Efficacy and Safety of Angiotensin Receptor Blockers in a Pre-Clinical Model of Arrhythmogenic Cardiomyopathy

Arrhythmogenic Cardiomyopathy (ACM) is a familial heart disease, characterized by contractile dysfunction, ventricular arrhythmias (VAs), and the risk of sudden cardiac death. Currently, implantable cardioverter defibrillators and antiarrhythmics are the mainstays in ACM therapeutics. Angiotensin receptor blockers (ARBs) have been highlighted in the treatment of heart diseases, including ACM. Yet, recent research has additionally implicated ARBs in the genesis of VAs and myocardial lipolysis via the peroxisome proliferator-activated receptor gamma (PPARγ) pathway. The latter is of particular interest, as fibrofatty infiltration is a pathological hallmark in ACM. Here, we tested two ARBs, Valsartan and Telmisartan, and the PPAR agonist, Rosiglitazone, in an animal model of ACM, homozygous Desmoglein-2 mutant mice (Dsg2mut/mut). Cardiac function, premature ventricular contractions (PVCs), fibrofatty scars, PPARα/γ protein levels, and PPAR-mediated mRNA transcripts were assessed. Of note, not a single mouse treated with Rosiglitazone made it to the study endpoint (i.e., 100% mortality: n = 5/5). Telmisartan-treated Dsg2mut/mut mice displayed the preservation of contractile function (percent ejection fraction [%EF]; 74.8 ± 6.8%EF) compared to Vehicle- (42.5 ± 5.6%EF) and Valsartan-treated (63.1 ± 4.4%EF) mice. However, Telmisartan-treated Dsg2mut/mut mice showed increased cardiac wall motion abnormalities, augmented %PVCs, electrocardiographic repolarization/depolarization abnormalities, larger fibrotic lesions, and increased expression of PPARy-regulated gene transcripts compared to their Dsg2mut/mut counterparts. Alternatively, Valsartan-treated Dsg2mut/mut mice harbored fewer myocardial scars, reduced %PVC, and increased Wnt-mediated transcripts. Considering our findings, caution should be taken by physicians when prescribing medications that may increase PPARy signaling in patients with ACM.

Arrhythmogenic Cardiomyopathy: Exercise Pitfalls, Role of Connexin-43, and Moving beyond Antiarrhythmics

Arrhythmogenic Cardiomyopathy (ACM), a Mendelian disorder that can affect both left and right ventricles, is most often associated with pathogenic desmosomal variants that can lead to fibrofatty replacement of the myocardium, a pathological hallmark of this disease. Current therapies are aimed to prevent the worsening of disease phenotypes and sudden cardiac death (SCD). Despite the use of implantable cardioverter defibrillators (ICDs) there is no present therapy that would mitigate the loss in electrical signal and propagation by these fibrofatty barriers. Recent studies have shown the influence of forced vs. voluntary exercise in a variety of healthy and diseased mice; more specifically, that exercised mice show increased Connexin-43 (Cx43) expression levels. Fascinatingly, increased Cx43 expression ameliorated the abnormal electrical signal conduction in the myocardium of diseased mice. These findings point to a major translational pitfall in current therapeutics for ACM patients, who are advised to completely cease exercising and already demonstrate reduced Cx43 levels at the myocyte intercalated disc. Considering cardiac dysfunction in ACM arises from the loss of cardiomyocytes and electrical signal conduction abnormalities, an increase in Cx43 expression-promoted by low to moderate intensity exercise and/or gene therapy-could very well improve cardiac function in ACM patients.

S-Nitrosylation of Sarcomeric Proteins Depresses Myofilament Ca2+)Sensitivity in Intact Cardiomyocytes

AIMS

The heart responds to physiological and pathophysiological stress factors by increasing its production of nitric oxide (NO), which reacts with intracellular glutathione to form S-nitrosoglutathione (GSNO), a protein S-nitrosylating agent. Although S-nitrosylation protects some cardiac proteins against oxidative stress, direct effects on myofilament performance are unknown. We hypothesize that S-nitrosylation of sarcomeric proteins will modulate the performance of cardiac myofilaments.

RESULTS

Incubation of intact mouse cardiomyocytes with S-nitrosocysteine (CysNO, a cell-permeable low-molecular-weight nitrosothiol) significantly decreased myofilament Ca(2+) sensitivity. In demembranated (skinned) fibers, S-nitrosylation with 1 μM GSNO also decreased Ca(2+) sensitivity of contraction and 10 μM reduced maximal isometric force, while inhibition of relaxation and myofibrillar ATPase required higher concentrations (≥ 100 μM). Reducing S-nitrosylation with ascorbate partially reversed the effects on Ca(2+) sensitivity and ATPase activity. In live cardiomyocytes treated with CysNO, resin-assisted capture of S-nitrosylated protein thiols was combined with label-free liquid chromatography-tandem mass spectrometry to quantify S-nitrosylation and determine the susceptible cysteine sites on myosin, actin, myosin-binding protein C, troponin C and I, tropomyosin, and titin. The ability of sarcomere proteins to form S-NO from 10-500 μM CysNO in intact cardiomyocytes was further determined by immunoblot, with actin, myosin, myosin-binding protein C, and troponin C being the more susceptible sarcomeric proteins.

INNOVATION AND CONCLUSIONS

Thus, specific physiological effects are associated with S-nitrosylation of a limited number of cysteine residues in sarcomeric proteins, which also offer potential targets for interventions in pathophysiological situations.

Redox state of troponin C cysteine in the D/E helix alters the C-domain affinity for the thin filament of vertebrate striated muscle

BACKGROUND

Despite a broad spectrum of structural studies, it is not yet clear whether the D/E helix of troponin C (TnC) contributes to the interaction of TnC with troponin I (TnI). Redox modifications at Cys 98 in the D/E helix were explored for clues to TnC binding to the thin filament off-state, using recombinant wild-type TnC and an engineered mutant without Cys (Cys98Leu).

METHODS

Recombinant proteins and rabbit psoas skinned fibres were reduced with dithiothreitol (DTT) and variously recombined. Changes in affinity of reduced or oxidised TnC for the thin filament were evaluated via TnC binding and dissociation, using a standardized test for maximal force as an index of fibre TnC content.

RESULTS

All oxidation and reduction effects observed were reversible and led to changes in TnC content. Oxidation (H(2)O(2)) reduced TnC affinity for the filament; reduction (DTT) increased it. Reducing other fibre proteins had no effect. Binding of the Cys-less TnC mutant was not altered by DTT, nor was dissociation of wild-type TnC from reconstituted hybrids (skeletal TnC in cardiac trabeculae). Thus when Cys 98 in the D/E helix of TnC is fully reduced, its binding affinity for the thin filament of skeletal muscle is enhanced and helps to anchor it to the filament.

GENERAL SIGNIFICANCE

Signal transmission between TnC and the other proteins of the regulatory complex is sensitive to the redox state of Cys 98.

Chronic allograft dysfunction-is there a treatment?

BACKGROUND

The major causes of renal transplant loss are death and chronic allograft dysfunction (CAD). The aims of this study were to determine the incidence of CAD in our population and the relation between allograft survival and immunosuppressive regimens.

METHODS

We studied retrospectively 473 patients who received deceased donor kidney transplants with at least 1 allograft biopsy between January 1990 and May 2007. Clinical data included age, gender, biopsy data, and immunosuppression before and after kidney biopsy. Mean age was 45.4 +/- 12.7 years including 65% males with a mean follow-up of 6.7 +/- 4.5 years. CAD was observed in 177 of 473 biopsies: 48 patients showed interstitial fibrosis (IF); 101 chronic rejection (CR); 16 transplant glomerulopathy (TG); and 12, CR and TG. Mean follow-up since the discovery of the histologic feature was 60.5 +/- 50.5 months for IF; 38.3 +/- 40.8 for CR, and 18.2 +/- 19.2 for TG.

RESULTS

CAD, which was more common in younger patients (P = .03), correlated upon univariate and multivariate analysis with CKD stage 5d development (P < .001). Deposition of C4d in peritubular capillaries was more frequent among CAD patients (P = .004), an association with particular relevance to recipients with CR (P = .02) and TG (P < .001). When we analyzed CAD subpopulation, we observed a positive correlation between allograft survival and immunosuppression modification after biopsy. Substitution of sirolimus (40/177) was shown in univariate, multivariate and Cox regression analyses to be a renal protector (P < .002). Allograft survival was also correlated with initial mycophenolate mofetil versus azathioprine, (62/177) immunosuppression (P < .001).

CONCLUSION

CAD, a frequent histologic feature, may benefit from sirolimus conversion.

Ca(2+) and Mg(2+) binding to weak sites of TnC C-domain induces exposure of a large hydrophobic surface that leads to loss of TnC from the thin filament

The C-domain of troponin C, the Ca(2+)-binding subunit of the troponin complex, has two high-affinity sites for Ca(2+) that also bind Mg(2+) (Ca(2+)/Mg(2+) sites), whereas the N-domain has two low-affinity sites for Ca(2+). Two more sites that bind Mg(2+) with very low affinity (K(a)<10(3)M(-1)) have been detected by several laboratories but have not been localized or studied in any detail. Here we investigated the effects of Ca(2+) and Mg(2+) binding to isolated C-domain, focusing primarily on low-affinity sites. Since TnC has no Trp residues, we utilized a mutant with Phe 154 replaced by Trp (F154W/C-domain). As expected from previous reports, the changes in Trp fluorescence revealed different conformations induced by the addition of Ca(2+) or Mg(2+) (Ca(2+)/Mg(2+) sites). Exposure of hydrophobic surfaces of F154W/C-domain was monitored using the fluorescence intensity of bis-anilino naphthalene sulfonic acid. Unlike the changes reported by Trp, the increments in bis-ANS fluorescence were much greater (4.2-fold) when Ca(2+)+Mg(2+) were both present or when Ca(2+) was present at high concentration. Bis-ANS fluorescence increased as a function of [Ca(2+)] in two well-defined steps: one at low [Ca(2+)], consistent with the Ca(2+)/Mg(2+) sites (K(a) approximately 1.5 x 10(6)M(-1)), and one of much lower affinity (K(a) approximately 52.3M(-1)). Controls were performed to rule out artifacts due to aggregation, high ionic strength and formation of the bis-ANS-TnC complex itself. With a low concentration of Ca(2+) (0.6mM) to occupy the Ca(2+)/Mg(2+) sites, a large increase in bis-ANS binding also occurred as Mg(2+) occupied a class of low-affinity sites (K(a) approximately 59 M(-1)). In skinned fibers, a high concentration of Mg(2+) (10-44 mM) caused TnC to dissociate from the thin filament. These data provide new evidence for a class of weak binding sites for divalent cations. They are located in the C-domain, lead to exposure of a large hydrophobic surface, and destabilize the binding of TnC to the regulatory complex even when sites III and IV are occupied.

Bronchial asthma in children: clinical and epidemiologic approach in different Portuguese speaking countries

BACKGROUND

Geographical differences in asthma prevalence are currently accepted, but evidence is sparse due to the lack of multicentre studies using the same protocol.

OBJECTIVES

To compare the prevalence of asthma and atopy among schoolchildren from Portuguese speaking countries (ISAAC and Portuguese Study) and evaluate some environmental variables, such as house dust mite exposure.

MATERIAL AND METHODS

Significant random samples of schoolchildren studied with standard validated methods--questionnaires, skin prick tests, methacholine bronchial challenge tests; dust bed sampling for analysis of mite antigens.

RESULTS

In the ISAAC study, in the 13-14 year-old age group, statistical significant differences were found, with higher wheezing prevalence in Brazil than in Portugal (two-fold). In the Portuguese Study, atopy prevalence ranged between 6.0 and 11.9% in Sal and S. Vicente (Cape Verde), up to 48.6 and 54.1% in Macau and Madeira. Active asthma had the higher values in Madeira (14.6%), and the lower in Macau (1.3%). Cape Verde had intermediate asthma prevalence (10.6 and 7.0%). The bronchial challenge test was positive in 25, 66 and 70% of asthmatic children from Sal, S. Vicente and Madeira respectively. Significant HDM antigen concentrations (Der p1) were found in Cape Verde and Madeira.

CONCLUSIONS

There are significant variations in asthma and atopy prevalence between these pediatric populations. The reasons remain under discussion, but genetics linked to race, seem to play a central role, modulated by environmental and lifestyle variables.

Atopy and enteroparasites

There are not many studies about the intestinal parasitosis (IP) and atopic asthma (AA) relationship, and these show discordant results, possibly due to different studies design and differences in population selection. On the basis of personal results obtained by an epidemiological inquiry designed to estimate the prevalence of enteroparasitoses in asthmatic children and vice vesa, the aim of this study was to compare the prevalence of IP in AA and in a control group (CG) by a cross sectional study using clinical and laboratorial parameters, applied to 63 children (47 with AA and 16 in CG) aged 6 to 11 years, 37 males and 26 females, Caucasians, with the same socioeconomical conditions, consecutively selected in our Hospital. The results showed: The IP in AA children was 21.3%; the IP in CG was 25%; in the group with AA and IP, 40% of them had symptomology of IP; in the CG with IP, 100% had symptoms.

CONCLUSIONS

The IP prevalence in AA was not statistically different from the IP in CG (p > 0.05) More data are needed to clarify the significant differences between the symptomatology rates of IP in asthmatic and non asthmatics; the reduced number of patients with symptoms in AA may reflect modulation of IP in AA and/or different parasite load.

Bovine papillomavirus transmission and chromosomal aberrations: an experimental model

Enzootic haematuria and urinary bladder cancer in cattle are associated with feeding on bracken fern and bovine papillomavirus (BPV) infection. An increased rate of chromosomal aberrations in peripheral blood lymphocytes from chronically affected haematuric cows raised in bracken fern pastures has been reported, suggesting the presence of BPV in the peripheral blood of afflicted animals. The purpose of the present investigation was to examine the role of peripheral blood as a potential BPV-transmitting agent and search for clastogenic effects in experimentally infected animals kept on a bracken fern-free diet. Healthy cows were inoculated with blood samples of haematuric animals every two weeks for 18 months. Recipient cows, their offspring, donor animals and a control group were kept on a bracken fern-free diet throughout the experiment. Clinical and molecular analyses for detection of BPV infection were carried out periodically in all groups. Short-term lymphocyte cultures were performed to assess chromosomal aberration levels. The donor cows, the recipient cows and their offspring presented increased levels of chromosomal aberrations. BPV-2 DNA was identified by Southern blotting, PCR and cycle-sequencing of PCR products in peripheral blood of donor and recipient animals and in the progeny of recipient animals. Data support both the concept that BPV can be transmitted through blood and the hypothesis that infection with the virus causes the clastogenic alterations observed in the present experimental model. The presence of BPV-2 DNA and chromosomal alterations in peripheral blood of offspring at the moment of birth is evidence for vertical transmission of BPV.

Autosomal dominant polycystic kidney disease: evidence for the existence of a third locus in a Portuguese family

Autosomal dominant polycystic kidney disease is characterized by clinical and genetic heterogeneity. Two loci implicated in the disease have previously been mapped (PKD1 on chromosome 16 and PKD2 on chromosome 4). By two point and multipoint linkage analysis, negative lod scores have been found for both chromosome 16 and chromosome 4 markers in a large Portuguese family, indicating that a third PKD locus is involved in the development of the disease.

Long-term effect of lovastatin on lipoprotein profile in patients with primary nephrotic syndrome

Eight patients with biopsy-proven primary nephrotic syndrome were included in an open, prospective, two-year study of lovastatin. One patients was withdrawn after 6 months due to an asymptomatic rise in creatinine phosphokinase, which was rapidly reversed after interruption of lovastatin. In the remaining patients, treatment was well-tolerated and produced no side effects. After 2 years of treatment, these 7 patients had decreases in total cholesterol from 446 +/- 165 to 250 +/- 57 mg/dl (p < 0.001), LDL cholesterol from 343 +/- 121 to 174 +/- 49 mg/dl (p < 0.001), Apo B lipoprotein from 162 +/- 60 to 108 +/- 42 mg/dl (p < 0.05), triglycerides from 336 +/- 273 to 182 +/- 71 mg/dl (p < 0.04). There was no change in HDL cholesterol. The LDL/HDL cholesterol and the total/HDL cholesterol ratios fell from 15.0 +/- 12.1 and 19.1 +/- 17.2 mg/dl before the study to 4.4 +/- 1.2 and 6.3 +/- 1.6 mg/dl, respectively, at 2 years. A decrease in proteinuria from 8.6 +/- 4.6 to 5.0 +/- 3.7 g/24 h (p < 0.02) was noted in 4 patients on concomitant ACE inhibitor therapy. Renal function remained stable in all patients throughout the study, except for one whose moderate impairment progressed to end-stage renal failure requiring dialysis 3 months poststudy. We conclude that long-term lovastatin in patients with primary nephrotic syndrome is an effective and generally safe treatment for accompanying dyslipidemia.

[Sporadic amyotrophic lateral sclerosis. Diagnostic criteria]

The authors report two cases of amyotrophic lateral sclerosis (ALS) misdiagnosis (a craniocervical junction disorder, and a cervical spinal cord ependymoma). They review some causes of ALS-like syndrome and propose a protocol to be adopted for the study of all patients who present clinical abnormalities suggesting ALS.

[Intracranial saccular aneurysm: report of 3 cases in a same family]

The authors report the cases of three patients from the same family, all with intracranial saccular aneurysm (left carotid artery, anterior communicating artery, and middle cerebral artery). All three patients were operated on with good recovery and no complications. The authors call attention for some etiopathogenic aspects of familial saccular aneurysms.

Effect of low protein diet on the renal response to meat ingestion in diabetic nephropathy

We measured the renal haemodynamic and proteinuric response to a meat meal (MM) in ten persistently proteinuric insulin-dependent diabetic patients in a randomized cross-over study of 3 weeks on low protein diet (LPD) or normal protein intake (NPD). On LPD, protein intake (0.64 +/- 0.05 vs 1.15 +/- 0.09 g kg-1 body weight (BW) per day, P less than 0.001), plasma urea (6.6 +/- 1.3 vs 11.0 +/- 2.0 mmol l-1, P less than 0.01) and urea appearance (0.06 +/- 0.01 vs 0.16 +/- 0.03 gN kg-1 body weight per day, P less than 0.001) were lower. Baseline glomerular filtration rate (GFR), renal plasma flow (RPF) and renal vascular resistance (RVR) were similar on the two diets and there were no significant average changes in these variables after the meat meal on either diet (NPD, before vs after MM: GFR: 67 +/- 11 vs 71 +/- 13 ml min-1 1.73 m-2; RPF: 479 +/- 70 vs 512 +/- 81 ml min-1 1.73 m-2; RVR: 181 +/- 45 vs 179 +/- 52 mmHg min-1 l-1); (LPD, before vs after MM: GFR: 64 +/- 10 vs 67 +/- 11 ml min-1 1.73 m-2; RPF: 506 +/- 60 vs 533 + 52 ml min-1 1.73 m-2; RVR: 151 +/- 28 vs 146 +/- 32 mmHg min-1 l-1). However, all patients with baseline GFR above 60 ml min-1 1.73 m-2 showed a GFR rise in response to the meat meal on both diets, while patients with lower baseline values tended to reduce their GRF.(ABSTRACT TRUNCATED AT 250 WORDS)