Interleukin-1β induces death in chondrocyte-like ATDC5 cells through mitochondrial dysfunction and energy depletion in a reactive nitrogen and oxygen species-dependent manner

IL-1 (interleukin-1) acts as a key mediator of the degeneration of articular cartilage in RA (rheumatoid arthritis) and OA (osteoarthritis), where chondrocyte death is observed. It is still controversial, however, whether IL-1 induces chondrocyte death. In the present study, the viability of mouse chondrocyte-like ATDC5 cells was reduced by the treatment with IL-1β for 48 h or longer. IL-1β augmented the expression of the catalytic gp91 subunit of NADPH oxidase, gp91^phox, as well as inducible NO synthase in ATDC5 cells. Generation of nitrated guanosine and tyrosine suggested the formation of reactive nitrogen species including ONOO⁻ (peroxynitrite), a reaction product of NO and O₂⁻, in ATDC5 cells and rat primary chondrocytes treated with IL-1β. Death of ATDC5 cells after IL-1β treatment was prevented by an NADPH-oxidase inhibitor, AEBSF [4-(2-aminoethyl)benzenesulphonyl fluoride], an NO synthase inhibitor, L-NAME (N^G-nitro-L-arginine methyl ester), and a ONOO⁻ scavenger, uric acid. The viability of ATDC5 cells was reduced by the ONOO⁻-generator 3-(4-morpholinyl)sydnonimine hydrochloride, but not by either the NO-donor 1-hydroxy-2-oxo-3-(N-methyl-2-aminopropyl)-3-methyl-1-triazene or S-nitrosoglutathione. Disruption of mitochondrial membrane potential and ATP deprivation were observed in IL-1β-treated ATDC5 cells, both of which were restored by L-NAME, AEBSF or uric acid. On the other hand, no morphological or biochemical signs indicating apoptosis were observed in these cells. These results suggest that the death of chondrocyte-like ATDC5 cells was mediated at least in part by mitochondrial dysfunction and energy depletion through ONOO⁻ formation after IL-1β treatment.