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The Journal of Pain May 2023Venom-derived Na1.7 channel blockers have promising prospects in pain management. The 34-residue tarantula peptide GpTx-1 is a potent Na1.7 channel blocker. Its powerful...
Venom-derived Na1.7 channel blockers have promising prospects in pain management. The 34-residue tarantula peptide GpTx-1 is a potent Na1.7 channel blocker. Its powerful analog [Ala, Phe, Leu, Arg]GpTx-1 (GpTx-1-71) displayed excellent Na1.7 selectivity and analgesic properties in mice. The current study aimed to elucidate the anti-hyperalgesic activities of GpTx-1-71 in inflammatory pain and reveal the underlying mechanisms. Our results demonstrated that intrathecal and intraplantar injections of GpTx-1-71 dose-dependently attenuated CFA-induced inflammatory hypersensitivity in rats. Moreover, GpTx-1-71-induced anti-hyperalgesia was significantly reduced by opioid receptor antagonists and the enkephalin antibody and diminished in proenkephalin (Penk) gene knockout animals. Consistently, GpTx-1-71 treatment increased the enkephalin level in the spinal dorsal horn and promoted the Penk transcription and enkephalin release in primary dorsal root ganglion (DRG) neurons, wherein sodium played a crucial role in these processes. Mass spectrometry analysis revealed that GpTx-1-71 mainly promoted the secretion of Met-enkephalin but not Leu-enkephalin from DRG neurons. In addition, the combination of subtherapeutic Met-enkephalin and GpTx-1-71 produced synergistic anti-hyperalgesia in CFA-induced inflammatory hypersensitivity. These findings suggest that the endogenous enkephalin pathway is essential for GpTx-1-71-induced spinal and peripheral analgesia in inflammatory pain. PERSPECTIVE: This article presents a possible pharmacological mechanism underlying Na1.7 blocker-induced analgesia in inflammatory pain, which helps us to better understand and develop venom-based painkillers for incurable pain.
Topics: Rats; Mice; Animals; Pain; Hyperalgesia; Analgesics; Enkephalins; Enkephalin, Methionine; Ganglia, Spinal; NAV1.7 Voltage-Gated Sodium Channel
PubMed: 36586660
DOI: 10.1016/j.jpain.2022.12.012 -
The Journal of Comparative Neurology Nov 1983The immunocytochemical distribution of [Leu]enkephalin and an adrenal enkephalin precursor fragment (BAM-22P) immunoreactivity was investigated in the diencephalon and...
The immunocytochemical distribution of [Leu]enkephalin and an adrenal enkephalin precursor fragment (BAM-22P) immunoreactivity was investigated in the diencephalon and brainstem of rats pretreated with relatively high doses of colchicine (300-400 micrograms/10 microliters intracerebroventricularly). The higher ranges of colchicine pretreatment allowed the visualization of extensive enkephalin-containing systems in these brain regions, some of which are reported for the first time. Immunoreactive perikarya were found in many hypothalamic and thalamic nuclei, interpeduncular nucleus, substantia nigra, the colliculi, periaqueductal gray, parabrachial nuclei, trigeminal motor and spinal nuclei, nucleus raphe magnus and other raphe nuclei, nucleus reticularis paragigantocellularis, vestibular nuclei, several noradrenergic cell groups, nucleus tractus solitarius, as well as in the spinal cord dorsal horn. In addition to the above regions, immunoreactive fibers were also noted in the habenular nuclei, trigeminal sensory nuclei, locus coeruleus, motor facial nucleus, cochlear nuclei, dorsal motor nucleus of the vagus, and hypoglossal nucleus. When adjacent sections of those stained for [Leu]enkephalin were processed for BAM-22P immunoreactivity, it was found that these two immunoreactivities were distributed identically at almost all anatomical locations. BAM-22P immunoreactivity was generally less pronounced and ws preferentially localized to neuronal perikarya. The results of the present as well as the preceding studies (Khachaturian et al., '83) strongly suggest substantial structural similarity between the adrenal proenkephalin precursor and that which occurs in the brain. Also discussed are some differences and parallels between the distribution of [Leu]enkephalin and dynorphin immunoreactivities.
Topics: Animals; Brain Stem; Diencephalon; Enkephalin, Leucine; Enkephalin, Methionine; Enkephalins; Immunoenzyme Techniques; Male; Protein Precursors; Rats; Rats, Inbred Strains; Spinal Cord; Tissue Distribution
PubMed: 6358277
DOI: 10.1002/cne.902200305 -
Journal of Neurophysiology Oct 1998The effects of methionine-enkephalin (ME) on visualized bulbospinal neurons of the rostral ventrolateral medulla (RVL) were characterized in thin slices at 32 degrees C...
The effects of methionine-enkephalin (ME) on visualized bulbospinal neurons of the rostral ventrolateral medulla (RVL) were characterized in thin slices at 32 degrees C using the whole cell patch-clamp technique. Thirty-five percent of the recorded neurons were found to be tyrosine hydroxylase immunoreactive (C1 neurons). In voltage-clamp recordings, ME (3 microM) induced an outward current in 66% of RVL bulbospinal neurons. A similar percentage of C1 and non-C1 neurons were opioid sensitive. The current induced by ME was inwardly rectifying, reversed close to the potassium equilibrium potential, and was blocked by barium. Most spontaneous postsynaptic currents recorded in these neurons were tetrodotoxin (TTX)-resistant miniature postsynaptic currents (mPSCs). Approximately, 75% of mPSCs had rapid kinetics (decay time = 4.7 ms) and were glutamatergic [miniature excitatory postsynaptic currents (mEPSCs)] because they were blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM). The remaining mPSCs had much slower kinetics (decay time = 19.6 ms) and were GABAergic [miniature inhibitory postsynaptic currents (mIPSCs)] as they were blocked by gabazine (3 microM) but not by strychnine (3-10 microM). ME decreased the frequency of mEPSCs and mIPSCs by 69 and 43%, respectively. The inhibitory effects of ME were mimicked by the selective mu-opioid receptor agonist endomorphin-1 (EM, 3 microM) and were blocked by naloxone (1 microM). In the absence of TTX, excitatory PSCs evoked by focal electrical stimulation were isolated by application of gabazine and strychnine. EM reduced the amplitude of the evoked EPSCs by 41% without changing their decay time. We conclude that opioids inhibit the majority of RVL C1 and non-C1 bulbospinal neurons by activating a potassium conductance postsynaptically and by decreasing the presynaptic release of glutamate. These cellular mechanisms could explain the depressive cardiovascular effects and the sympathoinhibition produced by opioid transmitters in the RVL, in particular during hypotensive hemorrhage.
Topics: Animals; Electric Conductivity; Enkephalin, Methionine; Excitatory Postsynaptic Potentials; Medulla Oblongata; Narcotics; Neural Inhibition; Neurons; Potassium; Presynaptic Terminals; Rats; Rats, Sprague-Dawley; Spinal Cord; Synapses
PubMed: 9772256
DOI: 10.1152/jn.1998.80.4.2003 -
Zhongguo Yao Li Xue Bao = Acta... Mar 1996To study the host immune surveillance functions by the neuropeptide methionine enkephalin (met-enk).
AIM
To study the host immune surveillance functions by the neuropeptide methionine enkephalin (met-enk).
METHODS
To measure the effects of met-enk on NK activity, the production and gene expression of anti-tumor cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin-12 (IL-12) in vitro and in vivo.
RESULT
Met-enk promoted NK activity at 1 x 10(-8) - 1 x 10(-5) mol.L-1, increased TNF-alpha production both in vitro and in vivo, and enhanced IL-12 p35 gene transcription after ip 0.1 mg.kg-1 for 6 d.
CONCLUSION
The up-regulating effects of met-enk contribute to the host neuro-immunomodulating mechanism against tumors and invading antigens. Enkephalins and endorphins were originally described as the endogenous ligands for the morphine receptors in the brain. In addition to their central nervous activity, an immunomodulating action of the enkephalins was first reported in 1979. Methionine enkephalin (met-enk) regulated a variety of immunological responses, including enhancing the proliferation of human peripheral lymphocytes and mouse spleen cells, regulating antibody production, natural killer cells (NK) activity and synthesis of a number of cytokines. These results suggested that met-enk might be used to elevate the body resistance to cancer and other diseases, or diminish autoimmune responses which are detrimental to host. To elucidate that met-enk has the activity of anti-tumor through related immune regulating responses, this study is to investigate the effects of met-enk on immune surveillance and immune defence functions.
Topics: Animals; Cytotoxicity, Immunologic; Enkephalin, Methionine; Interleukin-12; Killer Cells, Natural; Macrophages, Peritoneal; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; RNA, Messenger; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha
PubMed: 9772675
DOI: No ID Found -
British Journal of Pharmacology 19801 Methionine (Met)-enkephalin, leucine (Leu)-enkephalin and their synthetic analogues were tested for effects on the spontaneous release of cortical acetylcholine (ACh)...
1 Methionine (Met)-enkephalin, leucine (Leu)-enkephalin and their synthetic analogues were tested for effects on the spontaneous release of cortical acetylcholine (ACh) in vivo. The ability of naloxone to reverse the action of enkephalins on ACh release was compared with its action against morphine. An enkephalin analogue, structurally related to Met-enkephalin, was tested for opiate antagonistic activity in ACh release experiments. 2 Intraventricular administration of Met-enkephalin, Leu-enkephalin, D-Ala2-Met5-enkephalinamide (DALA) and D-Ala2-D-Leu5-enkephalin (DALEU) produced a dose-related inhibition of cortical ACh release. Met- and Leu-enkephalin were very similar both in their potency and the time course of their action on ACh release. Both DALA and DALEU were more potent and had a longer duration of action than Leu-enkephalin. Systemic injections of two pentapeptides, D-Met2-Pro5-enkephalinamide and D-Ala2-MePhe4-Met5(O)-ol-enkephalin (33,824), produced a sustained inhibition of cortical ACh release. 3 Naloxone, administered systemically following the depression of ACh release induced by either intraventricular injections of enkephalins (DALA or DALEU), or systemic injections of enkephalins (D-Met2-Pro5-enkephalinamide or 33,824), reversed this depression and restored the release to baseline levels. The effect of D-Met2-Pro5-enkephalinamide on the release of ACh was reversed by naloxone with difficulty. Naloxone also reversed the inhibitory effect of systemic morphine and this reversal was associated with a large overshoot of ACh release. The latter was never observed in the enkephalin experiments. 4 Intraventricular injection of the pentapeptide, D-Ala2-D-Ala3-Met5-enkephalinamide (TAAPM), at doses that did not influence the basal ACh release, blocked or reversed the inhibitory effect of morphine on this release. This peptide did not block the effect of the non-opiate, chlorpromazine, under similar conditions. In two experiments TAAPM failed to reverse the inhibition of ACh release produced by systemically injected enkephalin, D-Met2-Pro5-enkephalinamide. 5 Effects of morphine and enkephalin on ACh release are discussed in terms of their action on difference opiate receptors.
Topics: Acetylcholine; Animals; Brain; Endorphins; Enkephalin, Methionine; Enkephalins; Injections, Intraventricular; Morphine; Naloxone; Rats
PubMed: 7470736
DOI: 10.1111/j.1476-5381.1980.tb10927.x -
Proceedings of the National Academy of... May 1986The structures of [Met5]enkephalin (Tyr-Gly-Gly-Phe-Met) and [Leu5]enkephalin (Tyr-Gly-Gly-Phe-Leu) have been determined from single crystal x-ray diffraction data and...
The structures of [Met5]enkephalin (Tyr-Gly-Gly-Phe-Met) and [Leu5]enkephalin (Tyr-Gly-Gly-Phe-Leu) have been determined from single crystal x-ray diffraction data and refined to residuals of 0.100 and 0.092, respectively. The [Met5]enkephalin structure consists of dimers forming antiparallel beta-sheets extending in the monoclinic ac plane with 10.6 water molecules per dimer. The two molecules, related by pseudo two-fold axes, have similar backbone conformations and similar tyrosine and phenylalanine side-chain conformations. Both methionine residues are disordered and the disorder is different in the two independent molecules. Additional hydrogen bonds connect adjacent dimers to form infinite sheets normal to the b axis. The water molecules are found mainly in the interstices between the sheets. [Leu5]Enkephalin crystallizes as a monohydrate that is isomorphous with the [Met5]enkephalin structure with respect to the beta-sheet but different with respect to the tyrosine and phenylalanine side-chain conformations and water content. The peptide chains in both structures are fully extended and more nearly planar than pleated. The planes of the peptide chains in the dimers form an angle of 143.3 degrees with one another in [Met5]enkephalin and 156.0 degrees in [Leu5]enkephalin. This produces a zigzag pattern or pleat in the beta-sheets perpendicular to the direction of the peptide chains and, therefore, perpendicular to the normal beta-sheet pleat. The average repeat distance between Ni and Ni+2 in the peptide chains of both structures is 7.10 A, versus an ideal value of 6.68 A.
Topics: Crystallography; Enkephalin, Leucine; Enkephalin, Methionine; Humans; Hydrogen Bonding; Protein Conformation
PubMed: 3458181
DOI: 10.1073/pnas.83.10.3272 -
Fertility and Sterility Nov 1985Immunoreactive (IR) beta-endorphin (beta-EP) and met-enkephalin (MET-ENK) have been found in peritoneal fluid (PF) and ovarian follicular fluid (FF). Gel chromatography...
Immunoreactive (IR) beta-endorphin (beta-EP) and met-enkephalin (MET-ENK) have been found in peritoneal fluid (PF) and ovarian follicular fluid (FF). Gel chromatography also revealed the presence of coeluting IR beta-lipotropin and gamma-lipotropin. IR beta-EP and IR MET-ENK levels in healthy menstruating women were from 10 to 40 times higher than those present in circulating plasma, which indicated a possible local production. The highest concentrations of IR beta-EP in FF were found in the largest follicles, whereas in the PF they correlated with the luteal period of the menstrual cycle and with progesterone concentrations. No relevant changes in IR MET-ENK were detected in the FF or in the PF in relation to the phase of the menstrual cycle. In postmenopausal women, the concentrations of the two IR opioid peptides were undetectable in both fluids.
Topics: Adult; Ascitic Fluid; Chromatography, Gel; Chromatography, High Pressure Liquid; Endorphins; Enkephalin, Methionine; Female; Humans; Luteal Phase; Menopause; Middle Aged; Ovarian Follicle; Progesterone; beta-Endorphin; beta-Lipotropin
PubMed: 2932351
DOI: 10.1016/s0015-0282(16)48976-4 -
The Journal of Neuroscience : the... Sep 1983Regulation of cellular content of the endogenous opioid peptides Met5-enkephalin and Leu5-enkephalin was investigated in neuroblastoma X glioma hybrid cells NG108-15...
Regulation of cellular content of the endogenous opioid peptides Met5-enkephalin and Leu5-enkephalin was investigated in neuroblastoma X glioma hybrid cells NG108-15 grown in both serum-supplemented and serum-free defined media. Untreated cells and cells induced to differentiate were stained using anti-Met5-enkephalin and anti-Leu5-enkephalin with the peroxidase-antiperoxidase immunocytochemical technique at the light microscopic level. In untreated NG108-15 cells grown in serum-supplemented medium, intense enkephalin-like immunoreactivity was localized in cell bodies and short processes of a select population of cells. The volume fraction of stained untreated cells remained constant throughout the time period investigated. When cells were induced to differentiate with N6,O2'-dibutyryl adenosine 3':5'-cyclic monophosphate (dBcAMP) or 8-bromo cyclic adenosine monophosphate (1.0 mM) treatment for 5 days, staining was found throughout the cytoplasm of perikarya and the extensive processes which were expressed, and the volume fraction of stained cells increased over 2-fold. Receptor-mediated stimulation of adenylate cyclase by prostaglandin E1 (10 microM) for 5 days produced results similar to those with dBcAMP. Pure cultures of differentiated cells with intense staining were obtained by further treatment of cultures, grown in the presence or absence of dBcAMP, with arabinosylcytosine (araC). Untreated, dBcAMP-treated and araC-treated NG108-15 cells grown in defined medium expressed staining patterns and volume fractions of stained cells similar to those grown in serum-supplemented medium; sodium butyrate (1.0 mM), however, increased the volume fraction of stained cells grown in defined medium over 3-fold, whereas it had little effect on staining of cells grown with serum. The presence of both Met5- and Leu5-enkephalin-like activities in NG108-15 cells was confirmed in acid extracts of cells by radioreceptor assay after separation by reverse phase high pressure liquid chromatography. Induction of differentiation in NG108-15 cells by dBcAMP treatment increased the cellular concentration of both enkephalins to over 2 times the levels found in untreated cells. The biochemical analysis for Met5-enkephalin- and Leu5-enkephalin-like activity compared well with the immunocytochemical data indicating that the enkephalin content is correlated with the state of differentiation of NG108-15 cells.
Topics: 8-Bromo Cyclic Adenosine Monophosphate; Bucladesine; Cell Differentiation; Culture Media; Cyclic AMP; Enkephalin, Leucine; Enkephalin, Methionine; Glioma; Hybrid Cells; Immunochemistry; Neuroblastoma; Staining and Labeling
PubMed: 6193253
DOI: 10.1523/JNEUROSCI.03-09-01713.1983 -
British Journal of Pharmacology Dec 1980The inhibitory effects of intracerebroventricular administration of saline on the plasma corticosterone response to ether stress in mice was reduced by Met-enkephalin...
The inhibitory effects of intracerebroventricular administration of saline on the plasma corticosterone response to ether stress in mice was reduced by Met-enkephalin and enhanced by Leu-enkephalin. When administered simultaneously the effects of the two peptides opposed each other. Met and Leu-enkephalin may subserve different physiological functions in the response of the hypothalamus-pituitary-adrenal system to stress.
Topics: Animals; Corticosterone; Endorphins; Enkephalin, Leucine; Enkephalin, Methionine; Enkephalins; Ether; Ethyl Ethers; Hypothalamo-Hypophyseal System; Male; Mice; Pituitary-Adrenal System; Stress, Physiological
PubMed: 7470727
DOI: 10.1111/j.1476-5381.1980.tb09767.x -
Endocrinologia Japonica Aug 1985The present study was performed to investigate whether or not there were enkephalins in plasma and urine in normal subjects and in patients with various diseases. Two...
The present study was performed to investigate whether or not there were enkephalins in plasma and urine in normal subjects and in patients with various diseases. Two kinds of antisera were developed to detect M-enk and L-enk. One has specific affinity with the C-terminus of methionine-enkephalin sulfoxide (M-O-enk), the oxidized form of M-enk, and the other with the N-terminus of L-enk. M-enk-like substance (MELS) was present in blood and urine in normal subjects, but not L-enk-like substance (LELS). Plasma MELS and its urinary output averaged 38 +/- 14 pg/ml (N = 19) and 605 +/- 235 ng/day (N = 15, M. +/- S.D.), respectively. There was a significant increase in plasma MELS and its urinary output in patients with pheochromocytoma. Plasma MELS did not show any significant increase or decrease in Cushing's disease. Addison's disease, panhypopituitarism or chronic glomerulonephritis. The urinary output of MELS was significantly increased in patients with essential hypertension, renovascular hypertension and primary aldosteronism, but was decreased in central diabetes insipidus.
Topics: Addison Disease; Cross Reactions; Cushing Syndrome; Enkephalin, Leucine; Enkephalin, Methionine; Glomerulonephritis; Humans; Hypotension; Pheochromocytoma; Radioimmunoassay
PubMed: 4085413
DOI: 10.1507/endocrj1954.32.517