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Isolation of Functional Cardiac Immune Cells
Published on: December 5, 2011
Interleukin 6 induction in the canine myocardium after cardiopulmonary bypass
W J Dreyer1, S C Phillips, M L Lindsey
1Lillie Frank Abercrombie Section of Cardiology, Department of Pediatrics, and the Section of Cardiovascular Sciences, Baylor College of Medicine, Houston, TX, USA. wdreyer@bcm.tmc.edu
Insights
The heart muscle (myocardium) produces interleukin-6 after heart surgery (cardiopulmonary bypass). This local interleukin-6 production may impact heart function after surgery.
Area of Science:
- Cardiovascular Science
- Immunology
- Molecular Biology
Background:
- Interleukin-6 (IL-6) is a pro-inflammatory cytokine.
- Plasma IL-6 levels rise after cardiopulmonary bypass (CPB).
- The origin of IL-6 post-CPB remains unclear.
Purpose of the Study:
- To investigate the myocardium as a potential source of IL-6 following CPB.
- To analyze IL-6 and intercellular adhesion molecule-1 (ICAM-1) expression in the myocardium post-CPB.
Main Methods:
- Canine model undergoing 90 minutes of hypothermic CPB with cardioplegic arrest.
- Myocardial tissue sampling at 3 and 6 hours post-reperfusion.
- Analysis using Northern blot, RT-PCR, and in situ hybridization.
- Comparison with time-matched controls without CPB.
Main Results:
- Myocardial IL-6 messenger RNA (mRNA) significantly increased 3 and 6 hours post-CPB.
- Cardiac myocytes were identified as a primary source of IL-6 mRNA.
- Myocardial ICAM-1 was also upregulated post-CPB.
- No significant IL-6 induction was found in blood leukocytes.
Conclusions:
- The myocardium is a significant source of IL-6 synthesis after CPB, even with cardioplegic protection.
- Local IL-6 production in the myocardium may play a critical role in post-operative cardiac function.
Objective:
Interleukin 6 is a proinflammatory cytokine with a plasma concentration that has been noted to increase in response to cardiopulmonary bypass. The source of interleukin 6 after cardiopulmonary bypass is unknown. This study examined the myocardium as a potential source of interleukin 6 in this context.
Methods:
Dogs underwent 90 minutes of hypothermic cardiopulmonary bypass with 60 minutes of cardioplegic arrest. After rewarming, they were reperfused with the chest open for either 3 (n = 4) or 6 (n = 4) hours, at the end of which myocardial samples were obtained. Four additional animals undergoing open thoracotomy without bypass served as time-matched controls. Northern blot analysis, reverse transcriptase-polymerase chain reaction, and in situ hybridization were used to examine the myocardium for the induction of interleukin 6 and intercellular adhesion molecule-1.
Results:
Northern blot analysis and reverse transcriptase-polymerase chain reaction demonstrated a marked increase in myocardial interleukin 6 messenger RNA in 3 of 4 dogs at 3 hours after bypass and 3 of 4 dogs at 6 hours after bypass, which was not present in sham-bypass control animals. Northern blots at 3 hours after cardiopulmonary bypass also demonstrated myocardial intercellular adhesion molecule-1 induction. In situ hybridization studies confirmed that cardiac myocytes were a principal source of interleukin 6 messenger RNA early after cardiopulmonary bypass. Northern blots of messenger RNA extracted from isolated neutrophils and mononuclear leukocytes obtained from blood samples before bypass, at the end of bypass, and 3 hours after bypass failed to demonstrate interleukin 6 induction.
Conclusion:
Despite protection with cold cardioplegic arrest, the myocardium was a significant source of interleukin 6 synthesis after cardiopulmonary bypass. Local production of interleukin 6 may play a pivotal role in postoperative myocardial function.
