Anti-inflammatory Effects of Poly-L-lysine in Intestinal Mucosal System Mediated by Calcium-Sensing Receptor Activation

Effects of dietary supplement of ε-polylysine hydrochloride on laying performance, egg quality, serum parameters, organ index, intestinal morphology, gut microbiota and volatile fatty acids in laying hens

BACKGROUND

ε-polylysine hydrochloride (ε-PLH) is a naturally occurring antimicrobial peptide extensively utilized in the food and medical industries. However, its impact on animal husbandry remains to be further explored. Therefore, the present study aimed to determine the effect of ε-PLH on laying hens' health and laying performance.

RESULTS

Dietary supplementation with ε-PLH to the diet significantly increased average egg weight during weeks 1-8. Meanwhile, compared with the control group, supplementation with ε-PLH decreased the feed egg ratio during weeks 9-12 and egg breakage rate during weeks 9-16 ，whereas it increased eggshell strength during weeks 1-4 and 13-16 . The ε-PLH 0.05% group increased yolk percentage during weeks 5-8 and yolk color during weeks 1-4 . Furthermore, ε-PLH supplementation significantly increased the concentrations of total protein, albumin, globulin and reproductive hormones estradiol, as well as decreased interleukin-1 beta and malondialdehyde in the serum. Compared with the control group, supplementation with 0.05% ε-PLH significantly increased the relative abundance of Cyanobacteria and Gastranaerophilales and decreased the abundance of Desulfovibrio and Streptococcus in the cecum microbiota. In addition, ε-PLH 0.1% supplementation also increased acetic acid content in the cecum.

CONCLUSION

Dietary supplementation with ε-PLH has a positive impact on both productive performance and egg quality in laying hens. Furthermore, ε-PLH can also relieve inflammation by promoting the immunity and reducing oxidative damage during egg production. ε-PLH has been shown to improve intestinal morphology, gut microbial diversity and intestinal health. © 2023 Society of Chemical Industry.

The calcium-sensing receptor modulates the prostaglandin E2 pathway in intestinal inflammation

Introduction: The prostaglandin E2 (PGE2) pathway is one of the main mediators of intestinal inflammation. As activation of the calcium-sensing receptor (CaSR) induces expression of inflammatory markers in the colon, we assessed the impact of the CaSR on the PGE2 pathway regulation in colon cancer cells and the colon in vitro and in vivo. Methods and Results: We treated CaSR-transfected HT29 and Caco-2 colon cancer cell lines with different orthosteric ligands or modulators of the CaSR and measured gene expression and PGE2 levels. In CaSR-transfected HT29CaSR-GFP and Caco-2CaSR-GFP cells, the orthosteric CaSR ligand spermine and the positive allosteric CaSR modulator NPS R-568 both induced an inflammatory state as measured by IL-8 gene expression and significantly increased the expression of the PGE2 pathway key enzymes cyclooxygenase (COX)-2 and/or prostaglandin E2 synthase 1 (PGES-1). Inhibition of the CaSR with the calcilytic NPS 2143 abolished the spermine- and NPS R-568-induced pro-inflammatory response. Interestingly, we observed cell-line specific responses as e.g. PGES-1 expression was affected only in HT29CaSR-GFP but not in Caco-2CaSR-GFP cells. Other genes involved in the PGE2 pathway (COX-1, or the PGE2 receptors) were not responsive to the treatment. None of the studied genes were affected by any CaSR agonist in GFP-only transfected HT29GFP and Caco-2GFP cells, indicating that the observed gene-inducing effects of spermine and R-568 were indeed mediated by the CaSR. In vivo, we had previously determined that treatment with the clinically approved calcimimetic cinacalcet worsened symptoms in a dextran sulfate sodium (DSS)-induced colitis mouse model. In the colons of these mice, cinacalcet significantly induced gene expression of PGES-2 and the EP3 receptor, but not COX-2; while NPS 2143 increased the expression of the PGE2-degrading enzyme 15-hydroxyprostaglandin dehydrogenase (15-PGDH). Importantly, neither treatment had any effect on the colons of non-DSS treated mice. Discussion: Overall, we show that activation of the CaSR induces the PGE2 pathway, albeit with differing effects in vitro and in vivo. This may be due to the different microenvironment in vivo compared to in vitro, specifically the presence of a CaSR-responsive immune system. Since calcilytics inhibit ligand-mediated CaSR signaling, they may be considered for novel therapies against inflammatory bowel disease.

Anti-inflammatory role of extracellular l-arginine through calcium sensing receptor in human renal proximal tubular epithelial (HK-2) cells

Renal tubular epithelial cells are capable of synthesizing interleukins (IL) in response to a variety of proinflammatory cytokines. Moreover, elevated urinary levels of IL have been shown in patients with various forms of nephritic diseases. However, the underlying intracellular signaling mechanism is unclear. Here we show the immunological signaling role of l-Arginine (l-Arg) through Ca2+-sensing receptor (CaSR) in human kidney 2 (HK-2) renal proximal tubular epithelial cells, using Ca2+ imaging and patch clamp techniques and its mechanistic link to the downstream cellular function. Both pharmacological and siRNA inhibitors support the activation CaSR by extracellular l-Arg to induced Ca2+ entry via a Transient receptor potential canonical (TRPC) channel in HK-2 cells mainly through the receptor operated Ca2+ entry (ROCE). Activation of CaSR by l-Arg led to the rise in p-p38/p38 expression suggesting [Ca2+]i as a regulator for p38-signaling pathways. Notably, l-Arg activated CaSR-induced Ca2+ signaling reduced the expressions of key fibrotic, inflammatory, and apoptotic genes, suggesting its nephroprotective role via Ca2+ signaling through CaSR in HK-2 cells. Since we found that the IL-6 expressions were inversely proportional to the increasing concentrations of l-Arg in HK-2 cells, we measured the release of IL-6, which steadily decreased as the concentrations of l-Arg were elevated. Taken together, extracellular l-Arg is a negative regulator for IL-6-induced inflammatory process, through the activation of CaSR and TRPC channel by ROCE pathway and can have a potential to alleviate inflammatory renal diseases.

Freshwater Clam Extract Attenuates Indomethacin-Induced Gastric Damage In Vitro and In Vivo

Contemporary pharmacological studies have reported that freshwater clam (Corbicula fluminea) can provide a broad spectrum of bioactivities, including antioxidant, anticancer, antihypertensive, hepatoprotective, and hypocholesterolemic effects. The aim of this study was to evaluate the gastroprotective effects of water extract of freshwater clam (WEC) on indomethacin (IND)-induced gastric mucosal cell damage in vitro and gastric ulcer in vivo. The cell viability of rat gastric mucosa RGM-1 cells was markedly decreased by 0.8 mM of IND treatment, and pre-treated with various concentration of WEC significantly restored IND-induced cell damage in a dose-dependent manner. WEC also significantly attenuated the elevated reactive oxygen species (ROS) levels, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, and nuclear factor-κB (NF-κB) p65 nuclear translocation induced by IND. In the in vivo study, IND caused severe gastric ulcer in Wistar rats, while WEC pretreatment effectively reduced the ulcer area and edema in the submucosa. We found that WEC significantly restored glutathione (GSH) content in gastric mucosa in a dose-dependent manner (p < 0.05). The reduction of prostaglandin E2 (PGE2) caused by IND was also improved with higher doses of WEC administration. Moreover, the overexpression of COX-2, iNOS, and tumor necrosis factor-α (TNF-α) proteins in gastric mucosa was downregulated by administration of WEC. Consequently, WEC can be used as a potential nutritional supplement to improve NSAIDs-caused gastric mucosal lesions.

The calcium-sensing receptor in inflammation: Recent updates

The Calcium-Sensing Receptor (CaSR) is a member of the class C of G-proteins coupled receptors (GPCRs), it plays a pivotal role in calcium homeostasis by directly controlling calcium excretion in the kidneys and indirectly by regulating parathyroid hormone (PTH) release from the parathyroid glands. The CaSR is found to be ubiquitously expressed in the body, playing a plethora of additional functions spanning from fluid secretion, insulin release, neuronal development, vessel tone to cell proliferation and apoptosis, to name but a few. The present review aims to elucidate and clarify the emerging regulatory effects that the CaSR plays in inflammation in several tissues, where it mostly promotes pro-inflammatory responses, with the exception of the large intestine, where contradictory roles have been recently reported. The CaSR has been found to be expressed even in immune cells, where it stimulates immune response and chemokinesis. On the other hand, CaSR expression seems to be boosted under inflammatory stimulus, in particular, by pro-inflammatory cytokines. Because of this, the CaSR has been addressed as a key factor responsible for hypocalcemia and low levels of PTH that are commonly found in critically ill patients under sepsis or after burn injury. Moreover, the CaSR has been found to be implicated in autoimmune-hypoparathyroidism, recently found also in patients treated with immune-checkpoint inhibitors. Given the tight bound between the CaSR, calcium and vitamin D metabolism, we also speculate about their roles in the pathogenesis of severe acute respiratory syndrome coronavirus-19 (SARS-COVID-19) infection and their impact on patients' prognosis. We will further explore the therapeutic potential of pharmacological targeting of the CaSR for the treatment and management of aberrant inflammatory responses.

Mechanisms of action of anti-inflammatory proteins and peptides with anti-TNF-alpha activity and their effects on the intestinal barrier: A systematic review

Several studies in animal models of intestinal inflammation have been performed with the aim of understanding the mechanisms of action of anti-inflammatory proteins and peptides that reduce TNF-α. In order to present the best targets, effects and strategies for the treatment of intestinal inflammation in experimental models, this systematic review (SR) aimed to answer the following question: what are the mechanisms of action of molecules with anti-TNF-α activity on the intestinal barrier? The SR protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO, number CRD42019131862) and guided by the methodological procedures used for the elaboration of the SR. Articles that were part of the SR were selected considering the eligibility criteria according to the PICO (Population, Intervention, Comparison/Control and Outcomes) and were searched in the PubMed, Scopus, Web of Science, Excerpta Medica Database (EMBASE) and ScienceDirect databases. Twenty-five articles reporting studies in rats and mice were selected and the risk of bias was assessed using the tool from the SYstematic Review Center for Laboratory Animal Experimentation (SYRCLE). A descriptive synthesis of the results obtained was carried out. Based on the results, the anti-inflammatory molecules that reduced TNF-α acted mainly on the TNF-TNFR1/TNFR2 and TLR4/MD2 complex signaling pathways, and consequently on the NF-κB pathway. This improved the aspects of the inflammatory diseases studied. In addition, these mechanisms also improved the macroscopic, histological and permeability aspects in the intestine of the animals. These findings point to the potential of protein and peptide molecules that act on inflammatory pathways for medical applications with specific and promising strategic targets, aiming to improve inflammatory diseases that affect the intestine. This systematic review also highlights the need for more details during the methodological description of preclinical studies, since this was a limitation found.

Alleviation of dry eye syndrome with one dose of antioxidant, anti-inflammatory, and mucoadhesive lysine-carbonized nanogels

Most dry eye syndromes (DES) are caused by oxidative stress and an overactive inflammatory response, leading to tear deficiency and excessive tear evaporation. Conventional eye drops for DES treatment require high doses and frequent administration due to their insufficient precorneal residence time. To overcome these problems, in this study, we have developed carbonized nanogels (CNGs) via the straightforward pyrolysis of lysine hydrochloride (Lys) to provide a long-lasting eye drop formulation for topical DES therapy. This methodology thermally converts Lys-into nitrogen-doped crosslinked polymers with embedded nanographitic structures, which enable efficient free radical scavenging. The cationic and crosslinked polymeric features of the Lys-CNGs also prolong the precorneal retention time and improve ocular bioavailability. These Lys-CNGs exhibit high biocompatibility with corneal epithelial cells both in vitro and in vivo, indicating their safety as eye drops. In a DES rabbit model, a single dose of Lys-CNGs (50 µg mL^-1) can effectively alleviate the signs of DES within 4 days, whereas multiple treatments of 10-fold higher concentration of cyclosporine A are needed to achieve similar therapeutic effects (one dose every 12 h; 500 µg mL^-1). The topical administration of Lys-CNGs enable a reduced therapeutic dose and extended dosing interval, thereby demonstrating a superior therapeutic efficacy compared to the commercial cyclosporine A eye drops. These Lys-CNGs, which exhibit significant free radical scavenging, anti-inflammatory activity, high biocompatibility, and a remarkable ocular bioadhesive property, hold great potential as a long-lasting eye drop formulation for the treatment of dry eye disease. STATEMENT OF SIGNIFICANCE: Multifunctional nanobiomaterial-based eye drops can render an ideal pharmaceutical formulation for the treatment of a variety of ocular surface diseases. To our knowledge, this is the first report describing the development of carbonized nanogels as topically administered therapeutics for alleviating dry eye syndrome (DES). We present evidence that the thermal transformation of lysine hydrochloride into carbonized nanogels (Lys-CNGs) endows superior antioxidant, anti-inflammatory, and bioadhesive properties. While a single dose of Lys-CNGs (50 µg mL^-1) is sufficient to relieve the symptoms of DES for 4 days, multiple treatments of 10-fold higher concentration of commercially available cyclosporine eye drops are needed to achieve similar therapeutic outcomes (one dose every 12 h; 500 µg mL^-1), suggesting an effective and long-lasting ocular carbonized nanomedicine.

Cubic multi-ions-doped Na2TiO3 nanorod-like coatings: Structure-stable, highly efficient platform for ions-exchanged release to immunomodulatory promotion on vascularized bone apposition

The dissolution-derived release of bioactive ions from ceramic coatings on metallic implants, despite improving osseointegration, renders a concern on the interfacial breakdown of the metal/coating/bone system during long-term service. Consequently, persistent efforts to seek alternative strategies instead of dissolution-derived activation are pressingly carrying out. Inspired by bone mineral containing ions as Ca²⁺, Mg²⁺, Sr²⁺ and Zn²⁺, here we hydrothermally grew the quadruple ions co-doped Na₂TiO₃ nanorod-like coatings. The co-doped ions partially substitute Na⁺ in Na₂TiO₃, and can be efficiently released from cubic lattice via exchange with Na⁺ in fluid rather than dissolution, endowing the coatings superior long-term stability of structure and bond strength. Regulated by the coatings-conditioned extracellular ions, TLR4-NFκB signalling is enhanced to act primarily in macrophages (MΦs) at 6 h while CaSR-PI3K-Akt1 signalling is potentiated to act predominately since 24 h, triggering MΦs in a M1 response early and then in a M2 response to sequentially secrete diverse cytokines. Acting on endothelial and mesenchymal stem cells with the released ions and cytokines, the immunomodulatory coatings greatly promote Type-H (CD31^hiEmcn^hi) angiogenesis and osteogenesis in vitro and in vivo, providing new insights into orchestrating insoluble ceramics-coated implants for early vascularized osseointegration in combination with long-term fixation to bone.

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Co-doped Ca²⁺, Mg²⁺, Sr²⁺ and Zn²⁺ in Na₂TiO₃ efficiently release via ion exchange.

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QID elevates extracellular concentrations of the ions and MΦ intracellular [Ca²⁺].

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Co-doped Na₂TiO₃ coatings promote immunomodulatory apposition of vascularized bone.

"Radio-Protective Effect of Aminocaproic Acid in Human Spermatozoa"

BACKGROUND

The negative effects of ionizing radiation on organs and the reproductive system are well known and documented. Exposure to gamma radiation can lead to oligospermia, azoospermia and DNA damage. Up to date, there is no effective pharmaceutical compound for protecting the male reproductive system and sperm.

OBJECTIVE

This study aimed at investigating the ability of Ɛ-aminocaproic acid (EACA) to prevent the damage of human spermatozoa and DNA induced by ionizing radiation.

MATERIALS AND METHODS

Sperm samples were obtained from healthy volunteers (35 men; 31.50 ± 7.34 years old). There were 4 experimental groups: 1) control group (CG), 2) group exposed to maximal radiation dose 67.88 mGy (RMAX), 3) low-dose radiation (minimal) 22.62 mGy (RMIN), and 4) group treated with radiation (67.88 mGy) and EACA (dose 50 ng/ml). Sperm motility, viability, and DNA damage were assessed.

RESULTS

We observed a significant decrease in total sperm motility of the RMAX group compared to CG (p < 0.05). Sperm viability in the RMAX group was also reduced in comparison to the control (p < 0.05). A significant increase in DNA fragmentation was detected in the RMAX group. The results demonstrated that the treatment of sperm with EACA led to a decrease in the fragmentation of the sperm DNA (compared to the RMAX group) (p < 0.05).

CONCLUSION

The results indicate that EACA effectively protects human spermatozoa from DNA damage induced by ionizing radiation. Treatment of spermatozoa with EACA led to the preservation of cell motility, viability, and DNA integrity upon radiation exposure.

Sensation of dietary nutrients by gut taste receptors and its mechanisms

Nutrients sensing is crucial for fundamental metabolism and physiological functions, and it is also an essential component for maintaining body homeostasis. Traditionally, basic taste receptors exist in oral cavity to sense sour, sweet, bitter, umami, salty and et al. Recent studies indicate that gut can sense the composition of nutrients by activating relevant taste receptors, thereby exerting specific direct or indirect effects. Gut taste receptors, also named as intestinal nutrition receptors, including at least bitter, sweet and umami receptors, have been considered to be activated by certain nutrients and participate in important intestinal physiological activities such as eating behavior, intestinal motility, nutrient absorption and metabolism. Additionally, gut taste receptors can regulate appetite and body weight, as well as maintain homeostasis via targeting hormone secretion or regulating the gut microbiota. On the other hand, malfunction of gut taste receptors may lead to digestive disorders, and then result in obesity, type 2 diabetes and gastrointestinal diseases. At present, researchers have confirmed that the brain-gut axis may play indispensable roles in these diseases via the secretion of brain-gut peptides, but the mechanism is still not clear. In this review, we summarize the current observation of knowledge in gut taste systems in order to shed light on revealing their important nutritional functions and promoting clinical implications.

Phloretin is protective in a murine salmonella enterica serovar typhimurium infection model

Salmonella, an important zoonotic pathogen, causes significant morbidity and mortality in both humans and animals. Phloretin mainly isolated from strawberries and apples has the effects of treating inflammation and pathogenic bacteria, but its protective efficacy and mechanism of action against Salmonella spp. are less clear. In this study, we found that phloretin alleviated body weight loss, colon length shortening, and colonic pathological damage caused by S. Typhimurium. Phloretin also decreased S. Typhimurium translocation to the mesenteric lymph nodes (MLN) and spleen. Further mechanism studies showed that phloretin significantly inhibited inflammation and oxidative stress levels in the colonic tissue. Phloretin also prevented S. Typhimurium-mediated impairment in the colon epithelium barrier by the regulation ZO-1 and occludin levels. Interestingly, phloretin did not inhibit S. typhimurium growth in vitro, but reduced the internalization of S. Typhimurium into Caco-2 cells. Taken together, these findings indicated that phloretin may be a new dietary strategy to combat the disease.

Tryptophan Promotes Intestinal Immune Defense through Calcium-Sensing Receptor (CaSR)-Dependent Metabolic Pathways

The gastrointestinal tract forms a robust line of defense against invading pathogens through the production of endogenous antimicrobial peptides (AMPs), which are crucial molecules of the innate defense system. Tryptophan could modulate intestinal immunity through promoting the expression of AMPs. However, the precise mechanism needs to be further clarified. In this study, we show that treatment with tryptophan for 24 h triggers (p < 0.05) the expression of porcine β-defensin (pBD) 1 (62.67 ± 3.10 pg/mL) and pBD2 (74.41 ± 1.33 pg/mL) in the porcine intestinal epithelial cells (IPEC-J2) though calcium-sensing receptor (CaSR)-tryptophan metabolic pathways. Meanwhile, tryptophan alleviates (p < 0.05) intestinal inflammation induced by lipopolysaccharide (LPS) through induction of the defensins and activation of the CaSR-AMP-activated protein kinase (AMPK) pathways in vitro and in vivo. Moreover, the activation of CaSR induces the expression of defensins and decreases the levels of IL-1β (75.26 ± 2.74 pg/mL) and TNF-α (449.8 ± 23.31 pg/mL) induced by LPS (p < 0.05). Importantly, tryptophan maintains kynurenine homeostasis through the activation of CaSR during the inflammatory response. To that end, the work identifies a regulatory circuit between CaSR signaling and tryptophan metabolic pathways involved in the tryptophan-trigged AMP expression, which contributes to improving intestinal immune defense.

Stereo-Specific Modulation of the Extracellular Calcium-Sensing Receptor in Colon Cancer Cells

Pharmacological allosteric agonists (calcimimetics) of the extracellular calcium-sensing receptor (CaSR) have substantial gastro-intestinal side effects and induce the expression of inflammatory markers in colon cancer cells. Here, we compared the effects of both CaSR-specific (R enantiomers) and -unspecific (S enantiomers) enantiomers of a calcimimetic (NPS 568) and a calcilytic (allosteric CaSR antagonists; NPS 2143) to prove that these effects are indeed mediated via the CaSR, rather than via off-target effects, e.g., on β-adrenoceptors or calcium channels, of these drugs. The unspecific S enantiomer of NPS 2143 and NPS S-2143 was prepared using synthetic chemistry and characterized using crystallography. NPS S-2143 was then tested in HEK-293 cells stably transfected with the human CaSR (HEK-CaSR), where it did not inhibit CaSR-mediated intracellular Ca²⁺ signals, as expected. HT29 colon cancer cells transfected with the CaSR were treated with both enantiomers of NPS 568 and NPS 2143 alone or in combination, and the expression of CaSR and the pro-inflammatory cytokine interleukin 8 (IL-8) was measured by RT-qPCR and ELISA. Only the CaSR-selective enantiomers of the calcimimetic NPS 568 and NPS 2143 were able to modulate CaSR and IL-8 expression. We proved that pro-inflammatory effects in colon cancer cells are indeed mediated through CaSR activation. The non-CaSR selective enantiomer NPS S-2143 will be a valuable tool for investigations in CaSR-mediated processes.

Impact of food-derived bioactive peptides on gut function and health

The gastrointestinal tract (GIT) is the largest interface between our body and the environment. It is an organ system extending from the mouth to the anus and functions for food intake, digestion, transport and absorption of nutrients, meanwhile providing protection from environmental factors, like toxins, antigens, and pathogens. Diet is one of the leading factors modulating the function of the GIT. Bioactive peptides presenting naturally in food or derived from food proteins during digestion or processing have been revealed multifunctional in diverse biological processes, including maintaining gut health and function. This review summarizes the available evidence regarding the effects of food-derived bioactive peptides on gut function and health. Findings and insights from studies based on in vitro and animal models are discussed. The gastrointestinal mucosa maintains a delicate balance between immune tolerance to nutrients and harmful components, which is crucial for the digestive system's normal functions. Dietary bioactive peptides positively impact gastrointestinal homeostasis by modulating the barrier function, immune responses, and gut microbiota. However, there is limited clinical evidence on the safety and efficacy of bioactive peptides, much less on the applications of dietary peptides for the treatment or prevention of diseases related to the GIT. Further study is warranted to establish the applications of bioactive peptides in regulating gut health and function.

How Can a Polymeric Formula Induce Remission in Crohn's Disease Patients?

Crohn’s disease is an inflammatory bowel disease whose prevalence is increasing worldwide. Among medical strategies, dietary therapy with exclusive enteral nutrition is recommended as a first-line option, at least for children, because it induces clinical remission and mucosal healing. Modulen^®, a polymeric TGF-β2 enriched formula, has good palatability and is widely used. For the first time in the literature, this review outlines and discusses the clinical outcomes obtained with this therapy, as well as the potential mechanisms of action of its compounds. It can be explained by its TGF-β2 content, but also by its protein and lipid composition. Further well-designed studies are required to improve our knowledge and to optimize therapeutic strategies.

Polylysine-bilirubin conjugates maintain functional islets and promote M2 macrophage polarization

Macrophage polarization is one of the main factors contributing to the proinflammatory milieu of transplanted islets. It causes significant islet loss. Bilirubin exhibits protective effects during the islet transplantation process, but the mode of delivering drugs along with the islet graft has not yet been developed. In addition, it remains unclear whether bilirubin or its derivatives can modulate macrophage polarization during islet transplantation. Therefore, this study aimed to develop an ε-polylysine-bilirubin conjugate (PLL-BR) to encapsulate the islets for protection and to explore its macrophage modulation activities. In in vitro studies, the PLL-BR was shown to tightly adhere to the islet surface. It also exhibited enhanced cytoprotective effects against oxidative and inflammatory conditions by promoting M2-type macrophage polarization. In in vivo studies, the PLL-BR-protected islets successfully prolonged the euglycemia period in diabetic mice and accelerated the blood glucose clearance rate by maintaining the insulin secretion function. Compared to the untreated islets, the PLL-BR-encapsulated islets induced anti-inflammatory responses that were characterized by elevated levels of M2 macrophage markers and local vascularization. In conclusion, PLL-BR can be used as a tool for reprograming macrophage polarization while providing a more efficient immune protection for transplanted islets. STATEMENT OF SIGNIFICANCE: Macrophage polarization is one main factor that caused significant loss of transplanted islets. Bilirubin possesses protective effects toward pancreatic islet, but how to deliver the drug along with the islet graft has not yet been harnessed. More importantly, whether bilirubin or its derivatives could modulate macrophage polarization during the host rejections has also not been answered. In this study, we developed an ε-polylysine-bilirubin conjugate (PLL-BR) to encapsulate the islets and explore its role in macrophage modulation activities. PLL-BR could attach to the surface of islets and exerted high oxidation resistance and anti-inflammatory effect. For the first time, we demonstrate that bilirubin and its derivatives effectively promoted the M2-type macrophage polarization, and optimize the immune microenvironment for islets survival and function.

Effects of pharmacological calcimimetics on colorectal cancer cells over-expressing the human calcium-sensing receptor

The calcium-sensing receptor (CaSR) is a ubiquitously expressed multifunctional G protein-coupled receptor. Several studies reported that the CaSR plays an anti-inflammatory and anti-tumorigenic role in the intestine, and that it is down-regulated during colorectal carcinogenesis. We hypothesized that positive allosteric CaSR modulators (type II calcimimetics) selectively targeting the intestinal cells could be used for the treatment of intestinal pathologies. Therefore, the aim of this study was to determine the effect of pharmacological stimulation of CaSR on gene expression in vitro and on tumor growth in vivo. We stably transduced two colon cancer cell lines (HT29 and Caco2) with lentiviral vectors containing either the CaSR fused to GFP or GFP only. Using RNA sequencing, RT-qPCR experiments and ELISA, we determined that CaSR over-expression itself had generally little effect on gene expression in these cells. However, treatment with 1 μM of the calcimimetic NPS R-568 increased the expression of pro-inflammatory factors such as IL-23α and IL-8 and reduced the transcription of various differentiation markers in the cells over-expressing the CaSR. In vivo, neither the presence of the CaSR nor p.o. treatment of the animals with the calcimimetic cinacalcet affected tumor growth, tumor cell proliferation or tumor vascularization of murine HT29 xenografts. In summary, CaSR stimulation in CaSR over-expressing cells enhanced the expression of inflammatory markers in vitro, but was not able to repress colorectal cancer tumorigenicity in vivo. These findings suggest potential pro-inflammatory effects of the CaSR and type II calcimimetics in the intestine.

Anti-Inflammatory Potential of Cow, Donkey and Goat Milk Extracellular Vesicles as Revealed by Metabolomic Profile

In recent years, extracellular vesicles (EVs), cell-derived micro and nano-sized structures enclosed in a double-layer membrane, have been in the spotlight for their high potential in diagnostic and therapeutic applications. Indeed, they act as signal mediators between cells and/or tissues through different mechanisms involving their complex cargo and exert a number of biological effects depending upon EVs subtype and cell source. Being produced by almost all cell types, they are found in every biological fluid including milk. Milk EVs (MEVs) can enter the intestinal cells by endocytosis and protect their labile cargos against harsh conditions in the intestinal tract. In this study, we performed a metabolomic analysis of MEVs, from three different species (i.e., bovine, goat and donkey) by mass spectroscopy (MS) coupled with Ultrahigh-performance liquid chromatography (UHPLC). Metabolites, both common or specific of a species, were identified and enriched metabolic pathways were investigated, with the final aim to evaluate their anti-inflammatory and immunomodulatory properties in view of prospective applications as a nutraceutical in inflammatory conditions. In particular, metabolites transported by MEVs are involved in common pathways among the three species. These metabolites, such as arginine, asparagine, glutathione and lysine, show immunomodulating effects. Moreover, MEVs in goat milk showed a greater number of enriched metabolic pathways as compared to the other kinds of milk.

International Union of Basic and Clinical Pharmacology. CVIII. Calcium-Sensing Receptor Nomenclature, Pharmacology, and Function

The calcium-sensing receptor (CaSR) is a class C G protein-coupled receptor that responds to multiple endogenous agonists and allosteric modulators, including divalent and trivalent cations, L-amino acids, γ-glutamyl peptides, polyamines, polycationic peptides, and protons. The CaSR plays a critical role in extracellular calcium (Ca2+ o) homeostasis, as demonstrated by the many naturally occurring mutations in the CaSR or its signaling partners that cause Ca2+ o homeostasis disorders. However, CaSR tissue expression in mammals is broad and includes tissues unrelated to Ca2+ o homeostasis, in which it, for example, regulates the secretion of digestive hormones, airway constriction, cardiovascular effects, cellular differentiation, and proliferation. Thus, although the CaSR is targeted clinically by the positive allosteric modulators (PAMs) cinacalcet, evocalcet, and etelcalcetide in hyperparathyroidism, it is also a putative therapeutic target in diabetes, asthma, cardiovascular disease, and cancer. The CaSR is somewhat unique in possessing multiple ligand binding sites, including at least five putative sites for the "orthosteric" agonist Ca2+ o, an allosteric site for endogenous L-amino acids, two further allosteric sites for small molecules and the peptide PAM, etelcalcetide, and additional sites for other cations and anions. The CaSR is promiscuous in its G protein-coupling preferences, and signals via Gq/11, Gi/o, potentially G12/13, and even Gs in some cell types. Not surprisingly, the CaSR is subject to biased agonism, in which distinct ligands preferentially stimulate a subset of the CaSR's possible signaling responses, to the exclusion of others. The CaSR thus serves as a model receptor to study natural bias and allostery. SIGNIFICANCE STATEMENT: The calcium-sensing receptor (CaSR) is a complex G protein-coupled receptor that possesses multiple orthosteric and allosteric binding sites, is subject to biased signaling via several different G proteins, and has numerous (patho)physiological roles. Understanding the complexities of CaSR structure, function, and biology will aid future drug discovery efforts seeking to target this receptor for a diversity of diseases. This review summarizes what is known to date regarding key structural, pharmacological, and physiological features of the CaSR.

Simulated gastrointestinal digests of corn protein hydrolysate alleviate inflammation in caco-2 cells and a mouse model of colitis

Inflammatory bowel disease, a typical chronic inflammatory disease of the gastrointestinal tract, make up a growing share of the global disease burden. This study firstly evaluated the anti-inflammatory effects of corn protein hydrolysate (CPH) using a cell model of tumor cell necrosis factor-α (TNF-α)-induced inflammation and a mouse model of colitis induced by dextran sodium sulfate. CPH digests significantly inhibited the expression of cyclooxygenase-2 and inducible nitric oxide synthase, and reduced the secretion of interleukin-8 in TNF-α-induced inflammation in Caco-2 cells. In mice, CPH digests significantly improved the body weight loss, clinical scores, shortening of the colon and histological symptoms, and decreased the myeloperoxidase activity, and down regulated the expression of TNF-α, and interleukin-6 in the colon. The above results indicate that the CPH can potentially be used as a health food/nutraceutical for the treatment/management of intestinal inflammation.

Tojapride prevents CaSR-mediated NLRP3 inflammasome activation in oesophageal epithelium irritated by acidic bile salts

Impairment of the oesophageal epithelium in patients with reflux oesophagitis (RE) is a cytokine-mediated injury rather than a chemical burn. The present study was conducted to explore CaSR/NLRP3 inflammasome pathway activation and cytokines IL-1β and IL-18 release in oesophageal epithelia injured by refluxates and the effects of Tojapride on that signal regulation. Using a modified RE rat model with Tojapride administration and Tojapride-pretreated SV40-immortalized human oesophageal epithelial cells (HET-1A) exposed to acidic bile salts pretreated with Tojapride, we evaluated the therapeutic effects of Tojapride on oesophageal epithelial barrier function, the expression of CaSR/NLRP3 inflammasome pathway-related proteins and the release of downstream cytokines in response to acidic bile salt irritation. In vivo, Tojapride treatment ameliorated the general condition and pathological lesions of the oesophageal epithelium in modified RE rats. In addition, Tojapride effectively blocked the CaSR-mediated NLRP3 inflammasome activation in modified RE rats. In vitro, Tojapride treatment can reverse the harmful effect of acidic bile salts, which reduced transepithelial electrical resistance (TEER), up-regulated the CaSR-mediated NLRP3 inflammasome pathway and increased caspase-1 activity, LDH release and cytokines secretion. Taken together, these data show that Tojapride can prevent CaSR-mediated NLRP3 inflammasome activation and alleviate oesophageal epithelial injury induced by acidic bile salt exposure.

Nutritional and Pharmacological Targeting of the Calcium-Sensing Receptor Influences Chemically Induced Colitis in Mice

The calcium-sensing receptor (CaSR) is the main regulator of extracellular Ca2+ homeostasis. It has diverse functions in different tissues, including the intestines. Intestine-specific knockout of the CaSR renders mice more susceptible to dextran sulphate sodium (DSS)-induced colitis. To test our hypothesis that the CaSR reduces intestinal inflammation, we assessed the effects of nutritional and pharmacological agonists of the CaSR in a colitis model. We treated female Balb/C mice with dietary calcium and protein (nutritional agonists of the CaSR) or pharmacological CaSR modulators (the agonists cinacalcet and GSK3004774, and the antagonist NPS-2143; 10 mg/kg), then induced colitis with DSS. The high-protein diet had a strong pro-inflammatory effect-it shortened the colons (5.3 ± 0.1 cm vs. 6.1 ± 0.2 cm normal diet, p < 0.05), lowered mucin expression and upregulated pro-inflammatory cytokines, such as interferon-γ, (4.2-fold, p < 0.05) compared with the normal diet. Cinacalcet reduced mucin expression, which coincided with an increase in tumor necrosis factor-α (4.4-fold, p < 0.05) and IL-6 (4.9-fold, p < 0.05) in the plasma, compared with vehicle. The CaSR antagonist, NPS-2143, significantly reduced the cumulative inflammation score compared with the vehicle control (35.3 ± 19.1 vs. 21.9 ± 14.3 area under the curve, p < 0.05) and reduced infiltration of inflammatory cells. While dietary modulation of the CaSR had no beneficial effects, pharmacological inhibition of the CaSR may have the potential of a novel add-on therapy in the treatment of inflammatory bowel diseases.

Mucosal healing progression after acute colitis in mice

BACKGROUND

Mucosal healing has become a therapeutic goal to achieve stable remission in patients with inflammatory bowel diseases. To achieve this objective, overlapping actions of complex cellular processes, such as migration, proliferation, and differentiation, are required. These events are longitudinally and tightly controlled by numerous factors including a wide range of distinct regulatory proteins. However, the sequence of events associated with colon mucosal repair after colitis and the evolution of the luminal content characteristics during this process have been little studied.

AIM

To document the evolution of colon mucosal characteristics during mucosal healing using a mouse model with chemically-induced colitis.

METHODS

C57BL/6 male mice were given 3.5% dextran sodium sulfate (DSS) in drinking water for 5 d. They were euthanized 2 (day 7), 5 (day 10), 8 (day 13), and 23 (day 28) d after DSS removal. The colonic luminal environment and epithelial repair processes during the inflammatory flare and colitis resolution were analyzed with reference to a non-DSS treated control group, euthanized at day 0. Epithelial repair events were assessed histo-morphologically in combination with functional permeability tests, expression of key inflammatory and repairing factors, and evaluation of colon mucosa-adherent microbiota composition by 16S rRNA sequencing.

RESULTS

The maximal intensity of colitis was concomitant with maximal alterations of intestinal barrier function and histological damage associated with goblet cell depletion in colon mucosa. It was recorded 2 d after termination of the DSS-treatment, followed by a progressive return to values similar to those of control mice. Although signs of colitis were severe (inflammatory cell infiltrate, crypt disarray, increased permeability) and associated with colonic luminal alterations (hyperosmolarity, dysbiosis, decrease in short-chain fatty acid content), epithelial healing processes were launched early during the inflammatory flare with increased gene expression of certain key epithelial repair modulators, including transforming growth factor-β, interleukin (Il)-15, Il-22, Il-33, and serum amyloid A. Whereas signs of inflammation progressively diminished, luminal colonic environment alterations and microscopic abnormalities of colon mucosa persisted long after colitis induction.

CONCLUSION

This study shows that colon repair can be initiated in the context of inflamed mucosa associated with alterations of the luminal environment and highlights the longitudinal involvement of key modulators.

L-Lysine protects against sepsis-induced chronic lung injury in male albino rats

Sepsis is a severe, life-threatening condition primarily caused by the cellular response to infection. Sepsis leads to increased tissue damage and mortality in patients in the intensive care unit. L-Lysine is an essential amino acid required for protein biosynthesis and is abundant in lamb, pork, eggs, red meat, fish oil, cheese, beans, peas, and soy. Male albino rats were divided into sham, control, 10-mg/kg bwt L-lysine, and 20-mg/kg bwt L-lysine groups. At the end of treatment, we determined the levels of oxidative and inflammatory markers, myeloperoxidase (MPO) and catalase activities, total cell count, the wet/dry ratio of lung tissue, and total protein content. Furthermore, the effect of L-lysine on the cellular architecture of lung tissue was evaluated. L-Lysine significantly reduced the magnitude of lipid peroxidation; total protein content; wet/dry ratio of lung tissue; tumor necrosis factor-alpha, interleukin-8, and macrophage inhibitory factor levels; MPO activity; and total cell, neutrophil, and lymphocyte counts, and it increased the reduced glutathione levels and the glutathione peroxidase, superoxide dismutase, and catalase activities. A normal cellular architecture was noted in rats in the sham group, whereas proinflammatory changes, such as edema and neutrophilic infiltration, were detected in rats in the control group. L-lysine significantly ameliorated these proinflammatory changes. Thus, L-lysine has the potential for the treatment of sepsis-induced CLI.

Distribution and localization of porcine calcium sensing receptor in different tissues of weaned piglets1

Taste receptors including calcium sensing receptor (CaSR) are expressed in various animal tissues, and CaSR plays important roles in nutrient sensing and the physiology, growth, and development of animals. However, molecular distribution of porcine CaSR (pCaSR) in different tissues, especially along the longitudinal axis of the digestive tract in weaned piglets, is still unknown. In the present study, we investigated the distribution and localization of pCaSR in the different tissues including intestinal segments of weaned piglets. Six male pigs were anesthetized and euthanized. Different tissues such as intestinal segments were collected. The pCaSR mRNA abundance, protein abundance, and localization were measured by real-time PCR, Western blotting, and immunohistochemistry, respectively. The mRNA and protein of pCaSR were detected in the kidney, lung, liver, stomach, duodenum, jejunum, ileum, and colon. The pCaSR mRNA was much higher (five to 180 times) in the kidney when compared with other tissues (P < 0.05). The ileum had higher pCaSR mRNA and protein abundances than the stomach, duodenum, jejunum, and colon (P < 0.05). Immunohistochemical staining results indicated that the pCaSR protein was mostly located in the epithelia of the stomach, duodenum, jejunum, ileum, and colon. These results demonstrate that pCaSR is widely expressed in different tissues including intestinal segments in weaned piglets and the ileum has a higher expression level of pCaSR. Further research is needed to confirm the expression of CaSR in the different types of epithelial cells isolated from weaned piglets and characterize the functions of pCaSR, its potential ligands and cell signaling pathways related to CaSR activation in enteroendocrine cells and potentially in enterocytes.

The protective role of phloretin against dextran sulfate sodium-induced ulcerative colitis in mice

Phloretin, a dihydrogen chalcone flavonoid, is mainly isolated from apples and strawberries. Phloretin has been proven to have many biological activities such as anti-inflammatory and anti-oxidative. Herein, we investigated the protective efficacy and potential mechanism of phloretin in dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) in mice. The results showed that phloretin resulted in a reduced DSS-induced disease activity index (DAI), colon length shortening and colonic pathological damage. The levels of pro-inflammatory cytokines in the colon were also decreased by the administration of phloretin. Exploration of the potential mechanism demonstrated that phloretin suppressed the inflammatory response by regulating the nuclear factor-κB (NF-κB), toll-like receptor 4 (TLR4) and peroxisome proliferator-activated receptor γ (PPARγ) pathways. Phloretin also inhibited the DSS-induced (NOD)-like receptor family and pyrin domain containing 3 (NLRP3) inflammasome activations. Further studies found that phloretin reduced key markers of oxidative stress as well as regulated the expression of zonula occludens-1 (ZO-1) and occludin. Interestingly, the concentration of serum lipopolysaccharide (LPS) was significantly decreased. Escherichia coli (E. coli) and Lactobacillus levels were also re-balanced after phloretin treatment. These results indicate that phloretin might be a new dietary strategy for the treatment of UC.

Hookworm-Derived Metabolites Suppress Pathology in a Mouse Model of Colitis and Inhibit Secretion of Key Inflammatory Cytokines in Primary Human Leukocytes

Iatrogenic hookworm therapy shows promise for treating disorders that result from a dysregulated immune system, including inflammatory bowel disease (IBD). Using a murine model of trinitrobenzenesulfonic acid-induced colitis and human peripheral blood mononuclear cells, we demonstrated that low-molecular-weight metabolites derived from both somatic extracts (LMWM-SE) and excretory-secretory products (LMWM-ESP) of the hookworm, Ancylostoma caninum, display anti-inflammatory properties. Administration to mice of LMWM-ESP as well as sequentially extracted fractions of LMWM-SE using both methanol (SE-MeOH) and hexane-dichloromethane-acetonitrile (SE-HDA) resulted in significant protection against T cell-mediated immunopathology, clinical signs of colitis, and impaired histological colon architecture. To assess bioactivity in human cells, we stimulated primary human leukocytes with lipopolysaccharide in the presence of hookworm extracts and showed that SE-HDA suppressed ex vivo production of inflammatory cytokines. Gas chromatography-mass spectrometry (MS) and liquid chromatography-MS analyses revealed the presence of 46 polar metabolites, 22 fatty acids, and five short-chain fatty acids (SCFAs) in the LMWM-SE fraction and 29 polar metabolites, 13 fatty acids, and six SCFAs in the LMWM-ESP fraction. Several of these small metabolites, notably the SCFAs, have been previously reported to have anti-inflammatory properties in various disease settings, including IBD. This is the first report showing that hookworms secrete small molecules with both ex vivo and in vivo anti-inflammatory bioactivity, and this warrants further exploration as a novel approach to the development of anti-inflammatory drugs inspired by coevolution of gut-dwelling hookworms with their vertebrate hosts.

Calcium-sensing receptor in colorectal inflammation and cancer: Current insights and future perspectives

The extracellular calcium-sensing receptor (CaSR) is best known for its action in the parathyroid gland and kidneys where it controls body calcium homeostasis. However, the CaSR has different roles in the gastrointestinal tract, where it is ubiquitously expressed. In the colon, the CaSR is involved in controlling multiple mechanisms, including fluid transport, inflammation, cell proliferation and differentiation. Although the expression pattern and functions of the CaSR in the colonic microenvironment are far from being completely understood, evidence has been accumulating that the CaSR might play a protective role against both colonic inflammation and colorectal cancer. For example, CaSR agonists such as dipeptides have been suggested to reduce colonic inflammation, while dietary calcium was shown to reduce the risk of colorectal cancer. CaSR expression is lost in colonic malignancies, indicating that the CaSR is a biomarker for colonic cancer progression. This dual anti-inflammatory and anti-tumourigenic role of the CaSR makes it especially interesting in colitis-associated colorectal cancer. In this review, we describe the clinical and experimental evidence for the role of the CaSR in colonic inflammation and colorectal cancer, the intracellular signalling pathways which are putatively involved in these actions, and the possibilities to exploit these actions of the CaSR for future therapies of colonic inflammation and cancer.

Calcium-sensing receptor in nutrient sensing: an insight into the modulation of intestinal homoeostasis

The animal gut effectively prevents the entry of hazardous substances and microbes while permitting the transfer of nutrients, such as water, electrolytes, vitamins, proteins, lipids, carbohydrates, minerals and microbial metabolites, which are intimately associated with intestinal homoeostasis. The gut maintains biological functions through its nutrient-sensing receptors, including the Ca-sensing receptor (CaSR), which activates a variety of signalling pathways, depending on cellular context. CaSR coordinates food digestion and nutrient absorption, promotes cell proliferation and differentiation, regulates energy metabolism and immune response, stimulates hormone secretion, mitigates secretory diarrhoea and enhances intestinal barrier function. Thus, CaSR is crucial to the maintenance of gut homoeostasis and protection of intestinal health. In this review, we focused on the emerging roles of CaSR in the modulation of intestinal homoeostasis including related underlying mechanisms. By elucidating the relationship between CaSR and animal gut homoeostasis, effective and inexpensive methods for treating intestinal health imbalance through nutritional manipulation can be developed. This article is expected to provide experimental data of the effects of CaSR on animal or human health.

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).

Immunomodulating peptides for food allergy prevention and treatment

Among the most promising strategies currently assayed against IgE-mediated allergic diseases stands the possibility of using immunomodulating peptides to induce oral tolerance toward offending food allergens or even to prevent allergic sensitization. This review focuses on the beneficial effects of food derived immunomodulating peptides on food allergy, which can be directly exerted in the intestinal tract or once being absorbed through the intestinal epithelial barrier to interact with immune cells. Food peptides influence intestinal homeostasis by maintaining and reinforcing barrier function or affecting intestinal cell-signalling to nearby immune cells and mucus secretion. In addition, they can stimulate cells of the innate and adaptive immune system while supressing inflammatory responses. Peptides represent an attractive alternative to whole allergens to enhance the safety and efficacy of immunotherapy treatments. The conclusions drawn from curative and preventive experiments in murine models are promising, although there is a need for more pre-clinical studies to further explore the immunomodulating strategy and its mechanisms and for a deeper knowledge of the peptide sequence and structural requirements that determine the immunoregulatory function.

Intervention of Dietary Dipeptide Gamma-l-Glutamyl-l-Valine (γ-EV) Ameliorates Inflammatory Response in a Mouse Model of LPS-Induced Sepsis

Sepsis, the systemic inflammatory response syndrome (SIRS) with infection is one of the leading causes of death in critically ill patients in the developed world due to the lack of effective antisepsis treatments. This study examined the efficacy of dietary dipeptide gamma-l-glutamyl-l-valine (γ-EV), which was characterized previously as an anti-inflammatory peptide, in an LPS-induced mouse model of sepsis. BALB/c mice were administered γ-EV via oral gavage followed by an intraperitoneal injection of LPS to induce sepsis. The γ-EV exhibited antisepsis activity by reducing the expression of pro-inflammatory cytokines TNF-α, IL-6, and IL-1β in plasma and small intestine. γ-EV also reduced the phosphorylation of the signaling proteins JNK and IκBα. We concluded that γ-EV could possess an antisepsis effect against bacterial infection in intestine. This study proposes a signaling mechanism whereby the calcium-sensing receptor (CaSR) allosterically activated by γ-EV stimulates the interaction of β-arrestin2 with the TIR(TLR/IL-1R) signaling proteins TRAF6, TAB1, and IκBα to suppress inflammatory signaling.

In Vivo Study of the Efficacy of the Essential Oil of Zanthoxylum bungeanum Pericarp in Dextran Sulfate Sodium-Induced Murine Experimental Colitis

The purpose of this study was to investigate the protective effects and mechanisms of the essential oil of Zanthoxylum bungeanum pericarp (ZBEO) on dextran sulfate sodium (DSS)-induced experimental colitis in mice. ZBEO decreased DSS-induced body weight loss, the disease activity index, colon length shortening, colonic pathological damage, and myeloperoxidase activities. The production of pro-inflammatory mediators was significantly alleviated by ZBEO. Further mechanistic analysis showed that ZBEO inhibited inflammation by regulating NF-κB and PPARγ pathways. ZBEO also inhibited NLRP3 activation in colitis in mice. Furthermore, ZBEO contributed to the maintenance of tight junction architecture by regulating the expression of zonula occludens-1 during colitis. Surprisingly, treatment with ZBEO increased levels of the commensal bacteria containing Lactobacillus and Bifidobacteria but reduced Escherichia coli levels in the feces of mice. These results suggested that supplementation with ZBEO might provide a new dietary strategy for the prevention of ulcerative colitis.

Dietary Protein and Amino Acid Supplementation in Inflammatory Bowel Disease Course: What Impact on the Colonic Mucosa?

Inflammatory bowel diseases (IBD), after disease onset, typically progress in two cyclically repeated phases, namely inflammatory flare and remission, with possible nutritional status impairment. Some evidence, either from epidemiological, clinical, and experimental studies indicate that the quantity and the quality of dietary protein consumption and amino acid supplementation may differently influence the IBD course according to the disease phases. For instance, although the dietary protein needs for mucosal healing after an inflammatory episode remain undetermined, there is evidence that amino acids derived from dietary proteins display beneficial effects on this process, serving as building blocks for macromolecule synthesis in the wounded mucosal area, energy substrates, and/or precursors of bioactive metabolites. However, an excessive amount of dietary proteins may result in an increased intestinal production of potentially deleterious bacterial metabolites. This could possibly affect epithelial repair as several of these bacterial metabolites are known to inhibit colonic epithelial cell respiration, cell proliferation, and/or to affect barrier function. In this review, we present the available evidence about the impact of the amount of dietary proteins and supplementary amino acids on IBD onset and progression, with a focus on the effects reported in the colon.

Intervention of Isomaltodextrin Mitigates Intestinal Inflammation in a Dextran Sodium Sulfate-Induced Mouse Model of Colitis via Inhibition of Toll-like Receptor-4

Isomaltodextrin (IMD), a highly branched α-glucan, is a type of resistant starch. Earlier studies have indicated that polysaccharides could prevent inflammation and can be effective in reducing the complications of chronic gastrointestinal diseases such as inflammatory bowel disease (IBD). Therefore, the aim of the present study was to evaluate the anti-inflammatory effect of IMD in dextran sodium sulfate (DSS)-induced colitis in a mouse model. IMD (0.5, 1.0, 2.5, and 5.0% (w/v)) was given orally for 23 days to female Balb/c mice, and then 5% DSS was administered to induce colitis (from day 15 onward to the end of the trial). IMD could not prevent DSS-induced weight loss or colon shortening. However, IMD could reduce inflammatory cytokines, TNF-α and IL-6, in the colon. Gene expression indicated the tendency of IMD to suppress pro-inflammatory cytokines IL-1β, MCP-1, and IL-17 and to increase an anti-inflammatory cytokine, IL-10. Further study revealed that the anti-inflammatory action of IMD mediates through inhibition of the expression of Toll-like receptor-4.

Calcium-Sensing Receptor in Human Peripheral Blood T Lymphocytes Is Involved in the AMI Onset and Progression through the NF-κB Signaling Pathway

Acute myocardial infarction (AMI) is a condition triggered by an inflammatory process that seriously affects human health. Calcium-sensing receptor (CaSR) in T lymphocytes is involved during the inflammation reaction. However, the relationship between them is not very clear. In this study, we collected human peripheral blood T lymphocytes from patients with AMI and in different stages of percutaneous coronary intervention (PCI) (at the onset of AMI, the first day after PCI (PCI-1), PCI-3, and PCI-5) to study the CaSR and NF-κB pathway protein expression, cytokine release and T cell apoptosis. The results showed that the expressions of CaSR, P-p65, Caspase-12, and the secretions of Th-1 and Th-2 type cytokines were increased at the onset of AMI, especially on the PCI-1. Meanwhile, the apoptosis rate of CD(3+), CD(4+) and CD(8+) T lymphocytes also increased. However, from PCI-3, all the indicators began to decline. In addition, we also found that positive CaSR small interfering RNA (siRNA) transfection in T lymphocytes and NF-κB pathway blocker Bay-11-7082 reversed the increased expressions of CaSR, P-p65, Caspase-12, reduced the secretions of Th-1 and Th-2 type cytokines, and decreased T lymphocytes apoptosis rate not only in the AMI patients but also in the normal controls. All of these results indicated that CaSR in the human peripheral blood T lymphocytes were involved in the AMI onset and progression, which probably was related to the NF-κB pathway. Our study demonstrated the relationship between AMI and CaSR, and will provide new effective prevention theory and new targets for drug treatment.

The Extracellular Calcium-Sensing Receptor in the Intestine: Evidence for Regulation of Colonic Absorption, Secretion, Motility, and Immunity

Different from other epithelia, the intestinal epithelium has the complex task of providing a barrier impeding the entry of toxins, food antigens, and microbes, while at the same time allowing for the transfer of nutrients, electrolytes, water, and microbial metabolites. These molecules/organisms are transported either transcellularly, crossing the apical and basolateral membranes of enterocytes, or paracellularly, passing through the space between enterocytes. Accordingly, the intestinal epithelium can affect energy metabolism, fluid balance, as well as immune response and tolerance. To help accomplish these complex tasks, the intestinal epithelium has evolved many sensing receptor mechanisms. Yet, their roles and functions are only now beginning to be elucidated. This article explores one such sensing receptor mechanism, carried out by the extracellular calcium-sensing receptor (CaSR). In addition to its established function as a nutrient sensor, coordinating food digestion, nutrient absorption, and regulating energy metabolism, we present evidence for the emerging role of CaSR in the control of intestinal fluid homeostasis and immune balance. An additional role in the modulation of the enteric nerve activity and motility is also discussed. Clearly, CaSR has profound effects on many aspects of intestinal function. Nevertheless, more work is needed to fully understand all functions of CaSR in the intestine, including detailed mechanisms of action and specific pathways involved. Considering the essential roles CaSR plays in gastrointestinal physiology and immunology, research may lead to a translational opportunity for the development of novel therapies that are based on CaSR's unique property of using simple nutrients such as calcium, polyamines, and certain amino acids/oligopeptides as activators. It is possible that, through targeting of intestinal CaSR with a combination of specific nutrients, oral solutions that are both inexpensive and practical may be developed to help in conditioning the gut microenvironment and in maintaining digestive health.

Adenine Inhibits TNF-α Signaling in Intestinal Epithelial Cells and Reduces Mucosal Inflammation in a Dextran Sodium Sulfate-Induced Colitis Mouse Model

Adenine (6-amino-6H-purine), found in molokheiya (Corchorus olitorius L.), has exerted vasorelaxation effects in the thoracic aorta. However, the mode of action of the anti-inflammatory effect of adenine is unclear. Thus, we investigated to clarify the effect of adenine on chronic inflammation of the gastrointestinal tract. In intestinal epithelial cells, adenine significantly inhibited tumor necrosis factor-α-induced interleukin-8 secretion. The inhibition of adenine was abolished under the treatment of inhibitors of adenyl cyclase (AC) and protein kinase A (PKA), indicating the effect of adenine was mediated through the AC/PKA pathway. Adenine (5, 10, and 50 mg/kg BW/day) was administered orally for 14 days to female BALB/c mice, and then 5% dextran sodium sulfate (DSS) was given to induce colitis. Adenine (5 mg/kg BW/day) significantly prevented DSS-induced colon shortening, expression of pro-inflammatory cytokines, and histological damage in the colon. These results suggest that adenine can be a promising nutraceutical for the prevention of intestinal inflammation.