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Background- Vascular smooth muscle cell (VSMC) proliferation is a critical factor in the neointima formation that causes restenosis after coronary angioplasty (PTCA). Desferri-exochelin 772SM (D-EXO), a highly diffusible, lipophilic iron chelator secreted by Mycobacterium tuberculosis, inhibits proliferation of VSMCs in culture. We hypothesized that treatment with D-EXO would inhibit neointima formation in balloon-injured vessels in vivo. Methods and Results- We subjected 24 pigs to overstretch coronary artery injury with standard PTCA balloons and then administered intramural injections of either D-EXO (n=14) or vehicle (n=10) through an Infiltrator catheter. Treatments were randomized, and the investigators were blinded with regard to treatment group until data analysis was completed. One month later, we euthanized the pigs, excised the injured coronary segments, made multiple sections of each segment, and identified the site of maximal neointima formation. An injury score based on the degree of disruption of the internal or external elastic lamina or media was assigned. D-EXO reduced stenosis index (neointima area divided by the area within the internal elastic lamina), adjusted for injury score, by 47%. Neointima thickness was also reduced. Conclusions- D-EXO, injected intramurally, substantially inhibited formation of neointima in a porcine vascular injury model.

Background: Estrogens have vascular effects through the activation of estrogen receptors (ERs). In addition to ERalpha, the first ER to be cloned, a second subtype called ERbeta has recently been discovered., Methods and Results: Using a reverse-transcriptase polymerase chain reaction assay that employs the same primer pair to simultaneously amplify ERalpha and ERbeta transcripts, we found that ERbeta is the ER form that is predominantly expressed in human vascular smooth muscle, particularly in women. The transcriptional effects of the 2 ERs in transfected HeLa cells differed. In response to 17beta-estradiol, ERalpha is a stronger transactivator than ERbeta at low receptor concentrations. However, at higher receptor concentrations, ERalpha activity self-squelches, and ERbeta is a stronger transactivator. Tamoxifen has partial agonist effects with ERalpha but not with ERbeta., Conclusions: The protective effects of estrogens in the cardiovascular system of women may be due to the genomic effects of ERbeta in vascular tissue.

Background: Estrogens stimulate growth of breast or uterine cells but have the opposite effect on vascular smooth muscle cells, in which they protect against coronary artery disease with or without concomitant administration of progesterone. A possible cause of differences in hormone action is variable tissue-specific expression of hormone receptor. Therefore, we analyzed the structure of estrogen receptors (ERs) and progesterone receptors (PRs) in human vascular smooth muscle., Methods and Results: RNA was isolated from human vascular smooth muscle, and the functional domains of ER-alpha and PR were characterized by reverse transcriptase and polymerase chain reaction. Interestingly, in addition to wild-type ER-alpha and PR, 5 variant ER-alpha and 2 variant PR transcripts were found. These variants contained precise deletions of exons encoding regions of the hormone-binding domain. The PR transcripts lacked exon 4 (PRDelta4) and exon 6 (PRDelta6). The ER-alpha transcripts were missing exon 4 (ERDelta4), exon 5 (ERDelta5), exon 6 (ERDelta6), exon 7 (ERDelta7), and exons 6 and 7, (ERDelta6,7). ER-beta variants were also detected. The PR variants were functionally characterized, and PRDelta6 was found to be a dominant-negative transcription inhibitor of wild-type receptors. Variant PR was present in premenopausal women but absent in postmenopausal women., Conclusions: Variant PR and ER transcripts are extensively expressed in human vascular smooth muscle. The complex tissue-specific effects of sex hormones may be mediated by the expression of heterogeneous forms of their cognate receptors. The presence of variant ERs and PRs may be of importance in altering the physiological effects of estrogens or progestins in vascular smooth muscle.

Background: Estrogen-mediated cardiovascular protection is incompletely explained by its beneficial lipid-modifying effects. Previous studies interrogating direct vascular effects of estrogens have used models of either diet- or injury-induced atherosclerosis. The purpose of this study was to determine the influence of ovarian ablation alone on vascular remodeling. We hypothesized that estrogens are atheroprotective, independent of their influence on lipid metabolism, by directly influencing the production and effects of a prototypical atherogenic mediator, basic fibroblast growth factor (bFGF)., Methods and Results: Twenty-five female sheep were randomized to sham operation, ovariectomy, or ovariectomy plus 17beta-estradiol replacement. Serum cholesterol and triglyceride levels were serially measured for 1 year and were similar among groups and in the normal range (30 to 60 mg/dL). At 6, 9, and 12 months, ovariectomy resulted in aortoiliac intimal hyperplasia compared with sham (P<0.01) and hormone replacement (P<0.01) groups. The neointima of ovariectomized animals was characterized immunohistochemically by increased vascular smooth muscle cells (VSMCs). Levels of bFGF protein were determined in adjacent aortic segments. Ovariectomized sheep had 2-fold more FGF than sham or ovariectomized sheep that received hormone replacement. In vitro, estradiol inhibited the mitogenic effect of bFGF on human aortic VSMCs., Conclusions: Without dietary manipulation, ovarian ablation alone induces aortic intimal hyperplasia in the ewe. Estradiol abrogates this response independently of its effects on serum lipids. Hormone replacement decreases the accumulation of the atherogenic peptide bFGF in vivo and inhibits the mitogenic response of VSMCs to bFGF in vitro. These results suggest that estrogens may provide atheroprotection both by modulating local production and by attenuating the influence of bFGF on VSMC growth.

Background: Polymorphonuclear leukocytes, particularly neutrophils, are important mediators of ischemia/reperfusion-induced myocardial and coronary vascular injury. The selectin family of glycoprotein receptors mediates neutrophil "rolling," a loose, transient adhesion to the coronary endothelium that precedes the firmer adhesion associated with cardiovascular injury. The oligosaccharide sialyl-Lewis(x) (SLe(x)) is the probable neutrophil counterligand for endothelial E- and P-selectin. Administration of analogues of SLe(x) could potentially prevent neutrophil rolling by competing for the selectin-adhesion sites. We investigated the effects of treatment with an analogue of SLe(x) in a chronic canine model of ischemia/reperfusion., Methods and Results: Anesthetized mongrel dogs were subjected to 90 minutes of ischemia through occlusion of the left anterior descending coronary artery and 48 hours of reperfusion. Five minutes before the onset of reperfusion, dogs received either the SLe(x) analogue CY-1503 at a dose of 20 mg/kg or normal saline. Myocardial infarct size was measured through triphenyltetrazolium chloride staining, and polymorphonuclear leukocyte accumulation was evaluated through measurement of cardiac myeloperoxidase activity. After adjustment for blood flow, the mean infarct size of control dogs (44.7 +/- 4.2%) was not different from that of treated dogs (33.4 +/- 4.0%, P = .06), although there was a trend toward a slightly lower value in the treated dogs. Myeloperoxidase activity was not different in the infarcted myocardium of the treated group compared with that of the control group (2.7 +/- 0.71 treated versus 1.08 +/- 0.41 units/mg protein control, P = .06)., Conclusions: We conclude that CY-1503 does not substantially or consistently reduce myocardial infarct size or neutrophil accumulation in dogs subjected to ischemia followed by a prolonged period (48 hours) of reperfusion.