Biochemical and structural alterations of hamster lungs in response to intratracheal administration of bleomycin

MOXIBUSTION HAS A POSITIVE EFFECT ON PULMONARY FIBROSIS: AN ALTERNATIVE APPROACH

BACKGROUND

An increasing number of people suffered idiopathic fibrosis (IPF) and the current treatment was far from clinical satisfaction. Moxibustion, another effective and safe unconventional therapy, had been introduced to treat this refractory disease. The study aimed to investigate the effect of moxibustion on a bleomycin A5-induced pulmonary fibrosis model.

MATERIALS AND METHODS

Sprague-dawley (SD) rats were randomly allocated to the blank group, model group, moxibustion group, and prednisone group, for which they received no treatment, modeling, moxibustion treatment and prednisone treatment. After four-week treatment, the rats were euthanized for Hematoxylin and Eosin (H.E.) staining, and TGF-β1 and IFN-γ protein and mRNA detection in lungs.

RESULTS

In the model group, TGF-β1 was significantly increased and IFN-γ was significantly decreased at both protein and mRNA levels in comparison to the blank group. In the moxibustion and prednisone group, however, TGF-β1 was decreased and IFN-γ was increased at both protein and mRNA levels in comparison to the model groups. Compared with prednisone, moxibustion showed comparable effect in lowing TGF-β1 (P>0.05) and better effect in up-regulating IFN-γ (P>0.05).

CONCLUSION

The study concludes moxibustion protected pulmonary fibrosis by downregulating TGF-β1 and upregulating IFN-γ cytokines at both mRNA and protein levels, and the effect was comparable to prednisone. Moxibustion could be used as a therapeutic alternative treatment for pulmonary fibrosis.

Dapson in heterocyclic chemistry, part VIII: synthesis, molecular docking and anticancer activity of some novel sulfonylbiscompounds carrying biologically active 1,3-dihydropyridine, chromene and chromenopyridine moieties

Several new sulfonebiscompounds having a biologically active 1,2-dihydropyridine-2-one 3-19, acrylamide 20, chromene 21, 22 and chromenopyridine 23, 24 moieties were synthesized and evaluated as potential anticancer agents. The structures of the products were confirmed via elemental analyses and spectral data. The screening tests showed that many of the biscompounds obtained exhibited good anticancer activity against human breast cell line (MCF7) comparable to doxorubicin which was used as reference drug. Compounds 11, 17 and 24 showed IC50 values 35.40 μM, 29.86 μM and 30.99 μM, respectively. In order to elucidate the mechanism of action of the synthesized compounds as anticancer agents, docking on the active site of farnesyltransferase and arginine methyltransferase was also performed and good results were obtained.

A novel single-chain-Fv antibody against connective tissue growth factor attenuates bleomycin-induced pulmonary fibrosis in mice

BACKGROUND AND OBJECTIVE

Connective tissue growth factor (CTGF) has been identified as playing critical roles in fibrosis and is a promising therapeutic target. In a previous study, we used a phage display library to develop a humanized single-chain variable fragment antibody (scFv) against CTGF. In the present study, the protective effect of anti-CTGF scFv against bleomycin (BL)-induced pulmonary fibrosis was investigated in mice.

METHODS

The expression of α-smooth muscle actin in human embryonic lung fibroblast (HELF) cells was analysed by western blotting. A mouse model of pulmonary fibrosis was established by tracheal injection of BL (5 mg/kg). Mice received anti-CTGF scFv (4 mg/kg, three times a week) by i.v. injection. The effects of anti-CTGF scFv were evaluated by leukocyte counts in BAL fluid, hydroxyproline measurements in lung tissue and pathological examination.

RESULTS

α-Smooth muscle actin expression was decreased in HELF cells treated with anti-CTGF scFv. Anti-CTGF scFv significantly reduced the numbers of inflammatory leukocytes (total and differential count) in BAL fluid, as well as the hydroxyproline content of lung tissue. The severity of alveolitis and fibrosis in the mouse model was markedly attenuated by treatment with anti-CTGF scFv.

CONCLUSIONS

Anti-CTGF scFv may potentially be developed as a useful inhibitor of pulmonary fibrosis.

Phosphoinositide 3-kinase γ plays a critical role in bleomycin-induced pulmonary inflammation and fibrosis in mice

PI3Kγ is central in signaling diverse arrays of cellular functions and inflammation. Pulmonary fibrosis is associated with pulmonary inflammation, angiogenesis, and deposition of collagen and is modeled by instillation of bleomycin. The role of PI3Kγ in mediating bleomycin-induced pulmonary inflammation and fibrosis in mice and potential mechanisms involved was investigated here. WT or PI3Kγ KO mice were instilled with bleomycin and leukocyte subtype influx, cytokine and chemokine levels, and angiogenesis and tissue fibrosis evaluated. The activation of lung-derived leukocytes and fibroblasts was evaluated in vitro. The relevance of PI3Kγ for endothelial cell function was evaluated in HUVECs. PI3Kγ KO mice had greater survival and weight recovery and less fibrosis than WT mice after bleomycin instillation. This was associated with decreased production of TGF-β(1) and CCL2 and increased production of IFN-γ and IL-10. There was reduced expression of collagen, fibronectin, α-SMA, and von Willebrand factor and decreased numbers and activation of leukocytes and phosphorylation of AKT and IκB-α. PI3Kγ KO mice had a reduced number and area of blood vessels in the lungs. In vitro, treatment of human endothelial cells with the PI3Kγ inhibitor AS605240 decreased proliferation, migration, and formation of capillary-like structures. AS605240 also decreased production of collagen by murine lung-derived fibroblasts. PI3Kγ deficiency confers protection against bleomycin-induced pulmonary injury, angiogenesis, and fibrosis through the modulation of leukocyte, fibroblast, and endothelial cell functions. Inhibitors of PI3Kγ may be beneficial for the treatment of pulmonary fibrosis.

Therapeutic effects of evasin-1, a chemokine binding protein, in bleomycin-induced pulmonary fibrosis

CC chemokines play an important role in the pathogenesis of idiopathic pulmonary fibrosis. Few studies have evaluated the efficacy of therapeutically targeting CC chemokines and their receptors during interstitial lung diseases. In the present study, the therapeutic effects of Evasin-1, a tick-derived chemokine-binding protein that has high affinity for CCL3/microphage inflammatory protein (MIP)-1α, was investigated in a murine model of bleomycin-induced lung fibrosis. CCL3/MIP-1α concentrations in lung homogenates increased significantly with time after bleomycin challenge, and this was accompanied by increased number of leukocytes and elevated levels of CCL2/monocyte chemoattractant protein (MCP)-1, CCL5/regulated upon activation, normal T cell expressed and secreted, TNF-α and transforming growth factor-β(1), and pulmonary fibrosis. Administration of evasin-1 on a preventive (from the day of bleomycin administration) or therapeutic (from Day 8 after bleomycin) schedule decreased number of leukocytes in the lung, reduced levels of TNF-α and transforming growth factor-β(1), and attenuated lung fibrosis. These protective effects were similar to those observed in CCL3/MIP-1α-deficient mice. In conclusion, targeting CCL3/MIP-1α by treatment with evasin-1 is beneficial in the context of bleomycin-induced lung injury, even when treatment is started after the fibrogenic insult. Mechanistically, evasin-1 treatment was associated with decreased recruitment of leukocytes and production of fibrogenic cytokines. Modulation of CCL3/MIP-1α function by evasin-1 could be useful for the treatment of idiopathic pulmonary fibrosis.

Role of the chemokine receptor CXCR2 in bleomycin-induced pulmonary inflammation and fibrosis

Pulmonary fibrosis is characterized by chronic inflammation and excessive collagen deposition. Neutrophils are thought to be involved in the pathogenesis of lung fibrosis. We hypothesized that CXCR2-mediated neutrophil recruitment is essential for the cascade of events leading to bleomycin-induced pulmonary fibrosis. CXCL1/KC was detected as early as 6 hours after bleomycin instillation and returned to basal levels after Day 8. Neutrophils were detected in bronchoalveolar lavage and interstitium from 12 hours and peaked at Day 8 after instillation. Treatment with the CXCR2 receptor antagonist, DF2162, reduced airway neutrophil transmigration but led to an increase of neutrophils in lung parenchyma. There was a significant reduction in IL-13, IL-10, CCL5/RANTES, and active transforming growth factor (TGF)-beta(1) levels, but not on IFN-gamma and total TGF-beta(1,) and enhanced granulocyte macrophage-colony-stimulating factor production in DF2162-treated animals. Notably, treatment with the CXCR2 antagonist led to an improvement of the lung pathology and reduced collagen deposition. Using a therapeutic schedule, DF2162 administered from Days 8 to 16 after bleomycin reduced pulmonary fibrosis and levels of active TGF-beta(1) and IL-13. DF2162 treatment reduced bleomycin-induced expression of von Willebrand Factor, a marker of angiogenesis, in the lung. In vitro, DF2162 reduced the angiogenic activity of IL-8 on human umbilical vein endothelial cells. In conclusion, we show that CXCR2 plays an important role in mediating fibrosis after bleomycin instillation. The compound blocks angiogenesis and the production of pro-angiogenic cytokines, and decreases IL-8-induced endothelial cell activation. An effect on neutrophils does not appear to account for the major effects of the blockade of CXCR2 in the system.

Halofuginone does not reduce fibrosis in bleomycin-induced lung injury

Halofuginone, a coccidiostatic alkaloid, has anti-fibrotic properties, and may be useful as a therapeutic agent in lung fibrosis. To test this hypothesis we investigated the effect of halofuginone on bleomycin-induced lung fibrosis in Sprague-Dawley rats. Treatment groups included: (1) a single intratracheal (IT) instillation of 1.2U bleomycin, and intraperitoneal (IP) injection of halofuginone (0.5 mg/dose), every other day; (2) IT 1.2U bleomycin and IP distilled water (D.W.), every other day; (3) IT 0.8U bleomycin and daily IP halofuginone (0.5 mg/dose); (4) IT 0.8U bleomycin and daily IP D.W.; (5) IT saline and IP halofuginone, every other day; (6) IT saline and daily IP D.W.; (7) IT 0.625U bleomycin and oral halofuginone (10 mg/kg rodent lab chow); (8) IT 0.625U bleomycin and standard lab chow. Animals were studied 14 days after IT instillation. Lung injury was evaluated by total and differential cell count in bronchoalveolar lavage fluid, by a semi-quantitative morphological index of lung injury, and by biochemical analysis of lung hydroxyproline content. Overt signs of lung injury were apparent in bleomycin-treated rats by all measures. These changes were not affected by treatment with halofuginone, irrespective of the treatment regimen used. This study does not support the use of halofuginone to prevent or ameliorate lung fibrosis.

All-trans-retinoic acid (ATRA) is of no benefit in bleomycin-induced lung injury

All-trans-retinoic acid (ATRA) has anti-fibrotic and antiinflammatory properties, and may be useful as a therapeutic agent in lung fibrosis. To test this hypothesis we investigated the effect of ATRA on bleomycin-induced lung fibrosis in Sprague-Dawley rats. Treatment groups included: (1) a single intratracheal (i.t.) instillation of bleomycin and daily intraperitoneal (i.p.) injection of 0.5 mg/kg per day ATRA; (2) i.t. bleomycin and i.p. ATRA, 2 mg/kg per day, (3) i.t. bleomycin and i.p. diluent (cottonseed oil); (4) i.t. saline and i.p. ATRA, 0.5 mg/kg per day, (5) i.t. saline and i.p. ATRA, 2 mg/kg per day; and (6) i.t. saline and i.p. diluent. Animals were studied 14 days after i.t. instillation. Lung injury was evaluated by total and differential cell count in bronchoalveolar lavage fluid, by a semi-quantitative morphological index of lung injury, and by biochemical analysis of lung hydroxyproline content. Overt signs of lung injury were apparent in bleomycin-treated rats by all measures. These changes were not affected by treatment with ATRA at either dose. This study does not support the use of ATRA to prevent or ameliorate lung fibrosis.

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.

Perspective article: transforming growth factor-beta: crossroad of glucocorticoid and bleomycin regulation of collagen synthesis in lung fibroblasts

Fibrosis is a consequence of injury which is characterized by accumulation of excess collagen and other extracellular matrix components, resulting in the destruction of normal tissue architecture and function. Transforming growth factor-beta, a potent wound healing agent, has also been shown to be an agent that can produce fibrosis because it is a potent stimulator of collagen synthesis. Both glucocorticoids and bleomycin have recently been shown to affect collagen synthesis in opposite directions, by utilizing a common pathway of involving transforming growth factor-beta activator protein binding to the transforming growth factor-beta element. This article presents a mechanistic overview of collagen synthesis regulation by glucocorticoids and bleomycin through the transforming growth factor-beta pathway.

gamma-Linolenic acid-containing diet attenuates bleomycin-induced lung fibrosis in hamsters

Although bleomycin (BLM), an antineoplastic drug, is used in the treatment of a variety of tumors, the mechanism(s) that contribute to its induced lung injury and fibrosis are not fully elucidated. Since alterations in the levels of certain fatty acid metabolites have been associated with BLM-induced lung injury, we tested the effects of dietary gamma-linolenic acid (GLA)-containing evening primrose oil on BLM-induced morphological alterations in the hamster lung, the marked elevation of tissue hydroxyproline (a marker for collagen synthesis), and elevated generation of arachidonic acid metabolites (marker of inflammatory mediators). Our data revealed that after 14 d of dietary GLA-containing oil (i) BLM-induced elevation of lung hydroxyproline was suppressed (P < 0.05), (ii) the marked BLM-induced elevation of lung leukotriene B4 (LTB4) (a marker of polymorphanuclear generation of proinflammatory LTB4) was significantly suppressed (P < 0.05). The decrease in LTB4 was accompanied by marked elevations (P < 0.05) of lung prostaglandin E1 (PGE1) and 15-hydroxyeicosatrienoic acid (15-HETrE), both with known antiinflammatory properties. Taken together, data from these studies suggest that dietary GLA-containing oil contributes to tissue elevation of PGE1 and 15-HETrE, which in vivo may attenuate lung inflammation and fibrosis.

Direct toxic effect of bleomycin on alveolar type 2 cells

We studied the in vitro toxicity of bleomycin (BLM) on primary cultures of rat alveolar type 2 cells (T2 cells). It was shown that BLM was directly toxic for T2 cells in a dose- and time-dependent manner. Lung fibroblasts (LF) appear to be more resistant than T2 cells. Modulation of intracellular glutathione concentration was associated with changes in cytotoxicity. Furthermore, the addition of O-phenanthroline to the cellular medium reduced significantly BLM toxicity, suggesting the involvement of intra-cellular ferric ion. We also found that BLM toxicity was associated with a decreased release of phosphatidylcholine by T2 cells, the main component of surfactant. Protective effect of O-phenanthroline and the involvement of glutathione may be an alternative approach to the protection of BLM-induced damage.

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.

Modulation of cyclophosphamide-induced early lung injury by curcumin, an anti-inflammatory antioxidant

Cyclophosphamide causes lung injury in rats through its ability to generate free radicals with subsequent endothelial and epithelial cell damage. In order to observe the protective effects of a potent anti-inflammatory antioxidant, curcumin (diferuloyl methane) on cyclophosphamide-induced early lung injury, healthy, pathogen free male Wistar rats were exposed to 20 mg/100 g body weight of cyclophosphamide, intraperitoneally as a single injection. Prior to cyclophosphamide intoxication oral administration of curcumin was performed daily for 7 days. At various time intervals (2, 3, 5 and 7 days post insult) serum and lung samples were analyzed for angiotensin converting enzyme, lipid peroxidation, reduced glutathione and ascorbic acid. Bronchoalveolar lavage fluid was analyzed for biochemical constituents. The lavage cells were examined for lipid peroxidation and glutathione content. Excised lungs were analyzed for antioxidant enzyme levels. Biochemical analyses revealed time course increases in lavage fluid total protein, albumin, angiotensin converting enzyme (ACE), lactate dehydrogenase, N-acetyl-beta-D-glucosaminidase, alkaline phosphatase, acid phosphatase, lipid peroxide levels and decreased levels of glutathione (GSH) and ascorbic acid 2, 3, 5 and 7 days after cyclophosphamide intoxication. Increased levels of lipid peroxidation and decreased levels of glutathione and ascorbic acid were seen in serum, lung tissue and lavage cells of cyclophosphamide groups. Serum angiotensin converting enzyme activity increased which coincided with the decrease in lung tissue levels. Activities of antioxidant enzymes were reduced with time in the lungs of cyclophosphamide groups.(ABSTRACT TRUNCATED AT 250 WORDS)

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 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.

Application of alkaline unwinding to analysis of strand breaks induced by bleomycin in hamster lung DNA in vivo

Strand breaks in hamster lung DNA were analyzed following in vivo exposure to bleomycin. An alkaline unwinding procedure involving separation of single-strand from double-strand DNA by hydroxylapatite chromatography followed by fluorescence detection of DNA with bisbenzimide was adapted for these studies. Procedures were developed that allowed preparation of DNA from lungs of control animals with a relatively low amount of single-strand DNA relative to double-strand DNA. Time dependence of unwinding was demonstrated using samples that were damaged deliberately by brief probe sonication. To verify that residual bleomycin remaining in lungs at the time of sacrifice did not cause strand breaks during sample preparation, bleomycin was added to minced lung in vitro. Under these conditions, the ratio of single-strand to double-strand DNA was not increased significantly. Substantial strand breaks were produced in vivo at 15 min and 1 h following intratracheal instillation of bleomycin into hamsters, as evidenced by a 5-6-fold increase in the ratio of single-strand to double-strand DNA relative to controls. The DNA damage appeared to be repaired within 1 day following exposure.

Mechanisms of bleomycin-induced lung damage

Bleomycins are a family of compounds produced by Streptomyces verticillis. They have potent tumour killing properties which have given them an important place in cancer chemotherapy. They cause little marrow suppression, but pulmonary toxicity is a major adverse effect. The mechanisms of cell toxicity are well described based on in vitro experiments on DNA. The bleomycin molecule has two main structural components: a bithiazole component which partially intercalates into the DNA helix, parting the strands, as well as pyrimidine and imidazole structures, which bind iron and oxygen forming an activated complex capable of releasing damaging oxidants in close proximity to the polynucleotide chains of DNA. This may lead to chain scission or structural modifications leading to release of free bases or their propenal derivatives. The mechanisms are well described based on in vitro experiments on DNA, but how they relate to intact cells in whole animals is more tenuous. Bleomycin is able to cause cell damage independent from its effect on DNA by induction lipid peroxidation. This may be particularly important in the lung and in part account for its ability to cause alveolar cell damage and subsequent pulmonary inflammation. The lung injury seen following bleomycin comprises an interstitial oedema with an influx of inflammatory and immune cells. This may lead to the development of pulmonary fibrosis, characterized by enhanced production and deposition of collagen and other matrix components. Several polypeptide mediators capable of stimulating fibroblasts replication or excessive collagen deposition have been implicated in this, but the precise role of these in bleomycin-induced fibrosis is yet to be demonstrated. Current therapy for bleomycin-induced lung damage is inadequate, with corticosteroids most often used. Given the mechanism of action described above, antioxidants and iron chelators might be beneficial. Although, studies to date are equivocal and there is insufficient evidence to promote their use clinically. Novel drugs are currently being developed and it is hoped these may be more useful.

The effect of bleomycin on the uptake and incorporation of [14C]choline into phospholipids in hamster lung tissue slices

Intratracheal administration of the anticancer drug bleomycin to hamsters produced an increase in the uptake and incorporation of [14C]choline into phospholipids of lung slices in vitro. The stimulatory effect is opposite to the results obtained previously using [14C]acetate and would appear to occur distal to cytidine diphosphocholine. Although alternate explanations are possible, the results are consistent with morphological evidence, published by others, indicating an increase in lung phospholipid following bleomycin treatment, and illustrate the significance of precursor selection when evaluating the effects of xenobiotics on phospholipid synthesis.

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.

Characterization of a phospholipase A2 in hamster lung and in vitro and in vivo effects of bleomycin on this enzyme

Phospholipase A2 (PLA2) activity from adult hamster lung was characterized using L-alpha-1-palmitoyl-2-arachidonyl-[arachidonyl-1-14C]-phosphatidylcholine as the substrate. The released [14C]-arachidonic acid was separated by TLC. The enzyme activity increased with increasing incubation time (0-120 minutes), calcium ion concentration (0-25.0 mM) and protein (0-2.0 mg). The optimum pH was 8.0. Deoxycholate had a concentration dependent (0.1 to 0.5 mM) inhibitory effect on the activity. PLA2 specific activity was the highest in mitochondrial fraction. PLA2 activity following incubation with bleomycin was increased in a dose related fashion. In vivo study showed that both PLA2 activity and collagen content in hamster lung were significantly elevated at 14 days followed intratracheal instillation of bleomycin. The activation of PLA2 may play an important role in bleomycin-induced pulmonary toxicity.

Dietary fish oil inhibits bleomycin-induced pulmonary fibrosis in the rat

Intratracheal bleomycin induces pulmonary fibrosis in experimental animals, but the mechanisms involved are poorly understood. Since altered levels of fatty acid metabolites are associated with bleomycin-induced lung injury, we examined the effects of a change in dietary fat on bleomycin-induced fibrosis. Previously we have shown that an essential fatty acid-deficient diet can reduce the severity of bleomycin-induced pulmonary fibrosis. The present study examined the effect of replacement of usual dietary fat with menhaden oil, rich in eicosapentaenoic acid, on the development of pulmonary fibrosis. Weanling rats were raised on a standard laboratory diet or a diet consisting of a fat-free powder to which was added 25% (w/w) of menhaden oil. After 8 weeks of feeding, the animals received either 1.5 units of bleomycin or an equivalent volume of saline intratracheally. In animals receiving the laboratory diet, bleomycin treatment produced a 44% increase in total lung protein content when compared to saline-treated controls (p less than 0.001) and a 77% increase in total lung hydroxyproline content (p less than 0.01). In contrast, bleomycin-treated animals receiving the menhaden oil diet had only small increases, which did not reach statistical significance, in protein and hydroxyproline content in the lung. Bronchoalveolar lavage cellularity did not differ among the treatment groups, but the percentage of lavage macrophages was slightly diminished in bleomycin-treated animals receiving the laboratory diet. Cellular differentials of lavage fluid did not differ significantly between bleomycin- and saline-treated animals receiving the menhaden oil diet. Bleomycin-induced histologic changes, quantitated by morphometric analysis, were significantly reduced with the menhaden oil diet. We conclude that a diet rich in eicosapentaenoic acid can significantly ameliorate bleomycin-induced pulmonary fibrosis, possibly via alterations in eicosanoid metabolism.

Effects of chronic administration of doxorubicin on myocardial alpha-adrenergic receptors, histamine, cyclic nucleotides, calcium, norepinephrine, calmodulin, and guanylate cyclase activity, and plasma catecholamines in rats

The present study examined changes in the levels of plasma catecholamines and myocardial histamine, guanylate cyclase activity, cyclic nucleotides, calcium, calmodulin, and norepinephrine following chronic administration of doxorubicin (DXR). In addition, changes in myocardial alpha 1-adrenergic receptor density and dissociation constant were measured. Rats received DXR (2 mg/kg) or vehicle weekly by the SC route for 2, 4, 8, and 13 weeks. Rats were sacrificed one week after their last dose. One group of rats treated for 13 weeks was sacrificed at 19 weeks, six weeks after the last dose. Heart histamine was unchanged at 3, 5, 9, and 19 weeks, yet at 14 weeks it was significantly elevated in DXR-treated rats over controls. Cardiac calcium, norepinephrine, and cyclic GMP levels were unchanged throughout the course of the study. Cardiac cAMP and calmodulin levels were unchanged at 3, 5, 9, and 14 weeks. At 19 weeks in DXR-treated rats, cAMP was depressed while calmodulin was elevated. Plasma catecholamines and myocardial guanylate cyclase activity examined at 14 weeks were unchanged. In contrast, alpha 1 receptor density examined at 14 weeks in DXR-treated rats was significantly depressed while the dissociation constant was unchanged. Changes in cAMP and calmodulin are suggestive of a redistribution of calcium, although total levels of calcium were unchanged. The depression of cAMP indicates damage to the membrane bound enzyme, adenylate cyclase, and that the membrane interaction of doxorubicin appears to be an integral part of the biochemical mechanism of its toxicity.

Increases in severity of lung damage and mortality by treatment with cyclo and lipoxygenase inhibitors in bleomycin and hyperoxia model of lung injury in hamsters

Effects of ibuprofen (I), a cyclooxygenase inhibitor, and of nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, on bleomycin (B) and hyperoxia (H) induced acute lung damage and mortality were studied in hamsters. Hamsters, after receiving bleomycin, 0.25 unit, intratracheally were treated subcutaneously with vehicle (BHV group), ibuprofen, 10 mg/kg, (BHI group) or NDGA 10 mg/kg (BHNDGA group) and then exposed to 70% oxygen (O2) for 72 h. Daily treatment in each case continued for 14 days. The cumulative mortality at 0, 2, 4, 7, and 14 days after O2 exposure was as follows: 0, 5, 13, 26, and 50%, in BHV; 0, 10, 21, 33, and 67% in BHI; and 2, 21, 51, 71, and 92% in BHNDGA groups, respectively. The lung hydroxyproline content in pooled control hamsters averaged 721.1 +/- 22.3 (SE) micrograms/lung. The lung hydroxyproline content in animals in BHV, BHI, and BHNDGA groups was significantly increased at 4, 7, and 14 days after exposure when compared to controls. There were, however, no significant differences in the hydroxyproline content of the lungs among animals in BHV, BHI, and BHNDGA groups at any post-exposure time. Morphology of lungs of the BHV group showed an infiltrate of monocytes, lymphocytes, and some neutrophils (PMN) at 2 days but was composed primarily of monocytes and macrophages at 4, 7, and 14 days post-exposure. Multifocal fibrosis was observed at 7 days and was more diffuse by 14 days. Multifocal fibrosis in lungs from the BHI group was seen at 4 days with foci being larger at 7 and 14 days. Multifocal epithelial necrosis was observed at 14 days.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Effects of dietary fats on bleomycin-induced pulmonary fibrosis

Bleomycin treatment has been used for the experimental induction of pulmonary fibrosis, but the mechanisms involved are poorly understood. Since alterations in the levels of certain fatty acid metabolites have been associated with bleomycin-induced lung injury, we examined the effects of different dietary fats on the development of bleomycin-induced pulmonary fibrosis. Weanling rats were raised on standard laboratory feed or a diet consisting of a fat-free powder to which was added either coconut oil or beef tallow (25% w/w). After 8 weeks of feeding, animals received either 1.5 units bleomycin or an equivalent volume of saline intratracheally. Bleomycin treatment resulted in significant increases in total lung hydroxyproline content in the groups fed the standard lab diet (p less than 0.001) and beef tallow diet (p less than 0.001), but not in the group receiving the coconut oil diet. Furthermore, the lung hydroxyproline content in bleomycin-treated animals was less with the beef tallow diet compared with standard lab feed (p less than 0.05). Bleomycin treatment resulted in an increase in thiobarbituric acid-reactive products, an index of lipid peroxidation, in lungs from animals fed the standard lab diet, but not in the other diet groups. The percentage of diseased lung, as determined by morphometric analysis, was increased in bleomycin-treated animals from all diet groups (p less than 0.05). We conclude that alterations in dietary fats can reduce the severity of pulmonary fibrosis resulting from bleomycin treatment. Possible mechanisms for this effect include alterations in eicosanoid metabolism or changes in immune or effector cell function.

Pharmacokinetics, subcellular distribution, and covalent binding of [3H]bleomycin in hamsters after intratracheal administration

Pharmacokinetics, subcellular distribution (SCD), and covalent binding of a single dose of 1 microCi of [S-methyl-3H]bleomycin ([3H]-BLM]) in combination with one unit of unlabeled bleomycin were studied in hamsters following intratracheal (IT) injection. The radioactivity decreased from the lung biexponentially with time. The apparent half-time of absorption for the alpha-phase was 1.1 and 17.9 hr for the beta-phase. The plasma disappearance curve of [3H]BLM fits to a two-compartmental model with the apparent half-life removal for the alpha-phase being 1.6 hr and for the beta-phase 116.9 hr. The radioactivity was detected in all studied tissues. The radioactivity from spleen, testicle, liver, fat, RBC, brain, adrenal, and kidney manifested only the alpha-phase of the disappearance curve, while the beta-phase was complicated by redistribution processes. Of the eight tissues, the spleen had the shortest (2.0 hr) and kidney the longest (12.1 hr), and the remaining tissues had half-lives which ranged from 4 to 10 hr. The SCD study revealed that 85 to 95% of the total radioactivity in the lung and liver homogenate was associated with the soluble fraction (SF) at 30 min after treatment, thereafter, the radioactivity from both tissues gradually decreased to 60% of the total at 24 hr. The SF of the lung homogenate had the highest specific radioactivity (SRA) of any of the fractions during the period between 0.5 and 6 hr. The SRA, however, decreased biexponentially and attained a value similar to that of the mitochondrial and microsomal fractions at 12 and 24 hr after treatment. In the case of liver, the SF had the highest, the nuclear the lowest, and mitochondrial and microsomal fractions the same level of SRA at 30 min. Thereafter, the SRA of all fractions were increased with time. A significant amount of radioactivity from [3H]BLM was covalently bound to lung, liver, and plasma proteins. The SF of the lung contained an increasing amount of radioactivity covalently bound after 1.5 hr of [3H]BLM injection and nearly all radioactivity measured in the plasma was covalently bound. It was concluded from the findings of this study that the presence of a major portion of [3H]BLM in the SF of the lung and its covalent linkage with the proteins of this fraction might initiate the complex sequence of events at the metabolic level necessary for the pneumotoxicity.

Interstitial pulmonary fibrosis

The study of animal models of IPF has demonstrated that there is a stereotyped response of the respiratory airspace walls to a wide variety of injuries. Inflammatory and immune effector cells play a major and complex role in the fibrosing process. They may contribute to the injury of the lung beyond the original insult. These cells secrete substances that play an important role in determining cell traffic in the lungs and in controlling the connective tissue-producing cells. Products derived from the inflammatory response may interfere with protection of normal lung matrix, although injury to lung matrix itself does not lead to fibrosis. Injury to endothelial cells and especially type I epithelial cells appears to play a major role in the fibrogenic response. Further understanding of the factors that injure these cells, the development of methods of protecting them from injury, and a clear understanding of their role in the fibrogenic process appear to be key to developing better methods of preventing and treating interstitial pulmonary fibrosis.

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

The purpose of this study was to analyze the cellular and noncellular components of bronchoalveolar lavage fluid (BALF) at varying times during the development of pulmonary fibrosis induced by bleomycin. Hamsters were killed and lavaged in situ following the administration of a single intratracheal injection of 1 unit of bleomycin or an equivalent volume of sterile isotonic saline. The results show that the total cell counts in the BALF of bleomycin-treated hamsters, as compared with controls, were increased 7.7, 4.4, 2.4, 1.6, and 1.9-fold at 2, 4, 7, 14, and 21 days after treatment, respectively. The predominant cell types in the BALF of control animals were macrophages which constituted 84% of the total cells, followed by lymphocytes, 11%. The predominant cell types in the BALF of bleomycin-treated animals were polymorphonuclear leukocytes (PMN) which constituted 65% at two days and approximately 50% of the total at 4, 7, and 14 days; at 21 days macrophages were the predominant cell type constituting 50%, followed by lymphocytes at 30%. However, the total number of lymphocytes was not increased at 21 days compared to previous times. The noncellular protein content of BALF from bleomycin-treated hamsters, an index of pulmonary vascular permeability, was increased to 224, 559, 637, and 270% of control (2.7 mg/lung) at 2, 4, 7, and 14 days after treatment, respectively, and returned to control levels at 21 days. The acid phosphatase activity in the supernatant of BALF of bleomycin-treated animals was significantly increased to 181, 181, 199, 176, and 125% of control (258 units/lung) at 2, 4, 7, 14, and 21 days, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

A new model of diffuse interstitial pulmonary fibrosis in the rat

We have produced experimental diffuse interstitial pulmonary fibrosis in rats with a combination of low and repeated doses of paraquat plus continuous exposure to normobaric 74% O2 in the breathing air for several weeks. Pulmonary fibrosis was evaluated histologically and biochemically, through the determination of total collagen content in the lung. Our procedure is characterized by low initial mortality, the development of extensive distortion of the pulmonary architecture, and the presence of severe and diffuse interstitial fibrosis. The model was compared with bleomycin-induced pulmonary fibrosis in the same rat strain, in which the process is focal and leaves most of the lung unaffected. We conclude that lung damage produced by the combination of low doses of paraquat plus normobaric 74% O2 concentration in the breathing air is an adequate experimental model of diffuse interstitial pulmonary fibrosis as it occurs in many of the human cases of this condition.

The effect of bleomycin on lung metabolism of prostaglandin E2 in hamster

Lung is a major site of prostaglandin synthesis and degradation. One site of metabolism has been shown to be the endothelial cell. Metabolism of prostaglandins has been shown to be influenced by both physiological and pathological mechanism. Furthermore, it has been suggested that a relationship might exist between pulmonary disease and the lung's ability to synthesize and/or degrade prostaglandins. Therefore, we evaluated if bleomycin-induced fibrosis, a model of human pulmonary fibrosis, affects the ability of lung to metabolize prostaglandins. Single pass metabolism of prostaglandin E2 was evaluated in an isolated, perfused and ventilated lung of hamsters at 5 and 500 nM concentrations 4,7,14,21 and 28 days after intratracheal bleomycin. The metabolism of prostaglandin E2 was not changed at the 5 nM level, but was significantly decreased at 500 nM level on day 14 and day 28 after intratracheal bleomycin. The results suggest that intratracheal bleomycin causes alterations in prostaglandin metabolism; the mechanism(s) is unknown but may be related to endothelial cell damage and possible changes in alveolar-capillary surface area.

Effects of bleomycin on 14C-proline uptake, its incorporation into proteins and hydroxylation in collagenous proteins of hamster lung slices

The uptake of 14C-proline by lung slices and its incorporation into trichloroacetic-acid (TCA)-insoluble proteins and hydroxylation in collagenous proteins were studied. They were found to be linearly increased with the incubation time for as long as 8 h. The effects of different concentrations of bleomycin on these parameters were subsequently investigated. Bleomycin at 10(-3) M significantly reduced the uptake of 14C-proline to 75% of the control value. The incorporation of 14C-proline into TCA-insoluble proteins was reduced to 84%, 78% and 75% of the control at 2.5 X 10(-4) M, 5 X 10(-4) M and 10(-3) M concentrations of bleomycin, respectively. Bleomycin failed to alter the proline pool size of the lung slices at any of these concentrations. In addition, bleomycin also inhibited the hydroxylation of 14C-proline into collagen to 72% and 69% of the control at 5 X 10(-4) M and 10(-3) M, respectively. These findings show that bleomycin-induced increases in collagen synthesis in vivo is probably secondary to inflammatory reactions of the lung and bleomycin per se has little effect on increased collagen synthesis responsible for lung fibrosis.

Increases in lung prolyl hydroxylase and superoxide dismutase activities during bleomycin-induced lung fibrosis in hamsters

Intratracheal administration of bleomycin causes pulmonary fibrosis in hamsters. Using this model the activities of lung prolyl hydroxylase and superoxide dismutase and the accumulation of neutral salt soluble and insoluble collagens have been determined. One unit of bleomycin was injected intratracheally to hamsters, whereas control animals received an equivalent volume of sterile saline by the same route. Total lung prolyl hydroxylase activity was significantly elevated at all times following bleomycin treatment. The activity was increased as early as 2 days, peaked to a maximum value of 400% of the control at 14 days, followed by a sharp decline to 235% and 180% of the control activity at 21 and 28 days after bleomycin treatment, respectively. Except for the earliest time (2 days), lung prolyl hydroxylase specific activity was also significantly elevated at all times after bleomycin treatment. A significant increase in both total and specific activities of lung superoxide dismutase was also observed at all times after bleomycin treatment. Total activity peaked to a maximum value of 315% of the control activity at 14 days and the specific activity to a maximum value of 190% of the control at 21 days after bleomycin treatment. Thereafter, both activities declined, but were still significantly elevated over the control at 28 days after the treatment. Lung proline pool size was significantly increased at all times and attained a maximum value of 372% of the control at 14 days after bleomycin treatment. Increases in the lung prolyl hydroxylase and superoxide dismutase activities and in the proline pool size preceded the significant increases in neutral salt soluble and insoluble collagens which occurred at 7 days after bleomycin treatment and continued to be significantly elevated for the remaining period of the study.

Effects of intratracheal administration of bleomycin on GSH-shuttle enzymes, catalase, lipid peroxidation, and collagen content in the lungs of hamsters

Intratracheal administration of one unit of bleomycin increased significantly the glucose-6-phosphate dehydrogenase activity to 147, 135, 163, 207, 278, and 148% of the control at 1, 2, 4, 7, 14, and 21 days post-treatment, respectively. The glutathione peroxidase activity was significantly increased to 147 and 124% of the control at 7 and 14 days post-treatment, respectively. The glutathione reductase and catalase activities were significantly elevated to 132, 174, and 145% of the control in the former and 160, 213, and 160% of the control in the latter case at 7, 14, and 21 days post-treatment, respectively. The amount of thiobarbituric acid reacting products as an index of lipid peroxidation was found to be significantly increased to 251, 248, and 253% of the control at 4, 7, and 14 days after treatment, respectively. The amount of total lung collagen in treated hamsters was significantly increased to 140, 197, and 245% of the control at 7, 14, and 21 days post-treatment, respectively. These findings indicate that the increases in the activities of antioxidant enzymes in lungs of bleomycin-treated hamsters result from the multiple cyto-dynamic events such as infiltration of inflammatory cells, and reparative and proliferative processes which generally follow lung injury caused by any oxidant.

The in vitro synthesis and degradation of prostaglandins during the development of bleomycin-induced pulmonary fibrosis in hamsters

Subsequent to optimization of conditions for enzyme assay, we examined the in vitro synthesis and degradation of prostaglandins by the lung during the development of bleomycin-induced pulmonary fibrosis in hamsters. It was found that the microsomal protein content on a per lung basis was significantly increased to 144, 129, 134, and 121% of control (2.3 mg protein/lung) at 4, 7, 14 and 21 days post-treatment, respectively. The synthesis of PGD2 was significantly elevated to 10.2, 10.8, and 12.5 nmoles/lung at 7, 21 and 28 days, respectively, as compared to the control value of 5.6 nmoles/lung. Significant increases in PGF2 alpha synthesis from the control value of 3.3 nmoles/lung to 5.2, 8.2 and 5.5 nmoles/lung were found at 4, 7 and 21 days post-treatment, respectively. The synthesis of PGE2 also showed significant increases above the control value of 6.1 nmoles/lung to 10.5, 12.2 and 11.0 nmoles/lung at 7, 21 and 28 days post-treatment, respectively. Similarly, the synthesis of 6-keto-PGF1 alpha was significantly increased to 7.4, 7.5 and 8.6 nmoles/lung at 7, 21 and 28 days post-treatment, respectively, as compared to the control value of 4.4 nmoles/lung. The synthesis of TxB2 was also significantly increased from the control value of 3.9 nmoles/lung to 7.5 and 6.4 nmoles/lung at 7 and 21 days post-treatment, respectively. Accompanying the increased synthesis of prostaglandins in general, the in vitro degradation of PGF2 alpha was significantly increased from the control value of 71.1 nmoles/lung to 173.5, 131.7 and 143.3 nmoles/lung at 2, 4 and 7 days after bleomycin treatment, respectively. We conclude that bleomycin-induced pulmonary fibrosis leads to changes in prostaglandin synthesis and degradation possibly as a result of an accompanying inflammatory response and resident cellular proliferation.

Minor role of lipid peroxidation in acute bleomycin toxicity in rats

Bleomycin was injected i.p. in rats, and the amount of expired ethane which indicates lipid peroxidation was followed up for 78 h. Compared to controls neither 1 x 30 mg/kg and 2 x 30 mg/kg nor 1 x 70 mg/kg bleomycin led to increased ethane expiration, although body weight loss indicated toxicity. That pulmonary toxicity had been developed due to the acute bleomycin treatment could be demonstrated by histological examinations of lungs of the animals of the highest dosage group. The combined treatment of rats with bleomycin and ferrous ions neither resulted in an increase of ethane expired compared to that of the ferrous ion-treated animals. Rather a decrease was observed. Our results indicate that acute bleomycin toxicity is not associated with increased lipid peroxidation. Furthermore, our data suggest that the bleomycin-ferrous-complex does not initiate lipid peroxidation in vivo.