- Acetylated chitosan oligosaccharides act as antagonists against glutamate-induced PC12 cell death via Bcl-2/Bax signal pathway
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Chitosan oligosaccharides (COSs), depolymerized products of chitosan composed of β-(1→4) D-glucosamine units, have broad range of biological activities such as antitumour, antifungal, and antioxidant activities. In this study, peracetylated chitosan oligosaccharides (PACOs) and N-acetylated chitosan oligosaccharides (NACOs) were prepared from the COSs by chemcal modification. The structures of these monomers were identified using NMR and ESI-MS spectra. Their antagonist effects against glutamate-induced PC12 cell death were investigated. The results showed that pretreatment of PC12 cells with the PACOs markedly inhibited glutamate-induced cell death in a concentration-dependent manner. The PACOs were better glutamate antagonists compared to the COSs and the NACOs, suggesting the peracetylation is essential for the neuroprotective effects of chitosan oligosaccharides. In addition, the PACOs pretreatment significantly reduced lactate dehydrogenase release and reactive oxygen species production. It also attenuated the loss of mitochondrial membrane potential. Further studies indicated that the PACOs inhibited glutamate-induced cell death by preventing apoptosis through depressing the elevation of Bax/Bcl-2 ratio and caspase-3 activation. These results suggest that PACOs might be promising antagonists against glutamate-induced neural cell death.
- Hao, Cui,Gao, Lixia,Zhang, Yiran,Wang, Wei,Yu, Guangli,Guan, Huashi,Zhang, Lijuan,Li, Chunxia
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p. 1267 - 1289
(2015/04/14)
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- Synthesis of 4-Methylcoumarin-7-yloxy Tetra-N-acetyl-β-chitotetraoside, a Novel Synthetic Substrate for the Fluorometric Assay of Lysozyme
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4-Methylcoumarin-7-yloxy tetra-N-acetyl-β-chitotetraoside (10) was synthesized from chitin in pure form by a novel procedure.After acetolysis of chitin, chitotetraose tetradecaacetate (4) was isolated by Sephadex LH-20 column chromatography.Compound 4 was chlorinated with dry hydrogen chloride to produce tridecaacetyl chitotetraosyl chloride (6). 7-Hydroxy-4-methylcoumarin sodium salt was condensed with 6 under Koenigs-Knorr reaction conditions, and the final product (10) was obtained by de-O-acetylation of condensation product (8) with sodium methoxide. 4-Methylcoumarin-7-yloxy tri-N-acetyl-β-chitotrioside (9) was also synthesized through chitotriose undecaacetate (3) isolated together with 4 in the same chromatography.Compound 10 was used in a fluorometric assay of lysozyme in comparison with 9.The high sensitivity of fluorometric determination of 7-hydroxy-4-methylcoumarin (12) made it possible to determine lysozyme concentration in the microgram range by using this substrate (10).Unlike the assay using Micrococcus lysodeikticus cell powder, lysozyme assay with this synthetic substrate (10) could be performed directly in biological materials.Keywords - synthesis; lysozyme; enzyme assay; fluorometry; substrate; Sephadex LH-20; 7-hydroxy-4-methylcoumarin; 4-methylcoumarin-7-yloxy tetra-N-acetyl-β-chitotetraoside; 4-methylcoumarin-7-yloxy tri-N-acetyl-β-chitotrioside
- Inaba, Toyoaki,Ohgushi, Tadayasu,Iga, Yoshiro,Hasegawa, Eiichi
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p. 1597 - 1603
(2007/10/02)
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