Salort G, Álvaro-Bartolomé M, García-Sevilla JA. Regulation of cannabinoid CB
2 receptor constitutive activity in vivo: repeated treatments with inverse agonists reverse the acute activation of JNK and associated apoptotic signaling in mouse brain.
Psychopharmacology (Berl) 2017;
234:925-941. [PMID:
28127623 DOI:
10.1007/s00213-017-4537-5]
[Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 01/07/2017] [Indexed: 01/29/2023]
Abstract
RATIONALE
CB2 receptors express constitutive activity and inverse agonists regulate receptor basal activity, which might be involved in death mechanisms. This study assessed the effects of a selective CB2 agonist (JWH133) and different CB2 inverse agonists (AM630, JTE907, raloxifene) on death pathways in brain.
OBJECTIVES
The acute (JWH13) and the acute/chronic effects (AM630, JTE907, raloxifene) of CB2 ligands regulating pro-apoptotic c-Jun NH2-terminal kinase (p-JNK/JNK ratio) and associated signaling of extrinsic (Fas receptor, Fas-Associated death domain protein, FADD) and intrinsic (Bax, cytochrome c) death pathways (nuclear poly (ADP-ribose) polymerase PARP) were investigated in mouse brain.
METHODS
Mice were treated with CB2 drugs and target protein contents were assessed by western blot analysis.
RESULTS
JWH133 reduced cortical JNK (-27-45%) whereas AM630 acutely increased JNK in cortex (+61-148%), cerebellum (+34-40%), and striatum (+33-42%). JTE907 and raloxifene also increased cortical JNK (+31%-57%). Acute AM630, but not JWH133, increased cortical FADD, Bax, cytochrome c, and PARP cleavage. Repeated treatments with the three CB2 inverse agonists were associated with a reversal of the acute effects resulting in decreases in cortical JNK (AM630: -36%; JTE907: -25%; raloxifene: -11%). Chronic treatments also induced a reversal with down-regulation (AM630) or only tolerance (JTE907 and raloxifene) on other apoptotic markers (FADD, Bax, cytochrome c, PARP).
CONCLUSIONS
AM630 and JTE907 are CB2 protean ligands. Thus, chronic inverse agonists abolished CB2 constitutive activity and then the ligands behaved as agonists reducing (like JWH133) JNK activity. Acute and chronic treatments with CB2 inverse agonists regulate in opposite directions brain death markers.
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