Probiotic E. coli treatment mediates antimicrobial human beta-defensin synthesis and fecal excretion in humans - PubMed (original) (raw)

Probiotic E. coli treatment mediates antimicrobial human beta-defensin synthesis and fecal excretion in humans

M Möndel et al. Mucosal Immunol. 2009 Mar.

Abstract

Inducible epithelial human beta-defensins (hBD) play an important role in intestinal barrier function. In vitro studies showed that clinically effective probiotics induce antimicrobial hBD-2. Here, we aimed to assess the in vivo effect in healthy volunteers and also addressed how defensins affect probiotic survival. Symbioflor 2 containing one strain of several viable genotypes of Escherichia coli was administered to 23 healthy individuals. After 3 weeks, fecal hBD-2 peptide was increased in 78% (mean 3.7-fold; P<0.0001). Interestingly, the fecal hBD-2 peptide was still elevated 9 weeks after treatment (P=0.008). In vitro studies revealed that this effect was mediated by only one out of three tested E. coli genotypes and comparable to probiotic E. coli Nissle 1917 (10- to 15-fold). Functional assays showed that all tested bacteria were similarly killed by defensins allowing to speculate about a suicidal character of this effect. Defensin induction seems to be a common and important mechanism of probiotic treatment.

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Figures

Figure 1

Figure 1

Probiotics stimulate hBD-2 protein secretion in vivo. (a) hBD-2 peptide secretion after 3 weeks of placebo treatment in five individuals. (b) In total, 23 individuals received preparations of Symbioflor 2 for 3 weeks. HBD-2 peptide was determined by ELISA in stool samples. Data were normalized to hBD-2 levels before treatment that were set as 1 and represent the mean±s.e.m. (c) Probiotics exert a post-treatment effect on hBD-2 secretion. HBD-2 peptide levels are shown in a subset at day 0, after 3 weeks of probiotic treatment and 9 weeks after stop of treatment. Paired _t_-tests were used for the comparison of values before and after treatment. The data represent the means±s.e.m. **P<0.01; ***P<0.001. PowerPoint slide

Figure 2

Figure 2

Symbioflor 2 induces hBD-2 in intestinal epithelial cells in vitro. (a) Incubation of Caco-2 cells with three genotypes of Symbioflor 2 E. coli strain (G1, G2, G3). Caco-2 cells were incubated for 6 h with the heat-killed test bacteria and two probiotic strains as controls (optical density of 0.3). RNA was isolated, reverse-transcribed into cDNA, and the amount of hBD-2 copies was determined by real-time PCR. (b) Time course of hBD-2 induction by Symbioflor 2. Caco-2 cells were treated with the three genotypes (G1, G2, G3) of Symbioflor 2 E. coli strain for 3, 6, 9, and 12 h. (c) Dose dependence, Caco-2 cells were treated for 6 h with elevating doses of the genotype G2 of the Symbioflor 2 E. coli strain. The data represent the mean±s.e.m. of three independent experiments performed in duplicates. Unpaired _t_-tests were used to evaluate the statistical significance for comparisons between the groups. The data represent the means±s.e.m. *P<0.05; **P<0.01. PowerPoint slide

Figure 3

Figure 3

Antimicrobial resistance of probiotic and control E. coli toward antimicrobial peptides. (a) hBD-2, (b) hBD-3, (c) lysozyme. Representative antimicrobial plate assays are shown for each antimicrobial (upper part). The data represent the mean±s.e.m. and were analyzed for statistical significance using one sample _t_-test. **P<0.01; ***P<0.001. PowerPoint slide

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