dalargin (leu-enkephalin) / Burnasyan Federal Medical & Biophysical Center - LARVOL DELTA

Combining Leu-enkephalin nanomedicines with enkephalinase inhibitors: a promising painkiller strategy? (PubMed, Drug Deliv Transl Res) - "This study investigates the potential of a novel nanomedicine approach relying on squalene nanoparticles of endogenous enkephalinase inhibitors (EEI) - opiorphin (OPN) and STR-324 - to alleviate pain by potentiating the action of enkephalins in vivo, in a model of acute inflammatory pain. EEI-SQ NPs administered subcutaneously successfully enhanced the anti-hyperalgesic effect of LENK-SQ NPs. However, it was considered as not relevant enough regarding the observed local toxicity."

Journal • Pain • PENK

CORRELATION BETWEEN OPIOID LIGANDS AND RESPONSE TO OPIOID ANTAGONIST IN CHOLESTATIC PATIENTS WITH PRURITUS (AASLD 2025) - "In our recent work, we showed that nalmefene—a Mu and delta opioid receptor antagonist and kappa receptor agonist—reduced pruritus intensity in individuals with cholestatic liver disease...ELISA kits (Qayeebio, China) were used to test the following ligands: Dynorphin (Kappa agonist), Beta-Endorphin (Mu agonist), Met-Enkephalin and Leu-Enkephalin (Mu and Kappa agonists)... Leu-Enkephalin is an endogenous opioid peptide that primarily acts on delta-opioid receptors but also interacts with mu-opioid receptors. Previous studies, such as Dull (2021), found no correlation between endogenous opioid ligand levels and pruritus severity in cholestatic liver disease. Our findings represent the first reported association between Leu-enkephalin levels and itch reduction following treatment with an opioid antagonist, and suggest a potential role for delta opioid receptors in cholestatic pruritus (Smith KM, 2023)."

Clinical • Cholestasis • Dermatology • Hepatology • Pruritus • PENK

Beta-endorphin is the key endogenous opioid influencing morphine µ-opioid receptor occupancy in rat hypothalamus: a binding kinetic model analysis. (PubMed, Eur J Pharm Sci) - "µ-OR occupancies were simulated using morphine brain extracellular fluid concentration data, for different static levels of the endogenous opioids, including beta-endorphin, Dynorphin-A 1-17, Endomorphin-2, Leu-enkephalin, and Met-enkephalin. We conclude that beta-endorphin plays an important role in morphine µ-OR occupancy, which could therefore play a key role in explaining interindividual variability in the analgesic effects of morphine. Finally, this study demonstrates the utility of a mathematical model workflow in deciphering the role of endogenous ligands in morphine's µ-OR occupancy."

Journal • Preclinical • Pain

Highly sensitive in vivo detection of dynamic changes in enkephalins following acute stress in mice. (PubMed, Elife) - "We present an analytical method for real-time, simultaneous detection of Met- and Leu-enkephalin (Met-Enk and Leu-Enk) in the mouse nucleus accumbens shell (NAcSh) after acute stress...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 posttranslational products. This approach increases spatiotemporal resolution, optimizes the detection of Met-Enk through methionine oxidation, and provides novel insight into the relationship between Met- and Leu-Enk following stress."

Journal • Preclinical

Synthesis of Mono-Boc-2,5-Diketopiperazine: A Key Building Block for Amide and Peptide Synthesis. (PubMed, J Org Chem) - "The synthetic utility of mono-Boc-DKPs was showcased in peptide synthesis by synthesizing pentapeptide Boc-l-Tyr(t-Bu)-Gly-l-Phe-Gly-l-Val-OtBu by 2-fold peptide elongation with two mono-Boc-DKPs. Furthermore, we synthesized Leu-enkephalin pentapeptide by reacting cyclo(Boc-l-Tyr(t-Bu)-Gly-) with H-Gly-l-Phe-l-Leu-Ot-Bu, resulting in a good yield and excellent optical purity."

Journal

Inhibition of the angiotensin-converting enzyme N-terminal catalytic domain prevents endogenous opioid degradation in brain tissue. (PubMed, bioRxiv) - "Additionally, application of a selective N-terminal domain inhibitor (RXP 407) reduced degradation of both exogenously applied and endogenously released MERF, without affecting degradation of endogenously released Met-enkephalin or Leu-enkephalin. Taken together, our results suggest that the ACE N-terminal domain is the primary site of MERF degradation in brain tissue, and that N-terminal domain inhibition is sufficient to reduce degradation of this specific endogenous opioid peptide. Our results have exciting implications for the development of novel pharmacotherapies that target the endogenous opioid system to treat psychiatric and neurological disorders."

Journal • CNS Disorders • Psychiatry • PENK

Kappa-opioid receptor blockade in the inferior colliculus of prey threatened by pit vipers decreases anxiety and panic-like behaviour. (PubMed, Acta Neuropsychiatr) - "These structures are rich in beta-endorphinergic and leu-enkephalinergic neurons and receive GABAergic inputs from substantia nigra pars reticulata...Pretreatment of the IC with microinjections of nor-binaltorphimine at higher concentrations significantly decreased the frequency and duration of both anxiety- and panic-attack-like behaviours. These findings suggest that κ-opioid receptor blockade in the IC causes anxiolytic- and panicolytic-like responses in threatening conditions, and that kappa-opioid receptor-selective antagonists can be a putative coadjutant treatment for panic syndrome treatment."

Journal • Mood Disorders • Psychiatry

Inflammatory pain resolution by mouse serum-derived small extracellular vesicles. (PubMed, Brain Behav Immun) - "These sEVs transiently increased basal mechanical thresholds, an effect mediated by opioid signaling as this outcome was blocked by naltrexone. Mass Spectrometry of sEVs detected endogenous opioid peptide leu-enkephalin...Flow cytometry confirmed increases in CD206+ macrophages in the spinal cord in sEV-treated mice. Collectively, these studies demonstrate multiple mechanisms by which sEVs can attenuate pain."

Journal • Preclinical • Neuralgia • Pain • MRC1

Effects of Neonatal Administration of Non-Opiate Analogues of Leu-Enkephalin on the Delayed Cardiac Consequences of Intrauterine Hypoxia. (PubMed, Bull Exp Biol Med) - "Correction of the delayed posthypoxic changes, similar to the effects of NALE peptide, was observed after neonatal administration of its arginine-free analogue, G peptide (Phe-D-Ala-Gly-Phe-Leu-Gly; 100 μg/kg). Non-opiate analogues of leu-enkephalin NALE and G peptides can be considered as promising substances capable of preventing long-term cardiac consequences of intrauterine hypoxia."

Journal • BECN1 • CASP3 • NOS3 • TP53

Ketamine and major ketamine metabolites function as allosteric modulators of opioid receptors. (PubMed, Mol Pharmacol) - "All three opioid receptors (mu, delta, and kappa) showed synergism with submicromolar concentrations of ketamine and either Met-enkephalin, Leu-enkephalin, and/or dynorphin A17, albeit the extent of synergy was variable between receptors and peptides...Importantly, the ketamine metabolite 6-hydroxynorketamine showed robust allosteric modulatory activity at mu opioid receptors; this metabolite is known to have analgesic and antidepressant activity but does not bind to glutamate receptors...Significance Statement We found that ketamine and its major biologically-active metabolites function as potent allosteric modulators of mu, delta, and kappa opioid receptors, with submicromolar concentrations of these compounds synergizing with endogenous opioid peptides such as enkephalin and dynorphin. This allosteric activity may contribute to ketamine's therapeutic effectiveness for treating acute and chronic pain and as a fast-acting antidepressant drug."

Journal • Anesthesia • Pain • PENK

A nanomedicine approach for the treatment of long-lasting pain. (PubMed, J Control Release) - "This study explores the potential of a nanomedicine approach, using Leu-enkephalin-squalene nanoparticles (LENK-SQ NPs) for managing long-lasting pain. On the other hand, the biodistribution of fluorescently labelled LENK-SQ NPs revealed their selective accumulation in the incised paw within the first hour post administration, followed by a disassembly of the NPs, starting 24 h later. The study proposes the following multi-step mechanism for the anti-nociceptive pharmacological activity of LENK-SQ NPs: (i) protection of the neuropeptide from metabolization into the bloodstream, (ii) targeted accumulation of the nanoparticles within the incised painful tissue and (iii) gradual release of LENK at the onset of the inflammatory process, leading to the observed analgesic activity."

Journal • Pain

Amadori and Heyns rearrangement products of bioactive peptides as potential new ligands of galectin-3. (PubMed, Carbohydr Res) - "The binding interactions between galectin-3 and the Amadori and Heyns compounds of leucine-enkephalin (YGGFL), leucine-enkephalin methyl ester (YGGFL-OMe), truncated enkephalin (YGG and Y) and tetrapeptide (LSKL) were measured using the AlphaScreen competitive binding assay. The affinity of galectin-3 for Amadori and Heyns compounds depends on both the sugar moiety and the amino acid sequence of the model compounds. The best results were obtained with Leu-enkephalin derivatives of Amadori (IC50 = 6.06 μm) and Heyns (IC50 = 8.6 μm) compound, respectively."

Journal

Site-Specific Photochemistry along a Protonated Peptide Scaffold. (PubMed, J Am Chem Soc) - "We present a detailed study of the time-dependent photophysics and photochemistry of a known conformation of the two protonated pentapeptides Leu-enkephalin (Tyrosine-Glycine-Glycine-Phenylalanine-Leucine, YGGFL) and its chromophore-swapped analogue FGGYL, carried out under cryo-cooled conditions in the gas phase...Finally, IR excitation in the S1 or Tn(v) states fragments the peptide backbone exclusively at amide(4), producing the b4 cation. We postulate that this selective fragmentation results from intersystem crossing to produce vibrationally excited triplets with enough energy to launch the proton along a proton conduit present in the known starting structure."

Journal

A Novel Ophthalmic Solution Containing Glicopro® Complex for the Treatment of Patients with Dry Eye Disease: Results from a Pilot Study. (PubMed, J Clin Med) - "Analysis of the tear content of proenkephalin and Met/Leu-enkephalin was also performed...(4) Our novel tear substitute based on GlicoPro® resulted in a significant improvement in ocular discomfort symptoms, tear volume, and stability in the patients treated. The increase in active peptides processed in tears may represent the pathophysiological substrate underlying this finding."

Journal • Dry Eye Disease • Ophthalmology • PENK

Stapling of leu-enkephalin analogs with bifunctional reagents for prolonged analgesic activity. (PubMed, Chem Commun (Camb)) - "The CD conformational studies of the stapled analogs suggest that the peptides adopt the type I β-turn conformation, which is in agreement with the theoretical analysis. The analog containing a trithiocyanuric acid derivative with a benzyl substituent shows potent analgesic activity."

Journal • Pain • PENK

Effect of dalargin on apoptosis of l929 fibroblasts during cold stress. (PubMed, Cryo Letters) - "In addition to their fundamental value, these findings are of practical importance since neuropeptides, in particular dalargin, added to perfusion solutions and media for hypothermic preservation of organs and cells, can improve their efficiency. Doi.org/10.54680/fr23610110212."

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A Novel Leu-Enkephalin Prodrug Produces Pain-Relieving and Antidepressant Effects. (PubMed, Mol Pharm) - "Leucine-enkephalin (Leu-ENK), the endogenous delta opioid receptor agonist, controls pain and mood and produces potent analgesia with reduced adverse effects compared to conventional opioids. The pain-alleviating effect of KK-103 primarily resulted from activating the delta opioid receptor after the likely conversion of KK-103 to Leu-ENK in vivo. Finally, KK-103 produced an antidepressant-like activity comparable to the antidepressant desipramine, but with minimal gastrointestinal inhibition and no incidence of sedation."

Journal • Addiction (Opioid and Alcohol) • Anesthesia • CNS Disorders • Depression • Gastrointestinal Disorder • Pain • Psychiatry

ClickArr: a novel, high-throughput assay for evaluating β-arrestin isoform recruitment. (PubMed, Front Pharmacol) - "We further find that the partial δOR agonist TAN67 has a significant efficacy bias for β-arrestin 2 over β-arrestin 1 when recruitment is normalized to the reference agonist leu-enkephalin. We confirm that ClickArr reports this bias when run either as a high-throughput endpoint or high-throughput kinetic assay, and cross-validate this result using the PathHunter assay, an orthogonal commercial assay for reporting β-arrestin recruitment to the δOR. Our results suggest that agonist:GPCR complexes can have relative β-arrestin isoform bias, a novel signaling bias that may potentially open up a new dimension for drug development."

Journal • ARRB1

Rapid Droplet Sampling Interface for Low-Volume, High-Throughput Mass Spectrometry Analysis. (PubMed, Anal Chem) - "A sampling rate of 5 Hz was achieved for droplets containing 1 μM propranolol or 5 μM leu-enkephalin with each droplet fully baseline-resolved (138 ± 32 ms baseline-to-baseline). The range of analyte coverage was exemplified by measures of peptides and drugs in methanol, water, and buffer solutions. In a comparison to the Open Port Sampling Interface (OPSI) implemented on the same system, the RDSI had 78× greater sensitivity, 6× greater throughput and used significantly less carrier solvent."

Journal

Effects of Non-Opiate Analogue of Leu-Enkephalin on the Ion Currents, Number of Nucleoli, and p53 Expression in Isolated Cardiomyocytes of Albino Rats. (PubMed, Bull Exp Biol Med) - "The exposure of cardiomyocytes to NALE in a concentration 1000 μg/liter induced similar changes in the studied parameters (increase in Ca L-type current and number of p53 cardiomyocytes); an increase in the mean number of nucleoli was also observed. Our findings suggest that NALE peptide has direct effect on cardiomyocytes and NOP receptors are involved in this effect."

Journal • Preclinical • Addiction (Opioid and Alcohol) • TP53

Electromembrane extraction of peptides based on hydrogen bond interactions. (PubMed, Anal Chim Acta) - "The current experiments are important because they indicate that small peptides of low polarity may be extracted selectively in EME based on hydrogen bond interactions, in systems not suffering from electrolysis."

Journal

MD-DFT computational studies on the mechanistic and conformational parameters for the chemoselective tyrosine residue reactions of G-Protein-Coupled Receptor Peptides with [Cp*Rh(H2O)3](OTf)2 in water to form their [(η6-Cp*Rh-Tyr#)-GPCR Peptide]2+ comple (ACS-Fall 2023) - "Furthermore, the influence of the [Cp*Rh]2+ group on the lowest energy conformations for the structures of [(η6-Cp*Rh-Tyr1)-Leu-enkephalin](OTf)2, [(η6-Cp*Rh-Tyr4)-Neurotensin(8-13)](OTf)2, and [(η6-Cp*Rh-Tyr3)-Octreotide](OTf)2, were also assessed, including the essential intramolecular, non-covalent interactions that determined the lowest conformations of [(η6-Cp*Rh-Tyr1,4,3) GPCR peptide]2+ complexes, in comparison to their ligands, GPCR peptides. This represented, to our knowledge, the first MD/DFT study on mechanisms of an organometallic aqua complex reacting in an aqueous media with GPCR peptides, while also determining the critical secondary forces; for example, intramolecular, non-covalent H-bonding interactions that further defined the most stable conformations of the GPCR peptides, and those of their [(η6-Cp*Rh-Tyr1,4,3) GPCR peptide]2+ complexes"

Avian opioid peptides: evolutionary considerations, functional roles and a challenge to address critical questions. (PubMed, Front Physiol) - "Proenkephalin (PENK) encodes Met- and Leu-enkephalin together with peptides containing met enkephalin motifs in birds, mammals and reptiles. The opioid peptides exert effects related to pain together with other biological actions such as growth/development acting via a series of opioid receptors. What is unclear, particularly in birds, is the biological roles and interactions (additivity, antagonistic and synergistic) for the individual opioid peptides, the processing of the prohormones in different tissues and the physiological relevance of the different peptides and, particularly, of the circulating forms."

Journal • Review • Pain • POMC-null Obesity • PENK

Influence of Mutations of Conserved Arginines on Neuropeptide Binding in the DPP III Active Site. (PubMed, Molecules) - "Molecular dynamics simulations of wild-type (WT) and mutant DPP III complexes with Leu-enkephalin, tynorphin, valorphin, and Arg-2NA in conjunction with calculations of binding free energies revealed that the lower inhibitory potency of slow substrates in the R669A mutant can be explained by the lower binding affinity of tynorphin and the higher propensity of valorphin to hydrolyze in the mutant than in WT. The R399A mutation was shown to affect the binding and/or hydrolysis of both good and slow substrates, with the effects on Leu-enkephalin being the most pronounced."

Journal • Targeted Protein Degradation

Na1.7 Channel Blocker [Ala, Phe, Leu, Arg]GpTx-1 Attenuates CFA-induced Inflammatory Hypersensitivity in Rats via Endogenous Enkephalin Mechanism. (PubMed, J Pain) - "Mass spectrometry analysis revealed that GpTx-1-71 mainly promoted the secretion of Met-enkephalin but not Leu-enkephalin from DRG neurons. 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."

Journal • Preclinical • Addiction (Opioid and Alcohol) • Immunology • Pain • PENK