Abstract 188: Investigation of the Mechanism of Action of Hydrogen Gas in Hemorrhagic Shock

Abstract

Background: Molecular hydrogen gas (H 2 ) is known to alleviate ischemia-reperfusion injury; however, the mechanism of action involved remains unknown. Metabolome analysis of tissue subjected to ischemia-reperfusion injury has revealed xanthine oxidoreductase (XOR) as a candidate target molecule for H 2. Purpose: The effects of H 2 and the XOR inhibitor (XORi) on resuscitation after hemorrhagic shock (HS) were examined. Methods: Male Sprague-Dawley rats were subjected to HS by the withdrawal of blood to maintain a mean arterial pressure (MBP) of 35 mmHg for 60 minutes (T0 to T60). They were then resuscitated with lactated Ringer’s solution with 3 times the shed blood volume over 30 minutes (T60 to T90). The animals were randomly assigned into 3 groups: H 2 inhalation (1.3% H 2 ) from T30 (n=6), XORi administration (Topiroxostat 10 mg/kg, orally administered at 60 minutes before induction of HS) (n=5), and control (CTL) (n=5). The rats were observed until 2 hours after fluid resuscitation (T210). Results: Compared to that in the control group, the lactate level at 60 minutes after introduction of HS was lower in the XORi group, while the MBP after 2 hours of fluid resuscitation was higher in the H 2 group. XOR activity in the plasma, liver, kidney, and lung tissue was suppressed in the XORi group, but not in the H 2 group. Increased permeability of the pulmonary vasculature associated with increased levels of plasma inflammatory cytokines and plasma Syndecan-1 (a marker of endothelial glycocalyx degradation) after 2 hours of fluid resuscitation was ameliorated only in the H 2 group. Conclusion: The mechanisms of action possibly differ between H 2 and XORi. XORi confers resistance to ischemia by suppressing anaerobic glycolysis during ischemia. On the other hand, H 2 stabilizes hemodynamics via suppression of inflammation and vascular hyperpermeability after resuscitation.