Enhancement of sodium fluoride-induced cell death by centrifugal force

As an initial step in the study of the influence of orthodontic force on cellular function in vitro, the effects of centrifugal force on the cytotoxicity induced by various apoptosis inducers were investigated. When human oral squamous cell carcinoma (HSC-2) and human promyelocytic leukemia (HL-60) cell lines were treated with increasing magnitudes of centrifugal force (evaluated by g-value), the viability assessed by the MTT method and trypan blue dye exclusion began to decline. Centrifugal force enhanced the cytotoxicity of sodium fluoride (NaF), but not that of redox compounds (hydrogen peroxide, sodium ascorbate, gallic acid) or chemotherapeutic agents (daunorubicin, doxorubicin, idarubicin, mitoxantrone, peplomycin, 5-FU). The combination of NaF and centrifugal force enhanced caspase-3 activity. The present study suggests that centrifugal force is an additional factor that modifies the biological activity of NaF.