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Poitras TM, Komirishetty P, Areti A, Larouche M, Krishnan A, Chandrasekhar A, Munchrath E, Zochodne DW. Manipulation of the Myc Interactome to Enhance Nerve Regeneration in a Murine Model. Ann Neurol 2024. [PMID: 38818756 DOI: 10.1002/ana.26950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 04/03/2024] [Accepted: 04/12/2024] [Indexed: 06/01/2024]
Abstract
OBJECTIVE This study was undertaken to explore manipulation of the Myc protein interactome, members of an oncogene group, in enhancing the intrinsic growth of injured peripheral adult postmitotic neurons and the nerves they supply. New approaches to enhance adult neuron growth properties are a key strategy in improving nerve regeneration. METHODS Expression and impact of Myc interactome members c-Myc, N-Myc, Mad1, and Max were evaluated within naive and "preconditioned" adult sensory neurons and Schwann cells (SCs), using siRNA and transfection of CRISPR/Cas9 or luciferase reporter in vitro. Morphological, behavioral, and electrophysiological indices of nerve regeneration were analyzed in vivo. RESULTS c-Myc, N-Myc, Max, and Mad were expressed in adult sensory neurons and in partnering SCs. In vitro knockdown (KD) of either Mad1 or Max, competitive inhibitors of Myc, unleashed heightened neurite outgrowth in both naive uninjured or preconditioned adult neurons. In contrast, KD or inhibition of both isoforms of Myc was required to suppress growth. In SCs, Mad1 KD not only enhanced migratory behavior but also conditioned increased outgrowth in separately cultured adult sensory neurons. In vivo, local Mad1 KD improved electrophysiological, behavioral, and structural indices of nerve regeneration out to 60 days of follow-up. INTERPRETATION Members of the Myc interactome, specifically Mad1, are novel targets for improving nerve regeneration. Unleashing of Myc growth signaling through Mad1 KD enhances the regrowth of both peripheral neurons and SCs to facilitate better regrowth of nerves. ANN NEUROL 2024.
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Affiliation(s)
- Trevor M Poitras
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Prashanth Komirishetty
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Aparna Areti
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Matt Larouche
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Anand Krishnan
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
- Department of Anatomy, Physiology, and Pharmacology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Ambika Chandrasekhar
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Easton Munchrath
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Douglas W Zochodne
- Division of Neurology, Department of Medicine, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
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Long RM, Ong H, Wang WX, Komirishetty P, Areti A, Chandrasekhar A, Larouche M, Lefebvre JL, Zochodne DW. The Role of Protocadherin γ in Adult Sensory Neurons and Skin Reinnervation. J Neurosci 2023; 43:8348-8366. [PMID: 37821230 PMCID: PMC10711737 DOI: 10.1523/jneurosci.1940-22.2023] [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: 10/14/2022] [Revised: 10/02/2023] [Accepted: 10/04/2023] [Indexed: 10/13/2023] Open
Abstract
The clustered protocadherins (cPcdhs) play a critical role in the patterning of several CNS axon and dendritic arbors, through regulation of homophilic self and neighboring interactions. While not explored, primary peripheral sensory afferents that innervate the epidermis may require similar constraints to convey spatial signals with appropriate fidelity. Here, we show that members of the γ-Pcdh (Pcdhγ) family are expressed in both adult sensory neuron axons and in neighboring keratinocytes that have close interactions during skin reinnervation. Adult mice of both sexes were studied. Pcdhγ knock-down either through small interfering RNA (siRNA) transduction or AAV-Cre recombinase transfection of adult mouse primary sensory neurons from floxed Pcdhγ mice was associated with a remarkable rise in neurite outgrowth and branching. Rises in outgrowth were abrogated by Rac1 inhibition. Moreover, AAV-Cre knock-down in Pcdhγ floxed neurons generated a rise in neurite self-intersections, and a robust rise in neighbor intersections or tiling, suggesting a role in sensory axon repulsion. Interestingly, preconditioned (3-d axotomy) neurons with enhanced growth had temporary declines in Pcdhγ and lessened outgrowth from Pcdhγ siRNA. In vivo, mice with local hindpaw skin Pcdhγ knock-down by siRNA had accelerated reinnervation by new epidermal axons with greater terminal branching and reduced intra-axonal spacing. Pcdhγ knock-down also had reciprocal impacts on keratinocyte density and nuclear size. Taken together, this work provides evidence for a role of Pcdhγ in attenuating outgrowth of sensory axons and their interactions, with implications in how new reinnervating axons following injury fare amid skin keratinocytes that also express Pcdhγ.SIGNIFICANCE STATEMENT The molecular mechanisms and potential constraints that govern skin reinnervation and patterning by sensory axons are largely unexplored. Here, we show that γ-protocadherins (Pcdhγ) may help to dictate interaction not only among axons but also between axons and keratinocytes as the former re-enter the skin during reinnervation. Pcdhγ neuronal knock-down enhances outgrowth in peripheral sensory neurons, involving the growth cone protein Rac1 whereas skin Pcdhγ knock-down generates rises in terminal epidermal axon growth and branching during re-innervation. Manipulation of sensory axon regrowth within the epidermis offers an opportunity to influence regenerative outcomes following nerve injury.
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Affiliation(s)
- Rebecca M Long
- Division of Neurology, Department of Medicine and the Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Honyi Ong
- Division of Neurology, Department of Medicine and the Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Wendy Xueyi Wang
- Program for Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5R 0A3, Canada
| | - Prashanth Komirishetty
- Division of Neurology, Department of Medicine and the Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Aparna Areti
- Division of Neurology, Department of Medicine and the Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Ambika Chandrasekhar
- Division of Neurology, Department of Medicine and the Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Matt Larouche
- Division of Neurology, Department of Medicine and the Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Julie L Lefebvre
- Program for Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5R 0A3, Canada
| | - Douglas W Zochodne
- Division of Neurology, Department of Medicine and the Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
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Pan W, Huang X, Yu Z, Ding Q, Xia L, Hua J, Gu B, Xiong Q, Yu H, Wang J, Xu Z, Zeng L, Bai G, Liu H. Netrin-3 Suppresses Diabetic Neuropathic Pain by Gating the Intra-epidermal Sprouting of Sensory Axons. Neurosci Bull 2023; 39:745-758. [PMID: 36587114 PMCID: PMC10169969 DOI: 10.1007/s12264-022-01011-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 11/08/2022] [Indexed: 01/02/2023] Open
Abstract
Diabetic neuropathic pain (DNP) is the most common disabling complication of diabetes. Emerging evidence has linked the pathogenesis of DNP to the aberrant sprouting of sensory axons into the epidermal area; however, the underlying molecular events remain poorly understood. Here we found that an axon guidance molecule, Netrin-3 (Ntn-3), was expressed in the sensory neurons of mouse dorsal root ganglia (DRGs), and downregulation of Ntn-3 expression was highly correlated with the severity of DNP in a diabetic mouse model. Genetic ablation of Ntn-3 increased the intra-epidermal sprouting of sensory axons and worsened the DNP in diabetic mice. In contrast, the elevation of Ntn-3 levels in DRGs significantly inhibited the intra-epidermal axon sprouting and alleviated DNP in diabetic mice. In conclusion, our studies identified Ntn-3 as an important regulator of DNP pathogenesis by gating the aberrant sprouting of sensory axons, indicating that Ntn-3 is a potential druggable target for DNP treatment.
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Affiliation(s)
- Weiping Pan
- Department of Pharmaceutical Sciences, Zhejiang University City College, Hangzhou, 310015, China
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Xueyin Huang
- Department of Neurobiology and Department of Neurology of The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Zikai Yu
- Department of Pharmaceutical Sciences, Zhejiang University City College, Hangzhou, 310015, China
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Qiongqiong Ding
- Department of Pharmaceutical Sciences, Zhejiang University City College, Hangzhou, 310015, China
| | - Liping Xia
- Department of Anesthesiology and Department of Neurobiology of The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Jianfeng Hua
- Department of Neurobiology and Department of Neurology of The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Bokai Gu
- Department of Neurobiology and Department of Neurology of The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Qisong Xiong
- Department of Pharmaceutical Sciences, Zhejiang University City College, Hangzhou, 310015, China
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Hualin Yu
- Department of Pharmaceutical Sciences, Zhejiang University City College, Hangzhou, 310015, China
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Junbo Wang
- Department of Pharmaceutical Sciences, Zhejiang University City College, Hangzhou, 310015, China
| | - Zhenzhong Xu
- Department of Anesthesiology and Department of Neurobiology of The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Linghui Zeng
- Department of Pharmaceutical Sciences, Zhejiang University City College, Hangzhou, 310015, China
| | - Ge Bai
- Department of Neurobiology and Department of Neurology of The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China.
- Liangzhu Laboratory, MOE Frontier Science Center for Brain Science and Brain-machine Integration, State Key Laboratory of Brain-machine Intelligence, Zhejiang University, Hangzhou, 311121, China.
- NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University, Hangzhou, 310058, China.
- Institute of Brain and Cognition, Zhejiang University City College School of Medicine, Hangzhou, 310015, China.
| | - Huaqing Liu
- Department of Pharmaceutical Sciences, Zhejiang University City College, Hangzhou, 310015, China.
- Institute of Brain and Cognition, Zhejiang University City College School of Medicine, Hangzhou, 310015, China.
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Sendel M, Dunst A, Forstenpointner J, Hüllemann P, Baron R. Capsaicin treatment in neuropathic pain: axon reflex vasodilatation after 4 weeks correlates with pain reduction. Pain 2023; 164:534-542. [PMID: 35857438 DOI: 10.1097/j.pain.0000000000002735] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 06/27/2022] [Indexed: 11/26/2022]
Abstract
ABSTRACT Capsaicin, an agonist at the transient receptor potential vanilloid 1, is used for the topical treatment of peripheral neuropathic pain. Reversible receptor defunctionalization and degeneration and subsequent regeneration of cutaneous nociceptors are discussed as its mechanism of action. Here, we hypothesize an accelerated functional recovery of a subclass of nociceptive afferents, the peptidergic vasoactive nociceptors, as the potential cause of capsaicin analgesia. In this noninterventional exploratory trial, 23 patients with peripheral neuropathic pain were treated with one topical high-concentration capsaicin application. Baseline pain ratings, comorbidities, and quality of life were assessed. Functional laser speckle contrast analysis (heat-evoked neurogenic vasodilatation to assess functional properties of peptidergic nociceptors) and quantitative sensory testing were performed in the affected skin. Four weeks after treatment, functional laser speckle contrast analysis and questionnaires were repeated. Telephone interviews were conducted at weeks 2, 10, and 12. Topical capsaicin treatment induced a significant reduction in pain intensity with a maximum at 4 weeks. At the same time, heat-evoked neurogenic vasodilatation was on average similar to pretreatment values. Half of the patients not only showed a functional recovery but also an improvement in vasodilatation, indicating regeneration of nerve fibers. Patients with improved heat-evoked neurogenic vasodilatation at week 4 showed a greater pain reduction than those with deterioration. The degree of vasodilatation significantly correlated with pain reduction. These findings suggest that (1) regeneration of peptidergic nociceptors may be the mechanism behind capsaicin-induced analgesia and (2) that a disease-modifying effect of capsaicin on these fibers already occurs 4 weeks after application.
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Affiliation(s)
- Manon Sendel
- Division of Neurological Pain Research and Therapy, Department of Neurology, University Hospital Schleswig-Holstein, 24105, Kiel, Germany
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Bagood MD, Isseroff RR. TRPV1: Role in Skin and Skin Diseases and Potential Target for Improving Wound Healing. Int J Mol Sci 2021; 22:ijms22116135. [PMID: 34200205 PMCID: PMC8201146 DOI: 10.3390/ijms22116135] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 05/31/2021] [Accepted: 06/01/2021] [Indexed: 12/14/2022] Open
Abstract
Skin is innervated by a multitude of sensory nerves that are important to the function of this barrier tissue in homeostasis and injury. The role of innervation and neuromediators has been previously reviewed so here we focus on the role of the transient receptor potential cation channel, subfamily V member 1 (TRPV1) in wound healing, with the intent of targeting it in treatment of non-healing wounds. TRPV1 structure and function as well as the outcomes of TRPV1-targeted therapies utilized in several diseases and tissues are summarized. In skin, keratinocytes, sebocytes, nociceptors, and several immune cells express TRPV1, making it an attractive focus area for treating wounds. Many intrinsic and extrinsic factors confound the function and targeting of TRPV1 and may lead to adverse or off-target effects. Therefore, a better understanding of what is known about the role of TRPV1 in skin and wound healing will inform future therapies to treat impaired and chronic wounds to improve healing.
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Affiliation(s)
- Michelle D. Bagood
- Department of Dermatology, School of Medicine, UC Davis, Sacramento, CA 95816, USA;
| | - R. Rivkah Isseroff
- Department of Dermatology, School of Medicine, UC Davis, Sacramento, CA 95816, USA;
- Dermatology Section, VA Northern California Health Care System, Mather, CA 95655, USA
- Correspondence: ; Tel.: +1-(916)-551-2606
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Taminato M, Tomita K, Yano K, Otani N, Kuroda K, Kubo T. Targeted sensory reinnervation by direct neurotization of skin: An experimental study in rats. J Plast Reconstr Aesthet Surg 2021; 74:2379-2386. [PMID: 33583760 DOI: 10.1016/j.bjps.2020.12.101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 12/15/2020] [Accepted: 12/26/2020] [Indexed: 12/01/2022]
Abstract
BACKGROUND No effective methods currently exist for breast neurotization in implant-based breast reconstruction. Here, we focused on direct neurotization (DN), in which axons regenerating from nerve stumps are directed to the mastectomy flap and aimed to assess whether DN can generate a new mechano-nociceptive field using a rat model of back skin sensory denervation. METHODS Dorsal cutaneous nerves (DCNs) of rats were exposed and transected, leaving only the left medial branch of the DCN of thoracic segment 13 (mDCN-T13) intact. This procedure resulted in an isolated innervated field surrounded by a denervated field. The mDCN-T13 was transected, and the proximal nerve stump was sutured to the subdermis (DN subdermal group, n = 6) or dermis (DN dermal group, n = 5) of a different region of the denervated field. In the Crush group (n = 5), the intact mDCN-T13 was only crushed. We evaluated the generation of a new mechano-nociceptive field over time using the cutaneous trunci muscle (CTM) reflex test and histomorphometrically evaluated regenerating nerves in the reinnervated region. RESULTS In the DN groups, the CTM reflex appeared in the DN area after postoperative week 4. The new mechano-nociceptive field gradually expanded afterwards, and by postoperative week 12, the area was substantially larger than the original region innervated by the mDCN-T13 in the DN dermal group, although not as large as that in the Crush group. In histomorphometric evaluations, many S100-positive myelinated fibers were observed in the dermis of the reinnervated area for all groups. CONCLUSION In targeted sensory reinnervation, DN of the skin is revolutionary in that it allows a new innervated area to be generated at a desired location regardless of whether a distal nerve stump is available. DN may present an effective approach for breast neurotization in breast reconstruction after mastectomy, particularly for procedures that cannot use sensate flaps such as implant-based breast reconstruction.
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Affiliation(s)
- Mifue Taminato
- Department of Plastic and Reconstructive Surgery, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Koichi Tomita
- Department of Plastic and Reconstructive Surgery, Graduate School of Medicine, Osaka University, Osaka, Japan.
| | | | - Naoya Otani
- Department of Plastic and Reconstructive Surgery, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Kazuya Kuroda
- Department of Plastic and Reconstructive Surgery, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Tateki Kubo
- Department of Plastic and Reconstructive Surgery, Graduate School of Medicine, Osaka University, Osaka, Japan
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Chandrasekhar A, Komirishetty P, Areti A, Krishnan A, Zochodne DW. Dual Specificity Phosphatases Support Axon Plasticity and Viability. Mol Neurobiol 2021; 58:391-407. [PMID: 32959171 DOI: 10.1007/s12035-020-02119-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Accepted: 09/05/2020] [Indexed: 02/07/2023]
Abstract
In peripheral neuropathies, axonal degeneration (AxD) impairs the prognosis for recovery. Here, we describe a role for dual specificity phosphatases (DUSPs; MAP kinase phosphatases, MKPs), in supporting autonomous axon plasticity and viability. Both DUSPs 1 and 4 were identified within intact or axotomized sensory neurons. Knockdown of DUSP 1 or 4 independently or combined impaired neurite outgrowth in adult dissociated sensory neurons. Furthermore, adult sensory neurons with DUSP knockdown were rendered sensitive to axonopathy in vitro following exposure to low, subtoxic TrpV1 (transient receptor potential cation channel subfamily V member 1) activation by capsaicin, an intervention normally supportive of growth. This was not prevented by concurrent DLK (dual leucine zipper kinase) knockdown. Ex vivo neurofilament dissolution was heightened by DUSP inhibition within explanted nerves. In vivo DUSP knockdown or inhibition was associated with more rapid loss of motor axon excitability. The addition of SARM1 (sterile alpha and TIR motif containing 1) siRNA abrogated DUSP1 and 4 mediated loss of excitability. DUSP knockdown accelerated neurofilament breakdown and there was earlier morphological evidence of myelinated axon degeneration distal to axotomy. Taken together, the findings identify a key role for DUSPs in supporting axon plasticity and survival.
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Affiliation(s)
- Ambika Chandrasekhar
- Neuroscience and Mental Health Institute and Division of Neurology, Department of Medicine, University of Alberta, 7-132A Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada
| | - Prashanth Komirishetty
- Neuroscience and Mental Health Institute and Division of Neurology, Department of Medicine, University of Alberta, 7-132A Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada
| | - Aparna Areti
- Neuroscience and Mental Health Institute and Division of Neurology, Department of Medicine, University of Alberta, 7-132A Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada
| | - Anand Krishnan
- Neuroscience and Mental Health Institute and Division of Neurology, Department of Medicine, University of Alberta, 7-132A Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, Canada
| | - Douglas W Zochodne
- Neuroscience and Mental Health Institute and Division of Neurology, Department of Medicine, University of Alberta, 7-132A Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada.
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Fight fire with fire: Neurobiology of capsaicin-induced analgesia for chronic pain. Pharmacol Ther 2020; 220:107743. [PMID: 33181192 DOI: 10.1016/j.pharmthera.2020.107743] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 11/04/2020] [Indexed: 12/12/2022]
Abstract
Capsaicin, the pungent ingredient in chili peppers, produces intense burning pain in humans. Capsaicin selectively activates the transient receptor potential vanilloid 1 (TRPV1), which is enriched in nociceptive primary afferents, and underpins the mechanism for capsaicin-induced burning pain. Paradoxically, capsaicin has long been used as an analgesic. The development of topical patches and injectable formulations containing capsaicin has led to application in clinical settings to treat chronic pain conditions, such as neuropathic pain and the potential to treat osteoarthritis. More detailed determination of the neurobiological mechanisms of capsaicin-induced analgesia should provide the logical rationale for capsaicin therapy and help to overcome the treatment's limitations, which include individual differences in treatment outcome and procedural discomfort. Low concentrations of capsaicin induce short-term defunctionalization of nociceptor terminals. This phenomenon is reversible within hours and, hence, likely does not account for the clinical benefit. By contrast, high concentrations of capsaicin lead to long-term defunctionalization mediated by the ablation of TRPV1-expressing afferent terminals, resulting in long-lasting analgesia persisting for several months. Recent studies have shown that capsaicin-induced Ca2+/calpain-mediated ablation of axonal terminals is necessary to produce long-lasting analgesia in a mouse model of neuropathic pain. In combination with calpain, axonal mitochondrial dysfunction and microtubule disorganization may also contribute to the longer-term effects of capsaicin. The analgesic effects subside over time in association with the regeneration of the ablated afferent terminals. Further determination of the neurobiological mechanisms of capsaicin-induced analgesia should lead to more efficacious non-opioidergic analgesic options with fewer adverse side effects.
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Anti-Aging Effects of GDF11 on Skin. Int J Mol Sci 2020; 21:ijms21072598. [PMID: 32283613 PMCID: PMC7177281 DOI: 10.3390/ijms21072598] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 04/02/2020] [Accepted: 04/07/2020] [Indexed: 12/24/2022] Open
Abstract
Human skin is composed of three layers: the epidermis, the dermis, and the hypodermis. The epidermis has four major cell layers made up of keratinocytes in varying stages of progressive differentiation. Skin aging is a multi-factorial process that affects every phase of its biology and function. The expression profiles of inflammation-related genes analyzed in resident immune cells demonstrated that these cells have a strong ability to regenerate adult skin stem cells and to produce endogenous substances such as growth differentiation factor 11 (GDF11). GDF11 appears to be the key to progenitor proliferation and/or differentiation. The preservation of youthful phenotypes has been tied to the presence of GDF11 in different human tissues, and, in the skin, this factor inhibits inflammatory responses. The protective role of GDF11 depends on a multi-factorial process implicating various types of skin cells such as keratinocytes, fibroblasts and inflammatory cells. GDF11 should be further studied for the purpose of developing novel therapies for the treatment of skin diseases.
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Carlin D, Halevi AE, Ewan EE, Moore AM, Cavalli V. Nociceptor Deletion of Tsc2 Enhances Axon Regeneration by Inducing a Conditioning Injury Response in Dorsal Root Ganglia. eNeuro 2019; 6:ENEURO.0168-19.2019. [PMID: 31182472 PMCID: PMC6595439 DOI: 10.1523/eneuro.0168-19.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 05/15/2019] [Accepted: 05/18/2019] [Indexed: 12/30/2022] Open
Abstract
Neurons of the PNS are able to regenerate injured axons, a process requiring significant cellular resources to establish and maintain long-distance growth. Genetic activation of mTORC1, a potent regulator of cellular metabolism and protein translation, improves axon regeneration of peripheral neurons by an unresolved mechanism. To gain insight into this process, we activated mTORC1 signaling in mouse nociceptors via genetic deletion of its negative regulator Tsc2. Perinatal deletion of Tsc2 in nociceptors enhanced initial axon growth after sciatic nerve crush, however by 3 d post-injury axon elongation rate became similar to controls. mTORC1 inhibition prior to nerve injury was required to suppress the enhanced axon growth. Gene expression analysis in purified nociceptors revealed that Tsc2-deficient nociceptors had increased activity of regeneration-associated transcription factors (RATFs), including cJun and Atf3, in the absence of injury. Additionally, nociceptor deletion of Tsc2 activated satellite glial cells and macrophages in the dorsal root ganglia (DRG) in a similar manner to nerve injury. Surprisingly, these changes improved axon length but not percentage of initiating axons in dissociated cultures. The pro-regenerative environment in naïve DRG was recapitulated by AAV8-mediated deletion of Tsc2 in adult mice, suggesting that this phenotype does not result from a developmental effect. Consistently, AAV8-mediated Tsc2 deletion did not improve behavioral recovery after a sciatic nerve crush injury despite initially enhanced axon growth. Together, these data show that neuronal mTORC1 activation induces an incomplete pro-regenerative environment in the DRG that improves initial but not later axon growth after nerve injury.
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Affiliation(s)
- Dan Carlin
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110
| | - Alexandra E Halevi
- Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, St. Louis, MO 63110
| | - Eric E Ewan
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110
| | - Amy M Moore
- Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, St. Louis, MO 63110
| | - Valeria Cavalli
- Department of Neuroscience, Center of Regenerative Medicine, Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO 63110
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