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Inokuchi-Sakata S, Narita R, Takahashi Y, Ishiuji Y, Asahina A, Kato F. Region-specific activation in the accumbens nucleus by itch with modified scratch efficacy in mice - a model-free multivariate analysis. Mol Brain 2024; 17:27. [PMID: 38783364 PMCID: PMC11119306 DOI: 10.1186/s13041-024-01101-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Accepted: 05/15/2024] [Indexed: 05/25/2024] Open
Abstract
Itch is a protective/defensive function with divalent motivational drives. Itch itself elicits an unpleasant experience, which triggers the urge to scratch, relieving the itchiness. Still, it can also result in dissatisfaction when the scratch is too intense and painful or unsatisfactory due to insufficient scratch effect. Therefore, it is likely that the balance between the unpleasantness/pleasure and satisfaction/unsatisfaction associated with itch sensation and scratching behavior is determined by complex brain mechanisms. The physiological/pathological mechanisms underlying this balance remain largely elusive. To address this issue, we targeted the "reward center" of the brain, the nucleus accumbens (NAc), in which itch-responsive neurons have been found in rodents. We examined how neurons in the NAc are activated or suppressed during histamine-induced scratching behaviors in mice. The mice received an intradermal injection of histamine or saline at the neck, and the scratching number was analyzed by recording the movement of the bilateral hind limbs for about 45 min after injection. To experimentally manipulate the scratch efficacy in these histamine models, we compared histamine's behavioral and neuronal effects between mice with intact and clipped nails on the hind paws. As expected, the clipping of the hind limb nail increased the number of scratches after the histamine injection. In the brains of mice exhibiting scratching behaviors, we analyzed the expression of the c-fos gene (Fos) as a readout of an immediate activation of neurons during itch/scratch and dopamine receptors (Drd1 and Drd2) using multiplex single-molecule fluorescence in situ hybridization (RNAscope) in the NAc and surrounding structures. We performed a model-free analysis of gene expression in geometrically divided NAc subregions without assuming the conventional core-shell divisions. The results indicated that even within the NAc, multiple subregions responded differentially to various itch/scratch conditions. We also found different clusters with neurons showing similar or opposite changes in Fos expression and the correlation between scratch number and Fos expression in different itch/scratch conditions. These regional differences and clusters would provide a basis for the complex role of the NAc and surrounding structures in encoding the outcomes of scratching behavior and itchy sensations.
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Affiliation(s)
- Sanae Inokuchi-Sakata
- Department of Dermatology, The Jikei University School of Medicine, Minato-Ku, Tokyo, 105-8461, Japan
- Department of Neuroscience, The Jikei University School of Medicine, Minato-ku, Tokyo, 105-8461, Japan
| | - Ryo Narita
- Department of Neuroscience, The Jikei University School of Medicine, Minato-ku, Tokyo, 105-8461, Japan
- Center for Neuroscience of Pain, The Jikei University School of Medicine, Minato-Ku, Tokyo, 105-8461, Japan
| | - Yukari Takahashi
- Department of Neuroscience, The Jikei University School of Medicine, Minato-ku, Tokyo, 105-8461, Japan
- Center for Neuroscience of Pain, The Jikei University School of Medicine, Minato-Ku, Tokyo, 105-8461, Japan
| | - Yozo Ishiuji
- Department of Dermatology, The Jikei University School of Medicine, Minato-Ku, Tokyo, 105-8461, Japan
- Center for Neuroscience of Pain, The Jikei University School of Medicine, Minato-Ku, Tokyo, 105-8461, Japan
| | - Akihiko Asahina
- Department of Dermatology, The Jikei University School of Medicine, Minato-Ku, Tokyo, 105-8461, Japan
| | - Fusao Kato
- Department of Neuroscience, The Jikei University School of Medicine, Minato-ku, Tokyo, 105-8461, Japan.
- Center for Neuroscience of Pain, The Jikei University School of Medicine, Minato-Ku, Tokyo, 105-8461, Japan.
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Kleuser B, Bäumer W. Sphingosine 1-Phosphate as Essential Signaling Molecule in Inflammatory Skin Diseases. Int J Mol Sci 2023; 24:ijms24021456. [PMID: 36674974 PMCID: PMC9863039 DOI: 10.3390/ijms24021456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/04/2023] [Accepted: 01/06/2023] [Indexed: 01/13/2023] Open
Abstract
Sphingolipids are crucial molecules of the mammalian epidermis. The formation of skin-specific ceramides contributes to the formation of lipid lamellae, which are important for the protection of the epidermis from excessive water loss and protect the skin from the invasion of pathogens and the penetration of xenobiotics. In addition to being structural constituents of the epidermal layer, sphingolipids are also key signaling molecules that participate in the regulation of epidermal cells and the immune cells of the skin. While the importance of ceramides with regard to the proliferation and differentiation of skin cells has been known for a long time, it has emerged in recent years that the sphingolipid sphingosine 1-phosphate (S1P) is also involved in processes such as the proliferation and differentiation of keratinocytes. In addition, the immunomodulatory role of this sphingolipid species is becoming increasingly apparent. This is significant as S1P mediates a variety of its actions via G-protein coupled receptors. It is, therefore, not surprising that dysregulation in the signaling pathways of S1P is involved in the pathophysiological conditions of skin diseases. In the present review, the importance of S1P in skin cells, as well as the immune cells of the skin, is elaborated. In particular, the role of the molecule in inflammatory skin diseases will be discussed. This is important because interfering with S1P signaling pathways may represent an innovative option for the treatment of inflammatory skin diseases.
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Affiliation(s)
- Burkhard Kleuser
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise Str. 2+4, 14195 Berlin, Germany
- Correspondence: (B.K.); (W.B.)
| | - Wolfgang Bäumer
- Department of Veterinary Medicine, Institute of Pharmacology and Toxicology, Freie Universität Berlin, Koserstr. 20, 14195 Berlin, Germany
- Correspondence: (B.K.); (W.B.)
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Mitochondrial Reactive Oxygen Species Elicit Acute and Chronic Itch via Transient Receptor Potential Canonical 3 Activation in Mice. Neurosci Bull 2022; 38:373-385. [PMID: 35294713 PMCID: PMC9068852 DOI: 10.1007/s12264-022-00837-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 12/13/2021] [Indexed: 02/08/2023] Open
Abstract
Mitochondrial reactive oxygen species (mROS) that are overproduced by mitochondrial dysfunction are linked to pathological conditions including sensory abnormalities. Here, we explored whether mROS overproduction induces itch through transient receptor potential canonical 3 (TRPC3), which is sensitive to ROS. Intradermal injection of antimycin A (AA), a selective inhibitor of mitochondrial electron transport chain complex III for mROS overproduction, produced robust scratching behavior in naïve mice, which was suppressed by MitoTEMPO, a mitochondria-selective ROS scavenger, and Pyr10, a TRPC3-specific blocker, but not by blockers of TRPA1 or TRPV1. AA activated subsets of trigeminal ganglion neurons and also induced inward currents, which were blocked by MitoTEMPO and Pyr10. Besides, dry skin-induced chronic scratching was relieved by MitoTEMPO and Pyr10, and also by resveratrol, an antioxidant. Taken together, our results suggest that mROS elicit itch through TRPC3, which may underlie chronic itch, representing a potential therapeutic target for chronic itch.
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Samineni VK, Grajales-Reyes JG, Grajales-Reyes GE, Tycksen E, Copits BA, Pedersen C, Ankudey ES, Sackey JN, Sewell SB, Bruchas MR, Gereau RW. Cellular, circuit and transcriptional framework for modulation of itch in the central amygdala. eLife 2021; 10:68130. [PMID: 34032210 PMCID: PMC8172243 DOI: 10.7554/elife.68130] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 05/24/2021] [Indexed: 01/06/2023] Open
Abstract
Itch is an unpleasant sensation that elicits robust scratching and aversive experience. However, the identity of the cells and neural circuits that organize this information remains elusive. Here, we show the necessity and sufficiency of chloroquine-activated neurons in the central amygdala (CeA) for both itch sensation and associated aversion. Further, we show that chloroquine-activated CeA neurons play important roles in itch-related comorbidities, including anxiety-like behaviors, but not in some aversive and appetitive behaviors previously ascribed to CeA neurons. RNA-sequencing of chloroquine-activated CeA neurons identified several differentially expressed genes as well as potential key signaling pathways in regulating pruritis. Finally, viral tracing experiments demonstrate that these neurons send projections to the ventral periaqueductal gray that are critical in modulation of itch. These findings reveal a cellular and circuit signature of CeA neurons orchestrating behavioral and affective responses to pruritus in mice.
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Affiliation(s)
- Vijay K Samineni
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
| | - Jose G Grajales-Reyes
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
- Medical Scientist Training Program, Washington University School of MedicineSt. LouisUnited States
- Neuroscience Program, Washington University School of MedicineSt. LouisUnited States
| | - Gary E Grajales-Reyes
- Department of Pathology & Immunology, Washington University School of MedicineSt. LouisUnited States
| | - Eric Tycksen
- Genome Technology Access Center, Washington University School of MedicineSeattleUnited States
| | - Bryan A Copits
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
| | - Christian Pedersen
- Department of Biomedical Engineering, University of WashingtonSeattleUnited States
| | - Edem S Ankudey
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
| | - Julian N Sackey
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
| | - Sienna B Sewell
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
| | - Michael R Bruchas
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
- Departments of Anesthesiology and Pharmacology, University of WashingtonSeattleUnited States
- Departmentsof Neuroscience and Biomedical Engineering, Washington University School of MedicineSt.LouisUnited States
| | - Robert W Gereau
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
- Department of Biomedical Engineering, University of WashingtonSeattleUnited States
- Departmentsof Neuroscience and Biomedical Engineering, Washington University School of MedicineSt.LouisUnited States
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