Study On The Effect Of Nano-SiO₂ Particles On IgE-mediated Mast Cell Activation To Aggravate Allergic Inflammation And The Allergen Profilin Of Platanus Bispinus Polle

Part Ⅰ.Nano-silica particles synergistically IgE-mediated mast cell activation exacerbating allergic inflammationBackground:Allergic diseases have become a global health problem.The worsened air quality accompanied by increased air pollutants such as atmospheric particulate matter,diesel exhaust particles,and environmental tobacco smoke has dramatically increased the health burden brought by environmental exposure.Air pollutants have become an important environmental factor in developing allergic diseases.The sources and compositions of atmospheric particulate matter are diverse,including many biologically and non-biologically active components.The interaction between the components complicates the mechanism of atmospheric particulate matter-induced allergic diseases.However,studies are limited on the effects of inorganic components and particulate matter with different particle sizes in atmospheric particulates on allergic diseases,and the possible molecular mechanism of inducing allergies has not been thoroughly studied.Objective:To explore the relationship and possible molecular mechanism between the non-biologically active components in different particle sizes and allergic effects,and evaluate the effects of non-biologically active components in the atmospheric particulate matter on allergic disease scientifically.Methods:This study selected four standard mineral components in atmospheric particulate matter containing nanometer(nm)and micrometer(μm)particle sizes as representatives,including Al2O3,TiO2,Fe2O3,and SiO2.By culturing mouse bone marrowderived mast cells,establishing an ovalbumin-induced allergic asthma mouse particulate matter exposure model,and pollen-sensitized mouse particulate matter exposure model to evaluate the biological effects of particulate matter exposure and possible molecular mechanisms.Results:(1)Exposure to high concentrations of particles with different particle sizes had obvious cytotoxicity.Exposure to 20 nm SiO2 particles could synergistically enhance the activation effect of IgE-mediated mast cells with a particular concentration-effect relationship.(2)Although the exposure of low-dose nano-SiO2 particles did not cause significant damage to the pulmonary airway structure,infiltration of many inflammatory cells,and noticeable fibrotic changes in normal mice,it still increased mucus secretion in the large airways and serum histamine levels.(3)Nano-SiO2 particles exposure increased the secretion of cytokines IL-4 and IL-6 in OVA-induced asthmatic mice,recruited mast cells to inflammatory sites in lung tissue,enhanced mast cells activation and histamine secretion,increased airway mucus secretion,enhanced airway hyperresponsiveness,and aggravated allergic airway inflammation.(4)Nano-SiO2 particles exposure aggravated the damage of nasal mucosa epithelial cells in pollen-sensitized mice,increased goblet cells and mucus secretion,increased serum IL4 and IL-6 levels,and further aggravated the imbalance between Thl/Th2 cells,led to the disorder of the metabolic mechanism represented by niacin and nicotinamide and aggravated allergic inflammatory response.(5)Mast cells could uptake nano-SiO2 particles,which did not affect the expression of FcεRI and the ability to bind IgE in mast cells but increased the phosphorylation level of ERK1/2 and activated the MAPK signaling pathway to enhance the activation effect of IgE-mediated mast cells synergistically.Conclusion:The results indicated that the exposure of nano-SiO2 may synergistically enhance the activation effect of IgE-mediated mast cells by activating the MAPK signaling pathway,increasing the secretion of inflammatory factors such as histamine,IL-4,and IL6,and aggravating allergic airway inflammation.Our research provided a theoretical basis for preventing and treating allergic diseases induced by atmospheric particulate matter.Part Ⅱ.Identification,expression,and sensitization study of the profilin from Platanus acerifolia pollenBackground:Platanus acerifolia(P.acerifolia)is one of the most common allergens in spring in China,and it has become an important factor inducing allergic respiratory diseases.However,studies on the allergenic components of P.acerifolia pollen are very limited,and many unknown components have not been identified.There is a strong correlation between P.acerifolia pollen and plant food allergy,suggesting profilin may be an important allergenic component in P.acerifolia pollen.However,the molecular characterization and sensitization of the profilin have not been fully studied yet.Objective:The study aimed to identify and characterize the allergenic component profilin from the P.acerifolia pollen.Methods:The coding sequence of profilin was amplified,cloned,and then expressed in Escherichia coli BL21 cells and purified by nickel affinity chromatography.The amino acid sequence alignment,molecular physicochemical properties,and protein structure simulation analysis were performed.The allergenicity and cross-reactivity were assessed by enzyme-linked immunosorbent assay(ELISA),western blot(WB),and basophil activation test(BAT)using the sera from P.acerifolia allergic patients.Result:(1)The cDNA sequence of the allergenic component profilin was cloned with a 396 bp open reading frame coding for 131 amino acids,with a molecular weight of about 14 kDa.Its amino acid sequence had a high homology identity with profilin in other aeroallergens and food allergens,and the predicted structure consisted of 3 α-helixes and 7 β-sheets.Physicochemical analysis indicated that the profilin was an acidic,stable,relatively thermostable,and relatively conserved protein.(2)The IgE-binding activity of the recombinant profilin was determined by ELISA,WB,and BAT using the serum of P.acerifolia pollen allergic patients,which suggested a relatively high IgE sensitization rate(76.9%,30/39).And observed a significant crossreactivity with Pop n 2,the profilin from Populus nigra,in the IgE-inhibition assay.Conclusion:In this study,the allergenic component profilin was identified and characterized at the molecular and immunological levels and confirmed as one of the maj or component allergens in P.acerifolia pollen.The results provided useful information for component-resolved diagnostics and the development of individualized specific immunotherapy vaccines for P.acerifolia pollen allergic patients.