Effects of High-Pressure Oxygen Therapy on Brain Tissue Water Content and AQP4 Expression in Rabbits with Cerebral Hemorrhage

Abstract

To investigate the effects of different atmosphere absolutes (ATA) of high-pressure oxygen (HPO) on brain tissue water content and Aquaporin-4 (AQP4) expression in rabbits with cerebral hemorrhage. 180 New Zealand white rabbits were selected and randomly divided into normal group (n = 30), control group (n = 30) and cerebral hemorrhage group (n = 120), and cerebral hemorrhage group was divided into group A, B, C and D with 30 rabbits in each group. The groups received 1.0, 1.8, 2.0 and 2.2 ATA of HPO treatments, respectively. Ten rabbits in each group were killed at first, third and fifth day to detect the brain tissue water content and change of AQP4 expression. In cerebral hemorrhage group, brain tissue water content and AQP4 expression after model establishment were first increased, then decreased and reached the maximum on third day (p < 0.05). Brain tissue water content and AQP4 expression in control group and cerebral hemorrhage group were significantly higher than normal group at different time points (p < 0.05). In contrast, brain tissue water content and AQP4 expression in group C were significantly lower than in group A, group B, group D and control group (p < 0.05). In control group, AQP4-positive cells significantly increased after model establishment, which reached maximum on third day, and positive cells in group C were significantly less than in group A, group B and group D. We also found that AQP4 expression were positively correlated with brain tissue water content (r = 0.719, p < 0.05) demonstrated by significantly increased AQP4 expression along with increased brain tissue water content. In conclusion, HPO can decrease AQP4 expression in brain tissue of rabbits with cerebral hemorrhage to suppress the progression of brain edema and promote repairing of injured tissue. 2.0 ATA HPO exerts best effects, which provides an experimental basis for ATA selection of HPO in treating cerebral hemorrhage.

The efficacy of hyperbaric oxygen in hemorrhagic stroke: experimental and clinical implications

“…The intervention resulted in a 38.7% reduction in perihematomal edema 24 h after ICH [ 24 ]. Thus, the brain water reduction was more modest than the complete reduction achieved with 2 ATA and the 74.8% reduction with 2.2 ATA as shown previously by Wu et al at 24 h after ICH in rabbits [ 21 ].…”

“…These authors found that HBO at 2 ATA exerted an optimal effect. At 2 ATA, the excess in brain tissue water content over the sham level was reduced by 67.7% on day 3 and 79.5% on day 5 as compared to the untreated control [ 21 ]. The HBO at other pressures (1.8 ATA and 2.2 ATA) reduced brain water content by about 40% on the third and fifth days.…”

“…In these studies, preconditioning yielded smaller reductions in brain water content than with early post-treatment with HBO at 2 ATA, associated with a 67.7% reduction rate on day 3 [ 21 ]. Likewise, the reductions in AQP4 expression were smaller with 2 ATA HBO-PC as compared to 2 ATA HBO treatment: 39.2% vs. 66.7% and 52.83% vs. 89%, as determined on days 3 and 5, respectively [ 21 , 28 ].…”

“…This 30–40% edema reduction range with HBOT (or closer to 20% in permanent ischemia) has been reported by most experimental studies of focal ischemic stroke [ 36 , 37 ]. Thus, reductions in brain water content with HBO seem smaller after focal brain ischemia than after hemorrhage, with over 70% reductions reported with HBOT and 50% with HBO-PC at 24 h after hemorrhage [ 21 , 26 ]. This result may indicate that relatively mild, predominantly perihematomal edema after hemorrhage more effectively responds to HBOT.…”