Pereira Avril, Dean Brian
Rebecca L. Cooper Research Laboratories, Mental Health Research Institute of Victoria, Parkville 3052, Victoria, Australia.
Biochem Pharmacol. 2006 Sep 14;72(6):783-93. doi: 10.1016/j.bcp.2006.06.006. Epub 2006 Jul 17.
Clozapine, an atypical antipsychotic drug effective in treatment of refractory schizophrenia causes potentially life-threatening agranulocytosis. The drug undergoes bioactivation to a toxic, chemically reactive intermediate with capacity to target stromal cells, central components of the bone marrow microenvironment implicated in neutrophil development. To identify possible mechanisms underpinning disruption of stroma as a site of drug bioactivation, toxicity was induced in vitro. Therefore metabolite generation procedures utilizing HOCl or HRP-H(2)O(2) as primary components involved in clozapine metabolism were adapted for stromal culture and coupled with viability determinations. Drug oxidation by HOCl was less toxic to stromal cells than HRP-H(2)O(2) based methods. More specifically, clozapine bioactivation by HRP-H(2)O(2) caused dose-dependent inhibition of stromal viability at therapeutically relevant concentrations. Differences in susceptibility of HAS303 and LP101 cells to the clozapine nitrenium ion were also evident. Stromal cell death was attributed to clozapine in the presence of a complete metabolising system comprising HRP and H(2)O(2). In the absence of a complete metabolising system clozapine was not cytotoxic. For LP101 cells, drug plus HRP (minus H(2)O(2)) also induced toxicity. Importantly, other antipsychotic drugs including risperidone, olanzapine and haloperidol when bioactivated, were not cytotoxic, indicating system specificity for clozapine. Exogenous GSH, N-acetylcysteine, l-ascorbic acid, catalase, and sodium azide afforded protection to cells whereas S-methylGSH, GSSG, ketoprofen and proadifen did not. Thus functional data derived from the in vitro stromal system defined in these studies may enable further investigation of the mechanisms subserving stromal impairment in clozapine-induced agranulocytosis and direct attention to improved methods for its prevention.
氯氮平是一种对难治性精神分裂症有效的非典型抗精神病药物，可导致潜在的危及生命的粒细胞缺乏症。该药物经生物活化形成一种有毒的化学反应性中间体，能够靶向基质细胞，而基质细胞是骨髓微环境中参与中性粒细胞发育的核心成分。为了确定作为药物生物活化位点的基质破坏的潜在机制，在体外诱导了毒性。因此，将利用次氯酸（HOCl）或辣根过氧化物酶-H₂O₂（HRP-H₂O₂）作为氯氮平代谢主要成分的代谢物生成程序应用于基质培养，并与活力测定相结合。与基于HRP-H₂O₂的方法相比，HOCl对基质细胞的药物氧化毒性较小。更具体地说，在治疗相关浓度下，HRP-H₂O₂介导的氯氮平生物活化导致基质活力呈剂量依赖性抑制。HAS303和LP101细胞对氯氮平氮宾离子的敏感性差异也很明显。在包含HRP和H₂O₂的完整代谢系统存在的情况下，基质细胞死亡归因于氯氮平。在没有完整代谢系统的情况下，氯氮平没有细胞毒性。对于LP101细胞，药物加HRP（不含H₂O₂）也会诱导毒性。重要的是，其他抗精神病药物，包括利培酮、奥氮平和氟哌啶醇在生物活化时没有细胞毒性，表明氯氮平具有系统特异性。外源性谷胱甘肽（GSH）、N-乙酰半胱氨酸、L-抗坏血酸、过氧化氢酶和叠氮化钠可为细胞提供保护，而S-甲基谷胱甘肽、氧化型谷胱甘肽（GSSG）、酮洛芬和丙磺舒则不能。因此，这些研究中定义的体外基质系统获得的功能数据可能有助于进一步研究氯氮平诱导的粒细胞缺乏症中基质损伤的机制，并直接关注其预防的改进方法。
