Moderate hypothermia delays proinflammatory cytokine production of human peripheral blood mononuclear cells

Objective: To clarify the influence of moderate hypothermia on the production of proinflammatory cytokines. Design: Controlled in vitro study. Setting: Research laboratory. Subjects: Peripheral blood mononuclear cells from healthy adult human subjects. Interventions. Stimulation with 1 mug/mL lipopolysaccharide at 33degreesC and 37degreesC. Measurements: Concentrations of released tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 were measured chronologically by enzyme immunoassay. The number of mRNA copies of these cytokines was determined by competitive reverse transcriptase-polymerase chain reaction analysis, and nuclear factor-kappaB activations were assessed by electrophoretic mobility shift assay. Main Results: Significant reduction of the released-tumor necrosis factor-alpha concentration was observed 1 and 2 hrs after the stimulation with lipopolysaccharide at 33degreesC compared with 37degreesC. The peak release of interleukin-1beta at 33degreesC was delayed 12 hrs later than that at 37degreesC. A delayed peak in the release of interleukin-6 also was observed at 33degreesC. The peaks of cytokines were confirmed at the mRNA expression level by competitive reverse transcriptase-polymerase chain reaction analysis at both temperatures. The peak of the tumor necrosis factor-alpha mRNA expression level was observed at 1 hr after the stimulation at 37degreesC and 2 hrs after the stimulation at 33degreesC. In the interleukin-1beta mRNA expression, at 37degreesC the first peak appeared 1 hr and the second 6 his after the stimulation. In contrast, at 33degreesC, the first peak appeared 2 hrs and the second 12 hrs after the stimulation. Whereas interleukin-6 mRNA expression at 37degreesC peaked 6 hrs after the stimulation, no definite peak was observed at 33degreesC and the expression level was approximately half of that at 37degreesC. The maximum intensity of nuclear factor-kappaB activation at 33degreesC was delayed by 1.5 hrs compared with that at 37degreesC. Conclusions: Moderate hypothermia delays the induction of proinflammatory cytokines in human peripheral blood mononuclear cells.