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Senger JLB, Rabey KN, Acton L, Lin YHS, Lingrell S, Chan KM, Webber CA. Recovering the regenerative potential in chronically injured nerves by using conditioning electrical stimulation. J Neurosurg 2022; 136:1442-1454. [PMID: 34653977 DOI: 10.3171/2021.4.jns21398] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/28/2021] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Chronically injured nerves pose a significant clinical challenge despite surgical management. There is no clinically feasible perioperative technique to upregulate a proregenerative environment in a chronic nerve injury. Conditioning electrical stimulation (CES) significantly improves sensorimotor recovery following acute nerve injury to the tibial and common fibular nerves. The authors' objective was to determine if CES could foster a proregenerative environment following chronically injured nerve reconstruction. METHODS The tibial nerve of 60 Sprague Dawley rats was cut, and the proximal ends were inserted into the hamstring muscles to prevent spontaneous reinnervation. Eleven weeks postinjury, these chronically injured animals were randomized, and half were treated with CES proximal to the tibial nerve cut site. Three days later, 24 animals were killed to evaluate the effects of CES on the expression of regeneration-associated genes at the cell body (n = 18) and Schwann cell proliferation (n = 6). In the remaining animals, the tibial nerve defect was reconstructed using a 10-mm isograft. Length of nerve regeneration was assessed 3 weeks postgrafting (n = 16), and functional recovery was evaluated weekly between 7 and 19 weeks of regeneration (n = 20). RESULTS Three weeks after nerve isograft surgery, tibial nerves treated with CES prior to grafting had a significantly longer length of nerve regeneration (p < 0.01). Von Frey analysis identified improved sensory recovery among animals treated with CES (p < 0.01). Motor reinnervation, assessed by kinetics, kinematics, and skilled motor tasks, showed significant recovery (p < 0.05 to p < 0.001). These findings were supported by immunohistochemical quantification of motor endplate reinnervation (p < 0.05). Mechanisms to support the role of CES in reinvigorating the regenerative response were assessed, and it was demonstrated that CES increased the proliferation of Schwann cells in chronically injured nerves (p < 0.05). Furthermore, CES upregulated regeneration-associated gene expression to increase growth-associated protein-43 (GAP-43), phosphorylated cAMP response element binding protein (pCREB) at the neuronal cell bodies, and upregulated glial fibrillary acidic protein expression in the surrounding satellite glial cells (p < 0.05 to p < 0.001). CONCLUSIONS Regeneration following chronic axotomy is impaired due to downregulation of the proregenerative environment generated following nerve injury. CES delivered to a chronically injured nerve influences the cell body and the nerve to re-upregulate an environment that accelerates axon regeneration, resulting in significant improvements in sensory and motor functional recovery. Percutaneous CES may be a preoperative strategy to significantly improve outcomes for patients undergoing delayed nerve reconstruction.
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Affiliation(s)
- Jenna-Lynn B Senger
- 1Division of Plastic Surgery, Department of Surgery, Faculty of Medicine and Dentistry, University of Alberta
| | - Karyne N Rabey
- 2Division of Anatomy, Department of Surgery, Faculty of Medicine and Dentistry, University of Alberta
- 4Department of Anthropology, Faculty of Science, University of Alberta, Edmonton, Alberta, Canada
| | - Leah Acton
- 2Division of Anatomy, Department of Surgery, Faculty of Medicine and Dentistry, University of Alberta
| | - Ying-Ho S Lin
- 2Division of Anatomy, Department of Surgery, Faculty of Medicine and Dentistry, University of Alberta
| | - Susanne Lingrell
- 2Division of Anatomy, Department of Surgery, Faculty of Medicine and Dentistry, University of Alberta
| | - K Ming Chan
- 3Division of Physical Medicine and Rehabilitation, Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta; and
| | - Christine A Webber
- 2Division of Anatomy, Department of Surgery, Faculty of Medicine and Dentistry, University of Alberta
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Inhibiting cortical protein kinase A in spinal cord injured rats enhances efficacy of rehabilitative training. Exp Neurol 2016; 283:365-74. [PMID: 27401133 DOI: 10.1016/j.expneurol.2016.07.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 04/05/2016] [Accepted: 07/07/2016] [Indexed: 02/08/2023]
Abstract
Elevated levels of the second messenger molecule cyclic adenosine monophosphate (cAMP) are often associated with neuron sprouting and neurite extension (i.e., neuroplasticity). Phosphokinase A (PKA) is a prominent downstream target of cAMP that has been associated with neurite outgrowth. We hypothesized that rehabilitative motor training following spinal cord injuries promotes neuroplasticity via PKA activation. However, in two independent experiments, inhibition of cortical PKA using Rp-cAMPS throughout rehabilitative training robustly increased functional recovery and collateral sprouting of injured corticospinal tract axons, an indicator of neuroplasticity. Consistent with these in vivo findings, using cultured STHdh neurons, we found that Rp-cAMPS had no effect on the phosphorylation of CREB (cAMP response element-binding protein), a prominent downstream target of PKA, even with the concomitant application of the adenylate cyclase agonist forskolin to increase cAMP levels. Conversely, when cAMP levels were increased using the phosphodiesterase inhibitor IBMX, Rp-cAMPS potently inhibited CREB phosphorylation. Taken together, our results suggest that an alternate cAMP dependent pathway was involved in increasing CREB phosphorylation and neuroplasticity. This idea was supported by an in vitro neurite outgrowth assay, where inhibiting PKA did enhance neurite outgrowth. However, when PKA inhibition was combined with inhibition of EPAC2 (exchange protein directly activated by cAMP), another downstream target of cAMP in neurons, neurite outgrowth was significantly reduced. In conclusion, blocking PKA in cortical neurons of spinal cord injured rats increases neurite outgrowth of the lesioned corticospinal tract fibres and the efficacy of rehabilitative training, likely via EPAC.
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Abstract
Sense organ deposits have been described in temporal bones from patients with vestibular neuronitis, Meniere's disease, and benign paroxysmal positional vertigo that are not found in a comparable series of temporal bones without vestibulopathy. Because the recurrent vestibulopathies are caused by vestibular ganglionitis and the vestibulocochlear anastomosis was degenerated in these temporal bones, the deposits may represent the end buds of regenerating efferent axons injured in passage through the vestibular ganglion. Such neural buds have been described with transmission electron microscopy in animals after vestibular nerve transection and in a human temporal bone with endolymphatic hydrops. The buds may be visible by light microscopy, because their size is comparable to that of hair cell nuclei and they stain blue with hematoxylin because of their nucleic acid content. The variable location and size of these deposits (buds) in the labyrinthine sense organs is described to aid in the recognition of efferent system injury in human temporal bones.
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Affiliation(s)
- Richard R Gacek
- Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of South Alabama College of Medicine, Mobile, Alabama 36688-0002, USA
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4
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Singh B, Krishnan A, Micu I, Koshy K, Singh V, Martinez JA, Koshy D, Xu F, Chandrasekhar A, Dalton C, Syed N, Stys PK, Zochodne DW. Peripheral neuron plasticity is enhanced by brief electrical stimulation and overrides attenuated regrowth in experimental diabetes. Neurobiol Dis 2015; 83:134-51. [PMID: 26297317 DOI: 10.1016/j.nbd.2015.08.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 07/20/2015] [Accepted: 08/12/2015] [Indexed: 01/01/2023] Open
Abstract
Peripheral nerve regrowth is less robust than commonly assumed, particularly when it accompanies common clinical scenarios such as diabetes mellitus. Brief extracellular electrical stimulation (ES) facilitates the regeneration of peripheral nerves in part through early activation of the conditioning injury response and BDNF. Here, we explored intrinsic neuronal responses to ES to identify whether ES might impact experimental diabetes, where regeneration is attenuated. ES altered several regeneration related molecules including rises in tubulin, Shh (Sonic hedgehog) and GAP43 mRNAs. ES was associated with rises in neuronal intracellular calcium but its strict linkage to regrowth was not confirmed. In contrast, we identified PI3K-PTEN involvement, an association previously linked to diabetic regenerative impairment. Following ES there were declines in PTEN protein and mRNA both in vitro and in vivo and a PI3K inhibitor blocked its action. In vitro, isolated diabetic neurons were capable of mounting robust responsiveness to ES. In vivo, ES improved electrophysiological and behavioral indices of nerve regrowth in a chronic diabetic model of mice with pre-existing neuropathy. Regrowth of myelinated axons and reinnervation of the epidermis were greater following ES than sham stimulation. Taken together, these findings identify a role for ES in supporting regeneration during the challenges of diabetes mellitus.
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Affiliation(s)
- B Singh
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - A Krishnan
- Division of Neurology, Department of Medicine, Neurosciences and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2B7, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - I Micu
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - K Koshy
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - V Singh
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - J A Martinez
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - D Koshy
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - F Xu
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - A Chandrasekhar
- Division of Neurology, Department of Medicine, Neurosciences and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2B7, Canada
| | - C Dalton
- Electrical and Computer Engineering, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - N Syed
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - P K Stys
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - D W Zochodne
- Division of Neurology, Department of Medicine, Neurosciences and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2B7, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, AB, T2N 4N1, Canada.
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Carmel JB, Young W, Hart RP. Flipping the transcriptional switch from myelin inhibition to axon growth in the CNS. Front Mol Neurosci 2015; 8:34. [PMID: 26236189 PMCID: PMC4505142 DOI: 10.3389/fnmol.2015.00034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 07/06/2015] [Indexed: 01/01/2023] Open
Abstract
Poor regeneration of severed axons in the central nervous system (CNS) limits functional recovery. Regeneration failure involves interplay of inhibitory environmental elements and the growth state of the neuron. To find internal changes in gene expression that might overcome inhibitory environmental cues, we compared several paradigms that allow growth in the inhibitory environment. Conditions that allow axon growth by axotomized and cultured dorsal root ganglion (DRG) neurons on CNS myelin include immaturity (the first few postnatal days), high levels of cyclic adenosine mono phosphate (cAMP), and conditioning with a peripheral nerve lesion before explant. This shift from inhibition to growth depends on transcription. Seeking to understand the transcriptome changes that allow axon growth in the CNS, we collaborated with the Marie Filbin laboratory to identify several mRNAs that are functionally relevant, as determined by gain- and loss-of-function studies. In this Perspective, we review evidence from these experiments and discuss the merits of comparing multiple regenerative paradigms to identify a core transcriptional program for CNS axon regeneration.
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Affiliation(s)
- Jason B Carmel
- Brain Mind Research Institute and Departments of Pediatrics and Neurology, Weill Cornell Medical College New York, NY, USA ; Burke-Cornell Medical Research Institute White Plains, NY, USA
| | - Wise Young
- W.M. Keck Center for Collaborative Neuroscience and the Department of Cell Biology and Neuroscience, Rutgers University Piscataway, NJ, USA
| | - Ronald P Hart
- W.M. Keck Center for Collaborative Neuroscience and the Department of Cell Biology and Neuroscience, Rutgers University Piscataway, NJ, USA
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Christie K, Koshy D, Cheng C, Guo G, Martinez JA, Duraikannu A, Zochodne DW. Intraganglionic interactions between satellite cells and adult sensory neurons. Mol Cell Neurosci 2015; 67:1-12. [DOI: 10.1016/j.mcn.2015.05.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 04/12/2015] [Accepted: 05/11/2015] [Indexed: 11/25/2022] Open
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Ma TC, Barco A, Ratan RR, Willis DE. cAMP-responsive element-binding protein (CREB) and cAMP co-regulate activator protein 1 (AP1)-dependent regeneration-associated gene expression and neurite growth. J Biol Chem 2014; 289:32914-25. [PMID: 25296755 DOI: 10.1074/jbc.m114.582460] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
To regenerate damaged axons, neurons must express a cassette of regeneration-associated genes (RAGs) that increases intrinsic growth capacity and confers resistance to extrinsic inhibitory cues. Here we show that dibutyrl-cAMP or forskolin combined with constitutive-active CREB are superior to either agent alone in driving neurite growth on permissive and inhibitory substrates. Of the RAGs examined, only arginase 1 (Arg1) expression correlated with the increased neurite growth induced by the cAMP/CREB combination, both of which were AP1-dependent. This suggests that cAMP-induced AP1 activity is necessary and interacts with CREB to drive expression of RAGs relevant for regeneration and demonstrates that combining a small molecule (cAMP) with an activated transcription factor (CREB) stimulates the gene expression necessary to enhance axonal regeneration.
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Affiliation(s)
- Thong C Ma
- From the Burke-Cornell Medical Research Institute, White Plains, New York 10605 and
| | - Angel Barco
- the Instituto de Neurociencias de Alicante (Universidad Miguel Hernández de Elche-Consejo Superior de Investigaciones Científicas), San Juan de Alicante, 03550 Alicante, Spain
| | - Rajiv R Ratan
- From the Burke-Cornell Medical Research Institute, White Plains, New York 10605 and
| | - Dianna E Willis
- From the Burke-Cornell Medical Research Institute, White Plains, New York 10605 and
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Singh B, Singh V, Krishnan A, Koshy K, Martinez JA, Cheng C, Almquist C, Zochodne DW. Regeneration of diabetic axons is enhanced by selective knockdown of the PTEN gene. ACTA ACUST UNITED AC 2014; 137:1051-67. [PMID: 24578546 DOI: 10.1093/brain/awu031] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Diabetes mellitus renders both widespread and localized irreversible damage to peripheral axons while imposing critical limitations on their ability to regenerate. A major failure of regenerative capacity thereby imposes a 'double hit' in diabetic patients who frequently develop focal neuropathies such as carpal tunnel syndrome in addition to generalized diffuse polyneuropathy. The mechanisms of diabetic neuron regenerative failure have been speculative and few approaches have offered therapeutic opportunities. In this work we identify an unexpected but major role for PTEN upregulation in diabetic peripheral neurons in attenuating axon regrowth. In chronic diabetic neuropathy models in mice, we identified significant PTEN upregulation in peripheral sensory neurons of messenger RNA and protein compared to littermate controls. In vitro, sensory neurons from these mice responded to PTEN knockdown with substantial rises in neurite outgrowth and branching. To test regenerative plasticity in a chronic diabetic model with established neuropathy, we superimposed an additional focal sciatic nerve crush injury and assessed morphological, electrophysiological and behavioural recovery. Knockdown of PTEN in dorsal root ganglia ipsilateral to the side of injury was achieved using a unique form of non-viral short interfering RNA delivery to the ipsilateral nerve injury site and paw. In comparison with scrambled sequence control short interfering RNA, PTEN short interfering RNA improved several facets of regeneration: recovery of compound muscle action potentials, reflecting numbers of reconnected motor axons to endplates, conduction velocities of both motor and sensory axons, reflecting their maturation during regrowth, numbers and calibre of regenerating myelinated axons distal to the injury site, reinnervation of the skin by unmyelinated epidermal axons and recovery of mechanical sensation. Collectively, these findings identify a novel therapeutic approach, potentially applicable to other neurological conditions requiring specific forms of molecular knockdown, and also identify a unique target, PTEN, to treat diabetic neuroregenerative failure.
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Affiliation(s)
- Bhagat Singh
- Department of Clinical Neurosciences and the Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
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9
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Webber CA, Salame J, Luu GLS, Acharjee S, Ruangkittisakul A, Martinez JA, Jalali H, Watts R, Ballanyi K, Guo GF, Zochodne DW, Power C. Nerve growth factor acts through the TrkA receptor to protect sensory neurons from the damaging effects of the HIV-1 viral protein, Vpr. Neuroscience 2013; 252:512-25. [PMID: 23912036 DOI: 10.1016/j.neuroscience.2013.07.046] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 06/30/2013] [Accepted: 07/22/2013] [Indexed: 01/19/2023]
Abstract
Distal sensory polyneuropathy (DSP) with associated neuropathic pain is the most common neurological disorder affecting patients with human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS). Viral protein R (Vpr) is a neurotoxic protein encoded by HIV-1 and secreted by infected macrophages. Vpr reduces neuronal viability, increases cytosolic calcium and membrane excitability of cultured dorsal root ganglion (DRG) sensory neurons, and is associated with mechanical allodynia in vivo. A clinical trial with HIV/AIDS patients demonstrated that nerve growth factor (NGF) reduced the severity of DSP-associated neuropathic pain, a problem linked to damage to small diameter, potentially NGF-responsive fibers. Herein, the actions of NGF were investigated in our Vpr model of DSP and we demonstrated that NGF significantly protected sensory neurons from the effects of Vpr. Footpads of immunodeficient Vpr transgenic (vpr/RAG1(-/-)) mice displayed allodynia (p<0.05), diminished epidermalinnervation (p<0.01) and reduced NGF mRNA expression (p<0.001) compared to immunodeficient (wildtype/RAG1(-/-)) littermate control mice. Compartmented cultures confirmed recombinant Vpr exposure to the DRG neuronal perikarya decreased distal neurite extension (p<0.01), whereas NGF exposure at these distal axons protected the DRG neurons from the Vpr-induced effect on their cell bodies. NGF prevented Vpr-induced attenuation of the phosphorylated glycogen synthase-3 axon extension pathway and tropomyosin-related kinase A (TrkA) receptor expression in DRG neurons (p<0.05) and it directly counteracted the cytosolic calcium burst caused by Vpr exposure to DRG neurons (p<0.01). TrkA receptor agonist indicated that NGFacted through the TrkA receptor to block the Vpr-mediated decrease in axon outgrowth in neonatal and adult rat and fetal human DRG neurons (p<0.05). Similarly, inhibiting the lower affinity NGF receptor, p75, blocked Vpr's effect on DRG neurons. Overall, NGF/TrkA signaling or p75 receptor inhibition protects somatic sensory neurons exposed to Vpr, thus laying the groundwork for potential therapeutic options for HIV/AIDS patients suffering from DSP.
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Affiliation(s)
- C A Webber
- Division of Anatomy, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
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Singh B, Xu Y, McLaughlin T, Singh V, Martinez JA, Krishnan A, Zochodne DW. Resistance to trophic neurite outgrowth of sensory neurons exposed to insulin. J Neurochem 2012; 121:263-76. [DOI: 10.1111/j.1471-4159.2012.07681.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Zigmond RE. gp130 cytokines are positive signals triggering changes in gene expression and axon outgrowth in peripheral neurons following injury. Front Mol Neurosci 2012; 4:62. [PMID: 22319466 PMCID: PMC3262188 DOI: 10.3389/fnmol.2011.00062] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 12/28/2011] [Indexed: 01/24/2023] Open
Abstract
Adult peripheral neurons, in contrast to adult central neurons, are capable of regeneration after axonal damage. Much attention has focused on the changes that accompany this regeneration in two places, the distal nerve segment (where phagocytosis of axonal debris, changes in the surface properties of Schwann cells, and induction of growth factors and cytokines occur) and the neuronal cell body (where dramatic changes in cell morphology and gene expression occur). The changes in the axotomized cell body are often referred to as the "cell body response." The focus of the current review is a family of cytokines, the glycoprotein 130 (gp130) cytokines, which produce their actions through a common gp130 signaling receptor and which function as injury signals for axotomized peripheral neurons, triggering changes in gene expression and in neurite outgrowth. These cytokines play important roles in the responses of sympathetic, sensory, and motor neurons to injury. The best studied of these cytokines in this context are leukemia inhibitory factor (LIF) and interleukin (IL)-6, but experiments with conditional gp130 knockout animals suggest that other members of this family, not yet determined, are also involved. The primary gp130 signaling pathway shown to be involved is the activation of Janus kinase (JAK) and the transcription factors Signal Transducers and Activators of Transcription (STAT), though other downstream pathways such as mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) may also play a role. gp130 signaling may involve paracrine, retrograde, and autocrine actions of these cytokines. Recent studies suggest that manipulation of this cytokine system can also stimulate regeneration by injured central neurons.
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Affiliation(s)
- Richard E. Zigmond
- Department of Neurosciences, Case Western Reserve University, ClevelandOH, USA
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Blesch A, Lu P, Tsukada S, Alto LT, Roet K, Coppola G, Geschwind D, Tuszynski MH. Conditioning lesions before or after spinal cord injury recruit broad genetic mechanisms that sustain axonal regeneration: superiority to camp-mediated effects. Exp Neurol 2011; 235:162-73. [PMID: 22227059 DOI: 10.1016/j.expneurol.2011.12.037] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 12/14/2011] [Accepted: 12/17/2011] [Indexed: 11/24/2022]
Abstract
Previous studies indicate that peripheral nerve conditioning lesions significantly enhance central axonal regeneration via modulation of cAMP-mediated mechanisms. To gain insight into the nature and temporal dependence of neural mechanisms underlying conditioning lesion effects on central axonal regeneration, we compared the efficacy of peripheral sciatic nerve crush lesions to cAMP elevations (in lumbar dorsal root ganglia) on central sensory axonal regeneration when administered either before or after cervical spinal cord lesions. We found significantly greater effects of conditioning lesions compared to cAMP elevations on central axonal regeneration when combined with cellular grafts at the lesion site and viral neurotrophin delivery; further, these effects persisted whether conditioning lesions were applied prior to or shortly after spinal cord injury. Indeed, conditioning lesions recruited extensively greater sets of genetic mechanisms of possible relevance to axonal regeneration compared to cAMP administration, and sustained these changes for significantly greater time periods through the post-lesion period. We conclude that cAMP-mediated mechanisms account for only a portion of the potency of conditioning lesions on central axonal regeneration, and that recruitment of broader genetic mechanisms can extend the effect and duration of cellular events that support axonal growth.
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Affiliation(s)
- Armin Blesch
- Spinal Cord Injury Center, University Hospital Heidelberg, 69118 Heidelberg, Germany.
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Singh B, Xu QG, Franz CK, Zhang R, Dalton C, Gordon T, Verge VMK, Midha R, Zochodne DW. Accelerated axon outgrowth, guidance, and target reinnervation across nerve transection gaps following a brief electrical stimulation paradigm. J Neurosurg 2011; 116:498-512. [PMID: 22149377 DOI: 10.3171/2011.10.jns11612] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT Regeneration of peripheral nerves is remarkably restrained across transection injuries, limiting recovery of function. Strategies to reverse this common and unfortunate outcome are limited. Remarkably, however, new evidence suggests that a brief extracellular electrical stimulation (ES), delivered at the time of injury, improves the regrowth of motor and sensory axons. METHODS In this work, the authors explored and tested this ES paradigm, which was applied proximal to transected sciatic nerves in mice, and identified several novel and compelling impacts of the approach. Using thy-1 yellow fluorescent protein mice with fluorescent axons that allow serial in vivo tracking of regeneration, the morphological, electrophysiological, and behavioral indices of nerve regrowth were measured. RESULTS The authors show that ES is associated with a 30%-50% improvement in several indices of regeneration: regrowth of axons and their partnered Schwann cells across transection sites, maturation of regenerated fibers in gaps spanning transection zones, and entry of axons into their muscle and cutaneous target zones. In parallel studies, the authors analyzed adult sensory neurons and their response to extracellular ES while plated on a novel microelectrode array construct designed to deliver the identical ES paradigm used in vivo. The ES accelerated neurite outgrowth, supporting the concept of a neuron-autonomous mechanism of action. CONCLUSIONS Taken together, these results support a robust role for brief ES following peripheral nerve injuries in promoting regeneration. Electrical stimulation has a wider repertoire of impact than previously recognized, and its impact in vitro supports the hypothesis that a neuron-specific reprogrammed injury response is recruited by the ES protocol.
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Affiliation(s)
- Bhagat Singh
- Hotchkiss Brain Institute and Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, Alberta, Canada
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Fricke R, Zentis PD, Rajappa LT, Hofmann B, Banzet M, Offenhäusser A, Meffert SH. Axon guidance of rat cortical neurons by microcontact printed gradients. Biomaterials 2011; 32:2070-6. [DOI: 10.1016/j.biomaterials.2010.11.036] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Accepted: 11/18/2010] [Indexed: 10/18/2022]
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Cheng C, Webber CA, Wang J, Xu Y, Martinez JA, Liu WQ, McDonald D, Guo GF, Nguyen MD, Zochodne DW. Activated RHOA and peripheral axon regeneration. Exp Neurol 2008; 212:358-69. [PMID: 18554585 DOI: 10.1016/j.expneurol.2008.04.023] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2008] [Revised: 03/17/2008] [Accepted: 04/08/2008] [Indexed: 11/16/2022]
Abstract
The regeneration of adult peripheral neurons after transection is slow, incomplete and encumbered by severe barriers to proper regrowth. The role of RHOA GTPase has not been examined in this context. We examined the expression, activity and functional role of RHOA GTPase and its ROK effector, inhibitors of regeneration, during peripheral axon outgrowth. We used qRT-PCR, quantitative immunohistochemistry, and assays of RHOA activation to examine expression in sensory neurons of rats with sciatic transection injuries. In vitro, we exposed dissociated adult sensory neurons, not grown on inhibitory substrates, to a RHOA-ROK inhibitor HA-1077 and measured neurite initiation and outgrowth. In vivo, we exposed early regenerating axons and Schwann cells directly to HA-1077 in a conduit connecting the proximal and distal stumps of transected sciatic nerves. Intact adult dorsal root ganglia sensory neurons expressed RHOA and ROK 1 mRNAs and protein and there were rises in RHOA after injury. Activated GTP-bound RHOA, undetectable in intact ganglia, was dramatically upregulated in both neurons and axons after injury. Adult rat sensory neurons in vitro demonstrated a dose-related increase in the initiation of neurite outgrowth, and in the proportion with long neurites when they were exposed to a ROK antagonist. Regenerative bridges that were directly exposed to the ROK inhibitor had a dose-related rise in the extent and distance of in vivo axon and partnered Schwann cell regrowth within them. RHOA activation and signaling are features of adult peripheral axon regeneration within its own milieu, independent of myelin. Inhibition of its activation may benefit peripheral axon lesions.
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Affiliation(s)
- C Cheng
- University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
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Spencer TK, Mellado W, Filbin MT. BDNF activates CaMKIV and PKA in parallel to block MAG-mediated inhibition of neurite outgrowth. Mol Cell Neurosci 2008; 38:110-6. [PMID: 18381242 DOI: 10.1016/j.mcn.2008.02.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Accepted: 02/13/2008] [Indexed: 12/12/2022] Open
Abstract
The environment of the adult CNS prevents axonal regeneration after injury. This inhibition of axonal regeneration can be blocked by elevating cAMP. Previously, we showed that the cAMP pathway can be activated via pre-treatment with neurotrophins and requires activation of several signaling pathways which converge at activation of the transcription factor, CREB. Here, we show that calcium/calmodulin-dependent kinase IV (CaMKIV) is necessary for the neurotrophin-induced phosphorylation of CREB and the block of myelin-mediated inhibition of axonal growth. Pharmacological inhibition of CaMKIV or over-expression of a dominant-negative mutant form of CaMKIV blocks the neurotrophin effect. Interestingly, CaMKIV activation is not necessary if cAMP levels is already elevated. Finally, calcium flux from intracellular stores is necessary for this CaMKIV signaling. These results demonstrate that CaMKIV is another player in the neurotrophin-induced signaling which leads to axonal regeneration and therefore, is a potential target for therapeutic intervention following injury to the adult CNS.
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Affiliation(s)
- Timothy K Spencer
- Department of Biological Sciences, Hunter College, City University of New York, New York, New York 10065, USA.
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17
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Bozkurt A, Brook GA, Moellers S, Lassner F, Sellhaus B, Weis J, Woeltje M, Tank J, Beckmann C, Fuchs P, Damink LO, Schügner F, Heschel I, Pallua N. In Vitro Assessment of Axonal Growth Using Dorsal Root Ganglia Explants in a Novel Three-Dimensional Collagen Matrix. ACTA ACUST UNITED AC 2007; 13:2971-9. [DOI: 10.1089/ten.2007.0116] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Ahmet Bozkurt
- Department of Plastic and Hand Surgery, Burn Center, University Hospital, RWTH Aachen University, Aachen, Germany
| | - Gary A. Brook
- Department of Neurology, University Hospital, RWTH Aachen University, Aachen, Germany
- Institute of Neuropathology, RWTH Aachen University, Aachen, Germany
| | - Sven Moellers
- Department of Neurology, University Hospital, RWTH Aachen University, Aachen, Germany
| | | | - Bernd Sellhaus
- Institute of Neuropathology, RWTH Aachen University, Aachen, Germany
| | - Joachim Weis
- Institute of Neuropathology, RWTH Aachen University, Aachen, Germany
| | | | - Julian Tank
- Department of Plastic and Hand Surgery, Burn Center, University Hospital, RWTH Aachen University, Aachen, Germany
| | - Christina Beckmann
- Department of Plastic and Hand Surgery, Burn Center, University Hospital, RWTH Aachen University, Aachen, Germany
| | - Paul Fuchs
- Department of Plastic and Hand Surgery, Burn Center, University Hospital, RWTH Aachen University, Aachen, Germany
| | | | | | | | - Norbert Pallua
- Department of Plastic and Hand Surgery, Burn Center, University Hospital, RWTH Aachen University, Aachen, Germany
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18
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Geremia NM, Gordon T, Brushart TM, Al-Majed AA, Verge VMK. Electrical stimulation promotes sensory neuron regeneration and growth-associated gene expression. Exp Neurol 2007; 205:347-59. [PMID: 17428474 DOI: 10.1016/j.expneurol.2007.01.040] [Citation(s) in RCA: 286] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Revised: 01/16/2007] [Accepted: 01/19/2007] [Indexed: 12/29/2022]
Abstract
Brief electrical stimulation enhances the regenerative ability of axotomized motor [Nix, W.A., Hopf, H.C., 1983. Electrical stimulation of regenerating nerve and its effect on motor recovery. Brain Res. 272, 21-25; Al-Majed, A.A., Neumann, C.M., Brushart, T.M., Gordon, T., 2000. Brief electrical stimulation promotes the speed and accuracy of motor axonal regeneration. J. Neurosci. 20, 2602-2608] and sensory [Brushart, T.M., Jari, R., Verge, V., Rohde, C., Gordon, T., 2005. Electrical stimulation restores the specificity of sensory axon regeneration. Exp. Neurol. 194, 221-229] neurons. Here we examined the parameter of duration of stimulation on regenerative capacity, including the intrinsic growth programs, of sensory neurons. The effect of 20 Hz continuous electrical stimulation on the number of DRG sensory neurons that regenerate their axons was evaluated following transection and surgical repair of the femoral nerve trunk. Stimulation was applied proximal to the repair site for 1 h, 3 h, 1 day, 7 days or 14 days at the time of nerve repair. Following a 21-day regeneration period, DRG neurons that regenerated axons into the muscle and cutaneous sensory nerve branches were retrogradely identified. Stimulation of 1 h led to a significant increase in DRG neurons regenerating into cutaneous and muscle branches when compared to 0 h (sham) stimulation or longer periods of stimulation. Stimulation for 1 h also significantly increased the numbers of neurons that regenerated axons beyond the repair site 4 days after lesion and was correlated with a significant increase in expression of growth-associated protein 43 (GAP-43) mRNA in the regenerating neurons at 2 days post-repair. An additional indicator of heightened plasticity following 1 h stimulation was elevated expression of brain-derived neurotrophic factor (BDNF). The effect of brief stimulation on enhancing sensory and motoneuron regeneration holds promise for inducing improved peripheral nerve repair in the clinical setting.
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Affiliation(s)
- Nicole M Geremia
- Department of Anatomy and Cell Biology, Cameco MS/Neuroscience Research Center University of Saskatchewan, Saskatoon City Hospital, Saskatchewan, Canada
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19
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Chen MJ, Russo-Neustadt AA. Running exercise- and antidepressant-induced increases in growth and survival-associated signaling molecules are IGF-dependent. Growth Factors 2007; 25:118-31. [PMID: 17852404 DOI: 10.1080/08977190701602329] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
It is known that physical exercise increases hippocampal brain-derived neurotrophic factor (BDNF) mRNA and protein, as well as the expression of several pro-survival signaling proteins and that many of these effects depend on the uptake of peripheral insulin-like growth factor-1 (IGF-1) into the CNS. Because treatment with antidepressants has similar effects upon neurotrophin expression, we investigated whether antidepressant-induced BDNF changes also depend on IGF-1 uptake, as well as whether IGF-1 plays a role in the exercise/antidepressant-induced expression of molecules associated with plasticity/growth (GAP-43, SCG-10) and the intracellular activation of molecules associated with neuronal survival (Akt, ERK1/2). We evaluated the effects of a well known monoamine oxidase inhibitor, tranylcypromine, on BDNF mRNA and protein levels and phospho-Akt and phospho-ERK1/2 immunoreactivity, both with and without systemic blockade of IGF-1 uptake through the use of an antiserum raised against IGF-1. Anti-IGF-1 reversed the increase in BDNF mRNA and protein elicited by exercise as well as tranylcypromine. Exercise also significantly enhanced transcription of axon growth protein, GAP-43, an effect that was also evidenced to be IGF-1-dependent. The combination of exercise-plus-tranylcypromine also increased several cell survival signaling measures, but the BDNF changes associated with the combination treatment appeared to be independent of IGF-1 uptake. Together, these results indicate that the uptake of peripheral IGF-1 in the CNS is essential for antidepressant- as well as exercise-induced enhancement in hippocampal BDNF expression and thus, enhanced hippocampal neuronal survival and plasticity.
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Affiliation(s)
- Michael J Chen
- Department of Biological Sciences, California State University, 5151 State University Drive, Los Angeles, CA 90032, USA.
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20
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Gold BG, Armistead DM, Wang MS. Non-FK506-binding protein-12 neuroimmunophilin ligands increase neurite elongation and accelerate nerve regeneration. J Neurosci Res 2005; 80:56-65. [PMID: 15732051 DOI: 10.1002/jnr.20447] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Neurotrophic activity of neuroimmunophilin ligands (FK506 and its nonimmunosuppressant derivatives) has been assumed to be mediated by the FK506-binding protein-12 (FKBP-12). We recently showed that activity is retained in hippocampal neurons from FKBP-12 knockout mice, indicating that binding to FKBP-12 is not necessary. Here we show that three nonimmunosuppressant FK506 derivatives (V-13,450, V-13,629, and V-13,670) that do not bind FKBP-12 (>12.5 mM affinity) are equipotent to FKBP-12 ligands (FK506, V-10,367, and V-13,449) for increasing neurite elongation in SH-SY5Y cells. One non-FKBP-12 ligand (V-13,670) is also shown to accelerate functional recovery and nerve regeneration in the rat sciatic nerve crush model. Surprisingly, it exhibited an unusual dose-response effect upon oral administration, showing a novel bimodal dose-response for behavioral functional recovery and myelination, but not for axonal size, suggesting both Schwann cell and neuronal targets. Orally active non-FKBP-12 neuroimmunophilin ligands may be useful for the treatment of human neurological disorders without any potential side effects resulting from FKBP-12 binding.
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Affiliation(s)
- Bruce G Gold
- Department of Neurology, Oregon Health and Science University, Portland, Oregon 97239-3098, USA.
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21
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Ahmed MR, Basha SH, Gopinath D, Muthusamy R, Jayakumar R. Initial upregulation of growth factors and inflammatory mediators during nerve regeneration in the presence of cell adhesive peptide-incorporated collagen tubes. J Peripher Nerv Syst 2005; 10:17-30. [PMID: 15703015 DOI: 10.1111/j.1085-9489.2005.10105.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Neurotrophic factors play an important modulatory role in axonal sprouting during nerve regeneration involving the proliferation of hematogenous and Schwann cells in damaged tissue. We have exposed lesioned sciatic nerves to a collagen prosthesis with covalently bonded small cell adhesive peptides Arg-Gly-Asp-Ser (RGDS), Lys-Arg-Asp-Ser (KRDS), and Gly-His-Lys (GHK) to study local production of growth factors and cytokines in the regenerating tissues. Western/enzyme-linked immunosorbent assay (ELISA) studies were performed after 10 days of regeneration, when the tubular prosthesis is filled with fibrous matrix infiltrated by hematogenous cells and proliferating Schwann cells with growth factors produced locally. Regeneration was also analyzed by morphometrical methods after 30 days. The quantification of growth factors and proteins by ELISA revealed that there was an enhanced expression of the neurotrophic factors nerve growth factor (NGF) and neurotrophins (NT-3 and NT-4) in the regenerating tissues. This was further established by Western blot to qualitatively analyze the presence of the antigens in the regenerating tissues. Schwann cells were localized in the regenerating tissues using antibodies against S-100 protein. Other growth factors including growth-associated protein 43 (GAP-43), apolipoprotein E (Apo E), and pro-inflammatory cytokine like interleukin-1alpha (IL-1alpha) expression in the peptide groups were evaluated by ELISA and confirmed by Western blotting. Cell adhesive integrins in the proliferating cells were localized using integrin-alpha V. The combined results suggest that the early phase of regeneration of peripheral nerves in the presence of peptide-incorporated collagen tubes results in the enhanced production of trophic factors by the recruited hematogenous cells and Schwann cells, which in turn help in the secretion of certain vital trophic and tropic factors essential for early regeneration. Furthermore, hematogenous cells recruited within the first 10 days of regeneration help in the production of inflammatory mediators like interleukins that in turn stimulate Schwann cells to produce NGF for axonal growth.
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Affiliation(s)
- Mohamed Rafiuddin Ahmed
- Bio-organic and Neurochemistry Laboratory, Central Leather Research Institute, Adyar, Chennai, India
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22
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O'Driscoll CM, Gorman AM. Hypoxia induces neurite outgrowth in PC12 cells that is mediated through adenosine A2A receptors. Neuroscience 2005; 131:321-9. [PMID: 15708476 DOI: 10.1016/j.neuroscience.2004.11.015] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/15/2004] [Indexed: 11/20/2022]
Abstract
Development of the nervous system is a complex process, involving coordinated regulation of diverse cellular processes including proliferation, differentiation and synaptogenesis. Disturbances to brain development such as pre- and perinatal hypoxia have been linked to behavioural and late onset of neurological disorders. This study examines the effect of hypoxia on neurite outgrowth in PC12 cells. Hypoxia not only caused a rapid induction of neurite outgrowth, but also synergistically enhanced nerve growth factor (NGF)-induced neurite outgrowth up to 24 h. Transactivation of TrkA receptors was ruled out since the TrkA inhibitor K252a did not block hypoxia-induced neurite outgrowth. Adenosine deaminase prevented hypoxia-induced neurite outgrowth indicating that the effect is mediated by adenosine. Use of the specific adenosine A2A receptor agonist CGS21680 and antagonist 8-3(chlorostyryl)caffeine demonstrated that activation of this receptor is critical for hypoxia-induced neurite outgrowth. Hypoxia-induced neurite outgrowth was blocked by the adenylate cyclase inhibitor, MDL-12,330A, indicating a role for activation of this enzyme in the pathway. Hypoxia was further shown to cause a decrease in growth-associated protein (GAP)-43 levels and a lack of induction of betaIII tubulin, in contrast to NGF treatment which resulted in increased cellular levels of both of these proteins. These findings suggest that hypoxia induces neurite outgrowth in PC12 cells via a pathway distinct from that activated by NGF. Thus, exposure to hypoxia at critical stages of development may contribute to aberrant neurite outgrowth and could be a factor in the pathogenesis of certain delayed developmental neurological disorders.
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Affiliation(s)
- C M O'Driscoll
- Department of Biochemistry, National University of Ireland, Galway, Ireland
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23
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Mosevitsky MI. Nerve Ending “Signal” Proteins GAP‐43, MARCKS, and BASP1. INTERNATIONAL REVIEW OF CYTOLOGY 2005; 245:245-325. [PMID: 16125549 DOI: 10.1016/s0074-7696(05)45007-x] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Mechanisms of growth cone pathfinding in the course of neuronal net formation as well as mechanisms of learning and memory have been under intense investigation for the past 20 years, but many aspects of these phenomena remain unresolved and even mysterious. "Signal" proteins accumulated mainly in the axon endings (growth cones and the presynaptic area of synapses) participate in the main brain processes. These proteins are similar in several essential structural and functional properties. The most prominent similarities are N-terminal fatty acylation and the presence of an "effector domain" (ED) that dynamically binds to the plasma membrane, to calmodulin, and to actin fibrils. Reversible phosphorylation of ED by protein kinase C modulates these interactions. However, together with similarities, there are significant differences among the proteins, such as different conditions (Ca2+ contents) for calmodulin binding and different modes of interaction with the actin cytoskeleton. In light of these facts, we consider GAP-43, MARCKS, and BASP1 both separately and in conjunction. Special attention is devoted to a discussion of apparent inconsistencies in results and opinions of different authors concerning specific questions about the structure of proteins and their interactions.
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Affiliation(s)
- Mark I Mosevitsky
- Division of Molecular and Radiation Biophysics, Petersburg Nuclear Physics Institute, Russian Academy of Sciences, 188300 Gatchina Leningrad District, Russian Federation
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24
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Monsul NT, Geisendorfer AR, Han PJ, Banik R, Pease ME, Skolasky RL, Hoffman PN. Intraocular injection of dibutyryl cyclic AMP promotes axon regeneration in rat optic nerve. Exp Neurol 2004; 186:124-33. [PMID: 15026251 DOI: 10.1016/s0014-4886(03)00311-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2002] [Revised: 06/04/2003] [Accepted: 06/13/2003] [Indexed: 11/26/2022]
Abstract
The optic nerve is a CNS pathway containing molecules capable of inhibiting axon elongation. The growth program in embryonic retinal ganglion cell (RGC) neurons enables axons to regenerate in the optic nerve through at least two mechanisms. Namely, high cyclic AMP (cAMP) levels abrogate the ability of CNS molecules to inhibit elongation, and the pattern of gene expression enables axons to undergo rapid, sustained, and lengthy elongation. In adult mammals, recovery of visual function after optic nerve injury is limited by both the death of most RGC neurons and the inability of surviving axons to regenerate. We now report that a single intraocular injection of the membrane-permeable cAMP analogue dibutyryl cAMP (db cAMP) promotes the regeneration of RGC axons in the optic nerves of adult rats, but does not prevent the death of RGC neurons. This regeneration in optic nerves crushed within the orbit (2 mm from the eye) was equally effective either 1 day before or 1 day after db cAMP injection. The number of regenerating axons, which was maximal 14 days after crush, declined with increasing time after injury (i.e., 28, 56, and 112 days) and distance beyond the crush site (i.e., 0.25, 0.5, and 1.0 mm). Thus, db cAMP promotes optic nerve regeneration without increasing the survival of axotomized RGC neurons. Furthermore, since db cAMP does not enable axons to undergo rapid, sustained, and lengthy elongation, strategies that increase survival and promote these changes in elongation may critically complement the ability of db cAMP to promote regeneration.
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Affiliation(s)
- Nicholas T Monsul
- Department of Neurology, The Johns Hopkins School of Medicine, Baltimore, MD 21287-6953, USA
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25
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Anderson KD, Merhege MA, Morin M, Bolognani F, Perrone-Bizzozero NI. Increased expression and localization of the RNA-binding protein HuD and GAP-43 mRNA to cytoplasmic granules in DRG neurons during nerve regeneration. Exp Neurol 2003; 183:100-8. [PMID: 12957493 DOI: 10.1016/s0014-4886(03)00103-1] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The neuronal-specific RNA-binding protein, HuD, binds to a U-rich regulatory element of the 3' untranslated region (3' UTR) of the GAP-43 mRNA and delays the onset of its degradation. We have recently shown that overexpression of HuD in embryonic rat cortical cells accelerated the time course of normal neurite outgrowth and resulted in a twofold increase in GAP-43 mRNA levels. Given this evidence, we sought to investigate the involvement of HuD during nerve regeneration. It is known that HuD protein and GAP-43 mRNA are expressed in the dorsal root ganglia (DRG) of adult rat and that GAP-43 is upregulated in DRG neurons during regeneration. In this study, we examined the expression patterns and levels of HuD and GAP-43 mRNA in DRG neurons following sciatic nerve injury using a combination of in situ hybridization, immunocytochemistry, and quantitative RT-PCR. GAP-43 and HuD expression increased in the ipsilateral DRG during the first 3 weeks of regeneration, with peak values seen at 7 days postcrush. At this time point, the levels of HuD and GAP-43 mRNAs in the ipsilateral DRG increased by twofold and sixfold, respectively, relative to the contralateral DRG. Not only were the temporal patterns of expression of HuD protein and GAP-43 mRNA similar, but also they were found to colocalize in the cytoplasm of DRG neurons. Moreover, both molecules were distributed in cytoplasmic granules containing ribosomal RNA. In conclusion, our results suggest that HuD is involved in the upregulation of GAP-43 expression observed at early stages of peripheral nerve regeneration.
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Affiliation(s)
- K D Anderson
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87131-5223, USA
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Raggo C, Rapin N, Stirling J, Gobeil P, Smith-Windsor E, O'Hare P, Misra V. Luman, the cellular counterpart of herpes simplex virus VP16, is processed by regulated intramembrane proteolysis. Mol Cell Biol 2002; 22:5639-49. [PMID: 12138176 PMCID: PMC133973 DOI: 10.1128/mcb.22.16.5639-5649.2002] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Luman is a human basic leucine zipper transcription factor that, like the herpes simplex virus transcription factor VP16, requires the host cell factor, HCF, for activity. Although both HCF and Luman have been implicated in cell growth, their biological roles have not been clearly defined. Luman conforms to a type II membrane-associated glycoprotein with its carboxyl terminus embedded in cellular membranes and its amino terminus, which contains all its identified functional domains, in the cytoplasm. Here we show that Luman is processed by regulated intramembrane proteolysis (RIP). The site 1 protease (S1P), a Golgi apparatus-resident enzyme responsible for catalyzing the first step in the RIP pathway of the sterol regulatory element binding proteins (SREBPs) and ATF6, may also be involved in the processing of Luman. Thus, processing of Luman was highly stimulated by brefeldin A, a compound that causes the reflux of Golgi apparatus enzymes to the endoplasmic reticulum (ER). In addition, coexpression of Luman with S1P containing a KDEL ER retrieval signal resulted in virtually quantitative cleavage of Luman in the absence of any treatment. Finally, Luman contains a sequence, RQLR, immediately downstream from the transmembrane domain which bears similarity to the consensus S1P cleavage site identified by others. Substitution of arginine residues within this motif abolished S1P cleavage, providing robust evidence that S1P is involved in Luman processing. We observed that following S1P cleavage, the majority of the cleaved Luman was retained in cytoplasmic membranes, indicating that an additional step or enzymes yet to be identified are involved in complete cleavage and release to yield the product which ultimately enters the nuclei of cells.
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Affiliation(s)
- Camilo Raggo
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B4, Canada
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27
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Neumann S, Bradke F, Tessier-Lavigne M, Basbaum AI. Regeneration of sensory axons within the injured spinal cord induced by intraganglionic cAMP elevation. Neuron 2002; 34:885-93. [PMID: 12086637 DOI: 10.1016/s0896-6273(02)00702-x] [Citation(s) in RCA: 418] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The peripheral branch of primary sensory neurons regenerates after injury, but there is no regeneration when their central branch is severed by spinal cord injury. Here we show that microinjection of a membrane-permeable analog of cAMP in lumbar dorsal root ganglia markedly increases the regeneration of injured central sensory branches. The injured axons regrow into the spinal cord lesion, often traversing the injury site. This result mimics the effect of a conditioning peripheral nerve lesion. We also demonstrate that sensory neurons exposed to cAMP in vivo, when subsequently cultured in vitro, show enhanced growth of neurites and an ability to overcome inhibition by CNS myelin. Thus, stimulating cAMP signaling increases the intrinsic growth capacity of injured sensory axons. This approach may be useful in promoting regeneration after spinal cord injury.
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Affiliation(s)
- Simona Neumann
- Department of Anatomy and W.M. Keck Foundation Center for Integrative Neuroscience, University of California, San Francisco, CA 94143, USA
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28
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Abstract
Injuries to the spinal cord that result in disruption of axonal continuity have devastating consequences for injured patients. Current therapies that use biologically active agents to promote neuronal survival and/or growth have had modest success in allowing injured neurons to regrow through the area of the lesion. Strategies for successful regeneration will require an engineering approach. We propose the design of cell-free grafts of biocompatible materials to build a bridge across the injured area through which axons can regenerate. There are three critical regions of this bridge: the on-ramp, the surface of the bridge itself, and the off-ramp. Each of these regions has specific design requirements, which, if met, can promote regeneration of axons in the injured spinal cord. These requirements, and proposed solutions, are discussed.
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Affiliation(s)
- Herbert M Geller
- Division of Intramural Research, National Heart, Lung and Blood Institute, Bethesda, Maryland 20892, USA
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29
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Abstract
Corticospinal neurons support rapid growth of axons toward spinal cord targets in the perinatal period. Initial axon growth is accompanied by elevated expression of growth-associated protein-43 (GAP-43), which then declines in postnatal development. To investigate whether expression of GAP-43 mRNA is regulated by retrograde signals, we injected colchicine into the corticospinal tract to block retrograde axonal transport during a time when GAP-43 is normally declining in corticospinal neurons. Colchicine caused a prolongation of high GAP-43 mRNA expression in neurons located in layer V (but not other layers) of sensorimotor cortex. We next used osmotic minipumps to infuse soluble adult spinal cord extract into the sensorimotor cortex. This resulted in a premature downregulation of GAP-43 mRNA in identified corticospinal neurons. GAP-43 repressive activity was found in extracts of the spinal cord tissue as young as postnatal day 8. The effect of spinal cord extract in vivo was not mimicked by adult cerebellar or muscle extracts. Cultures of postnatal cortical neurons also underwent downregulation of GAP-43 mRNA when treated with spinal cord extract. Activation of cAMP signaling also repressed GAP-43 mRNA in cortical cultures, and the repressive effect of spinal cord extract was diminished by an adenyl cyclase inhibitor. Thus, GAP-43 mRNA may be downregulated late in development by a target-derived retrograde repressive factor, and this effect may be mediated by cAMP second messenger signaling.
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