Hydrogen Gas Inhalation Attenuates Endothelial Glycocalyx Damage and Stabilizes Hemodynamics in a Rat Hemorrhagic Shock Model

BACKGROUND: Hydrogen gas (H(2)) inhalation during hemorrhage stabilizes post-resuscitation hemodynamics, improving short-term survival in a rat hemorrhagic shock and resuscitation (HS/R) model. However, the underlying molecular mechanism of H(2) in HS/R is unclear. Endothelial glycocalyx (EG) damage causes hemodynamic failure associated with HS/R. In this study, we tested the hypothesis that H(2) alleviates oxidative stress by suppressing xanthine oxidoreductase (XOR) and/or preventing tumor necrosis factor-alfa (TNF-α)-mediated syndecan-1 shedding during EG damage. METHODS: HS/R was induced in rats by reducing mean arterial pressure (MAP) to 35 mm Hg for 60 min followed by resuscitation. Rats inhaled oxygen or H(2) + oxygen after achieving shock either in the presence or absence of an XOR inhibitor (XOR-I) for both the groups. In a second test, rats received oxygen alone or antitumor necrosis factor (TNF)-α monoclonal antibody with oxygen or H(2). Two hours after resuscitation, XOR activity, purine metabolites, cytokines, syndecan-1 were measured and survival rates were assessed 6 h after resuscitation. RESULTS: H(2) and XOR-I both suppressed MAP reduction and improved survival rates. H(2) did not affect XOR activity and the therapeutic effects of XOR-I and H(2) were additive. H(2) suppressed plasma TNF-α and syndecan-1 expression; however, no additional H(2) therapeutic effect was observed in the presence of anti-TNF-α monoclonal antibody. CONCLUSIONS: H(2) inhalation after shock stabilized hemodynamics and improved survival rates in an HS/R model independent of XOR. The therapeutic action of H(2) was partially mediated by inhibition of TNF-α-dependent syndecan-1 shedding.