Synthesis of Biotin-Tagged Chitosan Oligosaccharides and Assessment of Their Immunomodulatory Activity

Abstract

Chitin, a polymer of β-(1→4)-linked N-acetyl-d-glucosamine, is one of the main polysaccharide components of the fungal cell wall. Its N-deacetylated form, chitosan, is enzymatically produced in the cell wall by chitin deacetylases. It exerts immunomodulative, anti-inflammatory, anti-cancer, anti-bacterial, and anti-fungal activities with various medical applications. To study the immunobiological properties of chitosan oligosaccharides, we synthesized a series of β-(1→4)-linked N-acetyl-d-glucosamine oligomers comprising 3, 5, and 7 monosaccharide units equipped with biotin tags. The key synthetic intermediate employed for oligosaccharide chain elongation, a disaccharide thioglycoside, was prepared by orthogonal glycosylation of a 4-OH thioglycoside acceptor with a glycosyl trichloroacetimidate bearing the temporary 4-O-tert-butyldimethylsilyl group. The use of silyl protection suppressed aglycon transfer and provided a high yield for the target disaccharide donor. Using synthesized chitosan oligomers, as well as previously obtained chitin counterparts, the immunobiological relationship between these synthetic oligosaccharides and RAW 264.7 cells was studied in vitro. Evaluation of cell proliferation, phagocytosis, respiratory burst, and Th1, Th2, Th17, and Treg polarized cytokine expression demonstrated effective immune responsiveness and immunomodulation in RAW 264.7 cells exposed to chitin- and chitosan-derived oligosaccharides. Macrophage reactivity was accompanied by significant inductive dose- and structure-dependent protective Th1 and Th17 polarization, which was greater with exposure to chitosan- rather than chitin-derived oligosaccharides. Moreover, no antiproliferative or cytotoxic effects were observed, even following prolonged 48 h exposure. The obtained results demonstrate the potent immunobiological activity of these synthetically prepared chito-oligosaccharides.

Exploitation of Marine Molecules to Manage Alzheimer’s Disease

“…To increase the applications in biomedical applications, chitosan is transformed into chitosan oligosaccharides, molecules easily soluble in water [ 144 ]. Activities linked to chitosan and chitosan oligosaccharides include antioxidant, antibacterial, anti-HIV, anti-inflammatory, antidiabetic, and immunomodulatory [ 145 ]. In AD, chitosan has a protective effect; it controls the level of amyloid-beta through the expression and activity of the BACE-1 enzyme.…”

“…The main natural sources of chitin are shrimp and crab shells, which are an abundant byproduct of the food-processing industry and provide large quantities of these polysaccharides to be used in biomedical applications [ 112 ]. They can be also obtained by synthesis [ 145 ]. The extraction of chitin from the shell includes mainly demineralization and deproteinization [ 185 , 186 , 187 ].…”

Nigella sativa: A Dietary Supplement as an Immune-Modulator on the Basis of Bioactive Components

“…Generally, macrophages are crucial to innate cellular immune responses and play a significant role in the phagocyte cell system, which is programmed to identify, engulf, and eliminate apoptotic cells, bacteria, etc. (10,38). The immune system functions to maintain the physiological health of the body and protect it from pathogens through an increased release of inflammatory cytokines (39).…”

“…In addition, investigation has also shown that arabinoxylans with immunomodulatory effect could be considered effective bioactive food supplements associated with many health amelioration functions (46). In vitro immunobiological evaluation of chitin-and chitosan-derived oligosaccharides on RAW 264.7 cells obtained results that indicated a beneficial immunomodulation effect referring to the development of cytokine release, phagocytosis, cell proliferation, and respiratory burst (10).…”

“…Synthetic agents show typical side effects manifested as infection, blood constipation, disorders, and so on, while natural drugs are comparatively safe (9). Some dietary constituents of phytochemicals are essential to the balance and development of the immune system and in the amelioration of chronic inflammation (10).…”