CATECHOLAMINES, ANTIOXIDANTS AND OXIDATIVE STRESS

众所周知，易自氧化的儿茶酚胺由于其固有的氧化还原特性，在有氧条件下会产生活性自由基和过氧化氢。因此，儿茶酚胺能神经元固有地受到高氧化应激和自由基损伤。儿茶酚胺能神经元在衰老和帕金森氏病等中枢神经系统疾病以及苯丙胺等非法药物的使用中的退化，被归因于儿茶酚胺介导的大脑受影响区域过度产生氧自由基和/或过氧化氢。虽然大多数活性自由基和氧化剂可以被酶防御机制和细胞氧化剂有效清除，但它们的过度产生可能会导致广泛的细胞损伤。高浓度抗坏血酸(ASC)的存在、复杂的ATPase驱动、b561介导的ASC再生系统(ARS)、高效的儿茶酚胺摄取机制以及儿茶酚胺储存囊泡中缺乏谷胱甘肽等抗氧化剂表明，除了为多巴胺β-单加氧酶(DbetaM)和肽基α-羟化单加氧酶(PHM)反应提供电子外，ASC还必须在保护儿茶酚胺诱导的儿茶酚胺能神经元免受自由基损伤方面发挥关键作用。因此，质子转运ATPase、ARS或单胺转运体的故障可能导致高氧化应激，导致指数级联的自由基生成和广泛的细胞损伤。尽管有这些令人信服的证据，但儿茶酚胺能神经元整合病理特征的生化机制尚未完全探索。因此，更准确地描述(A)儿茶酚胺代谢中的生化步骤和(B)抗氧化剂在保护儿茶酚胺免受氧化从而缓解氧化应激中的作用可能是我们理解儿茶酚胺能神经元功能障碍的重要进展。这项研究的总体目标是以嗜铬粒和颗粒幽灵为模型，采用多学科方法在分子水平上研究单胺转运体、质子转运ATPase、ARS和DbetaM的功能偶联。随着对这些蛋白质的功能偶联有了更好的了解，这些蛋白质在保护儿茶酚胺储存囊泡免受氧化应激中的作用以及氧化应激对其个体和协调功能的影响将被研究。

Easily autooxidizable catecholamines are known to generate reactive radicals and H2O2 under aerobic conditions due to their inherent redox properties. Consequently, catecholaminergic neurons are inherently subjected to high oxidative stress and free radical damage. The degneration of catecholaminergic neurons in aging and central nervous system diseases such as Parkinson's Disease, as well as in the use of illicit drugs such as amphetamines have been attributed to the catecholamine mediated excessive production of oxygen free radicals and/or H2O2 in the affected areas of the brain. Although, most of the reactive radical species and oxidants are effectively scavenged by enzymatic defense mechanisms and by cellular oxidants, their excessive generation may lead to extensive cellular damage. Presence of high concentrations of ascorbate (Asc), an intricate ATPase drive, b561-mediated, Asc regenerating system (ARS), and an efficient catecholamine uptake mechanism together with the absence of antioxidants such as glutathione in catecholamine storage vesicles suggest that, in addition to providing electrons for dopamine beta-monooxygenase (DbetaM) and peptidyl alpha- hydroxylating monooxygenase (PHM) reactions, Asc must also play a key role in the protection of catecholaminergic neurons from catecholamine induced free radical damage. Therefore, the malfunctioning of proton translocating ATPase, ARS, or monoamine transporter could result in high oxidative stress leading to an exponentially propagating cascade of radical generation and extensive cellular damage. Despite this convincing evidence, the biochemical mechanisms that my integrate the pathological features in catecholaminergic neurons have not been fully explored. Thus, a more precise description of (a) the biochemical steps in catecholamine metabolism and (b) the role of antioxidants in protecting catecholamines from oxidation, consequently relieving oxidative stress could be a significant advancement in our understanding of the dysfunction of catecholaminergic neurons. The overall objective of the proposed studies is to examine the functional coupling of the monoamine transporter, proton translocating ATPase, ARS, and DbetaM at the molecular level using multidisciplinary approaches using chromaffin granules and granule ghosts as a model. With a better understanding of the functional coupling of these proteins, the role of these proteins in protecting catecholamine storage vesicles from oxidative stress as well as the effect of oxidative stress on their individual and coordinated functions will be examined.