Background & Objectives: Hydrogen gas is widely considered to be a novel antioxidant1). It has been demonstrated that inhalation of hydrogen gas reduced ischemic cerebral injury in several investigations. However, it remains unclear whether the neuroprotective effect of hydrogen gas is reproducible in a rat transient forebrain ischemia model (i.e. the Smith model). The current study was conducted to evaluate the effect of hydrogen gas on histological outcome after 7-day recovery period in rats subjected to transient forebrain ischemia.
Materials & Methods: After approval by the animal research committee, male Sprague-Dawley rats were randomly assigned to one of the following 2 groups: control group, or hydrogen gas group (n=6 in each group). In the hydrogen gas group, transient forebrain ischemia was induced by a combination of hemorrhagic hypotension (mean arterial pressure= 40 mmHg) and bilateral carotid artery occlusion following 2.5% of sevoflurane anesthesia. The brain was reperfused 10 minutes after the onset of ischemia, and after 1 hour, the sevoflurane anesthesia was discontinued. 1.3% hydrogen gas inhalation began 10 min prior to the onset of ischemia, and was continued until the discontinuation of the anesthesia. Temporalis muscle temperature was maintained at approximately 37.5 degrees throughout the procedure. In the control group, all treatments were the same as the hydrogen gas group except for the hydrogen gas inhalation. Seven days after ischemia, the rats were sacrificed for histological evaluation. The brain slices were stained with hematoxilin and eosin, and the coronal sections at hippocampal level were examined light-microscopically. The degree of neuronal damage in the CA1 subfield of the hippocampus was assessed using the following scale: 1 = no ischemic neurons; 2 = less than 20% ischemic neurons; 3 = 20~50% ischemic neurons; 4 = 50~80% ischemic neurons; 5 = more than 80% ischemic neurons; 6 = no intact neurons. Statistical analysis was performed with Mann-Whitney U test for group comparison.
Results: The median hippocampal injury scale was greater in the control group than in the hydrogen gas group (5 vs. 4; median [interquartile range], respectively, p=0.07).
Conclusion: The current study indicates that the treatment with 1.3% hydrogen gas is likely to provide a modest neuroprotective effect in a rat transient forebrain ischemia model.
References: 1. Ohsawa et al: Hydrogen acts as a therapeutic antioxidant by selectively reducing cytotoxic oxygen radicals. Nature Medicine 13: 688–94, 2007
Disclosure of Interest: G. Nagasaki Research grant/funding from: Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Tokyo, Japan, Y. Masaki: None declared, T. Horiguchi: None declared, T. Nishikawa: None declared, M. Takahashi: None declared