Figure 4.

LPLI inhibits arecoline-induced CCN2 promoter activation by dual luciferase assay. HGFs were cotransfected with the pTS589 vector and pTK-Renilla vector. Then, the cells were cultured in the absence or presence of arecoline (200 μmol·L⁻¹), forskolin (60 μmol·L⁻¹), and SQ22536 (100 μmol·L⁻¹), and the cells were treated with or without LPLI (8 J·cm⁻²). The cells were collected, and luciferase activity was measured as described under “Materials and Methods” section. The results are expressed as the mean±standard deviation from three independent experiments. The statistical levels are indicated as follows: *P<0.05 compared with the arecoline group, and ^#P<0.05 compared with the indicated group. HGF, human gingival fibroblast; LPLI, low-power laser irradiation.