title: Endomorphin-1 analogues (MELs) penetrate the blood-brain barrier and exhibit good analgesic effects with minimal side effects.
abstract: Endomorphins are endogenous opioid peptides in mammals and display a strong antinociceptive effect after central administration. However, the clinical usage of these peptides is limited because of their diminished analgesic effect following systemic injection and their inability to cross the blood-brain barrier. In this study, we characterized the in vivo effects of four novel endomorphin-1 analogues (termed MELs), which previously showed potential as highly potent analgesics with a good pharmacological profile in vitro. The analogues were administered intravenously to several rodent pain models to examine their antinociception and blood-brain barrier permeability. The tested peptides, especially MEL1214, showed good analgesic activity and blood-brain barrier permeability. Behavioral studies showed dose-dependent analgesic effect after systematic administration of MEL1214 in the tested pain models. Pre-treatment of subcutaneous administration of naloxone methiodide did not affect the antinociception of these peptides. As compared to morphine, MEL1214 was less prone to induce tolerance after consecutive intravenous administration for 5 days. Gastrointestinal transit was evaluated by the isolated colon response and bead expulsion to determine the potential constipation effect. In contrast to morphine, MEL1214 produced no significant constipation effect at an equivalent dose. MEL1214 shows promise as a suitable compound to treat pain with reduced side effects, and exhibits good potential to be further developed as a novel opioid analgesic in pain treatment.
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, Institute of Biochemistry and Molecular Biology, Department of Pharmacology, School of Basic Medical Sciences, School of Life Science, Lanzhou University, Lanzhou, 730000, PR China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, Institute of Biochemistry and Molecular Biology, Department of Pharmacology, School of Basic Medical Sciences, School of Life Science, Lanzhou University, Lanzhou, 730000, PR China.
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, Institute of Biochemistry and Molecular Biology, Department of Pharmacology, School of Basic Medical Sciences, School of Life Science, Lanzhou University, Lanzhou, 730000, PR China.
authors.forename: Dan
authors.initials: D
authors.lastname: Wang
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, Institute of Biochemistry and Molecular Biology, Department of Pharmacology, School of Basic Medical Sciences, School of Life Science, Lanzhou University, Lanzhou, 730000, PR China.
authors.forename: Junxian
authors.initials: J
authors.lastname: Yang
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, Institute of Biochemistry and Molecular Biology, Department of Pharmacology, School of Basic Medical Sciences, School of Life Science, Lanzhou University, Lanzhou, 730000, PR China.
authors.forename: Long
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, Institute of Biochemistry and Molecular Biology, Department of Pharmacology, School of Basic Medical Sciences, School of Life Science, Lanzhou University, Lanzhou, 730000, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Yu
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, Institute of Biochemistry and Molecular Biology, Department of Pharmacology, School of Basic Medical Sciences, School of Life Science, Lanzhou University, Lanzhou, 730000, PR China. Electronic address: wangrui@lzu.edu.cn.
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
mesh_terms: D000701:Analgesics, Opioid / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000494:pharmacology*; D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism; D002199:Capillary Permeability; D003106:Colon / Q000187:drug effects; D003248:Constipation / Q000139:chemically induced; D004195:Disease Models, Animal; D004361:Drug Tolerance; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D059226:Nociceptive Pain / Q000188:drug therapy*; D009842:Oligopeptides / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000494:pharmacology*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D009842:Oligopeptides; D000644:Quaternary Ammonium Compounds; C000607693:Tyr-Pro-Trp-(2-furyl)Map-NH2; C105293:endomorphin 1; D009270:Naloxone; C041269:N-methylnaloxone; D009020:Morphine
keywords: Antinociception; Blood–brain barrier; Constipation; Endomorphin; Tolerance