Postconditioning With Inhaled Hydrogen Promotes Survival Of Retinal Ganglion Cells In A Rat Model Of Retinal Ischemia/Reperfusion Injury

Objective:Our study aims to explore whether postconditioning with inhaled H₂ can protect retinal ganglion cells（RGCs）in a rat model of retinal I/R injury.Methods:Retinal I/R injury was performed on the right eyes of rats and was followed by inhalation of 67%H₂ mixed with 33%oxygen immediately after ischemia for 1 h daily for one week.RGC density was counted using haematoxylin and eosin（HE）staining and retrograde labelling with cholera toxin beta（CTB）.Visual function was assessed using flash visual evoked potentials（FVEP）and pupillary light reflex（PLR）.Potential biomarkers of retinal oxidative stress and inflammatory responses were measured,including the expression of 4-Hydroxynonenalv（4-HNE）,interleukin-1beta（IL1-β）and tumour necrosis factor alpha（TNF-α）.The apotosis was determined using TUNEL assays.Results:HE and CTB tracing showed that the survival rate of RGCs in the H₂-treated group was significantly higher than the rate in the I/R group.Rats with H₂ inhalation showed better visual function in assessments of FVEP and PLR.Moreover,H₂treatment significantly decreased the number of 4-HNE-stained cells in the ganglion cell layer and inhibited the retinal overexpression of IL1-βand TNF-αthat was induced by retinal I/R injury.The number of TUNEL-positive cells/HPF in the GCL was effectively reduced by postconditioning with high-dose H₂ inhalation.Conclusion:Our results demonstrate that postconditioning with inhaled high-dose H₂appears to confer neuroprotection against retinal I/R injury via anti-oxidative,anti-inflammatory and anti-apotosis pathways.