title: Activation state of alpha4beta1 integrin on sickle red blood cells is linked to the duffy antigen receptor for chemokines (DARC) expression.
abstract: In sickle cell anemia, reticulocytes express enhanced levels of α4β1 integrin that interact mainly with vascular cell adhesion molecule-1 and fibronectin, promoting vaso-occlusion. These interactions are known to be highly sensitive to the inflammatory chemokine IL-8. The Duffy antigen receptor for chemokines (DARC) modulates the function of inflammatory processes. However, the link between α4β1 activation by chemokines and DARC erythroid expression is not or poorly explored. Therefore, the capacity of α4β1 to mediate Duffy-negative and Duffy-positive sickle reticulocyte (SRe) adhesion to immobilized vascular cell adhesion molecule-1 and fibronectin was evaluated. Using static adhesion assays, we found that, under basal conditions, Duffy-positive SRe adhesion was 2-fold higher than that of Duffy-negative SRes. Incubating the cells with IL-8 or RANTES (regulated on activation normal T cell expressed and secreted) increased Duffy-positive SRe adhesion only, whereas Mn(2+) increased cell adhesion independently of the Duffy phenotype. Flow cytometry analyses performed with anti-β1 and anti-α4 antibodies, including a conformation-sensitive one, in the presence or absence of IL-8, revealed that Duffy-positive and Duffy-negative SRes displayed similar erythroid α4β1 expression levels, but with distinct activation states. IL-8 did not affect α4β1 affinity in Duffy-positive SRes but induced its clustering as corroborated by immunofluorescence microscopy. Our results indicate that in Duffy-negative SRes α4β1 integrin is constitutively expressed in a low affinity state, whereas in Duffy-positive SRes α4β1 is expressed in a higher chemokine-sensitive affinity state. This activation state associated with DARC RBC expression may influence the intensity of the inflammatory responses encountered in sickle cell anemia and participate in its interindividual clinical expression variability.
authors.affiliation: INSERM UMR_S763, F97159 Pointe-à-Pitre, Guadeloupe, France.
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Durpès
authors.forename: Marie-Dominique
authors.initials: MD
authors.lastname: Hardy-Dessources
authors.forename: Wassim
authors.initials: W
authors.lastname: El Nemer
authors.forename: Julien
authors.initials: J
authors.lastname: Picot
authors.forename: Nathalie
authors.initials: N
authors.lastname: Lemonne
authors.forename: Jacques
authors.initials: J
authors.lastname: Elion
authors.forename: Monique
authors.initials: M
authors.lastname: Decastel
mesh_terms: D000328:Adult; D000755:Anemia, Sickle Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002448:Cell Adhesion / Q000187:drug effects / Q000235:genetics; D018946:Chemokine CCL5 / Q000378:metabolism / Q000494:pharmacology; D004375:Duffy Blood-Group System / Q000096:biosynthesis* / Q000235:genetics; D004913:Erythrocytes, Abnormal / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D006801:Humans; D039041:Integrin alpha4beta1 / Q000235:genetics / Q000378:metabolism*; D016209:Interleukin-8 / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D008345:Manganese / Q000378:metabolism / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000096:biosynthesis* / Q000235:genetics; D012156:Reticulocytes / Q000378:metabolism / Q000473:pathology
chemical_list: C473745:ACKR1 protein, human; C483024:CCL5 protein, human; C508606:CXCL8 protein, human; D018946:Chemokine CCL5; D004375:Duffy Blood-Group System; D039041:Integrin alpha4beta1; D016209:Interleukin-8; D011956:Receptors, Cell Surface; D008345:Manganese