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Nsairat H, Ibrahim AA, Jaber AM, Abdelghany S, Atwan R, Shalan N, Abdelnabi H, Odeh F, El-Tanani M, Alshaer W. Liposome bilayer stability: emphasis on cholesterol and its alternatives. J Liposome Res 2024; 34:178-202. [PMID: 37378553 DOI: 10.1080/08982104.2023.2226216] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 05/15/2023] [Accepted: 06/12/2023] [Indexed: 06/29/2023]
Abstract
Liposomes are spherical lipidic nanocarriers composed of natural or synthetic phospholipids with a hydrophobic bilayer and aqueous core, which are arranged into a polar head and a long hydrophobic tail, forming an amphipathic nano/micro-particle. Despite numerous liposomal applications, their use encounters many challenges related to the physicochemical properties strongly affected by their constituents, colloidal stability, and interactions with the biological environment. This review aims to provide a perspective and a clear idea about the main factors that regulate the liposomes' colloidal and bilayer stability, emphasising the roles of cholesterol and its possible alternatives. Moreover, this review will analyse strategies that offer possible approaches to provide more stable in vitro and in vivo liposomes with enhanced drug release and encapsulation efficiencies.
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Affiliation(s)
- Hamdi Nsairat
- Pharmacological and Diagnostic Research Center, Faculty of Pharmacy, Al-Ahliyya Amman University, Amman, Jordan
| | - Abed Alqader Ibrahim
- Department of Nanoscience, Joint School of Nanoscience and Nanoengineering, University of North Carolina at Greensboro, Greensboro, NC, USA
| | - Areej M Jaber
- Pharmacological and Diagnostic Research Center, Faculty of Pharmacy, Al-Ahliyya Amman University, Amman, Jordan
| | | | - Randa Atwan
- Pharmacological and Diagnostic Research Center, Faculty of Pharmacy, Al-Ahliyya Amman University, Amman, Jordan
| | - Naeem Shalan
- Pharmacological and Diagnostic Research Center, Faculty of Pharmacy, Al-Ahliyya Amman University, Amman, Jordan
| | - Hiba Abdelnabi
- Faculty of Pharmacy, The University of Jordan, Amman, Jordan
- Cell Therapy Center, The University of Jordan, Amman, Jordan
| | - Fadwa Odeh
- Department of Chemistry, The University of Jordan, Amman, Jordan
| | - Mohamed El-Tanani
- Pharmacological and Diagnostic Research Center, Faculty of Pharmacy, Al-Ahliyya Amman University, Amman, Jordan
- Institute of Cancer Therapeutics, University of Bradford, Bradford, UK
| | - Walhan Alshaer
- Cell Therapy Center, The University of Jordan, Amman, Jordan
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2
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Saha P, Basak D, Biswas S, More PA, Madhavan N. Small Peptidic Ionophore for Calcium Transport. Bioconjug Chem 2022; 33:2143-2148. [DOI: 10.1021/acs.bioconjchem.2c00396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Parichita Saha
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076, India
| | - Debajyoti Basak
- Department of Chemistry, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
| | - Sayantan Biswas
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076, India
| | - Priyanka A. More
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076, India
| | - Nandita Madhavan
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076, India
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3
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Saha P, Kumari Agarwala P, Dadhich R, Adhyapak P, Kapoor S, Madhavan N. Ligand Induced Cu II Transport Restricts Cancer and Mycobacterial Growth: Towards a Plug-and-Select Ion Channel Scaffold. Chembiochem 2021; 22:1424-1429. [PMID: 33347676 DOI: 10.1002/cbic.202000731] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 12/01/2020] [Indexed: 11/09/2022]
Abstract
Synthetic channels with high ion selectivity are attractive drug targets for diseases involving ion dysregulation. Achieving selective transport of divalent ions is highly challenging due their high hydration energies. A small tripeptide amphiphilic scaffold installed with a pybox ligand selectively transports CuII ions across membranes. The peptide forms stable dimeric pores in the membrane and transports ions by a Cu2+ /H+ antiport mechanism. The ligand-induced excellent CuII selectivity as well as high membrane permeability of the peptide is exploited to promote cancer cell death. The peptide's ability to restrict mycobacterial growth serves as seeds to evolve antibacterial strategies centred on selectively modulating ion homeostasis in pathogens. This simple peptide can potentially function as a universal, yet versatile, scaffold wherein the ion selectivity can be precisely controlled by modifying the ligand at the C terminus.
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Affiliation(s)
- Parichita Saha
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Prema Kumari Agarwala
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Ruchika Dadhich
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Pranav Adhyapak
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Shobhna Kapoor
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Nandita Madhavan
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
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4
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Saha P, Madhavan N. Macrocyclic Transmembrane Anion Transporters via a One-Pot Condensation Reaction. Org Lett 2020; 22:5104-5108. [PMID: 32610925 DOI: 10.1021/acs.orglett.0c01699] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Synthetic chloride transporters are potential therapeutic agents for cystic fibrosis and cancer. Reported herein are macrocyclic transmembrane chloride transporters prepared by a one-pot condensation reaction. The most efficient macrocycle possesses a fine balance of hydrophobicity for membrane permeation and hydrophilicity for ion recognition. The macrocycle transports chloride ions by forming channels in the membrane. Hydrogen bonds and anion-π interactions assist chloride transport.
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Affiliation(s)
- Parichita Saha
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India
| | - Nandita Madhavan
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India
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5
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Scida K, Plaxco KW, Jamieson BG. High frequency, real-time neurochemical and neuropharmacological measurements in situ in the living body. Transl Res 2019; 213:50-66. [PMID: 31361988 DOI: 10.1016/j.trsl.2019.07.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 05/20/2019] [Accepted: 07/11/2019] [Indexed: 12/18/2022]
Abstract
The beautiful and complex brain machinery is perfectly synchronized, and our bodies have evolved to protect it against a myriad of potential threats. Shielded physically by the skull and chemically by the blood brain barrier, the brain processes internal and external information so that we can efficiently relate to the world that surrounds us while simultaneously and unconsciously controlling our vital functions. When coupled with the brittle nature of its internal chemical and electric signals, the brain's "armor" render accessing it a challenging and delicate endeavor that has historically limited our understanding of its structural and neurochemical intricacies. In this review, we briefly summarize the advancements made over the past 10 years to decode the brain's neurochemistry and neuropharmacology in situ, at the site of interest in the brain, with special focus on what we consider game-changing emerging technologies (eg, genetically encoded indicators and electrochemical aptamer-based sensors) and the challenges these must overcome before chronic, in situ chemosensing measurements become routine.
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Affiliation(s)
- Karen Scida
- Diagnostic Biochips, Inc., Glen Burnie, Maryland
| | - Kevin W Plaxco
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California
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6
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Fukui Y, Kameyama S, Fujimoto K. Preparation of free-standing hybrid colloidal membranes via assembly of liponanocapsules. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION 2017; 28:1010-1024. [DOI: 10.1080/09205063.2017.1297219] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Yuuka Fukui
- Center for Chemical Biology, School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Yokohama, Japan
| | - Shuhei Kameyama
- Center for Chemical Biology, School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Yokohama, Japan
| | - Keiji Fujimoto
- Center for Chemical Biology, School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Yokohama, Japan
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7
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Rabben HL, Zhao CM, Hayakawa Y, Wang TC, Chen D. Vagotomy and Gastric Tumorigenesis. Curr Neuropharmacol 2017; 14:967-972. [PMID: 26791481 PMCID: PMC5333586 DOI: 10.2174/1570159x14666160121114854] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 11/20/2015] [Accepted: 01/20/2016] [Indexed: 01/17/2023] Open
Abstract
Vagotomy reduces gastric acid secretion and was therefore introduced as a surgical treatment for peptic ulcers in the 1970s. Later, it was replaced by acid reducing medication, such as histamine type 2 (H2) receptor antagonists and proton pump inhibitors (PPIs). A large body of evidence has indicated that drug-induced hypochlorhydria per se does not increase the risk of gastric cancer. Early studies on the effects of vagotomy in chemically-induced rodent models of gastric cancer reported an increased risk of developing gastric cancer. This was most likely due to a delayed gastric emptying, which later has been accounted for by including an additional drainage procedure, e.g. pyloroplasty. In a recent study using three different mouse models of gastric cancer (including genetically engineered, chemically-induced and Helicobacter pylori-infected mice), either unilateral vagotomy or bilateral truncal vagotomy with pyloroplasty was found to significantly attenuate tumorigenesis in the denervated side of the stomach at early preneoplastic stages as well as at later stages of tumorigenesis. Consistently, pharmacological denervation using botulinum toxin A or muscarinic acetylcholine receptor 3 (M3R) blockade inhibited tumorigenesis. Moreover, it was found that recurrence of gastric cancer was reduced in patients following vagotomy. Thus, these new findings suggest the potential treatment strategies to target the nerve, neurotransmitters, corresponding receptors and their downstream signaling pathways for the malignancy.
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Affiliation(s)
| | | | | | | | - Duan Chen
- Department of Cancer Research and Molecular Medicine, The Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
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8
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Wu Y, Gu W, Tang J, Xu ZP. Devising new lipid-coated calcium phosphate/carbonate hybrid nanoparticles for controlled release in endosomes for efficient gene delivery. J Mater Chem B 2017; 5:7194-7203. [DOI: 10.1039/c7tb01635b] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
New hybrid nanoparticles can efficiently deliver dsDNA/siRNA to cancer cells, with the gene release precisely controlled in the endosomal pH range.
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Affiliation(s)
- Yilun Wu
- Australian Institute for Bioengineering and Nanotechnology
- the University of Queensland
- St. Lucia
- Australia
| | - Wenyi Gu
- Australian Institute for Bioengineering and Nanotechnology
- the University of Queensland
- St. Lucia
- Australia
| | - Jie Tang
- Australian Institute for Bioengineering and Nanotechnology
- the University of Queensland
- St. Lucia
- Australia
| | - Zhi Ping Xu
- Australian Institute for Bioengineering and Nanotechnology
- the University of Queensland
- St. Lucia
- Australia
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9
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Fukui Y, Kabayama N, Fujimoto K. Fine-tuning in mineral cross-linking of biopolymer nanoparticle for incorporation and release of cargo. Colloids Surf B Biointerfaces 2015; 136:168-74. [DOI: 10.1016/j.colsurfb.2015.09.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 08/13/2015] [Accepted: 09/05/2015] [Indexed: 01/13/2023]
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10
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Frost SJ, Firth GB, Chakraborty J. A Novel Colourimetric Homogeneous Liposomal Immunoassay Using Sulphorhodamine B. J Liposome Res 2008; 4:1159-1182. [DOI: 10.3109/08982109409018627] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Stephen J Frost
- Department of Clinical Biochemistry, The Princess Royal Hospital, Haywards Heath, Sussex, UK
- School of Biological Sciences, University of Surrey, Guildford, Surrey, UK
| | - Gary B Firth
- Department of Clinical Biochemistry, The Princess Royal Hospital, Haywards Heath, Sussex, UK
| | - Jessie Chakraborty
- School of Biological Sciences, University of Surrey, Guildford, Surrey, UK
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11
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Huang C, Cheng H, Hao S, Zhou H, Zhang X, Gao J, Sun QH, Hu H, Wang CC. Heat shock protein 70 inhibits alpha-synuclein fibril formation via interactions with diverse intermediates. J Mol Biol 2006; 364:323-36. [PMID: 17010992 DOI: 10.1016/j.jmb.2006.08.062] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2006] [Revised: 08/18/2006] [Accepted: 08/21/2006] [Indexed: 11/23/2022]
Abstract
alpha-Synuclein (AS) is a main component of Lewy bodies in midbrain dopamine neurons pathologically characteristic of Parkinson's disease. We show that heat shock protein (Hsp) 70 inhibits AS fibril formation via preventing the formation of prefibrillar AS (PreAS), binding with PreAS to impede nuclei formation, and binding with nuclei to retard fibril elongation. Also, Hsp70 suppresses the PreAS-induced permeabilization of vesicular membrane through interactions with PreAS. The substrate-binding domain alone is sufficient for Hsp70 to inhibit AS fibril formation. The binding of Hsp70 with PreAS only requires the substrate-binding subdomain, and the binding with AS nuclei requires the C-terminal lid subdomain as well. The results may form the molecular basis for elucidating the mechanism of AS fibril formation and the crucial roles of chaperones in protecting proteins from toxic conversion in many conformational diseases.
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Affiliation(s)
- Chunjuan Huang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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12
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Ramundo-Orlando A, Serafino A, Villalobo A. Gap junction channels reconstituted in two closely apposed lipid bilayers. Arch Biochem Biophys 2005; 436:128-35. [PMID: 15752717 DOI: 10.1016/j.abb.2005.01.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2004] [Revised: 01/19/2005] [Indexed: 10/25/2022]
Abstract
Intercellular communication mediated by gap junction channels plays an important role in many cellular processes. In contrast to other channels, gap junction channels span two plasma membranes resulting in an intracellular location for both ends of the junctional pore and the regulatory sites for channel gating. This configuration presents unique challenges for detailed experimental studies of junctional channel physiology and ligand-activation in situ. Availability of an appropriate model system would significantly facilitate future studies of gap junction channel function and structure. Here we show that the double-membrane channel can be reconstituted in pairs of closely apposed lipid bilayers, as experienced in cells. We have trapped the calcium-sensitive dye, arsenazo III (AIII), partially calcium-saturated (AIII-Ca), in one population of connexin32 reconstituted-liposomes, and EGTA in a second one. In such mixtures, the interaction of EGTA with AIII-Ca was measured by a large color shift from blue to red (decreased absorbance at 652 nm). The exchange of these compounds through gap junctions was proportional to these decrements. Results indicate that these connexon-mediated interliposomal channels are functional and are inhibited by the addition of alpha-glycyrrhetinic acid and by flufenamic acid, two gap junction communication inhibitors. Future use of this model system has the potential to improve our understanding of the permeability and modulation of junctional channels in its native intercellular assembly.
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Affiliation(s)
- Alfonsina Ramundo-Orlando
- Institute of Neurobiology and Molecular Medicine, National Research Council Via del Fosso del Cavaliere, 00133 Rome, Italy.
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13
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Abstract
Liposomes have gained increased attention as systemic drug delivery vehicles following recent regulatory approvals of several vesicle-formulated drugs. These products have demonstrated improved therapeutic indices over their corresponding conventional drugs by avoiding sensitive tissues and/or increasing delivery to specific targets in vivo. They have achieved these improvements primarily through physical means: (1) by retaining drug within vesicles while in the circulation, thus avoiding or minimizing uptake by sensitive normal tissues; and (2) by selectively extravasating into target tissues, releasing active drug. In order to improve upon these therapies in the future, clinically active liposome delivery systems most likely will need to include site-directed surface ligands to further enhance their selective delivery. This may be crucial for the in vivo transport and delivery of macromolecules, including antisense, oligonucleotide aptamers, and genes, which-unlike most conventional drugs-do not circulate well and often require cellular uptake by fusion, endocytosis, or other processes to reach their active sites. This manuscript reviews technologies applicable to directing liposomes and their contents to selected in vivo targets using surface-bound, site-specific ligands. Presented are the biological barriers to be overcome, criteria for selecting the determinants to be targeted, various targeting ligands and overall delivery system design considerations. Several novel targets as well as novel ligand constructs for site-directed therapy are reviewed and discussed. Systemic liposome therapy, which currently must be administered by the intravenous route, is the principal focus of this analysis.
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Affiliation(s)
- M Willis
- NeXstar Pharmaceuticals, Inc., Boulder, CO, USA
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14
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Morigaki K, Dallavalle S, Walde P, Colonna S, Luisi PL. Autopoietic Self-Reproduction of Chiral Fatty Acid Vesicles. J Am Chem Soc 1997. [DOI: 10.1021/ja961728b] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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15
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Stopper H, Metzler M. Carcinogenic oestrogens induce respiration deficiency mutation in yeast. Toxicol In Vitro 1991; 5:487-91. [DOI: 10.1016/0887-2333(91)90078-r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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16
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Lau HY, Pearce FL. Effects of antihistamines on isolated rat peritoneal mast cells and on model membrane systems. AGENTS AND ACTIONS 1990; 29:151-61. [PMID: 1692660 DOI: 10.1007/bf01966440] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We have examined the effect of a range of histamine H1- and H2-receptor agonists and antagonists on rat peritoneal mast cells. Most of the compounds had a dual action: at low concentrations they inhibited the histamine release produced by immunologic activation of the cell whereas at higher concentrations they themselves induced a cytotoxic release of the amine. The test agents did not affect intracellular levels of cyclic AMP. In model systems, the majority of the drugs had no effect on the integrity of artificial liposomes but did protect rat erythrocytes against osmotic shock. We then propose that these agents produce their effects on mast cells by a direct action on the cell membrane, with low concentrations becoming incorporated into the bilayer in such a way as to stabilize the structure and high concentrations disrupting the membrane and leading to cell lysis.
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Affiliation(s)
- H Y Lau
- Department of Chemistry, University College London, UK
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17
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McKee MD, Warshawsky H. Banding patterns in rat incisor enamel stained by histochemical complexing methods for calcium. Anat Rec (Hoboken) 1989; 224:7-13. [PMID: 2471424 DOI: 10.1002/ar.1092240103] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A characteristic banding pattern can be visualized at the surface of the rat incisor in the maturation zone of amelogenesis by staining with glyoxal bis(2-hydroxyanil) (GBHA). Other banding patterns can be obtained with certain histological and fluorochrome stains and by radioautography following 45Ca injection. In this study, several histochemical reagents known to complex with different states of calcium were used to stain the surface of enamel. Rat incisors were quickly dissected and immediately immersed in solutions containing the following calcium-binding reagents: arsenazo III, calmagite, murexide, N,N-naphthaloylhydroxylamine, and calcein. Routinely, one contralateral lower incisor from each pair was counterstained with GBHA in order to relate each of the staining patterns to the banded distribution of maturation ameloblasts that is reflected by the characteristic GBHA staining pattern in the enamel. Each of the reagents used in this study demonstrated a staining pattern consisting of a series of broad bands running transversely and obliquely across the enamel. In all cases, the dyes stained predominantly that enamel associated with ruffle-ended ameloblasts, i.e. enamel left unstained by GBHA. Some of the reagents also stained enamel in the secretion zone. The appearance and distribution of the staining patterns reflect the banded distribution of maturation ameloblasts and appear to be controlled on a time scale related to the rapid modulation of these cells.
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Affiliation(s)
- M D McKee
- Department of Anatomy, McGill University, Montreal, Quebec, Canada
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18
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Blau L, Weissmann G. Transmembrane calcium movements mediated by ionomycin and phosphatidate in liposomes with Fura 2 entrapped. Biochemistry 1988; 27:5661-6. [PMID: 3179270 DOI: 10.1021/bi00415a040] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A novel liposomal method permits studies of Ca movements across the bilayers of multilamellar vesicles (MLV) which had entrapped the Ca-dependent, fluorescent indicator dye Fura 2. Ionomycin-mediated Ca translocation across MLV of phosphatidylcholine (PC)/dicetyl phosphate (DCP), 9:1, obeyed simple first-order kinetics since log-log plots of initial rates versus ionomycin or Ca concentration yielded slopes of approximately 1. Since Ca is translocated in a Ca-dependent fashion in the course of stimulus-response coupling of cells which form diacylglycerol (DAG) and phosphatidate (PA) from polyphosphoinositides, we compared effects of PA with those of DAG. PA and DAG were preincorporated in PC/DCP vesicles, in which trace amounts of ionomycin provided transmembrane potential (due to Ca2+/H+ exchange). Significant increases in Ca movements were observed in the presence of egg lecithin PA, dioleoyl-PA, and dipalmitoyl-PA when compared with DCP- or DAG-containing MLV. DAGs such as 1-oleoyl-2-acetoylglycerol or 1,2-dioleoylglycerol in liposomes decreased rates of Ca translocation. Ca influx into PA-containing MLV was dependent on the mole percent of the PA in bilayers; the complex kinetics of Ca influx were compatible with the formation of nonbilayer states. Incorporation of cholesterol into the liposomes inhibited initial rates of Ca uptake by MLV presumably by condensing the bilayers. Ca influx increased with increasing pH of the external medium from 6.9 to 7.9 in liposomes with an internal pH of 7.4.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L Blau
- Department of Chemistry, Yeshiva University, New York, New York 10016
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19
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Grønberg M, Flatmark T. Inhibition of the H+-ATPase in bovine adrenal chromaffin granule ghosts by diethylstilbestrol. Evidence for a tight coupling between ATP hydrolysis and proton translocation. FEBS Lett 1988; 229:40-4. [PMID: 2894326 DOI: 10.1016/0014-5793(88)80793-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Diethylstilbestrol (DES) was found to inhibit reversibly the hydrolysis of MgATP (80% at 100 microM) and proton pump activity (I50 approximately equal to 15 microM, complete at 100 microM) in chromaffin granule ghosts. The parallel inhibition suggests a tight kinetic coupling between the two activities. The Mg2+-ATPase activity, but not proton pumping, was partially restored by N,N'-dicyclohexylcarbodiimide, indicating that the two inhibitors in combination cause a partial uncoupling. The non-competitive type of inhibition shows that the action of DES is distal to the site of ATP binding and hydrolysis. Although unspecific, the interaction of DES with the chromaffin granule membrane seems primarily to affect the H+-ATPase.
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Affiliation(s)
- M Grønberg
- Department of Biochemistry, University of Bergen, Norway
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20
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Chauhan A, Chauhan VP, Brockerhoff H. Effect of cholesterol on Ca2+-induced aggregation of liposomes and calcium diphosphatidate membrane traversal. Biochemistry 1986; 25:1569-73. [PMID: 3707894 DOI: 10.1021/bi00355a017] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Sonicated cholesterol-phosphatidylcholine (PC) liposomes containing 4 mol % phosphatidic acid (PA) aggregate in 10 mM Ca2+, slowly at low molar fractions of cholesterol (up to 30%) and 15 times faster at higher concentrations; the inflection point is at ca. 35 mol % bilayer cholesterol. O-[[(Methoxyethoxy)ethoxy]ethyl]cholesterol (OH-blocked cholesterol) does not give this rate enhancement. If PC is replaced by diether PC (CO groups abolished), cholesterol does not accelerate aggregation at concentrations in the bilayer below 50 mol %. No change in Ca2+-induced aggregation rates was observed if the ester CO groups of the bridge-forming PA only were replaced by CH2 (diether PA) in liposomes containing PC and cholesterol. PA-mediated Ca2+ membrane traversal seems to be accelerated by the addition of cholesterol to the PC-PA membrane, but analysis shows that the effect is due to the bilayer condensation effect of cholesterol resulting in an increase in the surface concentration of PA and that membrane cholesterol in fact slightly reduces the rate of Ca(PA)2 traversal; OH-blocked cholesterol, however, increases this rate 3-fold. It appears that lipid OH and CO groups interact, directly or with the mediation of water, in establishing the structure of the membrane "hydrogen belts", i.e., the strata containing those hydrogen-bond donors and acceptors. Cholesterol hydroxyl above 33 mol % (saturation of a 2:1 PC/cholesterol complex?) causes a restructuring of the hydrogen belts that facilitates membrane-water-membrane dehydration, the prerequisite for liposome aggregation by trans-Ca(PA)2 formation. On the other hand, the formation of the dehydrated cis-Ca(PA)2 complex that precedes Ca2+ membrane traversal is not accelerated by presence of the cholesterol hydroxyl group.
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21
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Eanes ED, Hailer AW, Costa JL. Calcium phosphate formation in aqueous suspensions of multilamellar liposomes. Calcif Tissue Int 1984; 36:421-30. [PMID: 6435840 DOI: 10.1007/bf02405354] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The present study examined calcium phosphate precipitation in aqueous suspensions of multilamellar liposomes as a possible in vitro model for matrix vesicle mineralization. Liposomes were prepared by dispersing CHCl3-evaporated thin films of 7:2:1 and 7:1:1 molar mixtures of phosphatidylcholine, dicetyl phosphate, and cholesterol in aqueous solutions containing 0, 25, or 50 mM PO4 and 0 or 0.8 mM Mg. After removal of unencapsulated PO4 by gel filtration, the liposomes were suspended in 1.33 mM Ca/0.8 mM Mg solutions and made permeable to these cations by the addition of the ionophore X-537A. All experiments were carried out at pH 7.4, 22 degrees C, and 240 mOsm. In the absence of entrapped PO4, Ca2+ taken up by the liposomes was largely bound to inner membrane surfaces. With PO4 present, Ca2+ uptake increased as much as sixfold with maximum accumulations well above values sufficient for solid formation. Precipitated solids appeared to be located predominantly in the aqueous intermembranous spaces of the liposomes. Amorphous calcium phosphate (ACP) precipitated initially in the presence of entrapped Mg2+, then subsequently converted to apatite intermixed with some octacalcium phosphate. The stability of the liposomal ACP was somewhat greater than that observed in bulk solutions under comparable conditions of pH, temperature, and electrolyte makeup. In time, the mineral deposits caused entrapped PO4 to leak from the liposomes. These findings suggest that the precipitation within liposomes is similar to that which occurs in macro-volume synthetic systems but that the precipitated solid eventually impairs the integrity of the surrounding intermembranous space.(ABSTRACT TRUNCATED AT 250 WORDS)
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Weidner E, Byrd W. The microsporidian spore invasion tube. II. Role of calcium in the activation of invasion tube discharge. J Cell Biol 1982; 93:970-5. [PMID: 6811603 PMCID: PMC2112170 DOI: 10.1083/jcb.93.3.970] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
A swelling response by the polaroplast organelle initiated microsporidian invasion tube extrusions by Glugea hertwigi spores. The tumescence was induced by the displacement of internal calcium. Sodium citrate, phosphate, and the calcium ionophore A23187 were effective in initiating polaroplast swelling and spore discharge; however, the addition of external CaCl2 switched the expanded polaroplasts to a contracted state and blocked spore discharge. Unlike CaCl2, equivalent concentrations of KCl, NaCl, MgCl2, and BaCl2 did not induced polaroplast contraction, and spore discharge was not blocked. 45CaCl2 readily incorporated into spores with expanded polaroplasts; however, little calcium uptake was apparent in spores with contracted polaroplasts. Metallochromic arsenazo III yielded a color spectrum characteristic of the dye-Ca++ complex in the polaroplast region; furthermore, a membrane association with calcium was indicated by strong chlorotetracycline fluorescence within the polaroplast; this fluorescence was extinguished by pretreating spores with ionophore A23187. An association of the membrane with calcium was also indicated by a potassium ferrocyanide-osmium tetroxide technique. All evidence indicates that an internal calcium displacement is an important initial step in the swelling response of the polaroplast organelle.
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Dorogi PL, Neumann E. Spectrophotometric determination of reaction stoichiometry and equilibrium constants of metallochromic indicators. Biophys Chem 1981; 13:125-31. [PMID: 17000162 DOI: 10.1016/0301-4622(81)80011-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/1980] [Indexed: 11/20/2022]
Abstract
The analytical method described in the preceding article was applied to spectrophotometric Ca2+-titrations of the metallochromic indicator arsenazo III (Ar). At various reactant concentrations it was determined that Ar forms 1:1,1:2 and 2 : 1 complexes with calcium. The equilibrium constants and extinction coefficients at 602 nm were determined. Corrected to zero ionic strength at 293 K and pH 7.0, the reactions Ca + Ar = CaAr, CaAr + Ar = CaAr2 and CaAr + Ca = Ca2Ar are associated with dissociation equilibrium constants k(11) = 1.6 x 10(-6)M, K12 = 3.2 x 10(-4)M and K21 = 5.8 x 10(-3)M. respectively. The extinction coefficient of unbound indicator is (602) = 9.6 (+/-0.3) x 10(3) cm(-1) M(-1). Arscnazo III complexes with monovalent ions like Na+ and K+ : at zero ionic strength, the dissociation constant of the Na+-Ar complex is about 0.1 M.
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Affiliation(s)
- P L Dorogi
- Max-Planck-Institut für Biochemie, D-8033 Martinsried, Munich, FRG
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Stout RG, Cleland RE. Partial characterization of fusicoccin binding to receptor sites on oat root membranes. PLANT PHYSIOLOGY 1980; 66:353-9. [PMID: 16661436 PMCID: PMC440633 DOI: 10.1104/pp.66.3.353] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The possibility that fusicoccin (FC) binds to plasma membrane-associated ATPases of oat (cv. Victory) roots has been examined. Specific FC-binding in vitro is localized primarily on plasma membrane-enriched fractions. This FC-binding is greatly reduced by pretreatment of the membrane vesicles at temperatures above 45 C or with trypsin, and the same treatments cause the release of already bound FC. These results support the idea that the FC receptor is a protein located on the plasma membrane.Both active ATPases and FC-binding proteins were solubilized using 1% Triton X-100. When this material was fractionated using gel chromatography, the ATPase activity could be separated from the FC-binding proteins. The identity of the FC-binding proteins is discussed with regard to the extensive evidence which supports the involvement of plasma membrane-ATPase H(+)/K(+) pumps in FC-stimulated acidification and K(+) uptake.
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Affiliation(s)
- R G Stout
- Botany Department, University of Washington, Seattle, Washington 98195
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Abstract
Initiation of germination of heat-activated Streptomyces viridochromogenes spore occurs in media containing only calcium ions and organic buffer. The calcium-induced initiation of germination was accompanied by a decrease in absorbance of the spore suspension, an increased rate of endogenous metabolism, the loss of spore carbon, and the loss of heat resistance. Calcium amounts to 0.28% of the dry weight of freshly harvested spores. The amount of calcium remained the same after incubation of spores in water after heat activation. The spore content of calcium doubled after incubation in 0.5 mM CaCl2 for 5 min at 4 degrees C and during calcium-induced germination. Nearly all of the calcim appears to be bound to sites external to the spore membrane, since the chelating agents (ethylenedinitrilo) tetraacetic acid and arsenazo III removed virtually all of the calcium ions. The calcium ions must be present during the entire initiation of germination period. Germination ceases after an (ethylenedinitrilo) tetraacetic acid wash and begins again immediately after addition of calcium ions.
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Weissmann G, Anderson P, Serhan C, Samuelsson E, Goodman E. A general method, employing arsenazo III in liposomes, for study of calcium ionophores: results with A23187 and prostaglandins. Proc Natl Acad Sci U S A 1980; 77:1506-10. [PMID: 6769114 PMCID: PMC348524 DOI: 10.1073/pnas.77.3.1506] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Multilamellar (MLV) and large unilamellar (LUV) lipid vesicles (liposomes) trap the metallochromic dye arsenazo III [2,7-bis(arsonophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid ] in their aqueous compartments. When ionophore A23187 was preincorporated into either MLV or LUV above 0.001 mol%, addition of Ca to the outside of liposomes produced spectral shifts characteristic of the Ca . AIII2 complex. The method permitted detection of two molecules of A23187 per liposome. Liposomes with A23187 were permselective: divalent cations were translocated in the order Mn greater than Ca greater than Sr greater than Mg congruent to Ba. Because prostaglandins (PGs) may act as Ca ionophores, we have incorporated into MLVs and LUVs stable prostaglandins (PGE2, PGI2, PGB1), endoperoxide analogs, and a water-soluble, polymeric derivative of PGB1:PGBx. None acted as ionophore. In contrast, when added to the outside of preformed MLV or LUV, PGBx, at concentrations above 1 micro M, provoked permselective uptake of Ca equivalent to that induced by 10 nM A23187. These studies demonstrate not only that liposomes containing arsenazo III may be employed in a sensitive asssay for agents that translocate divalent cations, but that a water-soluble derivative of a naturally occurring fatty acid, PGBx, is a potent ionophore.
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Giorgi EP. The transport of steroid hormones into animal cells. INTERNATIONAL REVIEW OF CYTOLOGY 1980; 65:49-115. [PMID: 6993407 DOI: 10.1016/s0074-7696(08)61959-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Chiu VC, Haynes D. The pH dependence and the binding equilibria of the calcium indicator--arsenazo III. MEMBRANE BIOCHEMISTRY 1980; 3:169-83. [PMID: 7382839 DOI: 10.3109/09687688009063884] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The underlying principles of binding equilibria of arsenazo III with Ca2+ and Mg2+ are presented. Ca2+ and Mg2+ can bind arsenazo III in several different protonated forms depending on pH. The binding affinities of these different protonated forms of arsenazo III with Ca2+ increase in the order of H4A4- less than H3A5- less than H2A6- and with Mg2+, H4A4- congruent to H3A5- less than H2A6-. Arsenazo III is not membrane bound. The sensitivity ratio of arsenazo III with Ca2+ to arsenazo III with Mg2+ is close to two orders of magnitude. Arsenazo III and its complexes are extremely sensitive to pH changes. With 5 microM arsenazo III, the minimum detectable amount of Ca2+ can be as low as 0.08 microM. Contrary to current belief, we found that Mg2+ can bind to arsenazo III in a slightly acidic medium. Potential applications of arsenazo III to the study of membrane Ca2+ transport are also discussed.
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Sassa S, Bradlow H, Kappas A. Steroid induction of delta-aminolevulinic acid synthase and porphyrins in liver. Structure-activity studies and the permissive effects of hormones on the induction process. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(19)86666-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Fraley RT, Fornari CS, Kaplan S. Entrapment of a bacterial plasmid in phospholipid vesicles: potential for gene transfer. Proc Natl Acad Sci U S A 1979; 76:3348-52. [PMID: 386338 PMCID: PMC383822 DOI: 10.1073/pnas.76.7.3348] [Citation(s) in RCA: 71] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Entrapment of pBR322 DNA within liposomes was demonstrated by (i) its comigration with liposomes on Sepharose 4B columns, (ii) resistance of its biological activity to DNase digestion, and (iii) identification of plasmid DNA on agarose gels after lipid extraction. The biological activity of the liposome-entrapped plasmid was determined by transformation assays. The incubation of intact liposomes, containing entrapped pBR322, with competent Escherichia coli cells in the standard transformation mixture resulted in the appearance of tetracycline-resistant colonies at a frequency of 1% of the control frequency. Importantly, this frequency was unaffected by the addition of DNase to the incubation mixture, whereas transformation by free pBR322 DNA was totally eliminated after treatment with DNase.
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Dannenberg AM. The antinflammatory effects of glucocorticosteroids. A brief review of the literature. Inflammation 1979; 3:329-43. [PMID: 383608 DOI: 10.1007/bf00914190] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The effects of glucocorticosteroids on immune and inflammatory responses are reviewed. The steroids seem to change the number or function of cell receptors for regulating agents, so that in areas of inflammation: (a) blood vessels dilate less, (b) lymphocytes proliferate less, (c) all leukocytes infiltrate less, (d) macrophages become less activated (digesting and secreting less), and (e) fibroblasts produce less collagen and ground substance. In addition, the corticosteroids seem to alter the response of cells to various signals from their receptors by affecting the prostaglandin system, cyclic nucleotides, and perhaps other internal mediators.
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Balke NE, Hodges TK. Effect of diethylstilbestrol on ion fluxes in oat roots. PLANT PHYSIOLOGY 1979; 63:42-7. [PMID: 16660689 PMCID: PMC542762 DOI: 10.1104/pp.63.1.42] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Effects of diethylstilbestrol (DES) on ion fluxes in oat roots (Avena sativa L.) were investigated by measuring K(+) and Cl(-) absorption and K(+) efflux. DES rapidly decreased the absorption of K(+) ((86)Rb) and (36)Cl(-) by excised roots; 10(-4) molar DES inhibited Cl(-) absorption in 1 minute and K(+) absorption in 1 to 2 minutes. With a 10-minute incubation period, K(+) and Cl(-) absorption were inhibited 50% by 1.1x10(-5) molar and 8.4x10(-6) molar DES, respectively. Treatment for 3 minutes with 10(-4) molar DES caused irreversible inhibition of K(+) absorption. Increasing concentrations of KCl in the absorption media decreased the DES inhibition. Experiments with the DES analogs, DES dipropionate, dienestrol and hexestrol, showed that the steric configuration and the hydroxyl group of the DES molecule are important in determining the inhibitory capacity of the compound.DES increased the efflux of (86)Rb from excised roots only after a 10-minute lag period. In 10(-4) molar DES, roots lost 82% of their radionuclide content in 1 hour. Comparison of efflux curves for roots loaded for 20 hours and those loaded for 15 minutes suggested that DES increased the permeability of the plasma membrane after about 10 minutes and the permeability of the tonoplast after 10 to 20 minutes. Oligomycin and dinitrophenol also increased the loss of (86)Rb, but the lag period was about 4 hours.The rapid effect of DES on ion absorption and the slower effect on ion efflux suggest that DES initially inhibits ion uptake by affecting the transport mechanism at the plasma membrane in some manner other than alteration of membrane permeability.
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Affiliation(s)
- N E Balke
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907
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Weissmann G, Korchak H, Finkelstein M, Smolen J, Hoffstein S. Uptake of enzyme-laden liposomes by animal cells in vitro and in vivo. Ann N Y Acad Sci 1978; 308:235-49. [PMID: 279291 DOI: 10.1111/j.1749-6632.1978.tb22026.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Abstract
The ability of adrenal corticosteroids to both both suppress inflammation and compromise host defenses has been well documented. Recently, a series of in vitro and in vivo experiments, based on our new knowledge of the cell biology of inflammation and the biochemistry of the phagocytic cell itself, has provided new insights into the mechanism of steroid action in the inflammatory process. Evidence is presented that pharmacologic doses of steroids are capable of inhibiting each of the steps in phagocytic-micro-organism interaction: chemotaxis, recognition and opsonization, phagocytosis, membrane fusion, and degranulation. In addition, steroid alteration of the postphagocytic superoxide production, hydrogen peroxide generation, and prostaglandin and thromboxane synthesis is described. The antiinflammatory effects of aspirin and indomethacin can be explained almost entirely by virtue of their ability to inhibit cyclooxygenase, this preventing the transformation of arachidonic acid to both prostaglandins and thromboxanes. The cortisol-induced inhibition of endoperoxides, prostaglandins, and thromboxanes (at a site proximal to the release of arachidonic acid) may well explain those antiinflammatory actions that cortisone shares with aspirin. However, patients treated with nonsteroidal antiinflammatory agents effectively combat infections. In contrast, corticosteroids have more profound effects, as can be seen by the inhibition of superoxide production, with the subsequent decrease in hydrogen peroxide generation and the diminution in release of the antibacterial lysosomal hydrolases within the phagocytic vacuole. Thus, corticosteroids interfere with the killing of microorganisms. This new understanding of the pharmacologic action of cortisol on phagocytic cells explains, we believe, how glucocorticoids alleviate inflammation while, at the same time, they permit multiplication of the offending microorganism within the phagocyte.
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Dunham P, Babiarz P, Israel A, Zerial A, Weissmann G. Membrane fusion: studies with a calcium-sensitive dye, arsenazo III, in liposomes. Proc Natl Acad Sci U S A 1977; 74:1580-4. [PMID: 404639 PMCID: PMC430834 DOI: 10.1073/pnas.74.4.1580] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Fusion between vesicles, cells, or organelles may be defined as confluence of two membrane-bound compartments without access of their solutes to external milieu. To study fusion by this criterion, we have trapped the metallochromic calcium-sensitive dye, arsenazo III (AIII), partially calcium-saturated (AIII-Ca) in one population of liposomes (phoshatidylcholine 90:dicetylphosphate 10), and ethylene glycol-bis(beta-aminoethyl ether)-N,N'-tetraacetate (EGTA) in a second. In such mixtures, interaction of EGTA with AIII-Ca was measured by a large color shift from blue leads to red (decreased absorbance at 660 nm). Fusion of liposomes (but also lysis and diffusion across the membranes) was proportional to these decrements. The exogenous "fusogens," lysolecithin and retinol, were added to liposomes for 5-24 hr at 37 degrees; after rechromatography, measurements were made of total dye, fraction of dye converted from AIII-Ca to AIII, and total lipid. After correction for lysis and diffusion, lysolecithin (200 microng/ml) induced 23% fusion (volume of AIII liposomes confluent with EGTA liposomes) and retinol (300 microng/ml) induced 15%. With one molar percent cortisol (a membrane stabilizer) in the liposome membranes, fusion induced by fusogens was reduced 2-fold. Neither multi-nor unilamellar liposomes fused with each other in the absence of exogenous fusogens, despite wide variations in molar lipid ratios. Results suggest that liposome-liposome fusion is a slow process requiring exogenous fusogens, which may depend upon contributions of other membrane constituents to mimic closely the fusion of natural membranes.
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Abstract
To correct a genetic defect, it would not be enough, say, to inject the missing enzyme, since the body's immune defenses would rapidly destroy it. A "Trojan horse" is needed to evade immune surveillance. The evolution of such an approach is described, as well as how it has been used to "cure" Tay-Sachs disease in culture, utilizing immunoglobulin-disguised liposomes to bring hexosaminidase A to deficient cells.
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