Effect of ascorbic acid on arylsulfatase activities and sulfated proteoglycan metabolism in chondrocyte cultures

Abstract

A correlation between increased arylsulfatase activities and decreased sulfated proteoglycan content in human osteoarthritic articular cartilage suggested a possible interrelationship between these parameters. Since we had previously shown that ascorbate caused a decrease in levels of arylsulfatase A and B activities in normal chondrocyte cultures, the validity of the above relationship was examined by measuring the effect of vitamin C on the biosynthesis and distribution of 35S-labeled proteoglycans and arylsulfatase A and B activities in cell extracts of chondrocytes derived from normal and osteoarthritic tissue. Arylsulfatase A and B activities were found to be reduced in the presence of ascorbic acid in all normal and osteoarthritic cell lines examined when measured 3, 6, 10, and 13 days after the introduction of the vitamin in the culture medium. Acid phosphatase activity, on the other hand, was found to be elevated in the presence of ascorbate. The inhibitory effect by ascorbic acid on arylsulfatase activities could be reversed by withdrawing the vitamin from the nutrient medium. Addition of EDTA to the cell extracts before assay also reversed the inhibiton. Sulfated proteoglycan biosynthesis as reflected in 35S-sulfate uptake per milligram of DNA was significantly increased in the presence of ascorbic acid. The distribution of the newly synthesized molecules between the cell layer and medium fractions was altered. In the presence of ascorbate, more deposition into the cell layer of newly synthesized macromolecules occurred. These data suggest an inverse relationship between arylsulfatase activities and the stability of the newly synthesized sulfated proteoglycans in the extracellular matrix.