Related Experiment Videos
P-selectin expression in myocardium of children undergoing cardiopulmonary bypass
S A Burns1, B J DeGuzman, J W Newburger
1Department of Cardiology, Children's Hospital, Boston, MA 02115, USA.
Insights
Cardiopulmonary bypass reduces P-selectin mRNA and protein expression in the heart, contrasting with increased E-selectin and ICAM-1. This suggests P-selectin has a limited role in the inflammatory response post-bypass.
Area of Science:
- Cardiovascular Biology
- Inflammation Research
- Endothelial Cell Biology
Background:
- Cardiopulmonary bypass (CPB) induces myocardial ischemia-reperfusion and inflammation.
- Previous studies indicate increased E-selectin and intercellular adhesion molecule-1 (ICAM-1) mRNA after CPB.
- The role of P-selectin in the CPB-associated inflammatory response remains unclear.
Purpose of the Study:
- To investigate the expression of P-selectin mRNA and protein in human myocardium following CPB.
- To compare P-selectin expression with E-selectin and ICAM-1 during the inflammatory response to CPB.
- To elucidate the role of endothelial P-selectin in the post-CPB inflammatory cascade.
Main Methods:
- Analysis of paired atrial biopsy specimens from pediatric patients before and after CPB using ribonuclease protection assay for P-selectin mRNA.
- Immunocytochemical examination of endothelial cell surface expression of P-selectin, E-selectin, and ICAM-1 in additional patients.
- In vitro study of cultured human endothelial cells treated with tumor necrosis factor-alpha.
Main Results:
- P-selectin mRNA expression showed variability pre-CPB but decreased modestly post-CPB in most patients (p = 0.016).
- P-selectin protein was abundant in the vascular bed pre-CPB but largely absent on capillaries post-CPB.
- E-selectin was induced post-CPB in one patient, while ICAM-1 showed no significant change; in vitro studies showed inverse regulation of P-selectin and ICAM-1 mRNA.
Conclusions:
- Endothelial P-selectin is transcriptionally downregulated after CPB when E-selectin and ICAM-1 are induced.
- E-selectin and ICAM-1 expression occurs at different times and sites compared to P-selectin.
- These findings suggest a limited role for endothelial P-selectin in the inflammatory response following cardiopulmonary bypass.
Abstract:
Cardiopulmonary bypass is a planned support technique that results in a period of myocardial ischemia and reperfusion. In addition, it is associated with an inflammatory response likely involving endothelial cell activation. In previous studies, we showed that E-selectin and intercellular adhesion molecule-1 (ICAM-1) messenger ribonucleic acid (mRNA) are increased in human myocardium after cardiopulmonary bypass. We have now examined the expression of P-selectin mRNA by ribonuclease protection in paired atrial biopsy specimens from 12 patients before and after cardiopulmonary bypass. By means of immunocytochemistry, we have also examined the endothelial cell surface expression of P-selectin protein, as well as that of E-selectin and ICAM-1 in three additional patients. Patient ages ranged from 1 day to 8.5 years (median 12 months), and cardiopulmonary bypass times ranged from 46 to 196 minutes (median 144 minutes). By ribonuclease protection, there was marked variability in the expression of P-selectin in biopsy specimens before bypass. However, when compared with prebypass levels, P-selectin mRNA decreased modestly in 10 of 12 patients after bypass (median decrease 1.5-fold, p = 0.016). As seen with immunocytochemistry, P-selectin protein was distributed diffusely through the vascular bed on large vessels and small vessels before bypass but was virtually absent on capillaries in specimens taken after bypass. E-selectin, which was absent in prebypass biopsy specimens, was induced in one of the three specimens after bypass, but no change in ICAM-1 protein expression above baseline was noted. We also find that cultured human endothelial cells treated with tumor necrosis factor-alpha in doses which induce ICAM-1 mRNA simultaneously decrease their expression of P-selectin mRNA as compared with untreated cells. These observations suggest that endothelial P-selectin is transcriptionally downregulated after cardiopulmonary bypass at times when E-selectin and ICAM-1 are induced. Furthermore, we find that E-selectin and ICAM-1 are expressed at times and at sites where P-selectin is absent. Although it is possible that P-selectin may have been induced and lost at early times before reperfusion, these data suggest that endothelial P-selectin plays a limited role in the inflammatory response that ensues after cardiopulmonary bypass.