MECHANISMS OF HEMATOLOGICAL TOXICITY OF ANTI-AIDS DRUGS

本提案的总体长期目标是调查 与艾滋病治疗中药物诱导毒性相关的机制。 的 齐多夫定（AZT）的血液学毒性仍然是 艾滋病的临床管理，是最重要的并发症 需要停止治疗。 这项建议的具体目标是 因此旨在研究骨髓毒性的机制 AZT和其他抗艾滋病药物引起的。 由于高水平的血浆 促红细胞生成素（Epo）在某些患者中无效， 改善AZT诱导的贫血，我们假设AZT干扰 Epo受体的表达与功能。 初步结果显示， 实验室确实已经证明AZT会导致剂量依赖性降低 Epo受体表达的调节与抑制 CFU-E衍生集落。 骨髓祖细胞与 Epo阻止AZT介导的Epo受体下调，但不 完全恢复增殖能力，表明AZT 干扰Epo受体表达和信号通路。 我们 因此，建议用125 I-Epo定量Epo受体数量 和/或生物素化的Epo 用不同剂量的AZT加或不加Epo治疗。 我们将 进一步检测Epo受体mRNA的稳态水平、半衰期、 和红系祖细胞的转化率 其他ddn 因为Epo配体的跨膜信号 受体复合物涉及蛋白激酶C（PKC）激活，我们 初步数据表明， 通过AZT，我们建议进一步研究AZT的抑制作用， 这种酶，并描绘特定的异构体， 压抑 由于Epo诱导的原癌基因（c-myc和 c-fos）已被证明是红系细胞中的早期细胞事件 增殖和分化，并与PKC激活，我们 还将研究AZT和其他ddN对 由c-myc、c-fos和raf-1转录的mRNA。 我们已经初步表明， 实验表明AZT下调c-fos mRNA，而c-myc mRNA不受影响。 建议的研究将提供（a）深入的 了解血液学毒性相关机制 AZT和其他ddN和（B）有效治疗方法的基础 来克服AZT引起的骨髓毒性。

The overall long-term objective of this proposal is to investigate the mechanisms associated with drug-induced toxicities in AIDS therapy. The hematological toxicity of zidovudine (AZT) remains a limiting factor in clinical management of AIDS and is the most important complication requiring cessation of therapy. The specific aims of this proposal are therefore directed to investigate the mechanisms of bone marrow toxicity induced by AZT and other anti-AIDS drugs. Since high plasma levels of erythropoietin (Epo) in certain patients have been ineffective in ameliorating AZT-induced anemia, we hypothesize that AZT interferes with Epo receptor expression and function. Preliminary results from our laboratory have indeed demonstrated that AZT causes a dose-dependent down regulation of Epo receptor expression which correlated with inhibition of CFU-E derived colonies. Incubation of bone marrow progenitor cells with Epo prevented AZT mediated down regulation of Epo receptor but did not completely restore the proliferative capacity suggesting that AZT interferes with both Epo receptor expression and signalling pathways. We therefore, propose to quantitate the Epo receptor numbers with 125I-Epo and/or biotinylated Epo after exposure of the human bone marrow erythroid progenitor cells with various doses of AZT with or without Epo. We will further examine the steady state levels of Epo receptor mRNA, half life and turn over rates in erythroid progenitor cells upon exposure to AZT and other ddNs. Since transmembrane signalling by the Epo ligand-- receptor complex involves protein kinase C (PKC) activation and our preliminary data have demonstrated significant inhibition of PKC activity by AZT, we propose to further investigate the inhibitory effect of AZT on this enzyme and to delineate the specific isoforms which may be inhibited. Since Epo-induced expression of protooncogenes (c-myc and c-fos) has been shown to be an early cellular event in erythroid proliferation and differentiation and is linked to PKC activation, we will also investigate the effects of AZT and other ddNs on the levels of mRNA transcribed by c-myc, c-fos and raf-1. We have shown in preliminary experiments that AZT down regulated c-fos mRNA whereas levels of c-myc mRNA were unaffected. The proposed studies will provide (a) an in-depth understanding of the mechanisms associated with hematological toxicity of AZT and other ddNs and (b) a basis for effective therapeutic approaches to overcome AZT-induced bone marrow toxicity.