MYLEOPEROXIDASE AND LEUKOCYTE GRANULE COMPONENTS

刺激嗜中性白细胞导致分泌有毒的 蛋白质和酶髓过氧化物酶（MPO）从细胞质颗粒， 激活中性粒细胞氧（O2）代谢，产生有毒氧化剂。 神经毒素通过杀死入侵的微生物来对抗感染， 也有助于炎症组织的破坏。 长期目标是 为了表征氧化剂，确定它们在抗微生物中的作用， 活性和损害宿主细胞，并阐明机制， 它们的效力和选择性。 工作假设是氢 过氧化物（H2 O2）和MPO/H2 O2/氯化物（Cl-）体系的产物是 主要的氧化毒素 超氧化物（02-）是白细胞的第一个产物 02代谢，但02-的主要作用不是作为毒素。 相反地， 02-是H2 O2生产的中间体和细胞外的氧化剂 还原剂如抗坏血酸盐（维生素C）和巯基化合物。 这些还原剂被O2氧化增加了H2 O2的产生并消耗了 使它们不能使H2 O2和MPO的产物解毒 系统 MPO系统的毒性也受氨（NH 4+）调节， 和来自细胞质颗粒的富含赖氨酸的肽。 MPO催化了 Cl-被H2 O2氧化以产生次氯酸（HOCl），其反应 与NH 4+反应生成杀菌剂一氯胺（NH 2Cl）。 然而，在这方面， NH 2Cl还可以通过抑制嗜中性粒细胞O2代谢来抑制毒性， NH_4 ~+或NH_2Cl可抑制MPO的分泌。 HOC 1与 赖氨酸肽产生相对无毒但寿命长的 肽-氯胺。 拟议的研究将描述 O2-、H2 O2和MPO系统的产物与抗坏血酸的相互作用， 其他细胞外还原剂，并检查还原剂对 分离的中性粒细胞的抗菌和细胞毒活性。 的 锰（Mn 2+）促进MPO氧化还原剂的能力将 进行研究，以确定MPO是否可以作为氧化酶并产生 具有缺陷O2代谢的嗜中性粒细胞中的毒性氧化剂。 的影响 NH 4+对中性粒细胞O2代谢、MPO分泌和抗菌活性的影响 将被测量，并且赖氨酸肽与MPO的相互作用 系统将使用纯化的肽进行研究， MPO。 这些研究将为氧化剂的作用提供新的见解， 减少中性粒细胞功能，并可能导致改善的方法， 对抗感染，同时抑制对宿主组织的损害。

Stimulation of neutrophilic leukocytes results in secretion of toxic proteins and the enzyme myeloperoxidase (MPO) from cytoplasmic granules and activates neutrophil oxygen (O2) metabolism, which produces toxic oxidants. Neutrophil toxins combat infection by killing invading microorganisms but also contribute to inflammatory tissue destruction. Long-range goals are to characterize the oxidants, determine their role in antimicrobial activity and damage to host cells, and elucidate mechanisms that regulate their potency and selectivity. The working hypothesis is that hydrogen peroxide (H202) and products of the MPO/H202/chloride (C1-) system are the major oxidative toxins. Superoxide (02-) is the first product of leukocyte 02 metabolism, but the principal role of 02- is not as a toxin. Instead, 02- is an intermediate in H202 production and an oxidant for extracellular reductants such as ascorbate (vitamin C) and sulfhydryl compounds. Oxidation of these reductants by 02-increases H202 production and consumes the reductants so that they can't detoxify H202 and products of the MPO system. Toxicity of the MPO system is also regulated by ammonia (NH4+), and lysine-rich peptides from the cytoplasmic granules. MPO catalyzed the oxidation of Cl- by H202 to yield hypochlorous acid (HOC1), which reacts with NH4+ to yield the bactericidal agent monochloramine (NH2C1). However, NH2C1 can also suppress toxicity by inhibiting neutrophil 02 metabolism, and NH4+ or NH2C1 may inhibit MPO secretion. The reaction of HOC1 with the lysine-peptides yields relatively non-toxic though long-lived peptide-chloramines. The proposed studies will characterize the interaction of 02-, H202, and products of the MPO system with ascorbate and other extracellular reductants, and examine effects of the reductants on antibacterial and cytotoxic activities of isolated neutrophils. The ability of manganese (Mn2+) to promote oxidation of reductants by MPO will be studied, to determine whether MPO could act as an oxidase and produce toxic oxidants in neutrophils with defective 02 metabolism. The effect of NH4+ on neutrophil 02 metabolism, MPO secretion, and antibacterial activity will be measured, and the interaction of lysine-peptides with the MPO system will be studied using purified peptides and MPO. These studies will provide new insights into the role of oxidants and reductants in neutrophil function and may lead to improved methods for combating infection while suppressing damage to host tissues.