Pharmacological and biochemical characterization of A3 adenosine receptors in Jurkat T cells

1. The present work was devoted to the study of A3 adenosine receptors in Jurkat cells, a human leukemia line. 2. The A3 subtype was found by means of RT-PCR experiments and characterized by using the new A3 adenosine receptor antagonist [3H]-MRE 3008F20, the only A3 selective radioligand currently available. Saturation experiments revealed a single high affinity binding site with K(D) of 1.9+/-0.2 nM and B(max) of 1.3+/-0.1 pmol mg(-1) of protein. 3. The pharmacological profile of [3H]-MRE 3008F20 binding on Jurkat cells was established using typical adenosine ligands which displayed a rank order of potency typical of the A3 subtype. 4. Thermodynamic data indicated that [3H]-MRE 3008F20 binding to A3 subtype in Jurkat cells was entropy- and enthalpy-driven, according with that found in cells expressing the recombinant human A3 subtype. 5. In functional assays the high affinity A3 agonists Cl-IB-MECA and IB-MECA were able to inhibit cyclic AMP accumulation and stimulate Ca(2+) release from intracellular Ca(2+) pools followed by Ca(2+) influx. 6. The presence of the other adenosine subtypes was investigated in Jurkat cells. A1 receptors were characterized using [3H]-DPCPX binding with a K(D) of 0.9+/-0.1 nM and B(max) of 42+/-3 fmol mg(-1) of protein. A2A receptors were studied with [3H]-SCH 58261 binding and revealed a K(D) of 2.5+/-0.3 nM and a B(max) of 1.4+/-0.2 pmol mg(-1) of protein. 7. In conclusion, by means of the first antagonist radioligand [3H]-MRE 3008F20 we could demonstrate the existence of functional A3 receptors on Jurkat cells.     

Toxicogenomics of A375 human malignant melanoma cells

Toxicogenomics applications are increasingly applied to the evaluation of preclinical drug safety, and to explain toxicities associated with compounds at the mechanism level. In this review, we aim to describe the application of toxicogenomics tools for studying the genotoxic effect of active compounds on the gene-expression profile of A375 human malignant melanoma cells, through the other molecular functions of target genes, regulatory pathways and mechanisms of malignant melanomas. It also includes the current systems biology approaches, which are very useful for analyzing the biological system and understanding the entire mechanisms of malignant melanomas. We believe that this review would be very potent and useful for studying the toxicogenomics of A375 melanoma cells, and for further diagnostic and therapeutic applications.     

Pharmacological characterization of novel adenosine ligands in recombinant and native human A2B receptors

The present study was designed to evaluate the effects of novel and recognised compounds at human recombinant A(2B) adenosine receptors expressed in Chinese hamster ovary (hA(2B)CHO), in human embryonic kidney 293 (hA(2B)HEK-293) and at endogenous A(2B) receptors in human mast cells (HMC-1). Saturation binding experiments performed using the new high affinity A(2B) adenosine radioligand [(3)H]-N-benzo[1,3]dioxol-5-yl-2-[5-(2,6-dioxo-1,3-dipropyl-2,3,6,7-tetra hydro-1H-purin-8-yl)-1-methyl-1H-pyrazol-3-yloxy]-acetamide ([(3)H]-MRE 2029F20) revealed a single class of binding sites in hA(2B)CHO, hA(2B)HEK-293 and HMC-1 cells with K(D) (nM) of 1.65+/-0.18, 2.83+/-0.34, 2.62+/-0.27 and B(max) (fmol/mg protein) of 36+/-4, 475+/-50 and 128+/-15, respectively. The pharmacological profile of new compounds, determined in inhibition binding experiments in hA(2B)HEK-293 cells using [(3)H]-MRE 2029F20, showed a rank order of potency typical of the A(2B) receptors with K(i) values in the range 3.2-28nM. In functional assays, recognised agonists and antagonists were studied by evaluating their capability to modulate the cAMP production in hA(2B)CHO and in HMC-1 cells. Novel compounds were able to decrease NECA-stimulated cAMP production in hA(2B)CHO and in HMC-1 cells showing a high potency. New compounds were also able to inhibit cAMP levels in the absence of NECA and in the presence of forskolin stimulation in hA(2B)CHO and in HMC-1 cells. In HEK-293 cells MRE 2029F20 reduced cAMP basal levels with an IC(50) value of 2.9+/-0.3nM. These results suggest that novel compounds are antagonists with an inverse agonist activity in recombinant and native human A(2B) receptors.     

Pharmacological and biochemical characterization of purified A2a adenosine receptors in human platelet membranes by [3H]-CGS 21680 binding.

1. The binding properties of human platelet A2a adenosine receptors, assayed with the A2a-selective agonist, [3H]-2-[p-(2-carboxyethyl)-phenethylamino]-5''-N-ethylcarboxamidoad enosine ([3H]-CGS 21680), are masked by a non-receptorial component, the adenotin site. In order to separate A2a receptors from adenotin sites, human platelet membranes were solubilized with 1% 3-[(3-cholamidopropyl)dimethyl-ammonio]-1-propanesulphonate (CHAPS). The soluble platelet extract was precipitated with polyethylene glycol (PEG) and the fraction enriched in adenosine receptors was isolated from the precipitate by differential centrifugation. 2. The present paper describes the binding characteristics of the selective A2a agonist, [3H]-CGS 21680, to this purified platelet membrane preparation. In addition, receptor affinity and potency of several adenosine agonists and antagonists were determined in binding and adenylyl cyclase studies. 3. Saturation experiments revealed a single class of binding site with Kd and Bmax values of 285 nM and 2.07 pmol mg-1 of protein respectively. Adenosine receptor ligands competed for the binding of 50 nM [3H]-CGS 21680 to purified protein, showing a rank order of potency consistent with that typically found for interactions with the A2a adenosine receptors. In the adenylyl cyclase assay the compounds examined exhibited a rank order of potency very close to that observed in binding experiments. 4. Thermodynamic data indicated that [3H]-CGS 21680 binding to the purified receptor is totally entropy-driven in agreement with results obtained in rat striatal A2a adenosine receptors. 5. It is concluded that in the purified platelet membranes there is a CGS 21680 binding site showing the characteristic properties of the A2a receptor. This makes it possible to use this compound for reliable radioligand binding studies on the A2a adenosine receptor of human platelets.     

Pharmacological characterization of A1 adenosine receptors in isolated rat ventricular myocytes

Summary The aim of the present study was the characterization of adenosine receptors in isolated rat ventricular myocytes. The CAMP-levels of rat ventricular myocytes in the presence of 1 mol/l isoprenaline were reduced by up to 48% by adenosine analogues; the rank order of potency was: R-N⁶-phenylisopropyladenosine (IC₅₀ 60 nmol/1), 5-N-ethylcarboxamidoadenosine (IC₅₀ 360 nmol/l) and S-N⁶-phenylisopropyladenosine (IC₅₀ 16 ol/l). The adenosine receptor antagonist XAC (xanthine amine congener) antagonized the effect of R-N⁶-phenylisopropyladenosine in a concentration-dependent manner with a K_i-value of 20 nmol/l. The A₁ receptor-selective radioligand R-N⁶-¹²⁵I-p-hydroxyphenylisopropyladenosine bound to membranes prepared from rat ventricular myocytes in a saturable manner with a B _max of 17.7 fmol/mg protein and a K _D-value of 1.1 nmol/l. Adenosine analogues competed for the binding with the same rank order of potency as for the inhibition of the isoprenaline-induced cAMP-increase. GTP inhibited radioligand binding with an IC₅₀-value of 73 ol/l. These results suggest the presence of A₁ adenosine receptors on rat ventricular myocytes, which mediate an inhibition of adenylate cyclase. The receptors may be responsible for the effects of adenosine and its analogues on the heart.Abbreviations ¹²⁵I-HPIA R-N⁶-¹²⁵I-p-hydroxyphenylisopropyladenosine - PIA N⁶-phenylisopropyladenosine - NECA 5-N-ethyl-carboxamidoadenosine - XAC 8-4-[([(2-aminoethyl)aminocarbonyl]methyl)oxy]phenyl-1,3-dipropylxanthine (xanthine amine congener) - Ro 20-1724 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone - ScAMPTME 2-O-monosuccinyladenosine-3,5-cyclic monophosphate tyrosyl methyl ester - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - GTP guanosine-5-tri-phosphate Send offprint requests to D. Martens     

Action of adenosine and characterization of adenosine receptors in human placental vasculature.

1. Adenosine induced concentration-dependent relaxations in segments of human chorionic arteries and veins precontracted with 75 mM K+, which were attenuated by 1-methyl-3-isobutylxanthine (MIX). In the same conditions, L-phenylisopropyladenosine (L-PIA), N-ethylcarboxamideadenosine (NECA) and dibutyryl-cyclic AMP (Db-cAMP) also produced concentration-dependent vasodilations. 2. The order of potency with respect to EC50 was in arteries: NECA greater than or equal to L-PIA greater than Db-cAMP greater than or equal to adenosine, and in veins: L-PIA greater than or equal to NECA greater than adenosine greater than or equal to Db-cAMP. 3. In segments precontracted with 10(-6) M PGF2 alpha, adenosine, NECA and L-PIA induced similar relaxations, which were markedly larger than those found in K+ contracted segments. 4. Db-cAMP (15 min preincubation) inhibited more potently K+ (75 mM) contractions than adenosine. 5. Adenosine reduced Ca addition-induced contractions in depolarized segments exposed to Ca-free medium, as well as 45Ca uptake elicited by 75 mM K+. 6. It is concluded that there exists a similar population of adenosine A1 and A2 receptors in chorionic vessels, which mediate adenosine relaxation. This effect appears to be mainly produced by inhibition of Ca influx, but not by a cAMP-dependent mechanism.     

In vitro antiproliferative effect of a water-soluble Laminaria japonica polysaccharide on human melanoma cell line A375

A water-soluble polysaccharide WPS-2-1, purified from Laminaria japonica, has been found to have antitumor activity. In this study, WPS-2-1 exhibited high anti-proliferative activity on A375 cells in a dosedependent manner. Further investigation indicated that WPS-2-1 induced A375 cells apoptosis. Moreover, WPS-2-1-induced apoptosis was associated with the alteration in expressions of Bcl-2 family proteins. Mitochonadrial apoptotic pathway was involved in WPS-2-1-induced apoptosis, which included the loss of mitochondrial membrane and activation of caspase-3/9. The results in this study suggested that WPS-2-1 could effectively inhibit proliferation of A375 cells in vitro and induce apoptosis via mitochondrial apoptotic pathway. It might serve as a potential antitumor agent.     

Pharmacological characterization of histamine receptors in the human temporal artery.

1. The subtypes of histamine-receptors which mediate dilatation of small human temporal arteries have been characterized in vitro using 'selective' agonists and antagonists. 2. Dilatory responses were studied after preconstriction with prostaglandin F2 alpha since contraction was not seen at histamine concentrations up to 10(-4) M. Histamine caused a concentration-related relaxation of cerebral vessels with an IC50 value of 2.8 +/- 0.6 X 10(-7) M. 3. Cimetidine caused a parallel shift to the right of the histamine concentration-response curve whereas mepyramine was without observable effect. This suggests the presence of histamine H2-receptors only. However, combined treatment with mepyramine and cimetidine caused a more marked displacement of the concentration-response curve to the right. Schild analysis indicated that in situations of near complete blockade of the histamine H1-receptor subtypes, simple competitive antagonism at H2-receptors can be revealed with a pA2 value of 6.58 for cimetidine. The apparent pA2 value for mepyramine was 8.58. 4. The 'selective' H1-receptor agonists pyridylethylamine, 2-methylhistamine and thiazolylethylamine, and the H2-receptor agonists dimaprit, impromidine and 4-methylhistamine all mimicked the histamine response, but all except impromidine were less potent than histamine. The order of potency was impromidine greater than thiazolylamine greater than 4-Me-histamine greater than 2-Me-histamine greater than dimaprit greater than pyridylethylamine greater than tele-Me-histamine. 5. These results indicate that the histamine-induced dilatation in small human temporal arteries is mediated by both H1- and H2-receptors and that the latter subtype of histamine receptors predominates.     

芍药苷对人恶性黑色素瘤细胞A375增殖的体外抑制作用及其机制研究

目的探讨芍药苷对人恶性黑色素瘤细胞A375增殖的体外抑制作用及其作用机制.方法不同浓度芍药苷(3、10、30μmol/L)作用于黑色素瘤细胞A375,MTT法检测细胞活力,流式细胞术检测细胞周期情况,Western blotting法检测NFκB p65信号通路激活情况及下游靶分子Bax、Bcl-2、Cyclin D1、Cyclin E的表达.结果与对照组比较,随着给药浓度的增加,芍药苷对黑色素瘤细胞A375抑制作用逐渐增强,30μmol/L作用48 h时抑制作用最高,并使A375细胞周期阻滞在G1期;芍药苷显著抑制NFκB p65、IκBα的磷酸化,下调Bcl-2、Cyclin D1、Cyclin E的表达,上调Bax表达,差异均具有统计学意义(P<0.01).结论 芍药苷能抑制人黑色素瘤细胞A375体外增殖,可能是通过NF-κB信号通路发挥作用的.     

Pharmacological characterization of adenosine A1 and A2 receptors in the bladder: evidence for a modulatory adenosine tone regulating non-adrenergic non-cholinergic neurotransmission.

1. The nerve-evoked contractions elicited by transmural electrical stimulation of mouse urinary bladders superfused in modified Krebs Ringer buffer containing 1 microM atropine plus 3.4 microM guanethidine were inhibited by adenosine (ADO) and related nucleoside analogues with the following rank order of potency: R-phenylisopropyladenosine (R-PIA) greater than cyclohexyladenosine (CHA) greater than 5'N-ethylcarboxamido adenosine (NECA) greater than ADO greater than S-phenylisopropyladenosine (S-PIA). Tissue preincubation with 8-phenyltheophylline (8-PT) displaced to the right, in a parallel fashion, the NECA concentration-response curve. 2. The contractions elicited by application of exogenous adenosine 5'-triphosphate (ATP) were also inhibited by ADO and related structural analogues. The rank order of potency to reduce the motor response to ATP was: NECA greater than 2-chloroadenosine (CADO) greater than R-PIA greater than ADO greater than CHA greater than S-PIA. 3. The ADO-induced ATP antagonism was of a non-competitive nature and was not specific. Tissue incubation with 10 microM NECA not only reduced the motor responses elicited by ATP, but also 5-hydroxytryptamine, acetylcholine and prostaglandin F2 alpha. The action of NECA was antagonized following tissue preincubation with 8-PT. The inhibitory action of NECA was not mimicked by 10 microM CHA. 4. The maximal bladder ATP contractile response was significantly increased by tissue preincubation with 5-30 microM 8-PT. 5. The 0.15 Hz evoked muscular twitch was significantly increased by 8-PT while dipyridamole consistently reduced the magnitude of the twitch response. These results are consonant with the hypothesis that an endogenous ADO tone modulates the bladder neurotransmission.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacological characterization of adenosine receptors in PGT-beta mouse pineal gland tumour cells

1. The adenosine receptor in mouse pinealocytes was identified and characterized using pharmacological and physiological approaches. 2. Expression of the two adenosine receptor subtypes A2B and A3 was detected in mouse pineal glands and PGT-beta cells by polymerase chain reaction and nucleotide sequencing. 3. Adenosine and 5'-N-ethylcarboxamidoadenosine (NECA) evoked cyclic AMP generation but the A2)-selective agonist 2-(4-(2-carboxyethyl)phenylethylamino)adenosine-5'-N-ethylcarboxamideadenosine (CGS 21680) and the A1-specific agonists R-N(6)-(2-phenylisopropyl)adenosine (R-PIA) and N(6)-cyclopentyladenosine (CPA) had little effect on intracellular cyclic AMP levels. The A2B receptor selective antagonists alloxazine and enprofylline completely blocked NECA-mediated cyclic AMP accumulation. 4. Treatment of cells with the A3-selective agonist N(6)-(3-iodobenzyl)-5'-(N-methylcarbamoyl)adenosine (IB-MECA) inhibited the elevation of the cyclic AMP level induced by NECA or isoproterenol in a concentration-dependent manner with maximal inhibition of 40 - 50%. These responses were blocked by the specific A3 adenosine receptor antagonist MRS 1191. Pretreatment of the cells with pertussis toxin attenuated the IB-MECA-induced responses, suggesting that this effect occurred via the pertussis toxin-sensitive inhibitory G proteins. 5. IB-MECA also caused a concentration-dependent elevation in [Ca(2+)]i and IP3 content. Both the responses induced by IB-MECA were attenuated by treatment with U73122 or phorbol 12-myristate 13-acetate. 6. These data suggest the presence of both A2B and A3 adenosine receptors in mouse pineal tumour cells and that the A2B receptor is positively coupled to adenylyl cyclase whereas the A3 receptor is negatively coupled to adenylyl cyclase and also coupled to phospholipase C.     

人参皂苷Rh2对人黑色素瘤A375—S2细胞的促凋亡作用

目的;研究人参皂苷G－Rh2诱导人黑色素肿瘤细胞A375－S2凋亡的分子生物学机制。方法：用结晶紫染色的方法测定细胞的死亡率。用置显微镜观察细胞形态学的变化。用琼脂糖凝胶电泳检测核酸片断。用流式细胞仪检测细胞凋亡和细胞周期。结果：G－Rh2抑制A375－S2细胞增殖并在20μmol/L可以诱导A375－S2细胞产生凋亡,Caspase抑制剂z-VAD-fmk(caspase家族）,z-DEVD-fmk(caspase-3)或z-IETD-fmk(caspase-8)能部分抑制细胞凋亡,但是Ac-YVAD-cmk(caspase-1)不能抑制A375－S2细胞凋亡。结论：GRh2在体外抑制A375－S2细胞的增殖,通过细胞形态学和核酸片断分析,G－Rh2能够诱导A375－S2细胞产生凋亡。这种作用是通过细胞内caspase一类半胱氨酸蛋白酶进行传导的,G－Rh2对A375－S2细胞的周期没有影响。     

Pharmacological properties of adenosine receptors and adenosine binding proteins

Two major subtypes of adenosine receptors occur in different tissues which have been distinguished by pharmacological and biochemical criteria. The A₁ adenosine receptor has a high-affinity for adenosine and mediates inhibition of adenylyl cyclase, whereas the A₂ adenosine receptor usually has a lower affinity and mediates stimulation of the enzyme. Furthermore, evidence has been obtained that A₁ receptors increase the conductance of receptor-regulated potassium channels, induce inactivation of calcium channels, and modulate the breakdown of phosphoinositides by phospholipase C. Selective agonists and antagonists have been developed for both receptor subtypes. In addition, both adenosine receptors have extensively been characterized by radioligand binding studies. Suitable radioligands for the A₁ receptor are the agonist [³H]2-chloro-N⁶-cyclopentyladenoisine (CCPA) and the antagonist [³H]8-cyclopentyl-1,3-dipropylxanthine (DPCPX)and for the A_2a receptor [³H]2-[p-(carboxyethyl)phenethylamino]- 5′-N-carboxamidoadenosine (CGS 21860). Furthermore, photoaffinity ligands were developed from adenosine derivatives, which can be covalently incorporated into the binding unit of both receptor subtypes. With this approach, it has been shown that the A₁ receptor has an apparent molecular weight of approximately 36 kDa and the A_2a receptor of 45 kDa. A second approach to elucidate the structure of adenosine receptors involves the purification of receptor protein by affinity chromatography. With this procedure, cerebral A₁ receptors have been purified to apparent homogeneity. More recently, the structure of receptor subtypes has been elucidated by cloning the receptors from a cDNA library. Furthermore, a novel adenosine binding with [³H] 5′ -N-ethylcarboxamidoadenosine ([³H]NECA). The pharmacological profile of this NECA-binding protein has been determined in competition experiments with adenosine receptor ligands. It can be distinguished from that of A_2a adenosine receptors and other adenosine binding proteins. We propose the name A_x for this unique adenosine binding protein. © 1993 Wiley-Liss, Inc.     

异甘草素诱导人黑色素瘤A375细胞凋亡研究

目的研究异甘草素诱导人黑色素瘤(A375)细胞凋亡及其初步机制。方法采用硫氰酸盐B(SRB)法测定异甘草素对A375细胞生长的抑制效应,AO/EB和Hoechst33258荧光染色法观察细胞凋亡形态,流式细胞技术检测A375细胞凋亡率;荧光染料二乙酸-2’,7’-二氯荧光素(DCFH-DA)测定A375细胞内活性氧的变化。5,5',6,6'-四氯-1,1',3,3'-四乙基苯并咪唑羰花青碘化物(JC-1)测定线粒体膜电势的变化,利用试剂盒检测异甘草素处理后的A375细胞内ATP和培养液中的乳酸、葡萄糖含量。结果异甘草素能抑制A375细胞的增殖,并呈浓度依赖性;在荧光显微镜下发现,异甘草素处理后的A375细胞出现明显的凋亡形态;细胞凋亡率随异甘草素浓度的增加而升高;异甘草素处理后的细胞内活性氧有明显上升趋势,细胞线粒体膜电位明显下降;异甘草素作用后胞内ATP含量下降(P<0.05或P<0.01),培养液中的乳酸含量下降,葡萄糖含量上升(P<0.05或P<0.01)。结论异甘草素能够抑制A375细胞的恶性增殖,最终诱导细胞凋亡。推测异甘草素通过活性氧升高,引起线粒体膜电势下降,从而影响A375细胞的糖酵解途径而导致细胞凋亡。     

Cytotoxic activity of Apomine is due to a novel membrane-mediated cytolytic mechanism independent of apoptosis in the A375 human melanoma cell line

Summary Apomine, a novel bisphosphonate ester, has demonstrated anticancer activity in a variety of cancer cell lines; however, its mechanism of cytotoxicity is not well understood. Previous work has demonstrated that Apomine induces cell death by activation of caspase-3 in several cancer cell types. However, we have demonstrated that Apomine induces cell death in the A375 human melanoma cell line through a novel membrane-mediated mechanism that is independent of caspase-3 activation. This mechanism of membrane lysis may apply to other bisphosphonates and may be an important mechanism for overcoming resistance to apoptosis. Interestingly, Apomine-mediated cell death in the A375 and UACC 3093 human melanoma cell lines is also independent of N-Ras farnesylation, which was a previously described mechanism of action for Apomine in other cancer cell types. These data suggest that Apomine induces cell death through a novel plasma membrane-mediated cytolytic pathway, independent of caspase-3 activation and N-Ras farnesylation.     

Pharmacological characterization of a novel cell line expressing human alpha(4)beta(3)delta GABA(A) receptors

1: The pharmacology of the stable cell line expressing human alpha(4)beta(3)delta GABA(A) receptor was investigated using whole-cell patch-clamp techniques. 2: alpha(4)beta(3)delta receptors exhibited increased sensitivity to GABA when compared to alpha(4)beta(3)gamma(2) receptors, with EC(50)'s of 0.50 (0.46, 0.53) microM and 2.6 (2.5, 2.6) microM respectively. Additionally, the GABA partial agonists piperidine-4-sulphonate (P4S) and 4,5,6,7-tetrahydroisothiazolo-[5,4-c]pyridin-3-ol (THIP) displayed markedly higher efficacy at alpha(4)beta(3)delta receptors, indeed THIP demonstrated greater efficacy than GABA at these receptors. 3: The delta subunit conferred slow desensitization to GABA, with rate constants of 4.8+/-0.5 s for alpha(4)beta(3)delta and 2.5+/-0.2 s for alpha(4)beta(3)gamma(2). However, both P4S and THIP demonstrated similar levels of desensitization on both receptor subtypes suggesting this effect is agonist specific. 4: alpha(4)beta(3)delta and alpha(4)beta(3)gamma(2) demonstrated equal sensitivity to inhibition by the cation zinc (2-3 microM IC(50)). However, alpha(4)beta(3)delta receptors demonstrated greater sensitivity to inhibition by lanthanum. The IC(50) for GABA antagonists SR-95531 and picrotoxin, was similar for alpha(4)beta(3)delta and alpha(4)beta(3)gamma(2). Likewise, inhibition was observed on both subtypes at high and low pH. 5: alpha(4)beta(3)delta receptors were insensitive to modulation by benzodiazepine ligands. In contrast Ro15-4513 and bretazenil potentiated GABA responses on alpha(4)beta(3)gamma(2) cells, and the inverse agonist DMCM showed allosteric inhibition of alpha(4)beta(3)gamma(2) receptors. 6: The efficacy of neurosteroids at alpha(4)beta(3)delta receptors was greatly enhanced over that observed at alpha(4)beta(3)gamma(2) receptors. The greatest effect was observed using THDOC with 524+/-71.6% potentiation at alpha(4)beta(3)delta and 297.9+/-49.7% at alpha(4)beta(3)gamma(2) receptors. Inhibition by the steroid pregnenolone sulphate however, showed no subtype selectivity. The efficacy of both pentobarbitone and propofol was slightly augmented and etomidate greatly enhanced at alpha(4)beta(3)delta receptors versus alpha(4)beta(3)gamma(2) receptors. 7: We show that the alpha(4)beta(3)delta receptor has a distinct pharmacology and kinetic profile. With its restricted distribution within the brain and unique pharmacology this receptor may play an important role in the action of neurosteroids and anaesthetics. British Journal of Pharmacology (2002) 136, 965-974     

文冠果壳苷诱导人恶性黑色素瘤A375.S2细胞的凋亡及机制

目的观察文冠果壳苷对人恶性黑色素瘤A375.S2细胞增殖抑制作用及诱导凋亡的机理。方法采用四甲基噻唑蓝法(MTT法)检测化合物对细胞的生长抑制作用,光学显微镜及荧光显微镜观察细胞形态学变化,免疫印迹法(Western blotting)检测p-p38、p38、核转录因子-κB(nuclear factor kappa B,NF-κB)p65及核转录抑制因子-κB(nuclear factor kappa B inhibitor,I-κB)蛋白表达水平,检测细胞核内NF-κB p65表达水平。结果文冠果壳苷可浓度依赖性地抑制A375.S2细胞增殖,并优于5-氟尿嘧啶(5-FU);10μmol·L-1文冠果壳苷作用于A375.S2细胞,形态学观察发现明显的凋亡小体和核固缩;Western blotting检测发现文冠果壳苷可时间依赖性地降低p-p38、p38、NF-κB p65及I-κB的蛋白表达水平;文冠果壳苷抑制NF-κB p65自细胞浆到细胞核的转位。结论文冠果壳苷可能通过抑制NF-κB和p38的活化诱导人恶性黑色素瘤A375.S2细胞凋亡。     

Functional expression of adenosine A2A and A3 receptors in the mouse dendritic cell line XS-106

There is increasing evidence to suggest that adenosine receptors can modulate the function of cells involved in the immune system. For example, human dendritic cells derived from blood monocytes have recently been described to express functional adenosine A1, A2A and A3 receptors. Therefore, in the present study, we have investigated whether the recently established murine dendritic cell line XS-106 expresses functional adenosine receptors. The selective adenosine A3 receptor agonist 1-[2-chloro-6[[(3-iodophenyl)methyl]amino]-9H-purin-9-yl]-1-deoxy-N-methyl-beta-D-ribofuranuronamide (2-Cl-IB-MECA) inhibited forskolin-mediated [3H]cyclic AMP accumulation and stimulated concentration-dependent increases in p42/p44 mitogen-activated protein kinase (MAPK) phosphorylation. The selective adenosine A2A receptor agonist 4-[2-[[-6-amino-9-(N-ethyl-beta-D-ribofuranuronamidosyl)-9H-purin-2-yl]amino]ethyl]benzene-propanoic acid (CGS 21680) stimulated a robust increase in [3H]cyclic AMP accumulation and p42/p44 MAPK phosphorylation. In contrast, the selective adenosine A1 receptor agonist CPA (N6-cyclopentyladenosine) did not inhibit forskolin-mediated [3H]cyclic AMP accumulation or stimulate increases in p42/p44 MAPK phosphorylation. These observations suggest that XS-106 cells express functional adenosine A2A and A3 receptors. The non-selective adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine (NECA) inhibited lipopolysaccharide-induced tumour necrosis factor-alpha (TNF-alpha) release from XS-106 cells in a concentration-dependent fashion. Furthermore, treatment with Cl-IB-MECA (1 microM) or CGS 21680 (1 microM) alone produced a partial inhibition of lipopolysaccharide-induced TNF-alpha release (when compared to NECA), whereas a combination of both agonists resulted in the inhibition of TNF-alpha release comparable to that observed with NECA alone. Treatment of cells with the adenosine A2A receptor selective antagonists 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5ylamino]ethyl)phenol (ZM 241385; 100 nM) and 5-amino-2-(2-furyl)-7-phenylethyl-pyrazolo[4,3-e]-1,2,4-triazolo[1,5c]pyrimidine (SCH 58261; 100 nM) and the adenosine A3 receptor selective antagonist N-[9-chloro-2-(2-furanyl)[1,2,4]-triazolo[1,5-c]quinazolin-5-benzeneacetamide (MRS 1220; 100 nM) partially blocked the inhibitory effects of NECA on lipopolysaccharide-induced TNF-alpha release. Combined addition of MRS 1220 and SCH 58261 completely blocked the inhibitory effects of NECA on lipopolysaccharide-induced TNF-alpha release. In conclusion, we have shown that the mouse dendritic cell line XS-106 expresses functional adenosine A2A and A3 receptors, which are capable of modulating TNF-alpha release.