Effect of indomethacin and hydrocortisone upon joint tissue in vitro. Incorporation of [35S]sulphate into chondrocyte proteoglycans

Evaluation of the effect of antiarthritic drugs on the secretion of proteoglycans by lapine chondrocytes using a novel assay procedure

A new method is described for separating free 35SO4-- from 35SO4 labelled proteoglycans synthesised by rabbit articular chondrocytes cultured in the presence of excess 35SO4--. The procedure uses the low solubility product of barium sulphate to remove, by precipitation, free 35SO4-- from culture medium. Optimum recovery of 35SO4 labelled proteoglycans was achieved after papain digestion to release 35SO4-glycosaminoglycans, and addition of chondroitin sulphate before the precipitation step. Using this assay, we studied the effect of six drugs-indomethacin, diclofenac, sodium pentosan polysulphate, glycosaminoglycan polysulphate ester, tiaprofenic acid, and ketoprofen-on the secretion into the medium of labelled proteoglycans by lapine chondrocytes. The six drugs were tested at 0.1, 1, 10, 50, and 100 micrograms/ml over four consecutive 48 hour culture periods. A consistent concentration-response pattern was found for the four non-steroidal anti-inflammatory drugs (NSAIDs) studied. Generally they inhibited proteoglycan secretion at 50 and 100 micrograms/ml but had no effect at lower concentrations. Inhibition of secretion was strongest with indomethacin and diclofenac at 50 and 100 micrograms/ml. In contrast with the NSAIDs studied, the two sulphated polysaccharides (sodium pentosan polysulphate and glycosaminoglycan polysulphate ester) at low concentrations increased proteoglycan secretion by chondrocytes, with maximal stimulation occurring at 1 microgram/ml. Sodium pentosan polysulphate, but not glycosaminoglycan polysulphate ester, showed inhibitory activity at 50 and 100 micrograms/ml.

Incorporation of [35S]sulphate and [3H]thymidine into isolated bovine articular chondrocytes in vitro. Effect of autogenous conditioned synovial medium

The present work is a part of a study series concerned with the metabolic events taking place in the synovial joint tissues. We have previously reported that synovial products not only enhance the degradation of articular cartilage proteoglycans but also inhibit the synthesis of articular cartilage proteoglycans, and that these cellular interactions may be partly modulated by arachidonic acid metabolites. In the experiments reported here we show that the addition of conditioned synovial medium to confluent monolayer cultures of articular chondrocytes not only inhibits the synthesis of proteoglycans, measured as the incorporation of radiosulphate into cartilage proteoglycans but also inhibits the synthesis of DNA, measured as the incorporation of radiothymidine into the chondrocytes, in a dose-dependent manner. In our culture system, calf knee-joint synovial tissue produces PGE, and it has been reported that previous exposure to PGE2 affects the ability of the cell to respond to that same hormone. In these experiments, previous exposure to conditioned synovial medium affected neither the inhibition of the incorporation of radiosulphate nor the inhibition of the incorporation of radiothymidine.