Endothelin-1 peptides and IL-5 synergistically increase the expression of IL-13 in eosinophils.

The 21-amino acid-length endothelin-1 (ET-1)(1-21) and its novel derivative, 31 amino acid-length ET-1(1-31), have proinflammatory properties and induce significant eosinophil migration mediated by an increase in the local levels of eotaxin and IL-5. We have analyzed by reverse transcription polymerase chain reaction and enzyme immunoassay the effects of ETs on the expression of IL-13 mRNA and protein in eosinophils with or without cell priming with IL-5. The expression of the ETA receptor (ETAR) and its membrane localization were detected in the eosinophils, whereas the ETB receptor was undetectable. ET peptides synergistically increased the expression of IL-13 in eosinophils after priming with IL-5, and the increase was blocked by the ETAR antagonist BQ123, though these peptides did not directly influence the expression. These results may explain the presence of eosinophilia in the airways' epithelium of patients suffering from asthma, along with an increase in immunoreactive ETs.

The effect of topically applied secretory leukocyte protease inhibitor on the eosinophil response in the late phase of allergic conjunctivitis.

PURPOSE: This study examined the effects of secretory leukocyte protease inhibitor (SLPI), a protease inhibitor in tears, in allergic conjunctivitis. METHODS: Conjunctiva of male Hartley guinea pigs sensitized with ovalbumin were treated with SLPI or the vehicle 10 min before antigen challenge or simultaneously. The animals were sacrificed after antigen challenges of 0-24 h duration, and the inhibition of eosinophil conjunctival migration and degranulation by SLPI was analyzed histochemically. The effects of SLPI on mast cell chymase and tryptase were also examined. RESULTS: Treatment of sensitized guinea pigs with SLPI suppressed the conjunctival recruitment and degranulation of eosinophils after antigen challenge for 6 h, inhibiting the development of allergic conjunctivitis. The effects of SLPI were observed at concentrations > or =0.1 microM, with a peak at 5 microM. SLPI inhibited chymase in a dose-dependent manner, but had no effect on tryptase. CONCLUSION: The topical SLPI application may be therapeutic in allergic conjunctivitis.

Binding of a new bioactive 31-amino-acid endothelin-1 to an endothelin ET(B) or ET(B)-like receptor in porcine lungs.

Endothelin-1-(1-31) is a new bioactive 31-amino-acid-length peptide generated from big endothelin-1 by chymase or other chymotrypsin-type proteases with various pathophysiologic functions. In this study, we have detected the specific and monophasic binding of [125I]endothelin-1-(1-31) in porcine lung membranes. Competition studies of [125I]endothelin-1-(1-31) binding by unlabeled endothelin-1-(1-31), endothelin-1, endothelin-3, and antagonists and agonists of endothelin ET(A) and ET(B) receptors suggest that the binding protein is an endothelin ET(B) or ET(B)-like receptor rather than an endothelin ET(A) receptor in porcine lungs. Kinetic studies showed that the affinity of endothelin-1-(1-31) to its receptor was approximately one order of magnitude lower than that of endothelin-1, and that the specific binding of endothelin-1-(1-31) was about 19% of endothelin-1 binding. The binding of [125I]endothelin-1-(1-31) was extremely slow, slower even than that of endothelin-1, and nearly irreversible. This unique quasi-irreversibility may explain the slow-onset and long-lasting biologic effects of this peptide in vivo.