Gunjan Dhawan

Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Medical Laboratory Science


The major histopathologic hallmark of Alzheimer’s disease (AD) is the presence of (3-amyloid plaques that are often associated with reactive microglia in the brain. It has been suggested modulating the microglial phenotype to attenuate an inflammatory response may prove to be useful in determining therapies for prevention or delay of the disease. My dissertation supports he hypothesis that Ap stimulates microglial activation through a specific tyrosine kinase-dependent response involving the Src kinase family. Using primary mouse microglia we observed that both fibrillar and oligomeric Ap stimulated increased microglial protein phosphotyrosine levels including active levels of the kinase Src and a subsequent increase in secretion of the cytokine, tumor necrosis factor alpha (TNFa). This response was attenuated by using a Abl/Src family kinase inhibitor, dasatinib. Intracerebroventricular infusions of AP oligomer into C57BL/6 adult mice elevated hippocampal phosphotyrosine levels and microgliosis that were attenuate by dasatinib treatment. To evaluate the efficiency of dasatinib in a relevant transgenic model of AD, drug was subcutaneously infused into 13-month old APP/PS1 transgenic mice. Behavioral testing using T-maze showed better performance from dasatinib infused mice as compared to vehicle treated and control animals. Biochemical analyses demonstrated that dasatinib infused animals had lower total protein phosphotyrosine and pSrc levels in the hippocampus. Dasatinib is an FDA approved drug for treating chronic myeloid leukemia and can cross the blood brain barrier. Our demonstration of the microglial inhibitory action of this drug defines a novel use. Based upon the observation that AD brains showed increase in active, phosphorylated Lyn levels in reactive microglia, this kinase may also represent a possible microglial inhibitory target as well. Following a high throughput screening kinase assay, four drugs were identified. One compound LDDN-0003499 inhibited total protein phosphotyrosine as well as active pLyn levels in BV2 microglial cell line. LPS stimulated microglia treated with LDDN-0003499 demonstrated attenuation of TNF-a levels secretion. Collectively, our data supports the idea that non-receptor tyrosine kinase inhibition could be an important therapeutic goal for prevention and/or delay of AD.