Introduction of Percellome Project with special reference to the concept of “signal toxicity”
Case study: Single exposure adult studies with developmental cases, at signal dose levels, i.e. at the level of no overt cytotoxicity or organ toxicity monitorable by histopathology

Jun Kanno
Head
of Cellular and Molecular Toxicology Division,
NIHS, Japan
Dr Kanno explained the Percellome Toxicogenomics Project, with a focus on the concept of ‘signal toxicity’. The Percellome project was initiated in 2001 and uses fewer animals, exposed to lower doses, at single exposures or over short time periods. The objective is to mechanistically reinforce the ‘safety (uncertainty) factor’ used for the extrapolation of animal data to humans ― and eventually make the process in silico.
The project was designed to capture unpredicted toxicity resulting in the development of a normalisation method ‘Percellome (Aisaki et al, 2011; Kanno et al, 2006)’ for microarrays and Q-PCR in order to generate absolute copy numbers of mRNAs per single cell (on average). Quantified mRNA data of mouse liver (4 time points x 4 dose levels, n=3, 48 microarrays per organ per chemical) were obtained on over 100 chemicals. The project now includes studies on multi-organ relationships, low concentration inhalation, repeated dosing, etc. Data are visualised in 3D surface graphs (time x dose x mRNA copy number per cell) of each probe set of Affymetrix MOE430 2.0 GeneChip and subjected to comprehensive analysis by a series of in-house software.
Dr Kanno reported on the case studies on estragole (Kanno et al, 2012) and pentachlorophenol (Kanno et al, 2013); these were single-exposure adult studies, cases at signal does levels (i.e. at the level of no overt cytotoxicity or organ toxicity by histopathology). Findings showed networks of PPAR-alpha and interferon signalling networks respectively. Next steps, including systems biology (Garuda Project5) were also briefly presented.