Inhibition of endothelin A receptor by a novel, selective receptor antagonist enhances morphine-induced analgesia: Possible functional interaction of dimerized endothelin A and μ-opioid receptors

• Published in: Biomedicine & pharmacotherapy Vol. 141; p. 111800
• Main Authors: Kuroda, Yui, Nonaka, Miki, Kamikubo, Yuji, Ogawa, Haruo, Murayama, Takashi, Kurebayashi, Nagomi, Sakairi, Hakushun, Miyano, Kanako, Komatsu, Akane, Dodo, Tetsushi, Nakano-Ito, Kyoko, Yamaguchi, Keisuke, Sakurai, Takashi, Iseki, Masako, Hayashida, Masakazu, Uezono, Yasuhito
• Format: Journal Article
• Language: English
• Published: France Elsevier Masson SAS 01.09.2021
• Subjects: Analgesic; Analgesics, Opioid - administration & dosage; Animals; Dose-Response Relationship, Drug; Endothelin A receptor antagonist; Endothelin A Receptor Antagonists - administration & dosage; G protein-coupled receptor; HEK293 Cells; Humans; Male; Mice; Mice, Inbred C57BL; Morphine; Morphine - administration & dosage; Pain; Pain Measurement - drug effects; Pain Measurement - methods; Peptides, Cyclic - administration & dosage; Protein Multimerization - drug effects; Protein Multimerization - physiology; Receptor heterodimerization; Receptor, Endothelin A - metabolism; Receptors, Opioid, mu - metabolism; ETAR; included endothelin-1 (PubChem CID: 16212950); DTT; Morphine; Endothelin A receptor antagonist; cAMP; TIRF; Pain; Receptor heterodimerization; morphine hydrochloride (PubChem CID: 5464110); LDS; ETBR; G protein-coupled receptor; HT-488; BQ-123 sodium salt (PubChem CID: 52943236); DOR; s.c; KOR; and Bosentan Monohydrate (PubChem CID: 185462); p.o; BQ-788 sodium salt (PubChem CID: 23693553); MOR; ET-1; ST-594; Analgesic; GPCR; HBSS; CB1R
• ISSN: 0753-3322; 1950-6007; 1950-6007
• DOI: 10.1016/j.biopha.2021.111800

The misuse of opioids has led to an epidemic in recent times. The endothelin A receptor (ETAR) has recently attracted attention as a novel therapeutic target to enhance opioid analgesia. We hypothesized that endothelin A receptors may affect pain mechanisms by heterodimerization with μ opioid receptors. We examined the mechanisms of ETAR-mediated pain and the potential therapeutic effects of an ETAR antagonist, Compound-E, as an agent for analgesia. Real-time in vitro effect of Compound-E on morphine response was assessed in HEK293 cells expressing both endothelin A and μ opioid receptors through CellKey™ and cADDis cAMP assays. Endothelin A/μ opioid receptor dimerization was assessed by immunoprecipitation and live cell imaging. The in vivo effect of Compound-E was evaluated using a morphine analgesia mouse model that observed escape response behavior, body temperature, and locomotor activity. In CellKey™ and cAMP assays, pretreatment of cells with endothelin-1 attenuated morphine-induced responses. These responses were improved by Compound-E, but not by BQ-123 nor by bosentan, an ETAR and endothelin B receptor antagonist. Dimerization of ETARs and μ opioid receptors was confirmed by Western blot and total internal reflection fluorescence microscopy in live cells. In vivo, Compound-E potentiated and prolonged the analgesic effects of morphine, enhanced hypothermia, and increased locomotor activity compared to morphine alone. The results suggest that attenuation by endothelin-1 of morphine analgesia may be caused by dimerization of Endothelin A/μ opioid receptors. The novel ETAR antagonist Compound-E could be an effective adjunct to reduce opioid use. [Display omitted] •Endothelin-1 attenuated the effect of morphine.•Dimerized endothelin A/μ opioid receptors may cause attenuation of morphine effects.•A novel selective ETAR antagonist enhanced the morphine-induced analgesic effect.•The ETAR antagonist may reduce the required dosage of opioids.