BRAIN TARGETING OF THYROTROPIN RELEASING HORMONE ANALOGS

促甲状腺激素释放激素类似物的大脑靶向

• 批准号: 6392617
• 负责人: LASZLO PROKAI
• 金额: $ 23.95万
• 依托单位: UNIVERSITY OF FLORIDA
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-08-05 至 2003-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6392617
• 关键词: acetylcholine; amidine lyase; bioimaging /biomedical imaging; biotransformation; blood brain barrier; brain metabolism; drug delivery systems; drug design /synthesis /production; drug screening /evaluation; enzyme activity; esterase; frontal lobe /cortex; hormone receptor; hypothalamus; injection /infusion; laboratory mouse; laboratory rat; microdialysis; neuronal transport; neuropharmacology; pentobarbital; peptide hormone analog; pharmacokinetics; radiotracer; receptor binding; thyrotropin releasing hormone

Thyrotropin-releasing hormone (TRH) analogues offer potential treatment of various maladies of the central nervous system (associated mainly with cholinergic hypofunction due to motorneuron diseases, Alzheimer's disease, electroconvulsive shock therapy, etc.). The main objective of the project is to develop and evaluate chemical delivery systems for targeting centrally active analogues into the central nervous system (CNS) by a chemical-enzymatic approach. Due to covalently attached lipophilic functional groups (a 1,4-dihydrotrigonellyl and a lipophilic moiety) a "packaged" peptide crosses the BBB by passive transport and, once in the CNS, converts to an ionic trigonellyl derivative that is retained at the target site. Then, the biologically active peptide is obtained by sequential metabolism. New brain-targeting systems will be designed and synthesized based on systematically modifying a lead compound ([Leu2]TRH) to improve sequestration of the analog in the brain and/or enhance post-delivery stability of the biologically active peptide. These modifications will allow for a decrease of the systemically administered dose and also for an increase in the residence time of the experimental or therapeutic agent in the CNS. Our hypothesis is that the efficacy of CNS-sequestration can be improved by using alpha-hydroxyglycine to achieve carboxy-terminal amidation via peptidylamidoglycolate lyase (PGL, EC 4.3.2.5) action because of the higher rate of enzymatic bioactivation after esterase cleavage of the protecting ester function. Analogues in which the carboxy-terminal prolinamide is replaced by L-pipecolic acid or the amino-terminal pyroglutaminyl residue is subtituted by an unnatural moiety will also be incorporated into appropriate targeting systems. The design and development will be supported by theoretical calculations. The newly designed analogs will be tested for binding to brain TRH receptors to compare their intrinsic activity with that of the lead compound. In vitro stability and metabolism experiments will address optimization and practical development. Stability studies in brain tissue will address rates, sites and extent of peptide activation and/or cleavage to probe crucial steps in the CNS-sequestration. In vivo distribution and metabolism studies will assess the efficacy of the strategy to transport and sequester the TRH analogs in the brain. We will examine pharmacokinetics of brain-delivery, "lock-in" of the predicted precursors, and the release of the biologically active peptide after parenteral administration of the synthesized targeting systems. Comparative pharmacodynamic evaluation of the effect of brain-delivered analogues will be addressed via in vivo cerebral microdialysis studies in which changes in acetylcholine levels due to treatment will be assayed. Ultimately, pharmacological experiments will be carried out in animals to survey the potential of the approach to treat maladies associated with the loss of cholinergic functions. The antagonism of pentobarbital-induced sleeping will be used as general paradigm to assess the acute effects of brain-targeted compounds. Behavioral observations, dose-dependence and duration of action will also be addressed by appropriate method or study designs.

促甲状腺激素释放激素(TRH)类似物有可能治疗各种中枢神经系统疾病(主要与运动神经元病、阿尔茨海默病、电惊厥休克疗法等引起的胆碱能功能减退有关)。该项目的主要目标是开发和评估通过化学-酶方法将中枢活性类似物靶向中枢神经系统(CNS)的化学递送系统。由于共价连接的亲脂官能团(1，4-二氢三角基和亲脂基团)，被包装的多肽通过被动运输穿过血脑屏障，一旦进入中枢，就转化为保留在目标位置的离子三角花环衍生物。然后，通过序贯代谢获得生物活性多肽。将在系统地修饰先导化合物([Leu2]TRH)的基础上设计和合成新的脑靶向系统，以改善类似物在大脑中的隔离和/或增强生物活性多肽的交付后的稳定性。这些改进将允许减少全身给药剂量，并增加实验或治疗剂在中枢神经系统的滞留时间。我们的假设是，由于保护酯功能的酯酶裂解后酶的生物激活率较高，因此使用α-羟基甘氨酸通过肽基层乙醇酸裂解酶(PGL，EC 4.3.2.5)作用实现羧基末端酰胺化可以提高中枢神经系统的隔离效率。用L-吡喃甲酸取代羧基末端的脯氨酰胺或用非天然的部分取代氨基末端的焦谷氨酰胺残基的类似物也将被纳入适当的靶向系统。设计和开发将得到理论计算的支持。新设计的类似物将被测试与大脑TRH受体的结合，以比较它们与先导化合物的内在活性。体外稳定性和新陈代谢实验将解决优化和实用开发。脑组织的稳定性研究将解决多肽激活和/或切割的速度、位置和程度，以探索中枢神经系统隔离的关键步骤。体内分布和代谢研究将评估在大脑中运输和隔离TRH类似物的策略的有效性。我们将检查脑内给药的药代动力学，预测前体的“锁定”，以及合成靶向系统非肠外给药后生物活性多肽的释放。将通过活体脑微透析研究对脑给药类似物的效果进行比较药效学评估，在该研究中将分析由于治疗而引起的乙酰胆碱水平的变化。最终，将在动物身上进行药理学实验，以调查这种方法治疗与胆碱能功能丧失相关的疾病的潜力。戊巴比妥诱导的睡眠的拮抗作用将被用作评估脑靶向化合物的急性效应的一般范式。行为观察、剂量依赖和作用持续时间也将通过适当的方法或研究设计来解决。