Targeting eotaxin-1 and CCR3 receptor alleviates enteric neuropathy and colonic dysfunction in TNBS-induced colitis in guinea pigs

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.

Histological Image-based Ensemble Model to Identify Myenteric Plexitis and Predict Endoscopic Postoperative Recurrence in Crohn's Disease: A Multicentre, Retrospective Study

BACKGROUND AND AIMS

Myenteric plexitis is correlated with postoperative recurrence of Crohn's disease when relying on traditional statistical methods. However, comprehensive assessment of myenteric plexus remains challenging. This study aimed to develop and validate a deep learning system to predict postoperative recurrence through automatic screening and identification of features of the muscular layer and myenteric plexus.

METHODS

We retrospectively reviewed 205 patients who underwent bowel resection surgery from two hospitals. Patients were divided into a training cohort [n = 108], an internal validation cohort [n = 47], and an external validation cohort [n = 50]. A total of 190 960 patches from 278 whole-slide images of surgical specimens were analysed using the ResNet50 encoder, and 6144 features were extracted after transfer learning. We used five robust algorithms to construct classification models. The performances of the models were evaluated based on the area under the receiver operating characteristic curve [AUC] in three cohorts.

RESULTS

The stacking model achieved satisfactory accuracy in predicting postoperative recurrence of CD in the training cohort (AUC: 0.980; 95% confidence interval [CI] 0.960-0.999), internal validation cohort [AUC: 0.908; 95% CI 0.823-0.992], and external validation cohort [AUC: 0.868; 95% CI 0.761-0.975]. The accuracy for identifying the severity of myenteric plexitis was 0.833, 0.745, and 0.694 in the training, internal validation and external validation cohorts, respectively.

CONCLUSIONS

Our work initially established an interpretable stacking model based on features of the muscular layer and myenteric plexus extracted from histological images to identify the severity of myenteric plexitis and predict postoperative recurrence of CD.

Cancer Immunotherapy: The Checkpoint between Chronic Colitis and Colorectal Cancer

Inflammatory Bowel Disease (IBD) is a group of diseases that cause intestinal inflammation and lesions because of an abnormal immune response to host gut microflora. Corticosteroids, anti-inflammatories, and antibiotics are often used to reduce non-specific inflammation and relapse rates; however, such treatments are ineffective over time. Patients with chronic colitis are more susceptible to developing colorectal cancer, especially those with a longer duration of colitis. There is often a limit in using chemotherapy due to side effects, leading to reduced efficacy, leaving an urgent need to improve treatments and identify new therapeutic targets. Cancer immunotherapy has made significant advances in recent years and is mainly categorized as cancer vaccines, adoptive cellular immunotherapy, or immune checkpoint blockade therapies. Checkpoint markers are expressed on cancer cells to evade the immune system, and as a result checkpoint inhibitors have transformed cancer treatment in the last 5-10 years. Immune checkpoint inhibitors have produced long-lasting clinical responses in both single and combination therapies. Winnie mice are a viable model of spontaneous chronic colitis with immune responses like human IBD. Determining the expression levels of checkpoint markers in tissues from these mice will provide insights into disease initiation, progression, and cancer. Such information will lead to identification of novel checkpoint markers and the development of treatments with or without immune checkpoint inhibitors or vaccines to slow or stop disease progression.

Potent CCR3 Receptor Antagonist, SB328437, Suppresses Colonic Eosinophil Chemotaxis and Inflammation in the Winnie Murine Model of Spontaneous Chronic Colitis

Eosinophils and their regulatory molecules have been associated with chronic intestinal inflammation and gastrointestinal dysfunctions; eosinophil accumulation in the gut is prominent in inflammatory bowel disease (IBD). The chemokine receptor CCR3 plays a pivotal role in local and systemic recruitment and activation of eosinophils. In this study, we targeted CCR3-ligand interactions with a potent CCR3 receptor antagonist, SB328437, to alleviate eosinophil-associated immunological responses in the Winnie model of spontaneous chronic colitis. Winnie and C57BL/6 mice were treated with SB328437 or vehicle. Clinical and histopathological parameters of chronic colitis were assessed. Flow cytometry was performed to discern changes in colonic, splenic, circulatory, and bone marrow-derived leukocytes. Changes to the serum levels of eosinophil-associated chemokines and cytokines were measured using BioPlex. Inhibition of CCR3 receptors with SB328437 attenuated disease activity and gross morphological damage to the inflamed intestines and reduced eosinophils and their regulatory molecules in the inflamed colon and circulation. SB328437 had no effect on eosinophils and their progenitor cells in the spleen and bone marrow. This study demonstrates that targeting eosinophils via the CCR3 axis has anti-inflammatory effects in the inflamed intestine, and also contributes to understanding the role of eosinophils as potential end-point targets for IBD treatment.

The aryl hydrocarbon receptor contributes to tissue adaptation of intestinal eosinophils in mice

Eosinophils are potent sources of inflammatory and toxic mediators, yet they reside in large numbers in the healthy intestine without causing tissue damage. We show here that intestinal eosinophils were specifically adapted to their environment and underwent substantial transcriptomic changes. Intestinal eosinophils upregulated genes relating to the immune response, cell-cell communication, extracellular matrix remodeling, and the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor with broad functions in intestinal homeostasis. Eosinophils from AHR-deficient mice failed to fully express the intestinal gene expression program, including extracellular matrix organization and cell junction pathways. AHR-deficient eosinophils were functionally impaired in the adhesion to and degradation of extracellular matrix, were more prone to degranulation, and had an extended life span. Lack of AHR in eosinophils had wider effects on the intestinal immune system, affecting the T cell compartment in nave and helminth-infected mice. Our study demonstrates that the response to environmental triggers via AHR partially shapes tissue adaptation of eosinophils in the small intestine.

Bifidobacterium lactis BL-99 modulates intestinal inflammation and functions in zebrafish models

This study was designed to explore the therapeutics and the mechanisms of a patented and marked gastric acid and intestine juice-resistant probiotics Bifidobacterium lactis BL-99 (B. lactis BL-99) on the intestinal inflammation and functions in the zebrafish models. After feeding for 6 hours, B. lactis BL-99 was fully retained in the larval zebrafish intestinal tract and stayed for over 24 hours. B. lactis BL-99 promoted the intestinal motility and effectively alleviated aluminum sulfate-induced larval zebrafish constipation (p < 0.01). Irregular high glucose diet induced adult zebrafish intestinal functional and metabolic disorders. After fed with B. lactis BL-99, IL-1β gene expression was significantly down-regulated, and IL-10 and IL-12 gene levels were markedly up-regulated in this model (p < 0.05). The intestinal lipase activity was elevated in the adult zebrafish intestinal functional disorder model after B. lactis BL-99 treatment (p < 0.05), but tryptase content had no statistical changes (p > 0.05). B. lactis BL-99 improved the histopathology of the adult zebrafish intestinal inflammation, increased the goblet cell numbers, and up-and-down metabolites were markedly recovered after treatment of B. lactis BL-99 (p < 0.05). These results suggest that B. lactis BL-99 could relieve intestinal inflammation and promote intestinal functions, at least in part, through modulating intestinal and microbial metabolism to maintain intestinal health.

Chemokines and chemokine receptors in inflammatory bowel disease: Recent findings and future perspectives

Despite the benefits of current therapeutic options for treating inflammatory bowel disease (IBD), there are still patients who are refractory to these therapies. Moreover, the relapses caused by incomplete intestinal mucosa healing are frequent. Therefore, there is a need for novel pharmacological targets that can improve the existing IBD therapeutic armamentarium. Chemokine and chemokine receptors have emerged as appealing options to this end. As well as controlling leukocyte trafficking to inflamed tissues, these proteins regulate many other processes related to the development of intestinal inflammation. In this review, we summarise the most recent preclinical studies, along with the putative application of chemokine-based therapies in patients with IBD.

Targeting Enteric Neurons and Plexitis for the Management of Inflammatory Bowel Disease

Ulcerative colitis (UC) and Crohn's disease (CD) are pathological conditions with an unknown aetiology that are characterised by severe inflammation of the intestinal tract and collectively referred to as inflammatory bowel disease (IBD). Current treatments are mostly ineffective due to their limited efficacy or toxicity, necessitating surgical resection of the affected bowel. The management of IBD is hindered by a lack of prognostic markers for clinical inflammatory relapse. Intestinal inflammation associates with the infiltration of immune cells (leukocytes) into, or surrounding the neuronal ganglia of the enteric nervous system (ENS) termed plexitis or ganglionitis. Histological observation of plexitis in unaffected intestinal regions is emerging as a vital predictive marker for IBD relapses. Plexitis associates with alterations to the structure, cellular composition, molecular expression and electrophysiological function of enteric neurons. Moreover, plexitis often occurs before the onset of gross clinical inflammation, which may indicate that plexitis can contribute to the progression of intestinal inflammation. In this review, the bilateral relationships between the ENS and inflammation are discussed. These include the effects and mechanisms of inflammation-induced enteric neuronal loss and plasticity. Additionally, the role of enteric neurons in preventing antigenic/pathogenic insult and immunomodulation is explored. While all current treatments target the inflammatory pathology of IBD, interventions that protect the ENS may offer an alternative avenue for therapeutic intervention.

Eosinophilic recruitment in thermally injured older animals is associated with worse outcomes and higher conversion to full thickness burn

BACKGROUND

Partial burn injury in older patients is associated with higher rates of morbidity, mortality, and conversion to full thickness burn (Finnerty et al., 2009; Pham et al., 2009). Both human and mouse models demonstrate an altered systemic immune response in older subjects, however less is known about the localized response (Jeschke et al., 2016; Farinas et al., 2018; Mohs et al., 2017). We hypothesized that a mouse model could demonstrate differences in the localized inflammatory response of the old.

METHODS

Six old (66 weeks) and young (8 weeks) mice received partial thickness thermal burns. Localized and systemic expression of nine chemokines (TNFalpha, MCP-1, MIP-2, S100A9, EGF, IL-10, RANTES, G-CSF, and EOTAXIN) were evaluated at day 3 after burn using Luminex analysis. Vimentin immunostaining was used to evaluate injury depth.

RESULTS

Vimentin staining demonstrated increased burn depth in old mice (449±38μm) as compared to young (166±18μm) (p<0.05). Both groups exhibited increased localized expression of EOTAXIN after burn (p<0.05), however expression in old mice (83.6±6.1pg/ml) was lower than that of young (126.8±18.7pg/ml) (p<0.05). Systemically, however, old mice had increased baseline EOTAXIN expression (1332.40±110.78pg/ml) compared to young (666.12±45.8pg/ml) (p<0.005).

CONCLUSIONS

EOTAXIN is one of the primary chemoattractants for selective eosinophilic recruitment and activation. While eosinophils are important for wound healing, a hyperactive eosinophilic response can result in tissue damage. We hypothesize that the increased baseline serum EOTAXIN in the old may prime their hyperactive response, and may contribute to their worse clinical outcomes. Long-term eosinophil activation requires further study, however our findings indicate a role for EOTAXIN and eosinophils in burn response.

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.