Dexamethasone enhances interaction of endogenous Annexin 1 with L‐selectin and triggers shedding of L‐selectin in the monocytic cell line U‐937

Abstract

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. 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 μM) treatment. 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. 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. 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. 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. British Journal of Pharmacology (2003) 140, 133–145. doi:

Quantitative Proteomics Profiling of Murine Mammary Gland Cells Unravels Impact of Annexin-1 on DNA Damage Response, Cell Adhesion, and Migration

“…However, these were in conjunction with the observation that the presence of increased ANXA1 led to inhibition of adhesion of the inflammatory cells to the endothelial (44,45). One of the mechanisms proposed in this adhesion inhibition is the down- regulation and shedding of a cell adhesion molecule L-selectin on the leukocytes (46,47). Down-regulation of ANXA1 has also been shown in carcinogenic models to inhibit cell migration/invasion (15,48), suggesting that ANXA1 could possibly be pro-migratory in carcinogenesis.…”

Overexpression of annexin 1 in pancreatic cancer and its clinical significance

“…Annexin I is one of the more extensively studied annexins, which was initially cloned as phospholipase A2 (PLA2) inhibitor [11] . Annexin I is a steroid-regulated protein and thus implicated in some actions of glucocorticoids, including inhibition of cell proliferation, anti-inflammatory effects, the regulation of cell migration, differentiation, death and the hypothalamic-pituitary axis [12][13][14][15][16] . To date, there are some contradictory descriptions on annexin I expression in human cancers.…”

Anti-inflammatory functions of glucocorticoid-induced genes

“…AnxA1 was first identified as a factor that was released from GC-stimulated cells in vitro or in vivo, and exerted anti-inflammatory effects mirroring those of GCs. Most notably it inhibited release of proinflammatory prostaglandins, and impaired leukocyte extravasation at sites of inflammation (Chatterjee et al, 2005;de Coupade et al, 2003;Gavins et al, 2003;Lim and Pervaiz, 2007;Liu et al, 2005;Parente and Solito, 2004). AnxA1 is relocalized from the cytoplasm to the plasma membrane in response to a variety of agonists including GCs, and can be externalized or secreted via an uncharacterized mechanism.…”