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Cardiopulmonary bypass primes polymorphonuclear leukocytes
J D Schwartz1, P Shamamian, D S Schwartz
1Department of Surgery, New York University Medical Center, New York 10016, USA.
Abstract:
Polymorphonuclear leukocyte (PMN) superoxide (.O2-) production has been implicated in the pathogenesis of cardiopulmonary bypass (CPB)-related end organ injury. PMN "priming" has been described as an event which enhances the release of .O2- following a second, activating insult. We hypothesized that PMN priming occurs during CBP and is temporally related to the plasma level of complement (C3a), interleukin (IL)-6, and IL-8. PMNs were isolated from 10 CPB patients pre-bypass (preCPB), 5 min after protamine administration (PROT), and at 6 and 24 h post-CPB. PMN .O2- production was measured by a cytochrome c reduction assay in the presence or absence of either phorbol 12-myristate-13-acetate (PMA, 0.4 microgram/ml) or N-formyl-methionyl-leucyl-phenylalanine (FMLP, 1 microM) and also after priming with 2000 nM platelet-activating factor (PAF) followed by activation with either PMA or FMLP. Plasma levels of C3a, IL-6, and IL-8 were determined by enzyme-linked immunosorbent assay. PMA-activated PMN .O2- production was significantly elevated at 6 h post-CPB compared to pre-CPB levels (11.04 +/- 0.9 vs 7.62 +/- 0.57, P = 0.009), indicating that CPB is associated with in vivo PMN priming. When PMNs were primed in vitro with PAF and then activated with PMA or FMLP, .O2- release at 6 h post-CPB was also significantly greater than pre-CPB levels (16.04 +/- 0.74 vs 12.2 +/- 0.92, P = 0.038; and 17.33 +/- 1.38 vs 13.33 +/- 1.35, P < 0.05), indicating that CPB acts synergistically with PAF to prime PMNs. Levels of C3a rose significantly over pre-CPB levels at PROT (P = 0.001), and IL-6 and IL-8 rose over pre-CPB levels at 6 h post-CPB (P = 0.01 and P = 0.006, respectively). These findings demonstrate that CPB not only directly primes PMNs, but also potentiates priming of PMNs by PAF. This "primed" PMN state, which coincided with the increased plasma levels of inflammatory mediators, may suggest a mechanism of predisposition to organ dysfunction following CPB.
Insights
Cardiopulmonary bypass (CPB) primes polymorphonuclear leukocytes (PMNs), increasing their superoxide production. This primed PMN state correlates with elevated inflammatory mediators, potentially contributing to organ injury after CPB.
Area of Science:
- Immunology
- Cardiovascular Surgery
- Critical Care Medicine
Background:
- Polymorphonuclear leukocyte (PMN) superoxide production is linked to cardiopulmonary bypass (CPB)-related organ injury.
- PMN priming, an enhanced response to a secondary stimulus, is a potential mechanism for this injury.
Purpose of the Study:
- To investigate if PMN priming occurs during CPB.
- To determine if PMN priming is temporally related to plasma levels of complement C3a, IL-6, and IL-8.
Main Methods:
- Isolated PMNs from 10 CPB patients at various time points: pre-bypass, post-protamine, and 6/24 hours post-CPB.
- Measured PMN superoxide production using cytochrome c reduction assay, with and without priming (platelet-activating factor) and activation (PMA or FMLP).
- Quantified plasma levels of C3a, IL-6, and IL-8 via enzyme-linked immunosorbent assay.
Main Results:
- PMA-activated PMN superoxide production was significantly elevated 6 hours post-CPB, indicating in vivo PMN priming.
- CPB potentiated in vitro PMN priming by platelet-activating factor.
- Plasma levels of C3a increased at protamine administration, while IL-6 and IL-8 rose at 6 hours post-CPB.
Conclusions:
- CPB directly primes PMNs and enhances their priming response to platelet-activating factor.
- The primed PMN state coincides with increased inflammatory mediators.
- This suggests a mechanism for CPB-induced organ dysfunction.