The Compromised Inflammatory Response to Bacterial Components After Pediatric Cardiac Surgery is Associated with Cardiopulmonary Bypass-suppressed Toll-like Receptor Signal Transduction Pathways

Purpose: Cardiopulmonary bypass (CPB) during pediatric cardiac surgery often elicits a systemic inflammatory response followed by a compromised immune response, which has been attributed to the morbidity of postoperative infection; however, the underlying mechanism(s) has not yet been fully elucidated. We hypothesized that CPB inhibits the activation of Toll-like receptor (TLR) signal transduction pathways, thereby causing an immunosuppressive state after pediatric cardiac surgery.

Methods: We examined 20 children with congenital heart disease undergoing pediatric cardiac surgery.

Results: Cardiopulmonary bypass differentially affected lipopolysaccharide (LPS)- or bacterial lipoprotein (BLP)-stimulated ex vivo production of proinflammatory and anti-inflammatory cytokines, with significantly diminished tumor necrosis factor α, interleukin (IL) 1β, IL-6, and IL-8, but substantially enhanced IL-10 production. Consistent with the reduced inflammatory response, CPB strongly inhibited LPS- or BLP-activated TLR signal transduction pathways in monocytes with down-regulated expression of CD14, TLR4, and TLR2 and with suppressed phosphorylation of nuclear factor κB p65, p38, and extracellular signal-regulated kinase 1/2.

Conclusions: These results indicate that CPB during pediatric cardiac surgery causes substantially reduced production of inflammatory cytokines in response to bacterial component LPS or BLP stimulation, which is associated with CPB-induced suppression of TLR-mediated signal transduction pathways. This reduced inflammatory response after CPB in children with congenital heart disease may predispose them to an increased risk of postoperative infection.