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E Frei

Publications and source records attributed to E Frei.

At least 19 recordsLinked to original sources
PubMed2006

Oxidation pattern of the anticancer drug ellipticine by hepatic microsomes - similarity between human and rat systems.

Ellipticine is an antineoplastic agent, whose mode of action is based mainly on DNA intercalation, inhibition of topoisomerase II and formation of DNA adducts mediated by cytochrome P450 (CYP). We investigated the ability of CYP enzymes in rat, rabbit and human hepatic microsomes to oxidize ellipticine and evaluated suitable animal models mimicking its oxidation in humans. Ellipticine is oxidized by microsomes of all species to 7-hydroxy-, 9-hydroxy-, 12-hydroxy-, 13-hydroxyellipticine and ellipticine N(2)-oxide. However, only rat microsomes generated the pattern of ellipticine metabolites reproducing that formed by human microsomes. While rabbit microsomes favored the production of ellipticine N(2)-oxide, human and rat microsomes predominantly formed 13-hydroxyellipticine. The species difference in expression and catalytic activities of individual CYPs in livers are the cause of these metabolic differences. Formation of 7-hydroxy- and 9-hydroxyellipticine was attributable to CYP1A in microsomes of all species. However, production of 13-hydroxy-, 12-hydroxyellipticine and ellipticine N(2)-oxide, the metabolites generating DNA adducts, was attributable to the orthologous CYPs only in rats and humans. CYP3A predominantly generates these metabolites in rat and human microsomes, while CYP2C3 activity prevails in microsomes of rabbits. The results underline the suitability of rat species as a model to evaluate human susceptibility to ellipticine.

Animals↗
PubMed2002

The impact of induction duration and the number of high-dose cycles on the long-term survival of women with metastatic breast cancer treated with high-dose chemotherapy with stem cell rescue: an analysis of sequential phase I/II trials from the Dana-Farber/Beth Israel STAMP program.

Although high-dose chemotherapy (HDC) with stem cell rescue for the treatment of women with metastatic breast cancer (MBC) is currently a controversial strategy, we report the long-term outcomes of women undergoing high-dose therapy for MBC over the past 12 years while participating in a sequence of research studies transitioning between a single to a double intensification approach. Univariate and multivariate analyses provide a framework to understand the prognostic factors important for event-free and overall survival. Between May 1988 and April 1998, we enrolled 188 women with MBC into 3 trials of previously reported sequential transplantation strategies. Trial I (long induction/single transplantation) accepted 62 women in partial or complete response to an unspecified induction therapy and treated them with high-dose CTCb (cyclophosphamide, thiotepa, and carboplatin) supported by marrow or peripheral blood progenitor cells (PBPC). Trial II (long induction/double transplantation) accepted 68 women in partial or complete response to an unspecified induction therapy, and mobilized stem cells with 2 cycles of AF (doxorubicin and 5-fluorouracil) with granulocyte colony-stimulating factor (G-CSF). These women then received 1 cycle of high-dose single-agent melphalan followed 3 to 5 weeks later by CTCb, each with marrow or PBPC support. Trial III (short induction/double transplantation) enrolled 58 women prior to chemotherapy treatment for metastatic disease. Induction/mobilization consisted of 2 cycles given 14 days apart of doxorubicin and G-CSF. In contrast to trials I and II, patients with stable disease or better response to induction were eligible to proceed ahead with 2 cycles of HDC, 1 being CTCb and the other being dose escalated paclitaxel together with high-dose melphalan (TxM). These 2 HDC regimens were administered 5 weeks apart. TxM was given first in 32 patients and CTCb was given first in 26 patients. The median follow-up periods for trials I, II, and III were 98, 62, and 39 months from the initiation of induction chemotherapy and 92, 55, and 36 months from last high-dose therapy, respectively. The patient characteristics upon entry into these trials were similar. Important differences were that only those patients achieving a partial response or better to induction therapy were enrolled and analyzed for trials I and II, but all patients were analyzed on an intent-to-treat basis for trial III, including those who did not receive intensification. The median event-free survival (EFS) times from induction chemotherapy were 13, 19, and 27 months for trials I, II, and III, respectively (III versus I + II, P = .0004; III versus I, P = .0005; III versus II, P = .005; II versus I, P = .25). The median overall survival (OS) times from induction chemotherapy were 30, 29, and 57 months for trials I, II, and III, respectively (III versus I + II, P = .002; III versus I, P = .003; III versus II, P = .009; II versus I, P = .47). By multivariate Cox regression, participation in the short induction/double transplantation trial III and having no prior adjuvant chemotherapy remained favorable prognostic factors for both EFS and OS. The presence of visceral disease shortened EFS, and hormone sensitivity was of borderline significance. No substantive differences in the characteristics of the patient populations between the 3 trials appeared to interact with outcomes. In conclusion, we found that single transplantation in responding patients after long induction achieves a small cohort of long-term survivors, similar to the results reported by other transplantation centers. Adding a cycle of single-agent high-dose melphalan in this context delayed median time to relapse but did not affect long-term EFS or OS. The double transplantation approach using CTCb and TxM early in the course of treatment was associated with the best EFS and overall survival and was safe, feasible, and tolerable. Treatment duration was only 14 weeks, and this treatment option eliminated lengthy induction chemotherapy. Although selection biases may have in part contributed to this effect, a randomized comparison of standard therapy versus short induction/double transplantation is warranted.

Adult↗
PubMed2001

The anticancer agent ellipticine on activation by cytochrome P450 forms covalent DNA adducts.

Ellipticine is a potent antitumor agent whose mechanism of action is considered to be based mainly on DNA intercalation and/or inhibition of topoisomerase II. Using [3H]-labeled ellipticine, we observed substantial microsome (cytochrome P450)-dependent binding of ellipticine to DNA. In rat, rabbit, minipig, and human microsomes, in reconstituted systems with isolated cytochromes P450 and in Supersomes containing recombinantly expressed human cytochromes P450, we could show that ellipticine forms a covalent DNA adduct detected by [32P]-postlabeling. The most potent human enzyme is CYP3A4, followed by CYP1A1, CYP1A2, CYP1B1, and CYP2C9. Another minor adduct is formed independent of enzymatic activation. The [32P]-postlabeling analysis of DNA modified by activated ellipticine confirms the covalent binding to DNA as an important type of DNA modification. The DNA adduct formation we describe is a novel mechanism for the ellipticine action and might in part explain its tumor specificity.

Animals↗
PubMed2001

AIF-1 expression defines a proliferating and alert microglial/macrophage phenotype following spinal cord injury in rats.

Microglial cells are among the first and dominant cell types to respond to CNS injury. Following calcium influx, microglial activation leads to a variety of cellular responses, such as proliferation and release of cytotoxic and neurotrophic mediators. Allograft inflammatory factor-1, AIF-1 is a highly conserved EF-handed, putative calcium binding peptide, associated with microglia activation in the brain. Here, we have analyzed the expression of AIF-1 following spinal cord injury at the lesion site and at remote brain regions. Following spinal cord injury, AIF-1+ cells accumulated in parenchymal pan-necrotic areas and perivascular Virchow-Robin spaces. Subsequent to culmination at day 3--a situation characterized by infiltrating blood borne macrophages and microglia activation--AIF-1+ cell numbers decreased until day 7. In remote areas of Wallerian degeneration and delayed neuronal death, a more discrete and delayed activation pattern of AIF-1+ microglia/macrophages reaching maximum levels at day 14 was observed. There was a considerable match between AIF-1+ cells and PCNA (proliferating cell nuclear antigen) or Ki-67+ labeled cells. AIF-1 expression preceded the expression of ED1, thus indicating a pre-phagocytic role. It appears that AIF-1+ microglia/macrophages are among the earliest cells to respond to spinal cord injury. Our results suggest a role of AIF-1 in the initiation of the early microglial response leading to activation and proliferation essential for the acute response to CNS injury. AIF-1 might modulate microgliosis influencing the efficacy of tissue debris removal, myelin degradation, recruitment of oligodendrocytes and re-organisation of the CNS architecture.

Amino Acid Sequence↗
PubMed2001

N-nitrososdimethylamine is activated in microsomes from hepatocytes to reactive metabolites which damage DNA of non-parenchymal cells in rat liver.

The liver carcinogen N-nitrosodimethylamine (NDMA) has to be metabolically activated by specific cytochromes before it can react with cellular macromolecules (e.g. proteins or DNA). Although hepatocytes are believed to be responsible for this activation, the liver tumours originate mainly from non-parenchymal cells (NPC). To investigate their activation capacity we determined NDMA-demethylase activity in isolated microsomes from both liver cell types. The results demonstrate that only hepatocytes have activation capacity. Additional experiments were performed with hepatocytes and NPC using the single cell microgel electrophoresis assay (MGE). DNA damage appears in both cell types following in vivo exposure. Tested in vitro, however, the carcinogens induce DNA damages only in hepatocytes (the cells which activate these compounds). N-nitroso-hydroxymethyl-methylamine could be the responsible metabolite as it is stable enough to be transported from hepatocytes to NPC in an intact liver.

Animals↗
PubMed2001

Randomized controlled trial of laparoscopic transabdominal preperitoneal hernioplasty vs Shouldice repair.

BACKGROUND: There is a scarcity of data on long-term results after laparoscopic hernia repair. Herein we report on the outcome of a group of patients who were followed up for 5 years in a multicenter study on hernia repair. METHODS: A total of 100 patients with 127 hernias were randomized to undergo either transabdominal preperitoneal (TAPP) or Shouldice hernia repair. Follow-up was by clinical examination and standardized questionnaire. RESULTS: Of the 100 patients who underwent surgery, 84 were available for follow-up at 5 years. The TAPP procedure was less painful than the Shouldice repair, with fewer patients receiving narcotic analgesics. The median time to return to 100% activity was shorter in the laparoscopic group (21 days) than in the Shouldice group (40 days). Up to 60 months after the operation, the complication rate was lower in laparoscopically repaired hernias (19/66) than in the open group (25/61). There were two recurrences (3.9%) in the TAPP group and five in the Shouldice group (10.2%). CONCLUSION: The TAPP hernia repair yields comparable or better results than Shouldice herniorrhaphy in terms of postoperative pain, recovery, and recurrence rate.

Aged↗
PubMed2001

Evidence for reductive activation of carcinogenic aristolochic acids by prostaglandin H synthase -- (32)P-postlabeling analysis of DNA adduct formation.

Aristolochic acid (AA), a naturally occurring nephrotoxin and carcinogen, is implicated in an unique type of renal fibrosis, designated Chinese herbs nephropathy (CHN), which can develop to urothelial cancer. Understanding which enzymes are involved in AA activation and/or detoxication is important in the assessment of an individual susceptibility to this natural carcinogen. We examined the ability of prostaglandin H synthase (PHS) to activate AA to metabolites forming DNA adducts with the nuclease P1 and 1-butanol extraction enrichment procedure of the (32)P-postlabeling assay. PHS is a prominent enzyme in the kidney and urothelial tissues. Ram seminal vesicle (RSV) microsomes, which contain high levels of PHS, generated AA-DNA adduct patterns reproducing those found in renal tissues in CHN patients. 7-(Deoxyadenosin-N(6)-yl)aristolactam I, 7-(deoxyguanosin-N(2)-yl)aristolactam I and 7-(deoxyadenosin-N(6)-yl)aristolactam II were identified as AA-DNA adducts formed by AAI. Two adducts, 7-(deoxyguanosin-N(2)-yl)aristolactam II and 7-(deoxyadenosin-N(6)-yl)aristolactam II, were generated from AAII. According to the structures of the DNA adducts identified, nitroreduction is the crucial pathway in the metabolic activation of AA. The identity of PHS as the activating enzyme in RSV microsomes was proven with different cofactors and inhibitors. Only indomethacin, a selective inhibitor of PHS, significantly decreased the amount of adducts formed by RSV microsomes. The inhibitor of NADPH:CYP reductase (alpha-lipoic acid) and some selective inhibitors of cytochromes P450 (CYP) were not effective. Likewise, only cofactors of PHS, arachidonic acid and hydrogen peroxide, supported the DNA adduct formation of AAI and AAII, while NADPH and NADH were ineffective. These results demonstrate a key role of PHS in the activation pathway of AAI and AAII in the RSV microsomal system and were corroborated with the purified enzyme, namely ovine PHS-1. The results presented here are the first report demonstrating a reductive activation of nitroaromatic compounds by PHS-1.

Animals↗
PubMed2001

Localization of MDMA-induced brain activity in healthy volunteers using low resolution brain electromagnetic tomography (LORETA).

3,4-Methylenedioxymethamphetamine (MDMA; 'Ecstasy') is a psychostimulant drug producing heightened mood and facilitated social communication. In animal studies, MDMA effects are primarily mediated by serotonin (5-HT), but also by dopamine (DA) and possibly noradrenaline (NA). In humans, however, the neurochemical and neurophysiological basis of acute MDMA effects remains unknown. The distribution of active neuronal populations after administration of a single dose of MDMA (1.7 mg/kg) or placebo was studied in 16 healthy, MDMA-naïve volunteers. Thirty-one-channel scalp EEGs during resting with open and closed eyes was analyzed in the different EEG frequency bands. Scalp maps of power showed significant, global differences between MDMA and placebo in both eye conditions and all frequency bands. Low resolution brain electromagnetic tomography (LORETA) was used to compute 3D, functional images of electric neuronal activity from the scalp EEG data. MDMA produced a widespread decrease of slow and medium frequency activity and an increase of fast frequency activity in the anterior temporal and posterior orbital cortex, concomitant with a marked enhancement of mood, emotional arousal and increased extraversion. This activation of frontotemporal areas indicates that the observed enhancement of mood and possibly the increased extroversion rely on modulation of limbic orbitofrontal and anterotemporal structures known to be involved in emotional processes. Comparison of the MDMA-specific EEG pattern with that of various 5-HT, DA, and NA agonists indicates that serotonin, noradrenaline, and, to a lesser degree, dopamine, contribute to the effects of MDMA on EEG, and possibly also on mood and behavior.

Action Potentials↗
PubMed2001

Human cervical tumor cell (SiHa) surface alphavbeta3 integrin receptor has associated matrix metalloproteinase (MMP-2) activity.

PURPOSE: Integrins are transmembrane heterodimeric molecules that mediate cellular adhesion and are involved in different biological processes, such as tumor development and invasion of tumor cells. Matrixmetalloproteases (MMP) are a family of secreted or membrane proteins capable of digesting extracellular matrix. It has been shown that MMP-2 binds to alphavbeta3 integrin. Recent evidence suggests that a complex of membrane-type MMP (MT1-MMP) and tissue inhibitor of metalloptroteinase-2 (TIMP-2) participate in the activation of alphavbeta3-associated MMP-2. We investigated whether alphavbeta3 and MMP-2 are associated on the membranes of a human cell line, SiHa, and the possible involvement of MT1-MMP and TIMP-2 in the modulation of MMP-2 activity. METHODS: Immunoprecipitation of SiHa membrane extracts with monoclonal antibodies against alphav or MMP-2, and western blots of immunoprecipitates and serum-free conditioned media were performed. TIMP-2 in conditioned medium and MT1-MMP in the membrane fraction was assayed by western blot. Zymography of anti-alphav antibody immunoprecipitates and conditioned media were used to show gelatinolytic activity. RESULTS: The coprecipitation of MMP-2 with alphavbeta3 by anti-alphav antibody is a strong indication that SiHa cell surface alphavbeta3 integrin is a receptor for MMP-2. Immunoblot assays show the expression of MT1-MMP on SiHa cell membranes and secreted TIMP-2 and pro-MMP-2 in the medium. CONCLUSIONS: SiHa cells express all the molecules which are reported to form a complex to activate pro-MMP-2. Active MMP-2 associated with alphavbeta3 may regulate matrix degradation and thereby modulate directed motility of SiHa cells.

Biotinylation↗
PubMed2001

Human enzymes involved in the metabolic activation of carcinogenic aristolochic acids: evidence for reductive activation by cytochromes P450 1A1 and 1A2.

Aristolochic acid (AA), a naturally occurring nephrotoxin and rodent carcinogen, has recently been associated with the development of urothelial cancer in humans. Determining the capability of humans to metabolize AA and understanding, which human enzymes are involved in AA activation is important in the assessment of individual susceptibility. Using the nuclease P1-enhanced version of the (32)P-postlabeling assay, we compared the ability of human, minipig and rat hepatic microsomal samples to activate AA to metabolites forming DNA adducts. Human microsomes generated AA-DNA adduct profiles reproducing those found in renal tissues from humans exposed to AA. Identical patterns of AA-DNA adducts were also observed when AA was activated by minipig and rat microsomes. Therefore, microsomes of both animals are suitable in vitro systems mimicking the enzymatic activation of AA in humans. To define the role of specific P450 enzymes and NADPH:P450 reductase in the activation of AA by human microsomes we investigated the modulation of AA-DNA adduct formation by specific inducers or selective inhibitors of P450s and cofactors or inhibitors of NADPH:P450 reductase. The inducer of P450 1A1/2, beta-naphthoflavone, significantly stimulated the levels of AA-DNA adducts formed by rat microsomes, but inducers of P450 2B1/2 and 2E1 had no such effect. Furthermore, only inhibitors of the P450 1A subfamily (alpha-naphthoflavone, furafylline) significantly decreased the amount of adducts formed by microsomes from humans, minipigs and rats. alpha-Lipoic acid, an inhibitor of NADPH:P450 reductase, inhibited adduct formation too, but to a lower extent. On the basis of these results, we attribute most of the microsomal activation of AA to P450 1A1 and 1A2, although a role of NADPH:P450 reductase cannot be ruled out. With purified enzymes (recombinant P450 1A1/2 and NADPH:P450 reductase) and microsomes from baculovirus transfected insect cells expressing recombinant human P450 1A1/2 and NADPH:P450 reductase, the participation of these enzymes in the formation of AA-DNA adducts was confirmed. These results are the first report on the activation of AA by human enzymes and clearly demonstrate the role of P450 1A1, 1A2, and NADPH:P450 reductase in catalyzing the reductive activation of AA.

Animals↗
PubMed2001

A short course of induction chemotherapy followed by two cycles of high-dose chemotherapy with stem cell rescue for chemotherapy naive metastatic breast cancer.

A single cycle of high-dose chemotherapy with stem cell support (HDC) in women with responsive metastatic breast cancer (BC) consistently achieves over 50% complete and near complete response (CR/nCR). This significant cytoreduction results in a median event-free survival (EFS) of 8 months, and approximately 20% 3-year and 16% 5-year EFS in selected patients. To improve long-term outcomes, new strategies to treat minimal residual tumor burden are needed. Increased total dose delivered can be achieved with two cycles of HDC. Critical design issues include shortening induction chemotherapy to avoid development of drug resistance and the use of different agents for each HDC cycle. We have determined the maximum tolerated dose (MTD) for paclitaxel combined with high-dose melphalan in the context of a double transplant and explored the impact of a short induction phase. Between June 1994 and August 1996, we enrolled 32 women with metastatic BC on to this phase I double transplant trial. Induction consisted of doxorubicin 30 mg/m2/day days 1-3 given for 2 cycles every 14 days with G-CSF 5 microg/kg s.c. days 4-12. Stem cell collection was performed by leukapheresis in each cycle when the WBC recovered to above 1000/microl. Patients with stable disease or better response to induction were eligible to proceed with HDC. HDC regimen I (TxM) included paclitaxel with dose escalation from 0 to 300 mg/m2 given on day 1 and melphalan 180 mg/m2 in two divided doses given on day 3. HDC regimen II was CTCb (cyclophosphamide 6 g/m2, thiotepa 500 mg/m2, and carboplatin 800 mg/m2 total doses) delivered by 96-h continuous infusion. At the first dose level of 150 mg/m2 paclitaxel by 3 h infusion, four of five patients developed dose-limiting toxicity consisting of diffuse skin erythema and capillary leak syndrome. Only two of these five completed the second transplant. Subsequently, paclitaxel was delivered by 24-h continuous infusion together with 96 h of dexamethasone and histamine receptor blockade. This particular toxicity was not observed again. No toxic deaths occurred and dose-limiting toxicity was not encountered. Three patients were removed from study prior to transplant: one for insurance refusal and two for disease progression. All others completed both cycles of transplant. Complete and near complete response (CR/nCR) after completion of therapy was achieved in 23 (72%) of 32 patients. The median EFS is 26 months. The median overall survival has not yet been reached. At a median follow-up of 58 months, EFS and overall survival are 41% and 53%, respectively. This double transplant approach is feasible, safe, and tolerable. Treatment duration is only 14 weeks and eliminates lengthy induction chemotherapy. The observed event-free and overall survivals are promising and are better than expected following a single transplant. Whilst selection biases may in part contribute to this effect, a much larger phase II double transplant trial is warranted in preparation for a potential randomized comparison of standard therapy vs single vs double transplant.

Adult↗
PubMed2001

A short course of induction chemotherapy followed by two cycles of high-dose chemotherapy with stem cell rescue for chemotherapy naive metastatic breast cancer: sequential phase I/II studies.

Two cycles of high-dose chemotherapy with stem cell support (HDC) may increase the total dose delivered and dose intensity. A brief induction phase and different non-cross-resistant agents for each HDC cycle were used to avoid drug resistance. Twenty-six women with metastatic BC had induction and stem cell mobilization with two cycles of doxorubicin/G-CSF given every 14 days. Patients with stable disease or better after induction received HD CTCb followed by HD melphalan and dose-escalated paclitaxel. At 475 mg/m(2) of paclitaxel by 24-h infusion, dose-limiting transient peripheral sensory neuropathy was encountered. No toxic deaths occurred. Complete and near complete response after completion of therapy was achieved in 22 (85%) of 26 patients. The median EFS was 38 months. The median OS has not yet been reached. At a median follow-up of 33 (25-43) months, actuarial EFS and OS were 54% (95% confidence interval (CI), 39-69%) and 69% (95% CI, 56-79%), respectively. This double transplant approach lasts only 14 weeks and is feasible, safe, and tolerable. Whilst selection biases may in part contribute to favorable EFS and OS, a randomized comparison of standard therapy vs double transplant in both metastatic and locally advanced breast cancer is warranted.

Adult↗
PubMed2001

Cyclophosphamide, doxorubicin, vincristine, prednisone, and etoposide (CHOPE) for advanced-stage Hodgkin's disease: CALGB 8856.

Successful treatment of advanced-stage Hodgkin's disease (HD) may critically depend on dose intensity. Because mechlorethamine, Oncovin, procarbazine, and prednisone (MOPP), and Adriamycin, bleomycin, vinblastine, and dacarbazine (ABVD) are not suitable for major dose escalation, we evaluated the activity and toxicity of combined cyclophosphamide, doxorubicin, vincristine, prednisone, and etoposide (CHOPE) in advanced HD, here used at conventional dose intensity, as a preparatory study prior to using this regimen at higher dose intensity. Ninety-two patients were treated with CHOPE (cyclophosphamide, 750 mg/m2, day 1; doxorubicin, 50 mg/m2, day 1; vincristine, 1.4 mg/m2, days 1 and 8; prednisone, 100 mg/day, days 1-5; and etoposide, 80 mg/m2, days 1, 2, and 3) every 21 days. All had advanced HD with no prior chemotherapy with 46% stage IV, 63% with B symptoms, and 57% with bulky disease (> 5 cm). Radiation and growth factor support were not permitted. Full-dose vincristine (not capped at maximum 2 mg/dose) was used in the first 33 patients. An initial cohort of 41 patients was treated with four cycles of CHOPE to evaluate safety and efficacy followed by four cycles of ABVD. A second cohort of 51 patients was treated with 6-8 cycles of CHOPE alone. Toxicity was generally acceptable and primarily hematologic, with neutrophils < 500 in 63% of cohort I and 90% of cohort II, and platelets < 25,000 in 7% of cohort I and 8% of cohort II. The long-term neurotoxicity of full-dose, high-intensity vincristine was acceptable and largely reversible. In cohort I, 92% of patients achieved a complete response (CR) or partial response (PR) with four cycles of CHOPE and 85% were in CR after four additional cycles of ABVD. In cohort II, 77% achieved a CR with 6-8 cycles of CHOPE alone. FFS was 76% in cohort I and 59% in cohort II, with a median follow-up of 8.2 and 5.7 years, respectively. CHOPE, at conventional dose intensity as used here, is an effective first-line regimen for the treatment of advanced-stage HD and may warrant evaluation using higher doses of cyclophosphamide and etoposide with granulocyte colony stimulating factor (G-CSF) support.

Adult↗
PubMed2001

Headless flies generated by developmental pathway interference.

Ectopic expression of transcription factors in eye-antennal discs of Drosophila strongly interferes with their developmental program. Early ectopic expression in embryonic discs interferes with the developmental pathway primed by Eyeless and generates headless flies, which suggests that Eyeless is necessary for initiating cell proliferation and development of both the eye and antennal disc. Interference occurs through a block in the cell cycle that for some ectopic transcription factors is overcome by D-CycE or D-Myc. Late ectopic expression in cone cell precursors interferes with their differentiation. We propose that this developmental pathway interference is a general surveillance mechanism that eliminates most aberrations in the genetic program during development and evolution, and thus seriously restricts the pathways that evolution may take.

Animals↗
PubMed2001

Evidence for activation of carcinogenic o-anisidine by prostaglandin H synthase: 32P-postlabelling analysis of DNA adduct formation.

2-Methoxyaniline (o-anisidine) is a urinary bladder carcinogen in both mice and rats. Since the urinary bladder contains substantial peroxidase activity, we examined the ability of prostaglandin H synthase (PHS), a prominent enzyme in the urinary bladder, to activate this carcinogen to metabolites binding to macromolecules. Using [14C]-labeled o-anisidine, we observed substantial PHS-dependent binding of o-anisidine to protein, DNA and polydeoxyribonucleotides [poly(dX)]. This binding is inhibited by radical scavengers glutathione, ascorbate and NADH. The nuclease P1 and 1-butanol extraction enrichment procedure of the 32P-postlabeling analysis of DNA modified by activated o-anisidine provide evidence that covalent binding to DNA is the principal type of DNA modification. Deoxyguanosine is determined to be the major target for binding of o-anisidine in DNA. The possibility that o-anisidine is carcinogenic to the rodent urinary bladder via its activation by bladder PHS is suggested. The results presented here are the first report demonstrating a PHS-mediated activation of o-anisidine to reactive species forming covalent DNA adducts.

Aniline Compounds↗
PubMed2001

Carcinogenic and nephrotoxic alkaloids aristolochic acids upon activation by NADPH : cytochrome P450 reductase form adducts found in DNA of patients with Chinese herbs nephropathy.

Aristolochic acid (AA), a naturally occurring nephrotoxin and carcinogen, has been found to be implicated in an unique type of renal fibrosis, designated Chinese herbs nephropathy (CHN), and associated with the development of urothelial cancer in CHN patients. Understanding, which enzymes are involved in AA activation and/or detoxication is important in the assessment of individual susceptibility of humans to this natural carcinogen. Using the nuclease P1 version of the 32P-postlabeling assay we examined the ability of microsomal NADPH: CYP reductase to activate AA to metabolites forming DNA adducts. Renal and hepatic microsomes, containing NADPH:CYP reductase, generated AA-DNA adduct patterns reproducing those found in renal tissues in patients suffering from a renal fibrosis CHN and urothelial cancer. 7-(Deoxyadenosin-N6-yl)aristolactam I, 7-(deoxyguanosin-N2-yl)aristolactam I and 7-(deoxyadenosin-N6-yl)aristolactam II were identified as AA-DNA adducts formed by AAI. Two AA-DNA adducts, 7-(deoxyguanosin-N2-yl) aristolactam II and 7- (deoxyadenosin-N6-yl) aristolactam II, were generated from AAII. According to the structures of the DNA adducts identified, nitroreduction is the crucial pathway in the metabolic activation of AA. The identity of NADPH: CYP reductase as activating enzyme in microsomes has been proved with different cofactors and an enzyme inhibitor. Alpha-lipoic acid, a selective inhibitor of NADPH: CYP reductase, significantly decreased the amount of the adducts formed by microsomes. Likewise, only a cofactor of the enzyme, NADPH, supported the DNA adduct formation of AAI and AAII, while NADH was ineffective. These results demonstrate an involvement of NADPH: CYP reductase in the activation pathway of AAI and AAII in the microsomal system. Moreover, using the purified enzyme, the participation of this enzyme in the formation of AA-DNA adducts was confirmed. The results presented here are the first report demonstrating a reductive activation of natural nitroaromatic compounds, AA, by NADPH: CYP reductase.

Animals↗
PubMed2000

Mood state and brain electric activity in ecstasy users.

Resting EEG during open and closed eyes and subsequent mood ratings were obtained from 15 Ecstasy users and 14 Ecstasy-naive controls. Absolute spectral power on the scalp, and the three-dimensional, intracerebral distribution of neuroelectric activity using low resolution brain electromagnetic tomography (LORETA) were computed. LORETA revealed global increases of theta, alpha 1 and beta 2/3 power during eyes open in Ecstasy users, and spectral analyses revealed a right-posterior increase of alpha 2 power (confirmed by LORETA) and increased beta band activity during open eyes. Ecstasy users had higher levels of state depressiveness, emotional excitability and a trend-level increase in state anxiety. The observed differences may be related to regular exposure to Ecstasy or other illicit drugs, or may be pre-existing.

Adult↗