Eosinophil-derived neurotoxin (EDN) or eosinophil protein Χ (EPX) is a cationic glycoprotein released by activated eosinophils. It has strong cytotoxic characteristics and plays a significant role in the prevention of virus infections. The eosinophile granules release it in places where eosinophils are mainly found: in the skin, lungs, urogenital, and gastrointestinal tract, that is, in the organs acting as entry points for pathogens.
The accumulation of EPX in the intestine is associated with inflammation and tissue damage. Measuring EPX in stool can serve as an objective parameter for current clinical or sub-clinical chronic inflammation in the gastrointestinal area. In the case of ulcerative colitis and Crohn’s disease, the EPX measurement enables evaluating a disease’s activity and predicting relapse.
Indications for EPX measurement
- Crohn’s disease and ulcerative colitis
- Food allergies and intolerances
- Assessment of an elimination diet
- Investigations into the integrity of the intestinal mucous membrane (e.g., chronic inflammatory bowel disease, colon cancer)
- Intestinal parasites
Fecal proteins produced by eosinophils
Microscopic colitis is considered one of the most common causes of chronic, watery diarrhea in developed countries. Patients with microscopic colitis have normal endoscopic appearance, with occasional erythema and/or edema patchy distributed along the colon. Lymphocytic and collagenous colitis are the two primary histological forms of microscopic colitis.
Eosinophilic granulocytes are potent pro-inflammatory cells: they can induce epithelial damage by releasing several cytotoxic granule-derived proteins. In addition, they secrete other mediators, such as cytokines, chemokines, and leukotrienes, which modulate epithelial inflammation. Studies demonstrated that eosinophilic infiltration and degranulation were remarkably increased in collagenous colitis patients’ colonic mucosa compared to healthy controls. Consistently, further studies have shown that eosinophil-related inflammatory markers, such as eosinophil cationic protein (ECP) and eosinophil protein X (EPX), are significantly increased in fecal samples from collagenous colitis patients as compared to those of IBS patients.
Eosinophils are also indicative of drug-induced inflammation.
