In vitro inhibition of Escherichia coli β-glucuronidase by aripiprazole

BACKGROUND: Gut microbial β-glucuronidase (GUS) regulates the deconjugation of glucuronidated compounds, thereby influencing the enterohepatic circulation of xenobiotics and endogenous metabolites. Although many orally administered drugs reach the intestinal lumen, their direct effects on microbial enzyme functions remain incompletely understood. In this study, we systematically examined the impact of ten commonly prescribed central nervous system (CNS)-active drugs on microbial GUS activity. METHODS: GUS inhibition was evaluated using purified GUS from Escherichia coli (E. coli), E. coli cell lysates, and intact bacteria, with p-nitrophenyl β-D-glucuronide as the substrate. Intracellular drug accumulation was quantified by high-performance liquid chromatography-tandem mass spectrometry, bacterial growth was assessed by optical density, and GUS activity in mouse cecal contents was analyzed ex vivo. Molecular docking and molecular dynamics simulations were conducted to characterize drug-GUS interactions. RESULTS: Purified GUS screening identified aripiprazole (ARI) and duloxetine hydrochloride (DLX) as inhibitors. In intact E. coli, ARI, but not DLX, suppressed intracellular GUS activity without affecting bacterial growth. ARI also accumulated in E. coli at higher levels than DLX. In ex vivo assays, ARI showed inhibitory effects on GUS activity. Computational analyses suggested that ARI and DLX may preferentially interact with distinct regions of GUS, with ARI exhibiting more favorable binding energetics. CONCLUSIONS: These findings suggest that specific CNS-active drugs may directly modulate gut microbial GUS activity in E. coli under experimental conditions. In particular, ARI inhibited intracellular GUS activity, raising the possibility that certain neuropsychiatric drugs may influence microbial metabolic functions in addition to their canonical pharmacological targets.