Expression levels of heat shock proteins in enterocyte-like Caco-2 cells after exposure to Salmonella enteritidis

Influence of Pediococcus pentosaceus GT001 on Performance, Meat Quality, Immune Function, Antioxidant and Cecum Microbial in Broiler Chickens Challenged by Salmonella typhimurium

This study evaluated the effects of Pediococcus pentosaceus GT001 on Salmonella typhimurium (S. typhimurium)-challenged broiler chickens. Two hundred Ross 708 broiler day-old chicks with comparable weight were distributed at random into four treatments with five replicates and ten chicks per replicate. The following were the treatment groups: (B) basal diet (control); (B + S) basal diet and birds were challenged with S. typhimurium at 1.0 × 107 cfu/g; (B + P) basal diet + Pediococcus pentosaceus GT001 at 4.0 × 108 cfu/g; (B + P + S) basal diet + P. pentosaceus GT001 at 4.0 × 108 cfu/g and birds were challenged with S. typhimurium at 1.0 × 107 cfu/g. There was a significant reduction (p < 0.05) in the body weight of the Salmonella-infected birds compared to the other treatment groups. However, the FCRs of the broilers were comparable among the different treatment groups (p > 0.05). The lipid profile and liver function indices measured were significantly enhanced in the P. pentosaceus GT001-supplemented groups (B + P and B + P + S) compared to the group that was Salmonella-challenged (p < 0.05) but were similar to those in the control group. The serum antioxidant activities, such as the T-AOC, SOD, CAT, GHS-Px and MDA, were significantly improved in the P. pentosaceus GT001-supplemented groups (B + P and B + P + S) (p < 0.05). The MDA was similar in the B + P and B + P + S groups, but both were significantly lower than the control and the Salmonella groups. The administration of P. pentosaceus GT001 enhanced the lipase and amylase levels in both the serum and intestine of the broilers (p < 0.05). The immunoglobin (IgA, IgG, IgM) and cytokine (IL-10 and IL-6) levels in the serum were significantly higher in the B, B + P and B + P + S treatment groups (p < 0.05). The immune-related organs (bursa and spleen) were significantly influenced in the birds fed with P. pentosaceus GT001. No significant variation was noted among all the dietary treatments in terms of the measured meat quality indices. The small intestinal digesta content of the Salmonella load was below a detectable range after 14 days of infection (p < 0.05). No significant differences were observed among the different treatment groups in terms of the breast pH, drip loss and meat color (p > 0.05). The inclusion of P. pentosaceus GT001 also modified the community structure in the cecum. This indicates that it has health benefits and could be incorporated in the broiler diet.

Evaluation of Virulence of Salmonella Infantis and Salmonella Enteritidis with In Vitro and In Vivo Models

Salmonella Infantis and Enteritidis serovars have been reported as important causes of salmonellosis in humans worldwide. However, the virulence of these two serovars has yet to be compared. To evaluate the virulence of Salmonella Infantis (n = 23) and Salmonella Enteritidis (n = 7), we used two models: the Caco2 cells model (in vitro) and the Galleria mellonella model (in vivo). Additionally, the virulence genes of all tested strains were contrasted with phenotypic outcomes. Results showed that adhesion means were 18.2% for Salmonella Enteritidis and 38.2% for Salmonella Infantis strains. Invasion means were 77.1% for Salmonella Enteritidis and 56.2% for Salmonella Infantis strains. Significant differences were found between serovars in adherence and invasion assays. Mortality rates (58% for Salmonella Enteritidis and 62.6% for Salmonella Infantis) were not significantly different between serotypes. The distribution of virulence genes showed that genes fae (fimbrial adherence determinants) and shdA (nonfimbrial adherence determinants) were only found in Salmonella Infantis strains. On the other hand, the rck gene (invasion) and Plasmid-encoded fimbriae genes (pef A, B, C, D) were present in Salmonella Enteritidis exclusively. In conclusion, this study shows that Salmonella Enteritidis has a higher virulence potential under experimental conditions than Salmonella Infantis. However, more studies are needed to determine the risk that Salmonella Infantis could represent compared with Salmonella Enteritidis. Moreover, other in vivo models should be considered to assess the virulence of these serovars.

Insect chaperones Hsp70 and Hsp90 cooperatively enhance toxicity of Bacillus thuringiensis Cry1A toxins and counteract insect resistance

Bacillus thuringiensis (Bt) produces different insecticidal proteins effective for pest control. Among them, Cry insecticidal proteins have been used in transgenic plants for the control of insect pests. However, evolution of resistance by insects endangers this technology. Previous work showed that the lepidopteran insect Plutella xylostella PxHsp90 chaperone enhanced the toxicity of Bt Cry1A protoxins by protecting them from degradation by the larval gut proteases and by enhancing binding of the protoxin to its receptors present in larval midgut cells. In this work, we show that PxHsp70 chaperone also protects Cry1Ab protoxin from gut proteases degradation, enhancing Cry1Ab toxicity. We also show that both PxHsp70 and PxHsp90 chaperones act cooperatively, increasing toxicity and the binding of Cry1Ab439D mutant, affected in binding to midgut receptors, to cadherin receptor. Also, insect chaperones recovered toxicity of Cry1Ac protein to a Cry1Ac-highly resistant P. xylostella population, NO-QAGE, that has a disruptive mutation in an ABCC2 transporter linked to Cry1Ac resistance. These data show that Bt hijacked an important cellular function for enhancing its infection capability, making use of insect cellular chaperones for enhancing Cry toxicity and for lowering the evolution of insect resistance to these toxins.

Two-Stage Interpretation of Changes in TEER of Intestinal Epithelial Layers Protected by Adhering Bifidobacteria During E. coli Challenges

Mechanisms of gastrointestinal protection by probiotic bacteria against infection involve amongst others, modulation of intestinal epithelial barrier function. Trans-epithelial electrical resistance (TEER) is widely used to evaluate cellular barrier functions. Here, we developed a two-stage interpretative model of the time-dependence of the TEER of epithelial layers grown in a transwell during Escherichia coli challenges in the absence or presence of adhering bifidobacteria. E. coli adhesion in absence or presence of adhering bifidobacteria was enumerated using selective plating. After 4-8 h, E. coli challenges increased TEER to a maximum due to bacterial adhesion and increased expression of a tight-junction protein [zonula occludens-1 (ZO-1)], concurrent with a less dense layer structure, that is indicative of mild epithelial layer damage. Before the occurrence of a TEER-maximum, decreases in electrical conductance (i.e., the reciprocal TEER) did not relate with para-cellular dextran-permeability, but after occurrence of a TEER-maximum, dextran-permeability and conductance increased linearly, indicative of more severe epithelial layer damage. Within 24 h after the occurrence of a TEER maximum, TEER decreased to below the level of unchallenged epithelial layers demonstrating microscopically observable holes and apoptosis. Under probiotic protection by adhering bifidobacteria, TEER-maxima were delayed or decreased in magnitude due to later transition from mild to severe damage, but similar linear relations between conductance and dextran permeability were observed as in absence of adhering bifidobacteria. Based on the time-dependence of the TEER and the relation between conductance and dextran-permeability, it is proposed that bacterial adhesion to epithelial layers first causes mild damage, followed by more severe damage after the occurrence of a TEER-maximum. The mild damage caused by E. coli prior to the occurrence of TEER maxima was reversible upon antibiotic treatment, but the severe damage after occurrence of TEER maxima could not be reverted by antibiotic treatment. Thus, single-time TEER is interpretable in two ways, depending whether increasing to or decreasing from its maximum. Adhering bifidobacteria elongate the time-window available for antibiotic treatment to repair initial pathogen damage to intestinal epithelial layers.

Effects of multi-strain probiotic supplementation on intestinal microbiota, tight junctions, and inflammation in young broiler chickens challenged with Salmonella enterica subsp. enterica

Objective

This study assessed the effects of probiotics on cecal microbiota, gene expression of intestinal tight junction proteins, and immune response in the cecal tonsil of broiler chickens challenged with Salmonella enterica subsp. enterica.

Methods

One-day-old broiler chickens (n = 240) were randomly allocated to four treatments: negative control (Cont), multi-strain probiotic-treated group (Pro), Salmonella-infected group (Sal), and multi-strain probiotic-treated and Salmonella-infected group (ProSal). All chickens except those in the Cont and Pro groups were gavaged with 1×10⁸ cfu/mL of S. enterica subsp. enterica 4 days after hatching.

Results

Our results indicated that body weight, weight gain, and feed conversion ratio of birds were significantly reduced (p<0.05) by Salmonella challenge. Chickens challenged with Salmonella decreased cecal microbial diversity. Chickens in the Sal group exhibited abundant Proteobacteria than those in the Cont, Pro, and ProSal groups. Salmonella infection downregulated gene expression of Occludin, zonula occludens-1 (ZO1), and Mucin 2 in the jejunum and Occludin and Claudin in the ileum. Moreover, the Sal group increased gene expression of interferon-γ (IFN-γ), interleukin-6 (IL-6), IL-1β, and lipopolysaccharide-induced tumor necrosis factor-alpha factor (LITAF) and reduced levels of transforming growth factor-β4 and IL-10 compared with the other groups (p<0.05). However, chickens receiving probiotic diets increased Lactobacillaceae abundance and reduced Enterobacteriaceae abundance in the ceca. Moreover, supplementation with probiotics increased the mRNA expression of Occludin, ZO1, and Mucin 2 in the ileum (p<0.05). In addition, probiotic supplementation downregulated the mRNA levels of IFN-γ (p<0.05) and LITAF (p = 0.075) and upregulated IL-10 (p = 0.084) expression in the cecal tonsil.

Conclusion

The administration of multi-strain probiotics modulated intestinal microbiota, gene expression of tight junction proteins, and immunomodulatory activity in broiler chickens.

Exposure to a Nonionic Surfactant Induces a Response Akin to Heat-Shock Apoptosis in Intestinal Epithelial Cells: Implications for Excipients Safety

Amphipathic, nonionic, surfactants are widely used in pharmaceutical, food, and agricultural industry to enhance product features; as pharmaceutical excipients, they are also aimed at increasing cell membrane permeability and consequently improving oral drugs absorption. Here, we report on the concentration- and time-dependent succession of events occurring throughout and subsequent exposure of Caco-2 epithelium to a "typical" nonionic surfactant (Kolliphor HS15) to provide a molecular explanation for nonionic surfactant cytotoxicity. The study shows that the conditions of surfactant exposure, which increase plasma membrane fluidity and permeability, produced rapid (within 5 min) redox and mitochondrial effects. Apoptosis was triggered early during exposure (within 10 min) and relied upon an initial mitochondrial membrane hyperpolarization (5-10 min) as a crucial step, leading to its subsequent depolarization and caspase-3/7 activation (60 min). The apoptotic pathway appears to be triggered prior to substantial surfactant-induced membrane damage (observed ≥60 min). We hence propose that the cellular response to the model nonionic surfactant is triggered via surfactant-induced increase in plasma membrane fluidity, a phenomenon akin to the stress response to membrane fluidization induced by heat shock, and consequent apoptosis. Therefore, the fluidization effect that confers surfactants the ability to enhance drug permeability may also be intrinsically linked to the propagation of their cytotoxicity. The reported observations have important implications for the safety of a multitude of nonionic surfactants used in drug delivery formulations and to other permeability enhancing compounds with similar plasma membrane fluidizing mechanisms.

Regulation of Antimicrobial Pathways by Endogenous Heat Shock Proteins in Gastrointestinal Disorders

Heat shock proteins (HSPs) are essential mediators of cellular homeostasis by maintaining protein functionality and stability, and activating appropriate immune cells. HSP activity is influenced by a variety of factors including diet, microbial stimuli, environment and host immunity. The overexpression and down-regulation of HSPs is associated with various disease phenotypes, including the inflammatory bowel diseases (IBD) such as Crohn’s disease (CD). While the precise etiology of CD remains unclear, many of the putative triggers also influence HSP activity. The development of different CD phenotypes therefore may be a result of the disease-modifying behavior of the environmentally-regulated HSPs. Understanding the role of bacterial and endogenous HSPs in host homeostasis and disease will help elucidate the complex interplay of factors. Furthermore, discerning the function of HSPs in CD may lead to therapeutic developments that better reflect and respond to the gut environment.

Effects of Pediococcus acidilactici, mannan-oligosaccharide, butyric acid and their combination on growth performance and intestinal health in young broiler chickens challenged with Salmonella Typhimurium

This study compared the efficacy of Pediococcus acidilactici, mannan-oligosaccharide, butyric acid, and their combination on growth performance and intestinal health in broiler chickens challenged with S. Typhimurium. Ross 308 male broilers (n = 420) were randomly assigned to one of the 6 treatments, resulting in 5 replicate pens of 14 chicks per treatment. The treatments included a negative control [(NC), no additive, not challenged]; positive control [(PC), no additive, but challenged with S. Typhimurium at d 3 posthatch], and 4 groups whereby birds were challenged with S. Typhimurium at d 3 posthatch and fed diets supplemented with either probiotic [0.1 g/kg Pediococcus acidilactici (PA)], prebiotic [2 g/kg mannan-oligosaccharides (MOS)], organic acid [0.5 g/kg butyric acid (BA)], or a combination of the 3 additives (MA). The S. Typhimurium challenge decreased feed intake, body weight gain and increased feed conversion ratio and reduced jejunum villus height (VH) and VH to crypt depth (CD) ratio (P < 0.05). Birds on the MA treatment exhibited similar performance to birds on the NC treatment (P > 0.05) and had a lower population of Salmonella in the ceca compared with birds on the PC treatment, at d 14 and 21 post-challenge (P < 0.05). The lowest heterophil to lymphocyte ratio was observed in birds on the MA and NC treatments (P < 0.05). Birds fed diets supplemented with MA or PA had greater VH and VH: CD ratio than birds on the PC treatment at d 7, 14 and 21 d post-challenge (P < 0.05). Suppressed amylase and protease activity was observed as a result of the S. Typhimurium challenge; the enzyme levels were restored in birds fed the additive-supplemented diets, when compared to the birds on the PC treatment, particularly at d 21 post-challenge (P < 0.05). These results indicate that dietary supplementation with a combination of PA, BA, and MOS in broiler chickens could be used as an effective tool for controlling S. Typhimurium and promoting growth performance.

Giardia's Epithelial Cell Interaction In Vitro: Mimicking Asymptomatic Infection?

The protozoan parasite Giardia duodenalis is responsible for more than 280 million cases of gastrointestinal complaints ("giardiasis") every year, worldwide. Infections are acquired orally, mostly via uptake of cysts in contaminated drinking water. After transformation into the trophozoite stage, parasites start to colonize the duodenum and upper jejunum where they attach to the intestinal epithelium and replicate vegetatively. Outcome of Giardia infections vary between individuals, from self-limiting to chronic, and asymptomatic to severely symptomatic infection, with unspecific gastrointestinal complaints. One proposed mechanism for pathogenesis is the breakdown of intestinal barrier function. This has been studied by analyzing trans-epithelial electric resistances (TEER) or by indicators of epithelial permeability using labeled sugar compounds in in vitro cell culture systems, mouse models or human biopsies and epidemiological studies. Here, we discuss the results obtained mainly with epithelial cell models to highlight contradictory findings. We relate published studies to our own findings that suggest a lack of barrier compromising activities of recent G. duodenalis isolates of assemblage A, B, and E in a Caco-2 model system. We propose that this epithelial cell model be viewed as mimicking asymptomatic infection. This view will likely lead to a more informative use of the model if emphasis is shifted from aiming to identify Giardia virulence factors to defining non-parasite factors that arguably appear to be more decisive for disease.

The sirtuin inhibitor tenovin-6 upregulates death receptor 5 and enhances cytotoxic effects of 5-fluorouracil and oxaliplatin in colon cancer cells

It has been reported that upregulated SIRT1 (NAD(+)-dependent class III histone deacetylase) deacetylates the p53 protein, represses its function, and allows for tumor cell growth in various cancers. Here we investigated antitumor effects of tenovin-6, a small-molecule inhibitor of SIRT1 and SIRT2, in various colon cancer cell lines. Tenovin-6 induced apoptosis in all five colon cancer cell lines investigated (two cell lines with wild-type p53 and three with mutant p53) regardless of the p53 mutation status. This effect was accompanied by accumulation of death receptor 5 (DR5) in most cell lines. DR5 silencing in HCT116 cells strongly attenuated tenovin-6-induced apoptosis. We investigated the effect of combining tenovin-6 with conventional anticancer agents 5-fluorouracil (5-FU), SN-38 (an active metabolite of irinotecan), and oxaliplatin. Synergistic antitumor effects of tenovin-6 were observed in combination with either 5-FU or oxaliplatin in vitro. The combination of tenovin-6 and oxaliplatin exhibited potent growth inhibition of HCT116 xenograft tumors in vivo. In conclusion, tenovin-6 induced apoptosis in human colon cancer cells through the activation of the DR5 signaling pathway and enhanced the antitumor properties of 5-FU and oxaliplatin. These results may help develop a novel treatment option for colorectal cancer using a SIRT inhibitor.

Antitumor effects of a sirtuin inhibitor, tenovin-6, against gastric cancer cells via death receptor 5 up-regulation

Up-regulated sirtuin 1 (SIRT1), an NAD⁺-dependent class III histone deacetylase, deacetylates p53 and inhibits its transcriptional activity, leading to cell survival. SIRT1 overexpression has been reported to predict poor survival in some malignancies, including gastric cancer. However, the antitumor effect of SIRT1 inhibition remains elusive in gastric cancer. Here, we investigated the antitumor mechanisms of a sirtuin inhibitor, tenovin-6, in seven human gastric cancer cell lines (four cell lines with wild-type TP53, two with mutant-type TP53, and one with null TP53). Interestingly, tenovin-6 induced apoptosis in all cell lines, not only those with wild-type TP53, but also mutant-type and null versions, accompanied by up-regulation of death receptor 5 (DR5). In the KatoIII cell line (TP53-null), DR5 silencing markedly attenuated tenovin-6-induced apoptosis, suggesting that the pivotal mechanism behind its antitumor effects is based on activation of the death receptor signal pathway. Although endoplasmic reticulum stress caused by sirtuin inhibitors was reported to induce DR5 up-regulation in other cancer cell lines, we could not find marked activation of its related molecules, such as ATF6, PERK, and CHOP, in gastric cancer cells treated with tenovin-6. Tenovin-6 in combination with docetaxel or SN-38 exerted a slight to moderate synergistic cytotoxicity against gastric cancer cells. In conclusion, tenovin-6 has potent antitumor activity against human gastric cancer cells via DR5 up-regulation. Our results should be helpful for the future clinical development of sirtuin inhibitors.

Stress-induced HSP70 from Musca domestica plays a functionally significant role in the immune system

As important molecular chaperones, members of the 70kDa heat shock protein (HSP70) family play essential roles in stress tolerance and innate immunity in organisms. The full-length complementary DNA (cDNA) of a novel inducible HSP70, named as MdHSP70, was isolated from Musca domestica. The cDNA clone consisted of 2411 bp with a 1956 bp open reading frame which encodes 651 amino acids. Using real-time quantitative polymerase chain reaction (qPCR), we investigated the transcriptional profile of the gene under heat shock, cadmium stress and in response to bacteria. Increased expression of MdHSP70 was observed in response to both heat shock and Cd stress. The expression of MdHSP70 was significantly induced by Escherichia coli or Staphylococcus aureus stimulation. Larvae were fed bacteria expressing dsRNA targeting the MdHSP70 gene. Our results showed high mortality in larvae treated with dsRNA of MdHSP70 at heat shock, Cd stress and bacterial invasion, suggesting that MdHSP70 is potentially involved in the stress and immune responses of the house fly and perhaps contributes to protection against cellular injury.

Effect of xylanase and a blend of essential oils on performance and Salmonella colonization of broiler chickens challenged with Salmonella Heidelberg

The present experiment examined the influence of xylanase supplementation and a blend of essential oils (EO; cinnamaldehyde and thymol) on performance and Salmonella horizontal transmission in broiler chickens challenged with Salmonella. Two thousand 1-d-old broiler chicks were randomly assigned to 5 dietary treatments (8 pens/treatment of 50 male broilers each). Four dietary treatments were challenged with Salmonella: 1) control, 2) basal diets supplemented with EO, 3) basal diet supplemented with xylanase (2,000 U/kg of feed), and 4) basal diet supplemented with a combination of EO and xylanase (2,000 U/kg of feed). One treatment served as an unchallenged control and was not supplemented with either additive. Broiler starter and finisher diets, based on wheat and soybean meal, were formulated, pelleted, and fed ad libitum. At d 1, before placement, half of the birds from each pen were tagged and dosed with Salmonella enterica serovar Heidelberg (5 × 10(5) cfu/mL). On d 42, 5 random untagged birds from each pen were killed and their ceca removed and tested for Salmonella. Performance data were analyzed as a completely randomized design using GLM. The frequency of positive Salmonella in the untagged birds was compared between treatments by using a chi-squared test of homogeneity. Challenging the birds with Salmonella had no effect (P > 0.05) on any of the measured performance parameters. Xylanase and EO supplementation improved (P < 0.05) the 42-d BW gain and feed efficiency, with no effect (P > 0.05) on feed intake, compared with that of the control treatment. Xylanase supplementation improved (P < 0.05) BW gain and feed efficiency compared with the results of EO supplementation. The combination treatment of xylanase and EO numerically improved BW gain and feed efficiency compared with the xylanase treatment. Xylanase and EO supplementation reduced (P < 0.05) the incidence of horizontal transmission of Salmonella infection between birds by 61 and 77%, respectively, compared with the control. The results of the current study suggested that dietary addition of EO and xylanase could improve broiler performance and contribute to food safety by lowering the incidence of horizontal transmission of Salmonella infection.

Cloning and expression of a heat shock protein (HSP) 90 gene in the haemocytes of Crassostrea hongkongensis under osmotic stress and bacterial challenge

Heat shock protein 90 (HSP90) is a highly conserved and multi-functional molecular chaperone that plays an essential role in both cellular metabolism and stress response. Here, we report the cloning of the HSP90 homologue in Crassostrea hongkongensis (ChHSP90) through SSH in combination with RACE from cDNA of haemocytes. The full-length cDNA of ChHSP90 is 2459 bp in length, consisting of a 3', 5'-untranslated region (UTR) and an open reading frame of 2169 bp encoding 722 amino acids. The identity analysis of the amino acid sequence of HSP90 revealed that ChHSP90 is highly conserved. Distribution of ChHSP90 mRNA in gonad, heart, adductor muscle, mantle, gill, digestive gland, and haemocytes suggested that ChHSP90 is ubiquitously expressed. The mRNA levels of ChHSP90 under salinity and bacterial challenges were analyzed by real-time PCR. Under hypo-osmotic treatment, ChHSP90 mRNA in gonad, heart and haemocytes were significantly up-regulated on day 2 and onwards; while in gill, digestive gland and adductor muscle it was significantly down-regulated; the expression in mantle was decreased significantly on day 2 and 3 (P < 0.01), and then up-regulated on day 4 (P < 0.05). Under hyper-osmotic treatment, the mRNA level in gonad, heart, adductor muscle was increased on day 2 and onwards; in gill, it was firstly increased, and then gradually decreased, reaching a minimum on day 3. On day 4, the expression level in gill recovered to pre-treatment level; in mantle and digestive gland, the expression levels were decreased, reaching to the minimum on day 3. During Vibrio alginolyticus challenge, the mRNA level of ChHSP90 increased 3-fold at 4 h post-infection, returned to its pre-challenge level at 6 h post-infection, then was further up-regulated from 8 to 36 h post-infection. These experiments demonstrate that ChHSP90 mRNA is constitutively expressed in various tissues and apparently inducible in haemocytes under salinity and bacterial challenges, suggesting its important role in response to both osmotic stress and bacterial invasion.

Listeria monocytogenes uses Listeria adhesion protein (LAP) to promote bacterial transepithelial translocation and induces expression of LAP receptor Hsp60

Listeria monocytogenes interaction with the intestinal epithelium is a key step in the infection process. We demonstrated that Listeria adhesion protein (LAP) promotes adhesion to intestinal epithelial cells and facilitates extraintestinal dissemination in vivo. The LAP receptor is a stress response protein, Hsp60, but the precise role for the LAP-Hsp60 interaction during Listeria infection is unknown. Here we investigated the influence of physiological stressors and Listeria infection on host Hsp60 expression and LAP-mediated bacterial adhesion, invasion, and transepithelial translocation in an enterocyte-like Caco-2 cell model. Stressors such as heat (41°C), tumor necrosis factor alpha (TNF-α) (100 U), and L. monocytogenes infection (10(4) to 10(6) CFU/ml) significantly (P < 0.05) increased plasma membrane and intracellular Hsp60 levels in Caco-2 cells and consequently enhanced LAP-mediated L. monocytogenes adhesion but not invasion of Caco-2 cells. In transepithelial translocation experiments, the wild type (WT) exhibited 2.7-fold more translocation through Caco-2 monolayers than a lap mutant, suggesting that LAP is involved in transepithelial translocation, potentially via a paracellular route. Short hairpin RNA (shRNA) suppression of Hsp60 in Caco-2 cells reduced WT adhesion and translocation 4.5- and 3-fold, respectively, while adhesion remained unchanged for the lap mutant. Conversely, overexpression of Hsp60 in Caco-2 cells enhanced WT adhesion and transepithelial translocation, but not those of the lap mutant. Furthermore, initial infection with a low dosage (10(6) CFU/ml) of L. monocytogenes increased plasma membrane and intracellular expression of Hsp60 significantly, which rendered Caco-2 cells more susceptible to subsequent LAP-mediated adhesion and translocation. These data provide insight into the role of LAP as a virulence factor during intestinal epithelial infection and pose new questions regarding the dynamics between the host stress response and pathogen infection.

Microbial products from probiotic bacteria inhibit Salmonella enteritidis 857-induced IL-8 synthesis in Caco-2 cells

Oral administration of Lactobacillus spp. as probiotics is gaining importance in the treatment of intestinal inflammations. However, their mechanism of action is unknown. We investigated whether nonspecific binding Lactobacillus casei Shirota (LcS) and mannose-specific Lactobacillus plantarum 299v (Lp) and their spent culture supernatant (SCS) affect Salmonella enteritidis 857 (Se) growth, IL-8 and Hsp70 syntheses. In one set of experiments human enterocyte-like Caco-2 cells were infected with LcS, Lp or Se at 1-500 bacteria per cell for 1 h. In another set, cells were exposed to Se (0-200 per cell, 1 h) after exposure to lactobacilli (LB) (500 per cell, 30 min) or by co-incubation of Se and LB (1 h). The third set of experiments involved exposure of cells for 1 h to SCS or Se (100 per cell) pretreated (1 h) in SCS. The effect of LB SCS on Se growth was evaluated by agar plate diffusion test. IL-8 and Hsp70 were assessed over 2-24 h using ELISA and Western blotting, respectively. Neither LcS nor Lp affected the Se growth and IL-8 production. In addition, they did not induce Hsp70 expression by Caco-2 cells. Instead, their SCS inhibited the Se growth and IL-8 production and induced the expression of Hsp70 by both crypt- and villus-like cells. The beneficial effect of Lactobacillus spp. to the intestinal inflammations might be associated with a decrease in IL-8 levels. This effect could be mediated, at least in part, via a secreted antimicrobial product(s) either directly against the pathogens or indirectly through the synthesis of Hsp70.

Inhibition of heat shock protein expression by Helicobacter pylori

Heat shock proteins (HSPs) are primarily known as molecular chaperones that are induced by cell stress and prevent protein aggregation and facilitate folding. Recent evidence suggests that exposure of cells to microbial pathogens can also induce HSPs, which then modulate both innate and adaptive immune responses. Paradoxically, Helicobacter pylori has been found to decrease expression of HSPs. We sought to investigate this phenomenon further and to examine the role of different H. pylori strains and recognized virulence factors in cell culture and in the mouse model. Co-culture of H. pylori with two gastric carcinoma cell lines reduced expression of HSP70 and, to a lesser extent, HSP60. Down modulation of HSPs was not dependent on the presence of the vacuolating cytotoxin (VacA) or the cag pathogenicity island (cag PAI). C57BL/6 mice infected with a human H. pylori strain also demonstrated reduced expression of HSP70, HSP8, and heat shock factor 1 (HSF-1), a transcriptional activator of HSP70. In contrast, the bacterial pathogen, S. Typhimurium up-regulated HSP expression. Since HSPs are thought to function as danger signals during microbial infection, H. pylori down-regulation of HSPs may be a mechanism of immune evasion that promotes chronic infection.

Salmonella enterica serovar Typhimurium adhesion and cytotoxicity during epithelial cell stress is reduced by Lactobacillus rhamnosus GG

Background

Physiological stressors may alter susceptibility of the host intestinal epithelium to infection by enteric pathogens. In the current study, cytotoxic effect, adhesion and invasion of Salmonella enterica serovar Typhimurium (S. Typhimurium) to Caco-2 cells exposed to thermal stress (41°C, 1 h) was investigated. Probiotic bacteria have been shown to reduce interaction of pathogens with the epithelium under non-stress conditions and may have a significant effect on epithelial viability during infection; however, probiotic effect on pathogen interaction with epithelial cells under physiological stress is not known. Therefore, we investigated the influence of Lactobacillus rhamnosus GG and Lactobacillus gasseri on Salmonella adhesion and Salmonella-induced cytotoxicity of Caco-2 cells subjected to thermal stress.

Results

Thermal stress increased the cytotoxic effect of both S. Typhimurium (P = 0.0001) and nonpathogenic E. coli K12 (P = 0.004) to Caco-2 cells, and resulted in greater susceptibility of cell monolayers to S. Typhimurium adhesion (P = 0.001). Thermal stress had no significant impact on inflammatory cytokines released by Caco-2 cells, although exposure to S. Typhimurium resulted in greater than 80% increase in production of IL-6 and IL-8. Blocking S. Typhimurium with anti-ShdA antibody prior to exposure of Salmonella decreased adhesion (P = 0.01) to non-stressed and thermal-stressed Caco-2 cells. Pre-exposure of Caco-2 cells to L. rhamnosus GG significantly reduced Salmonella-induced cytotoxicity (P = 0.001) and Salmonella adhesion (P = 0.001) to Caco-2 cells during thermal stress, while L. gasseri had no effect.

Conclusion

Results suggest that thermal stress increases susceptibility of intestinal epithelial Caco-2 cells to Salmonella adhesion, and increases the cytotoxic effect of Salmonella during infection. Use of L. rhamnosus GG as a probiotic may reduce the severity of infection during epithelial cell stress. Mechanisms by which thermal stress increases susceptibility to S. Typhimurium colonization and by which L. rhamnosus GG limits the severity of infection remain to be elucidated.

Sodium arsenite reduces severity of dextran sulfate sodium-induced ulcerative colitis in rats

The histopathological features and the associated clinical findings of ulcerative colitis (UC) are due to persistent inflammatory response in the colon mucosa. Interventions that suppress this response benefit UC patients. We tested whether sodium arsenite (SA) benefits rats with dextran sulfate sodium (DSS)-colitis. The DSS-colitis was induced by 5% DSS in drinking water. SA (10 mg/kg; intraperitoneally) was given 8 h before DSS treatment and then every 48 h for 3 cycles of 7, 14 or 21 d. At the end of each cycle rats were sacrificed and colon sections processed for histological examination. DSS induced diarrhea, loose stools, hemoccult positive stools, gross bleeding, loss of body weight, loss of epithelium, crypt damage, depletion of goblet cells and infiltration of inflammatory cells. The severity of these changes increased in the order of Cycles 1, 2 and 3. Treatment of rats with SA significantly reduced this severity and improved the weight gain.

Effect of herbal medicine Juzentaihoto on hepatic and intestinal heat shock gene expression requires intestinal microflora in mouse

AIM: To evaluate the role of intestinal microflora in the effects of multi-herbal medicine on gene expression in the gut and liver.

METHODS: The multi-herbal medicine Juzentaihoto (JTX) was administered to five germ-free mice and regular mice for 2 wk. Among the results of the comprehensive gene chip analysis of the intestine and liver, we featured heat shock proteins (HSPs) 70 and 105 because their gene expression changed only in the presence of microflora. Real-time RT-PCR was performed to confirm the expression levels of these HSP genes. To determine whether JTX acts directly on the HSP genes, sodium arsenite (SA) was used to induce the heat shock proteins directly. To examine the change of the intestinal microflora with administration of JTX, the terminal restriction fragment polymorphism (T-RFLP) method was used. To identify the changed bacteria, DNA sequencing was performed.

RESULTS: Heat shock protein gene expression, documented by gene chip and real-time RT-PCR, changed with the administration of JTX in the regular mice but not in the germ-free mice. JTX did not suppress the direct induction of the HSPs by SA. T-RFLP suggested that JTX decreased unculturable bacteria and increased Lactobacillus johnsoni. These data suggested that JTX changed the intestinal microflora which, in turn, changed HSP gene expression.

CONCLUSION: Intestinal microflora affects multi-herbal product JTX on the gene expression in the gut and liver.

Inhibition of Salmonella-induced IL-8 synthesis and expression of Hsp70 in enterocyte-like Caco-2 cells after exposure to non-starter lactobacilli

Oral administration of lactobacilli as probiotics is gaining importance in the treatment of intestinal inflammations. We investigated the effect of non-starter lactobacilli Lactobacillus casei subsp casei 2756, Lactobacillus curvatus 2775, and Lactobacillus plantarum 2142 as well as their spent culture supernatants (SCS) on Salmonella enteritidis 857 growth, interleukin (IL)-8 and heat shock protein 70 (Hsp70) synthesis in undifferentiated crypt-like and differentiated villus-like Caco-2 cells. The cells were infected with graded numbers of non-starter lactobacilli or S. enteritidis 857 for 1 h and allowed to recover for 24 h or exposed to 200 bacteria/cell for 1 h and allowed to recover for different periods of time. In another experiment S. enteritidis 857 was first pre-treated with SCS-lactobacilli for 1 h before infecting the cells. The levels of IL-8 and Hsp70 were assessed using sandwich ELISA and immunostaining of Western blots, respectively. The effect of SCS-lactobacilli on S. enteritidis 857 growth was evaluated by agar plate diffusion test. The non-starter lactobacilli induced a significant increase in the levels of both IL-8 and Hsp70. However, compared with the S. enteritidis 857 induced IL-8 synthesis, the levels of IL-8 induced by the lactobacilli at any equivalent bacterial number were far lower. After exposure of Caco-2 cells to S. enteritidis 857 pre-treated with SCS-lactobacilli, it appeared that their SCS inhibited the S. enteritidis 857 growth and IL-8 synthesis and in addition induced the expression of Hsp70. The differences in response of crypt- and villus-like Caco-2 cells are merely a reflection of their differentiation status. Our data suggest that the beneficial effect of non-starter lactobacilli to the intestinal inflammations might be associated with a decrease of the IL-8 levels. This effect could be mediated, at least in part, by the bacteria themselves or via a secreted antimicrobial product(s) either directly against the pathogens or indirectly through the synthesis of Hsp70.

Interference ofSalmonella enteritidis andLactobacillus spp. with IL-8 levels and transepithelial electrical resistance of enterocyte-like caco-2 cells

Caco-2 cells (exhibiting characteristics of mature villus enterocytes) were used to determine bacteria (Salmonella enteritidis causing human gastroenteritis)-intestinal cell interactions. The interference of bacteria with the transepithelial electrical resistance (TEER) of filter-grown Caco-2 cells and the production of IL-8 after exposure of the cells to S. enteritidis 857 and/or Lactobacillus strains (L. gasseri LF221 and L. rhamnosus BGT10) was evaluated. The strain 857 decreased TEER of filter-grown Caco-2 cells; in contrast, lactobacilli had a little or no effect. The effect of S. enteritidis on the TEER decreased if Caco-2 cells were pre-incubated with lactobacilli. This strain induced high levels of IL-8 (which can lead to cell damage). Compared to the IL-8 synthesis after exposure of Caco-2 cells to S. enteritidis 857, simultaneous exposure of Caco-2 cells to S. enteritidis and lactobacilli inhibited the IL-8 synthesis after short recovery periods.

Gut myoelectrical activity induces heat shock response in Escherichia coli and Caco-2 cells

The heat shock response is associated with the intracellular expression of a number of highly conserved heat shock proteins (Hsps). According to their molecular size, Hsps have been divided into several groups, which are strongly conserved and show high homology between the species, e.g., Hsp70, MW 70 kDa (Lindquist & Craig, 1998; Morimoto, 1998; Jolly & Morimoto, 2000; Zylicz et al. 2001). In all organisms the Hsp expression under stress conditions is regulated at transcriptional level, e.g., in humans by the heat shock transcription factor Hsf1 (Morimoto, 1998; Wu, 1995), while in Escherichia coli by replacement of the sigma factor sigma(70) in RNA polymerase by the sigma factor sigma(32) (Gross, 1987). The Hsps allow cell survival under stress conditions by renaturating of denaturated proteins, protecting of stress-labile proteins, preventing protein aggregation (chaperone functions), and by degradation of damaged proteins (protease activities) (Lindquist & Craig, 1988; Morimoto, 1998; Jolly & Morimoto, 2000). They have also many housekeeping functions under non-stressful conditions during the cell cycle, growth, development, and differentiation (Morimoto, 1998). Among a number of plausible inducing factors already studied, extremely low artificial electromagnetic fields have been shown to induce stress response in various cells, such as expression of sigma(32) mRNA (Cairo et al. 1998) and induction of DnaJ and DnaK proteins in Eschericha coli (Chow & Tung, 2000); expression of hsp-16 gene in Caenorhabditis elegans (Miyakawa et al., 2001); induction of heat shock transcription factor Hsf1 and Hsp70, Hsp90 and Hsp27 in human cells (Lin et al. 1997; Lin et al. 1998; Goodman & Blank, 1998; Pipkin et al. 1999). Nevertheless, the role of endogenous electromagnetic fields, i.e., generated by electrically active cells within a body remains controversial. Heat shock proteins (Hsps) protect cells against various environmental and endogenous stressors. Cytoprotection caused by Hsps involves tolerance induced by one agent against other, more severe agents. We have found that exposure of prokaryotic (Escherichia coli) and eukaryotic (Caco-2) cells to an electrical field (EF) connected with a myoelectrical migrating complex (MMC) generated by the small intestine smooth muscle induces the heat shock response. Using Western blot analysis, we have detected an elevated level of sigma factor 32 in E. coli cells exposed to MMC-related EF, and confocal microscopy indicated an increased level of the inducible form of Hsp70 protein in EF-stimulated Caco-2 cells. Additionally, we have found that this induced level of Hsp70 protected the Caco-2 cells against apoptosis caused by camptothecin. Our observations suggest that the myoelectrical activity of the gut may induce heat shock mechanisms in the cells of gut epithelium as well as in gastrointestinal micro-organisms.