title: Differential regulation of neutrophil CD18 integrin function by di- and tri-valent cations: manganese vs. gadolinium.
abstract: Affinity regulation of integrin function plays an important role during both leukocyte-endothelial and leukocyte-leukocyte interactions. We compared the roles of Mn(2+) (Manganese) and Gd(3+) (Gadolinium) in regulating leukocyte CD18-integrin function. We observed that: (i) Both cations prolonged neutrophil homotypic aggregation following chemoattractant IL-8 stimulation, with Gd(3+) being effective at doses two orders of magnitude (10 microM range) lower that Mn(2+). (ii) While both Gd(3+) and Mn(2+) mediate homotypic cell aggregation via L: -selectin and CD18 integrins, their effects on the integrin subunits, LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18), was different. Gd(3+) altered both LFA-1 and Mac-1 function, while the dominant effect of Mn(2+) was on Mac-1. This effect of Gd(3+) on LFA-1 function was confirmed in cell-free studies that measured the binding of recombinant ICAM-1 to LFA-1 immobilized on beads. (iii) Both ions augmented the binding of 327C, an antibody that recognizes active CD18 on human neutrophils, both in the presence and absence of exogenous IL-8. The effects of Mn(2+) was more pronounced since it caused 3-4-fold increase in mAb 327C binding to neutrophils compared to Gd(3+) which increased antibody binding by only approximately 80%. 327C binding was partially reduced by Ca(2+). Further, 327C binding induced by Mn(2+) did not correlate tightly with cell adhesion function. (iv) In studies that monitored intracellular Ca(2+) ([Ca(2+)](i)), the addition of Mn(2+) but not Gd(3+) to neutrophils altered [Ca(2+)](i) levels. Overall, while both Gd(3+) and Mn(2+) stabilize high affinity CD18 mediated cell adhesion, Gd(3+) affects integrin conformation while Mn(2+) may also trigger other effects.
authors.affiliation: Department of Chemical and Biological Engineering, State University of New York, 906 Furnas Hall, Buffalo, NY 14260, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Heather N
authors.initials: HN
authors.lastname: Hayenga
authors.forename: Melissa R
authors.initials: MR
authors.lastname: Sarantos
authors.forename: Scott I
authors.initials: SI
authors.lastname: Simon
authors.forename: Sriram
authors.initials: S
authors.lastname: Neelamegham
mesh_terms: D018821:CD18 Antigens / Q000378:metabolism*; D002412:Cations / Q000378:metabolism / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002449:Cell Aggregation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005682:Gadolinium / Q000008:administration & dosage / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D008345:Manganese / Q000008:administration & dosage / Q000378:metabolism*; D018375:Neutrophil Activation / Q000187:drug effects / Q000502:physiology*; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*
chemical_list: D018821:CD18 Antigens; D002412:Cations; D015815:Cell Adhesion Molecules; D008345:Manganese; D005682:Gadolinium