Reactivation of Intestinal Inflammation Is Suppressed by Catestatin in a Murine Model of Colitis via M1 Macrophages and Not the Gut Microbiota

Microbiome in cancer: A comparative analysis between humans and dogs

Cancer is a major cause of death in humans and animals worldwide. While cancer survival rates have increased over recent decades, further research to identify risk factors for the onset and progression of disease, and safe and highly efficacious treatments, is needed. Spontaneous tumours in pets represent an excellent model for neoplastic disease in humans. In this regard, dogs are an interesting species, as the divergence between the dog and human genome is low, humans and dogs have important similarities in the development and functioning of the immune system, and both species often share the same physical environment. There is also a higher homology between the canine and human microbiome than murine model. This review aims to describe and organize recently published information on canine microbiome assemblages and their relationship with the onset and progression of colorectal cancer, breast cancer and lymphoma, and to compare this with human disease. In both species, dysbiosis can induce variations in the gut microbiota that strongly influence shifts in status between health and disease. This can produce an inflammatory state, potentially leading to neoplasia, especially in the intestine, thus supporting canine studies in comparative oncology. Intestinal dysbiosis can also alter the efficacy and side effects of cancer treatments. Fewer published studies are available on changes in the relevant microbiomes in canine lymphoma and mammary cancer, and further research in this area could improve our understanding of the role of microbiota in the development of these cancers.

FAM76B regulates PI3K/Akt/NF-κB-mediated M1 macrophage polarization by influencing the stability of PIK3CD mRNA

Macrophage polarization is closely related to inflammation development, yet how macrophages are polarized remains unclear. In our study, the number of M1 macrophages was markedly increased in Fam76b knockout U937 cells vs. wild-type U937 cells, and FAM76B expression was decreased in M1 macrophages induced from different sources of macrophages. Moreover, Fam76b knockout enhanced the mRNA and protein levels of M1 macrophage-associated marker genes. These results suggest that FAM76B inhibits M1 macrophage polarization. We then further explored the mechanism by which FAM76B regulates macrophage polarization. We found that FAM76B can regulate PI3K/Akt/NF-κB pathway-mediated M1 macrophage polarization by stabilizing PIK3CD mRNA. Finally, FAM76B was proven to protect against inflammatory bowel disease (IBD) by inhibiting M1 macrophage polarization through the PI3K/Akt/NF-κB pathway in vivo. In summary, FAM76B regulates M1 macrophage polarization through the PI3K/Akt/NF-κB pathway in vitro and in vivo, which may inform the development of future therapeutic strategies for IBD and other inflammatory diseases.

The Role of Catestatin in Preeclampsia

Preeclampsia (PE) is a unique pregnancy disorder affecting women across the world. It is characterized by the new onset of hypertension with coexisting end-organ damage. Although the disease has been known for centuries, its exact pathophysiology and, most importantly, its prevention remain elusive. The basis of its associated molecular changes has been attributed to the placenta and the hormones regulating its function. One such hormone is chromogranin A (CgA). In the placenta, CgA is cleaved to form a variety of biologically active peptides, including catestatin (CST), known inter alia for its vasodilatory effects. Recent studies indicate that the CST protein level is diminished both in patients with hypertension and those with PE. Therefore, the aim of the present paper is to review the most recent and most relevant in vitro, in vivo, and clinical studies to provide an overview of the proposed impact of CST on the molecular processes of PE and to consider the possibilities for future experiments in this area.

Catestatin: Antimicrobial Functions and Potential Therapeutics

The rapid increase in drug-resistant and multidrug-resistant infections poses a serious challenge to antimicrobial therapies, and has created a global health crisis. Since antimicrobial peptides (AMPs) have escaped bacterial resistance throughout evolution, AMPs are a category of potential alternatives for antibiotic-resistant "superbugs". The Chromogranin A (CgA)-derived peptide Catestatin (CST: hCgA352-372; bCgA344-364) was initially identified in 1997 as an acute nicotinic-cholinergic antagonist. Subsequently, CST was established as a pleiotropic hormone. In 2005, it was reported that N-terminal 15 amino acids of bovine CST (bCST1-15 aka cateslytin) exert antibacterial, antifungal, and antiyeast effects without showing any hemolytic effects. In 2017, D-bCST1-15 (where L-amino acids were changed to D-amino acids) was shown to exert very effective antimicrobial effects against various bacterial strains. Beyond antimicrobial effects, D-bCST1-15 potentiated (additive/synergistic) antibacterial effects of cefotaxime, amoxicillin, and methicillin. Furthermore, D-bCST1-15 neither triggered bacterial resistance nor elicited cytokine release. The present review will highlight the antimicrobial effects of CST, bCST1-15 (aka cateslytin), D-bCST1-15, and human variants of CST (Gly364Ser-CST and Pro370Leu-CST); evolutionary conservation of CST in mammals; and their potential as a therapy for antibiotic-resistant "superbugs".

Chromogranin A: An Endocrine Factor of Pregnancy

Pregnancy is a state of physiological and hormonal changes. One of the endocrine factors involved in these processes is chromogranin A, an acidic protein produced, among others, by the placenta. Although it has been previously linked to pregnancy, no existing articles have ever managed to clarify the role of this protein regarding this subject. Therefore, the aim of the present study is to gather knowledge of chromogranin A's function with reference to gestation and parturition, clarify elusive information, and, most importantly, to formulate hypotheses for the future studies to verify.

NF-κB p65 and SETDB1 expedite lipopolysaccharide-induced intestinal inflammation in mice by inducing IRF7/NLR-dependent macrophage M1 polarization

Macrophages exhibit distinct phenotypes that are pro-inflammatory (M1) or anti-inflammatory (M2) in response to inflammation. In this study, we tried to identify the roles and mechanisms of interferon regulatory factor 7 (IRF7) in modulating the phenotypes of macrophages in lipopolysaccharide (LPS)-induced intestinal inflammation. The mouse model of intestinal inflammation was induced by lipopolysaccharide (LPS), and mouse bone marrow-derived macrophages (BMDMs) and mouse intestinal epithelial cells were selected for experimental verification in vitro. Results demonstrated that IRF7 was highly expressed in the mouse model of intestinal inflammation, while IRF7 deficiency repressed macrophage M1 polarization and attenuated intestinal inflammation in mice. p65 and SET domain bifurcated 1 (SETDB1) synergistically promoted histone 3 lysine 4 trimethylation (H3K4me3) methylation to elevate IRF7 expression, which activated the Nod-like receptor (NLR) pathway to induce macrophage M1 polarization. Through this mechanism, IRF7 in BMDMs functioned to accelerate intestinal epithelial cell apoptosis and their release of pro-inflammatory proteins. Furthermore, the promoting effect of p65 and SETDB1 on LPS-induced intestinal inflammation was validated in vivo. To sum up, NF-κB p65 and SETDB1 facilitated IRF7-mediated macrophage M1 polarization, thereby aggravating the LPS-induced intestinal inflammation. Hence, this study highlights the appealing value of these factors as anti-inflammatory targets.

Lycium barbarum polysaccharide alleviates dextran sodium sulfate-induced inflammatory bowel disease by regulating M1/M2 macrophage polarization via the STAT1 and STAT6 pathways

Disruption of colonic homeostasis caused by aberrant M1/M2 macrophage polarization contributes to the development of inflammatory bowel disease (IBD). Lycium barbarum polysaccharide (LBP) is the primary active constituent of traditional Chinese herbal Lycium barbarum L., which has been widely demonstrated to have important functions in regulating immune activity and anti-inflammatory. Thus, LBP may protect against IBD. To test this hypothesis, the DSS-induced colitis model was established in mice, then the mice were treated with LBP. The results indicated that LBP attenuated the weight loss, colon shortening, disease activity index (DAI), and histopathological scores of colon tissues in colitis mice, suggesting that LBP could protect against IBD. Besides, LBP decreased the number of M1 macrophages and the protein level of Nitric oxide synthase 2(NOS2) as a marker of M1 macrophages and enhanced the number of M2 macrophages and the protein level of Arginase 1(Arg-1) as a marker of M2 macrophages in colon tissues from mice with colitis, suggesting that LBP may protect against IBD by regulating macrophage polarization. Next, the mechanistic studies in RAW264.7 cells showed that LBP inhibited M1-like phenotype by inhibiting the phosphorylation of STAT1, and promoted M2-like phenotype by promoting the phosphorylation of STAT6. Finally, immunofluorescence double-staining results of colon tissues showed that LBP regulated STAT1 and STAT6 pathways in vivo. The results in the study demonstrated that LBP could protect against IBD by regulating macrophage polarization through the STAT1 and STAT6 pathways.

Recent Advances in Multifunctional Antimicrobial Peptides as Immunomodulatory and Anticancer Therapy: Chromogranin A-Derived Peptides and Dermaseptins as Endogenous versus Exogenous Actors

Antimicrobial peptides (AMPs) are produced by all living organisms exhibiting antimicrobial activities and representing the first line of innate defense against pathogens. In this context, AMPs are suggested as an alternative to classical antibiotics. However, several researchers reported their involvement in different processes defining them as Multifunctional AMPs (MF-AMPs). Interestingly, these agents act as the endogenous responses of the human organism against several dangerous stimuli. Still, they are identified in other organisms and evaluated for their anticancer therapy. Chromogranin A (CgA) is a glyco-phosphoprotein discovered for the first time in the adrenal medulla but also produced in several cells. CgA can generate different derived AMPs influencing numerous physiological processes. Dermaseptins (DRSs) are a family of α-helical-shaped polycationic peptides isolated from the skin secretions of several leaf frogs from the Phyllomedusidae family. Several DRSs were identified as AMPs and, until now, more than 65 DRSs have been classified. Recently, these exogenous molecules were characterized for their anticancer activity. In this review, we summarize the role of these two classes of MF-AMPs as an example of endogenous molecules for CgA-derived peptides, able to modulate inflammation but also as exogenous molecules for DRSs, exerting anticancer activities.

The antimicrobial peptides secreted by the chromaffin cells of the adrenal medulla link the neuroendocrine and immune systems: From basic to clinical studies

The increasing resistance to antibiotic treatments highlights the need for the development of new antimicrobial agents. Antimicrobial peptides (AMPs) have been studied to be used in clinical settings for the treatment of infections. Endogenous AMPs represent the first line defense of the innate immune system against pathogens; they also positively interfere with infection-associated inflammation. Interestingly, AMPs influence numerous biological processes, such as the regulation of the microbiota, wound healing, the induction of adaptive immunity, the regulation of inflammation, and finally express anti-cancer and cytotoxic properties. Numerous peptides identified in chromaffin secretory granules from the adrenal medulla possess antimicrobial activity: they are released by chromaffin cells during stress situations by exocytosis via the activation of the hypothalamo-pituitary axis. The objective of the present review is to develop complete informations including (i) the biological characteristics of the AMPs produced after the natural processing of chromogranins A and B, proenkephalin-A and free ubiquitin, (ii) the design of innovative materials and (iii) the involvement of these AMPs in human diseases. Some peptides are elective biomarkers for critical care medicine, may play an important role in the protection of infections (alone, or in combination with others or antibiotics), in the prevention of nosocomial infections, in the regulation of intestinal mucosal dynamics and of inflammation. They could play an important role for medical implant functionalization, such as catheters, tracheal tubes or oral surgical devices, in order to prevent infections after implantation and to promote the healing of tissues.

Prognostic Value of Catestatin in Severe COVID-19: An ICU-Based Study

Catestatin is a pleiotropic peptide with a wide range of immunomodulatory effects. Considering that patients with a severe COVID-19 infection have a major immunological dysregulation, the aim of this study was to evaluate catestatin levels in patients with COVID-19 treated in the intensive care unit (ICU) and to compare them between the fatal and non-fatal outcomes. The study included 152 patients with severe COVID-19, out of which 105 had a non-fatal outcome and 47 had a fatal outcome. Serum catestatin levels were estimated by an enzyme-linked immunosorbent assay in a commercially available diagnostic kit. The results show that catestatin levels were significantly lower in the fatal group compared to the non-fatal group (16.6 ± 7.8 vs. 23.2 ± 9.2 ng/mL; p < 0.001). Furthermore, there was a significant positive correlation between serum catestatin levels and vitamin D levels (r = 0.338; p < 0.001) while there was also a significant positive correlation between serum catestatin levels and growth differentiation factor-15 (GDF-15) levels (r = −0.345; p < 0.001). Furthermore, multivariate logistic regression showed that catestatin, GDF-15 and leukocyte count were significant predictors for COVID-19 survival. These findings imply that catestatin could be playing a major immunomodulatory role in the complex pathophysiology of the COVID-19 infection and that serum catestatin could also be a predictor of a poor COVID-19 outcome.

Catestatin induces glycogenesis by stimulating the phosphoinositide 3-kinase-AKT pathway

AIM

Defects in hepatic glycogen synthesis contribute to post-prandial hyperglycaemia in type 2 diabetic patients. Chromogranin A (CgA) peptide Catestatin (CST: hCgA352-372 ) improves glucose tolerance in insulin-resistant mice. Here, we seek to determine whether CST induces hepatic glycogen synthesis.

METHODS

We determined liver glycogen, glucose-6-phosphate (G6P), uridine diphosphate glucose (UDPG) and glycogen synthase (GYS2) activities; plasma insulin, glucagon, noradrenaline and adrenaline levels in wild-type (WT) as well as in CST knockout (CST-KO) mice; glycogen synthesis and glycogenolysis in primary hepatocytes. We also analysed phosphorylation signals of insulin receptor (IR), insulin receptor substrate-1 (IRS-1), phosphatidylinositol-dependent kinase-1 (PDK-1), GYS2, glycogen synthase kinase-3β (GSK-3β), AKT (a kinase in AKR mouse that produces Thymoma)/PKB (protein kinase B) and mammalian/mechanistic target of rapamycin (mTOR) by immunoblotting.

RESULTS

CST stimulated glycogen accumulation in fed and fasted liver and in primary hepatocytes. CST reduced plasma noradrenaline and adrenaline levels. CST also directly stimulated glycogenesis and inhibited noradrenaline and adrenaline-induced glycogenolysis in hepatocytes. In addition, CST elevated the levels of UDPG and increased GYS2 activity. CST-KO mice had decreased liver glycogen that was restored by treatment with CST, reinforcing the crucial role of CST in hepatic glycogenesis. CST improved insulin signals downstream of IR and IRS-1 by enhancing phospho-AKT signals through the stimulation of PDK-1 and mTORC2 (mTOR Complex 2, rapamycin-insensitive complex) activities.

CONCLUSIONS

CST directly promotes the glycogenic pathway by (a) reducing glucose production, (b) increasing glycogen synthesis from UDPG, (c) reducing glycogenolysis and (d) enhancing downstream insulin signalling.

Serum catestatin levels in patients with rheumatoid arthritis

Catestatin (CST) is an important peptide that influences various inflammatory diseases. Our goal was to investigate CST concentrations in patients with RA compared to healthy subjects. This cross-sectional observational study included 80 patients with RA and 80 healthy control subjects. Demographic characteristics and laboratory parameters were recorded. Serum CST levels were determined by an enzyme-linked immunosorbent assay (ELISA). Serum CST levels were significantly higher in RA patients than in the control group (10.53 ± 3.90 vs 5.24 ± 2.37 ng/mL, p < 0.001). In RA patients, there was a statistically significant correlation between CST and patient age (r = 0.418, p < 0.001) and both DAS28 (r = 0.469, p < 0.001) and HAQ scores (r = 0.483, p < 0.001). There was a statistically significant correlation between serum CST levels and RA duration (r = 0.583, p < 0.001). Multiple linear regression analysis showed that serum CST levels retained a significant association with RA duration (β ± SE, 0.13 ± 0.04, p = 0.002) and DAS28 score (0.94 ± 0.45, p = 0.039) after model adjustment for age, body mass index (BMI) and HAQ score, with serum CST levels as a dependent variable. These findings imply that CST is possibly associated with RA complex pathophysiology and disease activity. However, future larger multicentric longitudinal studies are necessary to define the role of CST in RA.

Putative regulation of macrophage-mediated inflammation by catestatin

Catestatin (CST) is a bioactive cleavage product of the neuroendocrine prohormone chromogranin A (CgA). Recent findings show that CST can exert anti-inflammatory and antiadrenergic effects by suppressing the inflammatory actions of mammalian macrophages. However, recent findings also suggest that macrophages themselves are major CST producers. Here, we hypothesize that macrophages produce CST in an inflammation-dependent manner and thereby might self-regulate inflammation in an autocrine fashion. CST is associated with pathological conditions hallmarked by chronic inflammation, including autoimmune, cardiovascular, and metabolic disorders. Since intraperitoneal injection of CST in mouse models of diabetes and inflammatory bowel disease has been reported to be beneficial for mitigating disease, we posit that CST should be further investigated as a candidate target for treating certain inflammatory diseases.

Chromogranin A regulates gut permeability via the antagonistic actions of its proteolytic peptides

AIM

A "leaky" gut barrier has been implicated in the initiation and progression of a multitude of diseases, for example, inflammatory bowel disease (IBD), irritable bowel syndrome and celiac disease. Here we show how pro-hormone Chromogranin A (CgA), produced by the enteroendocrine cells, and Catestatin (CST: hCgA_352-372 ), the most abundant CgA-derived proteolytic peptide, affect the gut barrier.

METHODS

Colon tissues from region-specific CST-knockout (CST-KO) mice, CgA-knockout (CgA-KO) and WT mice were analysed by immunohistochemistry, western blot, ultrastructural and flowcytometry studies. FITC-dextran assays were used to measure intestinal barrier function. Mice were supplemented with CST or CgA fragment pancreastatin (PST: CgA_250-301 ). The microbial composition of cecum was determined. CgA and CST levels were measured in blood of IBD patients.

RESULTS

Plasma levels of CST were elevated in IBD patients. CST-KO mice displayed (a) elongated tight, adherens junctions and desmosomes similar to IBD patients, (b) elevated expression of Claudin 2, and (c) gut inflammation. Plasma FITC-dextran measurements showed increased intestinal paracellular permeability in the CST-KO mice. This correlated with a higher ratio of Firmicutes to Bacteroidetes, a dysbiotic pattern commonly encountered in various diseases. Supplementation of CST-KO mice with recombinant CST restored paracellular permeability and reversed inflammation, whereas CgA-KO mice supplementation with CST and/or PST in CgA-KO mice showed that intestinal paracellular permeability is regulated by the antagonistic roles of these two peptides: CST reduces and PST increases permeability.

CONCLUSION

The pro-hormone CgA regulates the intestinal paracellular permeability. CST is both necessary and sufficient to reduce permeability and primarily acts by antagonizing PST.

Stimulation of regulatory T cells with Lactococcus lactis expressing enterotoxigenic E. coli colonization factor antigen 1 retains salivary flow in a genetic model of Sjögren's syndrome

BACKGROUND

Sjögren's syndrome (SjS), one of the most common autoimmune diseases, impacts millions of people annually. SjS results from autoimmune attack on exocrine (salivary and lacrimal) glands, and women are nine times more likely to be affected than men. To date, no vaccine or therapeutic exists to treat SjS, and patients must rely on lifelong therapies to alleviate symptoms.

METHODS

Oral treatment with the adhesin from enterotoxigenic Escherichia coli colonization factor antigen I (CFA/I) fimbriae protects against several autoimmune diseases in an antigen (Ag)-independent manner. Lactococcus lactis, which was recently adapted to express CFA/I fimbriae (LL-CFA/I), effectively suppresses inflammation by the induction of infectious tolerance via Ag-specific regulatory T cells (Tregs), that produce IL-10 and TGF-β. To test the hypothesis that CFA/I fimbriae can offset the development of inflammatory T cells via Treg induction, oral treatments with LL-CFA/I were performed on the spontaneous, genetically defined model for SjS, C57BL/6.NOD-Aec1Aec2 mice to maintain salivary flow.

RESULTS

Six-week (wk)-old C57BL/6.NOD-Aec1Aec2 mice were orally dosed with LL-CFA/I and treated every 3 wks; control groups were given L. lactis vector or PBS. LL-CFA/I-treated mice retained salivary flow up to 28 wks of age and showed significantly reduced incidence of inflammatory infiltration into the submandibular and lacrimal glands relative to PBS-treated mice. A significant increase in Foxp3+ and IL-10- and TGF-β-producing Tregs was observed. Moreover, LL-CFA/I significantly reduced the expression of proinflammatory cytokines, IL-6, IL-17, GM-CSF, and IFN-γ. Adoptive transfer of CD4+ T cells from LL-CFA/I-treated, not LL vector-treated mice, restored salivary flow in diseased SjS mice.

CONCLUSION

These data demonstrate that oral LL-CFA/I reduce or halts SjS progression, and these studies will provide the basis for future testing in SjS patients.

Plasma Catestatin Levels and Advanced Glycation End Products in Patients on Hemodialysis

Catestatin (CST) is a pleiotropic peptide involved in cardiovascular protection with its antihypertensive and angiogenic effects. Considering that patients with end-stage renal disease (ESRD) who are undergoing hemodialysis (HD) are associated with higher cardiovascular risk, the aim of this study was to investigate plasma CST levels in HD patients, compare them to healthy controls and evaluate possible CST associations with advanced glycation end products (AGEs) and laboratory, anthropometric and clinical parameters. The study included 91 patients on HD and 70 healthy controls. Plasma CST levels were determined by an enzyme-linked immunosorbent assay in a commercially available diagnostic kit, while AGEs were determined using skin autofluorescence. Plasma CST levels were significantly higher in the HD group compared to the controls (32.85 ± 20.18 vs. 5.39 ± 1.24 ng/mL, p < 0.001) and there was a significant positive correlation between CST and AGEs (r = 0.492, p < 0.001). Furthermore, there was a significant positive correlation between plasma CST levels with both the Dialysis Malnutrition Score (r = 0.295, p = 0.004) and Malnutrition-Inflammation Score (r = 0.290, p = 0.005). These results suggest that CST could be playing a role in the complex pathophysiology of ESRD/HD and that it could affect the higher cardiovascular risk of patients on HD.

Roles of Macrophages in the Development and Treatment of Gut Inflammation

Macrophages, which are functional plasticity cells, have the ability to phagocytize and digest foreign substances and acquire pro-(M1-like) or anti-inflammatory (M2-like) phenotypes according to their microenvironment. The large number of macrophages in the intestinal tract, play a significant role in maintaining the homeostasis of microorganisms on the surface of the intestinal mucosa and in the continuous renewal of intestinal epithelial cells. They are not only responsible for innate immunity, but also participate in the development of intestinal inflammation. A clear understanding of the function of macrophages, as well as their role in pathogens and inflammatory response, will delineate the next steps in the treatment of intestinal inflammatory diseases. In this review, we discuss the origin and development of macrophages and their role in the intestinal inflammatory response or infection. In addition, the effects of macrophages in the occurrence and development of inflammatory bowel disease (IBD), and their role in inducing fibrosis, activating T cells, reducing colitis, and treating intestinal inflammation were also reviewed in this paper.

Pancreastatin Reduces Alternatively Activated Macrophages, Disrupts the Epithelial Homeostasis and Aggravates Colonic Inflammation. A Descriptive Analysis

Ulcerative colitis (UC) is characterized by modifying alternatively activated macrophages (AAM) and epithelial homeostasis. Chromogranin-A (CHGA), released by enterochromaffin cells, is elevated in UC and is implicated in inflammation progression. CHGA can be cleaved into several derived peptides, including pancreastatin (PST), which is involved in proinflammatory mechanisms. Previously, we showed that the deletion of Chga decreased the onset and severity of colitis correlated with an increase in AAM and epithelial cells’ functions. Here, we investigated PST activity in colonic biopsies of participants with active UC and investigated PST treatment in dextran sulfate sodium (DSS)-induced colitis using Chga^−/− mice, macrophages, and a human colonic epithelial cells line. We found that the colonic protein expression of PST correlated negatively with mRNA expression of AAM markers and tight junction (TJ) proteins and positively with mRNA expression of interleukin (IL)-8, IL18, and collagen in human. In a preclinical setting, intra-rectal administration of PST aggravated DSS-induced colitis by decreasing AAM’s functions, enhancing colonic collagen deposition and disrupting epithelial homeostasis in Chga^+/+ and Chga^−/− mice. This effect was associated with a significant reduction in AAM markers, increased colonic IL-18 release, and decreased TJ proteins’ gene expression. In vitro, PST reduced Chga^+/+ and Chga^−/− AAM polarization and decreased anti-inflammatory mediators’ production. Conditioned medium harvested from PST-treated Chga^+/+ and Chga^−/− AAM reduced Caco-2 cell migration, viability, proliferation, and mRNA levels of TJ proteins and increased oxidative stress-induced apoptosis and proinflammatory cytokines release. In conclusion, PST is a CHGA proinflammatory peptide that enhances the severity of colitis and the inflammatory process via decreasing AAM functions and disrupting epithelial homeostasis.

Mucosal immunity and tRNA, tRF, and tiRNA

Mucosal immunity has crucial roles in human diseases such as respiratory tract infection, inflammatory bowel diseases (IBD), and colorectal cancer (CRC). Recent studies suggest that the mononuclear phagocyte system, cancer cells, bacteria, and viruses induce the mucosal immune reaction by various pathways, and can be major factors in the pathogenesis of these diseases. Transfer RNA (tRNA) and its fragments, including tRNA-derived RNA fragments (tRFs) and tRNA-derived stress-induced RNAs (tiRNAs), have emerged as a hot topic in recent years. They not only are verified as essential for transcription and translation but also play roles in cellular homeostasis and functions, such as cell metastasis, proliferation, and apoptosis. However, the specific relationship between their biological regulation and mucosal immunity remains unclear to date. In the present review, we carry out a comprehensive discussion on the specific roles of tRNA, tRFs, and tiRNAs relevant to mucosal immunity and related diseases.

LncRNA NEAT1 Sponges MiRNA-148a-3p to Suppress Choroidal Neovascularization and M2 macrophage polarization

PURPOSE

Long noncoding RNAs (lncRNAs) have emerged as essential regulators in many biological processes; however, little is known about the role of lncRNAs in choroidal neovascularization (CNV). The aim of this study was to investigate the role of lncRNA NEAT1 in CNV formation, and assessed whether inhibition of lncRNA NEAT1 could suppress M2-type macrophage polarization and CNV.

METHODS

The expression profiles of lncRNAs in a CNV mice model were accessed via microarray analysis. The role of lncRNA NEAT1 on macrophage polarization was assessed both in vitro and vivo. The interaction between lncRNA NEAT1, miR-148a-3p, and PTEN was assessed using a dual-luciferase reporter assay and RNA immunoprecipitation assay. Additionally, to evaluate the role of lncRNA NEAT1 on CNV development, eyes of mice in the mice CNV model were examined by Fluorescein Angiography (FA) and choroidal flatmounts on days 3 and 7 after intravitreal injection.

RESULTS

The results revealed that 128 lncRNAs were significantly altered in the RPE-choroid-sclera complexes of CNV mice (P < 0.05, fold change > 2.0). Additionally, lncRNA NEAT1 increased in CNV formation and M2 macrophage polarization. LncRNA NEAT1 sponging miRNA-148a-3p targeting PTEN can modulate M2 macrophage polarization in mice CNV models as well as in bone marrow-derived macrophages cultured in vitro. Inhibition of lncRNA NEAT1 can suppress M2 macrophage both in vitro and vivo. Moreover, the intravitreal injection of a lncRNA NEAT1 Smart Silencer can inhibit CNV leakage and neovascularization.

CONCLUSION

LncRNA NEAT1 via miRNA-148a-3p targeting PTEN plays a significant role in M2 macrophage polarization, while the inhibition of lncRNA NEAT1 can suppress choroidal neovascularization by inhibiting M2 macrophage polarization.

The immune-sleep crosstalk in inflammatory bowel disease

Sleep disorders are progressively common and sometimes are associated with aberrant regulation of the adaptive and innate immune responses. Sleep interruption can increase the inflammatory burden by enhancing the pro-inflammatory cytokines particularly in patients with chronic diseases such as inflammatory bowel disease (IBD). IBD is a chronic inflammatory disease characterized by immune dysregulation, dysbiosis of gut microbiome, and poor-quality life. Therefore, this review highlights the crosstalk between sleep and immune responses during the progression of IBD.

Serum Catestatin Levels and Arterial Stiffness Parameters Are Increased in Patients with Inflammatory Bowel Disease

Catestatin (CST) is an important peptide in the pathophysiology of chronic inflammatory disorders. However, clinical studies on inflammatory bowel disease (IBD) patients are lacking. Our goal was to investigate CST concentrations in IBD patients compared to healthy subjects. Additionally, we aimed to determine arterial stiffness parameters in relation to CST. This cross-sectional study compared 80 IBD patients (45 Crohn's disease (CD) and 35 ulcerative colitis (UC) patients) with 75 control subjects. Serum CST levels were significantly higher in the IBD group compared to control subjects (11.29 ± 9.14 vs. 7.13 ± 6.08 ng/mL, p = 0.001) and in the UC group compared to CD patients (13.50 ± 9.58 vs. 9.03 ± 6.92 ng/mL, p = 0.021), irrespective of age and BMI. IBD patients exhibited significantly higher values of heart rate adjusted central augmentation index (cAIx-75) (14.88 ± 10.59 vs. 6.87 ± 9.50 %, p < 0.001) and pulse wave velocity (PWV) (8.06 ± 3.23 vs. 6.42 ± 1.47 m/s, p < 0.001) compared to control group. Furthermore, PWV was the only significant independent correlate of CST (B = 1.20, t = 4.15, p < 0.001), while CST, PWV, cAIx-75, high-sensitivity C-reactive protein and BMI were significant predictors of positive IBD status (1.089 (1.022-1.161), 1.515 (1.166-1.968), 1.060 (1.024-1.097), 1.458 (1.116-1.906), 0.793 (0.683-0.920), respectively). Serum CST levels were significantly higher in IBD patients compared to controls and an independent positive correlation of CST with PWV existed. Therefore, it is possible that CST could have a role in the complex pathophysiology of IBD and its cardiovascular complications.

Semaphorin-3E attenuates intestinal inflammation through the regulation of the communication between splenic CD11C+ and CD4+ CD25- T-cells

BACKGROUND AND PURPOSE

An alteration in the communication between the innate and adaptive immune cells is a hallmark of ulcerative colitis (UC). Semaphorin-3E (SEMA3E), a secreted guidance protein, regulates various immune responses.

EXPERIMENTAL APPROACH

We investigated the expression of SEMA3E in colonic biopsies of active UC patients and its mechanisms in Sema3e-/- mice using an experimental model of UC.

KEY RESULTS

SEMA3E level was decreased in active UC patients and negatively correlated with pro-inflammatory mediators. Colonic expression of SEMA3E was reduced in colitic Sema3e+/+ mice, and recombinant (rec-) Plexin-D1 treatment exacerbated disease severity. In vivo rec-SEMA3E treatment restored SEMA3E level in colitic Sema3e+/+ mice. In Sema3e-/- mice, disease severity was increased, and rec-SEMA3E ameliorated these effects. Lack of Sema3e increased the expression of CD11c and CD86 markers. Colitic Sema3e-/- splenocytes and splenic CD11c+ cells produced more IL-12/23 and IFN-γ compared to Sema3e+/+ , and rec-SEMA3E reduced their release as much as NF-κB inhibitors, whereas an NF-κB activator increased their production and attenuated the effect of rec-SEMA3E. Colitic Sema3e-/- splenic CD11c+ /CD4+ CD25- T-cell co-cultures produced higher concentrations of IFN-γ and IL-17 when compared to colitic Sema3e+/+ splenic cell co-cultures, and rec-SEMA3E decreased these effects. In vitro, anti-IL-12p19 and -12p35 antibodies and rec-IL-12 and -23 treatment confirmed the crosstalk between CD11c+ and CD4+ CD25- T-cells.

CONCLUSION AND IMPLICATIONS

SEMA3E is reduced in colitis and modulates colonic inflammation by regulating the interaction between CD11c+ and CD4+ CD25- T-cells via an NF-κB-dependent mechanism. Thus, SEMA3E could be a potential therapeutic target for UC patients.

Mucosal immunity and gut microbiota in dogs with chronic enteropathy

Chronic enteropathy (CE) in dogs is a chronic and relapsing immunopathology, of unknown etiology, that usually manifests with a plethora of clinical signs reflecting the underlying heterogeneity in its pathogenesis. Alterations of the mucosal immune responses and the gut microbiota composition are thought to play an essential role in CE. Similar to humans, it is hypothesized that the breakdown in mucosal tolerance leads to aberrant and pathological immune responses toward the gut microbiota, that in turn, may contribute to the severity of disease, at least for certain CE subsets. Therefore, in this review, we discuss some of the most relevant and recent insights microbiological and immunological aspects characterizing CE in dogs.

Catestatin as a Target for Treatment of Inflammatory Diseases

It is increasingly clear that inflammatory diseases and cancers are influenced by cleavage products of the pro-hormone chromogranin A (CgA), such as the 21-amino acids long catestatin (CST). The goal of this review is to provide an overview of the anti-inflammatory effects of CST and its mechanism of action. We discuss evidence proving that CST and its precursor CgA are crucial for maintaining metabolic and immune homeostasis. CST could reduce inflammation in various mouse models for diabetes, colitis and atherosclerosis. In these mouse models, CST treatment resulted in less infiltration of immune cells in affected tissues, although in vitro monocyte migration was increased by CST. Both in vivo and in vitro, CST can shift macrophage differentiation from a pro- to an anti-inflammatory phenotype. Thus, the concept is emerging that CST plays a role in tissue homeostasis by regulating immune cell infiltration and macrophage differentiation. These findings warrant studying the effects of CST in humans and make it an interesting therapeutic target for treatment and/or diagnosis of various metabolic and immune diseases.

Catestatin Regulates Epithelial Cell Dynamics to Improve Intestinal Inflammation

Ulcerative colitis (UC) is characterized by aberrant regulation of tight junctions (TJ), signal transducer and activator of transcription 3 (STAT3), and interleukin (IL)-8/18, which lead to intestinal barrier defects. Catestatin (CST), an enterochromaffin-derived peptide, regulates immune communication and STAT-3 in the inflamed intestine. Here, we investigated the effects of CST during the development of inflammation using human biopsies from patients with active UC, human colonic epithelial cells (Caco2), and an experimental model of UC (dextran sulfate sodium [DSS]-colitis). In UC patients, the protein and mRNA level of CST was significantly decreased. Colonic expression of CST showed a strong positive linear relationship with TJ proteins and STAT3, and a strong negative correlation with IL-8 and IL-18. Intra-rectal administration of CST reduced the severity of experimental colitis, IL-18 colonic levels, maintained TJ proteins and enhanced the phosphorylation of STAT3. CST administration increased proliferation, viability, migration, TJ proteins, and p-STAT3 levels, and reduced IL-8 &amp; IL-18 in LPS- &amp; DSS-induced Caco2 cell epithelial injury, and the presence of STAT-3 inhibitor abolished the beneficial effect of CST. In inflammatory conditions, we conclude that CST could regulate intestinal mucosal dynamic via a potential STAT3-dependent pathway that needs to be further defined. Targeting CST in intestinal epithelial cells (IECs) should be a promising therapeutic approach such as when intestinal epithelial cell homeostasis is compromised in UC patients.

Implications of Antioxidant Systems in Inflammatory Bowel Disease

The global incidence of inflammatory bowel disease (IBD), a group of chronic gastrointestinal disorders, has been rising. The preponderance of evidence demonstrates that oxidative stress (OS) performs a critical function in the onset of IBD and the manner of its development. The purpose of this review is to outline the generation of reactive oxygen species and antioxidant defense mechanisms in the gastrointestinal tract and the role played by OS in marking the onset and development of IBD. Furthermore, the review demonstrates the various ways through which OS is related to genetic susceptibility and the mucosal immune response. The experimental results suggest that certain therapeutic regimens for IBD could have a favorable impact by scavenging free radicals, reducing cytokine and prooxidative enzyme concentrations, and improving the antioxidative capabilities of cells. However, antioxidative activity characterized by a high level of specificity may be fundamental for the development of clinical therapies and for relapsing IBD patients. Therefore, additional research is required to clarify the ways through which OS is related to the pathogenesis and progression of IBD.

Chromogranin-A and its derived peptides and their pharmacological effects during intestinal inflammation

The gastrointestinal tract is the largest endocrine organ that produces a broad range of active peptides. Mucosal changes during inflammation alter the distribution and products of enteroendocrine cells (EECs) that play a role in immune activation and regulation of gut homeostasis by mediating communication between the nervous, endocrine and immune systems. Patients with inflammatory bowel disease (IBD) typically have altered expression of chromogranin (CHG)-A (CHGA), a major soluble protein secreted by EECs that functions as a pro-hormone. CHGA gives rise to several bioactive peptides that have direct or indirect effects on intestinal inflammation. In IBD, CHGA and its derived peptides are correlated with the disease activity. In this review we describe the potential immunomodulatory roles of CHGA and its derived peptides and their clinical relevance during the progression of intestinal inflammation. Targeting CHGA and its derived peptides could be of benefit for the diagnosis and clinical management of IBD patients.

Chromogranin-A Regulates Macrophage Function and the Apoptotic Pathway in Murine DSS colitis

Chromogranin-A (CHGA) is elevated in inflammatory bowel disease (IBD), but little is known about its role in colonic inflammation. IBD is associated with impaired functions of macrophages and increased apoptosis of intestinal epithelial cells. We investigated CHGA expression in human subjects with active ulcerative colitis (UC) and the underlying mechanisms in Chga ^-/- mice. In UC, CHGA, classically activated macrophage (M1) markers, caspase-3, p53, and its associated genes were increased, while alternatively activated macrophage (M2) markers were decreased without changes in the extrinsic apoptotic pathway. CHGA correlated positively with M1 and the apoptotic pathway and negatively with M2. In the murine dextran sulfate sodium (DSS)-induced colitis, Chga deletion reduced the disease severity and onset, pro-inflammatory mediators, M1, and p53/caspase-3 activation, while it upregulated anti-inflammatory cytokines and M2 markers with no changes in the extrinsic apoptotic markers. Compared to Chga ^+/+ , M1 and p53/caspase-3 activation in Chga ^-/- macrophages were decreased in vitro, while M2 markers were increased. CHGA plays a critical role during colitis through the modulation of macrophage functions via the caspase-3/p53 pathway. Strategies targeting CHGA to regulate macrophage activation and apoptosis might be developed to treat UC patients.

KEY MESSAGES

• Chromogranin-A (CHGA) is pro-hormone and is secreted in the gut. CHGA is elevated in colitis and is associated with the disease severity. The lack of GHGA has beneficial immunomodulatory properties during the development of intestinal inflammation. The lack of CHGA regulates the plasticity of macrophages and p53/caspase activation in colitis. Functional analysis of CHGA may lead to a novel therapy for IBD.

Chromofungin Ameliorates the Progression of Colitis by Regulating Alternatively Activated Macrophages

Ulcerative colitis (UC) is characterized by a functional dysregulation of alternatively activated macrophage (AAM) and intestinal epithelial cells (IECs) homeostasis. Chromogranin-A (CHGA) secreted by neuroendocrine cells is implicated in intestinal inflammation and immune dysregulation. CHGA undergoes proteolytic processing to generate CHGA-derived peptides. Chromofungin (CHR: CHGA_47–66) is a short CHGA-derived peptide encoded by CHGA Exon-IV and is involved in innate immune regulation, but the basis is poorly investigated. We investigated the expression of CHR in colonic tissue of patients with active UC and assessed the effects of the CHR in dextran sulfate sodium (DSS) colitis in mice and on macrophages and human colonic epithelial cells. We found that mRNA expression of CHR correlated positively with mRNA levels of AAM markers and gene expression of tight junction (TJ) proteins and negatively with mRNA levels of interleukin (IL)-8, IL-18, and collagen in patients with active UC. Moreover, AAM markers correlated positively with gene expression of TJ proteins and negatively with IL-8, IL-18, and collagen gene expression. Experimentally, intracolonic administration of CHR protected against DSS-induced colitis by priming macrophages into AAM, reducing colonic collagen deposition, and maintaining IECs homeostasis. This effect was associated with a significant increase of AAM markers, reduction of colonic IL-18 release and conservation of gene expression of TJ proteins. In vitro, CHR enhanced AAM polarization and increased the production of anti-inflammatory mediators. CHR-treated AAM conditioned medium increased Caco-2 cell migration, viability, proliferation, and mRNA levels of TJ proteins, and decreased oxidative stress-induced apoptosis and proinflammatory cytokines release. Direct CHR treatments had the same effect. In conclusion, CHR treatment reduces the severity of colitis and the inflammatory process via enhancing AAM functions and maintaining IECs homeostasis. CHR is involved in the pathogenesis of inflammation in experimental colitis. These findings provide insight into the mechanisms of colonic inflammation and could lead to new therapeutic strategies for UC.