A influência do diabetes experimental e da metformina na evolução da osteonecrose mandibular induzida por bisfosfonato em ratos

Abstract

Zoledronic acid (AZ) is frequently used in the treatment of some cancers to prevent bone metastases. However, this drug is immeasurably associated with mandibular osteonecrosis (BRONJ), interfering with quality of life of patients. Considering that the concentration of pro inflammatory mediators and local microcirculation conditions are factors possibly involved in the pathogenesis of BRONJ, our study evaluated the influence of inflammation caused by hyperglycemia, which characterizes Diabetes Mellitus (DM), as well as the administration of metformin (MET), a drug with possible immunomodulatory potential, on the cellular profile and expression of osteoclastic and inflammatory markers in BRONJ induced by AZ (0.2 mg/kg orally). For this, 50 Wistar rats were subjected to DM and/or BRONJ induction protocols. They had their body mass and fasting blood glucose levels routinely measured. Animals treated with MET received this drug (250 mg/kg) daily by gavage. After euthanasia, mandibular arches subjected to extraction and their gums were obtained for analysis. Furthermore, RAW 264.7 cells were incubated with AZ and/or MET for cell viability tests and analysis of IL 1β expression. BRONJ did not cause significant changes in fasting blood glucose or body mass variation in the animals. The DM induction protocol was satisfactory, as it induced hyperglycemia satisfactorily, with discrepant reduced values of body mass compared to non diabetic animals. Treatment with MET induced lower glycemic and body weight values compared to the Naive and BRONJ groups. In the post extraction socket, BRONJ was characterized by an increase in the number of empty osteocyte lacunae, the total number of osteoclasts and apoptotic osteoclasts, the expression of TRAP and F4/80, as well as an increase in the total number of leukocytes. In the inflammatory evaluation of the gingival tissue, an increase in myeloperoxidase activity (MPO) was observed. In cell culture, AZ treatment increased IL 1β expression. DM, in itself, induced osteonecrosis and increased inflammatory parameters evaluated in vivo. However, when associated with BRONJ, hyperglycemia potentiated the inflammatory, but not bone, effects of AZ in animal specimens. The use of MET reduced the percentage of empty osteocyte lacunae and apoptotic OCs, without influencing the compensatory increase in OCs, and intensified the expression of TRAP caused by AZ. Furthermore, MET reduced both the expression of F4/80 and the number of leukocytes in alveolar bone, as well as MPO activity in gingival samples from animals with BRONJ. In fact, MET also prevented the increase in IL 1β expression caused by AZ in vitro. Thus, DM potentiated the inflammatory parameters of BRONJ, without significantly influencing the alveolar bone. Meanwhile, MET treatment alleviated BRONJ, with influences on the expressions of osteoclastic markers. It is suggested that such effects probably resulted from the anti inflammatory potential of this drug presented in our study.