Influx and efflux membrane transporters play an important role in the cellular and tissular pharmacokinetics of drugs , in particular with regard to absorption (in the gut), distribution (passage through the hemato-tissular barriers) and elimination in the liver and kidneys. They also potentially play a part in the absorption of drugs through the pulmonary tract and in placental transfer.
Moreover, the regulation of their expression and activity by many drugs can cause medication interaction, which has prompted drugs agencies to request that the potential interaction of new drugs with membrane transporters should be systematically characterized.
Like drugs, chemical environmental contaminants may potentially interact with xenobiotics membrane transporters. Such interactions and the effects of environmental contaminants in toxicokinetic and cellular toxicity terms, remain relatively unexplored. Our program therefore aims to define the nature of such interactions and characterize their potential contribution to the detrimental effects of environmental contaminants via an in vitro cellular/molecular approach and an in silico modelling approach, particularly at the pulmonary barrier level.
In vitro cellular and molecular approaches
Interaction between chemical environmental contaminants(pesticides, endocrine disruptors, petrol-like aromas, heavy metals, etc.) either alone or in combination, and membrane transporters (inhibition, uptake) are analysed using cellular models that over-express the transporters (transfected clones) or represent various biological barriers such as pulmonary epithelial cells, hepatocytes, intestinal cells; placental cells, etc.
The techniques used involve fluorescent, radiometric or HPLC tandem mass spectrometry quantification methods. In parallel, we study the role of the passive diffusion of contaminants in their cellular pharmaco-kinetics. The regulation of membrane transporter expression by environmental contaminants in various cellular models (pulmonary cells, hepatocytes, placental cells, etc.) is also studied by reverse transcription (RT-qPCR), Western-blot protein visualisation and functional analysis.
The potential implication of transporter-contaminant interaction in causing toxic effects is analyzed via general cellular toxicity techniques (viability, apostosis, barrier integrity) or specific techniques such as cellular endocrine disruption measurement.
In silico approach
The in silico approach is mainly based on environmental contaminant molecular descriptor analysis and their role in predicting membrane transporter interaction, membrane passage and toxico-kinetics in the contaminants under study. It is partly based on the analysis of the data generated by our in vitro cellular/molecular approach. The bioinformatics approach is implemented using on line or off-the-shelf pharmaco-kinetic prediction software. We also carry out a modelling and docking approach on the active transporter sites. We should eventually be able to incorporate these results in PBTK and TDTK models, which will enable us to predict the contamination of exposed subjects and the detrimental effects expected, according to the actual exposure level, in particular with regard to pulmonary exposure.