Consequences Of Mitochondrial Dysfunction Research Articles

MITOCHONDRIA – AS A TARGET OF ENVIRONMENTAL FACTORS

Mitochondria—tiny organelles in the cell that each possess their own DNA—have come under a growing scientific spotlight. The traditional view of mitochondria as static organelles has been reassessed. Scientists increasingly believe they play a central role in many, if not most, human illnesses. Mitochondria are often target of toxicity of environmental toxicants resulting in multisystem disorders involving different cells, tissues, and organs. The purpose of this review is to discuss the mechanism and consequences of mitochondrial dysfunction caused by environmental factors. Recognition of the key role of mtDNA integrity and mitochondrial function in health has grown greatly in recent years. The environment can influence human health and disease in many harmful ways. One such mechanism for this is through environmental factors increasing oxidative stress in the cell, and this stress can subsequently lead to alterations in DNA molecule. Research shows that mitochondrial DNA is uniquely susceptible to the damaging effects of reactive oxygen species (ROS). These effects are more extensive and longer-lasting in mitochondrial DNA than they are in the nuclear genome. In humans, the most concerning chemicals may be mitochondrial toxins with long half-lives. Examples include lipophilic chemical mixtures such as persistent organic pollutants (POPs) and heavy metals. Other examples of chronic exposure to mitochondrial toxins are air pollution and cigarette smoking. Compared with its nuclear counterpart, mitochondrial DNA generally has less capacity to repair itself. It specifically can’t delete the large DNA helix–distorting adducts formed when mitochondrial DNA bases are damaged by mutagens such as polyaromatic hydrocarbons and ultraviolet radiation. Conclusion - Despite numerous existing researches, the specified question requires further study. it is necessary clearer understanding of what specific environmental factors damage mitochondria and how they do so, this is important way to prevent many diseases induced by mitochondrial dysfunction. Keywords: Mitochondria; Environmental Factors; Mitochondrial dysfunction;

Mitochondrial membrane potential acts as a retrograde signal to regulate cell cycle progression.

Mitochondria are central to numerous metabolic pathways whereby mitochondrial dysfunction has a profound impact and can manifest in disease. The consequences of mitochondrial dysfunction can be ameliorated by adaptive responses that rely on crosstalk from the mitochondria to the rest of the cell. Such mito-cellular signalling slows cell cycle progression in mitochondrial DNA-deficient (ρ0) Saccharomyces cerevisiae cells, but the initial trigger of the response has not been thoroughly studied. Here, we show that decreased mitochondrial membrane potential (ΔΨm) acts as the initial signal of mitochondrial stress that delays G1-to-S phase transition in both ρ0 and control cells containing mtDNA. Accordingly, experimentally increasing ΔΨm was sufficient to restore timely cell cycle progression in ρ0 cells. In contrast, cellular levels of oxidative stress did not correlate with the G1-to-S delay. Restored G1-to-S transition in ρ0 cells with a recovered ΔΨm is likely attributable to larger cell size, whereas the timing of G1/S transcription remained delayed. The identification of ΔΨm as a regulator of cell cycle progression may have implications for disease states involving mitochondrial dysfunction.

The multifaceted role of kidney tubule mitochondrial dysfunction in kidney disease development.

More than 800 million people suffer from kidney disease. Genetic studies and follow-up animal models and cell biological experiments indicate the key role of proximal tubule metabolism. Kidneys have one of the highest mitochondrial densities. Mitochondrial biogenesis, mitochondrial fusion and fission, and mitochondrial recycling, such as mitophagy are critical for proper mitochondrial function. Mitochondrial dysfunction can lead to an energetic crisis, orchestrate different types of cell death (apoptosis, necroptosis, pyroptosis, and ferroptosis), and influence cellular calcium levels and redox status. Collectively, mitochondrial defects in renal tubules contribute to epithelial atrophy, inflammation, or cell death, orchestrating kidney disease development.

Hepatoprotective Effect of Coenzyme Q10 in Rats with Diclofenac Toxicity.

The liver and kidney are the most important organs in the body, and they both act as target structures for drug-induced injury as a consequence of their functions in metabolisms, detoxifications, storage, elimination of medications, and their metabolites. The present study aimed to examine the role of the natural and free radical scavenger "CoQ10" against diclofenac-induced hepatic and renal tissue injury. In total, 36 adult Wistar rats were randomly divided into three equal groups (n=12). The animals in the control group did not receive any medication or treatments, and the second group included animals that received intramuscular (IM) injection of Diclofenac (DF) (at a dose of 10 mg/kg once daily for 14 days). Moreover, the third group was given the IM injection of DF (at a dose of 10 mg/kg once daily for 14 days) +CoQ10. After 14 days, DF prompted signified hepatic and renal injury indicated by elevated biochemical parameters, such as total serum bilirubin, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, blood urea nitrogen, creatinine, and uric acid, compared to the control and the third group. However, the group that received Diclofenac+CoQ10 had significantly lower hepatic and renal dysfunctions, compared to the second treated group. DF toxic effects could be the consequences of mitochondrial dysfunction and free radical effects. Remarkably, therapeutic supplementation of CoQ10 diminished the DF-induced toxic oxidative injury and apoptotic cell death. The protective effects of CoQ10 were attributed to its antioxidants and free radical scavenger activity.

A NEET Way to Impair Mitochondrial Function in α- and β-Cells.

Glucose homeostasis requires a carefully orchestrated balance between the release of insulin and glucagon by β- and α-cells, respectively, in pancreatic islets. During fasting, the rate of insulin secretion falls to slow glucose utilization, whereas that of glucagon secretion rises to promote gluconeogenesis, thereby preventing hypoglycemia. After a mixed meal, glucose stimulates insulin secretion while inhibiting glucagon secretion. This “yin and yang” pattern of β- and α-cell activation and inhibition is very important for the regulation of glucose homeostasis, and dysregulation of pancreatic hormones is a prominent feature of diabetes. It has been appreciated for some time that mitochondrial dysfunction is observed in the β-cells of patients with diabetes (1,2) and that mitochondrial DNA mutations in humans or targeted disruption of mitochondrial genome maintenance in mice are sufficient to drive β-cell dysfunction (3,4). However, the primary mitochondrial defects studied in β-cells to date have generally been severe, and neither the cause nor the consequences of the milder mitochondrial dysfunction observed in the majority of patients with diabetes have been firmly established. Moreover, the consequences of mitochondrial dysfunction in α-cells are relatively unexplored. In this issue of Diabetes , Kusminski et al. (5) introduce tetracycline-inducible expression mitochondrial protein mitoNEET in α- or β-cells as a model of graded mitochondrial dysfunction. MitoNEET (named for its COOH-terminal Asn-Glu-Glu-Thr amino acid sequence) is a mitochondrial outer membrane protein that is oriented toward the cytoplasm and binds iron–sulfur clusters (6,7). Its …

ChemInform Abstract: Mitochondrial Drug Targets in Neurodegenerative Diseases

AbstractReview: 161 refs.

Mitochondrial drug targets in neurodegenerative diseases.

Growing evidence suggests that mitochondrial dysfunction is the main culprit in neurodegenerative diseases. Given the fact that mitochondria participate in diverse cellular processes, including energetics, metabolism, and death, the consequences of mitochondrial dysfunction in neuronal cells are inevitable. In fact, new strategies targeting mitochondrial dysfunction are emerging as potential alternatives to current treatment options for neurodegenerative diseases. In this review, we focus on mitochondrial proteins that are directly associated with mitochondrial dysfunction. We also examine recently identified small molecule modulators of these mitochondrial targets and assess their potential in research and therapeutic applications.

Unraveling biochemical pathways affected by mitochondrial dysfunctions using metabolomic approaches.

Mitochondrial dysfunction(s) (MDs) can be defined as alterations in the mitochondria, including mitochondrial uncoupling, mitochondrial depolarization, inhibition of the mitochondrial respiratory chain, mitochondrial network fragmentation, mitochondrial or nuclear DNA mutations and the mitochondrial accumulation of protein aggregates. All these MDs are known to alter the capacity of ATP production and are observed in several pathological states/diseases, including cancer, obesity, muscle and neurological disorders. The induction of MDs can also alter the secretion of several metabolites, reactive oxygen species production and modify several cell-signalling pathways to resolve the mitochondrial dysfunction or ultimately trigger cell death. Many metabolites, such as fatty acids and derived compounds, could be secreted into the blood stream by cells suffering from mitochondrial alterations. In this review, we summarize how a mitochondrial uncoupling can modify metabolites, the signalling pathways and transcription factors involved in this process. We describe how to identify the causes or consequences of mitochondrial dysfunction using metabolomics (liquid and gas chromatography associated with mass spectrometry analysis, NMR spectroscopy) in the obesity and insulin resistance thematic.

The Intrinsic Apoptosis Pathway Mediates the Pro-Longevity Response to Mitochondrial ROS in C. elegans

The increased longevity of the C. elegans electron transport chain mutants isp-1 and nuo-6 is mediated by mitochondrial ROS (mtROS) signaling. Here we show that the mtROS signal is relayed by the conserved, mitochondria-associated, intrinsic apoptosis signaling pathway (CED-9/Bcl2, CED-4/Apaf1, and CED-3/Casp9) triggered by CED-13, an alternative BH3-only protein. Activation of the pathway by an elevation of mtROS does not affect apoptosis but protects from the consequences of mitochondrial dysfunction by triggering a unique pattern of gene expression that modulates stress sensitivity and promotes survival. In vertebrates, mtROS induce apoptosis through the intrinsic pathway to protect from severely damaged cells. Our observations in nematodes demonstrate that sensing of mtROS by the apoptotic pathway can, independently of apoptosis, elicit protective mechanisms that keep the organism alive under stressful conditions. This results in extended longevity when mtROS generation is inappropriately elevated. These findings clarify the relationships between mitochondria, ROS, apoptosis, and aging.

The SFT-1 and OXA-1 respiratory chain complex assembly factors influence lifespan by distinct mechanisms in C. elegans

BackgroundC. elegans mitochondrial (Mit) mutants have disrupted mitochondrial electron transport chain function, yet, surprisingly, they are often long-lived, a property that has offered unique insights into the molecular mechanisms of aging. In this study, we examine the phenotypic consequences of reducing the expression of the respiratory chain complex assembly factors sft-1 (homologous to human SURF1) and oxa-1 (homologous to human OXA1) by RNA interference (RNAi). Mutations in human SURF1 are associated with Leigh syndrome, a neurodegenerative condition of the brain caused by cytochrome oxidase (COX) deficiency. Both SURF1 and OXA1 are integral proteins of the inner mitochondrial membrane, functioning in the COX assembly pathway.ResultsRNAi of both of these genes in C. elegans is associated with increased longevity, but the mechanism by which lifespan is extended is different in each case. sft-1(RNAi) animals display lifespan extension that is dependent on the daf-16 insulin-like signaling pathway, and associated with sensitivity to oxidative stress. oxa-1(RNAi) animals, in contrast, exhibit increased longevity that is at least partially independent of daf-16, and associated with a reduced developmental rate and increased resistance to oxidative stress.ConclusionsThis study further delineates the consequences of mitochondrial dysfunction within a whole organism that will ultimately help provide new models for human mitochondrial-associated diseases. The difference in phenotype observed upon down-regulation of these two COX assembly factors, as well as phenotypic differences between these factors and other respiratory chain components analyzed thus far, illustrates the complex inter-relationships that exist among energy metabolism, reproduction and aging even in this simplest of metazoan model organisms.

Barth syndrome: Cellular compensation of mitochondrial dysfunction and apoptosis inhibition due to changes in cardiolipin remodeling linked to tafazzin (TAZ) gene mutation

Cardiolipin is a mitochondrion-specific phospholipid that stabilizes the assembly of respiratory chain complexes, favoring full-yield operation. It also mediates key steps in apoptosis. In Barth syndrome, an X chromosome-linked cardiomyopathy caused by tafazzin mutations, cardiolipins display acyl chain modifications and are present at abnormally low concentrations, whereas monolysocardiolipin accumulates. Using immortalized lymphoblasts from Barth syndrome patients, we showed that the production of abnormal cardiolipin led to mitochondrial alterations. Indeed, the lack of normal cardiolipin led to changes in electron transport chain stability, resulting in cellular defects. We found a destabilization of the supercomplex (respirasome) I+III2+IVn but also decreased amounts of individual complexes I and IV and supercomplexes I+III and III+IV. No changes were observed in the amounts of individual complex III and complex II. We also found decreased levels of complex V. This complex is not part of the supercomplex suggesting that cardiolipin is required not only for the association/stabilization of the complexes into supercomplexes but also for the modulation of the amount of individual respiratory chain complexes. However, these alterations were compensated by an increase in mitochondrial mass, as demonstrated by electron microscopy and measurements of citrate synthase activity. We suggest that this compensatory increase in mitochondrial content prevents a decrease in mitochondrial respiration and ATP synthesis in the cells. We also show, by extensive flow cytometry analysis, that the type II apoptosis pathway was blocked at the mitochondrial level and that the mitochondria of patients with Barth syndrome cannot bind active caspase-8. Signal transduction is thus blocked before any mitochondrial event can occur. Remarkably, basal levels of superoxide anion production were slightly higher in patients' cells than in control cells as previously evidenced via an increased protein carbonylation in the taz1Δ mutant in the yeast. This may be deleterious to cells in the long term. The consequences of mitochondrial dysfunction and alterations to apoptosis signal transduction are considered in light of the potential for the development of future treatments.

Mitochondria in vascular disease

Mitochondria are often regarded as the powerhouse of the cell by generating the ultimate energy transfer molecule, ATP, which is required for a multitude of cellular processes. However, the role of mitochondria goes beyond their capacity to create molecular fuel, to include the generation of reactive oxygen species, the regulation of calcium, and activation of cell death. Mitochondrial dysfunction is part of both normal and premature ageing, but can contribute to inflammation, cell senescence, and apoptosis. Cardiovascular disease, and in particular atherosclerosis, is characterized by DNA damage, inflammation, cell senescence, and apoptosis. Increasing evidence indicates that mitochondrial damage and dysfunction also occur in atherosclerosis and may contribute to the multiple pathological processes underlying the disease. This review summarizes the normal role of mitochondria, the causes and consequences of mitochondrial dysfunction, and the evidence for mitochondrial damage and dysfunction in vascular disease. Finally, we highlight areas of mitochondrial biology that may have therapeutic targets in vascular disease.

Metabolic manipulators: a well founded strategy to combat mitochondrial dysfunction

Whilst the pathophysiology and genetics of mitochondrial disease are slowly being unraveled, currently no effective remedy for mitochondrial disorders is available. One particular strategy in mitochondrial medicine presently under study is metabolic manipulation. This approach is aimed at counteracting the deranged cell biological homeostasis caused by mitochondrial dysfunction, using dietary modifications or small molecule therapy. Cell biological alterations caused by mitochondrial dysfunction include increased reactive oxygen species production, enhanced lipid peroxidation and altered cellular calcium homeostasis. This review covers the five principles of metabolic manipulation: (1) prevention of oxidative damage by reactive oxygen species, (2) amelioration of lipid peroxidation, (3) correction of altered membrane potential, (4) restoration of calcium homeostasis, and (5) transcription regulation interference. We hypothesize that a combination of compounds targeting different metabolic pathways will abolish cellular disturbance arising as a consequences of mitochondrial dysfunction, and thereby improve or stabilize clinical features. However, only a handful of compounds have reached efficacy testing in mammals, and it remains unknown to what extent metabolic manipulation will affect the whole organism. Until a potent remedy is found, patients will remain dependent on supportive, not curative, interventions.

Potential Mechanisms of Muscle Mitochondrial Dysfunction in Aging and Obesity and Cellular Consequences

Mitochondria play a key role in the energy metabolism in skeletal muscle. A new concept has emerged suggesting that impaired mitochondrial oxidative capacity in skeletal muscle may be the underlying defect that causes insulin resistance. According to current knowledge, the causes and the underlying molecular mechanisms at the origin of decreased mitochondrial oxidative capacity in skeletal muscle still remain to be elucidated. The present review focuses on recent data investigating these issues in the area of metabolic disorders and describes the potential causes, mechanisms and consequences of mitochondrial dysfunction in the skeletal muscle.

Mitochondrial dysfunction and amyotrophic lateral sclerosis

The causes of motor neuron death in amyotrophic lateral sclerosis (ALS) are still unknown. Several lines of evidence suggest that mitochondrial dysfunction may be involved in the pathogenesis of ALS. Biochemical and morphological mitochondrial abnormalities have been demonstrated in postmortem spinal cords of ALS patients. Furthermore, in transgenic mice expressing mutant Cu,Zn-superoxide dismutase (SOD1), the antioxidant enzyme associated with familial ALS (FALS), mitochondrial abnormalities precede the disease onset, suggesting that mitochondrial dysfunction is causally involved in the pathogenesis of SOD1-FALS. Despite this evidence, it is not yet fully understood how mutant SOD1 damages mitochondria. Recent work has demonstrated that a portion of mutant SOD1 is localized in mitochondria, both in transgenic mice and in FALS patients, where it forms proteinaceous aggregates. These findings have opened new avenues of investigation addressing the hypothesis that mutant SOD1 may directly damage mitochondria. Major future challenges will be to better understand the mechanisms and the consequences of mitochondrial dysfunction in ALS. If mitochondrial dysfunction is convincingly involved in ALS pathogenesis, either as a primary cause or as contributing factor, it is likely to become a novel target for therapeutic intervention.

Mitochondrial Respiratory Deficiencies Signal Up-regulation of Genes for Heat Shock Proteins

The consequences of mitochondrial dysfunction are not limited to the development of oxidative stress or initiation of apoptosis but can result in the establishment of stress tolerance. Using maize mitochondrial mutants, we show that permanent mitochondrial deficiencies trigger novel Ca(2+)-independent signaling pathways, leading to constitutive expression of genes for molecular chaperones, heat shock proteins (HSPs) of different classes. The signaling to activate hsp genes appears to originate from a reduced mitochondrial transmembrane potential. Upon depolarization of mitochondrial membranes in transient assays, gene induction for mitochondrial HSPs occurred more rapidly than that for cytosolic HSPs. We also demonstrate that in the nematode Caenorhabditis elegans transcription of hsp genes can be induced by RNA interference of nuclear respiratory genes. In both organisms, activation of hsp genes in response to mitochondrial impairment is distinct from their responses to heat shock and is not associated with oxidative stress. Thus, mitochondria-to-nucleus signaling to express a hsp gene network is apparently a widespread retrograde mechanism to facilitate cell defense and survival.

The mitochondrial death/life regulator in apoptosis and necrosis.

Both physiological cell death (apoptosis) and, in some cases, accidental cell death (necrosis) involve a two-step process. At a first level, numerous physiological and some pathological stimuli trigger an increase in mitochondrial membrane permeability. The mitochondria release apoptogenic factors through the outer membrane and dissipate the electrochemical gradient of the inner membrane. Mitochondrial permeability transition (PT) involves a dynamic multiprotein complex formed in the contact site between the inner and outer mitochondrial membranes. The PT complex can function as a sensor for stress and damage, as well as for certain signals connected to receptors. Inhibition of PT by pharmacological intervention on mitochondrial structures or mitochondrial expression of the apoptosis-inhibitory oncoprotein Bcl-2 prevents cell death, suggesting that PT is a rate-limiting event of the death process. At a second level, the consequences of mitochondrial dysfunction (collapse of the mitochondrial inner transmembrane potential, uncoupling of the respiratory chain, hyperproduction of superoxide anions, disruption of mitochondrial biogenesis, outflow of matrix calcium and glutathione, and release of soluble intermembrane proteins) entails a bioenergetic catastrophe culminating in the disruption of plasma membrane integrity (necrosis) and/or the activation of specific apoptogenic proteases (caspases) by mitochondrial proteins that leak into the cytosol (cytochrome c, apoptosis-inducing factor) with secondary endonuclease activation (apoptosis). The relative rate of these two processes (bioenergetic catastrophe versus protease and endonuclease activation) determines whether a cell will undergo primary necrosis or apoptosis. The acquisition of the biochemical and ultrastructural features of apoptosis critically relies on the liberation of apoptogenic proteases or protease activators from mitochondria. The fact that mitochondrial events control cell death has major implications for the development of cytoprotective and cytotoxic drugs.

Neuroradiological features of six kindreds with MELAS tRNALeu A3243G point mutation: implications for pathogenesis

OBJECTIVETo determine the neuroradiological abnormalities associated with subjects carrying the mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS) tRNALeu(UUR)A3243G point mutationMETHODSMitochondrial genetic analysis was performed on 24 subjects from...

Mitochondrial implication in accidental and programmed cell death: apoptosis and necrosis.

Both physiological cell death (apoptosis) and at least some cases of accidental cell death (necrosis) involve a two-step-process. At first level, numerous physiological or pathological stimuli can trigger mitochondrial permeability transition which constitutes a rate-limiting event and initiates the common phase of the death process. Mitochondrial permeability transition (PT) involves the formation of proteaceous, regulated pores, probably by apposition of inner and outer mitochondrial membrane proteins which cooperate to form the mitochondrial PT pore complex. Inhibition of PT by pharmacological intervention on mitochondrial structures or mitochondrial expression of the apoptosis-inhibitory oncoprotein Bcl-2 thus can prevent cell death. At a second level, the consequences of mitochondrial dysfunction (collapse of the mitochondrial transmembrane potential, uncoupling of the respiratory chain, hyperproduction of superoxide anions, disruption of mitochondrial biogenesis, outflow of matrix calcium and glutathione, and release of soluble intermembrane proteins) can entail a biogenetic catastrophe culminating in the disruption of plasma membrane integrity (necrosis) and/or the activation and action of apoptogenic proteases with secondary endonuclease activation and consequent oligonucleosomal DNA fragmentation (apoptosis). The acquisition of the biochemical and ultrastructural features of apoptosis critically relies on the liberation of apoptogenic proteases or protease activators from the mitochondrial intermembrane space. This scenario applies to very different models of cell death. The notion that mitochondrial events control cell death has major implications for the development of death-inhibitory drugs.

Clinical and physiologic aspects in the diagnosis and treatment of chronic pulmonary diseases

Many neurodegenerative diseases feature mitochondrial dysfunction. This includes both common sporadic and rare Mendelian disorders. In some cases, mitochondrial defects mediate disease pathology, and in others, the defects actually initiate and drive the disease. Understanding the causes and consequences of mitochondrial dysfunction provides insight into neurodegenerative diseases and reveals potential therapeutic targets that could lead to new treatments. This chapter provides an overview of mitochondrial function and its role in cell physiology, presents current perceptions about the relevance of mitochondrial and bioenergetic dysfunction to neurodegenerative diseases, and discusses targeting mitochondria for therapeutic purposes.