Effect of EPEC endotoxin and bifidobacteria on intestinal barrier function through modulation of toll-like receptor 2 and toll-like receptor 4 expression in intestinal epithelial cell-18

Type III Secretion System in Intestinal Pathogens and Metabolic Diseases

Modern lifestyle changes, especially the consumption of a diet high in salt, sugar, and fat, have contributed to the increasing incidence and prevalence of chronic metabolic diseases such as diabetes, obesity, and gout. Changing lifestyles continuously shape the gut microbiota which is closely related to the occurrence and development of metabolic diseases due to its specificity of composition and structural diversity. A large number of pathogenic bacteria such as Yersinia, Salmonella, Shigella, and pathogenic E. coli in the gut utilize the type III secretion system (T3SS) to help them resist host defenses and cause disease. Although the T3SS is critical for the virulence of many important human pathogens, its relationship with metabolic diseases remains unknown. This article reviews the structure and function of the T3SS, the disruption of intestinal barrier integrity by the T3SS, the changes in intestinal flora containing the T3SS in metabolic diseases, the possible mechanisms of the T3SS affecting metabolic diseases, and the application of the T3SS in the treatment of metabolic diseases. The aim is to provide insights into metabolic diseases targeting the T3SS, thereby serving as a valuable reference for future research on disease diagnosis, prevention, and treatment.

Mizhuo Guanchangye enema delays the decline of renal function in rats with chronic kidney disease by intervening in the TLR4/MyD88/NF-κB pathway

Background

Chronic kidney disease (CKD) is a prevalent chronic condition that poses a significant threat to human health. There is a close connection between the gut and kidneys, jointly influencing the onset and progression of CKD through the "gut-kidney axis." Traditional Chinese medicine has shown potential in CKD treatment, but the specific mechanisms require further investigation.

Objectives

This study aims to explore the protective effects of Mizhuo Enema (MZGCY) on kidney function in CKD rats by regulating the TLR4/MyD88/NF-κB signaling pathway.

Methods

The researcher employed a CKD rat model, which was divided into four groups: Control, Model, half-dose Mizhuo Guanchangye (1/2 MZGCY), and full-dose Mizhuo Guanchangye (MZGCY). Post enema administration, assessments were conducted on kidney function indicators, which included blood urea nitrogen (BUN), serum creatinine (SCR), and 24-h urinary protein. Additionally, measurements were taken for intestinal toxic substances such as indoxyl sulfate (IS) and lipopolysaccharide (LPS), as well as inflammatory factors interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α). Examinations of pathological changes in both the intestines and kidneys were also performed. During this process, immunofluorescence was utilized to detect the expression levels of proteins toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), and nuclear factor kappa B (NF-κB) in the intestinal tissues.

Results

It was found that after enema treatment, the BUN, SCR, and 24-h urinary protein levels in the MZGCY and 1/2 MZGCY groups significantly decreased, indicating notable improvement in kidney function. Compared to the model group, the IS, LPS, IL-6, and TNF-α levels in the MZGCY and 1/2 MZGCY groups were significantly reduced. Immunofluorescence showed a marked decrease in the expression of TLR4, MyD88, and NF-κB proteins in the intestines of the MZGCY group.

Conclusion

MZGCY significantly reduces the levels of intestinal toxins and inflammatory factors in the serum of CKD rats by interfering with the TLR4/MyD88/NF-κB signaling pathway, thereby improving intestinal and renal pathological changes and delaying CKD progression. This study demonstrates that MZGCY has significant renal protective effects, providing a new potential approach for CKD treatment.

Associations between impulsivity and fecal microbiota in individuals abstaining from methamphetamine

INTRODUCTION

Methamphetamine (MA) abuse is a major public problem, and impulsivity is both a prominent risk factor and a consequence of addiction. Hence, clarifying the biological mechanism of impulsivity may facilitate the understanding of addiction to MA. The microbiota-gut-brain axis was suggested to underlie a biological mechanism of impulsivity induced by MA.

METHODS

We therefore recruited 62 MA addicts and 50 healthy controls (HCs) to investigate the alterations in impulsivity and fecal microbiota and the associations between them in the MA group. Thereafter, 25 MA abusers who abstained from MA for less than 3 months were followed up for 2 months to investigate the relationship between impulsivity and microbiota as abstinence became longer. 16S rRNA sequencing was conducted for microbiota identification.

RESULTS

Elevated impulsivity and dysbiosis characterized by an increase in opportunistic pathogens and a decrease in probiotics were identified in MA abusers, and both the increased impulsivity and disrupted microbiota tended to recover after longer abstinence from MA. Impulsivity was related to microbiota, and the effect of MA abuse on impulsivity was mediated by microbiota.

CONCLUSION

Our findings potentially highlighted the importance of abstention and implicated the significant role of the microbiota-gut-brain axis in the interrelationship between microbiota and behaviors, as well as the potential of microbiota as a target for intervention of impulsivity.

Understanding the role of gut microfloral bifidobacterium in cancer and its potential therapeutic applications

Gut microbiota research has gained a tremendous amount of attention from the scientific community because of its contribution to gut homeostasis, human health, and various pathophysiological conditions. The early colonizer of the human gut, i.e., bifidobacteria, has emerged as an efficient probiotic in various diseased conditions, including cancer. This review explores the pros and cons of Bifidobacterium in various malignancies and various therapeutic strategies. We have illustrated the controversial role of bifidobacteria participating in various malignancies as well as described the current knowledge regarding its use in anticancer therapies. Ultimately, this article also addresses the need for further extensive research in elucidating the mechanism of how bifidobacteria is involved and is indirectly affecting the tumor microenvironment. Exhaustive and large-scale research is also required to solve the controversial questions regarding the involvement of bifidobacteria in cancer research.

Establishment of a gut-on-a-chip device with controllable oxygen gradients to study the contribution of Bifidobacterium bifidum to inflammatory bowel disease

Supplemental Bifidobacterium has been shown to aid in the prevention, alleviation, and treatment of inflammatory bowel disease (IBD), but the progression and mechanisms are largely unstudied, partly because of a lack of appropriate models. In vitro human gut models must accurately recreate oxygen concentration gradients consistent with those in vivo to mimic gene expression, metabolism, and host-microbiome interactions. A non-equipment-intensive and inexpensive method for constructing the gut-on-a-chip with physiological oxygen concentration gradients remains challenging. Here, we propose a simple strategy using numerical simulations in a dual-channel gut-on-a-chip to guide chip design and achieve controllable oxygen gradients. By varying the size of microchannels, blocking the oxygen penetration of the polydimethylsiloxane layer at a given location, and controlling the flow of hypoxic/aerobic media, this strategy creates steep gradients across the intestinal epithelium. IBD symptoms were induced on the chip by tumor necrosis factor-α and lipopolysaccharide treatment. Bifidobacterium bifidum has been validated to contribute to the stability of the intestinal epithelial barrier, including preventing epithelial barrier disruption and promoting the repair of damaged intestinal epithelial cell monolayers. These effects may be associated with the co-localization of Bifidobacterium bifidum and ZO-1. This simple but robust approach for designing microfluidic devices is applicable to various organs-on-chips in which fluid dynamics and concentration profiles between different media must be considered. With the customized chip, the integration of activated Bifidobacterium bifidum provides an initial step toward developing a multi-factorial IBD platform. The approach could be scaled up for disease modeling, high-throughput drug screening and personalized medicine.

Bifidobacterium: Host-Microbiome Interaction and Mechanism of Action in Preventing Common Gut-Microbiota-Associated Complications in Preterm Infants: A Narrative Review

The development and health of infants are intertwined with the protective and regulatory functions of different microorganisms in the gut known as the gut microbiota. Preterm infants born with an imbalanced gut microbiota are at substantial risk of several diseases including inflammatory intestinal diseases, necrotizing enterocolitis, late-onset sepsis, neurodevelopmental disorders, and allergies which can potentially persist throughout adulthood. In this review, we have evaluated the role of Bifidobacterium as commonly used probiotics in the development of gut microbiota and prevention of common diseases in preterm infants which is not fully understood yet. The application of Bifidobacterium as a therapeutical approach in the re-programming of the gut microbiota in preterm infants, the mechanisms of host-microbiome interaction, and the mechanism of action of this bacterium have also been investigated, aiming to provide new insights and opportunities in microbiome-targeted interventions in personalized medicine.

Bifidobacterium bifidum and Bacteroides fragilis Induced Differential Immune Regulation of Enteric Glial Cells Subjected to Exogenous Inflammatory Stimulation

Enteric glial cells (EGCs) are involved in intestinal inflammation. In this study, we will investigate how Bifidobacterium bifidum (B.b.) and Bacteroides fragilis (B.f.) influence EGC regulation. After pretreatment with lipopolysaccharide (LPS) and interferon-γ (IFN-γ), the expressions of major histocompatibility complex class II (MHC-II), CD80, CD86, glial cell line-derived neurotrophic factor (GDNF), toll-like receptor 2 (TLR-2), and tumor necrosis factor-α (TNF-α) in EGCs were detected using polymerase chain reaction and western blot after co-culture with the supernatants of B.b. or B.f. (multiplicity of infection, 40:1 or 80:1). Finally, EGCs were co-cultured with naive CD4+ T cells, and the expressions of interleukin (IL)-2, IL-4, IL-10, and IL-17 in supernatant were measured using enzyme-linked immunosorbent assay (ELISA). The mRNA expressions of MHC-II and CD86 in EGCs were increased after combined stimulation with LPS and IFN-γ. The expressions of MHC-II, GDNF, TLR-2, and TNF-α were all significantly upregulated in stimulated EGCs. The B.b. supernatant downregulated the expressions of MHC-II, GDNF, TLR-2, and TNF-α in stimulated EGCs, whereas the B.f. supernatant upregulated TLR-2 expression and downregulated MHC-II expression. The expressions of IL-4, IL-2, and IL-17 after co-culture of naive CD4+ T cells and stimulated EGCs were significantly increased. The supernatant of B.b. or B.f. downregulated the expressions of these cytokines. The low-concentration B.b. supernatant upregulated IL-10 expression. Conclusions B.b. and B.f. may influence intestinal inflammation by regulating MHC-II, GDNF, TLR-2, and TNF-α expression in EGCs and IL-4, IL-2, IL-17, and IL-10 secretion.

Current Perspectives on Gastrointestinal Models to Assess Probiotic-Pathogen Interactions

There are different models available that mimic the human intestinal epithelium and are thus available for studying probiotic and pathogen interactions in the gastrointestinal tract. Although, in vivo models make it possible to study the overall effects of a probiotic on a living subject, they cannot always be conducted and there is a general commitment to reduce the use of animal models. Hence, in vitro methods provide a more rapid tool for studying the interaction between probiotics and pathogens; as well as being ethically superior, faster, and less expensive. The in vitro models are represented by less complex traditional models, standard 2D models compromised of culture plates as well as Transwell inserts, and newer 3D models like organoids, enteroids, as well as organ-on-a-chip. The optimal model selected depends on the research question. Properly designed in vitro and/or in vivo studies are needed to examine the mechanism(s) of action of probiotics on pathogens to obtain physiologically relevant results.

TLR4 Deficiency Affects the Microbiome and Reduces Intestinal Dysfunctions and Inflammation in Chronic Alcohol-Fed Mice

Chronic alcohol abuse causes an inflammatory response in the intestinal tract with damage to the integrity of the mucosa and epithelium, as well as dysbiosis in the gut microbiome. However, the role of gut bacteria in ethanol effects and how these microorganisms interact with the immune system are not well understood. The aim of the present study was to evaluate if TLR4 alters the ethanol-induced intestinal inflammatory response, and whether the response of this receptor affects the gut microbiota profile. We analyzed the 16S rRNA sequence of the fecal samples from wild-type (WT) and TLR4-knockout (TLR4-KO) mice with and without ethanol intake for 3 months. The results demonstrated that chronic ethanol consumption reduces microbiota diversity and causes dysbiosis in WT mice. Likewise, ethanol upregulates several inflammatory genes (IL-1β, iNOS, TNF-α) and miRNAs (miR-155-5p, miR-146a-5p) and alters structural and permeability genes (INTL1, CDH1, CFTR) in the colon of WT mice. Our results further demonstrated that TLR4-KO mice exhibit a different microbiota that can protect against the ethanol-induced activation of the immune system and colon integrity dysfunctions. In short, our results reveal that TLR4 is a key factor for determining the gut microbiota, which can participate in dysbiosis and the inflammatory response induced by alcohol consumption.

TLR2 and TLR4 in Parkinson's disease pathogenesis: the environment takes a toll on the gut

Parkinson's disease (PD) is an incurable, devastating disorder that is characterized by pathological protein aggregation and neurodegeneration in the substantia nigra. In recent years, growing evidence has implicated the gut environment and the gut-brain axis in the pathogenesis and progression of PD, especially in a subset of people who exhibit prodromal gastrointestinal dysfunction. Specifically, perturbations of gut homeostasis are hypothesized to contribute to α-synuclein aggregation in enteric neurons, which may spread to the brain over decades and eventually result in the characteristic central nervous system manifestations of PD, including neurodegeneration and motor impairments. However, the mechanisms linking gut disturbances and α-synuclein aggregation are still unclear. A plethora of research indicates that toll-like receptors (TLRs), especially TLR2 and TLR4, are critical mediators of gut homeostasis. Alongside their established role in innate immunity throughout the body, studies are increasingly demonstrating that TLR2 and TLR4 signalling shapes the development and function of the gut and the enteric nervous system. Notably, TLR2 and TLR4 are dysregulated in patients with PD, and may thus be central to early gut dysfunction in PD. To better understand the putative contribution of intestinal TLR2 and TLR4 dysfunction to early α-synuclein aggregation and PD, we critically discuss the role of TLR2 and TLR4 in normal gut function as well as evidence for altered TLR2 and TLR4 signalling in PD, by reviewing clinical, animal model and in vitro research. Growing evidence on the immunological aetiology of α-synuclein aggregation is also discussed, with a focus on the interactions of α-synuclein with TLR2 and TLR4. We propose a conceptual model of PD pathogenesis in which microbial dysbiosis alters the permeability of the intestinal barrier as well as TLR2 and TLR4 signalling, ultimately leading to a positive feedback loop of chronic gut dysfunction promoting α-synuclein aggregation in enteric and vagal neurons. In turn, α-synuclein aggregates may then migrate to the brain via peripheral nerves, such as the vagal nerve, to contribute to neuroinflammation and neurodegeneration typically associated with PD.

Effect of Food Endotoxin on Infant Health

Endotoxin is a complex molecule derived from the outer membrane of Gram-negative bacteria, and it has strong thermal stability. The processing of infant food can kill pathogenic bacteria but cannot remove endotoxin. Because the intestinal structure of infants is not fully developed, residual endotoxin poses a threat to their health by damaging the intestinal flora and inducing intestinal inflammation, obesity, and sepsis, among others. This paper discusses the sources and contents of endotoxin in infant food and methods for preventing endotoxin from harming infants. However, there is no clear evidence that endotoxin levels in infant food cause significant immune symptoms or even diseases in infants. However, in order to improve the safety level of infant food and reduce the endotoxin content, this issue should not be ignored. The purpose of this review is to provide a theoretical basis for manufacturers and consumers to understand the possible harm of endotoxin content in infant formula milk powder and to explore how to reduce its level in infant formula milk powder. Generally, producers should focus on cleaning the milk source, securing the cold chain, avoiding long-distance transportation, and shortening the storage time of raw milk to reduce the level of bacteria and endotoxin. After production and processing, the endotoxin content should be measured as an important index to test the quality of infant formula milk powder so as to provide high-quality infant products for the healthy growth of newborns.

Short-Term Lincomycin Exposure Depletion of Murine Microbiota Affects Short-Chain Fatty Acids and Intestinal Morphology and Immunity

Lincomycin, as one of the most commonly used antibiotics, may cause intestinal injury, enteritis and other side effects, but it remains unknown whether these effects are associated with microbial changes and the effects of different doses of lincomycin on infants. Here, 21-day old mice were exposed to 1 and 5 g/L lincomycin to explore the effects of lincomycin on the gut microbiota, metabolites and inflammation. Compared to the control mice, 1 g/L lincomycin exposure decreased the body weight gain of mice (p < 0.05). Both 1 and 5 g/L lincomycin exposure reduced the diversity and microbial composition of mice (p < 0.05). Furthermore, 1 and 5 g/L lincomycin reduced the relative concentrations of acetate, propionate, butyrate, valerate, isobutyric acid and isovaleric acid in the colon chyme of mice (p < 0.05). In addition, 5 g/L lincomycin exposure reduced the villus height, crypt depth, and relative expression of TLR2, TLR3, TLR4, IL-18, TNF-α, and p65 in the jejunum of mice (p < 0.05), while 1 g/L lincomycin exposure reduced the relative expression of TLR2, TLR3, TNF-α, and p65 (p < 0.05). Collectively, these results highlight the depletion effect of short-term lincomycin exposure on microbiota and the further regulatory effect on intestinal morphology and immunosuppression in infant mice.

Protective effects of the combination Bifidobacterium longum plus lactoferrin against NSAID-induced enteropathy

OBJECTIVES

Nonsteroidal anti-inflammatory drugs can exert detrimental effects in the lower digestive tract. The aim of this study was to examine the protective effects of a combination of the probiotic Bifidobacterium longum BB536 (Bifidobacterium) with the prebiotic lactoferrin in a rat model of diclofenac-induced enteropathy.

METHODS

Enteropathy was induced in 40-wk-old male rats by intragastric diclofenac (4 mg/kg twice daily for 14 d). Lactoferrin (100 mg/kg twice daily), Bifidobacterium (2.5 × 10⁶ CFU/rat twice daily) or their combination were administered 1 h before diclofenac. At the end of treatments, the ileum was processed for the evaluation of histologic damage, myeloperoxidase (MPO) and malondialdehyde (MDA) levels, as well as the expression of Toll-like receptors 2 and 4 (TLR-2/-4) and the activation of downstream signaling molecules (MyD88 and nuclear factor [NF]-κB p65). Blood hemoglobin and fecal calprotectin were also assessed.

RESULTS

Diclofenac induced intestinal damage, along with increments of MPO and MDA, overexpression of TLR-2, TLR-4, MyD88, and NF-κB p65, increased fecal calprotectin and decreased blood hemoglobin levels. Lactoferrin or Bifidobacterium alone prevented diclofenac-induced enteric damage, and the changes in blood hemoglobin, MPO, MDA, fecal calprotectin, and NF-κB p65. Bifidobacterium, but not lactoferrin, decreased TLR-4 expression, although none of them affected MyD88 overexpression. TLR-2 expression was slightly enhanced by all treatments. The combined administration of lactoferrin and Bifidobacterium reduced further the intestinal damage, and restored MPO and blood hemoglobin levels.

CONCLUSIONS

Diclofenac induced ileal mucosal lesions by activation of inflammatory and pro-oxidant mechanisms. These detrimental actions were prevented by the combination of lactoferrin with Bifidobacterium likely through the modulation of TLR-2/-4/NF-κB proinflammatory pathways.

Probiotic mechanisms of action

Intestinal dysbiosis is associated with a large number of disease processes including necrotizing enterocolitis and late-onset sepsis in preterm infants and colic and antibiotic-associated diarrhea in term infants. Probiotic microbes are increasingly administered to infants with the intent of decreasing risk of these acute diseases as well as chronic diseases of childhood such as asthma and atopic disease. The mechanisms by which probiotics decrease inflammation, decrease intestinal permeability, alter the intestinal microbiota, and influence metabolism have been discovered through both in vitro studies and in vivo in animal models. We review key mechanisms by which probiotic microbes improve health with emphasis on recent discoveries in the field.

Poor short-term glycemic control in patients with type 2 diabetes impairs the intestinal mucosal barrier: a prospective, single-center, observational study

BACKGROUND

To determine the relation between daily glycemic fluturation and the intestinal mucosal barrier dysfunction in type 2 diabetes mellitus (T2DM).

METHODS

Totally 66 patients with T2DM were enrolled, 33 healthy volunteers were also recruited according to the enrolled patients' gender and age in a ratio of 2: 1. Patients were bisected by the median of endotoxins level into low(< 12.31 μ/l, n = 33) and high(≥12.31 μ/l, n = 33) blood endotoxin groups. Clinical data and blood glucose fluctuations were compared between groups. Multivariate regression analysis was used to determine the independent factors affecting the intestinal mucosal barrier.

RESULTS

Serum endotoxin [12.1 (4.2~22.0) vs 3.2 (1.3~6.0), P < 0.001] and fasting blood glucose levels [9.8 ± 3.6 vs 5.4 ± 0.7, P < 0.001] were significantly higher in patients with T2DM than the control group. The standard deviation of blood glucose (SDBG) within 1 day [2.9 (2.0~3.3) vs. 2.1 (1.6~2.5), P = 0.012] and the largest amplitude of glycemic excursions (LAGE) [7.5 (5.4~8.9) vs. 5.9 (4.3~7.4), P = 0.034] were higher in the high endotoxin group than in the low endotoxin group. A multiple linear stepwise regression revealed a positive correlation between SDBG with endotoxin (standard partial regression coefficient = 0.255, P = 0.039).

CONCLUSIONS

T2DM patients who incapable of maintaining stable blood glucose level are at a higher risk to associated with intestinal mucosal barrier injury.

Intestinal in vitro and ex vivo Models to Study Host-Microbiome Interactions and Acute Stressors

The gut microbiome is extremely important for maintaining homeostasis with host intestinal epithelial, neuronal, and immune cells and this host-microbe interaction is critical during times of stress or disease. Environmental, nutritional, and cognitive stress are just a few factors known to influence the gut microbiota and are thought to induce microbial dysbiosis. Research on this bidirectional relationship as it pertains to health and disease is extensive and rapidly expanding in both in vivo and in vitro/ex vivo models. However, far less work has been devoted to studying effects of host-microbe interactions on acute stressors and performance, the underlying mechanisms, and the modulatory effects of different stressors on both the host and the microbiome. Additionally, the use of in vitro/ex vivo models to study the gut microbiome and human performance has not been researched extensively nor reviewed. Therefore, this review aims to examine current evidence concerning the current status of in vitro and ex vivo host models, the impact of acute stressors on gut physiology/microbiota as well as potential impacts on human performance and how we can parlay this information for DoD relevance as well as the broader scientific community. Models reviewed include widely utilized intestinal cell models from human and animal models that have been applied in the past for stress or microbiology research as well as ex vivo organ/tissue culture models and new innovative models including organ-on-a-chip and co-culture models.