Bacillus subtilis plays a role in the inhibition of transporter ABCB1 in Caco-2 cells

Backgrounds: The mechanism of drug-resistant epilepsy has been incompletely understood, and the transporter hypothesis is one of the most cited theories. The association between gut microbiome and epilepsy is increasingly recognized but the mechanism remains unclear. We hypothesize that gut microbiome plays a role of pharmacokinetics of antiseizure medicines (ASMs) through transporters at the host-microbe interface. This study aimed to screen the key subspecies of gut microbiota related to drug-resistant epilepsy and explore their effects on the ASMs resistance mechanism through the regulation of transporter ATP-binding cassette B1 (ABCB1). Methods: Three groups of participants were designed, 10 drug-resistant epilepsy patients (DR group), 10 nondrug-resistant epilepsy patients (NDR group), and 19 healthy controls (Control group). Fresh stool samples were collected. Based on the 16S rRNA sequencing results of their fecal samples, we selected the Bacillus subtilis (B. subtilis) to explore its effect on the ASMs efflux mediated by transporter ABCB1 whose expression were detected through quantitative PCR and Western blot analysis in Caco-2 cell model. Further, we conducted the Rhodamine 123 accumulation assay to evaluate the activity of the transporter ABCB1 in Caco-2 cell and the highperformance liquid chromatography (HPLC) to measure the concentrations of ASMs. Results: We found that the Phylum Firmicutes were enriched in the patients with drug-resistant epilepsy (70.82%) and picked up B. subtilis as the key type of bacteria relevant to drug-resistant epilepsy. The B. subtilis not only downregulated the expression level and the efflux activity of ABCB1 in Caco-2 cells treated with ASMs (P < 0.01), but also reduced the carbamazepine efflux in the Caco-2 cells (P < 0.05). Conclusion: Our study identified B. subtilis as the key bacterial type associated with patients affected by drugresistant epilepsy and revealed that it also ameliorated resistance to ASMs by downregulating the transporter ABCB1.