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PubMed1982

Structural basis for the deoxyribonucleic acid affinity of bleomycins.

The role of the bithiazole moiety of bleomycin in the interaction of the antibiotic with DNA has been studied by the use of synthetic bithiazole derivatives. The DNA affinity of individual C-terminal (bithiazole) analogues of bleomycin was measured in terms of the ability of these species to block the binding of bleomycin to DNA, as judged by diminution of the DNA degradation that attends bleomycin binding. DNA degradation was monitored both by release of [3H]thymine from radiolabeled PM-2 DNA and by alteration of bleomycin-treated DNA oligomers of defined sequence derived from Escherichia coli plasmid pLJ3. It was found that the affinity of the bithiazole derivatives for DNA depended on the presence of the bithiazole moiety itself but more importantly on the number and spacing of positively charged groups; 2'-(2-aminoethyl)-2,4'-bithiazole-4-[3-[(4-aminobutyl) amino]propyl]carboxamide (14), having three positively charged groups at neutral pH, was a reasonably effective inhibitor of DNA degradation by bleomycin. Consistent with the importance of the spacing of the positively charged groups, tetrapeptide S (12) was found to be significantly less inhibitory toward DNA degradation by bleomycin than tripeptide S, in spite of their equal number of positively charged groups and the greater structural similarity of the former to bleomycin A2. Bleomycin is known to cleave DNA perferentially at certain sequences. It was shown that the inhibitors employed in this study diminished DNA cleavage proportionately at each cleavage site; no alteration was observed in the specificity of cleavage. A number of the bithiazole analogues employed as inhibitors of bleomycin-mediated DNA degradation were also utilized in fluorescence quenching experiments with calf thymus DNA. Consistent with the belief that these species inhibit bleomycin degradation by competitive binding to the DNA substrate, the best inhibitors exhibited the greatest fluorescence quenching upon admixture of DNA.

Bacteriophages↗
PubMed1996

Influence of the antioxidant N-acetylcysteine and its metabolites on damage induced by bleomycin in PM2 bacteriophage DNA.

Bleomycin is considered to be a useful model compound for studying environmental carcinogenesis, due to its broad spectrum of DNA damaging properties. In addition, bleomycin is a useful antitumor drug because of its cytotoxic properties. To investigate the influence of the antioxidant N-acetylcysteine and its metabolites glutathione and cysteine on bleomycin-induced DNA damage and more importantly to gain insight into the biological relevance of such damage, PM2 DNA was exposed to Cu(2+)-bleomycin in the presence and absence of the thiols N-acetylcysteine, glutathione and cysteine. It was found that the presence of these thiols led to a considerable enhancement of bleomycin-induced single- and double-strand breaks and a concomitant decrease in the biological activity of PM2 DNA in a dose-dependent way. A similar observation was made when ascorbic acid was used. Bleomycin showed no DNA damaging activity when PM2 DNA was pretreated with the strong Fe ion chelator desferal and its activity was strongly inhibited by the addition of Cu2+ ions or under hypoxic (N2) conditions. Cu(2+)-bleomycin under our conditions is not active by itself, but most probably after binding to DNA exchanges Cu2+ for Fe3+ bound to DNA. Fe(3+)-bleomycin is then reduced to Fe(2+)-bleomycin, a process potentiated by the added antioxidants, and subsequently activated by O2. The contribution to biological inactivation of bleomycin alone or in the presence of ascorbic acid is only approximately 15%. The contribution to lethality in the presence of thiols is higher. These results indicate that ascorbic acid only enhances the DNA damaging properties of bleomycin, whereas the thiol compounds in addition influence the type of DNA damage. The remainder of the biological inactivation is probably caused by double damage, such as single-strand breaks with closely opposed alkali-labile sites or base damage.

Acetylcysteine↗
PubMed1994

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.

Animals↗
PubMed1987

Development of acute lung injury after the combination of intravenous bleomycin and exposure to hyperoxia in rats.

Pulmonary toxicity is an important adverse effect of bleomycin treatment. Very little is known of the mechanisms underlying the development of lung injury, especially after intravenous administration, or how it can be modulated. In this study acute lung injury induced by bleomycin has been examined in rats by assessment of alveolar lavage cell profiles, histological examination, and measurement of the total pulmonary extravascular albumin space. Intratracheal instillation of bleomycin 1.5 mg resulted in a severe pneumonitis with influx of inflammatory cells into the alveoli as assessed by alveolar lavage, oedema of the alveolar walls, and up to an eight fold increase in the total pulmonary extravascular albumin space, maximal at 72 hours. Intravenous bleomycin 0.15-5 mg produced no detectable injury when assessed in these ways. Exposure to hyperoxia (40-90%) after intravenous bleomycin, however, induced lung injury similar to that produced by intratracheal bleomycin. A much more severe injury followed administration of intravenous bleomycin after an exposure to hyperoxia, which itself resulted in lung injury; but lung injury was still detectable after bleomycin when the exposure to hyperoxia was insufficient to induce changes in control animals. Lung injury was not observed when the exposure to hyperoxia preceded bleomycin treatment. These results indicate the importance of oxygen in the pathways leading to acute lung injury following intravenous bleomycin. We conclude that exposure to oxygen might induce lung injury during and after bleomycin treatment, and suggest that in these circumstances oxygen therapy should be kept to a minimum.

Animals↗
PubMed1994

Fluoromicroscopic studies of bleomycin-induced intracellular oxidation in alveolar macrophages and its inhibition by taurine.

The mechanism of bleomycin-induced pulmonary fibrosis is not yet clear. Recent studies have shown that alveolar macrophages (AM) can be stimulated by bleomycin in vitro releasing inflammatory cytokines, suggesting that the interaction of bleomycin with AM is an important step in the drug-induced fibrotic process. Bleomycin is known to bind DNA and generate oxygen radicals through complexation with Fe2+ and oxygen. To provide more insight into the cellular oxidative property of bleomycin, we have developed a fluoromicroscopic method using 2',7'-dichlorofluorescin diacetate (DCFHDA) as an oxidative fluorescence probe to study the bleomycin-induced intracellular oxidation in rat AM and the inhibition of the oxidation by taurine, a compound known to inhibit the bleomycin-induced fibrosis. Bleomycin at 5 to 20 micrograms/ml has a moderate stimulatory effect (1.87- to 2.66-fold) on the secretion of superoxide anion. A high concentration of bleomycin (20 micrograms/ml), however, inhibits cell response to zymosan-induced secretion of superoxide anion. At 4 micrograms/ml, bleomycin has no effect on cell membrane integrity or morphology but results in a significant increase in intracellular oxidation. This oxidative process is Fe(2+)-dependent and is accompanied by an increase in intracellular calcium (35 nM). Both the intracellular oxidation and calcium rise induced by internalized bleomycin are inhibited by pretreatment of cells with varying concentrations of taurine (25, 125, and 187.5 microM). The inhibitory effect on intracellular oxidation was found to be 36, 57, and 60%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

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.

Animals↗
PubMed1985

Radioimmunoassay of bleomycins.

Rabbit antisera highly specific to the bleomycinic acid moiety of bleomycins were obtained by immunizing with a conjugate of copper-complex of bleomycin A5 and bovine serum albumin. These antisera not only reacted with bleomycin A5 but also with other bleomycins such as bleomycin A2, bleomycin B2 and peplomycin. The antisera showed little cross-reactivity with deamido-, depyruvamido- and decarbamoyl-bleomycins. Thus, these antisera were found to be highly specific for the intact bleomycinic acid moiety. One of the antisera was successfully applied to radioimmunoassay of bleomycin and peplomycin in mouse and human sera. The detection limit was 1 ng/ml. This radioimmunoassay is expected to be widely used for the determination of active bleomycins in biological and clinical samples.

Animals↗
PubMed1992

Reaction of DNA-bound Co(II)bleomycin with dioxygen.

The aerobic oxidation of Co(II)bleomycin bound to calf thymus DNA has been investigated in relation to the mechanism of reaction in solution in the absence of DNA. Kinetics of dioxygenation of the Co(II) complex were followed by spectrophotometric and electron spin resonance spectroscopy as well as dioxygen analysis. The reaction is slower than when carried out in solution; its rate is inversely related to the ratio of DNA base pairs to Co(II)bleomycin. The subsequent oxidation reaction, observed spectrophotometrically and by dioxygen analysis, is second order in cobalt complex. The calculated second order rate constant is also inversely related to the base pair to metal complex ratio. Once this ratio exceeds three, the reaction rate slows significantly with each additional increment of DNA added to the starting reaction mixture. Taking advantage of the high stability of O(2)-Co(II)bleomycin bound to greater than a 3-fold excess of DNA base pairs, it could be demonstrated that the rate constant for oxidation of two O(2)-Co(II)bleomycin molecules is much slower than that for O(2)-Co(II)bleomycin plus Co(II)bleomycin. With the same technique it was observed that the metal centers of O(2)-Co(II)bleomycin and Fe(II)bleomycin also undergo oxidation. The binding to DNA of both solution products of the oxidation of Co(II)bleomycin by O2 was examined by 1H NMR spectroscopy. Peroxy-Co(III)bleomycin, Form I, binds with higher affinity than Co(III)bleomycin, Form II. At lower ionic strength, the size of the DNA binding site for each form is about 2 base pairs/molecule of drug.

Animals↗
PubMed1988

Effects of repeated administration of N-acetyl-L-cysteine on sulfhydryl levels of different tissues and bleomycin-induced lung fibrosis in hamsters.

N-Acetyl-L-cysteine (NAC), 50, 100, 200, or 400 mg/kg, was injected intraperitoneally once a day for 13 days. No change was seen in the total sulfhydryl (TSH) and nonprotein sulfhydryl (NPSH) contents of the liver, kidney, and plasma at any dose. The heart TSH level remained unchanged, but the NPSH level was increased from the control value of 16 nmol/mg to 18, 19, and 18 nmol/mg protein at 50, 100, and 200 mg/kg, respectively. The lung TSH and NPSH levels both were increased from the control values of 65 and 8 nmol/mg to 80 and 16 nmol/mg protein, respectively, at 200 mg/kg. The lung TSH level at 400 mg/kg NAC was not changed, but the NPSH level increased to 13.5 nmol/mg protein. The ratio of TSH to NPSH levels in the liver and kidney was 4:1, whereas in the lung and heart it was 7:1 and 8:1, respectively. Based on amount per milligram of protein, TSH and NPSH levels were highest in the liver, followed by the amounts in the kidney, heart, and lung. The lung had the lowest level of TSH and NPSH. The daily treatment with NAC (200 mg/kg) for 13 days after and 2 days before intratracheal injection of bleomycin (7.5 U/kg) had little effect on lung collagen accumulation. The lung collagen level measured as hydroxyproline in bleomycin and in NAC plus bleomycin was significantly increased to 175% and 183% of the control levels, respectively. There was no difference in the lung hydroxyproline content between the control and NAC groups. The histopathology study also revealed no marked difference between the bleomycin and bleomycin plus NAC groups. Alternatively, treatment with NAC (200 mg/kg) for 13 days before bleomycin made the animals more susceptible to bleomycin toxicity and tended to add to the bleomycin-induced accumulation of collagen in the lung. NAC per se caused no mortality at any dose. The lung TSH and NPSH levels in bleomycin-treated (7.5 U/kg) hamsters were increased to 136% and 111% of control, respectively, whereas the TSH and NPSH levels both were increased to 155% of the levels of their respective controls in hamsters in the NAC plus bleomycin group. The differential effects of NAC treatment on the sulfhydryl content of tissues, the treatment's inability to alter the course of bleomycin-induced lung inflammation and collagen accumulation, and the potential for exacerbation of lung toxicity in response to repeated administration of NAC before exposure to fibrogenic agents are discussed.

Acetylcysteine↗
PubMed1982

Deglyco-bleomycin. Degradation of DNA and formation of a structurally unique Fe(II) . CO complex.

In analogy with bleomycin, deglyco-bleomycin B2 has been found to form a stable, diamagnetic complex with Fe(II) and CO. Although the stoichiometry of this complex appeared to be the same as that formed with bleomycin, the geometry of the deglyco-bleomycin complex was fundamentally different, especially as regards orientation of the beta-aminoalanine moiety. In the presence of Fe(II) and O2, deglyco-bleomycin A2 and deglyco-bleomycin B2 were found to release [3H]thymine from radiolabeled PM-2 DNA; when employed at limiting concentrations, deglyco-bleomycin A2 and B2 gave about half as much [3H]thymine release as the respective bleomycins. In view of the spectral evidence (Burger, R. M., Horwitz, S. B., Peisach, J., and Wittenberg, J. B. (1979) J. Biol. Chem. 254, 12299-12302) that Fe(II) . bleomycin . CO has the same geometry as the complex formed by initial association of bleomycin, Fe(II), and O2, the accumulated data suggest strongly that all metal complexes of bleomycin (derivatives) capable of DNA degradation need not have the same geometry.

Bleomycin↗
PubMed1983

[Clinical study of the auxiliary action of bleomycin in surgery and radiotherapy of cervical cancer and evaluation of modes of administration for the enhancement of the effects and alleviation of the adverse effects].

A total of 54 cases of carcinoma of the uterine cervix were treated with bleomycin adjuvant to surgery and radiation. Bleomycin was injected intravenously or continuously intraarterially or, using oleaginous bleomycin, locally into the infravaginal portion of the cervix, and its significance in administration routes was evaluated in terms of a five-year survival rate. Furthermore, how bleomycin concentrates in the blood, cancerous lesions and regional lymphnodes was examined after administration using following various methods: an aqueous bleomycin, intravenously, continuously intraarterially, and through dispersion to intrapelvic dead space or injected as an oleaginous bleomycin locally to infravaginal portion or applied as vaginal suppository and cervical pellet. Most appropriate routes with increased focal concentrations and reduced blood concentrations proved to enhance anti-neoplastic effects and alleviate side effects. Among them, results with local injection of oleaginous bleomycin to infravaginal portion and continuous intraarterial injection of aqueous bleomycin were most satisfactory. Complete relief from cervical carcinoma by single administration of bleomycin alone is hardly attainable; however, the efficacy of bleomycin as an adjuvant therapy, using a several types of the bleomycins, is highly appreciated in combination with pre- and post-operative treatment and radiotherapy.

Adult↗
PubMed1983

Hyperthermia and bleomycin schedules on V79 Chinese hamster cell cytotoxicity in vitro.

The effect of sequence and timing of hyperthermia (43 degrees) and bleomycin on Chinese hamster cells (V79) has been investigated. Hyperthermia preceding bleomycin treatment produced a greater cytotoxic effect than bleomycin treatment preceding hyperthermia. Furthermore, it appears that the combination of hyperthermia and bleomycin becomes less effective if the application of bleomycin is delayed. The enhancement of cytotoxicity with hyperthermia first may be related to the effect of heat on the intracellular bleomycin degradation ability and protein synthesis. V79 cells treated with a protein synthesis inhibitor, cycloheximide, before bleomycin (but not in the reversed sequence) also showed a markedly lower level of survival. As for hyperthermia treatment, pretreatment with cycloheximide did not change the uptake of bleomycin. These results suggest that hyperthermia and cycloheximide have increased the effectiveness of bleomycin and are consistent with the observation on chromosome damage induced by hyperthermia-bleomycin and cycloheximide-bleomycin treatments reported in the literature.

Animals↗
PubMed1997

Prevention of bleomycin-induced lung injury in rats by keratinocyte growth factor.

Intratracheal instillation of bleomycin produces pulmonary fibrosis in rats. Alveolar type II cell proliferation is thought to minimize the fibrotic response after lung injury. Because keratinocyte growth factor (KGF) stimulates type II cell proliferation in the rat, we designed experiments to evaluate whether intratracheal KGF before or after intratracheal bleomycin would prevent pulmonary fibrosis. Intratracheal bleomycin without KGF resulted in moderate to severe lung injury and subsequent fibrosis. Conversely, intratracheal KGF pretreatment at 48 or 72 hr before bleomycin resulted in minimal to no visible lung injury. Rats pretreated with phosphate buffered saline before bleomycin had significantly more neutrophils and protein in bronchoalveolar lavage fluid at 4 and 6 days and higher hydroxyproline levels after bleomycin as compared to KGF-pretreated rats. Pretreatment with KGF at 48 hr protected against bleomycin-induced alterations in pulmonary physiology and increased surfactant protein C-positive (SP-C)-positive cells and SP-A, SP-B, SP-C, and SP-D mRNA levels after bleomycin instillation when compared to saline pretreated rats on day 1 or day 7. KGF posttreatment protocols did not prevent bleomycin lung injury and fibrosis. We conclude that KGF pretreatment attenuates bleomycin lung injury and increases type II cell proliferation and surfactant protein gene expression after bleomycin instillation in the rat.

Animals↗
PubMed2000

Animal model of sclerotic skin. III: Histopathological comparison of bleomycin-induced scleroderma in various mice strains.

We have recently established a mouse model for scleroderma by repeated local bleomycin treatment. In this study, we compared the susceptibility to bleomycin in the development of dermal sclerosis among Balb/c, C3H/He, C57BL/6J, A/J, DBA/2, B10.BR, B10.A, and B10.D2 mouse strains. After either bleomycin or PBS treatment, skin from the injection site was histologically examined. Dermal sclerosis was induced by bleomycin treatment for 4 weeks in all of the strains examined. In particular, C3H/He, DBA/2, B10.D2 and B10.A mice developed intense dermal sclerosis characterized by deposition of homogeneous material in the dermis and thickened collagen bundles. Dermal thickness showed a more than twofold increase following bleomycin treatment, as compared with PBS treatment, except in C57BL/6J and DBA/2 mice. In A/J, C3H/He, B10.A, and B10.D2 mice, dermal thickness showed a more than 2.5-fold increase. Mast cell numbers in sclerotic skin were significantly greater than in PBS-treated skin in Balb/c and B10.A mice after 4 weeks of treatment. We also examined whether bleomycin treatment for 3 weeks could induce dermal sclerosis in C3H mice. Histological examination revealed that epidermal thickness as well as dermal sclerosis was increased in C3H mice following bleomycin treatment for 3 weeks. Increased hydroxyproline content as well as mRNA expression of alpha1(I) collagen, as determined by Northern blot analysis, were observed following bleomycin treatment. Taken together, we conclude that C3H/He and B10.A mouse strains are bleomycin-'susceptible', and these strains are considered to be a suitable experimental model of bleomycin-induced scleroderma.

Animals↗
PubMed2003

Disruption of the Saccharomyces cerevisiae cell-wall pathway gene SLG1 causes hypersensitivity to the antitumor drug bleomycin.

Bleomycin is an antitumor drug that damages DNA via a free radical-dependent mechanism, and yeast mutants defective in DNA repair are hypersensitive to the drug. To identify possible pathways that may contribute to bleomycin resistance in yeast, we characterized a panel of bleomycin-sensitive mutants that were previously isolated by insertion mutagenesis using the transposon miniTn3::Leu2::LacZ::AMP( R). One of these mutants harbored a single insertion in the SLG1 gene, which encodes a cell membrane protein that senses cell wall stress, and functions to maintain cell wall function by activating the protein kinase C signaling pathway. Deletion of the SLG1 gene in parental strains caused hypersensitivity to bleomycin, and this correlated with an accumulation of damaged DNA. A plasmid that expresses the native SLG1 gene or that increases PKC1 gene dosage restored bleomycin resistance to the slg1Delta mutant. Two-dimensional gel electrophoresis revealed that exposure to bleomycin triggered the expression of certain proteins, presumably to maintain cell wall function, in a Slg1-dependent manner. In addition, mutants lacking cell wall function were found to be hypersensitive to bleomycin. We conclude that mutants deficient in proteins that maintain cell wall function are severely compromised in their ability to limit bleomycin entry into the cell. Therefore, these mutants are burdened with increased genotoxicity upon exposure to bleomycin in the medium. Our results show that major mechanisms other than DNA repair are operating in yeast to mediate bleomycin resistance.

Antibiotics, Antineoplastic↗
PubMed1992

Properties of redox-inactivated bleomycins. In vitro DNA damage and inhibition of Ehrlich cell proliferation.

Blenoxane, bleomycin A2, bleomycin B2, and demethyl bleomycin A2 and products of their reactions with Fe2+ and oxygen were used to explore the relationship between their capacity to carry out in vitro DNA strand scission and their growth inhibitory activity against Ehrlich cells. Reaction of Fe2+, bleomycin and O2 in the absence of DNA decreased the subsequent effectiveness of various bleomycin congeners to degrade DNA in the presence of Fe2+ and oxygen. In comparison with controls, this loss of strand scission activity was not paralleled by equivalent decreases in growth inhibition. Demethyl bleomycin A2 retained full biological activity relative to bleomycin A2, despite being only 30% as effective as bleomycin A2 in its ability to cleave DNA in vitro. Prior reaction of bleomycins with Fe2+ did not alter their capacity to reduce oxygen or affect their ability to generate the activated intermediate which, for native bleomycin structures, is competent to cleave DNA in vitro.

Animals↗
PubMed1990

The role of redox-active metals in the mechanism of action of bleomycin.

Belomycin is a glycopeptide antibiotic routinely used to treat human cancer. It is commonly thought to exert its biological effects as a metallodrug, which oxidatively damages DNA. This review systematically examines the properties of bleomycin which contribute to its reaction with DNA in vitro and may be important in the breakage of DNA in cells. Because strand cleavage results from the reductive activation of dioxygen by metallobleomycins, the mechanism of this process is given primary attention. Current understanding of the structures of the coordination sites of various metallobleomycins, their thermodynamic stabilities, their propensity to form adduct species, and their properties in ligand substitution reactions provide a foundation for consideration of the chemistry of dioxygen activation as well as a basis for thinking about the metal-speciation of bleomycin in biological systems. Oxidation-reduction pathways of iron-bleomycin, copper-bleomycin, and other metal-bleomycin species with O2 are then examined, including information on photochemical activation. With this background, structural and thermodynamic features of the binding interactions of DNA with bleomycin, its metal complexes, and adducts of metallobleomycins are reviewed. Then, the DNA cleavage reaction involving iron-bleomycin is scrutinized on the basis of the preceding discussion. Particular emphasis is placed on the constraints which the presence of DNA places on the mechanism of dioxygen activation. Similarly, the reactions of other metalloforms of bleomycin with DNA are reviewed. The last topic is an analysis of current understanding of the relationship of bleomycin-induced cellular DNA damage to the model developed above, which has evolved on the basis of chemical experimentation. Consideration is given to the question of the importance of DNA strand breakage caused by bleomycin for the mechanism of cytotoxic activity of the drug.

Animals↗
PubMed1989

ICRF 187 and polyhydroxyphenyl derivatives fail to protect against bleomycin induced lung injury.

The potential protective effects of ICRF 187, Didox, Amidox and VF 165 were investigated in models of bleomycin, or bleomycin and hyperoxia induced lung injury. ICRF 187, a bispiperazinedione compound, is a strong chelating agent which blocks a number of free radical mediated processes. The polyhydroxyphenyl derivatives, Didox, Amidox and VF 165, demonstrate degrees of Fe chelating activities and free radical scavenging abilities. Hamsters treated with 5.0 U/kg bleomycin followed by treatment with ICRF 187 or Didox exhibited similar mortality to the bleomycin alone treated group. In a second study, a low dose of bleomycin (1.2 U/kg) was used followed by exposure to 70% oxygen. Treatment with ICRF 187, Didox, Amidox, or VF 165 failed to protect against lung injury; with the ICRF 187 and Amidox groups exhibiting significantly increased rates of mortality over that seen in animals treated only with bleomycin and hyperoxia. No animals treated with the agents alone died. Histopathology documented that all bleomycin-treated hamsters died of severe pneumonitis. Additionally, in the agent-treated groups there was a prominent proliferation of type II pneumocytes, which demonstrated marked anaplasia, a feature not typical of early bleomycin and hyperoxia lung injury. In conclusion, ICRF 187 and the polyhydroxyphenyl derivative, Amidox, paradoxically increase bleomycin- and hyperoxia-induced lung injury. The possible mechanisms of this interaction include: (1) increased availability of Fe to bleomycin; (2) interference with the healing process; or (3) inhibition of endogenous protective effects of SOD.

2,4-Dichlorophenoxyacetic Acid↗