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International Immunopharmacology Dec 2023This study aimed to investigate the underlying regulatory effects of methionine enkephalin (MENK) on osteosarcoma.
OBJECTIVE
This study aimed to investigate the underlying regulatory effects of methionine enkephalin (MENK) on osteosarcoma.
METHODS
The Cell Counting Kit-8 assay, clone formation, wound healing, transwell assay, and flow cytometry were performed to measure the effects of MENK on the proliferation, migration, invasion, and apoptosis of MG-63 and Saos-2 cells. Opiate growth factor receptor expression (OGFr) in cells was stably knocked down using siRNA. A tumor model was established by inoculating MG-63 cells into mice. Flow cytometry was performed to identify alterations in mice bone marrow, spleen, and tumor tissue immune cells. The phenotype of tumor-associated macrophages was determined using immunohistochemistry. After OGFr knockdown or/and treatment with MENK, Bax, Bcl-2, caspase 3, caspase 9, and PARP expression levels were characterized using qRT-PCR, western blot, and WES, respectively.
RESULTS
MENK could significantly inhibit the proliferation, invasion, and migration of MG-63 and Saos-2, arrest the cell cycle in the G0/G1 phase, upregulate Bax, caspase 3, caspase 9, and PARP expression, and downregulate Bcl-2 expression. Tumor size and weight were lower in the MENK group than those in the control group. MENK-treated mice exhibited a reduced ratio of CD11b + Gr-1 + myeloid-derived suppressor cells. MENK increased the ratio of M1-type macrophages and decreased the proportion of M2-type macrophages in tumor tissue. Furthermore, the level of TNF-α significantly increased while that of IL-10 decreased in MENK-treated mice. The effect of MENK could be partly reversed by OGFr knockdown.
CONCLUSION
MENK reduces the abundance of myeloid-derived suppressor cells, induces M1 polarization of macrophages, and exhibits an inhibitory effect on osteosarcoma.
Topics: Animals; Mice; Caspase 3; Caspase 9; Poly(ADP-ribose) Polymerase Inhibitors; bcl-2-Associated X Protein; Osteosarcoma; Enkephalin, Methionine; Bone Neoplasms
PubMed: 37976597
DOI: 10.1016/j.intimp.2023.111226 -
Fish & Shellfish Immunology Jul 2024In this study, the expressions and distributions of methionine-enkephalin (Met-enk) and δ opioid receptor in the nervous system of Octopus ocellatus, and the immune...
In this study, the expressions and distributions of methionine-enkephalin (Met-enk) and δ opioid receptor in the nervous system of Octopus ocellatus, and the immune regulatory mechanisms of Met-enk on O. ocellatus were explored. The distributions and expressions of Met-enk and δ opioid receptor were assessed by immunohistochemistry and enzyme-linked immunosorbent assay. UV-spectrophotometer, microplate reader, and flow cytometer were used to examine the effects of different concentrations of Met-enk on phagocytosis, antioxidant effects, and body surface mucus immunity of O. ocellatus hemocytes. The data were used to study the mechanisms of Met-enk immunity regulation in O. ocellatus. According to the results, the expression levels of Met-enk and δ opioid receptor in O. ocellatus lymphocytes were higher than those in hemocytes. The expression levels of Met-enk in the ganglia of O. ocellatus decreased in the following order: pedal ganglia > cerebral ganglia > visceral ganglia > optic ganglia > stellate ganglia. Moreover, the phagocytic activity of O. ocellatus hemocytes was enhanced with increasing Met-enk concentration. With increasing Met-enk concentration, the expressions of nitric oxide, total nitric oxide synthase, inducible nitric oxide synthase, catalase, hydrogen peroxide, myeloperoxidase, reduced glutathione, α-naphthy acetate esterase, and methionine aminopeptidases decreased in serums of O. ocellatus in the experimental group compared to the blank group. Similarly, the content of reduced glutathione in the hemocytes of O. ocellatus was also lower in the experimental group than in the blank group; however, the expressions of other substances were higher compared to the blank group. Furthermore, α-naphthy acetate esterase, myeloperoxidase, and hydrogen peroxide expressions in mucus immunity trials of the body surface were lower in the experimental group compared to the blank group. These results indicate that the distributions and expressions of Met-enk and δ opioid receptor in the nervous system of O. ocellatus were related to axoplasmic transport and immune regulation mechanisms. Met-enk participates in cellular immunity, humoral immunity, and mucus immunity in the form of neurotransmitters, thereby regulating the immune response of O. ocellatus.
Topics: Animals; Enkephalin, Methionine; Receptors, Opioid, delta; Octopodiformes; Immunity, Innate; Hemocytes; Gene Expression Regulation
PubMed: 38754647
DOI: 10.1016/j.fsi.2024.109637 -
Cell Reports Sep 2022Low dopamine D2 receptor (D2R) availability in the striatum can predispose for cocaine abuse; though how low striatal D2Rs facilitate cocaine reward is unclear....
Low dopamine D2 receptor (D2R) availability in the striatum can predispose for cocaine abuse; though how low striatal D2Rs facilitate cocaine reward is unclear. Overexpression of D2Rs in striatal neurons or activation of D2Rs by acute cocaine suppresses striatal Penk mRNA. Conversely, low D2Rs in D2-striatal neurons increases striatal Penk mRNA and enkephalin peptide tone, an endogenous mu-opioid agonist. In brain slices, met-enkephalin and inhibition of enkephalin catabolism suppresses intra-striatal GABA transmission. Pairing cocaine with intra-accumbens met-enkephalin during place conditioning facilitates acquisition of preference, while mu-opioid receptor antagonist blocks preference in wild-type mice. We propose that heightened striatal enkephalin potentiates cocaine reward by suppressing intra-striatal GABA to enhance striatal output. Surprisingly, a mu-opioid receptor antagonist does not block cocaine preference in mice with low striatal D2Rs, implicating other opioid receptors. The bidirectional regulation of enkephalin by D2R activity and cocaine offers insights into mechanisms underlying the vulnerability for cocaine abuse.
Topics: Analgesics, Opioid; Animals; Cocaine; Cocaine-Related Disorders; Corpus Striatum; Enkephalin, Methionine; Enkephalins; Mice; Narcotic Antagonists; RNA, Messenger; Receptors, Dopamine D1; Receptors, Dopamine D2; Reward; gamma-Aminobutyric Acid
PubMed: 36170833
DOI: 10.1016/j.celrep.2022.111440 -
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 -
Experimental Biology and Medicine... Dec 2018This mini-review presents information on the intermittent blockade of the opioid growth factor (OGF)-OGF receptor (OGFr) axis by low-dose naltrexone (LDN), and the role... (Review)
Review
This mini-review presents information on the intermittent blockade of the opioid growth factor (OGF)-OGF receptor (OGFr) axis by low-dose naltrexone (LDN), and the role of enkephalin (i.e. OGF) in autoimmune disorders, specifically multiple sclerosis, Crohn's, and fibromyalgia. Clinical reports on subjects taking LDN have documented reduced fatigue, few side-effects, and improved overall health. Preclinical studies on mice with experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis, revealed that immunization for EAE reduces serum OGF. Intermittent OGFr blockade with LDN restores serum enkephalin levels that correlate with reduced behavioral and pathological signs of EAE; LDN also increases enkephalin levels in naïve mice. The interplay between LDN, and the onset and treatment of autoimmune diseases, chronic pain, and other addictive behaviors requires further investigation, but highlights a central role for enkephalins and intermittent blockade of the OGF-OGFr pathway in pathogenesis and treatment of these disorders.
Topics: Animals; Encephalomyelitis, Autoimmune, Experimental; Humans; Mice; Multiple Sclerosis; Naltrexone; Narcotic Antagonists; Receptors, Opioid
PubMed: 30541348
DOI: 10.1177/1535370218817746 -
European Journal of Pharmacology Sep 2020Methionine enkephalin (MENK) is an opioid peptide composed of five amino acids with multiple biological activities. Since its discovery, MENK has become prominent in... (Review)
Review
Methionine enkephalin (MENK) is an opioid peptide composed of five amino acids with multiple biological activities. Since its discovery, MENK has become prominent in neuroregulation and immunoregulation. Tumors have increasingly been a spotlight because of their terrible trends and refractory characteristic. The therapeutic potential of MENK was investigated on a large scale, and there are numerous evidences that MENK exerts anti-tumor effects via two mechanisms. The first mechanism explains the enhanced anti-tumor immune effects of MENK. The second mechanism shows that MENK directly inhibits tumor cell proliferation. However, numerous reports have clarified the pro-tumor role of MENK by inhibiting T and B cell proliferation, promoting tumor cell growth by binding to opioid receptors, leading to desensitization of lymphocytes, and inducing tolerance. It is particularly intriguing that dual reactions are triggered when MENK combines with its opioid receptors; thus, anti-tumor response of the whole body is influenced. This review will expound the dual roles of MENK in tumor responses based on immune cells, cytokines, and tumor cells to provide better suggestions for its application in tumor treatment.
Topics: Animals; Antineoplastic Agents; Enkephalin, Methionine; Humans; Neoplasms
PubMed: 32535097
DOI: 10.1016/j.ejphar.2020.173253 -
International Journal of Molecular... Sep 2022Pain is a worldwide public health problem and its treatment is still a challenge since clinically available drugs do not completely reverse chronic painful states or...
Pain is a worldwide public health problem and its treatment is still a challenge since clinically available drugs do not completely reverse chronic painful states or induce undesirable effects. Crotalphine is a 14 amino acids synthetic peptide that induces a potent and long-lasting analgesic effect on acute and chronic pain models, peripherally mediated by the endogenous release of dynorphin A and the desensitization of the transient receptor potential ankyrin 1 (TRPA1) receptor. However, the effects of crotalphine on the central nervous system (CNS) and the signaling pathway have not been investigated. Thus, the central effect of crotalphine was evaluated on the partial sciatic nerve ligation (PSNL)-induced chronic neuropathic pain model. Crotalphine (100 µg/kg, p.o.)-induced analgesia on the 14th day after surgery lasting up to 24 h after administration. This effect was prevented by intrathecal administration of CB1 (AM251) or CB2 (AM630) cannabinoid receptor antagonists. Besides that, crotalphine-induced analgesia was reversed by CTOP, nor-BNI, and naltrindole, antagonists of , , and -opioid receptors, respectively, and also by the specific antibodies for β-endorphin, dynorphin-A, and met-enkephalin. Likewise, the analgesic effect of crotalphine was blocked by the intrathecal administration of minocycline, an inhibitor of microglial activation and proliferation. Additionally, crotalphine decreased the PSNL-induced IL-6 release in the spinal cord. Importantly, in vitro, crotalphine inhibited LPS-induced CD86 expression and upregulated CD206 expression in BV-2 cells, demonstrating a polarization of microglial cells towards the M2 phenotype. These results demonstrated that crotalphine, besides activating opioid and cannabinoid analgesic systems, impairs central neuroinflammation, confirming the neuromodulatory mechanism involved in the crotalphine analgesic effect.
Topics: Amino Acids; Analgesia; Analgesics; Analgesics, Opioid; Ankyrins; Cannabinoid Receptor Antagonists; Cannabinoids; Dynorphins; Enkephalin, Methionine; Humans; Interleukin-6; Lipopolysaccharides; Microglia; Minocycline; Neuralgia; Peptides; Phenotype; Receptors, Opioid; Spinal Cord; beta-Endorphin
PubMed: 36232883
DOI: 10.3390/ijms231911571 -
Science (New York, N.Y.) Mar 2022Angiotensin-converting enzyme (ACE) regulates blood pressure by cleaving angiotensin I to produce angiotensin II. In the brain, ACE is especially abundant in striatal...
Angiotensin-converting enzyme (ACE) regulates blood pressure by cleaving angiotensin I to produce angiotensin II. In the brain, ACE is especially abundant in striatal tissue, but the function of ACE in striatal circuits remains poorly understood. We found that ACE degrades an unconventional enkephalin heptapeptide, Met-enkephalin-Arg-Phe, in the nucleus accumbens of mice. ACE inhibition enhanced µ-opioid receptor activation by Met-enkephalin-Arg-Phe, causing a cell type-specific long-term depression of glutamate release onto medium spiny projection neurons expressing the Drd1 dopamine receptor. Systemic ACE inhibition was not intrinsically rewarding, but it led to a decrease in conditioned place preference caused by fentanyl administration and an enhancement of reciprocal social interaction. Our results raise the enticing prospect that central ACE inhibition can boost endogenous opioid signaling for clinical benefit while mitigating the risk of addiction.
Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Behavior, Animal; Captopril; Enkephalin, Methionine; Female; Fentanyl; Male; Mice; Miniature Postsynaptic Potentials; Neuronal Plasticity; Nucleus Accumbens; Opioid Peptides; Patch-Clamp Techniques; Peptidyl-Dipeptidase A
PubMed: 35201898
DOI: 10.1126/science.abl5130