Serum amyloid A low-density lipoprotein levels and smoking status in obese Japanese patients.

Serum amyloid A low-density lipoprotein (SAA-LDL) is formed by an oxidative interaction and is considered to be a new marker related to oxidative modification of LDL. As the effect of smoking on oxidized LDL is of concern, this study investigated the association between SAA-LDL and smoking status. A total of 578 Japanese obese outpatients (mean ± SD age 50.5 ± 14.3 years) were studied. Smoking status was examined via a self-reported questionnaire. Cardio metabolic variables, including high-sensitivity Creactive protein (hsCRP), were analysed in addition to SAA-LDL. There was an increasing trend in SAA-LDL levels from non- to ex- to current smokers, and significantly higher SAA-LDL levels were observed in current smokers versus non-smokers (median SAA-LDL level 36 µg/ml versus 28 µg/ml, respectively). This significant difference was reduced after adjusting for multiple confounders, including lipid levels. Smoking may be associated with increased levels of SAA-LDL in an obese Japanese population, but further studies are needed.

Endothelin-1 binding to endothelin receptors in the rat anterior pituitary gland: interaction in the recognition of endothelin-1 between ETA and ETB receptors.

1. 125I-Endothelin (ET)-1 binding to the rat anterior pituitary gland was saturable and single, with a Kd of 71 pM and a Bmax of 120 fmol/mg. 2. When 1.0 microM BQ-123 (ETA antagonist) was added to the incubation buffer, the binding parameters were 8.3 pM and 8.0 fmol/mg, whereas 10 nM sarafotoxin S6c (ETB agonist) exerted little change in these binding parameters (Kd, 72 pM; Bmax, 110 fmol/mg). 3. ETB receptor-related compounds such as sarafotoxin S6c, ET-3, IRL1620, and BQ-788 competitively inhibited 125I-ET-1 binding, only when 1.0 microM BQ-123 was present in the incubation buffer. 4. Thus, the ETB receptor is capable of binding ET-1 when the ETA receptor is being occupied by BQ-123. A collaboration mechanism between the ETA and the ETB receptor may function in the recognition of ET-1, a typical "bivalent" ligand.

Endothelin receptor in microvessels isolated from human meningiomas: quantification with radioluminography.

1. We characterized specific 125I-endothelin-1 (125I-ET-1) binding sites in microvessels isolated from human meningiomas, using an in vitro quantitative receptor autoradiographic technique coupled to a radioluminographic imaging plate system. 2. This newly developed and highly sensitive method revealed high-affinity ET receptors present in pellet sections of the microvessels from all the meningiomas studied, regardless of histological subtypes (dissociation constant, 1.2 +/- 0.3 nM; maximum binding capacity, 185 +/- 56 fmol/mg; means +/- SE for nine tumors). 3. In five cases of meningiomas, ET-3 competed for 125I-ET-1 binding to microvessels from those tumors with a low affinity [50% inhibiting concentration (IC50) of 1.6 +/- 0.4 x 10(-6) M], and a selective ETB receptor agonist, sarafotoxin S6c, up to 10(-6) M, did not displace ET binding from the sections. 4. In the sections of microvessels from four other tumors, biphasic competition curves were obtained in the case of incubation in the presence of increasing concentrations of ET-3, with an IC50 of 1.1 +/- 0.2 x 10(-9) M for the high-affinity component and 1.6 +/- 0.3 x 10(-6) M for the low-affinity component, respectively. In addition, S6c competed for ET binding to those sections (IC50 = 2.3 +/- 0.2 x 10(-10) M) and 10(-6) M S6c displaced 30% of the control, corresponding to the high-affinity component of competition curves obtained in the presence of ET-3. 5. Our results suggest that (a) capillaries in human meningiomas express a large number of high-affinity ETA (non-ETB) receptors with a small proportion of ETB receptors, and (b) ET may have a role in neovascularization, tumor blood flow, and/or function of the blood-tumor barrier in meningioma tissues by interacting with specific receptors present on the surface of the endothelium.

Enhanced expression of an endothelin ETA receptor in capillaries from human glioblastoma: a quantitative receptor autoradiographic analysis using a radioluminographic imaging plate system.

We identified and characterized 125I-endothelin-1 (125I-ET-1) binding sites in tumor capillaries isolated from human glioblastomas, using the quantitative receptor autoradiographic technique with pellet sections. Quantification was done using the computerized radioluminographic imaging plate system. High-affinity ET receptors were localized in capillaries from glioblastomas and the surrounding brain tissues (KD = 4.7 +/- 1.0 x 10(-10) and 1.6 +/- 0.3 x 10(-10) M, respectively; Bmax = 161 +/- 38 and 140 +/- 37 fmol/mg, respectively; mean +/- SEM, n = 5). BQ-123, a selective antagonist for the ETA receptor, potently competed for 125I-ET-1 binding to sections of the microvessels with IC50 values of 5.1 +/- 0.3 and 5.1 +/- 1.5 nM, and 10(-6) M BQ-123 displaced 84 and 58% of ET binding to capillaries from tumors and brains, respectively. In addition, competition curves obtained in the presence of increasing concentrations of ET-3 showed two components (IC50 = 5.7 +/- 2.5 x 10(-10) and 1.4 +/- 0.2 x 10(-6) M for tumor microvessels, 1.8 +/- 0.6 x 10(-10) and 1.1 +/- 0.3 x 10(-6) M for brain microvessels, respectively). Our results indicate that (a) the method we used is simple and highly sensitive for detecting and characterizing various receptors in tumor capillaries, especially in the case of a sparse specimen, and (b) capillaries in glioblastomas express specific high-affinity ET binding sites, candidates for biologically active ET receptors, which predominantly belong to the ETA subtype.

A selective endothelin ETA antagonist, BQ-123, inhibits 125I-endothelin-1 (125I-ET-1) binding to human meningiomas and antagonizes ET-1-induced proliferation of meningioma cells.

1. We studied the effects of BQ-123, a selective ETA receptor antagonist, on 125I-endothelin-1 (125I-ET-1) binding to cell surface receptors in surgically exercised human meningiomas and on ET-1-induced DNA synthesis in cultured human meningioma cells in vitro, using a quantitative receptor autoradiographic technique with radioluminography and 3H-thymidine incorporation, respectively. 2. All of the human meningiomas expressed high-affinity binding sites for 125I-ET-1, regardless of differences in histological subtypes (Kd = 2.6 +/- 0.2 nM, Bmax = 374 +/- 93 fmol/mg; mean +/- SE; n = 9). 3. BQ-123 competed for 125I-ET-1 binding to sections of meningiomas with IC50S of 3.2 +/- 0.9 x 10(-7) M, and 10(-4) M BQ-123 displaced 80% of the binding. 4. ET-1 significantly stimulated DNA synthesis in cultured human meningioma cells, up to 170% of the basal level in the presence of 10(-9) M ET-1. BQ-123 inhibited ET-1 (10(-9) M)-induced DNA synthesis in meningioma cells, in a dose-dependent manner, and 10(-5) M BQ-123 reduced it to 120% of the basal level. 5. The number of meningioma cells determined after 4 days in culture was dose dependently increased in the presence of ET-1 (10(-9) and 10(-7) M). The growth rate of meningioma cells, incubated with 10(-9) M ET-1, was reduced by 50% in the presence of 10(-7) M BQ-123.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of a functional endothelin (ETA) receptor in human meningiomas.

Endothelin (ET) receptor subtypes (ETA and ETB) in human meningiomas were characterized using quantitative receptor autoradiography. A single class of high-affinity 125I-ET-1 binding sites was localized in all meningioma tissue studied (dissociation constant: 2.4 +/- 0.3 nM, maximum binding capacity: 319 +/- 66 fmol/mg (mean +/- standard error of the mean for 13 tumors)). Unlabeled ET-1 showed a strong affinity for 125I-ET-1 binding to tissue sections of the tumors with a 50% inhibiting concentration (IC50) of 2.9 +/- 0.7 x 10(-9) M, whereas ET-3 showed a much lower affinity (IC50: 8.4 +/- 2.5 x 10(-6) M). Sarafotoxin S6c, a selective agonist for the ETB receptor, could not compete for 125I-ET-1 binding to meningiomas. Endothelin-1 significantly stimulated deoxyribonucleic acid (DNA) synthesis in a dose-dependent manner in cultured human meningioma cells. In contrast, no significant stimulation of DNA synthesis occurred with an S6c concentration up to 10(-7) M. Pretreatment of the meningioma cells with pertussis toxin, a bacterial toxin that adds adenosine 5'-diphosphate-ribose to the alpha subunit of guanine nucleotide binding (G) proteins such as Gi or G(o), induced a concentration-dependent reduction in ET-stimulated DNA synthesis in meningioma cells, but did not affect the epidermal growth factor-induced DNA synthesis. These observations suggest that the ETA receptor is predominantly expressed in human meningioma tissue and that ET may act as a growth factor on the meningioma cells by interacting with the ETA receptor and by pertussis toxin-sensitive mechanisms.

Effect of suramin on 125I-insulin-like growth factor-I binding to human meningiomas and on proliferation of meningioma cells.

Suramin, a polyanionic compound, has been shown to inhibit the binding of various growth factors to cell surface receptors. The effects of suramin on 125I-insulin-like growth factor (IGF)-I binding to human meningioma tissues and IGF-I-induced deoxyribonucleic acid (DNA) synthesis in cultured meningioma cells were examined using the quantitative receptor autoradiographic method and 3H-thymidine incorporation, respectively. Suramin inhibited specific 125I-IGF-I binding to meningioma tissue sections in concentration-dependent manner, with a 50% inhibiting concentration (IC50) of 8.7 +/- 0.5 x 10(-5) M. The addition of 10(-3) M suramin to the incubation buffer potently dissociated 125I-IGF-I previously bound to meningioma tissue as a function of time (dissociation half-life (T1/2) 6.8 minutes). After preincubation of tissue sections with 10(-3) M suramin for 120 minutes, there was no inhibition of the subsequent 125I-IGF-I binding to meningiomas. Suramin inhibited the IGF-I-induced incorporation of 3H-thymidine into meningioma cells in a dose-dependent manner, with an IC50 of 4.6 +/- 1.4 x 10(-5) M. The growth rate of meningioma cells (determined 4 days after seeding) was reduced by 10%, 20%, and 50% of the control culture in the presence of 10(-6), 10(-5), and 10(-4) M suramin, respectively. These results suggest that suramin interferes with IGF-I binding to meningioma tissue and inhibits proliferation of cells, at least partially by preventing IGF-I-induced DNA synthesis and probably by interacting with IGF-I directly rather than with its binding sites.

Biphasic effects of suramin on 125I-epidermal growth factor binding to human meningiomas.

1. We studied the effects of suramin, a nonspecific growth factor antagonist, on epidermal growth factor (EGF) binding to cell surface receptors in surgically excised human meningiomas, using quantitative receptor autoradiographic methods with radioluminography. 2. High concentrations (10(-4) - 10(-2) M) of suramin inhibited 125I-EGF binding to meningioma sections with IC50's of 3.2 +/- 0.4 x 10(-4) M, whereas lower concentrations (10(-5) - 10(-4) M) of the drug significantly enhanced EGF binding to the tumor. Scatchard analysis of EGF binding profile revealed significant increases in binding affinity following incubation in the presence of 5 x 10(-5) M suramin, without significant alterations in maximal binding capacity. 3. The addition of 10(-3) M suramin to the incubation buffer rapidly dissociated 125I-EGF previously bound to meningioma tissues as a function of time (dissociation half-life, T1/2 = 12.4 min). 4. Preincubation in the presence of 5 x 10(-5) M suramin resulted in significant increases in the subsequent binding of 125I-EGF to meningiomas, compared to findings in the control. 5. Our data indicate that (a) suramin exerts biphasic effects on EGF binding to the tissue sections of meningiomas in vitro, depending on the concentration of the drug; and (b) low concentrations of suramin enhance the affinity of the EGF receptor in the tumor sections, probably by interacting with the EGF receptor molecule rather than with the EGF peptide. 6. The functional role of increased EGF receptor affinity in meningioma sections in the presence of lower concentrations of suramin remains to be determined.