Probiotic lactobacilli and VSL#3 induce enterocyte beta-defensin 2

Area of Science:

• Microbiology
• Immunology
• Gastroenterology

Background:

• Probiotic bacteria may improve gut barrier integrity.
• Antimicrobial peptides, such as defensins, are key components of this barrier function.
• The specific mechanisms by which probiotics induce defensins require further elucidation.

Purpose of the Study:

• To investigate the induction mechanism of human beta defensin-2 (hBD-2) gene expression by probiotic Lactobacillus strains.
• To identify the signaling pathways involved in hBD-2 gene induction by probiotics.

Main Methods:

• Treatment of Caco-2 intestinal cells with various Lactobacillus strains and the VSL#3 probiotic mixture.
• Analysis of hBD-2 mRNA expression levels.
• Reporter assays using modified hBD-2 promoter constructs with deleted NF-kappaB and AP-1 binding sites.
• Inhibition studies using specific MAPK pathway inhibitors (ERK1/2, p38, JNK).
• Enzyme-linked immunosorbent assay (ELISA) to measure hBD-2 peptide secretion.

Main Results:

• Probiotic treatment significantly increased hBD-2 mRNA expression in a dose- and time-dependent manner.
• NF-kappaB and AP-1 signaling pathways are essential for probiotic-induced hBD-2 expression.
• MAPK pathways, including ERK1/2, p38, and JNK, are involved in hBD-2 induction.
• Lactobacillus strains and VSL#3 induced hBD-2 peptide secretion into the cell culture medium.

Conclusions:

• Lactobacillus species and the VSL#3 probiotic mixture enhance intestinal barrier function.
• This enhancement is mediated by the up-regulation of hBD-2.
• The induction mechanism involves the activation of pro-inflammatory pathways, including NF-kappaB, AP-1, and MAPKs.