Action of hypochlorous acid on polymeric components of cartilage. Use of 13C NMR spectroscopy.

It is a well known fact that neutrophil-derived hypochlorous acid plays an important role in cartilage destruction during rheumatoid arthritis. It has been shown by 1H NMR spectroscopy in a previous paper (Schiller et al. (1994), Biol. Chem. Hoppe-Seyler 375, 167-172) that sodium hypochlorite affects primarily the N-acetyl side chains of polymeric carbohydrates of cartilage like chondroitinsulphate and hyaluronic acid. An instable intermediate, likely to be a chloramine, is involved in these processes. The present paper deals with the application of carbon NMR spectroscopy for the study of these degradation processes, because carbon NMR gives the opportunity to detect changes on the single sugar ring carbons. Although it was not possible to prove the involvement of an intermediate, because of its fast hydrolysis, we were able to show that the reaction between sodium hypochlorite and N-acetylglucosamine affects mainly the side chain, accompanied by the formation of acetate. The application of a large excess of sodium hypochlorite leads to a breakdown of the carbohydrate ring under the formation of formiate.