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ABSTRACT: This study examined CD200 expression in different peripheral nerves and ganglia. Intense CD200 immunoreactivity was consistently localized in unmyelinated nerve fibers as opposed to a faint immunostaining in the myelinated nerve fibers. By light microscopy, structures resembling the node of Ranvier and Schmidt-Lanterman incisures in the myelinated nerve fibers displayed CD200 immunoreactivity. Ultrastructural study revealed CD200 expression on the neurilemma of Schwann cells whose microvilli and paranodal loops at the node of Ranvier were immunoreactive. The CD200 immunoexpression was also localized in the satellite glial cells of sensory and autonomic ganglia and in the enteric glial cells. Double labeling of CD200 with specific antigens of satellite glia or Schwann cells in the primary cultures of dorsal root ganglia had shown a differential expression of CD200 in the peripheral glial cells. The existence of CD200 in glial cells in the peripheral nervous system (PNS) was corroborated by the expression of CD200 mRNA and protein in a rat Schwann cell line RSC96. Using the model of crush or transected sciatic nerve, it was found that CD200 expression was attenuated or diminished at the site of lesion. A remarkable feature, however, was an increase in incidence of CD200-labelled Schmidt-Lanterman incisures proximal to the injured site at 7 days postlesion. Because CD200 has been reported to impart immunosuppressive signal, we suggest that its localization in PNS glial cells may play a novel inhibitory role in immune homeostasis in both normal and pathological conditions.
Neuroscience 03/2011; 183:32-46. · 3.38 Impact Factor
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ABSTRACT: In vivo and in vitro studies have clearly demonstrated that signaling mediated by the interaction of CD200 and its cognate receptor, CD200R, results in an attenuation of inflammatory or autoimmune responses through multiple mechanisms. The present results have shown a differential expression of CD200 in the respiratory tract of intact rats. Along the respiratory passage, CD200 was specifically distributed at the bronchiolar epithelia with intense CD200 immunoreactivity localized at the apical surface of some ciliated epithelial cells; only a limited expression was detected on the Clara cells extending into the alveolar duct. In the alveolar septum, double immunofluorescence showed intense CD200 immunolabeling on the capillary endothelia. A moderate CD200 labeling was observed on the alveolar type II epithelial cells. It was, however, absent in the alveolar type I epithelial cells and the alveolar macrophages. Immunoelectron microscopic study has revealed a specific distribution of CD200 on the luminal front of the thin portion of alveolar endothelia. During endotoxemia, the injured lungs showed a dose- and time-dependent decline of CD200 expression accompanied by a vigorous infiltration of immune cells, some of them expressing ionized calcium binding adapter protein 1 or CD200. Ultrastructural examination further showed that the marked reduction of CD200 expression was mainly attributable to the loss of alveolar endothelial CD200. It is therefore suggested that CD200 expressed by different lung cells may play diverse roles in immune homeostasis of normal lung, in particular, the molecules on alveolar endothelia that may control regular recruitment of immune cells via CD200-CD200R interaction. Additionally, it may contribute to intense infiltration of immune cells following the loss or inefficiency of CD200 under pathological conditions.
Journal of Anatomy 03/2010; 216(3):407-16. · 2.37 Impact Factor
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ABSTRACT: CD200 is a highly glycosylated cell surface protein containing two immunoglobulin superfamily domains in the extracellular region and performs immunosuppressive activities. It is widely distributed in various tissues including the vascular endothelium. We report here the distribution of CD200 in rat endothelia from different vascular beds. Endothelial CD200 immunoreactivity was weakly expressed in most arteries but was intensely expressed in the arterioles, most veins and venules, as well as continuous and fenestrated capillaries. The distribution of CD200 in the sinusoidal and lymphatic endothelia was variable. Immunoelectron microscopic studies revealed that endothelial CD200 varied considerably not only in different microvasculatures but also in the membrane domains at the subcellular level. Endothelial CD200 expression was differentially regulated by lipopolysaccharide in cell types both in vivo and in vitro. Functional assessments of endothelial CD200 suggested that the physical binding between CD200 and CD200 receptor (CD200R) was involved in T-cell adhesion to the endothelium but not in macrophage-endothelium interaction. In the latter, however, CD200 agonist, a synthetic peptide from complementarity-determining region 3 of mouse CD200, may trigger CD200R signaling in macrophages to suppress their adhesion to the endothelium. Our findings demonstrate that the distribution, subcellular localization, and lipopolysaccharide-regulation of endothelial CD200 are heterogeneous, and provide evidence elucidating the functional roles of endothelial CD200 during tissue inflammation.
Journal of Anatomy 02/2009; 214(1):183-95. · 2.37 Impact Factor
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ABSTRACT: Autophagy is a cellular response against stresses which include the infection of viruses and bacteria. We unravel that Dengue virus-2 (DV2) can trigger autophagic process in various infected cell lines demonstrated by GFP-LC3 dot formation and increased LC3-II formation. Autophagosome formation was also observed under the transmission electron microscope. DV2-induced autophagy further enhances the titers of extracellular and intracellular viruses indicating that autophagy can promote viral replication in the infected cells. Moreover, our data show that ATG5 protein is required to execute DV2-induced autophagy. All together, we are the first to demonstrate that DV can activate autophagic machinery that is favorable for viral replication.
Virology 06/2008; 374(2):240-8. · 3.35 Impact Factor
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ABSTRACT: Hyperglycemia is a well-known factor in reducing nocturnal pineal melatonin production. However, the mechanism underlying diabetes-induced insufficiency of pineal melatonin has remained uncertain. This study was undertaken to examine the structure, innervation and functional activity of the pineal gland in streptozotocin (STZ)-induced diabetes in rats by immunohistochemistry, Western blotting and image analysis. The number of the pinealocytes and the volume of pineal were also estimated using stereologic quantification including the optical fractionator and Cavalieri's method. It has also shown a progressive reduction of the total area of the pineal gland and the nuclear size of pinealocytes beginning at 4 weeks of induced diabetes. Surprisingly, the immunoreactive intensities and protein amounts of serotonin (5-HT) and protein gene product (PGP) 9.5 in the pineal gland were progressively increased from 4 weeks of diabetes. Meanwhile, nerve fibers immunoreactive for PGP 9.5 had disappeared. Diabetes-induced neuropathy was observed in nerve fibers containing tyrosine hydroxylase (TH). The affected nerve fibers appeared swollen and smooth in outline but they showed a distribution pattern, packing density and protein levels comparable to those of the age-matched control animals. Ultrastructural observations have revealed diabetes-induced deformity of Schwann cells and basal lamina, accumulation of synaptic vesicles and deprivation of the dense-core vesicles in the axon terminals and varicosities. The increase in immunoreactivities in 5-HT and PGP 9.5 and shrinkage of pineal gland in the diabetic rats suggest an inefficient enzyme activity of the pinealocytes. This coupled with the occurrence of anomalous TH nerve fibers, may lead to an ineffective sympathetic innervation of the pinealocytes resulting in reduced melatonin production in STZ-induced diabetes.
Neuroscience Research 04/2008; 60(3):233-43. · 2.25 Impact Factor
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ABSTRACT: The aim of this study was to investigate reactive changes of astrocytes and Müller glial cells in rats subjected to kainate treatment, which leads to neuronal degeneration in the ganglion cell layer and the inner border of the inner nuclear layer as confirmed by labelling with Fluoro-Jade B, a marker for degenerating neurons and fibres. Both the astrocytes and the Müller glial cells reacted vigorously to kainate injection as shown by their up-regulated expression of nestin, glial fibrillary acidic protein and glutamine synthetase. A major finding was the induced expression of nestin together with glial fibrillary acidic protein beginning at 1 day post-injection of kainate. The marked nestin expression appeared to be most intense at 1 day and was sustained till 2 weeks as compared with the untreated/normal retina. Western blotting analysis confirmed a marked increase in expression of nestin, glial fibrillary acidic protein and glutamine synthetase as compared with untreated/normal retina. Double labelling study revealed that astrocytes and Müller glial cells expressed the radial glia marker nestin, and incorporated bromodeoxyuridine 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. Indeed, with the acquisition of an immature molecular profile as manifested by the induced expression of brain lipid-binding protein and doublecortin in astrocytes and Müller glial cells, the potential of these cells to de-differentiate in retinal neurodegeneration is greatly amplified.
Journal of Anatomy 02/2007; 210(1):54-65. · 2.37 Impact Factor
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ABSTRACT: The present study was aimed to elucidate how retinal microglia/macrophages would respond to neuronal death after intravitreal kainate injection. An increased expression of the complement receptor type 3 (CR3) and an induction of the major histocompatibility complex (MHC) class II and ED-1 antigens were mainly observed in the inner retina after kainate injection. Prominent cell death revealed by Fluoro Jade B (FJB) staining and ultrastructural examination appeared at the inner border of the inner nuclear layer (INL) at 1 day post-injection. Interestingly, some immunoreactive cells appeared at 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. In conclusion, retinal microglia/macrophages responded vigorously to kainate-induced neuronal cell death that may also trigger the recruitment of macrophages from neighboring tissues and induce the phagocytotic activity of cells other than retinal microglia/macrophages.
Neuroscience Research 04/2006; 54(3):202-12. · 2.25 Impact Factor
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ABSTRACT: An increase in incidence and severity of gram-positive infections has emerged in the past decade. In this regard, attention has been focused recently on immune responses of microglial cells in the central nervous system to gram-positive bacteria. The underlying immunological and cellular events in microglial activation induced by specific bacterial toxin of gram-positive bacteria, however, have not yet been clarified fully. This study reports that a simple cell wall product, lipoteichoic acid (LTA), derived from gram-positive bacteria (Staphylococcus aureus) could trigger microglial activation in vitro. Microglia challenged with LTA showed intense ruffling of plasma membrane in the form of lamellipodia or rounded up forming cell aggregates. MTT assay and Western blot analysis with anti-proliferating cell nuclear antigen antibody showed a significant microglial proliferation that may be induced at the later phases of LTA treatment with low doses but at the early period with a high dose. Concentrated LTA also caused apoptotic death of cultured microglia showing fragmented nuclei and increased expression of annexin V or caspase 3. In response to LTA, isolated microglia increased the expression of inducible nitric oxide synthase and major histocompatibility complex class II antigen. Microglial LTA receptors such as CD14 molecule, complement receptor type 3, and macrophage scavenger receptor were upregulated concurrently. In conclusion, staphylococcal LTA can exert an immunomodulatory effect on microglial morphology, cell cycle, and immunomolecules, including its receptors.
Journal of Neuroscience Research 12/2005; 82(4):515-24. · 2.74 Impact Factor
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ABSTRACT: Lipopolysaccharide (LPS), the major proinflammatory component of gram-negative bacteria, is well known to induce sepsis and microglial activation in the CNS. On the contrary, the effect of products from gram-positive bacteria especially in areas devoid of blood-brain barrier remains to be explored. In the present study, a panel of antibodies, namely, OX-6, OX-42 and ED-1 was used to study the response of microglia/macrophages in the pineal gland of rats given an intravenous LPS or lipoteichoic acid (LTA). These antibodies recognize MHC class II antigens, complement type 3 receptors and unknown lysosomal proteins in macrophages, respectively. In rats given LPS (50 microg/kg) injection and killed 48 h later, the cell density and immunoexpression of OX-6, OX-42 and ED-1 in pineal microglia/macrophages were markedly increased. In rats receiving a high dose (20 mg/kg) of LTA, OX-42 and OX-6, immunoreactivities in pineal microglia/macrophages were also enhanced, but that of ED-1 was not. In addition, both bacterial toxins induced an increase in astrocytic profiles labelled by glial fibrillary acid protein. An interesting feature following LPS or LTA treatment was the lowering effect on serum melatonin, enhanced serotonin immunolabelling and cellular vacuolation as studied by electron microscopy in pinealocytes. The LPS- or LTA-induced vacuoles appeared to originate from the granular endoplasmic reticulum as well as the Golgi saccules. The present results suggest that LPS and LTA could induce immune responses of microglia/macrophages and astroglial activation in the pineal gland. Furthermore, the metabolic and secretory activity of pinealocytes was modified by products from both gram-positive and -negative bacteria.
Journal of Pineal Research 02/2005; 38(1):17-26. · 5.79 Impact Factor
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ABSTRACT: Using specific macrophage antibodies (OX-42, OX-6, ED-1 and ED-2), this study examined the distribution of macrophages/microglia in the pineal gland of adult rats. Except for ED-2, all antibodies labeled distinct subpopulations of macrophages/microglia in the gland; ED-2 labeling was hardly detectable. The quantitative study showed that the pineal macrophages/microglia (PMM) expressing complement type 3 receptors (OX-42) were more numerous than those expressing the major histocompatibility complex class II antigen (OX-6) or unknown cytoplasmic/lysosomal antigens (ED-1). The PMM were ubiquitous, especially the OX-42 labeled cells which were distributed from the dorsal to the ventral aspect of the gland. The macrophages/microglia labeled with OX-6 or ED-1 were localized mainly in the intermediate portion of the pineal gland. Immunolabeled cells were sparsely distributed in the distal portion of the pineal gland. A notable feature was that the OX-6 labeled macrophages/microglia showed a proximal-distal gradient in cell density. Another interesting feature was the occurrence of prominent cell aggregations around the larger blood vessels. These cells were mostly round and exhibited different immunoreactivity. Confocal microscopic study with triple immunolabeling further revealed that individual PMM cell possessed two or more different antigens (ED-1+/OX-6+, OX-42+/OX-6+ or OX-42+/ED-1+). Remarkably, a large population co-expressed ED-1+/OX-6+/OX-42+. The present results show that the expression of immunoreactive molecules in PMM varies in topographical distribution of the cells. It is suggested that this may be linked to their immunoregulatory functions in the gland.
Journal of Pineal Research 09/2003; 35(1):45-53. · 5.79 Impact Factor
