Karanian David A, Karim Sanjida L, Wood JodiAnne T, Williams John S, Lin Sonyuan, Makriyannis Alexandros, Bahr Ben A
Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT 06269-3092, USA.
J Pharmacol Exp Ther. 2007 Sep;322(3):1059-66. doi: 10.1124/jpet.107.120147. Epub 2007 Jun 1.
Endocannabinoids are released in response to pathogenic insults, and inhibitors of endocannabinoid inactivation enhance such on-demand responses that promote cellular protection. Here, AM374 (palmitylsulfonyl fluoride), an irreversible inhibitor of fatty acid amide hydrolase (FAAH), was injected i.p. into rats to test for endocannabinoid enhancement. AM374 caused a prolonged elevation of anandamide levels in several brain regions, including the hippocampus, and resulted in rapid activation of the extracellular signal regulated-kinase/mitogen-activated protein kinase pathway that has been linked to survival. To evaluate the neuroprotective nature of the FAAH inhibitor, we tested AM374 in a seizure model involving rats insulted with kainic acid (KA). AM374 was injected immediately after KA administration, and seizure scores were significantly reduced throughout a 4-h observation period. The KA-induced seizures were associated with calpain-mediated cytoskeletal breakdown, reductions in synaptic markers, and loss of CA1 hippocampal neurons. FAAH inhibition protected against the excitotoxic damage and neuronal loss assessed 48 h postinsult. AM374 also preserved pre- and postsynaptic markers to levels comparable with those found in noninsulted animals, and the synaptic marker preservation strongly correlated with reduced seizure scores. With regard to behavioral deficits in the excitotoxic rats, AM374 produced nearly complete functional protection, significantly improving balance and coordination across different behavioral paradigms. These data indicate that AM374 crosses the blood-brain barrier, enhances endocannabinoid responses in key neuronal circuitries, and protects the brain against excitotoxic damage.
内源性大麻素会在受到病原体攻击时释放，而内源性大麻素失活抑制剂可增强这种促进细胞保护的按需反应。在此，将脂肪酸酰胺水解酶（FAAH）的不可逆抑制剂AM374（棕榈酰磺酰氟）腹腔注射到大鼠体内，以测试内源性大麻素的增强作用。AM374导致包括海马体在内的几个脑区中花生四烯酸乙醇胺水平长时间升高，并导致与存活相关的细胞外信号调节激酶/丝裂原活化蛋白激酶途径迅速激活。为了评估FAAH抑制剂的神经保护特性，我们在涉及用 kainic 酸（KA）损伤大鼠的癫痫模型中测试了AM374。在给予KA后立即注射AM374，在整个4小时的观察期内癫痫发作评分显著降低。KA诱导的癫痫发作与钙蛋白酶介导的细胞骨架破坏、突触标志物减少以及海马体CA1神经元丧失有关。FAAH抑制可防止损伤后48小时评估的兴奋性毒性损伤和神经元丧失。AM374还将突触前和突触后标志物维持在与未受损伤动物相当的水平，并且突触标志物的维持与癫痫发作评分降低密切相关。关于兴奋性毒性大鼠的行为缺陷，AM374产生了几乎完全的功能保护，显著改善了不同行为范式下的平衡和协调能力。这些数据表明，AM374可穿过血脑屏障，增强关键神经回路中的内源性大麻素反应，并保护大脑免受兴奋性毒性损伤。
