Plant miRNAs, a group of 19–24 nt noncoding RNAs from plant foods, were recently found to have immunomodulatory and nutritional effects on mammalian and human bodies. However, how the miRNAs survive gastrointestinal (GI) environment and how the stable miRNAs are absorbed, which serve the basis for their biological functions, were not unraveled. Here, we investigated the stabilities of six typical plant miRNAs in simulated gastric and intestinal environments, and the absorption mechanisms by Caco-2 cells. The results showed that the miRNAs can survive the environment with certain concentrations. The mixture of food ingredients enhanced the stabilities of the plant miRNAs in the gastric conditions, while 2′-O-methyl modification protects the miRNAs in intestinal juice. The stabilities of the miRNAs vary significantly in the environment and are related to their secondary structures. The stable plant miRNAs can be absorbed by Caco-2 cells via clathrin- and caveolin-mediated endocytosis. Uptake of the miRNAs was sequence dependent, facilitated by NACh and TLR9, two typical receptors on cell membrane. The results suggest that some of plant miRNAs are stable in the mimic GI environment and can be absorbed by Caco-2 cells, underlying the potential of their cross-kingdom regulation effects.

植物 miRNA 是一组来自植物性食品的 19-24 nt 非编码 RNA，最近发现对哺乳动物和人体具有免疫调节和营养作用。然而，miRNA如何在胃肠道（GI）环境中生存以及稳定的miRNA如何被吸收（这是其生物学功能的基础）尚不清楚。在这里，我们研究了六种典型植物 miRNA 在模拟胃和肠道环境中的稳定性以及 Caco-2 细胞的吸收机制。结果表明，miRNA可以在一定浓度的环境中存活。食品成分的混合物增强了植物miRNA在胃中的稳定性，而2'- O-甲基修饰则保护了肠液中的miRNA。 miRNA的稳定性在环境中差异很大，并且与其二级结构有关。稳定的植物 miRNA 可以通过网格蛋白和小窝蛋白介导的内吞作用被 Caco-2 细胞吸收。 miRNA 的摄取具有序列依赖性，由细胞膜上的两种典型受体 NACh 和 TLR9 促进。结果表明，一些植物 miRNA 在模拟胃肠道环境中稳定，并且可以被 Caco-2 细胞吸收，潜在地发挥跨界调节作用。