Activation of the alternative pathway of human complement by apoptotic human umbilical vein endothelial cells

Complement activation generally does not occur on homologous cells. We observed C3 deposition on cultured human umbilical vein endothelial cells (HUVEC) when those which had died of apoptosis were treated with human serum. The C3 deposition on apoptotic HUVEC required Mg2+ but not Ca2+. In addition, the incubation of apoptotic HUVEC with purified C3, B, and D in the presence of Mg2+ resulted in C3 deposition. These results indicated that the C3 deposition on apoptotic HUVEC is mediated by the activation of the alternative complement pathway. C3 contains an intrachain thioester bond in the alpha chain (110 kDa) and upon activation to C3b, binds with membrane molecules by forming an ester or amide bond. Western blotting of reduced C3b-membrane molecule complexes, isolated from serum-treated apoptotic HUVEC by immunoprecipitation with anti-C3, revealed the covalent binding of C3b to several membrane molecules. Most of the C3b-membrane molecule complexes were cleaved by hydroxylamine, suggesting covalent binding via an ester bond. The molecular mass of the major alpha chain fragment released by hydroxylamine treatment was not 105 kDa but 68 kDa, which corresponds to the alpha 1 fragment of iC3b. These results indicate that most of the C3b on HUVEC was cleaved at its alpha' chain to yield iC3b, which consists of three disulfide-linked polypeptide chains and is a ligand of the complement receptor type 3 (CR3) of phagocytes. These results suggest that apoptotic HUVEC can activate the alternative pathway of the homologous complement and that the complement is related to the clearance of apoptotic cells by phagocytes.     

Calcium entry activated by store depletion in human umbilical vein endothelial cells

We have used the patch clamp technique combined with simultaneous measurement of intracellular Ca2+ to record ionic currents activated by depletion of intracellular Ca(2+)-stores in endothelial cells from human umbilical veins. Two protocols were used to release Ca2+ from intracellular stores, i.e. loading of the cells via the patch pipette with Ins(1,4,5)P3, and extracellular application of thapsigargin. Ins(1,4,5)P3 (10 microM) evoked a transient increase in [Ca2+]i in cells exposed to Ca(2+)-free extracellular solutions. A subsequent reapplication of extracellular Ca2+ induced an elevation of [Ca2+]i. These changes in [Ca2+]i were very reproducible. The concomitant membrane currents were neither correlated in time nor in size with the changes in [Ca2+]i. Similar changes in [Ca2+]i and membrane currents were observed if the Ca(2+)-stores were depleted with thapsigargin. Activation of these currents was prevented and holding currents at -40 mV were small if store depletion was induced in the presence of 50 microM NPPB. This identifies the large currents, which are activated as a consequence of store-depletion, as mechanically activated Cl- currents, which have been described previously [1,2]. Loading the cells with Ins(1,4,5)P3 together with 10 mM BAPTA induced only a very short lasting Ca2+ transient, which was not accompanied by activation of a detectable current, even in a 10 mM Ca(2+)-containing extracellular solution. Also thapsigargin does not activate any membrane current if the pipette solution contains 10 mM BAPTA (ruptured patches). The contribution of Ca(2+)-influx to the membrane current during reapplication of 10 mM extracellular calcium to thapsigargin-pretreated cells was estimated from the first time derivative of the corresponding Ca2+ transients at different holding potentials. These current values showed strong inward rectification, with a maximal amplitude of 1.0 +/- 0.3 pA at -80 mV (n = 8; membrane capacitance 59 +/- 9 pF).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of estrogen on tight junctional resistance in cultured human umbilical vein endothelial cells

OBJECTIVE: To study the effects of estrogen on transendothelial paracellular permeability in women. METHODS: Human umbilical vein endothelial cells (HUVEC) obtained from women were grown on filters. The paracellular permeability characteristics were determined in terms of changes in the permeability to the polar acid pyranine (Ppyr) and as changes in the transendothelial electrical resistance (RTE). Tight junctional resistance characteristics were assayed by lowering luminal NaCl and measuring the dilution potential, and were expressed as the ratio of monoion mobility uCl/uNa (cation selectivity). RESULTS: Low extracellular calcium and hyperosmolarity increased Ppyr and decreased RTE. The former but not the latter condition abolished the endothelium-specific cation selectivity. Treatment with 10 nM of estradiol-17 beta had no effect on RTE, but it increased the cation selectivity. The effect of estradiol required 1-6 hours' incubation with the hormone; it was dose dependent and saturable, with a median effective concentration of estradiol of 1 nM. Diethylstilbestrol, but not estriol, could mimic the effect of estradiol, and the estrogen receptor antagonist ICI-182, 780 blocked it. CONCLUSION: Cultured HUVEC cells form patent tight junctions. Estrogens increase the cation selectivity across HUVEC cultures. The effect of estrogen may be mediated by an estrogen receptor. These effects may be important for vasculoprotection in cases of sudden changes in ions levels across the capillary wall, such as ischemia or reperfusion.     

Gestational hypertension plasma and human umbilical vein endothelial cells: an in vitro study

A case of metastatic dermatofibrosarcoma protuberans (DFSP) in a 47-year-old woman is presented. Dermatofibrosarcoma protuberans occasionally recurs, but rarely metastasizes. The patient underwent local removal of the nuchal tumor by a general practitioner, followed by a rapid recurrence. She underwent total removal of the tumor and a diagnosis of spindle cell sarcoma was made after an incisional biopsy was performed. This lesion had both a typical DFSP-like area and a fibrosarcoma (FS)-like area. After 7 years, an abnormal lung shadow was observed and a segmental lung resection was performed. Histologically, the lung tumor was similar to the FS-like area in the nuchal tumor. Confirming CD34 expression in the tumor cells, this lung tumor was diagnosed as metastatic DFSP. Usually CD34 expression is unique to DFSP but almost negative in FS-like areas. In the present case, the FS-like area in the nuchal tumor showed decreased CD34 reactivity, as previously reported, but the FS-like area in the metastatic tumor still widely preserved CD34 expression. The presented case suggests that the FS-like area in DFSP is histogenetically different from typical FS or malignant fibrous histiocytoma.     

Protein C activation and factor Va inactivation on human umbilical vein endothelial cells

The inactivation of factor Va was examined on primary cultures of human umbilical vein endothelial cells (HUVECs), either after addition of activated protein C (APC) or after addition of alpha-thrombin and protein C (PC) zymogen. Factor Va proteolysis was visualized by Western blot analysis using a monoclonal antibody (alpha HVaHC No. 17) to the factor Va heavy chain (HC), and cofactor activity was followed both in a clotting assay using factor V-deficient plasma and by quantitation of prothrombinase function. APC generation was monitored using the substrate 6-(D-VPR)amino-1-naphthalenebutylsulfonamide (D-VPR-ANSNHC4H9), which permits quantitation of APC at 10 pmol/L. Addition of APC (5 nmol/L) to an adherent HUVEC monolayer (3.5 x 10(5) cells per well) resulted in a 75% inactivation of factor Va (20 nmol/L) within 10 minutes, with complete loss of cofactor activity within 2 hours. Measurements of the rate of cleavage at Arg506 and Arg306 in the presence and absence of the HUVEC monolayer indicated that the APC-dependent cleavage of the factor Va HC at Arg506 was accelerated in the presence of HUVECs, while cleavage at Arg306 was dependent on the presence of the HUVEC surface. Factor Va inactivation proceeded with initial cleavage of the factor Va HC at Arg506, generating an M(r) 75,000 species. Further proteolysis at Arg306 generated an M(r) 30,000 product. When protein C (0.5 mumol/L), alpha-thrombin (1 nmol/L), and factor Va (20 nmol/L) were added to HUVECs an APC generation rate of 1.56 +/- 0.11 x 10(-14) mol/min per cell was observed. With APC generated in situ, cleavage at Arg506 on the HUVEC surface is followed by cleavage at Arg306, generating M(r) 75,000 and M(r) 30,000 fragments, respectively. In addition, the appearance of two novel products derived from the factor Va HC are observed when thrombin is present on the HUVEC surface: the HC is processed through limited thrombin proteolysis to generate an M(r) 97,000 fragment, which is further processed by APC to generate an M(r) 43,000 fragment. NH2-terminal sequence analysis of the M(r) 97,000 fragment revealed that the thrombin cleavage occurs in the COOH-terminus of the intact factor Va HC since both the intact HC as well as the M(r) 97,000 fragment have the same sequence. Our data demonstrate that the inactivation of factor Va on the HUVEC surface, initiated either by APC addition or PC activation, follows a mechanism whereby cleavage is observed first at Arg506 followed by a second cleavage at Arg306. The latter cleavage is dependent on the availability of the HUVEC surface. This mechanism of inactivation of factor Va is similar to that observed on synthetic phospholipid vesicles.     

Heat shock provides delayed protection against oxidative injury in cultured human umbilical vein endothelial cells

During both mild and severe ischemia, vascular endothelial cells lining large and small vessels of the ischemic organ are exposed to oxygen-derived free radicals resulting in oxidative damage to the organ. Heat shock has been shown to induce thermotolerance and also protect against ischemic injury, possibly via increased synthesis of heat shock proteins (HSPs). We hypothesized that heat shock preconditioning may protect human endothelial cells against oxidative damage. Cultured human umbilical vein endothelial cells (HUVEC) were subjected to heat shock (42 degrees C, 1 h) and allowed to recover for 2 or 20 h, at which times the cells were oxidatively stressed for 1 h by exposing them to 100-200 mumol/l of hydrogen peroxide (H2O2). Cellular damage was assessed immediately and 18 h later by morphology and release of lactate dehydrogenase (LDH). No protection of HUVEC was seen using the 2-hour recovery interval, but a significant protection (P < 0.05) was observed after the 20-hour delay. Northern blot analysis at 1 and 2 h after heating showed induction of HSP-70 mRNA. Western blot analysis demonstrated a significant increase in HSP-72 protein after 2 as well as 20 h of recovery from heat shock, although the amounts of protein at the two times were not significantly different. Furthermore, no differences in the activity of the antioxidant enzyme catalase were observed between heated and unheated HUVEC at 2 and 20 h after heat preconditioning. Thus, heat shock preconditioning induces delayed protection against oxidative injury in HUVEC, and the mechanism of protection appears to involve more than the expression of HSP-72 or activity of catalase.     

Release of cytokines from human umbilical vein endothelial cells treated with platinum compounds in vitro

Endothelial cells (EC) produce cytokines, such as interleukin (IL)-1, IL-6, IL-8 and granulocyte-macrophage colony-stimulating factor (GM-CSF). These cytokines have an important role in the proliferation and differentiation of hematopoietic progenitor cells. On the other hand, anticancer agents generally cause hematopoietic disorders. However, little is known about the effects of chemotherapeutic agents on the secretion of cytokines from EC. Therefore, we investigated if treatment with platinum compounds may stimulate EC to secrete cytokines. EC newly isolated from a human umbilical vein were exposed to cisplatin, carboplatin, or TRK-710 for 80 min, then the cells were washed and placed in fresh medium. The levels of cytokines in the fresh medium were measured by the ELISA method, the levels of intracellular hydrogen peroxide (H2O2) were measured by flow cytometry, and the rhodamine 123-stained live mitochondria of the EC were observed under a confocal laser microscope. Platinum compounds induced cytokine production in human EC: cisplatin most prominently induced the release of IL-1 and IL-6, and TRK-710 had the greatest ability to induce the release of GM-CSF. Intracellular H2O2 production and IL-8 release were transiently induced immediately after treatment with platinum compounds, leading to IL-1 release when H2O2 production was eliminated. These results may provide new insights into the hematological toxicity induced by anticancer agents and the role of IL-1 and IL-6 secreted from EC in this toxicity.     

Angiotensin II AT1 receptors and Na+/K+ ATPase in human umbilical vein endothelial cells

Cultured human umbilical vein endothelial cells (HUVECs) at passage 4 specifically bound 70 +/- 12 fmol [3,5-3H]Tyr4-Ile5-angiotensin (Ang) II/mg protein, with a Kd of 0.9 +/- 0.36 nM. Binding was eliminated in cells preincubated with a monoclonal antibody (6313/G2) raised against the subtype AT1 of the Ang II receptor. Freshly seeded HUVECs were positive for 6313/G2 antibody by immunocytochemistry, and such immunoreactivity was still retained at passage 4. Incubation of HUVECs for 20 min with different concentrations of Ang II provoked a significant increment in Na+/K+ ATPase activity compared with controls, in a dose- and time-dependent manner. Maximal response was obtained with 1000 pM Ang II after 20 min stimulation and resulted in a 2.2-fold increment in Na+/K+ ATPase activity. This stimulation was abolished when cells were incubated with 1000 pM Ang II in the presence of 1 microM of the specific AT1 subtype inhibitor, DuP753. Moreover, preincubation of HUVECs with 6313/G2 or with 1 mM dithiothreitol also inhibited the stimulatory effect of Ang II. These results suggest that the AT1 receptor subtype mediates the Na+/K+ ATPase response to Ang II in these cells.     

Oxidized low density lipoprotein induces apoptosis in cultured human umbilical vein endothelial cells by common and unique mechanisms

Oxidized low density lipoprotein (oxLDL) induces apoptosis in vascular cells. To elucidate the mechanisms involved in this apoptosis, we studied the apoptosis-inducing activity in lipid fractions of oxLDL and the roles of two common mechanisms, ceramide generation and the activation of caspases, in apoptosis in human umbilical vein endothelial cells treated with oxLDL. We also studied the effects of antioxidants and cholesterol. oxLDL induced endothelial apoptosis in a time- and dose-dependent fashion. Apoptosis-inducing activity was recovered in the neutral lipid fraction of oxLDL. Various oxysterols in this fraction induced endothelial apoptosis. Neither the phospholipid fraction nor its component lysophosphatidylcholine induced apoptosis. oxLDL induced ceramide accumulation temporarily at 15 min in a dose-dependent fashion. Two inhibitors of acid sphinogomyelinase inhibited both the increase in ceramide and the apoptosis induced by oxLDL. Furthermore, a membrane-permeable ceramide (C2-ceramide) induced endothelial apoptosis. These findings demonstrated that ceramide generation by acid sphingomyelinase is indispensable for the endothelial apoptosis induced by oxLDL. Inhibitors of both caspase-1 and caspase-3 inhibited the apoptosis, suggesting that oxLDL induced apoptosis by activating these cysteine proteases. The antioxidants butylated hydroxytoluene and superoxide dismutase but not catalase inhibited the apoptosis induced by oxLDL or 25-hydroxycholesterol. This suggests not only that superoxide plays an important role but also that a critical interaction between oxLDL and the cell takes place on the outer surface of the membrane, because superoxide dismutase is not membrane-permeable. Exogenous cholesterol also inhibited the apoptosis. Our study demonstrated that neutral lipids in oxLDL induce endothelial apoptosis by activating membrane sphingomyelinase in a superoxide-dependent manner, as well as by activating caspases.     

Effect of flupirtine on cell death of human umbilical vein endothelial cells induced by reactive oxygen species

Flupirtine (KATADOLON), known as a nonopiate centrally acting analgesic drug, was tested as to its potential to prevent apoptosis of human endothelial cells induced by reactive oxygen species (ROS). It was found that Flupirtine displayed no effect on viability and cell proliferation of human umbilical vein endothelial cells (HUVEC) up to a concentration of 10 microg/mL. Apoptosis, induced by ROS and generated by hypoxanthine/xanthine oxidase (EC 1.1.3.22) (HX/XOD) or t-butyl hydroperoxide, was reduced after preincubation with Flupirtine for 3 hr by 35% and 41%, respectively. The maximal cytoprotective effect against apoptosis was observed at a drug concentration of 1 to 3 microg/mL. Flow cytometric studies revealed that Flupirtine was able to decrease the number of necrotic cells as well as of apoptotic cells. Neither the simultaneous administration of Flupirtine with the apoptosis-inducing agent nor the preincubation of HUVEC with Flupirtine influenced the increase in the intracellular Ca2+ concentration [Ca2+]i caused by the production of ROS.     

Lipoprotein(a) enhances the expression of intercellular adhesion molecule-1 in cultured human umbilical vein endothelial cells

Quite a substantial number of human disorders have been associated with a primary or a secondary impairment of one or several of the dopaminergic pathways. Among disorders associated with a primary impairment of dopaminergic transmission are Parkinson's disease, striatonigral degeneration, progressive supranuclear palsy, and possibly schizophrenia. Diseases of secondary dopamine dysfunction are chiefly represented by Huntington's disease in which dopaminergic transmission is being interrupted by progressive loss of the striatal neurons bearing the postsynaptic D1- and D2-dopamine receptors. Central dopaminergic systems have anatomical as well as organizational properties that render them unique by comparison to other neurotransmission systems, making them able to play a pivotal role in the modulation of various important brain functions such as locomotor activity, attention, and some cognitive abilities. These properties of dopamine neurons have obviously several implications in the clinical expression of human disorders involving dopamine neuron dysfunction. In addition, they can greatly influence the clinical/behavioral consequences of experimental lesions in animal models of dopamine dysfunctions.     

Effects of flavonoids isolated from scutellariae radix on fibrinolytic system induced by trypsin in human umbilical vein endothelial cells

Studies on the effects of flavonoids isolated from the roots of Scutellaria baicalensis on the fibrinolytic system induced by trypsin in cultured human umbilical vein endothelial cells (HUVECs) showed that baicalein (1) strongly inhibited the reduction of t-PA production and the elevation of PAI-1 production induced by trypsin. The IC50 for PAI-1 production was 3.7 microM. In addition, wogonin (3), oroxylin A (5), skullcapflavone II (6), and 2',5,5',7-tetrahydroxy-6',8-dimethoxyflavone (7) inhibited the elevation of PAI-1 induced by trypsin, though less strongly; their IC50 were 105, 61, 110, and 88 microM, respectively. These findings suggest that baicalein prevents the thrombotic tendency induced by trypsin.     

TNF-alpha stimulates the biosynthesis of complement C3 and factor B by human umbilical cord vein endothelial cells

The effect of basic fibroblast growth factor (bFGF) on apoptosis in normal rat palatal fibroblasts and rat palatal scar fibroblasts was examined by the TUNEL method in order to clarify the mechanism of apoptosis induction in myofibroblasts during the scar formation process. A percentage of scar fibroblasts undergoing apoptosis was significantly higher than that of palatal fibroblasts when they were treated with bFGF succeeding to serum starvation. Palatal fibroblasts, phenotypically modulated into myofibroblasts by the pretreatment with transforming growth factor-beta 1 (TGF-beta 1), similarly showed a higher level of apoptosis induction by bFGF-treatment. TGF-beta 1 elevated protein and mRNA level of FGF receptor (FGFR) in palatal fibroblasts. Tyrosine autophosphorylation of FGFR upon stimulation by bFGF was significantly higher in scar fibroblasts than in normal palatal fibroblasts. These findings suggested that bFGF may be a potential stimulator of apoptosis in myofibroblasts during palatal scar formation and that FGFR may be responsible for this process.     

Induction and release of manganese superoxide dismutase caused by tumor necrosis factor-alpha from mitochondria in human umbilical vein endothelial cells

The effects of tumor necrosis factor-alpha (TNF-alpha) on cultured human umbilical vein endothelial cells (EC) and five cancer cell lines, A549, ME180, A2780, KURAMOCHI, and Hela, were compared. While A549, A2780, KURAMOCHI, and Hela cells were fairly resistant to the cytolytic effects of TNF-alpha, ME180 cells were sensitive. EC were also less sensitive to TNF-alpha than ME180 cells as judged by the viability of individual cells and by the release of lactate dehydrogenase (LDH) into the medium. Manganese superoxide dismutase (Mn-SOD) was markedly induced by these cytokines in EC and in A549 cells but not in ME180 cells. The levels of Mn-SOD in the conditioned medium of EC were dramatically increased after stimulation with cytokines, whereas those in ME180 and A549 cells were relatively low. The amount of Mn-SOD released appears to be comparable to that from cells lysed by other means. Immunoblot analysis of Mn-SOD in the medium showed that the molecular mass of the immunoreactive protein was the same as mitochondrial Mn-SOD, indicating that no proteolysis had occurred. These data suggest that in vivo the TNF-alpha produced by cancer cells may induce Mn-SOD in vascular endothelial cells, resulting in release of a relatively large amount of this protein into the serum.     

Listeria monocytogenes-infected human umbilical vein endothelial cells: internalin-independent invasion, intracellular growth, movement, and host cell responses

Tissue concentrations of mercury were determined by cold vapor atomic absorption spectrometry in different inbred mouse strains after continuous treatment with HgCl2 (3 weekly sc injections of 0.5 mg/kg bw) for up to 12 weeks. Except for the thymus, in which steadily increasing mercury concentrations were found, in steady state levels of mercury were reached in blood and liver after 4 weeks and in spleen and kidney after 8 weeks. In the closely related strains C57BL/6, B10.D2, and B10.S, which differ only or primarily at the major histocompatibility complex, mercury concentrations in blood and liver were about twofold lower and renal concentrations were about three- to fivefold lower than those detected in strains A.SW and DBA/2. Another strain difference was observed in the spleen: after 8 and 12 weeks of continuous HgCl2 treatment, mercury concentrations in the spleen of strains A.SW, C57BL/6, and B10.S were significantly higher than those in strains DBA/2 and B10.D2. The strain difference in the spleen, an organ of the immune system, correlates with the susceptibility to the HgCl2-induced systemic autoimmune syndrome in mice in that the strains showing a higher mercury accumulation in the spleen are susceptible to this form of chemically induced autoimmunity, whereas the strains with lower mercury concentrations in the spleen are resistant.     

Histamine induces nuclear factor of activated T cell-mediated transcription and cyclosporin A-sensitive interleukin-8 mRNA expression in human umbilical vein endothelial cells

Strong evidence indicates that virions of mammalian reoviruses undergo proteolytic processing by acid-dependent cellular proteinases as an essential step in productive infection. Proteolytic processing takes the form of a series of cleavages of outer-capsid proteins final sigma3 and mu1/mu1C. Previous studies showed an effect of both NH4Cl and E-64 on these cleavages, indicating that one or more of the acid-dependent cysteine proteinases in mammalian cells (cathepsins B and L, for example) is required; however, these studies did not address whether acid-dependent aspartic proteinases in those cells (cathepsin D, for example) may also be required. To determine the role of aspartic proteinases in reovirus entry, studies with pepstatin A, a specific inhibitor of aspartic proteinases, were performed. The results showed that pepstatin A neither blocks nor slows reovirus infection of L or MDCK cells. Experiments using ribonuclease A and other proteins as cleavable substrates showed that cathepsin-D-like proteinases from these cells are inhibited within the tested range of pepstatin A concentrations both in vitro and within living cells. In other experiments, virion-bound final sigma3 protein was shown to be a poor substrate for cleavage by cathepsin D in vitro, consistent with the findings with inhibitors. In sum, the data indicate that cathepsin-D-like aspartic proteinases provide little or no activity toward proteolytic events required for infection of L or MDCK cells with reovirus virions.     

Biodegradation of glutaraldehyde-tanned human umbilical vein grafts

A retrospective analysis of the long-term behavior of 111 glutaraldehyde-tanned human umbilical vein (HUV) grafts implanted between September 1977 and December 1993 was conducted. A total of 81 patients, with a mean age of 68.7 years, received the grafts and were followed up for between 1 and 131 months. The 5-year primary cumulative patency rate for above-knee femoropopliteal bypass was 83.1%, whereas that of other bypasses was 60.9%. An aneurysm of the graft was defined as a physically apparent localized dilatation, with diffuse ectasia being excluded. There were 11 aneurysms found in 9 grafts, 2 of which arose at the factory-made suture lines. The accumulated incidence of aneurysms had reached 21.9% by the 6th year. One aneurysm compressed the graft and resulted in limb-threatening ischemia and another resulted in frank rupture. Moreover, reinforcement of the mesh could not prevent aneurysm development, the repair of which is mandatory due to the risk of rupture and acute thrombosis. The HUV grafts showed an acceptable patency rate in the above-knee location, but the incidence of aneurysm formation after 5 years was abnormally high. Thus, both the risks and benefits of HUV grafts must be taken into account when considering their clinical application.     

Ability of reconstituted high density lipoproteins to inhibit cytokine-induced expression of vascular cell adhesion molecule-1 in human umbilical vein endothelial cells

Previous studies have shown that both high density lipoproteins (HDL) isolated from human plasma and reconstituted HDL (rHDL) are effective inhibitors of adhesion molecule expression in human endothelial cells. In this study rHDL have been used to investigate whether HDL particle shape, size, apolipoprotein composition or lipid composition are important determinants of the ability of HDL to inhibit the TNF-alpha induced expression of vascular cell adhesion molecule-1 (VCAM-1) in human umbilical vein endothelial cells (HUVECs). On the basis of these studies it is possible to draw several firm conclusions. i) Neither phospholipid-containing vesicles nor lipid-free apolipoprotein (apo) A-I inhibit VCAM-1 expression in HUVECs. ii) Simple discoidal complexes containing only phospholipid and apoA-I (discoidal (A-I)rHDL) are sufficient to inhibit the TNF-alpha-induced expression of VCAM-1 in HUVECs. iii) Spherical apoA-I-containing rHDL (spherical (A-I)rHDL) are superior to discoidal (A-I)rHDL as inhibitors. iv) The particle size of spherical (A-I)rHDL has no influence on the inhibition. v) Spherical rHDL that contain apoA-I are superior as inhibitors of VCAM-1 to those containing apoA-II when the rHDL preparations are equated for apolipoprotein molarity. However, when compared at equivalent particle molarities, this difference is no longer apparent. vi) Replacement of cholesteryl esters with triglyceride in the core of spherical (A-I)rHDL has no effect on the ability of these particles to inhibit VCAM-1 expression. From these results it is tempting to speculate that variations in inhibitory activity may contribute to the variations observed in the anti-atherogenicity of different HDL subpopulations.-Baker, P. W., K-A. Rye, J. R. Gamble, M. A. Vadas, and P. J. Barter. Ability of reconstituted high density lipoproteins to inhibit cytokine-induced expression of vascular cell adhesion molecule-1 in human umbilical vein endothelial cells.