Different lung responses to cigarette smoke in two strains of mice sensitive to oxidants.

The development of cigarette smoke-induced pulmonary changes in C57 Bl/6J and DBA/2 mice was investigated. Both strains are sensitive to oxidants and C57Bl/6J mice are moderately deficient in serum alpha1-proteinase inhibitor. Following chronic exposure to cigarette smoke, patchy emphysema was present in mice of both strains, but developed faster in DBA/2 mice. A positive reaction for mouse neutrophil elastase was seen on the septa of both strains. Additionally, the DBA/2 mice developed a uniform parenchymal dilation that was preceded by the appearance of apoptotic cells in areas with a low signal for vascular endothelial growth factor-receptor 2. Fibrotic areas scattered throughout the parenchyma, coupled with a positive immunohistochemical reaction for transforming growth factor-beta was seen only in DBA/2 mice. Both DBA/2 and C57Bl/6J strains showed epithelial cell injury and areas of deciliation in their airways. However, the appearance of goblet cell metaplasia was common in C57Bl/6J mice but rare in DBA/2 mice. A positive immunohistochemical reaction for interleukin (IL)-4, IL-13 and MUC5AC was seen only in the airways of C57Bl/6J mice. Strain characteristics (alpha1-proteinase inhibitor levels, sensitivity to oxidants, and constitutive levels of vascular endothelial growth factor-receptor 2) and phenotypical responses (apoptosis and cytokine distribution) may condition parenchymal and airway changes to cigarette smoke.

Effects of cigarette smoke in mice with different levels of alpha(1)-proteinase inhibitor and sensitivity to oxidants.

The role of strain difference in the response to cigarette smoke was investigated in mice. Mice of the strains DBA/2 and C57BL/6J responded to acute cigarette smoke with a decrease of the antioxidant defenses of their bronchoalveolar lavage (BAL) fluids. On the other hand, under these conditions ICR mice increased their BAL antioxidant defenses. Mice of these three strains were then exposed to cigarette smoke (three cigarettes/d, 5 d/wk) for 7 mo. Lung elastin content was significantly decreased in C57BL/6J and DBA/2 but not in ICR mice. Also, emphysema, assessed morphometrically using three methods, was present in C57BL/6J and DBA/2 but not in ICR mice. In an additional study pallid mice, with a severe serum alpha(1)-proteinase inhibitor (alpha(1)-PI) deficiency and that develop spontaneous emphysema, were exposed to cigarette smoke for 4 mo. This resulted in an acceleration of the development of the spontaneous emphysema assessed with morphometrical and biochemical (lung elastin content) methods. All these results indicate that sensitivity to the effects of cigarette smoke is strain-dependent and cigarette smoke accelerates the effects of alpha(1)-PI deficiency.

Human SLPI inactivation after cigarette smoke exposure in a new in vivo model of pulmonary oxidative stress.

The role of oxidative stress in inactivating antiproteases is the object of debate. To address this question, we developed an in vivo model of pulmonary oxidative stress induced by cigarette smoke (CS) in mice. The major mouse trypsin inhibitor contrapsin is not sensitive to oxidation, and the mouse secretory leukoprotease inhibitor (SLPI) does not inhibit trypsin. Instead, human recombinant (hr) SLPI inhibits trypsin and is sensitive to oxidation. Thus we determined the effect of CS in vivo on hrSLPI antiproteolytic function in the airways of mice. CS caused a significant decrease in total antioxidant capacity in bronchoalveolar lavage fluid (BALF) and significant changes in oxidized glutathione, ascorbic acid, protein thiols, and 8-epi-PGF(2alpha). Intratracheal hrSLPI significantly increased BALF antitryptic activity. CS induced a 50% drop in the inhibitory activity of hrSLPI. Pretreatment with N-acetylcysteine prevented the CS-induced loss of hrSLPI activity, the decrease in antioxidant defenses, and the elevation of 8-epi-PGF-(2alpha). Thus an inactivation of hrSLPI was demonstrated in this model. This is a novel model for studying in vivo the effects of CS oxidative stress on human protease inhibitors with antitrypsin activity.

Genetic deficiency of alpha1-PI in mice influences lung responses to bleomycin.

It has recently been suggested that proteinase inhibitors modulate the fibrotic response in the lung. This study investigated the development of bleomycin-induced pulmonary changes in pallid mice, deficient in serum alpha1-proteinase inhibitor, and with a lower elastase inhibitory capacity, and in congenic C57Bl/6J mice. Male pallid and C57Bl/6J mice received a single intratracheal instillation of either saline or bleomycin. The investigation was carried out by means of biochemical, morphological and morphometrical methods. In both strains, 21 and 72 h after bleomycin, the lungs showed foci of inflammatory cell infiltration associated with emphysema. Fibrosis developed with time after bleomycin. At 14 days fibrosis affected 23.46+/-9.48% (mean +/- SD) and 40.62+/-13.34% (p < 0.01) of the lungs of C57Bl/6J and pallid mice, respectively. Emphysema affected 3.68+/-3.11% and 12.57+/-4.13% (p<0.01) of lung in C57Bl/6J and pallid mice, respectively. In C57Bl/6J mice bleomycin increased lung hydroxyproline content by 34% and desmosine content by 44% (p < 0.01 for both). In pallid mice these increases were only 21% (p < 0.01) and 6% which may reflect parenchymal loss. Thus, the lung destructive response (emphysema) and the subsequent proliferative reaction (fibrosis) to bleomycin are potentiated in alpha1-proteinase inhibitor deficiency.

Neutrophil influx into the lungs of beige mice is followed by elastolytic damage and emphysema.

The beige mouse is currently used as a model of elastase and cathepsin G deficiency to demonstrate or exclude the role of these proteases in a variety of pathologic conditions. We recently demonstrated that beige cathepsin G is tightly bound to neutrophil lysosomal membranes but is released in near normal quantities during exocytosis. Also, beige neutrophils contain a latent form of elastase that undergoes spontaneous activation when released under in vitro or in vivo conditions. However, the pathogenic potential of this enzyme in matrix degradation has not been ascertained previously. The possibility that in beige mice elastolytic proteases from neutrophils recruited into the lung have the capability to damage alveolar septa was investigated following an intratracheal instillation of N-formyl-L-methionyl-L-leucyl-L-phenylalanine (200 microg). Neutrophil influx was followed by a decrease in lung elastin content (-18%) and by a significant increase of the mean linear intercept (+30%) and of morphologic emphysema. The onset of pulmonary lesion was preceded by a marked increase of neutrophil elastase burden on the alveolar interstitium. The appearance of emphysema was prevented by administration of the serine protease inhibitor 4-(2-aminoetyl)-benzenesulfonyl fluoride hydrochloride (2. 4 microg/ml saline). These results demonstrate that the lung elastin degradation and emphysema can occur in beige lungs. The fact that the beige mouse does develop lung elastolytic changes after neutrophil recruitment indicates that this mutant cannot be considered a model of neutrophil function deficiency and used as a model of elastase deficiency.