Effects of hydrogen-rich saline on inflammatory responses during transient cerebral ischemia-reperfusion in rats

Abstract

Objective To evaluate the effect of hydrogen-rich saline on inflammatory responses during transient cerebral ischemia-reperfusion (I/R) in rats. Methods Forty-five male Sprague-Dawley rats, aged 5-6 yr, weighing 180-250 g, were randomly divided into 3 groups (n=15 each) using a random number table: sham operation group (group S), group I/R and hydrogen-rich saline group (group H). The rats were anesthetized with intraperitoneal 10% chloral hydrate 0.3 ml/100 g. Transient cerebral ischemia was induced by bilateral common carotid artery occlusion with hypotension for 15 min, followed by reperfusion. Five rats were randomly chosen from each group, and Morris water maze was used to assess the cognitive function starting from 5 days before establishment of the model. Place navigation test lasted for 5 consecutive days. The escape latency, swimming speed and swimming distance were recorded. Spatial probe test was carried out on 1 and 3 days after establishment of the model. The time of staying at the target platform quadrant, frequency of crossing the original platform and swimming speed were recorded. The rats were sacrificed after the end of spatial probe test on 3 days after the model was established, and hippocampi were removed to examine the morphology of neurons in hippocampal CA1 region with light microscope. Five rats randomly chosen from each group were sacrificed on 1 day after the model was established, and hippocampi were removed to detect the contents of tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β). The rest 5 rats in each group were sacrificed, and hippocampi were removed for determination of nuclear factor kappa B (NF-κB) activity (by immuno-histochemistry). Results In place navigation test before the model was established, the escape latency and swimming distance were gradually shortened with the prolonging training time, and no significant change was found in the swimming speed with the prolonging training time in the three groups. Compared with group S, the time of staying at the target platform quadrant was significantly shortened, and the frequency of crossing the original platform was reduced on 1 and 3 days after establishment of the model, and the contents of TNF-α and IL-1β and NF-κB activity were increased on 1 day after establishment of the model in group I/R. Compared with group I/R, the time of staying at the target platform quadrant was significantly prolonged, and the frequency of crossing the original platform was increased on 1 and 3 days after establishment of the model, and the contents of TNF-α and IL-1β and NF-κB activity were decreased on 1 day after establishment of the model in group H. There was no significant change in the swimming speed during spatial probe test on 1 and 3 days after establishment of the model. Conclusion The mechanism by which hydrogen-rich saline reduces transient cerebral I/R injury may be related to inhibition of inflammatory responses in rats. Key words: Hydrogen; Reperfusion injury; Brain; Inflammation