Preventive and curative effects of probiotics in atopic patients

A metagenome-wide association study of the gut microbiota in recurrent aphthous ulcer and regulation by thalidomide

Recurrent aphthous ulcer (RAU), one of the most common diseases in humans, has an unknown etiology and is difficult to treat. Thalidomide is an important immunomodulatory and antitumor drug and its effects on the gut microbiota still remain unclear. We conducted a metagenomic sequencing study of fecal samples from a cohort of individuals with RAU, performed biochemical assays of cytokines, immunoglobulins and antimicrobial peptides in serum and saliva, and investigated the regulation effects of thalidomide administration and withdrawal. Meanwhile we constructed the corresponding prediction models. Our metagenome-wide association results indicated that gut dysbacteriosis, microbial dysfunction and immune imbalance occurred in RAU patients. Thalidomide regulated gut dysbacteriosis in a species-specific manner and had different sustainable effects on various probiotics and pathogens. A previously unknown association between gut microbiota alterations and RAU was found, and the specific roles of thalidomide in modulating the gut microbiota and immunity were determined, suggesting that RAU may be affected by targeting gut dysbacteriosis and modifying immune imbalance. In-depth insights into sophisticated networks consisting of the gut microbiota and host cells may lead to the development of emerging treatments, including prebiotics, probiotics, synbiotics, and postbiotics.

A reassessment of the PROPATRIA study and its implications for probiotic therapy

The PROPATRIA (Probiotics in Pancreatitis Trial) study was a multicenter, double-blind, placebo-controlled clinical trial that aimed to reduce infectious complications in patients with predicted severe acute pancreatitis by the enteral use of a multispecies probiotic preparation. An unprecedented 24 of 152 patients (16%) in the group receiving probiotics died versus 9 of 144 (6%) in the placebo group. This high mortality rate in the probiotic-treated group contrasts strongly with observations from a previous smaller study and from our observations regarding the effects of abundant intestinal lactobacilli in patients with short small bowel (SSB) syndrome. We argue here that a lethal combination of mainly proteolytic pancreas enzymes and probiotic therapy resulted in the high mortality rate of the PROPATRIA trial and that elevated levels of lactic acid produced by bacterial fermentation of carbohydrates were a key contributing factor. We suggest that probiotic therapy may not be counter-indicated for the prevention of secondary infections associated with acute pancreatitis, provided that future clinical studies (i) start probiotic therapy immediately after first onset of disease symptoms, (ii) limit the supply of fermentable carbohydrates, (iii) prevent bacterial (over)growth of patient's own intestinal flora and (iv) massively increase the dose of probiotic bacteria.

Inhibition of pathogenic and spoilage bacteria by a novel biofilm-forming Lactobacillus isolate: a potential host for the expression of heterologous proteins

BACKGROUND

Bacterial biofilms are a preferred mode of growth for many types of microorganisms in their natural environments. The ability of pathogens to integrate within a biofilm is pivotal to their survival. The possibility of biofilm formation in Lactobacillus communities is also important in various industrial and medical settings. Lactobacilli can eliminate the colonization of different pathogenic microorganisms. Alternatively, new opportunities are now arising with the rapidly expanding potential of lactic acid bacteria biofilms as bio-control agents against food-borne pathogens.

RESULTS

A new isolate Lactobacillus plantarum PA21 could form a strong biofilm in pure culture and in combination with several pathogenic and food-spoilage bacteria such as Salmonella enterica, Bacillus cereus, Pseudomonas fluorescens, and Aeromonas hydrophila. Exposure to Lb. plantarum PA21 significantly reduced the number of P. fluorescens, A. hydrophila and B. cereus cells in the biofilm over 2-, 4- and 6-day time periods. However, despite the reduction in S. enterica cells, this pathogen showed greater resistance in the presence of PA21 developed biofilm, either in the planktonic or biofilm phase. Lb. plantarum PA21 was also found to be able to constitutively express GFP when transformed with the expression vector pMG36e which harbors the gfp gene as a reporter demonstrating that the newly isolated strain can be used as host for genetic engineering.

CONCLUSION

In this study, we evaluate the ability of a new Lactobacillus isolate to form strong biofilm, which would provide the inhibitory effect against several spoilage and pathogenic bacteria. This new isolate has the potential to serve as a safe and effective cell factory for recombinant proteins.

Modulation of immunity and inflammatory gene expression in the gut, in inflammatory diseases of the gut and in the liver by probiotics

The potential for the positive manipulation of the gut microbiome through the introduction of beneficial microbes, as also known as probiotics, is currently an active area of investigation. The FAO/WHO define probiotics as live microorganisms that confer a health benefit to the host when administered in adequate amounts. However, dead bacteria and bacterial molecular components may also exhibit probiotic properties. The results of clinical studies have demonstrated the clinical potential of probiotics in many pathologies, such as allergic diseases, diarrhea, inflammatory bowel disease and viral infection. Several mechanisms have been proposed to explain the beneficial effects of probiotics, most of which involve gene expression regulation in specific tissues, particularly the intestine and liver. Therefore, the modulation of gene expression mediated by probiotics is an important issue that warrants further investigation. In the present paper, we performed a systematic review of the probiotic-mediated modulation of gene expression that is associated with the immune system and inflammation. Between January 1990 to February 2014, PubMed was searched for articles that were published in English using the MeSH terms “probiotics" and "gene expression" combined with “intestines", "liver", "enterocytes", "antigen-presenting cells", "dendritic cells", "immune system", and "inflammation". Two hundred and five original articles matching these criteria were initially selected, although only those articles that included specific gene expression results (77) were later considered for this review and separated into three major topics: the regulation of immunity and inflammatory gene expression in the gut, in inflammatory diseases of the gut and in the liver. Particular strains of Bifidobacteria, Lactobacilli, Escherichia coli, Propionibacterium, Bacillus and Saccharomyces influence the gene expression of mucins, Toll-like receptors, caspases, nuclear factor-κB, and interleukins and lead mainly to an anti-inflammatory response in cultured enterocytes. In addition, the interaction of commensal bacteria and probiotics with the surface of antigen-presenting cells in vitro results in the downregulation of pro-inflammatory genes that are linked to inflammatory signaling pathways, whereas other anti-inflammatory genes are upregulated. The effects of probiotics have been extensively investigated in animal models ranging from fish to mice, rats and piglets. These bacteria induce a tolerogenic and hyporesponsive immune response in which many genes that are related to the immune system, in particular those genes expressing anti-inflammatory cytokines, are upregulated. By contrast, information related to gene expression in human intestinal cells mediated by the action of probiotics is scarce. There is a need for further clinical studies that evaluate the mechanism of action of probiotics both in healthy humans and in patients with chronic diseases. These types of clinical studies are necessary for addressing the influence of these microorganisms in gene expression for different pathways, particularly those that are associated with the immune response, and to better understand the role that probiotics might have in the prevention and treatment of disease.

Human intestinal dendritic cells decrease cytokine release against Salmonella infection in the presence of Lactobacillus paracasei upon TLR activation

Probiotic bacteria have been shown to modulate immune responses and could have therapeutic effects in allergic and inflammatory disorders. However, little is known about the signalling pathways that are engaged by probiotics. Dendritic cells (DCs) are antigen-presenting cells that are involved in immunity and tolerance. Monocyte-derived dendritic cells (MoDCs) and murine DCs are different from human gut DCs; therefore, in this study, we used human DCs generated from CD34+ progenitor cells (hematopoietic stem cells) harvested from umbilical cord blood; those DCs exhibited surface antigens of dendritic Langerhans cells, similar to the lamina propria DCs in the gut. We report that both a novel probiotic strain isolated from faeces of exclusively breast-fed newborn infants, Lactobacillus paracasei CNCM I-4034, and its cell-free culture supernatant (CFS) decreased pro-inflammatory cytokines and chemokines in human intestinal DCs challenged with Salmonella. Interestingly, the supernatant was as effective as the bacteria in reducing pro-inflammatory cytokine expression. In contrast, the bacterium was a potent inducer of TGF-β2 secretion, whereas the supernatant increased the secretion of TGF-β1 in response to Salmonella. We also showed that both the bacteria and its supernatant enhanced innate immunity through the activation of Toll-like receptor (TLR) signalling. These treatments strongly induced the transcription of the TLR9 gene. In addition, upregulation of the CASP8 and TOLLIP genes was observed. This work demonstrates that L. paracasei CNCM I-4034 enhanced innate immune responses, as evidenced by the activation of TLR signalling and the downregulation of a broad array of pro-inflammatory cytokines. The use of supernatants like the one described in this paper could be an effective and safe alternative to using live bacteria in functional foods.

Analysis of the human intestinal epithelial cell transcriptional response to Lactobacillus acidophilus, Lactobacillus salivarius, Bifidobacterium lactis and Escherichia coli

The complex microbial population residing in the human gastrointestinal tract consists of commensal, potential pathogenic and beneficial species, which are probably perceived differently by the host and consequently could be expected to trigger specific transcriptional responses. Here, we provide a comparative analysis of the global in vitro transcriptional response of human intestinal epithelial cells to Lactobacillus acidophilus NCFM™, Lactobacillus salivarius Ls-33, Bifidobacterium animalis subsp. lactis 420, and enterohaemorrhagic Escherichia coli O157:H7 (EHEC). Interestingly, L. salivarius Ls-33 DCE-induced changes were overall more similar to those of B. lactis 420 than to L. acidophilus NCFM™, which is consistent with previously observed in vivo immunomodulation properties. In the gene ontology and pathway analyses both specific and unspecific changes were observed. Common to all was the regulation of apoptosis and adipogenesis, and lipid-metabolism related regulation by the probiotics. Specific changes such as regulation of cell-cell adhesion by B. lactis 420, superoxide metabolism by L. salivarius Ls-33, and regulation of MAPK pathway by L. acidophilus NCFM™ were noted. Furthermore, fundamental differences were observed between the pathogenic and probiotic treatments in the Toll-like receptor pathway, especially for adapter molecules with a lowered level of transcriptional activation of MyD88, TRIF, IRAK1 and TRAF6 by probiotics compared to EHEC. The results in this study provide insights into the relationship between probiotics and human intestinal epithelial cells, notably with regard to strain-specific responses, and highlight the differences between transcriptional responses to pathogenic and probiotic bacteria.

Allergen-free probiotics

Food sensitivities are constantly increasing in "westernized" countries and may pose serious health risks to sensitized individuals. Severe allergy episodes have also been reported after the intake of probiotic products containing milk protein residues, especially in children. The need for safe and effective probiotic strains and food supplements, which contain them, is now emerging clearly. The present work describes the way of achieving this aim by the avoidance of any kind of raw materials at risk, both in probiotic strain industrial manufacturing and finished product formulation. Allergen-free probiotics represent, without any doubt, an innovative and safe tool for human health.

Effect of four probiotic strains and Escherichia coli O157:H7 on tight junction integrity and cyclo-oxygenase expression

Controversy exists as to whether contact between a probiotic bacterial cell and an epithelial cell in the gut is needed to confer beneficial effects of probiotics, or whether metabolites from probiotics are sufficient to cause this effect. To address this question, Caco-2 cells were treated with cell-free supernatants of four probiotics, Bifidobacterium lactis 420, Bifidobacterium lactis HN019, Lactobacillus acidophilus NCFM, Lactobacillus salivarius Ls-33, and by a cell-free supernatant of a pathogenic bacteria, Escherichia coli O157:H7 (EHEC). Tight junction integrity as well as expression of cyclo-oxygenases, which are prostaglandin-producing enzymes, were measured. Probiotic-specific as well as EHEC-specific effects on tight junction integrity and cyclo-oxygenase expression were evident, indicating that live bacterial cells were not necessary for the manifestation of the effects. B. lactis 420 cell-free supernatant increased tight junction integrity, while EHEC cell-free supernatant induced damage on tight junctions. In general, EHEC and probiotics had opposite effects upon cyclo-oxygenase expression. Furthermore, B. lactis 420 cell-free supernatant protected the tight junctions from EHEC-induced damage when administered prior to the cell-free supernatant of EHEC. These results indicate that probiotics produce bioactive metabolites, suggesting that consumption of specific probiotic bacteria might be beneficial in protecting intestinal epithelial cells from the deleterious effects of pathogenic bacteria.

Probiotics for the treatment or prevention of atopic dermatitis: a review of the evidence from randomized controlled trials

Probiotics are defined as live microorganisms which, when administered in adequate amounts, confer a health benefit on the host. To synthesize the evidence for the effectiveness of probiotics in the treatment or prevention of atopic dermatitis (AD) in children, we reviewed the results of 13 relevant randomized (placebo)-controlled trials (RCTs), 10 of which evaluated probiotics as treatment and 3 for prevention of AD. The main outcome measure in 9 RCTs was the change in SCORAD (SCORing Atopic Dermatitis). Four RCTs suggested that there was a statistically significant decrease in SCORAD after probiotic administration to infants or children with AD for 1 or 2 months compared with that after placebo, while in two RCTs SCORAD was significantly reduced after treatment with lactobacilli only in children with IgE-associated AD. In four of these six RCTs, clinical improvement was associated with a change in some inflammatory markers. In three RCTs, the change in SCORAD was not statistically significant between probiotic- and placebo-treated children, although in one of these trials SCORAD was significantly lower after probiotic than with placebo treatment in food-sensitized children. In most RCTs, probiotics did not cause a statistically significant change in interferon-gamma, interleukin-4, tumor necrosis factor-alpha, eosinophil cationic protein or transforming growth factor-beta compared with placebo. Regarding the effectiveness of probiotics in the prevention of AD, in two RCTs, infants at high risk for atopy who received probiotics developed AD significantly less frequently during the first 2 years of life than infants who received placebo. In these studies, mothers were administered Lactobacillus rhamnosus GG with or without other probiotics perinatally, followed by treatment of the infants with the same probiotics for the first 6 months of life. However, in another trial, neither the frequency nor the severity of AD during the first year of life were significantly different between infants with atopic mothers who received L. acidophilus for the first 6 months of life compared with infants who received placebo.Probiotics, especially L. rhamnosus GG, seem to be effective for the prevention of AD. They were also found to reduce the severity of AD in approximately half of the RCTs evaluated, although they were not found to change significantly most of the inflammatory markers measured in the majority of the RCTs evaluated. More RCTs need to be conducted to elucidate whether probiotics are useful for the treatment or prevention of AD.

What of apoptosis is important: The decay process or the causative origin?

Apoptosis is defined as the process of ''programmed cell death'' (PCD), during which many cells simultaneously die from within along a very orderly pattern. PCD is as intrinsic for cells as mitosis and is involved in both degenerative and developmental processes of organs and organisms. The pattern of apoptotic cell decay is caused by the total cellular content. Since all body cells possess the same genome, they are similar in many aspects and, therefore, the major processes are nearly identical in all cell types. The same destructive processes also occur continuously in healthy living cells, but then the capacity of repair mechanisms is sufficient to effect cellular integrity. Decay processes become visible, as soon as repair can no more be sufficient. PCD starts as soon as produced energy is permanently insufficient to repress decay. Decreased energy production may arise due to (i) turning off the pivotal tricarbonic acid cycle, (ii) turning off oxidative phosphorylation, (iii) damage of mitochondria, and (iv) inhibition of mitochondrial biogenesis regarding both the mitochondrial and the nuclear part. The consequence of this kind of decreased energy production will be a massive, inefficient fermentative energy production with enormous amounts of lactic acid. Increasing acidity and falling pH will slow down enzymatic activities and thus also intracellular processes. As soon as energy for repair has become insufficient, cellular decay becomes irreversible and the cell will die. Thus, the mitochondrial apoptotic pathway is suggested to arise due to low mitochondrial energy production. For optimal functioning cells need adequate internal conditions and cellular morphology. Cellular morphology depends on (i) the intracellular turgor, (ii) the intracellular cytoskeleton, and (iii) close intercellular contact with neighbour cells. Lack of energy implies decrease of turgor and, consequently, a strong decline of conditions needed for adequate functioning of the cell. Thus, if this lack of energy cannot be repaired in time, it will contribute to cellular decay. Various cellular components or systems that are not directly linked to mitochondria, may be functionally inhibited or damaged and thus contribute to apoptosis. These components or systems that probably constitute the non-mitochondrial pathway are (i) the cellular uptake systems for energy-rich substrates, (ii) extra-mitochondrial enzymes that are involved in non-mitochondrial processes of oxidative energy production, (iii) cytoplasmatic, non-mitochondrial protein synthesis, (iv) the system that regulates osmotic conditions and turgor, and (v) the synthesis and repair of the cytoskeleton. After this careful reflection I am convinced that apoptosis is merely the complex machinery of cellular decay after energy generation has irreversibly stopped. Therefore, apoptosis research for health care should be focussed on processes that hinder energy production. For therapeutic aims research should be focussed on metabolic aspects of energy production and on mitochondrial processes.

Primary prevention of allergic diseases: current concepts and mechanisms

: Atopic diseases, the new "epidemic of the twenty-first century" and a central health problem of industrial nations, call for the development of innovative primary prevention strategies. The present review provides an overview of current experimental and immunomodulatory procedures and their underlying mechanisms.

Beneficial lactobacilli in food and feed: long-term use, biodiversity and proposals for specific and realistic safety assessments

Lactobacilli have played a crucial role in the production of fermented products for millennia. Their probiotic effects have recently been studied and used in new products. Isolated cases of lactobacillemia have been reported in at-risk populations, but lactobacilli present an essentially negligible biological risk. We analyzed the current European guidelines for safety assessment in food/feed and conclude that they are not relevant for the Lactobacillus genus. We propose new specific guidelines, beginning by granting a 'long-standing presumption of safety' status to Lactobacillus genus based on its long history of safe use. Then, based on the available body of knowledge and intended use, only such tests as are useful will be necessary before attributing 'qualified presumption of safety' status.