Adipsin, a biomarker of gastrointestinal toxicity mediated by a functional gamma-secretase inhibitor.
Functional gamma-secretase inhibitors (FGSIs) can block the cleavage of several transmembrane proteins including amyloid precursor protein (APP), and the cell fate regulator Notch-1. FGSIs, by inhibiting APP processing, block the generation of amyloid beta (Abeta) peptides and may slow the development of Alzheimer's disease. FGSIs used to inhibit APP processing may disrupt Notch processing, thus interfering with cell fate determination. Described herein is a FGSI-mediated gastrointestinal toxicity characterized by cell population changes in the ileum of rats, which are indicative of Notch signaling disruption. Microarray analysis of ileum from FGSI-treated rats revealed differential expression responses in a number of genes indicative of Notch signaling perturbation, including the serine protease adipsin. We were able to show that FGSI-treated rats had elevated levels of adipsin protein in gastrointestinal contents and feces, and by immunohistochemistry demonstrated that adipsin containing ileum crypt cells were increased in FGSI-treated rats. The mouse Adipsin proximal promoter contains a putative binding site for the Notch-induced transcriptional regulator Hes-1, which we demonstrate is able to bind Hes-1. Additional studies in 3T3-L1 preadipocytes demonstrate that this FGSI inhibits Hes-1 expression while up-regulating adipsin expression. Overexpression of Hes-1 was able to down-regulate adipsin expression and block pre-adipocyte differentiation. We propose that adipsin is a Hes-1-regulated gene that is de-repressed during FGSI-mediated disruption of Notch/Hes-1 signaling. Additionally, the aberrant expression of adipsin, and its presence in feces may serve as a noninvasive biomarker of gastrointestinal toxicity associated with perturbed Notch signaling.
Searfoss
George H
GH
Department of Lead Optimization Toxicology, Pathology, Investigative Toxicology, BioRTP and Neuroscience, Lilly Research Laboratories, Division of Eli Lilly and Company, Greenfield, Indiana 46140, USA.
Jordan
William H
WH
Calligaro
David O
DO
Galbreath
Elizabeth J
EJ
Schirtzinger
Linda M
LM
Berridge
Brian R
BR
Gao
Hong
H
Higgins
Marnie A
MA
May
Patrick C
PC
Ryan
Timothy P
TP
D041721:3T3-L1 Cells; D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D016282:Aspartic Acid Endopeptidases; D001483:Base Sequence; D001665:Binding Sites; D002454:Cell Differentiation; D011416:Complement Factor D; D004064:Digestive System / Q000378:metabolism*; D015536:Down-Regulation; D010450:Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007082:Ileum / Q000378:metabolism; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008956:Models, Chemical; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D051381:Rats; D051880:Receptors, Notch; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000737:chemistry*; D015398:Signal Transduction; D013997:Time Factors; D014158:Transcription, Genetic; D015854:Up-Regulation
D016229:Amyloid beta-Peptides; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D051880:Receptors, Notch; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D012697:Serine Endopeptidases; D011416:Complement Factor D; C493491:complement factor D, mouse; D016282:Aspartic Acid Endopeptidases; C509282:Bace1 protein, mouse