MECHANISMS OF DMBA INDUCED BONE MARROW TOXICITY

DMBA 引起骨髓毒性的机制

• 批准号: 6418367
• 负责人: CHARLES Joseph CZUPRYNSKI
• 金额: $ 3.2万
• 依托单位: UNIVERSITY OF WISCONSIN-MADISON
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-05-01 至 2003-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6418367
• 关键词: B lymphocyte; adduct; apoptosis; benzanthracenes; bone marrow disorder; carbopolycyclic compound; cell cell interaction; chemical carcinogenesis; cytochrome P450; cytotoxicity; gene targeting; genetically modified animals; growth factor; laboratory mouse; mixed tissue /cell culture; pharmacokinetics; toxicology; toxin metabolism

DESCRIPTION: (Adapted from the Investigator's Abstract) 7,12-Dimethylbenzo[a]anthracene has been studied extensively as a model for carcinogenic and immuno-suppressive polycyclic aromatic hydrocarbons. Most of the biological effects of DMBA require activation by some member of the cytochrome P450 family. One of the most striking effects of DMBA on the immune system is bone marrow toxicity, resulting in severe depletion of progenitor B- lymphocytes. The long-term goal of this project is to identify the mechanisms involved in the bone marrow toxicity of DMBA. In preliminary studies, the investigators found that bone marrow stromal cells have high constitutive levels of cytochrome P450lBl (CYPlBl) that metabolizes DMBA to carcinogenic metabolites in vitro. The investigators also observed that progenitor B- lymphocytes undergo apoptosis when co-cultured with DMBA and bone marrow stromal cells in vitro, but not when incubated with DMBA alone. The central hypothesis is that DMBA metabolism by CYP1B1 in bone marrow stromal cells results in release of metabolites that, directly or indirectly, cause apoptosis in progenitor B- lymphocytes. The rationale for this study is based on: i) the critical importance of stromal cell-B cell interactions in normal B cell development; ii) the high constitutive levels of CYPlBl in stromal cells and its absence in pre B cells; and iii) the ability of DMBA to cause apoptosis in pre-B cells only when co-cultured with bone marrow stromal cells. Death of progenitor B cells might result from: DMBA-DNA adduct formation in pre B cells; loss of an obligatory growth signal from DMBA-treated bone marrow stromal cells; or the release of a toxic moiety for pre B cells by DMBA- treated bone marrow stromal cells. To resolve these possibilities, the investigators will pursue to following three specific aims: 1) Use gene knockout mice in a series of in vivo and in vitro experiments to delineate the roles of CYP1B1, and the AhR, in DMBA-induced pre B cell apoptosis. 2) Distinguish possible mechanisms (i.e., DNA-adduct formation, loss of growth signals, release of Fas ligand or other mediators) that could be responsible for the ability of DMBA-treated bone marrow stromal cells to cause apoptosis in pre-B cells; 3) Identify growth factors and associated regulatory mechanisms that affect CYP1B1 expression in bone marrow stromal cells. At the completion of this project, the investigators expect to have evaluated the role of bone marrow stromal cell CYP1B1, and resulting effector mechanisms, in DMBA-mediated apoptosis in progenitor B cells. These findings could lead to new insights into the mechanisms by which the toxicants cause bone marrow toxicity.

描述：（改编自研究者摘要）7,12-二甲基苯并[a]蒽作为致癌和免疫抑制多环芳烃的模型已被广泛研究。 DMBA 的大部分生物效应需要细胞色素 P450 家族的某些成员激活。 DMBA 对免疫系统最显着的影响之一是骨髓毒性，导致祖 B 淋巴细胞严重耗竭。该项目的长期目标是确定 DMBA 骨髓毒性的机制。在初步研究中，研究人员发现骨髓基质细胞具有高水平的细胞色素P450lBl (CYPlBl)，其在体外将DMBA代谢为致癌代谢物。研究人员还观察到，在体外与 DMBA 和骨髓基质细胞共培养时，祖 B 淋巴细胞会发生凋亡，但单独与 DMBA 一起培养时则不会发生凋亡。中心假设是骨髓基质细胞中CYP1B1对DMBA的代谢导致代谢物的释放，这些代谢物直接或间接导致祖B淋巴细胞凋亡。这项研究的基本原理是基于：i) 基质细胞与 B 细胞相互作用在正常 B 细胞发育中的至关重要性； ii)基质细胞中CYP1B1的高组成水平并且其在前B细胞中不存在； iii) 仅当与骨髓基质细胞共培养时，DMBA 才能够引起前 B 细胞凋亡。祖 B 细胞死亡的原因可能是： 前 B 细胞中 DMBA-DNA 加合物的形成； DMBA 处理的骨髓基质细胞的必需生长信号丢失；或通过 DMBA 处理的骨髓基质细胞释放前 B 细胞的毒性部分。为了解决这些可能性，研究人员将追求以下三个具体目标：1) 在一系列体内和体外实验中使用基因敲除小鼠来描述 CYP1B1 和 AhR 在 DMBA 诱导的前 B 细胞凋亡中的作用。 2) 区分 DMBA 处理的骨髓基质细胞引起前 B 细胞凋亡的可能机制（即 DNA 加合物形成、生长信号丢失、Fas 配体或其他介质的释放）； 3) 确定影响骨髓基质细胞中CYP1B1表达的生长因子和相关调节机制。该项目完成后，研究人员希望评估骨髓基质细胞 CYP1B1 在 DMBA 介导的 B 祖细胞凋亡中的作用以及由此产生的效应机制。这些发现可能会给毒物引起骨髓毒性的机制带来新的见解。