Chronic treatment with zoledronic acid alters the expression levels of inflammatory, bone, and apoptotic markers and Toll-like receptors 2 and 4 in rat dental pulp

Objective: The aim of this study was to evaluate the immunostaining of inflammatory, apoptotic, and bone markers, as well as Toll-like-receptors (TLRs) 2 and 4 in the dental pulp in rats treated with zoledronic acid (ZA).

Study design: We administered 4 intravascular infusions of saline (control group) or 0.20 mg.kg^-1 ZA in Wistar rats (n = 6/group). After 70 days, the 3 rights molars (n = 18/group) were microscopically evaluated (presence of ectasic/dilated blood vessels and inflammatory cells). Immunohistochemistry was performed for tartrate resistant acid phosphatase 5 (TRAP; cell counting), cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), TLR2, TLR4, receptor activator of nuclear kappa B ligand (RANKL), osteoprotegerin (OPG), and caspase-3 (scored 0-3 in odontoblast and nonodontoblast dental pulp cells). Mann-Whitney and Fisher's exact tests and Spearman's correlation were used (GraphPad Prism 5.0).

Results: There was no alteration in ectasic/dilated blood vessels (P = .101) or inflammatory cells (P = .500), but the number of TRAP-positive cells was reduced in the ZA-group (P = .027). In ZA-group odontoblasts, immunostaining for COX-2 (P = .044), TLR4 (P = .003), OPG (P = .035) and caspase-3 (P = .039) increased, and that for RANKL (P = 0.045) decreased. In nonodontoblast dental pulp cells, RANKL immunostaining decreased (P = .009). In the ZA group, the RANKL/OPG ratio decreased in odontoblast (P = .022) and nonodontoblast dental pulp cells (P = .007). IL-6 did not differ between the groups.

Conclusions: ZA increases the expression levels of inflammatory, apoptotic markers, and TLR4 and alters bone makers in the dental pulp of rats.