Inhibition of human leukocyte elastase by mineral dust particles.

After isolation, purification, and radiolabeling of elastin from baboon aorta and lung, the rates of hydrolysis of both 3H-labeled elastins by porcine pancreatic elastase (PPE or by human leukocyte elastase (HLE) were compared. PPE (30 nM) degraded aorta and lung elastins at rates of 40 and 75 micrograms/h, respectively, leading to their complete solubilization. In contrast, the low rate of hydrolysis of lung elastin (10 micrograms/h) by HLE was paradoxically accompanied with a fivefold decrease in the Michaelis constant value and became negligible after 1 h of incubation. Moreover, HLE adsorption isotherms showed that 0.87 nmol HLE was adsorbed on 1 mg of aorta elastin vs. 1.30 nmol/mg lung elastin. Also, increasing ionic strength was found to enhance the elastolytic potential of HLE toward lung elastin. Investigations were carried out to explain why baboon lung elastin exhibited low susceptibility to hydrolysis by HLE. Solubilization of lung elastin with PPE produced a residue that exhibited inhibitory capacity toward HLE when either 3H-labeled aorta elastin or succinyl trialanine nitroanilide was used as a substrate. When analyzed by transmission electron microscopy, this residue was found to consist of several mineral dust particles, mainly kaolinite (53%) of environmental origin. 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 micrograms of either kaolinite or montmorillonite totally abolished the activity of 0.45 micrograms of HLE. All these results allowed us to propose that HLE inhibition by aluminium-silicate dusts may be of importance in the pathogenesis of industrial pneumoconiosis and in opportunistic lung infections.

Evaluation of tumor necrosis factor-alpha (TNF) as an exposure or risk marker in three French coal mining regions.

Several studies have shown the crucial role of the tumor necrosis factor-alpha (TNF) in the fibrosis induced by dusts containing silica and its role in the transition from simple pneumoconiosis (CWSP) to progressive massive fibrosis (PMF). To evaluate the nocivity of dust exposure among coal miners (n = 474) from different mining regions in France (e.g., Nord-Pas de Calais, Lorraine, and Provence), spontaneous and LPS or silica-induced TNF released by peripheral blood monocytes was quantified. The primary aim of this effort was to study the link between the prevalence of coal workers pneumoconiosis (CWP) and TNF release. TNF levels were significantly different between active miners from the three regions. However, after correction for age and region, TNF was found not to be related to dust exposure. Interestingly, a very low, homogeneous expression of TNF was observed in the group from Provence. These results are probably related to the absence of pneumoconiosis in this area. A positive relation between profusion and TNF release was found for all stimulants among retired miners with PMF. Although in retired miners TNF release was consistently higher, the design of the study does not allow this effect to be separated from that of age. Both silica and nonstimulated TNF release were found to increase with increasing radiological symptoms; the opposite was found for LPS-induced release.