线粒体异常与帕金森病相关性简

帕金森病为中枢神经系统退行性疾病。尽管其确切的发病机制尚不清楚,但近年来越来越多的研究表明线粒体异常是帕金森病发病的关键。本文主要从线粒体动态变化、线粒体自噬、线粒体DNA突变,以及线粒体复合物I抑制等方面对线粒体异常与帕金森病发病的相关性进行概述。     

Bid mediates fission,membrane permeabilization and peri-nuclear accumulation of mitochondria as a prerequisite for oxidative neuronal cell death

Mitochondria are highly dynamic organelles that undergo permanent fusion and fission, a process that is important for mitochondrial function and cellular survival. Emerging evidence suggests that oxidative stress disturbs mitochondrial morphology dynamics, resulting in detrimental mitochondrial fragmentation. In particular, such fatal mitochondrial fission has been detected in neurons exposed to oxidative stress, suggesting mitochondrial dynamics as a key feature in intrinsic death pathways. However, the regulation of mitochondrial fission in neurons exposed to lethal stress is largely unknown. Here, we used a model of glutamate toxicity in HT-22 cells for investigating mitochondrial fission and fusion in neurons exposed to oxidative stress. In these immortalized hippocampal neurons, glutamate induces glutathione depletion and increased formation of reactive oxygen species (ROS). Glutamate toxicity resulted in mitochondrial fragmentation and peri-nuclear accumulation of the organelles. Further, mitochondrial fission was associated with loss of mitochondrial outer membrane potential (MOMP). The Bid-inhibitor BI-6c9 prevented MOMP and mitochondrial fission, and protected the cells from cell death. In conclusion, oxidative stress induced by glutamate causes mitochondrial translocation of Bid thereby inducing mitochondrial fission and associated mitochondrial cell death pathways. Inhibiting regulators of pathological mitochondrial fragmentation is proposed as an efficient strategy of neuroprotection.     

Abnormal mitochondria in the Rett syndrome

Two girls with Rett syndrome were investigated including muscle biopsy. The electron microscopy study revealed abnormally swollen and dumb-bell shaped mitochondria. Based on the findings of mitochondrial changes it can be assumed that such changes are due to a mitochondrial mutation steered by an X-borne gene mutation. As a result and because the mitochondrial DNA is maternally inherited, the male zygote may not be implanted or it will proceed to an early embryonal death. The mitochondrial changes with the ensuing effects may be the basic cause of the syndrome.     

MITOCHONDRIA–RELATED ENCEPHALOMYOPATHIES

Owing to advances in morphological and biochemical techniques, the mitochondria-related myopathies and encephalomyopathies have emerged as a still rapidly growing group of primary and secondary metabolic disorders, which may extend from infancy to late adulthood. Impairment of the biochemically diversified mitochondria is reflected in an enormous number of deficiencies, often affecting several mitochondrial enzymes in the same patient; morphologically abnormal mitochondria are common and are thus not specific to individual mitochondrial enzyme deficiencies. Skeletal muscle biopsies have provided a wealth of data through histological and histochemical studies and from isolated mitochondria. As a similar abundance of biochemical and morphological findings has not been obtained from brain tissue in mitochondrial encephalomyopathies, investigation of these disorders is still in its infancy; interpretation of these conditions and their encephalopathic components has largely been based on comparison of data not derived from brain tissues. Therefore, it has been, and still is, largely the link between an encephalopathy and an associated mitochondrial myopathy that identifies the brain lesions as clinical and morphological expressions of a mitochondrial defect. As enzyme histochemical and electron microscopic investigations of mitochondrial encephalopathies have not yielded a comparable rich spectrum of morphological findings, it is conceivable that the spectrum of mitochondrial encephalopathies may be much larger than defined by the hitherto identified encephalomyopathies. This may be especially so when the myopathic component is of minor nosological significance.     

Should autistic children be evaluated for mitochondrial disorders?

Autism is etiologically heterogeneous; medical conditions are implicated in only a minority of cases, whereas metabolic disorders are even less common. Recently, there have been articles describing the association of autism with mitochondrial abnormalities. We critically review the current literature and conclude that mitochondrial disorders are probably a rare and insignificant cause of pure autism; however, evidence is accumulating that both autosomal recessive and maternally inherited mitochondrial disorders can present with autistic features. Most patients will present with multisystem abnormalities associated with autistic behavior. Finding biochemical or structural mitochondrial abnormalities in an autistic child does not necessarily imply a primary mitochondrial disorder but can also be secondary to technical inaccuracies or another genetic disorder. Clinicians should be careful in diagnosing a mitochondrial disorder in an autistic child because it has important implications for accurate genetic counseling, prognosis, and therapy.     

Cerebrovascular and mitochondrial abnormalities in Alzheimer’s disease: a brief overview

Multiple lines of evidence suggest that vascular alterations contribute to Alzheimer’s disease (AD) pathogenesis. It is also well established that mitochondrial abnormalities occur early in course of AD. Here, we give an overview of the vascular and mitochondrial abnormalities occurring in AD, including mitochondrial alterations in vascular endothelial cells within the brain, which is emerging as a common feature that bridges cerebral vasculature and mitochondrial metabolism.     

The calcium uniporter regulates the permeability transition pore in isolated cortical mitochondria

To investigate the influence of the mitochondrial calcium uniporter on the mitochondrial permeability transition pore, the present study observed mitochondrial morphology in cortical neurons isolated from adult rats using transmission electron microscopy, and confirmed the morphology and activity of isolated mitochondria by detecting succinic dehydrogenase and monoamine oxidase, two mitochondrial enzymes. Isolated mitochondria were treated with either ruthenium red, an inhibitor of the uniporter, spermine, an activator of the uniporter, or in combination with cyclosporin A, an inhibitor of the mitochondrial permeability transition pore. Results showed that ruthenium red inhibited CaCl2-induced mitochondrial permeability transition pore opening, spermine enhanced opening, and cyclosporin A attenuated the effects of spermine. Results demonstrated that the mitochondrial calcium uniporter plays a role in regulating the mitochondrial permeability transition pore in mitochondria isolated from the rat brain cortex.     

Is Parkinson's disease a mitochondrial disorder?

Parkinson's disease (PD) is a common degenerative disease, but its etiology is still unknown. However, since the discovery of MPTP, many investigators have been interested in the mitochondrial function in PD. We investigated mitochondrial functions in PD patients using the methods which have successfully been applied to mitochondrial myopathies (MM), i.e. assay of lactate and pyruvate, measurement of muscle mitochondrial respiratory enzyme activities and Southern blot analysis of muscle mitochondrial DNA. Parkinson's disease patients did not differ from controls in the mean blood and CSF (cerebrospinal fluid) lactate and pyruvate levels at the basal resting state or during an aerobic exercise. But mitochondrial complex I activity of the skeletal muscle was significantly decreased in PD. In the Southern blot analysis, we could not find major deletions or insertions of mitochondrial DNA in PD. Our studies disclosed a differential mitochondrial impairment between PD and MM. We discuss the implication of our observation.     

Mitochondrial DNA HV lineage increases the susceptibility to schizophrenia among Israeli Arabs

Haplotypes and haplogroups are linked sets of common DNA variants, acting as susceptibility or protective factors to complex disorders. Growing evidence suggests that dysfunction of mitochondrial bioenergetics contributes to the schizophrenia phenotype. We studied mitochondrial DNA haplogroups in schizophrenia patients. Since mitochondria are inherited from the mothers, we used healthy fathers as an ideal case-control group. Analysis of the distribution of mitochondrial haplogroups in schizophrenia patients compared to their healthy fathers (202 pairs) resulted in an over-representation of the mtDNA lineage cluster, HV, in the patients (p=0.01), with increased relative risk (odds ratio) of 1.8. Since mitochondrial DNA is small relative to nuclear DNA, a total mitochondrial genome analysis was possible in a hypothesis-free manner. However, mitochondrial DNA haplogroups are highly variable in human population and it will be necessary to replicate our results in other human ethnic groups.     

Leigh syndrome in an infant resulting from mitochondrial DNA depletion

Leigh syndrome is an encephalomyelopathy that results from a heterogeneous group of mitochondrial disorders characterized by symmetric brainstem spongioform lesions. An infant born with hypotonia and lactic acidosis was found to have symmetric brainstem lesions on T(2)-weighted magnetic resonance imaging consistent with Leigh syndrome. Muscle biopsy failed to reveal ragged-red fibers or cells devoid of cytochrome C oxidase or succinate dehyrogenase. Southern blot analysis of mitochondrial DNA isolated from the patient's quadriceps muscle indicated severe mitochondrial DNA depletion, which was suggested as the cause for the Leigh syndrome seen in this patient. Consideration of mitochondrial DNA depletion as an etiology when evaluating the patient with Leigh syndrome is encouraged.     

Amyloid-beta-induced mitochondrial dysfunction

As an important molecule in the pathogenesis of Alzheimer's disease (AD), amyloid-beta (Abeta) interferes with multiple aspects of mitochondrial function, including energy metabolism failure, production of reactive oxygen species (ROS) and permeability transition pore formation. Recent studies have demonstrated that Abeta progressively accumulates within mitochondrial matrix, providing a direct link to mitochondrial toxicity. Abeta-binding alcohol dehydrogenase (ABAD) is localized to the mitochondrial matrix and binds to mitochondrial Abeta. Interaction of ABAD with Abeta exaggerates Abeta-mediated mitochondrial and neuronal perturbation, leading to impaired synaptic function, and dysfunctional spatial learning/memory. Thus, blockade of ABAD/Abeta interaction may be a potential therapeutic strategy for AD.     

Zinc rescues dopaminergic SK-N-SH cell lines from methamphetamine-induced toxicity

Methamphetamine (METH) is a potent inducer of dopamine (DA) release, and is toxic to DA neurons. It has been reported that the formation of free radicals is an early signaling event that mediates cell death caused by METH. Currently, studies suggest that the generation of free radicals by oxidative catabolism of DA and dysfunction of the mitochondrial respiration chain are important mediators of neuronal death in Parkinson's disease (PD) and one process may counter the effect of the other. In our previous study, we investigated the deleterious effects of METH-induced reactive oxygen species (ROS) and mitochondrial dysfunction in dopaminergic SK-N-SH cells in culture, and assessed whether zinc-metallothionein induction provided mitochondrial protection against METH-induced mitochondrial dysfunction. Our present data demonstrate that METH enhances lipid peroxidation and mitochondrial manganese superoxide dismutase (MnSOD) enzyme levels, and decreases the antioxidant-reduced glutathione (GSH) together with an inhibition of mitochondrial complex-I activity. Pre-treatment with zinc markedly prevents the increase of lipid peroxidation and provides mitochondrial protection by scavenging free radicals via metallothionein and by increasing mitochondrial GSH and complex-I levels, thus rescuing SK-N-SH cells from METH toxicity. It should be emphasized that, however, it is still not clear that effects of METH on cultured SK-N-SH reliably model the effects of METH in the intact animal. Further studies in the intact animal are needed.     

Effects of Long-Term Rice Bran Extract Supplementation on Survival,Cognition and Brain Mitochondrial Function in Aged NMRI Mice

Aging represents a major risk factor for the development of neurodegenerative diseases like Alzheimer’s disease (AD). As mitochondrial dysfunction plays an important role in brain aging and occurs early in the development of AD, the prevention of mitochondrial dysfunction might help to slow brain aging and the development of neurodegenerative diseases. Rice bran extract (RBE) contains high concentrations of vitamin E congeners and γ-oryzanol. We have previously shown that RBE increased mitochondrial function and protected from mitochondrial dysfunction in vitro and in short-term in vivo feeding studies. To mimic the use of RBE as food additive, we have now investigated the effects of a long-term (6 months) feeding of RBE on survival, behavior and brain mitochondrial function in aged NMRI mice. RBE administration significantly increased survival and performance of aged NMRI mice in the passive avoidance and Y-maze test. Brain mitochondrial dysfunction found in aged mice was ameliorated after RBE administration. Furthermore, data from mRNA and protein expression studies revealed an up-regulation of mitochondrial proteins in RBE-fed mice, suggesting an increase in mitochondrial content which is mediated by a peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α)-dependent mechanism. Our findings suggest that a long-term treatment with a nutraceutical containing RBE could be useful for slowing down brain aging and thereby delaying or even preventing AD.     

The aerobic forearm exercise test, a non-invasive tool to screen for mitochondrial disorders

The diagnosis of a mitochondrial disorder is often difficult. Therefore, new approaches and diagnostic criteria are being developed. One of these tests is the aerobic forearm exercise test, a screening tool that can contribute to assess whether or not the patient suffers from a mitochondrial myopathy. With this simple, non-invasive test, the oxidative metabolism of muscle can be evaluated in rest and during exercise. We performed the aerobic forearm exercise test in patients with a mitochondrial disorder and an identified pathogenic gene mutation, in patients with a suspected mitochondrial disorder based on their clinical presentation and biochemical results, but without a molecular diagnosis, and in patients with atypical fatigue and no characteristics of a mitochondrial myopathy. In the first two groups, abnormal oxygen extraction from the blood during exercise was observed in four out of twelve patients. In the third group no abnormalities were found. The number of patients that we could test so far was limited, but all the patients experienced the aerobic forearm exercise as an easy test. We would like to stimulate clinicians to perform this test whenever a mitochondrial myopathy is suspected, as it can be a valuable diagnostic screening tool.     

Novel homozygous TSFM pathogenic variant associated with encephalocardiomyopathy with sensorineural hearing loss and peculiar neuroradiologic findings

neurogenetics - TSFM is a nuclear gene encoding the elongation factor Ts (EFTs), an essential component of mitochondrial translational machinery. Impaired mitochondrial translation is responsible...     

Blockade of the mitochondrial permeability transition pore diminishes infarct size in the rat after transient middle cerebral artery occlusion.

The mitochondrial permeability transition pore is an inducer of cell death. During the reperfusion phase after cerebral ischemia, calcium accumulates in mitochondria, and a burst of free radical formation occurs, conditions that favor the activation of the mitochondrial permeability transition pore. Here the authors demonstrate that a blocker of the mitochondrial permeability transition pore, the nonimmunosuppressive cyclosporin A analogue N-methyl-Val-4-cyclosporin A (10 mg/kg intraperitoneally), administered during reperfusion and at 24 hours of reperfusion, diminishes infarct size in a rat model of transient focal ischemia of 2 hours' duration. The mitochondrial permeability transition pore may be an important target for drugs against stroke.     

Regional and cellular distribution of mitochondrial ferritin in the mouse brain

Iron and mitochondrial dysfunction are important in many neurodegenerative diseases. Several iron transport proteins have been identified that are associated with mitochondria, most recently mitochondrial ferritin. Here we describe the cellular distribution of mitochondrial ferritin in multiple regions of the brain in C57/BL6 mice. Mitochondrial ferritin was found in all regions of the brain, although staining intensity varied between regions. Mitochondrial ferritin was detected throughout the layers of cerebral cortex and in the cerebellum, hippocampus, striatum, choroid plexus, and ependymal cells. The cell type in the brain that stains most prominently for mitochondrial ferritin is neuronal, but oligodendrocytes also stain strongly in both gray matter and in white matter tracts. Mice deficient in H‐ferritin do not differ in the mitochondrial ferritin staining pattern or intensity compared with C57/BL6 mice, suggesting that there is no compensatory expression of these proteins. In addition, by using inbred mouse strains with differing levels of iron content, we have shown that regional brain iron content does not affect expression of mitochondria ferritin. The expression of mitochondria ferritin appears to be more influenced by mitochondrial density. Indeed, at an intracellular level, mitochondrial ferritin immunoreaction product is strongest where mitochondrial density is high, as seen in the ependymal cells. Given the importance and relationship between iron and mitochondrial activity, understanding the role of mitochondrial ferritin can be expected to contribute to our knowledge of mitochondrial dysfunction and neurodegenerative disease. © 2010 Wiley‐Liss, Inc.     

A Novel Method for Analyzing Mitochondrial Movement: Inhibition by Paclitaxel in a Pheochromocytoma Cell Model

A method was developed to assess mitochondrial movement in the living cell that is dependent, in part, on microtubule and/or associating protein interactions. The leader sequence from cytochrome-c was used to drive DsRed2 fluorescent proteins to accumulate in the mitochondria, thus enabling to follow mitochondrial (cytochrome-c’s) movement. For calculating the percentage of mitochondrial movement, an image-processing program was used (ImageJ). Paclitaxel, an antitumor agent, is a potent microtubule-stabilizing agent that increases the stability of tubulin polymers, inhibiting mitosis and mitochondrial activity in dividing cells. Here, we tested whether paclitaxel inhibits mitochondrial movement in pheochromocytoma cells (a neuronal model, when tested in a differentiated state). While a 2-day exposure to paclitaxel resulted in cellular toxicity (measured as inhibition of mitochondrial activity), 2–3 h exposure to paclitaxel were sufficient to inhibit mitochondrial movement as assessed in 10–20-s imaging sessions in living cells. Mitotracker deep-red staining validated the staining obtained with DsRed2-cytochrome-c and identified intact mitochondria. Results showed a significant paclitaxel dose-dependent inhibition of mitochondrial movement. This new method should enable further assessment of microtubule-interacting drugs and other cytoskeletal components for their potential influence of mitochondrial movement as a test for activity and side effects.