Stimulation of leukocyte/endothelium interaction by oxidized low-density lipoprotein in hairless mice. Involvement of CD11b/CD18 adhesion receptor complex.
BACKGROUND
The adhesion of leukocytes to the vascular endothelium has been identified as a constant, early feature of atherogenesis. Using a skinfold chamber model in hamsters for intravital microscopy, we have recently demonstrated the chemotactic and adhesion-promoting action of oxidatively modified low density lipoprotein (oxLDL) in vivo.


METHODS
In order to rule out a species specificity of the experimental approach, and to investigate the involvement of leukocyte adhesion receptors in oxLDL-induced leukocyte/endothelium interaction, we have adapted the skinfold chamber model to hairless mice. Using intravital fluorescence microscopy, leukocyte/endothelium interaction in a fine striated skin muscle was assessed during the time course after intravenous injection of native human LDL (4 mg/kg body weight) and oxLDL (oxidized in vitro by 7.5 microM Cu2+, 6 hours, 37 degrees C) into control mice and into mice pretreated with either the selective inhibitor of leukotriene biosynthesis MK-886 (20 mumol/kg body weight, intravenously, 10 minutes before oxLDL) or with a monoclonal antibody directed towards the CD11b subunit of the CD11b/CD18 adhesion receptor complex on leukocytes (monoclonal antibody anti-Mac1, 0.5 mg/kg, iv, 10 minutes before oxLDL).


RESULTS
We demonstrate in this study that injection of oxLDL (4 mg LDL-cholesterol/kg, intravenously, oxidized by 7.5 microM Cu2+, 6 hours, 37 degrees C), but not of native LDL or LDL-free Cu(2+)-solution, elicits the adhesion of fluorescently stained leukocytes to the endothelium of postcapillary venules (173 +/- 75 cells/mm2 at 20 minutes after oxLDL, mean +/- SD) and arterioles (119 +/- 74 cells/mm2 at 20 minutes after oxLDL, mean +/- SD) in the mice. OxLDL-induced leukocyte adhesion was entirely prevented by pretreatment of the animals with the inhibitor of leukotriene biosynthesis or with monoclonal antibody anti-Mac-1.


CONCLUSIONS
These results demonstrate the involvement of leukotrienes and of the CD11b/CD18 adhesion receptor complex in oxLDL-induced leukocyte adhesion in vivo and rule out a species specificity of this pathophysiologic event.
Lehr
H A
HA
Institute for Surgical Research, University of Munich, Germany.
Kröber
M
M
Hübner
C
C
Vajkoczy
P
P
Menger
M D
MD
Nolte
D
D
Kohlschütter
A
A
Messmer
K
K
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000276:immunology / Q000378:metabolism*; D018845:CD11 Antigens; D018821:CD18 Antigens; D004730:Endothelium, Vascular / Q000502:physiology*; D007275:Injections, Intravenous; D007962:Leukocytes / Q000502:physiology*; D020024:Leukotriene Antagonists; D015289:Leukotrienes / Q000096:biosynthesis; D008077:Lipoproteins, LDL / Q000494:pharmacology / Q000502:physiology*; D051379:Mice; D008812:Mice, Hairless; D008833:Microcirculation / Q000187:drug effects; D010084:Oxidation-Reduction; D016028:Receptors, Leukocyte-Adhesion / Q000378:metabolism*; D012884:Skin Window Technique
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018845:CD11 Antigens; D018821:CD18 Antigens; D020024:Leukotriene Antagonists; D015289:Leukotrienes; D008077:Lipoproteins, LDL; D016028:Receptors, Leukocyte-Adhesion