Miyata Seiji, Nakatani Yoshihiro, Hayashi Noriko, Nakashima Toshihiro
Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Kyoto, Japan.
Brain Res. 2005 Oct 5;1058(1-2):1-9. doi: 10.1016/j.brainres.2005.07.027. Epub 2005 Sep 16.
The hypothalamo-neurohypophysial system (HNS), synthesizing arginine vasopressin (AVP) and oxytocin (OXT), is well known to show structural plasticity during chronic physiological stimulation such as salt loading and lactation. In the present study, we undertook in the HNS to study localization and activity-dependent changes in the expression of matrix-degrading enzymes such as tissue plasminogen activator (tPA) and matrix metalloprotease-3 (MMP-3). Double labeling confocal microscopy demonstrated that the immunoreactivity of tPA was localized at AVP-positive dendrites in the supraoptic nucleus (SON) and AVP-positive terminals in the neurohypophysis (NH). The immunoreactivity of tPA was also seen at astrocytic processes in the HNS. Likewise, the immunoreactivity of MMP-3 was observed at AVP-positive dendrites and terminals. High magnification observation further revealed punctate distribution of tPA and MMP-3 immunoreactivity at dendrites and terminals, suggesting that they are localized at neurosecretory granules. Salt loading, known as the chronic stimulation to cause the structural plasticity, increased protein and mRNA levels of tPA in the SON but reduced protein levels of it in the NH. The chronic stimulation also increased protein levels of urokinase plasminogen activator in the SON, but the stimulation did not change protein levels of MMP-3 in the SON and NH. Depolarizing agent KCl released tPA from isolated neurosecretosomes, and this depolarization-dependent release was abolished by verapamil, a Ca(2+) channel blocker. These results demonstrate that tPA and MMP-3 are localized mainly at dendrites and terminals of AVP-expressing magnocellular neurons and tPA is released in an activity-dependent manner, suggesting that matrix-degrading proteases are candidate molecules to be concerned with the structural plasticity in the HNS.
下丘脑 - 神经垂体系统（HNS）可合成精氨酸加压素（AVP）和催产素（OXT），众所周知，在诸如盐负荷和泌乳等慢性生理刺激过程中，该系统会表现出结构可塑性。在本研究中，我们对HNS进行研究，以探讨组织纤溶酶原激活物（tPA）和基质金属蛋白酶 - 3（MMP - 3）等基质降解酶表达的定位及活性依赖性变化。双标共聚焦显微镜显示，tPA的免疫反应性定位于视上核（SON）中AVP阳性树突以及神经垂体（NH）中AVP阳性终末。在HNS的星形胶质细胞突起处也可见tPA的免疫反应性。同样，在AVP阳性树突和终末观察到MMP - 3的免疫反应性。高倍观察进一步揭示了树突和终末处tPA和MMP - 3免疫反应性的点状分布，表明它们定位于神经分泌颗粒。盐负荷作为引起结构可塑性的慢性刺激，增加了SON中tPA的蛋白质和mRNA水平，但降低了NH中tPA的蛋白质水平。这种慢性刺激还增加了SON中尿激酶型纤溶酶原激活物的蛋白质水平，但该刺激并未改变SON和NH中MMP - 3的蛋白质水平。去极化剂氯化钾从分离的神经分泌小体中释放tPA，而这种去极化依赖性释放被钙通道阻滞剂维拉帕米所阻断。这些结果表明，tPA和MMP - 3主要定位于表达AVP的大细胞神经元的树突和终末，且tPA以活性依赖性方式释放，提示基质降解蛋白酶是与HNS结构可塑性相关的候选分子。
