Effect of diosmetin on airway remodeling in a murine model of chronic asthma

Hydrangea serrata extract attenuates PM-exacerbated airway inflammation in the CARAS model by modulating the IL-33/ST2/NF-κB signaling pathway

Particulate matter (PM) significantly contributes to the global health crisis of respiratory diseases. It is known to induce and exacerbate conditions such as asthma and respiratory infections. Long exposure to PM can increase the risk of combined allergic rhinitis and asthma syndrome (CARAS). Although therapeutic drugs can be used to improve symptoms of respiratory diseases caused by PM, their usage is often accompanied by side effects. Therefore, many studies are being conducted to discover functional food materials that can more effectively treat respiratory diseases while minimizing the side effects of these therapeutic drugs. This study was conducted to investigate the efficacy of Hydrangea serrata extract (HSE) in airway inflammation in a mouse model of CARAS exacerbated by PM. In the CARAS mouse model worsened by PM, the airway inflammation improvement effect of HSE was evaluated by analyzing allergic nasal symptoms, changes in inflammatory cells, OVA-specific immunoglobulin (Ig) levels, cytokines, mast cell activation, and histopathological findings of both nasal mucosa and lung tissue. HSE effectively reduced OVA-specific IgE and IgG1 and inhibited the production of T helper type 2 (Th2)-related cytokines such as IL-4 and IL-5. Importantly, HSE reduced IL-33 and ST2 expression and inhibited the activation of the NF-κB signaling pathway. In addition, HSE inhibited airway hypersensitivity, mucus production, and inflammatory cell infiltration. These results suggest that HSE may inhibit airway inflammation in CARAS/PM mice by regulating the IL-33/ST2/NF-κB signaling pathway, opening avenues for considering HSE as a potential material for treating allergic airway inflammation diseases in the future.

Rosuvastatin and diosmetin inhibited the HSP70/TLR4 /NF-κB p65/NLRP3 signaling pathways and switched macrophage to M2 phenotype in a rat model of acute kidney injury induced by cisplatin

Numerous efforts to manage acute kidney injury (AKI) were unsuccessful because its pathophysiology is still poorly understood. Thus, our research hotspot was to explore the possible renoprotective effects of rosuvastatin (Ros) and diosmetin (D) on macrophage polarization and the role of HSP70/TLR4/MyD88/NF-κB p65/NLRP3/STAT3 signaling in cis-induced AKI and study the activity of D against uropathogenic bacteria. Fifty-four albino male rats were randomized into 9 groups equally: Control, Ros, D20, D40, untreated Cis, and Cis groups cotreated with Ros, D20, D40 and Ros+D40 for 10 days. Our results indicated that Ros and D, in a dose-dependent manner, markedly restored body weight, systolic blood pressure, and renal histological architecture besides significantly upregulated SOD levels, expression of anti-inflammatory CD163 macrophages, arginase1levels, IL-10 levels,STAT3 and PCNA immunoreactivity. Also, they significantly downregulated renal index, serum urea, serum creatinine, serum cystatin c, inflammatory biomarkers (C reactive protein, IL1β & TNF-α), MDA levels, HSP70/TLR4/MyD88/NF-κB p65/NLRP3 expressions, proinflammatory CD68 macrophages and caspase-3 immunoreactivity, resulting in a reversal of cis-induced renal damage. These findings were further confirmed by molecular docking that showed the binding affinity of Ros and D towards TLR4 and NLRP3. Furthermore, D had antibacterial action with a minimum inhibitory concentration ranging from 128 to 256 µg/mL and caused a delay in the growth of the tested isolates, and negatively affected the membrane integrity. In conclusion, Ros and D had antioxidant, anti-inflammatory and antiapoptotic properties and switched macrophage from proinflammatory CD68 to anti-inflammatory CD163. Additionally, the targeting of HSP70/TLR4/MyD88/NF-κB p65/NLRP3/STAT3 signals are effective therapeutic strategy in AKI.

Can We Improve Diosmetin Activity? The State-of-the-Art and Promising Research Directions

Diosmetin is a natural substance widely distributed in nature, with documented multidirectional biological effects. The wide spectrum of biological activity of diosmetin gives hope that derivatives of this flavonoid may also be used as drugs or dietary supplements used in many diseases. Modification of the structure may, on the one hand, lead to an increase in biological potency, new biological activity, or an increase in solubility and thus bioavailability. This is an important direction of research because the use of pure diosmetin is limited due to its low bioavailability. This work is an attempt to collect information on the possibility of modifying the structure of diosmetin and its impact on biological activity.

Medicine Targeting Epithelial-Mesenchymal Transition to Treat Airway Remodeling and Pulmonary Fibrosis Progression

Objective. Dysregulation of epithelial-mesenchymal transition (EMT) in the airway epithelium is associated with airway remodeling and the progression of pulmonary fibrosis. Many treatments have been shown to inhibit airway remodeling and pulmonary fibrosis progression in asthma and chronic obstructive pulmonary disease (COPD) by regulating EMT and have few side effects. This review aimed to describe the development of airway remodeling through the EMT pathway, as well as the potential therapeutic targets in these pathways. Furthermore, this study aimed to review the current research on drugs to treat airway remodeling and their effects on the EMT pathway. Findings. The dysregulation of EMT was associated with airway remodeling in various respiratory diseases. The cytokines released during inflammation may induce EMT and subsequent airway remodeling. Various drugs, including herbal formulations, specific herbal compounds, cytokines, amino acid or protein inhibitors, microRNAs, and vitamins, may suppress airway remodeling by inhibiting EMT-related pathways.

Antioxidant Flavonoid Diosmetin Is Cardioprotective in a Rat Model of Myocardial Infarction Induced by Beta 1-Adrenergic Receptors Activation

Myocardial infarction (MI) is a common and life-threatening manifestation of ischemic heart diseases (IHD). The most important risk factor for MI is hypertension. Natural products from medicinal plants have gained considerable attention globally due to their preventive and therapeutic effects. Flavonoids have been found to be efficacious in ischemic heart diseases (IHD) by alleviating oxidative stress and beta-1 adrenergic activation, but the mechanistic link is not clear. We hypothesized that antioxidant flavonoid diosmetin is cardioprotective in a rat model of MI induced by beta 1-adrenergic receptor activation. To test this hypothesis, we evaluated the cardioprotective potential of diosmetin on isoproterenol-induced MI in rats by performing lead II electrocardiography (ECG), cardiac biomarkers including troponin I (cTnI) and creatinine phosphokinase (CPK), CK-myocardial band, (CK-MB), lactate dehydrogenase (LDH), alanine aminotransferase (ALT), and aspartate aminotranferase (AST) by using biolyzer 100, as well as histopathological analysis. We found that diosmetin (1 and 3 mg/kg) attenuated isoproterenol-induced elevation in the T-wave and deep Q-wave on the ECG, as well as heart-to-body weight ratio and infarction size. In addition, pretreatment with diosmetin attenuated the isoproterenol-induced increase in serum troponin I. These results demonstrate that flavonoid diosmetin may provide therapeutic benefit in myocardial infarction.

The Role of Eosinophil-Derived Neurotoxin and Vascular Endothelial Growth Factor in the Pathogenesis of Eosinophilic Asthma

Asthma is a chronic complex pulmonary disease characterized by airway inflammation, remodeling, and hyperresponsiveness. Vascular endothelial growth factor (VEGF) and eosinophil-derived neurotoxin (EDN) are two significant mediators involved in the pathophysiology of asthma. In asthma, VEGF and EDN levels are elevated and correlate with disease severity and airway hyperresponsiveness. Diversity in VEGF polymorphisms results in the variability of responses to glucocorticosteroids and leukotriene antagonist treatment. Targeting VEGF and eosinophils is a promising therapeutic approach for asthma. We identified lichochalcone A, bevacizumab, azithromycin (AZT), vitamin D, diosmetin, epigallocatechin gallate, IGFBP-3, Neovastat (AE-941), endostatin, PEDF, and melatonin as putative add-on drugs in asthma with anti-VEGF properties. Further studies and clinical trials are needed to evaluate the efficacy of those drugs. AZT reduces the exacerbation rate and may be considered in adults with persistent symptomatic asthma. However, the long-term effects of AZT on community microbial resistance require further investigation. Vitamin D supplementation may enhance corticosteroid responsiveness. Herein, anti-eosinophil drugs are reviewed. Among them are, e.g., anti-IL-5 (mepolizumab, reslizumab, and benralizumab), anti-IL-13 (lebrikizumab and tralokinumab), anti-IL-4 and anti-IL-13 (dupilumab), and anti-IgE (omalizumab) drugs. EDN over peripheral blood eosinophil count is recommended to monitor the asthma control status and to assess the efficacy of anti-IL-5 therapy in asthma.

Diosmetin alleviates benzo[a]pyrene-exacerbated H1N1 influenza virus-induced acute lung injury and dysregulation of inflammation through modulation of the PPAR-γ-NF-κB/P38 MAPK signaling axis

The severity of a viral respiratory illness was greatly exacerbated after exposure to a contaminant containing benzo[a]pyrene (B[a]P). Flavonoid-rich fruit intake has gained intense interest due to their health-promoting benefits for viral respiratory diseases, including influenza viruses. In our study, diosmetin (3',5,7-trihydroxy-4'-methoxyflavone), a naturally occurring hydroxylated methoxyflavone that is abundant in Citrus fruits, was explored for its effects on B[a]P-exacerbated H1N1 influenza virus-mediated inflammation and lung injury. Initially, in vivo results demonstrated that diosmetin protected against H1N1 virus-elicited acute lung injury. Simultaneously, H1N1 virus or B[a]P-stimulated A549 cells treated with diosmetin inhibited NF-κB and P-P38 activation, resulting in suppression of pro-inflammatory cytokines and apoptosis. Interestingly, diosmetin obviously promoted the expression of PPAR-γ as well as nuclear translocation of PPAR-γ, whereas, PPAR-γ inhibition by GW9662 weakened the inhibitory effects of diosmetin on H1N1 virus or B[a]P-mediated activation of NF-κB and P-P38, elevated expression of pro-inflammatory mediators as well as apoptosis. Furthermore, it was surprising to discover that mice exposed to both B[a]P and H1N1 viruses contributed to exacerbated acute lung injury, which were significantly ameliorated by diosmetin administration. In vitro studies showed that A549 cells with the combination of B[a]P and H1N1 virus augmented NF-κB and P-P38 activation, accompanied by higher levels of pro-inflammatory mediators and apoptosis, all of which were also significantly reduced by diosmetin treatment. Repressing PPAR-γ abrogated the inhibitory effects of diosmetin on B[a]P-exacerbated H1N1 virus-mediated NF-κB and P-P38 activation, inflammation, and apoptosis in A549 cells. Our findings suggest that diosmetin protected against B[a]P-exacerbated H1N1 virus-mediated lung injury by suppressing the exacerbation of NF-κB and P38 kinase activation in a PPAR-γ-dependent manner, suggesting potential benefits for B[a]P-exacerbated influenza-related illness therapeutics.

Dinebra retroflexa Herbal Phytotherapy: A Simulation Study Based on Bleomycin-Induced Pulmonary Fibrosis Retraction Potential in Swiss Albino Rats

Background and Objectives: Fibrotic lung disease is one of the main complications of many medical conditions. Therefore, the use of anti-fibrotic agents may provide a chance to prevent, or at least modify, such complication. The aim of this study was to evaluate the protective pulmonary anti-fibrotic and anti-inflammatory effects of Dinebra retroflexa. Materials and methods: Dinebra retroflexa methanolic extract and its synthesized silver nanoparticles were tested on bleomycin-induced pulmonary fibrosis. Pulmonary fibrosis was induced by intratracheal instillation of bleomycin (5 mg/5 mL/kg-Saline) as a supposed model for induced lung fibrosis. The weed evaluation was performed by intratracheal instillation of Dinebra retroflexa methanolic extract and its silver nanoparticles (35 mg/100 mL/kg-DMSO, single dose). Results: The results showed that both Dinebra retroflexa methanolic extract and its silver nanoparticles had a significant pulmonary fibrosis retraction potential, with Ashcroft scores of three and one, respectively, and degrees of collagen deposition reduction of 33.8 and 46.1%, respectively. High-resolution UHPLC/Q-TOF-MS/MS metabolic profiling and colorimetrically polyphenolic quantification were performed for further confirmation and explanation of the represented effects. Such activity was believed to be due to the tentative identification of twenty-seven flavonoids and one phenolic acid along with a phenolic content of 57.8 mg/gm (gallic acid equivalent) and flavonoid content of 22.5 mg/gm (quercetin equivalent). Conclusion: Dinebra retroflexa may be considered as a promising anti-fibrotic agent for people at high risk of complicated lung fibrosis. The results proved that further clinical trials would be recommended to confirm the proposed findings.

Investigation into the Antihypertensive Effects of Diosmetin and Its Underlying Vascular Mechanisms Using Rat Model

Objective: Diosmetin is a flavonoid that is found in many important medicinal plants that have antihypertensive therapeutic potential. Diosmetin has been shown to have antiplatelet, anti-inflammatory and antioxidant properties, which suggests that it could be a potential candidate for use in antihypertensive therapy. Methods: In vivo and in vitro methods were used for our investigation into the antihypertensive effects of diosmetin. Results: Diosmetin significantly decreased the mean arterial pressure (MAP). The effects of diosmetin on the MAP and heart rate were more pronounced in hypertensive rats. To explore the involvement of the muscarinic receptors-linked NO pathway, Nω-nitro-L-arginine methyl ester (L-NAME) and atropine were pre-administered in vivo. The pretreatment with L-NAME did not significantly change the effects of diosmetin on the MAP by excluding the involvement of NO. Unlike L-NAME, the atropine pretreatment reduced the effects of diosmetin on the MAP, which demonstrated the role of the muscarinic receptors. In the in vitro study, diosmetin at lower concentrations produced endothelium-dependent and -independent (at higher concentrations) vasorelaxation, which was attenuated significantly by the presence of atropine and indomethacin but not L-NAME. Diosmetin was also tested for high K+-induced contractions. Diosmetin induced significant relaxation (similar to verapamil), which indicated its Ca2+ antagonistic effects. This was further confirmed by diosmetin shifting the CaCl₂ CRCs toward the right due to its suppression of the maximum response. Diosmetin also suppressed phenylephrine peak formation, which indicated its antagonist effects on the release of Ca2+. Moreover, BaCl₂ significantly inhibited the effects of diosmetin, followed by 4-AP and TEA, which suggested that the K+ channels had a role as well. Conclusions: The obtained data showed the Ca2+ channel antagonism, potassium channel activation and antimuscarinic receptor-linked vasodilatory effects of diosmetin, which demonstrated its antihypertensive potential.

PM2.5 Exposure and Asthma Development: The Key Role of Oxidative Stress

Oxidative stress is defined as the imbalance between reactive oxygen species (ROS) production and the endogenous antioxidant defense system, leading to cellular damage. Asthma is a common chronic inflammatory airway disease. The presence of asthma tends to increase the production of reactive oxygen species (ROS), and the antioxidant system in the lungs is insufficient to mitigate it. Therefore, asthma can lead to an exacerbation of airway hyperresponsiveness and airway inflammation. PM2.5 exposure increases ROS levels. Meanwhile, the accumulation of ROS will further enhance the oxidative stress response, resulting in DNA, protein, lipid, and other cellular and molecular damage, leading to respiratory diseases. An in-depth study on the relationship between oxidative stress and PM2.5-related asthma is helpful to understand the pathogenesis and progression of the disease and provides a new direction for the treatment of the disease. This paper reviews the research progress of oxidative stress in PM2.5-induced asthma as well as highlights the therapeutic potentials of antioxidant approaches in treatment of asthma.

Mechanism underlying the vasodilation induced by diosmetin in porcine coronary artery

Diosmetin is a flavonoid present naturally in citrus fruit. Plants containing diosmetin have been reported to have anti-hypertensive and vasorelaxant effects. Therefore, experiments were carried out to study the effects of diosmetin in segments of the porcine coronary artery (PCA). PCA rings were mounted for isometric tension recording in isolated tissue baths and pre-contracted with the thromboxane A₂ mimetic U46619 or KCl. Cumulative concentration response curves to diosmetin were then carried out in the presence or absence of inhibitors or activators of different signaling pathways. The effect on calcium channels was determined by investigating the effect of a single concentration of diosmetin (30 μM) on calcium-induced contractions or contractions to BAY K8644. Diosmetin caused a concentration-dependent relaxation after pre-contraction with U46619 or KCl, which was unaffected by removal of the endothelium. Tetraethylammonium (TEA), and 4-aminopyridine (4-AP), but not barium chloride, caused significant inhibition of the diosmetin-mediated vasorelaxation, indicating a role for potassium channels. Diosmetin inhibited calcium-induced contractions and contractions to the L-type calcium channel opener BAY K8644. Furthermore, diosmetin inhibited the contractions in response to caffeine, cyclopiazonic acid and ionomycin, indicating a general effect on calcium-induced contractions. Contractions in response to the protein kinase C (PKC) activator Phorbol 12-myristate 13-acetate (PMA) were also inhibited by diosmetin, suggesting that it may inhibit a calcium-activated PKC isoform. In summary, diosmetin produced significant vasodilatory effects. The data indicate a role for potassium channels as well as an effect on calcium-induced contractile pathways, possible through inhibition of PKC.

Diosmetin alleviates hypoxia‑induced myocardial apoptosis by inducing autophagy through AMPK activation

Diosmetin has shown great potential in the control of several diseases. The aim of the present study was to evaluate the role of diosmetin as a candidate agent for the treatment of myocardial infarction which was mainly caused by hypoxia. The model of hypoxia‑injured myocardial cells was established using the H9c2 cell line. Cell viability was determined using Cell Counting Kit‑8, cell apoptosis was determined by Annexin V‑FITC Apoptosis Detection Kit and cleaved caspase‑3 level was assessed by western blot analysis. Autophagy was monitored using a commercial kit, and a well‑established reporter system was used to confirm the role of diosmetin in autophagy. The activity of adenosine 5'‑monophosphate‑activated protein kinase (AMPK) signaling was detected by western blot analysis. Cell viability assay indicated that diosmetin alleviated hypoxia‑induced cell death of H9c2 cells in a dose‑dependent manner. Data of the apoptosis assay revealed that diosmetin reduced the proportion of apoptotic cells in the hypoxia‑injured H9c2 cells. It was also found that the occurrence of autophagy was promoted when hypoxia‑injured cells were treated with diosmetin alone, and results of the western blot analysis revealed that AMPK signaling was activated by diosmetin. Administration of diosmetin together with an inhibitor of autophagy (3‑methyladenine, 3‑MA) or AMPK (Compound C) was able to decrease the diosmetin‑induced autophagy as well as the cytoprotective effects in the hypoxia‑injured cells. Our study concluded that diosmetin exhibits a cytoprotective effect on hypoxia‑injured myocardial cells by inducing autophagy and alleviating apoptosis. AMPK was demonstrated to regulate the observed effects caused by diosmetin. This investigation confirmed diosmetin as a promising drug candidate for myocardial infarction treatment. The present findings regarding the inherent molecular mechanisms involved in the protective effects of diosmetin promote the clinical application of diosmetin.

Role of Differential Estrogen Receptor Activation in Airway Hyperreactivity and Remodeling in a Murine Model of Asthma

Evidence suggests that airway hyperresponsiveness (AHR) is a characteristic feature of asthma. Epidemiological studies have confirmed that the severity of asthma is greater in women, suggesting a critical role of female sex steroid hormones (especially estrogen). Very few in vivo studies have examined the role of sex steroid hormones in asthma, and the sequence of events that occur through differential activation of estrogen receptors (ERs) remains to be determined in asthmatic airways. Our recent in vitro findings indicated that ERβ had increased expression in asthmatic airway smooth muscle (ASM), and that its activation by an ERβ-specific agonist downregulated airway remodeling. In this study, we translated the in vitro findings to a murine asthma model and examined the differential role of ER activation in modulating lung mechanics. C57BL/6J male, female, and ovariectomized mice were exposed to mixed allergen (MA) and subcutaneously implanted with sustained-release pellets of placebo, an ERα agonist (4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol [PPT]), and/or an ERβ agonist (WAY-200070). We then evaluated the effects of these treatments on airway mechanics, biochemical, molecular, and histological parameters. Mice exposed to MA showed a significant increase in airway resistance, elastance, and tissue damping, and a decrease in compliance; pronounced effects were observed in females. Compared with PPT, WAY treatment significantly reversed the MA-induced changes. The increased mRNA/protein expression of ERα, ERβ, and remodeling genes observed in MA-treated mice was significantly reversed in WAY-treated mice. This novel study indicates that activation of ERβ signaling downregulates AHR and airway remodeling, and is a promising target in the development of treatments for asthma.

Inhibitory effect of diosmetin on inflammation and lipolysis in coculture of adipocytes and macrophages

The interaction between adipocytes and macrophages in obese tissues plays a critical role in the onset of metabolic syndromes. This study aimed to evaluate the modulatory effect of diosmetin on anti-inflammatory and anti-lipolytic activities in the coculture of macrophages and adipocytes. The secretion of inflammatory mediators increased in a coculture medium, however, diosmetin significantly reduced the levels of these inflammatory mediators such as nitric oxide (NO), tumor necrosis factor-α, and monocyte chemoattractant protein. Diosmetin down-regulated the protein expression of inducible NO synthase in cocultured macrophages and adipocytes, and inhibited the phosphorylation of mitogen-activated protein kinases and the translocation of p65 and p50 to the nucleus. Moreover, it suppressed the phosphorylation of hormone-sensitive lipase and the production of fatty acid-binding protein 4, and increased the mRNA expression of adiponectin in cocultured adipocytes by 18%-35%. These results indicate that diosmetin inhibited inflammation and lipolysis in the crosstalk between adipocytes and macrophages; diosmetin-containing foods could be used in dietary therapy for the prevention of obesity-related metabolic syndromes. PRACTICAL APPLICATIONS: Diosmetin occurs naturally in citrus fruits that have a high inhibitory effect on inflammation in cocultured adipocytes and macrophages via the inactivation of the MAPKs/NF-kB pathway. Diosmetin also inhibited lipolysis via the reduction of FFA and free glycerol. The present study suggests that treatment of diosmetin may be useful for the prevention of obesity and inflammation-related metabolic syndromes.

Role of Estrogen Receptors α and β in a Murine Model of Asthma: Exacerbated Airway Hyperresponsiveness and Remodeling in ERβ Knockout Mice

Epidemiological data suggests increased prevalence of asthma in females than males, suggesting a plausible role for sex-steroids, especially estrogen in the lungs. Estrogen primarily acts through estrogen-receptors (ERα and ERβ), which play a differential role in asthma. Our previous studies demonstrated increased expression of ERβ in asthmatic human airway smooth muscle (ASM) cells and its activation diminished ASM proliferation in vitro and airway hyperresponsiveness (AHR) in vivo in a mouse (wild-type, WT) model of asthma. In this study, we evaluated the receptor specific effect of circulating endogenous estrogen in regulating AHR and remodeling using ERα and ERβ knockout (KO) mice. C57BL/6J WT, ERα KO, and ERβ KO mice were challenged intranasally with a mixed-allergen (MA) or PBS. Lung function was measured using flexiVent followed by collection of broncho-alveolar lavage fluid for differential leukocyte count (DLC), histology using hematoxylin and eosin (H&E) and Sirius red-fast green (SRFG) and detecting αsmooth muscle actin (α-SMA), fibronectin and vimentin expression using immunofluorescence (IF). Resistance (Rrs), elastance (Ers), tissue-damping (G) and tissue-elasticity (H) were significantly increased, whereas compliance (Crs) was significantly decreased in WT, ERα KO, and ERβ KO mice (males and females) challenged with MA compared to PBS. Interestingly, ERβ KO mice showed declined lung function compared to ERα KO and WT mice at baseline. MA induced AHR, remodeling and immune-cell infiltration was more prominent in females compared to males across all populations, while ERβ KO females showed maximum AHR and DLC, except for neutrophil count. Histology using H&E suggests increased smooth muscle mass in airways with recruitment of inflammatory cells, while SRFG staining showed increased collagen deposition in MA challenged ERβ KO mice compared to ERα KO and WT mice (males and females), with pronounced effects in ERβ KO females. Furthermore, IF studies showed increased expression of α-SMA, fibronectin and vimentin in MA challenged populations compared to PBS, with prominent changes in ERβ KO females. This novel study indicates ERβ plays a pivotal role in airway remodeling and AHR and understanding the mechanisms involved might help to surface it out as a potential target to treat asthma.

Inhibition of TGF-β Signaling in Gliomas by the Flavonoid Diosmetin Isolated from Dracocephalum peregrinum L

Background: Dracocephalum peregrinum L., a traditional Kazakh medicine, has good expectorant, anti-cough, and to some degree, anti-asthmatic effects. Diosmetin (3',5,7-trihydroxy-4'-methoxyflavone), a natural flavonoid found in traditional Chinese herbs, is the main flavonoid in D. peregrinum L. and has been used in various medicinal products because of its anticancer, antimicrobial, antioxidant, estrogenic, and anti-inflammatory effects. The present study aimed to investigate the effects of diosmetin on the proliferation, invasion, and migration of glioma cells, as well as the possible underlying mechanisms. Methods: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), scratch wound, and Transwell assays were used to demonstrate the effects of diosmetin in glioma. Protein levels of Bcl-2, Bax, cleaved caspase-3, transforming growth factor-β (TGF-β), E-cadherin, and phosphorylated and unphosphorylated smad2 and smad3 were determined by Western blots. U251 glioma cell development and progression were measured in vivo in a mouse model. Results: Diosmetin inhibited U251 cell proliferation, migration, and invasion in vitro, the TGF-β signaling pathway, and Bcl-2 expression. In contrast, there was a significant increase in E-cadherin, Bax, and cleaved caspase-3 expression. Furthermore, it effectively reduced the tumorigenicity of glioma cells and promoted apoptosis in vivo. Conclusion: The results of this study suggest that diosmetin suppresses the growth of glioma cells in vitro and in vivo, possibly by activating E-cadherin expression and inhibiting the TGF-β signaling pathway.

VEGF and FGF-2: Promising targets for the treatment of respiratory disorders

The endothelial cells play a crucial role in the progression of angiogenesis, which causes cell re-modulation, proliferation, adhesion, migration, invasion and survival. Angiogenic factors like cytokines, cell adhesion molecules, growth factors, vasoactive peptides, proteolytic enzymes (metalloproteinases) and plasminogen activators bind to their receptors on endothelial cells and activate the signal transduction pathways like epidermal growth factor receptor (EGFR phosphatidylinositol 3-kinase and (PI3K)/AKT/mammalian target of rapamycin (mTOR) which initiate the process of angiogenesis. Cytokines that stimulate angiogenesis include direct and indirect proangiogenic markers. The direct proangiogenic group of markers consists of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-2) and hepatocyte growth factor (HGF) whereas the indirect proangiogenic markers include transforming growth factor-beta (TGF-β), interleukin 6 (IL-6), interleukin 8 (IL-8) and platelet-derived growth factor (PDGF). VEGF and FGF-2 are the strongest activators of angiogenesis which stimulate migration and proliferation of endothelial cells in existing vessels to generate and stabilize new blood vessels. VEGF is released in hypoxic conditions as an effect of the hypoxia-inducible factor (HIF-1α) and causes re-modulation and inflammation of bronchi cell. Cell re-modulation and inflammation leads to the development of various lung disorders like pulmonary hypertension, chronic obstructive pulmonary disease, asthma, fibrosis and lung cancer. This indicates that there is a firm link between overexpression of VEGF and FGF-2 with lung disorders. Various natural and synthetic drugs are available for reducing the overexpression of VEGF and FGF-2 which can be helpful in treating lung disorders. Researchers are still searching for new angiogenic inhibitors which can be helpful in the treatment of lung disorders. The present review emphasizes on molecular mechanisms and new drug discovery focused on VEGF and FGF-2 inhibitors and their role as anti-angiogenetic agents in lung disorders.

Diosmetin Suppresses Neuronal Apoptosis and Inflammation by Modulating the Phosphoinositide 3-Kinase (PI3K)/AKT/Nuclear Factor-κB (NF-κB) Signaling Pathway in a Rat Model of Pneumococcal Meningitis

Bacterial meningitis has a high mortality rate and can be challenging to diagnose and manage. This study aimed to evaluate the effect of diosmetin in a rat model of Streptococcus pneumoniae meningitis and to investigate the mechanism of action.

Forty rats included a treatment group (n=30) that underwent intracisternal injection with S. pneumoniae, and a sham group (n=10) that underwent intracisternal injection with normal saline. In the treatment group, four days before the inoculation of the bacteria, rats were pre-treated with oral diosmetin 100 mg/kg (n=10) and 200 mg/kg (n=10), and the negative control was pre-treated with normal saline (n=10). Bacterial meningitis was confirmed one day after inoculation by cerebrospinal fluid (CSF) bacterial titer and neurological score. In rat brain tissue, levels of inflammatory mediators were determined by enzyme-linked immunosorbent assay (ELISA) and western blot for protein kinase B (Akt), phosphoinositide 3-kinase (PI3K), myeloid differentiation primary response 88 (MyD88), and nuclear factor-κB (NF-κB), and the TUNEL assay for apoptosis was performed.

In the diosmetin-treated group compared with negative control group, the CSF bacterial titer and the level of pro-inflammatory mediators, and the neurological score, were significantly reduced (p<0.01). In the rat hippocampal tissue, levels of Akt, PI3K, MyD88 and NF-κB, and the number of TUNEL-positive apoptotic cells were significantly reduced in the diosmetin-treated group compared with negative control group (p<0.01).

In a rat model of bacterial meningitis due to S. pneumoniae, diosmetin reduced neuroinflammation, and neuronal apoptosis by modulating the PI3K/AKT/NF-κB signaling pathway.

Diosmetin Attenuates Akt Signaling Pathway by Modulating Nuclear Factor Kappa-Light-Chain-Enhancer of Activated B Cells (NF-κB)/Inducible Nitric Oxide Synthase (iNOS) in Streptozotocin (STZ)-Induced Diabetic Nephropathy Mice

Background

We evaluated the nephroprotective effect of diosmetin in streptozotocin (STZ)-induced diabetic nephropathy (DN) mice.

Material/Methods

Diabetes was induced by injecting STZ (50 mg/kg) i.p. for 5 days. Biochemical parameters, such as fasting blood glucose, creatinine, BUN in the serum, and albumin in the urine, were determined in STZ-induced DN mice after the 8^th week of STZ administration. The level of inflammatory mediators in the serum and oxidative stress parameters in the tissue homogenate was estimated in STZ-induced DN mice. Expressions of Akt, NF-κB, and iNOS in the tissue homogenate were assessed by Western blot analysis.

Results

Our data reveal that treatment with diosmetin significantly reduces the fasting blood glucose (FBG), serum creatinine, and blood urea nitrogen (BUN) in the serum and albumin in urine compared to the negative control group. Treatment with diosmetin attenuated the altered level of oxidative stress parameters and inflammatory cytokines in the STZ-induced DN mice. Expression of Akt and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) was significantly reduced and inducible nitric oxide synthase (iNOS) was enhanced in the tissue homogenate of diosmetin-treated mice compared to the negative control group. Data from immunohistochemical analysis suggest that the expressions of NF-κB was significantly reduced in tissues of the diosmetin-treated group compared to the negative control group.

Conclusions

Our study shows that diosmetin protects against renal injury in STZ-induced diabetic nephropathy mice by modulating the Akt/NF-κB/iNOS signaling pathway.

Cancer chemoprevention revisited: Cytochrome P450 family 1B1 as a target in the tumor and the microenvironment

Cancer chemoprevention is the use of synthetic, natural or biological agents to prevent or delay the development or progression of malignancies. Intriguingly, many phytochemicals with anti-inflammatory and anti-angiogenic effects, recently proposed as chemoprevention strategies, are inhibitors of Cytochrome P450 family 1B1 (CYP1B1), an enzyme overexpressed in a wide variety of tumors and associated with angiogenesis. In turn, pro-inflammatory cytokines were reported to boost CYP1B1 expression, suggesting a key role of CYP1B1 in a positive loop of inflammatory angiogenesis. Other well-known pro-tumorigenic activities of CYP1B1 rely on metabolic bioactivation of xenobiotics and steroid hormones into their carcinogenic derivatives. In contrast to initial in vitro observations, in vivo studies demonstrated a protecting role against cancer for the other CYP1 family members (CYP1A1 and CYP1A2), suggesting that the specificity of CYP1 family inhibitors should be carefully taken into account for developing potential chemoprevention strategies. Recent studies also proposed a role of CYP1B1 in multiple cell types found within the tumor microenvironment, including fibroblasts, endothelial and immune cells. Overall, our review of the current literature suggests a positive loop between inflammatory cytokines and CYP1B1, which in turn may play a key role in cancer angiogenesis, acting on both cancer cells and the tumor microenvironment. Strategies aiming at specific CYP1B1 inhibition in multiple cell types may translate into clinical chemoprevention and angioprevention approaches.

Diosmetin protects against ischemia/reperfusion-induced acute kidney injury in mice

BACKGROUND

Renal ischemia/reperfusion (I/R)-induced acute kidney injury remains to be a troublesome condition in clinical practice. Although the exact molecular mechanisms underlying renal I/R injury are incompletely understood, the deleterious progress of renal I/R injury involves inflammation, apoptosis, and oxidative stress. Diosmetin is a member of the flavonoid glycosides family, which suppresses the inflammatory response and cellular apoptosis and enhances antioxidant activity. The purpose of this study was to investigate the protective effect of diosmetin on I/R-induced renal injury in mice.

METHODS

Thirty BALB/c mice were randomly divided into five groups. Four groups of mice received diosmetin (0.25, 0.5, and 1 mg/kg) or vehicle (I/R group) before ischemia. Another group received vehicle without ischemia to serve as a negative control (sham-operated group). Twenty-four hours after reperfusion, serum and renal tissues were harvested to evaluate renal function and histopathologic features. In addition, the expression of inflammation-related proteins, apoptotic molecules, and antioxidant enzymes was analyzed.

RESULTS

Compared with sham mice, the I/R group significantly exacerbated renal function and renal tube architecture and increased the inflammatory response and renal tubule apoptosis. Nevertheless, pretreatment with diosmetin reversed these changes. In addition, diosmetin treatment resulted in a marked increase in antioxidant protein expression compared with I/R mice.

CONCLUSIONS

The renoprotective effects of diosmetin involved suppression of the nuclear factor-κB and mitochondrial apoptosis pathways, as well as activation of the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 pathway. Diosmetin has significant potential as a therapeutic intervention to ameliorate renal injury after renal I/R.

Regioselective Glucuronidation of Diosmetin and Chrysoeriol by the Interplay of Glucuronidation and Transport in UGT1A9-Overexpressing HeLa Cells

This study aimed to determine the reaction kinetics of the regioselective glucuronidation of diosmetin and chrysoeriol, two important methylated metabolites of luteolin, by human liver microsomes (HLMs) and uridine-5′-diphosphate glucuronosyltransferase (UGTs) enzymes. This study also investigated the effects of breast cancer resistance protein (BCRP) on the efflux of diosmetin and chrysoeriol glucuronides in HeLa cells overexpressing UGT1A9 (HeLa—UGT1A9). After incubation with HLMs in the presence of UDP-glucuronic acid, diosmetin and chrysoeriol gained two glucuronides each, and the OH—in each B ring of diosmetin and chrysoeriol was the preferable site for glucuronidation. Screening assays with 12 human expressed UGT enzymes and chemical-inhibition assays demonstrated that glucuronide formation was almost exclusively catalyzed by UGT1A1, UGT1A6, and UGT1A9. Importantly, in HeLa—UGT1A9, Ko143 significantly inhibited the efflux of diosmetin and chrysoeriol glucuronides and increased their intracellular levels in a dose-dependent manner. This observation suggested that BCRP-mediated excretion was the predominant pathway for diosmetin and chrysoeriol disposition. In conclusion, UGT1A1, UGT1A6, and UGT1A9 were the chief contributors to the regioselective glucuronidation of diosmetin and chrysoeriol in the liver. Moreover, cellular glucuronidation was significantly altered by inhibiting BCRP, revealing a notable interplay between glucuronidation and efflux transport. Diosmetin and chrysoeriol possibly have different effects on anti-cancer due to the difference of UGT isoforms in different cancer cells.

Diosmetin prevents TGF-β1-induced epithelial-mesenchymal transition via ROS/MAPK signaling pathways

AIMS

Epithelial-mesenchymal transition (EMT) plays a critical role in airway repair and remodeling in many respiratory diseases such as asthma and pulmonary fibrosis. The flavone aglycone, diosmetin, possesses anti-remodeling activity in a murine model of chronic asthma, but little is known about its effects on EMT. Herein, we investigated whether diosmetin inhibits transforming growth factor-β1 (TGF-β1)-induced EMT with underlying mechanisms in human bronchial epithelial (HBE) cells.

MAIN METHODS

HBE cells were incubated with TGF-β1 (10ng/ml), either alone or in combination with diosmetin for indicated times. We measured reactive oxygen species (ROS) levels using FACScan and immunofluorescent assays. We assessed protein expression of NADPH oxidase 4 (NOX4), superoxide dismutase (SOD), catalase, Akt, Erk, p38, and phosphorylation levels of Akt, Erk and p38 by Western blot analysis.

KEY FINDINGS

TGF-β1 promoted EMT and ROS generation in HBE cells. Diosmetin significantly suppressed TGF-β1-induced increases in cell migration and altered N-cadherin, E-cadherin, and α-smooth muscle actin expression. In addition, diosmetin prevented TGF-β1-induced intracellular ROS generation, down-regulated NOX4, and up-regulated SOD and catalase expression. Furthermore, diosmetin remarkably inhibited TGF-β1-induced phosphorylation of phosphoinositide 3-kinase (PI3K)/Akt and mitogen activated protein kinase (MAPK) pathways in HBE cells.

SIGNIFICANCE

Our results demonstrate for the first time that diosmetin alleviates TGF-β1-induced EMT by inhibiting ROS generation and inactivating PI3K/Akt and MAPK pathways. Our findings revealed a new role for diosmetin in reducing airway remodeling and fibrogenesis.