Modelo experimental de hipernocicepção facial e artrite na articulação temporomandibular induzida por zymosan em ratos e estudo da via da hemeoxigenase-1/biliverdina/monóxido de carbono

Abstract

Temporomandibular disorders (TMDs) encompass a group of musculoskeletal and neuromuscular conditions that involve the temporomandibular joints (TMJs), the masticatory muscles, and all associated tissues, although the mechanisms involved in the TMJ inflammation and pain are not clear. Beyond the great interest of the hemeoxigenase-1 (HO-1) and the evidence of its citoprotector and antiinflammatory effects, the role of the pathway HO-1/bilivedin (BVD)/carbon monoxide (CO) in the TMJ inflammation and pain was not yet investigated.The purpose of the study is to propose an experimental model of articular hypernociception and TMJ arthritis induced by zymosan (Zy), to investigate the role of the HO-1/BVD/CO and its mechanisms through GMPc/ K+ channel ATP sensitive pathway on these events and to evaluate its relationship with TNFα and IL-1β in rats. Inflammation was induced by intra-articular injection of zymosan (0.25, 0.5, 1 or 2mg) or saline into left TMJ. Mechanical hypernociception, cell influx, vascular permeability, myeloperoxidase activity, and histological changes were measured in TMJ lavages or tissues at selected time points. Hemin (0.1, 0.3 or 1 mg/kg), DMDC (0.025, 0.25 or 2.5 µmol/kg), Biliverdin (1, 3 or 10 mg/kg) or ZnPP (1, 3 or 9 mg/kg) was injected (s.c.) 60 min before zymosan. ODQ (12.5 µmol/kg; s.c.) or Glibenclamide (10 mg/kg; i.p.) was administered 1 h and 30 min prior to DMDC (2.5 µMol/Kg; s.c). The gene expression for mRNA from HO-1, TNF-α and IL-1β in the TMJ tissues and the trigeminal ganglia, and the gene expression was studied at selected time points. The level of bilirrubin in plasma and the level of IL-1β in the synovial lavage were determined. Zymosan-induced TMJ arthritis caused a time-dependent leucocyte migration, plasma extravasation, mechanical hypernociception, and neutrophil accumulation between 4 and 24 h. Histopathological analysis of TMJ of Zy injected animals showed inflammatory cell infiltration in synovial membrane (SM), in conective periarticular tissue, in squeletic muscle tissue and thickness of SM in 6 h after TMJ arthritis. Initiating on the 10th day of TMJ arthritis, it was observed continuous leucocyte infiltration, composed mainly with mononuclear cells, thickness and fibrosis of SM. Hemin (1 mg/kg), DMDC (2.5 µmol/kg) and Biliverdin (10 mg/kg) reduced facial mechanical hypernociception, leucocyte migration, and neutrophil accumulation, confirmed by histopathological analysis. ZnPP (3 mg/kg) potentiated all the parameters. ODQ and glibenclamide reverted the antinociceptive and antiinflammatory effects of the DMDC. It was also observed increased expression of mRNA for HO-1, TNF-α and IL-1β in the TMJ tissues and in the trigeminal ganglia, and it was identified, through imunohistochemistry reaction, that chondhrocytes, synoviocytes and neutrophils are the source of these proteins in the TMJ, and aferente neuron cell body and satellite glial cells are the source of these protein in the trigeminal ganglia. The level of bilirrubin was increased in the plasma, as well as IL-1β level in the synovial lavage. These results sugest that zymosan-induced TMJ arthritis is a reproducible model that may be used to assess both the mechanisms underlying TMJ pain and inflammation and the potential tools for therapies. Furthermore, HO-1/BVD/CO/GMPc/K+ channel ATP sensitive pathway participate in the physiopathological mechanisms of TMJ pain and inflammation, emphasizing that this is the first study to show this pathway on theTMJ articular hypernociception. Beyond, the balance between HO-1, TNFα and IL-1β activity is important on the development of the TMJ pain and inflammation.