Examining the Role of Arginase1 Overexpression in an Animal Model of Tauopathy
Alzheimer’s disease (AD) is a neurodegenerative disorder that is becoming increasingly widespread worldwide. This debilitating disease is characterized by neurofibrillary tangles and plaques in the brain composed of tau and amyloid beta peptide plaques, respectively. One of the leading causes of plaques and tangles is the hyperphosphorylation of tau, which is associated with cognitive impairment and decline in memory processes.
It has been found that polyamines may have a neuroprotective role and are currently being investigated further. An essential pathway that leads to production of polyamines is the L-arginine pathway. Metabolism of L-arginine can go two ways; metabolism via arginase produces polyamines and other essential molecules. Metabolism via nitric oxide synthase produces nitric oxide and other harmful molecules that contribute to nitric oxide stress. Because of the possible beneficial role of polyamines, metabolism of arginine by arginase is of interest. Recently, our lab has recently shown that arginase1 overexpression has the ability to reduce phosphorylated tau and neurofibrillary tangles in rTg4510 and PS19 tau transgenic mice. Based on these data, we utilized the transgenic tetO MAPT*P301L mouse model to examine a potential therapeutic gene of interest, arginase1, in an animal model of tauopathy. The model used in this study is unique, in that the administration of the viral-mediated gene therapy (adeno-associated virus serotype 9; AAV9) not only activates the mouse transgene (under a tetracycline activator protein (tTa2) promoter), but also the viral tandem gene with the viral construct. In doing so, we were able to effectively deliver treatments to regions that are concurrently expressing tau neuropathology: regionally in the hippocampus rather than global expression. The design of this study involves six different groups: (1) non-transgenic given AAV9-Empty Capsid, (2) non-transgenic given AAV9-tTA-GFP, (3) non-transgenic given AAV9-tTA-ARG1, (4) tetO MAPT*P301L mice given AAV9-Empty Capsid, (5) tetO MAPT*P301L given AAV9-tTA-GFP, and (6) tetO MAPT*P301L given AAV9-tTA-ARG1. All mice were injected bilaterally in the hippocampus and allowed to incubate for a period of 14-weeks before tissue collection. This study examined whether arginase1 overexpression was able to prevent the accumulation of neuropathology in an animal model of tauopathy using western blot. These data identify arginase1 as a potential therapeutic for the treatment of tauopathy and neuropathology.