Analysis of bronchoalveolar lavage fluid from bleomycin-induced pulmonary fibrosis in hamsters

Modulators of inflammation in Bronchopulmonary Dysplasia

Over 50 years after its first description, Bronchopulmonary Dysplasia (BPD) remains a devastating pulmonary complication in preterm infants with respiratory failure and develops in 30-50% of infants less than 1000-gram birth weight. It is thought to involve ventilator- and oxygen-induced damage to an immature lung that results in an inflammatory response and ends in aberrant lung development with dysregulated angiogenesis and alveolarization. Significant morbidity and mortality are associated with this most common chronic lung disease of childhood. Thus, any therapies that decrease the incidence or severity of this condition would have significant impact on morbidity, mortality, human costs, and healthcare expenditure. It is clear that an inflammatory response and the elaboration of growth factors and cytokines are associated with the development of BPD. Numerous approaches to control the inflammatory process leading to the development of BPD have been attempted. This review will examine the anti-inflammatory approaches that are established or hold promise for the prevention or treatment of BPD.

Protective effect of cysteinyl leukotriene receptor antagonist montelukast in bleomycin-induced pulmonary fibrosis

Background

This study aims to investigate the early- and late-term effects of pharmacological inhibition of cysteinyl leukotriene activity by using montelukast in bleomycin-induced inflammatory and oxidative lung injury in an animal model.

Methods

The study included 48 male Wistar albino rats (weighing 250 g to 300 g). Rats were administered intratracheal bleomycin or saline and assigned into groups to receive montelukast or saline. Bronchoalveolar lavage fluid and lung tissue samples were collected four and 15 days after bleomycin administration.

Results

Bleomycin resulted in significant increases in tumor necrosis factor-alpha levels (4.0±1.4 pg/mL in controls vs. 44.1±14.5 pg/mL in early-term vs. 30.3±5.7 pg/mL in late-term, p<0.001 and p<0.001, respectively), transforming growth factor beta 1 levels (28.6±6.6 pg/mL vs. 82.3±14.1 pg/mL in early-term vs. 60.1±2.9 pg/mL in late-term, p<0.001 and p<0.001, respectively), and fibrosis score (1.85±0.89 in early-term vs. 5.60±1.14 in late-term, p<0.001 and p<0.01, respectively). In bleomycin exposed rats, collagen content increased only in the late-term (15.3±3.0 ?g/mg in controls vs. 29.6±9.1 ?g/mg in late-term, p<0.001). Montelukast treatment reversed all these biochemical indices as well as histopathological alterations induced by bleomycin.

Conclusion

Montelukast attenuates bleomycin-induced inflammatory and oxidative lung injury and prevents lung collagen deposition and fibrotic response. Thus, cysteinyl leukotriene receptor antagonists might be regarded as new therapeutic agents for idiopathic pulmonary fibrosis.

The pathogenesis of bleomycin-induced lung injury in animals and its applicability to human idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a devastating disease of unknown etiology, for which there is no curative pharmacological therapy. Bleomycin, an anti-neoplastic agent that causes lung fibrosis in human patients has been used extensively in rodent models to mimic IPF. In this review, we compare the pathogenesis and histological features of human IPF and bleomycin-induced pulmonary fibrosis (BPF) induced in rodents by intratracheal delivery. We discuss the current understanding of IPF and BPF disease development, from the contribution of alveolar epithelial cells and inflammation to the role of fibroblasts and cytokines, and draw conclusions about what we have learned from the intratracheal bleomycin model of lung fibrosis.

Rupatadine protects against pulmonary fibrosis by attenuating PAF-mediated senescence in rodents

A similar immune response is implicated in the pathogenesis of pulmonary fibrosis and allergic disorders. We investigated the potential therapeutic efficacy and mechanism of rupatadine, a dual antagonist of histamine and platelet-activation factor (PAF), in bleomycin- (BLM-) and silica-induced pulmonary fibrosis. The indicated dosages of rupatadine were administered in rodents with bleomycin or silica-induced pulmonary fibrosis. The tissue injury, fibrosis, inflammatory cells and cytokines, and lung function were examined to evaluate the therapeutic efficacy of rupatadine. The anti-fibrosis effect of rupatadine was compared with an H1 or PAF receptor antagonist, and efforts were made to reveal rupatadine’s anti-fibrotic mechanism. Rupatadine promoted the resolution of pulmonary inflammation and fibrosis in a dose-dependent manner, as indicated by the reductions in inflammation score, collagen deposition and epithelial-mesenchymal transformation, and infiltration or expression of inflammatory cells or cytokines in the fibrotic lung tissue. Thus, rupatadine treatment improved the declined lung function and significantly decreased animal death. Moreover, rupatadine was able not only to attenuate silica-induced silicosis but also to produce a superior therapeutic efficacy compared to pirfenidone, histamine H1 antagonist loratadine, or PAF antagonist CV-3988. The anti-fibrotic action of rupatadine might relate to its attenuation of BLM- or PAF-induced premature senescence because rupatadine treatment protected against the in vivo and in vitro activation of the p53/p21-dependent senescence pathway. Our studies indicate that rupatadine promotes the resolution of pulmonary inflammation and fibrosis by attenuating the PAF-mediated senescence response. Rupatadine holds promise as a novel drug to treat the devastating disease of pulmonary fibrosis.

A further investigation concerning correlation between anti-fibrotic effect of liposomal quercetin and inflammatory cytokines in pulmonary fibrosis

It is widely accepted that inflammatory cells and cytokines play vital roles in the process of pulmonary fibrosis. The aim of this study was to evaluate the preventative effects of liposomal quercetin against bleomycin-induced pulmonary fibrosis in vivo. The underlying molecular mechanisms were also investigated. Bleomycin was injected intratracheally at a single dose of 5 U/kg for pulmonary fibrosis induction. Liposomal quercetin was intravenously injected 1 day prior to bleomycin administration and continued to the end of the study (for 4 weeks). Our results showed that liposomal quercetin diminished the increase of total cell counts and macrophage counts in bronchoalveolar lavage fluid. The neutrophil and lymphocyte counts were also significantly decreased both on day 7 and 14 after liposomal quercetin injection (P<0.05). The levels of TNF-alpha, IL-1beta, and IL-6 in bronchoalveolar lavage fluid at day 7 were strikingly reduced in liposomal quercetin treated group compared with bleomycin-induced group (TNF-alpha: 56.21+/-3.16 pg/ml vs.79.85+/-6.91 pg/ml; IL-1beta: 37.64+/-2.10 pg/ml vs. 73.29+/-5.78 pg/ml; IL-6: 88.52+/-5.96 pg/ml vs. 128.56+/-8.72 pg/ml; P<0.05). Moreover, the treatment with liposomal quercetin exerted approximately 35.8% reduction of the hydroxyproline content in contrast to the bleomycin-induced group (P<0.05). Histopathological assessment revealed that treatment with liposomal quercetin apparently lessened the lung fibrosis areas and collagen deposition accompanied with decreased expression of TGF-beta1. Thus, our results suggested that liposomal quercetin could attenuate the bleomycin-induced pulmonary fibrosis in vivo by the suppression of inflammatory cytokines.

Red blood cells increase secretion of matrix metalloproteinases from human lung fibroblasts in vitro

Tissue remodeling is an important process in many inflammatory and fibrotic lung disorders. RBC may in these conditions interact with extracellular matrix (ECM). Fibroblasts can produce and secrete matrix components, matrix-degrading enzymes (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Imbalance in matrix synthesis/degradation may result in rearrangement of tissue architecture and lead to diseases such as emphysema or fibrosis. Neutrophil elastase (NE), a protease released by neutrophils, is known to activate MMP. We hypothesized that RBC can stimulate secretion of MMPs from human lung fibroblasts and that NE can augment this effect. Human fetal lung fibroblasts were cultured in floating collagen gels with or without RBC. After 4 days, the culture medium was analyzed with gelatin zymography, Western blot, and ELISA for MMP-1, -2, -3 and TIMP-1, -2. RBC augmented NE-induced fibroblast-mediated collagen gel contraction compared with NE alone (18.4+/-1.6%, 23.7+/-1.4% of initial gel area, respectively). A pan-MMP inhibitor (GM-6001) completely abolished the stimulating effect of NE. Gelatin zymography showed that RBC stimulated MMP-2 activity and that NE enhanced conversion to the active form. Addition of GM-6001 completely inhibited MMP-2 activity in controls, whereas it only partially altered RBC-induced MMP activity. Western blot confirmed the presence of MMP-1 and MMP-3 in fibroblasts stimulated with RBC, and ELISA confirmed increased concentrations of pro-MMP-1. We conclude that stimulation of MMP secretion by fibroblasts may explain the ability of RBC to augment fibroblast-mediated collagen gel contraction. This might be a potential mechanism by which hemorrhage in inflammatory conditions leads to ECM remodeling.

Erdosteine prevents bleomycin-induced pulmonary fibrosis in rats

Oxidative stress plays an important role in the pathogenesis of idiopathic pulmonary fibrosis. Therefore, erdosteine, an antioxidant, is expected to have an inhibitor potential against the disease. Rats were given one dose of bleomycin in pulmonary fibrosis groups and saline in controls. The first dose of oral erdosteine (10 mg/kg/day) was given 2 days before the bleomycin injection to achieve the plateau level in blood and continued until killing. At day 14, fibrotic changes were evaluated, using Aschoft's criteria and lung hydroxyproline content. Bleomycin produced a fivefold increase in fibrosis score that was decreased by 87% by erdosteine (P>0.001) and almost twofold increases in hydroxyproline content which were completely prevented by erdosteine. Myeloperoxidase activities and MDA levels, which were significantly higher in the bleomycin group, were then significantly attenuated by erdosteine. These results revealed that oral erdosteine may prevent the development of acute pulmonary inflammation caused by bleomycin injection via the repression of neutrophil accumulation and lipid peroxidation, resulting in the inhibition of subsequent lung fibrosis.

Inhibitory effect of caffeic acid phenethyl ester on bleomycine-induced lung fibrosis in rats

BACKGROUND

Pulmonary fibrosis (PF) induced by anticancerogenic bleomycin (BLM) is one of the more common side effects encountered during cancer treatment. It has been suggested in the last decades that the main responsible agent in PF is reactive oxygen species which were generated also in normal physiological conditions in the human body. In this experimental study, we investigated the preventive or attenuating effects of caffeic acid phenethyl ester (CAPE) that has been demonstrated to have anti-inflammatory, cytocytatic, anticancerogenic, antiprolipherative and antioxidant effects on BLM-induced PF.

METHODS

Thirty-six Sprague-Dawley rats were divided randomly into four groups as sham operation, BLM, BLM + vitamin E (vit E), and BLM + CAPE groups. BLM (7.5 mg/kg, single dose) was applied intratracheally, and CAPE and vit E intraperitoneally in the appropriate groups. At the end of the fibrosis processes, lung tissues were removed and the levels of tissues hydroxyproline (OH-proline), malondialdehyde (MDA) and NO as well as the activities of superoxide dismutase (SOD), catalase (CAT) and myeloperoxidase (MPO) were determined. Also, the weights of the rats were recorded at 7th and 14th days of the experiments.

RESULTS

BLM application to the rats resulted in a significant increase in the OH-proline level as compared to the controls. Administration of CAPE and vit E led to the remarkable reduction of total lung OH-proline levels compared to the rats treated with BLM alone (p < 0.0001). There were a decreases in antioxidant enzyme (SOD and CAT) activities while an increase in MPO activity in BLM group was found vs. the control group (p < 0.0001). CAPE had a regulator effect on these parameters: the increase in CAT and SOD activities and the decrease in MPO activity were seen after CAPE application. NO, MDA and OH-proline levels were increased in BLM group vs. the control group. CAPE was more effective in decreasing the tissue levels of NO, MDA and OH-proline than vit E. MPO activity, as a good marker of neutrophil sequestration to the tissues, in the BLM group was decreased by CAPE approximately to the control group.

CONCLUSION

We suggest that CAPE is more effective on the prevention of BLM-induced fibrosis via antioxidant and free radical scavenger properties than vit E at the doses used in the present study. CAPE has some attenuating effects on BLM-induced PF affecting both oxidant and antioxidant systems as well as neutrophils sequestration.

Novel pharmacological approaches to manage interstitial lung fibrosis in the twenty-first century

Pharmacological agents currently in use to treat interstitial lung fibrosis are either ineffective or too toxic in humans. This review addresses mechanistically based novel approaches that have the potential to minimize the accumulation of collagen in the lung, a hallmark of lung fibrosis. These approaches include maintaining the intracellular levels of NAD(+) and ATP, blocking the biological activities of TGF-beta and integrins, evaluating the effectiveness of PAF-receptor antagonists and NOS inhibitors, and developing a new generation of cysteine pro-drugs with an adequate degree of bioavailability. A critical analysis of each approach as it relates to management of IPF in humans is presented.

Bilirubin ameliorates bleomycin-induced pulmonary fibrosis in rats

Many possible treatments for pulmonary fibrosis have been investigated, but except for some current clinical trials, none have succeeded in clinical trials. On the basis of the antioxidant action of bilirubin (BIL), we examined the effects of hyperbilirubinemia on the development of bleomycin (BLM)-induced pulmonary fibrosis in rats. The animals' plasma BIL level was kept within 3 and 10 mg/dl by repeated intravenous infusion of a high dose of BIL. We studied the inhibitory effects of hyperbilirubinemia on BLM-induced pulmonary fibrosis through histopathologic and biochemical analyses. Mortality of rats with BLM-induced pulmonary fibrosis was significantly lower in the three groups with hyperbilirubinemia. The ameliorating effect of hyperbilirubinemia on pulmonary fibrosis was shown by lung histology, as well as by a decreased lung content of hydroxyproline and reduced bronchoalveolar lavage fluid (BALF) concentration of transforming growth factor (TGF)-beta(1). The number of polymorphonuclear leukocytes and lymphocytes in BALF was also decreased in the groups with hyperbilirubinemia. Furthermore, oxidative metabolites of BIL in urine were present at significantly higher levels in BLM-treated rats with hyperbilirubinemia than in those without hyperbilirubinemia. These data suggest that the antioxidative action of BIL can attenuate BLM-induced pulmonary fibrosis, partly by inhibiting lung inflammation and production of TGF-beta1.

Effect of antibody against integrin alpha4 on bleomycin-induced pulmonary fibrosis in mice

Integrins are a family of transmembrane glycoproteins that can interact with components of the extracellular matrix. The alpha4beta1 and alpha4beta7 integrins are heterodimeric leukocyte cell surface molecules critical to their cell and matrix adhesive interactions. Evidence for a central role for the alpha4 integrins in leukocyte pathophysiology in the lung is well documented. In this study, we tested the hypothesis that neutralizing antibody for integrin alpha4 (PS2) may reduce bleomycin (BL)-induced lung fibrosis in vivo. Male C57BL/6 mice were injected intratracheally with saline (SA) or BL (0.08 U/mouse) followed by intraperitoneal injection of SA, isotype control antibody (1E6), or PS2 (100 microg) three times a week. Twenty-one days after the intratracheal instillation, mice were killed for bronchoalveolar lavage (BAL), biochemical, histopathological, and immunohistological analyses. Treatment with PS2 significantly reduced BL-induced increases in lung lipid peroxidation and hydroxyproline content. Lung histopathology also showed reduced fibrotic lesions in the BL-treated lungs by treatment with PS2. BL-treated mouse lungs also showed induction of cells with the myofibroblast phenotype, as indicated by the increased expression of alpha-smooth muscle actin (alphaSMA), whereas treatment with PS2 minimized the BL-induced alphaSMA expression. Furthermore, treatment with PS2 reduced the BL-induced increase in the BAL total cell number, and attenuated the BL-induced increase in the BAL protein level. It is concluded that integrin alpha4 may play an important role in BL-induced pulmonary fibrosis, and the use of anti-alpha4 antibody offers therapeutic antifibrotic potential in vivo.

Pirfenidone inhibits PDGF isoforms in bleomycin hamster model of lung fibrosis at the translational level

Pirfenidone (PD) is known for its antifibrotic effects in the bleomycin (BL) hamster model of lung fibrosis. We evaluated whether pretreatment of hamsters with PD could influence the effects of BL-induced overexpression of platelet-derived growth factor (PDGF)-A and PDGF-B genes and proteins in the same model of lung fibrosis. We demonstrate elevated levels of PDGF-A and PDGF-B mRNAs in bronchoalveolar lavage (BAL) cells from lungs of BL-treated compared with saline control hamsters by RT-PCR analysis. However, these levels were not altered in BAL cells obtained from BL-treated hamsters on diets containing 0.5% PD. Western blot analysis of BAL fluid for PDGF isoforms demonstrated that PD treatment inhibited the synthesis of both PDGF-A and PDGF-B isoforms. PD treatment also decreased the mitogenic activity in the BAL fluid from BL-treated hamster lungs. Taken together, these data provide evidence that the protective effects of PD against BL-induced lung fibrosis may be mediated by a reduction in PDGF isoforms produced by lung macrophages.

Regulation of transforming growth factor-beta1 mRNA expression by taurine and niacin in the bleomycin hamster model of lung fibrosis

We have reported that taurine (T) and niacin (N) inhibit the expression of procollagen type I and type III genes at the level of gene transcription in the bleomycin (BL) hamster model of lung fibrosis. In the present study, we have investigated the effects of TN in diet on the temporal expression of transforming growth factor-beta1 (TGF-beta1) mRNA and TGF-beta1 protein production in the same model of lung fibrosis to determine whether the decreased transcription of procollagen genes is associated with downregulation of TGF-beta1 mRNA. Our results demonstrate that expression of TGF-beta1 mRNA in lungs is increased in BL-treated hamsters in the BL + control diet (CD) group, compared to saline controls in the saline-instilled (SA) + CD group, by 3.5-, 2.5-, 4-, and 2-fold at 3, 7, 14, and 21 d, respectively, and TN treatment caused significant decreases in TGF-beta1 mRNA expression in BL-treated animals in the BL + TN group from Day 3 through Day 21. In addition, TN treatment also reduced TGF-beta1 protein in bronchoalveolar lavage fluid (BALF) from BL-treated animals in the BL + TN group. These decreases in TGF-beta1 mRNA and TGF-beta1 protein correlated with decreased lung collagen content in hamsters in the BL + TN group as demonstrated in our earlier study. To confirm that the TGF-beta1 activity observed in BALF is reflected at the transcriptional level, total RNA was isolated from lavaged cells. Reverse transcriptase-polymerase chain reaction analysis demonstrated maximal expression of TGF-beta1 mRNA transcripts in BL-treated lavaged cells from animals in the BL + CD group and only low levels were detected in both saline control groups, and in BL + TN-treated lavaged cells. Nuclear runoff analysis indicated that TN-mediated reduction of TGF-beta1 mRNA steady-state levels was a result of decreased gene transcription, suggesting a transcriptional downregulation mechanism. Our results indicate that the combined treatment with TN ameliorates BL-induced lung fibrosis, at least in part, via inhibition of TGF-beta1 mRNA expression.

Induction of leukotriene production by bleomycin and asparaginase in mast cells in vitro and in patients in vivo

Bleomycin and asparaginase are widely used antineoplastic agents which may induce allergic or inflammatory side-effects. Mast cells are implicated as effector cells in allergic and inflammatory responses. The aim of this study was to establish whether bleomycin or asparaginase modulate leukotriene production in vitro and in vivo. Leukotriene C4 (LTC4) production by murine bone marrow-derived mast cells (BMMC) was determined by radioimmunoassay (RIA). Leukotriene production in patients was assessed by determining leukotriene E4 and N-acetyl-leukotriene E4 in urine by means of combined HPLC and RIA. Bleomycin induced an up to 2.1-fold increase in LTC4 production both in unstimulated and in calcium ionophore-stimulated mast cells. In 3 of 7 patients treated with bleomycin, a greater than 2-fold increase in endogenous leukotriene production was observed. This effect was associated with febrile responses and was most pronounced in a patient who developed an Adult Respiratory Distress Syndrome (ARDS). Asparaginase increased leukotriene production up to 10-fold in stimulated but not in unstimulated BMMC. In a patient who developed an anaphylactic reaction after treatment with asparaginase, a pronounced increase in urinary leukotriene concentration was observed. In contrast to bleomycin or asparaginase, a number of other cytostatic agents did not significantly change leukotriene production by BMMC. Our data indicate that some of the inflammatory and allergic side-effects of bleomycin and asparaginase could be mediated by leukotrienes, a possible source of which may be mast cells.

Lung fibrosis is ameliorated by pirfenidone fed in diet after the second dose in a three-dose bleomycin-hamster model

Interstitial lung fibrosis (ILF) is a life-threatening disease which has no known drug for prevention and cure. In the present study, we evaluated the antifibrotic potential of pirfenidone (PD) (5-methyl-1-phenyl-2-(1H)-pyridone) in a three-dose bleomycin (BL)-hamster model of lung fibrosis. Hamsters were intratracheally (IT) instilled with three consecutive doses of bleomycin sulfate (2.5 U/kg/5mL, 2.0 U/kg/5mL, 1.5 U/kg/3.75 mL) or an equivalent volume of saline at weekly intervals. Hamsters were fed a diet after the second dose of BL containing 0.5% PD and hamsters in the control groups were fed the same diet without the drug. The four groups were saline-instilled fed control diet (SCD); saline-instilled fed the same diet containing PD (SPD); BL-instilled fed control diet (BCD); and BL-instilled fed the diet containing PD (BPD). Hamsters were sacrificed at 28 days after IT instillation of last dose of saline or BL and their lungs processed for various assays. Lung hydroxyproline, an index of fibrosis, in SCD, SPD, BCD and BPD were 830, 804, 1609, 1235 micrograms/lung, respectively. Lung prolyl hydroxylase activities in the SPD, BCD and BPD groups were 103%, 313%, 157% of the control SCD group (5.99 x 10(4) dpm/lung/30 min) respectively. Malondialdehyde equivalent levels and superoxide dismutase activity in the corresponding groups were 99, 79, 240 and 145 nmoles/lung and 412, 433, 538 and 410 units/lung respectively. Lung myeloperoxidase activities in the corresponding groups were 56%, 179%, and 116% of the control group (0.44 units/lung). It is concluded that PD is a novel antifibrotic drug that has therapeutic potential in arresting the progression of an ongoing fibrotic process in the lung.

Antifibrotic effect of decorin in a bleomycin hamster model of lung fibrosis

We reported previously that treatment with antibody to transforming growth factor-beta (TGF-beta) caused a marked attenuation of bleomycin (BL)-induced lung fibrosis (LF) in mice. Decorin (DC), a proteoglycan, binds TGF-beta and thereby down-regulates all of its biological activities. In the present study, we evaluated the antifibrotic potential of DC in a three-dose BL-hamster model of lung fibrosis. Hamsters were placed in the following groups: (1) saline (SA) + phosphate-buffered saline (PBS) (SA + PBS); (2) SA + DC; (3) BL + PBS; and (4) BL + DC. Under pentobarbital anesthesia, SA (4 mL/kg) or BL was instilled intratracheally in three consecutive doses (2.5, 2.0, 1.5 units/kg/4 mL) at weekly intervals. DC (1 mg/mL) or PBS was instilled intratracheally in 0.4 mL/hamster on days 3 and 5 following instillation of each dose of SA or BL. In week 4, hamsters received three doses of either DC or PBS every other day. The hamsters were killed at 30 days following the first instillation, and their lungs were appropriately processed. Lung hydroxyproline levels in SA + PBS, SA + DC, BL + PBS, and BL + DC groups were 965, 829, 1854, and 1387 microg/lung, respectively. Prolyl hydroxylase activities were 103, 289, and 193% of SA + PBS control in SA + DC, BL + PBS, and BL + DC groups, respectively. The myeloperoxidase activities in the corresponding groups were 222, 890, and 274% of control (0.525 units/lung). Intratracheal instillation of BL caused significant increases in these biochemical markers, and instillation of DC diminished these increases in the BL + DC group. DC treatment also caused a significant reduction in the infiltration of neutrophils in the bronchoalveolar lavage fluid (BALF) of hamsters in the BL + DC group. However, DC treatment had little effect on BL-induced increases in lung superoxide dismutase activity and lipid peroxidation and leakage of plasma proteins in the BALF of the BL + DC group. Hamsters in the BL + PBS group showed severe multifocal fibrosis and accumulation of mononuclear inflammatory cells and granulocytes. In contrast, hamsters in the BL + DC group showed mild multifocal septal thickening with aggregations of mononuclear inflammatory cells. Hamsters in both control groups (SA + PBS and SA + DC) showed normal lung structure. Frozen lung sections following immunohistochemical staining revealed an intense staining for EDA-fibronectin and collagen type I in the BL + PBS group as compared with all other groups. It was concluded that DC potentially offers a novel pharmacological intervention that may be useful in treating pulmonary fibrosis.

Amelioration of bleomycin-induced lung fibrosis by treatment with the platelet activating factor receptor antagonist WEB 2086 in hamsters

Therapeutic use of bleomycin, an antineoplastic drug, is complicated by the development of a dose-dependent lung toxicity leading to fibrosis. This study tested the effectiveness of a platelet activating factor (PAF) receptor antagonist, WEB 2086, against bleomycin (BLEO)-induced lung fibrosis in hamsters. The animals were assigned to four groups: (1) saline (SA) + SA, (2) WEB 2086 (WEB) + SA, (3) SA + BLEO, and (4) WEB + BLEO. Sterile isotonic saline or WEB 2086 (10 mg/kg IP) was administered daily for the duration of the study starting 2 days prior to intratracheal (IT) instillation of saline or bleomycin (2.5, 2.0, and 1.5 units/kg 5 mL-1) in three consecutive doses at weekly intervals. The animals were killed at 21 days after the last IT instillation and their lungs were processed for various studies. The lung hydroxyproline levels in SA + SA, WEB + SA, SA + BLEO, and WEB + BLEO groups were 932 +/- 31, 943 +/- 48, 1302 +/- 72, and 964 +/- 63 micrograms/lung, respectively. The lung myeloperoxidase (MPO) activity and malondialdehyde equivalent, an index of lipid peroxidation, in the corresponding groups were 10 +/- 2, 8 +/- 2, 14 +/- 3, and 5 +/- 1 units/lung and 93 +/- 7, 77 +/- 5, 102 +/- 8, and 75 +/- 6 nmol/lung, respectively. The lung prolyl hydroxylase activity in the WEB + SA, SA + BLEO, and WEB + BLEO groups was 130.1 +/- 7.7, 236.2 +/- 12.8, and 138.1 +/- 7.0% of the SA + SA control group (8.3 x 10(4) dpm/lung 30 min-1), respectively. Daily treatment with WEB 2086 caused significant (p < or = .05) reductions in the BLEO-induced increases in the lung hydroxyproline content, prolyl hydroxylase and MPO activities, lipid peroxidation, and acid phosphatase activity of the BALF supernatant. Although daily treatment with WEB 2086 reduced the bleomycin-induced increases in the BALF total and neutrophil cell counts, BALF supernatant protein, and morphometric estimates of the lesions, these parameters were not significantly different from those of the SA-BLEO group. Histopathologic studies revealed that there were no lesions of alveolar consolidation and fibrosis in the lungs of WEB + BLEO group as compared with the SA + BLEO group. The results suggest that PAF is involved in the BLEO-induced lung fibrosis and that PAF-receptor antagonist may therefore be potentially useful in the attenuation of lung fibrosis caused by bleomycin.

Effect of antibody to transforming growth factor beta on bleomycin induced accumulation of lung collagen in mice

BACKGROUND

Increased production of transforming growth factor beta (TGF-beta) seems to have an important role in the pathophysiology of bleomycin induced lung fibrosis. This is attributed to the ability of TGF-beta to stimulate infiltration of inflammatory cells and promote synthesis of connective tissue, leading to collagen deposition.

METHODS

The study was designed to evaluate the antifibrotic potential of TGF-beta antibody in mice treated with bleomycin, which is a model of lung fibrosis. Under methoxyflurane anaesthesia, each mouse received intratracheally either 50 microliters sterile isotonic saline or 0.125 units bleomycin in 50 microliters. Within five minutes after the instillation, mice received into the tail vein 100 microliters non-immune rabbit IgG, TGF-beta 2 antibody, or a combination of TGF-beta 2 and TGF-beta 1 antibodies at various dose regimens. Mice were killed 14 days after the instillation and their lungs processed for morphological and biochemical studies.

RESULTS

Administration of 250 micrograms of TGF-beta 2 antibody after instillation of bleomycin followed by 100 micrograms on day 5 and 100 micrograms on day 9 significantly reduced the bleomycin induced increases in the accumulation of lung collagen from 445.8 (42.3) micrograms/lung to 336.7 (56.6) micrograms/lung at 14 days. Similarly, the combined treatment with 250 micrograms TGF-beta 2 antibody and 250 micrograms TGF-beta 1 antibody after bleomycin instillation followed by 100 micrograms of each antibody on day 5 also caused a significant reduction in bleomycin induced increases in lung collagen accumulation and myeloperoxidase activity at 14 days.

CONCLUSIONS

These results suggest that TGF-beta has an important role in the aetiology of bleomycin induced lung fibrosis; the neutralisation of TGF-beta by systemic treatment with its antibodies offers a new mode of pharmacological intervention which may be useful in treating lung fibrosis.

Development of a bleomycin hamster model of subchronic lung fibrosis

The existing bleomycin (BLM)-rodent model of lung fibrosis requires large doses and is often associated with morbidity and high mortality. We have developed an intratracheal multiple-dose BLM-hamster model of lung fibrosis. In this model, 3 consecutive doses of BLM (2.5 U, 2.0 U and 1.5 U/5mL/kg) were instilled intratracheally, one dose per week. The hamsters were killed at 10, 20, 30, 60 and 90 days after the last IT instillation and the lungs were lavaged or perfused with saline. This regimen of BLM administration was devoid of morbidity and caused only 6% overall mortality. Lung prolyl hydroxylase activity at 10 days and hydroxyproline content at 20, 30, 60 and 90 days were significantly higher than noted for the controls. Bronchoalveolar lavage fluid-supernatant protein and the total number of recovered cells of all types were significantly higher than observed for the controls at all times, except at 90 days. Lungs showed a multifocal mixed mononuclear infiltrate at 10 and 20 days and septal fibrosis, which was most severe and organized at 30 days and less severe at 60 and 90 days. The parenchymal lesions were significantly greater than those of the controls at all times, except at 10 days. This model, which required only 6 U BLM/kg, induced a moderate level of lung fibrosis. It has been concluded, therefore, that this model, inasmuch as it is not associated with an overwhelmingly acute inflammation, would be more applicable for screening potential antifibrotic agents than existing models of lung fibrosis.

Effects of an interferon inducer bropirimine on bleomycin-induced lung fibrosis in hamsters

The antifibrotic effect of an interferon inducer, bropirimine (2-amino-5-bromo-6-phenyl-4(3H)-pyrimidinone, ABPP) was evaluated in bleomycin (BLM)-hamster model of lung fibrosis. ABPP is an orally active biological response modifier and has immunomodulatory, antiviral, and antineoplastic activities. The hamsters were randomized in four groups and treated with either bropirimine (100 mg/kg, intraperitoneally) suspended in carboxymethylcellulose (CMC, 10 mg/10 mg/ml) or CMC alone each day for sixteen days. After two days, the hamsters received either single bolus of BLM (7.5 U/5 ml/kg) or an equivalent volume of saline by the transoral endotracheal route. Groupings were assigned as: CMC + saline (CS), ABPP + saline (AS), CMC + BLM (CB) and ABPP + BLM (AB). Animals were sacrificed at fourteen days after intratracheal installation of either BLM or saline. Their lungs were lavaged and processed for morphometric and biochemical studies. ABPP had little effect in preventing BLM-induced weight loss and lung injury. ABPP was found to reduce the BLM-induced accumulation of collagen in the lung as measured by hydroxyproline content. The hamsters in AB group had significantly less collagen than the hamsters in CB group: 995 and 1157 micrograms hydroxyproline/lung, respectively. Administration of ABPP prevented the BLM-induced increase in the lung prolyl hydroxylase activity. The total number of monocytes and eosinophils recovered from the bronchoalveolar lavage fluid (BALF) of the AB group were significantly lower than that of the animals in CB group. However, the BALF supernatant protein content from animals in AB group (7.9 mg/lung) was significantly higher than that of CB group (4.5 mg/lung).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of dibutyrylcyclic adenosine monophosphate on bleomycin-induced lung toxicity in hamsters

Cyclic nucleotides play an important role in the regulation of fibroblast proliferation and collagen metabolism. In the present study, the antifibrotic potential of dibutyrylcAMP (Bt2cAMP) was evaluated in the bleomycin (BLM)-hamster model of pulmonary fibrosis. Bt2cAMP (10 mg kg-1, s.c.) or saline (SA, s.c.) was given daily two days prior to the first intratracheal (i.t.) dose of BLM or SA and thereafter throughout the study. BLM or SA was instilled i.t. in three consecutive doses (2.5, 2.0 and 1.5 U 5ml-1 kg-1) at weekly intervals. Hamsters were killed at 7, 14 and 20 days after the third i.t. instillation. Bt2cAMP significantly reduced the contents of lung hydroxyproline and lung thiobarbituric acid reactive substance equivalents in BLM-treated animals at 7 and 14 days. Bt2cAMP significantly elevated lung superoxide dismutase activity in BLM-treated animals at 7 days. Lung prolyl hydroxylase activity was significantly elevated at 14 and 20 days in SABLM- and Bt2cAMPBLM-treated animals. The ratio of cAMP/cGMP was significantly reduced at all time points in SABLM-treated animals but only at 7 and 14 days in Bt2cAMPBLM-treated animals. Bt2cAMP caused no significant changes in lung calcium and calmodulin levels and protein content of the bronchoalveolar lavage. BLM significantly increased various inflammatory cell counts in the lavage at all three time points. The cell counts in the Bt2cAMPBLM groups were generally lower at 7 days and higher at 20 days than those of the SABLM groups. Histological evaluation showed that the lungs of Bt2cAMPBLM-treated hamsters progressed from an inflammatory cell lesion to a fibrotic lesion at a slower rate than the SABLM groups. It was concluded that Bt2cAMP attenuated BLM-induced pulmonary fibrosis in hamsters in part by delaying the acute phase of the inflammatory reaction.

Taurine and niacin offer a novel therapeutic modality in prevention of chemically-induced pulmonary fibrosis in hamsters

The bleomycin (BL)-hamster model of interstitial pulmonary fibrosis (IPF) is generally associated with increased lung lipid peroxidation, measured as malondialdehyde equivalent (MDAE), calcium and collagen content; and superoxide dismutase (SOD), prolyl hydroxylase (PH) and poly(ADP-ribose) polymerase activities. We found that combined treatment with taurine in drinking water (1%) and niacin IP (250 mg/kg) daily, significantly decreased the BL-induced increases in lung MDAE and calcium content, and SOD, PH and poly(ADP-ribose) polymerase activities. This treatment almost completely ameliorated the BL-induced increases in the lung collagen accumulation as well. Findings of a similar nature were also demonstrated when taurine (2.5%) and niacin (2.5%) were supplemented in the diet of hamsters used in the same BL model of IPF. The diet supplemented with taurine (2.5%), niacin (2.5%), or taurine (2.5%) + niacin (2.5%) also reduced AD-induced increases in lung collagen accumulation, phospholipids, MDAE and SOD activity. It was concluded that diet supplemented with taurine and/or niacin would completely or partially ameliorate chemically-induced pulmonary fibrosis.

Repeated episodes of C5a-induced neutrophil influx do not result in pulmonary fibrosis

Multiple reactive oxygen species-induced epithelial injury by glucose, glucose oxidase, and lactoperoxidase instillation in the lung results in a progressive interstitial fibrosis. To test the hypothesis that multiple pulmonary inflammatory responses alone would not result in fibrosis, three sequential inflammatory reactions were produced at weekly intervals in hamster lungs via intratracheal instillation of human recombinant C5a. Numbers of neutrophils and total inflammatory cells in bronchoalveolar lavage (BALF) increased significantly at 24 h after each C5a treatment compared with saline controls. Neutrophils increased by 3-, 33-, and 34-fold compared with the corresponding controls at 24 h after the first, second, and third doses, respectively, but returned to control levels by six days postinstillation. LTB4 levels increased by 24% and 20% compared with the corresponding controls at 24 h after the first and second doses but were not different from controls at other times. Hydroxyproline levels in treated animals did not differ significantly from control levels throughout the study. Protein levels were significantly increased at 24 h after the second and third doses and six days after the third dose compared with the corresponding controls. Occasional foci of neutrophils in alveolar spaces were observed at 24 h after each dose, but they decreased in frequency after six days. No foci of neutrophils were observed six days after the final dose, although some epithelial degeneration was observed by transmission electron microscopy. Our results indicate that pulmonary inflammation resulting from repeated influx of neutrophils in response to multiple instillations of C5a in the lung does not cause sufficient injury to result in pulmonary fibrosis.

Epithelial injury, inflammation, and repair in the hamster lung following intratracheal instillation of enzyme-generated oxidants

Oxidant-induced inflammatory and morphologic changes evoked by intratracheally instilled glucose, active glucose oxidase, and lactoperoxidase in hamsters are described. Similar solutions containing heat-denatured (DE) glucose oxidase served as a control treatment. During the 7-week post-treatment period, animals were sacrificed and lavaged, and their lungs were preserved for later study. Although a neutrophil-rich alveolitis was observed initially in both groups, the leukocytic influx and mild morphologic changes in DE-treated animals resolved within 7 days. In contrast, glucose oxidase mixtures caused necrotic alveolar epithelium, fibrin-like exudate, and significantly higher neutrophil and protein levels in bronchoalveolar lavage fluid (BALF) after 1 day. At 4 days, type II cell hyperplasia was extensive and BALF levels of all inflammatory cell types were significantly greater than BALF counts in DE animals. By 7 days, BALF macrophage and lymphocyte levels remained significantly elevated, and epithelial hyperplasia coincided with marked increases in lung hydroxyproline and interstitial cells. BALF parameters suggested that inflammation induced by glucose oxidase resolved within 15 days, yet total hydroxyproline levels remained elevated at 15 days and epithelial lesions were still detectable at 29 days. Oxidant-induced inflammation and epithelial injury were transient and preceded moderate collagen deposition.

Effects and levels of coenzyme Q10 in lung and liver in bleomycin-hamster model of lung fibrosis

As part of an ongoing study to search for potential antifibrotic agents which may reduce bleomycin-induced fibrosis of lung, hamsters were treated with 25 mg/kg coenzyme Q10 (CoQ10) for 2 days prior to and daily for 14 days after intratracheal instillation of bleomycin (5 U/kg body wt.). CoQ10 was found not to attenuate bleomycin-induced lung fibrosis. Treatment with CoQ10 did not raise the lung and liver content of CoQ10. On the other hand, bleomycin treatment alone tended to increase the lung and liver content of CoQ10. At the higher dose (7.5 U/kg), bleomycin almost doubled the hepatic CoQ10 content. Treatment with the lower dose (5 U/kg) of bleomycin and CoQ10 was always associated with higher levels of CoQ10 in both liver and lungs than treatment with either of them alone.

89Strontium-induced bone marrow depression suppresses the early inflammatory response and fibrosis caused by intratracheal bleomycin

To investigate the effect of bone marrow depression on the development of bleomycin-induced lung injury, F-344/Crl rats were given an intraperitoneal (IP) injection of 89SrCl2 (2 mCi/kg body weight) 7 days prior to the intratracheal (IT) instillation of 7.0 U/kg body weight bleomycin (Sr-bleomycin group). A second group of rats was given an IP injection of saline followed 7 days later by IT bleomycin (bleomycin group). Additional rats were given 89Sr IP and saline IT (Sr group) or saline IP and saline IT (saline group). Rats were sacrificed at 0, 3, 10, 21, and 30 days after the intratracheal instillations. 89Sr administration resulted in significantly lower numbers of circulating blood neutrophils and monocytes in the Sr-bleomycin group compared with the bleomycin group through at least the first 21 days following the IT instillations. Lymphocyte numbers were also depressed in the Sr-bleomycin group at days 3 and 21. Analysis of bronchoalveolar lavage fluid (BALF) revealed significantly reduced protein and lymphocyte numbers in the BALF from the 89Sr-bleomycin group compared with the bleomycin group at day 3, but not at later time points. Neutrophils in BALF were also lower (though not significantly) in the 89Sr-Bleomycin group at day 3. There was no difference in the number of BALF macrophages between the Sr-bleomycin and bleomycin groups at any time point throughout the study. Histology and morphometry showed the same trends as the BALF data with much less severe lesions in the 89SR-Bleomycin group compared with the bleomycin group at day 3, but not at later time points. At day 10, hydroxyproline values were significantly higher in the bleomycin group (47% increase above saline group) than the Sr-bleomycin group (only 18% increase above Sr group), but by day 21, there was no longer a significant difference between these two groups. These results demonstrate that bone marrow depression significantly suppresses the early inflammatory response and collagen deposition caused by a single IT dose of bleomycin, but has little effect on the resolution of bleomycin-induced injury.

Polyinosinic-polycytidylic acid, an interferon inducer, ameliorates bleomycin-induced lung fibrosis in mice

The inhibitory effect of polyinosinic-polycytidylic acid (Poly IC), an inducer of interferons, on bleomycin-induced lung collagen accumulation was investigated in mice. Poly IC (10 mg/kg, intraperitoneally) or saline was given for 2 days and immediately prior to intratracheal instillation of bleomycin (0.125 units/mouse) or an equivalent volume of saline and thereafter daily for 13 days. Lung hydroxyproline levels in saline-saline (control), Poly IC-saline (Poly IC), bleomycin-saline and bleomycin-Poly IC groups averaged 279, 287, 459, and 358 micrograms/lung, respectively. The bleomycin + Poly IC mice had significantly less lung hydroxyproline than bleomycin mice, but significantly more hydroxyproline than control or Poly IC mice. Similarly, bleomycin + Poly IC mice had significantly less protein in bronchoalveolar lavage fluid (BALF) supernatant than bleomycin mice, but significantly more protein than control or Poly IC mice. Total cell counts for cells recovered from BALF showed significant increases of 174 and 167% in bleomycin and bleomycin + Poly IC as compared to controls, while the Poly IC group showed a significant decrease of 47% which was primarily due to a decrease in alveolar macrophages. The bleomycin group had significantly more neutrophils, monocytes, macrophages, and lymphocytes than control mice, while bleomycin + Poly IC mice lacked the significant increase in lymphocytes. Bleomycin + Poly IC mice had significantly more monocytes than the bleomycin group. All bleomycin-treated mice had lung lesions, but no lesions were observed in control or Poly IC mice. Bleomycin + Poly IC mice had significantly more (58%) lesions than bleomycin. In contrast, the volume of interstitial lesion in bleomycin + Poly IC mice showed significantly less extracellular fibers (decreased by 62%) and no difference in fibroblasts as compared to bleomycin mice. Fibrotic lesions in bleomycin mice were multifocal and varied from large areas of organized connective tissue to thickened septa lined by cuboidal epithelial cells. Interstitial lesions in bleomycin + Poly IC had a significantly greater volume of mononuclear phagocytes and lymphocytes, but less organized connective tissue than the bleomycin group. Poly IC treatment ameliorated bleomycin-induced lung collagen accumulation.

Effects of three cysteine pro-drugs on bleomycin-induced lung fibrosis in hamsters

The cysteine pro-drug Z2196 ((2RS, 4R)-2-methylthiazolidine carboxylic acid) and two drugs with methyl esters attached to Z2196 (Z2197 and Z2199) were evaluated for antifibrotic effects in the hamster bleomycin model of lung fibrosis. Each drug or phosphate-buffered saline (PBS) was given daily (300 mg/kg intraperitoneally) for 2 days before intratracheal instillation of bleomycin (7.5 units/kg) or saline for an additional 13 days. Lung collagen measured as hydroxyproline was significantly increased to 138% of the control groups in the PBS + Bleomycin treated group, but the Z2196 + Bleomycin group was increased to 108% and was not statistically different from controls. Protein content of bronchoalveolar lavage supernatant in PBS + Bleomycin treated hamsters was significantly increased to 326% of controls. The protein content of bronchoalveolar lavage supernatant for all cysteine pro-drug + Bleomycin treated hamsters was increased to 160% of PBS + Bleomycin treated hamsters. All the Bleomycin treated hamsters had significantly more cells and more neutrophils recovered in bronchoalveolar lavage than controls. The PBS + Bleomycin treated hamsters had significantly more lymphocytes in bronchoalveolar lavage than all the other treatment groups. The Z2196 + Bleomycin and Z2197 + Bleomycin hamsters had significantly less monocytes in BALF than PBS + Bleomycin hamsters. The lung total sulfhydryl and nonprotein sulfhydryl in PBS + Bleomycin treated hamsters were increased to 210% and 253% of controls, respectively, whereas in Z2196 + Bleomycin hamsters they were increased to 152% and 153%, respectively. Histopathology of PBS + Bleomycin hamsters showed a diffuse mixed mononuclear alveolitis, multifocal fibrosis and peribronchiolar fibrosis, whereas Z2196 + Bleomycin hamsters showed notably less alveolitis and fibrosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Niacin attenuates bleomycin-induced lung fibrosis in the hamster

Bleomycin (BLM)-induced lung fibrosis has been shown to be accompanied by the activation of poly(ADP-ribose) polymerase and depletion of nicotinamide adenine dinucleotide (NAD) in the lung. Niacin, a precursor of NAD, was used in the present study to investigate its possible ameliorating effect on BLM-induced pulmonary fibrosis in hamsters. Niacin (500 mg/kg IP) or saline (IP) was injected daily for 16 or 23 days. On day 3, hamsters were treated with BLM (7.5 U/5 mL/kg) or an equivalent volume of saline intratracheally. BLM alone significantly increased lung hydroxyproline levels, bronchoalveolar lavage fluid protein concentration, and various inflammatory cell counts in the lavage in both experiments. In addition, BLM alone elevated prolyl hydroxylase and poly(adenosine-5'-diphosphate [ADP]-ribose) polymerase activities in the 3-week study. Niacin treatment significantly decreased BLM-elevated lung hydroxyproline, prolyl hydroxylase, and poly(ADP-ribose) polymerase activities. Histopathology revealed that niacin treatment attenuated BLM-induced thickened alveolar septa, foci of fibrotic consolidation, and accumulations of inflammatory cells in the parenchyma and air spaces. The ability of niacin to attenuate BLM-induced lung fibrosis in hamsters suggests that it may have potential as an antifibrotic agent in humans.

Dose-related effects of enzyme-generated oxidants on the biochemistry and morphology of the hamster lung

Reactive oxygen species (ROS) have been closely associated with a number of pathological disorders, including interstitial pulmonary fibrosis. While models of ROS-induced fibrosis offer advantages over chemically-induced fibrosis, the biochemical and morphological features of ROS-induced fibrosis have yet to be extensively documented. In this study, we evaluated the effect of initial ROS dose on lung injury and repair. Male hamsters received a single dose of glucose, glucose oxidase and lactoperoxidase via the intratracheal route. From 3 to 14 days post-treatment, a significant dose-related body weight loss was observed. There was a trend towards greater mortality with increasing dose. After 2 weeks, we noted significant, dose-related increases in lung levels of collagen, lipid peroxidation products, nucleic acids, and protein. Similarly, total lung catalase, lactic dehydrogenase and glutathione reductase activities were also elevated significantly above control values in a dose-related fashion. A concurrent, dose-dependent thickening of alveolar septa in ROS-treated lungs was composed of epithelial hyperplasia, hyperemia, edema and accumulations of interstitial fibers and macrophages. Interstitial and alveolar macrophages in ROS-induced lesions were enlarged and contained numerous primary and secondary lysosomes. These results demonstrate that, in the hamster lung, injury induced by enzyme-generated ROS can initiate dose-dependent fibroproliferative changes which eventuate into interstitial fibrosis.

Impairment in coupled beta-adrenergic receptor and adenylate cyclase system during bleomycin-induced lung fibrosis in hamsters

The purpose of this study was to evaluate the coupled beta-adrenergic receptor (BAR) and adenylate cyclase (AC) system of the lung during the course of the bleomycin-(Bleo) induced pulmonary fibrosis in hamsters. The BAR population, dissociation constants (Kd), AC activity, and its sensitivity to various stimulators were studied at 2, 4, 7, 14, and 21 days after intratracheal administration of either 1 unit of Bleo or an equivalent volume of saline. The BAR population in the lungs of Bleo-treated animals did not differ from control at the early times, but it was significantly reduced to 5.9 X 10(3) fmol and 3.6 X 10(3) fmol from the control values of 1.1 X 10(4) fmol and 1.5 X 10(4) fmol per lung at 14 and 21 days after treatment, respectively. The Kd values for control hamster lung ranged from 2.5 X 10(-11) M to 3.7 X 10(-11) M, and for Bleo-treated hamster lung, from 2.7 X 10(-11) M to 4.8 X 10(-11) M. The Kd at the earliest time, 2 days after treatment, did not differ significantly from the Kd values at the subsequent times in control, while for Bleo-treated hamster lung, the Kd values at 7, 14, and 21 days were significantly higher than the Kd at 2 days after treatment. The Kd values for Bleo-treated hamster lung were also significantly higher than control at 14 and 21 days. The AC activity of the lung in Bleo-treated hamster was significantly reduced to 67%, 40%, 38%, and 50% of their respective controls in response to H2O (basal), GTP (10(-4) M), GTP + isoproterenol (10(-4) M each), and NaF (10 mM) at 21 days after treatment. The extent of AC stimulation in Bleo-treated hamster lung in response to various stimulators was generally less than that of saline control. Reductions in the BAR population and increased Kd values in Bleo-treated hamster lung were attributed to its fibrogenic ability and not to nutritional deficiency, which may partly be accountable for decreased AC activity of the lung in these animals. However, there were qualitative differences in the lung AC activity between Bleo-treated and nutritionally deprived hamsters, since the enzyme from the latter group was generally more responsive to stimulators than the enzyme from the former group. It was concluded from the findings of this study that an impairment in the coupled BAR and AC system of the lung may be partly responsible for the fibrogenic ability of bleomycin.