缺氧缺血新生大鼠脑组织水通道蛋白4的表达变化

目的 研究缺氧缺血性脑损伤(HIBD)病理过程中水通道蛋白4(aquaporin-4,AQP-4)的作用及其意义.方法 120只7日龄新生Wistar大鼠按照完全随机化方法分为4部分,每部分(n=30)再分为对照组、HIBD后6 h、24 h、3 d、5 d和7 d共6组,每组5只.分别测定脑组织含水量;原位杂交和免疫组化检测AQP-4表达;检测脑组织病理变化.结果 HIBD组6 h,24 h,3 d的脑组织含水量较对照组显著增加(P＜0.05);且各组脑组织含水量随时间延长而增加,组间差异有统计学意义(P＜0.05);HIBD 5 d,7 d组脑组织含水量与对照组比较差异无统计学意义(P＞0.05).对照组AQP-4 mRNA和AQP-4蛋白少量表达(吸光度A值为0.29±0.07和0.06±0.01).与对照组相比,HIBD后6～24 h,AQP-4 mRNA和AQP-4蛋白表达显著增加.AQP-4 mRNA的A值由0.42±0.04上升到0.80±0.02(P＜0.05);AQP-4蛋白A值由0.14±0.03上升到0.23±0.05(P＜0.05),同时光镜下可见脑组织轻度水肿;3 d时AQP-4 mRNA和蛋白表达达高峰,AQP-4 mRNA的A值为0.91±0.08,AQP-4蛋白A值为0.41±0.04,此时脑组织严重水肿,神经元、胶质细胞和内皮细胞明显肿胀;第5～7天AQP-4的表达已下降(尤其mRNA明显),但仍显著高于对照组(P＜0.05),此时脑水肿已减轻.在整个HIBD脑水肿形成的过程中,AQP-4 mRNA和蛋白的表达呈正相关(rs＞0.82,Ps＜0.05).结论 AQP-4参与了HIBD的发生发展过程,AQP-4在HIBD脑水肿的形成过程中可能起重要作用.

Changes of aquaporin-4 expression in brain tissue of hypoxic-ischemic neonatal rats

Objective To study the relationship between the expression of aquaporin-4(AQP-4) and hypoxic-ischemic brain damage (HIBD) in neonatal rats. Metheods Totally 120 seven-day-old Wistar rats were assigned to four parts, each part (n=30) was divided into six groups, including control group, HIBD 6 h,24 h,3 d,5 d,7 d(n=5 per group ). The model of HIBD was induced by unilateral carotid ligation followed by exposure to 8% oxygen. In situ hybridization and immunohistochemistry were respectively used to evaluate AQP-4 mRNA and protein expression, and the light microscopic changes were observed by HE staining.Results The brain water content was increased markedly in HIBD group after 6 h,24 h, 3 d of HIBD and increased further with time in neonatal rats compared with that in the control group. The expression levels of AQP-4 mRNA and protein were low in the control group. Compared with the control group, there showed significant increase in AQP-4 mRNA and protein expression on the cerebral tissue at the 6th and 24th hour in rats following HIBD. AQP-4 mRNA expression(A Value) increased from 0.42±0.04 to 0.80±0. 02 (P＜0. 05) and AQP-4 protein expression (A) increased from 0.14±0.03 to 0.23±0.05. Histological study showed that the cerebral tissue had a light swelling. At day 3, the expression levels of AQP-4 mRNA and protein reached at its maximum. AQP-4 mRNA expression(A) reached at 0.91±0.08 and AQP-4 protein expression(A) at 0.41±0. 04 (P＜0.05 ). The brain edema became remarkable, neurons and glias together with endothelial cells were all remarkably swelling. At day 5 and 7, the expression levels of AQP-4 mRNA and protein in HIBD group were still higher than those in the control group(P＜0.05), and the brain edema were not remarkable. The AQP-4 mRNA expression showed a positive correlation with the AQP-4 protein expression during the HIBD formation (rs＞0. 82, Ps＜0.05 ). Conclusions The increased expression of AQP-4 participates in the development of cerebral edema after HIBD. AQP-4 may play an important role in the pathological development of HIBD.