Release of Apoptotic Cytochrome c From Mitochondria by Dimethylarsinous Acid Occurs Through Interaction With Voltage-Dependent Anion Channel In Vitro

Abstract

Arsenic is known to be a human carcinogen as well as one of the most effective drugs for treatment of patients with acute promyelocytic leukemia. The intermediate metabolites of arsenic, monomethylarsonous acid (MMA(III)) and dimethylarsinous acid (DMA(III)), are formed by methylation reactions, and they are more reactive and toxic than the inorganic precursor arsenite (iAs(III)); however, the detailed mechanism of toxicity is poorly understood. Here, we studied the effects of three arsenic compounds (i.e., iAs(III), MMA(III), and DMA(III)) on mitochondrial permeability transition pore (mPTP) and release of apoptotic cytochrome c (Cyt c) after incubating with rat liver mitochondria. Inorganic iAs(III) had no effect on mitochondrial swelling even at higher concentrations ranging up to 100 μM, but swelling was significantly induced in the presence of Ca(2+). Additionally, mitochondrial swelling was strongly induced by exposure to the methylated forms of MMA(III) and DMA(III) in a dose-dependent manner in the absence of Ca(2+), suggesting that the methylated forms may have potent effects on cellular mitochondria. Although mitochondrial swelling was completely inhibited in the presence of cyclosporin-A (an inhibitor of mitochondrial permeability transition) or ruthenium red (an inhibitor of Ca(2+) uniporter) following exposure to methylated arsenicals, the release of apoptotic Cyt c from mitochondria was not inhibited, indicating that release of Cyt c is probably not dependent on mPTP opening. In addition, inhibitors of Bax (e.g., Bax-inhibiting peptide) did not reduce the release of Cyt c from the mitochondria by formation of Bax-voltage-dependent anion channel (VDAC) complex, whereas the recombinant Bcl-x(L )proteins significantly reduced the release of Cyt c after exposure to DMA(III), suggesting that dimethylated DMA(III) directly interacted with the VDAC in mitochondria and caused the release of Cyt c from mitochondria.

Bufalin induces apoptosis in the U-2OS human osteosarcoma cell line via triggering the mitochondrial pathway

“…In the process of apoptosis triggered by the mitochondria-mediated signaling pathway, the opening of the PTP and subsequent perforation of the mitochondrial membrane decreases the ΔΨm and leads to the release of cytochrome c into the cytoplasm, were it activates caspases, which amplify the apoptotic signal and disassemble the cytoskeleton (31). The present study revealed that bufalin reduced the viability and induced apoptosis in the U-2OS human OS cell line in a time-and dose-dependent manner.…”

Extracts from Curcuma zedoaria Inhibit Proliferation of Human Breast Cancer Cell MDA‐MB‐231 In Vitro

“…Washed cell pellets (3 × 10 5 cells) were resuspended in protease buffer containing 10 mM Tris-buffer (pH 7.6), 1.5 mM MgCl 2 , 1 mM EDTA, 10 mM KCl, 1 mM phenylmethylsulphonyl fluoride (PMSF), and protease inhibitor tablets (contain 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF), E-64, bestatin, leupeptin, aprotinin, and EDTA for inhibition of serine, cysteine, and metalloproteases). Whole cell extracts were prepared according to the published methods [14]. Briefly, MDA-MB-231 cells were washed once in cold PBS, followed by the cell pellets which were lysed by a single freeze-thaw cycle in the presence of protease inhibitors and whole cell extracts were obtained by centrifugation at 14000 rpm for 40 min after extraction with 0.5 M NaCl.…”

Apoptosis Induced by Microbubble-Assisted Acoustic Cavitation in K562 Cells: The Predominant Role of the Cyclosporin A-Dependent Mitochondrial Permeability Transition Pore

“…Moreover, the proapoptotic protein Bax can increase the opening of VDAC by forming the Bax-VDAC complex or form a pore in the mitochondrial outer membrane on oligomerization (Narita et al 1998). In fact, there are two main pathways closely involved in the induction of Cyt c release from the mitochondria, a CsA-sensitive progress and a CsA-insensitive Bax-associated process (Naranmandura et al 2012;Weiss et al 2003); however, there is little information regarding which potential mPTP pathway is the main mediator of the release of Cyt c from the mitochondria during microbubble-assisted acoustic cavitation.…”