Putrescine mitigates intestinal atrophy through suppressing inflammatory response in weanling piglets

The role of intestinal microbiota and metabolites in intestinal inflammation

With the imbalance of intestinal microbiota, the body will then face an inflammatory response, which has serious implications for human health. Bodily allergies, injury or pathogens infections can trigger or promote inflammation and alter the intestinal environment. Meanwhile, excessive changes in the intestinal environment cause the imbalance of microbial homeostasis, which leads to the proliferation and colonization of opportunistic pathogens, invasion of the body's immune system, and the intensification of inflammation. Some natural compounds and gut microbiota and metabolites can reduce inflammation; however, the details of how they interact with the gut immune system and reduce the gut inflammatory response still need to be fully understood. The review focuses on inflammation and intestinal microbiota imbalance caused by pathogens. The body reacts differently to different types of pathogenic bacteria, and the ingestion of pathogens leads to inflamed gastrointestinal tract disorders or intestinal inflammation. In this paper, unraveling the interactions between the inflammation, pathogenic bacteria, and intestinal microbiota based on inflammation caused by several common pathogens. Finally, we summarize the effects of intestinal metabolites and natural anti-inflammatory substances on inflammation to provide help for related research of intestinal inflammation caused by pathogenic bacteria.

Putrescine Supplementation Limits the Expansion of pks+ Escherichia coli and Tumor Development in the Colon

Escherichia coli that harbor the polyketide synthase (pks) genomic island produce colibactin and are associated with sporadic colorectal cancer development. Given the considerable prevalence of pks+ bacteria in healthy individuals, we sought to identify strategies to limit the growth and expansion of pks+ E. coli. We found that culture supernatants of the probiotic strain E. coli Nissle 1917 were able to inhibit the growth of the murine pathogenic strain pks+ E. coli NC101 (EcNC101). We performed a nontargeted analysis of the metabolome in supernatants from several E. coli strains and identified putrescine as a potential postbiotic capable of suppressing EcNC101 growth in vitro. The effect of putrescine supplementation was then evaluated in the azoxymethane/dextran sulfate sodium mouse model of colorectal cancer in mice colonized with EcNC101. Putrescine supplementation inhibited the growth of pks+ E. coli, reduced the number and size of colonic tumors, and downmodulated the release of inflammatory cytokines in the colonic lumen. Additionally, putrescine supplementation led to shifts in the composition and function of gut microbiota, characterized by an increase in the Firmicutes/Bacteroidetes ratio and enhanced acetate production. The effect of putrescine was further confirmed in vitro using a pks+ E. coli strain isolated from a patient with colorectal cancer. These results suggest that probiotic-derived metabolites can be used as an alternative to live bacteria in individuals at risk of developing colorectal cancer due to the presence of pks+ bacteria in their colon.

SIGNIFICANCE

Putrescine supplementation inhibits the growth of cancer-promoting bacteria in the gut, lowers inflammation, and reduces colon cancer development. The consumption of healthy foods rich in putrescine may be a potential prophylactic approach for individuals at risk of developing colorectal cancer due to the presence of pks+ bacteria in their colon.

Plasma polyamines during pregnancy and their relationships with maternal allergies and the immune response of the neonates

BACKGROUND

Some studies have reported that polyamine levels may influence immune system programming. The aim of this study was to evaluate the polyamine profile during gestation and its associations with maternal allergy and cytokine production in cord blood cells in response to different allergenic stimuli.

METHODS

Polyamines were determined in plasma of pregnant women (24 weeks, N = 674) and in umbilical cord samples (N = 353 vein and N = 160 artery) from the Mediterranean NELA birth cohort. Immune cell populations were quantified, and the production of cytokines in response to different allergic and mitogenic stimuli was assessed in cord blood.

RESULTS

Spermidine and spermine were the most prevalent polyamines in maternal, cord venous, and cord arterial plasma. Maternal allergies, especially allergic conjunctivitis, were associated with lower spermine in umbilical cord vein. Higher levels of polyamines were associated with higher lymphocyte number but lower Th2-related cells in cord venous blood. Those subjects with higher levels of circulating polyamines in cord showed lower production of inflammatory cytokines, especially IFN-α, and lower production of Th2-related cytokines, mainly IL-4 and IL-5. The effects of polyamines on Th1-related cytokines production were uncertain.

CONCLUSIONS

Spermidine and spermine are the predominant polyamines in plasma of pregnant women at mid-pregnancy and also in umbilical cord. Maternal allergic diseases like allergic conjunctivitis are related to lower levels of polyamines in cord vein, which could influence the immune response of the newborn. Cord polyamine content is related to a decreased Th2 response and inflammatory cytokines production, which might be important to reduce an allergenic phenotype in the neonate.

Gut metabolic changes during pregnancy reveal the importance of gastrointestinal region in sample collection

INTRODUCTION

Studies of gastrointestinal physiology and the gut microbiome often consider the influence of intestinal region on experimental endpoints. However, this same consideration is not often applied to the gut metabolome. Understanding the contribution of gut regionality may be critically important to the rapidly changing metabolic environments, such as during pregnancy.

OBJECTIVES

We sought to characterize the difference in the gut metabolome in pregnant mice stratified by region-comparing the small intestine, cecum, and feces. Pre-pregnancy feces were collected to understand the influence of pregnancy on the fecal metabolome.

METHODS

Feces were collected from CD-1 female mice before breeding. On gestation day (GD) 18, gut contents were collected from the small intestine, cecum, and descending colon. Metabolites were analyzed with LC-MS/MS using the Biocrates MetaboINDICATOR™ MxP® Quant 500 kit.

RESULTS

Of the 104 small molecule metabolites meeting analysis criteria, we found that 84 (81%) were differentially abundant based on gut region. The most significant regional comparison observed was between the cecum and small intestines, with 52 (50%) differentially abundant metabolites. Pregnancy itself altered 41 (39.4%) fecal small molecule metabolites.

CONCLUSIONS

The regional variation observed in the gut metabolome are likely due to the microbial and physiological differences between the different parts of the intestines. Additionally, pregnancy impacts the fecal metabolome, which may be due to evolving needs of both the dam and fetus.

Putrescine promotes MMP9-induced angiogenesis in skeletal muscle through hydrogen peroxide/METTL3 pathway

Blood vessels play a crucial role in the development of skeletal muscle, ensuring the supply of nutrients and oxygen. Putrescine, an essential polyamine for eukaryotic cells, has an unclear impact on skeletal muscle angiogenesis. In this study, we observed lower vessel density and reduced putrescine level in the muscle of low-birth-weight piglet models, and identified a positive correlation between putrescine content and muscle vessel density. Furthermore, putrescine was found to promote angiogenesis in skeletal muscle both in vitro and in vivo by targeting matrix metalloproteinase 9 (MMP9). On a mechanistic level, putrescine augmented the expression of methyltransferase like 3 (METTL3) by attenuating hydrogen peroxide production, thereby increasing the level of N6-methyladenosine (m6A)-modified MMP9 mRNA. This m6A-modified MMP9 mRNA was subsequently recognized and bound by the YTH N6-methyladenosine RNA binding protein 1 (YTHDF1), enhancing the stability of MMP9 mRNA and its protein expression, consequently accelerating angiogenesis in skeletal muscle. In summary, our findings suggest that putrescine enhances MMP9-mediated angiogenesis in skeletal muscle via the hydrogen peroxide/METTL3 pathway.

Polyamines and hormesis: Making sense of a dose response dichotomy

The diverse biological effects of polyamines (putrescine, spermidine and spermine) were reviewed in the context of hormesis in an integrative manner for the first time. The findings illustrate that each of these polyamines commonly induces hormetic dose responses in a wide range of biological models and types of cells for multiple endpoints in numerous plant species and animal models. Plant research emphasized preconditioning experimental studies in which the respective polyamines conferred some protection against the damaging effects of a broad range of environmental stressors such as drought, salinity, cold/heat, heavy metals and UV-damage in an hormetic manner. Polyamine-based animal hormesis studies emphasized biomedical endpoints such as longevity and neuroprotection. These findings have important biological and biomedical implications and should guide experimental designs of low dose investigations.

Mechanism of Qingchang Suppository on repairing the intestinal mucosal barrier in ulcerative colitis

Ulcerative colitis (UC) is a refractory inflammatory bowel disease, and the outcomes of conventional therapies of UC, including 5-aminosalicylic acid, glucocorticoids, immunosuppressants, and biological agents, are not satisfied with patients and physicians with regard to adverse reactions and financial burden. The abnormality of the intestinal mucosal barrier in the pathogenesis of UC was verified. Qingchang Suppository (QCS) is an herbal preparation and is effective in treating ulcerative proctitis. The mechanism of QCS and its active ingredients have not been concluded especially in mucosal healing. This review elucidated the potential mechanism of QCS from the intestinal mucosal barrier perspective to help exploring future QCS research directions.

The use of functional amino acids in different categories of pigs - A review

The present review deals with a particularly important topic: the use of functional amino acids in different categories of pigs. It is especially relevant in the context of the current efforts to reduce the use of antibiotics in pig farming and the search for possible alternatives to replace them. The review is based on the definition that functional amino acids (FAAs) are classified as dispensable amino acids, but with additional biological functions, i.e., not only are they used for protein formation, but they are also involved in regulating essential metabolic pathways to improve health, survival, growth, and development. We describe the mechanism of action of individual FAAs and their potential use in pigs, including glutamate, glutamine, arginine, branched-chain amino acids (i.e., leucine, isoleucine, and valine), tryptophan and glycine. The work is divided into three parts. The first part deals with the FAAs and their role in the overall health of sows and their offspring. The second part describes the use of functional amino acids in piglets after weaning. Part three examines the use of functional amino acids in growing and fattening pigs and their impact on meat quality.

Multispecies probiotic supplementation in diet with reduced crude protein levels altered the composition and function of gut microbiome and restored microbiome-derived metabolites in growing pigs

Both crude protein (CP) and probiotics can modulate the gut microbiome of the host, thus conferring beneficial effects. However, the benefits of low CP diet supplemented with multispecies probiotics on gut microbiome and its metabolites have not been investigated in pigs. Thus, we investigated the combinatory effects of low CP diet supplemented with multispecies probiotics on gut microbiome composition, function, and microbial metabolites in growing pigs. In total, 140 6 week-old piglets (Landrace × Yorkshire × Duroc) were used in this study. The pigs were divided into four groups with a 2 × 2 factorial design based on their diets: normal-level protein diet (16% CP; NP), low-level protein diet (14% CP; LP), NP with multispecies probiotics (NP-P), and LP with multispecies probiotics (LP-P). After the feeding trial, the fecal samples of the pigs were analyzed. The fecal scores were improved by the probiotic supplementation, especially in LP-P group. We also observed a probiotic-mediated alteration in the gut microbiome of pigs. In addition, LP-P group showed higher species richness and diversity compared with other groups. The addition of multispecies probiotics in low CP diet also enhanced gut microbiota metabolites production, such as short-chain fatty acids (SCFAs) and polyamines. Correlation analysis revealed that Oscillospiraceae UCG-002, Eubacterium coprostanoligenes, Lachnospiraceae NK4A136 group, and Muribaculaceae were positively associated with SCFAs; and Prevotella, Eubacterium ruminantium, Catenibacterium, Alloprevotella, Prevotellaceae NK3B31 group, Roseburia, Butyrivibrio, and Dialister were positively correlated with polyamines. Supplementation with multispecies probiotics modulated the function of the gut microbiome by upregulating the pathways for protein digestion and utilization, potentially contributing to enriched metabolite production in the gut. The results of this study demonstrate that supplementation with multispecies probiotics may complement the beneficial effects of low CP levels in pig feed. These findings may help formulate sustainable feeding strategies for swine production.

Composition of mucus- and digesta-associated bacteria in growing pigs with and without diarrhea differed according to the presence of colonic inflammation

BACKGROUND

In the pig production, diarrhea can occur during different growth stages including the period 4-16 weeks post weaning, during which a diarrheal outbreak also termed as colitis-complex diarrhea (CCD) can occur and it is distinct from post-weaning diarrhea (1-2 weeks post weaning). We hypothesized that CCD in growing pigs is associated with changes in colonic microbiota composition and fermentation patterns, and the aim of the present observational study was to identify changes in digesta-associated bacteria (DAB) and mucus-associated bacteria (MAB) in the colon of growing pigs with and without diarrhea. A total number of 30 pigs (8, 11, and 12 weeks of age) were selected; 20 showed clinical signs of diarrhea and 10 appeared healthy. Based on histopathological examination of colonic tissues, 21 pigs were selected for further studies and classified as follows: without diarrhea, no colon inflammation (NoDiar; n = 5), with diarrhea, without colonic inflammation (DiarNoInfl; n = 4), and with diarrhea, with colonic inflammation (DiarInfl; n = 12). Composition (based on 16S rRNA gene amplicon sequencing) and fermentation pattern (short-chain fatty acids; SCFA profile) of the DAB and MAB communities were characterized.

RESULTS

The DAB showed higher alpha diversity compared to MAB in all pigs, and both DAB and MAB showed lowest alpha diversity in the DiarNoInfl group. Beta diversity was significantly different between DAB and MAB as well as between diarrheal groups in both DAB and MAB. Compared to NoDiar, DiarInfl showed increased abundance of various taxa, incl. certain pathogens, in both digesta and mucus, as well as decreased digesta butyrate concentration. However, DiarNoInfl showed reduced abundance of different genera (mainly Firmicutes) compared to NoDiar, but still lower butyrate concentration.

CONCLUSION

Diversity and composition of MAB and DAB changed in diarrheal groups depending on presence/absence of colonic inflammation. We also suggest that DiarNoInfl group was at the earlier stage of diarrhea compared with DiarInfl, with a link to dysbiosis of colonic bacterial composition as well as reduced butyrate concentration, which plays a pivotal role in gut health. This could have led to diarrhea with inflammation due to a dysbiosis, associated with an increase in e.g., Escherichia-Shigella (Proteobacteria), Helicobacter (Campylobacterota), and Bifidobacterium (Actinobacteriota), which may tolerate or utilize oxygen and cause epithelial hypoxia and inflammation. The increased consumption of oxygen in epithelial mucosal layer by infiltrated neutrophils may also have added up to this hypoxia. Overall, the results confirmed that changes in DAB and MAB were associated with CCD and reduced butyrate concentration in digesta. Moreover, DAB might suffice for future community-based studies of CCD.

Uterine histotroph and conceptus development: III. Adrenomedullin stimulates proliferation, migration and adhesion of porcine trophectoderm cells via AKT-TSC2-MTOR cell signaling pathway

Adrenomedullin (ADM) as a highly conserved peptide hormone has been reported to increase significantly in the uterine lumen during the peri-implantation period of pregnancy in pigs, but its functional roles in growth and development of porcine conceptus (embryonic/fetus and its extra-embryonic membranes) as well as underlying mechanisms remain largely unknown. Therefore, we conducted in vitro experiments using our established porcine trophectoderm cell line (pTr2) isolated from Day-12 porcine conceptuses to test the hypothesis that porcine ADM stimulates cell proliferation, migration and adhesion via activation of mechanistic target of rapamycin (MTOR) cell signaling pathway in pTr2 cells. Porcine ADM at 10^-7 M stimulated (P < 0.05) pTr2 cell proliferation, migration and adhesion by 1.4-, 1.5- and 1.2-folds, respectively. These ADM-induced effects were abrogated (P < 0.05) by siRNA-mediated knockdown of ADM (siADM) and its shared receptor component calcitonin-receptor-like receptor (CALCRL; siCALCRL), as well as by rapamycin, the inhibitor of MTOR. Using siRNA-mediated knockdown of CALCRL coupled with Western blot analyses, ADM signaling transduction was determined in which ADM binds to CALCRL to increase phosphorylation of MTOR, its downstream effectors (4EBP1, P70S6K, and S6), and upstream regulators (AKT and TSC2). Collectively, these results suggest that porcine ADM in histotroph acts on its receptor component CALCRL to activate AKT-TSC2-MTOR, particularly MTORC1 signaling cascade, leading to elongation, migration and attachment of conceptuses.

Periodontal disease is associated with increased gut colonization of pathogenic Haemophilus parainfluenzae in patients with Crohn's disease

Intestinal colonization of the oral bacterium Haemophilus parainfluenzae has been associated with Crohn's disease (CD) severity and progression. This study examines the role of periodontal disease (PD) as a modifier for colonization of H. parainfluenzae in patients with CD and explores the mechanisms behind H. parainfluenzae-mediated intestinal inflammation. Fifty subjects with and without CD were evaluated for the presence of PD, and their oral and fecal microbiomes were characterized. PD is associated with increased levels of H. parainfluenzae strains in subjects with CD. Oral inoculation of H. parainfluenzae elicits strain-dependent intestinal inflammation in murine models of inflammatory bowel disease, which is associated with increased intestinal interferon-γ (IFN-γ)+ CD4+ T cells and disruption of the host hypusination pathway. In summary, this study establishes a strain-specific pathogenic role of H. parainfluenzae in intestinal inflammation and highlights the potential effect of PD on intestinal colonization by pathogenic H. parainfluenzae strains in patients with CD.

Aminoclay Nanoparticles Induce Anti-Inflammatory Dendritic Cells to Attenuate LPS-Elicited Pro-Inflammatory Immune Responses

Although 3-aminopropyl functionalized magnesium phyllosilicate nanoparticles (hereafter aminoclay nanoparticles, ACNs) are well-known nanomaterials employed as drug carriers, their effects on immune cells remain unclear. To address this issue, we explored murine dendritic cells (DCs) as these cells belong to the innate arm of the immune system and function as antigen-presenting cells to elicit adaptive immune responses. We examined the in vitro effects of ACNs on DCs isolated from B6 mice. ACN treatment significantly down-regulated the expression of inflammasome-related markers, including NLRP3, caspase-1, and IL1β. The ACNs-induced anti-inflammatory DC phenotype was further confirmed by down-regulation of the AKT/mTOR/HIF1α signaling pathway. Such anti-inflammatory effects of ACNs on DCs occurred independently of DC subtypes. To document the effects of ACNs on DCs more clearly, we examined their anti-inflammatory effects on lipopolysaccharide (LPS)-activated DCs. As expected, excessive inflammatory responses (increased mitochondrial ROS and Th1-type cytokines such as IL12 and IL1β) of LPS-activated DCs were dramatically attenuated by ACN treatment. Furthermore, ACNs down-regulated IFNγ production by antigen-specific CD4⁺ T cells, which is consistent with a reduced inflammatory phenotype of DCs. Overall, our results provide support for employing ACNs as drug delivery materials with therapeutic potential to control inflammatory disorders.

STIM1 promotes IPEC-J2 porcine epithelial cell restitution by TRPC1 signaling

Intestinal epithelial restitution is partly dependent on cell migration, which reseals superficial wounding after injury. Here, we tested the hypothesis that stromal interaction molecule 1(STIM1) regulates porcine intestinal epithelial cell migration by activating transient receptor potential canonical 1 (TRPC1) signaling. Results showed that the knockdown of STIM1 repressed cell migration after wounding, reduced the protein concentration of STIM1 and TRPC1, and decreased the inositol trisphosphate (IP3) content in IPEC-J2 cells (p < 0.05). However, overexpression of STIM1 obtained opposite results (p < 0.05). The inhibition of TRPC1 activity by treatment with SKF96365 in cells overexpressing wild-type and mutant STIM1 attenuated the STIM1 overexpression-induced increase of cell migration, STIM1, TRPC1 and IP3 (p < 0.05). In addition, polyamine depletion caused by α-difluoromethylornithine (DFMO) resulted in the decrease of above-mentioned parameters, and exogenous polyamine could attenuate the negative effects of DFMO on IPEC-J2 cells (p < 0.05). Moreover, the overexpression of STIM1 could rescue cell migration, the protein level of STIM1 and TRPC1, and IP3 content in polyamine-deficient IPEC-J2 cells (p < 0.05). These results indicated that STIM1 could enhance porcine intestinal epithelial cell migration via the TRPC1 signaling pathway. Inhibition of cell migration by polyamine depletion resulted from the reduction of STIM1 activity.

Rooibos (Aspalathus linearis) alters secretome trace amine profile of probiotic and commensal microbes in vitro

ETHNOPHARMACOLOGY RELEVANCE

Aspalathus linearis (Burm.f.) R. Dahlgren (rooibos) tea is anecdotally renowned for its calming effect in the context of gastrointestinal discomfort, but little scientific support is available to elucidate potential mechanisms of action. Enhancement of dietary polyphenol content to improve gut health via prebiotic-like modulation of the gut microbiota has gained significant research interest. Given the known high polyphenol content of rooibos, rooibos tea may potentially exert a prebiotic effect in the gut to facilitate an improvement in chronic inflammatory gastrointestinal conditions.

AIM OF THE STUDY

This study aimed to determine the prebiotic or health-modulating potential of rooibos tea in terms of its effect on gut microbial growth and secretome trace amine composition, as well as to determine how differential rooibos processing alters this activity.

METHODS

Three rooibos preparations (green and fermented leave aqueous extracts, as well as a green leaf ethanol extract) were compared in terms of their phenolic composition (qTOF-LC/MS). Moreover, the effect of rooibos exposure on growth and secretome trace amine levels of probiotic and commensal microbes were assessed (LC/MS). In addition, given the known female bias prevalent for many gastrointestinal disorders, experiments were conducted in the absence and presence of estradiol.

RESULTS

Polyphenolic composition of rooibos was drastically reduced by fermentation. Aqueous extracts of both green and fermented rooibos improved microbial growth, although fermented rooibos had the most pronounced effect (p < 0.01). In terms of secretome trace amine profile, both aqueous extracts of rooibos seemed to facilitate increased putrescine secretion (p < 0.0001) and decreased tryptamine production (p < 0.0001). Estradiol seemed to suppress trace amine secretion by bacteria (Lactobacillus plantarum, Lactobacillus reuteri and Enterococcus mundtii) but increased it in yeast (Saccharomyces boulardii).

CONCLUSION

Rooibos altered gut probiotic and commensal microbial growth and secretome trace amine profiles in vitro, suggesting it has potential to modulate gut microbial composition and functionality as a prebiotic. Current data suggest that these effects are highly dependent on raw material processing. Finally, rooibos may be able to prevent estradiol-associated alterations in trace amine profile, which may have important implications for patient management in female-predominant gastrointestinal disorders.

Role of the microbiome and its metabolites in ankylosing spondylitis

Ankylosing spondylitis (AS), a chronic condition that commonly influences the spine and sacroiliac joints, usually progresses to stiffness and progressive functional limitation. Its fundamental etiology and pathogenesis are likely multifactorial and remain elusive. As environmental factors, gut microbiota performs critical functions in the pathogenesis of AS through various mechanisms, including interacting with genes, enhancing intestinal permeability, activating the gut mucosa immune system, and affecting the intestinal microbiota metabolites. This review provides an overview of recent advances in investigating gut microbiota in AS pathogenesis and discusses potential methods for future therapeutic intervention.

The role of polyamine metabolism in remodeling immune responses and blocking therapy within the tumor immune microenvironment

The study of metabolism provides important information for understanding the biological basis of cancer cells and the defects of cancer treatment. Disorders of polyamine metabolism is a common metabolic change in cancer. With the deepening of understanding of polyamine metabolism, including molecular functions and changes in cancer, polyamine metabolism as a new anti-cancer strategy has become the focus of attention. There are many kinds of polyamine biosynthesis inhibitors and transport inhibitors, but not many drugs have been put into clinical application. Recent evidence shows that polyamine metabolism plays essential roles in remodeling the tumor immune microenvironment (TIME), particularly treatment of DFMO, an inhibitor of ODC, alters the immune cell population in the tumor microenvironment. Tumor immunosuppression is a major problem in cancer treatment. More and more studies have shown that the immunosuppressive effect of polyamines can help cancer cells to evade immune surveillance and promote tumor development and progression. Therefore, targeting polyamine metabolic pathways is expected to become a new avenue for immunotherapy for cancer.

Gut microbiome-produced metabolites in pigs: a review on their biological functions and the influence of probiotics

The gastrointestinal tract is a complex ecosystem that contains a large number of microorganisms with different metabolic capacities. Modulation of the gut microbiome can improve the growth and promote health in pigs. Crosstalk between the host, diet, and the gut microbiome can influence the health of the host, potentially through the production of several metabolites with various functions. Short-chain and branched-chain fatty acids, secondary bile acids, polyamines, indoles, and phenolic compounds are metabolites produced by the gut microbiome. The gut microbiome can also produce neurotransmitters (such as γ-aminobutyric acid, catecholamines, and serotonin), their precursors, and vitamins. Several studies in pigs have demonstrated the importance of the gut microbiome and its metabolites in improving growth performance and feed efficiency, alleviating stress, and providing protection from pathogens. The use of probiotics is one of the strategies employed to target the gut microbiome of pigs. Promising results have been published on the use of probiotics in optimizing pig production. This review focuses on the role of gut microbiome-derived metabolites in the performance of pigs and the effects of probiotics on altering the levels of these metabolites.

Calcium-sensing receptor protects intestinal integrity and alleviates the inflammatory response via the Rac1/PLCγ1 signaling pathway

This study aimed to test the hypothesis that the calcium-sensing receptor (CaSR) can protect intestinal epithelial barrier integrity and decrease inflammatory response mediated by the Ras-related C3 botulinum toxin substrate 1 (Rac1)/phospholipase Cγ1 (PLC-γ1) signaling pathway. IPEC-J2 monolayers were treated without or with TNF-α in the absence or presence of CaSR antagonist (NPS 2143), CaSR overexpression, and Rac1 silencing, PLCγ1 silencing or spermine. Results showed that spermine increased transepithelial electrical resistance (TER), tight junction protein levels, the protein concentration of Rac1/PLC-γ1 signaling pathway, and decreased paracellular permeability in the presence of TNF-α. NPS2143 inhibited spermine-induced change in above-mentioned parameters. CaSR overexpression increased TER, the levels of tight junction proteins and the protein concentration of CaSR, phosphorylated PLCγ1, Rac1, and IP3, and decreased paracellular permeability and contents of interleukin-8 (IL-8) and TNF-α after TNF-α challenge. Rac1 and PLCγ1 silencing inhibited CaSR-induced increase in barrier function and the protein concentration of phosphorylated PLCγ1, Rac1, and IP3, and decrease in contents of IL-8 and TNF-α after TNF-α challenge. These results suggest that CaSR activation protects intestinal integrity and alleviates the inflammatory response by activating Rac1 and PLCγ1 signaling after TNF-α challenge, and spermine can maintain barrier function via CaSR/Rac1/PLC-γ1 pathway.

Bacterial-Induced Blood Pressure Reduction: Mechanisms for the Treatment of Hypertension via the Gut

Hypertension is a major risk factor for the development of cardiovascular disease. As more research into the gut microbiome emerges, we are finding increasing evidence to support that these microbes may have significant positive and negative effects on blood pressure and associated disorders. The bacterial-derived metabolites that are produced in the gut are capable of widespread effects to several tissue types and organs in the body. It is clear that the extensive metabolic function that is lost with gut dysbiosis is unlikely to be replenished with a single metabolite or bacterial strain. Instead, combinations of bacteria and concomitant therapies will provide a more well-rounded solution to manage hypertension. The bioactive molecules that are recognized in this review will inform on ideal characteristics of candidate bacteria and provide direction for future research on the gut microbiome in hypertension.

Effect of calcium-sensing receptor on the migration and proliferation of porcine intestinal epithelial cells

The rapid healing of impaired intestinal surface plays a role in maintaining intestinal homeostasis. This study investigated the effect of calcium-sensing receptor (CaSR) on the migration and proliferation of intestinal porcine epithelial cells (IPEC-J2). Results showed that cell migration area and width were increased by R568 (CaSR activator) and decreased by NPS2143 (CaSR inhibitor). The protein level of GTP-rac1 and the phosphorylation of phospholipase C gamma 1 (PLCγ1) were increased by 2 µM R568. Furthermore, R568 + 120 µM NSC23766 (Rac1 inhibitor) and R568 + 1 µM U73122 (PLCγ1 inhibitor) decreased the protein level of GTP-rac1 and the phosphorylated PLCγ1, respectively, and both inhibited cell migration compared with R568. In addition, spermine increased the protein expression levels of CaSR and the levels of GTP-rac1 and the phosphorylated PLCγ1 and thereby promoted the migration of IPEC-J2 cells. Moreover, R568 improved the proliferation of the IPEC-J2 cells. Spermine increased cell proliferation, but NPS2143 incubated with spermine decreased cell proliferation compared with the spermine group. This study suggests that CaSR activation increased cell migration by activating Rac1 and PLCγ1 signaling and improved cell proliferation, and both effects were regulated by spermine by activating CaSR.

Effects of spermine on the proliferation and migration of porcine intestinal epithelial cells

Whether spermine promotes the repair of porcine intestinal epithelium damage through Ras-related C3 botulinum toxin substrate 1 (Rac1)/phospholipase C-γ1 (PLC-γ1) signaling remains unclear. The current study investigated the effects of spermine addition on the proliferation and migration of IPEC-J2 cells and the effects of Rac1/PLC-γ1 signaling on cell migration. We showed that the inhibitors of Rac1 (NSC-23766) and PLC-γ1 (U73122) reduced cell migration and decreased the protein levels of Rac1 and PLC-γ1 in the cells. Moreover, spermine promoted the proliferation and migration of the IPEC-J2 cells, that is, 1 µM spermine exhibited the best effect, and spermine treatment increased the protein levels of Rac1 and PLC-γ1. Further experiments showed that spermine treatment increased cell migration and enhanced Rac1 and PLC-γ1 protein levels, compared with NSC-23766 and U73122 treatments with spermine. In conclusion, spermine treatment promoted the repair of damaged porcine intestinal epithelium by accelerating cell proliferation and migration mediated by Rac1/PLC-γ1 signaling.

Gallic acid mitigates LPS-induced inflammatory response via suppressing NF-κB signalling pathway in IPEC-J2 cells

Gallic acid is a phenolic compound that exhibits antibacterial, antioxidative and anti-inflammatory functions. In a previous study, we found that dietary supplementation with gallic acid decreased incidence of diarrhoea and protected intestinal integrity in weaning piglets. However, the underlying mechanism remains unclear. Here, a pig intestinal epithelial cell line (IPEC-J2) was used as an in vitro model to explore the antioxidant and anti-inflammatory capacity of gallic acid. IPEC-J2 cells were stimulated with hydrogen peroxide (H₂ O₂ ) and lipopolysaccharide (LPS) to establish oxidative and inflammatory models, respectively. Results showed that H₂ O₂ significantly decreased catalase (CAT) secretion and CAT mRNA abundance in the cells (p < 0.05), while pretreatment with gallic acid did not prevent the decrease in CAT expression induced by H₂ O₂ . However, gallic acid pretreatment mitigated the increased expression of the tumour necrosis factor-α and interleukin-8 genes caused by LPS in IPEC-J2 cells (p < 0.05). In addition, pretreatment with gallic acid significantly suppressed phosphorylation of NF-κB and IκBα in LPS-stimulated IPEC-J2 cells. Moreover, LPS stimulation decreased the protein abundance of zona occludens 1 (ZO-1) and occludin, while pretreatment with gallic acid preserved expression level of tight junction proteins ZO-1 and occludin in LPS-stimulated IPEC-J2 cells (p < 0.05). In conclusion, gallic acid may mitigate LPS-induced inflammatory responses by inhibiting the NF-κB signalling pathway, exerting positive effects on the barrier function of IPEC-J2 cells.

Metabolome-Microbiome Responses of Growing Pigs Induced by Time-Restricted Feeding

Time-restricted feeding (TRF) mode is a potential strategy in improving the health and production of farm animals. However, the effect of TRF on microbiota and their metabolism in the large intestine of the host remains unclear. Therefore, the present study aimed to investigate the responses of microbiome and metabolome induced by TRF based on a growing-pig model. Twelve crossbred growing barrows were randomly allotted into two groups with six replicates (1 pig/pen), namely, the free-access feeding group (FA) and TRF group. Pigs in the FA group were fed free access while the TRF group were fed free access within a regular time three times per day at 07:00–08:00, 12:00–13:00, and 18:00–19:00, respectively. Results showed that the concentrations of NH4-N, putrescine, cadaverine, spermidine, spermine, total biogenic amines, isobutyrate, butyrate, isovalerate, total SCFA, and lactate were increased while the pH value in the colonic digesta and the concentration of acetate was decreased in the TRF group. The Shannon index was significantly increased in the TRF group; however, no significant effects were found in the Fisher index, Simpson index, ACE index, Chao1 index, and observed species between the two groups. In the TRF group, the relative abundances of Prevotella 1 and Eubacterium ruminantium group were significantly increased while the relative abundances of Clostridium sensu sticto 1, Lactobacillus, and Eubacterium coprostanoligenes group were decreased compared with the FA group. PLS-DA analysis revealed an obvious and regular variation between the FA and TRF groups, further pathway enrichment analysis showed that these differential features were mainly enriched in pyrimidine metabolism, nicotinate and nicotinamide metabolism, glycerolipid metabolism, and fructose and mannose metabolism. In addition, Pearson's correlation analysis indicated that the changes in the microbial genera were correlated with the colonic metabolites. In conclusion, these results together indicated that although the overall microbial composition in the colon was not changed, TRF induced the gradient changes of the nutrients and metabolites which were correlated with certain microbial genera including Lactobacillus, Eubacterium_ruminantium group, Eubacterium coprostanoligenes group, Prevotella 1, and Clostridium sensu sticto 1. However, more studies are needed to understand the impacts of TRF on the health and metabolism of growing pigs.

Pyrroloquinoline quinone regulates the redox status in vitro and in vivo of weaned pigs via the Nrf2/HO-1 pathway

Background

Oxidative stress is a main cause of piglet gut damage and diarrhea. Pyrroloquinoline quinone (PQQ), is a novel redox cofactor with antioxidant properties. However, the effect and mechanism that PQQ supplementation decreases oxidative injury in weaned pigs is not understood. Therefore, the aim of this study is to confirm the effect of PQQ on regulating redox status in weaned pigs and the mechanism for antioxidant function by porcine intestinal epithelial cell line (IPEC-J2) challenged with H₂O₂.

Results

Experiment 1, 144 Duroc × Landrace × Yorkshire pigs (weaned at 28 d) were allocated to four groups: received a basal diet (control) and diets supplemented with 0.15%, 0.30% and 0.45% PQQ, respectively. On d 28, growth performance, diarrhea incidence and redox factors were measured. Experiment 2, IPEC-J2 were treated with or without PQQ in the presence or absence of H₂O₂ for indicated time points. Experiment 3, IPEC-J2 were transfected with or without Nrf2 siRNA, then treated according to Experiment 2. The cell viability, redox factors, protein of tight junctions and Nrf2 pathway were determined.

In vivo, PQQ supplementation demonstrated dose-related improvements in average daily gain, and gain to feed ratio (Linear P < 0.05). During d 0–28, compared to controls, 0.45% PQQ supplementation for pigs decreased diarrhea incidence and MDA content in liver and jejunum, and increased concentration of SOD in liver; 0.3% PQQ supplementation decreased ileal and liver MDA concentration; and 0.15% PQQ supplementation decreased ileal MDA concentration (P < 0.05). In vitro, compared to cells cultured with H₂O₂, pre-treatment with PQQ increased cell viability, tight junction proteins expression including ZO-1, ZO-2, Occludin and Claudin-1; and decreased ROS concentration and level of Caspase-3 (P < 0.05); as well as upregulated the ratio of Bcl-2 to Bax and protein expression of nuclear Nrf2, HO-1. Notably, Nrf2 knockdown by transfection with Nrf2 siRNA largely abrogated the positive effects of PQQ pretreatment on H₂O₂-induced intracellular changes.

Conclusions

PQQ administration attenuated oxidative stress in weaned pigs which is associated with activation of Nrf2/HO-1 pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00595-x.

ODC (Ornithine Decarboxylase)-Dependent Putrescine Synthesis Maintains MerTK (MER Tyrosine-Protein Kinase) Expression to Drive Resolution

OBJECTIVE

ODC (ornithine decarboxylase)-dependent putrescine synthesis promotes the successive clearance of apoptotic cells (ACs) by macrophages, contributing to inflammation resolution. However, it remains unknown whether ODC is required for other arms of the resolution program. Approach and Results: RNA sequencing of ODC-deficient macrophages exposed to ACs showed increases in mRNAs associated with heightened inflammation and decreases in mRNAs related to resolution and repair compared with WT (wild type) macrophages. In zymosan peritonitis, myeloid ODC deletion led to delayed clearance of neutrophils and a decrease in the proresolving cytokine, IL (interleukin)-10. Nanoparticle-mediated silencing of macrophage ODC in a model of atherosclerosis regression lowered IL-10 expression, decreased efferocytosis, enhanced necrotic core area, and reduced fibrous cap thickness. Mechanistically, ODC deletion lowered basal expression of MerTK (MER tyrosine-protein kinase)-an AC receptor-via a histone methylation-dependent transcriptional mechanism. Owing to lower basal MerTK, subsequent exposure to ACs resulted in lower MerTK-Erk (extracellular signal-regulated kinase) 1/2-dependent IL-10 production. Putrescine treatment of ODC-deficient macrophages restored the expression of both MerTK and AC-induced IL-10.

CONCLUSIONS

These findings demonstrate that ODC-dependent putrescine synthesis in macrophages maintains a basal level of MerTK expression needed to optimally resolve inflammation upon subsequent AC exposure. Graphic Abstract: A graphic abstract is available for this article.

Microbial-derived antigens and metabolites in spondyloarthritis

Spondyloarthritis (SpA) is a group of chronic, immune-mediated, inflammatory diseases affecting the bone, synovium, and enthesis. Microbiome, the community of microorganisms that has co-evolved with human hosts, plays a pivotal role in human health and disease. This invisible "essential organ" supplies the host with a myriad of chemicals and molecules. In turn, microbial metabolites can serve as messengers for microbes to communicate with each other and in the cross-talk with host cells. Gut dysbiosis in SpA is associated with altered microbial metabolites, and an accumulated body of research has contributed to the understanding that changes in intestinal microbiota can modulate disease pathogenesis. We review the novel findings from human and animal studies to provide an overview of the contribution of individual microbial metabolites and antigens to SpA.

Impacts of Amino Acids on the Intestinal Defensive System

The intestine interacts with a diverse community of antigens and bacteria. To keep its homeostasis, the gut has evolved with a complex defense system, including intestinal microbiota, epithelial layer and lamina propria. Various factors (e.g., nutrients) affect the intestinal defensive system and progression of intestinal diseases. This review highlights the current understanding about the role of amino acids (AAs) in protecting the intestine from harm. Amino acids (e.g., arginine, glutamine and tryptophan) are essential for the function of intestinal microbiota, epithelial cells, tight junction, goblet cells, Paneth cells and immune cells (e.g., macrophages, B cells and T cells). Through the modulation of the intestinal defensive system, AAs maintain the integrity and function of the intestinal mucosa and inhibit the progression of various intestinal diseases (e.g., intestinal infection and intestinal colitis). Thus, adequate intake of functional AAs is crucial for intestinal and whole-body health in humans and other animals.