Prostaglandin D2 receptor D-type prostanoid receptor 2 mediates eosinophil trafficking into the esophagus

Breaking down the complex pathophysiology of eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a chronic and progressive immune-mediated disease of the esophagus associated with antigen-driven type 2 inflammation and symptoms of esophageal dysfunction. Our understanding of EoE pathophysiology has evolved since its initial recognition more than 20 years ago and has translated into diagnostic and novel therapeutic approaches that are affecting patient care. The mechanisms underlying disease development and progression are influenced by diverse factors, such as genetics, age, allergic comorbidities, and allergen exposures. Central to EoE pathophysiology is a dysregulated feed-forward cycle that develops between the esophageal epithelium and the immune system. Allergen-induced, type 2-biased immune activation by the esophageal epithelium propagates a cycle of impaired mucosal barrier integrity and allergic inflammation, eventually leading to tissue remodeling and progressive organ dysfunction. Herein, we review the current understanding of fundamental pathophysiological mechanisms contributing to EoE pathogenesis.

Metabolic Profiling Implicates a Critical Role of Cyclooxygenase-2-Mediated Arachidonic Acid Metabolism in Radiation-Induced Esophageal Injury in Rats

Radiation-induced esophageal injury (RIEL) is a major dose-limiting complication of radiotherapy, especially for esophageal and thoracic cancers. RIEL is a multi-factorial and multi-step process, which is regulated by a complex network of DNA, RNA, protein and metabolite. However, it is unclear which esophageal metabolites are altered by ionizing radiation and how these changes affect RIEL progression. In this work, we established a rat model of RIEL with 0-40 Gy X-ray irradiation. Esophageal irradiation using ≥25 Gy induced significant changes to rats, such as body weight, food intake, water intake and esophageal structure. The metabolic changes and related pathways of rat esophageal metabolites were investigated by liquid chromatography-mass spectrometry (LC-MS). One hundred eighty metabolites showed an up-regulation in a dose-dependent manner (35 Gy ≥ 25 Gy > controls), and 199 metabolites were downregulated with increasing radiation dose (35 Gy ≤ 25 Gy < controls). The KEGG analysis showed that ionizing radiation seriously disrupted multiple metabolic pathways, and arachidonic acid metabolism was the most significantly enriched pathway. 20 metabolites were dysregulated in arachidonic acid metabolism, including up-regulation of five prostaglandins (PGA2, PGJ2, PGD2, PGH2, and PGI2) in 25 or 35 Gy groups. Cyclooxygenase-2 (COX-2), the key enzyme in catalyzing the biosynthesis of prostaglandins from arachidonic acid, was highly expressed in the esophagus of irradiated rats. Additionally, receiver operating characteristic (ROC) curve analysis revealed that PGJ2 may serve as a promising tissue biomarker for RIEL diagnosis. Taken together, these findings indicate that ionizing radiation induces esophageal metabolic alterations, which advance our understanding of the pathophysiology of RIEL from the perspective of metabolism.

Type 2 Inflammation in Eosinophilic Esophagitis: From Pathophysiology to Therapeutic Targets

Eosinophilic esophagitis (EoE) is a chronic immune-mediated disease of the esophagus characterized clinically by symptoms related to esophageal dysfunction and histologically by eosinophil-predominant inflammation, whose incidence is rising. It significantly affects patients’ quality of life and, if left untreated, results in fibrotic complications. Although broad consensus has been achieved on first-line therapy, a subset of patients remains non-responder to standard therapy. The pathogenesis of EoE is multifactorial and results from the complex, still mostly undefined, interaction between genetics and intrinsic factors, environment, and antigenic stimuli. A deep understanding of the pathophysiology of this disease is pivotal for the development of new therapies. This review provides a comprehensive description of the pathophysiology of EoE, starting from major pathogenic mechanisms (genetics, type 2 inflammation, epithelial barrier dysfunction, gastroesophageal reflux, allergens, infections and microbiota) and subsequently focusing on the single protagonists of type 2 inflammation (involved cells, cytokines, soluble effectors, surface proteins and transcription factors) that could represent present and future therapeutic targets, while summarizing previous therapeutic approaches in literature.

Kidney in the net of acute and long-haul coronavirus disease 2019: a potential role for lipid mediators in causing renal injury and fibrosis

PURPOSE OF REVIEW

Severe COVID-19 disease is often complicated by acute kidney injury (AKI), which may transition to chronic kidney disease (CKD). Better understanding of underlying mechanisms is important in advancing therapeutic approaches.

RECENT FINDINGS

SARS-CoV-2-induced endothelial injury initiates platelet activation, platelet-neutrophil partnership and release of neutrophil extracellular traps. The resulting thromboinflammation causes ischemia-reperfusion (I/R) injury to end organs. Severe COVID-19 induces a lipid-mediator storm with massive increases in thromboxane A2 (TxA2) and PGD2, which promote thromboinflammation and apoptosis of renal tubular cells, respectively, and thereby enhance renal fibrosis. COVID-19-associated AKI improves rapidly in the majority. However, 15-30% have protracted renal injury, raising the specter of transition from AKI to CKD.

SUMMARY

In COVID-19, the lipid-mediator storm promotes thromboinflammation, ischemia-reperfusion injury and cytotoxicity. The thromboxane A2 and PGD2 signaling presents a therapeutic target with potential to mitigate AKI and transition to CKD. Ramatroban, the only dual antagonist of the thromboxane A2/TPr and PGD2/DPr2 signaling could potentially mitigate renal injury in acute and long-haul COVID. Urgent studies targeting the lipid-mediator storm are needed to potentially reduce the heavy burden of kidney disease emerging in the wake of the current pandemic.

Eosinophils in Eosinophilic Esophagitis: The Road to Fibrostenosis is Paved With Good Intentions

Eosinophilic esophagitis (EoE) is an antigen-driven disease associated with epithelial barrier dysfunction and chronic type 2 inflammation. Eosinophils are the defining feature of EoE histopathology but relatively little is known about their role in disease onset and progression. Classically defined as destructive, end-stage effector cells, eosinophils (a resident leukocyte in most of the GI tract) are increasingly understood to play roles in local immunity, tissue homeostasis, remodeling, and repair. Indeed, asymptomatic esophageal eosinophilia is observed in IgE-mediated food allergy. Interestingly, EoE is a potential complication of oral immunotherapy (OIT) for food allergy. However, we recently found that patients with peanut allergy may have asymptomatic esophageal eosinophilia at baseline and that peanut OIT induces transient esophageal eosinophilia in most subjects. This is seemingly at odds with multiple studies which have shown that EoE disease severity correlates with tissue eosinophilia. Herein, we review the potential role of eosinophils in EoE at different stages of disease pathogenesis. Based on current literature we suggest the following: (1) eosinophils are recruited to the esophagus as a homeostatic response to epithelial barrier disruption; (2) eosinophils mediate barrier-protective activities including local antibody production, mucus production and epithelial turnover; and (3) when type 2 inflammation persists, eosinophils promote fibrosis.

Pathogenesis of Eosinophilic Esophagitis: A Comprehensive Review of the Genetic and Molecular Aspects

Eosinophilic esophagitis (EoE) is a relatively new condition described as an allergic-mediated disease of the esophagus. Clinically, it is characterized by dysphagia, food impaction, and reflux-like symptoms. Multiple genome-wide association studies (GWAS) have been conducted to identify genetic loci associated with EoE. The integration of numerous studies investigating the genetic polymorphisms in EoE and the Mendelian diseases associated with EoE are discussed to provide insights into the genetic risk of EoE, notably focusing on CCL26 and CAPN14. We focus on the genetic loci investigated thus far, and their classification according to whether the function near the loci is known. The pathophysiology of EoE is described by separately presenting the known function of each cell and molecule, with the major contributors being eosinophils, Th2 cells, thymic stromal lymphopoietin (TSLP), transforming growth factor (TGF)-β1, and interleukin (IL)-13. This review aims to provide detailed descriptions of the genetics and the comprehensive pathophysiology of EoE.

Therapeutic Potential of Hematopoietic Prostaglandin D2 Synthase in Allergic Inflammation

Worldwide, there is a rise in the prevalence of allergic diseases, and novel efficient therapeutic approaches are still needed to alleviate disease burden. Prostaglandin D₂ (PGD₂) has emerged as a central inflammatory lipid mediator associated with increased migration, activation and survival of leukocytes in various allergy-associated disorders. In the periphery, the hematopoietic PGD synthase (hPGDS) acts downstream of the arachidonic acid/COX pathway catalysing the isomerisation of PGH₂ to PGD₂, which makes it an interesting target to treat allergic inflammation. Although much effort has been put into developing efficient hPGDS inhibitors, no compound has made it to the market yet, which indicates that more light needs to be shed on potential PGD₂ sources and targets to determine which particular condition and patient will benefit most and thereby improve therapeutic efficacy. In this review, we want to revisit current knowledge about hPGDS function, expression in allergy-associated cell types and their contribution to PGD₂ levels as well as beneficial effects of hPGDS inhibition in allergic asthma, rhinitis, atopic dermatitis, food allergy, gastrointestinal allergic disorders and anaphylaxis.

Involvement of EP2 and EP4 Receptors in Eosinophilic Esophagitis: A Pilot Study

BACKGROUND

The prostaglandin D₂ receptor DP2 has been implicated in eosinophil infiltration and the development of eosinophilic esophagitis (EoE).

AIMS AND METHODS

In this study, we investigated an involvement of PGE₂ (EP1-EP4) and PGD₂ (DP1) receptors in EoE by measuring their expression in peripheral blood eosinophils and esophageal mucosal biopsies of EoE patients and by performing migration and adhesion assays with eosinophils from healthy donors.

RESULTS

Expression of EP2 and EP4, but not EP1 and EP3, was decreased in blood eosinophils of patients with EoE vs. control subjects. Adhesion of eosinophils to esophageal epithelial cells was decreased by EP2 receptor agonist butaprost and EP4 agonist ONO-AE1-329, whereas DP1 agonist BW245C increased adhesion. In chemotaxis assays with supernatant from human esophageal epithelial cells, only ONO-AE1-329 but not butaprost or BW245C inhibited the migration of eosinophils. Expression of EP and DP receptors in epithelial cells and eosinophils was detected in sections of esophageal biopsies from EoE patients by immunohistochemistry. qPCR of biopsies from EoE patients revealed that gene expression of EP4 and DP1 was the highest among PGE₂ and PGD₂ receptors. Esophageal epithelial cells in culture showed high gene expression for EP2 and EP4. Activation of EP2 and EP4 receptors decreased barrier integrity of esophageal epithelial cells in impedance assays.

CONCLUSIONS

Activation of EP2 and EP4 receptors may inhibit eosinophil recruitment to the esophageal mucosa. However, their activation could negatively affect esophageal barrier integrity suggesting that eosinophilic rather than epithelial EP2 and EP4 have a protective role in EoE.

Pathophysiology of Eosinophilic Esophagitis

Eosinophilic esophagitis (EoE) is a chronic inflammatory disease of the esophagus associated with an atopic predisposition which appears to be increasing in prevalence over the last few decades. Symptoms stem from fibrosis, swelling, and smooth muscle dysfunction. In the past two decades, the etiology of EoE has been and is continuing to be revealed. This review provides an overview of the effects of genetics, environment, and immune function including discussions that touch on microbiome, the role of diet, food allergy, and aeroallergy. The review further concentrates on the pathophysiology of the disease with particular focus on the important concepts of the molecular etiology of EoE including barrier dysfunction and allergic hypersensitivity.

DP1 receptor signaling prevents the onset of intrinsic apoptosis in eosinophils and functions as a transcriptional modulator

Prostaglandin (PG) D₂ is the ligand for the G-protein coupled receptors DP1 (D-type prostanoid receptor 1) and DP2 (also known as chemoattractant receptor homologous molecule, expressed on Th2 cells; CRTH2). Both, DP1 and DP2 are expressed on the cellular surface of eosinophils; although it has become quite clear that PGD₂ induces eosinophil migration mainly via DP2 receptors, the role of DP1 in eosinophil responses has remained elusive. In this study, we addressed how DP1 receptor signaling complements the pro-inflammatory effects of DP2. We found that PGD₂ prolongs the survival of eosinophils via a DP1 receptor-mediated mechanism that inhibits the onset of the intrinsic apoptotic cascade. The DP1 agonist BW245c prevented the activation of effector caspases in eosinophils and protected mitochondrial membranes from depolarization which-as a consequence-sustained viability of eosinophils. DP1 activation in eosinophils enhanced the expression of the anti-apoptotic gene BCL-X_L , but also induced pro-inflammatory genes, such as VLA-4 and CCR3. In HEK293 cells that overexpress recombinant DP1 and/or DP2 receptors, activation of DP1, but not DP2, delayed cell death and stimulated proliferation, along with induction of serum response element (SRE), a regulator of anti-apoptotic, early-response genes. We conclude that DP1 receptors promote the survival via SRE induction and induction of pro-inflammatory genes. Therefore, targeting DP1 receptors, along with DP2, may contribute to anti-inflammatory therapy in eosinophilic diseases.

Type 2 immunity is protective in metabolic disease but exacerbates NAFLD collaboratively with TGF-β

Nonalcoholic fatty liver disease (NAFLD) is now the most common progressive liver disease in developed countries and is the second leading indication for liver transplantation due to the extensive fibrosis it causes. NAFLD progression is thought to be tied to chronic low-level type 1 inflammation originating in the adipose tissue during obesity; however, the specific immunological mechanisms regulating the progression of NAFLD-associated fibrosis in the liver are unclear. To investigate the immunopathogenesis of NAFLD more completely, we investigated adipose dysfunction, nonalcoholic steatohepatitis (NASH), and fibrosis in mice that develop polarized type 1 or type 2 immune responses. Unexpectedly, obese interleukin-10 (IL-10)/IL-4-deficient mice (type 1-polarized) were highly resistant to NASH. This protection was associated with an increased hepatic interferon-γ (IFN-γ) signature. Conversely, IFN-γ-deficient mice progressed rapidly to NASH with evidence of fibrosis dependent on transforming growth factor-β (TGF-β) and IL-13 signaling. Unlike increasing type 1 inflammation and the marked loss of eosinophils seen in expanding adipose tissue, progression of NASH was associated with increasing eosinophilic type 2 liver inflammation in mice and human patient biopsies. Finally, simultaneous inhibition of TGF-β and IL-13 signaling attenuated the fibrotic machinery more completely than TGF-β alone in NAFLD-associated fibrosis. Thus, although type 2 immunity maintains healthy metabolic signaling in adipose tissues, it exacerbates the progression of NAFLD collaboratively with TGF-β in the liver.

Role of lipid mediators and control of lymphocyte responses in type 2 immunopathology

Type 2 immunopathology is a cardinal feature of allergic diseases and involves cooperation between adaptive immunity and innate effector responses. Virtually all cell types relevant to this pathology generate leukotriene and/or prostaglandin mediators that derive from arachidonic acid, express receptors for such mediators, or both. Recent studies highlight prominent functions for these mediators in communication between the innate and adaptive immune systems, as well as amplification or suppression of type 2 effector responses. This review focuses on recent advances and insights, and highlights existing and potential therapeutic applications of drugs that target these mediators or their receptors, with a special emphasis on their regulation of the innate and adaptive lymphocytes relevant to type 2 immunopathology.

Eosinophilic esophagitis: unclear roles of IgE and eosinophils

Eosinophilic esophagitis (EoE) is a chronic inflammatory disease of the oesophagus. Recognized as a distinct entity only two decades ago, the emergence of the disease along with the availability of new technologies has rapidly opened new research avenues and outlined the main features of the pathogenesis of EoE. Yet, each advance in our understanding of the disease has raised new questions about the previous consensus. Currently, new subsets of the disease challenge our diagnostic criteria. For instance, it was believed that EoE did not respond to proton pump inhibitor (PPI) therapy; however, it has now been shown that a substantial proportion of EoE patients indeed respond to PPIs. In addition, a new subset of patients not even presenting eosinophil infiltrates in the oesophagus has also been described. Moreover, approaches for better understanding the heritability of the disease bring into question the dogma of predominant genetic involvement. Furthermore, the specificity and sensitivity of allergy testing for targeted food avoidance is highly controversial, and the production of specific antibodies in EoE now includes IgG4 in addition to IgE. In conclusion, EoE is perceived as 'a moving target' and the aim of this review was to summarize the current understanding of EoE pathogenesis.

Lipid Mediators of Allergic Disease: Pathways, Treatments, and Emerging Therapeutic Targets

Bioactive lipids are critical regulators of inflammation. Over the last 75 years, these diverse compounds have emerged as clinically-relevant mediators of allergic disease pathophysiology. Animal and human studies have demonstrated the importance of lipid mediators in the development of asthma, allergic rhinitis, urticaria, anaphylaxis, atopic dermatitis, and food allergy. Lipids are critical participants in cell signaling events which influence key physiologic (bronchoconstriction) and immune phenomena (degranulation, chemotaxis, sensitization). Lipid-mediated cellular mechanisms including: (1) formation of structural support platforms (lipid rafts) for receptor signaling complexes, (2) activation of a diverse family of G-protein coupled receptors, and (3) mediating intracellular signaling cascades by acting as second messengers. Here, we review four classes of bioactive lipids (platelet activating factor, the leukotrienes, the prostanoids, and the sphingolipids) with special emphasis on lipid synthesis pathways and signaling, atopic disease pathology, and the ongoing development of atopy treatments targeting lipid mediator pathways.

Eosinophilic disorders of the gastro-intestinal tract: an update

Eosinophilic diseases of the gastrointestinal tract, including eosinophilic esophagitis (EoE) and eosinophilic gastroenteritis (EGE), are rare chronic pathologies of the digestive system, with an immuno-mediated pathogenesis. Recent data suggest that, together with the “classic” IgE-response to allergens, also a delayed hypersensitivity mechanism could be involved in the development of eosinophilic disorders. EoE and EGE were studied only in the latest decades and as a consequence accurate data are not yet available, concerning not only pathogenesis, but also epidemiology, treatment and outcomes. The diagnosis of EoE is centered on endoscopic findings but the certainty is obtained by histological examination from biopsy samples, that has a sensitivity of 100% when based on five samples. The currently available treatments include topical corticosteroids, specific diets and endoscopic treatment. Concerning EGE, three subtypes (mucosal, muscular, and serosal) were identified. The diagnosis is based, as for EoE, on endoscopic and histological assessment, and the treatment includes pharmacological and dietetic approaches. Further studies are warranted in order to better define the etiology and pathogenesis of eosinophilic diseases of the gastrointestinal tract, and thus to develop more appropriate and specific therapies.

The Immunologic Mechanisms of Eosinophilic Esophagitis

Eosinophilic esophagitis (EoE) is a chronic allergic inflammatory disease that is triggered by food and/or environmental allergens and is characterized by a clinical and pathologic phenotype of progressive esophageal dysfunction due to tissue inflammation and fibrosis. EoE is suspected in patients with painful swallowing, among other symptoms, and is diagnosed by the presence of 15 or more eosinophils per high-power field in one or more of at least four esophageal biopsy specimens. The prevalence of EoE is increasing and has now reached rates similar to those of other chronic gastrointestinal disorders such as Crohn's disease. In recent years, our understanding of the immunologic mechanisms underlying this condition has grown considerably. Thanks to new genetic, molecular, cellular, animal, and translational studies, we can now postulate a detailed pathway by which exposure to allergens results in a complex and coordinated type 2 inflammatory cascade that, if not intervened upon, can result in pain on swallowing, esophageal strictures, and food impaction. Here, we review the most recent research in this field to synthesize and summarize our current understanding of this complex and important disease.

Mechanisms of Disease of Eosinophilic Esophagitis

Eosinophilic esophagitis (EoE) is a recently recognized inflammatory disease of the esophagus with clinical symptoms derived from esophageal dysfunction. The etiology of EoE is now being elucidated, and food hypersensitivity is emerging as the central cornerstone of disease pathogenesis. Herein, we present a thorough picture of the current clinical, pathologic, and molecular understanding of the disease with a focus on disease mechanisms.

Recent discoveries and emerging therapeutics in eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is an allergy-mediated disease culminating in severe eosinophilic inflammation and dysfunction of the esophagus. This chronic disorder of the esophagus causes significant morbidity, poor quality of life, and complications involving fibrosis and esophageal remodeling. Overlapping features between EoE and gastroesophageal reflux disease (GERD) pose great challenges to differentiating the two conditions, although the two disorders are not mutually exclusive. Recent findings suggest that the confounding condition proton pump inhibitor - responsive esophageal eosinophilia (PPI-REE) is likely a subset of EoE. Since PPIs have therapeutic properties that can benefit EoE, PPIs should be considered as a therapeutic option for EoE rather than a diagnostic screen to differentiate GERD, PPI-REE, and EoE. Other current treatments include dietary therapy, corticosteroids, and dilation. Immunomodulators and biologic agents might have therapeutic value, and larger trials are needed to assess efficacy and safety. Understanding the pathophysiology of EoE is critical to the development of novel therapeutics.

Allergic mechanisms of Eosinophilic oesophagitis

Eosinophilic oesophagitis (EoE) is characterized by oesophageal dysfunction and oesophageal eosinophilia refractory to proton-pump-inhibitor treatment. EoE is a food allergy, as elimination of food trigger(s) abrogates the disease, while trigger reintroduction causes recurrence. The allergic mechanism of EoE involves both IgE and non-IgE processes. There is a break in oral tolerance, the immune mechanism allowing enteric exposure to food and micro-organisms without causing deleterious immune responses. Changes in life-style, alterations in gut flora and use of antibiotics may be increasing disease prevalence. Mouse models of EoE and human studies revealed the role of regulatory T-cells and iNKT-cells in the pathogenesis. Th2-cytokines like IL-4, IL-5 and IL-13, and other cytokines like TGFβ and TSLP are involved, but perhaps no one cytokine is critically important for driving the disease. Control of EoE may require a pharmaceutical approach that blocks more than one target in the Th2-inflammatory pathway.

Pediatric Eosinophilic Esophagitis Symptom Scores (PEESS v2.0) identify histologic and molecular correlates of the key clinical features of disease

BACKGROUND

The Pediatric Eosinophilic Esophagitis Symptom Score (PEESS v2.0) measures patient-relevant outcomes. However, whether patient-identified domains (dysphagia, gastroesophageal reflux disease [GERD], nausea/vomiting, and pain) align with clinical symptomology and histopathologic and molecular features of eosinophilic esophagitis (EoE) is unclear.

OBJECTIVE

The purpose of this study was to determine whether clinical features of EoE, measured through PEESS v2.0, associate with histopathologic and molecular features of EoE. This represents a novel approach for analysis of allergic diseases, given the availability of allergic tissue biopsy specimens.

METHODS

We systematically recruited treated and untreated pediatric patients with EoE (aged 2-18 years) and examined parent proxy-reported symptoms using the PEESS v2.0. Clinical symptomology was collected by questionnaire. Esophageal biopsy samples were quantified for levels of eosinophils, eosinophil peroxidase (EPX) immunohistochemical staining, and mast cells. Molecular features were assessed by using the EoE Diagnostic Panel (94 EoE-related gene transcripts). Associations between domain scores and clinical symptoms and biological features were analyzed with Wilcoxon rank sum and Spearman correlation.

RESULTS

The PEESS v2.0 domains correlated to specific parent-reported symptoms: dysphagia (P = .0012), GERD (P = .0001), and nausea/vomiting (P < .0001). Pain correlated with multiple symptoms (P < .0005). Dysphagia correlated most strongly with overall histopathology, particularly in the proximal esophagus (P ≤ .0049). Markers of esophageal activity (EPX) were significantly associated with dysphagia (strongest r = 0.37, P = .02). Eosinophil levels were more associated with pain (r = 0.27, P = .06) than dysphagia (r = 0.24, P = .13). The dysphagia domain correlated most with esophageal gene transcript levels, predominantly with mast cell-specific genes.

CONCLUSION

We have (1) established a validated, parent proxy-reported measure for pediatric EoE, the PEESS v2.0; (2) verified that the parent proxy effectively captures symptoms; (3) determined that the dysphagia domain most closely aligns with symptoms and tissue-based molecular biomarkers; (4) established that symptoms correlate with EPX staining; and (5) observed association between mast cells and dysphagia.

Molecular pathogenesis of eosinophilic esophagitis

PURPOSE OF REVIEW

Eosinophilic esophagitis (EoE) is an esophageal disease characterized by an accumulation of eosinophils in the esophagus, which is normally devoid of eosinophils. The interest of the scientific community in EoE has grown considerably over the past two decades, and understanding of the molecular mechanisms involved in this disease has increased greatly in the last 2 years.

RECENT FINDINGS

Important new insights into the pathogenesis of EoE recently have been achieved. Recent evaluations considering genetic and the environmental risk factors have led to the concept that some still-unknown environmental factors influence the risk of developing EoE more than the genetic predisposition. New molecules (in addition to interleukin-13, eotaxin-3, transforming growth factor-β1, thymic stromal lymphopoietin, filaggrin, or interleukin-5) also have been shown to be involved in the disease pathogenesis.

SUMMARY

The present review describes recent advances in the understanding of the molecular mechanisms underlying EoE, and how these new findings have enhanced understanding of the pathogenesis of this new esophageal disorder.

Translating new developments in eosinophilic esophagitis pathogenesis into clinical practice

OPINION STATEMENT

New developments in eosinophilic esophagitis (EoE) pathogenesis are shaping our current therapeutic and management strategies. EoE is a chronic allergic inflammatory disease with progression to fibrostenotic disease. The disease warrants early diagnosis and long-term maintenance therapy. The diagnosis of EoE should be based on the concept of an allergy-mediated disease with esophageal dysfunction and esophageal eosinophilia. Recent findings suggest that proton pump inhibitor (PPI)-responsive esophageal eosinophilia (PPI-REE) is likely a continuum of EoE or a similar T-helper 2 (Th2)-mediated allergic process. PPIs have therapeutic properties that can benefit both gastroesophageal reflux disease (GERD) and EoE. Therefore, PPIs should be considered not a diagnostic tool but, rather, a therapeutic option for EoE. If patients are PPI nonresponsive, then dietary therapy or steroid therapy should be considered. Dilation can be reserved as adjuvant therapy for severe fibrostenotic lesions.

Allergic mechanisms in eosinophilic esophagitis

Eosinophilic esophagitis is rapidly increasing in incidence. It is associated with food antigen-triggered, eosinophil-predominant inflammation, and the pathogenic mechanisms have many similarities to other chronic atopic diseases. Studies in animal models and from patients have suggested that allergic sensitization leads to food-specific IgE and T-helper lymphocyte type 2 cells, both of which seem to contribute to the pathogenesis along with basophils, mast cells, and antigen-presenting cells. In this review our current understandings of the allergic mechanisms that drive eosinophilic esophagitis are outlined, drawing from clinical and translational studies in humans as well as experimental animal models.