Luo Ying, Kuang Shengnan, Li Huan, Ran Dongzhi, Yang Junqing
Department of Pharmacology, Chongqing Medical University, Chongqing, China.
Chongqing Key Laboratory of Biochemistry and Molecular Pharmacology, Chongqing, China.
Oncotarget. 2017 May 30;8(22):35558-35572. doi: 10.18632/oncotarget.16009.
To investigate the mechanism of cyclooxygenase 2 (COX2) in learning and memory impairments in rats subjected to chronic unpredictable mild stress (CUMS), meloxicam was used intragastrically to inhibit the activity of cyclooxygenase 2. Moreover, cyclooxygenase 2 over-expressing or RNA interfere lentivirus was injected intraventricularly to increase or decrease the enzyme's expression, respectively. The body weights and sucrose consumption were used to analyze depressive behaviors, while the Morris water maze and step-down-type passive avoidance tests were carried out to evaluate the learning-memory functions. The levels of inflammatory cytokines were measured to estimate inflammation and the contents of cyclic adenosine monophosphate (cAMP) were used to measure the levels of the second messenger. Changes in cyclooxygenase 2 mRNA levels were analyzed using reverse transcription polymerase chain reaction. Moreover, the expression of cyclooxygenase 2, brain-derived neurotrophic factor (BDNF), prostaglandins receptor 3 (EP3), protein kinase A (PKA), cAMP response element binding protein (CREB), and phosphorylated CREB were estimated using immunohistochemical staining or western blotting. The results showed that CUMS led to significant depressive-like behaviors and learning and memory dysfunctions. Also, the cAMP levels decreased significantly, while levels of inflammatory cytokines and prostaglandins E2 increased significantly. The expressions of PKA, BDNF, phosphorylated CREB/CREB declined and cyclooxygenase 2 was increased. Meloxicam and cyclooxygenase 2 RNA interfere lentivirus reversed the changes caused by CUMS while cyclooxygenase 2-overexpressing lentivirus worsened these abnormalities. The findings also showed that CUMS increased cyclooxygenase 2 expression, which can cause learning and memory impairments, mainly through activating the hippocampal neuronal cAMP/PKA-CREB-BDNF signaling pathways.
为研究环氧化酶2（COX2）在慢性不可预测性轻度应激（CUMS）大鼠学习记忆障碍中的作用机制，采用美洛昔康灌胃抑制环氧化酶2的活性。此外，分别脑室内注射环氧化酶2过表达或RNA干扰慢病毒以增加或降低该酶的表达。通过体重和蔗糖消耗量分析抑郁行为，同时进行Morris水迷宫和跳台法被动回避试验评估学习记忆功能。检测炎症细胞因子水平以评估炎症反应，采用环磷酸腺苷（cAMP）含量检测第二信使水平。运用逆转录聚合酶链反应分析环氧化酶2 mRNA水平的变化。此外，采用免疫组织化学染色或蛋白质印迹法检测环氧化酶2、脑源性神经营养因子（BDNF）、前列腺素受体3（EP3）、蛋白激酶A（PKA）、cAMP反应元件结合蛋白（CREB）及磷酸化CREB的表达情况。结果显示CUMS导致大鼠出现明显的抑郁样行为及学习记忆功能障碍。同时，cAMP水平显著降低，而炎症细胞因子及前列腺素E2水平显著升高。PKA、BDNF、磷酸化CREB/CREB的表达下降，环氧化酶2表达增加。美洛昔康及环氧化酶2 RNA干扰慢病毒可逆转CUMS所致的改变，而环氧化酶2过表达慢病毒则加重这些异常。研究结果还表明，CUMS可增加环氧化酶2表达，其主要通过激活海马神经元cAMP/PKA-CREB-BDNF信号通路导致学习记忆障碍。
