Anders Bergdahl

Increase in cardiac P2X1-and P2Y2-receptor mRNA levels in congestive heart failure

We wanted to study the expression of P2-receptors at the mRNA-level in the heart and if it is affected by congestive heart failure (CHF). To quantify the P2 receptor mRNA-expression we used a competitive RT-PCR protocol which is based on an internal RNA standard. The P2 receptor mRNA-expression was quantified in hearts from CHF rats and compared to sham-operated rats. Furthermore, the presence of receptor mRNA was studied in the myocardium from patients with heart failure. In the sham operated rats the G-protein coupled P2Y-receptors were expressed at a higher level than the ligand gated ion-channel receptor (P2X1). Among the P2Y-receptors the P2Y6-receptor was most abundantly expressed (P2Y6 > P2Y1 > P2Y2 = P2Y4 > P2X1). A prominent change was seen for the P2X1- and P2Y2-receptor mRNA levels which were increased 2.7-fold and 4.7-fold respectively in the myocardium from the left ventricle of CHF-rats. In contrast, the P2Y1-, P2Y4- and P2Y6-receptor mRNA levels were not significantly altered in CHF rats. In human myocard the P2X1-, P2Y1-, P2Y2-, P2Y6- and P2Y11-receptors were detected by RT-PCR in both right and left atria and ventricles, while the P2Y4-receptor band was weak or absent. In conclusion, most of the studied P2-receptors were expressed in both rat and human hearts. Furthermore, the P2X1- and P2Y2-receptor mRNA were upregulated in CHF, suggesting a pathophysiological role for these receptors in the development of heart failure.

Neuropeptide Y potentiates noradrenaline-induced contraction through the neuropeptide Y Y1 receptor

To elucidate which neuropeptide Y receptor subtype is responsible for the neuropeptide Y-induced potentiation of the noradrenaline-evoked contraction in human omental arteries we used antisense oligodeoxynucleotide (Antisense), the new selective neuropeptide Y Y1 receptor antagonist, BIBP3226 {(R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl) methyl]-D-arginine-amide} and the reverse transcriptase-polymerase chain reaction (RT-PCR). Neuropeptide Y significantly potentiated the noradrenaline-induced contraction in non-incubated vessels (pEC50 6.4 +/- 0.2 vs. 5.9 +/- 0.2) and in vessels incubated with 1 microM Sense oligodeoxynucleotide (Sense) (pEC50 6.0 +/- 0.1 vs. 5.6 +/- 0.2). In vessels incubated with 1 microM Antisense the potentiating effect of neuropeptide Y was completely abolished. BIBP3226 (1 microM) inhibited the neuropeptide Y-induced potentiation in human omental arteries (pEC50 5.8 +/- 0.3 vs. 6.4 +/- 0.2). Finally, messenger RNA for the neuropeptide Y Y1 receptor was detected using RT-PCR. On the basis of our results we conclude that the neuropeptide Y-induced potentiation of the noradrenaline-induced contraction is mediated by the neuropeptide Y Y1 receptor.

Innervation of human epicardial coronary veins: immunohistochemistry and vasomotility

OBJECTIVE The aim was to investigate the innervation and vasomotor responses to classical and putative transmitters of the coronary venous bed. METHODS The innervation of human epicardial coronary veins was investigated using acetylcholinesterase histochemistry and immunofluorescence staining, together with antisera against the general neuronal marker protein gene product 9.5 (PGP 9.5), the catecholamine synthesising enzyme tyrosine hydroxylase, and neuropeptides [neuropeptide Y, vasoactive intestinal peptide (VIP), substance P, and calcitonin gene related peptide (CGRP)]. The vasomotor responses to noradrenaline, acetylcholine, neuropeptide Y, substance P, human alpha calcitonin gene related peptide (alpha CGRP), and VIP were tested on isolated circular human epicardial coronary vein segments. RESULTS A network of nerve fibres was shown in the major epicardial coronary veins by means of an antiserum to PGP 9.5. The majority of the perivascular nerve fibres possessed neuropeptide Y and tyrosine hydroxylase immunoreactivity. Only a few nerve fibres displayed substance P, CGRP, and VIP immunoreactivity and acetylcholinesterase activity. Noradrenaline and acetylcholine induced powerful contractions of all the tested segments, whereas no contraction was induced by neuropeptide Y, alpha CGRP, substance P, or VIP. All segments precontracted with U46619 responded with potent relaxation to alpha CGRP, substance P, and VIP, whereas noradrenaline and acetylcholine only in low concentrations induced weak relaxation of a few of the segments. No relaxation was induced by neuropeptide Y. CONCLUSIONS This is the first study to demonstrate comprehensively the perivascular innervation of human coronary veins and corresponding vasomotor effects, suggesting a role in regulation of the coronary venous circulation.

Congestive heart failure induces downregulation of P2X1-receptors in resistance arteries.

OBJECTIVE Congestive heart failure (CHF) is accompanied by enhanced peripheral sympathetic nerve activity, increased vascular resistance and impaired peripheral blood flow. Besides noradrenaline and neuropeptide Y, the sympathetic nervous system also releases ATP, which has contractile effects mediated by different subtypes of P2-receptors on the vascular smooth muscle cells. The present study was designed to examine postsynaptic changes of the contractile responses to ATP and other extracellular nucleotides in CHF. METHODS CHF was induced by left coronary artery ligation resulting in a reproducible myocardial infarction in Sprague-Dawley rats. Contractile responses were examined in cylindrical segments of aorta and the mesenteric artery after endothelium removal. To determine if an altered response was regulated on the transcriptional level, competitive reverse transcription polymerase chain reaction (RT-PCR) was used to estimate the amount of P2X1-receptor mRNA. RESULTS ATP, which is both a P2X1- and a P2Y-receptor agonist, induced a weaker contraction in the mesenteric artery from CHF as compared to sham operated rats. A decrease in both potency and maximum contraction was shown for the selective P2X1-receptor agonist, alpha beta-MeATP, in the mesenteric artery (pEC50 = 6.04 vs. 5.76, Cmax = 57% vs. 33%, sham vs. CHF operated rats), but not in the aorta. Competitive RT-PCR also revealed decreased P2X1-receptor mRNA levels in CHF operated rats in the mesenteric artery (9106 x 10(3) vs. 714 x 10(3) molecules/microgram, sham vs. CHF operated rats), while it remained unaltered in the aorta. To study the P2Y-receptor induced contractile effects, the P2X1-receptors were first desensitised with alpha beta-MeATP (10(-5) M for 8 min). After P2X1-receptors desensitisation, UTP and UDP induced strong contractions in both the mesenteric artery and in the aorta, while ATP and ADP were much less effective. These contractions were not altered by CHF, indicating that vascular contraction mediated by P2Y-receptors are unaffected by CHF. CONCLUSION CHF induces downregulation of P2X1-receptor stimulated contraction in the mesenteric artery depending on decreased mRNA synthesis for the receptor, while the P2Y-receptor activity remains unchanged. Downregulation of P2X1-receptors appears to be specific for peripheral resistance arteries. This may represent a compensatory response to enhanced peripheral sympathetic nerve activity and increased vascular resistance in CHF.

Relationships between plasma levels of catecholamines and neuropeptides and the survival time in patients with congestive heart failure

Abstract. Objectives. To evaluate the importance of various variables reflecting neuroendocrine activation in relation to prognosis in patients with congestive heart failure (CHF).

Vascular alpha-2 adrenoceptor function is decreased in rats with congestive heart failure

OBJECTIVE Vascular alpha-2 adrenoceptor function of rats with congestive heart failure (CHF) was characterized in both in vivo and in vitro experiments. METHODS CHF was induced in Sprague-Dawley rats by coronary artery ligation. Sham-operated rats served as normal controls. Postjunctional alpha-2 adrenergic responsiveness was assessed in vivo using the pithed rat model and in vitro in organ bath. Vascular alpha-2 adrenoceptor density was studied by receptor binding assay. RESULTS Four to 6 weeks after this surgical procedure, plasma catecholamines were markedly increased in CHF rats. In vivo vascular responses to alpha-2 adrenoceptor agonists BHT933 and clonidine were significantly decreased in CHF rats (P < 0.001). Clonidine elicited dose-dependent responses in endothelium intact mesenteric arteries in both CHF and sham-operated rats. The dose-response curve in CHF was shifted to the right with a pD2 value of 5.5 +/- 0.2 compared with control rats 6.2 +/- 0.2 (P < 0.05). The response to clonidine was selectively blocked by an alpha-2 adrenergic antagonist rauwolscine in both groups. Endothelium denuded arteries showed an enhanced response to clonidine in both CHF and control rats. However, the response to clonidine is still decreased in CHF compared to sham-operated rats (P < 0.05). Alpha-2 adrenoreceptor density, as determined by [3H]yohimbine binding in membrane preparations from mesenteric arteries was decreased in CHF compared to sham-operated rats (Bmax 43 +/- 6 vs. 104 +/- 20 fmol/mg protein, P < 0.05). CONCLUSIONS Vascular alpha-2 adrenoceptor function is decreased in rats with CHF.

Enhanced endothelin-1-induced contractions in mesenteric arteries from rats with congestive heart failure: role of ETB receptors

Studies of congestive heart failure (CHF) in man and in experimental CHF have demonstrated elevated circulating levels of endothelin (ET). In order to examine whether there are concomitant ET receptor alterations, the vasomotor effects of endothelin‐1 (ET‐1) and sarafotoxin 6c (S6c) were examined in endothelium‐intact and ‐denuded isolated mesenteric arteries from rats with CHF. CHF was induced by ligation of the left anterior descending coronary artery. Vasomotor responses were studied using small mesenteric arteries (approx. 250 μm in diameter, determined after normalisation). The antagonists IRL2500 and FR139317 were used in order to characterise the ET‐1‐induced response. In mesenteric arteries with intact endothelium, ET‐1‐induced contractions were more potent in CHF as compared to sham (pEC50 9.6 ± 0.2 and 9.1 ± 0.1, respectively, P < 0.01). In endothelium‐denuded arteries, there was no difference in potency of ET‐1 between CHF and sham arteries, or in maximum contraction. In the presence of IRL2500, a selective ETB‐receptor antagonist, ET‐1 was more potent in endothelium‐denuded arteries of CHF rats, while this difference was not seen in sham arteries. S6c had no consistent contractile or dilatory effect in CHF and sham rats. The results indicate that the enhanced contractile effects of ET‐1 noted in CHF might be due to an attenuated endothelial function and that inhibition of smooth muscle cell ETB receptors increase the effects of contractile ETA receptors in CHF rats.

Renal and Cardiovascular Role of the Neuropeptide Y Y1 Receptor in Ischaemic Heart Failure Rats

The cardiovascular role of the neuropeptide Y Y1 receptors in‐vivo and in‐vitro in ischaemic heart failure was evaluated by using the novel neuropeptide Y Y1 selective antagonist BIBP 3226 (R‐N2‐(diphenylacetyl)‐N‐[(4‐hydroxyphenyl)methyl]‐D‐arginine‐amide).

Enhanced Ca2+ -induced contractions and attenuated α-adrenoceptor responses in resistance arteries from rats with congestive heart failure

The aim of the present study was to examine the role of Ca2+ ‐mediated contractile responses in isolated mesenteric resistance arteries from rats with congestive heart failure (CHF).

Microcalorimetric study of myocardial tissue metabolism in heart failure after experimental myocardial infarction in rats

Abstract Using microcalorimetry and measuring oxygen consumption rate, we have studied metabolic activity in myocardial tissue from rats suffering from congestive heart failure (CHF) after ligation of the left coronary artery followed by myocardial infarction, comprising 30–40% of the endocardial circumference, known to be large enough to induce heart failure and neuroendocrine counter-regulation. The heat production in the preserved part of the left ventricle, harbouring the myocardial infarction, was 0.94 ± 0.05 mW g −1 ( n = 10) and not different from the controls i.e 0.94 ± 0.05 mW g −1 , ( n = 23). The oxygen consumption rate was 1.36 ± 0.20 nmol O 2 s −1 g −1 in CHF myocardium and 1.55 ± 0.24 nmol O 2 s −1 g −1 in the control rats, ( n = 20), n.s. The calculated contribution from aerobic metabolism to total heat production was 71 ± 9% in the CHF rats and 80 ± 6% in the control group, n.s. In tissue samples taken from the region of the border of and into the macroscopically damaged area of the myocardial infarction ( n = 5), the value for heat production was 1.15 ± 0.13 mW g −1 and oxygen uptake 1.79 ± 0.23 nmol O 2 s −1 g −1 . These results show that the contribution from aerobic metabolism to total energy expenditure in preserved left ventricular tissue is not higher than normal and suggest that the effects of left coronary occlusion are not limited to the generation of a myocardial infarction, but may also have a substantial impact on the ability of myocardial cells to increase metabolic activity in macro- and microscopically preserved regions of the left ventricle. In addition, the data demonstrate persistent metabolic activity within the region of ischemically damaged myocardium not different from that found in undamaged myocardium.