Differential genotoxicity of Polygoni Multiflori in rat and human: insights from Ames test and S9 metabolic activation system.

The Ames test is used worldwide to initially screen the mutagenic potential of new chemicals. In the standard Ames test, S. typhimurium strains (TA100, TA98, TA1535, and TA1537) and Escherichia coli (WP2uvrA) are treated with substances with/without cytochrome P450s (CYPs)-induced rat S9 fractions for identifying mutagens and pro-mutagens. However, many substances show completely different toxicity patterns depending on whether the liver S9 fraction belongs to rats or humans. The natural product Polygoni Multiflori Radix (PMR) can also show bacterial reverse mutation, followed by the rat or human liver S9 fraction. While PMR elicits reverse mutations in the TA1537 strain in rat liver S9 but not in human liver S9, this mechanism has not been verified yet. To explain this, the differences in metabolic enzymes compositions commonly observed between rats and humans have been implicated. This study aimed to explore the key factors that cause differences in the genotoxicity of PMR between rat and human liver S9 metabolic enzymes. The results of next-generation sequencing (NGS) analysis showed that both rat and human metabolic enzymes caused similar mutations in TA1537. However, when the metabolic enzymes in each S9 fraction were analyzed using ion mobility tandem mass spectrometry (IM-MS), rat- and human-specific enzymes were identified among the cytochrome (CYP) family, especially aryl hydrocarbon receptor (AHR)-related CYPs. These findings suggest that CYP1A1 isoforms contribute to the mechanism of PMR in the Ames test. Therefore, an in vitro Ames test might be more reliable in predicting genotoxicity for both rodents and humans. This will also help overcome the limitations of laboratory animal-based toxicity evaluations, which provide unreliable results due to interspecies differences between humans and rodents.

Genotoxicity assessment of root extracts of Paeonia lactiflora Pall.

The roots of Paeonia lactiflora Pall., (Paeoniae Radix, PL) are a well-known herbal remedy used to treat fever, rheumatoid arthritis, systemic lupus erythematosus, hepatitis, and gynecological disorders in East Asia. Here we evaluated the genetic toxicity of PL extracts (as a powder [PL-P] and hot-water extract [PL-W]) in accordance with the Organization for Economic Co-operation and Development guidelines. The Ames test revealed that PL-W was not toxic to S. typhimurium strains and E. coli in absence and presence of the S9 metabolic activation system at concentrations up to 5000 µg/plate, but PL-P produced a mutagenic response to TA100 in the absence of S9 mix. PL-P was cytotoxic in in vitro chromosomal aberrations (more than a 50 % decrease in cell population doubling time), and it increased the frequency of structural and numerical aberrations in absence and presence of S9 mix in a concentration-dependent manner. PL-W was cytotoxic in the in vitro chromosomal aberration tests (more than a 50 % decrease in cell population doubling time) only in the absence of S9 mix, and it induced structural aberrations only in the presence of S9 mix. PL-P and PL-W did not produce toxic response during the in vivo micronucleus test after oral administration to ICR mice and did not induce positive results in the in vivo Pig-a gene mutation and comet assays after oral administration to SD rats. Although PL-P showed genotoxic in two in vitro tests, the results from physiologically relevant in vivo Pig-a gene mutation and comet assays illustrated that PL-P and PL-W does not cause genotoxic effects in rodents.