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The deactivation of selective catalytic reduction (SCR) catalysts caused by alkali metal poisoning remains an insurmountable challenge. In this study, we examined the impact of Na poisoning on the performance of Fe and Mo co-doped TiO2 (FeaMobTiOx) catalysts in the SCR reaction and revealed the related alkali resistance mechanism. On the obtained Fe1Mo2.6TiOx catalyst, the synergistic catalytic effect of uniformly dispersed FeOx and MoOx species leads to remarkable catalytic activity, with over 90% NO conversion achieved in a wide temperature range of 210-410 °C. During the Na poisoning process, Na ions predominantly adsorb on the MoOx species, which exhibit stronger alkali resistance, effectively safeguarding the FeOx species. This preferential adsorption minimizes the negative effect of Na poisoning on Fe1Mo2.6TiOx. Moreover, Na poisoning has little influence on the Eley-Rideal reaction pathway involving adsorbed NHx reacting with gaseous NOx. After Na poisoning, the Lewis acid sites were deteriorated, while the abundant Brønsted acid sites ensured sufficient NHx adsorption. As a benefit from the self-defense effects of active MoOx species for alkali capture, FeaMobTiOx exhibits exceptional alkali resistance in the SCR reaction. This research provides valuable insights for the design of highly efficient and alkali-resistant SCR catalysts.
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Álcalis , Amoníaco , Catálisis , Ácidos de Lewis , MetalesRESUMEN
Solvent effects in catalytic reactions have received widespread attention as they can promote reaction rates and product selectivities by orders of magnitude. It is well accepted that the stable five-membered cyclic intermediates formed between the solvent molecules and Ti species are crucial to the alkene epoxidation in a heterogeneous Ti(IV)-H2O2 system. However, the direct spectroscopic evidence of these intermediates is still missing and the corresponding reaction pathway for the alkene epoxidation remains unclear. By combining in situ 13C MAS NMR, two-dimensional (2D) 1H-13C heteronuclear correlation (HETCOR) NMR spectroscopy and theoretical calculations, the five-membered ring structures, where the protic solvents (ROH), and aprotic solvent (acetone), coordinate and stabilize the active Ti species, are identified for the first time over Ti-Beta/H2O2 system. Moreover, the role of these cyclic intermediates in the alkene epoxidation/hydration conversion is clarified. These results provide new insights into the solvent effect in liquid-phase epoxidation/hydration reactions over Ti(IV)-H2O2 system.
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Olefin selectivity and catalyst lifetime are two key metrics for industrial methanol-to-olefin catalysts. Currently, it is very difficult to obtain high olefin selectivity and long catalyst lifetime at the same time. Herein, a feasible strategy combining precoking and steaming to directionally construct the active naphthalenic species within the crystal center of the SAPO-34 catalyst has been developed, which can not only promote the lower olefin selectivity to â¼89% (ethylene and propylene) but also prolong the catalyst lifetime by â¼3.7-fold in the methanol-to-olefin conversion. Structured illumination microscopy, in situ ultraviolet-visible spectroscopy, and online mass spectrometry elucidate the spatiotemporal distribution and evolution of the naphthalenic species during the precoking and steaming processes. This one-stone-two-birds strategy is applicable to a commercial SAPO-34 catalyst containing a binder, demonstrating its bright prospect in the methanol-to-olefin industry.
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ConspectusZeolites, accompanied by their initial discovery as natural mines and the subsequent large-scale commercial production, have played indispensable roles in various fields such as petroleum refining and the chemical industry. Understanding the characteristics of zeolites, in contrast to their counterparts with similar chemical compositions and the origin thereof, is always a hot and challenging topic. Zeolites are known as intrinsic confined systems with ordered channels on the molecular scale, and structural confinement has been proposed to explain the unique chemical behaviors of zeolites. Generally, the channels of zeolites can regulate the diffusion of molecules, leading to a visible difference in molecular transportation and the ultimate shape-selective catalysis. On the other hand, the local electric field within the zeolite channels or cages can act on the guest molecules and change their energy levels. Confinement can be simply interpreted from both spatial and electronic issues; however, the nature of zeolite confinement is ambiguous and needs to be clarified.In this Account, we make a concise summary and analysis of the topics of confinement in a zeolite and zeolite catalysis from two specific views of spatial constraint and a local electric field to answer two basic questions of why zeolites and what else can we do with zeolites. First, it is shown how to construct functional sites including Brønsted acid sites, Lewis acid sites, extraframework cation sites, and entrapped metal or oxide aggregates in zeolites via confinement and how to understand the specific role of confinement in their reactivity. Second, the multiple impacts of confinement in zeolite-catalyzed reactions are discussed, which rationally lead to several unique processes, namely, Brønsted acid catalysis confined in zeolites, Lewis acid catalysis confined in zeolites, catalysis by zeolite-confined coordinatively unsaturated cation sites, and a cascade reaction within the confined space of zeolites. Overall, confinement effects do exist in zeolite systems and have already played extremely important roles in adsorption and catalysis. Although confinement might exist in many systems, the confinement by zeolites is more straightforward thanks to their well-ordered and rigid structure, deriving unique chemical behaviors within the confined space of zeolites. A zeolite is a fantastic scaffold for constructing isolated sites spatially and electrostatically confined in its matrix. Furthermore, zeolites containing well-defined transition-metal sites can be treated as inorganometallic complexes (i.e., a zeolite framework as the ligand of transition-metal ions) and can catalyze reactions resembling organometallic complexes or even metalloenzymes. The local electric field within the confined space of zeolites is strong enough to induce or assist the activation of small molecules, following the working fashion of frustrated Lewis pairs. The tactful utilization of structural confinement, both spatially and electronically, becomes the key to robust zeolites for adsorption and catalysis.
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Rhoptry neck protein 2 (RON2) binds to the hydrophobic groove of apical membrane antigen 1 (AMA1), an interaction essential for invasion of red blood cells (RBCs) by Plasmodium falciparum (Pf) parasites. Vaccination with AMA1 alone has been shown to be immunogenic, but unprotective even against homologous challenge in human trials. However, the AMA1-RON2L (L is referred to as the loop region of RON2 peptide) complex is a promising candidate, as preclinical studies with Freund's adjuvant have indicated complete protection against lethal challenge in mice and superior protection against virulent infection in Aotus monkeys. To prepare for clinical trials of the AMA1-RON2L complex, identity and integrity of the candidate vaccine must be assessed, and characterization methods must be carefully designed to not dissociate the delicate complex during evaluation. In this study, we developed a native Tris-glycine gel method to separate and identify the AMA1-RON2L complex, which was further identified and confirmed by Western blotting using anti-AMA1 monoclonal antibodies (mAbs 4G2 and 2C2) and anti-RON2L polyclonal Ab coupled with mass spectrometry. The formation of complex was also confirmed by Capillary Isoelectric Focusing (cIEF). A short-term (48 h and 72 h at 4°C) stability study of AMA1-RON2L complex was also performed. The results indicate that the complex was stable for 72 h at 4°C. Our research demonstrates that the native Tris-glycine gel separation/Western blotting coupled with mass spectrometry and cIEF can fully characterize the identity and integrity of the AMA1-RON2L complex and provide useful quality control data for the subsequent clinical trials.
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Antígenos de Protozoos , Vacunas contra la Malaria , Animales , Antígenos de Protozoos/química , Antígenos de Protozoos/metabolismo , Glicina , Focalización Isoeléctrica , Vacunas contra la Malaria/química , Proteínas de la Membrana/química , Ratones , Proteínas Protozoarias/química , Proteínas Protozoarias/metabolismoRESUMEN
Toxic toluene can be completely oxidized in CO2 and H2O with novel three-dimensional (3D) In2S3@Bi2WO6 hierarchical crystals under visible light. Dense and uniform In2S3 nanoflakes are rooted in Bi2WO6 nanoplates which intercross with each other and are anchored on a pliable tungsten mesh. This leads to the construction of a stable and porous interface for adsorbing and decomposing target gaseous toluene. The firm contact between In2S3 and Bi2WO6 initiates the formation of a built-in electric field that helps in channeling the photogenerated electrons in Bi2WO6 CB to quench the holes in2S3 VB. This results in highly capable electrons and holes, as well as notable increase in the yields of â¢O2- and â¢OH. 99.7% of toluene is removed and 93.4% is converted to CO2 when it is degraded in simulated air. This validates its remarkable efficacy in detoxifying toluene.
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Preerythrocytic vaccines prevent malaria by targeting parasites in the clinically silent sporozoite and liver stages and preventing progression to the virulent blood stages. The leading preerythrocytic vaccine, RTS,S/AS01E (Mosquirix), entered implementation programs in 2019 and targets the major sporozoite surface antigen, circumsporozoite protein (CSP). However, in phase III clinical trials, RTS,S conferred partial protection with limited durability, indicating a need to improve CSP-based vaccination. Previously, we identified highly expressed liver-stage proteins that could potentially be used in combination with CSP; they are referred to as preerythrocytic vaccine antigens (PEVAs). Here, we developed heterologous prime-boost CSP vaccination models to confer partial sterilizing immunity against Plasmodium yoelii (protein prime-adenovirus 5 [Ad5] boost) and Plasmodium berghei (DNA prime-Ad5 boost) in mice. When combined as individual antigens with P. yoelii CSP (PyCSP), three of eight P. yoelii PEVAs significantly enhanced sterile protection against sporozoite challenge, compared to PyCSP alone. Similar results were obtained when three P. berghei PEVAs and P. berghei CSP were combined in a single vaccine regimen. In general, PyCSP antibody responses were similar after CSP alone versus CSP plus PEVA vaccinations. Both P. yoelii and P. berghei CSP plus PEVA combination vaccines induced robust CD8+ T cell responses, including signature gamma interferon (IFN-γ) increases. In the P. berghei model system, IFN-γ responses were significantly higher in hepatic versus splenic CD8+ T cells. The addition of novel antigens may enhance the degree and duration of sterile protective immunity conferred by a human vaccine such as RTS,S.
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Antígenos de Protozoos/inmunología , Vacunas contra la Malaria/inmunología , Proteínas Protozoarias/inmunología , Animales , Linfocitos T CD8-positivos/inmunología , Interferón gamma/biosíntesis , Activación de Linfocitos , Malaria/prevención & control , Ratones , Ratones Endogámicos BALB C , VacunaciónRESUMEN
Understanding the unique behaviors of atomically dispersed catalysts and the origin thereof is a challenging topic. Herein, we demonstrate a facile strategy to encapsulate Ptδ+ species within Y zeolite and reveal the nature of selective hydrogenation over a Pt@Y model catalyst. The unique configuration of Pt@Y, namely atomically dispersed Ptδ+ stabilized by the surrounding oxygen atoms of six-membered rings shared by sodalite cages and supercages, enables the exclusive heterolytic activation of dihydrogen over Ptδ+···O2- units, resembling the well-known classical Lewis pairs. The charged hydrogen species, i.e., H+ and Hδ-, are active reagents for selective hydrogenations, and therefore, the Pt@Y catalyst exhibits remarkable performance in the selective hydrogenation of α,ß-unsaturated aldehydes to unsaturated alcohols and of nitroarenes to arylamines.
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Despite the existence of numerous photocatalyst heterostructures, their separation efficiency and charge flow precision remain low due to the poor study on interfacial properties. The photocatalysts with confined defects can effectively control the photogenerated carrier migration, but the metastability of such defects considerably decreases the photocatalyst stability. Meanwhile, the introduction of defective region can increase the coordinative unsaturation and delocalize local electrons to promote their interactions with the molecules/ions in that region. The selective growth of modulated heterogeneous interface by defect-induced strategy may not only increase the stability of defective structures, but also enhance the migration of interfacial charges. Using this method, photocatalytic heterostructures with low contact resistances and intimate interfaces are constructed to achieve the optimal charge migration in terms of efficiency and accuracy. In this work, the point, linear, and planar heterogeneous interfaces and related defect engineering techniques are discussed. Particularly, it is focused on the external, defect-induced interfacial heterogeneities with various spatial and dimensional configurations, which exhibit modulated and controllable interfacial properties. Furthermore, the main aspects of fabricating photocatalyst heterostructures by the defect-induced strategy, including the i) controllable generation of defects, ii) advanced characterization methods, and iii) elaborate construction of the minimal interface, are described.
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The diffusion of saturated and unsaturated hydrocarbons is of fundamental importance for many zeolite-catalyzed processes. Transport of small alkenes in the confined zeolite pores can become hindered, resulting in a significant impact on the ultimate product selectivity and separation. Herein, intracrystalline light olefin/paraffin diffusion through the 8-ring windows of zeolite SAPO-34 is characterized by a complementary set of first-principle molecular dynamics simulations, PFG-NMR experiments, and pulse-response temporal analysis of products measurements, yielding information at different length and time scales. Our results clearly show a promotional effect of the presence of Brønsted acid sites on the diffusion rate of ethene and propene, whereas transport of alkanes is found to be insensitive to the presence of acid sites. The enhanced diffusivity of unsaturated hydrocarbons is ascribed to the formation of favorable π-H interactions with acid protons, as confirmed by IR spectroscopy measurements. The acid site distribution is proven to be an important design parameter for optimizing product distributions and separations.
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The selective hydrogenation of alkynes to alkenes is an important type of organic transformation with large-scale industrial applications. This transformation requires efficient catalysts with precise selectivity control, and palladium-based metallic catalysts are currently employed. Here we show that four-coordinated cationic nickel(II) confined in zeolite can efficiently catalyze the selective hydrogenation of acetylene to ethylene, a key process for trace acetylene removal prior to the polymerization process. Under optimized conditions, 100% acetylene conversion and an ethylene selectivity up to 97% are simultaneously achieved. This catalyst system also exhibits good stability and recyclability for potential applications. Spectroscopy investigations and density functional theory calculations reveal the heterolytic dissociation of hydrogen molecules and the importance of hydride and protons in the selective hydrogenation of acetylene to ethylene. This work provides an efficient strategy toward active and selective zeolite catalysts by utilizing the local electrostatic field within the zeolite confined space for small-molecule activation and by linking heterogeneous and homogeneous catalysis.
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Experimental evidence for the presence of tert-butyl cations, which are important intermediates in acid-catalyzed heterogeneous reactions, on solid acids has still not been provided to date. By combining density functional theory (DFT) calculations with (1)H/(13)C magic-angle-spinning NMR spectroscopy, the tert-butyl cation was successfully identified on zeolite H-ZSM-5 upon conversion of isobutene by capturing this intermediate with ammonia.
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A wide variety of parameters as, e.g., temperature, humidity, particle size, and cation state are known to influence the agglomeration process of two-dimensional (2D) nanosheets, called self-assembly, in inorganic layered materials. The detailed studies on which parameters are decisive and how they influence the self-assembly, however, have not been performed yet. Here, the long-term self-assembly was studied for layered stevensite and hectorite, and compared with our previous data of saponite for elucidating an influence of local states of the interlayer cations. The results were analyzed with respect to a recently established rheological model, in which 2D nanosheets migrate parallel to the layer direction aided by water molecules as lubricants [K. Sato et al., J. Phys. Chem. C, 2012, 116, 22954]. With decreasing the strength of the local electric fields facing to the interlayer spaces, cation positions split into two or three, which makes the distribution of water molecules more uniformly. These water molecules enhance the rheological motion of the 2D nanosheets parallel to the layer direction, thus accelerating the self-assembly process.
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Nowadays, it is becoming increasingly urgent to lower the escalating carbon dioxide (CO2) to reduce greenhouse effect. Fortunately, it is an ideal strategy by using the inexhaustible solar energy as the driving force to manipulate the cycloaddition reaction, the atomic efficiency of which is 100 %. This work represents the first attempt on utilization of rare-earth metal Tb with atomic dispersion, and the structure of Tb coordinated with 4 N-atoms and 2B-atoms was constructed on interconnected carbon hollow spheres. The introduction of electron-deficient B reduces the electron density of Tb, thereby boosting Lewis acidity and promoting the occurrence of ring-opening reaction. The mechanism exploration enunciates that TbN4B2/C is a photothermal synergistic catalyst, the combined action of photogenerated electrons and strong Lewis acidic site of Tb reduces the free energy of the rate-determining step, and then improving the yield of cyclic carbonate up to 739 mmol g-1h-1.
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Employing electric energy to convert carbon dioxide (CO2) into valuable small molecules is a potentially practical method in energy storage and greenhouse gas alleviation. A huge challenge for electrocatalytic CO2 reduction is to reduce overpotential to improve energy efficiency. Herein, we demonstrate that doping alloy Pd49Ag30Te4 (PAT) with rare-earth element Tb is beneficial for selective exposure of (111) crystal plane, which is a highly active crystal plane for producing carbon monoxide (CO). The as-prepared Tb2.9PAT exhibited high electrocatalytic performance with 95.7 % CO faradic efficiency at - 0.8 V (vs RHE), far exceeding that of PAT, and coupled with good durability. In situ spectral study and theoretical calculations disclose that the introduction of Tb regulates the d-band center of PAT alloy, weakens the Pd - C bonding ability, and promotes the desorption of *CO in the rate-determining step. This study provides a method for doping induced selective exposure of crystal face, which provides new idea for improving catalytic performance.
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BACKGROUND: Jieduhuayu No.3 (JDHY3) is a modified Chinese herbal formula beneficial for treating hypopharyngeal carcinoma (HC), but its pharmacological mechanism is unknown. OBJECTIVE: This study aimed to explore the mechanism of the herbal formula JDHY3 in inhibiting cell proliferation and promoting apoptosis in HC in vitro and in vivo. METHODS: In this study, HC cells were treated with cisplatin and different concentrations of JDHY3. The apoptosis rate was detected by flow cytometry. Western blotting was used to detect the proteins related to cell proliferation and apoptosis. Afterward, the xenograft mouse model was established and treated with cisplatin and JDHY3. Mouse tumour volume was measured, and the tumour tissues were assessed by HE staining and immunohistochemistry. RESULTS: JDHY3 significantly inhibited the proliferation of FaDu and Detroit-562 cells. In addition, JDHY3 significantly increased the apoptosis rate of HC cells and downregulated p-PI3K and p-Akt. In addition, JDHY3 upregulated the expression of the apoptosis-promoting proteins Bax, P53, and cleaved caspase-3. In addition, the expression of the antiapoptotic protein Bcl-2 was downregulated. Coincubation with SC79 attenuated the decrease in cell proliferation induced by JDHY3, further confirming that the proapoptotic effect of JDHY3 is associated with the inhibition of PI3K/Akt pathway activation. CONCLUSIONS: The results of in vivo experiments showed that JDHY3 could effectively inhibit the proliferation of HC cells, and HE staining showed that JDHY3 reduced the invasion of HC cells. Immunohistochemistry showed that the expression of P53 and cleaved caspase-3 was significantly increased in the tissues of the JDHY3-treated group.
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Carcinoma , Proteínas Proto-Oncogénicas c-akt , Humanos , Ratones , Animales , Proteínas Proto-Oncogénicas c-akt/metabolismo , Cisplatino/farmacología , Caspasa 3/metabolismo , Transducción de Señal , Fosfatidilinositol 3-Quinasas/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Apoptosis , Proliferación Celular , Línea Celular TumoralRESUMEN
The selective hydrogenation of CO2 to methanol by renewable hydrogen source represents an attractive route for CO2 recycling and is carbon neutral. Stable catalysts with high activity and methanol selectivity are being vigorously pursued, and current debates on the active site and reaction pathway need to be clarified. Here, we report a design of faujasite-encaged mononuclear Cu centers, namely Cu@FAU, for this challenging reaction. Stable methanol space-time-yield (STY) of 12.8 mmol gcat-1 h-1 and methanol selectivity of 89.5% are simultaneously achieved at a relatively low reaction temperature of 513 K, making Cu@FAU a potential methanol synthesis catalyst from CO2 hydrogenation. With zeolite-encaged mononuclear Cu centers as the destined active sites, the unique reaction pathway of stepwise CO2 hydrogenation over Cu@FAU is illustrated. This work provides a clear example of catalytic reaction with explicit structure-activity relationship and highlights the power of zeolite catalysis in complex chemical transformations.
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Photocatalytic CO2 reduction has been regarded as an ideal method to simulate photosynthesis for achieving carbon neutralization. However, poor charge transfer efficiency limits its development. Herein, an efficient Co/CoP@C catalyst was prepared with compact contact of Co and CoP layer by using MOF as precursor. At the interface of Co/CoP, the difference in functionality between the two phases may result in uneven distribution of electrons, thus forming a self-driven space-chare region. In this region, spontaneous electron transfer is guaranteed, thus facilitating the effective separation of photogenerated carriers as well as boosting the utilization of solar energy. Furthermore, the electron density of active site Co in CoP is increased and more active sites are exposed, which promotes the adsorption and activation of CO2 molecules. Together with suitable redox potential, low energy barrier for *COOH formation and easy desorption of CO, the reduction rate of CO2 catalyzed by Co/CoP@C is 4 times higher than that of CoP@C.
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Cancer stem cells (CSCs) play a central role in ovarian cancer (OC), understanding regulatory mechanisms governing their stemness is critical. Here, we report ISYNA1, the rate-limiting enzyme in myo-inositol biosynthesis, as a suppressor of OC regulating cancer stemness. We identified ISYNA1 as a differentially expressed gene in normal ovary and ovarian cancer tissues, as well as OC cells and OCSCs. Low ISYNA1 expression correlated with poor prognosis in OC patients. In addition, ISYNA1 was negatively correlated with cancer stem cell (CSC) markers, and ISYNA1-related pathways were enriched in Wnt, Notch, and other critical cancer pathways. ISYNA1 deficiency promoted OC cell growth, migration, and invasion ability in vitro and in vivo. Knockdown of ISYNA1 increased stemness of OC cells, including self-renewal, CSC markers expression, ALDH activity, and proportion of CD44+/CD117+ CSCs. Conversely, ectopic overexpression of ISYNA1 suppresses cell proliferation, migration, invasion and stemness of OC cells. Mechanistically, ISYNA1 inhibits OC stemness by regulating myo-inositol to suppress Notch1 signaling. In summary, these data provide evidence that ISYNA1 act as a tumor suppressor in OC and a regulator of stemness, providing insight into potentially targetable pathways for ovarian cancer therapy.
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Neoplasias Ováricas , Femenino , Humanos , Línea Celular Tumoral , Proliferación Celular/genética , Inositol/metabolismo , Células Madre Neoplásicas/metabolismo , Neoplasias Ováricas/patología , Receptor Notch1/metabolismo , Transducción de SeñalRESUMEN
OBJECTIVE: To compare the effects of mometasone furoate in combination with loratadine and montelukast sodium on inflammatory factors and pulmonary function in children with allergic rhinitis (AR). METHODS: In this retrospective study, a total of 89 children with AR admitted to our hospital from March 2020 to October 2021 were enrolled. Among them, 47 children who received mometasone furoate combined with loratadine were designated group A, while the other 42 with mometasone furoate combined with montelukast sodium were group B. The clinical efficacy of both groups was compared, and the levels of inflammatory factors IL-6 and TNF-α as well as the changes of pulmonary function levels were tested during the treatment. Adverse reactions during treatment were recorded. Finally, children were followed up for 3 months to record rhinitis recurrence after discontinuation of the treatment. RESULTS: There was no statistical difference in clinical treatment efficacy between both groups (P>0.05), while the levels of IL-6, TNF-α, and IgE were lower in children in group A than in group B at 2 weeks of treatment. Group A's lung function indexes, including forced expiratory volume in one second (FEV1%), forced expiratory volume in one second/forced vital capacity (FEV1/FVC) and peak expiratory flow (PEF), were higher than in group B (all P<0.05). The total incidence of adverse reactions was dramatically lower in group A than group B (P<0.05). Follow-up demonstrated no difference in the recurrence rate of rhinitis between both groups of children (P>0.05). Higher TNF-α after treatment, history of allergy, family history of rhinitis, combined asthma, and parental history of smoking were independent risk factors for relapse after discontinuation of the drug in children. CONCLUSION: Both mometasone furoate combined with either loratadine or montelukast sodium had good effects in AR, while the first option had a faster inhibitory effect on inflammatory factors and a better protection of lung function in children.