7,8-Dihydroneopterin protects cells intracellularly from oxidative stress-induced death, but its mode of transport across the cell membrane is unknown. Nucleosides, such as guanosine, are transported via nucleoside transporters of the equilibrative and concentrative forms. Therefore, the objective of this study was to identify which membrane transporters are responsible for 7,8-dihydroneopterin transport in cells and whether this is necessary for protection against oxidative stress. Monocytic cell lines U937, THP-1 and human monocytes were incubated with varying concentrations of 7,8-dihydroneopterin with or without nucleoside transporter inhibitors nitrobenzylthioinosine (NBMPR; ENT1), dipyridamole (DP; ENT1 and ENT2) or indomethacin (INDO; CNT). Only DP inhibited 7,8-dihydroneopterin uptake in U937 cells, while NBMPR and DP inhibited 7,8-dihydroneopterin uptake in THP-1 cells. All three inhibitors limited 7,8-dihydroneopterin uptake in human monocytes at short time points only. When the cells were incubated with 10 mM of the peroxyl radical generator 2,2'-azobis-2-methyl-propanimidamide, dihydrochloride (AAPH) a 50–80% loss of cell viability was measured. 7,8-dihydroneopterin protected all cell lines against AAPH-induced cell death, which was prevented with DP in U937 cells, NBMPR in THP-1 cells and a combination of all three nucleoside inhibitors in human monocytes. These data indicate 7,8-dihydroneopterin is transported across the cell membrane of monocytic cells via equilibrative and concentrative nucleoside transporters in a cell lineage-dependent manner. The data also indicate protection from peroxyl radical-generated cell death with 7,8-dihydroneopterin is intracellular and facilitated through nucleoside transporters in monocytic cells.

7,8-Dihydroneopterin保护细胞内细胞免受氧化应激诱导的死亡，但其跨细胞膜的运输方式尚不清楚。核苷，例如鸟苷，通过平衡和集中形式的核苷转运蛋白。因此，这项研究的目的是确定哪些膜转运蛋白负责细胞中7,8-二氢蝶呤的转运，以及这是否对保护氧化应激是必需的。将单核细胞系U937，THP-1和人类单核细胞与不同浓度的7,8-二氢蝶呤一起孵育，可以使用或不使用核苷转运蛋白抑制剂硝基苄硫代肌苷（NBMPR; ENT1），双嘧达莫（DP; ENT1和ENT2）或消炎痛（INDO; CNT） 。在U937细胞中，只有DP抑制7,8-二氢蝶呤的摄取，而THP-1细胞中NBMPR和DP抑制7,8-二氢蝶呤的摄取。所有这三种抑制剂仅在短时间点限制了人类单核细胞摄取7,8-二氢蝶呤。当将细胞与10 mM过氧自由基产生剂2,2'-偶氮双-2-甲基-丙酰胺酰胺，二盐酸盐（AAPH）孵育时，测得细胞活力损失了50-80％。7,8-二氢蝶呤可保护所有细胞系免受AAPH诱导的细胞死亡，U937细胞中的DP，THP-1细胞中的NBMPR以及人单核细胞中所有三种核苷抑制剂的组合均可以预防AAPH诱导的细胞死亡。这些数据表明7,8-dihydroneopterin跨单核细胞的细胞膜转运通过平衡和集中的核苷转运蛋白以细胞谱系依赖性的方式进行。数据还表明，在细胞内并通过单核细胞中的核苷转运蛋白促进了由7，8-二氢蝶呤类对过氧自由基产生的细胞死亡的保护。