Chemogenetic Neurovascular Oxidative Stress: Neurodegeneration and Cardiac Remodeling - Oxidative stress is a hallmark of neurodegeneration and has been implicated in the pathobiology of vascular contributions to cognitive impairment and dementia (VCID). Our “chemogenetic” approach allows us to dynamically modulate reactive oxygen species (ROS) in target cells in vivo using the yeast enzyme D-amino acid oxidase (DAAO) to produce the ROS hydrogen peroxide (H2O2). We generated two new transgenic mouse lines that express DAAO by crossing a conditionally activatable DAAO transgenic mouse line (which we developed) with commercially available mouse lines expressing Cre recombinase under control of two distinct putatively “endothelial cell-specific” Cdh5 or Tie2 promoters. Both the DAAO-TGCdh5 and DAAO-TGTie2 lines express DAAO and generate H2O2 in endothelial cells. Within 2 days of providing D-alanine to DAAO-TGCdh5 mice, the animals develop a striking sensory ataxia, and have a highly specific pattern of neurodegeneration and mitochondrial disarray in dorsal root ganglia and nodose (vagal sensory) ganglia. Importantly, DAAO-TGCdh5 mice treated with D-alanine also develop cardiac hypertrophy. The combination of sensory neuropathy and cardiac hypertrophy is similar to the phenotype of Friedreich’s ataxia, the most common form of hereditary ataxia in humans. By contrast, the DAAO-TGTie2 transgenic line, which expresses DAAO in endothelium under control of the Tie2 promoter, shows no ataxia, has no transgene expression in DRG, and does not develop cardiac hypertrophy. But the DAAO-TGTie2 mice does develop marked disruption of the blood barrier following long-term D-alanine feeding. Here we propose studies to test the hypotheses that neurovascular oxidative stress leads to neurodegeneration, BBB disruption, cognitive dysfunction, and cardiac hypertrophy. We propose to pursue transcriptomic, proteomic, metabolomic, and biochemical studies of DRG, nodose ganglia, brain, and cardiac tissues following chemogenetic oxidative stress in vivo, and we will study the behavioral and physiological phenotypes in the DAAO-TGCdh5 and DAAO-TGTie2 mouse lines. We will identify the temporal sequence and the molecular mechanisms whereby neurovascular oxidative stress causes degeneration of DRG and nodose ganglia and leads to cardiac hypertrophy. We will establish the pathways by which vascular oxidative stress disrupts the BBB and leads to cognitive impairment. The Specific Aims are: Aim 1: Identify the molecular mechanisms whereby neurovascular oxidative stress causes degeneration of DRG; Aim 2: Characterize the molecular processes whereby neurovascular oxidative stress causes disruption of the blood-brain barrier and leads to cognitive impairment; Aim 3: Define the pathways whereby neurovascular oxidative stress causes cardiac hypertrophy. The proposed studies may lead to the identification of new pharmacological targets for prevention and treatment of Alzheimer’s Disease and related dementias, Friedreich’s ataxia, adverse cardiac remodeling, and the many other chronic disease states in which oxidative stress has been implicated.
