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Gu YJ, Qian HY, Zhou F, Zhang L, Chen L, Song Y, Chen YN, Zhang HL. Folic acid relieves bone cancer pain by downregulating P2X2/3 receptors in rats. Brain Res 2023; 1811:148405. [PMID: 37164174 DOI: 10.1016/j.brainres.2023.148405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 05/04/2023] [Accepted: 05/06/2023] [Indexed: 05/12/2023]
Abstract
BACKGROUND Bone cancer pain (BCP) remains a clinical challenge due to the limited and side effects of therapeutic methods. Folic acid has been known as an FDA approved dietary supplement and proved to have an analgesic effect in neuropathic pain. Here we investigate the role and mechanism of folic acid in bone cancer pain of a rat model. METHODS Walker 256 tumor cells were inoculated into the left tibia of rats to induce bone cancer pain model. Pain reflex were assessed by paw withdrawal threshold (PWT) response to Von Frey filaments and paw withdrawal latency (PWL) response to thermal stimulation. Folic acid was injected intraperitoneally to evaluate its analgesic effect in rats with bone cancer pain. Western blotting and qPCR were used to determine P2X2/3 receptor protein and mRNA levels in ipsilateral L4-6 dorsal root ganglion (DRG) and spinal dorsal horn (SDH). RESULTS The PWT and PWL of rats with bone cancer pain were obviously decreased compared to the naïve and sham rats. Interestingly, continuous folic acid treatment significantly increased the PWT and PWL of rats with bone cancer pain. P2X2 and P2X3 receptors were clearly upregulated at both mRNA and protein expression in L4-6 DRG and SDH of rats with bone cancer pain. P2X2 and P2X3 receptors were mainly localized with CGRP (calcitonin gene-related peptide) or IB4 (isolectin B4) positive neurons in L4-6 DRG of rats with bone cancer pain. Notably, continuous folic acid treatment significantly reduced the expression of P2X2 and P2X3 receptors in L4-6 DRG and SDH of rats with bone cancer pain. Finally, intrathecal injection of A317491 (a selective antagonist of P2X2/3 receptors) markedly elevated the PWT and PWL of rats with bone cancer pain. CONCLUSION These results suggest that folic acid has an effective antinociceptive effect on bone cancer pain, which is mediated by downregulating P2X2/3 receptors in L4-6 DRG and SDH of rats with bone cancer pain. Folic acid may be a novel therapeutic strategy in cancer patients for pain relief.
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Affiliation(s)
- Yong-Juan Gu
- Center for Translational Medicine, Affiliated Zhangjiagang Hospital of Soochow University, Zhangjiagang 215600, China; Department of Oncology, Affiliated Zhangjiagang Hospital of Soochow University, Zhangjiagang 215600, China
| | - He-Ya Qian
- Center for Translational Medicine, Affiliated Zhangjiagang Hospital of Soochow University, Zhangjiagang 215600, China; Department of Oncology, Affiliated Zhangjiagang Hospital of Soochow University, Zhangjiagang 215600, China
| | - Fang Zhou
- Center for Translational Medicine, Affiliated Zhangjiagang Hospital of Soochow University, Zhangjiagang 215600, China; Department of Oncology, Affiliated Zhangjiagang Hospital of Soochow University, Zhangjiagang 215600, China
| | - Ling Zhang
- Center for Translational Medicine, Affiliated Zhangjiagang Hospital of Soochow University, Zhangjiagang 215600, China
| | - Long Chen
- Center for Translational Medicine, Affiliated Zhangjiagang Hospital of Soochow University, Zhangjiagang 215600, China
| | - Yu Song
- Department of Oncology, Affiliated Zhangjiagang Hospital of Soochow University, Zhangjiagang 215600, China
| | - Ya-Nan Chen
- Department of Oncology, Affiliated Zhangjiagang Hospital of Soochow University, Zhangjiagang 215600, China.
| | - Hai-Long Zhang
- Center for Translational Medicine, Affiliated Zhangjiagang Hospital of Soochow University, Zhangjiagang 215600, China; Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience, Soochow University, Suzhou 215123, China.
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Maynard JP, Sfanos KS. P2 purinergic receptor dysregulation in urologic disease. Purinergic Signal 2022; 18:267-287. [PMID: 35687210 PMCID: PMC9184359 DOI: 10.1007/s11302-022-09875-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 05/25/2022] [Indexed: 11/25/2022] Open
Abstract
P2 purinergic receptors are involved in the normal function of the kidney, bladder, and prostate via signaling that occurs in response to extracellular nucleotides. Dysregulation of these receptors is common in pathological states and often associated with disease initiation, progression, or aggressiveness. Indeed, P2 purinergic receptor expression is altered across multiple urologic disorders including chronic kidney disease, polycystic kidney disease, interstitial cystitis, urinary incontinence, overactive bladder syndrome, prostatitis, and benign prostatic hyperplasia. P2 purinergic receptors are likewise indirectly associated with these disorders via receptor-mediated inflammation and pain, a common characteristic across most urologic disorders. Furthermore, select P2 purinergic receptors are overexpressed in urologic cancer including renal cell carcinoma, urothelial carcinoma, and prostate adenocarcinoma, and pre-clinical studies depict P2 purinergic receptors as potential therapeutic targets. Herein, we highlight the compelling evidence for the exploration of P2 purinergic receptors as biomarkers and therapeutic targets in urologic cancers and other urologic disease. Likewise, there is currently optimism for P2 purinergic receptor-targeted therapeutics for the treatment of inflammation and pain associated with urologic diseases. Further exploration of the common pathways linking P2 purinergic receptor dysregulation to urologic disease might ultimately help in gaining new mechanistic insight into disease processes and therapeutic targeting.
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Affiliation(s)
- Janielle P Maynard
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA. .,Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, USA.
| | - Karen S Sfanos
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, USA.,Department of Urology, James Buchanan Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Mai Y, Guo Z, Yin W, Zhong N, Dicpinigaitis PV, Chen R. P2X Receptors: Potential Therapeutic Targets for Symptoms Associated With Lung Cancer - A Mini Review. Front Oncol 2021; 11:691956. [PMID: 34268121 PMCID: PMC8276243 DOI: 10.3389/fonc.2021.691956] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 06/07/2021] [Indexed: 12/12/2022] Open
Abstract
Symptoms associated with lung cancer mainly consist of cancer-associated pain, cough, fatigue, and dyspnea. However, underlying mechanisms of lung cancer symptom clusters remain unclear. There remains a paucity of effective treatment to ameliorate debilitating symptoms and improve the quality of life of lung cancer survivors. Recently, extracellular ATP and its receptors have attracted increasing attention among researchers in the field of oncology. Extracellular ATP in the tumor microenvironment is associated with tumor cell metabolism, proliferation, and metastasis by driving inflammation and neurotransmission via P2 purinergic signaling. Accordingly, ATP gated P2X receptors expressed on tumor cells, immune cells, and neurons play a vital role in modulating tumor development, invasion, progression, and related symptoms. P2 purinergic signaling is involved in the development of different lung cancer-related symptoms. In this review, we summarize recent findings to illustrate the role of P2X receptors in tumor proliferation, progression, metastasis, and lung cancer- related symptoms, providing an outline of potential anti-neoplastic activity of P2X receptor antagonists. Furthermore, compared with opioids, P2X receptor antagonists appear to be innovative therapeutic interventions for managing cancer symptom clusters with fewer side effects.
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Affiliation(s)
- Yonglin Mai
- Department of Allergy and Clinical Immunology, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Health, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Zhihua Guo
- Department of Thoracic Surgery, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Health, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Weiqiang Yin
- Department of Thoracic Surgery, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Health, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Nanshan Zhong
- Department of Allergy and Clinical Immunology, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Health, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Peter V Dicpinigaitis
- Department of Medicine, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, NY, United States
| | - Ruchong Chen
- Department of Allergy and Clinical Immunology, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Health, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
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Adebiyi MG, Manalo J, Kellems RE, Xia Y. Differential role of adenosine signaling cascade in acute and chronic pain. Neurosci Lett 2019; 712:134483. [PMID: 31494223 DOI: 10.1016/j.neulet.2019.134483] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 06/14/2019] [Accepted: 09/04/2019] [Indexed: 12/21/2022]
Abstract
Adenosine is a signaling molecule induced under stress such as energy insufficiency and ischemic/hypoxic conditions. Adenosine controls multiple physiological and pathological cellular and tissue function by activation of four G protein-coupled receptors (GPCR). Functional role of adenosine signaling in acute pain has been widely studied. However, the role of adenosine signaling in chronic pain is poorly understood. At acute levels, adenosine can be beneficial to anti-pain whereas a sustained elevation of adenosine can be detrimental to promote chronic pain. In recent years, extensive progress has been made to define the role of adenosine signaling in chronic pain and to dissect molecular new insight underlying the development of chronic pain. In this review, we summarize the differential role of adenosine signaling cascade in acute and chronic pain with a major focus on recent studies revealing adenosine ADORA2B receptor activation in the pathology of chronic pain. We further provide a therapeutic outlook of how multiple adenosine signaling components can be useful to treat chronic pain.
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Affiliation(s)
- Morayo G Adebiyi
- Department of Biochemistry and Molecular Biology, The University of Texas McGovern Medical School, Houston, TX, USA; The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Jeanne Manalo
- Department of Biochemistry and Molecular Biology, The University of Texas McGovern Medical School, Houston, TX, USA; The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Rodney E Kellems
- Department of Biochemistry and Molecular Biology, The University of Texas McGovern Medical School, Houston, TX, USA; The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Yang Xia
- Department of Biochemistry and Molecular Biology, The University of Texas McGovern Medical School, Houston, TX, USA; The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, USA.
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Cheng FK. Cancer-Induced Bone Pain Management Through Buddhist Beliefs. JOURNAL OF RELIGION AND HEALTH 2017; 56:2251-2266. [PMID: 28439682 DOI: 10.1007/s10943-017-0401-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Dealing with physical pain represents a huge public health expenditure, especially for cancer-induced bone pain, one of the most difficult health issues, which impairs appetite, sleep, and mobility, negatively impacting quality of life and evoking mental problems. Although some literature has reported positive correlation between religion and pain management, there is a dearth of research examining the effectiveness of Buddhism on this topic. This study investigates the usefulness of Buddhist beliefs in managing cancer-induced bone pain through a case example. It illustrates how an advanced cancer patient, with the assistance of a counsellor, perceived pain and coped with it and pain-induced mental problems via Buddhist teachings and practices, including the four noble truths, the law of dependent origination, and karma. It offers alternative perspectives for helping professionals (such as physicians, nurses, counsellors, social workers, hospice and palliative service providers, and pain management practitioners) who are keen to equip themselves with a wider worldview and life view to better serve their clients.
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Lucchesi M, Lanzetta G, Antonuzzo A, Rozzi A, Sardi I, Favre C, Ripamonti CI, Santini D, Armento G. Developing drugs in cancer-related bone pain. Crit Rev Oncol Hematol 2017; 119:66-74. [PMID: 28893462 DOI: 10.1016/j.critrevonc.2017.08.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 07/13/2017] [Accepted: 08/19/2017] [Indexed: 12/19/2022] Open
Abstract
INTRODUCTION Cancer-related bone pain is a frequent and important key problem for metastatic patients that may reduce quality of life, with related limitations in daily activities and morbidity. Often traditional approach to pain may fail given the complex pathophysiology of this phenomenon. METHODS The aim of this review is to describe promising therapies for cancer-related bone pain, from the pathophysiology to the clinical trials currently ongoing. Moreover, any new evidence for better approach to cancer-related bone pain with the traditional drugs is also considered. CONCLUSIONS In clinical practice opioids remain the most important pharmacologic treatment for severe pain related to bone cancer. Regard developing drugs, anti-NGF and anti-TrkA are the most investigated new drug in this setting, but a future role in clinical practice is still uncertain.
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Affiliation(s)
- Maurizio Lucchesi
- Thoracic Cancer Centre, Pulmonology Unit, University Hospital of Pisa, Pisa, Italy; Department of Pediatric Oncology and Hematology, Anna Meyer Children's University Hospital, Florence, Italy.
| | - Gaetano Lanzetta
- Medical Oncology Unit, IRCCS Neuromed, Pozzilli, Italy; Medical Oncology Unit, Italian Neuro-Traumatology Institute, Grottaferrata, Italy.
| | - Andrea Antonuzzo
- Medical Oncology Unit 1 SSN, Pisa University Hospital, Pisa, Italy.
| | - Antonio Rozzi
- Medical Oncology Unit, Italian Neuro-Traumatology Institute, Grottaferrata, Italy.
| | - Iacopo Sardi
- Department of Pediatric Oncology and Hematology, Anna Meyer Children's University Hospital, Florence, Italy.
| | - Claudio Favre
- Department of Pediatric Oncology and Hematology, Anna Meyer Children's University Hospital, Florence, Italy.
| | - Carla Ida Ripamonti
- Supportive Care in Cancer Unit, IRCCS National Cancer Institute, Milan, Italy.
| | - Daniele Santini
- Medical Oncology Unit, Campus Biomedico University Hospital, Rome, Italy.
| | - Grazia Armento
- Medical Oncology Unit, Campus Biomedico University Hospital, Rome, Italy.
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Ishchenko Y, Shakirzyanova A, Giniatullina R, Skorinkin A, Bart G, Turhanen P, Määttä JA, Mönkkönen J, Giniatullin R. Selective Calcium-Dependent Inhibition of ATP-Gated P2X3 Receptors by Bisphosphonate-Induced Endogenous ATP Analog ApppI. J Pharmacol Exp Ther 2017; 361:472-481. [PMID: 28404687 DOI: 10.1124/jpet.116.238840] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 04/07/2017] [Indexed: 12/30/2022] Open
Abstract
Pain is the most unbearable symptom accompanying primary bone cancers and bone metastases. Bone resorptive disorders are often associated with hypercalcemia, contributing to the pathologic process. Nitrogen-containing bisphosphonates (NBPs) are efficiently used to treat bone cancers and metastases. Apart from their toxic effect on cancer cells, NBPs also provide analgesia via poorly understood mechanisms. We previously showed that NBPs, by inhibiting the mevalonate pathway, induced formation of novel ATP analogs such as ApppI [1-adenosin-5'-yl ester 3-(3-methylbut-3-enyl) triphosphoric acid diester], which can potentially be involved in NBP analgesia. In this study, we used the patch-clamp technique to explore the action of ApppI on native ATP-gated P2X receptors in rat sensory neurons and rat and human P2X3, P2X2, and P2X7 receptors expressed in human embryonic kidney cells. We found that although ApppI has weak agonist activity, it is a potent inhibitor of P2X3 receptors operating in the nanomolar range. The inhibitory action of ApppI was completely blocked in hypercalcemia-like conditions and was stronger in human than in rat P2X3 receptors. In contrast, P2X2 and P2X7 receptors were insensitive to ApppI, suggesting a high selectivity of ApppI for the P2X3 receptor subtype. NBP, metabolite isopentenyl pyrophosphate, and endogenous AMP did not exert any inhibitory action, indicating that only intact ApppI has inhibitory activity. Ca2+-dependent inhibition was stronger in trigeminal neurons preferentially expressing desensitizing P2X3 subunits than in nodose ganglia neurons, which also express nondesensitizing P2X2 subunits. Altogether, we characterized previously unknown purinergic mechanisms of NBP-induced metabolites and suggest ApppI as the endogenous pain inhibitor contributing to cancer treatment with NBPs.
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Affiliation(s)
- Yevheniia Ishchenko
- A. I. Virtanen Institute (Y.I., A.Sh., Rai.G., G.B., Ras.G.) and School of Pharmacy (P.T., J. M.), University of Eastern Finland, Kuopio, Finland; Kazan Institute of Biochemistry and Biophysics, Kazan, Russia (A.Sh., A.Sk.); Institute of Biomedicine, University of Turku, Turku, Finland (J.A.M.); and Kazan Federal University, Kazan, Russia (A.Sh., A.Sk., R.Gas.)
| | - Anastasia Shakirzyanova
- A. I. Virtanen Institute (Y.I., A.Sh., Rai.G., G.B., Ras.G.) and School of Pharmacy (P.T., J. M.), University of Eastern Finland, Kuopio, Finland; Kazan Institute of Biochemistry and Biophysics, Kazan, Russia (A.Sh., A.Sk.); Institute of Biomedicine, University of Turku, Turku, Finland (J.A.M.); and Kazan Federal University, Kazan, Russia (A.Sh., A.Sk., R.Gas.)
| | - Raisa Giniatullina
- A. I. Virtanen Institute (Y.I., A.Sh., Rai.G., G.B., Ras.G.) and School of Pharmacy (P.T., J. M.), University of Eastern Finland, Kuopio, Finland; Kazan Institute of Biochemistry and Biophysics, Kazan, Russia (A.Sh., A.Sk.); Institute of Biomedicine, University of Turku, Turku, Finland (J.A.M.); and Kazan Federal University, Kazan, Russia (A.Sh., A.Sk., R.Gas.)
| | - Andrei Skorinkin
- A. I. Virtanen Institute (Y.I., A.Sh., Rai.G., G.B., Ras.G.) and School of Pharmacy (P.T., J. M.), University of Eastern Finland, Kuopio, Finland; Kazan Institute of Biochemistry and Biophysics, Kazan, Russia (A.Sh., A.Sk.); Institute of Biomedicine, University of Turku, Turku, Finland (J.A.M.); and Kazan Federal University, Kazan, Russia (A.Sh., A.Sk., R.Gas.)
| | - Genevieve Bart
- A. I. Virtanen Institute (Y.I., A.Sh., Rai.G., G.B., Ras.G.) and School of Pharmacy (P.T., J. M.), University of Eastern Finland, Kuopio, Finland; Kazan Institute of Biochemistry and Biophysics, Kazan, Russia (A.Sh., A.Sk.); Institute of Biomedicine, University of Turku, Turku, Finland (J.A.M.); and Kazan Federal University, Kazan, Russia (A.Sh., A.Sk., R.Gas.)
| | - Petri Turhanen
- A. I. Virtanen Institute (Y.I., A.Sh., Rai.G., G.B., Ras.G.) and School of Pharmacy (P.T., J. M.), University of Eastern Finland, Kuopio, Finland; Kazan Institute of Biochemistry and Biophysics, Kazan, Russia (A.Sh., A.Sk.); Institute of Biomedicine, University of Turku, Turku, Finland (J.A.M.); and Kazan Federal University, Kazan, Russia (A.Sh., A.Sk., R.Gas.)
| | - Jorma A Määttä
- A. I. Virtanen Institute (Y.I., A.Sh., Rai.G., G.B., Ras.G.) and School of Pharmacy (P.T., J. M.), University of Eastern Finland, Kuopio, Finland; Kazan Institute of Biochemistry and Biophysics, Kazan, Russia (A.Sh., A.Sk.); Institute of Biomedicine, University of Turku, Turku, Finland (J.A.M.); and Kazan Federal University, Kazan, Russia (A.Sh., A.Sk., R.Gas.)
| | - Jukka Mönkkönen
- A. I. Virtanen Institute (Y.I., A.Sh., Rai.G., G.B., Ras.G.) and School of Pharmacy (P.T., J. M.), University of Eastern Finland, Kuopio, Finland; Kazan Institute of Biochemistry and Biophysics, Kazan, Russia (A.Sh., A.Sk.); Institute of Biomedicine, University of Turku, Turku, Finland (J.A.M.); and Kazan Federal University, Kazan, Russia (A.Sh., A.Sk., R.Gas.)
| | - Rashid Giniatullin
- A. I. Virtanen Institute (Y.I., A.Sh., Rai.G., G.B., Ras.G.) and School of Pharmacy (P.T., J. M.), University of Eastern Finland, Kuopio, Finland; Kazan Institute of Biochemistry and Biophysics, Kazan, Russia (A.Sh., A.Sk.); Institute of Biomedicine, University of Turku, Turku, Finland (J.A.M.); and Kazan Federal University, Kazan, Russia (A.Sh., A.Sk., R.Gas.)
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Wu JX, Yuan XM, Wang Q, Wei W, Xu MY. Rho/ROCK acts downstream of lysophosphatidic acid receptor 1 in modulating P2X3 receptor-mediated bone cancer pain in rats. Mol Pain 2016; 12:12/0/1744806916644929. [PMID: 27094551 PMCID: PMC4956381 DOI: 10.1177/1744806916644929] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 03/20/2016] [Indexed: 12/27/2022] Open
Abstract
Background Lysophosphatidic acid receptor 1 and Rho/ROCK signaling is implicated in bone cancer pain development. However, it remains unknown whether the two signaling pathways function together in P2X3 receptor-mediated bone cancer pain. Results In this study, using a rat model of bone cancer, we examined the expression of P2X3 and lysophosphatidic acid receptor 1 in rat dorsal root ganglion neurons and further dissected whether lysophosphatidic acid receptor 1 and Rho/ROCK-mediated pathways interacted in modulating rat pain behavior. Bone cancer was established by inoculating Walker 256 cells into the left tibia of female Wistar rats. We observed a gradual and yet significant decline in mean paw withdrawal threshold in rats with bone cancer, but not in control rats. Our immunohistochemical staining revealed that the number of P2X3- and lysophosphatidic acid receptor 1-positive dorsal root ganglion neurons was significantly greater in rats with bone cancer than control rats. Lysophosphatidic acid receptor 1 blockade with VPC32183 significantly attenuated decline in mean paw withdrawal threshold. Flinching behavior test further showed that lysophosphatidic acid receptor 1 inhibition with VPC32183 transiently but significantly attenuated α,β-meATP-induced increase in paw lift time per minute. Rho inhibition by intrathecal BoTXC3 caused a rapid reversal in decline in mean paw withdrawal threshold of rats with bone cancer. Flinching behavior test showed that BoTXC3 transiently and significantly attenuated α,β-meATP-induced increase in paw lift time per minute. Similar findings were observed with ROCK inhibition by intrathecal Y27632. Furthermore, VPC32183 and BoTXC3 effectively aborted the appearance of lysophosphatidic acid-induced calcium influx peak. Conclusions Lysophosphatidic acid and its receptor LPAR1, acting through the Rho-ROCK pathway, regulate P2X3 receptor in the development of both mechanical and spontaneous pain in bone cancer.
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Affiliation(s)
- Jing-Xiang Wu
- Department of Anesthesiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, PR China
| | - Xiao-Min Yuan
- Department of Anesthesiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, PR China
| | - Qiong Wang
- Department of Anesthesiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, PR China
| | - Wang Wei
- Department of Anesthesiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, PR China
| | - Mei-Ying Xu
- Department of Anesthesiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, PR China
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10
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Falk S, Schwab S, Frøsig-Jørgensen M, Clausen R, Dickenson A, Heegaard AM. P2X7 receptor-mediated analgesia in cancer-induced bone pain. Neuroscience 2015; 291:93-105. [DOI: 10.1016/j.neuroscience.2015.02.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 01/19/2015] [Accepted: 02/05/2015] [Indexed: 11/28/2022]
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Ide S, Nishizawa D, Fukuda KI, Kasai S, Hasegawa J, Hayashida M, Minami M, Ikeda K. Haplotypes of P2RX7 gene polymorphisms are associated with both cold pain sensitivity and analgesic effect of fentanyl. Mol Pain 2014; 10:75. [PMID: 25472448 PMCID: PMC4265416 DOI: 10.1186/1744-8069-10-75] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 11/18/2014] [Indexed: 12/12/2022] Open
Abstract
Background The P2X7 receptor is a member of the P2X family of adenosine 5′-triphosphate-gated cation channels. Several recent studies have demonstrated that this receptor is involved in mechanisms related to pain and inflammation. However, unknown is whether polymorphisms of the P2RX7 gene that encodes the human P2X7 receptor influence pain sensitivity and analgesic effects of opioids. The P2RX7 gene is known to be highly polymorphic. Thus, the present study examined associations between fentanyl sensitivity and polymorphisms in the P2RX7 gene in 355 Japanese patients who underwent painful orofacial cosmetic surgery. Results We first conducted linkage disequilibrium (LD) analyses for 55 reported single-nucleotide polymorphisms (SNPs) in the region within and around the P2RX7 gene using genomic samples from 100 patients. In our samples, 42 SNPs were polymorphic, and a total of five LD blocks with six Tag SNPs (rs2708092, rs1180012, rs1718125, rs208293, rs1718136, and rs7132846) were observed. Thus, we further analyzed associations between genotypes/haplotypes of these Tag SNPs and clinical data using a total of 355 samples. In the genotype-based association study, only the rs1718125 G > A SNP tended to be associated with higher pain scores on a visual analog scale 24 h after surgery (VAS24). The haplotype-based association study showed that subjects with homozygous haplotype No.3 (GTAAAC; estimated frequency: 15.0%) exhibited significantly higher cold pain sensitivity and lower analgesic effects of fentanyl for acute cold pain in the cold pressor test. Conversely, subjects who carried haplotype No.1 (ACGGAC; estimated frequency: 24.5%) tended to exhibit lower cold pain sensitivity and higher analgesic effects of fentanyl. Furthermore, subjects with homozygous haplotype No.2 (GCGGAC; estimated frequency: 22.9%) exhibited significantly lower VAS24 scores. Conclusions Cold pain sensitivity and analgesic effects of fentanyl were related to the SNP and haplotypes of the P2RX7 gene. The patients with the rs1718125 G>A SNP tended to show higher VAS24 scores. Moreover, the combination of polymorphisms from the 5′-flanking region to exon 5 recessively affected cold pain sensitivity and analgesic effects of opioids for acute cold pain. The present findings shed light on the involvement of P2RX7 gene polymorphisms in naive cold pain sensitivity and analgesic effects of fentanyl. Electronic supplementary material The online version of this article (doi:10.1186/1744-8069-10-75) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | | | | | - Kazutaka Ikeda
- Addictive Substance Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan.
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12
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Franceschini A, Adinolfi E. P2X receptors: New players in cancer pain. World J Biol Chem 2014; 5:429-436. [PMID: 25426266 PMCID: PMC4243147 DOI: 10.4331/wjbc.v5.i4.429] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 08/26/2014] [Accepted: 09/17/2014] [Indexed: 02/05/2023] Open
Abstract
Pain is unfortunately a quite common symptom for cancer patients. Normally pain starts as an episodic experience at early cancer phases to become chronic in later stages. In order to improve the quality of life of oncological patients, anti-cancer treatments are often accompanied by analgesic therapies. The P2X receptor are adenosine triphosphate (ATP) gated ion channels expressed by several cells including neurons, cancer and immune cells. Purinergic signaling through P2X receptors recently emerged as possible common pathway for cancer onset/growth and pain sensitivity. Indeed, tumor microenvironment is rich in extracellular ATP, which has a role in both tumor development and pain sensation. The study of the different mechanisms by which P2X receptors favor cancer progression and relative pain, represents an interesting challenge to design integrated therapeutic strategies for oncological patients. This review summarizes recent findings linking P2X receptors and ATP to cancer growth, progression and related pain. Special attention has been paid to the role of P2X2, P2X3, P2X4 and P2X7 in the genesis of cancer pain and to the function of P2X7 in tumor growth and metastasis. Therapeutic implications of the administration of different P2X receptor blockers to alleviate cancer-associated pain sensations contemporarily reducing tumor progression are also discussed.
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Burnstock G, Di Virgilio F. Purinergic signalling and cancer. Purinergic Signal 2014; 9:491-540. [PMID: 23797685 DOI: 10.1007/s11302-013-9372-5] [Citation(s) in RCA: 234] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Accepted: 06/06/2013] [Indexed: 01/24/2023] Open
Abstract
Receptors for extracellular nucleotides are widely expressed by mammalian cells. They mediate a large array of responses ranging from growth stimulation to apoptosis, from chemotaxis to cell differentiation and from nociception to cytokine release, as well as neurotransmission. Pharma industry is involved in the development and clinical testing of drugs selectively targeting the different P1 nucleoside and P2 nucleotide receptor subtypes. As described in detail in the present review, P2 receptors are expressed by all tumours, in some cases to a very high level. Activation or inhibition of selected P2 receptor subtypes brings about cancer cell death or growth inhibition. The field has been largely neglected by current research in oncology, yet the evidence presented in this review, most of which is based on in vitro studies, although with a limited amount from in vivo experiments and human studies, warrants further efforts to explore the therapeutic potential of purinoceptor targeting in cancer.
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Syhr KMJ, Kallenborn-Gerhardt W, Lu R, Olbrich K, Schmitz K, Männich J, Ferreiros-Bouzas N, Geisslinger G, Niederberger E, Schmidtko A. Lack of effect of a P2Y6 receptor antagonist on neuropathic pain behavior in mice. Pharmacol Biochem Behav 2014; 124:389-95. [PMID: 25042778 DOI: 10.1016/j.pbb.2014.07.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 06/22/2014] [Accepted: 07/11/2014] [Indexed: 01/12/2023]
Abstract
Accumulating evidence indicates that various subtypes of purinergic receptors (P2X and P2Y receptor families) play an essential role in the development and the maintenance of neuropathic pain. However, there is only limited data available about the role of P2Y6 receptors in pain processing. Here we detected P2Y6 receptor immunoreactivity in primary afferent neurons of mice and observed an upregulation in response to peripheral nerve injury. However, systemic and intrathecal administration of the P2Y6 receptor antagonist MRS2578 failed to affect the injury-induced neuropathic pain behavior. Our results suggest that P2Y6 receptors, in contrast to other purinergic receptor subtypes, are not critically involved in nerve injury-induced neuropathic pain processing in mice.
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Affiliation(s)
- Katharina Martina Janice Syhr
- Pharmazentrum Frankfurt/ZAFES, Institut für Klinische Pharmakologie, Universitätsklinikum Frankfurt, 60590 Frankfurt am Main, Germany
| | - Wiebke Kallenborn-Gerhardt
- Pharmazentrum Frankfurt/ZAFES, Institut für Klinische Pharmakologie, Universitätsklinikum Frankfurt, 60590 Frankfurt am Main, Germany
| | - Ruirui Lu
- Institut für Pharmakologie und Toxikologie, ZBAF, Universität Witten/Herdecke, 58453 Witten, Germany
| | - Katrin Olbrich
- Pharmazentrum Frankfurt/ZAFES, Institut für Klinische Pharmakologie, Universitätsklinikum Frankfurt, 60590 Frankfurt am Main, Germany
| | - Katja Schmitz
- Pharmazentrum Frankfurt/ZAFES, Institut für Klinische Pharmakologie, Universitätsklinikum Frankfurt, 60590 Frankfurt am Main, Germany
| | - Julia Männich
- Pharmazentrum Frankfurt/ZAFES, Institut für Klinische Pharmakologie, Universitätsklinikum Frankfurt, 60590 Frankfurt am Main, Germany
| | - Nerea Ferreiros-Bouzas
- Pharmazentrum Frankfurt/ZAFES, Institut für Klinische Pharmakologie, Universitätsklinikum Frankfurt, 60590 Frankfurt am Main, Germany
| | - Gerd Geisslinger
- Pharmazentrum Frankfurt/ZAFES, Institut für Klinische Pharmakologie, Universitätsklinikum Frankfurt, 60590 Frankfurt am Main, Germany; Fraunhofer Institute for Molecular Biology and Applied Ecology, Project Group Translational Medicine and Pharmacology (IME-TMP), 60590 Frankfurt am Main, Germany
| | - Ellen Niederberger
- Pharmazentrum Frankfurt/ZAFES, Institut für Klinische Pharmakologie, Universitätsklinikum Frankfurt, 60590 Frankfurt am Main, Germany
| | - Achim Schmidtko
- Pharmazentrum Frankfurt/ZAFES, Institut für Klinische Pharmakologie, Universitätsklinikum Frankfurt, 60590 Frankfurt am Main, Germany; Institut für Pharmakologie und Toxikologie, ZBAF, Universität Witten/Herdecke, 58453 Witten, Germany.
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Falk S, Patel R, Heegaard A, Mercadante S, Dickenson A. Spinal neuronal correlates of tapentadol analgesia in cancer pain: A back-translational approach. Eur J Pain 2014; 19:152-8. [DOI: 10.1002/ejp.530] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/27/2014] [Indexed: 12/16/2022]
Affiliation(s)
- S. Falk
- Department of Drug Design and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Denmark
| | - R. Patel
- Departments of Neuroscience, Physiology and Pharmacology; University College London; UK
| | - A. Heegaard
- Department of Drug Design and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Denmark
| | - S. Mercadante
- Department of Anesthesia and Intensive Care & Pain Relief and Palliative Care; La Maddalena Cancer Center; Palermo Italy
| | - A.H. Dickenson
- Departments of Neuroscience, Physiology and Pharmacology; University College London; UK
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Ye Y, Ono K, Bernabé DG, Viet CT, Pickering V, Dolan JC, Hardt M, Ford AP, Schmidt BL. Adenosine triphosphate drives head and neck cancer pain through P2X2/3 heterotrimers. Acta Neuropathol Commun 2014; 2:62. [PMID: 24903857 PMCID: PMC4229781 DOI: 10.1186/2051-5960-2-62] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2014] [Accepted: 05/20/2014] [Indexed: 11/15/2022] Open
Abstract
Introduction Cancer pain creates a poor quality of life and decreases survival. The basic neurobiology of cancer pain is poorly understood. Adenosine triphosphate (ATP) and the ATP ionotropic receptor subunits, P2X2 and P2X3, mediate cancer pain in animal models; however, it is unknown whether this mechanism operates in human, and if so, what the relative contribution of P2X2- and P2X3-containing trimeric channels to cancer pain is. Here, we studied head and neck squamous cell carcinoma (HNSCC), which causes the highest level of function-induced pain relative to other types of cancer. Results We show that the human HNSCC tissues contain significantly increased levels of ATP compared to the matched normal tissues. The high levels of ATP are secreted by the cancer and positively correlate with self-reported function-induced pain in patients. The human HNSCC microenvironment is densely innervated by nerve fibers expressing both P2X2 and P2X3 subunits. In animal models of HNSCC we showed that ATP in the cancer microenvironment likely heightens pain perception through the P2X2/3 trimeric receptors. Nerve growth factor (NGF), another cancer-derived pain mediator found in both human and mouse HNSCC, induces P2X2 and P2X3 hypersensitivity and increases subunit expression in murine trigeminal ganglion (TG) neurons. Conclusions These data identify a key peripheral mechanism in cancer pain and highlight the clinical potential of specifically targeting nociceptors expressing both P2X2 and P2X3 subunits (e.g., P2X2/3 heterotrimers) to alleviate cancer pain. Electronic supplementary material The online version of this article (doi:10.1186/2051-5960-2-62) contains supplementary material, which is available to authorized users.
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Falk S, Dickenson AH. Pain and nociception: mechanisms of cancer-induced bone pain. J Clin Oncol 2014; 32:1647-54. [PMID: 24799469 DOI: 10.1200/jco.2013.51.7219] [Citation(s) in RCA: 209] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Cancer pain, especially pain caused by metastasis to bone, is a severe type of pain, and unless the cause and consequences can be resolved, the pain will become chronic. As detection and survival among patients with cancer have improved, pain has become an increasing challenge, because traditional therapies are often only partially effective. Until recently, knowledge of cancer pain mechanisms was poor compared with understanding of neuropathic and inflammatory pain states. We now view cancer-induced bone pain as a complex pain state involving components of both inflammatory and neuropathic pain but also exhibiting elements that seem unique to cancer pain. In addition, the pain state is often unpredictable, and the intensity of the pain is highly variable, making it difficult to manage. The establishment of translational animal models has started to reveal some of the molecular components involved in cancer pain. We present the essential pharmacologic and neurobiologic mechanisms involved in the generation and continuance of cancer-induced bone pain and discuss these in the context of understanding and treating patients. We discuss changes in peripheral signaling in the area of tumor growth, examine spinal cord mechanisms of sensitization, and finally address central processing. Our aim is to provide a mechanistic background for the sensory characteristics of cancer-induced bone pain as a basis for better understanding and treating this condition.
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Affiliation(s)
- Sarah Falk
- Sarah Falk, University of Copenhagen, Copenhagen, Denmark; and Anthony H. Dickenson, University College London, London, United Kingdom
| | - Anthony H Dickenson
- Sarah Falk, University of Copenhagen, Copenhagen, Denmark; and Anthony H. Dickenson, University College London, London, United Kingdom.
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Minett MS, Falk S, Santana-Varela S, Bogdanov YD, Nassar MA, Heegaard AM, Wood JN. Pain without nociceptors? Nav1.7-independent pain mechanisms. Cell Rep 2014; 6:301-12. [PMID: 24440715 PMCID: PMC3969273 DOI: 10.1016/j.celrep.2013.12.033] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 11/22/2013] [Accepted: 12/20/2013] [Indexed: 11/20/2022] Open
Abstract
Nav1.7, a peripheral neuron voltage-gated sodium channel, is essential for pain and olfaction in mice and humans. We examined the role of Nav1.7 as well as Nav1.3, Nav1.8, and Nav1.9 in different mouse models of chronic pain. Constriction-injury-dependent neuropathic pain is abolished when Nav1.7 is deleted in sensory neurons, unlike nerve-transection-related pain, which requires the deletion of Nav1.7 in sensory and sympathetic neurons for pain relief. Sympathetic sprouting that develops in parallel with nerve-transection pain depends on the presence of Nav1.7 in sympathetic neurons. Mechanical and cold allodynia required distinct sets of neurons and different repertoires of sodium channels depending on the nerve injury model. Surprisingly, pain induced by the chemotherapeutic agent oxaliplatin and cancer-induced bone pain do not require the presence of Nav1.7 sodium channels or Nav1.8-positive nociceptors. Thus, similar pain phenotypes arise through distinct cellular and molecular mechanisms. Therefore, rational analgesic drug therapy requires patient stratification in terms of mechanisms and not just phenotype. Phenotypically identical pain models have different underlying molecular mechanisms Nav1.7 expression is required for sympathetic sprouting after neuronal damage Oxaliplatin and cancer-induced bone pain are both Nav1.7-independent Deleting Nav1.7 in adult mice reverses nerve damage-induced neuropathic pain
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Affiliation(s)
- Michael S Minett
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK
| | - Sarah Falk
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
| | - Sonia Santana-Varela
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK
| | - Yury D Bogdanov
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK
| | - Mohammed A Nassar
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK
| | - Anne-Marie Heegaard
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
| | - John N Wood
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK.
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Uhelski ML, Cain DM, Harding-Rose C, Simone DA. The non-selective cannabinoid receptor agonist WIN 55,212-2 attenuates responses of C-fiber nociceptors in a murine model of cancer pain. Neuroscience 2013; 247:84-94. [PMID: 23673278 DOI: 10.1016/j.neuroscience.2013.05.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Revised: 04/24/2013] [Accepted: 05/03/2013] [Indexed: 02/07/2023]
Abstract
Pain from cancer can be severe, difficult to treat, and greatly diminishes patients' quality of life. It is therefore important to gain new information on the mechanisms of cancer pain and develop new treatment strategies. We have used a murine model of bone cancer pain to investigate underlying peripheral neural mechanisms and novel treatment approaches. In this model, implantation of fibrosarcoma cells into and around the calcaneous bone produces mechanical and thermal hyperalgesia in mice. C-fiber nociceptors in tumor-bearing mice develop spontaneous ongoing activity and sensitization to thermal stimuli. However, it is unclear whether sensitization of nociceptors to mechanical stimuli underlies the mechanical hyperalgesia seen in tumor-bearing mice. We therefore examined responses of C-fiber nociceptors to suprathreshold mechanical stimuli in tumor-bearing mice and found they did not differ from those of C-nociceptors in control mice. Thus, sensitization of C-fiber nociceptors to mechanical stimulation does not appear to underlie tumor-evoked mechanical hyperalgesia in this murine model of bone cancer pain. We also examined the effect of the non-selective cannabinoid receptor agonist, WIN 55,212-2, on spontaneous activity and responses evoked by mechanical stimuli of C-fiber nociceptors innervating the tumor-bearing paw. Selective CB1 and CB2 antagonists were administered to determine the contribution of each receptor subtype to the effects of WIN 55,212-2. Intraplantar administration of WIN 55,212-2 attenuated spontaneous discharge and responses evoked by mechanical stimulation of C-fiber nociceptors. These effects were inhibited by prior intraplantar administration of selective CB1 (AM281) or CB2 (AM630) receptor antagonists but not by vehicle. These results indicate that activation of either CB1 or CB2 receptors reduced the spontaneous activity of C-fiber nociceptors associated with tumor growth as well as their evoked responses. Our results provide further evidence that activation of peripheral cannabinoid receptors may be a useful target for the treatment of cancer pain.
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Affiliation(s)
- M L Uhelski
- Department of Diagnostic and Biological Sciences, University of Minnesota, Minneapolis, MN 55447, United States
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Astrocytes--multitaskers in chronic pain. Eur J Pharmacol 2013; 716:120-8. [PMID: 23528354 DOI: 10.1016/j.ejphar.2013.03.023] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2012] [Revised: 02/20/2013] [Accepted: 03/04/2013] [Indexed: 12/31/2022]
Abstract
Treatment of chronic pain remains a clinical challenge and sufficient pharmacological management is difficult to achieve without concurrent adverse drug effects. Recently the concept of chronic pain as a solely neuron-mediated phenomenon has evolved and it is now appreciated that also glial cells are of critical importance in pain generation and modulation. Astrocytes are macroglial cells that have close structural relationships with neurons; they contact neuronal somata and dendrites and enwrap synapses, where small astrocytic processes have been shown to be highly motile. This organization allows astrocytes to directly influence and coordinate neurons located within their structural domains. Moreover, astrocytes form astroglial networks and calcium wave propagations can spread through neighbouring astrocytes. ATP, which is released from astrocytes in response to elevated intracellular calcium concentrations, can contribute to the central mechanisms in chronic pain via purinergic receptors. In this review we highlight the structural organization and the functionalities of astrocytes that allow them to undertake critical roles in pain processing and we stress the possibility that astrocytes contribute to chronic pain not via a single pathway, but by undertaking various roles depending on the pain condition.
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