Heterogeneous Role of the Glutathione Antioxidant System in Modulating the Response of ESFT to Fenretinide in Normoxia and Hypoxia

Glutathione (GSH) is implicated in drug resistance mechanisms of several cancers and is a key regulator of cell death pathways within cells. We studied Ewing's sarcoma family of tumours (ESFT) cell lines and three mechanistically distinct anticancer agents (fenretinide, doxorubicin, and vincristine) to investigate whether the GSH antioxidant system is involved in the reduced sensitivity to these chemotherapeutic agents in hypoxia. Cell viability and death were assessed by the trypan blue exclusion assay and annexin V-PI staining, respectively. Hypoxia significantly decreased the sensitivity of all ESFT cell lines to fenretinide-induced death, whereas the effect of doxorubicin or vincristine was marginal and cell-line-specific. The response of the GSH antioxidant system in ESFT cell lines to hypoxia was variable and also cell-line-specific, although the level of GSH appeared to be most dependent on de novo biosynthesis rather than recycling. RNAi-mediated knockdown of key GSH regulatory enzymes γ-glutamylcysteine synthetase or glutathione disulfide reductase partially reversed the hypoxia-induced resistance to fenretinide, and increasing GSH levels using N-acetylcysteine augmented the hypoxia-induced resistance in a cell line-specific manner. These observations are consistent with the conclusion that the role of the GSH antioxidant system in modulating the sensitivity of ESFT cells to fenretinide is heterogeneous depending on environment and cell type. This is likely to limit the value of targeting GSH as a therapeutic strategy to overcome hypoxia-induced drug resistance in ESFT. Whether targeting the GSH antioxidant system in conjunction with other therapeutics may benefit some patients with ESFT remains to be seen

Biomarkers of aging in Drosophila

Low environmental temperature and dietary restriction (DR) extend lifespan in diverse organisms. In the fruit fly Drosophila, switching flies between temperatures alters the rate at which mortality subsequently increases with age but does not reverse mortality rate. In contrast, DR acts acutely to lower mortality risk; flies switched between control feeding and DR show a rapid reversal of mortality rate. Dietary restriction thus does not slow accumulation of aging-related damage. Molecular species that track the effects of temperatures on mortality but are unaltered with switches in diet are therefore potential biomarkers of aging-related damage. However, molecular species that switch upon instigation or withdrawal of DR are thus potential biomarkers of mechanisms underlying risk of mortality, but not of aging-related damage. Using this approach, we assessed several commonly used biomarkers of aging-related damage. Accumulation of fluorescent advanced glycation end products (AGEs) correlated strongly with mortality rate of flies at different temperatures but was independent of diet. Hence, fluorescent AGEs are biomarkers of aging-related damage in flies. In contrast, five oxidized and glycated protein adducts accumulated with age, but were reversible with both temperature and diet, and are therefore not markers either of acute risk of dying or of aging-related damage. Our approach provides a powerful method for identification of biomarkers of aging.This work was supported by the Wellcome Trust and in part by I+D grants from the Spanish Ministry of Education and Science (BFU2006-14495 ⁄ BFI), the Spanish Ministry of Health (ISCIII, Red de Envejecimiento y Fragilidad, RD06 ⁄ 0013 ⁄ 0012), and the Generalitat of Catalunya (2005SGR00101) to R.P; the Spanish Ministry of Health (FIS PI081843), Spanish Ministry of Education and Science (AGL2006-12433), and ‘‘La Caixa’’ Foundation to M.P.O. Also supported by the Max Planck Society (J.J. and L.P), COST B-35 Action; Research into Ageing (A.J.L.) and the Medical Research Council and National Institutes of Health (P01 AG025901, PL1 AG032118 and P30 AG025708) (M.D.B.)

Effects of chloroquine treatment on antioxidant enzymes in rat liver and kidney.

A journal article with illustrations,The effect of chloroquine (CHQ) administration on antioxidant enzymes in rat liver and kidney was studied. Male Sprague-Dawley rats were administered 20 mglkg CHQ once a week for 4 weeks (chronic treatment) or a single dose at 10 or 20 mglkg (acute treatment). Antioxidant enzyme activities were determined in cytosolic fractions of liver and kidney, whereas reduced glutathione (GSH) and malondialdehyde (MDA) were determined in tissue samples. Results indicate minimal effects of acute CHQ treatment, whereas chronic treatment with CHQ differentially affected antioxidant enzymes in the two organs. Superoxide dismutase activity was increased nearly twofold, while activities of selenium glutathione peroxidase (GPX), catalase, and NAD (P) H: quinone oxidoreductase were decreased in livers of CHQ-treated rats compared to controls. No significant effects of CHQ on glutathione reductase, GSH, and MDA levels were seen in the liver. Fewer effects of CHQ were observed in the kidney where a decrease in GPX activity and an increase in MDA levels was seen. Lowering of antioxidant enzymes activities in the liver by CHQ could render the organ more susceptible to subsequent oxidative stress; while increased MDA production after CHQ treatment in the kidney indicate that the organ is being subjected to oxidative stress. This could have implications for prolonged chloroquine intake.,International Programme in the Chemical Sciences (IPICS), Uppsala University, Sweden, and the University of Zimbabwe Research Board

Chloroquine has not disappeared

Chloroquine (CHQ), an antimalarial, is also used as an anti-inflammatory drug for systemic lupus erythematosus and rheumatoid arthritis (RA). Hydroxychloroquine (HCQ) reduces the frequency of organ involvement and disease flares, and relieves skin and joint symptoms. CHQ reduces the immunologically-mediated inflammation of the joints. HCQ and combination therapies have a significant benefit on synovitis, pain and physical disability on RA. We advocate the investment of resistance Plasmodium prevalence determinations in countries beset by malaria, and to match thereafter the quantity of persons administered CHQ. Follow-up investigations are essential to diagnose and prevent visual damage

Mini review - Chloroquine has not disappeared

Chloroquine (CHQ), an antimalarial, is also used as an anti-inflammatory drug for systemic lupus erythematosus and rheumatoid arthritis (RA). Hydroxychloroquine (HCQ) reduces the frequency of organ involvement and disease flares, and relieves skin and joint symptoms. CHQ reduces the immunologically-mediated inflammation of the joints. HCQ and combination therapies have a significant benefit on synovitis, pain and physical disability on RA.We advocate the investment of resistance Plasmodium prevalence determinations in countries beset by malaria, and to match thereafter the quantity of persons administered CHQ. Follow-up investigations are essential to diagnose and prevent visual damage. Keywords: Antimalarial; Chloroquine; Rheumatoid arthritis; Systemic lupus erythematosus African Health Sciences Vol. 7 (3) 2007: pp. 185-18