Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, GA 30602, USA.
Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, GA 30602, USA.
Exp Neurol. 2014 Feb;252:18-27. doi: 10.1016/j.expneurol.2013.11.018. Epub 2013 Nov 22.
Dysfunctional glial glutamate transporters and over production of pro-inflammatory cytokines (including interleukin-1β, IL-1β) are two prominent mechanisms by which glial cells enhance neuronal activities in the spinal dorsal horn in neuropathic pain conditions. Endogenous molecules regulating production of IL-1β and glial glutamate functions remain poorly understood. In this study, we revealed a dynamic alteration of GSK3β activities and its role in regulating glial glutamate transporter 1 (GLT-1) protein expression in the spinal dorsal horn and nociceptive behaviors following the nerve injury. Specifically, GSK3β was expressed in both neurons and astrocytes in the spinal dorsal horn. GSK3β activities were suppressed on day 3 but increased on day 10 following the nerve injury. In parallel, protein expression of GLT-1 in the spinal dorsal horn was enhanced on day 3 but reduced on day 10. In contrast to these time-dependent changes, the activation of astrocytes and over-production of IL-1β were found on both day 3 and day 10. Meanwhile, thermal hyperalgesia was observed from day 2 through day 10 and mechanical allodynia from day 4 through day 10. Pre-emptive pharmacological inhibition of GSK3β activities significantly ameliorated thermal hyperalgesia and mechanical allodynia at the late stage but did not have effects at the early stage. These were accompanied with the suppression of GSK3β activities, prevention of decreased GLT-1 protein expression, inhibition of astrocytic activation, and reduction of IL-1β in the spinal dorsal horn on day 10. These data indicate that the increased GSK3β activity in the spinal dorsal horn is attributable to the downregulation of GLT-1 protein expression in neuropathic rats at the late stage. Further, we also demonstrated that the nerve-injury-induced thermal hyperalgesia on day 10 was transiently suppressed by pharmacological inhibition of GSK3β. Our study suggests that GSK3β may be a potential target for the development of analgesics for chronic neuropathic pain.
功能失调的神经胶质谷氨酸转运体和过度产生的促炎细胞因子(包括白细胞介素-1β,IL-1β)是胶质细胞在神经病理性疼痛条件下增强脊髓背角神经元活动的两个突出机制。内源性分子调节 IL-1β和神经胶质谷氨酸功能的产生仍知之甚少。在这项研究中,我们揭示了 GSK3β 活性的动态变化及其在调节脊髓背角神经胶质谷氨酸转运体 1(GLT-1)蛋白表达和神经损伤后的伤害感受行为中的作用。具体来说,GSK3β在脊髓背角的神经元和星形胶质细胞中均有表达。神经损伤后第 3 天,GSK3β 活性受到抑制,但第 10 天则增加。与此相一致的是,脊髓背角 GLT-1 蛋白表达在第 3 天增加,但在第 10 天减少。与这些时间依赖性变化相反,在第 3 天和第 10 天都发现星形胶质细胞的激活和 IL-1β的过度产生。同时,从第 2 天到第 10 天观察到热痛觉过敏,从第 4 天到第 10 天观察到机械性痛觉过敏。预先进行 GSK3β 活性的药理学抑制显著改善了晚期的热痛觉过敏和机械性痛觉过敏,但对早期没有影响。这些都伴随着 GSK3β 活性的抑制、GLT-1 蛋白表达的降低、星形胶质细胞激活的抑制和脊髓背角 IL-1β的减少。这些数据表明,在神经病理性大鼠的晚期,脊髓背角中 GSK3β 活性的增加归因于 GLT-1 蛋白表达的下调。此外,我们还证明,通过药理学抑制 GSK3β,可暂时抑制神经损伤引起的第 10 天的热痛觉过敏。我们的研究表明,GSK3β 可能是治疗慢性神经病理性疼痛的潜在药物靶点。