In vitro effect of curcumin-mediated antimicrobial photodynamic therapy on fibroblasts: viability and cell signaling for apoptosis

Abstract

Although it was demonstrated that curcumin-mediated antimicrobial photodynamic therapy (aPDT) is effective for reducing the viability of microbial cells and the vitality of oral biofilms, the cytotoxicity of this therapeutic approach for host cells has not been yet elucidated. Hence, the aim of this study was to evaluate the cytotoxicity and apoptotic effects of curcumin-mediated aPDT on mouse fibroblasts. Cells were treated with 0.6 or 6 μmol.L^-1 curcumin combined with 0.075 or 7.5 J.cm^-2 LED at 455 nm. Cytotoxicity was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and crystal violet (CV) assays, while quantitative reverse transcriptase-PCR (qRT-PCR) was used to assess the expression of Bax, Bad, Bcl-2, VDAC-1, cytochrome C, and Fas-L genes for apoptosis. The differences between groups were detected by Kruskal-Wallis and post hoc Dunn's tests for MTT and CV assays and by ANOVA and post hoc Tukey test for qRT-PCR (P < 0.05). The effect of 0.6 μmol.L^-1 curcumin plus 0.075 J.cm^-2 LED (minimum parameter) did not differ statistically from control group; however, the combination of 0.6 μmol.L^-1 curcumin plus 7.5 J.cm^-2 LED reduced viable cells in 34%, while the combinations of 6 μmol.L^-1 curcumin plus 0.075 and 7.5 J.cm^-2 LED reduced viable cells in 47% and 99%, respectively. aPDT increased significantly the relative expression of Bax/Bcl-2, cytochrome C, VDAC-1, and Fas-L genes, without influence on the ratio Bad/Bcl-2. Therefore, curcumin-mediated aPDT activated Bcl-2 apoptosis signaling pathways in mouse fibroblasts regarding present conditions, reducing the viability of cells with the increase of curcumin concentrations and light energies.

Keywords: Antimicrobial photodynamic therapy; Bcl-2 family; Cell viability; Curcumin; Photochemotherapy.