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Al Zahabi K, Hassan L, Maldonado R, Boehm MW, Baier SK, Sharma V. Pinching dynamics, extensional rheology, and stringiness of saliva substitutes. SOFT MATTER 2024; 20:2547-2561. [PMID: 38407364 DOI: 10.1039/d3sm01662e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Saliva substitutes are human-made formulations extensively used in medicine, food, and pharmaceutical research to emulate human saliva's biochemical, tribological, and rheological properties. Even though extensional flows involving saliva are commonly encountered in situations such as swallowing, coughing, sneezing, licking, drooling, gleeking, and blowing spit bubbles, rheological evaluations of saliva and its substitutes in most studies rely on measured values of shear viscosity. Natural saliva possesses stringiness or spinnbarkeit, governed by extensional rheology response, which cannot be evaluated or anticipated from the knowledge of shear rheology response. In this contribution, we comprehensively examine the rheology of twelve commercially available saliva substitutes using torsional rheometry for rate-dependent shear viscosity and dripping-onto-substrate (DoS) protocols for extensional rheology characterization. Even though most formulations are marketed as having suitable rheology, only three displayed measurable viscoelasticity and strain-hardening. Still, these too, failed to emulate the viscosity reduction with the shear rate observed for saliva or match perceived stringiness. Finally, we explore the challenges in creating saliva-like formulations for dysphagia patients and opportunities for using DoS rheometry for diagnostics and designing biomimetic fluids.
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Affiliation(s)
- Karim Al Zahabi
- Department of Chemical Engineering, University of Illinois at Chicago, Chicago, IL 60607, USA.
| | - Lena Hassan
- Department of Chemical Engineering, University of Illinois at Chicago, Chicago, IL 60607, USA.
| | - Ramiro Maldonado
- Department of Chemical Engineering, University of Illinois at Chicago, Chicago, IL 60607, USA.
| | | | - Stefan K Baier
- Motif FoodWorks Inc., Boston, MA 02210, USA
- School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Vivek Sharma
- Department of Chemical Engineering, University of Illinois at Chicago, Chicago, IL 60607, USA.
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2
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Kavishvar D, Ramachandran A. The yielding behaviour of human mucus. Adv Colloid Interface Sci 2023; 322:103049. [PMID: 38039907 DOI: 10.1016/j.cis.2023.103049] [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: 02/13/2023] [Revised: 10/03/2023] [Accepted: 11/06/2023] [Indexed: 12/03/2023]
Abstract
Mucus is a viscoelastic material with non-linear rheological properties such as a yield stress of the order of a few hundreds of millipascals to a few tens of pascals, due to a complex network of mucins in water along with non-mucin proteins, DNA and cell debris. In this review, we discuss the origin of the yield stress in human mucus, the changes in the rheology of mucus with the occurrence of diseases, and possible clinical applications in disease detection as well as cure. We delve into the domain of mucus rheology, examining both macro- and microrheology. Macrorheology involves investigations conducted at larger length scales (∼ a few hundreds of μm or higher) using traditional rheometers, which probe properties on a bulk scale. It is significant in elucidating various mucosal functions within the human body. This includes rejecting unwanted irritants out of lungs through mucociliary and cough clearance, protecting the stomach wall from the acidic environment as well as biological entities, safeguarding cervical canal from infections and providing a swimming medium for sperms. Additionally, we explore microrheology, which encompasses studies performed at length scales ranging from a few tens of nm to a μm. These microscale studies find various applications, including the context of drug delivery. Finally, we employ scaling analysis to elucidate a few examples in lung, cervical, and gastric mucus, including settling of irritants in lung mucus, yielding of lung mucus in cough clearance and cilial beating, spreading of exogenous surfactants over yielding mucus, swimming of Helicobacter pylori through gastric mucus, and lining of protective mucus in the stomach. The scaling analyses employed on the applications mentioned above provide us with a deeper understanding of the link between the rheology and the physiology of mucus.
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Affiliation(s)
- Durgesh Kavishvar
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, ON, Canada.
| | - Arun Ramachandran
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, ON, Canada.
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3
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Singh S, Moran JL. Autonomously Propelled Colloids for Penetration and Payload Delivery in Complex Extracellular Matrices. MICROMACHINES 2021; 12:mi12101216. [PMID: 34683267 PMCID: PMC8541468 DOI: 10.3390/mi12101216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Revised: 10/01/2021] [Accepted: 10/03/2021] [Indexed: 11/30/2022]
Abstract
For effective treatment of diseases such as cancer or fibrosis, it is essential to deliver therapeutic agents such as drugs to the diseased tissue, but these diseased sites are surrounded by a dense network of fibers, cells, and proteins known as the extracellular matrix (ECM). The ECM forms a barrier between the diseased cells and blood circulation, the main route of administration of most drug delivery nanoparticles. Hence, a stiff ECM impedes drug delivery by limiting the transport of drugs to the diseased tissue. The use of self-propelled particles (SPPs) that can move in a directional manner with the application of physical or chemical forces can help in increasing the drug delivery efficiency. Here, we provide a comprehensive look at the current ECM models in use to mimic the in vivo diseased states, the different types of SPPs that have been experimentally tested in these models, and suggest directions for future research toward clinical translation of SPPs in diverse biomedical settings.
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Affiliation(s)
- Shrishti Singh
- Department of Bioengineering, George Mason University, Fairfax, VA 22030, USA;
| | - Jeffrey L. Moran
- Department of Bioengineering, George Mason University, Fairfax, VA 22030, USA;
- Department of Mechanical Engineering, George Mason University, Fairfax, VA 22030, USA
- Correspondence:
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4
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Huijghebaert S, Hoste L, Vanham G. Essentials in saline pharmacology for nasal or respiratory hygiene in times of COVID-19. Eur J Clin Pharmacol 2021; 77:1275-1293. [PMID: 33772626 PMCID: PMC7998085 DOI: 10.1007/s00228-021-03102-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 01/28/2021] [Indexed: 12/11/2022]
Abstract
PURPOSE Nasal irrigation or nebulizing aerosol of isotonic or hypertonic saline is a traditional method for respiratory or nasal care. A recent small study in outpatients with COVID-19 without acute respiratory distress syndrome suggests substantial symptom resolution. We therefore analyzed pharmacological/pharmacodynamic effects of isotonic or hypertonic saline, relevant to SARS-CoV-2 infection and respiratory care. METHODS Mixed search method. RESULTS Due to its wetting properties, saline achieves an improved spreading of alveolar lining fluid and has been shown to reduce bio-aerosols and viral load. Saline provides moisture to respiratory epithelia and gels mucus, promotes ciliary beating, and improves mucociliary clearance. Coronaviruses and SARS-CoV-2 damage ciliated epithelium in the nose and airways. Saline inhibits SARS-CoV-2 replication in Vero cells; possible interactions involve the viral ACE2-entry mechanism (chloride-dependent ACE2 configuration), furin and 3CLpro (inhibition by NaCl), and the sodium channel ENaC. Saline shifts myeloperoxidase activity in epithelial or phagocytic cells to produce hypochlorous acid. Clinically, nasal or respiratory airway care with saline reduces symptoms of seasonal coronaviruses and other common cold viruses. Its use as aerosol reduces hospitalization rates for bronchiolitis in children. Preliminary data suggest symptom reduction in symptomatic COVID-19 patients if saline is initiated within 48 h of symptom onset. CONCLUSIONS Saline interacts at various levels relevant to nasal or respiratory hygiene (nasal irrigation, gargling or aerosol). If used from the onset of common cold symptoms, it may represent a useful add-on to first-line interventions for COVID-19. Formal evaluation in mild COVID-19 is desirable as to establish efficacy and optimal treatment regimens.
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Affiliation(s)
| | - Levi Hoste
- Pediatric Pulmonology, Infectious Diseases and Immunology, Ghent University Hospital, Ghent, Belgium
- Primary Immunodeficiency Research Lab, Center for Primary Immunodeficiency Ghent, Jeffrey Modell Diagnosis and Research Center, Ghent University Hospital, Ghent, Belgium
| | - Guido Vanham
- Department of Biomedical Sciences, Institute of Tropical Medicine and University of Antwerp, Antwerp, Belgium
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5
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Pancsa R, Schad E, Tantos A, Tompa P. Emergent functions of proteins in non-stoichiometric supramolecular assemblies. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2019; 1867:970-979. [PMID: 30826453 DOI: 10.1016/j.bbapap.2019.02.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 02/18/2019] [Accepted: 02/25/2019] [Indexed: 12/12/2022]
Abstract
Proteins are the basic functional units of the cell, carrying out myriads of functions essential for life. There are countless reports in molecular cell biology addressing the functioning of proteins under physiological and pathological conditions, aiming to understand life at the atomistic-molecular level and thereby being able to develop remedies against diseases. The central theme in most of these studies is that the functional unit under study is the protein itself. Recent rapid progress has radically challenged and extended this protein-function paradigm, by demonstrating that novel function(s) may emerge when proteins form dynamic and non-stoichiometric supramolecular assemblies. There is an increasing number of cases for such collective functions, such as targeting, localization, protection/shielding and filtering effects, as exemplified by signaling complexes and prions, biominerals and mucus, amphibian adhesions and bacterial biofilms, and a broad range of membraneless organelles (bio-condensates) formed by liquid-liquid phase separation in the cell. In this short review, we show that such non-stoichiometric organization may derive from the heterogeneity of the system, a mismatch in valency and/or geometry of the partners, and/or intrinsic structural disorder and multivalency of the component proteins. Either way, the resulting functional features cannot be simply described by, or predicted from, the properties of the isolated single protein(s), as they belong to the collection of proteins.
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Affiliation(s)
- Rita Pancsa
- Institute of Enzymology, Research Centre for Natural Sciences of the Hungarian Academy of Sciences, Budapest, Hungary
| | - Eva Schad
- Institute of Enzymology, Research Centre for Natural Sciences of the Hungarian Academy of Sciences, Budapest, Hungary
| | - Agnes Tantos
- Institute of Enzymology, Research Centre for Natural Sciences of the Hungarian Academy of Sciences, Budapest, Hungary
| | - Peter Tompa
- Institute of Enzymology, Research Centre for Natural Sciences of the Hungarian Academy of Sciences, Budapest, Hungary; VIB Center for Structural Biology (CSB), Brussels, Belgium; Structural Biology Brussels (SBB), Vrije Universiteit Brussel (VUB), Brussels, Belgium.
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6
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Demouveaux B, Gouyer V, Magnien M, Plet S, Gottrand F, Narita T, Desseyn JL. [Gel-forming mucins structure governs mucus gels viscoelasticity]. Med Sci (Paris) 2018; 34:806-812. [PMID: 30451674 DOI: 10.1051/medsci/2018206] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mucus is the first line of innate mucosal defense in all mammals. Gel‑forming mucins control the rheological properties of mucus hydrogels by forming a network in which hydrophilic and hydrophobic regions coexist, and it has been revealed that the network is formed through both covalent links and reversible links such as hydrophobic interactions in order to modulate the structure as a function of the physiological necessities. Here, we review the structure and functions of the mucus in terms of the gel-forming mucins protein-protein interactions, also called interactome. Since it is difficult to characterize the low energy reversible interactions due to their dependence on physico-chemical environment, their role is not well understood. Still, they constitute a promising target to counteract mucus abnormalities observed in mucus-associated diseases.
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Affiliation(s)
- Bastien Demouveaux
- Inserm, Université de Lille, CHU Lille, LIRIC UMR 995, F-59000 Lille, France
| | - Valérie Gouyer
- Inserm, Université de Lille, CHU Lille, LIRIC UMR 995, F-59000 Lille, France
| | - Mylène Magnien
- Inserm, Université de Lille, CHU Lille, LIRIC UMR 995, F-59000 Lille, France
| | - Ségolène Plet
- Inserm, Université de Lille, CHU Lille, LIRIC UMR 995, F-59000 Lille, France
| | - Frédéric Gottrand
- Inserm, Université de Lille, CHU Lille, LIRIC UMR 995, F-59000 Lille, France
| | - Tetsuharu Narita
- PSL Research University, UPMC Univ. Paris 06, ESPCI Paris, CNRS UMR 7615, Laboratoire Sciences et Ingénierie de la Matière Molle, 10, rue Vauquelin, 75231, Paris Cedex 05, France - Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japon
| | - Jean-Luc Desseyn
- Inserm, Université de Lille, CHU Lille, LIRIC UMR 995, F-59000 Lille, France
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7
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Surfing Motility: a Conserved yet Diverse Adaptation among Motile Bacteria. J Bacteriol 2018; 200:JB.00394-18. [PMID: 30224438 DOI: 10.1128/jb.00394-18] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 09/11/2018] [Indexed: 11/20/2022] Open
Abstract
Bacterial rapid surfing motility is a novel surface adaptation of Pseudomonas aeruginosa in the presence of the glycoprotein mucin. Here, we show that other Gram-negative motile bacterial species, including Escherichia coli, Salmonella enterica, Vibrio harveyi, Enterobacter cloacae, and Proteus mirabilis, also exhibit the physical characteristics of surfing on the surface of agar plates containing 0.4% mucin, where surfing motility was generally more rapid and less dependent on medium viscosity than was swimming motility. As previously observed in Pseudomonas aeruginosa, all surfing species exhibited some level of broad-spectrum adaptive resistance, although the antibiotics to which they demonstrated surfing-mediated resistance differed. Surfing motility in P. aeruginosa was found to be dependent on the quorum-sensing systems of this organism; however, this aspect was not conserved in other tested bacterial species, including V. harveyi and S. enterica, as demonstrated by assaying specific quorum-sensing mutants. Thus, rapid surfing motility is a complex surface growth adaptation that is conserved in several motile bacteria, involves flagella, and leads to diverse broad-spectrum antibiotic resistance, but it is distinct in terms of dependence on quorum sensing.IMPORTANCE This study showed for the first time that surfing motility, a novel form of surface motility first discovered in Pseudomonas aeruginosa under artificial cystic fibrosis conditions, including the presence of high mucin content, is conserved in other motile bacterial species known to be mucosa-associated, including Escherichia coli, Salmonella enterica, and Proteus mirabilis Here, we demonstrated that key characteristics of surfing, including the ability to adapt to various viscous environments and multidrug adaptive resistance, are also conserved. Using mutagenesis assays, we also identified the importance of all three known quorum-sensing systems, Las, Rhl, and Pqs, in P. aeruginosa in regulating surfing motility, and we also observed a conserved dependence of surfing on flagella in certain species.
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8
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Demouveaux B, Gouyer V, Gottrand F, Narita T, Desseyn JL. Gel-forming mucin interactome drives mucus viscoelasticity. Adv Colloid Interface Sci 2018; 252:69-82. [PMID: 29329667 DOI: 10.1016/j.cis.2017.12.005] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 12/14/2017] [Accepted: 12/15/2017] [Indexed: 12/31/2022]
Abstract
Mucus is a hydrogel that constitutes the first innate defense in all mammals. The main organic component of mucus, gel-forming mucins, forms a complex network through both reversible and irreversible interactions that drive mucus gel formation. Significant advances in the understanding of irreversible gel-forming mucins assembly have been made using recombinant protein approaches. However, little is known about the reversible interactions that may finely modulate mucus viscoelasticity, which can be characterized using rheology. This approach can be used to investigate both the nature of gel-forming mucins interactions and factors that influence hydrogel formation. This knowledge is directly relevant to the development of new drugs to modulate mucus viscoelasticity and to restore normal mucus functions in diseases such as in cystic fibrosis. The aim of the present review is to summarize the current knowledge about the relationship between the mucus protein matrix and its functions, with emphasis on mucus viscoelasticity.
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Affiliation(s)
| | - Valérie Gouyer
- Univ. Lille, Inserm, CHU Lille, LIRIC UMR 995, F-59000 Lille, France
| | - Frédéric Gottrand
- Univ. Lille, Inserm, CHU Lille, LIRIC UMR 995, F-59000 Lille, France
| | - Tetsuharu Narita
- Laboratoire Sciences et Ingénierie de la Matière Molle, PSL Research University, UPMC Univ Paris 06, ESPCI Paris, CNRS, 10 rue Vauquelin, 75231 Paris Cedex 05, France; Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan
| | - Jean-Luc Desseyn
- Univ. Lille, Inserm, CHU Lille, LIRIC UMR 995, F-59000 Lille, France.
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Reid AT, Veerati PC, Gosens R, Bartlett NW, Wark PA, Grainge CL, Stick SM, Kicic A, Moheimani F, Hansbro PM, Knight DA. Persistent induction of goblet cell differentiation in the airways: Therapeutic approaches. Pharmacol Ther 2017; 185:155-169. [PMID: 29287707 DOI: 10.1016/j.pharmthera.2017.12.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Dysregulated induction of goblet cell differentiation results in excessive production and retention of mucus and is a common feature of several chronic airways diseases. To date, therapeutic strategies to reduce mucus accumulation have focused primarily on altering the properties of the mucus itself, or have aimed to limit the production of mucus-stimulating cytokines. Here we review the current knowledge of key molecular pathways that are dysregulated during persistent goblet cell differentiation and highlights both pre-existing and novel therapeutic strategies to combat this pathology.
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Affiliation(s)
- Andrew T Reid
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia; Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute, The University of Newcastle, New South Wales, Australia.
| | - Punnam Chander Veerati
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia; Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute, The University of Newcastle, New South Wales, Australia
| | - Reinoud Gosens
- Department of Molecular Pharmacology, University of Groningen, Groningen, The Netherlands; Groningen Research Institute for Asthma and COPD (GRIAC), University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Nathan W Bartlett
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia; Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute, The University of Newcastle, New South Wales, Australia
| | - Peter A Wark
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia; Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute, The University of Newcastle, New South Wales, Australia; Department of Respiratory and Sleep Medicine, John Hunter Hospital, Newcastle, New South Wales, Australia
| | - Chris L Grainge
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia; Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute, The University of Newcastle, New South Wales, Australia; Department of Respiratory and Sleep Medicine, John Hunter Hospital, Newcastle, New South Wales, Australia
| | - Stephen M Stick
- School of Paediatrics and Child Health, University of Western Australia, Nedlands 6009, Western Australia, Australia; Telethon Kids Institute, University of Western Australia, Nedlands 6009, Western Australia, Australia; Department of Respiratory Medicine, Princess Margaret Hospital for Children, Perth 6001, Western Australia, Australia; Centre for Cell Therapy and Regenerative Medicine, School of Medicine and Pharmacology, University of Western Australia, Nedlands 6009, Western Australia, Australia
| | - Anthony Kicic
- School of Paediatrics and Child Health, University of Western Australia, Nedlands 6009, Western Australia, Australia; Telethon Kids Institute, University of Western Australia, Nedlands 6009, Western Australia, Australia; Department of Respiratory Medicine, Princess Margaret Hospital for Children, Perth 6001, Western Australia, Australia; Centre for Cell Therapy and Regenerative Medicine, School of Medicine and Pharmacology, University of Western Australia, Nedlands 6009, Western Australia, Australia; Occupation and Environment, School of Public Health, Curtin University, Bentley 6102, Western Australia, Australia
| | - Fatemeh Moheimani
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia; Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute, The University of Newcastle, New South Wales, Australia
| | - Philip M Hansbro
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia; Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute, The University of Newcastle, New South Wales, Australia
| | - Darryl A Knight
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia; Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute, The University of Newcastle, New South Wales, Australia; Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
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10
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Schenck DM, Fiegel J. Tensiometric and Phase Domain Behavior of Lung Surfactant on Mucus-like Viscoelastic Hydrogels. ACS APPLIED MATERIALS & INTERFACES 2016; 8:5917-5928. [PMID: 26894883 PMCID: PMC5226205 DOI: 10.1021/acsami.6b00294] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Lung surfactant has been observed at all surfaces of the airway lining fluids and is an important contributor to normal lung function. In the conducting airways, the surfactant film lies atop a viscoelastic mucus gel. In this work, we report on the characterization of the tensiometric and phase domain behavior of lung surfactant at the air-liquid interface of mucus-like viscoelastic gels. Poly(acrylic acid) hydrogels were formulated to serve as a model mucus with bulk rheological properties that matched those of tracheobronchial mucus secretions. Infasurf (Calfactant), a commercially available pulmonary surfactant derived from calf lung extract, was spread onto the hydrogel surface. The surface tension lowering ability and relaxation of Infasurf films on the hydrogels was quantified and compared to Infasurf behavior on an aqueous subphase. Infasurf phase domains during surface compression were characterized by fluorescence microscopy and phase shifting interferometry. We observed that increasing the bulk viscoelastic properties of the model mucus hydrogels reduced the ability of Infasurf films to lower surface tension and inhibited film relaxation. A shift in the formation of Infasurf condensed phase domains from smaller, more spherical domains to large, agglomerated, multilayer structures was observed with increasing viscoelastic properties of the subphase. These studies demonstrate that the surface behavior of lung surfactant on viscoelastic surfaces, such as those found in the conducting airways, differs significantly from aqueous, surfactant-laden systems.
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Affiliation(s)
- Daniel M. Schenck
- Department of Pharmaceutical Sciences and Experimental Therapeutics, The University of Iowa, Iowa City, IA, 52242, USA
| | - Jennifer Fiegel
- Department of Pharmaceutical Sciences and Experimental Therapeutics, The University of Iowa, Iowa City, IA, 52242, USA
- Department of Chemical and Biochemical Engineering, The University of Iowa, Iowa City, IA, 52242, USA
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11
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Frenkel ES, Ribbeck K. Salivary mucins in host defense and disease prevention. J Oral Microbiol 2015; 7:29759. [PMID: 26701274 PMCID: PMC4689954 DOI: 10.3402/jom.v7.29759] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 11/16/2015] [Accepted: 11/17/2015] [Indexed: 12/15/2022] Open
Abstract
Mucus forms a protective coating on wet epithelial surfaces throughout the body that houses the microbiota and plays a key role in host defense. Mucins, the primary structural components of mucus that creates its viscoelastic properties, are critical components of the gel layer that protect against invading pathogens. Altered mucin production has been implicated in diseases such as ulcerative colitis, asthma, and cystic fibrosis, which highlights the importance of mucins in maintaining homeostasis. Different types of mucins exist throughout the body in various locations such as the gastrointestinal tract, lungs, and female genital tract, but this review will focus on mucins in the oral cavity. Salivary mucin structure, localization within the oral cavity, and defense mechanisms will be discussed. These concepts will then be applied to present what is known about the protective function of mucins in oral diseases such as HIV/AIDS, oral candidiasis, and dental caries.
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Affiliation(s)
- Erica Shapiro Frenkel
- Biological Sciences in Dental Medicine, Harvard University, Cambridge, MA, USA.,Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Katharina Ribbeck
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA;
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12
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Wang X, Du M, Song YH, Zheng Q. Mucin from loach skin mucus and its interfacial behavior on gold surface. CHINESE JOURNAL OF POLYMER SCIENCE 2014. [DOI: 10.1007/s10118-014-1524-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Kim D, Liao J, Hanrahan JW. The buffer capacity of airway epithelial secretions. Front Physiol 2014; 5:188. [PMID: 24917822 PMCID: PMC4042063 DOI: 10.3389/fphys.2014.00188] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Accepted: 04/28/2014] [Indexed: 01/20/2023] Open
Abstract
The pH of airway epithelial secretions influences bacterial killing and mucus properties and is reduced by acidic pollutants, gastric reflux, and respiratory diseases such as cystic fibrosis (CF). The effect of acute acid loads depends on buffer capacity, however the buffering of airway secretions has not been well characterized. In this work we develop a method for titrating micro-scale (30 μl) volumes and use it to study fluid secreted by the human airway epithelial cell line Calu-3, a widely used model for submucosal gland serous cells. Microtitration curves revealed that HCO−3 is the major buffer. Peak buffer capacity (β) increased from 17 to 28 mM/pH during forskolin stimulation, and was reduced by >50% in fluid secreted by cystic fibrosis transmembrane conductance regulator (CFTR)-deficient Calu-3 monolayers, confirming an important role of CFTR in HCO−3 secretion. Back-titration with NaOH revealed non-volatile buffer capacity due to proteins synthesized and released by the epithelial cells. Lysozyme and mucin concentrations were too low to buffer Calu-3 fluid significantly, however model titrations of porcine gastric mucins at concentrations near the sol-gel transition suggest that mucins may contribute to the buffer capacity of ASL in vivo. We conclude that CFTR-dependent HCO−3 secretion and epithelially-derived proteins are the predominant buffers in Calu-3 secretions.
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Affiliation(s)
- Dusik Kim
- Department of Physiology, McGill University Montréal, QC, Canada
| | - Jie Liao
- Department of Physiology, McGill University Montréal, QC, Canada
| | - John W Hanrahan
- Department of Physiology, McGill University Montréal, QC, Canada ; McGill University Health Centre Research Institute Montréal, QC, Canada
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14
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Abstract
Complex biological systems operate under non-equilibrium conditions and exhibit emergent properties associated with correlated spatial and temporal structures. These properties may be individually unpredictable, but tend to be governed by power-law probability distributions and/or correlation. This article reviews the concepts that are invoked in the treatment of complex systems through a wide range of respiratory-related examples. Following a brief historical overview, some of the tools to characterize structural variabilities and temporal fluctuations associated with complex systems are introduced. By invoking the concept of percolation, the notion of multiscale behavior and related modeling issues are discussed. Spatial complexity is then examined in the airway and parenchymal structures with implications for gas exchange followed by a short glimpse of complexity at the cellular and subcellular network levels. Variability and complexity in the time domain are then reviewed in relation to temporal fluctuations in airway function. Next, an attempt is given to link spatial and temporal complexities through examples of airway opening and lung tissue viscoelasticity. Specific examples of possible and more direct clinical implications are also offered through examples of optimal future treatment of fibrosis, exacerbation risk prediction in asthma, and a novel method in mechanical ventilation. Finally, the potential role of the science of complexity in the future of physiology, biology, and medicine is discussed.
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Affiliation(s)
- Béla Suki
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, USA.
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15
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Mitran S. Continuum-kinetic-microscopic model of lung clearance due to core-annular fluid entrainment. JOURNAL OF COMPUTATIONAL PHYSICS 2013; 244:193-211. [PMID: 23729842 PMCID: PMC3665523 DOI: 10.1016/j.jcp.2013.01.037] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The human lung is protected against aspirated infectious and toxic agents by a thin liquid layer lining the interior of the airways. This airway surface liquid is a bilayer composed of a viscoelastic mucus layer supported by a fluid film known as the periciliary liquid. The viscoelastic behavior of the mucus layer is principally due to long-chain polymers known as mucins. The airway surface liquid is cleared from the lung by ciliary transport, surface tension gradients, and airflow shear forces. This work presents a multiscale model of the effect of airflow shear forces, as exerted by tidal breathing and cough, upon clearance. The composition of the mucus layer is complex and variable in time. To avoid the restrictions imposed by adopting a viscoelastic flow model of limited validity, a multiscale computational model is introduced in which the continuum-level properties of the airway surface liquid are determined by microscopic simulation of long-chain polymers. A bridge between microscopic and continuum levels is constructed through a kinetic-level probability density function describing polymer chain configurations. The overall multiscale framework is especially suited to biological problems due to the flexibility afforded in specifying microscopic constituents, and examining the effects of various constituents upon overall mucus transport at the continuum scale.
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Affiliation(s)
- Sorin Mitran
- Department of Mathematics, University of North Carolina, Chapel Hill, NC, 27599-3250
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16
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Suki B. The major transitions of life from a network perspective. Front Physiol 2012; 3:94. [PMID: 22514542 PMCID: PMC3322530 DOI: 10.3389/fphys.2012.00094] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 03/26/2012] [Indexed: 11/16/2022] Open
Abstract
Many attempts have been made to understand the origin of life and biological complexity both at the experimental and theoretical levels but neither is fully explained. In an influential work, Maynard Smith and Szathmáry (1995) argued that the majority of the increase in complexity is not gradual, but it is associated with a few so-called major transitions along the way of the evolution of life. For each major transition, they identified specific mechanisms that could account for the change in complexity related to information transmission across generations. In this work, I propose that the sudden and unexpected improvement in the functionality of an organism that followed a major transition was enabled by a phase transition in the network structure associated with that function. The increase in complexity following a major transition is therefore directly linked to the emergence of a novel structure-function relation which altered the course of evolution. As a consequence, emergent phenomena arising from these network phase transitions can serve as a common organizing principle for understanding the major transitions. As specific examples, I analyze the emergence of life, the emergence of the genetic apparatus, the rise of the eukaryotic cells, the evolution of movement and mechanosensitivity, and the emergence of consciousness. Finally, I discuss the implications of network associated phase transitions to issues that bear relevance to the history, the immediate present and perhaps the future, of life.
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Affiliation(s)
- Béla Suki
- Department of Biomedical Engineering, Boston UniversityBoston, MA, USA
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17
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Graham LD, Danon SJ, Johnson G, Braybrook C, Hart NK, Varley RJ, Evans MDM, McFarland GA, Tyler MJ, Werkmeister JA, Ramshaw JAM. Biocompatibility and modification of the protein-based adhesive secreted by the Australian frog Notaden bennetti. J Biomed Mater Res A 2010; 93:429-41. [PMID: 19569213 DOI: 10.1002/jbm.a.32559] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
When provoked, Notaden bennetti frogs secrete a proteinaceous exudate, which rapidly forms a tacky and elastic glue. This material has potential in biomedical applications. Cultured cells attached and proliferated well on glue-coated tissue culture polystyrene, but migrated somewhat slower than on uncoated surfaces. In organ culture, dissolved glue successfully adhered collagen-coated perfluoropolyether lenses to debrided bovine corneas and supported epithelial regrowth. Small pellets of glue implanted subcutaneously into mice were resorbed by surrounding tissues, and all of the animals made a full recovery. An initial but transient skin necrosis at the implant site was probably caused by some of the potentially toxic metabolites present in the frog secretion; these include sterols and carotenoids, as well as fatty alcohols, aldehydes, ketones, acids, and aromatic compounds. Removal of the carotenoid pigments did not significantly alter the glue's material properties. In contrast, peroxidase treatment of dissolved glue introduced unnatural crosslinks between molecules of the major protein (Nb-1R) and resulted in the formation of a soft hydrogel, which was very different to the original material.
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Affiliation(s)
- Lloyd D Graham
- CSIRO Molecular and Health Technologies, Sydney Laboratory, P.O. Box 184, North Ryde, New South Wales 1670, Australia.
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18
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Celli JP, Turner BS, Afdhal NH, Ewoldt RH, McKinley GH, Bansil R, Erramilli S. Rheology of gastric mucin exhibits a pH-dependent sol-gel transition. Biomacromolecules 2007; 8:1580-6. [PMID: 17402780 DOI: 10.1021/bm0609691] [Citation(s) in RCA: 215] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Gastric mucin, a high molecular weight glycoprotein, is responsible for providing the gel-forming properties and protective function of the gastric mucus layer. Bulk rheology measurements in the linear viscoelastic regime show that gastric mucin undergoes a pH-dependent sol-gel transition from a viscoelastic solution at neutral pH to a soft viscoelastic gel in acidic conditions, with the transition occurring near pH 4. In addition to pH-dependent gelation behavior in this system, further rheological studies under nonlinear deformations reveal shear thinning and an apparent yield stress in this material which are also highly influenced by pH.
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Affiliation(s)
- Jonathan P Celli
- Department of Physics, Boston University, Boston, Massachusetts 02215, USA
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19
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Broughton-Head VJ, Smith JR, Shur J, Shute JK. Actin limits enhancement of nanoparticle diffusion through cystic fibrosis sputum by mucolytics. Pulm Pharmacol Ther 2006; 20:708-17. [PMID: 17055310 DOI: 10.1016/j.pupt.2006.08.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Revised: 08/17/2006] [Accepted: 08/22/2006] [Indexed: 10/24/2022]
Abstract
BACKGROUND The secretions in the cystic fibrosis (CF) airways contains high concentrations of polymers, including the respiratory mucins and varying amounts of DNA and actin, the debris of an aggressive neutrophilic inflammatory response to infection. Physical and chemical interactions between these polymers contribute to the viscoelastic nature of a material that is hard to clear without the use of mucolytics. Secretions retained in the CF airway not only restrict airflow and invite infection, but also act as a barrier to the delivery of inhaled drugs and gene therapy vectors to the underlying airway epithelium. The aim of this investigation was to develop a simple, sensitive, assay to measure the diffusion of nanospheres the size of liposomal gene therapy vectors through CF sputum, and to model the polymer interactions that limit diffusion and the diffusion-enhancing activity of mucolytics. METHODS The diffusion of 200 nm fluorescent carboxylated nanospheres through CF sputum was investigated using a diffusion assay based on the micro-Boyden chamber. Atomic force microscopy (AFM) was used to visualise and measure the pore diameter in CF sputum. The effect of the mucolytics deoxyribonuclease (DNase), N-acetylcysteine and gelsolin on the diffusion of nanospheres though synthetic biogels comprising mixtures of DNA, mucin and F-actin was also investigated. RESULTS CF sputum significantly retarded the diffusion of 200 nm nanospheres. Pore diameter in CF sputum was highly variable, with a mean greater than 200 nm. At concentrations found in the CF airway, DNA (1-10 mg/ml) and mucin (25-50 mg/ml) also significantly reduced the diffusion of nanospheres. The barrier effects of DNA and mucin were not additive, and the additional presence of F-actin (5 mg/ml) did not influence diffusion of the nanospheres. However, actin (5mg/ml) completely inhibited the ability of DNase (2.9 microg/ml) and N-acetylcysteine (5 mM) to enhance diffusion. The activity of the mucolytics, DNase and N-acetylcysteine, was not restored by the addition of the actin depolymerising agent gelsolin (250nM). CONCLUSION Actin does not contribute to the barrier properties of CF sputum, but is a key determinant of the ability of mucolytics to enhance drug diffusion through synthetic and biological mucus.
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Affiliation(s)
- Victoria J Broughton-Head
- School of Pharmacy and Biomedical Sciences, Institute of Biomedical and Biomolecular Sciences, University of Portsmouth, St Michael's Building, White Swan Road, Portsmouth, PO1 2DT, UK
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20
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Abstract
Mucus secretions have played a central role in the evolution of multicellular organisms, enabling adaptation to widely differing environments. In vertebrates, mucus covers and protects the epithelial cells in the respiratory, gastrointestinal, urogenital, visual, and auditory systems, amphibian's epidermis, and the gills in fishes. Deregulation of mucus production and/or composition has important consequences for human health. For example, mucus obstruction of small airways is observed in chronic airway diseases, including chronic obstructive pulmonary disease, asthma, and cystic fibrosis. The major protein component in the mucus is a family of large, disulfide-bonded glycoproteins known as gel-forming mucins. These proteins are accumulated in large, regulated secretory granules (the mucin granules) that occupy most of the apical cytoplasm of specialized cells known as mucous/goblet cells. Since mucin oligomers have contour dimensions larger than the mucin granule average diameter, the question arises how these highly hydrophilic macromolecules are organized within these organelles. I review here the intraluminal organization of the mucin granule in view of our knowledge on the structure, biosynthesis, and biophysical properties of gel-forming mucins, and novel imaging studies in living mucous/goblet cells. The emerging concept is that the mucin granule lumen comprises a partially condensed matrix meshwork embedded in a fluid phase where proteins slowly diffuse.
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Affiliation(s)
- Juan Perez-Vilar
- Cystic Fibrosis/Pulmonary Research and Treatment Center, School of Medicine, University of North Carolina at Chapel Hill, NC 27599-7248, USA.
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21
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Tang JX, Wen Q, Bennett A, Kim B, Sheils CA, Bucki R, Janmey PA. Anionic poly(amino acid)s dissolve F-actin and DNA bundles, enhance DNase activity, and reduce the viscosity of cystic fibrosis sputum. Am J Physiol Lung Cell Mol Physiol 2005; 289:L599-605. [PMID: 15964901 DOI: 10.1152/ajplung.00061.2005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Bundles of F-actin and DNA present in the sputum of cystic fibrosis (CF) patients but absent from normal airway fluid contribute to the altered viscoelastic properties of sputum that inhibit clearance of infected airway fluid and exacerbate the pathology of CF. Previous strategies to remove these filamentous aggregates have focused on DNase to enzymatically depolymerize DNA to constituent monomers and gelsolin to sever F-actin to small fragments. The high densities of negative surface charge on DNA and F-actin suggest that the bundles of these filaments, which alone exhibit a strong electrostatic repulsion, may be stabilized by multivalent cations such as histones, antimicrobial peptides, and other positively charged molecules prevalent in airway fluid. This study reports that bundles of DNA or F-actin formed after addition of histone H1 or lysozyme are efficiently dissolved by soluble multivalent anions such as polymeric aspartate or glutamate. Addition of poly-aspartate or poly-glutamate also disperses DNA and actin-containing bundles in CF sputum and lowers the elastic moduli of these samples to levels comparable to those obtained after treatment with DNase I or gelsolin. Addition of poly-aspartic acid also increased DNase activity when added to samples containing DNA bundles formed with histone H1. When added to CF sputum, poly-aspartic acid significantly reduced the growth of bacteria, suggesting activation of endogenous antibacterial factors. These findings suggest that soluble multivalent anions have potential alone or in combination with other mucolytic agents to selectively dissociate the large bundles of charged biopolymers that form in CF sputum.
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Affiliation(s)
- Jay X Tang
- Dept. of Physics, Brown University, Providence, Rhode Island, USA
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22
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Nielsen H, Hvidt S, Sheils CA, Janmey PA. Elastic contributions dominate the viscoelastic properties of sputum from cystic fibrosis patients. Biophys Chem 2005; 112:193-200. [PMID: 15572248 DOI: 10.1016/j.bpc.2004.07.019] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2004] [Revised: 07/02/2004] [Accepted: 07/02/2004] [Indexed: 10/26/2022]
Abstract
Sputum samples from cystic fibrosis (CF) patients were investigated by oscillatory, creep and steady shear rheological techniques over a range of time scales from 10(-3) to 10(6) s. The viscoelastic changes obtained by mixing sputa with the actin-filament-severing protein gelsolin and with the thiol-reducing agent dithiothreitol (DTT) were also investigated. At small strains sputum behaves like a viscoelastic solid rather than a liquid. A nearly constant steady shear viscosity at low shear rates is only observed after long shearing times which cause irreversible changes in the samples. Creep-recovery tests confirm that sputa exhibit viscoelastic properties, with a significant elastic recovery. The results suggest that measurements of elastic moduli, rather than viscosities are more closely related to the mechanical properties of sputum in situ. Severing of actin filaments lowers the elastic modulus by 30-40%, but maintains viscoelastic integrity, while reduction of thiols in the glycoproteins nearly completely fluidizes the samples.
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Affiliation(s)
- Heidi Nielsen
- Department of Chemistry, Roskilde University, DK-4000 Roskilde, Denmark
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23
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Raynal BDE, Hardingham TE, Sheehan JK, Thornton DJ. Calcium-dependent protein interactions in MUC5B provide reversible cross-links in salivary mucus. J Biol Chem 2003; 278:28703-10. [PMID: 12756239 DOI: 10.1074/jbc.m304632200] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The macromolecular organization within saliva was investigated by tracer diffusion measurements of fluorescent polystyrene microspheres by fluorescence recovery after photobleaching using a confocal microscope (confocal-FRAP). There was a concentration-dependent reduction in microsphere diffusion; this was much greater in the presence of calcium (10 mm) and was reduced by the addition of EGTA (10 mm). These effects on tracer diffusion showed that native saliva contained a macromolecular organization that was sensitive to free calcium concentrations. This was supported by a major increase in the weight average molecular weight of the high molecular weight mucin fraction in saliva (10-62 x 106) and an increase in intrinsic viscosity of saliva (733 to 1203 ml/g) both caused by calcium. Analysis of the change in tracer diffusion in saliva showed a 20-fold increase in the apparent pore size (from 130 nm in 10 mm CaCl2 to 2600 nm in 10 mm EGTA at physiological concentration). The effect was specific for calcium and was unaffected by up to 2 m NaCl. The calcium binding activity was contained in a high buoyant density fraction of saliva excluded from Sepharose CL-2B. Calcium binding to this fraction gave an approximate Kd of 7 x 10-6 m, and the binding was irreversibly destroyed by treatment with 6 m guanidinium chloride and by mild reduction, suggesting it to be to a protein site. This fraction of saliva was shown to contain MUC5B as the single major protein species by positive ion electrospray ionization-tandem mass spectrometry analysis. The results suggested that oligomeric MUC5B in saliva is assembled into much larger linear or branched assemblies through calcium-mediated protein cross-links.
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Affiliation(s)
- Bertrand D E Raynal
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, 2.205 Stopford Bldg., University of Manchester, Manchester M13 9PT, United Kingdom
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24
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Raynal BDE, Hardingham TE, Thornton DJ, Sheehan JK. Concentrated solutions of salivary MUC5B mucin do not replicate the gel-forming properties of saliva. Biochem J 2002; 362:289-96. [PMID: 11853536 PMCID: PMC1222388 DOI: 10.1042/0264-6021:3620289] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have developed a new approach to study the molecular organization of salivary mucus and salivary mucins using confocal fluorescence recovery after photobleaching (confocal-FRAP). MUC5B mucin, its reduced subunit and T-domains were prepared from saliva and fluorescently labelled. The translational self-diffusion coefficients were determined up to 3.6 mg/ml by confocal-FRAP. The results suggest that, in solutions of purified MUC5B mucin, at concentrations at which the hydrodynamic domains overlap, the intermolecular interactions are predominantly due to dynamic entanglements, and there was no evidence of specific self-association of MUC5B mucin, or of its subunits, or T-domains. The analysis of the salivary mucus gel also showed no specific interactions with the purified MUC5B components, but it was much less permeable than expected from its MUC5B content. The saliva was completely permeable to microspheres of 207 nm diameter, but showed size-dependent effects on the diffusion of larger microspheres (499 nm and 711 nm diameter). From these analyses the salivary mucus was shown to be both permeable and dynamic, and with the characteristics of a semi-dilute transient network at physiological concentration. Comparison of the results from saliva and purified MUC5B mucin solutions showed that the network properties of saliva were equivalent to a solution of purified MUC5B mucin of 10-20 times higher concentration. This showed that saliva has additional structure and organization not present in the purified MUC5B mucin and suggests there are other interactions and/or components within saliva that combine with MUC5B to produce its complete properties.
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Affiliation(s)
- Bertrand D E Raynal
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, University of Manchester, 2.205 Stopford Building, Manchester M13 9PT, UK
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25
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Abstract
Aggregation phenomena in aqueous solutions of purified human tracheobronchial mucin have been studied by rheological methods, steady-state fluorescence, quasielastic light scattering, and spin probe techniques. At temperatures below 30 degrees C and concentrations above 15 mg/mL and in the absence of chaotropic agents, mucin solutions are viscoelastic gels. A gel-sol transition is observed at temperatures above 30 degrees C that is manifested by the diminishing storage modulus and a loss tangent above unity throughout the studied frequency range of the oscillatory shear. No decline in the mucin molecular weight is observed by size-exclusion chromatography above 30 degrees C in the absence of redox agents or proteolytic enzymes. Aggregation of hydrophobic protein segments of the mucin chains at 37 degrees C is indicated by QELS experiments. The decreasing polarity of the microenvironment of pyrene solubilized into mucin solutions at temperatures above 30 degrees C, concomitant with the gel-sol transition, shows the hydrophobicity of the formed aggregates. ESR spectra of the fatty acid spin probe, 16-doxylstearic acid indicate that the aggregate-aqueous interface becomes more developed at elevated temperatures.
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Affiliation(s)
- L E Bromberg
- Department of Physics, Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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26
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Kubba H, Pearson JP, Birchall JP. The aetiology of otitis media with effusion: a review. CLINICAL OTOLARYNGOLOGY AND ALLIED SCIENCES 2000; 25:181-94. [PMID: 10944048 DOI: 10.1046/j.1365-2273.2000.00350.x] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Otitis media with effusion (OME) is the most common cause of deafness in children in the developed world. In this article we aim to present an overview of current research developments on the aetiology of OME and the resulting implications for treatment. In the model we describe, the primary event is inflammation of the middle ear mucosa, usually due to the presence of bacteria. This leads to the release of inflammatory mediators, which cause secretion of a mucin-rich effusion by up-regulating mucin genes. Prolonged stimulation of the inflammatory response and poor mucociliary clearance lead to persistence of the middle ear fluid, giving rise to the clinical presentation of OME. We describe OME in the following sequence: the initial production of the effusion, the composition of the effusion produced, and factors impairing clearance of the effusion.
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Affiliation(s)
- H Kubba
- Royal Hospital for Sick Children, Yorkhill, Glasgow, UK.
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27
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Abstract
Role of CFTR in Airway Disease. Physiol. Rev. 79, Suppl.: S215-S255, 1999. - Cystic fibrosis (CF) is caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR), which accounts for the cAMP-regulated chloride conductance of airway epithelial cells. Lung disease is the chief cause of morbidity and mortality in CF patients. This review focuses on mechanisms whereby the deletion or impairment of CFTR chloride channel function produces lung disease. It examines the major themes of the channel hypothesis of CF, which involve impaired regulation of airway surface fluid volume or composition. Available evidence indicates that the effect of CFTR deletion alters physiological functions of both surface and submucosal gland epithelia. At the airway surface, deletion of CFTR causes hyperabsorption of sodium chloride and a reduction in the periciliary salt and water content, which impairs mucociliary clearance. In submucosal glands, loss of CFTR-mediated salt and water secretion compromises the clearance of mucins and a variety of defense substances onto the airway surface. Impaired mucociliary clearance, together with CFTR-related changes in the airway surface microenvironment, leads to a progressive cycle of infection, inflammation, and declining lung function. Here, we provide the details of this pathophysiological cascade in the hope that its understanding will promote the development of new therapies for CF.
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Affiliation(s)
- J M Pilewski
- Departments of Medicine and of Cell Biology and Physiology, University of Pittsburgh, Pennsylvania, USA
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28
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McCullagh CM, Gupta R, Jamieson AM, Blackwell J. Gelation of fractionated canine submaxillary mucin in a chaotropic solvent. Int J Biol Macromol 1996; 18:247-53. [PMID: 8739128 DOI: 10.1016/0141-8130(95)01086-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Rheological measurements have been performed on three molecular weight fractions of purified canine submaxillary mucin (CSM) dissolved in the chaotropic solvent 6 M guanidine hydrochloride (GdnHCI). Solutions of the lower molecular weight fractions are viscoelastic sols, and their dynamic moduli can be scaled with respect to molecular weight and concentration according to linear viscoelasticity theory. In contrast, preparations of the highest molecular weight fraction form viscoelastic gels that exhibit an equilibrium shear modulus, Ge', which scales with mucin concentration as Ge' approximately c3. Amino acid and carbohydrate analyses of all three fractions are similar; thus, the differences in rheological behavior are attributed to molecular weight differences, which affect the degree of coil overlap in solutions of a given concentration. These observations demonstrate conclusively that mucin glycoproteins of high molecular weight form gels under conditions in which the mucin chains physically interpenetrate, even when non-covalent intermolecular interactions are extensively disrupted. A comparison of these results with previous studies of purified submaxillary and tracheobronchial mucins indicates that the carbohydrate side-chain length, in addition to molecular weight, is an important determinant of the observed elastic response and the ability to form physical gels.
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Affiliation(s)
- C M McCullagh
- Department of Macromolecular Science, Case Western Reserve University, Cleveland, Ohio 44106-7202, USA
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