Hyaluronan reversed proteoglycan synthesis inhibited by mechanical stress: possible involvement of antioxidant effect.

Abnormal mechanical stress loaded on the cartilage leads to the osteoarthritis (OA). Although intraarticular hyaluronan (HA) injection is an effective treatment for OA, the underlying mechanism has not been made clear. Mechanical compression was loaded on the bovine cartilage using the Biopress system. Proteoglycan (PG) and reactive oxygen species (ROS) synthesis were measured with [(35)S] incorporation and fluorescent dye, respectively. Accumulation of peroxynitrite was determined with western blotting using nitrotyrosine antibody. Mechanical compression inhibited PG synthesis and enhanced ROS. Externally added HA reversed stress-inhibited PG synthesis and attenuated ROS synthesis. HA also significantly decreased the generation of nitrotyrosine. HA neutralized stress-enhanced ROS synthesis and resulted in the reversing of PG synthesis. These data suggest that HA plays an anabolic effect as an antioxidant.