Leukotriene A4 hydrolase and leukotriene C4 synthase activities in human chondrocytes: Transcellular biosynthesis of leukotrienes during granulocyte-chondrocyte interaction

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Abstract
Objective To investigate the cooperation of chondrocytes and polymorphonuclear cells (PMN) in the biosynthesis of leukotrienes (LT). Methods PMN, resting and interleukin‐1β‐stimulated cultured human chondrocytes, and mixtures of both cell types were incubated with A23187 and/or 14C‐arachidonic acid (14C‐AA). To explore the presence of LTC4 synthase and LTA4 hydrolase, the chondrocytes were incubated with authentic LTA4. Eicosanoids were analyzed using high performance liquid chromatography techniques. Results Chondrocytes formed only prostaglandin E2 and minor amounts of 15‐HETE and 11‐HETE, the production of all of which was inhibited by 1 µM indomethacin. Incubation of PMN and chondrocytes produced more LTC4 from endogenous and exogenous AA, and more LTB4 from endogenous AA, than incubation of PMN alone, which was consistent with the presence of LTC4 synthase and LTA4 hydrolase activities in chondrocytes. Chondrocytes also slightly increased the level of PMN production of all 5‐lipoxygenase (5‐LO)‐derived products from endogenous AA. Conclusion Human chondrocytes form eicosanoids from AA only by the cyclooxygenase pathway. Chondrocytes cooperate in the transcellular biosynthesis of LT since they possess LTA4 hydrolase and LTC4 synthase activities and increase metabolism by the 5‐LO pathway in PMN.

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