Oyagawa Caitlin R M, de la Harpe Sara M, Saroz Yurii, Glass Michelle, Vernall Andrea J, Grimsey Natasha Lillia
Department of Pharmacology and Clinical Pharmacology, School of Medical Sciences, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand.
Centre for Brain Research, School of Medical Sciences, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand.
Front Pharmacol. 2018 Nov 20;9:1202. doi: 10.3389/fphar.2018.01202. eCollection 2018.
Cannabinoid receptor 2 (CB) is predominantly distributed in immune tissues and cells and is a promising therapeutic target for modulating inflammation. In this study we designed and synthesised a series of 2,4,6-trisubstituted 1,3,5-triazines with piperazinylalkyl or 1,2-diethoxyethane (PEG2) chains as CB agonists, all of which were predicted to be considerably more polar than typical cannabinoid ligands. In this series, we found that triazines containing an adamantanyl group were conducive to CB binding whereas those with a cyclopentyl group were not. Although the covalent attachment of a PEG2 linker to the adamantyl triazines resulted in a decrease in binding affinity, some of the ligands produced very interesting hCB signalling profiles. Six compounds with notable hCB orthosteric binding were functionally characterised in three pathways; internalisation, cyclic adenosine monophosphate (cAMP) and ERK phosphorylation (pERK). These were predominantly confirmed to be hCB agonists, and upon comparison to a reference ligand (CP 55,940), four compounds exhibited signalling bias. Triazines (UOSD017) and were biased towards internalisation over cAMP and pERK, and was biased away from pERK activation relative to cAMP and internalisation. Intriguingly, the triazine with an amino-PEG2-piperazinyl linker ( [UOSD008]) was identified to be a mixed agonist/inverse agonist, exhibiting apparent neutral antagonism in the internalisation pathway, transient inverse agonism in the cAMP pathway and weak partial agonism in the pERK pathway. Both the cAMP and pERK signalling were pertussis toxin (PTX) sensitive, implying that is acting as both a weak agonist and inverse agonist at CB via Gα. Compound (UOSD015) acted as a balanced high intrinsic efficacy agonist with the potential to produce greater hCB-mediated efficacy than reference ligand CP 55,940. As includes a Boc-protected PEG2 moiety it is also a promising candidate for further modification, for example with a secondary reporter or fluorophore. The highest affinity compound in this set of relatively polar hCB ligands was compound , which acted as a slightly partial balanced agonist in comparison with CP 55,940. The ligands characterised here may therefore exhibit unique functional properties and have the potential to be valuable in the future development of CB-directed therapeutics.
大麻素受体2（CB）主要分布于免疫组织和细胞中，是调节炎症的一个有前景的治疗靶点。在本研究中，我们设计并合成了一系列带有哌嗪基烷基链或1,2 - 二乙氧基乙烷（PEG2）链的2,4,6 - 三取代1,3,5 - 三嗪作为CB激动剂，预计所有这些化合物的极性都比典型的大麻素配体大得多。在这个系列中，我们发现含有金刚烷基的三嗪有利于CB结合，而含有环戊基的则不然。尽管将PEG2连接体共价连接到金刚烷基三嗪上会导致结合亲和力下降，但一些配体产生了非常有趣的人源CB（hCB）信号传导特征。六种具有显著hCB正构结合的化合物在三条途径中进行了功能表征：内化、环磷酸腺苷（cAMP）和细胞外调节蛋白激酶磷酸化（pERK）。这些主要被确认为hCB激动剂，与参考配体（CP 55,940）相比，四种化合物表现出信号偏向性。三嗪（UOSD017）在内化方面相对于cAMP和pERK存在偏向性，并且相对于cAMP和内化，其在远离pERK激活方面存在偏向性。有趣的是，带有氨基 - PEG2 - 哌嗪基连接体的三嗪（[UOSD008]）被鉴定为混合激动剂/反向激动剂，在内化途径中表现出明显的中性拮抗作用，在cAMP途径中表现出短暂的反向激动作用，在pERK途径中表现出微弱的部分激动作用。cAMP和pERK信号传导均对百日咳毒素（PTX）敏感，这意味着它在CB上通过Gα既作为弱激动剂又作为反向激动剂起作用。化合物（UOSD015）作为一种平衡的高内在效能激动剂，有可能产生比参考配体CP 55,940更大的hCB介导的效能。由于它包含一个Boc保护的PEG2部分，它也是进一步修饰的有前景的候选物，例如与二级报告基团或荧光团结合。在这组相对极性的hCB配体中，亲和力最高的化合物是化合物，与CP 55,940相比，它作为一种轻微的部分平衡激动剂起作用。因此，这里表征的配体可能表现出独特的功能特性，并且在未来CB导向治疗的开发中具有潜在价值。
