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Appl. Environ. Microbiol. doi:10.1128/AEM.02944-06
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Lactobacillus rhamnosus strain GG reduces aflatoxin B₁ transport, metabolism and toxicity in Caco-2 cells

Department of Clinical Nutrition, University of Kuopio, P. O. Box 1627, 70211 Kuopio, Finland; Food and Health Research Centre, University of Kuopio, P. O. Box 1627, 70211 Kuopio, Finland; Department of Pharmacology and Toxicology, University of Kuopio, P. O. Box 1627, 70211 Kuopio, Finland; Molecular Epidemiology Unit, Centre for Epidemiology and Biostatistics, LIGHT Laboratories, University of Leeds, LS2 9JT Leeds, United Kingdom

^* To whom correspondence should be addressed. Email: silvia.gratz{at}uku.fi.

	Abstract

The probiotic Lactobacillus rhamnosus GG (GG) is able to bind the potent hepatocarcinogen aflatoxin B₁ (AFB₁) and thus potentially restrict its rapid absorption from the intestine. In this study we investigated the potential of GG to reduce AFB₁ availability in vitro in Caco-2 cells adapted to express CYP 3A4, such that both transport and toxicity could be assessed. Caco-2 cells were grown as confluent monolayers on transmembrane filters for 21 days prior to all studies. AFB₁ levels in culture medium were measured by HPLC. In CYP 3A4 induced monolayers AFB₁ transport from the apical to the basolateral chamber was reduced from 11.1 ±1.9% to 6.4 ±2.5% (p=0.019) and 3.3 ±1.8% (p=0.002) within the first hour in monolayers co-incubated with GG (1 and 5x10¹⁰ CFU/ml, respectively). GG (1 and 5x10¹⁰ CFU/ml) bound 40.1±8.3% and 61.0±6.0% of added AFB₁ after 1 hour, respectively. AFB₁ caused a significant reduction in transepithelial resistance by 30.1% (p=0.01), 49.4% (p=0.004) and 64.4% (p<0.001) after 24, 48 and 72 hours respectively. Co-incubation with 1x10¹⁰ CFU/ml GG after 24 hours protected against AFB₁ induced reductions in transepithelial resistance at both 24 hours (p=0.002), and 48 hours (p=0.04). DNA fragmentation was apparent in AFB₁ only treated cells but not in cells co-incubated with either 1 or 5x10¹⁰ CFU/ml GG. GG reduced AFB₁ uptake and protected against both membrane and DNA damage in the Caco-2 model. These data are suggestive of beneficial role of GG against dietary exposure to aflatoxin.