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Updated: Jun 12, 2026
Intravenous Endotoxin Challenge in Healthy Humans: An Experimental Platform to Investigate and Modulate Systemic Inflammation
Published on: May 16, 2016
Early immunomodulatory effects of linezolid in a human whole blood endotoxin model
Abstract:
Gram-negative sepsis resulting in endotoxin triggered septic shock is one of the leading causes of death in critically ill patients. Because treatment options are limited, recent approaches focus on immunomodulatory effects of antimicrobials. Thus, we characterized the immunomodulatory effects of linezolid at mRNA and on cytokine levels in supernatants of an ex vivo model of endotoxemia. Whole blood from 10 healthy volunteers was incubated with 50 pg/ml LPS with or without 13 microg/ml linezolid (concentrations were chosen to reflect in vivo conditions) for 2 and 4 hours (h). Quantitative real-time PCR was performed from messenger RNA (mRNA) of IL-1beta;, IL-6, IL-8 or TNF-alpha;. Cytokine levels in the supernatant were measured by ELISA for IL-6, IL-8 and TNF-alpha;. Incubation of human whole blood with LPS increased mRNA levels of cytokines several thousand fold compared with baseline. The addition of linezolid significantly reduced mRNA levels of IL-1beta, IL-6, IL-8 and TNF-alpha; (p < 0.05) after 2 and 4 h. LPS stimulation also increased levels of IL-6, IL-8 and TNF-alpha between 100 and 1000-fold. However, in contrast to mRNA - except for IL-6 - no significant reduction at protein level was observed. These results indicate that immunosuppressive effects of linezolid on mRNA transcription are only partially reflected by cytokine release.
Insights
Linezolid significantly reduces pro-inflammatory cytokine mRNA in endotoxemia models. However, these effects on mRNA transcription are not fully reflected in protein levels, except for IL-6.
Area of Science:
- Immunology
- Pharmacology
- Critical Care Medicine
Background:
- Gram-negative sepsis and endotoxin-triggered septic shock are leading causes of mortality in critically ill patients.
- Limited treatment options necessitate exploring immunomodulatory effects of antimicrobials.
Purpose of the Study:
- To characterize the immunomodulatory effects of linezolid on mRNA and cytokine levels in an ex vivo endotoxemia model.
- Investigate linezolid's impact on key inflammatory mediators.
Main Methods:
- Human whole blood was incubated with lipopolysaccharide (LPS) ± linezolid.
- Quantitative real-time PCR assessed mRNA levels of IL-1β, IL-6, IL-8, and TNF-α.
- ELISA measured supernatant cytokine levels (IL-6, IL-8, TNF-α).
Main Results:
- LPS stimulation significantly increased cytokine mRNA levels (thousands-fold).
- Linezolid markedly reduced mRNA levels of IL-1β, IL-6, IL-8, and TNF-α (p < 0.05).
- While protein levels of IL-6, IL-8, and TNF-α also increased, linezolid only significantly reduced IL-6 protein levels.
Conclusions:
- Linezolid demonstrates immunosuppressive effects at the mRNA transcription level for key inflammatory cytokines.
- These observed immunosuppressive effects on mRNA are only partially translated to protein levels, highlighting a complex regulatory mechanism.
