Antioxidant effect of hyaluronan on polymorphonuclear leukocyte-derived reactive oxygen species is dependent on its molecular weight and concentration and mainly involves the extracellular space.

INTRODUCTION: Hyaluronan (HA), a component of the extracellular matrix, may regulate immune cell functions through its interactions with cellular receptors. Besides its effect on cytokine and chemokine production, its antioxidant properties have been described. However, the mechanisms of this are not fully elucidated. The aim of this study was to evaluate the relationship between HA concentration and molecular weight and its antioxidant properties towards human neutrophils. Also assessed was whether the antioxidant effect of HA is connected with a reduction in intracellular oxygen potential, which could indicate its direct effect on neutrophil respiratory burst. MATERIALS/
METHODS: The relationship between HA's antioxidant properties and its concentration and molecular weight was assessed by the luminol-enhanced chemiluminescence method (CL). To evaluate the effect of HA on intracellular oxygen potential selectively, the dihydrorhodamine 123 (DHR123) flow cytometric method was used.
RESULTS: Reduction of both HA molecular weight and its concentration decreased its antioxidant properties in the CL method. A selective effect of HA on intracellular oxygen potential measured by the DHR123 method was not shown.
CONCLUSIONS: The antioxidant properties of HA are related to both its molecular weight and its concentration. The lack of an antioxidant effect of HA in the DHR123 test compared with a significant reduction in CL values at the same HA concentration suggests that HA acts mainly as a chemical ROI scavenger in the extracellular space.