Low molecular weight elastase inhibitors in cells and tissues of alveolar regions: seek and ye shall find

Modification of the proteinase/anti-proteinase balance in the respiratory tract of Sprague-Dawley rats after single intratracheal instillation of benzo[A]pyrene-coated onto Fe(2)O(3) particles

Available data suggest that repeated concurrent exposure to haematite (Fe(2)O(3)) and benzo[A]pyrene (B[A]P) results in a decreased latency and an increased incidence of lung tumours in rodents compared to exposure to B[A]P alone. Moreover, the reactive oxygen species (ROS) formed by the lung cells themselves and/or by activated inflammatory cells may possibly contribute to the development of pulmonary disorders such as cancer formation. In order to investigate the precise role of iron in the injury induced by B[A]P-coated onto Fe(2)O(3) particles, we tend to address the hypothesis that Fe(2)O(3) and B[A]P, alone or in association, can induce oxidative stress conditions (malondialdehyde) and/or inflammatory reactions (interleukin-6) and thereby disrupt the proteinase/anti-proteinase balance (cathepsins B and L, polynuclear neutrophil (PNN) elastase, alpha-1 proteinase inhibitor (alpha(1)PI) and its inhibitory capacity) in the rat respiratory tract. Thus, Fe(2)O(3) or B[A]P-coated onto Fe(2)O(3) particles produce oxidative stress conditions through not only iron-catalysed oxidative reactions but also inflammatory processes. However, B[A]P initiates only inflammatory responses. These pollutants generate increased levels of proteases and decrease the concentrations of free alpha(1)PI. There is also a clear relationship between the partial inactivation of alpha(1)PI and the occurrence of ROS after exposure to Fe(2)O(3), alone or as a carrier of B[A]P. Hence, the proteinase/anti-proteinase balance might be more disrupted by Fe(2)O(3) or B[A]P-coated onto Fe(2)O(3) particles than by B[A]P alone. These results suggest a mechanism that can explain why B[A]P-coated onto Fe(2)O(3) particles are more injurious than B[A]P alone.

Purification and characterization of a novel Kazal-type serine proteinase inhibitor of neutrophil elastase from sheep lung

A Kazal-type elastase inhibitor was purified by trichloroacetic acid precipitation of sheep lung lavage fluid followed by chymotrypsin affinity and gel-filtration chromatography of the supernatant. Sheep lung elastase inhibitor (SLEI) is glycosylated. Laser desorption mass spectrometry indicated that SLEI has a molecular mass of 16.8-17.3 kDa. Partial protein sequence of SLEI and of a peptide derived from SLEI showed 31-52% and 51-66% homology at the N-terminus and at the inhibitory site respectively with Kazal-type double-headed proteinase inhibitors (bikazins). SLEI inhibited human leukocyte elastase and porcine pancreatic elastase but not human cathepsin G. It was inactivated by chloramine-T and reactivated when incubated with methionine sulfoxide peptide reductase and dithiothreitol, indicating the presence of a methionine at the active site. The concentration of SLEI in bronchoalveolar lavage fluid (BALF) and lung lymph was 0.28 microM (0.23-0.49); 0.24 microM (0.20-0.31) (median, (range), n = 5), respectively and was undetectable in plasma (< 0.03 microM) suggesting that SLEI is produced in the lung. The median molar ratios of SLEI to alpha1-proteinase inhibitor in BALF and lung lymph were 3.2 to 1 and 0.017 to 1, respectively. These results indicate that SLEI probably makes an important contribution to antielastase defence in epithelial lining liquid.

Assessment of the antielastase activities in bronchoalveolar lavage fluid: effect of assay buffer ionic strength

OBJECTIVE

To evaluate the effect of assay buffer ionic strength on assessment of the antielastase activities in bronchoalveolar lavage fluid.

METHOD

An improved assay protocol in which elastase (in Tris-HCI buffer) is added to increasing volumes of test samples (made up to equal volume with phosphate-buffered saline) was used.

RESULTS

The percent NE activity inhibited by BALF decreased with increasing NaCl concentration of the buffer. Inhibition of pancreatic elastase (PE) was not affected. One hundred percent inhibition of NE by pure AAT and SLPI standards occurred at molar ratios of 0.91 +/- 0.03 for AAT-to-NE and 0.83 +/- 0.02 for SLPI-to-NE when assayed in buffer with < or = 0.15 mol NaCl/L, compared to ratios of 0.99 +/- 0.02 and 1.06 +/- 0.02, respectively, for assays in buffers with 0.50-1.00 mol NaCl/L (p < 0.05 for AAT-to-NE; p < 0.02 for SLPI-to-NE). The AAT-to-PE molar ratio at 100% inhibition of PE was not affected. Assays in buffer with < or = 0.15 mol NaCl/L indicated that 86.9 +/- 4.1% of AAT and 100.9 +/- 4.9% of SLPI in BALF were active against NE, while assays in buffer with 0.50-1.00 mol NaCl/L showed that 84.4 +/- 3.5% of AAT and 81.6 +/- 5.9% of SLPI present were active. AAT inhibited NE and PE equally only in buffer with 0.50-1.00 mol NaCl/L.

CONCLUSIONS

The results of assays of BALF antielastase activities depend on the assay buffer NaCl concentration, which may account for the conflicting reports in the literature. The buffer with 0.50-1.00 mol NaCl/L appear to be optimal for valid quantitation of anti-NE activities in BALF.