Objective: Chloride channels were suggested to act as fluoride exporters that protect bacteria from environmental fluoride toxicity. The involvement of chloride channels in fluoride resistance in mammalian cells remains unknown. The purpose of this study was to investigate the differential genetic expression of the CLCN family of voltage-gated chloride channel and the cystic fibrosis transmembrane conductance regulator (CFTR) between regular and induced fluoride-resistant L-929 cells in vitro.
Methods: Fluoride-resistant L-929 cells to 90 ppm were induced in vitro by sequential exposure of regular L-929 cells (ATCC CCL-1, Manassas, VA) to concentration gradient ascending fluoride media. Total cellular RNA was isolated from both regular and 90ppm fluoride-resistant L-929 cells. cDNA was synthesized from extracted RNA and quantitative real-time PCR were used to determine the mRNA expression of CFTR and CLCN family (including CLCN1, CLCN2, CLCN3, CLCN4, CLCN5, CLCN6, CLCN7, CLCNKA and CLCNKB) in both types of L-929 cells.
Results: In 90 ppm fluoride-resistant L-929 cells, the genetic expression of CLCN2 was up-regulated to about twice as that in the regular L-929 cells (p<0.05), whereas the expression of CLCN1, CLCN3, CLCN4 and CFTR were down-regulated compared to the regular L-929 cells (p<0.05). There were no significant difference in the genetic expression of CLCN5, CLCN6, CLCN7, CLCNKA and CLCNKB between the regular and 90 ppm fluoride-resistant L-929 cells.
Conclusion: Under the condition of the present study, the results suggest that CLCN1, CLCN2, CLCN3, CLCN4 and CFTR play a potential role in the resistance of L-929 cells to high concentration of extracellular fluoride.
Key words: Fluoride-resistant, Chloride channels, Gene expression, Fibroblasts