Opposing effects mediated by the chemokine receptor CXCR2 on myocardial ischemia-reperfusion injury: recruitment of potentially damaging neutrophils and direct myocardial protection.
BACKGROUND
The timely reperfusion of ischemic myocardium limits infarction, but components of reperfusion, such as inflammation, may be injurious. The chemokine receptor CXCR2 mediates neutrophil chemotaxis. CXCR2 activation also inhibits hypoxia-induced death of isolated cardiac myocytes. This study assesses whether CXCR2 mediates protection in the intact heart and, if so, the magnitude of this protection relative to CXCR2-mediated chemotaxis of potentially damaging inflammatory cells.


RESULTS
After ischemia-reperfusion in vivo, CXCR2-/- mice exhibited infarcts that were 50.5% smaller (P<0.05) with 44.3% fewer inflammatory cells (P<0.05) than wild type mice. These data suggest that in this model, CXCR2-mediated chemotaxis may be important in myocardial cell death. To isolate the role of CXCR2 specifically on blood cells, adoptive transfer experiments were performed. After ischemia-reperfusion, infarcts were 53.4% smaller (P<0.05) and contained 65.0% fewer inflammatory cells (P<0.05) in lethally irradiated wild type mice reconstituted with CXCR2-/- compared with wild type bone marrow. Thus, CXCR2 on blood cells is important in myocardial damage, most likely because of CXCR2-mediated chemotaxis. To unmask whether CXCR2 mediates direct myocardial protection in the intact heart, wild type and CXCR2-/- hearts were studied in the absence of blood using Langendorff preparations. In this case, infarcts were 19.7% larger in CXCR2-/- than wild type hearts (P<0.05), revealing a novel CXCR2-mediated cardioprotective effect.


CONCLUSIONS
CXCR2 exerts opposing effects on myocardial viability during ischemia-reperfusion with recruitment of damaging inflammatory cells predominant over direct tissue protection.
Tarzami
Sima T
ST
Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx, NY 10461, USA.
Miao
Wenfeng
W
Mani
Kartik
K
Lopez
Lillie
L
Factor
Stephen M
SM
Berman
Joan W
JW
Kitsis
Richard N
RN
D019264:Adoptive Transfer; D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism; D016026:Bone Marrow Transplantation; D016923:Cell Death; D015687:Cell Hypoxia; D002634:Chemotaxis, Leukocyte / Q000502:physiology*; D007249:Inflammation; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D009203:Myocardial Infarction / Q000276:immunology / Q000473:pathology; D017202:Myocardial Ischemia / Q000276:immunology / Q000473:pathology*; D015428:Myocardial Reperfusion Injury / Q000276:immunology / Q000473:pathology*; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology; D009928:Organ Specificity; D011828:Radiation Chimera; D023063:Receptors, Interleukin-8B / Q000502:physiology*
D023063:Receptors, Interleukin-8B