Cinnabar-containing Chinese medicine Hua-Feng-Dan differs from mercury sulfide and mercury chloride in affecting gut microbiota in mice

Background: Cinnabar (HgS) is included in ~6.7% recipes of Chinese medicines, including Hua-Feng-Dan. We have shown the protective effects of Hua-Feng-Dan against LPS plus rotenone or MPTP induced neurodegeneration with modulatory effects on gut microbiota. This study further used DNA sequencing to examine the effects of Hua-Feng-Dan on gut microbiome in comparison to HgS and HgCl2 for safety evaluation. Methods: Mice were given orally with Hua-Feng-Dan at clinical doses (0.6 and 1.5 g/kg), approximate Hg as HgS (30 mg/kg), or HgCl2 (33.6 mg/kg) for 7 days. Intestinal histology and accumulation of Hg in the duodenum were examined. Bacterial DNA from the large intestine content was extracted and subjected to DNA sequencing and qPCR verification with 16S rRNA probes. Results: Hua-Feng-Dan and HgS did not affect animal body weight, intestinal histology and produce overt intestinal Hg accumulation (1-2 fold). In contrast, HgCl2 retarted body weight gain, produced spotted mild inflammation, and produced 20-fold Hg accumulation in the intestine. Operational taxonomic unit (OTU) from DNA sequencing showed that at phyla levels, HgS increased Firmicutes and decreased Bacteroidetes, while HgCl2 produced opposite effects; At the family levels, Hua-Feng-Dan increased Streptococcaceae and Dehalobacteriaceae, HgS had similar effects; At the genus levels, Hua-Feng-Dan and HgS increased Streptococcaceae__garvieae and Paraprevotellaceae__Prevotella; HgS increased Verrucomicrobiaceae__Akkermansia, while HgCl2 increased Dehalobacteriaceae__Dehalobacterium and Odoribacteraceae__Odoribacter. HgS produced more alterations in gut microbiome. Conclusions: Hua-Feng-Dan had minimal effects on animal health, gut histology and Hg accumulation but produced alterations of gut microbiome. Effects of Hua-Feng-Dan on gut microbiome are different from HgS and HgCl2.