scholarly journals Bioreductive metabolism of small molecule nitroaromatics and N-oxides in hypoxia

2012 ◽  
Author(s):  
◽  
Anuruddha Rajapakse
Keyword(s):  
Dna Damage ◽  
Xanthine Oxidase ◽  
Tumor Therapy ◽  
Authentic Sample ◽  
Strong Impact ◽  
P450 Reductase ◽  
Hypoxic Conditions ◽  
Show Evidence ◽  
Dehydration Mechanism ◽  
Nadph:Cytochrome P450 Reductase

Hypoxia in tumors causes adverse effects to therapy and negatively impacts on patient prognosis. Identification and quantification of hypoxia is considered to have a strong impact on treatments in tumor therapy. Fluorescent-based detection to mark hypoxia may be vital to be used along with available methods such as radiochemical and immunohistochemical staining. In this work, the non-fluorescent 6-nitroquinoline (42) was used to investigate the production of a fluorescent 6-aminoquinoline (43) and other metabolites under bio-reducing hypoxic conditions. In the presence of the enzymatic reducing system NADPH:cytochrome P450 reductase/NADPH, 6-nitroquinoline (42) produced the fluorescent helicene (44), along with the non-florescent azo (45). An authentic sample of (44) was chemically synthesized and characterized and used to confirm the production of this molecule in the enzymatic process. Interestingly, the expected fluorophore (43) is not produced by NADPH:cytochrome P450 reductase/NADPH. In another study, the enzymatic reducing system xanthine/xanthine oxidase was used to reduce (42) under hypoxia to obtain (43). In these experiments (43) was produced and the yield is increased with xanthine concentration. Metabolic identification revealed that intermediates of typical nitro reduction pathway are present along with 6-nitroquinolone (51).which is formed by xanthine oxidase mediated oxidation of (42). The absence of (44) as a metabolite with xanthine/xanthine oxidase system highlights the complexity of bioreduction of nitroaromatics under hypoxia. In our laboratory, bio-activation of di-N-oxides such as tirapazamine (TPZ, 42) has been studied. TPZ undergoes one-electron bio-reduction to produce oxidizing radical, which causes DNA damage under hypoxia. In our laboratory, the mechanism by which TPZ mediated DNA damage has been investigated using TPZ and its analogs. Our evidence suggests that upon undergoing bio-reduction, TPZ produces hydroxyl radical as the DNA damaging radical species. Others have suggested another mechanism, which proposes the formation benzotriazine radical (38) upon dehydration process over the bio-reduction step. In the current work, TPZ analog 1,2,4-benzotraizine-1,4-dioxide (55) and deuterated (60) were used to test the dehydration mechanism. Isotopic content analysis of metabolites, derived from bio-reducing metabolism of (55) and its deuterated analog (60), using HRMS show evidence against the dehydration mechanism.

scholarly journals Bioreductive metabolism of small molecule nitroaromatics and N-oxides in hypoxia

2012 ◽  
Author(s):  
◽  
Anuruddha Rajapakse
Keyword(s):  
Dna Damage ◽  
Xanthine Oxidase ◽  
Tumor Therapy ◽  
Authentic Sample ◽  
Strong Impact ◽  
P450 Reductase ◽  
Hypoxic Conditions ◽  
Show Evidence ◽  
Dehydration Mechanism ◽  
Nadph:Cytochrome P450 Reductase

Hypoxia in tumors causes adverse effects to therapy and negatively impacts on patient prognosis. Identification and quantification of hypoxia is considered to have a strong impact on treatments in tumor therapy. Fluorescent-based detection to mark hypoxia may be vital to be used along with available methods such as radiochemical and immunohistochemical staining. In this work, the non-fluorescent 6-nitroquinoline (42) was used to investigate the production of a fluorescent 6-aminoquinoline (43) and other metabolites under bioreducing hypoxic conditions. In the presence of the enzymatic reducing system NADPH:cytochrome P450 reductase/NADPH, 6-nitroquinoline (42) produced the fluorescent helicene (44), along with the non-florescent azo (45). An authentic sample of (44) was chemically synthesized and characterized and used to confirm the production of this molecule in the enzymatic process. Interestingly, the expected fluorophore (43) is not produced by NADPH:cytochrome P450 reductase/NADPH. In another study, the enzymatic reducing system xanthine/xanthine oxidase was used to reduce (42) under hypoxia to obtain (43). In these experiments (43) was produced and the yield is increased with xanthine concentration. Metabolic identification revealed that intermediates of typical nitro reduction pathway are present along with 6-nitroquinolone (51).which is formed by xanthine oxidase mediated oxidation of (42). The absence of (44) as a metabolite with xanthine/xanthine oxidase system highlights the complexity of bio-reduction of nitroaromatics under hypoxia. In our laboratory, bio-activation of di-N-oxides such as tirapazamine (TPZ, 42) has been studied. TPZ undergoes one-electron bio-reduction to produce oxidizing radical, which causes DNA damage under hypoxia. In our laboratory, the mechanism by which TPZ mediated DNA damage has been investigated using TPZ and its analogs. Our evidence suggests that upon undergoing bio-reduction, TPZ produces hydroxyl radical as the DNA damaging radical species. Others have suggested another mechanism, which proposes the formation benzotriazine radical (38) upon dehydration process over the bioreduction step. In the current work, TPZ analog 1,2,4-benzotraizine-1,4-dioxide (55) and deuterated (60) were used to test the dehydration mechanism. Isotopic content analysis of metabolites, derived from bio-reducing metabolism of (55) and its deuterated analog (60), using HRMS show evidence against the dehydration mechanism.

scholarly journals Evaluation of the Protective Effects of Quercetin, Rutin, Naringenin, Resveratrol and Trolox Against Idarubicin-Induced DNA Damage

2010 ◽  
Vol 13 (2) ◽  
pp. 231 ◽  
Author(s):  
Haydar Çelik ◽  
Emel Arinç
Keyword(s):  
Dna Damage ◽  
Cytochrome P450 ◽  
Mitomycin C ◽  
Dna Strand Breaks ◽  
Protective Effects ◽  
Cytochrome P450 Reductase ◽  
Strand Breaks ◽  
P450 Reductase ◽  
Nadph Cytochrome P450 Reductase ◽  
Dna Strand

PURPOSE. Idarubicin is a synthetic anthracycline anticancer drug widely used in the treatment of some hematological malignancies. The studies in our laboratory have clearly demonstrated that idarubicin can undergo reductive bioactivation by NADPH-cytochrome P450 reductase to free radicals with resulting formation of DNA strand breaks, which can potentially contribute to its genotoxic effects [Çelik, H., Arinç, E., Bioreduction of idarubicin and formation of ROS responsible for DNA cleavage by NADPH-cytochrome P450 reductase and its potential role in the antitumor effect. J Pharm Pharm Sci, 11(4):68-82, 2008]. In the current study, our aim was to investigate the possible protective effects of several phenolic antioxidants, quercetin, rutin, naringenin, resveratrol and trolox, against the DNA-damaging effect of idarubicin originating from its P450 reductase-catalyzed bioactivation. METHODS. DNA damage was measured by detecting single-strand breaks in plasmid pBR322 DNA using a cell-free agarose gel method. RESULTS. Our results indicated that, among the compounds tested, quercetin was the most potent antioxidant in preventing DNA damage. Quercetin significantly decreased the extent of DNA strand breaks in a dose-dependent manner; 100 μM of quercetin almost completely inhibited the DNA strand breakage. Unlike quercetin, its glycosidated conjugate rutin, failed to provide any significant protection against idarubicin-induced DNA strand breaks except at the highest concentration tested (2 mM). The protective effects of other antioxidants were significantly less than that of quercetin even at high concentrations. Quercetin was found to be also an effective protector against DNA damage induced by mitomycin C. CONCLUSION. We conclude that quercetin, one of the most abundant flavonoids in the human diet, is highly effective in reducing the DNA damage caused by the antitumor agents, idarubicin and mitomycin C, following bioactivation by P450 reductase.

scholarly journals Cytotoxicity of, and DNA damage by, active oxygen species produced by xanthine oxidase

FEBS Letters ◽  
1991 ◽  
Vol 291 (2) ◽  
pp. 173-176 ◽  
Author(s):  
Mariella Chiricolo ◽  
Pier Luigi Tazzari ◽  
Ada Abbondanza ◽  
Angelo Dinota ◽  
Maria Giulia Battelli
Keyword(s):  
Dna Damage ◽  
Xanthine Oxidase ◽  
Active Oxygen Species ◽  
Active Oxygen ◽  
Oxygen Species

scholarly journals Hypoxia-Induced Gene Expression Occurs Solely through the Action of Hypoxia-Inducible Factor 1α (HIF-1α): Role of Cytoplasmic Trapping of HIF-2α

2003 ◽  
Vol 23 (14) ◽  
pp. 4959-4971 ◽  
Author(s):  
Sang-ki Park ◽  
Agnes M. Dadak ◽  
Volker H. Haase ◽  
Lucrezia Fontana ◽  
Amato J. Giaccia ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcriptional Activity ◽  
Hypoxia Inducible Factor ◽  
Low Oxygen ◽  
Hypoxic Conditions ◽  
Show Evidence ◽  
Dependent Protein ◽  
A Cell ◽  
Cell Type Specific ◽  
Inducible Genes

ABSTRACT The hypoxia-inducible factors 1α (HIF-1α) and 2α (HIF-2α) have extensive structural homology and have been identified as key transcription factors responsible for gene expression in response to hypoxia. They play critical roles not only in normal development, but also in tumor progression. Here we report on the differential regulation of protein expression and transcriptional activity of HIF-1α and -2α by hypoxia in immortalized mouse embryo fibroblasts (MEFs). We show that oxygen-dependent protein degradation is restricted to HIF-1α, as HIF-2α protein is detected in MEFs regardless of oxygenation and is localized primarily to the cytoplasm. Endogenous HIF-2α remained transcriptionally inactive under hypoxic conditions; however, ectopically overexpressed HIF-2α translocated into the nucleus and could stimulate expression of hypoxia-inducible genes. We show that the factor inhibiting HIF-1 can selectively inhibit the transcriptional activity of HIF-1α but has no effect on HIF-2α-mediated transcription in MEFs. We propose that HIF-2α is not a redundant transcription factor of HIF-1α for hypoxia-induced gene expression and show evidence that there is a cell type-specific modulator(s) that enables selective activation of HIF-1α but not HIF-2α in response to low-oxygen stress.

scholarly journals Advances in nanomaterials for treatment of hypoxic tumor

2020 ◽  
Author(s):  
Mei-Zhen Zou ◽  
Wen-Long Liu ◽  
Han-Shi Chen ◽  
Xue-Feng Bai ◽  
Fan Gao ◽  
...  
Keyword(s):  
Tumor Microenvironment ◽  
High Mortality ◽  
Therapeutic Efficacy ◽  
Tumor Invasion ◽  
Tumor Recurrence ◽  
Tumor Therapy ◽  
Functional Nanomaterials ◽  
Oxygen Levels ◽  
Hypoxic Conditions ◽  
Hypoxic Tumor

Abstract The hypoxic tumor microenvironment is characterized by disordered vasculature and rapid proliferation of tumors, resulting from tumor invasion, progression and metastasis. The hypoxic conditions restrict efficiency of tumor therapies, such as chemotherapy, radiotherapy, phototherapy and immunotherapy, leading to serious results of tumor recurrence and high mortality. Recently, research has concentrated on developing functional nanomaterials to treat hypoxic tumors. In this review, we categorize such nanomaterials into (i) nanomaterials that elevate oxygen levels in tumors for enhanced oxygen-dependent tumor therapy and (ii) nanomaterials with diminished oxygen dependence for hypoxic tumor therapy. To elevate oxygen levels in tumors, oxygen-carrying nanomaterials, oxygen-generating nanomaterials and oxygen-economizing nanomaterials can be used. To diminish oxygen dependence of nanomaterials for hypoxic tumor therapy, therapeutic gas-generating nanomaterials and radical-generating nanomaterials can be used. The biocompatibility and therapeutic efficacy of these nanomaterials are discussed.

Role of hepatic cytochromes P450 in bioactivation of the anticancer drug ellipticine: Studies with the hepatic NADPH:Cytochrome P450 reductase null mouse

2008 ◽  
Vol 226 (3) ◽  
pp. 318-327 ◽  
Author(s):  
Marie Stiborová ◽  
Volker M. Arlt ◽  
Colin J. Henderson ◽  
C. Roland Wolf ◽  
Věra Kotrbová ◽  
...  
Keyword(s):  
Anticancer Drug ◽  
Cytochromes P450 ◽  
Null Mouse ◽  
P450 Reductase ◽  
Nadph:Cytochrome P450 Reductase
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