Changes in the Viscosity of Hyaluronic Acid After Exposure to a Myeloperoxidase‐derived Oxidant

Abstract

Both purified hyaluronic acid (HA) and bovine synovial fluid react with OC1-, the major oxidant produced by the myeloperoxidase (MPO)/H202/CI-system, resulting in a decrease in their specific viscosity. This reaction is inhibited in the presence of excess methionine. H202 alone decreases the viscosity of HA, presumably by the Fenton reaction, in the absence (but not in the presence) of the iron chelator, diethyltriaminepentacetic acid (DETAPAC). In the presence of DETAPAC, incubation of HA with the complete MPO/ H202/CI-system lowered the viscosity of HA. Analysis of 3H-HA exposed to OC1-by gel filtration chromatography indicated that cleavage of HA occurred only at higher OCI-concentrations. We suggest that the reduction in viscosity of HA by the MPO/H202/CI-system may be due to a combination of oxidative cleavage and changes in the conformation of the molecule. We speculate that the changes in the molecular size of rheumatoid synovial fluid HA may be due to the action of the neutrophil MPO/H202/CI-system. Submitted for publication June 20, 1988; accepted in revised form November 7, 1988. sible for the viscosity of SF, and it has been argued that it is also responsible for the lubricating properties of SF (1,2). In inflammatory arthritides, such as rheumatoid arthritis (RA), SF loses viscosity (3,4), and depolymerization of the HA molecule has been suggested as the cause (5). The loss of HA viscosity within the arthritic joint is accompanied by the infiltration of large numbers of polymorphonuclear leukocytes (PMNs) into the joint space. These phagocytic cells are known to release oxygen free radicals and their products (e.g., O,, HO-, H,02) during the "respiratory burst,'' in addition to numerous proteolytic and microbicidal enzymes (elastase, cathepsin G, lysozyme, and myeloperoxidase [MPO]) into either the phagosome or extracellular space during degranulation. Hyaluronic acid (HA) is the major macromolecular component of synovial fluid (SF).Because no hyaluronidase activity has been identified in neutrophils, synovium, pathologic SF, or articular cartilage (3), an alternative mechanism for the loss of SF viscosity must exist. Because SF contains little, if any, of the 0, and H,02 scavenging enzymes (superoxide dismutase [SOD] or catalase, respectively [6]), the present hypothesis is that SF HA is degraded by the extremely reactive hydroxyl radical (HO.) produced via the 0; radical-driven Fenton reaction after release of 0; from "activated" PMNs (33-7). This reaction requires not only sources of H202 and a suitable reductant, such as O;, but also accessible transition metal ions (e.g., Fe3+). Recently, low levels of bleomycin-detectable Fe3+ bound to an asyet-unidentified SF protein were found in -40% of RA patient SFs (8).An alternative mechanism by which "activated" PMNs may decrease SF viscosity during RA involves the heme enzyme MPO. Any H202 released during the "respiratory burst" could be metabolized, 462BAKER ET AL within the extracellular space, by MPO simultaneously expelled from azurophil granu...

Hyaluronan Oligosaccharides Induce Matrix Metalloproteinase 13 via Transcriptional Activation of NFκB and p38 MAP Kinase in Articular Chondrocytes

“…Whether fragmentation of HA occurs in vivo remains to be determined. There are suggestions that HA oligosaccharides might be generated during periods of inflammation (69,70) or otherwise generated through the action of chondrocytederived reactive oxygen species or other free radicals (71,72). Nonetheless, several mechanisms can lead to a disruption of HA-cell interactions, all with similar results that include the activation of potent matrix metalloproteinases.…”

Hyaluronan fragments activate nitric oxide synthase and the production of nitric oxide by articular chondrocytes

“…The average molecular weight of HA in normal synovial fluid is ~7 million, but is decreased in rheumatoid synovial fluid to 4.8 million (Al-Assaf, Navaratnam, Parsons, & Phillips, 2003;Pitsillides, Worrall, Wilkinson, Bayliss, & Edwards, 1994). Superoxide radical anions from neutrophils in the synovial fluid are key candidates for the initiation of damage to HA and the consequent reduction in molecular weight (Baker, Green, & Lowther, 1989). Released NO may also generate peroxynitrite-a compound that has been proposed as an alternative reactive species that could cause the degradation of HA (Al-Assaf et al, 2003).…”

Serum hyaluronate level as a predictor of radiologic progression in early rheumatoid arthritis

“…The finding that the levels of HA in the RA patients we studied were not as high as those in other RA patient groups (43) may reflect the fact that all of our patients had early disease, and thus had less inflamed synovial tissue mass than would be found in patients with more advanced RA. Elevated concentrations of HA in the serum of RA patients appear to be related to acceler- ated production of HA in inflamed joints, and the resultant increase in the amount of degradation products appearing in the serum (17)(18)(19)(20). Monokines, especially tumor necrosis factor CY and interleukin-1 a, which are detected in increased quantities in the joints of RA patients (21,22), stimulate HA production by synovial fibroblast-like cells (23).…”