markers of cardiac remodeling were determined.

RESULTS

In Goto-Kakizaki rats, MI induced systolic heart failure, pronounced cardiac hypertrophy in the remote area, and sustained cardiomyocyte apoptosis. Postinfarct cardiac remodeling was associated with increased atrial natriuretic peptide, interleukin-6 and connective tissue growth factor mRNA expressions, as well as three-fold increased cardiomyocyte senescence, measured as cardiac p16 mRNA expression. Levosimendan improved cardiac function and prevented postinfarct cardiomyocyte hypertrophy, cardiomyocyte apoptosis, and cellular senescence. Levosimendan also ameliorated MI-induced atrial natriuretic peptide, IL-6, and connective tissue growth factor overexpression as well as MI-induced disturbances in calcium-handling proteins (SERCA2, Na-Ca exchanger) without changes in diabetic status or systemic blood pressure. In nondiabetic Wistar rats, MI induced systolic heart failure; however, the postinfarct cardiac remodeling was associated with less pronounced cardiac hypertrophy, cardiomyocyte apoptosis, inflammatory reaction, and induction of cellular senescence. Levosimendan only partially prevented postinfarct heart failure and cardiac remodeling in Wistar rats.

CONCLUSION

Our findings suggest a therapeutic role for oral levosimendan in prevention of postinfarct heart failure and cardiac remodeling in type 2 diabetes and underscore the importance of sustained cardiomyocyte apoptosis and induction of cellular senescence in the pathogenesis.

Sirtuin1-p53, forkhead box O3a, p38 and post-infarct cardiac remodeling in the spontaneously diabetic Goto-Kakizaki rat

Background

Diabetes is associated with changes in myocardial stress-response pathways and is recognized as an independent risk factor for cardiac remodeling. Using spontaneously diabetic Goto Kakizaki rats as a model of type 2 DM we investigated whether post-translational modifications in the Akt - FOXO3a pathway, Sirt1 - p53 pathway and the mitogen activated protein kinase p38 regulator are involved in post-infarct cardiac remodeling

Methods

Experimental myocardial infarction (MI) was induced by left anterior descending coronary artery ligation in spontaneously diabetic Goto-Kakizaki rats and non-diabetic Wistar controls. Cardiac function was studied by echocardiography. Myocardial hypertrophy, cardiomyocyte apoptosis and cardiac fibrosis were determined histologically 12 weeks post MI or Sham operation. Western blotting was used to study Caspase-3, Bax, Sirt1, acetylation of p53 and phosphorylation of p38, Akt and FOXO3a. Electrophoretic mobility shift assay was used to assess FOXO3a activity and its nuclear localization.

Results

Post-infarct heart failure in diabetic GK rats was associated with pronounced cardiomyocyte hypertrophy, increased interstitial fibrosis and sustained cardiomyocyte apoptosis as compared with their non-diabetic Wistar controls. In the GK rat myocardium, Akt- and FOXO3a-phosphorylation was decreased and nuclear localization of FOXO3a was increased concomitantly with increased PTEN protein expression. Furthermore, increased Sirt1 protein expression was associated with decreased p53 acetylation, and phosphorylation of p38 was increased in diabetic rats with MI.

Conclusions

Post-infarct heart failure in diabetic GK rats was associated with more pronounced cardiac hypertrophy, interstitial fibrosis and sustained cardiomyocyte apoptosis as compared to their non-diabetic controls. The present study suggests important roles for Akt-FOXO3a, Sirt1 - p53 and p38 MAPK in the regulation of post-infarct cardiac remodeling in type 2 diabetes.

Anti-perforin neutralizing antibody reduces myocardial injury in viral myocarditis

AIM

To investigate the role of anti-perforin neutralizing antibody in viral myocarditis.

METHODS

We divided 45 Balb/c mice randomly into 3 groups, a normal control group, a control group inoculated with coxsackie virus B3, and a group inoculated with anti-perforin neutralizing antibody. The second group was inoculated with 0.15 milliliters coxsackie virus B3, and the third group additionally with 0.1 milligrams/kilogram anti-perforin neutralizing antibody at time points of 6 hours and 3 days after infection. Histopathology was performed using haematoxylin and eosin, with apoptosis examined by the terminal transferase-mediated 2'-deoxyuridine 5'-triphosphate-biotin nick, end-labeling method, or Tunel. The expression of caspase-3 in myocardium was investigated by immunohistochemistry and reverse-transcription polymerase chain reaction.

RESULTS

The pathologic score, myocardial viral titers, average percentages of apoptotic cardiomyocytes, expression of active caspase-3 protein and messenger ribonucleic acid in the myocardium of the mice receiving anti-PFP neutralizing antibody therapy were all significantly reduced when compared to values from the group inoculated with coxsackie virus B3. The rates of expression of Caspase-3 and myocardial apoptosis were positively correlated with the scores for myocardial pathology.

CONCLUSION

Our results suggest that anti- perforin neutralizing antibody can reduce the myocardial damage by blocking the perforin/granzyme pathway, and downregulating the expression of messenger ribonucleic acid and protein of Caspase-3. These approaches may offer promising novel therapeutic strategies for the clinical treatment of viral myocarditis.

Enterovirus-related activation of the cardiomyocyte mitochondrial apoptotic pathway in patients with acute myocarditis

AIMS

We examined the impact of enterovirus (EV) cardiac replication activity on the endomyocardial mitochondrial pathway in patients with acute myocarditis.

METHODS AND RESULTS

Levels of apoptotic cardiomyocytes were determined by TUNEL and ligation-mediated polymerase chain reaction (PCR) assays and EV replication activity was assessed by immunostaining of EV VP1 capsid protein in ventricular myocytes of patients with acute myocarditis (n = 25), and healthy heart controls (n = 15). Ratio of cytosolic/mitochondrial cytochrome c concentrations was determined by ELISA assay, levels of active caspase-9 were determined by western blot analysis and Bax/Bcl2 mRNA ratio was assessed by real-time reverse transcription-polymerase chain reaction (RT-PCR) in the same cardiac tissues. Patients with EV-associated acute myocarditis (n = 15) exhibited a significantly higher number of apoptotic cardiomyocytes than those with non-EV-associated acute myocarditis (n = 10) and controls (n = 15) (P < 0.001). Endomyocardial ratio of cytosolic/mitochondrial cytochrome c concentrations and levels of active caspase-9 protein were significantly increased in EV than in non-EV-related myocarditis patients (P < 0.001). Moreover, Bax/Bcl2 mRNA ratio was significantly increased in EV than in non-EV-related myocarditis patients (P < 0.001).

CONCLUSION

Our findings evidence an EV-related activation of the cardiomyocyte mitochondrial apoptotic pathway in patients with acute myocarditis. Moreover, our results indicate that this EV-induced pro-apoptotic mechanism could be partly related to an up-regulation of Bax expression, and suggest that inhibition of this cell death process may constitute the basis for novel therapies.

Effects of levosimendan in experimental acute coxsackievirus myocarditis

BACKGROUND

Acute heart failure is a potentially fatal manifestation of viral myocarditis. Development of myocardial damage in myocarditis involves cardiomyocyte apoptosis. Levosimendan is a novel calcium sensitizing inotropic agent with anti-apoptotic properties. We studied the feasibility of inotropic treatment with levosimendan and its effects on apoptosis in experimental acute heart failure caused by coxsackievirus myocarditis.

MATERIALS AND METHODS

Adolescent BALB/c mice were infected with myocarditic Woodruff variant of coxsackievirus B3 (2 x 10(4) plaque-forming units). Mice were randomized into those receiving levosimendan 0.33 mg kg(-1) (total dose 1 mg kg(-1) day(-1)) (n = 20) or vehicle (n = 19) given orally by gauge three times a day for 7 days after infection. Left ventricular function was evaluated by transthoracic echocardiography and the mice were euthanized on day 7. Histopathology, amount of virus in the heart (virus titration assay) and cardiomyocyte apoptosis (TUNEL assay) were studied. Uninfected untreated control mice were also studied.

RESULTS

Infection resulted in histopathologically severe myocarditis and significant impairment of left ventricular function. Levosimendan treatment significantly improved ventricular function (fractional shortening 0.32 +/- 0.04 vs. 0.23 +/- 0.05, P = 0.005; contractility 0.60 +/- 0.12 vs. 0.39 +/- 0.14, P = 0.007 and myocardial performance index 0.36 +/- 0.06 vs. 0.62 +/- 0.15, P < 0.0001) compared with vehicle. Levosimendan also reduced cardiomyocyte apoptosis (0.26 +/- 0.08% vs. 0.44 +/- 0.15% in vehicle, P = 0.008), but did not have an effect on areas of myocardial necrosis or inflammation, or the amount of virus in the heart. Levosimendan treatment did not affect mortality (total mortality 63%). CONCLUSIONS; Levosimendan improves ventricular function and inhibits cardiomyocyte apoptosis; therefore, it is suggested as a potentially feasible therapy in acute heart failure caused by viral myocarditis.

Apoptosis in patients with acute myocarditis

Acute myocarditis is an acute inflammatory syndrome characterized by acute myocardial damage and dysfunction followed by a variable recovery over time with some patients progressing toward severe dilated cardiomyopathy. Cardiomyocyte apoptosis, a key pathologic feature of heart failure, may play a critical role in functional recovery in patients with acute myocarditis. The aim of the study was to investigate whether apoptosis predicts functional recovery in patients with acute myocarditis. Sixteen patients with biopsy-documented acute myocarditis were followed for 1 year with serial transthoracic echocardiography. Functional recovery was defined as 12-month left ventricular ejection fraction >40%. Cardiomyocyte apoptosis, leukocyte infiltration, and cell proliferation was assessed in all samples. A group of cases in which the diagnosis of acute myocarditis was made after death was also selected for comparison, and morphologically normal hearts from patients who died from a noncardiac cause were selected as controls. Six patients (38%) had functional recovery at 12 months, whereas 10 (62%) did not. The 2 groups had similar characteristics except for lower baseline left ventricular ejection fraction in the group with functional recovery. Apoptotic rate was found to be significantly higher in patients with acute myocarditis than in control hearts, and, unexpectedly, patients with functional recovery had significantly higher apoptotic rates than patients without recovery (3.2% vs 0.5%, p = 0.001). None of the patients with apoptotic rates below the median had functional recovery versus 86% of patients with apoptotic rates above the median (p <0.001). In conclusion, higher rates of cardiomyocyte apoptosis in patients with acute myocarditis are associated with functional recovery at 1 year.

Cardiac cell-specific apoptotic and cytokine responses to reovirus infection: determinants of myocarditic phenotype

BACKGROUND

The pathophysiologic mechanisms underlying viral myocarditis are not well defined. As a result, effective treatments do not exist and viral myocarditis remains a potentially lethal infection of the heart.

METHODS AND RESULTS

We used cultured rat cardiac myocytes and fibroblasts to investigate apoptosis and cytokine production in response to infection by myocarditic vs. non-myocarditic strains of reovirus. Myocarditic reovirus strain 8B and non-myocarditic strain DB188 replicate comparably in each cardiac cell type. However, strain 8B and related myocarditic reoviruses preferentially increase apoptosis of myocytes relative to fibroblasts, whereas DB188 and nonmyocarditic strains preferentially increase fibroblast apoptosis. Infection of cardiac fibroblasts with the nonmyocarditic strain DB188 elicits substantial increases in a panel of cytokines compared to fibroblasts infected with strain 8B or mock-infected controls. Analysis of culture supernatants using cytometric bead arrays revealed that DB188 enhanced release of interleukin (IL)-1beta, IL-4, IL-6, IL-10, IL-12(p70), GRO-KC, tumor necrosis factor-alpha, and MCP-1 relative to 8B or mock-infected controls (all P < .05).

CONCLUSION

We hypothesize that differential cytokine production and cell-specific apoptosis are important determinants of myocarditic potential of reoviral strains. Therapies that target the beneficial effects of cytokines in limiting cytopathic damage may offer an effective and novel treatment approach to viral myocarditis.

Novel therapeutic targets in viral myocarditis

Viral myocarditis is an elusive infection of the heart that is currently without an effective or definitive treatment. Viral myocarditis has a complex disease progression that can be divided into early, middle and late phases. Direct cytopathic injury, apoptosis, activation of the innate and adaptive immune system and cardiac remodeling have all been implicated in the pathogenesis of viral myocarditis. Novel treatment approaches are evolving at a rapid pace. The purpose of this review is to provide an update on current research focused on identifying potential treatment options for viral myocarditis.

Effects of levosimendan on cardiac remodeling and cardiomyocyte apoptosis in hypertensive Dahl/Rapp rats

BACKGROUND AND PURPOSE

Progression of heart failure in hypertensive Dahl rats is associated with cardiac remodeling and increased cardiomyocyte apoptosis. This study was conducted to study whether treatment with a novel inotropic vasodilator compound, levosimendan, could prevent hypertension-induced cardiac remodeling and cardiomyocyte apoptosis.

EXPERIMENTAL APPROACH

6-week-old salt-sensitive Dahl/Rapp rats received levosimendan (0.3 mg kg(-1) and 3 mg kg(-1) via drinking fluid) and high salt diet (NaCl 7%) for 7 weeks, Dahl/Rapp rats on low-salt diet served as controls. Blood pressure, cardiac functions by echocardiography, cardiomyocyte apoptosis by TUNEL technique, tissue morphology, myocardial expression of calcium cycling proteins, and markers of neurohumoral activation were determined.

KEY RESULTS

Untreated Dahl/Rapp rats on high salt diet developed severe hypertension, cardiac hypertrophy and moderate systolic dysfunction. 38% of Dahl/Rapp rats (9/24) survived the 7-week-follow-up period. Cardiomyocyte apoptosis was increased by 6-fold during high salt diet. Levosimendan improved survival (survival rates in low- and high-dose levosimendan groups 12/12 and 9/12, p<0.001 and p=0.05, respectively), increased cardiac function, and ameliorated cardiac hypertrophy. Levosimendan dose-dependently prevented cardiomyocyte apoptosis. Levosimendan normalized salt-induced increased expression of natriuretic peptide, and decreased urinary noradrenaline excretion. Levosimendan also corrected salt-induced decreases in myocardial SERCA2a protein expression and myocardial SERCA2a/NCX-ratio.

CONCLUSIONS AND IMPLICATIONS

Improved survival by the novel inotropic vasodilator levosimendan in hypertensive Dahl/Rapp rats is mediated, at least in part, by amelioration of hypertension-induced cardiac remodeling and cardiomyocyte apoptosis.

Antioxidant vitamin therapy alters sepsis-related apoptotic myocardial activity and inflammatory responses

This study examined the effects of antioxidant vitamins on several aspects of sepsis-related myocardial signaling cascades. Sprague-Dawley rats were divided into four groups: group 1, vehicle-treated shams; group 2, sham-operated rats given antioxidant vitamins (vitamin C, 24 mg/kg; vitamin E, 20 U/kg; vitamin A, 417 U/kg; and zinc, 3.7 ng/kg) by oral gavage in 0.5 ml water twice daily for 3 days and no septic challenge (vitamin-treated, sham-operated rats); group 3, intratracheal delivery of Streptococcus pneumoniae, 4 × 106 colony forming units in a volume of 0.3 ml phosphate buffer solution; group 4, S. pneumonia challenge as described for group 3 plus antioxidant vitamins (as described for group 2). Hearts collected 24 h after septic challenge were used to examine several aspects of cell signaling and ventricular function. As a result, when compared with sham-operated rats, sepsis in the absence of antioxidant therapy promoted NF-κB activation, increased mitochondrial cytochrome c release, increased myocyte cytokine secretion, increased caspase activation, and impaired left ventricular function. Antioxidant vitamin therapy plus septic challenge prevented NF-κB activation, reduced mitochondrial cytochrome c release, decreased caspase activity, abrogated cardiomyocyte secretion of inflammatory cytokines, and improved myocardial contractile function. In conclusion, antioxidant vitamin therapy abrogated myocardial inflammatory cytokine signaling and attenuated sepsis-related contractile dysfunction, suggesting that antioxidant vitamin therapy may be a potential approach to treat injury and disease states characterized by myocardial dysfunction.

Fatal myocardial necrosis caused by Staphylococcus lugdunensis and cytomegalovirus in a patient with scleroderma

A 42-year-old woman developed a rapidly progressing fatal heart failure. At the autopsy extensive necrosis of the myocardium was seen, with an almost complete absence of inflammatory cells and the presence of bacterial structures identified as Staphylococcus lugdunensis by PCR. In addition, the cytomegalovirus genome was found to be located inside the cardiomyocytes.

Novel role for integrin-linked kinase in modulation of coxsackievirus B3 replication and virus-induced cardiomyocyte injury

Viral myocarditis is a major cause of sudden cardiac death in children and young adults. Among viruses, coxsackievirus B3 (CVB3) is the most common agent for myocarditis. Recently, more consideration has been given to the role of signaling pathways in pathogenesis of enteroviral myocarditis, providing new platform for identifying a new potential therapeutic target for this, so far, incurable disease. Previously, we reported on the role of the protein kinase-B/Akt in CVB3 replication and virus-induced cell injury. Here, we report on regulation of virus-induced Akt activation by the integrin-linked kinase in infected mouse cardiomyocytes and HeLa cells. This study also presents the first observation that inhibition of ILK in CVB3-infected cells significantly improves the viability of infected cells, while blocking viral replication and virus release. Complementary experiments using a constitutively active form of Akt1 revealed that the observed protective effect of ILK inhibition is dependent on the associated downregulation of virus-induced Akt activation. To our knowledge, this is the first report of such beneficial effects of ILK inhibition in a viral infection model and conveys new insights in our efforts to characterize a novel therapeutic target for treatment of enteroviral myocarditis.