Yoon Hee Chung

Immunocytochemical study on the distribution of nitrotyrosine in the brain of the transgenic mice expressing a human Cu/Zn SOD mutation

In the previous study, we reported increased NOS expression in the astrocytes in the spinal cord of the transgenic mice that are used as ALS animal model. In the present study, we performed immunocytochemical studies to investigate the changes of nitrotyrosine-immunoreactivity in the brains of the transgenic mice, and demonstrated in vivo evidence of peroxynitrite-mediated oxidative damage in the pathogenesis of ALS. In the spinal cord of the transgenic mice, immunocytochemistry showed intensely stained nitrotyrosine-IR glial cells with the appearance of astrocytes, but no nitrotyrosine-IR glial cells were observed in the spinal cord of the control mice. In the transgenic mice, nitrotyrosine-IR neurons were observed in the hypoglossal nucleus, lateral reticular nucleus, medullary reticular formation and cerebellar nuclei. Interestingly, nitrotyrosine-IR neurons were observed in the hippocampal formation and septal area of the transgenic mice. In the hippocampus, nitrotyrosine-IR neurons in the CA1 region showed intense staining, and the immunoreactivity was localized mainly in the pyramidal cell layer. Recent studies have shown that antioxidants and selective neuronal NOS inhibitor increase survival in the SOD1 transgenic mouse model of FALS. It is possible that therapy with these agents may slow the neurodegenerative process in human ALS, perhaps through reduction of nitrotyrosine formation.

Age-related changes in CREB binding protein immunoreactivity in the cerebral cortex and hippocampus of rats.

Although the role of cAMP-response-element-binding protein (CREB) binding protein (CBP) in the neuroprotective mechanisms has been the focus of many studies, very little is known about the expression or function of CBP in aged brains. We have therefore examined age-related changes in CBP expression in the cerebral cortex and hippocampus with an immunohistochemical technique. In the cerebral cortex, the distribution patterns were not different between adult and aged groups, but the staining intensity of CBP was significantly decreased in aged rats. In the hippocampus, a distinct immunoreactivity pattern was observed in the CA1-3 areas and dentate gyrus. CBP immunoreactivity was significantly deceased in the pyramidal layer of CA1-3 regions in aged hippocampus. In the dentate gyrus of aged rats, significant decreases were also found in the granule cell layer and polymorphic layer. The first demonstration of age-related decreases in CBP expression in the cerebral cortex and hippocampus may provide useful data for investigating the pathogenesis of age-related neurodegenerative diseases and depression.

Immunohistochemical study on the distribution of six members of the Kv1 channel subunits in the rat cerebellum

Voltage-gated K(+) (Kv) channels are critical for a wide variety of processes, and play an essential role in neurons. In the present study, we have demonstrated a unique pattern of expression of the six Kv1 channel subunits in the rat cerebellum, for the first time. The greatest concentration of Kv1.2 was found in the basket cell axon plexus and terminal regions around the Purkinje cells. Relatively weak immunoreactivity for Kv1.1 was also found in this area. The somatodendritic Purkinje cell areas were intensely stained with anti-Kv1.5 antibodies. In the cerebellar nuclei, the cell bodies of cerebellar output neurons showed strong Kv1.5 and Kv1.6 immunoreactivities in the nucleus medialis, interpositus and lateralis. Interestingly, Kv1.2 immunoreactivity was found in some neurons with their processes. Our immunohistochemical results may support the notion that the formation of heteromultimeric Kv channels possibly represents an important contribution to the generation of Kv channel diversity in the brain, especially in the cerebellum.

Age-related changes in the distribution of nitrotyrosine in the cerebral cortex and hippocampus of rats.

A wealth of indirect evidence implicates oxidative damage of cellular constituents in aging, as well as in the pathogenesis of the neurodegenerative diseases of later years. In the present study, we have determined age-related changes in the distribution of 3-nitrotyrosine (3-NT) in the cerebral cortex and hippocampus of rats. In adult rats, no 3-NT-immunoreactive cells were found in the cerebral cortex and hippocampus, whereas 3-NT immunoreactivity was significantly increased in aged rats. Some pyramidal cells of CA3 area and granule cells of the dentate gyrus highly expressed 3-NT in aged rats. Many interneurons located within stratum pyramidale and stratum oriens of CA1 were strongly immunoreactive for 3-NT. Our first demonstrations of increased 3-NT in the cerebral cortex and hippocampus during aging implicate these areas as sites for functionally significant oxidative damage. The mechanisms underlying the increased immunoreactivity for 3-NT, and the functional implications of this increase, require elucidation.

Immunocytochemical study on the distribution of NOS-immunoreactive neurons in the cerebral cortex of aged rats

NITRIC oxide (NO) involvement has been demonstrated in mechanisms of synaptic plasticity, particularly in hippocampal long-term potentiation, a mechanism that underlies certain forms of learning and memory. Several findings suggest that NO production may be decreased in the aged rats. Changes in the nNOS-containing neurons with ageing were demonstrated by immunocytochemistry. NOS-immunoreactive (IR) cells in aged rats were present in all cortical areas and the hippocampus, and the pattern of distribution was similar to that of the control group. The number of NOS-IR cells in the cerebral cortex was significantly decreased in the aged rats, but the extent of changes was variable in each area, and ranged from mild decrease (< 30 %) to severe decrease (> 50%). Severely decreased areas were the cingulate cortex, parietal cortex area 1, temporal cortex area 1, 2, 3, medial part of occipital cortex area 2, monocular and binocular part of occipital cortex area 1, entorhinal cortex, hippocampus proper, dentate gyrus and subiculum. Morphologically, the number of dendritic branches seemed to be decreased in aged group and the length of dendrites of NOS-IR neurons showed a tendency to shorten. These results indicate the involvement of neuronal system containing NOS in the ageing brain, and provide the first morphological evidence for the loss of NOS neurons in the cerebral cortex of the aged rats by immunocytochemistry.

Region-specific alterations in insulin-like growth factor receptor type I in the cerebral cortex and hippocampus of aged rats

In the present study, we investigated age-related changes in IGF-I receptor localization in the cerebral cortex and hippocampus of Sprague-Dawley rats using immunohistochemistry. In the cerebral cortex of adult rats, weakly stained cells were seen in layers II-III and layer V/VI in several cortical regions. In aged rats, there was a significant increase in IGF-I receptor immunoreactivity in the pyramidal cells in the same cortical regions. In the hippocampus of adult rats, several moderately stained neurons were seen in CA1-3 areas and the dentate gyrus. Levels of IGF-I receptor protein increased substantially with age in the CA3 area of the hippocampus. Our first morphological data concerning the differential regulation of IGF-I receptors in aged cerebral cortex and hippocampus may provide insights into age-related changes in trophic support as well as basic knowledge required for the study of neurodegenerative diseases such as Alzheimers disease.

Immunohistochemical study on the distribution of MnSOD in the central nervous system of the transgenic mice expressing a human Cu/Zn SOD mutation

In the present study, we used the SOD1(G93A) mutant transgenic mice as an animal model of amyotrophic lateral sclerosis (ALS) and performed immunohistochemical studies to investigate the changes of MnSOD in the central nervous system of transgenic mice at the age of 8, 13, and 18 weeks. In the spinal cord of wild-type SOD1 (wtSOD1) and SOD1(G93A) transgenic mice, MnSOD-immunoreactive neurons were distributed mainly in the anterior horn, although they were also observed in the posterior horn. The staining intensity of MnSOD was significantly increased in the spinal cord of SOD1(G93A) transgenic mice at presymptomatic and symptomatic stage. In the brainstem of symptomatic SOD1(G93A) transgenic mice, significantly increased immunoreactivity for MnSOD was observed in abducens nucleus, facial nucleus, dorsal motor nucleus of vagus, hypoglossal nucleus, medullary and pontine reticular formation, superior and inferior olivary nucleus, and cochlear nucleus. The present study provides the first evidence that MnSOD immunoreactivity was increased in the central nervous system of SOD(G93A) transgenic mice, suggesting that mitochondria may play an important role in the pathogenesis and progress of ALS. The mechanisms underlying the increased immunoreactivity for MnSOD, and the functional implications of these increases, require elucidation.

Enhanced expression of L-type Ca2+ channels in reactive astrocytes after ischemic injury in rats.

In the present study, we have examined the expression of voltage-gated calcium channels in a rat model of transient focal ischemia using immunohistochemistry. Increased expression of class C L-type Ca2+ channels was clearly detected in reactive astrocytes in each region of the hippocampus 7 days after ischemic injury. On the contrary, class D L-type Ca2+ channels were not expressed in reactive astrocytes under these conditions. These patterns were also observed in reactive astrocytes in the affected cerebral cortex and fiber tracts. Our study showed the spatial and temporal localization of class C L-type Ca2+ channels in reactive astrocytes in ischemic rat brain, for the first time. The present studies may provide useful data for future investigations to understand the role of Ca2+ channels in reactive astrocytes following ischemia or glutamate toxicity.

Immunocytochemical localization of neuronal and inducible nitric oxide synthase in the retina of zebrafish, Brachydanio rerio.

Several previous studies have revealed the distribution of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in the retina of various species. However, nothing has been reported on the nNOS and iNOS expression in zebrafish retina, even though it has been used as an effective model for developmental studies. In this study on nNOS and iNOS immunoreactivity (IR) in the zebrafish retina, iNOS-IR signals were detected in the ganglion cell layer (GC), the inner plexiform layer (IP), the outer plexiform layer (OP) and the photoreceptor layer (PR). nNOS-IR signals were also intensely detected in the GC, IP, OP and PR. These signals were very similar to the iNOS-IR signals, except for some minor differences in relative intensities. This could be explained by the speculation that the synthesis of nitric oxide by iNOS may represent a compensatory mechanism in the absence of nNOS. We described for the first time the distribution of nNOS and iNOS-IR cells in zebrafish retina. This could provide the basis for further study on the nNOS and iNOS properties of zebrafish retina.

Immunohistochemical study on the distribution of insulin-like growth factor I (IGF-I) receptor in the central nervous system of SOD1G93A mutant transgenic mice

In the present study, we used the SOD1(G93A) mutant transgenic mice as an in vivo model of ALS and performed immunohistochemical studies to investigate the changes of insulin-like growth factor I (IGF-I) receptor in the central nervous system. IGF-I receptor-immunoreactive astrocytes were detected in the spinal cord, brainstem, central gray and cerebellar nuclei of SOD1(G93A) transgenic mice. In contrast to transgenic mice, no IGF-I receptor-immunoreactive astrocytes were observed in any brain region of wtSOD1 transgenic mice although a few moderately stained neurons were observed. In the hippocampal formation of SOD1(G93A) transgenic mice, IGF-I receptor immunoreactivity was increased in the pyramidal cells of the CA1-3 regions and granule cells of the dentate gyrus. The present study provides the first evidence that IGF-I receptor immunoreactivity was increased in reactive astrocytes in the central nervous system of SOD(G93A) transgenic mice, suggesting that reactive astrocytes may play an important role in the pathogenesis and progress of ALS. The mechanisms underlying the increased immunoreactivity for IGF-I receptor, and the functional implications of these increases, require elucidation.