Lucius R, Sievers J, Mentlein R
Anatomisches Institut, Universität Kiel, Germany.
J Neurochem. 1995 Apr;64(4):1841-7. doi: 10.1046/j.1471-4159.1995.64041841.x.
Rat microglia in culture showed a high capacity to degrade neuropeptides compared with other glial cells. Leu-enkephalin was readily hydrolyzed to free tyrosine and Gly-Gly-Phe-Leu. Inhibition experiments and immunostaining revealed that aminopeptidase N (CD13) on the surface of microglia was responsible for enkephalin cleavage. Endopeptidase-24.11 ("enkephalinase"), angiotensin-converting enzyme, or carboxypeptidases could not be detected on microglia. Aminopeptidase N activity in microglia was considerably higher than in rat peripheral monocytes and macrophages, which both also exhibited low endopeptidase 24.11 activities. Activity of aminopeptidase N was upregulated by culture of microglia on astrocytes and down-regulated by exposure of microglia to lipopolysaccharide. The occurrence of aminopeptidase N on microglia is in line with the view that they originate from the monocytic lineage.
与其他神经胶质细胞相比，培养的大鼠小胶质细胞显示出较高的神经肽降解能力。亮脑啡肽很容易被水解为游离酪氨酸和甘氨酰-甘氨酰-苯丙氨酰-亮氨酸。抑制实验和免疫染色表明，小胶质细胞表面的氨肽酶N（CD13）负责脑啡肽的裂解。在小胶质细胞上未检测到内肽酶-24.11（“脑啡肽酶”）、血管紧张素转换酶或羧肽酶。小胶质细胞中的氨肽酶N活性明显高于大鼠外周单核细胞和巨噬细胞，这两者的内肽酶24.11活性也较低。小胶质细胞在星形胶质细胞上培养可上调氨肽酶N的活性，而小胶质细胞暴露于脂多糖则可下调其活性。小胶质细胞上氨肽酶N的存在与它们起源于单核细胞谱系的观点一致。
