The Ca channel blocker flunarizine induces caspase-10-dependent apoptosis in Jurkat T-leukemia cells
Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia, B3H 1X5, Canada. Apoptosis
(Impact Factor: 3.69).
05/2010; 15(5):597-607. DOI: 10.1007/s10495-010-0454-3
Flunarizine is a Ca(2+) channel blocker that can be either cytoprotective or cytotoxic, depending on the cell type that is being examined. We show here that flunarizine was cytotoxic for Jurkat T-leukemia cells, as well as for other hematological maligancies, but not for breast or colon carcinoma cells. Treatment of Jurkat cells with flunarizine resulted in caspase-3 activation, poly (ADP-ribose) polymerase cleavage, and laddering of DNA fragments, all of which are hallmarks of apoptosis. Flunarizine-induced DNA fragmentation was inhibited by the caspase-3 inhibitor z-DEVD-fmk, the caspase-8/caspase-10 inhibitor z-IETD-fmk, and the caspase-10 inhibitor z-AEVD-fmk, but was not reduced in caspase-8-deficient Jurkat cells, indicating the involvement of caspase-10 upstream of caspase-3 activation. Interestingly, FADD recruitment to a death receptor was not involved since flunarizine caused DNA fragmentation in FADD-deficient Jurkat cells. Flunarizine treatment of Jurkat cells also resulted in reactive oxygen species production, dissipation of mitochondrial transmembrane potential, release of cytochrome c from mitochondria, and caspase-9 activation, although none of these events were necessary for apoptosis induction. Collectively, these findings indicate that flunarizine triggers apoptosis in Jurkat cells via FADD-independent activation of caspase-10. Flunarizine warrants further investigation as a potential anti-cancer agent for the treatment of hematological malignancies.
Available from: Sujay Ramanathan
- "The requirement of caspase-10 activation downstream of mitochondria in taxol-induced apoptosis has been reported earlier [13,18]. Earlier it was shown that caspase-10 is involved in etiposide-induced apoptosis in U937 human leukemic cell line  and flunarizine (Ca(2+) channel blocker)-induced apoptosis in Jurkat cells . In this study, Specific involvement of caspase-10 has been demonstrated in apoptosis of JR4-Jurkat cells induced by fungal taxol and baccatin III, employing the inhibitors of caspase-9, -3, -2 and -10. "
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ABSTRACT: Taxol (generic name paclitaxel), a plant-derived antineoplastic agent, used widely against breast, ovarian and lung cancer, was originally isolated from the bark of the Pacific yew, Taxus brevifolia. The limited supply of the drug has prompted efforts to find alternative sources, such as chemical synthesis, tissue and cell cultures of the Taxus species both of which are expensive and yield low levels. Fermentation processes with microorganisms would be the methods of choice to lower the costs and increase yields. Previously we have reported that F. solani isolated from T. celebica produced taxol and its precursor baccatin III in liquid grown cultures J Biosci 33:259-67, 2008]. This study was performed to evaluate the inhibition of proliferation and induction of apoptosis of cancer cell lines by the fungal taxol and fungal baccatin III of F. solani isolated from T. celebica.
Cell lines such as HeLa, HepG2, Jurkat, Ovcar3 and T47D were cultured individually and treated with fungal taxol, baccatin III with or without caspase inhibitors according to experimental requirements. Their efficacy on apoptotic induction was examined.
Both fungal taxol and baccatin III inhibited cell proliferation of a number of cancer cell lines with IC50 ranging from 0.005 to 0.2 muM for fungal taxol and 2 to 4 muM for fungal baccatin III. They also induced apoptosis in JR4-Jurkat cells with a possible involvement of anti-apoptotic Bcl2 and loss in mitochondrial membrane potential, and was unaffected by inhibitors of caspase-9,-2 or -3 but was prevented in presence of caspase-10 inhibitor. DNA fragmentation was also observed in cells treated with fungal taxol and baccatin III.
The cytotoxic activity exhibited by fungal taxol and baccatin III involves the same mechanism, dependent on caspase-10 and membrane potential loss of mitochondria, with taxol having far greater cytotoxic potential.
Available from: Harald Krug
- "able to activate directly caspases as has been demonstrated earlier  . Another evidence for caspase-10 dependency with no or only less involvement of FADD-adaptor protein has been described recently for another chemical but with the same set of Jurkat cells . This group found the same total inhibition of all effects by the caspase-10 inhibitor zAEVDfmk and no reduction in caspase-8-deficient cells. "
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ABSTRACT: Tributyltin (TBT) is one of the most toxic compounds produced by man and distributed in the environment. A multitude of toxic activities have been described, for example, immunotoxic, neurotoxic, and endocrine disruptive effects. Moreover, it has been shown for many cell types that they undergo apoptosis after treatment with TBT and the cell death of immune cells could be the molecular background of its immunotoxic effect. As low as 200 nM up to 1
M of TBT induces all signs of apoptosis in Jurkat T cells within 1 to 24 hrs of treatment. When compared to Fas-ligand control stimulation, the same sequence of events occurs: membrane blebbing, phosphatidylserine externalisation, the activation of the “death-inducing signalling complex,” and the following sequence of cleavage processes. In genetically modified caspase-8-deficient Jurkat cells, the apoptotic effects are only slightly reduced, whereas, in FADD-negative Jurkat cells, the TBT effect is significantly diminished. We could show that caspase-10 is recruited by the TRAIL-R2 receptor and apoptosis is totally prevented when caspase-10 is specifically inhibited in all three cell lines.
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ABSTRACT: This study was aimed to evaluate the protective effect of flunarizine on cisplatin-induced acute renal failure. Administration of cisplatin (6 mg/kg, i.p. on day 6) significantly increased serum blood urea nitrogen and creatinine, urinary N-acetyl β-D-glucosaminidase, tissue thiobarbituric acid reactive substances and total calcium whereas, decreased body weight, fractional excretion of sodium, creatinine clearance tissue-reduced glutathione, mitochondrial cytochrome c oxidase, and ATP levels were observed in acute renal failure rats. Moreover, cisplatin produced histopathological changes in the renal tissue. Furthermore, flunarizine (100, 200, and 300 μM/kg, p.o., for six consecutive days) was administered to evaluate its therapeutic potential in acute renal failure, and the results were compared with cyclosporin A (50 μM/kg, p.o., for six consecutive days) as a reference drug. Flunarizine resulted in the attenuation of cisplatin-induced renal dysfunction, oxidative stress marker, mitochondrial damage, and histopathological changes in rats. Medium and higher doses of flunarizine produced significant renal protective effect which was comparable to cyclosporin A. The results of this study clearly revealed that flunarizine protected the kidney against the nephrotoxic effect of cisplatin via mitochondrial permeability transition pore inactivation potential.
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