Abstract 1054 Poster Session II, Sunday, 5/2 (poster 27)

Nitric oxide (NO) is a potent vasodilator produced by many tissues. Inflammatory response cells produce increased levels of NO and superoxide anion, which combine to produce peroxynitrite. At physiological pH, peroxynitrite is one of the most powerful degradative agents in nature. Under acidic conditions, found in certain areas of the intestinal tract, NO forms nitrous acid, a chemical tool used for the breakdown of glycosaminoglycans (GAGs). The extracellular matrix (ECM) supports cells, and serves as a barrier to cell invasion. It consists of collagens, glycoproteins and proteoglycans. Proteoglycans contain a core protein attached to GAG chains. GAGs are complex polysaccharides with alternating amino sugar and (usually) uronic acid residues. Any degradation of the GAGs in the ECM can disrupt the structural integrity of tissues. Inflammation results in tissue damage, including degradation of ECM components. Our previous studies (Vilar et al, Biochem. J., 324:473-479, 1997) have shown that NO and its derivatives degrade GAGs, particularly heparin, heparan sulfate, chondroitin sulfates and hyaluronan. Keratan sulfate (KS) is another GAG found in extracellular matrix, cornea and cartilage. KS contains galactose residues instead of uronic acid. The purpose of this study was to determine whether the NO donor, S-nitroso-N-acetylpenicillamine (S-NAP), and synthetic peroxynitrite can degrade KS. Based on previous studies, S-NAP (at pH 4.0) and peroxynitrite (at pH 7.4) were incubated for one week with KS at 37°C. Breakdown of KS was assessed by gel filtration chromatography when compared to the untreated incubated control. There was substantial degradation of the samples incubated with both S-NAP (21%) and peroxynitrite (36%). The presence of galactose in the KS structure, as opposed to uronic acid in other GAGs, accounts for increased susceptibility to peroxynitrite degradation, when compared to the chondroitin sulfates. Analogous to our previous studies, this study with KS also shows that derivatives of NO break down GAGs. Thus, NO and its derivatives degrade GAGs of the ECM, which will cause a breach of tissue structural integrity. These reactions may explain part of the pathophysiology of inflammatory tissue injury.