Abstract
1,3,8-Trihydroxy-6-methylanthaquinone (emodin) is recognized as an antiproliferative compound. In the present study, however, we show that emodin has both toxic and survival effects in glioma cells and that the survival effects involve Mdr1a. Emodin inhibited the proliferation and induced apoptosis of C6 cells in a 12-h treatment, but C6 cells survived a 72-h drug treatment, indicating resistance to emodin. Emodin-induced apoptosis was reduced by inhibition of the expression and activation of apoptosis-associated proteins including p53, Bax, Bcl-2, Fas, and caspase-3. C6 cells could express antioxidant proteins (superoxide dismutase and catalase) to decrease reactive oxygen species-induced cytotoxicity of emodin and overexpress multidrug resistance genes (Mdr1a, MRP2, MRP3, and MRP6) to decrease the intracellular accumulation of emodin. Electrophoretic mobility shift analysis showed that emodin decreased nuclear factor κB (NF-κB) expression in 24 h of treatment, but in 48 h, emodin increased NF-κB activity. A confocal microscope showed that emodin induced NF-κB translocation from cytoplasm to nuclei. C6 cells would activate the mitogen-activated protein kinase survival pathway and express the DNA repair gene (MGMT) and associated proteins (PARP and XRCC1) to recover the cell activity. C6 cells also expressed GRP78 to decrease emodin-induced endoplasmic reticulum (ER) stress that would cause apoptosis in C6 cells, and GRP78 inhibited the expression of GADD153 to enhance the expression of Bcl-2 that could balance the ER- and mitochondria-induced apoptosis of C6 cells.
Footnotes
-
This work was supported by the China Medical University, Taichung, Taiwan [Grant CMU95–056]. T.-C.K. and J.-S.Y. contributed equally to this work.
-
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
-
doi:10.1124/jpet.109.153007.
-
ABBREVIATIONS: PKC, protein kinase C; BSA, bovine serum albumin; DCF, dichlorodihydrofluorescein; DMSO, dimethyl sulfoxide; EMSA, electrophoretic mobility shift assay; ER, endoplasmic reticulum; FITC, fluorescein isothiocyanate; KMHF, Kaighn's modification of Ham's F-12 medium; MAPK, mitogen-activated protein kinase; NF-κB, nuclear factor κB; PBS, phosphate-buffered saline; PDCT, pyrrolidine dithiocarbamate; PI3K, phosphatidylinositol 3′-kinase; PI, propidium iodide; ROS, reactive oxygen species; siRNA, small interfering RNA; SP600125, anthra[1–9cd]pyrazol-6(2H)-one; SB203580, 4-(4′-fluorophenyl)-2-(4′-methylsulfinylphenyl)-5-(4′-pyridyl) imidazole; NF-κB, nuclear factor κB.
-
↵ The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
- Received March 3, 2009.
- Accepted June 23, 2009.
- U.S. Government work not protected by U.S. copyright
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|