Detection of protein and mRNA of various components of the NADPH oxidase complex in an immortalized human chondrocyte line.

The immortalized human chondrocyte cell line C-20/A4 has the ability to produce superoxide constitutively at low levels of 5.4 x 10(-2) nmol/min/10(6) cells (S.E.M. = +/-0.5, n = 30) and at raised levels upon stimulation with ionomycin and phorbol 12-myristate 13-acetate. Priming and anti-priming effects of interleukin (IL)-1 beta and IL-4, respectively, are also demonstrated. Reverse transcriptase polymerase chain reaction (RT-PCR) amplification using oligonucleotide primers to components of the NADPH oxidase enzyme complex showed mRNA expression of p22-phox, p40-phox and p47-phox. Western blot analysis using polyclonal antisera indicated the presence of the p47-phox p67-phox polypeptide components. These results show that the C-20/A4 cells contain an NADPH oxidase-like complex, similar to that found in other cell types, which produces superoxide anions.