RESUMEN
Microglia and astrocytes are the cellular key players in many neurological disorders associated with oxidative stress and neuroinflammation. Previously, we have shown that microglia activated by lipopolysaccharides (LPS) induce the expression of antioxidative enzymes in astrocytes and render them more resistant to hydrogen peroxide (H2O2). In this study, we examined the mechanisms involved with respect to the cellular action of different peroxides, the ability to detoxify peroxides, and the status of further antioxidative systems. Astrocytes were treated for 3 days with medium conditioned by purified quiescent (microglia-conditioned medium, MCM[-]) or LPS-activated (MCM[+]) microglia. MCM[+] reduced the cytotoxicity of the organic cumene hydroperoxide in addition to that of H2O2. Increased peroxide resistance was not accompanied by an improved ability of astrocytes to remove H2O2 or an increased expression/activity of peroxide eliminating antioxidative enzymes. Neither peroxide-induced radical generation nor lipid peroxidation were selectively affected in MCM[+] treated astrocytes. The glutathione content of peroxide resistant astrocytes, however, was increased and superoxide dismutase and heme oxygenase were found to be upregulated. These changes are likely to contribute to the higher peroxide resistance of MCM[+] treated astrocytes by improving their ability to detoxify reactive oxygen radicals and oxidation products. For C6 astroglioma cells a protective effect of microglia-derived factors could not be observed, underlining the difference of primary cells and cell lines concerning their mechanisms of oxidative stress resistance. Our results indicate the importance of microglial-astroglial cell interactions during neuroinflammatory processes.
Asunto(s)
Astrocitos/fisiología , Peroxidación de Lípido/fisiología , Estrés Oxidativo/fisiología , Peróxidos/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Animales , Astrocitos/química , Encéfalo/citología , Antígeno CD11b/metabolismo , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Medios de Cultivo Condicionados/farmacología , Relación Dosis-Respuesta a Droga , Glutatión/metabolismo , Glutatión Transferasa/genética , Glutatión Transferasa/metabolismo , Hemo-Oxigenasa 1/genética , Hemo-Oxigenasa 1/metabolismo , Peróxido de Hidrógeno/metabolismo , Peróxido de Hidrógeno/farmacología , Peroxidación de Lípido/efectos de los fármacos , Lipopolisacáridos/farmacología , Microglía/efectos de los fármacos , Óxido Nítrico/metabolismo , Estrés Oxidativo/efectos de los fármacos , Peróxidos/farmacología , Pregnanolona/análogos & derivados , Pregnanolona/farmacología , ARN Mensajero/metabolismo , Ratas , Ratas Wistar , Superóxido Dismutasa/genética , Superóxido Dismutasa/metabolismo , Factores de TiempoRESUMEN
It has been shown that oxidative damage contributes to the wide range of toxic effects of the mycotoxin ochratoxin A (OTA). Therefore, we examined the effects of alpha-tocopherol (alpha-TOC) and different polyphenols--catechin (CAT), daidzein (DAI), epicatechin (EC), epigallocatechin gallate (EGCG), genistein (GEN), and quercetin (QUE)--on OTA-induced cytotoxicity in HepG2 liver cells. Incubation of HepG2 cells with increasing concentrations of OTA resulted in a dose- and time-dependent cytotoxicity as measured by the neutral red assay. Half lethal concentrations (LC50) of OTA were 35 and 10 microM after 48 and 72 h incubation, respectively. Incubation of HepG2 cells with alpha-TOC as well as with different polyphenols (exhibiting different antioxidant potency as determined by the FRAP, TEAC and DPPH assays) did not counteract OTA-induced cytotoxicity. These findings indicate that OTA may exert its toxic effects by affecting other hepatic mechanisms than those directly modulated by alpha-TOC and polyphenols.