Augmentation by eosinophils of gelatinase activity in the airway mucosa: comparative effects as a putative mediator of epithelial injury

Abstract

We have studied the release of gelatin‐degrading enzymes from isolated sheets of bronchial mucosa in the presence and absence of eosinophils. Isolated sheets of bovine bronchial mucosa released gelatin‐degrading activity in similar amounts from both the apical and basolateral aspects of the tissue. Gelatinolytic activity could not be increased by treatment of the mucosal sheets with calcium ionophore, A23187. The activity of the released gelatinases could be inhibited by chelation of divalent cations or by the matrix metalloproteinase inhibitors, BB‐94 and BB‐250. However, inhibitors of serine proteinases, or of cysteine proteinases were without effect. In zymography, major bands of gelatin‐degrading activity consistent with gelatinases A and B were identified. Addition of guinea‐pig eosinophils to the basolateral aspect of bronchial mucosa for 60 min resulted in an increase in the gelatinolytic activity of the conditioned medium, irrespective of whether the eosinophils were stimulated with ionophore A23187 or not. However, only ionophore‐stimulated eosinophils reacted to produce sufficient tissue damage to increase the transepithelial flux of serum albumin. Purified eosinophils were a poor source of gelatinolytic activity, indicating that when interacting with the bronchial mucosa their effect is to increase the apparent release and/or activation of gelatinases derived from the airway mucosa. After organomercurial activation, recombinant human progelatinase A increased the permeability of the bronchial mucosa to mannitol. However, the activity of enzyme and duration of exposure required to do this were greater than the amounts of gelatinase activity detected during eosinophil‐mediated injury. Sheets of airway mucosa were also resistant to injury evoked by high concentrations of hydrogen peroxide or plasmin. Collectively, these results suggest that if gelatinases are involved in eosinophil‐mediated injury and repair of the bronchial mucosa, they require other mediators to act in concert to bring about outright epithelial cell detachment. This does not preclude the possibility that gelatinases are crucial in rendering the airway mucosa hyperfragile.

Class specific inhibition of house dust mite proteinases which cleave cell adhesion, induce cell death and which increase the permeability of lung epithelium

“…If the effect of the HDM proteinases were to activate epithelial cells to produce a metalloproteinase capable of cleaving Fas ligand then the inhibitory effect of BB‐250 could be simply explained. It is known that epithelial cells derived from lung can produce the matrix metalloproteinases gelatinase A and gelatinase B (Herbert et al , 1996; Robinson et al , 1997a; Canete‐Soler et al , 1994; Yao et al , 1996) but it is not known whether these enzymes cleave Fas ligand in this situation. A second possibility is that metalloproteinases are embedded in the Matrigel undercoats on which the epithelial cells are cultured and that these become activated by the HDM proteinases.…”

Implications for matrix metalloproteinases as modulators of pediatric lung disease

“…Additional sources of MMPs in the lung may be inflammatory cells that migrate into the lung during an inflammatory response (12). To date, a comprehensive examination of MMPs produced by lung-derived cells has not been performed in the normal human lung or in pathological conditions associated with lung injury.…”

Tight junction properties of the immortalized human bronchial epithelial cell lines Calu‐3 and 16HBE14o‐

“…For example, it has been suggested that allergic sensitization might be facilitated by peptidase allergens that lead to cleavage of the extracellular domains of TJs [12,13]. It has also been speculated that activated eosinophils cause the bronchial epithelium to become hyperfragile by promoting cleavage of both lateral and basal adhesions of epithelial cells [14,15].…”