Characteristics and Regulation of Human Eosinophil ETosis In Vitro.

Cytolytic ETosis is a type of programmed cell death distinct from apoptosis and necrosis and plays a major role in the innate immune system and disease progression. Through the process of ETosis, cells release their chromatin with diverse antimicrobial proteins into the extracellular milieu, forming extracellular traps (ETs). Although ETosis has been reported in several leukocyte types, few studies have compared ETosis and the component proteins of ETs in leukocytes. The aim of this study was to better understand the characteristics of eosinophil ETosis (EETosis) compared with other leukocytes. We isolated human blood eosinophils, neutrophils, basophils, monocytes, and lymphocytes and stimulated them with known ETosis inducers, a protein kinase C activator PMA, or a calcium ionophore A23187. Both stimuli induced eosinophil cell death and ET release after 180 minutes of stimulation in a NADPH-oxidase-dependent manner. PMA also induced NADPH-oxidase-dependent ETosis in neutrophils, whereas little or no significant ETosis was observed in basophils, monocytes, or lymphocytes at 180 minutes. Mass spectrometry-based proteomic analysis of eosinophil- and neutrophil-derived ETs identified 997 and 1415 proteins, respectively. Among the physiological stimuli tested, immobilized IgA and IgG induced EETosis. C-C motif chemokine ligand 11 (CCL11) and interleukin 5 (IL-5) were weak inducers of EETosis, but co-stimulation significantly induced rapid EETosis. Under high serum or albumin conditions, co-stimulation with CCL11 and IL-5 paradoxically prolonged cell survival by preventing spontaneous apoptosis. This study provides an in-depth characterization of EETosis and highlights the precise regulation of eosinophil survival and cell death pathways.

Constitutional mismatch repair deficiency in childhood colorectal cancer harboring a de novo variant in the MSH6 gene: a case report.

BACKGROUND: Constitutional mismatch repair deficiency (CMMRD) is caused by biallelic pathogenic variants in one of the mismatch repair genes, and results in early onset colorectal cancer, leukemia, brain tumors and other childhood malignancies. Here we report a case of CMMRD with compound heterozygous variants in the MSH6 gene, including a de novo variant in multiple colorectal cancers. CASE PRESENTATION: An 11-year-old girl, who presented with multiple spots resembling café-au-lait macules since birth, developed abdominal pain, diarrhea and bloody stool over two months. Colonoscopy revealed multiple colonic polyps, including a large epithelial tumor, and pathological examination revealed tubular adenocarcinoma. Brain magnetic resonance imaging (MRI) showed an unidentified bright object (UBO), commonly seen in neurofibromatosis type 1 (NF1). Genetic testing revealed compound heterozygous variants, c. [2969T > A (p.Leu990*)] and [3064G > T (p.Glu1022*)] in the MSH6 gene; c.2969T > A (p.Leu990*) was identified as a de novo variant. CONCLUSIONS: We present the first report of a CMMRD patient with a de novo variant in MSH6, who developed colorectal cancer in childhood. CMMRD symptoms often resemble NF1, as observed here. Physicians should become familiar with CMMRD clinical phenotypes for the screening and early detection of cancer.

First case report of dichorionic diamniotic twins with chronic enteropathy associated with the SLCO2A1 gene.

We report the case of twins diagnosed with chronic enteropathy associated with the SLCO2A1 gene (CEAS) based on characteristic ulcer findings, which required 8 years to diagnose. Both twins had similar symptoms, including anemia and growth failure but the gastrointestinal tract was not evaluated initially because of mild symptoms that were considered consistent with psychological etiology. The endoscopic findings of the firstborn child showed spiral ulcer scars and pseudodiverticulum formation without Helicobacter pylori infection or eosinophilic infiltration in the duodenum. Since the twins presented with ulcers of an unknown cause simultaneously and the first-born child had a spiral ulcer, CEAS was suspected. Genetic analysis and high levels of prostaglandin E major urinary metabolites in the urine led to a definitive diagnosis of CEAS.

Case of hypereosinophilic syndrome with gastrointestinal involvement showing tissue eosinophil cytolysis.

Hypereosinophilic syndrome (HES), which is characterized by eosinophilia in the peripheral blood, often causes various organ disorders, including those of the gastrointestinal (GI) tract. The eosinophils play a key role in inflammation in eosinophilic GI disorders (EGIDs), including HES with GI involvement. Here, we report a case of HES with GI involvement that showed major basic proteins (MBPs) deposition in the absence of marked eosinophilic infiltration in the mucosa of the GI tract. An 11-year-old boy presented with nausea and epigastric pain for one week. He had a history of idiopathic HES with eosinophilic cystitis, diagnosed at the age of 2 years. He had been taking a low dose of corticosteroids for 9 years. The peripheral blood eosinophil count was 2,254/µL. Endoscopy revealed a swelling of the duodenal bulb mucosa. Histological findings of the duodenal mucosa revealed chronic inflammation, but no evidence of significant eosinophil infiltration and we could not diagnose him with HES with GI involvement or EGID. Immunofluorescent staining for MBP and galectin-10 was performed to detect intact and cytolytic eosinophils (eosinophil extracellular trap cell death: EETosis). Marked MBP deposition was evident in a small number of intact eosinophils in tissues from the duodenum, gastric antrum, and terminal ileum. The current case illustrates the utility of immunostaining for the detection of persistent eosinophilic inflammation, especially when cytolytic eosinophils are dominant.