Lack of metabolism as the biochemical basis of bleomycin-induced pulmonary toxicity

Skin and lung fibrosis induced by bleomycin in mice: a systematic review

OBJECTIVE

Scleroderma, or systemic sclerosis (SSc), is a chronic autoimmune connective disease with an unknown etiology and poorly understood pathogenesis. The striking array of autoimmune, vascular, and fibrotic changes that develop in almost all patients makes SSc unique among connective tissue diseases. Although no animal model developed for SSc to date fully represents all features of human disease, some animal models that demonstrate features of SSc may help to better understand the pathogenesis of the disease and to develop new therapeutic options. In this review, we aimed to evaluate skin fibrosis and lung involvement in a bleomycin (BLM)-induced mouse model and to evaluate the differences between studies.

METHODS

A systematic literature review (PRISMA guideline) on PubMed and EMBASE (until May 2023, without limits) was performed. A primary literature search was conducted using the PubMed and EMBASE databases for all articles published from 1990 to May 2023. Review articles, human studies, and non-dermatological studies were excluded. Of the 38 non-duplicated studies, 20 articles were included.

RESULTS

Among inducible animal models, the BLM-induced SSc is still the most widely used. In recent years, the measurement of tissue thickness between the epidermal-dermal junction and the dermal-adipose tissue junction (dermal layer) has become more widely accepted.

CONCLUSIONS

In animal studies, it is important to simultaneously evaluate lung tissues in addition to skin fibrosis induced in mice by subcutaneous BLM application, following the 3R (replacement, reduction, and refinement) principle to avoid cruelty to animals.

A new approach for the treatment of bleomycin-induced rat pulmonary injury by combined protein fraction of major royal jelly protein 2 and its isoform X1

Nowadays, royal jelly (RJ) has gained great interest as a functional food due to its valuable pharmacological effects. We investigated the therapeutic potency of combined protein fraction (PF50) of major RJ protein 2 and its isoform X1 on bleomycin (Bleo)-induced pulmonary injury in rats. Our study examined the impact of PF50 on pulmonary oxidative and inflammatory stress as well as smooth muscle alpha-actin (α-SMA). In addition, the predicted impacts of this PF on the activity of matrix metalloproteinase (MMP)- 8 and 15-prostaglandin dehydrogenase (15-PGDH) and the E-type prostanoid 2 (EP2) and IL-13 α2 subunit (IL13α2R) receptors, were evaluated using molecular docking. The results showed that PF50 reduced pulmonary inflammatory cells and their secreted pro-inflammatory mediators, including NF-κB, IKK, IL-4, IL-6, and NO. Additionally, the levels of IgE and mucin were diminished after treatment with PF50. Moreover, PF50 treatment improved pulmonary oxidative stress indices such as lipid peroxidation, GSH, SOD, and GPX. The histopathological findings, chest conventional X-ray, and immunohistochemistry of α-SMA confirmed the ameliorating effect of PF50. The docking outcomes reported the probable competitive inhibitory influence of PF50 on MMP-8 and a postulated blocking effect on EP2 and IL13α2R. Thus, PF50 could be a novel approach for treating pulmonary injuries.

Berberine attenuates epithelial mesenchymal transition in bleomycin-induced pulmonary fibrosis in mice via activating A2aR and mitigating the SDF-1/CXCR4 signaling

AIMS

Berberine is endowed with anti-oxidant, anti-inflammatory and anti-fibrotic effects. This study explored the role of adenosine A_2a receptor (A_2aR) activation and SDF-1/CXCR4 signaling suppression in the protective effects of berberine in bleomycin-induced pulmonary fibrosis in mice.

MAIN METHODS

Pulmonary fibrosis was generated in mice by injecting bleomycin (40 U/kg, i.p.) on days 0, 3, 7, 10 and 14. Mice were treated with berberine (5 mg/kg, i.p.) from day 15 to day 28.

KEY FINDINGS

Severe lung fibrosis and increased collagen content were observed in the bleomycin-challenged mice. Pulmonary A_2aR downregulation was documented in bleomycin-induced pulmonary fibrosis animals and was accompanied by enhanced expression of SDF-1/CXCR4. Moreover, TGF-β1elevation and pSmad2/3 overexpression were reported in parallel with enhanced epithelial mesenchymal transition (EMT) markers expression, vimentin and α-SMA. Besides, bleomycin significantly elevated the inflammatory and pro-fibrogenic mediator NF-κB p65, TNF-α and IL-6. Furthermore, bleomycin administration induced oxidative stress as depicted by decreased Nrf2, SOD, GSH and catalase levels. Interestingly, berberine administration markedly ameliorated the fibrotic changes in lungs by modulating the purinergic system through the inhibition of A_2aR downregulation, mitigating EMT and effectively suppressing inflammation and oxidative stress. Strikingly, A_2aR blockade by SCH 58261, impeded the pulmonary protective effect of berberine.

SIGNIFICANCE

These findings indicated that berberine could attenuate the pathological processes of bleomycin-induced pulmonary fibrosis at least partially via upregulating A_2aR and mitigating the SDF-1/CXCR4 related pathway, suggesting A_2aR as a potential therapeutic target for the management of pulmonary fibrosis.

Pulmonary Delivery of Recombinant Human Bleomycin Hydrolase Using Mannose-Modified Hierarchically Porous UiO-66 for Preventing Bleomycin-Induced Pulmonary Fibrosis

Bleomycins (BLMs) are widely used in clinics as antitumor agents. However, BLM-based chemotherapies often accompany severe pulmonary fibrosis (PF). Human bleomycin hydrolase is a cysteine protease that can convert BLMs into inactive deamido-BLMs. In this study, mannose-modified hierarchically porous UiO-66 (MHP-UiO-66) nanoparticles (NPs) were used to encapsulate the recombinant human bleomycin hydrolase (rhBLMH). When rhBLMH@MHP-UiO-66 was intratracheally instilled into the lungs, the NPs were transported into the epithelial cells, and rhBLMH prevented the lungs from PF during BLM-based chemotherapies. Encapsulation of rhBLMH in the MHP-UiO-66 NPs protects the enzyme from proteolysis in physiological conditions and enhances cellular uptake. In addition, the MHP-UiO-66 NPs significantly enhance the pulmonary accumulation of intratracheally instilled rhBLMH, thus providing more efficient protection of the lungs against BLMs during the chemotherapies.

Evaluation of renal damage in a bleomycin-induced murine model of systemic sclerosis

Objectives

Systemic sclerosis (SSc) is an autoimmune disease of unknown etiology with a high mortality rate. Renal crisis has been reported as one of the predictors of early mortality in these patients. The present study was performed to evaluate bleomycin-induced SSc using an osmotic minipump as a possible model for the analysis of renal damage in SSc.

Materials and Methods

Male CD1 mice were implanted with osmotic minipumps loaded with saline or bleomycin and sacrificed at 6 and 14 days. Histopathological analysis was performed through hematoxylin and eosin (H&E) and Masson's trichrome staining. The expression of endothelin 1 (ET-1), inducible nitric oxide synthase (iNOS), transforming growth factor β (TGF-β), and 8-hydroxy-2-deoxyguanosine (8-OHdG) was also evaluated by immunohistochemistry.

Results

The administration of bleomycin induced a decrease in the length of Bowman's space (3.6 μm, P<0.001); an increase in collagen deposition (14.6%, P<0.0001); and an increase in the expression of ET-1 (7.5%, P<0.0001), iNOS (10.8%, P<0.0001), 8-OHdG (161 nuclei, P<0.0001), and TGF-β (2.4% µm, P<0.0001) on Day 6. On Day 14, a decrease in the length of Bowman's space (2.6 μm, P<0.0001); increased collagen deposition (13.4%, P<0.0001); and increased expression of ET-1 (2.7%, P<0.001), iNOS (10.1%, P<0.0001), 8-OHdG (133 nuclei, P<0.001), and TGF-β (0.6%, P<0.0001) were also observed.

Conclusion

Systemic administration of bleomycin via an osmotic minipump produces histopathological changes in the kidneys, similar to kidney damage in SSc. Therefore, this model would allow the study of molecular alterations associated with SSc-related renal damage.

Needle-free jet injection-induced small-droplet aerosol formation during intralesional bleomycin therapy

OBJECTIVES

Needle-free jet injectors are frequently used in dermatological practice. Injection-generated small-droplet aerosols could be harmful upon inhalation when chemotherapeutics, like bleomycin, are used. Here, we aim to explore jet injector-induced small-droplet aerosol formation of bleomycin in relation to air ventilation and to provide safety measures for clinical practice.

MATERIALS AND METHODS

With a professional particle sensor, we measured airborne aerosol particles (0.2-10.0 µm) after electronic pneumatic injection (EPI), spring-loaded jet injection (SLI), and needle injection (NI) of bleomycin and saline (100 μl) on ex vivo human skin. Three levels of air ventilation were explored: no ventilation, room ventilation, and room ventilation with an additional smoke evacuator.

RESULTS

EPI and SLI induced significant small-droplet aerosol formation compared with none after NI (0.2-1.0 µm; no ventilation). The largest bleomycin aerosol generation was observed for the smallest particles (0.2-1.0 µm) with 673.170 (528.802-789.453) aerosol particles/liter air (EPI; no ventilation). Room ventilation and smoke evacuation led to a reduction of ≥99% and 100% of measured aerosols, respectively.

CONCLUSION

Jet injectors generate a high number of small-droplet aerosols, potentially introducing harmful effects to patients and healthcare personnel. Room ventilation and smoke evacuation are effective safety measures when chemotherapeutics are used in clinical practice.

Decapping Enzyme NUDT12 Partners with BLMH for Cytoplasmic Surveillance of NAD-Capped RNAs

RNA polymerase II transcripts receive a protective 5',5'-triphosphate-linked 7-methylguanosine (m⁷G) cap, and its removal by decapping enzymes like DCP2 is critical for initiation of RNA decay. Alternative RNA caps can be acquired when transcription initiation uses metabolites like nicotinamide adenine dinucleotide (NAD), generating NAD-RNAs. Here, we identify human NUDT12 as a cytosolic NAD-RNA decapping enzyme. NUDT12 is active only as homodimers, with each monomer contributing to creation of the two functional catalytic pockets. We identify an ∼600-kDa dodecamer complex between bleomycin hydrolase (BLMH) and NUDT12, with BLMH being required for localization of NUDT12 to a few discrete cytoplasmic granules that are distinct from P-bodies. Both proteins downregulate gene expression when artificially tethered to a reporter RNA in vivo. Furthermore, loss of Nudt12 results in a significant upregulation of circadian clock transcripts in mouse liver. Overall, our study points to a physiological role for NUDT12 in the cytosolic surveillance of NAD-RNAs.

To breathe or not to breathe? Hypoxia after pulsed-electric field treatment reduces the effectiveness of electrochemotherapy in vitro

Bleomycin, which is the most widely used drugs in electrochemotherapy, requires oxygen to be able to make single- or double-strand brakes in DNA. However, the concentration of oxygen in tumours can be lower than 1%. The aim of this study was to find out whether oxygen concentration in the medium in which cells loaded with bleomycin are incubated, affects the effectiveness of electrochemotherapy in vitro. Experiments were carried out on mouse hepatoma MH-22A cells. Cells were loaded with bleomycin by using a single square-wave electric pulse (2 kV/cm, 100 μs) under normoxic conditions, seeded into Petri dishes, and grown under normoxic and hypoxic conditions. Cell viability was determined by means of a colony-forming assay. We demonstrated that when cells loaded with bleomycin were incubated in hypoxia (0.2% O₂), up to 5.3-fold higher concentrations of bleomycin were needed to kill them in comparison with cells grown in normoxia (18.7% O₂).

Modeling pulmonary fibrosis through bleomycin delivered by osmotic minipump: a new histomorphometric method of evaluation

The systemic delivery of bleomycin (BLM) to mice through subcutaneously implanted osmotic minipumps may be used to experimentally mimic the typical features of systemic sclerosis and related interstitial lung diseases. The published studies on this model principally have focused on induced dermal modifications, probably because lung lesions are typically mild, subpleurally localized, and difficult to analyze. The use of high BLM doses to increase their severity has been proposed but is ethically questionable because of the compromising of animal welfare. We propose a tailored histomorphometric method suitable to detect and quantify this type of mild lung lesions. Using a two-step automated image analysis, a peripheral region of interest with a depth of 250 µm from the pleural edge was defined on whole slide images, and the fibrotic foci were histomorphometrically characterized. The effects of different BLM doses on lung alterations were evaluated in C57BL/6 mice and 60 U/kg resulted in a fair compromise between fibrotic lesions and animal welfare. This dose was also tested in time course experiments. The analysis revealed a peak of histological fibrotic-like alterations, cytokine expression, metalloprotease, and macrophagic activation between the 21st and 28th day after pump implant. The induced dermal fibrosis was characterized by the progressive loss of the white dermal adipose layer, an increase in dermal thickness, dermal hyperplasia, and more compacted collagen fibers. Despite the trend toward spontaneous resolution, our model allowed a double organ readout of the BLM effect and the identification of a therapeutic window for testing pharmacological compounds without using life-threatening doses.

A Novel Gene Underlies Bleomycin-Response Variation in Caenorhabditis elegans

Bleomycin is a powerful chemotherapeutic drug used to treat a variety of cancers. However, individual patients vary in their responses to bleomycin. The identification of genetic differences that underlie this response variation could improve treatment outcomes by tailoring bleomycin dosages to each patient. We used the model organism Caenorhabditis elegans to identify genetic determinants of bleomycin-response differences by performing linkage mapping on recombinants derived from a cross between the laboratory strain (N2) and a wild strain (CB4856). This approach identified a small genomic region on chromosome V that underlies bleomycin-response variation. Using near-isogenic lines, and strains with CRISPR-Cas9 mediated deletions and allele replacements, we discovered that a novel nematode-specific gene (scb-1) is required for bleomycin resistance. Although the mechanism by which this gene causes variation in bleomycin responses is unknown, we suggest that a rare variant present in the CB4856 strain might cause differences in the potential stress-response function of scb-1 between the N2 and CB4856 strains, thereby leading to differences in bleomycin resistance.

Electrochemotherapy of superficial tumors - Current status:: Basic principles, operating procedures, shared indications, and emerging applications

Treatment of superficial tumors with electrochemotherapy (ECT) has shown a steep rise over the past decade and indications range from skin cancers to locally advanced or metastatic neoplasms. Based on reversible electroporation, which is a physical method to achieve transient tumor cell membrane permeabilization by means of short electric pulses, ECT increases cellular uptake of bleomycin and cisplatin and their cytotoxicity by 8,000- and 80-fold, respectively. Standard operating procedures were established in 2006 and updated in 2018. Ease of administration, patient tolerability, efficacy across histotypes, and repeatability are peculiar advantages, which make standard ECT (ie, ECT using fixed-geometry electrodes) a reliable option for controlling superficial tumor growth locally and preventing their morbidity. Consolidated indications include superficial metastatic melanoma, breast cancer, head and neck skin tumors, nonmelanoma skin cancers, and Kaposi sarcoma. In well-selected patients with oropharyngeal cancers, ECT ensures appreciable symptom control. Emerging applications include skin metastases from visceral or hematological malignancies, vulvar cancer, and some noncancerous skin lesions (keloids and capillary vascular malformations). Repeatability and integration with other oncologic therapies allow for consolidation of response and sustained tumor control. In this review, we present the basic principles of ECT, recently updated operating procedures, anesthesiological management, and provide a synthesis of the efficacy of standard ECT across histotypes.

A Commensal Dipeptidyl Aminopeptidase with Specificity for N-Terminal Glycine Degrades Human-Produced Antimicrobial Peptides in Vitro

Proteases within the C1B hydrolase family are encoded by many organisms. We subjected a putative C1B-like cysteine protease secreted by the human gut commensal Parabacteroides distasonis to mass spectrometry-based substrate profiling to find preferred peptide substrates. The P. distasonis protease, which we termed Pd_dinase, has a sequential diaminopeptidase activity with strong specificity for N-terminal glycine residues. Using the substrate sequence information, we verified the importance of the P2 glycine residue with a panel of fluorogenic substrates and calculated k_cat and K_M for the dipeptide glycine-arginine-AMC. A potent and irreversible dipeptide inhibitor with a C-terminal acyloxymethyl ketone warhead, glycine-arginine- AOMK, was then synthesized and demonstrated that the Pd_dinase active site requires a free N-terminal amine for potent and rapid inhibition. We next determined the homohexameric Pd_dinase structure in complex with glycine-arginine- AOMK and uncovered unexpected active site features that govern the strict substrate preferences and differentiate this protease from members of the C1B and broader papain-like C1 protease families. We finally showed that Pd_dinase hydrolyzes several human antimicrobial peptides and therefore posit that this P. distasonis enzyme may be secreted into the extracellular milieu to assist in gut colonization by inactivation of host antimicrobial peptides.

Activities of recombinant human bleomycin hydrolase on bleomycins and engineered analogues revealing new opportunities to overcome bleomycin-induced pulmonary toxicity

The bleomycins (BLMs) are widely used in combination therapies for the treatment of various cancers. Dose-dependent and cumulative pulmonary toxicity is the major cause of BLM-associated morbidity, limiting the broad uses of BLMs as anticancer drugs. The organ specificity of BLM-induced toxicity has been correlated with the expression of the hBLMH gene, encoding the human bleomycin hydrolase (hBLMH), which is poorly expressed in the lung. hBLMH hydrolyzes BLMs into the biologically inactive deamido BLMs, thereby protecting organs from BLM-induced toxicity. Here we report (i) expression of hBLMH and production and isolation of recombinant human bleomycin hydrolase (rhBLMH) from E. coli, (ii) structural characterization of deamido BLM A2 and B2 isolated from rhBLMH-catalyzed hydrolysis of BLM A2 and B2, and (iii) kinetic characterization of the rhBLMH-catalyzed hydrolysis of BLM A2 and B2, in comparison with five BLM analogues. rhBLMH from E. coli catalyzes rapid and efficient hydrolysis of all BLMs tested, exhibiting a superior catalytic efficiency for BLM B2. These findings reveal new opportunities to overcome BLM-induced pulmonary toxicity in chemotherapies, potentially by exploring BLM B2 as the preferred congener, engineering designer BLMs with optimized activity for rhBLMH, or co-administrating rhBLMH directly into the lung as a potential protein therapeutic.

The Interaction of the Metallo-Glycopeptide Anti-Tumour Drug Bleomycin with DNA

The cancer chemotherapeutic drug, bleomycin, is clinically used to treat several neoplasms including testicular and ovarian cancers. Bleomycin is a metallo-glycopeptide antibiotic that requires a transition metal ion, usually Fe(II), for activity. In this review, the properties of bleomycin are examined, especially the interaction of bleomycin with DNA. A Fe(II)-bleomycin complex is capable of DNA cleavage and this process is thought to be the major determinant for the cytotoxicity of bleomycin. The DNA sequence specificity of bleomycin cleavage is found to at 5′-GT* and 5′-GC* dinucleotides (where * indicates the cleaved nucleotide). Using next-generation DNA sequencing, over 200 million double-strand breaks were analysed, and an expanded bleomycin sequence specificity was found to be 5′-RTGT*AY (where R is G or A and Y is T or C) in cellular DNA and 5′-TGT*AT in purified DNA. The different environment of cellular DNA compared to purified DNA was proposed to be responsible for the difference. A number of bleomycin analogues have been examined and their interaction with DNA is also discussed. In particular, the production of bleomycin analogues via genetic manipulation of the modular non-ribosomal peptide synthetases and polyketide synthases in the bleomycin gene cluster is reviewed. The prospects for the synthesis of bleomycin analogues with increased effectiveness as cancer chemotherapeutic agents is also explored.

An Experimental Model of Anterior Urethral Stricture in Rabbits With Local Injections of Bleomycin

OBJECTIVE

To develop an experimental model of anterior urethral stricture in rabbits using a bleomycin (BLM) injection technique.

MATERIALS AND METHODS

Thirty adult male New Zealand rabbits were randomly divided into 4 groups. In group 1 (BLM group), BLM was injected into the urethral submucosal tissue every other day through a catheter for 6 weeks at the 3-, 6-, 9-, and 12-o'clock positions of the urethra in 12 rabbits. In group 2 (phosphate-buffered saline [PBS] group), PBS was injected instead of BLM in 6 rabbits. In group 3 (stricture control group), an 8 × 20 mm urethral defect was created in 6 rabbits. In group 4 (normal group), 6 normal rabbits were included. All rabbits in the PBS group and stricture control group, as well as 6 rabbits in the BLM group, were sacrificed at 6 weeks. The remaining 6 rabbits in the BLM group were sacrificed at 10 weeks. Urethrography was performed in all rabbits before sacrifice, and the urethra was harvested for histologic analysis.

RESULTS

All rabbits in the BLM group showed mild urethral stricture at 4 weeks and significant urethral stricture at 6 weeks, without spontaneous resolution of the stricture at 10 weeks. No urethral stricture was observed in the PBS group at 4 and 6 weeks. Histologic examination confirmed the presence of fibrosis in the BLM group without spontaneous improvement.

CONCLUSION

BLM injection can induce an experimental model of anterior urethral stricture in rabbits. This simple, highly efficient, reproducible method can be carried out in any laboratory.

F2-isoprostanes can mediate bleomycin-induced lung fibrosis

F₂-isoprostanes (F₂-IsoPs) have been considered markers of oxidative stress in various pulmonary diseases, but little is known about their possible role in pulmonary fibrosis. In this study, we have investigated the potential key role of F₂-IsoPs as markers and mediators of bleomycin (BLM)-induced pulmonary fibrosis in rats. During the in vivo study, plasma F₂-IsoPs showed a peak at 7 days and remained elevated for the entire experimental period. Lung F₂-IsoP content nearly tripled 7 days following the intratracheal instillation of BLM, and by 28 days, the value increased about fivefold compared to the controls. Collagen deposition correlated with F₂-IsoP content in the lung. Furthermore, from day 21 onwards, lung sections from BLM-treated animals showed α-smooth muscle actin (α-SMA) positive cells, which were mostly evident at 28 days. In vitro studies performed in rat lung fibroblasts (RLF) demonstrated that either BLM or F₂-IsoPs stimulated both cell proliferation and collagen synthesis. Moreover, RLF treated with F₂-IsoPs showed a significant increase of α-SMA expression compared to control, indicating that F₂-IsoPs can readily activate fibroblasts to myofibroblasts. Our data demonstrated that F₂-IsoPs can be mediators of key events for the onset and development of lung fibrosis, such as cell proliferation, collagen synthesis and fibroblast activation. Immunocytochemistry analysis, inhibition and binding studies demonstrated the presence of the thromboxane A₂ receptor (TP receptor) on lung fibroblasts and suggested that the observed effects may be elicited through the binding to this receptor. Our data added a new perspective on the role of F₂-IsoPs in lung fibrosis by providing evidence of a profibrotic role for these mediators in the pathogenesis of pulmonary fibrosis.

Modeling DNA damage-induced pneumopathy in mice: insight from danger signaling cascades

Radiation-induced pneumonitis and fibrosis represent severe and dose-limiting side effects in the radiotherapy of thorax-associated neoplasms leading to decreased quality of life or - as a consequence of treatment with suboptimal radiation doses - to fatal outcomes by local recurrence or metastatic disease. It is assumed that the initial radiation-induced damage to the resident cells triggers a multifaceted damage-signalling cascade in irradiated normal tissues including a multifactorial secretory program. The resulting pro-inflammatory and pro-angiogenic microenvironment triggers a cascade of events that can lead within weeks to a pronounced lung inflammation (pneumonitis) or after months to excessive deposition of extracellular matrix molecules and tissue scarring (pulmonary fibrosis).The use of preclinical in vivo models of DNA damage-induced pneumopathy in genetically modified mice has helped to substantially advance our understanding of molecular mechanisms and signalling molecules that participate in the pathogenesis of radiation-induced adverse late effects in the lung. Herein, murine models of whole thorax irradiation or hemithorax irradiation nicely reproduce the pathogenesis of the human disease with respect to the time course and the clinical symptoms. Alternatively, treatment with the radiomimetic DNA damaging chemotherapeutic drug Bleomycin (BLM) has frequently been used as a surrogate model of radiation-induced lung disease. The advantage of the BLM model is that the symptoms of pneumonitis and fibrosis develop within 1 month.Here we summarize and discuss published data about the role of danger signalling in the response of the lung tissue to DNA damage and its cross-talk with the innate and adaptive immune systems obtained in preclinical studies using immune-deficient inbred mouse strains and genetically modified mice. Interestingly we observed differences in the role of molecules involved in damage sensing (TOLL-like receptors), damage signalling (MyD88) and immune regulation (cytokines, CD73, lymphocytes) for the pathogenesis and progression of DNA damage-induced pneumopathy between the models of pneumopathy induced by whole thorax irradiation or treatment with the radiomimetic drug BLM. These findings underline the importance to pursue studies in the radiation model(s) if we are to unravel the mechanisms driving radiation-induced adverse late effects.A better understanding of the cross-talk of danger perception and signalling with immune activation and repair mechanisms may allow a modulation of these processes to prevent or treat radiation-induced adverse effects. Vice-versa an improved knowledge of the normal tissue response to injury is also particularly important in view of the increasing interest in combining radiotherapy with immune checkpoint blockade or immunotherapies to avoid exacerbation of radiation-induced normal tissue toxicity.

Bleomycin-induced flagellate hyperpigmentation

A 27‐year old male with Hodgkin's lymphoma was treated with combined chemotherapy that included bleomycin. He presented with pruritic erythematous, edematous linear lesions and was diagnosed to have flagellate hyperpigmentation, a rare side effect of bleomycin chemotherapy.

Bleomycin-induced skin toxicity: is it always flagellate erythema?

Bleomycin-induced skin toxicity is a rare and unique complication. We report a 35-year-old man with nodular lymphocytic predominant Hodgkin's lymphoma, stage IVB, who was started on adriamycin, bleomycin, vinblastin and dacarbazine (ABVD) chemotherapy. He developed pruritic hyperpigmented, patchy skin lesions on the neck, back, chest and thighs after IA cycle of ABVD chemotherapy. Lesions were not typical flagellate rash but hyperpigmented, patchy and mildly pruritic lesions over the trunk and proximal extremities. Lesions increased with continuation of bleomycin and improved gradually after removing the drug from chemotherapy schedule. The patient was in complete remission after VI cycles of chemotherapy (AVD Regimen) and skin lesions healed with minimal residual hyperpigmentation.

Bleomycin-Induced Pneumonitis in the Treatment of Ovarian Sex Cord-Stromal Tumors: A Systematic Review and Meta-analysis

OBJECTIVE

Adult ovarian sex cord-stromal tumors (SCSTs) are a rare histological subtype of ovarian cancer associated with a favorable prognosis. Bleomycin-containing regimens are standards of care, although pneumonitis may cause potentially fatal dose-limiting toxicity. We aimed to evaluate the safety of bleomycin in SCST treatment.

METHODS

We performed a systematic literature review of all studies of bleomycin therapy for SCSTs that were referenced in MEDLINE (PubMed), EMBASE, and Cochrane Central Register of Controlled Trials and published from 1986 to 2014.

RESULTS

Eight studies totaling 221 patients were included. Rates of pneumonitis (7.7%; 95% confidence interval, 4.2-11.2) and mortality (1.8%; 95% confidence interval, 0.1-3.6) related to bleomycin were significant. However, these results were very similar to those reported for men who were treated with bleomycin for a male germ cell tumor, suggesting that women with ovarian SCSTs are not particularly vulnerable to bleomycin lung toxicity. The main risk factors of bleomycin-induced pneumonitis are high cumulative bleomycin dose (>400 U or mg), age older than 40 years, and impaired renal function. Whether granulocyte colony-stimulating factor is a risk factor remains controversial.

CONCLUSIONS

Bleomycin-induced pneumonitis frequently occurs in patients with SCSTs and lacks effective treatment. Prevention lies in limiting cumulative bleomycin dose, monitoring pulmonary function during treatment, discontinuing bleomycin at the onset of pulmonary symptoms or if pulmonary function is impaired, and avoiding bleomycin in older patients.

Bleomycin induced flagellate erythema in a patient with thalamic mixed germ cell tumour: Report of a rare adverse effect

Bleomycin induced flagellate dermatitis is an uncommon and unique adverse effect. With the declining use of bleomycin, this complication is becoming increasingly infrequent in day-to-day clinical practice. We herein describe a case of a 13year old male patient with left thalamic mixed germ cell tumour treated by multimodality approach, who developed flagellate erythema after two cycles of combination chemotherapy with bleomycin, etoposide and cisplatin (BEP). This brief report highlights the importance of awareness and timely identification and management of this dermatological toxicity in patients undergoing bleomycin based combination chemotherapy.

Bleomycin-induced Flagellate Erythema: A Rare and Unique Drug Rash

Bleomycin-induced flagellate erythema is a rare rash associated with the use of the drug. The rash has a characteristic and intermingled lacy appearance as if it has been whipped. Lack of detoxifying enzymes for bleomycin in the skin makes it a vulnerable site for the adverse effects of bleomycin, along with the lungs. We report the case of young girl with germ cell tumour who developed bleomycin-induced flagellate erythema.

Bleomycin-induced flagellate erythema in a patient with Hodgkin’s lymphoma – A case report and review of literature

Bleomycin is a glycopeptide used as a chemotherapeutic agent for lymphomas, germ cell tumors, and pleurodesis of malignant pleural effusions. The pulmonary toxicity of bleomycin is well known while the cutaneous side effects are uncommon and varies from generalized hyperpigmentation, sclerodermoid changes, erythema multiformae, and gangrene to flagellate dermatosis. Here we report a characteristic but rare side effect of flagellate erythema, which developed secondary to bleomycin in a 27-year old woman with Hodgkin’s lymphoma after two cycles of treatment with adriamycin, bleomycin, vinblastine, dacarbazine regimen. The rash subsided after discontinuation of bleomycin and treatment with steroids.

A modified murine model of systemic sclerosis: bleomycin given by pump infusion induced skin and pulmonary inflammation and fibrosis

Daily subcutaneous (sc) injection of bleomycin (BLM) causes dermal fibrosis but rarely causes lung changes in mice. There are also significant disadvantages to this traditional model for systemic sclerosis, including a variable distribution of lesions and a requirement for repetitive procedures. The present study was undertaken to develop a convenient method of BLM administration that yields stable dermal inflammation and fibrosis with extensive and reproducible interstitial lung disease (ILD) in mice. Osmotic minipumps containing BLM (150 mg/kg) or saline were implanted sc in C57BL/6 mice and the drug was delivered as a continuous infusion over 1∼4 weeks. The time course of morphological features, collagen content, and pro-inflammatory cytokine expression in the skin and the lungs were analyzed. Pathological examination demonstrated dominant inflammatory infiltrates at week 1 and significant fibrosis at week 4. Decreased microvessel density and increased myofibroblast counts were observed in the skin of BLM-treated mice at week 4. In addition, there were obvious increases in dermal infiltration of CD45(+) leukocytes, including F4/80(+) macrophages, Gr-1(+) neutrophils, and CD3(+) T lymphocytes in BLM-treated mice. IL-1β, IL-4, and CXCL2 transcripts were continually upregulated by BLM in the skin and lung tissues. In addition, lungs from BLM-treated mice showed significant inflammatory infiltrates and confluent subpleural fibrosis at week 4. In conclusion, this modified murine model for drug-induced systemic inflammation and fibrosis uses a single procedure and provides reproducible skin and lung lesions, mimicking human systemic sclerosis (SSc) with ILD-like manifestation.

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

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

Bleomycin induced urethral stricture in Hodgkin's disease

Bleomycin is a glycoprotein that is extensively used in combination with other anti-cancer agents because of its relative lack of hematological and gastrointestinal toxicity. However, pulmonary toxicity is common with bleomycin and limits its therapeutic utility. Urethral stricture as a result of bleomycin toxicity has not been reported in literature. In this case report, a young male patient who developed urethral stricture after bleomycin-based chemotherapy is described and the possible effects of bleomycin on the urethra are discussed.

Animal models of acute lung injury

Acute lung injury in humans is characterized histopathologically by neutrophilic alveolitis, injury of the alveolar epithelium and endothelium, hyaline membrane formation, and microvascular thrombi. Different animal models of experimental lung injury have been used to investigate mechanisms of lung injury. Most are based on reproducing in animals known risk factors for ARDS, such as sepsis, lipid embolism secondary to bone fracture, acid aspiration, ischemia-reperfusion of pulmonary or distal vascular beds, and other clinical risks. However, none of these models fully reproduces the features of human lung injury. The goal of this review is to summarize the strengths and weaknesses of existing models of lung injury. We review the specific features of human ARDS that should be modeled in experimental lung injury and then discuss specific characteristics of animal species that may affect the pulmonary host response to noxious stimuli. We emphasize those models of lung injury that are based on reproducing risk factors for human ARDS in animals and discuss the advantages and disadvantages of each model and the extent to which each model reproduces human ARDS. The present review will help guide investigators in the design and interpretation of animal studies of acute lung injury.

Variation in Bleomycin Hydrolase Gene Is Associated With Reduced Survival After Chemotherapy for Testicular Germ Cell Cancer

Purpose

Response to chemotherapy may be determined by gene polymorphisms involved in metabolism of cytotoxic drugs. A plausible candidate is the gene for bleomycin hydrolase (BLMH), an enzyme that inactivates bleomycin, an essential component of chemotherapy regimens for disseminated testicular germ-cell cancer (TC). We investigated whether the single nucleotide polymorphism (SNP) A1450G of the BLMH gene (rs1050565) is associated with survival.

Patients and Methods

Data were collected on survival and BLMH genotype of 304 patients with TC treated with bleomycin-containing chemotherapy at the University Medical Center Groningen, the Netherlands, between 1977 and 2003. Survival according to genotype was analyzed using Kaplan-Meier curves with log-rank testing and Cox regression analysis with adjustment for confounders.

Results

BLMH gene SNP A1450G has a significant effect on TC-related survival (log-rank P = .001). The homozygous variant (G/G) genotype (n = 31) is associated with decreased TC related survival compared with the heterozygous variant (A/G; n = 133) and the wild-type (A/A; n = 140). With Cox regression the G/G genotype proves to be an unfavorable prognostic factor, in addition to the commonly used International Germ Cell Consensus Classification prognosis group, with a hazard ratio of 4.97 (95% CI, 2.17 to 11.39) for TC-related death. Furthermore, the G/G genotype shows a higher prevalence of early relapses.

Conclusion

The homozygous variant G/G of BLMH gene SNP A1450G is associated with reduced survival and higher prevalence of early relapses in TC patients treated with bleomycin-containing chemotherapy. This association is hypothesis generating and may eventually be of value for risk classification and selection for alternative treatment strategies in patients with disseminated TC.

Male sex hormones exacerbate lung function impairment after bleomycin-induced pulmonary fibrosis

The roles of sex hormones as modulators of lung function and disease have received significant attention as differential sex responses to various lung insults have been recently reported. The present study used a bleomycin-induced pulmonary fibrosis model in C57BL/6 mice to examine potential sex differences in physiological and pathological outcomes. Endpoints measured included invasive lung function assessment, immunological response, lung collagen deposition, and a quantitative histological analysis of pulmonary fibrosis. Male mice had significantly higher basal static lung compliance than female mice (P < 0.05) and a more pronounced decline in static compliance after bleomycin administration when expressed as overall change or percentage of baseline change (P < 0.05). In contrast, there were no significant differences between the sexes in immune cell infiltration into the lung or in total lung collagen content after bleomycin. Total lung histopathology scores measured using the Ashcroft method did not differ between the sexes, while a quantitative histopathology scoring system designed to determine where within the lung the fibrosis occurred indicated a tendency toward more fibrosis immediately adjacent to airways in bleomycin-treated male versus female mice. Furthermore, castrated male mice exhibited a female-like response to bleomycin while female mice given exogenous androgen exhibited a male-like response. These data indicate that androgens play an exacerbating role in decreased lung function after bleomycin administration, and traditional measures of fibrosis may miss critical differences in lung function between the sexes. Sex differences should be carefully considered when designing and interpreting experimental models of pulmonary fibrosis in mice.

Antioxidants as potential therapeutics for lung fibrosis

Interstitial lung disease encompasses a large group of chronic lung disorders associated with excessive tissue remodeling, scarring, and fibrosis. The evidence of a redox imbalance in lung fibrosis is substantial, and the rationale for testing antioxidants as potential new therapeutics for lung fibrosis is appealing. Current animal models of lung fibrosis have clear involvement of ROS in their pathogenesis. New classes of antioxidant agents divided into catalytic antioxidant mimetics and antioxidant scavengers are being developed. The catalytic antioxidant class is based on endogenous antioxidant enzymes and includes the manganese-containing macrocyclics, porphyrins, salens, and the non-metal-containing nitroxides. The antioxidant scavenging class is based on endogenous antioxidant molecules and includes the vitamin E analogues, thiols, lazaroids, and polyphenolic agents. Numerous studies have shown oxidative stress to be associated with many interstitial lung diseases and that these agents are effective in attenuating fibroproliferative responses in the lung of animals and humans.

Astrogliosis and behavioral changes in mice lacking the neutral cysteine protease bleomycin hydrolase

Bleomycin hydrolase (BLMH) is a multifaceted neutral cysteine protease with a suggested role in antigen presentation, homocysteine-thiolactone metabolism, and Alzheimer's disease pathogenesis. Deletion of the protease in mice results in increased neonatal mortality and dermatopathology. Immunohistochemical and behavioral studies of BLMH knockout mice were undertaken to further evaluate the role of the protease in the brain. No gross abnormalities in the CNS were observed upon preliminary histological examination of B6.129Blmhtm1Geh/J null animals. However, glial fibrillary acid protein immunohistochemistry revealed a global reactive astrogliosis in the aged null animals, indicative of undefined brain pathology. The role of BLMH in the brain was further explored by characterizing the behavioral phenotype of hybrid [129S6-Blmhtm1Geh/JxB6.129 Blmhtm1Geh/J]F1 null and littermate controls using multiple behavioral paradigms. In the water maze, deletion of BLMH resulted in poorer performance during water maze probe trials without detectable effect of the mutation on sensorimotor function. In addition, no age-dependent decline in discriminative performance on probe trials was observed in null animals. These data suggest a physiological non-redundant function for BLMH in the CNS.

Genetic variation in the bleomycin hydrolase gene and bleomycin-induced pulmonary toxicity in germ cell cancer patients

OBJECTIVE

Use of bleomycin as a cytotoxic agent is limited by its pulmonary toxicity. Bleomycin is mainly excreted by the kidneys, but can also be inactivated by bleomycin hydrolase (BMH). An 1450A>G polymorphic site in the BMH gene results in an amino acid substitution in the C-terminal domain of the protein. Deletion of this domain, including the polymorphic site, reduces enzymatic activity. We investigated the relation between the BMH genotype and the risk of bleomycin-induced pneumonitis (BIP).

METHODS

From male germ cell cancer patients, treated with bleomycin-containing chemotherapy at the University Hospital Groningen, The Netherlands, between 1977 and 2003, data were collected on age, cumulative bleomycin dose, pretreatment creatinine clearance, pulmonary metastases, lung function parameters, and occurrence of BIP. BIP was defined as: death due to BIP, or presence of clinical and/or radiographic signs of BIP during or following treatment. Polymerase chain reaction and restriction fragment length polymorphism were used to determine the BMH genotype.

RESULTS

BIP developed in 38 (11%) of 340 patients; four of these cases were fatal. BMH genotype distribution did not differ between patients with and those without BIP. Patients with BIP were older and had a lower pretreatment creatinine clearance. Changes in pulmonary function tests were similar in patients with different genotypes.

CONCLUSIONS

The BMH genotype was not associated with the development of BIP nor with changes in pulmonary function tests. Since renal function is important for bleomycin pharmacokinetics, variations in renal clearance may have obscured significant effects of the BMH genotype.

Bleomycins: towards better therapeutics

Bleomycins are a family of glycopeptide antibiotics that have potent antitumour activity against a range of lymphomas, head and neck cancers and germ-cell tumours. The therapeutic efficacy of the bleomycins is limited by development of lung fibrosis. The cytotoxic and mutagenic effects of the bleomycins are thought to be related to their ability to mediate both single-stranded and double-stranded DNA damage, which requires the presence of specific cofactors (a transition metal, oxygen and a one-electron reductant). Progress in understanding the mechanisms involved in the therapeutic efficacy of the bleomycins and the unwanted toxicity and elucidation of the biosynthetic pathway of the bleomycins sets the stage for developing a more potent, less toxic therapeutic agent.

Cellular resistance to bleomycin in Saccharomyces cerevisiae is not affected by changes in bleomycin hydrolase levels

Bleomycin is a glycopeptide drug that exerts potent genotoxic potential and is highly effective in the treatment of certain cancers when used in combination therapy. Unfortunately, however, tumors often develop resistance against bleomycin, and the mechanism of this resistance remains unclear. It has been postulated that bleomycin hydrolase, a protease encoded by the BLH1 gene in humans, may account for tumor resistance to bleomycin. In support of such a notion, earlier studies showed that exogenous expression of yeast Blh1 in human cells can enhance resistance to bleomycin. Here we show that (i) yeast blh1delta mutants are not sensitive to bleomycin, (ii) bleomycin-hypersensitive yeast mutants were no more sensitive to this agent upon deletion of the BLH1/LAP3/GAL6 gene, and (iii) overproduction of Blhl in either the parent or bleomycin-hypersensitive mutants did not confer additional resistance to these strains. Therefore, yeast Blh1 apparently has no direct role in protecting this organism from the lethal effects of bleomycin, even though the enzyme can degrade the drug in vitro. Clearly, additional studies are required to establish the actual biological role of Blh1 in yeast.

Protective mechanisms against the antitumor agent bleomycin: lessons from Saccharomyces cerevisiae

Bleomycin is a small glycopeptide antibiotic used in combination therapy for the treatment of a few types of human cancer. The antitumor effect of bleomycin is most likely caused by its ability to bind to DNA and induce the formation of toxic DNA lesions via a free radical reactive (Fe.bleomycin) complex. However, the chemotherapeutic potential of bleomycin is limited, as it causes pulmonary fibrosis and tumor resistance at high doses. The chemical structure and modes of action of bleomycin have been extensively studied and these provide a foundation towards improving the therapeutic value of the drug. This review provides a first account of the current state of knowledge of the cellular processes that can allow the yeast Saccharomyces cerevisiae to evade the lethal effects of bleomycin. This model organism is likely to provide rapid clues in our understanding of bleomycin resistance in tumor cells.

Total synthesis of deamido bleomycin a(2), the major catabolite of the antitumor agent bleomycin

Metabolic inactivation of the antitumor antibiotic bleomycin is believed to be mediated exclusively via the action of bleomycin hydrolase, a cysteine proteinase that is widely distributed in nature. While the spectrum of antitumor activity exhibited by the bleomycins is believed to reflect the anatomical distribution of bleomycin hydrolase within the host, little has been done to characterize the product of the putative inactivation at a chemical or biochemical level. The present report describes the synthesis of deamidobleomycin demethyl A(2) (3) and deamido bleomycin A(2) (4), as well as the respective aglycones. These compounds were all accessible via the key intermediate N(alpha)-Boc-N(beta)-[1-amino-3(S)-(4-amino-6-carboxy-5-methylpyrimidin-2-yl)propion-3-yl]-(S)-beta-aminoalanine tert-butyl ester (16). Synthetic deamido bleomycin A(2) was shown to be identical to the product formed by treatment of bleomycin A(2) with human bleomycin hydrolase, as judged by reversed-phase HPLC analysis and (1)H NMR spectroscopy. Deamido bleomycin A(2) was found to retain significant DNA cleavage activity in DNA plasmid relaxation assays and had the same sequence selectivity of DNA cleavage as bleomycin A(2). The most significant alteration of function noted in this study was a reduction in the ability of deamido bleomycin A(2) to mediate double-strand DNA cleavage, relative to that produced by BLM A(2).

Anti-HIV effect of iron chelators: different mechanisms involved

BACKGROUND

Drugs for the treatment of AIDS have been directed to specific events in the human immunodeficiency virus (HIV-1) life cycle, aimed to stop viral replication by inhibition of reverse transcriptase or protease activity. Studies showing that oxidative stress and iron may be important in the activation of HIV-1 have focused attention on the potential therapeutic use of iron chelators.

OBJECTIVES

The goal of this review is to describe several possibilities as to how iron is involved in the replication of HIV and how iron chelation may interfere in this process.

STUDY DESIGN

First some physico-chemical properties of iron concerning solubility, oxidation-reduction potential, catalysis, and chelation will be discussed. In the second part, the role of iron in various biochemical systems is explained.

RESULTS

Nuclear factor kappa B (NF-kappaB) activation, regulating proviral transcription, can be influenced by iron through the production of reactive oxygen species. A second route by which iron chelation could influence HIV replication, is by inhibition of DNA synthesis through inactivation of iron-dependent ribonucleotide reductase. Another strategy which can be employed in targeting iron chelators against HIV-1, is direct oxidative viral RNA/DNA attack. This could be achieved by bleomycin, a cytostatic agent with the ability to form a complex with DNA and RNA.

CONCLUSION

Chelation may withhold iron from viral metabolism but on the other hand may also favor catalysis of reactive oxygen species directed to viral constituents. In combination with existing antivirals, iron chelation could add to improve the treatment of HIV-disease.

NF1 microdeletion syndrome: refined FISH characterization of sporadic and familial deletions with locus-specific probes

Two familial and seven sporadic patients with neurofibromatosis 1-who showed dysmorphism, learning disabilities/mental retardation, and additional signs and carried deletions of the NF1 gene-were investigated by use of a two-step FISH approach to characterize the deletions. With FISH of YAC clones belonging to a 7-Mb 17q11.2 contig, we estimated the extension of all of the deletions and identified the genomic regions harboring the breakpoints. Mosaicism accounted for the mild phenotype in two patients. In subsequent FISH experiments, performed with locus-specific probes generated from the same YACs by means of a novel procedure, we identified the smallest region of overlapping (SRO), mapped the deletion breakpoints, and identified the genes that map to each deletion interval. From centromere to telomere, the approximately 0.8-Mb SRO includes sequence-tagged site 64381, the SUPT6H gene (encoding a transcription factor involved in chromatin structure), and NF1. Extending telomerically from the SRO, two additional genes-BLMH, encoding a hydrolase involved in bleomycin resistance, and ACCN1, encoding an amiloride-sensitive cation channel expressed in the CNS-were located in the deleted intervals of seven and three patients, respectively. An apparently common centromeric deletion breakpoint was shared by all of the patients, whereas a different telomeric breakpoint defined a deletion interval of 0.8-3 Mb. There was no apparent correlation between the extent of the deletion and the phenotype. This characterization of gross NF1 deletions provides the premise for addressing correctly any genotype-phenotype correlation in the subset of patients with NF1 deletions.

Exacerbation of bleomycin-induced lung injury in mice by amifostine

Bleomycin (BLM) induces lung injury and fibrosis in the murine lung and enhances tumor necrosis factor (TNF)-alpha and collagen mRNA expression in the murine lung. Amifostine is a cytoprotective agent that protects normal tissues from the cytotoxic effects of chemo- and radiation therapy. We investigated the effect of amifostine in BLM-induced lung injury in mice. Mice received intraperitoneal amifostine (200 mg/kg) 30 min before and/or 1, 3, and 7 days after an intratracheal injection of saline or BLM (4 U/kg). The animals were killed 14 days after BLM exposure, and their lungs were studied for TNF-alpha and collagen mRNA expression, hydroxyproline content, and histopathology. Light microscopy demonstrated that amifostine exacerbated the BLM-induced lung injury in mice. Increased TNF-alpha mRNA expression as a result of BLM exposure was not modulated by amifostine treatment. In contrast, amifostine treatment enhanced the BLM-induced expression of alpha(1)(I) procollagen mRNA in the lung. Similarly, mice treated with amifostine before BLM exposure accumulated significantly higher amounts of hydroxyproline (111 +/- 5 microg/lung) than BLM-treated animals (90 +/- 6 microg/lung). These data suggest that amifostine treatment exacerbates BLM-induced lung injury in mice.

Crystal structure of human bleomycin hydrolase, a self-compartmentalizing cysteine protease

BACKGROUND

Bleomycin hydrolase (BH) is a cysteine protease that is found in all tissues in mammals as well as in many other eukaryotes and prokaryotes. Although its conserved cellular function is as yet unknown, human bleomycin hydrolase (hBH) has clinical significance in that it is thought to be the major cause of tumor cell resistance to bleomycin chemotherapy. In addition, it has been reported that an allelic variant of hBH is genetically linked to Alzheimer's disease.

RESULTS

We have determined the crystal structures of wild-type hBH and of a mutant form of the enzyme. The overall structure is very similar to that of the previously determined yeast homolog, however, there is a striking difference in the charge distribution. The central channel, which has a strong positive electrostatic potential in the yeast protein, is slightly negative in hBH. We have determined that hBH does not have the DNA-binding activity of the yeast protein and that the enzyme is localized to the cytoplasm.

CONCLUSIONS

The difference in charge distribution between the yeast and human BH enzymes is most likely responsible for the difference in DNA-binding activity. Nevertheless, the C-terminal autoprocessing activity and the role of the C terminus as a determinant for peptidase activity are conserved between the yeast and human forms. The structure of hBH suggests that the putative Alzheimer's disease linked variation does not directly alter the intrinsic peptidase activity. Rather, the position of the mutation suggests that it could affect interactions with another protein, which may modulate peptidase activity through repositioning of the C terminus.

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.