Explore the vast range of titles available.

Background. Chronic heart failure (CHF) is the end stage of cardiac disease with a 5-year mortality rate reaching 50%. Simvastatin is an antioxidant with lipid-lowering effects, which is commonly used to treat CHF. Resistance training is a nondrug treatment for CHF and exerts a positive effect on both the myocardial structure and function. Objective. This study is aimed at exploring the effects and outcomes of simvastatin combined with resistance training on the mitochondrial membrane potential (MMP) of peripheral blood lymphocytes and the Janus kinase/signal transducer and activator of the transcription 3 (JAK/STAT3) signaling pathway in patients with CHF. Methods. One hundred and eleven patients with CHF were allocated to the control group (CNG) (n=55) and intervention group (IG) (n=56) using the random number table method. The CNG received simvastatin treatment only, whereas the IG received simvastatin treatment plus resistance training. Treatment efficacy, diastolic interventricular septal thickness (IVST), left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVDD), MMP fluorescence intensity, JAK mRNA and STAT3 mRNA relative expression levels, serum C-reactive protein (CRP), galectin-3, interleukin-6 (IL-6), N-terminal–probrain natriuretic peptide (NT-proBNP), high-sensitivity cardiac troponin T (hs-cTnT), and heart-type fatty acid-binding protein (H-FABP) levels were compared in both groups. Results. After 6 months of treatment, diastolic IVST, LVDD, and serum levels of CRP, galectin-3, IL-6, NT-proBNP, hs-cTnT, and H-FABP decreased in both groups and were lower in the IG than in the CNG (P<0.05), whereas LVEF, JAK and STAT3 mRNA relative expression levels, and MMP fluorescence intensity of peripheral blood lymphocytes were higher in the IG than in the CNG (P<0.05). Conclusion. Simvastatin combined with resistance training improves heart function and reduces myocardial damage as well as the occurrence of adverse cardiac events compared with simvastatin alone. The mechanism may be related to the increase of expression of MMP, JAK, and STAT3, the regulation of MMP and JAK/STAT3 signaling pathways in peripheral lymphocytes, the alleviation of mitochondrial damage, and the inhibition of inflammatory response.

Melatonin has been speculated to be mainly synthesized by mitochondria. This speculation is supported by the recent discovery that aralkylamine N-acetyltransferase/serotonin N-acetyltransferase (AANAT/SNAT) is localized in mitochondria of oocytes and the isolated mitochondria generate melatonin. We have also speculated that melatonin is a mitochondria-targeted antioxidant. It accumulates in mitochondria with high concentration against a concentration gradient. This is probably achieved by an active transportation via mitochondrial melatonin transporter(s). Melatonin protects mitochondria by scavenging reactive oxygen species (ROS), inhibiting the mitochondrial permeability transition pore (MPTP), and activating uncoupling proteins (UCPs). Thus, melatonin maintains the optimal mitochondrial membrane potential and preserves mitochondrial functions. In addition, mitochondrial biogenesis and dynamics is also regulated by melatonin. In most cases, melatonin reduces mitochondrial fission and elevates their fusion. Mitochondrial dynamics exhibit an oscillatory pattern which matches the melatonin circadian secretory rhythm in pinealeocytes and probably in other cells. Recently, melatonin has been found to promote mitophagy and improve homeostasis of mitochondria.

Mitofusins are large GTPases that trigger fusion of mitochondrial outer membranes. Similarly to the human mitofusin Mfn2, which also tethers mitochondria to the endoplasmic reticulum (ER), the yeast mitofusin Fzo1 stimulates contacts between Peroxisomes and Mitochondria when overexpressed. Yet, the physiological significance and function of these “PerMit” contacts remain unknown. Here, we demonstrate that Fzo1 naturally localizes to peroxisomes and promotes PerMit contacts in physiological conditions. These contacts are regulated through co-modulation of Fzo1 levels by the ubiquitin–proteasome system (UPS) and by the desaturation status of fatty acids (FAs). Contacts decrease under low FA desaturation but reach a maximum during high FA desaturation. High-throughput genetic screening combined with high-resolution cellular imaging reveal that Fzo1-mediated PerMit contacts favor the transit of peroxisomal citrate into mitochondria. In turn, citrate enters the TCA cycle to stimulate the mitochondrial membrane potential and maintain efficient mitochondrial fusion upon high FA desaturation. These findings thus unravel a mechanism by which inter-organelle contacts safeguard mitochondrial fusion.

The complex architecture and biochemistry of the inner mitochondrial membrane generate ultra-structures with different phospholipid and protein compositions, shapes, characteristics, and functions. The crista junction (CJ) serves as an important barrier separating the cristae (CM) and inner boundary membranes (IBM). Thereby CJ regulates the movement of ions and ensures distinct electrical potentials across the cristae (ΔΨ C ) and inner boundary (ΔΨ IBM ) membranes. We have developed a robust and flexible approach to visualize the CJ permeability with super-resolution microscopy as a readout of local mitochondrial membrane potential (ΔΨ mito ) fluctuations. This method involves analyzing the distribution of TMRM fluorescence intensity in a model that is restricted to the mitochondrial geometry. We show that mitochondrial Ca 2+ elevation hyperpolarizes the CM most likely caused by Ca 2+ sensitive increase of mitochondrial tricarboxylic acid cycle (TCA) and subsequent oxidative phosphorylation (OXPHOS) activity in the cristae. Dynamic multi-parameter correlation measurements of spatial mitochondrial membrane potential gradients, ATP levels, and mitochondrial morphometrics revealed a CJ-based membrane potential overflow valve mechanism protecting the mitochondrial integrity during excessive cristae hyperpolarization.

Mitochondrial dysfunction is a prominent feature of Alzheimer disease but the underlying mechanism is unclear. In this study, we investigated the effect of amyloid precursor protein (APP) and amyloid β on mitochondrial dynamics in neurons. Confocal and electron microscopic analysis demonstrated that [almost equal to]40% M17 cells overexpressing WT APP (APPwt M17 cells) and more than 80% M17 cells overexpressing APPswe mutant (APPswe M17 cells) displayed alterations in mitochondrial morphology and distribution. Specifically, mitochondria exhibited a fragmented structure and an abnormal distribution accumulating around the perinuclear area. These mitochondrial changes were abolished by treatment with β-site APP-cleaving enzyme inhibitor IV. From a functional perspective, APP overexpression affected mitochondria at multiple levels, including elevating reactive oxygen species levels, decreasing mitochondrial membrane potential, and reducing ATP production, and also caused neuronal dysfunction such as differentiation deficiency upon retinoic acid treatment. At the molecular level, levels of dynamin-like protein 1 and OPA1 were significantly decreased whereas levels of Fis1 were significantly increased in APPwt and APPswe M17 cells. Notably, overexpression of dynamin-like protein 1 in these cells rescued the abnormal mitochondrial distribution and differentiation deficiency, but failed to rescue mitochondrial fragmentation and functional parameters, whereas overexpression of OPA1 rescued mitochondrial fragmentation and functional parameters, but failed to restore normal mitochondrial distribution. Overexpression of APP or Aβ-derived diffusible ligand treatment also led to mitochondrial fragmentation and reduced mitochondrial coverage in neuronal processes in differentiated primary hippocampal neurons. Based on these data, we concluded that APP, through amyloid β production, causes an imbalance of mitochondrial fission/fusion that results in mitochondrial fragmentation and abnormal distribution, which contributes to mitochondrial and neuronal dysfunction.

Facilitated pyruvate transport across the mitochondrial inner membrane is a critical step in carbohydrate, amino acid, and lipid metabolism. We report that clinically relevant concentrations of thiazolidinediones (TZDs), a widely used class of insulin sensitizers, acutely and specifically inhibit mitochondrial pyruvate carrier (MPC) activity in a variety of cell types. Respiratory inhibition was overcome with methyl pyruvate, localizing the effect to facilitated pyruvate transport, and knockdown of either paralog, MPC1 or MPC2, decreased the EC ₅₀ for respiratory inhibition by TZDs. Acute MPC inhibition significantly enhanced glucose uptake in human skeletal muscle myocytes after 2 h. These data (i) report that clinically used TZDs inhibit the MPC, (ii) validate that MPC1 and MPC2 are obligatory components of facilitated pyruvate transport in mammalian cells, (iii) indicate that the acute effect of TZDs may be related to insulin sensitization, and (iv) establish mitochondrial pyruvate uptake as a potential therapeutic target for diseases rooted in metabolic dysfunction.

Parkinson's disease genes PINK1 and parkin encode kinase and ubiquitin ligase, respectively. The gene products PINK1 and Parkin are implicated in mitochondrial autophagy, or mitophagy. Upon the loss of mitochondrial membrane potential (ΔΨm), cytosolic Parkin is recruited to the mitochondria by PINK1 through an uncharacterised mechanism – an initial step triggering sequential events in mitophagy. This study reports that Ser65 in the ubiquitin-like domain (Ubl) of Parkin is phosphorylated in a PINK1-dependent manner upon depolarisation of ΔΨm. The introduction of mutations at Ser65 suggests that phosphorylation of Ser65 is required not only for the efficient translocation of Parkin, but also for the degradation of mitochondrial proteins in mitophagy. Phosphorylation analysis of Parkin pathogenic mutants also suggests Ser65 phosphorylation is not sufficient for Parkin translocation. Our study partly uncovers the molecular mechanism underlying the PINK1-dependent mitochondrial translocation and activation of Parkin as an initial step of mitophagy.

Mitochondria contribute to shape intraneuronal Ca 2+ signals. Excessive Ca 2+ taken up by mitochondria could lead to cell death. Amyloid beta (Aβ) causes cytosolic Ca 2+ overload, but the effects of Aβ on mitochondrial Ca 2+ levels in Alzheimer’s disease (AD) remain unclear. Using a ratiometric Ca 2+ indicator targeted to neuronal mitochondria and intravital multiphoton microscopy, we find increased mitochondrial Ca 2+ levels associated with plaque deposition and neuronal death in a transgenic mouse model of cerebral β-amyloidosis. Naturally secreted soluble Aβ applied onto the healthy brain increases Ca 2+ concentration in mitochondria, which is prevented by blockage of the mitochondrial calcium uniporter. RNA-sequencing from post-mortem AD human brains shows downregulation in the expression of mitochondrial influx Ca 2+ transporter genes, but upregulation in the genes related to mitochondrial Ca 2+ efflux pathways, suggesting a counteracting effect to avoid Ca 2+ overload. We propose lowering neuronal mitochondrial Ca 2+ by inhibiting the mitochondrial Ca 2+ uniporter as a novel potential therapeutic target against AD. Calvo-Rodriguez et al. show elevated calcium levels in neuronal mitochondria in a mouse model of cerebral β-amyloidosis after plaque deposition, which precede rare neuron death events in this model. The mechanism involves toxic extracellular Aβ oligomers and the mitochondrial calcium uniporter.

Viability of the tsetse fly-transmitted African trypanosome Trypanosoma brucei depends on maintenance and expression of its kinetoplast (kDNA), the mitochondrial genome of this parasite and a putative target for veterinary and human antitrypanosomatid drugs. However, the closely related animal pathogens T. evansi and T. equiperdum are transmitted independently of tsetse flies and survive without a functional kinetoplast for reasons that have remained unclear. Here, we provide definitive evidence that single amino acid changes in the nuclearly encoded F ₁F O–ATPase subunit γ can compensate for complete physical loss of kDNA in these parasites. Our results provide insight into the molecular mechanism of compensation for kDNA loss by showing F O-independent generation of the mitochondrial membrane potential with increased dependence on the ADP/ATP carrier. Our findings also suggest that, in the pathogenic bloodstream stage of T. brucei , the huge and energetically demanding apparatus required for kDNA maintenance and expression serves the production of a single F ₁F O–ATPase subunit. These results have important implications for drug discovery and our understanding of the evolution of these parasites.

Mitochondrial Ca 2+ channel identified Central to the role of the mitochondrion in cellular metabolism is its ability to control the fluxes of the key signalling ion, Ca 2+ . This is done by a highly selective ion channel known as the mitochondrial calcium uniporter. The molecular nature of this channel has remained elusive, but now two groups report the identification of a 40-kilodalton protein in the inner membrane of mitochondria as the active channel of the uniporter. This protein contains two transmembrane domains and exhibits calcium-channel activity in vitro and in vivo . Mitochondrial Ca 2+ homeostasis has a key role in the regulation of aerobic metabolism and cell survival 1 , but the molecular identity of the Ca 2+ channel, the mitochondrial calcium uniporter 2 , is still unknown. Here we have identified in silico a protein (named MCU) that shares tissue distribution with MICU1 (also known as CBARA1), a recently characterized uniporter regulator 3 , is present in organisms in which mitochondrial Ca 2+ uptake was demonstrated and whose sequence includes two transmembrane domains. Short interfering RNA (siRNA) silencing of MCU in HeLa cells markedly reduced mitochondrial Ca 2+ uptake. MCU overexpression doubled the matrix Ca 2+ concentration increase evoked by inositol 1,4,5-trisphosphate-generating agonists, thus significantly buffering the cytosolic elevation. The purified MCU protein showed channel activity in planar lipid bilayers, with electrophysiological properties and inhibitor sensitivity of the uniporter. A mutant MCU, in which two negatively charged residues of the putative pore-forming region were replaced, had no channel activity and reduced agonist-dependent matrix Ca 2+ concentration transients when overexpressed in HeLa cells. Overall, these data demonstrate that the 40-kDa protein identified is the channel responsible for ruthenium-red-sensitive mitochondrial Ca 2+ uptake, thus providing a molecular basis for this process of utmost physiological and pathological relevance.