Cultured Human Periodontal Ligament Cells Produce Nitric Oxide Through the Interleukin-1β-independent mechanism

Abstract

Nitric oxide (NO) has been implicated as a biological mediator in a number of organs. We found that cultured human periodontal ligament (hPDL) cells spontaneously produce NO in a serum-free condition. This NO production was not affected by culturing the cells with interleukin-1β(IL-1β). The amount of NO production in the hPDL cells (1.0×10⁶ cells/well) was 0.28±0.23 nmol/12 h when the cells were cultured with a serum-free medium and was 0.41±0.22 nmol/12 h with a medium containing 20 ng/ml IL-1β. In contrast, NO production in the mechanically stimulated hPDL cells(4.0×10⁵ cells/well)was 9.22±1.37nmol/12h in αMEM containing 10% fetal calf serum. The value was significantly higher (p<0.001) than the control value (1.04±0.22nmol/12h) obtained from unstimulated cells. The NO production was dependent on both magnitude of the tension force and frequency of the stretching cycle.
These results indicate that hPDL cells produce NO independently of IL-1β and that the NO production was enhanced by mechanical stimuli.