Tauroursodeoxycholic acid modulates p53-mediated apoptosis in Alzheimer’s disease mutant neuroblastoma cells Rita M. Ramalho,* Pedro M. Borralho,* Rui E. Castro,* Susana Sola ´,* Clifford J. Steer  , à and Cecı ´lia M. P. Rodrigues* *Centro de Patoge ´nese Molecular, Faculty of Pharmacy, University of Lisbon, Portugal  Department of Medicine and àDepartment of Genetics, Cell Biology, and Development, University of Minnesota Medical School, Minneapolis, Minnesota, USA Abstract Early onset familial Alzheimer’s disease (FAD) is linked to autosomal dominant mutations in the amyloid precursor protein (APP) and presenilin 1 and 2 (PS1 and PS2) genes. These are critical mediators of total amyloid b-peptide (Ab) production, inducing cell death through uncertain mecha- nisms. Tauroursodeoxycholic acid (TUDCA) modulates exo- genous Ab-induced apoptosis by interfering with E2F-1/p53/ Bax. Here, we used mouse neuroblastoma cells that express either wild-type APP, APP with the Swedish mutation (APPswe), or double-mutated human APP and PS1 (APP- swe/DE9), all exhibiting increased Ab production and aggregation. Cell viability was decreased in APPswe and APPswe/DE9 but was partially reversed by z-VAD.fmk. Nuclear fragmentation and caspase 2, 6 and 8 activation were also readily detected. TUDCA reduced nuclear frag- mentation as well as caspase 2 and 6, but not caspase 8 activities. p53 activity, and Bcl-2 and Bax changes, were also modulated by TUDCA. Overexpression of p53, but not mu- tant p53, in wild-type and mutant neuroblastoma cells was sufficient to induce apoptosis, which, in turn, was reduced by TUDCA. In addition, inhibition of the phosphatidylinositide 3¢-OH kinase pathway reduced TUDCA protection against p53-induced apoptosis. In conclusion, FAD mutations are associated with the activation of classical apoptotic path- ways. TUDCA reduces p53-induced apoptosis and modu- lates expression of Bcl-2 family. Keywords: amyloid b-peptide, apoptosis, bile acids, familial Alzheimer’s disease, neuroprotection. J. Neurochem. (2006) 98, 1610–1618. Alzheimer’s disease (AD) is a neurodegenerative disorder usually classified into sporadic, more frequent form, and familial AD (FAD) with rare gene mutations. Both sporadic and familial AD, however, present the same histopatholog- ical hallmarks, including deposition of amyloid b-peptide (Ab), formation of neuritic plaques and neurofibrillary tangles, and loss of synapses (Masters et al. 1985; Selkoe 1990, 1997). Ab is derived from the processing of the amyloid precursor protein (APP), an integral membrane glycoprotein (Kang et al. 1987). A variety of APP mutations has been linked to autosomal FAD. In this regard, a double mutation at codons 670 and 671 (APPswe) has been identified in a Swedish family (Mullan et al. 1992). The b- secretase cleavage site of APP is mutated, resulting in very strong b-secretase activity and, consequently, increased Ab production. The majority of early onset FAD, however, is linked to mutations in the presenilin genes PS1 and PS2. Since its discovery, more than 35 different mutations have been described in the PS1 gene, and all appear to be associated with high levels of Ab production and aggregation (Schellenberg et al. 1992). Previous studies have shown that Ab-induced cytotoxicity involves oxidative stress, inflammation and perturbation of Received April 7, 2006; revised manuscript received April 25, 2006; accepted April 25, 2006. Address correspondence and reprint requests to Cecı ´lia M. P. Rodri- gues, PhD, Av. das Forc ¸as Armadas, 1600–083 Lisbon, Portugal. E-mail: cmprodrigues@ff.ul.pt Abbreviations used: AD, Alzheimer’s disease; Ab, amyloid b-pep- tide; APP, amyloid precursor protein; APPwt, APP wild-type, APPswe, APP with the Swedish mutation; APPswe/DE9, APP double-mutated human APP and PS1; FAD, familial form of Alzheimer’s disease; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide; PBS, phosphate-buffered saline; PI3K, phosphatidylinositide 3¢-OH kinase; pNA, p-nitroanilide; PS1, and PS2, presenilins 1 and 2; TNF-R1, tumor necrosis factor type receptor 1; TUDCA, tauroursodeoxycholic acid; UDCA, ursodeoxycholic acid. Journal of Neurochemistry , 2006, 98, 1610–1618 doi:10.1111/j.1471-4159.2006.04007.x 1610 Journal Compilation Ó 2006 International Society for Neurochemistry, J. Neurochem. (2006) 98, 1610–1618 Ó 2006 The Authors