Bone remodeling is characterized by the coupling of osteoclast-mediated bone resorption and osteoblast-mediated bone formation. The process is tightly regualted at the local level by an incompletely known netwotk of peptide and non-peptide fators. Nitric oxide(NO), synthesized by nitric oxide synthetase(NOS) from L-arginine, is becoming recognized as an important bio-regualtory molecule in a variety of tissue, but little is known about its possible role in periodontal tissue.
The purpose of this study is to investigate the expression of nitric oxide synthetase(NOS) in inflamed gingiva and the effects of cytokine on the expression of NOS protein. The expression of NOS in gingival tissue was evaluated by immunohistochemical staining for NOS,, NOS2, NOS3. The effect of cytokine on the expression of NOS in human periodontal ligament cells and osteoblast-like HOS cells by western blot analysis. Further, we studied that NO functions in periodontal ligment cells as a regulatory molecule. PDL cells incubated with NOS inhibitor and donor. The protein expression, type I collagen & non-collagenous protein, nitrate production and cell proliferation were evaluated.
1. NOSi, NOS2, NOS3 was rarely distributed in healthy gingi--a, but stronger stained in gingival
epithelium, endothelial cells, and mononuclear cells of inflammed gingiva.
2. The cytokine stimulated NOS,, and NOS3 protein were not inducing or inhibitory effect to
compared with control in PDL and HOS cells.
3. Incubation of cells with combination of TNF- a , IFN- y , LPS result in a time dependant
increase in NOS2 expression, reaching a maximal level after 24 hours of stimulation.
4. The osteonectin protein inhibitory effect of NMA, inhibitor of NOS, was reversed by
L-arginine in dose dependant manner.
5. NMA decreased cell proliferation and nitrate production, but the inhibitory efffect of NMA was also prevented by . the NO donor, sodium nitropruiside.
These results suggest that exogenously synthesized NO was playing a stimulating effect on cell proliferation or on non-collagenous protein expression. Therefore NO have an important role in mediation of localized bone destruction associated inflammatory bone disease such as periodontitis.
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