Phosphodiesterases (PDEs) have previously been implicated in oligodendrocyte maturation and myelination of central nervous system axons. Sildenafil citrate is a phosphodiesterase inhibitor known to block PDE5, which also reduces inflammation in the experimental autoimmune encephalomyelitis demyelinating model. To find out whether this inhibitor might exert beneficial effects on central nervous system myelin repair activities, we investigated to what degree sildenafil modulates differentiation and maturation of cultured primary rat oligodendroglial precursor cells (OPCs). To this end, gene and protein expression of 2',3'-cyclic-nucleotide 3'-phosphodiesterase, myelin basic protein, and myelin oligodendrocyte glycoprotein, as well as of negative regulators of myelin expression (Hes1, Hes5, Id2, Id4, Rock2, and p57Kip2) were measured in OPCs treated with sildenafil. Moreover, the subcellular distribution of the p57kip2 protein was determined after sildenafil treatment, as this revealed to be an early predictor of the oligodendroglial differentiation capacity. In vitro myelination assays were done to measure the myelination capacity of oligodendrocytes treated with sildenafil. We found that sildenafil significantly diminished myelin gene expression and protein expression. Moreover, sildenafil also increased the expression of Id2 and Id4 negative transcriptional regulators, and the degree of OPCs with cytoplasmic p57kip2 protein localization was reduced, providing evidence that the PDE blocker impaired the differentiation capacity. Finally, sildenafil also interfered with the establishment of internodes as revealed by in vitro myelination assays. We therefore conclude that blocking PDE5 activities exerts a negative impact on intrinsic oligodendroglial differentiation processes.

中文翻译：

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西地那非抑制少突胶质细胞前体细胞的髓磷脂表达和髓鞘形成。

磷酸二酯酶（PDE）先前被认为与中枢神经系统轴突的少突胶质细胞成熟和髓鞘形成有关。柠檬酸西地那非是一种已知可阻断 PDE5 的磷酸二酯酶抑制剂，它还能减少实验性自身免疫性脑脊髓炎脱髓鞘模型中的炎症。为了查明这种抑制剂是否可能对中枢神经系统髓磷脂修复活性产生有益影响，我们研究了西地那非在多大程度上调节培养的原代大鼠少突胶质细胞前体细胞 (OPC) 的分化和成熟。为此，2',3'-环核苷酸3'-磷酸二酯酶、髓磷脂碱性蛋白和髓磷脂少突胶质细胞糖蛋白以及髓磷脂表达负调节因子（Hes1、Hes5、Id2、Id4、 Rock2 和 p57Kip2) 在用西地那非处理的 OPC 中进行测量。此外，在西地那非治疗后测定了 p57kip2 蛋白的亚细胞分布，因为这表明这是少突胶质细胞分化能力的早期预测因子。进行体外髓鞘形成测定以测量用西地那非处理的少突胶质细胞的髓鞘形成能力。我们发现西地那非显着降低髓磷脂基因表达和蛋白质表达。此外，西地那非还增加了Id2和Id4负转录调节因子的表达，并且OPCs胞质p57kip2蛋白定位的程度降低，这提供了PDE阻断剂损害分化能力的证据。最后，体外髓鞘形成试验表明，西地那非还干扰节间的建立。因此，我们得出结论，阻断 PDE5 活性会对内在少突胶质细胞分化过程产生负面影响。