Effects of Interleukin-1 and Lipopolysaccharides on Protein and Carbohydrate Metabolism in Bovine Articular Cartilage Organ Cultures

Abstract

The long term (18 day) metabolic response of bovine articular cartilage to treatment with either E. Coli lipopolysaccharide (LPS) or interleukin 1 was studied. For LPS treatment, incorporation of [³⁵S]sulfate into the large proteoglycan population was inhibited 80% while that into the small interstitial proteoglycans was only inhibited 40%. Incorporation of [³H]serine into the large proteoglycan population was inhibited approximately 72% while incorporation into other protein was inhibited only 16%. Furthermore, the rate of catabolism of [³H]serine labeled proteoglycans was increased 2-fold by LPS treatment while the rate of ³H-labeled general protein catabolism was not affected. Incorporation of [³H]glucosamine into hyaluronate was increased; however a correction for changes in the specific activity of the intracellular [³H]glucosamine precursor pool in LPS-treated cultures indicated that the net amount of hyaluronate synthesized was not altered by LPS treatment. The ³H/³⁵S ratios in isolated chondroitin sulfate disaccharides labeled with [³⁵S]sulfate and [³H]glucosamine precursors were significantly changed during long term LPS treatment, suggesting that general carbohydrate pathways are altered. The ³H/³⁵S changes were larger in the disaccharides isolated from the small proteoglycans indicating that different precursor pools, probably in different cell populations, preferentially synthesize this proteoglycan population. Interleukin-1 affected the same chondrocytic pathways as LPS as shown by a) the extent of inhibition of proteoglycan synthesis, b) the selective inhibition of synthesis of the large proteoglycan species, c) acceleration of proteoglycan catabolism, d) net depletion of proteoglycans from the tissue, e) increases in guanidine HC1 extractable [³H]hyaluronate, f) increases in levels of prostaglandin E2 synthesis, g) changes in ³H/³⁵S ratios in glycosaminoglycan chains and, h) minimal effects on general protein synthesis.