High-Conductance Channel Formation in Yeast Mitochondria is Mediated by F-ATP Synthase e and g Subunits

Background/Aims: The permeability transition pore (PTP) is an unselective, Ca2+-dependent high conductance channel of the inner mitochondrial membrane whose molecular identity has long remained a mystery. The most recent hypothesis is that pore formation involves the F-ATP synthase, which consistently generates Ca2+-activated channels. Available structures do not display obvious features that can accommodate a channel; thus, how the pore can form and whether its activity can be entirely assigned to F-ATP synthase is the matter of debate. In this study, we investigated the role of F-ATP synthase subunits e, g and b in PTP formation. Methods: Yeast null mutants for e, g and the first transmembrane (TM) α-helix of subunit b were generated and evaluated for mitochondrial morphology (electron microscopy), membrane potential (Rhodamine123 fluorescence) and respiration (Clark electrode). Homoplasmic C23S mutant of subunit a was generated by in vitro mutagenesis followed by biolistic transformation. F-ATP synthase assembly was evaluated by BN-PAGE analysis. Cu2+ treatment was used to induce the formation of F-ATP synthase dimers in the absence of e and g subunits. The electrophysiological properties of F-ATP synthase were assessed in planar lipid bilayers. Results: Null mutants for the subunits e and g display dimer formation upon Cu2+ treatment and show PTP-dependent mitochondrial Ca2+ release but not swelling. Cu2+ treatment causes formation of disulfide bridges between Cys23 of subunits a that stabilize dimers in absence of e and g subunits and favors the open state of wild-type F-ATP synthase channels. Absence of e and g subunits decreases conductance of the F-ATP synthase channel about tenfold. Ablation of the first TM of subunit b, which creates a distinct lateral domain with e and g, further affected channel activity. Conclusion: F-ATP synthase e, g and b subunits create a domain within the membrane that is critical for the generation of the high-conductance channel, thus is a prime candidate for PTP formation. Subunits e and g are only present in eukaryotes and may have evolved to confer this novel function to F-ATP synthase

Calcium and regulation of the mitochondrial permeability transition

Recent years have seen renewed interest in the permeability transition pore, a high conductance channel responsible for permeabilization of the inner mitochondrial membrane, a process that leads to depolarization and Ca2+ release. Transient openings may be involved in physiological Ca2+ homeostasis while long-lasting openings may trigger and/or execute cell death. In this review we specifically focus (i) on the hypothesis that the PTP forms from the F-ATP synthase and (ii) on the mechanisms through which Ca2+ can reversibly switch this energy-conserving nanomachine into an energy-dissipating device. (C) 2017 Elsevier Ltd. All rights reserved

The Effects of Idebenone on Mitochondrial and Cellular Bioenergetics

6sinonenoneGiorgio, V; Petronilli, V; Prato, M; Ghelli, A; Rugolo, M; Bernardi, PGiorgio, V; Petronilli, V; Prato, M; Ghelli, A; Rugolo, M; Bernardi,

Hidden in the heart a peculiar type of left ventricular remodeling after acute myocardial infarction

We reported an unusual case of left ventricular pouch, in a 72-year-old man who had an acute coronary syndrome treated with percutaneous revascularization. The echocardiogram showed a sort of pouch, delimited by epicardium and endocardium, confirmed by 3D echo. This finding appeared as an echo free area, with a really slight color flow inside. We consequently supposed it would be a dissecting hematoma, a rare complication of the ischemic disease, due to the rupture of the intramyocardial vessels among the spiral myocardial fibers. This would produce a hemorrhagic pouch contained by epicardial and endocardial layers, which could evolve into mural thrombi

Value of two-dimensional longitudinal strains analysis to assess the impact of thrombus aspiration during primary percutaneous coronary intervention on left ventricular function: A speckle tracking imaging substudy of the EXPIRA trial

Background: Thrombectomy during primary percutaneous coronary intervention (Th-PCI) improves myocardial reperfusion in the absence of significant changes, in the acute phase, in traditional two-dimensional (2D) echo indexes of left ventricular (LV) function. The aim of this study was to evaluate the potential of 2D speckle tracking echocardiography (2DSTE) analysis in assessing the efficacy of thrombectomy as compared to standard 2D echo and cardiac magnetic resonance (CMR) data. Methods: Two-dimensional speckle tracking echocardiography analysis was performed in 60 anterior ST-segment elevation myocardial infarction (STEMI) patients to assess global (GLS), segmental (SLS) and regional longitudinal strain (RLS). 2D echo and CMR were performed within 5 days after PCI. Patients were divided into 2 groups according to the different methods of reperfusion used: 28 pts Th-PCI and 32 pts standard PCI (S-PCI). Results: Baseline clinical and angiographic characteristics, 2D echo, and DE-CMR data before and after PCI were similar in the 2 groups, except for microvascular obstruction (MVO), significantly lower (P = 0.001) in Th-PCI group. Conversely, GLS was significantly higher in Th-PCI group (P < 0.001), and in particular in the subset of patients without MVO (P = 0.012). RLS was also significantly higher in Th-PCI group (P = 0.001). GLS significantly correlates with infarct size, (R = 0.47; P = 0.03) and MVO (R = 0.69, P = 0.001). Finally, SLS was significantly lower in the DE segments (P < 0.001). Conclusions: Patients treated with Th-PCI had a more preserved microvascular integrity resulting in a better myocardial longitudinal deformation. 2DSTE analysis adds significant information on the efficacy of thrombus aspiration as compared to standard echocardiography and it is closely related to the extent of microvascular damage. © 2013, Wiley Periodicals, Inc

Significant increase of flow kinetic energy in “nonresponders” patients to cardiac resynchronization therapy

Backgrounds: It’s still unclear if different patterns of intraventricular flow dynamics may be detected in patients nonresponders to cardiac resynchronization therapy (CRT) as compared to responders ones. Aim of this study was to evaluate the characteristics of left ventricular (LV) flow dynamics 6-months after CRT to identify Echo-particle imaging velocity (PIV) patterns were more frequently detected in nonresponders patients. Methods: Thirty-two patients with dilated cardiomyopathy, undergoing CRT, were enrolled in this study. All patients underwent 2D and 3D echo and fluid dynamics assessment 6 months after CRT, during active CRT (CRT-ON) and during a temporarily discontinued state (CRT-OFF). LV volumes systolic and diastolic volumes (LVESV and LVEDV), ejection fraction (LVEF), global longitudinal strain (GLS), systolic dyssynchrony index (SDI), and several geometrical and functional Echo-PIV- derived parameters were calculated. Patients were divided in two groups: “responders” to CRT (decrease in LVESV>15% 6 months after CRT) and “nonresponders.” Results: During CRT-OFF, LVEF, LS were lower, while SDI and LVESV were higher in nonresponders group (P=.030, P=.051, P=.035, and P=.025, respectively). Energy dissipation, vortex area, and vorticity fluctuation were higher in “nonresponders” patients during CRT-OFF (P=.038, P=.054, and P=.035, respectively). During CRT-ON, energy dissipation, vortex area, and vorticity fluctuation further increase in nonresponders patients (P=.020, P=.038, and P=.030, respectively) with concomitant worsening of SDI (P=.045). Conclusion: Our data show a significant worsening in flow-derived parameters in CRT “nonresponders” patients as compared with responders. Further larger longitudinal studies are necessary to assess whether these more chaotic intraventricular flow-patterns may contribute to a persistent adverse remodeling observed in this subset of patiientsBackgrounds: It’s still unclear if different patterns of intraventricular flow dynamics may be detected in patients nonresponders to cardiac resynchronization therapy (CRT) as compared to responders ones. Aim of this study was to evaluate the characteristics of left ventricular (LV) flow dynamics 6-months after CRT to identify Echo-particle imaging velocity (PIV) patterns were more frequently detected in nonresponders patients. Methods: Thirty-two patients with dilated cardiomyopathy, undergoing CRT, were enrolled in this study. All patients underwent 2D and 3D echo and fluid dynamics assessment 6 months after CRT, during active CRT (CRT-ON) and during a temporarily discontinued state (CRT-OFF). LV volumes systolic and diastolic volumes (LVESV and LVEDV), ejection fraction (LVEF), global longitudinal strain (GLS), systolic dyssynchrony index (SDI), and several geometrical and functional Echo-PIV- derived parameters were calculated. Patients were divided in two groups: “responders” to CRT (decrease in LVESV>15% 6 months after CRT) and “nonresponders.” Results: During CRT-OFF, LVEF, LS were lower, while SDI and LVESV were higher in nonresponders group (P=.030, P=.051, P=.035, and P=.025, respectively). Energy dissipation, vortex area, and vorticity fluctuation were higher in “nonresponders” patients during CRT-OFF (P=.038, P=.054, and P=.035, respectively). During CRT-ON, energy dissipation, vortex area, and vorticity fluctuation further increase in nonresponders patients (P=.020, P=.038, and P=.030, respectively) with concomitant worsening of SDI (P=.045). Conclusion: Our data show a significant worsening in flow-derived parameters in CRT “nonresponders” patients as compared with responders. Further larger longitudinal studies are necessary to assess whether these more chaotic intraventricular flow-pattern