Effect of melatonin on human nighttime endotoxaemia: Randomized, double-blinded, cross-over study

Background: Endotoxaemia is widely used as an experimental model to study sepsis under controlled conditions. Nighttime endotoxaemia induces a more pronounced inflammatory stress response compared to daytime. Previously, we have shown that melatonin has antioxidative and anti-inflammatory effects in inflammatory response to daytime endotoxaemia. Herein, we examined the effect of melatonin in response to human nighttime endotoxaemia. Patients and Methods: Twelve healthy male volunteers were enrolled in a randomized, placebocontrolled, double-blinded cross-over trial. Subjects were induced by lipopolysaccharide (LPS) endotoxin 0.3 ng/kg body weight intravenously at 24:00. One hour prior to induction of endotoxaemia, an 8-h infusion of melatonin 100 mg or placebo was initiated. Blood samples were drawn before and 2, 4, 6 and 8 h after induction of endotoxaemia and plasma was tested for pro-inflammatory markers (tumor necrosis factor alpha, TNF-α, interleukin-1β, IL-1β, interleukin-1, IL-6, and YKL-40 ), anti-inflammatory markers (interleukin-1 receptor antagonist, IL-1Ra, interleukin-10, IL-10, soluble tumor necrosis factor receptors I and II, sTNF-RI and sTNF-RII ), marker for oxidative damage (malondialdehyde (MDA)) and antioxidative enzyme (ascorbic acid (AA) and dehydroascorbic acid (DHA)). Results: Compared to placebo, melatonin did not reduce plasma levels of any of pro- and anti-inflammatory markers and it also failed to influence levels of AA, DHA and MDA. Conclusion: Melatonin has no beneficial effect on inflammation and oxidative damage induced by nighttime endotoxaemia in contrast to daytime endotoxaemia.