-
American Journal of Respiratory Cell... Nov 2020Cigarette smoke (CS) exposure increases the risk for acute respiratory distress syndrome in humans and promotes alveolar-capillary barrier permeability and acute lung...
Cigarette smoke (CS) exposure increases the risk for acute respiratory distress syndrome in humans and promotes alveolar-capillary barrier permeability and acute lung injury in animal models. However, the underlying mechanisms are not well understood. Mitochondrial fusion and fission are essential for mitochondrial homeostasis in health and disease. In this study, we hypothesized that CS caused endothelial injury via an imbalance of mitochondrial fusion and fission and resultant mitochondrial oxidative stress and dysfunction. We noted that CS altered mitochondrial morphology by shortening mitochondrial networks and causing perinuclear accumulation of damaged mitochondria in primary rat lung microvascular endothelial cells. We also found that CS increased mitochondrial fission likely by decreasing Drp1-S637 and increasing FIS1, Drp1-S616 phosphorylation, mitochondrial translocation, and tetramerization and reduced mitochondrial fusion likely by decreasing Mfn2 in lung microvascular endothelial cells and mouse lungs. CS also caused aberrant mitophagy, increased mitochondrial oxidative stress, and reduced mitochondrial respiration. An inhibitor of mitochondrial fission and a mitochondria-specific antioxidant prevented CS-induced increased endothelial barrier dysfunction and apoptosis. Our data suggest that excessive mitochondrial fission and resultant oxidative stress are essential mediators of CS-induced endothelial injury and that inhibition of mitochondrial fission and mitochondria-specific antioxidants may be useful therapeutic strategies for CS-induced endothelial injury and associated pulmonary diseases.
Topics: Animals; Apoptosis; Capillary Permeability; Cell Respiration; Dynamins; Endothelial Cells; Lung; Male; Mice; Microvessels; Mitochondria; Mitochondrial Dynamics; Mitophagy; Models, Biological; Oxidative Stress; Protein Transport; Rats; Smoking
PubMed: 32672471
DOI: 10.1165/rcmb.2020-0008OC -
Nature Communications Dec 2021Blood microcirculation supplies neurons with oxygen and nutrients, and contributes to clearing their neurotoxic waste, through a dense capillary network connected to...
Blood microcirculation supplies neurons with oxygen and nutrients, and contributes to clearing their neurotoxic waste, through a dense capillary network connected to larger tree-like vessels. This complex microvascular architecture results in highly heterogeneous blood flow and travel time distributions, whose origin and consequences on brain pathophysiology are poorly understood. Here, we analyze highly-resolved intracortical blood flow and transport simulations to establish the physical laws governing the macroscopic transport properties in the brain micro-circulation. We show that network-driven anomalous transport leads to the emergence of critical regions, whether hypoxic or with high concentrations of amyloid-β, a waste product centrally involved in Alzheimer's Disease. We develop a Continuous-Time Random Walk theory capturing these dynamics and predicting that such critical regions appear much earlier than anticipated by current empirical models under mild hypoperfusion. These findings provide a framework for understanding and modelling the impact of microvascular dysfunction in brain diseases, including Alzheimer's Disease.
Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Biological Transport; Blood Circulation; Brain; Humans; Microcirculation; Microvessels; Oxygen
PubMed: 34911962
DOI: 10.1038/s41467-021-27534-8 -
Journal of Chemical Theory and... Jun 2017A Bayesian-based methodology is developed to estimate diffusion tensors from molecular dynamics simulations of permeants in anisotropic media, and is applied to oxygen...
A Bayesian-based methodology is developed to estimate diffusion tensors from molecular dynamics simulations of permeants in anisotropic media, and is applied to oxygen in lipid bilayers. By a separation of variables in the Smoluchowski diffusion equation, the multidimensional diffusion is reduced to coupled one-dimensional diffusion problems that are treated by discretization. The resulting diffusivity profiles characterize the membrane transport dynamics as a function of the position across the membrane, discriminating between diffusion normal and parallel to the membrane. The methodology is first validated with neat water, neat hexadecane, and a hexadecane slab surrounded by water, the latter being a simple model for a lipid membrane. Next, a bilayer consisting of pure 1-palmitoyl 2-oleoylphosphatidylcholine (POPC), and a bilayer mimicking the lipid composition of the inner mitochondrial membrane, including cardiolipin, are investigated. We analyze the detailed time evolution of oxygen molecules, in terms of both normal diffusion through and radial diffusion inside the membrane. Diffusion is fast in the more loosely packed interleaflet region, and anisotropic, with oxygen spreading more rapidly in the membrane plane than normal to it. Visualization of the propagator shows that oxygen enters the membrane rapidly, reaching its thermodynamically favored center in about 1 ns, despite the free energy barrier at the headgroup region. Oxygen transport is quantified by computing the oxygen permeability of the membranes and the average radial diffusivity, which confirm the anisotropy of the diffusion. The position-dependent diffusion constants and free energies are used to construct compartmental models and test assumptions used in estimating permeability, including Overton's rule. In particular, a hexadecane slab surrounded by water is found to be a poor model of oxygen transport in membranes because the relevant energy barriers differ substantially.
Topics: Alkanes; Bayes Theorem; Biological Transport; Cell Membrane; Cell Membrane Permeability; Diffusion; Lipid Bilayers; Molecular Conformation; Molecular Dynamics Simulation; Oxygen; Phosphatidylcholines; Thermodynamics; Water
PubMed: 28482659
DOI: 10.1021/acs.jctc.7b00039 -
International Journal of Molecular... Dec 2016Melatonin has been speculated to be mainly synthesized by mitochondria. This speculation is supported by the recent discovery that aralkylamine... (Review)
Review
Melatonin has been speculated to be mainly synthesized by mitochondria. This speculation is supported by the recent discovery that aralkylamine -acetyltransferase/serotonin -acetyltransferase (AANAT/SNAT) is localized in mitochondria of oocytes and the isolated mitochondria generate melatonin. We have also speculated that melatonin is a mitochondria-targeted antioxidant. It accumulates in mitochondria with high concentration against a concentration gradient. This is probably achieved by an active transportation via mitochondrial melatonin transporter(s). Melatonin protects mitochondria by scavenging reactive oxygen species (ROS), inhibiting the mitochondrial permeability transition pore (MPTP), and activating uncoupling proteins (UCPs). Thus, melatonin maintains the optimal mitochondrial membrane potential and preserves mitochondrial functions. In addition, mitochondrial biogenesis and dynamics is also regulated by melatonin. In most cases, melatonin reduces mitochondrial fission and elevates their fusion. Mitochondrial dynamics exhibit an oscillatory pattern which matches the melatonin circadian secretory rhythm in pinealeocytes and probably in other cells. Recently, melatonin has been found to promote mitophagy and improve homeostasis of mitochondria.
Topics: Animals; Antioxidants; Circadian Rhythm; Enzyme Activation; Humans; Melatonin; Membrane Potential, Mitochondrial; Mitochondria; Mitochondrial Dynamics; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Mitochondrial Uncoupling Proteins; Mitophagy; Plants; Reactive Oxygen Species
PubMed: 27999288
DOI: 10.3390/ijms17122124 -
International Journal of Molecular... Oct 2020Symbiotic nitrogen fixation requires the transfer of fixed organic nitrogen compounds from the symbiotic bacteria to a host plant, yet the chemical nature of the...
Symbiotic nitrogen fixation requires the transfer of fixed organic nitrogen compounds from the symbiotic bacteria to a host plant, yet the chemical nature of the compounds is in question. bacteroids were isolated anaerobically from soybean nodules and assayed at varying densities, varying partial pressures of oxygen, and varying levels of l-malate. Ammonium was released at low bacteroid densities and high partial pressures of oxygen, but was apparently taken up at high bacteroid densities and low partial pressures of oxygen in the presence of l-malate; these later conditions were optimal for amino acid excretion. The ratio of partial pressure of oxygen/bacteroid density of apparent ammonium uptake and of alanine excretion displayed an inverse relationship. Ammonium uptake, alanine and branch chain amino acid release were all dependent on the concentration of l-malate displaying similar K values of 0.5 mM demonstrating concerted regulation. The hyperbolic kinetics of ammonium uptake and amino acid excretion suggests transport via a membrane carrier and also suggested that transport was rate limiting. Glutamate uptake displayed exponential kinetics implying transport via a channel. The chemical nature of the compounds released were dependent upon bacteroid density, partial pressure of oxygen and concentration of l-malate demonstrating an integrated metabolism.
Topics: Alanine; Ammonium Compounds; Bacterial Proteins; Bradyrhizobium; Malates; Membrane Transport Proteins; Nitrogen Fixation; Oxygen; Root Nodules, Plant; Glycine max
PubMed: 33066093
DOI: 10.3390/ijms21207542 -
The Plant Journal : For Cell and... Feb 2021Phosphorus absorbed in the form of phosphate (H PO ) is an essential but limiting macronutrient for plant growth and agricultural productivity. A comprehensive...
Phosphorus absorbed in the form of phosphate (H PO ) is an essential but limiting macronutrient for plant growth and agricultural productivity. A comprehensive understanding of how plants respond to phosphate starvation is essential for the development of more phosphate-efficient crops. Here we employed label-free proteomics and phosphoproteomics to quantify protein-level responses to 48 h of phosphate versus phosphite (H PO ) resupply to phosphate-deprived Arabidopsis thaliana suspension cells. Phosphite is similarly sensed, taken up and transported by plant cells as phosphate, but cannot be metabolized or used as a nutrient. Phosphite is thus a useful tool for differentiating between non-specific processes related to phosphate sensing and transport and specific responses to phosphorus nutrition. We found that responses to phosphate versus phosphite resupply occurred mainly at the level of protein phosphorylation, complemented by limited changes in protein abundance, primarily in protein translation, phosphate transport and scavenging, and central metabolism proteins. Altered phosphorylation of proteins involved in core processes such as translation, RNA splicing and kinase signaling was especially important. We also found differential phosphorylation in response to phosphate and phosphite in 69 proteins, including splicing factors, translation factors, the PHT1;4 phosphate transporter and the HAT1 histone acetyltransferase - potential phospho-switches signaling changes in phosphorus nutrition. Our study illuminates several new aspects of the phosphate starvation response and identifies important targets for further investigation and potential crop improvement.
Topics: Arabidopsis; Arabidopsis Proteins; Biological Transport; Carbon; Cell Respiration; Cells, Cultured; Phosphates; Phosphites; Phosphoproteins; Phosphorylation; Proteome; Proteomics
PubMed: 33184936
DOI: 10.1111/tpj.15078 -
International Journal of Molecular... Mar 2021Active transport of sugars into bacteria occurs through symporters driven by ion gradients. is the most well-studied proton sugar symporter, whereas is the most... (Review)
Review
Active transport of sugars into bacteria occurs through symporters driven by ion gradients. is the most well-studied proton sugar symporter, whereas is the most characterized sodium sugar symporter. These are members of the major facilitator (MFS) and the amino acid-Polyamine organocation (APS) transporter superfamilies. While there is no structural homology between these transporters, they operate by a similar mechanism. They are nano-machines driven by their respective ion electrochemical potential gradients across the membrane. has 12 transmembrane helices (TMs) organized in two 6-TM bundles, each containing two 3-helix TM repeats. has a core structure of 10 TM helices organized in two inverted repeats (TM 1-5 and TM 6-10). In each case, a single sugar is bound in a central cavity and sugar selectivity is determined by hydrogen- and hydrophobic- bonding with side chains in the binding site. In vSGLT, the sodium-binding site is formed through coordination with carbonyl- and hydroxyl-oxygens from neighboring side chains, whereas in the proton (HO) site is thought to be a single glutamate residue (Glu325). The remaining challenge for both transporters is to determine how ion electrochemical potential gradients drive uphill sugar transport.
Topics: Binding Sites; Biological Transport, Active; Escherichia coli Proteins; Glucose; Lactose; Membrane Transport Proteins; Models, Molecular; Monosaccharide Transport Proteins; Protein Conformation; Sodium-Glucose Transport Proteins; Sugars; Symporters
PubMed: 33808202
DOI: 10.3390/ijms22073572 -
American Journal of Physiology. Renal... Mar 2015Uremic cardiomyopathy (UCM) is characterized by metabolic remodelling, compromised energetics, and loss of insulin-mediated cardioprotection, which result in...
Uremic cardiomyopathy (UCM) is characterized by metabolic remodelling, compromised energetics, and loss of insulin-mediated cardioprotection, which result in unsustainable adaptations and heart failure. However, the role of mitochondria and the susceptibility of mitochondrial permeability transition pore (mPTP) formation in ischemia-reperfusion injury (IRI) in UCM are unknown. Using a rat model of chronic uremia, we investigated the oxidative capacity of mitochondria in UCM and their sensitivity to ischemia-reperfusion mimetic oxidant and calcium stressors to assess the susceptibility to mPTP formation. Uremic animals exhibited a 45% reduction in creatinine clearance (P < 0.01), and cardiac mitochondria demonstrated uncoupling with increased state 4 respiration. Following IRI, uremic mitochondria exhibited a 58% increase in state 4 respiration (P < 0.05), with an overall reduction in respiratory control ratio (P < 0.01). Cardiomyocytes from uremic animals displayed a 30% greater vulnerability to oxidant-induced cell death determined by FAD autofluorescence (P < 0.05) and reduced mitochondrial redox state on exposure to 200 μM H2O2 (P < 0.01). The susceptibility to calcium-induced permeability transition showed that maximum rates of depolarization were enhanced in uremia by 79%. These results demonstrate that mitochondrial respiration in the uremic heart is chronically uncoupled. Cardiomyocytes in UCM are characterized by a more oxidized mitochondrial network, with greater susceptibility to oxidant-induced cell death and enhanced vulnerability to calcium-induced mPTP formation. Collectively, these findings indicate that mitochondrial function is compromised in UCM with increased vulnerability to calcium and oxidant-induced stressors, which may underpin the enhanced predisposition to IRI in the uremic heart.
Topics: Animals; Calcium; Cardiomyopathies; Cell Respiration; Cells, Cultured; Disease Models, Animal; In Vitro Techniques; Male; Mitochondria; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Myocardial Reperfusion Injury; Myocytes, Cardiac; Oxidative Stress; Rats, Sprague-Dawley; Uremia
PubMed: 25587120
DOI: 10.1152/ajprenal.00442.2014 -
American Journal of Physiology. Renal... May 2015The goal of this study was to investigate the reciprocal interactions among oxygen (O2), nitric oxide (NO), and superoxide (O2 (-)) and their effects on medullary...
The goal of this study was to investigate the reciprocal interactions among oxygen (O2), nitric oxide (NO), and superoxide (O2 (-)) and their effects on medullary oxygenation and urinary output. To accomplish that goal, we developed a detailed mathematical model of solute transport in the renal medulla of the rat kidney. The model represents the radial organization of the renal tubules and vessels, which centers around the vascular bundles in the outer medulla and around clusters of collecting ducts in the inner medulla. Model simulations yield significant radial gradients in interstitial fluid oxygen tension (Po2) and NO and O2 (-) concentration in the OM and upper IM. In the deep inner medulla, interstitial fluid concentrations become much more homogeneous, as the radial organization of tubules and vessels is not distinguishable. The model further predicts that due to the nonlinear interactions among O2, NO, and O2 (-), the effects of NO and O2 (-) on sodium transport, osmolality, and medullary oxygenation cannot be gleaned by considering each solute's effect in isolation. An additional simulation suggests that a sufficiently large reduction in tubular transport efficiency may be the key contributing factor, more so than oxidative stress alone, to hypertension-induced medullary hypoxia. Moreover, model predictions suggest that urine Po2 could serve as a biomarker for medullary hypoxia and a predictor of the risk for hospital-acquired acute kidney injury.
Topics: Acute Kidney Injury; Animals; Biological Transport; Cell Hypoxia; Computer Simulation; Hypertension; Kidney Concentrating Ability; Kidney Medulla; Kidney Tubules; Models, Biological; Nitric Oxide; Nonlinear Dynamics; Oxidative Stress; Oxygen; Rats; Renal Circulation; Sodium; Superoxides
PubMed: 25651567
DOI: 10.1152/ajprenal.00600.2014 -
Plant Physiology Apr 2021Membrane voltage arises from the transport of ions through ion-translocating ATPases, ion-coupled transport of solutes, and ion channels, and is an integral part of the...
Membrane voltage arises from the transport of ions through ion-translocating ATPases, ion-coupled transport of solutes, and ion channels, and is an integral part of the bioenergetic "currency" of the membrane. The dynamics of membrane voltage-so-called action, systemic, and variation potentials-have also led to a recognition of their contributions to signal transduction, both within cells and across tissues. Here, we review the origins of our understanding of membrane voltage and its place as a central element in regulating transport and signal transmission. We stress the importance of understanding voltage as a common intermediate that acts both as a driving force for transport-an electrical "substrate"-and as a product of charge flux across the membrane, thereby interconnecting all charge-carrying transport across the membrane. The voltage interconnection is vital to signaling via second messengers that rely on ion flux, including cytosolic free Ca2+, H+, and the synthesis of reactive oxygen species generated by integral membrane, respiratory burst oxidases. These characteristics inform on the ways in which long-distance voltage signals and voltage oscillations give rise to unique gene expression patterns and influence physiological, developmental, and adaptive responses such as systemic acquired resistance to pathogens and to insect herbivory.
Topics: Biological Transport; Cell Membrane; Ion Transport; Plant Development; Signal Transduction; Voltage-Dependent Anion Channels
PubMed: 33598675
DOI: 10.1093/plphys/kiab032