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Hassan MM, Hettiarachchi M, Kilani M, Gao X, Sankari A, Boyer C, Mao G. Sustained A1 Adenosine Receptor Antagonist Drug Release from Nanoparticles Functionalized by a Neural Tracing Protein. ACS Chem Neurosci 2021; 12:4438-4448. [PMID: 34672533 DOI: 10.1021/acschemneuro.1c00538] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Respiratory dysfunction is a major cause of death in people with spinal cord injury (SCI). A remaining unsolved problem in treating SCI is the intolerable side effects of the drugs to patients. In a significant departure from conventional targeted nanotherapeutics to overcome the blood-brain barrier (BBB), this work pursues a drug-delivery approach that uses neural tracing retrograde transport proteins to bypass the BBB and deliver an adenosine A1 receptor antagonist drug, 1,3-dipropyl-8-cyclopentyl xanthine, exclusively to the respiratory motoneurons in the spinal cord and the brainstem. A single intradiaphragmatic injection at one thousandth of the native drug dosage induces prolonged respiratory recovery in a hemisection animal model. To translate the discovery into new treatments for respiratory dysfunction, we carry out this study to characterize the purity and quality of synthesis, stability, and drug-release properties of the neural tracing protein (wheat germ agglutinin chemically conjugated to horseradish peroxidase)-coupled nanoconjugate. We show that the batch-to-batch particle size and drug dosage variations are less than 10%. We evaluate the nanoconjugate size against the spatial constraints imposed by transsynaptic transport from pre to postsynaptic neurons. We determine that the nanoconjugate formulation is capable of sustained drug release lasting for days at physiologic pH, a prerequisite for long-distance transport of the drug from the diaphragm muscle to the brainstem. We model the drug-release profiles using a first-order reaction model and the Noyes-Whitney diffusion model. We confirm via biological electron microscopy that the nanoconjugate particles do not accumulate in the tissues at the injection site. We define the nanoconjugate storage conditions after monitoring the solution dispersion stability under various conditions for 4 months. This study supports further development of neural tracing protein-enabled nanotherapeutics for treating respiratory problems associated with SCI.
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Affiliation(s)
- Md. Musfizur Hassan
- School of Chemical Engineering, University of New South Wales (UNSW Sydney), Sydney, New South Wales 2052, Australia
| | - Malsha Hettiarachchi
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Mohamed Kilani
- School of Chemical Engineering, University of New South Wales (UNSW Sydney), Sydney, New South Wales 2052, Australia
| | - Xiaohua Gao
- School of Medicine, Wayne State University, Detroit, Michigan 48201, United States
| | - Abdulghani Sankari
- School of Medicine, Wayne State University, Detroit, Michigan 48201, United States
| | - Cyrille Boyer
- School of Chemical Engineering, University of New South Wales (UNSW Sydney), Sydney, New South Wales 2052, Australia
- Australian Centre for Nanomedicine, Sydney, New South Wales 2052, Australia
| | - Guangzhao Mao
- School of Chemical Engineering, University of New South Wales (UNSW Sydney), Sydney, New South Wales 2052, Australia
- Australian Centre for Nanomedicine, Sydney, New South Wales 2052, Australia
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Liu F, Zhang Y, Schafer J, Mao G, Goshgarian HG. Diaphragmatic recovery in rats with cervical spinal cord injury induced by a theophylline nanoconjugate: Challenges for clinical use. J Spinal Cord Med 2019; 42:725-734. [PMID: 30843479 PMCID: PMC6830233 DOI: 10.1080/10790268.2019.1577058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Context: Following a spinal cord hemisection at the second cervical segment the ipsilateral hemidiaphragm is paralyzed due to the disruption of the rostral ventral respiratory group (rVRG) axons descending to the ipsilateral phrenic motoneurons (PN). Systemically administered theophylline activates a functionally latent crossed phrenic pathway (CPP) which decussates caudal to the hemisection and activates phrenic motoneurons ipsilateral to the hemisection. The result is return of function to the paralyzed hemidiaphragm. Unfortunately, in humans, systemically administered theophylline at a therapeutic dose produces many unwanted side effects.Design and setting: A tripartite nanoconjugate was synthesized in which theophylline was coupled to a neuronal tracer, wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP), using gold nanoparticles as the coupler. Following intradiaphragmatic injection of the nanoconjugate, WGA-HRP selectively targets the theophylline-bound nanoconjugate to phrenic motoneurons initially, followed by neurons in the rVRG by retrograde transsynaptic transport.Participants: (N/A)Interventions: (N/A)Outcome Measures: Immunostaining, Electromyography (EMG).Results: Delivery of the theophylline-coupled nanoconjugate to the nuclei involved in respiration induces a return of respiratory activity as detected by EMG of the diaphragm and a modest return of phrenic nerve activity.Conclusion: In addition to the modest return of phrenic nerve activity, there were many difficulties using the theophylline nanoconjugate because of its chemical instability, which suggests that the theophylline nanoconjugate should not be developed for clinical use as explained herein.
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Affiliation(s)
- Fangchao Liu
- Departments of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michagan, USA
| | - Yanhua Zhang
- Departments of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michagan, USA
| | - Janelle Schafer
- Department of Ophthalmology, Visual and Anatomical Sciences (OVAS), School of Medicine, Wayne State University, Detroit, Michagan, USA
| | - Guangzhao Mao
- Departments of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michagan, USA
| | - Harry G. Goshgarian
- Department of Ophthalmology, Visual and Anatomical Sciences (OVAS), School of Medicine, Wayne State University, Detroit, Michagan, USA,Correspondence to: Harry G. Goshgarian, Department of Ophthalmology, Visual and Anatomical Sciences (OVAS), School of Medicine, Wayne State University, 540 East Canfield Street, Detroit, MI 48201, USA; Ph: 1-313-577-1045; 1-313-577-3125.
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Pulmonary outcomes following specialized respiratory management for acute cervical spinal cord injury: a retrospective analysis. Spinal Cord 2017; 55:559-565. [PMID: 28220822 PMCID: PMC5457341 DOI: 10.1038/sc.2017.10] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Revised: 12/29/2016] [Accepted: 01/05/2017] [Indexed: 12/25/2022]
Abstract
Study Design Retrospective analysis. Objectives To identify multivariate interactions of respiratory function that are sensitive to spinal cord injury level and pharmacological treatment to promote strategies that increases successful liberation from mechanical ventilation. Setting United States regional spinal cord injury (SCI) treatment center. Methods Retrospective chart review of patients consecutively admitted to Santa Clara Valley Medical Center (SCVMC) between May 2013 and December 2014 for ventilator weaning with C1-5 AIS A or B SCI, < 3 months from injury and who had a tracheostomy in place. A non-linear, categorical principal component analysis (NL-PCA) was performed to test the multivariate interaction of respiratory outcomes from patients (N=36) being weaned off ventilator support after acute SCI with (N=15) or without (N=21) theophylline treatment. Results 36 patients met inclusion criteria (2 C1, 5 C2, 11 C3, 14 C4, 4 C5). The NL-PCA returned 3 independent components that accounted for 95% of the variance in the dataset. Multivariate general linear models (GLM) hypothesis tests revealed a significant syndromic interaction between theophylline treatment and SCI level (Wilks’ Lambda, p=0.028, F(12,64)=2.116, η2=0.256, 1−β=0.838), with post-hoc testing demonstrating a significant interaction on PC1, explained by a positive correlation between improved forced vital capacity and time it took to reach 16 hours of ventilator free breathing. Thirty-three patients (92%) achieved 16 hours ventilator-free breathing (VFB), 30 (83%) achieved 24 hours VFB. Conclusions We suspect that some portion of the high success rate of ventilator weaning may be attributable to theophylline use in higher cervical SCI; in addition to our aggressive regimen of high volume ventilation, medication optimization, and pulmonary toilet (positive pressure treatments and mechanical insufflation-exsufflation).
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Abstract
The cervical spine is the most common site of traumatic vertebral column injuries. Respiratory insufficiency constitutes a significant proportion of the morbidity burden and is the most common cause of mortality in these patients. In seeking to enhance our capacity to treat specifically the respiratory dysfunction following spinal cord injury, investigators have studied the "crossed phrenic phenomenon", wherein contraction of a hemidiaphragm paralyzed by a complete hemisection of the ipsilateral cervical spinal cord above the phrenic nucleus can be induced by respiratory stressors and recovers spontaneously over time. Strengthening of latent contralateral projections to the phrenic nucleus and sprouting of new descending axons have been proposed as mechanisms contributing to the observed recovery. We have recently demonstrated recovery of spontaneous crossed phrenic activity occurring over minutes to hours in C1-hemisected unanesthetized decerebrate rats. The specific neurochemical and molecular pathways underlying crossed phrenic activity following injury require further clarification. A thorough understanding of these is necessary in order to develop targeted therapies for respiratory neurorehabilitation following spinal trauma. Animal studies provide preliminary evidence for the utility of neuropharmacological manipulation of serotonergic and adenosinergic pathways, nerve grafts, olfactory ensheathing cells, intraspinal microstimulation and a possible role for dorsal rhizotomy in recovering phrenic activity following spinal cord injury.
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Transporter Protein-Coupled DPCPX Nanoconjugates Induce Diaphragmatic Recovery after SCI by Blocking Adenosine A1 Receptors. J Neurosci 2016; 36:3441-52. [PMID: 27013674 DOI: 10.1523/jneurosci.2577-15.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 01/08/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Respiratory complications in patients with spinal cord injury (SCI) are common and have a negative impact on the quality of patients' lives. Systemic administration of drugs that improve respiratory function often cause deleterious side effects. The present study examines the applicability of a novel nanotechnology-based drug delivery system, which induces recovery of diaphragm function after SCI in the adult rat model. We developed a protein-coupled nanoconjugate to selectively deliver by transsynaptic transport small therapeutic amounts of an A1 adenosine receptor antagonist to the respiratory centers. A single administration of the nanoconjugate restored 75% of the respiratory drive at 0.1% of the systemic therapeutic drug dose. The reduction of the systemic dose may obviate the side effects. The recovery lasted for 4 weeks (the longest period studied). These findings have translational implications for patients with respiratory dysfunction after SCI. SIGNIFICANCE STATEMENT The leading causes of death in humans following SCI are respiratory complications secondary to paralysis of respiratory muscles. Systemic administration of methylxantines improves respiratory function but also leads to the development of deleterious side effects due to actions of the drug on nonrespiratory sites. The importance of the present study lies in the novel drug delivery approach that uses nanotechnology to selectively deliver recovery-inducing drugs to the respiratory centers exclusively. This strategy allows for a reduction in the therapeutic drug dose, which may reduce harmful side effects and markedly improve the quality of life for SCI patients.
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Sandhu MS, Lee KZ, Gonzalez-Rothi EJ, Fuller DD. Repeated intravenous doxapram induces phrenic motor facilitation. Exp Neurol 2013; 250:108-15. [PMID: 24013015 DOI: 10.1016/j.expneurol.2013.08.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 08/22/2013] [Accepted: 08/27/2013] [Indexed: 11/26/2022]
Abstract
Doxapram is a respiratory stimulant used to treat hypoventilation. Here we investigated whether doxapram could also trigger respiratory neuroplasticity. Specifically, we hypothesized that intermittent delivery of doxapram at low doses would lead to long-lasting increases (i.e., facilitation) of phrenic motor output in anesthetized, vagotomized, and mechanically-ventilated rats. Doxapram was delivered intravenously in a single bolus (2 or 6mg/kg) or as a series of 3 injections (2mg/kg) at 5min intervals. Control groups received pH-matched saline injections (vehicle) or no treatment (anesthesia time control). Doxapram evoked an immediate increase in phrenic output in all groups, but a persistent increase in burst amplitude only occurred after repeated dosing with 2mg/kg. At 60min following the last injection, phrenic burst amplitude was 168±24% of baseline (%BL) in the group receiving 3 injections (P<0.05 vs. controls), but was 103±8%BL and 112±4%BL in the groups receiving a single dose of 2 or 6mg/kg, respectively. Following bilateral section of the carotid sinus nerves, the acute phrenic response to doxapram (2mg/kg) was reduced by 68% suggesting that at low doses the drug was acting primarily via the carotid chemoreceptors. We conclude that intermittent application of doxapram can trigger phrenic neuroplasticity, and this approach might be of use in the context of respiratory rehabilitation following neurologic injury.
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Affiliation(s)
- M S Sandhu
- Department of Physical Therapy, College of Public Health and Health Professions, McKnight Brain Institute, University of Florida, P.O. Box 100154, 100 S. Newell Drive, Gainesville, FL 32610, USA
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Galeiras Vázquez R, Rascado Sedes P, Mourelo Fariña M, Montoto Marqués A, Ferreiro Velasco ME. Respiratory management in the patient with spinal cord injury. BIOMED RESEARCH INTERNATIONAL 2013; 2013:168757. [PMID: 24089664 PMCID: PMC3781830 DOI: 10.1155/2013/168757] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 07/11/2013] [Accepted: 07/30/2013] [Indexed: 12/19/2022]
Abstract
Spinal cord injuries (SCIs) often lead to impairment of the respiratory system and, consequently, restrictive respiratory changes. Paresis or paralysis of the respiratory muscles can lead to respiratory insufficiency, which is dependent on the level and completeness of the injury. Respiratory complications include hypoventilation, a reduction in surfactant production, mucus plugging, atelectasis, and pneumonia. Vital capacity (VC) is an indicator of overall pulmonary function; patients with severely impaired VC may require assisted ventilation. It is best to proceed with intubation under controlled circumstances rather than waiting until the condition becomes an emergency. Mechanical ventilation can adversely affect the structure and function of the diaphragm. Early tracheostomy following short orotracheal intubation is probably beneficial in selected patients. Weaning should start as soon as possible, and the best modality is progressive ventilator-free breathing (PVFB). Appropriate candidates can sometimes be freed from mechanical ventilation by electrical stimulation. Respiratory muscle training regimens may improve patients' inspiratory function following a SCI.
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Affiliation(s)
- Rita Galeiras Vázquez
- Critical Care Unit, Complexo Hospitalario Universitario A Coruña, CP. 15006, A Coruña, Spain
| | - Pedro Rascado Sedes
- Critical Care Unit, Complexo Hospitalario Universitario de Santiago de Compostela, CP. 15702, Santiago de Compostela, Spain
| | - Mónica Mourelo Fariña
- Critical Care Unit, Complexo Hospitalario Universitario A Coruña, CP. 15006, A Coruña, Spain
| | - Antonio Montoto Marqués
- Spinal Cord Injury Unit, Complexo Hospitalario Universitario A Coruña, CP. 15006, A Coruña, Spain
- Department of Medicine, University of A Coruña, CP. 15006, A Coruña, Spain
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Wood GC, Boucher AB, Johnson JL, Wisniewski JN, Magnotti LJ, Croce MA, Swanson JM, Boucher BA, Fabian TC. Effectiveness of pseudoephedrine as adjunctive therapy for neurogenic shock after acute spinal cord injury: a case series. Pharmacotherapy 2013; 34:89-93. [PMID: 23918202 DOI: 10.1002/phar.1335] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
STUDY OBJECTIVE To evaluate the effectiveness of pseudoephedrine as adjunctive therapy for neurogenic shock in patients with acute spinal cord injury (SCI). DESIGN Case series. SETTING Academic medical center. PATIENTS Thirty-eight patients admitted to the trauma intensive care unit between September 2005 and October 2012 with an acute SCI and who received more than 1 day of pseudoephedrine for one or more of the following: treatment of bradycardia (heart rate ≤ 50 beats/min), treatment of hypotension (systolic blood pressure < 90 mm Hg), or were receiving intravenous vasopressor support. MEASUREMENTS AND MAIN RESULTS The effect of adjunctive pseudoephedrine (PSE) was categorized as a success if vasopressors were discontinued after the initiation of PSE or improvement in the number of episodes of bradycardia was noted after the initiation of PSE as evidenced by decreased use of atropine. The effect of pseudoephedrine was categorized as a failure if it did not meet one of the criteria for success. The effect of pseudoephedrine was categorized as inconclusive if there were confounding factors such as vasopressors being restarted for another indication after initial discontinuation. Pseudoephedrine was successful in 31/38 (82%) patients, failed in 2/38 (5%) patients, and had inconclusive results in 5/38 (13%) patients. The mean ± SD time to successful weaning of intravenous vasopressors was 7 ± 7 days. Daily maximum pseudoephedrine doses ranged from 60-720 mg. Mean ± SD duration of pseudoephedrine therapy was 32 ± 23 days (range 2-135 days), with 64.5% of surviving patients discharged while receiving pseudoephedrine. CONCLUSION These data suggest that pseudoephedrine is an effective adjunctive therapy in facilitating the discontinuation of intravenous vasopressors and/or atropine in patients with acute SCI with neurogenic shock, although patients will typically require long durations of therapy.
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Affiliation(s)
- G Christopher Wood
- Department of Clinical Pharmacy, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee
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Kongenitale myotone Dystrophie mit Zwerchfellparese. Monatsschr Kinderheilkd 2012. [DOI: 10.1007/s00112-012-2721-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Nantwi KD. Recovery of respiratory activity after C2 hemisection (C2HS): involvement of adenosinergic mechanisms. Respir Physiol Neurobiol 2009; 169:102-14. [PMID: 19651244 DOI: 10.1016/j.resp.2009.07.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 07/14/2009] [Accepted: 07/14/2009] [Indexed: 11/18/2022]
Abstract
Consequences of spinal cord injury (SCI) depend on the level and extent of injury. Cervical SCI often results in a compromised respiratory system. Primary treatment of SCI patients with respiratory insufficiency continues to be with mechanical ventilatory support. In an animal model of SCI, an upper cervical spinal cord hemisection paralyzes the hemidiaphragm ipsilateral to the side of injury. However, a latent respiratory motor pathway can be activated to restore respiratory function after injury. In this review, restoration of respiratory activity following systemic administration of theophylline, a respiratory stimulant will be discussed. Pharmacologically, theophylline is a non-specific adenosine receptor antagonist, a phosphodiesterase inhibitor and a bronchodilator. It has been used in the treatment of asthma and other respiratory-related diseases such as chronic obstructive pulmonary disease (COPD) and in treatment of apnea in premature infants. However, the clinical use of theophylline to improve respiration in SCI patients with respiratory deficits is a more recent approach. This review will focus on the use of theophylline to restore respiratory activity in an animal model of SCI. In this model, a C2 hemisection (C2HS) interrupts the major descending respiratory pathways and paralyzes the ipsilateral hemidiaphragm. The review also highlights involvement of central and peripheral adenosine receptors in functional restitution. Biochemical binding assays that highlight changes in adenosine receptors after chronic theophylline administration are discussed as they pertain to understanding adenosine receptor-mediation in functional recovery. Finally, the clinical application of theophylline in SCI patients with respiratory deficits in particular is discussed.
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Affiliation(s)
- Kwaku D Nantwi
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI 48202, USA.
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Golder FJ. Spinal NMDA receptor activation is necessary for de novo, but not the maintenance of, A2a receptor-mediated phrenic motor facilitation. J Appl Physiol (1985) 2009; 107:217-23. [PMID: 19407255 DOI: 10.1152/japplphysiol.00183.2009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adenosine 2a (A2a) receptor agonists elicit persistent increases in phrenic nerve activity by transactivating the neurotrophin receptor, TrkB, near phrenic motoneurons. Our working model proposes that A2a receptor-mediated TrkB receptor activation strengthens glutamatergic synapses onto phrenic motoneurons. Activation of glutamate N-methyl d-aspartate (NMDA) receptors has been implicated in other models of phrenic motor plasticity. Thus we hypothesized that NMDA receptor activation also would contribute to A2a receptor-mediated phrenic motor facilitation. Adult male Sprague-Dawley rats were anesthetized with urethane, mechanically ventilated, neuromuscularly paralyzed, and bilaterally vagotomized. The A2a receptor agonist CGS-21680 and the NMDA receptor-channel blocker MK-801 were administered intrathecally over the C4 spinal segment. Phrenic nerve activity was recorded before, during, and after drug administration. MK-801 (concentration range 0.1, 1.0, 10.0, and 100 microM) was administered 30 min before CGS-21680 (50 microM). MK-801 dose-dependently blocked A2a receptor-mediated phrenic motor facilitation. When administered at 60 min post-CGS-21680, MK-801 prevented further increases in phrenic nerve activity compared with the CGS-21680 alone (CGS-21680 alone at 120 min: 114 +/- 19%; CGS-21680 and MK-801 at 60 min post-CGS-21680: 61 +/- 11%, above baseline, P < 0.05) but did not return phrenic motor output to baseline values. Our data suggest that NMDA receptor activation is necessary for de novo A2a receptor-mediated phrenic motor facilitation and that the maintenance of preexisting phrenic motor facilitation does not involve NMDA receptor-dependent mechanisms.
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Affiliation(s)
- F J Golder
- Dept. of Clinical Studies-Philadelphia, School of Veterinary Medicine, Univ. of Pennsylvania, 3900 Delancey St., Philadelphia, PA 19104, USA.
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Roos M, Kobza R, Jamshidi P, Bauer P, Resink T, Schlaepfer R, Stulz P, Zuber M, Erne P. Improved cardiac performance through pacing-induced diaphragmatic stimulation: a novel electrophysiological approach in heart failure management? Europace 2008; 11:191-9. [DOI: 10.1093/europace/eun377] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Inskip JA, Ramer LM, Ramer MS, Krassioukov AV. Autonomic assessment of animals with spinal cord injury: tools, techniques and translation. Spinal Cord 2008; 47:2-35. [DOI: 10.1038/sc.2008.61] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Abstract
Acute intermittent hypoxia elicits a form of spinal, brain-derived neurotrophic factor (BDNF)-dependent respiratory plasticity known as phrenic long-term facilitation. Ligands that activate G(s)-protein-coupled receptors, such as the adenosine 2a receptor, mimic the effects of neurotrophins in vitro by transactivating their high-affinity receptor tyrosine kinases, the Trk receptors. Thus, we hypothesized that A2a receptor agonists would elicit phrenic long-term facilitation by mimicking the effects of BDNF on TrkB receptors. Here we demonstrate that spinal A2a receptor agonists transactivate TrkB receptors in the rat cervical spinal cord near phrenic motoneurons, thus inducing long-lasting (hours) phrenic motor facilitation. A2a receptor activation increased phosphorylation and new synthesis of an immature TrkB protein, induced TrkB signaling through Akt, and strengthened synaptic pathways to phrenic motoneurons. RNA interference targeting TrkB mRNA demonstrated that new TrkB protein synthesis is necessary for A2a-induced phrenic motor facilitation. A2a receptor activation also increased breathing in unanesthetized rats, and improved breathing in rats with cervical spinal injuries. Thus, small, highly permeable drugs (such as adenosine receptor agonists) that transactivate TrkB receptors may provide an effective therapeutic strategy in the treatment of patients with ventilatory control disorders, such as obstructive sleep apnea, or respiratory insufficiency after spinal injury or during neurodegenerative diseases.
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Kajana S, Goshgarian HG. Administration of phosphodiesterase inhibitors and an adenosine A1 receptor antagonist induces phrenic nerve recovery in high cervical spinal cord injured rats. Exp Neurol 2008; 210:671-80. [PMID: 18289533 DOI: 10.1016/j.expneurol.2007.12.021] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Revised: 12/20/2007] [Accepted: 12/21/2007] [Indexed: 02/01/2023]
Abstract
High cervical spinal cord hemisection interrupts the descending respiratory drive from the medulla to the ipsilateral phrenic motoneurons, consequently leading to the paralysis of the ipsilateral hemidiaphragm. Previous studies have shown that chronic oral administration of theophylline, a phosphodiesterase inhibitor and an adenosine receptor antagonist, can restore function to the quiescent phrenic nerve and hemidiaphragm ipsilateral to hemisection. Both of these actions of theophylline result in an increase in 3'-5'-cyclic adenosine monophosphate (cAMP). Furthermore, the chronic theophylline-mediated respiratory recovery persists long after the animals have been weaned from the drug. To date, the precise cellular mechanisms underlying the recovery induced by theophylline are still not known. Since theophylline has two modes of action, in the present study we tested whether chronic administration of pentoxifylline, a non-selective phosphodiesterase inhibitor, rolipram, a phosphodiesterase-4 specific inhibitor, and 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), an adenosine A1 receptor antagonist, would induce recovery similar to that induced by theophylline in male Sprague-Dawley rats following a left C2 spinal cord lesion. Recovery of left phrenic nerve activity was assessed at 5 or 10 days after the last drug administrations to assess the persistent nature of the recovery. Pentoxifylline, rolipram and DPCPX, all capable of modulating 3',5'-cyclic monophosphate (cAMP) levels, brought about long-term respiratory recovery in the phrenic nerve ipsilateral to the left C2 lesion at 5 and 10 days after the last drug administration. Therefore, these results suggest that compounds capable of regulating cAMP levels may be therapeutically useful in promoting functional recovery following spinal cord injury.
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Affiliation(s)
- S Kajana
- Department of Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI 48201, USA
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Whitman CB, Schroeder WS, Ploch PJ, Raghavendran K. Efficacy of Aminophylline for Treatment of Recurrent Symptomatic Bradycardia After Spinal Cord Injury. Pharmacotherapy 2008; 28:131-5. [DOI: 10.1592/phco.28.1.131] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Zimmer MB, Nantwi K, Goshgarian HG. Effect of spinal cord injury on the respiratory system: basic research and current clinical treatment options. J Spinal Cord Med 2007; 203:98-108. [PMID: 17853653 DOI: 10.1016/j.resp.2014.08.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 08/11/2014] [Accepted: 08/12/2014] [Indexed: 02/09/2023] Open
Abstract
Spinal cord injury (SCI) often leads to an impairment of the respiratory system. The more rostral the level of injury, the more likely the injury will affect ventilation. In fact, respiratory insufficiency is the number one cause of mortality and morbidity after SCI. This review highlights the progress that has been made in basic and clinical research, while noting the gaps in our knowledge. Basic research has focused on a hemisection injury model to examine methods aimed at improving respiratory function after SCI, but contusion injury models have also been used. Increasing synaptic plasticity, strengthening spared axonal pathways, and the disinhibition of phrenic motor neurons all result in the activation of a latent respiratory motor pathway that restores function to a previously paralyzed hemidiaphragm in animal models. Human clinical studies have revealed that respiratory function is negatively impacted by SCI. Respiratory muscle training regimens may improve inspiratory function after SCI, but more thorough and carefully designed studies are needed to adequately address this issue. Phrenic nerve and diaphragm pacing are options available to wean patients from standard mechanical ventilation. The techniques aimed at improving respiratory function in humans with SCI have both pros and cons, but having more options available to the clinician allows for more individualized treatment, resulting in better patient care. Despite significant progress in both basic and clinical research, there is still a significant gap in our understanding of the effect of SCI on the respiratory system.
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Affiliation(s)
- M Beth Zimmer
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan 48201, USA.
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Zimmer MB, Nantwi K, Goshgarian HG. Effect of spinal cord injury on the respiratory system: basic research and current clinical treatment options. J Spinal Cord Med 2007; 30:319-30. [PMID: 17853653 PMCID: PMC2031930 DOI: 10.1080/10790268.2007.11753947] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2006] [Accepted: 02/05/2007] [Indexed: 10/21/2022] Open
Abstract
Spinal cord injury (SCI) often leads to an impairment of the respiratory system. The more rostral the level of injury, the more likely the injury will affect ventilation. In fact, respiratory insufficiency is the number one cause of mortality and morbidity after SCI. This review highlights the progress that has been made in basic and clinical research, while noting the gaps in our knowledge. Basic research has focused on a hemisection injury model to examine methods aimed at improving respiratory function after SCI, but contusion injury models have also been used. Increasing synaptic plasticity, strengthening spared axonal pathways, and the disinhibition of phrenic motor neurons all result in the activation of a latent respiratory motor pathway that restores function to a previously paralyzed hemidiaphragm in animal models. Human clinical studies have revealed that respiratory function is negatively impacted by SCI. Respiratory muscle training regimens may improve inspiratory function after SCI, but more thorough and carefully designed studies are needed to adequately address this issue. Phrenic nerve and diaphragm pacing are options available to wean patients from standard mechanical ventilation. The techniques aimed at improving respiratory function in humans with SCI have both pros and cons, but having more options available to the clinician allows for more individualized treatment, resulting in better patient care. Despite significant progress in both basic and clinical research, there is still a significant gap in our understanding of the effect of SCI on the respiratory system.
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Affiliation(s)
- M Beth Zimmer
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan 48201, USA.
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Tzelepis GE, Bascom AT, Badr MS, Goshgarian HG. Effects of theophylline on pulmonary function in patients with traumatic tetraplegia. J Spinal Cord Med 2006; 29:227-33. [PMID: 16859226 PMCID: PMC1864809 DOI: 10.1080/10790268.2006.11753878] [Citation(s) in RCA: 18] [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] [Indexed: 10/21/2022] Open
Abstract
BACKGROUND/OBJECTIVES To assess the effects of theophylline on pulmonary function in patients with chronic traumatic tetraplegia, we conducted a double-blind placebo-controlled crossover study in 10 patients. METHODS The patients (age: 41 +/- 3 years; time from injury: 16 +/- 3 years; neurological levels: C3 to C7-T1) were randomized to receive oral theophylline or placebo for 6 weeks. After 2 months of washout, the patients received the medication not taken in the first trial for an additional 6 weeks. We measured lung volumes, expiratory flow rates, maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) at both baseline and at the end of each treatment arm. Theophylline blood serum assays were measured during the first week of the treatment and on the day of respiratory measurements. RESULTS Mean theophylline level on the day of treatment completion was 12.6 +/- 1.4 microg/mL. In analyzing the data from the group of 10 patients, the percent changes from baseline in total lung capacity, forced vital capacity, forced expiratory volume at 1 second, MIP, and MEP did not differ significantly between the two treatment arms (P > 0.05 in all). CONCLUSION These data show that in this small group of 10 subjects with chronic tetraplegia, administration of oral theophylline did not improve pulmonary function.
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Affiliation(s)
| | - Amy T Bascom
- Wayne State University School of Medicine, Detroit, Michigan
| | - M Safwan Badr
- John D. Dingell Veterans Affairs Medical Center and
- Wayne State University School of Medicine, Detroit, Michigan
| | - Harry G Goshgarian
- Wayne State University School of Medicine, Detroit, Michigan
- Please address correspondence to Harry G. Goshgarian, PhD, Department of Anatomy and Cell Biology, Wayne State University School of Medicine, 540 E. Canfield, Detroit, MI 48201; phone: 313.577.1045; fax: 313.577.3125 (e-mail: )
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Saharan RS, Nantwi KD. Changes in the biochemical profiles of mid-cervically located adenosine A1 receptors after repeated theophylline administration in adult rats. J Spinal Cord Med 2006; 29:520-6. [PMID: 17274491 PMCID: PMC1949029 DOI: 10.1080/10790268.2006.11753902] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
BACKGROUND/OBJECTIVE Adenosine A1 receptors localized in the phrenic motoneurons (PMNs), where the axons of the descending bulbospinal respiratory make synaptic contacts, may be involved in theophylline-induced respiratory-related activity in rats. The objective of this study was to characterize the biochemical profiles of adenosine A1 receptors in 2 groups of rats: (a) naïve and (b) theophylline-treated (3-day oral administration). METHODS Biochemical binding characteristics of adenosine A1 receptors in the C3 to C5 (PMN) of adult rats were assessed in naïve (n = 6) and theophylline-treated animals (n = 6) using [3H]-DPCPX (10 pmol/L to 30 nmol/L), the specific adenosine A1 receptor antagonist in saturation-binding assays. Competition assays used theophylline as the competing ligand (20 mmol/L to 20 pmol/L), and protein concentration was determined with the Bradford assay using a range of standards (0.016-1.0 mg/mL). RESULTS In saturation-binding assays in naïve animals, the A1 receptor was characterized by a single binding site with Bmax and Kd values of 256.00 +/- 32.13 fmol/mg protein and 2.89 +/- 0.45 nmol/L, respectively. Analysis of the isotherm in theophylline-treated animals showed 1 site with Bmax and Kd values of 219.00 +/- 26.3 fmol/mg protein and 0.60 +/- 0.21 nmol/L, respectively, and a second site characterized by Bmax and Kd values of 492.6 +/- 3.15 fmol/mg protein and 14.09 +/- 2.06 nmol/L, respectively. CONCLUSIONS Theophylline administration revealed 2 binding sites on receptors (characterized by the specific adenosine A1 antagonist, [3H]-DPCPX) located in the vicinity of phrenic motoneurons (C3-C5). Alteration of the receptor profiles after theophylline may underlie the respiratory-related actions of the drug.
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Affiliation(s)
- Rubabe S Saharan
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan
| | - Kwaku D Nantwi
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan
- Please address correspondence to Kwaku D. Nantwi, PhD, Wayne State University, School of Medicine, Department of Anatomy and Cell Biology, 540 East Canfield Avenue, Detroit, MI 48202; phone: 313.577.7925; fax: 313.577.3125 (e-mail: )
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James E, Nantwi KD. Involvement of peripheral adenosine A2 receptors in adenosine A1 receptor-mediated recovery of respiratory motor function after upper cervical spinal cord hemisection. J Spinal Cord Med 2006; 29:57-66. [PMID: 16572566 PMCID: PMC1864794 DOI: 10.1080/10790268.2006.11753857] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
BACKGROUND/OBJECTIVE In an animal model of spinal cord injury, a latent respiratory motor pathway can be pharmacologically activated through central adenosine A1 receptor antagonism to restore respiratory function after cervical (C2) spinal cord hemisection that paralyzes the hemidiaphragm ipsilateral to injury. Although respiration is modulated by central and peripheral mechanisms, putative involvement of peripheral adenosine A2 receptors in functional recovery in our model is untested. The objective of this study was to assess the effects of peripherally located adenosine A2 receptors on recovery of respiratory function after cervical (C2) spinal cord hemisection. METHODS Respiratory activity was electrophysiologically assessed (under standardized recording conditions) in C2-hemisected adult rats with the carotid bodies intact (H-CBI; n=12) or excised (H-CBE; n=12). Animals were administered the adenosine A2 receptor agonist, CGS-21680, followed by the A1 receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), or administered DPCPX alone. Recovered respiratory activity, characterized as drug-induced activity in the previously quiescent left phrenic nerve of C2-hemisected animals in H-CBI and H-CBE rats, was compared. Recovered respiratory activity was calculated by dividing drug-induced activity in the left phrenic nerve by activity in the right phrenic nerve. RESULTS Administration of CGS-21680 before DPCPX (n=6) in H-CBI rats induced a significantly greater recovery (58.5 +/- 3.6%) than when DPCPX (42.6 +/- 4.6%) was administered (n=6) alone. In H-CBE rats, prior administration of CGS-21680 (n=6) did not enhance recovery over that induced by DPCPX (n=6) alone. Recovery in H-CBE rats amounted to 39.7 +/- 3.7% and 38.4 + 4.2%, respectively. CONCLUSIONS Our results suggest that adenosine A2 receptors located in the carotid bodies can enhance the magnitude of adenosine A1 receptor-mediated recovery of respiratory function after C2 hemisection. We conclude that a novel approach of targeting peripheral and central adenosine receptors can be therapeutically beneficial in alleviating compromised respiratory function after cervical spinal cord injury.
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Affiliation(s)
- Elysia James
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan
| | - Kwaku D Nantwi
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan
- Please address correspondence to Kwaku D. Nantwi, PhD, Wayne State University, School of Medicine, Department of Anatomy and Cell Biology, 540 East Canfield Avenue, Detroit, MI 48202; phone: 313.577.7925; fax: 313.577.3125 (e-mail: )
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