Inhibition of neutrophil responses by ecSOD

描述（由申请人提供）：吞噬性氧化爆发产生活性氧/氮（ROS/RNS），直接参与杀死细菌病原体，但当过量产生时也会导致组织损伤。吞噬细胞利用NADPH氧化酶产生超氧化物（O2 -），而一氧化氮（NO）由iNOS酶产生。细胞外超氧化物歧化酶（ecSOD）是一种将O2 -转化为过氧化氢（H2O2）的抗氧化酶，从而保护组织免受氧化应激和免疫介导的炎症。虽然中性粒细胞是清除细菌病原体所必需的，但目前尚不清楚ecSOD如何影响中性粒细胞的功能。单核增生李斯特菌（Listeria monocytogenes, Lm）是一种细胞内细菌，被广泛用作研究免疫反应和宿主/病原体相互作用的模型病原体。Lm感染导致非常高的死亡率（~25%），是一个严重的公共卫生问题。临床感染Lm可引起妇女自然流产，免疫功能低下者可引起胃肠炎、败血症、心内膜炎和脑膜炎。利用表达不同水平ecSOD活性（ecSOD HI、ecSOD WT和ecSOD KO）的新型基因小鼠，我们最近证明了宿主ecSOD的存在显著降低中性粒细胞功能和宿主对Lm感染的抵抗力。这些新的观察结果导致了我们的中心假设：实质细胞产生ecSOD抑制中性粒细胞杀死细菌，从而导致Lm的清除减少。在体外，离体和体内的方法将被用来测试以下具体目标。特异性目的1：确定在Lm感染期间ecSOD如何抑制保护性中性粒细胞反应。我们的工作假设是，在Lm感染期间，中性粒细胞吞噬ecSOD导致氧化破裂和细菌杀伤减少。目的2：确定造血细胞或实质细胞产生ecSOD是否会降低Lm的清除率。我们的工作假设是实质细胞产生的ecSOD通过抑制中性粒细胞反应来降低对Lm的抗性。在完成这一小型但概念创新的R03拨款的目标后，我们将深入了解ecsod介导的Lm感染期间中性粒细胞功能抑制的机制。这些研究将促进转化研究，从而导致在细菌感染和疫苗接种期间的治疗选择。调节宿主ecSOD活性可能在涉及中性粒细胞的无数感染性和炎症性疾病状态中是有益的。重要的是，人类ecSOD基因存在多态性，导致酶活性改变并影响疾病易感性。因此，我们的研究以及由此产生的未来疗法可能对人类健康和疾病产生直接影响。

DESCRIPTION (provided by applicant): Phagocytic oxidative burst generates reactive oxygen/nitrogen species (ROS/RNS) that are directly involved in killing bacterial pathogens, but can also cause tissue damage when produced in excess. Phagocytic cells utilize the NADPH oxidase to produce superoxide (O2 -), while nitric oxide (NO) is produced by the iNOS enzyme. Extracellular superoxide dismutase (ecSOD) is an anti-oxidant enzyme that converts O2 - into hydrogen peroxide (H2O2), thus protecting tissues from oxidative stress and immune-mediated inflammation. Although it is well established that neutrophils are required for the clearance of bacterial pathogens, it is not known how ecSOD impacts the function of neutrophils. Listeria monocytogenes (Lm) is an intracellular bacterium that is widely used as a model pathogen to study immune responses and host/pathogen interactions. Lm infection causes a very high mortality rate (~25%), and is a serious public health concern. Clinical infection with Lm can cause spontaneous abortions in women, and gastroenteritis, septicemia, endocarditis, and meningitis in immunocompromised individuals. Using novel congenic mice that express varying levels of ecSOD activity (ecSOD HI, ecSOD WT, and ecSOD KO), we have recently demonstrated that the presence of host ecSOD significantly decreases neutrophil function and host resistance to Lm infection. These novel observations have led to our central hypothesis: production of ecSOD by parenchymal cells inhibits bacterial killing by neutrophils, thus leading to reduced clearance of Lm. In vitro, ex vivo, and in vivo approaches will be utilized to test the following specific aims. Specific Aim 1: To determine how ecSOD inhibits protective neutrophil responses during Lm infection. Our working hypothesis is that phagocytosis of ecSOD by neutrophils results in decreased oxidative burst and bacterial killing during Lm infection. Specifi Aim 2: To determine whether ecSOD production by hematopoietic or parenchymal cells decreases the clearance of Lm. Our working hypothesis is that parenchymal cell production of ecSOD decreases resistance to Lm by inhibiting neutrophil responses. Upon completion of the aims of this small, yet conceptually innovative R03 grant, we will gain insight into the mechanism of ecSOD-mediated inhibition of neutrophil function during Lm infection. These studies will prompt translational research that leads to treatment options during bacterial infection and vaccination. Modulating host ecSOD activity could be beneficial during a myriad of infectious and inflammatory disease states involving neutrophils. Importantly, there are polymorphisms in the human ecSOD gene which lead to altered activity of the enzyme and impact disease susceptibility. Therefore, our studies, and future therapies resulting from them, may have a direct impact on human health and disease.