Blockade of avidity and focal clustering of beta 2-integrin by cysteinyl leukotriene antagonism attenuates eosinophil adhesion.
BACKGROUND
Cysteinyl leukotriene (cysLT) antagonism attenuates migration of eosinophils into airways during immune challenge in human subjects and animal models. The intracellular signaling mechanism by which this occurs has not been elucidated.


OBJECTIVE
We sought to determine the relative efficacy and mechanism by which 5-lipoxygenase (5-LO) inhibition and cysLT(1) receptor (cysLT(1)R) antagonism block beta(2)-integrin adhesion in isolated human eosinophils in vitro.


METHODS
Human blood eosinophils were isolated by means of immunomagnetic separation. Upregulation of CD11b expression, active conformation of CD11b, and focal clustering of beta(2)-integrin caused by IL-5, eotaxin-1 or leukotriene (LT) B(4) was assessed by means of flow cytometry and confocal microscopy. The effect and mechanism of cysLT(1)R or 5-LO blockade on these components of beta(2)-integrin adhesion were determined.


RESULTS
Montelukast, a cysLT(1)R antagonist, and AA861, a 5-LO enzyme inhibitor, blocked (1) avidity of beta(2)-integrin, (2) beta(2)-integrin-mediated adhesion to intercellular adhesion molecule 1, and (3) focal clustering of CD11b elicited by LTB(4). However, adhesion caused by either IL-5 or eotaxin-1 was not attenuated for eosinophils pretreated with either montelukast or AA861.


CONCLUSIONS
Our data demonstrate that (1) LTB(4) causes autocrine upregulation of adhesion through secretion of cysLTs, and (2) blockade of cysLT(1)R blocks the avidity and focal clustering of CD11b/CD18 for eosinophils activated by LTB(4) but not by IL-5 or eotaxin-1.


CONCLUSIONS
Unlike cysLT-induced adhesion, adhesion caused by IL-5 or eotaxin-1 is not regulated through the cysLT(1)R, suggesting that cysLTs have specific but limited potential to upregulate eosinophil adhesion.
Meliton
Angelo Y
AY
Section of Pulmonary and Critical Care Medicine, Department of Medicine, The University of Chicago, Chicago, IL 60637, USA.
Munoz
Nilda M
NM
Leff
Alan R
AR
D000085:Acetates / Q000494:pharmacology; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D016227:Benzoquinones / Q000494:pharmacology; D039481:CD11b Antigen / Q000096:biosynthesis / Q000235:genetics; D018821:CD18 Antigens / Q000378:metabolism* / Q000502:physiology; D002448:Cell Adhesion / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D054413:Chemokine CCL11 / Q000502:physiology; D003521:Cyclopropanes; D003545:Cysteine / Q000037:antagonists & inhibitors* / Q000502:physiology; D004804:Eosinophils / Q000187:drug effects / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism*; D006801:Humans; D018836:Inflammation Mediators / Q000037:antagonists & inhibitors* / Q000502:physiology; D015848:Interleukin-5 / Q000502:physiology; D020024:Leukotriene Antagonists / Q000494:pharmacology*; D007975:Leukotriene B4 / Q000502:physiology; D015289:Leukotrienes / Q000502:physiology; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D013440:Sulfides
D000085:Acetates; D016227:Benzoquinones; D039481:CD11b Antigen; D018821:CD18 Antigens; D054413:Chemokine CCL11; D003521:Cyclopropanes; C509295:ITGAM protein, human; D018836:Inflammation Mediators; D015848:Interleukin-5; D020024:Leukotriene Antagonists; D015289:Leukotrienes; D016859:Lipoxygenase Inhibitors; D011804:Quinolines; D013440:Sulfides; C112381:cysteinyl-leukotriene; D007975:Leukotriene B4; C036837:2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone; D001094:Arachidonate 5-Lipoxygenase; D003545:Cysteine; C093875:montelukast