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

Herbal decoctions always contain numerous plant microRNAs, 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 microRNAs are more likely to be absorbed. Thus, two antiviral herbal decoctions, Qingfei Paidu and Qingre Huashi Kangdu, were administered to human volunteers and rats, respectively, to investigate the characteristics of orally absorbed decoction-borne plant microRNAs. MIR-6240 - 3 p was identified as an absorbed plant microRNA in humans and is most highly expressed in Qingfei Paidu decoction. Therefore, the kinetics of MIR-6240 - 3 p were monitored in humans following the administration of the Qingfei Paidu decoction, and its antiviral effect on human coronavirus type 229E (HCoV-229E) was examined in vitro. There were 586 176 small RNAs identified in Qingfei Paidu decoction, of which 100 276 were orally absorbed by humans. In the Qingre Huashi Kangdu decoction, 124 026 small RNAs were detected, with 7484 being orally absorbed by rats. Logistical repression analysis revealed that absorbable plant small RNAs in both humans and rats presented higher expression levels, greater minimum free energy, and increased AU/UA frequencies compared to nonabsorbable plant small RNAs. The amount of MIR-6240 - 3 p in humans increased between 1 and 3 h after the administration of the Qingfei Paidu decoction. In addition, MIR-6240 - 3 p significantly reduced the RNA copy number and TCID₅₀ of HCoV-229E in vitro. These results suggest that herbal decoction-borne plant small RNAs with a 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.