Viral myocarditis induced by Coxsackievirus B3 in A.BY/SnJ mice: analysis of changes in the myocardial proteome

Pathophysiological Mechanisms of Cardiac Dysfunction in Transgenic Mice with Viral Myocarditis

Viral myocarditis is pathologically associated with RNA viruses such as coxsackievirus B3 (CVB3), or more recently, with SARS-CoV-2, but despite intensive research, clinically proven treatment is limited. Here, by use of a transgenic mouse strain (TG) containing a CVB3ΔVP0 genome we unravel virus-mediated cardiac pathophysiological processes in vivo and in vitro. Cardiac function, pathologic ECG alterations, calcium homeostasis, intracellular organization and gene expression were significantly altered in transgenic mice. A marked alteration of mitochondrial structure and gene expression indicates mitochondrial impairment potentially contributing to cardiac contractile dysfunction. An extended picture on viral myocarditis emerges that may help to develop new treatment strategies and to counter cardiac failure.

The repressor and co-activator HsfB1 regulates the major heat stress transcription factors in tomato

Plants code for a multitude of heat stress transcription factors (Hsfs). Three of them act as central regulators of heat stress (HS) response in tomato (Solanum lycopersicum). HsfA1a regulates the initial response, and HsfA2 controls acquired thermotolerance. HsfB1 is a transcriptional repressor but can also act as co-activator of HsfA1a. Currently, the mode of action and the relevance of the dual function of HsfB1 remain elusive. We examined this in HsfB1 overexpression or suppression transgenic tomato lines. Proteome analysis revealed that HsfB1 overexpression stimulates the co-activator function of HsfB1 and consequently the accumulation of HS-related proteins under non-stress conditions. Plants with enhanced levels of HsfB1 show aberrant growth and development but enhanced thermotolerance. HsfB1 suppression has no significant effect prior to stress. Upon HS, HsfB1 suppression strongly enhances the induction of heat shock proteins due to the higher activity of other HS-induced Hsfs, resulting in increased thermotolerance compared with wild-type. Thereby, HsfB1 acts as co-activator of HsfA1a for several Hsps, but as a transcriptional repressor on other Hsfs, including HsfA1b and HsfA2. The dual function explains the activation of chaperones to enhance protection and regulate the balance between growth and stress response upon deviations from the homeostatic levels of HsfB1.

Chronic β-adrenergic stimulation reverses depressed Ca handling in mice overexpressing inhibitor-2 of protein phosphatase 1

RATIONALE

A higher expression/activity of type 1 serine/threonine protein phosphatase 1 (PP1) may contribute to dephosphorylation of cardiac regulatory proteins triggering the development of heart failure.

OBJECTIVE

Here, we tested the putatively protective effects of PP1 inhibitor-2 (I₂) overexpression using a heart failure model induced by chronic β-adrenergic stimulation.

METHODS AND RESULTS

Transgenic (TG) and wild-type (WT) mice were subjected to isoprenaline (ISO) or isotonic NaCl solution supplied via osmotic minipumps for 7 days. I₂ overexpression was associated with a depressed PP1 activity. Basal contractility was unchanged in catheterized mice and isolated cardiomyocytes between TG^NaCl and WT^NaCl. TG^ISO mice exhibited more fibrosis and a higher expression of hypertrophy marker proteins as compared to WT^ISO. After acute administration of ISO, the contractile response was accompanied by a higher sensitivity in TG^ISO as compared to WT^ISO. In contrast to basal contractility, the peak amplitude of [Ca]_i and SR Ca load were reduced in TG^NaCl as compared to WT^NaCl. These effects were normalized to WT levels after chronic ISO stimulation. Cardiomyocyte relaxation and [Ca]_i decay kinetics were hastened in TG^ISO as compared to WT^ISO, which can be explained by a higher phospholamban phosphorylation at Ser¹⁶. Chronic catecholamine stimulation was followed by an enhanced expression of GSK3β, whereas the phosphorylation at Ser⁹ was lower in TG as compared to the corresponding WT group. This resulted in a higher I₂ phosphorylation that may reactivate PP1.

CONCLUSION

Our findings suggest that the basal desensitization of β-adrenergic signaling and the depressed Ca handling in TG by inhibition of PP1 is restored by a GSK3β-dependent phosphorylation of I₂.

Integration of "omics" techniques: Dronedarone affects cardiac remodeling in the infarction border zone

Dronedarone improves microvascular flow during atrial fibrillation and reduces the infarct size in acute models of myocardial infarction. However, dronedarone might be harmful in patients with recent decompensated heart failure and increases mortality in patients with permanent atrial fibrillation. A pathophysiological explanation for these discrepant data is lacking. This study investigated the effects of dronedarone on gene and protein expression in the infarcted area and border zone in pigs subjected to anterior ischemia/reperfusion myocardial infarction. The ischemia/reperfusion myocardial infarction was induced in 16 pigs. Eight pigs were treated with dronedarone for 28 days after myocardial infarction, the remaining pigs served as control. Microarray-based transcriptome profiling and 2D-DIGE-based proteome analysis were used to assess the effects of dronedarone on left ventricular gene expression in healthy (LV), infarcted (MI), and border zone tissue. Selected targets were validated by RT-qPCR or immunoblot analyses, with special emphasize given to the transcriptome/proteome overlap. Combined "omics" analysis was performed to identify most significant disease and function charts affected by dronedarone and to establish an integrated network. The levels of 879 (BZ) or 7 (MI) transcripts and 51 (LV) or 15 (BZ) proteins were significantly altered by dronedarone, pointing to a substantial efficacy of dronedarone in the border zone. Transcriptome and proteome data indicate that dronedarone influences post-infarction remodeling processes and identify matricellular proteins as major targets of dronedarone in this setting. This finding is fully supported by the disease and function charts as well as by the integrated network established by combined "omics". Dronedarone therapy alters myocardial gene expression after acute myocardial infarction with pronounced effects in the border zone. Dronedarone promotes infarct healing via regulation of periostin and might contribute to the limitation of its expansion as well as cardiac rupture. Thus, there are no experimental hints that dronedarone per se has direct harmful effects after MI in ventricular tissue. Impact statement Dronedarone reduced the infarct size in models of acute myocardial infarction (MI). Here, we show that dronedarone attenuates many of the substantial changes in gene expression that are provoked by acute myocardial infarction (AMI) in pigs. Dronedarone modifies the expression of gene panels related to post-infarction cardiac healing and remodeling processes and, most remarkably, this occurs predominantly in the infarction border-zone and much less so in the vital or infarcted myocardium. Combined "omics" identified matricellular proteins and ECM as major dronedarone-regulated targets and emphasizes their relevance for Disease Charts and Tox Function Charts associated with tissue remodeling and cellular movement. The results demonstrate dronedarone's capability of regulating cardiac repair and remodeling processes specifically in the infarction border zone and identify underlying mechanisms and pathways that might be employed in future therapeutic strategies to improve long-term cardiac tissue function and stability.

[Increased myocardial expression of Toll-like receptors 2 and 9 as a marker of active myocarditis and a possible predictor of therapeutic effectiveness]

AIM

to investigate the myocardial expression of some structural proteins and markers of cellular proliferation and innate immunity for assessing their possible diagnostic and prognostic role in patients with chronic myocarditis.

SUBJECTS AND METHODS

The investigation enrolled 23 patients (16 men; mean age, 52.0±12.4 years (range, 27 to 73) with various forms of noncoronarogenic myocardial injury who underwent right ventricular endomyocardial biopsy (n=4), intraoperative left ventricular biopsy (n=17) or autopsy (n=2). Prior to their morphological examination, the patients were divided into two groups: 1) 10 patients with dilated cardiomyopathy and presumptive myocarditis; 2) 13 patients with valvular heart disease, hypertrophic cardiomyopathy, myxoma, and chronic pulmonary thromboembolism, presumptively without myocarditis. Along with myocardial histological and immunohistochemical (IHC) examinations, the expression of vimentin, desmin, c-kit, Ki-67, and Toll-like receptors (TLR) 2 and 9 was determined. Polymerase chain reaction was used to identify whether herpes viruses of and parvovirus B19 genomes were present in the blood and myocardial samples; indirect ELISA was applied to estimate the blood level of antibodies against various cardiac antigens.

RESULTS

According to the histological findings, active/borderline lymphocytic myocarditis was diagnosed in all the patients (Group 1) and in 6 patients (Group 2) in conjunction with the underlying disease (only in 9 and 7 patients, respectively), viral genome was detected in the myocardium of 15 patients, including in 5 without morphological signs of myocarditis (parvovirus B19 (n=11), herpesvirus 6 (n=4), herpes simplex virus types 1 and 2 (n=1), Epstein-Barr virus (n=2), and cytomegalovirus (n=1)), and in the blood (n=4). A marked correlation was found between TLR2 and TLR9 expressions and the morphological pattern of active myocarditis in the absence of this correlation with the expression level of other studied markers. The expression level of TLR2 in patients with and without borderline myocarditis was 0 [0; 0,75] and in those with active myocarditis was 1.5 [1; 1,5] points; that of TLR9 was 2 [2; 2] and 4 [3; 4] points, respectively (p<0.001). The expression of TLR2 and TLR9 in patients with borderline myocarditis was lower than in those without myocarditis (0 [0; 0] versus 0 [0; 1] and 2 [1,5; 2] versus 2 [2; 3] points), which can reflect cardiomyocyte destruction/depletion at later stages of the disease. There was also a close correlation between the expression level of TLR2 and that of TLR9 (r=0.824; p<0.001) and with Ki-67 levels (r=-0.531 and r=-0.702; p<0.01). There was also a correlation of the expression of the studied markers with viral persistence (desmin), the degree of myocardial dysfunction and cardiosclerosis (c-kit), which calls for further investigations.

CONCLUSION

Determination of the myocardial expression level of TLR2 and TLR9 may serve as an immunohistochemical marker for myocarditis and preservation of its activity, which is especially valuable in patients with borderline forms. The marked expression of these markers for innate immunity may reflect both one of the mechanisms of genetic predisposition to myocarditis and its severe course and their secondary activation in the pathogenesis of the disease and is a potential target of therapy.

Personalized medicine in inflammatory cardiomyopathy

Inflammatory cardiomyopathy is the result of persistent myocardial inflammation which can arise from both infectious or noninfectious causes. While most patients with acute myocarditis recover, up to 20% develop inflammatory cardiomyopathy with chronic heart failure. The interaction between host factors and factors of the agent that triggered myocardial inflammation must be considered to fully understand the individual mechanism of disease. Several inflammatory biomarkers, histology, immunohistochemistry, advanced imaging technologies as well as molecular high-throughput sequencing techniques help to identify disease pathways and to establish a comprehensive, individualized treatment approach, which can include anti-inflammatory medication, antiviral drugs and heart failure therapy. This might help to prevent transition from acute inflammation to persistent heart failure and to restore cardiac function.

Dynamic adaptation of myocardial proteome during heart failure development

Heart failure (HF) development is characterized by huge structural changes that are crucial for disease progression. Analysis of time dependent global proteomic adaptations during HF progression offers the potential to gain deeper insights in the disease development and identify new biomarker candidates. Therefore, hearts of TAC (transverse aortic constriction) and sham mice were examined by cardiac MRI on either day 4, 14, 21, 28, 42, and 56 after surgery (n = 6 per group/time point). At each time point, proteomes of the left (LV) and right ventricles (RV) of TAC and sham mice were analyzed by mass spectrometry (MS). In TAC mice, systolic LV heart function worsened from day 4 to day 14, remained on a stable level from day 14 to day 42, and showed a further pronounced decline at day 56. MS analysis identified in the LV 330 and in RV 246 proteins with altered abundance over time (TAC vs. sham, fc≥±2). Functional categorization of proteins disclosed the time-dependent alteration of different pathways. Heat shock protein beta-7 (HSPB7) displayed differences in abundance in tissue and serum at an early stage of HF. This study not only provides an overview of the time dependent molecular alterations during transition to HF, but also identified HSPB7 as a novel blood biomarker candidate for the onset of cardiac remodeling.

Sizing up models of heart failure: Proteomics from flies to humans

Cardiovascular disease is the leading cause of death in the western world. Heart failure is a heterogeneous and complex syndrome, arising from various etiologies, which result in cellular phenotypes that vary from patient to patient. The ability to utilize genetic manipulation and biochemical experimentation in animal models has made them indispensable in the study of this chronic condition. Similarly, proteomics has been helpful for elucidating complicated cellular and molecular phenotypes and has the potential to identify circulating biomarkers and drug targets for therapeutic intervention. In this review, the use of human samples and animal model systems (pig, dog, rat, mouse, zebrafish, and fruit fly) in cardiac research is discussed. Additionally, the protein sequence homology between these species and the extent of conservation at the level of the phospho-proteome in major kinase signaling cascades involved in heart failure are investigated.

MiR-126 promotes coxsackievirus replication by mediating cross-talk of ERK1/2 and Wnt/β-catenin signal pathways

Coxsackievirus B3 (CVB3) is one of the most prevalent causes of viral myocarditis and is associated with many other pathological conditions. CVB3 replication relies on host cellular machineries and causes direct damage to host cells. MicroRNAs have been found to regulate viral infections but their roles in CVB3 infection are still poorly understood. Here we describe a novel mechanism by which miR-126 regulates two signal pathways essential for CVB3 replication. We found that CVB3-induced ERK1/2 activation triggered the phosphorylation of ETS-1 and ETS-2 transcription factors, which induced miR-126 upregulation. By using both microRNA mimics and inhibitors, we proved that the upregulated miR-126 suppressed sprouty-related, EVH1 domain containing 1 (SPRED1) and in turn enhanced ERK1/2 activation. This positive feedback loop of ERK1/2-miR-126-ERK1/2 promoted CVB3 replication. Meanwhile, miR-126 expression stimulated GSK-3β activity and induced degradation of β-catenin through suppressing LRP6 and WRCH1, two newly identified targets in the Wnt/β-catenin pathway, which sensitized the cells to virus-induced cell death and increased viral progeny release to initiate new infections. Our results demonstrate that upregulated miR-126 upon CVB3 infection targets SPRED1, LRP6, and WRCH1 genes, mediating cross-talk between ERK1/2 and Wnt/β-catenin pathways, and thus promoting viral replication and contributes to the viral cytopathogenicity.

Proteomic analyses of age related changes in A.BY/SnJ mouse hearts

Background

A.BY/SnJ mice are used to study pathological alterations in the heart due to enteroviral infections. Since age is a well-known factor influencing the susceptibility of mice to infection, response to stress and manifestation of cardiovascular diseases, the myocardial proteome of A.BY/SnJ mice aged 1 and 4 months was comparatively studied using two dimensional-differential in-gel electrophoresis (2D-DIGE) and liquid chromatography tandem mass spectrometry (LC-MS/MS).

Results

Complementary analyses by 2D-DIGE and gel-free LC-MS/MS revealed 96 distinct proteins displaying age associated alterations in their levels. Proteins related to protein transport, and transport chain, lipid metabolism and fatty acid transport showed significant changes in 4 months old mouse hearts compared to juvenile hearts. Proteins involved in lipid metabolism and transport were identified at significantly higher levels in older mice and dysregulation of proteins of the respiratory transport chain were observed.

Conclusion

The current proteomics study discloses age dependent changes occurring in the hearts already in young mice of the strain A.BY/SnJ. Besides alterations in protein transport, we provide evidence that a decrease of ATP synthase in murine hearts starts already in the first months of life, leading to well-known low expression levels manifested in old mice thereby raising the possibility of reduced energy supply. In the first few months of murine life this seems to be compensated by an increased lipid metabolism. The functional alterations described should be considered during experimental setups in disease related studies.

Proteomic and biochemical analyses reveal the activation of unfolded protein response, ERK-1/2 and ribosomal protein S6 signaling in experimental autoimmune myocarditis rat model

BACKGROUND

To investigate the molecular and cellular pathogenesis underlying myocarditis, we used an experimental autoimmune myocarditis (EAM)-induced heart failure rat model that represents T cell mediated postinflammatory heart disorders.

RESULTS

By performing unbiased 2-dimensional electrophoresis of protein extracts from control rat heart tissues and EAM rat heart tissues, followed by nano-HPLC-ESI-QIT-MS, 67 proteins were identified from 71 spots that exhibited significantly altered expression levels. The majority of up-regulated proteins were confidently associated with unfolded protein responses (UPR), while the majority of down-regulated proteins were involved with the generation of precursor metabolites and energy metabolism in mitochondria. Although there was no difference in AKT signaling between EAM rat heart tissues and control rat heart tissues, the amounts and activities of extracellular signal-regulated kinase (ERK)-1/2 and ribosomal protein S6 (rpS6) were significantly increased. By comparing our data with the previously reported myocardial proteome of the Coxsackie viruses of group B (CVB)-mediated myocarditis model, we found that UPR-related proteins were commonly up-regulated in two murine myocarditis models. Even though only two out of 29 down-regulated proteins in EAM rat heart tissues were also dysregulated in CVB-infected rat heart tissues, other proteins known to be involved with the generation of precursor metabolites and energy metabolism in mitochondria were also dysregulated in CVB-mediated myocarditis rat heart tissues, suggesting that impairment of mitochondrial functions may be a common underlying mechanism of the two murine myocarditis models.

CONCLUSIONS

UPR, ERK-1/2 and S6RP signaling were activated in both EAM- and CVB-induced myocarditis murine models. Thus, the conserved components of signaling pathways in two murine models of acute myocarditis could be targets for developing new therapeutic drugs or methods aimed at treating enigmatic myocarditis.