Apigenin from Croton betulaster Müll restores the immune profile of microglia against glioma cells.

The flavonoid apigenin, extracted from the Brazilian plant Croton betulaster Müll. has demonstrated the ability to inhibit proliferation, induce differentiation, and modify the inflammatory profile of glioma cells. The aim of the present study was to evaluate the effect of apigenin on chemotaxis and regulation of inflammatory cytokines of microglia cells and these impacts on glioma cell growth. In cultures of isolated rat microglia, it was observed that apigenin induced changes in Iba1-positive cells to an ameboid phenotype, associated to an increase in the expression of the activated M1 profile marker OX-42 and iNOS and a reduction in the expression of the M2 profile marker CD206. Besides, apigenin modulated the tumor necrosis factor and IL-10 release by microglia. Treatment of C6 glioma cells with conditioned medium of microglia treated with apigenin-induced reduction of tumor migration and viability, associated with significant reduction in IL-6 levels. On the other hand, treatment of C6 cells with apigenin-induced microglia chemotaxis to glioma in vitro. Moreover, apigenin treatment of microglia/C6 co-cultures induced preferentially reduction in the viability of C6 cells and increased microglia-activated phenotype, associated with a change in the balance of TNF/IL-10 levels. Together, these results demonstrated that the flavonoid apigenin restores the immune profile of microglia against glioma cells.

Flavonoids from the Brazilian plant Croton betulaster inhibit the growth of human glioblastoma cells and induce apoptosis

Abstract This study investigated the effects of the flavonoids 5-hydroxy-7,4′-dimethoxyflavone, casticin, and penduletin, isolated from Croton betulaster Müll Arg., Euphorbiaceae, a plant utilized in popular medicine in Brazil, on the growth and viability of the human glioblastoma cell line GL-15. We observed that 5-hydroxy-7,4′-dimethoxyflavone and casticin were not toxic to GL-15 cells after 24 h of exposure. However, casticin and penduletin inhibited the metabolic activity of glioblastoma cells significantly at a concentration of 10 µM (p ≤ 0.05). Flavonoids casticin and penduletin also induced a significant and dose-dependent growth inhibition beginning at 24 h of exposure, and the most potent flavonoid was penduletin. It was also observed that penduletin and casticin induced an enlargement of the cell body and a reduction of cellular processes, accompanied by changes in the pattern of expression of the cytoskeletal protein vimentin. Signs of apoptosis, such as the externalization of membrane phosphatidyl serine residues, nuclear condensation, and fragmentation, were also detected in cells treated with 50–100 µM flavonoids. Our results indicate that flavonoids extracted from C. betulaster present antitumoral activity to glioblastoma cells, with penduletin proving to be the most potent of the tested flavonoids. Our results also suggest that these molecules may be promising supplementary drugs for glioblastoma treatment.

Effects of the flavonoid casticin from Brazilian Croton betulaster in cerebral cortical progenitors in vitro: direct and indirect action through astrocytes.

Neurodegenerative diseases are a major constraint on the social and economic development of many countries. Evidence has suggested that phytochemicals have an impact on brain pathology; however, both their mechanisms of action and their cell targets are incompletely known. Here, we investigated the effects of the flavonoid casticin, extracted from Croton betulaster, a common plant in the state of Bahia in Brazil, on rat cerebral cortex neurons in vitro. Treatment of neural progenitors with 10 microM casticin increased the neuronal population positive for the neuronal marker beta-tubulin III and the neuronal transcriptional factor Tbr2 by approximately 20%. This event was followed by a 50% decrease in neuronal death. Pools of astrocyte (GFAP and S100beta), neural (nestin), and oligodendrocyte (Olig2 and NG2) progenitors were not affected by casticin. Neither neuronal commitment nor proliferation of progenitors was affected by casticin, suggesting a neuroprotective effect of this compound. Culture of neural progenitors on casticin-treated astrocyte monolayers increased the neuronal population by 40%. This effect was reproduced by conditioned medium derived from casticin-treated astrocytes, suggesting the involvement of a soluble factor. ELISA assays of the conditioned medium revealed a 20% increase in interleukin-6 level in response to casticin. In contrast to the direct effect, neuronal death was unaffected, but a 52% decrease in the death of nestin-positive progenitors was observed. Together our data suggest that casticin influences the neuronal population by two mechanisms: 1) directly, by decreasing neuronal death, and 2) indirectly, via astrocytes, by modulating the pool of neuronal progenitors.