Human peritoneal macrophages synthesize leukotrienes B4 and C4.

Macrophages were isolated from the dialysis fluid of patients undergoing continuous ambulatory peritoneal dialysis and separated by gradient centrifugation and purification on 50% Percoll. The cells were prelabeled with [14C]arachidonic acid for 1.5 h. The labeled cells were then incubated with calcium ionophore A23187 (1 microM), serum-treated zymosan (200 micrograms/ml), and a lipoxygenase inhibitor, nordihydroguairetic acid (1 X 10(-5) M). The arachidonate metabolites in the medium were separated on Sep-Pak columns, and finally purified by reverse-phase high-pressure liquid chromatography (HPLC). The labeled products co-chromatographed with authentic leukotriene B4 and leukotriene C4 standards. Serum-treated zymosan and A23187 significantly stimulated and nordihydroguairetic acid significantly inhibited leukotriene synthesis. Leukotriene D4 was not detected, which suggests that these cells contain low gamma-glutamyltranspeptidase or high dipeptidase activity. These results establish, for the first time, that human peritoneal macrophages synthesize the lipoxygenase products, leukotriene B4 and leukotriene C4.

Peptide inhibition of myointimal proliferation by angiopeptin, a somatostatin analogue.

Vascular smooth muscle cell hyperplasia is a major component of atherogenesis in various animal models. Angiopeptin, a cyclic octapeptide analogue of somatostatin, markedly inhibits myointimal proliferation in response to endothelial cell injury in the rat carotid artery, rabbit aorta and iliac arteries and in coronary arteries of transplanted rabbit hearts. Angiopeptin does not affect serum lipid profiles in nonhuman primates. It is unlikely, therefore, that its antiproliferative effect is mediated by alterations in cholesterol metabolism. Angiopeptin and other peptide analogues of somatostatin are potent inhibitors of growth hormone release and insulin-like growth factor-1 production. However, inhibition of smooth muscle cell proliferation in vivo is not a property common to all somatostatin analogues. This suggests that plasma growth hormone and growth hormone-dependent insulin-like growth factor-1 production are not physiologic stimuli for myointimal proliferation in vivo. Angiopeptin inhibits 3H-thymidine incorporation into rat carotid artery explants, suggesting a local effect on autocrine or paracrine mechanisms regulating cell growth. In view of its potent inhibitory effect on smooth muscle cell replication, angiopeptin may have clinical utility in preventing restenosis after percutaneous transluminal coronary angioplasty and in preventing accelerated coronary atherosclerosis after cardiac transplantation.

Dose-dependent stimulation of insulin-like growth factor-binding protein-1 by lanreotide, a somatostatin analog.

It was recently reported that octreotide, besides its many, almost obligatory, inhibitory actions, stimulates the release of insulin-like growth factor-binding protein-1. The present study sought to exclude the possibility that the inescapable preceding somatostatin analog-induced reduction in serum insulin participated in the observed effect. We, therefore, administered sc two clinically relevant doses (5 and 80 micrograms/kg) of lanreotide, another somatostatin octapeptide analog, which induced identical 60% initial suppressions of serum insulin. In spite of this, clear dose-dependent increases in insulin-like growth factor-binding protein-1 were observed, starting between 1-2 h after administration of lanreotide, and levels were still elevated several-fold 5 h after administration of 80 micrograms/kg lanreotide. In addition, we found that infusion of amino acids had no discernible effect on binding protein-1 release. The changes found in immunoreactive binding protein-1 were confirmed employing Western ligand blotting. The data indicate that the lanreotide-induced increase in binding protein-1 levels in serum is not due to the changes in circulating insulin. The magnitude and duration of the increase raise the possibility that the stimulation may have clinically relevant implications in somatostatin analog treatment.

Inhibition of coronary artery transplant atherosclerosis in rabbits with angiopeptin, an octapeptide.

Accelerated coronary atherosclerosis of cardiac allograft occurs in 30-40% of cardiac transplant patients and remains an unsolved clinical problem. The etiology is unknown and anti-platelet drugs are used without conspicuous success. The inhibitory effect of the octapeptide, angiopeptin on coronary atherosclerosis was studied in a previously described rabbit heterotopic cardiac transplant model where allograft rejection is prevented by daily administration of cyclosporin A (CsA, 10 mg/kg per day s.c.). Twenty male New Zealand white rabbits (2.6-2.8 kg) received a heterotopic cardiac transplant from rabbits of the same strain. Donors and recipients were fed a 0.5% cholesterol diet 1 week prior to transplantation which was continued for the recipient until death 6 weeks later. The control group (n = 16) received CsA and saline injections twice daily and the treatment group (n = 4) received CsA and angiopeptin (60 micrograms/rabbit daily s.c.) in 2 divided doses. The treatment began after completion of the transplantation. Coronary artery transplant atherosclerosis was uniformly distributed (tubular) in the entire length of the coronary arteries. Angiopeptin inhibited the intimal hyperplasia in the transplanted heart from 47.5 +/- 2.4% (mean +/- SE) to 25.0 +/- 6.9% and in the native heart from 24.2 +/- 1.4% to 15.7 +/- 1.5%. The intimal hyperplasia is expressed as area of intimal hyperplasia/total vessel area x 100%. A similar inhibition by angiopeptin was seen in lipid deposition in the donor ascending aorta which is transplanted with the heart. Angiopeptin attenuated significantly the hyperplasia and the lipid deposition of the native coronary arteries and aorta but to a lesser extent.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of myointimal proliferation of the rat carotid artery by the peptides, angiopeptin and BIM 23034.

Proliferation of vascular smooth muscle is an early and major event in the formation of an atherosclerotic lesion. Here we report for the first time the inhibitory effects on myointimal proliferation of the rat carotid artery by a synthetic peptide, angiopeptin, and its closely related congener, BIM 23034. Proliferation was initiated in the carotid artery of anesthetized rats by air-drying of the endothelium. After 15 days the rats were killed and the carotid artery was pressure-fixed and subjected to morphologic analysis for evaluation of the degree of myointimal thickening. Five synthetic somatostatin-like peptides were tested by pretreating rats (20 and 50 micrograms/kg/rat s.c. daily) for 2 days prior to and for 5 days after the endothelial injury. Angiopeptin and the closely related octapeptide (BIM 23034) significantly inhibited myointimal thickening. Angiopeptin was also effective when the pretreatment period was reduced from 2 days to 30 min. The inhibitory effect of angiopeptin was further confirmed in an additional experiment involving [3H]thymidine incorporation. In this experiment angiopeptin (100 micrograms/kg/day s.c.) was also administered for 2 days prior to and five days following the endothelial injury and it significantly inhibited thymidine uptake. All the peptides tested inhibit the release of growth hormone. However, only angiopeptin and BIM 23034 inhibited myointimal proliferation. Thus the effect of angiopeptin and its congener is unlikely to be mediated through growth hormone. Since angiopeptin inhibits myointimal proliferation it may have clinical utility in preventing restenosis following angioplasty and coronary artery by-pass procedures.

Prolongation of experimental cardiac allograft survival with thromboxane-related drugs.

A novel receptor antagonist, 3-hydroxymethyl-dibenzo (b,f) thiepin 5,5-dioxide (L-640,035) and the thromboxane synthase inhibitor, sodium (E) -3-(4-[3-pyridylmethyl phenyl]) -2-methyl-acrylate (OKY 1581) were evaluated for their effect in promoting the survival of cardiac allografts in Lewis rats that received cardiac allografts from Lewis x Brown-Norway F1 rats. Neither of these drugs or azathioprine alone significantly prolonged graft survival. However a combination of azathioprine with either of the two drugs significantly increased graft survival. Because L-640,035 inhibits platelet and smooth muscle responses to thromboxane-mimics, and because OKY 1581 is a specific thromboxane synthase inhibitor, we conclude that thromboxane may have a causal role in experimental cardiac allograft rejection in rats.

Estradiol 17-beta represses insulin-like growth factor I receptor expression in smooth muscle cells from rabbit cardiac recipients.

BACKGROUND: A crucial step in cell cycle progression is the activation of the insulin-like growth factor I (IGF-I) receptor (IGF-IR) by its ligand. Earlier, we found estradiol 17-beta treatment of cardiac allograft recipients attenuates transplant arteriosclerosis; this was associated with inhibition of vascular cell proliferation induced by IGF-I. The current study demonstrates regulation of IGF-IR by estradiol 17-beta in vivo and in vitro in recipient native and allograft aorta and in aorta smooth muscle cells (SMCs). METHODS: Twenty cardiac transplant recipient rabbits were treated with estradiol 17-beta (100 microg/kg/day) or placebo for 6 weeks. IGF-IR expression in the coronary arteries of rabbits was demonstrated by immunohistochemistry. Reverse transcription-polymerase chain reaction and RNase protection assay were used to detect IGF-IR mRNA in rabbit aortas and cultured aortic SMCs in the presence or absence of estradiol 17-beta in vitro. IGF-I-induced cell proliferation was performed with the aorta explants and aorta SMCs from estradiol- or placebo-treated rabbits. RESULTS: Estradiol 17-beta treatment of rabbits significantly inhibited IGF-IR expression in the allograft coronary arteries and abrogated cell proliferation induced by IGF-I in the allograft aorta compared with placebo-treated recipients (65.4+/-5% vs. 500+/-139%, P<0.002). Expression of IGF-IR mRNA in the allograft aorta of placebo-treated recipients was significant higher than that of the native aorta (286+/-56%, P<0.02). Estradiol treatment significantly inhibited IGF-IR mRNA expression in the aorta versus that of the placebo-treated recipients (65+/-8.5% vs. 140+/-23%, P<0.02). Repression of IGF-IR mRNA expression in aortic SMCs by estradiol in vitro was in a concentration-dependent manner (P<0.02). CONCLUSION: Repression of IGF-IR protein and mRNA by estradiol 17-beta in vivo and in vitro suggest that one of the mechanisms of estradiol inhibition of SMC proliferation and transplant arteriosclerosis is down-regulation of IGF-IR.

Acceleration of arteriosclerosis of the rat aorta allograft by insulin growth factor-I.

We demonstrate here, for the first time, the mitogenic effect of insulin-like growth factor-I (IGF-I) on the development of transplant arteriosclerosis in a rat orthotopic aorta allotransplantation model (Brown Norway to Lewis). 125I-IGF-I uptake by the abdominal aorta of male Brown Norway rats occurred within 30 min. Consequently, we exposed the donor abdominal aorta to 0, 200, or 500 ng/ml IGF-I at 37 degrees C for 30 min ex vivo (n=7 per group), before transplantation. Fourteen days after transplantation, intimal thickening of the allografts in each of the three groups was 0.18+/-0.02 (IGF-I at 0 ng/ml), 0.23+/-0.03 (IGF-I at 200 ng/ml), and 0.30+/-0.03 (IGF-I at 500 ng/ml), respectively (mean+/-SEM, P<0.005 for 500 ng/ml vs. 0 ng/ml). [3H]thymidine incorporation (cpm/microg protein) in the transplanted grafts at 7 days after transplantation (n=4 per group) was 40.6+/-7.6, 78.5+/-12.3, and 66.9+/-10.1, respectively (P<0.01 for 200 ng/ml vs. 0 ng/ml). [3H]thymidine incorporation in the native thoracic aorta of the recipient was 23.4+/-4.4. We conclude that acceleration of allograft myointimal proliferation and intimal thickening was induced directly by IGF-I.

Urine immunoreactive thromboxane B2 in rat cardiac allograft rejection.

Increases in urinary excretion of immunoreactive thromboxane B2 (i-TXB2), the stable break-down product of thromboxane A2, have been described in kidney allograft rejection in patients. We investigated these findings by monitoring daily urine i-TXB2 excretion in a heterotopic cardiac allograft rat model using Lewis rats as recipients. In order to obtain differences in allograft survival, a donor was used that was either ACI or LewisxBrown Norway F1 (LxB-NF1). The ACI-to-Lewis model rejected on day 6.2 +/- 0.2 (n = 6). The LxB-NF1-to-Lewis model received, in addition, azathioprine (5 mg/kg/daily) and rejected on day 9.1 +/- 0.8 (n = 9). Urinary i-TXB2 excretion increased significantly in both groups, compared with i-TXB2 values measured following sham surgery or isograft transplantation. Thus increases in urinary i-TXB2 appear to be associated with cardiac allograft rejection.

Inhibition of myointimal hyperplasia and macrophage infiltration by estradiol in aorta allografts.

A major cause of organ graft loss after heart transplantation is accelerated atherosclerosis. In this study we used aorta allografts and investigated the effect of estradiol-17 beta treatment on both the degree of myointimal hyperplasia and morphological changes evaluated by light and electron microscopy. Outbred New Zealand white male rabbits (2.7-3.5 kg) were fed cholesterol (0.5%) from one week prior to transplantation, and until sacrifice three weeks later. The donor abdominal aorta was transplanted end-to-end to the right carotid artery of the recipient animals. Immediately following surgery, cyclosporine (10 mg/kg/d s.c.) was administered to prevent graft rejection. The allograft recipients were randomly assigned to one of five groups and treated with cottonseed oil (placebo) or estradiol cypionate at 1, 10, 100, or 1000 micrograms/kg/d i.m. for 3 weeks. The aorta grafts were harvested and fixed for transmission electron microscopy and morphometry. The area of myointimal thickening was calculated as a percent of total vessel area (mean +/- SEM); the control group was 6.6 +/- 0.5% (n = 5). Estradiol treatment significantly inhibited (P less than 0.05) myointimal hyperplasia at all doses. The values were 3.9 +/- 0.6% (n = 6) for 1 microgram/kg/day; 4.4 +/- 0.7% (n = 5) for 10 micrograms/kg/day; 3.5 +/- 0.4% (n = 6) for 100 micrograms/kg/day; and 2.9 +/- 0.1% (n = 3) for 1000 micrograms/kg/day. Electron microscopic evaluation revealed that the four doses of estradiol protected the endothelium from the degenerative changes seen in all aorta allografts from the animals in the control group. Furthermore 10, 100, and 1000 micrograms/kg/day of estradiol prevented the appearance of vacuolized macrophages (foam cells) and also the vacuolization of smooth muscle cells that was observed in the aorta allografts from the control group and the group treated with 1 microgram/kg/day of estradiol. We conclude that the inhibitory effect of estradiol on the development of graft atherosclerosis may be due to inhibition of smooth muscle cell proliferation and preservation of ultrastructurally normal endothelial cells. The inhibitory effect on foam cell production and a concomitant vacuolization of smooth muscle cells may play a lesser role. We suggest that estrogen replacement therapy may be beneficial in postmenopausal women with organ allografts.

Urinary thromboxane excretion in cardiac allograft rejection in immunosuppressed rats.

Increased urinary excretion of immunoreactive thromboxane B2 (iTxB2) was found to have a high predictive value, with high sensitivity as an indicator of cardiac allograft rejection in both the immunosuppressed and nonimmunosuppressed rat. In the animals receiving an allograft, urinary iTxB2 excretion significantly increased prior to the onset of rejection, remained elevated, and returned to basal values following completion of the episode. Urinary iTxB2 remained at baseline values in the control animals. The association between rejection and iTxB2 excretion was preserved regardless of the presence or nature of immunosuppression. Urinary iTxB2 excretion increased significantly prior to the reduction of graft beat or histological evidence of rejection. Evaluation of urinary iTxB2 monitoring as a noninvasive indicator for surveillance of clinical cardiac allograft rejection appears to be warranted.

Preservation of renal compensatory growth in uninephrectomized rats by low-dose cyclosporine.

The growth-inhibitory effect of prednisone is a serious drawback to its use in kidney graft recipients. At high doses, cyclosporine also inhibits somatic growth in animals. Furthermore, cyclosporine, in addition to being nephrotoxic in patients, is reported to inhibit compensatory renal growth in uninephrectomized rats. It is unclear whether the latter effect is specific to the kidney. In the present study, we have tested, in the uninephrectomized rat model, the effect of a low dose cyclosporine that is immunosuppressive but does not inhibit somatic growth. Compared with sham operation, uninephrectomy resulted in a significantly greater kidney-to-body weight ratio 2 and 7 days postsurgery. In uninephrectomized rats treated daily with 10 mg/kg cyclosporine s.c., compensatory renal growth was intact. Kidney wet weight, dry weight, and kidney-to-body weight ratios were similar in vehicle and cyclosporine treated, uninephrectomized animals. Similarly, body weight, food consumption, and size of other organs were not adversely affected by the 10 mg/kg/day cyclosporine treatment. Thus, by reducing cyclosporine to levels that are not generally toxic, renal growth is preserved. Our results suggest that the present trend toward using lower doses of cyclosporine in kidney transplant recipients will not only reduce nephrotoxicity, but will also be of benefit in terms of somatic and renal growth, which are important considerations in pediatric transplant patients.

Coronary artery ultrastructural changes in cardiac transplant atherosclerosis in the rabbit.

Accelerated coronary atherosclerosis is the limiting factor for long-term survival of cardiac transplant recipients, but its pathogenesis is poorly understood. Morphologic and ultrastructural changes in suitable models may help explain the underlying mechanisms. In this study, early (3, 7, 14, and 21 days) and late (42 days) ultrastructural changes of the coronary artery were characterized in rabbit cardiac allografts. Thirty-four New Zealand white male rabbits (3.0-4.0 kg) served as donors and recipients. All recipients received cyclosporine (10 mg/kg/day i.m.) as immunosuppressant. In order to increase the normally very low cholesterol levels in rabbits, both the donor and recipient animals were fed a 0.5% cholesterol diet. Recipient animals were sacrificed between 3 days and 6 weeks after transplantation. The specimens from both donor and recipient were examined by transmission electron microscopy, immunohistochemistry, and morphometry. Our data indicate that intimal thickening was initiated with smooth muscle cell migration within 1 week after transplantation, and occurrence of macrophage-derived foam cells and vacuolized smooth muscle cells 3 weeks after transplantation. These changes occurred in the presence of an ultrastructurally intact endothelium. Platelets were only seldom seen adhering to the endothelium. In contrast, lymphocytes and monocytes were frequently found adhering to the endothelium at 2 and 3 weeks posttransplantation. From 3 weeks posttransplantation, lymphocytes were seen only occasionally in the intima but not in the media. This study suggests that early events elicit a change in the smooth muscle cells in the media to the secretory phenotype that migrates to the intima and proliferate. Lymphocyte and monocyte adhesion to the endothelium may enhance smooth muscle migration and proliferation. The large macrophage involvement may relate to the high serum cholesterol levels induced by the cholesterol diet. All these changes occurred in the presence of a structurally normal endothelium and without apparent platelet involvement.

The effect of prednisolone, thromboxane, and platelet-activating factor receptor antagonists on lymphocyte and platelet migration in experimental cardiac transplantation.

Three agents that significantly prolong cardiac allograft survival were tested in Lewis rats that were recipients of hearts from Lewis X Brown-Norway F1 hybrid donors. In the presence of azathioprine, the effects of daily administration of either the thromboxane antagonist (L 640,035), the platelet-activating factor (PAF) antagonist (BN 52021) or prednisolone were evaluated on the infiltration of cardiac allografts by syngeneic lymphocytes and platelets labeled with 111indium. As anticipated, platelet deposition was reduced by the thromboxane antagonist and unaffected by the PAF antagonist; the latter is likely due to the known absence of PAF receptors in rat platelets. In addition prednisolone had no effect. The increased accumulation of lymphocytes on days 4-5 was also unaffected by all three drugs. These experiments indicate that, in this model, graft survival is not necessarily related to lymphocyte and platelet infiltration of the graft. The data also provide evidence for the efficacy of the thromboxane receptor antagonist L 640,035 in preventing platelet deposition in vivo.

Long-term lung preservation with the PAF antagonist BN 52021.

Platelet activating factor (PAF, 1-alkyl-2(R)-acetyl-glycero-3- phosphorylcholine) is a phospholipid that is released by a variety of cells. The similarity between the pathophysiological effects of PAF and posttransplant pulmonary dysfunction led to an evaluation of a PAF antagonist as an adjunct to lung preservation. The ginkgolide B, BN 52021, was selected as the PAF antagonist to be studied because of the large data base available on this compound. BN 52021 was given to the donor and recipient (10 mg/kg i.v.) prior to harvest and transplantation and was included in 1 L of preservation solution (10 mg/kg) used for flushing the pulmonary artery and for storage. Left single-lung transplantation was performed following a 22-hr preservation period at 10 degrees C. Arterial oxygen tension (pO2), pulmonary vascular resistance (PVR), alveolar arterial oxygen difference (A-aDO2), and dynamic lung compliance (DLC) were recorded for 6 hours following ligation of the native pulmonary artery. At the end of 6 hr pO2 was 243.5 +/- 61.5 vs. 71.7 +/- 10.2 mmHg (P less than 0.02) for the controls. A-aDO2 was less in the BN 52021 groups: 431.8 +/- 58.3 vs. 606.0 +/- 9.8 mmHg in the control groups (P less than 0.001), and PVR was significantly less in the BN 52021 group: 346 +/- 70.8 vs. 663 +/- 64.3 dynes/sec/cm-5 (P less than 0.035). We conclude that PAF antagonists like BN 52021 may be useful adjuncts for lung preservation. The effects of BN 52021 are easily explained by PAF antagonist activity in ischemic and reperfusion-induced pulmonary dysfunction. However this study does not exclude that BN 52021 may have direct effects.

Estradiol inhibits allograft-inducible major histocompatibility complex class II antigen expression and transplant arteriosclerosis in the absence of immunosuppression.

BACKGROUND: The etiology of transplant arteriosclerosis is unknown, but current data point to the alloimmune response. Previously, we found that estradiol-17beta (E2) with immunosuppressant cyclosporine abolishes major histocompatibility complex (MHC) class II expression in the allograft. This study determines the effect of E2 on MHC class II antigen expression in the allograft, in the absence of immunosuppression. METHODS: Lewis male rats received orthotopic abdominal aorta allografts from male Brown-Norway rats. The recipients were treated continuously subcutaneously with either 20 microg x kg(-1) x day1 of E2 (n=20) or placebo (n=20), from 2 days before transplantation until death on posttransplant days 1, 3, 7, and 14. The allografts were harvested and processed for morphometry and for immunohistochemical staining of MHC class II antigens, macrophages, CD4 and CD8 T lymphocytes, interferon-gamma (IFN-gamma), and IFN-gamma receptor. RESULTS: With E2 treatment, we observed that inducible MHC class II antigen expression is abolished in the media of the vascular allograft; the expression of IFN-gamma and IFN-gamma receptor is unaffected; and macrophage infiltration of the vascular allograft is inhibited significantly (P<0.01), whereas the CD4 and CD8 T lymphocytes are not significantly (P=0.07) suppressed. The myointimal hyperplasia in the allografts from E2-treated-recipients was 3-4-fold less than that from the placebo-treated recipients. CONCLUSIONS: Without immunosuppression, E2 inhibition of transplant arteriosclerosis is still associated with inhibition of inducible MHC class II antigen expression in the allografts. The estradiol-17beta abolition of inducible MHC class II antigen expression in the aorta allograft occurs in spite of up-regulation of IFN-gamma ligand and receptor protein.

Exposure of vascular allografts to insulin-like growth factor-I (IGF-I) increases vascular expression of IGF-I ligand and receptor protein and accelerates arteriosclerosis in rats.

BACKGROUND: Accelerated arteriosclerosis limits the survival of transplanted hearts. We hypothesized that insulin-like growth factor-I (IGF-I) is crucial in accelerating transplant arteriosclerosis. Recently, we reported that exposure to IGF-I prior to transplantation accelerates transplant arteriosclerosis in the rat aorta allograft model. Here, we studied the mechanism whereby IGF-I exposure accelerates transplant arteriosclerosis. METHODS: The abdominal aorta was harvested from male Brown Norway rats and exposed to 0, 200, or 500 ng/ml of IGF-I at 37 degrees C for 30 min prior to transplantation to the abdominal position of male Lewis rats. The allografts were harvested 14 days later and processed for immunohistochemical staining for alpha-actin, growth factors (IGF-I, IGF-I receptor, platelet-derived growth factor-BB, and basic fibroblast growth factor), and immunological markers (major histocompatibility complex class II antigen, macrophage, and CD4- and CD8-positive T cells). RESULTS: By 14 days, the ex vivo IGF-I donor aorta treatment with IGF-I increased in a concentration-dependent manner the expression of IGF-I and IGF-I receptor in both the intima and the adventitia. In contrast, the expression of platelet-derived growth factor-BB was decreased in a concentration-dependent manner in the intima while basic fibroblast growth factor remained unchanged. The cell-mediated immune response was not affected by IGF-I at 14 days after transplantation, which suggests that the immune events associated with acceleration of transplant arteriosclerosis may occur at an earlier time. CONCLUSION: Acceleration of transplant arteriosclerosis by exposure to IGF-I is associated with increased IGF-I ligand and receptor expression in the allograft vascular wall. These data further suggest that IGF-I may be a major factor in mediating graft arteriosclerosis.

Leukotrienes C4 and D4 induce prostaglandin and thromboxane release from rat peritoneal macrophages.

The present study examined the effect of leukotrienes C4 and D4, the products of the 5'lipoxygenase pathway on prostaglandins and thromboxane release from rat peritoneal macrophages. Incubation of rat peritoneal macrophages with leukotrienes C4 and D4 enhanced the release of prostaglandin E2 (PGE2), 6-keto PGF1 alpha and thromboxane B2 (TxB2) in a dose-dependent manner. The increase of PGE2 was more pronounced than that of 6-keto-PGF1 alpha and TxB2. Lipopolysaccharide, a known stimulator of these cells elicited a similar pattern of increase of the arachidonate metabolites assayed. These results suggest that leukotrienes C4 and D4 are potential activators of macrophages. Since leukotrienes C4 and D4 are produced by these cells, it is suggested that endogenous leukotrienes may be involved in activation of macrophages.

Lanreotide, a somatostatin analogue, reduces insulin-like growth factor I accumulation in proliferating aortic tissue in rabbits in vivo. A preliminary study.

Coronary artery restenosis following percutaneous transluminal angioplasty occurs with a very high incidence. Major efforts have been aimed at revealing the mechanisms and at developing therapies that might prevent or delay the myointimal proliferation. Most clinical trials have been unsuccessful. Endothelial denudation was induced in 30 rabbits using balloon catheterization of iliac arteries and aorta. Immunoreactive insulin-like growth factor I (IGF-I) was measured in arterial tissue samples obtained 1, 2 and 4 days postoperatively using a double extraction procedure to remove IGF-I binding proteins. Half of the animals were treated with subcutaneous injections of lanreotide, 10 micrograms/kg twice daily, and the other half served as controls. In the latter group, arterial IGF-I was unaltered from baseline at day 1 and increased by 300 and 400% at days 2 and 4. No increase was observed in the rabbits treated with lanreotide. The results indicate that initial local accumulation of IGF-I may be one of the mechanisms involved in myointimal proliferation after experimental arterial injury. The reduction of local IGF-I accumulation by lanreotide may be involved in the previously observed reduction in myointimal proliferation.

Specific effects of estrogen on growth factor and major histocompatibility complex class II antigen expression in rat aortic allograft.

OBJECTIVE: Transplant arteriosclerosis is the major determinant for long-term survival of cardiac transplants. Estradiol treatment inhibits transplant arteriosclerosis. The objective of this study is to determine, in the absence of immunosuppression, the temporal effect of estradiol treatment on the expression of insulin-like growth factor, platelet-derived growth factor, basic fibroblast growth factor, and major histocompatibility complex class II antigen in rat aortic allografts. METHODS: Orthotopic abdominal aortic allograft transplantation was performed in male rats with Brown-Norway rats used as donors and Lewis rats as recipients. The recipients (n = 50) were treated with estradiol 20 micrograms/kg per day or placebo by osmotic minipump for 2 days before the operation and until they were put to death on postoperative days 1, 3, 7, 14, or 21. The allografts were harvested and insulin-like growth factor, platelet-derived growth factor, basic fibroblast growth factor, and major histocompatibility complex class II antigen expression were determined by immunohistochemical staining. Myointimal thickening was measured by morphometric analysis. RESULTS: In the placebo-treated group, insulin-like growth factor protein progressively increased in all three layers of the allograft, whereas platelet-derived growth factor protein peaked at day 3 and basic fibroblast growth factor protein increased only moderately. Estradiol treatment inhibited the continuous increase in insulin-like growth factor expression, the peak in platelet-derived growth factor expression at day 3, the moderate-basic fibroblast growth factor increase at day 21, and major histocompatibility complex class II antigen expression in all three layers of the allograft at day 21. Intimal thickening of allografts from estradiol-treated recipients was twofold to threefold less than that of the placebo-treated recipients at day 21. CONCLUSION: The development of transplant arteriosclerosis is associated with an early alloimmune response involving sustained increase in insulin-like growth factor expression. Estradiol treatment of the recipient inhibits transplant arteriosclerosis and suppresses insulin-like growth factor and major histocompatibility complex class II antigen expression but not platelet-derived growth factor or basic fibroblast growth factor in all three layers of the allograft during the early posttransplantation alloimmune rejection phase.