Molecular hydrogen potentiates hypothermia and prevents hypotension and fever in LPS-induced systemic inflammation.

Molecular hydrogen (H2) exerts anti-oxidative, anti-apoptotic, and anti-inflammatory effects. Here we tested the hypothesis that H2 modulates cardiovascular, inflammatory, and thermoregulatory changes in systemic inflammation (SI) induced by lipopolysaccharide (LPS) at different doses (0.1 or 1.5 mg/kg, intravenously, to induce mild or severe SI) in male Wistar rats (250-300 g). LPS or saline was injected immediately before the beginning of 360-minute inhalation of H2 (2% H2, 21% O2, balanced with nitrogen) or room air (21% O2, balanced with nitrogen). Deep body temperature (Tb) was measured by dataloggers pre-implanted in the peritoneal cavity. H2 caused no change in cardiovascular, inflammatory parameters, and Tb of control rats (treated with saline). During mild SI, H2 reduced plasma surges of proinflammatory cytokines (TNF-α and IL-6) while caused an increase in plasma IL-10 (anti-inflammatory cytokine) and prevented fever. During severe SI, H2 potentiated hypothermia, and prevented fever and hypotension, which coincided with reduced plasma nitric oxide (NO) production. Moreover, H2 caused a reduction in surges of proinflammatory cytokines (plasma TNF-α and IL-1ß) and prostaglandin E2 [(PGE2), in plasma and hypothalamus], and an increase in plasma IL-10. These data are consistent with the notion that H2 blunts fever in mild SI, and during severe SI potentiates hypothermia, prevents hypotension reducing plasma NO production, and exerts anti-inflammatory effects strong enough to prevent fever by altering febrigenic signaling and ultimately down-modulating hypothalamic PGE2 production.