BACE-1 inhibition prevents the γ-secretase inhibitor evoked Aβ rise in human neuroblastoma SH-SY5Y cells.
BACKGROUND
Accumulation of amyloid β-peptide (Aβ) in the plaques is one of the major pathological features in Alzheimer's disease (AD). Sequential cleavage of amyloid precursor protein (APP) by β-site APP cleaving enzyme 1 (BACE-1) and γ-secretase results in the formation of Aβ peptides. Preventing Aβ formation is believed to attenuate AD progression and BACE-1 and γ-secretase are thus attractive targets for AD drug development.


METHODS
Combining BACE-1 and γ-secretase inhibition on Aβ secretion from human neuroblastoma SH-SY5Y cells was evaluated in this study. Secreted Aβ40 and Aβ42 levels were measured from SH-SY5Y cells stably transfected with APPwt or APPswe genes. A selective BACE inhibitor and the γ-secretase inhibitor LY450139 (semagacestat) were used to inhibit respective secretase.


RESULTS
LY450139 increased Aβ40 and Aβ42 secretion from SH-SY5Y APPwt cells at low concentrations (by 60% at 3 nM) followed by subsequent inhibition at higher concentrations (IC(50) 90 nM). Washout studies showed that the Aβ increase evoked by 3 nM LY450139 was not due to enhanced cleavage following substrate accumulation but rather to activation of Aβ formation. By contrast, LY450139 inhibited Aβ formation from SH-SY5Y APPswe in a monophasic manner (IC(50) 18 nM). The BACE inhibitor per se inhibited Aβ secretion from both SH-SY5Y APPwt and SH-SY5Y APPswe cells with IC(50)s ranging between 7 - 18 nM and also prevented the increased Aβ secretion evoked by 3 nM LY450139. Combining the BACE inhibitor with higher inhibitory concentrations of LY450139 failed to demonstrate any clear additive or synergistic effects.


CONCLUSIONS
BACE-1 inhibition attenuates the Aβ increase evoked by LY450139 while not providing any obvious synergistic effects on LY450139-mediated inhibition.
Medivir AB, Huddinge, Sweden.
Anne
A
Jämsä
Oscar
O
Belda
Michael
M
Edlund
Erik
E
Lindström
D000409:Alanine / Q000031:analogs & derivatives / Q000494:pharmacology; D000544:Alzheimer Disease / Q000378:metabolism*; D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors*; D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors*; D001381:Azepines / Q000494:pharmacology; D001581:Benzothiadiazines / Q000494:pharmacology; D045744:Cell Line, Tumor; D003499:Cyclic S-Oxides / Q000494:pharmacology; D006801:Humans; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000378:metabolism
D016229:Amyloid beta-Peptides; D001381:Azepines; D001581:Benzothiadiazines; D003499:Cyclic S-Oxides; C570234:N-(1-benzyl-3-(cyclopropylamino)-2-hydroxypropyl)-7-ethyl-1-methyl-3,4-dihydro-1H-(1,2,5)thiadiazepino(3,4,5-hi)indole-9-carboxamide 2,2-dioxide; C484278:N2-((2S)-2-(3,5-difluorophenyl)-2-hydroxyethanoyl)-N1-((7S)-5-methyl-6-oxo-6,7-dihydro-5H-dibenzo(b,d)azepin-7-yl)-L-alaninamide; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; D000409:Alanine