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Poddar S, Mondal H, Podder I. Aetiology, pathogenesis and management of neuropathic itch: A narrative review with recent updates. Indian J Dermatol Venereol Leprol 2024; 90:5-18. [PMID: 37317726 DOI: 10.25259/ijdvl_846_2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Accepted: 02/17/2023] [Indexed: 06/16/2023]
Abstract
Neuropathic itch is a relatively common yet under-reported cause of systemic pruritus. It is a debilitating condition often associated with pain, which impairs the patient's quality of life. Although much literature exists about renal and hepatic pruritus, there is a dearth of information and awareness about neuropathic itch. The pathogenesis of neuropathic itch is complex and can result from an insult at any point along the itch pathway, ranging from the peripheral receptors and nerves until the brain. There are several causes of neuropathic itch, many of which do not produce any skin lesions and are thus, often missed. A detailed history and clinical examination are necessary for the diagnosis, while laboratory and radiologic investigations may be needed in select cases. Several therapeutic strategies currently exist involving both non-pharmacological and pharmacological measures, the latter including topical, systemic, and invasive options. Further research is ongoing to clarify its pathogenesis and to design newer targeted therapies with minimal adverse effects. This narrative review highlights the current understanding of this condition, focusing on its causes, pathogenesis, diagnosis, and management, along with newer investigational drugs.
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Affiliation(s)
- Shreya Poddar
- Department of Dermatology, Asansol District Hospital, Asansol, West Bengal, India
| | - Himel Mondal
- Department of Physiology, All India Institute of Medical Sciences (AIIMS), Deoghar, Jharkhand, India
| | - Indrashis Podder
- Department of Dermatology, College of Medicine & Sagore Dutta Hospital, Kolkata, West Bengal, India
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2
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Abstract
This JAMA Network Insight reviews the underlying mechanisms and management of peripheral sensory itch conditions.
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Affiliation(s)
- Kelsey L Auyeung
- Kimberly and Eric J. Waldman Department of Dermatology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Blair A Jenkins
- Department of Dermatology, Columbia University Vagelos College of Physicians and Surgeons, New York, New York
| | - Brian S Kim
- Kimberly and Eric J. Waldman Department of Dermatology, Icahn School of Medicine at Mount Sinai, New York, New York
- Mark Lebwohl Center for Neuroinflammation & Sensation, Icahn School of Medicine at Mount Sinai, New York, New York
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3
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Nattkemper LA, Vander Does A, Stull CM, Lavery MJ, Valdes-Rodriguez R, McGregory M, Chan YH, Yosipovitch G. Prolonged Antipruritic Effect of Botulinum Toxin Type A on Cowhage-induced Itch: A Randomized, Single-blind, Placebo-controlled Trial. Acta Derm Venereol 2023; 103:adv6581. [PMID: 37584094 PMCID: PMC10442928 DOI: 10.2340/actadv.v103.6581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 05/17/2023] [Indexed: 08/17/2023] Open
Abstract
Botulinum toxin type A (Botox) is thought to have antipruritic effects through inhibition of pruritic factors, including acetylcholine, substance P, and glutamate. The aim of this randomized, single-blind, placebo-controlled trial was to test the effect of botulinum toxin type A on cowhage, a non-histaminergic model for chronic itch. Botulinum toxin type A was injected into the arm of 35 healthy subjects, with a saline control injected into the contralateral arm. Thermal sensory parameters (warmth and heat thresholds and heat pain intensity) and itch intensity after cowhage application were examined on test areas. Botulinum toxin type A reduced itch intensity, overall perceived itch (area under the curve (AUC); percentage change from baseline), and peak itch intensity compared with the control at 1 week, 1 month, and 3 months. Botulinum toxin type A had no effect on thermal thresholds or heat pain intensity. In conclusion, botulinum toxin type A reduced cowhage itch for at least 3 months, which suggests that botulinum toxin type A is a potential long-lasting treatment for localized, non-histaminergic itch.
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Affiliation(s)
- Leigh A Nattkemper
- Department of Dermatology, Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Ashley Vander Does
- Department of Dermatology, Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Carolyn M Stull
- Department of Dermatology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | - Michael J Lavery
- Department of Dermatology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | - Rodrigo Valdes-Rodriguez
- Department of Dermatology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | - Marlene McGregory
- Department of Dermatology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | - Yiong Huak Chan
- Biostatistics Unit, National University of Singapore Lon Lin School of Medicine, Singapore, Singapore
| | - Gil Yosipovitch
- Department of Dermatology, Miami Itch Center, University of Miami Miller School of Medicine, Miami, FL, USA.
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Vander Does A, Ju T, Mohsin N, Chopra D, Yosipovitch G. How to get rid of itching. Pharmacol Ther 2023; 243:108355. [PMID: 36739914 DOI: 10.1016/j.pharmthera.2023.108355] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 01/01/2023] [Accepted: 01/31/2023] [Indexed: 02/05/2023]
Abstract
Itch is an unpleasant sensation arising from a variety of dermatologic, neuropathic, systemic, and psychogenic etiologies. Various itch pathways are implicated according to the underlying etiology. A variety of pruritogens, or itch mediators, as well as receptors have been identified and provide potential therapeutic targets. Recent research has primarily focused on targeting inflammatory cytokines and Janus kinase signaling, protease-activated receptors, substance P and neurokinin, transient receptor potential-vanilloid ion channels, Mas-related G-protein-coupled receptors (MRGPRX2 and MRGPRX4), the endogenous opioid and cannabinoid balance, and phosphodiesterase 4. Periostin, a newly identified pruritogen, should be further explored with clinical trials. Drugs targeting neural sensitization including the gabergic system and P2X3 are other potential drugs for chronic itch. There is a need for more targeted therapies to improve clinical outcomes and reduce side effects.
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Affiliation(s)
- Ashley Vander Does
- Dr Phillip Frost Department of Dermatology and Miami Itch Center, University of Miami, Miami, FL, USA
| | - Teresa Ju
- Dr Phillip Frost Department of Dermatology and Miami Itch Center, University of Miami, Miami, FL, USA
| | - Noreen Mohsin
- Dr Phillip Frost Department of Dermatology and Miami Itch Center, University of Miami, Miami, FL, USA
| | - Divya Chopra
- Dr Phillip Frost Department of Dermatology and Miami Itch Center, University of Miami, Miami, FL, USA
| | - Gil Yosipovitch
- Dr Phillip Frost Department of Dermatology and Miami Itch Center, University of Miami, Miami, FL, USA.
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Gazerani P. How Does Botulinum Toxin Inhibit Itch? Toxins (Basel) 2022; 14:toxins14100701. [PMID: 36287970 PMCID: PMC9610088 DOI: 10.3390/toxins14100701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 10/06/2022] [Accepted: 10/10/2022] [Indexed: 12/04/2022] Open
Abstract
Two decades after reports of the anti-pruritic effects of botulinum neurotoxins (BoNTs), there is still no approved product for the anti-itch indication of BoNTs, and most clinical case reports still focus on the off-label use of BoNTs for various itchy conditions. Few randomized clinical trials have been conducted with controversial results, and the beneficial effects of BoNTs against itch are mainly based on case studies and case series. These studies are valuable in presenting the potential application of BoNTs in chronic pruritic conditions, but due to the nature of these studies, they are categorized as providing lower levels of evidence or lower grades of recommendation. To obtain approval for the anti-pruritic indication of BoNTs, higher levels of evidence are required, which can be achieved through conducting large-scale and well-designed studies with proper control groups and established careful and reliable primary and secondary outcomes. In addition to clinical evidence, presenting the mechanism-based antipruritic action of BoNTs can potentially strengthen, accelerate, and facilitate the current efforts towards further investments in accelerating the field towards the potential approval of BoNTs for itchy conditions. This review, therefore, aimed to provide the state-of-the-art mechanisms underlying the anti-itch effect of BoNTs from basic studies that resemble various clinical conditions with itch as a hallmark. Evidence of the neuronal, glial, and immune modulatory actions of BoNTs in reducing the transmission of itch are presented, and future potential directions are outlined.
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Affiliation(s)
- Parisa Gazerani
- Department of Life Sciences and Health, Faculty of Health Sciences, Oslo Metropolitan University, 0130 Oslo, Norway; or
- Department of Health Science and Technology, Faculty of Medicine, Aalborg University, 9220 Aalborg East, Denmark
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6
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Is myasthenia gravis a contraindication for botulinum toxin? J Clin Neurosci 2021; 95:44-47. [PMID: 34929650 DOI: 10.1016/j.jocn.2021.11.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 11/06/2021] [Accepted: 11/11/2021] [Indexed: 11/20/2022]
Abstract
Botulinum toxin (BTX) is a neurotoxin that has been used to treat various disorders and has also become a popular choice for cosmetic indications, yet traditionally, myasthenia gravis (MG) is considered a contraindication for BTX. To determine whether BTX should be avoided in MG patients, clinical data from our MG and dystonia specialist clinic were analyzed retrospectively. In addition, a systematic literature review was conducted to identify all published cases associated with the co-existence of MG and BTX treatments. Here, we described one patient from our clinic, who received BTX injections before being given MG diagnosis. After the literature review, 8 cases with subclinical MG previously treated with BTX for dystonia or cosmetic reasons ("BTX injections before MG diagnosis") were identified. Markedly, 8 out of 8 (100%) patients developed obvious muscle weakness. In contrast, 10 patients presenting MG as comorbidity had received BTX for dystonia or overactive bladder ("BTX injection after MG diagnosis"), and 8 out of 10 (80%) experienced improved symptoms through appropriate dose modifications and adequate treatment for MG before receiving BTX injections. These findings support that, under proper management of co-existing MG, BTX could be used safely and successfully in patients presenting MG comorbidities in the future.
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Huang SH, Wu KW, Lo JJ, Wu SH. Synergic Effect of Botulinum Toxin Type A and Triamcinolone Alleviates Scar Pruritus by Modulating Epidermal Hyperinnervation: A Preliminary Report. Aesthet Surg J 2021; 41:NP1721-NP1731. [PMID: 33662123 DOI: 10.1093/asj/sjab105] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Patients often experience scar-related pruritus, which adversely affects quality of life. Triamcinolone acetonide (TAC) is widely used to treat pathologic scars, and botulinum toxin type A (BTX-A) reportedly improves scarring and associated discomfort. OBJECTIVES The aim of this study was to investigate the clinical efficacy of combining TAC and BTX-A to reduce scar itch; potential mechanisms were investigated via an animal model. METHODS For the clinical study, each scar on a patient was divided into 2 equal parts, with one part receiving TAC/BTX-A and the other TAC alone. Therapeutic interventions were administered over 3 sessions at 4-week intervals. Itch intensity was measured on a visual analog scale before each therapeutic intervention (V1, V2, V3) and 4 weeks after the last intervention (V4). For the animal model, rats were allocated into 5 groups: control, untreated burn, TAC, BTX-A, and TAC/BTX-A. We evaluated alloknesis in the right hind paw and analyzed possible molecular mechanisms. RESULTS In humans, TAC/BTX-A significantly reduced scar itch compared with TAC alone at V4 (P = 0.04). In rats, post-burn itch was mitigated at 4 weeks after treatment with TAC, BTX-A, and TAC/BTX-A (P = 0.03, P = 0.0054, and P = 0.0053, respectively). TAC/BTX-A significantly decreased the density of intraepidermal nerve fibers post-burn relative to the untreated burn (P = 0.0008). TAC/BTX-A downregulated the expressions of nerve growth factor and protein transient receptor potential vanilloid subtype 1. CONCLUSIONS TAC/BTX-A therapy exhibited enhanced and sustained clinical efficacy in relieving scar itch, possibly via modulating epidermal innervation and expression of transient receptor potential vanilloid subtype 1 . LEVEL OF EVIDENCE: 2
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Affiliation(s)
- Shu-Hung Huang
- Division of Plastic Surgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Kuo-Wei Wu
- Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Jing-Jou Lo
- Department of General Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Sheng-Hua Wu
- Department of Anesthesiology, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
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Gold MH. Commentary on: Synergic Effect of Botulinum Toxin Type A and Triamcinolone Alleviates Scar Pruritus by Modulating Epidermal Hyperinnervation: A Preliminary Report. Aesthet Surg J 2021; 41:NP1732-NP1733. [PMID: 33822858 DOI: 10.1093/asj/sjab063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Sutaria N, Adawi W, Goldberg R, Roh YS, Choi J, Kwatra SG. Itch: Pathogenesis and treatment. J Am Acad Dermatol 2021; 86:17-34. [PMID: 34648873 DOI: 10.1016/j.jaad.2021.07.078] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 07/22/2021] [Accepted: 07/23/2021] [Indexed: 12/19/2022]
Abstract
Itch pathogenesis is broadly characterized into histaminergic and nonhistaminergic pathways and transmitted via 2 main receptor families: G protein-coupled receptors and transient receptor potential channels. In the skin, itch is primarily transmitted by unmyelinated type C and thinly myelinated type Aδ nerve fibers. Crosstalk between the immune and neural systems modulates itch transmission at the skin, spinal cord, and brain. Among the many known pruritogens, Th2 cytokines, such as interleukin-4, interleukin-13, interleukin-31, and thymic stromal lymphopoietin, are particularly important mediators that signal through shared Janus kinase pathways, representing novel targets for novel itch therapeutics. Emerging evidence has also revealed that the opioidergic system is a potent modulator of itch transmission, with increased μ-opioid activity and decreased κ-opioid activity contributing to itch pathogenesis. Optimal management of itch requires that treatment approaches be tailored to specific etiologic itch subtypes. When the etiology is unknown and patients are given a diagnosis of chronic pruritus of unknown origin, treatment should be guided by the presence of Th2 polarization, often reflected by increased blood eosinophils. In the second article of this 2-part series, we outline our current understanding of itch pathogenesis and discuss available and emerging treatments for itch.
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Affiliation(s)
- Nishadh Sutaria
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Waleed Adawi
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Rebecca Goldberg
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Youkyung S Roh
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Justin Choi
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Shawn G Kwatra
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, Maryland; Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
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10
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Meng J, Li Y, Fischer MJM, Steinhoff M, Chen W, Wang J. Th2 Modulation of Transient Receptor Potential Channels: An Unmet Therapeutic Intervention for Atopic Dermatitis. Front Immunol 2021; 12:696784. [PMID: 34276687 PMCID: PMC8278285 DOI: 10.3389/fimmu.2021.696784] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Accepted: 06/15/2021] [Indexed: 12/12/2022] Open
Abstract
Atopic dermatitis (AD) is a multifaceted, chronic relapsing inflammatory skin disease that affects people of all ages. It is characterized by chronic eczema, constant pruritus, and severe discomfort. AD often progresses from mild annoyance to intractable pruritic inflammatory lesions associated with exacerbated skin sensitivity. The T helper-2 (Th2) response is mainly linked to the acute and subacute phase, whereas Th1 response has been associated in addition with the chronic phase. IL-17, IL-22, TSLP, and IL-31 also play a role in AD. Transient receptor potential (TRP) cation channels play a significant role in neuroinflammation, itch and pain, indicating neuroimmune circuits in AD. However, the Th2-driven cutaneous sensitization of TRP channels is underappreciated. Emerging findings suggest that critical Th2-related cytokines cause potentiation of TRP channels, thereby exaggerating inflammation and itch sensation. Evidence involves the following: (i) IL-13 enhances TRPV1 and TRPA1 transcription levels; (ii) IL-31 sensitizes TRPV1 via transcriptional and channel modulation, and indirectly modulates TRPV3 in keratinocytes; (iii) The Th2-cytokine TSLP increases TRPA1 synthesis in sensory neurons. These changes could be further enhanced by other Th2 cytokines, including IL-4, IL-25, and IL-33, which are inducers for IL-13, IL-31, or TSLP in skin. Taken together, this review highlights that Th2 cytokines potentiate TRP channels through diverse mechanisms under different inflammatory and pruritic conditions, and link this effect to distinct signaling cascades in AD. This review strengthens the notion that interrupting Th2-driven modulation of TRP channels will inhibit transition from acute to chronic AD, thereby aiding the development of effective therapeutics and treatment optimization.
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Affiliation(s)
- Jianghui Meng
- School of Life Sciences, Henan University, Kaifeng, China.,National Institute for Cellular Biotechnology, Dublin City University, Dublin, Ireland
| | - Yanqing Li
- School of Life Sciences, Henan University, Kaifeng, China
| | - Michael J M Fischer
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Martin Steinhoff
- Department of Dermatology and Venereology, Hamad Medical Corporation, Doha, Qatar.,Translational Research Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar.,Dermatology Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar.,Department of Dermatology, Weill Cornell Medicine-Qatar, Doha, Qatar.,Qatar University, College of Medicine, Doha, Qatar.,Department of Dermatology, Weill Cornell Medicine, New York, NY, United States
| | - Weiwei Chen
- School of Life Sciences, Henan University, Kaifeng, China
| | - Jiafu Wang
- School of Life Sciences, Henan University, Kaifeng, China.,School of Biotechnology, Faculty of Science and Health, Dublin City University, Dublin, Ireland
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11
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Ahn YH, Kang HR. Pathophysiology, diagnosis, and management of chronic pruritus. ALLERGY ASTHMA & RESPIRATORY DISEASE 2021. [DOI: 10.4168/aard.2021.9.4.189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Yoon Hae Ahn
- Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea
| | - Hye-Ryun Kang
- Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea
- Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea
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12
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Introduction to the Toxins Special Issue on Botulinum Neurotoxins in the Nervous System: Future Challenges for Novel Indications. Toxins (Basel) 2020; 12:toxins12090601. [PMID: 32957443 PMCID: PMC7551742 DOI: 10.3390/toxins12090601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 09/14/2020] [Indexed: 11/18/2022] Open
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13
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Repeated intrastriatal application of botulinum neurotoxin-A did not influence choline acetyltransferase-immunoreactive interneurons in hemiparkinsonian rat brain - A histological, stereological and correlational analysis. Brain Res 2020; 1742:146877. [PMID: 32387181 DOI: 10.1016/j.brainres.2020.146877] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 04/06/2020] [Accepted: 05/05/2020] [Indexed: 12/29/2022]
Abstract
In Parkinson's disease, dopamine depletion leads to hyperactivity of cholinergic interneurons in the caudate-putamen (CPu). Botulinum neurotoxin-A (BoNT-A) inhibits the release of acetylcholine in the peripheral nervous system and is also thought to act as a local anticholinergic drug when injected intrastriatally. In hemiparkinsonian (hemi-PD) rats, a unilateral intrastriatal injection of 1 ng BoNT-A significantly diminished apomorphine-induced rotation behavior for at least 3 months, the effect fading thereafter. A second intrastriatal BoNT-A application, 6 months after the first one, led to a stronger and longer-lasting, beneficial behavioral reaction. As a single BoNT-A injection was not cytotoxic in the rat striatum and resembled BoNT-A treatment in clinical practice, here, we investigated the structural outcome of repeated intrastriatal BoNT-A injections with respect to striatal volume, the number of choline acetyltransferase-immunoreactive (ChAT-ir) interneurons and of the length of their dendritic arbors, and the numeric density of ChAT-ir BoNT-A-induced varicosities (BiVs). Repeated unilateral intrastriatal BoNT-A application decreased the volume of the injected CPu, but did not significantly change the number of striatal ChAT-ir interneurons. Also, the total dendrite length of ChAT-ir interneurons after repeated BoNT-A application resembled the values in double vehicle-injected hemi-PD rats. In repeatedly BoNT-A-injected hemi-PD rats, the numeric density of ChAT-ir BiVs in the CPu was increased compared with rats only intrastriatally injected once with BoNT-A. Even repeated BoNT-A injections in rat striata did not cause substantial morphological changes in ChAT-ir neuron, except for the increased numeric density of ChAT-ir BiVs.
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Yosipovitch G, Rosen JD, Hashimoto T. Itch: From mechanism to (novel) therapeutic approaches. J Allergy Clin Immunol 2019; 142:1375-1390. [PMID: 30409247 DOI: 10.1016/j.jaci.2018.09.005] [Citation(s) in RCA: 183] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 08/27/2018] [Accepted: 09/07/2018] [Indexed: 12/13/2022]
Abstract
Itch is a common sensory experience that is prevalent in patients with inflammatory skin diseases, as well as in those with systemic and neuropathic conditions. In patients with these conditions, itch is often severe and significantly affects quality of life. Itch is encoded by 2 major neuronal pathways: histaminergic (in acute itch) and nonhistaminergic (in chronic itch). In the majority of cases, crosstalk existing between keratinocytes, the immune system, and nonhistaminergic sensory nerves is responsible for the pathophysiology of chronic itch. This review provides an overview of the current understanding of the molecular, neural, and immune mechanisms of itch: beginning in the skin, proceeding to the spinal cord, and eventually ascending to the brain, where itch is processed. A growing understanding of the mechanisms of chronic itch is expanding, as is our pipeline of more targeted topical and systemic therapies. Our therapeutic armamentarium for treating chronic itch has expanded in the last 5 years, with developments of topical and systemic treatments targeting the neural and immune systems.
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Affiliation(s)
- Gil Yosipovitch
- Department of Dermatology and Cutaneous Surgery and Miami Itch Center Miller School of Medicine University of Miami, Miami, Fla.
| | - Jordan Daniel Rosen
- Department of Dermatology and Cutaneous Surgery and Miami Itch Center Miller School of Medicine University of Miami, Miami, Fla
| | - Takashi Hashimoto
- Department of Dermatology and Cutaneous Surgery and Miami Itch Center Miller School of Medicine University of Miami, Miami, Fla
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