Visit our Expo - Redox and Inflammation signaling 2012

Session X : Cell death in cancer Poster X, 4
Endosulfan inhibits cell growth and apoptosis through activation of ERK1/2 and AKT
signaling pathways
S. Antherieu 1, N. Ledirac 1, P. Lenormand 2 and R. Rahmani 1
1 INRA UMR-1112, Equipe de Toxicologie Cellulaire et Moléculaire, et Génomique,
Sophia-Antipolis, France, e-mail: antherieu@antibes.inra.fr
2 CNRS UMR-6543, Centre Antoine Lacassagne, Nice, France.
Endosulfan is an organochlorine insecticide reported to be a potential carcinogen in humans.
This insecticide was previously described to alterate MAP kinases signaling pathways and
suspected to affect cell growth and differentiation in keratinocytes. In the present study, we
assessed the mitogenic and apoptogenic potentials of endosulfan in HaCaT keratinocytes.
We first confirmed its mutagenicity by using the AMES assay, which demonstrated that
unchanged endosulfan rather than metabolites, was at the origin of mutagenic effects
(negative results in the presence of S9 hepatic fractions).
Moreover, we showed that endosulfan led to a persistent ERK1/2 phosphorylation with an
accumulation of the phosphorylated form both in cytosol and nucleus. This sustained
activation is responsible for a decreased cell proliferation, since untreated cells reached
confluency after 3 days, whereas confluency is reached after 4 days in endosulfan-treated
cells. These data were also confirmed by BrdU incorporation which was strongly decreased
after insecticide treatment.
In addition, reactive oxygen species (ROS) has been shown to be involved in endosulfaninduced
ERK1/2 activation; we demonstrated that blockade of this oxidative stress by NAC
(N-acetylcystein) strongly prevented inhibition of proliferation by endosulfan. These results
clearly showed that endosulfan-induced ROS were involved in cell growth decrease.
Finally, endosulfan apoptogenic potential was investigated and a reduction of caspases 3/7
activation and PARP cleavage was evidenced. This inhibition of apoptosis is probably
correlated to endosulfan-induced AKT pathway, since a 3-fold induction of phospho-AKT
was observed after 1 h of treatment.
On the whole, this study demonstrates that endosulfan is a mutagenic agent, responsible of a
ROS-induced proliferation decrease and apoptosis inhibition. These processes in turn prevent
elimination of altered cells and therefore may contribute to carcinogenesis.
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