Alzheimer's disease (AD) is a progressive neurodegenerative disorder that remains a major cause of dementia worldwide. It is now widely accepted that chronic inflammation plays a major role in the pathophysiology of AD. AD is associated with increased oxidative stress and oxidative DNA damage (1). Reactive oxygen species (ROS) generated due to normal cellular metabolism and/or dysregulated inflammatory response, are known to cause DNA base oxidation. Most of these DNA lesions are mutagenic and/or toxic and have been implicated in a wide variety of pathophysiological states. Oxidized DNA base lesions are primarily repaired via the DNA base excision repair (BER) pathway. Several reports indicate that AD is associated with an abnormal BER pathway (1, 2). Large nationwide epidemiologic studies have shown that asthma is associated with an increased risk of developing Alzheimer's disease (Hazard ratio 2.62, 95% CI: 1.71-4.02) (3, 4). Allergic asthma (AA) and allergic rhinitis (AR) are highly prevalent chronic inflammatory diseases of the airways. These diseases affect about 10% to 30% of the world population. Chronic inflammation negatively affects tissue functionality. We have reported that asthma and allergic airway inflammation is associated with oxidative stress, oxidative DNA damage and abnormal BER in the lungs (5-9). However the contribution of chronic allergic airway inflammation to abnormal DNA damage and BER in the brain is a gap in knowledge that we propose to explore in this proposal. In the preliminary studies of the parent R01 we showed the formation of a cytosolic DNA-protein interactome that recruits cGAS and IRF3 together with the DNA-BER enzyme NEIL2 to the abnormal location in cytosol of lung cells in mice allergic to cat dander but not in nave mice exposed to cat dander. We name this lung complex Allergosome. Surprisingly, intrapulmonary delivery of endotoxin free recombinant NEIL2 significantly reduced lung inflammation in CDE-challenged mice lung. Furthermore, we found that inflammation in the lung not only induces DNA damage in the lungs, also induces DNA damage in the brain. We hypothesize that allergen-induced dysregulated inflammation due to suboptimum level of NEIL2 will cause excessive ROS generation, which in turn will lead to increased cellular DNA damage both in the lungs and brain. This positive feed back loop will be critical in perpetuating an inflammatory microenvironment in the brain tissues resulting in the accumulation of severe DNA damage that may enhance neuronal cell death, leading to promotion and eventually progression of AD pathologies. Here we propose to carry out a systemic study to i). Evaluate chemokine/cytokine production and gene expression by multiplex analysis of the brains of nave wild type (WT) vs Neil2-null mice exposed to cat dander, as well as mice chronically sensitized to cat dander, ii). Examine for the presence of oxidative DNA damage, abnormal DNA BER, and cytosolic DNA-protein interactome in such animals, iii). Carry out such studies after intrapulmonary administration of rNEIL2 using two different peptide carriers that will target the protein either in the lungs or mouse brain, and finally (iv). Generate conditional brain-specific Neil2-null mice to understand the critical role of DNA BER in ameliorating AD pathogenesis. Successful completion of this study will be instrumental to generate the preliminary data required for submitting a full-length NIH R01 or P01 grant proposal in the future to undertake a comprehensive mechanistic study in understanding AD pathology. References: 1. Lillenes MS, Rabano A, Stoen M, Riaz T, Misaghian D, Mollersen L, Esbensen Y, Gunther CC, Selnes P, Stenset VT, et al. Altered DNA base excision repair profile in brain tissue and blood in Alzheimer's disease. Mol Brain. 2016;9(1):61. 2. Weissman L, Jo DG, Sorensen MM, de Souza-Pinto NC, Markesbery WR, Mattson MP, and Bohr VA. Defective DNA base excision repair in brain from individuals with Alzheimer's disease and amnestic mild cognitive impairment. Nucleic Acids Res. 2007;35(16):5545-55. 3. Chen MH, Li CT, Tsai CF, Lin WC, Chang WH, Chen TJ, Pan TL, Su TP, and Bai YM. Risk of dementia among patients with asthma: a nationwide longitudinal study. J Am Med Dir Assoc. 2014;15(10):763-7. 4. Peng YH, Wu BR, Su CH, Liao WC, Muo CH, Hsia TC, and Kao CH. Adult asthma increases dementia risk: a nationwide cohort study. J Epidemiol Community Health. 2015;69(2):123-8. 5. Hosoki K, Jaruga P, Itazawa T, Aguilera-Aguirre L, Coskun E, Hazra TK, Boldogh I, Dizdaroglu M, and Sur S. Excision release of 5?hydroxycytosine oxidatively induced DNA base lesions from the lung genome by cat dander extract challenge stimulates allergic airway inflammation. Clin Exp Allergy. 2018;48(12):1676-87. 6. Hosoki K, Redding D, Itazawa T, Chakraborty A, Tapryal N, Qian S, Qi H, Aguilera-Aguirre L, Brasier AR, Phani VS, et al. Innate mechanism of pollen- and cat dander-induced oxidative stress and DNA damage in the airways. J Allergy Clin Immunol. 2017;140(5):1436-9 e5. 7. Hosoki K, Boldogh I, Aguilera-Aguirre L, Sun Q, Itazawa T, Hazra T, Brasier AR, Kurosky A, and Sur S. Myeloid differentiation protein 2 facilitates pollen- and cat dander-induced innate and allergic airway inflammation. J Allergy Clin Immunol. 2016;137(5):1506-13 e2. 8. Bacsi A, Aguilera-Aguirre L, Szczesny B, Radak Z, Hazra TK, Sur S, Ba X, and Boldogh I. Down-regulation of 8-oxoguanine DNA glycosylase 1 expression in the airway epithelium ameliorates allergic lung inflammation. DNA Repair (Amst). 2013;12(1):18-26. 9. Boldogh I, Bacsi A, Choudhury BK, Dharajiya N, Alam R, Hazra TK, Mitra S, Goldblum RM, and Sur S. ROS generated by pollen NADPH oxidase provide a signal that augments antigen-induced allergic airway inflammation. J Clin Invest. 2005;115(8):2169-79.
Alzheimer?s disease is the most common type of dementia worldwide; and its prevalence is expected to increase over the next few decades with aging population. AD is a complex disease and despite decades of research, and many fundamental questions regarding the etiology of the disease still remains unanswered. Increasing evidence suggest that neuroinflammation plays an important role in the pathogenesis of AD. We recently made an important observation that NEIL2, and oxidized base-specific DNA glycosylase primarily involved in transcription-coupled DNA base excision repair (TC-BER), plays an important role in innate immunity. We will test here whether selectively targeting endotoxin free recombinant NEIL2 in mouse brain can mitigate AD pathology.
