Bleomycin-induced Lung Injury In Rats Research Articles

Creation of Lung-Targeted Dexamethasone Immunoliposome and Its Therapeutic Effect on Bleomycin-Induced Lung Injury in Rats

ObjectiveAcute lung injury (ALI), is a major cause of morbidity and mortality, which is routinely treated with the administration of systemic glucocorticoids. The current study investigated the distribution and therapeutic effect of a dexamethasone(DXM)-loaded immunoliposome (NLP) functionalized with pulmonary surfactant protein A (SP-A) antibody (SPA-DXM-NLP) in an animal model.MethodsDXM-NLP was prepared using film dispersion combined with extrusion techniques. SP-A antibody was used as the lung targeting agent. Tissue distribution of SPA-DXM-NLP was investigated in liver, spleen, kidney and lung tissue. The efficacy of SPA-DXM-NLP against lung injury was assessed in a rat model of bleomycin-induced acute lung injury.ResultsThe SPA-DXM-NLP complex was successfully synthesized and the particles were stable at 4°C. Pulmonary dexamethasone levels were 40 times higher with SPA-DXM-NLP than conventional dexamethasone injection. Administration of SPA-DXM-NLP significantly attenuated lung injury and inflammation, decreased incidence of infection, and increased survival in animal models.ConclusionsThe administration of SPA-DXM-NLP to animal models resulted in increased levels of DXM in the lungs, indicating active targeting. The efficacy against ALI of the immunoliposomes was shown to be superior to conventional dexamethasone administration. These results demonstrate the potential of actively targeted glucocorticoid therapy in the treatment of lung disease in clinical practice.

Intravenous administration of adipose-derived stromal cells does not ameliorate bleomycin-induced lung injury in rats

Background: Mesenchymal stromal cells (MSCs) have been studied intensively in regenerative medicine. Among MSCs, adipose tissue-derived stromal cells (ASCs) are relatively easy to obtain from a patient. Since ASCs are ideal candidates for use in the treatment of disease states including pulmonary fibrosis, we investigated whether intravenous injection of ASCs could exert a therapeutic effect against bleomycin-induced lung injury in rats. Methods: Rats were intratracheally administered bleomycin, and one week later ASCs were isolated and cultured. Two weeks after bleomycin treatment ASCs or PBS (phosphate-buffered saline) were injected to the rats. Three or six weeks after bleomycin instillation, the total cell counts and their profile in bronchoalveolar lavage fluid (BALF) were measured, and a histological evaluation was semi-quantitatively assessed for the injured lungs, followed by cell tracing. Results: The BALF cell counts and its profiles were not significantly different in the ASCs and PBS groups. Furthermore, ASC treatment led to no significant histological effect compared with the PBS treatment. Using a fluorescent cell tracer, it was noted that the ASCs homed to the injured lung areas, but some ASCs accumulated around scars, and scarcely migrated into the fibrotic areas. Conclusions: In the present study, the intravenous administration of ASCs could not reduce the severity of bleomycin-induced lung injury in a rat model. Although the ASC counts and passage numbers were suitable, the older age and fibrotic disease stage of the rats were likely responsible for the treatment failure.

Antedrug Budesonide by Intrapulmonary Treatment Attenuates Bleomycin-Induced Lung Injury in Rats with Minimal Systemic Adverse Effects

Corticosteroids are routinely used in patients with pulmonary fibrosis, yet they have several adverse effects. To improve this situation, we used an animal model of pulmonary injury and early fibrosis and investigated whether the combination of an intrapulmonary inhalation device with antedrug budesonide (BUD) administered to the lung had greater efficacy and fewer systemic adverse effects compared to long-acting dexamethasone (DEX). BUD or DEX was administrated either intrapulmonary or intravenously to bleomycin-treated rats. Anti-inflammatory and antifibrotic effects were evaluated according to inflammatory cell count, total protein concentration and soluble collagen concentration in bronchoalveolar lavage fluid. The systemic immunosuppressive effects were also assessed by measuring body, spleen and thymus weight. BUD and DEX were compared with respect to their pharmacokinetic profiles in plasma and lung. Intrapulmonary treatment of BUD attenuates various inflammatory and early fibrotic indices with minimal systemic adverse effects compared with DEX. The area under the curve (AUC) of BUD by intrapulmonary spray was 6.6-fold higher than the AUC of DEX in the lung. This study suggests that antedrug BUD by intrapulmonary treatment has local anti-inflammatory and antifibrotic effects with minimal systemic adverse effects.

Noninvasive Monitoring of Bleomycin-induced Lung Injury in Rats Using Pulmonary Function Test.

AbstrqactThe single intratracheal instillation (ITI) of bleomycin (BLM) is a widely used method for inducing experimental pulmonary fibrosis in rat model. In the present study, pulmonary function tests (PFTs) of tidal volume (VT), minute volume (VM), and respiratory frequency (FR) have been applied to study their possibility as a tool to monitor the progress of BLM-induced lung injury in rat model. Rats were treated with a single ITI of BLM (2.5 mg/kg) or saline (control). Animals were euthanized at 3, 7, 14, 21, and 28 days post-ITI. Lung toxicity effects were evaluated by inflammatory cell count, lactate dehydrogenase (LDH) activity in the bronchoalveolar lavage fluid (BALF), and light microscopic examination of lung injury. The PFT parameters were measured immediately before the animals were sacrificed. BLM treatment induced significant cellular changes in BALF-increase in number of total cells, neutrophils, and lymphocytes along with sustained increase in number of macrophages compared to the controls at days 3, 7, and 14. BALF LDH level was significantly increased compared to that in the controls up to day 14. On day 3, infiltration of neutrophils was observed in the alveolar spaces. These changes developed into marked peribronchiolar and interstitial infiltration by inflammatory cells, and extensive thickening of the interalveolar septa on day 7. At 14, 21, and 28 days, mild peribronchiolar fibrosis was observed along with inflammatory cell infiltration. The results of PFT show significant consistencies compared to the results of other toxicity tests. These data demonstrate that the most suitable time point for assessing lung fibrosis in this model is 14 days post-ITI of BLM based on the observation of fibrosis at 14, 21, and 28 days. Further, the progress of lung injury can be traced by monitoring the PFT parameters of FR, VT, and VM.

Therapeutic Effects of Bone Marrow-Derived Mesenchymal Stem Cells Engraftment on Bleomycin-Induced Lung Injury in Rats

Previous studies have demonstrated that bone marrow-derived mesenchymal stem cell (MSC) engraftment attenuated lung injury in a model induced by bleomycin in mice. However, the mechanisms are not completely understood. The primary objective of the present study was to determine whether MSC engraftment can also protect lungs against bleomycin-induced injury in rats and to observe any beneficial effects of cytokines. Twelve hours after bleomycin (5 mg/kg) or phosphate-buffered saline was perfused into the trachea, 5×10 6 DAPI-labeled MSCs or DMEM-F 12 were injected into the tail vein of rats. Two weeks later, MSCs labeled with DAPI were detected by pan-cytokeratin staining. The level of laminin and hyaluronan in bronchoalveolar lavage fluid was measured by radioimmunoassay. Collagen content in lung tissue was calculated by the hydroxyproline assay. TGF-β 1, PDGF-A, B, and IGF-I were measured by real-time PCR. It was observed that some MSCs positive for pan-cytokeratin staining, an indicator of alveolar epithelial cells, were present in injured lung tissue. Bleomycin injection increased the content of hydroxyproline in lung tissue, as well as laminin and hyaluronan in bronchoalveolar lavage fluid, markers for lung injury and fibrosis. However, these effects were attenuated by MSC treatment. Furthermore, the increased mRNA levels of TGF-β 1, PDGF-A, PDGF-B, and IGF-I following bleomycin injection were also significantly decreased by MSC treatment. These observations provided evidence that MSCs are still present in the lung 2 weeks after the initial MSC treatment in rats, as well as documented the beneficial effects of MSC engraftment against bleomycin-induced lung injury associated with changes in TGF-β 1, PDGF-A, PDGF-B, and IGF-I. These results may provide an experimental base for clinical therapy of pulmonary fibrosis in the future.

PRODUCTION AND EFFECTS OF α-MELANOCYTE-STIMULATING HORMONE DURING ACUTE LUNG INJURY

Alpha-melanocyte-stimulating hormone (alpha-MSH) is a peptide with broad anti-inflammatory effects. The present research was designed to determine production and effects of alpha-MSH in acute bleomycin-induced lung injury in rats. Intratracheal bleomycin instillation induced alpha-MSH expression in lung infiltrating cells and a marked peptide increase in the circulation. In experiments on the therapeutic potential of alpha-MSH on lung injury, we determined influences of the synthetic alpha-MSH analogue [Nle4-dPhe7]-alpha-MSH (NDP-alpha-MSH) on pulmonary edema, circulating nitric oxide, and gene expression profile in lungs 8 and 24 h after bleomycin instillation. Three main gene categories, known to be involved in the development of acute lung injury, were explored: stress response, inflammation, and fluid homeostasis. Peptide treatment was associated with a significant reduction in interstitial edema, with a virtually normal wet/dry weight ratio. Several stress-related genes, which were either upregulated or reduced by bleomycin, were only marginally altered during NDP-alpha-MSH treatment. NDP-alpha-MSH prevented bleomycin-related transcriptional alterations in genes involved in lung fluid homeostasis, including upregulation of Na/K-transporting ATPase and epithelial sodium channels and downregulation of cystic fibrosis transmembrane conductance regulator. Bleomycin-induced expression of proinflammatory and profibrotic factors (interleukin 6, tumor necrosis factor-alpha, transforming growth factor-beta1, and inducible nitric oxide synthase) and chemokines (chemokine [C-C motif] ligand 2 and chemokine [C-C motif] ligand 5) was likewise significantly reduced by NDP-alpha-MSH. In conclusion, treatment with the alpha-MSH analogue NDP-alpha-MSH greatly improved the clinical and molecular picture of bleomycin-induced lung injury. Treatment with alpha-MSH-related agents can exert beneficial effects in acute lung injury.

Resveratrol alleviates bleomycin-induced lung injury in rats

Antioxidant therapy may be useful in diseases with impaired oxidant–antioxidant balance such as pulmonary fibrosis. This study was designed to examine the effects of resveratrol, an antioxidant agents, against bleomycin-induced pulmonary fibrosis and oxidative damage. Wistar albino rats were administered a single dose of bleomycin (5 mg/kg; via the tracheal cannula) followed by either saline or resveratrol (10 mg/kg; orally) for 14 days. The effect of resveratrol on pulmonary oxidative damage was studied by cell count and analysis of cytokine levels (TGF- β, TNF- α, IL-1 β and IL-6) in the bronchoalveolar lavage fluid (BALF) and biochemical measurements of malondialdehyde (MDA), an end product of lipid peroxidation; glutathione (GSH), a key antioxidant; and myeloperoxidase (MPO) activity, an index of neutrophil infiltration, in the lung tissue. Bleomycin-induced lung fibrosis was determined by lung collagen contents and also microscopically. Bleomycin caused a significant decrease in lung GSH, which was accompanied with significant increases in MDA level, MPO activity, and collagen contents of the lung tissue concomitant with increased levels of the pro-inflammatory mediators and cell count in BALF. On the other hand, resveratrol treatment reversed all these biochemical indices as well as histopathological alterations induced by bleomycin. The results demonstrate the role of oxidative mechanisms in bleomycin-induced pulmonary fibrosis, and resveratrol, by its antioxidant properties, ameliorates oxidative injury and fibrosis due to bleomycin. Thus, an effective supplement with resveratrol as an adjuvant therapy may be a very promising agent in alleviating the side effects of bleomycin, an effective chemotherapeutic agent.

Cathepsins in bleomycin-induced lung injury in rat.

Endogenous inhibitors tightly control the activity of proteinases in the extracellular space. Proteinase/antiproteinase imbalance may be caused by predominance of proteinases, resulting in severe tissue damage or abundance of proteinase inhibitors, leading to a shift in the balance of synthesis and degradation of extracellular matrix proteins and accumulation of these matrix components. Lung fibrosis is characterised by accumulation of fibrous matrix proteins in the alveolar interstitium. The activity of cathepsin D and amounts of cathepsins D and B in bleomycin-injured rat lung tissue and alveolar macrophages were examined. In addition, the activities of cathepsins and cysteine proteinase inhibitors (CPIs) in bronchoalveolar lavage fluid (BALF) were determined. No cathepsin but high CPI activity and large amounts of procathepsin B were detected in the BALF. In the alveolar lumen, the disturbed proteinase/antiproteinase balance for cysteine proteinases was clearly dominated by CPIs. In alveolar macrophages, the main source of increased cathepsin levels, large changes in cathepsin B and D content were observed during the inflammatory phase, corresponding to the occurrence of procathepsin B in BALF. With the end of the phase of tissue remodelling, imbalances in cathepsin and CPI activities were largely eliminated. Immunoblot data, revealing an increase in cathepsin D levels in myofibroblast-like cells compared to fibroblasts and in resting fibroblasts compared to proliferating cells, implicate this proteinase in the differentiation and conversion processes occurring at the beginning of the fibrotic phase of lung injury. The results show that cathepsin amounts and activities are increased transiently in lung tissue during regeneration processes in bleomycin-induced lung injury. Imbalances of cathepsin and cysteine proteinase inhibitors activities are also a phenomenon of the phase of tissue remodelling initiated by lung injury.

Effects of granulocyte colony-stimulating factor on the kinetics of inflammatory cells in the peripheral blood and pulmonary lesions during the development of bleomycin-induced lung injury in rats

We evaluated the effects of granulocyte colony-stimulating factor (G-CSF) on the kinetics of inflammatory cells during the development of inflammation in bleomycin (BLM)-induced lung injury. G-CSF (100 microg/kg/day, s.c.) was administered to rats treated with or without BLM (2 mg/200 microl, intratracheally) for up to 14 days (Day 14) immediately after BLM treatment. In the BLM + G-CSF group, the lung injury score increased on Days 1 and 14, and the score of lung fibrosis on Day 14, respectively. Except for neutrophils, there were no effects of G-CSF on the number of inflammatory cells both in the peripheral blood and in the lung in both BLM-treated and -untreated rats at the acute inflammatory phase. In the G-CSF-treated groups, the number of neutrophil counts in the peripheral blood drastically increased on Day 1, temporally decreased on Day 3, and increased again on Days 7 and 14. The number of neutrophils in the lung markedly increased on Day 1 and then remained at a plateau level until Day 14. The neutrophil alkaline phosphatase score in the lung commenced to increase on Day 1, reached the maximal level on Day 7, and then remained at a plateau level until Day 14. Correlations between the numbers of neutrophils in the lung and the peripheral blood or the lung lesion score were only observed on Day 14. These findings suggest that the exacerbating effect of G-CSF on the lung injury coincided with the increase in the number of alkaline phosphatase-positive neutrophils infiltrating in the pulmonary lesion at the acute inflammatory phase and it lasted to the fibrogenic phase. The exacerbating effect of G-CSF on the severe BLM-induced lung injury seems to be related not only to the pulmonary accumulation of activated neutrophils but also to the severity of lung injury caused by the direct effects of BLM.

Changes in xylosyltransferase activity and in proteoglycan deposition in bleomycin-induced lung injury in rat.

Several lines of evidence support the hypothesis of the involvement of altered proteoglycan deposition in the development of lung diseases. UDP-D-xylose: core protein beta-D-xylosyltransferase (UDP-xylosyltransferase; EC 2.4.2.26) is a key enzyme for the glycosylation of proteoglycan core proteins. This study examined the catalytic activity of UDP-xylosyltransferase in lung tissue and in isolated fibroblasts, as well as the deposition of the proteoglycans versican, biglycan and decorin in rat lung tissue during bleomycin-induced lung injury. Rats were given, endotracheally, a single dose of bleomycin. Deposition of proteoglycans in lung tissue was assessed by immunohistochemistry and the catalytic activity of xylosyltransferase was determined with an acceptor peptide of the sequence Q-E-E-E-G-S-G-G-G-Q-G-G as a substrate. The results show coincidence of increasing xylosyltransferase activities in lung tissue with accumulation of versican at alveolar entrance rings and in fibrotic regions in close proximity to alpha-smooth muscle actin-positive cells. In contrast, no changes in biglycan and decorin deposition in fibrotic lungs were observed, except for decorin in alveolar type II pneumocytes and alveolar macrophages. Bleomycin treatment of isolated rat lung fibroblasts resulted in a concentration-dependent increase of xylosyltransferase activity up to 2 mU bleomycin x mL(-1). The data suggest a participation of myofibroblasts with increased xylosyltransferase activities in accumulation of versican in fibrotic foci of injured lung tissue at the early stages of development of lung fibrosis.

Attenuation by oral N-acetylcysteine of bleomycin-induced lung injury in rats.

Antioxidant therapy may be useful in diseases with impaired oxidant-antioxidant balance such as pulmonary fibrosis. This study examines the effect of N-acetylcysteine (NAC) on bleomycin-induced lung fibrosis in rats. NAC (3 mmol x kg(-1); oral) was given daily from 1 week prior to a single intratracheal instillation of bleomycin (2.5 U x kg(-1)) or saline, until 14 days postinstillation. NAC partially decreased the augmented collagen deposition in bleomycin-exposed rats (hydroxyproline content was 4,354+/-386 and 3,416+/-326 microg x lung(-1) in vehicle-treated and NAC-treated rats, respectively; p < 0.05). The histological assessment using a semiquantitative score showed less collagen deposition and inflammatory cells in NAC-treated rats compared to those receiving bleomycin alone. NAC failed to inhibit the bleomycin-induced increases in lung wet weight and in cell counts and protein levels of bronchoalveolar lavage fluid, but significantly increased total glutathione and taurine levels in bronchoalveolar lavage fluid. These results indicate that oral N-acetylcysteine improves the pulmonary antioxidant protection and may be useful in reducing lung damage produced by bleomycin.

Effects of vitamin A treatment on hyaluronan and water accumulation during the early inflammatory phase of bleomycin-induced lung injury in rats

The purpose of this study was to investigate the effect of vitamin A treatment on bleomycin-induced lung injury, especially during the early phase of alveolitis. The rats in the two treatment groups were given bleomycin intratracheally and oil vehicle (BO) or vitamin A (BA) orally. The rats in the control groups were given saline intratracheally and oil vehicle (CO) or vitamin A (CA) orally. Rats were killed 4, 7, and 30 days after bleomycin administration. Histologic signs of inflammation and fibrotic injury showed larger decreases in the BA group compared with the BO group at 7 days. After 30 days, most signs of inflammation had disappeared, and focal areas with further increased septal fibrosis were seen in the BO group and to a lesser extent in the BA group. The relative water content (%H 2O) in the lung tissue was significantly increased at 4 and 7 days in the BA and BO groups compared with the CA and CO groups, but not at 30 days. No significant differences in %H 2O values were found between the BA and BO groups at any time. Hyaluronan levels at 4 and 7 days in the BO group were significantly higher than in the CO group at 7 days. No other differences between groups were seen in hyaluronan levels. The messenger ribonucleic acid level for pro-alpha1(I) collagen in the BA group was reduced compared with the BO group but was higher than in the controls (groups CO and CA) after 7 days (n = 2 in each group). In bronchoalveolar lavage, performed in separate groups on day 4 after bleomycin administration, significant increases in hyaluronan levels and in the number of inflammatory cells were seen between both the BA and BO groups and the CO group, but no differences were observed between the BA and BO groups. These results indicate that vitamin A treatment does not inhibit early alveolitis in bleomycin-induced lung injury, although retinoids may partly modulate the later fibrotic phase in this experimental model.

Mechanism of impaired local hyaluronan turnover in bleomycin-induced lung injury in rat.

Hyaluronan, a linear polysaccharide, is accumulated in lung interstitium during different pathological conditions, causing interstitial edema and thereby impaired lung function. We investigated the mechanism of local hyaluronan turnover during the early phase of bleomycin-induced fibrotic lung injury in rats. The binding of [3H]hyaluronan to alveolar macrophages (AM) established from bleomycin-treated rats 1 and 5 days after induction of injury was decreased 8- and 15-fold, respectively, compared with that of AM from saline-treated control counterparts, but at day 14 returned almost to the normal level. Data was confirmed by quantitative cytochemistry, using fluorescein-labeled hyaluronan. Analysis of the expression of CD44, a receptor for hyaluronan, by Western blotting revealed a 30% increase of CD44 molecules expressed on AM from bleomycin-treated rats at day 5 compared with control rats. In particular a lower molecular mass form of CD44 appeared. No expression of the receptor for hyaluronan-mediated motility (RHAMM) could be detected. The internalization and degradation of [3H]hyaluronan by AM, obtained from bleomycin-treated rats at days 1, 5, and 14, were decreased about 65%, 35%, and 30%, respectively, compared with AM from the control rats. The AM lysosomal hyaluronidase activity did not differ significantly between bleomycin-treated and control rats. Our results indicate that a decreased hyaluronan binding capacity of AM may account for the impairment of internalization and thereby degradation of excessive hyaluronan during the early phase of fibrotic lung injury.

Curcumin protects bleomycin-induced lung injury in rats

The present study was designed to determine the protective effects of curcumin against bleomycin (BLM)-induced inflammatory and oxidant lung injury. The data indicate that BLM-mediated lung injury resulted in increases in lung lavage fluid biomarkers such as total protein, angiotensin-converting enzyme (ACE), lactate dehydrogenase (LDH), N-acetyl-β-D-glucosaminidase (NAG), lipid peroxidation (LPO) products, Superoxide dismutase (SOD) and catalase. Bleomycin administration also resulted in increased levels of malondialdehyde (MDA) in bronchoalveolar lavage fluid (BALF) and bronchoalveolar lavage (BAL) cells and greater amounts of alveolar macrophage (AM) Superoxide dismutase activity. By contrast, lower levels of reduced glutamione (GSH) were observed in lung lavage fluid, BAL cells and AM. Stimulated Superoxide anion and hydrogen peroxide release by AM from BLM rats were found to be higher. Curcumin treatment resulted in a significant reduction in lavage fluid biomarkers. In addition, curcumin treatment resulted in the restoration of antioxidant status in BLM rats. These data suggest that curcumin treatment reduces the development of BLM-induced inflammatory and oxidant activity. Therefore, curcumin offers the potential for a novel pharmacological approach in the suppression of drug or chemical-induced lung injury.

SYSTEMIC AND INTRATRACHEAL STEROIDS DECREASE THE PRODUCTION OF HYALURONAN(HA) AND REDUCE THE EXPRESSION OF THE HA RECEPTOR RHAMM DURING BLEOMYCIN-INDUCED PULMONARY INFLAMMATION. ▴ 1975

We have previously shown that hyaluronan (HA) and its receptor RHAMM(Receptor for HA-Mediated Motility) regulate macrophage motility during bleomycin-induced pulmonary inflammation. Since steroid therapy has been used to limit inflammation in this model, and may limit the severity of bronchopulmonary dysplasia in premature infants, we hypothesized that, in addition to reducing the inflammatory response, steroids would reduce the expression of RHAMM and HA after bleomycin-induced lung injury in rats. Sprague-Dawley rats (n=5/group) were treated with either 30 mg/kg solumedrol intramuscularly (IM), or 1 mg budesonide intratracheally (IT) 1 day prior to and daily for 4 days after intratracheal bleomycin. Control animals received an equal volume of normal saline by the same routes. Four days after injury, bronchoalveolar lavage (BAL) was performed. The cells from the BAL were separated from the lavage fluid by centrifugation. The HA content of the lavage fluid was measured using an ELISA-like assay, while the cells were analyzed for RHAMM content by western blot, and macrophage content by glucosaminidase activity. Steroid treatment decreased HA content of the lavage fluid by 40%, and decreased RHAMM expression by 40% (IM) and 90% (IT) as compared to controls. Both treatments resulted in a 40% reduction in macrophage accumulation in the lungs of injured animals. We conclude that, in addition to decreasing pulmonary inflammation after intratracheal bleomycin, steroids decrease the expression of RHAMM and HA in vivo. We speculate that the anti-inflammatory action of steroids in lung injury may be explained in part by the inhibition of RHAMM and HA.

Characterization of the mechanism involved in bleomycin-induced increased hyaluronan production in rat lung.

The molecular mechanisms behind the accumulation of hyaluronan during bleomycin-induced lung injury in rats were investigated. The stimulatory effects of bronchoalveolar lavage fluid (BALF) and alveolar macrophage (AM)-conditioned media on hyaluronan synthesis in normal rat lung fibroblast cultures were studied as well as the hyaluronan binding activity on AM. BALF obtained on days 1 and 5 after bleomycin instillation exhibited hyaluronan stimulatory activity similar to that of 10% fetal serum; the activity returned to control values on day 14 after bleomycin treatment. Conditioned media from cultures of AM obtained from bleomycin-treated rats exhibited stimulatory effects higher than that of media from AM of control rats and equal to or higher than that of 10% fetal calf serum. The stimulatory activity in BALF was significantly inhibited by neutralizing antibodies against transforming growth factor-beta; the activity in AM-conditioned media was only partially affected. Neutralizing antibodies against platelet-derived growth factor-BB or -AA had no such inhibiting effect. Interestingly, AM from bleomycin-treated rats exhibited low hyaluronan binding activity. [3H]Hyaluronan binding by AM on days 1 and 5 after bleomycin administration was about 2-fold and 4-fold lower, respectively, compared with that by AM derived from saline-treated rats. This decrease was normalized 14 days after bleomycin treatment. In conclusion, our results indicate that factors with high potential to stimulate hyaluronan synthesis in rat lung fibroblasts are accumulated in BALF from bleomycin-treated rats and that AM are likely to be one source of such stimulatory factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of type II alveolar epithelial cell proliferation by TGF-beta during bleomycin-induced lung injury in rats.

Three isoforms of transforming growth factor-beta (TGF-beta) are found in mammalian cells and are potent regulators of inflammation, connective tissue synthesis, cellular proliferation, and differentiation. To determine the distribution and regulation of TGF-beta isoforms during pulmonary injury, a rat model of bleomycin-induced lung inflammation and repair was used. Using immunohistochemistry, we demonstrate that TGF-beta 2 and TGF-beta 3 were localized to alveolar macrophages as well as epithelial and smooth muscle cells of both normal rat lungs and rat lungs obtained at all time intervals after bleomycin administration. Early in bleomycin-induced lung injury, when there is active proliferation of type II alveolar epithelial cells, there was an increase in the number of type II alveolar epithelial cells isolated per lung and an increase in DNA synthesis by explanted type II alveolar epithelial cells. At this time, the secretion of biologically active TGF-beta 1-3, which are potent inhibitors of epithelial cell proliferation, was decreased. However, the secretion of TGF-beta 1-3 activity was markedly increased later in the injury response and coincided with a reduction in the number of type II alveolar epithelial cells isolated per lung and DNA synthesis in vitro. Furthermore, the addition of TGF-beta 1, 2, and 3 to cultures of actively proliferating type II alveolar epithelial cells resulted in inhibition of [3H]thymidine incorporation, whereas, in the presence of anti-TGF-beta 1-3 antibody, there was an increase in [3H]thymidine incorporation. Our findings suggest that altered secretion of TGF-beta 1-3 activity by type II alveolar epithelial cells during bleomycin-induced lung injury may regulate pulmonary alveolar epithelial cell proliferation during injury and repair phases.

Expression of transforming growth factor-alpha and epidermal growth factor receptor is increased following bleomycin-induced lung injury in rats.

To investigate the potential role of transforming growth factor-alpha (TGF-alpha) and the epidermal growth factor receptor (EGF-R) in the fibroproliferative response to acute lung injury, we determined lung steady-state TGF-alpha and EGF-R mRNA levels, TGF-alpha protein levels, and the distribution of TGF-alpha and EGF-R immunoreactive protein of bleomycin-injured and control rat lungs. At 2 and 4 days after a single intratracheal injection of bleomycin, TGF-alpha mRNA levels increased to 159% and 184% of control values, respectively. EGF-R mRNA levels increased to 163%, 314%, and 170% of control values at 1, 7, and 14 days after bleomycin instillation. TGF-alpha protein levels in whole lung extracts increased to 230% of control values at 4 days after bleomycin administration. TGF-alpha and EGF-R immunoreactivity was detected in macrophages, alveolar septal cells, and airway epithelium of control and bleomycin-injured animals with an apparent increase in the intensity and number of specifically immunostained cells following lung injury. TGF-alpha and EGF-R immunoreactive proteins were detected in foci of cellular proliferation and in areas of intraalveolar fibrosis. We conclude that TGF-alpha and the EGF-R are present in normal and bleomycin-injured rat lung and that the expression of this growth factor and its receptor are up-regulated following lung injury. These results suggest that increased expression of TGF-alpha and the EGF-R may be an important mechanism that modulates the fibroproliferative response to acute lung injury.

Bleomycin-induced lung injury in rats selectively abolishes hypoxic pulmonary vasoconstriction: evidence against a role for platelet-activating factor.

1. The role of platelet-activating factor in the attenuated hypoxic pulmonary vasoconstriction associated with lung injury was evaluated using specific platelet-activating factor antagonists and an isolated perfused lung preparation. 2. Intratracheal bleomycin was administered to rats to produce acute lung injury. Animals received intratracheal saline (control), intratracheal bleomycin or the platelet-activating factor antagonists BN 52021, WEB 2170 or WEB 2086 before and after bleomycin treatment. Forty-eight hours after intratracheal administration of bleomycin or saline the animals were killed. 3. The increases in pulmonary artery pressure during two periods of hypoxic ventilation and in response to 0.2 microgram of angiotensin II were measured. Acetylcholine-induced vasodilatation after pre-constriction with prostaglandin F2 alpha was also measured. To quantify lung injury, the wet/dry ratio of lung weight was determined. 4. Bleomycin treatment attenuated the first and second hypoxic pressor responses by 93% and 77%, respectively, but not the pressor response to angiotensin II nor the vasodilator response to acetylcholine. BN 52021 plus bleomycin augmented the first hypoxic pressor response compared with bleomycin treatment alone, but the structurally unrelated platelet-activating factor antagonists WEB 2170 and WEB 2086 had no significant effect on the bleomycin-induced attenuation of hypoxic pulmonary vasoconstriction. None of the platelet-activating factor antagonists blocked the increase in the wet/dry lung weight ratio induced by bleomycin. 5. Bleomycin-induced lung injury selectively attenuates hypoxic pulmonary vasoconstriction, an effect that does not appear to be mediated by platelet-activating factor. The mechanism remains to be elucidated, but may involve destruction of the hypoxic 'sensor' within the respiratory tract.