Long-term selenium deficiency increases the pathogenicity of a Citrobacter rodentium infection in mice

Phospholipid-rich krill oil promotes intestinal health by strengthening beneficial gut microbial interactions in an infectious colitis model

Krill oil (KO) is rich in bioactive ingredients including phospholipids, omega-3 fatty acids, and astaxanthin. While health benefits and roles of KO in modulating lipid metabolism are well documented, its ability to alleviate symptoms related to infectious colitis and modulate gut microbial interactions is still largely unknown. Here we used a multi-omics approach, including transcriptome, microbiome, and metabolome analyses, to understand how KO mediates gut microbial interactions and promotes epithelial healing in an infectious colitis model. KO reversed the infection-induced intestinal hyperplasia to baseline. KO dampened intestinal inflammation via multiple targets, mediating several proinflammatory pathways, including IL17 signaling, and reducing luminal histamine levels. KO supplementation enriched butyrate-producing bacteria, including Roseburia and Clostridium, and strengthened beneficial microbial interactions in the gut microbial community. Supplementation with phospholipid-rich KO also increased microbial phylogenetic diversity. KO enhanced mucosal barrier function by increasing the production of Muc6 and the antimicrobial peptide, Leap2. KO played an active role during epithelial healing by inhibiting the expression of granzyme K while increasing the expression of a colitis protective factor, Dclk1. Together, our findings demonstrate that KO rich in omega-3 phospholipids can play a protective role in infectious colitis and should be considered a dietary option for promoting gut health.

Ellagitannin Punicalagin Disrupts the Pathways Related to Bacterial Growth and Affects Multiple Pattern Recognition Receptor Signaling by Acting as a Selective Histone Deacetylase Inhibitor

Punicalagin (PA) is a key ellagitannin abundant in pomegranate with wide-ranging biological activities. In this study, we examined the biological processes by which PA regulates bacterial growth and inflammation in human cells using multiomics and molecular docking approaches. PA promoted macrophage-mediated bacterial killing and inhibited the growth of Citrobacter rodentium by inducing a distinct metabolome pattern. PA acted as a selective regulator of histone deacetylases (HDACs) and affected 37 pathways in macrophages, including signaling mediated by pattern recognition receptors, such as Toll-like and NOD-like receptors. In silico simulation showed that PA can bind with high affinity to HDAC7. PA downregulated HDAC7 at both mRNA and protein levels and resulted in a decrease in the level of histone 3 lysine 27 acetylation. Our findings provide evidence that PA exerts its biological effects via multiple pathways, which can be exploited in the development of this bioactive food ingredient for disease management.

Supplementary selenium in the form of selenylation α-D-1,6-glucan ameliorates dextran sulfate sodium induced colitis in vivo

The deficiency of selenium has been found in clinical IBD patients and supplementation selenium is recognized as beneficial for colitis treatment. In this study, an organic selenium compound-selenylation α-D-1,6-glucan (sCPA) was prepared, and the effect of sCPA on DSS induced colitis mice was investigated. The results suggested that sCPA prevented the weight loss, colon length shortening, and stool loose of colitis mice. It protected colon mucosal barrier by promoting tight junction protein ZO-1 and Occludin expression. Moreover, sCPA reduced oxidative stress via regulating SOD and MDA levels, and decreased the contents of inflammatory proteins NF-κB and NLRP3 and adjusted TNF-α, IFN-γ, IL-1β, and IL-10 inflammatory cytokines. Furthermore, sCPA repaired intestinal microbiota composition especially Bacteroidetes, Firmicutes, Proteobacteria, and Actinobacteria that altered by DSS in colitis mice. Meanwhile, SCFAs produced by gut microbiota were restored by sCPA close to the level in the normal group. In conclusion, these findings indicated that the sCPA might be a potential dietary selenium supplementation for the prevention and treatment of colitis.

Neonatal Selenoenzyme Expression Is Variably Susceptible to Duration of Maternal Selenium Deficiency

Maternal selenium (Se) deficiency is associated with decreased neonatal Se levels, which increases the risk for neonatal morbidities. There is a hierarchy to selenoprotein expression after Se deficiency in adult rodents, depending on the particular protein and organ evaluated. However, it is unknown how limited Se supply during pregnancy impacts neonatal selenoprotein expression. We used an Se-deficient diet to induce perinatal Se deficiency (SeD), initiated 2–4 weeks before onset of breeding and continuing through gestation. Neonatal plasma, liver, heart, kidney, and lung were collected on the day of birth and assessed for selenoproteins, factors required for Se processing, and non-Se containing antioxidant enzymes (AOE). Maternal SeD reduced neonatal circulating and hepatic glutathione peroxidase (GPx) activity, as well as hepatic expression of Gpx1 and selenophosphate synthetase 2 (Sps2). In contrast, the impact of maternal SeD on hepatic thioredoxin reductase 1, hepatic non-Se containing AOEs, as well as cardiac, renal, and pulmonary GPx activity, varied based on duration of maternal exposure to SeD diet. We conclude that the neonatal liver and circulation demonstrate earlier depletion in selenoenzyme activity after maternal SeD. Our data indicate that prolonged maternal SeD may escalate risk to the neonate by progressively diminishing Se-containing AOE across multiple organs.

Hepatic-Specific Decrease in the Expression of Selenoenzymes and Factors Essential for Selenium Processing After Endotoxemia

Background

Selenium (Se) levels decrease in the circulation during acute inflammatory states and sepsis, and are inversely associated with morbidity and mortality. A more specific understanding of where selenoproteins and Se processing are compromised during insult is needed. We investigated the acute signaling response in selenoenzymes and Se processing machinery in multiple organs after innate immune activation in response to systemic lipopolysaccharide (LPS).

Methods

Wild type (WT) adult male C57/B6 mice were exposed to LPS (5 mg/kg, intraperitoneal). Blood, liver, lung, kidney and spleen were collected from control mice as well as 2, 4, 8, and 24 h after LPS. Plasma Se concentration was determined by ICP-MS. Liver, lung, kidney and spleen were evaluated for mRNA and protein content of selenoenzymes and proteins required to process Se.

Results

After 8 h of endotoxemia, plasma levels of Se and the Se transporter protein, SELENOP were significantly decreased. Consistent with this timing, the transcription and protein content of several hepatic selenoenzymes, including SELENOP, glutathione peroxidase 1 and 4 were significantly decreased. Furthermore, hepatic transcription and protein content of factors required for the Se processing, including selenophosphate synthetase 2 (Sps2), phosphoseryl tRNA kinase (Pstk), selenocysteine synthase (SepsecS), and selenocysteine lyase (Scly) were significantly decreased. Significant LPS-induced downregulation of these key selenium processing enzymes was observed in isolated hepatocytes. In contrast to the acute and dynamic changes observed in the liver, selenoenzymes did not decrease in the lung, kidney or spleen.

Conclusion

Hepatic selenoenzyme production and Se processing factors decreased after endotoxemia. This was temporally associated with decreased circulating Se. In contrast to these active changes in the regulation of Se processing in the liver, selenoenzymes did not decrease in the lung, kidney or spleen. These findings highlight the need to further study the impact of innate immune challenges on Se processing in the liver and the impact of targeted therapeutic Se replacement strategies during innate immune challenge.

Dietary Indole-3-Carbinol Alleviated Spleen Enlargement, Enhanced IgG Response in C3H/HeN Mice Infected with Citrobacter rodentium

Enteropathogenic and enterohemorrhagic Escherichia coli are important enteric pathogens that induce hemorrhagic colitis or even fatal hemolytic uremic syndrome. Emerging evidence shows that some bio-actives derived from fruits and vegetables may serve as alternatives to antibiotics for overcoming multidrug resistant E. coli infections. In this study, the Citrobacter rodentium (Cr) infection model was utilized to mimic E. coli-induced acute intestinal inflammation, and the effects of a cruciferous vegetable-derived cancer protective compound, indole-3-carbinol (I3C), on the immune responses of Cr-susceptible C3H/HeN mice were investigated. Dietary I3C significantly inhibited the loss of body weight and the increase in spleen size in Cr infected mice. In addition, I3C treatment reduced the inflammatory response to Cr infection by maintaining anti-inflammatory cytokine IL-22 mRNA levels while reducing expression of other pro-inflammatory cytokines including IL17A, IL6, IL1β, TNF-α, and IFN-γ. Moreover, the serum cytokine levels of IL17, TNF-α, IL12p70, and G-CSF also were down-regulated by I3C in Cr-infected mice. Additionally, dietary I3C specifically enhanced the Cr-specific IgG response to Cr infection. In general, dietary I3C reduced the Cr-induced pro-inflammatory response in susceptible C3H/HeN mice and alleviated the physiological changes and tissue damage induced by Cr infection but not Cr colonization.

Searching potential antiviral candidates for the treatment of the 2019 novel coronavirus based on DFT calculations and molecular docking

In the present work, the succinic acid (SA), L-pyroglutamic acid (L-PGA), N-phenyl-thioacetamide (N-NPTA), 2-amino-5-chloropyridine hydrogen succinate (ACPS), epigallocatechine Gallate (EGCG) or KDH and, selenomethionine (SeM) compounds have been proposed as potential antiviral candidates to treatment of COVID-19 based on B3LYP/6-311++G∗∗ calculations and molecular docking. Solvation energies, stabilization energies, topological properties have been evaluated as function of acceptors and donors groups present in their structures. ACPS presents the higher reactivity in solution possibly because has the higher nucleophilicity and elecrophilicity indexes while KDH evidence the higher solvation energy probably due to the higher quantity of donors and acceptors groups. NBO studies show that KDH is the most stable in solution. Mapped MEP surfaces have evidenced stronger nucleophilic and electrophilic sites in ACPS, in agreement with the three C=O and two N-H and O-H groups present in this species while KDH has only a C=O group but a total of 19 acceptors and donors groups. From the above studies for six species we can propose that the better potential antiviral candidate to treatment of COVID-19 is ACPS and then, KDH. For a better prediction of the antiviral and anti-inflammatory properties of the proposed compounds, molecular docking calculations were performed by using four structures of COVID-19. Docking results were discussed basing on binding affinities and the interaction types among ligands and different amino acid residues, indicating the powerful ability of KDH and then ACPS ligands on front of the novel coronavirus disease especially for the first and the fourth species (6LU7, 7BTF).

Pomegranate peel extract reduced colonic damage and bacterial translocation in a mouse model of infectious colitis induced by Citrobacter rodentium

The pomegranate fruit peel is a rich source of polyphenols including punicalins, punicalagins, and ellagic acids, but is considered an agricultural waste product. Pomegranate derived products have been reported to have a wide variety of health promoting benefits including antibacterial properties in vitro but there is limited evidence of their antibacterial properties in vivo. The purpose of this study was to test the in vivo antibacterial properties of a pomegranate peel extract (PPX) containing punicalin, punicalagin, and ellagic acid. C3H/He mice were orally pre-treated with water or PPX prior to infection with the mouse bacterial pathogen, Citrobacter rodentium (Cr) that mimics many aspects of human enteropathogenic Escherichia coli infections. Fecal excretion of Cr was monitored and mice were euthanized on day 12 post-infection to assess Cr colonization of the colon and spleen, histological changes, and gene expression. PPX-treatment reduced Cr infection induced weight loss and mortality that was observed in water-treated infected mice. However, Cr colonization of the colon and clearance was unaffected by PPX-treatment. Consistent with this, PPX treatment did not alter the potent Th1/Th17 pro-inflammatory response elicited by Cr infection. Significant colonization of the spleen was only seen in water-treated infected mice and was inversely correlated with the dose of PPX administered. PPX treatment decreased the extent of Cr-induced colon damage that correlated with decreased mortality and reduced colonization of the spleen. Thus, a pomegranate peel extract contains bioactive compounds that mitigate the deleterious effects of an in vivo infection with the model enteropathogenic bacteria, Cr.

Role of Selenoproteins in Bacterial Pathogenesis

The trace element selenium is an essential micronutrient that plays an important role in maintaining homeostasis of several tissues including the immune system of mammals. The vast majority of the biological functions of selenium are mediated via selenoproteins, proteins which incorporate the selenium-containing amino acid selenocysteine. Several bacterial infections of humans and animals are associated with decreased levels of selenium in the blood and an adjunct therapy with selenium often leads to favorable outcomes. Many pathogenic bacteria are also capable of synthesizing selenocysteine suggesting that selenoproteins may have a role in bacterial physiology. Interestingly, the composition of host microbiota is also regulated by dietary selenium levels. Therefore, bacterial pathogens, microbiome, and host immune cells may be competing for a limited supply of selenium. Elucidating how selenium, in particular selenoproteins, may regulate pathogen virulence, microbiome diversity, and host immune response during a bacterial infection is critical for clinical management of infectious diseases.

On the diverse and opposing effects of nutrition on pathogen virulence

Climate change and anthropogenic activity are currently driving large changes in nutritional availability across ecosystems, with consequences for infectious disease. An increase in host nutrition could lead to more resources for hosts to expend on the immune system or for pathogens to exploit. In this paper, we report a meta-analysis of studies on host-pathogen systems across the tree of life, to examine the impact of host nutritional quality and quantity on pathogen virulence. We did not find broad support across studies for a one-way effect of nutrient availability on pathogen virulence. We thus discuss a hypothesis that there is a balance between the effect of host nutrition on the immune system and on pathogen resources, with the pivot point of the balance differing for vertebrate and invertebrate hosts. Our results suggest that variation in nutrition, caused by natural or anthropogenic factors, can have diverse effects on infectious disease outcomes across species.

Impact of Micronutrients on the Immune Response of Animals

Vitamins and minerals (micronutrients) play an important role in regulating and shaping an immune response. Deficiencies generally result in inadequate or dysregulated cellular activity and cytokine expression, thereby affecting the immune response. Decreased levels of natural killer, granulocyte, and phagocytic cell activity and T and B cell proliferation and trafficking are associated with inadequate levels of micronutrients, as well as increased susceptibility to various adverse health conditions, including inflammatory disorders, infection, and altered vaccine efficacy. In addition, most studies of micronutrient modulation of immune responses have been done in rodents and humans, thus limiting application to the health and well-being of livestock and companion animals. This exploratory review elucidates the role of vitamins and minerals on immune function and inflammatory responses in animals (pigs, dogs, cats, horses, goats, sheep, and cattle), with reference to rodents and humans.

Bidirectional brain-gut interactions and chronic pathological changes after traumatic brain injury in mice

OBJECTIVES

Traumatic brain injury (TBI) has complex effects on the gastrointestinal tract that are associated with TBI-related morbidity and mortality. We examined changes in mucosal barrier properties and enteric glial cell response in the gut after experimental TBI in mice, as well as effects of the enteric pathogen Citrobacter rodentium (Cr) on both gut and brain after injury.

METHODS

Moderate-level TBI was induced in C57BL/6mice by controlled cortical impact (CCI). Mucosal barrier function was assessed by transepithelial resistance, fluorescent-labelled dextran flux, and quantification of tight junction proteins. Enteric glial cell number and activation were measured by Sox10 expression and GFAP reactivity, respectively. Separate groups of mice were challenged with Cr infection during the chronic phase of TBI, and host immune response, barrier integrity, enteric glial cell reactivity, and progression of brain injury and inflammation were assessed.

RESULTS

Chronic CCI induced changes in colon morphology, including increased mucosal depth and smooth muscle thickening. At day 28 post-CCI, increased paracellular permeability and decreased claudin-1 mRNA and protein expression were observed in the absence of inflammation in the colon. Colonic glial cell GFAP and Sox10 expression were significantly increased 28days after brain injury. Clearance of Cr and upregulation of Th1/Th17 cytokines in the colon were unaffected by CCI; however, colonic paracellular flux and enteric glial cell GFAP expression were significantly increased. Importantly, Cr infection in chronically-injured mice worsened the brain lesion injury and increased astrocyte- and microglial-mediated inflammation.

CONCLUSION

These experimental studies demonstrate chronic and bidirectional brain-gut interactions after TBI, which may negatively impact late outcomes after brain injury.

SeMet mediates anti-inflammation in LPS-induced U937 cells targeting NF-κB signaling pathway

In previous studies, selenium (Se) was reported to play critical roles in anti-inflammatory activities. Nevertheless, limited information could be obtained during inflammation about selenomethionine (SeMet) in U937 human macrophage cells. The purpose of this study was to investigate the effects of SeMet on the inflammatory responses to lipopolysaccharide (LPS)-induced U937 macrophage cells and the signaling pathways targeted. U937 cells were pretreated with SeMet (1 μM) and subsequently induced with LPS (1 μg/ml) for 24 h. In the cell counting kit-8 assay (CCK-8), SeMet significantly inhibits the proliferation of U937 cells. SeMet also inhibited the production of nitric oxide (NO) and prostaglandin E2 (PGE2) stimulated by LPS. In the Western blot assay and real-time polymerase chain reaction (RT-PCR), SeMet significantly reduced protein expression and production of inducible NO synthase (iNOS), tumor necrosis factor-alpha (TNF-α), and COX-2 in U937 cells. Furthermore, SeMet markedly suppressed the LPS-mediated activation of nuclear factor-kappa B (NF-κB) by blocking the degradation of inhibitor-κB proteins (IκBα) and lessening the translocations of P50 subunit content of NF-κB in the nucleus. These findings suggested the anti-inflammatory activity of SeMet in U937 cells; indicating that SeMet might be a potential treatment for inflammation therapy.

Selenium and selenoproteins in inflammatory bowel diseases and experimental colitis

Inadequate dietary intake of the essential trace element selenium (Se) is thought to be a risk factor for several chronic diseases associated with oxidative stress and inflammation. Biological actions of Se occur through low-molecular weight metabolites and through selenoproteins. Several key selenoproteins including glutathione peroxidases; selenoproteins M, P, and S; and selenium-binding protein 1 have been detected in the intestine. Interestingly, Se and antioxidant selenoproteins are known to modulate differentiation and function of immune cells and contribute to avoid excessive immune responses. This review discusses the role of Se and intestinal selenoproteins in inflammatory bowel diseases, based on data from human, animal, and in vitro studies. In humans, Se deficiency is commonly observed in patients with Crohn's disease. In animal models of experimental colitis, the Se status was negatively correlated with the severity of the disease. While the cause-effect relationship of these observations remains to be clarified, the beneficial outcome of dietary Se supplementation and an optimization of selenoprotein biosynthesis in murine inflammatory bowel disease models have led to investigations of targets and actions of Se in the gastrointestinal tract. The Se status affects gene expression, signaling pathways, and cellular functions in the small and large intestine as well as the gut microbiome composition. This data, particularly from animal experiments, hold promise that adequate dietary Se supply may counteract chronic intestinal inflammation in humans.

The Gdac1 locus modifies spontaneous and Salmonella-induced colitis in mice deficient in either Gpx2 or Gpx1 gene

We previously identified the Gdac1 (Gpx-deficiency-associated colitis 1) locus, which influences the severity of spontaneous colitis in Gpx1- and Gpx2-double-knockout (Gpx1/2-DKO) mice. Congenic Gpx1/2-DKO mice in the 129S1/SvImJ (129) background but carrying the Gdac1(B6) allele have milder spontaneous colitis than 129 Gpx1/2-DKO mice carrying the Gdac1(129) allele. Here, we evaluated the effect of the Gdac1(B6) allele on 129 strain non-DKO mice that had a wild-type (WT) Gpx1 or Gpx2 allele and WT mice. We found that the congenic Gdac1(B6) Gpx2-KO, Gpx1-KO, and WT mice also had better health than the corresponding 129 mice measured by at least one of the parameters including disease signs, colon length, or weight gain. The Gdac1(B6) allele prevented loss of goblet cells and crypt epithelium exfoliation in the Gpx1/2-DKO mice, but did not affect epithelial cell apoptosis or proliferation. Because Gdac1(B6) affects gut dysbiosis in the DKO mice, we then tested its impact on bacteria-induced colitis in non-DKO mice. First, we found both Gpx1-KO and Gpx2-KO mice were susceptible to Salmonella enterica serotype typhimurium (S. Tm)-induced colitis under conditions where WT B6 and 129 mice were resistant. Second, the S. Tm-infected Gdac1(B6) Gpx1-KO mice had stronger inflammatory responses than 129 Gpx1-KO or 129 Gpx2-KO with both Gdac1 alleles and WT mice by having higher mRNA levels of Nod2, Nox2, Tnf, and Cox2. We conclude that the Gdac1 locus affects both spontaneous and S. Tm-induced colitis in 129 non-DKO mice, although in opposite directions.

Selenium status alters the immune response and expulsion of adult Heligmosomoides bakeri worms in mice

Heligmosomoides bakeri is a nematode with parasitic development exclusively in the small intestine of infected mice that induces a potent STAT6-dependent Th2 immune response. We previously demonstrated that host protective expulsion of adult H. bakeri worms from a challenge infection was delayed in selenium (Se)-deficient mice. In order to explore mechanisms associated with the delayed expulsion, 3-week-old female BALB/c mice were placed on a torula yeast-based diet with or without 0.2 ppm Se, and after 5 weeks, they were inoculated with H. bakeri infective third-stage larvae (L3s). Two weeks after inoculation, the mice were treated with an anthelmintic and then rested, reinoculated with L3s, and evaluated at various times after reinoculation. Analysis of gene expression in parasite-induced cysts and surrounding tissue isolated from the intestine of infected mice showed that the local-tissue Th2 response was decreased in Se-deficient mice compared to that in Se-adequate mice. In addition, adult worms recovered from Se-deficient mice had higher ATP levels than worms from Se-adequate mice, indicating greater metabolic activity in the face of a suboptimal Se-dependent local immune response. Notably, the process of worm expulsion was restored within 2 to 4 days after feeding a Se-adequate diet to Se-deficient mice. Expulsion was associated with an increased local expression of Th2-associated genes in the small intestine, intestinal glutathione peroxidase activity, secreted Relm-β protein, anti-H. bakeri IgG1 production, and reduced worm fecundity and ATP-dependent metabolic activity.