Adenosine signaling driven by the gut microbiota underlies chronic alcohol-induced anesthetic resistance.

Long-term alcohol exposure reduces anesthetic efficacy in both humans and mice, prolonging induction time and shortening maintenance duration.

• The phenomenon was demonstrated in both human subjects with chronic alcohol consumption and in mouse models of long-term alcohol exposure.
• Anesthetic resistance manifested as prolonged induction (time to reach anesthetic state) and shortened maintenance (duration of anesthetic effect).
• This constitutes the core clinical and translational observation of the study.

Fecal microbiota transplantation (FMT) from alcohol-exposed donors recapitulated anesthetic resistance in naive mice, establishing a causal role for gut microbiome alterations.

• Naive recipient mice that received FMT from alcohol-exposed donors exhibited the same anesthetic resistance phenotype as the alcohol-exposed donors.
• This FMT experiment provided causal evidence that gut microbiome changes, not direct alcohol effects, are sufficient to transfer the anesthetic resistance phenotype.
• The result indicates the gut microbiota plays a mechanistically causal role, not merely a correlative one, in alcohol-induced anesthetic tolerance.

Metagenomic and metabolomic analyses identified elevated adenosine as a key microbiota-derived metabolite associated with chronic alcohol exposure.

• Both metagenomic (gut microbiota composition) and metabolomic (metabolite profiling) analyses were performed to identify relevant microbial changes.
• Adenosine was identified as significantly elevated among microbiota-derived metabolites in the alcohol-exposed condition.
• Adenosine was identified as the key mediator linking gut microbiota alterations to anesthetic resistance.

Adenosine supplementation decreased anesthetic sensitivity in mice, phenocopying the alcohol-induced anesthetic resistance.

• Direct administration of adenosine to naive mice reduced their sensitivity to anesthesia.
• This experiment confirmed that elevated adenosine levels are sufficient to recapitulate the anesthetic resistance phenotype without alcohol exposure.
• The finding supports adenosine as a functional downstream effector of the gut microbiota-mediated mechanism.

The mechanism of adenosine-mediated anesthetic resistance likely involves downregulation of gamma-aminobutyric acid (GABA) receptors.

• GABA receptor downregulation was identified as a likely molecular mechanism underlying the reduced anesthetic sensitivity.
• GABA receptors are well-established targets of many common anesthetics, making their downregulation mechanistically plausible for anesthetic resistance.
• The authors describe this as a 'gut microbiota-adenosine pathway' mediating the downregulation of GABA receptors.

The study establishes a gut microbiota-adenosine signaling pathway as the mechanistic basis for chronic alcohol-induced anesthetic resistance.

• The pathway proceeds from chronic alcohol exposure to gut microbiota alterations, leading to elevated microbiota-derived adenosine, which downregulates GABA receptors and reduces anesthetic efficacy.
• Prior to this study, the in vivo mechanisms underlying increased anesthetic tolerance in chronic alcohol consumers remained unclear.
• The findings integrate clinical observation, FMT causality experiments, multi-omics analyses, and mechanistic supplementation experiments into a unified pathway.