Induction of cyclooxygenase and suppression of 12-lipoxygenase in human erythroleukemia cells upon phorbol ester-induced differentiation

Mahmud, Ishtiaq; Suzuki, Toshiko; Yamamoto, Yuhei; Suzuki, Hiroshi; Takahashi, Yoshitaka; Yoshimoto, Tanihiro; Yamamoto, Shozo

doi:10.1016/0005-2760(93)90099-u

Cited by 15 publications

(1 citation statement)

References 17 publications

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“…The crude extract was prepared from human platelets and HEL cells according to the previous report (Mahmud et al ., 1993). Briefly, 10 9 platelets and 5×10 7 HEL cells were suspended in 2 ml of 50 m M Tris‐HCl buffer at pH 7.4 containing 1 m M EDTA.…”

Section: Methodsmentioning

confidence: 99%

An anti‐platelet agent, OPC‐29030, inhibits translocation of 12‐lipoxygenase and 12‐hydroxyeicosatetraenoic acid production in human platelets

Ozeki

Nagamura

Ito

et al. 1999

British J Pharmacology

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In human platelets, arachidonic acid is mainly metabolized by the two enzyme systems; cyclo‐oxygenase and 12‐lipoxygenase. Cyclo‐oxygenase produces prostaglandin H2 which is further converted to thromboxane B2. 12‐Lipoxygenase synthesizes 12(S)‐hydroperoxyeicosatetraenoic acid which is reduced to 12(S)‐hydroxyeicosatetraenoic acid (12(S)‐HETE). An anti‐platelet compound, OPC‐29030, dose‐dependently inhibited 12(S)‐HETE production with an IC50 of 0.06±0.01 μM, but not synthesis of thromboxane B2 in human platelets. Although the compound suppressed 12(S)‐HETE production in human platelets, cytosolic 12‐lipoxygenase activity was not inhibited up to 10 μM. Essentially identical data were obtained with a 12‐lipoxygenase of human erythroleukaemia cells which had megakaryocyte/platelet‐like properties. OPC‐29030 also suppressed production of 5(S)‐HETE, a 5‐lipoxygenase product, in rat basophilic leukaemia cells without inhibiting enzyme activity. It has been shown that 5‐lipoxygenase binds to membrane 5‐lipoxygenase‐activating protein (FLAP) to produce 5(S)‐HETE, and thus FLAP inhibitor suppresses cellular 5(S)‐HETE production. A FLAP inhibitor, L‐655,238, suppressed platelet 12(S)‐HETE production, but had no effect on the 12‐lipoxygenase activity. Western blot analysis showed that platelet 12‐lipoxygenase translocated from cytosol to membranes upon thrombin stimulation, and OPC‐29030 suppressed this process in a dose‐dependent manner. These results suggest that the 12‐lipoxygenase of human platelets binds to FLAP or a similar protein, and OPC‐29030 suppresses 12(S)‐HETE production by inhibiting a certain step of the 12‐lipoxygenase translocation. British Journal of Pharmacology (1999) 128, 1699–1704; doi:

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Section: Methodsmentioning

confidence: 99%