Effects of alanyl-glutamine dipeptide on the expression of colon-inflammatory mediators during the recovery phase of colitis induced by dextran sulfate sodium. Eur J Nutr. 2013;52:1089-1098. [PMID: 22847641 DOI: 10.1007/s00394-012-0416-3]

Glutamine Peptides: Preparation, Analysis, Applications, and Their Role in Intestinal Barrier Protection

Background: Glutamine peptides refer to a series of peptides containing glutamine, and the activity of glutamine peptides is characterized by the content of non-nitrogen terminal glutamine in the peptide. It has been found that glutamine peptides are a stable substitute for glutamine monomer, and they are increasingly studied in nutrition and physiology due to their functional properties. Methods: An extensive search of the literature was conducted in the PubMed, Web of Science, Scopus, and Google Scholar databases up to December 2024. Inclusion criteria focused on the role of glutamine peptides in intestinal health, and the included literature was screened and summarized. Results: This study systematically reviews the current status of research on the preparation, analysis, applications of glutamine peptides and their role in intestinal barrier protection. Furthermore, the challenges faced by the current research and the development direction in the future are discussed. Conclusions: Glutamine peptides can play a role in protecting the intestinal barrier by regulating tight junctions, mucin, inflammatory response, and intestinal flora. In addition, further and intensive investigations are urgently required to address the current challenges pertaining to the structure-activity relationships of glutamine peptides and their transport and absorption mechanism in the gut. This review contributes to a better understanding of the mechanism of glutamine peptides to protect intestinal barrier function and also provides a reference for the development of functional foods with protective effects of intestinal barrier function.

Harnessing nature's pharmacy: investigating natural compounds as novel therapeutics for ulcerative colitis

Backgrounds

Ulcerative colitis (UC) is a form of chronic inflammatory bowel disease, and UC diagnosis rates continue to rise throughout the globe. The research and development of new drugs for the treatment of UC are urgent, and natural compounds are an important source. However, there is a lack of systematic summarization of natural compounds and their mechanisms for the treatment of UC.

Methods

We reviewed the literature in the databases below from their inception until July 2023: Web of Science, PubMed, China National Knowledge Infrastructure, and Wanfang Data, to obtain information on the relationship between natural compounds and UC.

Results

The results showed that 279 natural compounds treat UC through four main mechanisms, including regulating gut microbiota and metabolites (Mechanism I), protecting the intestinal mucosal barrier (Mechanism II), regulating intestinal mucosal immune response (Mechanism III), as well as regulating other mechanisms (Mechanism Ⅳ) such as cellular autophagy modulation and ferroptosis inhibition. Of these, Mechanism III is regulated by all natural compounds. The 279 natural compounds, including 62 terpenoids, 57 alkaloids, 52 flavonoids, 26 phenols, 19 phenylpropanoids, 9 steroids, 9 saponins, 8 quinonoids, 6 vitamins, and 31 others, can effectively ameliorate UC. Of these, terpenoids, alkaloids, and flavonoids have the greatest potential for treating UC. It is noteworthy to highlight that a total of 54 natural compounds exhibit their therapeutic effects by modulating Mechanisms I, II, and III.

Conclusion

This review serves as a comprehensive resource for the pharmaceutical industry, researchers, and clinicians seeking novel therapeutic approaches to combat UC. Harnessing the therapeutic potential of these natural compounds may significantly contribute to the improvement of the quality of life of patients with UC and promotion of disease-modifying therapies in the future.

Amino acid HPLC-FLD analysis of spirulina and its protective mechanism against the combination of obesity and colitis in wistar rats

Objective

The cafeteria diet (CD), designed as an experimental diet mimicking the obesogenic diet, may contribute to the pathogenesis of inflammatory bowel diseases (IBD). This study delves into the influence of spirulina (SP) on obesity associated with colitis in Wistar rats.

Methods

The amino acids composition of SP was analyzed using HPLC-FLD. Animals were equally separated into eight groups, each containing seven animals and treated daily for eight weeks as follows: Control diet (SD), cafeteria diet (CD) group, CD + SP (500 mg/kg) and SD + SP. Ulcerative colitis was provoked by rectal injection of acetic acid (AA) (3 % v/v, 5 ml/kg b.w.) on the last day of treatment in the following groups: SD + AA, SD + AA + SP, CD + AA, and CD + AA + SP.

Results

Findings revealed that UC and/or CD increased the abdominal fat, weights gain, and colons. Moreover, severe colonic alteration, perturbations in the serum metabolic parameters associated with an oxidative stress state in the colonic mucosa, defined by overproduction of reactive oxygen species (ROS) and increased levels of plasma scavenging activity (PSA). Additionally, obesity exacerbated the severity of AA-induced UC promoting inflammation marked by the overexpression of pro-inflammatory cytokines. Significantly, treatment with SP provided notable protection against inflammation severity, reduced histopathological alterations, attenuated lipid peroxidation (MDA), and enhanced antioxidant enzyme activities (CAT, SOD, and GPX) along with non-enzymatic antioxidants (GSH and SH-G).

Conclusions

Thus, the antioxidant effects and anti-inflammatory proprieties of SP could be attributed to its richness in amino acids, which could potentially mitigate inflammation severity in obese subjects suffering from ulcerative colitis. These results imply that SP hold promise as a therapeutic agent for managing of UC, particularly in individuals with concomitant obesity. Understanding SP's mechanisms of action may lead novel treatment strategies for inflammatory bowel diseases and hyperlipidemia in medical research.

Alanyl-Glutamine (Ala-Gln) Ameliorates Dextran Sulfate Sodium (DSS)-Induced Acute Colitis by Regulating the Gut Microbiota, PI3K-Akt/NF-κB/STAT3 Signaling, and Associated Pulmonary Injury

The aim of this study was to investigate the protective effect of alanyl-glutamine (Ala-Gln) on acute colitis complicated by pulmonary injury induced by dextran sulfate sodium (DSS) in C57BL/6 mice. The results showed that Ala-Gln intervention alleviated weight loss, the disease activity index (DAI), colon shortening, and pathological injury and regulated the absolute number of CD4⁺T-cell subsets in mesenteric lymph nodes (MLNs). In addition, Ala-Gln intervention significantly ameliorated the composition of the gut microbiota in mice with DSS- induced acute colitis, significantly decreasing the relative abundance of Desulfovibrionaceae and increasing the abundances of Gastranaerophilales, Clostridia-vadinBB60, and Alistipes. Moreover, Ala-Gln treatment significantly inhibited the activation of the PI3K-Akt/NF-κB/STAT3 inflammatory signaling pathways in the colon of mice with DSS-induced acute colitis. Notably, Ala-Gln intervention also alleviated the pulmonary injury as well as the imbalance in levels of CD4⁺T-cell subsets in pulmonary tissue in mice with DSS-induced acute colitis. In conclusion, Ala-Gln alleviates DSS-induced acute colitis by regulating the gut microflora and PI3K-Akt/NF-κB/STAT3 signaling pathways, as well as by alleviating accompanying pulmonary injury.

Effects of dietary tryptophan on the antioxidant capacity and immune response associated with TOR and TLRs/MyD88/NF-κB signaling pathways in northern snakehead, Channa argus (Cantor, 1842)

Introduction

Dietary tryptophan (Trp) has been shown to influence fish feed intake, growth, immunity and inflammatory responses. The purpose of this study was to investigate the effect and mechanism of Trp on immune system of juvenile northern snakehead (Channa argus Cantor, 1842).

Methods

A total of 540 fish (10.21 ± 0.11 g) were fed six experimental diets containing graded levels of Trp at 1.9, 3.0, 3.9, 4.8, 5.9 and 6.8 g/kg diet for 70 days, respectively.

Results and Discussion

The results showed that supplementation of 1.9-4.8 g/kg Trp in diets had no effect on the hepatosomatic index (HSI) and renal index (RI), while dietary 3.9 and 4.8 g/kg Trp significantly increased spleen index (SI) of fish. Dietary 3.9, 4.8, 5.9 and 6.8 g/kg Trp enhanced the total hemocyte count (THC), the activities of total antioxidant capacity (T-AOC) and superoxide dismutase (SOD). Malondinaldehyde (MDA) levels in the blood were significantly decreased by consuming 3.9 and 4.8 g/kg Trp. Fish fed with 3.0 and 3.9 g/kg Trp diets up-regulated interleukin 6 (il-6) and interleukin 8 (il-8) mRNA levels. The expression of tumor necrosis factor α (tnf-α) was highest in fish fed with 3.0 g/kg Trp diet, and the expression of interleukin 1β (il-1β) was highest in fish fed with 3.9 g/kg Trp diet. Dietary 4.8, 5.9 and 6.8 g/kg Trp significantly decreased il-6 and tnf-α mRNA levels in the intestine. Moreover, Trp supplementation was also beneficial to the mRNA expression of interleukin 22 (il-22). Additionally, the mRNA expression levels of target of rapamycin (tor), toll-like receptor-2 (tlr2), toll-like receptor-4 (tlr4), toll-like receptor-5 (tlr5) and myeloid differentiation primary response 88 (myd88) of intestine were significantly up-regulated in fish fed 1.9, 3.0 and 3.9 g/kg Trp diets, and down-regulated in fish fed 4.8, 5.9 and 6.8 g/kg Trp diets. Dietary 4.8 and 5.9 g/kg Trp significantly increased the expression of inhibitor of nuclear factor kappa B kinase beta subunit (ikkβ) and decreased the expression of inhibitor of kappa B (iκbα), but inhibited nuclear transcription factor kappa B (nf-κb) mRNA level. Collectively, these results indicated that dietary 4.8 g/kg Trp could improve antioxidant capacity and alleviate intestinal inflammation associated with TOR and TLRs/MyD88/NF-κB signaling pathways.

Humic acids alleviate dextran sulfate sodium-induced colitis by positively modulating gut microbiota

Humic acids (HAs) are natural polymers with diverse functional groups that have been documented and utilized in traditional Chinese medicine. Dextran sulfate sodium (DSS)-induced colitis has been used as a model to study inflammatory bowel disease. In this research, we investigate the effect of HAs on ameliorating DSS-induced colitis in mice. Our aim here was to investigate if HAs could be a remedy against colitis and the mechanisms involved. The results show that HAs facilitated a regain of body weight and restoration of intestinal morphology after DSS-induced colitis. HAs treatment alters the community of gut microbiota with more Lactobacillus and Bifidobacterium. Changes in bacterial community result in lower amounts of lipopolysaccharides in mouse sera, as well as lower levels of inflammatory cytokines through the Toll-like receptor 4 (TLR4)-NF-κB pathway. HAs also promoted the expression of tight junction proteins, which protect the intestinal barrier from DSS damage. Cell experiments show that HAs display an inhibitory effect on DSS growth as well. These results suggest that HAs can alleviate colitis by regulating intestinal microbiota, reducing inflammation, maintaining mucosal barriers, and inhibiting pathogen growth. Thus, HAs offer great potential for the prevention and treatment of colitis.

TDAG51 deficiency attenuates dextran sulfate sodium-induced colitis in mice

Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, is a group of chronic inflammatory diseases of the gastrointestinal tract. Although the multifactorial etiology of IBD pathogenesis is relatively well documented, the regulatory factors that confer a risk of IBD pathogenesis remain less explored. In this study, we report that T-cell death-associated gene 51 (TDAG51/PHLDA1) is a novel regulator of the development of dextran sulfate sodium (DSS)-induced colitis in mice. TDAG51 expression was elevated in the colon tissues of DSS-induced experimental colitis mice. TDAG51 deficiency protected mice against acute DSS-induced lethality and body weight changes and disease severity. DSS-induced structural damage and mucus secretion in colon tissues were significantly reduced in TDAG51-deficient mice compared with wild-type mice. We observed similar results in a DSS-induced chronic colitis mouse model. Finally, we showed that the production of inflammatory mediators, including proinflammatory enzymes, molecules and cytokines, was decreased in DSS-treated TDAG51-deficient mice compared with DSS-treated wild-type mice. Thus, we demonstrated that TDAG51 deficiency plays a protective role against DSS-induced colitis by decreasing the production of inflammatory mediators in mice. These findings suggest that TDAG51 is a novel regulator of the development of DSS-induced colitis and is a potential therapeutic target for IBD.

AI-2/LuxS Quorum Sensing System Promotes Biofilm Formation of Lactobacillus rhamnosus GG and Enhances the Resistance to Enterotoxigenic Escherichia coli in Germ-Free Zebrafish

The LuxS enzyme plays a key role in both quorum sensing (QS) and the regulation of bacterial growth. It catalyzes the production of autoinducer-2 (AI-2) signaling molecule, which is a component of the methyl cycle and methionine metabolism. This study aimed at investigating the differences between the Lactobacillus rhamnosus GG (LGG) wild-type strain (WT) and its luxS mutant (ΔluxS) during biofilm formation and when resisting to inflammation caused by Enterotoxigenic Escherichia coli (ETEC) in germ-free zebrafish. Our results suggest that in the absence of luxS when LGG was knocked out, biofilm formation, extracellular polysaccharide secretion and adhesion were all compromised. Addition of synthetic AI-2 indeed rescued, at least partially, the deficiencies observed in the mutant strain. The colonizing and immunomodulatory function in WT versus ΔluxS mutants were further studied in a germ-free zebrafish model. The concentration of AI-2 signaling molecules decreased sharply in zebrafish infected with the ΔluxS. At the same time, compared with the ΔluxS, the wild-type strain could colonize the germ-free zebrafish more effectively. Our transcriptome results suggest that genes involved in immunity, signal transduction, and cell adhesion were downregulated in zebrafish infected with ΔluxS and WT. In the WT, the immune system of germ-free zebrafish was activated more effectively through the MAPK and NF-κB pathway, and its ability to fight the infection against ETEC was increased. Together, our results demonstrate that the AI-2/LuxS system plays an important role in biofilm formation to improve LGG and alleviate inflammation caused by ETEC in germ-free zebrafish.

IMPORTANCELactobacillus rhamnosus GG is a widely used probiotic to improve host intestinal health, promote growth, reduce diarrhea, and modulate immunity. In recent years, the bacterial quorum sensing system has attracted much attention; however, there has not been much research on the effect of the LuxS/AI-2 quorum sensing system of Lactobacillus on bacteriostasis, microbial ecology balance, and immune regulation in intestine. In this study, we used germ-free zebrafish as an animal model to compare the differences between wild-type and luxS mutant strains. We showed how AI-2/LuxS QS affects the release of AI-2 and how QS regulates the colonization, EPS synthesis and biofilm formation of LGG. This study provides an idea for the targeted regulation of animal intestinal health with probiotics by controlling bacteria quorum sensing system.

L-glutamine for sickle cell disease: more than reducing redox

Oxidative stress is a major contributor to the pathophysiology of sickle cell disease (SCD) including hemolysis and vaso-occlusive crisis (VOC). L-glutamine is a conditionally essential amino acid with important roles, including the synthesis of antioxidants, such as reduced glutathione and the cofactors NAD(H) and NADP(H), as well as nitric oxide. Given the increased levels of oxidative stress and lower (NADH):(NAD +  + NADH) ratio in sickle erythrocytes that adversely affects the blood rheology compared to normal red blood cells, L-glutamine was investigated for its therapeutic potential to reduce VOC. While L-glutamine was approved by the United States (US) Food and Drug Administration to treat SCD, its impact on the redox environment in sickle erythrocytes is not fully understood. The mechanism through which L-glutamine reduces VOC in SCD is also not clear. In this paper, we will summarize the results of the Phase 3 study that led to the approval of L-glutamine for treating SCD and discuss its assumed mechanisms of action. We will examine the role of L-glutamine in health and propose how the extra-erythrocytic functions of L-glutamine might contribute to its beneficial effects in SCD. Further research into the role of L-glutamine on extra-erythrocyte functions might help the development of an improved formulation with more efficacy.

The Influence of the Western Diet on Microbiota and Gastrointestinal Immunity

Diet exerts a major influence upon host immune function and the gastrointestinal microbiota. Although components of the human diet (including carbohydrates, fats, and proteins) are essential sources of nutrition for the host, they also influence immune function directly through interaction with innate and cell-mediated immune regulatory mechanisms. Regulation of the microbiota community structure also provides a mechanism by which food components influence host immune regulatory processes. Here, we consider the complex interplay between components of the modern (Western) diet, the microbiota, and host immunity in the context of obesity and metabolic disease, inflammatory bowel disease, and infection.

Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Effects of glutamine on the IKK/IκB/NF-кB system in the enterocytes of turbot Scophthalmus maximus L. stimulated with soya-saponins

Soya-saponins represent key anti-nutritional factors that contribute to soybean meal-induced enteritis, and glutamine is an effective fish intestine protectant that combats the negative effects of soya-saponins. Nuclear transcription factor-kappa B (NF-кB) systems are involved in the interactions between soya-saponins and glutamine, and the goal of the present work was to clarify the related molecular mechanisms used by the NF-кB kinase (IKK)/inhibitor of NF-κB (IκB)/NF-кB system. Primary cultured turbot (Scophthalmus maximus L.) intestinal epithelial cells were concurrently administrated with 1 mg/mL of soya-saponins and several levels of glutamine (0, 0.5, 1.0 and 2.0 mM) for 12 h and then subjected to real-time PCR and Western blot assays. Compared with cells treated with soya-saponins alone, glutamine significantly decreased the expression of interleukin-1 beta, interleukin 8 and tumor necrosis factor α genes, significantly reduced nuclear and cytosolic NF-κB p65 abundance levels in a dose-dependent manner, increased the IκBα protein level but decreased its phosphorylation, and down-regulated the IKKα/β and phosphorylated IKKα/β levels. In conclusion, this in vitro work confirmed that glutamine attenuated soya-saponin-induced inflammatory responses in turbot intestines. Moreover, it identified molecular pathways in which glutamine first decreased the p65 level and then prevented its nuclear translocation. In addition, glutamine reduced IκBα phosphorylation and maintained its level. Finally, glutamine decreased IKK expression and phosphorylation.

NO, way to go: critical amino acids to replenish nitric oxide production in treating mucositis

PURPOSE OF REVIEW

There is still an unmet need for preventive and treatment strategies for chemotherapy-induced and radiotherapy-induced mucositis and its associated systemic inflammatory response (SIR) in cancer patients. Because of citrulline depletion due to cytotoxic therapy, nitric oxide (NO) production can be reduced, limiting its effect in many physiological processes. Restoring NO production could relieve mucositis severity by supporting host damage control mechanisms. Amino acids glutamine, arginine and citrulline are involved in NO production. This review including recent literature of preclinical and clinical studies will discuss the potential benefits of glutamine, arginine and citrulline on mucositis development with focus on NO production.

RECENT FINDINGS

Mucositis severity is more defined by host response to DNA damage than by DMA damage itself. Citrulline depletion because of afunctional enterocytes could be responsible for NO depletion during cytotoxic therapy. Restoring NO production during cytotoxic therapy could have a beneficial effect on mucositis development. Citrulline seems a more promising NO donor than glutamine or arginine during cytotoxic therapy, although clinical studies in mucositis patients are currently lacking.

SUMMARY

Glutamine, arginine and citrulline show in-vitro beneficial effects on inflammatory processes involved in mucositis. Translation to the clinic is difficult as demonstrated with use of glutamine and arginine. Citrulline, being the most potent NO donor with excellent oral bio-availability, is very promising as treatment choice for mucositis and its use deserves to be investigated in clinical trials with mucositis patients.

Roles of Lipid Peroxidation-Derived Electrophiles in Pathogenesis of Colonic Inflammation and Colon Cancer

Redox stress is a common feature of gut disorders such as colonic inflammation (inflammatory bowel disease or IBD) and colorectal cancer (CRC). This leads to increased colonic formation of lipid-derived electrophiles (LDEs) such as 4-hydroxynonenal (4-HNE), malondialdehyde (MDA), trans, trans-2,4-decadienal (tt-DDE), and epoxyketooctadecenoic acid (EKODE). Recent research by us and others support that treatment with LDEs increases the severity of colitis and exacerbates the development of colon tumorigenesis in vitro and in vivo, supporting a critical role of these compounds in the pathogenesis of IBD and CRC. In this review, we will discuss the effects and mechanisms of LDEs on development of IBD and CRC and lifestyle factors, which could potentially affect tissue levels of LDEs to regulate IBD and CRC development.

Dietary Bioactive Peptide Alanyl-Glutamine Attenuates Dextran Sodium Sulfate-Induced Colitis by Modulating Gut Microbiota

Inflammatory bowel disease (IBD) is a chronic intestinal disorder threatening human health. Di-peptide alanyl-glutamine (Ala-Gln) has various beneficial effects on gut health. However, its role and functional mechanism in treating IBD are still not clear. Therefore, the protective effects of Ala-Gln and glutamine (Gln) on dextran sulfate sodium- (DSS-) induced colitic mice were investigated in this study. The results showed that oral supplementation of Ala-Gln or Gln significantly attenuated the colitis symptoms in mice, including body weight loss, colon length, disease activity index, histological scores, and tissue apoptosis. The concentrations of interleukin- (IL-) 1β, IL-6, tumor necrosis factor-α, and myeloperoxidase were significantly decreased, while the concentrations of immunoglobulins (IgA, IgG, and IgM) and superoxide dismutase were significantly increased by Ala-Gln or Gln supplementation. The expression of occludin and peptide transporter 1 (PepT1) was significantly increased by Ala-Gln or Gln. Interestingly, Ala-Gln had better beneficial effects than Gln in alleviating colitis. In addition, 16S rDNA sequencing showed that the DSS-induced shifts of the microbiome (community diversity, evenness, richness, and composition) in the mouse colon were restored by Gln and Ala-Gln, including Lactobacillus, Bacteroides_acidifaciens, Bacteroidales, Firmicutes, Clostridia, Helicobacter, and Bacteroides. Correspondingly, the functions of the microflora metabolism pathways were also rescued by Ala-Gln, including fatty acid metabolism, membrane transporters, infectious diseases, and immune system. In conclusion, the results revealed that Ala-Gln can prevent colitis through PepT1, enhancing the intestinal barrier and modulating gut microbiota and microflora metabolites.

Salvia miltiorrhiza stems and leaves total phenolic acids combination with tanshinone protect against DSS-induced ulcerative colitis through inhibiting TLR4/PI3K/AKT/mTOR signaling pathway in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Salvia miltiorrhiza Bge. as a traditional Asian medicinal plant, roots and rhizomes (Danshen) are used to treat chronic hepatitis and coronary heart disease. In recent years, the medicinal value of S. miltiorrhiza stems and leaves total phenolic acids extract (JF) similar to roots and rhizomes has received increasing attention. S. miltiorrhiza roots and rhizome tanshinone extract (DT) has a good anti-inflammatory effect.

AIM OF THE STUDY

To explore the therapeutic effect and possible molecular mechanisms of JF and DT alone or in combination on dextran sulfate sodium (DSS)-induced colitis mice.

MATERIALS AND METHODS

Colitis was induced by received 2% DSS in drinking water for 7 consecutive days. Then mice were administered orally for 7 days. Disease activity index (DAI) scores and body weight were recorded daily. After the end of the experiment, colon was removed, colon length was measured and histopathological analysis was performed. Inflammatory factors expression was determined by ELISA, its mRNA expression was detected by real-time quantitative PCR, and the expression of related proteins on TLR4/PI3K/AKT/mTOR signal was analyzed by Western blot.

RESULTS

Treatment with JF and DT alone or in combination reduced DAI scores, increase body weight, improved colon shortening, and decreased colon histology scores. In addition, the expression level of inflammatory factors was inhibited. The combination of JF and DT had a better inhibitory effect on inflammatory factors compared to JF alone. We also found that DT alone and JF combined with DT inhibited TLR4/PI3K/AKT/mTOR signaling-related proteins expression levels (including TLR4, p-PI3K p110α/PI3K p110α, p-AKT (ser473)/AKT, mTOR, p-mTOR, NF-κB p65), showing an effective anti-inflammatory effect.

CONCLUSIONS

We demonstrated for the first time that, JF and DT alone or in combination effectively ameliorated DSS-induced ulcerative colitis in mice, possibly by inhibiting the TLR4/PI3K/AKT/mTOR signaling pathway.

Alanylglutamine Relieved Asthma Symptoms by Regulating Gut Microbiota and the Derived Metabolites in Mice

OBJECTIVE

Allergic asthma is a chronic inflammatory disease, which seriously affects the life quality of patients, especially children. Alanylglutamine is a nutritional supplement with potential protective and anti-inflammatory effects, but its function in allergic asthma remains elusive. In this study, we focused on the investigations of the roles and functional mechanism of Alanylglutamine in asthma.

METHODS

Ovalbumin (OVA) induction was utilized to establish a mouse asthma model. 16S rDNA sequencing was performed to compare the diversity of intestinal microorganisms under different treatments. Gas chromatography was utilized to screen the intestinal microbe-short-chain fatty acids in the stool. The lung tissue was extracted to determine signaling pathways, including AMPK, NF-κB, mTOR, STAT3, IKKβ, TGF-β, and IL-1β through Western blot or RT-qPCR.

RESULTS

It was observed that Alanylglutamine reduced the cytokine in OVA-induced allergic asthma mice. H&E staining showed obvious pneumonia symptoms in the asthma group, while Alanylglutamine alleviated the inflammatory infiltration. Alanylglutamine reversed gut microbiota compositions in OVA-induced allergic asthma mice and enhanced the butyric acid level. The protective role of Alanylglutamine may be associated with the gut microbiota-butyric acid-GPR43 pathway in asthma mice. In contrast to the OVA group, Alanylglutamine activated the protein expression of P-AMPK/AMPK and inhibited the protein expression of P-mTOR/mTOR, P-P65/P65, P-STAT3/STAT3, P-IKKβ/IKKβ, TGF-β, and IL-1β, with similar effects from butyric acid.

CONCLUSION

The results indicated that Alanylglutamine might be beneficial for asthma, and its effect was achieved through the regulation on microbiota and the derived metabolites. The therapeutic effects might be associated with AMPK, NF-κB, mTOR, and STAT3 signaling pathways. These findings will help identify effective therapeutic direction to alleviate allergic inflammation of the lungs and airways.

Lactobacillus plantarum PMO 08 as a Probiotic Starter Culture for Plant-Based Fermented Beverages

Lactobacillus plantarum PMO 08 was evaluated as a starter culture for plant-based probiotic beverages. Its viability under various culture conditions and acidification ability in standardized tomato medium, fermentation parameters, and beverage properties were assessed. Lactobacillus plantarum PMO 08 could grow under various culture conditions; there was a high correlation between the incubation time to reach the optimal conditions and the inoculation concentration of lactic acid bacteria (LAB) (r² = 0.997). Acidity (0.958 ± 0.002%) and LAB count (9.78 ± 0.14 Log₁₀ CFU/mL) were significantly higher when fermented with L. plantarum than with the yogurt starter culture. A survival rate of 96% and 95% in artificial gastric juice and artificial intestinal juice, respectively, indicated that the probiotic requirements were met. The total polyphenol and glutamine content, and antioxidant activity increased after fermentation. The proline content significantly increased in L. plantarum PMO 08- fermented beverage. Thus, L. plantarum PMO 08 is an effective starter culture for non-dairy probiotic beverages whose functional quality may be improved by fermentation.

The Potential of Food Protein-Derived Bioactive Peptides against Chronic Intestinal Inflammation

Inflammation can cause various chronic diseases like inflammatory bowel diseases. Various food protein-derived bioactive peptides (BAPs) with anti-inflammatory activity have the potential to manage these diseases. The aim of this paper is to overview the mechanisms and the molecular targets of BAPs to exert anti-inflammatory activity. In this review, the in vitro and in vivo effects of BAPs on intestinal inflammation are highlighted. The mechanism, pathways, and future perspectives of BAPs as the potential sources of therapeutic treatments to alleviate intestinal inflammation are provided, including nuclear factor-κB, mitogen-activated protein kinase, Janus kinase-signal transducer and activator of transcription, and peptide transporter 1 (PepT1), finding that PepT1 and gut microbiota are the promising targets for BAPs to alleviate the intestinal inflammation. This review provides a comprehensive understanding of the role of dietary BAPs in attenuating inflammation and gives a novel direction in nutraceuticals for people or animals with intestinal inflammation.

Exploring the food-gut axis in immunotherapy response of cancer patients

Nowadays, immunotherapy is widely used to treat different cancer types as it boosts the body's natural defenses against the malignancy, with lower risk of adverse events compared to the traditional treatments. The immune system is able to control cancer growth but, unfortunately, many cancers take advantage of immune checkpoints pathways for the immune evasion. An intricate network of factors including tumor, host and environmental variables influence the individual response to immune checkpoints' inhibitors. Between them, the gut microbiota (GM) has recently gained increasing attention because of its emerging role as a modulator of the immune response. Several studies analyzed the diversities between immunotherapy-sensitive and immunotherapy-resistant cohorts, evidencing that particular GM profiles were closely associated to treatment effect. In addition, other data documented that interventional GM modulation could effectively enhance efficacy and relieve resistance during immunotherapy treatment. Diet represents one of the major GM determinants, and ongoing studies are examining the role of the food-gut axis in immunotherapy treatment. Here, we review recent studies that described how variations of the GM affects patient's responsivity to anti-cancer immunotherapy and how diet-related factors impact on the GM modulation in cancer, outlining potential future clinical directions of these recent findings.

The natural flavonoid galangin ameliorates dextran sulphate sodium-induced ulcerative colitis in mice: Effect on Toll-like receptor 4, inflammation and oxidative stress

This study was carried out to investigate the potential therapeutic effect of galangin, a promising active principle of honeybee propolis, in dextran sulphate sodium (DSS)-induced colitis in mice. We explored the possible underlying mechanisms for galangin action and the therapeutic benefit of adding galangin to the standard therapy sulphasalazine. A galangin dose of 40 mg/kg was selected based on a preliminary dose-selection study for investigation in a 4-week cyclical model of DSS-induced colitis. Mice received 3% DSS in their drinking water during the first and third weeks and were administered the treatments (40 mg/kg galangin, 100 mg/kg sulphasalazine and a combination of 20 mg/kg galangin and 50 mg/kg sulphasalazine) daily starting from the second week. Galangin significantly ameliorated DSS-induced histopathological alterations and tissue injury, down-regulated Toll-like receptor 4 expression, suppressed NF-κB p65 activation, lowered inflammatory cytokine levels and demonstrated antioxidant effects. The combination of galangin and sulphasalazine at half doses yielded comparable results to either drug alone at full dose. This study highlights galangin as a promising therapy for colitis management.

Protective Effects Oncorneal Endothelium During Intracameral Irrigation Using N-(2)-l-alanyl-l-Glutamine

Corneal endothelial disease is a global sight-threatening disease, and corneal transplantation using donor corneas remains the sole therapeutic option. A previous work demonstrated that N (2)-alanyl-glutamine (Ala-Gln) protected against apoptosis and cellular stress, and maintained intestinal tissue integrity. In this pursuit, the present study aimed to examine the effect of Ala-Gln in the protection of the corneal endothelium and expand its range of potential clinical applications. Mice in the control group were intracamerally irrigated with Ringers lactate injection, whereas those in the experimental group were irrigated with Ringers lactate injection containing Ala-Gln. The mean intraocular pressure increased to 44 ± 3.5 mm Hg during intracameral irrigation (normal range 10.2 ± 0.4 mmHg). In vivo confocal microscopy results showed that the addition of Ala-Gln protected the morphology, structure, and density of the corneal endothelial cells. Optical Coherence Tomography (OCT) measurements showed that corneal thickness was not significantly different between the two groups, because of the immediate corneal edema after irrigation, but the addition of Ala-Gln obviously promoted the recovery of the corneal edema. Scanning electron microscopy indicated that the corneal endothelial cells were severely ruptured and exfoliated in the Ringer’s group accompanied with cellular edema, when compared with the Ala-Gln group. The intracameral irrigation using Ala-Gln protected the structure and expression of cytoskeleton and Na-K-ATPase, which exhibited a regular distribution and significantly increased expression in comparison to Ringer’s group. Furthermore, Ala-Gln maintained the mitochondrial morphology and increased the activity of mitochondria. Moreover, transmission electron microscopy showed that intracameral irrigation of Ala-Gln reversed the ultrastructural changes induced by the acute ocular hypertension in mice. Our study demonstrates that the intracameral irrigation of Ala-Gln effectively maintained the corneal endothelial pump function and barrier function by protecting the mitochondrial function and preventing the rearrangement of cytoskeleton in acute ocular hypertension in mice.

Korean Traditional Medicine (Jakyakgamcho-tang) Ameliorates Colitis by Regulating Gut Microbiota

The objective of this study was to examine the anti-colitis activity of Jakyakgamcho-tang (JGT) in dextran sulfate sodium (DSS)-induced colitis and explore changes of the gut microbial community using 16S rRNA amplicon sequencing and metabolomics approaches. It was found that treatment with JGT or 5-aminosalicylic acid (5-ASA) alleviated the severity of colitis symptoms by suppressing inflammatory cytokine levels of IL-6, IL-12, and IFN-γ. The non-metric multidimensional scaling analysis of gut microbiome revealed that JGT groups were clearly separated from the DSS group, suggesting that JGT administration altered gut microbiota. The operational taxonomic units (OTUs) that were decreased by DSS but increased by JGT include Akkermansia and Allobaculum. On the other hand, OTUs that were increased by DSS but decreased by 5-ASA or JGT treatments include Bacteroidales S24-7, Ruminococcaceae, and Rikenellaceae, and the genera Bacteroides, Parabacteroides, Oscillospira, and Coprobacillus. After JGT administration, the metabolites, including most amino acids and lactic acid that were altered by colitis induction, became similar to those of the control group. This study demonstrates that JGT might have potential to effectively treat colitis by restoring dysbiosis of gut microbiota and host metabolites.

Effects of dietary exposure to chlorpyrifos on immune cell populations and inflammatory responses in mice with dextran sulfate sodium-induced colitis

This study investigated the effects of chlorpyrifos (CPF) on immune-cell populations and intestinal inflammation using a mouse model of inflammatory bowel disease induced by dextran sulfate sodium (DSS). C57BL/6 mice were randomly assigned to five groups with one normal control (NC) and four DSS-treated groups. Mice in the NC group were given distilled water, whereas the DSS-treated groups received distilled water containing 3% DSS for 6 days to induce colitis. The NC and disease control (DC) groups were fed a control semipurified diet, while the remaining groups were exposed to CPF in the AIN-93 diet at doses of 1, 2.5, or 5 mg/kg/day throughout the study. Results showed that dietary exposure to CPF in colitic mice significantly increased circulating classical monocytes and upregulated gene expressions of chemokines in the colon compared to the NC group. Meanwhile, CPF exposure groups had lower plasma cholinesterase activities and higher percentages of circulating neutrophils than those of the DC group. A shorten length, tissue edema, and lipid peroxidation of the colon were also observed in all CPF-exposed mice. These findings suggest that dietary exposure to CPF affected immune-cell populations and inflammatory responses, which led to more severe tissue injury in mice with DSS-induced colitis.

Functions and Signaling Pathways of Amino Acids in Intestinal Inflammation

Intestine is always exposed to external environment and intestinal microorganism; thus it is more sensitive to dysfunction and dysbiosis, leading to intestinal inflammation, such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), and diarrhea. An increasing number of studies indicate that dietary amino acids play significant roles in preventing and treating intestinal inflammation. The review aims to summarize the functions and signaling mechanisms of amino acids in intestinal inflammation. Amino acids, including essential amino acids (EAAs), conditionally essential amino acids (CEAAs), and nonessential amino acids (NEAAs), improve the functions of intestinal barrier and expressions of anti-inflammatory cytokines and tight junction proteins but decrease oxidative stress and the apoptosis of enterocytes as well as the expressions of proinflammatory cytokines in the intestinal inflammation. The functions of amino acids are associated with various signaling pathways, including mechanistic target of rapamycin (mTOR), inducible nitric oxide synthase (iNOS), calcium-sensing receptor (CaSR), nuclear factor-kappa-B (NF-κB), mitogen-activated protein kinase (MAPK), nuclear erythroid-related factor 2 (Nrf2), general controlled nonrepressed kinase 2 (GCN2), and angiotensin-converting enzyme 2 (ACE2).

Baicalein ameliorates TNBS-induced colitis by suppressing TLR4/MyD88 signaling cascade and NLRP3 inflammasome activation in mice

Baicalein (5,6,7-trihydroxyflavone), a predominant bioactive component isolated from the root of Scutellaria baicalensis Georgi, has established potent anti-inflammatory activity via multi-targeted mechanisms. However, little is known about the effect of baicalein on 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis, which shares pathology related to human Crohn’s disease (CD). The present study demonstrated that baicalein alleviated the severity of TNBS-induced colitis in mice by decreasing the activity of myeloperoxidase (MPO) and the expression of pro-inflammatory mediators. The decline in the activation of nuclear factor-kappa B (NF-κB) and p38 mitogen-activated protein kinase (MAPK) correlated with a decrease in the expression of mucosal toll-like receptor 4 (TLR4) and its adaptor myeloid differentiation factor 88 (MyD88). In vitro, baicalein down-regulated the TLR4/MyD88 signaling cascades (NF-κB and MAPKs) in lipopolysaccharide (LPS)-stimulated macrophages. At the upstream level, baicalein bound to the hydrophobic region of the myeloid differentiation protein-2 (MD-2) pocket and inhibited the formation of the LPS-induced MD-2/TLR4 complex. Furthermore, baicalein reduced NOD-like receptor 3 (NLRP3) inflammasome activation and downstream interleukin-1β expression in a dose-dependent manner. Our study provided evidence for the first time that baicalein attenuated TNBS-induced colitis, at least in part, via inhibition of TLR4/MyD88 signaling cascade as well as inactivation of NLRP3 inflammasome.

The Impact of Western Diet and Nutrients on the Microbiota and Immune Response at Mucosal Interfaces

Recent findings point toward diet having a major impact on human health. Diets can either affect the gut microbiota resulting in alterations in the host’s physiological responses or by directly targeting the host response. The microbial community in the mammalian gut is a complex and dynamic system crucial for the development and maturation of both systemic and mucosal immune responses. Therefore, the complex interaction between available nutrients, the microbiota, and the immune system are central regulators in maintaining homeostasis and fighting against invading pathogens at mucosal sites. Westernized diet, defined as high dietary intake of saturated fats and sucrose and low intake of fiber, represent a growing health risk contributing to the increased occurrence of metabolic diseases, e.g., diabetes and obesity in countries adapting a westernized lifestyle. Inflammatory bowel diseases (IBD) and asthma are chronic mucosal inflammatory conditions of unknown etiology with increasing prevalence worldwide. These conditions have a multifactorial etiology including genetic factors, environmental factors, and dysregulated immune responses. Their increased prevalence cannot solely be attributed to genetic considerations implying that other factors such as diet can be a major contributor. Recent reports indicate that the gut microbiota and modifications thereof, due to a consumption of a diet high in saturated fats and low in fibers, can trigger factors regulating the development and/or progression of both conditions. While asthma is a disease of the airways, increasing evidence indicates a link between the gut and airways in disease development. Herein, we provide a comprehensive review on the impact of westernized diet and associated nutrients on immune cell responses and the microbiota and how these can influence the pathology of IBD and asthma.

The Roles of Glutamine in the Intestine and Its Implication in Intestinal Diseases

Glutamine, the most abundant free amino acid in the human body, is a major substrate utilized by intestinal cells. The roles of glutamine in intestinal physiology and management of multiple intestinal diseases have been reported. In gut physiology, glutamine promotes enterocyte proliferation, regulates tight junction proteins, suppresses pro-inflammatory signaling pathways, and protects cells against apoptosis and cellular stresses during normal and pathologic conditions. As glutamine stores are depleted during severe metabolic stress including trauma, sepsis, and inflammatory bowel diseases, glutamine supplementation has been examined in patients to improve their clinical outcomes. In this review, we discuss the physiological roles of glutamine for intestinal health and its underlying mechanisms. In addition, we discuss the current evidence for the efficacy of glutamine supplementation in intestinal diseases.

Glutamine and the regulation of intestinal permeability: from bench to bedside

PURPOSE OF REVIEW

Glutamine is the most abundant amino acid in plasma and plays a key role in maintaining the integrity of intestinal barrier.

RECENT FINDINGS

Experimental studies showed that glutamine is able to modulate intestinal permeability and tight junction protein expression in several conditions. Recent articles underlined its putative beneficial role in gastrointestinal disorders such as irritable bowel syndrome.

SUMMARY

Glutamine is a major nutrient to maintain intestinal barrier function in animals and humans. Depletion of glutamine results in villus atrophy, decreased expression of tight junction proteins and increased intestinal permeability. Moreover, glutamine supplementation can improve gut barrier function in several experimental conditions of injury and in some clinical situations. Furthermore, preventive effects of glutamine in experimental models of intestinal injuries have been recently reported. Despite promising data in experimental models, further studies are needed to evaluate glutamine supplementation in clinical practice.

Disease Severity and Immune Activity Relate to Distinct Interkingdom Gut Microbiome States in Ethnically Distinct Ulcerative Colitis Patients

Significant gut microbiota heterogeneity exists among ulcerative colitis (UC) patients, though the clinical implications of this variance are unknown. We hypothesized that ethnically distinct UC patients exhibit discrete gut microbiotas with unique metabolic programming that differentially influence immune activity and clinical status. Using parallel 16S rRNA and internal transcribed spacer 2 sequencing of fecal samples (UC, 30; healthy, 13), we corroborated previous observations of UC-associated bacterial diversity depletion and demonstrated significant Saccharomycetales expansion as characteristic of UC gut dysbiosis. Furthermore, we identified four distinct microbial community states (MCSs) within our cohort, confirmed their existence in an independent UC cohort, and demonstrated their coassociation with both patient ethnicity and disease severity. Each MCS was uniquely enriched for specific amino acid, carbohydrate, and lipid metabolism pathways and exhibited significant luminal enrichment of the metabolic products of these pathways. Using a novel ex vivo human dendritic cell and T-cell coculture assay, we showed that exposure to fecal water from UC patients caused significant Th2 skewing in CD4⁺ T-cell populations compared to that of healthy participants. In addition, fecal water from patients in whom their MCS was associated with the highest level of disease severity induced the most dramatic Th2 skewing. Combined with future investigations, these observations could lead to the identification of highly resolved UC subsets based on defined microbial gradients or discrete microbial features that may be exploited for the development of novel, more effective therapies.

Despite years of research, the etiology of UC remains enigmatic. Diagnosis is difficult and the patient population heterogeneous, which represents a significant barrier to the development of more effective, tailored therapy. In this study, we demonstrate the clinical utility of the gut microbiome in stratifying UC patients by identifying the existence of four distinct interkingdom pathogenic microbiotas within the UC patient population that are compositionally and metabolically distinct, covary with clinical markers of disease severity, and drive discrete CD4⁺ T-cell expansions ex vivo. These findings offer new insight into the potential value of the gut microbiome as a tool for subdividing UC patients, opening avenues to the development of more personalized treatment plans and targeted therapies.

Food, nutrients and nutraceuticals affecting the course of inflammatory bowel disease

Inflammatory bowel diseases (ulcerative colitis; Crohn's disease) are debilitating relapsing inflammatory disorders affecting the gastrointestinal tract, with deleterious effect on quality of life, and increasing incidence and prevalence. Mucosal inflammation, due to altered microbiota, increased intestinal permeability and immune system dysfunction underlies the symptoms and may be caused in susceptible individuals by different factors (or a combination of them), including dietary habits and components. In this review we describe the influence of the Western diet, obesity, and different nutraceuticals/functional foods (bioactive peptides, phytochemicals, omega 3-polyunsaturated fatty acids, vitamin D, probiotics and prebiotics) on the course of IBD, and provide some hints that could be useful for nutritional guidance. Hopefully, research will soon offer enough reliable data to slow down the spread of the disease and to make diet a cornerstone in IBD therapy.

The anti-inflammatory effect and potential mechanism of cardamonin in DSS-induced colitis

Cardamonin is a naturally occurring chalcone with strong anti-inflammatory activity. However, the direct effect of cardamonin on intestinal inflammation remains elusive. In the present study, we found that cardamonin markedly ameliorated dextran sulfate sodium-induced mouse body weight loss, diarrhea, colon shortening, spleen swelling, and histological damage, which correlated with a decline in the activity of myeloperoxidase and the production of nitric oxide, tumor necrosis factor-α and interleukin-6 in the colon. The upregulation of toll-like receptor 4 after dextran sulfate sodium treatment was associated with an increase in the activation of myeloid differentiation factor 88, interleukin-1 receptor-associated kinase-1, nuclear factor-κB (NF-κB) p65, inhibitor κBα, and inhibitor κB kinase-α/β, as well as the mitogen-activated protein kinase molecules of extracellular signal-regulated kinase and c-Jun NH2-terminal kinase, and this upregulation was reversed by cardamonin administration. Moreover, cardamonin blocked the nuclear translocation of NF-κB p65, inhibited NF-κB-luciferase activity, and downregulated NF-κB target genes expression. The present study clearly demonstrates a beneficial effect of cardamonin on experimental inflammatory bowel disease via a mechanism associated with suppression of toll-like receptor 4 expression and inactivation of NF-κB and mitogen-activated protein kinase pathways. This study may give insight into the further evaluation of the therapeutic potential of cardamonin or its derivatives for human inflammatory bowel disease.

Longitudinal study of circulating protein biomarkers in inflammatory bowel disease

Inflammatory bowel diseases (IBDs) are chronic and progressive inflammatory disorders of the gastrointestinal tract. In IBD, protein serological biomarkers could be relevant tools for assessing disease activity, performing early-stage diagnosis and managing the treatment. Using the interleukin-10 knockout (IL-10(-/-)) mouse, a model that develops a time-dependent IBD-like disorder that predominates in the colon; we performed longitudinal studies of circulating protein biomarkers in IBD. Circulating protein profiles in serum samples collected from 30-, 93-, to 135-day-old IL-10(-/-) mice were investigated using two-dimensional differential gel electrophoresis and MALDI-TOF/TOF tandem mass spectrometry. A total of 15 different proteins were identified and confirmed by ELISA and Western blot to be differentially accumulated in serum samples from mid- to late-stage IL-10(-/-) mice compared to early non-inflamed IL-10(-/-) mice. The use of another model of colitis and an extra-intestinal inflammation model validated this biomarker panel and demonstrated that comprised some global inflammatory markers, some intestinal inflammation-specific markers and some chronic intestinal inflammation markers. Statistical analyses using misclassification error rate charts validated the use of these identified proteins as powerful biomarkers of colitis. Unlike standard biomarker screening studies, our analyses identified a panel of proteins that allowed the definition of protein signatures that reflect colitis status.

BIOLOGICAL SIGNIFICANCE

Crohn's disease (CD) and ulcerative colitis (UC) are the most common inflammatory bowel diseases (IBDs) occurring in humans. The major current diagnosis tool is colonoscopy, which is invasive and could lead to false diagnosis. The emergence of serological biomarkers enables the use of new diagnosis tools such as protein signatures for IBD diagnosis/management. Using 2D-DIGE coupled to mass spectrometry, our longitudinal study in a mouse model of colitis identified a signature of protein biomarkers for specific stages of disease.

Glutamine supplementation attenuates expressions of adhesion molecules and chemokine receptors on T cells in a murine model of acute colitis

Background. Migration of T cells into the colon plays a major role in the pathogenesis in inflammatory bowel disease. This study investigated the effects of glutamine (Gln) supplementation on chemokine receptors and adhesion molecules expressed by T cells in mice with dextran sulfate sodium- (DSS-) induced colitis. Methods. C57BL/6 mice were fed either a standard diet or a Gln diet replacing 25% of the total nitrogen. After being fed the diets for 5 days, half of the mice from both groups were given 1.5% DSS in drinking water to induce colitis. Mice were killed after 5 days of DSS exposure. Results. DSS colitis resulted in higher expression levels of P-selectin glycoprotein ligand- (PSGL-) 1, leukocyte function-associated antigen- (LFA-) 1, and C-C chemokine receptor type 9 (CCR9) by T helper (Th) and cytotoxic T (Tc) cells, and mRNA levels of endothelial adhesion molecules in colons were upregulated. Gln supplementation decreased expressions of PSGL-1, LFA-1, and CCR9 by Th cells. Colonic gene expressions of endothelial adhesion molecules were also lower in Gln-colitis mice. Histological finding showed that colon infiltrating Th cells were less in the DSS group with Gln administration. Conclusions. Gln supplementation may ameliorate the inflammation of colitis possibly via suppression of T cell migration.

Serum amino acids profile and the beneficial effects of L-arginine or L-glutamine supplementation in dextran sulfate sodium colitis

This study was conducted to investigate serum amino acids profile in dextran sulfate sodium (DSS)-induced colitis, and impacts of graded dose of arginine or glutamine supplementation on the colitis. Using DSS-induced colitis model, which is similar to human ulcerative colitis, we determined serum profile of amino acids at day 3, 7, 10 and 12 (5 days post DSS treatment). Meanwhile, effects of graded dose of arginine (0.4%, 0.8%, and 1.5%) or glutamine (0.5%, 1.0% and 2.0%) supplementation on clinical parameters, serum amino acids, colonic tight junction proteins, colonic anti-oxidative indicators [catalase, total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px)], colonic pro-inflammatory cytokines [interleukin-1 beta (IL-1β), IL-6, IL-17 and tumor necrosis factor alpha (TNF-α)] in DSS-induced colitis were fully analyzed at day 7 and 12. Additionally, the activation of signal transduction pathways, including nuclear factor kappa B (NF-κB), mitogen-activated protein kinases (MAPK), phosphoinositide-3-kinases (PI3K)/PI3K-protein kinase B (Akt), and myosin light chain kinase (MLCK)-myosin light chain (MLC20), were analyzed using immunoblotting. Serum amino acids analysis showed that DSS treatment changed the serum contents of amino acids, such as Trp, Glu, and Gln (P<0.05). Dietary arginine or glutamine supplementation had significant (P<0.05) influence on the clinical and biochemical parameters (T-SOD, IL-17 and TNF-α) in colitis model. These results were associated with colonic NF-κB, PI3K-Akt and MLCK signaling pathways. In conclusion, arginine or glutamine could be a potential therapy for intestinal inflammatory diseases.

Paeoniflorin abrogates DSS-induced colitis via a TLR4-dependent pathway

Paeonia lactiflora Pall is one of the most well-known herbs in China, Korea, and Japan for more than 1,200 years. Paeoniflorin, the major bioactive component of peony root, has recently been reported to have anticolitic activity. However, the underlying molecular mechanism is unclear. The present study was to explore the possible mechanism of paeoniflorin in attenuating dextran sulfate sodium (DSS)-induced colitis. Pre- and coadministration of paeoniflorin significantly reduced the severity of colitis and resulted in downregulation of several inflammatory parameters in the colon, including the activity of myeloperoxidase (MPO), the levels of TNF-α and IL-6, and the mRNA expression of proinflammatory mediators (MCP-1, Cox2, IFN-γ, TNF-α, IL-6, and IL-17). The decline in the activation of NF-κB p65, ERK, JNK, and p38 MAPK correlated with a decrease in mucosal Toll-like receptor 4 (TLR4) but not TLR2 or TLR5 expression. In accordance with the in vivo results, paeoniflorin downregulated TLR4 expression, blocked nuclear translocation of NF-κB p65, and reduced the production of IL-6 in LPS-stimulated mouse macrophage RAW264.7 cells. Transient transfection assay performed in LPS-stimulated human colon cancer HT-29 cells indicated that paeoniflorin inhibits NF-κB transcriptional activity in a dose-dependent manner. TLR4 knockdown and overexpression experiments demonstrated a requirement for TLR4 in paeoniflorin-mediated downregulation of inflammatory cytokines. Thus, for the first time, the present study indicates that paeoniflorin abrogates DSS-induced colitis via decreasing the expression of TLR4 and suppressing the activation of NF-κB and MAPK pathways.

Mitochondria: sensors and mediators of innate immune receptor signaling

By integrating stress signals with inputs from other cellular organelles, eukaryotic mitochondria are dynamic sensing systems that can confer substantial impact on innate immune signaling in both health and disease. This review highlights recently discovered elements of innate immune receptor signaling (TLR, RLR, NLR, and CLR) associated with mitochondrial function and discusses the role of mitochondria in the initiation and/or manifestation of inflammatory diseases and disorders. We also highlight the role of mitochondria as therapeutic targets for inflammatory disease.

Seeing citrulline: development of a phenylglyoxal-based probe to visualize protein citrullination

Protein arginine deiminases (PADs) catalyze the hydrolysis of peptidyl arginine to form peptidyl citrulline. Abnormally high PAD activity is observed in a host of human diseases, but the exact role of protein citrullination in these diseases and the identities of specific citrullinated disease biomarkers remain unknown, largely because of the lack of readily available chemical probes to detect protein citrullination. For this reason, we developed a citrulline-specific chemical probe, rhodamine-phenylglyoxal (Rh-PG), which we show can be used to investigate protein citrullination. This methodology is superior to existing techniques because it possesses higher throughput and excellent sensitivity. Additionally, we demonstrate that this probe can be used to determine the kinetic parameters for a number of protein substrates, monitor drug efficacy, and identify disease biomarkers in an animal model of ulcerative colitis that displays aberrantly increased PAD activity.