Metabolic Activity Of Mitochondria Research Articles

Hexokinase 1 forms rings that regulate mitochondrial fission during energy stress

Metabolic enzymes can adapt during energy stress, but the consequences of these adaptations remain understudied. Here, we discovered that hexokinase 1 (HK1), a key glycolytic enzyme, forms rings around mitochondria during energy stress. These HK1-rings constrict mitochondria at contact sites with the endoplasmic reticulum (ER) and mitochondrial dynamics protein (MiD51). HK1-rings prevent mitochondrial fission by displacing the dynamin-related protein 1 (Drp1) from mitochondrial fission factor (Mff) and mitochondrial fission 1 protein (Fis1). The disassembly of HK1-rings during energy restoration correlated with mitochondrial fission. Mechanistically, we identified that the lack of ATP and glucose-6-phosphate (G6P) promotes the formation of HK1-rings. Mutations that affect the formation of HK1-rings showed that HK1-rings rewire cellular metabolism toward increased TCA cycle activity. Our findings highlight that HK1 is an energy stress sensor that regulates the shape, connectivity, and metabolic activity of mitochondria. Thus, the formation of HK1-rings may affect mitochondrial function in energy-stress-related pathologies.

Mitochondrial Function in Health and Disease: Responses to Helicobacter pylori Metabolism and Impact in Gastric Cancer Development.

Mitochondria are major cellular organelles that play an essential role in metabolism, stress response, immunity, and cell fate. Mitochondria are organized in a network with other cellular compartments, functioning as a signaling hub to maintain cells' health. Mitochondrial dysfunctions and genome alterations are associated with diseases including cancer. Mitochondria are a preferential target for pathogens, which have developed various mechanisms to hijack cellular functions for their benefit. Helicobacter pylori is recognized as the major risk factor for gastric cancer development. H. pylori induces oxidative stress and chronic gastric inflammation associated with mitochondrial dysfunction. Its pro-apoptotic cytotoxin VacA interacts with the mitochondrial inner membrane, leading to increased permeability and decreased ATP production. Furthermore, H. pylori induces mitochondrial DNA damage and mutation, concomitant with the development of gastric intraepithelial neoplasia as observed in infected mice. In this chapter, we present diverse aspects of the role of mitochondria as energy supplier and signaling hubs and their adaptation to stress conditions. The metabolic activity of mitochondria is directly linked to biosynthetic pathways. While H. pylori virulence factors and derived metabolites are essential for gastric colonization and niche adaptation, they may also impact mitochondrial function and metabolism, and may have consequences in gastric pathogenesis. Importantly, during its long way to reach the gastric epithelium, H. pylori faces various cellular types along the gastric mucosa. We discuss how the mitochondrial response of these different cells is affected by H. pylori and impacts the colonization and bacterium niche adaptation and point to areas that remain to be investigated.

Red Blood Cells as a "Central Hub" for Sulfide Bioactivity: Scavenging, Metabolism, Transport, and Cross-Talk with Nitric Oxide.

Significance: Sulfide was revealed to be an endogenous signaling molecule regulating a plethora of cellular functions. It is involved in the regulation of fundamental processes, including blood pressure regulation, suspended animation, and metabolic activity of mitochondria, pain, and inflammation. The underlying biochemical pathways and pharmacological targets are still largely unidentified. Recent Advances: Red blood cells (RBCs) are known as oxygen transporters and were proposed to contribute to cardiovascular homeostasis by regulating nitric oxide (NO) metabolism, also via interaction of hemoglobin with nitrite and NO itself. Interestingly, recent evidence indicates that RBCs may also play a central role in systemic sulfide metabolism and homeostasis, and, potentially, in the crosstalk with NO. Heme-containing proteins such as hemoglobin were shown to be targeted by both NO and sulfide. In this article, we aim at revising and discussing the potential impact of RBCs on systemic sulfide metabolism in the cardiovascular system. Critical Issues: Although the synthetic pathways and the reactivity of hemoglobin and other heme proteins with sulfide and NO are known, the in vivo role of RBCs in sulfide metabolism, physiology, pharmacology, and its pathophysiological implications have not been characterized so far. Future Directions: To allow a better understanding of the role of RBCs in systemic sulfide metabolism and its cross-talk with NO, basic and translational science studies should be focused on dissecting the enzymatic and nonenzymatic sulfur metabolic pathways in RBCs in vivo and their impact on the cardiovascular system in animal models and clinical settings.

Circadian Rheb oscillation alters the dynamics of hepatic mTORC1 activity and mitochondrial morphology.

The morphological structure and metabolic activity of mitochondria are coordinately regulated by circadian mechanisms. However, the mechanistic interplay between circadian mechanisms and mitochondrial architecture remains poorly understood. Here, we demonstrate circadian rhythmicity of Rheb protein in liver, in line with that of Per2. Using genetic mouse models, we show that Rheb, a small GTPase that binds mTOR, is critical for circadian oscillation of mTORC1 activity in liver. Disruption of Rheb oscillation in hepatocytes by persistent expression of Rheb transgene interrupted mTORC1 oscillation. We further show that Rheb-regulated mTORC1 altered mitochondrial fission factor DRP1 in liver, leading to altered mitochondrial dynamics. Our results suggest that Rheb/mTORC1 regulated DRP1 oscillation involves ubiquitin-mediated proteolysis. This study identifies Rheb as a nodal point that couples circadian clock and mitochondrial architecture for optimal mitochondrial metabolism.

A Validated Set of Fluorescent-Protein-Based Markers for Major Organelles in Yeast (Saccharomyces cerevisiae)

ABSTRACTEukaryotic cells share a basic scheme of internal organization featuring membrane-based organelles. The use of fluorescent proteins (FPs) greatly facilitated live-cell imaging of organelle dynamics and protein trafficking. One major limitation of this approach is that the fusion of an FP to a target protein can and often does compromise the function of the target protein and alter its subcellular localization. The optimization process to obtain a desirable fusion construct can be time-consuming or even unsuccessful. In this work, we set out to provide a validated set of FP-based markers for major organelles in the budding yeast (Saccharomyces cerevisiae). Out of over 160 plasmids constructed, we present a final set of 42 plasmids, the recommendations for which are backed up by meticulous evaluations. The tool set includes three colors (green, red, and blue) and covers the endoplasmic reticulum (ER), nucleus, Golgi apparatus, endosomes, vacuoles, mitochondria, peroxisomes, and lipid droplets. The fidelity of the markers was established by systematic cross-comparison and quantification. Functional assays were performed to examine the impact of marker expression on the secretory pathway, endocytic pathway, and metabolic activities of mitochondria and peroxisomes. Concomitantly, our work constitutes a reassessment of organelle identities in this model organism. Our data support the recognition that “late Golgi” and “early endosomes,” two seemingly distinct terms, denote the same compartment in yeast. Conversely, all other organelles can be visually separated from each other at the resolution of conventional light microscopy, and quantification results justify their classification as distinct entities.

Canagliflozin Impairs Blood Reperfusion of the Ischemic Lower Limb by Inhibiting the Retention and Paracrine Function of Mesenchymal Stem Cells

Background: Canagliflozin (CANA) administration increases amputation risk of the lower limb in the clinic. The present study aimed to investigate whether and how CANA interferer with intracellular physiological processes of mesenchymal stem cells (MSCs), and its contribution to ischemic lower limb. Methods: The in vivo blood flow recovery of ischemic lower limb following CANA treatment was evaluated. The cellular function of MSCs after CANA treatment were also assessed in vitro. In silico docking analysis and mutant substitution assay were conducted to confirm the interaction of CANA and glutamate dehydrogenase 1 (GDH1). Findings: Following CANA treatment, attenuated angiogenesis and hampered recovery of blood flow were observed in ischemic region, and the proliferation inhibition, migration inhibition, and apoptosis of MSCs was evidenced. CANA was involved in MSC mitochondrial respiratory malfunction, ATP production inhibition, cytochrome c release and vessel endothelial growth factor A (VEGFA) secretion inhibition, which contribute to reduced tissue repair capacity of MSCs, resulting in compromised angiogenesis and blood reperfusion in ischemic region. The detrimental effects of CANA on MSCs result from the inhibition of GDH1 by CANA (evidenced by in silico docking analysis and H199A-GDH1/ N392A-GDH1 mutant substitution). Interpretation: Our work highlights that GDH1 activity inhibition by CANA interferes with metabolic activity of mitochondria, which deteriorates retention and VEGFA secretion of MSCs, hampering angiogenesis and the recovery of blood flow following lower limb ischemia. Funding Statement: This study was financially supported by National Natural Science Foundation of China (grant # 81800314 for J. N.), Natural Science Foundation of Zhejiang Province (grant # LQ18H090007 for Z. L.) and Wenzhou Science and Technology Bureau Foundation (grant # Y20190163 for Y. L.). Declaration of Interests: The authors declare no competing financial interests. Ethics Approval Statement: All experimental protocols were approved by the Animal Care and Use Committee of Wenzhou Medical University.

Characterization of the mechanism and impact of staphylokinase on the formation of Candida albicans and Staphylococcus aureus polymicrobial biofilms.

Candida albicans and Staphylococcus aureus can be co-isolated in biofilm-associated infections. However, treatments have not been well established due to a lack of antibiofilm strategies. Hence, this study aims to characterize the mechanism and impact of Staphylokinase (Sak) on fungal-bacterial polymicrobial biofilms. Sak generation levels were obtained via chromogenic analysis. C. albicans and S. aureus polymicrobial biofilm formation and integrity were analysed using a bright-field microscope and scanning electron microscopy (SEM). Metabolic mitochondrial activity, growth rate and adhesive capacity were also measured. Quantification real-time RT-PCR (qRT-PCR) was carried out to evaluate the expression levels of biofilm-related genes. Furthermore, the biofilm inhibitory potential of Sak alone or combined with antimicrobials was investigated. Sak production levels varied, ranging from 0.130 to 0.648. A strong decrease of biomass, metabolic activity andearly stage growth rate was demonstrated in the Sak-treated group. SEM showed S. aureus attached on hyphae of C. albicans in sporadic small microcolonies after Sak treatment. Moreover, the gene expression levels of HWP1, EFG1 and NRG1 were significantly altered, while no obvious difference was observed in ALS3. Finally, Sak had a notable impact on mature polymicrobial biofilms alone or when combined with vancomycin and fluconazole. The effect induced by Sak to C. albicans and S. aureus polymicrobial biofilms is caused by decreased biomass, biofilm integrity, metabolic activity and early stage growth rate. Alterations of gene expression levels were consistent with Sak-induced phenotypic change. Combined treatment strategies are essential for optimal activities against fungal-bacterial polymicrobial biofilms.

Simple, reliable, and time-efficient colorimetric method for the assessment of mitochondrial function and toxicity.

Mitochondria are organelles involved in the production of cellular energy, regulation of Ca2+ and redox signaling, and are critical for normal functioning of eukaryotic cells. The dysfunction of mitochondria has been implicated in a wide range of diseases, including metabolic and neurodegenerative disorders and different types of cancers. To better understand the role of mitochondria in healthy and disease states, the development of efficient and reliable tools for the assessment of mitochondrial function is particularly important. Janus green B (JG-B) is a supravital lipophilic cationic dye which, in its oxidized form, has a green-blue color. As JG-B is taken up and reduced by metabolically active mitochondria, the dye has been used for assessing the purity, integrity and metabolic activity of mitochondria with microscopy-based methods. Here we present a simple, time- and cost-efficient JG-B-based colorimetric assay for assessing mitochondrial function, activity and toxicity. The method is based upon reduction of JG-B by mitochondrial dehydrogenases to diethylsafranine, which is pink colored and has a maximum absorption at 550 nm. In this proof of principle study, using in vitro mitochondrial preparations isolated from rat brain, we provide evidence that monitoring JG-B conversion to diethylsafranine can be used as a reliable and robust indicator of mitochondrial activity and toxicity. Because of its simplicity and efficiency in terms of costs and time, this assay has a wide potential in analytical as well as therapeutic areas of biomedical research.

Bhlhe40 differentially regulates the function and number of peroxisomes and mitochondria in myogenic cells

PGC-1α is a key regulator of oxidative metabolism facilitating the expression of genes critical for the function and biogenesis of the two key oxidative organelles, mitochondria and peroxisomes, in skeletal muscle (SKM) and other organs. Our recent studies have found that the transcription factor Bhlhe40 negatively regulates PGC-1α gene expression and its coactivational activity, therefore, this factor should have profound influence on the biogenesis and metabolic activity of mitochondria and peroxisomes. Here we found that both the number and activity of peroxisomes were increased upon knockdown of Bhlhe40 expression but were repressed by its over-expression. Mitochondrial efficiency was significantly reduced by Bhlhe40 knockdown, resulting in the burst of ROS. Over-expression of a constitutively active PGC-1α-interactive domain (named as VBH135) of Bhlhe40 mimicked the effects of its knockdown on peroxisomes but simultaneously reduced ROS level. Furthermore, the efficiency, but not the number, of mitochondria was also increased by VBH135, suggesting differential regulation of peroxisomes and mitochondria by Bhlhe40. Unsaturated fatty acid oxidation, insulin response, and oxidative respiration were highly enhanced in Bhlhe40 knockdown or VBH135 over-expressed cells, suggesting the importance of Bhlhe40 in the regulation of unsaturated fatty acid and glucose oxidative metabolism. Expression profiling of genes important for either organelle also supports differential regulation of peroxisomes and mitochondria by Bhlhe40. These observations have established the important role of Bhlhe40 in SKM oxidative metabolism as the critical regulator of peroxisome and mitochondrion biogenesis and functions, and thus should provide a novel route for developing drugs targeting SKM metabolic diseases.

Dynamics of humanin release and consumption of amino acids by differentiating C2C12 myoblasts

In the differentiating culture of myoblasts, the formation of myofibrils is accompanied by the consumption of amino acids and the release of their derivatives into the medium. The enhancement of mitochondrial metabolism precedes the formation of myofibrils. In this work, the release of a humanin-like peptide (HNLP, mt-RNR-peptide) and amino acid derivatives into the medium was studied in the differentiation of C2C12 myoblasts. Cells of the C2C12 line were cultured using standard techniques in plates with control of myofibril formation and samples selection for analysis at 0 (induction), 2, 4, 7, 9 and 11 days of differentiation. HNLP was determined by enzyme immunoassay, and amino acids and their metabolites by liquid chromatography. From the essential amino acids, branched chain - Val, Leu, Ile were most intensively consumed up to day 7 of differentiation. There was observed a mutual correlation between the daily production of arginine derivatives - homoarginine (hArg) and ornithine (r = 0.53, p = 0.008) with a maximum on day 2, a significant decrease of hArg production on day 4 and trace secretion after day 7. The release of HNLP, unlike hArg, lasts up to 4 days. Secretion of HNLP in course differentiating myoblasts is an early marker of the mitochondrial metabolism development. Its decrease by day 7 is associated to inhibition of the further existence of already differentiated myocytes. The early stage of cell culture differentiation is more clearly checked not by the level of essential amino acids intake, which presented in the cultivation medium at high concentrations, but by the formation of amino acid products of specialized metabolic pathways, including hArg and ornithine. The metabolic activity of mitochondria is confirmed by the secretion of HNLP. The specific functional activity of myocytes depends on the metabolic activity of the mitochondria, which can be checked without violating the integrity of the culture, according to the level of secreted HNLP.

Reduction of Candida biofilm adhesion by incorporation of prereacted glass ionomer filler in denture base resin

ObjectivesThis study investigated the influence of surface reaction-type prereacted glass ionomer (S-PRG) fillers on Candida albicans adhesion on denture base resin. MethodsDiscs were prepared by incorporating the S-PRG filler into the polymer powder of a polymethyl methacrylate (PMMA)-based, heat-polymerizing resin at 0 (control), 5%, 10%, and 20% (w/w). The surface roughness of all disc surfaces was measured. Elemental analysis of released Na+, Sr2+, SiO32−, Al3−, BO33−, and F− was performed after water immersion. Each disc was placed in a well with artificial saliva to form acquired pellicle, incubated, washed with phosphate-buffered saline, and immersed in a C. albicans (JCM2085) cell suspension standardized at 104 cells/ml. After aerobic incubation at 37°C for 24h, the metabolic mitochondrial activity, total biofilm biomass, and biofilm thickness were evaluated. The morphogenetic transition of C. albicans in the early culture stage (1 and 3h) was observed. ResultsThere was a slight but significant increase in the surface roughness with an increase in the filler content. The metabolic activity and total biomass volume were significantly lower in all filler groups than in the control group, although there were no significant differences among the filler groups. Groups with at least 5% filler content exhibited a thinner biofilm compared with the control group. All filler groups showed hyphal forms at 3h, with the length of the hyphae being lesser than those in the control group. ConclusionsAlthough the incorporation of S-PRG filler slightly increases the surface roughness of denture base resin, it reduces the adhesion of C. albicans. Clinical significanceThe S-PRG filler has the potential to reduce Candida albicans adhesion on denture base resin and may lower the risk of denture stomatitis. However, filler incorporation can increase the surface roughness of heat-polymerizing denture base resin.

Microcalorimetric investigation of five Aconitum L. plants on the metabolic activity of mitochondria isolated from rat liver

The fact that mitochondria still have metabolic activity and can live for a week with appropriate nutrients after isolated from the rat liver provides us a useful means to investigate the metabolic process of mitochondria influenced by chemicals. Using the TAM air isothermal microcalorimeter, the HP-time curves of the metabolic activity of mitochondria were measured. The effects of five Aconitum L. plants, Radix Aconiti Lateralis Preparata (RALP), Radix Aconiti (RA), Radix Aconiti Kusnezoffii (RAK), Radix Aconiti Brachypodi (RAB), and Radix Aconiti Singularis (RAS) on the metabolic activity of mitochondria were investigated, respectively. The quantitative information, such as k, Q, P max, T max, T lag, and P av obtained from the HP-time curves, were accumulated for analysis. With the help of PCA method, P av was selected as the standard for comparing the different effects of five Aconitum L. plants on metabolic activity of mitochondria. The potential sequence of efficiency was RAS > RAK > RAB > RA > RALP, and the EC50 were separately 1.43, 2.31, 1.10, 1.61, and 2.56 mg mL−1. The results demonstrated that the five Aconitum L. plants had different bioeffects on the mitochondria metabolism. Meanwhile, this study indicated that microcalorimetry was a powerful tool to evaluate the drugs’ efficiency on living system, providing some useful references for the application of five Aconitum L. plants in practice.

Mitochondria in ageing: there is metabolism beyond the ROS

Mitochondria are responsible for a series of metabolic functions. Superoxide leakage from the respiratory chain and the resulting cascade of reactive oxygen species-induced damage, as well as mitochondrial metabolism in programmed cell death, have been intensively studied during ageing in single-cellular and higher organisms. Changes in mitochondrial physiology and metabolism resulting in ROS are thus considered to be hallmarks of ageing. In this review, we address 'other' metabolic activities of mitochondria, carbon metabolism (the TCA cycle and related underground metabolism), the synthesis of Fe/S clusters and the metabolic consequences of mitophagy. These important mitochondrial activities are hitherto less well-studied in the context of cellular and organismic ageing. In budding yeast, they strongly influence replicative, chronological and hibernating lifespan, connecting the diverse ageing phenotypes studied in this single-cellular model organism. Moreover, there is evidence that similar processes equally contribute to ageing of higher organisms as well. In this scenario, increasing loss of metabolic integrity would be one driving force that contributes to the ageing process. Understanding mitochondrial metabolism may thus be required for achieving a unifying theory of eukaryotic ageing.

Proteome-wide study of endoplasmic reticulum stress induced by thapsigargin in N2a neuroblastoma cells

Disturbances in intraluminal endoplasmic reticulum (ER) Ca2+ concentration leads to the accumulation of unfolded proteins and perturbation of intracellular Ca2+ homeostasis, which has a huge impact on mitochondrial functioning under normal and stress conditions and can trigger cell death. Thapsigargin (TG) is widely used to model cellular ER stress as it is a selective and powerful inhibitor of sarcoplasmic/endoplasmic reticulum Ca2+ ATPases. Here we provide a representative proteome-wide picture of ER stress induced by TG in N2a neuroblastoma cells. Our proteomics study revealed numerous significant protein expression changes in TG-treated N2a cell lysates analysed by two-dimensional electrophoresis followed by mass spectrometric protein identification. The proteomic signature supports the evidence of increased bioenergetic activity of mitochondria as several mitochondrial enzymes with roles in ATP-production, tricarboxylic acid cycle and other mitochondrial metabolic processes were upregulated. In addition, the upregulation of the main ER resident proteins confirmed the onset of ER stress during TG treatment. It has become widely accepted that metabolic activity of mitochondria is induced in the early phases in ER stress, which can trigger mitochondrial collapse and subsequent cell death. Further investigations of this cellular stress response in different neuronal model systems like N2a cells could help to elucidate several neurodegenerative disorders in which ER stress is implicated.

Microcalorimetric study of the effect of artesunate on the growth metabolism of mitochondria isolated from rat liver

In this study, the metabolic thermogenic curves of mitochondria isolated from rat liver tissue were drawn, and the effects of artesunate on metabolic activity of mitochondria were studied using TAM Air Isothermal Microcalorimeter. After isolation from the rat liver, mitochondria still have metabolic activity and can live for a week with appropriate nutrients. With the addition of artesunate (7.5 μM/mL), the metabolic activity of mitochondria was completely lost at this concentration. From the thermogenic curves, we obtained the thermokinetic equations under different conditions: Tmax = 2512.24 + 1761.53c, R = 0.9375; and Tlag (min) = 707.26 + 285.17c, R = 0.9846. The results showed that artesunate was a mitochondria-targeted drug having obvious effects on mitochondrial metabolism.

Resveratrol and genistein as adenosine triphosphate–depleting agents in fat cells

Resveratrol and genistein are plant-derived compounds known to exert pleiotropic effects in many cell types, including adipocytes. However, the effects of these compounds on the energetic status of fat cells are unknown. The present study aimed to determine whether resveratrol and genistein influence adenosine triphosphate (ATP) levels in freshly isolated rat adipocytes. To determine the effects of resveratrol and genistein on adipocyte ATP content, cells were exposed to insulin and glucose or insulin and alanine without tested compounds or with 6.25 to 50 μmol/L resveratrol or genistein. Resveratrol substantially reduced glucose- and alanine-derived ATP in adipocytes. This was not due to the inhibition of glucose transport because the influence of the test compound on insulin-stimulated glucose uptake by adipocytes appeared to be stimulatory. Moreover, resveratrol reduced both alanine oxidation and mitochondrial membrane hyperpolarization. It was also demonstrated that preincubation of cells with resveratrol slightly diminished ATP levels despite the withdrawal of the tested compound from the buffer. The genistein effect was accompanied by attenuation of the mitochondrial membrane hyperpolarization. The compound failed to significantly affect insulin-stimulated glucose uptake by fat cells. Similarly to resveratrol, preincubation of adipocytes with genistein slightly reduced ATP in cells exposed to glucose and insulin. Results of the present study revealed the potent ability of resveratrol to reduce ATP in rat adipocytes, whereas genistein appeared to be less effective. It is suggested that both tested compounds diminish adipocyte ATP via attenuation of the metabolic activity of mitochondria. Because numerous cellular events are strongly ATP dependent, the ATP-depleting effects of resveratrol and genistein may have pleiotropic consequences for adipocyte functions.

Microcalorimetric Study on the Effect of Sodium Arsenite on Metabolic Activity of Mitochondria Isolated fromCarassius auratus Liver Tissue

Metabolic thermogenic curves of mitochondria isolated from liver tissue of Carassius auratus and the effect of different concentration of NaAsO2 on it were investigated by TAM air isothermal microcalorimeter, ampoule method, at 28.00 °C. From the thermogenic curves, activity recovery rate constants k, the maximum heat production rate (Pmax) and the total heat produced (Q) were obtained. The values of k and Pmax decline gradually with the increase of the concentration of NaAsO2, and both of the values of Pmax and k are highly correlated to the concentration of NaAsO2. When concentration of NaAsO2 reached 16.0 µg/mL, the maximum heat production rate dropped to 70.8% of the control group, and the corresponding percentage of k was 71.4% of the control group. This experimental result indicates that the addition of NaAsO2 has restrained the metabolic activities of mitochondria in vitro.

Binding and release of cytochrome c in brain mitochondria is influenced by membrane potential and hydrophobic interactions with cardiolipin.

Factors influencing the release and anchorage of cytochrome c to the inner membrane of brain mitochondria have been investigated. Metabolic activity of mitochondria caused a decrease in the membrane potential delta psi(m), accompanied by detachment of the protein from the inner membrane. In a model system of cytochrome c reconstituted in cardiolipin (CL) liposomes, phosphate was used to breach the hydrophilic lipid-protein interactions. About 44% cytochrome c was removable when heart CL (80% 18:2n-6) was employed, whereas the remaining protein accounted for the tightly bound conformation characterized by hydrophobic lipid-protein interactions. Cytochrome c release from brain CL liposomes was higher compared to heart CL, consistent with lower polyunsaturated fatty acid content. The release was even higher with CL extracted from metabolically stressed mitochondria, exhibiting more saturated fatty acid profile compared to control (30% vs. 17%). Therefore, weakening of the hydrophobic interactions due to saturation of CL may account for the observed cytochrome c release from mitochondria following metabolic stress. Moreover, mitochondria enriched with polyunsaturated CL exhibited higher delta psi(m), compared to less unsaturated species, suggesting that CL fatty acid composition influences delta psi(m). Mitochondria incorporated exogenous cytochrome c without protease-sensitive factors or delta psi(m). The internalized protein anchored to the inner membrane without producing swelling, as monitored by forward and side light scattering, but produced delta psi(m) consumption, suggesting recovery of respiratory activity. The delta psi(m) decrease is ascribed to a selected mitochondrial population containing the incorporated cytochrome c.

Effects of middle‐level static magnetic field on metabolic activity of mitochondria

AbstractThis study intends to clarify the effect of a static magnetic field on cellular activities. It is concerned with the metabolic activity of mitochondria from the viewpoint of their energy level. As a preliminary examination, the time required to render the cells to the low‐energy state (G0/G1 phase of the cell cycle) and to reduce their energy level was examined by maintaining the cells in medium with low‐density fetal bovine serum. Then, we examined the effect of the magnetic field on mitochondrial energy activity from the viewpoint of cell metabolism estimated by the MTT assay. We also examined the cell respiration, expecting that the mitochondrial energy activity level would be reflected in the respiration. The magnetic field was kept at 100 mT, with 0 mT as the control. The results of the MTT assay indicated that the mitochondrial energy activity was enhanced by a factor of 1.5. We found that the cell respiration was increased by a factor of 1.3 on exposure to the magnetic field. The t‐test showed the difference to be statistically significant. It is thus concluded that mitochondrial energy activity is enhanced in the G0/G1 phase of the cell cycle by exposure to a magnetic field. On the other hand, we also found that the mitochondrial energy cycle period is little affected. © 2001 Scripta Technica, Electr Eng Jpn, 137(1): 36–41, 2001

ミトコンドリアの代謝活性への中程度静磁界の影響

ミトコンドリアの代謝活性への中程度静磁界の影響