Santa Lucia Foundation IRCCS, Rome, Italy.
Department of Experimental Medicine, Section of Physiology and Biochemistry, University of Perugia, Perugia, Italy.
Cell Death Dis. 2018 Feb 12;9(2):204. doi: 10.1038/s41419-017-0221-2.
Parkinson's disease (PD) is a neurodegenerative disorder in which genetic and environmental factors synergistically lead to loss of midbrain dopamine (DA) neurons. Mutation of leucine-rich repeated kinase2 (Lrrk2) genes is responsible for the majority of inherited familial cases of PD and can also be found in sporadic cases. The pathophysiological role of this kinase has to be fully understood yet. Hyperactivation of Lrrk2 kinase domain might represent a predisposing factor for both enhanced striatal glutamatergic release and mitochondrial vulnerability to environmental factors that are observed in PD. To investigate possible alterations of striatal susceptibility to mitochondrial dysfunction, we performed electrophysiological recordings from the nucleus striatum of a G2019S Lrrk2 mouse model of PD, as well as molecular and morphological analyses of G2019S Lrrk2-expressing SH-SY5Y neuroblastoma cells. In G2019S mice, we found reduced striatal DA levels, according to the hypothesis of alteration of dopaminergic transmission, and increased loss of field potential induced by the mitochondrial complex I inhibitor rotenone. This detrimental effect is reversed by the D2 DA receptor agonist quinpirole via the inhibition of the cAMP/PKA intracellular pathway. Analysis of mitochondrial functions in G2019S Lrrk2-expressing SH-SY5Y cells revealed strong rotenone-induced oxidative stress characterized by reduced Ca buffering capability and ATP synthesis, production of reactive oxygen species, and increased mitochondrial fragmentation. Importantly, quinpirole was able to prevent all these changes. We suggest that the G2019S-Lrrk2 mutation is a predisposing factor for enhanced striatal susceptibility to mitochondrial dysfunction induced by exposure to mitochondrial environmental toxins and that the D2 receptor stimulation is neuroprotective on mitochondrial function, via the inhibition of cAMP/PKA intracellular pathway. We suggest new possible neuroprotective strategies for patients carrying this genetic alteration based on drugs specifically targeting Lrrk2 kinase domain and mitochondrial functionality.
帕金森病（PD）是一种神经退行性疾病，其中遗传和环境因素协同导致中脑多巴胺（DA）神经元的丧失。富含亮氨酸重复激酶 2（Lrrk2）基因突变负责大多数遗传性家族性 PD 病例，也可在散发性病例中发现。这种激酶的病理生理作用尚未完全了解。Lrrk2 激酶结构域的过度激活可能代表 PD 中观察到的增强纹状体谷氨酸能释放和线粒体对环境因素易感性的一个易感因素。为了研究纹状体对线粒体功能障碍的易感性的可能变化，我们对帕金森病 G2019S Lrrk2 小鼠模型的纹状体核进行了电生理记录，以及 G2019S Lrrk2 表达的 SH-SY5Y 神经母细胞瘤细胞的分子和形态分析。在 G2019S 小鼠中，根据多巴胺能传递改变的假设，我们发现纹状体 DA 水平降低，并且线粒体复合物 I 抑制剂鱼藤酮诱导的场电位丧失增加。这种有害作用通过 D2 DA 受体激动剂喹吡罗尔通过抑制 cAMP/PKA 细胞内途径而逆转。在 G2019S Lrrk2 表达的 SH-SY5Y 细胞中分析线粒体功能，发现鱼藤酮诱导的氧化应激强烈，其特征在于 Ca 缓冲能力降低和 ATP 合成减少、活性氧物质的产生以及线粒体片段化增加。重要的是，喹吡罗尔能够预防所有这些变化。我们认为，G2019S-Lrrk2 突变是暴露于线粒体环境毒素后纹状体对线粒体功能障碍易感性增加的易感因素，并且 D2 受体刺激通过抑制 cAMP/PKA 细胞内途径对线粒体功能具有神经保护作用。我们建议基于专门针对 Lrrk2 激酶结构域和线粒体功能的药物，为携带这种遗传改变的患者提供新的可能的神经保护策略。
