Carbohydrate- and CD18-dependent neutrophil adhesion to cardiac myocytes: effects of adenosine.
OBJECTIVE
Adenosine inhibits neutrophil adhesion and injury to isolated cardiac myocytes. In the present study, the contribution of selectin and CD18 interactions to neutrophil-myocyte adhesion and their sensitivity to adenosine were assessed.


METHODS
Activated human neutrophils and canine myocytes were incubated with inhibitors of CD18 or selectin binding, adenosine, or combinations of both for 30-50 min at 37 degrees C. Neutrophils were pretreated with 0.1 microM fMLP for 10 min to study L-selectin-independent adhesion. Adhesion was measured by phase contrast microscopy.


RESULTS
Anti-L-selectin mAb and the selectin-blocking carbohydrates sialyl Lewisx or mannose-6-phosphate, as well as anti-CD18 or anti-ICAM-1 mAbs, inhibited cell adhesion (by 84-99%, P < 0.05). CD11a, but not CD11b, was responsible for most of the CD18-mediated binding. An L-selectin-independent interaction between neutrophils and cardiac myocytes was observed that was delayed (peak adhesion at 40-50 min, rather than 30 min), but still inhibited by anti-CD18 mAb (by 65 +/- 11%, P < 0.05) and carbohydrates (by 87-97%, each P < 0.05). Adenosine (100 nM) inhibited this late CD18-dependent/L-selectin-independent phase of adhesion (by 61 +/- 14%, P < 0.05). The combination of adenosine and anti-CD18 mAb was additive such that adhesion was completely blocked (P < 0.05, compared to either agent alone). Inhibition of adhesion by adenosine was prevented by the A2 antagonist, DMPX (100 nM), and mimicked by the A2 agonist, CGS-21680 (10 nM) or the adenosine regulating agents, acadesine (100 microM) or GP531 (10 microM).


CONCLUSIONS
Neutrophil-myocyte adhesion involved both L-selectin-dependent and L-selectin-independent carbohydrate binding as well as CD11a/CD18. Inhibition of adhesion by adenosine interferes with L-selectin-independent carbohydrate binding and possibly CD18.
Bullough
D A
DA
Department of Cardiovascular Pharmacology, Gensia, Inc., San Diego, CA 92121, USA.
Magill
M J
MJ
Mullane
K M
KM
Firestein
G S
GS
D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D018821:CD18 Antigens / Q000276:immunology / Q000502:physiology*; D002448:Cell Adhesion / Q000187:drug effects; D002478:Cells, Cultured; D004285:Dogs; D018799:Intercellular Adhesion Molecule-1 / Q000276:immunology; D019041:L-Selectin / Q000378:metabolism / Q000502:physiology*; D007983:Lewis Blood Group Antigens; D016256:Lewis X Antigen; D008858:Microscopy, Phase-Contrast; D009206:Myocardium / Q000166:cytology*; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D009844:Oligosaccharides / Q000494:pharmacology; D011485:Protein Binding; D018047:Receptors, Purinergic P1 / Q000187:drug effects; D000080506:Sialyl Lewis X Antigen
D000911:Antibodies, Monoclonal; D018821:CD18 Antigens; D007983:Lewis Blood Group Antigens; D016256:Lewis X Antigen; D009844:Oligosaccharides; D018047:Receptors, Purinergic P1; D000080506:Sialyl Lewis X Antigen; D018799:Intercellular Adhesion Molecule-1; D019041:L-Selectin; D000241:Adenosine