Emodin Alleviates the Airway Inflammation of Cough Variant Asthma in Mice by Regulating the Notch Pathway

Advances in the pharmacological effects and molecular mechanisms of emodin in the treatment of metabolic diseases

Rhubarb palmatum L., Polygonum multijiorum Thunb., and Polygonum cuspidatum Sieb. Et Zucc. are traditional Chinese medicines that have been used for thousands of years. They are formulated into various preparations and are widely used. Emodin is a traditional Chinese medicine monomer and the main active ingredient in Rhubarb palmatum L., Polygonum multijiorum Thunb., and Polygonum cuspidatum Sieb. Et Zucc. Modern research shows that it has a variety of pharmacological effects, including promoting lipid and glucose metabolism, osteogenesis, and anti-inflammatory and anti-autophagy effects. Research on the toxicity and pharmacokinetics of emodin can promote its clinical application. This review aims to provide a basis for further development and clinical research of emodin in the treatment of metabolic diseases. We performed a comprehensive summary of the pharmacology and molecular mechanisms of emodin in treating metabolic diseases by searching databases such as Web of Science, PubMed, ScienceDirect, and CNKI up to 2023. In addition, this review also analyzes the toxicity and pharmacokinetics of emodin. The results show that emodin mainly regulates AMPK, PPAR, and inflammation-related signaling pathways, and has a good therapeutic effect on obesity, hyperlipidemia, non-alcoholic fatty liver disease, diabetes and its complications, and osteoporosis. In addition, controlling toxic factors and improving bioavailability are of great significance for its clinical application.

Fallopia japonica Root Extract Ameliorates Ovalbumin-Induced Airway Inflammation in a CARAS Mouse Model by Modulating the IL-33/TSLP/NF-κB Signaling Pathway

Fallopia japonica (Asian knotweed) is a medicinal herb traditionally used to treat inflammation, among other conditions. However, the effects of F. japonica root extract (FJE) on airway inflammation associated with combined allergic rhinitis and asthma (CARAS) and the related mechanisms have not been investigated. This study examined the effect of FJE against CARAS in an ovalbumin (OVA)-induced CARAS mouse model. Six-week-old male BALB/c mice were randomly segregated into six groups. Mice were sensitized intraperitoneally with OVA on days 1, 8, and 15, and administered saline, Dexamethasone (1.5 mg/kg), or FJE (50, 100, or 200 mg/kg) once a day for 16 days. Nasal symptoms, inflammatory cells, OVA-specific immunoglobulins, cytokine production, mast cell activation, and nasal histopathology were assessed. Administration of FJE down-regulated OVA-specific IgE and up-regulated OVA-specific IgG2a in serum. FJE reduced the production of T helper (Th) type 2 cytokines, and the Th1 cytokine levels were enhanced in nasal and bronchoalveolar lavage fluid. Moreover, FJE positively regulated allergic responses by reducing the accumulation of inflammatory cells, improving nasal and lung histopathological characteristics, and inhibiting inflammation-associated cytokines. FJE positively modulated the IL-33/TSLP/NF-B signaling pathway, which is involved in regulating inflammatory cells, immunoglobulin levels, and pro-inflammatory cytokines at the molecular level.

The Role and Mechanisms of Traditional Chinese Medicine for Airway Inflammation and Remodeling in Asthma: Overview and Progress

Asthma as an individual disease has blighted human health for thousands of years and is still a vital global health challenge at present. Though getting much progress in the utilization of antibiotics, mucolytics, and especially the combination of inhaled corticosteroids (ICS) and long-acting β-agonists (LABA), we are confused about the management of asthmatic airway inflammation and remodeling, which directly threatens the quality of life for chronic patients. The blind addition of ICS will not benefit the remission of cough, wheeze, or sputum, but to increase the risk of side effects. Thus, it is necessary to explore an effective therapy to modulate asthmatic inflammation and airway remodeling. Traditional Chinese Medicine (TCM) has justified its anti-asthma effect in clinical practice but its underlying mechanism and specific role in asthma are still unknown. Some animal studies demonstrated that the classic formula, direct exacts, and natural compounds isolated from TCM could significantly alleviate airway structural alterations and exhibit the anti-inflammatory effects. By investigating these findings and data, we will discuss the possible pathomechanism underlined airway inflammation and remodeling in asthma and the unique role of TCM in the treatment of asthma through regulating different signaling pathways.

Effects of Anthraquinones on Immune Responses and Inflammatory Diseases

The anthraquinones (AQs) and derivatives are widely distributed in nature, including plants, fungi, and insects, with effects of anti-inflammation and anti-oxidation, antibacterial and antiviral, anti-osteoporosis, anti-tumor, etc. Inflammation, including acute and chronic, is a comprehensive response to foreign pathogens under a variety of physiological and pathological processes. AQs could attenuate symptoms and tissue damages through anti-inflammatory or immuno-modulatory effects. The review aims to provide a scientific summary of AQs on immune responses under different pathological conditions, such as digestive diseases, respiratory diseases, central nervous system diseases, etc. It is hoped that the present paper will provide ideas for future studies of the immuno-regulatory effect of AQs and the therapeutic potential for drug development and clinical use of AQs and derivatives.

NEDD4 attenuates phosgene-induced acute lung injury through the inhibition of Notch1 activation

Phosgene gas leakage can cause life-threatening acute lung injury (ALI), which is characterized by inflammation, increased vascular permeability, pulmonary oedema and oxidative stress. Although the downregulation of neuronal precursor cell-expressed developmentally downregulated 4 (NEDD4) is known to be associated with inflammation and oxidative damage, its functions in phosgene-induced ALI remain unclear. In this study, rats with phosgene-induced ALI were intravenously injected with NEDD4-overexpressing lentiviruses to determine the functions of NEDD4 in this inflammatory condition. NEDD4 expression was decreased in the lung parenchyma of phosgene-exposed control rats, whereas its expression level was high in the NEDD4-overexpressing rats. Phosgene exposure increased the wet-to-dry lung weight ratio, but NEDD4 abrogated this effect. NEDD4 overexpression attenuated phosgene-induced lung inflammation, lowering the high lung injury score (based on total protein, inflammatory cells and inflammatory factors in bronchoalveolar lavage fluid) and also reduced phosgene-induced oxidative stress and cell apoptosis. Finally, NEDD4 was found to interact with Notch1, enhancing its ubiquitination and thereby its degradation, thus attenuating the inflammatory responses to ALI. Therefore, we demonstrated that NEDD4 plays a protective role in alleviating phosgene-induced ALI, suggesting that enhancing the effect of NEDD4 may be a new approach for treating phosgene-induced ALI.

Artemisia sieversiana pollen allergy and immunotherapy in mice

This study developed a murine model of asthma using Artemisia sieversiana pollen extract (ASE) and subcutaneous immunotherapy (SCIT) without an adjuvant. BALB/c mice were sensitized subcutaneously with 25 μg of ASE and challenged with 0.1% ASE aerosol. To investigate the efficacy of SCIT, mice were subcutaneously injected with 0.3 mg ASE without adjuvant once a week for 8 weeks, followed by challenge for 3 additional days. Airway hyperresponsiveness (AHR) to methacholine, pulmonary inflammatory cell infiltration, cytokine levels of bronchoalveolar lavage fluid, histopathology of the lung, and serum allergen-specific serum IgE and IgG2a levels were assessed following the final challenge. Mice sensitized with ASE developed AHR and had significantly higher interleukin (IL)-4, IL-5, and IL-13 levels as well as lower IL-12 level than those of control mice. Moreover, mice sensitized with ASE showed increased plasma levels of allergen-specific IgE, and histologic analyses showed peribranchial infiltration of inflammatory cells and mucosal hyperplasia. After SCIT, allergic symptoms and immunological parameters were effectively improved, and the plasma level of allergen-specific IgG2a was significantly increased cmpared to that in the vehicle group. These findings described successful development of an A. sieversiana pollen-induced asthma model in BALB/c mice, with in vivo findings revealing that SCIT without adjuvant significantly improved the symptoms and pathophysiology of asthmatic mice.

Emodin inhibits NF-κB signaling pathway to protect obese asthmatic rats from pathological damage via Visfatin

PURPOSE

Emodin has a protective effect on asthma. Obesity is closely related to asthma. We further explored the role of Emodin in obese asthmatic rats.

METHODS

Ovalbumin (OVA) was used to induce asthma model, and high fat diet (HFD) was used to induce obese rat model. Body weight was measured before and after the modeling. Serum lipid levels were evaluated using commercial kits. Then, lung tissue and airway tissue of rat were separated forin vivo. Hematoxylin-eosin staining (HE) analyzed the extent of lung lesions. Quantitative reverse transcription PCR assessed the mRNA expression of Visfatin and Enzyme linked immunosorbent assay measured NF-κB protein expression in airway tissues. MTT, Brdu and Western blot detected cell viability, proliferation and NF-κB level of human bronchial epithelial cells 16HBE, respectively.

RESULTS

Asthma and Emodin alone had no effect on the body weight of normal rats, while HFD promoted the body weight of rats and could be reversed by Emodin. Both asthma and obesity promoted the pathological damage of rat lungs, including emphysema, lipid accumulation, edema changes, lymphoid hypertrophy and airway smooth muscle hyperplasia as well as lipid accumulation in surum, and Emodin treatment could reduce the damage. In the airway tissues of asthma and obesity models, up-regulated Visfatin mRNA and NF-κB protein were observed. In 16HBE, Emodin reversed Visfatin's role in promoting cell viability, proliferation and activating NF-κB signaling pathway.

CONCLUSION

Emodin inhibited NF-κB expression to relieve the pathological symptoms of obese asthmatic rats by Visfatin.

Advances in the study of emodin: an update on pharmacological properties and mechanistic basis

Rhei Radix et Rhizoma, also known as rhubarb or Da Huang, has been widely used as a spice and as traditional herbal medicine for centuries, and is currently marketed in China as the principal herbs in various prescriptions, such as Da-Huang-Zhe-Chong pills and Da-Huang-Qing-Wei pills. Emodin, a major bioactive anthraquinone derivative extracted from rhubarb, represents multiple health benefits in the treatment of a host of diseases, such as immune-inflammatory abnormality, tumor progression, bacterial or viral infections, and metabolic syndrome. Emerging evidence has made great strides in clarifying the multi-targeting therapeutic mechanisms underlying the efficacious therapeutic potential of emodin, including anti-inflammatory, immunomodulatory, anti-fibrosis, anti-tumor, anti-viral, anti-bacterial, and anti-diabetic properties. This comprehensive review aims to provide an updated summary of recent developments on these pharmacological efficacies and molecular mechanisms of emodin, with a focus on the underlying molecular targets and signaling networks. We also reviewed recent attempts to improve the pharmacokinetic properties and biological activities of emodin by structural modification and novel material-based targeted delivery. In conclusion, emodin still has great potential to become promising therapeutic options to immune and inflammation abnormality, organ fibrosis, common malignancy, pathogenic bacteria or virus infections, and endocrine disease or disorder. Scientifically addressing concerns regarding the poor bioavailability and vague molecular targets would significantly contribute to the widespread acceptance of rhubarb not only as a dietary supplement in food flavorings and colorings but also as a health-promoting TCM in the coming years.

Arachidonic Acid 15-Lipoxygenase: Effects of Its Expression, Metabolites, and Genetic and Epigenetic Variations on Airway Inflammation

Arachidonic acid 15-lipoxygenase (ALOX15) is an enzyme that can oxidize polyunsaturated fatty acids. ALOX15 is strongly expressed in airway epithelial cells, where it catalyzes the conversion of arachidonic acid to 15-hydroxyeicosatetraenoic acid (15-HETE) involved in various airway inflammatory diseases. Interleukin (IL)-4 and IL-13 induce ALOX15 expression by activating Jak2 and Tyk2 kinases as well as signal transducers and activators of transcription (STATs) 1/3/5/6. ALOX15 up-regulation and subsequent association with phosphatidylethanolamine-binding protein 1 (PEBP1) activate the mitogen-activated extracellular signal-regulated kinase (MEK)-extracellular signal-regulated kinase (ERK) pathway, thus inducing eosinophil-mediated airway inflammation. In addition, ALOX15 plays a significant role in promoting the migration of immune cells, such as immature dendritic cells, activated T cells, and mast cells, and airway remodeling, including goblet cell differentiation. Genome-wide association studies have revealed multiple ALOX15 variants and their significant correlation with the risk of developing airway diseases. The epigenetic modifications of the ALOX15 gene, such as DNA methylation and histone modifications, have been shown to closely relate with airway inflammation. This review summarizes the role of ALOX15 in different phenotypes of asthma, chronic obstructive pulmonary disease, chronic rhinosinusitis, aspirin-exacerbated respiratory disease, and nasal polyps, suggesting new treatment strategies for these airway inflammatory diseases with complex etiology and poor treatment response.

Emodin alleviates hypertrophic scar formation by suppressing macrophage polarization and inhibiting the Notch and TGF-β pathways in macrophages

Hypertrophic scar (HS) formation is a common complication that develops after skin injury; however, there are few effective and specific therapeutic approaches for HS. Emodin has previously been reported to inhibit mechanical stress-induced HS inflammation. Here, we investigated the molecular mechanisms underlying the inhibitory effects of emodin on HS formation. First, we conducted in vitro assays that revealed that emodin inhibited M1 and M2 polarization in rat macrophages. We subsequently established a combined rat model of tail HS and dorsal subcutaneous polyvinyl alcohol (PVA) sponge-induced wounds. Rats were treated with emodin or vehicle (DMEM). Tail scar specimens were harvested at 14, 28, and 42 days post-incision and subjected to H&E staining and Masson's trichrome staining. Histopathological analyses confirmed that emodin attenuated HS formation and fibrosis. Macrophages were separated from wound cells collected from the PVA sponge at 3 and 7 days after implantation. Flow cytometry analysis demonstrated that emodin suppressed in vivo macrophage recruitment and polarization at the wound site. Finally, we explored the molecular mechanisms of emodin in modulating macrophage polarization by evaluating the expression levels of selected effectors of the Notch and TGF-β pathways in macrophages isolated from PVA sponges. Western blot and qPCR assays showed that Notch1, Notch4, Hes1, TGF-β, and Smad3 were downregulated in response to emodin treatment. Taken together, our findings suggested that emodin attenuated HS formation and fibrosis by suppressing macrophage polarization, which is associated with the inhibition of the Notch and TGF-β pathways in macrophages.

Emodin inhibits lipid accumulation and inflammation in adipose tissue of high-fat diet-fed mice by inducing M2 polarization of adipose tissue macrophages

Adipose tissue macrophages (ATMs) represent the most abundant leukocytes in adipose tissue (AT). An increase in number and a phenotypical switch of ATMs during the development of obesity contribute to chronic inflammation and metabolic disorders, which have been regarded as potential therapeutic targets to restore AT homeostasis. Emodin has been shown to exert strong anti-inflammatory property via acting on macrophages in a range of disease models. However, whether emodin exerts a beneficial effect on obesity via modulating ATMs has not been reported. In high-fat diet (HFD)-induced obese mice, emodin significantly inhibited the increase of body weight and lipid accumulation in ATs. Emodin apparently reduced glucose and insulin levels and ameliorated serum lipid profiles in HFD-fed mice. Moreover, the local and systemic inflammation was dramatically alleviated by emodin. We next discovered that M2 macrophage percentage was greatly increased by emodin although total ATMs was not altered, which resulted in a net increase of M2 macrophages in AT. In vitro studies confirmed that emodin promoted the polarization of macrophages towards M2. Gene ontology (GO) analysis showed that myeloid leukocyte differentiation and activation were among the most significant biological processes in emodin-treated ATMs. We further identified that TREM2 was the most dramatically upregulated molecule by emodin and emodin-induced M2 macrophage polarization was dependent on TREM2. Furthermore, silencing TREM2 apparently abrogated the effect of emodin on AT inflammation and adipogenesis. We, for the first time, disclosed that emodin inhibited obesity by promoting M2 macrophage polarization via TREM2, suggesting that emodin may be explored as a clinical and translational candidate in preventing obesity and its related metabolic diseases.

Anti-DLL4 ameliorates toluene diisocyanate-induced experimental asthma by inhibiting Th17 response

Toluene diisocyanate (TDI) exhibits an ability to induce steroid insensitive asthma with the involvement of Th17 cells. And emerging evidence has indicated that DLL4 signaling promotes Th17 differentiation through directly upregulating Rorc and IL-17 transcription. Thus, we sought to evaluate the effects of DLL4 blocking antibody on TDI-induced asthma model. Female BALB/c mice were sensitized and challenged with TDI to generate an asthma model. TDI-exposed mice were intraperitoneally injected with anti-DLL4 antibody and then analyzed for various parameters of the airway inflammatory responses. Increased expression of DLL4 in spleen and lung was detected in TDI-exposed mice. Furthermore, anti-DLL4 treatment alleviated TDI-induced airway hyperreactivity (AHR), airway inflammation, airway epithelial injury and airway smooth muscle (ASM) thickening. In the meantime, neutralizing DLL4 also blunted Th17 response via downregulation of ROR-γt expression, while had no effect on Th2 cells and regulatory T (Treg) cells. Overall, anti-DLL4 ameliorated TDI-induced experimental asthma by inhibiting Th17 response, implying the feasibility of targeting DLL4 for therapy of Th17-predominant severe asthma.

Active ingredients from Chinese medicine plants as therapeutic strategies for asthma: Overview and challenges

Although considerable advance has been made in diagnosing and treating, asthma is still a serious public health challenge. Traditional Chinese medicine (TCM) is an effective therapy of complementary and alternative medicine. More and more scientific evidences support the use of TCM for asthma treatment, and active ingredients from Chinese medicine plants are becoming a hot issue.

PURPOSE OF REVIEW

To summarize the frontier knowledge on the function and underlying mechanisms of the active ingredients in asthma treatments and provide a fully integrated, reliable reference for exploring innovative treatments for asthma.

METHODS

The cited literature was obtained from the PubMed and CNIK databases (up to September 2020). Experimental studies on the active ingredients of Chinese medicine and their therapeutic mechanisms were identified. The key words used in the literature retrieval were "asthma" and "traditional Chinese medicine" or "Chinese herbal medicine". The literature on the active ingredients was then screened manually.

RESULTS

We summarized the effect of these active ingredients on asthma, primarily including the effect through which these ingredients can regulate the immunologic equilibrium mechanism by acting on a number of signalling pathways, such as Notch, JAK-STAT-MAPK, adiponectin-iNOS-NF-κB, PGD2-CRTH2, PI3K/AKT, Keap1-Nrf2/HO-1, T-bet/Gata-3 and Foxp3-RORγt, thereby regulating the progression of asthma.

CONCLUSION

The active ingredients from Chinese medicine have multilevel effects on asthma by regulating the immunologic equilibrium mechanism or signalling pathways, giving them great clinical value. However, the safety and functional mechanism of these ingredients still must be further determined.

Emodin inhibiting neutrophil elastase-induced epithelial-mesenchymal transition through Notch1 signalling in alveolar epithelial cells

The transition of alveolar type II epithelial cells into fibroblasts has been reported to cause and/or aggravate pulmonary fibrosis (PF), which is characterized by fibroblast proliferation, an enhanced production and accumulation of ECM (extracellular matrix), alveolar wall damage and functional capillary unit loss. Traditional Chinese medicine Emodin has been reported to inhibit TGF‐β‐induced epithelial‐mesenchymal transition (EMT) in alveolar epithelial cells through Notch signalling. In the present study, neutrophil elastase (NE, also known as ELA2) treatment promoted EMT, Notch1 cleavage (NICD/Notch1 ratio increase) and NICD nuclear translocation in RLE‐6TN cells and A549 cells. The promotive roles of NE treatment in these events were significantly reversed by Notch1 knockdown. Traditional Chinese medicine Emodin treatment remarkably inhibited the enzyme activity of NE, suppressed EMT, Notch1 cleavage and NICD nuclear translocation within RLE‐6TN and A549 cells, while NE treatment significantly reversed the effects of Emodin. Moreover, in RLE‐6TN, the effects of NE on EMT, Notch1 cleavage and NICD nuclear translocation were remarkably attenuated by Emodin treatment and more attenuated by the combination of Emodin and neutrophil elastase inhibitor Sivelestat or notch signal pathway inhibitor DAPT. In conclusion, we revealed the involvement of NE‐induced Notch1 cleavage in the functions of Emodin suppressing NE‐caused EMT in RLE‐6TN cells and A549 cells. This novel mechanism of Emodin inhibiting EMT might extend the application of Emodin in PF treatment.

Notch1 contributes to TNF-α-induced proliferation and migration of airway smooth muscle cells through regulation of the Hes1/PTEN axis

Notch1 has been implicated in asthma pathogenesis. However, the function of Notch1 in regulating airway smooth muscle (ASM) cell proliferation and migration during airway remodeling of asthma remains unknown. Using an in vitro model induced by tumor necrosis factor (TNF)-α, we reported in this study that Notch1 participated in TNF-α-induced proliferation and migration of ASM cells. Our results demonstrated that Notch1 expression was significantly upregulated in ASM cells exposed to TNF-α. Notch1 inhibition significantly repressed TNF-α-induced ASM cell proliferation and migration, while Notch1 overexpression promoted the opposite effect. Moreover, Notch1 inhibition downregulated the expression of Notch-1 intracellular domain (NICD) and Hes1, while upregulated PTEN expression in TNF-α-exposed cells. Notably, Hes1 overexpression partially reversed the Notch1-inhibition-mediated inhibitory effect on TNF-α-induced ASM cell proliferation and migration. In addition, the promoting effect of Notch1 inhibition on PTEN expression was markedly abrogated by Hes1 overexpression. Overall, these findings demonstrated that Notch1 inhibition repressed TNF-α-induced ASM cell proliferation and migration by modulating the Hes1/PTEN signaling axis, a finding that highlights the involvement of Notch1/Hes1/PTEN in regulating airway remodeling of asthma.

Folium Sennae and emodin reverse airway smooth muscle contraction

The objective of this project was to find a bronchodilatory compound from herbs and clarify the mechanism. We found that the ethanol extract of Folium Sennae (EEFS) can relax airway smooth muscle (ASM). EEFS inhibited ASM contraction, induced by acetylcholine, in mouse tracheal rings and lung slices. High-performance liquid chromatography assay showed that EEFS contained emodin. Emodin had a similar reversal action. Acetylcholine-evoked contraction was also partially reduced by nifedipine (a selective inhibitor of L-type voltage-dependent Ca²⁺ channels, LVDCCs), YM-58483 (a selective inhibitor of store-operated Ca²⁺ entry, SOCE), as well as Y-27632 (an inhibitor of Rho-associated protein kinase). In addition, LVDCC- and SOCE-mediated currents and cytosolic Ca²⁺ elevations were inhibited by emodin. Emodin reversed acetylcholine-caused increases in phosphorylation of myosin phosphatase target subunit 1. Furthermore, emodin, in vivo, inhibited acetylcholine-induced respiratory system resistance in mice. These results indicate that EEFS-induced relaxation results from emodin inhibiting LVDCC, SOCE, and Ca²⁺ sensitization. These findings suggest that Folium Sennae and emodin may be new sources of bronchodilators.