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Macrophage Involvement in Medication-Related Osteonecrosis of the Jaw (MRONJ): A Comprehensive, Short Review. Cancers (Basel) 2022; 14:cancers14020330. [PMID: 35053492 PMCID: PMC8773732 DOI: 10.3390/cancers14020330] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 01/07/2022] [Accepted: 01/07/2022] [Indexed: 02/04/2023] Open
Abstract
Simple Summary Medication-related Osteonecrosis of the Jaw (MRONJ) is a significant complication mainly of antiresorptive medications used in the management of bone diseases. MRONJ development may be accompanied by pain, eating discomfort, self-consciousness, and other symptoms that overall disturb patients’ everyday life. Hence, MRONJ occurrence is of growing clinical concern and affects treatment decisions. Although MRONJ has been extensively studied since being first reported in 2003, the mechanisms of disease pathogenesis have not yet been determined and disease management is mostly empirical. Recent data investigate the effects of antiresorptive medications on immune system components including macrophages and introduce these cells as key players in MRONJ pathogenesis. Considering macrophage versatility, developmental plasticity, and its pivotal role in immune response, the current short review focused on the potential involvement of these multi-potential cells in MRONJ pathogenesis. Understanding the complex role of macrophages in MRONJ pathophysiology will add new valuable data on disease prevention and control. Abstract Antiresorptive agents such as bisphosphonates (BP) and denosumab are commonly prescribed for the management of primary bone malignancy, bone metastasis, osteoporosis, Paget disease, or other bone disorders. Medication-related osteonecrosis of the Jaws (MRONJ) is a rare but significant complication of antiresorptive medications. Duration, dose, and antiresorptive potency as well as concomitant diseases, additional medications, and local factors affect MRONJ incidence and severity. MRONJ pathophysiology is still poorly understood. Nevertheless, decreased bone resorption due to osteoclastic inhibition along with trauma, infection/inflammation, or blood supply inhibition are considered synergistic factors for disease development. In addition, previous data research examined the effects of antiresorptive medication on immune system components and introduced potential alterations on immune response as novel elements in MRONJ pathogenesis. Considering that macrophages are the first cells in the nonspecific immune response, it is not surprising that these multifaceted players attracted increased attention in MRONJ research recently. This current review attempted to elucidate the effects of antiresorptive medications on several aspects of macrophage activity in relation to the complex inflammatory microenvironment of MRONJ. Collectively, unravelling the mode of action and extent of macrophages’ potential contribution in MRONJ occurrence will provide novel insight in disease pathogenesis and potentially identify intrinsic therapeutic targets.
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Altered macrophagic THP-1 cell phagocytosis and migration in bisphosphonate-related osteonecrosis of the jaw (BRONJ). Clin Oral Investig 2015; 20:1043-54. [DOI: 10.1007/s00784-015-1584-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 08/26/2015] [Indexed: 12/25/2022]
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Responses to cell loss become restricted as the supporting cells in mammalian vestibular organs grow thick junctional actin bands that develop high stability. J Neurosci 2014; 34:1998-2011. [PMID: 24478379 DOI: 10.1523/jneurosci.4355-13.2014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Sensory hair cell (HC) loss is a major cause of permanent hearing and balance impairments for humans and other mammals. Yet, fish, amphibians, reptiles, and birds readily replace HCs and recover from such sensory deficits. It is unknown what prevents replacement in mammals, but cell replacement capacity declines contemporaneously with massive postnatal thickening of F-actin bands at the junctions between vestibular supporting cells (SCs). In non-mammals, SCs can give rise to regenerated HCs, and the bands remain thin even in adults. Here we investigated the stability of the F-actin bands between SCs in ears from chickens and mice and Madin-Darby canine kidney cells. Pharmacological experiments and fluorescence recovery after photobleaching (FRAP) of SC junctions in utricles from mice that express a γ-actin-GFP fusion protein showed that the thickening F-actin bands develop increased resistance to depolymerization and exceptional stability that parallels a sharp decline in the cell replacement capacity of the maturing mammalian ear. The FRAP recovery rate and the mobile fraction of γ-actin-GFP both decreased as the bands thickened with age and became highly stabilized. In utricles from neonatal mice, time-lapse recordings in the vicinity of dying HCs showed that numerous SCs change shape and organize multicellular actin purse strings that reseal the epithelium. In contrast, adult SCs appeared resistant to deformation, with resealing responses limited to just a few neighboring SCs that did not form purse strings. The exceptional stability of the uniquely thick F-actin bands at the junctions of mature SCs may play an important role in restricting dynamic repair responses in mammalian vestibular epithelia.
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Russell S, Cancel LM, Tarbell JM, Rumschitzki DS. A protein diffusion model of the sealing effect. Chem Eng Sci 2009; 64:4504-4514. [PMID: 36588620 PMCID: PMC9802672 DOI: 10.1016/j.ces.2009.05.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Water transport across the arterial endothelium is believed primarily to occur through breaks in the tight junction strands at the cell periphery between neighboring cells. Additional proteins arriving at the tight junction can close these breaks, thereby attenuating this water flux. Motivated by evidence that the diffusion of presynthesized protein from the interior of the cell to and incorporation into the cell border is the mechanism of endothelial tight junctional sealing, we develop a diffusion-limited mathematical model of intercellular gap sealing. A single endothelial cell is represented as a thin, axisymmetric disk, initially containing a uniform distribution of junctional protein that does not interact with the apical or basal cell surfaces. Upon application of a transmural pressure gradient, water flows through the junctional cleft, and tight junction remodeling begins. We assume that proteins at the junction are instantaneously incorporated into its strand, dropping the free protein concentration at the cell periphery to zero. This sets the diffusion of intracellular proteins toward the junction in motion. The solution of this one-dimensional initial value problem provides excellent fits to current and previously published experimental data over a wide variety of conditions. It yields three physically meaningful parameters for each fit, including a protein diffusivity in the cytoplasm that varies little within experimental treatments. Statistical variation of these parameters allows rational comparison of experimental runs and identification of outlier runs.
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Affiliation(s)
- Stewart Russell
- Department of Biomedical Engineering, The City College of New York, The Graduate School, University Center of CUNY, New York, NY 10031, USA
| | - Limary M. Cancel
- Department of Biomedical Engineering, The City College of New York, The Graduate School, University Center of CUNY, New York, NY 10031, USA
| | - John M. Tarbell
- Department of Biomedical Engineering, The City College of New York, The Graduate School, University Center of CUNY, New York, NY 10031, USA
| | - David S. Rumschitzki
- Department of Biomedical Engineering, The City College of New York, The Graduate School, University Center of CUNY, New York, NY 10031, USA
,Corresponding author. (D.S. Rumschitzki)
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5
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Fan Y, Gong Y, Ghosh PK, Graham LM, Fox PL. Spatial coordination of actin polymerization and ILK-Akt2 activity during endothelial cell migration. Dev Cell 2009; 16:661-74. [PMID: 19460343 DOI: 10.1016/j.devcel.2009.03.009] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2008] [Revised: 02/04/2009] [Accepted: 03/11/2009] [Indexed: 10/20/2022]
Abstract
Eukaryotic cell migration proceeds by cycles of protrusion, adhesion, and contraction, regulated by actin polymerization, focal adhesion assembly, and matrix degradation. However, mechanisms coordinating these processes remain largely unknown. Here, we show that local regulation of thymosin-beta4 (Tbeta4) binding to actin monomer (G-actin) coordinates actin polymerization with metalloproteinase synthesis to promote endothelial cell motility. In particular and quite unexpectedly, FRET analysis reveals diminished interaction between Tbeta4 and G-actin at the cell leading edge despite their colocalization there. Profilin-dependent dissociation of G-actin-Tbeta4 complexes simultaneously liberates actin for filament assembly and facilitates Tbeta4 binding to integrin-linked kinase (ILK) in the lamellipodia. Tbeta4-ILK complexes then recruit and activate Akt2, resulting in matrix metalloproteinase-2 production. Thus, the actin-Tbeta4 complex constitutes a latent coordinating center for cell migratory behavior, allowing profilin to initiate a cascade of events at the leading edge that couples actin polymerization to matrix degradation.
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Affiliation(s)
- Yi Fan
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
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6
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Salvarezza SB, Deborde S, Schreiner R, Campagne F, Kessels MM, Qualmann B, Caceres A, Kreitzer G, Rodriguez-Boulan E. LIM kinase 1 and cofilin regulate actin filament population required for dynamin-dependent apical carrier fission from the trans-Golgi network. Mol Biol Cell 2008; 20:438-51. [PMID: 18987335 DOI: 10.1091/mbc.e08-08-0891] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The functions of the actin cytoskeleton in post-Golgi trafficking are still poorly understood. Here, we report the role of LIM Kinase 1 (LIMK1) and its substrate cofilin in the trafficking of apical and basolateral proteins in Madin-Darby canine kidney cells. Our data indicate that LIMK1 and cofilin organize a specialized population of actin filaments at the Golgi complex that is selectively required for the emergence of an apical cargo route to the plasma membrane (PM). Quantitative pulse-chase live imaging experiments showed that overexpression of kinase-dead LIMK1 (LIMK1-KD), or of LIMK1 small interfering RNA, or of an activated cofilin mutant (cofilin S3A), selectively slowed down the exit from the trans-Golgi network (TGN) of the apical PM marker p75-green fluorescent protein (GFP) but did not interfere with the apical PM marker glycosyl phosphatidylinositol-YFP or the basolateral PM marker neural cell adhesion molecule-GFP. High-resolution live imaging experiments of carrier formation and release by the TGN and analysis of peri-Golgi actin dynamics using photoactivatable GFP suggest a scenario in which TGN-localized LIMK1-cofilin regulate a population of actin filaments required for dynamin-syndapin-cortactin-dependent generation and/or fission of precursors to p75 transporters.
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Affiliation(s)
- Susana B Salvarezza
- Margaret Dyson Vision Research Institute and Department of Cell and Developmental Biology, HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Medical College of Cornell University, New York, NY 10065, USA
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7
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Lustyik G. Photobleaching measurements of diffusion in cell membranes and aqueous cell compartments. CURRENT PROTOCOLS IN CYTOMETRY 2008; Chapter 2:Unit 2.12. [PMID: 18770695 DOI: 10.1002/0471142956.cy0212s16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This commentary unit discusses in great detail the theoretical nature of fluorescence recovery after photobleaching (FRAP). This information is crucial to an understanding of how and why FRAP works in a cell system. Further, understanding how to interpret the data sets requires a sound knowledge of the processes involved. Of primary importance are the nature of membrane diffusion and the nature of the multiple compartments into which fluorescent dyes can enter. The unit provides a complete discussion of all aspects of FRAP from the perspective of cellular measurements.
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Affiliation(s)
- G Lustyik
- University of Pécs, Faculty of Medicine, Pécs, Hungary
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8
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Rabodzey A, Yao Y, Luscinskas FW, Shaw SK, Dewey CF. Early response of endothelial cells to flow is mediated by VE-cadherin. ACTA ACUST UNITED AC 2008; 14:195-209. [PMID: 18163230 DOI: 10.1080/15419060701755792] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Endothelial cells are known to respond to flow onset by increasing actin turnover rate. Current models assume that an increase in the actin turnover rate should result in a rise in cell crawling speed. Here we report that confluent endothelial monolayer shows an unexpected behavior: cell crawling speed decreases by approximately 40% within the first 30 min of flow onset. A drop in crawling speed has not been observed in either subconfluent endothelial cells or in VE-cadherin-deficient cells. We found that flow onset caused an increase in the number of VE-cadherin-GFP molecules in the junctions and elicited changes in the cytoskeleton-associated fractions of alpha, beta -catenins and VE-cadherin. Flow application also increased the strength of interactions of endothelial cells with surfaces coated with recombinant VE-cadherin. These observations suggest that endothelial cell junctional proteins respond to flow transiently by increasing the strength of intercellular attachments early after flow onset and support the view on the active role of intercellular adhesions in mechanotransduction.
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Affiliation(s)
- Aleksandr Rabodzey
- Hatsopoulos Microfluids Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
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Michelman-Ribeiro A, Horkay F, Nossal R, Boukari H. Probe Diffusion in Aqueous Poly(vinyl alcohol) Solutions Studied by Fluorescence Correlation Spectroscopy. Biomacromolecules 2007; 8:1595-600. [PMID: 17441767 DOI: 10.1021/bm061195r] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report fluorescence correlation spectroscopy measurements of the translational diffusion coefficient of various probe particles in dilute and semidilute aqueous poly(vinyl alcohol) solutions. The range of sizes of the particles (fluorescent molecules, proteins, and polymers) was chosen to explore various length scales of the polymer solutions as defined by the polymer-polymer correlation length. For particles larger than the correlation length, we find that the diffusion coefficient, D, decreases exponentially with the polymer concentration. This can be explained by an exponential increase in the solution viscosity, consistent with the Stokes-Einstein equation. For probes on the order of the correlation length, the decrease of the diffusion coefficient cannot be accounted for by the Stokes-Einstein equation, but can be fit by a stretched exponential, D approximately exp(-alphacn), where we find n = 0.73-0.84 and alpha is related to the probe size. These results are in accord with a diffusion model of Langevin and Rondelez (Polymer 1978, 19, 1875), where these values of n indicate a good solvent quality.
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Affiliation(s)
- Ariel Michelman-Ribeiro
- Laboratory of Integrative and Medical Biophysics, National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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Campbell JJ, Knight MM. An improved confocal FRAP technique for the measurement of long-term actin dynamics in individual stress fibers. Microsc Res Tech 2007; 70:1034-40. [PMID: 17722058 DOI: 10.1002/jemt.20513] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The present study describes an improved fluorescent recovery after photobleaching (FRAP) technique, which has been successfully used to quantify actin dynamics within individual fibers. Chondrocytes were transfected with an eGFP-actin plasmid and cultured on glass coverslips. In cells expressing eGFP-actin, confocal microscopy was used to bleach 3 x 1 microm regions accurately positioned along individual stress fibers. The subsequent fluorescent recovery over a 10-min imaging period was assessed from a series of intensity profiles, positioned along the length of the stress fibers and spanning the bleach region. From these profiles, the normalized fluorescent intensity values were plotted against time. In this way, the technique provided sufficient spatial precision to describe the long-term behavior within individual stress fibers while accounting for the inherent movement. An identical procedure was used to examine FRAP for eGFP-actin within the interfiber region. The FRAP curves for stress fibers were accurately modeled by two phase exponentials which indicated only partial recovery with a mobile fraction of 46%. This suggests that some of the F-actin molecules were in a tightly bound configuration with negligible turnover. The interfiber region exhibited similar two phase exponential FRAP with a mobile fraction of 68%. This partial recovery may be due to the presence, within the interfiber region, of both G-actin and fine F-actin fibers beneath the resolution of the confocal microscope. In conclusion, the present FRAP methodology overcomes many of the limitations of previous studies in order to provide new data describing long-term actin dynamics within individual stress fibers.
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Affiliation(s)
- J J Campbell
- Department of Engineering, Medical Engineering Division, Queen Mary University of London, London E1 4NS, United Kingdom
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11
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Abstract
In the past, inflammation has been associated with infections and with the immune system. But more recent evidence suggests that a much broader range of diseases have telltale markers for inflammation. Inflammation is the basic mechanism available for repair of tissue after an injury and consists of a cascade of cellular and microvascular reactions that serve to remove damaged and generate new tissue. The cascade includes elevated permeability in microvessels, attachment of circulating cells to the vessels in the vicinity of the injury site, migration of several cell types, cell apoptosis, and growth of new tissue and blood vessels. This review provides a summary of the major microvascular, cellular, and molecular mechanisms that regulate elements of the inflammatory cascade. The analysis is largely focused on the identification of the major participants, notably signaling and adhesion molecules, and their mode of action in the inflammatory cascade. We present a new hypothesis for the generation of inflammatory mediators in plasma that are derived from the digestive pancreatic enzymes responsible for digestion. The inflammatory cascade offers a large number of opportunities for development of quantitative models that describe various aspects of human diseases.
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Affiliation(s)
- Geert W Schmid-Schönbein
- Department of Bioengineering, The Whitaker Institute for Biomedical Engineering, University of California San Diego, La Jolla, California 92093-0412, USA.
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12
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McDonald D, Carrero G, Andrin C, de Vries G, Hendzel MJ. Nucleoplasmic beta-actin exists in a dynamic equilibrium between low-mobility polymeric species and rapidly diffusing populations. ACTA ACUST UNITED AC 2006; 172:541-52. [PMID: 16476775 PMCID: PMC2063674 DOI: 10.1083/jcb.200507101] [Citation(s) in RCA: 201] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
β-Actin, once thought to be an exclusively cytoplasmic protein, is now known to have important functions within the nucleus. Nuclear β-actin associates with and functions in chromatin remodeling complexes, ribonucleic acid polymerase complexes, and at least some ribonucleoproteins. Proteins involved in regulating actin polymerization are also found in the interphase nucleus. We define the dynamic properties of nuclear actin molecules using fluorescence recovery after photobleaching. Our results indicate that actin and actin-containing complexes are reduced in their mobility through the nucleoplasm diffusing at ∼0.5 μm2 s−1. We also observed that ∼20% of the total nuclear actin pool has properties of polymeric actin that turns over rapidly. This pool could be detected in endogenous nuclear actin by using fluorescent polymeric actin binding proteins and was sensitive to drugs that alter actin polymerization. Our results validate previous reports of polymeric forms of nuclear actin observed in fixed specimens and reveal that these polymeric forms are very dynamic.
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Affiliation(s)
- Darin McDonald
- Department of Oncology and 2Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 1Z2
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Lele TP, Thodeti CK, Ingber DE. Force meets chemistry: Analysis of mechanochemical conversion in focal adhesions using fluorescence recovery after photobleaching. J Cell Biochem 2006; 97:1175-83. [PMID: 16408278 DOI: 10.1002/jcb.20761] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Mechanotransduction--the process by which mechanical forces are converted into changes of intracellular biochemistry--is critical for normal cell and tissue function. Integrins facilitate mechanochemical conversion by transferring physical forces from the extracellular matrix, across the cell surface, and to cytoskeletal-associated proteins within focal adhesions. It is likely that force alters biochemistry at these sites by altering molecular binding affinities of a subset of focal adhesion proteins, but this has been difficult to quantify within living cells. Here, we describe how the fluorescence recovery after photobleaching (FRAP) technique can be adapted and used in conjunction with mathematical models to directly measure force-dependent alterations in molecular binding and unbinding rate constants of individual focal adhesion proteins in situ. We review these recent findings, and discuss the strengths and limitations of this approach for analysis of mechanochemical signaling in focal adhesions and other cellular structures. The ability to quantify molecular binding rate constants in the physical context of the living cytoplasm should provide new insight into the molecular basis of cellular mechanotransduction. It also may facilitate future efforts to bridge biological experimentation and mathematical modeling in our quest for a systems biology level description of cell regulation.
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Affiliation(s)
- Tanmay P Lele
- Vascular Biology Program, Department of Pathology and Surgery, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
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Ponti A, Matov A, Adams M, Gupton S, Waterman-Storer CM, Danuser G. Periodic patterns of actin turnover in lamellipodia and lamellae of migrating epithelial cells analyzed by quantitative Fluorescent Speckle Microscopy. Biophys J 2005; 89:3456-69. [PMID: 16100274 PMCID: PMC1366841 DOI: 10.1529/biophysj.104.058701] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2004] [Accepted: 07/14/2005] [Indexed: 01/06/2023] Open
Abstract
We measured actin turnover in lamellipodia and lamellae of migrating cells, using quantitative Fluorescent Speckle Microscopy. Lamellae disassembled at low rates from the front to the back. However, the dominant feature in their turnover was a spatially random pattern of periodic polymerization and depolymerization moving with the retrograde flow. Power spectra contained frequencies between 0.5 and 1 cycle/min. The spectra remained unchanged when applying Latrunculin A and Jasplakinolide in low doses, except that additional frequencies occurred beyond 1 cycle/min. Whereas Latrunculin did not change the rate of mean disassembly, Jasplakinolide halted it completely, indicating that the steady state and the dynamics of actin turnover are differentially affected by pharmacological agents. Lamellipodia assembled in recurring bursts at the leading edge and disassembled approximately 2.5 microm behind. Events of polymerization correlated spatially and temporally with transient formation of Arp2/3 clusters. In lamellae, Arp2/3 accumulation and polymerization correlated only spatially, suggesting an Arp2/3-independent mechanism for filament nucleation. To acquire these data we had to enhance the resolution of quantitative Fluorescent Speckle Microscopy to the submicron level. Several algorithmic advances in speckle image processing are described enabling the analysis of kinetic and kinematic activities of polymer networks at the level of single speckles.
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Affiliation(s)
- A Ponti
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, USA
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15
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Picart C, Mutterer J, Arntz Y, Voegel JC, Schaaf P, Senger B. Application of fluorescence recovery after photobleaching to diffusion of a polyelectrolyte in a multilayer film. Microsc Res Tech 2005; 66:43-57. [PMID: 15816028 DOI: 10.1002/jemt.20142] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The diffusion coefficient, D, and the proportion of mobile molecules, p, is measured for a fluorescently labeled polyelectrolyte in a multilayer film using fluorescence recovery after photobleaching (FRAP). The film was composed of poly(L-lysine) (PLL) and hyaluronan (HA). The labeled polyelectrolyte (PLL(FITC)) was either deposited on top of the film or embedded within it. A circular area of diameter approximately 60 microm was bleached using a confocal laser scanning microscope. Because molecules do already diffuse during the bleaching step, the initial light intensity profile is not characteristic of a uniformly bleached circular area. A formalism is developed in which a simple mathematical representation of a measured profile serves as starting profile. This radial distribution is introduced in the equation describing the time evolution of the labeled molecule concentration under the hypothesis that the recovery results from pure, two-dimensional Brownian diffusion of the mobile molecules according to Fick's law. The analysis of a series of images taken at successive times after bleaching (up to approximately one hour) leads to estimates of D of the order of 0.2 microm(2) s(-1) for labeled molecules deposited on top of the film and a 5-fold smaller value for the molecules embedded in the film. However, p is remarkably insensitive to the position in the multilayer architecture (p approximately 0.40).
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Affiliation(s)
- Catherine Picart
- Institut National de la Santé et de la Recherche Médicale, Unité 595, Faculté de Chirurgie Dentaire, Université Louis Pasteur, 67085 Strasbourg Cedex, France
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Abstract
Leucocytes in the bloodstream respond rapidly to inflammatory signals by crossing the blood vessel wall and entering the tissues. This process involves adhesion to, and subsequent transmigration across, the endothelium, mediated by a cascade of interactions between adhesion molecules and stimulation of intracellular signalling pathways in both leucocytes and endothelial cells. This leads to changes in endothelial cell morphology that assist leucocyte extravasation, including endothelial cell contraction, intercellular junction disruption, increased permeability, remodelling of the endothelial apical surface and alterations in vesicle trafficking. Rho GTPases play a central role in many of the endothelial responses to leucocyte interaction. In this review, we discuss recent findings on leucocyte-induced alterations to endothelial cells, and the roles of Rho GTPases in these responses.
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Affiliation(s)
- Jaime Millán
- Ludwig Institute for Cancer Research, Royal Free and University College School of Medicine, 91 Riding House Street, London W1W 7BS, U.K., and Department of Biochemistry and Molecular Biology, University College London, Gower Street, London, U.K
| | - Anne J. Ridley
- Ludwig Institute for Cancer Research, Royal Free and University College School of Medicine, 91 Riding House Street, London W1W 7BS, U.K., and Department of Biochemistry and Molecular Biology, University College London, Gower Street, London, U.K
- To whom correspondence should be addressed, at the Ludwig Institute for Cancer Research (email )
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Kole TP, Tseng Y, Huang L, Katz JL, Wirtz D. Rho kinase regulates the intracellular micromechanical response of adherent cells to rho activation. Mol Biol Cell 2004; 15:3475-84. [PMID: 15146061 PMCID: PMC452598 DOI: 10.1091/mbc.e04-03-0218] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Local sol-gel transitions of the cytoskeleton modulate cell shape changes, which are required for essential cellular functions, including motility and adhesion. In vitro studies using purified cytoskeletal proteins have suggested molecular mechanisms of regulation of cytoskeleton mechanics; however, the mechanical behavior of living cells and the signaling pathways by which it is regulated remains largely unknown. To address this issue, we used a nanoscale sensing method, intracellular microrheology, to examine the mechanical response of the cell to activation of the small GTPase Rho. We observe that the cytoplasmic stiffness and viscosity of serum-starved Swiss 3T3 cells transiently and locally enhances upon treatment with lysophosphatidic acid, and this mechanical behavior follows a trend similar to Rho activity. Furthermore, the time-dependent activation of Rho decreases the degree of microheterogeneity of the cytoplasm. Our results reveal fundamental differences between intracellular elasticity and cellular tension and suggest a critical role for Rho kinase in the regulation of intracellular mechanics.
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Affiliation(s)
- Thomas P Kole
- Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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Sims MR, Ashworth JF, Sampson WJ. Upregulation of immunoreactivity of endothelin-1 and alpha-SMA in PDL microvasculature following acute tooth loading: an immunohistochemical study in the marmoset. Orthod Craniofac Res 2003; 6:74-82. [PMID: 12809268 DOI: 10.1034/j.1600-0854.2003.o200.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
OBJECTIVES To test the hypothesis that a continuous mechanical tooth load would elevate immunoreactivity of endothelin-1 (ET-1) and alpha-smooth muscle actin (alpha-SMA) in the periodontal ligament (PDL) microvasculature. DESIGN A randomized control study employing 1.5 h of loading to first molars. SETTING AND SAMPLE POPULATION Orthodontic Research Laboratory, Dental School, Adelaide University. Four young adult, male marmoset monkeys were consecutively anaesthetized and treated. EXPERIMENTAL VARIABLE An external telescoping frame applied a jaw closing load (120-200 g) transmitted occlusally, via a rubber pad, to randomly assigned mandibular left or right first molars. Contralateral molars were used as controls. OUTCOME MEASURE Undemineralized, midsagittal, mandibular molar slices, approximately 150 microm thick were immunolabelled with ET-1 and alpha-SMA antibodies and examined in a confocal laser scanning microscope (CLSM) for vascular endothelium and smooth muscle immunolabelling. RESULTS Three categories of post-capillary-sized venule endothelial cell immunolabelling occurred: endothelium labelled solely with ET-1; endothelium labelled solely with alpha-SMA; endothelium labelled with both ET-1 and alpha-SMA. In endothelial cells, the alpha-SMA showed a moderate cytoplasmic distribution with dense peripheral concentration. Loading increased arteriole alpha-SMA actin labelling. CONCLUSION Scattered expression of ET-1 is the default state in primate PDL endothelial cells. Increased antigenicity of endothelial cells to both ET-1 and alpha-SMA, and of arteriolar smooth muscle to alpha-SMA, is a response to shear and compression loads.
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Affiliation(s)
- M R Sims
- Microcirculation and Lymphology Laboratory, Flinders University, Visiting Research Fellow Orthodontic Unit, Dental School, Adelaide University, South Australia, Australia
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Carballido-López R, Errington J. The bacterial cytoskeleton: in vivo dynamics of the actin-like protein Mbl of Bacillus subtilis. Dev Cell 2003; 4:19-28. [PMID: 12530960 DOI: 10.1016/s1534-5807(02)00403-3] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mbl is a bacterial actin homolog that controls cell morphogenesis in Bacillus subtilis. A functional GFP-Mbl fusion protein was used to examine the behavior of the helical cables formed by Mbl protein in live B. subtilis cells. The cables undergo dynamic changes during cell cycle progression. They are stable but not rigid while elongating in parallel with cell growth, and they require septum formation to divide/cleave. Fluorescence recovery after photobleaching (FRAP) analysis showed that the cables are continuously remodeled during cell elongation. Turnover occurs along the length of the helical Mbl filaments, with no obvious polarity and a recovery half-time of about 8 min. These findings have important implications for the nature of bacterial cell wall architecture and synthesis.
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Affiliation(s)
- Rut Carballido-López
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, OX1 3RE, Oxford, United Kingdom
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McGrath JL, Osborn EA, Tardy YS, Dewey CF, Hartwig JH. Regulation of the actin cycle in vivo by actin filament severing. Proc Natl Acad Sci U S A 2000; 97:6532-7. [PMID: 10823888 PMCID: PMC18648 DOI: 10.1073/pnas.100023397] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Cycling of actin subunits between monomeric and filamentous phases is essential for cell crawling behavior. We investigated actin filament turnover rates, length, number, barbed end exposure, and binding of cofilin in bovine arterial endothelial cells moving at different speeds depending on their position in a confluent monolayer. Fast-translocating cells near the wound edge have short filament lifetimes compared with turnover values that proportionately increase in slower moving cells situated at increasing distances from the wound border. Contrasted with slow cells exhibiting slow actin filament turnover speeds, fast cells have less polymerized actin, shorter actin filaments, more free barbed ends, and less actin-associated cofilin. Cultured primary fibroblasts manifest identical relationships between speed and actin turnover as the endothelial cells, and fast fibroblasts expressing gelsolin have higher actin turnover rates than slow fibroblasts that lack this actin-severing protein. These results implicate actin filament severing as an important control mechanism for actin cycling in cells.
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Affiliation(s)
- J L McGrath
- Hematology Division, Brigham and Women's Hospital, Boston, MA 02115, USA.
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Moldovan L, Moldovan NI, Sohn RH, Parikh SA, Goldschmidt-Clermont PJ. Redox changes of cultured endothelial cells and actin dynamics. Circ Res 2000; 86:549-57. [PMID: 10720417 DOI: 10.1161/01.res.86.5.549] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We studied the association between the production of reactive oxygen species, actin organization, and cellular motility. We have used an endothelial cell monolayer-wounding assay to demonstrate that the cells at the margin of the wound thus created produced significantly more free radicals than did cells in distant rows. The rate of incorporation of actin monomers into filaments was fastest at the wound margin, where heightened production of free radicals was detected. We have tested the effect of decreasing reactive oxygen species production on the migration of endothelial cells and on actin polymerization. The NADPH inhibitor diphenylene iodonium and the superoxide dismutase mimetic manganese (III) tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP) virtually abolished cytochalasin D-inhibitable actin monomer incorporation at the fast-growing barbed ends of filaments. Moreover, endothelial cell migration within the wound was significantly retarded in the presence of both diphenylene iodonium and MnTMPyP. We conclude that migration of endothelial cells in response to loss of confluence includes the intracellular production of reactive oxygen species, which contribute to the actin cytoskeleton reorganization required for the migratory behavior of endothelial cells.
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Affiliation(s)
- L Moldovan
- Heart and Lung Institute and Division of Cardiology, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, USA
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