Induction of early apoptosis and ROS-generation activity in human gingival fibroblasts (HGF) and human submandibular gland carcinoma (HSG) cells treated with curcumin

SummaryObjectiveCurcumin [1] is well known to possess apoptosis-inducing activity in some cancer cells, but little is known about its activity in normal cells of oral origin, such as HGF. The aim of the present study was to clarify the relationship between early apoptosis in HGF and the induction of reactive oxygen species (ROS) generation by curcumin.DesignWe treated HGF and HSG cells with curcumin [1] and the related compounds biseugenol [2], eugenol [3], α-diisoeugenol [4], and isoeugenol [5] and measured cell survival (MTT method), ROS generation (DCFH-DA staining), and induction of early apoptosis. Early apoptosis was detected by monitoring loss of mitochondrial membrane potential (ΔΨm) by JC-1 staining and externalization of phosphatidylserine (PS) on the cell surface by annexin V-FITC/PI staining combined with flow cytometry.ResultsThe cytotoxic activities of curcumin [1] and [4] were similar and were nearly 10- to 100-fold stronger than those of the other compounds. Only curcumin was able to induce ROS generation and early apoptosis. Loss of ΔΨm, PS externalization and ROS generation were significantly more pronounced in HGF cells than in HSG cells at curcumin concentrations lower than about 15 μM, and were inhibited by the addition of the antioxidants N-acetyl-l-cysteine and glutathione.ConclusionThe potent PS externalization and loss of ΔΨm in curcumin-treated HGF cells appears to be mediated by ROS generation.