Peripherally Active CB1 Receptor Antagonists for Alcohol-Induced Liver Fibrosis

描述(由申请人提供)：以进行性肝纤维化为特征的肝硬变是全球慢性酒精滥用导致发病率的主要原因之一。肝星状细胞(简称HSCs)在这一过程中起着关键作用。导致纤维化的一个中心事件是HSCs从静止的富含维生素A的细胞类型激活和转变为缺乏维生素A的、增殖的、成纤维的肌成纤维细胞。最近的证据表明，大麻素受体(简称CBR)在这一过程中起着重要作用。虽然CB1R和CB2R在正常肝脏中有少量表达，但在肝硬变肝脏中显著上调，主要在纤维化间隔内的平滑肌α-肌动蛋白表达细胞中。有趣的是，CB1R在激活时是促纤维化的，而CB2R起到抗纤维化的作用。因此，拮抗CB1R是抑制HSC活化和纤维化进展的合理途径。因此，由美国国家酒精滥用和酒精中毒研究所(NIAAA)赞助的一项研究选择性CB1R拮抗剂SR141716治疗酒精中毒的临床试验正在进行中。不幸的是，长期使用这种药物可能会对患者产生不良影响，特别是由于SR141716在中枢神经系统(简称CNS)的活动。因此，靶向CB1R的有效策略是开发不能通过血脑屏障(简称BBB)的外周活性CB1R拮抗剂。这一策略将把CB1R拮抗作用限制在外周，从而消除与中枢神经系统有关的慢性抑制CB1R的担忧，同时保留这些化合物有益的抗纤维化潜力。因此，我们建议通过以下两个具体目标来合成和测试外周活性的CB1R拮抗剂。通过目标1，将合成含有季铵或氨基酸部分的带电类似物SR141716，并测试其对CB1Rs的拮抗作用。这种方法的理论基础是，带电化合物不会穿过BBB，除非由特定的转运体运输，而不是它们的中性亲脂类似物(即SR141716)通常可以通过简单的扩散穿透BBB。通过目标2，将通过三个分目标对这些化合物进行表征。(A)将使用功能体外试验测试化合物对CB1R的拮抗作用。(B)这些化合物穿越血脑屏障的能力将在血脑屏障转运的体外预测模型中进行研究。(C)将使用放射性配基竞争结合分析来确定这些化合物对CB1R相对于CB2R的选择性。总之，这些研究旨在合成和测试SR141716类似物作为外周活性CB1R拮抗剂的有效性，这可能成为酒精性肝纤维化治疗开发的早期先导。

DESCRIPTION (provided by applicant): Hepatic cirrhosis characterized by progressive liver fibrosis is one of the leading causes of morbidity from chronic abuse of ethanol worldwide. Hepatic stellate cells (abbreviated HSCs) are critical to this process. A central event leading up to fibrosis is the activation and transition of HSCs from a quiescent vitamin A-rich cell type to a vitamin A-deficient, proliferative, fibrogenic myofibroblast. Recent evidence suggests that cannabinoid receptors (abbreviated CBRs) are important to this process. While CB1R and CB2R are marginally expressed in normal liver, they undergo marked upregulation in the cirrhotic liver, predominantly in smooth muscle a-actin expressing cells within the fibrotic septa. Interestingly, CB1R is pro-fibrotic upon activation, whereas CB2R plays an anti-fibrotic role. Therefore, antagonism of CB1R is a rational approach to inhibit HSC activation and progression of fibrosis. Accordingly, a clinical trial examining the efficacy of the selective CB1R antagonist SR141716 in alcoholism sponsored by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) is underway. Unfortunately, chronic use of this medication may have undesirable adverse effects in patients particularly due to the activity of SR141716 in the central nervous system (abbreviated CNS). Thus, an effective strategy to target the CB1R that could by-pass some or most of these concerns is to develop peripherally active CB1R antagonists that cannot cross the blood-brain barrier (abbreviated BBB). This strategy would restrict the effect of CB1R antagonism to the periphery, and thereby eliminate the CNS-related concerns of chronically inhibiting central CB1R while retaining the beneficial antifibrotic potential of these compounds. Thus, we propose to synthesize and test peripherally active CB1R antagonists through the following two specific aims. Through aim 1, charged analogs of SR141716 bearing either a quaternary ammonium or an amino acid moiety will be synthesized and tested for antagonism of CB1Rs. This approach is based on the rationale that charged compounds do not cross the BBB, unless transported by specific transporters, in contrast to their neutral lipophilic analogs (i.e., SR141716) that can often penetrate the BBB by simple diffusion. Through aim 2, characterization of these compounds will be performed via three sub-aims. (a) The compounds will be tested for CB1R antagonism using a functional in vitro assay. (b) The ability of these compounds to cross the BBB will be studied in an in vitro predictive model of BBB transport. (c) The selectivity of these compounds for CB1R over CB2R using radioligand competition binding assays will be determined. In total, these studies are designed to synthesize and test the utility of SR141716 analogs as peripherally active CB1R antagonists, which may serve as early leads for therapeutics development for alcohol-induced liver fibrosis.