Inhibition of retinal ischemia–reperfusion injury in rats by inhalation of low-concentration hydrogen gas

Purpose: To investigate the inhibitory effect of hydrogen gas inhalation on retinal ischemia reperfusion (I/R) injury using a rat model. Methods: Six-week-old male Sprague–Dawley rats were used. A 27G needle connected by a tube to a saline bottle placed 200 cm above the eye was inserted into the anterior eye chamber to create a rat retinal I/R model. In the ischemia-plus-hydrogen-gas group (H₂(+) group), the ischemia time was set to 90 min, and 1.8% hydrogen was added to the air delivered by the anesthesia mask simultaneously with the start of ischemia. In the non-hydrogen-treatment ischemia group (H₂(−) group), I/R injury was created similarly, but only air was inhaled. ERGs were measured; after removal of the eyes, the retina was examined for histological, immunostaining, and molecular biological analyses. Results: The mean thickness of the inner retinal layer in the H₂(+) group was 107.2 ± 16.0 μm (n = 5), significantly greater than that in the H₂(−) group (60.8 ± 6.7 μm). Immunostaining for Iba1 in the H₂(−) group showed increased numbers of microglia and microglial infiltration into the subretinal space, while there was no increase in microglia in the H₂(+) group. B-wave amplitudes in the H₂(+) group were significantly higher than in the H₂(−) group. In the membrane antibody array, levels of interleukin-6, monocyte chemotactic protein 1, and tumor necrosis factor alpha were significantly lower in the H₂(+) group than in the H₂(−) group. Conclusion: Inhalation of 1.8% hydrogen gas inhibited the induction of inflammation, morphological/structural changes, and glial cell increase caused by retinal I/R injury.