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Liu Y, Suhail Y, Novin A, Afzal J, Pant A, Kshitiz. Lactate in breast cancer cells is associated with evasion of hypoxia-induced cell cycle arrest and adverse patient outcome. Hum Cell 2024; 37:768-781. [PMID: 38478356 PMCID: PMC11256967 DOI: 10.1007/s13577-024-01046-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 02/14/2024] [Indexed: 04/15/2024]
Abstract
Tumor hypoxia is a common microenvironmental factor in breast cancers, resulting in stabilization of Hypoxia-Inducible Factor 1 (HIF-1), the master regulator of hypoxic response in cells. Metabolic adaptation by HIF-1 results in inhibition of citric acid cycle, causing accumulation of lactate in large concentrations in hypoxic cancers. Lactate can therefore serve as a secondary microenvironmental factor influencing cellular response to hypoxia. Presence of lactate can alter the hypoxic response of breast cancers in many ways, sometimes in opposite manners. Lactate stabilizes HIF-1 in oxidative condition, as well as destabilizes HIF-1 in hypoxia, increases cellular acidification, and mitigates HIF-1-driven inhibition of cellular respiration. We therefore tested the effect of lactate in MDA-MB-231 under hypoxia, finding that lactate can activate pathways associated with DNA replication, and cell cycling, as well as tissue morphogenesis associated with invasive processes. Using a bioengineered nano-patterned stromal invasion assay, we also confirmed that high lactate and induced HIF-1α gene overexpression can synergistically promote MDA-MB-231 dissemination and stromal trespass. Furthermore, using The Cancer Genome Atlas, we also surprisingly found that lactate in hypoxia promotes gene expression signatures prognosticating low survival in breast cancer patients. Our work documents that lactate accumulation contributes to increased heterogeneity in breast cancer gene expression promoting cancer growth and reducing patient survival.
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Affiliation(s)
- Yamin Liu
- Department of Biomedical Engineering, University of Connecticut Health, Farmington, CT, USA
| | - Yasir Suhail
- Department of Biomedical Engineering, University of Connecticut Health, Farmington, CT, USA
- Center for Cell Analysis and Modeling, University of Connecticut Health, Farmington, CT, USA
| | - Ashkan Novin
- Department of Biomedical Engineering, University of Connecticut Health, Farmington, CT, USA
| | - Junaid Afzal
- Department of Medicine, University of California San Francisco, San Francisco, CA, USA
| | - Aditya Pant
- Department of Biomedical Engineering, University of Connecticut Health, Farmington, CT, USA
- NEAG Comprehensive Cancer Center, University of Connecticut Health, Farmington, CT, USA
| | - Kshitiz
- Department of Biomedical Engineering, University of Connecticut Health, Farmington, CT, USA.
- Center for Cell Analysis and Modeling, University of Connecticut Health, Farmington, CT, USA.
- Department of Medicine, University of California San Francisco, San Francisco, CA, USA.
- NEAG Comprehensive Cancer Center, University of Connecticut Health, Farmington, CT, USA.
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2
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Yuan Z, Zou Y, Liu X, Wang L, Chen C. Longitudinal study on blood and biochemical indexes of Tibetan and Han in high altitude area. Front Public Health 2023; 11:1282051. [PMID: 38035283 PMCID: PMC10685451 DOI: 10.3389/fpubh.2023.1282051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 10/30/2023] [Indexed: 12/02/2023] Open
Abstract
Objective This study aims to review the blood routine and biochemical indicators of the plateau population for three consecutive years, and analyze the impact of the plateau on these blood indicators of the Tibetan population and the Han immigrant population. Method These parameters were extracted from the Laboratory Department of Ali District People's Hospital in Tibet from January 2019 to December 2021, including blood routine, liver and kidney function, blood lipids, myocardial enzyme spectrum, and rheumatic factor indicators. Changes in these parameters were analyzed over 3 consecutive years according to inclusion and exclusion criteria. Result A total of 114 Tibetans and 93 Hans participated in the study. These parameters were significantly different between Tibetan and Han populations. Red blood cells (RBC), hemoglobin (HGB), hematocrit (HCT), mean hemoglobin content (MCH), mean corpuscular hemoglobin concentration (MCHC), white blood cells (WBC), lymphocytes (LYMPH) and monocytes (MONO) were significantly higher in Hans than Tibetans (p < 0.05). Biochemically, total bilirubin (TBIL), direct bilirubin (DBIL), albumin (ALB), urea nitrogen (Urea), creatinine (Cr), uric acid (UA), glucose (GLU), triglycerides (TG) and creatine kinase isoenzyme (CKMB) were significantly higher in Hans than Tibetans; aspartate aminotransferase (AST), glutamyl transpeptidase (GGT), alkaline phosphatase (ALP), antistreptolysin (ASO), and C-reactive protein (CRP) were significantly higher in Tibetans than Hans (p < 0.05). There were no obvious continuous upward or downward trend of the parameters for 3 consecutive years. Conclusion In high-altitude areas, Han immigrants have long-term stress changes compared with Tibetans. The main differences are reflected in the blood system, liver and kidney functions, etc., which provide basic data for further research on the health status of plateau populations.
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Affiliation(s)
- ZhiMin Yuan
- Department of Clinical Laboratory, Shaanxi Provincial Cancer Hospital Affiliated to Xi'an Jiaotong University, Xi'an, China
- Department of Clinical Laboratory, Ali District People's Hospital, Tibet Ali, China
| | - YuanWu Zou
- Department of Clinical Laboratory, Tuberculosis Prevent and Care Hospital of Shanxi Province, Xi’an, China
| | - XiaoXing Liu
- Department of Clinical Laboratory, Ali District People's Hospital, Tibet Ali, China
| | - LongHao Wang
- Department of Otolaryngology and Neck Surgery, Shanghai Ninth People’s Hospital, Shanghai Jiaotong University, Shanghai, China
| | - Cheng Chen
- Department of Clinical Laboratory, Ali District People's Hospital, Tibet Ali, China
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, College of Stomatology, Xi'an Jiaotong University, Xi'an, China
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Vardar Acar N, Özgül RK. A big picture of the mitochondria-mediated signals: From mitochondria to organism. Biochem Biophys Res Commun 2023; 678:45-61. [PMID: 37619311 DOI: 10.1016/j.bbrc.2023.08.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 08/02/2023] [Accepted: 08/16/2023] [Indexed: 08/26/2023]
Abstract
Mitochondria, well-known for years as the powerhouse and biosynthetic center of the cell, are dynamic signaling organelles beyond their energy production and biosynthesis functions. The metabolic functions of mitochondria, playing an important role in various biological events both in physiological and stress conditions, transform them into important cellular stress sensors. Mitochondria constantly communicate with the rest of the cell and even from other cells to the organism, transmitting stress signals including oxidative and reductive stress or adaptive signals such as mitohormesis. Mitochondrial signal transduction has a vital function in regulating integrity of human genome, organelles, cells, and ultimately organism.
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Affiliation(s)
- Neşe Vardar Acar
- Department of Pediatric Metabolism, Institute of Child Health, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - R Köksal Özgül
- Department of Pediatric Metabolism, Institute of Child Health, Faculty of Medicine, Hacettepe University, Ankara, Turkey.
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Abstract
Endogenous photosensitizers play a critical role in both beneficial and harmful light-induced transformations in biological systems. Understanding their mode of action is essential for advancing fields such as photomedicine, photoredox catalysis, environmental science, and the development of sun care products. This review offers a comprehensive analysis of endogenous photosensitizers in human skin, investigating the connections between their electronic excitation and the subsequent activation or damage of organic biomolecules. We gather the physicochemical and photochemical properties of key endogenous photosensitizers and examine the relationships between their chemical reactivity, location within the skin, and the primary biochemical events following solar radiation exposure, along with their influence on skin physiology and pathology. An important take-home message of this review is that photosensitization allows visible light and UV-A radiation to have large effects on skin. The analysis presented here unveils potential causes for the continuous increase in global skin cancer cases and emphasizes the limitations of current sun protection approaches.
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Affiliation(s)
- Erick L Bastos
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
| | - Frank H Quina
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
- Department of Chemical Engineering, Polytechnic School, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
| | - Maurício S Baptista
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
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Friberg M, Woeller K, Iberi V, Mancheno PP, Riedeman J, Bohman L, Davis CC. Development of in vitro methods to model the impact of vaginal lactobacilli on Staphylococcus aureus biofilm formation on menstrual cups as well as validation of recommended cleaning directions. FRONTIERS IN REPRODUCTIVE HEALTH 2023; 5:1162746. [PMID: 37671283 PMCID: PMC10475951 DOI: 10.3389/frph.2023.1162746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 07/25/2023] [Indexed: 09/07/2023] Open
Abstract
Introduction Menstrual cups (MC) are a reusable feminine hygiene product. A recent publication suggested that Staphylococcus aureus (S. aureus) biofilms can form on MCs which may lead to increased risk of menstrual Toxic Shock Syndrome (mTSS). Additionally, there is concern that buildup of residual menses may contribute to microbial growth and biofilm formation further increasing mTSS risk. Quantitative and qualitative analysis of in vitro tests were utilized to determine if S. aureus biofilm could form on MC in the presence of the keystone species Lactobacillus after 12 h of incubation. The methodology was based on a modification of an anaerobic in vitro method that harnesses the keystone species hypothesis by including a representative of vaginal lactic acid bacteria. Methods MCs were incubated anaerobically for 12 h in Vaginal Defined Media (VDM) with the two morphologically distinct bacteria, Lactobacillus gasseri (L. gasseri) and S. aureus. Colony Forming Units (CFU) for each organism from the VDM broth and sonicated MC were estimated. In addition, a separate experiment was conducted where S. aureus was grown for 12 h in the absence of L. gasseri. Qualitative analysis for biofilm formation utilized micro-CT (µ-CT) and cryogenic scanning electron microscopy (Cryo-SEM). Results Samples collected from the media control had expected growth of both organisms after 12 h of incubation. Samples collected from VDM broth were similar to media control at the end of the 12-h study. Total S. aureus cell density on MC following sonication/rinsing was minimal. Results when using a monoculture of S. aureus demonstrated that there was a significant growth of the organism in the media control and broth as well as the sonicated cups indicating that the presence of L. gasseri was important for controlling growth and adherence of S. aureus. Few rod-shaped bacteria (L. gasseri) and cocci (S. aureus) could be identified on the MCs when grown in a dual species culture inoculum and no biofilm was noted via µ-CT and cryo-SEM. Additionally, efforts to model and understand the validity of the current labeled recommendations for MC cleaning in-between uses are supported. Discussion The data support continued safe use of the Tampax® cup when used and maintained as recommended.
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Affiliation(s)
- Maria Friberg
- Baby, Feminine and Family Care Microbiology, The Procter & Gamble Company, Mason, OH, United States
| | - Kara Woeller
- Baby, Feminine and Family Care, Global Product Stewardship, The Procter & Gamble Company, Cincinnati, OH, United States
| | - Vighter Iberi
- Corporate Functions Analytical, The Procter & Gamble Company, Mason, OH, United States
| | | | - James Riedeman
- Baby, Family and Feminine Care Analytical Chemistry, The Procter & Gamble Company, Cincinnati, OH, United States
| | - Lisa Bohman
- Data Modeling and Sciences, The Procter & Gamble Company, Mason, OH, United States
| | - Catherine C. Davis
- Department of Medical Microbiology and Immunology, School of Medicine, Creighton University, Omaha, NE, United States
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Wirth G, Juusola G, Tarvainen S, Laakkonen JP, Korpisalo P, Ylä-Herttuala S. Capillary Dynamics Regulate Post-Ischemic Muscle Damage and Regeneration in Experimental Hindlimb Ischemia. Cells 2023; 12:2060. [PMID: 37626870 PMCID: PMC10453415 DOI: 10.3390/cells12162060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 07/20/2023] [Accepted: 07/23/2023] [Indexed: 08/27/2023] Open
Abstract
This study aimed to show the significance of capillary function in post-ischemic recovery from the perspective of physiological parameters, such as blood flow, hemoglobin oxygenation and tissue regeneration. Muscle-level microvascular alterations of blood flow and hemoglobin oxygenation, and post-ischemic myofiber and capillary responses were analyzed in aged, healthy C57Bl/6J mice (n = 48) and aged, hyperlipidemic LDLR-/-ApoB100/100 mice (n = 69) after the induction of acute hindlimb ischemia using contrast ultrasound, photoacoustic imaging and histological analyses, respectively. The capillary responses that led to successful post-ischemic muscle repair in C57Bl/6J mice included an early capillary dilation phase, preceding the return of arterial driving pressure, followed by an increase in capillary density that further supported satellite cell-induced muscle regeneration. Initial capillary enlargement was absent in the LDLR-/-ApoB100/100 mice with lifelong moderate hypercholesterolemia and led to an inability to recover arterial driving pressure, with a resulting increase in distal necrosis, chronic tissue damage and a delay in the overall recovery after ischemia. To conclude, this manuscript highlights, beyond arterial collateralization, the importance of the proper function of the capillary endothelium in post-ischemic recovery and displays how post-ischemic capillary dynamics associate beyond tissue blood flow to both hemoglobin oxygenation and tissue regeneration.
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Affiliation(s)
- Galina Wirth
- Heart Center, Kuopio University Hospital, FI-70200 Kuopio, Finland (P.K.)
- A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, FI-70211 Kuopio, Finland
| | - Greta Juusola
- Heart Center, Kuopio University Hospital, FI-70200 Kuopio, Finland (P.K.)
- A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, FI-70211 Kuopio, Finland
| | - Santeri Tarvainen
- Heart Center, Kuopio University Hospital, FI-70200 Kuopio, Finland (P.K.)
- A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, FI-70211 Kuopio, Finland
| | - Johanna P. Laakkonen
- A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, FI-70211 Kuopio, Finland
| | - Petra Korpisalo
- Heart Center, Kuopio University Hospital, FI-70200 Kuopio, Finland (P.K.)
- A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, FI-70211 Kuopio, Finland
| | - Seppo Ylä-Herttuala
- Heart Center, Kuopio University Hospital, FI-70200 Kuopio, Finland (P.K.)
- A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, FI-70211 Kuopio, Finland
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7
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Pias SC. Do Vascular and Extracellular Measurements Consistently Reflect Intracellular pO 2? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1438:185-190. [PMID: 37845459 DOI: 10.1007/978-3-031-42003-0_29] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2023]
Abstract
Oxygen measurements are routinely made either in the vasculature or in the extracellular fluid surrounding the cells of tissues. Yet, metabolic oxygen availability depends on the pO2 within the cells, as does the enhancing effect of oxygen on radiotherapy outcomes. This article reports quantitative modeling work examining the effect of cellular plasma membrane composition on tissue permeability, as a window into tissue oxygen gradients. Previous application of the model indicates that lipid-mediated diffusion pathways accelerate oxygen transfer from capillaries to intracellular compartments and that the extent of acceleration is modulated by membrane lipid and protein composition. Here, the effects of broken intercellular junctions and increased gap size between cells in the model are addressed. The conclusion is reached that the pO2 gradient will likely be consistent among similar, healthy tissues but may increase with increased interstitial fluid fraction and broken intercellular junctions. Therefore, tissue structural changes in tumors and other diseased or damaged tissues may lead to aberrations in permeability that confound interpretation of extracellular oxygen measurements.
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Affiliation(s)
- Sally C Pias
- Department of Chemistry, New Mexico Institute of Mining and Technology, Socorro, NM, USA.
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8
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Guette-Marquet S, Roques C, Bergel A. Direct electrochemical detection of trans-plasma membrane electron transfer: A possible alternative pathway for cell respiration. Biosens Bioelectron 2022; 220:114896. [DOI: 10.1016/j.bios.2022.114896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 11/04/2022] [Accepted: 11/06/2022] [Indexed: 11/09/2022]
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9
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Computational Modeling and Imaging of the Intracellular Oxygen Gradient. Int J Mol Sci 2022; 23:ijms232012597. [PMID: 36293452 PMCID: PMC9604273 DOI: 10.3390/ijms232012597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 10/13/2022] [Accepted: 10/17/2022] [Indexed: 11/30/2022] Open
Abstract
Computational modeling can provide a mechanistic and quantitative framework for describing intracellular spatial heterogeneity of solutes such as oxygen partial pressure (pO2). This study develops and evaluates a finite-element model of oxygen-consuming mitochondrial bioenergetics using the COMSOL Multiphysics program. The model derives steady-state oxygen (O2) distributions from Fickian diffusion and Michaelis–Menten consumption kinetics in the mitochondria and cytoplasm. Intrinsic model parameters such as diffusivity and maximum consumption rate were estimated from previously published values for isolated and intact mitochondria. The model was compared with experimental data collected for the intracellular and mitochondrial pO2 levels in human cervical cancer cells (HeLa) in different respiratory states and under different levels of imposed pO2. Experimental pO2 gradients were measured using lifetime imaging of a Förster resonance energy transfer (FRET)-based O2 sensor, Myoglobin-mCherry, which offers in situ real-time and noninvasive measurements of subcellular pO2 in living cells. On the basis of these results, the model qualitatively predicted (1) the integrated experimental data from mitochondria under diverse experimental conditions, and (2) the impact of changes in one or more mitochondrial processes on overall bioenergetics.
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Fagiolino P, Vázquez M. Tissue Drug Concentration. Curr Pharm Des 2022; 28:1109-1123. [PMID: 35466869 DOI: 10.2174/1381612828666220422091159] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 02/25/2022] [Indexed: 11/22/2022]
Abstract
Blood flow enables the delivery of oxygen and nutrients to the different tissues of the human body. Drugs follow the same route as oxygen and nutrients; thus, drug concentrations in tissues are highly dependent on the blood flow fraction delivered to each of these tissues. Although the free drug concentration in blood is considered to correlate with pharmacodynamics, the pharmacodynamics of a drug is actually primarily commanded by the concentrations of drug in the aqueous spaces of bodily tissues. However, the concentrations of drug are not homogeneous throughout the tissues, and they rarely reflect the free drug concentration in the blood. This heterogeneity is due to differences in the blood flow fraction delivered to the tissues and also due to membrane transporters, efflux pumps, and metabolic enzymes. The rate of drug elimination from the body (systemic elimination) depends more on the driving force of drug elimination than on the free concentration of drug at the site from which the drug is being eliminated. In fact, the actual free drug concentration in the tissues results from the balance between the input and output rates. In the present paper, we develop a theoretical concept regarding solute partition between intravascular and extravascular spaces; discuss experimental research on aqueous/non-aqueous solute partitioning and clinical research on microdialysis; and present hypotheses to predict in-vivo elimination using parameters of in-vitro metabolism.
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Affiliation(s)
- Pietro Fagiolino
- Pharmaceutical Sciences Department, Faculty of Chemistry, Universidad de la República, Montevideo, Uruguay
| | - Marta Vázquez
- Pharmaceutical Sciences Department, Faculty of Chemistry, Universidad de la República, Montevideo, Uruguay
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11
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Oxygen flux from capillary to mitochondria: integration of contemporary discoveries. Eur J Appl Physiol 2022; 122:7-28. [PMID: 34940908 PMCID: PMC8890444 DOI: 10.1007/s00421-021-04854-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 11/18/2021] [Indexed: 01/03/2023]
Abstract
Resting humans transport ~ 100 quintillion (1018) oxygen (O2) molecules every second to tissues for consumption. The final, short distance (< 50 µm) from capillary to the most distant mitochondria, in skeletal muscle where exercising O2 demands may increase 100-fold, challenges our understanding of O2 transport. To power cellular energetics O2 reaches its muscle mitochondrial target by dissociating from hemoglobin, crossing the red cell membrane, plasma, endothelial surface layer, endothelial cell, interstitial space, myocyte sarcolemma and a variable expanse of cytoplasm before traversing the mitochondrial outer/inner membranes and reacting with reduced cytochrome c and protons. This past century our understanding of O2's passage across the body's final O2 frontier has been completely revised. This review considers the latest structural and functional data, challenging the following entrenched notions: (1) That O2 moves freely across blood cell membranes. (2) The Krogh-Erlang model whereby O2 pressure decreases systematically from capillary to mitochondria. (3) Whether intramyocyte diffusion distances matter. (4) That mitochondria are separate organelles rather than coordinated and highly plastic syncytia. (5) The roles of free versus myoglobin-facilitated O2 diffusion. (6) That myocytes develop anoxic loci. These questions, and the intriguing notions that (1) cellular membranes, including interconnected mitochondrial membranes, act as low resistance conduits for O2, lipids and H+-electrochemical transport and (2) that myoglobin oxy/deoxygenation state controls mitochondrial oxidative function via nitric oxide, challenge established tenets of muscle metabolic control. These elements redefine muscle O2 transport models essential for the development of effective therapeutic countermeasures to pathological decrements in O2 supply and physical performance.
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Vervust W, Ghysels A. Oxygen Storage in Stacked Phospholipid Membranes Under an Oxygen Gradient as a Model for Myelin Sheaths. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1395:301-307. [PMID: 36527653 DOI: 10.1007/978-3-031-14190-4_49] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Axons in the brain and peripheral nervous system are enveloped by myelin sheaths, which are composed of stacked membrane bilayers containing large fractions of cholesterol, phospholipids, and glycolipids. The oxygen availability to the nearby oxygen consuming cytochrome c oxidase in the mitochondria is essential for the well-functioning of a cell. By constructing a rate network model based on molecular dynamics simulations, and solving it for steady-state conditions, this work calculates the oxygen storage in stacked membranes under an oxygen gradient. It is found that stacking membranes increases the oxygen storage capacity, indicating that myelin can function as an oxygen reservoir. However, it is found that the storage enhancement levels out for stacks with a large number of bilayers, suggesting why myelin sheaths consist of only 10-300 membranes rather than thousands. The presence of additional water between the stacked bilayers, as seen in cancer cells, is shown to diminish myelin oxygen storage enhancement.
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Subczynski WK, Widomska J, Stein N, Swartz HM. Factors determining barrier properties to oxygen transport across model and cell plasma membranes based on EPR spin-label oximetry. APPLIED MAGNETIC RESONANCE 2021; 52:1237-1260. [PMID: 36267674 PMCID: PMC9581439 DOI: 10.1007/s00723-021-01412-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 07/23/2021] [Accepted: 08/04/2021] [Indexed: 06/01/2023]
Abstract
This review is motivated by the exciting new area of radiation therapy using a phenomenon termed FLASH in which oxygen is thought to have a central role. Well-established principles of radiation biology and physics suggest that if oxygen has a strong role, it should be the level at the DNA. The key aspect discussed is the rate of oxygen diffusion. If oxygen freely diffuses into cells and rapidly equilibrates, then measurements in the extracellular compartment would enable FLASH to be investigated using existing methodologies that can readily measure oxygen in the extracellular compartment. EPR spin-label oximetry allows evaluation of the oxygen permeability coefficient across lipid bilayer membranes. It is established that simple fluid phase lipid bilayers are not barriers to oxygen transport. However, further investigations indicate that many physical and chemical (compositional) factor can significantly decrease this permeation. In biological cell plasma membranes, the lipid bilayer forms the matrix in which integral membrane proteins are immersed, changing organization and properties of the lipid matrix. To evaluate oxygen permeability coefficients across these complex membranes, oxygen permeation across all membrane domains and components must be considered. In this review, we consider many of the factors that affect (decrease) oxygen permeation across cell plasma membranes. Finally, we address the question, can the plasma membrane of the cell form a barrier to the free diffusion of oxygen into the cell interior? If there is a barrier then this must be considered in the investigations of the role of oxygen in FLASH.
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Affiliation(s)
- Witold K. Subczynski
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Justyna Widomska
- Department of Biophysics, Medical University of Lublin, Jaczewskiego 4, Lublin, Poland
| | - Natalia Stein
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Harold M. Swartz
- Department of Radiology, The Geisel School of Medicine at Dartmouth, Lebanon, NH 03766, USA
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Angles G, Hail A, Dotson RJ, Pias SC. Atomistic simulations modify interpretation of spin-label oximetry data. Part 1: intensified water-lipid interfacial resistances. APPLIED MAGNETIC RESONANCE 2021; 52:1261-1289. [PMID: 37292189 PMCID: PMC10249954 DOI: 10.1007/s00723-021-01398-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 07/14/2021] [Accepted: 07/16/2021] [Indexed: 06/10/2023]
Abstract
The role of membrane cholesterol in cellular function and dysfunction has been the subject of much inquiry. A few studies have suggested that cholesterol may slow oxygen diffusive transport, altering membrane physical properties and reducing oxygen permeability. The primary experimental technique used in recent years to study membrane oxygen transport is saturation-recovery electron paramagnetic resonance (EPR) oximetry, using spin-label probes targeted to specific regions of a lipid bilayer. The technique has been used, in particular, to assess the influence of cholesterol on oxygen transport and membrane permeability. The reliability of such EPR recordings at the water-lipid interface near the phospholipid headgroups has been challenged by all-atom molecular dynamics (MD) simulation data that show substantive agreement with spin-label probe measurements throughout much of the bilayer. This work uses further MD simulations, with an updated oxygen model, to determine the location of the maximum resistance to permeation and the rate-limiting barrier to oxygen permeation in 1-palmitoyl,2-oleoylphosphatidylcholine (POPC) and POPC/cholesterol bilayers at 25 and 35°C. The current simulations show a spike of resistance to permeation in the headgroup region that was not detected by EPR but was predicted in early theoretical work by Diamond and Katz. Published experimental nuclear magnetic resonance (NMR) oxygen measurements provide key validation of the MD models and indicate that the positions and relative magnitudes of the phosphatidylcholine resistance peaks are accurate. Consideration of the headgroup-region resistances predicts bilayer permeability coefficients lower than estimated in EPR studies, giving permeabilities lower than the permeability of unstirred water layers of the same thickness. Here, the permeability of POPC at 35°C is estimated to be 13 cm/s, compared with 10 cm/s for POPC/cholesterol and 118 cm/s for simulation water layers of similar thickness. The value for POPC is 12 times lower than estimated from EPR measurements, while the value for POPC/cholesterol is 5 times lower. These findings underscore the value of atomic resolution models for guiding the interpretation of experimental probe-based measurements.
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Affiliation(s)
| | | | | | - Sally C. Pias
- Corresponding author: , Department of Chemistry, New Mexico Institute of Mining and Technology (New Mexico Tech), 801 Leroy Place, Socorro, NM 87801, USA
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15
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Pias SC, Wang Q, Dotson RJ. Metabolism, measurement and modelling: understanding and exploiting tissue oxygenation. J Physiol 2021; 599:1743-1744. [PMID: 33719049 DOI: 10.1113/jp281213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Sally C Pias
- Department of Chemistry, New Mexico Institute of Mining and Technology (New Mexico Tech), Socorro, NM, USA
| | - Qi Wang
- Department of Chemistry, New Mexico Institute of Mining and Technology (New Mexico Tech), Socorro, NM, USA
| | - Rachel J Dotson
- Department of Chemistry, New Mexico Institute of Mining and Technology (New Mexico Tech), Socorro, NM, USA
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