博士 / 國立臺灣大學 / 解剖學研究所 / 95 / The present study aimed to investigate the interaction between glial cells and neurons in the adult rat retina after kainic acid (KA)-induced excitotoxicity. First, prominent cell death revealed by Fluoro Jade B (FJB) staining appeared in the ganglion cell layer (GCL) and inner border of the inner nuclear layer (INL) at 1 day post-injection. The immunoreactivity of NR1 (NMDA receptor) and GluR2/3 (AMPA receptor) was decreased initially at the same time intervals but elevated at 7 days. However, the expression of GluR5/6/7 (KA receptor) and EAAT1 (excitatory amino acid transporters 1) were increased at 1 day after KA treatment. Double labeling study has revealed that the retinal Müller glial cells expressed concurrently GFAP and NR1 antigens (GFAP+/NR1+), GluR2/3 (GFAP+/GluR2/3+) or GluR5/6/7 (GFAP+/GluR5/6/7+) after 3 days KA challenge. Calbindin (CB) labelled ganglion cells and horizontal cells showed no significant changes throughout the excitotoxic lesion. On the contrary, parvalbumin (PV) immunoreactivity in ganglion cells was decreased. Remarkably, KA-induced neurotoxicity also resulted in the expression of CB or PV in cells scattered throughout the shrunk retina. Present results suggest that different iGluRs subunits probably play different roles in mediating kainate-induced excitotoxicity. That the retinal Müller glial cells and astrocytes were induced to express EAAT1 and GFAP/ iGluRs further indicates that they are linked to neuronal degeneration in the glutamatergic system in this KA-induced excitotoxicity.
Second, an increased expression of the complement receptor type 3 (CR3), the major histocompatibility complex (MHC) class II and ED-1 antigens were mainly observed in the inner retina after kainate injection. Interestingly, some immunoreactive cells appeared in the outer segment of photoreceptor layer (OSPRL) at different time intervals. Our quantitative analysis further showed that CR3 immunoreactivity was drastically increased peaking at 7 days but subsided thereafter. MHC class II and ED-1 immunoreactivities showed a moderate but steady increase peaking at 3 days and declined thereafter. Double labeling study further revealed that retinal microglia/macrophages expressed concurrently CR3 and ED-1 antigens (OX-42+/ED-1+) or MHC class II molecules (OX-42+/OX-6+) and remained branched in shape at early stage of kainate challenge. By electron microscopy, microglia/macrophages with CR3 immunoreactivity displayed abundant cytoplasm containing a few vesicles and phagosomes. Other cells ultrastructurally similar to Müller cells or astrocytes could also engulf exogenous substances.
Third, both the astrocytes and Müller glial cells reacted vigorously to kainate injection as shown by their up-regulated expression of nestin, glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS). A major finding was the induced expression of nestin together with GFAP beginning at 1 day post-injection of kainate. Western blotting analysis confirmed a marked increase in expression of nestin, GFAP and GS when compared to untreated/normal retina. Double labeling study has revealed that astrocytes and Müller glial cells expressed radial glia marker, nestin, and incorporated bromodeoxyuridine (BrdU) to re-enter into their cell cycle. The induced expression of these proteins in astrocytes and Müller glial cells indicated an induction of gliotic responses and de-differentiation that may be associated with regenerative efforts after kainate-induced injury. Additionally, induced expression of brain lipid-binding protein (BLBP) and doublecortin (DCX) in kainate-impacted astrocytes and Müller glial cells re-strengthened the potentiality of these cells to de-differentiate and reacquire an immature molecular profile in retinal neurodegeneration.
| Identifer | oai:union.ndltd.org:TW/095NTU05391004 |
| Date | January 2006 |
| Creators | Min-Lin Chang, 章敏玲 |
| Contributors | , 溫振源, 謝正勇 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 148 |
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