Eotaxin-3 is a natural antagonist for CCR2 and exerts a repulsive effect on human monocytes

Abstract

Eotaxin-3 (CCL26) belongs to the group of CC chemokines that attract eosinophils, basophils, and Th2 lymphocytes. Like eotaxin (CCL11) and eotaxin-2 (CCL24), eotaxin-3 mediates its activity through CCR3. Here we show that eotaxin-3 also binds to CCR2 on monocytes and CCR2-transfected cells. In contrast to monocyte chemotactic protein 1 (MCP-1; CCL2), eotaxin-3 does not trigger intracellular calcium mobilization, enzyme release, or phosphorylation of the mitogenactivated protein (MAP) kinase ERK and induces a weak chemotaxis in monocytes. Instead, eotaxin-3 inhibits MCP-1-mediated responses, thus acting as a natural antagonist for CCR2. This study also demonstrates that eotaxin-3 promotes active movement of monocytes away from a gradient of eotaxin-3 in vitro. This repellent effect is amplified when an additional gradient of MCP-1 is applied, demonstrating that the 2 mechanisms are synergistic. Eotaxin-3 effects on monocytes are largely abolished when cells are pretreated with MCP-1 or CCR2 antagonists. Like MCP-1-mediated migration, repulsion is sensitive to Bordetella pertussis toxin, indicating the involvement of G i protein-coupled receptors. However, using transfected cells expressing CCR2 we could not detect F-actin formation or an active movement away induced by eotaxin-3, suggesting that either expression of a single receptor type is not sufficient to mediate cell repulsion or that the used transfected cell lines lack additional interaction molecules that are required for reverse migration. Eotaxin-3 was expressed by vascular endothelial cells and was essential for endothelial transmigration of eosinophils. Our data provide a mechanism by which 2 chemokine gradients that are oriented in opposite directions could cooperate in efficiently driving out monocytes from blood vessels into tissue. IntroductionLike eotaxin (CCL11) and eotaxin-2 (CCL24), eotaxin-3 (CCL26) has been reported as a selective stimulus for eosinophilic granulocytes by interacting with the chemokine receptor CCR3. [1][2][3][4] This receptor is highly expressed on eosinophils, basophils, and Th2 lymphocytes, [5][6][7][8][9] and is therefore involved mainly in allergic inflammation. 10,11 CCR3-recruiting chemokines and monocyte chemotactic protein 1 (MCP-1) were found to be expressed in several tissues, especially in pathologic reactions, in which Th2-type cytokines are produced. [12][13][14][15][16] In addition to eosinophils, basophils, and Th2 lymphocytes, which are typically found in allergic inflammations and express CCR3, these infiltrates also contain monocytes that lack CCR3. 17 Eotaxin-3 is expressed in vascular endothelial cells and dermal fibroblasts after interleukin 4 (IL-4) and 18,19 and in bronchial tissue on allergen challenge. 20,21 In a current report, its relevance for transendothelial migration of eosinophils has been elucidated, 22 whereas the significance of the constitutive expression in the reproductive system and the heart 2 remains to be clarified. Eotaxin-3 is as efficient as eotaxin in attracting eosinophils and...

Systemic human Netrin-1 gene delivery by adeno-associated virus type 8 alters leukocyte accumulation and atherogenesis in vivo

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Synergy‐inducing chemokines enhance CCR2 ligand activities on monocytes

“…Activated ERK was detected as previously described with an anti-phospho ERK (SIGMA M 8159, Sigma-Aldrich Chemicals) [48]. Equal loading was confirmed by re-probing with an antibody against total ERK-2 (C-14, Santa Cruz Biotechnology, CA, USA).…”

“…CD14 1 monocytes were isolated as previously described [48]. Stable transfection of human CCR2 and CCR7 in murine pre-B 300.19 and of human D6 in CHO cells was performed as described before [16,34].…”

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