Mitochondrial defects in cardiomyopathy and neuromuscular disease

Mitochondrial respiration in peripheral arterial disease depends on stage severity

Peripheral arterial disease (PAD) is an increasing cause of morbidity and its severity is graded based on clinical manifestation. To investigate the influence of the different stages on myopathy of ischemic muscle we analysed severity-dependent effects of mitochondrial respiration in PAD. Eighteen patients with severe PAD, defined as chronic limb-threatening ischemia, 47 patients with intermittent claudication (IC) and 22 non-ischemic controls were analysed. High-resolution respirometry (HRR) was performed on muscle biopsies of gastrocnemius and vastus lateralis muscle of patients in different PAD stages to investigate different respiratory states. Results from HRR are given as median and interquartile range and were normalized to citrate synthase activity (CSA), a marker for mitochondrial content. In order to account for inter-individual differences between patients and controls, we calculated the ratio of O₂-flux in gastrocnemius muscle over vastus muscle ('GV ratio'). CSA of the gastrocnemius muscle as a proxy for mitochondrial content was significantly lower in critical ischemia compared to controls. Mitochondrial respiration normalized to CSA was higher in IC compared to controls. Likewise, the GV ratio was significantly higher in IC compared to control. Mitochondrial respiration and CSA of PAD patients showed stage-dependent modifications with greater changes in the mild PAD stage group (IC).

Cytochrome c oxidase deficiency detection in human fibroblasts using scanning electrochemical microscopy

Cytochrome c oxidase deficiency (COXD) is an inherited disorder characterized by the absence or mutation in the genes encoding for the cytochrome c oxidase protein (COX). COX deficiency results in severe muscle weakness, heart, liver, and kidney disorders, as well as brain damage in infants and adolescents, leading to death in many cases. With no cure for this disorder, finding an efficient, inexpensive, and early means of diagnosis is essential to minimize symptoms and long-term disabilities. Furthermore, muscle biopsy, the traditional detection method, is invasive, expensive, and time-consuming. This study demonstrates the applicability of scanning electrochemical microscopy to quantify COX activity in living human fibroblast cells. Taking advantage of the interaction between the redox mediator N, N, N', N'-tetramethyl-para-phenylene-diamine, and COX, the enzymatic activity was successfully quantified by monitoring current changes using a platinum microelectrode and determining the apparent heterogeneous rate constant k0 using numerical modeling. This study provides a foundation for developing a diagnostic method for detecting COXD in infants, which has the potential to increase treatment effectiveness and improve the quality of life of affected individuals.

Ndufaf2, a protein in mitochondrial complex I, interacts in vivo with methionine sulfoxide reductases

BACKGROUND

Methionine sulfoxide reductases are found in all aerobic organisms. They function in antioxidant defense, cellular regulation by reversible oxidation of methionine in proteins, and in protein structure. However, very few in vivo binding partners or substrates of the reductases have been identified.

METHODS

We implemented a proximity labeling method, TurboID, to covalently link mitochondrial methionine sulfoxide reductase A (MSRA) to its binding partners in HEK293 cells. Proteomic analyses were performed to identify putative binding partners.

RESULTS

We show that human Ndufaf2, also called mimitin, is a binding partner of MSRA as well as all 3 MSRBs. We found that both methionine residues in Ndufaf2 were susceptible to oxidation by hydrogen peroxide and that the methionine sulfoxide reductases can reduce these methionine sulfoxide residues back to methionine.

CONCLUSION

Methionine sulfoxide reductases can reduce methionine sulfoxide back to methionine in Ndufaf2. In addition to a repair function, it also creates a mechanism that could regulate cellular processes by modulation of methionine oxidation in Ndufaf2.

Subcellular Fractionation for DIGE-Based Proteomics

Mass spectrometry-based protein methodologies have revolutionized the field of analytical biochemistry and enable the identification of hundreds to thousands of proteins in biological fluids, cell lines, and tissue. This methodology requires the initial separation of a protein constellation, and this has been successfully achieved using gel-based techniques, particularly that of fluorescence two-dimensional difference gel electrophoresis (2D-DIGE). However, given the complexity of the proteome, fractionation techniques may be required to optimize the detection of low-abundance proteins, which are often underrepresented but which may represent important players in health and disease. Such subcellular fractionation protocols typically utilize density-gradient centrifugation and have enabled the enrichment of crude microsomes, the cytosol, the plasmalemma, the nuclei, and the mitochondria. In this chapter, we describe the experimental steps involved in the enrichment of crude microsomes from the skeletal muscle using differential centrifugation and subsequent verification of enrichment by gel electrophoresis and immunoblotting, prior to comparative 2D-DIGE analysis.

Effects of mitochondrial dysfunction on bone metabolism and related diseases: a scientometric study from 2003 to 2022

Background

In recent years, mitochondrial dysfunction has been extensively studied and published, but research on the effects of mitochondrial dysfunction on bone metabolism and related diseases is only just beginning. Furthermore, no studies have been carried out to systematically illustrate this area from a scientometric point of view. The goal of this research is to review existing knowledge and identify new trends and possible hotspots in this area.

Methods

All publications related to the relationship between mitochondrial dysfunction and bone metabolism and related diseases from 2003 to 2022 were searched at the Web of Science Core Collection (WoSCC) on May 7, 2022. Four different analytical tools: VOSviewer 1.6.18, CiteSpace V 6.1, HistorCite (12.03.07), and Excel 2021 were used for the scientometric research.

Results

The final analysis included 555 valid records in total. Journal of Biological Chemistry (Co-citations = 916) is the most famous journal in this field. China (Percentage = 37%), the United States (Percentage = 24%), and Korea (Percentage = 12%) are the most productive countries. Blanco FJ and Choi EM are the main researchers with significant academic influence. Current research hotspots are basic research on mitochondrial dysfunction and the prevention or treatment of bone metabolism-related diseases.

Conclusion

The study of the consequences of mitochondrial dysfunction on bone metabolism and associated diseases is advancing rapidly. Several prominent researchers have published extensive literature and are widely cited. Future research in this area will focus on oxidative stress, aging, gene expression, and the pathogenesis of bone metabolism-related diseases.

Targeting Myocardial Substrate Metabolism in the Failing Heart: Ready for Prime Time?

PURPOSE OF REVIEW

We review the clinical benefits of altering myocardial substrate metabolism in heart failure.

RECENT FINDINGS

Modulation of cardiac substrates (fatty acid, glucose, or ketone metabolism) offers a wide range of therapeutic possibilities which may be applicable to heart failure. Augmenting ketone oxidation seems to offer great promise as a new therapeutic modality in heart failure. The heart has long been recognized as metabolic omnivore, meaning it can utilize a variety of energy substrates to maintain adequate ATP production. The adult heart uses fatty acid as a major fuel source, but it can also derive energy from other substrates including glucose and ketone, and to some extent pyruvate, lactate, and amino acids. However, cardiomyocytes of the failing heart endure remarkable metabolic remodeling including a shift in substrate utilization and reduced ATP production, which account for cardiac remodeling and dysfunction. Research to understand the implication of myocardial metabolic perturbation in heart failure has grown in recent years, and this has raised interest in targeting myocardial substrate metabolism for heart failure therapy. Due to the interdependency between different pathways, the main therapeutic metabolic approaches include inhibiting fatty acid uptake/fatty acid oxidation, reducing circulating fatty acid levels, increasing glucose oxidation, and augmenting ketone oxidation.

Bio-active components in medicinal plants: A mechanistic review of their effects on fish growth and physiological parameters

World population is increasing at a tremendous rate so is the demand for animal-based protein. Aquaculture is a promising industry that has the potential to supply high quality protein for mankind with minimum environmental impact. In the past decade, aquaculture practices have been shifting from extensive to intensive culture. To achieve maximum production per unit area, high stocking densities are maintained in intensive aquaculture. If not managed properly, this may lead to stress in fish. Fish under stress condition show decreased growth, suppressed appetite, weakened immunity and increased susceptibility to infections. Chemicals, vaccines and antibiotics are used for the treatment of diseased fish. Use of synthetic chemicals, vaccines and antibiotics is not sustainable because pathogens develop resistance against them and they have high residues. Moreover, certain chemicals used for the treatment of fish diseases are not safe for humans therefore, are banned in some countries. Plant parts and their extracts are used in traditional medicines to cure many diseases and to improve health of mankind. In aquaculture industry, use of plants and their derivatives in fish feed to improve health status of fish is increasing. Several plants improve growth and overall health status of fish, some provide protection against pathogens by improving the immune system while others increase appetite by direct action on neuro-endocrine axis of fish. This review provides an in depth and up to date information about use of medicinal plants and their derivatives to improve growth and physiological status of fish and their possible mechanism of action.

Versatile role of sirtuins in metabolic disorders: From modulation of mitochondrial function to therapeutic interventions

Sirtuins (SIRT1-7) are distinct histone deacetylases (HDACs) whose activity is determined by cellular metabolic status andnicotinamide adenine dinucleotide (NAD⁺ ) levels. HDACs of class III are the members of the SIRT's protein family. SIRTs are the enzymes that modulate mitochondrial activity and energy metabolism. SIRTs have been linked to a number of clinical and physiological operations, such as energy responses to low-calorie availability, aging, stress resistance, inflammation, and apoptosis. Mammalian SIRT2 orthologs have been identified as SIRT1-7 that are found in several subcellular sections, including the cytoplasm (SIRT1, 2), mitochondrial matrix (SIRT3, 4, 5), and the core (SIRT1, 2, 6, 7). For their deacetylase or ADP-ribosyl transferase action, all SIRTs require NAD⁺ and are linked to cellular energy levels. Evolutionarily, SIRT1 is related to yeast's SIRT2 as well as received primary attention in the circulatory system. An endogenous protein, SIRT1 is involved in the development of heart failure and plays a key role in cell death and survival. SIRT2 downregulation protects against ischemic-reperfusion damage. Increase in human longevity is caused by an increase in SIRT3 expression. Cardiomyocytes are also protected by SIRT3 from oxidative damage and aging, as well as suppressing cardiac hypertrophy. SIRT4 and SIRT5 perform their roles in the heart. SIRT6 has also been linked to a reduction in heart hypertrophy. SIRT7 is known to be involved in the regulation of stress responses and apoptosis in the heart.

The Role of Mitochondrial DNA Variation in Drug Response: A Systematic Review

Background: The triad of drug efficacy, toxicity and resistance underpins the risk-benefit balance of all therapeutics. The application of pharmacogenomics has the potential to improve the risk-benefit balance of a given therapeutic via the stratification of patient populations based on DNA variants. A growth in the understanding of the particulars of the mitochondrial genome, alongside the availability of techniques for its interrogation has resulted in a growing body of literature examining the impact of mitochondrial DNA (mtDNA) variation upon drug response. Objective: To critically evaluate and summarize the available literature, across a defined period, in a systematic fashion in order to map out the current landscape of the subject area and identify how the field may continue to advance. Methods: A systematic review of the literature published between January 2009 and December 2020 was conducted using the PubMed database with the following key inclusion criteria: reference to specific mtDNA polymorphisms or haplogroups, a core objective to examine associations between mtDNA variants and drug response, and research performed using human subjects or human in vitro models. Results: Review of the literature identified 24 articles reporting an investigation of the association between mtDNA variant(s) and drug efficacy, toxicity or resistance that met the key inclusion criteria. This included 10 articles examining mtDNA variations associated with antiretroviral therapy response, 4 articles examining mtDNA variants associated with anticancer agent response and 4 articles examining mtDNA variants associated with antimicrobial agent response. The remaining articles covered a wide breadth of medications and were therefore grouped together and referred to as "other." Conclusions: Investigation of the impact of mtDNA variation upon drug response has been sporadic to-date. Collective assessment of the associations identified in the articles was inconclusive due to heterogeneous methods and outcomes, limited racial/ethnic groups, lack of replication and inadequate statistical power. There remains a high degree of idiosyncrasy in drug response and this area has the potential to explain variation in drug response in a clinical setting, therefore further research is likely to be of clinical benefit.

The Role of Mitochondrial Function in Peripheral Arterial Disease: Insights from Translational Studies

Recent evidence demonstrates an involvement of impaired mitochondrial function in peripheral arterial disease (PAD) development. Specific impairments have been assessed by different methodological in-vivo (near-infrared spectroscopy, ³¹P magnetic resonance spectroscopy), as well as in-vitro approaches (Western blotting of mitochondrial proteins and enzymes, assays of mitochondrial function and content). While effects differ with regard to disease severity, chronic malperfusion impacts subcellular energy homeostasis, and repeating cycles of ischemia and reperfusion contribute to PAD disease progression by increasing mitochondrial reactive oxygen species production and impairing mitochondrial function. With the leading clinical symptom of decreased walking capacity due to intermittent claudication, PAD patients suffer from a subsequent reduction of quality of life. Different treatment modalities, such as physical activity and revascularization procedures, can aid mitochondrial recovery. While the relevance of these modalities for mitochondrial functional recovery is still a matter of debate, recent research indicates the importance of revascularization procedures, with increased physical activity levels being a subordinate contributor, at least during mild stages of PAD. With an additional focus on the role of revascularization procedures on mitochondria and the identification of suitable mitochondrial markers in PAD, this review aims to critically evaluate the relevance of mitochondrial function in PAD development and progression.

Mitochondrial tRNA Mutations Associated With Essential Hypertension: From Molecular Genetics to Function

Essential hypertension (EH) is one of the most common cardiovascular diseases worldwide, entailing a high level of morbidity. EH is a multifactorial disease influenced by both genetic and environmental factors, including mitochondrial DNA (mtDNA) genotype. Previous studies identified mtDNA mutations that are associated with maternally inherited hypertension, including tRNA^Ile m.4263A>G, m.4291T>C, m.4295A>G, tRNA^Met m.4435A>G, tRNA^Ala m.5655A>G, and tRNA^Met/tRNA^Gln m.4401A>G, et al. These mtDNA mutations alter tRNA structure, thereby leading to metabolic disorders. Metabolic defects associated with mitochondrial tRNAs affect protein synthesis, cause oxidative phosphorylation defects, reduced ATP synthesis, and increase production of reactive oxygen species. In this review we discuss known mutations of tRNA genes encoded by mtDNA and the potential mechanisms by which these mutations may contribute to hypertension.

Doxorubicin‑induced oxidative and nitrosative stress: Mitochondrial connexin 43 is at the crossroads

Oxidative stress is widely accepted as a key factor of doxorubicin (Doxo)-induced cardiotoxicity. There is evidence to indicate that nitrosative stress is involved in this process, and that Doxo interacts by amplifying cell damage. Mitochondrial connexin 43 (mitoCx43) can confer cardioprotective effects through the reduction of mitochondrial reactive oxygen species production during Doxo-induced cardiotoxicity. The present study aimed to evaluate the involvement of mitoCx43 in Doxo-induced nitrosative stress. Rat H9c2 cardiomyoblasts were treated with Doxo in the absence or presence of radicicol, an inhibitor of Hsp90, the molecular chaperone involved in Cx43 translocation to the mitochondria that underlies its role in cardioprotection. FACS analysis and RT-qPCR revealed that Doxo increased superoxide dismutase, and catalase gene and protein expression. As shown by hypodiploid nuclei and confirmed by western blot analysis, Doxo increased caspase 9 expression and reduced procaspase 3 levels, which induced cell death. Moreover, a significant increase in the activation of the NF-κB signaling pathway was observed. It is well known that the increased expression of inducible nitric oxide synthase results in nitric oxide overproduction, which then rapidly reacts with hydrogen peroxide or superoxide generated by the mitochondria, to form highly reactive and harmful peroxynitrite, which ultimately induces nitrotyrosine formation. Herein, these interactions were confirmed and increased effects were observed in the presence of radicicol. On the whole, the data of the present study indicate that an interplay between oxidative and nitrosative stress is involved in Doxo-induced cardiotoxicity, and that both aspects are responsible for the induction of apoptosis. Furthermore, it is demonstrated that the mechanisms that further increase mitochondrial super-oxide generation (e.g., the inhibition of Cx43 translocation into the mitochondria) significantly accelerate the occurrence of cell death.

Skeletal muscle: A review of molecular structure and function, in health and disease

Decades of research in skeletal muscle physiology have provided multiscale insights into the structural and functional complexity of this important anatomical tissue, designed to accomplish the task of generating contraction, force and movement. Skeletal muscle can be viewed as a biomechanical device with various interacting components including the autonomic nerves for impulse transmission, vasculature for efficient oxygenation, and embedded regulatory and metabolic machinery for maintaining cellular homeostasis. The "omics" revolution has propelled a new era in muscle research, allowing us to discern minute details of molecular cross-talk required for effective coordination between the myriad interacting components for efficient muscle function. The objective of this review is to provide a systems-level, comprehensive mapping the molecular mechanisms underlying skeletal muscle structure and function, in health and disease. We begin this review with a focus on molecular mechanisms underlying muscle tissue development (myogenesis), with an emphasis on satellite cells and muscle regeneration. We next review the molecular structure and mechanisms underlying the many structural components of the muscle: neuromuscular junction, sarcomere, cytoskeleton, extracellular matrix, and vasculature surrounding muscle. We highlight aberrant molecular mechanisms and their possible clinical or pathophysiological relevance. We particularly emphasize the impact of environmental stressors (inflammation and oxidative stress) in contributing to muscle pathophysiology including atrophy, hypertrophy, and fibrosis. This article is categorized under: Physiology > Mammalian Physiology in Health and Disease Developmental Biology > Developmental Processes in Health and Disease Models of Systems Properties and Processes > Cellular Models.

Contribution of Mitochondrial DNA Variation to Chronic Disease in East Asian Populations

Mitochondria are the main producers of energy in eukaryotic cells. Mitochondrial dysfunction is associated with specific mitochondrial DNA (mtDNA) variations (haplogroups), and these variations can contribute to human disease. East Asian populations show enrichment of many mitochondrial haplogroups, including A, B, D, G, M7, M8, M9, N9, R9, and exhibit half of the known haplogroups of worldwide. In this review, we summarize the current research in the field of mtDNA variation and associated disease in East Asian populations and discuss the physiological and pathological relevance of mitochondrial biology. mtDNA haplogroups are associated with various metabolic disorders ascribed to altered oxidative phosphorylation. The same mitochondrial haplogroup can show either a negative or positive association with different diseases. Mitochondrial dynamics, mitophagy, and mitochondrial oxidative stress, ultimately influence susceptibility to various diseases. In addition, mitochondrial retrograde signaling pathways may have profound effects on nuclear-mitochondrial interactions, affecting cellular morphology, and function. Other complex networks including proteostasis, mitochondrial unfolded protein response and reactive oxygen species signaling may also play pivotal roles in metabolic performance.

Mitochondrial Involvement in the Adaptive Response to Chronic Exposure to Environmental Pollutants and High-Fat Feeding in a Rat Liver and Testis

In our modern society, exposure to stressful environmental stimuli, such as pollutants and/or chronic high-fat feeding, continuously induce tissular/organ metabolic adaptation to promote cellular survival. In extreme conditions, cellular death and tissular/organ damage occur. Mitochondria, as a cellular energy source, seem to play an important role in facing cellular stress induced by these environmental stimuli. On the other hand, mitochondrial dysfunction and oxidative stress play a key role in environmental stress-induced metabolic diseases. However, little is known about the combined effect of simultaneous exposure to chronic high-fat feeding and environmental pollutants on metabolic alterations at a tissular and cellular level, including mitochondrial dysfunction and oxidative stress induction. Our research group recently addressed this topic by analysing the effect of chronic exposure to a non-toxic dose of the environmental pollutant dichlorodiphenyldichloroethylene (DDE) associated with high-fat feeding in male Wistar rats. In this review, we mainly summarize our recent findings on mitochondrial adaptive response and oxidative stress induction in the liver, the main tissue involved in fat metabolism and pollutant detoxification, and in male gonads, the main targets of endocrine disruption induced by both high-fat feeding and environmental pollutants.

Metabolic and chemical regulation of tRNA modification associated with taurine deficiency and human disease

Modified uridine containing taurine, 5-taurinomethyluridine (τm5U), is found at the anticodon first position of mitochondrial (mt-)transfer RNAs (tRNAs). Previously, we reported that τm5U is absent in mt-tRNAs with pathogenic mutations associated with mitochondrial diseases. However, biogenesis and physiological role of τm5U remained elusive. Here, we elucidated τm5U biogenesis by confirming that 5,10-methylene-tetrahydrofolate and taurine are metabolic substrates for τm5U formation catalyzed by MTO1 and GTPBP3. GTPBP3-knockout cells exhibited respiratory defects and reduced mitochondrial translation. Very little τm5U34 was detected in patient's cells with the GTPBP3 mutation, demonstrating that lack of τm5U results in pathological consequences. Taurine starvation resulted in downregulation of τm5U frequency in cultured cells and animal tissues (cat liver and flatfish). Strikingly, 5-carboxymethylaminomethyluridine (cmnm5U), in which the taurine moiety of τm5U is replaced with glycine, was detected in mt-tRNAs from taurine-depleted cells. These results indicate that tRNA modifications are dynamically regulated via sensing of intracellular metabolites under physiological condition.

Estrogen-SIRT1 Axis Plays a Pivotal Role in Protecting Arteries Against Menopause-Induced Senescence and Atherosclerosis

Aim: Menopause causes arterial senescence and atherosclerotic development through decrease of estrogen. Recently, histone deacetylase SIRT1 has been reported to have protective effects against arterial senescence and atherosclerosis. However, the relationship between estrogen and SIRT1 in the context of menopause-induced arterial senescence is not well understood. The present study aims to investigate whether SIRT1 is involved in the etiology of menopause-induced arterial senescence and atherosclerotic development.

Methods: Twelve-week old female apolipoprotein E-knockout (ApoE-KO) mice underwent ovariectomy (OVX) or sham surgery.

Results: SIRT1 expression and endothelial nitric oxide synthase (eNOS) activation in the aorta were significantly lower in OVX mice than they were in sham mice (OVX vs. sham, n = 5 per group). Senescence-associated β-galactosidase activity, protein expression of Ac-p53 and PAI-1, and aortic atherosclerosis lesions were significantly greater in OVX mice than they were in sham mice. Administration of 17β-estradiol (E2) for eight weeks to OVX mice restored aortic SIRT1 expression, activated eNOS, and retarded OVX-induced arterial senescence and atherosclerotic development (E2 vs. control, n = 5 per group). The effects of E2 on SIRT1 upregulation, anti-senescence and anti-atherosclerosis were attenuated by administration of a SIRT1 inhibitor, sirtinol. In vitro experiment using human endothelial cells demonstrated that E2 also increased SIRT1 expression and retarded oxidized low density lipoprotein-induced premature senescence, which were also abolished by sirtinol. These results suggested that estrogen modulated arterial senescence and atherosclerosis through SIRT1. Additionally a selective estrogen receptor modulator (SERM), bazedoxifene, also augmented SIRT1 and inhibited arterial senescence and atherosclerotic development (SERM vs. control, n = 3 per group).

Conclusions: Downregulation of SIRT1 causes OVX-induced arterial senescence and atherosclerosis in ApoE-KO mice. Administration of estrogen or SERM enables OVX mice to restore these alterations by SIRT1 induction.

Oxidative stress and antioxidant treatment in patients with peripheral artery disease

Peripheral artery disease is an atherosclerotic disease of arterial vessels that mostly affects arteries of lower extremities. Effort induced cycles of ischemia and reperfusion lead to increased reactive oxygen species production by mitochondria. Therefore, the pathophysiology of peripheral artery disease is a consequence of metabolic myopathy, and oxidative stress is the putative major operating mechanism behind the structural and metabolic changes that occur in muscle. In this review, we discuss the evidence for oxidative damage in peripheral artery disease and discuss management strategies related to antioxidant supplementation. We also highlight the major pathways governing oxidative stress in the disease and discuss their implications in disease progression. Potential therapeutic targets and diagnostic methods related to these mechanisms are explored, with an emphasis on the Nrf2 pathway.

Decreased accumulation of superoxide dismutase 2 within mitochondria in the yeast model of Shwachman-Diamond syndrome

Mutations in the human SBDS gene is the most common cause of Shwachman-Diamond syndrome (SDS). The SBDS protein participates in ribosome biogenesis; however, effects beyond reduced translation efficiency are thought to be involved in SDS progression. Impaired mitochondrial function has been reported for cells lacking either SBDS or Sdo1p, the Saccharomyces cerevisiae SBDS ortholog. To better understand how the loss of SBDS/Sdo1p leads to mitochondria damage, we utilized the S. cerevisiae model of SDS. Yeast deleted for SDO1 show increased oxidative damage to mitochondrial proteins and a marked decrease in protein levels and activity of mitochondrial superoxide dismutase 2 (Sod2p), a key enzyme involved in defense against oxidants. Immature forms of Sod2p are observed in sdo1∆ cells suggesting a defect in proteolysis of the presequence. Yeast deleted for CYM1, encoding a presequence protease, display a similar reduction in Sod2p activity as sdo1∆ cells, as well as elevated oxidative damage, to mitochondrial proteins. Sod2p protein levels and activity are largely restored in a por1∆ sdo1∆ strain, lacking the major mitochondrial voltage-dependent anion channel. Together these results indicate that mitochondrial insufficiency in sdo1∆ cells may be linked to the accumulation of immature presequence containing proteins and this effect is a consequence, at least in part, from loss of counter-regulation of Por1p by Sdo1p.

Ndufs2, a Core Subunit of Mitochondrial Complex I, Is Essential for Acute Oxygen-Sensing and Hypoxic Pulmonary Vasoconstriction

RATIONALE

Hypoxic pulmonary vasoconstriction (HPV) optimizes systemic oxygen delivery by matching ventilation to perfusion. HPV is intrinsic to pulmonary artery smooth muscle cells (PASMCs). Hypoxia dilates systemic arteries, including renal arteries. Hypoxia is sensed by changes in mitochondrial-derived reactive oxygen species, notably hydrogen peroxide (H₂O₂) ([H₂O₂]_mito). Decreases in [H₂O₂]_mito elevate pulmonary vascular tone by increasing intracellular calcium ([Ca²⁺]_i) through reduction-oxidation regulation of ion channels. Although HPV is mimicked by the Complex I inhibitor, rotenone, the molecular identity of the O₂ sensor is unknown.

OBJECTIVE

To determine the role of Ndufs2 (NADH [nicotinamide adenine dinucleotide] dehydrogenase [ubiquinone] iron-sulfur protein 2), Complex I's rotenone binding site, in pulmonary vascular oxygen-sensing.

METHODS AND RESULTS

Mitochondria-conditioned media from pulmonary and renal mitochondria isolated from normoxic and chronically hypoxic rats were infused into an isolated lung bioassay. Mitochondria-conditioned media from normoxic lungs contained more H₂O₂ than mitochondria-conditioned media from chronic hypoxic lungs or kidneys and uniquely attenuated HPV via a catalase-dependent mechanism. In PASMC, acute hypoxia decreased H₂O₂ within 112±7 seconds, followed, within 205±34 seconds, by increased intracellular calcium concentration, [Ca²⁺]_i. Hypoxia had no effects on [Ca²⁺]_i in renal artery SMC. Hypoxia decreases both cytosolic and mitochondrial H₂O₂ in PASMC while increasing cytosolic H₂O₂ in renal artery SMC. Ndufs2 expression was greater in PASMC versus renal artery SMC. Lung Ndufs2 cysteine residues became reduced during acute hypoxia and both hypoxia and reducing agents caused functional inhibition of Complex I. In PASMC, siNdufs2 (cells/tissue treated with Ndufs2 siRNA) decreased normoxic H₂O₂, prevented hypoxic increases in [Ca²⁺]_i, and mimicked aspects of chronic hypoxia, including decreasing Complex I activity, elevating the nicotinamide adenine dinucleotide (NADH/NAD⁺) ratio and decreasing expression of the O₂-sensitive ion channel, Kv1.5. Knocking down another Fe-S center within Complex I (Ndufs1, NADH [nicotinamide adenine dinucleotide] dehydrogenase [ubiquinone] iron-sulfur protein 1) or other mitochondrial subunits proposed as putative oxygen sensors (Complex III's Rieske Fe-S center and COX4i2 [cytochrome c oxidase subunit 4 isoform 2] in Complex IV) had no effect on hypoxic increases in [Ca²⁺]_i. In vivo, siNdufs2 significantly decreased hypoxia- and rotenone-induced constriction while enhancing phenylephrine-induced constriction.

CONCLUSIONS

Ndufs2 is essential for oxygen-sensing and HPV.

Mitochondrial Disease Caused by a Novel Homozygous Mutation (Gly106del) in the SCO1 Gene

The cytochrome C oxidase assembly protein SCO1 gene encodes a mitochondrial protein essential for the mammalian energy metabolism. Only three pedigrees of SCO1mutations have thus far been reported. They all presented with lactate acidosis and encephalopathy. Two had hepatopathy and hypotonia, and the other presented with intrauterine growth retardation and hypertrophic cardiomyopathy leading to cardiac failure. Mitochondrial disease may manifest in neonates, but early diagnosis has so far been difficult. Here, we present a novel mutation in the SCO1 gene: in-frame deletion (Gly106del)with a different phenotype without encephalopathy, hepatopathy, hypotonia, or cardiac involvement. Within the first 2 h the girl developed hypoglycemia and severe chronic lactate acidosis. Because of the improved technique in whole exome sequencing, an early diagnosis was made when the girl was only 9 days old, which enabled the prediction of prognosis as well as level of treatment. She died at 1 month of age.

The effect of oxygen in Sirt3-mediated myocardial protection: a proof-of-concept study in cultured cardiomyoblasts

Sirtuin 3 is a nicotinamide adenine dinucleotide dependent mitochondrial deacetylase that governs mitochondrial metabolism and oxidative defense. The demise in myocardial function following myocardial ischemia has been associated with mitochondrial dysfunction. Sirt3 maintains myocardial contractile function and protects from cardiac hypertrophy. The role of Sirt3 in ischemia is controversial. Our objective was to understand, under what circumstances Sirt3 is protective in different facets of ischemia, using an in vitro proof-of-concept approach based on simulated ischemia in cultured cardiomyoblasts. Cultured H9c2 cardiomyoblasts were subjected to hypoxia and/or serum deprivation, the combination of which we refer to as simulated ischemia. Apoptosis, as assessed by Annexin V staining in life-cell imaging and propidium-iodide inclusion in flow cytometry, was enhanced following simulated ischemia. Interestingly, serum deprivation was a stronger trigger of apoptosis than hypoxia. Knockdown of Sirt3 further increased apoptosis upon serum deprivation, whereas no such effect occurred upon additional hypoxia. Similarly, only upon serum deprivation but not upon simulated ischemia, silencing of Sirt3 led to a deterioration of mitochondrial function in extracellular flux analysis. In the absence of oxygen these Sirt3-dependent effects were abolished. These data indicate, that Sirt3-mediated myocardial protection is oxygen-dependent. Thus, mitochondrial respiration takes center-stage in Sirt3-dependent prevention of stress-induced myocardial damage.

Does Levetiracetam Administration Prevent Cardiac Damage in Adulthood Rats Following Neonatal Hypoxia/Ischemia-Induced Brain Injury?

Cardiovascular abnormalities are widespread when a newborn is exposed to a hypoxic-ischemic injury in the neonatal period. Although the neuroprotective effects of levetiracetam (LEV) have been reported after hypoxia, the cardioprotective effects of LEV have not been documented. Therefore, we aimed to investigate whether levetiracetam (LEV) has a protective effect on cardiac-contractility and ultrastructure of heart muscle in rats exposed to hypoxia-ischemia (HI) during the neonatal period. A total of 49 seven-day-old rat pups were separated into four groups. For HI induction, a combination of right common carotid artery ligation with 8% oxygen in seven-day-old rat pups for 2 h was performed for saline, LEV100, and LEV200 groups. Just after hypoxia, LEV100 and LEV200 groups were administered with 100 mg/kg and 200 mg/kg of LEV, respectively. The arteries of rats in the control group were only detected; no ligation or hypoxia was performed. At the end of the 16th week after HI, cardiac mechanograms were recorded, and samples of tissue were explored by electronmicroscopy.While ventricular contractility in the control group was similar to LEV100, there were significant decreases in both saline and LEV200 groups (p < 0.05). Although ventricular contractile duration of the control and saline groups was found to be similar, durations in the LEV100 and LEV200 groups were significantly higher (p < 0.05). After HI, mitochondrial damage and ultrastructural deteriorative alterations in ventricles and atriums of the LEV-administered groups were significantly less severe than the saline group. The present study showed that neonatal HI caused long-term cardiac dysfunction and ultrastructural deteriorations in cardiac muscles. LEV administration just after HI might possess some protective effects against myocardial damage and contractility.

Co-expression Network Approach Reveals Functional Similarities among Diseases Affecting Human Skeletal Muscle

Diseases affecting skeletal muscle exhibit considerable heterogeneity in intensity, etiology, phenotypic manifestation and gene expression. Systems biology approaches using network theory, allows for a holistic understanding of functional similarities amongst diseases. Here we propose a co-expression based, network theoretic approach to extract functional similarities from 20 heterogeneous diseases comprising of dystrophinopathies, inflammatory myopathies, neuromuscular, and muscle metabolic diseases. Utilizing this framework we identified seven closely associated disease clusters with 20 disease pairs exhibiting significant correlation (p < 0.05). Mapping the diseases onto a human protein-protein interaction network enabled the inference of a common program of regulation underlying more than half the muscle diseases considered here and referred to as the “protein signature.” Enrichment analysis of 17 protein modules identified as part of this signature revealed a statistically non-random dysregulation of muscle bioenergetic pathways and calcium homeostasis. Further, analysis of mechanistic similarities of less explored significant disease associations [such as between amyotrophic lateral sclerosis (ALS) and cerebral palsy (CP)] using a proposed “functional module” framework revealed adaptation of the calcium signaling machinery. Integrating drug-gene information into the quantitative framework highlighted the presence of therapeutic opportunities through drug repurposing for diseases affecting the skeletal muscle.

Diminished stress resistance and defective adaptive homeostasis in age-related diseases

Adaptive homeostasis is defined as the transient expansion or contraction of the homeostatic range following exposure to subtoxic, non-damaging, signaling molecules or events, or the removal or cessation of such molecules or events (Mol. Aspects Med. (2016) 49, 1-7). Adaptive homeostasis allows us to transiently adapt (and then de-adapt) to fluctuating levels of internal and external stressors. The ability to cope with transient changes in internal and external environmental stress, however, diminishes with age. Declining adaptive homeostasis may make older people more susceptible to many diseases. Chronic oxidative stress and defective protein homeostasis (proteostasis) are two major factors associated with the etiology of age-related disorders. In the present paper, we review the contribution of impaired responses to oxidative stress and defective adaptive homeostasis in the development of age-associated diseases.

Exposure to decabromodiphenyl ether (BDE-209) produces mitochondrial dysfunction in rat liver and cell death

Polybrominated diphenyl ethers (PBDE) are ubiquitous environmental pollutants. Exposure to these chemicals has been associated with developmental neurotoxicity, endocrine dysfunctions, reproductive disorders, and hepatotoxicity. The widespread use of PBDE as flame retardants has culminated in daily exposure of humans and wildlife to these contaminants and resulted in their banned use. Thus assessment of the potential effects of each PBDE congener on living organisms has become cause for concern. The aim of this study was to (1) examine the effects of decabromodiphenyl ether (BDE)-209 on different functions of HepG2 cells and (2) investigate whether this congener is involved in mitochondrial toxicity. The use of multiple methods was employed to (i) study the influence of BDE-209 on mitochondrial permeability transition (MPT) process in mitochondria isolated from rat liver and (ii) determine the consequential cellular damage. Our results showed that BDE-209 induced matrix swelling related to MPT with 10 µM and ATP depletion with 0.1 µM. In addition, 0.5 μM BDE-209 reduced HepG2 cell viability, produced collapse of membrane potential, but increased levels of reactive oxygen species (ROS) after 48 h incubation. After 24 h with 5 μM treatment elevated levels of ROS, DNA fragmentation and cytochrome c release, accompanied by caspase 9 and caspase 3 activation was noted. Taken together, these results suggest that short-duration exposure (24 or 48 h) to 0.5 μM or 5 μM BDE-209 concentrations diminished HepG2 cell viability due to apoptosis associated with mitochondrial dysfunction.

Molecular characterization of a pedigree carrying the hypertension‑associated mitochondrial tRNAGln T4363C mutation

Mitochondrial DNA mutations have been reported to be associated with essential hypertension. The present study reported the clinical and molecular features of a Chinese pedigree with maternally inherited hypertension. A total of 6 matrilineal relatives in this pedigree presented with variable degrees of hypertension; the age of onset ranged between 39 and 63 years, and the average age of onset was 53 years. Analysis of the mitochondrial genome in members of this family demonstrated the occurrence of a homoplasmic T4363C mutation in the transfer (t)RNA^Gln gene and 25 genetic polymorphisms belonging to mitochondrial haplogroup B4. Notably, the T4363C mutation was localized at the anticodon stem of tRNA^Gln, which is highly conserved across various species (conventional position 38). To determine its potential pathogenicity, RNA Fold software was used to predict the secondary structure of tRNA^Gln with and without this mutation. The results indicated that the T4363C mutation induced a significant alteration in the secondary structure of tRNA^Gln, and may reduce the steady-state levels of tRNA^Gln. Furthermore, matrilineal relatives carrying the T4363C mutation exhibited different age of onset and variable degrees of blood pressure, thus indicating that the T4363C mutation itself was insufficient to produce the clinical phenotype. Therefore, other modified factors, including environmental factors, and nuclear gene and epigenetic modifications, may be involved in the pathogenesis of hypertension. In conclusion, the present study provided valuable information regarding the association between tRNA mutations and hypertension.

Remodeling pathway control of mitochondrial respiratory capacity by temperature in mouse heart: electron flow through the Q-junction in permeabilized fibers

Fuel substrate supply and oxidative phosphorylation are key determinants of muscle performance. Numerous studies of mammalian mitochondria are carried out (i) with substrate supply that limits electron flow, and (ii) far below physiological temperature. To analyze potentially implicated biases, we studied mitochondrial respiratory control in permeabilized mouse myocardial fibers using high-resolution respirometry. The capacity of oxidative phosphorylation at 37 °C was nearly two-fold higher when fueled by physiological substrate combinations reconstituting tricarboxylic acid cycle function, compared with electron flow measured separately through NADH to Complex I or succinate to Complex II. The relative contribution of the NADH pathway to physiological respiratory capacity increased with a decrease in temperature from 37 to 25 °C. The apparent excess capacity of cytochrome c oxidase above physiological pathway capacity increased sharply under hypothermia due to limitation by NADH-linked dehydrogenases. This mechanism of mitochondrial respiratory control in the hypothermic mammalian heart is comparable to the pattern in ectotherm species, pointing towards NADH-linked mt-matrix dehydrogenases and the phosphorylation system rather than electron transfer complexes as the primary drivers of thermal sensitivity at low temperature. Delineating the link between stress and remodeling of oxidative phosphorylation is important for understanding metabolic perturbations in disease evolution and cardiac protection.

Pathophysiology of anthracycline cardiotoxicity

Anthracyclines (ANTs) are powerful drugs that have reduced the mortality of cancer patients. However, their use is limited by the development of cardiotoxicity (CTX), which is dose dependent and may lead to left ventricular dysfunction and heart failure. Although various strategies have been suggested to reduce the negative effects of ANTs, CTX is still an important unresolved clinical issue. This may be due at least partly to the incomplete characterization of the molecular and cellular mechanisms of ANT-induced CTX. In addition, although various forms of cardiac damage have been demonstrated with the use of these drugs in experimental studies, it is not yet clear how these translate to the clinical setting. Appropriate characterization of potential candidates for ANT-based therapies is essential to decide whether to administer these drugs. Hopefully, new information from genetic profiling will help to identify patients who are at high risk of developing CTX.

Molecular characterization of mitochondrial transferRNAGln and transferRNAMet A4401G mutations in a Chinese family with hypertension

Mutations in mitochondrial (mt)transfer (t)RNA (mt‑tRNA) have been reported to serve important roles in hypertension. To determine the underlying molecular mechanisms of mt‑tRNA mutations in hypertension, the present study screened for mt‑tRNA mutations in a Chinese family with a high incidence of essential hypertension. Sequence analysis of the mt‑tRNA genes in this family revealed the presence of an A4401G mutation in the glycine‑and methionine‑tRNA genes, and a G5821A mutation in the cysteine‑tRNA (tRNACys) gene. The G5821A mutation was located at a position conserved in various species, and disrupted G6‑C67 base‑pairing. It was hypothesized that the G5821A mutation may decrease the baseline expression levels of tRNACys, and consequently result in failure of tRNA metabolism. The A4401G mutation was reported to cause the mitochondrial dysfunction responsible for hypertension. Thus, the combination of G5821A and A4401G mutations may contribute to the high incidence of hypertension in this family. Mt‑tRNA mutations may serve as potential biomarkers for hypertension.

Generation of reactive oxygen species in the anterior eye segment. Synergistic codrugs of N-acetylcarnosine lubricant eye drops and mitochondria-targeted antioxidant act as a powerful therapeutic platform for the treatment of cataracts and primary open-angle glaucoma

Senile cataract is a clouding of the lens in the aging eye leading to a decrease in vision. Symptoms may include faded colors, blurry vision, halos around light, trouble with bright lights, and trouble seeing at night. This may result in trouble driving, reading, or recognizing faces. Cataracts are the cause of half of blindness and 33% of visual impairment worldwide. Cataracts result from the deposition of aggregated proteins in the eye lens and lens fiber cells plasma membrane damage which causes clouding of the lens, light scattering, and obstruction of vision. ROS induced damage in the lens cell may consist of oxidation of proteins, DNA damage and/or lipid peroxidation, all of which have been implicated in cataractogenesis. The inner eye pressure (also called intraocular pressure or IOP) rises because the correct amount of fluid can't drain out of the eye. With primary open-angle glaucoma, the entrances to the drainage canals are clear and should be working correctly. The clogging problem occurs further inside the drainage canals, similar to a clogged pipe below the drain in a sink. The excessive oxidative damage is a major factor of the ocular diseases because the mitochondrial respiratory chain in mitochondria of the vital cells is a significant source of the damaging reactive oxygen species superoxide and hydrogen peroxide. However, despite the clinical importance of mitochondrial oxidative damage, antioxidants have been of limited therapeutic success. This may be because the antioxidants are not selectively taken up by mitochondria, but instead are dispersed throughout the body, ocular tissues and fluids' moieties. This work is an attempt to integrate how mitochondrial reactive oxygen species (ROS) are altered in the aging eye, along with those protective and repair therapeutic systems believed to regulate ROS levels in ocular tissues and how damage to these systems contributes to age-onset eye disease and cataract formation. Mitochondria-targeted antioxidants might be used to effectively prevent ROS-induced oxidation of lipids and proteins in the inner mitochondrial membrane in vivo. The authors developed and patented the new ophthalmic compositions including N-acetylcarnosine acting as a prodrug of naturally targeted to mitochondria l-carnosine endowed with pluripotent antioxidant activities, combined with mitochondria-targeted rechargeable antioxidant (either MitoVit E, Mito Q or SkQs) as a potent medicine to treat ocular diseases. Such specificity is explained by the fact that developed compositions might be used to effectively prevent ROS-induced oxidation of lipids and proteins in the inner mitochondrial membrane in vivo and outside mitochondria in the cellular and tissue structures of the lens and eye compartments. Mitochondrial targeting of compounds with universal types of antioxidant activity represents a promising approach for treating a number of ROS-related ocular diseases of the aging eye and can be implicated in the management of cataracts and primary open-angle glaucoma.

Oxidative mitochondrial DNA damage in peripheral blood mononuclear cells is associated with reduced volumes of hippocampus and subcortical gray matter in chronically HIV-infected patients

Cross-sectional relationships were examined between regional brain volumes and mitochondrial DNA (mtDNA) 8-hydroxy-2-deoxyguanosine (8-oxo-dG) in peripheral blood mononuclear cells (PBMCs) of 47 HIV patients [mean age 51years; 81% with HIV RNA ≤50copies/mL] on combination antiretroviral therapy. The gene-specific DNA damage and repair assay measured mtDNA 8-oxo-dG break frequency. Magnetic resonance imaging was performed at 3T. Higher mtDNA 8-oxo-dG was associated with lateral ventricular enlargement and with decreased volumes of hippocampus, pallidum, and total subcortical gray matter, suggesting the involvement of systemic mitochondrial-specific oxidative stress in chronic HIV-related structural brain changes and cognitive difficulties. Clarification of the mechanism may provide potential therapeutic targets.

Chemotherapy-Induced Cardiotoxicity: Overview of the Roles of Oxidative Stress

Chemotherapy-induced cardiotoxicity is a serious complication that poses a serious threat to life and limits the clinical use of various chemotherapeutic agents, particularly the anthracyclines. Understanding molecular mechanisms of chemotherapy-induced cardiotoxicity is a key to effective preventive strategies and improved chemotherapy regimen. Although no reliable and effective preventive treatment has become available, numerous evidence demonstrates that chemotherapy-induced cardiotoxicity involves the generation of reactive oxygen species (ROS). This review provides an overview of the roles of oxidative stress in chemotherapy-induced cardiotoxicity using doxorubicin, which is one of the most effective chemotherapeutic agents against a wide range of cancers, as an example. Current understanding in the molecular mechanisms of ROS-mediated cardiotoxicity will be explored and discussed, with emphasis on cardiomyocyte apoptosis leading to cardiomyopathy. The review will conclude with perspectives on model development needed to facilitate further progress and understanding on chemotherapy-induced cardiotoxicity.

Protective effects of sirtuins in cardiovascular diseases: from bench to bedside

Sirtuins (Sirt1–Sirt7) comprise a family of nicotinamide adenine dinucleotide (NAD⁺)-dependent enzymes. While deacetylation reflects their main task, some of them have deacylase, adenosine diphosphate-ribosylase, demalonylase, glutarylase, and desuccinylase properties. Activated upon caloric restriction and exercise, they control critical cellular processes in the nucleus, cytoplasm, and mitochondria to maintain metabolic homeostasis, reduce cellular damage and dampen inflammation—all of which serve to protect against a variety of age-related diseases, including cardiovascular pathologies. This review focuses on the cardiovascular effects of Sirt1, Sirt3, Sirt6, and Sirt7. Most is known about Sirt1. This deacetylase protects from endothelial dysfunction, atherothrombosis, diet-induced obesity, type 2 diabetes, liver steatosis, and myocardial infarction. Sirt3 provides beneficial effects in the context of left ventricular hypertrophy, cardiomyopathy, oxidative stress, metabolic homeostasis, and dyslipidaemia. Sirt6 is implicated in ameliorating dyslipidaemia, cellular senescence, and left ventricular hypertrophy. Sirt7 plays a role in lipid metabolism and cardiomyopathies. Most of these data were derived from experimental findings in genetically modified mice, where NFκB, Pcsk9, low-density lipoprotein-receptor, PPARγ, superoxide dismutase 2, poly[adenosine diphosphate-ribose] polymerase 1, and endothelial nitric oxide synthase were identified among others as crucial molecular targets and/or partners of sirtuins. Of note, there is translational evidence for a role of sirtuins in patients with endothelial dysfunction, type 1 or type 2 diabetes and longevity. Given the availability of specific Sirt1 activators or pan-sirtuin activators that boost levels of the sirtuin cofactor NAD⁺, we anticipate that this field will move quickly from bench to bedside.

Private mitochondrial DNA variants in danish patients with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic cardiac disease primarily caused by mutations in genes coding for sarcomeric proteins. A molecular-genetic etiology can be established in ~60% of cases. Evolutionarily conserved mitochondrial DNA (mtDNA) haplogroups are susceptibility factors for HCM. Several polymorphic mtDNA variants are associated with a variety of late-onset degenerative diseases and affect mitochondrial function. We examined the role of private, non-haplogroup associated, mitochondrial variants in the etiology of HCM. In 87 Danish HCM patients, full mtDNA sequencing revealed 446 variants. After elimination of 312 (69.9%) non-coding and synonymous variants, a further 109 (24.4%) with a global prevalence > 0.1%, three (0.7%) haplogroup associated and 19 (2.0%) variants with a low predicted in silico likelihood of pathogenicity, three variants: MT-TC: m.5772G>A, MT-TF: m.644A>G, and MT-CYB: m.15024G>A, p.C93Y remained. A detailed analysis of these variants indicated that none of them are likely to cause HCM. In conclusion, private mtDNA mutations are frequent, but they are rarely, if ever, associated with HCM.

WIN 55,212-2, agonist of cannabinoid receptors, prevents amyloid β1-42 effects on astrocytes in primary culture

Alzheimer´s disease (AD), a neurodegenerative illness involving synaptic dysfunction with extracellular accumulation of Aβ_1-42 toxic peptide, glial activation, inflammatory response and oxidative stress, can lead to neuronal death. Endogenous cannabinoid system is implicated in physiological and physiopathological events in central nervous system (CNS), and changes in this system are related to many human diseases, including AD. However, studies on the effects of cannabinoids on astrocytes functions are scarce. In primary cultured astrocytes we studied cellular viability using MTT assay. Inflammatory and oxidative stress mediators were determined by ELISA and Western-blot techniques both in the presence and absence of Aβ_1-42 peptide. Effects of WIN 55,212-2 (a synthetic cannabinoid) on cell viability, inflammatory mediators and oxidative stress were also determined. Aβ_1-42 diminished astrocytes viability, increased TNF-α and IL-1β levels and p-65, COX-2 and iNOS protein expression while decreased PPAR-γ and antioxidant enzyme Cu/Zn SOD. WIN 55,212-2 pretreatment prevents all effects elicited by Aβ_1-42. Furthermore, cannabinoid WIN 55,212-2 also increased cell viability and PPAR-γ expression in control astrocytes. In conclusion cannabinoid WIN 55,212-2 increases cell viability and anti-inflammatory response in cultured astrocytes. Moreover, WIN 55,212-2 increases expression of anti-oxidant Cu/Zn SOD and is able to prevent inflammation induced by Aβ_1-42 in cultured astrocytes. Further studies would be needed to assess the possible beneficial effects of cannabinoids in Alzheimer's disease patients.

Estrogen-related receptor α (ERRα) and ERRγ are essential coordinators of cardiac metabolism and function

Almost all cellular functions are powered by a continuous energy supply derived from cellular metabolism. However, it is little understood how cellular energy production is coordinated with diverse energy-consuming cellular functions. Here, using the cardiac muscle system, we demonstrate that nuclear receptors estrogen-related receptor α (ERRα) and ERRγ are essential transcriptional coordinators of cardiac energy production and consumption. On the one hand, ERRα and ERRγ together are vital for intact cardiomyocyte metabolism by directly controlling expression of genes important for mitochondrial functions and dynamics. On the other hand, ERRα and ERRγ influence major cardiomyocyte energy consumption functions through direct transcriptional regulation of key contraction, calcium homeostasis, and conduction genes. Mice lacking both ERRα and cardiac ERRγ develop severe bradycardia, lethal cardiomyopathy, and heart failure featuring metabolic, contractile, and conduction dysfunctions. These results illustrate that the ERR transcriptional pathway is essential to couple cellular energy metabolism with energy consumption processes in order to maintain normal cardiac function.

Sexual dimorphism in the expression of mitochondria-related genes in rat heart at different ages

Cardiovascular disease (CVD) is the leading cause of mortality worldwide. Moreover, sex and age are considered major risk factors in the development of CVDs. Mitochondria are vital for normal cardiac function, and regulation of mitochondrial structure and function may impact susceptibility to CVD. To identify potential role of mitochondria in sex-related differences in susceptibility to CVD, we analyzed the basal expression levels of mitochondria-related genes in the hearts of male and female rats. Whole genome expression profiling was performed in the hearts of young (8-week), adult (21-week), and old (78-week) male and female Fischer 344 rats and the expression of 670 unique genes related to various mitochondrial functions was analyzed. A significant (p<0.05) sexual dimorphism in expression levels of 46, 114, and 41 genes was observed in young, adult and old rats, respectively. Gene Ontology analysis revealed the influence of sex on various biological pathways related to cardiac energy metabolism at different ages. The expression of genes involved in fatty acid metabolism was significantly different between the sexes in young and adult rat hearts. Adult male rats also showed higher expression of genes associated with the pyruvate dehydrogenase complex compared to females. In young and adult hearts, sexual dimorphism was not noted in genes encoding oxidative phosphorylation. In old rats, however, a majority of genes involved in oxidative phosphorylation had higher expression in females compared to males. Such basal differences between the sexes in cardiac expression of genes associated with energy metabolism may indicate a likely involvement of mitochondria in susceptibility to CVDs. In addition, female rats showed lower expression levels of apoptotic genes in hearts compared to males at all ages, which may have implications for better preservation of cardiac mass in females than in males.

Energy metabolic reprogramming in the hypertrophied and early stage failing heart: a multisystems approach

BACKGROUND

An unbiased systems approach was used to define energy metabolic events that occur during the pathological cardiac remodeling en route to heart failure (HF).

METHODS AND RESULTS

Combined myocardial transcriptomic and metabolomic profiling were conducted in a well-defined mouse model of HF that allows comparative assessment of compensated and decompensated (HF) forms of cardiac hypertrophy because of pressure overload. The pressure overload data sets were also compared with the myocardial transcriptome and metabolome for an adaptive (physiological) form of cardiac hypertrophy because of endurance exercise training. Comparative analysis of the data sets led to the following conclusions: (1) expression of most genes involved in mitochondrial energy transduction were not significantly changed in the hypertrophied or failing heart, with the notable exception of a progressive downregulation of transcripts encoding proteins and enzymes involved in myocyte fatty acid transport and oxidation during the development of HF; (2) tissue metabolite profiles were more broadly regulated than corresponding metabolic gene regulatory changes, suggesting significant regulation at the post-transcriptional level; (3) metabolomic signatures distinguished pathological and physiological forms of cardiac hypertrophy and served as robust markers for the onset of HF; and (4) the pattern of metabolite derangements in the failing heart suggests bottlenecks of carbon substrate flux into the Krebs cycle.

CONCLUSIONS

Mitochondrial energy metabolic derangements that occur during the early development of pressure overload-induced HF involve both transcriptional and post-transcriptional events. A subset of the myocardial metabolomic profile robustly distinguished pathological and physiological cardiac remodeling.

Gene therapy for mitochondrial diseases: Leber Hereditary Optic Neuropathy as the first candidate for a clinical trial

Mitochondrial disorders cannot be ignored anymore in most medical disciplines; indeed their minimum estimated prevalence is superior to 1 in 5000 births. Despite the progress made in the last 25 years on the identification of gene mutations causing mitochondrial pathologies, only slow progress was made towards their effective treatments. Ocular involvement is a frequent feature in mitochondrial diseases and corresponds to severe and irreversible visual handicap due to retinal neuron loss and optic atrophy. Interestingly, three clinical trials for Leber Congenital Amaurosis due to RPE65 mutations are ongoing since 2007. Overall, the feasibility and safety of ocular Adeno-Associated Virus delivery in adult and younger patients and consistent visual function improvements have been demonstrated. The success of gene-replacement therapy for RPE65 opens the way for the development of similar approaches for a broad range of eye disorders, including those with mitochondrial etiology such as Leber Hereditary Optic Neuropathy (LHON).

Peroxisome proliferator-activated receptor γ coactivator 1 (PGC-1)- and estrogen-related receptor (ERR)-induced regulator in muscle 1 (Perm1) is a tissue-specific regulator of oxidative capacity in skeletal muscle cells

Mitochondrial oxidative metabolism and energy transduction pathways are critical for skeletal and cardiac muscle function. The expression of genes important for mitochondrial biogenesis and oxidative metabolism are under the control of members of the peroxisome proliferator-activated receptor γ coactivator 1 (PGC-1) family of transcriptional coactivators and the estrogen-related receptor (ERR) subfamily of nuclear receptors. Perturbations in PGC-1 and/or ERR activities have been associated with alterations in capacity for endurance exercise, rates of muscle atrophy, and cardiac function. The mechanism(s) by which PGC-1 and ERR proteins regulate muscle-specific transcriptional programs is not fully understood. We show here that PGC-1α and ERRs induce the expression of a so far uncharacterized muscle-specific protein, PGC-1- and ERR-induced regulator in muscle 1 (Perm1), which regulates the expression of selective PGC-1/ERR target genes. Perm1 is required for the basal as well as PGC-1α-enhanced expression of genes with roles in glucose and lipid metabolism, energy transfer, and contractile function. Silencing of Perm1 in cultured myotubes compromises respiratory capacity and diminishes PGC-1α-induced mitochondrial biogenesis. Our findings support a role for Perm1 acting downstream of PGC-1α and ERRs to regulate muscle-specific pathways important for energy metabolism and contractile function. Elucidating the function of Perm1 may enable novel approaches for the treatment of disorders with compromised skeletal muscle bioenergetics, such as mitochondrial myopathies and age-related/disease-associated muscle atrophies.

Mitochondrial dysfunction in myocardium obtained from clinically normal dogs, clinically normal anesthetized dogs, and dogs with dilated cardiomyopathy

OBJECTIVE

To compare mitochondrial complex I and complex IV activity in myocardial mitochondria of clinically normal dogs, clinically normal dogs exposed to inhalation anesthesia, and dogs affected with dilated cardiomyopathy.

SAMPLE

Myocardial samples obtained from 21 euthanized dogs (6 clinically normal [control] dogs, 5 clinically normal dogs subjected to inhalation anesthesia with isoflurane prior to euthanasia, 5 dogs with juvenile-onset dilated cardiomyopathy, and 5 dogs with adult-onset dilated cardiomyopathy).

PROCEDURES

Activity of mitochondrial complex I and complex IV was assayed spectrophotometrically in isolated mitochondria from left ventricular tissue obtained from the 4 groups of dogs.

RESULTS

Activity of complex I and complex IV was significantly decreased in anesthetized dogs, compared with activities in the control dogs and dogs with juvenile-onset or adult-onset dilated cardiomyopathy.

CONCLUSIONS AND CLINICAL RELEVANCE

Inhalation anesthesia disrupted the electron transport chain in the dogs, which potentially led to an outburst of reactive oxygen species that caused mitochondrial dysfunction. Inhalation anesthesia depressed mitochondrial function in dogs, similar to results reported in other species. This effect is important to consider when anesthetizing animals with myocardial disease and suggested that antioxidant treatments may be beneficial in some animals. Additionally, this effect should be considered when designing studies in which mitochondrial enzyme activity will be measured. Additional studies that include a larger number of animals are warranted.

Human neuronal coenzyme Q10 deficiency results in global loss of mitochondrial respiratory chain activity, increased mitochondrial oxidative stress and reversal of ATP synthase activity: implications for pathogenesis and treatment

Disorders of coenzyme Q(10) (CoQ(10)) biosynthesis represent the most treatable subgroup of mitochondrial diseases. Neurological involvement is frequently observed in CoQ(10) deficiency, typically presenting as cerebellar ataxia and/or seizures. The aetiology of the neurological presentation of CoQ(10) deficiency has yet to be fully elucidated and therefore in order to investigate these phenomena we have established a neuronal cell model of CoQ(10) deficiency by treatment of neuronal SH-SY5Y cell line with para-aminobenzoic acid (PABA). PABA is a competitive inhibitor of the CoQ(10) biosynthetic pathway enzyme, COQ2. PABA treatment (1 mM) resulted in a 54 % decrease (46 % residual CoQ(10)) decrease in neuronal CoQ(10) status (p < 0.01). Reduction of neuronal CoQ(10) status was accompanied by a progressive decrease in mitochondrial respiratory chain enzyme activities, with a 67.5 % decrease in cellular ATP production at 46 % residual CoQ(10). Mitochondrial oxidative stress increased four-fold at 77 % and 46 % residual CoQ(10). A 40 % increase in mitochondrial membrane potential was detected at 46 % residual CoQ(10) with depolarisation following oligomycin treatment suggesting a reversal of complex V activity. This neuronal cell model provides insights into the effects of CoQ(10) deficiency on neuronal mitochondrial function and oxidative stress, and will be an important tool to evaluate candidate therapies for neurological conditions associated with CoQ(10) deficiency.

Activation of PARP by oxidative stress induced by β-amyloid: implications for Alzheimer's disease

Alzheimer's disease (AD) is a major neurodegenerative disease of old age, characterised by progressive cognitive impairment, dementia and atrophy of the central nervous system. The pathological hallmarks include the accumulation of the peptide β-amyloid (Aβ) which itself is toxic to neurons in culture. Recently, it has been discovered that Aβ activates the protein poly(ADP-ribosyl) polymerase-1 (PARP-1) specifically in astrocytes, leading indirectly to neuronal cell death. PARP-1 is a DNA repair enzyme, normally activated by single strand breaks associated with oxidative stress, which catalyses the formation of poly ADP-ribose polymers from nicotinamide adenine dinucleotide (NAD(+)). The pathological over activation of PARP-1 causes depletion of NAD(+) and leads to cell death. Here we review the relationship between AD and PARP-1, and explore the role played by astrocytes in neuronal death. AD has so far proven refractory to any effective treatment. Identification of these pathways represents a step towards a greater understanding of the pathophysiology of this devastating disease with the potential to explore novel therapeutic targets.

Clinical and molecular characterization of a Han Chinese family with high penetrance of essential hypertension

Mutations in mitochondrial DNA are associated with cardiovascular diseases. We reported here molecular characterization of a three-generation Han Chinese family with maternally transmitted hypertension. Most strikingly, this family exhibited a high penetrance of hypertension. Sequence analysis of mitochondrial genome showed the presence of 12,338T>C mutation and 12,330A>G mutation and distinct sets of polymorphisms belonging to the Asian haplogroup F2b. Interestingly, the well-known 12,338T>C mutation, which caused a change of methionine in the translational initiation codon of ND5, also localized in two nucleotides adjacent to the 3' end of tRNA(Leu(CUN)), was implied to cause a decrease in ND5 mRNA level as well as to alter tRNA(Leu(CUN)) stability level. Moreover, the highly conserved 12,330A>G mutation, which disrupted the base pairing (6T-67A) in acceptor arm of tRNA(Leu(CUN)), may result in the failure of tRNA(Leu(CUN)) metabolism. Therefore, the combination of ND5 12,338T>C and tRNA(Leu(CUN)) 12,330A>G mutations may contribute to the high penetrance of hypertension in this Chinese family.

Telomeres and mitochondria in the aging heart

Studies in humans and in mice have highlighted the importance of short telomeres and impaired mitochondrial function in driving age-related functional decline in the heart. Although telomere and mitochondrial dysfunction have been viewed mainly in isolation, recent studies in telomerase-deficient mice have provided evidence for an intimate link between these two processes. Telomere dysfunction induces a profound p53-dependent repression of the master regulators of mitochondrial biogenesis and function, peroxisome proliferator-activated receptor gamma coactivator (PGC)-1α and PGC-1β in the heart, which leads to bioenergetic compromise due to impaired oxidative phosphorylation and ATP generation. This telomere-p53-PGC mitochondrial/metabolic axis integrates many factors linked to heart aging including increased DNA damage, p53 activation, mitochondrial, and metabolic dysfunction and provides a molecular basis of how dysfunctional telomeres can compromise cardiomyocytes and stem cell compartments in the heart to precipitate cardiac aging.