Lungs Of Exposed Rats Research Articles

Ex Vivo Lung Perfusion with β-Nicotinamide Adenine Dinucleotide (NAD+) Improves Ischemic Lung Function

Ischemia-reperfusion injury compromises short- and long-term outcomes after lung transplantation. The scarce existing data on NAD+ suggest effects on hypoxia-induced vasoconstriction, on reactive oxygen species and on tampering inflammation. We exposed rat lungs to 14 h of cold ischemic storage and perfused them in a rat ex vivo lung perfusion (EVLP) system for 4 h. A control group (n = 6) was compared to groups receiving 100 µM (n = 6) or 200 µM NAD+ (n = 6) in the preservation solution and groups receiving 200 µM (n = 4) or 2000 µM (n = 6) NAD+ every 30 min in the perfusate, starting at 1 h of EVLP. Compared to the control, significant effects were only achieved in the 2000 µM NAD+ group. During the 4 h of EVLP, we monitored higher vascular flow, lower mean pulmonary arterial pressure and increased oxygenation capacity. Tissue inflammation estimated with the myeloperoxidase assay was lower in the 2000 µM NAD+ group. We observed higher levels of anti-inflammatory IL-10, higher anti-inflammatory IL-6/IL-10 ratios and lower levels of pro-inflammatory IL-12 and IL-18 as well as a trend of more anti-inflammatory IFNy in the 2000 µM NAD+ perfusate. In the bronchoalveolar lavage, the pro-inflammatory levels of IL-1α and IL-1β were lower in the 2000 µM NAD+ group. NAD+ administered during EVLP is a promising agent with both anti-inflammatory properties and the ability to improve ischemic lung function.

Proteomic profile of TGF-β1 treated lung fibroblasts identifies novel markers of activated fibroblasts in the silica exposed rat lung

We performed liquid chromatography-tandem mass spectrometry (LC-MS/MS) on control and TGF-β1-exposed rat lung fibroblasts to identify proteins differentially expressed between cell populations. A total of 196 proteins were found to be differentially expressed in response to TGF-β1 treatment. Guided by these results, we next determined whether similar changes in protein expression were detectable in the rat lung after chronic exposure to silica dust. Of the five proteins selected for further analysis, we found that levels of all proteins were markedly increased in the silica-exposed rat lung, including the proteins for the very low density lipoprotein receptor (VLDLR) and the transmembrane (type I) heparin sulfate proteoglycan called syndecan 2 (SDC2). Because VLDLR and SDC2 have not, to our knowledge, been previously linked to the pathobiology of silicosis, we next examined whether knockdown of either gene altered responses to TGF-β1 in MRC-5 lung fibroblasts. Interestingly, we found knockdown of either VLDLR or SDC2 dramatically reduced collagen production to TGF-β1, suggesting that both proteins might play a novel role in myofibroblast biology and pathogenesis of silica-induced pulmonary fibrosis. In summary, our findings suggest that performing LC-MS/MS on TGF-β1 stimulated lung fibroblasts can uncover novel molecular targets of activated myofibroblasts in silica-exposed lung.

Metabolic Changes Precede the Development of Pulmonary Hypertension in the Monocrotaline Exposed Rat Lung.

There is increasing interest in the potential for metabolic profiling to evaluate the progression of pulmonary hypertension (PH). However, a detailed analysis of the metabolic changes in lungs at the early stage of PH, characterized by increased pulmonary artery pressure but prior to the development of right ventricle hypertrophy and failure, is lacking in a preclinical animal model of PH. Thus, we undertook a study using rats 14 days after exposure to monocrotaline (MCT), to determine whether we could identify early stage metabolic changes prior to the manifestation of developed PH. We observed changes in multiple pathways associated with the development of PH, including activated glycolysis, increased markers of proliferation, disruptions in carnitine homeostasis, increased inflammatory and fibrosis biomarkers, and a reduction in glutathione biosynthesis. Further, our global metabolic profile data compare favorably with prior work carried out in humans with PH. We conclude that despite the MCT-model not recapitulating all the structural changes associated with humans with advanced PH, including endothelial cell proliferation and the formation of plexiform lesions, it is very similar at a metabolic level. Thus, we suggest that despite its limitations it can still serve as a useful preclinical model for the study of PH.

Perinatal nicotine exposure suppresses PPARγ epigenetically in lung alveolar interstitial fibroblasts.

Due to the active inhibition of the adipogenic programming, the default destiny of the developing lung mesenchyme is to acquire a myogenic phenotype. We have previously shown that perinatal nicotine exposure, by down-regulating PPARγ expression, accentuates this property, culminating in myogenic pulmonary phenotype, though the underlying mechanisms remained incompletely understood. We hypothesized that nicotine-induced PPARγ down-regulation is mediated by PPARγ promoter methylation, controlled by DNA methyltransferase 1 (DNMT1) and methyl CpG binding protein 2 (MeCP2), two known key regulators of DNA methylation. Using cultured alveolar interstitial fibroblasts and an in vivo perinatal nicotine exposure rat model, we found that PPARγ promoter methylation is strongly correlated with inhibition of PPARγ expression in the presence of nicotine. Methylation inhibitor 5-aza-2'-deoxycytidine restored the nicotine-induced down-regulation of PPARγ expression and the activation of its downstream myogenic marker fibronectin. With nicotine exposure, a specific region of PPARγ promoter was significantly enriched with antibodies against chromatin repressive markers H3K9me3 and H3K27me3, dose-dependently. Similar data were observed with antibodies against DNA methylation regulatory factors DNMT1 and MeCP2. The knock down of DNMT1 and MeCP2 abolished nicotine-mediated increases in DNMT1 and MeCP2 protein levels, and PPARγ promoter methylation, restoring nicotine-induced down regulation of PPARγ and upregulation of the myogenic protein, fibronectin. The nicotine-induced alterations in DNA methylation modulators DNMT1 and MeCP2, PPARγ promoter methylation, and its down-stream targets, were also validated in perinatally nicotine exposed rat lung tissue. These data provide novel mechanistic insights into nicotine-induced epigenetic silencing of PPARγ that could be exploited to design novel targeted molecular interventions against the smoke exposed lung injury in general and perinatal nicotine exposure induced lung damage in particular.

Sildenafil Potentiates Bone Morphogenetic Protein Signaling in Pulmonary Arterial Smooth Muscle Cells and in Experimental Pulmonary Hypertension

Mutations in the bone morphogenetic protein type II receptor (BMPR-II) are responsible for the majority of cases of heritable pulmonary arterial hypertension (PAH), and BMPR-II deficiency contributes to idiopathic and experimental forms of PAH. Sildenafil, a potent type-5 nucleotide-dependent phosphodiesterase inhibitor, is an established treatment for PAH, but whether sildenafil affects bone morphogenetic protein (BMP) signaling in the pulmonary circulation remains unknown. Studies were undertaken in human pulmonary arterial smooth muscle cells (PASMCs) and in vivo in the monocrotaline rat model of PAH. In PASMCs, sildenafil enhanced BMP4-induced phosphorylation of Smad1/5, Smad nuclear localization, and Inhibitor of DNA binding protein 1 gene and protein expression. This effect was mimicked by 8-bromo-cyclic GMP. Pharmacological inhibition or small interfering RNA knockdown of cyclic GMP-dependent protein kinase I inhibited the effect of sildenafil on BMP signaling. In functional studies, we observed that sildenafil potentiated the antiproliferative effects of BMP4 on PASMC proliferation. Furthermore, sildenafil restored the antiproliferative response to BMP4 in PASMCs harboring mutations in BMPR-II. In the monocrotaline rat model of PAH, which is characterized by BMPR-II deficiency, sildenafil prevented the development of pulmonary hypertension and vascular remodeling, and partly restored Smad1/5 phosphorylation and Inhibitor of DNA binding protein 1 gene expression in vivo in monocrotaline exposed rat lungs. Sildenafil enhances canonical BMP signaling via cyclic GMP and cyclic GMP-dependent protein kinase I in vitro and in vivo, and partly restores deficient BMP signaling in BMPR-II mutant PASMCs. Our findings demonstrate a novel mechanism of action of sildenafil in the treatment of PAH and suggest that targeting BMP signaling may be beneficial in this disease.

Genomic instability in quartz dust exposed rat lungs: Is inflammation responsible?

Exposure to quartz dusts has been associated with lung cancer and fibrosis. Although the responsible mechanisms are not completely understood, progressive inflammation with associated induction of persistent oxidative stress has been discussed as a key event for these diseases. Previously we have evaluated the kinetics of pulmonary inflammation in the rat model following a single intratracheal instillation of 2mg DQ12 quartz, either in its native form or upon its surface modification with polyvinylpyridine-N-oxide or aluminium lactate. This model has been applied now to evaluate the role of inflammation in the kinetics of induction of DNA damage and response at 3, 7, 28, and 90 days after treatment. Bronchoalveolar lavage (BAL) cell counts and differentials as well as BAL fluid myeloperoxidase activity were used as markers of inflammation. Whole lung homogenate was investigated to determine the induction of the oxidative and pre-mutagenic DNA lesion 8-hydroxy-2-deoxy-guanosine (8-OHdG) by HPLC/ECD, while mRNA and protein expression of oxidative stress and DNA damage response genes including hemeoxygenase-1 (HO-1) and apurinic/apyrimidinic endonuclease (APE/Ref-1) were evaluated using Western blotting and real time PCR. Isolated lung epithelial cells from the treated rats were used for DNA strand breakage analysis using the alkaline comet assay as well as for micronucleus scoring in May-Gruenwald-Giemsa stained cytospin preparations. In the rats that were treated with quartz, no increased 8-OHdG levels were observed, despite the presence of a marked and persistent inflammation. However, DNA strand breakage in the lung epithelial cells of the quartz treated rats was significantly enhanced at 3 days, but not at 28 days. Moreover, significantly enhanced micronucleus frequencies were observed for all four time points investigated. In the animals that were treated with the PVNO modified quartz, micronuclei scores did not differ from controls, while in those treated with the aluminium coated quartz intermediate effects were found. These findings were in line with the kinetics of inflammation and epithelial proliferation in the rat lungs for the different treatments. Notably, a highly significant correlation was observed between neutrophil numbers and micronucleus frequencies, indicative for a role of inflammation in eliciting genomic instability in target cells of quartz-induced carcinogenesis. Our ongoing investigations focus on the evaluation of the causality between both in relation to quartz exposure.

Lung responses to secondary endotoxin challenge in rats exposed to pig barn air

BackgroundSwine barn air contains endotoxin and many other noxious agents. Single or multiple exposures to pig barn air induces lung inflammation and loss of lung function. However, we do not know the effect of exposure to pig barn air on inflammatory response in the lungs following a secondary infection. Therefore, we tested a hypothesis that single or multiple exposures to barn air will result in exaggerated lung inflammation in response to a secondary insult with Escherichia coli LPS (E. coli LPS).MethodsWe exposed Sprague-Dawley rats to ambient (N = 12) or swine barn air (N = 24) for one or five days and then half (N = 6/group) of these rats received intravenous E. coli LPS challenge, observed for six hours and then euthanized to collect lung tissues for histology, immunohistochemistry and ELISA to assess lung inflammation.ResultsCompared to controls, histological signs of lung inflammation were evident in barn exposed rat lungs. Rats exposed to barn air for one or five days and challenged with E. coli LPS showed increased recruitment of granulocytes compared to those exposed only to the barn. Control, one and five day barn exposed rats that were challenged with E. coli LPS showed higher levels of IL-1β in the lungs compared to respective groups not challenged with E. coli LPS. The levels of TNF-α in the lungs did not differ among any of the groups. Control rats without E. coli LPS challenge showed higher levels of TGF-β2 compared to controls challenged with E. coli LPS.ConclusionThese results show that lungs of rats exposed to pig barn air retain the ability to respond to E. coli LPS challenge.

The study on differential gene expression profiling in pulmonary tissue of rats exposed to silica early

To study the differential gene expression profiling of rats exposed to silica using the normal rats as control. Animal models were established using intratracheal injection of the lung and 22 107 genes were screened in the differential expression profiling of silicosis by using oligonucleotide bead array. Differential expression profiling data were analyzed by using DAVID bioinformation software. Totally 1567 differentially expressed genes were identified in lungs of silica exposed rats including 765 up-regulated genes and 802 down-regulated genes as compared to the normal controls. Among 406 annotated genes in KEGG pathways, 204 genes and 11 pathways were up-regulated as well as 202 genes and 3 pathways were down-regulated in silica exposed rats. All 1567 genes are involved in the formation of silicosis. The differential gene expression profile of silicosis describes the general changes in the gene expressions in silicosis at transcriptional level. Further analysis of the identified genes might help reveal the molecular mechanism of pulmonary fibrosis induced by silica.

Assessment of the Pulmonary Genotoxicity of Bitumen Fumes in Big Blue® Transgenic Rats

Occupational and environmental exposures to bitumen fumes during road paving or roofing activities represent a safety issue since this complex mixture of volatile compounds and particles contains carcinogenic polycyclic aromatic hydrocarbons (PAH). However, epidemiological and experimental animal studies failed to draw unambiguous conclusions concerning bitumen fumes toxicity. In order to gain better insights on their genotoxic potential, we used an experimental device able to generate bitumen fumes at 170°C (upper range used during road paving operations) with a total particulate matter of 112 ± 13 mg/m3 and a mass median aerodynamic diameter of 4.6 μ m. The nose-only exposure of Big Blue® transgenic rats was performed 6 h/day for 5 consecutive days. Biological exposure to this aerosol was monitored by measuring the rat urinary levels of 1-hydroxypyrene and lungs were collected at various time-points after the end of treatment for further analysis. As determined by the 32P post-labeling method, no DNA bulky adduct was found in control animal lungs, while one was detected in exposed rats 3 and 30 days after the end of treatment, suggesting that this genetic alteration was rather stable. However, there was no correlation between the amount of DNA adduct and the level of urinary of 1-hydroxypyrene. The pulmonary mutagenic properties of bitumen fumes were determined by analyzing the mutation frequency and spectrum of the neutral reporter gene cII inserted into the transgenic rodent genome. Thirty days after exposure, the cII mutant frequency was similar in control and exposed rat lungs. However, a modification of the mutation spectrum was noticeable in treated animals. The most striking difference was an increase of G:C to T:A and A:T to C:G transversions in exposed rodents. In addition, the increased occurrence of G:C to T:A transversions at CpG dinucleotides in treated animals was consistent with DNA adduction by PAH. Even though these data failed to demonstrate a clear pulmonary mutagenic potential of bitumen fumes in our experimental conditions, the analysis of the mutational spectrum provides a sensitive measure of a quantitative increase of specific mutations which may be associated with DNA adduct formation. The weak mutagenic response might also be related to the small inhalable fraction of bitumen fume particles reaching the deep lung. In conclusion, these results could give insights on the mechanism of action of bitumen fumes and provide additional information concerning human risk assessment associated with bitumen exposure.

Toll-like Receptor-4 message is up-regulated in LPS exposed rat lung pericytes

Introduction: Toll-Like Receptor 4 (TLR-4) has been implicated as the proximal transmembrane receptor for the LPS/CD 14 complex during the activation of LPS induced sepsis. TLR-4 is highly expressed in cells that respond to LPS, such as peripheral blood leukocytes, macrophages, and monocytes. Additionally, TLR-4 has been shown to be expressed on epithelial surfaces of the gastrointestinal tract, dendritic cells, and microvascular endothelial cells, but no data exists about the presence of TLR-4 in lung pericytes. Pericytes are multifunctional, polymorphic perivascular cells that lie within the microvessel basal lamina, located on the abluminal side of endothelial cells, and thought to play a regulatory role in capillary leak seen in sepsis. Lung pericytes incubated with LPS cause relaxation in a concentration dependant manner, but less is known about the mechanism of this action. It is our hypothesis that TLR-4 is present on lung pericytes and is up-regulated in response to LPS. Methods: Rat microvascular lung pericyte were isolated and cultured. Cells from passage 3-5 were used and treated with LPS (control, 10ng/ml, and 100ng/ml) for 18 hours. Immunostaining and immunoblotting were performed to detect the presence of CD-14, TLR-2, and TLR-4 at the protein level. Real-Time PCR was used to analyze the presence and quantity of mRNA for CD-14, TLR-2, and TLR-4. Results: Immunostaining and immunoblotting revealed the presence of CD-14, TLR-2, and TLR-4 in pericytes from each treatment group, and RT-PCR confirmed the presence of mRNA for CD-14, TLR-2, and TLR-4. A minimal increase in the mRNA was seen in CD-14 and TLR-2 as the cells were treated with increasing LPS, and a substantial increase in the mRNA for TLR-4 was noted in the presence of increasing LPS. Conclusions: This is the first report that clearly defines the presence of TLR-4 in lung pericytes. The substantial up-regulation of TLR-4 compared to that of CD-14 and TLR-2 in the presence of increasing LPS suggests its importance in pericyte LPS-induced activation. Pericyte TLR-4 recognition of LPS may play a role in capillary leak seen in gram-negative sepsis. This data also demonstrates that pericytes, once thought to be passive participants in the inflammatory cascade, may be active members.

The Effect of Lung Burden on Biopersistence and Pulmonary Effects in Rats Exposed to Potassium Octatitanate Whiskers by Inhalation

The effect of lung burden on biopersistence and histopathological changes caused by potassium octatitanate whiskers (POW) which is one of the asbestos substitutes were investigated for 1-yr and 4-wk inhalation periods. In the 1-yr inhalation experiment, male Wistar rats were exposed to POW (TW) for 6 h/d, 5 d/wk under the same conditions as a previous study of POW (PT1, JFM fiber) which is made by different manufacturer. The exposure concentration was 1.9 +/- 0.7 mg/m(3) and the mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) in the chamber were 1.6 microm and 2.9. Rats were sacrificed at 3 d and 1 yr after the inhalation experiment and TW deposits in the lungs were determined by ICP-AES. Lung burden at 3 d and 1 yr after the inhalation was 2.39 +/- 0.50 mg and 1.37 +/- 0.96 mg, respectively, the deposition fraction was 8.1% and biological half time (BHT) was 15 months. Aggregated dust cells and mild fibrotic changes around these dust cells were observed in the exposed rat lung. These results were almost the same as those obtained in the previous 1-yr PT1 study. In the 4-wk inhalation experiment, to investigate the effect of lung burden on biopersistence and histopathological change, male Wistar rats were exposed to PT1. The exposure concentration was 102 +/- 21 mg/m(3), MMAD (GSD), the geometiric mean length and diameter (GSD) of the PT1 in the chamber were 1.6 microm (3.0), 2.2 microm (1.8) and 0.33 microm (1.5), respectively. Rats were sacrificed at 3 d, 1 wk, and 1, 3, 6 and 12 months after the inhalation experiment. The lung burden of POW at 3 d after 4 wk inhalation was 1.49 +/- 0.19 mg, which was close to the estimated amount of overload. The BHT of the total mass (4.1 months) was not prolonged, but aggregated dust cells were observed in the subpleural region and around the bronchioles and mild fibrotic changes were observed only around the dust cells at one year after the 4-wk inhalation. It is considered that the excessive exposure which impairs the function of alveolar macrophage mediated clearance may cause the aggregation of dust cells and fibrotic changes.

ALTERED GENE EXPRESSION PROFILES OF RAT LUNG IN RESPONSE TO AN EMISSION PARTICULATE AND ITS METAL CONSTITUENTS

Comprehensive and systematic approaches are needed to understand the molecular basis for the health effects of particulate matter (PM) reported in epidemiological studies. Due to the complex nature of the pollutant and the altered physiological conditions of predisposed populations, it has been difficult to establish a direct cause and effect relationship. A high-throughput technology such as gene expression profiling may be useful in identifying molecular networks implicated in the health effects of PM and its causative constituents. Differential gene expression profiles derived for rat lungs exposed to PM and its constituent metals using a custom rat cardiopulmonary cDNA array are presented here. This array consists of 84 cardiopulmonary-related genes representing various biological functions such as lung injury/inflammation, repair/remodeling, structural and matrix alterations, and vascular contractility, as well as six expressed sequence tags (ESTs). The cDNA array was hybridized with 32 P-labeled cDNA generated from rat lung RNA. Total lung RNA was isolated from male Sprague-Dawley rats at 3 and 24 h following intratracheal instillation of either saline, residual oil fly ash (ROFA; 3.3 mg/kg), or its most toxic metallic constituents, nickel (NiSO 4 ; 3.3 mmol/kg) and vanadium (VSO 4 ; 5.7 mmol/kg). Metal concentrations reflected the levels present in one ROFA instillate. Densitometric scans of the array blots indicated ROFA- and metal-specific increased expression (1.5 to 3-fold) of stress response, inflammatory, and repair-related genes, and also genes involved in vascular contractility and thrombogenic activity. Expression of multiple cytokines in ROFA exposed rat lung compared to Ni and V suggest the role and importance of understanding constituent interactions in PM toxicity. Expression profiling using genomic approaches will aid in our understanding of toxicant-specific altered molecular pathways in lung injury and pathogenesis.

Early Oxidative DNA Damages and Late Development of Lung Cancer in Diesel Exhaust-Exposed Rats

To demonstrate DNA damages in the early stage of diesel exhaust exposure, an inhalation study of 1 through 12 months was conducted. The lung burden of diesel soot increased with increase in exposure duration. Histologically, hyperplastic foci of alveolar epithelia were found at 6-month exposure and became prominent at the 12th month, with slight nuclear atypia and positive p53 staining. The level of 8-OH-hydroxyguanosine (8-OH-dG) in the exposed rat lungs showed an increase from 1 month of exposure, followed by a gradual increase, reaching almost a plateau level at the 9th month. An in vitro experiment demonstrated significant 8-OH-dG formation when diesel particles and H2O2 were added to the DNA solution. The level of bulky aromatic DNA adducts peaked at the 1st month of exposure, followed by a decrease. By the end of the observation period of 30 months, lung tumors developed even in the 6-month exposure group, and the earliest lung tumors were found only in rats that survived longer than 18 months. In conclusion, persisting oxidative stress on DNA induced in the early phase of diesel exhaust exposure, together with inflammation, seems to play an important role in carcinogenesis at advance ages after a long latent period.

Upregulation of the PDGF-alpha receptor precedes asbestos-induced lung fibrosis in rats.

Platelet-derived growth factor-AA (PDGF-AA) and its matching alpha receptor (PDGF-R alpha) are upregulated in rat lung fibroblasts (RLFs) after exposure to chrysotile asbestos fibers in vitro, which results in asbestos-induced RLF proliferation. We now report our in vivo observations, which show an increase in the expression of PDGF-R alpha mRNA, but not PDGF-beta receptor mRNA, in asbestos-exposed rat lungs when compared with RNA from air-exposed (sham) and iron-exposed lungs. Western analysis of membrane preparations confirmed the observations on mRNA expression by demonstrating an increase in PDGF-R alpha peptide expression in the asbestos-exposed rat lungs, compared with that in the air-exposed lungs. Immunohistochemistry for the PDGF-R alpha was performed on air- and asbestos-exposed rat lungs and revealed a clear increase in staining within interstitial and subepithelial compartments in the exposed animals. These observations, along with our previous report demonstrating an increase in the PDGF-AA isoform expression immediately after asbestos-exposure, suggest a scenario in which a potent lung mesenchymal cell mitogen, PDGF-AA, and its alpha-receptor are upregulated prior to the development of a fibroproliferative lung lesion, and thus may play a central role in the pathogenesis of asbestos-induced lung fibrosis.

Impaired Regulation of Surfactant Phospholipid Metabolism in the Isolated Rat Lung after Nitrogen Dioxide Inhalation

Various drugs have been shown to stimulate surfactant phospholipid metabolism. Particularly β-adrenergic agonists play an important role under physiologic conditions. For the first time we have studied whether nitrogen dioxide (NO2) inhalation alters β-adrenergic regulation of surfactant phospholipid metabolism in the model of the isolated lung. Rats were continuously exposed in vivo to a 5 ppm NO2-containing atmosphere for 48 hr. The lungs were isolated and perfused in presence of the β-adrenergic agonist dopexamine and surfactant metabolism was studied in three lung compartments: (1) lung lavage, (2) lung tissue, and (3) lavagable free alveolar cells. We found that (1) in normal rat lungs dopexamine increased the incorporation of palmitate and choline from the perfusate into lung lavage phospholipids. In nitrogen dioxide exposed rat lungs β-adrenergic stimulation did not cause an increase in precursor incorporation. No significant difference in unstimulated precursor incorporation was found for normal and NO2-exposed rat lungs. (2) Lung tissue from rats exposed to NO2 showed a decreased precursor incorporation into disaturated phosphatidylcholine due to an augmented cellular pool size. (3) Lavagable alveolar cells showed an increased palmitate uptake after nitrogen dioxide inhalation and by β-adrenergic stimulation. From these data we conclude that nitrogen dioxide inhalation impairs the β-adrenergic regulation of surfactant phospholipid metabolism. Moreover these data underline the importance of β-adrenergic agonists in surfactant metabolism.

Early biochemical changes in kerosene exposed rat lungs

The activities of enzymes, which detoxify oxygen free radical species directly or indirectly were studied in lungs of kerosene-treated rats after 1,4,8 and 16 days of exposure. In the kerosene-exposed animals, activities of glutathione peroxidase (GP), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PD) and glutathione-s-transferase (GST) were significantly increased; thiobarbituric acid (TBA) - reacting products of lipid peroxidation and reduced glutathione (GSH) content were also significantly increased in the lungs. The increase in reduced glutathione content and elevations in the activities of enzymes and products of lipid peroxidation are suggestive of oxidative stress in the lungs of kerosene exposed animals.

Relationship of age to rat lung collagen synthesis in response to ozone exposure

We investigated the relationship of age to rat lung collagen synthesis in response to ozone (O3) exposure. Specific pathogen-free Sprague-Dawley male rats 24, 30, 45, 60, 94, 182 and 365 days old were exposed to either 0.8 ±.05 ppm O3 for 3 days or to 0.8 ± 0.5 ppm O3 for 3 days followed by 4.0 ±.2 ppm O3 for 8 hours and 60 days recovery in air. A matched number of rats from each age group received filtered air and served as controls. Lung dry weight, protein content, hydroxyproline content, 14C proline incorporation and 14C hydroxyproline formation were determined in control and exposed rat lungs. Rats exposed to 0.8 ppm O3 for 3 days had greater dry weight, protein content, incorporation of 14C proline, and formation of 14C hydroxyproline per lung relative to controls, with the greatest changes occurring in rats older than 60 days. Rats 24 and 94 days old, exposed to 0.8 ppm O3 for 3 days followed by 4.0 ppm O3 for 8 hours and 60 days recovery in air, had greater lung collagen content than controls: 50% and 80%, respectively. These results suggest that collagen synthesis was increased following O3 exposure and that the degree of change was influenced by age in the rat. Age, therefore, may be an important factor in the lung’s response to pulmonary injury.

Age-related ozone effects on glucose utilization in rat lungs

We examined the relationship between animal age and pulmonary biochemical effects of O3 exposure using young to adult rats ranging in age from 24 to 90 days. Glucose uptake and production of pyruvate and lactate, determined in lung tissue slices, were used as indices of O3-produced metabolic alterations. In control rats, the lung weights increased with animal age until they stabilized between 60 and 90 days of age. The rate of glucose metabolism, expressed per lung, increased with animal age paralleling the increase in lung weights. After exposure to 0.8 ppm (1568 ug/m3) O3 for 3 days, the lung weights and all three parameters of glucose metabolism increased in exposed rats relative to their age-matched controls. These increases were relatively small for younger rats but much larger for adult rats. Regression of percent differences in these parameters between control and exposed rat lungs against animal age indicates that the response to O3 was age-related.

Augmentation of mitochondrial oxidative metabolish in lung tissue during recovery of animals from acute ozone exposure

After O 3-mediated lung injury in rats (3 ppm O 3 exposure for 4 hr) recovery was studied in terms of alteration in lung mitochondrial oxidative metabolism. As judged from O 2 consumption, succinate oxidation in lung homogenate exhibited a 20% ( P < 0.05) decrease at 0 hr but attained the control rate (0.6 μmole O 2/min/lung) within 12 hr and the peak rate (55% over control, P < 0.001) within 48 hr of recovery. Thereafter, the rate plateaued and at about the fifth day began to decline, exhibiting only a 15% ( P < 0.05) increase over control after 21 days. The half-life for duration of this augmentation appeared to be 10 days. During recovery, the yield of isolated mitochondria was increasingly greater for exposed lungs relative to control (viz., 25–30% increase after 96 hr) as viewed from mitochondrial packed volume and protein content. Mitochondria from exposed lungs exhibited a 17–24% ( P < 0.05) increase in activity (per mg of protein) for oxidation of 2-oxoglutarate, succinate, glycerol-1-phosphate, and ascorbate-Wurster's blue. The over-all augmentation of O 2 consumption observed in exposed rat lungs, therefore, would be attributable primarily to increase in population of mitochondria. Enhanced mitochondrial metabolism might serve as an index for assessing the repair process of injured lung.

Ozone interaction with rodent lung. II. Effects on oxygen consumption of mitochondria.

Abstract In order to examine oxidant effects on lung cellular oxidative metabolism, mitochondrial O 2 consumption (substrate oxidation) was studied in the lungs of O 3 -exposed animals. Male rats (60 to 90-day-old) were exopsed to O 3 either acutely (2 p.p.m. for 8 hours) or subacutely (0.8 p.p.m. for 10 to 20 days). For in vitro experiments suspensions of rat lung homogenates or rat lung mitochondria were exposed to a flow of 10 to 15 p.p.m. O 3 per minute for 20 minutes; both homogenate and mitochondrial preparations absorbed O 3 at a rate of 2.3 to 5.0 p.p.m. per minute (depending upon the amount of tissue). A total of 30 to 40 nmoles O 3 per milligram of protein was absorbed during this period. Subsequent to acute exposures, the rate of O 2 consumption (oxidation of succinate) in lung homogenate or mitochondrial fraction decreased approximately 25 per cent (p 3 exposures, subacute exposures resulted in an augmentation of lung cellular O 2 utilization. As high as 45 per cent (p 2 consumption occurred in homogenates of subacutely exposed rat lungs compared to those of control rat lungs. The specific activity (e.g., succinate oxidase activity per milligram protein) in the isolated mitochondral fraction was only 15 per cent (p