4-型磷酸二酯酶(PDE4)对饮酒行为的调节作用及其细胞内信号机制

Alcoholism and alcohol abuse are serious social and health problems in many countries in the world particularly in China. Unfortunately, there are no effective therapeutic approaches for these due to the lack of ideal drug targets for excessive alcohol drinking. Our recent studies have demonstrated that phosphodiesterase-4 (PDE4), an enzyme that catalyzes the hydrolysis of the second messenger cyclic AMP (cAMP), is an important target for regulating alcohol consumption. PDE4 inhibitors increase cAMP levels in the striatum of the brain and decrease alcohol intake and preference in rodents that normally drink excessive alcohol. However, emesis, which is the major side effect of PDE4 inhibitors, has limited the clinical utility of this class of drugs. PDE4 has four subtypes (PDE4A-D), which are encoded by four distinct genes. Among them, PDE4B is predominantly distributed in the striatum, a brain region that is important in the mediation of alcoholism and alcohol abuse. Given the fairly low expression in emesis-related brain regions such as the area postrema and the nucleus of the solitary tract, PDE4B may be a unique target for treatment of alcoholism and alcohol abuse. In the proposed project, we will determine the roles of PDE4, its subtype PDE4B, and PDE4B1 (one of the five PDE4B splice variants) in the striatum in regulating alcohol drinking and preference using approaches of pharmacology, gene knockout, and lentiviral vector-mediated gene knockdown and overexpression. In addition, the contribution of individual PDE4 subtypes to emetic responses also will be examined. Successful completion of the proposed experiments will not only help understand the important role of PDE4 in regulating alcohol drinking behavior and its mechanisms and develop highly selective PDE4B inhibitors with great efficacy and minimal side effects, but could lead to a breakthrough in studies of identifying the role of other PDE families such as PDE1 and PDE10, which are enriched in the striatum, in the mediation of alcoholism.

酒精依赖是我国面临的严重的社会与健康问题。但因缺乏理想药物作用靶，目前尚无有效的治疗手段。我们发现，催化cAMP水解的4-型磷酸二酯酶(PDE4)是调节饮酒行为的重要靶标。PDE4抑制剂增高脑内纹状体cAMP，减少动物对酒精的偏爱，但也产生呕吐样副反应。在四种PDE4亚型(A-D)中，PDE4B在纹状体(调节酒精成瘾的重要脑区)分布占绝对优势，并以PDE4B1(五个PDE4B剪切变异体之一)表达最高。鉴于PDE4B在延髓呕吐中枢分布很低，故它作为治疗酒精依赖和成瘾药物的靶标将独具特色。本项目用特异脑区给药、基因敲除、敲减或过表达等技术，从行为、神经化学和分子生物学等多层次研究纹状体内PDE4、PDE4B及其变异体PDE4B1对饮酒行为的调节作用及其机制。这不仅将为研发高效低毒的选择性PDE4B抑制剂奠定基础，而且对探讨纹状体表达丰富的其它PDE的中枢调节功能将具有开拓性的意义。

环腺苷酸—蛋白激酶A(cAMP-PKA)信号通路已被证明调节酒精依赖。4-型磷酸二酯酶(PDE4)是催化cAMP的重要水解酶。在四种PDE4亚型(A-D)中，PDE4B在纹状体(调节酒精成瘾的重要脑区)分布占绝对优势，并以PDE4B1(五个PDE4B剪切变异体之一)表达最高。本研究的目的是探讨PDE4B，PDE4B1在调节饮酒行为中的作用及其作用机制。我们首先检查的PDE4B在对酒精明显偏爱的C57BL / 6 j (B6)小鼠和对酒精不偏爱的DBA / 2 j(DBA)小鼠中的差异。然后特异性脑区（纹状体）给予rolipram，采用双瓶选择实验观察其对B6小鼠饮酒行为的影响及其机制。我们采用腺相关病毒制备PDE4B1基因敲减或过表达小鼠，观察其饮酒行为。结果显示，B6小鼠纹状体内PDE4B的表达明显高于DBA小鼠。且B6小鼠饮酒后纹状体内PDE4B明显增加。而纹状体内给予rolipram后，不仅B6小鼠饮酒行为和纹状体PDE4B减少，cAMP，pCREB和BDNF表达也有所增加。提示，纹状体内PDE4B可能通过cAMP-CREB-BDNF信号通路调控小鼠行为。PDE4B1基因敲减或过表达小鼠结果显示，PDE4B1过表达小鼠饮酒行为明显高于对照小鼠，而PDE4B1敲减小鼠的饮酒行为少于对照小鼠。与此同时cAMP-CREB-BDNF信号通路在PDE4B1过表达小鼠纹状体内被抑制，而在在PDE4B1敲减小鼠纹状体内被激活。这些结果表明，PDE4B，尤其是PDE4B1，通过介导cAMP信号在调控饮酒行为的中起到关键作用。因此，PDE4B1可能是治疗酒精成瘾的一个新靶标。并且PDE7等亚型参与饮酒行为。综上所述，PDE是调节饮酒行为的重要靶标。

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