2011 Volume 54 Issue 2 Pages 88-96
Mechanical stress and periodontopathogenic bacteria induce the production of inflammatory cytokines in human periodontal ligament cells. These cytokines cause periodontitis and influence periodontal tissue including the periodontal ligament. Recently, although it is reported that β-cryptoxanthin (β-cryptoxanthin; β-cry) containing Citrus unshiu inhibits alveolar bone absorption, there has been no report showing that it influences inflammation in the periodontal ligament as periodontal tissue that includes alveolar bone. In the present study, we investigated whether β-cryptoxanthin influences the cytokine production of human periodontal ligament in response to mechanical stress caused by pressure during physiological occlusion or Porphyromonas gingivalis. The hPDL cells were obtained from a healthy erupted maxillary third molar. Cells were cultured in DMEM supplemented with 10% FBS and seeded onto Petri dishes at a concentration of 1×105cells/ml. β-cry was added to the Petri dishes (1×10-7mol/l) and stimulated with mechanical stress (1 or 6MPa) (MS group) or P. gingivalis (1×107CFU/ml) (bacteria group). IL-1β, IL-6, IL-8 and TNF-α were analyzed by RT-PCR and ELISA. Morphologic changes of hPDL cells were observed using an inverted optical microscope. The Ethics Committee of Kyoto Prefectural University of Medicine approved this experimental procedure. Regardless of the presence of β-cry, expressions of all inflammatory cytokines were detected, and the amounts of IL-6 and IL-8 were increased in the MS group and bacteria group. Furthermore, the amounts of IL-6 and IL-8 in the bacteria group were higher than those in the MS group. However, with the addition of β-cry to the medium, the amounts of IL-6 and IL-8 decreased in the MS group and bacteria group. Moreover, the ratio of change in cytokine production based on the addition/non-addition of β-cry was lower in the MS group than in the bacteria group. The morphology of hPDL cells did not change. These findings indicate that mechanical stress caused by pressure during physiological occlusion has a locally injurious property, and this property was weaker in the MS group than in the bacteria group. β-cry inhibited cytokine production in response to mechanical stress and periodontopathogenic bacteria in the periodontal ligament and mechanical stress has a stronger anti-inflammatory influence than periodontopathogenic bacteria. Ingestion of β-cry is usually useful for health maintenance and promotion, and it is possible that the anti-inflammatory properties of β-cry could be useful for drug development.
