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James E Zadina - One of the best experts on this subject based on the ideXlab platform.

  • Mu-opioid receptor is present in dendritic targets of Endomorphin-2 axon terminals in the nuclei of the solitary tract.
    Neuroscience, 2005
    Co-Authors: Marc Silverman, Sam M. Hermes, James E Zadina, Sue A. Aicher
    Abstract:

    Endomorphins represent a group of endogenous opioid peptides with high affinity for the mu-opioid receptor. In the brainstem, Endomorphin-2 is found in trigeminal dorsal horn and the nuclei of the solitary tract, suggesting its presence in both nociceptive and visceral primary afferents. If Endomorphin-2 were an endogenous ligand for the mu-opioid receptor, we would expect to find the receptor at cellular sites in close association with the peptide. We used dual-labeling immunocytochemistry combined with electron microscopy to examine interactions between Endomorphin-2-immunoreactive and mu-opioid receptor-immunoreactive profiles within the nuclei of the solitary tract in the rat. Endomorphin-2-immunoreactivity was found primarily in unmyelinated axons and axon terminals in nuclei of the solitary tract and the majority of these terminals contained dense core vesicles. Endomorphin-2-immunoreactive axon terminals often formed asymmetric synapses with dendritic spines lacking mu-opioid receptor-immunoreactivity, but mu-opioid receptor-immunoreactivity was found in many of the larger dendritic targets of Endomorphin-2-immunoreactive terminals. Thus, mu-opioid receptor-immunoreactivity was found in the postsynaptic targets of Endomorphin-2-immunoreactive axon terminals, consistent with the hypothesis that Endomorphin-2 is an endogenous ligand for this receptor within the nuclei of the solitary tract. A small number of Endomorphin-2-immunoreactive somata, dendrites, and axon terminals also contained mu-opioid receptor-immunoreactivity. Cells that contain both the opioid peptide and its receptor may be a substrate for potential autoregulation of nuclei of the solitary tract neurons by opioid ligands. Finally, using tract tracing and confocal microscopy, we found Endomorphin-2-immunoreactivity in a subset of vagal afferents. Together these findings support the hypothesis that Endomorphin-2 is a ligand for the mu-opioid receptor within nuclei of the solitary tract and that the peptide is at least partially derived from primary visceral afferents.

  • Postnatal development of ectopic sensory fibers containing Endomorphin-2 in the white matter of the spinal cord of a transgenic mouse expressing nerve growth factor in oligodendrocytes
    Neuroscience, 2005
    Co-Authors: H.n. Dorfman, James E Zadina, Andrea L Bailey, M. St. Louis, Alfredo Ribeiro-da-silva
    Abstract:

    Transgenic mice ectopically expressing nerve growth factor in oligodendrocytes have high levels of nerve growth factor immunoreactivity in the white matter of the spinal cord from birth until 2 months of age. The nerve growth factor over-expression leads to the appearance of ectopic substance P containing sensory fibers in the white matter of the spinal cord that persist throughout the life of the animal. These transgenic mice have been found to display hypersensitivity to a thermal stimulus following a sensitizing pinch stimulus known to release endogenous substance P. Surprisingly, this hypersensitivity is completely reversed following the administration of morphine, to the extent that transgenic mice become less sensitive to pain than the wild type mice given morphine. Endomorphin-2, an endogenous opioid peptide, has been found co-localized with substance P in primary sensory fibers in the spinal cord. In this study, we show that the ectopic fibers also express Endomorphin-2, and describe the postnatal development of such expression, as detected by immunocytochemistry. We confirmed that Endomorphin-2 expression starts later in the postnatal period than substance P. Surprisingly, transgenic animals had delayed appearance of Endomorphin-2 in the superficial dorsal horn, compared with wild type, and expressed particularly high levels of Endomorphin-2 immunoreactivity in the ectopic fibers from postnatal days 10-30, coinciding with the peak of nerve growth factor expression in oligodendrocytes. Endomorphin-2 immunoreactivity was still readily detected in ectopic fibers of 120-day-old animals. Furthermore, we detected immunoreactivity for the mu-opioid receptor in the ectopic fibers, where it was co-localized with Endomorphin-2 immunoreactivity. In the superficial dorsal horn, there were no apparent differences in the distribution and intensity of mu-opioid receptor immunoreactivity between wild type and transgenic animals. Taken together, these data could provide an explanation for the enhanced effect of opioid analgesics in transgenic mice, when compared with control mice, as well as provide the basis for studies of the postnatal development of the hyperalgesia and allodynia demonstrated by these animals.

  • Endomorphin-2 axon terminals contact mu-opioid receptor-containing dendrites in trigeminal dorsal horn.
    Brain research, 2003
    Co-Authors: Sue A. Aicher, Jennifer L. Mitchell, Kristin C. Swanson, James E Zadina
    Abstract:

    The Endomorphins represent a novel group of endogenous opioid peptides that have high affinity for the mu-opioid receptor (MOR1). Endomorphin-2 is present in high density in the spinal and trigeminal dorsal horns and is localized to primary afferents. If Endomorphin-2 were an endogenous ligand for the MOR1, we would expect to find the receptor at cellular sites in close association with the peptide. We used dual-labeling immunocytochemical methods combined with electron microscopy to determine if a cellular substrate exists for functional interactions between Endomorphin-2 and MOR1. We confirmed the localization of Endomorphin-2 to unmyelinated axons and axon terminals in the trigeminal dorsal horn. A small proportion of these Endomorphin-2 axons contained MOR1, but many of the dendritic targets of Endomorphin-2 terminals contained MOR1. Consistent with previous studies, Endomorphin-2 was contained primarily in dense core vesicles and MOR1 was located primarily at non-synaptic sites. These morphological characteristics are consistent with the hypothesis that peptides are released extra-synaptically and their receptors may be located at sites distal to the synaptic junction. These anatomical data support the hypothesis that Endomorphin-2 is a ligand for MORs in the trigeminal dorsal horn, particularly at postsynaptic sites.

  • Electron microscopic examination of the Endomorphin 2-like immunoreactive neurons in the rat hypothalamus.
    Brain research, 2003
    Co-Authors: Q-p Wang, James E Zadina, Abba J Kastin, J-l Guan, S Shioda
    Abstract:

    Endomorphins are endogenous opioid peptides with high affinity and selectivity for the mu-opioid receptor. In the present study, we examined the morphology of the Endomorphin 2-like immunoreactive (EM2-LI) neurons in the hypothalamus at the light and electron microscopic levels. At the light microscopic level, EM2-LI neurons were found mostly distributed in the regions between the dorsomedial and ventromedial hypothalamic nuclei and the region near the third ventricle. At the electron microscopic level, EM2-LI perikarya could be divided into two groups. Type I perikarya contained relatively undeveloped endoplasmic reticulum and Golgi apparatus while type II perikarya contained well-developed rough-surfaced endoplasmic reticulum and Golgi apparatus. Both type I and type II neurons contained numerous EM2-LI dense-cored vesicles. Type II perikarya and dendrites received synapses and showed immunoreactivity in the endoplasmic reticulum and Golgi apparatus. EM2-LI axon terminals formed synapses with both immunonegative and immunopositive dendrites. In some cases, the axon terminals contained both immunonegative and immunopositive dense-cored vesicles. EM2-LI neurons often had synaptic relationships with neurons containing immunonegative dense-cored vesicles. Myelinated axon shafts containing EM2-LI were also found. This first demonstration of the ultrastructure and synaptic relationships of EM2-LI neurons in the hypothalamus provides morphological evidence that suggests (1) Endomorphin 2-containing neurons modulate physiological function through synaptic relationships; (2) Endomorphin 2 may coexist with other neurotransmitters in the same neurons; and (3) Endomorphin 2-containing neurons could modulate other Endomorphin 2-containing neurons as well as those containing other neurotransmitters.

  • Endomorphin-2 immunoreactivity in the cervical dorsal horn of the rat spinal cord at the electron microscopic level.
    Neuroscience, 2002
    Co-Authors: Qing-ping Wang, James E Zadina, Abba J Kastin, Jian-lian Guan, Hisayuki Funahashi, Seiji Shioda
    Abstract:

    Abstract Endomorphin-2 is a newly discovered endogenous opioid peptide with high affinity and selectivity for the μ-opioid receptor, and potent analgesic activity, particularly in the spinal cord. Using immunoelectron microscopy, we examined the ultrastructure of the Endomorphin-2-like immunoreactive processes and their synaptic relationships in the spinal cord. Endomorphin-2-like immunopositive dense-cored vesicles were observed in many axon terminals, and, in a few cases, were observed together with immunonegative dense-cored vesicles. Immunopositive axons with or without myelination were also observed. The Endomorphin-2-like immunoreactive axon terminals formed synapses with both immunopositive and immunonegative processes. Most synapses were asymmetrical, but symmetrical synapses were also found. Examples of axo-dendritic, axo-somatic and axo-axonic contacts were observed. This first demonstration of the ultrastructure and synaptic relationships of Endomorphin-2-like immunoreactive axon terminals in the spinal cord dorsal horn provides morphological evidence that this peptide functions as a transmitter regulating pain processes.

Leon F Tseng - One of the best experts on this subject based on the ideXlab platform.

  • Paradoxical hyperalgesia induced by mu-opioid receptor agonist Endomorphin-2, but not Endomorphin-1, microinjected into the centromedial amygdala of the rat.
    European journal of pharmacology, 2006
    Co-Authors: Maia Terashvili, Emma T. Schwasinger, Leon F Tseng
    Abstract:

    The effects of Endomorphin-2 or Endomorphin-1 microinjected into the centromedial amygdala on the thermally-induced tail-flick response were studied in male CD rats. Microinjection of Endomorphin-2 (8.7-35.0 nmol) given into the centromedial amygdala time- and dose-dependently decreased the tail-flick latencies. On the other hand, Endomorphin-1 (8-32.6 nmol) given into the same site did not cause any change of the tail-flick latency. However, Endomorphin-1 (32.6 nmol) or Endomorphin-2 (35.0 nmol) given into the basolateral site of amygdala did not affect the tail-flick latency. Pretreatment with the antiserum against dynorphin A(1-17) (200 microg) significantly reversed the decrease of the tail-flick latency induced by Endomorphin-2. The decrease of the tail-flick latency induced by Endomorphin-2 was also blocked by the Endomorphin-2 selective micro-opioid receptor antagonist 3-methoxynaltrexone (6.4 pmol) and by the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 (30 nmol), but not by the kappa-opioid receptor antagonist nor-binaltorphimine (6.6 nmol). It is concluded that Endomorphin-2, but not Endomorphin-1, given into the centromedial amygdala stimulates a 3-methoxynaltrexone-sensitive mu-opioid receptor subtype to induce the release of dynorphin A(1-17), which then acts on the NMDA receptor, but not kappa-opioid receptor for producing hyperalgesia. This conclusion is further supported by the additional findings that dynorphin A(1-17) (2.3 nmol) given into the centromedial amygdala also caused the decrease of the tail-flick latency, which was similarly blocked by the NMDA receptor antagonist MK-801 (30 nmol), but not kappa-opioid receptor antagonist nor-binaltorphimine (6.6 nmol).

  • Paradoxical hyperalgesia induced by μ-opioid receptor agonist Endomorphin-2, but not Endomorphin-1, microinjected into the centromedial amygdala of the rat
    European Journal of Pharmacology, 2006
    Co-Authors: Maia Terashvili, Emma T. Schwasinger, Leon F Tseng
    Abstract:

    The effects of Endomorphin-2 or Endomorphin-1 microinjected into the centromedial amygdala on the thermally induced tail-flick response were studied in male CD rats. Microinjection of Endomorphin-2 (8.7–35.0 nmol) given into the centromedial amygdala time- and dose-dependently decreased the tail-flick latencies. On the other hand, Endomorphin-1 (8–32.6 nmol) given into the same site did not cause any change of the tail-flick latency. However, Endomorphin-1 (32.6 nmol) or Endomorphin-2 (35.0 nmol) given into the basolateral site of amygdala did not affect the tail-flick latency. Pretreatment with the antiserum against dynorphin A(1–17) (200 µg) significantly reversed the decrease of the tail-flick latency induced by Endomorphin-2. The decrease of the tail-flick latency induced by Endomorphin-2 was also blocked by the Endomorphin-2 selective μ-opioid receptor antagonist 3-methoxynaltrexone (6.4 pmol) and by the Nmethyl-D-aspartate (NMDA) receptor antagonist MK-801 (30 nmol), but not by the κ-opioid receptor antagonist nor-binaltorphimine (6.6 nmol). It is concluded that Endomorphin-2, but not Endomorphin-1, given into the centromedial amygdala stimulates a 3-methoxynaltrexone-sensitive μ-opioid receptor subtype to induce the release of dynorphin A(1–17), which then acts on the NMDA receptor, but not κ-opioid receptor for producing hyperalgesia. This conclusion is further supported by the additional findings that dynorphin A(1–17) (2.3 nmol) given into the centromedial amygdala also caused the decrease of the tail-flick latency, which was similarly blocked by the NMDA receptor antagonist MK-801 (30 nmol), but not κ-opioid receptor antagonist nor-binaltorphimine (6.6 nmol).

  • Increased release of immunoreactive dynorphin A1-17 from the spinal cord after intrathecal treatment with Endomorphin-2 in anesthetized rats.
    European journal of pharmacology, 2004
    Co-Authors: Randy J. Leitermann, Hirokazu Mizoguchi, Andrew D. Clithero, Maia Terashvili, Franklin Chen, Leon F Tseng
    Abstract:

    We previously demonstrated pretreatment with antiserum against dynorphin A1-17 attenuates Endomorphin-2-induced analgesia and antianalgesia, suggesting that these Endomorphin-2 effects are mediated by the release of dynorphin A1-17. Lumbar-cisternal spinal perfusion was used to measure the release of immunoreactive dynorphin A1-17 into spinal perfusates from urethane-anesthetized rats following Endomorphin-2 or Endomorphin-1 treatment within the perfusion solution. Treatment with Endomorphin-2 (5-50 nmol) for 3 min caused a dose-dependent increase of immunoreactive dynorphin A1-17 in spinal perfusates, with a maximal increase detected between 24 and 48 min after Endomorphin-2 treatment, while levels returned to baseline within 60 min. Endomorphin-2-induced release of immunoreactive dynorphin A1-17 was attenuated by pretreatment with mu-opioid receptor antagonist naloxone or 3-methoxynaltrexone. Endomorphin-1 induced a slight increase in immunoreactive dynorphin1-17 as well, but only at the highest dose used (50 nmol). Our results suggest that Endomorphin-2 stimulated a specific subtype of mu-opioid receptor to induce the release of immunoreactive dynorphin A1-17 in spinal cords of rats.

  • Opposite conditioned place preference responses to Endomorphin-1 and Endomorphin-2 in the mouse.
    Neuroscience letters, 2004
    Co-Authors: Ryan S Macdougall, Andrew D. Clithero, Randy J. Leitermann, Maia Terashvili, Leon F Tseng
    Abstract:

    Abstract An unbiased conditioned place preference paradigm was used to evaluate the reward effect of selective endogenous μ-opioid ligands, Endomorphin-1 and Endomorphin-2, in male CD-1 mice. Pre- and post-conditioning free-movement were measured on day 1 and day 5, respectively. Conditioning sessions were conducted twice daily from day 2 through day 4 consisting of the alternate injection of conditioning drug or vehicle. Intracerebroventricular (i.c.v.) injection of Endomorphin-1 (0.3–10 μg) induced place preference in a dose-dependent manner; whereas, Endomorphin-2 (1–10 μg) dose-dependently induced place aversion. Both Endomorphin-1-induced place preference and Endomorphin-2-induced place aversion were blocked by pretreatment i.c.v. with μ-opioid receptor antagonist, β-funaltrexamine. Selective δ-opioid receptor antagonist, naltrindole, co-administered i.c.v. with Endomorphin-1 or Endomorphin-2 did not affect reward effect. However, Endomorphin-2-induced place aversion, but not Endomorphin-1-induced place preference, was blocked by the i.c.v.-administered selective κ-opioid receptor antagonist, WIN 44,441-3. It is concluded that Endomorphin-1 produces conditioned place preference, which is mediated by the stimulation of μ-, but not δ- or κ-opioid receptors, while Endomorphin-2 produces conditioned place aversion, which is mediated by the stimulation of μ- and κ-, but not δ-opioid receptors.

  • d-Pro2-Endomorphin-1 andd-Pro2-Endomorphin-2, Respectively, Attenuate the Antinociception Induced by Endomorphin-1 and Endomorphin-2 Given Intrathecally in the Mouse
    The Journal of pharmacology and experimental therapeutics, 2002
    Co-Authors: Kuei-chun Hung, Tsukasa Sakurada, Shinobu Sakurada, Hirokazu Mizoguchi, Toru Okayama, Tsutomu Fujimura, Kimie Murayama, James M. Fujimoto, Leon F Tseng
    Abstract:

    First, the antinociception with the tail-flick test ofd-Pro2-Endomorphin-1 andd-Pro2-Endomorphin-2 given i.t. was compared with that produced by Endomorphin-1 and -2 in male CD-1 mice. High doses of d-Pro2-Endomorphin-1 (0.2–0.4 pmol) and d-Pro2-Endomorphin-2 (300–800 pmol) given i.t. produced antinociception with low intrinsic activity [about 25% maximum possible effect (MPE)] compared with that of Endomorphin-1 (16.4 nmol) and Endomorphin-2 (35 nmol) (>90% MPE). Second, coadministration of a low dose ofd-Pro2-Endomorphin-1 (0.1 pmol), which given alone did not affect the tail-flick latencies, markedly attenuated the antinociception induced by Endomorphin-1 (16.4 nmol) but not by Endomorphin-2 (35 nmol). Similarly, coadministration of a low dose ofd-Pro2-Endomorphin-2 (200 pmol), which given alone did not affect the tail-flick latencies, significantly attenuated the antinociception induced by Endomorphin-2 (35 nmol) and, to a much lesser extent, Endomorphin-1 (16.4 nmol). It is concluded thatd-Pro2-Endomorphin-1 andd-Pro2-Endomorphin-2 at high doses were partial opioid receptor agonists to produce antinociception, and at low doses were opioid receptor antagonists to block selectively the antinociception induced by Endomorphin-1 and Endomorphin-2, respectively. Furthermore, our results are consistent with the view that the antinociception induced by Endomorphin-1 and Endomorphin-2 is mediated by the stimulation of different subtypes of μ-opioid receptors.

Anna Janecka - One of the best experts on this subject based on the ideXlab platform.

  • Correction for "Synthesis of Mixed Opioid Affinity Cyclic Endomorphin-2 Analogues with Fluorinated Phenylalanines".
    ACS medicinal chemistry letters, 2016
    Co-Authors: Justyna Piekielna, Csaba Tömböly, Jean-claude Do Rego, Renata Perlikowska, Jean Luc Do-rego, Maria Camilla Cerlesi, Girolamo Calo, Alicja Kluczyk, Krzysztof Łapiński, Anna Janecka
    Abstract:

    Our manuscript by Piekielna et al. entitled “Synthesis of mixed opioid affinity cyclic Endomorphin-2 analogues with fluorinated phenylalanines” (DOI: 10.1021/acsmedchemlett.5b00056) was published in ACS Medicinal Chemistry Letters in April 2015.

  • Structural comparison of Endomorphin-2 and its conformationally restricted analog
    Open Chemistry, 2012
    Co-Authors: Attila Borics, Géza Tóth, Jakub Fichna, Katarzyna Gach, Dariusz Sobolewski, Anna Janecka
    Abstract:

    In the present study, the effect of a conformational constraint introduced into the Endomorphin-2 (Tyr-Pro-Phe-Phe-NH2, EM-2) structure was studied using computational analysis and radioligand binding assay. EM-2 was modified by connecting nitrogen atoms of both phenylalanine residues by a methylene bridge. The obtained analog did not bind to the µ- or δ-opioid receptors in the in vitro studies. The computational analysis of this analog showed twisted, type IV turns and the absence of canonical β-turns typical for the EM-2 structure, which can be explained by the lack of hydrogen bonds involving Phe4. Our results show that the introduction of chemical constraint in the EM-2 structure has a significant effect on opioid receptor affinity and in vitro bioactivity.

  • Novel highly potent μ-opioid receptor antagonist based on Endomorphin-2 structure
    Bioorganic & medicinal chemistry letters, 2008
    Co-Authors: Jakub Fichna, Jean Costentin, Jean-claude Do Rego, Tomasz Janecki, Renata Staniszewska, Jeroen Poels, Jozef Vanden Broeck, Peter W. Schiller, Anna Janecka
    Abstract:

    Abstract The μ-opioid agonists Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) and Endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) exhibit an extremely high selectivity for the μ-opioid receptor and thus represent a potential framework for modification into μ-antagonists. Here we report on the synthesis and biological evaluation of novel [ d -2-Nal4]Endomorphin-2 analogs, [Sar2, d -2-Nal4]Endomorphin-2 and [Dmt1,Sar2, d -2-Nal4]Endomorphin-2 (Dmt = 2′6′-dimethyltyrosine; Sar = N-methylglycine, sarcosine; d -2-Nal = 3-(2-naphthyl)- d -alanine). [Dmt1,Sar2, d -2-Nal4]Endomorphin-2 possessed very high affinity for the μ-opioid receptor (IC50 = 0.01 ± 0.001 nM) and turned out to be a potent and extremely selective μ-opioid receptor antagonist, as judged by the in vitro aequorin luminescence-based calcium assay (pA2 = 9.19). However, in the in vivo hot plate test in mice this analog was less potent than our earlier μ-opioid receptor antagonist, [Dmt1, d -2-Nal4]Endomorphin-2 (antanal-2). The exceptional μ-opioid receptor in vitro activity and selectivity of [Dmt1, Sar2, d -2-Nal4]Endomorphin-2 makes this analog a valuable pharmacological tool, but further modifications are needed to improve its in vivo profile.

  • Antidepressant-Like Effect of Endomorphin-1 and Endomorphin-2 in Mice
    Neuropsychopharmacology, 2007
    Co-Authors: Jakub Fichna, Anna Janecka, Mariola Piestrzeniewicz, Jean Costentin, Jean-claude Do Rego
    Abstract:

    Endomorphin-1 (Tyr-Pro-Trp-Phe-NH_2) and Endomorphin-2 (Tyr-Pro-Phe-Phe-NH_2) are two recently isolated μ -opioid selective peptides with a potent antinociceptive activity, involved in a number of physiological processes, including food intake, vasomotricity, sexual behavior, as well as neuroendocrine and cardiorespiratory functions. The neuroanatomical distribution of Endomorphins prompted us to study their antidepressant activity in two animal behavioral models of depression: forced-swimming and tail-suspension tests. In both tests, the intracerebroventricular (i.c.v.) injection of either Endomorphin-1 or Endomorphin-2 significantly decreased the duration of immobility, interpreted as an expression of ‘behavioral despair’, which could be related to the depression syndrome. These effects of Endomorphins did not result from the stimulation of the animal motor activity. We have also demonstrated that the antidepressant-like effect of Endomorphins was antagonized by the universal opioid antagonist, naloxone and the μ -opioid receptor selective antagonist, β -funaltrexamine. In contrast, this effect was not antagonized by δ - and κ -opioid receptor selective antagonists, naltrindole and nor-binaltorphimine, respectively. The results of the present study demonstrate that Endomorphin-1 and Endomorphin-2 produce potent antidepressant-like effects after i.c.v. injection in mice. We may suggest that Endomorphins and the μ -opioid receptors might be involved in the physiopathology of depressive disorders, and that the Endomorphinergic system could serve as a novel target for the development of antidepressant drugs.

  • Antidepressant-like effect of Endomorphin-1 and Endomorphin-2 in mice.
    Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 2006
    Co-Authors: Jakub Fichna, Anna Janecka, Mariola Piestrzeniewicz, Jean Costentin, Jean-claude Do Rego
    Abstract:

    Endomorphin-1 (Tyr-Pro-Trp-Phe-NH(2)) and Endomorphin-2 (Tyr-Pro-Phe-Phe-NH(2)) are two recently isolated mu-opioid selective peptides with a potent antinociceptive activity, involved in a number of physiological processes, including food intake, vasomotricity, sexual behavior, as well as neuroendocrine and cardiorespiratory functions. The neuroanatomical distribution of Endomorphins prompted us to study their antidepressant activity in two animal behavioral models of depression: forced-swimming and tail-suspension tests. In both tests, the intracerebroventricular (i.c.v.) injection of either Endomorphin-1 or Endomorphin-2 significantly decreased the duration of immobility, interpreted as an expression of 'behavioral despair', which could be related to the depression syndrome. These effects of Endomorphins did not result from the stimulation of the animal motor activity. We have also demonstrated that the antidepressant-like effect of Endomorphins was antagonized by the universal opioid antagonist, naloxone and the mu-opioid receptor selective antagonist, beta-funaltrexamine. In contrast, this effect was not antagonized by delta- and kappa-opioid receptor selective antagonists, naltrindole and nor-binaltorphimine, respectively. The results of the present study demonstrate that Endomorphin-1 and Endomorphin-2 produce potent antidepressant-like effects after i.c.v. injection in mice. We may suggest that Endomorphins and the mu-opioid receptors might be involved in the physiopathology of depressive disorders, and that the Endomorphinergic system could serve as a novel target for the development of antidepressant drugs.

Géza Tóth - One of the best experts on this subject based on the ideXlab platform.

  • Transport characteristics of Endomorphin-2 analogues in brain capillary endothelial cells.
    Chemical biology & drug design, 2012
    Co-Authors: Jayapal Reddy Mallareddy, Géza Tóth, Csilla Fazakas, Judit Molnár, Péter Nagyőszi, Andrzej W. Lipkowski, István A. Krizbai, Imola Wilhelm
    Abstract:

    Because of their poor metabolic stability and limited blood-brain barrier permeability, Endomorphins have a low analgesic efficacy when administered systemically. Therefore, it is of great importance to design analogues with improved peptidase resistance and better delivery to the central nervous system. Recently, novel Endomorphin-2 analogues have been synthesized, which proved to bind with high affinity and selectivity to the μ-opioid receptors and showed proteolytic resistance. In this study, we have analysed the transport characteristics of Endomorphin-2 and three of its analogues [Dmt-Pro-Phe-Phe-NH(2) , Tyr-(1S,2R)Acpc-Phe-Phe-NH(2) and Tyr-(1S,2R)Achc-Phe-Phe-NH(2) ] using an in vitro blood-brain barrier model. The lipophilicity of the analogues, as assessed by their octanol/water partition coefficients, was higher than that of Endomorphin-2. The flux of all four peptides from the apical (blood) side to the basolateral (brain) side was not saturable in the 10nm-1mm concentration range, suggesting that a passive mechanism plays a major role in their transport. The permeability coefficient of the analogues was significantly higher than that of Endomorphin-2, suggesting increased blood-brain barrier penetration properties. We conclude that because of their good peptidase resistance and improved transport through brain endothelial cells, these Endomorphin-2 analogues will have better analgesic properties in vivo.

  • Structural comparison of Endomorphin-2 and its conformationally restricted analog
    Open Chemistry, 2012
    Co-Authors: Attila Borics, Géza Tóth, Jakub Fichna, Katarzyna Gach, Dariusz Sobolewski, Anna Janecka
    Abstract:

    In the present study, the effect of a conformational constraint introduced into the Endomorphin-2 (Tyr-Pro-Phe-Phe-NH2, EM-2) structure was studied using computational analysis and radioligand binding assay. EM-2 was modified by connecting nitrogen atoms of both phenylalanine residues by a methylene bridge. The obtained analog did not bind to the µ- or δ-opioid receptors in the in vitro studies. The computational analysis of this analog showed twisted, type IV turns and the absence of canonical β-turns typical for the EM-2 structure, which can be explained by the lack of hydrogen bonds involving Phe4. Our results show that the introduction of chemical constraint in the EM-2 structure has a significant effect on opioid receptor affinity and in vitro bioactivity.

  • Immunoreactive Endomorphin 2 is generated extracellularly in rat isolated L4,5 dorsal root ganglia by DPP-IV.
    Regulatory Peptides, 2009
    Co-Authors: András Z. Rónai, Géza Tóth, Erzsébet Szemenyei, Zsuzsanna Darula, Kornél Király, Andrea Szebeni, Zoltán Prohászka, Ibolya Till, Balázs Szalay, Erzsébet Kató
    Abstract:

    Abstract Background and aims The gene(s) encoding for Endomorphin precursor(s) is/are still unknown. We have raised the possibility of and did find some evidence for a potential de novo biosynthetic route starting from Tyr-Pro precursor. To pursue further this possibility we measured the generation of immunoreactive Endomorphin-2 (E2-IR) in adult rat isolated L4,5 dorsal root ganglia. Results and conclusions In rat isolated dorsal root ganglia the combination of presumed biosynthetic precursor of Endomorphin 2 (E2), Tyr-Pro with the dipeptidyl peptidase IV (DPP-IV) inhibitor Ile-Pro-Ile generated 1.60 ± 0.37 pg/mg Wet Tissue Weight_30min E2-IR in the bathing fluid (n = 4) with an 8-fold increase upon depolarization whereas the tissue content was low (0.50 ± 0.08 pg/mg_WTW). Substance P, as determined by ELISA in the pilot experiments, was found almost exclusively within the tissues. It is concluded that E2-IR was generated extracellularly by a membrane-bound DPP-IV, which was switched to “synthase” mode by the hydrolase inhibitor Ile-Pro-Ile. DPP-IV was depolarization-sensitive in “synthase” functional mode.

  • Detection of a novel immunoreactive Endomorphin 2-like peptide in rat brain extracts.
    Regulatory peptides, 2008
    Co-Authors: Erzsébet Szemenyei, Géza Tóth, István Barna, Zsuzsa Mergl, Attila Keresztes, Zsuzsanna Darula, Erzsébet Kató, András Z. Rónai
    Abstract:

    To pursue further the possible de novo biosynthetic pathway of Endomorphins in rat brain we raised antibodies to Endomorphin-2 conjugate in rabbits. Antiserum R1 recognized Endomorphin-2 with good selectivity as compared to Endomorphin-1 with a median detection value of 65.5+/-7.5 pg/tube (n=7), whereas R4 antiserum recognized both Endomorphins with similar sensitivity. Neither antisera recognized YP-related di- or tripeptides or YGGF-related opioid sequences (enkephalins, beta-endorphin, dynorphin). Using the same rat brain extraction-RP-HPLC-gradient separation paradigm as previously, antisera detected 144.6+/-40.0 (n=3) pg/g wet brain weight Endomorphin-2-like immunoreactivity in the fraction corresponding to standard Endomorphin-2 retention time and also in the fraction matching Endomorphin-2-OH standard retention time (179.1+/-30.1 pg/g). Since R1 failed to recognize authentic Endomorphin-2-OH, the second immunoreactive species must be different from both Endomorphin-2 and Endomorphin-2-OH. Possible biosynthetic intermediates to Endomorphins, synthetic YPFFG and YPWFG had retention times close to the parent Endomorphin standards in RP-HPLC gradient separation profile. The former was a mu-opioid receptor agonist of medium potency in the in vitro assays (rat brain RBA>P gamma S binding and mouse vas deferens), whereas the latter was a weak mu-opioid receptor agonist with a significant delta-opioid receptorial action as well and a definite indication of partial agonism.

  • Detection of a novel immunoreactive Endomorphin 2-like peptide in rat brain extracts.
    Regulatory Peptides, 2008
    Co-Authors: Erzsébet Szemenyei, Géza Tóth, István Barna, Zsuzsa Mergl, Attila Keresztes, Zsuzsanna Darula, Erzsébet Kató, András Z. Rónai
    Abstract:

    Abstract To pursue further the possible de novo biosynthetic pathway of Endomorphins in rat brain we raised antibodies to Endomorphin-2 conjugate in rabbits. Antiserum R1 recognized Endomorphin-2 with good selectivity as compared to Endomorphin-1 with a median detection value of 65.5 ± 7.5 pg/tube (n = 7), whereas R4 antiserum recognized both Endomorphins with similar sensitivity. Neither antisera recognized YP-related di- or tripeptides or YGGF-related opioid sequences (enkephalins, β-endorphin, dynorphin). Using the same rat brain extraction-RP-HPLC-gradient separation paradigm as previously, antisera detected 144.6 ± 40.0 (n = 3) pg/g wet brain weight Endomorphin-2-like immunoreactivity in the fraction corresponding to standard Endomorphin-2 retention time and also in the fraction matching Endomorphin-2-OH standard retention time (179.1 ± 30.1 pg/g). Since R1 failed to recognize authentic Endomorphin-2-OH, the second immunoreactive species must be different from both Endomorphin-2 and Endomorphin-2-OH. Possible biosynthetic intermediates to Endomorphins, synthetic YPFFG and YPWFG had retention times close to the parent Endomorphin standards in RP-HPLC gradient separation profile. The former was a μ-opioid receptor agonist of medium potency in the in vitro assays (rat brain RBA>PγS binding and mouse vas deferens), whereas the latter was a weak μ-opioid receptor agonist with a significant δ-opioid receptorial action as well and a definite indication of partial agonism.

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  • Structural comparison of Endomorphin-2 and its conformationally restricted analog
    Open Chemistry, 2012
    Co-Authors: Attila Borics, Géza Tóth, Jakub Fichna, Katarzyna Gach, Dariusz Sobolewski, Anna Janecka
    Abstract:

    In the present study, the effect of a conformational constraint introduced into the Endomorphin-2 (Tyr-Pro-Phe-Phe-NH2, EM-2) structure was studied using computational analysis and radioligand binding assay. EM-2 was modified by connecting nitrogen atoms of both phenylalanine residues by a methylene bridge. The obtained analog did not bind to the µ- or δ-opioid receptors in the in vitro studies. The computational analysis of this analog showed twisted, type IV turns and the absence of canonical β-turns typical for the EM-2 structure, which can be explained by the lack of hydrogen bonds involving Phe4. Our results show that the introduction of chemical constraint in the EM-2 structure has a significant effect on opioid receptor affinity and in vitro bioactivity.

  • Novel highly potent μ-opioid receptor antagonist based on Endomorphin-2 structure
    Bioorganic & medicinal chemistry letters, 2008
    Co-Authors: Jakub Fichna, Jean Costentin, Jean-claude Do Rego, Tomasz Janecki, Renata Staniszewska, Jeroen Poels, Jozef Vanden Broeck, Peter W. Schiller, Anna Janecka
    Abstract:

    Abstract The μ-opioid agonists Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) and Endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) exhibit an extremely high selectivity for the μ-opioid receptor and thus represent a potential framework for modification into μ-antagonists. Here we report on the synthesis and biological evaluation of novel [ d -2-Nal4]Endomorphin-2 analogs, [Sar2, d -2-Nal4]Endomorphin-2 and [Dmt1,Sar2, d -2-Nal4]Endomorphin-2 (Dmt = 2′6′-dimethyltyrosine; Sar = N-methylglycine, sarcosine; d -2-Nal = 3-(2-naphthyl)- d -alanine). [Dmt1,Sar2, d -2-Nal4]Endomorphin-2 possessed very high affinity for the μ-opioid receptor (IC50 = 0.01 ± 0.001 nM) and turned out to be a potent and extremely selective μ-opioid receptor antagonist, as judged by the in vitro aequorin luminescence-based calcium assay (pA2 = 9.19). However, in the in vivo hot plate test in mice this analog was less potent than our earlier μ-opioid receptor antagonist, [Dmt1, d -2-Nal4]Endomorphin-2 (antanal-2). The exceptional μ-opioid receptor in vitro activity and selectivity of [Dmt1, Sar2, d -2-Nal4]Endomorphin-2 makes this analog a valuable pharmacological tool, but further modifications are needed to improve its in vivo profile.

  • Antidepressant-Like Effect of Endomorphin-1 and Endomorphin-2 in Mice
    Neuropsychopharmacology, 2007
    Co-Authors: Jakub Fichna, Anna Janecka, Mariola Piestrzeniewicz, Jean Costentin, Jean-claude Do Rego
    Abstract:

    Endomorphin-1 (Tyr-Pro-Trp-Phe-NH_2) and Endomorphin-2 (Tyr-Pro-Phe-Phe-NH_2) are two recently isolated μ -opioid selective peptides with a potent antinociceptive activity, involved in a number of physiological processes, including food intake, vasomotricity, sexual behavior, as well as neuroendocrine and cardiorespiratory functions. The neuroanatomical distribution of Endomorphins prompted us to study their antidepressant activity in two animal behavioral models of depression: forced-swimming and tail-suspension tests. In both tests, the intracerebroventricular (i.c.v.) injection of either Endomorphin-1 or Endomorphin-2 significantly decreased the duration of immobility, interpreted as an expression of ‘behavioral despair’, which could be related to the depression syndrome. These effects of Endomorphins did not result from the stimulation of the animal motor activity. We have also demonstrated that the antidepressant-like effect of Endomorphins was antagonized by the universal opioid antagonist, naloxone and the μ -opioid receptor selective antagonist, β -funaltrexamine. In contrast, this effect was not antagonized by δ - and κ -opioid receptor selective antagonists, naltrindole and nor-binaltorphimine, respectively. The results of the present study demonstrate that Endomorphin-1 and Endomorphin-2 produce potent antidepressant-like effects after i.c.v. injection in mice. We may suggest that Endomorphins and the μ -opioid receptors might be involved in the physiopathology of depressive disorders, and that the Endomorphinergic system could serve as a novel target for the development of antidepressant drugs.

  • Antidepressant-like effect of Endomorphin-1 and Endomorphin-2 in mice.
    Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 2006
    Co-Authors: Jakub Fichna, Anna Janecka, Mariola Piestrzeniewicz, Jean Costentin, Jean-claude Do Rego
    Abstract:

    Endomorphin-1 (Tyr-Pro-Trp-Phe-NH(2)) and Endomorphin-2 (Tyr-Pro-Phe-Phe-NH(2)) are two recently isolated mu-opioid selective peptides with a potent antinociceptive activity, involved in a number of physiological processes, including food intake, vasomotricity, sexual behavior, as well as neuroendocrine and cardiorespiratory functions. The neuroanatomical distribution of Endomorphins prompted us to study their antidepressant activity in two animal behavioral models of depression: forced-swimming and tail-suspension tests. In both tests, the intracerebroventricular (i.c.v.) injection of either Endomorphin-1 or Endomorphin-2 significantly decreased the duration of immobility, interpreted as an expression of 'behavioral despair', which could be related to the depression syndrome. These effects of Endomorphins did not result from the stimulation of the animal motor activity. We have also demonstrated that the antidepressant-like effect of Endomorphins was antagonized by the universal opioid antagonist, naloxone and the mu-opioid receptor selective antagonist, beta-funaltrexamine. In contrast, this effect was not antagonized by delta- and kappa-opioid receptor selective antagonists, naltrindole and nor-binaltorphimine, respectively. The results of the present study demonstrate that Endomorphin-1 and Endomorphin-2 produce potent antidepressant-like effects after i.c.v. injection in mice. We may suggest that Endomorphins and the mu-opioid receptors might be involved in the physiopathology of depressive disorders, and that the Endomorphinergic system could serve as a novel target for the development of antidepressant drugs.

  • [35S]GTPγS binding stimulated by Endomorphin-2 and morphiceptin analogs
    Biochemical and biophysical research communications, 2006
    Co-Authors: Jakub Fichna, Jean Costentin, Jean-claude Do Rego, Piotr Kosson, Peter W. Schiller, Anna Janecka
    Abstract:

    Abstract The ability of several μ-selective opioid peptides to activate G-proteins was measured in rat thalamus membrane preparations. The μ-selective ligands used in this study were three structurally related peptides, Endomorphin-1, Endomorphin-2 and morphiceptin, and their analogs modified in position 3 or 4 by introducing 3-(1-naphthyl)- d -alanine ( d -1-Nal) or 3-(2-naphthyl)- d -alanine ( d -2-Nal). The results obtained for these peptides in [ 35 S]GTPγS binding assay were compared with those obtained for a standard μ-opioid agonist DAMGO. [ d -1-Nal 3 ]Morphiceptin was more potent in G-protein activation (EC 50 value of 82.5 ± 4.5 nM) than DAMGO (EC 50  = 105 ± 9 nM). [ d -2-Nal 3 ]Morphiceptin, as well as Endomorphin-2 analogs substituted in position 4 by either d -1-Nal or d -2-Nal failed to stimulate [ 35 S]GTPγS binding and were shown to be potent antagonists against DAMGO. It seems that the topographical location of the aromatic ring of position 3 and 4 amino acid residues can result in a completely different mode of action, producing either agonists or antagonists.