231 Apoptotic neurons in Alzheimer’s disease frequently show intracellular Aβ 42 labeling D.H. Chui a,∗ , E. Dobo a , T. Makifuchi b , H. Akiyama c , S. Kawakatsu d , A. Petit e , F. Checler e , W. Araki a , K. Takahashi a and T. Tabira a,∗ a Department of Demyelinating Disease and Aging, National Institute of Neuroscience, NCNP, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan b Saigata National Hospital, Saigata, Nakakubikigun 949-3100, Japan c Tokyo Institute of Psychiatry, Kamikitazawa, Setagaya, Tokyo, Japan d Yamagata University Faculty of Medicine, Yamagata 990-9585, Japan e Institute de Pharmacologie Mol ´ eculaire et Cellulaire, CNRS, Valbonne 06560, France It is widely accepted that Aβ plays a pivotal role in the patho- genesis of Alzheimer’s disease (AD) [27]. Attention has been focused mainly on how extracellular Aβ exerts its effects on neuronal cells [7,11,16,32]. However, neuronal degeneration from an accumulation of intracellular Aβx-42 (iAβ42) oc- curs in presenilin 1 (PS1) mutant mice without extracellu- lar Aβ deposits [5]. In the present study, intracellular de- posits of iAβ42 are correlated with apoptotic cell death in AD and PS-1 familial AD (PS1 FAD) brains by means of triple staining with antibodies to Aβ, TUNEL, and staining with Hoechst 33342. Neurons simultaneously positive for iAβ42 and the TUNEL assay were significantly more abundant in AD brains than in controls. The number of apoptotic neu- rons with intracellular neurofibrillary tangles (iNFTs) was in- significant. Our results indicate that intraneuronal deposition of a neurotoxic form of Aβ seems to be an early event in the neurodegeneration of AD. ∗ Corresponding author: D.H. Chui or T. Tabira, Department of De- myelinating Disease and Aging, National Institute of Neuroscience, NCNP, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan. Tel.: +81 42341 1717; Fax: +81 42346 1747; E-mail: dchui@attglobal.net or tabira@ncnp.go.jp. 1. Introduction Alzheimer’s disease (AD) is the most common form of dementia in the elderly, characterized clinically by the insidious onset and inexorable progression of dementia, and pathologically by the abnormal accu- mulation of amyloid plaques in vulnerable brain re- gions [27]. Attention has been focused mostly on ex- tracellular Aβ [7,11,16]. However, Aβx-42 (Aβ42)- containing neurons were found to be more abundant in presenilin 1 (PS-1) mutant mice [5]. Recently, intra- neuronal deposits of Aβ42 in human brain were de- scribed by Gouras et al. [9] and Mochizuki et al. [22]. Although apoptosis has been proposed to be a predom- inant pathway of neuronal destruction in AD [19], the relation between Aβ42 accumulation and apoptosis is not yet known in AD brain. To address this issue, we focused on intracellular Aβ42 and apoptosis in human brain. In the present study, intracellular deposits of iAβ42 are correlated with apoptotic cell death in AD and PS-1 familial AD (PS1 FAD) brains. 2. Materials and methods 2.1. Subjects Brain specimens were obtained from seven sporadic AD patients (ages of death 52–82; mean age of death, 71.1 ± 5.2 years), two FAD patients carrying PS-1 mu- tation H163R (age of onset 47, age of death 59) or G384A (age of onset 35, age of death 48) [29], two pa- tients with progressive supranuclear palsy (PSP) (ages of death 58 and 79; mean age of death, 68.5), and eight controls with no known history of neurological disor- ders (ages of death 52–84, mean age of death, 70.1±4.0 years). Diagnosis of AD was based on clinical and neuropathological criteria [21,30]. All controls were without amyloid plaques. Minor neurofibrillary tan- gles were found in the temporal cortex in three of the eight controls. In all subjects, the postmortem interval ranged from 1.5 to 6 hours. Journal of Alzheimer’s Disease 3 (2001) 231–239 ISSN 1387-2877 / $8.00  2001, IOS Press. All rights reserved