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Chen Y, He Y, Zhao S, He X, Xue D, Xia Y. Hypoxic/Ischemic Inflammation, MicroRNAs and δ-Opioid Receptors: Hypoxia/Ischemia-Sensitive Versus-Insensitive Organs. Front Aging Neurosci 2022; 14:847374. [PMID: 35615595 PMCID: PMC9124822 DOI: 10.3389/fnagi.2022.847374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2022] [Accepted: 03/21/2022] [Indexed: 11/15/2022] Open
Abstract
Hypoxia and ischemia cause inflammatory injury and critically participate in the pathogenesis of various diseases in various organs. However, the protective strategies against hypoxic and ischemic insults are very limited in clinical settings up to date. It is of utmost importance to improve our understanding of hypoxic/ischemic (H/I) inflammation and find novel therapies for better prevention/treatment of H/I injury. Recent studies provide strong evidence that the expression of microRNAs (miRNAs), which regulate gene expression and affect H/I inflammation through post-transcriptional mechanisms, are differentially altered in response to H/I stress, while δ-opioid receptors (DOR) play a protective role against H/I insults in different organs, including both H/I-sensitive organs (e.g., brain, kidney, and heart) and H/I-insensitive organs (e.g., liver and muscle). Indeed, many studies have demonstrated the crucial role of the DOR-mediated cyto-protection against H/I injury by several molecular pathways, including NLRP3 inflammasome modulated by miRNAs. In this review, we summarize our recent studies along with those of others worldwide, and compare the effects of DOR on H/I expression of miRNAs in H/I-sensitive and -insensitive organs. The alternation in miRNA expression profiles upon DOR activation and the potential impact on inflammatory injury in different organs under normoxic and hypoxic conditions are discussed at molecular and cellular levels. More in-depth investigations into this field may provide novel clues for new protective strategies against H/I inflammation in different types of organs.
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Affiliation(s)
- Yimeng Chen
- Department of Urology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Yichen He
- Department of Urology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Shuchen Zhao
- Department of Urology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Xiaozhou He
- Department of Urology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Dong Xue
- Department of Urology, The Third Affiliated Hospital of Soochow University, Changzhou, China
- *Correspondence: Dong Xue,
| | - Ying Xia
- Shanghai Key Laboratory of Acupuncture Mechanism and Acupoint Function, Fudan University, Shanghai, China
- Ying Xia,
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Xu Y, Zhi F, Mao J, Peng Y, Shao N, Balboni G, Yang Y, Xia Y. δ-opioid receptor activation protects against Parkinson's disease-related mitochondrial dysfunction by enhancing PINK1/Parkin-dependent mitophagy. Aging (Albany NY) 2020; 12:25035-25059. [PMID: 33197884 PMCID: PMC7803568 DOI: 10.18632/aging.103970] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 07/31/2020] [Indexed: 04/11/2023]
Abstract
Our previous studies have shown that the δ-opioid receptor (DOR) is an important neuroprotector via the regulation of PTEN-induced kinase 1 (PINK1), a mitochondria-related molecule, under hypoxic and MPP+ insults. Since mitochondrial dysfunctions are observed in both hypoxia and MPP+ insults, this study further investigated whether DOR is cytoprotective against these insults by targeting mitochondria. Through comparing DOR-induced responses to hypoxia versus MPP+-induced parkinsonian insult in PC12 cells, we found that both hypoxia and MPP+ caused a collapse of mitochondrial membrane potential and severe mitochondrial dysfunction. In sharp contrast to its inappreciable effect on mitochondria in hypoxic conditions, DOR activation with UFP-512, a specific agonist, significantly attenuated the MPP+-induced mitochondrial injury. Mechanistically, DOR activation effectively upregulated PINK1 expression and promoted Parkin's mitochondrial translocation and modification, thus enhancing the PINK1-Parkin mediated mitophagy. Either PINK1 knockdown or DOR knockdown largely interfered with the DOR-mediated mitoprotection in MPP+ conditions. Moreover, there was a major difference between hypoxia versus MPP+ in terms of the regulation of mitophagy with hypoxia-induced mitophagy being independent from DOR-PINK1 signaling. Taken together, our novel data suggest that DOR activation is neuroprotective against parkinsonian injury by specifically promoting mitophagy in a PINK1-dependent pathway and thus attenuating mitochondrial damage.
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Affiliation(s)
- Yuan Xu
- Department of Neurosurgery, The First People’s Hospital of Changzhou, Changzhou, Jiangsu, China
- Modern Medical Research Center, The Third Affiliated Hospital of Soochow University, Changzhou, Jiangsu, China
- Shanghai Key Laboratory of Acupuncture Mechanism and Acupoint Function, Department of Aeronautics and Astronautics, Fudan University, Shanghai, China
| | - Feng Zhi
- Department of Neurosurgery, The First People’s Hospital of Changzhou, Changzhou, Jiangsu, China
- Modern Medical Research Center, The Third Affiliated Hospital of Soochow University, Changzhou, Jiangsu, China
| | - Jiahao Mao
- Department of Neurosurgery, The First People’s Hospital of Changzhou, Changzhou, Jiangsu, China
- Modern Medical Research Center, The Third Affiliated Hospital of Soochow University, Changzhou, Jiangsu, China
| | - Ya Peng
- Department of Neurosurgery, The First People’s Hospital of Changzhou, Changzhou, Jiangsu, China
| | - Naiyuan Shao
- Department of Neurosurgery, The First People’s Hospital of Changzhou, Changzhou, Jiangsu, China
| | - Gianfranco Balboni
- Department of Life and Environment Sciences, University of Cagliari, Cagliari, Italy
| | - Yilin Yang
- Department of Neurosurgery, The First People’s Hospital of Changzhou, Changzhou, Jiangsu, China
- Modern Medical Research Center, The Third Affiliated Hospital of Soochow University, Changzhou, Jiangsu, China
| | - Ying Xia
- Shanghai Key Laboratory of Acupuncture Mechanism and Acupoint Function, Department of Aeronautics and Astronautics, Fudan University, Shanghai, China
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Xu Y, Zhi F, Balboni G, Yang Y, Xia Y. Opposite Roles of δ- and μ-Opioid Receptors in BACE1 Regulation and Alzheimer's Injury. Front Cell Neurosci 2020; 14:88. [PMID: 32425755 PMCID: PMC7204847 DOI: 10.3389/fncel.2020.00088] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Accepted: 03/26/2020] [Indexed: 12/16/2022] Open
Abstract
Alzheimer’s disease (AD) is characterized by amyloid plaques and neurofibrillary tangles. Substantial evidence for AD pathogenesis suggests that β-site APP cleaving enzyme 1 (BACE1) and γ-secretase enzyme initiate the amyloidogenic pathway and produces toxic Aβ peptides that prone to aggregate in the brain. Therefore, the inhibition of BACE1 expression and function is an attractive strategy for AD therapy. In the present work, we made the first finding that activating δ-opioid receptors (DOR) with a specific DOR agonist significantly attenuated BACE1 expression and activity in the highly differentiated PC12 cells with mimicked AD injury, while the application of DOR inhibitor naltrindole reversed the UFP-512 effects, and even caused a major increase in BACE1 expression and activity as well as Aβ42 production in physiological conditions. Knocking-down DOR also enhanced BACE1 protein expression and its activity for APP processing, associating with a significant increase in Aβ42 production. In sharp contrast, activation of μ-opioid receptor (MOR) with DAMGO greatly promoted BACE1 expression and activity with an acceleration of APP cleavage, thus contributing to increased Aβ42 production. DADLE, a less selective DOR agonist that may bind to MOR, had no stable inhibitory effect on BACE1. Similar results were also found in APP mutant (APPswe) SH-SY5Y cell line, providing further validation of the DOR action on BACE1 regulation. Our novel data demonstrated entirely different roles of DOR and MOR in the regulation of BACE1 expression and activity with DOR being neuroprotective against AD injury. These findings provided a novel clue for new strategies of AD therapy via targeting endogenous opioid receptors.
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Affiliation(s)
- Yuan Xu
- Shanghai Key Laboratory of Acupuncture Mechanism and Acupoint Function, Department of Aeronautics and Astronautics, Fudan University, Shanghai, China.,Modern Medical Research Center, The Third Affiliated Hospital of Soochow University, Changzhou, China.,Department of Neurosurgery, The First People's Hospital of Changzhou, Changzhou, China
| | - Feng Zhi
- Modern Medical Research Center, The Third Affiliated Hospital of Soochow University, Changzhou, China.,Department of Neurosurgery, The First People's Hospital of Changzhou, Changzhou, China
| | - Gianfranco Balboni
- Department of Life and Environment Sciences, University of Cagliari, Cagliari, Italy
| | - Yilin Yang
- Modern Medical Research Center, The Third Affiliated Hospital of Soochow University, Changzhou, China.,Department of Neurosurgery, The First People's Hospital of Changzhou, Changzhou, China
| | - Ying Xia
- Shanghai Key Laboratory of Acupuncture Mechanism and Acupoint Function, Department of Aeronautics and Astronautics, Fudan University, Shanghai, China
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Chen YM, He XZ, Wang SM, Xia Y. δ-Opioid Receptors, microRNAs, and Neuroinflammation in Cerebral Ischemia/Hypoxia. Front Immunol 2020; 11:421. [PMID: 32269564 PMCID: PMC7109255 DOI: 10.3389/fimmu.2020.00421] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 02/24/2020] [Indexed: 12/26/2022] Open
Abstract
Hypoxia and ischemia are the main underlying pathogenesis of stroke and other neurological disorders. Cerebral hypoxia and/or ischemia (e.g., stroke) can lead to neuronal injury/death and eventually cause serious neurological disorders or even death in the patients. Despite knowing these serious consequences, there are limited neuroprotective strategies against hypoxic and ischemic insults in clinical settings. Recent studies indicate that microRNAs (miRNAs) are of great importance in regulating cerebral responses to hypoxic/ischemic stress in addition to the neuroprotective effect of the δ-opioid receptor (DOR). Moreover, new discovery shows that DOR can regulate miRNA expression and inhibit inflammatory responses to hypoxia/ischemia. We, therefore, summarize available data in current literature regarding the role of DOR and miRNAs in regulating the neuroinflammatory responses in this article. In particular, we focus on microglia activation, cytokine production, and the relevant signaling pathways triggered by cerebral hypoxia/ischemia. The intent of this review article is to provide a novel clue for developing new strategies against neuroinflammatory injury resulting from cerebral hypoxia/ischemia.
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Affiliation(s)
- Yi-Meng Chen
- Department of Urology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Xiao-Zhou He
- Department of Urology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Shu-Ming Wang
- Department of Anesthesiology, University of Connecticut, Mansfield, CT, United States
| | - Ying Xia
- Shanghai Key Laboratory of Acupuncture Mechanism and Acupoint Function, Fudan University, Shanghai, China
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Han C, Lei D, Liu L, Xie S, He L, Wen S, Zhou H, Ma T, Li S. Morphine induces the differentiation of T helper cells to Th2 effector cells via the PKC-θ-GATA3 pathway. Int Immunopharmacol 2020; 80:106133. [PMID: 31931364 DOI: 10.1016/j.intimp.2019.106133] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 11/28/2019] [Accepted: 12/12/2019] [Indexed: 11/16/2022]
Abstract
BACKGROUND T help 2 (Th2) cell differentiation by morphine has been verified. However, the underlying mechanism of morphine induces Th2 cell differentiation remains elusive. The aim of the present study was to explore the possible basis of morphine induced Th2 cell differentiation. METHODS Flow cytometry analysis was used to detect the content of T help 1(Th1) cell and Th2 cell. Enzyme linked immunosorbent assay (ELISA) was performed to determine the levels of IL-4 and IFN-γ. Real-time quantitative polymerase chain reaction, electrophoretic mobility shift assay and Western blotting was conducted in this study. RESULTS Th2 cell subset and IL-4 level were elevated in morphine induced naïve T cells. Pathway determining found the protein phosphorylation level of PKC-θ and the expression and activity of the transcription factor GATA3 was also enhanced in the naïve T cells challenged by morphine. Moreover, inhibitor of morphine(naltrexone) or PKC-θ(AEB071) can reverse morphine-induced Th2 cell differentiation. CONCLUSION These results suggested that morphine induce naïve T cell differentiation to Th2 cells via the PKC-θ/GATA3 signal pathway.
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Affiliation(s)
- Chao Han
- Department of Anesthesiology, The Affiliated Yixing Hospital of Jiangsu University, Yixing, Jiangsu, China; Yixing Clinical College, Medical College of Yangzhou University, Yixing, Jiangsu, China
| | - Daoyun Lei
- Department of Anesthesiology, The Affiliated Yixing Hospital of Jiangsu University, Yixing, Jiangsu, China
| | - Li Liu
- Department of Anesthesiology, The Affiliated Yixing Hospital of Jiangsu University, Yixing, Jiangsu, China
| | - Songhui Xie
- Department of Anesthesiology, The Affiliated Yixing Hospital of Jiangsu University, Yixing, Jiangsu, China
| | - Lianping He
- School of Experience Industry, Anhui Polytechnic University, Wuhu, Anhui, China
| | - Shuang Wen
- Department of Immunology, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Hong Zhou
- Department of Immunology, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Tieliang Ma
- Department of Anesthesiology, The Affiliated Yixing Hospital of Jiangsu University, Yixing, Jiangsu, China; Yixing Clinical College, Medical College of Yangzhou University, Yixing, Jiangsu, China.
| | - Shitong Li
- Department of Anesthesiology, Shanghai General Hospital of Nanjing Medical University, Shanghai, China
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Moghal ETB, Venkatesh K, Sen D. The delta opioid peptide D-Alanine 2, Leucine 5 Enkephaline (DADLE)-induces neuroprotection through cross-talk between the UPR and pro-survival MAPK-NGF-Bcl2 signaling pathways via modulation of several micro-RNAs in SH-SY5Y cells subjected to ER stress. Cell Biol Int 2018; 42:543-569. [DOI: 10.1002/cbin.10923] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 12/15/2017] [Indexed: 01/08/2023]
Affiliation(s)
- Erfath Thanjeem Begum Moghal
- Cellular and Molecular Therapeutics Laboratory; Centre for Biomaterials, Cellular and Molecular Theranostics, Vellore Institute of Technology (VIT); Vellore Tamil Nadu 632014 India
| | - Katari Venkatesh
- Cellular and Molecular Therapeutics Laboratory; Centre for Biomaterials, Cellular and Molecular Theranostics, Vellore Institute of Technology (VIT); Vellore Tamil Nadu 632014 India
| | - Dwaipayan Sen
- Cellular and Molecular Therapeutics Laboratory; Centre for Biomaterials, Cellular and Molecular Theranostics, Vellore Institute of Technology (VIT); Vellore Tamil Nadu 632014 India
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Morphine Preconditioning Downregulates MicroRNA-134 Expression Against Oxygen-Glucose Deprivation Injuries in Cultured Neurons of Mice. J Neurosurg Anesthesiol 2017; 28:195-202. [PMID: 26372418 DOI: 10.1097/ana.0000000000000204] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Brain protection by narcotics such as morphine is clinically relevant due to the extensive use of narcotics in the perioperative period. Morphine preconditioning induces neuroprotection in neurons, but it remains uncertain whether microRNA-134 (miR-134) is involved in morphine preconditioning against oxygen-glucose deprivation-induced injuries in primary cortical neurons of mice. The present study examined this issue. MATERIALS AND METHODS After cortical neurons of mice were cultured in vitro for 6 days, the neurons were transfected by respective virus vector, such as lentiviral vector (LV)-miR-control-GFP, LV-pre-miR-134-GFP, LV-pre-miR-134-inhibitor-GFP for 24 hours; after being normally cultured for 3 days again, morphine preconditioning was performed by incubating the transfected primary neurons with morphine (3 μM) for 1 hour, and then neuronal cells were exposed to oxygen-glucose deprivation (OGD) for 1 hour and oxygen-glucose recovery for 12 hours. The neuronal cells survival rate and the amount of apoptotic neurons were determined by MTT assay or TUNEL staining at designated time; and the expression levels of miR-134 were detected using real-time reverse transcription polymerase chain reaction at the same time. RESULTS The neuronal cell survival rate was significantly higher, and the amount of apoptotic neurons was significantly decreased in neurons preconditioned with morphine before OGD than that of OGD alone. The neuroprotection induced by morphine preconditioning was partially blocked by upregulating miR-134 expression, and was enhanced by downregulating miR-134 expression. The expression of miR-134 was significantly decreased in morphine-preconditioned neurons alone without transfection. CONCLUSIONS By downregulating miR-134 expression, morphine preconditioning protects primary cortical neurons of mice against injuries induced by OGD.
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Raina R, Sen D. Can crosstalk between DOR and PARP reduce oxidative stress mediated neurodegeneration? Neurochem Int 2017; 112:206-218. [PMID: 28739183 DOI: 10.1016/j.neuint.2017.07.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 07/15/2017] [Accepted: 07/19/2017] [Indexed: 12/20/2022]
Abstract
The progressive loss of structure and function of neurons leads to neurodegenerative processes which become the causative reason for various neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD) etc. These diseases are multifactorial in nature but they have been seen to possess similar causative agents to a certain extent. Oxidative Stress (OS) has been identified as a major stressor and a mediator in most of these diseases. OS not only leads to the generation of free radical species but if persistent, can possibly lead to lipid peroxidation, protein damage, DNA damage, and cell death. Anti-oxidants are endogenously present in our body to tackle oxygen metabolites but their levels reduce greatly under continuous OS conditions. In such a case, dietary supplements to replenish the anti-oxidant levels in our body is a good way of treatment but it is very slow and may not be as effective in chronic stress conditions. Thus, there is a need for more effective mechanisms to attenuate OS. Two such mechanisms which can be considered are the activation of Delta opioid receptor (DOR) and Inhibition of Poly (ADP-ribose)-polymerase1 (PARP1), which have been suggested to protect neurons and increase neuronal cell survivability in both in-vitro and in-vivo disease models. Various signaling pathways have been highlighted to probably play a significant role in attenuating OS by the activation of DOR. It would be an interesting topic of investigation to see if one of the probable mechanisms by which DOR attenuates OS could be by modulation of PARP through a cascade of intracellular signaling reactions.
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Affiliation(s)
- Rutika Raina
- Cellular and Molecular Therapeutics Laboratory, Centre for Biomaterials, Cellular and Molecular Theranostics (CBCMT), VIT University, Vellore, Tamil Nadu, India
| | - Dwaipayan Sen
- Cellular and Molecular Therapeutics Laboratory, Centre for Biomaterials, Cellular and Molecular Theranostics (CBCMT), VIT University, Vellore, Tamil Nadu, India.
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Morrone LA, Scuteri D, Rombolà L, Mizoguchi H, Bagetta G. Opioids Resistance in Chronic Pain Management. Curr Neuropharmacol 2017; 15:444-456. [PMID: 28503117 PMCID: PMC5405610 DOI: 10.2174/1570159x14666161101092822] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2015] [Revised: 08/11/2016] [Accepted: 10/24/2016] [Indexed: 01/07/2023] Open
Abstract
Chronic pain management represents a serious healthcare problem worldwide. Chronic pain affects approximately 20% of the adult European population and is more frequent in women and older people. Unfortunately, its management in the community remains generally unsatisfactory and rarely under the control of currently available analgesics. Opioids have been used as analgesics for a long history and are among the most used drugs; however, while there is no debate over their short term use for pain management, limited evidence supports their efficacy of long-term treatment for chronic non-cancer pain. Therapy with opioids is hampered by inter-individual variability and serious side effects and some opioids often result ineffective in the treatment of chronic pain and their use is controversial. Accordingly, for a better control of chronic pain a deeper knowledge of the molecular mechanisms underlying resistance to opiates is mandatory.
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Affiliation(s)
- Luigi A. Morrone
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende, Italy
- University Consortium for Adaptive Disorders and Head Pain (UCADH), Section of Neuropharmacology of Normal and Pathological Neuronal Plasticity, University of Calabria, Rende, Italy
| | - Damiana Scuteri
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende, Italy
| | - Laura Rombolà
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende, Italy
| | - Hirokazu Mizoguchi
- Department of Physiology and Anatomy, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan
| | - Giacinto Bagetta
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende, Italy
- University Consortium for Adaptive Disorders and Head Pain (UCADH), Section of Neuropharmacology of Normal and Pathological Neuronal Plasticity, University of Calabria, Rende, Italy
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Chao D, Wang Q, Balboni G, Ding G, Xia Y. Attenuating Ischemic Disruption of K+ Homeostasis in the Cortex of Hypoxic-Ischemic Neonatal Rats: DOR Activation vs. Acupuncture Treatment. Mol Neurobiol 2015; 53:7213-7227. [DOI: 10.1007/s12035-015-9621-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 12/07/2015] [Indexed: 12/29/2022]
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Liang J, Chao D, Sandhu HK, Yu Y, Zhang L, Balboni G, Kim DH, Xia Y. δ-Opioid receptors up-regulate excitatory amino acid transporters in mouse astrocytes. Br J Pharmacol 2015; 171:5417-30. [PMID: 25052197 DOI: 10.1111/bph.12857] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Revised: 07/07/2014] [Accepted: 07/17/2014] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND AND PURPOSE Astrocytic excitatory amino acid transporters (EAATs) regulate extracellular glutamate concentrations and play a role in preventing neuroexcitotoxicity. As the δ-opioid receptor (DOP receptor) is neuroprotective against excitotoxic injury, we determined whether DOP receptor activation up-regulates EAAT expression and function. EXPERIMENTAL APPROACH We measured mRNA and protein expression of EAAT1, EAAT2 and EAAT3 in cultured mouse astrocytes exposed to a specific DOP receptor agonist (UFP-512) with or without a DOP receptor antagonist, DOP receptor siRNA or inhibitors of PKC, PKA, PI3K, p38, MAPK, MEK and ERK, and evaluated the function of EAATs by measuring glutamate uptake. KEY RESULTS Astrocytic DOP receptor mRNA and protein were suppressed by DOP receptor siRNA knockdown. DOP receptor activation increased mRNA and protein expression of EAAT1 and EAAT2, but not EAAT3, thereby enhancing glutamate uptake of astrocytes. DOP receptor-induced EAAT1 and EAAT2 expression was largely reversed by DOP receptor antagonist naltrindole or by DOP receptor siRNA knockdown, and suppressed by inhibitors of MEK, ERK and p38. DOP receptor-accelerated glutamate uptake was inhibited by EAAT blockers, DOP receptor siRNA knockdown or inhibitors of MEK, ERK or p38. In contrast, inhibitors of PKA, PKC or PI3K had no significant effect on DOP receptor-induced EAAT expression. CONCLUSIONS AND IMPLICATIONS DOP receptor activation up-regulates astrocytic EAATs via MEK-ERK-p38 signalling, suggesting a critical role for DOP receptors in the regulation of astrocytic EAATs and protection against neuroexcitotoxicity. As decreased EAAT expression contributes to pathophysiology in many neurological diseases, including amyotrophic lateral sclerosis, our findings present a new platform for potential treatments of these diseases.
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Affiliation(s)
- Jianfeng Liang
- Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, TX, USA; Yale University School of Medicine, New Haven, CT, USA; Department of Neurosurgery, China-Japan Friendship Hospital, Beijing, China
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Yang L, Islam MR, Karamyan VT, Abbruscato TJ. In vitro and in vivo efficacy of a potent opioid receptor agonist, biphalin, compared to subtype-selective opioid receptor agonists for stroke treatment. Brain Res 2015; 1609:1-11. [PMID: 25801116 DOI: 10.1016/j.brainres.2015.03.022] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 02/03/2015] [Accepted: 03/12/2015] [Indexed: 12/31/2022]
Abstract
To meet the challenge of identification of new treatments for stroke, this study was designed to evaluate a potent, nonselective opioid receptor (OR) agonist, biphalin, in comparison to subtype selective OR agonists, as a potential neuroprotective drug candidate using in vitro and in vivo models of ischemic stroke. Our in vitro approach included mouse primary neuronal cells that were challenged with glutamate and hypoxic/aglycemic (H/A) conditions. We observed that 10nM biphalin, exerted a statistically significant neuroprotective effect after glutamate challenge, compared to all selective opioid agonists, according to lactate dehydrogenase (LDH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Moreover, 10nM biphalin provided superior neuroprotection after H/A-reoxygenation compared to selective opioid agonists in all cases. Our in vitro investigations were supported by in vivo studies which indicate that the nonselective opioid agonist, biphalin, achieves enhanced neuroprotective potency compared to any of the selective opioid agonists, evidenced by reduced edema and infarct ratios. Reduction of edema and infarction was accompanied by neurological improvement of the animals in two independent behavioral tests. Collectively these data strongly suggest that concurrent agonist stimulation of mu, kappa and delta ORs with biphalin is neuroprotective and superior to neuroprotection by activation of any single OR subtype.
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Affiliation(s)
- Li Yang
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, 1300 S Coulter Drive, Amarillo, TX 79106, USA; Center for Blood-Brain Barrier Research, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX, USA
| | - Mohammad R Islam
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, 1300 S Coulter Drive, Amarillo, TX 79106, USA; Center for Blood-Brain Barrier Research, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX, USA
| | - Vardan T Karamyan
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, 1300 S Coulter Drive, Amarillo, TX 79106, USA; Center for Blood-Brain Barrier Research, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX, USA
| | - Thomas J Abbruscato
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, 1300 S Coulter Drive, Amarillo, TX 79106, USA; Center for Blood-Brain Barrier Research, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX, USA.
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Cao S, Chao D, Zhou H, Balboni G, Xia Y. A novel mechanism for cytoprotection against hypoxic injury: δ-opioid receptor-mediated increase in Nrf2 translocation. Br J Pharmacol 2015; 172:1869-81. [PMID: 25439010 DOI: 10.1111/bph.13031] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 11/24/2014] [Accepted: 11/27/2014] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND AND PURPOSE Hypoxia/reoxygenation induces synthesis of reactive oxygen species (ROS) which can attack macromolecules and cause brain injury. The transcription factor, nuclear factor (erythroid-derived 2)-like 2, (Nrf2), ia potent activator of genes with an antioxidant responsive element and Nrf2 can counteract oxidative injury by increasing expression of several antioxidative genes in response to ROS stress. Here, we show that activation of the δ-opioid receptor (DOR) increasedNrf2 protein expression and translocation, thereby leading to cytoprotection. EXPERIMENTAL APPROACH We used HEK293t cells exposed to 0.5% O2 for 16 h and then reoxygenated for 4 h as a model of hypoxia-reperfusion (H/R) injury. Real time PCR, Western blotting, siRNA and immunohistochemical techniques were used to follow Nrf2 expression and activity. Cell viability and damage (as LDH leakage) were also measured. KEY RESULTS H/R injury triggered Nrf2 translocation into the nucleus and up-regulated expression of several downstream genes, relevant to antioxidation, such as NAD(P)H quinone oxidoreductase (NQO1). Incubation with the DOR agonist UFP-512 enhanced Nrf2 protein expression and translocation and up-regulated its downstream genes in normoxia and further increased Nrf2 expression and translocation after H/R, protecting the cells against loss of viability and damage. The effect of UFP-512 on Nrf2 nuclear translocation was blocked by the DOR antagonist, naltrindole. Also, DOR-mediated cytoprotection was strongly inhibited after transfection of HEK293t cells with Nrf2 siRNA. CONCLUSIONS AND IMPLICATIONS The DOR agonist UFP-512 was cytoprotective against H/R injury and this effect was partly dependent on DOR-mediated increase in Nrf2 function.
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Affiliation(s)
- Shan Cao
- Department of Neurosurgery, University of Texas Medical School at Houston, Houston, Texas, USA; Department of Clinical Pharmacology, Xiangya Hospital and Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha, Hunan, China
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14
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Chen F, Qi Z, Luo Y, Hinchliffe T, Ding G, Xia Y, Ji X. Non-pharmaceutical therapies for stroke: mechanisms and clinical implications. Prog Neurobiol 2014; 115:246-69. [PMID: 24407111 PMCID: PMC3969942 DOI: 10.1016/j.pneurobio.2013.12.007] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Revised: 12/19/2013] [Accepted: 12/27/2013] [Indexed: 12/14/2022]
Abstract
Stroke is deemed a worldwide leading cause of neurological disability and death, however, there is currently no promising pharmacotherapy for acute ischemic stroke aside from intravenous or intra-arterial thrombolysis. Yet because of the narrow therapeutic time window involved, thrombolytic application is very restricted in clinical settings. Accumulating data suggest that non-pharmaceutical therapies for stroke might provide new opportunities for stroke treatment. Here we review recent research progress in the mechanisms and clinical implications of non-pharmaceutical therapies, mainly including neuroprotective approaches such as hypothermia, ischemic/hypoxic conditioning, acupuncture, medical gases and transcranial laser therapy. In addition, we briefly summarize mechanical endovascular recanalization devices and recovery devices for the treatment of the chronic phase of stroke and discuss the relative merits of these devices.
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Affiliation(s)
- Fan Chen
- Cerebrovascular Diseases Research Institute, Xuanwu Hospital of Capital Medical University, Beijing, Beijing 100053, China
| | - Zhifeng Qi
- Cerebrovascular Diseases Research Institute, Xuanwu Hospital of Capital Medical University, Beijing, Beijing 100053, China
| | - Yuming Luo
- Cerebrovascular Diseases Research Institute, Xuanwu Hospital of Capital Medical University, Beijing, Beijing 100053, China
| | - Taylor Hinchliffe
- The Vivian L. Smith Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, TX 77030, USA
| | - Guanghong Ding
- Shanghai Research Center for Acupuncture and Meridian, Shanghai 201203, China
| | - Ying Xia
- The Vivian L. Smith Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, TX 77030, USA.
| | - Xunming Ji
- Cerebrovascular Diseases Research Institute, Xuanwu Hospital of Capital Medical University, Beijing, Beijing 100053, China.
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15
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Chen T, Li J, Chao D, Sandhu HK, Liao X, Zhao J, Wen G, Xia Y. δ-Opioid receptor activation reduces α-synuclein overexpression and oligomer formation induced by MPP(+) and/or hypoxia. Exp Neurol 2014; 255:127-36. [PMID: 24613828 DOI: 10.1016/j.expneurol.2014.02.022] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 02/14/2014] [Accepted: 02/21/2014] [Indexed: 02/07/2023]
Abstract
Hypoxic/ischemic brain injury is a potential cause of Parkinson's disease (PD) with ɑ-synuclein playing a critical role in the pathophysiology. Since δ-opioid receptor (DOR) is neuroprotective against hypoxic/ischemic insults, we sought to determine if DOR regulates ɑ-synuclein under hypoxia and/or MPP(+) stress. We found that in HEK293 cells 1) MPP(+) in normoxia enhanced ɑ-synuclein expression and the formation of ɑ-synuclein oligomers thereby causing cytotoxic injury; 2) hypoxia at 1% O2 for 48h or at 0.5% O2 for 24h also induced ɑ-synuclein overexpression and its oligomer formation with cell injury; 3) however, hypoxia at 1% O2 for 24h, though increasing ɑ-synuclein expression, did not cause ɑ-synuclein oligomer formation and cell injury; 4) UFP-512 mediated DOR activation markedly attenuated the hypoxic cell injury and ɑ-synuclein overexpression, which was largely attenuated by DOR antagonism with naltrindole or siRNA "knock-down" of the DOR; and 5) DOR activation enhanced CREB phosphorylation and prevented the collapse of mitochondrial membrane potential (△ψm). These findings suggest that DOR activation attenuates MPP(+) or severe hypoxia induced ɑ-synuclein expression/aggregation via a CREB pathway.
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Affiliation(s)
- Tao Chen
- Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, TX 77030, USA; Department of Neurology, Hainan General Hospital, Haikou, Hainan 570311, China
| | - Jessica Li
- Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, TX 77030, USA
| | - Dongman Chao
- Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, TX 77030, USA
| | - Harleen K Sandhu
- Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, TX 77030, USA
| | - Xiaoping Liao
- Department of Neurology, Hainan General Hospital, Haikou, Hainan 570311, China
| | - Jianlong Zhao
- Department of Neurology, Hainan General Hospital, Haikou, Hainan 570311, China
| | - Guoqiang Wen
- Department of Neurology, Hainan General Hospital, Haikou, Hainan 570311, China
| | - Ying Xia
- Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, TX 77030, USA.
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16
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Abstract
This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367, United States.
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17
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He X, Sandhu HK, Yang Y, Hua F, Belser N, Kim DH, Xia Y. Neuroprotection against hypoxia/ischemia: δ-opioid receptor-mediated cellular/molecular events. Cell Mol Life Sci 2013; 70:2291-303. [PMID: 23014992 PMCID: PMC11113157 DOI: 10.1007/s00018-012-1167-2] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 09/08/2012] [Accepted: 09/10/2012] [Indexed: 12/24/2022]
Abstract
Hypoxic/ischemic injury remains the most dreaded cause of neurological disability and mortality. Despite the humbling experiences due to lack of promising therapy, our understanding of the complex cascades underlying the neuronal insult has led to advances in basic science research. One of the most noteworthy has been the effect of opioid receptors, especially the delta-opioid receptor (DOR), on hypoxic/ischemic neurons. Our recent studies, and those of others worldwide, present strong evidence that sheds light on DOR-mediated neuroprotection in the brain, especially in the cortex. The mechanisms of DOR neuroprotection are broadly categorized as: (1) stabilization of the ionic homeostasis, (2) inhibition of excitatory transmitter release, (3) attenuation of disrupted neuronal transmission, (4) increase in antioxidant capacity, (5) regulation of intracellular pathways-inhibition of apoptotic signals and activation of pro-survival signaling, (6) regulation of specific gene and protein expression, and (7) up-regulation of endogenous opioid release and/or DOR expression. Depending upon the severity and duration of hypoxic/ischemic insult, the release of endogenous opioids and DOR expression are regulated in response to the stress, and DOR signaling acts at multiple levels to confer neuronal tolerance to harmful insult. The phenomenon of DOR neuroprotection offers a potential clue for a promising target that may have significant clinical implications in our quest for neurotherapeutics.
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Affiliation(s)
- Xiaozhou He
- The Third Clinical College of Suzhou University, Changzhou, Jiangsu China
| | - Harleen K. Sandhu
- The Vivian L Smith Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, 77030 TX USA
| | - Yilin Yang
- The Third Clinical College of Suzhou University, Changzhou, Jiangsu China
| | - Fei Hua
- The Third Clinical College of Suzhou University, Changzhou, Jiangsu China
| | - Nathalee Belser
- The Vivian L Smith Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, 77030 TX USA
| | - Dong H. Kim
- The Vivian L Smith Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, 77030 TX USA
| | - Ying Xia
- The Vivian L Smith Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, 77030 TX USA
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18
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He X, Yang Y, Zhi F, Moore ML, Kang X, Chao D, Wang R, Balboni G, Salvadori S, Kim DH, Xia Y. δ-Opioid receptor activation modified microRNA expression in the rat kidney under prolonged hypoxia. PLoS One 2013; 8:e61080. [PMID: 23596515 PMCID: PMC3626642 DOI: 10.1371/journal.pone.0061080] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 03/05/2013] [Indexed: 12/25/2022] Open
Abstract
Hypoxic/ischemic injury to kidney is a frequently encountered clinical problem with limited therapeutic options. Since microRNAs are differentially involved in hypoxic/ischemic events and δ-opioid receptor (DOR) activation is known to protect against hypoxic/ischemic injury, we speculated on the involvement of DOR activation in altering the microRNA (miRNA) expression in kidney under hypoxic condition. We selected 31 miRNAs based on microarray data for quantitative PCR analysis. Among them, 14 miRNAs were significantly altered after prolonged hypoxia, DOR activation or a combination of both. We found that 1) DOR activation alters miRNA expression profiles in normoxic conditions; 2) hypoxia differentially alters miRNA expression depending on the duration of hypoxia; and 3) DOR activation can modify hypoxia-induced changes in miRNA expression. For example, 10-day hypoxia reduced the level of miR-212 by over 70%, while DOR activation could mimic such reduction even in normoxic kidney. In contrast, the same stress increased miR-29a by >100%, which was reversed following DOR activation. These first data suggest that hypoxia comprehensively modifies the miRNA profile within the kidney, which can be mimicked or modified by DOR activation. Ascertaining the targeted pathways that regulate the diverse cellular and molecular functions of miRNA may provide new insights into potential therapies for hypoxic/ischemic injury of the kidney.
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Affiliation(s)
- Xiaozhou He
- Research Institute of Modern Medicine, The Third Clinical College of Soochow University, Changzhou, Jiangsu, People’s Republic of China
| | - Yilin Yang
- Research Institute of Modern Medicine, The Third Clinical College of Soochow University, Changzhou, Jiangsu, People’s Republic of China
| | - Feng Zhi
- Research Institute of Modern Medicine, The Third Clinical College of Soochow University, Changzhou, Jiangsu, People’s Republic of China
| | - Meredith L. Moore
- Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, Texas, United States of America
| | - Xuezhi Kang
- Laboratory of Molecular Neurology, Shanghai Research Center for Acupuncture and Meridians, Shanghai, People’s Republic of China
| | - Dongman Chao
- Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, Texas, United States of America
- Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Rong Wang
- Research Institute of Modern Medicine, The Third Clinical College of Soochow University, Changzhou, Jiangsu, People’s Republic of China
| | - Gianfranco Balboni
- Department of Life and Environment Sciences, University of Cagliari, Cagliari, Italy
| | - Severo Salvadori
- Department of Pharmaceutical Sciences, University of Ferrara, Ferrara, Italy
| | - Dong H. Kim
- Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, Texas, United States of America
| | - Ying Xia
- Department of Neurosurgery, The University of Texas Medical School at Houston, Houston, Texas, United States of America
- Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, United States of America
- * E-mail:
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Chao D, Shen X, Xia Y. From Acupuncture to Interaction between δ-Opioid Receptors and Na (+) Channels: A Potential Pathway to Inhibit Epileptic Hyperexcitability. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE : ECAM 2013; 2013:216016. [PMID: 23662118 PMCID: PMC3638623 DOI: 10.1155/2013/216016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 11/10/2012] [Accepted: 12/13/2012] [Indexed: 11/17/2022]
Abstract
Epilepsy is one of the most common neurological disorders affecting about 1% of population. Although the precise mechanism of its pathophysiological changes in the brain is unknown, epilepsy has been recognized as a disorder of brain excitability characterized by recurrent unprovoked seizures that result from the abnormal, excessive, and synchronous activity of clusters of nerve cells in the brain. Currently available therapies, including medical, surgical, and other strategies, such as ketogenic diet and vagus nerve stimulation, are symptomatic with their own limitations and complications. Seeking new strategies to cure this serious disorder still poses a big challenge to the field of medicine. Our recent studies suggest that acupuncture may exert its antiepileptic effects by normalizing the disrupted neuronal and network excitability through several mechanisms, including lowering the overexcited neuronal activity, enhancing the inhibitory system, and attenuating the excitatory system in the brain via regulation of the interaction between δ -opioid receptors (DOR) and Na(+) channels. This paper reviews the progress in this field and summarizes new knowledge based on our work and those of others.
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Affiliation(s)
- Dongman Chao
- The University of Texas Medical School at Houston, Houston, TX 77030, USA
- Yale University School of Medicine, New Haven, CT 06520, USA
- Shanghai Research Center for Acupuncture and Meridians, Shanghai 201203, China
| | - Xueyong Shen
- Shanghai Research Center for Acupuncture and Meridians, Shanghai 201203, China
- Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China
| | - Ying Xia
- The University of Texas Medical School at Houston, Houston, TX 77030, USA
- Yale University School of Medicine, New Haven, CT 06520, USA
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δ-opioid receptor activation and microRNA expression of the rat cortex in hypoxia. PLoS One 2012; 7:e51524. [PMID: 23272113 PMCID: PMC3521741 DOI: 10.1371/journal.pone.0051524] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Accepted: 11/01/2012] [Indexed: 11/19/2022] Open
Abstract
Prolonged hypoxic/ischemic stress may cause cortical injury and clinically manifest as a neurological disability. Activation of the δ-opioid receptor (DOR) may induce cortical protection against hypoxic/ischemic insults. However, the mechanisms underlying DOR protection are not clearly understood. We have recently found that DOR activation modulates the expression of microRNAs (miRNAs) in the kidney exposed to hypoxia, suggesting that DOR protection may involve a miRNA mechanism. To determine if the miRNAs expressed in the cortex mediated DOR neuroprotection, we examined 19 miRNAs that were previously identified as hypoxia- and DOR-regulated miRNAs in the kidney, in the rat cortex treated with UFP-512, a potent and specific DOR agonist under hypoxic condition. Of the 19 miRNAs tested, 17 were significantly altered by hypoxia and/or DOR activation with the direction and amplitude varying depending on hypoxic duration and times of DOR treatment. Expression of several miRNAs such as miR-29b, -101b, -298, 324-3p, -347 and 466b was significantly depressed after 24 hours of hypoxia. Similar changes were seen in normoxic condition 24 hours after DOR activation with one-time treatment of UFP-512. In contrast, some miRNAs were more tolerant to hypoxic stress and showed significant reduction only with 5-day (e.g., miR-31 and -186) or 10-day (e.g., miR-29a, let-7f and -511) exposures. In addition, these miRNAs had differential responses to DOR activation. Other miRNAs like miRs-363* and -370 responded only to the combined exposure to hypoxia and DOR treatment, with a notable reduction of >70% in the 5-day group. These data suggest that cortical miRNAs are highly yet differentially sensitive to hypoxia. DOR activation can modify, enhance or resolve the changes in miRNAs that target HIF, ion transport, axonal guidance, free radical signaling, apoptosis and many other functions.
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