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Early inhibition of myointimal proliferation by angiopeptin after balloon catheter injury in the rabbit

PURPOSEnCoronary artery restenosis after percutaneous transluminal angioplasty occurs in more than 40% of patients. Angiopeptin, a stable synthetic octapeptide analogue of somatostatin, attenuates accelerated coronary artery myointimal thickening in rabbit cardiac allografts and myointimal thickening after arterial injury. In this study the temporal relationship between the angiopeptin treatment schedule and efficacy was explored. The relationship between inhibition of myointimal thickening by angiopeptin and inhibition of vascular cell proliferation was also examined.nnnMETHODSnThe aorta and the common and external iliac arteries of the rabbit underwent balloon injury. Angiopeptin (2 to 200 micrograms/kg/day) was administered for 1 day before injury and for 1, 5, and 21 days after injury. Morphometric studies were performed to determine measurement of intimal thickening. Inhibition of vascular cell proliferation by angiopeptin was evaluated by tritiated thymidine incorporation into the balloon-injured rabbit aorta. Thymidine was either administered intraperitoneally or added ex vivo to aorta segments of rabbits treated with angiopeptin (2, 20, or 200 micrograms/kg/day) from 1 day before injury until sacrifice 72 hours later.nnnRESULTSnAdministration of angiopeptin (2 to 200 micrograms/kg/day) significantly reduced intimal thickening by approximately 50% in all three vessels when evaluated 3 weeks after injury. This inhibitory effect was unrelated to duration of treatment and dose. Treatment initiated at the time of injury was found to be effective, but delaying treatment for 8, 18, or 27 hours abrogated the inhibitory effect of angiopeptin on myointimal thickening. Angiopeptin treatment significantly decreased thymidine-labeled nuclei of smooth muscle cells in vitro. Angiopeptin treatment similarly inhibited thymidine uptake in vitro by balloon-injured aorta segments.nnnCONCLUSIONnAngiopeptin significantly inhibits myointimal thickening by inhibiting vascular cell proliferation. Administration of angiopeptin for 2 days is as efficacious as 3 weeks treatment in inhibiting myointimal thickening. Delaying treatment for as little as 8 hours after injury abrogates the inhibitory effects of angiopeptin. This speaks to the importance of early events immediately after vascular tissue injury, suggesting that angiopeptin inhibits the expression of early genes causally related to the vascular injury response and thereby triggering vascular cell proliferation.

Expression of IGF-1, IGF-1 receptor and TGF-β following balloon angioplasty in atherosclerotic and normal rabbit iliac arteries: An immunocytochemical study

Growth factors have been implicated in the pathogenesis of restenosis (myointimal hyperplasia after coronary interventions). In this study, we examined the expression of insulin-like growth factor-I (IGF-1), IGF-1 receptor, and transforming growth factor-beta (TGF-beta) in atherosclerotic and normal rabbit iliac arteries following overstretch balloon angioplasty of the iliac arteries to create a vascular lesion. Animals were sacrificed at 0, 3, 7, 15 and 42 days post angioplasty. The iliac arteries were processed for immunocytochemical localization of IGF-1, IGF-1 receptor and TGF-beta using colloidal gold and the data were quantitatively analyzed. IGF-1, IGF-1 receptor and TGF-beta immunoreactivity were all significantly increased in atherosclerotic arteries compared to control at all of the time points examined. Following balloon angioplasty, the levels of IGF-1 and IGF-1 receptor increased significantly in both control and even further in hypercholesterolemic vessels. In control vessels, the IGF-1 levels returned to preintervention levels, while in atherosclerotic vessels, the levels of IGF-1 and IGF-1 receptor remained elevated. In addition, TGF-beta levels in control vessels showed an initial rise in the first week following injury but then returned to baseline levels. In contrast, atherosclerotic vessels demonstrated a sustained expression of TGF-beta. Thus, IGF-1 and TGF-beta expression is different in normal vs. atherosclerotic vessels following vascular injury. The intensity of expression of IGF-1 and its receptor, which is not reduced at 42 days compared to 15 days following injury, support a role for IGF-1 in smooth muscle cell proliferation and migration. The sustained increase in TGF-beta could facilitate extracellular matrix (ECM) accumulation. Local vascular therapy that is directed towards modulating the effects of IGF-1 and TGF-beta could reduce restenosis.

Specific binding of estradiol to rat coronary artery smooth muscle cells.

We report the expression and characteristics of the estrogen receptor in rat coronary artery-derived smooth muscle cells. Polymerase chain reaction analyses of total and poly(A) + mRNA from rat coronary artery-derived smooth muscle cells indicate the presence of estrogen receptor mRNA. Binding analyses reveal the presence of high affinity binding sites for 17 beta-estradiol, with a Kd equivalent to that observed for authentic estrogen receptors in other estrogen responsive tissues. Scatchard and Hill plot analyses of the properties of receptor-ligand binding indicate the presence of a single site, and the absence of cooperative binding. Unlabeled E2 but not testosterone, dexamethasone or progesterone compete with [3H] 17 beta-estradiol for binding sites. The affinity, specificity and non-cooperative nature of the estrogen binding sites are identical to those observed in other estrogen-responsive tissues. These cells may provide a novel model in which to study the effects of estrogens on the proliferation, differentiation and function of vascular smooth muscle cells.

Short-term angiopeptin therapy and the incidence of graft vessel disease after heart transplantation

BACKGROUNDnGraft vessel disease, the major limitation for long-term success after heart transplantation, is triggered by injury to the graft vessel endothelium, resulting in the expression of adhesion molecules, the migration of leukocytes into the graft, and the release of growth factors. Angiopeptin, a stable analog of somatostatin, is a growth-hormone inhibitor with additional anti-proliferative effects. We evaluated angiopeptin for prevention of graft vasculopathy after cardiac transplantation in the first prospective, randomized, double-blind, clinical trial.nnnMETHODSnThirty-one patients received treatment with either angiopeptin (n = 13) or placebo (n = 18). Patients were randomized according to the presence of hypercholesterolemia, recipient cytomegalovirus-antibody status, and donor age. All patients received standard triple-drug immunosuppression. Angiopeptin 1.5 mg or placebo was given subcutaneously immediately before surgery and twice a day after transplantation from Day 1 to Day 14. Furthermore, 1.5 mg was added to each liter of cardioplegic solution, 1.5 mg was given intravenously during surgery, and another 3 mg was given during the first 6 post-operative hours. During the first post-operative year, angiopeptin 1.5 mg or placebo was added to each treatment for acute rejection (twice a day subcutaneously). Baseline angiography was performed within the first 4 post-operative weeks and annually thereafter. Twenty-three patients each underwent an additional intracoronary ultrasound.nnnRESULTSnOne- and 4-year survival rates were comparable: 85% and 85% for the group receiving angiopeptin, and 89% and 78% for the placebo group, respectively. One patient in the control group died of myocardial infarction caused by graft vessel disease. Although the mean number of rejection and infection episodes was similar, the overall incidence of newly occurring graft vessel disease after 2 and 4 years was greater in the control cohort: 9% vs 38% after 2 years and 27% vs 44% after 4 years (p = 0.183, 0.448). Comparison of the results of intracoronary ultrasound performed in a sub-group of patients confirmed that trend: the modified Stanford score, the mean intimal thickness, and the mean intimal index were lower in the angiopeptin group. Again, because of the relatively small number of patients available for evaluation, the difference did not reach statistical significance.nnnCONCLUSIONSnShort-term peri-operative angiopeptin treatment along with additional injections during rejection episodes within the first year resulted in a marked decrease in graft vessel disease 2 and 4 years after heart transplantation. Based on our results, continuous, long-term application of slow-release angiopeptin could significantly decrease or even prevent graft vessel disease.