Connective tissue damage in emphysema. An electron microscopic study of papain-induced emphysema in rats

Bone Marrow-Derived Mononuclear Cell Therapy in Papain-Induced Experimental Pulmonary Emphysema

Murine papain-induced emphysema is a model that reproduces many of the features found in patients. Bone marrow-derived mononuclear cells (BMMC) have already been used to repair the alveolar epithelium in respiratory diseases, but not in the papain model. Thus, we hypothesized that BMMC could prevent the pathophysiological processes in papain-induced experimental emphysema. Female BALB/c mice received intratracheal instillation of 50 μL of saline (S groups) or papain (P groups, 10 IU/50 μl of saline) on days 1 and 7 of the experimental protocol. On the 14th day, 2 × 10⁶ BMMC of male BALB/c mice (SC21 and PC21) or saline (SS21 and PS21) were injected by the jugular vein. Analyses were done on days 14 (S14 and P14) and 21 (SS21, PS21, SC21, and PC21) of the protocol. qPCR evaluated the presence of the Y chromosome in the lungs of BMMC recipient animals. Functional residual capacity (FRC), alveolar diameter, cellularity, elastic fiber content, concentrations of TNF-α, IL-1β, IL-6, MIP-2, KC, IFN-γ, apoptosis, mRNA expression of the dual oxidase (DUOX1 and DUOX2), production of H₂O₂ and DUOX activity were evaluated in lung tissue. We did not detect the Y chromosome in recipients' lungs. FRC, alveolar diameter, polymorphonuclear cells (PMN) and levels of KC, MIP-2, and IFN-γ increased in P14 and PS21 groups; the changes in the latter were reverted by BMMC. TNF-α, IL-1β e IL-6 were similar in all groups. The amount of elastic fibers was smaller in P14 and PS21 than in other groups, and BMMC did not increase it in PC21 mice. PS21 animals showed increased DUOX activity and mRNA expression for DUOX1 and 2. Cell therapy reverted the activity of DUOX and mRNA expression of DUOX1. BMMC reduced mRNA expression of DUOX2. Apoptosis index was elevated in PS21 mice, which was reduced by cell therapy in PC21. Static compliance, viscoelastic component of elastance and pressure to overcome viscoelasticity were increased in P14 and PS21 groups. These changes and the high resistive pressure found on day 21 were reverted by BMMC. In conclusion, BMMC showed potent anti-inflammatory, antiapoptotic, antioxidant, and restorative roles in papain-triggered pulmonary emphysema.

Experimental pulmonary emphysema induced in the rat by intratracheally administered elastase: morphogenesis

Emphysema was produced experimentally in rats by administration of porcine pancreatic elastase at dose levels of 75, 100, 125, and 150 units elastase activity/100 g body wt. All doses studied were equally effective in producing emphysema. Dose levels of over 75 units activity/100 g offered no advantage in terms of degree or severity of emphysema produced; however, such doses exacerbated hemorrhage and edema, resulting in relatively high post-instillation mortality. Lesion morphogenesis at all doses tested paralleled those described in this and in other species by other investigators. The 75-unit activity produced a quantifiable degree of emphysema which was relatively constant among animals. Results suggest that because of group differences in susceptibility to elastase (or variations in batches of elastase), dose-range studies should be performed on each new group of animals.

Stimulation of human leukocyte elastase by platelet factor 4. Physiologic, morphologic, and biochemical effects on hamster lungs in vitro

The purpose of this study was to determine if human platelet factor 4 (PF4) stimulates human leukocyte elastase (HLE) against lung elastin. Lung elastin was purified from hamster lungs and tritiated by reduction with NaB3H4. We found that HLE activity against this substrate is increased by concentrations of PF4 as low as 1.6 microgram/ml, and that this stimulation increased linearly with additional PF4. Lungs removed from hamsters and inflated with solutions containing buffer alone, low dose HLE, HLE plus PF4, or PF4 alone were incubated for 2 h at 37 degrees C. Whereas low-dose HLE failed to lower lung elastin when compared to control animals, HLE stimulated by PF4 lowered lung elastin by 20%. PF4 alone had no effect. Furthermore, low-dose HLE failed to alter the mechanical properties of hamster lungs as measured by pressure-volume curves in saline, although there was a significant loss of lung elasticity in the mid- and high-lung volume ranges in lungs treated with HLE and PF4. Morphologic studies revealed that low dose HLE resulted in a minimal emphysemalike lesion whereas HlE plus PF4 caused a significantly more severe lesion. PF4 is capable of stimulating HLE against lung elastin, and this effect may have a role in the pathogenesis of emphysema.

Pulmonary disease in workers exposed to papain: clinico-physiological and immunological studies

Of the twenty-three employees at a pharmaceutical plant manufacturing a new product containing papain, twelve had respiratory symptoms of cough, wheezing, dyspnoea, or chest paint. Most were studied with in-depth interviews by a doctor, extensive pulmonary function tests, and immunoserological tests for IgE and precipitating antibodies specific for papain, as well as total IgE antibodies to common natural allergens. There were significant correlates (all P values < 0.05) between the presence of specific IgE antibodies to papain and decreases of FEV1, FEF75--85, TLC, RV, and response to bronchodilators as percentage change from baseline for all spirographic flow rates. Atopic workers developed pulmonary symptoms and antipapain antibodies significantly sooner after papain exposure than did the others. Duration of exposure had no effect on symptomatology, pulmonary function, or immunological response. However, those judged to have the greatest amount of dust exposure per work-day had significantly more pulmonary symptoms (P < 0.005). Papain produced lung diseases by acting as an inhalant allergen rather than a proteolytic enzyme. Papain is a potent sensitizer in humans for the production of respiratory disease. The pulmonary reactions, based on physiological data, seem to involve small airways, alveolar, and interstitial lung tissue in an inflammatory rather than destructive manner, and thus resemble bronchitis and interstitial lung disease rather than pulmonary emphysema or typical bronchial asthma.

Injury and repair of the lung: response to intravenous Freund's adjuvant

Tissue from the lungs of rabbits was examined at intervals up to 24 weeks after the animals had received a single intravenous injection of Freund's complete adjuvant. Though this is not a conventional method for damaging the peripheral lung, it had the advantage of producing multiple lesions in which most tissue components were altered for a prolonged period. White blood cells were present within the tissue and air spaces of these damaged areas. They persisted for 6 weeks in large numbers and gradually decreased over the next 12 weeks. There was replacement of type A by type B alveolar lining cells. Basement membranes were displaced and lost. Elastic and collagen fibres were distorted and destroyed. Blood vessels were occluded. Epithelioid cell and foreign body granulomas developed. Interalveolar septa disappeared, and air spaces were compressed. Despite all these changes the lungs regained near normal structure by 24 weeks after the initial injury. These results do not support the importance that has been placed on damage to various structural components of the lung as an explanation for chronic pulmonary disease. They do give some insight into the capacity of peripheral lung tissue for regenerationa following a single injury that induces a prolonged inflammatory response.

Pathogenesis of papain-induced emphysema in the hamster

In an effort to determine the mechanism of papain action in causing an emphysema-like lesion in hamsters, the number and types of cells and the activities of two lysosomal enzymes in the lung were determined after papain exposure. Three and four weeks after a 3-h exposure to an aerosol of 3% papain the following alterations in lung structure and function were observed: (1) the mean linear intercept, or average distance between adjacent alveoli, was increased; (2) the internal surface area declined; (3) the dynamic compliance was elevated at low breathing frequencies. The numbers of cells present free in the lung increased from a control value of 2.0 +/- 0.2 x 10 (6) to 6.6 +/- 0.5 x 10 (6) 5 days after exposure. The free beta-glucuronidase, alysosomal enzyme, likewise increased over threefold during the first 3 days after exposure. These results are consistent with the hypothesis that papain induces an inflammatory-type responses, and this may be in part responsible for inducing the lesion.

A comparative study of experimental and spontaneous emphysema

Normal lung architecture of the rat, mouse, hamster, horse, and human was compared to that of emphysematous lungs from the same species by utilizing a light microscope and a scanning electron microscope (SEM). The results obtained by SEM examination of normal and emphysematous lungs corresponded to those obtained with the light microscope. However, the SEM provided a view of alveoli and airway morphology not obtainable with the light microscope. Because of the variability in pore size and number of pores per alveolus, a pore-to-alveolus ratio was determined with the SEM on the normal lungs of the above species plus the rabbit, dog, guinea pig, and rhesus monkey. Depending on the extent of other pathways for collateral ventilation, differences in number of pores per alveolus may affect a species' susceptibility to a given mechanism in the genesis of spontaneous or induced emphysema. The small number of pores per alveolus in the rat, mouse, rabbit, and hamster suggests that they would not be responsible for emphysematous changes. Pores do appear to be involved in human and horse emphysema.

The pathology of elastase-induced panacinar emphysema in hamsters

A single dose of crystalline, porcine pancreatic elastase injected intratracheally into hamsters induces widespread alveolar enlargement with subpleural bullae. A uniformly severe lesion is consistently induced by 0-2 mg elastase per 100 g body weight and with negligible mortality. Compared with controls, which showed no lesion, elastase-damaged lungs show a highly significant (P less than or equal to 0-001) increase in alveolar size and a decrease in internal surface area. Taken with the associated physiological abnormalities, these findings closely simulate human emphysema of the panlobular (panacinar) type. Histologically it appears that elastase converts the fine elastic fibres in alveolar walls and pleura into thickened, nodular fibres which may also be broken along their length. With higher doses of elastase, i.e., 0-5 mg/100 g body weight, many pulmonary arteries showed segmental loss of inner and outer elastic laminae, usually with thrombosis on the overlying endothelium. The mechanism of this thrombosis is unclear. These experiments suggest that damage to elastic fibres may be an important element in the development of human panacinar emphysema, and that the damage could be one pathogenetic mechanism which produces damage of elastic fibres.