Lactobacillus acidophilus LA14 Alleviates Liver Injury

Abstract

Although the probiotic Lactobacillus acidophilus LA14 is used worldwide, its effect on liver diseases remains unelucidated. Here, 32 rats were divided into four groups, gavaged with L. acidophilus LA14 (3 × 10⁹ CFU) or phosphate-buffered saline for 7 days, and then intraperitoneally injected with d-galactosamine or saline. After 24 h, blood, liver, ileum, and feces samples were collected for liver injury, inflammation, intestinal barrier, gut microbiota, metabolome, and transcriptome analyses. Pretreatment with L. acidophilus LA14 alleviated the d-galactosamine-induced elevation of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and bile acids; mitigated the histological injury to the liver and gut; and suppressed the inflammatory cytokines macrophage inflammatory protein 1α (MIP-1α), MIP-3α, and MCP-1. L. acidophilus LA14 also ameliorated the d-galactosamine-induced dysbiosis of the gut microbiota and metabolism, such as the enrichment of Bacteroides sp. strain dnLKV3 and the depletion of Streptococcus, butanoic acid, and N-acetyl-d-glucosamine. The underlying mechanism of L. acidophilus LA14 included prevention of not only the d-galactosamine-induced upregulation of infection- and tumor-related pathways but also the d-galactosamine-induced downregulation of antioxidation-related pathways during this process, as reflected by the liver transcriptome and proteome analyses. Furthermore, the administration of L. acidophilus LA14 to healthy rats did not alter the tested liver indicators but significantly enriched the beneficial Lactobacillus and Bifidobacterium species, promoted metabolism and regulated pathways to improve immunity. The ability of L. acidophilus LA14 to alleviate liver injury was further confirmed with an acetaminophen-induced mouse model. These results might provide a reference for future studies on the application of L. acidophilus LA14 for the prevention of liver injury. IMPORTANCE The probiotic Lactobacillus acidophilus LA14 is widely used, but its effect on liver diseases has not been elucidated. We explored the protective effect of L. acidophilus LA14 on the liver using rats with d-galactosamine-induced liver injury. Pretreatment with L. acidophilus LA14 alleviated the d-galactosamine-induced elevation of serum ALT, AST, ALP, and bile acids, mitigated the histological injury to the liver and gut, and suppressed the inflammatory cytokines MIP-1α, MIP-3α, and MCP-1. These effects were correlated with the modulations of the gut microbiome, metabolome, and hepatic gene expression induced by L. acidophilus LA14. Moreover, the ability of L. acidophilus LA14 to alleviate liver injury was further confirmed with an acetaminophen-induced mouse model. These results might provide a reference for future studies on the application of L. acidophilus LA14 for the prevention of liver injury.

Keywords: Lactobacillus acidophilus; acute liver injury; metabolome; microbiota; transcriptome.

FIG 1

L. acidophilus LA14 attenuated d-galactosamine-induced liver and ileum injury. (A) Liver function of each group. (B) Hepatic inflammatory cytokines MIP-1α, MIP-3α, and MCP-1. (C) Representative images of hepatic HE staining and histological scores of the livers. Scale bar, 100 μm. The black arrow indicates a lipid vacuole, the blue arrow indicates hemorrhage, and the white arrow points to neutrophil and macrophage accumulation. (D) L. acidophilus LA14 alleviated d-galactosamine-induced terminal ileum injury. Representative images of ileal HE staining and histological scores of the ileums. Scale bar, 100 μm. The data are shown as the means ± the SEM (*, P < 0.05; **, P < 0.01; ns, the difference is not significant).

FIG 2

L. acidophilus LA14 alleviated d-galactosamine-induced gut microbiota dysbiosis. (A) Differences in the amounts of observed species. The values are expressed as the medians with interquartile ranges. (B) PCoA plot with weighted UniFrac distance based on OTUs of the gut microbiota. (C) The relative abundances of gut bacteria were altered after d-GalN injection but significantly reversed by L. acidophilus LA14. (E) The relative abundance of gut bacterial taxa differed between the Ctrl and Ctrl+GalN groups but not between the Ctrl+GalN and LA14+GalN groups. (F) The relative abundance of genera and species in healthy rats was significantly altered after the oral administration of L. acidophilus LA14. The data are shown as means ± the SEM (*, P < 0.05; **, P < 0.01; ns, the difference is not significant).

FIG 3

L. acidophilus LA14 alleviated d-galactosamine-induced gut metabolome dysbiosis. (A) OPLS-DA score plots of metabolome profiles of the four groups. (B) VIP values with jack-knifed confidence intervals. Only metabolites with a VIP of >1.5 are shown. (C) Peak areas of metabolites altered after d-GalN injection but significantly reversed by L. acidophilus LA14. (D) Peak areas of metabolites different between the Ctrl and Ctrl+GalN groups but not between the Ctrl+GalN and LA14+GalN groups. (E) Peak areas of metabolites significantly altered after the oral administration of L. acidophilus LA14 in healthy rats. The data are shown as means ± the SEM (*, P < 0.05; **, P < 0.01; ns, the difference is not significant).

FIG 4

L. acidophilus LA14 regulated the transcription and/or expression of certain genes in the liver. (A and B) Genes (A) and KEGG pathways (B) that were altered after d-GalN injection but significantly alleviated by LA14 at the transcriptional level. FPKM, fragments per kilobase per million; #, P_adj < 0.05. (C and D) Proteins (C) and their related KEGG pathways (D) that were altered after d-GalN injection but significantly alleviated by LA14. *, P < 0.05. (E) Proteins of eight genes altered by d-GalN but alleviated by LA14 at both the transcription and expression levels. The data are shown as means ± the SEM (*, P < 0.05; **, P < 0.01; ns, the difference is not significant).

FIG 5

(A) Correlations of altered gut bacteria with altered gut metabolites. (B) Correlations of altered liver function indicators and inflammatory cytokines with hepatic genes altered at the transcription level. (C) Correlations of altered liver function indicators and inflammatory cytokines with altered hepatic proteins. (D) Correlations of altered gut bacteria and gut metabolites with altered liver function indicators, inflammatory cytokines, and hepatic genes altered at the transcription level. (E) Correlations of altered gut bacteria and gut metabolites with altered liver function indicators, inflammatory cytokines, and hepatic proteins. All of the results shown in the heatmap are significant at P < 0.05. The color key and circle size indicate the strength of the correlation (r value). Red indicates a positive correlation, and blue indicates a negative correlation.

FIG 6

L. acidophilus LA14 also attenuated acetaminophen-induced liver injury. (A) Liver function of each group. (B) Hepatic inflammatory cytokine IL-1α in each group. (C) Representative images of hepatic HE staining and histological scores of the livers. Scale bar, 50 μm. The black arrow points to hemorrhage, and the white arrow indicates nuclear shrinkage. The data are shown as means ± the SEM (*, P < 0.05; **, P < 0.01; ns, the difference is not significant).

FIG 7

General view of the beneficial effects of L. acidophilus LA14 on acute liver injury.