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Ann Thorac Surg. 2007 Jan;83(1):146-52.

Leukocyte effects of C5a-receptor blockade during simulated extracorporeal circulation.

Author information

  • 1Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut 06520-8051, USA. christine.rinder@yale.edu

Abstract

BACKGROUND:

Distinct pathways of leukocyte activation during simulated cardiopulmonary bypass are mediated by the complement C5a anaphylatoxin. We hypothesized that a human C5a receptor antagonist would specifically inhibit the inflammatory response of neutrophils to simulated extracorporeal circulation, while preserving the C5b-9 pathway for innate immunity.

METHODS:

An in vitro extracorporeal circuit recirculated fresh heparinized whole blood through a membrane oxygenator with and without addition of a small molecule human C5a receptor antagonist. Samples were periodically drawn over 90 minutes for complement and leukocyte activation studies.

RESULTS:

Addition of the C5a receptor antagonist to simulated extracorporeal circulation abrogated both neutrophil CD11b upregulation and interleukin 8 release (p < 0.01 for both), despite full generation of C3a and C5b-9; however, elastase release from neutrophils was unaffected. Although C5a receptor blockade only trended toward inhibiting monocyte CD11b upregulation (p = 0.09), circuit clearance of both monocytes (p = 0.04) and neutrophils (p = 0.01) was significantly decreased. In addition, the C5a receptor antagonist completely blocked both neutrophil-platelet and monocyte-platelet conjugate formation (p < 0.001 for both), without affecting platelet P-selectin expression.

CONCLUSIONS:

C5a receptor blockade during simulated extracorporeal circulation completely blocked neutrophil beta2 integrin upregulation and induction of plasma interleukin 8, suggesting an acute downregulatory effect on neutrophil chemotaxis-related pathways, while preserving terminal complement generation and neutrophil elastase release. Inhibition of leukocyte-platelet conjugate formation suggests a novel function for leukocyte adhesive receptors, possibly related to preservation of elastase generation.

Comment in

  • Invited commentary. [Ann Thorac Surg. 2007]
PMID:
17184649
[PubMed - indexed for MEDLINE]
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