0
selected
-
1.
Structural comparison of yeast and human intra-mitochondrial lipid transport systems.
Miliara, X, Matthews, S
Biochemical Society transactions. 2016;(2):479-85
Abstract
Mitochondria depend on a tightly regulated supply of phospholipids. The protein of relevant evolutionary and lymphoid interest (PRELI)/Ups1 family together with its mitochondrial chaperones [TP53-regulated inhibitor of apoptosis 1 (TRIAP1)/Mdm35] represents a unique heterodimeric lipid-transfer system that is evolutionary conserved from yeast to man. Recent X-ray crystal structures of the human and yeast systems are compared and discuss here and shed new insight into the mechanism of the PRELI/Ups1 system.
-
2.
Platelet mitochondrial dysfunction in critically ill patients: comparison between sepsis and cardiogenic shock.
Protti, A, Fortunato, F, Artoni, A, Lecchi, A, Motta, G, Mistraletti, G, Novembrino, C, Comi, GP, Gattinoni, L
Critical care (London, England). 2015;(1):39
Abstract
INTRODUCTION Platelet mitochondrial respiratory chain enzymes (that produce energy) are variably inhibited during human sepsis. Whether these changes occur even during other acute critical illness or are associated with impaired platelet aggregation and secretion (that consume energy) is not known. The aims of this study were firstly to compare platelet mitochondrial respiratory chain enzymes activity between patients with sepsis and those with cardiogenic shock, and secondly to study the relationship between platelet mitochondrial respiratory chain enzymes activity and platelet responsiveness to (exogenous) agonists in patients with sepsis. METHODS This was a prospective, observational, case-control study. Platelets were isolated from venous blood of 16 patients with severe sepsis or septic shock (free from antiplatelet drugs) and 16 others with cardiogenic shock, within 48 hours from admission to Intensive Care. Platelet mitochondrial respiratory chain enzymes activity was measured with spectrophotometry and expressed relative to citrate synthase activity, a marker of mitochondrial density. Platelet aggregation and secretion in response to adenosine di-phosphate (ADP), collagen, U46619 and thrombin receptor activating peptide were measured with lumiaggregometry only in patients with sepsis. In total, 16 healthy volunteers acted as controls for both spectrophotometry and lumiaggregometry. RESULTS Platelets of patients with sepsis or cardiogenic shock similarly had lower mitochondrial nicotinamide adenine dinucleotide dehydrogenase (NADH) (P < 0.001), complex I (P = 0.006), complex I and III (P < 0.001) and complex IV (P < 0.001) activity than those of controls. Platelets of patients with sepsis were generally hypo-responsive to exogenous agonists, both in terms of maximal aggregation (P < 0.001) and secretion (P < 0.05). Lower mitochondrial NADH (R (2) 0.36; P < 0.001), complex I (R (2) 0.38; P < 0.001), complex I and III (R (2) 0.27; P = 0.002) and complex IV (R (2) 0.43; P < 0.001) activity was associated with lower first wave of aggregation with ADP. CONCLUSIONS Several platelet mitochondrial respiratory chain enzymes are similarly inhibited during human sepsis and cardiogenic shock. In patients with sepsis, mitochondrial dysfunction is associated with general platelet hypo-responsiveness to exogenous agonists. TRIAL REGISTRATION ClinicalTrials.gov NCT00541827 . Registered 8 October 2007.
-
3.
Methods to monitor and compare mitochondrial and glycolytic ATP production.
Patergnani, S, Baldassari, F, De Marchi, E, Karkucinska-Wieckowska, A, Wieckowski, MR, Pinton, P
Methods in enzymology. 2014;:313-32
Abstract
ATP is commonly considered as the main energy unit of the cell and participates in a variety of cellular processes. Thus, intracellular ATP concentrations rapidly vary in response to a wide variety of stimuli, including nutrients, hormones, cytotoxic agents, and hypoxia. Such alterations not necessarily affect cytosolic and mitochondrial ATP to similar extents. From an oncological perspective, this is particularly relevant in the course of tumor progression as well as in the response of cancer cells to therapy. In normal cells, mitochondrial oxidative phosphorylation (OXPHOS) is the predominant source of ATP. Conversely, many cancer cells exhibit an increased flux through glycolysis irrespective of oxygen tension. Assessing the relative contribution of glycolysis and OXPHOS to intracellular ATP production is fundamental not only for obtaining further insights into the peculiarities and complexities of oncometabolism but also for developing therapeutic and diagnostic tools. Several techniques have been developed to measure intracellular ATP levels including enzymatic methods based on hexokinase, glucose-6-phosphate dehydrogenase, and firefly luciferase. Here, we summarize conventional methods for measuring intracellular ATP levels and we provide a detailed protocol based on cytosol- and mitochondrion-targeted variants of firefly luciferase to determine the relative contribution of glycolysis and OXPHOS to ATP synthesis.
-
4.
Photosynthetic water oxidation vs. mitochondrial oxygen reduction: distinct mechanistic parallels.
Silverstein, TP
Journal of bioenergetics and biomembranes. 2011;(4):437-46
Abstract
The photosynthetic oxygen evolving complex (PSII-OEC) and the mitochondrial cytochrome c oxidase (CcO) not only catalyze anti-parallel reactions (the OEC oxidizes water to dioxygen, whereas CcO reduces dioxygen to water), they also share a number of uncanny molecular and mechanistic similarities. Both feature a redox-active polymetallic cluster that includes a key tyrosine, and both utilize a two-phase mechanism. In one phase the polymetallic cluster undergoes four sequential one-electron transfers: In the PSII-OEC, four successive photooxidations of the photosystem II reaction center P680 (to P680(+)) allows acceptance of 4 × 1e- from the Mn(4)Ca cluster; in CcO, four reduced cytochrome c Fe(2+) cations donate 4 × 1e- to the bimetallic center. In the second phase for each enzyme, the polymetallic cluster undergoes a single four-electron transfer with the O(2)/2 H(2)O redox couple. Intriguing mechanistic similarities between these two complex redox enzymes first delineated over a decade ago by Hoganson/Proshlyakov/Babcock et al. are updated and expanded in this article.
-
5.
[Evaluation of an antioxidant and mitochondria-stimulating cream formula on the skin of patients with stable common vitiligo].
Rojas-Urdaneta, JE, Poleo-Romero, AG
Investigacion clinica. 2007;(1):21-31
Abstract
Vitiligo is a chronic illness of a yet unknown etiology, characterized by an acquired and progressive depigmentation of the skin. There are diverse treatments for this condition around the world, but up to now, none has been completely effective. The objective of this work was to evaluate the application of an antioxidant and mitochondrial stimulating formula, of topic use in leukodermic areas of patients with stable vulgar vitiligo. A clinical, experimental, randomized, double blind study was carried out in 50 male and 50 female patients with stable vulgar vitiligo. The patients were distributed in five groups as follows: Group 1 (labelled as VitilVenz AF): application of antioxidant and mitochondrial stimulating cream and oral administration of antioxidants and phenylalanine. Group 2 (labelled as Placebo AF): application of a placebo cream and oral administration of antioxidants and phenylalanine. Group 3 (labelled as without cream AF): oral administration of antioxidants and phenylalanine. Group 4 (labelled as Placebo cream): application of a placebo cream. Group 5 (labelled as VitilVenz): application of the antioxidant and mitochondrial stimulating cream. The following were measured in all patients: the clinical area of newly formed pigment every 30 days, during five months; and the presence of melanocytes in the histological study, at the beginning and at the end of treatment. The test of multiple comparison of Turkey-Kramer was used for the analysis of the results. The scheme of treatment that produced the best results was that of the Group 1, which consisted of the joint application of the antioxidant and mitochondrial stimulating cream and oral administration of antioxidants and phenylalanine (p < 0.001); followed by Group 5 that only received the topical treatment with the antioxidant and mitochondrial stimulating cream. The clinical and histological responses of these two groups (1 and 5) were significantly different to the rest of the groups. We concluded that the melanocytes in these patients could be in a dysfunctional state, product of the formation of free radicals that cause cellular and mitochondrial toxicity; and that these free radicals are removed by the antioxidant and mitochondrial stimulating elements present in the cream, turning the melanocytes functional and producing melanin in the achromic area of the vitiligo. This effect would be potentiated by the use of oral antioxidants and phenylalanine.
-
6.
Absence of sustained hyperlactatemia in HIV-infected patients with risk factors for mitochondrial toxicity.
Wohl, DA, Pilcher, CD, Evans, S, Revuelta, M, McComsey, G, Yang, Y, Zackin, R, Alston, B, Welch, S, Basar, M, et al
Journal of acquired immune deficiency syndromes (1999). 2004;(3):274-8
Abstract
BACKGROUND The prevalence of asymptomatic hyperlactatemia among HIV-infected individuals has been reported to be 4% to 36%. This variability may reflect differences in the definition of and risk factors for hyperlactatemia and/or techniques for venous lactate collection. METHODS We examined the prevalence of elevated venous lactate collected in accordance with Adult AIDS Clinical Trials Group (AACTG) guidelines among HIV-infected and nucleoside analogue-treated subjects with risk factors associated with hyperlactatemia. Sustained hyperlactatemia was defined as 2 consecutive levels >or=1.5 but RESULTS Eighty-three subjects were enrolled. Two thirds had >or=2 risk factors, with 11% having >4 risk factors. The median entry venous lactate level was 1.2 mmol/L (range: 0.7-5.1 mmol/L). Two subjects had a lactate level >1.5 times the ULN: 1 with a value of 2.1 times the ULN at entry and a week 2 level of 1.2 times the ULN and a second subject with a week 2 value of 1.9 times the ULN but an entry level of 1.4 times the ULN. The latter subject developed symptomatic lactic acidosis 3 weeks following study discontinuation. CONCLUSIONS Sustained asymptomatic hyperlactatemia among subjects with risk factors associated with hyperlactatemia was not observed when venous lactate was measured in a standardized fashion. One case of hyperlactatemia that evolved into symptomatic lactic acidosis was diagnosed soon after the completion of the study, however. Our findings indicate that asymptomatic hyperlactatemia is either very rare or an artifact of collection technique.
-
7.
Superior hepatic mitochondrial oxidation-reduction state in normothermic cardiopulmonary bypass.
Hashimoto, K, Sasaki, T, Hachiya, T, Onoguchi, K, Takakura, H, Oshiumi, M, Takeuchi, S
The Journal of thoracic and cardiovascular surgery. 2001;(6):1179-86
-
-
Free full text
-
Abstract
OBJECTIVE This study is the first comparative investigation of hepatic blood flow and oxygen metabolism during normothermic and hypothermic cardiopulmonary bypass. METHODS Twenty-four patients undergoing coronary bypass operations were randomly divided into 2 groups according to their perfusion temperatures, either normothermia (36 degrees C) or hypothermia (30 degrees C). The clearance of indocyanine green was measured at 3 points. Arterial and hepatic venous ketone body ratios (an index of mitochondrial redox potential) and hepatic venous saturation were measured. RESULTS Hepatic blood flow in both groups was identical before, during, and after cardiopulmonary bypass (normothermia, 499 +/- 111, 479 +/- 139, and 563 +/- 182 mL/min, respectively; hypothermia, 476 +/- 156, 491 +/- 147, and 560 +/- 202 mL/min, respectively). The hepatic venous saturation levels were significantly lower during cardiopulmonary bypass in the normothermic group (normothermia, 41% +/- 13%; hypothermia, 61% +/- 18%; P <.01), indicating a higher level of oxygen extraction use. The arterial ketone body ratio in the hypothermic group decreased severely after the onset of cardiopulmonary bypass (P <.01) and did not return to its subnormal value (>0.7) until the second postoperative day. However, the reduction in arterial ketone body ratio was less severe in the normothermic group. The difference in hepatic venous ketone body ratios was more obvious, and the hepatic venous ketone body ratios in the normothermic group were statistically superior to those of the hypothermic group throughout the course (P <.05-.01). CONCLUSIONS Normothermic cardiopulmonary bypass provides adequate liver perfusion and results in a better hepatic mitochondrial redox potential than hypothermic cardiopulmonary bypass. Because arterial ketone body ratios reflect hepatic energy potential, normothermia was considered to be physiologically more advantageous for hepatic function.
-
8.
The mitochondrial cyanide-resistant oxidase: structural conservation amid regulatory diversity.
Siedow, JN, Umbach, AL
Biochimica et biophysica acta. 2000;(2-3):432-9
Abstract
Mitochondria from all plants, many fungi and some protozoa contain a cyanide-resistant, alternative oxidase that functions in parallel with cytochrome c oxidase as the terminal oxidase on the electron transfer chain. Characterization of the structural and potential regulatory features of the alternative oxidase has advanced considerably in recent years. The active site is proposed to contain a di-iron center belonging to the ribonucleotide reductase R2 family and modeling of a four-helix bundle to accommodate this active site within the C-terminal two-thirds of the protein has been carried out. The structural features of this active site are conserved among all known alternative oxidases. The post-translational regulatory features of the alternative oxidase are more variable among organisms. The plant oxidase is dimeric and can be stimulated by either alpha-keto acids or succinate, depending upon the presence or absence, respectively, of a critical cysteine residue found in a conserved block of amino acids in the N-terminal region of the plant protein. The fungal and protozoan alternative oxidases generally exist as monomers and are not subject to organic acid stimulation but can be stimulated by purine nucleotides. The origins of these diverse regulatory features remain unknown but are correlated with sequence differences in the N-terminal third of the protein.