Atherosclerotic heart disease is the leading cause of death in the USA. Chronic inflammation is a key component of this process and manipulation of inflammation may yield novel treatments. Recent studies have highlighted IL-1?, as a key inflammatory cytokine in chronic inflammation, including vasculitis and atherosclerosis, and clinical trials are underway to neutralize IL-1? in type 2 diabetes and atherosclerosis. Previous studies showed a key role of IL-1? and apoptosis in plaque progression, but no mechanistic connections were drawn between these two processes and the exact mechanism by which IL-1?is activated was not known until now. We have recently discovered the elusive mechanism of NLRP3 inflammasome activation for IL-1?production, and linked apoptosis and mitochondrial (Mt) oxidative DNA damage to this pathway. We showed that danger signals that induce Mt dysfunction and ROS in the Mt, result in damaged (oxidized) mtDNA that is released into the cytosol where it binds to and activates the NLRP3 inflammasome, the machinery by which active IL-1? is made. Based on these recent seminal findings, the main goal of this exploratory R21 proposal is to investigate the role of mtDNA damage during apoptosis and induction of IL-1? as it relates to vascular inflammation and atherosclerosis in order to find novel and more efficient ways to prevent and treat this disease. We will manipulate the mitochondrial DNA repair system to investigate its potential as a new treatment strategy that would prevent the activation of IL-1? (as well as IL-18- the other NLRP3-dependent cytokine), as opposed to current strategies to neutralize IL-1? after it is already released and led to downstream activation. Based upon these key findings, we propose the following two Aims focused around the central hypothesis that oxidative mtDNA damage that occurs during vascular inflammation activates the NLRP3 inflammasome for IL-1?production and plays a proinflammatory role in atherogenesis.Inhibition of oxidative DNA damage will prevent NLRP3 inflammasome activation and result in decreased vascular inflammation and atherosclerosis.
Specific AIM 1 - To define the role of mitochondrial DNA damage during NLRP3 inflammasome activation in a diet-induced hypercholesterolemic mouse models of atherosclerosis using mice deficient in the DNA damage repair gene Ogg1.
AIM 2 - To investigate the therapeutic role of blocking mitochondrial DNA induced NLRP3 activation by synthetic 8-OH-dG administration and to determine the role of augmenting the Mt DNA repair with Ogg1 gene transfer.
The important role of IL-1 in the development and progression of atherosclerosis was highlighted by preclinical animal studies. In clinical studies, IL-1 beta wa found in greater concentration in atherosclerotic human coronary arteries and clinical studies are currently underway to block IL-1 beta in human atherosclerotic coronary disease. This project will focus on the role of oxidative damage to mitochondrial DNA in triggering IL- 1beta activation in efforts to develop more focused and effective novel therapeutic approaches to prevent progression of atherosclerosis.