Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A free radical is any species capable of independent existence that contains one or more unpaired electrons. Free radical reactions have been implicated in the pathology of more than 50 human diseases. Radicals and other reactive oxygen species are formed constantly in the human body, both by deliberate synthesis (e.g. by activated phagocytes) and by chemical side-reactions. They are removed by enzymic and nonenzymic antioxidant defence systems. Oxidative stress, occurring when antioxidant defences are inadequate, can damage lipids, proteins, carbohydrates and DNA. A few clinical conditions are caused by oxidative stress, but more often the stress results from the disease. Sometimes it then makes a significant contribution to the disease pathology, and sometimes it does not. Several antioxidants are available for therapeutic use. They include molecules naturally present in the body [superoxide dismutase (SOD), alpha-tocopherol, glutathione and its precursors, ascorbic acid, adenosine, lactoferrin and carotenoids] as well as synthetic antioxidants [such as thiols, ebselen (PZ51), xanthine oxidase inhibitors, inhibitors of phagocyte function, iron ion chelators and probucol]. The therapeutic efficacy of SOD, alpha-tocopherol and ascorbic acid in the treatment of human disease is generally unimpressive to date although dietary deficiencies of the last two molecules should certainly be avoided. Xanthine oxidase inhibitors may be of limited relevance as antioxidants for human use. Exciting preliminary results with probucol (antiatherosclerosis), ebselen (anti-inflammatory), and iron ion chelators (in thalassaemia, leukaemia, malaria, stroke, traumatic brain injury and haemorrhagic shock) need to be confirmed by controlled clinical trials. Clinical testing of N-acetylcysteine in HIV-1-positive subjects may also be merited. A few drugs already in clinical use may have some antioxidant properties, but this ability is not widespread and drug-derived radicals may occasionally cause significant damage.
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PMID:Drug antioxidant effects. A basis for drug selection? 172 62

Procarbazine causes dose-dependent decreases in sperm count after a single i.p. injection in (C57BL/6 X DBA/2)F1 male mice. Two antioxidants, N-acetylcysteine and sodium ascorbate, administered with equimolar doses of procarbazine decreased the spermatotoxicity of procarbazine. At the highest doses of procarbazine (400 mg/kg) that caused a 56% decrease in sperm count, equimolar doses of N-acetylcysteine coadministered with procarbazine caused only a 17% decrease in sperm count, and equimolar doses of ascorbate coadministered with procarbazine caused only a 13% decrease in sperm count. Thus, protection against the spermatotoxic effects of procarbazine was demonstrated with either antioxidant. The effect of the antioxidants on the chemotherapeutic efficacy of procarbazine against murine L1210 leukemia was also assessed. Procarbazine at the highest dose (600 mg/kg) increased mean survival time of mice inoculated i.p. with 1 X 10(5) L1210 leukemia cells by 31%. Simultaneous administration of equimolar doses of either N-acetylcysteine or ascorbate given with procarbazine caused no change in the increased mean survival time of tumor-bearing mice. These results indicate a decrease in the toxicity of procarbazine when coadministered with antioxidants, via decreased spermatotoxicity without changing anticancer efficacy. The results also indicate that different mechanisms are involved in the spermatotoxicity and anticancer activity of procarbazine.
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PMID:Separate mechanisms for procarbazine spermatotoxicity and anticancer activity. 381 55

This study was undertaken to investigate the effect of exogenous sulfhydryl compound administration on the toxicity of doxorubicin in mice. Pretreatment of CDF1 mice with a pharmacologic dose (2,000 mg/kg) of n-acetyl-l-cysteine 1 h before doxorubicin (20 mg/kg, i.p.) decreased lethality from 100% (n = 44) to 37.7% (n = 53), P less than 0.001. Variation in the timing and dose of n-acetylcysteine significantly diminished its protective activity. Pretreatment with n-acetylcysteine also significantly reduced long-term mortality in animals receiving multiple doses of doxorubicin; 10 wk after the third of three doxorubicin doses (5 mg/kg, i.p.) administered at 2-wk intervals, survival in the n-acetylcysteine pretreated group was 51.4% (n = 35) compared with 16.7% (n = 30) for animals receiving saline before doxorubicin, P less than 0.01. In this experiment, n-acetylcysteine pretreatment also diminished doxorubicin-related losses in total body weight and heart wet weight by 55.2% (P less than 0.05), and 60.9% (P less than 0.02), respectively, compared with animals pretreated with saline. N-acetylcysteine pretreatment also ablated electron microscopic evidence of doxorubicin cardiomyopathy without alleviating morphological features of its toxic effects on the liver or small intestinal mucosa. The cardioprotective action of n-acetylcysteine may be partially explained by the 429 +/- 60% increase in cardiac nonprotein sulfhydryl content (P less than 0.01) that was measured one hour after n-acetylcysteine administration; nonprotein sulfhydryl concentration in the liver at the same time was insignificantly different from control levels. Treatment with n-acetylcysteine also increased the nonprotein sulfhydryl content of P388 leukemia cells nearly threefold; however, it did not after the chemotherapeutic activity of doxorubicin against this murine tumor. Whereas n-acetylcysteine blocked doxorubicin cardiac toxicity, it did not affect the uptake or metabolism of doxorubicin in the heart or liver. These results suggest that the concentration of free sulfhydryl groups in the heart may play a role in the development of doxorubicin cardiac toxicity and that augmenting cardiac nonprotein sulfhydryl group content with n-acetylcysteine may provide a means to enhance the chemotherapeutic index of doxorubicin.
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PMID:Prevention of doxorubicin cardiac toxicity in the mouse by N-acetylcysteine. 728 1

We investigated the role of reactive oxygen intermediates and protein kinase C in the induction of expression of the c-jun gene in human ML-2 leukemic cells and normal human DET-551 fibroblasts by comparing the effects of exposure to either ionizing radiation or H2O2 in the presence or absence of appropriate inhibitors. In these cell types, the radiation- and H2O2-mediated increase in c-jun mRNA levels could be prevented by pretreatment of the cells with N-acetylcysteine, an antioxidant, or H7, an inhibitor of protein kinase C and protein kinase A, but not by HA1004, a specific inhibitor of protein kinase A and G. These results suggest a role for protein kinase C and reactive oxygen intermediates in the induction of c-jun gene expression in both normal and tumor cells. We also investigated potential differences in c-jun gene expression induced by radiation or H2O2 in normal and tumor cells by examining steady-state c-jun mRNA levels in a number of human fibroblast, leukemia, melanoma, sarcoma and carcinoma cell types. We observed heterogeneity in the steady-state level of c-jun mRNA in both the untreated normal and tumor cells and in such cells exposed to ionizing radiation or to H2O2. Exposure to radiation produced a varied response which ranged from little or no induction to an increase in the steady-state level of the c-jun mRNA of more than two orders of magnitude. Exposure to H2O2 gave a pattern similar to that of ionizing radiation. The basis for the differential induction in response to these agents may be attributable to either cell lineage or genetic heterogeneity or a combination of these two parameters.
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PMID:Heterogeneity in c-jun gene expression in normal and malignant cells exposed to either ionizing radiation or hydrogen peroxide. 772 34

Retinoic acid and hydrocortisone (HC) have been shown to regulate the drug sensitivity of the blast cells of acute myeloblastic leukemia (AML). We asked if the proto-oncogene bcl-2 played a role in this regulation. As target cells we used the continuous lines, OCI/AML-1, OCI/AML-2 or OCI/AML-5; expression of bcl-2 can be detected by Northern analysis of RNA from OCI/AML-2 or OCI/AML-5 cells; bcl-2 expression can be found in OCI/AML-1 cells only by using RT-PCR. Exposure of OCI/AML-2 or OCI/AML-5 cells to retinoic acid (all-trans retinoic acid, ATRA) led to a down-regulation of bcl-2 expression that was first seen after 2 h of exposure and was complete after a day. The down-regulation could be prevented by exposing the cells to ara-C either before or after ATRA; decrease in bcl-2 protein was moderate and only obvious after 36 h of ATRA treatment. Nuclear run-on experiments provided evidence that bcl-2 down-regulation was occurring at transcriptional and post-translational levels. Since bcl-2 is considered to have anti-oxidant activity, we tested the sensitivity of the three cell lines to H2O2; we found that OCI/AML-1, the line with very low bcl-2 expression, was a 100-fold more H2O2-sensitive than OCI/AML-2 or OCI/AML-5, where bcl-2 expression can be detected readily. We then asked if H2O2 sensitivity could be regulated. We found that exposure of cells to HC before H2O2 was protective while ATRA after peroxide treatment increased killing; this is the same pattern of regulation observed when AML blasts are exposed to HC before, or ATRA after ara-C. Finally, we asked whether N-acetylcysteine (NAC), a known radical scavenger would protect cells against ara-C killing. Significant protection was observed when NAC was given before drug, but not if given after drug. NAC protection against ara-C killing was seen for OCI/AML-1 and 2 cells, but not for OCI/AML-5 cells. We interpret the results as follows: ara-C kills cells in two ways: first, directly, by incorporation into DNA and chain termination; second, indirectly, by inducing the production of toxic radicals. Bcl-2 reduces the oxidant activity of such radicals, and is protective. ATRA regulates ara-C toxicity by its action on bcl-2. Left unexplained are the action of HC, which does not affect bcl-2 expression and the mechanism by which ara-C prevents down-regulation of bcl-2 by ATRA.
Leukemia 1995 May
PMID:Mechanism of cytosine arabinoside toxicity to the blast cells of acute myeloblastic leukemia: involvement of free radicals. 776 41

Diethyldithiocarbamate (DDTC) and N-acetylcysteine (NAC) are nucleophile sulfur-containing compounds which can protect the platinum-induced nephrotoxicity. Combinations of cis-diamminedichloroplatinum(II) (cis-DDP) and DDTC or NAC were tested on the leukemia L1210 and melanoma B 16 tumor models. Nephrotoxicity of cis-DDP alone and in combination with DDTC or NAC was evaluated. On both of the investigated tumor models clastogenic effects in bone marrow cells were detected. DNA synthetic and mitotic activity of L1210 cells in vivo were evaluated by 3H-thymidine incorporation and cytogenetic analysis. Amelioration of the platinum induced nephrotoxicity and preservation of the antitumor activity of cis-DDP through combined application with DDTC or NAC were obtained at the L1210 model. Maximal inhibition of the DNA synthesis in L1210 cells was detected with the cis-DDP treatment. The sulfurcontaining nucleophiles DDTC or NAC could modulate the inhibitory effect of cis-DDP on the incorporation of 3H-thymidine into the nuclei of L1210 cells. Enhanced mitotic activity was detected during cytotoxic therapy with cis-DDP. Cis-DDP alone and in combination with DDTC or NAC caused a significant growth inhibition on the s.c. tumor of the melanoma B16 bearing mice. Two times better therapeutic results at this model were obtained with cis-DDP alone (T/C = 234.09%, T/C = 136.36% for cis-DDP+DDTC and T/C = 151.14% for cis-DDP+NAC). The usefulness of DDTC or NAC as adjuvants in the platinum based chemotherapy of human cancers have been discussed. Clastogenic effect and antitumor activity are probably connected and it is supposed that the reduction of the genotoxicity could lead to a decreased antitumor activity of the platinum complex.
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PMID:Antitumor, nephrotoxic and clastogenic effect of cis-DDP with DDTC or NAC. 785 94

Human thioredoxin, which was previously recognized as adult T-cell leukemia-derived factor, has many physiologic activities, one of which is a radical scavenger effect. Its ability to reduce reperfusion injury was assessed in vivo in a canine lung transplantation model. In 19 dogs, left lung allotransplantation was performed after 100 minutes of warm ischemia. The function of the transplanted lung was assessed after clamping of the contralateral pulmonary artery. In the human thioredoxin group (n = 6), human thioredoxin 30 mg/kg was given to the recipients during reperfusion. In the N-acetylcysteine group (n = 5), N-acetylcysteine 150 mg/kg, known as a radical scavenger, was given in the same manner. In both groups, arterial oxygen tension was significantly higher than in the control group (n = 8). In the human thioredoxin group, peak inspiratory pressure was significantly lower than in the control group. Macroscopic and microscopic examinations showed an almost normal appearance of the lung tissues in the human thioredoxin and N-acetylcysteine groups, in contrast to the abnormal findings in the control group. Thus it would appear that human thioredoxin has a protective effect on transplanted lungs, as does N-acetylcysteine, and that its action may be a radical scavenger effect.
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PMID:Inhibition of reperfusion injury by human thioredoxin (adult T-cell leukemia-derived factor) in canine lung transplantation. 796 75

Myeloperoxidase (MPO) has recently been shown in an in vitro, cell-free system to catalyze the peroxidative degradation of vincristine (VCR). Oxidation of VCR involves a ring fission between positions 20' and 21', and is thought to be facilitated by the presence of an hydroxyl (-OH) group at position 20'. We report here two different approaches, both with potential clinical application, to decrease MPO-catalyzed vinca degradation. Firstly, we tested the hypothesis that -OH substitution at position 20' increases vinca susceptibility to peroxidation by comparing the relative extent of degradation of vinorelbine (Navelbine or NVB), which lacks a 20' hydroxyl substitution, with that of VCR. As anticipated, NVB was significantly less susceptible to MPO-catalyzed peroxidation than was VCR (p < 0.01). Secondly, we screened an array of compounds that are in current clinical use for their ability to inhibit MPO. Acetaminophen, N-acetylcysteine, propylthiouracil, D-penicillamine, mefenamic acid, dapsone, and methimazole all inhibited MPO at clinically achievable concentrations. Insofar as increased MPO activity has been observed in patients with acute myeloid leukemia, these findings suggest potential strategies for improving the activity of vinca alkaloids in this disease.
Leukemia 1994 Apr
PMID:Potential strategies for circumventing myeloperoxidase-catalyzed degradation of vinca alkaloids. 815 63

Mercapturic acid pathway metabolites of phenylethyl isothiocyanate inhibited the growth of human leukaemia 60 (HL60) cells in vitro. The adduct with L-cysteine, S-(N-phenylethylthiocarbamoyl)cysteine, was the most potent with strong antileukaemic activity: the median growth inhibitory concentration (GC50) value was 336 +/- 1 nM (N = 18) compared with GC50 values of the precursor formed from dietary glucosinolates, phenylethyl isothiocyanate, 1.49 +/- 0.01 microM (N = 8), and the initial mercapturic acid pathway metabolite S-(N-phenylethylthiocarbamoyl)glutathione 5.46 +/- 0.36 microM (N = 18). S-(N-Benzylthiocarbamoyl)cysteine and S-(N-phenylpropylthiocarbamoyl)cysteine also had antiproliferative activity but S-(N-phenylethylthiocarbamoyl)cysteine was the most potent compound studied. The latter induced DNA fragmentation in HL60 cells but DNA laddering characteristic of apoptosis was not observed. It had low toxicity to corresponding differentiated cells, neutrophils, in culture, and therefore the cytotoxicity had selectivity for leukaemia cells. The antiproliferative activity of S-(N-phenylethylthiocarbamoyl)cysteine was lost during preincubation with culture medium, attributed to s-thiocarbamoyl transfer to serum proteins, which may decrease its effectiveness in vivo. The antiproliferative activity of S-(N-phenylalkylthiocarbamoyl)cysteine derivatives, by inhibiting tumour growth in pre-clinical development, may contribute to the association of decreased cancer incidence with dietary glucosinolate consumption.
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PMID:Inhibition of human leukaemia 60 cell growth by mercapturic acid metabolites of phenylethyl isothiocyanate. 864 65

The study was designed to evaluate the implication of apoptosis in myeloid leukemic cell death induced by daunorubicin (DNR) and to identify the possible factors which may influence this process. DNR-induced apoptosis was characterized by morphology and DNA fragmentation in six leukemic myeloid cell lines which expressed different differentiation phenotypes. In phenotypically mature HL-60 and U937 cells, DNR induced typical apoptosis with characteristic morphological changes and intense internucleosomal DNA fragmentation within a narrow concentration range (0.5-2 microM). When these cells were treated with higher doses of DNR, large DNA fragments (100 kbp), but not internucleosomal fragments, were identified. DNR-induced DNA fragmentation in HL-60 and U937 was inhibited by antioxidants such as N-acetylcysteine (N-ac) or pyrrolidine-dithiocarbamate (PDTC). In the phenotypically immature KG1a, KG1, HEL and ML1 cell lines DNR induced no characteristic apoptotic morphological features as well as very low levels of internucleosomal DNA fragmentation, whereas large DNA fragments (200 kbp) were observed in KG1a treated with 7 microM DNR. Since the latter expressed P-glycoprotein (P-gp), the role of P-gp in the lack of apoptotic response to DNR was investigated. One P-gp inhibitor (verapamil) slightly improved DNR-induced DNA fragmentation in KG1a cells whereas the combination of verapamil and buthionine-sulfoximine (BSO), which depletes glutathion store, further increased internucleosomal DNA fragmentation. In conclusion, DNR induced internucleosomal DNA fragmentation in some but not all AML cells; the magnitude of this process being influenced by both intracellular drug concentration and oxidative balance.
Leukemia 1996 Mar
PMID:Daunorubicin-induced internucleosomal DNA fragmentation in acute myeloid cell lines. 864 56


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