The Imapct of Oxidative Stress on the Pathogenesis of COPD---An Ivestigation into Its Relationship with Abnormal Inflammation, Dna Instability, Epigenetics and Cell Metabolism

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory airway disease with systemic inflammation and manifestations, currently lacking effective treatment to modify its progression and to decrease mortality. The inflammation of COPD is abnormal with the characteristics of amplification, self-perpetuation and insensitive to steroid. Other pathogenesis includes premature aging process, apoptosis, DNA damage, impairment in microbial defense, etc. Excessive oxidative stress has long been implicated in these complicated conditions with unclear mechanisms. We has reported that NF-κB repressing factor (NRF), an endogenous repressor of the pivotal inflammatory transcription factor NF-κB-response genes, is reduced in peripheral blood mononuclear cells (PBMC) of COPD patients, which is a link toward systemic inflammation of COPD. Oxidative stress has been implicated in this dysregulation. Our preliminary data indicated that oxidative stress was increased in serum of COPD patients. COPD PBMC was vulnerable to H2O2 stimulation to produce inflammatory cytokines. Importantly, we found a trend toward reduction in expression of the anti-aging SIRT1 and the repressive epigenetic enzyme SUV39H1. SIRT1 is a stress sensor mediating anti-oxidative stress response. SIRT1 has been reported to upregualte SUV39H1, ensuring genome protection. Our preliminary data also revealed that, instead of induction as in normal conditions, H2O2 seemed to reduce SIRT1 and SUV39H1 in COPD PBMC. In cells with SUV39H1 inhibition, H2O2 suppression of PKM2, another oxidative stress sensor and a critical enzyme for metabolism, seemed to be prevented. Data also suggested that inhibiting proteasome deteriorated H2O2-induced inflammation whilst stimulating autophagy seemed to reverse this effect. Further data indicated that SUV39H1 might be involved in glucocorticoid suppressive effects. Taken together, we hypothesized that cells of COPD are vulnerable to oxidative stress and impaired SIRT1/SUV39H1 oxidative stress response plays a central role in mediating this effect. This impairment is a link to other manifestations of COPD, e.g. sustained inflammation, genome instability, premature aging and insensitivity to glucocorticoids. This 3-year project is designed to test this hypothesis. We will enroll 180 subjects, including 30 each of normal non-smokers, healthy smokers and stage I-IV COPD patients. SIRT1/SUV39H1 and the related molecules will be correlated to the clinical data. PBMC, monocyte cell lines and respiratory epithelial cell lines will be used to explore the mechanism. Stable clones of SIRT1/SUV39H1 overexpression and knockdown will be established to mimic cells in COPD. Pharmacological inhibitors, stimulators, and over-expression or RNAi by transient transfection will be used to confirm the roles of each molecule. Gene expression microarrays and chip-on-ChIP will be used to study the genes affected at the global level. This study will not only advance our knowledge into the mechanism whereby abnormal inflammation of COPD and the insensitivity to glucocorticoids is induced, but also will possibly provide new biomarkers and a novel therapeutic direction for developing effective therapy for COPD.