Brain-specific glycosylation of protein tyrosine phosphatase receptor type Z (PTPRZ) marks a demyelination-associated astrocyte subtype.

Astrocytes are the most abundant glial cell type in the brain, where they participate in various homeostatic functions. Transcriptomically, diverse astrocyte subpopulations play distinct roles during development and disease progression. However, the biochemical identification of astrocyte subtypes, especially by membrane surface protein glycosylation, remains poorly investigated. Protein tyrosine phosphatase receptor type zeta (PTPRZ) is a highly expressed membrane protein in CNS glia cells that can be modified with diverse glycosylation, including the unique HNK-1 capped O-mannosyl (O-Man) core M2 glycan mediated by brain-specific branching enzyme GnT-IX. Although PTPRZ modified with HNK-1 capped O-Man glycans (HNK-1-O-Man+ PTPRZ) is increased in reactive astrocytes of demyelination model mice, whether such astrocytes emerge in a broad range of disease-associated conditions or are limited to conditions associated with demyelination remains unclear. Here, we show that HNK-1-O-Man+ PTPRZ localizes in hypertrophic astrocytes of damaged brain areas in patients with multiple sclerosis. Furthermore, we show that astrocytes expressing HNK-1-O-Man+ PTPRZ are present in two demyelination mouse models (cuprizone-fed mice and a vanishing white matter disease model), while traumatic brain injury does not induce glycosylation. Administration of cuprizone to Aldh1l1-eGFP and Olig2KICreER/+ ;Rosa26eGFP mice revealed that cells expressing HNK-1-O-Man+ PTPRZ are derived from cells in the astrocyte lineage. Notably, GnT-IX but not PTPRZ mRNA was up-regulated in astrocytes isolated from the corpus callosum of cuprizone model mice. These results suggest that the unique PTPRZ glycosylation plays a key role in the patterning of demyelination-associated astrocytes.

Loss of branched O-mannosyl glycans in astrocytes accelerates remyelination.

In demyelinating diseases such as multiple sclerosis, a critical problem is failure of remyelination, which is important for protecting axons against degeneration and restoring conduction deficits. However, the underlying mechanism of demyelination/remyelination remains unclear. N-acetylglucosaminyltransferase-IX (GnT-IX; also known as GnT-Vb) is a brain-specific glycosyltransferase that catalyzes the branched formation of O-mannosyl glycan structures. O-Mannosylation of α-dystroglycan is critical for its function as an extracellular matrix receptor, but the biological significance of its branched structures, which are exclusively found in the brain, is unclear. In this study, we found that GnT-IX formed branched O-mannosyl glycans on receptor protein tyrosine phosphatase ß (RPTPß) in vivo. Since RPTPß is thought to play a regulatory role in demyelinating diseases, GnT-IX-deficient mice were subjected to cuprizone-induced demyelination. Cuprizone feeding for 8 weeks gradually promoted demyelination in wild-type mice. In GnT-IX-deficient mice, the myelin content in the corpus callosum was reduced after 4 weeks of treatment, but markedly increased at 8 weeks, suggesting enhanced remyelination under GnT-IX deficiency. Furthermore, astrocyte activation in the corpus callosum of GnT-IX-deficient mice was significantly attenuated, and an oligodendrocyte cell lineage analysis indicated that more oligodendrocyte precursor cells differentiated into mature oligodendrocytes. Together, branched O-mannosyl glycans in the corpus callosum in the brain are a necessary component of remyelination inhibition in the cuprizone-induced demyelination model, suggesting that modulation of O-mannosyl glycans is a likely candidate for therapeutic strategies.

Identification of ectonucleotide pyrophosphatase/phosphodiesterase 3 (ENPP3) as a regulator of N-acetylglucosaminyltransferase GnT-IX (GnT-Vb).

Our previous studies on a ß1,6-N-acetylglucosaminyltransferase, GnT-IX (GnT-Vb), a homolog of GnT-V, indicated that the enzyme has a broad GlcNAc transfer activity toward N-linked and O-mannosyl glycan core structures and that its brain-specific gene expression is regulated by epigenetic histone modifications. In this study, we demonstrate the existence of an endogenous inhibitory factor for GnT-IX that functions as a key regulator for GnT-IX enzymatic activity in Neuro2a (N2a) cells. We purified this factor from N2a cells and found that it is identical to ectonucleotide pyrophosphatase/phosphodiesterase 3 (ENPP3), as evidenced by mass spectrometry and by the knockdown and overexpression of ENPP3 in cultured cells. Kinetic analyses revealed that the mechanism responsible for the inhibition of GnT-IX caused by ENPP3 is the ENPP3-mediated hydrolysis of the nucleotide sugar donor substrate, UDP-GlcNAc, with the resulting generation of UMP, a potent and competitive inhibitor of GnT-IX. Indeed, ENPP3 knockdown cells had significantly increased levels of intracellular nucleotide sugars and displayed changes in the total cellular glycosylation profile. In addition to chaperones or other known regulators of glycosyltransferases, the ENPP3-mediated hydrolysis of nucleotide sugars would have widespread and significant impacts on glycosyltransferase activities and would be responsible for altering the total cellular glycosylation profile and modulating cellular functions.

Evaluation of an edible blue-green alga, Aphanothece sacrum, for its inhibitory effect on replication of herpes simplex virus type 2 and influenza virus type A.

A hot-water extract of Aphanothece sacrum, an edible aquacultured blue-green alga, was found to show a remarkable inhibitory effect on the replication of enveloped viruses including herpes simplex virus type 2 (HSV-2) and influenza virus type A (IFV-A, H1N1) in vitro. The main active components were suggested to be sulfated polysaccharides in non-dialyzable portion (ASWPH). ASWPH was found to inhibit the viral adsorption to the receptor of the host cells involved in the replication process of HSV-2 and IFV-A. In addition, while the penetration stage of HSV-2 was also significantly suppressed with ASWPH, no such effect was observed in the replication of IFV-A. These results suggest that ASWPH might be useful in the prevention of infectious diseases caused by HSV-2 as well as IFV-A.

Structures of filum terminale and characteristics of ependymal cells of its central canal in rats.

The filum terminale (FT) is a potential source of ependymal cells for transplantation. The present study was performed to clarify the characteristics of ependymal cells of the central canal (CC) of the FT in rats. The FT was a thin strand continuous with the conus medullaris (CM), a caudal end of the main spinal cord, situated at the L3-4 level in adult rats. The border between the CM and FT was not visible, but could be defined as the site where the strand was as thin as its more caudal segment. While the CM contained an appreciable amount of white and grey matter associated with the CC at its center, the FT had no or only a negligible amount of such spinal cord parenchymal tissue. The FT was tracked ca. 4 cm from the site defined above to the level of S4-5 in adult rats. The rostral part of the FT (FTI) included within the cauda equina is exposed to cerebrospinal fluid, whereas the more caudal part (FTE) was surrounded by a dense layer of connective tissue. Almost all ependymal cells were immunostained for Sox2, Sox9, FoxJ1, and CD133, generally recognized immunochemical markers for ependymal cells of the CC in the spinal cord. Ependymal cells of the CC of FT exhibited almost the same structural and immunohistochemical characteristics as those of the CC of the main spinal cord. Ependymal cells of FTI covered by a thin layer of connective tissue are considered appropriate for transplantation.

Defensive effects of a fucoidan from brown alga Undaria pinnatifida against herpes simplex virus infection.

Fucoidan, a sulfated polysaccharide isolated from an edible brown alga Undaria pinnatifida, was previously shown to be a potent inhibitor of the in vitro replication of herpes simplex virus type 1 (HSV-1). HSV-1 is a member of herpes viruses that cause infections ranging from trivial mucosal ulcers to life-threatening disorders in immunocompromised hosts. In the in vivo conditions, the replication of HSV-1 is controlled under the immunoresponse coordinated by both the innate and adaptive immune systems. In the present study, the effects of the fucoidan were examined on in vivo viral replication and the host's immune defense system. Oral administration of the fucoidan protected mice from infection with HSV-1 as judged from the survival rate and lesion scores. Phagocytic activity of macrophages and B cell blastogenesis in vitro were significantly stimulated by the fucoidan, while no significant change in the release of NO(2)(-) by macrophages was observed. In in vivo studies, oral administration of the fucoidan produced the augmentation of NK activity in HSV-1-infected mice immunosuppressed by 5-fluorouracil treatment. CTL activity in HSV-1-infected mice was also enhanced by oral administration of the fucoidan. The production of neutralizing antibodies in the mice inoculated with HSV-1 was significantly promoted during the oral administration of the fucoidan for 3 weeks. These results suggested that oral intake of the fucoidan might take the protective effects through direct inhibition of viral replication and stimulation of both innate and adaptive immune defense functions.

[Structure and antiviral activity of an acidic polysaccharide from an edible blue-green alga, Nostoc flagelliforme].

Recently, the development of antiviral agents with novel mechanisms of action has been required since many types of infectious disease have become a serious problem in our society. In the present study, we isolated a novel acidic polysaccharide, nostoflan (NSF), from a terrestrial blue-green alga, Nostoc flagelliforme, and examined its structure and antiviral activity. The sugar composition and methylation analyses of NSF revealed that it is mainly composed of (-->4)- D-Glcp-(1-->, -->6,4)-D-Glcp-(1-->, -->4)-D-Galp-(1-->, -->4)-D-Xylp-(1-->, D-GlcAp-(1-->, D-Manp-(1-->) with a ratio of ca. 1:1:1:1:0.8:0.2. Oligosaccharide analysis after partial acid hydrolysis of NSF revealed that this polysaccharide might be mainly composed of the sugar sequences of (-->4)-beta-D-Glcp-(1-->4)-D-Xylp-(1 and-->4)-[beta-D-GlcAp-(1-->6)-]-beta-D-Glcp-(1-->4)-D-Galp-(1-->). NSF showed potent antiviral activities against several enveloped viruses including herpes simplex virus type 1, type 2 (HSV-1, HSV-2), human cytomegalovirus, and influenza A virus (IFV). NSF selectively inhibited the attachment of HSV-1 to host cells but not its penetration phase. In an experimental animal study where IFV-infected mice received NSF intranasally, the mortality of mice was significantly decreased. Neutralizing titers in sera of mice treated with NSF were higher than in those treated with oseltamivir. From these results, NSF was found to be a novel polysaccharide that shows antiviral activity in vitro and in vivo in spite of a nonsulfated polysaccharide.

Effects of Intrathecal Injection of the Conditioned Medium from Bone Marrow Stromal Cells on Spinal Cord Injury in Rats.

Bone marrow stromal cells (BMSCs) have been studied for the treatment of spinal cord injury (SCI). In previous studies, we showed that the transplantation of BMSCs, even though they disappeared from the host spinal cord within 1-3 weeks after transplantation, improved locomotor behaviors and promoted axonal regeneration. This result led to the hypothesis that BMSCs might release some neurotrophic factors effective for the treatment of SCI. The present study examined this by injecting the conditioned medium (CM) of BMSCs to treat SCI in rats. The spinal cord was contusion-injured, followed immediately by continuous injection for 2 weeks of the CM of BMSCs through the cerebrospinal fluid via the 4th ventricle using an Alzet osmotic pump. Locomotor behaviors evaluated by the Basso-Beattie-Bresnahan score were markedly improved in the CM-injection group, compared with the control group, at 1 to 4 weeks post-injection. The contusion-injured site of the spinal cord was identified as an astrocyte-devoid area, which contained no astrocytes but was filled with collagen matrices and empty cavities of various sizes. Collagen matrices contained type I collagen and laminin. Numerous axons extended through the collagen matrices of the astrocyte-devoid area. Axons were surrounded by Schwann cells, exhibiting the same morphological characteristics as peripheral nerve fibers. The density of axons extending through the astrocyte-devoid area was higher in the CM-injection group, compared with the control group. CM injection had beneficial effects on locomotor improvements and tissue repair, including axonal regeneration, meaning that the BMSC-CM stimulated the intrinsic ability of the spinal cord to regenerate. Activation of the intrinsic ability of the spinal cord to regenerate by the injection of neurotrophic factors such as BMSC-CM is considered to be a safe and preferable method for the clinical treatment of SCI.

Effects of Multiple Injection of Bone Marrow Mononuclear Cells on Spinal Cord Injury of Rats.

The effects of multiple injection of bone marrow mononuclear cells (BMNCs) on spinal cord injury (SCI) were compared with those of single injection in rats. BMNCs separated by density-gradient centrifugation from a bone marrow perfusate were injected three times (once weekly) through the cerebrospinal fluid (CSF) via the fourth ventricle, and the locomotor improvement and tissue recovery, including axonal regeneration, were compared with those of single injection. While the single-injection group showed a steep elevation of the Basso-Beattie-Bresnahan (BBB) score 1 week after transplantation, the multiple-injection group maintained a similar steep elevation for 2 weeks after transplantation, and the BBB scores of the multiple-injection group remained thereafter at a level approximately 2-3 points higher than those of the single-injection group until the end of the experiment. There were significant differences between the single- and multiple-injection groups at 3, 4, and 8 weeks after transplantation. The difference in BBB scores at 8 weeks after transplantation suggested that there was a marked difference in the quality of locomotor behaviors between the single-and multiple-injection groups at this stage. An extensive outgrowth of regenerating axons through the astrocyte-devoid areas and a marked reduction of cavity formation were found in both the single- and multiple-injection groups. There were, however, no significant differences in the density of regenerating axons or volumes of cavities between the single- and multiple-injection groups. These results showed that although tissue recoveries were similar between single and multiple injection, the multiple injection of BMNCs was more beneficial for locomotor improvement than single injection for the treatment of SCI. Considering the technically simple and low-cost procedures for the preparation and injection of BMNCs, multiple injection of BMNCs by lumbar puncture has an advantage over single injection on clinical application.

Points regarding cell transplantation for the treatment of spinal cord injury.

Transplantation of somatic cells, including bone marrow stromal cells (BMSCs), bone marrow mononuclear cells (BMNCs), and choroid plexus epithelial cells (CPECs), enhances the outgrowth of regenerating axons and promotes locomotor improvements. They are not integrated into the host spinal cord, but disappear within 2-3 weeks after transplantation. Regenerating axons extend at the spinal cord lesion through the astrocyte-devoid area that is filled with connective tissue matrices. Regenerating axons have characteristics of peripheral nerves: they are associated with Schwann cells, and embedded in connective tissue matrices. It has been suggested that neurotrophic factors secreted from BMSCs and CPECs promote "intrinsic" ability of the spinal cord to regenerate. Transplanted Schwann cells survive long-term, and are integrated into the host spinal cord, serving as an effective scaffold for the outgrowth of regenerating axons in the spinal cord. The disadvantage that axons are blocked to extend through the glial scar at the border of the lesion is overcome. Schwann cells have been approved for clinical applications. Neural stem/progenitor cells (NSPCs) survive long-term, proliferate, and differentiate into glial cells and/or neurons after transplantation. No method is available at present to manipulate and control the behaviors of NPSCs to allow them to appropriately integrate into the host spinal cord. NPSP transplantation is not necessarily effective for locomotor improvement.

Cell transplantation for the treatment of spinal cord injury - bone marrow stromal cells and choroid plexus epithelial cells.

Transplantation of bone marrow stromal cells (BMSCs) enhanced the outgrowth of regenerating axons and promoted locomotor improvements of rats with spinal cord injury (SCI). BMSCs did not survive long-term, disappearing from the spinal cord within 2-3 weeks after transplantation. Astrocyte-devoid areas, in which no astrocytes or oligodendrocytes were found, formed at the epicenter of the lesion. It was remarkable that numerous regenerating axons extended through such astrocyte-devoid areas. Regenerating axons were associated with Schwann cells embedded in extracellular matrices. Transplantation of choroid plexus epithelial cells (CPECs) also enhanced axonal regeneration and locomotor improvements in rats with SCI. Although CPECs disappeared from the spinal cord shortly after transplantation, an extensive outgrowth of regenerating axons occurred through astrocyte-devoid areas, as in the case of BMSC transplantation. These findings suggest that BMSCs and CPECs secret neurotrophic factors that promote tissue repair of the spinal cord, including axonal regeneration and reduced cavity formation. This means that transplantation of BMSCs and CPECs promotes "intrinsic" ability of the spinal cord to regenerate. The treatment to stimulate the intrinsic regeneration ability of the spinal cord is the safest method of clinical application for SCI. It should be emphasized that the generally anticipated long-term survival, proliferation and differentiation of transplanted cells are not necessarily desirable from the clinical point of view of safety.

NTAK/neuregulin-2 secreted by astrocytes promotes survival and neurite outgrowth of neurons via ErbB3.

NTAK (neural- and thymus-derived activator for ErbB kinases), also known as neuregulin-2 (NRG2), is a member of the epidermal growth factor (EGF) family, which binds directly to ErbB3 and ErbB4, and transactivates ErbB2. NTAK/NRG2 is structurally homologous to NRG1. The biological function of NTAK/NRG2 still remains unknown, especially in the nervous system, whereas NRG1 is known to be essential for nervous system function. In the present study, we examined the functions of NTAK/NRG2 secreted from astrocytes to neurons. NTAK/NRG2 was expressed in both neurons and astrocytes, as evidenced by immunohistochemical staining and RT-PCR methods. The conditioned medium (CM) from astrocytes promoted survival and neurite outgrowth of neurons. The CM stimulated phosphorylation of ErbB3 in neurons. When phosphorylation of ErbB3 was blocked by AZD8931, an ErbB3 inhibitor, neuronal survival and neurite outgrowth were reduced. Conversely, canertinib, an ErbB4 inhibitor, did not affect survival or neurite outgrowth of neurons. Survival and neurite outgrowth of neurons were lower in CM of NTAK/NRG2-knockdown astrocytes than in the CM of control astrocytes, whereas the CM of NRG1-knockdown astrocytes had little effect on survival and neurite outgrowth. The present study demonstrated that NTAK/NRG2 secreted from astrocytes bound to ErbB3 on neurons, and promoted neuronal survival and neurite extension in vitro.

Transplantation of choroid plexus epithelial cells into contusion-injured spinal cord of rats.

PURPOSE: The effect of the transplantation of choroid plexus epithelial cells (CPECs) on locomotor improvement and tissue repair including axonal extension in spinal cord lesions was examined in rats with spinal cord injury (SCI). METHODS: CPECs were cultured from the choroid plexus of green fluorescent protein (GFP)-transgenic rats, and transplanted directly into the contusion-injured spinal cord lesions of rats of the same strain. Locomotor behaviors were evaluated based on BBB scores every week after transplantation until 4 weeks after transplantation. Histological and immunohistochemical examinations were performed at 2 days, and every week until 5 weeks after transplantation. RESULTS: Locomotor behaviors evaluated by the BBB score were significantly improved in cell-transplanted rats. Numerous axons grew, with occasional interactions with CPECs, through the astrocyte-devoid areas. These axons exhibited structural characteristics of peripheral nerves. GAP-43-positive axons were found at the border of the lesion 2 days after transplantation. Cavity formation was more reduced in cell-transplanted than control spinal cords. CPECs were found within the spinal cord lesion, and sometimes in association with astrocytes at the border of the lesion until 2 weeks after transplantation. CONCLUSION: The transplantation of CPECs enhanced locomotor improvement and tissue recovery, including axonal regeneration, in rats with SCI.

Use of glycan-targeted antibodies/lectins to study the expression/function of glycosyltransferases in the nervous system.

In the nervous system, various unique glycans not found in other tissues are expressed on glycoproteins, and their expression/functions have been studied using specific antibodies/lectins. Among brain-specific glycans in mammals, we focus on human natural killer-1 (HNK-1) and related Cat-315 epitopes, which can be detected using specific antibodies. It is known that the HNK-1 epitope is expressed on N- and O-mannosylated glycans and that Cat-315 mAb preferentially recognizes the HNK-1 epitope on brain-specific "branched O-mannose glycan." The ß1,6-branched O-mannose structure is synthesized by a brain-specific glycosyltransferase, N-acetylglucosaminyltransferase-IX (GnT-IX, also designated as GnT-Vb). Using GnT-IX gene-deficient mice and specific antibodies/lectins, the function of GnT-IX was found to be quite different from that of its ubiquitous homologue, GnT-V. Using Cat-315 mAb, the receptor protein tyrosine phosphatase-beta (RPTPß) was identified as an in vivo target glycoprotein for GnT-IX. Analysis of the function of branched O-mannose glycan on RPTPß indicated that its loss promoted the recovery process after myelin injury (called remyelination) in brain and that this phenomenon is probably caused in vivo by reduced activation of astrocytes in GnT-IX-deficient brain.

Anti-herpes simplex virus target of an acidic polysaccharide, nostoflan, from the edible blue-green alga Nostoc flagelliforme.

The acidic polysaccharide nostoflan was previously isolated as an antiviral component from the terrestrial alga Nostoc flagelliforme. In the present study, we examined the target for its anti-herpes simplex virus type 1 action. In time-of-addition experiments, the most sensitive stage of viral replication to nostoflan was found to be early events, including the virus binding and/or penetration processes. In order to determine what extent nostoflan may be involved in these processes, virus binding and penetration assays were separately performed. The results indicated that the inhibition of virus binding to but not penetration into host cells was responsible for the antiherpetic effect induced by nostoflan. Our study suggests that nostoflan may be a potential antiherpes agent.

Isolation of an antiviral polysaccharide, nostoflan, from a terrestrial cyanobacterium, Nostoc flagelliforme.

A novel acidic polysaccharide, nostoflan, was isolated from a terrestrial cyanobacterium, Nostoc flagelliforme. Nostoflan exhibited a potent anti-herpes simplex virus type 1 (HSV-1) activity with a selectivity index (50% cytotoxic concentration/50% inhibitory concentration against viral replication) of 13,000. Sugar composition and methylation analyses revealed that it was mainly composed of -->4)-D-Glcp-(1-->, -->6,4)-D-Glcp-(1-->, -->4)-D-Galp-(1-->, -->4)-D-Xylp-(1-->, D-GlcAp-(1-->, D-Manp-(1--> with a ratio of ca. 1:1:1:1:0.8:0.2. Two pyridylaminated oligosaccharides were prepared by partial acid hydrolysis and pyridylamination. On the basis of MALDI-TOF-MS and NMR analyses, they were found to be beta-D-Glcp-(1-->4)-D-Xyl-PA and beta-D-GlcAp-(1-->6)-beta-D-Glcp-(1-->4)-D-Gal-PA. From these results, nostoflan might be mainly composed of the following two types of sugar sequence: -->4)-beta-D-Glcp-(1-->4)-D-Xylp-(1--> and -->4)-[beta-D-GlcAp-(1-->6)-]-beta-D-Glcp-(1-->4)-D-Galp-(1-->. Besides anti-HSV-1 activity, nostoflan showed potent antiviral activities against HSV-2, human cytomegalovirus, and influenza A virus, but no activity against adenovirus and coxsackie virus was observed. Therefore, nostoflan has a broad antiviral spectrum against enveloped viruses whose cellular receptors are carbohydrates. Furthermore, nostoflan showed no antithrombin activity, unlike sulfated polysaccharides.