The Anti-food Allergic Activities Of Marine-derived Gracilaria Lemaneiformis Sulfated Oligosaccharides And Butyrolactone-?

The symptoms of food allergic diseases are severe and diversified,and the morbidity on the rise.However,there is still no definite effective radical cure for food allergy.Marine resources are rich in natural active substances and have various biological activities.Previous studies had found that Gracilaria lemaneiformis sulfated polysaccharide?GLSP?from shallow sea area could inhibit tropomyosin-induced food allergic reaction,but its molecular weight was large and its effective concentration was high.There are many kinds of microorganisms in the deep sea,and the metabolites of which in the deep-sea microorganisms had novel structure and many biological activities.At present,there are few reports focus on the inhibition of food allergy by deep-sea-derived compounds.Therefore,screening anti-food allergic active substances and exploring the possible anti-allergic reaction mechanism of Gracilaria lemaneiformis and deep-sea microorganisms is of great significance for the development of anti-allergic functional foods and new anti-allergic drugs.In this study,six methods of polysaccharide degradation were used to degrade the sulfated polysaccharides from Gracilaria lemaneiformis.It was found that the high temperature pressure combined with vitamin C treatment could degrade GLSP,and the Gracilaria lemaneiformis sulfated oligosaccharide?GLSO?was obtained.The average molecular weight of GLSO was2031,the sulfate content was 13.03%,the viscosity was 0.002 dL/g,and the reducing sugar ratio was 46.52%,and GLSO consisted of disaccharides,tetrasaccharides,hexoses and octasaccharides,accounting for 64.57%,15.74%,9.21%,and 7.23%,respectively.The degranulation and histamine release of rat basophils line?RBL?-2H3 and mouse bone marrow-derived mast cells?BMMCs?were significantly inhibited by GLSO,and the inhibition rate was obvious higher than GLSP.GLSO could reduce the phagocytosis of ovalbumin?OVA?by mouse bone marrow-derived dendritic cells and affect the expression of CD80 on the cell surface.It was found that 100 mg/kg of GLSO could significantly alleviate food allergic reactions and attenuate intestinal inflammation in mice,and the inhibitory activity was obvious higher than that of GLSP.GLSO could affect the gut microbiota of allergic mice,stimulating it to tend to the gut microbiota content of normal mice.In addition,the levels of IgE,histamine,mouse mast cell protease-1?mMCP-1?,interleukin?IL?-4,IL-6,IL-13,and tumor necrosis factor-?were inhibited by GLSO in mice serum.GLSO could significantly promote the production of IL-10and transforming growth factor-?.Furthermore,spleen lymphocyte assay revealed that GLSO affected the number of helper T?T helper,TH?cells and B cells and inhibited the polarization of TH2 cells.The anti-allergic mechanism of GLSO was to promote the immunosuppressive effect by inducing the differentiation of regulatory T cells,sequentially inhibit the proliferation of effector T cells and the activation of mast cells.Using the RBL-2H3 cell degranulation model,the 12 monomeric compounds with inhibition rate greater than 50%were obtained from 941 secondary metabolites isolated from marine microorganism.On the base of both consideration of yield and inhibitory activity,the Butyrolactone-??BTL-??isolated from the deep-sea fungus Aspergillus sp.was investigated for further anti-allergic activity.BTL-? is a butenolide compound with molecular formula of C₂₄H₂₄O₇ and molecular weight of 424.BTL-? could significantly inhibit the degranulation of RBL-2H3 cells and IC₅₀ value of 8.09?g/mL,which can also reduce the release of histamine from RBL-2H3 cells.In addition,BTL-? also has significant inhibitory activity on the activation of BMMCs.In the OVA-inducing food allergic model,BTL-? could alleviate the symptoms of food allergic reaction,reduce the diarrhea rate of mice,cause the body temperature of allergic mice to rise,and weaken the intestinal inflammation.BTL-? had a significant inhibitory effect on OVA-specific IgE,histamine and mMCP-1,it could reduce the number of B cells and mast cells in spleen and mesenteric lymphocytes of allergic mice.In addition,the mast cell-mediated passive skin allergic reactions in mice were attenuated by BTL-?,and the expression of c-KIT on the surface of mast cells were decreased by treatment with butyrolactone-I.It was finally confirmed that the mechanism of BTL-? exerting anti-food allergic activity was to interact with the inhibitory receptor Fc?RIIB,inhibit the activation of mast cell,and alleviate allergic reactions.In summary,the present study obtained a low molecular weight oligosaccharide mixture by degrading the GLSP,and the deep-sea-derived BTL-? with high inhibitory activity on mast cell degranulation was screened from 941 compounds.The anti-allergic activities of GLSO and BTL-? in vitro were verified by using the RBL-2H3 and BMMCs model.The OVA-induced food allergy mouse model was established to determine the inhibitory effects of GLSO and BTL-? on food allergic reactions.By detecting allergic-related immune cells proliferation in OVA-induced mice,it was explicit that the target cells of GLSO in vivo was Treg cells,which could inhibit the proliferation of effector T cells and activation of mast cells.While the target cells of BTL-? acting were B cells and mast cells in vivo.Due to the interaction between BTL-? and Fc?RIIB,BTL-? could inhibit the activation of mast cells,thereby alleviating food allergic reactions.The present results provide theoretical foundation for the development of anti-food allergy functional foods or drugs based on GLSO and BTL-?,which provides a new direction for the development and utilization of marine resources.