Background and Purpose
Mineralocorticoid receptor (MR) activation contributes to heart failure (HF) progression. Its overactivity in obesity is thought to accelerate cardiac remodelling and HF ...development. Given that MR antagonists (MRA) are beneficial in chronic HF patients, we hypothesized that early MRA treatment may target obesity‐related disorders and consequently delay the development of HF.
Experimental Approach
Twenty spontaneously hypertensive HF dyslipidaemic obese SHHFcp/cp rats and 18 non‐dyslipidaemic lean SHHF+/+ controls underwent regular monitoring for their metabolic and cardiovascular phenotypes with or without MRA treatment eplerenone (eple), 100 mg∙kg−1∙day−1 from 1.5 to 12.5 months of age.
Key Results
Eleven months of eple treatment in obese rats (SHHFcp/cpeple) reduced the obesity‐related metabolic disorders observed in untreated SHHFcp/cp rats by reducing weight gain, triglycerides and total cholesterol levels and by preserving adiponectinaemia. The MRA treatment predominantly preserved diastolic and systolic functions in obese rats by alleviating the eccentric cardiac hypertrophy observed in untreated SHHFcp/cp animals and preserving ejection fraction (70 ± 1 vs. 59 ± 1%). The MRA also improved survival independently of these pressure effects.
Conclusion and Implications
Early chronic eple treatment resulted in a delay in cardiac remodelling and HF onset in both SHHF+/+ and SHHFcp/cp rats, whereas SHHFcp/cp rats further benefited from the MRA treatment through a reduction in their obesity and dyslipidaemia. These findings suggest that preventive MRA therapy may provide greater benefits in obese patients with additional risk factors of developing cardiovascular complications.
OBJECTIVE—Pseudoxanthoma elasticum is an inherited metabolic disorder resulting from ABCC6 gene mutations. It is characterized by progressive calcification and fragmentation of elastic fibers in the ...skin, retina, and the arterial wall. Despite calcium accumulation in the arteries of patients with pseudoxanthoma elasticum, functional consequences remain unknown. In the present study, we investigated arterial structure and function in Abcc6 mice, a model of the human disease.
APPROACH AND RESULTS—Arterial calcium accumulation was evaluated using alizarin red stain and atomic absorption spectrometry. Expression of genes involved in osteochondrogenic differentiation was measured by polymerase chain reaction. Elastic arterial properties were evaluated by carotid echotracking. Vascular reactivity was evaluated using wire and pressure myography and remodeling using histomorphometry. Arterial calcium accumulation was 1.5- to 2-fold higher in Abcc6 than in wild-type mice. Calcium accumulated locally leading to punctuate pattern. Old Abcc6 arteries expressed markers of both osteogenic (Runx2, osteopontin) and chondrogenic lineage (Sox9, type II collagen). Abcc6 arteries displayed slight increase in arterial stiffness and vasoconstrictor tone in vitro tended to be higher in response to phenylephrine and thromboxane A2. Pressure-induced (myogenic) tone was significantly higher in Abcc6 arteries than in wild type. Arterial blood pressure was not significantly changed in Abcc6, despite higher variability.
CONCLUSIONS—Scattered arterial calcium depositions are probably a result of osteochondrogenic transdifferentiation of vascular cells. Lower elasticity and increased myogenic tone without major changes in agonist-dependent contraction evidenced in aged Abcc6 mice suggest a reduced control of local blood flow, which in turn may alter vascular homeostasis in the long term.
Clinical and experimental studies suggest that pharmacological postconditioning with Cyclosporin A (CsA) reduces infarct size in cardiac ischemia and reperfusion. CsA interacts with Cyclophilin D ...(CypD) preventing opening of the mitochondrial permeability transition pore (mPTP). Tissue kallikrein (TK) and its products kinins are involved in cardioprotection in ischemia. CypD knockout mice are resistant to the cardioprotective effects of both CsA and kinins suggesting common mechanisms of action. Using TK gene knockout mice, we investigated whether the kallikrein-kinin system is involved in the cardioprotective effect of CsA.
Homozygote and heterozygote TK deficient mice (TK−/−, TK+/−) and wild type littermates (TK+/+) were subjected to cardiac ischemia–reperfusion with and without CsA postconditioning. CsA reduced infarct size in TK+/+ mice but had no effect in TK+/− and TK−/− mice. Cardiac mitochondria isolated from TK−/− mice had indistinguishable basal oxidative phosphorylation and calcium retention capacity compared to TK+/+ mice but were resistant to CsA inhibition of mPTP opening. TK activity was documented in mouse heart and rat cardiomyoblasts mitochondria. By proximity ligation assay TK was found in close proximity to the mitochondrial membrane proteins VDAC and Tom22, and CypD.
Thus, partial or total deficiency in TK induces resistance to the infarct size reducing effect of CsA in cardiac ischemia in mice, suggesting that TK level is a critical factor for cardioprotection by CsA. TK is required for the mitochondrial action of CsA and may interact with CypD. Genetic variability in TK activity has been documented in man and may influence the cardioprotective effect of CsA.
Aims
An excessive production of aldosterone influences outcome in patients with heart failure (HF) and in obese patients. Findings from laboratory studies suggest that chronic aldosterone blockade ...maybe more beneficial in abdominally obese HF‐prone rats. In the current study, we investigated if the clinical response to a mineralocorticoid receptor antagonist in mildly symptomatic HF patients varied by abdominal obesity.
Methods and results
A total of 2587 NYHA class II, reduced ejection fraction HF (HFrEF) patients enrolled in the EMPHASIS‐HF trial were randomly assigned to eplerenone and placebo. In this post hoc analysis, patients were categorized according to waist circumference (WC) (normal if WC < 102 cm in men and < 88 cm in women; abdominal obesity if WC ≥ 102 cm in men and ≥ 88 cm women). The potential statistical interaction between the treatment and WC was assessed on the primary endpoint of death from cardiovascular causes or hospitalization for HF and other secondary endpoints. Over a median follow‐up of 21 months, a significant benefit of eplerenone for the primary outcome was noted in both normal hazard ratio (HR) 0.77, 95% confidence interval (CI) 0.61–0.98, P = 0.03 and increased (HR 0.48, 95% CI 0.37–0.63, P < 0.0001) WC subgroups, but the latter patients appeared to receive greater benefit than patients with normal WC (P for interaction = 0.01). This suggests a significant quantitative (treatment effect varies in magnitude by subgroup, but is always in same direction) rather than a qualitative interaction (direction of the treatment effect varies by subgroup) between eplerenone and WC in the adjusted analysis. Mean doses of eplerenone, blood pressure and serum potassium changes and adverse events were similar between WC subgroups.
Conclusion
In EMPHASIS‐HF, eplerenone improved outcomes in HFrEF patients with and without abdominal obesity, although the benefit appeared to be more pronounced among those with abdominal obesity. The findings are potentially hypothesis generating and need to be replicated in other HFrEF populations.
To investigate the glycosylation of the human bradykinin B2 receptor and the functional significance of this modification, we studied receptors mutated at single or multiple combinations of the three ...potential N-linked glycosylation sites, asparagines N3, N12 and N180, in COS-7, HEK 293 and CHO-K1 cells. Western blot experiments demonstrated that all three extracellular asparagines are glycosylated. The kinetics of bradykinin binding and receptor sequestration remained unchanged after glycosylation had been suppressed. However, the glycosylated receptors were expressed at the cell-surface to a much greater extent than the non-glycosylated receptor and coupling to phospholipase C was less efficient for receptor lacking N-terminal glycosylation. These results indicate that, for the human bradykinin B2 receptor, glycosylation is not required for optimal ligand binding, but plays an important role in cell-surface addressing and receptor function.
La déficience génétique du Système Kallicréine Kinines (SKK) conduit à un dysfonctionnement artériel, cardiaque et rénal. Des observations faites chez l’homme et l’animal (hypertension, ischémie ...reperfusion, diabète) ont suggéré qu’une activité réduite du SKK pourrait être la cause de l’induction de ces maladies cardiovasculaires ou participerait à leur progression, alors que certains traitements qui potentialisent les kinines, comme les IEC et la Cyclosporine A (CsA), sont cardioprotecteurs. Le SKK vasculaire aurait donc un rôle protecteur dans les maladies où une vasoconstriction excessive est délétère. Objectif Évaluer l’importance du niveau de stimulation du SKK sur le développement d’effets secondaires bénéfiques ou délétères de la CsA. L’administration chronique de l’immunosuppresseur CsA est responsable du développement d’une HTA chez l’homme et le rat. Dans ce modèle murin, la CsA stimule l’activité du SKK, ce qui atténuerait l’augmentation de la PA. Nous déterminerons la capacité de la CsA à modifier l’activité du SKK et évaluerons les effets secondaires liés à un traitement chronique à la CsA en présence (TK+/+) ou absence (Kallicréine Tissulaire Knockout, TK-/-) du SKK. Méthodes Traitement chronique (6 semaines) de souris femelles de 4 mois (TK-/-, n = 16 et leurs contrôles TK+/+, n = 16) par l’implantation de mini-pompe Alzet 2006 délivrant 30microg/g de souris/jour de CsA ou PBS. Suivis hebdomadaires du poids et de la Pression Artérielle, cage à métabolisme tous les 15 jours et recueil de plasma pour l’évaluation de la fonction rénale. Le sacrifice des animaux permettra la collecte des reins, cœur et gros troncs artériels et leur caractérisation du point de vue moléculaire (RTPCR, HIS, Wblot, et Immunohistologie, caractérisation des SKK, SRA, Endothéline, Vasopressine). Résultats Les résultats préliminaires de suivis de la PA à 28 jours montrent une augmentation significative de la PA de 15mmHg uniquement chez les TK-/-CsA par rapport aux groupes TK+/+ CsA (112.99 ± 6.83 mmHg vs 95.83 ± 4,65mmHg). La comparaison des résultats obtenus pour chacun des groupes étudiés révèlera l’importance du niveau de stimulation du SKK sur le développement de certains mécanismes de cardio- et néphrotoxicité médicamenteuse.
To investigate the palmitoylation of the human bradykinin B2 receptor, we have mutated individually or simultaneously into glycine two potential acylation sites (cysteines 324 and 329) located in the ...carboxyl terminus of the receptor and evaluated the effects of these mutations by transfection in COS-7, CHO-K1, and HEK 293T. The wild-type receptor and the single mutants, but not the double mutant, incorporated 3Hpalmitate, indicating that the receptor carboxyl tail can be palmitoylated at both sites. The mutants did not differ from the wild-type receptor for the kinetics of 3Hbradykinin binding, the basal and bradykinin-stimulated coupling to phospholipases C and A2, and agonist-induced phosphorylation. The nonpalmitoylated receptor had a 30% reduced capacity to internalize 3Hbradykinin. This indicates that palmitoylation does not influence the basal activity of the receptor and its agonist-driven activation. However, the mutants triggered phospholipid metabolism and MAP kinase activation in response to B2 receptor antagonists. Pseudopeptide and nonpeptide compounds that behaved as antagonists on the wild-type receptor became agonists on the nonpalmitoylated receptor and produced phospholipases C and A2 responses of 25−50% as compared to that of bradykinin. These results suggest that palmitoylation is required for the stabilization of the receptor−ligand complex in an uncoupled conformation.
We report a critical role for the T-box transcription factor Tbx5 in development and maturation of the cardiac conduction system. We find that Tbx5 is expressed throughout the central conduction ...system, including the atrioventricular bundle and bundle branch conduction system. Tbx5 haploinsufficiency in mice ( Tbx5 del/+ ), a model of human HoltâOram syndrome, caused distinct morphological and functional defects in the atrioventricular and bundle branch conduction systems. In the atrioventricular canal, Tbx5 haploinsufficiency caused a maturation failure of conduction system morphology and function. Electrophysiologic testing of Tbx5 del/+ mice suggested a specific atrioventricular node maturation failure. In the ventricular conduction system , Tbx5 haploinsufficiency caused patterning defects of both the left and right ventricular bundle branches, including absence or severe abnormalities of the right bundle branch. Absence of the right bundle branch correlated with right-bundle-branch block by ECG. Deficiencies in the gap junction protein gene connexin 40 ( Cx40 ), a downstream target of Tbx5 , did not account for morphologic conduction system defects in Tbx5 del/+ mice. We conclude that Tbx5 is required for Cx40 -independent patterning of the cardiac conduction system, and suggest that the electrophysiologic defects in HoltâOram syndrome reflect a developmental abnormality of the conduction system.
We identified a human mutation that causes dilated cardiomyopathy and heart failure preceded by sensorineural hearing loss (SNHL). Unlike previously described mutations causing dilated cardiomyopathy ...that affect structural proteins, this mutation deletes 4,846 bp of the human transcriptional coactivator gene EYA4. To elucidate the roles of eya4 in heart function, we studied zebrafish embryos injected with antisense morpholino oligonucleotides. Attenuated eya4 transcript levels produced morphologic and hemodynamic features of heart failure. To determine why previously described mutated EYA4 alleles cause SNHL without heart disease, we examined biochemical interactions of mutant Eya4 peptides. Eya4 peptides associated with SNHL, but not the shortened 193-amino acid peptide associated with dilated cardiomyopathy and SNHL, bound wild-type Eya4 and associated with Six proteins. These data define unrecognized and crucial roles for Eya4-Six-mediated transcriptional regulation in normal heart function.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
1
The human umbilical vein has been found to contract in response to bradykinin (BK) and desArg9BK.
2
The rank order of potency of agonists, in the presence of the B1 receptor antagonist ...LysLeu8desArg9BK, is as follows: Hyp3, Tyr(Me)8BK (pD2 8.88) = Hyp3BK (pD2 8.86) = LysBK (pD2 8.81) ≥BK (pD2 8.60) > >Aib7BK (pD2 6.38) > >desArg9BK and LysdesArg9BK (inactive).
3
Hoe 140 (pA2 8.42) inhibits the effects of BK while other B2 receptor peptide antagonists are very weak and WIN 64338 is practically inactive.
4
Venoconstrictor responses to desArg9BK of fresh tissues increase with time during the in vitro incubation and reach a maximum after 4–6 h. The activity of Hoe 140 (pA2 5.48) is negligible against B1 receptor agonists.
5
When measured in the presence of the selective B2 receptor antagonist Hoe 140 (400 nM), the order of potency of kinin related peptides on the B1 receptor is LysdesArg9BK (pD2 8.60)>desArg9BK (pD2 6.69). BK, LysBK, Hyp3BK and other B2 receptor agonists are inactive.
6
The B1 receptor antagonist, LysLeu8desArg9BK (pA2 7.99), inhibits the response of the human vein to B1 receptor agonists (LysdesArg9BK or desArg9BK), but do not alter the effect of BK.
7
The results summarized in this paper indicate that the human isolated umbilical vein is a sensitive preparation containing both B1 and B2 receptors. The human B2 receptor shows some similarity with that of the rabbit (at least for agonist potencies) and differs from the B2 receptor of the guinea‐pig. Compared to the rabbit B1 receptor, the human B1 receptor shows low sensitivity to peptides that lack the N‐terminal Lys.
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