In Vitro Nephrotoxicity Induced by Herb-Herb Interaction between Radix Glycyrrhizae and Radix Euphorbiae Pekinensis

Radix Glycyrrhizae (RG)-Radix Euphorbiae Pekinensis (REP) is a representative incompatible herbal pair of Eighteen Incompatible Medicaments (EIM) and has been disputed in clinical application for a long time. The present study was performed with the Madin-Darby canine kidney (MDCK) cell line using cell cytotoxicity assay, apoptosis detection, cell cycle measurement, reactive oxygen species (ROS) determination, and high content analysis (HCA) in combination with high-performance liquid chromatography (HPLC) fingerprint comparison to clarify whether RG and REP can be concomitantly used from the perspective of cytotoxicity, investigate the major correlated compounds, and elucidate the underlying mechanisms. The results showed that the toxicity of REP could be significantly enhanced through its concomitant use with RG in the ratio of 1 : 1, and this increased toxicity could be weakened with the further increased proportion of RG. 3,3'-di-O-methylellagic acid-4'-O-β-D-xylopyranoside (DEAX) and 3,3'-di-O-methylellagic acid (DEA) were shown to be mainly responsible for the toxicity induced by concomitant use of REP and RG. Both RG-REP decoctions and the above two compounds boosted cell apoptosis, cellular morphological change, ROS accumulation, and mitochondrial membrane potential (MMP) disruption. In conclusion, the incompatible use of RG and REP is conditionally established because of the bidirectional regulatory effect of RG, and the major compounds responsible for RG-REP incompatibility are DEAX and DEA, which result in toxicity through activation of mitochondria-dependent apoptosis induced by increased ROS production. This study provided a basis for understanding the incompatible use of RG and REP and the EIM theory.