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Xiong HY, Hendrix J, Schabrun S, Wyns A, Campenhout JV, Nijs J, Polli A. The Role of the Brain-Derived Neurotrophic Factor in Chronic Pain: Links to Central Sensitization and Neuroinflammation. Biomolecules 2024; 14:71. [PMID: 38254671 PMCID: PMC10813479 DOI: 10.3390/biom14010071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 01/02/2024] [Accepted: 01/03/2024] [Indexed: 01/24/2024] Open
Abstract
Chronic pain is sustained, in part, through the intricate process of central sensitization (CS), marked by maladaptive neuroplasticity and neuronal hyperexcitability within central pain pathways. Accumulating evidence suggests that CS is also driven by neuroinflammation in the peripheral and central nervous system. In any chronic disease, the search for perpetuating factors is crucial in identifying therapeutic targets and developing primary preventive strategies. The brain-derived neurotrophic factor (BDNF) emerges as a critical regulator of synaptic plasticity, serving as both a neurotransmitter and neuromodulator. Mounting evidence supports BDNF's pro-nociceptive role, spanning from its pain-sensitizing capacity across multiple levels of nociceptive pathways to its intricate involvement in CS and neuroinflammation. Moreover, consistently elevated BDNF levels are observed in various chronic pain disorders. To comprehensively understand the profound impact of BDNF in chronic pain, we delve into its key characteristics, focusing on its role in underlying molecular mechanisms contributing to chronic pain. Additionally, we also explore the potential utility of BDNF as an objective biomarker for chronic pain. This discussion encompasses emerging therapeutic approaches aimed at modulating BDNF expression, offering insights into addressing the intricate complexities of chronic pain.
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Affiliation(s)
- Huan-Yu Xiong
- Pain in Motion Research Group (PAIN), Department of Physiotherapy, Human Physiology and Anatomy, Faculty of Physical Education & Physiotherapy, Vrije Universiteit Brussel, 1090 Brussels, Belgium; (H.-Y.X.); (J.H.); (A.W.); (J.V.C.); (A.P.)
| | - Jolien Hendrix
- Pain in Motion Research Group (PAIN), Department of Physiotherapy, Human Physiology and Anatomy, Faculty of Physical Education & Physiotherapy, Vrije Universiteit Brussel, 1090 Brussels, Belgium; (H.-Y.X.); (J.H.); (A.W.); (J.V.C.); (A.P.)
- Department of Public Health and Primary Care, Centre for Environment & Health, KU Leuven, 3000 Leuven, Belgium
- Research Foundation—Flanders (FWO), 1000 Brussels, Belgium
| | - Siobhan Schabrun
- The School of Physical Therapy, University of Western Ontario, London, ON N6A 3K7, Canada;
- The Gray Centre for Mobility and Activity, Parkwood Institute, London, ON N6A 4V2, Canada
| | - Arne Wyns
- Pain in Motion Research Group (PAIN), Department of Physiotherapy, Human Physiology and Anatomy, Faculty of Physical Education & Physiotherapy, Vrije Universiteit Brussel, 1090 Brussels, Belgium; (H.-Y.X.); (J.H.); (A.W.); (J.V.C.); (A.P.)
| | - Jente Van Campenhout
- Pain in Motion Research Group (PAIN), Department of Physiotherapy, Human Physiology and Anatomy, Faculty of Physical Education & Physiotherapy, Vrije Universiteit Brussel, 1090 Brussels, Belgium; (H.-Y.X.); (J.H.); (A.W.); (J.V.C.); (A.P.)
| | - Jo Nijs
- Pain in Motion Research Group (PAIN), Department of Physiotherapy, Human Physiology and Anatomy, Faculty of Physical Education & Physiotherapy, Vrije Universiteit Brussel, 1090 Brussels, Belgium; (H.-Y.X.); (J.H.); (A.W.); (J.V.C.); (A.P.)
- Chronic Pain Rehabilitation, Department of Physical Medicine and Physiotherapy, University Hospital Brussels, 1090 Brussels, Belgium
- Department of Health and Rehabilitation, Unit of Physiotherapy, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, 41390 Göterbog, Sweden
| | - Andrea Polli
- Pain in Motion Research Group (PAIN), Department of Physiotherapy, Human Physiology and Anatomy, Faculty of Physical Education & Physiotherapy, Vrije Universiteit Brussel, 1090 Brussels, Belgium; (H.-Y.X.); (J.H.); (A.W.); (J.V.C.); (A.P.)
- Department of Public Health and Primary Care, Centre for Environment & Health, KU Leuven, 3000 Leuven, Belgium
- Research Foundation—Flanders (FWO), 1000 Brussels, Belgium
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BDNF guides neural stem cell-derived axons to ventral interneurons and motor neurons after spinal cord injury. Exp Neurol 2023; 359:114259. [PMID: 36309123 DOI: 10.1016/j.expneurol.2022.114259] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 10/11/2022] [Accepted: 10/21/2022] [Indexed: 12/30/2022]
Abstract
Neural stem cells (NSCs) implanted into sites of spinal cord injury (SCI) extend very large numbers of new axons over very long distances caudal to the lesion site, and support partial functional recovery. Newly extending graft axons distribute throughout host gray and white matter caudal to the injury. We hypothesized that provision of trophic gradients caudal to the injury would provide neurotrophic guidance to newly extending graft-derived axons to specific intermediate and ventral host gray matter regions, thereby potentially further improving neural relay formation. Immunodeficient rats underwent C5 lateral hemisection lesions, following by implants of human NSC grafts two weeks later. After an additional two weeks, animals received injections of AAV2-BDNF expressing vectors three spinal segments (9 mm) caudal to the lesion in host ventral and intermediate gray matter. After 2 months additional survival, we found a striking, 5.5-fold increase in the density of human axons innervating host ventral gray matter (P < 0.05) and 2.7-fold increase in intermediate gray matter (P < 0.01). Moreover, stem cell-derived axons formed a substantially greater number of putative synaptic connections with host motor neurons (P < 0.01). Thus, trophic guidance is an effective means of enhancing and guiding neural stem cell axon growth after SCI and will be used in future experiments to determine whether neural relay formation and functional outcomes can be improved.
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Li J, Zhang L, Xu C, Shen YY, Lin YH, Zhang Y, Wu HY, Chang L, Zhang YD, Chen R, Zhang ZP, Luo CX, Li F, Zhu DY. A pain killer without analgesic tolerance designed by co-targeting PSD-95-nNOS interaction and α2-containning GABA ARs. Am J Cancer Res 2021; 11:5970-5985. [PMID: 33897893 PMCID: PMC8058733 DOI: 10.7150/thno.58364] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 03/07/2021] [Indexed: 01/22/2023] Open
Abstract
Overactivation of N-methyl-D-aspartate receptor (NMDAR) in the spinal cord dorsal horn (SDH) in the setting of injury represents a key mechanism of neuropathic pain. However, directly blocking NMDAR or its downstream signaling, interaction between postsynaptic density-95 (PSD-95) and neuronal nitric oxide synthase (nNOS), causes analgesic tolerance, mainly due to GABAergic disinhibition. The aim of this study is to explore the possibility of preventing analgesic tolerance through co-targeting NMDAR downstream signaling and γ-aminobutyric acid type A receptors (GABAARs). Methods: Mechanical/thermal hyperalgesia were quantified to assess analgesic effects. Miniature postsynaptic currents were tested by patch-clamp recording to evaluate synaptic transmission in the SDH. GABA-evoked currents were tested on HEK293 cells expressing different subtypes of recombinant GABAARs to assess the selectivity of (+)-borneol and ZL006-05. The expression of α2 and α3 subunits of GABAARs and BDNF, and nNOS-PSD-95 complex levels were analyzed by western blotting and coimmunoprecipitation respectively. Open field test, rotarod test and Morris water maze task were conducted to evaluate the side-effect of ZL006-05. Results: (+)-Borneol selectively potentiated α2- and α3-containing GABAARs and prevented the disinhibition of laminae I excitatory neurons in the SDH and analgesic tolerance caused by chronic use of ZL006, a nNOS-PSD-95 blocker. A dual-target compound ZL006-05 produced by linking ZL006 and (+)-borneol through an ester bond blocked nNOS-PSD-95 interaction and potentiated α2-containing GABAAR selectively. Chronic use of ZL006-05 did not produce analgesic tolerance and unwanted side effects. Conclusion: By targeting nNOS-PSD-95 interaction and α2-containing GABAAR simultaneously, chronic use of ZL006-05 can avoid analgesic tolerance and unwanted side effects. Therefore, we offer a novel candidate drug without analgesic tolerance for treating neuropathic pain.
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Li J, Zhang L, Xu C, Lin YH, Zhang Y, Wu HY, Chang L, Zhang YD, Luo CX, Li F, Zhu DY. Prolonged Use of NMDAR Antagonist Develops Analgesic Tolerance in Neuropathic Pain via Nitric Oxide Reduction-Induced GABAergic Disinhibition. Neurotherapeutics 2020; 17:1016-1030. [PMID: 32632774 PMCID: PMC7609518 DOI: 10.1007/s13311-020-00883-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Neuropathic pain is usually persistent due to maladaptive neuroplasticity-induced central sensitization and, therefore, necessitates long-term treatment. N-methyl-D-aspartate receptor (NMDAR)-mediated hypersensitivity in the spinal dorsal horn represents key mechanisms of central sensitization. Short-term use of NMDAR antagonists produces antinociceptive efficacy in animal pain models and in clinical practice by reducing central sensitization. However, how prolonged use of NMDAR antagonists affects central sensitization remains unknown. Surprisingly, we find that prolonged blockage of NMDARs does not prevent but aggravate nerve injury-induced central sensitization and produce analgesic tolerance, mainly due to reduced synaptic inhibition. The disinhibition that results from the continuous decrease in the production of nitric oxide from neuronal nitric oxide synthase, downstream signal of NMDARs, leads to the reduction of GABAergic inhibitory synaptic transmission by upregulating brain-derived neurotrophic factor expression and inhibiting the expression and function of potassium-chloride cotransporter. Together, our findings suggest that chronic blockage of NMDARs develops analgesic tolerance through the neuronal nitric oxide synthase-brain-derived neurotrophic factor-potassium-chloride cotransporter pathway. Thus, preventing the GABAergic disinhibition induced by nitric oxide reduction may be necessary for the long-term maintenance of the analgesic effect of NMDAR antagonists.
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Affiliation(s)
- Jun Li
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
- Department of Pharmacy, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006, China
| | - Lin Zhang
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Chu Xu
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Yu-Hui Lin
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Yu Zhang
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Hai-Yin Wu
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Lei Chang
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Ying-Dong Zhang
- Department of Neurology, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006, China
| | - Chun-Xia Luo
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Fei Li
- Department of Medicinal Chemistry, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Dong-Ya Zhu
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China.
- Institution of Stem Cells and Neuroregeneration, Nanjing Medical University, Nanjing, 211166, China.
- Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangzhou, 510000, China.
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Manion J, Waller MA, Clark T, Massingham JN, Neely GG. Developing Modern Pain Therapies. Front Neurosci 2019; 13:1370. [PMID: 31920521 PMCID: PMC6933609 DOI: 10.3389/fnins.2019.01370] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 12/04/2019] [Indexed: 12/24/2022] Open
Abstract
Chronic pain afflicts as much as 50% of the population at any given time but our methods to address pain remain limited, ineffective and addictive. In order to develop new therapies an understanding of the mechanisms of painful sensitization is essential. We discuss here recent progress in the understanding of mechanisms underlying pain, and how these mechanisms are being targeted to produce modern, specific therapies for pain. Finally, we make recommendations for the next generation of targeted, effective, and safe pain therapies.
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Affiliation(s)
- John Manion
- The Dr. John and Anne Chong Lab for Functional Genomics, Charles Perkins Centre and School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, Australia
| | - Matthew A. Waller
- The Dr. John and Anne Chong Lab for Functional Genomics, Charles Perkins Centre and School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, Australia
| | - Teleri Clark
- The Dr. John and Anne Chong Lab for Functional Genomics, Charles Perkins Centre and School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, Australia
| | - Joshua N. Massingham
- The Dr. John and Anne Chong Lab for Functional Genomics, Charles Perkins Centre and School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, Australia
| | - G. Gregory Neely
- The Dr. John and Anne Chong Lab for Functional Genomics, Charles Perkins Centre and School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, Australia
- Genome Editing Initiative, The University of Sydney, Sydney, NSW, Australia
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The BDNF Protein and its Cognate mRNAs in the Rat Spinal Cord during Amylin-induced Reversal of Morphine Tolerance. Neuroscience 2019; 422:54-64. [PMID: 31689388 DOI: 10.1016/j.neuroscience.2019.09.034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 09/24/2019] [Accepted: 09/26/2019] [Indexed: 12/21/2022]
Abstract
The pancreatic peptide, Amylin (AMY), reportedly affects nociception in rodents. Here, we investigated the potential effect of AMY on the tolerance to morphine and on the expression of BDNF at both levels of protein and RNA in the lumbar spinal cord of morphine tolerant rats. Animals in both groups of control and test received a single daily dose of intrathecal (i.t.) morphine for 10 days. Rats in the test group received AMY (1, 10 and 60 pmoles) in addition to morphine from days 6 to10. Morphine tolerance was established at day 5. AMY alone showed enduring antinociceptive effects for 10 days. Real-Time PCR, western blotting and ELISA were used respectively to assess levels of BDNF transcripts and their encoded proteins. Rats tolerant to i.t. morphine showed increased expression of exons I, IV, and IX of the BDNF gene, and had elevated levels of pro-BDNF and BDNF protein in their lumbar spinal cord. AMY, when co-administered with morphine from days 6 to 10, reversed morphine tolerance and adversely affected the morphine-induced expression of the BDNF gene at both levels of protein and mRNAs containing exons I, IV and IX. AMY alone increased levels of exons I and IV transcripts. Levels of pro-BDNF and BDNF proteins remained unchanged in the lumbar spinal cord of rats treated by AMY alone. These results suggest that i.t. AMY not only abolished morphine tolerance, but also reduced the morphine induced increase in the expression of both BDNF transcripts and protein in the lumbar spinal cord.
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Targeted Genotyping Identifies Susceptibility Locus in Brain-derived Neurotrophic Factor Gene for Chronic Postsurgical Pain. Anesthesiology 2019; 128:587-597. [PMID: 29120944 DOI: 10.1097/aln.0000000000001977] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
BACKGROUND The purpose of this study was to evaluate the association between single-nucleotide polymorphisms and chronic postsurgical pain. METHODS Using GoldenGate genotyping assays, we genotyped 638 polymorphisms within 54 pain-related genes in 1,152 surgical patients who were enrolled in our Persistent Pain after Surgery Study. Patients were contacted by phone to determine whether they had chronic postsurgical pain at 12 months. Polymorphisms identified were validated in a matched cohort of 103 patients with chronic postsurgical pain and 103 patients who were pain free. The functions of targeted polymorphisms were tested in an experimental plantar incisional nociception model using knock-in mice. RESULTS At 12 months after surgery, 246 (21.4%) patients reported chronic postsurgical pain. Forty-two polymorphisms were found to be associated with chronic postsurgical pain, 19 decreased the risk of pain, and 23 increased the risk of pain. Patients carrying allele A of rs6265 polymorphism in brain-derived neurotrophic factor (BDNF) had a lower risk of chronic postsurgical pain in the discovery and validation cohorts, with an adjusted odds ratio (95% CI) of 0.62 (0.43 to 0.90) and 0.57 (0.39 to 0.85), respectively. Age less than 65 yr, male sex, and prior history of pain syndrome were associated with an increased risk of pain. Genetic polymorphisms had higher population attributable risk (7.36 to 11.7%) compared with clinical risk factors (2.90 to 5.93%). Importantly, rs6265 is a substitution of valine by methionine at amino acid residue 66 (Val66Met) and was associated with less mechanical allodynia in BDNF mice compared with BDNF group after plantar incision. CONCLUSIONS This study demonstrated that genetic variant of BDNF rs6265G>A is associated with decreased risk of chronic postsurgical pain.
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Abolhasanpour N, Eidi A, Hajebrahimi S, Reyhani-Rad S, Hashim H. Effect of cerebrolysin on bladder function after spinal cord injury in female Wistar rats. Int J Urol 2019; 26:917-923. [PMID: 31317583 DOI: 10.1111/iju.14059] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 06/12/2019] [Indexed: 11/27/2022]
Abstract
OBJECTIVES To study the effect of cerebrolysin on bladder function after spinal cord injury using functional measurements in rats. METHODS A total of 60 female rats were enrolled in this study. After induction of complete transection at T9-T10 spinal vertebrae, cerebrolysin was injected intraperitoneally, and daily in three dosages until 7 days (1 week) and continued until 28 days (4 weeks) in three groups to show the impact of that on the bladder function. Urodynamic parameters were measured in the different groups. RESULTS Cerebrolysin injection in a dose of 1 mL/kg for 1 week showed a slight improvement in urodynamic parameters. However, infusion of 2.5 and 5 mL/kg cerebrolysin for 1 week caused an elevation in contractions and a decrease in compliance. In long-term 2.5 mL/kg cerebrolysin injection, an improvement in compliance was observed, despite relative contractions. Furthermore, the bladder pressure pattern in the 2.5 mL/kg infused rats for 4 weeks was similar to the control group, but in the group receiving 5 mL/kg cerebrolysin for 4 weeks, reduced bladder contractions and function were observed. CONCLUSIONS Our findings suggest that cerebrolysin might be able to inhibit the emergence of neurogenic detrusor overactivity in spinal cord injured female rats.
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Affiliation(s)
- Nasrin Abolhasanpour
- Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
| | - Akram Eidi
- Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
| | - Sakineh Hajebrahimi
- Research Center for Evidence-Based Medicine, A Joanna Briggs Institute Affiliated Group, Urology Department, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Siamak Reyhani-Rad
- Department of Medical Laboratory Sciences, Islamic Azad University, Marand, Iran
| | - Hashim Hashim
- Bristol Urological Institute, Southmead Hospital, Bristol, UK
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Coelho A, Oliveira R, Antunes-Lopes T, Cruz CD. Partners in Crime: NGF and BDNF in Visceral Dysfunction. Curr Neuropharmacol 2019; 17:1021-1038. [PMID: 31204623 PMCID: PMC7052822 DOI: 10.2174/1570159x17666190617095844] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/23/2019] [Accepted: 06/03/2019] [Indexed: 12/12/2022] Open
Abstract
Neurotrophins (NTs), particularly Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF), have attracted increasing attention in the context of visceral function for some years. Here, we examined the current literature and presented a thorough review of the subject. After initial studies linking of NGF to cystitis, it is now well-established that this neurotrophin (NT) is a key modulator of bladder pathologies, including Bladder Pain Syndrome/Interstitial Cystitis (BPS/IC) and Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS. NGF is upregulated in bladder tissue and its blockade results in major improvements on urodynamic parameters and pain. Further studies expanded showed that NGF is also an intervenient in other visceral dysfunctions such as endometriosis and Irritable Bowel Syndrome (IBS). More recently, BDNF was also shown to play an important role in the same visceral dysfunctions, suggesting that both NTs are determinant factors in visceral pathophysiological mechanisms. Manipulation of NGF and BDNF improves visceral function and reduce pain, suggesting that clinical modulation of these NTs may be important; however, much is still to be investigated before this step is taken. Another active area of research is centered on urinary NGF and BDNF. Several studies show that both NTs can be found in the urine of patients with visceral dysfunction in much higher concentration than in healthy individuals, suggesting that they could be used as potential biomarkers. However, there are still technical difficulties to be overcome, including the lack of a large multicentre placebo-controlled studies to prove the relevance of urinary NTs as clinical biomarkers.
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Affiliation(s)
| | | | | | - Célia Duarte Cruz
- Address correspondence to this author at the Department of Experimental Biology, Experimental Biology Unit, Faculty of Medicine of the University of Porto, Alameda Hernâni Monteiro; Tel: 351 220426740; Fax: +351 225513655; E-mail:
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Antihyperalgesic effect of duloxetine and amitriptyline in rats after peripheral nerve injury: Influence of descending noradrenergic plasticity. Neurosci Lett 2015; 602:62-7. [DOI: 10.1016/j.neulet.2015.06.041] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Revised: 06/21/2015] [Accepted: 06/22/2015] [Indexed: 01/12/2023]
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Abstract
Neurotrophins (NTs) belong to a family of trophic factors that regulate the survival, growth and programmed cell death of neurons. In mammals, there are four structurally and functionally related NT proteins, viz. nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 and neurotrophin 4. Most research on NTs to date has focussed on the effects of NGF and BDNF signalling via their respective cognate high affinity neurotrophic tyrosine kinase viz TrkA and TrkB receptors. Apart from the key physiologic roles of NGF and BDNF in peripheral and central nervous system function, NGF and BDNF signalling via TrkA and TrkB receptors respectively have been implicated in mechanisms underpinning neuropathic pain. Additionally, NGF and BDNF signalling via the low-affinity pan neurotrophin receptor at 75 kDa (p75NTR) may also contribute to the pathobiology of neuropathic pain. In this review, we critically assess the role of neurotrophins signalling via their cognate high affinity receptors as well as the low affinity p75NTR in the pathophysiology of peripheral neuropathic and central neuropathic pain. We also identify knowledge gaps to guide future research aimed at generating novel insight on how to optimally modulate NT signalling for discovery of novel therapeutics to improve neuropathic pain relief.
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Frias B, Santos J, Morgado M, Sousa MM, Gray SMY, McCloskey KD, Allen S, Cruz F, Cruz CD. The role of brain-derived neurotrophic factor (BDNF) in the development of neurogenic detrusor overactivity (NDO). J Neurosci 2015; 35:2146-60. [PMID: 25653370 PMCID: PMC4315839 DOI: 10.1523/jneurosci.0373-14.2015] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 11/21/2014] [Accepted: 11/27/2014] [Indexed: 12/24/2022] Open
Abstract
Neurogenic detrusor overactivity (NDO) is a well known consequence of spinal cord injury (SCI), recognizable after spinal shock, during which the bladder is areflexic. NDO emergence and maintenance depend on profound plastic changes of the spinal neuronal pathways regulating bladder function. It is well known that neurotrophins (NTs) are major regulators of such changes. NGF is the best-studied NT in the bladder and its role in NDO has already been established. Another very abundant neurotrophin is BDNF. Despite being shown that, acting at the spinal cord level, BDNF is a key mediator of bladder dysfunction and pain during cystitis, it is presently unclear if it is also important for NDO. This study aimed to clarify this issue. Results obtained pinpoint BDNF as an important regulator of NDO appearance and maintenance. Spinal BDNF expression increased in a time-dependent manner together with NDO emergence. In chronic SCI rats, BDNF sequestration improved bladder function, indicating that, at later stages, BDNF contributes NDO maintenance. During spinal shock, BDNF sequestration resulted in early development of bladder hyperactivity, accompanied by increased axonal growth of calcitonin gene-related peptide-labeled fibers in the dorsal horn. Chronic BDNF administration inhibited the emergence of NDO, together with reduction of axonal growth, suggesting that BDNF may have a crucial role in bladder function after SCI via inhibition of neuronal sprouting. These findings highlight the role of BDNF in NDO and may provide a significant contribution to create more efficient therapies to manage SCI patients.
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Affiliation(s)
- Bárbara Frias
- Department of Experimental Biology, Faculty of Medicine of Porto, University of Porto, 4200-319 Porto, Portugal, Translational NeuroUrology and
| | - João Santos
- Department of Experimental Biology, Faculty of Medicine of Porto, University of Porto, 4200-319 Porto, Portugal
| | - Marlene Morgado
- Nerve Regeneration Group, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal
| | - Mónica Mendes Sousa
- Nerve Regeneration Group, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal
| | - Susannah M Y Gray
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, BT7 1 NN Belfast, United Kingdom
| | - Karen D McCloskey
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, BT7 1 NN Belfast, United Kingdom
| | - Shelley Allen
- Molecular Neurobiology Unit, University of Bristol, School of Clinical Sciences, BS10 5NB Bristol, United Kingdom
| | - Francisco Cruz
- Translational NeuroUrology and Department of Urology, Hospital de S. João, 4200-319 Porto, Portugal, and
| | - Célia Duarte Cruz
- Department of Experimental Biology, Faculty of Medicine of Porto, University of Porto, 4200-319 Porto, Portugal, Translational NeuroUrology and
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Wang D, Couture R, Hong Y. Activated microglia in the spinal cord underlies diabetic neuropathic pain. Eur J Pharmacol 2014; 728:59-66. [PMID: 24508519 DOI: 10.1016/j.ejphar.2014.01.057] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 01/23/2014] [Accepted: 01/29/2014] [Indexed: 12/22/2022]
Abstract
Diabetes mellitus is an increasingly common chronic medical condition. Approximately 30% of diabetic patients develop neuropathic pain, manifested as spontaneous pain, hyperalgesia and allodynia. Hyperglycemia induces metabolic changes in peripheral tissues and enhances oxidative stress in nerve fibers. The damages and subsequent reactive inflammation affect structural properties of Schwann cells and axons leading to the release of neuropoietic mediators, such as pro-inflammatory cytokines and pro-nociceptive mediators. Therefore, diabetic neuropathic pain (DNP) shares some histological features and underlying mechanisms with traumatic neuropathy. DNP displays, however, other distinct features; for instance, sensory input to the spinal cord decreases rather than increasing in diabetic patients. Consequently, development of central sensitization in DNP involves mechanisms that are distinct from traumatic neuropathic pain. In DNP, the contribution of spinal cord microglia activation to central sensitization and pain processes is emerging as a new concept. Besides inflammation in the periphery, hyperglycemia and the resulting production of reactive oxygen species affect the local microenvironment in the spinal cord. All these alterations could trigger resting and sessile microglia to the activated phenotype. In turn, microglia synthesize and release pro-inflammatory cytokines and neuroactive molecules capable of inducing hyperactivity of spinal nociceptive neurons. Hence, it is imperative to elucidate glial mechanisms underlying DNP for the development of effective therapeutic agents. The present review highlights the recent developments regarding the contribution of spinal microglia as compelling target for the treatment of DNP.
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Affiliation(s)
- Dongmei Wang
- College of Life Sciences and Provincial Key Laboratory of Developmental Biology and Neuroscience, Fujian Normal University, New campus, Fuzhou, Fujian 350108, People׳s Republic of China
| | - Réjean Couture
- Department of Physiology, Faculty of Medicine, Université de Montréal, C.P. 6128, Succursale Downtown, Montréal, Québec, Canada H3C 3J7
| | - Yanguo Hong
- College of Life Sciences and Provincial Key Laboratory of Developmental Biology and Neuroscience, Fujian Normal University, New campus, Fuzhou, Fujian 350108, People׳s Republic of China.
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TrkB.T1 contributes to neuropathic pain after spinal cord injury through regulation of cell cycle pathways. J Neurosci 2013; 33:12447-63. [PMID: 23884949 DOI: 10.1523/jneurosci.0846-13.2013] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Spinal cord injury (SCI) frequently causes severe, persistent central neuropathic pain that responds poorly to conventional pain treatments. Brain-derived neurotrophic factor (BDNF) signaling appears to contribute to central sensitization and nocifensive behaviors in certain animal models of chronic pain through effects mediated in part by the alternatively spliced truncated isoform of the BDNF receptor tropomyosin-related kinase B.T1 (trkB.T1). Mechanisms linking trkB.T1 to SCI-induced chronic central pain are unknown. Here, we examined the role of trkB.T1 in central neuropathic pain after spinal cord contusion. Genetic deletion of trkB.T1 in mice significantly reduced post-SCI mechanical hyperesthesia, locomotor dysfunction, lesion volumes, and white matter loss. Whole genome analysis, confirmed at the protein level, revealed that cell cycle genes were upregulated in trkB.T1(+/+) but not trkB.T1(-/-) spinal cord after SCI. TGFβ-induced reactive astrocytes from WT mice showed increased cell cycle protein expression that was significantly reduced in astrocytes from trkB.T1(-/-) mice that express neither full-length trkB nor trkB.T1. Administration of CR8, which selectively inhibits cyclin-dependent kinases, reduced hyperesthesia, locomotor deficits, and dorsal horn (SDH) glial changes after SCI, similar to trkB.T1 deletion, without altering trkB.T1 protein expression. In trkB.T1(-/-) mice, CR8 had no effect. These data indicate that trkB.T1 contributes to the pathobiology of SCI and SCI pain through modulation of cell cycle pathways and suggest new therapeutic targets.
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Nakajima K, Obata H, Iriuchijima N, Saito S. An increase in spinal cord noradrenaline is a major contributor to the antihyperalgesic effect of antidepressants after peripheral nerve injury in the rat. Pain 2012; 153:990-997. [PMID: 22424692 DOI: 10.1016/j.pain.2012.01.029] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 01/13/2012] [Accepted: 01/27/2012] [Indexed: 01/22/2023]
Abstract
Antidepressants are often used for the treatment of neuropathic pain. Clinical studies suggest that the efficacy of serotonin (5-HT) and noradrenaline (NA) reuptake inhibitors (SNRIs) for neuropathic pain is greater than that of selective 5-HT reuptake inhibitors (SSRIs). In the present study, we determined the efficacy and mechanisms involved in the antihyperalgesic effects of milnacipran, an SNRI, compared with paroxetine, an SSRI, and maprotiline, a selective NA reuptake inhibitor, using a rat model of neuropathic pain. Male Sprague-Dawley rats underwent spinal nerve ligation (SNL), and the withdrawal threshold to paw pressure was measured. Intraperitoneal injection of milnacipran (3-30mg/kg) produced a dose-dependent antihyperalgesic effect. The effect was reversed by intrathecal injection of the α(2)-adrenoceptor antagonist idazoxan (30μg), but not by various 5-HT receptor antagonists. Paroxetine produced an antihyperalgesic effect only at the highest dose tested (10mg/kg). This effect was reversed by intrathecal injection of both idazoxan and ondansetron (30μg), a 5-HT3 receptor antagonist. Maprotiline produced an antihyperalgesic effect (10 and 30mg/kg), and the effect was reversed by intrathecal idazoxan. In microdialysis studies, NA and 5-HT concentrations in the spinal dorsal horn were increased after injection of either milnacipran or paroxetine, and only NA was increased after maprotiline. Furthermore, the NA content in the spinal cord of SNL rats was greater than that in normal animals. These findings suggest that an increase in NA in the spinal cord plays an important role in the antihyperalgesic effects of not only NA reuptake inhibitors but also SSRIs.
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Affiliation(s)
- Kunie Nakajima
- Department of Anesthesiology, Gunma University Graduate School of Medicine, Gunma, Japan
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Sathyanesan A, Ogura T, Lin W. Automated measurement of nerve fiber density using line intensity scan analysis. J Neurosci Methods 2012; 206:165-75. [PMID: 22613744 DOI: 10.1016/j.jneumeth.2012.02.019] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2011] [Revised: 02/16/2012] [Accepted: 02/20/2012] [Indexed: 11/27/2022]
Abstract
Quantification of nerve fibers in peripheral and central nervous systems is important for the understanding of neuronal function, organization and pathological changes. However, current methods to quantify nerve fibers are resource-intensive and often provide an indirect measurement of nerve fiber density. Here, we describe an automated and efficient method for nerve fiber quantification, which we developed by making use of widely available software and analytical techniques, including Hessian-based feature extraction in NIH ImageJ and line intensity scan analysis. The combined use of these analytical tools through an automated routine enables reliable detection and quantification of nerve fibers from low magnification, non-uniformly labeled epifluorescence images. This allows for time-efficient determination of nerve density and also comparative analysis in large brain structures, such as hippocampus or between various regions of neural circuitry. Using this method, we have obtained accurate measurements of cholinergic fiber density in hippocampus and a large area of cortex in mouse brain sections immunolabeled with an antibody against the vesicular acetylcholine transporter (VAChT). The density values are comparable among animals tested, showing a high degree of reproducibility. Because our method can be performed at relatively low cost and in large tissue sections where nerve fibers can be labeled by various antibodies or visualized by expression of reporter proteins, such as green fluorescent protein in transgenic mice, we expect our method to be broadly useful in both research and clinical investigation. To our knowledge, this is the first method to reliably quantify nerve fibers through a rapid and automated protocol.
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Affiliation(s)
- Aaron Sathyanesan
- Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
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17
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Abstract
Spinal cord injury (SCI) has multiple consequences, ranging from molecular imbalances to glial scar formation to functional impairments. It is logical to think that a combination of single treatments implemented in the right order and at the right time will be required to repair the spinal cord. However, the single treatments that compose the combination therapy will need to be chosen with caution as many have multiple outcomes that may or may not be synergistic. Single treatments may also elicit unwanted side-effects and/or effects that would decrease the repair potential of other components and/or the entire combination therapy. In this chapter a number of single treatments are discussed with respect to their multiplicity of action. These include strategies to boost growth and survival (such as neurotrophins and cyclic AMP) and strategies to reduce inhibitory factors (such as antimyelin-associated growth inhibitors and digestion of glial scar-associated inhibitors). We also present an overview of combination therapies that have successfully or unsuccessfully been tested in the laboratory using animal models. To effectively design a combination therapy a number of considerations need to be made such as the nature and timing of the treatments and the method for delivery. This chapter discusses these issues as well as considerations related to chronic SCI and the logistics of bringing combination therapies to the clinic.
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Affiliation(s)
- M Oudega
- Departments of Physical Medicine and Rehabilitation, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
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18
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Efficacy and safety of lithium carbonate treatment of chronic spinal cord injuries: a double-blind, randomized, placebo-controlled clinical trial. Spinal Cord 2011; 50:141-6. [DOI: 10.1038/sc.2011.126] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Morgado C, Pereira-Terra P, Cruz CD, Tavares I. Minocycline completely reverses mechanical hyperalgesia in diabetic rats through microglia-induced changes in the expression of the potassium chloride co-transporter 2 (KCC2) at the spinal cord. Diabetes Obes Metab 2011; 13:150-9. [PMID: 21199267 DOI: 10.1111/j.1463-1326.2010.01333.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
AIM neuronal hyperactivity at the spinal cord during mechanical hyperalgesia induced by diabetes may result from a decrease in the local expression of the potassium chloride co-transporter 2 (KCC2), which shifts the action of the neurotransmitter γ-amminobutiric acid (GABA) from inhibitory to excitatory. In this study, we evaluated the effects of spinal microglia inhibition or brain-derived neurotrophic factor (BDNF) blockade on KCC2 expression, spinal neuronal activity and mechanically induced pain responses of streptozotocin (STZ)-diabetic rats. METHODS four weeks after induction of diabetes, the STZ-diabetic rats received daily intrathecal injections, for 3 days, of minocycline (microglia inhibitor), TrkB/Fc (BDNF sequester) or saline. Behavioural responses to mechanical nociceptive stimulation of STZ-diabetic rats were evaluated by the Randall-Selitto test. The lumbar spinal cord was immunoreacted against the Fos protein (marker of neuronal activation) or KCC2, which was also quantified by western blotting. BDNF levels at the spinal cord were quantified by an enzyme-linked immunosorbent assay (ELISA). RESULTS minocycline treatment reversed the mechanical hyperalgesia, increased Fos expression and decreased the KCC2 expression detected in STZ-diabetic rats to control levels. Treatment with TrkB/Fc was less effective, inducing moderate effects in mechanical hyperalgesia and Fos expression and only a partial correction of KCC2 expression. BDNF levels were not increased in STZ-diabetic rats. CONCLUSIONS this study demonstrates that the microglial activation at the spinal cord contributes to mechanical hyperalgesia and spinal neuronal hyperactivity induced by diabetes, apparently by regulating the KCC2 expression. These effects do not seem to be mediated by BDNF, which is an important difference from other chronic pain conditions. New targets directed to prevent spinal microglia activation should be considered for the treatment of mechanical hyperalgesia induced by diabetes.
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Affiliation(s)
- C Morgado
- Faculty of Medicine of Porto and IBMC, Institute of Histology and Embryology, University of Porto, Alameda Prof. Hernâni Monteiro, Porto, Portugal
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20
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Ramer MS. Endogenous neurotrophins and plasticity following spinal deafferentation. Exp Neurol 2010; 235:70-7. [PMID: 21195072 DOI: 10.1016/j.expneurol.2010.12.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 12/03/2010] [Accepted: 12/22/2010] [Indexed: 01/10/2023]
Abstract
Neurons intrinsic to the spinal cord dorsal horn receive input from various classes of long-distance projection systems. Two of the best known of these are primary afferent and descending monoaminergic axons. Together with intrinsic interneurons, activity in these axonal populations shapes the early part of the sensory experience before it is transmitted to supraspinal structures via ascending projection axons. Injury to dorsal roots, which contain the centrally projecting branches of primary afferent axons, results in their permanent disconnection from the spinal cord, as well as sensory dysfunction such as pain. In animals, experimental dorsal root injuries affecting a small number of roots produce dynamic behavioural changes, providing evidence for the now familiar concept that sensory processing at the level of the spinal cord is not hard-wired. Changes in behaviour following rhizotomy suggest changes in spinal sensory circuitry, and we and others have shown that the density of spinal serotonergic axons as well as processes of inhibitory interneurons increases following rhizotomy. Intact primary afferent axons are less apt to sprout into denervated territory. Recent work from our group has asked (1) what is the stimulus that induces sprouting of serotonergic (and other) axons and (2) what prevents spared primary afferent axons from occupying the territory of those lost to injury. This article will review the evidence that a single factor upregulated by dorsal root injury, brain-derived neurotrophic factor (BDNF), underpins both serotonergic sprouting and a lack of primary afferent plasticity. BDNF also differentially modulates some of the behavioural consequences of dorsal root injury: antagonizing endogenous BDNF improves spontaneous mechanosensory recovery but prevents recovery from rhizotomy-induced hypersensitivity to cold. These findings reinforce the notion that in disease states as complex and variable as spinal cord injury, single pharmacological interventions are unlikely to produce meaningful results. However, understanding the differences in capacity for plasticity among different systems, as well as their triggers, should allow for more patient-tailored therapies.
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Affiliation(s)
- Matt S Ramer
- Zoology and International Collaboration on Repair Discoveries, 818 W. 10th Ave., Vancouver, BC, Canada.
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21
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Lack of analgesic efficacy of spinal ondansetron on thermal and mechanical hypersensitivity following spinal nerve ligation in the rat. Brain Res 2010; 1352:83-93. [PMID: 20637741 DOI: 10.1016/j.brainres.2010.07.020] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Revised: 07/06/2010] [Accepted: 07/09/2010] [Indexed: 12/31/2022]
Abstract
The balance between descending inhibition and facilitation is thought to be disturbed in chronic pain states. Increased facilitation by spinally released serotonin has been suggested by demonstration that mechanically evoked neuronal responses of wide dynamic range neurons are inhibited by 5-HT3 receptor antagonists in rats following spinal nerve ligation (SNL) but not sham operation. Despite these physiologic data, the effects of spinal 5-HT3 receptor blockade on behavioral hypersensitivity and neurochemical alterations in spinal serotonergic system have not been thoroughly investigated following spinal nerve ligation in the rat. To test this, we acutely injected intrathecal ondansetron in rats between 14 and 30 days after SNL and assessed effects on thermal and mechanical hypersensitivity. We also determined the density of serotonergic nerve fibers, serotonin content and the levels of 5-HT3 receptors within the spinal cord at this time point. Intrathecal ondansetron (1, 3, 10, 30, and 100microg) produced no effect on behavioral measures of thermal or mechanical hypersensitivity whereas intrathecal morphine (1microg) and gabapentin (200microg) partially reversed thermal and mechanical hypersensitivity following SNL. In addition, SNL did not alter the density of serotonergic fibers or 5-HT3 receptor immunoreactivity or spinal tissue content of 5-HT within the dorsal horn. These results do not support anatomic plasticity of descending serotonergic pathways or tonic 5-HT3 receptor activity in maintaining hypersensitivity after nerve injury and in contrast to previous studies fail to demonstrate an anti-hypersensitivity effect of intrathecal injection of the 5-HT3 receptor antagonist ondansetron. Importantly, behavioral measures of mechanical hypersensitivity assess threshold responses whereas physiological studies of mechanically evoked neuronal responses involve application of suprathreshold stimuli. Thus, suprathreshold or more intense stimuli may be necessary to recruit descending serotonergic facilitatory drive required to observe the inhibitory effects of ondansetron on spinal neuronal excitability and behavioral hypersensitivity.
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Scott AL, Ramer MS. Differential regulation of dendritic plasticity by neurotrophins following deafferentation of the adult spinal cord is independent of p75NTR. Brain Res 2010; 1323:48-58. [DOI: 10.1016/j.brainres.2010.02.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Revised: 01/26/2010] [Accepted: 02/02/2010] [Indexed: 12/16/2022]
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Scott ALM, Ramer MS. Schwann cell p75NTR prevents spontaneous sensory reinnervation of the adult spinal cord. Brain 2010; 133:421-32. [PMID: 20047901 DOI: 10.1093/brain/awp316] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Schwann cells are attractive candidates for repair of the injured spinal cord. Transplanted Schwann cells are permissive to regeneration, but their ability to promote regeneration into distal spinal cord remains weak despite their production of growth-promoting neurotrophins. Schwann cell activation such as that which accompanies peripheral nerve injury results in massive upregulation of the p75(NTR) pan-neurotrophin-receptor. Here we test the hypothesis that this p75(NTR) upregulation following dorsal root injury limits availability of endogenous neurotrophin to axons and restricts regeneration of injured axons into the spinal cord. We injured dorsal roots (fourth cervical to second thoracic) in mice lacking the neurotrophin-binding domain of p75(NTR) and in wild-type littermates. Axonal regeneration was assessed by selective tracing of neurotrophin-responsive and non-responsive dorsal root ganglion neurons. Functional reinnervation of the spinal cord was assessed in behavioural experiments and via Fos immunohistochemistry following formalin injection into the forepaw. We also measured levels of nerve growth factor and neurotrophin-3 following nerve injury in knockout and wild-type mice, and used Trk-Fc receptor chimeras to block nerve growth factor and neurotrophin-3 signalling in dorsal root ganglion/Schwann cell co-cultures and following dorsal root injury in vivo. The roles of neuronal and glial p75(NTR) were assessed in transplant experiments in vivo and in co-cultures. We found that nerve growth factor and neurotrophin-3-responsive axons regenerated into the spinal cord of p75(NTR) knockout mice where they made functional connections with dorsal horn neurons. Despite equivalent levels of nerve growth factor and neurotrophin-3 in wild-type and knockout mice, successful regeneration in knockouts was neurotrophin-dependent. Transplantation of p75(-/-) neurons into a wild-type environment, p75(-/-) peripheral nerve grafts into the injured p75(+/+) spinal cord, and dissociated sensory neuron/Schwann cell co-cultures showed that the absence of p75(NTR) from glia, not from neurons, promotes regeneration. These findings indicate that Schwann cell p75(NTR) restricts neurotrophin availability to the extent that it prevents spontaneous sensory axon regeneration into the spinal cord. The implication is that inactivating p75(NTR) in Schwann (or olfactory ensheathing) cells may enable axons to grow beyond transplants, improving the outcome of spinal cord injury.
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Cragg JJ, Scott AL, Ramer MS. Depletion of spinal 5-HT accelerates mechanosensory recovery in the deafferented rat spinal cord. Exp Neurol 2010; 222:277-84. [PMID: 20079735 DOI: 10.1016/j.expneurol.2010.01.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Revised: 12/17/2009] [Accepted: 01/07/2010] [Indexed: 01/05/2023]
Abstract
Dorsal root injuries (DRIs), resulting in the permanent disconnection of nerve roots from the spinal cord, lead to sensory impairments, including both the loss of sensation and the development of neuropathic pain in the affected limb. DRI results in axonal sprouting of intraspinal serotonergic fibers, but the functional consequences of this response to spinal deafferentation remains unclear. Here we aimed to clarify the role of descending serotonergic projections in both mechanosensation and pain following DRI. By ablating serotonergic input to the spinal cord via 5,7-dihydroxytryptamine (5,7-DHT) prior to DRI in rats, we found that serotonergic input to the dorsal horn normally inhibits the recovery of mechanosensation but has no effect on the development or resolution of cold pain. Endogenous brain-derived neurotrophic factor (BDNF) is upregulated by activated microglia, is required for sprouting of serotonergic axons and neuropeptide tyrosine (NPY)-positive interneurons, and suppresses mechanosensory recovery following DRI. Intriguingly, we found that the density of activated microglia, the amount of BDNF protein, and density of NPY-positive processes were all significantly reduced in 5,7-DHT-treated rats, suggesting that serotonergic input to the deafferented dorsal horn is required for all of these consequences of spinal deafferentation. These results indicate that BDNF-dependent serotonergic and/or increases in NPY-positive fiber density slows, and ultimately halts, mechanosensory recovery following DRI.
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Affiliation(s)
- J J Cragg
- ICORD (International Collaboration on Repair Discoveries), Blusson Spinal Cord Centre, Vancouver, BC, Canada V5Z 1M9
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25
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Lloret Linares C, Declèves X, Oppert JM, Basdevant A, Clement K, Bardin C, Scherrmann JM, Lepine JP, Bergmann JF, Mouly S. Pharmacology of morphine in obese patients: clinical implications. Clin Pharmacokinet 2009; 48:635-51. [PMID: 19743886 DOI: 10.2165/11317150-000000000-00000] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Morphine is an analgesic drug used to treat acute and chronic pain. Obesity is frequently associated with pain of various origins (e.g. arthritis, fibromyalgia, cancer), which increases the need for analgesic drugs. Obesity changes drug pharmacokinetics, and for certain drugs, specific modalities of prescription have been proposed for obese patients. However, scant data are available regarding the pharmacokinetics and pharmacodynamics of morphine in obesity. Prescription of morphine depends on pain relief but the occurrence of respiratory adverse effects correlates with obesity, and is not currently taken into account. Variations in the volume of distribution, elimination half-life and oral clearance of morphine, as well as recent advances in the respective roles of drug-metabolizing enzymes, catechol-O-methyltransferase and the mu opioid receptor in morphine pharmacokinetics and pharmacodynamics, may contribute to differences between obese and non-obese patients. In addition, drug-drug interactions may alter the disposition of morphine and its glucuronide metabolites, which may either increase the risk of adverse effects or reduce drug efficacy.
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Affiliation(s)
- Célia Lloret Linares
- Unit of Therapeutic Research, Department of Internal Medicine, Hôpital Lariboisière, Assistance Publique-Hôpitaux de Paris, Paris, France
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26
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Lu VB, Biggs JE, Stebbing MJ, Balasubramanyan S, Todd KG, Lai AY, Colmers WF, Dawbarn D, Ballanyi K, Smith PA. Brain-derived neurotrophic factor drives the changes in excitatory synaptic transmission in the rat superficial dorsal horn that follow sciatic nerve injury. J Physiol 2009; 587:1013-32. [PMID: 19124536 DOI: 10.1113/jphysiol.2008.166306] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Peripheral nerve injury can promote neuropathic pain. The basis of the 'central sensitization' that underlies this often intractable condition was investigated using 14-20-day chronic constriction injury (CCI) of the sciatic nerve of 20-day-old rats followed by electrophysiological analysis of acutely isolated spinal cord slices. In addition, defined-medium organotypic spinal cord slice cultures were exposed for 5-6 days to brain-derived neurotrophic factor (BDNF, 200 ng ml(-1)) or to medium conditioned with activated microglia (aMCM). Since microglial activation is an early consequence of CCI, the latter manipulation allowed us to model the effect of peripheral nerve injury on the dorsal horn in vitro. Using whole-cell recording from superficial dorsal horn neurons, we found that both BDNF and CCI increased excitatory synaptic drive to putative excitatory 'radial delay' neurons and decreased synaptic excitation of inhibitory 'tonic islet/central' neurons. BDNF also attenuated synaptic excitation of putative GABAergic neurons identified by glutamic acid decarboxylase (GAD) immunoreactivity. Intrinsic neuronal properties (rheobase, input resistance and action potential discharge rates) were unaffected. Exposure of organotypic cultures to either BDNF or aMCM increased overall excitability of the dorsal horn, as seen by increased cytoplasmic Ca(2+) responses to 35 mm K(+) as monitored by confocal Fluo-4AM imaging. The effect of aMCM was attenuated by the recombinant BDNF binding protein TrkBd5 and the effect of BDNF persisted when GABAergic inhibition was blocked with SR95531. These findings suggest that CCI enhances excitatory synaptic drive to excitatory neurons but decreases that to inhibitory neurons. Both effects are mediated by nerve injury-induced release of BDNF from microglia.
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Affiliation(s)
- Van B Lu
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
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Wong JW, McPhail LT, Brastianos HC, Andersen RJ, Ramer MS, O'Connor TP. A novel diketopiperazine stimulates sprouting of spinally projecting axons. Exp Neurol 2008; 214:331-40. [DOI: 10.1016/j.expneurol.2008.08.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 07/02/2008] [Accepted: 08/30/2008] [Indexed: 12/13/2022]
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Ramer MS. Anatomical and functional characterization of neuropil in the gracile fasciculus. J Comp Neurol 2008; 510:283-96. [PMID: 18634004 DOI: 10.1002/cne.21785] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A fundamental organizational principle of the central nervous system is that gray matter is the province of neuronal somata, white matter their processes. However, the rat and primate dorsal columns (archetypal spinal "white matter" tracts) are actually of intermediate character, insofar as they contain a surprisingly prominent neuropil of unknown function. Here I report on the morphology, inputs, projections, and functional properties of these neurons. Small fusiform and larger lentiform neurons are most abundant in the gracile fasciculus of the cervical and lumbar enlargements and are absent from the cuneate fasciculus and corticospinal tract. Many have dendrites that run along the dorsal pia, and, although in transverse sections these neurons appear isolated from the gray matter, they are also connected to area X by varicose and sometimes loosely fasciculated dendrites. These neurons receive neurochemically diverse, compartmentalized synaptic inputs (primary afferent, intrinsic and descending), half express the substance P receptor, and some project supraspinally. Unlike substantia gelatinosa neurons, they do not express protein kinase C gamma. Functionally, they have small receptive fields, which are somatotopically appropriate with respect to their anterior-posterior position along the neuraxis. They respond to innocuous and/or noxious mechanical stimulation of the distal extremities, and some are prone to central sensitization or "windup." Morphologically, neurochemically, and functionally, therefore, these cells most closely resemble neurons in laminae III-VI in the dorsal horn. The proximity of their dorsal dendrites to the pia mater may also reflect an ability to integrate internal (e.g., changes in cerebrospinal fluid compostition) and external (e.g., somatic) stimuli.
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Affiliation(s)
- Matt S Ramer
- ICORD (International Collaboration on Repair Discoveries), University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
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29
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Soril LJ, Ramer LM, McPhail LT, Kaan TK, Ramer MS. Spinal brain-derived neurotrophic factor governs neuroplasticity and recovery from cold-hypersensitivity following dorsal rhizotomy. Pain 2008; 138:98-110. [DOI: 10.1016/j.pain.2007.11.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Revised: 11/07/2007] [Accepted: 11/19/2007] [Indexed: 12/22/2022]
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30
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Bertelli JA, Ghizoni MF. Pain after avulsion injuries and complete palsy of the brachial plexus: the possible role of nonavulsed roots in pain generation. Neurosurgery 2008; 62:1104-13; discussion 1113-4. [PMID: 18580808 DOI: 10.1227/01.neu.0000325872.37258.12] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE Pain after complete brachial palsy has been attributed to the deafferentation of the spinal cord subjected to root avulsion. However, the large majority of patients have at least one nonavulsed root. We postulated that pain, be it subacute or chronic, originates in the stump of the nonavulsed roots. METHODS Thirty-six patients underwent brachial plexus grafting within 8 months of their initial injury. Ten other patients with palsy that had lasted for more than 2 years underwent selective, computed tomography-guided anesthetic blocks of the nonavulsed root. Pain was evaluated at different intervals, using a numerical scale ranging from 0 (no pain) to 10 (severe pain). RESULTS In all groups, pain decreased substantially or disappeared after a local anesthetic block or grafting. In the patients who underwent grafting, pain reduction was noted the first day after surgery in 56% of the 36 patients. Three weeks after surgery, pain decreased dramatically, by 80% (P < 0.001). By 12 months after surgery, pain had decreased by 90%, and within 24 months, by 95%. Only the difference between 3 weeks and 24 months after surgery was significant (P < 0.001). At final evaluation, 80% of the patients receiving grafts reported either no or minimal pain. CONCLUSION Our data suggest that nonavulsed roots mediate pain in subacute and chronic complete brachial plexus palsy.
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Affiliation(s)
- Jayme A Bertelli
- Department of Orthopedic Surgery, Governador Celso Ramos Hospital, Florianpolis, SC, USA.
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31
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The impact of neurotrophin-3 on the dorsal root transitional zone following injury. Spinal Cord 2008; 46:804-10. [PMID: 18542093 DOI: 10.1038/sc.2008.57] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
STUDY DESIGN Morphological and Stereological assessment of the dorsal root transitional zone (DRTZ) following complete crush injury, using light microscopy (LM) and transmission electron microscopy (TEM). OBJECTIVES To assess the effect of exogenous neurotrophin-3 (NT-3) on the response of glial cells and axons to dorsal root damage. SETTING Department of Anatomy, University College Cork, Ireland and Department of Physiology, UMDS, University of London, UK. METHODS Cervical roots (C6-8) from rats which had undergone dorsal root crush axotomy 1 week earlier, in the presence (n=3) and absence (n=3) of NT-3, were processed for LM and TEM. RESULTS Unmyelinated axon number and size was greater in the DRTZ proximal (Central Nervous System; CNS) and distal (Peripheral Nervous System; PNS) compartments of NT-3-treated tissue. NT-3 was associated with a reduced astrocytic response, an increase in the proportion of oligodendrocytic tissue and a possible inhibition or delay of microglial activation. Disrupted-myelin volume in the DRTZ PNS and CNS compartments of treated tissue was lower, than in control tissue. In the PNS compartment, NT-3 treatment increased phagocyte and blood vessel numbers. It decreased myelinating activity, as sheath thickness was significantly lower and may also account for the noted lower Schwann cell and organelle volume in the test group. CONCLUSIONS Our observations suggest that NT-3 interacts with non-neuronal tissue to facilitate the regenerative effort of damaged axons. This may be as a consequence of a direct action or indirectly mediated by modulation of non-neuronal responses to injury.
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Bertelli JA, Ghizoni MF. PAIN AFTER AVULSION INJURIES AND COMPLETE PALSY OF THE BRACHIAL PLEXUS. Neurosurgery 2008. [DOI: 10.1227/01.neu.0000315302.60829.62] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Song XY, Li F, Zhang FH, Zhong JH, Zhou XF. Peripherally-derived BDNF promotes regeneration of ascending sensory neurons after spinal cord injury. PLoS One 2008; 3:e1707. [PMID: 18320028 PMCID: PMC2246162 DOI: 10.1371/journal.pone.0001707] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Accepted: 02/04/2008] [Indexed: 12/12/2022] Open
Abstract
Background The blood brain barrier (BBB) and truncated trkB receptor on astrocytes prevent the penetration of brain derived neurotrophic factor (BDNF) applied into the peripheral (PNS) and central nervous system (CNS) thus restrict its application in the treatment of nervous diseases. As BDNF is anterogradely transported by axons, we propose that peripherally derived and/or applied BDNF may act on the regeneration of central axons of ascending sensory neurons. Methodology/Principal Findings The present study aimed to test the hypothesis by using conditioning lesion of the sciatic nerve as a model to increase the expression of endogenous BDNF in sensory neurons and by injecting exogenous BDNF into the peripheral nerve or tissues. Here we showed that most of regenerating sensory neurons expressed BDNF and p-CREB but not p75NTR. Conditioning-lesion induced regeneration of ascending sensory neuron and the increase in the number of p-Erk positive and GAP-43 positive neurons was blocked by the injection of the BDNF antiserum in the periphery. Enhanced neurite outgrowth of dorsal root ganglia (DRG) neurons in vitro by conditioning lesion was also inhibited by the neutralization with the BDNF antiserum. The delivery of exogenous BDNF into the sciatic nerve or the footpad significantly increased the number of regenerating DRG neurons and regenerating sensory axons in the injured spinal cord. In a contusion injury model, an injection of BDNF into the footpad promoted recovery of motor functions. Conclusions/Significance Our data suggest that endogenous BDNF in DRG and spinal cord is required for the enhanced regeneration of ascending sensory neurons after conditioning lesion of sciatic nerve and peripherally applied BDNF may have therapeutic effects on the spinal cord injury.
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Affiliation(s)
- Xing-Yun Song
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Fang Li
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
- Department of Anatomy and Neurobiology, Xiangya School of Medicine, Central South University, Changsha, People's Republic of China
| | - Feng-He Zhang
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Jin-Hua Zhong
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Xin-Fu Zhou
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
- *E-mail:
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