The Characteristics and Functions of Orally Absorbed Herbal Decoction-borne Plant MicroRNAs.

Herbal decoctions always contain numerous plant microRNAs (miRNAs), and some of these can be absorbed orally to exert cross-kingdom gene regulation. However, little is known about which specific types of herbal decoction-borne plant miRNAs are more likely to be absorbed. Thus, two antiviral herbal decoctions, Qingfei Paidu (QFPD) and Qingre Huashi Kangdu (QRHS), were administered to human volunteers and rats, respectively, to investigate the characteristics of orally absorbed decoction-borne plant miRNAs. MIR-6240-3p was identified as an absorbed plant miRNA in humans and is most highly expressed in QFPD decoction. Therefore, the kinetics of MIR-6240-3p were monitored in humans following the administration of the QFPD decoction, and its antiviral effect on human coronavirus type 229E (HCoV-229E) was examined in vitro. 586,176 small RNAs (sRNAs) were identified in QFPD decoction, of which 100,276 were orally absorbed by humans. In the QRHS decoction, 124,026 sRNAs were detected, with 7484 being orally absorbed by rats. Logistical repression analysis revealed that absorbable plant sRNAs in both humans and rats presented higher expression levels, greater minimum free energy, and increased AU/UA frequencies compared to non-absorbable plant sRNAs. The amount of MIR-6240-3p in humans increased between 1- and 3-hours after the administration of the QFPD decoction. In addition, MIR-6240-3p significantly reduced the RNA copy number and TCID50 of HCoV-229E in vitro. These results suggest that herbal decoction-borne plant sRNAs with higher expression level, greater minimum free energy or an increased AU/UA frequency are more likely to be orally absorbed and could potentially mediate cross-kingdom gene regulation.