Antigenotoxicity of probiotics and prebiotics on faecal water-induced DNA damage in human colon adenocarcinoma cells

Six strains of lactic acid producing bacteria (LAB) were incubated (1 x 10(8)cfu/ml) with genotoxic faecal water from a human subject. HT29 human adenocarcinoma cells were then challenged with the resultant samples and DNA damage measured using the single cell gel electrophoresis (comet) assay. The LAB strains investigated were Bifidobacterium sp. 420, Bifidobacterium Bb12, Lactobacillus plantarum, Streptococcus thermophilus, Lactobacillus bulgaricus and Enterococcus faecium. DNA damage was significantly decreased by all bacteria used with the exception of Strep. thermophilus. Bif. Bb12 and Lact. plantarum showed the greatest protective effect against DNA damage. Incubation of faecal water with different concentrations of Bif. Bb12 and Lact. plantarum revealed that the decrease in genotoxicity was related to cell density. Non-viable (heat treated) probiotic cells had no effect on faecal water genotoxicity. In a second study, HT29 cells were cultured in the presence of supernatants of incubations of probiotics with various carbohydrates including known prebiotics; the HT29 cells were then exposed to faecal water. Overall, incubations involving Lact. plantarum with the fructooligosaccharide (FOS)-based prebiotics Inulin, Raftiline, Raftilose and Actilight were the most effective in increasing the cellular resistance to faecal water genotoxicity, whereas fermentations with Elixor (a galactooligosaccharide) and Fibersol (a maltodextrin) were less effective. Substantial reductions in faecal water-induced DNA damage were also seen with supernatants from incubation of prebiotics with Bif. Bb12. The supernatant of fermentations involving Ent. faecium and Bif. sp. 420 generally had less potent effects on genotoxicity although some reductions with Raftiline and Elixor fermentations were apparent.     

Metabolic and functional properties of lactic acid bacteria in the gastro-intestinal ecosystem: a comparative in vitro study between bacteria of intestinal and fermented food origin

Metabolic and functional properties of probiotic lactic acid bacteria (LAB) in the human gastro-intestinal ecosystem may be related to certain beneficial health effects. In this study, lactobacilli of either intestinal or fermented food origin were compared in their capability to survive low pH and bile, in their metabolic activity in the presence of bile salts and mucins, as well as in their potential to attach to enterocyte-like CaCO-2 cells. Food fermenting bacteria especially strains of the species Lactobacillus plantarum showed high tolerance to the consecutive exposure to hydrochloric acid (pH 1.5-2.5) and cholic acid (10 mM). Growth in and deconjugation of glycocholic (5 mM) and taurocholic acids (5 mM), as demonstrated for all lactobacilli of intestinal origin, was detected for food fermenting strains of the species L. plantarum, but not L. paracasei and L. sakei. Degradation of mucins was not observed for lactobacilli. Adhesion to the intestinal epithelial cell line CaCO-2 was demonstrated for several food fermenting bacterial strains in vitro. Soluble factors in the spent culture supernatants from intestinal and fermented food lactobacilli but not staphylococci cross reacted and synergized with cell wall components to promote adhesion to CaCO-2 cells. A competitive role of fecal bacteria on the adhesion of lactobacilli to CaCO-2 cells was demonstrated. In conclusion we have shown that metabolic and functional properties of intestinal lactobacilli are also found in certain bacteria of fermented food origin.     

健康仔猪肠道乳杆菌黑龙江地方株的鉴定与种属分析

为了从健康仔猪肠道中分离筛选用于研制微生态制剂的乳酸杆菌菌株,选择黑龙江省大庆、哈尔滨及宝泉岭地区部分猪场,采集12-60日龄健康仔猪肠道粪样64份。选用MRS乳酸杆菌专用培养基分离培养乳酸杆菌,通过分离株的形态特征和培养特性筛选出革兰阳性,厌氧,无芽胞杆菌48株。再通过生化试验鉴定和PCR种属分析,确定18株为乳酸杆菌。其中,罗伊乳杆菌7株,嗜酸乳杆菌5株,约氏乳杆菌2株,短乳杆菌1株,干酪乳杆菌假植物亚种1株,植物乳杆菌1株,詹氏乳杆菌1株。     

Recovery of Lactobacillus rhamnosus GG from human colonic biopsies

The colonization of Lactobacillus rhamnosus GG (ATCC 53103, henceforth L.GG) in five human colonoscopy patients was studied. The test subjects consumed whey drink fermented with the bacterium for 12 d before the colonoscopy. The presence of L.GG was subsequently checked both in the faecal samples and in the colonic biopsies obtained from various locations in the large intestine. In all patients L.GG was the dominant faecal lactic acid bacterium as a result of the administration. In four patients L.GG could also be recovered from the biopsies, while with one patient (suffering from ulcerative colitis diagnosed during the colonoscopy) no L.GG was detected in the biopsy samples. The results suggest that L.GG is able to adhere in vivo to the colon. Study of the faecal samples alone is apparently not sufficient for elucidation of the gastrointestinal ecology of probiotic bacteria.     

TNF-alpha sensitizes HT-29 colonic epithelial cells to intestinal lactobacilli

The ability of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) to influence epithelial interleukin (IL)-8 responses to the intestinal bacterium Lactobacillus plantarum 299v was analyzed in the human HT-29 colonic epithelial cell line. In the absence of TNF-alpha, IL-8 mRNA expression was not detectable by Northern blot analysis in HT-29 cells alone or in HT-29 cells co-cultured with L. plantarum 299v. However, TNF-alpha induced IL-8 mRNA expression, and co-culture of TNF-alpha-treated HT-29 cells with L. plantarum 299v significantly increased IL-8 mRNA expression above levels induced by TNF-alpha alone in an adhesion-dependent manner. The increase in IL-8 mRNA expression was not observed in TNF-alpha-treated HT-29/L. plantarum 299v co-cultures using heat-killed lactobacilli or when L. plantarum adhesion was prevented using mannoside or a trans-well membrane. Paradoxically, IL-8 secretion was decreased in TNF-alpha-treated HT-29 cells with L. plantarum 299v relative to cells treated with TNF-alpha alone. TNF-alpha-mediated responsiveness to L. plantarum 299v was further investigated by analyzing expression of a coreceptor for bacterial cell wall products CD14. HT-29 cells expressed CD14 mRNA and cell-surface CD14; however, TNF-alpha did not alter CD14 mRNA or cell-surface expression, and blockade of CD14 with monoclonal antibody MY4 did not alter the IL-8 response to L. plantarum 299v in TNF-alpha-treated HT-29 cells. These results indicate that although TNF-alpha sensitizes HT-29 epithelial cells to intestinal lactobacilli, the bacteria exert a protective effect by downregulating IL-8 secretion.     

Biodiversity-based identification and functional characterization of the mannose-specific adhesin of Lactobacillus plantarum

Lactobacillus plantarum is a frequently encountered inhabitant of the human intestinal tract, and some strains are marketed as probiotics. Their ability to adhere to mannose residues is a potentially interesting characteristic with regard to proposed probiotic features such as colonization of the intestinal surface and competitive exclusion of pathogens. In this study, the variable capacity of 14 L. plantarum strains to agglutinate Saccharomyces cerevisiae in a mannose-specific manner was determined and subsequently correlated with an L. plantarum WCFS1-based genome-wide genotype database. This led to the identification of four candidate mannose adhesin-encoding genes. Two genes primarily predicted to code for sortase-dependent cell surface proteins displayed a complete gene-trait match. Their involvement in mannose adhesion was corroborated by the finding that a sortase (srtA) mutant of L. plantarum WCFS1 lost the capacity to agglutinate S. cerevisiae. The postulated role of these two candidate genes was investigated by gene-specific deletion and overexpression in L. plantarum WCFS1. Subsequent evaluation of the mannose adhesion capacity of the resulting mutant strains showed that inactivation of one candidate gene (lp_0373) did not affect mannose adhesion properties. In contrast, deletion of the other gene (lp_1229) resulted in a complete loss of yeast agglutination ability, while its overexpression quantitatively enhanced this phenotype. Therefore, this gene was designated to encode the mannose-specific adhesin (Msa; gene name, msa) of L. plantarum. Domain homology analysis of the predicted 1,000-residue Msa protein identified known carbohydrate-binding domains, further supporting its role as a mannose adhesin that is likely to be involved in the interaction of L. plantarum with its host in the intestinal tract.     

A strain of Lactobacillus plantarum affects segmented filamentous bacteria in the intestine of immunosuppressed mice

Segmented filamentous bacteria (SFB) are present in the gastrointestinal tract of mice from weaning until the maturation of the immune system. Probiotic bacteria also have an effect on host immunity. To study the relationships established between these bacteria, samples from a mouse model fed with Lactobacillus plantarum under different immunological conditions were analysed. SFB populations were measured by a newly designed group-specific quantitative PCR assay. The results confirmed the presence of the probiotic in the intestine and an expansion of SFB in the ileum of immunocompromised mice, which was abolished upon administration of L. plantarum, an effect not described to date.     

Lactobacillus plantarum promotes Drosophila systemic growth by modulating hormonal signals through TOR-dependent nutrient sensing

There is growing evidence that intestinal bacteria are important beneficial partners of their metazoan hosts. Recent observations suggest a strong link between commensal bacteria, host energy metabolism, and metabolic diseases such as diabetes and obesity. As a consequence, the gut microbiota is now considered a "host" factor that influences energy uptake. However, the impact of intestinal bacteria on other systemic physiological parameters still remains unclear. Here, we demonstrate that Drosophila microbiota promotes larval growth upon nutrient scarcity. We reveal that Lactobacillus plantarum, a commensal bacterium of the Drosophila intestine, is sufficient on its own to recapitulate the?natural microbiota growth-promoting effect. L.?plantarum exerts its benefit by acting genetically upstream of the TOR-dependent host nutrient sensing system controlling hormonal growth signaling. Our results indicate that the intestinal microbiota should also be envisaged as a factor that influences the systemic growth of its host.     

Characterization of O-acetylation of N-acetylglucosamine: a novel structural variation of bacterial peptidoglycan

Peptidoglycan (PG) N-acetyl muramic acid (MurNAc) O-acetylation is widely spread in gram-positive bacteria and is generally associated with resistance against lysozyme and endogenous autolysins. We report here the presence of O-acetylation on N-acetylglucosamine (GlcNAc) in Lactobacillus plantarum PG. This modification of glycan strands was never described in bacteria. Fine structural characterization of acetylated muropeptides released from L. plantarum PG demonstrated that both MurNAc and GlcNAc are O-acetylated in this species. These two PG post-modifications rely on two dedicated O-acetyltransferase encoding genes, named oatA and oatB, respectively. By analyzing the resistance to cell wall hydrolysis of mutant strains, we showed that GlcNAc O-acetylation inhibits N-acetylglucosaminidase Acm2, the major L. plantarum autolysin. In this bacterial species, inactivation of oatA, encoding MurNAc O-acetyltransferase, resulted in marked sensitivity to lysozyme. Moreover, MurNAc over-O-acetylation was shown to activate autolysis through the putative N-acetylmuramoyl-L-alanine amidase LytH enzyme. Our data indicate that in L. plantarum, two different O-acetyltransferases play original and antagonistic roles in the modulation of the activity of endogenous autolysins.     

The effect of prebiotics on production of antimicrobial compounds, resistance to growth at low pH and in the presence of bile, and adhesion of probiotic cells to intestinal mucus

AIMS: Screening of five bile salt-resistant and low pH-tolerant lactic acid bacteria for inhibitory activity against lactic acid bacteria and bacterial strains isolated from the faeces of children with HIV/AIDS. Determining the effect of prebiotics and soy milk-base on cell viability and adhesion of cells to intestinal mucus. METHODS AND RESULTS: Lactobacillus plantarum 423, Lactobacillus casei LHS, Lactobacillus salivarius 241, Lactobacillus curvatus DF 38 and Pediococcus pentosaceus 34 produced the highest level of antimicrobial activity (12,800 AU ml(-1)) when grown in MRS broth supplemented with 2% (m/v) dextrose. Growth in the presence of Raftilose Synergy1, Raftilose L95 and Raftiline GR did not lead to increased levels of antimicrobial activity. Cells grown in the presence of Raftilose Synergy1 took longer to adhere to intestinal mucus, whilst cells grown in the absence of prebiotics showed a linear rate of binding. CONCLUSIONS: A broad range of gram-positive and gram-negative bacteria were inhibited. Dextrose stimulated the production of antimicrobial compounds. Adhesion to intestinal mucus did not increase with the addition of prebiotics. SIGNIFICANCE AND IMPACT OF THE STUDY: The strains may be incorporated in food supplements for HIV/AIDS patients suffering from gastro-intestinal disorders.     

接种植物乳杆菌(Lactobacillus plantarum)对小规模饲料稻青贮品质的影响

【目的】研究接种植物乳杆菌对小规模饲料稻品质的影响。【方法】以自然发酵的样品为对照,接种不同来源植物乳酸菌发酵饲料稻,发酵30 d后对饲料稻的感官进行评价;通过选择性平板对饲料稻青贮中的不同微生物进行计数;并采用V-Score评价法对发酵品质进行评定。【结果】相对自然发酵的样品而言,接种植物乳杆菌的青贮样品感官评分等级达到优良;乳酸菌为优势菌株,引起腐败变质的好氧菌、霉菌、大肠杆菌等受到抑制;接种发酵的样品中乳酸含量明显增加,氨态氮的产生量为对照的1/2左右,V-Score评分为满分。【结论】供试的植物乳杆菌,尤其是从青饲料和青贮材料中分离的菌株能有效改善饲料稻青贮的品质,可考虑用作青贮饲料稻发酵剂。     

A mannose-specific adherence mechanism in Lactobacillus plantarum conferring binding to the human colonic cell line HT-29.

Two Lactobacillus plantarum strains of human intestinal origin, strains 299 (= DSM 6595) and 299v (= DSM 9843), have proved to be efficient colonizers of the human intestine under experimental conditions. These strains and 17 other L. plantarum strains were tested for the ability to adhere to cells of the human colonic cell line HT-29.L.plantarum 299 and 299v and nine other L. plantarum strains, including all six strains that belong to the same genetic subgroup as L. plantarum 299 and 299v, adhered to HT-29 cells in a manner that could be inhibited by methyl-alpha-D-mannoside. The ability to adhere to HT-29 cells correlated with an ability to agglutinate cells of Saccharomyces cerevisiae and erythrocytes in a mannose-sensitive manner and with adherence to D-mannose-coated agarose beads. L. plantarum 299 and 299v adhered to freshly isolated human colonic and ileal enterocytes, but the binding was not significantly inhibited by methyl-alpha-D-mannoside. Periodate treatment of HT-29 cells abolished mannose-sensitive adherence, confirming that the cell-bound receptor was of carbohydrate nature. Proteinase K treatment of the bacteria also abolished adherence, indicating that the binding involved protein structures on the bacterial cell surface. Thus, a mannose-specific adhesin has been identified in L. plantarum; this adhesin could be involved in the ability to colonize the intestine.     

Effects of lactobacillus plantarum ZJ316 on pig growth and pork quality

ABSTRACT: BACKGROUND: Lactobacillus plantarum is a plant-associated bacterial species but it has also been found in human, mouse and porcine gastrointestinal tracts. It can ferment a broad spectrum of plant carbohydrates; it is tolerant of bile salts and low pH, and it has antagonistic potential against intestinal pathogens. However, experiments reporting the use of L. plantarum as a probiotic are limited. In this study, the effects of L. plantarum ZJ316 isolated from infant fecal samples on pig growth and pork quality were investigated. RESULTS: One hundred and fifty newly weaned pigs were selected randomly and divided into five groups. Group 1 was fed a diet supplemented with the antibiotic mequindox; Groups 2, 3 and 4 were fed a diet supplemented with L. plantarum and no antibiotic; and Group 5 was fed a mixture of mequindox and L. plantarum. After a 60 days initial treatment, samples were collected for evaluation. The results showed that, the L. plantarum ZJ316 has probiotic effects on pig growth and that these effects are dose dependent. The effects of a dose of 1 x 109 CFU/d were more pronounced than those of a dose of 5 x 109 CFU/d or 1 x 1010 CFU/d. In Group 2 (1 x 109 CFU/d), the diarrhea (p = 0.000) and mortality rates (p = 0.448) were lower than in antibiotic-treated pigs (Group 1), and the daily weight gain (p = 0.001) and food conversion ratios were better (p = 0.005). Improved pork quality was associated with Lactobacillus treatment. pH (45 min, p = 0.020), hardness (p = 0.000), stickiness (p = 0.044), chewiness (p = 0.000), gumminess (p = 0.000) and restoring force (p = 0.004) were all significantly improved in Lactobacillus-treated pigs (Group 2). Although we found that L. plantarum exerted probiotic effects on pig growth and pork quality, the mechanisms underlying its action require further study. Polymerase chain reaction-denaturing gradient gel electrophoresis results showed that the gut bacterial communities in Lactobacillus- and antibiotic-treated pigs were very similar and the quantity of L. plantarum ZJ316 was below the detection limits of DGGE-band sequencing. The concentration of short-chain fatty acids in Lactobacillus- and antibiotic-treated fecal samples were not significantly different (p = 0.086). However, the villus height of ilea (p = 0.003), jejuna (p = 0.000) and duodena (p = 0.036) were found to be significantly improved by Lactobacillus treatment. CONCLUSION: L. plantarum ZJ316 was found to have probiotic effects, improving pig growth and pork quality. The probiotic mechanism might not involve L. plantarum colonization and alteration of the gut bacterial community. Rather, it might be related to the inhibition of the growth of opportunistic pathogens and promotion of increased villus height.     

Alternative pathways of nitric oxide formation in lactobacilli: EPR evidence for nitric oxide synthase activity

The study of the ability of Lactobacillus plantarum 8P-A3 to synthesize nitric oxide (NO) showed that this strain lacks nitrite reductase. However, analysis by the EPR method revealed the presence of nitric oxide synthase activity in this strain. Like mammalian nitric oxide synthase, lactobacillar NO synthase is involved in the formation of nitric oxide from L-arginine. L. plantarum 8P-A3 does not produce NO in the course of denitrification process. The regulatory role of NO in symbiotic bacteria is discussed.     

Expression of immune-related genes in rainbow trout (Oncorhynchus mykiss) induced by probiotic bacteria during Lactococcus garvieae infection

The aim of the present study was to investigate the effect of lactic acid bacteria (LAB) on the control of lactococcosis as well as to assess the impact of probiotics on the expression of immune-related genes in the head kidney and intestine of rainbow trout (Oncorhynchus mykiss). Lactobacillus plantarum, Lactococcus lactis and Leuconostoc mesenteroides, were administered orally at 10? CFU g?1 feed to fish for 36 days. Twenty-one days after the start of the feeding period, fish were challenged with Lactococcus garvieae. Only the fish fed the diet containing Lb. plantarum showed significantly (P < 0.05) improved protection against L. garvieae compared to the control. Subsequently, real-time PCR was employed to determine the mRNA levels of IL-1β, IL-8, IL-10 and TNF-α in the head kidney, and IL-8, Tlr5 and IgT in the intestine of the control and Lb. plantarum groups. IL-1β, IL-10 and TNF-α gene expression were significantly up-regulated by Lb. plantarum. Moreover, the mRNA levels of IL-10, IL-8 and IgT were significantly higher in the Lb. plantarum group after L. garvieae infection, suggesting that Lb. plantarum can stimulate the immune response of rainbow trout. PCR-DGGE revealed no detectable levels of the probiotics or the pathogen present on the distal intestinal mucosa. These findings demonstrate that direct probiotic-host interactions with the intestine are not always necessary to induce host stimulatory responses which ultimately enhance disease resistance. Furthermore, as L. garvieae did not colonise the intestinal tract, and therefore likely did not infect via this route, the antagonistic properties of the probiotic candidate towards L. garvieae were likely of little influence in mediating the improved disease resistance which could be attributed to the elevated immunological response.     

Isolation of bovine intestinal Lactobacillus plantarum and Pediococcus acidilactici with inhibitory activity against Escherichia coli O157 and F5

Aims:  The growth rate of bovine lactic acid bacteria (LAB) in five different culture conditions, and their inhibitory activity against Escherichia coli O157 and F5 in two assays was assessed to identify LAB for potential prophylactic use in cattle.
Methods and Results:  106 bovine-derived faecal/intestinal LAB were tested in vitro for tolerance to pH 2·0, pH 4·0, 0·15% and 0·3% bile, aerobic incubation, and for inhibitory activity against E. coli O157 ( n  = 3) and F5 ( n  = 1). While no LAB grew at pH 2·0, LAB survivability varied between 35% and 100% on the other tests. Exactly 7·6% (8/106) of LAB supernatants inhibited the growth of E. coli in two assays, whereas 6·6% (7/106) of isolates enhanced the growth of all E. coli strains. Partial 16s rRNA gene sequencing of six best isolates (95th percentile) revealed that five were Lactobacillus plantarum and one Pediococcus acidilactici.
Conclusion:  Lactobacillus plantarum with acid/bile and aerobic resistance and inhibitory activity against E. coli O157 and F5 inhabit the intestinal tract of healthy cattle. Some LAB may enhance E. coli growth.
Significance and Impact of the Study:  Lactobacillus plantarum and P. acidilactici are natural plant micro-organisms and studied silage inoculants. Their identification from gastrointestinal samples of healthy cattle is prophylactically promising.     

Occurrence and activity of human intestinal bacteria involved in the conversion of dietary lignans

The human intestinal microbiota is necessary for the production of enterolignans from the dietary lignan secoisolariciresinol diglucoside (SDG). However, little is known about the bacteria that contribute to SDG conversion. Therefore, we aimed at describing the occurrence and activity of SDG metabolising bacteria. The data showed differences in conversion efficiency between SDG deglycosylating species, but SDG was completely deglycosylated within 20 h by five of six strains. The strain Clostridium sp. SDG-Mt85-3Db showed the highest initial rate of SDG deglycosylation. Furthermore, we found that Bacteroides distasonis and B. fragilis made up 0.5% and 3.3% of total faecal bacteria, respectively. However, Clostridium sp. SDG-Mt85-3Db was detected within the dominant microbiota of only two out of 20 faecal samples. Bacteria involved in the demethylation step of SDG conversion also demethylated a variety of compounds other than SDG. In particular, Peptostreptococcus productus demethylated the lignans pinoresinol, lariciresinol and matairesinol. Finally, Eggerthella lenta catalysed the reduction of pinoresinol and lariciresinol to secoisolariciresinol.     

Probiotic properties of Lactobacillus strains isolated from the feces of breast-fed infants and Taiwanese pickled cabbage

This study assessed potential probiotic Lactobacillus strains isolated from the feces of breast-fed infants and from Taiwanese pickled cabbage for their possible use in probiotic fermented foods by evaluating their (i) in vitro adhesive ability, resistance to biotic stress, resistance to pathogenic bacteria, and production of β-galactosidase; (ii) milk technological properties; and (iii) in vivo adhesive ability, intestinal survival and microbial changes during and after treatment. Five Lactobacillus isolates identified as Lactobacillus reuteri F03, Lactobacillus paracasei F08, Lactobacillus rhamnosus F14, Lactobacillus plantarum C06, and Lactobacillus acidophilus C11 that showed resistance to gastric juice and bile salts were selected for further evaluation of their probiotic properties. All the strains demonstrated the ability to adhere to Caco-2 cells, particularly, strain L. plantarum C06 and L. reuteri F03 showed satisfactory abilities, which were similar to that of the reference strain L. rhamnosus GG. The strains L. paracasei F08 and L. acidophilus C11 had the highest β-galactosidase activity. Most of the strains were resistant to aminoglycosides and vancomycin but sensitive to ampicillin, erythromycin, and penicillin. All the 5 strains elicited antibacterial activity against both Gram-positive (Bacillus cereus, Listeria monocytogenes and Staphylococcus aureus) and -negative (Escherichia coli and Salmonella enterica) pathogens. Moreover, the strains L. reuteri F03, L. paracasei F08, and L. plantarum C06 could grow rapidly in milk without nutrient supplementation and reached 10? cfu/mL after 24 h of fermentation at 37 °C. The viable cell counts of the 3 strains remained above 10? cfu/mL after 21 d of storage at 4 °C. In the animal feeding trial, the number of intestinal lactobacilli increased significantly after administration of milk fermented with the 3 strains, and the counts of fecal coliforms and Clostridium perfringens were markedly reduced. Lactobacillus strains could also survive in the ileal intestinal tissue of the treated rats. Technologically interesting Lactobacillus isolates may be used in the future as probiotic starter cultures for manufacturing novel fermented foods.     

Probiotics potentiate IL-6 production in IL-1beta-treated Caco-2 cells through a heat shock-dependent mechanism

IL-6 may exert anti-inflammatory and protective effects in intestinal mucosa and enterocytes. The influence of probiotics on mucosal and enterocyte IL-6 production is not known. We tested the hypothesis that the probiotic bacteria Lactobacillus paracasei and Lactobacillus plantarum regulate IL-6 production in intestinal epithelial cells. Cultured Caco-2 cells were treated with 1 ng/ml of IL-1beta in the absence or presence of different concentrations of L. paracasei or L. plantarum followed by measurement of IL-6 production. The role of heat shock response was examined by determining the expression of heat shock protein 70 (hsp70) and hsp27, by downregulating their expression with small interfering RNA (siRNA), or by treating cells with quercetin. Treatment of the Caco-2 cells with IL-1beta resulted in increased IL-6 production, confirming previous reports from this laboratory. Probiotics alone did not influence IL-6 production, but the addition of probitoics to IL-1beta-treated cells resulted in a substantial augmentation of IL-6 production. Treatment of the Caco-2 cells with live L. paracasei increased cellular levels of hsp70 and hsp27 and the potentiating effect on IL-6 production was inhibited by quercetin and by hsp70 or hsp27 siRNA. Results suggest that probiotics may enhance IL-6 production in enterocytes subjected to an inflammatory stimulus and that this effect may, at least in part, be heat shock dependent.