Protective effect of magnesium and potassium ions on the permeability of the external mitochondrial membrane

Gorgoglione, Vincenza; Laraspata, Daniela; Piana, Gianluigi La; Marzulli, Domenico; Lofrumento, N.E.

doi:10.1016/j.abb.2007.01.007

Cited by 15 publications

(31 citation statements)

References 36 publications

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“…To this end we utilized the test based on the activity of Sox present in the MIS to asses the impermeability of MOM to exogenous cyto-c. In both ceramide-treated [18] and hypotonic mitochondria [19] the Sox activity, determined utilizing sodium sulfite as donor and exogenous cyto-c as electron acceptor, has given direct evidence that while some endogenous cyto-c molecules are released outside the mitochondria, those molecules added to (or present in) the incubation medium do not permeate into the MIS. Titration of the effect of valinomycin on the permeability of MOM to both Sox and exogenous cyto-c is reported in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…1D. The rationale of the Sox test is extensively reported in [18,19]. Briefly, since the MOM is impermeable to both Sox and cyto-c the reduction of exogenous cyto-c induced by sulfite and catalyzed by Sox present in the MIS may occur whether the enzyme is released outside or cyto-c permeates into the MIS or both conditions hold.…”

Section: Resultsmentioning

confidence: 99%

“…These molecules may have been released either in the course of the isolation procedure, and thus they may be bound to the external side of MOM (the low value of control samples in the absence of valinomycin), or Sox molecules may be released from the MIS by valinomycininduced increase of MOM permeability. To have more direct information and overcome any criticism on the reliability of the trypsin approach, at the end of each incubation the Sox molecules present outside were separated from those present inside the mitochondria by the centrifugation method (see also [18,19]) and Sox activity determined in supernatants and pellets. The values obtained (not reported here) were overlapping those of Fig.…”

Section: Resultsmentioning

confidence: 99%

“…1). Mitochondrial suspensions containing no more than 2% of damaged mitochondria according to both the NADH oxidation test (a) and sulfite/ exogenous cyto-c test (c), have been thoroughly utilized (see also [19]). NADH oxidation was determined spectrophotometrically at the wavelength pair 340-374 nm (E = 4.28 mM -1 cm -1 ) and redox state of cyto-c, at the wavelength pair 548-540 (E = 21 mM -1 cm -1 ) to minimize the interference of cytochrome b 5 sited on the MOM.…”

Section: Isolation and Incubation Of Mitochondriamentioning

confidence: 99%

“…P/O ratios constantly had a value ranging between 1.9 and 2.1 with freshly isolated mitochondria. Intactness of mitochondrial membranes was routinely determined by four different but convergent and already described [11,12,19] integrity tests based on the following activities: (a) the oxidation of exogenously added NADH in the absence of both rotenone and exogenous cyto-c to assess the impermeability of NADH through the MIM; (b) the insensitivity of intermembrane Adk to proteolytic attack by added trypsin to reveal the increased permeability, if any, of the MOM in the course of incubation; (c) the succinate/exogenous cyto-c oxido-reductase activity to reveal the presence of damaged mitochondria with MIM intact but with the MOM permeable to exogenous cyto-c; (d) the sulfite/ exogenous cyto-c oxido-reductase activity present in the MIM and coupled to its sensitivity to trypsin to assess the impermeability of exogenous cyto-c through the MOM (see also panel d in Fig. 1).…”

Section: Isolation and Incubation Of Mitochondriamentioning

confidence: 99%

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Valinomycin induced energy-dependent mitochondrial swelling, cytochrome c release, cytosolic NADH/cytochrome c oxidation and apoptosis

et al. 2011

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In valinomycin induced stimulation of mitochondrial energy dependent reversible swelling, supported by succinate oxidation, cytochrome c (cyto-c) and sulfite oxidase (Sox) [both present in the mitochondrial intermembrane space (MIS)] are released outside. This effect can be observed at a valinomycin concentration as low as 1 nM. The rate of cytosolic NADH/cyto-c electron transport pathway is also greatly stimulated. The test on the permeability of mitochondrial outer membrane to exogenous cyto-c rules out the possibility that the increased rate of exogenous NADH oxidation could be ascribed either to extensively damaged or broken mitochondria. Accumulation of potassium inside the mitochondria, mediated by the highly specific ionophore valinomycin, promotes an increase in the volume of matrix (evidenced by swelling) and the interaction points between the two mitochondrial membranes are expected to increase. The data reported and those previously published are consistent with the view that "respiratory contact sites" are involved in the transfer of reducing equivalents from cytosol to inside the mitochondria both in the absence and the presence of valinomycin. Magnesium ions prevent at least in part the valinomycin effects. Rather than to the dissipation of membrane potential, the pro-apoptotic property of valinomycin can be ascribed to both the release of cyto-c from mitochondria to cytosol and the increased rate of cytosolic NADH coupled with an increased availability of energy in the form of glycolytic ATP, useful for the correct execution of apoptotic program.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Isolation and Incubation Of Mitochondriamentioning

confidence: 99%

Section: Isolation and Incubation Of Mitochondriamentioning

confidence: 99%

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Valinomycin induced energy-dependent mitochondrial swelling, cytochrome c release, cytosolic NADH/cytochrome c oxidation and apoptosis

et al. 2011

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Redox state-dependent aggregation of mitochondria induced by cytochrome c

Lemeshko

2011

Mol Cell Biochem

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Cytochrome c is known to play central role in apoptosis. Here, it is shown that ferricytochrome c, but not ferrocytochrome c is able to directly induce the aggregation of rat liver mitochondria, similar to the effect caused by magnesium ions at high concentrations. The aggregation was revealed by a decrease in light dispersion of mitochondrial suspension and it was confirmed by the optical microscopy. In the medium containing NADH and cytochrome c, mitochondrial aggregation was initiated only after exhaustion of NADH leading to oxidation of cytochrome c. The aggregation induced by 30 μM ferricytochrome c, but not by 5 mM MgCl(2), was completely inhibited by 30-100 μM ferricyanide, thus indicating that ferricyanide-cytochrome c specific interaction prevents mitochondrial aggregation. After completion of the aggregation caused by ferricytochrome c, this effect cannot be readily reversed by subsequent reduction of cytochrome c. The aggregation induced by ferricytochrome c and/or magnesium ions explains masking of the external NADH-oxidase activity of mitochondria in vitro reported in the literature. This new cytochrome c redox state-dependent phenomenon might also be involved in more complex mechanisms controlling aggregation (clustering) of mitochondria in vivo under the influence of pro-apoptotic factors and requires further study.

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Altered Heavy Metals and Transketolase Found in Autistic Spectrum Disorder

Obrenovich

Shamberger²,

Lonsdale³

2011

Biol Trace Elem Res

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Autism and autism spectrum disorder (ASD) are developmental brain disorders with complex, obscure, and multifactorial etiology. Our recent clinical survey of patient records from ASD children under the age of 6 years and their age-matched controls revealed evidence of abnormal markers of thiol metabolism, as well as a significant alteration in deposition of several heavy metal species, particularly arsenic, mercury, copper, and iron in hair samples between the groups. Altered thiol metabolism from heavy metal toxicity may be responsible for the biochemical alterations in transketolase, and are mechanisms for oxidative stress production, dysautonomia, and abnormal thiamine homeostasis. It is unknown why the particular metals accumulate, but we suspect that children with ASD may have particular trouble excreting thiol-toxic heavy metal species, many of which exist as divalent cations. Accumulation or altered mercury clearance, as well as concomitant oxidative stress, arising from redox-active metal and arsenic toxicity, offers an intriguing component or possible mechanism for oxidative stress-mediated neurodegeneration in ASD patients. Taken together, these factors may be more important to the etiology of this symptomatically diverse disease spectrum and may offer insights into new treatment approaches and avenues of exploration for this devastating and growing disease.

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Protective effect of magnesium and potassium ions on the permeability of the external mitochondrial membrane

Cited by 15 publications

References 36 publications

Valinomycin induced energy-dependent mitochondrial swelling, cytochrome c release, cytosolic NADH/cytochrome c oxidation and apoptosis

Valinomycin induced energy-dependent mitochondrial swelling, cytochrome c release, cytosolic NADH/cytochrome c oxidation and apoptosis

Redox state-dependent aggregation of mitochondria induced by cytochrome c

Altered Heavy Metals and Transketolase Found in Autistic Spectrum Disorder

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