Zhong Chunlong, Zhao Xueren, Sarva Jayaprakash, Kozikowski Alan, Neale Joseph H, Lyeth Bruce G
Department of Neurological Surgery, The Center for Neuroscience, University of California at Davis, Davis, California 95616-8797, USA.
J Neurotrauma. 2005 Feb;22(2):266-76. doi: 10.1089/neu.2005.22.266.
Traumatic brain injury (TBI) produces a rapid and excessive elevation in extracellular glutamate associated with excitotoxicity and secondary brain pathology. The peptide neurotransmitter Nacetylaspartylglutamate (NAAG) suppresses glutamate transmission through selective activation of presynaptic Group II metabotropic glutamate receptor subtype 3 (mGluR3). Thus, inhibition of NAAG peptidase activity and the prolong presence of synaptic NAAG were hypothesized to have significant potential for cellular protection following TBI. In the present study, a novel NAAG peptidase inhibitor, ZJ-43, was used in four different doses (0, 50, 100, or 150 mg/kg). Each dose was repeatedly administered i.p. (n=5/group) by multiple injections at three times (0 time, 8 h, 16 h) after moderate lateral fluid percussion TBI in the rat. An additional group was co-administered ZJ-43 (150 mg/kg) and the Group II mGluR antagonist, LY341495 (1 mg/kg), which was predicted to abolish any protective effects of ZJ-43. Rats were euthanized at 24 h after TBI, and brains were processed with a selective marker for degenerating neurons (Fluoro-Jade B) and a marker for astrocytes (GFAP). Ipsilateral neuronal degeneration and bilateral astrocyte loss in the CA2/3 regions of the hippocampus were quantified using stereological techniques. Compared with vehicle, ZJ-43 significantly reduced the number of the ipsilateral degenerating neurons (p<0.01) with the greatest neuroprotection at the 50 mg/kg dose. Moreover, LY341495 successfully abolished the protective effects of ZJ-43. 50 mg/kg of ZJ-43 also significantly reduced the ipsilateral astrocyte loss (p<0.05). We conclude that the NAAG peptidase inhibitor ZJ-43 is a potential novel strategy to reduce both neuronal and astrocyte damage associated with the glutamate excitotoxicity after TBI.
创伤性脑损伤（TBI）会导致细胞外谷氨酸迅速过度升高，这与兴奋性毒性和继发性脑病理改变有关。肽类神经递质N-乙酰天门冬氨酰谷氨酸（NAAG）通过选择性激活突触前II型代谢型谷氨酸受体亚型3（mGluR3）来抑制谷氨酸传递。因此，有人推测抑制NAAG肽酶活性并延长突触NAAG的存在时间在TBI后具有显著的细胞保护潜力。在本研究中，一种新型的NAAG肽酶抑制剂ZJ-43被用于四种不同剂量（0、50、100或150 mg/kg）。在大鼠中度侧方流体冲击性脑损伤后的三个时间点（0小时、8小时、16小时），通过多次腹腔注射（每组n = 5）重复给予每种剂量。另外一组同时给予ZJ-43（150 mg/kg）和II型mGluR拮抗剂LY341495（1 mg/kg），预计这会消除ZJ-43的任何保护作用。TBI后24小时对大鼠实施安乐死，并使用用于退化神经元的选择性标记物（荧光玉髓B）和星形胶质细胞标记物（GFAP）对大脑进行处理。使用体视学技术对海马体CA2/3区域同侧的神经元退化和双侧星形胶质细胞损失进行定量分析。与赋形剂相比，ZJ-43显著减少了同侧退化神经元的数量（p<0.01），50 mg/kg剂量时具有最大的神经保护作用。此外，LY341495成功消除了ZJ-43的保护作用。50 mg/kg的ZJ-43也显著减少了同侧星形胶质细胞的损失（p<0.05）。我们得出结论，NAAG肽酶抑制剂ZJ-43是一种潜在的新策略，可减少与TBI后谷氨酸兴奋性毒性相关的神经元和星形胶质细胞损伤。
