Experimental Emphysema Research Articles

Temporal/spatial expression of retinoid binding proteins and RAR isoforms in the postnatal lung.

Endogenous retinoids have been implicated in alveologenesis in both the rat and the mouse, and exogenous retinoic acid (RA) can reverse or partially reverse experimental emphysema in adult rat and mouse models by an unknown mechanism. In this study, we examine the cellular and molecular biology of retinoid signaling during alveologenesis in the mouse. We describe the temporal and spatial expression of the retinoid binding proteins CRBP-I, CRBP-II, and CRABP-I using RT-PCR and immunohistochemistry. We identify the retinoic acid receptor isoforms RAR-alpha 1, RAR-beta 2, RAR-beta 4, and RAR-gamma 2 and describe their temporal and spatial expression using RT-PCR and in situ hybridization. We demonstrate that both retinoid binding proteins and RAR isoforms are temporally regulated and found within the alveolar septal regions during alveologenesis. These data support a role of dynamic endogenous RA signaling during alveolar formation.

Sarcomeres Are Added in Series to Emphysematous Rat Diaphragm After Lung Volume Reduction Surgery

The diaphragm adapts to its shortened state in experimental emphysema primarily by losing sarcomeres in series, thus reducing its optimal operating length. One would expect improved diaphragmatic function after lung volume reduction surgery (LVRS) only if the muscle can readapt to its elevated, lengthened postoperative position by either adding back sarcomeres or lengthening sarcomeres. We used a model of elastase-induced emphysema in rats to test the hypothesis that sarcomere addition occurs following LVRS. A cohort of emphysematous rats was created by the intratracheal instillation of elastase. Five months after the instillation, one group of rats underwent measurement of in situ costal diaphragm length via laparotomy, the determination of optimal muscle fiber operating length (Lo) on stimulated diaphragm strips in vitro, and the measurement of sarcomere length by electron microscopy on strips fixed at Lo. Another group of rats underwent LVRS or sham sternotomy 5 months after the instillation, and 5 months following the operation these animals underwent the same series of diaphragmatic studies. Lo was significantly greater in rats that underwent LVRS than those that underwent sternotomy (mean [+/- SE] Lo after LVRS, 2.50 +/- 0.08 cm; mean Lo after sternotomy, 2.27 +/- 0.06 cm; p = 0.013). There was no significant difference in sarcomere lengths between the two groups (2.95 +/- 0.04 vs 3.04 +/- 0.04 microm, respectively; p = 0.10). Using Lo as the length basis, the mean sarcomere number was calculated to be 8,712 +/- 192 in animals that had undergone LVRS and 7,144 +/- 249 in animals that had undergone sternotomy (p < 0.001). Sarcomere length is not significantly altered but sarcomeres are added in series following LVRS in this experimental model of emphysema/LVRS. It is likely that this sarcomere addition is a prerequisite to the improvement in inspiratory muscle function that has been observed following LVRS in humans.

Modelo experimental de enfisema pulmonar em ratos induzido por papaína

Objetivo: Com a finalidade de estabelecer uma linha de pesquisa em cirurgia redutora de volume pulmonar, foi proposta a reprodução de um modelo experimental de enfisema em ratos através da instilação intratraqueal de papaína. Métodos: Foi feita a instilação orotraqueal de papaína (20mg/kg) dissolvida em 3,5ml/kg de solução fisiológica a 0,9%. Após 40 dias da instilação, os animais foram submetidos a mecânica ventilatória, com medidas de elastância e resistência do sistema respiratório, e sacrificados com retirada dos pulmões. O tecido pulmonar dos animais foi analisado qualitativamente com coloração de hematoxilina-eosina e submetido à análise morfométrica com medida do diâmetro alveolar médio. O tecido pulmonar foi também submetido à coloração de resorcina-fucsina, para identificação de fibras elásticas, que foram quantificadas em septos alveolares através de análise digital de imagem. Resultados: A análise histológica dos pulmões dos animais submetidos à instilação de papaína mostrou um enfisema pan-acinar, com rotura de septos alveolares e hiperdistensão alveolar. A análise morfométrica revelou médias superiores de diâmetro alveolar médio nos pulmões dos animais submetidos à papaína (149,08mim e 100,56mim), em comparação com o grupo de solução fisiológica (64,08mim e 75,90mim). A quantificação de fibras elásticas de septos alveolares de animais tratados com papaína foi 70% menor do que a de animais submetidos à solução fisiológica. A mecânica ventilatória não mostrou diferença na resistência do sistema respiratório de animais submetidos à papaína ou à solução fisiológica. Já no caso da elastância do sistema respiratório, esta foi menor nos animais do grupo com papaína, em comparação com o grupo com solução fisiológica, demonstrando comportamento funcional do grupo com papaína compatível com enfisema pulmonar, apresentando diminuição da capacidade de recolhimento elástico do tecido pulmonar. Conclusão: Foi possível reproduzir um modelo experimental de enfisema pulmonar pan-acinar em ratos, através da instilação de papaína pela árvore respiratória, com comprovação funcional e morfológica.

The effect of hyaluronan on elastic fiber injury in vitro and elastase-induced airspace enlargement in vivo.

This laboratory has previously described a method of preventing air-space enlargement in experimental pulmonary emphysema using aerosolized hyaluronan (HA). Although it was found that HA preferentially binds to elastic fibers (which undergo breakdown by elastases in emphysema), it remains to be shown that such attachment actually prevents damage to the fibers. In the current study, cell-free radiolabeled extracellular matrices, derived from rat pleural mesothelial cells, were used to test the ability of low molecular weight ( approximately 100 kDa) streptococcal HA to prevent elastolysis. Coating the matrices with HA significantly decreased elastolysis (P<0.05) induced by porcine pancreatic elastase (43%), human neutrophil elastase (53%), and human macrophage metalloelastase (80%). Concomitant in vivo studies examined the ability of an aerosol preparation of the streptococcal HA to prevent experimental emphysema induced by intratracheal administration of porcine pancreatic elastase. As seen with earlier studies involving bovine tracheal HA, a single aerosol exposure significantly decreased elastase-induced airspace enlargement, as measured by the mean linear intercept (107.5 vs 89.6 microm; P < 0. 05). Furthermore, repeated exposure to the HA aerosol for 1 month did not reveal any morphological changes in the lung. The results provide further evidence that aerosolized HA may be an effective means of preventing pulmonary emphysema and perhaps other lung diseases that involve elastic fiber injury.

Aerosol probes of lung injury in a 28-wk longitudinal study of mild experimental emphysema in dogs.

After baseline measurements of lung mechanics, effective air space diameter (EAD), and aerosol dispersion (AD), three dogs were exposed to two treatments of aerosolized papain (3 ml of a 4% solution), and measurements were repeated during a 28-wk follow-up period. EAD and AD were measured with boluses of 0.7-micrometer particles of di-2-ethylhexl sebacate, with Pen (i.e., volumetric bolus penetration/total lung capacity) between 0.1 and 0.4. After papain exposure, EAD increased a mean of 28% (P < 0.0001) and AD (Pen = 0.3, 0.4) increased 4-7% (P < 0.03). The progression of injury was indicated by increasing trends in total lung capacity (P < 0.05), residual volume (P < 0.05), and EAD (P = 0.06) through week 18. There was no evidence of disease progression between weeks 18 and 28, whereas some of the data for individual dogs suggested partial recovery from lung injury at week 28. The results show that aerosol probes can detect and characterize mild lung injury in experimental emphysema.

The Pulmonary Matrix, Glycosaminoglycans and Pulmonary Emphysema

This paper reviews recent evidence of the effect of intratracheal hyaluronan (HA) to limit the induction of experimental emphysema in hamsters. Experimental emphysema was induced by both neutrophil and pancreatic elastase instilled intratracheally. Emphysema was quantified anatomically by measurement of alveolar mean linear intercept. Hyaluronidase, instilled intratracheally, enhanced the induction of experimental emphysema. Air-space size measured one week after intratracheal instillation of elastase showed that administration of 1 mg HA immediately following elastase administration resulted in a marked reduction in air-space enlargement (82 μM vs 122 μM, p < 0.01). Similarly, animals given either 1 or 2 mg HA 2 h before elastase or 2 mg HA 1 h after elastase showed a significant decrease in air-space enlargement compared to controls (96μM, 88μM vs 120 μM and 66 μM vs 104μM, respectively; p < 0.05. Experimental emphysema induced by neutrophil elastase was also limited by the administration of 1 or 4 mg of HA, administered 2 h prior to elastase (57 and 59 μM, respectively vs 64 for controls, p < 0.05). Characterization of administered HA showed a mean molecular weight of 104,800 Da, less than 5% protein and a uronic acid/hexosamine ratio of 1, which is characteristic of HA.Studies using fluorescein-labeled hyaluronan (HA) showed fluorescence associated with interstitial, pleural and vascular elastic fibers. The mechanism of attachment of the administered HA to elastin remains unknown. Fluorescein labeling of elastin was visible for at least 4 h post-instillation. These studies indicate a protective effect of hyaluronan against elastase degradation of pulmonary elastin in vivo by both pancreatic and neutrophil elastases. The anatomical studies further suggest a mechanism of protective coating of hyaluronan which may limit access to pulmonary elastin from neutrophils and alveolar macrophages. Results also suggest that a reduction in pulmonary hyaluronan content increases the susceptibility of elastin to degradation by elastases. These studies provide evidence for an anti-elastase effect of hyaluronan which is not dependent upon enzyme inhibition but on anatomical protection of pulmonary elastin by other mechanisms.

AEROSOL MEASUREMENT OF AIRSPACE DIAMETER CORRELATES WITH MORPHOMETRY IN NORMAL AND PAPAIN-EXPOSED AIR DRIED LUNGS

Aerosol measures of effective airspace diameter (EAD) were correlated with morphometric parameters in a series of 8 canine lungs, 5 of which had been exposed to papain in order to cause experimental emphysema. In an effort to preserve alveolar dimensions without shrinkage, the lungs were fixed by air drying at total lung capacity. EAD was measured with 400-cm2 boluses, with mean penetration index (Pen), defined as volumetric bolus penetration / total lung capacity, equal to 0.34 (EAD400), and with 800-cm2 aerosol boluses, with mean Pen equal to 0.59 (EADdeep). Morphometric analysis, following measurement of EADs, determined the mean linear intercept and other parameters of the chordlength distribution, including the 90th, 95th, and 99th percentiles (p90, p95, p99), the standard deviation, and the geometric standard deviation (GSD). EAD400 was significantly correlated with Lm (r2=.68, P <. 05), p95, (r2=. 85, P <. 01), p99 (r2=. 94, P <. 001), and GSD (r2=. 94, P <. 001). Similar results were found with EADdeep. In general, correlations were stronger between EAD and p95, p99, or GSD than between EAD and Lm. A comparison with a previous similar study relating EAD to morphometry in a series of lungs fixed by formalin fixation found closer agreement between EAD and morphometry when lungs were fixed by air drying. Overall, the data support the validity of EAD as an in vivo method of determining airspace size at total lung capacity.

Pulmonary emphysema induced by passive smoking: an experimental study in rats.

We describe a short time model for inducing experimental emphysema in rats by chronic tobacco smoke inhalation. Three groups of male Wistar rats (6 months old) were studied: controls (N = 8), rats intoxicated for 45 days (s-45, N = 7) or for 90 days (s-90, N = 8). The exposed animals were intoxicated 3 times a day (10 cigarettes per exposure period), 5 days a week. Pulmonary damage was assessed by means of functional tests and quantitative pathological examination of the airways and lung parenchyma. The s-45 and s-90 animals were similar in terms of functional residual capacity (FRC) corrected for body weight (FRC/kg) but both groups of smoking rats exhibited significantly higher FRC/kg values than the controls (s-45 = 6.33; s-90 = 6.46; controls = 3.78; P < 0.05). When the two groups of smoking rats were pooled together and compared to controls, they showed decreased lung elastance (1.6 vs 2.19; P = 0.046) and increased mean linear intercept (Lm) (85.14 vs 66.44; P = 0.025). The s-90 animals presented higher inflammation and muscular hypertrophy at the level of the axial bronchus than the controls (P < 0.05). When smoking groups were pooled and compared to controls, they presented significantly higher inflammation at the lateral level (P = 0.028), as well as airway secretory hyperplasia (P = 0.024) and smooth muscle hypertrophy (P = 0.005) at the axial level. Due to its simplicity, low cost and short duration, this technique may be a useful model to obtain new information about airspace remodeling due to chronic tobacco consumption.

Retinoic acid treatment abrogates elastase-induced pulmonary emphysema in rats.

Pulmonary emphysema is a common disease in which destruction of the lung's gas-exchange structures (alveoli) leads to inadequate oxygenation, disability and frequently death; lung transplantation provides its only remediation. Because treatment of normal rats with all-trans-retinoic acid increases the number of alveoli, we tested whether a similar effect would occur in rats with emphysema. Elastase was instilled into rat lungs, producing changes characteristic of human and experimental emphysema: increased lung volume reflecting a loss of lung elastic recoil, larger but fewer alveoli and diminished volume-corrected alveolar surface area due to destruction of alveolar walls. Treatment with all-trans-retinoic acid reversed these changes providing nonsurgical remediation of emphysema and suggesting the possibility of a similar effect in humans.

THE TRYPSIN-INDUCED LEUCOSTASIS WHICH LEADS TO EMPHYSEMA IN THE HAMSTER IS NOT DUE TO CONTAMINATING ENDOTOXINS

Intravenous injection of trypsin in the rat induces early lung leucostasis and emphysema of delayed onset. This report confirms that this emphysema is not rat-specific and that the leucostasis is not related to the presence of contaminating endotoxin in the trypsin. In hamsters (n = 37), leucostasis did not occur when they were injected with heat-treated trypsin, but numerous granulocytes were sequestered in the vessels of hamsters receiving a fresh solution of trypsin. In these hamsters, the number of granulocytes harvested by lavage increased significantly (1.87 x 10(6) per ml, P < 0.001) compared with hamsters injected with either heat-denatured trypsin (0.89) or saline (0.86), or compared with controls (0.86). Emphysema was inconstantly observed in hamsters 6 or 12 weeks after injection with trypsin for 1 h. It was frequently (17/20) present and always (20/20) well developed (intercept + 180 per cent) in the 2-h perfused hamsters whose lungs were abnormally heterogeneous (index + 100 per cent) relative to the seven controls and to the nine saline-injected hamsters. The efficiency of trypsin in triggering emphysema (percentage of hamsters having abnormal values of intercept) was dependent on the time of perfusion. This form of experimental emphysema is thus considered to be due to an endotoxin-independent leucostasis.

Changes of myocardial capillary density in progression of experimental lung emphysema

A morphometrical analysis of changes in the heart of rats with experimental lung emphysema due to single intratracheal administration of papain solution has been done. Special attention has been paid to quantitative changes of capillaries and to the cardiomyocyte diameter in respective regions of the myocardium after one, three and six months following the administration of papain. A histological and morphometrical analysis of changes in the lungs has also been carried out and partial pressures of oxygen and carbon dioxide in the arterial blood of the examined animals have been marked. It has been found that a single administration of papain caused emphysematous changes in the lungs, growing more intense until the third month of the experiment. The progression of these changes corresponded to a capillary density increase in the right ventricle, interventricular septum and in the subendocardial layer of the left ventricle. The increase in the number of capillaries was interpreted as the first adaptive stage of cor pulmonale development and explained by the occurrence of angiogenesis. The changes co-existed with a decrease in partial pressure of oxygen in the arterial blood. After six months of the experiment, a reduction in capillary density in the heart regions mentioned above and a simultaneous increase in the cardiomycyte transversal diameter were observed, being the exponents of evident myocardial hypertrophy. Development of ultrastructural changes in the hearts of rats has been analysed too. Simultaneous development of changes in the right ventricle muscle and in the subendocardial layer of the heart left ventricle myocardium was observed. The role of hypoxia as a one of essential factors responsible for the observed morphologic changes has been discussed.

Protection of rat lung from elastase-induced elastic fiber degradation in vitro and from emphysema in vivo by a trifluoroacetylpeptide anilide inhibitor.

Trifluoroacetylpeptide anilides are powerful reversible inhibitors of human neutrophil elastase (HNE), a serine protease implicated in the pathogenesis of pulmonary emphysema. The in vitro effectiveness of three inhibitors, CF3CO-Phe-Ala-NH-p-C6H4-CF3 (1), CF3CO-Val-Ala-NH-p-C6H4-CF3 (2) and CF3CO-Lys-Ala-NH-p-C6H4-CH(CH3)2 (3) was analyzed. The protection of lung tissue sections of rats from the degradation induced by HNE has been evaluated quantitatively by automated image analysis. Inhibitor 1 (22 microM), 2 (50 microM) or 3 (35 and 70 microM) significantly reduced the HNE-induced degradation of the elastin network by 75, 42, 54 and 44%, respectively. Inhibitor 3 was tested intratracheally on an experimental model of pulmonary emphysema. Rats that received the elastase inhibitor 1 h before instillation of HNE were significantly protected by 40% from experimental emphysema. Reduced protections were observed with the treatment by the inhibitor 1 or 4 h after challenge with the enzyme.

Aerosol deposition and dispersion characterize lung injury in a canine model of emphysema

The deposition and dispersion of inhaled aerosol boluses were investigated as markers of lung injury in three dogs before and after emphysema was induced by papain exposure. After the experiments, lung damage was assessed histologically. Four unexposed dogs were used as controls. Effective air space diameter (EAD) was determined from aerosol deposition during a 5-s breath hold. Nonuniform ventilation was assessed from the spreading of the expired bolus, quantified as a coefficient of dispersion (CD), and from expired bolus skewness (SK). Experiments were done with a range of bolus penetrations and ventilatory flow rates. After papain exposure, EAD measured with the most penetrating boluses increased an average of 89% (P < 0.0001); CD and SK measured with boluses of medium penetration and a flow rate of 0.5 l/s increased an average of 24% (P < 0.02) and 98% (P < 0.002), respectively. The effects of lung injury on CD and SK increased with flow rate. Lung injury was confirmed by changes in lung mechanics and by histology. EAD measured with deeply penetrating boluses correlated significantly with the mean chord length measured morphometrically (P < 0.05). No correlation was found with more shallow boluses. The results indicate that EAD, CD, and SK are sensitive markers of lung injury in experimental emphysema and that EAD is a specific marker of increased air space size.

Apocynin improves the efficacy of secretory leukocyte protease inhibitor in experimental emphysema.

Secretory leukocyte protease inhibitor (SLPI) is a potent proteinase inhibitor produced in the lung. Stimulated neutrophils at sites of inflammation can inactivate SLPI by myeloperoxidase-mediated oxidation of the methionine residue in the active site of SLPI. Apocynin is a selective inhibitor of NADPH oxidase and may therefore protect SLPI against neutrophil-mediated oxidative inactivation. The aim of the present study was to determine the effect of apocynin on the efficacy of SLPI in preventing experimental emphysema. To investigate the effect of apocynin on emphysema without SLPI treatment, three groups of eight hamsters each received drinking water containing apocynin at concentrations of 2, 20, and 200 micrograms/ml, respectively. Emphysema was induced in these hamsters by intratracheal instillations of 500 micrograms of lipopolysaccharide (LPS) twice a week for 4 wk. In hamsters that received 200 micrograms/ml apocynin, the development of emphysema was reduced by 26.2% (p = 0.01). Other apocynin concentrations had no effect. The experiment was repeated, with SLPI added to the treatment. Of a total of six groups of hamsters, four groups (three with apocynin and one with solvent) received twice-weekly doses of a mixture of 500 micrograms of LPS and 1 mg SLPI in 200 microliters saline in the trachea for 4 wk. In addition, each LPS instillation was followed 24 and 48 h later by an instillation containing 1 mg of SLPI. Apocynin (20 and 200 micrograms/ml) improved the protective effect of SLPI from 37 to 64% and 79%, respectively (p < 0.01). We conclude that oral administration of apocynin can improve the efficacy of SLPI in preventing LPS-induced emphysema.

Pitfalls in antiprotease therapy of emphysema.

Many individuals with emphysema are unable to stop smoking despite the best efforts of specialists in smoking cessation. Because emphysema is a slowly progressive disease, it is rational to attempt to develop drugs for it. The hope is that drug therapy will slow the rate of decline of lung function, thereby delaying the onset of disability and prolonging life. The major emphasis in drug development has been on antiproteases having the ability to inhibit neutrophil elastase. There are a number of potential pitfalls in the development of such drugs. Although there is gathering evidence that elastin degradation is a part of the development of human emphysema, it is evident from studies in experimental emphysema that protease-antiprotease imbalance is not the only pathogenetic mechanism that gives rise to emphysema. There is strong evidence that human centrilobular and panacinar emphysema are different in pathogenesis. Indeed, airspace enlargement may be considered one of the stereotyped ways that the lung heals after a variety of injuries. There is accumulating evidence that macrophages as well as neutrophils may participate in elastolysis; antiproteases designed to inhibit neutrophil elastase may not inhibit the metalloproteases produced by macrophages. Some antiproteases may serve to transport elastase into the interstitium of the lung and actually increase the risk of emphysema. A process study of antiprotease therapy, using a measure of alteration of elastase burden of the lungs and urinary elastin peptides and desmosine measurements as markers of elastin degradation is now feasible. An outcome study of antiprotease therapy of emphysema should not be undertaken unless there is evidence from a process study that an antiprotease has biochemical efficacy and no unacceptable side effects.

Intratracheally-instilled antileukoprotease and α1-proteinase inhibitor: effect on human neutrophil elastase-induced experimental emphysema and pulmonary localization

The protective capacities of intratracheally-instilled antileukoprotease and alpha 1-proteinase inhibitor towards human neutrophil elastase (HNE)-induced pulmonary injuries were compared in hamsters. The antiproteases were instilled in equimolar amounts up to 20 h before HNE instillation. At all intervals, both inhibitors were able to inhibit HNE-induced emphysema efficiently. At 1 h before HNE instillation, alpha 1-proteinase inhibitor was more effective in this regard than antileukoprotease. alpha 1-Proteinase inhibitor, instilled 1 to 12 h before HNE, efficiently inhibited HNE-induced haemorrhage, while the antileukoprotease protected haemorrhage only when it was administered 1 h before HNE. The development of secretory cell metaplasia was affected only when both inhibitors were instilled 1 h before HNE. In a second series of experiments, the localization of the two antiproteases after intratracheal instillation in hamster was investigated using an indirect immunofluorescence technique. Up to 20 h after installation, antileukoprotease was found to be associated with elastin fibres at all points of time investigated. In contrast, alpha 1-proteinase inhibitor was observed to be located in the alveolar lining and diffusely in the alveolar lung tissue at all points of time investigated. No association of the inhibitor with elastin fibres was found. We conclude that the fraction of antileukoprotease associated with the elastic fibre may be important in the protection of HNE-induced pulmonary emphysema.

Intratracheally-instilled antileukoprotease and α1-proteinase inhibitor: effect on human neutrophil elastase-induced experimental emphysema and pulmonary localization

Intratracheally-instilled antileukoprotease and α1-proteinase inhibitor: effect on human neutrophil elastase-induced experimental emphysema and pulmonary localization

Diaphragm Structure and Function in Emphysematous Hamsters

OBJECTIVE: To determine if muscle fibre injury, reduced force output and fatigue of the diaphragm accompanied hyperinflation induced by experimental emphysema.DESIGN: Controlled and randomized.ANIMALS: Adult male golden Syrian hamsters: seven control and seven experimental emphysema hamsters were studied.INTERVENTIONS: Following anesthesia, experimental emphysema hamsters received a transtracheal injection of elastase. They also received injections of β‐aminopropionitrile every other day for five weeks. After five weeks, all hamsters we re anesthetized , and their diaphragm and lungs were excised.MAIN RESULTS: Measurements of the excised lungs showed an increased residual volume. functional residual capacity and total lung capacity in experimental emphysema hamsters. In vitro physiological study of diaphragm strips showed no difference in force output but a greater fatiguability during repetitive stimulation for 5 mins in experimental emphysema hamsters than in control hamsters. Histological examination did not show significant muscle injury in the diaphragm of experimental emphysema hamsters.CONCLUSION: The greater fatiguability and absence of muscle injury in the diaphragm of emphysematous hamsters may result from hyperinflation decreasing diaphragmatic load. Alternatively, muscle damage not detectable at the light microscopic level may have contributed to increased fatiguability of the diaphragm of experimental emphysematous hamsters.

Alveolar epithelial cells in experimental lung emphysema. Ultrastructural analysis of cells in situ in TEM.

A study was made of ultrastructural changes in alveolar epithelial cells after a single intratracheal papain injection. The experiment was carried out on male Wistar rats, of 180-220 g body weight. The animals were sacrificed after 1, 7, 14 and 28 days that followed proteolytic enzyme administration. The study revealed that the development of emphysematous changes in the rat lungs was accompanied by alterations in the epithelium of alveoli. In early stages of emphysema (up to 1 week), destructing changes dominated within the epithelial cells. Similar changes were observed in the endothelium of adjacent blood vessels. In later periods an increased number of type II pneumocytes were seen and focal accumulation of elastic and collagenic fibres was noticed in alveolar septa. Correlation was found between changes in the number of type II cells and their ultrastructure as well as between alveolar epithelium damage and alveolar septal interstitium alterations.

Interaction of Secretory Leukocyte Protease Inhibitor with Proteinase-3

Secretory leukocyte protease inhibitor (SLPI) is a 12 kD nonglycosylated serine antiproteinase secreted by cells of mucosal surfaces. In human lung, SLPI is present in the respiratory epithelium. It is the major barrier to tissue destruction mediated by the polymorphonuclear leukocyte (PMN) serine proteinases, elastase and cathepsin G, within the upper respiratory tract. We have recently described a third PMN serine proteinase, proteinase-3, that like elastase causes lung matrix destruction and experimental emphysema. The current studies examine interactions between SLPI and proteinase-3. The results show that: (1) SLPI and its reactive-site variants have no or minimal inhibitory activity against proteinase-3; (2) native SLPI does not complex with proteinase-3; (3) proteinase-3 selectively degrades both native and oxidized SLPI; (4) the cleavage of SLPI by proteinase-3 occurs at the peptide bond COOH-terminal to Ala-16 in the NH2-terminal domain of SLPI.