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

Background:Hydrogen gas (H²) 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 H²in HS/R is unclear. Endothelial glycocalyx (EG) damage causes hemodynamic failure associated with HS/R. In this study, we tested the hypothesis that H²alleviates 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 35mm Hg for 60min followed by resuscitation. Rats inhaled oxygen or H²+ 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 H². Two hours after resuscitation, XOR activity, purine metabolites, cytokines, syndecan-1 were measured and survival rates were assessed 6h after resuscitation.Results:H²and XOR-I both suppressed MAP reduction and improved survival rates. H²did not affect XOR activity and the therapeutic effects of XOR-I and H²were additive. H²suppressed plasma TNF-α and syndecan-1 expression; however, no additional H²therapeutic effect was observed in the presence of anti-TNF-α monoclonal antibody.Conclusions:H²inhalation after shock stabilized hemodynamics and improved survival rates in an HS/R model independent of XOR. The therapeutic action of H²was partially mediated by inhibition of TNF-α-dependent syndecan-1 shedding.