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Lu YC, Yin JB, Bai Y, Li X, Zhang T, Yang J, Yi XN, Zhang MM, Li YQ. Morphological Features of Endomorphin-2-immunoreactive Ultrastructures in the Dorsal Root Ganglion and Spinal Dorsal Horn of the Rat. J Chem Neuroanat 2022; 125:102142. [DOI: 10.1016/j.jchemneu.2022.102142] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 07/28/2022] [Accepted: 07/29/2022] [Indexed: 01/24/2023]
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Webster L, Schmidt WK. Dilemma of Addiction and Respiratory Depression in the Treatment of Pain: A Prototypical Endomorphin as a New Approach. PAIN MEDICINE 2021; 21:992-1004. [PMID: 31165885 DOI: 10.1093/pm/pnz122] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVE Although mu-opioid receptor agonists have been the mainstay of analgesic regimens for moderate to severe pain, they are associated with serious side effects, risks, and limitations. We evaluate the most serious risks associated with conventional opioids and compare these with the pharmacology of CYT-1010, a prototypical endomorphin and mu-opioid receptor agonist. RESULTS Addiction and respiratory depression are serious risks of traditional mu-opioid analgesics. Mitigation strategies have been inadequate at addressing the opioid crisis and may interfere with the effective treatment of pain. Improved understanding of mu-opioid receptor biology and the discovery in 1997 of an additional and unique family of endogenous opioid peptides (endomorphins) have provided a pathway for dissociating analgesia from opioid-related adverse events and developing new classes of mu-opioid receptor agonists that use biased signaling and/or target novel sites to produce analgesia with reduced side effect liability. Endomorphin-1 and -2 are endogenous opioid peptides highly selective for mu-opioid receptors that exhibit potent analgesia with reduced side effects. CYT-1010 is a cyclized, D-lysine-containing analog of endomorphin-1 with a novel mechanism of action targeting traditional mu- and exon 11/truncated mu-opioid receptor 6TM variants. CYT-1010 preclinical data have demonstrated reduced abuse potential and analgesic potency exceeding that of morphine. In an initial phase 1 clinical study, CYT-1010 demonstrated significant analgesia vs baseline and no respiratory depression at the dose levels tested. CONCLUSIONS CYT-1010 and other novel mu-opioid receptor agonists in clinical development are promising alternatives to conventional opioids that may offer the possibility of safer treatment of moderate to severe pain.
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Wang Y, Zhao X, Gao X, Gan Y, Liu Y, Zhao X, Hu J, Ma X, Wu Y, Ma P, Liang X, Zhang X. Original endomorphin-1 analogues exhibit good analgesic effects with minimal implications for human sperm motility. Bioorg Med Chem Lett 2017; 27:2119-2123. [DOI: 10.1016/j.bmcl.2017.03.067] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Revised: 03/17/2017] [Accepted: 03/23/2017] [Indexed: 12/18/2022]
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Block L. Glial dysfunction and persistent neuropathic postsurgical pain. Scand J Pain 2016; 10:74-81. [PMID: 28361776 DOI: 10.1016/j.sjpain.2015.10.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 10/10/2015] [Accepted: 10/13/2015] [Indexed: 12/30/2022]
Abstract
BACKGROUND Acute pain in response to injury is an important mechanism that serves to protect living beings from harm. However, persistent pain remaining long after the injury has healed serves no useful purpose and is a disabling condition. Persistent postsurgical pain, which is pain that lasts more than 3 months after surgery, affects 10-50% of patients undergoing elective surgery. Many of these patients are affected by neuropathic pain which is characterised as a pain caused by lesion or disease in the somatosensory nervous system. When established, this type of pain is difficult to treat and new approaches for prevention and treatment are needed. A possible contributing mechanism for the transition from acute physiological pain to persistent pain involves low-grade inflammation in the central nervous system (CNS), glial dysfunction and subsequently an imbalance in the neuron-glial interaction that causes enhanced and prolonged pain transmission. AIM This topical review aims to highlight the contribution that inflammatory activated glial cell dysfunction may have for the development of persistent pain. METHOD Relevant literature was searched for in PubMed. RESULTS Immediately after an injury to a nerve ending in the periphery such as in surgery, the inflammatory cascade is activated and immunocompetent cells migrate to the site of injury. Macrophages infiltrate the injured nerve and cause an inflammatory reaction in the nerve cell. This reaction leads to microglia activation in the central nervous system and the release of pro-inflammatory cytokines that activate and alter astrocyte function. Once the astrocytes and microglia have become activated, they participate in the development, spread, and potentiation of low-grade neuroinflammation. The inflammatory activated glial cells exhibit cellular changes, and their communication to each other and to neurons is altered. This renders neurons more excitable and pain transmission is enhanced and prolonged. Astrocyte dysfunction can be experimentally restored using the combined actions of a μ-opioid receptor agonist, a μ-opioid receptor antagonist, and an anti-epileptic agent. To find these agents we searched the literature for substances with possible anti-inflammatory properties that are usually used for other purposes in medicine. Inflammatory induced glial cell dysfunction is restorable in vitro by a combination of endomorphine-1, ultralow doses of naloxone and levetiracetam. Restoring inflammatory-activated glial cells, thereby restoring astrocyte-neuron interaction has the potential to affect pain transmission in neurons. CONCLUSION Surgery causes inflammation at the site of injury. Peripheral nerve injury can cause low-grade inflammation in the CNS known as neuroinflammation. Low-grade neuroinflammation can cause an imbalance in the glial-neuron interaction and communication. This renders neurons more excitable and pain transmission is enhanced and prolonged. Astrocytic dysfunction can be restored in vitro by a combination of endomorphin-1, ultralow doses of naloxone and levetiracetam. This restoration is essential for the interaction between astrocytes and neurons and hence also for modulation of synaptic pain transmission. IMPLICATIONS Larger studies in clinical settings are needed before these findings can be applied in a clinical context. Potentially, by targeting inflammatory activated glial cells and not only neurons, a new arena for development of pharmacological agents for persistent pain is opened.
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Affiliation(s)
- Linda Block
- Institute of Clinical Sciences at Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Department of Anesthesiology and Intensive Care, Sahlgrenska University Hospital, Gothenburg, Sweden
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Zadina JE, Nilges MR, Morgenweck J, Zhang X, Hackler L, Fasold MB. Endomorphin analog analgesics with reduced abuse liability, respiratory depression, motor impairment, tolerance, and glial activation relative to morphine. Neuropharmacology 2015; 105:215-227. [PMID: 26748051 DOI: 10.1016/j.neuropharm.2015.12.024] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 12/18/2015] [Accepted: 12/28/2015] [Indexed: 11/20/2022]
Abstract
Opioids acting at the mu opioid receptor (MOR) are the most effective analgesics, however adverse side effects severely limit their use. Of particular importance, abuse liability results in major medical, societal, and economic problems, respiratory depression is the cause of fatal overdoses, and tolerance complicates treatment and increases the risk of side effects. Motor and cognitive impairment are especially problematic for older adults. Despite the host of negative side effects, opioids such as morphine are commonly used for acute and chronic pain conditions. Separation of analgesia from unwanted effects has long been an unmet goal of opioid research. Novel MOR agonist structures may prove critical for greater success. Here we tested metabolically stable analogs of the endomorphins, endogenous opioids highly selective for the MOR. Compared to morphine, the analogs showed dramatically improved analgesia-to-side-effect ratios. At doses providing equal or greater antinociception than morphine in the rat, the analogs showed reduced a) respiratory depression, b) impairment of motor coordination, c) tolerance and hyperalgesia, d) glial p38/CGRP/P2X7 receptor signaling, and e) reward/abuse potential in both conditioned place preference and self-administration tests. Differential effects on glial activation indicate a mechanism for the relative lack of side effects by the analogs compared to morphine. The results suggest that endomorphin analogs described here could provide gold standard pain relief mediated by selective MOR activation, but with remarkably safer side effect profiles compared to opioids like morphine.
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Affiliation(s)
- James E Zadina
- SE LA Veterans Affairs Health Care System, Tulane University School of Medicine, New Orleans, LA 70112, USA; Department of Medicine, Tulane University School of Medicine, New Orleans, LA 70112, USA; Neuroscience Program, Tulane University School of Medicine, New Orleans, LA 70112, USA; Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA 70112, USA.
| | - Mark R Nilges
- Neuroscience Program, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Jenny Morgenweck
- Department of Medicine, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Xing Zhang
- SE LA Veterans Affairs Health Care System, Tulane University School of Medicine, New Orleans, LA 70112, USA; Department of Medicine, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Laszlo Hackler
- SE LA Veterans Affairs Health Care System, Tulane University School of Medicine, New Orleans, LA 70112, USA; Department of Medicine, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Melita B Fasold
- SE LA Veterans Affairs Health Care System, Tulane University School of Medicine, New Orleans, LA 70112, USA; Department of Medicine, Tulane University School of Medicine, New Orleans, LA 70112, USA
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Chen T, Li J, Feng B, Hui R, Dong YL, Huo FQ, Zhang T, Yin JB, Du JQ, Li YQ. Mechanism Underlying the Analgesic Effect Exerted by Endomorphin-1 in the rat Ventrolateral Periaqueductal Gray. Mol Neurobiol 2015; 53:2036-2053. [DOI: 10.1007/s12035-015-9159-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 03/25/2015] [Indexed: 12/11/2022]
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Cai J, Song B, Cai Y, Ma Y, Lam AL, Magiera J, Sekar S, Wyse BD, Ambo A, Sasaki Y, Lazarus LH, Smith MT, Li T. Endomorphin analogues with mixed μ-opioid (MOP) receptor agonism/δ-opioid (DOP) receptor antagonism and lacking β-arrestin2 recruitment activity. Bioorg Med Chem 2014; 22:2208-19. [PMID: 24613457 DOI: 10.1016/j.bmc.2014.02.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 02/11/2014] [Accepted: 02/13/2014] [Indexed: 11/16/2022]
Abstract
Analogues of endomorphin (Dmt-Pro-Xaa-Xaa-NH2) modified at position 4 or at positions 4 and 3, and tripeptides (Dmt-Pro-Xaa-NH2) modified at position 3, with various phenylalanine analogues (Xaa=Trp, 1-Nal, 2-Nal, Tmp, Dmp, Dmt) were synthesized and their effects on in vitro opioid activity were investigated. Most of the peptides exhibited high μ-opioid (MOP) receptor binding affinity (KiMOP=0.13-0.81nM), modest MOP-selectivity (Kiδ-opioid (DOP)/KiMOP=3.5-316), and potent functional MOP agonism (GPI, IC50=0.274-249nM) without DOP and κ-opioid (KOP) receptor agonism. Among them, compounds 7 (Dmt-Pro-Tmp-Tmp-NH2) and 9 (Dmt-Pro-1-Nal-NH2) were opioids with potent mixed MOP receptor agonism/DOP receptor antagonism and devoid of β-arrestin2 recruitment activity. They may offer a unique template for the discovery of potent analgesics that produce less respiratory depression, less gastrointestinal dysfunction and that have a lower propensity to induce tolerance and dependence compared with morphine.
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Affiliation(s)
- Jun Cai
- School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Bowen Song
- School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Yunxin Cai
- School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Yu Ma
- School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Ai-Leen Lam
- Centre for Integrated Preclinical Drug Development, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Julia Magiera
- Centre for Integrated Preclinical Drug Development, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Sunder Sekar
- Centre for Integrated Preclinical Drug Development, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Bruce D Wyse
- Centre for Integrated Preclinical Drug Development, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Akihiro Ambo
- Tohoku Pharmaceutical University, 4-1 Komatsushima 4-chome, Aoba-ku, Sendai 981-8558, Japan
| | - Yusuke Sasaki
- Tohoku Pharmaceutical University, 4-1 Komatsushima 4-chome, Aoba-ku, Sendai 981-8558, Japan
| | - Lawrence H Lazarus
- Medicinal Chemistry Group, Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Science, Research Triangle Park, NC 27709, USA
| | - Maree T Smith
- Centre for Integrated Preclinical Drug Development, The University of Queensland, Brisbane, QLD 4072, Australia.
| | - Tingyou Li
- School of Pharmacy, Nanjing Medical University, Nanjing 211166, China; Collaborative Innovation Center for Cardiovascular Disease Translational Medicine, Nanjing Medical University, Nanjing 211166, China.
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