Genetics of and pathogenic mechanisms in arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart disease, associated with a high risk of sudden cardiac death. ARVC has been termed a ‘disease of the desmosome’ based on the fact that in many cases, it is caused by mutations in genes encoding desmosomal proteins at the specialised intercellular junctions between cardiomyocytes, the intercalated discs. Desmosomes maintain the structural integrity of the ventricular myocardium and are also implicated in signal transduction pathways. Mutated desmosomal proteins are thought to cause detachment of cardiac myocytes by the loss of cellular adhesions and also affect signalling pathways, leading to cell death and substitution by fibrofatty adipocytic tissue. However, mutations in desmosomal proteins are not the sole cause for ARVC as mutations in non-desmosomal genes were also implicated in its pathogenesis. This review will consider the pathology, genetic basis and mechanisms of pathogenesis for ARVC.     

Heat shock protein 70 and anti-heat shock protein 70 antibodies in patients with chronic glomerulonephritis

We evaluated the heat shock system 70 (HSP70) in patients with chronic glomerulonephritis (CGN). Seventy-six patients with CGN patients were included in our study. Ten patients with mild proteinuria (median 0.48 [0.16–0.78] g/24 h) and ten healthy subjects served as positive and negative controls, respectively. Urinary levels of HSP70, interleukin-10, and serum levels of anti-HSP70 were measured by ELISA. The immunohistochemical peroxidase method was used to study the expression of HSP70 and Foxp3+ in kidney biopsies. Treg^FoxP3+ cells in the interstitium were determined morphometrically. Median urinary HSP70 levels in patients with nephrotic syndrome (NS) [6.57 (4.49–8.33) pg/mg] and subnephrotic range proteinuria [5.7 (4.12–6.9) pg/mg] were higher (p?<?0.05) than in positive [3.7 (2.5–4.82) pg/mg] and negative [3.78 (2.89–4.84) pg/mg] controls. HSP70 expression index in tubular cells positively correlated with urinary HSP70 (Rs?=?0.948, р?<?0.05) and proteinuria (Rs?=?0.362, p?<?0.05). The number of Treg^Foxp3+ cells in the kidney interstitium and interleukin-10 excretion were lower in patients with NS. Anti-HSP70 antibody serum levels in patients with NS [21.1 (17.47–29.72) pg/ml] and subnephrotic range proteinuria [24.9 (18.86–30.92) pg/ml] were significantly higher than in positive [17.8 (12.95–23.03) pg/ml] and negative [18.9 (13.5–23.9) pg/ml] controls. In patients with CGN, increasing proteinuria was associated with higher HSP70 renal tissue and urinary levels. However, activation of HSP70 in patients with nephrotic syndrome did not lead to an increase in tissue levels of Treg^Foxp3+ cells or to the release of IL-10.     

Cardiac arrest secondary to arrhythmogenic right ventricular cardiomyopathy in an adolescent male

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a rare, genetically-inherited cardiomyopathy that may be fatal. We present the case of a 17 year old male who presented after a witnessed cardiac arrest with indeterminate echocardiogram and electrocardiogram (ECG) findings for a specific etiology. Genetic testing revealed a mutation in the PKP2 and DSC2 genes, consistent with ARVC. This report outlines the presentation of ARVC as an aborted sudden cardiac death episode in a previously asymptomatic teenager, investigations for ARVC and highlights the importance of adequate cardiopulmonary resuscitation in the overall prognosis. Implantable cardiac defibrillator (ICD) placement for secondary prevention is necessary.     

TMEM43 mutations associated with arrhythmogenic right ventricular cardiomyopathy in non-Newfoundland populations

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a myocardial disease characterized by fibro-fatty replacement of right ventricular free wall myocardium and life-threatening ventricular arrhythmias. A missense mutation, c.1073C>T (p.S358L) in the transmembrane protein 43 (TMEM43) gene, has been genetically identified to cause ARVC type 5 in a founder population from Newfoundland. It is unclear whether this mutation occurs in other populations outside of this founder population or if other variants of TMEM43 are associated with ARVC disease. We sought to identify non-Newfoundland individuals with TMEM43 variants among patient samples sent for genetic assessment for possible ARVC. Of 195 unrelated individuals with suspected ARVC, mutation of desmosomal proteins was seen in 28 and the p.S358L TMEM43 mutation in six. We identified a de novo p.S358L mutation in a non-Newfoundland patient and five separate rare TMEM43 (four novel) sequence variants in non-Newfoundland patients, each occurring in an evolutionarily conserved amino acid. TMEM43 mutations occur outside of the founder population of the island of Newfoundland where it was originally described. TMEM43 sequencing should be incorporated into clinical genetic testing for ARVC patients.     

Soluble ST2 is associated with disease severity in arrhythmogenic right ventricular cardiomyopathy

Purpose: Diagnostic and prognostic evaluation remains challenging in arrhythmogenic right ventricular cardiomyopathy (ARVC). We measured plasma concentration of soluble ST2 (sST2) and assessed its association with right ventricular (RV) function and ventricular arrhythmias in patients with ARVC.

Methods: We included patients with ARVC and genotype positive relatives. Soluble ST2 was determined by ELISA. We assessed myocardial function by echocardiography including strain by speckle tracking technique.

Results: We included 44 subjects (age 41?±?15 years, 21 (48%) female). Soluble ST2 was associated with RV global strain (r?=?0.44; p?=?0.008), as well as with left ventricular (LV) function. Plasma levels of sST2 were higher in patients with ventricular arrhythmias than in patients without ventricular arrhythmias (35?±?13?ng/mL vs. 26?±?7?ng/mL, p?=?0.009). The association between sST2 and ventricular arrhythmias remained significant even after adjusting for RV function (Wald?=?5.2; p?=?0.02).

Conclusions: Soluble ST2 is associated with RV and LV function in patients with ARVC. Soluble ST2 may aid in the determination of disease severity in ARVC.     

A small heat shock protein cooperates with heat shock protein 70 systems to reactivate a heat-denatured protein

Small heat shock proteins (sHsps) are a diverse group of heat-induced proteins that are conserved in prokaryotes and eukaryotes and are especially abundant in plants. Recent in vitro data indicate that sHsps act as molecular chaperones to prevent thermal aggregation of proteins by binding non-native intermediates, which can then be refolded in an ATP-dependent fashion by other chaperones. We used heat-denatured firefly luciferase (Luc) bound to pea (Pisum sativum) Hsp18.1 as a model to define the minimum chaperone system required for refolding of a sHsp-bound substrate. Heat-denatured Luc bound to Hsp18.1 was effectively refolded either with Hsc/Hsp70 from diverse eukaryotes plus the DnaJ homologs Hdj1 and Ydj1 (maximum = 97% Luc reactivation with k(ob) = 1.0 x 10(-2)/min), or with prokaryotic Escherichia coli DnaK plus DnaJ and GrpE (100% Luc reactivation, k(ob) = 11.3 x 10(-2)/min). Furthermore, we show that Hsp18.1 is more effective in preventing Luc thermal aggregation than the Hsc70 or DnaK systems, and that Hsp18.1 enhances the yields of refolded Luc even when other chaperones are present during heat inactivation. These findings integrate the aggregation-preventive activity of sHsps with the protein-folding activity of the Hsp70 system and define an in vitro system for further investigation of the mechanism of sHsp action.     

Proteomic analysis of small heat shock protein isoforms in barley shoots

The analysis of stress-responsiveness in plants is an important route to the discovery of genes conferring stress tolerance and their use in breeding programs. High temperature is one of the environmental stress factors that can affect the growth and quality characteristics of barley (Hordeum vulgare). In this study a proteomic analysis (2D-PAGE, MS) was used to detect the effects of heat shock on the protein pattern of an abiotic stress-tolerant (Mandolina) and an abiotic stress-susceptible (Jubilant) barley cultivar. Evaluation of two-dimensional gels revealed several proteins to be differentially expressed as a result of heat stress in both cultivars. The protein spots of interest were, after an in-gel tryptic digestion, further investigated by mass spectrometry. For the analysis of the peptide mixture, we both used a matrix-assisted laser desorption/ionization (MALDI) tandem time of flight mass spectrometer (TOF/TOF) and an automated nano-HPLC system coupled to an electrospray ionization-quadrupole linear ion trap (Q-TRAP) instrument. The hyphenation of the latter techniques proved to be a powerful technique as shown by the identification of six isoforms of a 16.9 kDa sHSP in one single spot. We observed that S-adenosylmethionine synthetase (SAM-S) was differentially expressed between the two cultivars. Recent results refer to the role of SAM-S as being involved in abiotic stress tolerance. Furthermore, comparison of the heat shock treated samples also revealed several small heat shock proteins (sHSP), of which distinct isoforms could be characterised.     

Proteomic analysis of an imatinib-resistant K562 cell line highlights opposing roles of heat shock cognate 70 and heat shock 70 proteins in resistance

Understanding the molecular basis of resistance to imatinib, a tyrosine kinase inhibitor used as front-line therapy in chronic myeloid leukemia, remains a challenge for successful treatment. In an attempt to identify new mechanisms of resistance, we performed a comparative proteomic analysis of an imatinib-resistant cell line generated from the erythroblastic cell line K562 (K562-r) for which no known mechanism of resistance has been detected. Bidimensional gel electrophoresis was carried out to compare the protein expression pattern of imatinib-sensitive and of imatinib-resistant K562 cells. Among the 400 matched spots on five pairs of gels, only 14 spots had a significantly increased or decreased expression leading to the identification of 24 proteins identified as scaffold proteins, metabolic enzymes, DNA translation and maturation, and chaperon proteins. Among the chaperon family, only Hsp70 and Hsc70 are overexpressed in K562-r, results confirmed by Western blotting. We recently reported the participation of Hsp70 overexpression in imatinib resistance whereas a role for Hsc70 has yet to be determined. Hsc70 is not involved in imatinib resistance as the inhibition of its expression by siRNA does not restore sensitivity to imatinib. In contrast, the induced decreased expression of Hsc70 was accompanied by a greater overexpression of Hsp70. This proteomic study therefore suggests opposing roles of Hsp70 and Hsc70 in imatinib resistance.     

Proteomic analysis of left ventricular remodeling in an experimental model of heart failure

The development of chronic heart failure (CHF) following myocardial infarction is characterized by progressive alterations of left ventricle (LV) structure and function called left ventricular remodeling (LVR), but the mechanism of LVR remains still unclear. Moreover, information concerning the global alteration protein pattern during the LVR will be helpful for a better understanding of the process. We performed differential proteomic analysis of whole LV proteins using an experimental model of CHF in which myocardial infarction was induced in adult male rats by left coronary ligation. Among 1000 protein spots detected in 2D-gels, 49 were differentially expressed in LV of 2-month-old CHF-rats, corresponding to 27 different identified proteins (8 spots remained unidentified), classified in different functional groups as being heat shock proteins, reticulum endoplasmic stress proteins, oxidative stress proteins, glycolytic enzymes, fatty acid metabolism enzymes, tricarboxylic acid cycle proteins and respiratory chain proteins. We validated modulation of selected proteins using Western blot analysis. Our data showed that proteins involved in cardiac metabolism and oxidative stress are modulated during LVR. Interestingly, proteins of stress response showed different adaptation pathways in the early and late phase of LVR. Expression of four proteins, glyceraldehyde-3-phosphate dehydrogenase, alphaB-crystallin, peroxiredoxin 2, and isocitrate dehydrogenase, was linked to echographic parameters according to heart failure severity.     

The heat shock protein HSP70 and heat shock cognate protein HSC70 contribute to antimony tolerance in the protozoan parasite leishmania

Antimony-containing drugs are still the drugs of choice in the treatment of infections caused by the parasite Leishmania. Resistance to antimony is now common in some parts of the world, and several mechanisms of resistance have been described. By transfecting cosmid banks and selecting with potassium antimonyl tartrate (SbIII), we have isolated a cosmid associated with resistance. This cosmid contains 2 copies of the heat shock protein 70 (HSP70) and 1 copy of the heat shock cognate protein 70 (HSC70). Several data linked HSP70 to antimony response and resistance. First, several Leishmania species, both as promastigotes and amastigotes, increased the expression of their HSP70 proteins when grown in the presence of 1 or 2 times the Effect Concentration 50% of SbIII. In several mutants selected for resistance to either SbIII or to the related metal arsenite, the HSP70 proteins were found to be overexpressed. This increase was also observed in revertant cells grown for several passages in the absence of SbIII, suggesting that this increased production of HSP70 is stable. Transfection of HSP70 or HSC70 in Leishmania cells does not confer resistance directly, though these transfectants were better able to tolerate a shock with SbIII. Our results are consistent with HSP70 and HSC70 being a first line of defense against SbIII until more specific and efficient resistance mechanisms take over.     

Mutation in human desmoplakin domain binding to plakoglobin causes a dominant form of arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVD/C) is a genetically heterogeneous disease characterized by progressive degeneration of the right ventricular myocardium and increased risk of sudden death. Here, we report on a genome scan in one Italian family in which the disease appeared unlinked to any of the six different ARVD loci reported so far; we identify a mutation (S299R) in exon 7 of desmoplakin (DSP), which modifies a putative phosphorylation site in the N-terminal domain binding plakoglobin. It is interesting that a nonsense DSP mutation was reported elsewhere in the literature, inherited as a recessive trait and causing a biventricular dilative cardiomyopathy associated with palmoplantar keratoderma and woolly hairs. Therefore, different DSP mutations might produce different clinical phenotypes, with different modes of inheritance.     

Association of heat shock protein 70 with semen quality in boars

This study attempted to clarify the relationship between the levels of 70kDa heat shock protein (HSP70) and semen quality in boars. Semen samples from 29 (13 Duroc, 9 Landrace, and 7 Yorkshire) boars (mean age=25.2+/-2.2 months) were examined. Three to four ejaculates per boar, collected during cool and hot seasons, were evaluated in terms of the sperm concentration, sperm motility, percentage of normal and abnormal sperm, as well as percentage of sperm with proximal and distal plasma droplets. Significant seasonal and breed differences in semen quality were observed. Experimental results indicate that the semen quality of Landrace boars was better than those of Yorkshire and Duroc boars (P<0.05) and semen quality declined significantly during the hot season (P<0.05). One-dimensional SDS-PAGE analysis of spermatozoa proteins indicated that protein profiles did not significantly differ between seasons and among breeds. Both constitutive and stress-inducible form of HSP70 were detected in boar spermatozoa by Western blot analysis. The level of HSP70, which revealed no difference among breeds within a season, was significantly lower during the hot season in all the three breeds (P<0.05). Although there appeared to be low correlation coefficients between the level of HSP70 and semen quality traits, the semen quality tended to decline significantly in samples with a lower level of HSP70. Results in this study suggest that the levels of HSP70 in boar spermatozoa are significantly lower during the hot season and might be associated with semen quality.     

Gender differences in right ventricular function in patients with non-ischaemic cardiomyopathy

Aim

To evaluate sex-related differences in right ventricular (RV) function, assessed with cardiac magnetic resonance imaging, in patients with stable non-ischaemic dilated cardiomyopathy.

Methods

Prospective multicentre study. We included 71 patients (38 men) and 14 healthy volunteers.

Results

Mean age was 60.9 ± 12.2 years. Men presented higher levels of haemoglobin and white blood cell counts than women, and performed better in cardiopulmonary stress testing. A total of 24 patients (12 women) presented severe left ventricular (LV) systolic dysfunction, 32 (13 female) moderate and 15 (8 women) mild LV systolic dysfunction. In the group with severe LV systolic dysfunction, average right ventricular ejection fraction (RVEF) was normal in women (52 ± 4 %), whereas it was reduced in men (39 ± 3 %) p = 0.035. Only one woman (8 %) had severe RV systolic dysfunction (RVEF < 35 %) compared with 6 men (50 %) p < 0.001. In patients with moderate and mild LV dysfunction , the mean RVEF was normal in both men and women. In the 14 healthy volunteers, the lowest value of RVEF was 48 % and mean RVEF was normal in women (56 ± 2 %) and in men (51 ±  1 %), p = 0.08.

Conclusions

In patients with dilated cardiomyopathy, RV systolic dysfunction is found mainly in male patients with severe LV systolic dysfunction.     

Epicardial adipose tissue assessed by cardiac magnetic resonance imaging in patients with heart failure due to dilated cardiomyopathy

Objective:

We sought to investigate the association of the EAT with CMR parameters of ventricular remodelling and left ventricular (LV) dysfunction in patients with non‐ischemic dilated cardiomyopathy (DCM).

Design and Methods:

One hundred and fifty subjects (112 consecutive patients with DCM and 48 healthy controls) underwent CMR examination. Function, volumes, dimensions, the LV remodelling index (LVRI), the presence of late gadolinium enhancement (LGE) and the amount of EAT were assessed.

Results:

Compared to healthy controls, patients with DCM revealed a significantly reduced indexed EAT mass (31.7 ± 5.6 g/m² vs 24.0 ± 7.5 g/m², p<0.0001). There was no difference in the EAT mass between DCM patients with moderate and severe LV dysfunction (23.5 ± 9.8 g/m² vs 24.2 ± 6.6 g/m², P = 0.7). Linear regression analysis in DCM patients showed that with increasing LV end‐diastolic mass index (LV‐EDMI) (r = 0.417, P < 0.0001), increasing LV end‐diastolic volume index (r = 0.251, P = 0.01) and increasing LV end‐diastolic diameter (r = 0.220, P = 0.02), there was also a significantly increased amount of EAT mass. However, there was no correlation between the EAT and the LV ejection fraction (r = 0.0085, P = 0.37), right ventricular ejection fraction (r = 0.049, P = 0.6), LVRI (r = 0.116, P = 0.2) and the extent of LGE % (r = 0.189, P = 0.1). Among the healthy controls, the amount of EAT only correlated with increasing age (r = 0.461, P = 0.001), BMI (r = 0.426, P = 0.003) and LV‐EDMI (r = 0.346, P = 0.02).

Conclusion:

In patients with DCM the amount of EAT is decreased compared to healthy controls irrespective of LV function impairment. However, an increase in LV mass and volumes is associated with a significantly increase in EAT in patients with DCM.     

Proteomic profiling of heat shock protein 70 family members as biomarkers for hepatitis C virus-related hepatocellular carcinoma

To identify proteins linked to the pathogenesis of hepatocellular carcinoma (HCC) associated with hepatitis C virus (HCV), we profiled protein expression levels in samples of HCC. To identify essential proteins, ten samples of HCV-related HCC were analyzed by two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight mass spectrometry. These experiments revealed increased levels of nine proteins in cancerous tissues compared to levels in corresponding noncancerous liver tissues. We focused on four members of the heat shock protein 70 family: 78 kDa glucose-regulated protein (GRP78), heat shock cognate 71 kDa protein (HSC70), 75 kDa glucose-regulated protein (GRP75), and heat shock 70 kDa protein 1 (HSP70.1). These results were confirmed by immunoblot analysis. In an additional 11 samples, the same expression patterns of these four proteins were observed. In total, 21 samples showed statistically significant up-regulation of GRP78, GRP75 and HSP70.1 in cancerous tissues. HSC70 showed a tendency toward overexpression. There has been no report describing overexpression of these four proteins simultaneously in HBV-related HCC as well as nonviral HCC. Our results suggest that these four proteins play important roles in the pathogenesis of HCV-related HCC and could be molecular targets for diagnosis and treatment of this disease.     

Differential expression of the cardiac ryanodine receptor in normal and arrhythmogenic right ventricular cardiomyopathy canine hearts

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a form of cardiomyopathy characterized by ventricular tachyarrhythmias and a fibrofatty infiltrate that is believed to preferentially affect the right ventricle. Mutations in the cardiac ryanodine receptor (RyR2) gene have been identified in some human families with a unique form of ARVC, ARVC2. Although the RyR2 has significant importance in excitation–contraction coupling across the ventricles, mutations in the gene encoding for it appear to have the greatest impact on the right ventricle in ARVC2. Using a canine model (boxer), the RyR2 protein and message RNA in the right ventricle, left ventricle and interventricular septum from normal dogs and dogs with ARVC were investigated by immunoblotting and real time PCR. The cardiac RyR2 message and protein expression were differentially expressed across the cardiac walls in the normal heart, with the lowest concentration expressed in the right ventricle (P < 0.05). The message and protein expression of the RyR2 were reduced in all chambers in the canine model of ARVC. We propose that the increased susceptibility of the right ventricle to ARVC may be associated with the lower baseline protein concentration of RyR2 in the normal right ventricle compared to the left ventricle and interventricular septum and that all three areas are equally affected in this canine model of ARVC. Using this naturally occurring model of canine ARVC, we may have provided new insights into the pathogenesis of this cardiomyopathy.     

Carboxy terminus of heat shock protein (HSP) 70-interacting protein (CHIP) inhibits HSP70 in the heart

Heat shock protein (HSP) 70 plays a critical role in protecting the heart from various stressor-induced cell injuries; the mechanism remains to be further understood. The present study aims to elucidate the effect of a probiotics-derived protein, LGG-derived protein p75 (LGP), in alleviating the ischemia/reperfusion (I/R)-induced heart injury. We treated rats with the I/R with or without preadministration with LGP. The levels of HSP70 and carboxy terminus of HSP70-interacting protein (CHIP) in the heart tissue were assessed by enzyme-linked immunosorbent assay (ELISA) and Western blotting. The effect of CHIP on suppression of HSP70 and the effect of LGP on suppression of CHIP were investigated with an I/R rat model and a cell culture model. The results showed that I/R-induced infarction in the heart could be alleviated by pretreatment with LGP. HSP70 was detected in na?ve rat heart tissue extracts. I/R treatment significantly suppressed the level of HSP70 and increased the levels of CHIP in the heart. A complex of CHIP/HSP70 was detected in heart tissue extracts. The addition of recombinant CHIP to culture inhibited HSP70 in heart cells. LGP was bound CHIP in heart cells and prevented the CHIP from binding HSP70. In summary, I/R can suppress HSP70 and increase CHIP in heart cells. CHIP can suppress HSP70 that can be prevented by pretreatment with LGP. The results imply that CHIP may be a potential target in the prevention of I/R-induced heart cell injury.