1.
The antiparasitic clioquinol induces apoptosis in leukemia and myeloma cells by inhibiting histone deacetylase activity.
Cao, B, Li, J, Zhu, J, Shen, M, Han, K, Zhang, Z, Yu, Y, Wang, Y, Wu, D, Chen, S, et al
The Journal of biological chemistry. 2013;(47):34181-34189
Abstract
The antiparasitic clioquinol (CQ) represents a class of novel anticancer drugs by interfering with proteasome activity. In the present study, we found that CQ induced blood cancer cell apoptosis by inhibiting histone deacetylases (HDACs). CQ accumulated the acetylation levels of several key proteins including histone H3 (H3), p53, HSP90, and α-tubulin. In the mechanistic study, CQ was found to down-regulate HDAC1, -3, -4, and -5 in both myeloma and leukemia cells. Computer modeling analysis revealed that CQ was well docked into the active pocket of the enzyme, where the oxygen and nitrogen atoms in CQ formed stable coordinate bonds with the zinc ion, and the hydroxyl group from CQ formed an effective hydrogen bond with Asp-267. Moreover, co-treatment with CQ and zinc/copper chloride led to decreased Ac-H3. Furthermore, CQ inhibited the activity of Class I and IIa HDACs in the cell-free assays, demonstrating that CQ interfered with HDAC activity. By inhibiting HDAC activity, CQ induced expression of p21, p27, and p53, cell cycle arrest at G1 phase, and cell apoptosis. This study suggested that the HDAC enzymes are targets of CQ, which provided a novel insight into the molecular mechanism of CQ in the treatment of hematological malignancies.
2.
Andrographolide induces cell cycle arrest at G2/M phase and cell death in HepG2 cells via alteration of reactive oxygen species.
Li, J, Cheung, HY, Zhang, Z, Chan, GK, Fong, WF
European journal of pharmacology. 2007;(1-3):31-44
Abstract
The cytotoxicity of andrographolide to HepG2 human hepatoma cells was investigated in the present study. Growth of HepG2 cells was affected in the presence of andrographolide with an IC(50) of 40.2 microM after 48 h treatment. Flow cytometric analysis and DNA fragmentation assay revealed that andrographolide induced cell cycle arrest at G2/M phase and a late apoptosis of the cells. The occurrence of cell cycle arrest was accompanied by the collapse of mitochondrial membrane potential (MMP) and an intracellular increase of hydrogen peroxide (H(2)O(2)) but a decrease of superoxide radicals (O(2)(-)) and reduced glutathione. In the treated cells, expression of Bax as well as the transcriptional controller of this pro-apoptotic gene, p53, was upregulated but not other apoptotic proteins such as Bad, Bcl-2 and Bcl-X(L). Although the activity of caspase-3, which has direct effect on apoptosis, was also enhanced by the presence of andrographolide, cell death of HepG2 could neither be prevented by a specific inhibitor of capsase-3 nor the pan-caspase inhibitor-zVAD (Val-Ala-Asp), indicating that it was a caspase-independent cell death. Since the overall percentage of apoptotic cells was relatively small throughout the experimental studies, we conclude that the cytotoxic effect of andrographolide on HepG2 cells is primary attributed to the induction of cell cycle arrest via the alteration of cellular redox status.