de Coupade Catherine, Solito Egle, Levine Jon D
Department of Medicine and Oral and Maxillofacial Surgery, NIH Pain Center, Box 0440, University of California at San Francisco, 521 Parnassus Avenue, San Francisco, CA 94143, USA.
Br J Pharmacol. 2003 Sep;140(1):133-45. doi: 10.1038/sj.bjp.0705413. Epub 2003 Aug 11.
(1) L-selectin, constitutively expressed by leukocytes, is involved in the initial binding of leukocytes to activated endothelium. Anti-inflammatory drugs like glucocorticoids can induce shedding of L-selectin, but the mechanism is still unknown. Annexin 1, a protein whose synthesis and externalization/secretion are induced during the inflammatory response, has been proposed as a mediator of the anti-inflammatory actions of glucocorticoids. (2) The monocytic cell line U-937 strongly expresses Annexin 1 after 24 h of phorbol 12-myristate 13-acetate (PMA, 1 nm) treatment and externalizes/releases the protein after additional 16 h of dexamethasone (1 microm) treatment. (3) This study investigated the possible regulation of cell surface L-selectin shedding by endogenous Annexin 1, and its role in glucocorticoid-induced L-selectin shedding in the U-937 cell line. (4) PMA- and dexamethasone treatment-induced L-selectin shedding was potentially mediated by Annexin 1, since neutralizing antibodies against Annexin 1 reduced dexamethasone- and Annexin 1-induced shedding. (5) Immunoprecipitation and binding assays provided support for the suggestion that this effect could be mediated by an interaction between externalized Annexin 1 and L-selectin. Such interaction involved the N-terminal domain of Annexin 1 and was calcium-dependent. Confocal microscopy studies demonstrated increased colocalization of Annexin 1 and L-selectin on the cell surface. (6) Overall, our study provides new insights into the potential role of endogenous ANXA1 as a mediator of dexamethasone-induced L-selectin shedding, which may contribute to the anti-inflammatory activity of glucocorticoids.
(1) 白细胞组成性表达的L-选择素参与白细胞与活化内皮细胞的初始结合。糖皮质激素等抗炎药物可诱导L-选择素脱落，但其机制尚不清楚。膜联蛋白1是一种在炎症反应过程中其合成及外化/分泌被诱导的蛋白质，已被认为是糖皮质激素抗炎作用的介质。(2) 经佛波酯12-肉豆蔻酸酯13-乙酸酯（PMA，1 nM）处理24小时后，单核细胞系U-937强烈表达膜联蛋白1，再经地塞米松（1 μM）处理16小时后，该蛋白被外化/释放。(3) 本研究调查了内源性膜联蛋白1对细胞表面L-选择素脱落的可能调节作用，及其在U-937细胞系中糖皮质激素诱导的L-选择素脱落中的作用。(4) PMA和地塞米松处理诱导的L-选择素脱落可能由膜联蛋白1介导，因为针对膜联蛋白1的中和抗体可减少地塞米松和膜联蛋白1诱导的脱落。(5) 免疫沉淀和结合试验支持了这种效应可能由外化的膜联蛋白1与L-选择素之间的相互作用介导的观点。这种相互作用涉及膜联蛋白1的N端结构域，且依赖于钙。共聚焦显微镜研究表明，膜联蛋白1和L-选择素在细胞表面的共定位增加。(6) 总体而言，我们的研究为内源性膜联蛋白A1作为地塞米松诱导的L-选择素脱落的介质的潜在作用提供了新的见解，这可能有助于糖皮质激素的抗炎活性。
