Expression of angiotensin II and interleukin 6 in human coronary atherosclerotic plaques: potential implications for inflammation and plaque instability

BACKGROUND

Patients with an activated renin-angiotensin system (RAS) or genetic alterations of the RAS are at increased risk of myocardial infarction (MI). Administration of ACE inhibitors reduces the risk of MI, and acute coronary syndromes are associated with increased interleukin 6 (IL-6) serum levels. Accordingly, the present study evaluated the expression of angiotensin II (Ang II) in human coronary atherosclerotic plaques and its influence on IL-6 expression in patients with coronary artery disease.

METHODS AND RESULTS

Immunohistochemical colocalization of Ang II, ACE, Ang II type 1 (AT(1)) receptor, and IL-6 was examined in coronary arteries from patients with ischemic or dilated cardiomyopathy undergoing heart transplantation (n=12), in atherectomy samples from patients with unstable angina (culprit lesion; n=8), and in ruptured coronary arteries from patients who died of MI (n=13). Synthesis and release of IL-6 was investigated in smooth muscle cells and macrophages after Ang II stimulation. Colocalization of ACE, Ang II, AT(1) receptor, and IL-6 with CD68-positive macrophages was observed at the shoulder region of coronary atherosclerotic plaques and in atherectomy tissue of patients with unstable angina. Ang II was identified in close proximity to the presumed rupture site of human coronary arteries in acute MI. Ang II induced synthesis and release of IL-6 shortly after stimulation in vitro in macrophages and rat smooth muscle cells.

CONCLUSIONS

Ang II, AT(1) receptor, and ACE are expressed at strategic sites of human atherosclerotic coronary arteries, suggesting that Ang II is produced primarily by ACE within coronary plaques. The observation that Ang II induces IL-6 and their colocalization with the AT(1) receptor and ACE is consistent with the notion that the RAS may contribute to inflammatory processes within the vascular wall and to the development of acute coronary syndromes.

Angiotensin-converting enzyme gene expression in skeletal muscle in patients with chronic heart failure

BACKGROUND

Skeletal muscle factors may influence functional limitation in patients with heart failure. The renin-angiotensin system is activated in chronic heart failure. Treatment with angiotensin-converting enzyme (ACE) inhibitors improve symptoms and prognosis. The goal of this study was to quantify and localize skeletal muscle ACE-mRNA in patients with chronic heart failure and in control subjects, and to elucidate skeletal muscle fiber area and capillary density.

METHODS AND RESULTS

Biopsies from the lateral vastus muscle were taken from 9 patients before and after treatment with enalapril and in 10 control subjects. ACE-mRNA was quantified with reverse transcription polymerase chain reaction. Immunohistochemistry was used to localize ACE within skeletal muscle. No difference in ACE-mRNA transcripts between patients and control subjects was detected, nor did ACE gene expression change after treatment with enalapril. The number of ACE-mRNA transcripts was related to muscle fiber area, whereas an inverse relationship between the number of ACE transcripts and capillary density was found. ACE was detected in the endothelial cells of capillaries in skeletal muscle.

CONCLUSION

ACE is expressed in skeletal muscle and is confined to endothelial cells. The close relationship between capillary density and number of ACE transcripts indicate that activation of the renin-angiotensin system has an impact on capillary growth.

Endoluminal local delivery of PCNA/cdc2 antisense oligonucleotides by porous balloon catheter does not affect neointima formation or vessel size in the pig coronary artery model of postangioplasty restenosis

Localized delivery of antisense oligonucleotides directed against cell cycle regulatory proteins has been proposed as a means to prevent restenosis after angioplasty. To test whether single endoluminal delivery of a combination of proliferating cell nuclear antigen (PCNA) and cell-division cycle 2 kinase (cdc2) antisense might affect restenosis, we delivered 2 ml of lipid-complexed PCNA/cdc2 antisense oligomers (1.35 mg) to the coronary arteries of pigs after balloon overstretch angioplasty (AS group) and performed planimetric histomorphometry on arterial sections of the tissue, harvested at 4 wk. Compared with controls receiving 3'-5' reversed sequence oligomers (REV group), there were no differences in absolute intimal area (AS 1.36 +/- 0.08 mm2, REV 1.23 +/- 0.10 mm2, P = NS), intimal area normalized to extent of injury (AS 0.67 +/- 0.03, REV 0.77 +/- 0.10, P = NS), or vessel perimeter (AS 7.72 +/- 0.19 mm, REV 7.36 +/- 0.22 mm, P = NS). We conclude that single endoluminal delivery of antisense against key cell cycle regulatory proteins does not affect neointima formation or vessel size in this model of restenosis.

Pharmacokinetics and tissue localization of antisense oligonucleotides in balloon-injured pig coronary arteries after local delivery with an iontophoretic balloon catheter

When delivered locally to the arterial wall by passive fluid transfer systems such as perforated balloons, water-soluble compounds in aqueous solution are not readily taken up by tissue, show low levels of cellular localization, and are quickly lost by wash-out. One approach to improve delivery is addition of an "active" component to the catheter system to change the nature of the drug-to-tissue interaction. Using an iontophoretic balloon catheter to deliver antisense oligonucleotide (ODN) to pig coronary arteries after balloon angioplasty, we determined the quantity and localization of ODN in the tissue. By radiolabeling, 7.3 +/- 2.4 micrograms ODN was present at 30 min, 1.5 +/- 0.6 at 2 h, 0.52 +/- 0.35 at 24 h, and 0.26 +/- 0.11 at 7 d. By fluorescent labeling, circumferential medial uptake and adventitial delivery at the site of medial injury was observed, with primarily cellular localization. The iontophoretic catheter thus appears to be a useful device for ODN delivery to arterial tissue.

Differential effects of kinins on cardiomyocyte hypertrophy and interstitial collagen matrix in the surviving myocardium after myocardial infarction in the rat

BACKGROUND

Left ventricular remodeling after myocardial infarction (MI) involves the hypertrophic growth of cardiomyocytes and the accumulation of fibrillar collagen in the interstitial space. We evaluated the role of kinins in postinfarction ventricular remodeling and their potential contribution to the antiremodeling effects of ACE inhibition and angiotensin II type 1 (AT1) receptor blockade.

METHODS AND RESULTS

Rats underwent coronary artery ligation followed by chronic B2 kinin receptor blockade with icatibant. Additional groups of infarcted rats were treated with the ACE inhibitor lisinopril or the AT1 receptor antagonist ZD7155, each separately and in combination with icatibant. B2 kinin receptor blockade enhanced the interstitial deposition of collagen after MI, whereas morphological and molecular markers of cardiomyocyte hypertrophy (cardiac weight, myocyte cross-sectional area, prepro-atrial natriuretic factor mRNA expression) were not affected. Chronic ACE inhibition and AT1 receptor blockade reduced collagen deposition and cardiomyocyte hypertrophy after MI. The inhibitory action of ACE inhibition and AT1 receptor blockade on interstitial collagen was partially reversed by B2 kinin receptor blockade. However, B2 kinin receptor blockade did not attenuate the effects of ACE inhibition and AT1 receptor blockade on cardiomyocyte hypertrophy.

CONCLUSIONS

(1) Kinins inhibit the interstitial accumulation of collagen but do not modulate cardiomyocyte hypertrophy after MI. (2) Kinins contribute to the reduction of myocardial collagen accumulation by ACE inhibition and AT1 receptor blockade. (3) The effects of ACE inhibition and AT1 receptor blockade on cardiomyocyte hypertrophy are related to a reduced generation/receptor blockade of angiotensin II.

Development and prevention of skeletal muscle structural alterations after experimental myocardial infarction

The present study was designed to assess whether structural alterations develop within skeletal muscle 1 yr after myocardial infarction (MI) and failure and, if so, whether these structural alterations can be prevented by angiotensin-converting enzyme (ACE) inhibition. Infarcted rats were randomized and treated for 1 yr with either placebo (MI-IP, n = 9), a low dose of lisinopril (MI-LL, 0.5 mg.kg-1.day-1, n = 12), or a high dose of lisinopril (MI-LH, 5 mg.kg-1.day-1, n = 9). Sham-operated animals served as controls (SH, n = 14). One year after MI, in situ fixation of rat hindlimb was performed to investigate interstitial collagen volume fraction (CVF), capillary density, and media thickness of resistance vessels (80-200 microns) of musculus quadriceps femoris muscle. Infarct size was similar in all infarct groups and averaged 26 +/- 4%. Right ventricular weight was increased in MI-IP compared with SH, MI-LL, and MI-LH. Both left ventricular (LV) CVF and skeletal muscle CVF were increased in MI-IP. LV CVF and skeletal muscle CVF were closely related to each other (n = 44, r = 0.5377, P < 0.002). In infarcted rats, high-dose ACE inhibition significantly reduced skeletal muscle and LV CVF. Skeletal muscle capillary density and capillary-to-muscle fiber ratio were significantly decreased in infarcted rats but were restored by low- and high-dose ACE inhibition. Media thickness of intramuscular resistance vessels was increased in the MI-IP group and significantly reduced by high-dose ACE inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Electroporation of pp60c-src antibodies inhibits the angiotensin II activation of phospholipase C-gamma 1 in rat aortic smooth muscle cells

Our previous study has shown that angiotensin II induces the rapid tyrosine phosphorylation and activation of phospholipase C-gamma 1 in cultured rat aortic smooth muscle (RASM) cells (Marrero, M.B., Paxton, W.G., Duff, J. L., Berk, B. C., and Bernstein, K. E. (1994) J. Biol. Chem, 269, 10935-10939). This signaling pathway is initiated by ligand binding to the AT1 receptor, a cell surface G protein-coupled receptor. Antibodies to pp60c-src were introduced into RASM cells by electroporation. Angiotensin II-stimulated tyrosine phosphorylation of phospholipase C-gamma 1 was eliminated by the anti-pp60c-src antibodies but not by anti-mouse IgG or bovine serum albumin. Angiotensin II also induced the rapid tyrosine phosphorylation of pp120, a known pp60c-src kinase substrate, and this phosphorylation was also specifically inhibited by anti-pp60c-src antibodies. Electroporation of RASM cells with anti-pp60c-src antibodies had no effect on platelet-derived growth factor-stimulated tyrosine phosphorylation of PLC-gamma 1. Anti-pp60c-src also reduced the angiotensin II-stimulated inositol 1,4,5-trisphosphate production by 78%, while it had no effect on the platelet-derived growth factor-stimulated inositol 1,4,5-trisphosphate production. These data provide the first evidence for a direct involvement of pp60c-src kinase in angiotensin II-mediated PLC-gamma 1 phosphorylation and activation. Furthermore, it also describes a pathway in which a seven-transmembrane receptor can stimulate an intracellular tyrosine kinase.