Adenosine infusion attenuates soluble RAGE in endotoxin-induced inflammation in human volunteers

To evaluate possible anti-inflammatory effects of pre-treatment with adenosine in a human experimental inflammatory model.

The study design was double-blind, crossover, placebo-controlled and randomized. In the Intensive Care Unit of a university hospital, 16 healthy male volunteers were treated for 5.5 h with infusions of adenosine 40 microg kg(-1) min(-1) or placebo. Thirty minutes after the start of adenosine or placebo, 2 ng kg(-1)E-Coli endotoxin was administered. Heart rate, body temperature, blood pressure, plasma cytokines (TNF-alpha, IL-6 and IL-10), soluble RAGE and resistin, exhaled nitric oxide and nitrite/nitrate in urine were determined.

Endotoxin elicited the expected clinical signs of an inflammatory reaction (tachycardia, fever) and led to prominent release of the cytokines studied (P < 0.001). Resistin in plasma increased after endotoxin (P < 0.001). After placebo treatment, soluble RAGE (sRAGE) in plasma increased 5 h after the endotoxin challenge (P < 0.001) but not after adenosine. After placebo, orally exhaled NO increased with a peak at 4 h (P < 0.001), although there was no statistically significant difference between the two treatments. Nitrite/nitrate in urine (n = 11) did not differ between adenosine and placebo treatments.

In conclusion, adenosine infusion starting before endotoxin challenge in humans attenuated sRAGE significantly but otherwise had no clear anti-inflammatory effect. Adenosine as a potential anti-inflammatory treatment in humans needs further study, including use of higher doses. The mechanism underlying the effect of adenosines on sRAGE remains unknown.