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PubMed1978

Spin-label study of the relation between enzymatic activity and lipid-protein organization in reconstituted cytochrome c oxidase.

Lipid-depleted cytochrome c oxidase (EC 1.9.3.1) containing less than 20 microgram lipids per milligram protein was reconstituted with pure phospholipids of well-defined chemical structure and fatty acid composition without using detergents and (or) sonication. For the maximal restoration of electron transport activity, lipid-depleted cytochrome c oxidase required acidic phospholipds such as phosphatidylglycerol or phosphatidylserine or lysophospholipids such as lysophosphatidylcholine or lysophosphatidic acid, but no specific phospholipid fatty acid composition was necessary. The organization of the lipid environment of the reconstituted cytochrome c oxidase, having a well-defined lipid composition, morphology, and a high specific activity, was examined by electron spin resonance spectroscopy using 2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxyl (16-doxyl stearic acid) and 16-doxyl stearic acid - containing phosphatidylglycerol. The presence of boundary lipid was established in both lamellar and micellar organizations of reconstituted cytochrome c oxidase and was not necessarily related to the enzymatic activity of the complex. Our results have established that aside from structural considerations, the boundary lipid, at least in the reconstituted cytochrome c oxidase, is a necessary but not sufficient condition for the enzymatic expression of cytochrome c oxidase.

Animals↗
PubMed1977

Degradation of mitochondria by cytosolic factors in reticulocytes.

The degradation process of mitochondria in rabbit reticulocytes proceeds predominately directly in the cytosol rather than in secondary lysosomes as judged by electronmicroscopy. At least five cytosolic protein factors are present in reticulocytes, which could be related to the degradation of mitochondria: the two inhibitory proteins of the respiratory chain RF and RC and three enzymes which cause a lysis of mitochondria in vitro (lipoxygenase, proteinase, phospholipase A). The properties of these factors are the subject of this paper. A hypothetic scheme of the degradation of mitochondria in reticulocytes is proposed. The degradation of mitochondria in reticulocytes is viewed as a complex interplay of various cytosolic factors and the functional state of the mitochondrial membranes. The lipoxygenase damages the membranes and triggers the penetration of the respiratory inhibitors. In this manner, a catastrophic cycle is initiated which leads to the complete breakdown of the mitochondria.

5-Aminolevulinate Synthetase↗
PubMed1989

Increased cytochrome oxidase activity in the diabetic rat retinal pigment epithelium.

We have investigated the effects of diabetes on retinal oxidative metabolism. Since activity of the mitochondrial enzyme, cytochrome oxidase, has been demonstrated to be a reliable indicator of oxidative metabolism and physiological activity, we used cytochemical techniques to study the activity of this enzyme in spontaneously diabetic, streptozotocin-diabetic, and control rat retinas. Light microscope results showed an increase in staining for cytochrome oxidase activity in the diabetic RPE cell layer as compared with the control. Quantitative electron microscope analysis showed a significant increase in RPE cells with highly reactive mitochondria as compared with the controls. Mitochondrial staining within the diabetic photoreceptor and retinal vascular endothelial cells was normal. RPE cell volume and surface area, as well as number and volume of mitochondria, were unchanged. This increase in oxidative enzyme activity is further evidence of RPE cell alteration in diabetes.

Animals↗
PubMed1993

The occurrence of mitochondrial variations including large mitochondria in osteoclasts following calcitonin treatment.

Calcitonin-treated osteoclasts with mitochondrial variations, including large mitochondria, and osteoclasts not treated with calcitonin (control osteoclasts) were examined using cytochrome c oxidase activity and morphological analysis of mitochondria. The calcitonin-treated osteoclasts were divided into two types. One was osteoclasts with only a clear zone, which contained many type 1 mitochondria with the reaction products of cytochrome c oxidase in both the inner membrane of the cristae and the outer compartment in the vascular side and a comparatively small number of type 1 mitochondria in the resorptive side. The other type was osteoclasts with a mature ruffled border, in which many type 1 mitochondria were observed in both sides. Most of the large mitochondria were type 1, and these were observed only in the vascular side of the osteoclasts with only a clear zone, and in both sides of the osteoclasts with a mature ruffled border. In statistical analysis, the cross-sectional area of mitochondria in the vascular side of calcitonin-treated osteoclasts was larger than that of those in the resorptive side, and the numerical percentage of type 1 mitochondria in the vascular side was greater than that in the resorptive side. In contrast, the cross-sectional area of mitochondria in the vascular side of control osteoclasts was smaller than that in the resorptive side, and there was no significant difference between the two groups in the numerical percentage of type 1 mitochondria.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2004

Cytochrome c oxidase subunit IV as a marker of protein kinase Cepsilon function in neonatal cardiac myocytes: implications for cytochrome c oxidase activity.

We have previously demonstrated that low concentrations of phorbol esters stimulate the selective translocation of protein kinase C (PKC) alpha and epsilon from the cell soluble to the particulate fraction in NCMs (neonatal rat cardiac myocytes). We therefore determined if the in vitro phosphorylation of substrates in these fractions could be used as assays of PKCalpha or epsilon activation. Intact cell phorbol ester treatment caused a decline in the in vitro (32)P-incorporation into several proteins in the cell-soluble fraction. These declines occurred in the presence or absence of in vitro Ca(2+) and probably reflected the exit of PKC isoenzymes from the soluble fraction. In contrast, an approx. 18 kDa protein incorporated (32)P in particulate fractions isolated from 4beta-PMA-treated cells in a Ca(2+)-independent manner. Proteomic and immunoprecipitation analyses indicated that the protein is subunit IV of the cytochrome c oxidase complex (COIV). In vitro phosphorylation of COIV was attenuated by PKC pseudosubstrate peptides. Introduction of an PKCepsilon-selective translocation inhibitor [Johnson, Gray, Chen and Mochly-Rosen (1996) J. Biol. Chem. 271, 24962-24966] into NCMs before 4beta-PMA treatments also attenuated the in vitro phosphorylation of COIV. In mitochondrial extracts from 4beta-PMA-treated NCMs, the PKCepsilon isoenzyme coimmunoprecipitated with COIV, and cytochrome c oxidase activity was enhanced 2-fold. The in vitro phosphorylation of COIV reflects a novel approach for monitoring PKCepsilon function in NCMs. Furthermore, PKCepsilon probably interacts with COIV in NCM mitochondria to enhance electron-transport chain complex IV activity.

Animals↗
PubMed1996

Multiple mitochondrial DNA deletions in sporadic inclusion body myositis: a study of 56 patients.

Inclusion body myositis, a chronic inflammatory disorder, is the most common cause of myopathy in adults over the age of 50. Diagnosis is based on clinical features and distinctive morphological findings by both light and electron microscopy. The causes of inclusion body myositis are still unknown. Ultrastructural mitochondrial changes and ragged-red fibers are common in patients with sporadic inclusion body myositis, and multiple [correction of mutiple] mitochondrial DNA (mtDNA) deletions have been reported in 3 such patients, suggesting that mtDNA mutations may have a pathogenetic role. We studied 56 patients with sporadic inclusion body myositis, using a combination of clinical, morphological, biochemical, and molecular genetic analyses to determine the frequency and the distribution of mtDNA deletions. Using the polymerase chain reaction, we found multiple mtDNA deletions in 73% of patients, compared to 40% of normal age-matched control subjects and 47% of disease control subjects. The presence of deletions correlated with morphological evidence of ragged-red, cytochrome c oxidase-negative fibers, and with defects of complexes I and IV of the electron transport chain. Although aging may account for a proportion of mtDNA deletions in patients with sporadic inclusion body myositis and control subjects, mtDNA alterations may be accelerated in sporadic inclusion body myositis.

Adult↗
PubMed1991

Immunohistochemical studies on complexes I, II, III, and IV of mitochondria in Parkinson's disease.

We examined the substantia nigra of 8 patients with Parkinson's disease immunohistochemically using antisera against complexes I, II, III, and IV of the mitochondrial electron transport system. In the patients with Parkinson's disease, a fair proportion of the nigral neurons showed reduced staining against the complex I antibody. The proportion of the neurons with reduced staining ranged from 12.7 to 74.1% of the melanized nigral neurons. Although neurons with reduced immunostaining for complex I were also observed in control subjects, the proportion among the nigral neurons was significantly smaller than in parkinsonian patients. Staining for complexes III and IV appeared normal. Staining of substantia nigra for complex II was decreased in 3 parkinsonian patients. These results are consistent with our findings that there is a deletion of gene coding for the four subunits in the mitochondrial DNA located in the striata of parkinsonian patients.

Adult↗
PubMed1996

MPP(+)-induced neurotoxicity in mouse is age-dependent: evidenced by the selective inhibition of complexes of electron transport.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), has been demonstrated to cause selective neurotoxicity by inhibiting complex I in mitochondria, through its toxic metabolite 1-methyl-4-phenylpyridine (MPP+) which is formed during the bioactivation of MPTP by monoamine oxidase B. In this report, we have evaluated the effect of MPP+ on the 4 mitochondrial respiratory chain complexes by incubating brain mitochondria of mice at 3 different age groups with MPP+ (200 microM) and monitoring enzyme activities of complexes I, II, III, and IV at 5, 10, 15, 30, 60, and 120 min. Complexes I, III, and IV showed significant inhibition within 15 min in all the age groups studied, followed by some recovery in enzyme activities upon further incubation for complexes I and IV. However, complex II was not affected by MPP+ at any age. Our data suggest that inhibition of complexes I, III, and IV by MPP+ efficiently restrict the transport of electrons down the respiratory chain which ultimately leads to decreased ATP production. This could further aggravate oxidative stress as ATP is required for the synthesis of glutathione (GSH), one of the important scavengers of free radicals. In this study, inhibition was more severe in mitochondrial preparations from older rather than younger mice. Additionally, young animals showed faster recovery following inhibition than old animals for complex I. Impaired respiratory chain function in older animals compared to younger ones supports the hypothesis of accumulation of age-related mitochondrial DNA mutations which partly encode for subunits of complexes I, III, and IV. From this study, it seems that inhibition of complexes I, III, and IV may be the underlying cause of neurotoxicity due to MPP+ which could be intensified by age-associated dysfunction of electron transport.

1-Methyl-4-phenylpyridinium↗
PubMed2001

Disruption of mitochondrial respiration by melatonin in MCF-7 cells.

Clinical and laboratory studies have provided evidence of oncostatic activity by the pineal neurohormone melatonin. However, these studies have not elucidated its mechanism of action. The following series of MCF-7 breast tumor cell studies conducted in the absence of exogenous steroid hormones provide evidence for a novel mechanism of oncostatic activity by this endogenous hormone. We observed a 40--60% loss of MCF-7 cells after 20-h treatment with 100 nM melatonin, which confirmed and extended previous reports of its oncostatic potency. Interestingly, there were no observed changes in tritiated thymidine uptake, suggesting a lack of effect on cell cycle/nascent DNA synthesis. Further evidence of a cytocidal effect came from morphologic observations of acute cell death and autophagocytosis accompanied by degenerative changes in mitochondria. Studies of mitochondrial function via standard polarography revealed a significant increase in oxygen consumption in melatonin-treated MCF-7 cells. Enzyme-substrate studies of electron transport chain (complex IV) activity in detergent permeabilized cells demonstrated a concomitant 53% increase (p < 0.01) in cytochrome c oxidase activity. Additional studies of succinate dehydrogenase activity (complex II) as determined by reduction of (3-4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide demonstrated a significant increase (p < 0.05) in melatonin-treated cells and further confirmed the accelerated ET activity. Finally, there was a 64% decrease (p < 0.05) in cellular ATP levels in melatonin-treated cells. The G-protein-coupled melatonin receptor antagonist luzindole abrogated the cytotoxic and mitochondrial effects. These studies suggest a receptor-modulated pathway of cytotoxicity in melatonin-treated MCF-7 tumor cells with apparent uncoupling of oxidative phosphorylation.

Adenocarcinoma↗
PubMed1970

Promitochondria of anaerobically grown yeast. IV. Conversion into respiring mitochondria.

Promitochondria of anaerobically grown Saccharomyces cerevisiae were selectively labeled in vivo by incubating the cells with [(3)H]leucine and cycloheximide. When the labeled cells were washed free of cycloheximide and adapted to oxygen in the presence of unlabeled leucine, the respiring mitochondria formed during adaptation proved to be radioactive. In contrast, only insignificant label was found in iso-1-cytochrome c which is synthesized de novo during adaptation. Respiratory adaptation of anaerobically grown yeast thus involves differentiation of promitochondrial organelles.

Adenosine Triphosphatases↗
PubMed1984

Local cytochrome oxidase activity in the cerebral cortex of the rat, histochemically detected with the DAB-method: a micro-densitometric and electron microscope study.

For demonstration of the local cytochrome oxidase activity, coronal sections through the frontal cortex of four Sprague-Dawley rats were incubated with DAB medium after Seligman et al. (1968). The pattern of distribution of the DAB reaction product (DAB-RP) was measured at a wavelength of 460 nm. Cryostat sections were scanned with a microdensitometer. The cytochrome reaction product was accumulated in the laminae I and IV. A comparative morphometric study of mitochondrial profiles in ultra-thin sections through equivalent cortical regions showed an approximately similar distribution in percentage of areal density of the mitochondria labeled by DAB-RP. On average 30% of the mitochondrial profiles were labeled with DAB-RP which was localized in the intracristate spaces and the outer mitochondrial compartment. The marked mitochondria mainly occurred in dendrites. Furthermore, the mean and median value of the size distribution of marked mitochondrial profiles was shifted to greater values when compared with non-marked ones.

3,3'-Diaminobenzidine↗