STI571 prevents apoptosis, tau phosphorylation and behavioural impairments induced by Alzheimer's β-amyloid deposits

There is evidence that amyloid beta-protein (A beta) deposits or A intermediates trigger pathogenic factors in Alzheimers disease patients. We have previously reported that c-Abl kinase activation involved in cell signalling regulates the neuronal death response to A fibrils (A beta(f)). In the present study we investigated the therapeutic potential of the selective c-Abl inhibitor STI57I on both the intrahippocampal injection of Af and APPsw/PSENI Delta E9 transgenic mice Alzheimers disease models. Injection of A beta(f) induced an increase in the numbers of p73 and c-Abl immunoreactive cells in the hippocampal area near to the lesion. Chronic intraperitoneal administration of STI571 reduced the rat behavioural deficit induced by A beta(f), as well as apoptosis and tau phosphorylation. Our in vitro studies suggest that inhibition of the c-Abl/p73 signalling pathway is the mechanism underlying of the effects of STI571 on A beta-induced apoptosis for the following reasons: (i) A beta(f) induces p73 phosphorylation, the TAp73 isoform levels increase so as to enhance its proapoptotic function, and all these effects where reduced by STI571; (ii) c-Abl kinase activity is required for neuronal apoptosis and (iii) STI571 prevents the A beta-induced increase in the expression of apoptotic genes. Furthermore, in the A-injected area there was a huge increase in phosphorylated p73 and a larger number of TAp73-positive cells, with these changes being prevented by STI571 coinjection. Moreover, the intraperitoneal administration of STI571 rescued the cognitive decline in APPsw/PSENI Delta E9 mice, p73 phosphorylation, tau phosphorylation and caspase-3 activation in neurons around A beta deposits. Besides, we observed a decrease in the number and size of A beta deposits in the APPsw/PSENI Delta E9-STI571-treated mice. These results are consistent with the role of the c-Abl/p73 signalling pathway in A beta neurodegeneration, and suggest that STI571-like compounds would be effective in therapeutic treatments of Alzheimer disease.