Tumour necrosis factor-α and apoptosis in the rat temporomandibular joint

The purpose of this investigation was to investigate the roles that tumour necrosis factor-α (TNF-α) and apoptosis play during acute inflammation of the temporomandibular joint (TMJ). Adult male Sprague–Dawley rats were injected with complete Freund’s adjuvant (CFA) into the TMJ or kept as uninjected controls. The TMJ tissues were removed 2 days post-injection to mimic conditions of acute inflammation and analysed for changes in expression of TNF-α, the receptor TNF-R1, caspase-3 and -8, and apoptosis. Concentrations of TNF-α, TNF-R1, caspase-3 and -8, and apoptosis were significantly elevated in CFA-injected animals compared to uninjected controls. Tissue incubation with TNF-α caused a significant increase in caspase-3 and -8. Also, levels of apoptosis were significantly increased during inflammation, which could be inhibited by the addition of either anti-TNF-α neutralising antibody or caspase inhibitors. TNF-α may play a significant role in the onset of acute CFA-induced TMJ inflammation, and activation of apoptosis signalling pathways may be involved.