Soluble Siglec-5 associates to PSGL-1 and displays anti-inflammatory activity

Marion Pepin (1) , Soraya Mezouar (2) , Julie Pegon (1) , Vincent Muczynski (1) , Frédéric Adam (1) , Elsa P Bianchini (1) , Amine Bazaa (1) , Valerie Proulle (1, 3) , Alain Rupin (4) , Jerome Paysant (4) , Laurence Panicot-Dubois (2) , Olivier D. Christophe (1) , Christophe Dubois (2) , Peter J Lenting (1) , Cécile V Denis (1)

1 HITH - U1176 Inserm - CHU Bicêtre - Hémostase, Inflammation, Thrombose
2 VRCM - Vascular research center of Marseille
3 Service d'hématologie, immunologie biologiques et cytogénétique
4 IRIS - Institut de Recherches Internationales Servier [Suresnes]

Interactions between endothelial selectins and the leukocyte counter-receptor PSGL1 mediates leukocyte recruitment to inflammation sites. PSGL1 is highly sialylated, making it a potential ligand for Siglec-5, a leukocyte-receptor that recognizes sialic acid structures. Binding assays using soluble Siglec-5 variants (sSiglec-5/C4BP and sSiglec-5/Fc) revealed a dose- and calcium-dependent binding to PSGL1. Pre-treatment of PSGL1 with sialidase reduced Siglec-5 binding by 79 ± 4%. In confocal immune-fluorescence assays, we observed that 50% of Peripheral Blood Mononuclear Cells (PBMCs) simultaneously express PSGL1 and Siglec-5. Duolink-proximity ligation analysis demonstrated that PSGL1 and Siglec-5 are in close proximity (<40 nm) in 31 ± 4% of PBMCs. In vitro perfusion assays revealed that leukocyte-rolling over E- and P-selectin was inhibited by sSiglec-5/Fc or sSiglec-5/C4BP, while adhesion onto VCAM1 was unaffected. When applied to healthy mice (0.8 mg/kg), sSiglec-5/C4BP significantly reduced the number of rolling leukocytes under basal conditions (10.9 ± 3.7 versus 23.5 ± 9.3 leukocytes/field/min for sSiglec-5/C4BP-treated and control mice, respectively; p = 0.0093). Moreover, leukocyte recruitment was inhibited over a 5-h observation period in an in vivo model of TNFalpha-induced inflammation following injection sSiglec-5/C4BP (0.8 mg/kg). Our data identify PSGL1 as a ligand for Siglec-5, and soluble Siglec-5 variants appear efficient in blocking PSGL1-mediated leukocyte rolling and the inflammatory response in general.

Mots clés: SIALIC-ACID; IN-VIVO; NEUTROPHILS; IMMUNE-SYSTEM; CD33-RELATED SIGLECS; MYELOID CELLS; GLYCOPROTEIN LIGAND; P-SELECTIN; E-SELECTIN LIGAND-1; VON-WILLEBRAND-FACTOR

Domaines: Sciences du Vivant [q-bio]

Marion Pepin, Soraya Mezouar, Julie Pegon, Vincent Muczynski, Frédéric Adam, et al.. Soluble Siglec-5 associates to PSGL-1 and displays anti-inflammatory activity. Scientific Reports, 2016, 6 (1), pp.37953. ⟨10.1038/srep37953⟩. ⟨hal-01455400⟩