IL-1α and TNF-α Expression in Rat Periapical Lesions and Dental Pulp after Unilateral Sympathectomy

Abstract

Objectives: Apical periodontitis is an inflammatory disease characterized by bone resorption, and sympathetic nerves are known to modulate bone resorption and bone remodeling. Higher numbers of osteoclasts and larger periapical lesions have been observed after sympathectomy in rats, but the mechanisms underlying the inhibitory effect of sympathetic nerves on osteoclasts are unknown. This study aimed to test the hypothesis that sympathetic nerves inhibit the production of the bone-resorbing pro-inflammatory cytokines IL-1α and TNF-α in rat periapical lesions. Methods: Rats were unilaterally sympathectomized and apical lesions were induced by exposing the dental pulp of molar teeth to the oral microflora. We quantified the cytokines IL-1α and TNF-α by enzyme-linked immunosorbent assay, and immunohistochemical analysis was done for qualitative localization. Pulp from intact incisor teeth was tested as a control. Results: We showed that IL-1α was increased, but not TNF-α, in the periapical lesions on the sympathectomized side. Both IL-1α and TNF-α were expressed in unexposed pulp. TNF-α was significantly decreased in the denervated incisor pulp, whereas the level of IL-1α remained unchanged. Conclusions: This study suggests that sympathetic nerves have an inhibitory effect on IL-1α in periapical lesions and a stimulatory effect on TNF-α in the intact rat pulp.