Glass M J, Huang J, Oselkin M, Tarsitano M J, Wang G, Iadecola C, Pickel V M
Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, NY 10021, USA.
Neuroscience. 2006 Dec 1;143(2):547-64. doi: 10.1016/j.neuroscience.2006.08.051. Epub 2006 Oct 4.
Superoxide produced by the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase mediates crucial intracellular signaling cascades in the medial nucleus of the solitary tract (mNTS), a brain region populated by catecholaminergic neurons, as well as astroglia that play an important role in autonomic function. The mechanisms mediating NADPH oxidase (phagocyte oxidase) activity in the neural regulation of cardiovascular processes are incompletely understood, however the subcellular localization of superoxide produced by the enzyme is likely to be an important regulatory factor. We used immunogold electron microscopy to determine the phenotypic and subcellular localization of the NADPH oxidase subunits p47(phox), gp91(phox,) and p22(phox) in the mNTS in rats. The mNTS contains a large population of neurons that synthesize catecholamines. Significantly, catecholaminergic signaling can be modulated by redox reactions. Therefore, the relationship of NADPH oxidase subunit labeled neurons or glia with respect to catecholaminergic neurons was also determined by dual labeling for the superoxide producing enzyme and tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis. In the mNTS, NADPH oxidase subunits were present primarily in somatodendritic processes and astrocytes, some of which also contained TH, or were contacted by TH-labeled axons, respectively. Immunogold quantification of NADPH oxidase subunit localization showed that p47(phox) and gp91(phox) were present on the surface membrane, as well as vesicular organelles characteristic of calcium storing smooth endoplasmic reticula in dendritic and astroglial processes. These results indicate that NADPH oxidase assembly and consequent superoxide formation are likely to occur near the plasmalemma, as well as on vesicular organelles associated with intracellular calcium storage within mNTS neurons and glia. Thus, NADPH oxidase-derived superoxide may participate in intracellular signaling pathways linked to calcium regulation in diverse mNTS cell types. Moreover, NADPH oxidase-derived superoxide in neurons and glia may directly or indirectly modulate catecholaminergic neuron activity in the mNTS.
由烟酰胺腺嘌呤二核苷酸磷酸（NADPH）氧化酶产生的超氧化物介导孤束核内侧（mNTS）中的关键细胞内信号级联反应，mNTS是一个由儿茶酚胺能神经元以及在自主功能中起重要作用的星形胶质细胞组成的脑区。然而，在心血管过程的神经调节中介导NADPH氧化酶（吞噬细胞氧化酶）活性的机制尚未完全了解，但是该酶产生的超氧化物的亚细胞定位可能是一个重要的调节因子。我们使用免疫金电子显微镜来确定大鼠mNTS中NADPH氧化酶亚基p47（phox）、gp91（phox）和p22（phox）的表型和亚细胞定位。mNTS包含大量合成儿茶酚胺的神经元。值得注意的是，儿茶酚胺能信号传导可通过氧化还原反应进行调节。因此，还通过对产生超氧化物的酶和酪氨酸羟化酶（TH）（儿茶酚胺生物合成中的限速酶）进行双重标记，来确定NADPH氧化酶亚基标记的神经元或胶质细胞与儿茶酚胺能神经元的关系。在mNTS中，NADPH氧化酶亚基主要存在于树突-体细胞过程和星形胶质细胞中，其中一些星形胶质细胞还分别含有TH，或与TH标记的轴突接触。对NADPH氧化酶亚基定位进行免疫金定量分析表明，p47（phox）和gp91（phox）存在于表面膜以及树突和星形胶质细胞过程中储存钙的光滑内质网特征性囊泡细胞器上。这些结果表明，NADPH氧化酶组装以及随之而来的超氧化物形成可能发生在质膜附近，以及与mNTS神经元和胶质细胞内钙储存相关的囊泡细胞器上。因此，NADPH氧化酶衍生的超氧化物可能参与与多种mNTS细胞类型中钙调节相关的细胞内信号通路。此外，神经元和胶质细胞中NADPH氧化酶衍生的超氧化物可能直接或间接调节mNTS中儿茶酚胺能神经元的活性。
