Increased Mean Linear Intercept Research Articles

Bone marrow cells repair cigarette smoke-induced emphysema in rats

The therapeutic potential of stem cells in chronic obstructive pulmonary disease is not well known although stem cell therapy is effective in models of other pulmonary diseases. We tested the capacities of bone marrow cells (BMCs), mesenchymal stem cells (MSCs), and conditioned media of MSCs (MSC-CM) to repair cigarette smoke-induced emphysema. Inbred female Lewis rats were exposed to cigarette smoke for 6 mo and then received BMCs, MSCs, or MSC-CM from male Lewis rats. For 2 mo after injection, the BMC treatment gradually alleviated the cigarette smoke-induced emphysema and restored the increased mean linear intercept. The BMC treatment significantly increased cell proliferation and the number of small pulmonary vessels, reduced apoptotic cell death, attenuated the mean pulmonary arterial pressure, and inhibited muscularization in small pulmonary vessels. However, only a few male donor cells were detected from 1 day to 1 mo after BMC administration. The MSCs and cell-free MSC-CM also induced the repair of emphysema and increased the number of small pulmonary vessels. Our data show that BMC, MSCs, and MSC-CM treatment repaired cigarette smoke-induced emphysema. The repair activity of these treatments is consistent with a paracrine effect rather than stem cell engraftment because most of the donor cells disappeared and because cell-free MSC-CM also induced the repair.

Granulocyte Colony Stimulating Factor Attenuates Hyperoxia-Induced Lung Injury by Down-Modulating Inflammatory Responses in Neonatal Rats

PurposeGranulocyte colony stimulating factor (G-CSF) has been known to increase neutrophil production and have anti-inflammatory properties, but the effect of G-CSF on pulmonary system is in controversy. We investigated whether G-CSF treatment could attenuate hyperoxia-induced lung injury, and whether this protective effect is mediated by the down-modulation of inflammatory responses in a neonatal rat model.Materials and MethodsNewborn Sprague-Dawley rats (Orient Co., Seoul, Korea) were subjected to 14 days of hyperoxia (90% oxygen) beginning within 10 h after birth. G-CSF (20 µg/kg) was administered intraperitoneally on the fourth, fifth, and sixth postnatal days.ResultsThis treatment significantly improved hyperoxia-induced reduction in body weight gain and lung pathology such as increased mean linear intercept, mean alveolar volume, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling positive cells. Hyperoxia-induced activation of nicotinamide adenine dinucleotide phosphate oxidase, which is responsible for superoxide anion production, as evidenced by upregulation and membrane translocation of p67phox was significantly attenuated after G-CSF treatment, as were inflammatory responses such as increased myeloperoxidase activity and mRNA expression of transforming growth factor-β. However, the attenuation of other proinflammatory cytokines such as tumor necrosis factor-α and interleukin-6 was not significant.ConclusionIn sum, G-CSF treatment significantly attenuated hyperoxia-induced lung injury by down-modulating the inflammatory responses in neonatal rats.

α-PHENYL-N-tert-BUTYLNITRONE ATTENUATES HYPEROXIA-INDUCED LUNG INJURY BY DOWN-MODULATING INFLAMMATION IN NEONATAL RATS

This study was done to determine whether α -phenyl-N-tert-butylnitrone (PBN), a spin-trapping agent possessing significant anti-inflammatory capabilities, could attenuate hyperoxia-induced lung injury, and if so, whether this protective effect is mediated by the down-modulation of inflammation in neonatal rats. Newborn Sprague-Dawley rat pups were subjected to 14 days of hyperoxia (> 90% oxygen) within 10 hours after birth. PBN treatment, given 100 mg/kg intraperitoneally daily throughout the experiment, significantly attenuated hyperoxia-induced lung pathology, such as decreased radial alveolar count, increased mean linear intercept, and terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick end labeling–positive cells. Hyperoxia-indcued activation of nicotinamide adenine dinucleotide phosphate oxidase that is responsible for superoxide anion production, as evidenced by up-regulation and membrane translocation of p67phox, and the inflammatory responses, such as increased mRNA expression of tumor necrosis factor-α, interleukin-6, and transforming growth factor-β, were also significantly attenuated with PBN treatment. In summary, a spin-trapping agent PBN significantly attenuated hyperoxia-induced lung injury by down-regulating the inflammatory responses in neonatal rats.

Lung alveolar integrity is compromised by telomere shortening in telomerase-null mice

Shortened telomeres are a normal consequence of cell division. However, telomere shortening past a critical point results in cellular senescence and death. To determine the effect of telomere shortening on lung, four generations of B6.Cg-Terc(tm1Rdp) mice, null for the terc component of telomerase, the holoenzyme that maintains telomeres, were bred and analyzed. Generational inbreeding of terc-/- mice caused sequential shortening of telomeres. Lung histology from the generation with the shortest telomeres (terc-/- F4) showed alveolar wall thinning and increased alveolar size. Morphometric analysis confirmed a significant increase in mean linear intercept (MLI). terc-/- F4 lung showed normal elastin deposition but had significantly decreased collagen content. Both airway and alveolar epithelial type 1 cells (AEC1) appeared normal by immunohistochemistry, and the percentage of alveolar epithelial type 2 cells (AEC2) per total cell number was similar to wild type. However, because of a decrease in distal lung cellularity, the absolute number of AEC2 in terc-/- F4 lung was significantly reduced. In contrast to wild type, terc-/- F4 distal lung epithelium from normoxia-maintained mice exhibited DNA damage by terminal deoxynucleotidyltransferase (TdT)-mediated dUTP nick end labeling (TUNEL) and 8-oxoguanine immunohistochemistry. Western blotting of freshly isolated AEC2 lysates for stress signaling kinases confirmed that the stress-activated protein kinase (SAPK)/c-Jun NH(2)-terminal kinase (JNK) stress response pathway is stimulated in telomerase-null AEC2 even under normoxic conditions. Expression of downstream apoptotic/stress markers, including caspase-3, caspase-6, Bax, and HSP-25, was also observed in telomerase-null, but not wild-type, AEC2. TUNEL analysis of freshly isolated normoxic AEC2 showed that DNA strand breaks, essentially absent in wild-type cells, increased with each successive terc-/- generation and correlated strongly with telomere length (R(2) = 0.9631). Thus lung alveolar integrity, particularly in the distal epithelial compartment, depends on proper telomere maintenance.

Intratracheal Administration of Endotoxin Attenuates Hyperoxia-Induced Lung Injury in Neonatal Rats

PurposeThis study was undertaken to determine the effects of intratracheal administration of endotoxin on hyperoxia-induced lung injury in neonatal rats.Materials and MethodsNewborn Sprague Dawley rat pups were divided into four experimental groups: normoxia control (NC), normoxia with endotoxin treatment (NE), hyperoxia control (HC), and hyperoxia with endotoxin treatment (HE) groups. In HC and HE, rat pups were subjected to 14 days of hyperoxia (> 95% oxygen) within 12 hours after birth. In endotoxin treated group (NE and HE), Escherichia coli endotoxin (0.5µg in 0.03mL of saline) was given intratracheally at the 1st, 3rd and 5th postnatal day. Radial alveolar count (RAC), mean linear intercept (MLI), RAC/MLI ratios, and degree of fibrosis were measured to assess the changes in lung morphology.ResultsDuring the research period, survival rates in both HC and HE were notably reduced 7 days after endotoxin was administered, but body weight gain was considerably reduced only in HC. On day 14, significant arrest in alveolarization, as evidenced by the decrease of RAC and RAC/MLI ratio and increase of MLI as well as increased fibrosis, were noted in HC. Although slight but significant arrest in alveolarization and increased fibrosis score were observed in NE compared to NC, the hyperoxia-induced lung damage observed in HC was significantly improved in HE.ConclusionThis study suggests that intratracheal administration of endotoxin significantly attenuated hyperoxia-induced lung injury in neonatal rats.

Pulmonary Inflammation in Mice Exposed to Mainstream Cigarette Smoke

Male C57Bl/6 (C57) and ICR mice were exposed by nose-only inhalation to mainstream cigarette smoke (MS) from 2R4F reference cigarettes, at concentrations of 75, 250, and 600 μ g of total particulate matter (TPM) per liter, for up to 6 mo. Respiratory-tract tissue (nose, larynx, and lung), blood, and bronchoalveolar lavage fluid (BALF) samples were collected and analyzed at several time points. Blood samples were analyzed for biomarkers of exposure (COHb and nicotine). BALF was analyzed for biomarkers of cell injury, inflammation, oxidative stress, enzyme activity, and cytokines. Blood COHb and plasma nicotine concentrations increased in a dose-dependent manner, confirming smoke exposure. Mild emphysema was observed following 28 wk of exposure. Macrophage accumulation and inflammatory infiltrates were observed around the alveolar ducts and adjacent vasculature. There was a ∼ 13% increase in mean linear intercept (Lm) only in ICR mice exposed to 600 μ g/L TPM. There were no significant changes in biomarkers of oxidative stress secondary to smoke exposures; however, 8-isoprostane significantly increased following the 13-wk post-inhalation period. BALF macrophage and neutrophil counts were rapidly and consistently elevated, while lymphocyte counts gradually increased over time. MS-induced inflammatory responses observed in this study are comparable to changes reported in chronic smokers, supporting the role of chronic inflammation in the pathogenesis of emphysema. However, mild emphysema in minimal numbers of mice suggests that MS exposure concentration and/or duration in the current study were not sufficient to induce a definitive emphysema phenotype.

Erythropoietin Attenuates Hyperoxia-Induced Lung Injury by Down-modulating Inflammation in Neonatal Rats

This study was done to determine whether recombinant human erythropoietin (rhEPO) treatment could attenuate hyperoxia-induced lung injury, and if so, whether this protective effect is mediated by the down-modulation of inflammation in neonatal rats. Newborn Sprague Dawley rat pups were subjected to 14 days of hyperoxia (>95% oxygen) within 10 hr after birth. Treatment with rhEPO significantly attenuated the mortality and reduced body weight gain caused by hyperoxia. With rhEPO treatment, given 3 unit/gm intraperitoneally at 4th, 5th, and 6th postnatal day, hyperoxia-induced alterations in lung pathology such as decreased radial alveolar count, increased mean linear intercept, and fibrosis were significantly improved, and the inflammatory changes such as myeloperoxidase activity and tumor necrosis factor-alpha expression were also significantly attenuated. In summary, rhEPO treatment significantly attenuated hyperoxia-induced lung injury by down-modulating the inflammatory responses in neonatal rats.

Cigarette Smoke–induced Emphysema

Little is known about what drives the inflammatory reaction in the development of chronic obstructive lung disease. B cells have been found. To study the involvement of B cells in the development of emphysema. The presence of B-cell follicles and their interaction with other cells were investigated in lungs of patients with chronic obstructive pulmonary disease and of smoking mice. B cells were isolated from lymphoid follicles by laser microdissection and analyzed for the presence of immunoglobulin rearrangements and somatic mutations. Lymphoid follicles consisting of B cells and follicular dendritic cells with adjacent T cells were demonstrated both in the parenchyma and in bronchial walls of patients with emphysema. A clonal process was observed in all follicles and the presence of ongoing somatic mutations was observed in 75% of the follicles, indicating oligoclonal, antigen-specific proliferation. Similar lymphoid follicles were detected in mice that had developed pulmonary inflammation and progressive alveolar airspace enlargement after smoking. The increase in the number of B-cell follicles was progressive with time and correlated with the increase in mean linear intercept. Specific bacterial or viral nucleic acids could not be detected. B-cell follicles with an oligoclonal, antigen-specific reaction were found in men and mice with emphysema. In mice, the development was progressive with time and correlated with the increase in airspace enlargement. We hypothesize that these B cells contribute to the inflammatory process and/or the development and perpetuation of emphysema by producing antibodies against either tobacco smoke residues or extracellular matrix components.

Inhaled NO restores lung structure in eNOS-deficient mice recovering from neonatal hypoxia

We have previously shown that neonatal mice deficient in endothelial nitric oxide synthase (eNOS-/-) are more susceptible to hypoxic inhibition of alveolar and vascular growth. Although eNOS is downregulated, the role of nitric oxide (NO) during recovery after neonatal lung injury is poorly understood. We hypothesized that lung vascular and alveolar growth would remain impaired in eNOS-/- mice during recovery in room air and that NO therapy would augment compensatory lung growth in the eNOS-/- mice during recovery. Mice (1 day old) from heterozygous (eNOS+/-) parents were placed in hypobaric hypoxia (Fi(O2) = 0.16). After 10 days, pups were to recovered in room air (HR group) or inhaled NO (10 parts/million; HiNO group) until 3 wk of age, when lung tissue was collected. Morphometric analysis revealed that the eNOS-/- mice in the HR group had persistently abnormal lung structure compared with eNOS-sufficient (eNOS+/+) mice (increased mean linear intercept and reduced radial alveolar counts, nodal point density, and vessel density). Lung morphology of the eNOS+/- was not different from eNOS+/+. Inhaled NO after neonatal hypoxia stimulated compensatory lung growth in eNOS-/- mice that completely restored normal lung structure. eNOS+/- mice (HR group) had a 2.5-fold increase in lung vascular endothelial growth factor (VEGFR)-2 protein compared with eNOS+/+ (P < 0.05). eNOS-/- mice (HiNO group) had a 66% increase in lung VEGFR-2 protein compared with eNOS-/- (HR group; P < 0.01). We conclude that deficiency of eNOS leads to a persistent failure of lung growth during recovery from neonatal hypoxia and that, after hypoxia, inhaled NO stimulates alveolar and vascular growth in eNOS-/- mice.

Time course of cigarette smoke-induced pulmonary inflammation in mice

Inflammation of the airways and lung parenchyma plays a major role in the pathogenesis of chronic obstructive pulmonary disease. In the present study a murine model of tobacco smoke-induced emphysema was used to investigate the time course of airway and pulmonary inflammatory response, with a special emphasis on pulmonary dendritic cell (DC) populations. Groups of mice were exposed to either cigarette smoke or to control air for up to 24 weeks. In response to cigarette smoke, inflammatory cells (i.e. neutrophils, macrophages and lymphocytes) progressively accumulated both in the airways and lung parenchyma of mice. Furthermore, a clear infiltration of DCs was observed in airways (10-fold increase) and lung parenchyma (1.5-fold increase) of cigarette-exposed mice at 24 weeks. Flow cytometric analysis of bronchoalveolar lavage (BAL) DCs of smoke-exposed mice showed upregulation of major histocompatability complex II molecules and costimulatory molecules CD40 and CD86, compared with BAL DCs of air-exposed mice. Morphometric analysis of lung histology demonstrated a significant increase in mean linear intercept and alveolar wall destruction after 24 weeks of smoke exposure. In conclusion, the time course of the changes in inflammatory and dendritic cells in both bronchoalveolar lavage and the pulmonary compartment of cigarette smoke-exposed mice was carefully characterised.

NO 2-induced airway inflammation is associated with progressive airflow limitation and development of emphysema-like lesions in C57BL/6 mice

The major features of chronic obstructive pulmonary disease (COPD) comprise a not fully reversible airflow limitation associated with an abnormal inflammatory response, increased mucus production and development of emphysema-like lesions. Animal models that closely mimic these alterations represent an important issue for the investigation of pathophysiological mechanisms. Since most animal models in this area have focused on specific aspects of the disease, we aimed to investigate whether exposure of C57BL/6 mice to nitrogen dioxide (NO 2) may cause a more complex phenotype covering several of the characteristics of the human disease. Therefore, mice were exposed to NO 2 for 14 h each day for up to 25 days. Initial dose response experiments revealed the induction of a significant inflammatory response at a dose of 20 ppm NO 2. Mice developed progressive airway inflammation together with a focal inflammation of the lung parenchyma characterized by a predominant influx of neutrophils and macrophages. In addition, goblet cell hyperplasia was detected in the central airways and increased collagen deposition was found in the lung parenchyma. NO 2-exposed mice developed emphysema-like lesions as indicated by a significantly increased mean linear intercept as compared to control mice. Finally, the assessment of lung functional parameters revealed the development of progressive airway obstruction over time. In conclusion, our data provide evidence that the inflammatory response to NO 2 exposure is associated with increased mucus production, development of airspace enlargement and progressive airway obstruction. Thus, NO 2-exposed mice may serve as a model to investigate pathophysiological mechanisms that contribute to the development of human COPD.

Tumor necrosis factor-alpha drives 70% of cigarette smoke-induced emphysema in the mouse.

Mice lacking tumor necrosis factor-alpha (TNF-alpha) receptors (TNFRKO mice) do not develop an inflammatory infiltrate or matrix breakdown after a single acute cigarette smoke exposure. To determine the role of TNF-alpha in the long-term development of emphysema, mice were exposed to smoke for 6 months. TNFRKO mice demonstrated an 11% increase in mean linear intercept; wild-type mice had a 38% increase. TNFRKO mice had 65% fewer neutrophils and no increase in macrophages in lavage fluid. Whole lung matrix metalloprotease (MMP)-2, MMP-9, MMP-12, MMP-13, and matrix type-1 (MT1)-MMP proteins were increased in wild-type mice, but smaller increases in MMP-12, MMP-13, and MT1-MMP were also seen in TNFRKO mice. Lavage matrix breakdown products were elevated in wild-type mice and only partially reduced by anti-neutrophil antibody, implying both neutrophil- and non-neutrophil-mediated matrix breakdown. We conclude that TNF-alpha-mediated processes, probably driving neutrophil influx, are responsible for approximately 70% of airspace enlargement and the majority of inflammatory cell influx/matrix breakdown in the mouse model. TNF-alpha causes increased MMP production, but some increased MMP activity is present even in TNFRKO mice. These findings imply a second TNF-alpha-independent process, possibly related to direct MMP attack on matrix, that produces the remaining 30% of airspace enlargement.

Methylprednisolone causes matrix metalloproteinase-dependent emphysema in adult rats.

Previous investigations have shown that corticosteroids affect the development and maturation of the developing lung in utero and in neonatal animals. Systemic corticosteroids are routinely used for the treatment of acute exacerbations of chronic obstructive pulmonary disease, and inhaled corticosteroids are more frequently being prescribed for the long-term treatment of patients with chronic obstructive pulmonary disease. Because corticosteroids can affect matrix metalloproteinases and because the concept of protease/antiprotease imbalance is an important concept regarding the pathogenesis of emphysema, we examined the effects of chronic steroid treatment on lung structure in adult rats. Rats treated with 2 mg/kg of methylprednisolone daily for 1, 2, or 4 weeks had an increased mean linear intercept and a decrease of the surface-volume ratio when compared with age-matched control animals, and the animals showed increased matrix metalloproteinase-9 activity in their lungs on zymography. Rats treated concomitantly with methylprednisolone and a broad-spectrum matrix metalloproteinase inhibitor (GM6001) did not develop emphysema. We conclude that systemic treatment of adult rats with the antiinflammatory steroid methylprednisolone increases the activity of matrix metalloproteinases in the lung and causes emphysema.

Alpha1-antitrypsin determines the pattern of emphysema and function in tobacco smoke-exposed mice: parallels with human disease.

Cigarette smoking in humans is associated with various patterns of emphysema and functional consequences. We tested the hypothesis that variations in alpha1-antitrypsin expression modulate the pattern of emphysema and functional consequences in cigarette smoke-exposed mice. We compared the effects of up to 6 months of cigarette smoke exposure in C57BL/6J (C57) mice and in low-alpha1-antitrypsin, C57BL/6J pa+/pa+ (pallid) mice. At the end of the experiment, we determined lung mechanical properties, the extent (mean linear intercept) and type of emphysema, and the cellular inflammatory response. After 4 months of cigarette smoking, pallid smoking mice, but not C57 smoking mice, had a significant increase in mean linear intercept. After 6 months of smoke exposure, C57 smoking mice and pallid smoking mice had similar degrees of emphysema. The pattern of emphysema in pallid smoking mice was more diffuse than in C57 smoking mice, affecting all airspaces. Pallid mice, but not C57 mice, developed a T cell inflammation in the alveolar wall after 6 months of smoking (p < 0.01). Although lung compliance was not changed in C57 smoking mice after smoke exposure, it increased significantly in pallid smoking mice over the 6 months of exposure (p < 0.0082). In summary, cigarette smoking induces emphysema in C57 and pallid mice, but the emphysema, inflammatory infiltrate, and resulting physiologic abnormalities were substantially different in the two strains, with the C57 and pallid mice exhibiting features similar to centrilobular and panlobular emphysema, respectively.

Distal Airspace Enlargement in the Fawn-Hooded Rat: Influences of Aging and Alveolar Wall Destruction

Background: A recent study has revealed that the peripheral airspace in the lungs of the fawn-hooded rat (FHR) is enlarged. However, morphological and functional factors of the FHR lung have not been fully investigated. Objective: The purpose of our study was to examine the structural and functional changes in the FHR lung and to investigate the influence of aging on this process. Furthermore, morphological and functional measurements of the lungs of FHRs (4–48 weeks of age) were performed and the results compared with those of age-matched Wistar control rats (WCRs). Methods: All animals were studied under controlled conditions, and morphological and functional changes of the lungs were examined. Measurements of body and lung weights were recorded, and the lungs were subjected to morphological evaluation. Morphological measurements: mean linear intercept (MLI) and destructive index were determined. Functional evaluation of the lungs: total lung capacity, pressure-volume curve, and exponential constant (K) which describes the shape of the curve were analyzed. In addition, right ventricular hypertrophy measurements were performed to assess the severity of pulmonary hypertension. Statistical analysis was performed using the unpaired t test, analysis of variance, and the Fisher post hoc test (p < 0.05). Results: Morphological analysis revealed a significant increase in airspace size (MLI) in all FHRs as compared with the WCRs which was evident from an early age (4 weeks). The increase in MLI did not progress age dependently in the FHR, whereas a tendency for an age-dependent increase in MLI was observed in the WCR. The destructive index measurements revealed that the increase in MLI of FHR was not accompanied by alveolar wall destruction. Concerning the functional examination, a leftward and upward shift of the pressure-volume curve was observed in the FHRs as compared with the WCRs at all ages. As compared with the WCRs, a higher K value was observed in all FHRs which was evident from an early age (4 weeks). Age-dependent changes similar to those in MLI were observed in the K in both rat strains. Conclusions: The results of our study suggest that FHRs manifest characteristics of distal airspace enlargement accompanied by increased lung distensibility without alveolar wall destruction at an early age and that the changes do not progress age dependently. Neither an accelerated aging process nor destruction of the alveolar walls appears to be the mechanism responsible for the enlarged airspace in this rat strain.

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.

Effect of indomethacin on lung development in postnatal rats: possible role of prostaglandin in alveolar formation

We administered 1.3 mg ip of indomethacin, a prostaglandin synthetase inhibitor, per 100 g body wt to male rat pups daily on postnatal days 4-13 and examined their lungs on day 14. Indomethacin administration produced abnormal lung structure with diminished alveolar air, increased alveolar duct air, increased mean linear intercept (gas-exchanging wall distance), diminished gas-exchanging surface area and surface-to-volume ratio, increased septal wall thickness, diminished the number of alveolar crests, and increased the number of lamellar bodies in alveolar type II cells. However, this procedure did not alter quantitative lung growth (normal lung weights, volumes, and DNA and protein contents). Tissue prostaglandin content was decreased. The total amount of lung collagen or elastin was unchanged, but when collagen was analyzed into soluble and insoluble components, soluble collagen was increased. Supplementation with 1.0 g of prostaglandin E2 per 100 g body wt to animals treated with indomethacin reduced the abnormalities in pulmonary architecture. We conclude that indomethacin affects lung structure in growing rats and that it is an unusual model in that lung growth is normal, but lung development is abnormal. We also suggest that prostaglandins may play a significant role in alveolar formation in postnatal lung development in rats.

Oxidants from Neutrophil Myeloperoxidase Do not Enhance Elastase-lnduced Emphysema in the Hamster

Alpha-1-protease inhibitor is susceptible to oxidative impairment by the neutrophil myeloperoxidase (MPO) system. The purpose of this study was to assess the effect of the MPO oxidant system on elastase-induced emphysema in the hamster. Intratracheal instillation of 200 micrograms of human neutrophil elastase (HNE) induced a significant secretory cell metaplasia (SCM) and airspace enlargement [23% increase in mean linear intercept (MLI) as compared with control values]. Instillation of MPO system components [0.6 international units (U) of MPO, 5.5 U of glucose oxidase and glucose (0.02 M)] along with 200 micrograms HNE failed to enhance the severity of the SCM or emphysema induced by HNE alone. A second experiment was carried out using 50 micrograms of porcine pancreatic elastase (PPE) to induce emphysema. PPE produced a significant 45% increase in MLI, but the MPO system combined with PPE failed to enhance the emphysema induced by PPE alone. The MPO system alone had no measurable effect on airspace size or SCM. In vitro studies showed that PPE was partially inactivated by the MPO system; a 56% loss of elastolytic activity occurred during a 6-min incubation of PPE with the MPO system. This may explain why the MPO system did not exacerbate PPE-induced injury, but it does not explain the lack of enhancement for HNE. A 6-minute incubation of HNE with the MPO system resulted in a nonsignificant 10% decrease of elastolytic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

123I]HIPDM pulmonary imaging demonstrates elastase-induced pulmonary emphysema.

Because more than 90 percent of [123I]hydroxyiodobenzyl-propanediamine (HIPDM) is localized in the lung after intravenous injection, the radiopharmaceutical has been proposed as a lung imaging agent. Its potential usefulness for the detection of pulmonary emphysema was evaluated in an animal model of elastase-induced emphysema along with [99mTc]MAA lung perfusion imaging. To induce lung emphysema, Long-Evans rats (200-250 g) were given 400 IU/Kg elastase intratracheally under ether anesthesia. Four weeks after elastase treatment, 15 treated and 15 nontreated rats were paired and simultaneously imaged under a scintillation camera immediately following intravenous injection of 0.25-0.3 mCi[99mTc]MAA. The procedure was repeated 48 hr later using 0.25-0.3 mCi[123I]HIPDM. Activity in the region of interest (ROI) over the lungs was recorded after the injections. Total counts per ROI from each rat were measured and normalized by lung volume. The normalized lung activity ratio of treated/nontreated rats was computed. The mean ratios of HIPDM and MAA were 0.847 and 0.802, respectively. The significant decrease in uptake of both HIPDM (p < 0.021) and of MAA (p < 0.025) in the elastase-treated lungs indicates decrease in functioning vascular endothelium and decrease in number of pulmonary capillary vessels, respectively, reflecting damage in capillaries and small arterioles. The decrease in treated/nontreated ratios lung is consistent with a significant alteration in pulmonary function and a significant increase in mean linear intercept (p < 0.005) in treated lung. Since the imaging reflects pulmonary endothelial receptor function, [123I]HIPDM lung imaging may serve as an alternative diagnostic modality for pulmonary emphysema.

The effect of age on postpneumonectomy growth in rabbits

To assess the effect which age at pneumonectomy has on pulmonary compensatory growth, male New Zealand white rabbits underwent left pneumonectomy or sham thoracotomy at 10, 18, or 26 weeks of age. Morphometric and biochemical evaluation of the remaining lungs was carried out four weeks later. There was significant compensatory growth in terms of lung volume, weight, DNA, RNA, and protein in all three age groups. Lung volume response was incomplete, i.e., right lung volume of the experimental animals did not match the volume of both lungs of controls; other variables were not significantly different between the right lung of experimentals and both lungs of the controls. An unchanged surface area per unit volume accompanied by a stable mean linear intercept indicated that alveolar multiplication occurred in the 10 and 18 week age groups. The oldest group had significantly decreased surface area per unit volume and significantly increased mean linear intercept, suggesting an increase in the size of existing alveoli at 26 weeks of age.