细胞防护剂WR－2721研究进展

WR-2721(amifostine)是一种广谱的细胞保护剂，在体内通过其活性形式WR-1065保护正常细胞，减轻放、化疗毒副作用，促进造血细胞恢复，使患可以耐受大剂量放、化疗。WR-2721可能成为高恶性和耐药性肿瘤治疗新策略之一。     

WR-2721抗放效果的观察

WR-2721(S-2(3-氨丙基乙基)乙基硫代磷酸)是一种具有较高效价的辐射防护药。它能显著提高受照动物的活存率,可减轻造血组织、胃肠道等敏感器官的辐射损伤。为进一步分析了解WR-2721抗放作用的原理,本文观察了WR-2721对照射小鼠某些造血指标和免疫指标的影响。     

硫代磷酸盐对射线诱导睾丸RNA含量变化的抑制

硫代磷酸盐,WR-2721,是一种疗效很高的抗放药,应用剂量范围内副作用很小.在组织和细胞水平上,对WR-2721的作用机理和辐射防护效能方面的研究已做了大量工作,但在分子水平上,特别是体内系统的研究则甚少.本文选用成年雄性Swiss albino小鼠分成三大组,分别照射3、6、8Gy,每大组分成两个小组,其中一小组腹腔注射WR-2721 400mg/kg,另一小组注射蒸馏水作为对照,照射后的1/4、1、2、4、7和14天,用椎离     

WR-2721衍生物对培养细胞的辐射防护

经初步研究,作者发现S-2(3-氨丙基)氨基乙基硫代磷酸(WR-2721)对培养的V79-171细胞没有防护作用,但是在培养基中加入碱性磷酸酶可引起:①WR-2721在培养基中转化为它的硫醇形式(WR-1065)和二硫物形式(WRSS);②WR-1065和WRSS在细胞中的聚积;③对细胞的明显辐射防护作用。在本工作中,追踪这些现象是为了证实药物由细胞摄取的机制和药物产生辐射防护作用的形式。     

人的WR-2721药物代谢动力学研究

WR-2721做为辐射或化疗防护剂以及降低钙的药物正在进行临床试用。作者用电化学高效液相色谱技术测定血液和组织中的WR-2721和它的含巯基代谢产物WR-1065,和对称性二硫化物WR-33278。给13个肿瘤患者快速静脉注射WR-2721 150mg/m~2,给药后0、0.5、1、2、2.5、3、4、6、8、12、15、20、30、45分钟取血。在冰冷条件下血液收集在EDTA管,保存在酸性溶液中。作者实验空WR-1065和WR-33278的血液回收率各为104％和98％,而在小鼠肝脏中回收率分别为98％和95％。收集6个病人的尿液,贮存在-70℃备用。用Holford方法测定药物代谢动力学模型及其参数值。     

WR-2721对照射诱发红细胞和微粒体内脂质过氧化和酶释放的影响

本文研究了γ射线照射微粒体和红细胞后WR-2721对照射诱发的脂质过氧化和酶释放的影响.早已发现WR-2721防护正常组织和肿瘤细胞的差别,其在化学辐射防护方面是有意义的.此药不同防护效应的报告已证明WR-2721在脱磷酸作用后可能转变为它的防护形式.本文结果指出,WR-2721的脱磷酸作用对它的防护效应是必要的.     

WR-2721对免疫反应性T淋巴细胞的放射防护作用

S-2-(3-氨基丙基氨基)乙基硫代磷酸(WR-2721)保护正常组织抗电离辐射,而对实体瘤只有微弱保护或无保护作用。根据这种差异和该化合物在人体中毒性低,认为WR-2721在放疗病人中可减轻正常组织的损伤。因为辐射有明显的免疫抑制作用,故对免疫系统的化学防护有特殊的价值。典型的放射防护剂对急性致死率是有效的,但不保护免疫系统。Yuhas发现WR-2721保护小鼠脾空斑形成细胞(复合的T细胞依赖性B细胞终点)是高效的(DMF=3.46)。近来认为T淋巴细胞对肿瘤的排斥和再生长比B淋巴细胞更重要。作者研究W     

巯基丙酰甘氨酸对WR-2721防护辐射胃肠损伤和致死作用的改善

WR-2721的有效辐射防护剂量接近其耐受剂量,限制了其临床应用。无毒辐射防护剂巯基丙酰甘氨酸(以下简称MPG)与低剂量WR-2721合用则明显降低受15Gyγ射线照射小鼠肠     

照后服用葡聚糖增强WR-2721的辐射防护作用

作者研究了给小鼠照前服用WR-2721和照后服用葡聚糖产生的辐射防护协同作用.实验用雌性C3H/HeN小鼠,照前30分钟腹腔注射200mg/kgWR-2721,照后1小时尾静脉注射250mg/kg葡聚糖.~(60)Coγ线照射7～16Gy,剂量率为0.4Gy/min.检测30天的存活率、内源性造血脾结节形成(E-CFU)和粒-巨噬集落形成细胞(GM-CFC).结果如下.1.WR-2721、葡聚糖及二药合并对受照小鼠     

氨基硫醇WR-255581对快中子引起的哺乳动物细胞的致死和DNA损伤效应的辐射防护作用

已证实巯基化合物能保护受低LET照射的哺乳动物细胞的损伤,其作用机理可能是:引起细胞乏氧、自由基消除及靶分子损伤修复的综合因素,这类化合物对高LET射线引起的损伤的保护作用研究较少,但它对阐明辐射防护作用机理却很重要。 WR-255591〔CH_3NH(CH_2)_3NHCH_2CH_2SH〕是氨基磷酸硫酯WR-3689的游离巯基药物,小鼠实验表明WR-2721和WR-151327能明显地防护由中子引起的致死作用,WR-255591还可降低CHO细胞的DNA损伤。     

Effect of WR-2721 on radiation-induced lipid peroxidation and enzyme release in erythrocytes and microsomes

The effect of WR-2721 on radiation-induced lipid peroxidation and enzyme release was studied after gamma-irradiation of microsomes and erythrocytes. WR-2721 rendered protection to microsomes by reducing lipid peroxidation whereas it did not exert significant protection against radiation-induced lipid peroxidation in erythrocytes. The non-protective effect of WR-2721 was also observed in radiation-induced enzyme (AChE) release of erythrocytes. It is proposed that erythrocytes do not dephosphorylate WR-2721 into the free thiol derivative (WR-1065). This was confirmed by the microsomal treatment of erythrocytes that had shown the protective effect of WR-2721. Further, a significant increase in sulphydryl content in microsomes, and no such increase in erythrocytes, after the WR-2721 treatment indicated that dephosphorylation of WR-2721 is necessary for its protective effect.     

Drug combination against single drug treatment in radiation protection of the bone marrow CFU

The ability of WR-2721 to protect normal tissues against ionizing radiation is limited at its maximum protective dose owing to the toxicity of the drug per se. Previous studies had indicated that MPG (2-mercaptopropionylglycine) neutralizes to some extent the toxic effects of WR-2721 without impairing the protective efficiency. The effectiveness of two doses of WR-2721 (300 mg/kg and 150 mg/kg body weight) alone or in combination with an optimal dose (20 mg/kg body weight) of MPG, on the mouse bone marrow was studied by the exogenous spleen colony assay (CFU-s) after a single whole body exposure to 4.5 Gy of gamma radiation. Both the drugs individually increased the number of spleen colonies significantly above that of the irradiated control indicating higher stem cell survival. WR-2721 treatment gave better protection than MPG. MPG was more effective when administered within 5 min before or after irradiation than when given 30 to 25 min before irradiation. The combination of WR-2721, at either dose, with 20 mg/kg MPG gave an increase in the stem cell survival as compared to the single drug treatments and this effect was synergistic at 300 mg/kg WR-2721. MPG treatment within 5 min after irradiation produced a slightly higher CFU-s count than when the drug was injected before irradiation, though the difference was not statistically significant. It is concluded that in addition to the doses of the drug, the time of administration also could influence the effect of drug combinations.     

Chromosome protection by WR-2721 and MPG-single and combination treatments

The radioprotective action of thiol compounds 2-mercaptopropionylglycine (MPG) and S-2(aminopropylamino) ethyl phosphorothioic acid (WR-2721) was evaluated either alone or in combination on the bone marrow chromosomes of Swiss albino mice after 4.5 Gy of 60Co radiation. Single drug administration of WR-2721 at 300 mg/kg body weight resulted in a 50% reduction in the yield of aberrant cells at 24 hours post irradiation, while the other single drug doses were less effective. The combination of the two drugs increased the effect in the sense that 150 mg/kg WR-2721 with 20 mg/kg MPG gave equal protection as 300 mg/kg WR-2721 given alone. Moreover, on day 14, when WR-2721 produced an increase in the precent aberrant cells the above combination brought down the value to normal. It appears that MPG neutralizes to some extent the toxic effect of WR-2721, without impairing the protective efficiency.     

The effect of the radioprotector WR-2721 and WR-1065 on mitochondrial lipid peroxidation

The radioprotective agent WR-2721 is dephosphorylated to the free thiol form WR-1065 in vivo. The effects of WR-2721, WR-1065 and reduced glutathione on a mitochondrial lipid peroxidation system were compared. WR-2721 had no effect on mitochondrial lipid peroxidation in vitro, and could not prevent the inactivation of mitochondrial enzymes. Both WR-1065 and glutathione were effective inhibitors of mitochondrial lipid peroxidation induced by ADP/Fe/NADPH or by ADP/Fe/ascorbate. Both thiols correspondingly delayed the free radical-mediated inactivation of succinate dehydrogenase and isocitrate dehydrogenase. WR-1065 was able to reduce cumene hydroperoxide non-enzymatically, and proved to be weak substrate for glutathione peroxidase. The disulfide formed from WR-1065 could be reduced by glutathione without the participation of glutathione reductase. A redox cycle is proposed between WR-1065, glutathione and glutathione reductase to explain the inhibitory effect of WR-1065 on lipid peroxidation.     

Prevention of radiation-induced mammary tumours in rats by combined use of WR-2721 and tamoxifen

PURPOSE: This investigation evaluated the inhibitory effect of S-2-(3-aminopropylamino)-ethylphosphorothioic acid (WR-2721) against the initiation of mammary tumourigenesis by irradiation, and the antipromotion activity of tamoxifen in the development of radiation-initiated mammary tumours. MATERIALS AND METHODS: Lactating rats were injected with WR-2721 and then irradiated with gamma-rays (1.5 Gy) at day 21 of lactation. The rats were divided into three groups 1 month after irradiation and were implanted with a pellet either of cholesterol as an inert control, diethylstilbestrol (DES) as a tumour-promoting agent, or DES combined with tamoxifen. For the control experiments, non-irradiated and irradiated rats receiving saline instead of WR-2721 were treated with a pellet by the same procedures. RESULTS: The highest incidence (85%) for tumourigenesis of mammary glands was observed in the irradiated rats that had been previously injected with saline following treatment with DES Administration of WR-2721 prior to the irradiation significantly decreased the incidence of mammary tumours to 52.2%. The treatment with DES pellets combined with tamoxifen in the irradiated rats previously injected with saline also markedly suppressed the incidence of mammary tumours even further to 4.4%. Also, the development of mammary tumours was completely prevented in the rats treated with WR-2721 prior to irradiation and then implanted with DES pellets combined with tamoxifen. CONCLUSIONS: These results suggest that the administration of WR-2721 prior to irradiation has an inhibitory effect on the initiation phase, resulting in a partial reduction of mammary tumour development, and that the combination of WR-2721 at the initiation phase with tamoxifen at the promotion phase is quite effective in preventing mammary tumourigenesis induced by radiation.     

Prevention of radiation-induced mammary tumours in rats by combined use of WR-2721 and tamoxifen

Purpose : This investigation evaluated the inhibitory effect of S-2- (3-aminopropylamino)-ethylphosphorothioic acid (WR-2721) against the initiation of mammary tumourigenesis by irradiation, and the antipromotion activity of tamoxifen in the development of radiation-initiated mammary tumours. Materials and methods : Lactating rats were injected with WR-2721 and then irradiated with γ-rays (1.5 Gy) at day 21 of lactation. The rats were divided into three groups 1 month after irradiation and were implanted with a pellet either of cholesterol as an inert control, diethylstilbestrol (DES) as a tumour-promoting agent, or DES combined with tamoxifen. For the control experiments, non-irradiated and irradiated rats receiving saline instead of WR-2721 were treated with a pellet by the same procedures. Results : The highest incidence (85%) for tumourigenesis of mammary glands was observed in the irradiated rats that had been previously injected with saline following treatment with DES Administration of WR-2721 prior to the irradiation significantly decreased the incidence of mammary tumours to 52.2%. The treatment with DES pellets combined with tamoxifen in the irradiated rats previously injected with saline also markedly suppressed the incidence of mammary tumours even further to 4.4%. Also, the development of mammary tumours was completely prevented in the rats treated with WR-2721 prior to irradiation and then implanted with DES pellets combined with tamoxifen. Conclusions : These results suggest that the administration of WR2721 prior to irradiation has an inhibitory effect on the initiation phase, resulting in a partial reduction of mammary tumour development, and that the combination of WR-2721 at the initiation phase with tamoxifen at the promotion phase is quite effective in preventing mammary tumourigenesis induced by radiation.     

Modification of the oral radiation death syndrome with combined WR-2721 and misonidazole

In order to investigate the combined use of radioprotective and radiosensitizing chemicals we have used WR--2721 and misonidazole to study their combined chemical toxicity and radiomodifying effects in our model using the oral radiation death (ORD) syndrome as the endpoint. Our data demonstrate that WR-2721 does protect against the ORD syndrome. Misonidazole does not protect against the ORD syndrome. Misonidazole does not sensitize the normal oral cavity to local irradiation. WR-2721 and misonidazole produce additive toxicity when injected simultaneously and the combination can provide an overall protective response to the ORD syndrome. We conclude that the combination may be potentially useful for the treatment of cancers of the oral cavity.     

Prolonged radioprotective activity of WR-2721 linked to dextran.

The radioprotective agent WR-2721 was linked to dextran and poly(glutamic acid) respectively, to obtain a prolonged radioprotective ability. Male mice were administered these water soluble polymer conjugates one to 72 hours prior to a whole body irradiation with X-rays. A prolongation of radioprotective efficiency was achieved with two dextran-(WR-2721)-conjugates. For a period of 24 hours between administration, and irradiation dose reduction factors of 1.14 +/- 0.04 and 1.10 +/- 0.03 respectively were found. After 72 hours, no protective effect was observed. Histopathological investigations of the liver for formation of tumors 200 to 600 days after irradiation seems to indicate that a protective effect is not produced by the dextran-(WR-2721)-conjugates.     

In vivo protection by the aminothiol WR-2721 against neutron-induced carcinogenesis.

The ability of the compound S-2-(aminopropylamino)ethylphosphorothioic acid, designated WR-2721, to protect against neutron-induced carcinogenesis was investigated. Both sexes of the B6CF1 mouse were injected i.p. with 400 mg/kg of WR-2721 30 min prior to being irradiated by 10 cGy of neutrons. Neoplastic mortality in the groups receiving thiol was either reduced or delayed relative to irradiated mice not given protector. However, the time at which the protective effect of WR-2721 was expressed depended on the sex of the animal. Thiol-related shifts in the time of neoplastic death in females occurred only in the first half of the lifespan. Once a female survived to the mean age at death, no difference in the pattern of mortality could be detected between control and WR-2721-treated mice exposed to neutrons. Irrespective of thiol treatment, the timing of tumour-related death was nearly identical during the first half of life for males exposed to neutrons. In the last half of the lifespan, survival of thiol-protected males was enhanced relative to saline-injected males and even exceeded that observed in the control population.     

Inhibition of reduction in the testicular weight by WR-2721 in relation to the body weight after whole-body gamma irradiation

Male Swiss albino mice were irradiated with 60Co gamma rays at 3, 6 and 8 Gy dose levels in separate groups in the presence and absence of the radioprotective drug, WR-2721. The drug treated animals received intraperiotoneal injection of 400 mg/kg body weight aqueous solution (pH 6.2) of WR-2721. Animals were weighted and sacrificed at various post-irradiation intervals between day 1/4 to day 28. Testes were weighed for determining the testis/body weight ratios. The results indicated that testis/body weight ratio reduced after radiation exposure and the extent of this reduction depended on the dose of exposure. Injection of WR-2721 inhibited the body weight loss including the testicular mass loss after irradiation, as depicted by the significantly higher testis/body weight ratio in the drug pretreated animals.