Open Access

ARTICLE

Upregulation of cytokine mRNA in circulating leukocytes during human endotoxemia

Petra Jilma-Stohlawetz¹, Tuende Kliegel², Irene Kantner-Schlifke², Claudia Strasser-Marsik², Florian B. Mayr², Bernd Jilma²

1 Dept. of Laboratory Medicine, Medical University of Vienna, Vienna, Austria
2 Department of Clinical Pharmacology, Division of Immunology and Hematology, Medical University of Vienna, Austria

* Corresponding Author: Jilma B.,

European Cytokine Network 2017, 28(1), 19-26. https://doi.org/10.1684/ecn.2017.0389

Accepted 22 March 2017;

Abstract

Background: Endotoxemia induces pronounced changes in leukocyte count and enhances the release of many cytokines. However, the molecular regulation of this cytokine release is poorly characterized in humans. Methods: The time course of mRNA expression of 24 cytokines in circulating leukocytes was studied in a wellstandardized model of human endotoxemia (2 ng/kg). Real-time polymerase chain reaction (RT-PCR) was used to quantify the lipopolysaccharide (LPS)-inducible mRNA levels of leukocytes from 16 healthy volunteers in a randomized, placebo-controlled trial. Results: Baseline mRNA levels of interleukins including IL-1α, IL-3, IL-5, IL-6, IL-12p40, IL-13, IL-15, IL-17, granulocyte colony-stimulating factor (G-CSF) and granulocyte monocyte CSF (GM-CSF) were below detectable levels in normal blood of the healthy participants. After 2 h, LPS infusion increased median mRNA levels of IL-1α by >1100-fold and IL-1β and IL-8 by 33-fold and 46-fold, respectively. In contrast, levels of tumor necrosis factor (TNF-α) and IL-10 mRNA increased by only 7-fold, whereas changes in mRNA expression of other cytokines showed either a more than two fold increase or were undetectable. In vitro incubation of whole blood with 50 pg/mL LPS for 2 h enhanced transcription levels of IL-1α mRNA by >10,000- fold, IL-6 and IL-12p40 by >1000-fold, IL-1β by 400-fold, TNF-α by 100-fold, IL-8, IL-18, interferon γ (IFN-γ) and G-CSF by >10-25-fold, and IL-10, IL-12p35, TNF-β, and IL-13 by 10-25-fold. Conclusion: Only half of the 24 evaluated cytokines were expressed at the mRNA level in circulating leukocytes under basal conditions and after an LPS challenge. Only IL-1α, IL-1β, IL-10, IL-8, and TNF-α were upregulated in the circulating leukocytes, whereas several other cytokines (including IL-6 and G-CSF), were expressed on the mRNA level following in vitro incubation of blood with LPS. In addition, IL-1α and IL-1β might be potential diagnostic targets in inflammatory diseases.

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