Conflicting actions of 4-vinylcatechol in rat lymphocytes under oxidative stress induced by hydrogen peroxide.

4-Vinylcatechol (4VC) has been identified as an aroma compound in roasted foods, especially coffee. It is also a component in traditional herbal medicines. This compound may be subconsciously ingested through foods and herbs. Recent experimental evidence has shown that 4VC possesses an antioxidative action. However, the antioxidative action of 4VC at cellular levels is not well characterized. The effects of 4VC (0.1-100 µM) were examined on rat thymic lymphocytes without and with oxidative stress induced by 300 µM hydrogen peroxide (H2O2). Cell treatment with 100 µM 4VC alone for 4 h significantly increased the population of dead cells. Thus, 4VC at 100 µM or above elicits cytotoxicity. However, 4VC at sublethal concentrations (1-10 µM) significantly attenuated the H2O2-induced increase in cell lethality in a concentration-dependent manner. While application of 10 µM 4VC slowed the process of cell death induced by H2O2, 4VC did not antagonize the H2O2-induced reduction of cellular nonprotein thiols. Although 4VC at 10 µM did not affect intracellular Ca2+ and Zn2+ levels, the agent potentiated the H2O2-induced increases in these levels. These actions of 10 µM 4VC are adverse to the cells under the oxidative stress. However, 10 µM 4VC partly attenuated the cell death induced by 100 nM A23187, a calcium ionophore. There are conflicting actions of 4VC at 1-100 µM on the cells under oxidative stress although the agent is used for an antioxidant. Thus, caution is required when using 4VC as a therapeutic agent.

Cytometrical analysis of the adverse effects of indican, indoxyl, indigo, and indirubin on rat thymic lymphocytes.

Many businesses thrive by producing health supplements from agricultural products, as exemplified by the production of functional (or health) foods using plants traditionally cultivated in rural areas. Dyes, such as indican, indigo, indoxyl, and indirubin, present in dye plants, possess antibacterial, antifungal, and antiproliferative activities. However, these effects may also lead to cytotoxicity. Thus, studies on normal mammalian cells are necessary to identify cytotoxicity and prevent adverse effects of functional foods that contain these dyes. In this study, the effects of indican, indigo, indoxyl, and indirubin were evaluated by flow cytometry using appropriate fluorescent probes in rat thymic lymphocytes. Among the dyes analyzed, indirubin exerted distinct cellular activities. Treatment with indirubin (10-30 µM) increased the population of shrunken dead cells. The side scatter, but not forward scatter, increased in indirubin-treated living cells. It increased the population of annexin V-bound living and dead cells and that of dead cells without annexin V. Indirubin elevated intracellular Ca2+, but not Zn2+ levels. The cellular content of superoxide anions increased and that of glutathione decreased. Indirubin depolarized the cellular plasma and mitochondrial membranes. It did not potentiate or attenuate the cytotoxicity of A23187 (Ca2+ overload) and H2O2 (oxidative stress). The results suggested that indirubin induces both apoptotic and non-apoptotic cell death. It may be difficult to predict and prevent the adverse effects of indirubin due to its diverse activities on normal mammalian cells. Therefore, indirubin should be removed from products that contain dye plant extracts.