Phosphocitrate blocks nitric oxide-induced calcification of cartilage and chondrocyte-derived apoptotic bodies

Objective: To examine whether phosphocitrate (PC) will block nitric oxide-induced calcification of cartilage or chondrocyte-derived apoptotic bodies. Design: Articular cartilage vesicles (ACV) or apoptotic bodies (AB) were isolated from untreated or 1 mM sodium nitroprusside (SNP) treated porcine cartilage slices. Mineralization of ACV, AB, control untreated and SNP-treated cartilage were done in the presence or absence of PC (1 mM) +/- ATP (1 mM). Results: PC [1 mM] blocked both the ATP-dependent and -independent mineralization in ACV and AB, untreated and SNP treated cartilage. Moreover, PC had no effect on NTPPPH activity in either ACV or AB fraction in the presence or absence of ATP suggesting that PC did not block the mineralization through the inhibition of NTPPPH activity. Conclusions: PC inhibits nitric oxide-induced calcification of cartilage and cartilage-derived apoptotic bodies.