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Effect of Flavonoids on Glutathione Level, Lipid Peroxidation and Cytochrome P450 CYP1A1 Expression in Human Laryngeal Carcinoma Cell Lines

Flavonoids are phytochemicals exhibiting a wide range of biological activities, among which are antioxidant activity, the ability to modulate activity of several enzymes or cell receptors and possibility to interfere with essential biochemical pathways. Using human laryngeal carcinoma HEp2 cells and their drug-resistant CK2 subline, we examined the effect of five flavonoids, three structurally related flavons (quercetin, fisetin, and myricetin), one flavonol (luteolin) and one glycosilated flavanone (naringin) for their (a) ability to inhibit mitochondrial dehydrogenases as an indicator of cytotoxic effect (MTT test), (b) their influence on glutathione level (determined spectrophotometrically), (c) antioxidant/prooxidant effects (thiobarbituric acid-malondyaldehyde (TBA-MDA) formation as a measure of lipid peroxidation induced by flavonoids and hydrogen peroxide) and influence on cell membrane permeability (lactate dehydrogenase permeability from cell into growth media), and (d) effect on expression of cytochrome CYP1A1 (determined by Western blot analysis). Cytotoxic action of the investigated flavonoids after 72 hours of treatment follows this order: luteolin>quercetin>fisetin>naringin>myricetin. The highest non-toxic concentrations of flavonoids were established as follows: luteolin (4.12  M), quercetin (5.46  M), fisetin (5  M), naringin (38.1  M) and myricetin (41.2  M). These concentrations were used in all experiments. Our results show that CK2 were more resistant to toxic concentrations of flavonoids as compared to parental cells. Quercetin increased the total GSH level in both cell lines. CK2 cells are less perceptible to lipid peroxidation and damage caused by free radicals. Quercetin showed prooxidant effect in both cell lines, luteolin only in HEp2 cells, whereas other tested flavonoids did not cause lipid peroxidation in the tested cell lines. These data suggest that the same compound, quercetin, can act as a prooxidant, but also, it may prevent damage in cells caused by free radicasl, due to the induction of GSH, by forming less harmful complex. Quercetin treatment damaged cell membranes in both cell lines. Fisetin caused higher cell membrane permeability only in HEp2 cells. However, these two compounds did not enhance the damage caused by hydrogen peroxide. Quercetin, naringin, myricetin and fisetin increased the expression of CYP1A1 in both cell lines, while luteolin decreased basal level of CYP1A1 only in HEp2 cells. In conclusion, small differences in chemical structure of flavonoids lead to drastic change of their biological effects. These effects are strongly dependent on cell type as well as test systems used. Extensive studies on structure-function relationship of flavonoids in different test systems could provide rational approach to drug and chemopreventive agent design.

flavonoids ; tumor cells ; cytotoxicity ; glutathione ; lipid peroxidation ; cytochrome 1A1

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