Adenovirus-mediated gene transfer of glutamine:: fructose-6-phosphate amidotransferase antagonizes the effects of interleukin-1β on rat chondrocytes

Objective: To determine whether overexpression of glutamine: fructose-6-phosphate amidotransferase (GFAT) in synoviocytes will antagonize the response to interleukin-1beta (IL-1beta) of chondrocytes and synovial fibroblasts in co-culture. Methods: Synovial fibroblasts from the rat were transduced by an adenovirus carrying the cDNA for GFAT and then co-cultured with rat chondrocytes encapsulated in alginate beads. Following challenge with 1, 5, or 10 ng/ml of IL-1beta for 24 h, proteoglycan synthesis by the chondrocytes was determined by incorporation of (Na2SO4-)-S-35 Production of nitric oxide (NO) and prostaglandin E-2 (PGE(2)) were monitored by assay of conditioned medium from the co-culture. Results: IL-1beta treatment of untransduced-synoviocyte/chondrocyte co-cultures resulted in markedly decreased proteoglycan synthesis by the chondrocytes, and increased NO and PGE(2) levels in the culture medium. In contrast, adenovirus-mediated transfer of GFAT in synoviocytes prevented both the decrease in chondrocyte proteoglycan synthesis and increases in NO and PGE(2) provoked by IL-1beta. Conclusions: Our study suggests that in a synoviocyte/chondrocyte co-culture system, overexpression of GFAT by synoviocytes significantly inhibits subsequent stimulation by IL-1beta in vitro. Since GFAT is the rate limiting enzyme in the synthesis of intracellular glucosamine and its derivatives, these results may open new possibilities for osteoarthritis treatment. (C) 2003 OsteoArthritis Research Society International. Published by Elsevier Ltd. All rights reserved.