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International Immunopharmacology Jul 2021Cutaneous squamous cell carcinoma (CSCC) is a common skin tumour. Due to weak immunogenicity, recurrence is frequent after treatment. In this study, we explored the...
Cutaneous squamous cell carcinoma (CSCC) is a common skin tumour. Due to weak immunogenicity, recurrence is frequent after treatment. In this study, we explored the effects and mechanisms of methionine enkephalin (MENK), an endogenous opioid peptide and negative growth regulator, in CSCC. MENK inhibited A431 cell proliferation and promoted apoptosis through the opioid growth factor receptor (OGFr). Importantly, MENK also induced autophagy in CSCC and stimulated the emission of DAMPs in A431 cells, which resulted in enhanced activation of dendritic cells (DC).In conclusion, MENK provides an effective method with therapeutic potential to modulate the CSCC microenvironment by utilizing autophagy in the cancer cells.
Topics: Animals; Autophagy; Carcinoma, Squamous Cell; Cell Line, Tumor; Cell Proliferation; Dendritic Cells; Enkephalin, Methionine; Female; Histocompatibility Antigens Class II; Humans; Mice; Mice, Inbred BALB C; Neurotransmitter Agents; Skin Neoplasms; Xenograft Model Antitumor Assays
PubMed: 33965882
DOI: 10.1016/j.intimp.2021.107733 -
Journal of Chemical Neuroanatomy Sep 2021Enkephalins are a class of opioid peptides implicated in several physiological and neuroendocrine responses in vertebrates. In this study, using immunocytochemical or...
Enkephalins are a class of opioid peptides implicated in several physiological and neuroendocrine responses in vertebrates. In this study, using immunocytochemical or immunofluorescence technique, we examined the neuroanatomical distribution of methionine enkephalin (M-ENK) immunoreactivity in the central nervous system (CNS) of the cichlid fish Oreochromis mossambicus. In the telencephalon, no M-ENK-like-immunoreactive (M-ENK-L-ir) perikarya, but sparsely distributed fibres were detected in the glomerular layer and the granule cell layer of the olfactory bulb. Although intensely labeled M-ENK-L-ir cells and fibres were found in the pallium, no M-ENK immunoreactivity was observed in the subpallium. The preoptic area showed a few M-ENK-L-ir somata and dense innervations of fibres. In the hypothalamic area, M-ENK-L-ir cells and fibres were located in magnocellular and parvocellular subdivisions of the nucleus preopticus, and medial and lateral subdivisions of the nucleus lateralis tuberis. Surrounding the recessus lateralis of the third ventricle, several intensely stained and packed M-ENK-L-ir cells and fibres were seen in dorsal, lateral and ventral subdivisions of the nucleus recessus lateralis. In the diencephalon, M-ENK immunoreactivity was restricted to the habenula, the thalamus, the pretectal area and the nucleus posterior tuberis. Dense aggregations of M-ENK-L-ir fibres were seen in the mesencephalic subdivisions, the optic tectum and the torus semicircularis, whereas a few fusiform M-ENK-L-ir cells and fibres were scattered in the midbrain tegmentum. In the rhombencephalon, different populations of ovoid or spindle shaped M-ENK-L-ir cells were observed in the secondary gustatory nucleus, the sensory trigeminal nerve nucleus, the nucleus reticularis medialis and the vagal motor nucleus, whereas bands of fibres were seen in the rostral spinal cord. Collectively, the widespread distribution of M-ENK immunoreactivity in the CNS suggests a role for this opioid peptide in regulation of neuroendocrine control of reproduction and modulation of sensorimotor functions in fish.
Topics: Animals; Brain; Enkephalin, Methionine; Neurons; Tilapia
PubMed: 33957231
DOI: 10.1016/j.jchemneu.2021.101963 -
Pharmaceutical Research May 2021To evaluate the effect of excipients, including sugars and amino acids, on photo-degradation reactions in pharmaceutical buffers induced by near UV and visible light.
Pharmaceutical Excipients Enhance Iron-Dependent Photo-Degradation in Pharmaceutical Buffers by near UV and Visible Light: Tyrosine Modification by Reactions of the Antioxidant Methionine in Citrate Buffer.
PURPOSE
To evaluate the effect of excipients, including sugars and amino acids, on photo-degradation reactions in pharmaceutical buffers induced by near UV and visible light.
METHODS
Solutions of citrate or acetate buffers, containing 1 or 50 μM Fe, the model peptides methionine enkephalin (MEn), leucine enkephalin (LEn) or proctolin peptide (ProP), in the presence of commonly used amino acids or sugars, were photo-irradiated with near UV or visible light. The oxidation products were analyzed by reverse-phase HPLC and HPLC-MS/MS.
RESULTS
The sugars mannitol, sucrose and trehalose, and the amino acids Arg, Lys, and His significantly promote the oxidation of peptide Met to peptide Met sulfoxide. These excipients do not increase the yields of hydrogen peroxide, suggesting that other oxidants such as peroxyl radicals are responsible for the oxidation of peptide Met. The addition of free Met reduces the oxidation of peptide Met, but, in citrate buffer, causes the addition of Met oxidation products to Tyr residues of the target peptides.
CONCLUSIONS
Commonly used excipients enhance the light-induced oxidation of amino acids in model peptides.
Topics: Antioxidants; Buffers; Citric Acid; Drug Storage; Excipients; Hydrogen-Ion Concentration; Iron; Light; Methionine; Oxidation-Reduction; Peptides; Tandem Mass Spectrometry; Tyrosine; Ultraviolet Rays
PubMed: 33881737
DOI: 10.1007/s11095-021-03042-8 -
Physical Chemistry Chemical Physics :... Apr 2021A novel method dubbed ZULF-TOCSY results from the combination of Zero and Ultra-Low Field (ZULF) with high-field, high-resolution NMR, leading to a generalization of the...
A novel method dubbed ZULF-TOCSY results from the combination of Zero and Ultra-Low Field (ZULF) with high-field, high-resolution NMR, leading to a generalization of the concept of total correlation spectroscopy (TOCSY). ZULF-TOCSY is a new building block for NMR methods, which has the unique property that the polarization is evenly distributed among all NMR-active nuclei such as 1H, 13C, 15N, 31P, etc., provided that they belong to the same coupling network, and provided that their relaxation is not too fast at low fields, as may occur in macromolecules. Here, we show that ZULF-TOCSY correlations can be observed for peptides at natural isotopic abundance, such as the protected hexapeptide Boc-Met-enkephalin. The analysis of ZULF-TOCSY spectra readily allows one to make sequential assignments, thus offering an alternative to established heteronuclear 2D experiments like HMBC. For Boc-Met-enkephalin, we show that ZULF-TOCSY allows one to observe all expected cross-peaks between carbonyl carbons and α-CH protons, while the popular HMBC method provides insufficient information.
Topics: Enkephalin, Methionine; Magnetic Resonance Spectroscopy; Spectrum Analysis
PubMed: 33861279
DOI: 10.1039/d0cp06337a -
Proceedings of the National Academy of... Apr 2021Positive allosteric modulators (PAMs) of the mu-opioid receptor (MOR) have been hypothesized as potentially safer analgesics than traditional opioid drugs. This is based...
Positive allosteric modulators (PAMs) of the mu-opioid receptor (MOR) have been hypothesized as potentially safer analgesics than traditional opioid drugs. This is based on the idea that PAMs will promote the action of endogenous opioid peptides while preserving their temporal and spatial release patterns and so have an improved therapeutic index. However, this hypothesis has never been tested. Here, we show that a mu-PAM, BMS-986122, enhances the ability of the endogenous opioid Methionine-enkephalin (Met-Enk) to stimulate G protein activity in mouse brain homogenates without activity on its own and to enhance G protein activation to a greater extent than β-arrestin recruitment in Chinese hamster ovary (CHO) cells expressing human mu-opioid receptors. Moreover, BMS-986122 increases the potency of Met-Enk to inhibit GABA release in the periaqueductal gray, an important site for antinociception. We describe in vivo experiments demonstrating that the mu-PAM produces antinociception in mouse models of acute noxious heat pain as well as inflammatory pain. These effects are blocked by MOR antagonists and are consistent with the hypothesis that in vivo mu-PAMs enhance the activity of endogenous opioid peptides. Because BMS-986122 does not bind to the orthosteric site and has no inherent agonist action at endogenously expressed levels of MOR, it produces a reduced level of morphine-like side effects of constipation, reward as measured by conditioned place preference, and respiratory depression. These data provide a rationale for the further exploration of the action and safety of mu-PAMs as an innovative approach to pain management.
Topics: Allosteric Regulation; Analgesia; Analgesics; Analgesics, Opioid; Animals; CHO Cells; Cricetulus; Female; Male; Mice; Mice, 129 Strain; Mice, Inbred C57BL; Morphine; Narcotic Antagonists; Pain; Pain Management; Proof of Concept Study; Rats; Rats, Sprague-Dawley; Receptors, Opioid, mu
PubMed: 33846240
DOI: 10.1073/pnas.2000017118 -
Peptides Jul 2021Endomorphin analogs containing unnatural amino acids have demonstrated potent analgesic effects in our previous studies. In the present study, the differences in...
Endomorphin analogs containing unnatural amino acids have demonstrated potent analgesic effects in our previous studies. In the present study, the differences in antinociception and the mechanisms thereof for analogs 1-3 administered intracerebroventricularly and intrathecally were explored. All analogs at different routes of administration produced potent analgesia compared to the parent peptide endomorphin-1. Multiple antagonists and antibodies were used to explore the mechanisms of action of these analogs, and it was inferred that analogs 1-3 stimulated the μ opioid receptor to induce antinociception. Moreover, the antibody data suggested that analog 2 may induce the release of immunoreactive [Leu]-enkephaline and [Met]-enkephaline to produce a secondary component of antinociception at the spinal level and analog 3 may stimulate the the release of immunoreactive [Met]-enkephaline at the spinal level. Finally, analogs 2 and 3 produced no acute tolerance in the spinal cord. We hypothesize that the unique characteristics of the endomorphin analogs result from their capacities to stimulate the release of endogenous antinociceptive substances.
Topics: Analgesics; Animals; Chronic Pain; Dose-Response Relationship, Drug; Dynorphins; Enkephalin, Methionine; Enkephalins; Injections, Intraventricular; Mice; Naloxone; Narcotic Antagonists; Oligopeptides; Receptors, Opioid, mu; Spinal Cord
PubMed: 33794284
DOI: 10.1016/j.peptides.2021.170543 -
Multiple Sclerosis and Related Disorders May 2021Multiple sclerosis (MS) is an autoimmune-mediated degenerative disorder with increased peripheral inflammation disrupting the blood brain barrier. With increasing...
BACKGROUND
Multiple sclerosis (MS) is an autoimmune-mediated degenerative disorder with increased peripheral inflammation disrupting the blood brain barrier. With increasing MS-related healthcare costs, the requirement to validate minimally invasive biomarkers has become imperative.
METHODS
Relapsing-remitting MS patients on disease modifying therapies were consented at the Penn State Health MS Clinic to provide blood samples for analyses of serum cytokines and endogenous opioid peptides, as well as to complete the MSQOL-54 survey.
RESULTS
Serum OGF levels in MS patients on glatiramer acetate (mean = 326 pg/ml), dimethyl fumarate (mean = 193.3 pg/ml) and natalizumab (mean = 393.4 pg/ml) were significantly elevated (p < 0.01) compared to healthy controls (mean = 98.46 pg/ml). Individuals with elevated OGF levels also had increased levels of TNFα (r = 0.78) and IL-17A (r = 0.81). Only patients treated with glatiramer acetate had significant (p < 0.01) elevations in serum β-endorphin levels. Analyses of MS-QoL 54 data showed no significant differences in physical or mental composite scores between treatment groups. However, serum levels of β-endorphin had a direct correlation with physical health composite score (r = 0.70) in all treatments. Serum vitamin D levels had an indirect relationship with 25-foot walk test times (r = 0.47).
CONCLUSION
Both regression and cohort data suggest that serum levels of OGF, β-endorphin, and vitamin D are potential biomarkers for physical disease status in MS.
Topics: Biomarkers; Glatiramer Acetate; Humans; Multiple Sclerosis; Multiple Sclerosis, Relapsing-Remitting; Physical Functional Performance; Quality of Life; Receptors, Opioid; beta-Endorphin
PubMed: 33677409
DOI: 10.1016/j.msard.2021.102868 -
Pain Medicine (Malden, Mass.) Jul 2021The treatment for neuropathic pain is still a big challenge. Pulsed radiofrequency technique has been widely used to relieve neuropathic pain in recent years. The...
OBJECTIVES
The treatment for neuropathic pain is still a big challenge. Pulsed radiofrequency technique has been widely used to relieve neuropathic pain in recent years. The purpose of this study is to optimize the temperature for pulsed radiofrequency therapy.
DESIGN
Animal, experimental study.
METHODS
Seventy-five male SD rats were randomly divided into five groups: Sham operation group (Sham group), chronic constriction injury group (CCI group), PRF 42°C group (P42 group), PRF 50°C group (P50 group), and PRF 60°C group (P60 group). The hindpaw withdrawal threshold (HWT), paw thermal withdrawal latency (PTWL), sciatic nerve structure, and the concentration of spinal methionine enkephalin(M-ENK) were detected to identify which temperature is the best for PRF treatment.
RESULTS
PRF at 42°C, 50°C and 60°C significantly alleviated the pain in CCI rats. The therapeutic effects of 50°C and 60°C were similar, and both were better than 42°C. In addition, PRF using 42°C, 50°C, and 60°C mediated nerve injury to sciatic nerve were grade 1, 1, and 2, respectively. The concentration of M-ENK in spinal cord increased accompanying with the increasing of the temperature of PRF.
CONCLUSIONS
PRF using 50°C could induce less damage while achieving better improvement of mechanical and thermal pain threshold than 42°C and 60°C in CCI rats, which may be achieved by promoting the expression of M-ENK in spinal cord.
Topics: Animals; Constriction; Male; Neuralgia; Pulsed Radiofrequency Treatment; Rats; Rats, Sprague-Dawley; Sciatic Nerve; Temperature
PubMed: 33620466
DOI: 10.1093/pm/pnab045 -
Journal of the American Society For... Mar 2021Near-edge X-ray absorption mass spectrometry (NEXAMS) is an action-spectroscopy technique of growing interest for investigations into the spatial and electronic...
Near-edge X-ray absorption mass spectrometry (NEXAMS) is an action-spectroscopy technique of growing interest for investigations into the spatial and electronic structure of biomolecules. It has been used successfully to give insights into different aspects of the photodissociation of peptides and to probe the conformation of proteins. It is a current question whether the fragmentation pathways are sensitive toward effects of conformational isomerism, tautomerism, and intramolecular interactions in gas-phase peptides. To address this issue, we studied the cationic fragments of cryogenically cooled gas-phase leucine enkephalin ([LeuEnk+H]) and methionine enkephalin ([MetEnk+H]) produced upon soft X-ray photon absorption at the carbon, nitrogen, and oxygen K-edges. The interpretation of the experimental ion yield spectra was supported by density-functional theory and restricted-open-shell configuration interaction with singles (DFT/ROCIS) calculations. The analysis revealed several effects that could not be rationalized based on the peptide's amino acid sequences alone. Clear differences between the partial ion yields measured for both peptides upon C 1s → π*(C═C) excitations in the aromatic amino acid side chains give evidence for a sulfur-aromatic interaction between the methionine and phenylalanine side chain of [MetEnk+H]. Furthermore, a peak associated with N 1s → π*(C═N) transitions, linked to a tautomeric keto-to-enol conversion of peptide bonds, was only present in the photon energy resolved ion yield spectra of [MetEnk+H].
Topics: Enkephalin, Leucine; Enkephalin, Methionine; Enkephalins; Models, Molecular; Peptides; Protein Structure, Secondary; X-Ray Absorption Spectroscopy
PubMed: 33573373
DOI: 10.1021/jasms.0c00390 -
Blockade of OGFr delays the onset and reduces the severity of diabetic ocular surface complications.Experimental Biology and Medicine... Mar 2021The opioid growth factor (OGF)-OGF receptor (OGFr) pathway is present in the ocular surface and functions to maintain homeostasis of the epithelium. The OGF-OGFr pathway...
The opioid growth factor (OGF)-OGF receptor (OGFr) pathway is present in the ocular surface and functions to maintain homeostasis of the epithelium. The OGF-OGFr pathway has been reported to be dysregulated in diabetic individuals and animal models, and is reflected in elevations of the inhibitory growth factor, OGF, chemically termed [Met]-enkephalin. Recently, our laboratory reported elevated levels of OGF and OGFr in the serum and corneal epithelium of type 1 diabetic rats, suggesting that dysregulation of the OGF-OGFr axis may lead to dry eye, abnormal corneal surface sensitivity, and delayed re-epithelialization. Blockade of OGF-OGFr pathway using naltrexone, a potent opioid receptor antagonist, reverses dry eye symptoms and restores corneal surface sensitivity in diabetic rats when used as a therapy. Based on the evidence that both OGF and OGFr are elevated in type 1 diabetic rats, this study examined whether systemic or topical naltrexone treatment initiated at the time of induction of hyperglycemia could protect against the development of diabetic ocular surface complications. Diabetic male Sprague-Dawley rats treated systemically or topically with naltrexone had a delayed onset of dry eye and altered corneal surface sensitivity, and an improved healing rate for corneal wounds, that were comparable to non-diabetic rats. Serum levels of OGF were normal for rats receiving systemic naltrexone, and OGF tissue levels were normal for type 1 diabetic rats receiving twice daily naltrexone drops. OGFr levels remained elevated. These data support the role of the OGF-OGFr axis in regulation of ocular surface complications, and suggest that naltrexone therapy may be beneficial for pre-diabetic and early diabetic individuals.
Topics: Animals; Blood Glucose; Body Weight; Cornea; Diabetes Complications; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Enkephalin, Methionine; Eye; Male; Naltrexone; Rats, Sprague-Dawley; Receptors, Opioid; Severity of Illness Index; Time Factors; Rats
PubMed: 33203224
DOI: 10.1177/1535370220972060