Gardner I, Leeder J S, Chin T, Zahid N, Uetrecht J P
Faculties of Pharmacy, University of Toronto, Toronto, Canada.
Mol Pharmacol. 1998 Jun;53(6):999-1008.
Covalent binding of a reactive metabolite of clozapine to neutrophils or their precursors is thought to play a role in the development of clozapine-induced agranulocytosis. Immunoblotting studies with an anti-clozapine antiserum detected covalent binding of clozapine to human neutrophils in vitro when HOCl was used to generate clozapine reactive metabolite (major clozapine adducts of 31, 49, 58, 78, 86, 126, 160, and 204 kDa). In addition, incubating neutrophils with clozapine and H2O2 (major clozapine adducts of 49 and 58 kDa) or clozapine, H2O2, and human myeloperoxidase (major clozapine adducts of 31, 49, 58, and 126 kDa) also resulted in covalent binding of clozapine to the neutrophils. The covalent binding of clozapine to neutrophils was inhibited by extracellular glutathione when HOCl, but not H2O2 was used to generate reactive metabolite. We found that the antiserum against clozapine also recognized olanzapine, an antipsychotic drug that forms a similar reactive metabolite to clozapine but has not been associated with induction of agranulocytosis. Repeating the in vitro experiments with olanzapine revealed that the major olanzapine-modified polypeptides had molecular masses of 96, 130-170, and 218 kDa. Only relatively low levels of 31, 49, and 58 kDa adducts were observed. Clozapine-modified polypeptides also were detected in neutrophils from patients being treated with clozapine. A major 58-kDa clozapine-modified polypeptide was detected in all patients tested. In contrast, no drug-modified polypeptides were detected in neutrophils from patients taking olanzapine. The differences in covalent binding exhibited by the two compounds and, in particular, the lack of olanzapine binding to human neutrophils in vivo may help to explain the difference in toxicity of these two drugs.
氯氮平的活性代谢产物与中性粒细胞或其前体的共价结合被认为在氯氮平诱导的粒细胞缺乏症的发生中起作用。当使用次氯酸（HOCl）生成氯氮平活性代谢产物（主要的氯氮平加合物分子量为31、49、58、78、86、126、160和204 kDa）时，用抗氯氮平抗血清进行的免疫印迹研究在体外检测到氯氮平与人中性粒细胞的共价结合。此外，将中性粒细胞与氯氮平和过氧化氢（主要的氯氮平加合物分子量为49和58 kDa）或氯氮平、过氧化氢和人髓过氧化物酶（主要的氯氮平加合物分子量为31、49、58和126 kDa）一起孵育也导致氯氮平与中性粒细胞的共价结合。当使用HOCl而不是过氧化氢生成活性代谢产物时，细胞外谷胱甘肽可抑制氯氮平与中性粒细胞的共价结合。我们发现，抗氯氮平抗血清也识别奥氮平，奥氮平是一种抗精神病药物，形成与氯氮平类似的活性代谢产物，但与粒细胞缺乏症的诱导无关。用奥氮平重复体外实验发现，主要的奥氮平修饰多肽的分子量为96、130 - 170和218 kDa。仅观察到相对较低水平的31、49和58 kDa加合物。在接受氯氮平治疗的患者的中性粒细胞中也检测到了氯氮平修饰的多肽。在所有测试患者中均检测到一种主要的58 kDa氯氮平修饰多肽。相比之下，在服用奥氮平的患者的中性粒细胞中未检测到药物修饰的多肽。这两种化合物表现出的共价结合差异，特别是奥氮平在体内与人中性粒细胞缺乏结合，可能有助于解释这两种药物毒性的差异。
