Éditeur(s) : HAL CCSD Karger
Résumé : International audience
BACKGROUND: Polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (B[a]P), are ubiquitous toxic environmental pollutants capable of inducing cell death. Intracellular pH plays a key role in the regulation of cell survival and death. Our previous works have demonstrated that intracellular alkalinization mediated by Na(+)/H(+) exchanger 1 (NHE-1) is a critical event involved in B[a]P-induced apoptosis. The aim of this study was to further elucidate the mechanisms of NHE-1 activation upon B[a]P exposure. METHODS: We tested the effects of plasma membrane cholesterol enrichment or depletion on B[a]P-induced NHE-1 activation related to apoptosis. We isolated cholesterol-rich plasma membrane microdomains to assess NHE-1 submembrane location and immunoprecipitated NHE-1 from the different sub-membrane fractions obtained to examine NHE-1 protein interactions during B[a]P-induced apoptosis. RESULTS: We found that NHE-1 is preferentially located in cholesterol-rich microdomains and that B[a]P activates NHE-1 via its relocation and binding of calmodulin outside these specialized plasma membrane microstructures; these events are necessary for the execution of the apoptosis-related intracellular alkalinization. CONCLUSION: Plasma membrane location of NHE-1 affects its protein interactions and apoptotic function.
ISSN: 1015-8987

inserm-00871487
http://www.hal.inserm.fr/inserm-00871487
http://www.hal.inserm.fr/inserm-00871487/document
http://www.hal.inserm.fr/inserm-00871487/file/NHE-1_Relocation_Outside_Cholesterol.accepted.pdf
DOI : 10.1159/000171027

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Toxicology Letters
Stockholm, Sweden

hal-01122645
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01122645
DOI : 10.1016/j.toxlet.2012.03.439

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The mycotoxin alternariol (AOH), a frequent contaminant in fruit and cereal products, is known to induce DNA damage with subsequent cell cycle arrest. Here we elucidated the effects of AOH on stages of cell cycle progression using the RAW 264.7 macrophage model. AOH resulted in an accumulation of cells in the G2/M-phase (4N). Most cells exhibited a large G2 nucleus whereas numbers of true mitotic cells were reduced relative to control. Both cyclin B1 and p-cdc2 levels increased, while cyclin B1 remained in the cytoplasm; suggesting arrest in the G2/M transition point. Remarkably, after exposure to AOH for 24h, most of the cells exhibited abnormally shaped nuclei, as evidenced by partly divided nuclei, nuclear blebs, polyploidy and micronuclei (MN). AOH treatment also induced abnormal Aurora B bridges, suggesting that cytokinesis was interfered within cells undergoing karyokinesis. A minor part of the resultant G1 tetraploid (4N) cells re-entered the S-phase and progressed to 8N cells.
ISSN: 0378-4274

inserm-00871659
http://www.hal.inserm.fr/inserm-00871659
http://www.hal.inserm.fr/inserm-00871659/document
http://www.hal.inserm.fr/inserm-00871659/file/Alternariol_induces_abnormal_nuclear_morphology_and_cell_cycle_arrest_in_murine_RAW_264.7_macrophages-accepted.pdf
DOI : 10.1016/j.toxlet.2013.02.012

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Toxicology Letters
Stockholm, Sweden

hal-01122656
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01122656
DOI : 10.1016/j.toxlet.2012.03.489

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The early apoptotic events induced by environmental pollutants with carcinogenic properties are poorly understood. Here, we focus on the early cytotoxic effects of benzo[a]pyrene (B[a]P). In F258 rat hepatic epithelial cells, B[a]P induces intrinsic apoptosis via a mitochondrial dysfunction characterized by the release of hexokinase II (HKII) from the mitochondria. Cancer cells often have an anomalous cell energy metabolism; since HKII dysfunction regulates B[a]P-induced apoptosis in F258 cells, but may also alter cell energy metabolism, HKII release from the mitochondria may represent an important B[a]P-related carcinogenic issue. Thus in the present study, we aimed at deciphering the mechanisms underlying HKII dysfunction upon B[a]P exposure. We show that while glycogen synthase kinase 3 beta (GSK3β) regulated the expression of HKII at the transcriptional level, glycogen synthase kinase 3 alpha (GSK3α) was involved in B[a]P-induced apoptosis via a decrease in c-Myc expression. The reduced level of c-Myc caused the relocation of HKII from the mitochondria to the cytosol, thereby being involved in the formation of reactive oxygen species and apoptosis. In conclusion, we show that the couple GSK3α/c-Myc plays a key role in B[a]P-induced early apoptotic cell signaling via HKII dysfunction.
ISSN: 0887-2333

hal-00682104
https://hal.archives-ouvertes.fr/hal-00682104
https://hal.archives-ouvertes.fr/hal-00682104/document
https://hal.archives-ouvertes.fr/hal-00682104/file/1-s2.0-S0887233311003018-main%20Dendel%C3%A9_%7B75929874-2DF9-47C3-92F6-92AF398668E5%7D.pdf
DOI : 10.1016/j.tiv.2011.11.001

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Plasma membrane is an early target of polycyclic aromatic hydrocarbons (PAH). We previously showed that the PAH prototype, benzo[a]pyrene (B[a]P), triggers apoptosis via DNA damage-induced p53 activation (genotoxic pathway) and via remodeling of the membrane cholesterol-rich microdomains called lipid rafts, leading to changes in pH homeostasis (non-genotoxic pathway). As omega-3 (n-3) fatty acids can affect membrane composition and function or hamper in vivo PAH genotoxicity, we hypothesized that addition of physiologically relevant levels of polyunsaturated n-3 fatty acids (PUFAs) might interfere with B[a]P-induced toxicity. The effects of two major PUFAs, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), were tested on B[a]P cytotoxicity in the liver epithelial cell line F258. Both PUFAs reduced B[a]P-induced apoptosis. Surprisingly, pre-treatment with DHA increased the formation of reactive B[a]P metabolites, resulting in higher levels of B[a]P-DNA adducts. EPA had no apparent effect on B[a]P metabolism or related DNA damage. EPA and DHA prevented B[a]P-induced apoptotic alkalinization by affecting Na(+)/H(+) exchanger 1 activity. Thus, the inhibitory effects of omega-3 fatty acids on B[a]P-induced apoptosis involve a non-genotoxic pathway associated with plasma membrane remodeling. Our results suggest that dietary omega-3 fatty acids may have marked effects on the biological consequences of PAH exposure.
ISSN: 0009-2797

hal-00950341
https://hal.archives-ouvertes.fr/hal-00950341
https://hal.archives-ouvertes.fr/hal-00950341/document
https://hal.archives-ouvertes.fr/hal-00950341/file/DENDELE_et_al_2013-unmarked.pdf
PUBMED : 24246761

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The mycotoxin enniatin B (EnnB) is predominantly produced by species of the Fusarium genera, and often found in grain. The cytotoxic effect of EnnB has been suggested to be related to its ability to form ionophores in cell membranes. The present study examines the effects of EnnB on cell death, differentiation, proliferation and pro-inflammatory responses in the murine monocyte-macrophage cell line RAW 264.7. Exposure to EnnB for 24 h caused an accumulation of cells in the G0/G1-phase with a corresponding decrease in cyclin D1. This cell cycle-arrest was possibly also linked to the reduced cellular ability to capture and internalize receptors as illustrated by the lipid marker ganglioside GM1. EnnB also increased the number of apoptotic, early apoptotic and necrotic cells, as well as cells with elongated spindle-like morphology. The Neutral Red assay indicated that EnnB induced lysosomal damage; supported by transmission electron microscopy (TEM) showing accumulation of lipids inside the lysosomes forming lamellar structures/myelin bodies. Enhanced levels of activated caspase-1 were observed after EnnB exposure and the caspase-1 specific inhibitor ZYVAD-FMK reduced EnnB-induced apoptosis. Moreover, EnnB increased the release of interleukin-1 beta (IL-1β) in cells primed with lipopolysaccharide (LPS), and this response was reduced by both ZYVAD-FMK and the cathepsin B inhibitor CA-074Me. In conclusion, EnnB was found to induce cell cycle arrest, cell death and inflammation. Caspase-1 appeared to be involved in the apoptosis and release of IL-1β and possibly activation of the inflammasome through lysosomal damage and leakage of cathepsin B.
ISSN: 0041-008X

inserm-00871698
http://www.hal.inserm.fr/inserm-00871698
DOI : 10.1016/j.taap.2012.03.014
PUBMED : 22483798