Biomedical subjects

Hugh D Riordan

Publications and source records attributed to Hugh D Riordan.

12 recordsLinked to original sources

PubMed2005

Activation of Raf1 and the ERK pathway in response to l-ascorbic acid in acute myeloid leukemia cells.

L-ascorbic acid (LAA) shows cytotoxicity and induces apoptosis of malignant cells in vitro, but the mechanisms by which such effects occur have not been elucidated. In the present study, we provide evidence that the ERK MAP kinase pathway is activated in response to LAA (< 1 mM) in acute myeloid leukemia cell lines. LAA treatment of cells induces a dose-dependent phosphorylation of extracellular signal-regulated kinases (ERK) and results in activation of its catalytic domain. Our data also demonstrate that the small G protein Raf1 and MAPK-activated protein kinase 2 are activated by LAA as an upstream and a downstream regulator of ERK, respectively. Although the ERK pathway has been known to activate cell proliferation, pharmacologic inhibition of ERK reduces LAA-dependent apoptosis and growth inhibitory response of acute myeloid leukemia cell lines, suggesting that this signaling cascade positively regulates induction of apoptotic response by LAA.

Apoptosis↗

PubMed2004

L-ascorbic acid represses constitutive activation of NF-kappaB and COX-2 expression in human acute myeloid leukemia, HL-60.

There is increasing evidence that L-ascorbic acid (LAA) is selectively toxic to some types of cancer cells at pharmacological concentrations, functioning as a pro-oxidant rather than as an anti-oxidant. However, the molecular mechanisms by which LAA initiates cellular signaling leading to cell death are still unclear. In an effort to gain insight into these mechanisms, the effects of LAA on eukaryotic transcription nuclear factor NF-kappaB and cyclooxygenase-2 (COX-2) expression were investigated. In the present study, LAA suppressed DNA binding activity of NF-kappaB, composed of a p65/p50 heterodimer, through inhibition of degradation of inhibitory kappaB-alpha (IkappaB-alpha) and prevention of nuclear translocation of p65. The inhibitory effect of LAA on NF-kappaB activity was dependent upon glutathione levels in HL-60 cells, as well as generation of H2O2 but not superoxide anion. LAA also downregulated the expression of COX-2, which has a NF-kappaB binding site on its promoter, through repressing NF-kappaB DNA binding activity. Moreover, cotreatment of 1 microM arsenic trioxide (As2O3) with various concentrations of LAA enhanced an LAA-induced repression of NF-kappaB activity and COX-2 expression. In conclusion, our data suggest that LAA exerts its anti-tumor activity through downregulation of NF-kappaB activity and COX-2 expression, and these inhibitory effects can be enhanced by co-treatment with As2O3.

Apoptosis↗

PubMed2004

Vitamin C pharmacokinetics: implications for oral and intravenous use.

BACKGROUND: Vitamin C at high concentrations is toxic to cancer cells in vitro. Early clinical studies of vitamin C in patients with terminal cancer suggested clinical benefit, but 2 double-blind, placebo-controlled trials showed none. However, these studies used different routes of administration. OBJECTIVE: To determine whether plasma vitamin C concentrations vary substantially with the route of administration. DESIGN: Dose concentration studies and pharmacokinetic modeling. SETTING: Academic medical center. PARTICIPANTS: 17 healthy hospitalized volunteers. MEASUREMENTS: Vitamin C plasma and urine concentrations were measured after administration of oral and intravenous doses at a dose range of 0.015 to 1.25 g, and plasma concentrations were calculated for a dose range of 1 to 100 g. RESULTS: Peak plasma vitamin C concentrations were higher after administration of intravenous doses than after administration of oral doses (P < 0.001), and the difference increased according to dose. Vitamin C at a dose of 1.25 g administered orally produced mean (+/-sd) peak plasma concentrations of 134.8 +/- 20.6 micromol/L compared with 885 +/- 201.2 micromol/L for intravenous administration. For the maximum tolerated oral dose of 3 g every 4 hours, pharmacokinetic modeling predicted peak plasma vitamin C concentrations of 220 micromol/L and 13 400 micromol/L for a 50-g intravenous dose. Peak predicted urine concentrations of vitamin C from intravenous administration were 140-fold higher than those from maximum oral doses. LIMITATIONS: Patient data are not available to confirm pharmacokinetic modeling at high doses and in patients with cancer. CONCLUSIONS: Oral vitamin C produces plasma concentrations that are tightly controlled. Only intravenous administration of vitamin C produces high plasma and urine concentrations that might have antitumor activity. Because efficacy of vitamin C treatment cannot be judged from clinical trials that use only oral dosing, the role of vitamin C in cancer treatment should be reevaluated.

Administration, Oral↗

PubMed2004

L-Ascorbic acid induces apoptosis in acute myeloid leukemia cells via hydrogen peroxide-mediated mechanisms.

L-Ascorbic acid (LAA) is being investigated clinically for the treatment of patients with acute myeloid leukemia (AML) based on the observed effects of LAA on AML progenitor cells in vitro. However, the mechanism for LAA-induced cytoreduction remains to be elucidated. LAA at concentrations of 0.25-1.0 mM induced a dose- and time-dependent inhibition of proliferation in three AML cell lines and also in leukemic cells from peripheral blood specimens obtained from three patients with AML. In contrast, ovarian cancer cell lines were only minimally affected. Flow cytometric analysis showed that LAA at concentrations of 0.25-1.0 mM could significantly induce apoptosis in the AML cell lines. LAA induced oxidation of glutathione to oxidized form (GSSG) and subsequent H(2)O(2) accumulation in a concentration-dependent manner, in parallel to induction of apoptosis. The direct role of H(2)O(2) in the induction of apoptosis in AML cells was clearly demonstrated by the finding that catalase could completely abrogate LAA-induced apoptosis. Induction of apoptosis in LAA-treated AML cells involved a dose-dependent increase of Bax protein, release of cytochrome C from mitochondria to cytosol, activation of caspase 9 and caspase 3, and cleavage of poly[ADP-ribose]polymerase. In conclusion, LAA can induce apoptosis in AML cells, and this is clearly due to H(2)O(2) which accumulates intracellularly as a result of oxidation of reduced glutathione by LAA.

Apoptosis↗

PubMed2004

Cell membrane fatty acid composition differs between normal and malignant cell lines.

Twenty-eight fatty acids (C8:0 to C24:l n-9) were measured by gas chromatography in four normal cell lines (C3H / 10T1 / 2, CCD-18Co, CCD-25SK and CCD-37Lu) and seven cancer cell lines (C-41, Caov-3, LS-180, PC-3, SK-MEL-28, SK-MES-1 and U-87 MG). Results show differences in the content and proportions of fatty acids when comparing cancer cell lines with their normal counterparts. Cancer cell lines showed lower C20: 4 n-6, C24:1 n-9, polyunsaturated fatty acids (PUFA's) and ratios of C20:4 n-6 to C20:5 n-3 and C16:0 to C18:1 n-9 and stearic to oleic (SA/OA) than their normal counterparts. All cancer cell lines had SA/OA ratios lower than 7.0 while normal cell lines had ratios greater than 0.7 (p<0.05). In addition, the ratios of total saturated fatty acids (SFA) to PUFA'S and the concentration of C18:1 n-9, C18:2 n-6, C20:5 n-3 were higher in cancer cell lines as compared to normal cell lines. A positive correlation was detected between C16:0 and longer SFA'S (r = +0.511, p<0.05) in normal cell lines whereas a negative correlation (r=0.608, p<0.05) was obtained for malignant cell lines. Moreover, cancerous cell lines exhibited a particular desaturation defect and an abnormal incorporation of C18:2 n-6 and C20-4 n-6 fatty acids.

Animals↗

PubMed2004

Erythrocyte membrane fatty acid composition in cancer patients.

Essential fatty acids (EFA) have an important role in complex metabolic reactions. The metabolism of essential polyunsaturated fatty acids (PUFA) appears to be one of the critical targets in the complex metabolic stages that lead to, or are associated with cancer. The goal of our research was to analyze the erythrocyte specific types of membrane fatty acid content, level and distribution in cancer patients as compared to non-cancer patients. Changes in fatty acid composition may affect different aspects of cell structure and function, including proliferation. Analyses of RBCs membrane fatty acids were performed for 255 patients with different types of cancer (breast, prostate, liver, pancreas, colon, and lung), 2,800 non-cancer patients and 34 healthy volunteers. Our research study demonstrated a lower level of stearic acid and an increased content of oleic acid in RBC of cancer patients in comparison with control and non-cancer patients. According to the results of this investigation, the ratio of Eicosa pentaenoic acid (EPA) and Decosa hexaenoic acid (DHA) to Alpha-linolenic acid (ALA) may be useful to estimate PUFA imbalances in cancer patients. EPA and DHA acid may be recommended as supplementation and in addition to current therapy during cancer treatment.

Adult↗

PubMed2004

Intravenous vitamin C as a chemotherapy agent: a report on clinical cases.

A series of seven cases are presented in which intravenous vitamin C has been used as antineoplastic agent in the treatment of different types of cancers. The cancers cases reviewed are the following: Renal cell carcinoma (2), Colorectal cancer (1), Pancreatic cancer (1), Non-Hodgkin's lymphoma (2) and breast cancer (1). Toxic reactions were not observed at these high doses of intravenous Vitamin C. All patients were prescreened for Glucose 6--phosphate dehydrogenase deficiency before administering intravenous Vitamin C in order to prevent hemolysis.

Aged↗

PubMed2004

Intravenous ascorbic acid as a treatment for severe jellyfish stings.

We report a case of jellyfish envenomation in a 39 year old male. He was stung extensively on both lower limbs by an unidentified jellyfish. This occurred in shallow waters of a beach in the vicinity of Labuan Island, Malaysia. The patient received ambulatory treatment with parenteral and oral ascorbate with remarkable recovery.

Adult↗

PubMed2003

Intravenous ascorbic acid: protocol for its application and use.

High dose intravenous(i.v.) ascorbic acid (AA) has been used as therapy for infectious disease from bacterial and viral origin and adjuvant therapy for cancer. In this publication we describe a clinical protocol that has been developed over the past twenty years utilizing high dose i.v. AA as therapy for cancer. This includes principles of treatment, rationale, baseline workup, infusion protocol, precautions and side effects.

Anti-Infective Agents↗

PubMed2002

Inhibition of human breast carcinoma cell proliferation by ascorbate and copper.

We tested the effect of different concentrations of ascorbic acid (AA), 50, 100, 250 mg/500 mg/dL) with copper sulfate (CS), 10 mg/dL) on human breast carcinoma (MDA-MB231) cell proliferation in vitro. Cell proliferation was measured using a colori-metric assay (Cell proliferation kit II (XTT), Boehringer, NJ). The results of the mean absorbance of the tissue culture at different AA concentrations and a constant CS concentration were as follow: 0.82 +/- 0.03 (control, mean +/- SE), 0.64 +/- 0.02 (CS above); 0.48 +/- 0.03 (50 mg/dL) AA), 0.21 +/- 0.02 (100 mg/dL), 0.08 +/- 0.01 (250 mg/dL) AA, 0.60 +/- 0.05 (500 mg/dL). These results show that a combination of AA and CS inhibits human breast carcinoma cell proliferation in vitro. This cell proliferation inhibitory effect is directly proportional to the AA concentration with the exception of the 500 mg/dL AA dose. This chemotherapeutic effect was optimally enhanced when AA was added at a concentration of 250 mg/dL. The AA concentrations of 500 mg/dL had a biphasic effect on tumor cell proliferation probably due to back and forth redox reactions between AA and dehydroascorbic acid in a closed system. This study provides preliminary evidence that AA and SC can be used as biological response modifiers (BRM) for tumor growth inhibition.

Ascorbic Acid↗

PubMed2002

Orthomolecular oncology: a mechanistic view of intravenous ascorbate's chemotherapeutic activity.

The effect of vitamin C in cancer has been a subject of great controversy; mainly because of the inconsistent results obtained by oral intakes of ascorbate when used as an anticancer agent. We believe the intravenous application of ascorbate will provide more consistent results in cancer patients since Vitamin C blood levels attained are substantially higher in a range proven cytotoxic to malignant cells. In this article we will present and discuss our proposed mechanism on the chemotherapeutic activity exhibited by ascorbate.

Antioxidants↗

PubMed2002

Effects of a high molecular mass Convolvulus arvensis extract on tumor growth and angiogenesis.

BACKGROUND: Plant materials represent promising sources of anti-cancer agents. We developed and tested a novel extract from the ubiquitous plant Convolvulus arvensis. MATERIALS AND METHODS: Convolvulus arvensis components were extracted in boiling water, and small molecules were removed by high-pressure filtration. The extract's biological activity was assessed by measuring its effects on S-180 fibrosarcoma growth in Kun Ming mice and on heparin-induced angiogenesis in chick embryos. We also examined the extract's effects on lymphocytes ex vivo and tumor cell growth in vitro. RESULTS: The extract (primarily proteins and polysaccharides) inhibited tumor growth in a dose-dependent fashion when administered orally. At the highest dose tested, 200 mg/kg/day, tumor growth was inhibited by roughly seventy percent. Subcutaneous or intraperitoneal administration at 50 mg/kg/day also inhibited tumor growth by over seventy percent. The extract's acute LD50 in Kun Ming mice was 500 mg/kg/day when injected, indicating that tumor growth inhibition occurred at non-toxic doses. It inhibited angiogenesis in chick embryos, improved lymphocyte survival ex vivo, and enhanced yeast phagocytosis, but did not kill tumor cells in culture. CONCLUSION: High molecular mass extract deserves further study as an anti-cancer agent.

Animals↗