Linkage of Lung Inflammation to 8-oxoguanine and OGG1

描述（由申请人提供）：8-氧代-7，8-二氢鸟嘌呤（8-oxoG）通常用作氧化应激的标志物，由环境和内源性活性氧（ROS）在核酸中产生。它是DNA中的一种预致突变损伤，因为它在复制过程中可能与腺嘌呤错配。碱基8-oxoG通过DNA碱基切除修复（BER）途径中的8-oxoG DNA糖基化酶1（OGG 1）从DNA中去除。减少的修复和导致的8-oxoG积累与各种人类疾病和衰老有关，尽管其病因学作用知之甚少。炎症是大多数疾病的根源，包括呼吸系统、心血管系统、中枢神经系统和癌症。豚草花粉提取物（RWPE：具有促氧化剂和抗原成分）增加基因组中的8-oxoG水平和小鼠气道中的OGG 1活性。在RWPE暴露前致敏小鼠肺中OGG 1（但不是其他氧化碱基特异性DNA糖基化酶）的下调显著降低了过敏性气道炎症。重要的是，单独的EG 8-oxoG（基因组外8-oxoG）诱导小鼠肺中的趋化因子表达，沿着中性粒细胞积聚。我们的数据还显示，EG 8-oxoG增加了1）活化的小GTP酶; 2）Ras与Raf-1的结合;和3）MEK 1，2; 4）ERK 1，2;和5）RelA-Ser 276的磷酸化的水平。EG 8-oxoG诱导由CXCL-8启动子驱动的荧光素酶表达。值得注意的是，其他氧化嘌呤碱基没有这种作用。这些意想不到的观察结果使我们假设，通过OGG 1从DNA中释放的8-oxoG凭借其增加活化的小GTP酶水平的能力作为信号分子发挥作用，从而引发细胞活化事件的级联反应，导致促炎介质表达增加和炎症加剧。我们将通过追求三个具体目标来检验这一假设。我们将调查是否：目的1）8-oxoG修复缺陷使小鼠对炎症反应不敏感;目的2）OGG 1的糖基化酶活性在炎症反应后被调节以从DNA中释放EG 8-oxoG;目的3）EG 8-oxoG通过NF-？B，由Ras-Raf-MEK/ERK-MSK 1途径激活。肺部炎症的小鼠疾病模型将用于建立我们在培养细胞中产生的结果的病因学相关性。这些目标的完成将提供EG 8-oxoG是氧化应激介导的DNA损伤/修复和细胞应答之间的联系的第一证据，其通过充当诱导促炎趋化因子表达的信号传导分子。我们的机制研究也应该为新的治疗方法奠定基础。例如，将EG 8-oxoG捕获、释放或转化为非信号传导形式的药物应该不仅有益于预防气道中的炎症过程，而且有益于预防心血管和中枢神经系统或肥胖相关的炎症疾病等。 公共卫生相关性：呼吸系统疾病影响全世界>八亿人，并且在美国，每年约有两千万门诊就诊、两百万急诊室就诊和五十万住院与这些疾病相关。我们将氧化基因组损伤修复与炎症联系起来并随后确定其分子机制的新观察结果为探索非常规预防性治疗方法以抑制炎症并从而抑制随后的发病机制提供了机会。

DESCRIPTION (provided by applicant): 8-oxo-7,8-dihydroguanine (8-oxoG), often used as a marker of oxidative stress, is generated in nucleic acids by environmental and endogenous reactive oxygen species (ROS). It is a premutagenic lesion in DNA because of its mispairing potential with adenine during replication. The base 8-oxoG is removed from the DNA by 8-oxoG DNA glycosylase 1 (OGG1) in the DNA base excision repair (BER) pathway. Decreased repair and resulting accumulation of 8-oxoG have been related to various human diseases and aging, although its etiological role is poorly understood. Inflammation is the root of most diseases including those of the respiratory, cardiovascular, central nervous systems and of carcinogenesis. Ragweed pollen extract (RWPE: has pro-oxidant and antigenic components) increases the 8-oxoG level in the genome and OGG1 activity in the mouse airways. Downregulation of OGG1 (but not of other oxidized-base specific DNA glycosylases) in the lungs of sensitized mice before RWPE exposure significantly decreased allergic airway inflammation. Importantly, EG8-oxoG (extragenomic 8-oxoG) alone induced chemokine expression in mouse lungs, along with neutrophil accumulation. Our data also show that EG8-oxoG increased the levels of 1) activated small GTPases; 2) Ras to Raf-1 binding; and phosphorylation of 3) MEK1,2; 4) ERK1,2; and 5) RelA-Ser276. EG8-oxoG induced luciferase expression driven from the CXCL-8 promoter. Notably, other oxidized purine bases had no such effects. These unexpected observations led us to hypothesize that 8-oxoG liberated from DNA by OGG1 functions as a signaling molecule by virtue of its ability to increase levels of activated small GTPases, thereby initiating cascades of cellular activation events leading to increased pro-inflammatory mediator expression and exacerbation of inflammation. We will test this hypothesis by pursuing three Specific Aims. We will investigate whether: Aim 1) deficiency in 8-oxoG repair renders mice refractory to inflammation; Aim 2) OGG1's glycosylase activity is post-translationally modulated for release of EG8-oxoG from DNA; and Aim 3) EG8-oxoG enhances expression of pro-inflammatory mediators via NF-?B, activated by the Ras-Raf-MEK/ERK- MSK1 pathway. A mouse disease model for lung inflammation will be used to establish the etiological relevance of our results generated in cultured cells. Completion of these aims will provide the first evidence that EG8-oxoG is the link between oxidative stress- mediated DNA damage/repair and cellular responses, by acting as a signaling molecule inducing pro- inflammatory chemokine expression. Our mechanistic studies should also lay the foundation for novel therapeutic approaches. For example, drugs that trap, scavenge, or convert EG8-oxoG into a non-signaling form should be beneficial for the prevention of inflammatory processes not only in airways, but also in cardiovascular, and central nervous systems or in obesity-associated inflammatory diseases, among others. PUBLIC HEALTH RELEVANCE: Respiratory diseases affect >eight hundred million people worldwide, and in the US there are approximately twenty million outpatient visits, two million emergency room visits, and half million hospitalization per year related to these diseases. Our novel observations linking oxidative genome damage repair to inflammation and subsequently identifying its molecular mechanism provide an opportunity to explore unconventional preventive therapeutic approaches to inhibit inflammation and thereby subsequent pathogenesis.