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Biomedical subjects

A I Gotlieb

Publications and source records attributed to A I Gotlieb.

At least 19 recordsLinked to original sources
PubMed2005

Microtubules regulate aortic endothelial cell actin microfilament reorganization in intact and repairing monolayers.

To understand the role of microtubules and microfilaments in regulating endothelial monolayer integrity and repair, and since microtubules and microfilaments show some co-alignment in endothelial cells, we tested the hypothesis that microtubules organize microfilament distribution. Disruption of microtubules with colchicine in resting confluent aortic endothelial monolayers resulted in disruption of microfilament distribution with a loss of dense peripheral bands, an increase in actin microfilament bundles, and an associated increase of focal adhesion proteins at the periphery of the cells. However, when microfilaments were disrupted with cytochalasin B, microtubule distribution did not change. During the early stages of wound repair of aortic endothelial monolayers, microtubules and microfilaments undergo a sequential series of changes in distribution prior to cell migration. They are initially distributed randomly relative to the wound edge, then align parallel to the wound edge and then elongate perpendicular to the wound edge. When microtubules in wounded cultures were disrupted, dense peripheral bands and lamellipodia formation were lost with increases in central stress fibers. However, following microfilament disruption, microtubule redistribution was not disrupted and the microtubules elongated perpendicular to the wound edge similar to non-treated cultures. Microtubules may organize independently of microfilaments while microfilaments require microtubules to maintain normal organization in confluent and repairing aortic endothelial monolayers.

Actin Cytoskeleton↗
PubMed2003

Understanding the role of the cytoskeleton in the complex regulation of the endothelial repair.

Actin microfilaments and microtubules are important cytoskeletal proteins that regulate endothelial repair through alterations in cell shape and through regulation of cell migration following wounding of the endothelium. Upstream pathways have been identified in the regulation of actin and microtubule organization, especially small GTPases. Recently, there have been numerous proteins suggested to be capable of regulating interaction between microtubules and microfilaments to mediate microtubule regulation of endothelial repair, an important process in limiting injury to the artery wall and in reducing the extent of arterial disease. If disrupted, a rapid repair mechanism is important in reestablishing the integrity of the endothelium in order to reestablish its function as a macromolecular barrier, a thromboresistant surface, and a biologically active tissue. Strategies to improve repair should alter the pathobiology of the atherosclerotic plaque and thus improve the prognosis of patients with atherosclerosis.

Actins↗
PubMed2002

Measurement of the ultrasonic properties of human coronary arteries in vitro with a 50-MHz acoustic microscope.

Ultrasonic attenuation coefficient, wave propagation speed and integrated backscatter coefficient (IBC) of human coronary arteries were measured in vitro over the -6 dB frequency bandwidth (36 to 67 MHz) of a focused ultrasound transducer (50 MHz, focal distance 5.7 mm, f/number 1.7). Corrections were made for diffraction effects. Normal and diseased coronary artery sub-samples (N = 38) were obtained from 10 individuals at autopsy. The measured mean +/- SD of the wave speed (average over the entire vessel wall thickness) was 1581.04 +/- 53.88 m/s. At 50 MHz, the average attenuation coefficient was 4.99 +/- 1.33 dB/mm with a frequency dependence term of 1.55 +/- 0.18 determined over the 36- to 67-MHz frequency range. The IBC values were: 17.42 +/- 13.02 (sr.m)-1 for thickened intima, 11.35 +/- 6.54 (sr.m)-1 for fibrotic intima, 39.93 +/- 50.95 (sr.m)-1 for plaque, 4.26 +/- 2.34 (sr.m)-1 for foam cells, 5.12 +/- 5.85 (sr.m)-1 for media and 21.26 +/- 31.77 (sr.m)-1 for adventitia layers. The IBC results indicate the possibility for ultrasound characterization of human coronary artery wall tissue layer, including the situations of diseased arteries with the presence of thickened intima, fibrotic intima and plaque. The mean IBC normalized with respect to the mean IBC of the media layer seems promising for use as a parameter to differentiate a plaque or a thickened intima from a fibrotic intima.

Adult↗
PubMed2001

Effects of anastomotic angle on vascular tissue responses at end-to-side arterial grafts.

OBJECTIVE: Hemodynamics has been implicated in the late failure of arterial bypass grafts, which frequently occurs at the distal anastomosis site. This study was designed to assess the relationship between local hemodynamics and pathologic responses of the distal anastomosis by manipulation of the angle of anastomosis of the graft, a major determinant of local hemodynamics. METHODS: End-to-side anastomoses of the right carotid to the left carotid arteries of rabbits were performed at anastomotic angles of less than 10 degrees (acute), 45 degrees (intermediate), or 90 degrees (right angle), and then the upstream left carotid arteries were ligated to simulate pathologic occlusion. We examined tissue responses on the wall of the recipient vessel opposite the anastomosis site (the bed), where unusual hemodynamic forces are imposed. RESULTS: Three months after surgery, intimal thickening was observed on the upstream portion of the acute, and more rarely, the intermediate anastomoses only. Medial thinning caused by loss of cells and matrix, and an aneurysm-like dilation, was observed in the right angle and some intermediate anastomoses, but not in the acute anastomoses. En face confocal microscopy at 3 weeks after surgery revealed severe disruption of the internal elastic lamina in all anastomotic models. Zymography and Western immunoblotting demonstrated gelatinolytic activity, caused by expression and activation of MMP-2, that was lowest in the acute anastomoses, higher in the intermediate anastomoses, and highest in the right-angle anastomoses. CONCLUSIONS: We infer that very different pathologic changes to the vessel wall are elicited when local hemodynamics is manipulated by altering the anastomotic branch angle.

Anastomosis, Surgical↗
PubMed1999

Transient and steady-state effects of shear stress on endothelial cell adherens junctions.

Endothelial cells exhibit profound changes in cell shape in response to altered shear stress that may require disassembly/reassembly of adherens junction protein complexes that mediate cell-cell adhesion. To test this hypothesis, we exposed confluent porcine aortic endothelial cells to 15 dyne/cm(2) of shear stress for 0, 8.5, 24, or 48 hours, using a parallel plate flow chamber. Cells were fixed and stained with antibodies to vascular endothelial (VE) cadherin, alpha-catenin, beta-catenin, or plakoglobin. Under static conditions, staining for all proteins was intense and peripheral, forming a nearly continuous band around the cells at cell-cell junctions. After 8.5 hours of shear stress, staining was punctate and occurred only at sites of continuous cell attachment. After 24 or 48 hours of shear, staining for VE-cadherin, alpha-catenin, and beta-catenin was intense and peripheral, forming a band of "dashes" (adherens plaques) that colocalized with the ends of stress fibers that inserted along the lateral membranes of cells. Staining for plakoglobin was not observed after 24 hours of shear stress, but returned after 48 hours. Western blot analysis indicated that protein levels of VE-cadherin, alpha-catenin, and plakoglobin decreased, whereas beta-catenin levels increased after 8.5 hours of shear stress. As cell shape change reached completion (24 to 48 hours), all protein levels were upregulated except for plakoglobin, which remained below control levels. The partial disassembly of adherens junctions we have observed during shear induced changes in endothelial cell shape may have important implications for control of the endothelial permeability barrier and other aspects of endothelial cell function.

Animals↗
PubMed1999

Fibroblast growth factor 2 enhances early stages of in vitro endothelial repair by microfilament bundle reorganization and cell elongation.

As endothelial cells convert from quiescent to migrating cells over 8 h along a wound edge, actin microfilaments undergo well-defined sequential changes characterized by an initial random distribution followed by a parallel and then a perpendicular orientation of microfilaments with respect to the wound edge. The latter is associated with subsequent cell migration. We tested the hypothesis that fibroblast growth factor 2 (FGF-2) can enhance the very early stages of wound repair even prior to migration and that FGF-2 enhancement of wound repair is associated with changes in the endothelial actin cytoskeleton. Using an in vitro two-sided wound model, the addition of FGF-2 at the time of wounding enhanced the extent of wound closure over 8 h. Treatment with FGF-2 was associated with significantly longer cells along the wound edge at 4 and 8 h after wounding. When treated with increasing concentrations of neutralizing FGF-2 antibody, the extent of wound closure decreased over 8 h and was associated with a decrease in cell length along the wound edge. Actin microfilaments were localized using rhodamine phalloidin and viewed using laser confocal microscopy. At 4 h after wounding, FGF-2 treatment was associated with significantly more cells along the wound expressing perpendicular microfilaments compared to untreated cells, which suggested a more rapid transition of parallel to perpendicular microfilament distribution. Thus, FGF-2 affects the very early stages of wound repair prior to migration by enhancing wound closure due to the early appearance of perpendicular microfilaments and lengthening of cells along the wound edge.

Actin Cytoskeleton↗
PubMed1999

Early stages of endothelial wound repair: conversion of quiescent to migrating endothelial cells involves tyrosine phosphorylation and actin microfilament reorganization.

Endothelial repair to reestablish structural integrity following wounding is a complex process. Since the actin cytoskeleton undergoes specific changes in distribution as quiescent endothelial cells switch to activated migrating cells over a 6-h period following wounding (Lee et al. 1996), we studied tyrosine phosphorylation in association with actin microfilaments and adhesion proteins using double immunofluorescent confocal microscopy. We showed that in a confluent monolayer phosphotyrosine localized at the periphery of the cell at vinculin cell-cell adhesion sites within the actin-dense peripheral band (DPB) and centrally at talin/vinculin cell-substratum adhesion sites at the ends of central microfilaments. Over a period of 6 h following in vitro wounding there was a reduction of peripheral phosphotyrosine associated with the loss of both cell-cell adhesion sites and the DPB (stage I). Concomitantly, an increase in central phosphotyrosine was associated with an increase in cell-substratum adhesion sites and central microfilaments parallel to the wound edge (stage II), which subsequently redistributed perpendicular to the wound edge (stage III). We also localized FAK and paxillin at the ends of parallel and perpendicular central microfilaments. Immunoprecipitation of paxillin showed increased phosphotyrosine and protein levels when prominent central microfilaments were present and underwent remodeling. Inhibition of tyrosine kinases by genistein and tyrosine phosphatases by sodium orthovanadate resulted in reduced endothelial repair associated with disruption of adhesion site formation and central microfilament formation/redistribution in each stage of repair. We suggest that tyrosine phosphorylation of adhesion proteins, such as paxillin, may be important in regulating the early stages of endothelial wound repair.

Actin Cytoskeleton↗
PubMed1999

Reduced in vitro repair in endothelial cells harvested from the intercostal ostia of porcine thoracic aorta.

The ability of large-vessel endothelium to repair itself rapidly after injury is important in the maintenance of its barrier function and in limiting the development and progression of atherosclerosis. Because dysfunctional repair may be involved in the pathogenesis of some atherosclerotic plaques, including those at the ostia of aortic branches, linear mechanical denuding wounds were made in confluent monolayers of endothelial cells harvested by scraping from the flow divider, the upstream wall of the intercostal branch and unbranched regions in the thoracic aorta. The extent of wound closure was significantly lower in cells derived from either side of the intercostal branches, compared with cells from unbranched areas. The wound edge of cells harvested from the flow divider and its opposite wall closed by 22+/-0.084 microm and 22+/-1.3 microm, respectively, versus control, unbranched endothelial cells (30+/-2.2 microm) at 24 hours and by 48 hours, 48+/-3.4 microm and 47+/-3.6 microm compared with control (61+/-3.4 microm). Extent of wound closure in cells harvested by scraping from unbranched regions was comparable with collagenase-harvested endothelial cells at 24 and 48 hours. Distribution of F-actin microfilaments, tubulin and centrosomes have been shown to be disrupted at the wound edge in poorly migrating cells. In our study, however, no differences were observed in cytoskeletal distribution between cells from branched, unbranched and control areas. Thus, aortic endothelial cells from the intercostal branch region show a reduced ability to repair wounds compared with cells harvested from unbranched aorta. The mechanism for this difference is currently unknown.

Actins↗
PubMed1998

Alterations in endothelial F-actin microfilaments in rabbit aorta in hypercholesterolemia.

The current study tests whether hypercholesterolemia influences the distribution of endothelial cell microfilaments during the initiation and growth of fatty streak-type lesions. We classified the lesions occurring over a 20-week period into four types based on the location and extent of macrophage infiltration observed microscopically. The earliest lesion was characterized by leukocytes adherent to the endothelial surface. Minimal lesions were characterized by a few cells in the subendothelium. Intermediate lesions consisted of numerous subendothelial leukocytes in a minimally raised lesion. Advanced fatty streak lesions were elevated, with several layers of leukocytes. The organization of peripheral junctional actin (the dense peripheral band) and of central endothelial cell actin microfilament bundles was studied in each of these lesions by using fluorescent microscopy. We found that in the aorta away from branch sites and in areas away from lesions, the central microfilament distribution was unaffected by hypercholesterolemia. The macrophages entered the wall without any identifiable reorganization in the microfilaments. During the accumulation of subendothelial macrophages in minimal and intermediate lesions, stress fibers were initially increased in comparison to lesion-free areas. In raised advanced lesions, the central microfilaments became thinner and disappeared. However, at flow dividers, where central stress fibers are normally prominent, endothelial cells on the surface of intermediate lesions showed a reduction in central fibers, and peripheral bands became prominent. This finding was associated with changes in cell shape from elongated to cobblestone type. Thus, actin microfilament bundles in endothelial cells underwent substantial changes in distribution during the accumulation of subendothelial macrophages, forming hypercholesterolemia-induced fatty streak-type lesions. These changes may influence endothelial substrate adhesion, permeability, or repair after injury.

Actin Cytoskeleton↗
PubMed1996

Cell biology of valvular interstitial cells.

OBJECTIVE: To review the cell biology of the interstitial cells of heart valves. While studying the function of interstitial cells of heart valves, the authors observed that interstitial cells from porcine mitral valve have mixed phenotypic expression. DATA SOURCE: English-language literature from 1985-95 that discussed the cell biology of heart valve interstitial cells, including their structural and functional characteristics. RESULTS: Morphologically, heart valve interstitial cells have characteristics of both fibroblasts and smooth muscle cells. It is not clear, however, whether these cells represent a single (myofibroblast) cell type or whether there are two populations of cells within the valve. This review summarizes reports of the structural and functional characteristics of heart valve interstitial cells including ultrastructure, cell junctions, smooth muscle cell markers, cell growth, role in wound repair and contractility. CONCLUSIONS: Vascular interstitial cells play an important role in both normal and diseased valves. Our understanding of the heterogeneity of valvular interstitial cells is incomplete; however, this heterogeneity allows for multiple functions to be carried out including cell-cell communication, matrix secretion, wound repair and contractility. Future studies are needed to focus on the regulation of cellular heterogeneity as it relates to valve structure and function in health and disease.

Angiotensin II↗
PubMed1996

Fibroblast growth factor receptor-1 expression is associated with neointimal formation in vitro.

Neointimal formation was studied in a porcine aortic organ culture model that exhibits intimal smooth muscle cell accumulation after a brief time in culture. This in vitro model is dependent upon an intact endothelium, as removal of the endothelium at the time of harvesting results in the failure to develop a neointima. We previously showed that conditioned media from intact cultures induce neointimal formation in denuded aortic explants, and we speculated that basic fibroblast growth factor was the endothelial-derived factor in conditioned media promoting neointimal formation. However, the concentration of basic fibroblast growth factor in conditioned media from both intact and denuded explants, measured by an enzyme-linked immunosorbent assay, was not significantly different and, in fact, steadily decreased over the first 7 days of culture. Furthermore, the amount and intensity of immunoreactive basic fibroblast growth factor in tissue sections, also similar in both groups, decreased over the same time course. Nonetheless, exogenous basic fibroblast growth factor (1 ng/ml) induced neointimal formation in intact explants but was unable to do so in denuded explants. Western blot analysis of intimal lysates prepared from both intact and denuded explants showed a time-dependent increase in fibroblast growth factor receptor-1 expression over the first 7 days of culture, with higher levels seen in intimal lysates from intact explants at each time point examined. Immunoreactive fibroblast growth factor receptor-1 was detected in both endothelial cells and intimal smooth muscle cells of intact explant sections. These data indicate that, in the presence of the endothelium, neointimal formation may in part be mediated by upregulation of fibroblast growth factor receptor-1 in the intimal cells of porcine aortic explants.

Animals↗
PubMed1996

Decreased blood flow rate disrupts endothelial repair in vivo.

Both local hemodynamics and endothelial injury have been implicated in vascular disorders including bypass graft failure and atherogenesis, but little is known about the effect of local blood flow conditions on repair of endothelial injury. We decreased blood flow rates and shear stresses in common carotid arteries of rabbits by ligating the ipsilateral external carotid artery. After 24 hours, endothelial cells were less elongated, contained fewer central microfilament bundles, and showed less polarity of the centrosome toward the heart than endothelial cells in unmanipulated carotid arteries. To examine wound repair, we made narrow longitudinal intimal wounds at the time of flow reduction using a nylon monofilament device. In arteries with normal blood flows, endothelial cells at the edge of the wound initially spread and elongated in the direction of the wound. The dense peripheral band of actin was attenuated and central microfilaments became more prominent. Endothelial cells remained in close contact with their neighbors in the monolayer. The centrosome of cells adjacent to the wound was redistributed toward the wound side of the nucleus at 6 and 12 hours. Complete closure occurred by 24 hours, at which time the elongated endothelial cells covering the wound were organized in a herringbone pattern with their downstream ends at the center of the wound. With decreased flow and shear stress, the cells at the wound edge spread less than those in normal vessels at 12 hours after wounding and were randomly oriented and polygonal in shape. Also, re-endothelialization proceeded more slowly and there was a marked reduction of central microfilaments in cells at the wound edge. At 24 hours, the wounds were still open, the endothelial cells covering the central portion of the wound did not maintain intimate contact with their neighbors, and orientation of the centrosome toward the wound was reduced. We hypothesize that loss of cell-cell contact during repair at low flow rates and low shear stress disrupts intercellular communication and results in disruption of cytoskeletal reorganization during repair, thereby slowing the repair process.

Actin Cytoskeleton↗
PubMed1995

Chemical-induced vasculature injury. Summary of the symposium presented at the 32nd annual meeting of the Society of Toxicology, New Orleans, Louisiana, March 1993.

The cross-sectional structure of the vasculature is comparatively simple, comprising three layers--the intima, adjacent to the lumen, the media, and the adventitia. Notwithstanding this simplicity, the vessels are host to a variety of reactions to injury. Two cell types, endothelial cells of the intima and smooth muscle cells of the media, are principal targets of damage and repair. The endothelial cells of the intimal layer of the vessel wall present a macromolecular barrier and are important in maintaining vessel integrity. When the integrity is compromised by physical or chemical injury, endothelial cells play a key role in the repair processes. The use of single-cell wound models allows the mechanisms of damage and subsequent repair to be studied in depth. Repair processes can be observed using time-lapse photography and differences between cytoskeleton changes during repair and reendothelialization of small and large wounds can be discriminated. In rats treated with the plant toxin monocrotaline, pulmonary vascular injury occurs which manifests as thrombosis and remodeling with consequent progressive pulmonary hypertension. In vivo and in vitro studies of the mechanism of monocrotaline toxicity suggest that the endothelial cells are an important target. In vitro studies show monocrotaline to be directly cytotoxic; in cells that survive, there are functional changes to the endothelial cells, resulting in a decreased repair capability which may lead to the complex, progressive lung lesions that develop. The other target cells of the vasculature are the smooth muscle cells of the media. Ingestion of primary amines allylamine and beta-aminopropionitrile (beta-APN) results in chronic vasculotoxicity to the aorta and medium-sized arteries. For allylamine, subtle changes in smooth muscle result in medial hypertrophy and subintimal proliferation. The changes are slow to occur, taking weeks or months of repeated treatment. For beta-APN, which is the active ingredient of the toxic sweet pea Lathyrus odoratous, vascular toxicity is manifested by fatal rupture of aortic aneurysms. When these agents are administered concomitantly, a synergistic acute smooth muscle necrosis occurs in large elastic arteries and degenerative changes are seen in muscular arteries. A change in the target for toxicity of allylamine toward the vasculature may be responsible for this synergistic toxic insult. Medial smooth muscle necrosis is also noteworthy after administration of certain pharmaceutical agents of diverse structure and pharmacological activity. These agents induce arteriopathies in dogs and rats, although at different sites. In dogs, the coronary arteries are susceptible, whereas in rats the mesenteric arteries are the principal sites of injury.(ABSTRACT TRUNCATED AT 400 WORDS)

Amines↗
PubMed1995

Expression of tumour necrosis factor alpha and accumulation of fibronectin in coronary artery restenotic lesions retrieved by atherectomy.

BACKGROUND: The formation of coronary artery neointima experimentally induced in piglets after cardiac transplantation is related to an immune-inflammatory reaction associated with increased expression of T cells and inflammatory mediators (tumour necrosis factor alpha and interleukin 1 beta) and upregulation of fibronectin. In vivo blockade of tumour necrosis factor alpha in rabbits after cardiac transplantation results in reduced neointimal formation. The objective of this study was to investigate the hypothesis that coronary restenosis after atherectomy or percutaneous balloon angioplasty is associated with a similar inflammatory cascade initiated by mechanical injury. METHODS: Specimens taken at coronary atherectomy were analysed from 16 patients. Nine had had the procedure performed twice, firstly, to remove a primary lesion, and secondly, to remove a restenotic lesion. Seven had percutaneous balloon angioplasty after removal of restenotic tissue. Coronary atherectomy specimens were analysed by immunohistochemistry for the presence of T cells, macrophages, major histocompatibility complex II, interleukin 1 beta, tumour necrosis factor alpha, fibronectin, and the receptor for hyaluronan mediated motility. RESULTS: The groups were clinically and angiographically similar with equivalent lumens before and after atherectomy. Restenotic lesions had increased expression of tumour necrosis factor alpha and fibronectin compared with the primary lesions (P < 0.05 for both). There was also a trend towards a greater number of T cells and increased expression of interleukin 1 beta. CONCLUSIONS: Restenosis is associated with increased expression of tumour necrosis factor alpha and fibronectin, suggesting that an immune-inflammatory reaction probably contributes to neointimal formation and may represent a form of wound healing and repair secondary to mechanical injury.

Angioplasty, Balloon, Coronary↗
PubMed1995

Expression of ICAM-1 and VCAM-1 and monocyte adherence in arteries exposed to altered shear stress.

Local shear stresses generated by blood flow exert direct mechanical effects on adhesion of circulating leukocytes to vascular endothelium, but their effects on expression of endothelial-leukocyte adhesion molecules have not been determined. Shear stress in rabbit carotid arteries was increased by 170% or decreased by 73% in 5 days by surgical manipulations. En face immunofluorescence staining with the monoclonal antibody Rb1/9 revealed that vascular cell adhesion molecule-1 (VCAM-1) expression was greatly increased under low shear stress, but the distribution of staining was patchy. Thus, 71.4 +/- 7.8% of fields were VCAM-1 positive versus 2.4 +/- 0.47% of fields in control arteries. Frequently, large regions showed consistent but heterogeneous staining. Occasionally, small islands of cells were labeled intensely. Monocytes, detected by use of the monocyte-specific antibody HAM 56, adhered to endothelium under low shear stress; 64.5 +/- 8.2% of the monocytes colocalized with detectable VCAM-1, although many (83.2 +/- 2.8%) VCAM-1-positive regions were devoid of monocytes. VCAM-1 expression also increased significantly but to a lesser extent when shear stress was approximately doubled. Thus, 8.7 +/- 1.5% of fields were VCAM-1 positive under high shear versus 2.5 +/- 0.87% under normal shear stress. No monocytes were detected at high shear stress. At normal shear stresses, intercellular adhesion molecule-1 (ICAM-1), detected by use of the monoclonal antibody Rb2/3, was extensively distributed; thus, 53.5 +/- 5.5% of fields contained ICAM-1-positive cells. The junctional regions of the cells were heavily stained.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Increased elastin-degrading activity and neointimal formation in porcine aortic organ culture. Reduction of both features with a serine proteinase inhibitor.

We investigated the association between tissue elastolytic activity and the development of neointimal formation using a previously described porcine aortic organ culture. Neointimal formation is associated with the presence of intact endothelium (nondenuded cultures) but is markedly reduced if endothelial cells are removed (denuded cultures). In nondenuded organ cultures, elastolytic activity assessed by using [3H]elastin increased sixfold at day 3 after initiation of the culture (P < .01), a time earlier than the previously published increase in intimal smooth muscle cells (ISMCs). Elastolytic activity did not increase from day 3 to day 7 despite doubling of ISMCs but did double by day 14 (P < .01) and remained elevated to day 28, correlating with increases in ISMCs. In denuded organ cultures, elastolytic activity was much lower than in nondenuded organ cultures at day 3 (P < .05) but increased fivefold in the presence of nondenuded organ culture conditioned medium (P < .01). Addition of alpha 1-proteinase inhibitor for 14 days caused a 60% decrease in elastolytic activity in nondenuded organ cultures and a 27% reduction in ISMCs compared with untreated controls (P < .05 for both). The elastolytic activity, resolved as lytic bands on an elastin substrate gel, reflected candidate enzymes, one at 76 kD and perhaps a doublet at 43 and 50 kD. Our study suggests that endothelial cells release a soluble agent that enhances elastin-degrading activity in the aorta and may at least partially account for the initiation of neointimal formation.

Animals↗