Lactobacillus fermentum L930BB and Bifidobacterium animalis subsp. animalis IM386 initiate signalling pathways involved in intestinal epithelial barrier protection

The manipulation of intestinal microbiota with beneficial microbes represents a promising alternative or adjunct therapy in gastrointestinal disorders and inflammation. The current study aims to clarify the signalling pathways and evaluate the possible beneficial effects of the combination of two strains. We used a dextran sulphate sodium (DSS)-induced mouse model of colitis. RNA extracted from the middle part of the colon tissue was used for examination of the global gene expression with Affymetrix microarrays. An enrichment analysis of the KEGG pathways was performed, and a subset of genes associated with intestinal epithelial barrier function was verified with qPCR. A clinical condition assessment of the differently treated mice revealed that the combination of these two bacterial strains was safe for use as a dietary supplement. All animals treated with DSS had affected colons and suffered weight loss. There were very small differences between the diseased groups, although the depth of inflammation was lower when cyclosporine A or the strain mixture was used. We discovered that the prophylactic administration of the Lactobacillus fermentum L930BB (L930BB) and Bifidobacterium animalis subsp. animalis IM386 (IM386) strains led to an anti-apoptotic pathway through phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/Akt and to the activation of pathways involved in the regulation of actin cytoskeleton via protein kinase C and GTPases. Reorganisation of actin cytoskeleton and decreased apoptosis are both helpful in intestinal epithelial cell reconstitution. We confirm important previous observations, showing that these pathways are downstream targets of Toll-like receptor 2 and fibroblast growth factor initiated signalling. Taken together, these results suggest that the combination of L930BB and IM386 could aid in the regeneration of the intestinal epithelium during pathogenesis via pattern recognition receptors and the stimulation of growth factor synthesis.

Human intestinal mucosa-associated Lactobacillus and Bifidobacterium strains with probiotic properties modulate IL-10, IL-6 and IL-12 gene expression in THP-1 cells

Lactobacilli and bifidobacteria are considered one of the permanent genera of the physiological human intestinal microbiota and represent an enormous pool of potential probiotic candidates. Approximately 450 isolates of presumptive Lactobacillus or Bifidobacterium strains were obtained from bioptic samples of colonic and ileal mucosa from 15 adolescents aged 12 to 18 years. On the basis of randomly amplified polymorphic DNA (RAPD)-PCR analysis, 20 strains were selected for further taxonomic classification and characterisation, as well as assessment of probiotic properties and safety. Importantly, selected strains showed the capability of colonising different parts of the intestine. The most frequently isolated species was Lactobacillus paracasei followed by Lactobacillus fermentum. The majority of isolates were susceptible to antimicrobials of human and veterinary importance, however, tetracycline and/or erythromycin resistance was observed in Lactobacillus plantarum and L. fermentum strains. Thirteen strains were able to ferment more than 19 different carbon sources and three out of five tested strains exerted antagonistic activity against several different indicator strains. Two Lactobacillus isolates (L. paracasei L350 and L. fermentum L930 bb) and one Bifidobacterium isolate (Bifidobacterium animalis subsp. animalis IM386) fulfilled in vitro selection criteria for probiotic strains and exhibited strong downregulation of pro-inflammatory cytokines IL-6 and IL-12 and upregulation of anti-inflammatory IL-10. The selected strains represent suitable candidates for further studies regarding their positive influence on host health and could play an important role in ameliorating the symptoms of inflammatory bowel diseases.

Lactobacillus gasseri K7 modulates the blood cell transcriptome of conventional mice infected with Escherichia coli O157:H7

AIMS

As the immune cells underlying the intestinal barrier sense luminal microbial signals, blood cell transcriptomics may identify subclinical changes triggered by gut bacteria that may otherwise not be detected. We have therefore investigated how Lactobacillus gasseri K7 and enterohemorrhagic Escherichia coli O157:H7 modulate the blood cell transcriptome of mice possessing an intact microbiota.

METHODS AND RESULTS

We have analysed the transcriptome of five groups of C57BL/6J mice: (i) control, (ii) inoculated with a single dose of E. coli, (iii) inoculated during 2 weeks with Lact. gasseri, (iv) co-inoculated with E. coli and Lact. gasseri, (v) inoculated with Lact. gasseri prior to E. coli infection. The transcriptome could distinguish between the five treatment groups. Gene characteristics of bacterial infection, in particular inflammation, were upregulated in the mice inoculated with E. coli. Lact. gasseri had only mild effects on the transcriptome but modified the gene expression induced by E. coli.

CONCLUSIONS

The transcriptome differentiates mice inoculated orally with E. coli, Lact. gasseri and combinations of these two strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results suggest that the blood cell transcriptome can be used as a source of biomarkers to monitor the impact of probiotics in subclinical models of infectious disease.