title: Hyaluronan synthase-2 upregulation protects smpd3-deficient fibroblasts against cell death induced by nutrient deprivation, but not against apoptosis evoked by oxidized LDL.
abstract: The neutral type 2 sphingomyelinase (nSMase2) hydrolyzes sphingomyelin and generates ceramide, a major bioactive sphingolipid mediator, involved in growth arrest and apoptosis. The role of nSMase2 in apoptosis is debated, and apparently contradictory results have been observed on fibroblasts isolated from nSMase2-deficient fragilitas ossium (homozygous fro/fro) mice. These mice exhibit a severe neonatal dysplasia, a lack of long bone mineralization and delayed apoptosis patterns of hypertrophic chondrocytes in the growth plate. We hypothesized that apoptosis induced by nutrient deprivation, which mimics the environmental modifications of the growth plate, requires nSMase2 activation. In this study, we have compared the resistance of fro/fro fibroblasts to different death inducers (oxidized LDL, hydrogen peroxide and nutrient starvation). The data show that nSMase2-deficient fro/fro cells resist to apoptosis evoked by nutrient starvation (fetal calf serum/glucose/pyruvate-free DMEM), whereas wt fibroblasts die after 48h incubation in this medium. In contrast, oxidized LDL and hydrogen peroxide are similarly toxic to fro/fro and wt fibroblasts, indicating that nSMase2 is not involved in the mechanism of toxicity evoked by these agents. Interestingly, wt fibroblasts treated with the SMase inhibitor GW4869 were more resistant to starvation-induced apoptosis. The resistance of fro/fro cells to starvation-induced apoptosis is associated with an increased expression of hyaluronan synthase 2 (HAS2) mRNAs and protein, which is inhibited by ceramide. In wt fibroblasts, this HAS2 rise and its protective effect did not occur, but exogenously added HA exhibited a protective effect against starvation-induced apoptosis. The protective mechanism of HAS2 involves an increased expression of the heat-shock protein Hsp72, a chaperone with antiapoptotic activity. Taken together, these results highlight the role of nSMase2 in apoptosis evoked by nutrient starvation that could contribute to the delayed apoptosis of hypertrophic chondrocytes in the growth plate, and emphasize the antiapoptotic properties of HAS2.
authors.affiliation: INSERM UMR-1048, BP 84225, 31432 Toulouse Cedex 4, France; University of Toulouse, Toulouse, France.
authors.forename: Sandra
authors.initials: S
authors.lastname: Garoby-Salom
authors.affiliation: INSERM UMR-1048, BP 84225, 31432 Toulouse Cedex 4, France; University of Toulouse, Toulouse, France.
authors.forename: Myriam
authors.initials: M
authors.lastname: Rouahi
authors.affiliation: INSERM UMR-1048, BP 84225, 31432 Toulouse Cedex 4, France; University of Toulouse, Toulouse, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Mucher
authors.affiliation: INSERM UMR-1048, BP 84225, 31432 Toulouse Cedex 4, France; University of Toulouse, Toulouse, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Auge
authors.affiliation: INSERM UMR-1048, BP 84225, 31432 Toulouse Cedex 4, France; University of Toulouse, Toulouse, France.
authors.forename: Robert
authors.initials: R
authors.lastname: Salvayre
authors.affiliation: INSERM UMR-1048, BP 84225, 31432 Toulouse Cedex 4, France; University of Toulouse, Toulouse, France. Electronic address: anne.negre-salvayre@inserm.fr.
authors.forename: Anne
authors.initials: A
authors.lastname: Negre-Salvayre
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D014453:Glucuronosyltransferase / Q000096:biosynthesis* / Q000235:genetics; D050884:HSP72 Heat-Shock Proteins / Q000096:biosynthesis* / Q000378:metabolism; D000076002:Hyaluronan Synthases; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000494:pharmacology; D051379:Mice; D015398:Signal Transduction; D013108:Sphingomyelin Phosphodiesterase / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D050884:HSP72 Heat-Shock Proteins; D008077:Lipoproteins, LDL; C099252:oxidized low density lipoprotein; D006861:Hydrogen Peroxide; D014453:Glucuronosyltransferase; C491099:Has2 protein, mouse; D000076002:Hyaluronan Synthases; C491483:Smpd3 protein, mouse; D013108:Sphingomyelin Phosphodiesterase
keywords: Apoptosis; Hsp72; Hyaluronan synthase-2; Neutral sphingomyelinase-2; Nutrient starvation; Oxidized LDL