In vitro effects of soluble epoxide hydrolase inhibition on chondrocyte apoptosis and sensitization of peripheral sensory nerves

Abstract

Purpose: Chondrocyte apoptosis and neuronal sensitization are prominent features of osteoarthritis (OA) that are difficult to control with currently available therapies. Methods: To determine if soluble epoxide hydrolase (sEH) contributes to chondrocyte apoptosis, cultured immortalized human T/C28a2 chondrocytes were challenged with the apoptotic inducer tunicamycin (10 μg mL-1) for 24 hours concurrently with the sEH inhibitor t-TUCB (500 nM) or vehicle control, and apoptosis determined in duplicate via ELISA. To determine if soluble epoxide hydrolase (sEH) contributes to neuronal sensitization, peripheral sensory neurons from C57BL/6 mice (n=4; 25-65 cells/group) were cultured with and without tumor necrosis factor (TNF)-α (20 ng mL-1) and intracellular calcium responses to noxious cold (5°C) and heat (45°C) were determined in the presence or absence of t-TUCB (5 mM). Results were analyzed with repeated measures ANOVA and Sidak post-hoc test with p<0.05 considered significant. Data are mean±SD. Results: Tunicamycin-induced chondrocyte apoptosis (0.9±0.3 absorbance units) was significantly higher than controls (0.36±0.07) and was prevented by t-TUCB (0.48±0.1). Changes in intracellular calcium concentrations in TNF-α-treated sensory neurons in response to noxious cold and heat (18±7% and 17±8%, respectively) were significantly greater than controls (3±2 and 6±3) and was prevented by t-TUCB (4±3 and 9±6). Conclusion: Inhibition of sEH showed a protective effect on chondrocytes apoptosis and attenuated the responses of sensitized peripheral sensory neurons in vitro, and may constitute a potential target to control joint pain and decrease chondrocyte apoptosis in OA.