title: Aggrecan degradation in chondrocytes is mediated by reactive oxygen species and protected by antioxidants.
abstract: Reactive oxygen species (ROS) are implicated in aging of cartilage and in the pathogenesis of osteoarthritis. However, the biological role of chondrocytes-derived ROS has not been elucidated. An in-vitro model was developed to study the role of chondrocyte-derived ROS in cartilage matrix degradation. The primary articular chondrocytes were cultured and the aggrecan matrix was radiolabeled with 35-sulfate. The labeled aggrecan matrix was washed to remove unincorporated label and chondrocytes were returned to serum free balanced salt solution. The cell-monolayer-matrix sensitivity to oxidative damage due to either hydrogen peroxide or glucose oxidase was established by monitoring the release of labeled aggrecan into the medium. Lipopolysaccharide (LPS) treatment of chondrocyte-monolayer enhanced the release of labeled aggrecan. Catalase significantly prevented the release of labeled aggrecan in LPS-chondrocyte cultures, suggesting a role for chondrocyte-derived hydrogen peroxide in aggrecan degradation. Superoxide dismutase or boiled catalase had no such inhibitory effect. The effect of several antioxidants on LPS-chondrocyte-dependent aggrecan degradation was examined. Hydroxyl radical scavengers (mannitol and thiourea) significantly decreased aggrecan degradation. A spin trapping agent N-tert-butyl-phenylnitrone (but not its inactive analog tert-butyl-phenylcarbonate) significantly decreased aggrecan degradation. Butylated hydroxytoluene also inhibited aggrecan degradation, whereas the other lipophilic antioxidant tested, propyl gallate, had a marked dose-dependent inhibitory effect. These data indicate that general antioxidants, hydroxyl radical scavengers, antioxidant vitamins, iron chelating agents, lipophilic antioxidants, and spin trapping agents can influence chondrocyte-dependent aggrecan degradation. These studies support the role of a chondrocyte-dependent oxidative mechanism in aggrecan degradation and indicate that antioxidants can prevent matrix degradation and therefore may have a preventive or therapeutic value in arthritis. The enhancement of oxidative activity in chondrocytes and its damaging effect on matrix may be an important mechanism of matrix degradation in osteoarthritis.
authors.affiliation: Department of Medicine, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, NJ 08903-0019, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Tiku
authors.forename: S
authors.initials: S
authors.lastname: Gupta
authors.forename: D R
authors.initials: DR
authors.lastname: Deshmukh
mesh_terms: D053674:Aggrecans; D000818:Animals; D000975:Antioxidants / Q000378:metabolism* / Q000494:pharmacology; D002374:Catalase / Q000494:pharmacology; D019902:Chondrocytes / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism; D016326:Extracellular Matrix Proteins; D005260:Female; D006861:Hydrogen Peroxide / Q000494:pharmacology; D037181:Lectins, C-Type; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D011509:Proteoglycans / Q000187:drug effects / Q000378:metabolism*; D011817:Rabbits; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013462:Sulfur Radioisotopes
chemical_list: D053674:Aggrecans; D000975:Antioxidants; D016326:Extracellular Matrix Proteins; D037181:Lectins, C-Type; D008070:Lipopolysaccharides; D011509:Proteoglycans; D017382:Reactive Oxygen Species; D013462:Sulfur Radioisotopes; D006861:Hydrogen Peroxide; D002374:Catalase