Departments of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America.
Departments of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska, United States of America.
PLoS One. 2014 Apr 15;9(4):e95023. doi: 10.1371/journal.pone.0095023. eCollection 2014.
Juvenile Neuronal Ceroid Lipofuscinosis (JNCL) is a lysosomal storage disease caused by an autosomal recessive mutation in CLN3 that leads to vision loss, progressive cognitive and motor decline, and premature death. Morphological evidence of astrocyte activation occurs early in the disease process and coincides with regions where neuronal loss eventually ensues. However, the consequences of CLN3 mutation on astrocyte function remain relatively ill-defined. Astrocytes play a critical role in CNS homeostasis, in part, by their ability to regulate the extracellular milieu via the formation of extensive syncytial networks coupled by gap junction (GJ) channels. In contrast, unopposed hemichannels (HCs) have been implicated in CNS pathology by allowing the non-discriminant passage of molecules between the intracellular and extracellular milieus. Here we examined acute brain slices from CLN3 mutant mice (CLN3Δex7/8) to determine whether CLN3 loss alters the balance of GJ and HC activity. CLN3Δex7/8 mice displayed transient increases in astrocyte HC opening at postnatal day 30 in numerous brain regions, compared to wild type (WT) animals; however, HC activity steadily decreased at postnatal days 60 and 90 in CLN3Δex7/8 astrocytes to reach levels lower than WT cells. This suggested a progressive decline in astrocyte function, which was supported by significant reductions in glutamine synthetase, GLAST, and connexin expression in CLN3Δex7/8 mice compared to WT animals. Based on the early increase in astrocyte HC activity, CLN3Δex7/8 mice were treated with the novel carbenoxolone derivative INI-0602 to inhibit HCs. Administration of INI-0602 for a one month period significantly reduced lysosomal ceroid inclusions in the brains of CLN3Δex7/8 mice compared to WT animals, which coincided with significant increases in astrocyte GJ communication and normalization of astrocyte resting membrane potential to WT levels. Collectively, these findings suggest that alterations in astrocyte communication may impact the progression of JNCL and could offer a potential therapeutic target.
少年神经元蜡样脂褐质沉积症（JNCL）是一种溶酶体贮积病，由 CLN3 的常染色体隐性突变引起，导致视力丧失、进行性认知和运动能力下降以及过早死亡。星形胶质细胞激活的形态学证据在疾病过程的早期发生，与最终导致神经元丧失的区域相吻合。然而，CLN3 突变对星形胶质细胞功能的后果仍然相对不明确。星形胶质细胞在中枢神经系统（CNS）稳态中发挥关键作用，部分原因是它们通过形成广泛的合胞体网络并通过缝隙连接（GJ）通道偶联来调节细胞外环境。相比之下，未受抑制的半通道（HCs）通过允许分子在细胞内和细胞外环境之间无差别地通过，被牵连到 CNS 病理学中。在这里，我们检查了 CLN3 突变小鼠（CLN3Δex7/8）的急性脑切片，以确定 CLN3 缺失是否改变了 GJ 和 HC 活性的平衡。与野生型（WT）动物相比，CLN3Δex7/8 小鼠在许多脑区的出生后 30 天显示出星形胶质细胞 HC 打开的短暂增加；然而，CLN3Δex7/8 星形胶质细胞中的 HC 活性在出生后 60 天和 90 天稳步下降，达到低于 WT 细胞的水平。这表明星形胶质细胞功能逐渐下降，这得到了 CLN3Δex7/8 小鼠与 WT 动物相比，谷氨酰胺合成酶、GLAST 和连接蛋白表达显著减少的支持。基于星形胶质细胞 HC 活性的早期增加，CLN3Δex7/8 小鼠用新型 carbenoxolone 衍生物 INI-0602 治疗以抑制 HCs。INI-0602 治疗一个月可显著减少 CLN3Δex7/8 小鼠大脑中的溶酶体蜡样脂褐质包涵体，与 WT 动物相比，星形胶质细胞 GJ 通讯显著增加，星形胶质细胞静息膜电位恢复到 WT 水平。总的来说，这些发现表明星形胶质细胞通讯的改变可能会影响 JNCL 的进展，并为潜在的治疗靶点提供了依据。
