Lysosomes contribute to anomalous pharmacokinetic behavior of melanocortin-4 receptor agonists
Lysosomes contribute to anomalous pharmacokinetic behavior of melanocortin-4 receptor agonists
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DOI：
10.1007/s11095-007-9239-y
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发表时间：
2007-06-01
影响因子：
3.7
通讯作者：
Krise, Jeffrey P.
中科院分区：
文献类型：
--
作者：
Gong, Yuping;Zhao, Zhiyang;Krise, Jeffrey P.
目的.一系列开发用作抗肥胖剂的黑皮质素-4受体（MC 4 R）激动剂被发现具有不寻常的药代动力学行为，这是由于在肝脏中的过度保留引起的，在小鼠中口服给药后在血浆中几乎检测不到水平。这项工作研究了延长肝滞留的分子基础，为设计具有改善行为的类似物提供了合理的基础。收获小鼠的肝脏，并利用技术将其破碎成细胞器差异富集的池。使用细胞器特异性酶促测定法测定各组分中细胞器的分布。对给药小鼠的肝脏进行分级，并与细胞器分布进行比较，以帮助确定药物的亚细胞定位。在细胞培养系统中的进一步分析用于确认肝脏分级分离研究的结果，并且还允许进行更广泛的评价以检查细胞器区室化的机制。口服激动剂后肝脏的分级显示在溶酶体中的隔离。随后在细胞培养系统中的评价证实了这一发现。用于破坏溶酶体酸化的试剂导致药物的溶酶体蓄积减少，这涉及pH分配型螯合机制。这些发现导致了母体化合物类似物的合理合成，其具有减少溶酶体螯合的特性。当在小鼠中检查该化合物时，发现肝脏滞留大大减少，血浆水平相对于母体化合物显著升高。具有最佳物理化学性质的弱碱性药物可以根据pH分配型机制被广泛地隔离到溶酶体中。当在动物中口服给药时，这种特定的隔离事件可以表现为在肝脏中的长期保留和血液中的可忽略水平。这项工作揭示了肝脏滞留的机制，并为设计一种新的类似物提供了一个合理的平台，该类似物具有减少的肝脏蓄积和更好的药代动力学分析和治疗活性的机会。
Purpose. A series of melanocortin-4 receptor (MC4R) agonists, developed for use as anti-obesity agents, were found to have unusual pharmacokinetic behavior arising from excessive retention in the liver, with nearly undetectable levels in plasma following oral administration in mice. This work investigates the molecular basis of the prolonged liver retention that provided a rational basis for the design of an analog with improved behavior.Materials and Methods. The livers of mice were harvested and techniques were utilized to fractionate them into pools differentially enriched in organelles. The distribution of organelles in the fractions was determined using organelle-specific enzymatic assays. Livers from mice dosed with drug were fractionated and comparisons with organelle distributions assisted in determining the subcellular localization of the drug. Further analysis in cell culture systems was used to confirm results from liver fractionation studies and also allowed for more extensive evaluations to examine the mechanism for organelle compartmentalization.Results. Fractionation of livers following oral administration of the agonist showed sequestration in lysosomes. Subsequent evaluations in a cell culture system confirmed this finding. Agents used to disrupt acidification of lysosomes led to decreased lysosomal accumulation of the drug, which implicated a pH-partitioning type sequestration mechanism. These findings led to the rational synthesis of an analog of the parent compound with properties that reduced lysosomal sequestration. When this compound was examined in mice, the liver retention was found to be greatly reduced and plasma levels were significantly elevated relative to the parent compound.Conclusions. Weakly basic drugs with optimal physicochemical properties can be extensively sequestered into lysosomes according to a pH-partitioning type mechanism. When administered orally in animals, this particular sequestration event can manifest itself in long term retention in the liver and negligible levels in blood. This work revealed the mechanism for liver retention and provided a rational platform for the design of a new analog with decreased liver accumulation and better opportunity for pharmacokinetic analysis and therapeutic activity.