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Marciante AB, Tadjalli A, Burrowes KA, Oberto JR, Luca EK, Seven YB, Nikodemova M, Watters JJ, Baker TL, Mitchell GS. Microglia regulate motor neuron plasticity via reciprocal fractalkine/adenosine signaling. bioRxiv 2024:2024.05.07.592939. [PMID: 38765982 PMCID: PMC11100694 DOI: 10.1101/2024.05.07.592939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Microglia are innate CNS immune cells that play key roles in supporting key CNS functions including brain plasticity. We now report a previously unknown role for microglia in regulating neuroplasticity within spinal phrenic motor neurons, the neurons driving diaphragm contractions and breathing. We demonstrate that microglia regulate phrenic long-term facilitation (pLTF), a form of respiratory memory lasting hours after repetitive exposures to brief periods of low oxygen (acute intermittent hypoxia; AIH) via neuronal/microglial fractalkine signaling. AIH-induced pLTF is regulated by the balance between competing intracellular signaling cascades initiated by serotonin vs adenosine, respectively. Although brainstem raphe neurons release the relevant serotonin, the cellular source of adenosine is unknown. We tested a model in which hypoxia initiates fractalkine signaling between phrenic motor neurons and nearby microglia that triggers extracellular adenosine accumulation. With moderate AIH, phrenic motor neuron adenosine 2A receptor activation undermines serotonin-dominant pLTF; in contrast, severe AIH drives pLTF by a unique, adenosine-dominant mechanism. Phrenic motor neuron fractalkine knockdown, cervical spinal fractalkine receptor inhibition on nearby microglia, and microglial depletion enhance serotonin-dominant pLTF with moderate AIH but suppress adenosine-dominant pLTF with severe AIH. Thus, microglia play novel functions in the healthy spinal cord, regulating hypoxia-induced neuroplasticity within the motor neurons responsible for breathing.
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Marciante AB, Seven YB, Kelly MN, Perim RR, Mitchell GS. Magnitude and Mechanism of Phrenic Long-term Facilitation Shift Between Daily Rest Versus Active Phase. Function (Oxf) 2023; 4:zqad041. [PMID: 37753182 PMCID: PMC10519274 DOI: 10.1093/function/zqad041] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 07/26/2023] [Accepted: 07/27/2023] [Indexed: 09/28/2023] Open
Abstract
Plasticity is a fundamental property of the neural system controlling breathing. One key example of respiratory motor plasticity is phrenic long-term facilitation (pLTF), a persistent increase in phrenic nerve activity elicited by acute intermittent hypoxia (AIH). pLTF can arise from distinct cell signaling cascades initiated by serotonin versus adenosine receptor activation, respectively, and interact via powerful cross-talk inhibition. Here, we demonstrate that the daily rest/active phase and the duration of hypoxic episodes within an AIH protocol have profound impact on the magnitude and mechanism of pLTF due to shifts in serotonin/adenosine balance. Using the historical "standard" AIH protocol (3, 5-min moderate hypoxic episodes), we demonstrate that pLTF magnitude is unaffected by exposure in the midactive versus midrest phase, yet the mechanism driving pLTF shifts from serotonin-dominant (midrest) to adenosine-dominant (midactive). This mechanistic "flip" results from combined influences of hypoxia-evoked adenosine release and daily fluctuations in basal spinal adenosine. Since AIH evokes less adenosine with shorter (15, 1-min) hypoxic episodes, midrest pLTF is amplified due to diminished adenosine constraint on serotonin-driven plasticity; in contrast, elevated background adenosine during the midactive phase suppresses serotonin-dominant pLTF. These findings demonstrate the importance of the serotonin/adenosine balance in regulating the amplitude and mechanism of AIH-induced pLTF. Since AIH is emerging as a promising therapeutic modality to restore respiratory and nonrespiratory movements in people with spinal cord injury or ALS, knowledge of how time-of-day and hypoxic episode duration impact the serotonin/adenosine balance and the magnitude and mechanism of pLTF has profound biological, experimental, and translational implications.
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Affiliation(s)
- Alexandria B Marciante
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Yasin B Seven
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Mia N Kelly
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Raphael R Perim
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Gordon S Mitchell
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
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Seven ES, Kirbas Cilingir E, Bartoli M, Zhou Y, Sampson R, Shi W, Peng Z, Ram Pandey R, Chusuei CC, Tagliaferro A, Vanni S, Graham RM, Seven YB, Leblanc RM. Hydrothermal vs microwave nanoarchitechtonics of carbon dots significantly affects the structure, physicochemical properties, and anti-cancer activity against a specific neuroblastoma cell line. J Colloid Interface Sci 2023; 630:306-321. [DOI: 10.1016/j.jcis.2022.10.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 09/15/2022] [Accepted: 10/03/2022] [Indexed: 11/11/2022]
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Seven YB, Allen LL, Ciesla MC, Smith KN, Zwick A, Simon AK, Holland AE, Santiago JV, Stefan K, Ross A, Gonzalez-Rothi EJ, Mitchell GS. Intermittent Hypoxia Differentially Regulates Adenosine Receptors in Phrenic Motor Neurons with Spinal Cord Injury. Neuroscience 2022; 506:38-50. [PMID: 36273657 DOI: 10.1016/j.neuroscience.2022.10.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 10/04/2022] [Accepted: 10/07/2022] [Indexed: 11/09/2022]
Abstract
Cervical spinal cord injury (cSCI) impairs neural drive to the respiratory muscles, causing life- threatening complications such as respiratory insufficiency and diminished airway protection. Repetitive "low dose" acute intermittent hypoxia (AIH) is a promising strategy to restore motor function in people with chronic SCI. Conversely, "high dose" chronic intermittent hypoxia (CIH; ∼8 h/night), such as experienced during sleep apnea, causes pathology. Sleep apnea, spinal ischemia, hypoxia and neuroinflammation associated with cSCI increase extracellular adenosine concentrations and activate spinal adenosine receptors which in turn constrains the functional benefits of therapeutic AIH. Adenosine 1 and 2A receptors (A1, A2A) compete to determine net cAMP signaling and likely the tAIH efficacy with chronic cSCI. Since cSCI and intermittent hypoxia may regulate adenosine receptor expression in phrenic motor neurons, we tested the hypotheses that: 1) daily AIH (28 days) downregulates A2A and upregulates A1 receptor expression; 2) CIH (28 days) upregulates A2A and downregulates A1 receptor expression; and 3) cSCI alters the impact of CIH on adenosine receptor expression. Daily AIH had no effect on either adenosine receptor in intact or injured rats. However, CIH exerted complex effects depending on injury status. Whereas CIH increased A1 receptor expression in intact (not injured) rats, it increased A2A receptor expression in spinally injured (not intact) rats. The differential impact of CIH reinforces the concept that the injured spinal cord behaves in distinct ways from intact spinal cords, and that these differences should be considered in the design of experiments and/or new treatments for chronic cSCI.
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Affiliation(s)
- Yasin B Seven
- Breathing Research and Therapeutics Center, Department of Physical Therapy and, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Latoya L Allen
- Breathing Research and Therapeutics Center, Department of Physical Therapy and, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Marissa C Ciesla
- Breathing Research and Therapeutics Center, Department of Physical Therapy and, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Kristin N Smith
- Breathing Research and Therapeutics Center, Department of Physical Therapy and, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Amanda Zwick
- Breathing Research and Therapeutics Center, Department of Physical Therapy and, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Alec K Simon
- Breathing Research and Therapeutics Center, Department of Physical Therapy and, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Ashley E Holland
- Breathing Research and Therapeutics Center, Department of Physical Therapy and, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Juliet V Santiago
- Breathing Research and Therapeutics Center, Department of Physical Therapy and, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Kelsey Stefan
- Breathing Research and Therapeutics Center, Department of Physical Therapy and, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Ashley Ross
- Breathing Research and Therapeutics Center, Department of Physical Therapy and, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Elisa J Gonzalez-Rothi
- Breathing Research and Therapeutics Center, Department of Physical Therapy and, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Gordon S Mitchell
- Breathing Research and Therapeutics Center, Department of Physical Therapy and, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA.
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Burrowes KA, Michaelson AL, Seven YB, Mitchell GS. Phrenic Motor Neuron Fractalkine Expression After Intermittent Hypoxia and Spinal Cord Injury. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r3511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Kayla A. Burrowes
- College of Public Health and Health ProfessionsUniversity of FloridaGainesvilleFL
| | | | - Yasin B. Seven
- College of Public Health and Health ProfessionsUniversity of FloridaGainesvilleFL
| | - Gordon S. Mitchell
- College of Public Health and Health ProfessionsUniversity of FloridaGainesvilleFL
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Nair J, Marciante AB, Seven YB, Kelly MN, Lurk C, Oberto JR, Mitchell GS. Acute Intermittent Hypoxia Preconditioning Elicits Age and Sex‐Dependent Changes in Molecules Known to Regulate Phrenic Motor Plasticity. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r5610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Jayakrishnan Nair
- Physical TherapyBreathing Research and Therapeutics CenterDepartment of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Alexandria B. Marciante
- Physical TherapyBreathing Research and Therapeutics CenterDepartment of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Yasin B. Seven
- Physical TherapyBreathing Research and Therapeutics CenterDepartment of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Mia N. Kelly
- Physical TherapyBreathing Research and Therapeutics CenterDepartment of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Carter Lurk
- Physical TherapyBreathing Research and Therapeutics CenterDepartment of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Jose R. Oberto
- Physical TherapyBreathing Research and Therapeutics CenterDepartment of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Gordon S. Mitchell
- Physical TherapyBreathing Research and Therapeutics CenterDepartment of Physical TherapyUniversity of FloridaGainesvilleFL
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Sajjadi E, Seven YB, Ehrbar JG, Wymer JP, Mitchell GS, Smith BK. Acute intermittent hypoxia and respiratory muscle recruitment in people with amyotrophic lateral sclerosis: A preliminary study. Exp Neurol 2022; 347:113890. [PMID: 34624328 PMCID: PMC9488543 DOI: 10.1016/j.expneurol.2021.113890] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 09/28/2021] [Accepted: 10/03/2021] [Indexed: 01/03/2023]
Abstract
Respiratory failure is the main cause of death in amyotrophic lateral sclerosis (ALS). Since no effective treatments to preserve independent breathing are available, there is a critical need for new therapies to preserve or restore breathing ability. Since acute intermittent hypoxia (AIH) elicits spinal respiratory motor plasticity in rodent ALS models, and may restore breathing ability in people with ALS, we performed a proof-of-principle study to investigate this possibility in ALS patients. Quiet breathing, sniff nasal inspiratory pressure (SNIP) and maximal inspiratory pressure (MIP) were tested in 13 persons with ALS and 10 age-matched controls, before and 60 min post-AIH (15, 1 min episodes of 10% O2, 2 min normoxic intervals) or sham AIH (continuous normoxia). The root mean square (RMS) of the right and left diaphragm, 2nd parasternal, scalene and sternocleidomastoid muscles were monitored. A vector analysis was used to calculate summated vector magnitude (Mag) and similarity index (SI) of collective EMG activity during quiet breathing, SNIP and MIP maneuvers. AIH facilitated tidal volume and minute ventilation (treatment main effects: p < 0.05), and Mag (ie. collective respiratory muscle activity; p < 0.001) during quiet breathing in ALS and control subjects, but there was no effect on SI during quiet breathing. SNIP SI decreased in both groups post-AIH (p < 0.005), whereas Mag was unchanged (p = 0.09). No differences were observed in SNIP or MIP post AIH in either group. Discomfort was not reported during AIH by any subject, nor were adverse events observed. Thus, AIH may be a safe way to increase collective inspiratory muscle activity during quiet breathing in ALS patients, although a single AIH presentation was not sufficient to significantly increase peak inspiratory pressure generation. These preliminary results provide evidence that AIH may improve breathing function in people with ALS, and that future studies of prolonged, repetitive AIH protocols are warranted.
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Affiliation(s)
- Elaheh Sajjadi
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA, 32610,McKnight Brain Institute, University of Florida, Gainesville, FL, USA, 32610,Department of Physical Therapy, University of Florida, Gainesville, FL, USA, 32610
| | - Yasin B. Seven
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA, 32610,McKnight Brain Institute, University of Florida, Gainesville, FL, USA, 32610,Department of Physical Therapy, University of Florida, Gainesville, FL, USA, 32610
| | - Jessica G Ehrbar
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA, 32610
| | - James P. Wymer
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA, 32610,McKnight Brain Institute, University of Florida, Gainesville, FL, USA, 32610,Neurology, University of Florida, Gainesville, FL, USA, 32610
| | - Gordon S. Mitchell
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA, 32610,McKnight Brain Institute, University of Florida, Gainesville, FL, USA, 32610,Department of Physical Therapy, University of Florida, Gainesville, FL, USA, 32610
| | - Barbara K. Smith
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA, 32610,Department of Physical Therapy, University of Florida, Gainesville, FL, USA, 32610,Pediatrics, University of Florida, Gainesville, FL, USA, 32610
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Tadjalli A, Seven YB, Sharma A, McCurdy CR, Bolser DC, Levitt ES, Mitchell GS. Acute morphine blocks spinal respiratory motor plasticity via long-latency mechanisms that require toll-like receptor 4 signalling. J Physiol 2021; 599:3771-3797. [PMID: 34142718 DOI: 10.1113/jp281362] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Accepted: 06/15/2021] [Indexed: 12/22/2022] Open
Abstract
KEY POINTS While respiratory complications following opioid use are mainly mediated via activation of mu opioid receptors, long-latency off-target signalling via innate immune toll-like receptor 4 (TLR4) may impair other essential elements of breathing control such as respiratory motor plasticity. In adult rats, pre-treatment with a single dose of morphine blocked long-term facilitation (LTF) of phrenic motor output via a long-latency TLR4-dependent mechanism. In the phrenic motor nucleus, morphine triggered TLR4-dependent activation of microglial p38 MAPK - a key enzyme that orchestrates inflammatory signalling and is known to undermine phrenic LTF. Morphine-induced LTF loss may destabilize breathing, potentially contributing to respiratory side effects. Therefore, we suggest minimizing TLR-4 signalling may improve breathing stability during opioid therapy. ABSTRACT Opioid-induced respiratory dysfunction is a significant public health burden. While respiratory effects are mediated via mu opioid receptors, long-latency off-target opioid signalling through innate immune toll-like receptor 4 (TLR4) may modulate essential elements of breathing control, particularly respiratory motor plasticity. Plasticity in respiratory motor circuits contributes to the preservation of breathing in the face of destabilizing influences. For example, respiratory long-term facilitation (LTF), a well-studied model of respiratory motor plasticity triggered by acute intermittent hypoxia, promotes breathing stability by increasing respiratory motor drive to breathing muscles. Some forms of respiratory LTF are exquisitely sensitive to inflammation and are abolished by even a mild inflammation triggered by TLR4 activation (e.g. via systemic lipopolysaccharides). Since opioids induce inflammation and TLR4 activation, we hypothesized that opioids would abolish LTF through a TLR4-dependent mechanism. In adult Sprague Dawley rats, pre-treatment with a single systemic injection of the prototypical opioid agonist morphine blocks LTF expression several hours later in the phrenic motor system - the motor pool driving diaphragm muscle contractions. Morphine blocked phrenic LTF via TLR4-dependent mechanisms because pre-treatment with (+)-naloxone - the opioid inactive stereoisomer and novel small molecule TLR4 inhibitor - prevented impairment of phrenic LTF in morphine-treated rats. Morphine triggered TLR4-dependent activation of microglial p38 MAPK within the phrenic motor system - a key enzyme that orchestrates inflammatory signalling and undermines phrenic LTF. Morphine-induced LTF loss may destabilize breathing, potentially contributing to respiratory side effects. We suggest minimizing TLR-4 signalling may improve breathing stability during opioid therapy by restoring endogenous mechanisms of plasticity within respiratory motor circuits.
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Affiliation(s)
- Arash Tadjalli
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA.,Department of Physical Therapy, University of Florida, Gainesville, FL, USA
| | - Yasin B Seven
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA.,Department of Physical Therapy, University of Florida, Gainesville, FL, USA
| | - Abhisheak Sharma
- Department of Pharmaceutics, University of Florida, Gainesville, FL, USA
| | | | - Donald C Bolser
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA.,Department of Physiological Sciences, University of Florida, Gainesville, FL, USA
| | - Erica S Levitt
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA.,Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
| | - Gordon S Mitchell
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, USA.,Department of Physical Therapy, University of Florida, Gainesville, FL, USA
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Seven ES, Seven YB, Zhou Y, Poudel-Sharma S, Diaz-Rucco JJ, Kirbas Cilingir E, Mitchell GS, Van Dyken JD, Leblanc RM. Crossing the blood-brain barrier with carbon dots: uptake mechanism and in vivo cargo delivery. Nanoscale Adv 2021; 3:3942-3953. [PMID: 34263140 PMCID: PMC8243484 DOI: 10.1039/d1na00145k] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 05/30/2021] [Indexed: 06/10/2023]
Abstract
The blood-brain barrier (BBB) is a major obstacle for drug delivery to the central nervous system (CNS) such that most therapeutics lack efficacy against brain tumors or neurological disorders due to their inability to cross the BBB. Therefore, developing new drug delivery platforms to facilitate drug transport to the CNS and understanding their mechanism of transport are crucial for the efficacy of therapeutics. Here, we report (i) carbon dots prepared from glucose and conjugated to fluorescein (GluCD-F) cross the BBB in zebrafish and rats without the need of an additional targeting ligand and (ii) uptake mechanism of GluCDs is glucose transporter-dependent in budding yeast. Glucose transporter-negative strain of yeast showed undetectable GluCD accumulation unlike the glucose transporter-positive yeast, suggesting glucose-transporter-dependent GluCD uptake. We tested GluCDs' ability to cross the BBB using both zebrafish and rat models. Following the injection to the heart, wild-type zebrafish showed GluCD-F accumulation in the central canal consistent with the transport of GluCD-F across the BBB. In rats, following intravenous administration, GluCD-F was observed in the CNS. GluCD-F was localized in the gray matter (e.g. ventral horn, dorsal horn, and middle grey) of the cervical spinal cord consistent with neuronal accumulation. Therefore, neuron targeting GluCDs hold tremendous potential as a drug delivery platform in neurodegenerative disease, traumatic injury, and malignancies of the CNS.
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Affiliation(s)
- Elif S Seven
- Department of Chemistry, University of Miami 1301 Memorial Dr. Coral Gables FL 33146 USA
| | - Yasin B Seven
- Department of Physical Therapy, University of Florida 101 Newell Dr. Gainesville FL 32603 USA
- McKnight Brain Institute, University of Florida 1149 Newell Dr. Gainesville FL 32610 USA
| | - Yiqun Zhou
- Department of Chemistry, University of Miami 1301 Memorial Dr. Coral Gables FL 33146 USA
| | - Sijan Poudel-Sharma
- Department of Biology, University of Miami 1301 Memorial Dr. Coral Gables FL 33146 USA
| | - Juan J Diaz-Rucco
- Department of Chemistry, University of Miami 1301 Memorial Dr. Coral Gables FL 33146 USA
| | - Emel Kirbas Cilingir
- Department of Chemistry, University of Miami 1301 Memorial Dr. Coral Gables FL 33146 USA
| | - Gordon S Mitchell
- Department of Physical Therapy, University of Florida 101 Newell Dr. Gainesville FL 32603 USA
- McKnight Brain Institute, University of Florida 1149 Newell Dr. Gainesville FL 32610 USA
| | - J David Van Dyken
- Department of Biology, University of Miami 1301 Memorial Dr. Coral Gables FL 33146 USA
| | - Roger M Leblanc
- Department of Chemistry, University of Miami 1301 Memorial Dr. Coral Gables FL 33146 USA
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Tadjalli A, Seven YB, Perim RR, Mitchell GS. Systemic inflammation suppresses spinal respiratory motor plasticity via mechanisms that require serine/threonine protein phosphatase activity. J Neuroinflammation 2021; 18:28. [PMID: 33468163 PMCID: PMC7816383 DOI: 10.1186/s12974-021-02074-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 01/05/2021] [Indexed: 01/05/2023] Open
Abstract
Background Inflammation undermines multiple forms of neuroplasticity. Although inflammation and its influence on plasticity in multiple neural systems has been extensively studied, its effects on plasticity of neural networks controlling vital life functions, such as breathing, are less understood. In this study, we investigated the signaling mechanisms whereby lipopolysaccharide (LPS)-induced systemic inflammation impairs plasticity within the phrenic motor system—a major spinal respiratory motor pool that drives contractions of the diaphragm muscle. Here, we tested the hypotheses that lipopolysaccharide-induced systemic inflammation (1) blocks phrenic motor plasticity by a mechanism that requires cervical spinal okadaic acid-sensitive serine/threonine protein phosphatase (PP) 1/2A activity and (2) prevents phosphorylation/activation of extracellular signal-regulated kinase 1/2 mitogen activated protein kinase (ERK1/2 MAPK)—a key enzyme necessary for the expression of phrenic motor plasticity. Methods To study phrenic motor plasticity, we utilized a well-characterized model for spinal respiratory plasticity called phrenic long-term facilitation (pLTF). pLTF is characterized by a long-lasting, progressive enhancement of inspiratory phrenic nerve motor drive following exposures to moderate acute intermittent hypoxia (mAIH). In anesthetized, vagotomized and mechanically ventilated adult Sprague Dawley rats, we examined the effect of inhibiting cervical spinal serine/threonine PP 1/2A activity on pLTF expression in sham-vehicle and LPS-treated rats. Using immunofluorescence optical density analysis, we compared mAIH-induced phosphorylation/activation of ERK 1/2 MAPK with and without LPS-induced inflammation in identified phrenic motor neurons. Results We confirmed that mAIH-induced pLTF is abolished 24 h following low-dose systemic LPS (100 μg/kg, i.p.). Cervical spinal delivery of the PP 1/2A inhibitor, okadaic acid, restored pLTF in LPS-treated rats. LPS also prevented mAIH-induced enhancement in phrenic motor neuron ERK1/2 MAPK phosphorylation. Thus, a likely target for the relevant okadaic acid-sensitive protein phosphatases is ERK1/2 MAPK or its upstream activators. Conclusions This study increases our understanding of fundamental mechanisms whereby inflammation disrupts neuroplasticity in a critical population of motor neurons necessary for breathing, and highlights key roles for serine/threonine protein phosphatases and ERK1/2 MAPK kinase in the plasticity of mammalian spinal respiratory motor circuits.
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Affiliation(s)
- Arash Tadjalli
- Breathing Research and Therapeutics Center, Department of Physical Therapy and The McKnight Brain Institute, College of Public Health & Health Professions, University of Florida, 1225 Center Drive, PO Box 100154, Gainesville, FL, 32610, USA
| | - Yasin B Seven
- Breathing Research and Therapeutics Center, Department of Physical Therapy and The McKnight Brain Institute, College of Public Health & Health Professions, University of Florida, 1225 Center Drive, PO Box 100154, Gainesville, FL, 32610, USA
| | - Raphael R Perim
- Breathing Research and Therapeutics Center, Department of Physical Therapy and The McKnight Brain Institute, College of Public Health & Health Professions, University of Florida, 1225 Center Drive, PO Box 100154, Gainesville, FL, 32610, USA
| | - Gordon S Mitchell
- Breathing Research and Therapeutics Center, Department of Physical Therapy and The McKnight Brain Institute, College of Public Health & Health Professions, University of Florida, 1225 Center Drive, PO Box 100154, Gainesville, FL, 32610, USA.
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Ciesla MC, Seven YB, Allen LL, Smith KN, Asa ZA, Simon AK, Holland AE, Santiago JV, Stefan K, Ross A, Gonzalez-Rothi EJ, Mitchell GS. Serotonergic innervation of respiratory motor nuclei after cervical spinal injury: Impact of intermittent hypoxia. Exp Neurol 2021; 338:113609. [PMID: 33460645 DOI: 10.1016/j.expneurol.2021.113609] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 12/31/2020] [Accepted: 01/09/2021] [Indexed: 12/12/2022]
Abstract
Although cervical spinal cord injury (cSCI) disrupts bulbo-spinal serotonergic projections, partial recovery of spinal serotonergic innervation below the injury site is observed after incomplete cSCI. Since serotonin contributes to functional recovery post-injury, treatments to restore or accelerate serotonergic reinnervation are of considerable interest. Intermittent hypoxia (IH) was reported to increase serotonin innervation near respiratory motor neurons in spinal intact rats, and to improve function after cSCI. Here, we tested the hypotheses that spontaneous serotonergic reinnervation of key respiratory (phrenic and intercostal) motor nuclei: 1) is partially restored 12 weeks post C2 hemisection (C2Hx); 2) is enhanced by IH; and 3) results from sprouting of spared crossed-spinal serotonergic projections below the site of injury. Serotonin was assessed via immunofluorescence in male Sprague Dawley rats with and without C2Hx (12 wks post-injury); individual groups were exposed to 28 days of: 1) normoxia; 2) daily acute IH (dAIH28: 10, 5 min 10.5% O2 episodes per day; 5 min normoxic intervals); 3) mild chronic IH (IH28-5/5: 5 min 10.5% O2 episodes; 5 min intervals; 8 h/day); or 4) moderate chronic IH (IH28-2/2: 2 min 10.5% O2 episodes; 2 min intervals; 8 h/day), simulating IH experienced during moderate sleep apnea. After C2Hx, the number of ipsilateral serotonergic structures was decreased in both motor nuclei, regardless of IH protocol. However, serotonergic structures were larger after C2Hx in both motor nuclei, and total serotonin immunolabeling area was increased in the phrenic motor nucleus but reduced in the intercostal motor nucleus. Both chronic IH protocols increased serotonin structure size and total area in the phrenic motor nuclei of uninjured rats, but had no detectable effects after C2Hx. Although the functional implications of fewer but larger serotonergic structures are unclear, we confirm that serotonergic reinnervation is substantial following injury, but IH does not affect the extent of reinnervation.
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Affiliation(s)
- Marissa C Ciesla
- Breathing Research and Therapeutics Center, Department of Physical Therapy & McKnight Brain Institute, University of Florida, FL 32610, USA
| | - Yasin B Seven
- Breathing Research and Therapeutics Center, Department of Physical Therapy & McKnight Brain Institute, University of Florida, FL 32610, USA
| | - Latoya L Allen
- Breathing Research and Therapeutics Center, Department of Physical Therapy & McKnight Brain Institute, University of Florida, FL 32610, USA
| | - Kristin N Smith
- Breathing Research and Therapeutics Center, Department of Physical Therapy & McKnight Brain Institute, University of Florida, FL 32610, USA
| | - Zachary A Asa
- Breathing Research and Therapeutics Center, Department of Physical Therapy & McKnight Brain Institute, University of Florida, FL 32610, USA
| | - Alec K Simon
- Breathing Research and Therapeutics Center, Department of Physical Therapy & McKnight Brain Institute, University of Florida, FL 32610, USA
| | - Ashley E Holland
- Breathing Research and Therapeutics Center, Department of Physical Therapy & McKnight Brain Institute, University of Florida, FL 32610, USA
| | - Juliet V Santiago
- Breathing Research and Therapeutics Center, Department of Physical Therapy & McKnight Brain Institute, University of Florida, FL 32610, USA
| | - Kelsey Stefan
- Breathing Research and Therapeutics Center, Department of Physical Therapy & McKnight Brain Institute, University of Florida, FL 32610, USA
| | - Ashley Ross
- Breathing Research and Therapeutics Center, Department of Physical Therapy & McKnight Brain Institute, University of Florida, FL 32610, USA
| | - Elisa J Gonzalez-Rothi
- Breathing Research and Therapeutics Center, Department of Physical Therapy & McKnight Brain Institute, University of Florida, FL 32610, USA
| | - Gordon S Mitchell
- Breathing Research and Therapeutics Center, Department of Physical Therapy & McKnight Brain Institute, University of Florida, FL 32610, USA.
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12
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Perim RR, Kubilis PS, Seven YB, Mitchell GS. Hypoxia-induced hypotension elicits adenosine-dependent phrenic long-term facilitation after carotid denervation. Exp Neurol 2020; 333:113429. [PMID: 32735873 DOI: 10.1016/j.expneurol.2020.113429] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 07/06/2020] [Accepted: 07/25/2020] [Indexed: 11/19/2022]
Abstract
Moderate acute intermittent hypoxia (AIH) elicits a persistent, serotonin-dependent increase in phrenic amplitude, known as phrenic long-term facilitation (pLTF). Although pLTF was originally demonstrated by carotid sinus nerve stimulation, AIH still elicits residual pLTF in carotid denervated (CBX) rats via a distinct, but unknown mechanism. We hypothesized that exaggerated hypoxia-induced hypotension after carotid denervation leads to greater spinal tissue hypoxia and extracellular adenosine accumulation, thereby triggering adenosine 2A receptor (A2A)-dependent pLTF. Phrenic activity, arterial pressure and spinal tissue oxygen pressure were measured in anesthetized CBX rats. Exaggerated hypoxia-induced hypotension after CBX was prevented via intravenous phenylephrine; without the hypotension, spinal tissue hypoxia during AIH was normalized, and residual pLTF was no longer observed. Spinal A2A (MSX-3), but not serotonin 2 receptor (5-HT2) inhibition (ketanserin), abolished residual pLTF in CBX rats. Thus, pLTF regulation may be altered in conditions impairing sympathetic activity and arterial pressure regulation, such as spinal cord injury.
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Affiliation(s)
- Raphael R Perim
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Paul S Kubilis
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Yasin B Seven
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Gordon S Mitchell
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA.
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13
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Ciesla MB, Seven YB, Allen LL, Smith K, Asa Z, Simon A, Holland A, Santiago J, Stefan K, Ross A, Gonzalez-Rothi EJ, Mitchell GS. Recovery of Serotonergic Innervation in Spinal Motor Nuclei below Cervical Spinal Injury: Effects of Intermittent Hypoxia. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.02574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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14
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Oberto JR, Ciesla MC, Seven YB, Kelly MN, Allen LL, Smith K, Asa Z, Simon A, Holland A, Santiago J, Stefan K, Ross A, Gonzalez-Rothi EJ, Mitchell GS. BDNF in Phrenic Motor Neurons: Effects of Cervical Spinal Injury and Intermittent Hypoxia. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.03557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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15
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Sajjadi E, Ehrbar JG, Seven YB, Dickinson PG, Mitchell GS, Smith BK. Respiratory Muscle Activity during Maximal Efforts in ALS Patients and Healthy Controls. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.06199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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16
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Seven YB, Simon AK, Sajjadi E, Zwick A, Satriotomo I, Mitchell GS. Adenosine 2A receptor inhibition protects phrenic motor neurons from cell death induced by protein synthesis inhibition. Exp Neurol 2019; 323:113067. [PMID: 31629857 DOI: 10.1016/j.expneurol.2019.113067] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 09/12/2019] [Accepted: 09/18/2019] [Indexed: 01/31/2023]
Abstract
Respiratory motor neuron survival is critical for maintenance of adequate ventilation and airway clearance, preventing dependence to mechanical ventilation and respiratory tract infections. Phrenic motor neurons are highly vulnerable in rodent models of motor neuron disease versus accessory inspiratory motor pools (e.g. intercostals, scalenus). Thus, strategies that promote phrenic motor neuron survival when faced with disease and/or toxic insults are needed to help preserve breathing ability, airway defense and ventilator independence. Adenosine 2A receptors (A2A) are emerging as a potential target to promote neuroprotection, although their activation can have both beneficial and pathogenic effects. Since the role of A2A receptors in the phrenic motor neuron survival/death is not known, we tested the hypothesis that A2A receptor antagonism promotes phrenic motor neuron survival and preserves diaphragm function when faced with toxic, neurodegenerative insults that lead to phrenic motor neuron death. We utilized a novel neurotoxic model of respiratory motor neuron death recently developed in our laboratory: intrapleural injections of cholera toxin B subunit (CtB) conjugated to the ribosomal toxin, saporin (CtB-Saporin). We demonstrate that intrapleural CtB-Saporin causes: 1) profound phrenic motor neuron death (~5% survival); 2) ~7-fold increase in phrenic motor neuron A2A receptor expression prior to cell death; and 3) diaphragm muscle paralysis (inactive in most rats; ~7% residual diaphragm EMG amplitude during room air breathing). The A2A receptor antagonist istradefylline given after CtB-Saporin: 1) reduced phrenic motor neuron death (~20% survival) and 2) preserved diaphragm EMG activity (~46%). Thus, A2A receptors contribute to neurotoxic phrenic motor neuron death, an effect mitigated by A2A receptor antagonism.
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Affiliation(s)
- Yasin B Seven
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Alec K Simon
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Elaheh Sajjadi
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Amanda Zwick
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Irawan Satriotomo
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Gordon S Mitchell
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA.
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17
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Affiliation(s)
- Elif S. Seven
- Department of ChemistryUniversity of MiamiCoral GablesFL
| | - Yiqun Zhou
- Department of ChemistryUniversity of MiamiCoral GablesFL
| | - Yasin B. Seven
- McKnight Brain InstituteUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Gordon S. Mitchell
- McKnight Brain InstituteUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
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18
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Smith K, Allen LL, Seven YB, Ciesla M, Asa Z, Simon A, Holland A, Santiago J, Stefan K, Ross A, Gonzalez‐Rothi EJ, Mitchell GS. Neurochemical Plasticity of Phrenic Motor Neuron Adenosine 2A Receptors: Effects of Cervical Spinal Injury and Intermittent Hypoxia. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.844.9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Kristin Smith
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Latoya L. Allen
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
- Department of NeuroscienceUniversity of FloridaGainesvilleFL
| | - Yasin B. Seven
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Marissa Ciesla
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
- Department of NeuroscienceUniversity of FloridaGainesvilleFL
| | - Zachary Asa
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Alec Simon
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Ashley Holland
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Juliet Santiago
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Kelsey Stefan
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Ashley Ross
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Elisa J. Gonzalez‐Rothi
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
| | - Gordon S. Mitchell
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- Department of Physical TherapyUniversity of FloridaGainesvilleFL
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19
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Ciesla MC, Seven YB, Allen LL, Smith KN, Asa ZA, Iskandar BJ, Gonzalez‐Rothi EJ, Mitchell GS. Impact of Dietary Folate on Respiratory Recovery after Cervical SCI. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.731.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Marissa C. Ciesla
- NeuroscienceUniversity of FloridaGainesvilleFL
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Yasin B. Seven
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Latoya L. Allen
- NeuroscienceUniversity of FloridaGainesvilleFL
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Kristin N. Smith
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Zachary A. Asa
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | | | - Elisa J. Gonzalez‐Rothi
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Gordon S. Mitchell
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
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20
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Zwick A, Allen LL, Seven YB, Ciesla MC, Smith K, Asa Z, Simon A, Holland A, Santiago J, Stefan K, Ross A, Gonzalez‐Rothi EJ, Mitchell GS. Adenosine A
1
Receptor Expression on Phrenic Motor Neurons after Cervical Spinal Injury and Different Intermittent Hypoxia Exposures. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.844.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Amanda Zwick
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Latoya L. Allen
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- NeuroscienceUniversity of FloridaGainesvilleFL
| | - Yasin B. Seven
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Marissa C. Ciesla
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- NeuroscienceUniversity of FloridaGainesvilleFL
| | - Kristin Smith
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Zachary Asa
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Alec Simon
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Ashley Holland
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Juliet Santiago
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Kelsey Stefan
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Ashley Ross
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Elisa J. Gonzalez‐Rothi
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Gordon S. Mitchell
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
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21
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Ross A, Kelly MN, Allen LL, Seven YB, Mitchell GS. DARPP‐32 and Cdk5 Expression in the Ventral Cervical Spinal Cord of Rats. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.844.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Ashley Ross
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Mia N. Kelly
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Latoya L. Allen
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- NeuroscienceUniversity of FloridaGainesvilleFL
| | - Yasin B. Seven
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Gordon S. Mitchell
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
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22
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Seven YB, Allen LL, Tadjalli A, Zwick A, El‐Chami M, Perim RR, Gonzalez‐Rothi EJ, Mitchell GS. Adenosine 2A Receptor Antagonism in Acute Cervical Contusion/Compression Injury Preserves Serotonin‐Dependent Phrenic Motor Plasticity. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.843.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Yasin B. Seven
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Latoya L. Allen
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
- NeuroscienceUniversity of FloridaGainesvilleFL
| | - Arash Tadjalli
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Amanda Zwick
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Mohamad El‐Chami
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Raphael R. Perim
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Elisa J. Gonzalez‐Rothi
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Gordon S. Mitchell
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
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23
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Sajjadi E, Seven YB, Simon AK, Zwick A, Satriotomo I, Mitchell GS. Adenosine 2A Receptor Inhibition Promotes Neuroprotection Following Toxic Insult to Phrenic Motor Neurons. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.844.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Elaheh Sajjadi
- Physical TherapyUniversity of Florida and McKnight Brain InstituteGainesvilleFL
| | - Yasin B Seven
- Physical TherapyUniversity of Florida and McKnight Brain InstituteGainesvilleFL
| | - Alec K Simon
- Physical TherapyUniversity of Florida and McKnight Brain InstituteGainesvilleFL
| | - Amanda Zwick
- Physical TherapyUniversity of Florida and McKnight Brain InstituteGainesvilleFL
| | - Irawan Satriotomo
- Physical TherapyUniversity of Florida and McKnight Brain InstituteGainesvilleFL
| | - Gordon S Mitchell
- Physical TherapyUniversity of Florida and McKnight Brain InstituteGainesvilleFL
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Allen LL, Seven YB, Ciesla MC, Smith K, Asa Z, Simon A, Holland A, Santiago J, Stefan K, Ross A, Gonzalez‐Rothi EJ, Mitchell GS. Neurochemical Plasticity of Serotonin Receptors on Phrenic Motor Neurons: Effects of Cervical Spinal Injury and Intermittent Hypoxia. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.844.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Latoya L. Allen
- Physical TherapyUniversity of FloridaGainesvilleFL
- NeuroscienceUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Yasin B. Seven
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Marissa C. Ciesla
- Physical TherapyUniversity of FloridaGainesvilleFL
- NeuroscienceUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Kristin Smith
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Zachary Asa
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Alec Simon
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Ashley Holland
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Juliet Santiago
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Kelsey Stefan
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Ashley Ross
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Elisa J. Gonzalez‐Rothi
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Gordon S. Mitchell
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
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Allen LL, Seven YB, Baker TL, Mitchell GS. Cervical spinal contusion alters Na +-K +-2Cl- and K +-Cl- cation-chloride cotransporter expression in phrenic motor neurons. Respir Physiol Neurobiol 2019; 261:15-23. [PMID: 30590202 PMCID: PMC6939623 DOI: 10.1016/j.resp.2018.12.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Revised: 12/21/2018] [Accepted: 12/23/2018] [Indexed: 12/11/2022]
Abstract
Spinal chloride-dependent synaptic inhibition is critical in regulating breathing and requires neuronal chloride gradients established by cation-chloride cotransporters Na+-K+-2Cl- (NKCC1) and K+-Cl- (KCC2). Spinal transection disrupts NKCC1/KCC2 balance, diminishing chloride gradients in neurons below injury, contributing to spasticity and chronic pain. It is not known if similar disruptions in NKCC1/KCC2 balance occur in respiratory motor neurons after incomplete cervical contusion (C2SC). We hypothesized that C2SC disrupts NKCC1/KCC2 balance in phrenic motor neurons. NKCC1 and KCC2 immunoreactivity was assessed in CtB-positive phrenic motor neurons. Five weeks post-C2SC: 1) neither membrane-bound nor cytosolic NKCC1 expression were significantly changed, although the membrane/cytosolic ratio increased, consistent with net chloride influx; and 2) both membrane and cytosolic KCC2 expression increased, although the membrane/cytosolic ratio decreased, consistent with net chloride efflux. Thus, contrary to our original hypothesis, complex shifts in NKCC1/KCC2 balance occur post-C2SC. The functional significance of these changes remains unclear.
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Affiliation(s)
- Latoya L Allen
- Department of Physical Therapy, University of Florida, Gainesville, FL 32611 USA; Department of Neuroscience, University of Florida, Gainesville, FL 32610 USA; Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL 32611 USA
| | - Yasin B Seven
- Department of Physical Therapy, University of Florida, Gainesville, FL 32611 USA; Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL 32611 USA
| | - Tracy L Baker
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53706 USA
| | - Gordon S Mitchell
- Department of Physical Therapy, University of Florida, Gainesville, FL 32611 USA; Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL 32611 USA.
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Seven YB, Mitchell GS. Mechanisms of compensatory plasticity for respiratory motor neuron death. Respir Physiol Neurobiol 2019; 265:32-39. [PMID: 30625378 DOI: 10.1016/j.resp.2019.01.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 12/22/2018] [Accepted: 01/03/2019] [Indexed: 02/06/2023]
Abstract
Respiratory motor neuron death arises from multiple neurodegenerative and traumatic neuromuscular disorders. Despite motor neuron death, compensatory mechanisms minimize its functional impact by harnessing intrinsic mechanisms of compensatory respiratory plasticity. However, the capacity for compensation eventually reaches limits and pathology ensues. Initially, challenges to the system such as increased metabolic demand reveal sub-clinical pathology. With greater motor neuron loss, the eventual result is de-compensation, ventilatory failure, ventilator dependence and then death. In this brief review, we discuss recent advances in our understanding of mechanisms giving rise to compensatory respiratory plasticity in response to respiratory motor neuron death including: 1) increased central respiratory drive, 2) plasticity in synapses on spared phrenic motor neurons, 3) enhanced neuromuscular transmission and 4) shifts in respiratory muscle utilization from more affected to less affected motor pools. Some of these compensatory mechanisms may prolong breathing function, but hasten the demise of surviving motor neurons. Improved understanding of these mechanisms and their impact on survival of spared motor neurons will guide future efforts to develop therapeutic interventions that preserve respiratory function with neuromuscular injury/disease.
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Affiliation(s)
- Yasin B Seven
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, 32610, USA
| | - Gordon S Mitchell
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, 32610, USA.
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Rayaprolu S, Seven YB, Howard J, Duffy C, Altshuler M, Moloney C, Giasson BI, Lewis J. Partial loss of ATP13A2 causes selective gliosis independent of robust lipofuscinosis. Mol Cell Neurosci 2018; 92:17-26. [PMID: 29859891 DOI: 10.1016/j.mcn.2018.05.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 05/25/2018] [Accepted: 05/30/2018] [Indexed: 02/05/2023] Open
Abstract
Loss-of-function mutations in ATP13A2 are associated with three neurodegenerative diseases: a rare form of Parkinson's disease termed Kufor-Rakeb syndrome (KRS), a lysosomal storage disorder termed neuronal ceroid lipofuscinosis (NCL), and a form of hereditary spastic paraplegia (HSP). Furthermore, recent data suggests that heterozygous carriers of mutations in ATP13A2 may confer risk for the development of Parkinson's disease, similar to the association of mutations in glucocerebrosidase (GBA) with both Parkinson's disease and Gaucher's disease, a lysosomal storage disorder. Mutations in ATP13A2 are generally thought to be loss of function; however, the lack of human autopsy tissue has prevented the field from determining the pathological consequences of losing functional ATP13A2. We and others have previously neuropathologically characterized mice completely lacking murine Atp13a2, demonstrating the presence of lipofuscinosis within the brain - a key feature of NCL, one of the diseases to which ATP13A2 mutations have been linked. To determine if loss of one functional Atp13a2 allele can serve as a risk factor for disease, we have now assessed heterozygous Atp13a2 knockout mice for key features of NCL. In this report, we demonstrate that loss of one functional Atp13a2 allele leads to both microgliosis and astrocytosis in multiple brain regions compared to age-matched controls; however, levels of lipofuscin were only modestly elevated in the cortex of heterozygous Atp13a2 knockout mice over controls. This data suggests the possibility that partial loss of ATP13A2 causes inflammatory changes within the brain which appear to be independent of robust lipofuscinosis. This study suggests that heterozygous loss-of-function mutations in ATP13A2 are likely harmful and indicates that glial involvement in the disease process may be an early event that positions the CNS for subsequent disease development.
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Affiliation(s)
- Sruti Rayaprolu
- Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL 32610, USA; Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA
| | - Yasin B Seven
- McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA; Department of Physical Therapy, University of Florida, Gainesville, FL 32610, USA; Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL 32610, USA
| | - John Howard
- Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL 32610, USA; Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA
| | - Colin Duffy
- Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL 32610, USA; Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA
| | - Marcelle Altshuler
- Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL 32610, USA; Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA
| | - Christina Moloney
- Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL 32610, USA; Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA
| | - Benoit I Giasson
- Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL 32610, USA; Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA; McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA
| | - Jada Lewis
- Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL 32610, USA; Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA; McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA.
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Seven YB, Perim RR, Hobson OR, Simon AK, Tadjalli A, Mitchell GS. Phrenic motor neuron adenosine 2A receptors elicit phrenic motor facilitation. J Physiol 2018; 596:1501-1512. [PMID: 29388230 PMCID: PMC5899988 DOI: 10.1113/jp275462] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 01/25/2018] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS Although adenosine 2A (A2A ) receptor activation triggers specific cell signalling cascades, the ensuing physiological outcomes depend on the specific cell type expressing these receptors. Cervical spinal adenosine 2A (A2A ) receptor activation elicits a prolonged facilitation in phrenic nerve activity, which was nearly abolished following intrapleural A2A receptor siRNA injections. A2A receptor siRNA injections selectively knocked down A2A receptors in cholera toxin B-subunit-identified phrenic motor neurons, sparing cervical non-phrenic motor neurons. Collectively, our results support the hypothesis that phrenic motor neurons express the A2A receptors relevant to A2A receptor-induced phrenic motor facilitation. Upregulation of A2A receptor expression in the phrenic motor neurons per se may potentially be a useful approach to increase phrenic motor neuron excitability in conditions such as spinal cord injury. ABSTRACT Cervical spinal adenosine 2A (A2A ) receptor activation elicits a prolonged increase in phrenic nerve activity, an effect known as phrenic motor facilitation (pMF). The specific cervical spinal cells expressing the relevant A2A receptors for pMF are unknown. This is an important question since the physiological outcome of A2A receptor activation is highly cell type specific. Thus, we tested the hypothesis that the relevant A2A receptors for pMF are expressed in phrenic motor neurons per se versus non-phrenic neurons of the cervical spinal cord. A2A receptor immunostaining significantly colocalized with NeuN-positive neurons (89 ± 2%). Intrapleural siRNA injections were used to selectively knock down A2A receptors in cholera toxin B-subunit-labelled phrenic motor neurons. A2A receptor knock-down was verified by a ∼45% decrease in A2A receptor immunoreactivity within phrenic motor neurons versus non-targeting siRNAs (siNT; P < 0.05). There was no evidence for knock-down in cervical non-phrenic motor neurons. In rats that were anaesthetized, subjected to neuromuscular blockade and ventilated, pMF induced by cervical (C3-4) intrathecal injections of the A2A receptor agonist CGS21680 was greatly attenuated in siA2A (21%) versus siNT treated rats (147%; P < 0.01). There were no significant effects of siA2A on phrenic burst frequency. Collectively, our results support the hypothesis that phrenic motor neurons express the A2A receptors relevant to A2A receptor-induced pMF.
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Affiliation(s)
- Yasin B. Seven
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain InstituteUniversity of FloridaGainesvilleFL32610USA
| | - Raphael R. Perim
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain InstituteUniversity of FloridaGainesvilleFL32610USA
| | - Orinda R. Hobson
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain InstituteUniversity of FloridaGainesvilleFL32610USA
| | - Alec K. Simon
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain InstituteUniversity of FloridaGainesvilleFL32610USA
| | - Arash Tadjalli
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain InstituteUniversity of FloridaGainesvilleFL32610USA
| | - Gordon S. Mitchell
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain InstituteUniversity of FloridaGainesvilleFL32610USA
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Gonzalez‐Rothi EJ, Allen LA, Santiago‐Moreno J, Ciesla MC, Asa ZA, Smith KN, Tadjalli A, Perim R, Santiago JV, Holland AE, Stefan KA, Ross A, Satriotomo I, Kelly MN, Simon AK, Poirier AE, Seven YB, Yarrow JF, Mitchell GS. Long‐term Delivery of “Low Dose” Repetitive Intermittent Hypoxia is Not Associated with Detectable Pathology. FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.625.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Elisa Janine Gonzalez‐Rothi
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Latoya A. Allen
- Physical TherapyUniversity of FloridaGainesvilleFL
- NeuroscienceUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Juan Santiago‐Moreno
- NeuroscienceUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Marissa C. Ciesla
- Physical TherapyUniversity of FloridaGainesvilleFL
- NeuroscienceUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | | | | | | | - Raphael Perim
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | | | | | | | - Ashley Ross
- Physical TherapyUniversity of FloridaGainesvilleFL
| | - Irawan Satriotomo
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Mia N. Kelly
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Alec K. Simon
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | | | - Yasin B. Seven
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
| | - Joshua F. Yarrow
- Center of Innovation on Disability and Rehabilitation ResearchMalcolm Randall VA Medical CenterGainesvilleFL
| | - Gordon S. Mitchell
- Physical TherapyUniversity of FloridaGainesvilleFL
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleFL
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Seven YB, Nichols NL, Kelly MN, Hobson OR, Satriotomo I, Mitchell GS. Compensatory plasticity in diaphragm and intercostal muscle utilization in a rat model of ALS. Exp Neurol 2017; 299:148-156. [PMID: 29056361 DOI: 10.1016/j.expneurol.2017.10.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 07/29/2017] [Accepted: 10/17/2017] [Indexed: 12/13/2022]
Abstract
In SOD1G93A transgenic rat model of ALS, breathing capacity is preserved until late in disease progression despite profound respiratory motor neuron (MN) cell death. To explore mechanisms preserving breathing capacity, we assessed inspiratory EMG activity in diaphragm and external intercostal T2 (EIC2) and T5 (EIC5) muscles in anesthetized SOD1G93A rats at disease end-stage (20% decrease in body mass). We hypothesized that despite significant phrenic motor neuron loss and decreased phrenic nerve activity, diaphragm electrical activity and trans-diaphragmatic pressure (Pdi) are maintained to sustain ventilation. We alternatively hypothesized that EIC activity is enhanced, compensating for impaired diaphragm function. Diaphragm, EIC2 and EIC5 muscle EMGs and Pdi were measured in urethane-anesthetized, spontaneously breathing female SOD1G93A rats versus wild-type littermates during normoxia (arterial PO2 ~90mmHg, PCO2 ~45mmHg), maximal chemoreceptor stimulation (MCS: 10.5% O2/7% CO2), spontaneous augmented breaths and sustained tracheal occlusion. Phrenic MNs were counted in C3-5; T2 and T5 ventrolateral MNs were counted. In end-stage SOD1G93A rats, 29% of phrenic MNs survived (vs. wild-type), yet integrated diaphragm EMG amplitude was normal. Nevertheless, maximal Pdi decreased ~30% vs. wild type (p<0.01) and increased esophageal to gastric pressure ratio (p<0.05), consistent with persistent diaphragm weakness. Despite major T2 and T5 MN death, integrated EIC2 (100% greater than wild type) and EIC5 (300%) EMG amplitudes were increased in mutant rats during normoxia (p<0.01), possibly compensating for decreased Pdi. Thus, despite significant phrenic MN loss, diaphragm EMG activity is maintained; in contrast, Pdi was not, suggesting diaphragm dysfunction. Presumably, increased EIC EMG activity compensated for persistent diaphragm weakness. These adjustments contribute to remarkable preservation of breathing ability despite major respiratory motor neuron death and diaphragm dysfunction.
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Affiliation(s)
- Yasin B Seven
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, USA; Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Nicole L Nichols
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, USA
| | - Mia N Kelly
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Orinda R Hobson
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Irawan Satriotomo
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Gordon S Mitchell
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, USA; Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA.
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Seven YB, Mantilla CB, Sieck GC. Recruitment of rat diaphragm motor units across motor behaviors with different levels of diaphragm activation. J Appl Physiol (1985) 2014; 117:1308-16. [PMID: 25257864 DOI: 10.1152/japplphysiol.01395.2013] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Phrenic motor neurons are recruited across a range of motor behaviors to generate varying levels of diaphragm muscle (DIAm) force. We hypothesized that DIAm motor units are recruited in a fixed order across a range of motor behaviors of varying force levels, consistent with the Henneman Size Principle. Single motor unit action potentials and compound DIAm EMG activities were recorded in anesthetized, neurally intact rats across different motor behaviors, i.e., eupnea, hypoxia-hypercapnia (10% O2 and 5% CO2), deep breaths, sustained airway occlusion, and sneezing. Central drive [estimated by root-mean-squared (RMS) EMG value 75 ms after the onset of EMG activity (RMS75)], recruitment delay, and onset discharge frequencies were similar during eupnea and hypoxia-hypercapnia. Compared with eupnea, central drive increased (∼25%) during deep breaths, and motor units were recruited ∼12 ms earlier (P < 0.01). During airway occlusion, central drive was ∼3 times greater, motor units were recruited ∼30 ms earlier (P < 0.01), and motor unit onset discharge frequencies were significantly higher (P < 0.01). Recruitment order of motor unit pairs observed during eupnea was maintained for 98%, 87%, and 84% of the same pairs recorded during hypoxia-hypercapnia, deep breaths, and airway occlusion, respectively. Reversals in motor unit recruitment order were observed primarily if motor unit pairs were recruited <20 ms apart. These results are consistent with DIAm motor unit recruitment order being determined primarily by the intrinsic size-dependent electrophysiological properties of phrenic motor neurons.
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Affiliation(s)
- Yasin B Seven
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and
| | - Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
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Abstract
Motor units are the final element of neuromotor control. In manner analogous to the organization of neuromotor control in other skeletal muscles, diaphragm motor units comprise phrenic motoneurons located in the cervical spinal cord that innervate the diaphragm muscle, the main inspiratory muscle in mammals. Diaphragm motor units play a primary role in sustaining ventilation but are also active in other nonventilatory behaviors, including coughing, sneezing, vomiting, defecation, and parturition. Diaphragm muscle fibers comprise all fiber types. Thus, diaphragm motor units display substantial differences in contractile and fatigue properties, but importantly, properties of the motoneuron and muscle fibers within a motor unit are matched. As in other skeletal muscles, diaphragm motor units are recruited in order such that motor units that display greater fatigue resistance are recruited earlier and more often than more fatigable motor units. The properties of the motor unit population are critical determinants of the function of a skeletal muscle across the range of possible motor tasks. Accordingly, fatigue-resistant motor units are sufficient to generate the forces necessary for ventilatory behaviors, whereas more fatigable units are only activated during expulsive behaviors important for airway clearance. Neuromotor control of diaphragm motor units may reflect selective inputs from distinct pattern generators distributed according to the motor unit properties necessary to accomplish these different motor tasks. In contrast, widely distributed inputs to phrenic motoneurons from various pattern generators (e.g., for breathing, coughing, or vocalization) would dictate recruitment order based on intrinsic electrophysiological properties.
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Affiliation(s)
- Carlos B Mantilla
- Department of Anesthesiology, Mayo Clinic College of Medicine, Rochester MN, USA; Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, USA.
| | - Yasin B Seven
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, USA
| | - Gary C Sieck
- Department of Anesthesiology, Mayo Clinic College of Medicine, Rochester MN, USA; Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, USA
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Mantilla CB, Greising SM, Zhan WZ, Seven YB, Sieck GC. Prolonged C2 spinal hemisection-induced inactivity reduces diaphragm muscle specific force with modest, selective atrophy of type IIx and/or IIb fibers. J Appl Physiol (1985) 2012. [PMID: 23195635 DOI: 10.1152/japplphysiol.01122.2012] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The diaphragm muscle (DIAm) is critically responsible for sustaining ventilation. Previously we showed in a commonly used model of spinal cord injury, unilateral spinal cord hemisection at C(2) (SH), that there are minimal changes to muscle fiber cross-sectional area (CSA) and fiber type distribution following 14 days of SH-induced ipsilateral DIAm inactivity. In the present study, effects of long-term SH-induced inactivity on DIAm fiber size and force were examined. We hypothesized that prolonged inactivity would not result in substantial DIAm atrophy or force loss. Adult rats were randomized to control or SH groups (n = 34 total). Chronic bilateral DIAm electromyographic (EMG) activity was monitored during resting breathing. Minimal levels of spontaneous recovery of ipsilateral DIAm EMG activity were evident in 42% of SH rats (<25% of preinjury root mean square amplitude). Following 42 days of SH, DIAm specific force was reduced 39%. There was no difference in CSA for type I or IIa DIAm fibers in SH rats compared with age, weight-matched controls (classification based on myosin heavy chain isoform expression). Type IIx and/or IIb DIAm fibers displayed a modest 20% reduction in CSA (P < 0.05). Overall, there were no differences in the distribution of fiber types or the contribution of each fiber type to the total DIAm CSA. These data indicate that reduced specific force following prolonged inactivity of the DIAm is associated with modest, fiber type selective adaptations in muscle fiber size and fiber type distribution.
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Affiliation(s)
- Carlos B Mantilla
- Department of Anesthesiology, Mayo Clinic, Collegeof Medicine, Rochester, MN, USA.
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Mantilla CB, Seven YB, Zhan WZ, Sieck GC. Diaphragm motor unit recruitment in rats. Respir Physiol Neurobiol 2010; 173:101-6. [PMID: 20620243 DOI: 10.1016/j.resp.2010.07.001] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2010] [Revised: 06/15/2010] [Accepted: 07/01/2010] [Indexed: 11/18/2022]
Abstract
We hypothesized that considerable force reserve exists for the diaphragm muscle (DIAm) to generate transdiaphragmatic pressures (Pdi) necessary to sustain ventilation. In rats, we measured Pdi and DIAm EMG activity during different ventilatory (eupnea and hypoxia (10% O(2))-hypercapnia (5% CO(2))) and non-ventilatory (airway occlusion and sneezing induced by intranasal capsaicin) behaviors. Compared to maximum Pdi (Pdi(max) generated by bilateral phrenic nerve stimulation), the Pdi generated during eupnea (21+/-2%) and hypoxia-hypercapnia (28+/-4%) were significantly less (p<0.0001) than that generated during airway occlusion (63+/-4%) and sneezing (94+/-5%). The Pdi generated during spontaneous sighs was 62+/-5% of Pdi(max). Relative DIAm EMG activity (root mean square [RMS] amplitude) paralleled the changes in Pdi during different ventilatory and non-ventilatory behaviors (r(2)=0.78; p<0.0001). These results support our hypothesis of a considerable force reserve for the DIAm to accomplish ventilatory behaviors. A model for DIAm motor unit recruitment predicted that ventilatory behaviors would require activation of only fatigue resistant units.
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Affiliation(s)
- Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
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Seven YB, Akalan NE, Yucesoy CA. Effects of back loading on the biomechanics of sit-to-stand motion in healthy children. Hum Mov Sci 2008; 27:65-79. [PMID: 18187221 DOI: 10.1016/j.humov.2007.11.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2006] [Revised: 11/06/2007] [Accepted: 11/08/2007] [Indexed: 11/18/2022]
Affiliation(s)
- Yasin B Seven
- Biomedical Engineering Institute, Boğaziçi University, Istanbul, Turkey
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