Injury to murine airway epithelial cells by pollen enzymes

Abstract

Background-Pollens are important triggers for asthma but the mechanism of sensitisation to their proteins remains poorly understood. The intrinsic protease activity of some allergens may contribute to sensitisation by disrupting the integrity of the airway epithelial barrier. Pollens release a variety of enzymes, including proteases, upon hydration. The hypothesis that such enzymes might be able to damage airway epithelial cells was therefore tested. Methods-DiVusates from pollens of Lolium perenne (ryegrass), Poa pratensis (Kentucky bluegrass), Acacia longifolia (Sydney golden wattle), or Casuarina distyla (she-oak) were incubated with mouse tracheal epithelial cells in culture and cellular detachment was quantified using a methylene blue dye binding assay. Results-DiVusates prepared using 100 mg/ml of pollen caused detachment of 30-90% of airway epithelial cells in separate experiments. Within each experiment comparable detachment was observed with all diVusates tested, although total protein in the diVusates varied markedly between species. Viability of the cells recovered after exposure to Acacia diVusate was higher than after detachment by exposure to Lolium diVusate. Cellular detachment by all of the diVusates could be almost completely inhibited by addition of 10% serum. Aprotinin, an inhibitor of serine proteases, partially blocked activity in diVusates of Lolium pollen but not of Acacia pollen. In contrast, 1 -protease inhibitor and secretory leucocyte protease inhibitor (SLPI) were not able to block the activity of either diVusate at concentrations which inhibited cellular detachment by trypsin. Conclusions-Proteases released by pollens are able to cause detachment of airway epithelial cells from their substratum in vitro and may not be eVectively inhibited by endogenous antiproteases.

IL-33–dependent induction of allergic lung inflammation by FcγRIII signaling

“…It is thought that complex allergens may injure the lung epithelium and promote primary sensitization through a variety of components that contribute to their allergenicity: cysteine proteases, serine proteases, MD2 mimic, pattern-associated molecular patterns, chitinase, and others (35)(36)(37). However, many allergens are simple protein allergens lacking enzymatic activity, including animal proteins, seed proteins, flour, latex, OVA, and others (38).…”

Doença alérgica polínica: polens alergógenos e seus principais alérgenos

“…When hydrated, pollen grains may also release a variety of enzymes, including proteases. These proteases are biologically important as they may cause epithelial damage, and are not inactivated by endogenous protease inhibitors 15 . Protease release may generally cause rupture of epithelial junctions, facilitating protein transport, which in turn may sensitize individuals, resulting in increased allergen access to antigen-presenting subepithelial dendritic cells 16 .…”

The Biological Function of Allergens: Relevant for the Induction of Allergic Diseases?

“…It was shown to augment its own permeability in the bronchial epithelium by proteolytic activity [29]. An Aspergillus fumigatus proteinase was also able to induce human epithelial cell detachment [30]; tree and grass pollen enzymes led to injury of murine airway epithelial cells [31]. These examples do not explain the fact of how and why patients are specifically sensitized towards these allergens but they describe that allergenic molecules with enzymatic activity can irritate the human mucosal surface and facilitate their own processing.…”