ROLE OF POTASSIUM IONS IN NITRIC OXIDE BIOSYNTHESIS BY SMOOTH MUSCLE MITOCHONDRIA

The NO-synthase activity (mtNOS) in mitochondria of uterine smooth muscle was studied. The mitochondrial localization of NO synthesis in myocytes was proved using laser confocal microscopy method and specific fluorescent probes MitoTracker Orange (specific to mitochondria) and DAFFM (NO-sensitive fluorescent probe). It was demonstrated using flow cytometry that nitric oxide biosynthesis in isolated mytochondria decreased in the presence of a constitutive NOsynthase blocker 2-aminopyridine (100 μmol per l, 50% inhibition) and monoclonal antibodies (2.5 μg anti-Let m1 per 50 μg protein) against the H+-Ca2+-exchanger (Letm1 protein), but was’t sensitive to the mitochondrial permeability transition pore inhibitor cyclosporin A (5 μmol per l). A decrease of potassium ions concentration in the incubation medium and the presence of various types of potassium channel inhibitors significantly inhibited the NO-synthase reaction. We have concluded that potassium permeability of the inner mitochondrial membrane plays important role in the regulation of mtNOS activity.

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Potentiation by Nitric Oxide of Cyclosporin A and FK506-Induced Apoptosis in Renal Proximal Tubule Cells

Journal of the American Society of Nephrology ◽

10.1681/asn.v11122315 ◽

2000 ◽

Vol 11 (12) ◽

pp. 2315-2323

Author(s):

SONSOLES HORTELANO ◽

MANUELA CASTILLA ◽

ANA M. TORRES ◽

ALBERTO TEJEDOR ◽

LISARDO BOSCÁ

Keyword(s):

Nitric Oxide ◽

Cyclosporin A ◽

Mitochondrial Permeability Transition ◽

Permeability Transition Pore ◽

High Sensitivity ◽

Permeability Transition ◽

No Synthase ◽

Renal Diseases ◽

Common Mechanism ◽

Induced Apoptosis

Abstract. Proximal tubular epithelial cells (PTEC) exhibit a high sensitivity to undergo apoptosis in response to proinflammatory stimuli and immunosuppressors and participate in the onset of several renal diseases. This study examined the expression of inducible nitric oxide (NO) synthase after challenge of PTEC with bacterial cell wall molecules and inflammatory cytokines and analyzed the pathways that lead to apoptosis in these cells by measuring changes in the mitochondrial transmembrane potential and caspase activation. The data show that the apoptotic effects of proinflammatory stimuli mainly were due to the expression of inducible NO synthase. Cyclosporin A and FK506 inhibited partially NO synthesis. However, both NO and immunosuppressors induced apoptosis, probably through a common mechanism that involved the irreversible opening of the mitochondrial permeability transition pore. Activation of caspases 3 and 7 was observed in cells treated with high doses of NO and with moderate concentrations of immunosuppressors. The conclusion is that the cooperation between NO and immunosuppressors that induce apoptosis in PTEC might contribute to the renal toxicity observed in the course of immunosuppressive therapy.

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Physiopathology of the Permeability Transition Pore: Molecular Mechanisms in Human Pathology

Biomolecules ◽

10.3390/biom10070998 ◽

2020 ◽

Vol 10 (7) ◽

pp. 998 ◽

Cited By ~ 9

Author(s):

Massimo Bonora ◽

Simone Patergnani ◽

Daniela Ramaccini ◽

Giampaolo Morciano ◽

Gaia Pedriali ◽

...

Keyword(s):

Mitochondrial Membrane ◽

Molecular Mechanisms ◽

Mitochondrial Permeability Transition ◽

Permeability Transition Pore ◽

Permeability Transition ◽

Inner Mitochondrial Membrane ◽

Human Pathology ◽

Cell Death Mechanisms ◽

Mitochondrial Membrane Permeabilization

Mitochondrial permeability transition (MPT) is the sudden loss in the permeability of the inner mitochondrial membrane (IMM) to low-molecular-weight solutes. Due to osmotic forces, MPT is paralleled by a massive influx of water into the mitochondrial matrix, eventually leading to the structural collapse of the organelle. Thus, MPT can initiate outer-mitochondrial-membrane permeabilization (MOMP), promoting the activation of the apoptotic caspase cascade and caspase-independent cell-death mechanisms. The induction of MPT is mostly dependent on mitochondrial reactive oxygen species (ROS) and Ca2+, but is also dependent on the metabolic stage of the affected cell and signaling events. Therefore, since its discovery in the late 1970s, the role of MPT in human pathology has been heavily investigated. Here, we summarize the most significant findings corroborating a role for MPT in the etiology of a spectrum of human diseases, including diseases characterized by acute or chronic loss of adult cells and those characterized by neoplastic initiation.

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Inorganic polyphosphate is a potent activator of the mitochondrial permeability transition pore in cardiac myocytes

The Journal of General Physiology ◽

10.1085/jgp.201210788 ◽

2012 ◽

Vol 139 (5) ◽

pp. 321-331 ◽

Cited By ~ 67

Author(s):

Lea K. Seidlmayer ◽

Maria R. Gomez-Garcia ◽

Lothar A. Blatter ◽

Evgeny Pavlov ◽

Elena N. Dedkova

Keyword(s):

Mitochondrial Membrane ◽

Mitochondrial Permeability Transition Pore ◽

Mitochondrial Permeability Transition ◽

Permeability Transition Pore ◽

Permeability Transition ◽

Inner Mitochondrial Membrane ◽

Inorganic Polyphosphate ◽

Mitochondrial Permeability ◽

Mptp Opening

Mitochondrial dysfunction caused by excessive Ca2+ accumulation is a major contributor to cardiac cell and tissue damage during myocardial infarction and ischemia–reperfusion injury (IRI). At the molecular level, mitochondrial dysfunction is induced by Ca2+-dependent opening of the mitochondrial permeability transition pore (mPTP) in the inner mitochondrial membrane, which leads to the dissipation of mitochondrial membrane potential (ΔΨm), disruption of adenosine triphosphate production, and ultimately cell death. Although the role of Ca2+ for induction of mPTP opening is established, the exact molecular mechanism of this process is not understood. The aim of the present study was to test the hypothesis that the adverse effect of mitochondrial Ca2+ accumulation is mediated by its interaction with inorganic polyphosphate (polyP), a polymer of orthophosphates linked by phosphoanhydride bonds. We found that cardiac mitochondria contained significant amounts (280 ± 60 pmol/mg of protein) of short-chain polyP with an average length of 25 orthophosphates. To test the role of polyP for mPTP activity, we investigated kinetics of Ca2+ uptake and release, ΔΨm and Ca2+-induced mPTP opening in polyP-depleted mitochondria. polyP depletion was achieved by mitochondria-targeted expression of a polyP-hydrolyzing enzyme. Depletion of polyP in mitochondria of rabbit ventricular myocytes led to significant inhibition of mPTP opening without affecting mitochondrial Ca2+ concentration by itself. This effect was observed when mitochondrial Ca2+ uptake was stimulated by increasing cytosolic [Ca2+] in permeabilized myocytes mimicking mitochondrial Ca2+ overload observed during IRI. Our findings suggest that inorganic polyP is a previously unrecognized major activator of mPTP. We propose that the adverse effect of polyphosphate might be caused by its ability to form stable complexes with Ca2+ and directly contribute to inner mitochondrial membrane permeabilization.

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Effect of melatonin on oncosis of myocardial cells in the myocardial ischemia/reperfusion injury rat and the role of the mitochondrial permeability transition pore

Genetics and Molecular Research ◽

10.4238/2015.july.3.24 ◽

2015 ◽

Vol 14 (3) ◽

pp. 7481-7489 ◽

Cited By ~ 13

Author(s):

L.F. Liu ◽

Z.H. Qian ◽

Q. Qin ◽

M. Shi ◽

H. Zhang ◽

...

Keyword(s):

Mitochondrial Permeability Transition Pore ◽

Mitochondrial Permeability Transition ◽

Ischemia Reperfusion Injury ◽

Ischemia Reperfusion ◽

Permeability Transition Pore ◽

Permeability Transition ◽

Myocardial Cells ◽

Myocardial Ischemia Reperfusion Injury ◽

Myocardial Ischemia Reperfusion

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Abstract 3782: β2-Adrenergic Receptor Signaling Positively Modulates Pro-Survival Kinases and Ameliorates Mitochondrial Dysfunction during Doxorubicin Cardiotoxicity

Circulation ◽

10.1161/circ.118.suppl_18.s_485-c ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Giovanni Fajardo ◽

Mingming Zhao ◽

Gerald Berry ◽

Daria Mochly-Rosen ◽

Daniel Bernstein

Keyword(s):

Mitochondrial Dysfunction ◽

Mitochondrial Permeability Transition Pore ◽

Mitochondrial Permeability Transition ◽

Permeability Transition Pore ◽

Permeability Transition ◽

Surface Receptors ◽

Β2 Adrenergic Receptor ◽

Improvement In Survival ◽

Complex I Activity

β2-adrenergic receptors (β2-ARs) modulate cardioprotection through crosstalk with multiple pathways. We have previously shown that β2-ARs are cardioprotective during acute exposure to Doxorubicin (DOX). DOX cardiotoxicity is mediated through a Ca 2+ -dependent opening of the mitochondrial permeability transition pore (MPT) and mitochondrial dysfunction, however the upstream signals linking cell surface receptors and the MPT are not clear. The purpose of this study was to assess crosstalk between β2-AR signaling and mitochondrial function in DOX toxicity. DOX 10 mg/kg was administered to β2−/− and WT mice. Whereas there was no mortality in WT, 85% of β2−/− mice died within 30 min (n=20). Pro- and anti-survival kinases were assessed by immunobloting. At baseline, β2−/− showed normal levels of ϵPKC, but a 16% increase in δPKC compared to WT (p<0.05). After DOX, β2−/− showed a 64% decrease in ϵPKC (p<0.01) and 22% increase in δPKC (p<0.01). The ϵPKC activator ΨϵRACK decreased mortality by 40% in β2−/− mice receiving DOX; there was no improvement in survival with the δPKC inhibitor δV1–1. After DOX, AKT activity was decreased by 76% (p<0.01) in β2−/− but not in WT. The α1-AR blocker prazosin, inhibiting signaling through Gαq, restored AKT activity and reduced DOX mortality by 47%. We next assessed the role of mitochondrial dysfunction in β2−/− mediated DOX toxicity. DOX treated β2−/− mice, but not WT, show marked vacuolization of mitochondrial cristae. Complex I activity decreased 31% in β2−/− mice with DOX; but not in WT. Baseline rate of Ca2+ release and peak [Ca2+]i ratio were increased 85% and 17% respectively in β2−/− myocytes compared to WT. Verapamil decreased mortality by 27% in DOX treated β2−/− mice. Cyclosporine, a blocker of both MPT and calcineurin, reduced DOX mortality to 50%. In contrast, FK506, a blocker of calcineurin but not the MPT, did not reduce DOX mortality. Cyclosporine prevented the decrease in AKT activity in β2−/− whereas FK506 did not. These findings suggest that β2-ARs modulate pro-survival kinases and attenuate mitochondrial dysfunction during DOX cardiotoxicity; absence of β2-ARs enhances DOX toxicity via negative regulation of survival kinases and enhancement of intracellular Ca2+, sensitizing mitochondria to opening of the MPT.

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