Research on the expression of aquaporin 9 gene and efficacy of mannitol in neonatal rats with hypoxia-ischemic brain edema / 中国新生儿科杂志

ABSTRACT

Objective To study the relationship between aquaporin 9 (AQP 9) gene and brain edema in neonatal rats of hypoxic-ischemic brain damage (HIBD) and the therapeutic mechanism of mannitol.Method Healthy and 7-day-old SD rats were randomly assigned into three groupssham-operated group,HIBD group and mannitol group.Both HIBD and mannitol group were established on HIBD model.The mannitol group was given mannitol intraperitoneally at 0,24,48 h of HIBD.2 ml/kg of 2％ Evans blue (EB) were injected intraperitoneally before sacrifice.0,6,12,24,48 and 72 h after HIBD,the outcomes were analyzed including the brain water content,the expression of AQP 9 mRNA measured using RT-PCR and immunofluorescence staining methods,and the permeability of blood-brain barrier (BBB) measured with EB.Result In HIBD group,the brain water content was higher comparing with sham-operated group at 0 h after HIBD(P ＜ 0.05),and gradually increased over time,reaching peak at 48 h (89.3％ ± 1.9％) and then decreased.In mannitol group,brain water content started to decrease from 1 h after mannitol administration to the bottom at 12 h (86.5％ ±0.6％),then increased to peak at 72 h (87.2％ ± 1.7％),and brain water content were decreased during 0 ～ 48 h comparing with HIBD group.HIBD group's EB were higher than sham-operated group (P ＜ 0.05);Mannitol group's EB were decreased comparing with HIBD group (except 0 h,P ＜ 0.05).AQP 9 mRNA expression in the HIBD group was decreased at 0 h,and reached the bottom at 48 h (0.09 ± 0.07).Comparing with sham-operated group,it was higher in the HIBD group at0,6,72 h,and lower (P＜ 0.05) at 12,24,48 h.Higher AQP 9 mRNA expression were detected in mannitol group than HIBD group and sham-operated group at each time point (with the exception of 48 h) (P ＜ 0.05).AQP 9,which was closely related to water metabolism,were widely found in the pia mater and ependyma using immunofluorescence staining.After ischemia and hypoxia insult,an increasedecrease-increase pattern of AQP 9 expression was found.Conclusion AQP 9 is widely existed in various parts of the brain,influencing brain edema through a variety of pathways.AQP 9 also plays a role in alleviating brain edema in mannitol therapy.