Ekatherina Vassina

Cytokine expression in healthy and inflamed mucosa: Probing the role of eosinophils in the digestive tract

Background: In eosinophilic esophagitis (EE), the esophagus is infiltrated with activated eosinophils that often evoke tissue damage, but the intestines of these patients remain unaffected. We thus hypothesized that different tissue‐dwelling eosinophil populations may coexist: activated eosinophils that infiltrate the esophagus and resting eosinophils that reside in unaffected intestines. We sought to characterize different eosinophil subpopulations by comparing the expression of certain proinflammatory proteins in tissue‐dwelling eosinophils at different parts of the gastrointestinal tract. Methods: The 8 patients participating included 6 men and 2 women with a previously confirmed diagnosis of EE, whose average age was 39.4 years (range, 20‐55 yr) and average disease duration was 13.6 years (range, 2‐26 yr). Controls were 3 men and 1 woman, with a mean age of 43.3 years (range, 29‐56 yr) with untreated functional dyspepsia who underwent diagnostic esophagogastroduodenoscopy. Six additional individuals having normal blood eosinophils were recruited for cytokine measurements in blood eosinophils. Immunofluorescence and immunoassays charted expression of CD25 and the TH2 cytokines, interleukin (IL)‐4, IL‐5, IL‐10, and IL‐13, in esophageal, intestinal, and blood eosinophils from controls and patients. Results: Controls showed a small but significant proportion of intestinal, but no blood, eosinophils expressing CD25 and IL‐13, suggesting physiologic activation occurring in the digestive tract. On the other hand, eosinophils infiltrating the inflamed esophageal mucosa of patients with EE showed strong evidence of activation, with most expressing CD25, IL‐4, and IL‐13. Moreover, IL‐13‐positive intestinal eosinophils were increased in patients compared with controls. Conclusions: We thus conclude that tissue‐dwelling eosinophils show different and distinct cytokine expression patterns under noninflammatory and inflammatory conditions.

Inflammatory cell numbers and cytokine expression in atopic dermatitis after topical pimecrolimus treatment

Background:  In several clinical trials the topical application of pimecrolimus was shown to be effective in the treatment of atopic dermatitis (AD). By targeting calcineurin‐dependent signaling pathways, pimecrolimus controls cytokine gene expression. The purpose of this study was to investigate the effect of pimecrolimus on the inflammatory infiltrate and cytokine expression pattern in AD upon topical therapy.

cIAP‐2 and survivin contribute to cytokine‐mediated delayed eosinophil apoptosis

The exact molecular mechanisms leading to delayed apoptosis, a phenomenon frequently observed in eosinophil inflammatory responses, remain largely unknown. Here, we show that cultured eosinophils purified from blood of hypereosinophilic syndrome (HES) patients exhibit delayed spontaneous death and relative resistance towards ceramide‐ but not CD95‐mediated death. The subsequent investigation of members of the inhibitor of apoptosis (IAP) family revealed that HES but not normal eosinophils expressed high levels of cellular IAP‐2 (cIAP‐2) and survivin. The eosinophil hematopoietins IL‐3, IL‐5, and GM‐CSF increased the expression of cIAP‐2 and survivin in normal eosinophils in vitro. In the blood of HES patients, we observed increased concentrations of IL‐3 and/or IL‐5, suggesting that these cytokines are, at least partially, responsible for the elevated levels of cIAP‐2 and survivin in the eosinophils of these patients. Utilizing a cell‐free system in which caspase‐3 was activated in eosinophil cytosolic extracts by addition of cytochrome c and immunodepletion of cIAP‐2 or survivin resulted in accelerated caspase activation. These data suggest that some members of the IAP family including survivin are regulated by survival cytokines and inhibit the caspase cascade in HES eosinophils. The cytokine‐dependent mechanism of delayed eosinophil apoptosis described here may also apply to other eosinophilic diseases.