Related Experiment Videos
Carbohydrate- and CD18-dependent neutrophil adhesion to cardiac myocytes: effects of adenosine
D A Bullough1, M J Magill, K M Mullane
1Department of Cardiovascular Pharmacology, Gensia, Inc., San Diego, CA 92121, USA.
Insights
Adenosine effectively inhibits neutrophil adhesion to cardiac myocytes by targeting L-selectin-independent pathways. This interaction involves CD11a/CD18 and carbohydrate binding, with adenosine blocking the late phase of adhesion.
Area of Science:
- Cardiovascular Biology
- Immunology
- Cell Adhesion Research
Background:
- Neutrophil adhesion to cardiac myocytes contributes to myocardial injury.
- Adenosine is known to inhibit neutrophil adhesion and myocyte damage.
Purpose of the Study:
- To investigate the roles of selectin and CD18 interactions in neutrophil-myocyte adhesion.
- To determine the sensitivity of these interactions to adenosine inhibition.
Main Methods:
- Human neutrophils and canine myocytes were incubated with CD18 or selectin inhibitors and/or adenosine.
- L-selectin-independent adhesion was studied after neutrophil pre-treatment with fMLP.
- Adhesion was quantified using phase contrast microscopy.
Main Results:
- Selectin and CD18 interactions, including CD11a/CD18 and carbohydrate binding, mediated neutrophil-myocyte adhesion.
- Adenosine inhibited the L-selectin-independent, CD18-dependent phase of adhesion.
- Adenosine's effects were mediated via A2 receptors and potentiated by acadesine and GP531.
Conclusions:
- Neutrophil-myocyte adhesion involves both L-selectin-dependent and independent mechanisms, including carbohydrate binding and CD11a/CD18.
- Adenosine interferes with L-selectin-independent carbohydrate binding and potentially CD18 interactions.
- Adenosine represents a potential therapeutic target for reducing neutrophil-mediated cardiac injury.
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).
Conclusion:
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.