FLUORIDE-INDUCED APOPTOSIS IN HUMAN EPITHELIAL LUNG CELLS.

The apoptotic effect was partially reduced by the PKA inhibitor H89.
NaF induced a weak but sustained increase in PKC activity,
whereas
 the PKC activat or TPA induced a transient effect.

Human & Experimental TOXICOLOGY

FLUORIDE-INDUCED APOPTOSIS IN HUMAN EPITHELIAL LUNG CELLS

( A549 CELLS )

ROLE OF DIFFERENT G PROTEIN-LINKED SIGNAL SYSTEMS.

http://www.ncbi.nlm.nih.gov/pubmed 

Refsnes MSchwarze PEHolme JALåg M.

Source:
Division of Environmental Medicine,
Norwegian Institute of Public Health,
Geitmyrsvn. 75,
PO Box 4404 Nydalen,
N-0403 Oslo,
NORWAY.
magne.refsnes@fhi.no

Abstract:

 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 activat or 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 down regulation 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.

PMID: 12723891 [PubMed - indexed for MEDLINE]

Hum Exp Toxicol. 2003 Mar;22(3):111-23.

 

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