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D Siegel

Publications and source records attributed to D Siegel.

At least 19 recordsLinked to original sources
PubMed2006

Overexpression of NQO1 protects human SK-N-MC neuroblastoma cells against dopamine-induced cell death.

NAD(P)H quinone oxidoreductase 1 (NQO1) can metabolize dopamine-derived quinones (DAQ) and absence of NQO1 due to the NQO1*2 polymorphism has been suggested to be a risk factor for Parkinson's disease. In order to define whether NQO1 plays a protective role in dopamine toxicity, we have examined the potential role of NQO1 in the SK-N-MC human neuroblastoma cell line. SK-N-MC cells were stably transfected with NQO1 to generate stable clones with NQO1 enzymatic activity of 245 nmol/mgmin while vector control and parental cells had NQO1 activities of less than 12 nmol/mgmin. Incubation of dopamine for 24 h in both parental and vector control SK-N-MC cells resulted in 85% and 72% cell death as assessed by annexin-V/propidium iodide analysis. In agreement, 88% and 84% of parental and vector control cells, respectively underwent loss of mitochondrial membrane potential (MMP) assessed by tetramethylrhodamine ethyl ester. In contrast, NQO1-transfected cells were resistant to dopamine toxicity and both cell death and loss of MMP were markedly abrogated in NQO1-transfected SK-N-MC cells. When dopamine was added to medium, oxygen uptake could be detected indicating autoxidation with concomitant formation of oxygen radicals and quinones. However, dopamine-induced cell death was not affected by the inclusion of either superoxide dismutase or catalase suggesting that superoxide and hydrogen peroxide were not involved in toxicity. Quinones formed in medium may exert toxicity extracellularly or intracellularly but the protective role of NQO1 argues for an intracellular mechanism. In summary, transfection of SK-N-MC cells with NQO1 protects against dopamine-induced toxicity.

Annexin A5↗
PubMed2004

Expression of NAD(P)H:quinone oxidoreductase in the normal and Parkinsonian substantia nigra.

Dopamine (DA) autooxidation, and consequent formation of neurotoxic DA-derived quinones and reactive oxygen species, has been implicated in dopaminergic cell death and, hence, in the pathogenesis of Parkinson's disease (PD). Stimulation of pathways involved in the detoxication of DA-quinones in the brain is hypothesized to be an effective means to limit oxidative stress and to confer neuroprotection in PD. In this respect, the inducible flavoprotein NAD(P)H:quinone oxidoreductase (NQO1) is of particular interest as it is directly implicated in the detoxication of DA-quinones and, in addition, has broad spectrum anti-oxidant properties. To study the potential pathophysiological role of NQO1 in PD, the cellular expression of NQO1 was examined in the mesencephalon of PD patients and age-matched controls. In the substantia nigra pars compacta (SNpc), NQO1 was found to be expressed in astroglial and endothelial cells and, albeit less frequently, also in dopaminergic neurons. Moreover, while overt NQO1 immunoreactivity was absent in the surrounding nervous tissue, in the Parkinsonian SNpc a marked increase in the astroglial and neuronal expression of NQO1 was consistently observed.

Adult↗
PubMed2004

A phase 2 study of two doses of bortezomib in relapsed or refractory myeloma.

In a phase 2 open-label study of the novel proteasome inhibitor bortezomib, 54 patients with multiple myeloma who had relapsed after or were refractory to frontline therapy were randomized to receive intravenous 1.0 or 1.3 mg/m(2) bortezomib twice weekly for 2 weeks, every 3 weeks for a maximum of eight cycles. Dexamethasone was permitted in patients with progressive or stable disease after two or four cycles respectively. Responses were determined using modified European Group for Blood and Marrow Transplantation criteria. The complete response (CR) + partial response (PR) rate for bortezomib alone was 30% [90% confidence interval (CI), 15.7-47.1] and 38% (90% CI, 22.6-56.4) in the 1.0 mg/m(2) (8 of 27 patients) and 1.3 mg/m(2) (10 of 26 patients) groups respectively. The CR + PR rate for patients who received bortezomib alone or in combination with dexamethasone was 37% and 50% for the 1.0 and 1.3 mg/m(2) cohorts respectively. The most common grade 3 adverse events were thrombocytopenia (24%), neutropenia (17%), lymphopenia (11%) and peripheral neuropathy (9%). Grade 4 events were observed in 9% (five of 54 patients). Bortezomib alone or in combination with dexamethasone demonstrated therapeutic activity in patients with multiple myeloma who relapsed after frontline therapy.

Adult↗
PubMed2003

Updated investigations of the role of methylenetetrahydrofolate reductase in human neural tube defects.

Folate supplementation appears to reduce the risk for neural tube defects (NTDs). Methylenetetrahydrofolate reductase (MTHFR) is a candidate gene in the folate metabolism pathway that has been extensively studied in different human populations. We examined the risk associated with having the thermolabile variant (TT) of MTHFR in a study of 175 American Caucasians with NTDs and their families. We found a significant association in patients compared with 195 unrelated controls [odds ratio (OR) = 2.13, 95% confidence interval (95% CI) = 1.11-4.09)], but not in mothers (OR = 1.29, 95% CI = 0.622-2.67) or in fathers (OR = 1.45, 95% CI = 0.681-3.09). We found no evidence for unequal transmission from parents to an affected child (p > 0.10). We failed to find a previously reported association for a combined haplotype for MTHFR and cystathionine beta-synthase, except in subjects with NTDs compared with 559 pooled controls (OR = 2.87, 95% CI = 1.03-8.03). We found no evidence for an association for a novel CA-repeat polymorphism identified in a gene closely linked to MTHFR (p > 0.10). Our studies continue to suggest that additional candidate genes other than MTHFR may be responsible for an increased risk to NTD in some American Caucasian families.

Cystathionine beta-Synthase↗
PubMed2001

Characterization of a mechanism-based inhibitor of NAD(P)H:quinone oxidoreductase 1 by biochemical, X-ray crystallographic, and mass spectrometric approaches.

We report the characterization of 5-methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione (ES936) as a mechanism-based inhibitor of NQO1. Inactivation of NQO1 by ES936 was time- and concentration-dependent and required the presence of a pyridine nucleotide cofactor consistent with a need for metabolic activation. That ES936 was an efficient inhibitor was demonstrated in these studies by the low partition ratio (1.40 +/- 0.03). The orientation of ES936 in the active site of NQO1 was examined by X-ray crystallography and found to be opposite to that observed for other indolequinones acting as substrates. ES936 was oriented in such a manner that, after enzymatic reduction and loss of a nitrophenol leaving group, a reactive iminium species was located in close proximity to nucleophilic His 162 and Tyr 127 and Tyr 129 residues in the active site. To determine if ES936 was covalently modifying NQO1, ES936-treated protein was analyzed by electrospray ionization liquid chromatography/mass spectrometry (ESI-LC/MS). The control NQO1 protein had a mass of 30864 +/- 6 Da (n = 20, theoretical, 30868.6 Da) which increased by 217 Da after ES936 treatment (31081 +/- 7 Da, n = 20) in the presence of NADH. The shift in mass was consistent with adduction of NQO1 by the reactive iminium derived from ES936 (M + 218 Da). Chymotryptic digestion of the protein followed by LC/MS analysis located a tetrapeptide spanning amino acids 126-129 which was adducted with the reactive iminium species derived from ES936. LC/MS/MS analysis of the peptide fragment confirmed adduction of either Tyr 127 or Tyr 129 residues. This work demonstrates that ES936 is a potent mechanism-based inhibitor of NQO1 and may be a useful tool in defining the role of NQO1 in cellular systems and in vivo.

Catalytic Domain↗
PubMed2001

NAD(P)H: quinone oxidoreductase 1 expression in human bone marrow endothelial cells.

NAD(P)H:quinone oxidoreductase 1 (NQO1) participates in the detoxification of many environmental quinones and related compounds. Recent studies have suggested that individuals with a polymorphism in NQO1 (NQO1*2), which results in a decrease (heterozygous, NQO1*1/*2) or a total loss (homozygous, NQO1*2/*2) of NQO1, may be at increased risk for the development of leukemias. Previous studies have failed to detect NQO1 in freshly aspirated bone marrow including Ficoll-purified mononuclear cells and purified CD34(+) hematopoietic progenitor stem cells. In these studies we examined human bone marrow core biopsies by immunohistochemistry using monoclonal antibodies directed against NQO1. These studies revealed that NQO1 was expressed in human bone marrow but expression of NQO1 was limited to bone marrow endothelium and adipocytes. To confirm the expression of NQO1 in bone marrow endothelial cells we examined an immortalized human bone marrow endothelial cell line (HBMEC-60) for NQO1 protein expression. Immunoblot analysis and an activity assay confirmed the expression of NQO1 in HBMEC-60. These data demonstrate that NQO1 is present in human bone marrow. The increased risk of leukemia associated with a deficit in NQO1 levels due to the NQO1*2 polymorphism may reflect impaired quinone detoxification and an increased susceptibility of endothelial cells in bone marrow to environmental insults.

Animals↗
PubMed2001

Changes in the phamacologic treatment of hypertension in the Department of Veterans Affairs 1997-1999: decreased use of calcium antagonists and increased use of beta-blockers and thiazide diuretics.

Older studies of antihypertensive treatment have shown that prescribing patterns are not consistent with recommendations from expert national panels. We determined whether prescribing patterns for antihypertensive drugs changed recently in the largest integrated health care system in the United States. Specifically, we determine 1) patterns of antihypertensive medication use at all Department of Veterans Affairs (VA) medical facilities for fiscal years 1997 to 1999, 2) the cost of this care, and 3) savings associated with changes in treatment patterns. Data were aggregated by individual medication as well as by antihypertensive drug class. Estimates of VA national antihypertensive drug costs are based on the median cost and the number of units for each dosage form of each medication dispensed at all facilities. At VA medical facilities, calcium antagonist use went from 33% to 29.3% of antihypertensive treatment days between 1997 and 1999, angiotensin converting enzyme (ACE) inhibitor/angiotensin receptor blocker (ARB) use from 36.4% to 36.8%, beta-blockers from 19.1% to 21.1%, and thiazide diuretic use from at 11.5% to 12.8%. If treatment patterns had remained the same between 1997 and 1999 in terms of the proportion of medications from each drug class, an additional six million dollars would have been spent on antihypertensive medications in 1999. Although calcium antagonists and ACE inhibitors/ARB remained the most commonly dispensed antihypertensives at VA facilities from 1997 to 1999, there was a proportional decrease in calcium antagonist use and an increase in the use of thiazide diuretics and beta-blockers. These changes were consistent with improved compliance with VA national guidelines. The cost implications of these changes in practice patterns were considerable.

Adrenergic beta-Antagonists↗
PubMed2001

Where do adolescents get their condoms?

PURPOSE: To determine where adolescents obtain their condoms; the availability and accessibility of condoms; condom availability in relationship to different sexually transmitted disease (STD) rates; and the availability of safer sex information in places where condoms are sold. METHODS: We conducted a random digit-dialed telephone survey of 259 14-19-year-old adolescents in Monroe County, New York. Self-reported health services use, knowledge and use of confidential services, and where adolescents obtained or intended to obtain condoms were assessed. Research assistants visited all retail establishments in five areas of similar population size with gonorrhea rates from 887 to 12,427 per 100,000 adolescents to assess how available and accessible condoms were in each store. Perceived access and actual condom availability and accessibility were compared using Chi-square and Student's t-tests. RESULTS: Trained interviewers dialed 11,800 numbers in 1993, identifying 4449 (40%) households among 11,065 numbers reached successfully. Of these, 393 (8.8%) had eligible adolescents and 259 (66%) completed interviews. Most adolescents reported obtaining, or planning to obtain, condoms in stores rather than from free health care settings. Adolescents who have used condoms more often reported having obtained them without cost than having purchased them. Condoms were available at 101 (83%) of 122 stores identified. All drug stores and 75% of supermarkets sold condoms and displayed them openly. Most small grocery stores also sold condoms (92%), but were less likely to openly display them. No stores displayed or provided safer sex information. Areas with higher STD rates had more stores (p <.01), and more stores that sold condoms (p <.01). There was no difference in condom cost by area. CONCLUSIONS: Many adolescents obtain their condoms in retail stores. Condom accessibility varied by store type and area STD rate. Increasing condom visibility in private grocery stores may increase the accessibility of condoms to adolescents in areas with highest STD rates.

Adolescent↗
PubMed2001

Preceding chemotherapy, tumour load and age influence engraftment in multiple myeloma patients mobilized with granulocyte colony-stimulating factor alone.

Haematopoietic growth factors, especially granulocyte colony-stimulating factor (G-CSF), are frequently utilized alone for peripheral blood stem cell (PBSC) procurement to avoid the morbidity associated with high-dose chemotherapy (HDT). Moreover, the cytotoxic agents used may not be the most optimal therapy for the malignancy. It also makes scheduling of apheresis easier. Factors having an impact on PBSC procurement and engraftment after HDT were analysed in 117 multiple myeloma patients mobilized with G-CSF (10-16 microg/kg, median 12 microg/kg) alone using Cox regression analysis. A median of 6.2 x 10(6) CD34 cells/kg (range 0.6-34.1) were procured during leukapheresis and a median of 2.5 x 10(6) CD34 cells was infused after the first HDT (range 0.3-23.9). The only factor significantly affecting optimal PBSC procurement was duration of preceding conventional chemotherapy (P = 0.002). Granulocyte recovery was prompt in almost all patients, 75% of whom attained a granulocyte count of 0.5 x 10(9)/l by day 13 (median 11, range 7-19). However, platelet recovery to both 20 x 10(9)/l (median 12 d, range 8-50+) and 50 x 10(9)/l (median 20 d, range 7-205+) varied widely. On univariate analysis, factors influencing platelet recovery were the number of CD34 cells/kg infused, age, beta(2)-microglobulin levels, response to preceding therapy, bone marrow plasmacytosis and duration of prior therapy. Factors attaining significance on multivariate analysis included number of CD34 cells/kg infused (P = 0.007), beta(2)-microglobulin levels (P = 0.0001), most probably representing disease load, and age (P = 0.002). Patients with high tumour burden, i.e. beta(2)-microglobulin levels > 2.5 mg/l, probably benefit from chemotherapy for mobilization both in terms of cytoreduction and adequate stem cell mobilization resulting in accelerated engraftment.

Age Factors↗
PubMed2001

Immunohistochemical localization of NAD(P)H:quinone oxidoreductase in conjunctival melanomas and primary acquired melanosis.

PURPOSE: Mitomycin C has been used in the treatment of primary acquired melanosis and melanomas of the conjunctiva. Because there is increasing evidence that NAD(P)H:quinone oxidoreductase (EC 1.6.99.2, NQO1) or DT-diaphorase plays an important role in the bioactivation of mitomycin C, we examined pathologic specimens of these tumors for NQO1 by immunohistochemistry. METHODS: Formalin-fixed, paraffin-embedded sections with histologic diagnoses of primary acquired melanosis or conjunctival melanomas were obtained from the Eye Pathology Laboratory, University of Colorado Health Sciences Center. Detection of NQO1 in tissues was performed using standard immunohistochemical techniques with monoclonal antibodies against NQO1 and immunoperoxidase staining. Samples were examined by two independent reviewers and NQO1 staining was graded from 0 (no staining) to 3+ (intense staining). RESULTS: Eleven of 11 melanomas (95% confidence interval, 72% to 100%) and three of three lesions with primary acquired melanosis with atypia stained positively for NQO1. In the melanomas, staining was relatively uniform, while in primary acquired melanosis there was cell-to-cell variability in the staining. CONCLUSIONS: NQO1 was detected by immunohistochemistry in every examined section of primary acquired melanosis and melanoma of the conjunctiva, suggesting that NQO1 may play a role in the bioactivation of mitomycin C in these tumors.

Antibodies, Monoclonal↗
PubMed2001

Rapid polyubiquitination and proteasomal degradation of a mutant form of NAD(P)H:quinone oxidoreductase 1.

The NAD(P)H:quinone oxidoreductase 1 (NQO1)*2 polymorphism is characterized by a single proline-to-serine amino acid substitution. Cell lines and tissues from organisms genotyped as homozygous for the NQO1*2 polymorphism are deficient in NQO1 activity. In studies with cells homozygous for the wild-type allele and cells homozygous for the mutant NQO1*2 allele, no difference in the half-life of NQO1 mRNA transcripts was observed. Similarly, in vitro transcription/translation studies showed that both wild-type and mutant NQO1 coding regions were transcribed and translated into full-length protein with equal efficiency. Protein turnover studies in NQO1 wild-type and mutant cell lines demonstrated that the half-life of wild-type NQO1 was greater than 18 h, whereas the half-life of mutant NQO1 was 1.2 h. Incubation of NQO1 mutant cell lines with proteasome inhibitors increased the amount of immunoreactive NQO1 protein, suggesting that mutant protein may be degraded via the proteasome pathway. Additional studies were performed using purified recombinant NQO1 wild-type and mutant proteins incubated in a rabbit reticulocyte lysate system. In these studies, no degradation of wild-type NQO1 protein was observed; however, mutant NQO1 protein was completely degraded in 2 h. Degradation of mutant NQO1 was inhibited by proteasome inhibitors and was ATP-dependent. Mutant NQO1 incubated in rabbit reticulocyte lysate with MG132 resulted in the accumulation of proteins with increased molecular masses that were immunoreactive for both NQO1 and ubiquitin. These data suggest that wild-type NQO1 persists in cells whereas mutant NQO1 is rapidly degraded via ubiquitination and proteasome degradation.

Animals↗
PubMed2001

Renal effects of angiotensin-converting enzyme inhibitors that result in cost savings and improved patient outcomes.

BACKGROUND: In some patients with renal disease, use of angiotensin-converting enzyme (ACE) inhibitors is thought to improve renal function, whereas in others their use leads to worsening. Many questions remain about the categories of patients that benefit from ACE inhibitor use. OBJECTIVE: To clarify the use of ACE inhibitors in patients with renal disease. STUDY DESIGN: A literature review focusing on various renal diseases, ACE inhibitors, and criteria of cost effectiveness was performed. RESULTS: Almost 100 clinical studies were reviewed. Treatment with ACE inhibitors seems to have beneficial effects in type 1 and type 2 diabetes mellitus with nephropathy, AIDS nephropathy, and other nondiabetic renal diseases. Use of these agents in these diseases decreases the progression of renal disease and the need for dialysis, resulting in potential cost savings and improved quality of life. Data supporting goal blood pressures indicate the need to aggressively decrease this risk factor. Use of ACE inhibitors is hazardous in bilateral renal artery stenosis, particularly with volume depletion, but may be valuable in patients with unilateral stenosis. In African Americans, ACE inhibitor treatment is likely to be of benefit, although required doses may be higher than for whites, and caution must be exercised in certain situations. The potential efficacy of angiotensin receptor blockers and other new drugs that affect the renin-angiotensin system is assessed. CONCLUSIONS: Use of ACE inhibitors has benefit in renal disease states characterized by increased glomerular perfusion pressure, their use in other renal disease states, particularly those characterized by reduced glomerular perfusion pressure, may be risky. The benefits conferred by ACE inhibitor therapy are so dramatic in terms of cost savings and improved quality of life that their use in certain clinical situations should be strongly encouraged in managed care and other practice settings.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2000

NAD(P)H:quinone oxidoreductase 1 (NQO1): chemoprotection, bioactivation, gene regulation and genetic polymorphisms.

NAD(P)H:quinone oxidoreductase 1 (NQO1) is an obligate two-electron reductase that is involved in chemoprotection and can also bioactivate certain antitumor quinones. This review focuses on detoxification reactions catalyzed by NQO1 and its role in antioxidant defense via the generation of antioxidant forms of ubiquinone and vitamin E. Bioactivation reactions catalyzed by NQO1 are also summarized and the development of new antitumor agents for the therapy of solid tumors with marked NQO1 content is reviewed. NQO1 gene regulation and the role of the antioxidant response element and the xenobiotic response element in transcriptional regulation is summarized. An overview of genetic polymorphisms in NQO1 is presented and biological significance for chemoprotection, cancer susceptibility and antitumor drug action is discussed.

Animals↗
PubMed2000

L-Dopa stimulates expression of the antioxidant enzyme NAD(P)H:quinone oxidoreductase (NQO) in cultured astroglial cells.

The autooxidation of L-Dopa, a catecholamine used in the symptomatic treatment of Parkinson's disease, generally yields reactive oxygen species and neurotoxic quinones. NAD(P)H:quinone oxidoreductase (NQO) is a flavoenzyme that is implicated in the detoxication of quinones, including those formed during L-Dopa autooxidation. Through the action of this enzyme, deleterious redox-labile quinones are turned into less toxic and more stable hydroquinones that are amenable to further detoxication and/or cellular excretion. In the present study, using primary rat astrocytes and C6 astroglioma as a model to evaluate the neuroprotective response of astroglial cells upon exposure to L-Dopa, we demonstrate that this compound, or more correctly its quinone (auto)oxidation products, up-regulates astroglial NQO in a time- and concentration-dependent way as assessed at the level of mRNA expression, protein level, and enzymatic activity. Moreover, under similar conditions cellular glutathione content was enhanced. It is concluded that, similar to glutathione, the oxidative stress limiting NQO is likely to contribute to the capacity of astroglial cells to protect dopaminergic neurons against L-Dopa, and, hence, may be considered as a potential target for the development of neuroprotective strategies for Parkinson's disease.

Animals↗