Research topics of the team

The “Analytical Chemistry and Cell Toxicology” team was built by successive associations of personalities with specific know-how, at the best level in their respective fields, with the aim of allowing the emergence of original works at the interfaces of the different disciplines represented (Biology, Cell Toxicology, Analytical Chemistry, Organic Chemistry, Phytochemistry, Computerized Chemistry and Modelling). The two main tools hosted by that the team are the mass spectrometry and cell culture platforms, promoting initially the characterisation of toxicity markers on the cell models developed in the laboratory. The analytical methods then evolved logically towards metabolomics and more precisely towards lipidomic approaches, the lipid metabolism being particularly sensitive to alterations due to toxic exposures. The integration of the new approaches for spectral modelling and molecular networking developed by Grégory Genta-Jouve as part of his research activity in Phytochemistry proved to be extraordinarily valuable for the characterization of lipidomes. At the same time, the modelling of chemical reactions by the Density Functional Theory (DFT) and of spectral data gave a new momentum to the organic synthesis activity of the team, endorsed by Emmanuel Roulland. The latter’s chemist skills are used to decipher structural patterns specific to some molecular structures, as demonstrated by our most recent results on the characterization of positions and stereochemistry of unsaturations on lipid structures. The structuring of the topics which are presented below therefore remains artificial and only imperfectly describes the network of interactions that underlie them.

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ANALYTICAL TOXICOLOGY – MASS SPECTROMETRY – LIPIDOMICS (Nicolas Auzeil)

The team’s research in mass spectrometry focuses on the study of lipidomes in various contexts, including (i) the impact of endocrine disruptors on human neurodevelopment and their potential role in the occurrence of certain neuro-behavioral disorders and (ii) the mechanisms involved in the occurrence of eye dryness, particularly when linked to the use of cationic preservatives in eye drops.[1]

Ultimately, in both cases, the objective is the search for lipid biomarkers of exposures to environmental toxicants that can help in the diagnosis and/or prognostication of pathologies. This activity is based on the use of cellular models (cell lines of oligodendrocytes and cornea), animals (rodents) and samples taken from humans.

Lipidomic analyses are carried out by ultra-performance liquid chromatography coupled with high-resolution mass spectrometry, which allow the use of molecular networks after a pre-processing step of the raw data. This new and innovative approach (pioneer in the case of lipidomics) [2] provides very accurate information on the structure of lipids which are disturbed by exposure to a toxic or by pathological conditions. The use of single- and multivariate statistical analyses is also necessary.

 

The methods developed in the team are the result of close collaborations between the team’s analysts, around Nicolas Auzeil, and Grégory Genta-Jouve for the modelling and computational aspects, and Emmanuel Roulland for structurally specific chemical derivatives.

[1] R. Magny, K. Kessal, A. Regazzetti, A. Ben Yedder, C. Baudouin, S. Mélik Parsadaniantz, F. Brignole-Baudouin, O. Laprévote, N. Auzeil. BBA, Mol Cell Biol. Lp 2020, 1865(9), Article Number 158728 (2020)

[2] R. Magny, A. Regazzetti, K. Kessal, G. Genta-Jouve, C. Baudouin, S. Mélik Parsadaniantz, F. Brignole-Baudouin, O. Laprévote, N. Auzeil. Metabolites 2020 10(6), Article Number 225

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TOTAL SYNTHESIS (Emmanuel Roulland)

Total synthesis of Tiacumicine B

 

Scheme 1: Total synthesis of tiacumicin B and developments of related synthesis methods

Bacteria’s resistance to antibiotics is a major biomedical risk that is increasing dangerously. The discovery and exploitation of new molecules capable of counteracting these resistances is therefore a priority objective. Tiacumicin B (or fidaxomicin, Scheme 1) is a naturally occurring macrolide with unique antibiotic properties due to its action on the switch-region of bacterial RNA polymerase.

The program we are developing has led to the development of a total synthesis of tiacumicin B [1] which opens a reliable pathway to analogues of this molecule of interest. This total synthesis was made possible by innovations in the synthesis strategy involving new synthesis methods (Scheme 1) and the use of DFT computation.[1] The ANR agency supported this ambitious project led by Emmanuel Roulland in collaboration with the team of Jean-Marie Beau and Stephanie Norsikian of the ICSN-CNRS in Gif-sur-Yvette.

[1] a) S. Norsikian,  C. Tresse,  M. François-Eude, L. Jeanne-Julien, G. Masson, V. Servajean, G. Genta-Jouve, J.-M. Beau,E. Roulland,  Angew. Chem. Int. Ed., 2020, 59, 6612 – 6616. b) L. Jeanne-Julien, G. Masson, E. Astier, G. Genta-Jouve,V. Servajean, J.-M. Beau, S. Norsikian,  E. Roulland, J. Org. Chem.2018, 83, 921 – 929. c) L. Jeanne-Julien, G. Masson, E. Astier, G. Genta-Jouve,V. Servajean, J.-M. Beau, S. Norsikian,  E. Roulland, Org. Lett.2017, 19, 4006 – 4009. d) E. Roulland, Synthesis 2018, 50,4189 – 4200.

Structural Determination of a New Marine Natural Substance by Calculation and Confirmation by Total Synthesis

With an allene function in the middle of its chain and therefore with an axial chirality, the structure of the puna’auic acid (Scheme 2) is a exception in natural substances. Simulations of NMR and circular dichroism spectra based on DFT calculations performed by Grégory Genta-Jouve led to the choice of an enantiomer for puna’auic acid, this prediction being confirmed by total synthesis.[1]


Scheme 2 : puna’auic acid

The success of this approach underlines the relevance of DFT modeling of organic reactions and spectral data (Gregory Genta-Jouve) and coupled with total synthesis (Emmanuel Roulland).

[1] a) L. Jeanne-Julien, G. Masson, R. Kouoi, A. Regazzetti, G. Genta-Jouve, V. Gandon, E. Roulland, Org. Lett. 2019, 21, 3136 – 3141. b) L. Jeanne-Julien, E. Astier, R. Lai-Kuen, G. Genta-Jouve, E. Roulland, Org. Lett. 2018, 20, 1430 – 1434.c) E. Roulland, H. Solanki, K. Calabro, M. Zubia, G. Genta-Jouve, O. Thomas, Org. Lett 2018, 20, 2311 – 2314

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CELL TOXICOLOGY (Patrice Rat)

The Laboratory has made a specialty and a goal in the development of alternative methods to animal experimentation in the field of toxicology. Our most recent efforts have allowed us to propose a new method of studying endocrine disruptors which is based on human placental cell models and applicable to chemical molecules, plant extracts and oils. Indeed, it has emerged that different endocrine disruptors induce placental atrophy by activating degeneration pathways, including that of the inflammasome, initially identified in Alzheimer’s disease and which we have shown in macular degeneration.

This new approach on human placental models aims to identify the toxic mechanisms induced by endocrine disruptors through the activation of death and degeneration receptors, in particular the P2X7 receptor, the main target of study of the team’s studies, which stimulates placental degeneration.

This know-how allows us today to search for inflammasome modulators, on cellular models of the respiratory tree, that could be applied to the current COVID-19 pandemic.

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Anticipating marine and terrestrial natural products (Grégory Genta-Jouve).

In this axis, we are interested in the identification of original natural substances using numerical methods such as in silico metabolization and prediction of mass spectrometry fragmentation spectra. All these tools are brought together on a platform put online and accessible for free (https://metwork.pharmacie.parisdescartes.fr/). In contrast to the “classic” approach in phytochemistry that results from the initial analysis of extracts and the individual structural identification of their components, our approach allows us to anticipate the structures present in a given extract and confirm them at high speed by comparing the experimental data obtained by mass spectrometry with those resulting from the modeling of the spectra.[1]

[1] (a) C. Audoin, V. Cocandeau, O. P. Thomas, A. Bruschini, S. Holderith, G. Genta-Jouve, Metabolites 2014, 4(2), 421-432. (b) A. E. Fox Ramos, C. Pavesi, M. Litaudon, V. Dumontet, E. Poupon, P. Champy, G. Genta-Jouve*, M. A. Beniddir* Anal. Chem. 2019, 91(17), 11247–11252