Subclinical atherosclerosis and its progression are modulated by PLIN2 through a feed-forward loop between LXR and autophagy.

BACKGROUND: Hyperlipidaemia is a major risk factor for cardiovascular disease, and atherosclerosis is the underlying cause of both myocardial infarction and stroke. We have previously shown that the Pro251 variant of perilipin-2 reduces plasma triglycerides and may therefore be beneficial to reduce atherosclerosis development. OBJECTIVE: We sought to delineate putative beneficial effects of the Pro251 variant of perlipin-2 on subclinical atherosclerosis and the mechanism by which it acts. METHODS: A pan-European cohort of high-risk individuals where carotid intima-media thickness has been assessed was adopted. Human primary monocyte-derived macrophages were prepared from whole blood from individuals recruited by perilipin-2 genotype or from buffy coats from the Karolinska University hospital blood central. RESULTS: The Pro251 variant of perilipin-2 is associated with decreased intima-media thickness at baseline and over 30 months of follow-up. Using human primary monocyte-derived macrophages from carriers of the beneficial Pro251 variant, we show that this variant increases autophagy activity, cholesterol efflux and a controlled inflammatory response. Through extensive mechanistic studies, we demonstrate that increase in autophagy activity is accompanied with an increase in liver-X-receptor (LXR) activity and that LXR and autophagy reciprocally activate each other in a feed-forward loop, regulated by CYP27A1 and 27OH-cholesterol. CONCLUSIONS: For the first time, we show that perilipin-2 affects susceptibility to human atherosclerosis through activation of autophagy and stimulation of cholesterol efflux. We demonstrate that perilipin-2 modulates levels of the LXR ligand 27OH-cholesterol and initiates a feed-forward loop where LXR and autophagy reciprocally activate each other; the mechanism by which perilipin-2 exerts its beneficial effects on subclinical atherosclerosis.

The mir-200 family regulates key pathogenic events in ascending aortas of individuals with bicuspid aortic valves.

BACKGROUND: An individual with a bicuspid aortic valve (BAV) runs a substantially higher risk of developing aneurysm in the ascending aorta compared to the normal population with tricuspid aortic valves (TAV). Aneurysm formation in patients with BAV and TAV is known to be distinct at the molecular level but the underlying mechanisms are undefined. Here, we investigated the still incompletely described role of microRNAs (miRNAs), important post-transcriptional regulators of gene expression, in such aortic disease of patients with BAV as compared with TAV. METHODS AND RESULTS: Using a system biology approach, based on data obtained from proteomic analysis of non-dilated aortas from BAV and TAV patients, we constructed a gene-interaction network of regulatory microRNAs associated with the observed differential protein signature. The miR-200 family was the highest ranked miRNA, hence potentially having the strongest effect on the signalling network associated with BAV. Further, qRT-PCR and ChIP analyses showed lower expression of miR-200c, higher expression of miR-200 target genes, ZEB1/ZEB2 transcription factors, and higher chromatin occupancy of the miR-200c promoter by ZEB1/ZEB2 in BAV patients, indicating a miR-200c/ZEBs negative feedback loop and induction of endothelial/epithelial mesenchymal transition (EndMT/EMT). CONCLUSION: We propose that a miR-200-dependent process of EndMT/EMT is a plausible biological mechanism rendering the BAV ascending aorta more prone to aneurysm development. Although initially supported by a miR-200c/ZEB feedback loop, this process is most probably advanced by cooperation of other miRNAs.

Ceramides are associated with inflammatory processes in human mediastinal adipose tissue.

BACKGROUND AND AIM: Ceramides are poorly characterized in human adipose tissue. The aim of this study was to investigate concentrations of different ceramide species in human subcutaneous and visceral adipose tissue depots and to determine associations between ceramides and global gene expression profiles. METHODS AND RESULTS: Concentrations of six ceramide species were determined in plasma and in subcutaneous and mediastinal adipose tissue from 10 overweight subjects (BMI 29.4 ± 4.9 kg/m(2)). In the adipose tissue biopsies gene expression arrays were performed and relationships between ceramides and gene expression analyzed. Immunostaining of the two adipose tissue depots was performed in an independent group of 10 patients. Mediastinal adipose tissue contained significantly higher concentrations (p < 0.05) of all six ceramide species than the subcutaneous depot. Of the six ceramides in plasma, concentrations of only two (Cer d18:1/18:0 and Cer d18:1/22:0) correlated significantly (p < 0.05) with the corresponding species in mediastinal adipose tissue, but there were no significant correlations between ceramides in plasma and subcutaneous adipose tissue. Multivariate analysis identified significant correlations between the total ceramide concentration and global gene expression within mediastinal, but not subcutaneous adipose tissue, according to cross-validation. Gene ontology analysis of genes related to ceramides in the mediastinal depot revealed that genes positively correlated with ceramides were associated mainly with immune and inflammatory categories, while genes negatively correlated with ceramides were associated mainly with lipid and carbohydrate metabolism. CONCLUSIONS: Ceramides in human mediastinal adipose tissue may be involved in inflammation and lipid and carbohydrate metabolism.

Human mediastinal adipose tissue displays certain characteristics of brown fat.

BACKGROUND: The amount of intra-thoracic fat, of which mediastinal adipose tissue comprises the major depot, is related to various cardiometabolic risk factors. Autopsy and imaging studies indicate that the mediastinal depot in adult humans could contain brown adipose tissue (BAT). To gain a better understanding of this intra-thoracic fat depot, we examined possible BAT characteristics of human mediastinal in comparison with subcutaneous adipose tissue. MATERIALS AND METHODS: Adipose tissue biopsies from thoracic subcutaneous and mediastinal depots were obtained during open-heart surgery from 33 subjects (26 male, 63.7±13.8 years, body mass index 29.3±5.1 kg m(-2)). Microarray analysis was performed on 10 patients and genes of interest confirmed by quantitative PCR (qPCR) in samples from another group of 23 patients. Adipocyte size was determined and uncoupling protein 1 (UCP1) protein expression investigated with immunohistochemistry. RESULTS: The microarray data showed that a number of BAT-specific genes had significantly higher expression in the mediastinal depot than in the subcutaneous depot. Higher expression of UCP1 (24-fold, P<0.001) and PPARGC1A (1.7-fold, P=0.0047), and lower expression of SHOX2 (0.12-fold, P<0.001) and HOXC8 (0.14-fold, P<0.001) in the mediastinal depot was confirmed by qPCR. Gene set enrichment analysis identified two gene sets related to mitochondria, which were significantly more highly expressed in the mediastinal than in the subcutaneous depot (P<0.01). No significant changes in UCP1 gene expression were observed in the subcutaneous or mediastinal depots following lowering of body temperature during surgery. UCP1 messenger RNA levels in the mediastinal depot were lower than those in murine BAT and white adipose tissue. In some mediastinal adipose tissue biopsies, a small number of multilocular adipocytes that stained positively for UCP1 were observed. Adipocytes were significantly smaller in the mediastinal than the subcutaneous depot (cross-sectional area 2400±810 versus 3260±980 µm(2), P<0.001). CONCLUSIONS: Human mediastinal adipose tissue displays some characteristics of BAT when compared with the subcutaneous depot at microscopic and molecular levels.

Intravasal microdialysis is superior to intramyocardial microdialysis in detecting local ischaemia in experimental porcine myocardial infarction.

OBJECTIVE: A novel application of microdialysis was studied, where myocardial outflow of energy metabolites was monitored by intravasal microdialysis in the myocardial venous outflow during ischaemia and reperfusion. These levels where related to levels monitored by microdialysis catheters placed intramyocardially. METHODS: Microdialysis catheters were introduced into the great cardiac vein (GCV), ischaemic myocardium and non-ischaemic myocardium in 10 anaesthetized pigs. The left anterior descending coronary artery was occluded for 60 min in five pigs and five pigs served as controls. Ischaemia was followed by 120 min of reperfusion. Microdialysis samples were analysed for glucose, lactate, pyruvate and glycerol. Venous lactate and glucose levels were measured by blood samples from the femoral vein. RESULTS: All animals subjected to ischaemia developed myocardial infarction. Lactate, lactate/pyruvate ratio and glycerol increased in the microdialysis samples from the GCV and the catheter placed in ischaemic myocardium while no changes were detected in samples from the catheter placed in the non-ischaemic myocardium. CONCLUSION: In this study, we have demonstrated that intravasal microdialysis catheters rapidly and reliably detect local myocardial ischaemia, while intramyocardially placed microdialysis catheters will not show these changes if placed in a non-ischaemic area.

Off-pump coronary bypass surgery causes less immediate postoperative coronary endothelial dysfunction compared to on-pump coronary bypass surgery.

OBJECTIVE: In this study a comparison of the vascular reactivity in the coronary circulation was investigated by injection of acetylcholine (ACh) and adenosine (ADO) in coronary bypass patients, operated on with or without the assistance of heart-lung machine. The patients operated on with heart-lung machine were further divided into subjects with stable or unstable angina pectoris. METHODS: Nine patients with stable angina pectoris subjected to off-pump surgery (target arterial occlusion time of 11+/-0.5 min) and 18 patients subjected to on-pump surgery (nine patients with stable angina and nine patients with unstable angina; cross-clamp time of 43+/-3 and 32+/-2 min, respectively), received ACh (10 microg) and ADO (18 microg) given as bolus injections into a vein-graft anastomosed to a coronary vessel. The blood flow in the vein-graft (i.e. indirectly the flow in the targeted coronary circulation) and hemodynamics were observed. RESULTS: In the off-pump group, ACh evoked an increase with +14+/-12% of control in coronary blood flow, while in the stable on-pump group ACh decreased the blood flow with -60+/-7% of baseline and in the unstable on-pump group the flow was decreased with -38+/-8% of baseline (P<0.001 between the stable on- and off-pump groups, no significant difference between the stable and unstable on-pump groups). ADO significantly increased the coronary blood flow in all three groups; with +81+/-14% in the off-pump patients; with +95+/-14% in the stable on-pump group and with +74+/-13% in the unstable on-pump group (P<0.01 compared to baseline for all three groups). Neither ACh nor ADO injection caused any changes in hemodynamics. CONCLUSIONS: The present study demonstrates that on-pump coronary bypass surgery appears to be more harmful to the coronary endothelium, in terms of ACh-induced vasoconstriction, compared to off-bypass pump surgery. Furthermore, there is no significant difference in direct smooth muscle vascular reactivity between off-pump and on-pump coronary bypass surgery. No apparent dissimilarities in endothelial dysfunction were observed in the stable and unstable on-pump groups suggesting other causes for differences in post-operative outcome for these patients.

Partial left ventriculectomy for dilated cardiomyopathy: is this an alternative to transplantation?

OBJECTIVE: To determine the late effectiveness of partial left ventriculectomy and risk factors for failure. METHODS: Between May 1996 and December 1998, partial left ventriculectomy and concomitant mitral valve surgery were performed in 62 patients (95% transplant candidates) with a mean age of 54 years (range 17-72 years). All patients were in New York Heart Association functional class III (38%) or IV (62%) because of idiopathic dilated cardiomyopathy (59 patients) or ischemic, valvular, or familial cardiomyopathy (1 patient each). Outcomes considered for multivariable analysis included implantation of left ventricular assist device, return to class IV heart failure, relisting for transplantation, and death. RESULTS: Partial left ventriculectomy reduced the left ventricular end-diastolic diameter immediately preoperatively to immediately postoperatively (from 8.4 +/- 1.1 cm to 5.92 +/- 0.8 cm; P =.01), reduced the left ventricular end-diastolic volume index (from 133 +/- 48.6 mL to 64.1 +/- 26 mL; P <.0001), and increased the left ventricular ejection fraction (from 16 +/- 7.6 to 31.5 +/- 10.9; P <.0001). Survival was 80% and 60% at 1 and 3 years after surgery and freedom from failure was 49% and 26%, respectively. Increased systolic pulmonary artery pressure, decreased maximum exercise oxygen consumption, and increased left atrial pressure were associated with failure and/or death. The degree of preoperative mitral regurgitation did not correlate with clinical outcome. CONCLUSIONS: Early and late failures preclude the widespread use of partial left ventriculectomy. However, in view of its sometimes beneficial effect, use in situations that do not allow for transplantation or as a biologic bridge to transplantation may be appropriate.

Short ischemia causes endothelial dysfunction in porcine coronary vessels in an in vivo model.

BACKGROUND: The aim of this study was to evaluate the effects of a short period of ischemia (10 mins) and a prolonged period of ischemia (60 mins) followed by reperfusion on coronary flow changes induced by acetylcholine (ACh), adenosine (ADO), and endothelin (ET). METHODS: The left anterior descending coronary artery in anesthetized pigs was occluded for 10 or 60 minutes followed by 120 minutes reperfusion. Thereafter, the flow changes in the left anterior descending coronary artery were studied after intracoronary infusion of ACh, ADO, and ET. RESULTS: Short-term ischemia (10 minutes) caused a decrease in vasodilatation, but not the vasoconstriction response to ACh. Prolonged ischemia (60 minutes) impaired ADO induced vasodilatation and aggravated ET evoked vasoconstriction. CONCLUSIONS: The present findings suggest that a short period of ischemia (10 minutes) causes disturbances of the endothelial regulation of coronary vascular tone and that this endothelial regulation is more sensitive, and precedes changes in vascular smooth muscle function after ischemia and reperfusion.

Myocardial outflow of prostacyclin in relation to metabolic stress during off-pump coronary artery bypass grafting.

BACKGROUND: The metabolic changes, possible myocardial damage, and influence on the vascular endothelium during off-pump coronary artery bypass grafting have been investigated. METHODS: Coronary sinus and arterial blood samples were obtained before coronary arterial occlusion, after 10 minutes of ischemia, and after 1 and 10 minutes of reperfusion in 9 patients who had an anastomosis performed to the left anterior descending coronary artery off-pump bypass RESULTS: The mean ischemic time was 14 +/- 1 minutes. The arteriovenous difference in lactate decreased during ischemia to reach a minimum at 1 minute of reperfusion (-0.15 +/- 0.06 micromol/L compared to 0.21 +/- 10 micromol/L before ischemia; p < 0.01). Myocardial lactate extraction decreased from 14.2 +/- 6.8 micromol/min before ischemia to -10.9 +/- 6.5 micromol/min after 1 minute of reperfusion (p < 0.01). Simultaneously, the arteriovenous difference in 6-keto-PGF(1alpha), the stable metabolite of prostacyclin, decreased from -30 +/- 26 pg/mL to -258 +/- 80 pg/mL at 1 minute of reperfusion (p < 0.05), and the 6-keto-PGF(1alpha) extraction over the heart decreased -556 +/- 466 pg/min to -18,560 +/- 5,683 pg/min (p < 0.01). CONCLUSIONS: The localized myocardial ischemia associated with these procedures causes changes in the myocardium and endothelial influence. Coronary bypass surgery performed on the beating heart may not be superior in preventing cardiac ischemia and endothelial disturbance, compared with conventional bypass surgery.

Potential of calcitonin gene-related peptide in coronary heart disease.

A subpopulation of capsaicin-sensitive cardiac C-fibre afferents co-store calcitonin gene-related peptide (CGRP), substance P and neurokinin A. CGRP exerts positive inotropic and chronotropic effects and is one of the most potent endogenous vasodilators yet discovered. A number of endogenous agents and conditions cause activation of cardiac C-fibre afferents with subsequent local release of CGRP. In myocardial ischaemia with its clinical manifestations angina pectoris and infarction, C-fibre afferents not only convey the sensation of pain, but there is also a local 'efferent' release of CGRP in the heart. After being released, CGRP causes coronary vasodilatation and attenuates the development of myocardial infarction. CGRP may thus represent an endogenous local myocardial protective substance with interesting clinical implications.

Microdialysis of blood from the cardiac venous outflow: a technique for monitoring myocardial ischemia.

OBJECTIVE: To evaluate the possibility of using microdialysis of blood from the great cardiac vein for detecting myocardial ischemia. DESIGN: Microdialysis catheters were placed in the great cardiac vein and the left atrium of pigs for analysis of lactate, glycerol, pyruvate and glucose. Blood samples were drawn for measurement of aspartate aminotransferase, alanine aminotransferase, lactic dehydrogenase and myoglobin with the objective of verifying myocardial damage. Ischemia was induced for 3 h. RESULTS: Fifteen minutes after induction of ischemia a significant elevation of lactate to 917 +/- 223%; p < 0.001 in the great cardiac vein could be registered. No significant changes in lactate levels were detected in the left atrium. Changes in glycerol and pyruvate showed similar patterns, with an increase to 722 +/- 297%; p < 0.001 and to 281 +/- 56%; p < 0.05, respectively. The outflow of aspartate aminotransferase and myoglobine in the great cardiac vein increased significantly. CONCLUSION: Early detection of metabolic substances is possible through the assessment of metabolic substances using microdialysis in the great cardiac vein.

ET-1 infusion increases systemic vascular resistance and depresses cardiac output in patients with chronic hypoxaemia and pulmonary hypertension.

The pulmonary vascular effects of the endothelium-derived peptide endothelin (ET) vary depending on the existing vascular tone, modes of administration and species studied; ET can cause both pulmonary vasodilatation and vasoconstriction. Increased plasma levels of ET have been reported in hypoxic pulmonary hypertension, although it is unclear whether ET is a mediator or a marker of hypoxia-induced increase in pulmonary vascular resistance (PVR). In our study, the plasma levels of ET-1 and the functional effects of ET-1 infusion in patients (n = 4) with chronic hypoxaemia and elevated PVR were evaluated. At rest, the arterial and venous ET-1-levels (13 +/- 2 and 12 +/- 1 fmol/ml, respectively) were significantly higher than those detected in venous plasma of an age-matched healthy control group (7 +/- 1 fmol/ml). Consecutive 10 min infusions of ET-1 at 1, 5, 10 and 15 ng/kg/min into the pulmonary artery decreased cardiac output (by 32%) and stroke volume (by 33%) and increased the systemic vascular resistance (by 62%) and arteriovenous oxygen difference (by 83%) at the highest dose. No deleterious effect was observed in the pulmonary circulation. The present study therefore suggests that intra-pulmonarily administered ET does not attenuate the increased PVR associated with chronic hypoxaemia.

Haemodynamic influence and endothelin-1 plasma concentrations by selective or non-selective endothelin receptor antagonists in the pig in vivo.

In the present study the haemodynamical effects of endothelin (ET)-receptor antagonism was evaluated using selective and non-selective ET(A)- and ET(B)-receptor blockade in normoxic pigs in vivo. In addition, the influence of the ET-antagonists on circulating plasma ET-1 levels was determined. BMS-182874 (10 and 30 mg kg(-1) i.v.), a selective ET(A)-receptor antagonist decreased the pulmonary and systemic vascular resistances. bosentan (10 and 30 mg(-1) i.v.), a non-selective ET(A)- and ET(B)-receptor antagonist caused principally similar effects as ETA-antagonism alone. No effects were observed by selective ET(B)-blockade using BQ-788 (30 microg kg(-1) i.v.). Of the three antagonists used only bosentan increased the circulating plasma ET-1 levels. It may therefore be concluded that ET contributes to basal systemic and pulmonary vascular tone through ET(A)-receptor activation. ET(B)-receptors are likely to cause the elevated plasma levels of ET-1 observed after bosentan administration. Furthermore, circulating plasma levels of ET-1 do not reflect the physiological effects of ET-1.

Myocardial outflow of calcitonin gene-related peptide in relation to metabolic stress during coronary artery bypass grafting without cardiopulmonary bypass.

OBJECTIVE: Because of adverse effects of cardiopulmonary bypass and the prospect of shortening intensive care and hospital stay, coronary artery bypass grafting without cardiopulmonary bypass is gaining increased attention. The impact of the localized myocardial ischemia that is inherent in these procedures has not been thoroughly investigated in human beings. We have investigated metabolic changes, possible myocardial damage, and myocardial outflow of the vasodilator calcitonin gene-related peptide during coronary artery bypass grafting without cardiopulmonary bypass. METHODS: Coronary sinus and arterial blood was sampled before coronary arterial occlusion, after 10 minutes of ischemia, and after 1 and 10 minutes of reperfusion in 9 consecutive patients (mean age 70 +/- 5 years) who had an anastomosis performed to the left anterior descending artery without cardiopulmonary bypass. RESULTS: No perioperative myocardial infarctions occurred. The arteriovenous difference in lactate decreased during ischemia, to reach a minimum after 1 minute of reperfusion (-0.17 +/- 0.25 vs 0.15 +/- 0.25 mmol/L before ischemia; P =.008). Myocardial lactate extraction decreased (from 11.2 +/- 13.6 micromol/min before ischemia to -3.0 +/- 7.0 micromol/min after 1 minute of reperfusion; P =.012), that is, a net production of lactate. The arteriovenous difference in calcitonin gene-related peptide decreased from -0.1 +/- 2.6 pmol/L before ischemia to -30.5 +/- 26.5 pmol/L (P =.008) after 1 minute of reperfusion. CONCLUSIONS: The localized myocardial ischemia associated with these procedures causes metabolic changes in the myocardium, but no myocardial damage. The ischemia-related outflow of calcitonin gene-related peptide indicates that the vasodilating and cardioprotective properties of this peptide that are known from animal studies may be of importance in myocardial ischemia in human beings.

Arterial patch angioplasty for reconstruction of proximal coronary artery stenosis.

BACKGROUND: Ostium patch angioplasty and reconstruction with an onlay patch consisting of pericardium or the saphenous vein is an alternative surgical technique for patients with proximal coronary artery stenosis. Previously described surgical techniques comprise anterior or posterior approaches. In this article we report our experience of using a segment of the proximal right internal mammary artery as an onlay patch for surgical angioplasty. METHODS: Between June 1997 and April 1999, 18 patients (9 men and 9 women) were subjected to surgical patch angioplasty of the left main coronary artery, 3 patients had an additional angioplasty performed on the proximal right coronary artery. The first 12 patients were operated with a posterior incision technique, and six subsequent patients by a new technique performed through an oblique incision into the left main stem after transsection of the ascending aorta. RESULTS: All patients had an uneventful postoperative course, and were fully rehabilitated without clinical symptoms of ischemic heart disease at mean follow-up of 10 months (range 1-23 months). Postoperative catheterization after six days showed excellent results with a widely open and funnel-shaped neoostium. CONCLUSIONS: The use of a proximal segment of the right internal mammary artery as an onlay patch for reconstructing proximal coronary artery lesions is safe with no complications. Although the posterior approach may be used to obtain excellent results, transsection of the ascending aorta gives an optimal visualization and mobilization of the left main coronary artery when performing surgical angioplasty.

Aggravation of myocardial infarction in the porcine heart by capsaicin-induced depletion of calcitonin gene-related peptide (CGRP).

The potent vasodilator calcitonin gene-related peptide (CGRP) is stored in a population of C-fiber afferents that are sensitive to capsaicin. CGRP has been suggested to have a beneficial effect in myocardial ischemia. In this study we used capsaicin pretreatment to deplete cardiac C-fiber peptide stores and tried to evaluate the role of endogenous CGRP in myocardial ischemia. Six pigs were pretreated with capsaicin (50 mg/kg). Forty-eight hours later, they were subjected to 40min occlusion of the left anterior descending coronary artery. After 4 h of reperfusion, the heart was excised, and the extent of myocardial infarction was measured by using triphenyl tetrazolium chloride. Content of CGRP in the ischemic and the nonischemic myocardium was measured by radioimmunoassay. Capsaicin-treated pigs had more extensive myocardial infarction (56+/-6% vs. 26+/-8% of the area at risk; p=0.013) and a lower myocardial content of CGRP (14+/-6 vs. 32+/-5 pmol/g; p=0.039) compared with six untreated control pigs. Furthermore, capsaicin-treated pigs had significantly increased mean arterial blood pressure compared with controls. This study indicates that peptides released from cardiac C fibers have a beneficial effect in myocardial ischemia and reperfusion. In view of its potent effects in cardiovascular regulation, CGRP is a possible candidate for the mediation of the observed cardioprotective effect.

Ion channels involved in the release of calcitonin gene-related peptide by low pH, prostacyclin and capsaicin in the isolated guinea-pig heart.

The aim of this study was to characterise the release of calcitonin gene-related peptide (CGRP) by capsaicin, low pH and prostacyclin in terms of Ca2+ channel dependence, interactions with K(ATP) channels and the role of action potential propagation, in the isolated, perfused guinea-pig heart. The Ca2+ channel blocker omega-conotoxin reduced CGRP release evoked by 10(-7) M capsaicin, as well as CGRP release evoked by pH 7. CGRP release caused by capsaicin at low (10(-7) M) but not high (10(-6) M) concentrations was also attenuated by tetrodotoxin, indicating partial dependence on action potential propagation. CGRP release caused by prostacyclin was not altered by any of the tested drugs. The K(ATP) channel activator cromakalim and the K(ATP) channel blocker glibenclamide had no effect on CGRP release. Previous findings that low pH and capsaicin stimulate capsaicin-sensitive afferents in the isolated heart at least partly through common mechanisms are thus supported. Attenuation of capsaicin-evoked release of CGRP by tetrodotoxin suggests recruitment of additional nerve terminals by a local axon reflex.

Does sublingual 17 beta-oestradiol have any effects on exercise capacity and myocardial ischaemia in post-menopausal women with stable coronary artery disease?

BACKGROUND: A variety of vascular effects have been ascribed to 17 beta-oestradiol. These effects may partially explain the reduced incidence of cardiovascular disease found in post-menopausal women on oestrogen replacement therapy. OBJECTIVES: To evaluate the effects of 2 mg sublingual 17 beta-oestradiol on exercise capacity, exercise-induced myocardial ischaemia and circulating levels of endothelin-1 in post-menopausal women with stable coronary artery disease. METHODS: Twelve post-menopausal women, mean age 61 (range 52-72) years, with angiographically verified significant coronary artery disease, were randomly assigned to 2 mg of sublingual 17 beta-oestradiol, 2.5 mg of buccal nitroglycerine and to placebo in a double-blind cross-over study design with at least 2 days between each of the study arms. Antianginal medications, with the exception of beta-blockers, were discontinued before investigation. All study patients underwent a maximal bicycle exercise test 30 min after drug intake. Blood was withdrawn immediately before and up to 8 h after medication for analyses of circulating levels of oestradiol and endothelin-1. RESULTS: The mean serum levels of oestradiol increased from a control level of 72 +/- 28 pmol.l-1 to 3557 +/- 1731 pmol.l-1 after 30 min and to 5028 +/- 3971 pmol.l-1 after 60 min with a gradual decline thereafter. Sublingual 17 beta-oestradiol did not induce any improvement in exercise duration when compared with nitroglycerin and placebo (500 +/- 112 s, 505 +/- 107 s, 498 +/- 157 s), and did not influence time to onset of ST-segment depression (358 +/- 89 s, 436 +/- 93 s, 384 +/- 116 s). The plasma levels of endothelin-1 did not change after administration of 17 beta-oestradiol, nitroglycerin or placebo. CONCLUSIONS: No effects of exercise capacity, exercise-induced acute ischaemia, or plasma levels of endothelin-1 were found after a single dose of 2 mg 17 beta-oestradiol in post-menopausal women with documented coronary artery disease.

Calcitonin gene-related peptide in myocardial ischaemia and reperfusion in the pig.

OBJECTIVE: In myocardial ischaemia, slow conducting capsaicin-sensitive C-fibres are activated. Apart from the mediation of pain, activation of these fibres causes release of various peptides, such as calcitonin gene-related peptide (CGRP), which is a potent vasodilator. The aim of this study was to investigate the role of CGRP in the context of myocardial ischaemia in vivo. METHODS: The left anterior descending coronary artery (LAD) was occluded during 45 min in 27 anaesthetised open-chest pigs. LAD flow, mean arterial pressure (MAP), heart rate, peak dP/dt, arterial and coronary venous concentration of CGRP was measured prior to ischaemia, and during 4 h of reperfusion. The extent of myocardial infarction was measured using staining with triphenyl tetrazolium chloride. RESULTS: Retroinfusion of CGRP (100 micrograms) into the ischaemic myocardium was associated with a more pronounced hyperaemia, and systemic hypotension, during early reperfusion. The infarct size in relation to the area at risk was not affected by CGRP or the CGRP antagonist CGRP(8-37), and averaged 67 +/- 3%. There were no changes in plasma CGRP levels during ischaemia or reperfusion. CONCLUSION: Exogenously administered CGRP can cause systemic hypotension and augments postischaemic coronary flow. In this model, no cardioprotective effect of CGRP could be proven.

The ETA receptor antagonist, BMS-182874, reduces acute hypoxic pulmonary hypertension in pigs in vivo.

OBJECTIVE: Elevated levels of the potent vasoactive peptide endothelin (ET), have been found in pathophysiological conditions associated with pulmonary hypertension. In this study, we have investigated the effects of the ETA receptor antagonist, BMS-182874, on hypoxic pulmonary hypertension in pigs. METHODS: Pigs were subjected to acute, intermittent 15-min periods of hypoxia (FiO2 0.1). Following a first hypoxia establishing hypoxic baseline values, vehicle or BMS-182874 (10 or 30 mg/kg) was administered i.v. before a second hypoxic period. In separate groups of animals, the effects of the nitric oxide synthase inhibitor N omega-nitro-L-arginine (L-NNA) in combination with BMS-182874 (10 mg) during repeated hypoxia were investigated. The ET-1-blocking properties of BMS-182874 were studied in vivo by infusion of ET-1 during normoxia and in vitro using isolated porcine pulmonary arteries. RESULTS: The hypoxia-evoked increase in mean pulmonary artery pressure was reduced by administration of BMS-182874 (10 mg/kg i.v.; from 42 +/- 8 to 34 +/- 4 mmHg, P < 0.05 and 30 mg/kg i.v.; from 38 +/- 4 to 30 +/- 5 mmHg, P < 0.05). In addition, BMS-182874 at 30 mg/kg reduced the pulmonary vascular resistance during hypoxia (from 7.4 +/- 1.5 to 5.3 +/- 1.1 mmHg.min.l-1 P < 0.05). The hemodynamic response to repeated hypoxia was reproducible in control animals and unaffected by the cyclo-oxygenase inhibitor diclophenac (3 mg/kg). Infusion of L-NNA alone resulted in an augmented pulmonary vasoconstriction during hypoxia; pulmonary arterial pressure from 35 +/- 6 to 43 +/- 9 mmHg; P < 0.05 and vascular resistance from 7.2 +/- 1.1 to 9.9 +/- 1.8 mmHg.min.l-1; P < 0.05. L-NNA in combination with BMS-182874 (10 mg/kg) resulted in a hypoxic pulmonary vasoconstriction of similar magnitude as hypoxic baseline. In addition, BMS-182874 reduced the hemodynamic response to ET-1 in normoxic pigs and competitively antagonized the vasoconstrictor effect of ET-1 in isolated porcine pulmonary arteries. CONCLUSIONS: The non-peptide, selective ETA receptor antagonist, BMS-182874, reduces hypoxic pulmonary vasoconstriction in pigs. The reduction in pulmonary vascular response to hypoxia following BMS-182874 is at least partly independent of nitric oxide.