TiF4 and NaF varnishes induce low levels of apoptosis in murine and human fibroblasts through mitochondrial Bcl-2 family and death receptor signalling

Publication date: Available online 2 November 2018

Source: Archives of Oral Biology

Author(s): Priscila Maria Aranda Salomão, Flávia Amadeu de Oliveira, Daiana Moreli Soares dos Santos, João Paulo Domezi, Thiago José Dionísio, Rodrigo Cardoso de Oliveira, Ana Carolina Magalhães

Abstract

Objectives

This study evaluated the level and mechanism of apoptosis in human gingival fibroblasts (HGF) and murine fibroblasts (NIH/3T3) treated with a titanium tetrafluoride (TiF₄) varnish compared those treated with a sodium fluoride (NaF) varnish.

Methods

Cells were treated with a TiF₄, NaF (both 2.45%F) or placebo varnish for 6 h and were then examined using the TUNEL method. The activities of caspase-3, -8 and -9 were assessed. cDNA for Bax, Bad, Bcl-2 and Fas-L was amplified by quantitative PCR. Bax, Bcl-2 and Fas-L were further detected by western blot analysis.

Results

Both fluorides similarly increased the percentage of apoptosis, while they failed to activate caspases. The Bax/Bcl-2 gene expression ratio was not altered by either fluoride treatment regardless of the type of cell. NaF varnish increased the amplification of the Fas-L gene in NIH/3T3 and HGF cells, while treatment with the TiF₄ varnish resulted in a lower Bad/Bcl-2 expression ratio compared to that of the control for NIH/3T3 cells, but not for HGF cells. No effect of the fluorides was detected in the protein analysis.

Conclusions

NaF and TiF₄, at the studied conditions, similarly induce a low level of apoptosis, with consequent modest activation of the Bcl-2 and Fas-L-dependent signalling pathways. Generally, HGF cells are more susceptible to the fluoride effect than NIH/3T3 cells.

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