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Cell Jan 2023Opioids are effective analgesics, but their use is beset by serious side effects, including addiction and respiratory depression, which contribute to the ongoing opioid...
Opioids are effective analgesics, but their use is beset by serious side effects, including addiction and respiratory depression, which contribute to the ongoing opioid crisis. The human opioid system contains four opioid receptors (μOR, δOR, κOR, and NOPR) and a set of related endogenous opioid peptides (EOPs), which show distinct selectivity toward their respective opioid receptors (ORs). Despite being key to the development of safer analgesics, the mechanisms of molecular recognition and selectivity of EOPs to ORs remain unclear. Here, we systematically characterize the binding of EOPs to ORs and present five structures of EOP-OR-G complexes, including β-endorphin- and endomorphin-bound μOR, deltorphin-bound δOR, dynorphin-bound κOR, and nociceptin-bound NOPR. These structures, supported by biochemical results, uncover the specific recognition and selectivity of opioid peptides and the conserved mechanism of opioid receptor activation. These results provide a structural framework to facilitate rational design of safer opioid drugs for pain relief.
Topics: Humans; Analgesics, Opioid; Opioid Peptides; Receptors, Opioid, mu; Receptors, Opioid
PubMed: 36638794
DOI: 10.1016/j.cell.2022.12.026 -
International Journal of Molecular... Dec 2020β-Endorphins are peptides that exert a wide variety of effects throughout the body. Produced through the cleavage pro-opiomelanocortin (POMC), β-endorphins are the... (Review)
Review
β-Endorphins are peptides that exert a wide variety of effects throughout the body. Produced through the cleavage pro-opiomelanocortin (POMC), β-endorphins are the primarily agonist of mu opioid receptors, which can be found throughout the body, brain, and cells of the immune system that regulate a diverse set of systems. As an agonist of the body's opioid receptors, β-endorphins are most noted for their potent analgesic effects, but they also have their involvement in reward-centric and homeostasis-restoring behaviors, among other effects. These effects have implicated the peptide in psychiatric and neurodegenerative disorders, making it a research target of interest. This review briefly summarizes the basics of endorphin function, goes over the behaviors and regulatory pathways it governs, and examines the variability of β-endorphin levels observed between normal and disease/disorder affected individuals.
Topics: Animals; Behavior; Behavior, Animal; Brain; Energy Metabolism; Humans; Inflammation; Stress, Physiological; beta-Endorphin
PubMed: 33396962
DOI: 10.3390/ijms22010338 -
Neuropharmacology Jun 2020Neuropeptides play important modulatory roles throughout the nervous system, functioning as direct effectors or as interacting partners with other neuropeptide and... (Review)
Review
Neuropeptides play important modulatory roles throughout the nervous system, functioning as direct effectors or as interacting partners with other neuropeptide and neurotransmitter systems. Limbic brain areas involved in learning, memory and emotions are particularly rich in neuropeptides. This review will focus on the amygdala, a limbic region that plays a key role in emotional-affective behaviors and pain modulation. The amygdala is comprised of different nuclei; the basolateral (BLA) and central (CeA) nuclei and in between, the intercalated cells (ITC), have been linked to pain-related functions. A wide range of neuropeptides are found in the amygdala, particularly in the CeA, but this review will discuss those neuropeptides that have been explored for their role in pain modulation. Calcitonin gene-related peptide (CGRP) is a key peptide in the afferent nociceptive pathway from the parabrachial area and mediates excitatory drive of CeA neurons. CeA neurons containing corticotropin releasing factor (CRF) and/or somatostatin (SOM) are a source of long-range projections and serve major output functions, but CRF also acts locally to excite neurons in the CeA and BLA. Neuropeptide S (NPS) is associated with inhibitory ITC neurons that gate amygdala output. Oxytocin and vasopressin exert opposite (inhibitory and excitatory, respectively) effects on amygdala output. The opioid system of mu, delta and kappa receptors (MOR, DOR, KOR) and their peptide ligands (β-endorphin, enkephalin, dynorphin) have complex and partially opposing effects on amygdala function. Neuropeptides therefore serve as valuable targets to regulate amygdala function in pain conditions. This article is part of the special issue on Neuropeptides.
Topics: Affect; Amygdala; Animals; Chronic Pain; Corticotropin-Releasing Hormone; Emotions; Humans; Neuropeptides; Neurophysins; Oxytocin; Protein Precursors; Vasopressins
PubMed: 32188569
DOI: 10.1016/j.neuropharm.2020.108052 -
Neuropharmacology Aug 2020The opioid epidemic has led to a serious examination of the use of opioids for the treatment of pain. Opioid drugs are effective due to the expression of opioid... (Review)
Review
The opioid epidemic has led to a serious examination of the use of opioids for the treatment of pain. Opioid drugs are effective due to the expression of opioid receptors throughout the body. These receptors respond to endogenous opioid peptides that are expressed as polypeptide hormones that are processed by proteolytic cleavage. Endogenous opioids are expressed throughout the peripheral and central nervous system and regulate many different neuronal circuits and functions. One of the key functions of endogenous opioid peptides is to modulate our responses to pain. This review will focus on the descending pain modulatory circuit which consists of the ventrolateral periaqueductal gray (PAG) projections to the rostral ventromedial medulla (RVM). RVM projections modulate incoming nociceptive afferents at the level of the spinal cord. Stimulation within either the PAG or RVM results in analgesia and this circuit has been studied in detail in terms of the actions of exogenous opioids, such as morphine and fentanyl. Further emphasis on understanding the complex regulation of endogenous opioids will help to make rational decisions with regard to the use of opioids for pain. We also include a discussion of the actions of endogenous opioids in the amygdala, an upstream brain structure that has reciprocal connections to the PAG that contribute to the brain's response to pain.
Topics: Amygdala; Animals; Humans; Opioid Peptides; Pain; Pain Management; Pain Perception; Periaqueductal Gray; Receptors, Opioid
PubMed: 32422213
DOI: 10.1016/j.neuropharm.2020.108131 -
Cell Metabolism Feb 2021Low-grade mitochondrial stress can promote health and longevity, a phenomenon termed mitohormesis. Here, we demonstrate the opposing metabolic effects of low-level and...
Low-grade mitochondrial stress can promote health and longevity, a phenomenon termed mitohormesis. Here, we demonstrate the opposing metabolic effects of low-level and high-level mitochondrial ribosomal (mitoribosomal) stress in hypothalamic proopiomelanocortin (POMC) neurons. POMC neuron-specific severe mitoribosomal stress due to Crif1 homodeficiency causes obesity in mice. By contrast, mild mitoribosomal stress caused by Crif1 heterodeficiency in POMC neurons leads to high-turnover metabolism and resistance to obesity. These metabolic benefits are mediated by enhanced thermogenesis and mitochondrial unfolded protein responses (UPR) in distal adipose tissues. In POMC neurons, partial Crif1 deficiency increases the expression of β-endorphin (β-END) and mitochondrial DNA-encoded peptide MOTS-c. Central administration of MOTS-c or β-END recapitulates the adipose phenotype of Crif1 heterodeficient mice, suggesting these factors as potential mediators. Consistently, regular running exercise at moderate intensity stimulates hypothalamic MOTS-c/β-END expression and induces adipose tissue UPR and thermogenesis. Our findings indicate that POMC neuronal mitohormesis may underlie exercise-induced high-turnover metabolism.
Topics: Animals; Cell Line, Tumor; Energy Metabolism; Hypothalamus; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Mitochondria; Neurons; Physical Conditioning, Animal; Pro-Opiomelanocortin
PubMed: 33535098
DOI: 10.1016/j.cmet.2021.01.003 -
The Cochrane Database of Systematic... Jul 2019Polycystic ovarian syndrome (PCOS) is characterised by the clinical signs of oligo-amenorrhoea, infertility and hirsutism. Conventional treatment of PCOS includes a...
BACKGROUND
Polycystic ovarian syndrome (PCOS) is characterised by the clinical signs of oligo-amenorrhoea, infertility and hirsutism. Conventional treatment of PCOS includes a range of oral pharmacological agents, lifestyle changes and surgical modalities. Beta-endorphin is present in the follicular fluid of both normal and polycystic ovaries. It was demonstrated that the beta-endorphin levels in ovarian follicular fluid of otherwise healthy women who were undergoing ovulation were much higher than the levels measured in plasma. Given that acupuncture impacts on beta-endorphin production, which may affect gonadotropin-releasing hormone (GnRH) secretion, it is postulated that acupuncture may have a role in ovulation induction via increased beta-endorphin production effecting GnRH secretion. This is an update of our previous review published in 2016.
OBJECTIVES
To assess the effectiveness and safety of acupuncture treatment for oligo/anovulatory women with polycystic ovarian syndrome (PCOS) for both fertility and symptom control.
SEARCH METHODS
We identified relevant studies from databases including the Gynaecology and Fertility Group Specialised Register, CENTRAL, MEDLINE, Embase, PsycINFO, CNKI, CBM and VIP. We also searched trial registries and reference lists from relevant papers. CENTRAL, MEDLINE, Embase, PsycINFO, CNKI and VIP searches are current to May 2018. CBM database search is to November 2015.
SELECTION CRITERIA
We included randomised controlled trials (RCTs) that studied the efficacy of acupuncture treatment for oligo/anovulatory women with PCOS. We excluded quasi- or pseudo-RCTs.
DATA COLLECTION AND ANALYSIS
Two review authors independently selected the studies, extracted data and assessed risk of bias. We calculated risk ratios (RR), mean difference (MD), standardised mean difference (SMD) and 95% confidence intervals (CIs). Primary outcomes were live birth rate, multiple pregnancy rate and ovulation rate, and secondary outcomes were clinical pregnancy rate, restored regular menstruation period, miscarriage rate and adverse events. We assessed the quality of the evidence using GRADE methods.
MAIN RESULTS
We included eight RCTs with 1546 women. Five RCTs were included in our previous review and three new RCTs were added in this update of the review. They compared true acupuncture versus sham acupuncture (three RCTs), true acupuncture versus relaxation (one RCT), true acupuncture versus clomiphene (one RCT), low-frequency electroacupuncture versus physical exercise or no intervention (one RCT) and true acupuncture versus Diane-35 (two RCTs). Studies that compared true acupuncture versus Diane-35 did not measure fertility outcomes as they were focused on symptom control.Seven of the studies were at high risk of bias in at least one domain.For true acupuncture versus sham acupuncture, we could not exclude clinically relevant differences in live birth (RR 0.97, 95% CI 0.76 to 1.24; 1 RCT, 926 women; low-quality evidence); multiple pregnancy rate (RR 0.89, 95% CI 0.33 to 2.45; 1 RCT, 926 women; low-quality evidence); ovulation rate (SMD 0.02, 95% CI -0.15 to 0.19, I = 0%; 2 RCTs, 1010 women; low-quality evidence); clinical pregnancy rate (RR 1.03, 95% CI 0.82 to 1.29; I = 0%; 3 RCTs, 1117 women; low-quality evidence) and miscarriage rate (RR 1.10, 95% CI 0.77 to 1.56; 1 RCT, 926 women; low-quality evidence).Number of intermenstrual days may have improved in participants receiving true acupuncture compared to sham acupuncture (MD -312.09 days, 95% CI -344.59 to -279.59; 1 RCT, 141 women; low-quality evidence).True acupuncture probably worsens adverse events compared to sham acupuncture (RR 1.16, 95% CI 1.02 to 1.31; I = 0%; 3 RCTs, 1230 women; moderate-quality evidence).No studies reported data on live birth rate and multiple pregnancy rate for the other comparisons: physical exercise or no intervention, relaxation and clomiphene. Studies including Diane-35 did not measure fertility outcomes.We were uncertain whether acupuncture improved ovulation rate (measured by ultrasound three months post treatment) compared to relaxation (MD 0.35, 95% CI 0.14 to 0.56; 1 RCT, 28 women; very low-quality evidence) or Diane-35 (RR 1.45, 95% CI 0.87 to 2.42; 1 RCT, 58 women; very low-quality evidence).Overall evidence ranged from very low quality to moderate quality. The main limitations were failure to report important clinical outcomes and very serious imprecision.
AUTHORS' CONCLUSIONS
For true acupuncture versus sham acupuncture we cannot exclude clinically relevant differences in live birth rate, multiple pregnancy rate, ovulation rate, clinical pregnancy rate or miscarriage. Number of intermenstrual days may improve in participants receiving true acupuncture compared to sham acupuncture. True acupuncture probably worsens adverse events compared to sham acupuncture.No studies reported data on live birth rate and multiple pregnancy rate for the other comparisons: physical exercise or no intervention, relaxation and clomiphene. Studies including Diane-35 did not measure fertility outcomes as the women in these trials did not seek fertility.We are uncertain whether acupuncture improves ovulation rate (measured by ultrasound three months post treatment) compared to relaxation or Diane-35. The other comparisons did not report on this outcome.Adverse events were recorded in the acupuncture group for the comparisons physical exercise or no intervention, clomiphene and Diane-35. These included dizziness, nausea and subcutaneous haematoma. Evidence was very low quality with very wide CIs and very low event rates.There are only a limited number of RCTs in this area, limiting our ability to determine effectiveness of acupuncture for PCOS.
Topics: Abortion, Spontaneous; Acupuncture Therapy; Cyproterone Acetate; Drug Combinations; Ethinyl Estradiol; Female; Humans; Infertility, Female; Menstruation; Ovulation Induction; Polycystic Ovary Syndrome; Pregnancy; Pregnancy Outcome; Pregnancy Rate; Pregnancy, Multiple; Randomized Controlled Trials as Topic
PubMed: 31264709
DOI: 10.1002/14651858.CD007689.pub4 -
Experimental Dermatology Apr 2021In the light of substantial discoveries in epithelial and hair pigmentation pathophysiology, this review summarizes the current understanding of skin pigmentation... (Review)
Review
In the light of substantial discoveries in epithelial and hair pigmentation pathophysiology, this review summarizes the current understanding of skin pigmentation mechanisms. Melanocytes are pigment-producing cells, and their key regulating transcription factor is the melanocyte-specific microphthalmia-associated transcription factor (m-MITF). Ultraviolet (UV) radiation is a unique modulator of skin pigmentation influencing tanning pathways. The delayed tanning pathway occurs as UVB produces keratinocyte DNA damage, causing p53-mediated expression of the pro-opiomelanocortin (POMC) gene that is processed to release α-melanocyte-stimulating hormone (α-MSH). α-MSH stimulates the melanocortin 1 receptor (MC1R) on melanocytes, leading to m-MITF expression and melanogenesis. POMC cleavage also releases β-endorphin, which creates a neuroendocrine pathway that promotes UV-seeking behaviours. Mutations along the tanning pathway can affect pigmentation and increase the risk of skin malignancies. MC1R variants have received considerable attention, yet the allele is highly polymorphic with varied phenotypes. Vitiligo presents with depigmented skin lesions due to autoimmune destruction of melanocytes. UVB phototherapy stimulates melanocyte stem cells in the hair bulge to undergo differentiation and upwards migration resulting in perifollicular repigmentation of vitiliginous lesions, which is under sophisticated signalling control. Melanocyte stem cells, normally quiescent, undergo cyclic activation/differentiation and downward migration with the hair cycle, providing pigment to hair follicles. Physiological hair greying results from progressive loss of melanocyte stem cells and can be accelerated by acute stress-induced, sympathetic driven hyperproliferation of the melanocyte stem cells. Ultimately, by reviewing the pathways governing epithelial and follicular pigmentation, numerous areas of future research and potential points of intervention are highlighted.
Topics: Hair Follicle; Humans; Melanocytes; Microphthalmia-Associated Transcription Factor; Skin Pigmentation; Stem Cells; Ultraviolet Rays; Ultraviolet Therapy; Vitiligo
PubMed: 33320376
DOI: 10.1111/exd.14260 -
Science Advances Dec 2022Fatigue is a common adverse effect of external beam radiation therapy in cancer patients. Mechanisms causing radiation fatigue remain unclear, although linkage to skin...
Fatigue is a common adverse effect of external beam radiation therapy in cancer patients. Mechanisms causing radiation fatigue remain unclear, although linkage to skin irradiation has been suggested. β-Endorphin, an endogenous opioid, is synthesized in skin following genotoxic ultraviolet irradiation and acts systemically, producing addiction. Exogenous opiates with the same receptor activity as β-endorphin can cause fatigue. Using rodent models of radiation therapy, exposing tails and sparing vital organs, we tested whether skin-derived β-endorphin contributes to radiation-induced fatigue. Over a 6-week radiation regimen, plasma β-endorphin increased in rats, paralleled by opiate phenotypes (elevated pain thresholds, Straub tail) and fatigue-like behavior, which was reversed in animals treated by the opiate antagonist naloxone. Mechanistically, all these phenotypes were blocked by opiate antagonist treatment and were undetected in either β-endorphin knockout mice or mice lacking keratinocyte p53 expression. These findings implicate skin-derived β-endorphin in systemic effects of radiation therapy. Opioid antagonism may warrant testing in humans as treatment or prevention of radiation-induced fatigue.
PubMed: 36525492
DOI: 10.1126/sciadv.abn6025 -
Biomedicines Dec 2021Neuropeptides have been known for over 50 years as chemical signals in the brain. However, it is now well established that the synthesis of this class of peptides is not... (Review)
Review
Neuropeptides have been known for over 50 years as chemical signals in the brain. However, it is now well established that the synthesis of this class of peptides is not restricted to neurons. For example, human skin not only expresses several functional receptors for neuropeptides but, also, can serve as a local source of neuroactive molecules such as corticotropin-releasing hormone, melanocortins, and β-endorphin. In contrast, an equivalent of the hypothalamic-pituitary axis in the oral mucosa has not been well characterized to date. In view of the differences in the morphology and function of oral mucosal and skin cells, in this review I surveyed the existing evidence for a local synthesis of hypothalamic-pituitary, opiate, neurohypophyseal, and neuroendocrine neuropeptides in both epidermal and oral keratinocytes.
PubMed: 34944669
DOI: 10.3390/biomedicines9121854 -
Cancers May 2021Melanoma is one of the most aggressive skin cancers with a sharp rise in incidence in the last decades, especially in young people. Recognized as a significant public... (Review)
Review
Melanoma is one of the most aggressive skin cancers with a sharp rise in incidence in the last decades, especially in young people. Recognized as a significant public health issue, melanoma is studied with increasing interest as new discoveries in molecular signaling and receptor modulation unlock innovative treatment options. Stress exposure is recognized as an important component in the immune-inflammatory interplay that can alter the progression of melanoma by regulating the release of neuroendocrine factors. Various neurotransmitters, such as catecholamines, glutamate, serotonin, or cannabinoids have also been assessed in experimental studies for their involvement in the biology of melanoma. Alpha-MSH and other neurohormones, as well as neuropeptides including substance P, CGRP, enkephalin, beta-endorphin, and even cellular and molecular agents (mast cells and nitric oxide, respectively), have all been implicated as potential factors in the development, growth, invasion, and dissemination of melanoma in a variety of in vitro and in vivo studies. In this review, we provide an overview of current evidence regarding the intricate effects of neuroendocrine factors in melanoma, including data reported in recent clinical trials, exploring the mechanisms involved, signaling pathways, and the recorded range of effects.
PubMed: 34068618
DOI: 10.3390/cancers13092277