Study on Cytokine Production in the Lesions of Periodontal Disease : Interaction between Interleukin 1 (IL-1) and Tumor Necrosis Factor α (TNFα)

Interleukin 1 (IL-1) and tumor necrosis factor α (TNFα), two major immunoregulatory cytokines which produced by a variety of cells, have been shown to exert and share multiple biological effects on many target cells. Current evidence has demonstrated that their appearance is closely related with a feature of periodontal disease. This study, therefore, was designed to investigate their potential importance in the lesions of periodontal tissues in vitro and in vivo. At first in in vitro experiments, a dose-response and kinetics of IL-1α (like factor) production by macrophages and fibroblasts were investigated by measuring those amounts by ELISA at various time points after stimulation by LPS, heat-killed E. coli and rTNFα. The kinetics of IL-1α production of the macrophages in the presence of LPS differed from those observed in the presense of heat-killed E. coli. When combined at sub-optimal concentrations, LPS and rTNFα synergistically stimulated intra- and extracellular IL-1α production by the macrophages. A combined use of heat-killed E. coli followed with rTNFα (6 hours later addition) seemed to stimulate additively. On the other hand, LPS also increased IL-1α like factor production by the fibroblasts in a dose-dependent manner within a range from 0.1 to 5.0μg/ml. Especially, extracellular IL-1α like factor production by the fibroblasts was detected as early as 6 hours after LPS treatment and then reached a maximum level at 24 hours. No increase in IL-1α like factor production was observed in the fibroblasts stimulated by heat-killed E. coli. Futhermore, in vivo the kinetics of IL-1α like factor and TNFα like factor was studied in the samples extracted from the gingiva and serum after injection into the gingiva of rats with LPS and heat-killed E. coli. In LPS-injection group, the amounts of IL-1α like factor and TNFα like factor in gingival extracts were observed to have two peaks. The first increase reached a peak at 6 hours after injection, and the amounts of IL-1α like factor and TNFα like factor were maintained during the second peak (one day later). In heat-killed E. coli-injection group, a rapid-onset of IL-1α like factor production was observed in the gingival extracts. The first peak was recognized one hour and the second peak 3 days after injection. The amount of TNFα like factor was increased with two peaks. The first peak was observed 6 hours, the second peak one day after injection. Thus, the kinetics of IL-1α like factor production was differed from that of TNFα like factor production in the gingival extracts. On the other hand, no marked IL-1α like factor production was observed and no TNFα like factor was detectable in the serum by immunoassay. These findings suggest the possibility that IL-1 and TNFα may be key mediators in the initiation and regulation of many steps in the inflammatory and immunological response through interaction between cytokines (as a cytokine-network) in the lesions of periodontal disease.