Localization of IL-1RI in Rat Dental Pulp

Acute pulpitis is an inflammatory condition characterized by vascular responses such as vasodilatation and increased vessel permeability, and it may be painful. IL-1β is a major pro-inflammatory cytokine that is up-regulated during pulpitis. Although IL-1β seems to play a central role in the pathophysiology of pulpitis, there are no data on the exact sites of action of this cytokine in the dental pulp. Objectives: the purpose of this study was to identify binding sites of the pro-inflammatory cytokine IL-1β in rat dental pulp. Methods: Female Wistar rats (n = 6) were subjected to unilateral pulp exposures in the first maxillary and mandibular molars and the contralateral sides served as untreated controls. One, 2 and 3 weeks after pulp exposures the rats were sacrificed and the jaws were removed. Immunoreactivity (IR) for the interleukin-1 receptor type I (IL-1RI) was examined using multiple-labeling immunofluorescence together with calcitonin gene-related peptide (CGRP), Neuropeptide Y (NPY), CD31 and CD34 in parasagittal rat jaw sections. Results: IL-1RI was found on sensory (CGRP-IR) nerve fibers, on sympathetic (NPY-IR) nerve fibers and on blood vessels (CD34-IR). Conclusion: multiple binding sites of IL-1 were found in the rat pulp. The localization of IL-1RI on sensory nerve fibers implies a direct effect of IL-1β on nociceptor sensitization. The presence of IL-1RI on blood vessels indicates a direct effect of IL-1β on the vessel wall.