Beneficial cardiovascular effects of endothelin ET(A) receptor blockade in established long-term heart failure after myocardial infarction.

Although experimental prevention studies have suggested therapeutic potential of endothelin (ET) antagonists for the treatment of heart failure, the results of clinical trials using ET antagonists on top of standard heart failure medications have been largely disappointing. This experimental study investigated the effects of chronic ET(A) receptor blockade in long-term survivors of myocardial infarction who had developed stable chronic heart failure in the absence of other treatments. Systolic blood pressure, heart rate, organ weights of the right atrium and ventricle, and the lungs were determined, and tissue ET-1 peptide levels were measured in cardiac tissue, lung, and aorta. The results show that chronic blockade of ET(A) receptors stabilizes systolic blood pressure and reverses the heart failure-induced weight increases of right heart chambers and lung. The changes observed occurred independently of tissue ET-1 concentrations and heart rate, suggesting mechanisms independent of local cardiac or pulmonary ET-1 synthesis, which are yet to be identified.

Tumor necrosis factor-alpha -308G>A allelic variant modulates iron accumulation in patients with hereditary hemochromatosis.

BACKGROUND: In vitro and animal studies suggest that tumor necrosis factor alpha (TNF-alpha) modulates intestinal iron transport. We hypothesized that the effect of TNF-alpha might be particularly relevant if iron absorption is not effectively controlled by the HFE gene. METHODS: In patients with homozygous C282Y hemochromatosis, we investigated the influence of TNF-alpha -308G>A allelic variant on total body iron overload, determined in all patients by measuring iron removed during depletion therapy, and hepatic iron index and need for phlebotomy to prevent iron reaccumulation, measured in patient subgroups. RESULTS: Of 86 patients with hereditary hemochromatosis, 16 (19%) were heterozygous carriers and 1 (1%) was a homozygous carrier of the TNF-alpha promoter -308A allele. Mean (SD) total body iron overload was increased 2-fold in TNF-alpha -308A allele carriers [10.9 (7.6) g] compared with homozygous carriers of the G allele [5.6 (5.0) g, P<0.001]. Hepatic iron index differed markedly between TNF-alpha -308A allele carriers [5.6 (3.5) micromol/g/year] and homozygous G allele carriers [3.1 (2.2) micromol/g/year, P=0.040, n=30]. After iron depletion, the need for phlebotomy to prevent iron reaccumulation (maintenance therapy) was substantially higher in TNF-alpha -308A allele carriers than in homozygous G allele carriers (P=0.014, n=73). We used multiple regression analyses to exclude possible confounding effects of sex, age, family screening, body-mass index, and meat or alcohol intake. CONCLUSION: TNF-alpha -308G>A allelic variant modulates iron accumulation in patients with hereditary (homozygous C282Y) hemochromatosis, but the effect of the TNF-alpha -308A allele on clinical manifestations of hemochromatosis was less accentuated than expected from the increased iron load associated with this allele.

Education and a standardized management protocol improve the assessment and management of asthma in the emergency department.

STUDY OBJECTIVE: To evaluate the effect of a standardized management protocol on acute asthma care in the emergency department (ED). METHOD: We conducted a before-after study regarding acute asthma management. Deficiencies in acute asthma care over a time period of 19 month (January 1997- October 1998) were identified. Subsequently a management protocol consisting of an assessment sheet and written guidelines for the initial management of acute asthma in the emergency department, was developed. In addition, physicians and nurses of the emergency department were informed about the recommendations given in the guidelines, and instructed in peak-flow meter use. The assessment sheet was introduced in January 2002 and posted at several locations in the emergency department. Between February 2002 and August 2003 the acute asthma consultations in the emergency department were consecutively registered. Data on medical history, physical examination and objective measurements of airflow obstruction, as well as data on treatment and assessment of the response to therapy were collected. In addition, medication and instructions at discharge were reviewed and compared with the results before the introduction of the assessment sheet. RESULTS: The first group consisted of patients seen between January 1997 and October 1998; the second group consisted of all patients seen between February 2002 and August 2003 (104 vs 273 patients respectively). Both groups had a similar gender distribution (56% females in the first group vs 53% females in the second group) and the mean age of both groups was also alike (median 33 vs 36 years). Most patients had a known history of asthma (76% in the first group vs 70% in the second group). The self-referral rate was high in both groups (86% vs 96% respectively). Blood pressure and pulse rate were reported in the majority of patients (95% vs 98% respectively), whereas the respiratory rates were reported in 14% of patients in the first group vs 65% of patients in the second group. The introduction of the assessment sheet led to an increased measurement of initial airflow obstruction (53% of patients in the first group vs 96% of patients in the second group) as well as repeated measures under treatment (36% of patients in the first group vs 85% of patients in the second group). Repeated inhalations with short-acting inhaled beta-agonists, and use of systemic corticosteroid therapy at admission and at discharge increased significantly (from 31% to 84%, 43% to 68% and 37% to 70% respectively). CONCLUSION: The assessment and management of patients presenting to the emergency department with acute asthma can be improved with a guideline based management protocol, and by educating physicians and nurses in the management of acute asthma.

Effect of orlistat on postprandial lipemia, NMR lipoprotein subclass profiles and particle size.

Evidence suggests that metabolic phenomena during postprandial lipemia may be important in the pathogenesis of atherosclerosis. Both lipid concentrations and lipoprotein subclass patterns may be important cardiovascular risk modifiers. The pancreatic lipase inhibitor orlistat reduces fat absorption by 30% and is used for the treatment of overweight and obesity. We evaluated the effect of orlistat on postprandial lipemia and lipoprotein particle distribution after moderate-and high-fat meals in healthy volunteers. In this double-blind, randomized, cross-over study, 10 healthy young men received orlistat 120 mg plus a high-fat meal (HFO), orlistat plus a moderate-fat meal (MFO) or placebo plus a high-fat meal (HFP). Plasma triacylglycerol, glucose, insulin, and free fatty acids were measured at baseline (fasting) and postprandially for 8h. Lipoprotein subclass profile was assessed by nuclear magnetic resonance spectroscopy. The 8h postprandial mean triacylglycerol area under the curve (AUC) was significantly lower with MFO and HFO (0.79 versus 1.33 mmol/lh) versus HFP (4.33 mmol/lh; p=0.02). Mean change in large VLDL subclass concentration during the 4-8h and mean VLDL size after 8h was significantly lower with HFO and MFO versus HFP (p<0.001). Small HDL particle concentration decreased significantly with HFP versus MFO or HFO (p<0.001). There was no significant difference in postprandial concentrations of glucose, insulin or free fatty acids on the different regimens. The lowering of postprandial triacylglycerol AUC, shorter postprandial lipemia, lower concentration of large triacylglycerol-rich particles and decrease of VLDL particle size supports the hypothesis of a less atherogenic postprandial lipoprotein profile following orlistat ingestion.

Activation of pro-inflammatory and anti-inflammatory cytokines in host organs during chronic allograft rejection: role of endothelin receptor signaling.

This study investigated whether allograft rejection is associated with local inflammatory activation in host organs and whether endothelin ET(A) receptor signaling is involved. Expression of IL-1beta, IL-1ra, IL-6, IL-10 and TNF-alpha was investigated in host liver, lung and native heart in a rat model of chronic rejection 8 weeks after heterotopic cardiac transplantation in the absence of immunosuppression. In the presence of rejection, circulating levels of cytokines increased, while tissue level activation was dependent on the organ involved. Similarly, tissue-specific regulatory patterns were observed regarding transcriptional activation. Although chronic ET(A) receptor blockade did not reduce transplant vasculopathy or tissue protein expression, treatment had pronounced effects on plasma levels and transcriptional regulation of chemokines. These data provide evidence for distinct pro-inflammatory local activation in host organs during chronic rejection and suggest a role for ET(A) receptors contributing to regulation of cytokine plasma levels and transcriptional activity.

Progression of peripheral arterial occlusive disease is associated with Chlamydia pneumoniae seropositivity and can be inhibited by antibiotic treatment.

A possible influence of Chlamydia pneumoniae seropositivity on the clinical course of peripheral arterial occlusive disease (PAOD) has not been investigated previously. Though roxithromycin therapy was found to inhibit progression of PAOD, the nature of this effect (antibiotic or anti-inflammatory) has remained elusive. The course of PAOD was prospectively assessed in elderly men during 4 years, comparing 51 C. pneumoniae seropositive (IgG>/=1:128) with 46 seronegative patients (IgG<1:64 and IgA<1:32). Twenty of the seropositive patients were treated with roxithromycin (400 mg daily) for 4 weeks. Limitation of the walking distance to 200 m or less was observed in 55% of the seropositive untreated patients as compared to 30% of both, seronegative and macrolide-treated patients. The number of invasive revascularizations per patient was 1.7 in the seropositive untreated group as compared to 0.5 in the seronegative and the macrolide-treated group. Considering possible confounding variables, such as classical vascular risk factors, ordinal regression analyses showed a significant association of C. pneumoniae seropositivity with limitation of the walking distance (p=0.027) and need for invasive revascularization (p=0.037). The effect of macrolide treatment on these outcome measures was marked (p<0.001 and p=0.040, respectively) during 2.7 years but decreased in the second part of the observation period. This study provides good evidence that C. pneumoniae are involved in the progression of PAOD and that antibiotic treatment directed against C. pneumoniae is effective in inhibiting this process.

Anatomically distinct activation of endothelin-3 and the L-arginine/nitric oxide pathway in the kidney with advanced aging.

Aging is associated with spontaneous degenerative changes of renal function and structure. The aim of this study was to determine changes of the endothelin (ET) system and NO tissue bioactivity during the physiological aging process. Renal protein expression of ET-1 and ET-3, ETA, and ETB receptor mRNA expression, ET receptor binding and distribution, and tissue NO metabolite content were determined in adult, middle-aged, and senescent normotensive female Wistar rats. In senescent animals, medullary ET-3 content increased 3.4-fold (p<0.05 vs. adult), whereas aging did not affect ET-3 levels in the cortex. Local NO bioavailability, determined by NO metabolite tissue measurements, decreased in the cortex only. ET receptor binding capacity--predominantly due to ETB receptor binding--was lower in medulla than in cortex. Aging had no effect on ET-1 binding capacity or ET receptor distribution, whereas with advanced age gene expression of both receptors decreased. In conclusion, aging causes distinctive expressional changes of the renal endothelin system in otherwise healthy rats. The pronounced increase of endothelin-3 in the renal medulla is associated with preservation of local NO metabolite levels, changes not observed in the cortex. These findings could be important for pathologies and possibly therapy associated with renal aging.

Upregulation of vascular ET(B) receptor gene expression after chronic ET(A) receptor blockade in prediabetic NOD mice.

In the aorta of prediabetic non-obese diabetic mice, a model of human type 1 diabetes, we investigated gene expression of the endothelin receptors and contractility to big endothelin-1 and endothelin-1 at the ages of 10 and 16 weeks. A subgroup of 10- week-old animals was treated with the endothelin ETA receptor antagonist LU461314 (30 mg/kg per day for 6 weeks). Blood glucose levels were normal in all animals. Real-time polymerase chain reaction analysis revealed that vascular ETB receptor expression was higher in 10-week-old non-obese diabetic (NOD) mice compared with controls. In 16-week-old NOD mice, but not in control mice, ETB receptor mRNA was twofold lower (P < 0.05 vs 10-week-old NOD mice). In all groups ETA receptor expression was unaffected by age or treatment. Contractions to big endothelin-1 and endothelin-1 were lower in 10-week-old NOD mice compared with controls. Treatment with LU461314 increased ETB receptor expression in 16-week-old NOD mice, but had no effect on vascular contractility. These data indicate that dysregulation of ETB receptor expression and a decreased contractile response to big endothelin-1 and endothelin-1 are present in the prediabetic state of a model of human type 1 diabetes. These alterations occur independent of glucose levels. Furthermore, ETA receptor blockade is effective in increasing ETB receptor gene expression, suggesting a potential role for endothelin ETA antagonists in the treatment of type 1 diabetes.

Amiodarone acutely inhibits vascular activity of endothelin-converting enzymes.

Endothelin has been implicated in arrhythmogenesis. Amiodarone, initially developed for the treatment of angina pectoris, is a potent inhibitor of ventricular arrhythmias. We investigated whether amiodarone (34 microg/mL) affects the vascular endothelin system of healthy Wistar-Kyoto rats. Contractility to big endothelin-1 and endothelin-1 was determined in aortic and carotid artery rings suspended in organ chambers. Functional activity of endothelin-converting enzymes was calculated for each concentration, and endothelin-converting enzyme-1 gene expression was analyzed using real-time polymerase chain reaction. Activity of functional endothelin-converting enzymes was sevenfold higher in the carotid artery than in the aorta (P < 0.001). Contractions to big endothelin-1 (0.1 micromol/L) were attenuated by amiodarone in the carotid artery (50 +/- 9% vs 90 +/- 8%, P < 0.01) but not in the aorta. Accordingly, contractility to endothelin-1 (0.1 micromol/L) was decreased by amiodarone in carotid rings only (105 +/- 7% vs 132 +/- 6%, P < 0.01). After acute exposure to amiodarone, functional activity of endothelin-converting enzymes at 0.1 micromol/L was slightly increased in the aorta (17 +/- 2% vs 11 +/- 2%, P < 0.05), but decreased in the carotid artery (40 +/- 9% vs 76 +/- 5%, P < 0.05). Endothelin-converting enzyme-1 mRNA expression in the aorta was not affected by amiodarone treatment. Thus, amiodarone acutely affects the activity of vascular endothelin-converting enzymes depending on the anatomical localization of the artery. Acute effects of amiodarone on endothelin-converting enzymes may contribute to its antiarrhythmic properties.

Obesity increases prostanoid-mediated vasoconstriction and vascular thromboxane receptor gene expression.

OBJECTIVES: Vasoconstrictor prostanoids have been implicated in abnormal vasomotion in atherosclerosis and hypertension. METHOD: Using lean and diet-induced obese mice, we investigated whether obesity affects vascular function or expression of genes involved in prostanoid action. RESULTS: In lean C57BL/6J mice, at high concentrations acetylcholine caused endothelium-dependent contractions in the carotid artery but not in the aorta. Endothelium-dependent contractions to acetylcholine were blocked by the non-selective cyclooxygenase (COX) inhibitors indomethacin and meclofenamate, or a prostaglandin H2/thromboxane A2 receptor antagonist, but not by inhibitors of COX-2, thromboxane synthase or cytochrome P450 monooxygenase. Obesity increased endothelium-dependent contractions to acetylcholine in the carotid artery, and prostanoid-mediated vasoconstriction was now present in the aorta. Similarly, contractions to endothelin-1 were largely blocked by meclofenamate and were increased in the aorta of obese mice. Real-time quantitative polymerase chain reaction analysis of the thromboxane receptor gene in the carotid artery revealed a robust upregulation in obese animals (18-fold, 0.05); in comparison, obesity had a less pronounced effect on thromboxane synthase (2.1-fold increase, 0.05), or preproendothelin-1 gene expression (4.2-fold increase, 0.05). CONCLUSIONS: These data demonstrate that obesity augments prostanoid-dependent vasoconstriction and markedly increases vascular thromboxane receptor gene expression. These changes are likely to promote the development of vascular disease, hypertension and thrombosis associated with obesity.

Effects of obesity on endothelium-dependent reactivity during acute nitric oxide synthase inhibition: modulatory role of endothelin.

This study investigated vascular reactivity in response to acetylcholine, in the presence of acute inhibition of nitric oxide synthase, in the carotid artery and aorta of obese C57Bl6/J mice fed on a high-fat diet for 30 weeks, and of control mice. A subgroup of obese animals was also treated with the ET(A) receptor antagonist darusentan (50 mg x kg(-1) x day(-1)). In vascular rings from control animals, acetylcholine caused endothelium-dependent contractions in the carotid artery, but not in the aorta. In vascular rings from obese mice, contractility to acetylcholine was also evident in the aorta, and that in the carotid artery was increased compared with control mice. ET(A) receptor blockade by darusentan treatment of the obese mice prevented enhanced vasoconstriction to acetylcholine, resulting in mild vasodilatation. Thus obesity increases endothelium-dependent vasoconstriction in the absence of endothelial nitric oxide. This effect can be completely prevented by chronic ET(A) receptor blockade, suggesting that endothelin modulates increased endothelium-dependent vasoconstriction in obesity.

Nutritional factors in the control of blood pressure and hypertension.

Differing hypertension prevalence rates between certain population and age groups are partially due to differences in the intake of certain nutrients. Blood pressure is positively associated with higher sodium, alcohol, and protein intakes; it is inversely associated with potassium, calcium, and magnesium intakes. Salt may lead to an increase in blood pressure in the presence of salt sensitivity, but there is no inexpensive or easy strategy to identify salt-sensitive patients. Other risk factors for hypertension include obesity and lack of regular physical activity. The best strategy appears to be moderate salt restriction (6-7 g/day) in combination with an optimal compliance of the antihypertensive drug therapy, as well as adoption of the combination diet of the DASH study--a diet rich in fruits and vegetables, and thus rich in potassium. Current evidence does not support the increased intake of Ca2+ or Mg2+ for blood-pressure-lowering purposes only; however, calcium and magnesium may represent important components in the combination diet of the DASH study. It seems that it is the combination of these nutrients that is of crucial importance for the achievement of optimal blood-pressure reduction. Also recommended is a decrease in alcohol consumption and an increase in regular physical activity. Instead of a severe intervention with regard to 1 risk factor alone, positive changes in 5 habits combined--high salt intake, high sodium-to-potassium ratio, alcohol intake, calorie imbalance, and a sedentary life--may be the most realistic and effective strategy to counteract the present hypertension epidemic.