On resin click-chemistry-mediated synthesis of novel enkephalin analogues with potent anti-nociceptive activity

Modification and Delivery of Enkephalins for Pain Modulation

Chronic pain negatively affects patient's quality of life and poses a significant economic burden. First line pharmaceutical treatment of chronic pain, including NSAIDs or antidepressants, is often inefficient to reduce pain, or produces intolerable adverse effects. In such cases, opioids are frequently prescribed for their potent analgesia, but chronic opioid use is also frequently associated with debilitating side effects that may offset analgesic benefits. Nonetheless, opioids continue to be widely utilized due to the lack of effective alternative analgesics. Since their discovery in 1975, a class of endogenous opioids called enkephalins (ENKs) have been investigated for their ability to relieve pain with significantly reduced adverse effects compared to conventional opioids. Their low metabolic stability and inability to cross biological membranes, however, make ENKs ineffective analgesics. Over past decades, much effort has been invested to overcome these limitations and develop ENK-based pain therapies. This review summarizes and describes chemical modifications and ENK delivery technologies utilizing ENK conjugates, nanoparticles and ENK gene delivery approaches and discusses valid lessons, challenges, and future directions of this evolving field.

Targeting HER2-Receptors with 177Lu-Labeled Triazole Stapled Cyclic Peptidomimetic

In this study on-resin Cu(I)-catalyzed click reaction was performed to synthesize triazole-stapled cyclic peptidomimetic, DOTA-c[TZ]A9 targeting HER2 receptor expression in breast cancers. Spectroscopic (circular dichroism) and docking analysis provided evidence of enhanced helicity and secondary structure stabilization along with improved HER2 affinity in comparison to the corresponding linear peptide, DOTA-[Pra¹, Aza⁷]A9. ¹⁷⁷Lu-labeled cyclic peptide, ¹⁷⁷Lu-DOTA-c[TZ]A9 displayed higher in vitro serum stability and in vivo metabolic stability and better HER2 binding affinity {K_d of 16.93 ± 3.02 nM} than the linear counterpart, [¹⁷⁷Lu]DOTA-[Pra¹, Aza⁷]A9 {K_d of 26.28 ± 2.87 nM}. Biodistribution profile in SKBR3 tumor bearing SCID mice demonstrated elevated radioactivity levels and prolonged retention of cyclic peptide in the tumor compared to the linear peptide. Thus, solid phase click cyclization technique can be extended towards preparation of triazole-stapled peptides targeting different receptors with improved stability and efficacy.

Discovery and Structural Explorations of G-Protein Biased μ-Opioid Receptor Agonists

Compounds that activate only the G-protein signalling pathway represent an effective strategy for making safer opioids. In the present study, we report the design, synthesis and evaluation of two classes of novel PZM21 derivatives containing the benzothiophene ring and biphenyl ring group respectively as biased μ-opioid receptor (μOR) agonists. The new compound SWG-LX-33 showed potent μOR agonist activity and produced μOR-dependent analgesia. SWG-LX-33 does not activate the β-arrestin-2 signalling pathway in vitro even at high concentrations. Computational docking demonstrated the amino acid residue ASN150 to be critical for the weak efficacy and potency of μOR agonists in arrestin recruitment.

Design and synthesis of first environment-sensitive coumarin fluorescent agonists for MrgX2

Mas related G-protein-coupled receptor member X2 (MrgX2) has been identified as the crucial receptor in drug induced pseudo-allergic reactions and allergic diseases. In this research, the first type of fluorescent agonists (ZX1, ZX2 and ZX3) for MrgX2 were developed by conjugating environment-sensitive fluorophore coumarin to MrgX2 selective agonists (R)-ZINC-3573. Their environment-sensitive property was confirmed by the dramatically increase of fluorescent intensity after binding to the hydrophobic ligand binding domain MrgX2, which help to overcome the high background signal. Based on these characteristics, they can be used for selective visualization of MrgX2 in living cells even with their own background interference. Among these fluorescent agonists, compound ZX2 possessed splendid spectroscopic properties, outstanding pharmacological activities (EC₅₀ = 0.93 μM, K_D = 1.97 μM). And a competitive binding assay was established with ZX2 to analysis the binding affinity of MrgX2 agonists, which shown high coherence with the results of cell membrane chromatography. To our knowledge, these probes are the first fluorescent ligands of MrgX2 with agonistic activity and environment-sensitive property, which is expected to use for the development of MrgX2 molecular pharmacology and serve as a convenient high-throughput screening tool for the drug candidates targeting MrgX2.

LC-MS Based Analysis and Biological Properties of Pseudocedrela kotschyi (Schweinf.) Harms Extracts: A Valuable Source of Antioxidant, Antifungal, and Antibacterial Compounds

The impact of two extraction solvents on the phenolic composition, antioxidant, and enzymes inhibitory and antimicrobial activities of two parts (leaves and stem bark) of P. kotschyi was studied. Two different LC-DAD-MSⁿ approaches were used to identify and quantify the bioactive compounds in the different extracts. A total of thirty-two compounds were quantified, being the procyanidin the most abundant in stem bark while catechin and flavonoids are most abundant in leaves. Overall, the stem bark extraction using methanol showed higher amounts of total phenolic (131.83 ± 1.81 mg GAE/g) and flavanol (14.14 ± 0.11 mg CE/g) while the leaves extraction using water exhibited stronger levels of total flavonoid (44.95 ± 0.38 mg RE/g) and phenolic acid (63.58 ± 2.00 mg CAE/g). As regards the antioxidant assays, methanol stem bark extracts were characterized by the highest antioxidant activities (DPPH: 1.94 ± 0.01 mmol TE/g, ABTS: 3.31 ± 0.01 mmol TE/g, FRAP: 2.86 ± 0.02 mmol TE/g, CUPRAC: 5.09 ± 0.08 mmol TE/g, phosphomolybdenum: 5.16 ± 0.23 mmol TE/g and metal chelating: 17.12 ± 0.46 mg EDTAE/g). In addition, the methanolic extracts of stem bark had highest impact on acetylcholinesterase (2.54 mg GALAE/g), butyrylcholinesterase (5.48 mg GALAE/g). In contrast, the methanolic extracts of leaves was potent against tyrosinase (77.39 ± 0.21 mg KAE/g) and α-glucosidase (0.97 ± 0.01 mmol ACAE/g), while a higher anti-α–amylase (0.97 ± 0.01 mmol ACAE/g) was observed for water extracts of the same part. All of the tested extracts showed inhibitory effects on elastase, except methanolic leaves extracts. Additionally, the extracts exhibited appreciable antifungal toward A. ochraceus, A. fumigatus, P. ochrochloron, T. viride, and P. funiculosum and promising antibacterial activity against M. flavus, S. aureus, L. monocytogenes, E. coli, P. aeruginosa, E. cloacae, and S. typhimurium. Taken together, the outcomes demonstrated P. kotschyi as a novel source of bioactive molecules of interest with an evident therapeutic value.

Endogenous opiates and behavior: 2019

This paper is the forty-second consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2019 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Bone-Targeted Extracellular Vesicles from Mesenchymal Stem Cells for Osteoporosis Therapy

Background

Current drugs used for osteoporosis therapy show strong adverse effects. Stem cell-derived extracellular vesicles (EVs) provide another choice for osteoporosis therapy. Mouse mesenchymal stem cells (mMSCs)-derived EVs promote bone regeneration; however, their clinical application is limited due to non-specific tissue targeting. Alendronate specifically targets bone tissue via hydroxyapatite. Therefore, EVs were combined with alendronate to generate Ale-EVs by “click chemistry” to facilitate EVs targeting bone via alendronate/hydroxyapatite binding.

Methods

Ale-EVs were characterized based on size using dynamic light scattering analysis and morphology was visualized by transmission electron microscopy. Hydroxyapatite affinity of Ale-EVs was detected by flow cytometry. Bone targeting of Ale-EVs was tested by ex vivo fluorescent imaging. Cell viability was assessed by using WST-8 reduction assay kit for testing the ability of Ale-EVs to promote mMSCs proliferation. Alkaline phosphatase experiment was used to detect ability of Ale-EVs to promote differentiation of mouse mesenchymal stem cells in vitro. Western blotting and Q-PCR assay were used to detect the early marker of osteogenic differentiation. Antiosteoporotic effects of Ale-EVs were detected in ovariectomy (OVX)-induced osteoporosis rat model. The safety of the Ale-EVs in vivo was measured by H&E staining and serum markers assay.

Results

In vitro, Ale-EVs had high affinity with hydroxyapatite. Also, ex vivo data indicated that Ale-EVs-DiD treatment of mice induced strong fluorescece in bone tissues compared with EVs-DiD group. Furthermore, results suggested that Ale-EVs promoted the growth and differentiation of mouse MSCs. They also protected against osteoporosis in ovariectomy (OVX)-induced osteoporotic rats. Ale-EVs were well tolerated and no side effects were found, indicating that Ale-EVs specifically target bone and can be used as a new therapeutic in osteoporosis treatment.

Conclusion

We used the Ale-N3 to modify mouse mesenchymal stem cells-derived extracellular vesicles by copper-free “click chemistry” to generate a Ale-EVs system. The Ale-EVs had a high affinity for bone and have great potential for clinical applications in osteoporosis therapy with low systemic toxicity.

Pereira C, Stefanucci A, Mollica A, Zengin G, Llorent-Martínez EJ, Castilho PC, Custódio L. Phenolic Profile, Toxicity, Enzyme Inhibition, In Silico Studies, and Antioxidant Properties of Cakile maritima Scop. (Brassicaceae) from Southern Portugal

Cakile maritima Scop. (sea rocket) is an edible halophyte plant with several ethnomedicinal uses. This work reports the chemical profile and bioactivities of food grade extracts from sea rocket organs. Toxicity was determined on mammalian cells, and phenolic profiling and the quantitation of the main metabolites were made by high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS). Enzymatic inhibition was determined towards acetyl- and butyrylcholinesterase (AChE, BuChE), α-glucosidase, α-amylase, and tyrosinase. Docking studies were performed to tyrosinase, on the major metabolites, and samples were tested for antioxidant properties. Extracts were not toxic, were constituted mainly by flavonoids, and some compounds (roseoside and oleuropein) are here described for the first time in the species. The aerial organs' ethanol extract had relevant activity towards 2,2-diphenyl-1-picrylhydrazyl [DPPH, half maximal inhibitory concentration (IC50) = 0.59 mg/mL], and ferric-reducing activity power (FRAP, IC50 = 0.99 mg/mL). All samples were more active towards AChE than on BuChE. The ethanol fruits' extract inhibited α-glucosidase [2.19 mmol of equivalent of acarbose (ACAE)/g]. Samples were active against tyrosinase, especially the aerial organs' ethanol extracts [25.9 mg of equivalent of kojic acid (KAE)/g]. Quercetin and kaempferol glycosides fit well into the enzymatic pocket of tyrosinase. Our results suggest sea rocket as a candidate to be further explored as a source of bioactive products.

A Survey of Molecular Imaging of Opioid Receptors

The discovery of endogenous peptide ligands for morphine binding sites occurred in parallel with the identification of three subclasses of opioid receptor (OR), traditionally designated as μ, δ, and κ, along with the more recently defined opioid-receptor-like (ORL1) receptor. Early efforts in opioid receptor radiochemistry focused on the structure of the prototype agonist ligand, morphine, although N-[methyl-¹¹C]morphine, -codeine and -heroin did not show significant binding in vivo. [¹¹C]Diprenorphine ([¹¹C]DPN), an orvinol type, non-selective OR antagonist ligand, was among the first successful PET tracers for molecular brain imaging, but has been largely supplanted in research studies by the μ-preferring agonist [¹¹C]carfentanil ([¹¹C]Caf). These two tracers have the property of being displaceable by endogenous opioid peptides in living brain, thus potentially serving in a competition-binding model. Indeed, many clinical PET studies with [¹¹C]DPN or [¹¹C]Caf affirm the release of endogenous opioids in response to painful stimuli. Numerous other PET studies implicate μ-OR signaling in aspects of human personality and vulnerability to drug dependence, but there have been very few clinical PET studies of μORs in neurological disorders. Tracers based on naltrindole, a non-peptide antagonist of the δ-preferring endogenous opioid enkephalin, have been used in PET studies of δORs, and [¹¹C]GR103545 is validated for studies of κORs. Structures such as [¹¹C]NOP-1A show selective binding at ORL-1 receptors in living brain. However, there is scant documentation of δ-, κ-, or ORL1 receptors in healthy human brain or in neurological and psychiatric disorders; here, clinical PET research must catch up with recent progress in radiopharmaceutical chemistry.

Discovery of Orexant and Anorexant Agents with Indazole Scaffold Endowed with Peripheral Antiedema Activity

The endocannabinoid system represents an integrated neuronal network involved in the control of several organisms' functions, such as feeding behavior. A series of hybrids of 5-(4-chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-N-(piperidin-1-yl)-1H-pyrazole-3-carboxamide (mimonabant), a well-known inverse agonist of the type-1 cannabinoid receptor (CB1), once used as an antiobesity drug, and the N-(2S)-substitutes of 1-[(4-fluorophenyl)methyl]indazole-3-carboxamide with 1-amino-3-methyl-1-oxobutane (AB-Fubinaca), 1-amino-3,3-dimethyl-1-oxobutane (ADB-Fubinaca), and 3-methylbutanoate (AMB-Fubinaca), endowed with potent agonistic activity towards cannabinoid receptors CB1 and CB2 were in solution as C-terminal amides, acids, methyl esters and N-methyl amides. These compounds have been studied by binding assays to cannabinoid receptors and by functional receptor assays, using rat brain membranes in vitro. The most active among them as an agonist, (S)-1-(2,4-dichlorobenzyl)-N-(3,3-dimethyl-1-(methylamino)-1-oxobutan-2-yl)-1H-indazole-3-carboxamide (LONI11), and an antagonist, (S)-2-(1-(2,4-dichlorobenzyl)-1H-indazole-3-carboxamido)-3-methylbutanoic acid (LONI4), were tested in vivo in mic, to evaluate their ability to stimulate or suppress feeding behavior after intraperitoneal (i.p.) administration. For a LONI11 formalin test and a tail flick test after an administration by the subcutaneous (s.c.) and intracerebroventricular (i.c.v.) routes, respectively, were also carried out in vivo in mice to investigate the antinociceptive property at the central and peripheral levesl. We observed a significant orexant effect for LONI11 and an intense anorexant effect for (S)-methyl 2-(1-(2,4-dichlorobenzyl)-1H-indazole-3-carboxamido)-3,3-dimethylbutanoate (LONI2) and LONI4. In zymosan-induced edema and hyperalgesia, LONI11 reduced the percent of paw volume increase and paw latency after s.c. administration, also suggesting a possible peripheral anti-inflammatory activity.