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General and Comparative Endocrinology Oct 2023Although methionine-enkephalin (M-ENK) is implicated in the regulation of reproductive functions in vertebrates, its function in reptiles is little understood. This...
Although methionine-enkephalin (M-ENK) is implicated in the regulation of reproductive functions in vertebrates, its function in reptiles is little understood. This study aims to elucidate the role of M-ENK on seasonal and follicle stimulating hormone (FSH)-induced ovarian recrudescence in the gecko Hemidactylus frenatus. In the first experiment, administration of 5 µg M-ENK did not affect germinal bed activity or follicular developmental stages I, II, and III (previtellogenic) and IV (vitellogenic), but there were no stage V (vitellogenic) follicles in the ovary. However, there was a significant decrease in the mean numbers of oogonia and primary oocytes in the germinal bed associated with the complete absence of stage IV and V follicles in 25 µg M-ENK-treated lizards in contrast to experimental controls. Furthermore, there was a significant decrease in gonadotropin-releasing hormone - immunoreactive (GnRH-ir) content in the median eminence (ME) and pars distalis (PD) of the pituitary gland and sparse labelling of hypothalamic GnRH-ir neurons in 25 µg M-ENK-treated lizards. In the second experiment, treatment with FSH during the regression phase of the ovarian cycle resulted in the appearance of stage IV and V follicles, in contrast to their absence in the initial controls and treatment controls. However, treatment with 25 µg M-ENK + FSH did not result in the appearance of these follicles, indicating the inhibitory effect of M-ENK on FSH-induced ovarian recrudescence. These findings suggest that M-ENK inhibits the germinal bed and vitellogenic follicular growth in a dose-dependent manner, possibly mediated through the suppression of GnRH release in the ME and PD. In addition, M-ENK may also act at the level of the ovary in the gecko.
Topics: Female; Animals; Ovary; Follicle Stimulating Hormone; Analgesics, Opioid; Ovarian Follicle; Enkephalin, Methionine; Seasons; Gonadotropin-Releasing Hormone; Lizards; Methionine
PubMed: 37536461
DOI: 10.1016/j.ygcen.2023.114353 -
Acta Neurobiologiae Experimentalis 2023In the central nervous system, long‑term effects of a vagotomy include disturbance of monoaminergic activity of the limbic system. Since low vagal activity is observed...
In the central nervous system, long‑term effects of a vagotomy include disturbance of monoaminergic activity of the limbic system. Since low vagal activity is observed in major depression and autism spectrum disorder, the study aimed to determine whether animals fully recovered after subdiaphragmatic vagotomy demonstrates neurochemical indicators of altered well‑being and social component of sickness behavior. Bilateral vagotomy or sham surgery was performed in adult rats. After one month of recovery, rats were challenged with lipopolysaccharide or vehicle to determine the role of central signaling upon sickness. Striatal monoamines and met‑enkephalin concentrations were evaluated using HPLC and RIA methods. We also defined a concentration of immune‑derived plasma met‑enkephalin to establish a long‑term effect of vagotomy on peripheral analgesic mechanisms. The data indicate that 30 days after vagotomy procedure, striatal dopaminergic, serotoninergic, and enkephalinergic neurochemistry was altered, both under physiological and inflammatory conditions. Vagotomy prevented inflammation‑induced increases of plasma met‑enkephalin - an opioid analgesic. Our data suggest that in a long perspective, vagotomized rats may be more sensitive to pain and social stimuli during peripheral inflammation.
Topics: Rats; Animals; Enkephalin, Methionine; Autism Spectrum Disorder; Vagotomy; Vagus Nerve; Inflammation; Amines
PubMed: 37078817
DOI: 10.55782/ane-2023-009 -
Proteome Science Apr 2023Macrophages have a vital role in phagocytosis and antiviral effect against invading influenza viruses. Previously, we found that methionine enkephalin (MENK) inhibited...
Macrophages have a vital role in phagocytosis and antiviral effect against invading influenza viruses. Previously, we found that methionine enkephalin (MENK) inhibited influenza virus infection by upregulating the "antiviral state" of macrophages. To investigate the immunoregulatory mechanism of action of MENK on macrophages, we employed proteomic analysis to identify differentially expressed proteins (DEPs) between macrophages infected with the influenza-A virus and cells infected with the influenza-A virus after pretreatment with MENK. A total of 215 DEPs were identified: 164 proteins had upregulated expression and 51 proteins had downregulated expression. Proteomics analysis showed that DEPs were highly enriched in "cytokine-cytokine receptor interaction", "phagosome", and "complement and coagulation cascades pathway". Proteomics analysis revealed that MENK could be an immune modulator or prophylactic for the prevention and treatment of influenza. MENK promoted the polarization of M1 macrophages, activated inflammatory responses, and enhanced phagocytosis and killing function by upregulating opsonizing receptors.
PubMed: 37041527
DOI: 10.1186/s12953-023-00205-w -
International Immunopharmacology May 2023Metastasis is one of the most difficult challenges for clinical lung cancer treatment. Epithelial-mesenchymal transition (EMT) is the crucial step of tumor metastasis....
Methionine enkephalin suppresses lung cancer metastasis by regulating the polarization of tumor-associated macrophages and the distribution of myeloid-derived suppressor cells in the tumor microenvironment and inhibiting epithelial-mesenchymal transition.
Metastasis is one of the most difficult challenges for clinical lung cancer treatment. Epithelial-mesenchymal transition (EMT) is the crucial step of tumor metastasis. Immune cells in the tumor microenvironment (TME), such as tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs), promote cancer cell EMT. In this study, we explored the effect of methionine enkephalin (MENK) on the EMT process in vitro and in vivo, and its influence on TAMs, MDSCs, and associated cytokines in vivo. The results showed that MENK suppressed growth, migration, and invasion of lung cancer cells and inhibited the EMT process by interacting with opioid growth factor receptor. MENK reduced the number of M2 macrophages and MDSC infiltration, and downregulated the expression of interleukin-10 and transforming growth factor-β1 in both primary and metastatic tumors of nude mice. The present findings suggest that MENK is a potential target for suppressing metastasis in lung cancer treatment.
Topics: Animals; Mice; Myeloid-Derived Suppressor Cells; Epithelial-Mesenchymal Transition; Tumor-Associated Macrophages; Enkephalin, Methionine; Tumor Microenvironment; Mice, Nude; Cell Line, Tumor; Lung Neoplasms; Cell Movement
PubMed: 36989897
DOI: 10.1016/j.intimp.2023.110064 -
BioRxiv : the Preprint Server For... Aug 2023Enkephalins are opioid peptides that modulate analgesia, reward, and stress. detection of enkephalins remains difficult due to transient and low endogenous...
Enkephalins are opioid peptides that modulate analgesia, reward, and stress. detection of enkephalins remains difficult due to transient and low endogenous concentrations and inherent sequence similarity. To begin to address this we previously developed a system combining in vivo optogenetics with microdialysis and a highly sensitive mass spectrometry-based assay to measure opioid peptide release in freely moving rodents (Al-Hasani, 2018, eLife). Here not only do we show improved detection resolution but also a critical discovery in the stabilization of enkephalin detection, which together allowed us to investigate enkephalin release during acute stress. We present an analytical method for Met- and Leu-Enkephalin (Met-Enk & Leu-Enk) detection in the mouse Nucleus Accumbens shell (NAcSh) after acute stress. We confirm that acute stress activates enkephalinergic neurons in the NAcSh using fiber photometry and that this leads to the release of Met- and Leu-Enk. We also demonstrate the dynamics of Met- and Leu-Enk release as well as how they correlate to one another in the ventral NAc shell, which was previously difficult due to the use of approaches that relied on mRNA transcript levels rather than post-translational products. This approach increases spatiotemporal resolution, optimizes the detection of Met-Enkephalin through methionine oxidation, and provides novel insight into the relationship between Met- and Leu-Enkephalin following stress.
PubMed: 36824728
DOI: 10.1101/2023.02.15.528745 -
Neuropeptides Jun 2023The opioid growth factor (OGF) is an endogenous peptide that binds to the nuclear-associated receptor (OGFr), and plays a significant role in the proliferation of...
The opioid growth factor (OGF) is an endogenous peptide that binds to the nuclear-associated receptor (OGFr), and plays a significant role in the proliferation of developing, renewing, and healing tissues. The receptor is widely expressed in a variety of organs, however its distribution in the brain remains unknown. In this study, we investigated the distribution of OGFr in different brain regions of male heterozygous (-/+ Lepr /J), non -diabetic mice and determined the localization of the receptor in three major brain cell types, astrocytes, microglia, and neurons. Immunofluorescence imaging revealed that the highest number of OGFr was in hippocampal CA3 subregion followed by primary motor cortex, hippocampal CA2, thalamus, caudate and hypothalamus in a descending order. Double immunostaining revealed receptor colocalization with neurons and little or no colocalization in microglia and astrocytes. The highest percentage of OGFr positive neurons was identified in the CA3. Hippocampal CA3 neurons play an important role in memory processing, learning and behavior, and motor cortex neurons are important for muscle movement. However, the significance of the OGFr receptor in these brain regions and its relevance in diseased conditions are not known. Our findings provide a basis for understanding the cellular target and interaction of the OGF- OGFr pathway in neurodegenerative diseases such as Alzheimer's, Parkinson's, and stroke where hippocampus and cortex have an important role. This foundational data may also be useful in drug discovery to modulate OGFr by opioid receptor antagonist in various CNS diseases.
Topics: Animals; Male; Mice; Brain; Diabetes Mellitus, Experimental; Neurons; Receptors, Opioid
PubMed: 36812665
DOI: 10.1016/j.npep.2023.102325 -
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 -
Life Sciences Jan 2023Obesity and its related metabolic disorders, including insulin resistance and fatty liver, have become a serious global public health problem. Previous studies have...
AIMS
Obesity and its related metabolic disorders, including insulin resistance and fatty liver, have become a serious global public health problem. Previous studies have shown Methionine Enkephalin (MetEnk) has the potential on adipocyte browning, however, its effects on the potential mechanisms of its regulation in browning as well as its improvement in energy metabolic homeostasis remain to be deciphered.
MAIN METHODS
C57BL/6J male mice were fed with high-fat diet (HFD) to induce obesity model, and MetEnk was injected subcutaneously to detect changes in the metabolic status of mice, adipocytes and HepG2 cells were also treated with MetEnk, and transcriptomic, metabolomic were used to detect the changes of lipid metabolism, mitochondrial function, inflammation and other related factors.
KEY FINDINGS
We found that MetEnk effectively protected against obesity weight gain in HFD-induced C57BL/6J mice, significantly improved glucose tolerance and insulin sensitivity, reduced the expression levels of interleukin 6 (IL-6), promoted white fat browning, moreover, using a combination of transcriptomic, metabolomic and inhibitors, it was found that MetEnk improved mitochondrial function, promoted thermogenesis and lipolysis by activating cAMP/PKA pathway in adipocytes, further analysis found that MetEnk also promoted lipolysis and alleviated inflammation through AMP-activated protein kinase (AMPK) pathway in mice liver and HepG2 cells.
SIGNIFICANCE
Our study provides profound evidence for the role of MetEnk in improving lipid metabolism disorders. This study provides a mechanical foundation for investigating the potential of MetEnk to improve obesity and its associated metabolic disorders.
Topics: Male; Mice; Animals; Enkephalin, Methionine; Mice, Inbred C57BL; Adipose Tissue, White; Thermogenesis; Diet, High-Fat; Insulin Resistance; Obesity; Inflammation; Adipose Tissue, Brown
PubMed: 36396109
DOI: 10.1016/j.lfs.2022.121189