Intracellular Metabolism of 4-Hydroxynonenal in Primary Cultures of Rabbit Synovial Fibroblasts

The intracellular metabolism of 4-hydroxynonenal (HNE), a secondary product of lipid peroxidation and mediator of inflammation, which was found in the joints of patients with rheumatoid arthritis, was investigated in primary cultures of rabbit synovial fibroblasts. A consumption rate of 27.3 nmol/min × 10⁶ cells was measured for the cultivated fibroblasts. It could be shown, that 4-hydroxynonenal enters the synovial fibroblasts and is metabolized mainly oxidatively to 4-hydroxynonenoic acid, intermediates of the tricarboxylic acid cycle and water and by formation of the glutathione-HNE adduct. The share of protein-bound HNE was about up to 8% of the total added HNE after 10 min of incubation. All metabolites accumulates intracellularly within the incubation time except of 4-hydroxynonenal itself. An increase of 4-hydroxynonenoic acid could be detected also extracellularly during the intracellular metabolism of 4-hydroxynonenal. Therefore, an involvement of synovial fibroblasts in the secondary antioxidant defense system of the joints during conditions of higher HNE concentrations like rheumatoid arthritis is suggested. © 1997 Elsevier Science Inc.