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Targeting Casein Kinase 2 with Quercetin or Enzymatically Modified Isoquercitrin as a Strategy for Boosting the Type 1 Interferon Response to Viruses and Promoting Cardiovascular Health
... 124 One study revealed that CK2 may be involved in downregulating the ability of host cells to produce IFN during viral infection; as such, blocking CK2 may be considered an important antiviral therapeutic strategy. 125 Studies have shown that in cases of SARS-CoV-2 infection, CK2 was activated and directly targeted by the N protein and facilitated the rapid spread and movement of the virus between cells. 112 Given the essential roles of CK2 in viral infection, CK2 is a putative therapeutic target for SARS-CoV-2. ...
... Other CK2 inhibitors, including quercetin and enzymatically modified isoquercitrin (EMIQ), are also promising candidates for COVID-19 treatment. 125,3043 3.2.5 ...
The coronavirus disease 2019 (COVID-19) pandemic has affected a large portion of the global population, both physically and mentally. Current evidence suggests that the rapidly evolving coronavirus subvariants risk rendering vaccines and antibodies ineffective due to their potential to evade existing immunity, with enhanced transmission activity and higher reinfection rates that could lead to new outbreaks across the globe. The goal of viral management is to disrupt the viral life cycle as well as to relieve severe symptoms such as lung damage, cytokine storm, and organ failure. In the fight against viruses, the combination of viral genome sequencing, elucidation of the structure of viral proteins, and identifying proteins that are highly conserved across multiple coronaviruses has revealed many potential molecular targets. In addition, the time- and cost-effective repurposing of preexisting antiviral drugs or approved/clinical drugs for these targets offers considerable clinical advantages for COVID-19 patients. This review provides a comprehensive overview of various identified pathogenic targets and pathways as well as corresponding repurposed approved/clinical drugs and their potential against COVID-19. These findings provide new insight into the discovery of novel therapeutic strategies that could be applied to the control of disease symptoms emanating from evolving SARS-CoV-2 variants.
... CDK has also been the target of various infectious diseases where its expression and function are altered by viruses in the host cell (Klann et al., 2020), such as HIV, Herpes simplex virus (HSV), Zika virus, and hepatitis B virus (HBV) (Schang et al., 2006). Recent literature sheds light on the evidence of CK2's involvement in the mechanism of down-regulating the ability of the cell to generate IFN-in response to viral infection (DiNicolantonio and McCarty, 2020). Hence, intervention involving CK2 may be considered as one of the important strategies in antiviral treatment. ...
... To choose CK2 inhibitors as one of the potential therapies for COVID-19 treatment, a large number of inhibitors must be studied. Some of the CK2 inhibitors that may be considered or that are being suggested as potential candidates for COVID-19 infection include quercetin and enzymatically modified isoquercitrin (EMIQ) (Colunga Biancatelli et al., 2020;DiNicolantonio and McCarty, 2020). ...
Corona virus is quickly spreading around the world. The goal of viral management is to disrupt the virus’s life cycle, minimize lung damage, and alleviate severe symptoms. Numerous strategies have been used, including repurposing existing antivirals or drugs used in previous viral outbreaks. One such strategy is to repurpose FDA-approved kinase inhibitors that are potential chemotherapeutic agents and have demonstrated antiviral activity against a variety of viruses, including MERS, SARS-CoV-1, and others, by inhibiting the viral life cycle and the inflammatory response associated with COVID-19. The purpose of this article is to identify licensed kinase inhibitors that have the ability to reduce the virus’s life cycle, from entrance through viral propagation from cell to cell. Several of these inhibitors, including imatinib, ruxolitinib, silmitasertib, and tofacitinib (alone and in conjunction with hydroxychloroquine), are now undergoing clinical studies to determine their efficacy as a possible treatment drug. The FDA approved baricitinib (a Janus kinase inhibitor) in combination with remdesivir for the treatment of COVID-19 patients receiving hospital care in November 2020. While in vitro trials with gilteritinib, fedratinib, and osimertinib are encouraging, further research is necessary before these inhibitors may be used to treat COVID-19 patients.
... 152,153 Recent shreds of evidence suggest that CK2 is involved in various mechanisms to downregulate the potential of cells to generate IFN-1 in response to viral infection. 154 Thus, the pharmacological intervention of CK2 has been considered a potential strategy for antiviral treatment. CK2 is involved in the development of actin tails during vaccinia infection, which allows the virus to travel efficiently from cell to cell. ...
... For example, quercetin and enzymatically modified isoquercitrin (EMIQ) have been suggested as potential candidates. 154 4.1. Inhibitors of the p38 MAPK Signaling Pathway. ...
The global coronavirus disease-19 (COVID-19) has affected more than 140 million and killed more than 3 million people worldwide as of April 20, 2021. The novel human severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been identified as an etiological agent for COVID-19. Several kinases have been proposed as possible mediators of multiple viral infections, including life-threatening coronaviruses like SARS-CoV-1, Middle East syndrome coronavirus (MERS-CoV), and SARS-CoV-2. Viral infections hijack abundant cell signaling pathways, resulting in drastic phosphorylation rewiring in the host and viral proteins. Some kinases play a significant role throughout the viral infection cycle (entry, replication, assembly, and egress), and several of them are involved in the virus-induced hyperinflammatory response that leads to cytokine storm, acute respiratory distress syndrome (ARDS), organ injury, and death. Here, we highlight kinases that are associated with coronavirus infections and their inhibitors with antiviral and potentially anti-inflammatory, cytokine-suppressive, or antifibrotic activity.
... Flavonol, quercetin and their derivatives are found in abundance in apples which belong to the major dietary sources of favonoids (Herranz et al., 2019), and several studies have demonstrated that these bioactives have antioxidant potential , antimicrobial (Tian et al., 2021) anti-infammatory properties (Yong et al., 2020) antidepressive (Dimpfel, 2009) and anti-carcinogenic effects (Imran et al., 2020). These compounds also protect against diabetes (Ebrahimpour et al., 2020), arteriosclerosis (Ishizawa et al., 2011), oral diseases (Wang et al., 2020b) neurodegenerative (Sahoo et al., 2020) and cardiovascular diseases (DiNicolantonio and Mccarty, 2020). The benefcial effects of anthocyanins, favones, and favonols (Chang et al., 2018); phenolic acids (Veeriah et al., 2008); triterpenoids (He et al., 2012); pectin and pectic oligosaccharides (Chung et al., 2017) and polysaccharides found in apples on intestinal infammation and colorectal cancer (Bars-Cortina et al., 2020) have been studied by various researchers. ...
... With respect to the inhibition of CK2, a range of flavonones-including quercetin, myricetin, fisetin, kaempferol, luteolin, and apigenin-have been shown to inhibit CK2's kinase activity in high nanomolar concentrations that might be clinically relevant when high-absorption forms of these flavonols are ingested [190][191][192][193]. A number of studies have found that quercetin favorably influences bone density in rodent models of bone loss [194][195][196][197][198][199]. ...
There is a vast pre-clinical literature suggesting that certain nutraceuticals have the potential to aid the preservation of bone mass in the context of estrogen withdrawal, glucocorticoid treatment, chronic inflammation, or aging. In an effort to bring some logical clarity to these findings, the signaling pathways regulating osteoblast, osteocyte, and osteoclast induction, activity, and survival are briefly reviewed in the present study. The focus is placed on the following factors: the mechanisms that induce and activate the RUNX2 transcription factor, a key driver of osteoblast differentiation and function; the promotion of autophagy and prevention of apoptosis in osteoblasts/osteoclasts; and the induction and activation of NFATc1, which promotes the expression of many proteins required for osteoclast-mediated osteolysis. This analysis suggests that the activation of sirtuin 1 (Sirt1), AMP-activated protein kinase (AMPK), the Nrf2 transcription factor, and soluble guanylate cyclase (sGC) can be expected to aid the maintenance of bone mass, whereas the inhibition of the serine kinase CK2 should also be protective in this regard. Fortuitously, nutraceuticals are available to address each of these targets. Sirt1 activation can be promoted with ferulic acid, N1-methylnicotinamide, melatonin, nicotinamide riboside, glucosamine, and thymoquinone. Berberine, such as the drug metformin, is a clinically useful activator of AMPK. Many agents, including lipoic acid, melatonin, thymoquinone, astaxanthin, and crucifera-derived sulforaphane, can promote Nrf2 activity. Pharmacological doses of biotin can directly stimulate sGC. Additionally, certain flavonols, notably quercetin, can inhibit CK2 in high nanomolar concentrations that may be clinically relevant. Many, though not all, of these agents have shown favorable effects on bone density and structure in rodent models of bone loss. Complex nutraceutical regimens providing a selection of these nutraceuticals in clinically meaningful doses may have an important potential for preserving bone health. Concurrent supplementation with taurine, N-acetylcysteine, vitamins D and K2, and minerals, including magnesium, zinc, and manganese, plus a diet naturally high in potassium, may also be helpful in this regard.
... No in vitro experiments have been performed to investigate the capability of quercetin of modulating type I IFN production in virus infected barrier mucosal epithelial cells nor in the human bronchial epithelial cell line 16HBE, which is widely utilized as an experimental model for respiratory epithelial diseases and barrier function [68]. However, it has been recently hypothesized that quercetin, by its capability of inhibiting casein kinase 2, can restore the production of type I IFN in response to the interaction virus-RIG-I receptor, thus promoting the control of virus infections [69]. Moreover, some nonrespiratory barrier epithelial cell models have been used to investigate the regulation of inflammasome and autophagy by quercetin. ...
The COVID-19 pandemic is caused by SARS-CoV-2 and is leading to the worst health crisis of this century. It emerged in China during late 2019 and rapidly spread all over the world, producing a broad spectrum of clinical disease severity, ranging from asymptomatic infection to death (4.3 million victims so far). Consequently, the scientific research is devoted to investigating the mechanisms of COVID-19 pathogenesis to both identify specific therapeutic drugs and develop vaccines. Although immunological mechanisms driving COVID-19 pathogenesis are still largely unknown, new understanding has emerged about the innate and adaptive immune responses elicited in SARS-CoV-2 infection, which are mainly focused on the dysregulated inflammatory response in severe COVID-19. Polyphenols are naturally occurring products with immunomodulatory activity, playing a relevant role in reducing inflammation and preventing the onset of serious chronic diseases. Mainly based on data collected before the appearance of SARS-CoV-2, polyphenols have been recently suggested as promising agents to fight COVID-19, and some clinical trials have already been approved with polyphenols to treat COVID-19. The aim of this review is to analyze and discuss the in vitro and in vivo research on the immunomodulatory activity of quercetin as a research model of polyphenols, focusing on research that addresses issues related to the dysregulated immune response in severe COVID-19. From this analysis, it emerges that although encouraging data are present, they are still insufficient to recommend polyphenols as potential immunomodulatory agents against COVID-19.
... 44 45 More speculatively, supplementation with glucosamine or with high-absorption sources of quercetin may have potential for boosting the type-1 interferon response and reducing viral infection risk. [46][47][48][49] Hence, it is not unreasonable to suggest that a supplementation programme incorporating vitamin D, zinc, melatonin and possibly additional nutraceuticals could reduce risk for and aid control of COVID-19 and a range of other viral infections. ...
A recent retrospective study has provided evidence that COVID-19 infection may be notably less common in those using supplemental melatonin. It is suggested that this phenomenon may reflect the fact that, via induction of silent information regulator 1 (Sirt1), melatonin can upregulate K63 polyubiquitination of the mitochondrial antiviral-signalling protein, thereby boosting virally mediated induction of type 1 interferons. Moreover, Sirt1 may enhance the antiviral efficacy of type 1 interferons by preventing hyperacetylation of high mobility group box 1 (HMGB1), enabling its retention in the nucleus, where it promotes transcription of interferon-inducible genes. This nuclear retention of HMGB1 may also be a mediator of the anti-inflammatory effect of melatonin therapy in COVID-19—complementing melatonin’s suppression of nuclear factor kappa B activity and upregulation of nuclear factor erythroid 2-related factor 2. If these speculations are correct, a nutraceutical regimen including vitamin D, zinc and melatonin supplementation may have general utility for the prevention and treatment of RNA virus infections, such as COVID-19 and influenza.
... This anti-inflammatory effect might reflect up-regulated activity of the de-ubiquitinase A20, which opposes TRAF6 signaling [85]. Up-regulation of type 1 interferon induction may also play a role in the anti-viral effects of quercetin [86,87]. ...
Counterproductive lung inflammation and dysregulated thrombosis contribute importantly to the lethality of advanced COVID-19. Adenosine A2A receptors (A2AR), expressed by a wide range of immune cells, as well as endothelial cells and platelets, exert cAMP-mediated anti-inflammatory and anti-thrombotic effects that potentially could be highly protective in this regard. The venerable drug pentoxifylline (PTX) exerts both anti-inflammatory and antithrombotic effects that reflect its ability to boost the responsiveness of A2AR to extracellular adenosine. The platelet-stabilizing drug dipyridamole (DIP) blocks intracellular uptake of extracellularly-generated adenosine, thereby up-regulating A2AR signaling in a way that should be functionally complementary to the impact of PTX in that regard. Moreover, DIP has recently been reported to slow the cellular replication of SARS-CoV-2 in clinically feasible concentrations. Both PTX and DIP are reasonably safe, well-tolerated, widely available, and inexpensive drugs. When COVID-19 patients can be treated within several days of symptom onset, using PTX + DIP in conjunction with hydroxychloroquine (HCQ) and an antibiotic - azithromycin (AZM) or doxycycline – might be warranted. HCQ and AZM can suppress SARS-CoV-2 proliferation in vitro and may slow the cell-to-cell spread of the virus; a large case series evaluating this combination in early-stage patients reported an impressively low mortality rate. However, whereas HCQ and AZM can promote QT interval lengthening and may be contraindicated in more advanced COVID-19 entailing cardiac damage, doxycycline has no such effect and exerts a potentially beneficial anti-inflammatory action. In contrast to HCQ, we propose that the combination of PTX + DIP can be used in both early and advanced stages of COVID-19. Concurrent use of certain nutraceuticals – yeast beta-glucan, zinc, vitamin D, spirulina, phase 2 inducers, N-acetylcysteine, glucosamine, quercetin, and magnesium – might also improve therapeutic outcomes in COVID-19.
Owing to polymorphism, apple has extraordinary diversity. Depending on varieties, apple fruits can differ in colors and shades, and size. There are more than 10000 varieties of apple, which vary in taste, shape, juiciness, texture, color, firmness and other qualities. For this reason, apple has been diversely studied from time to time and many improvements have been made like that of introduction of high density cropping; rootstock breeding; or varietal development etc. Therefore it is important to understand and document the production ways and methods implemented over times for harvesting the maximum possible benefits of the crop. Apples: Preharvest & Postharvest Technology has documented all the production practice that are taken in practice with detailed illustration on varieties, rootstocks, important cultural practices and post harvest management. This book will therefore serve as a complete guide for apple production from farm to fork and will help students, scholars, researchers and scientists working in this domain. The book will benefit pomologists, horticulturalist, agricultural Scientists, food technologists, university scholars, researchers and college students.
As an easily adapted culture, with overloaded production in some parts of the globe, apples and their by-products are being redirected to pharmaceutical, canning and beverages industries , both alcoholic and non-alcoholic. Fermentation is generally considered to increase the bioa-vailability of bioactive compounds found in apple, by impacting, through a high degree of changes, the product's properties, including composition and health-promoting attributes, as well as their sensory profile. Probiotic apple beverages and apple vinegar are generally considered as safe and healthy products by the consumers. Recently, contributions to human health, both in vivo and in vitro studies, of non-alcoholic fermented apple-based products have been described. This review highlighted the advances in the process optimization of apple-based products considering vinegar, cider, pomace, probiotic beverages and spirits' technologies. The different processing impacts on physical-chemical, nutritional and sensory profiles of these products are also presented. Additionally , the harmful effects of toxic compounds and strategies to limit their content in cider and apple spirits are illustrated. New trends of fermented apple-based products applicability in tangential industries are summarized.
Melanoma is a life-threatening cancer with limited treatments. Retinoic acid-inducible gene I (RIG-I) is a cytosolic pattern recognition receptor (PRR) crucial to RNA virus sensing, interferon production, and tumor suppression. Quercetin, a natural flavonoid, has particularly therapeutic interests to prevent and treat cancer, for its pharmacological effects against oxidant, inflammation, and angiogenesis. Quercetin was investigated for its anti-melanoma activity and potential mechanisms in this study. We found that quercetin inhibited mouse melanoma growth in vivo, and suppressed proliferation and promoted apoptosis of both B16 and A375 cells in vitro. Quercetin upregulated IFN-α and IFN-β expression through activating RIG-I promoter in B16 cells. The induction of IFN-α and IFN-β, which could be severely impaired by silencing RIG-I induced interferon stimulated genes (ISGs). Moreover, RIG-I likely amplifies antitumor effects by activating signal transduction and activator of transcription 1 (STAT1) in the IFN-JAK-STAT pathway in an autocrine and paracrine manner. Our study provided novel insights regarding biological and anti-proliferative activities of quercetin against melanoma, and we identified RIG-I as a potential target in anti-tumor therapies.
This systematic review and meta-analysis of randomized controlled trials was performed to determine the effect of quercetin supplementation on glycemic control among patients with metabolic syndrome and related disorders. Databases including PubMed, MEDLINE, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials were searched until August 30, 2018. Nine studies with 10 effect sizes out of 357 selected reports were identified eligible to be included in current meta-analysis. The pooled findings indicated that quercetin supplementation did not affect fasting plasma glucose (FPG), homeostasis model of assessment-estimated insulin resistance, and hemoglobin A1c levels. In subgroup analysis, quercetin supplementation significantly reduced FPG in studies with a duration of ≥8 weeks (weighted mean difference [WMD]: -0.94; 95% confidence interval [CI; -1.81, -0.07]) and used quercetin in dosages of ≥500 mg/day (WMD: -1.08; 95% CI [-2.08, -0.07]). In addition, subgroup analysis revealed a significant reduction in insulin concentrations following supplementation with quercetin in studies that enrolled individuals aged <45 years (WMD: -1.36; 95% CI [-1.76, -0.97]) and that used quercetin in dosages of ≥500 mg/day (WMD: -1.57; 95% CI [-1.98, -1.16]). In summary, subgroup analysis based on duration of ≥8 weeks and used quercetin in dosages of ≥500 mg/day significantly reduced FPG levels.
The Protein kinase CK2 (formerly known as casein kinase 2) is a highly conserved serine/ threonine kinase overexpressed in various human carcinomas and its high expression often correlates with poor prognosis. CK2 protein is localized in the nucleus of many tumor cells and correlates with clinical features in many cases. Increased expression of CK2 in mice results in the development of various types of carcinomas (both solids and blood related tumors, such as (breast carcinoma, lymphoma, etc), which reveals its carcinogenic properties. CK2 plays essential roles in many key biological processes related to carcinoma, including cell apoptosis, DNA damage responses and cell cycle regulation. CK2 has become a potential anti-carcinoma target. Various CK2 inhibitors have been developed with anti-neoplastic properties against a variety of carcinomas. Some CK2 inhibitors have showed good results in in vitro and pre-clinical models, and have even entered in clinical trials. This article will review effects of CK2 and its inhibitors on common carcinomas in in vitro and pre-clinical studies.
Acute exacerbations are the major cause of morbidity and mortality in patients with chronic obstructive pulmonary disease (COPD). Rhinovirus, which causes acute exacerbations may also accelerate progression of lung disease in these patients. Current therapies reduces the respiratory symptoms and does not treat the root cause of exacerbations effectively. We hypothesized that quercetin, a potent antioxidant and anti-inflammatory agent with antiviral properties may be useful in treating rhinovirus-induced changes in COPD. Mice with COPD phenotype maintained on control or quercetin diet and normal mice were infected with sham or rhinovirus, and after 14 days mice were examined for changes in lung mechanics and lung inflammation. Rhinovirus-infected normal mice showed no changes in lung mechanics or histology. In contrast, rhinovirus-infected mice with COPD phenotype showed reduction in elastic recoiling and increase in lung inflammation, goblet cell metaplasia, and airways cholinergic responsiveness compared to sham-infected mice. Interestingly, rhinovirus-infected mice with COPD phenotype also showed accumulation of neutrophils, CD11b⁺/CD11c⁺ macrophages and CD8+ T cells in the lungs. Quercetin supplementation attenuated rhinovirus-induced all the pathologic changes in mice with COPD phenotype. Together these results indicate that quercetin effectively mitigates rhinovirus-induced progression of lung disease in a mouse model of COPD. Therefore, quercetin may be beneficial in the treatment of rhinovirus-associated exacerbations and preventing progression of lung disease in COPD.
The role of protein kinases p38 and CK2 (casein kinase II) in the response of RAW 264.7 macrophages to the lipopolysaccharide (LPS) from gram-negative bacteria was studied. Using specific p38 and CK2 inhibitors (p38 MAP kinase Inhibitor XI and casein kinase II Inhibitor III, respectively), we investigated the effects of these protein kinases on (i) LPS-induced activation of signaling pathways involving nuclear factor κB (NF-κB), stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), p38, and interferon regulatory factor 3 (IRF3); (ii) expression of Toll-like receptor 4 (TLR4) and inducible heat-shock proteins HSP72 and HSP90; and (iii) production of interleukins IL-1α, IL-1β, IL-6, tumor necrosis factor α, and IL-10. Activation of the proapoptotic signaling in the macrophages was evaluated from the ratio between the active and inactive caspase-3 forms and p53 phosphorylation. Six hours after LPS addition (2.5 μg/ml) to RAW 264.7 cells, activation of the TLR4 signaling pathways was observed that was accompanied by a significant increase in phosphorylation of IκB kinase α/β, NF-κB (at both Ser536 and Ser276), p38, JNK, and IRF3. Other effects of macrophage incubation with LPS were an increase in the contents of TLR4, inducible heat-shock proteins (HSPs), and pro- and anti-inflammatory cytokines, as well as slight activation of the pro-apoptotic signaling in the cells. Using inhibitor analysis, we found that during the early response of macrophages to the LPS, both CK2 and p38 modulate activation of MAP kinase and NF-κB signaling pathways and p65 phosphorylation at Ser276/Ser536 and cause accumulation of HSP72, HSP90 and the LPS-recognizing receptor TLR4. Suppression of the p38 MAP kinase and CK2 activities by specific inhibitors (Inhibitor XI and Inhibitor III, respectively) resulted in the impairment of the macrophage effector function manifested as a decrease in the production of the early-response proinflammatory cytokines and disbalance between the pro- and anti-apoptotic signaling pathways leading presumably to apoptosis development. Taken together, our data indicate the inefficiency of therapeutic application of p38 and CK2 inhibitors during the early stages of inflammatory response.
Promising experimental studies suggest that quercetin has potential anti-inflammatory effects. However, the results of current clinical trials on quercetin's effects on the C-reactive protein (CRP), a sensitive inflammatory biomarker, are ambiguous. We conducted a meta-analysis of available randomized controlled trials (RCTs) to resolve this inconsistency and quantify the net effect of quercetin on circulating CRP concentrations. A systematic search was performed in several databases including SCOPUS, PubMed-Medline and Google Scholar until 16 June 2016. We used a random-effects model in combination with weight mean difference (WMD) and 95% confidence intervals (CI) for data analysis. Standard methods were used for the assessment of heterogeneity, meta-regression, sensitivity analysis and publication bias. The meta-analysis of seven RCTs (10 treatment arms) showed a significant reduction of circulating CRP levels (WMD: -0.33 mg/l; 95% CI: -0.50 to -0.15; P<0.001) following quercetin supplementation. In the subgroup analysis, a significant reducing effect was observed in trials with ⩾500 mg/day dosage (WMD: -0.34 mg/l; 95% CI: -0.52, -0.16; P⩽0.001) and in those with CRP <3 mg/l (WMD: -0.34 mg/l; 95% CI: -0.51, -0.18; P⩽0.001). In meta-regression, there was no association between changes in CRP concentrations, dose of supplementation and CRP baseline values. Our findings showed a significant effect of quercetin supplementation on the C-reactive protein-especially at doses above 500 mg/day and in patients with CRP <3 mg/l.European Journal of Clinical Nutrition advance online publication, 24 May 2017; doi:10.1038/ejcn.2017.55.
Despite the encouraging results of the innovative therapeutic treatments, complete remission is uncommon in patients affected by chronic lymphocytic leukaemia, which remains an essentially incurable disease. Recently, clinical trials based on BH3-mimetic drugs showed positive outcomes in subjects with poor prognostic features. However, resistance to treatments occurs in a significant number of patients. We previously reported that the multi-kinase inhibitor quercetin, a natural flavonol, restores sensitivity to ABT-737, a BH3-mimetic compound, in both leukemic cell lines and B-cells isolated from patients. To identify the molecular target of quercetin, we employed a new cell line, HG3, obtained by immortalization of B-cells from a chronic lymphocytic leukaemia patient at the later stage of disease. We confirmed that quercetin in association with ABT-737 synergistically enhances apoptosis in HG3 (combination index < 1 for all fractions affected). We also reported that the cellular uptake of quercetin is extremely rapid, with an intracellular concentration of about 38.5 ng/106 cells, after treatment with 25 μM for 5 min. We demonstrated that the activity of protein kinase CK2, which positively triggers PI3K/Akt pathway by inactivating PTEN phosphatase, is inhibited by quercetin immediately after its addition to HG3 cells (0-2 min). PI3K activity was also inhibited by quercetin within 60 min from the treatment. The combined inhibition of CK2 and PI3K kinase activities by quercetin restored ABT-737 sensitivity and increased lethality in human leukemia cells.
The cytoplasmic viral sensor retinoic acid-inducible gene-I (RIG-I), which is also known as an IFN-stimulated gene (ISG), senses viral RNA to activate antiviral signaling. It is therefore thought that RIG-I is regulated in a STAT1-dependent manner. Although RIG-I-mediated antiviral signaling is indispensable for the induction of an appropriate adaptive immune response, the mechanism underlying the regulation of RIG-I expression remains elusive. Here, we examined the direct regulation of RIG-I expression by interferon regulatory factor 3 (IRF-3), which is an essential molecule for antiviral innate immunity. We initially found that RIG-I can be induced by dsRNA in both IFN-independent and IRF-3-dependent manners. A sequence analysis revealed that the RIG-I gene has putative IRF-3-binding sites in its promoter region. Using a combination of cellular, molecular biological, and mutational approaches, we first showed that IRF-3 can directly regulate the expression of RIG-I via a single IRF-element (IRF-E) site in the proximal promoter region of the RIG-I gene in response to dsRNA. IRF-3 is considered a master regulator in antiviral signaling for the generation of type I interferons (IFNs). Thus, our findings demonstrate that RIG-I expression induced by the IRF-3-mediated pathway may serve as a crucial antiviral factor for reinforcing a surveillance system against viral invasion through the regulation of the cytoplasmic viral sensor RIG-I.
The Influenza A virus is a great threat for human health, while various subtypes of the virus made it difficult to develop drugs. With the development of state-of-art computational chemistry, computational molecular docking could serve as a virtual screen of potential leading compound. In this study, we performed molecular docking for influenza A H1N1 (A/PR/8/34) with small molecules such as quercetin and chlorogenic acid, which were derived from traditional Chinese medicine. The results showed that these small molecules have strong binding abilities with neuraminidase from H1N1 (A/PR/8/34). Further details showed that the structural features of the molecules might be helpful for further drug design and development. The experiments in vitro, in vivo have validated the anti-influenza effect of quercetin and chlorogenic acid, which indicating comparable protection effects as zanamivir. Taken together, it was proposed that chlorogenic acid and quercetin could be employed as the effective lead compounds for anti-influenza A H1N1.
Influenza A viruses (IAVs) cause seasonal pandemics and epidemics with high morbidity and mortality, which calls for effective anti-IAV agents. The glycoprotein hemagglutinin of influenza virus plays a crucial role in the initial stage of virus infection, making it a potential target for anti-influenza therapeutics development. Here we found that quercetin inhibited influenza infection with a wide spectrum of strains, including A/Puerto Rico/8/34 (H1N1), A/FM-1/47/1 (H1N1), and A/Aichi/2/68 (H3N2) with half maximal inhibitory concentration (IC50) of 7.756 ± 1.097, 6.225 ± 0.467, and 2.738 ± 1.931 μg/mL, respectively. Mechanism studies identified that quercetin showed interaction with the HA2 subunit. Moreover, quercetin could inhibit the entry of the H5N1 virus using the pseudovirus-based drug screening system. This study indicates that quercetin showing inhibitory activity in the early stage of influenza infection provides a future therapeutic option to develop effective, safe and affordable natural products for the treatment and prophylaxis of IAV infections.
Catecholamines promote lipolysis both in brown and white adipocytes, whereas the same stimuli preferentially activate thermogenesis in brown adipocytes. Molecular mechanisms for the adipose-selective activation of thermogenesis remain poorly understood. Here, we employed quantitative phosphoproteomics to map global and temporal phosphorylation profiles in brown, beige, and white adipocytes under β3-adrenenoceptor activation and identified kinases responsible for the adipose-selective phosphorylation profiles. We found that casein kinase2 (CK2) activity is preferentially higher in white adipocytes than brown/beige adipocytes. Genetic or pharmacological blockade of CK2 in white adipocytes activates the thermogenic program in response to cAMP stimuli. Such activation is largely through reduced CK2-mediated phosphorylation of class I HDACs. Notably, inhibition of CK2 promotes beige adipocyte biogenesis and leads to an increase in whole-body energy expenditure and ameliorates diet-induced obesity and insulin resistance. These results indicate that CK2 is a plausible target to rewire the β3-adrenenoceptor signaling cascade that promotes thermogenesis in adipocytes.
By sensing viral nucleic acids, host innate receptors elicit signaling pathways converging on TBK1-IFN regulatory factor (IRF)3 axis in mediating IFN-αβ induction and defense mechanisms. In contrast, viruses have evolved with diverse immune evasion/interference mechanisms to undermine innate receptor signaling and IFN response. In this regard, approaches enabling host to overcome such immune evasion/interference mechanisms are urgently needed to combat infections by epidemic/pandemic viruses. In this study, we report that protein kinase CK2 serves as a key component controlling TBK1 and IRF3 activation in IFN-inducing TLR, RIG-I-like receptors, and cGAS/STING signaling pathways. Accordingly, knocking down of CK2 expression or genetic ablation of its kinase activity resulted in elevated IFN-αβ response in response to infection by DNA and RNA viruses. Moreover, PP2A was identified as one of the intermediate phosphatases responsible for CK2-regulated IFN response, suggesting that CK2 may regulate TBK1 and IRF3 activation indirectly. Importantly, blockade of CK2 activity by small molecule inhibitor was able to activate TBK1, whereby eliciting effective host defense mechanisms against hepatitis C virus infection. Taken together, our results identify CK2 as a novel regulator of TBK1 and IRF3 and suggest that targeting CK2 by small molecular inhibitor may be a viable approach to prevent and treat viral infections.
Copyright © 2015 by The American Association of Immunologists, Inc.
Small conductance calcium-activated K(+) (SK) channels regulate neuronal excitability. However, little is known about changes in SK channel activity of presympathetic neurons in the hypothalamic paraventricular nucleus (PVN) in essential hypertension. SK channels, calmodulin, and casein kinase II (CK2) form a molecular complex. Because CK2 is upregulated in the PVN in spontaneously hypertensive rats (SHRs), we hypothesized that CK2 increases calmodulin phosphorylation and contributes to diminished SK channel activity in PVN presympathetic neurons in SHRs. Perforated whole-cell recordings were performed on retrogradely labeled spinally projecting PVN neurons in Wistar-Kyoto (WKY) rats and SHRs. Blocking SK channels with apamin significantly increased the firing rate of PVN neurons in WKY rats but not in SHRs. CK2 inhibition restored the stimulatory effect of apamin on the firing activity of PVN neurons in SHRs. Furthermore, apamin-sensitive SK currents and depolarization-induced medium after-hyperpolarization potentials of PVN neurons were significantly larger in WKY rats than in SHRs. CK2 inhibition significantly increased the SK channel current and medium after-depolarization potential of PVN neurons in SHRs. In addition, CK2-mediated calmodulin phosphorylation level in the PVN was significantly higher in SHRs than in WKY rats. Although SK3 was detected in the PVN, its expression level did not differ significantly between SHRs and WKY rats. Our findings suggest that CK2-mediated calmodulin phosphorylation is increased and contributes to diminished SK channel function of PVN presympathetic neurons in SHRs. This information advances our understanding of the mechanisms underlying hyperactivity of PVN presympathetic neurons and increased sympathetic vasomotor tone in hypertension. This article is protected by copyright. All rights reserved.
Diabetes is associated with increased cardiovascular risk. We have recently shown that the naturally occurring flavonol quercetin (Que) or the synthetic flavonol 3',4'-dihydroxyflavonol (DiOHF) inhibits platelet function and delays thrombus formation in healthy mice. Therefore, the aim of this study was to investigate the effect of Que or DiOHF treatment on platelet function and ferric chloride-induced carotid artery thrombosis in a mouse model of type 1 diabetes. Diabetic mice treated with Que or DiOHF maintained blood flow at a significantly higher level than untreated diabetic mice at the end of the recording period. In addition, treatment with Que or DiOHF significantly reduced diabetes-induced platelet hyper-aggregability in response to platelet agonist stimulation. Furthermore, treatment with Que or DiOHF significantly inhibited dense, but not alpha, granule exocytosis in diabetic and control mice. Our demonstration that flavonols delay thrombus formation in diabetes suggests a potential clinical role for these compounds in anti-platelet therapy.
Flavonols are polyphenolic compounds with reported cardiovascular benefits and have been shown to exhibit antiplatelet properties in vitro. While some studies have shown inhibition of platelet aggregation following dietary supplementation with flavonol rich foods, few studies have assessed the ability of flavonols to inhibit platelet mediated thrombus generation in vivo. Furthermore, the duration of benefit and the influence of different dosing regimens remain unclear. In this study we investigate the ability of two structurally related flavonols; quercetin (Que) and 3',4'-dihydroxyflavonol (DiOHF) to inhibit platelet aggregation, platelet granule exocytosis and vessel occlusion in a well characterized mouse model of platelet mediated arterial thrombosis. We investigated the effect of a single 6 mg/kg intravenous bolus and daily 6 mg/kg intraperitoneal doses over seven consecutive days. Carotid artery blood flow after injury was better maintained in mice treated with both Que and DiOHF when compared to the vehicle for both dosage regimens. This improved blood flow corresponded to inhibition of platelet aggregation and platelet dense granule exocytosis following chemical stimulation of PAR4. We therefore provide evidence of inhibition of platelet-mediated arterial thrombosis by flavonols in vivo, and demonstrate that this effect persists for at least 24 h after the last intraperitoneal dose. These data suggest a potential clinical role for flavonols as anti-platelet therapy.
Rhinovirus (RV), which is responsible for the majority of common colds, also causes exacerbations in patients with asthma and chronic obstructive pulmonary disease. So far, there are no drugs available for treatment of rhinovirus infection. We examined the effect of quercetin, a plant flavanol on RV infection in vitro and in vivo. Pretreatment of airway epithelial cells with quercetin decreased Akt phosphosphorylation, viral endocytosis and IL-8 responses. Addition of quercetin 6h after RV infection (after viral endocytosis) reduced viral load, IL-8 and IFN responses in airway epithelial cells. This was associated with decreased levels of negative and positive strand viral RNA, and RV capsid protein, abrogation of RV-induced eIF4GI cleavage and increased phosphorylation of eIF2α. In mice infected with RV, quercetin treatment decreased viral replication as well as expression of chemokines and cytokines. Quercetin treatment also attenuated RV-induced airway cholinergic hyperresponsiveness. Together, our results suggest that quercetin inhibits RV endocytosis and replication in airway epithelial cells at multiple stages of the RV life cycle. Quercetin also decreases expression of pro-inflammatory cytokines and improves lung function in RV-infected mice. Based on these observations, further studies examining the potential benefits of quercetin in the prevention and treatment of RV infection are warranted.
Increased glutamatergic input in the paraventricular nucleus (PVN) is important for high sympathetic outflow in hypertension, but the associated molecular mechanisms remain unclear. Here, we determined the role of protein kinase CK2 (formerly casein kinase II) in increased N-methyl-d-aspartate receptor (NMDAR) activity in spinally projecting PVN neurons and sympathetic vasomotor tone in spontaneously hypertensive rats (SHRs). The selective CK2 inhibitors 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole (DRB) or 4,5,6,7-tetrabromobenzotriazole (TBB) significantly decreased the frequency of miniature EPSCs (mEPSCs) of labeled PVN neurons in SHRs but not in Wistar-Kyoto (WKY) normotensive rats. Also, DRB abolished the inhibitory effect of the NMDAR antagonist AP5 on the frequency of mEPSCs in SHRs. Treatment with DRB or TBB significantly reduced the amplitude of evoked NMDA-EPSCs but not AMPA-EPSCs in SHRs. Furthermore, DRB significantly decreased the firing activity of PVN neurons in SHRs but not in WKY rats. The membrane protein level of CK2α in the PVN, but not brainstem and prefrontal cortex, was significantly higher in SHRs than in WKY rats. Lowering blood pressure with celiac ganglionectomy in SHRs did not alter the increased CK2α level and the effects of DRB on mEPSCs and NMDA-EPSCs. In addition, intracerebroventricular injection of DRB not only significantly reduced blood pressure and lumbar sympathetic nerve discharges but also eliminated the inhibitory effect of AP5 microinjected into the PVN on sympathetic nerve activity in SHRs. Our findings suggest that augmented CK2 activity critically contributes to increased presynaptic and postsynaptic NMDAR activity in the PVN and elevated sympathetic vasomotor tone in essential hypertension.
RIG-I is an intracellular RNA virus sensor that mediates a signaling pathway that triggers the alpha/beta interferon (IFN-α/β)
immune defenses. However, the mechanism for regulation of RIG-I activity remains largely unknown. Here we show that RIG-I
activity is regulated by phosphorylation and dephosphorylation in its repressor domain (RD). Threonine at amino acid (aa)
770 and serine at aa 854 to 855 of RIG-I are phosphorylated by casein kinase II (CK2) in the resting state of the cell and
dephosphorylated when cells are infected by RNA virus. Mutation at aa position 770 or 854 to 855 of RIG-I renders it constitutively
active. Pharmacological inhibition of CK2 enhances virus-induced expression of IFN-β and suppresses virus proliferation, while
inhibition of phosphatase reduces virus-induced expression of IFN-β. Overexpression of CK2 suppresses RIG-I-mediated signaling,
while silencing of CK2 results in the increased suppression of virus proliferation. Our results reveal a novel mechanism of
the regulation of RIG-I activity during RNA virus infection.
The endothelial NO synthase (eNOS) is regulated by diverse protein kinase pathways, yet eNOS activity ultimately depends on the ubiquitous calcium regulatory protein calmodulin (CaM). In these studies, we establish that CaM itself undergoes phosphorylation in endothelial cells and that CaM phosphorylation attenuates eNOS activation. Using [(32)P]orthophosphoric acid biosynthetic labeling, we found that CaM is a phosphoprotein in bovine aortic endothelial cells (BAEC) and that the kinase CK2 promotes CaM phosphorylation in BAEC. Phosphorylation of CaM by purified CK2 in vitro reduces the V(max) of immunopurified eNOS by a factor of 2 but has no effect on the K(A) for CaM or calcium. Additionally, [(32)P]orthophosphoric acid biosynthetic labeling of mutant CaM-transfected BAEC revealed that phosphorylation of Ser-81 to alanine mutant CaM ("phosphonull" S81A mutant) is dramatically reduced relative to WT, whereas phosphorylation of the "phosphomimetic" Ser-81 to aspartate (S81D) mutant is unchanged. Further studies using Escherichia coli-expressed and phenyl-Sepharose-purified CaM mutants revealed that the S81A mutation abrogates in vitro CK2-mediated phosphorylation of CaM, whereas phosphorylation of the S81D CaM mutant by CK2 is preserved. Additionally, we found that the phosphomimetic S101D CaM mutant is impaired in its ability to activate eNOS. Taken together, these results suggest that phosphorylation of CaM inhibits eNOS catalysis and proceeds in a hierarchical manner, initially requiring phosphorylation of the CaM Ser-81 residue. We conclude that CaM phosphorylation may represent a unique pathway in the regulation of eNOS signaling and thereby may play a role in modulating NO-dependent vascular responses.
This study measured the influence of the flavonoid quercetin on immune changes and incidence rates of upper respiratory tract infections in ultramarathoners competing in the 160-km Western States Endurance Run. Sixty-three runners were randomized to quercetin and placebo groups, and under double-blinded methods ingested 1000 mg/day quercetin for 3 wks before, during, and 2 wks after the race. Thirty-nine of the 63 subjects (n = 18 for quercetin, n = 21 for placebo) finished the race and provided blood and saliva samples the morning before the race and 15 - 30 min postrace. Upper respiratory tract infections were assessed during the week before and the 2-wk period after the race using an illness symptom checklist. Race times did not differ significantly between quercetin and placebo groups. Significant pre- to postrace decreases were measured for natural killer cells (43 %), granulocyte respiratory burst activity (55 %), and salivary IgA output (48 %), and increases for neutrophil (288 %) and monocyte (211 %) cell counts, with no significant group differences. Postrace illness rates did not differ between groups. In conclusion, quercetin supplementation for 3 wks before and 2 wks after the Western States Endurance Run had no effect on illness rates, perturbations in leukocyte subset counts, or decreases in granulocyte respiratory burst activity and salivary IgA.
The serine-threonine kinase CK2, which targets over 300 cellular proteins, is overexpressed in all cancers, presumably reflecting its ability to promote proliferation, spread, and survival through a wide range of complementary mechanisms. Via an activating phosphorylation of Cdc373, a co-chaperone which partners with Hsp90, CK2 prolongs the half-life of protein kinases that promote proliferation and survival in many cancers, including Akt, Src, EGFR, Raf-1, and several cyclin-dependent kinases. CK2 works in other ways to boost the activity of signaling pathways that promote cancer aggressiveness and chemoresistance, including those driven by Akt, NF-kappaB, hypoxia-inducible factor-1, beta-catenin, TGF-beta, STAT3, hedgehog, Notch1, and the androgen receptor; it promotes the epidermal-mesenchymal transition and aids efficiency of DNA repair. Several potent and relatively specific inhibitors of CK2 are now being evaluated as potential cancer drugs; CX-4945 has shown impressive activity in cell culture studies and xenograft models, and is now entering clinical trials. Moreover, it has long been recognized that the natural flavone apigenin can inhibit CK2, with a Ki near 1 micromolar; more recent work indicates that a range of flavones and flavonols, characterized by a planar structure and hydroxylations at the 7 and 4’ positions – including apigenin, luteolin keampferol, fisetin, quercetin, and myricetin - can inhibit CK2 with Ki s in the sub-micromolar range. This finding is particularly intriguing in light of the numerous studies demonstrating that each of these agents can inhibit the growth of cancer cells lines in vitro and of human xenografts in nude mice. These studies attribute the cancer-retardant efficacy of flavones/flavonols to impacts on a bewildering array of cellular targets, including those whose activities are boosted by CK2; it is reasonable to suspect that, at least in physiologically achievable concentrations, these agents may be achieving these effects primarily via CK2 inhibition. Inefficient absorption and rapid conjugation limit the bioefficacy of orally administered flavonoids; however, the increased extracellular beta-glucuronidase of many tumors may give tumors privileged access to glucuronidated flavonoids, and nanopartical technology can improve the bioavailability of these agents. Enzymatically modified isoquercitrin has particular promise as a delivery vehicle for quercetin. Hence, it may be worthwhile to explore the clinical potential of flavones/flavonols as CK2 inhibitors for cancer therapy.
Context:
Clinical trials examining the cardiovascular protective effects of quercetin in humans have reported conflicting results.
Objective:
The aim of this systematic review was to summarize evidence of the effects of quercetin supplementation on plasma lipid profiles, blood pressure (BP), and glucose levels in humans by performing a meta-analysis of randomized controlled trials.
Data sources:
MEDLINE, Embase, and Scopus databases were searched electronically from their inception to July 2018 to identify randomized controlled trials that assessed the impact of quercetin on lipid profiles, BP, and glucose levels.
Study selection:
Randomized controlled trials assessing the effects of quercetin or a standardized quercetin-enriched extract on plasma lipid profiles, BP, and glucose levels in humans were eligible for inclusion.
Data extraction:
A random-effects model was used for data analysis. Continuous variables were expressed as weighted mean differences (WMDs) and 95%CIs. Subgroup analyses were conducted to explore possible influences of study characteristics. Sensitivity analyses were also performed, as were analyses of publication bias.
Results:
Seventeen trials (n = 896 participants total) were included in the overall analysis. Pooled results showed that quercetin significantly lowered both systolic BP (WMD, -3.09 mmHg; 95%CI, -4.59 to -1.59; P = 0.0001) and diastolic BP (WMD, -2.86 mmHg; 95%CI, -5.09 to -0.63; P = 0.01). Neither lipid profiles nor glucose concentrations changed significantly. In subgroup analyses, significant changes in high-density lipoprotein cholesterol and triglycerides were observed in trials with a parallel design and in which participants consumed quercetin for 8 weeks or more.
Conclusion:
Quercetin intake resulted in significantly decreased BP in humans. Moreover, participants who consumed quercetin for 8 weeks or more showed significantly changed levels of high-density lipoprotein cholesterol and triglycerides in trials with a parallel design.
A higher intake of foods rich in flavonoids such as quercetin can reduce the risk of cardiovascular disease. Enzymatically modified isoquercitrin (EMIQ®) has a bioavailability 17-fold higher than quercetin aglycone and has shown potential cardiovascular disease moderating effects in animal studies. The present study aimed to determine if acute ingestion of EMIQ® improves endothelial function, blood pressure, and cognitive function in human volunteers at risk of cardiovascular disease. Twenty-five participants (12 males, 13 females) with at least one cardiovascular disease risk factor completed this randomized, controlled, crossover study. In a random order, participants were given EMIQ® (2 mg aglycone equivalent)/kg body weight or placebo alongside a standard breakfast meal. Endothelial function, assessed by flow mediated dilatation (FMD) of the brachial artery was measured before and 1.5 hrs after intervention. Blood pressure (BP), arterial stiffness, cognitive function, BP during cognitive stress and measures of quercetin metabolites, oxidative stress and markers of nitric oxide (NO) production were assessed post-intervention. After adjustment for pre-treatment measurements and treatment order, EMIQ® treatment resulted in a significantly higher FMD response compared to the placebo [0.60%, 95% CI: 0.03, 1.17 (p=0.04)]. Plasma concentrations of quercetin metabolites were significantly higher (p<0.001) after EMIQ® treatment compared to the placebo. No changes in blood pressure, arterial stiffness, cognitive function, or biochemical parameters were observed. In this human intervention study, the acute administration of EMIQ® significantly increased circulating quercetin metabolites and improved endothelial function. Further clinical trials are required to assess whether health benefits are associated with long-term EMIQ® consumption.
This systematic review and meta‐analysis of randomized controlled trials was performed to determine the effect of quercetin supplementation on glycemic control among patients with metabolic syndrome and related disorders. Databases including PubMed, MEDLINE, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials were searched until August 30, 2018. Nine studies with 10 effect sizes out of 357 selected reports were identified eligible to be included in current meta‐analysis. The pooled findings indicated that quercetin supplementation did not affect fasting plasma glucose (FPG), homeostasis model of assessment‐estimated insulin resistance, and hemoglobin A1c levels. In subgroup analysis, quercetin supplementation significantly reduced FPG in studies with a duration of ≥8 weeks (weighted mean difference [WMD]: −0.94; 95% confidence interval [CI; −1.81, −0.07]) and used quercetin in dosages of ≥500 mg/day (WMD: −1.08; 95% CI [−2.08, −0.07]). In addition, subgroup analysis revealed a significant reduction in insulin concentrations following supplementation with quercetin in studies that enrolled individuals aged <45 years (WMD: −1.36; 95% CI [−1.76, −0.97]) and that used quercetin in dosages of ≥500 mg/day (WMD: −1.57; 95% CI [−1.98, −1.16]). In summary, subgroup analysis based on duration of ≥8 weeks and used quercetin in dosages of ≥500 mg/day significantly reduced FPG levels.
Thrombus formation is dependent on the interaction of platelets, leukocytes and endothelial cells as well as proteins of the coagulation cascade. This interaction is tightly controlled by phospho-regulated pathways involving protein kinase CK2. A growing number of studies have demonstrated an important role of this kinase in the regulation of primary and secondary hemostasis. Inhibition of CK2 downregulates the expression of important adhesion molecules on platelets and endothelial cells, such as glycoprotein (GP)IIb/IIIa, P-selectin, von Willebrand factor and vascular cell adhesion molecule. Moreover, the reduced CK2-dependent phosphorylation of different coagulation factors prevents the conversion of fibrinogen to fibrin. Targeting these mechanisms may open the door for the development of novel anti-thrombotic therapies.
Nature's providences are rather the choicest remedies for human health and welfare. One such is quercetin, which is nature's nominee for cancer cure and recently demonstrated against influenza attack. Quercetin is highly recognized for its anticancer applications. This review emphasizes on yet another gift that this compound has to offer for mankind, which is none other than combating the deadly evasive influenza virus. The chemistry of this natural bioflavonoid and its derivatives and its modus operandi against influenza virus is consolidated into this review. The advancements and achievements made in the anti-influenza clinical history are also documented. Further, the challenges facing the progress of this compound to emerge as a predominant anti-influenza drug are discussed, and the future perspective for breaking its limitations through integration with nanoplatforms is envisioned.
Ethnopharmacological relevance:
Esculentoside A (EsA) is a saponin isolated from the root of Phytolacca esculenta, an herb which has long been used in Traditional Chinese Medicine for various inflammatory diseases. EsA has been reported to have potent anti-inflammatory properties both in vitro and in vivo.
Aim of the study:
The present study focused on the molecular mechanism of EsA for its anti-inflammatory effects in RAW264.7 cells stimulated with lipopolysaccharide (LPS).
Methods and results:
Enzyme Linked Immunosorbent Assay (ELISA) showed EsA dose dependently inhibited the production of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) and nitric oxide in RAW264.7 cells. Real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR) assay further confirmed the suppression of LPS-induced TNF-α, IL-6 and iNOS gene expression by EsA on a transcriptional level. Moreover, EsA treatment markedly suppressed LPS-stimulated IκB phosphorylation and degradation as well as LPS-stimulated luciferase reporter construct driven by κB response elements in RAW264.7 cells. In addition, EsA significantly reduced LPS-induced stimulation of p38 and JNK, but not ERK1/2, phosphorylation. Furthermore, we used a computational method called "reverse docking" to search the possible binding proteins of EsA from the the potential drug target database (PDTD), and focused on CK2 as the primary binding protein of EsA. Afterward, we further tested EsA directly interacts with recombinant CK2 using SPR assay. In CK2 kinase activity assay, EsA inhibited recombinant CK2 holoenzyme activity obviously in a dose-dependent manner. In addition, TBB (4, 5, 6, 7-tetrabromo-2-benzotriazole, a pharmacological inhibitor of CK2) blocked IL-6 release in a dose-dependent manner, whereas co-treatment of cells with EsA and TBB did not have an additive effect.
Conclusions:
Taken together, these results indicate that EsA blocks the LPS-induced pro-inflammatory molecules expression, at least in part, by impediment of LPS-triggered activation of NF-κB and p38/JNK MAPK pathways in macrophages. Furthermore, we discovered for the first time EsA as a ligand for CK2, which was involved in the inhibition of EsA to the expression of inflammatory cytokines. These findings extended our understanding on the cellular and molecular mechanisms responsible for the anti-inflammatory activity of EsA.
Kimchi, a traditional fermented food regularly consumed in Korea, contains various types of antimicrobial compounds. Among the tested compounds present in common spices used in Kimchi, quercetin showed the highest selectivity index against influenza A virus (IAV) H1N1. In this study, the effect of pretreatment and periodic treatment with quercetin against IAV in Madin-Darby canine kidney cells was observed. Compared to pretreatment, periodic treatment resulted in significantly higher cell viability but lower relative expression of the IAV PA gene and total apoptosis and cell death. To explain the mechanisms underlying the antiviral effects of quercetin treatment, a comparative proteomic analysis was performed in four samples (mock, quercetin-treated, IAV-infected, and quercetin-treated IAV-infected). Among the 220 proteins, 56 proteins were classified non-hierarchically into three clusters and were differentially modulated by quercetin treatment in IAV-infected cells. Post-translational modifications were identified in 68 proteins. In conclusion, periodic treatment with quercetin is effective in reducing IAV infection, and differentially regulates the expression of key proteins, including heat shock proteins, fibronectin 1, and prohibitin to reduce IAV replication.
The flavonoid isoquercitrin (quercetin-3-O-β-d-glucopyranoside) is commonly found in medicinal herbs, fruits, vegetables and plant-derived foods and beverages. This article reviews the occurrence, preparation, bioavailability, pharmacokinetics, toxicology and biological activity of isoquercitrin and "enzymatically modified (α-glucosylated) isoquercitrin" (EMIQ). Pure isoquercitrin can now be obtained on a large scale by enzymatic rutin hydrolysis with α-L-rhamnosidase. Isoquercitrin has higher bioavailability than quercetin and displays a number of chemoprotective effects both in vitro and in vivo, against oxidative stress, cancer, cardiovascular disorders, diabetes and allergic reactions. Although small amounts of intact isoquercitrin can be found in plasma and tissues after oral application, it is extensively metabolized in the intestine and the liver. Biotransformation of isoquercitrin includes deglycosylation, followed by formation of conjugated and methylated derivatives of quercetin or degradation to phenolic acids and carbon dioxide. The acceptable daily intake of (95%) isoquercitrin and of EMIQ was estimated to be 5.4 and 4.9mg/kg/day, respectively. Adverse effects of higher doses in rats included mostly (benign) chromaturia; nevertheless some drug interactions may occur due to the modulation of the activity and/or expression of drug metabolizing/transporting systems. With respect to the safety, affordability and beneficial pharmacological activities, highly pure isoquercitrin is a prospective substance for food supplementation.
Dietary intake of quercetin is suggested to be potentially beneficial for the prevention of various diseases. We examined the effect of α-oligoglucosylation of the sugar moiety of quercetin monoglucoside on its bioavailability in humans. Enzymatically modified isoquercitrin (EMIQ) was prepared by enzymatic deglycosylation and the subsequent of α-oligoglucosylation of quercetin 3-O-β-rutinode (rutin). The plasma level of quercetin metabolites was instantly increased by oral intake of EMIQ and its absorption efficiency was significantly higher than that of isoquercitrin (quercetin 3-O-β-glucoside; Q3G), and rutin. The profile of plasma quercetin metabolites after EMIQ consumption did not differ from that after Q3G consumption. The apparent log P of EMIQ indicated that EMIQ is more hydrophilic than Q3G but less than quercetin 3,4′-O-β-diglucoside. These data indicated that enzymatic α-oligoglucosylation to the sugar moiety is effective for enhancing the bioavailability of quercetin glucosides in humans.
The antivirus effect of quercetin and oseltamivir on the Toll-like receptor 7 (TLR7) signaling pathway was observed when dendritic cells and macrophages were infected with H1N1. Leukomonocytes were obtained from umbilical cord blood and harvested after stimulation by recombinant human Granulocyte-Macrophage Colony-Stimulating Factor (rhGM-CSF) and recombinant human Interleukin 4 (rhIL-4). Virus-infected cell model was established by human bronchial epithelial cells (16HBE) infected with H1N1. After immunological cells and virus-infected cells were co-cultured, quercetin and oseltamivir were also added into the medium as a treatment intervention. Then the immunological cells were collected for Real Time PCR (RT-PCR) and Western blot to determine the expression levels of genes related to TLR7 pathway. Viral infection led to cell death and increased the gene expression levels of TLR7 signal pathway. Quercetin and oseltamivir increased cell viability and reduced the expression levels of TLR7 signal pathway.
Sixteen flavonoids and related compounds have been tested for their ability to inhibit three acidophilic Ser/Thr protein kinases: the Golgi apparatus casein kinase (G-CK) recently identified with protein FAM20C, protein kinase CK1, and protein kinase CK2. While G-CK is entirely insensitive to all compounds up to 40 μM concentration, consistent with the view that it is not a member of the kinome, and CK1 is variably inhibited in an isoform-dependent manner by fisetin and luteolin, and to a lesser extent by myricetin and quercetin, CK2 is susceptible to drastic inhibition by many flavonoids, displaying with six of them IC(50) values < 1 μM. A common denominator of these compounds (myricetin, quercetin, fisetin, kaempferol, luteolin, and apigenin) is a flavone scaffold with at least two hydroxyl groups at positions 7 and 4'. Inhibition is competitive with respect to the phospho-donor substrate ATP. The crystal structure of apigenin and luteolin in complex with the catalytic subunit of Zea mays CK2 has been solved, revealing their ability to interact with both the hinge region (Val116) and the positive area near Lys68 and the conserved water W1, the two main polar ligand anchoring points in the CK2 active site. Modeling experiments account for the observation that luteolin but not apigenin inhibits also CK1. The observation that luteolin shares its pyrocatechol moiety with tyrphostin AG99 prompted us to solve also the structure of this compound in complex with CK2. AG99 was found inside the ATP pocket, consistent with its mode of inhibition competitive with respect to ATP. As in the case of luteolin, the pyrocatechol group of AG99 is critical for binding, interacting with the positive area in the deepest part of the CK2 active site.
Influenza virus infects the respiratory system of human and animals causing mild to severe illness which could lead to death. Although vaccines are available, there is still a great need for influenza antiviral drugs to reduce disease progression and virus transmission. Currently two classes (M2 channel blockers and neuraminidase inhibitors) of FDA-approved influenza antiviral drugs are available, but there are great concerns of emergence of viral resistance. Therefore, timely development of new antiviral drugs against influenza viruses is crucial. Plant-derived polyphenols have been studied for antioxidant activity, anti-carcinogenic, and cardio- and neuroprotective actions. Recently, some polyphenols, such as resveratrol and epigallocatechin gallate, showed significant anti-influenza activity in vitro and/or in vivo. Therefore we investigated selected polyphenols for their antiviral activity against influenza A and B viruses. Among the polyphenols we tested, isoquercetin inhibited the replication of both influenza A and B viruses at the lowest effective concentration. In a double treatment of isoquercetin and amantadine, synergistic effects were observed on the reduction of viral replication in vitro. The serial passages of virus in the presence of isoquercetin did not lead to the emergence of resistant virus, and the addition of isoquercetin to amantadine or oseltamivir treatment suppressed the emergence of amantadine- or oseltamivir-resistant virus. In a mouse model of influenza virus infection, isoquercetin administered intraperitoneally to mice inoculated with human influenza A virus significantly decreased the virus titers and pathological changes in the lung. Our results suggest that isoquercetin may have the potential to be developed as a therapeutic agent for the treatment of influenza virus infection and for the suppression of resistance in combination therapy with existing drugs.
Flavonoids exert antiallergic and antioxidant effects. We investigated the efficacy of enzymatically modified isoquercitrin (EMIQ), a flavonoid, to relieve symptoms of pollinosis.
In a parallel-group, double-blind placebo-controlled study design, 20 subjects with Japanese cedar pollinosis took two capsules daily of 100 mg EMIQ or a placebo for 8 weeks during the pollen season. Subjective symptoms and activities of daily living (ADL) scores were recorded every day, and the quality of life (QOL) score was obtained every 4 weeks. Blood sampling was performed before and after the study to measure serum cytokines, chemokines, IgE, quercetin and oxidized biomarkers.
During the entire study period, total ocular score and ocular itching score for the EMIQ group were significantly lower (p < 0.05) than for the placebo group. When limited to the individual periods, total symptom score for the EMIQ group was significantly lower (p < 0.05, week 4-5) than that for the placebo group while other scores for the EMIQ group, such as total nasal score (p = 0.06, week 4-5), nasal obstruction score (p = 0.08, week 4-5), lacrimation score (p = 0.06, week 5-6), ocular congestion score (p = 0.08, week 4-7) and ADL score (p = 0.08, week 4-7), all tended to be lower. The levels of serum cytokines such as interleukin (IL)-4, IL-5, IL-12, IL-13, interferon-gamma, and eotaxin and IgE were not significantly downregulated by the intake of EMIQ but the serum concentrations of oxidized low-density lipoprotein and thymus and activation-regulated chemokine were reduced.
Intake of the quercetin glycoside EMIQ was safe and influenced ocular symptoms caused by pollinosis.
Enzymatically modified isoquercitrin (EMIQ), isoquercitrin with malto-oligosaccharides, has been recognized as "generally recognized as safe" by the Flavor and Extracts Manufacturers Association in the United States since 2003. The long-term antiatherogenic effect of EMIQ was examined using apolipoprotein E (apoE)-deficient atherogenic mice.
Male apoE-deficient mice (6 wk old) were fed with a high-fat diet alone or a diet containing EMIQ for 14 wk. At 20 wk old, atherosclerotic lesions in the aorta and aortic sinus were measured by morphometry and histomorphometry.
In apoE-deficient mice, EMIQ did not significantly affect body weight, plasma total cholesterol, triacylglycerol, and high-density lipoprotein cholesterol throughout the experiment. EMIQ significantly suppressed the aortic atherosclerotic lesion area (control 8.8 +/- 3.5% versus EMIQ 4.4 +/- 1.5%, mean +/- SD, P = 0.022). Similarly, atherosclerotic plaque lesions in the aortic sinus were significantly reduced by EMIQ (control 37.7 +/- 3.6% versus EMIQ 30.2 +/- 2.0%, P = 0.010). Of note, the immunostained area for macrophage or 4-hydroxy-2-nonenal, a well-recognized marker of oxidative stress, at the plaque in the aortic sinus was markedly suppressed, whereas the area for collagen or smooth muscle cell were increased by EMIQ, suggesting a plaque-stabilizing effect of EMIQ.
EMIQ has atheroprotective and plaque-stabilizing effects.
We have previously shown that the flavonoid luteolin inhibits the expression of pro-inflammatory molecules induced by LPS. In the present study we tested the ability of luteolin to block signalling pathways implicated in LPS-induced inflammatory gene expression in macrophages.
Exposure of the murine macrophage cell line RAW 264.7 to LPS increased phosphorylation of the mitogen-activated protein kinase family members ERK1/2, p38 and JNK1/2 in a time-dependent manner. Pretreatment of RAW 264.7 with luteolin inhibited the LPS-induced ERK1/2 and p38, but not JNK1/2, phosphorylation, and blocked the LPS-induced TNF-α release.
To investigate which of these pathways contribute to the inhibitory effects of luteolin on TNF-α release, cells were pretreated with pharmacological inhibitors of these pathways; PD98059 and SB203580 when used alone failed to inhibit TNF-α release, whereas pretreatment with both agents attenuated TNF-α release.
We have previously shown that luteolin blocks Akt phosphorylation in response to LPS in RAW 264.7 macrophages. To determine the role of Akt in TNF-α release, cells were transiently transfected with a dominant negative form of Akt (K179M). Overexpression of K179M Akt did not alter LPS-induced TNF-α release, suggesting that inhibition of this kinase does not mediate the inhibitory action of luteolin.
In addition, DRB (a pharmacological inhibitor of CK2) blocked TNF-α release in a concentration-dependent manner, whereas co-treatment of cells with luteolin and DRB did not have an additive effect.
We conclude that luteolin interferes with LPS signalling by reducing the activation of several MAPK family members and that its inhibitory action on TNF-α release correlates with inhibition of ERK, p38 and CK2 activation.
British Journal of Pharmacology (2002) 136, 1058–1064. doi:10.1038/sj.bjp.0704803
Casein kinase-2 (CK2) probably is the most pleiotropic member of the protein kinase family, with more than 200 substrates known to date. Unlike the great majority of protein kinases, which are tightly regulated enzymes, CK2 is endowed with high constitutive activity, a feature that is suspected to underlie its oncogenic potential and possible implication in viral infections. This makes CK2 an attractive target for anti-neoplastic and antiviral drugs. Here, we present an overview of our present knowledge about CK2 inhibitors, with special reference to the information drawn from two recently solved crystal structures of CK2alpha in complex with emodin and with 4,5,6,7-tetrabromo-2-azabenzimidazole (TBB), this latter being the most specific CK2 inhibitor known to date. A comparison with a series of anthraquinone and xanthenone derivatives highlights the crucial relevance of the hydroxyl group at position 3 for inhibition by emodin, and discloses the possibility of increasing the inhibitory potency by placing an electron withdrawing group at position 5. We also present mutational data corroborating the relevance of two hydrophobic residues unique to CK2, Val66 and Ile174, for the interactions with emodin and TBB, but not with the flavonoid inhibitors quercetin and fisetin. In particular, the CK2alpha mutant V66A displays 27- and 11-fold higher IC(50) values with emodin and TBB, respectively, as compared with the wild-type, while the IC(50) value with quercetin is unchanged. The data presented pave the road toward the rational design of more potent and selective inhibitors of CK2 and the generation of CK2 mutants refractory to inhibition, useful to probe the implication of CK2 in specific cellular functions.
Small conductance Ca(2+)-activated K+ channels (SK channels) couple the membrane potential to fluctuations in intracellular Ca2+ concentration in many types of cells. SK channels are gated by Ca2+ ions via calmodulin that is constitutively bound to the intracellular C terminus of the channels and serves as the Ca2+ sensor. Here we show that, in addition, the cytoplasmic N and C termini of the channel protein form a polyprotein complex with the catalytic and regulatory subunits of protein kinase CK2 and protein phosphatase 2A. Within this complex, CK2 phosphorylates calmodulin at threonine 80, reducing by 5-fold the apparent Ca2+ sensitivity and accelerating channel deactivation. The results show that native SK channels are polyprotein complexes and demonstrate that the balance between kinase and phosphatase activities within the protein complex shapes the hyperpolarizing response mediated by SK channels.
Quercetin, a flavonoid present in the human diet, which is found in high levels in onions, apples, tea and wine, has been shown previously to inhibit platelet aggregation and signaling in vitro. Consequently, it has been proposed that quercetin may contribute to the protective effects against cardiovascular disease of a diet rich in fruit and vegetables.
A pilot human dietary intervention study was designed to investigate the relationship between the ingestion of dietary quercetin and platelet function.
Human subjects ingested either 150 mg or 300 mg quercetin-4'-O-beta-D-glucoside supplement to determine the systemic availability of quercetin. Platelets were isolated from subjects to analyse collagen-stimulated cell signaling and aggregation.
Plasma quercetin concentrations peaked at 4.66 microm (+/- 0.77) and 9.72 microm (+/- 1.38) 30 min after ingestion of 150-mg and 300-mg doses of quercetin-4'-O-beta-D-glucoside, respectively, demonstrating that quercetin was bioavailable, with plasma concentrations attained in the range known to affect platelet function in vitro. Platelet aggregation was inhibited 30 and 120 min after ingestion of both doses of quercetin-4'-O-beta-D-glucoside. Correspondingly, collagen-stimulated tyrosine phosphorylation of total platelet proteins was inhibited. This was accompanied by reduced tyrosine phosphorylation of the tyrosine kinase Syk and phospholipase Cgamma2, components of the platelet glycoprotein VI collagen receptor signaling pathway.
This study provides new evidence of the relatively high systemic availability of quercetin in the form of quercetin-4'-O-beta-D-glucoside by supplementation, and implicates quercetin as a dietary inhibitor of platelet cell signaling and thrombus formation.
The interferon-gamma (IFN-gamma)-mediated regulation of macrophage gene expression is of crucial importance in the pathogenesis of atherosclerosis. The mechanisms underlying the actions of IFN-gamma signaling in macrophages were investigated using monocyte chemoattractant protein (MCP)-1 as a model gene.
The IFN-gamma-induced expression of MCP-1 in macrophages was attenuated by inhibitors of phosphoinositide-3-kinase (PI3K), casein kinase 2 (CK2), and Janus kinase (JAK)-2. AKT was the downstream target for PI3K action. Electrophoretic mobility shift assays and chromatin immunoprecipitation showed that signal transducer and activator of transcription (STAT)-1 interacted with IFN-gamma responsive elements in the MCP-1 gene promoter. The IFN-gamma-induced activity of the MCP-1 gene promoter and an artificial promoter containing STAT1 responsive elements was inhibited by expression of dominant negative forms of JAK-1 and -2, STAT1, CK2, and AKT. The action of CK2 and AKT on STAT1 activation was mediated, at least in part, through the regulation of serine 727 phosphorylation. Analysis of a number of other genes regulated by this cytokine and implicated in atherosclerosis revealed a gene-specific action for PI3K/AKT in IFN-gamma signaling.
These studies provide novel insights into the role of PI3K/AKT and CK2 in IFN-gamma signaling relevant to changes in macrophage gene expression during atherosclerosis.
The cytoplasmic CARD-containing DExD/H box RNA helicases RIG-I and MDA5 act as sensors of viral infections through recognition of viral double-stranded (ds) RNAs. They both associate with the mitochondrial adaptor IPS-1 (also referred to as MAVS, VISA, and CARDIF) through homotypic CARD-CARD interactions. IPS-1, in turn, triggers signaling pathways, including activation of the protein kinases TBK1 and IKKepsilon, responsible for the phosphorylation of IRF3, a key transcription factor involved in interferon (IFN) synthesis, one essential element of the innate immune response. RIG-I remains in an autoinhibited state in the absence of dsRNA, through an internal repressor domain (RD) that binds within both its CARD and its RNA helicase domains and therefore acts in cis to control its multimerization and interaction with IPS-1. Ectopic expression of the RD prevents signaling and increases cell permissiveness to viruses, including hepatitis C virus. LGP2, which is another DExD/H RNA helicase of the RIG-I and MDA5 family and which is devoid of CARD domain, negatively controls IFN induction at different levels: by sequestering dsRNA, by blocking RIG-I's multimerization in trans through a domain analogous to the RIG-I RD, and by competing with the protein kinase IKKepsilon for a common interaction site on IPS-1. The ability of RIG-I and LGP2 to exert such a feedback control at the earliest steps of IFN synthesis allows the cells to exert a tight regulation of the induction of the innate immune response.
Enzymatically modified isoquercitrin (EMIQ) is a water-soluble glycoside of quercetin produced from rutin by enzymatic treatment. We investigated the anti-hypertensive effect of orally administered EMIQ in spontaneously hypertensive rats (SHR). The systolic blood pressure (SBP) in SHR administered EMIQ at a dose of 3 and 26 mg/kg/d was significantly lower than that in the control group on d 22, 36 and 50 of administration. The effect of EMIQ (26 mg/kg/d) was higher than equimolar administration of quercetin. Diltiazem administered as a positive control also suppressed the increase in SBP. and the effect was stronger than that of EMIQ. In the control group, the mean values of mean blood pressure (MBP) and diastolic blood pressure (DBP) were increased after the start of administration. Although diltiazem suppressed the increase in MBP, no significant changes were observed in the EMIQ groups. Compared with the control group, EMIQ groups showed the incidental changes of MBP and heart rate on day 22 of administration only. These results indicate that EMIQ suppressed the increase in SBP in SHR dose-dependently, and was more effective than the aglycone quercetin. It was also speculated that EMIQ showed higher anti-hypertensive effect than quercetin due to the high bioavailability, and the mechanism of SBP suppression is possibly through the improvement of endothelial NO production. In conclusion, our results suggest that EMIQ shows possibility as a naturally-derived safe food material which has an antihypertensive effect.
To investigate the effects of quercetin supplementation on incidence of upper respiratory tract infections (URTI) and exercise-induced changes in immune function.
Trained male cyclists (N=40) were randomized to quercetin (N=20) or placebo (N=20) groups and, under double-blind procedures, received 3 wk quercetin (1000 mg.d(-1)) or placebo before, during, and for 2 wk after a 3-d period in which subjects cycled for 3 h.d(-1) at approximately 57% Wmax. Blood and saliva samples were collected before and after each of the three exercise sessions and assayed for natural killer cell activity (NKCA), PHA-stimulated lymphocyte proliferation (PHA-LP), polymorphonuclear oxidative-burst activity (POBA), and salivary IgA output (sIgA).
Pre- to postexercise changes in NKCA, PHA-LP, POBA, and sIgA did not differ significantly between quercetin and placebo groups. URTI incidence during the 2-wk postexercise period differed significantly between groups (quercetin=1/20 vs placebo=9/20, Kaplan-Meier analysis statistic=8.31, P=0.004).
Quercetin versus placebo ingestion did not alter exercise-induced changes in several measures of immune function, but it significantly reduced URTI incidence in cyclists during the 2-wk period after intensified exercise.