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Rana PS, Model MA. A Reverse-Osmosis Model of Apoptotic Shrinkage. Front Cell Dev Biol 2020; 8:588721. [PMID: 33195250 PMCID: PMC7644884 DOI: 10.3389/fcell.2020.588721] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 10/05/2020] [Indexed: 11/13/2022] Open
Abstract
The standard theory of apoptotic volume decrease (AVD) posits activation of potassium and/or chloride channels, causing an efflux of ions and osmotic loss of water. However, in view of the multitude of possible channels that are known to support apoptosis, a model based on specific signaling to a channel presents certain problems. We propose another mechanism of apoptotic dehydration based on cytoskeletal compression. As is well known, cytoskeleton is not strong enough to expel a substantial amount of water against an osmotic gradient. It is possible, however, that an increase in intracellular pressure may cause an initial small efflux of water, and that will create a small concentration gradient of ions, favoring their exit. If the channels are open, some ions will exit the cell, relieving the osmotic gradient; in this way, the process will be able to continue. Calculations confirm the possibility of such a mechanism. An increase in membrane permeability for water or ions may also result in dehydration if accompanied even by a constant cytoskeletal pressure. We review the molecular processes that may lead to apoptotic dehydration in the context of this model.
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Affiliation(s)
- Priyanka S Rana
- Department of Biological Sciences, Kent State University, Kent, OH, United States
| | - Michael A Model
- Department of Biological Sciences, Kent State University, Kent, OH, United States
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Bouffartigues E, Si Hadj Mohand I, Maillot O, Tortuel D, Omnes J, David A, Tahrioui A, Duchesne R, Azuama CO, Nusser M, Brenner-Weiss G, Bazire A, Connil N, Orange N, Feuilloley MGJ, Lesouhaitier O, Dufour A, Cornelis P, Chevalier S. The Temperature-Regulation of Pseudomonas aeruginosa cmaX-cfrX-cmpX Operon Reveals an Intriguing Molecular Network Involving the Sigma Factors AlgU and SigX. Front Microbiol 2020; 11:579495. [PMID: 33193206 PMCID: PMC7641640 DOI: 10.3389/fmicb.2020.579495] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 09/23/2020] [Indexed: 11/13/2022] Open
Abstract
Pseudomonas aeruginosa is a highly adaptable Gram-negative opportunistic pathogen, notably due to its large number of transcription regulators. The extracytoplasmic sigma factor (ECFσ) AlgU, responsible for alginate biosynthesis, is also involved in responses to cell wall stress and heat shock via the RpoH alternative σ factor. The SigX ECFσ emerged as a major regulator involved in the envelope stress response via membrane remodeling, virulence and biofilm formation. However, their functional interactions to coordinate the envelope homeostasis in response to environmental variations remain to be determined. The regulation of the putative cmaX-cfrX-cmpX operon located directly upstream sigX was investigated by applying sudden temperature shifts from 37°C. We identified a SigX- and an AlgU- dependent promoter region upstream of cfrX and cmaX, respectively. We show that cmaX expression is increased upon heat shock through an AlgU-dependent but RpoH independent mechanism. In addition, the ECFσ SigX is activated in response to valinomycin, an agent altering the membrane structure, and up-regulates cfrX-cmpX transcription in response to cold shock. Altogether, these data provide new insights into the regulation exerted by SigX and networks that are involved in maintaining envelope homeostasis.
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Affiliation(s)
- Emeline Bouffartigues
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Ishac Si Hadj Mohand
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Olivier Maillot
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Damien Tortuel
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Jordane Omnes
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Audrey David
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Ali Tahrioui
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Rachel Duchesne
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Cecil Onyedikachi Azuama
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Michael Nusser
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Gerald Brenner-Weiss
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Alexis Bazire
- Laboratoire de Biotechnologie et Chimie Marines (LBCM) EA3884, IUEM, Université de Bretagne-Sud, Lorient, France
| | - Nathalie Connil
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Nicole Orange
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Marc G J Feuilloley
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Olivier Lesouhaitier
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Alain Dufour
- Laboratoire de Biotechnologie et Chimie Marines (LBCM) EA3884, IUEM, Université de Bretagne-Sud, Lorient, France
| | - Pierre Cornelis
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
| | - Sylvie Chevalier
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) EA 4312, Normandie Université, Université de Rouen Normandie, Centre de Sécurité Sanitaire de Normandie, Evreux, France
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Comparing the Effects of Intracellular and Extracellular Magnetic Hyperthermia on the Viability of BxPC-3 Cells. NANOMATERIALS 2020; 10:nano10030593. [PMID: 32213961 PMCID: PMC7153512 DOI: 10.3390/nano10030593] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 03/13/2020] [Accepted: 03/22/2020] [Indexed: 12/20/2022]
Abstract
Magnetic hyperthermia involves the use of iron oxide nanoparticles to generate heat in tumours following stimulation with alternating magnetic fields. In recent times, this treatment has undergone numerous clinical trials in various solid malignancies and subsequently achieved clinical approval to treat glioblastoma and prostate cancer in 2011 and 2018, respectively. However, despite recent clinical advances, many questions remain with regard to the underlying mechanisms involved in this therapy. One such query is whether intracellular or extracellular nanoparticles are necessary for treatment efficacy. Herein, we compare the effects of intracellular and extracellular magnetic hyperthermia in BxPC-3 cells to determine the differences in efficacy between both. Extracellular magnetic hyperthermia at temperatures between 40–42.5 °C could induce significant levels of necrosis in these cells, whereas intracellular magnetic hyperthermia resulted in no change in viability. This led to a discussion on the overall relevance of intracellular nanoparticles to the efficacy of magnetic hyperthermia therapy.
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Bassnett S, Becker TM, Beebe DC. Ion concentrations, fluxes and electrical properties of the embryonic chicken lens. Exp Eye Res 1992; 55:215-24. [PMID: 1426057 DOI: 10.1016/0014-4835(92)90185-u] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The membrane properties of embryonic chicken lenses were characterized using isotopic and electrical techniques. The lenses had a relatively high water content (80%) and large extracellular space (12.5%). Isotopic uptake measurements indicated that the lens cytoplasm contained 118 mM K+ and 26 mM Cl-. A value for intracellular Na+ of 14 mM was obtained using Na(+)-sensitive microelectrodes. A double-exponential model was used to fit the efflux of 86Rb+, 22Na+, 36Cl- and [3H]mannitol (an extracellular space marker) from the lens. When perfused with artificial aqueous humor (AAH) solution, embryonic lenses exhibited membrane potentials of between -20 and -40 mV. The more negative values were generally observed in lenses from older embryos. A ouabain-sensitive component, contributing -7 mV to the membrane potential, was also identified. The relatively depolarized membrane potentials suggested that the lens membranes were only weakly selective for K+ over Na+. To test this further, lenses were perfused with AAH containing varying concentrations of K+. The resulting changes in potential were interpreted in terms of the Goldman model. The best fit of the Goldman potential equation indicated that, in the presence of ouabain, the chicken lens membranes had a relative permeability to K+, Na+ and Cl- of 1.0, 0.36, 0.51 respectively. Replacing most or all of the Na+ in the AAH caused only a small change in the membrane potential rather than the large hyperpolarization towards the K+ equilibrium potential predicted by the Goldman model. Including the K+ ionophore valinomycin in the low Na(+)-AAH solutions caused a large increase in 86Rb+ efflux but did not result in additional hyperpolarization. This suggested that the insensitivity of the membrane potential to reduced extracellular Na+ was not due to voltage or pH inactivation of lens K+ channels.
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Affiliation(s)
- S Bassnett
- Department of Anatomy and Cell Biology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799
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Naftilan AJ, Dzau VJ, Loscalzo J. Preliminary observations on abnormalities of membrane structure and function in essential hypertension. Hypertension 1986; 8:II174-9. [PMID: 3013768 DOI: 10.1161/01.hyp.8.6_pt_2.ii174] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
To test the hypothesis that structural abnormalities exist in the cell membrane in persons with essential hypertension and that these abnormalities affect membrane-related cellular functions, we examined several membrane-dependent phenomena and membrane lipid composition in the blood cells of subjects with essential hypertension. We analyzed platelet aggregability, membrane fluidity, membrane fatty acid composition, and erythrocyte deformability in four normolipidemic subjects with untreated essential hypertension and in five age-matched normotensive controls. As compared with the controls, the subjects with essential hypertension had platelets that aggregated at lower concentrations of adenosine 5'-diphosphate, platelet membranes that were less fluid, and erythrocytes that were more deformable. Lipid analysis of the membranes of platelets from the two study groups showed that although the cholesterol content was identical, the membranes from the essential hypertension group contained significantly less linoleic acid (18:2) than did those from the normotensive controls. Given the known effects of cis-unsaturated fatty acyl composition on membrane fluidity and membrane-related cellular functions, these data suggest that one factor contributing to essential hypertension is an inherent structural membrane abnormality that alters the physical and functional properties of the cell membrane.
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