Interleukin-1β and Interleukin-6 Alter Matrix Metalloproteinase Expression from Pulp Fibroblasts

Interleukin (IL)-1β and IL-6 have been implicated in the pathogenesis of many chronic diseases including pulpitis. Matrix metallproteinases (MMPs) have been suggested to play a role in the tissue destruction that occurs during pulpitis. Objectives: The purpose of this study was to determine the effects that IL-1β and IL-6 has on the expression of the MMPs and the tissue inhibitors of matrix metalloproteinase (TIMPs) from dental pulp fibroblasts (DPF), as well as their effects on DPF mediated collagen degradation. Methods: To examine their collagen degrading ability, DPF were seeded as single colonies on reconstituted Type I collagen with or without IL-1β and IL-6. The cells were then removed and the plates stained to visualize collagen degradation. The conditioned media from the DPF in the presence and absence of IL-1β and IL-6 was collected. To characterize the gelatinase activity, the conditioned media was subjected to zymography. Western blot analyses were also performed to examine the presence of select MMPs secreted into the conditioned media. Results: The collagen degrading ability of DPF was stimulated by IL-1β and IL-6 and this activity was inhibited by GM6001 (a MMP inhibitor). The zymogram demonstrated that the major proteinase in the conditioned media migrated at 72kDa. Weaker bands of proteolytic activity were also observed at 57/52kDa and 68kDa. IL-1β increased the 57/52kDa bands and slightly increased the 47/42kDa and 68kDa bands, but not the 72kDa band. IL-6 increased the activity of the 57/52kDa, 72kDa, and 68kDa bands, as well as slightly elevated the 47/42kDa bands. Western blot analyses demonstrated that IL-1β increased the expression of MMP-1, MMP-3, and TIMP-1. IL-6 increased the expression of MMP-1, MMP-2, MMP-3, TIMP-1, and TIMP-2. Conclusion: These results suggest that IL-1β and IL-6 can induce pulpal tissue destruction during pulpitis in part by differentially regulating MMP and TIMP expression from DPF.