Moderate temperature alterations affect Gram-negative immune signalling in ex vivo whole blood.
BACKGROUND
Alterations in body temperature may influence immune system function and consequently affect the risk of infection and inflammatory diseases. Lipopolysaccharide (LPS) from gram-negative bacteria induces production of inflammatory cytokines after ligand binding to Toll-like receptor 4 (TLR4) on immune cells (especially monocytes/ macrophages). Our aim was to explore how clinically relevant hypo- and hyperthermia affect this signalling in an ex vivo whole blood model, and investigate if the cytokine response was correlated with monocyte TLR4 expression level.


METHODS
Blood from 11 healthy volunteers was incubated with LPS 10 ng/ml for 6 h at 33, 37 or 40°C. The concentrations of selected pro-inflammatory (tumour necrosis factor-α (TNF-α) and interleukin (IL)-1β) and anti-inflammatory (IL-10) cytokines were measured in plasma, and the surface expression of TLR4 was quantified on CD14 + monocytes.


RESULTS
Monocyte TLR4 expression and plasma IL-1β were inversely related to temperature. The TNF-α production was unaffected by hypothermia but increased significantly during hyperthermia, whereas plasma IL-10 was significantly reduced during both hypo- and hyperthermic incubation. No correlation was found between TLR4 expression and cytokine concentrations. During hypothermia, the TNF-α/IL-10 and IL-1β/IL-10 ratios increased seven and nine times, respectively. Hyperthermia increased the TNF-α/IL-10 ratio, but to a lesser extent (doubling), whereas the IL-1β/IL-10 ratio remained unchanged.


CONCLUSIONS
Hypothermia significantly changed the cytokine ratios in the pro-inflammatory direction. In comparison, the effect of hyperthermia was sparse, with a modest increase in the TNF-α/IL-10 ratio only. No association was found between LPS-stimulated cytokine production and TLR4 expression on CD14 + monocytes.
Institute of Clinical Medicine, University of Oslo, Oslo. bard.lundeland@medisin.uio.no
Bård
B
Lundeland
Helene
H
Osterholt
Yngvar
Y
Gundersen
Per-Kristian
PK
Opstad
Ingjerd
I
Thrane
Yan
Y
Zhang
Richard W
RW
Olaussen
Per
P
Vaagenes
D000328:Adult; D002470:Cell Survival; D005434:Flow Cytometry; D006801:Humans; D006979:Hyperthermia, Induced; D007035:Hypothermia / Q000097:blood / Q000503:physiopathology*; D016753:Interleukin-10 / Q000096:biosynthesis*; D053583:Interleukin-1beta / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D015398:Signal Transduction / Q000502:physiology*; D013696:Temperature; D051197:Toll-Like Receptor 4 / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
D053583:Interleukin-1beta; D008070:Lipopolysaccharides; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10