Constitutive hydrogen inhalation prevents vascular remodeling via reduction of oxidative stress

Molecular hydrogen is thought to have an inhibitory effect on oxidative stress, thereby attenuating the onset and progression of various diseases including cardiovascular disease; however, few reports have assessed the preventive effect of constitutive inhalation of hydrogen gas on of vascular remodeling. Here, we investigated the effect of constitutive inhalation of hydrogen gas on vascular neointima formation using a cuff-induced vascular injury mouse model. After constitutive inhalation of compressed hydrogen gas (O2 21%, N2 77.7%, hydrogen 1.3%) or compressed air only (O2 21%, N2 79%) by C57BL/6 mice for 2 weeks from 8 weeks of age in a closed chamber, inflammatory cuff injury was induced by polyethylene cuff placement around the femoral artery under anesthesia, and hydrogen gas administration was continued until sampling of the femoral artery. Neointima formation, accompanied by an increase in cell proliferation, was significantly attenuated in the hydrogen group compared with the control group. NADPH oxidase NOX1 downregulation in response to cuff injury was shown in the hydrogen group, but the expression levels of NADPH oxidase subunits, p40phox and p47phox, did not differ significantly between the hydrogen and control groups. Although the increase in superoxide anion production did not significantly differ between the hydrogen and control groups, DNA damage was decreased as a result of reduction of reactive oxygen species such as hydroxyl radical (⋅OH) and peroxynitrite (ONOO-) in the hydrogen group. These results demonstrate that constitutive inhalation of hydrogen gas attenuates vascular remodeling partly via reduction of oxidative stress, suggesting that constitutive inhalation of hydrogen gas at a safe concentration in the living environment could be an effective strategy for prevention of vascular diseases such as atherosclerosis.普遍认为分子氢（Molecular hydrogen）对氧化应激（oxidative stress）具有抑制作用，由此可缓解包括心血管疾病（cardiovascular disease）在内的多种疾病的发生与进展；然而，目前鲜有研究评估持续性吸入氢气对血管重构（vascular remodeling）的预防效果。本研究采用袖带诱导血管损伤小鼠模型（cuff-induced vascular injury mouse model），探究了持续性吸入氢气对血管新内膜形成（neointima formation）的影响。C57BL/6小鼠自8周龄起，于密闭舱内分别持续性吸入压缩氢气（氧气21%、氮气77.7%、氢气1.3%）或仅吸入压缩空气（氧气21%、氮气79%），持续2周；随后在麻醉状态下于股动脉（femoral artery）周围放置聚乙烯袖带（polyethylene cuff）以诱导炎性袖带损伤，并持续给予氢气吸入直至股动脉取材。与对照组相比，氢气吸入组的新内膜形成（伴随细胞增殖水平升高）得到显著缓解。研究观察到，氢气吸入组中袖带损伤诱导的NADPH氧化酶NOX1（NADPH oxidase NOX1）表达下调，但两组间NADPH氧化酶亚基（NADPH oxidase subunits）p40phox与p47phox的表达水平无显著差异。尽管两组的超氧阴离子（superoxide anion）生成增幅无显著差异，但氢气吸入组可通过降低羟基自由基（hydroxyl radical ·OH）、过氧亚硝基阴离子（peroxynitrite ONOO-）等活性氧（reactive oxygen species）的水平，减少DNA损伤。上述结果表明，持续性吸入氢气可部分通过减轻氧化应激缓解血管重构，提示在生活环境中以安全浓度持续性吸入氢气，或可成为预防动脉粥样硬化（atherosclerosis）等血管疾病的有效策略。