Study Of The Regulatory Effects Of Alginate Oligosaccharide On Regulation Of Signal Transduction In Macrophages

Alginate is a natural acidic polysaccharide with a number of physiological activities, which is extracted from marine seaweeds. As effective bioactive agent, it has a number of physiological activities, such like antitumor, anticoagulants, antibacterial and so on. Furthermore, the alginate oligosaccharides(AOS) is derived from alginate polymers depolymerized by different degradations also showed various bioactivities including anti-inflammatory, antioxidant and neuroprotection. Being important members of innate immune, macrophages occupy a unique niche in the host defense against infection by recognition, phagocytic capacities, and expression of inflammatory mediators, including i NOS, COX-2, and inflammatory cytokines, such as TNF-α, IL-12, NO. Therefore it is significant to improve the immune function by activating macrophage. In previous studies, we found that the guluronate oligosaccharide(GOS) prepared by enzymatic degradation of alginate-derived polyguluronate(PG), which has a significant immune-modulating activity. For instance, it is mediated by the stimulation of immune cells and induction of cytokine production, such as TNF-α, IL-6 by activating of NF-κB pathway. Moreover, it can also improve the host defense against infection by increasing the bacterial phagocytosis of macrophages. While the molecular mechanisms and receptors of mediating immune regulation by GOS are still unkown.The present work focused on the immunoregulatory of GOS in RAW 264.7 cells and d THP-1 cells. Furthermore, the molecular mechanisms and receptors of mediating were immune-modulating activity of GOS were studied.The study demonstrated that the toll like receptor 4(TLR4) involves in the regulation of the endocytosis of GOS by RAW264.7 cellsand also proved that GOS was recognized by TLR4 on the surface of RAW264.7 cells, leading to the macrophage activation and signaling transduction. Following by activation of PI3 K and subsequently induced Akt phosphorylation, which triggered IκB phosphorylation, resulting in the translocation of NF-κB into nucleus. Meanwhile the m TOR and 70 S6 K were also activated by phospho-Akt. In addition, after binding to GOS, TLR4 could also induce the phosphorylation of JNK, which leads to the activation of downstream transcription factor such as AP-1. All these factors worked together or separately to induce the production of inflammatory mediators. On the other hand, we also noticed that the phospho-p38 and phospho-ERK induced by GOS were both contributing to the increase of inflammatory mediators, but this functions were not mediated by TLR4.In summary GOS activates Akt / NF-κB,Akt / m TOR and MAPK signaling pathways via identifying with TLR4, which regulate the immune response by increasing the secretion of TNF-α, NO. What’s more, it also found that GOS could increase the relative cell area ratio and the cell aspect ratio of RAW264.7 cells, which enhance the phagocytosis capacity of RAW264.7 cells by increases the contraction with external antigen. In addition, the animal experiments proved that the increased number of peritoneal macrophages can effectively improve the non-specific immunity, thereby boost the pathogen removal efficiency in mouse. The proteome analysis of alginate oligosaccharides in d THP-1 cells by LC-MS technology were also studied. The results show that GOS has an effect of immunoregulatory, as well as anti-tumor and antiviral in d THP-1 cells. GOS derived from abundant natural source, prossesses an unusual immunomodulatory effects, which has potential as a new immunoenhancer.