Beneficial effect of immunobiotic strains on attenuation of Salmonella induced inflammatory response in human intestinal epithelial cells

Examining the impact of probiotic Lactiplantibacillus pentosus 6MMI on inhibiting biofilm formation, adhesion, and virulence gene expression in Listeria monocytogenes ATCC 19115

Probiotic bacteria improve human health by secreting pro-microbial substances, balancing intestinal flora, binding to the mucous membrane and epithelium, strengthening the intestinal epithelial barrier, and creating interactions between the gastrointestinal microbiota and the immune system. This study aimed to investigate the probiotic potential, biofilm-related gene expression and anti-biofilm capabilities of Lactiplantibacillus pentosus 6MMI. The strain exhibited remarkable resilience to challenging conditions, including acidic environments, gastrointestinal settings, and bile salts. Notably, Lpb. pentosus demonstrated significant hydrophobicity (71.89 %), auto-aggregation (42.39 %), co-aggregation (51.28 %), antioxidant activity (ranging from 42.29 % to 64.61 %), and a cholesterol reduction capacity of 50.31 %. Its competitive abilities against Listeria monocytogenes were quantified, showing a competition rate of 54.51 %, displacement rate of 48.57 %, and inhibition of adhesion at 27.71 %. Also, Lpb. pentosus resulted an adhesion rate of 12.91 % to epithelial cells and showed no DNase or hemolytic activity. The strain exhibited the highest resistance to nalidixic acid, with an inhibition zone measuring 15.20 mm, while it was least resistant to chloramphenicol, which had an inhibition zone of 27.30 mm. Treatment with cell-free supernatant (CFS) from Lpb. pentosus significantly reduced biofilm formation by 91.25 % and 24.50 % and diminished mature biofilm formation by 83.82 % and 21.80 % on L. monocytogenes. Additionally, the CFS inhibited the transcription of the plcB, hly, and prfA genes in L. monocytogenes, suggesting a potential reduction in bacterial virulence through decreased hemolysin release and modulation of phospholipase activity. In the next step of the study, the Gaussian Process Regression (GPR) model accurately predicted bile tolerance and acid parameters with a high R2 of 0.99 and minimal Mean Absolute Percentage Error (MAPE) values of 0.33 % and 0.21 %, respectively. The residual errors showed a normal distribution, indicating reliable and consistent predictions. Overall, Lpb. pentosus 6MMI represents a valuable candidate for further investigation in probiotic development and biofilm management strategies.

Anticancer effect of a combinatorial treatment of 5-fluorouracil and cell extract of some probiotic lactobacilli strains isolated from camel milk on colorectal cancer cells

Colorectal cancer (CRC) has the highest mortality rate among cancer types, emphasizing the need for auxiliaries to 5-fluorouracil (5-FU) due to resistance and side effects. Metabolites produced by probiotic bacteria exhibit promising anticancer properties against CRC. In the current study, the anticancer effects of cell extract of three potential probiotic lactobacilli strains isolated from camel milk, Lactobacillus helveticus, Lactobacillus gallinarum, and Lactiplantibacillus plantarum, as well as that of the standard probiotic strain Lacticaseibacillus rhamnosus GG (LGG), on the human colon cancer cell line (HT-29) and the normal HEK293 cell line separately or in combination with 5-FU, were evaluated. This study isolated strains from camel milk and compared their probiotic properties to those of LGG. The cell viability, cell apoptosis, and Th17 cytokine production were assessed using the MTT assay, acridine orange/ethidium bromide (AO/EB) staining, and flow cytometry techniques, respectively. The cell extracts of lactobacilli strains combined with 5-FU reduced HT-29 cell viability effectively and increased cell apoptosis. Nevertheless, the cell extracts of lactobacilli strains combined with 5-FU controlled the cytotoxic impact of 5-FU on HEK-293 cell viability and reduced cell apoptosis. No significant differences were observed among the strains. Moreover, the cell extracts from the strains combined with 5-FU increased the levels of cytokines IFN-γ, TNF-α, and IL-17A, all of which contribute to immunity against tumors. The performance of the studied strains was similar to that of the standard probiotic strain (LGG). The investigation revealed that cell extracts from lactobacilli strains may serve as a promising complementary anticancer treatment.

Gut instinct: harnessing the power of probiotics to tame pathogenic signaling pathways in ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease (IBD) marked by persistent inflammation of the mucosal lining of the large intestine, leading to debilitating symptoms and reduced quality of life. Emerging evidence suggests that an imbalance of the gut microbiota plays a crucial role in UC pathogenesis, and various signaling pathways are implicated in the dysregulated immune response. Probiotics are live microorganisms that confer health benefits to the host, have attracted significant attention for their potential to restore gut microbial balance and ameliorate inflammation in UC. Recent studies have elucidated the mechanisms by which probiotics modulate these signaling pathways, often by producing anti-inflammatory molecules and promoting regulatory immune cell function. For example, probiotics can inhibit the nuclear factor-κB (NF-κB) pathway by stabilizing Inhibitor of kappa B alpha (IκBα), dampening the production of proinflammatory cytokines. Similarly, probiotics can modulate the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway, suppressing the activation of STAT1 and STAT3 and thus reducing the inflammatory response. A better understanding of the underlying mechanisms of probiotics in modulating pathogenic signaling pathways in UC will pave the way for developing more effective probiotic-based therapies. In this review, we explore the mechanistic role of probiotics in the attenuation of pathogenic signaling pathways, including NF-κB, JAK/STAT, mitogen-activated protein kinases (MAPKs), Wnt/β-catenin, the nucleotide-binding domain (NOD)-, leucine-rich repeat (LRR)- and pyrin domain-containing protein 3 (NLRP3) inflammasome, Toll-like receptors (TLRs), interleukin-23 (IL-23)/IL-17 signaling pathway in UC.

Controlled production of lipopolysaccharides increases immune activation in Salmonella treatments of cancer

Immunotherapies have revolutionized cancer treatment. These treatments rely on immune cell activation in tumours, which limits the number of patients that respond. Inflammatory molecules, like lipopolysaccharides (LPS), can activate innate immune cells, which convert tumour microenvironments from cold to hot, and increase therapeutic efficacy. However, systemic delivery of lipopolysaccharides (LPS) can induce cytokine storm. In this work, we developed immune-controlling Salmonella (ICS) that only produce LPS in tumours after colonization and systemic clearance. We tuned the expression of msbB, which controls production of immunogenic LPS, by optimizing its ribosomal binding sites and protein degradation tags. This genetic system induced a controllable inflammatory response and increased dendritic cell cross-presentation in vitro. The strong off state did not induce TNFα production and prevented adverse events when injected into mice. The accumulation of ICS in tumours after intravenous injection focused immune responses specifically to tumours. Tumour-specific expression of msbB increased infiltration of immune cells, activated monocytes and neutrophils, increased tumour levels of IL-6, and activated CD8 T cells in draining lymph nodes. These immune responses reduced tumour growth and increased mouse survival. By increasing the efficacy of bacterial anti-cancer therapy, localized production of LPS could provide increased options to patients with immune-resistant cancers.

The anticancer effect of potential probiotic L. fermentum and L. plantarum in combination with 5-fluorouracil on colorectal cancer cells

5-Fluorouracil (5-FU) is an effective chemotherapy drug in the treatment of colorectal cancer (CRC). However, auxiliary or alternative therapies must be sought due to its resistance and potential side effects. Certain probiotic metabolites exhibit anticancer properties. In this study evaluated the anticancer and potential therapeutic activities of cell extracts potential probiotic strains, Limosilactobacillus fermentum and Lactiplantibacillus plantarum isolated from the mule milk and the standard probiotic strain Lacticaseibacillus rhamnosus GG (LGG) against the human colon cancer cell line (HT-29) and the normal cell line (HEK-293) alone or in combination with 5-FU. In this study, L. plantarum and L. fermentum, which were isolated from mule milk, were identified using biochemical and molecular methods. Their probiotic properties were investigated in vitro and compared with the standard probiotic strain of the species L. rhamnosus GG. The MTT assay, acridine orange/ethidium bromide (AO/EB) fluorescent staining, and flow cytometry were employed to measure the viability of cell lines, cell apoptosis, and production rates of Th17 cytokines, respectively. The results demonstrated that the combination of lactobacilli cell extracts and 5-FU decreased cell viability and induced apoptosis in HT-29 cells. Furthermore, this combination protected HEK-293 cells from the cytotoxic effects of 5-FU, enhancing their viability and reducing apoptosis. Moreover, the combination treatment led to an increase in the levels of IL-17A, IFN-γ, and TNF-α, which can enhance anti-tumor immunity. In conclusion, the cell extracts of the lactobacilli strains probably can act as a potential complementary anticancer therapy.

Antigen surface display in two novel whole genome sequenced food grade strains, Lactiplantibacillus pentosus KW1 and KW2

BACKGROUND

Utilization of commensal bacteria for delivery of medicinal proteins, such as vaccine antigens, is an emerging strategy. Here, we describe two novel food-grade strains of lactic acid bacteria, Lactiplantibacillus pentosus KW1 and KW2, as well as newly developed tools for using this relatively unexplored but promising bacterial species for production and surface-display of heterologous proteins.

RESULTS

Whole genome sequencing was performed to investigate genomic features of both strains and to identify native proteins enabling surface display of heterologous proteins. Basic characterization of the strains revealed the optimum growth temperatures for both strains to be 35-37 °C, with peak heterologous protein production at 33 °C (KW1) and 37 °C (KW2). Negative staining revealed that only KW1 produces closely bound exopolysaccharides. Production of heterologous proteins with the inducible pSIP-expression system enabled high expression in both strains. Exposure to KW1 and KW2 skewed macrophages toward the antigen presenting state, indicating potential adjuvant properties. To develop these strains as delivery vehicles, expression of the mycobacterial H56 antigen was fused to four different strain-specific surface-anchoring sequences.

CONCLUSION

All experiments that enabled comparison of heterologous protein production revealed KW1 to be the better recombinant protein production host. Use of the pSIP expression system enabled successful construction of L. pentosus strains for production and surface display of an antigen, underpinning the potential of these strains as novel delivery vehicles.

Modulation of the Immune System Mechanisms using Probiotic Bacteria in Allergic Diseases: Focus on Allergic Retinitis and Food Allergies

Allergic illnesses occur when an organism's immune system is excessively responsive to certain antigens, such as those that are presented in the environment. Some people suffer from a wide range of immune system-related illnesses including allergic rhinitis, asthma, food allergies, hay fever, and even anaphylaxis. Immunotherapy and medications are frequently used to treat allergic disorders. The use of probiotics in bacteriotherapy has lately gained interest. Probiotics are essential to human health by modulating the gut microbiota in some ways. Due to probiotics' immunomodulatory properties present in the gut microbiota of all animals, including humans, these bacterial strains can prevent a wide variety of allergic disorders. Probiotic treatment helps allergy patients by decreasing inflammatory cytokines and enhancing intestinal permeability, which is important in the battle against allergy. By altering the balance of Th1 and Th2 immune responses in the intestinal mucosa, probiotics can heal allergic disorders. Numerous studies have shown a correlation between probiotics and a reduced risk of allergy disorders. A wide range of allergic disorders, including atopic dermatitis, asthma, allergic retinitis and food allergies has been proven to benefit from probiotic bacteria. Therefore, the use of probiotics in the treatment of allergic diseases offers a promising perspective. Considering that probiotic intervention in the treatment of diseases is a relatively new field of study, more studies in this regard seem necessary.

Harnessing the probiotic properties and immunomodulatory effects of fermented food-derived Limosilactobacillus fermentum strains: implications for environmental enteropathy

Introduction

Environmental enteropathy (EE), a chronic small intestine disease characterized by gut inflammation, is widely prevalent in low-income countries and is hypothesized to be caused by continuous exposure to fecal contamination. Targeted nutritional interventions using potential probiotic strains from fermented foods can be an effective strategy to inhibit enteric pathogens and prevent chronic gut inflammation.

Methods

We isolated potential strains from fermented rice water and lemon pickle and investigated their cell surface properties, antagonistic properties, adhesion to HT-29 cells, and inhibition of pathogen adherence to HT-29 cells. Bacteriocin-like inhibitory substances (BLIS) were purified, and in vivo, survival studies in Caenorhabditis elegans infected with Salmonella enterica MW116733 were performed. We further checked the expression pattern of pro and anti-inflammatory cytokines (IL-6, IL8, and IL-10) in HT-29 cells supplemented with strains.

Results

The strains isolated from rice water (RS) and lemon pickle (T1) were identified as Limosilactobacillus fermentum MN410703 and MN410702, respectively. Strains showed probiotic properties like tolerance to low pH (pH 3.0), bile salts up to 0.5%, simulated gastric juice at low pH, and binding to extracellular matrix molecules. Auto-aggregation of T1 was in the range of 85% and significantly co-aggregated with Klebsiella pneumoniae, S. enterica, and Escherichia coli at 48, 79, and 65%, respectively. Both strains had a higher binding affinity to gelatin and heparin compared to Bacillus clausii. Susceptibility to most aminoglycoside, cephalosporin, and macrolide classes of antibiotics was also observed. RS showed BLIS activity against K. pneumoniae, S. aureus, and S. enterica at 60, 48, and 30%, respectively, and the protective effects of BLIS from RS in the C. elegans infection model demonstrated a 70% survival rate of the worms infected with S. enterica. RS and T1 demonstrated binding efficiency to HT-29 cell lines in the 38-46% range, and both strains inhibited the adhesion of E. coli MDR and S. enterica. Upregulation of IL-6 and IL-10 and the downregulation of IL-8 were observed when HT-29 cells were treated with RS, indicating the immunomodulatory effects of the strain.

Discussion

The potential strains identified could effectively inhibit enteric pathogens and prevent environmental enteropathy.

Antibiotic-Therapy-Induced Gut Dysbiosis Affecting Gut Microbiota-Brain Axis and Cognition: Restoration by Intake of Probiotics and Synbiotics

Antibiotic therapy through short-term or repeated long-term prescriptions can have several damaging effects on the normal microbiota of the gastrointestinal tract. Changes in microbiota could be multiple including decreased diversity of species in gut microbiota, changed metabolic activity, and the occurrence of antibiotic-resistant strains. Antibiotic-induced gut dysbiosis in turn can induce antibiotic-associated diarrhoea and recurrent infections caused by Clostridioides difficile. There is also evidence that the use of different chemical classes of antibiotics for the treatment of a variety of ailments can lead to several health issues including gastrointestinal, immunologic, and neurocognitive conditions. This review discusses gut dysbiosis, its symptoms and one important cause, which is antibiotic therapy for the induction of gut dysbiosis. Since the maintenance of good gut health is important for the well-being and functioning of physiological and cognitive activities through the normal gut-microbiota-brain relationship, the condition of dysbiosis is not desirable. Specific therapies are prescribed by medical practitioners for the cure of a variety of ailments, and, if the prescription of antibiotics becomes unavoidable, there is a possibility of the onset of gut dysbiosis as the side or after effects. Therefore, the restoration of imbalanced gut microbiota to its balanced condition becomes necessary. A healthy relationship between gut microbiota and the brain can be achieved with the introduction of probiotic strains into the gut in a practical and consumer-friendly way, such as consumption of food and beverages prepared with the use of characterised probiotic species, fermented foods as the potential biotics, or synbiotic supplements.

Immunomodulatory Effect of Lactobacillus reuteri (Limosilactobacillus reuteri) and Its Exopolysaccharides Investigated on Epithelial Cell Line IPEC-J2 Challenged with Salmonella Typhimurium

The gastrointestinal tract is the largest and most complex component of the immune system. Each component influences the production and regulation of cytokines secreted by intestinal epithelial cells. The aim of this study was to see how the probiotic strain Limosilactobacillus reuteri L26 and its exopolysaccharide (EPS) affect porcine intestinal-epithelial cells IPEC-J2 infected with Salmonella Typhimurium. The results revealed that Salmonella infection up-regulated all studied pro-inflammatory cytokines such as TNF-α, IL-8, IL-6 and TLR4, TLR5 signaling pathways, while decreasing the expression of TGF-β. An immunosuppressive activity was found in EPS-treated wells, since the transcriptional levels of the studied pro-inflammatory cytokines were not increased, and the pretreatment with EPS was even able to attenuate up-regulated pro-inflammatory genes induced by Salmonella infection. However, there was a significant increase in the expression of mRNA levels of IL-8 and TNF-α in L26-treated cells, although this up-regulation was suppressed in the case of pretreatment. The immunoregulatory function of L. reuteri was also confirmed by the increased level of mRNA expression for TGF-β, a known immunosuppressive mediator. The most relevant finding of this ex vivo study was a case of immunity modulation, where the probiotic strain L. reuteri stimulated the innate immune-cell response which displayed both anti- and pro-inflammatory activities, and modulated the expression of TLRs in the IPEC-J2 cell line. Our findings also revealed that the pretreatment of cells with either EPS or live lactobacilli prior to infection has a suppressive effect on the inflammatory response induced by Salmonella Typhimurium.

Optimization of growth of Levilactobacillus brevis SP 48 and in vitro evaluation of the effect of viable cells and high molecular weight potential postbiotics on Helicobacter pylori

Several Levilactobacillus brevis strains have the potential to be used as probiotics since they provide health benefits due to the interaction of live cells, and of their secreted products, with the host (tissues). Therefore, the development of simple fermentation processes that improve cell viability to reduce industrial production costs, and at the same time the characterization and biological evaluation of cell-free postbiotics that can further promote application, are of great interest. In the present study, small scale batch fermentations on semi defined media, deprived of animal derived raw materials, were used to optimize growth of L. brevis SP48, reaching 1.2 ± 0.4 × 1010 CFU/ml of viable cells after 16 h of growth. Displacement, competition, and inhibition assays compared the effect, on Helicobacter pylori, of L. brevis cells to that of its partially purified potentially postbiotic fraction rich in exopolysaccharides and proteins. The expression of pro and anti-inflammatory biochemical markers indicated that both samples activated antimicrobial defenses and innate immunity in a gastric model. Moreover, these compounds also acted as modulators of the inflammatory response in a gut in vitro model. These data demonstrate that the high molecular weight compounds secreted by L. brevis SP48 can contrast H. pylori and reduce inflammation related to intestinal bowel disease, potentially overcoming issues related to the preservation of probiotic viability.

The Therapeutic Role of Short-Chain Fatty Acids Mediated Very Low-Calorie Ketogenic Diet-Gut Microbiota Relationships in Paediatric Inflammatory Bowel Diseases

The very low-calorie ketogenic diet (VLCKD) has been recognized as a promising dietary regimen for the treatment of several diseases. Short-chain fatty acids (SCFAs) produced by anaerobic bacterial fermentation of indigestible dietary fibre in the gut have potential value for their underlying epigenetic role in the treatment of obesity and asthma-related inflammation through mediating the relationships between VLCKD and the infant gut microbiota. However, it is still unclear how VLCKD might influence gut microbiota composition in children, and how SCFAs could play a role in the treatment of inflammatory bowel disease (IBD). To overcome this knowledge gap, this review aims to investigate the role of SCFAs as key epigenetic metabolites that mediate VLCKD-gut microbiota relationships in children, and their therapeutic potential in IBD.

IL-1R8 as Pathoimmunological Marker for Severity of Canine Chronic Enteropathy

Chronic enteropathy (CE) is a severe multifactorial gastrointestinal disease that affects dogs and is driven by poorly characterized inflammatory pathways. Imbalance of pro-inflammatory response regulators, including IL-1R8, may be due to different factors, among which the infection with Helicobacteraceae is known to lead to a vicious circle in which excessive pro-inflammatory signaling and gastrointestinal injury reinforce each other and boost the disease. We investigated the expression of IL-1R8 in large intestine biopsies of dogs with or without clinical signs of CE and with previously assessed enterohepatic Helicobacter spp. colonization status by mean of quantitative real-time PCR. Our study revealed that IL-1R8 is downregulated in both acutely (p = 0.0074) and chronically (p = 0.0159) CE affected dogs compared to healthy controls. The data also showed that IL-1R8 expression tends to decrease with colonization by Helicobacter spp. Interestingly, a negative correlation was detected between the level of expression of IL-1R8 and the severity of macroscopic lesions identified by endoscopy and the crypt hyperplasia score. We further compared the expression levels between males and females and found no statistically significant difference between the two groups. No significant difference was observed in IL-1R8 expression profiles with the age of the animals either. Interestingly, an association was uncovered between IL-1R8 expression level and dog breed. Together, our data advance knowledge on gastrointestinal pathoimmunology in dogs and highlight the potential utilization of IL-1R8 as a diagnostic, prognostic and therapeutic biomarker for canine chronic enteropathy.

Salmonella enterica serovar Typhi influences inflammation and autophagy in macrophages

Salmonella enterica serovar Typhi (S. Typhi) is a human enteropathogen that can survive in macrophages and cause systemic infection. Autophagy and inflammation are two important immune responses of macrophages that contribute to the elimination of pathogens. However, Salmonella has derived many strategies to evade inflammation and autophagy. This study investigated inflammation-related NF-κB signaling pathways and autophagy in S. Typhi-infected macrophages. RNA-seq and quantitative real-time PCR indicated that mRNA levels of NF-κB signaling pathway and autophagy-related genes were dynamically influenced in S. Typhi-infected macrophages. Western blots revealed that S. Typhi activated the NF-κB signaling pathway and induced the expression of inhibitor protein IκBζ. In addition, S. Typhi enhanced autophagy during early stages of infection and may inhibit autophagy during late stages of infection. Thus, we propose that S. Typhi can influence the NF-κB signaling pathway and autophagy in macrophages.

The Game for Three: Salmonella–Host–Microbiota Interaction Models

Colonization of the gastrointestinal (GI) tract by enteric pathogens occurs in a context strongly determined by host-specific gut microbiota, which can significantly affect the outcome of infection. The complex gameplay between the trillions of microbes that inhabit the GI tract, the host, and the infecting pathogen defines a specific triangle of interaction; therefore, a complete model of infection should consider all of these elements. Many different infection models have been developed to explain the complexity of these interactions. This review sheds light on current knowledge, along with the strengths and limitations of in vitro and in vivo models utilized in the study of Salmonella–host–microbiome interactions. These models range from the simplest experiment simulating environmental conditions using dedicated growth media through in vitro interaction with cell lines and 3-D organoid structure, and sophisticated “gut on a chip” systems, ending in various animal models. Finally, the challenges facing this field of research and the important future directions are outlined.

Effect of fermented foods on some neurological diseases, microbiota, behaviors: mini review

Fermented foods are among the traditional foods consumed for centuries. In recent years, awareness of fermented foods has been increasing due to their positive health benefits. Fermented foods contain beneficial microorganisms. Fermented foods, such as kefir, kimchi, sauerkraut, and yoghurt, contain Lactic acid bacteria (LAB), such as Lactobacilli, Bifidobacteria, and their primary metabolites (lactic acid). Although studies on the effect of consumption of fermented foods on diabetes, cardiovascular, obesity, gastrointestinal diseases on chronic diseases have been conducted, more studies are needed regarding the relationship between neurological diseases and microbiota. There are still unexplored mechanisms in the relationship between the brain and intestine. In this review, we answer how the consumption of fermented foods affects the brain and behavior of Alzheimer's disease, Parkinson's disease, multiple sclerosis disease, stroke, and gut microbiota.

Negative Regulation of the IL-1 System by IL-1R2 and IL-1R8: Relevance in Pathophysiology and Disease

Interleukin-1 (IL-1) is a primary cytokine of innate immunity and inflammation. IL-1 belongs to a complex family including ligands with agonist activity, receptor antagonists, and an anti-inflammatory cytokine. The receptors for these ligands, the IL-1 Receptor (IL-1R) family, include signaling receptor complexes, decoy receptors, and negative regulators. Agonists and regulatory molecules co-evolved, suggesting the evolutionary relevance of a tight control of inflammatory responses, which ensures a balance between amplification of innate immunity and uncontrolled inflammation. IL-1 family members interact with innate immunity cells promoting innate immunity, as well as with innate and adaptive lymphoid cells, contributing to their differentiation and functional polarization and plasticity. Here we will review the properties of two key regulatory receptors of the IL-1 system, IL-1R2, the first decoy receptor identified, and IL-1R8, a pleiotropic regulator of different IL-1 family members and co-receptor for IL-37, the anti-inflammatory member of the IL-1 family. Their complex impact in pathology, ranging from infections and inflammatory responses, to cancer and neurologic disorders, as well as clinical implications and potential therapeutic exploitation will be presented.

Probiotics and gut microbiota: mechanistic insights into gut immune homeostasis through TLR pathway regulation

Consumption of probiotics as a useful functional food improves the host's wellbeing, and, when paired with prebiotics (indigestible dietary fibre/carbohydrate), often benefits the host through anaerobic fermentation.

Toll-Like Receptors as Drug Targets in the Intestinal Epithelium

Toll-like receptors (TLRs) receptors are responsible for initiation of inflammatory responses by their recognition of molecular patterns present in invading microorganisms (such as bacteria, viruses or fungi) or in molecules released following tissue damage in disease states. Expressed in the intestinal epithelium, they initiate an intracellular signalling cascade in response to molecular patterns resulting in the activation of transcription factors and the release of cytokines, chemokines and vasoactive molecules. Intestinal epithelial cells are exposed to microorganisms on a daily basis and form part of the primary defence against pathogens by using TLRs. TLRs and their accessory molecules are subject to tight regulation in these cells so as to not overreact or react in unnecessary circumstances. TLRs have more recently been associated with chronic inflammatory diseases as a result of inappropriate regulation, this can be damaging and lead to chronic inflammatory diseases such as inflammatory bowel disease (IBD). Targeting Toll-like receptors offers a potential therapeutic approach for IBD. In this review, the current knowledge on the TLRs is reviewed along with their association with intestinal diseases. Finally, compounds that target TLRs in animal models of IBD, clinic trials and their future merit as targets are discussed.

Anti-inflammatory Effect of Probiotic Limosilactobacillus reuteri KUB-AC5 Against Salmonella Infection in a Mouse Colitis Model

Acute non-typhoidal salmonellosis (NTS) caused by Salmonella enterica Typhimurium (STM) is among the most prevalent of foodborne diseases. A global rising of antibiotic resistance strains of STM raises an urgent need for alternative methods to control this important pathogen. Major human food animals which harbor STM in their gut are cattle, swine, and poultry. Previous studies showed that the probiotic Limosilactobacillus (Lactobacillus) reuteri KUB-AC5 (AC5) exhibited anti-Salmonella activities in chicken by modulating gut microbiota and the immune response. However, the immunobiotic effect of AC5 in a mammalian host is still not known. Here, we investigated the anti-Salmonella and anti-inflammatory effects of AC5 on STM infection using a mouse colitis model. Three groups of C57BL/6 mice (prophylactic, therapeutic, and combined) were fed with 10⁹ colony-forming units (cfu) AC5 daily for 7, 4, and 11 days, respectively. Then, the mice were challenged with STM compared to the untreated group. By using a specific primer pair, we found that AC5 can transiently colonize mouse gut (colon, cecum, and ileum). Interestingly, AC5 reduced STM gut proliferation and invasion together with attenuated gut inflammation and systemic dissemination in mice. The decreased STM numbers in mouse gut lumen, gut tissues, and spleen possibly came from longer AC5 feeding duration and/or the combinatorial (direct and indirect inhibitory) effect of AC5 on STM. However, AC5 attenuated inflammation (both in the gut and in the spleen) with no difference between these three approaches. This study demonstrated that AC5 confers both direct and indirect inhibitory effects on STM in the inflamed gut.

Probiotic Bacteria and Their Cell Walls Induce Th1-Type Immunity Against Salmonella Typhimurium Challenge

Probiotics have been associated with a variety of health benefits. They can act as adjuvant to enhance specific immune response. Bacterial cell wall (CW) molecules are key structures that interact with host receptors promoting probiotic effects. The adjuvant capacity underlying this sub-cellular fraction purified from Lactobacillus casei CRL431 and L. paracasei CNCMI-1518 remains to be characterized. We interrogated the molecular and cellular events after oral feeding with probiotic-derived CW in addition to heat-inactivated Salmonella Typhimurium and their subsequent protective capacity against S. Typhimurium challenge. Intact probiotic bacteria were orally administered for comparison. We find that previous oral feeding with probiotics or their sub-cellular fraction reduce bacterial burden in spleen and liver after Salmonella challenge. Antibody responses after pathogen challenge were negligible, characterized by not major changes in the antibody-mediated phagocytic activity, and in the levels of total and Salmonella-specific intestinal sIgA and serum IgG, respectively. Conversely, the beneficial effect of probiotic-derived CW after S. Typhimurium challenge were ascribed to a Th1-type cell-mediated immunity which was characterized by augmentation of the delayed-type hypersensitivity response. The cell-mediated immunity associated with the oral feeding with probiotic-derived CW was accompanied with a Th1-cell polarizing cytokines, distinguished by increase IFN-γ/IL-4 ratio. Similar results were observed with the intact probiotics. Our study identified molecular events associated with the oral administration of sub-cellular structures derived from probiotics and their adjuvant capacity to exert immune modulatory function.

Interactions between Salmonella and host macrophages - Dissecting NF-κB signaling pathway responses

Salmonella not only invades host cells, but also replicates intracellularly to cause a range of diseases, including gastroenteritis and systemic infections such as typhoid fever. The body's first line of defense against pathogens is the innate immune response system that can protect against Salmonella invasion and replication. Nuclear factor κB (NF-κB) is an important transcriptional regulator that plays an important role in host inflammatory responses to pathogens. Both the canonical and non-canonical NF-κB signaling pathways are activated by Salmonella in many different ways through its virulence factors, leading to the release of inflammatory factors and the activation of inflammatory responses in mammalian hosts. Equally, Salmonella, as an enteropathogen, has accordingly evolved strategies to disturb NF-κB activation, such as secreting some effector proteins by type III secretion systems as well as inducing host cells to express NF-κB pathway inhibitors, allowing it to colonize and persistently infect the hosts. This review focuses on how Salmonella activates NF-κB signaling pathway and the strategies used by Salmonella to interfere with the NF-κB pathway activation.