Silver Ion Induces a Cyclosporine A-Insensitive Permeability Transition in Rat Liver Mitochondria and Release of Apoptogenic Cytochrome c

Abstract

Various reagents are known to open the mitochondrial permeability pore (PTP) and induce a permeability transition (PT), releasing apoptogenic proteins from the intermembrane space and triggering apoptosis. In this study, we examined the effect of Ag(+), a known cytotoxic sulfhydryl-reactive heavy metal, on isolated rat liver mitochondria. The following results were obtained: (1) Upon addition, Ag(+) instantly induced mitochondrial swelling and acceleration of respiration. (2) Cyclosporine A, a specific inhibitor of classical PT, was ineffective against the effect of Ag(+), indicating that silver ions induced non-classic PT. (3) Sulfhydryl reagents such as reduced glutathione completely inhibited the effects of Ag(+) on the mitochondria. (4) Experimental results using polyethylene glycol indicated that Ag(+) induced opening of a pore in the inner mitochondrial membrane, which could be PTP of another open state or a distinct pore. (5) Electron microscopic analysis of mitochondria treated with Ag(+) showed a novel mitochondrial configuration that was apparently different from that of normal mitochondria or Ca(2+)-treated mitochondria. (6) Ag(+) also induced the release of apoptogenic cytochrome c in a CsA-insensitive but GSH-sensitive manner. These results suggest that Ag(+) promotes a nonclassical permeability increase in the mitochondrial inner membrane that is clearly distinguishable from the classical PT and releases apoptogenic cytochrome c in a classical PT-independent manner.

Multidimensional effects of biologically synthesized silver nanoparticles in Helicobacter pylori, Helicobacter felis, and human lung (L132) and lung carcinoma A549 cells

“…The cell viability assays shows that A549 cells have significant inhibitory effect of AgNPs and are more sensitive than L132 lung normal cells (Figure 11). Our studies are consistent with previous studies which show that AgNP exposure could induce the changes of cell shape, reduce cell viability, increase LDH release, and finally result in cell apoptosis and necrosis [48,51,53,[109][110][111]. Effect of AgNPs on cell viability of L 132 and A549 cells.…”

Cd2+-induced cytochromecrelease in apoptotic proximal tubule cells: role of mitochondrial permeability transition pore and Ca2+uniporter

“…Possibly, other hydraulic permeability pathways in the IMM may also be affected by Cd 2ϩ . Thus we show that Cd 2ϩ can alter IMM permeability pathways and induce the release of Cyt c by processes that are independent of the PTP, which confirms that PTP opening is not the only mechanism underlying mitochondrial swelling (1,2,20,45). At the present stage, we can only speculate about the mechanism of Cd 2ϩ -induced activation of AQP8, but cysteine residues are important for AQP channel function and inhibition by Hg 2ϩ (44) and could be involved in the alteration of the AQP8-associated permeability of the membrane by Cd 2ϩ .…”

“…Accordingly, it has been suggested that Cd 2ϩ induces the release of Cyt c by modifying the interaction of members of the Bcl-2 protein family with mitochondrial membranes (27,28,35) and/or by activation of the permeability transition pore (PTP) (13,36). However, there is accumulating evidence that cytotoxic compounds may alter mitochondrial membrane permeability and the release of Cyt c by processes that are independent of these classic mechanisms (1,2,20,45). Thus the molecular processes underlying Cd 2ϩ -induced mitochondrial damage and dysfunction that are associated with Cyt c release still await clarification.…”

Differential Permeabilization Effects of Ca2+ and Valinomycin on the Inner and Outer Mitochondrial Membranes as Revealed by Proteomics Analysis of Proteins Released from Mitochondria

“…As a result, the PT and the release of cytochrome c were found to be induced not only by Ca 2ϩ but also by other agents (7)(8)(9). We also found that copper-o-phenanthroline (10), metal ions (11), and cyanine dyes (12,13) induced this PT and the release of cytochrome c from mitochondria. Furthermore we reported that valinomycin, known as a potassium-selective ionophore, also induces the release of cytochrome c from mitochondria but without the induction of PT (14).…”