Acetaldehyde exposure underlies functional defects in monocytes induced by excessive alcohol consumption

Sci Rep. 2021 Jul 1;11(1):13690. doi: 10.1038/s41598-021-93086-y.


Increased intestinal permeability and hepatic macrophage activation by endotoxins are involved in alcohol-induced liver injury pathogenesis. Long-term alcohol exposure conversely induces endotoxin immune tolerance; however, the precise mechanism and reversibility are unclear. Seventy-two alcohol-dependent patients with alcohol dehydrogenase-1B (ADH1B, rs1229984) and aldehyde dehydrogenase-2 (ALDH2, rs671) gene polymorphisms admitted for alcohol abstinence were enrolled. Blood and fecal samples were collected on admission and 4 weeks after alcohol cessation and were sequentially analyzed. Wild-type and ALDH2*2 transgenic mice were used to examine the effect of acetaldehyde exposure on liver immune responses. The productivity of inflammatory cytokines of peripheral CD14+ monocytes in response to LPS stimulation was significantly suppressed in alcohol dependent patients on admission relative to that in healthy controls, which was partially restored by alcohol abstinence with little impact on the gut microbiota composition. Notably, immune suppression was associated with ALDH2/ADH1B gene polymorphisms, and patients with a combination of ALDH2*1/*2 and ADH1B*2 genotypes, the most acetaldehyde-exposed group, demonstrated a deeply suppressed phenotype, suggesting a direct role of acetaldehyde. In vitro LPS and malondialdehyde-acetaldehyde adducted protein stimulation induced direct cytotoxicity on monocytes derived from healthy controls, and a second LPS stimulation suppressed the inflammatory cytokines production. Consistently, hepatic macrophages of ethanol-administered ALDH2*2 transgenic mice exhibited suppressed inflammatory cytokines production in response to LPS compared to that in wild-type mice, reinforcing the contribution of acetaldehyde to liver macrophage function. These results collectively provide new perspectives on the systemic influence of excessive alcohol consumption based on alcohol-metabolizing enzyme genetic polymorphisms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetaldehyde / adverse effects*
  • Alcohol Dehydrogenase / genetics
  • Alcohol Drinking / genetics
  • Alcohol Drinking / pathology*
  • Alcoholism / genetics
  • Alcoholism / pathology*
  • Aldehyde Dehydrogenase, Mitochondrial / genetics
  • Animals
  • Cells, Cultured
  • Genetic Predisposition to Disease
  • Humans
  • Liver Cirrhosis, Alcoholic / genetics
  • Liver Cirrhosis, Alcoholic / pathology
  • Male
  • Mice
  • Middle Aged
  • Monocytes / drug effects
  • Monocytes / pathology*
  • Polymorphism, Genetic


  • ADH1B protein, human
  • Alcohol Dehydrogenase
  • ALDH2 protein, human
  • Aldehyde Dehydrogenase, Mitochondrial
  • Acetaldehyde