Monocyte-vascular smooth muscle cell interaction enhances nitric oxide production.

OBJECTIVE: The adhesive interaction of monocytes and vascular smooth muscle cells (VSMCs) has been suggested to be a regulatory signal in the cellular activation that is involved in the pathogenesis of atherosclerosis. We investigated the effects of monocyte-VSMC interaction on inducible nitric oxide (NO) synthase expression. METHODS: NO production by the cultured cells was determined by measuring the nitrite content of the culture media using the Griess reagent. The expression of inducible NO synthase protein was assayed by Western blotting. RESULTS: Interleukin-1 beta (IL-1 beta) induced nitrite production by VSMCs in a time-dependent manner. The addition of the mouse monocyte cell line J774 to IL-1 beta-stimulated VSMCs further increased nitrite production in a monocyte number-dependent manner. Enhanced nitrite production by coculture was accompanied by increased inducible NO synthase protein accumulation. Addition of tumor necrosis factor-alpha (TNF-alpha) also enhanced IL-1 beta-induced nitrite production by VSMCs, but TNF-alpha showed no effect in the presence of monocytes. Coculture of monocytes and VSMCs in the presence of IL-1 beta secreted substantial amounts of TNF-alpha. The production of nitrite by coculture was markedly inhibited by an anti-TNF-alpha antibody. CONCLUSIONS: The present study revealed that direct cell-to-cell interaction between monocytes and VSMCs enhances NO production, suggesting an important role for their interaction in the pathogenesis of atherosclerosis.

Endothelin-1 production in coronary circulation in a new canine model of coronary thrombosis.

OBJECTIVE: The purpose of this study was to investigate whether endogenous endothelin-1 (ET-1) production in coronary circulation is associated with acute coronary thrombotic events in vivo. To achieve this goal, we have designed a new experimental canine model of coronary thrombosis. METHODS: In vivo occlusive thrombus was induced by the intracoronary application of radiofrequency energy (660 kHz, 50 W) in closed-chest dogs. Pathological and immunohistochemical examinations of thrombosed coronary artery were performed. In 12 dogs, plasminogen activator was administered intravenously and serial measurements of ET-1, thromboxane B2 (TXB2) and thrombin-antithrombin III complex (TAT) levels in plasma from the coronary sinus, aortic root and inferior vena cava were examined. RESULTS: Occlusive platelet-rich thrombi were attached to the deeply injured intimal surface. TAT and TXB2 increased rapidly soon after the intimal injury and declined after successful thrombolysis. In contrast, ET-1 in the coronary sinus was elevated after reperfusion and was significantly higher than in the aorta. Net ET-1 production in the coronary circulation showed a significant positive correlation with the peak TAT levels (r = 0.69, P < 0.05), but not with TXB2 or total occlusion time as an index of ischemic severity. CONCLUSIONS: Deep intimal injury leads to occlusive coronary thrombus. Thrombus formation and its subsequent lysis is associated with the activation and deactivation, respectively, of the coagulation cascade and platelets. Thrombin generation may stimulate ET-1 production in the coronary endothelium in acute coronary thrombotic events.

Human monocyte-endothelial cell interaction induces platelet-derived growth factor expression.

OBJECTIVE: The purpose of this study was to investigate whether the synthesis of platelet-derived growth factor (PDGF), a major mitogen and chemoattractant for vascular smooth muscle cells, was induced by the direct cell-to-cell interaction between human monocytes and umbilical vein endothelial cells (ECs). METHODS: PDGF protein and mRNA expression were determined by cellular ELISA, immunohistochemical and Northern blot analyses. RESULTS: Coculture of monocytes and ECs secreted a large amount of PDGF into the supernatant, whereas culture of ECs or monocytes alone induced low levels of PDGF production. In Northern blot analysis, substantial amounts of PDGF-A and -B mRNA were induced by coculture of monocytes with ECs. Immunohistochemistry revealed that PDGF-B chain protein was detectable in both ECs and monocytes. PDGF production by ECs induced by conditioned medium of the coculture was significantly inhibited by Abs against interleukin-1 beta (IL-1 beta) and tumor necrosis factor- alpha (TNF alpha). CONCLUSIONS: These results indicate that the direct cell-to-cell interaction between human monocytes and ECs induces PDGF synthesis in both types of cells, suggesting that PDGF produced locally by monocyte-EC adhesive interaction plays an important role in the pathogenesis of atherosclerosis by promoting the migration and accumulation of vascular smooth muscle cells.

Interaction between human monocytes and vascular smooth muscle cells induces vascular endothelial growth factor expression.

The objective of this study was to investigate whether synthesis of vascular endothelial growth factor (VEGF), a major mitogen for vascular endothelial cells, was induced by a cell-to-cell interaction between monocytes and vascular smooth muscle cells (VSMCs). Human VSMCs and THP-1 cells (human monocytoid cell) were cocultured. VEGF levels in the coculture medium were determined by enzyme-linked immunosorbent assay. Northern blot analysis of VEGF mRNA was performed using a specific cDNA probe. Immunohistochemistry was performed to determine which types of cell produce VEGF. Adding THP-1 cells to VSMCs for 24 h increased VEGF levels of the culture media, 8- and 10-fold relative to those of THP-1 cells and VSMCs alone, respectively. Northern blot analysis showed that VEGF mRNA expression was induced in the cocultured cells and peaked after 12 h. Immunohistochemistry disclosed that both types of cell in the coculture produced VEGF. Separate coculture experiments revealed that both direct contact and a soluble factor(s) contributed to VEGF production. Neutralizing anti-interleukin (IL)-6 antibody inhibited VEGF production by the coculture of THP-1 cells and VSMCs. A cell-to-cell interaction between monocytes and VSMCs induced VEGF synthesis in both types of cell. An IL-6 mediated mechanism is at least partially involved in VEGF production by the cocultures. Local VEGF production induced by a monocyte-VSMC interaction may play an important role in atherosclerosis and vascular remodeling.

Cytogenetic and DNA-fingerprint characterization of choriocarcinoma cell lines and a trophoblast/choriocarcinoma cell hybrid.

We report the successful fusion of human choriocarcinoma cells with normal human trophoblast cells to a choriocarcinoma/trophoblast hybrid. The hybrid cells ACH1P were derived from fusion of primary male trophoblast cells with the HGPRT-defective choriocarcinoma cell line AC1-1. The karyotypes of the parental choriocarcinoma cell line JEG-3, its HGPRT-defective mutant clones AC1-1, AC1-5, and AC1-9, and the choriocarcinoma/trophoblast hybrid ACH1P are presented, together with a detailed characterization of the AC1-specific chromosomal marker add(X)(q26) using conventional cytogenetic banding techniques and multiplex-fluorescence in situ hybridization (M-FISH). To our knowledge, this is the first report of a stably proliferating human cell hybrid of trophoblastic origin, providing a unique cell culture model to study trophoblast-related invasion and its underlying genetic mechanisms.

Monocytes modulate the fibrinolytic balance of endothelial cells.

Cultured endothelial cells (ECs) produced a constitutive plasminogen activator inhibitor-I (PAI-1), whereas primary culture of monocytes from blood did not produce a detectable amount of PAI-1. Addition of monocytes to ECs caused the accumulation of a large amount of PAI-1 in the supernatant in a dose- and time-dependent manner. Having almost no effect on the production of tissue-type plasminogen activator (t-PA), monocytes decreased the potential fibrinolytic activity of ECs. The 6 hours conditioned medium obtained from the coculture system between monocytes and either ECs or paraformaldehyde-fixed ECs had almost the same effect on the other ECs to produce PAI-1 and t-PA as monocytes that were direct contact with ECs. In addition, this effect was specifically inhibited by using two antibodies against interleukin-1 beta and tumor necrosis factor-alpha. These results indicate that interleukin-1 beta and tumor necrosis factor-alpha induced by the coculture are mostly responsible for decreasing the fibrinolytic activity of ECs.

Nitric oxide synthesis in rat cardiac myocytes and fibroblasts.

We investigated nitric oxide (NO) synthase activity in cultured neonatal rat cardiac myocytes and fibroblasts upon treatment with interleukin 1 beta (IL-1 beta) and lipopolysaccharide (LPS). Incubation of cardiac myocytes for 24 h with IL-1 beta or LPS caused a significant increase in NO and cGMP production. Simultaneous incubation of IL-1 beta with NG-monomethyl-L-arginine or transforming growth factor beta (TGF-beta) completely inhibited the IL-1 beta-induced NO and cGMP production in cardiac myocytes. In contrast, incubation of cardiac fibroblasts for 24 h with IL-1 beta or LPS showed no significant effect on NO or cGMP production. Addition of IL-1 beta decreased the beating rate of cardiac myocytes, but TGF-beta overcame that inhibition. These observations suggest the presence of iNOS in cardiac myocytes, which is an important regulator of contractile function of the heart.

Effect of a Change in the Sleep/Wake Cycle on the Diurnal Variation of Fibrinolytic Parameters.

The mechanism underlying the circadian rhythm of fibrinolysis is not well understood. To evaluate the influences of wakefulness and of the intrinsic circadian rhythm on fibrinolytic activity, we examined diurnal changes (8:00 am vs. 8:00 pm) in plasminogen activator inhibitor-1 (PAI-1) activity, tissue plasminogen activator (t-PA) antigen levels, and t-PA activity, as well as in plasma serum cortisol levels, in 10 healthy males (21 +/- 2 years) for two consecutive days. On the first day, subjects remained awake all day and night. They slept during the daytime (8:30 am to 5:30 pm) on the following day. PAI-1 activity and cortisol levels were significantly decreased, and t-PA activity tended to increase during the daytime on the first day. On the morning following overnight wakefulness, PAI-1 activity and cortisol levels did not return to the levels of the previous morning. On the second day, the afternoon decrease in PAI-1 activity, but not cortisol levels, was still observed, although its magnitude was substantially attenuated. No significant diurnal changes were observed in the levels of t-PA antigen throughout the study period. These findings suggest that the diurnal variation of fibrinolytic activity may be governed by an intrinsic circadian rhythm of PAI-1, which can be modified by a change in the time of wakefulness.

Elevation of histidine decarboxylase activity in the mandible of mice by Prevotella intermedia lipopolysaccharide and its augmentation by an aminobisphosphonate.

Lipopolysaccharide (LPS) produced by Gram-negative bacteria is an important cause of inflammation. Aminobisphosphonates are potent inhibitors of bone resorption but have inflammatory side-effects. Here, the effects of LPS from Prevotella intermedia (a prevalent Gram-negative bacterium both in periodontitis and endodontal infections) and alendronate (an aminobisphosphonate) on the activity of the histamine-forming enzyme, histidine decarboxylase (HDC), were examined in mouse mandible. Intravenous injection of P. intermedia LPS increased HDC activity in the mandible, maximal activity being induced within 3-6 h of the injection. The elevation of HDC activity was dependent on the dose of LPS, 10 microg/kg (0.25 microg/mouse) producing a significant elevation in enzyme activity. Intraperitoneal injection of alendronate (40 micromol/kg) also produced an increase in HDC activity. Moreover, the elevation of HDC activity induced by P. intermedia LPS was markedly augmented in mice given alendronate 3 days before the LPS injection. These results (i) suggest that P. intermedia LPS may stimulate the synthesis of histamine in the mandible and that the newly formed histamine may make at least some contribution to the development of inflammation (apical periodontitis and/or osteomyelitis); (ii) should encourage the clinical testing of antihistaminergic agents against inflammation; and (iii) confirm that care needs to be taken when administering aminobisphosphonates to patients.

PCDD/DF formations by the heterogeneous thermal reactions of phenols and their TiO2 photocatalytic degradation by batch-recycle system.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/DFs) formation by the thermal reactions of phenols with CuCl2 under oxygen flux were carried out in relation to their formation mechanisms. To evaluate the effect of photocatalytic degradation of titanium dioxide (TiO2) thin film prepared by the sol-gel method, the photocatalysis of PCDD/DFs in acetonitrile/water solution by batch-recycle system was conducted. For the thermal reaction system of powder mixtures of 2,4,5-trichlorophenol (2,4,5-TCP) and CuCl2, the formation rates were 8.1 microg/g-2,4,5-TCP/min for total PCDD/DFs and 6.9 microg/g-2,4,5-TCP/min for PCDDs, and total PCDD/DF rate was higher by approximately 40 fold compared to phenol vapor/oxygen/CuCl2 powder system. For the system of 2,4,5-TCP, PCDDs were mainly formed via ortho-phenoxyphenols (POP) intermediate by the condensation of 2,4,5-trichlorophenate. For PCDD/DF photocatalytic degradations, most PCDD congeners photodecomposed rapidly and the rates presented more than 70% (as dechlorination rates of 76% for PCDDs) at 24 h after irradiation, using PCDD/DFs formed with 2,4,5-TCP. The rate constants were in the order of 4.8-6.1 x 10(-3) min(-1), assuming the pseudo-first-order reactions for their low levels.

The suppressive mechanism of histamine release from rat peritoneal mast cells of iodine-enriched eggs.

We investigated the antiallergic activity of iodine-enriched egg by using rat peritoneal exudate cells. The effects were evaluated by the inhibition ratio of these compounds on histamine release from rat peritoneal exudate cells. Lipid and water-soluble fractions, which were separated from iodine-enriched egg yolk, were used for all experiments. Lipid fractionation of iodine-enriched eggs inhibited histamine release by compound-48/80 in a dose-dependent manner. Lipid fractionation of ordinary eggs had no effect. Neither the water-soluble fraction of iodine-enriched eggs nor ordinary eggs inhibited compound-48/80 induced histamine release. Neither lipid nor soluble fraction of iodine-enriched eggs inhibited histamine release in peritoneal exudate cells with Ca ionophore A23187 stimulation. The same fractions of ordinary eggs were also unable to inhibit histamine release. The lipid fraction, furthermore, was isolated to neutral and polar lipid fractionation. Although both neutral and polar lipid fractionation inhibited histamine release, the effect was dose-dependent in only neutral lipid fractionation. Neither fractions of ordinary egg inhibited histamine release. In conclusion, the components inhibiting histamine release in rat peritoneal exudate cells exist in the neutral lipid fraction of iodine-enriched eggs.

[Eight cases of diphyllobothriasis].

Eight cases of diphyllobothriasis have been experienced in the Juntendo University Hospital. Seven of the 8 patients excreted tapeworm fragments. Eggs of Diphyllobothrium latum were found in the feces in 5 cases. One patient had a history of ingestion of raw trout (Sushi), and 2 raw salmon. One might have been infected in foreign countries, and 3 could not tell the source of infection. Bithoinol was administered orally to 7 patients. Four of the 7 excreted the worm and the scolex was recognized in three of the four. Neither recurrence nor abnormal findings have been recognized so far.

Inhibition of inflammatory and bone-resorption-inhibitory effects of alendronate by etidronate.

Among the bisphosphonates (BPs), the aminobisphosphonates (aminoBPs) have much stronger bone-resorption-inhibitory activities (BRIAs) than nonaminobisphosphonates (nonaminoBPs). However, aminoBPs have inflammatory effects. We previously reported that in mice: (i) all aminoBPs tested (10-40 micromol/kg) induced various inflammatory reactions (including induction of histidine decarboxylase), whereas clodronate (a non-aminoBP) (10-160 micromol/kg) inhibited these reactions; and (ii) a clear sclerotic line (tentatively called the BP line) was detectable in the tibia by radiography a few weeks after a single injection of either alendronate (a typical aminoBP) (1.6 micromol/kg) or clodronate (160 micromol/kg), and this BP-line formation (a marker for the BRIAs of BPs) was not reduced in mice given both alendronate and clodronate. In this study, using this murine model, we compared clodronate, etidronate (another typical non-aminoBP), alendronate, etidronate + alendronate, and clodronate + alendronate in terms of their inflammatory effects and/or BP-line formation. For BP-line formation, 480 micromol/kg etidronate was needed (single injection). At 160 micromol/kg, etidronate inhibited the histidine decarboxylase induction, but not the other inflammatory reactions induced by alendronate. However, etidronate (unlike clodronate) also inhibited alendronate-induced BP-line formation (even at 40 micromol/kg). Etidronate (160 micromol/kg) also inhibited the physicochemical changes in the tibia induced by six, weekly injections of alendronate. Therefore, depending on the dose, etidronate can inhibit alendronate's inflammatory actions and its BRIA. These results, together with those reported previously, suggest that a strategy utilizing clodronate (but not etidronate) plus an aminoBP might prevent or reduce the inflammatory side effects induced by aminoBPs while preserving their powerful BRIAs. We discuss the mechanisms underlying the antagonism between aminoBPs and non-aminoBPs.

Inflammatory reactions in extraoral tissues in mice after intragingival injection of lipopolysaccharide.

Intragingival (ig) injection into mice of lipopolysaccharide (LPS) from Prevotella intermedia or Escherichia coli elevated the activity of the histamine-forming enzyme, histidine decarboxylase (HDC), in the mandible, liver, lung, and spleen, with a time course similar to that seen with intravenous (iv) injection. The effect of i.g. injection was less than that of i.v. injection but similar to that of intraperitoneal (ip) injection. The i.g. injection also increased hepatic serotonin, reflecting platelet accumulation. In galactosamine-treated mice, the minimum ig dose of LPS needed to induce lethal hepatitis was very small (less than that needed by ip injection). These results support the idea that the LPS produced in oral tissues may be transported easily to extraoral tissues and, in some cases, may cause inflammatory or immune responses. It also may influence the pathogenesis of some systemic diseases.

Effects of weekly administrations of alendronate+clodronate on young mouse tibia: localized action at the proximal growth plate.

Alendronate (A), a typical aminobisphosphonate (aminoBP), has a strong bone-resorption-inhibitory activity (BRIA). However, like other aminoBPs it has inflammatory side effects. In contrast, the BRIA of clodronate (C), a non-aminoBP, is much weaker, and in animal experiments it suppresses aminoBP-induced inflammatory reactions. In the present study, we examined the effects of weekly administrations of A (1.6 micro mol/kg) + C (160 micro mol/kg) on the tibias in young mice and compared them to those induced by A or C alone. Radiophotography showed that A increased bone density at a selective site in the tibia. Indeed, one week after the final injection of A (given alone), clear sclerotic lines (tentatively called BP-lines) were visible at sites corresponding to the location of the growth plate at the time of the each injection. C also produced BP-lines, although they were weaker than those produced by A. Combined administration of A and C produced similar BP-lines as seen in mice given A alone. These results together with other physicochemical effects of A on the tibia suggest that (1) each injection of A and C inhibits bone resorption selectively and transiently at the tibial growth plate in young mice, although minor effects on other sites cannot be excluded, and (2) the combination of A and C keeps still a strong BRIA. Our findings may suggest a strategy for the prevention or reduction of some inflammatory side effects of A or other aminoBPs.

Comparative study of placental protein 19, human chorionic gonadotrophin and pregnancy-specific beta 1-glycoprotein as immunohistochemical markers for extravillous trophoblast in pregnancy and trophoblastic disease.

PP19, a new placental tissue protein, has alpha 1-beta 1 electrophoretic mobility, a molecular weight of 36,500 and 3.9% carbohydrate. To study immunocytochemical PP19 localization in extravillous trophoblast, we obtained formalin-fixed specimens from extravillous tubal pregnancy at gestational weeks (GW) 7-9 (12 blocks); four early intrauterine pregnancies at GW 7-13 (12 blocks); four late pregnancies at GW 28-38 complicated with intramural uterine myoma, placenta increta and abruptio placenta (8 blocks); four invasive complete moles (9 blocks); and seven primary and metastatic gestational choriocarcinomas (12 blocks). Immunohistochemical staining was done for PP19, pregnancy-specific beta 1-glycoprotein (SP1) and human chorionic gonadotrophin (hCG) using the indirect-labeled antibody method [purified PP19 (Lot no. 225/242) and antibody against PP19 (Lot no. 632ZA) prepared by H. Bohn, antibodies against hCG (Behringwerke, Marburg, FRG) and SP1 (Dakopatts, Copenhagen, Denmark)]. In both early and late intrauterine pregnancies, the extravillous syncytiotrophoblastic cell (XST) showed positive staining for hCG and SP1 in the cytoplasm, as well as for PP19, which stained more intensively in the nucleus than in the cytoplasm. The three proteins were not seen in the evtravillous cytotrophoblastic cell (XCT) in the trophoblastic cell column and shell. The interstitial cytotrophoblast-like cell (ICT), which infiltrated into the decidua and myometrium, and their blood vessels, was immunoreactively positive for PP19 but negative for hCG and SP1 with the exception of SP1-positive ICT in the myometrium in late pregnancy. XST and ICT in the endosalpinx of tubal pregnancy stained for all three proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Characteristic differences in immunohistochemical localization of new placental proteins (PP1, PP19, PP21) in the human placenta.

The immunohistochemical localization in the human placenta of new placental proteins PP1, PP19, and PP21 was clarified using modified indirect enzyme-labeled antibody method and compared with that of pregnancy-specific beta 1-glycoprotein (SP1). The major results are as follows: positive staining for PP1 was seen at the nucleus and cytoplasm of villous cytotrophoblasts, the X cells at the basal plate, and of chorionic trophoblasts, while the decidua cells and amnion were not stained. PP19 was characteristically seen in the nucleus and cytoplasm of syncytiotrophoblasts. X cells in basal plate, chorionic trophoblasts, and maternal leukocytes. The villous cytotrophoblasts, decidua cells, and amnion were not stained. PP21 localization was found at the microvilli and basal membrane of syncytiotrophoblasts and at the cytotrophoblast plasma membrane of the chorionic villus in early gestation. In late gestation, increased staining was seen at the syncytiotrophoblast microvilli and the villous basement membrane, and moderate staining at plasma membrane of the amniotic epithelium and chorionic trophoblasts. SP1 was found only at the syncytiotrophoblast cytoplasm of chorionic villi. Studies using these four placental proteins simultaneously may therefore provide a new key learning about unknown metabolic functions of trophoblasts.

Abnormally large placenta associated with Beckwith-Wiedemann syndrome.

A 37-year-old G1-P1 was diagnosed by ultrasonography at 26 weeks of gestation as having an abnormally large placenta with hemangiomas and a fetus associated with exomphalos. Placental protein 5 levels were relatively high in placental protein levels in maternal serum. The infant, delivered by cesarean section at 34 weeks, had the typical clinical features associated with Beckwith-Wiedemann syndrome. The abnormally large placenta weighed 1,492 g, measured 25 X 25 X 5.1 cm, and featured multiple hemangiomas. Microscopic placental features included edematous villi, increased fibrin deposition, intervillous thrombi, and multiple angiomatous and cellular chorangiomas.

Concentration of placental protein 19 in body fluid and placental tissues.

Placental protein 19 (PP19) is one of the new placental tissue proteins identified in extracts from human term placenta by Bohn and Winkler. We measured the PP19 concentration in body fluids and placental tissue by radioimmunoassay; the minimum detectable dose of standard was 1.5 ng/ml. Although ethylene diamine tetraacetic acid (EDTA-2K) inhibited the immunoreaction between PP19 (225/242) and anti-PP19 antibody (632 ZA), the PP19 concentration did not differ between serum and heparin and sodium citrate plasmas. The serum PP19 concentration was increased by hemolysis. In blood cell fractions separated by the Ficoll-Paque/Macrodex method, polymorphonuclear leukocyte fraction contained the highest PP19 concentration. The circulating serum PP19 concentration was 4.5 +/- 1.1 ng/ml (mean +/- standard deviation) in the proliferative phase (n = 8) and 5.1 +/- 1.6 ng/ml in the secretory phase (n = 7) for nonpregnant women, and 4.6 +/- 2.2 ng/ml from men (n = 12). Seminal plasma (n = 8) contained 212.2 +/- 99.7 ng/ml. The maternal serum PP19 concentration in 291 normal pregnancies increased from 6.2 ng/ml (median) at 6-7 weeks of gestation to 34.1 ng/ml at 38-39 weeks. The mean PP19 concentration was higher in amniotic fluid and retroplacental blood, but lower in umbilical cord blood than that in circulating maternal serum. In hydatidiform mole, vesicular fluid contained high PP19 concentration (1154.6 +/- 659.5 ng/ml), although these maternal serum concentration was not statistically higher than normal range. The chorionic villous trophoblast contained more PP19 than decidua, chorion, and amnion. These results suggest that PP19 has an extraplacental source, even though the chorionic villous trophoblast may be the main source throughout pregnancy.

Nitric oxide attenuates adhesion molecule expression in human endothelial cells.

Leukocyte adhesion to vascular endothelium is a crucial step in the early stages of atherosclerosis, which may be mediated by the interaction of adhesion molecules expressed on the surfaces of both cell types. In this study, we investigated the effects of nitric oxide (NO) on the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in human umbilical vein endothelial cells (HUVECs). ICAM-1 and VCAM-1 protein and mRNA expression were determined by cellular ELISA and Northern blot analysis, respectively. Both ICAM-1 and VCAM-1 expression were increased markedly by interleukin-1 beta (IL-1 beta). This IL-1 beta-mediated induction of ICAM-1 and VCAM-1 expression was significantly inhibited in the presence of a NO donor 3-morpholino-sydnonimine (SIN-1) in a dose-dependent manner. The inhibitory effect of SIN-1 was abolished in the presence of a NO scavenger haemoglobin, while addition of 8-bromo-cGMP showed no significant effect on IL-1 beta-induced ICAM-1 or VCAM-1 expression. Northern blot analysis showed that IL-1 beta markedly increased ICAM-1 and VCAM-1 mRNA expression, while SIN-1 decreased the accumulation of these transcripts induced by IL-1 beta. These results suggest that NO could prevent the focal adhesion and accumulation of leukocytes through the inhibition of ICAM-1 and VCAM-1 expression in endothelial cells.