No abstract

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.

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.

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 ␣-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 ␤ (RPTP␤) in vivo. Since RPTP␤ is thought to play a regulatory role in demyelinating diseases, GnT-IX-deficient mice were subjected to cuprizoneinduced 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.

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.