Neutrophil adherence receptors (CD 18) in ischemia. Dissociation between quantitative cell surface expression and diapedesis mediated by leukotriene B4.
Neutrophils and eicosanoid chemoattractants are centrally involved with ischemia-reperfusion (I/R) injury. The CD 18 complex of adhesive glycoproteins, readily up-regulated by chemoattractants in vitro, is required for polymorphonuclear leukocyte (PMN) adherence to endothelium. This study tests whether CD 18 is up-regulated by ischemia in vivo and its role in mediating PMN diapedesis. Anesthetized rabbits underwent 3 h of bilateral hindlimb tourniquet ischemia (n = 16). Ten min after tourniquet release, levels of plasma leukotriene (LT)B4 increased to 390 +/- 62 pg/ml (mean +/- SE), higher than 134 +/- 26 pg/ml in control rabbits (n = 13, p less than 0.01). Aliquots of plasma were added to whole blood from normal rabbits (n = 6) for flow cytometric analysis of neutrophils with the CD 18 mAb R 15.7. Addition of I/R plasma failed to demonstrate an increase in surface expression of CD 18. Similarly, no CD 18 up-regulation was observed in vivo upon reperfusion in ischemic animals pretreated with mAb R 15.7 (n = 3). However, I/R plasma when introduced into plastic chambers taped atop dermabrasion sites in normal rabbits (n = 12) resulted in diapedesis, measured by the accumulation after 3 h of 1130 +/- 125 PMN/mm3 in the chambers relative to 120 +/- 31 PMN/mm3 with control plasma (p less than 0.01). Diapedesis in response to I/R plasma was abolished by pretreatment with mAb R 15.7 (less than 5 PMN/mm3, n = 6), was reduced by U 75,302, an LTB4 receptor antagonist (253 +/- 101 PMN/mm3, n = 6) (both p less than 0.01) and was not protein synthesis dependent. These results demonstrate that PMN diapedesis in response to I/R plasma is exclusively dependent upon the CD 18 glycoprotein complex by an LTB4-dependent mechanism, despite the fact that CD 18 is not up-regulated on circulating PMN in ischemia. These data indirectly indicate the functional importance of conformational changes of CD 18 in determining PMN adhesion.
Welbourn
R
R
Department of Surgery, Brigham and Women's Hospital, Boston, MA 02115.
Goldman
G
G
Kobzik
L
L
Paterson
I
I
Valeri
C R
CR
Shepro
D
D
Hechtman
H B
HB
D000818:Animals; D000911:Antibodies, Monoclonal; D018821:CD18 Antigens; D002448:Cell Adhesion; D002634:Chemotaxis, Leukocyte; D003609:Dactinomycin / Q000494:pharmacology; D005233:Fatty Alcohols / Q000494:pharmacology; D006018:Glycols / Q000494:pharmacology; D007975:Leukotriene B4 / Q000502:physiology*; D008297:Male; D009504:Neutrophils / Q000166:cytology*; D011817:Rabbits; D016028:Receptors, Leukocyte-Adhesion / Q000502:physiology*; D015427:Reperfusion Injury / Q000503:physiopathology*
D000911:Antibodies, Monoclonal; D018821:CD18 Antigens; D005233:Fatty Alcohols; D006018:Glycols; D016028:Receptors, Leukocyte-Adhesion; C062137:U 75302; D003609:Dactinomycin; D007975:Leukotriene B4