Effect of aging on expression of nitric oxide and inducible nitric oxide synthase in human gingival fibroblasts

In general, aging has been defined as a progressive decrease in the physiological capacity and the reduced ability to respond to environmental stresses lead to an increased susceptibility to disease 1) . It is well known that the severity of periodontal diseases is affected by the host s age 2) . In addition, recent studies have shown that the production of inflammatory mediators such as PGE2, IL-1β, IL-6, cyclooxygenase-2 and the plasminogen activator are higher in the gingival fibroblasts from the older animals or in vitro senescent fibroblasts compared with younger counterparts 3-7) . Although the severity of periodontal disease is affected by age, functional changes in the periodontal tissue cells during the aging process have not been well characterized.1) Recent studies have shown that activation of the iNOS pathway is essential for IL-1-stimulated bone resorption, both in vivo and in vitro 8,9) . Although the precise role of NO in the immunopathological process is unknown, the result of this process is the destruction and ultimately the loss of both the soft and hard tissues surrounding the tooth 10) . Immunohistological studies of human iNOS in gingival tissue have shown that iNOS is widely distributed in epithelial cells, endothelial cells, fibroblasts, macrophages, and polymorphonuclear leukocytes 11) . In addition, it has recently been demonstrated that synthesized NO and NO production was increased by stimulating the cultured human gingival fibroblasts