van Wiekert Gilst

Timing of erythropoietin treatment for cardioprotection in ischemia/reperfusion

Erythropoietin (EPO) is a hormone known to stimulate hematopoiesis. However, recent research suggests additional properties of EPO, such as protection against ischemia/reperfusion (I/R) injury in various tissues. We studied the effect of timing of EPO administration on cardioprotection during I/R in the heart. Male Sprague–Dawley rats were subjected to 45 minutes of coronary occlusion, followed by 24 hours of reperfusion. Animals were randomized to receive saline or single dose of EPO (5000 IU/kg) either 2 hours before I/R, at the start of ischemia, or after the onset of reperfusion. The ratio of infarct area/area at risk (planimetry), left ventricular (LV) function (pressure development), and apoptosis (number of active caspase-3 positive cells) were determined after 24-hour reperfusion. Administration of EPO during different time points resulted in a 19 to 23% (P < 0.05) reduction in the infarct area/area at risk, which was accompanied by a trend toward better LV hemodynamic parameters. Apoptosis was significantly attenuated in groups treated with EPO at the start of ischemia (29% reduction) and after the onset of reperfusion (38%), and to a lesser extent (16%) in the group pre-treated with EPO. Thus, in vivo administration of EPO at different time points protects the myocardial structure and preserves cardiac function during I/R. Cardioprotective effect of EPO is associated with inhibition of apoptosis.

Angiotensin II Type 1 Receptor A1166C Gene Polymorphism Is Associated With an Increased Response to Angiotensin II in Human Arteries

An adenine/cytosine (A/C) base substitution at position 1166 in the angiotensin II type 1 receptor (AT(1)R) gene is associated with the incidence of essential hypertension and increased coronary artery vasoconstriction. However, it is still unknown whether this polymorphism is associated with a difference in angiotensin II responsiveness. Therefore, we assessed whether the AT(1)R polymorphism is associated with different responses to angiotensin II in isolated human arteries. Furthermore, we evaluated whether inhibition of the renin-angiotensin system modifies the effect of the AT(1)R polymorphism. One hundred twelve patients who were undergoing coronary artery bypass graft surgery were prospectively randomized to receive an ACE inhibitor or a placebo for 1 week before surgery. Excess segments of the internal mammary artery were exposed to angiotensin II (0.1 nmol/L to 1 micromol/L) and KCl (60 mmol/L) in organ bath experiments. Patients homozygous for the C allele (n=17) had significantly greater angiotensin II responses (percentage of this maximal KCl-induced response) than did patients genotyped with AA+AC (n=95, P<0.05). Although ACE inhibition increased the response to angiotensin II, the difference in the response to angiotensin II, between CC and AA+AC patients remained intact in ACE inhibitor-treated patients. These results indicate increased responses to angiotensin II in patients with the CC genotype. The mechanism is preserved during ACE inhibition, which in itself also increased the response to angiotensin II. This reveals that the A1166C polymorphism may be in linkage disequilibrium with a functional mutation that alters angiotensin II responsiveness, which may explain the described relation between this polymorphism and cardiovascular abnormalities.

Angiotensin-(1–7) Is a Modulator of the Human Renin-Angiotensin System

The renin-angiotensin system is important for cardiovascular homeostasis. Currently, therapies for different cardiovascular diseases are based on inhibition of angiotensin-converting enzyme (ACE) or angiotensin II receptor blockade. Inhibition of ACE blocks metabolism of angiotensin-(1-7) to angiotensin-(1-5) and can lead to elevation of angiotensin-(1-7) levels in plasma and tissue. In animal models, angiotensin-(1-7) itself causes or enhances vasodilation and inhibits vascular contractions to angiotensin II. The function of angiotensin-(1-5) is unknown. We investigated whether angiotensin-(1-7) and angiotensin-(1-5) inhibit ACE or antagonize angiotensin-induced vasoconstrictions in humans. ACE activity in plasma and atrial tissue was inhibited by angiotensin-(1-7) up to 100%, with an IC(50) of 3.0 and 4.0 micromol/L, respectively. In human internal mammary arteries, contractions induced by angiotensin I and II and the non-ACE-specific substrate [Pro(11),D-Ala(12)]-angiotensin I were antagonized by angiotensin-(1-7) (10(-5) mol/L) in a noncompetitive way, with a 60% inhibition of the maximal response to angiotensin II. Contractions to ACE-specific substrate [Pro(10)]-angiotensin I were also inhibited, an effect only partly accounted for by antagonism of angiotensin II. Angiotensin-(1-5) inhibited plasma ACE activity with a potency equal to that of angiotensin I but had no effect on arterial contractions. In conclusion, angiotensin-(1-7) blocks angiotensin II-induced vasoconstriction and inhibits ACE in human cardiovascular tissues. Angiotensin-(1-5) only inhibits ACE. These results show that angiotensin-(1-7) may be an important modulator of the human renin-angiotensin system.

Accelerated decline and prognostic impact of renal function after myocardial infarction and the benefits of ACE inhibition : the CATS randomized trial

AIMS Information regarding the cardiorenal axis in patients after a myocardial infarction (MI) is limited. We examined the change in renal function after a first MI, the protective effect of angiotensin converting enzyme (ACE) inhibition and the prognostic value of baseline renal function. METHODS AND RESULTS The study population consisted of 298 patients with a first anterior wall MI who were randomized to the ACE inhibitor captopril or placebo after completion of streptokinase infusion. Renal function, by means of glomerular filtration rate (GFR), was calculated using the Cockroft-Gault equation (GFR(c)). In the placebo group, renal function (GFR(c)) declined by 5.5 min(-1)within 1 year, vs only 0.5 ml min(-1)in the ACE inhibitor group (P<0.05). This beneficial effect of captopril was most pronounced in patients with the most compromised renal function at baseline. The incidence of chronic heart failure (CHF) within 1 year increased significantly with decreasing GFR(c)(divided into tertiles: 24.0, 28.9, and 41.2%; P<0.01). The risk-ratio for GFR(c)<81 ml min(-1)vs >103 mL min(-1)was 1.86 (95% CI 1.11-3.13; P=0.019). CONCLUSIONS Renal function markedly deteriorates after a first MI, but is significantly preserved by ACE inhibition. Furthermore, an impaired baseline renal function adds to the prognostic risk of developing CHF in patients after a first anterior MI.

Alterations in Gene Expression of Proteins Involved in the Calcium Handling in Patients with Atrial Fibrillation

Gene Expression in Human Atrial Fibrillation. Introduction: Atrial fibrillation (AF) leads to a loss of atrial contraction within hours to days. During persistence of AF, cellular dedifferentiation and hypertrophy occur, eventually resulting in degenerative changes and cell death. Abnormalities in the calcium handling in response to tachycardia‐induced intracellular calcium overload play a pivotal role in these processes.

Endothelin System in Human Persistent and Paroxysmal Atrial Fibrillation

Endothelin System in Atrial Fibrillation. Introduction: Activation of the endothelin system is an important compensatory mechanism that is activated during left ventricular dysfunction. Whether this system plays a role at the atrial level during atrial fibrillation (AF) has not been examined in detail. The purpose of this study was to investigate mRNA and protein expression levels of the endothelin system in AF patients with and without concomitant underlying valve disease.

Myogenic constriction is increased in mesenteric resistance arteries from rats with chronic heart failure: instantaneous counteraction by acute AT1 receptor blockade

Increased vascular resistance in chronic heart failure (CHF) has been attributed to stimulated neurohumoral systems. However, local mechanisms may also importantly contribute to set arterial tone. Our aim, therefore, was to test whether pressure‐induced myogenic constriction of resistance arteries in vitro – devoid of acute effects of circulating factors – is increased in CHF and to explore underlying mechanisms. At 12 weeks after coronary ligation‐induced myocardial infarction or SHAM‐operations in rats, we studied isolated mesenteric arteries for myogenic constriction, determined as the active constriction (% of passive diameter) in response to stepwise increase in intraluminal pressure (20 – 160 mmHg), in the absence and presence of inhibitors of potentially involved modulators of myogenic constriction. We found that myogenic constriction in mesenteric arteries from CHF rats was markedly increased compared to SHAM over the whole pressure range, the difference being most pronounced at 60 mmHg (24±2 versus 4±3%, respectively, P<0.001). Both removal of the endothelium as well as inhibition of NO production (L‐NG‐monomethylarginine, 100 μM) significantly increased myogenic constriction (+16 and +25%, respectively), the increase being similar in CHF‐ and SHAM‐arteries (P=NS). Neither endothelin type A (ETA)‐receptor blockade (BQ123, 1 μM) nor inhibition of perivascular (sympathetic) nerve conduction (tetrodotoxin, 100 nM) affected the myogenic response in either group. Interestingly, increased myogenic constriction in CHF was fully reversed after angiotensin II type I (AT1)‐receptor blockade (candesartan, 100 nM; losartan, 10 μM), which was without effect in SHAM. In contrast, neither angiotensin‐converting enzyme (ACE) inhibition (lisinopril, 1 μM; captopril, 10 μM) or AT2‐receptor blockade (PD123319, 1 μM), nor inhibition of superoxide production (superoxide dismutase, 50 U ml−1), TXA2‐receptor blockade (SQ29,548, 1 μM) or inhibition of cyclooxygenase‐derived prostaglandins (indomethacin, 10 μM) affected myogenic constriction. Sensitivity of mesenteric arteries to angiotensin II (10 nM – 100 μM) was increased (P<0.05) in CHF (pD2 7.1±0.4) compared to SHAM (pD2 6.2±0.3), while the sensitivity to KCl and phenylephrine was not different. Our results demonstrate increased myogenic constriction in small mesenteric arteries of rats with CHF, potentially making it an important target for therapy in counteracting increased vascular resistance in CHF. Our results further suggest active and instantaneous participation of AT1‐receptors in increased myogenic constriction in CHF, involving increased sensitivity of AT1‐receptors rather than apparent ACE‐mediated local angiotensin II production.

Gender-specific correlations of plasminogen activator inhibitor-1 and tissue plasminogen activator levels with cardiovascular disease-related traits

Summary.  Background: The purpose of this study was to examine the correlations between plasma levels of plasminogen activator inhibitor‐1 (PAI‐1) and tissue plasminogen activator (t‐PA) and cardiovascular disease‐related traits in a general population and whether these correlations differed between females and males. Methods: Plasma PAI‐1 and t‐PA antigen levels and C‐reactive protein (CRP), HDL‐cholesterol, triglycerides, total cholesterol, systolic blood pressure, diastolic blood pressure, urinary albumin excretion, and glucose were measured in the population‐based PREVEND study in Groningen, the Netherlands (n = 2527). Results: Except for CRP and total cholesterol levels, all traits were significantly different between gender (P < 0.001). PAI‐1 levels were correlated with all measured cardiovascular disease‐related traits (P < 0.01) in both females and males. Except for urinary albumin excretion, similar results, albeit less significant, were found for t‐PA levels. Age‐adjusted correlations between PAI‐1 and CRP, triglycerides, total cholesterol, systolic blood pressure, and diastolic blood pressure differed significantly between females and males (P < 0.01). Many of the gender differences were predominantly present between premenopausal females and males. Conclusion: PAI‐1 and t‐PA levels were correlated with cardiovascular disease‐related traits in subjects obtained from the general population and several of these correlations differed across gender. The correlations found in the present study suggest the presence of coordinated patterns of cardiovascular risk factors and indicate which traits might influence PAI‐1 and t‐PA levels and thereby provide a framework and potential tool for therapeutic intervention to reduce thromboembolic events in the general population.

Improved functional recovery of the isolated rat heart after 24 hours of hypothermic arrest with a stable prostacyclin analogue (ZK 36 374)

Prostacyclin (PGI2) can protect the heart against ischemia, i.e. it can reduce myocardial damage [9, 10]. PGI2 protects the myocardium in vivo by preventing platelets from clumping and by dispersing preformed platelet aggregates [1,14]. However, also in the absence of platelets, PGI2 was shown to protect the myocardium against ischemia at concentrations that did not affect smooth muscle tone in the vessel wall [2]. This protective effect of PGI2 in vitro might be related to a stabilization of cell membranes in adrenergic nerve endings and hence to the prevention of ischemia-induced catecholamine release [13]. The instability of PGI2, both in vitro and in vivo, limits its application during long ischemic periods. Recently, a stable prostacyclin analogue, ZK 36 374, was demonstrated to have several prostacyclin-mimetic activities, both in vitro and in vivo [11,12]. In this communication we report upon the beneficial effect of this stable prostacyclin analogue at a low concentration (4 nM) on the extent of ischemic damage, on the recovery of myocardial function and on the occurrence of arrhythmias in the isolated rat heart after 24 h hypothermic cardiac arrest.

Ultrasound and microbubble-targeted delivery of therapeutic compounds: ICIN Report Project 49: Drug and gene delivery through ultrasound and microbubbles

The molecular understanding of diseases has been accelerated in recent years, producing many new potential therapeutic targets. A noninvasive delivery system that can target specific anatomical sites would be a great boost for many therapies, particularly those based on manipulation of gene expression. The use of microbubbles controlled by ultrasound as a method for delivery of drugs or genes to specific tissues is promising. It has been shown by our group and others that ultrasound increases cell membrane permeability and enhances uptake of drugs and genes. One of the important mechanisms is that microbubbles act to focus ultrasound energy by lowering the threshold for ultrasound bioeffects. Therefore, clear understanding of the bioeffects and mechanisms underlying the membrane permeability in the presence of microbubbles and ultrasound is of paramount importance. (Neth Heart J 2009;17:82-6.)