The probiotic Lactobacillus acidophilus stimulates chloride/hydroxyl exchange activity in human intestinal epithelial cells

Computational prediction of new therapeutic effects of probiotics

Probiotics are living microorganisms that provide health benefits to their hosts, potentially aiding in the treatment or prevention of various diseases, including diarrhea, irritable bowel syndrome, ulcerative colitis, and Crohn's disease. Motivated by successful applications of link prediction in medical and biological networks, we applied link prediction to the probiotic-disease network to identify unreported relations. Using data from the Probio database and International Classification of Diseases-10th Revision (ICD-10) resources, we constructed a bipartite graph focused on the relationship between probiotics and diseases. We applied customized link prediction algorithms for this bipartite network, including common neighbors, Jaccard coefficient, and Adamic/Adar ranking formulas. We evaluated the results using Area under the Curve (AUC) and precision metrics. Our analysis revealed that common neighbors outperformed the other methods, with an AUC of 0.96 and precision of 0.6, indicating that basic formulas can predict at least six out of ten probable relations correctly. To support our findings, we conducted an exact search of the top 20 predictions and found six confirming papers on Google Scholar and Science Direct. Evidence suggests that Lactobacillus jensenii may provide prophylactic and therapeutic benefits for gastrointestinal diseases and that Lactobacillus acidophilus may have potential activity against urologic and female genital illnesses. Further investigation of other predictions through additional preclinical and clinical studies is recommended. Future research may focus on deploying more powerful link prediction algorithms to achieve better and more accurate results.

Targeting Food Allergy with Probiotics

The globally dramatic increase in food allergy prevalence and severity is demanding effective preventive and therapeutic strategies. Food allergy derives from a defect of immune tolerance mechanisms. Immune tolerance is modulated by gut microbiome composition and function, and gut microbiome dysbiosis has been associated with the development of food allergy. Selected probiotic strains could regulate immune tolerance mechanisms. The mechanisms are multiple and are still not completely defined. Increasing evidence is providing useful information on the choice of optimal bacterial species/strains, dosage, and timing for intervention. The increased knowledge on the crucial role played by postbiotic gut microbiome-derived metabolites, such as butyrate, is also opening the way to a post- biotic approach in the stimulation of immune tolerance.

Milk Exosomes Facilitate Oral Delivery of Drugs against Intestinal Bacterial Infections

Biopharmaceutics Classification System (BCS) class II and IV drugs exhibit low solubility and suffer a limitation in oral administration. Exosomes have attracted intensive attention in the efficient delivery of such compounds. However, low gastrointestinal stability and high production cost of exosomes hinder their development as drug carriers. Here, milk exosomes are functionalized with phosphatidylserine and are capable of improving the solubility of BCS class II and IV drugs, resulting in facilitating the oral delivery of the drugs. A natural flavonoid, α-mangostin, is loaded into exosomes (AExo) to enhance the antibacterial efficiency, demonstrated by clearing 99% of bacteria in macrophages. Furthermore, AExo exhibits high mucus penetrability and shows a significant therapeutic efficacy in two animal infection models. Collectively, this work expands the application of exosomes from bovine milk with simple operation and low cost, shedding light on the potential of milk exosomes in improving the solubility of drugs to enhance the efficacy of oral administration.

High-protein diet prevents fat mass increase after dieting by counteracting Lactobacillus-enhanced lipid absorption

Dietary restriction is widely used to reduce fat mass and lose weight in individuals with or without obesity; however, weight regain after dieting is still a big challenge, and the underlying mechanisms remain largely elusive. Here we show that refeeding after various types of dieting induces quick fat accumulation in mice and enhanced intestinal lipid absorption contributes to post-dieting fat mass increase. Moreover, refeeding after short-term dietary restriction is accompanied by an increase in intestinal Lactobacillus and its metabolites, which contributes to enhanced intestinal lipid absorption and post-dieting fat mass increase; however, refeeding a high-protein diet after short-term dietary restriction attenuates intestinal lipid absorption and represses fat accumulation by preventing Lactobacillus growth. Our results provide insight into the mechanisms underlying fat mass increase after dieting. We also propose that targeting intestinal Lactobacillus to inhibit intestinal lipid absorption via high-protein diet or antibiotics is likely an effective strategy to prevent obesity after dieting.

Probiotic Escherichia coli NISSLE 1917 for inflammatory bowel disease applications

Escherichia coli NISSLE 1917 (EcN) is a Gram-negative strain with many prominent probiotic properties in the treatment of intestinal diseases such as diarrhea and inflammatory bowel disease (IBD), in particular ulcerative colitis. EcN not only exhibits antagonistic effects on a variety of intestinal pathogenic bacteria, but also regulates the secretion of immune factors in vivo and enhances the ability of host immunity. In this review, the mechanisms of EcN in the remission of inflammatory bowel disease are proposed and recent advances on the functionalized EcN are compiled to provide novel therapeutic strategies for the prevention and treatment of IBD.

Effects of Multispecies Probiotic on Intestinal Microbiota and Mucosal Barrier Function of Neonatal Calves Infected With E. coli K99

Altered gut microbiota are implicated in inflammatory neonatal calf diarrhea caused by E. coli K99. Beneficial probiotics are used to modulate gut microbiota. However, factors that mediate host-microbe interactions remain unclear. We evaluated the effects of a combination of multispecies probiotics (MSP) on growth, intestinal epithelial development, intestinal immune function and microbiota of neonatal calves infected with E. coli K99. Twelve newborn calves were randomly assigned as follows: C (control, without MSP); D (E. coli O78:K99 + gentamycin); and P (E. coli O78:K99 + supplemental MSP). All groups were studied for 21 d. MSP supplementation significantly (i) changed fungal Chao1 and Shannon indices of the intestine compared with group D; (ii) reduced the relative abundance of Bacteroides and Actinobacteria, while increasing Bifidobacteria, Ascomycetes, and Saccharomyces, compared with groups C and D; (iii) improved duodenal and jejunal mucosal SIgA and total Short Chain Fatty Acids (SCFA) concentrations compared with group D; (iv) increased relative ZO-1 and occludin mRNA expression in jejunal mucosa compared with group D; and (v) enhanced intestinal energy metabolism and defense mechanisms of calves by reducing HSP90 expression in E. coli K99, thereby alleviating the inflammatory response and promoting recovery of mucosal function. Our research may provide direct theoretical support for future applications of MSP in ruminant production.

A Systematic Review and Meta-Analysis: Lactobacillus acidophilus for Treating Acute Gastroenteritis in Children

The efficacy of probiotic strains of Lactobacillus acidophilus to manage acute gastroenteritis in children is still not established. We searched the Cochrane Library, PubMed, EMBASE, and three Chinese literature databases (CNKI, WanFang, and CBM) from their inception to February 2021 for RCTs that compared the use of Lactobacillus acidophilus with no Lactobacillus acidophilus. The grey literature was searched through Google Scholar. Authors of the original papers were contacted for additional data. The study included a total of 15 RCTs involving 1765 patients. Compared with placebo or no treatment, Lactobacillus acidophilus was associated with a reduced duration of diarrhea (moderate quality of evidence), but the effect was not statistically significant when only the individual probiotic strain was provided. Lactobacillus acidophilus was effective when used at a daily dose ≥ 10⁹ CFU. There was no difference in the effect of Lactobacillus acidophilus on diarrhea duration among Asian, European, or American countries. Lactobacillus acidophilus reduced the frequency of diarrhea on day 2 to day 5. However, it was statistically significant on day 3. When administered at a dosage of more than 10⁹ CFU to children with acute gastroenteritis, moderate- to low-quality data showed that Lactobacillus acidophilus reduced the duration of diarrhea and conferred a benefit for frequency of diarrhea.

Impact of Gut Microbiome Manipulation in 5xFAD Mice on Alzheimer's Disease-Like Pathology

The gut brain axis seems to modulate various psychiatric and neurological disorders such as Alzheimer's disease (AD). Growing evidence has led to the assumption that the gut microbiome might contribute to or even present the nucleus of origin for these diseases. In this regard, modifiers of the microbial composition might provide attractive new therapeutics. Aim of our study was to elucidate the effect of a rigorously changed gut microbiome on pathological hallmarks of AD. 5xFAD model mice were treated by antibiotics or probiotics (L. acidophilus and L. rhamnosus) for 14 weeks. Pathogenesis was measured by nest building capability and plaque deposition. The gut microbiome was affected as expected: antibiotics significantly reduced viable commensals, while probiotics transiently increased Lactobacillaceae. Nesting score, however, was only improved in antibiotics-treated mice. These animals additionally displayed reduced plaque load in the hippocampus. While various physiological parameters were not affected, blood sugar was reduced and serum glucagon level significantly elevated in the antibiotics-treated animals together with a reduction in the receptor for advanced glycation end products RAGE-the inward transporter of Aβ peptides of the brain. Assumedly, the beneficial effect of the antibiotics was based on their anti-diabetic potential.

Altered intestinal epithelial nutrient transport: an underappreciated factor in obesity modulated by diet and microbiota

Dietary nutrients absorbed in the proximal small intestine and assimilated in different tissues have a profound effect on overall energy homeostasis, determined by a balance between body's energy intake and expenditure. In obesity, altered intestinal absorption and consequently tissue assimilation of nutrients may disturb the energy balance leading to metabolic abnormalities at the cellular level. The absorption of nutrients such as sugars, amino acids and fatty acids released from food digestion require high-capacity transporter proteins expressed in the intestinal epithelial absorptive cells. Furthermore, nutrient sensing by specific transporters/receptors expressed in the epithelial enteroendocrine cells triggers release of gut hormones involved in regulating energy homeostasis via their effects on appetite and food intake. Therefore, the intestinal epithelial cells play a pivotal role in the pathophysiology of obesity and associated complications. Over the past decade, gut microbiota has emerged as a key factor contributing to obesity via its effects on digestion and absorption of nutrients in the small intestine, and energy harvest from dietary fiber, undigested component of food, in the large intestine. Various mechanisms of microbiota effects on obesity have been implicated. However, the impact of obesity-associated microbiota on the intestinal nutrient transporters needs extensive investigation. This review marshals the limited studies addressing the altered structure and function of the gut epithelium in obesity with special emphasis on nutrient transporters and role of diet and microbiota. The review also discusses the thoughts and controversies and research gaps in this field.

Characterization of Lactobacillus reuteri WQ-Y1 with the ciprofloxacin degradation ability

OBJECT

As a broad-spectrum fluoroquinolone antibiotic drug, ciprofloxacin (CIP) is frequently used in the treatment of a wide variety of infections. However, the residues of this antibiotic pose a big threat to the aquatic environment and human health. In this research, Lactobacillus reuteri WQ-Y1 with CIP degradation ability was screened and identified.

RESULTS

L. reuteri WQ-Y1 with a degradation rate of 65.1% for 4 µg mL^-1 CIP was screened from 17 lactic acid bacteria (LAB), and cytochrome P450 enzyme was confirmed to promote the degradation of CIP by L. reuteri WQ-Y1. Meanwhile, the CIP degradation rate were also higher in 48 h' culture time when co-cultured with 1 mg/mL of glucose in the culture media. Furthermore, result also proved that fluoroquinolone antibiotics with the similar piperazine ring structures could be degraded by L. reuteri WQ-Y1.

CONCLUSIONS

L. reuteri WQ-Y1 could degrade fluoroquinolone antibiotics with the similar piperazine ring structure. However, future work still needs to be done on the confirmation of the key enzymes in the cytochrome P450 enzymes family in the biodegradation. The isolated ciprofloxacin-degrading strain L. reuteri WQ-Y1 had a CIP degradation rate of 65.1% at 24 hours, and one biodegradation metabolite was identified and proved to be an important metabolite of CIP from cytochrome P450 enzymes family hydrolysis with UPLC-MS/MS spectrograms approach.

Visualization of Bacterial Colonization and Cellular Layers in a Gut-on-a-Chip System Using Optical Coherence Tomography

Imaging of cellular layers in a gut-on-a-chip system has been confined to two-dimensional (2D)-imaging through conventional light microscopy and confocal laser scanning microscopy (CLSM) yielding three-dimensional- and 2D-cross-sectional reconstructions. However, CLSM requires staining and is unsuitable for longitudinal visualization. Here, we compare merits of optical coherence tomography (OCT) with those of CLSM and light microscopy for visualization of intestinal epithelial layers during protection by a probiotic Bifidobacterium breve strain and a simultaneous pathogen challenge by an Escherichia coli strain. OCT cross-sectional images yielded film thicknesses that coincided with end-point thicknesses derived from cross-sectional CLSM images. Light microscopy on histological sections of epithelial layers at the end-point yielded smaller layer thicknesses than OCT and CLSM. Protective effects of B. breve adhering to an epithelial layer against an E. coli challenge included the preservation of layer thickness and membrane surface coverage by epithelial cells. OCT does not require staining or sectioning, making OCT suitable for longitudinal visualization of biological films, but as a drawback, OCT does not allow an epithelial layer to be distinguished from bacterial biofilms adhering to it. Thus, OCT is ideal to longitudinally evaluate epithelial layers under probiotic protection and pathogen challenges, but proper image interpretation requires the application of a second method at the end-point to distinguish bacterial and epithelial films.

The role of yoghurt consumption in the management of type II diabetes

Enrichment of yoghurt with specific ingrdients beneficially affects the management of Type II Diabetes Mellitus (DMII). As far as the role of yoghurt in the management of DMII is concerned, the limited number of randomized clinical trials (RCTs) which have been conducted suggest that daily intake of yoghurt enriched with vitamin D and/or calcium as well as probiotics positively influences glycemic regulation and may contribute to more effective control of the disease. It is argued that the various ingredients which are already contained in the complex matrix of food, such as bioactive peptides, calcium, B-complex vitamins and beneficial microbes, as well as the fact that it can be used as a vehicle for the inclusion of other effective ingredients can have an impact on the metabolic control of diabetic patients. The aim of this review is to present the RCTs which have been conducted in the last decade in patients with DMII in an attempt to highlight the positive effects of yoghurt in the management of the disease.

Probiotics supplementation improves hyperglycemia, hypercholesterolemia, and hypertension in type 2 diabetes mellitus: An update of meta-analysis

Background: Although many studies have shown that consumption of probiotics is relevant to diabetes, the effects of probiotics improves clinical outcomes in type 2 diabetes have yielded conflicting results. The aim of this meta-analysis was conducted to assess the effects of probiotics supplementation on glycemic, blood lipids, pressure and inflammatory control in type 2 diabetes.Methods: PubMed, Web of science, Embase and the Cochrane Library databases were searched for relevant studies from February 2015 up to Janurary 2020, with no language restrictions. The pooled results were calculated with the use of a random-effects model to assess the impact of supplemental probiotics on glycemic, blood lipids, pressure and inflammatory control in type 2 diabetes. Additionally, subgroup analysis was conducted based on patients age, body mass index (BMI), country and duration of the probiotics supplement, respectively.Results: 13 studies were included in this meta-analysis, involving a total of 818 participants in 8 countries. Overall, compared with control groups, the subjects who received multiple species of probiotics had a statistically significant reduction in fasting blood sugar (FBS), homeostasis model assessment of insulin resistance (HOMA-IR), total cholesterol (TC), triglycerides (TG), systolic blood pressure (SBP), diastolic blood pressure (DBP) and tumor necrosis factor (TNF) -α [standardized mean difference (SMD): -0.89 mg/Dl, 95% CI: -1.66, -0.12 mg/dL; SMD: -0.43, 95% CI: -0.63, -0.23; SMD: -0.19 mg/dL, 95% CI: -0.36, -0.01 mg/dL; SMD: -0.23 mg/dL, 95% CI: -0.40, -0.05 mg/dL; SMD: -5.61 mmHg, 95% CI: -9.78, -1.45 mmHg; SMD: -3.41 mmHg, 95% CI: -6.12, -0.69 mmHg; and SMD: 6.92 pg/ml, 95% CI: 5.95, 7.89 pg/ml, respectively]. However, the subjects who received single-species of probiotic or probiotic with co-supplements in food only changed FBS, HOMA-IR, DBP and TG levels. Moreover, subgroup analyses revealed that the effects of probiotics supplementation on FBS, HMOA-IR, SBP and DBP are significantly influenced by patients age, body mass index (BMI), country and duration of the probiotics supplement.Conclusion: Our analysis revealed that glycemic, lipids, blood pressure and inflammation indicators are significantly improved by probiotic supplementation, particularly the subjects who ages ≤ 55, baseline BMI< 30 kg/m², duration of intervention more than 8 weeks, and received multiple species probiotic.

A Microbiota-Derived Bacteriocin Targets the Host to Confer Diarrhea Resistance in Early-Weaned Piglets

Alternatives to antibiotics for preventing diarrhea in early-weaned farm animals are sorely needed. CM piglets (a native Chinese breed) are more resistant to early-weaning stress-induced diarrhea than the commercial crossbred LY piglets. Transferring fecal microbiota, but not saline, from healthy CM into LY piglets by oral administration prior to early weaning conferred diarrhea resistance. By comparing the relative abundance of intestinal microbiota in saline and microbiota transferred LY piglets, we identified and validated Lactobacillus gasseri LA39 and Lactobacillus frumenti as two bacterial species that mediate diarrhea resistance. Diarrhea resistance depended on the bacterial secretory circular peptide gassericin A, a bacteriocin. The binding of gassericin A to Keratin 19 (KRT19) on the plasma membrane of intestinal epithelial cells was essential for enhancement of fluid absorption and decreased secretion. These findings suggest the use of L. gasseri LA39 and L. frumenti as antibiotic alternatives for preventing diarrhea in mammals.

Gut Microbiome as Target for Innovative Strategies Against Food Allergy

The dramatic increase in food allergy prevalence and severity globally requires effective strategies. Food allergy derives from a defect in immune tolerance mechanisms. Immune tolerance is modulated by gut microbiota function and structure, and microbiome alterations (dysbiosis) have a pivotal role in the development of food allergy. Environmental factors, including a low-fiber/high-fat diet, cesarean delivery, antiseptic agents, lack of breastfeeding, and drugs can induce gut microbiome dysbiosis, and have been associated with food allergy. New experimental tools and technologies have provided information regarding the role of metabolites generated from dietary nutrients and selected probiotic strains that could act on immune tolerance mechanisms. The mechanisms are multiple and still not completely defined. Increasing evidence has provided useful information on optimal bacterial species/strains, dosage, and timing for intervention. The increased knowledge of the crucial role played by nutrients and gut microbiota-derived metabolites is opening the way to a post-biotic approach in the stimulation of immune tolerance through epigenetic regulation. This review focused on the potential role of gut microbiome as the target for innovative strategies against food allergy.

Avaliação da aplicabilidade de uma cepa probiótica de Saccharomyces cerevisiae em barras de cereais

Resumo O objetivo deste estudo foi avaliar a utilização de uma levedura probiótica na produção de barra de cereais, contribuindo para a produção de um alimento funcional inovador. Uma mistura de chocolate inoculada com 8 log10 células/mL viáveis da levedura foi inserida sobre a superfície da barra de cereais. Foram verificados os parâmetros físicos, químicos e sensoriais, e quantificado o número de células durante o período de armazenamento, até a morte celular da levedura. Os resultados demonstraram que a presença da levedura não afetou negativamente as propriedades físicas e químicas da barra de cereais. Nos parâmetros avaliados sensorialmente, não foi observada preferência em relação às barras sem levedura probiótica. A levedura se manteve viva (104 células/g) por 45 dias.

Antidiarrheal Action of Bacillus subtilis CU1 CNCM I-2745 and Lactobacillus plantarum CNCM I-4547 in Mice

Preventive actions of probiotics as antidiarrheal agents are well documented, but their mechanisms are poorly understood. Two selected probiotics, Bacillus subtilis CU1 and Lactobacillus plantarum CNCM I-4547, were tested in mouse experimental models of diarrhea and the possible mechanisms of action were investigated. Diarrhea was induced in mice by oral castor oil administration or by i.v. injection of lipopolysaccharide (LPS) of Salmonella enteritis. The antidiarrheal drug loperamide was used as control. Fecal water excretion was quantified for 2 h and paracellular permeability and electrical parameters of the colon were assessed in Ussing chambers. The expression of colonic exchangers or channels and of Toll-like receptor 4 (TLR4) was assessed by immunohistochemistry. Prophylactic treatment with B. subtilis CU1 or with L. plantarum CNCM I-4547 reduced LPS-induced diarrhea. The reduction of water excretion was in the same range as those induced by loperamide. In the castor oil model, this effect was only observed with B. subtilis CU1. The two probiotic treatments abolished the increase in paracellular permeability induced by LPS, but not by castor oil. However, only L. plantarum CNCM I-4547 treatment decreased the colonic expression of TLR-4. After B. subtilis CU1, colonic expression of cystic fibrosis transmembrane conductance regulator (CFTR) was reduced and that of Na⁺/H⁺ exchanger 3 (NHE3) increased. B. subtilis CU1 may increase the capacity of the colon to absorb excess of water in diarrheic conditions by acting on CFTR and NHE3 expression. The two probiotics strains showed an impact on diarrhea through limitation of water excretion that may involve paracellular permeability or electrolyte transport for L. plantarum CNCM I-4547 and B. subtilis CU1 respectively.

Proteomic studies on lactic acid bacteria: A review

Probiotics are amongst the most common microbes in the gastro-intestinal tract of humans and other animals. Prominent among probiotics are Lactobacillus and Bifidobacterium. They offer wide-ranging health promoting benefits to the host which include reduction in pathological alterations, stimulation of mucosal immunity and interaction with mediators of inflammation among others. Proteomics plays a vital role in understanding biological functions of a cell. Proteomics is also slowly and steadily adding to the existing knowledge on role of probiotics. In this paper, the proteomics of probiotics, with special reference to lactic acid bacteria is reviewed with a view to understand i) proteome map, ii) mechanism of adaptation to harsh gut environment such as low pH and bile acid, iii) role of cell surface proteins in adhering to intestinal epithelial cells, and iv) as a tool to answer basic cell functions. We have also reviewed various analytical methods used to carry out proteome analysis, in which 2D-MS and LC-MS/MS approaches were found to be versatile methods to perform high-throughput sample analyses even for a complex gut samples. Further, we present future road map of understanding gut microbes combining meta-proteomics, meta-genomics, meta-transcriptomics and -metabolomics.

In vitro antiviral activity of Lactobacillus casei and Bifidobacterium adolescentis against rotavirus infection monitored by NSP4 protein production

AIMS

The aim of this study was to determine the antiviral activity of four probiotic metabolites (Lactobacillus and Bifidobacetrium species) against rotavirus in vitro infection monitored by the NSP4 protein production and Ca(2+) release.

METHODS AND RESULTS

The antiviral effect of the metabolites was performed due a comparison between a blocking model and an intracelullar model on MA104 cells, with the response of NSP4 production and Ca(2+) liberation measured by flow cytometry. Significant results were obtained with the metabolites of Lactobacillus casei, and Bifidobacterium adolescentis in the reduction of the protein production (P = 0·04 and P = 0·014) and Ca(2+) liberation (P = 0·094 and P = 0·020) in the intracellular model, which suggests a successful antiviral activity against RV infection.

CONCLUSIONS

This study demonstrates that probiotic metabolites were able to interfere with the final amount of intracellular NSP4 protein and a successful Ca(2+) regulation, which suggests a new approach to the mechanism exerted by probiotics against the rotavirus infection.

SIGNIFICANCE AND IMPACT OF THE STUDY

A novel anti-rotaviral effect exerted by probiotic metabolites monitored by the NSP4 protein during the RV in vitro infection and the effect on the Ca(2+) release is reported; suggesting a reduction on the impact of the infection by decreasing the damage of the cells preventing the electrolyte loss.

The role of intestinal oxalate transport in hyperoxaluria and the formation of kidney stones in animals and man

The intestine exerts a considerable influence over urinary oxalate in two ways, through the absorption of dietary oxalate and by serving as an adaptive extra-renal pathway for elimination of this waste metabolite. Knowledge of the mechanisms responsible for oxalate absorption and secretion by the intestine therefore have significant implications for understanding the etiology of hyperoxaluria, as well as offering potential targets for future treatment strategies for calcium oxalate kidney stone disease. In this review, we present the recent developments and advances in this area over the past 10 years, and put to the test some of the new ideas that have emerged during this time, using human and mouse models. A key focus for our discussion are the membrane-bound anion exchangers, belonging to the SLC26 gene family, some of which have been shown to participate in transcellular oxalate absorption and secretion. This has offered the opportunity to not only examine the roles of these specific transporters, revealing their importance to oxalate homeostasis, but to also probe the relative contributions made by the active transcellular and passive paracellular components of oxalate transport across the intestine. We also discuss some of the various physiological stimuli and signaling pathways which have been suggested to participate in the adaptation and regulation of intestinal oxalate transport. Finally, we offer an update on research into Oxalobacter formigenes, alongside recent investigations of other oxalate-degrading gut bacteria, in both laboratory animals and humans.

Lactobacillus acidophilus counteracts inhibition of NHE3 and DRA expression and alleviates diarrheal phenotype in mice infected with Citrobacter rodentium

Impaired absorption of electrolytes is a hallmark of diarrhea associated with inflammation or enteric infections. Intestinal epithelial luminal membrane NHE3 (Na⁺/H⁺ exchanger 3) and DRA (Down-Regulated in Adenoma; Cl^-/HCO₃^- exchanger) play key roles in mediating electroneutral NaCl absorption. We have previously shown decreased NHE3 and DRA function in response to short-term infection with enteropathogenic E coli (EPEC), a diarrheal pathogen. Recent studies have also shown substantial downregulation of DRA expression in a diarrheal model of infection with Citrobacter rodentium, the mouse counterpart of EPEC. Since our previous studies showed that the probiotic Lactobacillus acidophilus (LA) increased DRA and NHE3 function and expression and conferred protective effects in experimental colitis, we sought to evaluate the efficacy of LA in counteracting NHE3 and DRA inhibition and ameliorating diarrhea in a model of C rodentium infection. FVB/N mice challenged with C rodentium [1 × 10⁹ colony-forming units (CFU)] with or without administration of live LA (3 × 10⁹ CFU) were assessed for NHE3 and DRA mRNA and protein expression, mRNA levels of carbonic anhydrase, diarrheal phenotype (assessed by colonic weight-to-length ratio), myeloperoxidase activity, and proinflammatory cytokines. LA counteracted C rodentium-induced inhibition of colonic DRA, NHE3, and carbonic anhydrase I and IV expression and attenuated diarrheal phenotype and MPO activity. Furthermore, LA completely blocked C rodentium induction of IL-1β, IFN-γ, and CXCL1 mRNA and C rodentium-induced STAT3 phosphorylation. In conclusion, our data provide mechanistic insights into antidiarrheal effects of LA in a model of infectious diarrhea and colitis.

Oxalobacter formigenes-Derived Bioactive Factors Stimulate Oxalate Transport by Intestinal Epithelial Cells

Hyperoxaluria is a major risk factor for kidney stones and has no specific therapy, although Oxalobacter formigenes colonization is associated with reduced stone risk. O. formigenes interacts with colonic epithelium and induces colonic oxalate secretion, thereby reducing urinary oxalate excretion, via an unknown secretagogue. The difficulties in sustaining O. formigenes colonization underscore the need to identify the derived factors inducing colonic oxalate secretion. We therefore evaluated the effects of O. formigenes culture conditioned medium (CM) on apical ¹⁴C-oxalate uptake by human intestinal Caco-2-BBE cells. Compared with control medium, O. formigenes CM significantly stimulated oxalate uptake (>2.4-fold), whereas CM from Lactobacillus acidophilus did not. Treating the O. formigenes CM with heat or pepsin completely abolished this bioactivity, and selective ultrafiltration of the CM revealed that the O. formigenes-derived factors have molecular masses of 10-30 kDa. Treatment with the protein kinase A inhibitor H89 or the anion exchange inhibitor 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid completely blocked the CM-induced oxalate transport. Knockdown of the oxalate transporter SLC26A6 also significantly restricted the induction of oxalate transport by CM. In a mouse model of primary hyperoxaluria type 1, rectal administration of O. formigenes CM significantly reduced (>32.5%) urinary oxalate excretion and stimulated (>42%) distal colonic oxalate secretion. We conclude that O. formigenes-derived bioactive factors stimulate oxalate transport in intestinal cells through mechanisms including PKA activation. The reduction in urinary oxalate excretion in hyperoxaluric mice treated with O. formigenes CM reflects the in vivo retention of biologic activity and the therapeutic potential of these factors.

A novel anti-inflammatory role of GPR120 in intestinal epithelial cells

GPR120 (free fatty acid receptor-4) is a G protein-coupled receptor for medium- and long-chain unsaturated fatty acids, including ω-3 fatty acids. Recent studies have shown GPR120 to play cardinal roles in metabolic disorders via modulation of gut hormone secretion and insulin sensitivity and to exert anti-inflammatory effects in macrophages and adipose tissues. However, information on anti-inflammatory role of GPR120 at the level of intestinal epithelium is very limited. Current studies demonstrated differential levels of GPR120 mRNA and protein along the length of the human, mouse, and rat intestine and delineated distinct anti-inflammatory responses following GPR120 activation in model human intestinal epithelial Caco-2 cells, but not in model mouse intestinal epithelial endocrine cell line STC-1. In Caco-2 cells, GPR120 was internalized, bound to β-arrestin-2, and attenuated NF-κB activation in response to 30-min exposure to the agonists GW9508, TUG-891, or docosahexaenoic acid. These effects were abrogated in response to small interfering RNA silencing of β-arrestin-2. Treatment of STC-1 cells with these agonists did not induce receptor internalization and had no effects on NF-κB activation, although treatment with the agonists GW9508 or TUG-891 for 6 h augmented the synthesis and secretion of the gut hormone glucagon-like peptide-1 in this cell line. Our studies for the first time demonstrated a GPR120-mediated novel anti-inflammatory pathway in specific intestinal epithelial cell types that could be of therapeutic relevance to intestinal inflammatory disorders.

Lactobacillus acidophilus counteracts enteropathogenic E. coli-induced inhibition of butyrate uptake in intestinal epithelial cells

Butyrate, a key short-chain fatty acid metabolite of colonic luminal bacterial action on dietary fiber, serves as a primary fuel for the colonocytes, ameliorates mucosal inflammation, and stimulates NaCl absorption. Absorption of butyrate into the colonocytes is essential for these intracellular effects. Monocarboxylate transporter 1 (MCT1) plays a major role in colonic luminal butyrate absorption. Previous studies (Tan J, McKenzie C, Potamitis M, Thorburn AN, Mackay CR, Macia L. Adv Immunol 121: 91-119, 2014.) showed decreased MCT1 expression and function in intestinal inflammation. We have previously shown (Borthakur A, Gill RK, Hodges K, Ramaswamy K, Hecht G, Dudeja PK. Am J Physiol Gastrointest Liver Physiol 290: G30-G35, 2006.) impaired butyrate absorption in human intestinal epithelial Caco-2 cells due to decreased MCT1 level at the apical cell surface following enteropathogenic E. coli (EPEC) infection. Current studies, therefore, examined the potential role of probiotic Lactobacilli in stimulating MCT1-mediated butyrate uptake and counteracting EPEC inhibition of MCT1 function. Of the five species of Lactobacilli, short-term (3 h) treatment with L. acidophilus (LA) significantly increased MCT1-mediated butyrate uptake in Caco-2 cells. Heat-killed LA was ineffective, whereas the conditioned culture supernatant of LA (LA-CS) was equally effective in stimulating MCT1 function, indicating that the effects are mediated by LA-secreted soluble factor(s). Furthermore, LA-CS increased apical membrane levels of MCT1 protein via decreasing its basal endocytosis, suggesting that LA-CS stimulation of butyrate uptake could be secondary to increased levels of MCT1 on the apical cell surface. LA-CS also attenuated EPEC inhibition of butyrate uptake and EPEC-mediated endocytosis of MCT1. Our studies highlight distinct role of specific LA-secreted molecules in modulating colonic butyrate absorption.

Secretory diarrhoea: mechanisms and emerging therapies

Diarrhoeal disease remains a major health burden worldwide. Secretory diarrhoeas are caused by certain bacterial and viral infections, inflammatory processes, drugs and genetic disorders. Fluid secretion across the intestinal epithelium in secretory diarrhoeas involves multiple ion and solute transporters, as well as activation of cyclic nucleotide and Ca(2+) signalling pathways. In many secretory diarrhoeas, activation of Cl(-) channels in the apical membrane of enterocytes, including the cystic fibrosis transmembrane conductance regulator and Ca(2+)-activated Cl(-) channels, increases fluid secretion, while inhibition of Na(+) transport reduces fluid absorption. Current treatment of diarrhoea includes replacement of fluid and electrolyte losses using oral rehydration solutions, and drugs targeting intestinal motility or fluid secretion. Therapeutics in the development pipeline target intestinal ion channels and transporters, regulatory proteins and cell surface receptors. This Review describes pathogenic mechanisms of secretory diarrhoea, current and emerging therapeutics, and the challenges in developing antidiarrhoeal therapeutics.

All-trans-retinoic Acid Increases SLC26A3 DRA (Down-regulated in Adenoma) Expression in Intestinal Epithelial Cells via HNF-1β

All-trans-retinoic acid (ATRA) is an active vitamin A derivative known to modulate a number of physiological processes, including growth and development, differentiation, and gene transcription. The protective effect of ATRA in gut inflammation and diarrheal diseases has been documented. In this regard, down-regulated in adenoma (DRA, a key luminal membrane Cl(-) transporter involved in NaCl absorption) has been shown to be suppressed in intestinal inflammation. This suppression of DRA is associated with diarrheal phenotype. Therefore, current studies were undertaken to examine the effects of ATRA on DRA expression. DRA mRNA levels were significantly elevated (∼4-fold) in response to ATRA with induction starting as early as 8 h of incubation. Similarly, ATRA increased DRA protein expression by ∼50%. Furthermore, DRA promoter activity was significantly increased in response to ATRA indicating transcriptional activation. ATRA effects on DRA expression appeared to be mediated via the RAR-β receptor subtype, as ATRA remarkably induced RAR-β mRNA levels, whereas RAR-β knockdown substantially attenuated the ability of ATRA to increase DRA expression. Results obtained from agonist (CH-55) and antagonist (LE-135) studies further confirmed that ATRA exerts its effects through RAR-β. Furthermore, ATRA treatment resulted in a significant increase in HNF-1β mRNA levels. The ability of ATRA to induce DRA expression was inhibited in the presence of HNF-1β siRNA indicative of its involvement in ATRA-induced effects on DRA expression. In conclusion, ATRA may act as an antidiarrheal agent by increasing DRA expression via the RAR-β/HNF-1β-dependent pathway.

Oxalobacter formigenes Colonization and Oxalate Dynamics in a Mouse Model

Animal and human studies have provided compelling evidence that colonization of the intestine with Oxalobacter formigenes reduces urinary oxalate excretion and lowers the risk of forming calcium oxalate kidney stones. The mechanism providing protection appears to be related to the unique ability of O. formigenes to rely on oxalate as a major source of carbon and energy for growth. However, much is not known about the factors that influence colonization and host-bacterium interactions. We have colonized mice with O. formigenes OxCC13 and systematically investigated the impacts of diets with different levels of calcium and oxalate on O. formigenes intestinal densities and urinary and intestinal oxalate levels. Measurement of intestinal oxalate levels in mice colonized or not colonized with O. formigenes demonstrated the highly efficient degradation of soluble oxalate by O. formigenes relative to other microbiota. The ratio of calcium to oxalate in diets was important in determining colonization densities and conditions where urinary oxalate and fecal oxalate excretion were modified, and the results were consistent with those from studies we have performed with colonized and noncolonized humans. The use of low-oxalate purified diets showed that 80% of animals retained O. formigenes colonization after a 1-week dietary oxalate deprivation. Animals not colonized with O. formigenes excreted two times more oxalate in feces than they had ingested. This nondietary source of oxalate may play an important role in the survival of O. formigenes during periods of dietary oxalate deprivation. These studies suggest that the mouse will be a useful model to further characterize interactions between O. formigenes and the host and factors that impact colonization.

Regulatory role of Lactobacillus acidophilus on inflammation and gastric dysmotility in intestinal mucositis induced by 5-fluorouracil in mice

PURPOSE

Lactobacillus acidophilus is widely used for gastrointestinal disorders, but its role in inflammatory conditions like in chemotherapy-induced mucositis is unclear. Here, we report the effect of L. acidophilus on 5-fluorouracil-induced (5-FU) intestinal mucositis in mice.

METHODS

Mice weighing 25-30 g (n = 8) were separated into three groups, saline, 5-FU, and 5-FU + L. acidophilus (5-FU-La) (16 × 10(9) CFU/kg). In the 5-FU-La group, L. acidophilus was administered concomitantly with 5-FU on the first day and alone for two additional days. Three days after the last administration of L. acidophilus, the animals were euthanized and the jejunum and ileum were removed for histopathological assessment and for evaluation of levels of myeloperoxidase activity, sulfhydryl groups, nitrite, and cytokines (TNF-α, IL-1β, CXCL-1, and IL-10). In addition, we investigated gastric emptying using spectrophotometry after feeding a 1.5-ml test meal by gavage and euthanasia. Data were submitted to ANOVA and Bonferroni's test, with the level of significance at p < 0.05.

RESULTS

Intestinal mucositis induced by 5-FU significantly (p < 0.05) reduced the villus height-crypt depth ratio and GSH concentration and increased myeloperoxidase activity and the nitrite concentrations compared with the control group. Furthermore, 5-FU significantly (p < 0.05) increased cytokine (TNF-α, IL-1β, and CXCL-1) concentrations and decreased IL-10 concentrations compared with the control group. 5-FU also significantly (p < 0.05) delayed gastric emptying and gastrointestinal transit compared with the control group. All of these changes were significantly (p < 0.05) reversed by treatment with L. acidophilus.

CONCLUSIONS

Lactobacillus acidophilus improves the inflammatory and functional aspects of intestinal mucositis induced by 5-FU.

Probiotics: an update

OBJECTIVE

Triggered by the growing knowledge on the link between the intestinal microbiome and human health, the interest in probiotics is ever increasing. The authors aimed to review the recent literature on probiotics, from definitions to clinical benefits, with emphasis on children.

SOURCES

Relevant literature from searches of PubMed, CINAHL, and recent consensus statements were reviewed.

SUMMARY OF THE FINDINGS

While a balanced microbiome is related to health, an imbalanced microbiome or dysbiosis is related to many health problems both within the gastro-intestinal tract, such as diarrhea and inflammatory bowel disease, and outside the gastro-intestinal tract such as obesity and allergy. In this context, a strict regulation of probiotics with health claims is urgent, because the vast majority of these products are commercialized as food (supplements), claiming health benefits that are often not substantiated with clinically relevant evidence. The major indications of probiotics are in the area of the prevention and treatment of gastro-intestinal related disorders, but more data has become available on extra-intestinal indications. At least two published randomized controlled trials with the commercialized probiotic product in the claimed indication are a minimal condition before a claim can be sustained. Today, Lactobacillus rhamnosus GG and Saccharomyces boulardii are the best-studied strains. Although adverse effects have sporadically been reported, these probiotics can be considered as safe.

CONCLUSIONS

Although regulation is improving, more stringent definitions are still required. Evidence of clinical benefit is accumulating, although still missing in many areas. Misuse and use of products that have not been validated constitute potential drawbacks.

Lactobacillus acidophilus attenuates downregulation of DRA function and expression in inflammatory models

Probiotics, including Lactobacilli, are commensal bacteria that have been used in clinical trials and experimental models for the prevention and treatment of diarrheal disorders. Our previous studies have shown that Lactobacillus acidophilus (LA) and its culture supernatant (CS) stimulated Cl(-)/HCO3 (-) exchange activity, acutely via an increase in the surface levels of downregulated in adenoma (DRA, SLC26A3) and in long-term treatments via increasing its expression involving transcriptional mechanisms. However, the role of LA in modulating DRA activity under inflammatory conditions is not known. Current in vitro studies using human intestinal epithelial Caco-2 cells examined the efficacy of LA or its CS in counteracting the inhibitory effects of interferon-γ (IFN-γ) on Cl(-)/HCO3 (-) exchange activity. Pretreatment of cells with LA or LA-CS for 1 h followed by coincubation with IFN-γ significantly alleviated the inhibitory effects of IFN-γ on Cl(-)/HCO3 (-) exchange activity. In the in vivo model of dextran sulfate sodium-induced experimental colitis (3% in drinking water for 7 days) in C57BL/6J mice, administration of live LA (3 × 10(9) colony-forming units) via oral gavage attenuated colonic inflammation. LA administration also counteracted the colitis-induced decrease in DRA mRNA and protein levels. Efficacy of LA or its secreted soluble factors in alleviating inflammation and inflammation-associated dysregulation of DRA activity could justify their therapeutic potential in inflammatory diarrheal diseases.

Probiotic Bifidobacterium species stimulate human SLC26A3 gene function and expression in intestinal epithelial cells

SLC26A3, or downregulated in adenoma (DRA), plays a major role in mediating Cl(-) absorption in the mammalian intestine. Disturbances in DRA function and expression have been implicated in intestinal disorders such as congenital Cl(-) diarrhea and gut inflammation. We previously showed that an increase in DRA function and expression by Lactobacillus acidophilus and its culture supernatant (CS) might underlie antidiarrheal effects of this probiotic strain. However, the effects of Bifidobacterium species, important inhabitants of the human colon, on intestinal Cl(-)/HCO3 (-) exchange activity are not known. Our current results demonstrate that CS derived from Bifidobacterium breve, Bifidobacterium infantis, and Bifidobacterium bifidum increased anion exchange activity in Caco-2 cells (∼1.8- to 2.4-fold). Consistent with the increase in DRA function, CS also increased the protein, as well as the mRNA, level of DRA (but not putative anion transporter 1). CS of all three Bifidobacterium sp. increased DRA promoter activity (-1,183/+114 bp) in Caco-2 cells (1.5- to 1.8-fold). Furthermore, the increase in DRA mRNA expression by CS of B. breve and B. infantis was blocked in the presence of the transcription inhibitor actinomycin D (5 μM) and the ERK1/2 MAPK pathway inhibitor U0126 (10 μM). Administration of live B. breve, B. infantis, and B. bifidum by oral gavage to mice for 24 h increased DRA mRNA and protein levels in the colon. These data demonstrate an upregulation of DRA via activation of the ERK1/2 pathway that may underlie potential antidiarrheal effects of Bifidobacterium sp.

Converging effects of a Bifidobacterium and Lactobacillus probiotic strain on mouse intestinal physiology

Evidence has grown to support the efficacy of probiotics in the management of gastrointestinal disorders, many of which are associated with dysregulated fluid and electrolyte transport. A growing body of evidence now suggests that the host microbiota and probiotics can influence intestinal ion transport and that these effects often occur in a strain-dependent manner. In this study, we sought to investigate the effects of two therapeutically relevant organisms, Bifidobacterium infantis 35,624 and Lactobacillus salivarius UCC118, on small intestinal transit, fecal output and water content, transepithelial resistance (TER), and colonic secretomotor function. Mice fed either strain displayed significantly reduced small intestinal transit in vivo, though neither strain influenced fecal pellet output or water content. Colon from mice fed both organisms displayed increased colonic TER, without a concomitant change in the gene expression of the tight junction proteins claudin 1 and occludin. However, L. salivarius UCC118 selectively inhibited neurally evoked ion secretion in tissues from animals fed this particular probiotic. Consistent with this finding, the neurotoxin tetrodotoxin (TTx) significantly inhibited the short-circuit current response induced by L. salivarius UCC118 following addition to colonic preparations in Ussing chambers. Responses to B. infantis 35,624 also displayed sensitivity to TTx, although to a significantly lesser degree than L. salivarius UCC118. Both strains similarly inhibited cholinergic-induced ion transport after addition to Ussing chambers. Taken together, these data suggest that B. infantis 35,624 and L. salivarius UCC118 may be indicated in disorders associated with increased small intestinal transit, and, in particular for L. salivarius UCC118, neurally mediated diarrhea.

Screening of indigenous oxalate degrading lactic acid bacteria from human faeces and South Indian fermented foods: assessment of probiotic potential

Lactic acid bacteria (LAB) have the potential to degrade intestinal oxalate and this is increasingly being studied as a promising probiotic solution to manage kidney stone disease. In this study, oxalate degrading LAB were isolated from human faeces and south Indian fermented foods, subsequently assessed for potential probiotic property in vitro and in vivo. Based on preliminary characteristics, 251 out of 673 bacterial isolates were identified as LAB. A total of 17 strains were found to degrade oxalate significantly between 40.38% and 62.90% and were subjected to acid and bile tolerance test. Among them, nine strains exhibited considerable tolerance up to pH 3.0 and at 0.3% bile. These were identified as Lactobacillus fermentum and Lactobacillus salivarius using 16S rDNA sequencing. Three strains, Lactobacillus fermentum TY5, Lactobacillus fermentum AB1, and Lactobacillus salivarius AB11, exhibited good adhesion to HT-29 cells and strong antimicrobial activity. They also conferred resistance to kanamycin, rifampicin, and ampicillin, but were sensitive to chloramphenicol and erythromycin. The faecal recovery rate of these strains was observed as 15.16% (TY5), 6.71% (AB1), and 9.3% (AB11) which indicates the colonization ability. In conclusion, three efficient oxalate degrading LAB were identified and their safety assessments suggest that they may serve as good probiotic candidates for preventing hyperoxaluria.

Lactobacillus acidophilus alleviates platelet-activating factor-induced inflammatory responses in human intestinal epithelial cells

Probiotics have been used as alternative prevention and therapy modalities in intestinal inflammatory disorders including inflammatory bowel diseases (IBD) and necrotizing enterocolitis (NEC). Pathophysiology of IBD and NEC includes the production of diverse lipid mediators, including platelet-activating factor (PAF) that mediate inflammatory responses in the disease. PAF is known to activate NF-κB, however, the mechanisms of PAF-induced inflammation are not fully defined. We have recently described a novel PAF-triggered pathway of NF-κB activation and IL-8 production in intestinal epithelial cells (IECs), requiring the pivotal role of the adaptor protein Bcl10 and its interactions with CARMA3 and MALT1. The current studies examined the potential role of the probiotic Lactobacillus acidophilus in reversing the PAF-induced, Bcl10-dependent NF-κB activation and IL-8 production in IECs. PAF treatment (5 µM×24 h) of NCM460 and Caco-2 cells significantly increased nuclear p65 NF-κB levels and IL-8 secretion (2-3-fold, P<0.05), compared to control, which were blocked by pretreatment of the cells for 6 h with L. acidophilus (LA) or its culture supernatant (CS), followed by continued treatments with PAF for 24 h. LA-CS also attenuated PAF-induced increase in Bcl10 mRNA and protein levels and Bcl10 promoter activity. LA-CS did not alter PAF-induced interaction of Bcl10 with CARMA3, but attenuated Bcl10 interaction with MALT1 and also PAF-induced ubiquitination of IKKγ. Efficacy of bacteria-free CS of LA in counteracting PAF-induced inflammatory cascade suggests that soluble factor(s) in the CS of LA mediate these effects. These results define a novel mechanism by which probiotics counteract PAF-induced inflammation in IECs.

The application of Ussing chambers for determining the impact of microbes and probiotics on intestinal ion transport

Host–microbe interactions have gained considerable attention in recent years with regards to their role in various organic disorders and diseases. In particular, research efforts have focused on the intestinal microbiota, where the largest and most diverse populations not only co-exist with the host, but also directly influence the state and function of the gastrointestinal (GI) tract. Moreover, both human and animal studies alike are now beginning to show a positive influence of probiotic bacteria on GI disorders associated with diarrhoea or constipation. Diarrheagenic GI diseases, such as those caused by Vibreo cholera or enterpathogenic Eschericia coli, have well-characterised interactions with the host that explain much of the observed symptoms, in particular severe diarrhoea. However, the mechanisms of action of nonpathogenic bacteria or probiotics on host physiology are less clearly understood. In the context of defining the mechanisms of action of probiotics in vitro, the Ussing chamber has proven to be a particularly useful tool. Here, we will present data from several studies that have defined molecular targets for microbes and putative probiotics in the regulation of intestinal secretory and absorptive function, and we will discuss these in the context of their application in pathogen- or inflammation-induced alterations in intestinal ion transport.

Influence of diets to Wistar rats supplemented with soya, flaxseed and lupine products treated by lactofermentation to improve their gut health

The present study proposes the contribution of lactic acid bacteria and plants rich in bioactive substances and high-quality proteins as alternative products for human diets in improving the gut environment as potential against pathogenic bacteria. The effect of diets supplemented with soya, flaxseed and lupine flours fermented with a Pediococcus acidilactici KTU05-7 probiotic strain in the gastrointestinal tract (GIT) of Wistar rats were analyzed. In vivo experiments showed a positive effect of long time lactofermentation of plant material on the body weight of rats. Diets with fermented yellow lupine resulted in enhanced activities of α-glucosidase, β-galactosidases, as well as high levels of lactic acid bacteria, bifidobacteria and enterococci in the GIT were determined. Lactofermentation of analyzed plant products had a significantly lowering effect on Escherichia coli compared with the control group. The dominant flora of large intestines like Bifidobacterium and anaerobic cocci were found in high levels after diets with fermented lupine.

Probiotics in Clostridium difficile infection: reviewing the need for a multistrain probiotic

In the past two years an enormous amount of molecular, genetic, metabolomic and mechanistic data on the host-bacterium interaction, a healthy gut microbiota and a possible role for probiotics in Clostridium difficile infection (CDI) has been accumulated. Also, new hypervirulent strains of C. difficile have emerged. Yet, clinical trials in CDI have been less promising than in antibiotic associated diarrhoea in general, with more meta-analysis than primary papers on CDI-clinical-trials. The fact that C. difficile is a spore former, producing at least three different toxins has not yet been incorporated in the rational design of probiotics for (recurrent) CDI. Here we postulate that the plethora of effects of C. difficile and the vast amount of data on the role of commensal gut residents and probiotics point towards a multistrain mixture of probiotics to reduce CDI, but also to limit (nosocomial) transmission and/or endogenous reinfection. On the basis of a retrospective chart review of a series of ten CDI patients where recurrence was expected, all patients on adjunctive probiotic therapy with multistrain cocktail (Ecologic®AAD/OMNiBiOTiC® 10) showed complete clinical resolution. This result, and recent success in faecal transplants in CDI treatment, are supportive for the rational design of multistrain probiotics for CDI.

Protection and Restitution of Gut Barrier by Probiotics: Nutritional and Clinical Implications

Probiotics are beneficial bacteria present in various dietary components and many of these colonize in the human and animal intestine. In the gut probiotics help the host by assisting in maintenance of normal mucosal homeostasis. Probiotics not only help maintain normal function of the gut mucosa, but also protect mucosa from injurious factors such as toxins, allergens and pathogens. The beneficial effect of probiotics is mediated by multiple mechanisms, including cytoprotection, cell proliferation, cell migration, resistance to apoptosis, synthesis of proteins and gene expression. One of the important cytoprotective effects of probiotics in the intestinal mucosa is to strengthen the epithelial tight junctions and preservation of mucosal barrier function. Probiotics not only enhance barrier function by inducing synthesis and assembly of tight junction proteins, but also preventing disruption of tight junctions by injurious factors. Bioactive factors released by probiotics trigger activation of various cell signaling pathways that lead to strengthening of tight junctions and the barrier function. This article reviews and summarizes the current understanding of various probiotics that are involved in the protection of gut barrier function, highlights the cellular and molecular mechanisms involved in the protective effect and addresses the clinical implications of probiotic supplementation.

The intestinal microbiome, probiotics and prebiotics in neurogastroenterology

The brain-gut axis allows bidirectional communication between the central nervous system (CNS) and the enteric nervous system (ENS), linking emotional and cognitive centers of the brain with peripheral intestinal functions. Recent experimental work suggests that the gut microbiota have an impact on the brain-gut axis. A group of experts convened by the International Scientific Association for Probiotics and Prebiotics (ISAPP) discussed the role of gut bacteria on brain functions and the implications for probiotic and prebiotic science. The experts reviewed and discussed current available data on the role of gut microbiota on epithelial cell function, gastrointestinal motility, visceral sensitivity, perception and behavior. Data, mostly gathered from animal studies, suggest interactions of gut microbiota not only with the enteric nervous system but also with the central nervous system via neural, neuroendocrine, neuroimmune and humoral links. Microbial colonization impacts mammalian brain development in early life and subsequent adult behavior. These findings provide novel insights for improved understanding of the potential role of gut microbial communities on psychological disorders, most particularly in the field of psychological comorbidities associated with functional bowel disorders like irritable bowel syndrome (IBS) and should present new opportunity for interventions with pro- and prebiotics.

Lactobacillus acidophilus upregulates intestinal NHE3 expression and function

A major mechanism of electroneutral NaCl absorption in the human ileum and colon involves coupling of Na(+)/H(+) and Cl(-)/HCO(3)(-) exchangers. Disturbances in these mechanisms have been implicated in diarrheal conditions. Probiotics such as Lactobacillus have been indicated to be beneficial in the management of gastrointestinal disorders, including diarrhea. However, the molecular mechanisms underlying antidiarrheal effects of probiotics have not been fully understood. We have previously demonstrated Lactobacillus acidophilus (LA) to stimulate Cl(-)/HCO3- exchange activity via an increase in the surface levels and expression of the Cl(-)/HCO3- exchanger DRA in vitro and in vivo. However, the effects of LA on NHE3, the Na(+)/H(+) exchanger involved in the coupled electroneutral NaCl absorption, are not known. Current studies were, therefore, undertaken to investigate the effects of LA on the function and expression of NHE3 and to determine the mechanisms involved. Treatment of Caco2 cells with LA or its conditioned culture supernatant (CS) for 8-24 h resulted in a significant increase in Na(+)/H(+) exchange activity, mRNA, and protein levels of NHE3. LA-CS upregulation of NHE3 function and expression was also observed in SK-CO15 cells, a human colonic adenocarcinoma cell line. Additionally, LA treatment increased NHE3 promoter activity, suggesting involvement of transcriptional mechanisms. In vivo, mice gavaged with live LA showed significant increase in NHE3 mRNA and protein expression in the ileum and colonic regions. In conclusion, LA-induced increase in NHE3 expression may contribute to the upregulation of intestinal electrolyte absorption and might underlie the potential antidiarrheal effects of probiotics.

Calcitonin receptor-mediated CFTR activation in human intestinal epithelial cells

High levels of calcitonin (CT) observed in medullary thyroid carcinoma and other CT-secreting tumours cause severe diarrhoea. Previous studies have suggested that CT induces active chloride secretion. However, the involvement of CT receptor (CTR) and the molecular mechanisms underlying the modulation of intestinal electrolyte secreting intestinal epithelial cells have not been investigated. Therefore, current studies were undertaken to investigate the direct effects of CT on ion transport in intestinal epithelial cells. Real time quantitative RT-PCR and Western blot analysis demonstrated the expression of CTR in intestinal epithelial T84 cells. Exposure of T84 cells to CT from the basolateral but not from apical side significantly increased short circuit current (I_SC) in a dose-dependent manner that was blocked by 1 μM of CTR antagonist, CT8–32. CT-induced I_SC was blocked by replacing chloride in the bath solutions with equimolar gluconate and was significantly inhibited by the specific cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor, CFTR_127inh. Further, biotinylation studies showed that CT increased CFTR levels on the apical membrane. The presence of either the Ca²⁺ chelator, bis(2-aminophenoxy)ethane tetraacetic acid-acetoxymethyl (BAPTA-AM) ester or the protein kinase A (PKA) inhibitor, H89, significantly inhibited I_SC induced by CT (∼32–58% reduction). Response to CT was retained after permeabilization of the basolateral or the apical membranes of T84 cells with nystatin. In conclusion, the activation of CTR by CT induced chloride secretion across T84 monolayers via CFTR channel and the involvement of PKA- and Ca²⁺-dependent signalling pathways. These data elucidate the molecular mechanisms underlying CT-induced diarrhoea.

LPA stimulates intestinal DRA gene transcription via LPA2 receptor, PI3K/AKT, and c-Fos-dependent pathway

DRA (downregulated in adenoma) or SLC26A3 is the major apical anion exchanger mediating Cl(-) absorption in intestinal epithelial cells. Disturbances in DRA function and expression have been implicated in diarrheal conditions such as congenital chloride diarrhea and inflammatory bowel diseases. Previous studies have shown that DRA is subject to regulation by short-term and transcriptional mechanisms. In this regard, we have recently shown that short-term treatment by lysophosphatidic acid (LPA), an important bioactive phospholipid, stimulates Cl(-)/HCO(3)(-)(OH(-)) exchange activity via an increase in DRA surface levels in human intestinal epithelial cells. However, the long-term effects of LPA on DRA at the level of gene transcription have not been examined. The present studies were aimed at investigating the effects of LPA on DRA function and expression as well as elucidating the mechanisms underlying its transcriptional regulation. Long-term LPA treatment increased the Cl(-)/HCO(3)(-) exchange activity in Caco-2 cells. LPA treatment (50-100 μM) of Caco-2 cells significantly stimulated DRA mRNA levels and DRA promoter activity (-1183/+114). This increase in DRA promoter activity involved the LPA2 receptor and phosphatidylinositol 3-kinase (PI3K)/AKT pathways. Progressive deletions from -1183/+114 to -790/+114 abrogated the stimulatory effects of LPA, indicating that the -1183/-790 promoter region harbors LPA response elements. Utilizing EMSA and mutational studies, our results showed that LPA induced the DRA promoter activity in a c-Fos-dependent manner. LPA also increased the protein expression of c-Fos and c-Jun in Caco-2 cells. Furthermore, overexpression of c-Fos but not c-Jun enhanced the DRA promoter activity. This increase in DRA transcription in response to LPA indicates that LPA may act as an antidiarrheal agent and could be exploited for the treatment of diarrhea associated with inflammatory or infectious diseases of the gut.

Upregulation of P-glycoprotein by probiotics in intestinal epithelial cells and in the dextran sulfate sodium model of colitis in mice

P-glycoprotein (P-gp) mediates efflux of xenobiotics and bacterial toxins from the intestinal mucosa into the lumen. Dysregulation of P-gp has been implicated in inflammatory bowel disease. Certain probiotics have been shown to be effective in treating inflammatory bowel disease. However, direct effects of probiotics on P-gp are not known. Current studies examined the effects of Lactobacilli on P-gp function and expression in intestinal epithelial cells. Caco-2 monolayers and a mouse model of dextran sulfate sodium-induced colitis were utilized. P-gp activity was measured as verapamil-sensitive [(3)H]digoxin transepithelial flux. Multidrug resistant 1 (MDR1)/P-gp expression was measured by real-time quantitative PCR and immunoblotting. Culture supernatant (CS; 1:10 or 1:50, 24 h) of Lactobacillus acidophilus or Lactobacillus rhamnosus treatment of differentiated Caco-2 monolayers (21 days postplating) increased (∼3-fold) MDR1/P-gp mRNA and protein levels. L. acidophilus or L. rhamnosus CS stimulated P-gp activity (∼2-fold, P < 0.05) via phosphoinositide 3-kinase and ERK1/2 MAPK pathways. In mice, L. acidophilus or L. rhamnosus treatment (3 × 10(9) colony-forming units) increased mdr1a/P-gp mRNA and protein expression in the ileum and colon (2- to 3-fold). In the dextran sulfate sodium (DSS)-induced colitis model (3% DSS in drinking water for 7 days), the degree of colitis as judged by histological damage and myeloperoxidase activity was reduced by L. acidophilus. L. acidophilus treatment to DSS-treated mice blocked the reduced expression of mdr1a/P-gp mRNA and protein in the distal colon. These findings suggest that Lactobacilli or their soluble factors stimulate P-gp expression and function under normal and inflammatory conditions. These data provide insights into a novel mechanism involving P-gp upregulation in beneficial effects of probiotics in intestinal inflammatory disorders.