LaCrosse Amber L, O'Donovan Sinead M, Sepulveda-Orengo Marian T, McCullumsmith Robert E, Reissner Kathryn J, Schwendt Marek, Knackstedt Lori A
Psychology Department, University of Florida, Gainesville, Florida 32611.
Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, Ohio 45267.
J Neurosci. 2017 Jun 14;37(24):5809-5821. doi: 10.1523/JNEUROSCI.3717-16.2017. Epub 2017 May 11.
Long-term treatment with ceftriaxone attenuates the reinstatement of cocaine seeking while increasing the function of the glutamate transporter 1 (GLT-1) and system xC- (Sxc) in the nucleus accumbens core (NAc). Sxc contributes the majority of nonsynaptic extracellular glutamate in the NAc, while GLT-1 is responsible for the majority of glutamate uptake. Here we used antisense to decrease the expression of GLT-1 and xCT (a catalytic subunit of Sxc) to determine the relative importance of both proteins in mediating the ability of ceftriaxone to prevent cue-induced reinstatement of cocaine seeking and normalize glutamatergic proteins in the NAc of rats. Intra-NAc xCT knockdown prevented ceftriaxone from attenuating reinstatement and from upregulating GLT-1 and resulted in increased surface expression of AMPA receptor subunits GluA1 and GluA2. Intra-NAc GLT-1 knockdown also prevented ceftriaxone from attenuating reinstatement and from upregulating xCT expression, without affecting GluA1 and GluA2 expression. In the absence of cocaine or ceftriaxone treatment, xCT knockdown in the NAc increased the expression of both GluA1 and GluA2 without affecting GLT-1 expression while GLT-1 knockdown had no effect. PCR and immunoprecipitation of GLT-1 revealed that ceftriaxone does not upregulate GLT-1 and xCT through a transcriptional mechanism, and their coregulation by ceftriaxone is not mediated by physical interaction. These data support important and distinct roles for xCT and GLT-1 in the actions of ceftriaxone and add to a body of literature finding evidence for coregulation of these transporters. Our results also point to xCT expression and subsequent basal glutamate levels as being a key mediator of AMPA receptor expression in the NAc. Ceftriaxone attenuates the reinstatement of cocaine, alcohol, and heroin seeking. The mechanism of action of this behavioral effect has been attributed to glutamate transporter 1 (GLT-1) and xCT (a catalytic subunit of Sxc)/Sxc upregulation in the nucleus accumbens core. Here we used an antisense strategy to knock down GLT-1 or xCT in the nucleus accumbens core and examined the behavioral and molecular consequences. While upregulation of both xCT and GLT-1 are essential to the ability of ceftriaxone to attenuate cue-induced reinstatement of cocaine seeking, each protein uniquely affects the expression of other glutamate receptor and transporter proteins. We also report that reducing basal glutamate levels through the manipulation of xCT expression increases the surface expression of AMPA receptor subunits, providing insight to the mechanism by which cocaine alters AMPA surface expression.
长期使用头孢曲松治疗可减弱可卡因觅药行为的恢复，同时增强伏隔核核心区（NAc）中谷氨酸转运体1（GLT-1）和系统xC-（Sxc）的功能。Sxc在NAc的非突触性细胞外谷氨酸中占大部分，而GLT-1则负责大部分谷氨酸的摄取。在这里，我们使用反义技术降低GLT-1和xCT（Sxc的催化亚基）的表达，以确定这两种蛋白在介导头孢曲松预防线索诱导的可卡因觅药行为恢复以及使大鼠NAc中谷氨酸能蛋白正常化的能力中的相对重要性。NAc内xCT基因敲低可阻止头孢曲松减弱觅药行为恢复以及上调GLT-1，并导致AMPA受体亚基GluA1和GluA2的表面表达增加。NAc内GLT-1基因敲低也可阻止头孢曲松减弱觅药行为恢复以及上调xCT表达，但不影响GluA1和GluA2的表达。在没有可卡因或头孢曲松治疗的情况下，NAc内xCT基因敲低可增加GluA1和GluA2的表达，而不影响GLT-1的表达，而GLT-1基因敲低则没有影响。对GLT-1进行PCR和免疫沉淀分析表明，头孢曲松不是通过转录机制上调GLT-1和xCT，并且头孢曲松对它们的共同调节不是由物理相互作用介导的。这些数据支持xCT和GLT-1在头孢曲松作用中具有重要且不同的作用，并补充了一系列发现这些转运体共同调节证据的文献。我们的结果还表明，xCT表达及随后的基础谷氨酸水平是NAc中AMPA受体表达的关键调节因子。头孢曲松可减弱可卡因、酒精和海洛因觅药行为的恢复。这种行为效应的作用机制归因于伏隔核核心区中谷氨酸转运体1（GLT-1）和xCT（Sxc的催化亚基）/Sxc的上调。在这里，我们使用反义策略在伏隔核核心区敲低GLT-1或xCT，并研究其行为和分子后果。虽然xCT和GLT-1的上调对于头孢曲松减弱线索诱导的可卡因觅药行为恢复的能力至关重要，但每种蛋白对其他谷氨酸受体和转运体蛋白的表达有独特影响。我们还报告说，通过操纵xCT表达降低基础谷氨酸水平会增加AMPA受体亚基的表面表达，这为可卡因改变AMPA表面表达的机制提供了见解。
