Galea E, Feinstein D L, Reis D J
Department of Neurology and Neuroscience, Cornell University Medical College, New York, NY 10021.
Proc Natl Acad Sci U S A. 1992 Nov 15;89(22):10945-9. doi: 10.1073/pnas.89.22.10945.
Exposure of primary cultures of neonatal rat cortical astrocytes to bacterial lipopolysaccharide (LPS) results in the appearance of nitric oxide synthase (NOS) activity. The induction of NOS, which is blocked by actinomycin D, is directly related to the duration of exposure and dose of LPS, and a 2-hr pulse can induce enzyme activity. Cytosol from LPS-treated astrocyte cultures, but not from control cultures, produces a Ca(2+)-independent conversion of L-arginine to L-citrulline that can be completely blocked by the specific NOS inhibitor NG-monomethyl-L-arginine. The induced NOS activity exhibits an apparent Km of 16.5 microM for L-arginine and is dependent on NADPH, FAD, and tetrahydrobiopterin. LPS also induces NOS in C6 glioma cells and microglial cultures but not in cultured cortical neurons. The expression of NOS in astrocytes and microglial cells has been confirmed by immunocytochemical staining using an antibody to the inducible NOS of mouse macrophages and by histochemical staining for NADPH diaphorase activity. We conclude that glial cells of the central nervous system can express an inducible form of NOS similar to the inducible NOS of macrophages. Inducible NOS in glia may, by generating nitric oxide, contribute to the neuronal damage associated with cerebral ischemia and/or demyelinating diseases.
将新生大鼠皮质星形胶质细胞的原代培养物暴露于细菌脂多糖（LPS）会导致一氧化氮合酶（NOS）活性的出现。NOS的诱导被放线菌素D阻断，它与LPS的暴露持续时间和剂量直接相关，2小时的脉冲即可诱导酶活性。LPS处理的星形胶质细胞培养物的胞质溶胶，而非对照培养物的胞质溶胶，会产生L-精氨酸到L-瓜氨酸的Ca(2+)非依赖性转化，该转化可被特异性NOS抑制剂NG-单甲基-L-精氨酸完全阻断。诱导的NOS活性对L-精氨酸的表观Km为16.5 microM，且依赖于NADPH、FAD和四氢生物蝶呤。LPS还可在C6胶质瘤细胞和小胶质细胞培养物中诱导NOS，但在培养的皮质神经元中则不会。使用针对小鼠巨噬细胞诱导型NOS的抗体进行免疫细胞化学染色以及对NADPH黄递酶活性进行组织化学染色，已证实星形胶质细胞和小胶质细胞中NOS的表达。我们得出结论，中枢神经系统的胶质细胞可表达一种类似于巨噬细胞诱导型NOS的诱导型NOS。胶质细胞中的诱导型NOS可能通过产生一氧化氮，促成与脑缺血和/或脱髓鞘疾病相关的神经元损伤。
