Anti-Allergic Rhinitis Effects of Medicinal Plants and Their Bioactive Metabolites via Suppression of the Immune System: A Mechanistic Review

Evaluation of Urtica dioica Phytochemicals against Therapeutic Targets of Allergic Rhinitis Using Computational Studies

Allergic rhinitis (AR) is a prevalent inflammatory condition affecting millions globally, with current treatments often associated with significant side effects. To seek safer and more effective alternatives, natural sources like Urtica dioica (UD) are being explored. However, UD's mechanism of action remains unknown. Therefore, to elucidate it, we conducted an in silico evaluation of UD phytochemicals' effects on known therapeutic targets of allergic rhinitis: histamine receptor 1 (HR1), neurokinin 1 receptor (NK1R), cysteinyl leukotriene receptor 1 (CLR1), chemoattractant receptor-homologous molecule expressed on type 2 helper T cells (CRTH2), and bradykinin receptor type 2 (BK2R). The docking analysis identified amentoflavone, alpha-tocotrienol, neoxanthin, and isorhamnetin 3-O-rutinoside as possessing a high affinity for all the receptors. Subsequently, molecular dynamics (MD) simulations were used to analyze the key interactions; the free energy of binding was calculated through Generalized Born and Surface Area Solvation (MMGBSA), and the conformational changes were evaluated. Alpha-tocotrienol exhibited a high affinity while also inducing positive conformational changes across all targets. Amentoflavone primarily affected CRTH2, neoxanthin targeted NK1R, CRTH2, and BK2R, and isorhamnetin-3-O-rutinoside acted on NK1R. These findings suggest UD's potential to treat AR symptoms by inhibiting these targets. Notably, alpha-tocotrienol emerges as a promising multi-target inhibitor. Further in vivo and in vitro studies are needed for validation.

A Supramolecular Assembly of EGCG for Long-Term Treatment of Allergic Rhinitis

Allergic rhinitis (AR) is a type-I hypersensitivity disease mediated by immunoglobulin E (IgE). Although antihistamines, glucocorticoids, leukotriene receptor antagonists, and other drugs are widely used to treat AR, the various adverse side effects of long-term use of these drugs should not be ignored. Therefore, more effective and safe natural alternative strategies are urgently needed. To this end, this study designed a nanosupramolecular delivery system composed of β-cyclodextrin supramolecular polymer (PCD), thiolated chitosan (TCS), and natural polyphenol epigallocatechin gallate (EGCG) for intranasal topical continuous treatment of AR. The TCS/PCD@EGCG nanocarriers exhibited an excellent performance in terms of retention and permeability in the nasal mucosa and released the vast majority of EGCG responsively in the nasal microenvironment, thus resulting in the significantly high antibacterial and antioxidant capacities. According to the in vitro model, compared with free EGCG, TCS/PCD@EGCG inhibited mast cell activity and abnormal histamine secretion in a more long-term and sustained manner. According to the in vivo model, whether in the presence of continuous or intermittent administration, TCS/PCD@EGCG substantially inhibited the secretion of allergenic factors and inflammatory factors, mitigated the pathological changes of nasal mucosa, alleviated the symptoms of rhinitis in mice, and produced a satisfactory therapeutic effect on AR. In particular, the therapeutic effect of TCS/PCD@EGCG systems were even superior to that of budesonide during intermittent treatment. Therefore, the TCS/PCD@EGCG nanocarrier is a potential long-lasting antiallergic medicine for the treatment of AR.

Synthesis of 2-(pyridylvinyl)chromen-4-ones and their N-oxide analogs for assessment of their biological activities as anticancer agents

2-Styrylchromones have been shown to possess a broad spectrum of biological activities. Replacing the carbon atom in 2-styrylchromones with a nitrogen atom in the benzene rings forms 2-(pyridylvinyl)chromen-4-ones (aza-2-styrylchromones). We have synthesized a series of novel 2-(pyridylvinyl)chromen-4-ones and their pyridine N-oxides to evaluate them as potential anticancer agents against human non-small-cell lung cancer cells (A549). Among the 18 synthesized molecules, compounds 18 and 8a exhibited comparable inhibitory effects to 5-fluorouracil and showed no toxicity against normal cells.

Xiaoqinglong decoction improves allergic rhinitis by inhibiting NLRP3-mediated pyroptosis in BALB/C mice

ETHNOPHARMACOLOGICAL RELEVANCE

Xiaoqinglong decoction (XQLD), first recorded in Shang Han Lun, is a traditional Chinese medicine prescribed for the treatment of allergic rhinitis (AR). XQLD alleviates the clinical symptoms of AR by inhibiting the occurrence of an inflammatory response, but the specific regulatory mechanism remains unclear.

AIM OF THE STUDY

NLRP3-mediated pyroptosis is closely related to AR pathogenesis. Hence, this study aimed to explore the potential role of NLRP3-mediated pyroptosis pathway in the AR-associated pharmacological mechanism of XQLD.

MATERIALS AND METHODS

BALB/C mice models of AR was established by using ovalbumin (OVA) and aluminum hydroxide sensitization. After intragastric administration of different dosages of XQLD, nasal allergic symptoms were observed. The expression of OVA-sIgE and Th2 inflammatory factors (IL-4, IL-5, and IL-13) in serum was detected by ELISA. The histopathological morphology and expression of inflammatory factors in nasal mucosa along with pyroptosis were investigated. Molecular docking was performed to analyze the binding of representative compounds of XQLD with NLRP3. Activation of the NLRP3 inflammasome was detected by immunofluorescence and western blotting.

RESULTS

XQLD significantly improved the nasal allergic symptoms of mice, reduced the degree of goblet cell proliferation, mast cell infiltration, and collagen fiber hyperplasia in nasal mucosa. Meanwhile, it could downregulate the expression of Th2 inflammatory factors (IL-4, IL-5, and IL-13) in serum and nasal mucosa. XQLD significantly reduced the number of GSDMD and TUNEL double-positive cells and IL-1β and IL-18 expression. Molecular docking confirmed that seven representative compounds of XQLD had good binding properties with NLRP3 and were able to inhibit the activation of the NLRP3 inflammasome.

CONCLUSIONS

The representative compounds of XQLD might inhibit pyroptosis in nasal mucosa mediated by the NLRP3 inflammasome to helping the recovery of AR, which provides a new modern pharmacological proof for XQLD to treat AR.

Clinical effectiveness of decoction form of herbal medicine in primary care treatment of allergic rhinitis: A retrospective cohort study

Background

The decoction form of herbal medicine (D-HM) is mainly prescribed to patients with allergic rhinitis (AR) in Korean Medicine (KM) clinics in the Republic of Korea; however, it is difficult to conduct clinical trials of D-HM due to regulatory issues. This study investigated the clinical safety and effectiveness of D-HM combination therapy for the treatment of AR by analyzing the AR outpatient data from 17 KM clinics.

Methods

This retrospective cohort study included patients who visited KM clinics for AR treatment from January 1, 2021, to March 31, 2022. Cases were collated using structured case report forms and divided into the D-HM with KM usual care group (D-HM group) and the KM usual care group (UC group). Since D-HM therapy could not be randomly assigned to the study population, we used optimal propensity score (PS) matching to investigate the effectiveness and safety of D-HM combination therapy in the treatment of AR.

Results

Data from 228 patients were collected. After PS matching, 144 patients were finally analyzed. The total nasal symptom score (TNSS) and mini-rhinoconjunctivitis quality of life questionnaire (mini-RQLQ) were significantly improved in the D-HM group compared with those in the UC group (TNSS: p=0.02; mini-RQLQ: p=0.04). Four patients in the D-HM group experienced minor adverse events that were mild and resolved within 15 days.

Conclusions

D-HM combination therapy may be beneficial in the management of symptoms and rhinitis-associated quality of life and potentially useful in clinical practice. However, randomized placebo-controlled clinical trials are required to confirm their effectiveness.

Study registration

This study has been registered at Clinical Research Information Service (KCT0007242).

Common Allergens and Immune Responses Associated with Allergic Rhinitis in China

Allergic rhinitis (AR) is a chronic allergic disease of the upper respiratory system that affects approximately 10-40% of the global population. Due to the large number of plant pollen allergens with obvious seasonal variations, AR is common in China. AR is primarily caused by the abnormal regulation of the immune system. Its pathophysiological mechanism involves a series of immune cells and immune mediators, including cytokines. The present review summarizes the common allergens in China and the complex pathophysiological mechanism of AR. Additionally, host allergen contact, signal transduction, immune cell activation, cytokine release, and a series of inflammatory reactions are described according to their sequence of occurrence.

Correlation between B-cell lymphoma 6 with the balance of T helper-1/2 and severity of allergic rhinitis

OBJECTIVE

Allergic rhinitis (AR) is a prevailing immune disorder affecting the nasal mucosa. B-cell lymphoma 6 (BCL6) imposes essential roles in immunity. This study probed into the serum expression of BCL6 and its effect on AR diagnosis and patients' quality of life (QOL).

METHODS

A total of 113 patients with AR including 38 cases with mild AR (MAR) and 75 cases with moderate-severe AR (MSAR) were enrolled, with 101 healthy people enrolled as control. Serum expression of BCL6 was detected by RT-qPCR and the diagnostic efficacy of BCL6 for AR was analyzed using the receiver operating characteristic curve. The proportion of T helper-1/2 (Th1/Th2) cells in CD4+ T cells in peripheral blood mononuclear cells was detected using flow cytometry. The correlation between BCL6 and Th1/Th2 cells and the effects of BCL6 expression on patients' QOL were assessed by Pearson analysis and Mini-RQLQ questionnaire.

RESULTS

BCL6 was downregulated in patients with AR, serum BCL6 level < 0.8450 had certain auxiliary diagnostic values for AR, and serum BCL6 level < 0.5400 could assist the diagnosis of AR severity. Th1 cell proportion in CD4+ T cells was decreased, whereas Th2 cell proportion was increased with AR severity. BCL6 was positively-linked with Th1 cells but inversely-correlated with Th2 cells in patients with AR. Patients with AR with low BCL6 expression had a poorer QOL compared with high BCL6 expression. The domains most affected by BCL6 expression were practical problems, nasal symptoms, and lacrimation.

CONCLUSION

Serum BCL6 is downregulated and low BCL6 expression greatly deteriorates QOL in patients with AR.

Antiallergic Effects of N,N-dicoumaroylspermidine Isolated from Lithospermum erythrorhizon on Mast Cells and Ovalbumin-Induced Allergic Rhinitis

In East Asia, the dried root of Lithospermum erythrorhizon has been utilized as an anti-inflammatory, antipyretic, detoxifying, and anti-inflammatory agent. Recently, we reported that L. erythrorhizon protects against allergic rhinitis; however, the component within L. erythrorhizon that exerts antiallergic activity remains unknown. The purpose of the current study was to isolate and characterize the antiallergic active components in an ethanolic extract of L. erythrorhizon roots. We examined the antiallergic effects of L. erythrorhizon reflux ethanol extracts in an ovalbumin (OVA)-induced allergic rhinitis mouse model, and compared the chemical compounds extracted using the hot reflux and cold extraction methods. Chromatographic separation identified two novel anthraquinones, erythrin A and B, one newly discovered compound from the Lithospermum genus, N1″,N3″-dicoumaroylspermidine, and nineteen other recognized compounds. Their chemical structures were elucidated by single (1D) and 2D analysis of nuclear magnetic resonance (NMR) spectroscopic data, as well as high resolution mass spectrometry. Among the identified compounds, N,N′-dicoumaroylspermidine strongly inhibited the release of β-hexosaminidase, as well as the production of IL-3, IL-4, and IL-13 by IgE-sensitized and BSA-stimulated RBL-2H3 cells. Using the OVA-induced allergic rhinitis mouse model, we showed that N,N′-dicoumaroylspermidine reduced the production of serum OVA-specific IgE and the number of inflammatory cells in nasal lavage fluid. N,N′-dicoumaroylspermidine isolated from L. erythrorhizon exhibits antiallergic properties, making it potentially effective for allergic rhinitis.

Astragalus Polysaccharide Relieves Inflammatory Responses in Guinea Pigs with Allergic Rhinitis via Ameliorating NF-kB-Mediated Treg/Th17 Imbalance

BACKGROUND

Allergic rhinitis (AR) is regarded as a prevalent and non-infectious inflammation in nasal mucosa, and astragalus polysaccharide (APS) could mitigate inflammation.

OBJECTIVES

Herein, this study probed the specific mechanism of APS in inflammatory responses in AR.

METHODS

Firstly, AR guinea pig models were established through the stimulation and sensitization of ovalbumin (OVA) and received APS treatment. Changes in nasal symptoms were assessed through counting the sneezing and rubbing times of guinea pigs. The change patterns of OVA-specific immunoglobulin-E (OVA-sIgE), OVA-specific immunoglobulin-G1 (OVA-sIgG1), tumor necrosis factor (TNF)-α, and interleukin (IL)-6 in guinea pig serum were identified. Meanwhile, the levels of IL-17, transforming growth factor (TGF)-β, IL-10, and forkhead box protein P3 (Foxp3) in the guinea pig tissues or serum were examined, and CD25⁺Foxp3⁺Treg or CD4⁺IL17⁺Th17 cell proportion was detected. Afterwards, nuclear factor-kappa B (NF-kB) expression in guinea pig nasal mucosa tissues were examined. Rescue experiments were designed to probe the role of NF-kB overexpression in inflammatory responses and Treg/Th17 imbalance in AR guinea pigs.

RESULTS

APS treatment reduced sneezing and rubbing times of AR guinea pigs and suppressed OVA-sIgE, OVA-sIgG1, TNF-α, and IL-6 levels in guinea pig serum, and meanwhile, increased CD25⁺Foxp3⁺Treg cell proportion while reduced CD4⁺IL17⁺Th17 cell proportion in AR guinea pig serum or tissues, in a dose-dependent manner. NF-kB was highly-expressed in AR guinea pigs and down-regulated after APS treatment. NF-kB overexpression facilitated inflammatory responses and Treg/Th17 imbalance in AR.

CONCLUSION

APS reduced Treg/Th17 imbalance via suppressing NF-kB expression, thereby ameliorating inflammatory responses in AR.

Tussilagone protects acute lung injury from PM2.5 via alleviating Hif-1α/NF-κB-mediated inflammatory response

Environmental pollution, especially particulate matter in the air, is a serious threat to human health. Long-term inhalation of particulate matter with a diameter < 2.5 μm (PM2.5) induced irreversible respiratory and lung injury. However, it is not clear whether temporary exposure to massive PM2.5 would result in epithelial damage and lung injury. More importantly, it is urgent to clarify the mechanisms of PM2.5 cytotoxicity and develop a defensive and therapeutic approach. In this study, we demonstrated that temporary exposure with PM2.5 induced lung epithelial cell apoptosis via promoting cytokines expression and inflammatory factors secretion. The cytotoxicity of PM2.5 could be alleviated by tussilagone (TSL), which is a natural compound isolated from the flower buds of Tussilago farfara. The mechanism study indicated that PM2.5 promoted the protein level of Hif-1α by reducing its degradation mediated by PHD2 binding, which furtherly activated NF-κB signaling and inflammatory response. Meanwhile, TSL administration facilitated the interaction of the Hif-1α/PHD2 complex and restored the Hif-1α protein level increased by PM2.5. When PHD2 was inhibited in epithelial cells, the protective function of TSL on PM2.5 cytotoxicity was attenuated and the expression of cytokines was retrieved. Expectedly, the in vivo study also suggested that temporary PM2.5 exposure led to acute lung injury. TSL treatment could effectively relieve the damage and decrease the expression of inflammatory cytokines by repressing Hif-1α level and NF-κB activation. Our findings provide a new therapeutic strategy for air pollution-related respiratory diseases, and TSL would be a potential preventive medicine for PM2.5 cytotoxicity.