The hidden bioactive molecules: miRNAs loaded in extracellular vesicles might act as bioactive constituents in European mistletoe

草药产品以药物或食品补充剂的形式被全球接受为有效的补充治疗系统。它们的生物活性成分以及相应的与人类的相互作用往往没有得到全面的表征。世界各地已经启动了各种研究，以开发以科学证据为基础的草药疗法。新的植物生物活性分子正在被发现。MicroRNAs(MiRNAs)是一类约22个核苷酸的单链非编码RNA，在基因表达中起着至关重要的作用。近年来，植物来源的miRNAs的跨王国研究引起了极大的关注。例如，水稻miRNAs被认为可以进入哺乳动物的血液，并在哺乳动物的新陈代谢中发挥作用。植物来源的miR159可以靶向人类基因，在体内外抑制乳腺癌细胞的生长。这些研究表明，人类基因可以受到食用植物miRNAs的调控，这为药用植物miRNAs可能是调节人类健康和疾病的隐藏生物活性化合物提供了令人兴奋的线索。槲寄生(Viscum Aligure L.)在欧洲传统上用于治疗癌症和心血管疾病已有数百年的历史，但其科学背景仍存在争议。通过高通量Illumina测序和生物信息学分析，我们先前的研究表明，槲寄生miRNAs可能参与了槲寄生的药理作用。目前迫切需要进一步的实验验证来确认这些植物miRNAs的生物活性。考虑到植物miRNAs在草药提取物和哺乳动物体液等酶环境中不稳定，将其包裹在细胞释放的膜包裹的纳米粒子胞外囊泡(EV)中，可以提供miRNAs的纳米穿梭，使其能够进行长距离旅行。在此，我们认为，槲寄生miRNAs可能是一个独立的活性成分类别，并可能负责或至少有助于槲寄生的药理作用(例如，抗肿瘤作用)。槲寄生电动载体可能作为有效的载体来传递具有完整功能的miRNAs，并介导槲寄生miRNAs的跨王国调控。拟议的研究将集中在跨王国调控miRNAs的概况，哺乳动物靶标的识别和槲寄生EVS介导的miRNA传递的可视化。如果我们的假设得到验证，将促进我们对药用植物中基于miRNA的生物活性成分的理解，为药用植物的民间药用和临床应用提供科学支持。更重要的是，它将为基于miRNA的疗法的开发开辟新的途径，以预防或治疗人类疾病。

Herbal products are globally accepted as a valid complementary system of therapy in the form of pharmaceuticals or food supplements. Often their bioactive constituents and corresponding interactions with human have not been comprehensively characterized. Various studies around the world have been initiated to develop scientific evidence-based herbal therapies. New plant bioactive molecules are being discovered. MicroRNAs (miRNAs) are a class of approximately 22 nucleotides single-stranded non-coding RNAs that play crucial roles in gene expression. Recently, the cross-kingdom of plant derived miRNAs has attracted great attraction. For example, the rice miRNAs have been suggested to enter mammalian bloodstream and have a functional role in mammalian metabolism. Plant-derived miR159 can target human genes and suppress breast cancer cell growth in vitro and in vivo. These studies suggested that human genes can be regulated by dietary plant miRNAs, providing thrilling clues that medicinal plants miRNAs might be the hidden bioactive compounds regulating human health and diseases. Mistletoe (Viscum album L.) has been used traditionally in Europe for centuries for the treatment of cancer and cardiovascular diseases but their scientific background is still controversially discussed. By using high-throughput Illumina sequencing and bioinformatics analysis, our previous study indicated that mistletoe miRNAs might be involved in the pharmacological effects of mistletoe. Further experimental validations are currently urgent to confirm the bioactivities of these plant miRNAs. Considering plant miRNAs are not stable in enzymatic environment such as herb extracts and mammalian body fluids, being encapsulated into extracellular vesicles (EVs) that are membrane-enclosed nano-sized particles released by cells, could offer miRNAs nano-shuttles allowing them to travel long distances. Herein, we propose that mistletoe miRNAs might serve as an independent category of active ingredients and might be responsible for or at least contribute to the pharmacological effects (e.g. anti-tumor effect) of mistletoe. Mistletoe EVs might act as effective vehicles to deliver miRNAs with intact functionality, and mediate the cross-kingdom regulation of mistletoe miRNAs. Proposed investigations will be focused on the profiling of cross-kingdom regulatory miRNAs, identification of mammalian targets and visualization of mistletoe EVs mediated miRNA delivery. If our hypothesis is proven, it will promote our understanding of miRNA-based bioactive ingredients in medicinal plants provide scientific support for folk medicinal use and clinical use of medicinal plants. More importantly, it will open new ways for the development of miRNA-based therapies to prevent or treat human diseases.