Explain Inhalation Toxicity-2

Animal-free mechanism-based toxicity testing – predict toxicity after repeated dose inhalation exposure by using a read across approach.

A collaborative project funded by the German Federal Ministry of Education and Research (BMBF) in the funding program
“e:ToP – Innovative Toxikologie zur Reduzierung von Tierversuchen”

ExITox-2 was built on the outcomes of ExITox-1 and aimed to develop an integrated approach for testing and assessment (IATA) to replace in vivo studies with repeated inhalation exposure. We established this IATA with the help of a read across (RAX) approach of ExITox-1, in which we tested groups of chemically similar compounds that share a specific mode of action (MoA) or adverse outcome pathway (AOP) in vivo. In ExITox-1 we showed that biological profiles based on the transcriptome changes and functional outcomes from in vitro and ex vivo models can be used to differentiate RAX groups with similar mode of action. Beside the RAX group vinyl ester from ExITox-1, we have included two new AOPs in second phase, namely pulmonary inflammation, and fibrosis. In the course of ExITox-2, geneXplain was expanded the “complete upstream analysis”, which is an integrated bioinformatics promoter analysis of the DEGs, identifying potential transcriptional regulators, with a proprietary pathway analysis controlling the activity of these transcriptional regulators and converge in defined sets of so-called master regulators (Kel et al., 2006).
Further the geneXplain platform was extended with lung-specific pathways up to newly constructed master pathways (for fibrosis and inflammation) to compare toxic effects to general systemic responses.

ExITox-2 integrated four new key aspects into the IATA:

  • The uptake of compounds after inhalation exposure were estimated by physiological pharmacokinetic modeling and QSAR models.
  • The onset of gene changes and miRNA regulation, by dose dependent testing, were investigated to better differentiate between group-specific changes and general stress responses related to high dosing.
  • We generated and used master pathways per group to differentiate AOP related changes from general cellular stress responses.
  • An IATA was developed, which allows to predict the toxicity of an untested compound in a read across context based on the generated data.
Further project info.


Koschmann, J., Bhar, A., Stegmaier,P., Kel, A. E. and Wingender, E. (2015) “Upstream Analysis”: An integrated promoter-pathway analysis approach to causal interpretation of microarray data. Microarrays 4, 270-286. doi:10.3390/microarrays4020270. Link

Niehof, M., Hildebrandt, T., Danov, O., Arndt, K., Koschmann, J., Dahlmann, F., Hansen, T. and Sewald, K. (2017) RNA isolation from precision-cut lung slices (PCLS) from different species. BMC Res. Notes 10, 121. doi: 10.1186/s13104-017-2447-6. Link

Further information

Structure of ExITox-II:

Project koordinator and partner: Fraunhofer ITEM

BMBF project announcement

Contract no.

FKZ 031L0120C

Contract period



The project is coordinated by Dr. Sylvia Escher, Fraunhofer Institute for Toxicology and Experimental Medicine (ITEM) in Hannover.

The 5 participants of the consortium are from Hannover, Göttingen, Emden, and Wolfenbüttel.