A study on the role of nitric oxide in the response of periodontal tissue to mechanical stimuli

Nitric oxide，a mediator of vascular function，neurotransmission，and immune system，has been recently shown to play an important role in adaptive response of bone to mechanical stress/strain.Periodontal tissue receives and adapts to various mechanical stimuli such as masticatory force and orthodontic force.Thus，it is possible that NO is a mediator of adaptive physiological response of periodontal tissue to these mechanical stimuli.In the present study，we tested this possibility both in vitro and in vivo.1)Effect of cyclic tension force on NO and prostaglandin E ei D22文件D2 production and mRNA expression of their synthases in human periodontal ligament cells.Application of cyclic tension force to human periodontal ligament cells induced a rapid and transient increase in NO release in the culture medium。Endothelial isoform of NO synthase(NOS)mRNA expression decreased.Release of prostaglandin E I D22文件D2 time-dependently increased by the application of force.Cyclooxygenase-2 mRNA表达式increased，whereas cyclooxygenase-1 mRNA表达式did not change.These results suggest that NO and PGE I D22齐埃D2 are involved in the adaptive response of periodontal ligament cells to mechanical stress/strain.2)Effect of topical administration of inhibitors of NO synthase and spontaneous NO donors on orthodontic tooth movement in rats.Upper first molars of male 8-week-old Wistar rats were moved buccally for 21 days.The topical administration of L-NAME(10 mg/mL)，a general inhibitor of NOS activity，caused a significant reduction of tooth movement。On the other hand，L-NIO(5 mg/mL)，a selective inhibitor of inducible isoform of NOS，had no effect on tooth movement。There was a tendency toward a decrease in tooth movement in animals treated with NO donors(NOR4and NOC)。These results suggest that NO sythesized by constitutive isoforms of NOS has an important role in orthodontic tooth movement。

Nitric oxide, a mediator of vascular function, neurotransmission, and immune system, has been recently shown to play an important role in adaptive response of bone to mechanical stress/strain. Periodontal tissue receives and adapts to various mechanical stimuli such as masticatory force and orthodontic force. Thus, it is possible that NO is a mediator of adaptive physiological response of periodontal tissue to these mechanical stimuli. In the present study, we tested this possibility both in vitro and in vivo.1) Effect of cyclic tension force on NO and prostaglandin EィイD22ィエD2 production and mRNA expression of their synthases in human periodontal ligament cells.Application of cyclic tension force to human periodontal ligament cells induced a rapid and transient increase in NO release in the culture medium. Endothelial isoform of NO synthase (NOS) mRNA expression decreased. Release of prostaglandin EィイD22ィエD2 time-dependently increased by the application of force. Cyclooxygenase-2 mRNA expression increased, whereas cyclooxygenase-1 mRNA expression did not change. These results suggest that NO and PGEィイD22ィエD2 are involved in the adaptive response of periodontal ligament cells to mechanical stress/strain.2) Effect of topical administration of inhibitors of NO synthase and spontaneous NO donors on orthodontic tooth movement in rats.Upper first molars of male 8-week-old Wistar rats were moved buccally for 21 days. The topical administration of L-NAME (10 mg/mL), a general inhibitor of NOS activity, caused a significant reduction of tooth movement. On the other hand, L-NIO (5 mg/mL), a selective inhibitor of inducible isoform of NOS, had no effect on tooth movement. There was a tendency toward a decrease in tooth movement in animals treated with NO donors (NOR4 and NOC). These results suggest that NO sythesized by constitutive isoforms of NOS has an important role in orthodontic tooth movement.