Oxidants and Cell Death

氧化剂和细胞死亡

基本信息

批准号：
6679777
负责人：
EMILY B SHACTER
金额：
--
依托单位：
依托单位国家：
美国
项目类别：
财政年份：
资助国家：
美国
起止时间：
至
项目状态：
未结题

项目摘要

Summary: We are investigating how inflammatory oxidants such as hydrogen peroxide (H2O2) kill tumor cells and how they may influence tumor cell recognition and elimination by the immune system. Most chemotherapeutic agents kill tumor cells by inducing apoptosis. Solid tumors are often infiltrated by inflammatory phagocytes which can generate oxidative stress within the tumor tissue. Previously, we found that in the presence of H2O2, human Burkitt's lymphoma (BL) cells are unable to undergo apoptosis in response to cancer chemotherapy drugs and die instead by a form of necrosis. One of the most important consequences of the interaction between H2O2 and the chemotherapy drugs is that the cells do not become phagocytosed by co-cultured macrophages until after their membranes have lysed. This can lead to an undesirable inflammatory reaction to the dying cells, which can further complicate tumor cell depletion. Studies carried out during the past year were aimed at identifying the molecular mechanism whereby H2O2 inhibits uptake of dying tumor cells by macrophages and at identifying cofactors for the phagocytic process. Shortly after the induction of apoptosis, dying cells are targeted for phagocytosis via the translocation of phosphatidylserine (PS) from the inner to the outer leaflet of the plasma membrane. Recently, we discovered that phagocytosis of apoptotic lymphoma cells requires the presence of protein S, a serum protein that regulates the activity of activated protein C. H2O2 inhibits the protein S-stimulated phagocytosis of BL cells even when they express PS on the exofacial surface of the plasma membrane. H2O2 treatment does not inhibit protein (annexin) binding to PS, nor does it modify the spatial distribution of PS on the apoptotic cell membrane (as determined by confocal microscopy). These results indicate that PS is necessary, but is not sufficient for recognition and uptake of apoptotic cells by macrophages. Further, they suggest that H2O2 acts by modifying a separate, as yet unidentified phagocytic marker on the surface of apoptotic cells. In a separate series of studies, we sought to determine whether the mechanism of cell killing by H2O2 is typical of all oxidants generated by inflammatory cells. Previously, we found that the primary mode of death induced in human B lymphoma cells by H2O2 is non-apoptotic. In more recent studies, we examined the mechanism of cell killing by the two other oxidants known to be generated by activated phagocytes. We found that superoxide kills cells entirely through formation of H2O2 such that the cells die primarily by pyknosis/necrosis. In contrast, HOCl kills the cells by apoptosis which is mediated by formation of aminoacyl chloramines in the growth medium. The molecular targets for these oxidants are being sought so that we may identify additional mechanisms of controlling cell death.

摘要：我们正在研究炎性氧化剂（例如过氧化氢（H2O2））如何杀死肿瘤细胞，以及它们如何影响免疫系统肿瘤细胞识别和消除。大多数化学治疗剂通过诱导凋亡杀死肿瘤细胞。实体瘤通常会被炎症性吞噬细胞浸润，这些吞噬细胞会在肿瘤组织中产生氧化应激。以前，我们发现在存在H2O2的情况下，人伯基特的淋巴瘤（BL）细胞无法响应癌症化学疗法药物而无法凋亡，而是因坏死形式而死。 H2O2与化学疗法药物之间相互作用的最重要后果之一是，直到膜裂解后，细胞才会被共培养的巨噬细胞吞噬。这可能导致对垂死细胞的不良炎症反应，这可能会使肿瘤细胞的耗竭复杂化。在过去的一年中进行的研究旨在鉴定H2O2通过巨噬细胞抑制染色肿瘤细胞的摄取并鉴定吞噬过程的辅助因子的分子机制。诱导凋亡后不久，通过磷脂酰丝氨酸（PS）从内部到质膜外叶的易位，将垂死的细胞靶向吞噬作用。最近，我们发现凋亡淋巴瘤细胞的吞噬作用需要蛋白S的存在，蛋白S是一种血清蛋白，该血清蛋白调节活化蛋白C的活性C. H2O2抑制了蛋白S刺激的BL细胞的吞噬作用，即使它们在PS上表达PS的PS在血浆膜膜上表面。 H2O2处理不会抑制与PS结合的蛋白质（膜联蛋白），也不会改变PS在凋亡细胞膜上的空间分布（通过共聚焦显微镜确定）。这些结果表明PS是必要的，但不足以通过巨噬细胞识别和吸收凋亡细胞。此外，他们建议H2O2通过修改凋亡细胞表面上的单独的吞噬标记来作用。在另一系列研究中，我们试图确定H2O2杀死细胞的机理是否是炎症细胞产生的所有氧化剂的典型代理。以前，我们发现H2O2在人B淋巴瘤细胞中诱导的主要死亡方式是非凋亡的。在最近的研究中，我们检查了已知的其他两种氧化剂被激活的吞噬细胞产生的其他氧化剂的机理。我们发现，超氧化物通过H2O2的形成完全杀死细胞，从而使细胞主要死于肾结变/坏死。相比之下，HOCL通过凋亡杀死细胞，这是通过生长培养基中氨基酰胺形成而介导的。寻求这些氧化剂的分子靶标，以便我们可以确定控制细胞死亡的其他机制。