Immunopathogenesis of experimental ulcerative colitis is mediated by eosinophil peroxidase

Eosinophil Depletion as a Potential Therapeutic Strategy in Acute and Chronic Intestinal Inflammation Based on a Dextran Sulfate Sodium Colitis Model

BACKGROUND

A role for eosinophils in intestinal inflammation and fibrosis in the context of inflammatory bowel disease has been suggested, yet the precise nature, whether causal or secondary remains debated. Hence, it remains unclear whether targeting eosinophils should be further explored as a treatment option in inflammatory bowel disease.

METHODS

Acute and chronic dextran sulfate sodium colitis was induced in wild-type C57BL/6 mice. Eosinophils were depleted by anti-CCR3 injections before colitis induction in a chronic model and after colitis onset in an acute model in order to investigate the impact of eosinophil depletion on pre-existing colitis. Inflammation was assessed using the disease activity index, macroscopic damage, and histological disease activity score. In the chronic model, fibrosis was assessed by examining colon weight/length ratio, collagen deposition through Martius Scarlet Blue staining, hydroxyproline assay, and COL1A1 expression. Protein and gene expression were assessed using the Meso Scale Discovery platform and real-time quantitative polymerase chain reaction.

RESULTS

In the acute and chronic colitis model, eosinophil depletion resulted in reduced disease activity and faster recovery, as observed via the total area under the curve of the disease activity index (P = .004 and P = .02, respectively), macroscopic damage score (P = .009 and P = .08, respectively), and histological disease activity score (P = .09 and P = .002, respectively). In the acute model, the accelerated recovery was accompanied by an increase in interleukin (IL)-10 (P = .03) and a decrease in IL-4 (P = .03) and IL-6 (P = .009). Colon weight/length ratio and collagen deposition were not affected by eosinophil depletion.

CONCLUSIONS

Eosinophil depletion prevents and decreases intestinal inflammation in a preclinical dextran sulfate sodium model without affecting fibrosis. These results pave the way for exploring eosinophil depletion as a novel treatment modality in addressing intestinal inflammation.

Colonization of microbiota derived from Macaca fascicularis, Bama miniature pigs, beagle dogs, and C57BL/6J mice alleviates DSS-induced colitis in germ-free mice

Fecal microbiota transplantation (FMT) is an innovative and promising treatment for inflammatory bowel disease (IBD), which is related to the capability of FMT to supply functional microorganisms to improve recipient gut health. Numerous studies have highlighted considerable variability in the efficacy of FMT interventions for IBD. Several factors, including the composition of the donor microorganisms, significantly affect the efficacy of FMT in the treatment of IBD. Consequently, identifying the functional microorganisms in the donor is crucial for enhancing the efficacy of FMT. To explore potential common anti-inflammatory bacteria with therapeutic implications for IBD, germ-free (GF) BALB/c mice were pre-colonized with fecal microbiota obtained from diverse donors, including Macaca fascicularis (MCC_FMT), Bama miniature pigs (BP_FMT), beagle dogs (BD_FMT), and C57BL/6 J mice (Mice_FMT). Subsequently, mice were treated with dextran sodium sulfate (DSS). As expected, the symptoms of colitis were alleviated by MCC_FMT, BP_FMT, BD_FMT, and Mice_FMT, as demonstrated by the prevention of an elevated disease activity index in mice. Additionally, the utilization of distinct donors protected the intestinal barrier and contributed to the regulation of cytokine homeostasis. Metagenomic sequencing data showed that the microbial community structure and dominant species were significantly different among the four groups, which may be linked to variations in the anti-inflammatory efficacy observed in the respective groups. Notably, Lactobacillus reuteri and Flavonifractor plautii were consistently present in all four groups. L. reuteri exhibited a significant negative correlation with IL-1β, and animal studies further confirmed its efficacy in alleviating IBD, suggesting the presence of common functional bacteria across different donors that exert anti-inflammatory effects. This study provides essential foundational data for the potential clinical applications of FMT.IMPORTANCEDespite variations in efficacy observed among donors, numerous studies have underscored the potential of fecal microbiota transplantation (FMT) for managing inflammatory bowel disease (IBD), indicating the presence of shared anti-IBD bacterial species. In the present study, the collective anti-inflammatory efficacy observed across all four donor groups prompted the identification of two common bacterial species using metagenomics. A significant negative correlation between Lactobacillus reuteri and IL-1β was revealed. Furthermore, mice gavaged with L. reuteri successfully managed the colitis challenge induced by dextran sodium sulfate (DSS), suggesting that L. reuteri may act as an efficacious bacterium mediating shared anti-inflammatory effects among variable donors. This finding highlights the utilization of variable donors to screen FMT core bacteria, which may be a novel strategy for developing FMT applications.

Spatial adaptation of eosinophils and their emerging roles in homeostasis, infection and disease

Eosinophils are bone marrow-derived granulocytes that are traditionally associated with type 2 immune responses, such as those that occur during parasite infections and allergy. Emerging evidence demonstrates the remarkable functional plasticity of this elusive cell type and its pleiotropic functions in diverse settings. Eosinophils broadly contribute to tissue homeostasis, host defence and immune regulation, predominantly at mucosal sites. The scope of their activities primarily reflects the breadth of their portfolio of secreted mediators, which range from cytotoxic cationic proteins and reactive oxygen species to multiple cytokines, chemokines and lipid mediators. Here, we comprehensively review basic eosinophil biology that is directly related to their activities in homeostasis, protective immunity, regeneration and cancer. We examine how dysregulation of these functions contributes to the physiopathology of a broad range of inflammatory diseases. Furthermore, we discuss recent findings regarding the tissue compartmentalization and adaptation of eosinophils, shedding light on the factors that likely drive their functional diversification within tissues.

Dietary fiber is a critical determinant of pathologic ILC2 responses and intestinal inflammation

Innate lymphoid cells (ILCs) can promote host defense, chronic inflammation, or tissue protection and are regulated by cytokines and neuropeptides. However, their regulation by diet and microbiota-derived signals remains unclear. We show that an inulin fiber diet promotes Tph1-expressing inflammatory ILC2s (ILC2INFLAM) in the colon, which produce IL-5 but not tissue-protective amphiregulin (AREG), resulting in the accumulation of eosinophils. This exacerbates inflammation in a murine model of intestinal damage and inflammation in an ILC2- and eosinophil-dependent manner. Mechanistically, the inulin fiber diet elevated microbiota-derived bile acids, including cholic acid (CA) that induced expression of ILC2-activating IL-33. In IBD patients, bile acids, their receptor farnesoid X receptor (FXR), IL-33, and eosinophils were all upregulated compared with controls, implicating this diet-microbiota-ILC2 axis in human IBD pathogenesis. Together, these data reveal that dietary fiber-induced changes in microbial metabolites operate as a rheostat that governs protective versus pathologic ILC2 responses with relevance to precision nutrition for inflammatory diseases.

Eosinophils and risk of ulcerative colitis in European population: Evidence from Mendelian randomization study

BACKGROUND

Observational studies have indicated that peripheral blood eosinophil count is elevated in individuals diagnosed with ulcerative colitis (UC) and correlates with the disease activity of UC. However, this conclusion contradicts with findings from other studies. Therefore, we employed Mendelian randomization (MR) method to assess the genetic link between eosinophil count and UC.

METHOD

This MR study utilized summary data from genome-wide association studies (GWAS) on eosinophil count and UC. The main approach used for conducting MR analysis was the inverse variance weighted (IVW) method. Meta-analysis of the IVW results was performed alongside multiple sensitivity analyses to confirm the robustness of the MR analysis results.

RESULTS

The IVW method unveiled a causal relationship between eosinophil count and UC (OR = 1.18, 95% CI: 1.04-1.33, p = .01) in the discovery cohort. This finding was further corroborated by the replication cohorts (OR = 1.16, 95% CI: 1.04-1.29, p = .01; OR = 1.12, 95% CI: 1.01-1.24, p = .03). The meta-analysis indicated that the overall odds ratio (OR) for all studies was 1.15 (common effect model, 95% CI: 1.08-1.23, p < .01). Sensitivity analysis suggested the absence of heterogeneity and horizontal pleiotropy in all MR analyses.

CONCLUSION

Based on bidirectional two-sample MR analysis, there is an indication that elevated eosinophil count may increase the risk of UC. However, potential confounding factors cannot be ruled out, and further research is necessary to explore how eosinophils contribute to the onset and progression of UC.

Eosinophils Exert Antitumorigenic Effects in the Development of Esophageal Squamous Cell Carcinoma

BACKGROUND AND AIMS

Eosinophils are present in several solid tumors and have context-dependent function. Our aim is to define the contribution of eosinophils in esophageal squamous cell carcinoma (ESCC), as their role in ESCC is unknown.

METHODS

Eosinophils were enumerated in tissues from 2 ESCC cohorts. Mice were treated with 4-NQO for 8 weeks to induce precancer or 16 weeks to induce carcinoma. The eosinophil number was modified by a monoclonal antibody to interleukin-5 (IL5mAb), recombinant IL-5 (rIL-5), or genetically with eosinophil-deficient (ΔdblGATA) mice or mice deficient in eosinophil chemoattractant eotaxin-1 (Ccl11-/-). Esophageal tissue and eosinophil-specific RNA sequencing was performed to understand eosinophil function. Three-dimensional coculturing of eosinophils with precancer or cancer cells was done to ascertain direct effects of eosinophils.

RESULTS

Activated eosinophils are present in higher numbers in early-stage vs late-stage ESCC. Mice treated with 4-NQO exhibit more esophageal eosinophils in precancer vs cancer. Correspondingly, epithelial cell Ccl11 expression is higher in mice with precancer. Eosinophil depletion using 3 mouse models (Ccl11-/- mice, ΔdblGATA mice, IL5mAb treatment) all display exacerbated 4-NQO tumorigenesis. Conversely, treatment with rIL-5 increases esophageal eosinophilia and protects against precancer and carcinoma. Tissue and eosinophil RNA sequencing revealed eosinophils drive oxidative stress in precancer. In vitro coculturing of eosinophils with precancer or cancer cells resulted in increased apoptosis in the presence of a degranulating agent, which is reversed with NAC, a reactive oxygen species scavenger. ΔdblGATA mice exhibited increased CD4 T cell infiltration, IL-17, and enrichment of IL-17 protumorigenic pathways.

CONCLUSION

Eosinophils likely protect against ESCC through reactive oxygen species release during degranulation and suppression of IL-17.

Eosinophils exert direct and indirect anti-tumorigenic effects in the development of esophageal squamous cell carcinoma

Background/Aims

Eosinophils are present in several solid tumors and have context-dependent function. Our aim is to define the contribution of eosinophils in esophageal squamous cell carcinoma (ESCC), since their role in ESCC is unknown.

Methods

Eosinophils were enumerated in tissues from two ESCC cohorts. Mice were treated with 4-nitroquinolone-1-oxide (4-NQO) for 8 weeks to induce pre-cancer or 16 weeks to induce carcinoma. Eosinophil number was modified by monoclonal antibody to IL-5 (IL5mAb), recombinant IL-5 (rIL-5), or genetically with eosinophil-deficient (ΔdblGATA) mice or mice deficient in eosinophil chemoattractant eotaxin-1 ( Ccl11 -/- ). Esophageal tissue and eosinophil specific RNA-sequencing was performed to understand eosinophil function. 3-D co-culturing of eosinophils with pre-cancer or cancer cells was done to ascertain direct effects of eosinophils.

Results

Activated eosinophils are present in higher numbers in early stage versus late stage ESCC. Mice treated with 4-NQO exhibit more esophageal eosinophils in pre-cancer versus cancer. Correspondingly, epithelial cell Ccl11 expression is higher in mice with pre-cancer. Eosinophil depletion using three mouse models ( Ccl11 -/- mice, ΔdblGATA mice, IL5mAb treatment) all display exacerbated 4-NQO tumorigenesis. Conversely, treatment with rIL-5 increases esophageal eosinophilia and protects against pre-cancer and carcinoma. Tissue and eosinophil RNA-sequencing revealed eosinophils drive oxidative stress in pre-cancer. In vitro co-culturing of eosinophils with pre-cancer or cancer cells resulted in increased apoptosis in the presence of a degranulating agent, which is reversed with N-acetylcysteine, a reactive oxygen species (ROS) scavenger. ΔdblGATA mice exhibited increased CD4 T cell infiltration, IL-17, and enrichment of IL-17 pro-tumorigenic pathways.

Conclusion

Eosinophils likely protect against ESCC through ROS release during degranulation and suppression of IL-17.

Whole intestinal microbiota transplantation is more effective than fecal microbiota transplantation in reducing the susceptibility of DSS-induced germ-free mice colitis

Fecal microbiota transplantation (FMT) is an emerging and effective therapy for the treatment of inflammatory bowel disease (IBD). Previous studies have reported that compared with FMT, whole intestinal microbiota transplantation (WIMT) can more precisely replicate the community structure and reduce the inflammatory response of the host. However, it remains unclear whether WIMT is more effective in alleviating IBD. To examine the efficacy of WIMT and FMT in the intervention of IBD, GF (Germ-free) BALB/c mice were pre-colonized with whole intestinal microbiota or fecal microbiota before being treated with dextran sodium sulfate (DSS). As expected, the symptoms of colitis were alleviated by both WIMT and FMT, as demonstrated by the prevention of body weight loss and decreased the Disease activity index and histological scores in mice. However, WIMT's anti-inflammatory effect was superior to that of FMT. In addition, the inflammatory markers myeloperoxidase (MPO) and eosinophil peroxidase were dramatically downregulated by WIMT and FMT. Furthermore, the use of two different types of donors facilitated the regulation of cytokine homeostasis in colitis mice; the level of the pro-inflammatory cytokine IL-1β in the WIMT group was significantly lower than that in the FMT group, while the level of the anti-inflammatory factor IL-10 was significantly higher than that in the FMT group. Both groups showed enhanced expression of occludin to protect the intestinal barrier in comparison with the DSS group, and the WIMT group demonstrated considerably increased levels of ZO-1. The sequencing results showed that the WIMT group was highly enriched in Bifidobacterium, whereas the FMT group was significantly enriched in Lactobacillus and Ochrobactrum. Correlation analysis revealed that Bifidobacterium was negatively correlated with TNF-α, whereas Ochrobactrum was positively correlated with MPO and negatively correlated with IL-10, which might be related to different efficacies. Functional prediction using PICRUSt2 revealed that the FMT group was considerably enriched in the L-arginine biosynthesis I and L-arginine biosynthesis IV pathway, whereas the WIMT group was enriched in the L-lysine fermentation to acetate and butanoate pathway. In conclusion, the symptoms of colitis were subsided to varying degrees by the two different types of donors, with the WIMT group being more effective than the FMT group. This study provides new information on clinical interventions for IBD.

Anti-nociceptive effects of magnolol via inhibition of TRPV1/P2Y and TLR4/NF-κB signaling in a postoperative pain model

AIMS

The current study explored the anti-nociceptive activity of magnolol in post-incisional inflammatory nociceptive pain.

MAIN METHODS

Preliminary, the anti-inflammatory, antioxidant, and cytoprotective potential of magnolol were confirmed against hydrogen peroxide (H₂O₂)-induced PC12 cells. Next, an in-vivo model of planter incision surgery was established in BALB/c mice. Tramadol 50 mg/kg intraperitoneal (i.p.) and magnolol (0.1, 1, 10 mg/kg i.p. + 10 mg/kg intra planter) were administered after plantar incision surgery and behavior parameters were measured.

KEY FINDINGS

The results indicate that magnolol significantly suppressed post-incision-induced mechanical allodynia, thermal hyperalgesia, and paw edema. Magnolol promisingly inhibited post-incision induces nitric oxide (NO), malondialdehyde (MDA), eosinophil peroxidase (EPO), and neutrophil infiltration. Magnolol strongly attenuated post-incision inducing the release of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and inhibited deoxyribonucleic acid (DNA) fragmentation. Magnolol markedly reverses post-incisional histopathological changes and biochemical composition of the incised paw. Magnolol markedly down-regulated post-incisional increase expression of transient receptor potential vanilloid 1 (TRPV1), purinergic (P2Y) nociceptors as well as toll-like receptor 4 (TLR4), nuclear factor kappa light chain enhancer of activated B cell (NF-κB), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) while upregulating the expression of inhibitor of nuclear kappa B alpha (IκB-α).

SIGNIFICANCE

The present study strongly suggests that magnolol significantly suppressed post-incisional inflammatory nociceptive pain by targeting TRPV1/P2Y and TLR4/NF-κB signaling.

Tenascin-C is a driver of inflammation in the DSS model of colitis

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Increased tenascin-C staining appeared to predominantly occur in damaged ulcerated areas.

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Tenascin-C knock-out mice were partly protected from DSS induced colitis.

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Mice deficient in tenascin-C had areas of + ve EpCAM staining indicating that crypt and epithelial integrity was maintained.

Inflammatory Bowel Disease (IBD) is a grouping of chronic inflammatory disorders of the gut. Tenascin-C is a pro-inflammatory, extracellular matrix protein found upregulated in IBD patients and whilst a pathological driver of chronic inflammation, its precise role in the etiology of IBD is unknown. To study tenascin-C’s role in colitis pathology we investigated its expression in a murine model of IBD. Wild-type (WT) or tenascin-C knockout (KO) male mice were left untreated or treated with dextran sodium sulphate (DSS) in their drinking water. Tenascin-C was upregulated at the mRNA level in the colitic distal colon of day eight DSS treated mice, coinciding with significant increases in gross and histological pathology. Immunohistochemistry localized this increase in tenascin-C to areas of inflammation and ulceration in the mucosa. Tenascin-C KO mice exhibited reduced gross pathology in comparison. These differences also extended to the histopathological level where reduced colonic inflammation and tissue damage were found in KO compared to WT mice. Furthermore, the severity of the distal colon lesions were less in the KO mice after 17 days of recovery from DSS treatment. This study demonstrates a role for tenascin-C as a driver of inflammatory pathology in a murine model of IBD and thus suggests neutralizing its pro-inflammatory activity could be explored as a therapeutic strategy for treating IBD.

N-Acetyldopamine Dimer Attenuates DSS-Induced Ulcerative Colitis by Suppressing NF-κB and MAPK Pathways

Ulcerative Colitis (UC) is a major form of chronic inflammatory bowel disease of the colonic mucosa and exhibits progressive morbidity. There is still a substantial need of small molecules with greater efficacy and safety for UC treatment. Here, we report a N-acetyldopamine dimer (NADD) elucidated (2R,3S)-2-(3′,4′-dihydroxyphenyl)-3-acetylamino-7-(N-acetyl-2″-aminoethyl)-1,4-benzodioxane, which is derived from traditional Chinese medicine Isaria cicadae, exhibits significant therapeutic efficacy against dextran sulfate sodium (DSS)-induced UC. Functionally, NADD treatment effectively relieves UC symptoms, including weight loss, colon length shortening, colonic tissue damage and expression of pro-inflammatory factors in pre-clinical models. Mechanistically, NADD treatment significantly inhibits the expression of genes in inflammation related NF-κB and MAPK signaling pathways by transcriptome analysis and western blot, which indicates that NADD inhibits the inflammation in UC might through these two pathways. Overall, this study identifies an effective small molecule for UC therapy.

Single cell genome sequencing of laboratory mouse microbiota improves taxonomic and functional resolution of this model microbial community

Laboratory mice are widely studied as models of mammalian biology, including the microbiota. However, much of the taxonomic and functional diversity of the mouse gut microbiome is missed in current metagenomic studies, because genome databases have not achieved a balanced representation of the diverse members of this ecosystem. Towards solving this problem, we used flow cytometry and low-coverage sequencing to capture the genomes of 764 single cells from the stool of three laboratory mice. From these, we generated 298 high-coverage microbial genome assemblies, which we annotated for open reading frames and phylogenetic placement. These genomes increase the gene catalog and phylogenetic breadth of the mouse microbiota, adding 135 novel species with the greatest increase in diversity to the Muribaculaceae and Bacteroidaceae families. This new diversity also improves the read mapping rate, taxonomic classifier performance, and gene detection rate of mouse stool metagenomes. The novel microbial functions revealed through our single-cell genomes highlight previously invisible pathways that may be important for life in the murine gastrointestinal tract.

Human Fecal Microbiota Transplantation Reduces the Susceptibility to Dextran Sulfate Sodium-Induced Germ-Free Mouse Colitis

In clinical practice, fecal microbiota transplantation (FMT) has been used to treat inflammatory bowel disease (IBD), and has shown certain effects. However, the selection of FMT donors and the mechanism underlying the effect of FMT intervention in IBD require further exploration. In this study, dextran sodium sulfate (DSS)-induced colitis mice were used to determine the differences in the protection of colitis symptoms, inflammation, and intestinal barrier, by FMT from two donors. Intriguingly, pre-administration of healthy bacterial fluid significantly relieved the symptoms of colitis compared to the ulcerative colitis (UC) bacteria. In addition, healthy donor (HD) bacteria significantly reduced the levels of inflammatory markers Myeloperoxidase (MPO) and Eosinophil peroxidase (EPO), and various pro-inflammatory factors, in colitis mice, and increased the secretion of the anti-inflammatory factor IL-10. Metagenomic sequencing indicated higher species diversity and higher abundance of anti-inflammatory bacteria in the HD intervention group, including Alistipes putredinis, Akkermansia muciniphila, Bifidobacterium adolescentis, short-chain fatty acids (SCFAs)-producing bacterium Christensenella minuta, and secondary bile acids (SBAs)-producing bacterium Clostridium leptum. In the UC intervention group, the SCFA-producing bacterium Bacteroides stercoris, IBD-related bacterium Ruminococcus gnavus, Enterococcus faecalis, and the conditional pathogen Bacteroides caccae, were more abundant. Metabolomics analysis showed that the two types of FMT significantly modulated the metabolism of DSS-induced mice. Moreover, compared with the UC intervention group, indoleacetic acid and unsaturated fatty acids (DHA, DPA, and EPA) with anti-inflammatory effects were significantly enriched in the HD intervention group. In summary, these results indicate that FMT can alleviate the symptoms of colitis, and the effect of HD intervention is better than that of UC intervention. This study offers new insights into the mechanisms of FMT clinical intervention in IBD.

HG-9-91-01 Attenuates Murine Experimental Colitis by Promoting Interleukin-10 Production in Colonic Macrophages Through the SIK/CRTC3 Pathway

BACKGROUND

Interleukin-10 (IL-10) is a potent immunoregulatory cytokine that plays a pivotal role in maintaining mucosal immune homeostasis. As a novel synthetic inhibitor of salt-inducible kinases (SIKs), HG-9-91-01 can effectively enhance IL-10 secretion at the cellular level, but its in vivo immunoregulatory effects remain unclear. In this study, we investigated the effects and underlying mechanism of HG-9-91-01 in murine colitis models.

METHODS

The anti-inflammatory effects of HG-9-91-01 were evaluated on 2, 4, 6-trinitrobenzene sulfonic acid (TNBS)-, dextran sulfate sodium-induced colitis mice, and IL-10 knockout chronic colitis mice. The in vivo effector cell of HG-9-91-01 was identified by fluorescence-activated cell sorting and quantitative real-time polymerase chain reaction. The underlying mechanism of HG-9-91-01 was investigated via overexpressing SIKs in ANA-1 macrophages and TNBS colitis mice.

RESULTS

Treatment with HG-9-91-01 showed favorable anticolitis effects in both TNBS- and DSS-treated mice through significantly promoting IL-10 expression in colonic macrophages but failed to protect against IL-10 KO murine colitis. Further study indicated that HG-9-91-01 markedly enhanced the nuclear level of cAMP response element-binding protein (CREB)-regulated transcription coactivator 3 (CRTC3), whereas treatment with lentiviruses encoding SIK protein markedly decreased the nuclear CRTC3 level in HG-9-91-01-treated ANA-1 macrophages. In addition, intracolonic administration with lentiviruses encoding SIK protein significantly decreased the nuclear CRTC3 level in the lamina propria mononuclear cells and ended the anti-inflammatory activities of HG-9-91-01.

CONCLUSIONS

We found that HG-9-91-01 promoted the IL-10 expression of colonic macrophages and exhibited its anticolitis activity through the SIK/CRTC3 axis, and thus it may represent a promising strategy for inflammatory bowel disease therapy.

Role of Eosinophils in Intestinal Inflammation and Fibrosis in Inflammatory Bowel Disease: An Overlooked Villain?

Eosinophils are leukocytes which reside in the gastrointestinal tract under homeostatic conditions, except for the esophagus which is normally devoid of eosinophils. Research on eosinophils has primarily focused on anti-helminth responses and type 2 immune disorders. In contrast, the search for a role of eosinophils in chronic intestinal inflammation and fibrosis has been limited. With a shift in research focus from adaptive to innate immunity and the fact that the eosinophilic granules are filled with inflammatory mediators, eosinophils are becoming a point of interest in inflammatory bowel diseases. In the current review we summarize eosinophil characteristics and recruitment as well as the current knowledge on presence, inflammatory and pro-fibrotic functions of eosinophils in inflammatory bowel disease and other chronic inflammatory conditions, and we identify research gaps which should be covered in the future.

CCL11 exacerbates colitis and inflammation-associated colon tumorigenesis

CCL11, also known as eotaxin-1, is described as an eosinophil chemoattractant, which has been implicated in allergic and Th2 inflammatory diseases. We have reported that CCL11 is significantly increased in the serum of inflammatory bowel disease (IBD) patients, colonic eosinophils are increased and correlate with tissue CCL11 levels in ulcerative colitis patients, and CCL11 is increased in dextran sulfate sodium (DSS)-induced murine colitis. Here, we show that CCL11 is involved in the pathogenesis of DSS-induced colitis and in colon tumorigenesis in the azoxymethane (AOM)-DSS model of colitis-associated carcinogenesis (CAC). Ccl11^-/- mice exposed to DSS then allowed to recover had significantly less body weight loss and a decrease in histologic injury versus wild-type (WT) mice. In the AOM-DSS model, Ccl11^-/- mice exhibited decreased colonic tumor number and burden, histologic injury, and colonic eosinophil infiltration versus WT mice. Ccl11 is expressed by both colonic epithelial and lamina propria immune cells. Studies in bone marrow chimera mice revealed that hematopoietic- and epithelial-cell-derived CCL11 were both important for tumorigenesis in the AOM-DSS model. These findings indicate that CCL11 is important in the regulation of colitis and associated carcinogenesis and thus anti-CCL11 antibodies may be useful for treatment and cancer chemoprevention in IBD.

Eosinophils, a Jack of All Trades in Immunity: Therapeutic Approaches for Correcting Their Functional Disorders

BACKGROUND AND OBJECTIVE

Eosinophils are primitive myeloid cells derived from bonemarrow precursors and require the intervention of interleukin (IL)-5 for their survival and persistence in blood and tissues. Under steady-state conditions, they contribute to immune regulation and homeostasis. Under pathological circumstances, eosinophils are involved in host protection against parasites and participate in allergy and inflammation.

DISCUSSION

Mostly, in asthma, eosinophils provoke airway damage via the release of granule contents and IL-13 with mucus hypersecretion and differentiation of goblet cells. Then, tissue remodeling follows with the secretion of transforming growth factor-β. Eosinophils are able to kill helminth larvae acting as antigen-presenting cells with the involvement of T helper (h)-2 cells and subsequent antibody response. However, they also exert pro-worm activity with the production of suppressive cytokine (IL- 10 and IL-4) and inhibition of nitric oxide. Eosinophils may play a pathogenic role in the course of chronic and autoimmune disease, e.g., inflammatory bowel disease and eosinophilic gastroenteritis, regulating Th2 responses and promoting a profibrotic effect. In atopic dermatitis, eosinophils are commonly detected and may be associated with disease severity. In cutaneous spontaneous urticaria, eosinophils participate in the formation of wheals, tissue remodeling and modifications of vascular permeability. With regard to tumor growth, it seems that IgE can exert anti-neoplastic surveillance via mast cell and eosinophil-mediated cytotoxicity, the so-called allergo-oncology. From a therapeutic point of view, monoclonal antibodies directed against IL-5 or the IL-5 receptors have been shown to be very effective in patients with severe asthma. Finally, as an alternative treatment, polyphenols for their anti-inflammatory and anti-allergic activities seem to be effective in reducing serum IgE and eosinophil count in bronchoalveolar lavage in murine asthma.

CONCLUSION

Eosinophils are cells endowed with multiple functions and their modulation with monoclonal antibodies and nutraceuticals may be effective in the treatment of chronic disease.

Intestinal eosinophils, homeostasis and response to bacterial intrusion

Eosinophils are traditionally considered as end-stage effector cells involved in the pathogenesis of Th2 immune-mediated disorders as well as in the protection against parasite infection. However, this restricted view has recently been challenged by a series of studies revealing the highly plastic nature of these cells and implication in various homeostatic processes. Large numbers of eosinophils reside in the lamina propria of the gastrointestinal tract, at the front line of host defence, where they contribute to maintain the intestinal epithelial barrier function in the face of inflammation-associated epithelial cell damage. Eosinophils confer active protection against bacterial pathogens capable of penetrating the mucosal barrier through the release of cytotoxic compounds and the generation of extracellular DNA traps. Eosinophils also integrate tissue-specific cytokine signals such as IFN-γ, which synergise with bacterial recognition pathways to enforce different context-dependent functional responses, thereby ensuring a rapid adaptation to the ever-changing intestinal environment. The ability of eosinophils to regulate local immune responses and respond to microbial stimuli further supports the pivotal role of these cells in the maintenance of tissue homeostasis at the intestinal interface.

Histopathologic Parameters at Diagnosis as Early Predictors of Histologic Remission along the Course of Ulcerative Colitis

Background

Currently, the treatment goal in ulcerative colitis (UC) is to achieve clinical and endoscopic remission; nevertheless, histologic remission is a potential new treatment goal since it is associated with favorable long-term clinical outcome lower rates of hospitalization, complications, and colectomies.

Aim

Evaluate clinical and histopathologic characteristics at diagnosis as potential predictors of histologic remission in patients with ulcerative colitis.

Methods

This is a retrospective cohort study from 2007 to 2014, including 260 patients. Clinical and demographic information and Mayo endoscopic and Riley histologic grade were obtained accordingly with the follow-up. Histological evaluation was made for all 260 patients; fifty-six patients with histologic remission at the follow-up underwent separate evaluation of mucosal biopsy at the moment of diagnosis. Univariate and multivariate analyses were applied to data from these 56 patients to identify histologic features at diagnosis associated with histologic remission during follow-up. The odds ratio (OR) was determined as a measure for the strength of association. A P value of less than 0.05 was taken as a level of significance.

Results

The frequency of histologic remission according to the Riley index in our study group was 21.5%. Factors associated with histologic remission were treatment with steroids (P = 0.01, OR = 0.38, CI 95% = 0.16-0.90), reduced mucin production (P = 0.02, OR = 0.23, CI 95% = 0.06-0.86), and less than 10 eosinophils per high power field (P = 0.001, OR = 6.66, CI 95% = 2.03-21.84).

Conclusion

Factors that impair histologic remission in patients with ulcerative colitis were treatment with steroids and reduced mucin production; meanwhile, less than 10 eosinophils per high power showed a predictive value for histologic remission.

Daikenchuto attenuates visceral pain and suppresses eosinophil infiltration in inflammatory bowel disease in murine models

BACKGROUND AND AIM

Daikenchuto (DKT), a traditional Japanese formula, comprises four herbal medicines and is used for abdominal pain. Inflammatory bowel disease (IBD) includes ulcerative colitis (UC) and Crohn's disease (CD) and is characterized by colonic inflammation and chronic abdominal pain. The present study aimed to investigate whether DKT suppresses colonic hypersensitivity and inflammation associated with IBD in animal models.

METHODS

Sprague-Dawley rats were administered 4% sodium dextran sulfate (DSS) or trinitrobenzene sulfate (TNBS) in the colon to establish UC or CD models, respectively. DKT and 5-aminosalicylic acid (5-ASA) were administered orally once a day from Days 3 to 7 after induction of colitis. On Day 7, visceral pain and inflammation were evaluated by measuring the visceromotor response (VMR) to colorectal distention (CRD) and inflammatory indicators, including histological score, length of leukocyte infiltration, MPO activity, and eosinophil count.

RESULTS

DSS and TNBS increased VMR to CRD and the inflammation indicators. DKT, but not 5-ASA, suppressed the VMR to CRD in DSS- and TNBS-treated rats. DKT and 5-ASA decreased the eosinophil count in both IBD models. In DSS-treated rats, 5-ASA, but not DKT, suppressed the MPO activity. In TNBS-treated rats, neither 5-ASA nor DKT suppressed MPO activity.

CONCLUSION

These results suggest that DKT is beneficial for abdominal pain associated with IBD. The anti-inflammatory effect of DKT on IBD may involve inhibition of eosinophils. The mechanism of anti-inflammatory effect of DKT partially differs from that of 5-ASA. Coapplication of DKT and conventional medicine may produce a positive synergy effect for IBD treatment.

Extra virgin olive oil and flaxseed oil have no preventive effects on DSS-induced acute ulcerative colitis

OBJECTIVES

The aim of this study was to evaluate the preventive effects of extra virgin olive oil (EVOO) or flaxseed oil (FO) on dextran sodium sulfate (DSS)-induced acute ulcerative colitis in female mice.

METHODS

Eighty C57BL/6J mice of 8-weeks-old were divided in four groups: Control (SO), 10%EVOO, 10%FO and 5%EVOO+5%FO. The oils were given through the AIN-93M diet. After 30 days, animals were divided in four more groups, in which half received 3%DSS in water for 5 days. Body weight loss, bleeding and stool consistency were verified for the Disease Activity Index (DAI). Animals were euthanized and their colon and spleen weighted and measured. Histopathological analysis, the concentrations of TNF-α, IL-1β, and IL-10 and the iNOS expression were evaluated in the colon samples.

RESULTS

Animals that received DSS presented with elevated disease activity index values; increased colon weight-to-length ratio; augmented leukocyte infiltration into the lamina propria and submucosa; and increased production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6, and greater inducible nitric oxide synthase expression in the distal colon. Individually or in combination, the oils were not able to reverse or mitigate any of the DSS-induced symptoms or damage. Additionally, the group of animals treated with DSS and supplemented with FO displayed increased spleen weight-to-body weight ratio, and the group that received a combination of EVOO and FO presented increased TNF-α levels compared with the respective control group.

CONCLUSION

Consumption of large amounts of EVOO and FO as a treatment for or prevention against ulcerative colitis could potentially elicit unwanted adverse effects.

Acetylcholinesterase Inhibitor Pyridostigmine Bromide Attenuates Gut Pathology and Bacterial Dysbiosis in a Murine Model of Ulcerative Colitis

BACKGROUND

Ulcerative colitis (UC) is a Th2 inflammatory bowel disease characterized by increased IL-5 and IL-13 expression, eosinophilic/neutrophilic infiltration, decreased mucus production, impaired epithelial barrier, and bacterial dysbiosis of the colon. Acetylcholine and nicotine stimulate mucus production and suppress Th2 inflammation through nicotinic receptors in lungs but UC is rarely observed in smokers and the mechanism of the protection is unclear.

METHODS

In order to evaluate whether acetylcholine can ameliorate UC-associated pathologies, we employed a mouse model of dextran sodium sulfate (DSS)-induced UC-like conditions, and a group of mice were treated with Pyridostigmine bromide (PB) to increase acetylcholine availability. The effects on colonic tissue morphology, Th2 inflammatory factors, MUC2 mucin, and gut microbiota were analyzed.

RESULTS

DSS challenge damaged the murine colonic architecture, reduced the MUC2 mucin and the tight-junction protein ZO-1. The PB treatment significantly attenuated these DSS-induced responses along with the eosinophilic infiltration and the pro-Th2 inflammatory factors. Moreover, PB inhibited the DSS-induced loss of commensal Clostridia and Flavobacteria, and the gain of pathogenic Erysipelotrichia and Fusobacteria.

CONCLUSIONS

Together, these data suggest that in colons of a murine model, PB promotes MUC2 synthesis, suppresses Th2 inflammation and attenuates bacterial dysbiosis therefore, PB has a therapeutic potential in UC.

Wheat gluten intake increases the severity of experimental colitis and bacterial translocation by weakening of the proteins of the junctional complex

Gluten is only partially digested by intestinal enzymes and can generate peptides that can alter intestinal permeability, facilitating bacterial translocation, thus affecting the immune system. Few studies addressed the role of diet with gluten in the development of colitis. Therefore, we investigate the effects of wheat gluten-containing diet on the evolution of sodium dextran sulphate (DSS)-induced colitis. Mice were fed a standard diet without (colitis group) or with 4·5 % wheat gluten (colitis + gluten) for 15 d and received DSS solution (1·5 %, w/v) instead of water during the last 7 d. Compared with the colitis group, colitis + gluten mice presented a worse clinical score, a larger extension of colonic injury area, and increased mucosal inflammation. Both intestinal permeability and bacterial translocation were increased, propitiating bacteria migration for peripheral organs. The mechanism by which diet with gluten exacerbates colitis appears to be related to changes in protein production and organisation in adhesion junctions and desmosomes. The protein α-E-catenin was especially reduced in mice fed gluten, which compromised the localisation of E-cadherin and β-catenin proteins, weakening the structure of desmosomes. The epithelial damage caused by gluten included shortening of microvilli, a high number of digestive vacuoles, and changes in the endosome/lysosome system. In conclusion, our results show that wheat gluten-containing diet exacerbates the mucosal damage caused by colitis, reducing intestinal barrier function and increasing bacterial translocation. These effects are related to the induction of weakness and disorganisation of adhesion junctions and desmosomes as well as shortening of microvilli and modification of the endocytic vesicle route.

The xenobiotic sensing pregnane X receptor regulates tissue damage and inflammation triggered by C difficile toxins

Clostridioides difficile (formerly Clostridium difficile; C difficile), the leading cause of nosocomial antibiotic‐associated colitis and diarrhea in the industrialized world, triggers colonic disease through the release two toxins, toxin A (TcdA) and toxin B (TcdB), glucosyltransferases that modulate monomeric G‐protein function and alter cytoskeletal function. The initial degree of the host immune response to C difficile and its pathogenic toxins is a common indicator of disease severity and infection recurrence. Thus, targeting the intestinal inflammatory response during infection could significantly decrease disease morbidity and mortality. In the current study, we sought to interrogate the influence of the pregnane X receptor (PXR), a modulator of xenobiotic and detoxification responses, which can sense and respond to microbial metabolites and modulates inflammatory activity, during exposure to TcdA and TcdB. Following intrarectal exposure to TcdA/B, PXR‐deficient mice (Nr1i2^−/−) exhibited reduced survival, an effect that was associated with increased levels of innate immune cell influx. This exacerbated response was associated with a twofold increase in the expression of Tlr4. Furthermore, while broad‐spectrum antibiotic treatment (to deplete the intestinal microbiota) did not alter the responses in Nr1i2^−/− mice, blocking TLR4 signaling significantly reduced TcdA/B‐induced disease severity and immune responses in these mice. Lastly, to assess the therapeutic potential of targeting the PXR, we activated the PXR with pregnenolone 16α‐carbonitrile (PCN) in wild‐type mice, which greatly reduced the severity of TcdA/B‐induced damage and intestinal inflammation. Taken together, these data suggest that the PXR plays a role in the host's response to TcdA/B and may provide a novel target to dampen the inflammatory tissue damage in C difficile infections.

N-Terminomics/TAILS Profiling of Proteases and Their Substrates in Ulcerative Colitis

Dysregulated protease activity is often implicated in the initiation of inflammation and immune cell recruitment in gastrointestinal inflammatory diseases. Using N-terminomics/TAILS (terminal amine isotopic labeling of substrates), we compared proteases, along with their substrates and inhibitors, between colonic mucosal biopsies of healthy patients and those with ulcerative colitis (UC). Among the 1642 N-termini enriched using TAILS, increased endogenous processing of proteins was identified in UC compared to healthy patients. Changes in the reactome pathways for proteins associated with metabolism, adherens junction proteins (E-cadherin, liver-intestinal cadherin, catenin alpha-1, and catenin delta-1), and neutrophil degranulation were identified between the two groups. Increased neutrophil infiltration and distinct proteases observed in ulcerative colitis may result in extensive break down, altered processing, or increased remodeling of adherens junctions and other cellular functions. Analysis of the preferred proteolytic cleavage sites indicated that the majority of proteolytic activity and processing comes from host proteases, but that key microbial proteases may also play a role in maintaining homeostasis. Thus, the identification of distinct proteases and processing of their substrates improves the understanding of dysregulated proteolysis in normal intestinal physiology and ulcerative colitis.

Eosinophils in Inflammatory Bowel Disease

Clinical investigations in inflammatory bowel disease (IBD) patients have provided increasing evidence that eosinophils contribute to chronic intestinal inflammation. Accumulation of eosinophils in the gastrointestinal tract correlates with the variations of eosinophil regulatory molecules; however, their role in gastrointestinal dysfunction in IBD has not been fully elucidated. This review will describe the development and characterization of gastrointestinal eosinophils, mechanisms of eosinophil recruitment to the gastrointestinal tract. Moreover, the eosinophil-induced changes to the enteric nervous system associated with disease severity and gastrointestinal dysfunction will be analyzed with suggestive molecular pathways for enteric neuronal injury. Current and potential therapeutic interventions targeting eosinophils will be discussed.

Combined IL-2 Immunocomplex and Anti-IL-5 mAb Treatment Expands Foxp3+ Treg Cells in the Absence of Eosinophilia and Ameliorates Experimental Colitis

Interleukin (IL)-2 is expressed during T cell activation and induces the proliferation and differentiation of T cells. CD4⁺Foxp3⁺ regulatory T cells (Tregs) constitutively express the high affinity IL-2 receptor (CD25/IL-2Rα) and rapidly respond to IL-2 to elaborate numerous suppressive mechanisms that limit immune-mediated pathologies. Accumulating evidence supports the concept that an aberrant balance between Tregs and Teff contribute to the pathology of intestinal inflammation and that the IL-2/Treg axis is a potential pathway to exploit for the treatment of inflammatory bowel disease (IBD). Here, we show that treatment of mice with IL-2/IL-2 antibody (JES6-1) immunocomplex during DSS-induced colitis induced Foxp3⁺ Treg expansion, but also potently stimulated GATA3⁺ type 2 innate lymphoid cell (ILC2) proliferation and high-level expression of IL-5. Furthermore, IL-2/JES6-1 treatment resulted in massive eosinophil accumulation and activation in the inflamed colon, and afforded only modest protection from colitis. In light of these findings, we observed that combined IL-2/JES6-1 and anti-IL-5 mAb treatment was most effective at ameliorating DSS-induced colitis compared to either treatment alone and that this regimen allowed for Foxp3⁺ Treg expansion without concomitant eosinophilia. Collectively, our findings provide insight into how blockade of IL-5 may aid in optimizing IL-2 immunotherapy for the treatment of intestinal inflammation.

Peroxidasin and eosinophil peroxidase, but not myeloperoxidase, contribute to renal fibrosis in the murine unilateral ureteral obstruction model

Renal fibrosis is the pathological hallmark of chronic kidney disease (CKD) and manifests as glomerulosclerosis and tubulointerstitial fibrosis. Reactive oxygen species contribute significantly to renal inflammation and fibrosis, but most research has focused on superoxide and hydrogen peroxide (H2O2). The animal heme peroxidases myeloperoxidase (MPO), eosinophil peroxidase (EPX), and peroxidasin (PXDN) uniquely metabolize H2O2 into highly reactive and destructive hypohalous acids, such as hypobromous and hypochlorous acid. However, the role of these peroxidases and their downstream hypohalous acids in the pathogenesis of renal fibrosis is unclear. Our study defines the contribution of MPO, EPX, and PXDN to renal inflammation and tubulointerstitial fibrosis in the murine unilateral ureteral obstruction (UUO) model. Using a nonspecific inhibitor of animal heme peroxidases and peroxidase-specific knockout mice, we find that loss of EPX or PXDN, but not MPO, reduces renal fibrosis. Furthermore, we demonstrate that eosinophils, the source of EPX, accumulate in the renal interstitium after UUO. These findings point to EPX and PXDN as potential therapeutic targets for renal fibrosis and CKD and suggest that eosinophils modulate the response to renal injury.

Assessment of eosinophils in gastrointestinal inflammatory disease of dogs

BACKGROUND

Accurate identification of eosinophils in the gastrointestinal (GI) tract of dogs with eosinophilic GI disease (EGID) by histological evaluation is challenging. The currently used hematoxylin and eosin (H&E) staining method detects intact eosinophils but does not detect degranulated eosinophils, thus potentially underrepresenting the number of infiltrating eosinophils.

OBJECTIVE

To develop a more sensitive method for identifying and quantifying both intact and degranulated eosinophils to diagnose EGID more accurately.

METHODS

Endoscopically obtained paraffin-embedded intestinal biopsy specimens from dogs with GI signs were examined. The study groups were dogs with eosinophilic enteritis (EE), lymphoplasmacytic and mixed enteritis, and control dogs with GI signs but no histologic changes on tissue sections. Consecutive sections were immunolabeled with monoclonal antibodies (mAbs) against the eosinophil granule protein eosinophil peroxidase (Epx) and stained by H&E, respectively. The number of eosinophils was manually quantified and classified as intact or degranulated.

RESULTS

The number of intact eosinophils detected in Epx mAb-labeled duodenal sections was significantly higher compared with that in H&E-stained sections, with a similar relationship noted in the colon and stomach. The Epx mAb allowed the unique assessment of eosinophil degranulation. The number of intact and degranulated eosinophils was significantly higher in duodenal lamina propria of the EE and mixed group compared to the control group.

CONCLUSION

Immunohistochemical detection of Epx provides a more precise method to detect GI tract eosinophils compared to H&E staining and could be used as an alternative and reliable diagnostic tool for assessment of biopsy tissues from dogs with EGID.

In vivo Evidence for Partial Activation of Eosinophils via the Histamine H4-Receptor: Adoptive Transfer Experiments Using Eosinophils From H4R-/- and H4R+/+ Mice

Our previous in vitro studies revealed that histamine via histamine the H₄-receptors (H₄R), as compared to other stimuli, such as eotaxin or formylpeptides, rather partially activates eosinophilic granulocytes (eosinophils). In order to evaluate the H₄R-mediated activation of eosinophils in vivo, we employed dextran sodium sulfate (DSS)-induced colitis in mice, closely resembling human ulcerative colitis (UC), which is largely characterized by a local eosinophilic infiltration of the colon. IL-5-deficient BALB/c mice served as a model with reduced endogenous numbers of eosinophils, in which wild-type (H₄R^+/+) or H₄R-deficient (H₄R^−/−) eosinophils were adoptively transferred during the course of DSS-induced colitis. During the 1-week observation period, transfer of eosinophils transiently reversed the acute clinical colitis-like phenotype (body weight loss, perianal bleeding, soft stool consistency) resulting from IL-5-deficiency. This reversion was significantly more pronounced upon transfer of eosinophils from H₄R^+/+ mice as compared to those from H₄R^−/− mice. Already at the end of the observation period, the clinical effects of the transfer of H₄R^+/+ and H₄R^−/− eosinophils became similar, as were the results of the histological examination of the cola and the analyses of cytokine production in cola and in re-stimulated lymph node cells performed at this time. Thus, analyzing clinical and pathological parameters representative of colitis in this model, we demonstrate that as well as in vitro, also in vivo histamine via the H₄R only partially activates eosinophils.

Acute infection with Strongyloides venezuelensis increases intestine production IL-10, reduces Th1/Th2/Th17 induction in colon and attenuates Dextran Sulfate Sodium-induced colitis in BALB/c mice

Helminth infection can reduce the severity of inflammatory bowel disease. However, the modulatory mechanisms elicited by helminth infection are not yet fully understood and vary depending on the experimental model. Herein we evaluated the effect of acute infection of BALB/c mice with Strongyloides venezuelensis on the clinical course of ulcerative colitis induced by Dextran Sulfate Sodium (DSS) treatment of these animals. For the experiments, S. venezuelensis-infected BALB/c mice were treated orally with 4% DSS solution for seven days. As controls, we used untreated S. venezuelensis infected, DSS-treated uninfected, and untreated/uninfected BALB/c mice. During DSS treatment, mice from the different groups were compared with regards to the clinical signs related to the severity of colitis and intestinal inflammation. Mice acutely infected with S. venezulensis and treated with DSS had reduced clinical score, shortening of the colon, and tissue inflammation. Moreover, DSS-treated and infected mice showed reduced IL-4, INF-γ, and IL-17 levels and increase of IL-10 production in the colon and/or in the supernatant of mesenteric lymph nodes cell cultures that resulted in lower eosinophil peroxidase and myeloperoxidase activity in colon homogenates, when compared with DSS-treated uninfected mice. DSS-treated infected mice also preserved the intestine architecture and had normal differentiation of goblet cells and mucus production in the colon mucosa. In conclusion, the data indicate that the clinical improvement reported in DSS-treated infected mice was accompanied by the lower production of Th1/Th2/Th17 pro-inflammatory cytokines, stimulation of IL-10, and induction of mucosal repair mechanisms.

Eosinophils Mediate Tissue Injury in the Autoimmune Skin Disease Bullous Pemphigoid

Eosinophils are typically associated with unique inflammatory settings, including allergic inflammation and helminth infections. However, new information suggests that eosinophils contribute more broadly to inflammatory responses and participate in local immune regulation and the tissue remodeling/repair events linked with a variety of diseases. Eosinophilic infiltration has long been a histologic hallmark of bullous pemphigoid (BP), a subepidermal autoimmune blistering disease characterized by autoantibodies directed against basement membrane protein BP180. However, the exact role of eosinophils in disease pathogenesis remains largely unknown. We show here that eosinophils are necessary for IgE autoantibody-mediated BP blister formation in a humanized IgE receptor mouse model of BP. Disease severity is IgE dose dependent and correlates with the degree of eosinophil infiltration in the skin. Furthermore, IgE autoantibodies fail to induce BP in eosinophil-deficient mice, confirming that eosinophils are required for IgE-mediated tissue injury. Thus, eosinophils provide the cellular link between IgE autoantibodies and skin blistering in this murine model of BP. These findings suggest a role for eosinophils in autoimmune disease and have important implications for the treatment of BP and other antibody-mediated inflammatory and autoimmune diseases.

Pharmacophore-based discovery of 2-(phenylamino)aceto-hydrazides as potent eosinophil peroxidase (EPO) inhibitors

There is an increasing interest in developing novel eosinophil peroxidase (EPO) inhibitors, in order to provide new treatment strategies against chronic inflammatory and neurodegenerative diseases caused by eosinophilic disorder. Within this study, a ligand-based pharmacophore model for EPO inhibitors was generated and used for in silico screening of large 3 D molecular structure databases, containing more than 4 million compounds. Hits obtained were clustered and a total of 277 compounds were selected for biological assessment. A class of 2-(phenyl)amino-aceto-hydrazides with different substitution pattern on the aromatic ring was found to contain the most potent EPO inhibitors, exhibiting IC₅₀ values down to 10 nM. The generated pharmacophore model therefore, represents a valuable tool for the selection of compounds for biological testing. The compounds identified as potent EPO inhibitors will serve to initiate a hit to lead and lead optimisation program for the development of new therapeutics against eosinophilic disorders.

Peripheral Eosinophilia in Patients With Inflammatory Bowel Disease Defines an Aggressive Disease Phenotype

OBJECTIVES

Peripheral blood eosinophilia (PBE) in inflammatory bowel disease (IBD) is associated with ulcerative colitis (UC) and active disease. Little data exist on the long-term impact of PBE on disease course. We aimed to investigate the multi-year patterns of PBE and its impact on disease severity in a large IBD cohort.

METHODS

We performed a registry analysis of a consented, prospective, natural history IBD cohort at a tertiary center from 2009 to 2014. Demographics, comorbidities, disease activity, healthcare utilization, and time to hospitalization or surgical resection of patients who displayed PBE were compared to patients without PBE.

RESULTS

Of the 2,066 IBD patients, 19.2% developed PBE. PBE was significantly associated with UC (P<0.001), extensive colitis (P<0.001), and shorter disease duration (P=0.03). Over six years, PBE patients had more active disease (Harvey-Bradshaw Index P=0.001; ulcerative colitis activity index P<0.001), concurrent C-reactive protein elevation (P<0.001), healthcare utilization (hospitalization P<0.001, IBD surgery P<0.001), and more aggressive medical therapy (prednisone P<0.001, anti-TNF P<0.001). Patients with PBE had a significantly reduced time to hospitalization in both UC (P<0.001) and Crohn's disease (CD) (P<0.001) and reduced time to colectomy in UC (P=0.003). On multivariable modeling, PBE remained significantly associated with hospitalization and surgery in both CD and UC. New diagnosis of UC with PBE was associated with increased steroid (P=0.007) and anti-TNF (P=0.001) requirement.

CONCLUSION

This multi-year study of a large IBD cohort suggests that peripheral blood eosinophilia represents a biomarker of a distinct IBD subgroup, with a unique inflammatory signature, and at risk for worse clinical outcomes.

Role of Hypohalous Acids in Basement Membrane Homeostasis

SIGNIFICANCE

Basement membranes (BMs) are sheet-like structures of specialized extracellular matrix that underlie nearly all tissue cell layers including epithelial, endothelial, and muscle cells. BMs not only provide structural support but are also critical for the development, maintenance, and repair of organs. Animal heme peroxidases generate highly reactive hypohalous acids extracellularly and, therefore, target BMs for oxidative modification. Given the importance of BMs in tissue structure and function, hypohalous acid-mediated oxidative modifications of BM proteins represent a key mechanism in normal development and pathogenesis of disease. Recent Advances: Peroxidasin (PXDN), a BM-associated animal heme peroxidase, generates hypobromous acid (HOBr) to form sulfilimine cross-links within the collagen IV network of BM. These cross-links stabilize BM and are critical for animal tissue development. These findings highlight a paradoxical anabolic role for HOBr, which typically damages protein structure leading to dysfunction.

CRITICAL ISSUES

The molecular mechanism whereby PXDN uses HOBr as a reactive intermediate to cross-link collagen IV, yet avoid collateral damage to nearby BM proteins, remains unclear.

FUTURE DIRECTIONS

The exact identification and functional impact of specific hypohalous acid-mediated modifications of BM proteins need to be addressed to connect these modifications to tissue development and pathogenesis of disease. As seen with the sulfilimine cross-link of collagen IV, hypohalous acid oxidative events may be beneficial in select situations rather than uniformly deleterious. Antioxid. Redox Signal. 27, 839-854.

Transcriptome profiling of mouse colonic eosinophils reveals a key role for eosinophils in the induction of s100a8 and s100a9 in mucosal healing

Eosinophils are bone marrow-derived cells that have been largely implicated in Th2-associated diseases. Recent data highlights a key role for eosinophils in mucosal innate immune responses especially in the gastrointestinal (GI) tract, which is one of the largest eosinophil reservoirs in the body. Although eosinophils express and synthesize a plethora of proteins that can mediate their effector activities, the transcriptome signature of eosinophils in mucosal inflammation and subsequent repair has been considerably overlooked. We demonstrate that eosinophils are recruited to the colon in acute inflammatory stages where they promote intestinal inflammation and remain in substantial numbers throughout the mucosal healing process. Microarray analysis of primary colonic eosinophils that were sorted at distinct stages of mucosal inflammation and repair revealed dynamic regulation of colonic eosinophil mRNA expression. The clinically relevant genes s100a8 and s100a9 were strikingly increased in colonic eosinophils (up to 550-fold and 80-fold, respectively). Furthermore, local and systemic expression of s100a8 and s100a9 were nearly diminished in eosinophil-deficient ΔdblGATA mice, and were re-constituted upon adoptive transfer of eosinophils. Taken together, these data may provide new insight into the involvement of eosinophils in colonic inflammation and repair, which may have diagnostic and therapeutic implications.

Eosinophils in Autoimmune Diseases

Eosinophils are multifunctional granulocytes that contribute to initiation and modulation of inflammation. Their role in asthma and parasitic infections has long been recognized. Growing evidence now reveals a role for eosinophils in autoimmune diseases. In this review, we summarize the function of eosinophils in inflammatory bowel diseases, neuromyelitis optica, bullous pemphigoid, autoimmune myocarditis, primary biliary cirrhosis, eosinophilic granulomatosis with polyangiitis, and other autoimmune diseases. Clinical studies, eosinophil-targeted therapies, and experimental models have contributed to our understanding of the regulation and function of eosinophils in these diseases. By examining the role of eosinophils in autoimmune diseases of different organs, we can identify common pathogenic mechanisms. These include degranulation of cytotoxic granule proteins, induction of antibody-dependent cell-mediated cytotoxicity, release of proteases degrading extracellular matrix, immune modulation through cytokines, antigen presentation, and prothrombotic functions. The association of eosinophilic diseases with autoimmune diseases is also examined, showing a possible increase in autoimmune diseases in patients with eosinophilic esophagitis, hypereosinophilic syndrome, and non-allergic asthma. Finally, we summarize key future research needs.

Eosinophil-derived IL-4 drives progression of myocarditis to inflammatory dilated cardiomyopathy

Diny et al. report a pathogenic role for eosinophils in autoimmune myocarditis and dilated cardiomyopathy. Eosinophils are required for progression of myocarditis to dilated cardiomyopathy and drive severe disease when present in large numbers. Activated cardiac eosinophils mediate this process through IL-4.

Inflammatory dilated cardiomyopathy (DCMi) is a major cause of heart failure in children and young adults. DCMi develops in up to 30% of myocarditis patients, but the mechanisms involved in disease progression are poorly understood. Patients with eosinophilia frequently develop cardiomyopathies. In this study, we used the experimental autoimmune myocarditis (EAM) model to determine the role of eosinophils in myocarditis and DCMi. Eosinophils were dispensable for myocarditis induction but were required for progression to DCMi. Eosinophil-deficient ΔdblGATA1 mice, in contrast to WT mice, showed no signs of heart failure by echocardiography. Induction of EAM in hypereosinophilic IL-5Tg mice resulted in eosinophilic myocarditis with severe ventricular and atrial inflammation, which progressed to severe DCMi. This was not a direct effect of IL-5, as IL-5TgΔdblGATA1 mice were protected from DCMi, whereas IL-5^−/− mice exhibited DCMi comparable with WT mice. Eosinophils drove progression to DCMi through their production of IL-4. Our experiments showed eosinophils were the major IL-4–expressing cell type in the heart during EAM, IL-4^−/− mice were protected from DCMi like ΔdblGATA1 mice, and eosinophil-specific IL-4 deletion resulted in improved heart function. In conclusion, eosinophils drive progression of myocarditis to DCMi, cause severe DCMi when present in large numbers, and mediate this process through IL-4.

Tissue and peripheral eosinophilia as predictors for disease outcome in children with ulcerative colitis

BACKGROUND

Eosinophils are implicated in the pathogenesis of ulcerative colitis.

AIMS

To evaluate the magnitude of mucosal and blood eosinophils in newly diagnosed pediatric ulcerative colitis patients and its significance in predicting disease outcomes.

METHODS

We retrospectively evaluated colorectal biopsies of 96 pediatric patients with ulcerative colitis and 50 age- and sex-matched controls. Samples were taken from diseased areas of the colon and examined by a gastrointestinal pathologist. The most inflamed site was used for assessment of mucosal eosinophils.

RESULTS

Samples from 96 diagnostic and 70 follow-up colonoscopies were evaluated. Median age was 13.3 years (IQR 10.1-15.3). Median duration of follow-up was 12.8 years (IQR 7.2-17.1). Median number of tissue eosinophils at diagnosis was 45 (IQR 22-73) compared to 10 eosinophils (IQR 8-25) during histologic remission (p<0.0001). Peripheral absolute eosinophil counts correlated with tissue inflammation and eosinophilia (p=0.001). Mucosal eosinophilic infiltration (p=0.02) and peripheral eosinophilia (p=0.04) was associated with clinical severity at diagnosis. Multivariate analysis showed that severe eosinophilic infiltration is associated with corticosteroid therapy following diagnosis (p=0.04) but not with long-term risk for step-up therapy or colectomy.

CONCLUSION

Tissue and peripheral eosinophilia correlate with ulcerative colitis severity at diagnosis and with short-term corticosteroid requirement but not with long-term outcomes.

Assessment of eosinophil peroxidase as a potential diagnostic and prognostic marker in dogs with inflammatory bowel disease

OBJECTIVE To evaluate a method for identifying intact and degranulated eosinophils in the small intestine of dogs with inflammatory bowel disease (IBD) by use of a monoclonal antibody (mAb) against eosinophil peroxidase (EPX). ANIMALS 11 untreated dogs with IBD, 5 dogs with IBD treated with prednisolone, and 8 control dogs with no clinical evidence of gastrointestinal tract disease and no immunosuppressive treatment. PROCEDURES 4-μm-thick sections of paraffin-embedded tissues from necropsy specimens were immunostained with EPX mAb. Stained intact and degranulated eosinophils in consecutive microscopic fields (400X magnification) of the upper (villus tips) and lower (between the muscularis mucosae and crypts) regions of the lamina propria of the jejunum were manually counted. RESULTS Compared with control and treated IBD dogs, untreated IBD dogs had a significantly higher number of degranulated eosinophils in the lower region of the lamina propria. However, no significant differences were detected in the number of intact eosinophils in this region among groups. In the upper region of the lamina propria, untreated IBD dogs had a significantly higher number of degranulated and intact eosinophils, compared with control and treated IBD dogs. Number of degranulated and intact eosinophils did not differ significantly between control and treated IBD dogs. CONCLUSIONS AND CLINICAL RELEVANCE Immunohistologic analysis with EPX mAb yielded prominent granule staining that allowed reliable morphological identification of degranulated and intact eosinophils, which may provide a strategy for quantitative and selective evaluation of eosinophils in gastrointestinal biopsy specimens and a potential method to diagnose IBD and evaluate treatment outcome.

A key requirement for CD300f in innate immune responses of eosinophils in colitis

Eosinophils are traditionally studied in the context of type 2 immune responses. However, recent studies highlight key innate immune functions for eosinophils especially in colonic inflammation. Surprisingly, molecular pathways regulating innate immune activities of eosinophil are largely unknown. We have recently shown that the CD300f is highly expressed by colonic eosinophils. Nonetheless, the role of CD300f in governing innate immune eosinophil activities is ill-defined. RNA sequencing of 162 pediatric Crohn's disease patients revealed upregulation of multiple Cd300 family members, which correlated with the presence of severe ulcerations and inflammation. Increased expression of CD300 family receptors was also observed in active ulcerative colitis (UC) and in mice following induction of experimental colitis. Specifically, the expression of CD300f was dynamically regulated in monocytes and eosinophils. Dextran sodium sulfate (DSS)-treated Cd300f^-/- mice exhibit attenuated disease activity and histopathology in comparison with DSS-treated wild type (WT). Decreased disease activity in Cd300f^-/- mice was accompanied with reduced inflammatory cell infiltration and nearly abolished production of pro-inflammatory cytokines. Monocyte depletion and chimeric bone marrow transfer experiments revealed a cell-specific requirement for CD300f in innate immune activation of eosinophils. Collectively, we uncover a new pathway regulating innate immune activities of eosinophils, a finding with significant implications in eosinophil-associated gastrointestinal diseases.

Eosinophils Contribute to Intestinal Inflammation via Chemoattractant Receptor-homologous Molecule Expressed on Th2 Cells, CRTH2, in Experimental Crohn's Disease

BACKGROUND AND AIMS

Prostaglandin [PG] D2 activates two receptors, DP and CRTH2. Antagonism of CRTH2 has been shown to promote anti-allergic and anti-inflammatory effects. We investigated whether CRTH2 may play a role in Crohn's disease [CD], focusing on eosinophils which are widely present in the inflamed mucosa of CD patients and express both receptors.

METHODS

Using the 2,4,6-trinitrobenzenesulfonic acid [TNBS]-induced colitis model, involvement of CRTH2 in colitis was investigated by pharmacological antagonism, immunohistochemistry, Western blotting, immunoassay, and leukocyte recruitment. Chemotactic assays were performed with isolated human eosinophils. Biopsies and serum samples of CD patients were examined for presence of CRTH2 and ligands, respectively.

RESULTS

High amounts of CRTH2-positive cells, including eosinophils, are present in the colonic mucosa of mice with TNBS colitis and in human CD. The CRTH2 antagonist OC-459, but not the DP antagonist MK0524, reduced inflammation scores and decreased TNF-α, IL-1β, and IL-6 as compared with control mice. OC-459 inhibited recruitment of eosinophils into the colon and also inhibited CRTH2-induced chemotaxis of human eosinophils in vitro. Eosinophil-depleted ΔdblGATA knockout mice were less sensitive to TNBS-induced colitis, whereas IL-5 transgenic mice with lifelong eosinophilia were more severely affected than wild types. In addition, we show that serum levels of PGD2 and Δ(12)-PGJ2 were increased in CD patients as compared with control individuals.

CONCLUSIONS

CRTH2 plays a pro-inflammatory role in TNBS-induced colitis. Eosinophils contribute to the severity of the inflammation, which is improved by a selective CRTH2 antagonist. CRTH2 may, therefore, represent an important target in the pharmacotherapy of CD.

The Importance of Intestinal Eotaxin-1 in Inflammatory Bowel Disease: New Insights and Possible Therapeutic Implications

BACKGROUND

Involvement of eotaxin-1 in inflammatory bowel disease has been previously suggested and increased levels of eotaxin-1 have been described in both ulcerative colitis and in Crohn's disease. The association between serum levels of eotaxin-1 and that within the colonic mucosa has not been well defined, as is the potential therapeutic value of targeting eotaxin-1.

AIMS

To characterize serum and intestinal wall eotaxin-1 levels in various inflammatory bowel disease patients and to explore the effect of targeting eotaxin-1 by specific antibodies in dextran sodium sulfate-induced colitis model.

METHODS

Eotaxin-1 levels were measured in colonic biopsies and in the sera of 60 ulcerative colitis patients, Crohn's disease patients and healthy controls. We also followed in experimental colitis the effect of targeting eotaxin-1 by a monoclonal antibody.

RESULTS

Colon eotaxin-1 levels were significantly increased in active but not in quiescent ulcerative colitis and Crohn's disease patients compared to healthy controls. Levels of eotaxin-1 in the colon were correlated with eosinophilia only in tissues from active Crohn's disease patients. Our results did not show any statistically significant change in serum eotaxin-1 levels among ulcerative colitis, Crohn's disease and healthy controls. Moreover, we demonstrate that in dextran sodium sulfate-induced colitis, targeting of eotaxin-1 with 2 injections of anti eotaxin-1 monoclonal antibody ameliorates disease activity along with decreasing colon weight and improving histologic inflammation.

CONCLUSION

Eotaxin-1 is increasingly recognized as a major mediator of intestinal inflammation. Our preliminary human and animal results further emphasize the value of targeting eotaxin-1 in inflammatory bowel disease.

Cyclophilin D regulates necrosis, but not apoptosis, of murine eosinophils

Eosinophil degranulation and clusters of free extracellular granules are frequently observed in diverse diseases, including atopic dermatitis, nasal polyposis, and eosinophilic esophagitis. Whether these intact granules are released by necrosis or a biochemically mediated cytolysis remains unknown. Recently, a peptidyl-prolyl isomerase located within the mitochondrial matrix, cyclophilin D (PPIF), was shown to regulate necrotic, but not apoptotic, cell death in vitro in fibroblasts, hepatocytes, and cardiomyocytes. Whether cyclophilin D regulates necrosis in hematopoietic cells such as eosinophils remains unknown. We used PPIF-deficient (Ppif(-/-)) mice to test whether cyclophilin D is required for regulating eosinophil necrosis. PPIF deficiency did not affect eosinophil development or maturation at baseline. After in vitro ionomycin or H2O2 treatment, Ppif(-/-) eosinophils were significantly protected from Ca(2+) overload- or oxidative stress-induced necrosis. Additionally, Ppif(-/-) eosinophils demonstrated significantly decreased necrosis, but not apoptosis, in response to Siglec-F cross-linking, a stimulus associated with eosinophil-mediated processes in vitro and in vivo. When treated with apoptosis inducers, Ppif(+/+) and Ppif(-/-) eosinophils exhibited no significant difference in apoptosis or secondary necrosis. Finally, in a dextran sodium sulfate-induced colitis model, although levels of colitogenic cytokines and eosinophil-selective chemokines were comparable between Ppif(+/+) and Ppif(-/-) mice, the latter exhibited decreased clinical outcomes. This correlated with significantly reduced eosinophil cytolysis in the colon. Collectively, our present studies demonstrate that murine eosinophil necrosis is regulated in vitro and in vivo by cyclophilin D, at least in part, thus providing new insight into the mechanism of eosinophil necrosis and release of free extracellular granules in eosinophil-associated diseases.

Bilirubin prevents acute DSS-induced colitis by inhibiting leukocyte infiltration and suppressing upregulation of inducible nitric oxide synthase

Bilirubin is thought to exert anti-inflammatory effects by inhibiting vascular cell adhesion molecule-1 (VCAM-1)-dependent leukocyte migration and by suppressing the expression of inducible nitric oxide synthase (iNOS). As VCAM-1 and iNOS are important mediators of tissue injury in the dextran sodium sulfate (DSS) murine model of inflammatory colitis, we examined whether bilirubin prevents colonic injury in DSS-treated mice. Male C57BL/6 mice were administered 2.5% DSS in the drinking water for 7 days, while simultaneously receiving intraperitoneal injections of bilirubin (30 mg/kg) or potassium phosphate vehicle. Disease activity was monitored, peripheral blood counts and serum nitrate levels were determined, and intestinal specimens were analyzed for histological injury, leukocyte infiltration, and iNOS expression. The effect of bilirubin on IL-5 production by HSB-2 cells and on Jurkat cell transendothelial migration also was determined. DSS-treated mice that simultaneously received bilirubin lost less body weight, had lower serum nitrate levels, and exhibited reduced disease severity than vehicle-treated animals. Concordantly, histopathological analyses revealed that bilirubin-treated mice manifested significantly less colonic injury, including reduced infiltration of eosinophils, lymphocytes, and monocytes, and diminished iNOS expression. Bilirubin administration also was associated with decreased eosinophil and monocyte infiltration into the small intestine, with a corresponding increase in peripheral blood eosinophilia. Bilirubin prevented Jurkat migration but did not alter IL-5 production. In conclusion, bilirubin prevents DSS-induced colitis by inhibiting the migration of leukocytes across the vascular endothelium and by suppressing iNOS expression.

Granulocyte Macrophage Colony-Stimulating Factor-Activated Eosinophils Promote Interleukin-23 Driven Chronic Colitis

The role of intestinal eosinophils in immune homeostasis is enigmatic and the molecular signals that drive them from protective to tissue damaging are unknown. Most commonly associated with Th2 cell-mediated diseases, we describe a role for eosinophils as crucial effectors of the interleukin-23 (IL-23)-granulocyte macrophage colony-stimulating factor (GM-CSF) axis in colitis. Chronic intestinal inflammation was characterized by increased bone marrow eosinopoiesis and accumulation of activated intestinal eosinophils. IL-5 blockade or eosinophil depletion ameliorated colitis, implicating eosinophils in disease pathogenesis. GM-CSF was a potent activator of eosinophil effector functions and intestinal accumulation, and GM-CSF blockade inhibited chronic colitis. By contrast neutrophil accumulation was GM-CSF independent and dispensable for colitis. In addition to TNF secretion, release of eosinophil peroxidase promoted colitis identifying direct tissue-toxic mechanisms. Thus, eosinophils are key perpetrators of chronic inflammation and tissue damage in IL-23-mediated immune diseases and it suggests the GM-CSF-eosinophil axis as an attractive therapeutic target.

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GM-CSF synergizes with IL-5 to exacerbate eosinopoiesis during chronic colitis

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GM-CSF-activated eosinophils promote IL-23 driven colitis

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Depletion of eosinophils, but not of neutrophils, dampens colitis

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GM-CSF increases eosinophil production of inflammatory cytokines TNF and IL-13