Blood group B gene is barely expressed in in vitro erythroid culture of Bm-derived CD34+ cells without an erythroid cell-specific regulatory element.

BACKGROUND AND OBJECTIVES: Previously, a weak phenotype Am or Bm was assumed to be caused by a reduction of A or B gene expression in bone marrow cells, but not in mucus-secreting cells. However, ABO expression has not been examined in erythroid progenitor cells of Am or Bm individuals. MATERIALS AND METHODS: We carried out in vitro erythroid differentiation of CD34(+) cells from peripheral blood of a Bm individual harbouring a 3.0-kb deletion including an erythroid cell-specific regulatory element, named the +5.8-kb site, in intron 1 of the human ABO blood group gene. RESULTS: During the in vitro differentiation of CD34(+) cells from this Bm individual into erythroid cells, B-antigens were not detectable on the cultured cells by flow cytometric analysis, and allele-specific RT-PCR consistently detected the transcripts from the O allele, but not from the B allele. Moreover, chromatin immunoprecipitation assay demonstrated that both RUNX1 and GATA-2 or GATA-1 were bound to the +5.8-kb site in cultured erythroid cells expressing ABO. CONCLUSION: It is likely that the +5.8-kb site enhances transcription from the ABO promoter in erythroid cells through binding of RUNX1 and GATA-2 or GATA-1.

Transcription factors NF-IL6 and CREB recognize a common essential site in the human prointerleukin 1 beta gene.

A site located between -2782 and -2729 of the human prointerleukin-1 beta (IL1B) gene functions as a strong lipopolysaccharide (LPS)-responsive enhancer independent of the previously identified enhancer located between -2896 and -2846 (F. Shirakawa, K. Saito, C.A. Bonagura, D.L. Galson, M. J. Fenton, A. C. Webb, and P. E. Auron, Mol. Cell. Biol. 13:1332-1344, 1993). Although these two enhancers appear to function cooperatively in the native sequence context, they function independently as LPS-responsive elements upon removal of an interposed silencer sequence. The new enhancer is not induced by dibutyryl cyclic AMP (dbcAMP) alone but is superinduced by costimulation with LPS-dbcAMP. This pattern of induction depends upon the nature of the sequence, a composite NF-IL6-cAMP response element (CRE) binding site. This pseudosymmetrical sequence is shown to contrast with a classical symmetric CRE which responds to dbcAMP but not LPS. DNA binding studies using in vivo nuclear extract, recombinant proteins, and specific antibodies show that LPS induces the formation of two different complexes at the enhancer: (i) an NF-IL6-CREB heterodimer and (ii) a heterodimer consisting of NF-IL6 and a non-CREB, CRE-binding protein. Cotransfection studies using NF-IL6 and CREB expression vectors show that NF-IL6 transactivates the enhancer in the presence of LPS, whereas CREB acts either positively or negatively, depending upon its cAMP-regulated phosphorylation state. Our data demonstrate that the newly identified enhancer is a specialized LPS-responsive sequence which can be modulated by cAMP as a result of the involvement of NF-IL6-CRE-binding protein heterodimers.

A novel STAT-like factor mediates lipopolysaccharide, interleukin 1 (IL-1), and IL-6 signaling and recognizes a gamma interferon activation site-like element in the IL1B gene.

Binding of many cytokines to their cognate receptors immediately activates Jak tyrosine kinases and their substrates, STAT (signal transducers and activators of transcription) DNA-binding proteins. The DNA binding targets of STATs are sequence elements related to the archetypal gamma interferon activation site, GAS. However, association of interleukin 1 (IL-1) with Jak-STAT signaling has remained unresolved. We now report an element termed LILRE (lipopolysaccharide [LPS] and IL-1-responsive element) in the human prointerleukin 1beta gene (IL1B) which can be immediately induced by either lipopolysaccharide (LPS) or IL-1 protein to bind a tyrosine-phosphorylated protein. This LPS- and IL-1-induced factor (LIL factor) is recognized by an antibody raised against the N terminus of Stat1, but not by those specific for either the C terminus of Stat1 or any other GAS-binding STAT. Phosphotyrosine (P-Tyr) specifically inhibits formation of the LIL factor-DNA complex, suggesting the importance of P-Tyr for the DNA-binding activity, as has been found for all STAT dimers. Analysis of DNA-binding specificity demonstrates that the LIL factor possesses a novel GAS-like binding activity that contrasts with those of other STATs in a requirement for a G residue at position 8 (TTCCTGAGA). Further investigation has revealed that IL-6, but neither IL-4 nor gamma interferon, activates the LIL factor. Thus, the existence of such a STAT-like factor (LIL-Stat) relates the LPS and IL-1 signaling pathway to other cytokine receptor signaling pathways via the activation of STATs. Moreover, the unique DNA-binding specificity and antigenicity of this factor suggest that LPS, IL-1, and IL-6 may use a common signaling pathway.

Mismatch of minor histocompatibility antigen contributes to a graft-versus-leukemia effect rather than to acute GVHD, resulting in long-term survival after HLA-identical stem cell transplantation in Japan.

We determined the alleles of five polymorphic molecules including HA-1 and four adhesion molecules for 106 patients transplanted with HLA-identical stem cell grafts and investigated the association of mismatches as correlates of relapse and graft-versus-host disease (GVHD). All 106 recipients underwent stem cell transplantation (SCT) after myeloablative conditioning between 1985 and 2002. Risk status of disease at SCT was standard (n=63) and high (n=42). After SCT, 36, 49 and 33 developed acute GVHD, chronic GVHD and relapsed, respectively. Our patients relapsed at rates of 16.7 and 38.6% with one or more and without incompatibilities (P=0.013). The relapse rates of patients with CD62L, CD31 codon 563, CD31 codon 125, HA-1 and CD49b incompatibilities were 5.9, 11.8, 15.4, 16.0 and 33.3%, respectively. The frequency of acute GVHD did not differ regardless of incompatibilities. In standard-risk group, the accumulated relapse rates of 19 and 44 patients with and without minor histocompatibility antigen incompatibility were 22% and unexpectedly 66%, respectively (P=0.02). The probability of 12-year survival was 88% in the former and 66% in the latter patients (P=0.03). Our data suggest that incompatibility of CD62L, CD31 codon 563 and CD31 codon 125 contributes to a graft-versus-leukemia effect rather than to GVHD, resulting in prolonged survival after HLA-identical SCT.

Regulation of Chk2 gene expression in lymphoid malignancies: involvement of epigenetic mechanisms in Hodgkin's lymphoma cell lines.

The tumor suppressor Chk2 kinase plays crucial roles in regulating cell-cycle checkpoints and apoptosis following DNA damage. We investigated the expression levels of the genes encoding Chk2 and several cell-cycle regulators in nine cell lines from lymphoid malignancies, including three Hodgkin's lymphoma (HL) lines. We found that all HL cell lines exhibited a drastic reduction in Chk2 expression without any apparent mutation of the Chk2 gene. However, expression of Chk2 in HL cells was restored following treatment with the histone deacetylase inhibitors trichostatin A (TsA) and sodium butyrate (SB), or with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5Aza-dC). Chromatin-immunoprecipitation (Chip) assays revealed that treatment of HL cells with TsA, SB or 5Aza-dC resulted in increased levels of acetylated histones H3 and H4, and decreased levels of dimethylated H3 lysine 9 at the Chk2 promoter. These results indicate that expression of the Chk2 gene is downregulated in HL cells via epigenetic mechanisms.

Effect of YM087, a potent nonpeptide vasopressin antagonist, on vasopressin-induced protein synthesis in neonatal rat cardiomyocyte.

OBJECTIVE: Hypertrophy of cardiomyocytes may play an important role in the pathogenesis of cardiac hypertrophy associated with various cardiovascular diseases such as congestive heart failure. The aim of this study was to investigate whether vasopressin (AVP) induces protein synthesis in cultured neonatal rat cardiomyocytes through its specific receptor and whether YM087, a newly synthesized nonpeptide AVP receptor antagonist, inhibits AVP-induced protein synthesis in vitro. METHODS: AVP receptors on cardiomyocytes were characterized using the radioligand [3H] AVP. The effects of AVP and YM087 on intracellular free calcium concentration ([Ca2+]i), mitogen-activated protein (MAP) kinase and [3H]-leucine incorporation were investigated in cultured neonatal rat cardiomyocytes. RESULTS: In cardiomyocytes, Scatchard analysis showed a single population of high-affinity binding sites with the expected AVP V1A receptor subtype profile. YM087 showed high affinity for cardiomyocyte V1A receptors with a Ki value of 0.63 nM. In these same cells, YM087 potently inhibited AVP-induced increases in [CA2+]I and activation of MAP kinase in a concentration-dependent manner. In addition, AVP concentration-dependently stimulated the synthesis of protein without changing the rate of DNA synthesis, and YM087 prevented AVP-induced protein synthesis in a concentration-dependent manner. CONCLUSIONS: These results suggest that AVP directly causes protein synthesis and YM087 is a potent inhibitor of AVP-induced protein synthesis of cardiomyocytes and thus may have beneficial effects in the development and regression of cardiomyocytic hypertrophy.

Phosphatidylinositol 3-kinase is recruited to a specific site in the activated IL-1 receptor I.

Interleukin 1 (IL-1) delivers a stimulatory signal which increases the expression of a set of genes by modulating the transcription factor NF-kappaB. The IL-1 receptors are transmembrane glycoproteins which lack a catalytic domain. The C-terminal portion of the type I IL-1 receptor (IL-IRI) is essential for IL-1 signalling and for IL-1 dependent activation of NF-kappaB. This portion contains a putative phosphatidylinositol 3-kinase (PI 3-kinase) binding domain (Tyr-E-X-Met), which is highly conserved between the human, mouse and chicken sequences, as well as the related cytoplasmic domain of the Drosophila receptor Toll. This observation prompted us to investigate the role of PI 3-kinase in IL-1 signalling. Here we report evidence that PI 3-kinase is recruited by the activated IL-IRI, causing rapid and transient activation of PI 3-kinase. We also show that the receptor is tyrosine phosphorylated in response to IL-1. Expression of a receptor mutant lacking the putative binding site for p85 demonstrates that Tyr479 in the receptor cytoplasmic domain is essential for PI 3-kinase activation by IL-1. Our results indicate that PI 3-kinase is likely to be an important mediator of some IL-1 effects, providing docking sites for additional signalling molecules.

Pharmacologic characterization of the oxytocin receptor in human uterine smooth muscle cells.

[(3)H]-oxytocin was used to characterize the oxytocin receptor found in human uterine smooth muscle cells (USMC). Specific binding of [(3)H]-oxytocin to USMC plasma membranes was dependent upon time, temperature and membrane protein concentration. Scatchard plot analysis of equilibrium binding data revealed the existence of a single class of high-affinity binding sites with an apparent equilibrium dissociation constant (K(d)) of 0.76 nM and a maximum receptor density (B(max)) of 153 fmol mg(-1) protein. The Hill coefficient (n(H)) did not differ significantly from unity, suggesting binding to homogenous, non-interacting receptor populations. Competitive inhibition of [(3)H]-oxytocin binding showed that oxytocin and vasopressin (AVP) receptor agonists and antagonists displaced [(3)H]-oxytocin in a concentration-dependent manner. The order of potencies for peptide agonists and antagonists was: oxytocin>[Asu(1,6)]-oxytocin>AVP= atosiban>d(CH(2))(5)Tyr(Me)AVP>[Thr(4),Gly(7)]-oxytocin>dDAVP, and for nonpeptide antagonists was: L-371257>YM087>SR 49059>OPC-21268>SR 121463A>OPC-31260. Oxytocin significantly induced concentration-dependent increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) and hyperplasia in USMC. The oxytocin receptor antagonists, atosiban and L-371257, potently and concentration-dependently inhibited oxytocin-induced [Ca(2+)](i) increase and hyperplasia. In contrast, the V(1A) receptor selective antagonist, SR 49059, and the V(2) receptor selective antagonist, SR 121463A, did not potently inhibit oxytocin-induced [Ca(2+)](i) increase and hyperplasia. The potency order of antagonists in inhibiting oxytocin-induced [Ca(2+)](i) increase and hyperplasia was similar to that observed in radioligand binding assays. In conclusion, these data provide evidence that the high-affinity [(3)H]-oxytocin binding site found in human USMC is a functional oxytocin receptor coupled to [Ca(2+)](i) increase and cell growth. Thus human USMC may prove to be a valuable tool in further investigation of the physiologic and pathophysiologic roles of oxytocin in the uterus. British Journal of Pharmacology (2000) 129, 131 - 139

Pharmacological characterization of the human vasopressin receptor subtypes stably expressed in Chinese hamster ovary cells.

Three subtypes of human (h) arginine vasopressin (AVP) receptors, hV1A, hV1B and hV2, were stably expressed in Chinese hamster ovary (CHO) cells and characterized by [3H]-AVP binding studies. In addition, the coupling of the expressed receptor protein to a variety of signal transduction pathways was investigated. Scatchard analysis of saturation isotherms for the specific binding of [3H]-AVP to membranes, prepared from CHO cells transfected with hV1A, hV1B and hV2 receptors, yielded an apparent equilibrium dissociation constant (Kd) of 0.39, 0.25 and 1.21 nM and a maximum receptor density (Bmax) of 1580 fmol mg(-1) protein, 5230 fmol mg(-1) protein and 7020 fmol mg(-1) protein, respectively. Hill coefficients did not differ significantly from unity, suggesting binding to homogenous, non-interacting receptor populations. Pharmacological characterization of the transfected human AVP receptors was undertaken by measuring the relative ability of nonpeptide AVP receptor antagonists, YM087, OPC-21268, OPC-31260, SR 49059 and SR 121463A, to inhibit binding of [3H]-AVP. At hV1A receptors, the relative order of potency was SR49059>YM087>OPC-31260>SR 121463A> >OPC-21268 and at hV2 receptors, YM087=SR 121463A>OPC-31260>SR 49059> >OPC-21268. In contrast, the relative order of potency, at hV1B receptors, was SR 49059> >SR 121463A=YM087=OPC-31260=OPC-21268. In CHO cells expressing either hV1A or hV1B receptors, AVP caused a concentration-dependent increase in intracellular Ca2+ concentration ([Ca2+]i) with an EC50 value of 1.13 nM and 0.90 nM, respectively. In contrast, stimulation of CHO cells expressing hV2 receptors resulted in an accumulation of cyclic AMP with an EC50 value of 2.22 nM. The potency order of antagonists in inhibiting AVP-induced [Ca2+]i or cyclic AMP response was similar to that observed in radioligand binding assays. In conclusion, we have characterized the pharmacology of human cloned V1A, V1B and V2 receptors and used these to determine the affinity, selectivity and potency of nonpeptide AVP receptor antagonists. Thus they may prove to be a valuable tool in further examination of the physiological and pathophysiological roles of AVP.

Effects of YM471, a nonpeptide AVP V(1A) and V(2) receptor antagonist, on human AVP receptor subtypes expressed in CHO cells and oxytocin receptors in human uterine smooth muscle cells.

YM471, (Z)-4'-[4,4-difluoro-5-[2-(4-dimethylaminopiperidino)-2-oxoethylidene]-2,3,4,5-tetrahydro-1H-1-benzoazepine-1-carbonyl]-2-phenylbenzanilide monohydrochloride, is a newly synthesized potent vasopressin (AVP) receptor antagonist. Its effects on binding to and signal transduction by cloned human AVP receptors (V(1A), V(1B) and V(2)) stably expressed in Chinese hamster ovary (CHO) cells, and oxytocin receptors in human uterine smooth muscle cells (USMC) were studied. YM471 potently inhibited specific [(3)H]-AVP binding to V(1A) and V(2) receptors with K(i) values of 0.62 nM and 1.19 nM, respectively. In contrast, YM471 exhibited much lower affinity for V(1B) and oxytocin receptors with K(i) values of 16.4 microM and 31.6 nM, respectively. In CHO cells expressing V(1A) receptors, YM471 potently inhibited AVP-induced intracellular Ca(2+) concentration ([Ca(2+)](i)) increase, exhibiting an IC(50) value of 0.56 nM. However, in human USMC expressing oxytocin receptors, YM471 exhibited much lower potency in inhibiting oxytocin-induced [Ca(2+)](i) increase (IC(50)=193 nM), and did not affect AVP-induced [Ca(2+)](i) increase in CHO cells expressing V(1B) receptors. Furthermore, in CHO cells expressing V(2) receptors, YM471 potently inhibited the production of cyclic AMP stimulated by AVP with an IC(50) value of 1.88 nM. In all assays, YM471 showed no agonistic activity. These results demonstrate that YM471 is a potent, nonpeptide human V(1A) and V(2) receptor antagonist which will be a valuable tool in defining the physiologic and pharmacologic actions of AVP.

Usefulness of neutral red uptake method for investigation of the effects of recombinant hemopoietic growth factors on leukemic blasts proliferation.

By a colorimetric assay with dye (neutral red), the effects of recombinant human hemopoietic growth factors (rhG-CSF, rhGM-CSF, rhIL-3 and rhEPO) on the proliferation of leukemic blasts in vitro were investigated. Leukemic blasts were obtained from eight patients with acute myeloid leukemia (AML) (M1: two cases, M3: two cases, M4: four cases) and from four patients with acute lymphoid leukemia (ALL) (L2: four cases). It was shown that rhG-CSF, rhGM-CSF and rhIL-3 stimulated the blast proliferation in most cases of AML, although the degree and pattern of responses showed a striking variability in different patients. Moreover, rhGM-CSF and rhIL-3 also stimulated the leukemic blasts from some cases of ALL. No clear morphological modification providing evidence for terminal differentiation was observed when assessed by Wright stain. On the other hand, rhEPO did not have any stimulating effects on leukemic blasts in all cases. These results indicate the necessity of investigating the responses of leukemic blasts to hemopoietic growth factors in each patient prior to clinical use of such factors. For this assay, neutral red uptake method is useful because of its simplicity, rapidity, precision and convenience for handling a large volume of materials.

Binding characteristics of YM087, an AVP receptor antagonist, in rhesus monkey liver and kidney membranes.

The binding characteristics of YM087, a nonpeptide vasopressin (AVP) V1A and V2 receptor antagonist, were studied using 3H-AVP binding to rhesus monkey liver and kidney membrane preparations. Both membrane preparations exhibited one class of high-affinity binding sites. However each membrane's receptors were different, with Kd values of 0.57 and 1.11 nM, Bmax values of 59.6 and 147 fmol/mg protein for liver and kidney, respectively. AVP receptor agonist or antagonist binding inhibition studies confirmed that these receptors belong to the V1A (liver) and V2 (kidney) subtypes. YM087 showed high affinity for both liver V1A and kidney V2 receptors with Ki values of 26.3 and 9.89 nM, respectively. These results show that YM087 is a potent, nonpeptide dual AVP V1A and V2 receptor antagonist, and would be a powerful tool for understanding the physiologic roles of AVP.

Characterization of rodent liver and kidney AVP receptors: pharmacologic evidence for species differences.

Radioligand binding studies with [3H]vasopressin (AVP) were used to determine the affinities of AVP receptor agonists and antagonists for mouse liver and kidney plasma membrane preparations. Both membrane preparations exhibited one class of high-affinity binding site. AVP ligand binding inhibition studies confirmed that mouse liver binding sites belong to the V1A subtype while kidney binding sites belong to the V2 receptor subtype. The affinity of each ligand for mouse V1A receptors was very similar to that for rat V1A receptors, showing differences in Ki values of less than 3-fold. In contrast, several peptide (d(CH2)5Tyr(Me)AVP) and nonpeptide (OPC-21268 and SR 49059) ligands had different affinities for mouse and rat kidney V2 receptors, with differences in Ki values ranging from 14- to 17-fold. These results indicate that mouse and rat kidney V2 receptors show significant pharmacologic differences.

Characterization of vasopressin receptor in rat lung.

This study characterized rat lung membrane arginine vasopressin (AVP) receptors in detail. Specific binding of [3H]AVP to rat lung membranes was dependent upon time, temperature and membrane protein concentration. Scatchard plot analysis of equilibrium binding data revealed the existence of a single class of high-affinity binding sites with a Kd of 0.45 nM and a Bmax of 76.6 fmol/mg protein. Competitive inhibition of [3H]AVP binding showed that neurohypophysial hormones as well as their synthetic analogues displaced [3H]AVP in a concentration-dependent manner. The order of potencies for the native peptides was: AVP > lysine vasopressin = arginine vasotocin > oxytocin. Furthermore, potent V1A receptor antagonists, d(CH2)5Tyr(Me)AVP and dPTyr(Me)AVP, showed high affinity for lung membranes. In contrast, the V2 receptor agonist, dDAVP, and the specific oxytocin receptor agonist, [Thr4,Gly7]oxytocin, did not affect AVP binding. These results suggest that the lung contains the V1A receptor subtype. The lung membrane AVP receptor characterized in this study may play an important role in mediating the physiological effects of AVP in the lung.

Enhancing effects of IL-2 on M-CSF production by human peripheral blood monocytes.

Monocytes have the capacity to produce granulopoietic factors such as M-CSF and G-CSF. Our findings here showed that interleukin-2 (IL-2), at a concentration of more than 0.05 ng/ml, led to a 12-fold increase in the production of M-CSF in the human peripheral blood mononuclear cells after 72 h incubation compared to the control culture. Even in purified monocyte cultures with added IL-2, a 3-fold increase in M-CSF production was observed at an IL-2 concentration of 50 ng/ml. The enhancing effect of IL-2 on M-CSF secretion was also observed when IL-2-stimulated non-phagocytic cell-conditioned medium was added to monocyte cultures. These results indicated that IL-2, both directly and indirectly, activated monocytes to enhance the production of M-CSF. In addition, the expression of IL-2 receptor (CD25) on monocytes was more enhanced in cultures containing IL-2 than in cultures without IL-2. On the other hand, IL-2 did not induce G-CSF production in purified monocytes. These in vitro results suggest that when IL-2 is used clinically, the various biological activities of M-CSF should also be taken into consideration.

Pharmacological profile of YM087, a novel nonpeptide dual vasopressin V1A and V2 receptor antagonist, in dogs.

The pharmacological profile of YM087 (4'-[(2-methyl-1,4,5,6-tetrahydroimidazo[4,5-d][1]benzazepin -6-yl) carbonyl]-2-phenylbenzanilide monohydrochloride) was investigated in dogs. YM087 showed high affinity for vasopressin V1A and V2 receptors in radioligand receptor binding studies with dog platelets (V1A) and kidney (V2). Intravenously injected YM087 (3-100 micrograms/kg) dose dependently inhibited the pressor response to exogenous vasopressin in anesthetized dogs. Intravenous (10-100 micrograms/kg) and oral (30-300 micrograms/kg) administration of YM087 dose dependently increased urine flow with little effect on urinary sodium and potassium excretion in normally hydrated conscious dogs. Concomitantly, the urine osmolality dropped below the plasma osmolality (300 mOsm/kg H2O). In contrast, intravenously injected furosemide (300 micrograms/kg) increased urine flow with marked increases in urinary sodium and potassium excretion. These results indicate that YM087 is the first orally effective dual vasopressin V1A and V2 receptor antagonist and that it will be a new tool in the investigation of the physiological and pathophysiological role of vasopressin in the cardiovascular system and kidney. YM087 may be useful for the treatment of patients with congestive heart failure, renal diseases and water-retaining diseases.

Cardiovascular and renal effects of conivaptan hydrochloride (YM087), a vasopressin V1A and V2 receptor antagonist, in dogs with pacing-induced congestive heart failure.

The systemic hemodynamic and renal responses to conivaptan hydrochloride (YM087; 4'-(2-methyl-1,4,5,6-tetrahydroimidazo[4,5-d][1]benzoazepine -6-carbonyl)-2-phenylbenzanilide monohydrochloride), a vasopressin V1A and V2 receptor antagonist, were determined in pentobarbital-anesthetized dogs after 2 to 3 weeks of rapid right ventricular pacing. Congestive heart failure, characterized by decreases in first derivative of left ventricular pressure (left ventricular d P/dt(max)) and cardiac output, and increases in left ventricular end-diastolic pressure and total peripheral vascular resistance, was induced by chronic rapid right ventricular pacing at 260-280 beats/min. Intravenous administration of conivaptan (0.1 mg/kg) significantly increased left ventricular dP/dt(max) and cardiac output and significantly decreased left ventricular end-diastolic pressure and total peripheral vascular resistance. Conivaptan also increased urine flow and reduced urine osmolality by markedly increasing free water clearance. These results indicate that conivaptan produced hemodynamic improvement and marked aquaresis in dogs with congestive heart failure. Therefore, conivaptan may find clinical use in treating patients with congestive heart failure.

Comparison of vasopressin binding sites in human uterine and vascular smooth muscle cells.

Several studies indicate that oxytocin and vasopressin receptors in the human uterus are heterogeneous. We have investigated whether oxytocin and vasopressin bind to separate receptors or one class of receptors in human uterine smooth muscle cells. [3H]d(CH2)5Tyr(Me)AVP, the vasopressin V1A receptor selective radioligand, was used for comparison of vasopressin binding sites in human uterine and vascular smooth muscle cell membranes. Both membrane preparations exhibited one class of high-affinity binding sites with Kd values of 6.44 and 0.47 nM, Bmax values of 166 and 34.8 fmol/mg protein for uterine and vascular smooth muscle cells, respectively. In vascular preparations, the selective vasopressin V1A receptor antagonist, SR 49059 ((2S) 1-[(2R 3S)-(5-chloro-3-(2-chlorophenyl)- -(3.4-dimethoxybenzenesulfonyl)-3-hydroxy-2,3-dihydro-1H-indole-2- carbonyl]-pyrrolidine-2-carboxamide), showed high affinity with Ki value of 0.98 nM, confirming that these receptors belong to the vasopressin V1A receptor subtype. On the contrary, in uterine preparations, binding of [3H]d(CH2)5Tyr(Me)AVP was more effectively displaced by oxytocin and the oxytocin receptor selective antagonist, L-371257, (1-[1-[4-[ N-Acetyl-4-piperidinyl)oxy]2-methoxybenzoyl]piperidin-4-yl]- 4H-3,1-benzoxazin-2(1H)-one), than vasopressin and SR 49059, suggesting that binding may be due to cross-reaction with the oxytocin receptors. These results suggest that human uterine smooth muscle cells express only a high density of oxytocin receptors.

Vasopressin increases vascular endothelial growth factor secretion from human vascular smooth muscle cells.

Vascular endothelial growth factor (VEGF) is a potent and specific mitogen of vascular endothelial cells which promotes neovascularization in vitro. To determine whether vasopressin induces VEGF secretion in human vascular smooth muscle cells, we performed enzyme-linked immunosorbent assays. Vasopressin potently induced a time-dependent and concentration-dependent (maximal, 10(-7) M) increase in VEGF secretion by human vascular smooth muscle cells that was maximal after 24 h. Furthermore, vasopressin also concentration-dependently caused mitogenic effect, as reflected by total protein content of cells per culture well. These vasopressin-induced VEGF secretion increase and mitogenic effect of these cells were potently inhibited by vasopressin V1A receptor antagonists, confirming this is a vasopressin V1A receptor-mediated event. These results indicate that vasopressin increases VEGF secretion in human vascular smooth muscle cells, the magnitude of VEGF secretion being temporally related to the mitogenic effect of vascular smooth muscle cells and the potency of the growth-promoting stimulus. Vasopressin-induced VEGF secretion by proliferating vascular smooth muscle cells could act as a paracrine hormone to powerfully influence the permeability and growth of the overlying vascular endothelium, vasopressin play a more fundamental role in the regulation of vascular function than has previously been recognized.

Pharmacological characterization of YM087, a potent, nonpeptide human vasopressin V1A and V2 receptor antagonist.

The effects of YM087 (4'-[(2-methyl-1,4,5,6-tetrahydroimidazo[4,5-d] [1]benzazepin-6-yl)-carbonyl]-2-phenylbenzanilide monohydrochloride), a novel nonpeptide vasopressin (AVP) receptor antagonist, on [3H]AVP binding to human AVP receptors (V1A, V1B and V2) cloned and transiently expressed in COS-1 cells generated from monkey renal tissue were studied. Scatchard analysis of saturation isotherms for the specific binding of [3H]AVP to membranes, prepared from COS-1 cells transfected with human V1A, V1B and V2 receptors, yielded an apparent equilibrium dissociation constant (Kd) of 0.67 nM, 0.28 nM and 2.14 nM and a maximum receptor density (Bmax) of 2180 fmol/mg protein, 369 fmol/mg protein and 2660 fmol/mg protein, respectively. YM087 showed high affinity for AVP V1A and V2 receptors with Ki values of 6.3 and 1.1 nM, respectively, but had no effect on [3H]AVP binding to AVP V1B receptors. In COS-1 cells expressing either AVP V1A or V1B receptors, AVP caused a concentration-dependent increase in intracellular Ca2+ concentration ([Ca2+]i). YM087 inhibited the AVP-induced increase in [Ca2+]i in COS-1 cells expressing AVP V1A receptors in a concentration-dependent manner with an IC50 value of 14.3 nM, but did not influence this increase in AVP V1B-receptor expressing cells. In contrast, stimulation of COS-1 cells expressing AVP V2 receptors resulted in an accumulation of cAMP. YM087 inhibited AVP-induced cAMP production in COS-1 cells expressing AVP V2 receptors in a concentration-dependent manner with an IC50 value of 1.95 nM. In all assays used, YM087 was devoid of any agonistic activity. These results suggest that YM087 is a potent nonpeptide dual human AVP V1A and V2 receptor antagonist, and that YM087 will be a powerful tool in investigation of the physiological and pathophysiological roles of AVP.