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

Superoxide-induced Type I collagen secretion depends on prolyl 4-hydroxylases

Reactive oxygen species (ROS) including superoxide (O₂^•-) play an important role in a variety of diseases, including Alzheimer's Disease, cancer, and atherosclerosis. Early reports showed that O₂^•- is a stimulant for collagen synthesis. However, the mechanism remains incompletely understood. Here we showed that LY83583 (6-anilinoquinoline-5,8-quinone), a substance known to induce O₂^•- production by smooth muscle cell (SMC), increases Type I collagen secretion. This effect could be blocked by treating the cells with Tiron, a scavenger for O₂^•-. LY83583-induced Type I collagen secretion required P4HA1 and P4HA2. Knockout of either P4ha1 or P4ha2 greatly reduced LY83583-stimulated Type I collagen maturation whereas silencing of both P4ha1 and P4ha2 completely blocked LY83583-induced Type I collagen maturation. Although significantly more hydroxyproline on purified Type I collagen was detected from LY83583 treated mouse embryonic fibroblast (MEF) cells by mass spectrometry, the level of prolyl 4-hydroxylases was not altered. Thus, LY83583 might increase the enzymatic activity of prolyl 4-hydroxylases to increase Type I collagen maturation. In addition, we found that LY83583 activated prolyl 4-hydrolases differed from ascorbate-activated prolyl 4-hydroxylase in two aspects: (1) LY83583 activated both P4HA1 and P4HA2 involved in collagen maturation whereas ascorbate mainly stimulated P4HA1 in collagen maturation; (2) LY83583 did not induce N259 glycosylation on P4HA1 as ascorbate did. The mechanisms remain to be investigated.

Ginkgo Biloba Extract (Egb 761) Modulates Bleomycin-induced Acute Lung Injury in Rats

The effect of Ginkgo biloba extract (EGb 761) on bleomycin (BLM)-induced acute lung injury was studied in rats. The responsiveness of isolated pulmonary arterial rings to 5-hydroxytryptamine (5-HT) as well as the levels of some relevant biochemical markers in the lung tissue were taken as evidence for the acute lung injury. BLM was given intraperitoneally at a dose of 15 mg/kg/day for five consecutive days. It was found that BLM treatment attenuated the vasoconstrictor effect of 5-HT on the isolated pulmonary arteries. In lung tissues BLM also elevated the level of lipid peroxides and enhanced the activity of glutathione peroxidase. On the other hand, the level of glutathione and the activity of alkaline phosphatase were reduced. Body weight, lung weight and tissue glutathione-S-transferase activity were, however, not altered. Oral administration of EGb 761 at a dose of 100 mg/kg/day for five consecutive days did not alter any of the chosen biochemical parameters in the lung tissue except for a slight reduction in alkaline phosphatase activity. However, treatment with EGb 761 reduced the responsiveness of the pulmonary artery to 5-HT. Administration of EGb 761 (100 mg/kg/day; po) two hours prior to BLM (15 mg/kg/day; ip), for five consecutive days blunted the occurrence of further reduction in the vasoconstrictor response of the pulmonary artery to 5-HT. Furthermore, EGb 761 tended to normalize BLM-induced alterations in the measured biochemical markers in the lung tissue. The apparent modulatory influence of EGb 761 on BLM-induced acute lung injury stems, at least in part, from its beneficial free radical scavenging properties that provide the extract with antioxidant activity.

Attenuation of amiodarone induced lung fibrosis and phospholipidosis in hamsters, by treatment with the platelet activating factor receptor antagonist, WEB 2086

Therapeutic use of amiodarone (AMD), a Class III antiarrhythmic drug is complicated by the development of lung fibrosis (LF) and phospholipidosis (PL). In the present study, the effectiveness of a PAF antagonist, WEB 2086, against AMD induced LF and PL has been tested in hamsters. The animals were randomly divided into four groups: (1) saline + H₂O; (2) WEB + H₂O; (3) saline + AMD; and (4) WEB + AMD. Saline or WEB (10 mg/kg i.p.) was given 2 days prior to intratracheal instillation of water or AMD (1.5 μmol/0.25 ml/100 g BW) and thereafter daily throughout the study. Twenty-eight days after intratracheal instillation, the animals were killed and the lungs processed for various assays. The amount of lung hydroxyproline, an index of LF, in saline + H₂O, WEB + H₂O, saline + AMD, and WEB + AMD groups were 959 ± 46, 1035 ± 51, 1605 ± 85 and 1374 ± 69 μg/lung, respectively. Total lung PL, an index of phospholipidosis, in the corresponding groups were 8.4 ± 0.4, 8.3 ± 0.3, 11.7 ± 0.3 and 9.9 μg/lung. Lung malondialdehyde, an index of lipid peroxidation and superoxide dismutase activity in saline + H₂O WEB + H₂O, saline + AMD, and WEB + AMD were 93.0 ± 4.3, 93.0 ± 2.7, 138.9 ± 6.0 and 109.0 ± 3.8 nmol/lung and 359.7 ± 13.9, 394.0 ± 22.8, 497.5 ± 19.7 and 425.5 ± 4.9 units/lung, respectively. Administration of AMD alone caused significant increases in all the above indexes of lung toxicity, and treatment with WEB 2086 minimized the AMD induced toxicity as reflected by significant decreases in these indexes. Histopathological studies revealed a marked reduction in the extent and severity of lung lesions in the WEB + AMD group compared with the saline + AMD group. Treatment with WEB 2086 also reduced the acute mortality from 35% in saline + AMD group to 22% in WEB + AMD group. It was concluded that PAF is involved in the AMD induced lung fibrosis and phospholipidosis and that the PAF receptor antagonist may, therefore, be potentially useful in reducing AMD induced lung toxicity.

Gadolinium exposure disrupts iron homeostasis in cultured cells

Human exposure to gadolinium-based contrast agents can be complicated by nephrogenic systemic fibrosis (NSF). Demonstration of significant quantities of insoluble gadolinium in the skin of NSF patients suggested transmetallation as a mechanism of toxicity of this injury. An alternative pathway for the biological effect of gadolinium is a disruption of iron homeostasis. We tested the postulate that cell exposure to gadolinium increases iron uptake to disrupt intracellular metal homeostasis and impact inflammatory events. Alveolar macrophages, THP1 cells, NHBE cells, and BEAS-2B cells all demonstrated a capacity to import gadolinium from both GdCl(3) and Omniscan. All four cell types similarly imported iron following exposure to ferric ammonium citrate (FAC). Exposure of all cell types to gadolinium and iron resulted in increased iron import relative to cell concentrations following incubation with FAC alone. To analyze for further evidence of changes in iron homeostasis, cell ferritin concentration was determined. Relative to incubation with FAC alone, co-incubation of BEAS-2B cells with gadolinium and FAC resulted in significant increases in ferritin level. Finally, potential effects of gadolinium uptake and associated changes in iron homeostasis on the inflammatory response were evaluated by measuring IL-8. Co-incubation of BEAS-2B cells with both gadolinium and iron resulted in diminished release of IL-8 relative to levels of the cytokine following incubation with gadolinium alone. We conclude that gadolinium impacts cell iron homeostasis to change import and storage of the metal and biological effects of exposure.

Pulmonary fibrosis and ferruginous bodies associated with exposure to synthetic fibers

Exposure to synthetic fibers with employment in textile mills can be associated with an elevated risk of interstitial lung disease (ILD). A mechanism of injury has not been determined. ILD can follow exposures to inorganic fibers (e.g., asbestos) which are associated with a mobilization of iron and catalysis of an oxidative stress. We describe 2 patients with ILD associated with exposure to synthetic textile fibers who demonstrated carbon-based ferruginous bodies suggesting an in vivo accumulation of iron by synthetic fibers after deposition in the lung. These iron-laden bodies varied from perfectly linear fibers to almost particulate matter. Linear structures were irregularly interrupted by deposition of iron-abundant material. The capacity of these synthetic fibers to complex iron and generate an oxidative stress is confirmed in vitro.

Abrogation of bleomycin-induced lung fibrosis by nitric oxide synthase inhibitor, aminoguanidine in mice

The effects of aminoguanidine (AG), a specific inhibitor of inducible nitric oxide synthase, on the bleomycin (BL)-induced lung fibrosis was evaluated in mice. The animals were placed into five groups: saline (SA)-instilled drinking water (SA+H(2)O), saline-instilled drinking water containing 0.5%AG (SA+0.5%AG), BL-instilled drinking water (BL+H(2)O), BL-instilled drinking water containing 0.2%AG (BL+0.2%AG), and BL-instilled drinking water containing 0.5%AG (BL+0.5%AG). The mice had free access to H(2)O or H(2)O containing AG and lab chow ad lib 2 days prior to intratracheal (IT) instillation of BL (0.07U/mouse/100 microL) or an equivalent volume of sterile isotonic saline. The mice in the SA+0.5%AG group consumed the greatest amount of AG without any ill effects than the mice in any other group. There were no differences in any of the measured biochemical determinants between the SA+H(2)O and SA+0.5%AG control groups. The IT instillation of BL in the BL+H(2)O group caused significant increases in the lipid peroxidation, hydroxyproline content, and prolyl hydroxylase activity of lungs and influx of inflammatory cells in the broncheoalveolar lavage fluid (BALF) as compared to both control groups. The intake of aminoguanidine by mice in the BL+0.5%AG group caused significant reductions in the BL-induced increases in all measured biochemical indices of lung fibrosis without any effects on the influx of inflammatory cells in the BALF. In fact, AG in both BL-treated groups additionally increased the total cell counts in the BALF from mice in the BL+0.2%AG and BL+0.5%AG groups as compared to the BL+H(2)O group. Histopathological evaluation of the lungs revealed that the mice in the BL+0.5%AG group had markedly fewer fibrotic lesions than mice in the BL+H(2)O group. These results demonstrate that aminoguanidine minimizes the BL-induced lung fibrosis at both the biochemical and the morphological level and support our earlier hypothesis that the production of nitric oxide plays a significant role in the pathogenesis lung fibrosis caused by BL.

Effect of pirfenidone against vanadate-induced kidney fibrosis in rats

Renal fibrosis is a complication of kidney injury and can contribute to organ failure. Currently, there are no drugs for the treatment of renal fibrosis. Pirfenidone (PD) has been proven to have antifibrotic effects in animal models of fibrosis. We tested the ability of PD against vanadate-induced kidney fibrosis in rats. The rats were injected subcutaneously with vehicle or vanadate solution (1mg vanadate/kg/day) for 12 or 16 days to produce varying degrees of kidney fibrosis. The vanadate- and vehicle-treated rats were fed a laboratory diet or the same diet mixed with 0.6% PD ad lib. One vanadate-injected group was initially fed the same diet without PD and later switched to the diet containing PD 2 days after the last injection. The rats were killed at 12 and 25 days following the last dose. The changes found in the kidney of vanadate-treated rats included increases in RNA and DNA content and increases in kidney weight. Treatment with PD diminished the vanadate-induced increases in kidney weight and RNA content. The hydroxyproline content of the kidney in vanadate-treated animals was increased significantly (P< or =0.05) from the control level of 1452 microg/kidney to 1765 microg/kidney. Treatment with PD for 37 days caused significant reductions in the vanadate-induced increases in the hydroxyproline level. Similarly, treatment for 41 days also caused significant reductions (1744 microg/kidney) in vanadate-induced increases in the hydroxyproline level (1996 microg/kidney). The histological evaluation revealed that the severity of the lesions in the vanadate-treated group was moderate to severe, and treatment with PD for 41 days decreased the severity to a mild level. In addition, the delayed treatment with PD also minimized the vanadate-induced increases in the collagen content of the kidney. Although it is speculative, PD may potentially be therapeutic in the management of renal fibrosis.

Role of extracellular superoxide dismutase in bleomycin-induced pulmonary fibrosis

Bleomycin administration results in well-described intracellular oxidative stress that can lead to pulmonary fibrosis. The role of alveolar interstitial antioxidants in this model is unknown. Extracellular superoxide dismutase (EC-SOD) is the primary endogenous extracellular antioxidant enzyme and is abundant in the lung. We hypothesized that EC-SOD plays an important role in attenuating bleomycin-induced lung injury. Two weeks after intratracheal bleomycin administration, we found that wild-type mice induced a 106 +/- 25% increase in lung EC-SOD. Immunohistochemical staining revealed that a large increase in EC-SOD occurred in injured lung. Using mice that overexpress EC-SOD specifically in the lung, we found a 53 +/- 14% reduction in bleomycin-induced lung injury assessed histologically and a 17 +/- 6% reduction in lung collagen content 2 wk after bleomycin administration. We conclude that EC-SOD plays an important role in reducing the magnitude of lung injury from extracellular free radicals after bleomycin administration.

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 NADPH-dependent microsomal lipid peroxidation and scavenges hydroxyl radicals

Pirfenidone (Pf), a new broad-spectrum anti-fibrotic agent, is known to offer protection against lung fibrosis in vivo in laboratory animals, and against mitogenesis and collagen formation by human lung fibroblasts in vitro. Because reactive oxygen species are thought to be involved in these events, we investigated the mechanism(s) by which Pf ameliorates oxidative stress and its effects on NADPH-dependent lipid peroxidation. Pf has been shown to cause inhibit NADPH-dependent lipid peroxidation in sheep liver microsomes in a dose-dependent manner. The concentration of Pf required to cause 50% inhibition of lipid peroxidation was approximately 6 mM. Pf was found to be ineffective as a superoxide radical scavenger. Pf was also ineffective in decomposing H2O2 and chelating iron. In deoxyribose degradation assays, Pf was a potent scavenger of hydroxyl radicals with a rate constant of 5.4 x 10(9) M(-1) sec(-1). EPR spectroscopy in combination with spin trapping techniques, using a Fenton type reaction and DMPO as a spin-trapping agent, Pf scavenged hydroxyl radicals in a dose-dependent manner. The concentration of Pf required to inhibit 50% signal height was approximately 2.5 mM. Because iron was used in the Fenton reaction, the ability of Pf in chelating iron was verified in a fluorescent competitive assay using calcein as the fluorescent probe. Pf up to 10 mM concentration was ineffective in chelating either Fe2+ or Fe3+ in this system. We propose that Pf exerts its beneficial effects, at least in part, through its ability to scavenge toxic hydroxyl radicals.

Reduction of bleomycin induced lung fibrosis by transforming growth factor beta soluble receptor in hamsters

BACKGROUND

Transforming growth factor beta (TGF-beta) is a key mediator of collagen synthesis in the development of lung fibrosis. It has previously been shown that the administration of TGF-beta antibody and TGF-beta binding proteoglycan, decorin, reduced bleomycin (BL) induced lung fibrosis in animals. The present study was carried out to investigate whether intratracheal instillation of TGF-beta soluble receptor (TR) would minimise the BL induced lung fibrosis in hamsters.

METHODS

The effect of a recombinant TR (TGFbetaRII) on the lung collagen accumulation was evaluated in a BL hamster model of pulmonary fibrosis. Animals were divided into four groups and intratracheally injected with saline or BL at 6.5 U/4 ml/kg followed by intratracheal instillation of phosphate buffered saline (PBS) or 4 nmol TR in 0.3 ml twice a week. Twenty days after the first intratracheal instillation the hamsters were killed for bronchoalveolar lavage (BAL) fluid, biochemical, and histopathological analyses.

RESULTS

Treatment of hamsters with TR after intratracheal instillation of BL significantly reduced BL induced lung fibrosis as shown by decreases in the lung hydroxyproline level and prolyl hydroxylase activity, although they were still significantly higher than those of the saline control. Histopathological examination showed a considerable decrease in BL induced fibrotic lesions by TR treatment. However, TR did not prevent the BL induced increases in total cells and protein in the BAL fluid.

CONCLUSIONS

These results suggest that TR has antifibrotic potential in vivo and may be useful in the treatment of fibrotic diseases where increased TGF-beta is associated with excess collagen accumulation.

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.

Oxidative damage and fibrogenesis

Various chronic disease processes are characterized by progressive accumulation of connective tissue under-going fibrotic degeneration. Evidence of oxidative reactions is often associated with fibrogenesis occurring in liver, lung, arteries, and nervous system. Moreover, an increasing bulk of experimental and clinical data supports a contributory role of oxidative stress in the pathogenesis of this kind of disease. Indeed, many etiological agents of fibrogenesis stimulate free radical reactions either directly or through inflammatory stimuli. Free radicals, as well as products of their reaction with biomolecules, appear to modulate the activity of the two cellular types mainly involved in the process, namely phagocytes and extracellular matrix-producing cells. Lipid peroxidation and certain lipid peroxidation products induce genetic overexpression of fibrogenic cytokines, the key molecules in the pathomechanisms of fibrosis, as well as increased transcription and synthesis of collagen. Both these events can be downregulated, at least in experimental models, by the use of antioxidants. The effect of oxidative stress on cytokine gene expression appears to be an important mechanism by which it promotes connective tissue deposition.

Dose-related effects of Ampligen (poly(I).poly(C12U)), a mismatched double-stranded RNA, in a bleomycin-mouse model of pulmonary fibrosis

The antifibrotic effect of the mismatched double-stranded RNA, Ampligen (poly(I).poly(C12U)), was evaluated in a bleomycin-mouse model of pulmonary fibrosis. Mice received a single intratracheal dose of bleomycin (0.125 U/mouse) or saline (50 microL) at the beginning of the experiment, followed by 5 or 6 intraperitoneal injections of Ampligen (1.0, 5.0, 10.0, 15.0, or 25.0 mg/kg) or saline at regular intervals for 2 weeks. Ampligen did not produce increased mortality or weight loss by itself. However, it produced varying degrees of mortality in combination with bleomycin. Five injections of 10 mg/kg Ampligen or three injections of 25 mg/kg Ampligen plus three injections of 10 mg/kg Ampligen in combination with bleomycin .produced significant reductions in lung collagen accumulation as indicated by lung hydroxyproline content compared to the bleomycin control group. Animals receiving bleomycin plus Ampligen at all dosages had significantly reduced prolyl hydroxylase activity compared to the bleomycin control group. Lipid peroxidation and bronchoalveolar lavage fluid (BALF)-supernatant protein content for the groups receiving bleomycin plus Ampligen were not reduced compared to the bleomycin control group. In the BALF-supernatant, the activity of acid phosphatase, a lysosomal enzyme produced by neutrophils, monocytes, and macrophages, was significantly decreased in the group receiving bleomycin plus 10 mg/kg Ampligen. Also, selected BALF differential immune cell counts were reduced in some of the groups receiving bleomycin plus Ampligen, but not in a consistent or dose-dependent manner. The results of this study indicate that Ampligen can significantly reduce the bleomycin-induced increased collagen accumulation and may be therapeutically useful in the management of lung fibrosis in humans.

Mechanism of antifibrotic effect of taurine and niacin in the multidose bleomycin-hamster model of lung fibrosis: inhibition of lysyl oxidase and collagenase

In the multiple-dose bleomycin-hamster model of pulmonary fibrosis, combined treatment with taurine and niacin blocks the increase in lung collagen deposition. We investigated the effects of taurine and niacin on lung lysyl oxidase and type I collagenase activities in this model. Hamsters were intratracheally instilled with three weekly doses of saline or bleomycin sulfate. Animals were fed either a diet containing 2.5% niacin and 2.5% taurine, or a control diet throughout the experiment. The four groups were saline-instilled with the control diet (BCD), bleomycin-instilled with the diet containing taurine and niacin (BTN), and saline-instilled with the diet containing taurine and niacin (STN). Animals were sacrificed at 1, 4, and 8 weeks after the last bleomycin instillation. Hydroxyproline per lung in the BCD group was significantly elevated by 38, 56, and 60% over the SCD group at 1, 4, and 8 weeks, respectively. Lysyl oxidase activity per lung in the BCD group was significantly elevated by 57.5 and 91.4% over the SCD controls at 1 and 4 week time periods, respectively. Type I collagenase activity per lung in the BCD group was significantly elevated by 65 and 80% over the SCD controls at 1 and 4 weeks, respectively. The combined treatment with taurine and niacin abolished the bleomycin-induced increases in the lung hydroxyproline content and lysyl oxidase and collagenase activities. It was postulated that one of the mechanisms for the antifibrotic effect of taurine and niacin may be the blockage of bleomycin-induced increases in the lung lysyl oxidase and collagenase activities.

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.

Dose and regimen effects of poly ICLC, an interferon inducer, in a multi-dose bleomycin model of interstitial pulmonary fibrosis

The antifibrotic effects of an interferon inducer, polyinosinic-polycytidylic acid complexed with poly-L-lysine (poly ICLC), was evaluated in a bleomycin-hamster model of pulmonary fibrosis. Hamsters received three consecutive intratracheal doses of bleomycin (2.5, 2.0, and 1.5 U/kg/5 ml) or saline at weekly intervals. Poly ICLC at three doses (0.5, 1.0, and 1.5 mg/kg body weight) or saline was injected intraperitoneally by daily and semiweekly regimens for four weeks, and animals were sacrificed at five weeks. In both the daily and semiweekly poly ICLC regimens, hamsters receiving bleomycin plus poly ICLC demonstrated increased mortality and decreased weight gain compared to the vehicle and bleomycin control groups. The groups receiving bleomycin plus daily poly ICLC demonstrated poly ICLC-dose related effects for weight changes, lung hydroxyproline and lung prolyl hydroxylase activity. Depending on the poly ICLC dose, bleomycin plus daily poly ICLC produced significantly decreased hydroxyproline or significantly increased hydroxyproline and prolyl hydroxylase activity compared to the bleomycin control group. In contrast, the groups receiving bleomycin plus semiweekly poly ICLC did not demonstrate poly ICLC-dose related effects or significant differences from the bleomycin control group for any of the biochemical assays performed. The results of this study indicate that, depending on dose and regimen, poly ICLC can reduce collagen accumulation or produce a synergistic toxicity when administered with multiple doses of bleomycin. The toxic effects may restrict the therapeutic potential of poly ICLC in combination with bleomycin for anticancer therapy.

Dietary supplementation with taurine and niacin prevents the increase in lung collagen cross-links in the multidose bleomycin hamster model of pulmonary fibrosis

Taurine and niacin have been previously found to block the accumulation of collagen in lung in the multidose bleomycin hamster model of pulmonary fibrosis. Previous studies have found an increase in the pulmonary collagen cross-links dihydroxylysinonoroleucine (DHLNL) and hydroxypyridinium (OHP) in the single dose bleomycin rat model. In this study, we asked if taurine and niacin would block the increase in DHLNL and OHP in the multidose bleomycin hamster model of lung fibrosis. Hamsters were intratracheally instilled with three consecutive doses of saline or bleomycin sulfate 1 week apart (2.5, 2.0, 1.5 units/5 mL/kg). Animals were fed diet containing either 2.5% niacin and 2.5% taurine or control diet throughout the experiment. The four groups were saline-instilled with control diet (SCD), bleomycin instilled with control diet (BCD), bleomycin-instilled with taurine-niacin in diet (BTN), and saline-instilled with taurine-niacin in diet (STN). Animals were sacrificed at 1, 4, and 8 weeks after the last bleomycin instillation. Hydroxyproline per lung in the BCD group was significantly elevated by 38, 56, and 60% over the SCD group at 1, 4, and 8 weeks, respectively. There were no statistically significant differences among the four groups in DHLNL (mmole) per mole collagen at the 1 or 8 week time point. At four weeks, DHLNL was significantly elevated by 46.4% in the BCD group over the SCD group. The OHP (mmole) per mole of collagen at 1 and 4 weeks in the BCD group was not statistically different from the SCD group.(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 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.

Effects of niacin on bleomycin-induced increases in myeloperoxidase, prolyl hydroxylase, and superoxide dismutase activities and collagen accumulation in the lungs of hamsters

It has been shown that lung nicotinamide adenine dinucleotide (NAD) depletion accompanies bleomycin (BL)-induced lung fibrosis in the hamster and that treatment with niacin (NA), a precursor of NAD, was found to attenuate lung fibrosis caused by this agent. Niacin was used in the present study to investigate changes in some biochemical parameters and enzymes involved in the development of BL-induced lung fibrosis in the hamster. Niacin (500 mg/kg, IP), or an equivalent volume of saline (SA, IP), was given daily 2 days prior to intratracheal instillation of BL (7.5 U/5 mL/kg) or SA and everyday thereafter throughout the study. Hamsters were killed at 1, 4, 7, 10, and 14 days after the BL or SA instillation and their lungs processed for various biochemical assays. Hydroxyproline content and superoxide dismutase (SOD) activity in SABL treated animals were significantly (P < or = 0.05) elevated at 7 and 10 days, peaking at 14 days to 161 +/- 11% and 159 +/- 11% of the SASA treated animals, respectively. Although the hydroxyproline level of NABL treated animals was significantly elevated at 7 and 10 days and peaked at 14 days to 123 +/- 8% of the NASA control, these values were significantly lower than the SABL treated animals at the corresponding times. The lung SOD activity of NABL groups was significantly higher at 4 days but significantly lower at 10 and 14 days than the SABL groups at the corresponding times. Prolyl hydroxylase (PH) activity and total lung calcium in SABL treated groups were significantly elevated compared to SASA treated groups starting at 4 days, with PH peaking at 10 days to 163 +/- 13% and calcium peaking at 7 days to 148 +/- 8% of SASA treated groups. The NABL treated animals displayed a significant elevation in PH activity at 4 days only (132 +/- 15%), while the calcium content in this group was significantly increased at 4 and 14 days compared to NASA treated animals. However, the activity of PH in the NABL treated animals was significantly lower than the SABL treated animals at 7, 10, and 14 days. The calcium content of the NABL group was significantly lower than the SABL group at 7 and 10 days. The thiobarbituric acid reactive substance equivalents (TBARS) content and myeloperoxidase (MPO) activity were significantly elevated at all time points in SABL groups as compared to SASA groups, with peak elevation of TBARS to 160 +/- 9% at 4 days and MPO to 268 +/- 40% at 1 day.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

Increase in lipoperoxides and prolyl hydroxylase activity in rat liver following chronic ethanol feeding

The effect of lipid peroxidation on hepatic collagen synthesis was investigated in male Wistar strain rats after 7 weeks of ethanol feeding. Compared with control rats, the ethanol-fed rats had a significantly higher lipoperoxide content and a significantly lower reduced glutathione content al all times following ethanol treatment. Except for the earliest time (2 days), hepatic prolyl hydroxylase activity was also significantly increased and finally reached up to 214% of the control level. Hepatic hydroxyproline content was slightly increased, but not statistically significant. The lipoperoxides content was significantly correlated with prolyl hydroxylase activity and inversely correlated with reduced glutathione content. These findings were also confirmed in ethanol-pyrazole-treated rats. These results suggest that elevated lipoperoxides mediate an acceleration of collagen synthesis, even at an early stage, in ethanol-induced hepatic injury.

Capillary microscopy is a potentially useful method for detecting bleomycin vascular toxicity

Capillary microscopy is an easy, noninvasive procedure to examine in vivo the dermis capillaries of the nailfold. It has demonstrated clinical use in the etiologic study of Raynaud's phenomenon. We consider a "vascular activity pattern" to be present at capillary microscopy when one of the following associations is observed: tortuous capillary vessels plus ramifications with or without loss of a moderate amount of capillaries. Capillary tortuousity alone is not considered pathologic. It is well known that bleomycin (BLEO) can occasionally induce vascular-associated diseases. To examine the vascular damage produced by BLEO, we performed capillary microscopic studies on 40 patients with neoplasia, 21 of whom had received BLEO during the previous year. The maximum accumulated doses ranged from 15 to 379 U. The other 19 patients had advanced neoplasia, and 10 of them had received antitumoral combinations that did not contain BLEO. No one had clinical signs attributable to vascular toxicity. Twenty-six patients had no pathologic patterns (11 received BLEO and 15 did not). In the group of 14 patients with activity patterns, 10 had received BLEO and 4 had not (P = 0.035). Ten of 11 patients treated with BLEO who had normal capillary microscopic studies received total doses of less than 100 U. We conclude that capillary microscopy may demonstrate the vascular damage induced by BLEO even in asymptomatic patients.

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.

Structure of the gene encoding the beta-subunit of chicken prolyl 4-hydroxylase

Prolyl 4-hydroxylase (EC 1.14.11.2) converts peptidyl proline to peptidyl hydroxyproline in procollagen polypeptides during collagen biosynthesis. The active enzyme is a tetramer which is composed of two pairs of non-identical subunits in a molecular form of alpha 2 beta 2. In addition to the tetrameric prolyl 4-hydroxylase (alpha 2 beta 2), the free beta-subunit is also found inside cells. Recently it was shown that the beta-subunit of prolyl 4-hydroxylase is identical to the protein disulfide isomerase and cellular thyroid hormone-binding protein. We previously isolated and characterized cDNAs of the beta-subunit of chicken prolyl 4-hydroxylase. The cDNA of beta-subunit was used to screen a chicken genomic DNA library constructed with the lambda EMBL-3 vector. Two clones, lambda gCPH beta-22 and beta-50, were isolated and characterized by restriction enzyme analysis, heteroduplex analysis, and nucleotide sequencing. The results showed that the 2.5-kb mRNA of the beta-subunit is divided into eleven exons and that the gene is 9.0 kb long. The gene contains consensus sequence for TATA at -24 bp and four CAAT at -57, -157, -194 and -223 bp in the 5' end flanking sequence of the transcription start point. In addition, there are three GC boxes upstream from the TATA box and four GC boxes in the first intron. This is similar to the structure of the alpha 1(I) collagen coding gene (COL1A1). These elements may interact with nuclear factors and play important roles in expression regulation of the beta-subunit gene as has been described in COL1A1.

Isolation of cDNA clones and genomic DNA clones of beta-subunit of chicken prolyl 4-hydroxylase

Prolyl 4-hydroxylase (EC 1.14.11.2) is a key enzyme in collagen biosynthesis. The active enzyme is a tetramer composed of two pairs of non-identical subunits, alpha and beta. Sheep antiserum directed against chicken proly 4-hydroxylase was initially used to screen two cDNA expression libraries. The cDNA was prepared from chicken smooth muscle mRNA and cloned into the plasmids pUC8- and pUC9. Antibodies identified twenty-five clones among the approximately 2 x 10(5) clones in the libraries. Ten clones were isolated pure and used in the subsequent analysis. Monospecific antibodies directed against beta subunit of the enzyme were used in Western-blot analyses of extracts of bacteria carrying the cDNA clones. The results indicated that the clone CPH 9-10B encodes a portion of beta-subunit. The cDNA from CPH 9-10B was used to screen another cDNA library prepared from mRNA from chicken skeletal muscle. Several overlapping clones were isolated. Together the cDNAs correspond to 2.4 kb which is the same as the corresponding mRNA. Three regions of the amino acid sequence deduced from the cDNA sequence matched with that of the NH2-terminus of beta-subunit and two CNBr peptides derived from beta-subunit. The cDNA of CPH 9-10B was also used to screen a genomic DNA library constructed with lambda EMBL-3. Two overlapping genomic clones lambda gCPH beta-22 and beta-50 were isolated and characterized by restriction enzyme analysis. The results indicate that lambda gCPH beta-22 contains the portion of the beta-subunit gene that is transcribed into the 5' portion of beta-subunit mRNA, whereas lambda gCPH beta-50 contains the 3' portion.

Increased prolyl hydroxylase activity and collagen synthesis in hepatocyte cultures exposed to superoxide

Primary monolayer cultures of rat hepatocytes at confluence were exposed to an exogenously added source of superoxide, and its influence on collagen synthesis was examined. Superoxide was generated by the addition of dihydroxyfumarate to the culture medium. Exposure of hepatocytes to dihydroxyfumarate greatly stimulated the activity of prolyl hydroxylase and the synthesis of collagen. A significant increase in prolyl hydroxylase activity was observed with 5 micrograms per ml dihydroxyfumarate in 24 hr relative to that in the untreated cultures. Maximum stimulation of greater than 3-fold compared to the control value was elicited by 25 micrograms per ml dihydroxyfumarate. When scavengers of superoxide such as superoxide dismutase and Cu(Lys)2 were added in the medium, the increase in prolyl hydroxylase activity induced by dihydroxyfumarate was nearly abolished. Experiments with actinomycin D indicated that synthesis of new RNA was involved in the stimulation of prolyl hydroxylase activity. Analysis of collagen synthesis in cultures exposed to dihydroxyfumarate also showed a marked increase compared to that of the untreated cultures. The presence of superoxide dismutase in the medium significantly reduced the increase in collagen synthesis. Our results indicate that superoxide mediates the stimulation of collagen synthesis in hepatocytes. These findings may provide a possible explanation for excess collagen formation during induced liver fibrosis.

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.

Poly(ADP-ribose) synthetase activity during bleomycin-induced lung fibrosis in hamsters

Bleomycin damages cellular DNA and is a potent inducer of pulmonary fibrosis. It has been shown to act through a superoxide-mediated mechanism. We are interested in determining the biochemical mechanisms involved in fibrosis and in this preliminary study we have examined the temporal relationship between early biochemical events associated with DNA damage and fibrosis, in lungs of hamsters after administration of 0.75 unit of bleomycin. The activities of poly(ADP-ribose) synthetase, an enzyme associated with DNA repair, inducible superoxide dismutase (SOD) and prolyl hydroxylase as well as the tissue levels of NAD+ and hydroxyproline in the lung were determined. All three enzyme activities expressed as per milligram DNA or per lung, increased upon bleomycin treatment over the saline-administered controls. Lung poly(ADP-ribose) synthetase activity which is sensitive to DNA breaks, increased first (24% over control in 1 day, P less than 0.0001), attained the maximum value on the 5th day (952% over control, P less than 0.0001), and started to decline thereafter and approached near the control value on 14th day. Bleomycin treatment induced a rapid change in the level of lung NAD+. After 1 day the level of NAD+ was reduced by 42% compared to the control (P less than 0.001), further declined to 65% (P less than 0.001) on the 3rd day, and stayed at that level until the 7th day. On the 14th day, however, the NAD+ level was still lower (29%, P less than 0.05) but approaching the value in the control animals. The activity of prolyl hydroxylase showed significant increase on the 3rd day (50% over control, P less than 0.0001) after bleomycin administration. The enzyme activity continued to increase until the end of the experiment (490% of control, P less than 0.0001, on Day 14). The content of undialyzable hydroxyproline, a marker for collagen, was also increased significantly in the lung tissue on the 3rd day (30% over control, P less than 0.05), continued to increase and reached the highest level on the 14th day (71% over control, P less than 0.001). A significant increase in the activity of SOD (19% over control, P less than 0.001) was seen on the 5th day which continued to increase and attained the highest value on Day 14 (115% over control, P less than 0.0001).(ABSTRACT TRUNCATED AT 400 WORDS)

Stimulation of poly(ADP-ribose) synthetase activity in the lungs of mice exposed to a low level of ozone

Toxic effects of O3 are mediated through the formation of free radicals, which can cause DNA strand breaks. Cellular DNA repair is dependent upon the formation of poly(ADP-ribose) (polyADPR) catalyzed by polyADPR synthetase. In order to evaluate whether O3 exposure inflicted DNA damage in lung tissue, we measured the activity of polyADPR synthetase (known to be activated in response to DNA damage) in mouse lungs after exposure to 0.45 ppm (882 micrograms/m3) O3 for up to 7 days. The enzyme activity was stimulated with O3 exposure relative to unexposed controls, showing a 20% (P less than 0.05) increase at Day 5 and 42% (P less than 0.001) at Day 7 of O3 exposure. In addition, the activity of superoxide dismutase (SOD), known to be stimulated in response to production of superoxide anion (.O2-), was measured as an indicator of free radical involvement. Relative to unexposed controls, the SOD activity in exposed animal lungs increased to the peak level at Day 5 (48%, P less than 0.001) and then declined at Day 7 of O3 exposure but was still higher than controls (17%, P less than 0.05). When animals, after 5 days of O3 exposure, were allowed to recover in filtered room air, the activities of both enzymes declined to their respective control values in 6 days. These results suggest a possible temporal relationship between O3 injury and the activities of polyADPR synthetase and a free radical scavenging enzyme, SOD. The stimulation of polyADPR synthetase activity with O3 exposure, reflecting a response to lung cellular DNA repair, may be a sensitive indicator for assessing DNA damage in oxidant injury.

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.

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.