Tumor necrosis factor alpha/cachectin stimulates eosinophil oxidant production and toxicity towards human endothelium.

Abstract

Eosinophils (EOs) participate in a variety of inflammatory states characterized by endothelial cell damage, such as vasculitis, pneumonitis, and endocarditis. We find that 100 U/ml TNF-alpha/cachectin (TNF), a concentration attainable in the blood of humans with parasitic infestations, stimulates highly purified populations of EOs to damage human umbilical vein endothelial cells (HUVEC), a model of human endothelium. This TNF-dependent EO cytotoxicity is strongly inhibited by heparin and methyprednisolone but unaffected by the platelet-activating factor antagonist BN52012 or scavengers of superoxide anion and H2O2, superoxide dismutase and catalase. However, addition of a physiologically relevant concentration of Br- (100 microM) enhances EO/TNF damage to HUVEC, implicating the possible participation of EO peroxidase (EPO) in the killing mechanism. EOs adherent to FCS-coated plastic wells more than double their production of superoxide anion and the cytotoxic EPO-derived oxidant HOBr when exposed to TNF, showing that TNF activates the respiratory burst of EOs attached to a "physiologic" surface. Unlike PMNs, EOs were not irreversibly activated to kill unopsonized endothelium by previous exposure to TNF, and did not degranulate or upregulate CR3 expression as detected by Mo1 in the presence of 100 U/ml TNF. HUVEC exposed 18 h to TNF were considerably more susceptible to lysis by PMA-activated EOs and reagent H2O2, demonstrating a direct effect of TNF upon endothelium, perhaps through inhibition of antioxidant defenses. These findings suggest that abnormally elevated serum levels of TNF may provoke EOs to damage endothelial cells and thereby play a role in the pathogenesis of tissue damage in hypereosinophilic states.

Eosinophils and Neutrophils of Human Neonates Have Similar Impairments of Quantitative Up-regulation of Mac-1 (CDllb/CD18) Expression In Vitro

“…This indicates that receptor expression on eosinophils as well as neutrophils is susceptible to nonspecific up-regulation during in vitro procedures. Previous studies of eosinophil Mac-1 expression have used methods involving incubation at 37°C as part of the purification procedure (15)(16)(17)(18)(19). This probably accounts for the finding of Thorne et al (19) that CDl l b expression was higher on neutrophils than eosinophils before specific stimulation.…”

Cytokine Regulation of Periportal Fibrosis in Humans Infected with Schistosoma mansoni: IFN-γ Is Associated with Protection Against Fibrosis and TNF-α with Aggravation of Disease

“…However, as in various pathologies, an imbalance between TNF-␣ and other regulatory cytokines may cause tissue damage. A possible mechanism for this damage is an exacerbation of the granuloma by overproduction of reactive oxygen species (4,25,26), as suggested in experimental schistosomiasis (42). The association between TNF-␣ and clinical disease in schistosomiasis has also been found in the sera and in the culture of blood mononuclear cells from subjects with hepatosplenomegaly (43,44).…”

Eosinophils generate brominating oxidants in allergen-induced asthma

“…GC/MS analyses of L-tyrosine oxidation products were performed after derivatization to their n-propyl per heptafluorylbutyryl or n-propyl per pentafluorylproprionyl derivatives (34) on a Finnigan Voyager GC/MS in the negative ion-chemical ionization mode. Results are normalized to the content of the precursor amino acid, L-tyrosine, which was similarly quantified by GC/MS (31) except for using L[ 13 C 9 15 N]tyrosine as internal standard. In all studies, intrapreparative formation of 3-bromo[ 13 C 9 15 N]tyrosine, 3,5-dibromo[ 13 C 9 15 N]tyrosine, or 3-chloro[ 13 C 9 15 N]tyrosine was negligible (i.e., < 5% of the level of the natural abundance product observed).…”