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Tuladhar A, Shaver JC, McGee WA, Yu K, Dorn J, Horne JL, Alhamad DW, Hagan ML, Cooley MA, Zhong R, Bollag W, Johnson M, Hamrick MW, McGee-Lawrence ME. Prkd1 regulates the formation and repair of plasma membrane disruptions (PMD) in osteocytes. Bone 2024; 186:117147. [PMID: 38866124 PMCID: PMC11246118 DOI: 10.1016/j.bone.2024.117147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 05/21/2024] [Accepted: 06/03/2024] [Indexed: 06/14/2024]
Abstract
We and others have seen that osteocytes sense high-impact osteogenic mechanical loading via transient plasma membrane disruptions (PMDs) which initiate downstream mechanotransduction. However, a PMD must be repaired for the cell to survive this wounding event. Previous work suggested that the protein Prkd1 (also known as PKCμ) may be a critical component of this PMD repair process, but the specific role of Prkd1 in osteocyte mechanobiology had not yet been tested. We treated MLO-Y4 osteocytes with Prkd1 inhibitors (Go6976, kbNB 142-70, staurosporine) and generated an osteocyte-targeted (Dmp1-Cre) Prkd1 conditional knockout (CKO) mouse. PMD repair rate was measured via laser wounding and FM1-43 dye uptake, PMD formation and post-wounding survival were assessed via fluid flow shear stress (50 dyn/cm2), and in vitro osteocyte mechanotransduction was assessed via measurement of calcium signaling. To test the role of osteocyte Prkd1 in vivo, Prkd1 CKO and their wildtype (WT) littermates were subjected to 2 weeks of unilateral axial tibial loading and loading-induced changes in cortical bone mineral density, geometry, and formation were measured. Prkd1 inhibition or genetic deletion slowed osteocyte PMD repair rate and impaired post-wounding cell survival. These effects could largely be rescued by treating osteocytes with the FDA-approved synthetic copolymer Poloxamer 188 (P188), which was previously shown to facilitate membrane resealing and improve efficiency in the repair rate of PMD in skeletal muscle myocytes. In vivo, while both WT and Prkd1 CKO mice demonstrated anabolic responses to tibial loading, the magnitude of loading-induced increases in tibial BMD, cortical thickness, and periosteal mineralizing surface were blunted in Prkd1 CKO as compared to WT mice. Prkd1 CKO mice also tended to show a smaller relative difference in the number of osteocyte PMD in loaded limbs and showed greater lacunar vacancy, suggestive of impaired post-wounding osteocyte survival. While P188 treatment rescued loading-induced increases in BMD in the Prkd1 CKO mice, it surprisingly further suppressed loading-induced increases in cortical bone thickness and cortical bone formation. Taken together, these data suggest that Prkd1 may play a pivotal role in the regulation and repair of the PMD response in osteocytes and support the idea that PMD repair processes can be pharmacologically targeted to modulate downstream responses, but suggest limited utility of PMD repair-promoting P188 in improving bone anabolic responses to loading.
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Affiliation(s)
- Anik Tuladhar
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States of America
| | - Joseph C Shaver
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States of America
| | - Wesley A McGee
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States of America
| | - Kanglun Yu
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States of America
| | - Jennifer Dorn
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States of America
| | - J Luke Horne
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States of America
| | - Dima W Alhamad
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States of America
| | - Mackenzie L Hagan
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States of America
| | - Marion A Cooley
- Department of Oral Biology and Diagnostic Sciences, Dental College of Georgia at Augusta University, Augusta, GA, United States of America
| | - Roger Zhong
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at AugustaUniversity, Augusta, GA, United States of America
| | - Wendy Bollag
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, GA, United States of America; Charlie Norwood VA Medical Center, Augusta, GA, United States of America
| | - Maribeth Johnson
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at AugustaUniversity, Augusta, GA, United States of America
| | - Mark W Hamrick
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States of America
| | - Meghan E McGee-Lawrence
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States of America.
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Crabtree A, Boehnke N, Bates F, Hackel B. Consequences of poly(ethylene oxide) and poloxamer P188 on transcription in healthy and stressed myoblasts. Proc Natl Acad Sci U S A 2023; 120:e2219885120. [PMID: 37094151 PMCID: PMC10161009 DOI: 10.1073/pnas.2219885120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 03/26/2023] [Indexed: 04/26/2023] Open
Abstract
Poly(ethylene oxide) (PEO) and poloxamers, a class of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers, have many personal and medical care applications, including the stabilization of stressed cellular membranes. Despite the widespread use, the cellular transcriptional response to these molecules is relatively unknown. C2C12 myoblasts, a model muscle cell, were subjected to short-term Poloxamer 188 (P188) and PEO181 (8,000 g/mol) treatment in culture. RNA was extracted and sequenced to quantify transcriptomic impact. The addition of moderate concentrations (14 µM) of either polymer to unstressed cells caused substantial differential gene expression, including at least twofold modulation of 357 and 588 genes, respectively. In addition, evaluation of the transcriptome response to osmotic stress without polymer treatment revealed dramatic change in RNA expression. Interestingly, the addition of polymer to stressed cells-at concentrations that provide physiological protection-did not yield a significant difference in expression of any gene relative to stress alone. Genome-scale expression analysis was corroborated by single-gene quantitative real-time PCR. Changes in protein expression were measured via western blot, which revealed partial alignment with the RNA results. Collectively, the significant changes to expression of multiple genes and resultant protein translation demonstrates an unexpectedly broad biochemical response to these polymers in healthy myoblasts in vitro. Meanwhile, the lack of substantial transcriptional response to polymer treatment in stressed cells highlights the physical nature of that protective mechanism.
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Affiliation(s)
- Adelyn A. Crabtree
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN55455
| | - Natalie Boehnke
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN55455
| | - Frank S. Bates
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN55455
| | - Benjamin J. Hackel
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN55455
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3
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Batti Angulski AB, Cohen H, Kim M, Hahn D, Van Zee N, Lodge TP, Hillmyer MA, Hackel BJ, Bates FS, Metzger JM. Molecular homing and retention of muscle membrane stabilizing copolymers by non-invasive optical imaging in vivo. Mol Ther Methods Clin Dev 2022; 28:162-176. [PMID: 36654800 PMCID: PMC9829555 DOI: 10.1016/j.omtm.2022.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 12/07/2022] [Indexed: 12/13/2022]
Abstract
First-in-class membrane stabilizer Poloxamer 188 (P188) has been shown to confer membrane protection in an extensive range of clinical conditions; however, elements of the systemic distribution and localization of P188 at the organ, tissue, and muscle fiber levels in vivo have not yet been elucidated. Here we used non-invasive fluorescence imaging to directly visualize and track the distribution and localization of P188 in vivo. The results demonstrated that the Alx647 probe did not alter the fundamental properties of P188 to protect biological membranes. Distribution kinetics in mdx mice demonstrated that Alx647 did not interface with muscle membranes and had fast clearance kinetics. In contrast, the distribution kinetics for P188-Alx647 was significantly slower, indicating a dramatic depot and retention effect of P188. Results further demonstrated the significant retention of P188-Alx647 in the skeletal muscle of mdx mice, showing a significant genotype effect with a higher fluorescence signal in the mdx muscles over BL10 mice. High-resolution optical imaging provided direct evidence of P188 surrounding the sarcolemma of skeletal and cardiac muscle cells. Taken together, these findings provide direct evidence of muscle-disease-dependent molecular homing and retention of synthetic copolymers in striated muscles thereby facilitating advanced studies of copolymer-membrane association in health and disease.
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Affiliation(s)
- Addeli Bez Batti Angulski
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, 6-125 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA
| | - Houda Cohen
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, 6-125 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA
| | - Mihee Kim
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Dongwoo Hahn
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, 6-125 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA
| | - Nicholas Van Zee
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Timothy P. Lodge
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Marc A. Hillmyer
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Benjamin J. Hackel
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
- Corresponding author Benjamin J. Hackel, Department of Chemical Engineering and Materials Science, University of Minnesota, 356 Amundsun Hall, Minneapolis, MN 55455, USA.
| | - Frank S. Bates
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Joseph M. Metzger
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, 6-125 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA
- Corresponding author Joseph M. Metzger, Department of Integrative Biology & Physiology, University of Minnesota Medical School, 6-125 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA.
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Crabtree AA, Bates FS, Hackel BJ. Concentration Threshold for Membrane Protection by PEO-PPO Block Copolymers with Variable Molecular Architectures. ACS APPLIED POLYMER MATERIALS 2022; 4:3259-3269. [PMID: 36777189 PMCID: PMC9907980 DOI: 10.1021/acsapm.1c01807] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Poloxamer 188, a poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer, protects cell membranes in several injury models. However, the nature of the copolymer/membrane interaction and the mechanism of membrane protection remain unknown. Systematic variations of the block copolymer architecture - including PPO-PEO-PPO triblocks and PPO-PEO diblocks - were used to probe the mechanism and evaluate the potential for alternative architectures to yield superior protection. To test the polymers, murine myoblasts were subjected to an osmotic stress, and membrane integrity was quantified by measuring lactate dehydrogenase (LDH) leakage. These experiments exposed a concentration threshold effect where all tested polymers reach 50% leakage of LDH compared to a non-treated buffer only control over a narrow concentration range of 0.8-4 μM. Differences in polymer protection at lower concentrations indicate that protection increases with the PPO-PEO-PPO molecular architecture and increasing hydrophobicity.
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Affiliation(s)
| | | | - Benjamin J. Hackel
- Corresponding Author: Benjamin J. Hackel – Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, Phone: 612-624-7102,
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5
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Di Meco A, Kemal S, Popovic J, Chandra S, Sadleir KR, Vassar R. Poloxamer-188 Exacerbates Brain Amyloidosis, Presynaptic Dystrophies, and Pathogenic Microglial Activation in 5XFAD Mice. Curr Alzheimer Res 2022; 19:317-329. [DOI: 10.2174/1567205019666220509143823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 03/21/2022] [Accepted: 03/28/2022] [Indexed: 11/22/2022]
Abstract
Background:
Alzheimer’s disease (AD) is initiated by aberrant accumulation of amyloid beta (Aβ) protein in the brain parenchyma. The microenvironment surrounding amyloid plaques is characterized by the swelling of presynaptic terminals (dystrophic neurites) associated with lysosomal dysfunction, microtubule disruption and impaired axonal transport. Aβ-induced plasma membrane damage and calcium influx could be potential mechanisms underlying dystrophic neurite formation.
Objective:
We tested whether promoting membrane integrity by brain administration of a safe FDA approved surfactant molecule poloxamer-188 (P188) could attenuate AD pathology in vivo.
Methods:
Three-month-old 5XFAD male mice were administered several concentrations of P188 in the brain for 42 days with mini-osmotic pumps. After 42 days, mice were euthanized and assessed for amyloid pathology, dystrophic neurites, pathogenic microglia activation, tau phosphorylation and lysosomal / vesicular trafficking markers in the brain.
Results:
P188 was lethal at the highest concentration of 10mM. Lower concentrations of P188 (1.2, 12 and 120μM) were well tolerated. P188 increased brain Aβ burden, potentially through activation of the γ-secretase pathway. Dystrophic neurite pathology was exacerbated in P188 treated mice as indicated by increased LAMP1 accumulation around Aβ deposits. Pathogenic microglial activation was increased by P188. Total tau levels were decreased by P188. Lysosomal enzyme cathepsin D and calcium-dependent vesicular trafficking regulator synaptotagmin-7 (SYT7) were dysregulated upon P188 administration.
Conclusion:
P188 brain delivery exacerbated amyloid pathology, dystrophic neurites and pathogenic microglial activation in 5XFAD mice. These effects correlated with lysosomal dysfunction and dysregulation of plasma membrane vesicular trafficking. P188 is not a promising therapeutic strategy against AD pathogenesis.
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Affiliation(s)
- Antonio Di Meco
- Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Shahrnaz Kemal
- Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Jelena Popovic
- Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Sidhanth Chandra
- Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | | | - Robert Vassar
- Northwestern University Feinberg School of Medicine, Chicago, IL 60611
- Mesulam Center for Cognitive Neurology and Alzheimer’s disease, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
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6
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Ryan SM, Almassey M, Burch AM, Ngo G, Martin JM, Myers D, Compton D, Archie S, Cross M, Naeger L, Salzman A, Virola‐Iarussi A, Barbee SA, Mortimer NT, Sanyal S, Vrailas‐Mortimer AD. Drosophila p38 MAPK interacts with BAG-3/starvin to regulate age-dependent protein homeostasis. Aging Cell 2021; 20:e13481. [PMID: 34674371 PMCID: PMC8590102 DOI: 10.1111/acel.13481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 08/23/2021] [Accepted: 09/09/2021] [Indexed: 12/25/2022] Open
Abstract
As organisms age, they often accumulate protein aggregates that are thought to be toxic, potentially leading to age‐related diseases. This accumulation of protein aggregates is partially attributed to a failure to maintain protein homeostasis. A variety of genetic factors have been linked to longevity, but how these factors also contribute to protein homeostasis is not completely understood. In order to understand the relationship between aging and protein aggregation, we tested how a gene that regulates lifespan and age‐dependent locomotor behaviors, p38 MAPK (p38Kb), influences protein homeostasis as an organism ages. We find that p38Kb regulates age‐dependent protein aggregation through an interaction with starvin, a regulator of muscle protein homeostasis. Furthermore, we have identified Lamin as an age‐dependent target of p38Kb and starvin.
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Affiliation(s)
- Sarah M. Ryan
- Department of Biological Sciences University of Denver Denver CO USA
| | - Michael Almassey
- School of Biological Sciences Illinois State University Normal IL USA
| | | | - Gia Ngo
- Department of Biological Sciences University of Denver Denver CO USA
| | - Julia M. Martin
- School of Biological Sciences Illinois State University Normal IL USA
| | - David Myers
- School of Biological Sciences Illinois State University Normal IL USA
| | - Devin Compton
- School of Biological Sciences Illinois State University Normal IL USA
| | - Shira Archie
- School of Biological Sciences Illinois State University Normal IL USA
| | - Megan Cross
- School of Biological Sciences Illinois State University Normal IL USA
| | - Lauren Naeger
- School of Biological Sciences Illinois State University Normal IL USA
| | - Ashley Salzman
- School of Biological Sciences Illinois State University Normal IL USA
| | | | - Scott A. Barbee
- Department of Biological Sciences University of Denver Denver CO USA
| | | | - Subhabrata Sanyal
- Department of Cell Biology Emory University Atlanta GA USA
- Calico San Francisco CA USA
| | - Alysia D. Vrailas‐Mortimer
- Department of Biological Sciences University of Denver Denver CO USA
- School of Biological Sciences Illinois State University Normal IL USA
- Department of Cell Biology Emory University Atlanta GA USA
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7
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Hagan ML, Balayan V, McGee-Lawrence ME. Plasma membrane disruption (PMD) formation and repair in mechanosensitive tissues. Bone 2021; 149:115970. [PMID: 33892174 PMCID: PMC8217198 DOI: 10.1016/j.bone.2021.115970] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 03/26/2021] [Accepted: 04/17/2021] [Indexed: 01/04/2023]
Abstract
Mammalian cells employ an array of biological mechanisms to detect and respond to mechanical loading in their environment. One such mechanism is the formation of plasma membrane disruptions (PMD), which foster a molecular flux across cell membranes that promotes tissue adaptation. Repair of PMD through an orchestrated activity of molecular machinery is critical for cell survival, and the rate of PMD repair can affect downstream cellular signaling. PMD have been observed to influence the mechanical behavior of skin, alveolar, and gut epithelial cells, aortic endothelial cells, corneal keratocytes and epithelial cells, cardiac and skeletal muscle myocytes, neurons, and most recently, bone cells including osteoblasts, periodontal ligament cells, and osteocytes. PMD are therefore positioned to affect the physiological behavior of a wide range of vertebrate organ systems including skeletal and cardiac muscle, skin, eyes, the gastrointestinal tract, the vasculature, the respiratory system, and the skeleton. The purpose of this review is to describe the processes of PMD formation and repair across these mechanosensitive tissues, with a particular emphasis on comparing and contrasting repair mechanisms and downstream signaling to better understand the role of PMD in skeletal mechanobiology. The implications of PMD-related mechanisms for disease and potential therapeutic applications are also explored.
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Affiliation(s)
- Mackenzie L Hagan
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1460 Laney Walker Blvd., CB1101, Augusta, GA, USA
| | - Vanshika Balayan
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1460 Laney Walker Blvd., CB1101, Augusta, GA, USA
| | - Meghan E McGee-Lawrence
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1460 Laney Walker Blvd., CB1101, Augusta, GA, USA; Department of Orthopaedic Surgery, Augusta University, Augusta, GA, USA.
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8
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The ties that bind: functional clusters in limb-girdle muscular dystrophy. Skelet Muscle 2020; 10:22. [PMID: 32727611 PMCID: PMC7389686 DOI: 10.1186/s13395-020-00240-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 07/16/2020] [Indexed: 12/13/2022] Open
Abstract
The limb-girdle muscular dystrophies (LGMDs) are a genetically pleiomorphic class of inherited muscle diseases that are known to share phenotypic features. Selected LGMD genetic subtypes have been studied extensively in affected humans and various animal models. In some cases, these investigations have led to human clinical trials of potential disease-modifying therapies, including gene replacement strategies for individual subtypes using adeno-associated virus (AAV) vectors. The cellular localizations of most proteins associated with LGMD have been determined. However, the functions of these proteins are less uniformly characterized, thus limiting our knowledge of potential common disease mechanisms across subtype boundaries. Correspondingly, broad therapeutic strategies that could each target multiple LGMD subtypes remain less developed. We believe that three major "functional clusters" of subcellular activities relevant to LGMD merit further investigation. The best known of these is the glycosylation modifications associated with the dystroglycan complex. The other two, mechanical signaling and mitochondrial dysfunction, have been studied less systematically but are just as promising with respect to the identification of significant mechanistic subgroups of LGMD. A deeper understanding of these disease pathways could yield a new generation of precision therapies that would each be expected to treat a broader range of LGMD patients than a single subtype, thus expanding the scope of the molecular medicines that may be developed for this complex array of muscular dystrophies.
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9
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Kwiatkowski TA, Rose AL, Jung R, Capati A, Hallak D, Yan R, Weisleder N. Multiple poloxamers increase plasma membrane repair capacity in muscle and nonmuscle cells. Am J Physiol Cell Physiol 2020; 318:C253-C262. [PMID: 31747313 PMCID: PMC7052616 DOI: 10.1152/ajpcell.00321.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 11/06/2019] [Accepted: 11/07/2019] [Indexed: 01/01/2023]
Abstract
Various previous studies established that the amphiphilic tri-block copolymer known as poloxamer 188 (P188) or Pluronic-F68 can stabilize the plasma membrane following a variety of injuries to multiple mammalian cell types. This characteristic led to proposals for the use of P188 as a therapeutic treatment for various disease states, including muscular dystrophy. Previous studies suggest that P188 increases plasma membrane integrity by resealing plasma membrane disruptions through its affinity for the hydrophobic lipid chains on the lipid bilayer. P188 is one of a large family of copolymers that share the same basic tri-block structure consisting of a middle hydrophobic propylene oxide segment flanked by two hydrophilic ethylene oxide moieties [poly(ethylene oxide)80-poly(propylene oxide)27-poly(ethylene oxide)80]. Despite the similarities of P188 to the other poloxamers in this chemical family, there has been little investigation into the membrane-resealing properties of these other poloxamers. In this study we assessed the resealing properties of poloxamers P181, P124, P182, P234, P108, P407, and P338 on human embryonic kidney 293 (HEK293) cells and isolated muscle from the mdx mouse model of Duchenne muscular dystrophy. Cell membrane injuries from glass bead wounding and multiphoton laser injury show that the majority of poloxamers in our panel improved the plasma membrane resealing of both HEK293 cells and dystrophic muscle fibers. These findings indicate that many tri-block copolymers share characteristics that can increase plasma membrane resealing and that identification of these shared characteristics could help guide design of future therapeutic approaches.
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Affiliation(s)
- Thomas A Kwiatkowski
- Department of Physiology & Cell Biology, The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Aubrey L Rose
- Department of Physiology & Cell Biology, The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Rachel Jung
- Department of Physiology & Cell Biology, The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Ana Capati
- Department of Physiology & Cell Biology, The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Diana Hallak
- Department of Physiology & Cell Biology, The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Rosalie Yan
- Department of Anesthesiology, Duke University Health System, Durham, North Carolina
| | - Noah Weisleder
- Department of Physiology & Cell Biology, The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
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10
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Houang EM, Sham YY, Bates FS, Metzger JM. Muscle membrane integrity in Duchenne muscular dystrophy: recent advances in copolymer-based muscle membrane stabilizers. Skelet Muscle 2018; 8:31. [PMID: 30305165 PMCID: PMC6180502 DOI: 10.1186/s13395-018-0177-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 09/13/2018] [Indexed: 02/07/2023] Open
Abstract
The scientific premise, design, and structure-function analysis of chemical-based muscle membrane stabilizing block copolymers are reviewed here for applications in striated muscle membrane injury. Synthetic block copolymers have a rich history and wide array of applications from industry to biology. Potential for discovery is enabled by a large chemical space for block copolymers, including modifications in block copolymer mass, composition, and molecular architecture. Collectively, this presents an impressive chemical landscape to leverage distinct structure-function outcomes. Of particular relevance to biology and medicine, stabilization of damaged phospholipid membranes using amphiphilic block copolymers, classified as poloxamers or pluronics, has been the subject of increasing scientific inquiry. This review focuses on implementing block copolymers to protect fragile muscle membranes against mechanical stress. The review highlights interventions in Duchenne muscular dystrophy, a fatal disease of progressive muscle deterioration owing to marked instability of the striated muscle membrane. Biophysical and chemical engineering advances are presented that delineate and expand upon current understanding of copolymer-lipid membrane interactions and the mechanism of stabilization. The studies presented here serve to underscore the utility of copolymer discovery leading toward the therapeutic application of block copolymers in Duchenne muscular dystrophy and potentially other biomedical applications in which membrane integrity is compromised.
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Affiliation(s)
- Evelyne M Houang
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, 6-125 Jackson Hall, 321 Church Street SE, Minneapolis, MN, 55455, USA
| | - Yuk Y Sham
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, 6-125 Jackson Hall, 321 Church Street SE, Minneapolis, MN, 55455, USA.,University of Minnesota Informatics Institute, MN, USA.,Bioinformatics and Computational Biology Program, University of Minnesota, MN, USA
| | - Frank S Bates
- Department of Chemical Engineering and Materials Science, University of Minnesota, MN, USA
| | - Joseph M Metzger
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, 6-125 Jackson Hall, 321 Church Street SE, Minneapolis, MN, 55455, USA.
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11
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Sreetama SC, Chandra G, Van der Meulen JH, Ahmad MM, Suzuki P, Bhuvanendran S, Nagaraju K, Hoffman EP, Jaiswal JK. Membrane Stabilization by Modified Steroid Offers a Potential Therapy for Muscular Dystrophy Due to Dysferlin Deficit. Mol Ther 2018; 26:2231-2242. [PMID: 30166241 PMCID: PMC6127637 DOI: 10.1016/j.ymthe.2018.07.021] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Revised: 07/15/2018] [Accepted: 07/24/2018] [Indexed: 11/16/2022] Open
Abstract
Mutations of the DYSF gene leading to reduced dysferlin protein level causes limb girdle muscular dystrophy type 2B (LGMD2B). Dysferlin facilitates sarcolemmal membrane repair in healthy myofibers, thus its deficit compromises myofiber repair and leads to chronic muscle inflammation. An experimental therapeutic approach for LGMD2B is to protect damage or improve repair of myofiber sarcolemma. Here, we compared the effects of prednisolone and vamorolone (a dissociative steroid; VBP15) on dysferlin-deficient myofiber repair. Vamorolone, but not prednisolone, stabilized dysferlin-deficient muscle cell membrane and improved repair of dysferlin-deficient mouse (B6A/J) myofibers injured by focal sarcolemmal damage, eccentric contraction-induced injury or injury due to spontaneous in vivo activity. Vamorolone decreased sarcolemmal lipid mobility, increased muscle strength, and decreased late-stage myofiber loss due to adipogenic infiltration. In contrast, the conventional glucocorticoid prednisolone failed to stabilize dysferlin deficient muscle cell membrane or improve repair of dysferlinopathic patient myoblasts and mouse myofibers. Instead, prednisolone treatment increased muscle weakness and myofiber atrophy in B6A/J mice—findings that correlate with reports of prednisolone worsening symptoms of LGMD2B patients. Our findings showing improved cellular and pre-clinical efficacy of vamorolone compared to prednisolone and better safety profile of vamorolone indicates the suitability of vamorolone for clinical trials in LGMD2B.
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Affiliation(s)
- Sen Chandra Sreetama
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA
| | - Goutam Chandra
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA
| | - Jack H Van der Meulen
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA
| | - Mohammad Mahad Ahmad
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA
| | - Peter Suzuki
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA
| | - Shivaprasad Bhuvanendran
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA
| | - Kanneboyina Nagaraju
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA; Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Binghamton University, Binghamton, NY 13902, USA
| | - Eric P Hoffman
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA; Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Binghamton University, Binghamton, NY 13902, USA
| | - Jyoti K Jaiswal
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA; Department of Genomics and Precision Medicine, George Washington University School of Medicine and Health Sciences, Washington, DC 20010, USA.
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12
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Abstract
PURPOSE OF REVIEW To construct a framework to understand the different molecular interventions for muscular dystrophy. RECENT FINDINGS The recent approval of antisense oligonucleotides treatment for Duchenne muscular dystrophy and spinal muscular atrophy and current clinical trials using recombinant adeno-associated virus for the treatment of those diseases suggests that we are at a tipping point where we are able to treat and potentially cure muscular dystrophies. Understanding the basic molecular pathogenesis of muscular dystrophies and the molecular biology of the treatment allows for critical evaluation of the proposed therapies.
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Affiliation(s)
- Ava Y Lin
- Department of Neurology, University of Washington, Box 356465, 1959 NE Pacific Street, Seattle, WA, 98195-6465, USA
| | - Leo H Wang
- Department of Neurology, University of Washington, Box 356465, 1959 NE Pacific Street, Seattle, WA, 98195-6465, USA.
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13
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Houang EM, Bates FS, Sham YY, Metzger JM. All-Atom Molecular Dynamics-Based Analysis of Membrane-Stabilizing Copolymer Interactions with Lipid Bilayers Probed under Constant Surface Tensions. J Phys Chem B 2017; 121:10657-10664. [PMID: 29049887 DOI: 10.1021/acs.jpcb.7b08938] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
An all-atom phospholipid bilayer and triblock copolymer model was developed for molecular dynamics (MD) studies. These were performed to investigate the mechanism of interaction between membrane-stabilizing triblock copolymer P188 and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) lipid bilayers under applied lateral surface tension (γ) to model membrane mechanical stress. Results showed that P188 insertion is driven by the hydrophobic poly(propylene oxide) (PPO) core and dependent on bilayer area per lipid. Moreover, insertion of P188 increased the bilayer's resistance to mechanical rupture, as observed by a significant increase in the absolute lateral pressure required to disrupt the bilayer. To further investigate the specific chemical features of P188 underlying membrane stabilizer function, a series of MD simulations with triblock copolymers of the same class as P188 but of varying chemical composition and sizes were performed. Results showed that triblock copolymer insertion into the lipid bilayer is dependent on overall copolymer hydrophobicity, with higher copolymer hydrophobicity requiring a reduced bilayer area per lipid ratio for insertion. Further analysis revealed that the effect of copolymer insertion on membrane mechanical integrity was also dependent on hydrophobicity. Here, P188 insertion significantly increased the absolute apparent lateral pressure required to rupture the POPC bilayer, thereby protecting the membrane against mechanical stress. In marked contrast, highly hydrophobic copolymers decreased the lateral pressure necessary for membrane rupture and thus rendering the membrane significantly more susceptible to mechanical stress. These new in silico findings align with recent experimental findings using synthetic lipid bilayers and in muscle cells in vitro and mouse models in vivo. Collectively, these data underscore the importance of PEO-PPO-PEO copolymer chemical composition in copolymer-based muscle membrane stabilization in vitro and in vivo. All-atom modeling with MD simulations holds promise for investigating novel copolymers with enhanced membrane interacting properties.
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Affiliation(s)
- Evelyne M Houang
- Integrative Biology and Physiology, University of Minnesota Medical School , Minneapolis, Minnesota 55455, United States
| | - Frank S Bates
- Department of Chemical Engineering and Materials Science, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Yuk Y Sham
- Integrative Biology and Physiology, University of Minnesota Medical School , Minneapolis, Minnesota 55455, United States.,University of Minnesota Informatics Institute , Minneapolis, Minnesota 55455, United States.,Bioinformatics and Computational Biology Program, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Joseph M Metzger
- Integrative Biology and Physiology, University of Minnesota Medical School , Minneapolis, Minnesota 55455, United States
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14
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Kim M, Haman KJ, Houang EM, Zhang W, Yannopoulos D, Metzger JM, Bates FS, Hackel BJ. PEO-PPO Diblock Copolymers Protect Myoblasts from Hypo-Osmotic Stress In Vitro Dependent on Copolymer Size, Composition, and Architecture. Biomacromolecules 2017; 18:2090-2101. [PMID: 28535058 DOI: 10.1021/acs.biomac.7b00419] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Poloxamer 188, a triblock copolymer of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), protects cellular membranes from various stresses. Though numerous block copolymer variants exist, evaluation of alternative architecture, composition, and size has been minimal. Herein, cultured murine myoblasts are exposed to the stresses of hypotonic shock and isotonic recovery, and membrane integrity was evaluated by quantifying release of lactate dehydrogenase. Comparative evaluation of a systematic set of PEO-PPO diblock and PEO-PPO-PEO triblock copolymers demonstrates that the diblock architecture can be protective in vitro. Short PPO blocks hinder protection with >9 PPO units needed for protection at 150 μM and >16 units needed at 14 μM. Addition of a tert-butyl end group enhances protection at reduced concentration. When the end group and PPO length are fixed, increasing the PEO length improves protection. This systematic evaluation establishes a new in vitro screening tool for evaluating membrane-sealing amphiphiles and provides mechanistic insight to guide future copolymer design for membrane stabilization in vivo.
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Affiliation(s)
- Mihee Kim
- Department of Chemical Engineering and Materials Science, ‡Department of Integrative Biology and Physiology, and §Department of Medicine, Cardiovascular Division, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Karen J Haman
- Department of Chemical Engineering and Materials Science, ‡Department of Integrative Biology and Physiology, and §Department of Medicine, Cardiovascular Division, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Evelyne M Houang
- Department of Chemical Engineering and Materials Science, ‡Department of Integrative Biology and Physiology, and §Department of Medicine, Cardiovascular Division, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Wenjia Zhang
- Department of Chemical Engineering and Materials Science, ‡Department of Integrative Biology and Physiology, and §Department of Medicine, Cardiovascular Division, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Demetris Yannopoulos
- Department of Chemical Engineering and Materials Science, ‡Department of Integrative Biology and Physiology, and §Department of Medicine, Cardiovascular Division, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Joseph M Metzger
- Department of Chemical Engineering and Materials Science, ‡Department of Integrative Biology and Physiology, and §Department of Medicine, Cardiovascular Division, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Frank S Bates
- Department of Chemical Engineering and Materials Science, ‡Department of Integrative Biology and Physiology, and §Department of Medicine, Cardiovascular Division, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Benjamin J Hackel
- Department of Chemical Engineering and Materials Science, ‡Department of Integrative Biology and Physiology, and §Department of Medicine, Cardiovascular Division, University of Minnesota , Minneapolis, Minnesota 55455, United States
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15
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Poellmann MJ, Lee RC. Repair and Regeneration of the Wounded Cell Membrane. REGENERATIVE ENGINEERING AND TRANSLATIONAL MEDICINE 2017. [DOI: 10.1007/s40883-017-0031-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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16
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Houang EM, Haman KJ, Filareto A, Perlingeiro RC, Bates FS, Lowe DA, Metzger JM. Membrane-stabilizing copolymers confer marked protection to dystrophic skeletal muscle in vivo. Mol Ther Methods Clin Dev 2015; 2:15042. [PMID: 26623440 PMCID: PMC4641511 DOI: 10.1038/mtm.2015.42] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 10/01/2015] [Accepted: 10/01/2015] [Indexed: 01/16/2023]
Abstract
Duchenne muscular dystrophy (DMD) is a fatal disease of striated muscle deterioration. A unique therapeutic approach for DMD is the use of synthetic membrane stabilizers to protect the fragile dystrophic sarcolemma against contraction-induced mechanical stress. Block copolymer-based membrane stabilizer poloxamer 188 (P188) has been shown to protect the dystrophic myocardium. In comparison, the ability of synthetic membrane stabilizers to protect fragile DMD skeletal muscles has been less clear. Because cardiac and skeletal muscles have distinct structural and functional features, including differences in the mechanism of activation, variance in sarcolemma phospholipid composition, and differences in the magnitude and types of forces generated, we speculated that optimized membrane stabilization could be inherently different. Our objective here is to use principles of pharmacodynamics to evaluate membrane stabilization therapy for DMD skeletal muscles. Results show a dramatic differential effect of membrane stabilization by optimization of pharmacodynamic-guided route of poloxamer delivery. Data show that subcutaneous P188 delivery, but not intravascular or intraperitoneal routes, conferred significant protection to dystrophic limb skeletal muscles undergoing mechanical stress in vivo. In addition, structure-function examination of synthetic membrane stabilizers further underscores the importance of copolymer composition, molecular weight, and dosage in optimization of poloxamer pharmacodynamics in vivo.
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Affiliation(s)
- Evelyne M Houang
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Karen J Haman
- Department of Chemical Engineering and Material Science, University of Minnesota, Minneapolis, Minnesota, USA
| | - Antonio Filareto
- Department of Medicine, Lillehei Heart Institute, University of Minnesota, Minneapolis, Minnesota, USA
| | - Rita C Perlingeiro
- Department of Medicine, Lillehei Heart Institute, University of Minnesota, Minneapolis, Minnesota, USA
| | - Frank S Bates
- Department of Chemical Engineering and Material Science, University of Minnesota, Minneapolis, Minnesota, USA
| | - Dawn A Lowe
- Rehabilitation Science and Program in Physical Therapy, University of Minnesota, Minneapolis, Minnesota, USA
| | - Joseph M Metzger
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, Minnesota, USA
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Chronic Dosing with Membrane Sealant Poloxamer 188 NF Improves Respiratory Dysfunction in Dystrophic Mdx and Mdx/Utrophin-/- Mice. PLoS One 2015; 10:e0134832. [PMID: 26248188 PMCID: PMC4527695 DOI: 10.1371/journal.pone.0134832] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Accepted: 07/14/2015] [Indexed: 01/19/2023] Open
Abstract
Poloxamer 188 NF (national formulary (NF) grade of P-188) improves cardiac muscle function in the mdx mouse and golden retriever muscular dystrophy models. However in vivo effects on skeletal muscle have not been reported. We postulated that P-188 NF might protect diaphragm muscle membranes from contraction-induced injury in mdx and mdx/utrophin-/- (dko) muscular dystrophy models. In the first study 7-month old mdx mice were treated for 22 weeks with subcutaneous (s.c.) injections of saline or P-188 NF at 3 mg/Kg. In the second, dkos were treated with saline or P-188 NF (1 mg/Kg) for 8 weeks beginning at age 3 weeks. Prednisone was the positive control in both studies. Respiratory function was monitored using unrestrained whole body plethysmography. P-188 NF treatment affected several respiratory parameters including tidal volume/BW and minute volume/BW in mdx mice. In the more severe dko model, P-188 NF (1 mg/Kg) significantly slowed the decline in multiple respiratory parameters compared with saline-treated dko mice. Prednisone’s effects were similar to those seen with P-188 NF. Diaphragms from P-188 NF or prednisone treated mdx and dko mice showed signs of muscle fiber protection including less centralized nuclei, less variation in fiber size, greater fiber density, and exhibited a decreased amount of collagen deposition. P-188 NF at 3 mg/Kg s.c. also improved parameters of systolic and diastolic function in mdx mouse hearts. These results suggest that P-188 NF may be useful in treating respiratory and cardiac dysfunction, the leading causes of death in Duchenne muscular dystrophy patients.
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18
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Fanin M, Nascimbeni AC, Angelini C. Muscle atrophy, ubiquitin-proteasome, and autophagic pathways in dysferlinopathy. Muscle Nerve 2014; 50:340-7. [PMID: 24395438 DOI: 10.1002/mus.24167] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2013] [Revised: 12/18/2013] [Accepted: 01/02/2014] [Indexed: 12/11/2022]
Abstract
INTRODUCTION Muscle fiber atrophy and the molecular pathways underlying this process have not been investigated in dysferlinopathy patients. METHODS In 22 muscles from dysferlinopathy patients we investigated fiber atrophy by morphometry and ubiquitin-proteasome and autophagic pathways using protein and/or transcriptional analysis of atrophy- and autophagy-related genes (MuRF1, atrogin1, LC3, p62, Bnip3). RESULTS Dysferlinopathy showed significant fiber atrophy and higher MuRF-1 protein and mRNA levels, which correlated with fiber size, suggesting activation of the atrophy program by proteasome induction. CONCLUSIONS Some of the MuRF-1 upregulation and proteasome induction may be attributed to the prominent regeneration found. A potential role of impaired autophagy was suggested by p62-positive protein aggregates in atrophic fibers and significantly higher levels of LC3-II and p62 proteins and overexpression of p62 and Bnip3 mRNA. Damaged muscle fibers and prominent inflammatory changes may also enhance autophagy due to the insufficient level of proteasomal degradation of mutant dysferlin.
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Affiliation(s)
- Marina Fanin
- Department of Neurosciences, University of Padova, Biomedical Campus "Pietro d'Abano," via Giuseppe Orus 2B, 35129, Padova, Italy
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Maguire KK, Lim L, Speedy S, Rando TA. Assessment of disease activity in muscular dystrophies by noninvasive imaging. J Clin Invest 2013; 123:2298-305. [PMID: 23619364 DOI: 10.1172/jci68458] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 02/21/2013] [Indexed: 01/26/2023] Open
Abstract
Muscular dystrophies are a class of disorders that cause progressive muscle wasting. A major hurdle for discovering treatments for the muscular dystrophies is a lack of reliable assays to monitor disease progression in animal models. We have developed a novel mouse model to assess disease activity noninvasively in mice with muscular dystrophies. These mice express an inducible luciferase reporter gene in muscle stem cells. In dystrophic mice, muscle stem cells activate and proliferate in response to muscle degeneration, resulting in an increase in the level of luciferase expression, which can be monitored by noninvasive, bioluminescence imaging. We applied this noninvasive imaging to assess disease activity in a mouse model of the human disease limb girdle muscular dystrophy 2B (LGMD2B), caused by a mutation in the dysferlin gene. We monitored the natural history and disease progression in these dysferlin-deficient mice up to 18 months of age and were able to detect disease activity prior to the appearance of any overt disease manifestation by histopathological analyses. Disease activity was reflected by changes in luciferase activity over time, and disease burden was reflected by cumulative luciferase activity, which paralleled disease progression as determined by histopathological analysis. The ability to monitor disease activity noninvasively in mouse models of muscular dystrophy will be invaluable for the assessment of disease progression and the effectiveness of therapeutic interventions.
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Affiliation(s)
- Katie K Maguire
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California 94305-5235, USA
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