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Sinha S, Gabriel VA, Arora RK, Shin W, Scott J, Bharadia SK, Verly M, Rahmani WM, Nickerson DA, Fraulin FO, Chatterjee P, Ahuja RB, Biernaskie JA. Interventions for postburn pruritus. Cochrane Database Syst Rev 2024; 6:CD013468. [PMID: 38837237 PMCID: PMC11152192 DOI: 10.1002/14651858.cd013468.pub2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 06/07/2024]
Abstract
BACKGROUND Postburn pruritus (itch) is a common and distressing symptom experienced on healing or healed burn or donor site wounds. Topical, systemic, and physical treatments are available to control postburn pruritus; however, it remains unclear how effective these are. OBJECTIVES To assess the effects of interventions for treating postburn pruritus in any care setting. SEARCH METHODS In September 2022, we searched the Cochrane Wounds Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), Ovid MEDLINE (including In-Process & Other Non-Indexed Citations), Ovid Embase, and EBSCO CINAHL Plus. We also searched clinical trials registries and scanned references of relevant publications to identify eligible trials. There were no restrictions with respect to language, publication date, or study setting. SELECTION CRITERIA Randomised controlled trials (RCTs) that enrolled people with postburn pruritus to compare an intervention for postburn pruritus with any other intervention, placebo or sham intervention, or no intervention. DATA COLLECTION AND ANALYSIS We used the standard methodological procedures expected by Cochrane. We used GRADE to assess the certainty of the evidence. MAIN RESULTS We included 25 RCTs assessing 21 interventions with 1166 randomised participants. These 21 interventions can be grouped into six categories: neuromodulatory agents (such as doxepin, gabapentin, pregabalin, ondansetron), topical therapies (such as CQ-01 hydrogel, silicone gel, enalapril ointment, Provase moisturiser, beeswax and herbal oil cream), physical modalities (such as massage therapy, therapeutic touch, extracorporeal shock wave therapy, enhanced education about silicone gel sheeting), laser scar revision (pulsed dye laser, pulsed high-intensity laser, fractional CO2 laser), electrical stimulation (transcutaneous electrical nerve stimulation, transcranial direct current stimulation), and other therapies (cetirizine/cimetidine combination, lemon balm tea). Most RCTs were conducted at academic hospitals and were at a high risk of performance, attrition, and detection bias. While 24 out of 25 included studies reported change in burn-related pruritus, secondary outcomes such as cost-effectiveness, pain, patient perception, wound healing, and participant health-related quality of life were not reported or were reported incompletely. Neuromodulatory agents versus antihistamines or placebo There is low-certainty evidence that doxepin cream may reduce burn-related pruritus compared with oral antihistamine (mean difference (MD) -2.60 on a 0 to 10 visual analogue scale (VAS), 95% confidence interval (CI) -3.79 to -1.42; 2 studies, 49 participants). A change of 2 points represents a minimal clinically important difference (MCID). Due to very low-certainty evidence, it is uncertain whether doxepin cream impacts the incidence of somnolence as an adverse event compared to oral antihistamine (risk ratio (RR) 0.64, 95% CI 0.32 to 1.25; 1 study, 24 participants). No data were reported on pain in the included study. There is low-certainty evidence that gabapentin may reduce burn-related pruritus compared with cetirizine (MD -2.40 VAS, 95% CI -4.14 to -0.66; 1 study, 40 participants). A change of 2 points represents a MCID. There is low-certainty evidence that gabapentin reduces the incidence of somnolence compared to cetirizine (RR 0.02, 95% CI 0.00 to 0.38; 1 study, 40 participants). No data were reported on pain in the included study. There is low-certainty evidence that pregabalin may result in a reduction in burn-related pruritus intensity compared with cetirizine with pheniramine maleate (MD -0.80 VAS, 95% CI -1.24 to -0.36; 1 study, 40 participants). A change of 2 points represents a MCID. There is low-certainty evidence that pregabalin reduces the incidence of somnolence compared to cetirizine (RR 0.04, 95% CI 0.00 to 0.69; 1 study, 40 participants). No data were reported on pain in the included study. There is moderate-certainty evidence that ondansetron probably results in a reduction in burn-related pruritus intensity compared with diphenhydramine (MD -0.76 on a 0 to 10 numeric analogue scale (NAS), 95% CI -1.50 to -0.02; 1 study, 38 participants). A change of 2 points represents a MCID. No data were reported on pain and adverse events in the included study. Topical therapies versus relevant comparators There is moderate-certainty evidence that enalapril ointment probably decreases mean burn-related pruritus compared with placebo control (MD -0.70 on a 0 to 4 scoring table for itching, 95% CI -1.04 to -0.36; 1 study, 60 participants). No data were reported on pain and adverse events in the included study. Physical modalities versus relevant comparators Compared with standard care, there is low-certainty evidence that massage may reduce burn-related pruritus (standardised mean difference (SMD) -0.86, 95% CI -1.45 to -0.27; 2 studies, 166 participants) and pain (SMD -1.32, 95% CI -1.66 to -0.98). These SMDs equate to a 4.60-point reduction in pruritus and a 3.74-point reduction in pain on a 10-point VAS. A change of 2 VAS points in itch represents a MCID. No data were reported on adverse events in the included studies. There is low-certainty evidence that extracorporeal shock wave therapy (ESWT) may reduce burn-related pruritus compared with sham stimulation (SMD -1.20, 95% CI -1.65 to -0.75; 2 studies, 91 participants). This equates to a 5.93-point reduction in pruritus on a 22-point 12-item Pruritus Severity Scale. There is low-certainty evidence that ESWT may reduce pain compared with sham stimulation (MD 2.96 on a 0 to 25 pressure pain threshold (PPT), 95% CI 1.76 to 4.16; 1 study, 45 participants). No data were reported on adverse events in the included studies. Laser scar revision versus untreated or placebo controls There is moderate-certainty evidence that pulsed high-intensity laser probably results in a reduction in burn-related pruritus intensity compared with placebo laser (MD -0.51 on a 0 to 1 Itch Severity Scale (ISS), 95% CI -0.64 to -0.38; 1 study, 49 participants). There is moderate-certainty evidence that pulsed high-intensity laser probably reduces pain compared with placebo laser (MD -3.23 VAS, 95% CI -5.41 to -1.05; 1 study, 49 participants). No data were reported on adverse events in the included studies. AUTHORS' CONCLUSIONS There is moderate to low-certainty evidence on the effects of 21 interventions. Most studies were small and at a high risk of bias related to blinding and incomplete outcome data. Where there is moderate-certainty evidence, practitioners should consider the applicability of the evidence for their patients.
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Affiliation(s)
- Sarthak Sinha
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada
| | - Vincent A Gabriel
- Departments of Clinical Neurosciences, Pediatrics and Surgery, University of Calgary, Calgary Firefighters' Burn Treatment Centre, Calgary, Canada
| | - Rohit K Arora
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada
| | - Wisoo Shin
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada
| | - Janis Scott
- Calgary Firefighters' Burn Treatment Centre, Calgary, Canada
| | - Shyla K Bharadia
- Departments of Clinical Neurosciences, Pediatrics and Surgery, University of Calgary, Calgary Firefighters' Burn Treatment Centre, Calgary, Canada
| | - Myriam Verly
- Division of Plastic and Reconstructive Surgery, University of Calgary, Calgary, Canada
| | - Waleed M Rahmani
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada
| | - Duncan A Nickerson
- Department of Plastic, Burn and Wound Surgery, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Frankie Og Fraulin
- Division of Plastic and Reconstructive Surgery, University of Calgary, Calgary, Canada
- Department of Surgery, Alberta Health Services, Alberta Children's Hospital, Calgary, Canada
| | - Pallab Chatterjee
- Department of Plastic Surgery, Surgical Division, Command Hospital Air Force, Bengaluru, India
| | - Rajeev B Ahuja
- Department of Plastic Surgery, Sir Ganga Ram Hospital, New Delhi, India
| | - Jeff A Biernaskie
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada
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Zhang P, Xiang S, Liu B, Wang X, Yang X, Ye C, Wang Z, Li Y, Zhou L, Wang C, Li H, Huang J, Peng A, Wang X, Wang D, Xiao J, Chen W, Cheng H, Mao N, Wang J, Yang L, Chen J. Randomized controlled trial of nalfurafine for refractory pruritus in hemodialysis patients. Ren Fail 2023; 45:2175590. [PMID: 36856148 PMCID: PMC9980412 DOI: 10.1080/0886022x.2023.2175590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2023] Open
Abstract
Background: Chronic kidney disease-associated pruritus (CKD-aP) is very common and sometimes refractory to treatment in hemodialysis patients. In a trial conducted in Japan, nalfurafine, effectively reduced itching of treatment-resistant CKD-aP. Our present bridging study aimed to evaluate the efficacy and safety of nalfurafine in Chinese cohort with refractory CKD-aP.Methods: In this phase III, multicenter bridging study conducted at 22 sites in China, 141 Chinese cases with refractory CKD-aP were randomly (2:2:1) assigned to receive 5 μg, 2.5 μg of nalfurafine or a placebo orally for 14 days in a double-blind manner. The primary end point was the mean decrease in the mean visual analogue scale (VAS) from baseline.Results: A total of 141 patients were included. The primary endpoint analysis based on full analysis set (FAS), the difference of mean VAS decrease between 5 μg nalfurafine and placebo group was 11.37 mm (p = .041); the difference of mean VAS decrease between 2.5 μg and placebo group was 8.81 mm, but not statistically significantly different. Both differences were greater than 4.13 mm, which met its predefined success criterion of at least 50% efficacy of the key Japanese clinical trial. The per protocol set (PPS) analysis got similar results. The incidence of adverse drug reactions (ADRs) was 49.1% in 5μg, 38.6% in 2.5 μg and 33.3% in placebo group. The most common ADR was insomnia, seen in 21 of the 114 nalfurafine patients.Conclusions: Oral nalfurafine effectively reduced itching with few significant ADRs in Chinese hemodialysis patients with refractory pruritus.
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Affiliation(s)
- Ping Zhang
- Kidney Disease Center, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China,Kidney Disease Center, Key Laboratory of Kidney Disease Prevention and Control Technology, Hangzhou, China,Kidney Disease Center, National Key Clinical Department of Kidney Diseases, Hangzhou, China,Institute of Nephrology, Zhejiang University, Hangzhou, China,Kidney Disease Center, Zhejiang Clinical Research Center of Kidney and Urinary System Disease, Hangzhou, China
| | - Shilong Xiang
- Kidney Disease Center, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China,Kidney Disease Center, Key Laboratory of Kidney Disease Prevention and Control Technology, Hangzhou, China,Kidney Disease Center, National Key Clinical Department of Kidney Diseases, Hangzhou, China,Institute of Nephrology, Zhejiang University, Hangzhou, China,Kidney Disease Center, Zhejiang Clinical Research Center of Kidney and Urinary System Disease, Hangzhou, China
| | - Bicheng Liu
- Department of Nephrology, ZhongDa Hospital, Southeast University, Chongqing, China
| | - Xiaohui Wang
- Department of Nephrology, Fifth Hospital in Wuhan, Wuhan, China
| | - Xiaoping Yang
- Department of Nephrology, The First Affiliated Hospital of Shihezi University School of Medicine, Shihezi, China
| | - Chaoyang Ye
- Department of Nephrology, Shuguang Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Zunsong Wang
- Department of Nephrology, Shandong Province QianFoshan Hospital, Jinan, China
| | - Yanlin Li
- Department of Nephrology, Zhongshan Traditional Chinese Medicine Hospital, Guangzhou, China
| | - Li Zhou
- Department of Nephrology, West China Hospital of Sichuan University, Chengdu, China
| | - Caili Wang
- Department of Nephrology, The First Affiliated Hospital of Baotou Medical College, Inner Mongolia University of Science and Technology, Baotou, China
| | - Hongbo Li
- Department of Nephrology, Wuhan No.1 Hospital, Wuhan, China
| | - Jian Huang
- Department of Nephrology, Jinhua Municipal Central Hospital, Jinhua, China
| | - Ai Peng
- Department of Nephrology, Shanghai Tenth People’s Hospital, Shanghai, China
| | - Xiaoping Wang
- Department of Nephrology, The Central Hospital of Jinan, Jinan, China
| | - Deguang Wang
- Department of Nephrology, The Second Hospital of Anhui Medical University, Hefei, China
| | - Jie Xiao
- Department of Nephrology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Wenli Chen
- Department of Nephrology, The Central Hospital of Wuhan, Wuhan, China
| | - Hong Cheng
- Department of Nephrology, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
| | - Nan Mao
- Department of Nephrology, The First Affiliated Hospital of Chengdu Medical College, Chengdu, China
| | - Jianqin Wang
- Department of Nephrology, Lanzhou University Second Hospital, Lanzhou, China
| | - Lin Yang
- Department of Nephrology, Yichang Central People’s Hospital, Yichang, China
| | - Jianghua Chen
- Kidney Disease Center, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China,Kidney Disease Center, Key Laboratory of Kidney Disease Prevention and Control Technology, Hangzhou, China,Kidney Disease Center, National Key Clinical Department of Kidney Diseases, Hangzhou, China,Institute of Nephrology, Zhejiang University, Hangzhou, China,Kidney Disease Center, Zhejiang Clinical Research Center of Kidney and Urinary System Disease, Hangzhou, China,CONTACT Jianghua Chen Kidney Disease Center, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
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Dalefield ML, Scouller B, Bibi R, Kivell BM. The Kappa Opioid Receptor: A Promising Therapeutic Target for Multiple Pathologies. Front Pharmacol 2022; 13:837671. [PMID: 35795569 PMCID: PMC9251383 DOI: 10.3389/fphar.2022.837671] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 05/20/2022] [Indexed: 11/13/2022] Open
Abstract
Kappa-opioid receptors (KOR) are widely expressed throughout the central nervous system, where they modulate a range of physiological processes depending on their location, including stress, mood, reward, pain, inflammation, and remyelination. However, clinical use of KOR agonists is limited by adverse effects such as dysphoria, aversion, and sedation. Within the drug-development field KOR agonists have been extensively investigated for the treatment of many centrally mediated nociceptive disorders including pruritis and pain. KOR agonists are potential alternatives to mu-opioid receptor (MOR) agonists for the treatment of pain due to their anti-nociceptive effects, lack of abuse potential, and reduced respiratory depressive effects, however, dysphoric side-effects have limited their widespread clinical use. Other diseases for which KOR agonists hold promising therapeutic potential include pruritis, multiple sclerosis, Alzheimer’s disease, inflammatory diseases, gastrointestinal diseases, cancer, and ischemia. This review highlights recent drug-development efforts targeting KOR, including the development of G-protein–biased ligands, mixed opioid agonists, and peripherally restricted ligands to reduce side-effects. We also highlight the current KOR agonists that are in preclinical development or undergoing clinical trials.
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Steinhoff M, Ahmad F, Pandey A, Datsi A, AlHammadi A, Al-Khawaga S, Al-Malki A, Meng J, Alam M, Buddenkotte J. Neuro-immune communication regulating pruritus in atopic dermatitis. J Allergy Clin Immunol 2022; 149:1875-1898. [PMID: 35337846 DOI: 10.1016/j.jaci.2022.03.010] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Revised: 02/13/2022] [Accepted: 03/10/2022] [Indexed: 11/26/2022]
Abstract
Atopic dermatitis (AD) is a common, chronic-relapsing inflammatory skin disease with significant disease burden. Genetic and environmental trigger factors contribute to AD, activating two of our largest organs, the nervous and immune system. Dysregulation of neuro-immune circuits plays a key role in the pathophysiology of AD causing inflammation, pruritus, pain, and barrier dysfunction. Sensory nerves can be activated by environmental or endogenous trigger factors transmitting itch stimuli to the brain. Upon stimulation, sensory nerve endings also release neuromediators into the skin contributing again to inflammation, barrier dysfunction and itch. Additionally, dysfunctional peripheral and central neuronal structures contribute to neuroinflammation, sensitization, nerve elongation, neuropathic itch, thus chronification and therapy-resistance. Consequently, neuro-immune circuits in skin and central nervous system may be targets to treat pruritus in AD. Cytokines, chemokines, proteases, lipids, opioids, ions excite/sensitize sensory nerve endings not only induce itch but further aggravate/perpetuate inflammation, skin barrier disruption, and pruritus. Thus, targeted therapies for neuro-immune circuits as well as pathway inhibitors (e.g., kinase inhibitors) may be beneficial to control pruritus in AD either in systemic and/or topical form. Understanding neuro-immune circuits and neuronal signaling will optimize our approach to control all pathological mechanisms in AD, inflammation, barrier dysfunction and pruritus.
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Affiliation(s)
- 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, USA.
| | - Fareed Ahmad
- Translational Research Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar; Dermatology Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar
| | - Atul Pandey
- Translational Research Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar; Dermatology Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar
| | - Angeliki Datsi
- Institute for Transplantational Diagnostics and Cell Therapeutics, University Hospital Düsseldorf, Düsseldorf, Germany
| | - Ayda AlHammadi
- Department of Dermatology and Venereology, Hamad Medical Corporation, Doha, Qatar
| | - Sara Al-Khawaga
- Department of Dermatology and Venereology, Hamad Medical Corporation, Doha, Qatar
| | - Aysha Al-Malki
- Department of Dermatology and Venereology, Hamad Medical Corporation, Doha, Qatar
| | - Jianghui Meng
- National Institute for Cellular Biotechnology, Dublin City University, Dublin, Ireland
| | - Majid Alam
- Translational Research Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar; Dermatology Institute, Academic Health System, Hamad Medical Corporation, Doha, Qatar
| | - Joerg Buddenkotte
- 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
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Cowan A, Liu-Chen LY, Inan S. Itching-like behavior: A common effect of the kappa opioid receptor antagonist 5′-guanidinonaltrindole and the biased kappa opioid receptor agonist 6′-guanidinonaltrindole in mice. MEDICINE IN DRUG DISCOVERY 2021. [DOI: 10.1016/j.medidd.2021.100097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
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Evaluation of Therapies for Peripheral and Neuraxial Opioid-induced Pruritus based on Molecular and Cellular Discoveries. Anesthesiology 2021; 135:350-365. [PMID: 34237130 DOI: 10.1097/aln.0000000000003844] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Opioids are a mainstay of treatment for pain worldwide. Pruritus, a common side effect of opioids, is a patient dissatisfier that limits their use in many clinical settings. Both parenteral and neuraxial administration of opioids frequently evoke pruritus. The ability of opioids to suppress pain while causing itch continues to perplex clinicians and researchers alike. Several mechanisms have been proposed to explain how opioids can give rise to pruritus, but specific knowledge gaps perpetuate debate. This review summarizes the clinical burden of opioid-induced pruritus and emphasizes recent discoveries of peripheral and central mechanisms for opioid-induced pruritus, particularly with respect to scientific and conceptual advances in spinal cord circuitry and mast cell biology. The mechanisms and effectiveness of existing medications used for clinical management of pruritus will be evaluated, and we will highlight the emerging preclinical utility of selective κ-opioid receptor agonists, such as nalfurafine, for the management of opioid-induced pruritus.
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Translational value of non-human primates in opioid research. Exp Neurol 2021; 338:113602. [PMID: 33453211 DOI: 10.1016/j.expneurol.2021.113602] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/06/2021] [Accepted: 01/10/2021] [Indexed: 01/02/2023]
Abstract
Preclinical opioid research using animal models not only provides mechanistic insights into the modulation of opioid analgesia and its associated side effects, but also validates drug candidates for improved treatment options for opioid use disorder. Non-human primates (NHPs) have served as a surrogate species for humans in opioid research for more than five decades. The translational value of NHP models is supported by the documented species differences between rodents and primates regarding their behavioral and physiological responses to opioid-related ligands and that NHP studies have provided more concordant results with human studies. This review highlights the utilization of NHP models in five aspects of opioid research, i.e., analgesia, abuse liability, respiratory depression, physical dependence, and pruritus. Recent NHP studies have found that (1) mixed mu opioid and nociceptin/orphanin FQ peptide receptor partial agonists appear to be safe, non-addictive analgesics and (2) mu opioid receptor- and mixed opioid receptor subtype-based medications remain the only two classes of drugs that are effective in alleviating opioid-induced adverse effects. Given the recent advances in pharmaceutical sciences and discoveries of novel targets, NHP studies are posed to identify the translational gap and validate therapeutic targets for the treatment of opioid use disorder. Pharmacological studies using NHPs along with multiple outcome measures (e.g., behavior, physiologic function, and neuroimaging) will continue to facilitate the research and development of improved medications to curb the opioid epidemic.
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Nieman AN, Li G, Zahn NM, Mian MY, Mikulsky BN, Hoffman DA, Wilcox TM, Kehoe AS, Luecke IW, Poe MM, Alvarez-Carbonell D, Cook JM, Stafford DC, Arnold LA. Targeting Nitric Oxide Production in Microglia with Novel Imidazodiazepines for Nonsedative Pain Treatment. ACS Chem Neurosci 2020; 11:2019-2030. [PMID: 32511908 PMCID: PMC7380323 DOI: 10.1021/acschemneuro.0c00324] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The goal of this research is the identification of new treatments for neuropathic pain. We characterized the GABAergic system of immortalized mouse and human microglia using electrophysiology and qRT-PCR. Cells from both species exhibited membrane current changes in response to γ-aminobutyric acid, with an EC50 of 260 and 1940 nM, respectively. Human microglia expressed high levels of the γ-aminobutyric acid type A receptor (GABAAR) α3 subunit, which can assemble with β1 and γ2/δ subunits to form functional GABAARs. Mouse microglia contained α2, α3, and α5, in addition to β1-3, γ1-2, and δ, mRNA, enabling a more diverse array of GABAARs than human microglia. Benzodiazepines are well-established modulators of GABAAR activity, prompting a screen of a library of diverse benzodiazepines in microglia for cellular effects. Several active compounds were identified by reduction of nitric oxide (NO) in interferon gamma and lipopolysaccharide activated microglia. However, further investigation with GABAAR antagonists flumazenil, picrotoxin, and bicuculline demonstrated that GABAARs were not linked to the NO response. A screen of 48 receptors identified the κ-opioid receptor and to a lesser extent the μ-opioid receptor as molecular targets, with opioid receptor antagonist norbinaltorphimine reversing benzodiazepine induced reduction of microglial NO. Functional assays identified the downregulation of inducible NO synthase as the mode of action of imidazodiazepines MP-IV-010 and GL-IV-03. Like other κ-opioid receptor agonists, GL-IV-03 reduced the agitation response in both phases of the formalin nociception test. However, unlike other κ-opioid receptor agonists, MP-IV-010 and GL-IV-03 did not impair sensorimotor coordination in mice. Thus, MP-IV-010 and GL-IV-03 represent a new class of nonsedative drug candidates for inflammatory pain.
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Affiliation(s)
- Amanda N. Nieman
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Guanguan Li
- Shenzhen Grubbs Institute and Department of Chemistry, Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Nicolas M. Zahn
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Md Yeunus Mian
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | | | - Dylan A. Hoffman
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Taylor M. Wilcox
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Alexander S. Kehoe
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Ian W. Luecke
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Michael M. Poe
- Department of Chemistry, Western Michigan University, Kalamazoo MI 49008, United States
| | - David Alvarez-Carbonell
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - James M. Cook
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Douglas C. Stafford
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
- Pantherics Incorporated, La Jolla, California 92037, United States
| | - Leggy A. Arnold
- Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
- Pantherics Incorporated, La Jolla, California 92037, United States
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Antipruritic Effects of Kappa Opioid Receptor Agonists: Evidence from Rodents to Humans. Handb Exp Pharmacol 2020; 271:275-292. [PMID: 33296031 DOI: 10.1007/164_2020_420] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Centrally administered bombesin induces scratching and grooming in rats. These behaviors were blocked by early benzomorphan kappa opioid receptor (KOR) agonists as reported by Gmerek and Cowan in 1984. This was the first evidence that KORs may be involved in the sensation of itch-like behaviors. Subsequent development of additional animal models for acute and chronic itch has led to important discoveries since then. For example, it was found that (a) gastrin-releasing peptide (GRP), natriuretic polypeptide b and their cognate receptors are keys for the transmission of itch sensation at the spinal cord level, (b) dynorphins (Dyns), the endogenous KOR agonists, work as inhibitory neuromodulators of itch at the spinal cord level, (c) in a mouse model for acute itch, certain KOR antagonists elicit scratching, (d) in mouse models of acute or chronic itch, KOR agonists (e.g., U50,488, nalfurafine, CR 845, nalbuphine) suppress scratching induced by different pruritogens, and (e) nalfurafine, CR 845, and nalbuphine are in the clinic or in clinical trials for pruritus associated with chronic kidney disease and chronic liver disease, as well as pruritus in chronic skin diseases.
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Sinha S, Gabriel VA, Nickerson DA, Fraulin FOG, Shin W, Rahmani WM, Chatterjee P, Ahuja RB, Biernaskie JA. Interventions for postburn pruritus. Hippokratia 2019. [DOI: 10.1002/14651858.cd013468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Sarthak Sinha
- University of Calgary; Skin Regeneration Team, Department of Comparative Biology and Experimental Medicine; Rm 403, Heritage Medical Research Building 3300 Hospital Dr NW Calgary AB Canada T2N 4N1
| | - Vincent A Gabriel
- University of Calgary, Calgary Firefighters’ Burn Treatment Centre; Departments of Clinical Neurosciences, Pediatrics and Surgery; Room AC 144 Special Services Building 1403 29 Street NW Calgary AB Canada T2N 2T9
| | - Duncan A Nickerson
- Alberta Health Services, Calgary Firefighters’ Burn Treatment Centre, Foothills Medical Centre; Department of Surgery; 200, 2004 14th Street NW Calgary AB Canada
| | - Frankie OG Fraulin
- Alberta Health Services, Alberta Children's Hospital; Department of Surgery; 2888 Shaganappi Trail NW Calgary AB Canada T3B 6A8
| | - Wisoo Shin
- University of Calgary; Department of Comparative Biology and Experimental Medicine; 3330 Hospital Dr. NW Calgary AB Canada T2N 4N1
| | - Waleed M Rahmani
- University of Calgary; Department of Comparative Biology and Experimental Medicine; 3330 Hospital Dr. NW Calgary AB Canada T2N 4N1
| | - Pallab Chatterjee
- Command Hospital Air Force; Department of Plastic Surgery, Surgical Division; Old Airport Road Bengaluru Karnataka India 560007
| | - Rajeev B Ahuja
- Sir Ganga Ram Hospital; Department of Plastic Surgery; Rajinder Nagar New Delhi Delhi India 110060
| | - Jeff A Biernaskie
- University of Calgary; Department of Comparative Biology and Experimental Medicine; 3330 Hospital Dr. NW Calgary AB Canada T2N 4N1
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11
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Nalbuphine, a kappa opioid receptor agonist and mu opioid receptor antagonist attenuates pruritus, decreases IL-31, and increases IL-10 in mice with contact dermatitis. Eur J Pharmacol 2019; 864:172702. [PMID: 31568781 DOI: 10.1016/j.ejphar.2019.172702] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 09/25/2019] [Accepted: 09/26/2019] [Indexed: 12/13/2022]
Abstract
Chronic itch is one of the disturbing symptoms of inflammatory skin diseases. Kappa opioid receptor agonists are effective in suppressing scratching in mice against different pruritogens. Nalbuphine, a nonscheduled kappa opioid receptor agonist and mu opioid receptor antagonist, has been in clinical use for post-operative pain management since the 1980s and recently has been in clinical trials for chronic itch of prurigo nodularis (https://www.trevitherapeutics.com/nalbuphine). We studied whether nalbuphine is effective against chronic scratching induced by rostral neck application of 1-fluoro-2,4-dinitrobenzene (DNFB), an accepted mouse model of contact dermatitis to study pruritoceptive itch. Mice were treated once a week with either saline or nalbuphine 20 min before the third, fifth, seventh, and ninth sensitizations with DNFB and the number of scratching bouts was counted for 30 min. Skin samples from the neck of mice at week 4 were used to measure protein levels and mRNA expressions of chemokines and cytokines. Different sets of mice were used to study sedation and anhedonic-like behavior of nalbuphine. We found that: nalbuphine (a) antagonized scratching in a dose- and time-dependent manner without affecting locomotion, b) decreased IL-31, and increased anti-inflammatory IL-10, and c) induced more elevations in the levels of CCL2, CCL3, CCL12, CXCL1, CXCL2, CXCL9, CXCL10, IL-1β, IL-16, TIMP-1, M-CSF, TREM-1 and M1-type macrophages compared to saline. Increases in chemokines and cytokines and M1 macrophages by nalbuphine suggest an inflammatory phase of healing in damaged skin due to scratching. Our data indicate that nalbuphine is an effective antipruritic in murine model of pruritoceptive itch.
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12
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Nakasone T, Wakuda H, Sugimoto Y, Kamei C. Effects of ICI204,448, naloxone methiodide and levocetirizine on the scratching behavior induced by a κ-opioid antagonist, nor-BNI, in ICR mice. Immunopharmacol Immunotoxicol 2017; 39:292-295. [DOI: 10.1080/08923973.2017.1354879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Tasuku Nakasone
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Yasuda Women’s University, Hiroshima, Japan
| | - Hirokazu Wakuda
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Yasuda Women’s University, Hiroshima, Japan
| | - Yumi Sugimoto
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Yasuda Women’s University, Hiroshima, Japan
| | - Chiaki Kamei
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Yasuda Women’s University, Hiroshima, Japan
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13
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Abstract
Itch is a unique sensation associated with the scratch reflex. Although the scratch reflex plays a protective role in daily life by removing irritants, chronic itch remains a clinical challenge. Despite urgent clinical need, itch has received relatively little research attention and its mechanisms have remained poorly understood until recently. The goal of the present review is to summarize our current understanding of the mechanisms of acute as well as chronic itch and classifications of the primary itch populations in relationship to transient receptor potential (Trp) channels, which play pivotal roles in multiple somatosensations. The convergent involvement of Trp channels in diverse itch signaling pathways suggests that Trp channels may serve as promising targets for chronic itch treatments.
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Affiliation(s)
- Shuohao Sun
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, 21205, USA
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, 21205, USA.
- Howard Hughes Medical Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, 21205, USA.
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14
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Chuquilin M, Alghalith Y, Fernandez KH. Neurocutaneous disease. J Am Acad Dermatol 2016; 74:197-212. [DOI: 10.1016/j.jaad.2015.04.060] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 04/06/2015] [Accepted: 04/22/2015] [Indexed: 12/14/2022]
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15
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Cowan A, Lyu RM, Chen YH, Dun SL, Chang JK, Dun NJ. Phoenixin: A candidate pruritogen in the mouse. Neuroscience 2015; 310:541-8. [PMID: 26415767 DOI: 10.1016/j.neuroscience.2015.09.055] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 09/21/2015] [Accepted: 09/21/2015] [Indexed: 12/15/2022]
Abstract
Phoenixin (PNX) is a 14-amino acid amidated peptide (PNX-14) or an N-terminal extended 20-residue amidated peptide (PNX-20) recently identified in neural and non-neural tissue. Mass spectrometry analysis identified a major peak corresponding to PNX-14, with negligible PNX-20, in mouse spinal cord extracts. Using a previously characterized antiserum that recognized both PNX-14 and PNX-20, PNX-immunoreactivity (irPNX) was detected in a population of dorsal root ganglion (DRG) cells and in cell processes densely distributed to the superficial layers of the dorsal horn; irPNX cell processes were also detected in the skin. The retrograde tracer, Fluorogold, injected subcutaneously (s.c.) to the back of the cervical and thoracic spinal cord of mice, labeled a population of DRG, some of which were also irPNX. PNX-14 (2, 4 and 8 mg/kg) injected s.c.to the nape of the neck provoked dose-dependent repetitive scratching bouts directed to the back of the neck with the hindpaws. The number of scratching bouts varied from 16 to 95 in 30 min, commencing within 5 min post-injection and lasted 10-15 min. Pretreatment of mice at -20 min with nalfurafine (20 μg/kg, s.c.), the kappa opioid receptor agonist, significantly reduced the number of bouts induced by PNX-14 (4 mg/kg) compared with that of saline-pretreated mice. Our results suggest that the peptide, PNX-14, serves as one of the endogenous signal molecules transducing itch sensation in the mouse.
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Affiliation(s)
- A Cowan
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Substance Abuse Research, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - R-M Lyu
- Phoenix Pharmaceuticals Inc., Burlingame, CA 94010, USA
| | - Y-H Chen
- Graduate Institute of Acupuncture Science, China Medical University, Taichung, Taiwan
| | - S L Dun
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - J-K Chang
- Phoenix Pharmaceuticals Inc., Burlingame, CA 94010, USA
| | - N J Dun
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
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16
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Investigation of the role of βarrestin2 in kappa opioid receptor modulation in a mouse model of pruritus. Neuropharmacology 2015; 99:600-9. [PMID: 26318102 DOI: 10.1016/j.neuropharm.2015.08.027] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Revised: 07/29/2015] [Accepted: 08/17/2015] [Indexed: 11/22/2022]
Abstract
The kappa opioid receptor (KOR) is involved in mediating pruritus; agonists targeting this receptor have been used to treat chronic intractable itch. Conversely, antagonists induce an itch response at the site of injection. As a G protein-coupled receptor (GPCR), the KOR has potential for signaling via G proteins and βarrestins, however, it is not clear which of these pathways are involved in the KOR modulation of itch. In this study asked whether the actions of KOR in pruritus involve βarrestins by using βarrestin2 knockout (βarr2-KO) mice as well as a recently described biased KOR agonist that biases receptor signaling toward G protein pathways over βarrestin2 recruitment. We find that the KOR antagonists nor-binaltorphimine (NorBNI) and 5'-guanidinonaltrindole (5'GNTI) induce acute pruritus in C57BL/6J mice, with reduced effects in KOR-KO mice. βArr2-KO mice display less of a response to KOR antagonist-induced itch compared to wild types, however no genotype differences are observed from chloroquine phosphate (CP)-induced itch, suggesting that the antagonists may utilize a KOR-βarrestin2 dependent mechanism. The KOR agonist U50,488H was equally effective in both WT and βarr2-KO mice in suppressing CP-induced itch. Furthermore, the G protein biased agonist, Isoquinolinone 2.1 was as effective as U50,488H in suppressing the itch response induced by KOR antagonist NorBNI or CP in C57BL/6J mice. Together these data suggest that the antipruritic effects of KOR agonists may not require βarrestins.
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17
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Salaga M, Polepally PR, Zielinska M, Marynowski M, Fabisiak A, Murawska N, Sobczak K, Sacharczuk M, Do Rego JC, Roth BL, Zjawiony JK, Fichna J. Salvinorin A analogues PR-37 and PR-38 attenuate compound 48/80-induced itch responses in mice. Br J Pharmacol 2015; 172:4331-41. [PMID: 26040667 DOI: 10.1111/bph.13212] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Revised: 05/26/2015] [Accepted: 06/01/2015] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND PURPOSE The opioid system plays a crucial role in several physiological processes in the CNS and in the periphery. It has also been shown that selective opioid receptor agonists exert potent inhibitory action on pruritus and pain. In this study we examined whether two analogues of Salvinorin A, PR-37 and PR-38, exhibit antipruritic properties in mice. EXPERIMENTAL APPROACH To examine the antiscratch effect of PR-37 and PR-38 we used a mouse model of compound 48/80-induced pruritus. In order to elucidate the mechanism of action of tested compounds, specific antagonists of opioid and cannabinoid receptors were used. The effect of PR-37 on the CNS was assessed by measuring motor parameters and exploratory behaviours in mice. KEY RESULTS PR-37 and PR-38, jnjected s.c., significantly reduced the number of compound 48/80-induced scratching behaviours in mice in a dose- and time-dependent manner. PR-38 was also active when orally administered. The antiscratch activity of PR-37 was blocked by the selective κ opioid receptor antagonist, nor-binaltorphimine, and that of PR-38 by the selective μ opioid receptor antagonist, β-funaltrexamine. CONCLUSION AND IMPLICATIONS In conclusion, a novel framework for the development of new antipruritic drugs derived from salvinorin A has been validated.
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Affiliation(s)
- M Salaga
- Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Lodz, Poland
| | - P R Polepally
- Department of BioMolecular Sciences, Division of Pharmacognosy and Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, MS, USA
| | - M Zielinska
- Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Lodz, Poland
| | - M Marynowski
- Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Lodz, Poland
| | - A Fabisiak
- Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Lodz, Poland
| | - N Murawska
- Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Lodz, Poland
| | - K Sobczak
- Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Lodz, Poland
| | - M Sacharczuk
- Department of Molecular Cytogenetic, Institute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzebiec, Poland
| | - J C Do Rego
- Platform of Behavioural Analysis (SCAC), Institute for Research and Innovation in Biomedicine (IRIB), Faculty of Medicine & Pharmacy, University of Rouen, Rouen Cedex, France
| | - B L Roth
- Department of Pharmacology, Division of Chemical Biology and Medicinal Chemistry, Medical School, NIMH Psychoactive Drug Screening Program, University of North Carolina, Chapel Hill, NC, USA
| | - J K Zjawiony
- Department of BioMolecular Sciences, Division of Pharmacognosy and Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, MS, USA
| | - J Fichna
- Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Lodz, Poland
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18
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Abstract
Pain and itch are generally regarded antagonistic as painful stimuli such as scratching suppresses itch. Moreover, inhibition of pain processing by opioids generates itch further supporting their opposing role. Separate specific pathways for itch and pain processing have been uncovered, and several molecular markers have been established in mice that identify neurons involved in the processing of histaminergic and non-histaminergic itch on primary afferent and spinal level. These results are in agreement with the specificity theory for itch and might suggest that pain and itch should be investigated separately on the level of neurons, mediators, and mechanisms. However, in addition to broadly overlapping mediators of itch and pain, there is also evidence for overlapping functions in primary afferents: nociceptive primary afferents can provoke itch when activated very locally in the epidermis, and sensitization of both nociceptors and pruriceptors has been found following local nerve growth factor application in volunteers. Thus, also mechanisms that underlie the development of chronic itch and pain including spontaneous activity and sensitization of primary afferents as well as spinal cord sensitization may well overlap to a great extent. Rather than separating itch and pain, research concepts should therefore address the common mechanisms. Such an approach appears most appropriate for clinical conditions of neuropathic itch and pain and also chronic inflammatory conditions. While itch researchers can benefit from the large body of information of the pain field, pain researchers will find behavioral readouts of spontaneous itch much simpler than those for spontaneous pain in animals and the skin as source of the pruritic activity much more accessible even in patients.
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Affiliation(s)
- Martin Schmelz
- Department of Anesthesiology and Intensive Care Medicine, Faculty of Medicine Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, Mannheim, 68167, Germany,
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19
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Cowan A, Kehner GB, Inan S. Targeting Itch with Ligands Selective for κ Opioid Receptors. Handb Exp Pharmacol 2015; 226:291-314. [PMID: 25861786 DOI: 10.1007/978-3-662-44605-8_16] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Several chemically diverse pruritogens, including bombesin, compound 48/80, norbinaltorphimine, and 5'-GNTI, cause rodents to scratch excessively in a stable, uniform manner and consequently provide convenient animal models of itch against which potential antipruritics may be evaluated, structure-activity relationships established, and the nature of spontaneous, repetitive behavior itself analyzed. Decreasing the number of scratching bouts in these apparently simple models has been the requisite first step in the progress of kappa opioid agonists such as nalbuphine, asimadoline, and CR845 toward clinical testing as antipruritics. Nalfurafine is the prime example of a kappa agonist spanning the developmental divide between scratching mice models and commercialization within 10 years. Patients undergoing hemodialysis and suffering from the itching associated with uremic pruritus, and potentially those inflicted with atopic dermatitis, are the beneficiaries.
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Affiliation(s)
- Alan Cowan
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA, 19140, USA,
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20
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Abstract
As we all can easily differentiate the sensations of itch and pain, the most straightforward neurophysiologic concept would consist of two specific pathways that independently encode itch and pain. Indeed, a neuronal pathway for histamine-induced itch in the peripheral and central nervous system has been described in animals and humans, and recently several non-histaminergic pathways for itch have been discovered in rodents that support a dichotomous concept differentiated into a pain and an itch pathway, with both pathways being composed of different "flavors." Numerous markers and mediators have been found that are linked to itch processing pathways. Thus, the delineation of neuronal pathways for itch from pain pathways seemingly proves that all sensory aspects of itch are based on an itch-specific neuronal pathway. However, such a concept is incomplete as itch can also be induced by the activation of the pain pathway in particular when the stimulus is applied in a highly localized spatial pattern. These opposite views reflect the old dispute between specificity and pattern theories of itch. Rather than only being of theoretic interest, this conceptual problem has key implication for the strategy to treat chronic itch as key therapeutic targets would be either itch-specific pathways or unspecific nociceptive pathways.
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Affiliation(s)
- Martin Schmelz
- Faculty of Medicine Mannheim, Department of Anesthesiology and Intensive Care Medicine, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68167, Mannheim, Germany,
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21
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Zhang Y, Dun SL, Chen YH, Luo JJ, Cowan A, Dun NJ. Scratching activates microglia in the mouse spinal cord. J Neurosci Res 2014; 93:466-74. [PMID: 25354468 DOI: 10.1002/jnr.23501] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 08/26/2014] [Accepted: 09/24/2014] [Indexed: 12/28/2022]
Abstract
This study tested the hypothesis that repetitive scratching provoked by two known pruritogens, compound 48/80 and 5'-guanidinonaltrindole (GNTI), is accompanied by activation of microglial cells in the mouse spinal cord. Immunohistochemical studies revealed that the complement receptor 3, also known as cluster determinant 11b (CD11b), a cell surface marker of microglial cells, was upregulated in the spinal cord 10-30 min after a subcutaneous (s.c.) injection of compound 48/80 (50 μg/100 μl) or GNTI (0.3 mg/kg) to the back of the mouse neck. Numerous intensely labeled CD11b-immunoreactive (CD11b-ir) cells, with the appearance of hypertrophic reactive microglia, were distributed throughout the gray and white matter. In contrast, weakly labeled CD11b-ir cells were distributed in the spinal cord from mice injected with saline. Western blots showed that CD11b expression levels were significantly increased in spinal cords of mice injected s.c. with either pruritogen, reached a peak response in about 30 min, and declined to about the basal level in the ensuing 60 min. In addition, phospho-p38 (p-p38) but not p38 levels were upregulated in spinal cords from mice injected with compound 48/80 or GNTI, with a time course parallel to that of CD11b expression. Pretreatment of the mice with nalfurafine (20 µg/kg; s.c.), a κ-opioid receptor agonist that has been shown to suppress scratching, reduced CD11b and p-p38 expression induced by either pruritogen. The results demonstrate, for the first time, that scratch behavior induced by the pruritogens GNTI and compound 48/80 is accompanied by a parallel activation of microglial cells in the spinal cord.
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Affiliation(s)
- Ying Zhang
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania; Department of Pathophysiology, Kunming Medical University, Kunming, China
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22
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Dimattio KM, Yakovleva TV, Aldrich JV, Cowan A, Liu-Chen LY. Zyklophin, a short-acting kappa opioid antagonist, induces scratching in mice. Neurosci Lett 2014; 563:155-9. [PMID: 24503508 DOI: 10.1016/j.neulet.2014.01.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 01/10/2014] [Accepted: 01/15/2014] [Indexed: 10/25/2022]
Abstract
It has been shown previously that norbinaltorphimine (norBNI) and 5'-guanidinonaltrindole (5'-GNTI), long-acting kappa opioid receptor (KOPR) antagonists, cause frenzied scratching in mice [1,2]. In the current study, we examined if zyklophin, a short-acting cyclic peptide KOPR antagonist, also elicited scratching behavior. When injected s.c. in the nape of the neck of male Swiss-Webster mice, zyklophin at doses of 0.1, 0.3 and 1mg/kg induced dose-related hindleg scratching of the neck between 3 and 15 min after injection. Pretreating mice with norBNI (20mg/kg, i.p.) at 18-20 h before challenge with zyklophin (0.3mg/kg) did not markedly affect scratching. Additionally, KOPR-/- mice given 0.3mg/kg of zyklophin displayed similar levels of scratching as wild-type animals. The absence of KOPR in KOPR-/- mice was confirmed with ex vivo radioligand binding using [(3)H]U69,593. Taken together, our data suggest that the presence of kappa receptors is not required for the excessive scratching caused by zyklophin. Thus, zyklophin, similar to the structurally different KOPR antagonist 5'-GNTI, appears to act at other targets to elicit scratching and potentially the sensation of itch.
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Affiliation(s)
- K M Dimattio
- Center for Substance Abuse Research and Department of Pharmacology, Temple University School of Medicine, 3500 North Broad Street, Philadelphia, PA 19140, USA.
| | - T V Yakovleva
- Department of Medicinal Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, KS 66045, USA.
| | - J V Aldrich
- Department of Medicinal Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, KS 66045, USA.
| | - A Cowan
- Center for Substance Abuse Research and Department of Pharmacology, Temple University School of Medicine, 3500 North Broad Street, Philadelphia, PA 19140, USA.
| | - L Y Liu-Chen
- Center for Substance Abuse Research and Department of Pharmacology, Temple University School of Medicine, 3500 North Broad Street, Philadelphia, PA 19140, USA.
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23
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Rossbach K, Bäumer W. PCR detects bands consistent with the expression of receptors associated with pruritus in canine dorsal root ganglia. Vet Dermatol 2013; 25:9-e4. [PMID: 24289149 DOI: 10.1111/vde.12093] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/12/2013] [Indexed: 01/17/2023]
Abstract
BACKGROUND Various mediators are involved in the induction of itch, i.e. pruritus; however, the in vivo pharmacology of pruritus seems to be different in distinct species, and little is known about receptors that are involved in the induction of itch in dogs. The species differences in the mediation of pruritus might be explained by species differences in receptor expression in the sensory nerves, including the dorsal root ganglia (DRG). HYPOTHESIS/OBJECTIVES The aim of the study was to analyse the expression of receptors for various mediators of pruritus in canine DRG. METHODS Dorsal root ganglia of 14 dogs, which were euthanized for reasons not related to this study, were analysed. Multiple DRG per dog were dissected and, after homogenization of the DRG tissues, total RNA was isolated, reverse transcribed to complementary DNA and amplified with custom-synthesized primers. RESULTS The following receptors were found in canine DRG: transient receptor potential cation channel subfamily V member 1, tachykinin receptor 1, Toll-like receptor 7, endothelin receptor type A, opioid receptors μ1 and κ1, histamine H1 -H4 receptors and the interleukin-31 receptor complex. CONCLUSIONS AND CLINICAL IMPORTANCE PCR analysis detected bands consistent with the expression of receptors associated with pruritus in canine DRG.
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Affiliation(s)
- Kristine Rossbach
- Institute of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Bünteweg 17, 30559, Hannover, Germany
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24
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Munro TA, Huang XP, Inglese C, Perrone MG, Van't Veer A, Carroll FI, Béguin C, Carlezon WA, Colabufo NA, Cohen BM, Roth BL. Selective κ opioid antagonists nor-BNI, GNTI and JDTic have low affinities for non-opioid receptors and transporters. PLoS One 2013; 8:e70701. [PMID: 23976952 PMCID: PMC3747596 DOI: 10.1371/journal.pone.0070701] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 06/21/2013] [Indexed: 01/16/2023] Open
Abstract
Background Nor-BNI, GNTI and JDTic induce selective κ opioid antagonism that is delayed and extremely prolonged, but some other effects are of rapid onset and brief duration. The transient effects of these compounds differ, suggesting that some of them may be mediated by other targets. Results In binding assays, the three antagonists showed no detectable affinity (Ki≥10 µM) for most non-opioid receptors and transporters (26 of 43 tested). There was no non-opioid target for which all three compounds shared detectable affinity, or for which any two shared sub-micromolar affinity. All three compounds showed low nanomolar affinity for κ opioid receptors, with moderate selectivity over μ and δ (3 to 44-fold). Nor-BNI bound weakly to the α2C-adrenoceptor (Ki = 630 nM). GNTI enhanced calcium mobilization by noradrenaline at the α1A-adrenoceptor (EC50 = 41 nM), but did not activate the receptor, displace radioligands, or enhance PI hydrolysis. This suggests that it is a functionally-selective allosteric enhancer. GNTI was also a weak M1 receptor antagonist (KB = 3.7 µM). JDTic bound to the noradrenaline transporter (Ki = 54 nM), but only weakly inhibited transport (IC50 = 1.1 µM). JDTic also bound to the opioid-like receptor NOP (Ki = 12 nM), but gave little antagonism even at 30 µM. All three compounds exhibited rapid permeation and active efflux across Caco-2 cell monolayers. Conclusions Across 43 non-opioid CNS targets, only GNTI exhibited a potent functional effect (allosteric enhancement of α1A-adrenoceptors). This may contribute to GNTI's severe transient effects. Plasma concentrations of nor-BNI and GNTI may be high enough to affect some peripheral non-opioid targets. Nonetheless, κ opioid antagonism persists for weeks or months after these transient effects dissipate. With an adequate pre-administration interval, our results therefore strengthen the evidence that nor-BNI, GNTI and JDTic are highly selective κ opioid antagonists.
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MESH Headings
- Allosteric Regulation
- Biological Transport
- Caco-2 Cells
- Calcium/metabolism
- Guanidines/metabolism
- Guanidines/pharmacology
- Humans
- Kinetics
- Morphinans/metabolism
- Morphinans/pharmacology
- Naltrexone/analogs & derivatives
- Naltrexone/metabolism
- Naltrexone/pharmacology
- Narcotic Antagonists/metabolism
- Narcotic Antagonists/pharmacology
- Norepinephrine/metabolism
- Norepinephrine Plasma Membrane Transport Proteins/metabolism
- Piperidines/metabolism
- Piperidines/pharmacology
- Protein Binding
- Receptors, Adrenergic, alpha/metabolism
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, kappa/antagonists & inhibitors
- Receptors, Opioid, kappa/metabolism
- Receptors, Opioid, mu/metabolism
- Tetrahydroisoquinolines/metabolism
- Tetrahydroisoquinolines/pharmacology
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Affiliation(s)
- Thomas A. Munro
- McLean Hospital, Belmont, Massachusetts, United States of America
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, United States of America
- School of Chemistry and Bio21 Institute, University of Melbourne, Parkville, Australia
- * E-mail:
| | - Xi-Ping Huang
- National Institute of Mental Health Psychoactive Drug Screening Program and Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America
| | - Carmela Inglese
- Dipartimento di Farmacia-Scienze del Farmaco, Università degli Studi di Bari, Bari, Italy
| | - Maria Grazia Perrone
- Dipartimento di Farmacia-Scienze del Farmaco, Università degli Studi di Bari, Bari, Italy
| | - Ashlee Van't Veer
- McLean Hospital, Belmont, Massachusetts, United States of America
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, United States of America
| | - F. Ivy Carroll
- Center for Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, North Carolina, United States of America
| | - Cécile Béguin
- McLean Hospital, Belmont, Massachusetts, United States of America
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, United States of America
| | - William A. Carlezon
- McLean Hospital, Belmont, Massachusetts, United States of America
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Nicola A. Colabufo
- Dipartimento di Farmacia-Scienze del Farmaco, Università degli Studi di Bari, Bari, Italy
| | - Bruce M. Cohen
- McLean Hospital, Belmont, Massachusetts, United States of America
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Bryan L. Roth
- National Institute of Mental Health Psychoactive Drug Screening Program and Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America
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Abstract
Chronic itch is a debilitating condition that affects one in 10 people. Little is known about the molecules that mediate chronic itch in primary sensory neurons and skin. We demonstrate that the ion channel TRPA1 is required for chronic itch. Using a mouse model of chronic itch, we show that scratching evoked by impaired skin barrier is abolished in TRPA1-deficient animals. This model recapitulates many of the pathophysiological hallmarks of chronic itch that are observed in prevalent human diseases such as atopic dermatitis and psoriasis, including robust scratching, extensive epidermal hyperplasia, and dramatic changes in gene expression in sensory neurons and skin. Remarkably, TRPA1 is required for both transduction of chronic itch signals to the CNS and for the dramatic skin changes triggered by dry-skin-evoked itch and scratching. These data suggest that TRPA1 regulates both itch transduction and pathophysiological changes in the skin that promote chronic itch.
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Abstract
INTRODUCTION Chronic pruritus (CP), defined as itch lasting for > 6 weeks, is a burdensome symptom of several different diseases, dermatological and systemic, with a high negative impact on the quality of life of patients. Given the manifold aetiologies of CP, therapy is often difficult. In recent years, however, novel substances have been developed for treatment of certain CP entities and identified targets. AREAS COVERED In this review, the authors present a survey of targets currently believed to be promising (H4R, IL-31, MOR, KOR, GRPR, NGF, NK-1R, TRP channels) and related investigational drugs that are in the preclinical or clinical stage of development. Some substances have already undergone clinical testing, but only one of them (nalfurafine) has been licensed so far. Many of them are most likely to exert their effects on the skin and interfere there with the cutaneous neurobiology of CP. EXPERT OPINION Currently, the most promising candidates for new therapeutic agents in CP are neurokinin-1 receptor antagonists and substances targeting the kappa- or mu-opioid receptor, or both. They have the potential to target the neuronal pathway of CP and are thus of interest for several CP entities. The goal for the coming years is to validate these concepts and move forward in developing new drugs for the therapy of CP.
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Affiliation(s)
- Heike Benecke
- University Medicine Göttingen, Center Nanoscale Microscopy and Molecular Physiology of the Brain, Humboldtallee 23, 37073 Göttingen, Germany
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Electroacupuncture Attenuates 5'-Guanidinonaltrindole-Evoked Scratching and Spinal c-Fos Expression in the Mouse. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2013; 2013:319124. [PMID: 23878596 PMCID: PMC3708416 DOI: 10.1155/2013/319124] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 04/25/2013] [Accepted: 04/26/2013] [Indexed: 12/13/2022]
Abstract
The present study was undertaken to investigate the influence of electroacupuncture (EA) on compulsive scratching in mice and c-Fos expression elicited by subcutaneous (s.c.) administration of a known puritogen, 5'-guanidinonaltrindole (GNTI) to the neck. Application of EA to Hegu (LI4) and Quchi (LI11) acupoints at 2 Hz, but not 100 Hz, attenuated GNTI-evoked scratching. In mice pretreated with the µ opioid receptor antagonist naloxone, EA 2 Hz did not attenuate GNTI-evoked scratching, whereas EA at 2 Hz did attenuate GNTI-evoked scratching in mice pretreated with the κ opioid receptor antagonist nor-binaltorphimine. Moreover, intradermal (i.d.) administration of the selective µ opioid receptor agonist [d-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin acetate (DAMGO) attenuated GNTI-evoked scratching behavior, while s.c. administration of DAMGO was ineffective. GNTI provoked c-Fos expression on the lateral side of the superficial layer of the dorsal horn of the cervical spinal cord. Application of 2 Hz EA to LI4 and LI11 decreased the number of c-Fos positive nuclei induced by GNTI. It may be concluded that application of 2 Hz EA to LI4 and LI11 attenuates scratching behavior induced by GNTI in mice and that the peripheral µ opioid system is involved, at least in part, in the anti-pruritic effects of EA.
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28
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Lin AP, Ko MC. The therapeutic potential of nociceptin/orphanin FQ receptor agonists as analgesics without abuse liability. ACS Chem Neurosci 2013; 4:214-24. [PMID: 23421672 DOI: 10.1021/cn300124f] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Although mu opioid (MOP) receptor agonists are the most commonly used analgesics for the treatment of moderate to severe pain in the clinic, the side effects of MOP agonists such as abuse liability limit their value as a medication. Research to identify novel analgesics without adverse effects is pivotal to advance the health care of humans. The nociceptin/orphanin FQ peptide (NOP) receptor, the fourth opioid receptor subtype, mediates distinctive actions in nonhuman primates which suggests the possibility that activity at this receptor may result in strong analgesia in the absence of virtually all of the side effects associated with MOP agonists. The present review highlights the recent progress of pharmacological studies of NOP-related ligands in primates. Selective NOP agonists, either peptidic or nonpeptidic, produce full analgesia in various assays in primates, when delivered systemically or intrathecally. Yet small molecule NOP agonists do not serve as reinforcers, indicating a lack of abuse liability. Given that NOP agonists have low abuse liability and that coactivation of NOP and MOP receptors produces synergistic antinociception, it is worth developing bifunctional NOP/MOP ligands. The outcomes of these studies and recent developments provide new perspectives to establish a translational bridge for understanding the biobehavioral functions of NOP receptors in primates and for facilitating the development of NOP-related ligands as a new generation of analgesics without abuse liability in humans.
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Affiliation(s)
- Ann P. Lin
- Department of Psychology, School
of Arts and Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Mei-Chuan Ko
- Department of Pharmacology,
Medical School, University of Michigan,
Ann Arbor, Michigan 48109, United States
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29
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Bobko SI, Lotts T, Metze D, Lvov AN, Staender S. Immunohistochemistry detection of kappa-opioid receptors in human skin. VESTNIK DERMATOLOGII I VENEROLOGII 2013. [DOI: 10.25208/vdv585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
The imbalance of p- and kappa-opioid receptors in the skin or central nervous system is currently deemed to be one of the reasons of chronic pruritus. A number of studies demonstrated a positive effect of system agonists of kappa-opioid receptors in the treatment of uremic pruritus, nodular pruritus, paraneoplastic and cholestatic pruritus. This research demonstrates an expression of kappa-opioid receptors in human skin (basal keratinocytes, dendritic cells, epidermal melanocytes and fibroblasts of the upper dermis) detected with the use of different immunochemistry methods.
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Ji W, Liang J, Zhang Z. Endothelin B receptors exert antipruritic effects via peripheral κ-opioid receptors. Exp Ther Med 2012. [PMID: 23181126 PMCID: PMC3503748 DOI: 10.3892/etm.2012.624] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Endothelin B receptor agonists exert antipruritic effects on itching induced via endothelin-1 (ET-1) and compound 48/80. Peripheral µ- and κ-opioid receptors (MORs and KORs, respectively) are reported to be involved in the anti-nociceptive properties triggered by ETB agonists. Therefore, we investigated the role of peripheral opioid receptors in the scratching response induced by ET-1. ETA and ETB antagonists and non-selective and selective opioid receptor antagonists were co-injected with ET-1 in the neck of mice and the number of scratching bouts was counted. Pretreatment with systemically administered naloxone significantly reduced the number of scratches, while co-injection of naloxone substantially augmented the effect of ET-1. Co-injection of nor-Binaltorphimine (nor-BNI), a KOR antagonist, significantly increased the number of scratches induced by ET-1. However, CTOP (a MOR antagonist) and naltrindole [a δ-opioid receptor (DOR) antagonist] did not alter the scratching response elicited by ET-1. These results indicate that peripheral KORs mediate the antipruritic effect of endothelin B receptor activation.
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Affiliation(s)
- Wenjin Ji
- Departments of Anesthesiology, and ; Postgraduate Institute, Southern Medical University, Guangzhou, P.R. China
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31
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Abstract
In psychophysical experiments, humans use different verbal responses to pruritic and algesic chemical stimuli to indicate the different qualities of sensation they feel. A major challenge for behavioural models in the mouse of chemical itch and pain in humans is to devise experimental protocols that provide the opportunity for the animal to exhibit a multiplicity of responses as well. One basic criterion is that chemicals that evoke primarily itch or pain in humans should elicit different types of responses when applied in the same way to the mouse. Meeting this criterion is complicated by the fact that the type of behavioural responses exhibited by the mouse depends in part on the site of chemical application such as the nape of the neck that evokes only scratching with the hind paw versus the hind limb that elicits licking and biting. Here, we review to what extent mice behaviourally differentiate chemicals that elicit itch versus pain in humans.
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Affiliation(s)
- Robert H LaMotte
- Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06520, USA.
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32
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Update on pruritic mechanisms of hypertrophic scars in postburn patients: the potential role of opioids and their receptors. J Burn Care Res 2011; 32:e118-25. [PMID: 21747328 DOI: 10.1097/bcr.0b013e3182223c32] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Although itching (or pruritus) in a scar is a very common and distressing symptom and is increasingly being recognized as a significant obstacle in burn rehabilitation, the exact mechanisms underlying this symptom have not been elucidated; hence, a reliable therapy has not been established. Recent findings have suggested that itching caused by inflammatory dermatosis can be reduced by antihistamines, but histamine antagonists cannot block all types of pruritus (eg, neuropathic itch). This indicates the presence of a histamine-independent pathway for itch. Itch or pruritus may also be evoked by direct activation of opioid receptors, which have recently been identified in the skin. This article aims to assess the current state of knowledge regarding the role of opioids in the generation of itch in hypertrophic scars in postburn patients. To this end, the authors have reviewed the relevant literature and present some clinical data. The authors hope that this review will form the basis for future research to elucidate the mechanism and treatment of itch.
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Taneda K, Tominaga M, Negi O, Tengara S, Kamo A, Ogawa H, Takamori K. Evaluation of epidermal nerve density and opioid receptor levels in psoriatic itch. Br J Dermatol 2011; 165:277-84. [PMID: 21457210 DOI: 10.1111/j.1365-2133.2011.10347.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Psoriasis is a complex, multifactorial inflammatory skin disease with genetic and environmental interactions. Patients with psoriasis exhibit erythematous plaques with itch, but the mechanisms of psoriatic itch are poorly understood. OBJECTIVES This study was performed to investigate epidermal nerve density and opioid receptor levels in psoriatic skin with or without itch. METHODS Twenty-four patients with psoriasis aged between 39 and 82 years were included in this study. The number of epidermal nerve fibres, the levels of semaphorin 3A (Sema3A) and the expression patterns of μ- and κ-opioid systems were examined immunohistologically in skin biopsies from psoriatic patients with or without itch and healthy volunteers as controls. RESULTS The number of epidermal nerve fibres tended to increase in approximately 40% of psoriatic patients with itch compared with healthy controls, while such intraepidermal nerves were not observed in other itchy patients. In comparison with healthy controls, Sema3A levels also tended to decrease in the epidermis of psoriatic patients with itch. However, no relationship was found between nerve density and Sema3A levels in the epidermis of psoriatic patients with itch. The levels of μ-opioid receptor and β-endorphin in the epidermis were the same in healthy controls and psoriatic patients with or without itch. The levels of κ-opioid receptor and dynorphin A were significantly decreased in the epidermis of psoriatic patients with itch compared with healthy controls. CONCLUSIONS Based on Sema3A levels in the epidermis, epidermal opioid systems, rather than hyperinnervation, may be involved in the pathogenesis of psoriatic itch.
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Affiliation(s)
- Kenichi Taneda
- Department of Dermatology, Juntendo University Urayasu Hospital, 2-1-1 Tomioka, Urayasu, Chiba 279-0021, Japan
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Aghahowa SE, Obianwu HO, Isah AO, Arhewoh IM. Chloroquine-induced Pruritus. Indian J Pharm Sci 2011; 72:283-9. [PMID: 21188034 PMCID: PMC3003158 DOI: 10.4103/0250-474x.70471] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 06/11/2010] [Accepted: 06/14/2010] [Indexed: 11/24/2022] Open
Abstract
Chloroquine-induced pruritus remains one of the most common side-effects in the use of chloroquine in the prophylaxis and treatment of uncomplicated malaria before the advent of artemisinin-based combination therapies. It has been reported to vary from a tolerable to intolerable intensity among susceptible individuals resulting in disruption of treatment and development of resistance to the drug thus leading to therapeutic failures as reported. This scourge is quite challenging due to the complex physiologic mechanism that has not been fully elucidated. Factors observed to be responsible in the induction of pruritus such as age, race, heredity, density of parasitaemia; impurities in formulations, plasmodial specie, dosage form and metabolites have been discussed in this review. Efforts to ameliorate this burden have necessitated the use of drugs of diverse pharmacological classes such as antihistamines, corticosteroids and multivitamins either alone or as a combination. This review is to look into the use of chloroquine retrospectively, and consider its re-introduction due to its safety. Efficacy can be attained if the pruritic effect is resolved.
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Affiliation(s)
- S E Aghahowa
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, University of Benin, Benin City, Nigeria
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35
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Yamamoto A, Sugimoto Y. Involvement of peripheral mu opioid receptors in scratching behavior in mice. Eur J Pharmacol 2010; 649:336-41. [DOI: 10.1016/j.ejphar.2010.07.039] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 06/19/2010] [Accepted: 07/12/2010] [Indexed: 01/15/2023]
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Cevikbas F, Steinhoff M, Ikoma A. Role of spinal neurotransmitter receptors in itch: new insights into therapies and drug development. CNS Neurosci Ther 2010; 17:742-9. [PMID: 20950328 DOI: 10.1111/j.1755-5949.2010.00201.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Targets for antipruritic therapies are now expanding from the skin to the central nervous system. Recent studies demonstrate that various neuronal receptors in the spinal cord are involved in pruritus. The spinal opioid receptor is one of the best-known examples. Spinal administration of morphine is frequently accompanied by segmental pruritus. In addition to μ-opioid receptor antagonists, κ-opioid receptor agonists have recently come into usage as novel antipruritic drugs, and are expected to suppress certain subtypes of itch such as hemodialysis- and cholestasis-associated itch that are difficult to treat with antihistamines. The gastrin-releasing peptide receptor in the superficial dorsal horn of the spinal cord has also received recent attention as a novel pathway of itch-selective neural transmission. The NMDA glutamate receptor appears to be another potential target for the treatment of itch, especially in terms of central sensitization. The development of NMDA receptor antagonists with less undesirable side effects on the central nervous system might be beneficial for antipruritic therapies. Drugs suppressing presynaptic glutamate-release such as gabapentin and pregabalin also reportedly inhibit certain subtypes of itch such as brachioradial pruritus. Spinal receptors of other neuromediators such as bradykinin, substance P, serotonin, and histamine may also be potential targets for antipruritic therapies, given that most of these molecules interfere not only with pain, but also with itch transmission or regulation. Thus, the identification of itch-specific receptors and understanding itch-related circuits in the spinal cord may be innovative strategies for the development of novel antipruritic drugs.
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Affiliation(s)
- Ferda Cevikbas
- Department of Dermatology, University of California, San Francisco, CA 94143-0660, USA
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37
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Schmelz M. Itch and pain. Neurosci Biobehav Rev 2010; 34:171-6. [DOI: 10.1016/j.neubiorev.2008.12.004] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Revised: 12/15/2008] [Accepted: 12/15/2008] [Indexed: 11/28/2022]
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Kumagai H, Ebata T, Takamori K, Muramatsu T, Nakamoto H, Suzuki H. Effect of a novel kappa-receptor agonist, nalfurafine hydrochloride, on severe itch in 337 haemodialysis patients: a Phase III, randomized, double-blind, placebo-controlled study. Nephrol Dial Transplant 2009; 25:1251-7. [PMID: 19926718 DOI: 10.1093/ndt/gfp588] [Citation(s) in RCA: 218] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Pruritus in haemodialysis patients is an intractable disease and substantially impairs their quality of life. Based on the results of our earlier clinical study, we hypothesized that the micro-(mu) opioid system is itch-inducible, whereas the kappa (kappa) system is itch-suppressive. METHODS The efficacy and safety of nalfurafine hydrochloride (a novel kappa-receptor agonist) were prospectively investigated by randomly (1:1:1) administering 5 or 2.5 microg of the drug or a placebo orally for 14 days using a double-blind design in 337 haemodialysis patients with itch that was resistant to currently available treatments, such as antihistamines. RESULTS The mean decrease in the visual analogue scale (VAS) from baseline, the study's primary endpoint, was significantly larger in the 5-microg nalfurafine hydrochloride group (n = 114) than in the placebo group (n = 111, P = 0.0002, one-sided test at 2.5% significance level). The decrease in the VAS in the 2.5-microg group (n = 112) was also significantly larger than that in the placebo group (P = 0.0001). The incidence of adverse drug reactions (ADRs) was 35.1% in the 5-microg group, 25.0% in the 2.5-microg group and 16.2% in the placebo group. Moderate to severe ADRs were observed in 10 of the 226 patients. The most common ADR was insomnia (sleep disturbance), seen in 24 of the 226 nalfurafine patients. CONCLUSIONS This Phase III, randomized, double-blind, placebo-controlled, parallel-group, prospective study based on VAS evaluations clearly showed that orally taken nalfurafine hydrochloride effectively reduced itches that were otherwise refractory to currently available treatments in maintenance haemodialysis patients, with few significant ADRs. This novel drug was officially approved for clinical use in January 2009 by the Ministry of Health, Labour and Welfare of Japan.
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Affiliation(s)
- Hiroo Kumagai
- Department of Nephrology, National Defense Medical College, Japan.
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39
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Inan S, Dun NJ, Cowan A. Nalfurafine prevents 5'-guanidinonaltrindole- and compound 48/80-induced spinal c-fos expression and attenuates 5'-guanidinonaltrindole-elicited scratching behavior in mice. Neuroscience 2009; 163:23-33. [PMID: 19524022 DOI: 10.1016/j.neuroscience.2009.06.016] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 05/27/2009] [Accepted: 06/06/2009] [Indexed: 10/20/2022]
Abstract
The aims of the present study were to establish if nalfurafine, a kappa opioid agonist, inhibits compulsive scratching in mice elicited by the s.c. administration (behind the neck) of 5'-guanidinonaltrindole (GNTI), a kappa opioid antagonist; to assess if nalfurafine prevents c-fos expression provoked by GNTI or compound 48/80, two chemically diverse pruritogens; and to distinguish on the basis of neuroanatomy, those neurons in the brainstem activated by either GNTI-induced itch or formalin-induced pain (both compounds given s.c. to the right cheek). Pretreatment of mice with nalfurafine (0.001-0.03 mg/kg s.c.) attenuated GNTI (0.3 mg/kg)-evoked scratching dose-dependently. A standard antiscratch dose of nalfurafine (0.02 mg/kg) had no marked effect on the spontaneous locomotion of mice. Tolerance did not develop to the antiscratch activity of nalfurafine. Both GNTI and compound 48/80 provoked c-fos expression on the lateral side of the superficial layer of the dorsal horn of the cervical spinal cord and pretreating mice with nalfurafine inhibited c-fos expression induced by both pruritogens. In contrast to formalin, GNTI did not induce c-fos expression in the trigeminal nucleus suggesting that pain and itch sensations are projected differently along the sensory trigeminal pathway. Our data indicate that the kappa opioid system is involved, at least in part, in the pathogenesis of itch; and that nalfurafine attenuates excessive scratching and prevents scratch-induced neuronal activity at the spinal level. On the basis of our results, nalfurafine holds promise as a potentially useful antipruritic in human conditions involving itch.
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Affiliation(s)
- S Inan
- Department of Pharmacology, Temple University School of Medicine, 3420 North Broad Street, Philadelphia, PA 19140, USA.
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Kremer AE, Beuers U, Oude-Elferink RPJ, Pusl T. Pathogenesis and treatment of pruritus in cholestasis. Drugs 2009; 68:2163-82. [PMID: 18840005 DOI: 10.2165/00003495-200868150-00006] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Pruritus is an enigmatic, seriously disabling symptom accompanying cholestatic liver diseases and a broad range of other disorders. Most recently, novel itch-specific neuronal pathways, itch mediators and their relevant receptors have been identified. In addition, new antipruritic therapeutic strategies have been developed and/or are under evaluation. This review highlights recent experimental and clinical findings focusing on the pathogenesis and actual treatment of pruritus in cholestatic liver disease. Evidence-based therapeutic recommendations, including the use of anion exchange resins cholestyramine, colestipol and colesevelam, the microsomal enzyme inducer rifampicin, the opioid receptor antagonists naltrexone and naloxone, and the serotonin reuptake inhibitor sertraline, are provided.
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Affiliation(s)
- Andreas E Kremer
- Liver Center, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
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41
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Ko MC, Husbands SM. Effects of atypical kappa-opioid receptor agonists on intrathecal morphine-induced itch and analgesia in primates. J Pharmacol Exp Ther 2008; 328:193-200. [PMID: 18842704 DOI: 10.1124/jpet.108.143925] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Itch/pruritus is the most common side effect associated with spinal administration of morphine given to humans for analgesia. The aim of this study was to investigate the effectiveness of kappa-opioid receptor (KOR) agonists with diverse chemical structures as antipruritics and to elucidate the receptor mechanism underlying the antipruritic effect in monkeys. In particular, previously proposed non-KOR-1 agonists, including nalfurafine [TRK-820, 17-cyclopropylmethyl-3,14 beta-dihydroxy-4,5 alpha-epoxy-6 beta-[N-methyl-trans-3-(3-furyl)acrylamido]morphinan], bremazocine [(+/-)-6-ethyl-1,2,3,4,5,6-hexahydro-3-[(1-hydroxycyclopropy)-methyl]-11,11-dimethyl-2,6-methano-3-benzazocin-8-ol], and GR 89696 [4-[(3,4-dichlorophenyl)acetyl]-3-(1-pyrrolidinylmethyl)-1-piperazinecarboxylic acid methyl ester] were studied in various behavioral assays for measuring itch/scratching, analgesia, and respiratory depression. Systemic administration of nalfurafine (0.1-1 microg/kg), bremazocine (0.1-1 microg/kg), or GR 89696 (0.01-0.1 microg/kg) dose-dependently attenuated intrathecal morphine (0.03 mg)-induced scratching responses without affecting morphine antinociception. The combination of intrathecal morphine with these KOR agonists did not cause sedation. In addition, pretreatment with effective antiscratching doses of nalfurafine, bremazocine, or GR 89696 did not antagonize systemic morphine-induced antinociception and respiratory depression. The dose-addition analysis revealed that there is no subadditivity for nalfurafine in combination with morphine in the antinociceptive effect. Furthermore, the KOR antagonist study revealed that antiscratching effects of both nalfurafine and a prototypical KOR-1 agonist, U-50488H [trans-(+/-)-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]-cyclohexyl)-benzeneacetamide], could be blocked completely by a selective KOR antagonist, nor-binaltorphimine (3 mg/kg). These findings suggest that the agonist action on KOR mainly contributes to the effectiveness of these atypical KOR agonists as antipruritics, and there is no evidence for KOR subtypes or mu-opioid antagonist action underlying the effects of these KOR agonists. This mechanism-based study further supports the clinical potential of KOR agonists as antipruritics under the context of spinal opioid analgesia.
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Affiliation(s)
- Mei-Chuan Ko
- Department of Pharmacology, University of Michigan Medical School, 1301 MSRB III, Ann Arbor, MI 48109-5632, USA.
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Shim WS, Oh U. Histamine-induced itch and its relationship with pain. Mol Pain 2008; 4:29. [PMID: 18667087 PMCID: PMC2519061 DOI: 10.1186/1744-8069-4-29] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Accepted: 07/31/2008] [Indexed: 05/25/2023] Open
Abstract
Itch is one of the major complications of skin diseases. Although there are various substances that induce itch or pruritus, it is evident that histamine is the best known endogenous agent that evokes itch. Even though histamine-induced itch has been studied for some time, the underlying mechanism of itch is just beginning to emerge. Although various downstream signaling pathways of histamine receptors have been revealed, more studies are required to determine the cause of histamine-induced itch. It appears that itch and pain involve different neuronal pathways. Pain generally inhibits itch, which indicates an inter-communication between the two. Complex interactions between itch and pain may be expected based on reports on disease states and opioids. In this review, we discuss the molecular mechanism and the pharmacological aspects of histamine-induced itch. Especially, the underlying mechanism of TRPV1 (an anti-pruritus target) has been determined to some extent.
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Affiliation(s)
- Won-Sik Shim
- National Research Laboratory of Transporters Targeted Drug Design, Research Institute of Pharmaceutical Sciences, College of Pharmacy,Seoul National University, Seoul, 151-742, Korea.
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Bigliardi-Qi M, Gaveriaux-Ruff C, Pfaltz K, Bady P, Baumann T, Rufli T, Kieffer BL, Bigliardi PL. Deletion of μ- and κ-Opioid Receptors in Mice Changes Epidermal Hypertrophy, Density of Peripheral Nerve Endings, and Itch Behavior. J Invest Dermatol 2007; 127:1479-88. [PMID: 17185983 DOI: 10.1038/sj.jid.5700661] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The mu- (MOR) and kappa- (KOR) opioid receptors have been implicated in the regulation of homeostasis of non-neuronal cells, such as keratinocytes, and sensations like pain and chronic pruritus. Therefore, we have studied the phenotype of skin after deletion of MOR and KOR. In addition, we applied a dry skin model in these knockout mice and compared the different mice before and after induction of the dermatitis in terms of epidermal thickness, epidermal peripheral nerve ending distribution, dermal inflammatory infiltrate (mast cells, CD4 positive lymphocytes), and scratching behavior. MOR knockout mice reveal as phenotype a significantly thinner epidermis and a higher density of epidermal fiber staining by protein gene product 9.5 than the wild-type counterparts. Epidermal hypertrophy, induced by the dry skin dermatitis, was significantly less developed in MOR knockout than in wild-type mice. Neither mast cells nor CD4 T(h)-lymphocytes are involved in the changes of epidermal nerve endings and epidermal homeostasis. Finally, behavior experiments revealed that MOR and KOR knockout mice scratch less after induction of dry skin dermatitis than wild-type mice. These results indicate that MOR and KOR are important in skin homeostasis, epidermal nerve fiber regulation, and pathophysiology of itching.
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Affiliation(s)
- Mei Bigliardi-Qi
- Department of Dermatology, CHUV Hôpital Beaumont, Lausanne, Switzerland
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Schmelz M, Paus R. Opioids and the Skin: “Itchy” Perspectives beyond Analgesia and Abuse. J Invest Dermatol 2007; 127:1287-9. [PMID: 17502859 DOI: 10.1038/sj.jid.5700634] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Opioids are intimately linked to central pain inhibition and their abuse potential. Thus, peripheral opioid receptors in the skin have been studied initially with a focus on their peripheral analgesic properties. Recent results, however, clearly indicate that opioids play a specific role in skin homeostasis by modulating keratinocyte differentiation, wound healing, and inflammatory responses.
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Affiliation(s)
- Martin Schmelz
- Department of Anesthesiology-Mannheim, University of Heidelberg, Heidelberg, Germany.
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Steinhoff M, Bienenstock J, Schmelz M, Maurer M, Wei E, Bíró T. Neurophysiological, neuroimmunological, and neuroendocrine basis of pruritus. J Invest Dermatol 2006; 126:1705-18. [PMID: 16845410 DOI: 10.1038/sj.jid.5700231] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Pruritus (itch) can be defined as an unpleasant cutaneous sensation associated with the immediate desire to scratch. Recent findings have identified potential classes of endogenous "itch mediators" and establish a modern concept for the pathophysiology of pruritus. First, there in no universal peripheral itch mediator, but disease-specific sets of involved mediators. Second, numerous mediators of skin cells can activate and sensitize pruritic nerve endings, and even modulate their growth. Our knowledge of itch processing in the spinal cord and the involved centers in the central nervous system is rapidly growing. This review summarizes the current information about the significance of neuron-skin interactions, ion channels, neuropeptides, proteases, cannabinoids, opioids, kinins, cytokines, biogenic amines, neurotransmitters, and their receptors in the pathobiology of pruritus. A deeper understanding of these circuits is required for the development of novel antipruritic strategies.
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Affiliation(s)
- Martin Steinhoff
- Department of Dermatology, IZKF Münster, Ludwig Boltzmann-Institute for Immunobiology of the Skin, University Hospital Muenster, Muenster, Germany.
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Abstract
The neurobiology of itch, which is formally known as pruritus, and its interaction with pain have been illustrated by the complexity of specific mediators, itch-related neuronal pathways and the central processing of itch. Scratch-induced pain can abolish itch, and analgesic opioids can generate itch, which indicates an antagonistic interaction. However, recent data suggest that there is a broad overlap between pain- and itch-related peripheral mediators and/or receptors, and there are astonishingly similar mechanisms of neuronal sensitization in the PNS and the CNS. The antagonistic interaction between pain and itch is already exploited in pruritus therapy, and current research concentrates on the identification of common targets for future analgesic and antipruritic therapy.
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Affiliation(s)
- Akihiko Ikoma
- Department of Dermatology, Kyoto University, Shogin-Kawahara-cho 54, Sakyo-ku, Kyoto 606-8507, Japan
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Ständer S, Schmelz M. Chronic itch and pain--similarities and differences. Eur J Pain 2006; 10:473-8. [PMID: 16678456 DOI: 10.1016/j.ejpain.2006.03.005] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Revised: 03/10/2006] [Accepted: 03/27/2006] [Indexed: 11/24/2022]
Abstract
Both, pruritus and pain are aversive, but clearly distinct sensations originating in the peripheral and central nervous system. During the last years, many interactions between itch and pain in acute transmission and sensitization processes have been identified. It is common experience that the itch sensation can be reduced by the painful sensations caused by scratching. Vice versa analgesia may reduce this inhibition and thus enhance itch. This phenomenon is particularly relevant to spinally administered mu-opioid receptor agonists, which induce segmental analgesia often combined with segmental pruritus. The peripheral and central sensitization to pain and to itch exhibits striking similarities. Classical inflammatory mediators such as bradykinin have been shown to sensitize nociceptors for both itch and pain. Also regulation of gene expression induced by trophic factors, such as NGF, plays a major role in persistently increased neuronal sensitivity for itch and pain. Finally, itch and pain exhibit corresponding patterns of central sensitization. The knowledge of antagonistic interaction, but also of similar sensitization processes has major implication for antipruritic therapeutic approaches.
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Affiliation(s)
- Sonja Ständer
- Clinical Neurodermatology, Department of Dermatology, University of Münster, Von-Esmarch-Strasse 58, D-48149 Münster, Germany.
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Abstract
The discovery of specific pathways for the processing of itch has greatly enhanced our understanding of the physiology of pruritus. However, the complex interactions between itch and pain are only partly understood. This review focuses on the neurophysiological basis of itch under experimental and clinical conditions. Chronic inflammatory diseases can locally sensitize nerve endings and thereby contribute to itch. In addition, there is increasing evidence that also central processing of itch can be sensitized in pruritus patients. Interestingly, this pattern of peripheral and central sensitization in pruritus has striking similarities to the one observed in chronic pain patients. The presumed similarities in underlying sensitizing mechanisms between itch and pain has major therapeutic consequences as successful therapies for chronic pain might be used also in chronic itch.
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Affiliation(s)
- M Schmelz
- Karl Feuerstein Professur, Klinik für Anästhesiologie und Operative Intensivmedizin, Fakultät für Klinische Medizin Mannheim, Ruprecht-Karls-Universität Heidelberg, Mannheim.
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Abstract
The discovery of a specialized neuronal pathway for itch has markedly improved our understanding of itch processing under physiological conditions. However, the complex interactions of pain and itch are only partly understood. This review focuses on the neurophysiological mechanisms involved in clinical and experimental itch conditions. There is emerging evidence that similar patterns of peripheral and central sensitization occur in chronic pain and chronic itch conditions. It will be of major interest to reveal whether the underlying mechanism for sensitization in the itch and pain pathways are also similar, as this might have major implications for therapy.
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Affiliation(s)
- Martin Schmelz
- Department of Anesthesiology and Intensive Care Medicine, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Mannheim, Germany.
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Schmelz M. Chapter 18 Itch and cold allodynia. HANDBOOK OF CLINICAL NEUROLOGY 2006; 81:249-260. [PMID: 18808840 DOI: 10.1016/s0072-9752(06)80022-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
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