Modulation of Nicotine Reward-Associated Behaviors by MicroRNAs

烟草使用的不良健康后果是全球可预防死亡的主要原因，每年导致约600万人死亡。烟草的成瘾成分是尼古丁，这是一种三级生物碱，可结合并激活烟碱乙酰胆碱受体（nAChR），即通常由内源性神经递质乙酰胆碱（ACh）激活的配体门控离子通道。神经元nAChR是由受体亚基的各种组合组装的五聚体，并且不同的亚基组合赋予受体亚型不同的亲和力和功能性。在哺乳动物神经元nAChR中已鉴定出11个亚基，<$2-<$7、<$9、<$10和<$2-<$4。有趣的是，慢性尼古丁或香烟烟雾暴露导致大脑中nAChR的上调，包括涉及奖励和成瘾的中皮质边缘多巴胺能（DA能）通路内的结构。虽然尚未完全理解，但尼古丁诱导的nAChR上调被认为通过改变神经网络而促成成瘾，可能导致对尼古丁的耐受性增加或敏感性改变。虽然有许多提出的nAChR上调的机制，它在很大程度上被认为是多种形式的转录后调节是负责这种现象。目前，还没有太多的了解哺乳动物nAChR亚基表达的转录后调控microRNA（miRNA），小的单链RNA分子，作为基因表达的负调控因子。然而，有新的证据表明，在各种啮齿动物组织类型中，响应于尼古丁暴露，miRNA表达降低。此外，最近的研究发现，miRNA在暴露于各种滥用药物（包括可卡因）时的失调可以影响药物的奖励特性并改变成瘾相关行为。我们最近产生的初步数据表明，一种新的监管机制，涉及miRNA可能是在尼古丁介导的nAChRs上调的工作。我们实验室的初步实验已经鉴定了几种预测靶向nAChR亚基mRNA转录物的miRNA，特别是分别靶向<$4和<$2转录物的miR-494和miR-542- 3 p。在目标1中，我将确定在原代中脑神经元培养物中miR- 494和/或miR-542- 3 p是否调节<$4和/或<$2。在目标2中，我将确定miR-494和/或miR- 542- 3 p是否是小鼠尼古丁奖励相关行为的调节剂。通过这些目标，我希望能够更好地了解miR-494和miR-542- 3 p在尼古丁奖励相关行为中的作用，可能揭示戒烟辅助药物开发的新靶点。

DESCRIPTION (provided by applicant): Adverse health consequences of tobacco use are the leading cause of preventable mortality worldwide, resulting in approximately 6 million deaths per year. The addictive component of tobacco is nicotine, a tertiary alkaloid that binds and activates nicotinic acetylcholine receptors (nAChRs), ligand-gated ion channels that are normally activated by the endogenous neurotransmitter acetylcholine (ACh). Neuronal nAChRs are pentamers assembled from various combinations of receptor subunits and different subunit combinations confer different affinities and functionalities to the receptor subtypes. Eleven subunits, ¿2- ¿7, ¿9, ¿10 and ¿2- ¿4, have been identified in mammalian neuronal nAChRs. Interestingly, chronic nicotine or cigarette smoke exposure results in the upregulation of nAChRs in the brain, including structures within the mesocorticolimbic dopaminergic (DAergic) pathway that is implicated in reward and addiction. While not completely understood, nicotine- induced upregulation of nAChRs is thought to contribute to addiction by altering the neural network, possibly resulting in increased tolerance or altered sensitivity to nicotine. While there are many proposed mechanisms for nAChR upregulation, it is largely believed that multiple forms of posttranscriptional regulation is responsible for this phenomenon. Currently, there is not much known about posttranscriptional regulation of mammalian nAChR subunit expression by microRNAs (miRNAs), small single stranded RNA molecules that function as negative regulators of gene expression. However, there is emerging evidence that miRNA expression is decreased in various rodent tissue types in response to nicotine exposure. In addition, recent studies have found that miRNA dysregulation in response to exposure to various drugs of abuse, including cocaine, can influence rewarding properties of the drug and alter addiction-associated behaviors. We have recently generated preliminary data suggesting that a novel regulatory mechanism involving miRNAs may be at work in the nicotine-mediated upregulation of nAChRs. Preliminary experiments from our lab have identified several miRNAs that are predicted to target nAChR subunit mRNA transcripts, in particular miR-494 and miR-542-3p that target ¿4 and ¿2 transcripts, respectively. In Aim 1, I will determine if ¿4 and/or ¿2 are modulated by miR- 494 and/or miR-542-3p in primary midbrain neuronal cultures. In Aim 2, I will determine if miR-494 and/or miR- 542-3p are modulators of nicotine reward-associated behavior in mice. Through these aims, I hope to achieve a better understanding of the role of miR-494 and miR-542-3p in nicotine reward-associated behaviors, possibly revealing new targets for the development of tobacco cessation aids.