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Hyaluronan is a biological polysaccharide that may exist in different degrees of polymerization. Several investigations reported that low molecular mass hyaluronan may have pro-inflammatory activity, while high molecular mass hyaluronan can exert beneficial effects. Starting from these data, the aim of this study was to investigate the effect of hyaluronan of different molecular mass in mouse articular chondrocyte cultures stimulated with lipopolysaccharide (LPS). Inflammation was induced in chondrocytes by acute treatment with 2.0 microg/ml LPS. High levels of tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, interferon (IFN)-gamma and iNOS gene expression and their related proteins were found in chondrocytes 24 h after treatment with LPS. High concentrations of NO, NF-kappaB activation, IkappaBalpha phosphorylation and apoptosis, evaluated by the increase in caspase-3 expression and its related protein amount were also produced by LPS stimulation. In contrast, LPS reduced aggrecan and collagen type II (Col2A) expression and their protein production. The treatment of chondrocytes with hyaluronan of different molecular mass produced the following effects: (i) low molecular mass hyaluronan exerted a slight inflammatory effect in untreated chondrocytes, while in LPS-treated chondrocytes it enhanced cytokine production and decreased aggrecan and Col2A compared with cells treated with LPS alone; (ii) no effect was exerted on LPS-induced apoptosis and NO production; (iii) medium molecular mass hyaluronan did not exert any inflammatory/anti-inflammatory activity in LPS-untreated/treated cells and failed to reduce apoptosis; and (iv) high molecular mass hyaluronan had no inflammatory effect in LPS-untreated cells while it was able to reduce all the detrimental effects stimulated by LPS treatment. These data confirm the multifactorial role played by hyaluronan and suggest, in particular, that hyaluronan may modulate inflammation during pathologies by its different degrees of polymerization.

Introduction: There have been several cases reporting a significant increase in chondroitin sulphate plasma levels in patients with different types of disease, such as systemic lupus erythematosus, rheumatoid arthritis, and liver disease. At present, the precise role of chondroitin sulphate molecules in blood is unclear. Previous investigations have shown that the addition of purified human plasma glycosaminoglycans (GAGs), containing a high percentage of chondroitin-4-sulphate (C4S) was able to inhibit lipid peroxidation and to protect cells from reactive oxygen species damage, suggesting antioxidant activity. Starting from these reports, the aim of this study was to evaluate the effectiveness of GAG structures purified from normal human plasma in reducing inflammation using a model of lipopolysaccharide (LPS)-induced increase of pro-inflammatory cytokines in mouse articular chondrocyte cultures., Results: Chondrocyte stimulation with LPS (50 microg/ml) for 24 h enhanced gene expression of tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta (IL-1beta), interleukin 6 (IL-6), interferon gamma (IFN-gamma), inducible nitric oxide synthase (iNOS) and increases in their related protein levels, as well as NF-kappaB activation, IkappaBalpha phosphorylation and apoptosis evaluated by the increase in caspase-3 expression and its related protein amount. LPS treatment also generated a high amount of nitric oxide (NO). The addition of different doses of purified human GAGs to LPS-stimulated chondrocytes reduced inflammatory cytokines and iNOS both at mRNA and protein levels, blocked NF-kappaB activation and cytoplasmic IkappaBalpha phosphorylation, limited cell death by inhibiting apoptosis, and reduced NO concentrations., Conclusions: These results further support the hypothesis that plasma GAGs may function as immunomodulators and their increased release and degradation could be a biological response acting to modulate inflammation during disease.