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 microg/mL lipopolysaccharide at 33 degrees C and 37 degrees C.
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 33 degrees C compared with 37 degrees C. The peak release of interleukin-1beta at 33 degrees C was delayed 12 hrs later than that at 37 degrees C. A delayed peak in the release of interleukin-6 also was observed at 33 degrees C. 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 37 degrees C and 2 hrs after the stimulation at 33 degrees C. In the interleukin-1beta mRNA expression, at 37 degrees C the first peak appeared 1 hr and the second 6 hrs after the stimulation. In contrast, at 33 degrees C, the first peak appeared 2 hrs and the second 12 hrs after the stimulation. Whereas interleukin-6 mRNA expression at 37 degrees C peaked 6 hrs after the stimulation, no definite peak was observed at 33 degrees C and the expression level was approximately half of that at 37 degrees C. The maximum intensity of nuclear factor-kappaB activation at 33 degrees C was delayed by 1.5 hrs compared with that at 37 degrees C.
Conclusions: Moderate hypothermia delays the induction of proinflammatory cytokines in human peripheral blood mononuclear cells.