Fluoride-induced apoptosis in human epithelial lung cells (A549 cells): role of different G protein-linked signal systems.
In the present study, possible mechanisms involved in fluoride-induced apoptosis in a human epithelial lung cell line (A549) were examined. Sodium fluoride (NaF) induced apoptosis in the A549 cells, with a maximum at 5-7.5 mM after 20 hours of exposure. The number of cells with plasma membrane damage (PI-positive cells) increased moderately up to 5 mM, but markedly at 7.5 mM. Deferoxamine (an Al3+ chelator) almost completely prevented these NaF-induced responses, which may suggest a role for G protein activation. The apoptotic effect was partially reduced by the PKA inhibitor H89. NaF induced a weak but sustained increase in PKC activity, whereas the PKC activator TPA induced a transient effect. TPA, which enhanced the NaF-induced PKC activity, was not apoptotic when added alone, but facilitated the NaF-induced apoptosis and the increase in PI-positive cells. PKC downregulation induced by TPA pretreatment almost completely prevented the NaF-induced apoptosis and the increase in PI-positive cells. Pretreatment with the PKC inhibitor GF109203X, which abolished the PKC activity after 3 hours, enhanced the NaF-induced apoptosis. KN93 (a CaM kinase II inhibitor) and W7 (a calmodulin inhibitor) seem to reduce the apoptotic effect of NaF, whereas BAPTA-AM (a Ca2+ chelator) was without effect. The tyrosine kinase inhibitor genistein also markedly reduced the NaF-induced apoptosis, whereas the PI-3 kinase inhibitor wortmannin augmented the response. In conclusion, the present results suggest that NaF induces an apoptotic effect and an increase in PI-positive A549 cells via similar mechanisms, involving PKC, PKA, tyrosine kinase and Ca2+-linked enzymes, whereas PI-3 kinase seems to exert a counteracting effect.
Division of Environmental Medicine, Norwegian Institute of Public Health, Geitmyrsvn. 75, PO Box 4404 Nydalen, N-0403 Oslo, Norway. magne.refsnes@fhi.no
Magne
M
Refsnes
Per E
PE
Schwarze
Jørn A
JA
Holme
Marit
M
Låg
D000077410:Aluminum Chloride; D017607:Aluminum Compounds / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002614:Chelating Agents / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D003676:Deferoxamine / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D008168:Lung / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D037342:Pertussis Toxin / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D012969:Sodium Fluoride / Q000633:toxicity*; D013449:Sulfonamides
D017607:Aluminum Compounds; D002614:Chelating Agents; D002712:Chlorides; D007546:Isoquinolines; D013449:Sulfonamides; D000077410:Aluminum Chloride; D012969:Sodium Fluoride; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D003676:Deferoxamine; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium