Visit our Expo - Redox and Inflammation signaling 2012

Session X : Cell death in cancer Poster X, 33
Membrane fluidity changes are associated with benzo[a]pyrene-induced apoptosis in
F258 cells: protection by exogenous cholesterol
1Morgane Gorria, 1Xavier Tekpli, 2Odile Sergent, 1Laurence Huc, 3François Gaboriau,
1Mary Rissel, 1Marie-Thérèse Dimanche-Boitrel, 1Dominique Lagadic-Gossmann
1Inserm U620, Université de Rennes 1; 2UPRES EA 3891, Université de Rennes 1;
3Inserm U522, Hôpital Ponchaillou, 35000 Rennes, FRANCE. E-mail:
morgane.gorria@univ-rennes1.fr
Polycyclic aromatic hydrocarbons (PAHs) are important environmental pollutants, to which
humans are largely exposed. Besides their well-known carcinogenic effects, PAHs also
induce apoptosis in different cell types such as hepatic cells (Huc et al., Faseb J, 2004;
Solhaug et al., Carcinogenesis, 2004). Although activation of p53 plays a primordial role in
this apoptosis, permissive pathways might also occur; indeed, we have recently evidenced a
parallel activation of Na+/H+ exchanger (NHE1) with consequences on apoptosis occurrence.
Such an activation might result from changes in membrane characteristics, especially as
PAHs are highly lipophilic molecules and have been shown to interact with biological
membranes (Jimenez et al., Environ Toxicol Chem, 2002). This study was therefore to
investigate the effects of benzo[a]pyrene (B[a]P) on the membrane fluidity of F258 cells and
to test the role of these changes in the related apoptosis.
Using the fluorescence polarization technique and the DPH probe, we first demonstrated that
B[a]P (50 nM) induced an increase in bulk membrane fluidity following 48 h of exposure.
This result was confirmed using EPR technique and the 12-DSA spin label. Using cariporide
(30 µM) to inhibit NHE1 activation observed at 48 h (Huc et al., Faseb J, 2004), we further
showed that this change in fluidity was partly related to this transporter. Exogenous
application of cholesterol (30 mg/mL), a well known membrane stabilizer, was then used to
test the involvement of membrane fluidization in B[a]P-induced apoptosis. Our data
demonstrated that a co-treatment with this compound, besides inhibiting any membrane
fluidization, significantly reduced apoptosis, as evidenced by a decrease of cell population
exhibiting nuclear fragmentation and of caspase 3/7 activity. We further showed that the
protective effect of cholesterol was mainly through inhibition of B[a]P-induced iron uptake,
leading to subsequent reduction of oxidative stress, and hence apoptosis.
In conclusion, this work suggest a role for membrane fluidity in early events of B[a]P-induced
apoptosis and an implication of NHE1 activation in B[a]P-induced membrane fluidization.
- 366 -