Currently, the incidence of Parkinson's disease (PD) is on the rise. More and more evidences suggest that mitochondrial dysfunction plays a crucial role in the etiology of PD, and dysfunction of mitochondrial complex I (MCI) is one of the most critical factors leading to mitochondrial dysfunction. On one hand, MCI dysfunction stimulates dopaminergic neurons to produce reactive oxygen species (ROS). On the other hand, MCI dysfunction decreases dopaminergic neuron viability and reduces ATP production. All these outcomes promote the pathological progression of PD. This review summarizes research progress on the role of MCI in the pathogenesis of PD, as well as PD treatment strategies based on MCI.
Parkinson Disease/metabolism* ; Humans ; Electron Transport Complex I/metabolism* ; Mitochondria/physiology* ; Reactive Oxygen Species/metabolism* ; Dopaminergic Neurons/metabolism* ; Animals ; Adenosine Triphosphate/metabolism*

Recent studies indicate that mitochondria are an important source of reactive oxygen species (ROS) in the spinal dorsal horn. In our previous study, application of malate, a mitochondrial electron transport complex I substrate, induced a membrane depolarization, which was inhibited by pretreatment with ROS scavengers. In the present study, we used patch clamp recording in the substantia geletinosa (SG) neurons of spinal slices, to investigate the cellular mechanism of mitochondrial ROS on neuronal excitability. DNQX (an AMPA receptor antagonist) and AP5 (an NMDA receptor antagonist) decreased the malate-induced depolarization. In an external calcium free solution and addition of tetrodotoxin (TTX) for blockade of synaptic transmission, the malateinduced depolarization remained unchanged. In the presence of DNQX, AP5 and AP3 (a group I metabotropic glutamate receptor (mGluR) antagonist), glutamate depolarized the membrane potential, which was suppressed by PBN. However, oligomycin (a mitochondrial ATP synthase inhibitor) or PPADS (a P2 receptor inhibitor) did not affect the substrates-induced depolarization. These results suggest that mitochondrial substrate-induced ROS in SG neuron directly acts on the postsynaptic neuron, therefore increasing the ion influx via glutamate receptors.
Animals ; Calcium ; Electron Transport Complex I ; Glutamic Acid ; Membrane Potentials ; Membranes ; Mitochondria ; Mitochondrial Proton-Translocating ATPases ; N-Methylaspartate ; Neurons* ; Oligomycins ; Rats* ; Reactive Oxygen Species ; Receptors, AMPA ; Receptors, Glutamate ; Receptors, Metabotropic Glutamate ; Spinal Cord Dorsal Horn ; Substantia Gelatinosa* ; Synaptic Transmission ; Tetrodotoxin

Mitochondrial respiratory chain deficiency is a common cause of mitochondrial disease in children. This study aimed to review the clinical, enzymatic and genetic characteristics of a Chinese boy with progressive intrahepatic cholestasis due to mitochondrial respiratory chain complex I deficiency. The boy developed diarrhea from the age of 13 months, followed by progressive body weight loss, jaundice and weakness. His urine organic acids, blood amino acids and acylcarnitines profiles were normal. Mitochondrial respiratory chain complexes I to V activities in peripheral leukocytes were measured using spectrophotometric assay. Complex I activity was reduced. 5821G>A mutation was indentified by gene sequencing on tRNA-cys of mitochondrial gene in the patient and his mother. Vitamin supplements, liver protection, antibiotics and plasma infusion were not effective in the patient. Unfortunately, the boy died at the age of 17 months. Mitochondrial respiratory chain complex I deficiency is the most common mitochondrial respiratory chain disorder. This was the first case of intrahepatic cholestasis due to complex I deficiency confirmed by mitochondrial respiratory chain enzyme activity assay and gene analysis in China. It was concluded that mitochondrial hepatopathy is one of major causes of metabolic hepatopathy. Biochemical assay, mitochondrial respiratory chain complex activities assay and genetic analysis are crucial for the etiological diagnosis of metabolic hepatopathy.
Cholestasis, Intrahepatic ; diagnosis ; etiology ; Diagnosis, Differential ; Electron Transport Complex I ; deficiency ; Humans ; Infant ; Male ; Mitochondrial Diseases ; complications

This study reviews a case of mitochondrial respiratory chain complex I deficiency due to the 10191T>C mutation in mitochondrial ND3 gene. The previously healthy boy progressively presented with blepharoptosis, weakness, epilepsy and motor regression at age 6 years. Elevated blood lactate and pyruvate were observed. Brain magnetic resonance imaging showed symmetrical lesions in the basal ganglia. Leigh syndrome was thus confirmed. The protein from the mitochondria and genomic DNA of the boy and his parents was collected from peripheral blood leucocytes for the activity test for mitochondrial complex I to V and genetic analysis. The results showed the activity of complex I (33.1 nmol /min in 1 milligram mitochondrial protein) was lower than normal reference value (44.0±5.4 nmol /min in 1 milligram mitochondrial protein). The ratio of complex I to citrate synthase (19.8%) was also lower than normal reference value (48%±11%). The activities of complexes II to V were normal. 10191T>C mutation in ND3 gene of mitochondria was identified in the boy. 10191T>C mutation and complex I deficiency were not detected in his parents. At present, he is 16 years old, and of normal intelligence with spastic paralysis in both lower extremities after treatment. It is concluded that a Chinese boy with isolated complex I deficiency due to 10191T>C mutation in ND3 gene was firstly diagnosed by peripheral leukocytes mitochondrial respiratory chain enzyme assay and gene analysis. This study can provide clinical data for the nosogenesis of Leigh syndrome.
Adolescent ; Brain ; pathology ; Electron Transport Complex I ; deficiency ; genetics ; Humans ; Leigh Disease ; genetics ; Magnetic Resonance Imaging ; Male ; Mitochondrial Diseases ; genetics ; Mutation

The present study was aimed to investigate the effect of hypoxic training on mitochondrial antioxidants and activities of respiratory chain complexes in mitochondria of skeletal muscle in rats. Forty healthy male Wistar rats were randomized to 5 groups (n=8): living low-training low (LoLo), living high-training high (HiHi), living high-training low (HiLo), living low-training high (LoHi), and living high-exercise high-training low (HiHiLo). All the animals were subjected to 5-week training in normoxic (atmospheric pressure=632 mmHg, altitude of about 1 500 m) or hypoxic environment (atmospheric pressure=493 mmHg, simulated altitude of about 3 500 m). Before exhaustive running, the animals stayed in normoxia for 3 d. Skeletal muscles were prepared immediately after exhaustive running. Muscle mitochondria were extracted by differential centrifugation. Spectrophotometric analysis was used to evaluate activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), malondialdehyde (MDA) level and respiratory chain complex (C) I-III activities in muscle homogenate and mitochondria. Results showed that SOD, GSH-Px, CAT activities and MDA level in skeletal muscle homogenate in HiHi and HiHiLo groups were significantly increased (P<0.05 or P<0.01) compared with those in LoLo group. Muscle mitochondrial MDA level in HiHi and HiHiLo groups was significantly lower (P<0.01), while activities of SOD, GSH-Px and CAT were remarkably higher (P<0.01) than those in LoLo group. Meanwhile, C I-III activities in HiHi and HiHiLo groups were increased significantly (P<0.01), and C II activity in HiLo group also was increased remarkably (P<0.01) compared with those in LoLo group. These results suggest that HiHiLo might be an ideal hypoxic training mode.
Adaptation, Physiological ; physiology ; Altitude ; Animals ; Antioxidants ; metabolism ; Electron Transport Complex I ; metabolism ; Glutathione Peroxidase ; metabolism ; Hypoxia ; metabolism ; physiopathology ; Male ; Mitochondria, Muscle ; metabolism ; Muscle, Skeletal ; metabolism ; physiology ; Physical Exertion ; physiology ; Rats ; Rats, Wistar ; Superoxide Dismutase ; metabolism

OBJECTIVETo study the clinical and enzymological characteristics of the children with mitochondrial respiratory chain complex III deficiency.

METHODThe clinical manifestations of five patients (3 males, 2 females) were summarized. Spectrophotometric assay was used for the analysis of respiratory chain complex I to V enzyme activity in peripheral blood leukocytes, after obtaining venous blood.

RESULT(1) Five patients were hospitalized at the age of 1 month to 15 years. Three patients had Leigh syndrome with progressive motor developmental delay or regression and weakness. One had severe liver damage and intrahepatic cholestasis. One presented muscle weakness. (2) Deficient complex I + III activity was identified in five patients. Their complex I + III activities in peripheral blood leukocytes were 3.0 to 14.2 nmol/min per mg mitochondrial protein (control: 84.4 ± 28.5 nmol/min per mg mitochondrial protein). The ratio of complex I + III to citrate synthase decreased to 3.5 to 22.9% (normal control 66.1 ± 14.7%). The activities of complex III decreased to 10.4 to 49.3% of the lowest control value, while complex I, II, IV and V activities were normal. The results supported the diagnosis of isolated respiratory chain complex III deficiency.

CONCLUSIONComplex III deficiency is a kind of disorder of energy metabolism with various manifestations. The complex I + III activities and the ratio of complex I + III to citrate synthase were lower than those of the control. The activities of complex I, II, IV and V were normal.

Adolescent ; Child ; Child, Preschool ; Electron Transport Complex I ; metabolism ; Electron Transport Complex II ; metabolism ; Electron Transport Complex III ; metabolism ; Female ; Humans ; Infant ; Leigh Disease ; Leukocytes, Mononuclear ; enzymology ; Male ; Mitochondrial Diseases ; diagnosis ; metabolism ; physiopathology

Fenazaquin (4-[[4 (1,1-dimethylethyl) pheynyl]ethoxy]quinazoline) is an insecticide that inhibits NADH ubiquinone oxidoreductase of the mitochondria, which is also known as complex I. An 83 year old female was brought to our emergency department (ED) having been found collapsed and unconscious at home by her family. She had ingested up to 100 ml from a bottle of 20% fenazaquin solution. In the ED, she showed severe persistent lactic acidosis despite a seemingly stable hemodynamic condition. Despite intensive supportive management, including positive pressure ventilation, packed red cell transfusion, hemodialysis, and intravenous N-acetylcysteine administration, the lactic acidosis did not respond. To our knowledge, this is the first report of fenazaquin poisoning in humans. No antidote for fenazaquin is known. In this case report, we discuss clinical characteristics and possible pathophysiologic mechanism of fenazaquin poisoning with a literature review.
Acetylcysteine ; Acidosis, Lactic ; Electron Transport Complex I ; Emergencies ; Female ; Hemodynamics ; Humans ; Mitochondria ; Positive-Pressure Respiration ; Quinazolines ; Renal Dialysis ; Unconscious (Psychology)

OBJECTIVETo report a Chinese Han family with two patients of Leigh syndrome (LS) and to scan the mutation in mitochondrial DNA(mtDNA).

METHODSThe clinical features and the laboratory findings were summarized. Mitochondrial DNA chip and direct sequencing were performed to detect the mutation in entire mtDNA.

RESULTSFailure of thrive, psychomotor retardation, hypotonia and weakness, cerebellar ataxia, and seizure were the main manifestations of the family. Brain magnetic resonance imaging (MRI) showed lesions at midbrain, periaqueductal gray matter, dentate nuclei of cerebellar and thalami. The levels of lactic acid and pyruvate were mildly abnormal. The mutation of ND5*13513 G to A was identified in the LS family.

CONCLUSIONPatients with ND5*13513 G to A mutation may have a characteristic clinical course and ND5 *13513 G to A might be a preferential candidate mutation of Leigh syndrome.

Base Sequence ; Child, Preschool ; DNA, Mitochondrial ; genetics ; Electron Transport Complex I ; genetics ; Female ; Humans ; Infant ; Leigh Disease ; diagnostic imaging ; genetics ; pathology ; physiopathology ; Magnetic Resonance Imaging ; Male ; Mitochondrial Proteins ; genetics ; Polymorphism, Single Nucleotide ; genetics ; Tomography, X-Ray Computed

Leigh syndrome is a genetically heterogeneous disease caused by defects in enzymes involved in aerobic energy metabolism and the Krebs', cycle. Mitonchondrial complex I deficiency is a main cause of Leigh syndrome. In this study, a Chinese child with Leigh syndrome caused by 13513G>A mutation was reported. The proband was the first child of his parents. The previously healthy boy presented with generalized epilepsy at 12 years of age. When he visited Peking University First Hospital at 13 years of age, he had subacute loss of vision in two eyes and temporal defect of visual field in the left eye. He walked with a spastic gait. His blood lactate and pyruvate levels were elevated. Muscle biopsy showed mild lipid accumulation in muscle fiber. An electrocardiogram showed incomplete right bundle branch block. Brain magnetic resonance imaging showed bilateral, symmetrical lesions in the basal ganglia, supporting the diagnosis of Leigh syndrome. 13513G>A mutation was identified by gene analysis in the patient, which led to mitochondrial respiratory chain complex I deficiency. Multivitamins and L-carnitine were administered. At present, the patient is 16 years old and has progressive deterioration with significant muscle weakness and body weight loss. He is absent from school. He has no obvious retardation in intelligence. 13513G>A mutation was first identified by gene analysis in Chinese population with Leigh syndrome. This may be helpful in genetic counseling.
Adolescent ; DNA, Mitochondrial ; genetics ; Electron Transport Complex I ; deficiency ; Humans ; Leigh Disease ; genetics ; Male ; Mutation

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a genetically heterogeneous mitochondrial disorder with variable clinical symptoms. Here, from the sequencing of the entire mitochondrial genome, we report a Korean MELAS family harboring two homoplasmic missense mutations, which were reported 9957T>C (Phe251Leu) transition mutation in the cytochrome c oxidase subunit 3 (COX3) gene and a novel 13849A>C (Asn505His) transversion mutation in the NADH dehydrogenase subunit 5 (ND5) gene. Neither of these mutations was found in 205 normal controls. Both mutations were identified from the proband and his mother, but not his father. The patients showed cataract symptom in addition to MELAS phenotype. We believe that the 9957T>C mutation is pathogenic, however, the 13849A>C mutation is of unclear significance. It is likely that the 13849A>C mutation might function as the secondary mutation which increase the expressivity of overlapping phenotypes of MELAS and cataract. This study also demonstrates the importance of full sequencing of mtDNA for the molecular genetic understanding of mitochondrial disorders.
Adult ; Asian Continental Ancestry Group ; DNA Mutational Analysis ; DNA, Mitochondrial/analysis/*genetics ; Electron Transport Complex I/*genetics ; Electron Transport Complex IV/*genetics ; Female ; Humans ; Korea ; MELAS Syndrome/*genetics ; Male ; Middle Aged ; Mitochondrial Proteins/*genetics ; *Mutation, Missense ; Pedigree ; Polymorphism, Genetic