Presence Of Smooth Muscle Cells Research Articles

Arterialization of human vein grafts is associated with tenascin-C expression

OBJECTIVESThis study was performed to test the hypothesis that tenascin-C (TN-C), an extracellular matrix (ECM) protein with counteradhesive chemotactic and vascular growth-promoting effects, is expressed in “arterialized” human saphenous vein grafts (SVGs).BACKGROUNDTenascin-C is expressed in the vessel wall after vascular injury in the experimental model, where it has been implicated in the formation of neointima. Overexpression of TN-C has also been implicated in the development and progression of pulmonary hypertension. Saphenous vein grafts are exposed to hemodynamic stress when interposed in the arterial circulation and mechanical stress upregulates expression of TN-C, whereas stress-relaxation suppresses its synthesis. We hypothesized that the hemodynamic stress of increased arterial pressure could also induce TN-C expression in SVG.METHODSWe examined the expression of TN-C protein and mRNA in normal vein and “arterialized” human SVG using immunohistochemistry and in situ hybridization, respectively.RESULTSTN-C protein was not detected in control human saphenous veins; however, it was uniformly and strongly expressed in the adventitia and media of patent human vein grafts, with minimal or no expression in the neointima (n = 27, 100%). In situ hybridization showed that TN-C mRNA was not detected in the neointima, but was strongly upregulated in the adventitia and media, corroborating immunostaining data (n = 10, 100%). Unlike patent SVG, TN-C was not expressed in the adventitia of occluded grafts, except for a low level of expression around the newly formed vessels in neointima (n = 5, 100%). Smooth muscle cell-specific staining demonstrated that the lack of expression of TN-C in occluded vein grafts is not due to the lack of presence of smooth muscle cells in the graft.CONCLUSIONSThese findings suggest that placement of a venous graft in the arterial system leads to expression of TN-C, which may in turn facilitate graft remodeling. Conversely, loss of flow and intravascular pressure, associated with vein graft occlusion, is accompanied by disappearance of TN-C expression.

Immunohistological and ultrastructural analysis of the intimal thickening in coarctation of human aorta.

The histological nature and characteristics of aortic coarctation are not clearly defined, the aim of this study is to analyse intimal thickening in aortic coarctation. In order to characterize the components of intimal thickening in coarctation, narrowed segments of aorta obtained after surgery from ten children were examined immunocytochemically and by electron microscopy. Histological analysis of aortic coarctation demonstrated a widened subendothelial region with separation of endothelial cells from the internal elastic lamina. Masson's trichrome staining showed a marked increase in extracellular matrix and cell numbers in the intimal thickening compared with normal aorta. Cellular component analysis demonstrated invagination of the intima by smooth muscle actin-positive cells, with a fragmentation of the internal elastic lamina. No proliferating smooth muscle and inflammatory cells were identified in the intima. In order to characterize the smooth muscle cell phenotypes, various smooth muscle cell markers were sought using specific monoclonal antibodies: alpha-smooth muscle actin, smooth muscle-myosin heavy chain, heavy caldesmon, desmin. In moderate coarcted aorta, at least two distinct smooth muscle phenotypes were identified. In the juxtamedial part of the intima smooth muscle, cells were differentiated and expressed all smooth muscle markers; in the subendothelial part of the intimal thickening, the majority of smooth muscle cells expressed only alpha-smooth muscle actin and appeared dedifferentiated. In regions of marked stenosis, a strong expression of smooth muscle-myosin heavy chain, and heavy caldesmon in the intimal thickening pointed to the presence of redifferentiated smooth muscle cells, not still expressing desmin. Electron microscopic examination also revealed a variety of smooth muscle cell phenotypes in the intimal thickening. In the superficial layer, smooth muscle cells appeared to be in the synthetic state, while in the deeper part, both synthetic and contractile components were identified. These observations indicated that human coarctation was characterized by intimal recruitment of non-proliferating smooth muscle cells with dedifferentiated phenotype. However, the presence of smooth muscle cells with an intermediate phenotype in the narrowest part of the coarctation suggest that the redifferentiation process could participate in the pathogenesis of aortic coarctation.

Smooth muscle differentiation in human vein wall at valvular level: comparison with nonvalvular wall and correlation with venous function.

The aim of this study was to evaluate local differences in smooth muscle differentiation in venous valves of patients suffering from chronic venous insufficiency, in relation to functional hemodynamic parameters measured by echo Doppler. These functional parameters did not correlate with smooth muscle differentiation at the valvular site. These results failed to support an initiating role of valvular structure in the development of chronic venous insufficiency. However, this work stresses differences in cellular differentiation of valve wall and nonvalvular smooth muscle cells in culture, and we found histologic differences in the structure of endovein and media (connective tissue relative content) between valvular and nonvalvular venous wall. The presence of smooth muscle cells in the valve cusp was demonstrated by smooth muscle alpha-actin-specific labeling and was observed to be restricted to one side of the valve cusp.

1998 ARRS President's Award. The potential of in vivo vascular tissue engineering for the treatment of vascular thrombosis: a preliminary report. American Roentgen Ray Society.

Current gene therapy and tissue engineering protocols suffer from a number of inherent limitations. In this study, we examine the feasibility of a new approach for the treatment of vascular thrombosis: in vivo tissue engineering. Rabbit femoral veins were transfected in situ with either a previously characterized adenoviral-construct-expressing tissue plasminogen activator or a viral (adenoviral-construct-expressing beta-galactosidase) or nonviral (buffer) control and used as cross sections (n = 3). Treated veins were then harvested and grafted into the ipsilateral common femoral artery as an interposition vein graft. A potent stimulus for thrombus formation was then introduced into the recipient artery downstream of the graft. Six days later, the rabbits were sacrificed, and the grafts and downstream arteries were harvested. Vessel segments were then examined for thrombus according to defined anatomic zones. Transfection efficiency and presence of smooth muscle cells in the vein graft were also evaluated. The engineered vein graft showed a significant reduction in thrombus formation within both the graft and the downstream artery relative to nonviral (buffer) and viral (adenoviral-Rous sarcoma virus beta-galactosidase [Adv/RSV-betagal]) controls. Underlying endothelial cell transfection efficiency of 90% was observed in viral controls (Adv/RSV-betagal). A 2.4-fold increase in smooth muscle alpha-actin positive cells in the engineered vein graft was seen compared with nonviral (phosphate-buffered saline) controls. A 10-fold increase in smooth muscle alpha-actin-positive cells in the engineered vein graft relative to viral (Adv/RSV-betagal) controls was also observed. In vivo tissue engineering is a new paradigm in molecular medicine that is a viable alternative to conventional gene therapy and tissue engineering for the treatment of vascular thrombosis.

Cutaneous Bronchogenic Cyst: Delineation of a Poorly Recognized Lesion

Abstract: Bronchogenic cyst is a benign congenital developmental abnormality of the embryonic foregut. The most common extrapulmonary location of these lesions is the mediastinum. Over 50 cases of cutaneous bronchogenic cyst were reported in the English literature. Nevertheless, it is poorly recognized by clinicians and is sometimes confused with branchial cyst. In almost all cases the diagnosis is established by histopathologic examination. We report an unusual clinical presentation of bronchogenic cyst in a 4‐year‐old girl and review the literature. This lesion is four times more common in males than in females. The most common location is the suprasternal notch, followed by the presternal area, neck, and scapula. The characteristic histologic findings are a ciliated pseudostratified epithelial lining with the presence of smooth muscle cells, goblet cells and, less frequently, cartilage. Our review of the clinical and histologic features of all reported cases further delineates this entity and may facilitate its clinical diagnosis. Bronchogenic cyst should be included in the differential diagnosis of congenital cystic and nodular skin lesions on the upper chest, upper back, and neck.

Early Injury to the Media After Saphenous Vein Grafting

Background. Injury to the smooth muscle cells of the media affects the remodeling process of vein grafts. The purpose of this study was to determine whether different techniques of surgical preparation influence the degree of medial smooth muscle injury. Methods. Carotid–saphenous vein interposition grafting was performed in crossbred pigs (n = 32), using distended (n = 16) or nondistended (n = 16) conduits. After 3 to 90 days, the media was evaluated for the presence of smooth muscle cells (desmin stains), myofibroblast formation (transient α-SM actin expression), and apoptosis (TdT-mediated dUTP nick end-labeling [TUNEL]). Results. Smooth muscle loss was uniformly severe; only 5% ± 5% ( p < 0.01) and 14% ± 9% ( p < 0.01) of the medial area of distended and nondistended veins were desmin positive in comparison with 80% ± 9% of controls. Apoptosis appeared to contribute to medial smooth muscle loss (5.7% ± 4.3% in vein grafts versus 0.0% ± 0.0% of TUNEL-positive cells in controls; p = 0.05). There was a time dependent increase in medial myofibroblast formation ( p < 0.05). Conclusions. Severe medial smooth muscle loss occurs in vein grafts, even when prepared without distension. Apoptosis contributes to the early disappearance of smooth muscle cells. Adjunctive measures, in addition to ideal surgical techniques, should be developed to prevent medial muscle loss.

Activated inflammatory cells are associated with plaque rupture in carotid artery stenosis

Background . Histologic studies of carotid plaques have demonstrated an association between symptomatic disease and plaque rupture. The purpose of this study was to characterize the cellular changes associated with plaque rupture. Methods . Carotid plaques were obtained from 61 patients undergoing carotid endarterectomy for established indications. Plaques were fixed in formalin, embedded in paraffin, and stained with hematoxylineosin and Movat pentachrome stain to demonstrate plaque structure. Each plaque was examined with light microscopy and classified as containing evidence of plaque rupture (n = 29) or no plaque ruptur (n = 32). By using immunohistochemical staining, the fibrous cap was examined for the presence of smooth muscle cells (α-actin), macrophages (KP-1), T lymphocytes (UCHL-1), and cell activation (HLA-DR). Data were analyzed with chi-squared analysis. Results . With plaque rupture, macrophages and T lymphocytes were significantly more common than in specimens without evidence of rupture. Similarly, macrophages and T lymphocytes expressing HLA-DR were more often found in sections containing plaque rupture. Furthermore, vascular smooth muscle cells were more common with intact fibrous caps and were diminished with cap thinning. Conclusions . Rupture of the fibrous cap in carotid artery lesions is associated with increased numbers of macrophages and T lymphocytes, which are in an activated state. The activated inflammatory cells may release cytokines or metalloproteinases, which may be responsible for loss of the fibrous cap. Thus inflammation appears to play a role in the pathogenesis of the neurologic symptoms associated with carotid artery stenosis.

Morphology of the pancreatic duct system in mammals.

The morphology of pancreatic excretory duct segments was reviewed in mammals. The fine structure of the epithelial lining was described in intercalated ducts, intra- and extralobular ducts, and in major pancreatic ducts. Morphological characteristics of the various cell types comprising to the duct epithelium were detailed. Principal cells in the epithelial linings of interlobular and major pancreatic ducts ("Wirsungiocytes") were discussed with respect to their appearance as either clear or dark variety. In addition, the capacity of both these cell types in elaborating mucoid glycoprotein, secretions was considered and intra- and extraepithelial mucoid glands of major pancreatic ducts (ductular glands, accessory glands) was described. Finally, the wall composition of the various excretory duct segments was described. The presence of smooth muscle cells, myofibroblasts, and a peculiar periductal vascular plexus in major interlobular ducts and in main pancreatic ducts was emphasized.

Morphology of the pancreatic duct system in mammals

The morphology of pancreatic excretory duct segments was reviewed in mammals. The fine structure of the epithelial lining was described in intercalated ducts, intra- and extralobular ducts, and in major pancreatic ducts. Morphological characteristics of the various cell types comprising to the duct epithelium were detailed. Principal cells in the epithelial linings of interlobular and major pancreatic ducts (“Wirsungiocytes”) were discussed with respect to their appearance as either clear or dark variety. In addition, the capacity of both these cell types in elaborating mucoid glycoprotein secretions was considered and intra- and extraepithelial mucoid glands of major pancreatic ducts (ductular glands, accessory glands) was described. Finally, the wall composition of the various excretory duct segments was described. The presence of smooth muscle cells, myofibroblasts, and a peculiar periductal vascular plexus in major interlobular ducts and in main pancreatic ducts was emphasized. Microsc. Res. Tech. 37:407–417, 1997. © 1997 Wiley-Liss, Inc.

Pulmonary artery structural changes in pulmonary hypertension complicating congenital diaphragmatic hernia

Primary pulmonary hypertension is characterized by the presence of smooth muscle cells in nonmuscular compartments or segments of the vessel and the abnormal deposition of collagen in both the small muscular arteries and arterioles and the large elastic arteries. Victorian blue van Gieson staining and immunostaining with anti-alpha smooth muscle actin (ASMA) were performed on lung tissues obtained during autopsy from 21 patients who had congenital diaphragmatic hernia (CDH) complicated by persistent pulmonary hypertension (PPH) and 10 control patients who died of sudden infant death syndrome (SIDS). The degree of medial thickening and adventitial thickening was measured in pulmonary arteries by image analysis and compared statistically. There was a significant increase in adventitial as well as medial thickness in arteries of all sizes in CDH patients compared with control patients ( P < .001). The most striking increase occurred in arteries with an external diameter (ED) of less than 75 μm. Calculation of the areas of the various components in the wall of each vessel showed that for smaller vessels (< 75 μm ED), the area of the lumen was smaller and the area of the media and adventitia was larger in CDH patients compared with control patients ( P < .001). In vessels greater than 75 μ ED, the areas of media in CDH was the same as in controls and the area of adventitia in CDH was significantly larger than controls ( P < .001). The present study provides evidence that an increase in adventitial thickness and adventitial area occurs in pulmonary arteries in CDH patients complicated by PPH. The structural changes in the adventitia of the pulmonary arteries may be an important factor in the development of PPH in patients with CDH.

Expression of amyloid precursor protein mRNA in vascular smooth muscle cells of the human brain

Amyloid deposition in the cerebral vessels is the hallmark of cerebral amyloid angiopathy (CAA). In order to establish which type of cell produces amyloid, we performed Northern blot analysis and in situ hybridization studies on human meningeal arteries. Northern blotting showed that amyloid precursor protein (APP) mRNA was expressed not only in the cerebral cortex, but also in the meninges. An antisense RNA probe that hybridizes with APP transcripts was used for in situ hybridization. This analytic modality revealed APP messages in the tunica media of the meningeal arteries and arterioles. The presence of smooth muscle cells in these vessels was verified immunohistochemically on consecutive serial sections. These observations indicate that APP is produced by vascular smooth muscle cells.

The structure of superficial lymphatics in the human thigh: precollectors.

Little is known about the morphology of precollectors, the lymphatic vessels connecting the absorbing and the collecting vessels, which are regarded as the initial drainage routes of lymph. The aim of this study was to describe the structural features of human precollectors. Samples of fat from around the saphenous veins were obtained from patients undergoing varicotomy, and serial sections were observed under light and transmission electron microscopy. Tridimensional reconstructions were also obtained by computer analysis. Precollectors were characterized by an irregular and discontinuous arrangement of smooth muscle cells in their wall. This arrangement was unrelated to the site of valves. When present, muscular elements were arranged helicoidally, as shown in tridimensional reconstructions. Under transmission electron microscopy, the endothelium of precollectors was similar to that of absorbing lymphatic vessels, irrespective of the presence of smooth muscle cells, and was thin, rich in pinocytotic vesicles, supported by a discontinous basal lamina, and connected by anchoring filaments to the surrounding connective tissue. Myoendothelial contacts were frequent. Valves were similar to those of collecting vessels, except for the presence of numerous zonulae adherentes connecting the characteristic "tip cells" of the free edge. Human thigh precollectors are characterized by the alternation of portions with a well-developed muscular coat and portions with an absorbing structure. These morphological features suggest that the precollectors contribute to fluid absorption and lymph propulsion. The frequent myoendothelial contacts suggest that smooth muscle contraction is regulated locally.

The influence of the adventitia on the presence of smooth muscle cells and macrophages in the arterial intima

To test the hypothesis that atherosclerosis may be initiated by hypoperfusion or thrombotic occlusion of the adventitial vasa vasonum. In a new model of atherogenesis, an early atherosclerotic lesion may be initiated by removal of the adventitia from the carotid artery of the New Zealand White rabbit, wherein lie the vasa vasorum. Animal laboratory, University Department of Surgery and Medicine. Immunocytochemistry was undertaken to demonstrate the presence of smooth muscle cells and macrophages within the intimal lesions. Smooth muscle cells were labelled with a monoclonal antibody designated HHF35 and macrophages were labelled with a rabbit specific, macrophage specific antibody, RAM11. CHIEF RESULTS: In rabbits fed a normal diet, at day 14, the intimal lesion was composed exclusively of smooth muscle cells. By day 28, such lesions had regressed. In rabbits fed a high cholesterol diet, at day 14, the intimal lesion was composed of a mixture of macrophages and smooth muscle cells. By day 42, the pattern of cellular distribution was such that macrophages (present as foam cells) were predominant. In the presence of persistent hypercholesterolaemia these lesions did not regress. This new model can produce two different cellular responses that may mimic the intimal lesions seen with re-stenosis after angioplasty or in hypercholesterolaemic man and as such, might be useful in separating out these two different pathophysiologies.

Vascular and anti‐platelet actions of 1,2‐ and 1,3‐glyceryl dinitrate

1. The aim of this study was to investigate whether two metabolites of glyceryl trinitrate (GTN), 1,2 and 1,3-glyceryl dinitrate (1,2-GDN and 1,3-GDN) could account for the pharmacological effects of GTN. To this end the formation of nitric oxide (NO) from 1,2- and 1,3-GDN in the presence of bovine aortic smooth muscle cells (SMC) or endothelial cells (EC) was studied. The effects of various thiols on NO formation from these dinitrates was also evaluated. 2. 1,2-GDN or 1,3-GDN (10(-10)-10(-5) M) caused a dose-dependent relaxation of rabbit aortic strips denuded of endothelium and precontracted with phenylephrine. The dinitrates were less than one tenth as potent as GTN. 3. Incubation of 1,2-GDN or 1,3-GDN (75-2400 microM) with SMC for 30 min led to a concentration-dependent increase in nitrite (NO2-) formation but this increase was less than that produced from GTN. Likewise incubation of 1,2-GDN or 1,3-GDN with N-acetylcysteine (NAC), glutathione (GSH) or thiosalicylic acid (TSA) (all at 1 mM) for 30 min at 37 degrees C produced a concentration-dependent increase in NO2- formation. 4. Platelet aggregation induced by thrombin (40 mu ml-1) was not modified by high concentrations of 1,2-GDN or 1,3-GDN (175-700 microM). However, aggregation was inhibited when platelets were exposed to 1,2-GDN or 1,3-GDN (700 microM) in the presence of SMC (0.24-1.92 x 10(5) cells) or EC (0.8-3.2 x 10(5) cells). These effects were abrogated by co-incubation with oxyhaemoglobin (OxyHb, 10 microM) indicating that they were due to NO release. The concentrations of the dinitrates required to inhibit platelet aggregation by 50% were about 15 times higher than for GTN in the presence of the same numbers of SMC or EC.5. When NAC or TSA (both at 0.5 mM) were co-incubated with platelets for 3 min in the presence of1,2-GDN or 1,3-GDN, a concentration-dependent inhibition of platelet aggregation was observed. These anti-platelet effects were abolished by co-incubation with OxyHb (10 microM). Glutathione had no potentiating effects.6. Thus the dinitrate metabolites of GTN are metabolized to NO by SMC or EC and are acted upon by thiols to form NO at concentrations about 10 times higher than those of GTN. In vivo, after oral or intravenous GTN, GDN levels are reached which are more than 10 times higher than those of GTN.These data support the notion that part of the effects of GTN are due to the generation of NO from 1,2-GDN and 1,3-GDN by the cells of the vascular wall.

Transbronchial biopsy in lymphangiomyomatosis of the lung. HMB45 for diagnosis.

We have investigated the presence of smooth muscle cells with immunoreactivity for melanoma-related marker HMB45 in pulmonary lymphangiomyomatosis (PLAM). Of 75 lung specimens, including a variety of lesions (obtained with both transbronchial and open lung biopsies), only PLAM (six specimens from three patients) showed the presence of HMB45-positive cells. In addition, 20 specimens of normal lung were unreactive with this monoclonal antibody. It is concluded that the smooth muscle cells of PLAM regularly exhibit a peculiar phenotype, characterized by HMB45 immunoreactivity, distinct from other smooth muscle proliferations; and the histological diagnosis of PLAM can be made when only a transbronchial biopsy is available.

Quantitative ultrasonic characterization of lesion composition and remodeling in atherosclerotic rabbit aorta.

We have previously shown that high-frequency, high-resolution ultrasound can characterize the acoustic properties and composition of fatty plaques in cholesterol-fed rabbits. To determine whether quantitative ultrasound can delineate the regression of atherosclerotic lesions by detecting a change in their composition from fatty to fibrous types induced by alterations in dietary regimen, we fed six New Zealand White rabbits a 2% cholesterol diet for 3 months, followed by a standard diet for 3 additional months to promote the development of fibrous intimal lesions. Segments of aortas were excised, and backscattered radiofrequency data were acquired from 400 to 600 independent sites in each specimen with an acoustic microscope operated at 50 MHz. Control data were provided by measuring backscatter from adjacent portions of the aortas devoid of lesions. Histological and immunocytochemical analyses of the fibrous intimal lesions confirmed the presence of smooth muscle cells and abundant connective tissue with little appreciable lipid. Backscatter from normal aortic segments (-30.7 +/- 1.0 dB) was approximately 10-fold greater than that from fibrous lesions (-42.4 +/- 1.0 dB; P < .05). We previously reported that integrated backscatter from fatty lesions was -50.6 +/- 0.7 dB, or approximately 10-fold less than that from fibrous lesions (P < .05). Values for integrated backscatter from the media of each tissue type were approximately equal (-30.0 +/- 1.7 versus -30.7 +/- 1.6 versus -33.4 +/- 0.8 dB for normal versus fibrous versus fatty tissues, respectively; P = not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Mitogenic effect of neuropeptide Y in rat vascular smooth muscle cells

Neuropeptide Y (NPY) is a vasoconstrictor released with norepinephrine from perivascular sympathetic nerves. Since sympathetic nerves appear to play a role in vascular smooth muscle cell (SMC) hypertrophy, we studied the effects of NPY on proliferation of cultured rat aorta- and vena cava-derived SMC. Both cell types displayed high-affinity NPY binding sites with displacement characteristics of [Pro 34]NPY > NPY(13–36) > NPY(18–36) in aorta and [Pro 34]NPY = NPY(13–36) = NPY(18–36) in the vena cava. Incubation with NPY (50–1000 n M) for 48 h increased by up to twofold cell number and [ 3H]-thymidine incorporation in both cell types (aortic more sensitive to NPY than venous). Following incubation with NPY, the disappearance of NPY immunoreactivity (-IR) from media was markedly delayed in the presence of SMC, and cell content of NPY-IR increased in a dose-dependent manner, indicating that SMC either diminish degradation of the peptide (possibly by internalization) or secrete endogenous NPY (or both). Structure-activity relationship studies with NPY(18–36) indicated involvement of Y1 receptors in mitogenesis. Thus, NPY has a mitogenic effect (probably mediated by Y1 receptors) and, therefore, may be a sympathetic trophic factor involved in vascular hypertrophy.

Significance of the smooth muscle cell component in Peutz-Jeghers and juvenile polyps

We have previously reported the presence of smooth muscle cells (SMCs) in the lamina propria of both tubular and villous adenomatous polyps. In the current study, we investigated the presence and distribution of SMCs with immunohistochemical techniques using anti-alpha smooth muscle actin and anti-desmin antibodies on a series of hamartomatous polyps. In five Peutz-Jeghers polyps, large tree-like branches of SMCs were observed, while in 13 juvenile polyps, rare elongated SMCs were found in the lamina propria, partially surrounding cystically dilated glands. Apart from the quantitative differences, the SMC distribution was similar in the two types of hamartomatous polyps and not dissimilar from the pattern described in neoplastic polyps. These findings make the category “juvenile polyp” less clear and its differentiation from other histologic types of polyp less sharp. Thus, the presence or absence of SMCs cannot form the basis of the differential diagnosis between adenomatous and hamartomatous polyps.

Correlation between oxidation of low density lipoproteins and prostacyclin synthesis in cultured smooth muscle cells

The effect of antioxidants on the oxidation of low density lipoproteins in relation to prosta-cyclin synthesis was investigated in the prescence of rabbit smooth muscle cells (SMC) and Fe-containing culture medium. The lipid peroxidation of low density lipoproteins (LDL) assayed as thiobarbituric acid reactive substances was increased from 0.5 to 1.4 nmol malondialdehyde mL by the presence of smooth muscle cells. Two potent antioxidants, nordihydroguairetic acid (NDGA) and butylated hydroxytoluene (BHT), inhibited lipoprotein oxidation by ic 50 values of 0.2 and 0.8 μM, respectively. Inhibition of lipoprotein oxidation was associated with an increased prostacyclin synthesis by the SMC, the effect being more pronounced with nordihydroguairetic acid than with butylated hydroxytoluene. The stable metabolite of the lipid hydroperoxide, 15-hydroxyeicosatetraenoic acid (15-HETE), formed in the 15-lipoxygenase pathway was measured following antioxidant treatment and found to be eliminated or greatly reduced by both antioxidants. The results presented show that lipid hydroperoxides, formed as a consequence of lipoprotein oxidation and promoted by the smooth muscle cells through a lipoxygenase reaction, may regulate prostacyclin synthase, a process which may be influenced by the addition of antioxidants.

Low density lipoprotein uptake by an endothelial-smooth muscle cell bilayer

To study the interaction of endothelial and smooth muscle cells, and the means by which such interaction may affect lipid permeability of the arterial wall, cell bilayers were established by use of a transwell culture system. After confluent growth of both cell types had been achieved, iodine 125 bound to low-density lipoprotein (10 ng protein/ml) was added to the media of the upper well. After a 3-hour incubation period, the iodine 125-bound low-density lipoprotein content of the upper and lower media demonstrated an impedance to lipoprotein movement across the endothelial cell monolayer as compared to the bare porous polycarbonate filter of the transwell (p less than 10(-6)). The presence of smooth muscle cells in the bottom well significantly enhanced the permeability of the endothelial cell layer (p less than 10(-60). This effect remained unchanged over a 9-day time course. Membrane binding and cellular uptake of low-density lipoprotein by endothelial cells was not altered by smooth muscle cells, indicating that this change in permeability could not be easily attributed to changes in receptor-mediated transport or transcytosis. Membrane binding (p less than 0.02) and cellular uptake (p less than 10(-6)) of low-density lipoprotein by smooth muscle cells in the bilayer, when adjusted for counts available in the smooth muscle cell media, were both reduced in the early incubation period as compared to isolated smooth muscle cells. The disproportionate reduction in uptake as compared to binding would suggest that this was not entirely a receptor-dependent process.(ABSTRACT TRUNCATED AT 250 WORDS)