Inhibition of human leucocyte elastase by mineral dust
particles.
Oberson, D, L. Desfontaines, H. Pezerat, W. Hornebeck, P. Sebastien,
and C. Lafuma.
Laboratoire de Biologie du Tissu Conjonctif, ER 74 CNRS,
Facult[acute]e de M[acute]edecine, 8 Rue du G[acute]en[acute]eral
Sarrail, 94010 Cr[acute]eteil, France, Institut National de
l'Environnement Industriel et des Risques (INERIS), Parc Alata, B.P.
N 60550 Verneuil en Halatte, France, Laboratoire de
R[acute]eactivit[acute]e de Surface et Structure, Universit[acute]e
Pierre et Marie Curie, 75352 Paris cedex 05, France, Institut de
Recherches en Sant[acute]e et S[acute]ecurit[acute]e au Travail du
Qu[acute]ebec, (IRSST), 505 West de Maisonneuve, Montr[acute]eal
Qu[acute]ebec H3A3C2, Canada, INSERM U296 de Physiologie
Respiratoire, Facult[acute]e de M[acute]edecine, 8 rue du
G[acute]en[acute]eral Sarrail, 94010 Cr[acute]eteil, France
APStracts 2:0217L, 1995.
Following isolation, purification and radiolabeling of elastin from
baboon aorta and lung, the rates of hydrolysis of both 3H elastins by
porcine pancreatic elastase (PPE) or by human leucocyte elastase
(HLE) were compared. PPE (30 nM) degraded aorta and lung elastins at
rates of 40 and 75 [mu]g/h respectively, leading to their complete
solubilization. PPE appeared as a more potent elastolytic enzyme than
HLE: HLE (30 nM) hydrolyzed 25 [mu]g/h aorta elastin and 10 [mu]g/h
lung elastin. In addition, the rate of hydrolysis of lung elastin by
HLE became negligible following one hour of incubation. The low rate
of hydrolysis of lung elastin by HLE as compared to aorta elastin was
paradoxically accompanied with a five-fold decrease in the Km value.
Also, HLE adsorption isotherms showed that 0.87 nmole HLE was
adsorbed on 1 mg of aorta elastin v.s. 1.30 nmole/mg lung elastin. 2-
Several investigations were carried out in order to understand why
baboon lung elastin exhibited low susceptibility to hydrolysis by HLE
and allowed us to suggest that some inorganic agent had been purified
concomitantly with elastin and was interacted with HLE leading to its
inhibition. 3- Indeed, solubilization of lung elastin with PPE excess
led to isolate a final insoluble residue that exhibited inhibitory
capacity towards HLE when either 3H labeled aorta elastin or
Suc(Ala)3NA were used as substrates. When analyzed by transmission
electron microscopy, this residue was found to consist of several
mineral dust particles, mainly clay mineral particles of the
kaolinite group (53 %) and particles from the illite group (18%) of
environmental origin. 4- The HLE inhibitory capacities of various
mineral or coal mine dust particles were then analyzed. Mineral
aluminium-silicate dusts were found to be potent HLE inhibitors: 5
[mu]g of either kaolinite or montmorillonite totally abolished the
activity of 0.45 [mu]g of HLE. The interaction between HLE and clay
particles responsible for HLE inhibition was progressively reduced by
addition of increasing amounts of a neutral electrolyte to the system
or by elevation of the pH to a value near the basic electric point.
These results are evidence of the key role played by both the amine
groups of HLE and the hydroxyl groups bound to octahedral Al3+ at the
solid-liquid interface of clay particles in the interaction with HLE.
Since aluminium phyllosilicates may accumulate in substantial amounts
in the lungs of coal miners, ant that physiological function of HLE
mainly involves extensive proteolysis and destruction of micro
-organisms, the HLE inhibitory capacity of aluminium phyllosilicates
is discussed as regards pathogenesis of industrial pneumoconiosis and
related opportunistic lung infections
Received 1 May 1995; accepted in final form 22 November 1995.
APS Manuscript Number L129-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95