Ambulatory electrocardiographic longitudinal monitoring in a canine model for Duchenne muscular dystrophy identifies decreased very low frequency power as a hallmark of impaired heart rate variability

Duchenne muscular dystrophy (DMD) patients exhibit a late left ventricular systolic dysfunction preceded by an occult phase, during which myocardial fibrosis progresses and some early functional impairments can be detected. These latter include electrocardiographic (ECG) and heart rate variability (HRV) abnormalities. This longitudinal study aimed at describing the sequence of ECG and HRV abnormalities, using Holter ECG in the GRMD (Golden retriever muscular dystrophy) dog model, known to develop a DMD-like disease, including cardiomyopathy. Most of the known ECG abnormalities described in DMD patients were also found in GRMD dogs, including increased heart rate, prolonged QT and shortened PR intervals, ventricular arrhythmias, and several of them could be detected months before the decrease of fractional shortening. The HRV was impaired like in DMD patients, one of the earliest evidenced abnormalities being a decrease in the very low frequency (VLF) component of the power spectrum. This decrease was correlated with the further reduction of fractional shortening. Such decreased VLF probably reflects impaired autonomic function and abnormal vasomotor tone. This study provides new insights into the knowledge of the GRMD dog model and DMD cardiomyopathy and emphasizes the interest to monitor the VLF power in DMD patients, still unexplored in this disease, whilst it is highly predictive of deleterious clinical events in many other pathological conditions.

Identification of a mechanism promoting mitochondrial sterol accumulation during myocardial ischemia-reperfusion: role of TSPO and STAR

Hypercholesterolemia is a major risk factor for coronary artery diseases and cardiac ischemic events. Cholesterol per se could also have negative effects on the myocardium, independently from hypercholesterolemia. Previously, we reported that myocardial ischemia-reperfusion induces a deleterious build-up of mitochondrial cholesterol and oxysterols, which is potentiated by hypercholesterolemia and prevented by translocator protein (TSPO) ligands. Here, we studied the mechanism by which sterols accumulate in cardiac mitochondria and promote mitochondrial dysfunction. We performed myocardial ischemia-reperfusion in rats to evaluate mitochondrial function, TSPO, and steroidogenic acute regulatory protein (STAR) levels and the related mitochondrial concentrations of sterols. Rats were treated with the cholesterol synthesis inhibitor pravastatin or the TSPO ligand 4'-chlorodiazepam. We used Tspo deleted rats, which were phenotypically characterized. Inhibition of cholesterol synthesis reduced mitochondrial sterol accumulation and protected mitochondria during myocardial ischemia-reperfusion. We found that cardiac mitochondrial sterol accumulation is the consequence of enhanced influx of cholesterol and not of the inhibition of its mitochondrial metabolism during ischemia-reperfusion. Mitochondrial cholesterol accumulation at reperfusion was related to an increase in mitochondrial STAR but not to changes in TSPO levels. 4'-Chlorodiazepam inhibited this mechanism and prevented mitochondrial sterol accumulation and mitochondrial ischemia-reperfusion injury, underlying the close cooperation between STAR and TSPO. Conversely, Tspo deletion, which did not alter cardiac phenotype, abolished the effects of 4'-chlorodiazepam. This study reveals a novel mitochondrial interaction between TSPO and STAR to promote cholesterol and deleterious sterol mitochondrial accumulation during myocardial ischemia-reperfusion. This interaction regulates mitochondrial homeostasis and plays a key role during mitochondrial injury.

Spatial and Temporal Non-Uniform Changes in Left Ventricular Myocardial Strain in Dogs with Duchenne Muscular Dystrophy

BACKGROUND

Understanding and effectively treating dystrophin-deficient cardiomyopathy is of high importance for Duchenne muscular dystrophy (DMD) patients due to their prolonged lifespan. We used two-dimensional speckle tracking echocardiography to analyze more deeply the non-uniformity of myocardial strain within the left ventricle during the progression of cardiomyopathy in golden retriever muscular dystrophy (GRMD) dogs.

METHODS

The circumferential strain (CS) and longitudinal strain (LS) of left ventricular (LV) endocardial, middle and epicardial layers were analyzed from three parasternal short-axis views and three apical views, respectively, in GRMD (n = 22) and healthy control dogs (n = 7) from 2 to 24 months of age.

RESULTS

In GRMD dogs, despite normal global systolic function (normal LV fractional shortening and ejection fraction), a reduction in systolic CS was detected in the three layers of the LV apex but not in the LV middle-chamber and base at 2 months of age. This spatial heterogeneity in CS progressed with age, whereas a decrease in systolic LS could be detected early at 2 months of age in the three layers of the LV wall from three apical views.

CONCLUSIONS

Analyzing the evolution of myocardial CS and LS in GRMD dogs reveals spatial and temporal non-uniform alterations of LV myocardial strain, providing new insights into the progression of dystrophin-deficient cardiomyopathy in this relevant model of DMD.

[The prognostic value of preoperative peripheral blood inflammatory biomarkers for intrahepatic cholangiocarcinoma after radical resection]

Objective: To explore the value of preoperative peripheral blood inflammatory biomarkers for predicting the prognosis of intrahepatic cholangiocarcinoma (ICC) after radical resection. Methods: A total of 124 patients who underwent radical resection for ICC in the First Affiliated Hospital of Xi'an Jiaotong University from January 2010 to December 2018 were retrospectively analyzed. Receiver operating characteristic (ROC) curve was conducted to determine the best cut-off values of neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), lymphocyte/monocyte ratio (LMR), systemic immune inflammatory index (SII), and systemic inflammatory response index (SIRI). Univariate and multivariate analyses of prognostic factors were performed using Cox proportional hazards regression model. Based on the independent prognostic factors screened by multivariate Cox regression analysis, a nomogram model of overall survival prediction for ICC patients after radical resection was established. Results: Among the 124 patients, 87 patients died and 37 patients survived during the follow-up period. The median overall survival time of the whole patients was 21 months. ROC curve analysis showed that the areas under the curve (AUC) of NLR, PLR, LMR, SII and SIRI for predicting the overall survival of ICC patients after radical resection were 57.86%, 64.21%, 60.61%, 67.57% and 66.03%, respectively. Univariate Cox regression analysis showed that the inflammatory biomarkers of NLR, PLR, SII, and SIRI were associated with overall survival of ICC after radical resection (HR=1.787, 95%CI: 1.165-2.741; HR=1.181, 95% CI: 1.224-2.892; HR=2.412, 95% CI: 1.565-3.717; HR=1.648, 95% CI: 1.081-2.513). Multivariate Cox regression analysis showed that the inflammatory biomarker of SII was an independent prognostic factor of ICC after radical resection (HR=1.863, 95% CI: 1.161-2.989). According to the best cut-off value of SII to predict the overall survival of ICC patients after radical resection (709.86×10(9)/L), the patients were divided into low SII group (SII≤709.86×10(9)/L) and high SII group (SII>709.86×10(9)/L). In the high SII group, the proportions of NLR>3.31, PLR>3.31, SIRI>1.30×10(9)/L, carbohydrate antigen 19-9>39.0 U/ml, Child-Pugh liver function (grade B), hemi-hepatic/extended hepatectomy, combined perineural invasion, N1 stage and TNM stage (ⅢB) were higher than those in the low SII group (P<0.05). Based on the independent prognostic factors screened by multivariate Cox regression analysis, a nomogram model of overall survival prediction for ICC after radical resection was established, the C-index values of the training set and testing set were 0.774 and 0.737, respectively. Conclusions: Preoperative peripheral blood inflammatory marker SII is an independent risk factor for the prognosis of intrahepatic cholangiocarcinoma patients after radical resection. The nomogram model of overall survival prediction established that included SII has a good predictive ability and can be used to evaluate the prognosis of intrahepatic cholangiocarcinoma patients after radical resection.

[Analysis of perineural invasion with clinicopathological factors and prognosis for curatively resected gallbladder carcinoma]

Objective: To examine the correlation between perineural invasion and clinicopathological factors and the role of perineural invasion on the prognosis of patients with curatively resected gallbladder carcinoma. Methods: The clinicopathological and follow-up data of 548 patients with gallbladder carcinoma who underwent radical surgery from the First Affiliated Hospital of Xi'an Jiaotong University from January 2013 to December 2020 were analyzed retrospectively. There were 173 males and 375 females,with age(M(IQR)) of 62(14)years(range:30 to 88 years). The correlations between perineural invasion and the clinicopathological features were analyzed. The relationship between prognosis and clinicopathological factors were further analyzed. The survival curve was drawn using the Kaplan-Meier method. The univariate analysis and multivariate analysis were done using the Log-rank test and Cox proportional hazard model respectively. Results: Radical resection was performed in 548 cases,including 59 cases(10.8%) with perineural invasion. The results of univariate analysis showed that perineural invasion was related to serum bilirubin level,serum carcinoembryonic antigen(CEA) level,CA19-9 level,T stage,lymph node metastasis,liver invasion,vessel invasion and tumor location(all P<0.05).The results of multivariate analysis showed that jaundice,high-level serum CA19-9,high-level serum CEA,T4 stage,vessel invasion and tumor located in the neck or cystic duct of the gallbladder were independent risk factors of perineural invasion in gallbladder carcinoma. Survival of 367 patients in T3-T4 stages were analyzed. The prognosis of gallbladder carcinoma patients with perineural invasion was significantly worse than that of patients without perineural invasion(median survival time:12.0 months vs. 34.7 months,P<0.01). Univariate analysis showed that perineural invasion,gallbladder stones,gallbladder polyps,CA125,CEA,CA19-9,serum bilirubin level,tumor location,N stage,liver invasion and pathological differentiation were independent risk factors affecting prognosis of patients with gallbladder carcinoma(all P<0.05). The results of Cox proportional hazard model showed that perineural invasion,N stage,liver invasion,gallbladder stones,pathological differentiation were independent risk factors affecting prognosis of patients with gallbladder carcinoma(all P<0.05). Conclusions: Jaundice,high-level serum CA19-9,high-level serum CEA,T4 stage,vessel invasion and tumor located in the neck or cystic duct of the gallbladder are independent risk factors for perineural invasion of gallbladder carcinoma. Perineural invasion is one of the independent risk factors affecting the prognosis of T3-T4 stage gallbladder carcinoma.

[Impact of adjuvant chemotherapy on prognosis in intrahepatic cholangiocarcinoma patients underwent radical resection]

Objectives: To investigate the clinical value of adjuvant chemotherapy(ACT) in patients with intrahepatic cholangiocarcinoma(ICC) who underwent radical resection and to explore the optimal population that can benefit from ACT. Methods: A retrospective cohort study method was adopted. The clinical and pathological data of 685 patients with ICC who underwent curative intent resection in 10 Chinese hepatobiliary surgery centers from January 2010 to December 2018 were collected;There were 355 males and 330 females. The age(M(IQR)) was 58(14) years (range: 22 to 83 years). Propensity score matching(PSM) was applied to balance the differences between the adjuvant and non-adjuvant chemotherapy groups. Log-rank test was used to compare the prognosis of the two groups of patients. A Bayesian network recurrence-free survival(RFS) prediction model was constructed using the median RFS time (14 months) as the target variable, and the importance of the relevant prognostic factors was ranked according to the multistate Birnbaum importance calculation. A survival prognostic prediction table was established to analyze the population benefiting from adjuvant chemotherapy. Results: Among 685 patients,214 received ACT and 471 did not receive ACT. A total of 124 pairs of patients were included after PSM, and patients in the ACT group had better overall survival (OS) and RFS than those in the non-ACT group(OS: 32.2 months vs. 18.0 months,P=0.003;RFS:18.0 months vs. 10.0 months,P=0.001). The area under the curve of the Bayesian network RFS prediction model was 0.7124. The results of the prognostic factors in order of importance were microvascular invasion (0.158 2),perineural invasion (0.158 2),N stage (0.155 8),T stage (0.120 9), hepatic envelope invasion (0.090 3),adjuvant chemotherapy (0.072 1), tumor location (0.057 5), age (0.042 3), pathological differentiation (0.034 0), sex (0.029 3), alpha-fetoprotein (0.028 9) and preoperative jaundice (0.008 5). A survival prediction table based on the variables with importance greater than 0.1 (microvascular invasion,perineural invasion,N stage,T staging) and ACT showed that all patients benefited from ACT (increase in the probability of RFS≥14 months from 2.21% to 7.68%), with a more significant increase in the probability of RFS≥14 months after ACT in early-stage patients. Conclusion: ACT after radical resection in patients with ICC significantly prolongs the OS and RFS of patients, and the benefit of ACT is greater in early patients.

Stabilizing Ryanodine Receptors Improves Left Ventricular Function in Juvenile Dogs With Duchenne Muscular Dystrophy

BACKGROUND

Duchenne muscular dystrophy is associated with progressive deterioration in left ventricular (LV) function. The golden retriever muscular dystrophy (GRMD) dog model recapitulates the pathology and clinical manifestations of Duchenne muscular dystrophy. Importantly, they develop progressive LV dysfunction starting at early age.

OBJECTIVES

The authors tested the cardioprotective effect of chronic administration of the ARM036, a small molecule that stabilizes the closed conformation of the cardiac sarcoplasmic reticulum ryanodine receptor/calcium release channel (RyR2) in young GRMD-dogs.

METHODS

Two-month-old GRMD-dogs were treated with ARM036 or placebo for 4 months. Healthy-dogs of the same genetic background served as controls. Cardiac function was evaluated by conventional and 2-dimensional speckle-tracking echocardiography. Cardiac cellular and molecular analyses were performed at 6 months old.

RESULTS

Conventional echocardiography showed normal LV dimensions and ejection fraction in 6-month-old GRMD dogs. Interestingly, 2-dimensional speckle-tracking echocardiography revealed decreased global longitudinal strain and the presence of hypokinetic segments in placebo-treated GRMD dogs. Single-channel measurements revealed higher RyR2 open probability at low resting Ca²⁺ in GRMD cardiomyocytes than in controls. ARM036 prevented those in vivo and in vitro dysfunctions in GRMD dogs. Myofilament Ca²⁺-sensitivity was increased in permeabilized GRMD cardiomyocytes at short sarcomere length. ARM036 had no effect on this parameter. Cross-bridge cycling kinetics were altered in GRMD myocytes and recovered with ARM036 treatment, which coincided with the level of myosin binding protein-C-S glutathionylation.

CONCLUSIONS

GRMD-dogs exhibit early LV dysfunction associated with altered myofilament contractile properties. These abnormalities were prevented pharmacologically by stabilizing RyR2 with ARM036.

[Prognostic value of preoperative peripheral blood neutrophil-to-lymphocyte ratio and γ-glutamyl transpeptidase-to-platelet ratio index in patients with hepatitis B virus related intrahepatic cholangiocarcinoma after radical resection]

Objective: To explore the value of preoperative neutrophil-to-lymphocyte ratio (NLR) and γ-glutamyl transpeptidase-to-platelet ratio index (GPRI) for predicting the prognosis of patients with HBV-related intrahepatic cholangiocarcinoma (ICC) after radical resection. Methods: The data of 79 patients who underwent radical resection for HBV-related ICC in the Department of Hepatobiliary Surgery of the First Affiliated Hospital of Xi'an Jiaotong University from January 2010 to December 2018 were retrospectively analyzed. Among them, 48(60.8%) patients were male and 31 (39.2%) patients were female, (56.9±11.2) years old. X-Tile statistical software was used to determine the best cut-off values of NLR and GPRI. The χ² test was conducted to analyze the relationship between preoperative NLR and GPRI and the clinicopathological characteristics, and the Cox proportional hazard regression model was conducted for multivariate analysis. A nomogram prognostic prediction model was established based on independent risk factors screened by Cox regression model. Results: The best cut-off values of NLR and GPRI were 3.13 and 1.31 determined by the X-Tile software, respectively. With the best cut-off value, 79 patients were divided into NLR≤3.13 group (45 cases) and NLR>3.13 group (34 cases). GPRI≤1.31 group (54 cases) and GPRI>1.31 group (25 cases). Compared with the preoperative NLR ≤3.13 group, the proportion of patients with liver cirrhosis and atrophy, poor pathological differentiation, tumor diameter>5 cm and late TNM stage was significantly increased in the NLR>3.13 group (all P<0.05); Compared with preoperative GPRI ≤1.31 group, the proportion of patients with liver cirrhosis and atrophy was significantly increased in the GPRI>1.31 group (P=0.025). The postoperative overall survival time of the included patients was 2 to 126 months, with the median survival time being 18 months, and the 1, 3-year overall survival rates were 63.3%, 32.8%, respectively. Multivariate analysis showed that NLR, GPRI, liver cirrhosis and atrophy, and lymphatic metastasis were independent risk factors affecting the overall survival of patients with HBV-related ICC after radical resection (P<0.05). A nomogram prediction model was established based on independent risk factors, with the C-index of 0.750, and the prediction effect was close to the actual survival outcome of the patients. Conclusion: Preoperative peripheral blood NLR and GPRI can be used to predict the prognosis of patients with HBV-related ICC after radical resection.

[Analysis of related factors for gallstones related gallbladder intraepithelial neoplasia and establishment of prediction models]

Objective: To evaluate the related factors of gallstones related gallbladder intraepithelial neoplasia(GBIN) and establish the prediction models for gallstones related GBIN. Methods: The clinicopathological data of 750 patients who underwent cholecystectomy for gallstones at Department of Hepatobiliary Surgery of the First Affiliated Hospital of Xi'an Jiaotong University from January 2013 to December 2018 and the postoperative pathological examination showed chronic cholecystitis or GBIN were analyzed retrospectively,including 150 cases of gallstones with GBIN and 600 cases of gallstones with chronic cholecystitis.There were 264 males and 486 females with age of (51.3±14.5) years (range: 18 to 90 years).The related factors for gallstones related GBIN were screened by χ2 test and Logistic regression model,and the prediction models were established based on independent related factors and internal validation was conducted.The original data were randomly divided into a training cohort(526 cases) and a validation cohort(224 cases) at a ratio of 7∶3,and the nomogram and tree augmented naïve Bayes were conducted to establish the prediction model for gallstones related GBIN.The consistency index(C-index),calibration chart,area under the receiver operating characteristic curve(AUC) and confusion matrix were used to evaluate the prediction performance of the two models. Results: Univariate analysis showed that age,gallstones history(years),gallbladder size,whether the gallbladder mucosa smooth or not,whether the gallbladder wall thickened or not,gallstones diameter,and number of gallstones were related factors for the occurrence of gallstones related GBIN (χ²=19.957,8.599,9.724,9.301,8.341,15.288,9.169,all P<0.05).Multivariate analysis showed that age (OR=2.23,95%CI:1.50-3.31,P<0.01),gallbladder size (OR=2.11,95%CI:1.17-3.80,P=0.013),whether the gallbladder mucosa smooth or not (OR=1.80,95%CI=1.13-2.88,P=0.014),gallstones diameter(OR=2.98,95%CI:1.71-5.21,P<0.01),and number of gallstones (OR=2.14,95%CI=1.34-3.42,P<0.01) were independent related factors for the occurrence of gallstones related GBIN; the C-index of the nomogram in training cohort and validation cohort were 0.708 and 0.696,respectively.The AUC of the two models in training cohort were 70.60% and 70.73%,and in validation cohort were 68.14% and 67.47%,respectively.The accuracy of the two models in training cohort were 69.96% and 70.72%,and in validation cohort were 66.96% and 67.41%,respectively. Conclusion: Age,gallbladder size,whether the gallbladder mucosa smooth or not,gallstones diameter and number of gallstones are independent related factors for the occurrence of gallstones related GBIN,and the nomogram and tree augmented naïve Bayes prediction models based on the above factors can be used to predict the occurrence of GBIN.

Protective effects of rimeporide on left ventricular function in golden retriever muscular dystrophy dogs

BACKGROUND

Alterations in intracellular Na+ and Ca2+ have been observed in patients with Duchenne muscular dystrophy (DMD) and in animal models of DMD, and inhibition of Na+-H+ exchanger 1 (NHE1) by rimeporide has previously demonstrated cardioprotective effects in animal models of myocardial ischemia and heart failure. Since heart failure is becoming a predominant cause of death in DMD patients, this study aimed to demonstrate a cardioprotective effect of chronic administration of rimeporide in a canine model of DMD.

METHODS

Golden retriever muscular dystrophy (GRMD) dogs were randomized to orally receive rimeporide (10 mg/kg, twice a day) or placebo from 2 months to 1 year of age. Left ventricular (LV) function was assessed by conventional and advanced echocardiography.

RESULTS

Compared with placebo-treated GRMD, LV function deterioration with age was limited in rimeporide-treated GRMD dogs as indicated by the preservation of LV ejection fraction as well as overall cardiac parameters different from placebo-treated dogs, as revealed by composite cardiac scores and principal component analysis. In addition, principal component analysis clustered rimeporide-treated GRMD dogs close to healthy control dogs.

CONCLUSIONS

Chronic administration of the NHE1 inhibitor rimeporide exerted a protective effect against LV function decline in GRMD dogs. This study provides proof of concept to explore the cardiac effects of rimeporide in DMD patients.

Improvement of left ventricular filling by ivabradine during chronic hypertension: involvement of contraction-relaxation coupling

Chronic hypertension is associated with left ventricular (LV) hypertrophy and LV diastolic dysfunction with impaired isovolumic relaxation and abnormal LV filling. Increased heart rate (HR) worsens these alterations. We investigated whether the I f channel blocker ivabradine exerts beneficial effects on LV filling dynamic. In this setting, we also evaluated the relationship between LV filling and isovolumic contraction as a consequence of contraction-relaxation coupling. Therefore, hypertension was induced by a continuous infusion of angiotensin II during 28 days in 10 chronically instrumented pigs. LV function was investigated after stopping angiotensin II infusion to offset the changes in loading conditions. In the normal heart, LV relaxation filling, LV early filling, LV peak early filling rate were positively correlated to HR. In contrast, these parameters were significantly reduced at day 28 vs. day 0 (18, 42, and 26 %, respectively) despite the increase in HR (108 ± 6 beats/min vs. 73 ± 2 beats/min, respectively). These abnormalities were corrected by acute administration of ivabradine (1 mg/kg, iv). Ivabradine still exerted these effects when HR was controlled at 150 beats/min by atrial pacing. Interestingly, LV relaxation filling, LV early filling and LV peak early filling were strongly correlated with both isovolumic contraction and relaxation. In conclusion, ivabradine improves LV filling during chronic hypertension. The mechanism involves LV contraction-relaxation coupling through normalization of isovolumic contraction and relaxation as well as HR-independent mechanisms.

Vascular endothelial dysfunction and pharmacological treatment

The endothelium exerts multiple actions involving regulation of vascular permeability and tone, coagulation and fibrinolysis, inflammatory and immunological reactions and cell growth. Alterations of one or more such actions may cause vascular endothelial dysfunction. Different risk factors such as hypercholesterolemia, homocystinemia, hyperglycemia, hypertension, smoking, inflammation, and aging contribute to the development of endothelial dysfunction. Mechanisms underlying endothelial dysfunction are multiple, including impaired endothelium-derived vasodilators, enhanced endothelium-derived vasoconstrictors, over production of reactive oxygen species and reactive nitrogen species, activation of inflammatory and immune reactions, and imbalance of coagulation and fibrinolysis. Endothelial dysfunction occurs in many cardiovascular diseases, which involves different mechanisms, depending on specific risk factors affecting the disease. Among these mechanisms, a reduction in nitric oxide (NO) bioavailability plays a central role in the development of endothelial dysfunction because NO exerts diverse physiological actions, including vasodilation, anti-inflammation, antiplatelet, antiproliferation and antimigration. Experimental and clinical studies have demonstrated that a variety of currently used or investigational drugs, such as angiotensin-converting enzyme inhibitors, angiotensin AT1 receptors blockers, angiotensin-(1-7), antioxidants, beta-blockers, calcium channel blockers, endothelial NO synthase enhancers, phosphodiesterase 5 inhibitors, sphingosine-1-phosphate and statins, exert endothelial protective effects. Due to the difference in mechanisms of action, these drugs need to be used according to specific mechanisms underlying endothelial dysfunction of the disease.

Ivabradine improves left ventricular function during chronic hypertension in conscious pigs

During chronic hypertension, increases in heart rate (HR) or adrenergic stimulation are associated with maladaptive left ventricular responses as isovolumic contraction and relaxation durations failed to reduce, impeding filling. We, therefore, investigated the effects of acute selective HR reduction with ivabradine on left ventricular dysfunction during chronic hypertension. Accordingly, chronically instrumented pigs received angiotensin II infusion during 4 weeks to induce chronic hypertension. Left ventricular function was investigated while angiotensin II infusion was stopped. A single intravenous dose of ivabradine was administered at days 0 and 28. Dobutamine infusion was also performed. HR was increased at day 28 versus day 0. Paradoxically, both isovolumic contraction and relaxation times failed to reduce and remained unchanged (57±3 versus 58±3 ms and 74±3 versus 70±3 at day 28 versus day 0, respectively). At day 28, ivabradine significantly reduced HR by 27%. Concomitantly, abnormal ventricular responses were corrected because both isovolumic contraction and relaxation times were significantly reduced while filling time was improved. Similarly at day 28, maladaptive responses of isovolumic contraction and relaxation to dobutamine were no longer observed during HR reduction with ivabradine. Correction of HR reduction with pacing showed that non-HR-related mechanisms also participated to these beneficial effects. In this model of chronic hypertension and left ventricular hypertrophy, acute HR reduction with ivabradine corrects the maladaptive responses of cardiac cycle phases by restoring a normal profile for isovolumic contraction and relaxation both at rest and under adrenergic stimuli, ultimately favoring filling.

AT1 blockade abolishes left ventricular hypertrophy in heterozygous cMyBP-C null mice: role of FHL1

This research investigated the impact of angiotensin AT1 receptor (Agtr1) blockade on left ventricular (LV) hypertrophy in a mouse model of human hypertrophic cardiomyopathy (HCM), which carries one functional allele of Mybpc3 gene coding cardiac myosin-binding protein C (cMyBP-C). Five-month-old heterozygous cMyBP-C knockout (Het-KO) and wild-type mice were treated with irbesartan (50 mg/kg/day) or vehicle for 8 weeks. Arterial blood pressure was measured by tail cuff plethysmography. LV dimension and function were accessed by echocardiography. Myocardial gene expression was evaluated using RT-qPCR. Compared with wild-type littermates, Het-KO mice had greater LV/body weight ratio (4.0 ± 0.1 vs. 3.3 ± 0.1 mg/g, P < 0.001), thicker interventricular septal wall (0.70 ± 0.02 vs. 0.65 ± 0.01 mm, P < 0.02), lower Mybpc3 mRNA level (-43%, P < 0.02), higher four-and-a-half LIM domains 1 (Fhl1, +110%, P < 0.01), and angiotensin-converting enzyme 1 (Ace1, +67%, P < 0.05), but unchanged Agtr1 mRNA levels in the septum. Treatment with irbesartan had no effect in wild-type mice but abolished septum-predominant LV hypertrophy and Fhl1 upregulation without changes in Ace1 but with an increased Agtr1 (+42%) in Het-KO mice. Thus, septum-predominant LV hypertrophy in Het-KO mice is combined with higher Fhl1 expression, which can be abolished by AT1 receptor blockade, indicating a role of the renin-angiotensin system and Fhl1 in cMyBP-C-related HCM.

Different cross-talk sites between the renin-angiotensin and the kallikrein-kinin systems

Targeting the renin-angiotensin system (RAS) constitutes a major advance in the treatment of cardiovascular diseases. Evidence indicates that angiotensin-converting enzyme inhibitors and angiotensin AT1 receptor blockers act on both the RAS and the kallikrein-kinin system (KKS). In addition to the interaction between the RAS and KKS at the level of angiotensin-converting enzyme catalyzing both angiotensin II generation and bradykinin degradation, the RAS and KKS also interact at other levels: 1) prolylcarboxypeptidase, an angiotensin II inactivating enzyme and a prekallikrein activator; 2) kallikrein, a kinin-generating and prorenin-activating enzyme; 3) angiotensin-(1-7) exerts kininlike effects and potentiates the effects of bradykinin; and 4) the angiotensin AT1 receptor forms heterodimers with the bradykinin B2 receptor. Moreover, angiotensin II enhances B1 and B2 receptor expression via transcriptional mechanisms. These cross-talks explain why both the RAS and KKS are up-regulated in some circumstances, whereas in other circumstances both systems change in the opposite manner, expressed as an activated RAS and a depressed KKS. As the cross-talks between the RAS and the KKS play an important role in response to different stimuli, taking these cross-talks between the two systems into account may help in the development of drugs targeting the two systems.

Impaired left ventricular function in the presence of preserved ejection in chronic hypertensive conscious pigs

Systolic function is often evaluated by measuring ejection fraction and its preservation is often assimilated with the lack of impairment of systolic left ventricular (LV) function. Considering the left ventricle as a muscular pump, we explored LV function during chronic hypertension independently of increased afterload conditions. Fourteen conscious and chronically instrumented pigs received continuous infusion of either angiotensin II (n = 8) or saline (n = 6) during 28 days. Hemodynamic recordings were regularly performed in the presence and 1 h after stopping angiotensin II infusion to evaluate intrinsic LV function. Throughout the protocol, the mean arterial pressure steadily increased by 55 ± 4 mmHg in angiotensin II-treated animals. There were no significant changes in stroke volume, LV fractional shortening or LV wall thickening, indicating the lack of alterations in LV ejection. In contrast, we observed maladaptive changes with (1) the lack of reduction in isovolumic contraction and relaxation durations with heart rate increases, (2) abnormally blunted isovolumic contraction and relaxation responses to dobutamine and (3) a linear correlation between isovolumic contraction and relaxation durations. None of these changes were observed in saline-infused animals. In conclusion, we provide evidence of impaired LV function with concomitant isovolumic contraction and relaxation abnormalities during chronic hypertension while ejection remains preserved and no sign of heart failure is present. The evaluation under unloaded conditions shows intrinsic LV abnormalities.

Bradykinin restores left ventricular function, sarcomeric protein phosphorylation, and e/nNOS levels in dogs with Duchenne muscular dystrophy cardiomyopathy

AIMS

Cardiomyopathy is a lethal result of Duchenne muscular dystrophy (DMD), but its characteristics remain elusive. The golden retriever muscular dystrophy (GRMD) dogs produce DMD pathology and mirror DMD patient's symptoms, including cardiomyopathy. We previously showed that bradykinin slows the development of pacing-induced heart failure. Therefore, the goals of this research were to characterize dystrophin-deficiency cardiomyopathy and to examine cardiac effects of bradykinin in GRMD dogs.

METHODS AND RESULTS

At baseline, adult GRMD dogs had reduced fractional shortening (28 ± 2 vs. 38 ± 2% in control dogs, P < 0.001) and left ventricular (LV) subendocardial dysfunction leading to impaired endo-epicardial gradient of radial systolic velocity (1.3 ± 0.1 vs. 3.8 ± 0.2 cm/s in control dogs, P < 0.001) measured by echocardiography. These changes were normalized by bradykinin infusion (1 µg/min, 4 weeks). In isolated permeabilized LV subendocardial cells of GRMD dogs, tension-calcium relationships were shifted downward and force-generating capacity and transmural gradient of myofilament length-dependent activation were impaired compared with control dogs. Concomitantly, phosphorylation of sarcomeric regulatory proteins and levels of endothelial and neuronal nitric oxide synthase (e/nNOS) in LV myocardium were significantly altered in GRMD dogs. All these abnormalities were normalized in bradykinin-treated GRMD dogs.

CONCLUSIONS

Cardiomyopathy in GRMD dogs is characterized by profound LV subendocardial dysfunction, abnormal sarcomeric protein phosphorylation, and impaired e/nNOS, which can be normalized by bradykinin treatment. These data provide new insights into the pathophysiological mechanisms accounting for DMD cardiomyopathy and open new therapeutic perspectives.

The inotropic adaptation during late preconditioning against myocardial stunning is associated with an increase in FKBP12.6

The inotropic adaptation during late preconditioning against myocardial stunning is associated with an increase in FKBP12.6. by Laurence Lucats, Laurent Vinet, Alain Bizé, Xavier Monnet, Didier Morin, Jin Bo Su, Patricia Rouet-Benzineb, Olivier Cazorla, Jean-Jacques Mercadier, Luc Hittinger, Alain Berdeaux, Bijan Ghaleh.

OBJECTIVES

Late preconditioning reduces contractile dysfunction during myocardial stunning. Mechanisms involving adaptation of calcium handling during excitation-contraction coupling to late preconditioning remain to be established. Thus, we investigated whether the late preconditioned myocardium is associated with contractile adaptation and changes in the cardiac ryanodine receptor (RyR2) and its regulatory protein FKBP12.6.

METHODS

Chronically instrumented conscious dogs (coronary occluder, ultrasonic crystals for sonomicrometry) underwent a 10-min coronary artery occlusion followed by reperfusion. They were studied 24 h later in the late preconditioned state (day 1).

RESULTS

Maximal velocity of wall thickening at day 1 was increased as compared to corresponding baseline at day 0 (39+/-4 vs. 30+/-3 mm/s, p < 0.05) although systolic wall thickening was similar (2.8+/-0.2 vs. 2.9+/-0.2 mm), demonstrating a significant change in left ventricular inotropic state. Intracoronary infusion of ryanodine (0.5-6 microg) induced a dose-dependent decrease in wall thickening. In the late preconditioned state, this negative inotropic response was significantly reduced vs. control state, suggesting changes in sarcoplasmic reticulum (SR) Ca2+-release through RyR2. Immunoquantification of FKBP12.6 revealed a 2.8 fold ventricular increase after late preconditioning as compared to the control state. The amount of RyR2 and its phosphorylated state were similar and binding experiments did not reveal any alterations in B(max) or K(D) for RyR2. Calsequestrin, SERCA2a and phospholamban levels were not altered by late preconditioning.

CONCLUSIONS

The late preconditioned myocardium is characterized by an adaptation of regional function associated with an increased expression of FKBP12.6. This demonstrates an adaptation of the SR Ca2+-release through RyR2 during late preconditioning.

Kinins and cardiovascular diseases

Kinins are synthesized from their precursors by different enzymes and participate in the regulation of cardiovascular function through bradykinin (BK) B1 and B2 receptors. They modulate blood coagulation by exerting antithrombotic and profibrinolytic actions. By activating B2 receptors that results in the release of nitric oxide and prostacyclin, kinins inhibit vascular smooth muscle growth and neointima formation, which may play an inhibitory role on the atherosclerosis development, while through the activation of B1 receptors, they may play a deleterious role in this disease. Kinins are potent endogenous vasodilators that are involved in the regulation of coronary vascular tone. However, due to their metabolic characteristics, these peptides act mainly as an autocrine/paracrine factor to locally regulate blood perfusion of organs. By modulating cellular energy metabolism and myocardial oxygen consumption, they protect cardiac and vascular endothelial function in myocardial ischemia and heart failure. Finally, mounting evidence indicates that kinins are involved in the actions of some drugs actually used in the treatment of cardiovascular diseases such as angiotensin-converting enzyme inhibitors and angiotensin AT1 receptor antagonists. Taken together, the kinin system constitutes a potential therapeutic target for cardiovascular diseases. Experiments in animals attempted to explore the kinin system as a therapeutic means, including the mobilization of endogenous kinins using pharmacological agents, searching BK analogs with long-acting properties and gene therapies. However, the potential values of the kinin system have not been taken into consideration in clinical practice for cardiovascular indications.

Tumor necrosis factor alpha and glutathione interplay in chronic heart failure

The pro-inflammatory cytokine, tumor necrosis factor alpha (TNF alpha), in concert with neurohormones, contributes to chronic heart failure (CHF) progression. This implies that TNF a antagonism may constitute an important target for CHF therapy. However, clinical trials in CHF patients using compounds that trap TNF alpha, comprising infliximab, an antibody directed to TNF alpha, and etanercept, a soluble recombinant receptor of TNF alpha, gave disappointing results bringing back to light the dual, short-term beneficial and long-term harmful effect of TNF alpha. This review focuses on the dual, concentration- and time-related effects of TNF alpha, the yin and yang action of TNF alpha in cardiac ischemia/reperfusion and contraction. Importantly, the harmful effects of TNF a are related to glutathione deficiency, a common hallmark to several other chronic inflammatory diseases. Recently, in rat models of CHF, oral administration of the glutathione precursor, N-acetylcysteine (NAC), was shown to hinder pathways of TNF alpha harmful signalling and to rescue cardiac structure and function. These results suggest that glutathione deficiency in association with TNF alpha activation may play a role in the pathophysiology of CHF and that NAC may represent a potential therapy in CHF.

N-acetylcysteine treatment normalizes serum tumor necrosis factor-alpha level and hinders the progression of cardiac injury in hypertensive rats

BACKGROUND

Studies in isolated cardiomyocytes showed that replenishment in cellular glutathione, achieved with the glutathione precursor N-acetylcysteine (NAC), abrogated deleterious effects of tumor necrosis factor-alpha (TNF-alpha).

METHODS AND RESULTS

We examined the ability of NAC to limit the progression of cardiac injury in the rat model of hypertension, induced by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) (50 mg/kg per day SC) and high-salt diet (HS) (8% NaCl). Four-week HS/L-NAME administration induced hypertension (193+/-8 versus 122+/-4 mm Hg for low-salt diet [LS] group) and left ventricular (LV) dysfunction, revealed by echocardiography and characterized by decreased LV shortening fraction (38+/-2% versus 49+/-4% for LS group; P<0.05) and decreased LV posterior wall thickening (49+/-3% versus 70+/-4% for LS group; P<0.05). LV dysfunction worsened further after 6-week HS/L-NAME administration. Importantly, increase in serum TNF-alpha level was strongly correlated with shortening fraction decrease and cardiac glutathione depletion. NAC (75 mg/d) was given as a therapeutic treatment in a subgroup of HS/L-NAME animals during weeks 5 and 6 of HS/L-NAME administration. NAC treatment, which replenished cardiac glutathione, had no effect on hypertension but reduced LV remodeling and dysfunction, normalized serum TNF-alpha level, and limited activation of matrix metalloproteinases -2 and -9 and collagen deposition in LV tissues.

CONCLUSIONS

These findings suggest that glutathione status determines the adverse effects of TNF-alpha in cardiac failure and that TNF-alpha antagonism may be achieved by glutathione supplementation.

Chronic infusion of bradykinin delays the progression of heart failure and preserves vascular endothelium-mediated vasodilation in conscious dogs

BACKGROUND

This study examined the effects of chronic bradykinin infusion on hemodynamics and myocardial and endothelial functions during the development of heart failure.

METHODS AND RESULTS

Sixteen instrumented dogs were randomized to receive through the left atria either vehicle or bradykinin (1 microg/min) during ventricular pacing (250 bpm, 5 weeks). Hemodynamic and left ventricular (LV) parameters and the vasodilator responses to intravenous acetylcholine (0.3 to 3 microg/kg) and nitroglycerin (1 to 10 microg/kg) were examined in the control and after 3 and 5 weeks of pacing. The expression of endothelial NOS in femoral, carotid, and renal arteries was determined by Western blot analysis. After 3 weeks of pacing, changes in LV diastolic and systolic parameters were significantly lower in bradykinin-treated than vehicle-treated dogs (LV end-diastolic pressure, +10+/-3 versus +19+/-2 mm Hg; time constant of LV isovolumic relaxation, +11+/-2 versus +17+/-1 ms; LV wall thickening, -33+/-18% versus -75+/-9%; and cardiac output, -16+/-6% versus -32+/-6%; all P<0.05). Compared with vehicle-treated dogs, bradykinin-treated dogs had a reduced rightward shift of the diastolic LV pressure-diameter relation and a reduced diastolic LV wall stress. Similar trends were observed after 5 weeks. The vasodilator response to nitroglycerin was preserved in both groups. The response to acetylcholine was blunted in vehicle-treated but preserved in bradykinin-treated dogs. Vascular endothelial NOS expression decreased in vehicle-treated but was preserved in bradykinin-treated dogs.

CONCLUSIONS

In conscious dogs, chronic bradykinin infusion delays the heart failure progression by preserving LV diastolic and systolic functions and by preserving vascular endothelial function.

[Electromechanical mapping of myocardial ischemia in coronary occlusion in the pig]

The NOGA-Biosense catheter-based mapping technique has been well studied experimentally in infarction model. However, chronic myocardial ischemia with this new device has not been well explored. Thus, the aim of our study was to assess electromechanical changes in a pig aneroid constricor model. To achieved this aim, ten pigs were studied 21 days after the implantation of an aneroid constrictor around the circumflex artery. Coronary reserve assess by intracoronary Doppler flow wire was reduced in the ischemic lateral area (ILA) compared with the nonischemic zone (NIZ) (1.3 +/- 0.1 in the ILA vs. 2.3 +/- 0.2 in the NSZ; p < 0.01). TM echocardiography was used to evaluate myocardial regional contractility under basal condition and after stress induced by rapid atrial pacing. In stress state, the ischemic zone showed an impaired contractility compared with basal state (wall thickening, 32.7 +/- 7.4% vs. 59.7 +/- 8.6%; p < 0.05) whereas the non ischemic zone did not (53.8 +/- 7.6% vs. 60.8 +/- 10.1%; p = ns). Constrast echography showed a decrease in contrast intensity in subendocardium of the ila compared with the niz (46.2 +/- 16.6 vs. 99.2 +/- 35.6; p = 0.03) in pacing. Ventricular mapping quantified unipolar (UV). bipolar (BV) voltage potentials and endocardial local shortening (LLS) in 9 left ventricular regions. In basal state, electrical potentials were preserved in both zones (UV: 9.1 +/- 1.8 mV in the ischemic vs 11.3 +/- 3.6 mV in the non ischemic zone; p = ns; BV: 4.2 +/- 1.1 mV in the ILA vs. 3.9 +/- 1.5 mV; p = ns). In contrast, LLS was significantly lower in the ischemic compared with non ischemic zone (6.4 +/- 5.4% vs. 17.9 +/- 3.0%, p < 0.001). In conclusion, ventricular mapping with the NOGA-Biosense system can identify the ischemic myocardium. In this pig model, the association of a preserved electrical activity and an impaired mechanical activity characterizes the ischemic myocardium. These findings could be interesting in this model in regard of the new developments of the system in particular in the field of angiogenesis.

[Aldosterone and its antagonists in heart failure]

THE ROLE OF ALDOSTERONE: Aldosterone is the key hormone in salt-water homeostasis. In heart failure, it participates in the appearance and maintenance of signs of congestion. Predominantly synthesised in the glomerular area of the cortico-adrenal glands, extra adrenal production areas have recently been identified notably in the brain, the heart and the large artery trunks. Aldosterone is activated in the cells by the intracellular mineral corticoid receptor. IN CARDIOVASCULAR-PATHOLOGIES: In chronic heart failure, patients treated with conversion enzyme inhibitor may escape from the renin-angiotensin blockade and this may lead to increased aldosterone plasma levels. This increase can induce not only vascular lesions and myocardial fibrosis but also renal and cerebral lesions.

THE EFFECTS OF SPIRONOLACTONE

In patients with NYHA stage III or IV heart failure, addition of spironolactone to the treatment with conversion enzyme inhibitor, diuretic and/or digitalis leads to a reduction in morbidity and mortality, as demonstrated in the RALES study. The mechanisms by which spironolactone has a beneficial effect remain discussed.

IN CLINICAL PRACTICE

The prescription of spironolactone is limited by hormonal side effects it provokes.

IN THE FUTURE

Eplerenone, a new competitive aldosterone receptor antagonist that appears to be devoid of such side effects and which, at least experimentally may well have the same beneficial effects, is presently under clinical assessment.

Different effects of mibefradil and amlodipine on coronary vessels and during beta-adrenergic stimulation in conscious dogs

Coronary effects of Ca -channel blockers mibefradil and amlodipine were compared in conscious dogs. Ten dogs were instrumented for measurement of aortic and left ventricular pressures, circumflex coronary blood flow velocity (CBFv), and coronary diameter (CD). A permanent catheter was implanted in the circumflex coronary artery. At doses having no systemic effects (7.5-150 micro g/kg), mibefradil and amlodipine increased CBFv and CD dose dependently. At the same dose, mibefradil increased less CBFv than amlodipine. However, for a similar increase in CBFv induced by amlodipine, mibefradil increased CD more. BAY K8644, an L-type Ca -channel agonist, prevented the CBFv and CD responses to amlodipine, but minimally affected the coronary responses to mibefradil. Intracoronary isoproterenol (6 ng/kg) increased LV dP/dt max, CBFv, and CD. Amlodipine markedly altered these responses, while mibefradil did not affect LV inotropic response and slightly altered CBFv response to isoproterenol. Thus, in conscious dogs, both mibefradil and amlodipine exert coronary vasodilation, with different patterns on coronary conductance and resistance vessels and during beta-adrenergic stimulation. These differences could be related to their actions on different Ca channels.

Reduced coronary vasodilator responses to amlodipine in pacing-induced heart failure in conscious dogs: role of nitric oxide

1. This study examined whether NO is involved in the in-vivo coronary vasodilator effects of amlodipine (a calcium channel blocker) and whether heart failure (HF) alters the coronary responses to amlodipine. 2. Nine conscious dogs were chronically instrumented to measure circumflex coronary blood flow (CBF) and coronary diameter (CD). Drugs were administered directly into the circumflex artery through an indwelling catheter to avoid systemic changes. HF was induced by right ventricular pacing (240 b.p.m., 3 weeks). 3. Compared with control (C), in HF, coronary responses to acetylcholine (1 - 10 ng kg(-1)) were reduced while responses to nitroglycerin (0.1 - 0.5 microg kg(-1)) were unchanged. In C, amlodipine (30 - 150 microg kg(-1)), increased dose-dependently CBF and CD. After LNA (a NO synthase inhibitor, 2 mg kg(-1)), amlodipine produced less increases in CBF and CD (+121+/-26 ml min(-1) and +76+/-35 microm versus +196+/-40 ml min(-1) and +153+/-39 microm respectively for 150 microg kg(-1) amlodipine alone, both P<0.05). In HF, the coronary responses to amlodipine were reduced (150 microg kg(-1) of amlodipine increased CBF and CD +121+/-23 ml min(-1) and +77+/-21 microm respectively, both P<0.05). After LNA, the CBF responses to amlodipine tended to be reduced (+94+/-19 ml min(-1) at 150 microg kg(-1)) but CD responses were significantly reduced (+41+/-16 microm, P<0.05). The supplementation with L-arginine did not enhance the coronary responses to amlodipine. 4. These results indicate that, in conscious dogs, NO participates in the coronary responses to amlodipine and in HF, the coronary responses to amlodipine are reduced, which is related to a reduced NO production.

Inflammation, cytokines and anti-inflammatory therapies in heart failure

Both experimental and clinical studies have shown a role for inflammation in the pathogenesis of heart failure. This seems related to an imbalance between pro-inflammatory and anti-inflammatory cytokines. Certain categories in patients with dilated cardiomyopathy have shown the presence of humoral and cellular immunity activation suggesting a possible relation between myocarditis and dilated cardiomyopathy. Recent studies suggest a link between the circulating levels of cytokines (TNF alpha IL-1 et IL-6), the clinical status and prognostic. However, the mechanisms connecting heart failure and cytokine activation are unclear and the sites of cytokines production remain controversial. In the clinical setting, specific measurements of cytokines are not available. As tests of inflammation, erythrocyte sedimentation rate and C-reactive protein concentration appear to have interesting pronostic values. Current conventional therapy i.e. ACE inhibitors, type I angiotensin II antagonist and beta-blockers have shown some anti-cytokine properties. Recently, immunosuppressive therapies have shown their ability to improve symptoms and LV ejection in selected patients with dilated cardiomyopathy and clear sign of myocardium inflammation. Specific anti-cytokine therapy have been developed and showed interesting results in preliminary clinical studies. However large clinical trials testing this new therapy have been stoppel prematurely because of deterious effects.

[Future molecules in heart failure]

TODAY: The management of heart failure (HF) has considerably progressed over the last two decades. Treatment today relies on prevention and treatment of congestion (limited salt intake, diuretics, converting enzyme inhibitors) and limiting neurohormone stimulation (converting enzyme inhibitors +/- aldactone, beta-blockers). IN THE YEARS TO COME: Based on new concepts, several therapeutic strategies are interesting: blocking over vasoconstrictor systems which have not been taking into account; stimulation of vasodilator and natriuretic systems; modulation of cardiac remodelling; modulation of the immune and inflammatory systems; modification in intrinsic contractility; prevention of rhythm disorders. Among these differing strategies and molecules, it is not easy to predict those that will change the HF prognosis. In any event, their efficacy and safety remain to be demonstrated with large cohort randomised studies. THE PRINCIPLES: To reduce the number of drugs administered, two options appear particularly interesting: measurement of hormone levels (BNP) in order to adjust treatment and administration of molecules with greatest efficacy and safety profiles; limit cardiac remodelling by using new imaging techniques to detect it more precisely and select the molecule(s) exerting the required effect. To target the new molecules better, patients should be classified according to their etiology, stage and progressive profile of their disease, cardiac remodelling, expression of principle endocrine systems and pro-inflammatory cytokines, expression of inflammatory and immune systems and inherent genetic characteristics and response to treatment. This would permit the adaptation of treatment to each individual patient with heart failure.

Stimulation of bradykinin B(1) receptors induces vasodilation in conductance and resistance coronary vessels in conscious dogs: comparison with B(2) receptor stimulation

BACKGROUND

Constitutive bradykinin B(1) receptors have been identified in dogs; however, their physiological implications involving the coronary circulation remain to be determined. This study examined, in conscious dogs, the coronary response to des-Arg(9)-bradykinin (a B(1) receptor agonist) and the mechanisms involved.

METHODS AND RESULTS

Eleven dogs were instrumented with a left ventricular micromanometer, a circumflex coronary catheter, a cuff occluder, a Doppler flow probe, and ultrasonic crystals to measure coronary blood flow velocity (CBFv) and coronary diameter (CD). Intracoronary des-Arg(9)-bradykinin (3 to 100 ng/kg) and bradykinin (0.1 to 10 ng/kg) did not modify systemic hemodynamics but dose-dependently increased CBFv and CD. Des-Arg(9)-bradykinin was less potent than bradykinin. Hoe 140 (a B(2) antagonist, 10 microg/kg) abolished the effects of bradykinin but did not influence the effects of des-Arg(9)-bradykinin. When CBFv increase was prevented by the cuff occluder, CD responses to bradykinin and des-Arg(9)-bradykinin were maintained. Intracoronary lisinopril (0. 75 mg) increased the CD response to bradykinin, with only minimal effect on CBFv, and extended the duration of the effect. Lisinopril did not alter des-Arg(9)-bradykinin responses. Intracoronary N(omega)-nitro-L-arginine (2 mg/kg) decreased the CD effect of bradykinin and prevented the CBFv and CD effects of des-Arg(9)-bradykinin. The relaxing effect of des-Arg(9)-bradykinin on isolated coronary rings was prevented by des-Arg(9), [Leu(8)]-bradykinin.

CONCLUSIONS

In the conscious dog, B(1) receptors are present in coronary vessels, and their stimulation produces vasodilation in conductance and resistance vessels, which is mediated essentially by NO but not modulated by angiotensin-converting enzyme. However, the coronary vasodilation induced by B(1) receptor stimulation is not as great as that produced by B(2) receptor stimulation.

Increased bradykinin levels accompany the hemodynamic response to acute inhibition of angiotensin-converting enzyme in dogs with heart failure

To determine the short-term effects of angiotensin-converting enzyme (ACE) inhibition on hemodynamics and circulating levels of norepinephrine, angiotensin, and bradykinin, responses to enalaprilat and perindoprilat were examined at doses of 0.03, 0.3, and 1 mg/kg in permanently instrumented conscious dogs with pacing-induced heart failure (right ventricular pacing, 240-250 beats/min, 3 weeks). All doses of the two inhibitors produced similar decrease in mean aortic pressure and increase in cardiac output. Neither inhibitor affected plasma norepinephrine level. Both compounds induced a similar 60-80% decrease in blood angiotensin II level, a similar two- to eightfold increase in blood angiotensin I level, and a 80-95% decrease in the angiotensin II/angiotensin I ratio. There were also a fourfold to 10-fold increase in blood bradykinin-(1-9) level, a twofold increase in blood bradykinin-(1-7) level, and a 70-85% decrease in bradykinin-(1-7)/bradykinin-(1-9) ratio. In addition, the changes in total peripheral resistance induced by the two ACE inhibitors were weakly but significantly correlated with the changes in blood angiotensin II or blood bradykinin-(1-9). Thus whatever the specificity of enalaprilat and perindoprilat, both inhibitors produced similar acute hemodynamic effects in dogs with heart failure, which was associated with marked decrease in circulating angiotensin II level and increase in bradykinin-(1-9) level. This study, which measures for the first time in heart failure the blood bradykinin level after ACE inhibitors, indicates, in concert with angiotensin II reduction, a role for increased bradykinin-(1-9) level in mediating short-term hemodynamic effects of ACE inhibition in this model of heart failure.

Preserved vasodilator effect of bradykinin in dogs with heart failure

BACKGROUND

In heart failure (HF), vasoconstrictor systems are activated and endothelium-derived vasodilation is blunted. Bradykinin, a potent vasodilator, may play an important role in this setting. However, it is not known whether its vasodilator effect is modified in HF.

METHODS AND RESULTS

Fourteen chronically instrumented dogs were studied in the control state and in pacing-induced HF (250 bpm for 3 weeks). The dose-dependent decrease in mean aortic pressure (MAP) induced by acetylcholine was significantly blunted in HF. In contrast, in both control and HF, bradykinin infusion caused similar dose-dependent decreases in MAP and increases in cardiac output (CO). This vasodilator effect of exogenous bradykinin was potentiated similarly in both states by enalaprilat, which blocks both angiotensin conversion and bradykinin degradation. For evaluating the role of endogenous bradykinin, the effects of enalaprilat were compared with those of ciprokiren, a pure renin inhibitor. In control, ciprokiren did not produce any effect. Enalaprilat, however, produced a significant decrease in MAP and a significant increase in CO, which were attributed to the inhibition of bradykinin degradation, because these effects were absent after pretreatment with Hoe 140 (a bradykinin B2 receptor antagonist). In contrast, in HF, vasodilator effects of ciprokiren were observed, but enalaprilat produced larger changes in MAP and CO, and after Hoe 140, the hemodynamic effects of enalaprilat were significantly decreased, showing the effects of endogenous bradykinin, which were similar to those measured in control.

CONCLUSIONS

In this model of HF with a blunted endothelium-derived vasodilation, the vasodilator effects of exogenous and endogenous bradykinin are preserved. These results suggest that bradykinin may play an important role in HF, in which vasoconstriction is present and endothelium-dependent vasodilation is blunted.

[Physiopathological basis of the treatment of heart failure]

Therapeutic advances have changed the mode of presentation of cardiac failure over the last decades: the main cause, nowadays, is myocardial ischaemia. The modern treatment of cardiac failure is based on relatively simple physiopathological mechanisms which take into account the different aspects of cardiac physiology: a pump, a muscle, a coronary circulation supplying oxygen to the myocardium, an automatic contraction. The concept of vasodilatation and the blocking of vasoconstrictive systems introduced during the 70s is the basis of modern treatment of cardiac failure which involves angiotensin converting enzyme inhibitors and, increasingly, betablockers. In the near future, with earlier treatment of cardiac failure, the stimulation of vasodilator systems could become a new therapeutic strategy. Early detection of ischaemia and its complications with the aim of limiting the loss of cardiac myocytes is a priority for slowing the progression of cardiac failure. The prevention of cardiac failure also depends on educating cardiologists to treat rapidly the factors predisposing to or prolonging episodes of even mild cardiac failure.

[Effects of high sodium intake on ventricular remodeling in mice]

BACKGROUND

Despite extensive research, controversy still exists regarding the role of dietary sodium intake on hypertension and left ventricular (LV) hypertrophy. Echocardiography is a powerful tool to assess LV hypertrophy and recent technical developments allow now its use in small animals.

METHODS

We examined the effect of high sodium intake on LV geometry using echocardiography in mice. Three groups of Swiss mice were submitted, for 8 weeks, to different salt diets (0.6, 2 and 4% NaCl; n = 12, n = 8 and n = 12 respectively). LV end-diastolic (ED) septal and posterior wall thicknesses, LV ED diameter were measured at baseline, 4 and 8 weeks.

RESULTS

At baseline, heart rate, LV ED septal and posterior wall thicknesses and LV ED diameter were similar between groups. At 8 weeks, for similar heart rate, LV ED posterior wall thickness were not different (0.6%: 0.64 +/- 0.01, 2%: 0.62 +/- 0.08 and 4%: 0.67 +/- 0.03 mm respectively) but LV septal wall thickness ass increased in a salt diet dependent manner (0.6%: 0.63 +/- 0.01, 2%: 0.75 +/- 0.01, 4%: 0.80 +/- 0.02 mm, p < 0.01). This increase was correlated with urinary sodium excretion (r = 0.84, p < 0.01) but occurred in the absence of change in arterial pressure (tail-cuff plethysmography; 0.6%: 135 +/- 6.2%: 127 +/- 4 and 4%: 139 +/- 9 mmHg respectively). The in-vivo interventricular septal remodeling was confirmed in perfused fixed preparations of hearts.

CONCLUSION

Echocardiography allows precise measurements of regional LV wall dimensions in mice, and high sodium intake, in the absence of hypertension, induces interventricular septal remodeling.

Bradykinin pathway is involved in acute hemodynamic effects of enalaprilat in dogs with heart failure

To determine the role of the renin-angiotensin system and the bradykinin pathway in the mechanism of action of angiotensin-converting enzyme inhibitors in heart failure, the acute effects of enalaprilat (1 mg/kg) were compared with those of a renin inhibitor (ciprokiren, 1 mg/kg i.v.) in 10 chronically instrumented conscious dogs with heart failure induced by right ventricular pacing (3 wk, 240 beats/min). The effects of enalaprilat and ciprokiren on bradykinin infusion (3, 10, and 30 micrograms/min) and the effects of enalaprilat in the presence of the bradykinin B2 receptor antagonist Hoe-140 (10 micrograms/kg i.v.) were also examined. Both inhibitors significantly decreased mean aortic pressure and increased cardiac output. However, enalaprilat induced significantly greater hemodynamic effects than ciprokiren (mean aortic pressure, -13 +/- 3 vs. -6 +/- 1 mmHg; cardiac output, 0.4 +/- 0.1 vs. 0.15 +/- 0.1 l/min). Bradykinin infusion led to dose-dependent decreases in mean aortic pressure and increases in cardiac output that were not modified by pretreatment with ciprokiren but were potentiated 10-fold by enalaprilat. Hoe-140 significantly reduced the hemodynamic effects of enalaprilat. Thus endogenous bradykinin is involved in the acute hemodynamic effects of enalaprilat in experimental heart failure.

Regional alterations of left ventricular contraction and inotropic reserve in conscious dogs with heart failure

OBJECTIVE

The goal was to examine left ventricular (LV) regional contraction alterations and especially, regional inotropic reserve changes in tachycardia-induced heart failure (HF).

METHODS

Eleven dogs were chronically instrumented to measure LV pressure and its first time derivative (LV dP/dt), left atrial and aortic pressures and to measure antero-apical (AS), -basal (BS) and postero-apical (PS) subendocardial segmental contractions by ultrasonic crystals. Dobutamine (5-15 micrograms/kg per min) and left atrial pacing (150-240 beats/min) were performed in the control state (C) and in HF induced by chronic right ventricular pacing (240 beats/min, 3 weeks).

RESULTS

In HF, as compared with in C, LV dP/dt max decreased and LV end-diastolic pressure and end-diastolic segmental lengths increased (Ps < 0.005). The percentage of systolic shortening was more depressed in PS (from 21 +/- 1% to 7 +/- 1%, P < 0.001) than in AS and BS (from 24 +/- 1% to 17 +/- 1% and from 20 +/- 2% to 13 +/- 1% respectively, Ps < 0.05). During dobutamine infusion, in HF as compared with C, the increases in LV dP/dt max were smaller (dobutamine 15 micrograms/kg per min: HF: + 36 +/- 6% vs C: + 68 +/- 11%, P < 0.01) and the increases in the systolic shortening of the three segments were also smaller. However, the responses of the three segments were similar in HF and in C. During left atrial pacing, LV dP/dt max increased less in HF than in C and the poststimulation potentiation of LV dP/dt max was impaired in HF. However, the responses of the systolic shortening during regular left atrial pacing and the increase in the percentage of systolic shortening of the first poststimulation beat were similar in all regions.

CONCLUSION

In tachycardia-induced HF, although LV regional contraction is heterogeneously altered, the inotropic reserve appears to be similarly modified in all regions.

Propranolol therapy in experimental heart failure in rabbits improves cardiac response to catecholamines without beta-adrenoceptor up-regulation

Beta-blockade has been shown to improve cardiac response to catecholamines in heart failure but cellular mechanisms of the improvement are unknown. The effect on left ventricular function of a 14 day propranolol treatment was studied in seven treated and eight non-treated rabbits with experimental heart failure. All animals were subjected to a volume (aortic insufficiency) plus pressure (aortic constriction) overload and were instrumented with a left ventricular catheter and ultrasonic crystals measuring anteroposterior left ventricular diameter. Beta-adrenoceptors were measured using 125I-Cyanopindolol in crude membranes. With isoproterenol, the heart rate was slower in treated rabbits than in non-treated rabbits (p < 0.005) and isoproterenol increased more systolic diameter shortening in treated than in non-treated rabbits (p < 0.05). With norepinephrine, for matched pressures, % delta D increased in the treated group but it did not change in the non-treated group. This improvement of ventricular function was due, in a large part, to an increased diastolic response to norepinephrine: end-diastolic diameter increased in the treated group but not in the non-treated group. In contrast with the improved ventricular response to catecholamines, beta-adrenergic receptor density in the treated group was identical to that of the non-treated group (27.8 fmoles/mg/proteins) and was significantly lower than that of normal rabbits (58.2 fmoles/mg, p < 0.01). The improvement of ventricular response to catecholamines appears to be due to a myocardial protection by propranolol against the toxic effect of catecholamines in heart failure and not, at least in this model, to an up-regulation of beta-adrenoceptors.

Limited left ventricular inotropic response to exercise in early phase of pressure overload in dogs

To study the mechanisms of myocardial adaptation to increased stress in the early phase of left ventricular (LV) pressure overload, 12 dogs were instrumented with LV micromanometer, LV dimensional ultrasonic crystals, aortic catheter, and aortic occluder cuff. After recovery, animals performed graded exercise with acute aortic stenosis (AS) or sustained (24 h) aortic stenosis (SS). At baseline, LV functional parameters with SS were not different from those obtained with AS. LV peak pressure increased similarly during exercise with AS or SS, but LV peak dP/dt was lower with SS than with AS (peak values, 6,292 +/- 525 vs. 7,570 +/- 432 mmHg/s; P < 0.05). LV end-diastolic pressure increased from 9.7 +/- 1.7 to 21.4 +/- 3.3 mmHg (P < 0.05) during exercise with SS, but was unchanged with AS. The decrease of the time constant of isovolumic pressure fall during exercise was significantly smaller after SS than during AS (P < 0.05). In addition, the percentage of subendocardial wall thickening did not increase during exercise with SS (30.3 +/- 3.6%), while it increased significantly with AS (from 29.3 +/- 3.3 to 39.4 +/- 4.5%; P < 0.01). Plasma catecholamine levels were similar at baseline and increased to similar levels during exercise with AS and SS. In the early phase of pressure overload, we conclude that exercise capacity is maintained but that the LV inotropic response to exercise is modified with an altered relaxation process and a lesser utilization of subendocardial inotropic reserve.

Species differences in myocardial beta-adrenergic receptor regulation in response to hyperthyroidism

The coupling between myocardial beta-adrenergic receptors, adenylate cyclase activity, and the in vivo cardiac response to catecholamines is controversial in hyperthyroidism. The possibility of species differences in beta-adrenoceptor regulation after thyroxine treatment was studied in dogs and in rats. In dogs instrumented with a left ventricular (LV) pressure micromanometer, hyperthyroidism was induced by L-thyroxine (0.5 mg/kg/day i.v. for 10 days). After hyperthyroidism, heart rate was increased to 167 +/- 10 beats/min (control, 107 +/- 8 beats/min; p less than 0.005) with an increase of peak LV dP/dt from 4,243 +/- 471 to 6,105 +/- 862 mm Hg/sec (p less than 0.01). LV response to injection of increasing doses of isoproterenol and dobutamine was not significantly different before and after induction of the hyperthyroid state, as shown by the unchanged slopes of the LV peak dP/dt versus the log of the dose of isoproterenol and dobutamine. Bmax of beta-receptors measured in crude membranes using 3H-CGP 12177 and in homogenates using 125I-cyanopindolol was not increased in hyperthyroid animals as compared with a control group. Basal adenylate cyclase activity was not different in control and hyperthyroid dogs (32 +/- 3 versus 29 +/- 3 pmol/mg/min), and maximal adenylate cyclase activity response to isoproterenol was similar in control and hyperthyroid dogs. In contrast, in rats subjected to hyperthyroidism (0.5 mg/kg/day i.p. L-thyroxine for 10 days), Bmax of adrenoceptors measured using the same methods was significantly increased as compared with control (+72.5% using 3H-CGP 12177 and +41% using 125I-cyanopindolol, but adenylate cyclase activity was not increased in hyperthyroid rats. We conclude that both adenylate cyclase activity and LV response to catecholamines are not increased by thyroxine-induced hyperthyroidism in dogs and that, in contrast with rats, beta-adrenergic density is not increased in hyperthyroid dogs. This indicates a species difference in myocardial beta-adrenoceptor regulation in response to hyperthyroidism.

Increased negative inotropic effect of calcium-channel blockers in hypertrophied and failing rabbit heart

The effects on ventricular function of calcium channel blockers and isoproterenol were studied in isovolumically beating perfused control rabbit hearts and in hearts subjected to a double pressure plus volume overload studied at the early phase of heart failure. In control hearts, isoproterenol produced an increase of systolic ventricular function and relaxation that was maximal at 10(-7) M. In failing hearts, inotropic state increase in response to isoproterenol was significantly smaller (P less than .01) with no observed lusitropic effect. In control hearts, verapamil and diltiazem produced dose-dependent decreases of ventricular function which were larger with verapamil than with diltiazem (median drug concentration50 of developed pressure was, respectively, 1163 +/- 131 nM and 4524 +/- 451 nM, P less than .001). In failing hearts, contractility decrease was larger than in control hearts (median drug concentration50 of developed pressure was 604 +/- 69 nM and 2691 +/- 580 nM with verapamil and diltiazem, respectively). In contrast, Ro 40-5967, a new calcium-channel blocker, did not produce reductions of inotropic state with concentrations up to 10(-5) M. All three calcium-channel blockers produced a 2-fold increase of coronary flow at 10(-6) M. We conclude that the deleterious effect of verapamil and diltiazem in heart failure is due, at least in part, to a direct depressant effect of these drugs on contractility, which is larger than in control hearts. Additionally, the in vivo sympathetic compensation is probably reduced, as indicated by the decreased ventricular responsiveness to isoproterenol.

Loading determinants of isovolumic pressure fall in closed-chest dogs

The respective roles of load level and loading sequence of the left ventricle (LV) are controversial in the in situ heart. They were analyzed under autonomic blockade and sedation in 17 dogs previously instrumented with a pressure micromanometer and ultrasonic crystals measuring LV diameters and wall thickness for computation of LV volume and stress. The time constant of isovolumic pressure fall (T) and end-systolic pressure (ESP) were calculated during the control state, caval occlusion, aortic constriction obtained by inflation of a hydraulic cuff occluder positioned around the aorta, and during the inflation of an intra-aortic balloon. Caval occlusion significantly decreased both ESP (from 124.0 +/- 6.6 to 88.7 +/- 3.7 mmHg; P less than 0.005) and T (from 29.0 +/- 2.2 to 18.8 +/- 2.4 ms; P less than 0.005), which were linearly correlated (mean r = 0.90 +/- 0.03) and inflation of an intra-aortic balloon increased both ESP (from 107.3 +/- 7.1 to 150.6 +/- 10.4 mmHg; P less than 0.005) and T (from 24.6 +/- 2.1 to 32.7 +/- 2.3 ms; P less than 0.005). Both interventions did not modify the loading sequence (analyzed by the evolution of systolic wall stress vs. time). In contrast, aortic constriction delayed to midsystole the time to which wall stress reached its peak and, for matched ESP with intra-aortic balloon inflation, T was not significantly different from control. We conclude that both the level of afterload and the loading sequence of LV are the determinants of T when contractility is not modified.

Preload-induced curvilinearity of left ventricular end-systolic pressure-volume relations. Effects on derived indexes in closed-chest dogs

End-systolic pressure-volume relations (ESPVRs) were analyzed in 10 closed-chest autonomically blocked dogs before and after volume loading that restored end-diastolic volume to its value measured in the control conscious state. Dogs had been previously instrumented with a left ventricular pressure micromanometer and ultrasonic crystals for measurements of major, anteroposterior, and septum-free wall diameters. Left ventricular volume was calculated with an ellipsoidal model in the left ventricular cavity. ESPVRs obtained during caval occlusion after volume loading were curvilinear as shown by the division of the relation into two parts. The initial part of the relation had a significantly smaller ESPVR slope (Ees, 12.0 +/- 1.8 mm Hg/ml) and ESPVR volume-axis intercept (Vd, - 3.5 +/- 0.8 ml) than the final part of the relation (19.5 +/- 3.1 mm Hg/ml and 0.0 +/- 0.6 ml, respectively, p less than 0.01). The end-diastolic volume-peak dP/dt relation showed a similar curvilinearity when end-diastolic volumes were larger than 1.5-1.7 times the minimal end-diastolic volume reached during caval occlusion. ESPVRs were not different during aortic constriction and caval occlusion when end-diastolic volume was small. In contrast, with large end-diastolic volumes, Ees and Vd were significantly smaller during caval occlusion than during aortic constriction. The final part of ESPVR (with small end-diastolic volume) had the same slope and intercept as that during aortic constriction. We conclude that preload produces a curvilinearity of ESPVR that significantly modifies derived indexes when the range of preload changes is large.