Salmosan, a β-galactomannan-rich product, in combination with Lactobacillus plantarum contributes to restore intestinal epithelial barrier function by modulation of cytokine production

Postbiotic Potential of Newly Isolated Riboflavin-Overproducing Lactiplantibacillus plantarum Strains

Lactic acid bacteria (LAB) are food-grade microorganisms able to produce and release bioactive compounds of interest to human health. Some LAB strains can synthesize vitamin B2, i.e., riboflavin, a micronutrient essential for cellular metabolism. In this work, six Lactiplantibacillus plantarum isolated from fruits of the Mediterranean area were exposed to the selective pressure of roseoflavin in order to select spontaneous riboflavin-overproducing phenotypes. The best strains, as determined by the level of riboflavin produced, were characterized for some basic probiotic features, including antibacterial activity, production of organic acids, antibiotic resistance, and survival under digestive stresses using an in vitro gut model. The strain L. plantarum Lp 187_B2, which produced the highest riboflavin level (6 mg/L), exhibited good resistance to gastro-intestinal stress and a relevant capacity to antagonize undesired bacteria, was selected for additional investigations to assess its capacity to protect intestinal homeostasis. When used as a postbiotic, Lp 187_B2 significantly increased trans-epithelial electrical resistance (TEER) in Caco-2 cell monolayers, an in vitro model of the intestinal barrier. Moreover, in a Caco-2/THP-1 co-culture system, mimicking the inflamed bowel, Lp 187_B2 postbiotics significantly inhibited the release of TNF-α by macrophages, thus pointing to gut-barrier strengthening and potential anti-inflammatory properties. Though a validation in vivo is required, our preliminary results indicate that L. plantarum Lp 187_B2 could be successfully applied as both probiotic and postbiotic formulations for improving human health.

Potential probiotic Lactiplantibacillus plantarum strains alleviate TNF-α by regulating ADAM17 protein and ameliorate gut integrity through tight junction protein expression in in vitro model

BACKGROUND

Lactiplantibacillus species are extensively studied for their ability to regulate host immune responses and functional therapeutic potentials. Nevertheless, there is a lack of understanding on the mechanisms of interactions with the hosts during immunoregulatory activities.

METHODS

Two Lactiplantibacillus plantarum strains MKMB01 and MKMB02 were tested for probiotic potential following Indian Council of Medical Research (ICMR) guidelines. Human colorectal adenocarcinoma cells such as HT-29, caco-2, and human monocytic cell THP-1 were also used to study the potential of MKMB01 and MKMB02 in regulating the host immune response when challenged with enteric pathogen Salmonella enterica typhimurium. Cells were pre-treated with MKMB01 and MKMB02 for 4 h and then stimulated with Salmonella. qRT-PCR and ELISA were used to analyze the genes and protein expression. Confocal microscopy and field emission scanning electron microscopy (FESEM) were used to visualize the effects. An Agilent Seahorse XF analyzer was used to determine real-time mitochondrial functioning.

RESULTS

Both probiotic strains could defend against Salmonella by maintaining gut integrity via expressing tight junction proteins (TJPs), MUC-2, and toll-like receptors (TLRs) negative regulators such as single Ig IL-1-related receptor (SIGIRR), toll-interacting protein (Tollip), interleukin-1 receptor-associated kinase (IRAK)-M, A20, and anti-inflammatory transforming growth factor-β and interleukin-10. Both strains also downregulated the expression of pro-inflammatory cytokines/chemokines interleukin-1β, monocyte chemoattractant protein (MCP)-1, tumor necrosis factor-alpha (TNF-α), interleukin 6, and nitric oxide (NO). Moreover, TNF-α sheddase protein, a disintegrin and metalloproteinase domain 17 (ADAM17), and its regulator iRhom2 were downregulated by both strains. Moreover, the bacteria also ameliorated Salmonella-induced mitochondrial dysfunction by restoring bioenergetic profiles, such as non-mitochondrial respiration, spare respiratory capacity (SRC), basal respiration, adenosine triphosphate (ATP) production, and maximal respiration.

CONCLUSIONS

MKMB01 and MKMB02 can reduce pathogen-induced gut-associated disorders and therefore should be further explored for their probiotic potential.

Recent progress in plant-derived polysaccharides with prebiotic potential for intestinal health by targeting gut microbiota: a review

Natural products of plant origin are of high interest and widely used, especially in the food industry, due to their low toxicity and wide range of bioactive properties. Compared to other plant components, the safety of polysaccharides has been generally recognized. As dietary fibers, plant-derived polysaccharides are mostly degraded in the intestine by polysaccharide-degrading enzymes secreted by gut microbiota, and have potential prebiotic activity in both non-disease and disease states, which should not be overlooked, especially in terms of their involvement in the treatment of intestinal diseases and the promotion of intestinal health. This review elucidates the regulatory effects of plant-derived polysaccharides on gut microbiota and summarizes the mechanisms involved in targeting gut microbiota for the treatment of intestinal diseases. Further, the structure-activity relationships between different structural types of plant-derived polysaccharides and the occurrence of their prebiotic activity are further explored. Finally, the practical applications of plant-derived polysaccharides in food production and food packaging are summarized and discussed, providing important references for expanding the application of plant-derived polysaccharides in the food industry or developing functional dietary supplements.

Direct Action of Non-Digestible Oligosaccharides against a Leaky Gut

The epithelial monolayer is the primary determinant of mucosal barrier function, and tight junction (TJ) complexes seal the paracellular space between the adjacent epithelial cells and represent the main "gate-keepers" of the paracellular route. Impaired TJ functionality results in increased permeation of the "pro-inflammatory" luminal contents to the circulation that induces local and systemic inflammatory and immune responses, ultimately triggering and/or perpetuating (chronic) systemic inflammatory disorders. Increased gut leakiness is associated with intestinal and systemic disease states such as inflammatory bowel disease and neurodegenerative diseases such as Parkinson's disease. Modulation of TJ dynamics is an appealing strategy aiming at inflammatory conditions associated with compromised intestinal epithelial function. Recently there has been a growing interest in nutraceuticals, particularly in non-digestible oligosaccharides (NDOs). NDOs confer innumerable health benefits via microbiome-shaping and gut microbiota-related immune responses, including enhancement of epithelial barrier integrity. Emerging evidence supports that NDOs also exert health-beneficial effects on microbiota independently via direct interactions with intestinal epithelial and immune cells. Among these valuable features, NDOs promote barrier function by directly regulating TJs via AMPK-, PKC-, MAPK-, and TLR-associated pathways. This review provides a comprehensive overview of the epithelial barrier-protective effects of different NDOs with a special focus on their microbiota-independent modulation of TJs.

Hydroxy-Selenomethionine, an Organic Selenium Source, Increases Selenoprotein Expression and Positively Modulates the Inflammatory Response of LPS-Stimulated Macrophages

The role of 2-hydroxy-(4-methylseleno)butanoic acid (OH-SeMet), a form of organic selenium (Se), in selenoprotein synthesis and inflammatory response of THP1-derived macrophages stimulated with lipopolysaccharide (LPS) has been investigated. Glutathione peroxidase (GPX) activity, GPX1 gene expression, selenoprotein P (SELENOP) protein and gene expression, and reactive oxygen species (ROS) production were studied in Se-deprived conditions (6 and 24 h). Then, macrophages were supplemented with OH-SeMet for 72 h and GPX1 and SELENOP gene expression were determined. The protective effect of OH-SeMet against oxidative stress was studied in H₂O₂-stimulated macrophages, as well as the effect on GPX1 gene expression, oxidative stress, cytokine production (TNFα, IL-1β and IL-10), and phagocytic and killing capacities after LPS stimulation. Se deprivation induced a reduction in GPX activity, GPX1 gene expression, and SELENOP protein and gene expression at 24 h. OH-SeMet upregulated GPX1 and SELENOP gene expression and decreased ROS production after H₂O₂ treatment. In LPS-stimulated macrophages, OH-SeMet upregulated GPX1 gene expression, enhanced phagocytic and killing capacities, and reduced ROS and cytokine production. Therefore, OH-SeMet supplementation supports selenoprotein expression and controls oxidative burst and cytokine production while enhancing phagocytic and killing capacities, modulating the inflammatory response, and avoiding the potentially toxic insult produced by highly activated macrophages.

Lactobacillus plantarum improves LPS-induced Caco2 cell line intestinal barrier damage via cyclic AMP-PKA signaling

Lactobacillus plantarum (LP) has been shown to exhibit protective effects on intestinal barrier function in septic rats, although the regulatory mechanism has not been established. We determined whether LP imparts such protective effects in a lipopolysaccharide (LPS)-induced Caco2 cell monolayer model and whether cAMP-PKA signaling is the underlying mechanism of action. The cyclic adenosine monophosphate (cAMP) agonist, forskolin (FSK), and the protein kinase A (PKA) inhibitor, HT89, were used to study the protective effect of LP on the destruction of the tight junction (TJ) structure of cells treated with LPS and the corresponding changes in cAMP-PKA signaling. Our experimental results demonstrated that LP promoted the expression of TJ proteins between Caco2 cells after LPS treatment, and increased the electrical barrier detection (TEER) between Caco2 cells. Moreover, transmission electron microscopy (TEM) revealed that the TJ structural integrity of cells treated with LPS + LP was improved compared to cells treated with LPS alone. In addition, our findings were consistent between the FSK and LP intervention group, while HT89 inhibited LP influence. Taken together, our results indicate that LP has an improved protective effect on LPS-induced damage to the monolayer membrane barrier function of Caco2 cells and is regulated by the cAMP-PKA pathway.

Effects of Two Polysaccharides from Lepidium meyenii (Maca) on Intestinal Immunity and Inflammation in vitro

In our previous studies, two polysaccharides (MC-1 and MC-2) were identified in the roots of maca (Lepidium meyenii). In this study, the effects of these two polysaccharides on intestinal immunity...

Harnessing the potential of Lactobacillus species for therapeutic delivery at the lumenal-mucosal interface

Lactobacillus species have been studied for over 30 years in their role as commensal organisms in the human gut. Recently there has been a surge of interest in their abilities to natively and recombinantly stimulate immune activities, and studies have identified strains and novel molecules that convey particular advantages for applications as both immune adjuvants and immunomodulators. In this review, we discuss the recent advances in Lactobacillus-related activity at the gut/microbiota interface, the efforts to probe the boundaries of the direct and indirect therapeutic potential of these bacteria, and highlight the continued interest in harnessing the native capacity for the production of biogenic compounds shown to influence nervous system activity. Taken together, these aspects underscore Lactobacillus species as versatile therapeutic delivery vehicles capable of effector production at the lumenal-mucosal interface, and further establish a foundation of efficacy upon which future engineered strains can expand.

Cyperus esculentus L. Tubers (Tiger Nuts) Protect Epithelial Barrier Function in Caco-2 Cells Infected by Salmonella Enteritidis and Promote Lactobacillus plantarum Growth

Cyperus esculentus L. tubers (tiger nuts) contain different compounds with several intestinal health-promoting properties. Here, we studied the capacity of tiger nuts from Valencia, Spain, to prevent epithelial barrier function disruption induced by Salmonella enteritidis in Caco-2 cell cultures. Paracellular permeability was assessed by transepithelial electrical resistance (TER) and tight junction protein immunolocalization. Moreover, the effect of tiger nuts on S. enteritidis agglutination, oxidative stress, and Lactobacillus plantarum growth was tested. Compared to controls, tiger nuts partially restored TER in S. enteritidis-infected cultures, an effect confirmed by immunolocalization of tight junction proteins ZO-1 and occludin. The results also revealed that this protective effect may be associated with the capacity to agglutinate the pathogen, restore TER in TNFα-stimulated cultures, and reduce reactive oxygen species in H₂O₂-stimulated cultures. Moreover, they favor L. plantarum growth. In conclusion, this study demonstrates that the tiger nut protects epithelial barrier function by reducing bacterial invasion, along with counteracting TNFα and H₂O₂ effects, thus giving an additional value to this tuber as a potential functional food.

Effects of dietary components on intestinal permeability in health and disease

Altered intestinal permeability plays a role in many pathological conditions. Intestinal permeability is a component of the intestinal barrier. This barrier is a dynamic interface between the body and the food and pathogens that enter the gastrointestinal tract. Therefore, dietary components can directly affect this interface, and many metabolites produced by the host enzymes or the gut microbiota can act as signaling molecules or exert direct effects on this barrier. Our aim was to examine the effects of diet components on the intestinal barrier in health and disease states. Herein, we conducted an in-depth PubMed search based on specific key words (diet, permeability, barrier, health, disease, and disorder), as well as cross references from those articles. The normal intestinal barrier consists of multiple components in the lumen, epithelial cell layer and the lamina propria. Diverse methods are available to measure intestinal permeability. We focus predominantly on human in vivo studies, and the literature is reviewed to identify dietary factors that decrease (e.g., emulsifiers, surfactants, and alcohol) or increase (e.g., fiber, short-chain fatty acids, glutamine, and vitamin D) barrier integrity. Effects of these dietary items in disease states, such as metabolic syndrome, liver disease, or colitis are documented as examples of barrier dysfunction in the multifactorial diseases. Effects of diet on intestinal barrier function are associated with precise mechanisms in some instances; further research of those mechanisms has potential to clarify the role of dietary interventions in treating diverse pathologic states.

The protective effects of enriched citrulline fermented milk with Lactobacillus helveticus on the intestinal epithelium integrity against Escherichia coli infection

This study examined the protective effects of citrulline enriched-fermented milk with live Lactobacillus helveticus ASCC 511 (LH511) on intestinal epithelial barrier function and inflammatory response in IPEC-J2 cells caused by pathogenic Escherichia coli. Five percent (v/v) of fermented milk with live LH511 and 4 mM citrulline (5%LHFM_Cit-4mM) significantly stimulated the population of IPEC-J2 cells by 36% as determined by MTT assay. Adhesion level of LH511 was significantly increased by 9.2% when incubated with 5%LHFM_Cit-4mM and 5%LHFM_Cit-4mM reduced the adhesion of enterohemorrhagic (EHEC) and entero-invasive (EIEC) E. coli in IPEC-J2 cells by 35.79% and 42.74%, respectively. Treatment with 5%LHFM_Cit-4mM ameliorated lipopolysaccharide (LPS) from E. coli O55:B5 induced activated inflammatory cytokines expression (TNF-α, IL-6 and IL-8) and concentration (IL-6 and IL-8) and early apoptosis. It restored the transepithelial electrical resistance (TEER) and regulated the expression and distribution of tight junction (TJ) proteins (zonula occluden-1 (ZO-1), occludin and claudin-1), toll-like receptors (TLRs) (TLR2 and TLR4) and negative regulators of TLRs signalling pathway (A20 and IRAK-M). In conclusion, our findings suggested that 5%LHFM_Cit-4mM might have the positive effects on improving and maintaining the intestinal epithelial cell integrity and inflammatory response under both normal and pathogenic LPS-stimulated conditions.

Anti-Inflammatory Effects of Different Astaxanthin Isomers and the Roles of Lipid Transporters in the Cellular Transport of Astaxanthin Isomers in Caco-2 Cell Monolayers

The anti-inflammatory effects and cellular transport mechanisms of all- E-astaxanthin and its 9Z- and 13Z-isomers were investigated in a Caco-2 cell monolayer model. All three astaxanthin isomers at 1.2 μM significantly reduced the TNF-α-induced secretion of IL-8 by 22-27%. Z-Astaxanthins, especially 9 Z-astaxanthin exhibited greater anti-inflammatory effect than all- E-astaxanthin by down-regulating pro-inflammatory cytokines COX-2 and TNF-α gene expression to 0.88 ± 0.01-fold and 0.83 ± 0.17-fold that of the negative control (NC), respectively. The anti-inflammatory effects of astaxanthin isomers were achieved via modulating the NF-κB signaling pathway as they down-regulated TNF-α-induced phosphorylation of IκBα from 5.3 ± 0.19-fold to 3.8 ± 0.33-4.5 ± 0.27-fold of NC. The scavenger receptor class B type I protein (SR-BI) was found to facilitate the cellular uptake of astaxanthin isomers. Its inhibitor (BLT-1) and antibody (Anti-SRBI) significantly reduced cellular uptake efficiency of all- E-astaxanthin (18.9% and 16.7%, respectively) and 13Z-astaxanthin (28.8% and 30.2%, respectively), but not of 9Z-astaxanthin. The molecular docking experiment showed that 13 Z-astaxanthin had significantly higher affinity with SR-BI (atomic contact energy: -420.31) than all- E-astaxanthin and 9 Z-astaxanthin, which at least partially supports the higher bioavailability of 13 Z-astaxanthin observed in vivo by others.