Methamphetamine administration causes differential alterations in gene expression and dynamic patterns of histone acetylation/hypoacetylation in the rat nucleus accumbens

Methamphetamine (METH) addiction is associated with a plethora of neuropsychiatric symptoms. In rodents, administration of the drug is accompanied by complex changes in gene expression in the dorsal striatum. Very little is known about the effects of the drug on gene expression and epigenetic modifications in the nucleus accumbens (NAc). The present study was conducted in order to investigate the effects of a single injection of METH on gene expression in that structure. We also queried whether changes in transcript levels were accompanied by alterations in histone acetylation as well as in the expression of the histone acetyltransferase (HAT), ATF2, and of the histone deacetylases (HDACs), HDAC1 and HDAC2. Microarray analyses revealed that METH caused significant time-dependent increases in the expression of several genes that had previously been implicated in the acute and longterm effects of psychostimulants in the brain. These include several immediate early genes (c-fos, Egrs, c-jun, and Nurr1) and corticotropin-releasing factor (Crf). There were also increases in the levels of neuromedin U, Tnf-alpha, and Kcnk18, among others. In contrast, the METH injection caused decreases in the expression of many genes including Npas4 and cholecystokin (Cck). Pathway analyses showed that differentially affected genes participate in behavioral performance, cell-to-cell signaling and interactions, and regulation of gene expression. Other differentially affected genes are known to be involved in cellular compromise and death pathways. PCR analyses were used to confirm the changes in the expression of c-fos, fosB, c-jun, junB, Crf, NmU, Cck, and Npas4 transcripts. Western blot analyses also identified METH-mediated decreases in the acetylation of histone H3 at lysine 9 (H3K9) and lysine 18 (H3K18) as well as in histone 4 at lysine 16 (H4K16). In contrast, the METH injection caused time-dependent increases in the acetylation of H4K8 and H4K12. The changes in histone acetylation were also accompanied by decreased expression of HDAC1 but increased expression of ATF2 and of HDAC2. These results suggest that METH-induced alterations in global gene expression might be due, in part, to diverse effects of METH-induced histone acetylation secondary to changes in HAT and HDAC expression.甲基苯丙胺（Methamphetamine, METH）成瘾与大量神经精神症状密切相关。在啮齿类动物中，给予该药物会伴随背侧纹状体基因表达的复杂改变。目前对于该药物对伏隔核（nucleus accumbens, NAc）内基因表达与表观遗传修饰的影响尚所知甚少。本研究旨在探究单次注射METH对该脑区基因表达的影响，并考察转录水平的变化是否伴随组蛋白乙酰化的改变，以及组蛋白乙酰转移酶（histone acetyltransferase, HAT）ATF2、组蛋白去乙酰化酶（histone deacetylases, HDACs）HDAC1与HDAC2的表达变化。基因芯片分析显示，METH可使多种与中枢神经系统精神兴奋剂急性及长期效应相关的基因表达出现显著的时间依赖性升高，其中包括多种即刻早期基因（c-fos、Egrs、c-jun及Nurr1）以及促肾上腺皮质激素释放因子（Crf）。此外，神经介素U、肿瘤坏死因子-α（Tnf-α）、Kcnk18等基因的表达水平也有所上调。与之相反，单次注射METH可导致包括神经PAS结构域蛋白4（Npas4）、胆囊收缩素（Cck）在内的多种基因表达下调。通路分析结果表明，受差异调控的基因参与了行为表现、细胞间信号传导与相互作用以及基因表达调控等生物学过程。另有部分受差异影响的基因已知参与细胞损伤与死亡通路。采用聚合酶链式反应（PCR）验证了c-fos、fosB、c-jun、junB、Crf、NmU、Cck及Npas4转录本的表达变化。蛋白质印迹（Western blot）分析还发现，METH介导了组蛋白H3赖氨酸9位点（H3K9）、赖氨酸18位点（H3K18）以及组蛋白H4赖氨酸16位点（H4K16）的乙酰化水平降低；与之相反，METH注射可引起H4K8与H4K12位点的乙酰化水平呈现时间依赖性升高。组蛋白乙酰化的变化同时伴随HDAC1表达下调，而ATF2与HDAC2的表达则出现上调。上述结果提示，METH诱导的全局基因表达改变可能部分归因于METH通过改变HAT与HDAC的表达，进而引发的多样化组蛋白乙酰化效应。