Abstract: Objective  To explore the protective effects and mechanism of hydrogen gas against acute kidney injury(AKI) induced by subarachnoid hemorrhage(SAH) in rats. 
Methods  SPF-grade male Sprague Dawley(SD) rats(weighing 350-400 g), were divided into control group(n=12), model group(n=12) and hydrogen treatment group(n=12) according to random number table method. In the model and hydrogen treatment group, SAH was induced by endovascular perforation combined with contrast agent and mannitol transfusion. At 24 h and 48 h after successful SAH modeling, the rats in the hydrogen treatment group were placed into anesthesia induction box filled with 2.9% hydrogen for 2 h, but the rats in the model group were only placed into the induction box filled with air. The rats in the control group were treated in the same fashion as model group except that the intracranial vessels were not punctured. At 72 h after SAH, 0.7-1.0 mL of blood samples was collected from aorta to measure the levels of blood urea nitrogen(BUN) and serum creatinine(SCr). After sampling via cardiac perfusion, the pathological changes of kidney, reactive oxygen species, expressions of B-cell lymphoma-2(bcl-2), bcl-2 associated-k(bak) and cleaved caspase-3, renal apoptosis were assessed by hematoxylin eosin staining, enzyme linked immunosorbent, western blot and TdT-mediated dUTP Nick-End Labeling(TUNEL) assays, respectively. In the cell experiment, renal tubular epithelial cells(NRK52E) were treated with 300 μmol/L hydrogen peroxide for 24 h to prepare an oxidative stress model. At 24 h, 48 h after intervention, the cells were treated with 2.9% hydrogen gas for 2 h. Then the contents of malondialdehyde(MDA), superoxide dismutase(SOD), and apoptotic rate of renal epithelial cells were detected. 
Results  The levels of BUN and SCr were higher in the model group and hydrogen treatment group than in the control group, which, however,were lower in hydrogen treatment group than in the model group(P＜0.05). The renal tubule injury scores were higher in the model group and hydrogen treatment group than in the control group, which, however, were lower in hydrogen treatment group than in the model group(P＜0.05). The ratio of bcl-2/bak protein in renal tissues of rats was lower, while the expression of cleaved caspase-3 was higher in the model group and hydrogen treatment group, as compared with those in the control group; the ratio of bcl-2/bak protein in renal tissues of rats was higher, while the expression of cleaved caspase-3 was lower in hydrogen treatment group, as compared with those in the model group(P＜0.05). The renal apoptosis significantly higher in the model group and hydrogen treatment group than in the model group, which was lower in hydrogen treatment group than in the model group(P＜0.05). In vitro, compared with control group, the MDA level and apoptosis rate of renal tubular epithelial cells were increased, but the SOD level and survival rate were decreased in the model group and hydrogen treatment group; the MDA level and apoptosis rate of renal tubular epithelial cells were lower, but the SOD level and survival rate were higher in the hydrogen treatment group, as compared with those in the model group(P＜0.05). 
Conclusion  Hydrogen gas exhibits a protective effect against SAH-induced AKI in rats, and the mechanism may be associated with the inhibition of ROS-induced renal cell apoptosis under hydrogen treatment. 

Key words: subarachnoid hemorrhage, acute kidney injury, hydrogen