Implications for tooth eruption of the effect of interleukin-1alpha on nuclear factor-kappaB gene expression in the rat dental follicle.

Tooth eruption is a localized event and a cascade of molecular signals generated in the dental follicle and stellate reticulum appears to initiate its onset. Consequently, mononuclear cells are recruited into the follicle and, in turn, fuse to become osteoclasts needed to resorb the alveolar bone to form an eruption pathway. One of the transcription factors involved in the sequence of molecular signalling may be nuclear factor (NF)kappaB. This study shows that NFkappaB is expressed and synthesized by cultured dental follicle cells. Moreover, its transcription, activation and translocation were enhanced by interleukin (IL)-1alpha, a potential eruption molecule. The enhancement of transcription of the NFkappaB gene by IL-1alpha was blocked by a tyrosine-specific kinase inhibitor, suggesting that the enhancement may require the phosphorylation of the NFkappaB complex. In vivo, NFkappaB is maximally expressed in the dental follicle of the rat first mandibular molar at day 3 postnatally, the age at which there is a peak influx of mononuclear cells into the follicle. Thus, a transcription factor apparently required for eruption (NFkappaB) is present in the tissue required for eruption, the dental follicle, and its gene expression is maximal at a critical time in eruption.