Kostic Milos, Zivkovic Nikola, Cvetanovic Ana, Stojanovic Ivana, Colic Miodrag
Department of Immunology, Medical Faculty, University of Nis, Blvd. dr Zorana Djindjica 81, 18000 Nis, Serbia.
Department of Pathology, Medical Faculty, University of Nis, Blvd. dr Zorana Djindjica 81, 18000 Nis, Serbia.
Mult Scler Relat Disord. 2017 Jan;11:12-17. doi: 10.1016/j.msard.2016.11.006. Epub 2016 Nov 14.
Th-17 cells have been exclusively referred to inflammatory events in multiple sclerosis (MS), while their importance in the development of glutamate excitotoxicity and the consequent neurodegeneration has been a completely unexplored concept. Accordingly, the objective of our study was to assess IL-17A effect on astrocyte ability to metabolize and release glutamate, considering that astrocytes had the central role in glutamate homeostasis.
By using primary rat astrocyte cultures, astrocyte ability to uptake glutamate was estimated by the alterations of glutamate transporters (GLAST and GLT-1) expression, whereas changes in glutamine synthetase expression were used to estimate the ability to metabolize glutamate. Gene expression was determined by real time polymerase chain reaction (rtPCR). IL-17A effect on astrocyte ability to produce glutamate was investigated directly, by measuring the level of released glutamate using high performance liquid chromatography (HPLC).
Lower concentrations of IL-17A reduced the expressions of both glutamate transporters and glutamine synthetase; however, this effect was lost when IL-17A was applied in a higher dose. IL-17A did not significantly modify glutamate release from astrocyte in basal conditions, but following Ca stimulation, as well as Ca removal from the culture medium, IL-17A stimulated glutamate release in dose-dependent manner.
Together, these results support that IL-17A could promote glutamate excitotoxicity by decreasing astrocyte ability to uptake and convert glutamate to non-toxic glutamine, but also by stimulating Ca dependent glutamate release. Such interactions between IL-17A and glutamate excitotoxicity implicate the potential link between inflammation and neurodegeneration during MS pathogenesis, and identify astrocytes as a potential target in achieving neuroprotective effects in MS.
Th-17细胞一直被认为仅与多发性硬化症（MS）中的炎症事件有关，而它们在谷氨酸兴奋性毒性及随之而来的神经退行性变发展过程中的重要性却是一个完全未被探索的概念。因此，鉴于星形胶质细胞在谷氨酸稳态中起核心作用，我们研究的目的是评估白细胞介素-17A（IL-17A）对星形胶质细胞代谢和释放谷氨酸能力的影响。
通过使用原代大鼠星形胶质细胞培养物，利用谷氨酸转运体（GLAST和GLT-1）表达的变化来估计星形胶质细胞摄取谷氨酸的能力，而谷氨酰胺合成酶表达的变化则用于估计代谢谷氨酸的能力。通过实时聚合酶链反应（rtPCR）测定基因表达。通过使用高效液相色谱法（HPLC）测量释放的谷氨酸水平，直接研究IL-17A对星形胶质细胞产生谷氨酸能力的影响。
较低浓度的IL-17A降低了谷氨酸转运体和谷氨酰胺合成酶的表达；然而，当以较高剂量应用IL-17A时，这种作用消失。在基础条件下，IL-17A并未显著改变星形胶质细胞释放谷氨酸的情况，但在钙刺激后以及从培养基中去除钙后，IL-17A以剂量依赖性方式刺激谷氨酸释放。
总之，这些结果支持IL-17A可通过降低星形胶质细胞摄取谷氨酸并将其转化为无毒谷氨酰胺的能力，以及通过刺激钙依赖性谷氨酸释放来促进谷氨酸兴奋性毒性。IL-17A与谷氨酸兴奋性毒性之间的这种相互作用暗示了MS发病机制中炎症与神经退行性变之间的潜在联系，并确定星形胶质细胞是在MS中实现神经保护作用的潜在靶点。
