scholarly journals A Molecular Biophysical Approach to Diclofenac Topical Gastrointestinal Damage

2018 ◽  
Vol 19 (11) ◽  
pp. 3411 ◽  
Author(s):  
Eduarda Fernandes ◽  
Telma Soares ◽  
Hugo Gonçalves ◽  
Sigrid Bernstorff ◽  
Maria Real Oliveira ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Drug Distribution ◽  
Model Systems ◽  
Dependent Manner ◽  
Inner Mitochondrial Membrane ◽  
Scanning Calorimetry ◽  
Drug Induced ◽  
Time Resolved ◽  
Contact Points ◽  
Calcein Leakage

Diclofenac (DCF), the most widely consumed non-steroidal anti-inflammatory drug (NSAID) worldwide, is associated with adverse typical effects, including gastrointestinal (GI) complications. The present study aims to better understand the topical toxicity induced by DCF using membrane models that mimic the physiological, biophysical, and chemical environments of GI mucosa segments. For this purpose, phospholipidic model systems that mimic the GI protective lining and lipid models of the inner mitochondrial membrane were used together with a wide set of techniques: derivative spectrophotometry to evaluate drug distribution at the membrane; steady-state and time-resolved fluorescence to predict drug location at the membrane; fluorescence anisotropy, differential scanning calorimetry (DSC), dynamic light scattering (DLS), and calcein leakage studies to evaluate the drug-induced disturbance on membrane microviscosity and permeability; and small- and wide-angle X-ray scattering studies (SAXS and WAXS, respectively), to evaluate the effects of DCF at the membrane structure. Results demonstrated that DCF interacts chemically with the phospholipids of the GI protective barrier in a pH-dependent manner and confirmed the DCF location at the lipid headgroup region, as well as DCF’s higher distribution at mitochondrial membrane contact points where the impairment of biophysical properties is consistent with the uncoupling effects reported for this drug.

Cytotoxic effects of cisplatin, cis-dichlorodiammineplatinum(II), on Tetrahymena

1988 ◽  
Vol 90 (4) ◽  
pp. 707-716
Author(s):  
J.R. Nilsson
Keyword(s):  
Mitochondrial Membrane ◽  
Prolonged Treatment ◽  
Dependent Manner ◽  
Inner Mitochondrial Membrane ◽  
Cell Organelles ◽  
Cell Content ◽  
Cytotoxic Effects ◽  
Dense Granules ◽  
High Concentrations ◽  
Dose Dependent

A study was made of the effects of cisplatin, cis-dichlorodiammineplatinum(II) (5–250 mg l-1), on the physiology and fine structure of Tetrahymena. The physiological effects observed were dose-dependent. Endocytosis was inhibited reversibly in all, but late in the high, concentrations. After an initial dose-related increase, due to division of cells most advanced in the cell cycle, proliferation ceased for at least two normal cell generations (6 h) in 50 and 100 mg drug l-1, but for 24 h in 250 mg l-1, after which multiplication was resumed in a dose-dependent manner. Exposure to cisplatin resulted in the appearance of small, refractive granules and platinum (i.e. electron-dense material) accumulated in these granules. Fine structural observations of cells exposed to 250 mg drug l-1 showed nucleolar fusion and appearance initially of lipid droplets, dense granules and autophagosomes. A time-dependent redistribution of cell organelles was revealed by morphometry; in particular, the mitochondria increased in number, but decreased in size. Moreover, after prolonged treatment (24 h) and without cell division, the inner mitochondrial membrane had diminished and the ratio of the inner to the outer mitochondrial membrane was only half of the value for control mitochondria. Concomitantly with this decrease, the cell content of ATP was reduced to a similar extent. The findings indicate a specific action of cisplatin on mitochondria, resembling that induced in Tetrahymena by chloramphenicol and methotrexate.

scholarly journals Alignment of sarcoplasmic reticulum-mitochondrial junctions with mitochondrial contact points

2011 ◽  
Vol 301 (5) ◽  
pp. H1907-H1915 ◽  
Author(s):  
Cecília García-Pérez ◽  
Timothy G. Schneider ◽  
György Hajnóczky ◽  
György Csordás
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Sarcoplasmic Reticulum ◽  
Ryanodine Receptor ◽  
Mitochondrial Membrane ◽  
Inner Mitochondrial Membrane ◽  
Mitofusin 2 ◽  
Atp Production ◽  
Contact Points ◽  
Transmission Electron

Propagation of ryanodine receptor (RyR2)-derived Ca2+ signals to the mitochondrial matrix supports oxidative ATP production or facilitates mitochondrial apoptosis in cardiac muscle. Ca2+ transfer likely occurs locally at focal associations of the sarcoplasmic reticulum (SR) and mitochondria, which are secured by tethers. The outer mitochondrial membrane and inner mitochondrial membrane (OMM and IMM, respectively) also form tight focal contacts (contact points) that are enriched in voltage-dependent anion channels, the gates of OMM for Ca2+. Contact points could offer the shortest Ca2+ transfer route to the matrix; however, their alignment with the SR-OMM associations remains unclear. Here, in rat heart we have studied the distribution of mitochondria-associated SR in submitochondrial membrane fractions and evaluated the colocalization of SR-OMM associations with contact points using transmission electron microscopy. In a sucrose gradient designed for OMM purification, biochemical assays revealed lighter fractions enriched in OMM only and heavier fractions containing OMM, IMM, and SR markers. Pure OMM fractions were enriched in mitofusin 2, an ∼80 kDa mitochondrial fusion protein and SR-mitochondrial tether candidate, whereas in fractions of OMM + IMM + SR, a lighter (∼50 kDa) band detected by antibodies raised against the NH2 terminus of mitofusin 2 was dominating. Transmission electron microscopy revealed mandatory presence of contact points at the junctional SR-mitochondrial interface versus a random presence along matching SR-free OMM segments. For each SR-mitochondrial junction at least one tether was attached to contact points. These data establish the contact points as anchorage sites for the SR-mitochondrial physical coupling. Close coupling of the SR, OMM, and IMM is likely to provide a favorable spatial arrangement for local ryanodine receptor-mitochondrial Ca2+ signaling.

Large-conductance Ca2+-activated potassium channel in mitochondria of endothelial EA.hy926 cells

2013 ◽  
Vol 304 (11) ◽  
pp. H1415-H1427 ◽  
Author(s):  
Piotr Bednarczyk ◽  
Agnieszka Koziel ◽  
Wieslawa Jarmuszkiewicz ◽  
Adam Szewczyk
Keyword(s):  
Potassium Channel ◽  
Mitochondrial Membrane ◽  
Single Channel ◽  
Dependent Manner ◽  
Channel Activity ◽  
Inner Mitochondrial Membrane ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
Α Subunit ◽  
Ea.Hy926 Cells

In the present study, we describe the existence of a large-conductance Ca2+-activated potassium (BKCa) channel in the mitochondria of the human endothelial cell line EA.hy926. A single-channel current was recorded from endothelial mitoplasts (i.e., inner mitochondrial membrane) using the patch-clamp technique in the mitoplast-attached mode. A potassium-selective current was recorded with a mean conductance equal to 270 ± 10 pS in a symmetrical 150/150 mM KCl isotonic solution. The channel activity, which was determined as the open probability, increased with the addition of calcium ions and the potassium channel opener NS1619. Conversely, the activity of the channel was irreversibly blocked by paxilline and iberiotoxin, BKCa channel inhibitors. The open-state probability was found to be voltage dependent. The substances known to modulate BKCa channel activity influenced the bioenergetics of mitochondria isolated from human endothelial EA.hy926 cells. In isolated mitochondria, 100 μM Ca2+, 10 μM NS1619, and 0.5 μM NS11021 depolarized the mitochondrial membrane potential and stimulated nonphosphorylating respiration. These effects were blocked by iberiotoxin and paxilline in a potassium-dependent manner. Under phosphorylating conditions, NS1619-induced, iberiotoxin-sensitive uncoupling diverted energy from ATP synthesis during the phosphorylating respiration of the endothelial mitochondria. Immunological analysis with antibodies raised against proteins of the plasma membrane BKCa channel identified a pore-forming α-subunit and an auxiliary β2-subunit of the channel in the endothelial mitochondrial inner membrane. In conclusion, we show for the first time that the inner mitochondrial membrane in human endothelial EA.hy926 cells contains a large-conductance calcium-dependent potassium channel with properties similar to those of the surface membrane BKCa channel.

scholarly journals Snapshot of an oxygen intermediate in the catalytic reaction of cytochrome c oxidase

2019 ◽  
Vol 116 (9) ◽  
pp. 3572-3577 ◽  
Author(s):  
Izumi Ishigami ◽  
Ariel Lewis-Ballester ◽  
Austin Echelmeier ◽  
Gerrit Brehm ◽  
Nadia A. Zatsepin ◽  
...  
Keyword(s):  
Protein Conformation ◽  
Mitochondrial Membrane ◽  
Proton Translocation ◽  
Conformational State ◽  
Inner Mitochondrial Membrane ◽  
Time Resolved ◽  
Metal Centers ◽  
Redox States ◽  
Distinct Structure ◽  
Serial Femtosecond Crystallography

Cytochrome c oxidase (CcO) reduces dioxygen to water and harnesses the chemical energy to drive proton translocation across the inner mitochondrial membrane by an unresolved mechanism. By using time-resolved serial femtosecond crystallography, we identified a key oxygen intermediate of bovine CcO. It is assigned to the PR-intermediate, which is characterized by specific redox states of the metal centers and a distinct protein conformation. The heme a3 iron atom is in a ferryl (Fe4+ = O2−) configuration, and heme a and CuB are oxidized while CuA is reduced. A Helix-X segment is poised in an open conformational state; the heme a farnesyl sidechain is H-bonded to S382, and loop-I-II adopts a distinct structure. These data offer insights into the mechanism by which the oxygen chemistry is coupled to unidirectional proton translocation.

scholarly journals Mitochondrial Cristae Architecture and Functions: Lessons from Minimal Model Systems

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 465
Author(s):  
Frédéric Joubert ◽  
Nicolas Puff
Keyword(s):  
Minimal Model ◽  
Mitochondrial Membrane ◽  
Energy Production ◽  
Lipid Membrane ◽  
Model Systems ◽  
Eukaryotic Cells ◽  
Membrane Composition ◽  
Inner Mitochondrial Membrane ◽  
Dynamic Membrane

Mitochondria are known as the powerhouse of eukaryotic cells. Energy production occurs in specific dynamic membrane invaginations in the inner mitochondrial membrane called cristae. Although the integrity of these structures is recognized as a key point for proper mitochondrial function, less is known about the mechanisms at the origin of their plasticity and organization, and how they can influence mitochondria function. Here, we review the studies which question the role of lipid membrane composition based mainly on minimal model systems.

scholarly journals Accumulation of Exogenous Amyloid-BetaPeptide in Hippocampal Mitochondria Causes Their Dysfunction: A Protective Role for Melatonin

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Sergio Rosales-Corral ◽  
Dario Acuna-Castroviejo ◽  
Dun Xian Tan ◽  
Gabriela López-Armas ◽  
José Cruz-Ramos ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mitochondrial Membrane ◽  
Respiratory Control ◽  
Hydrolytic Activity ◽  
Protective Role ◽  
Dependent Manner ◽  
Oxygen Species ◽  
Respiratory Control Ratio ◽  
Inner Mitochondrial Membrane ◽  
Subcellular Structure

Amyloid-beta(Aβ) pathology is related to mitochondrial dysfunction accompanied by energy reduction and an elevated production of reactive oxygen species (ROS). Monomers and oligomers of Aβ have been found inside mitochondria where they accumulate in a time-dependent manner as demonstrated in transgenic mice and in Alzheimer’s disease (AD) brain. We hypothesize that the internalization of extracellular Aβ aggregates is the major cause of mitochondrial damage and here we report that following the injection of fibrillar Aβ into the hippocampus, there is severe axonal damage which is accompanied by the entrance of Aβ into the cell. Thereafter, Aβ appears in mitochondria where it is linked to alterations in the ionic gradient across the inner mitochondrial membrane. This effect is accompanied by disruption of subcellular structure, oxidative stress, and a significant reduction in both the respiratory control ratio and in the hydrolytic activity of ATPase. Orally administrated melatonin reduced oxidative stress, improved the mitochondrial respiratory control ratio, and ameliorated the energy imbalance.

scholarly journals Mitochondrial Aurora kinase A induces mitophagy by interacting with MAP1LC3 and Prohibitin 2

2020 ◽  
Author(s):  
Giulia Bertolin ◽  
Marie-Clotilde Alves-Guerra ◽  
Agnès Burel ◽  
Claude Prigent ◽  
Roland Le Borgne ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Molecular Mechanisms ◽  
Mitochondrial Dynamics ◽  
Aurora Kinase ◽  
Dependent Manner ◽  
Inner Mitochondrial Membrane ◽  
Serine Threonine Kinase ◽  
Independent Manner ◽  
Atp Production ◽  
Core Components

AbstractEpithelial and haematologic tumours often show the overexpression of the serine/threonine kinase AURKA. Recently, AURKA was shown to localise at mitochondria, where it regulates mitochondrial dynamics and ATP production. Here we define the molecular mechanisms of AURKA in regulating mitochondrial turnover by mitophagy. When overexpressed, AURKA induces the rupture of the Outer Mitochondrial Membrane in a proteasome-dependent manner. Then, AURKA triggers the degradation of Inner Mitochondrial Membrane (IMM)/matrix proteins by interacting with core components of the autophagy pathway. On the IMM, the kinase forms a tripartite complex with MAP1LC3 and the mitophagy receptor PHB2. This complex is necessary to trigger mitophagy in a PARK2/Parkin-independent manner. The formation of the tripartite complex is induced by the phosphorylation of PHB2 on Ser39, which is required for MAP1LC3 to interact with PHB2. Last, treatment with the PHB2 ligand Xanthohumol blocks AURKA-induced mitophagy by destabilising the tripartite complex. This treatment also restores normal ATP production levels. Altogether, these data provide evidence for a previously undetected role of AURKA in promoting mitophagy through the interaction with PHB2 and MAP1LC3. This work paves the way to the use of function-specific pharmacological inhibitors to counteract the effects of the overexpression of AURKA in cancer.

scholarly journals Characterization of human cardiac mitochondrial ATP-sensitive potassium channel and its regulation by phorbol ester in vitro

2006 ◽  
Vol 290 (5) ◽  
pp. H1770-H1776 ◽  
Author(s):  
Ming Tao Jiang ◽  
Marko Ljubkovic ◽  
Yuri Nakae ◽  
Yang Shi ◽  
Wai-Meng Kwok ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Mitochondrial Membrane ◽  
Alternative Pathway ◽  
Dependent Manner ◽  
Inner Mitochondrial Membrane ◽  
Open Probability ◽  
Pharmaceutical Agents ◽  
Inactive Analog

Activation of the mitochondrial ATP-sensitive K+ channel (mitoKATP) and its regulation by PKC are critical events in preconditioning induced by ischemia or pharmaceutical agents in animals and humans. The properties of the human cardiac mitoKATP channel are unknown. Furthermore, there is no evidence that cytosolic PKC can directly regulate the mitoKATP channel located in the inner mitochondrial membrane (IMM) due to the physical barrier of the outer mitochondrial membrane. In the present study, we characterized the human cardiac mitoKATP channel and its potential regulation by PKC associated with the IMM. IMM fractions isolated from human left ventricles were fused into lipid bilayers in symmetrical potassium glutamate (150 mM). The conductance of native mitoKATP channels was usually below 80 pS (∼70%), which was reduced by ATP and 5-hydroxydecanoic acid (5-HD) in a dose- and time-dependent manner. The native mitoKATP channel is activated by diazoxide and inhibited by ATP and 5-HD. The PKC activator phorbol 12-myristate 13-acetate (2 μM) increased the cumulative open probability of the mitoKATP channel previously inhibited by ATP ( P < 0.05), but its inactive analog 4α-phorbol 12,13-didecanoate had no effect. Western blot analysis detected an inward rectifying K+ channel (Kir6.2) immunoreactive protein at 56 kDa and PKC-δ in the IMM. These data provide the first characterization of the human cardiac mitoKATP channel and its regulation by PKC(s) in IMM. This local PKC control mechanism may represent an alternative pathway to that proposed previously for cytosolic PKC during ischemic/pharmacological preconditioning.

scholarly journals Sorting switch of mitochondrial presequence translocase involves coupling of motor module to respiratory chain

2007 ◽  
Vol 179 (6) ◽  
pp. 1115-1122 ◽  
Author(s):  
Nils Wiedemann ◽  
Martin van der Laan ◽  
Dana P. Hutu ◽  
Peter Rehling ◽  
Nikolaus Pfanner
Keyword(s):  
Respiratory Chain ◽  
Mitochondrial Membrane ◽  
Early Stage ◽  
Dependent Manner ◽  
Inner Mitochondrial Membrane ◽  
En Bloc ◽  
Inner Membrane ◽  
The Matrix ◽  
Motor Module ◽  
In Transit

The mitochondrial presequence translocase transports preproteins to either matrix or inner membrane. Two different translocase forms have been identified: the matrix transport form, which binds the heat-shock protein 70 (Hsp70) motor, and the inner membrane–sorting form, which lacks the motor but contains translocase of inner mitochondrial membrane 21 (Tim21). The sorting form interacts with the respiratory chain in a Tim21-dependent manner. It is unknown whether the respiratory chain–bound translocase transports preproteins and how the switch between sorting form and motor form occurs. We report that the respiratory chain–bound translocase contains preproteins in transit and, surprisingly, not only sorted but also matrix-targeted preproteins. Presequence translocase-associated motor (Pam) 16 and 18, two regulatory components of the six-subunit motor, interact with the respiratory chain independently of Tim21. Thus, the respiratory chain–bound presequence translocase is not only active in preprotein sorting to the inner membrane but also in an early stage of matrix translocation. The motor does not assemble en bloc with the translocase but apparently in a step-wise manner with the Pam16/18 module before the Hsp70 core.

Modulation of the calcium-activated BK-channel of the inner mitochondrial membrane by hypoxia

2007 ◽  
Vol 34 (S 2) ◽  
Author(s):  
D Siemen ◽  
Y Cheng ◽  
X Gu ◽  
P Bednarczyk ◽  
GG Haddad ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Bk Channel ◽  
Inner Mitochondrial Membrane
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