Hosur Vishnu, Leppanen Scott, Abutaha Adham, Loring Ralph H
Department of Pharmaceutical Science, Northeastern University, Boston, Massachusetts, USA.
J Neurochem. 2009 Nov;111(3):848-58. doi: 10.1111/j.1471-4159.2009.06373.x. Epub 2009 Sep 1.
alpha4beta2 Nicotinic acetylcholine receptors play an important role in the reward pathways for nicotine. We investigated whether receptor up-regulation of alpha4beta2 nicotinic acetylcholine receptors involves expression changes for non-receptor genes. In a microarray analysis, 10 muM nicotine altered expression of 41 genes at 0.25, 1, 8 and 24 h in halpha4beta2 SH-EP1 cells. The maximum number of gene changes occurred at 8 h, around the initial increase in (3)[H]-cytisine binding. Quantitative RT-PCR corroborated gene induction of endoplasmic reticulum proteins CRELD2, PDIA6, and HERPUD1, and suppression of the pro-inflammatory cytokines IL-1beta and IL-6. Nicotine suppresses IL-1beta and IL-6 expression at least in part by inhibiting NFkappaB activation. Antagonists dihydro-beta-erythroidine and mecamylamine blocked these nicotine-induced changes showing that receptor activation is required. Antagonists alone or in combination with nicotine suppressed CRELD2 message while increasing alpha4beta2 binding. Additionally, small interfering RNA knockdown of CRELD2 increased basal alpha4beta2 receptor expression, and antagonists decreased CRELD2 expression even in the absence of alpha4beta2 receptors. These data suggest that endoplasmic reticulum proteins such as CRELD2 can regulate alpha4beta2 expression, and may explain antagonist actions in nicotine-induced receptor up-regulation. Further, the unexpected finding that nicotine suppresses inflammatory cytokines suggests that nicotinic alpha4beta2 receptor activation promotes anti-inflammatory effects similar to alpha7 receptor activation.
α4β2烟碱型乙酰胆碱受体在尼古丁的奖赏通路中发挥重要作用。我们研究了α4β2烟碱型乙酰胆碱受体的上调是否涉及非受体基因的表达变化。在微阵列分析中，10μM尼古丁在0.25、1、8和24小时改变了α4β2 SH-EP1细胞中41个基因的表达。基因变化的最大数量出现在8小时，此时正好是（3）[H]-金雀花碱结合开始增加的时候。定量逆转录聚合酶链反应证实了内质网蛋白CRELD2、PDIA6和HERPUD1的基因诱导，以及促炎细胞因子IL-1β和IL-6的抑制。尼古丁至少部分通过抑制NFκB激活来抑制IL-1β和IL-6的表达。拮抗剂二氢-β-刺桐啶和美加明阻断了这些尼古丁诱导的变化，表明需要受体激活。单独的拮抗剂或与尼古丁联合使用可抑制CRELD2信息，同时增加α4β2结合。此外，小干扰RNA敲低CRELD2可增加基础α4β2受体表达，即使在没有α4β2受体的情况下，拮抗剂也会降低CRELD2表达。这些数据表明，内质网蛋白如CRELD2可以调节α4β2表达，并可能解释拮抗剂在尼古丁诱导的受体上调中的作用。此外，尼古丁抑制炎性细胞因子这一意外发现表明，烟碱型α4β2受体激活促进了类似于α7受体激活的抗炎作用。
