Supplement for Preclinical evaluation of Tacrolimus in A Canine Model of Alzheimer's Disease

This project uses aging beagles and a longitudinal treatment design to test the potential of a calcineurin (CN) inhibiting strategy in Alzheimer’s disease (AD). Beagles are metabolically similar to humans and spontaneously develop amyloid-â (Aâ) deposition with advanced age. Consequently, the aging beagle model has shown exceptional predictive validity in regard to several high-profile anti-AD drug trials. The molecular target of our treatment strategy, CN, has recently emerged as a key mechanism for AD pathophysiology. Signs of CN hyperactivity are found during early stages of cognitive decline in humans and in mouse models of AD. Studies across numerous laboratories, using a variety of experimental models, suggest that CN activity is both necessary and sufficient for the progression of key AD biobehavioral markers including Aâ deposition, neurodegeneration, neuroinflammation/glial activation, synapse dysfunction, and cognitive loss. To inhibit CN, we will use tacrolimus, an FDA-approved drug for the prophylaxis of allograft rejection and a second line treatment for numerous immune/inflammatory disorders. In animal models, tacrolimus exhibits potent anti-inflammatory, neuroprotective, and perhaps lifespan extending properties. Moreover, a recent epidemiological study found that the incidence of dementia was strikingly reduced in human kidney transplant patients taking tacrolimus, relative to age-matched subjects in the general population. In this project, 5-6 month old beagles will undergo 1 year of behavioral/cognitive screening. At 6-7 months-of age (prior to the development of significant amyloid pathology), dogs will be sorted into two groups matched for cognitive status. One group will received tacrolimus (.075mg/kg/day, orally) continuously for the next two years, while the other group will receive placebo. Aim 1 will assess multidomain cognition and measure blood and CSF biomarkers (e.g. Aâ and cytokines) at multiple time points across the tacrolimus treatment period. Aim 2 will use MRI/MRS to measure longitudinal changes in cerebral perfusion, brain metabolism, and structural integrity. Aim 3 will use immunohistochemistry and a variety of biochemical assays to assess AD biomarkers (e.g. Aâ deposition, glial activation, synapse loss, and neurodegeneration) and CN-related signaling parameters (e.g. cell-type specific expression, CN proteolysis, and NFAT activation) in postmortem brain tissue. These studies will provide a rigorous test of the CN hypothesis of AD and possibly pave the way for investigating CN inhibition has a primary or complimentary treatment strategy in human AD clinical trials.Though no significant effects on cognition have been observed after one year of tacrolimus treatment, MRI results show evidence for significant neuroprotection and anti-inflammation. Based on MRI results, we would like to extend treatment from two years to three years. This work will maximize our chances of finding cognitive enhancing effects of tacrolimus treatment, and will also inform as to whether changes in MRI parameters predict future changes in cognition.