Fisetin, morin and myricetin attenuate CD36 expression and oxLDL uptake in U937-derived macrophages

CD36: a promising therapeutic target in hematologic tumors

Cluster of differentiation 36 (CD36) is a multiligand receptor with important roles in lipid metabolism, angiogenesis and innate immunity, and its diverse effects may depend on the binding of specific ligands in different contexts. CD36 is expressed not only on immune cells in the tumor microenvironment (TME) but also on some hematopoietic cells. CD36 is associated with the growth, metastasis and drug resistance in some hematologic tumors, such as leukemia, lymphoma and myelodysplastic syndrome. Currently, some targeted therapeutic agents against CD36 have been developed, such as anti-CD36 antibodies, CD36 antagonists (small molecules) and CD36 expression inhibitors. This paper not only innovatively addresses the role of CD36 in some hematopoietic cells, such as erythrocytes, hematopoietic stem cells and platelets, but also pays special attention to the role of CD36 in the development of hematologic tumors, and suggests that CD36 may be a potential cancer therapeutic target in hematologic tumors.

Vitamin D and Atherosclerosis: Unraveling the Impact on Macrophage Function

Vitamin D plays a crucial role in preventing atherosclerosis and in the regulation of macrophage function. This review aims to provide a comprehensive summary of the clinical evidence regarding the impact of vitamin D on atherosclerotic cardiovascular disease, atherosclerotic cerebrovascular disease, peripheral arterial disease, and associated risk factors. Additionally, it explores the mechanistic studies investigating the influence of vitamin D on macrophage function in atherosclerosis. Numerous findings indicate that vitamin D inhibits monocyte or macrophage recruitment, macrophage cholesterol uptake, and esterification. Moreover, it induces autophagy of lipid droplets in macrophages, promotes cholesterol efflux from macrophages, and regulates macrophage polarization. This review particularly focuses on analyzing the molecular mechanisms and signaling pathways through which vitamin D modulates macrophage function in atherosclerosis. It claims that vitamin D has a direct inhibitory effect on the formation, adhesion, and migration of lipid-loaded monocytes, thus exerting anti-atherosclerotic effects. Therefore, this review emphasizes the crucial role of vitamin D in regulating macrophage function and preventing the development of atherosclerosis.

The natural polyphenol fisetin in atherosclerosis prevention: a mechanistic review

The incidence and mortality rate of atherosclerotic cardiovascular disease (ASCVD) is increasing yearly worldwide. Recently, a growing body of evidence has unveiled the anti-atherosclerotic properties of fisetin, a natural polyphenol compound. In this article, we reviewed the pharmacologic actions of fisetin on experimental atherosclerosis and its protective effects on disease-relevant cell types such as endothelial cells, macrophages, vascular smooth muscle cells, and platelets. Based on its profound cardiovascular actions, fisetin holds potential for clinical translation and could be developed as a potential therapeutic option for atherosclerosis and its related complications. Large-scale randomized clinical trials are warranted to ascertain the safety and efficacy of fisetin in patients with or high risk for ASCVD.

The regulatory role of CD36 in hematopoiesis beyond fatty acid uptake

CD36 is a transmembrane glycoprotein, located on surface of numerous cell types. This review is aimed to explore regulatory role of CD36 in hematopoiesis beyond fatty acid uptake. CD36 acts as a pattern recognition receptor, regulates cellular fatty acid homeostasis, and negatively monitors angiogenesis. CD36 also mediates free fatty acid transportation to hematopoietic stem cells in response to infections. During normal physiology and pathophysiology, CD36 significantly participates in the activation and metabolic needs of platelets, macrophages, monocytes, T cells, B cells, and dendritic cells. CD36 has shown a unique relationship with Plasmodium falciparum-infected erythrocytes (PfIEs) as a beneficiary for both parasite and host. CD36 actively participates in pathogenesis of various hematological cancers as a significant prognostic biomarker including AML, HL, and NHL. CD36-targeting antibodies, CD36 antagonists (small molecules), and CD36 expression inhibitors/modulators are used to target CD36, depicting its therapeutic potential. Many preclinical studies or clinical trials were performed to assess CD36 as a therapeutic target; some are still under investigation. This review reflects the role of CD36 in hematopoiesis which requires more consideration in future research.

Anti-Cancer and Anti-Oxidant Bioactive Metabolites from Aspergillus fumigatus WA7S6 Isolated from Marine Sources: In Vitro and In Silico Studies

Cancer is a huge global disease burden. Every year, tens of millions of people worldwide are diagnosed with cancer, and more than half of them die as a result of it. The great biodiversity of the marine environment has increasingly piqued the interest of experts, especially in the field of drug discovery. The marine fungus Aspergillus fumigatus WA7S6 has been selected among a group of fungi isolated from marine sponges as it exhibits a pronounced antimicrobial activity toward a group of pathogenic microbes. The fungus has been identified genetically by amplification and analysis of its 18srRNA gene. The fungus crude extract has been obtained by cultivation of the fungus on rice media. The crude extract was tested for antibacterial activity against a variety of pathogenic microorganisms. The results demonstrated a pronounced antimicrobial action against P. aeruginosa, S. aureus, A. niger, and Candida albicans. Furthermore, we tested the antioxidant potential of the Aspergillus fumigatus WA7S6 crude extract using three different methods: ATBS, DPPH, and lipid peroxidation assays. Results showed that the crude extract WA7S6 had an IC50 value of 21.35 µg/mL. The anticancer potential of the crude extract was also evaluated against cancer cell lines such as Hela, MCF, and WI-38. The chemical profiling of the fungus extract was identified via GC-mass and in silico molecular docking of the identified compounds on heme oxygenase, as a stress protein included in cellular protection, antioxidant, and anti-inflammatory activities, suggesting that some compounds, such as 9-Tetradecynoic acid, 11-Hexadecynoic acid, methyl ester, and dehydromevalonic lactone, could be relevant for antioxidant purposes.

Fisetin treatment alleviates kidney injury in mice with diabetes-exacerbated atherosclerosis through inhibiting CD36/fibrosis pathway

Diabetes-related vascular complications include diabetic cardiovascular diseases (CVD), diabetic nephropathy (DN) and diabetic retinopathy, etc. DN can promote the process of end-stage renal disease. On the other hand, atherosclerosis accelerates kidney damage. It is really an urge to explore the mechanisms of diabetes-exacerbated atherosclerosis as well as new agents for treatment of diabetes-exacerbated atherosclerosis and the complications. In this study we investigated the therapeutic effects of fisetin, a natural flavonoid from fruits and vegetables, on kidney injury caused by streptozotocin (STZ)-induced diabetic atherosclerosis in low density lipoprotein receptor deficient (LDLR-/-) mice. Diabetes was induced in LDLR-/- mice by injecting STZ, and the mice were fed high-fat diet (HFD) containing fisetin for 12 weeks. We found that fisetin treatment effectively attenuated diabetes-exacerbated atherosclerosis. Furthermore, we showed that fisetin treatment significantly ameliorated atherosclerosis-enhanced diabetic kidney injury, evidenced by regulating uric acid, urea and creatinine levels in urine and serum, and ameliorating morphological damages and fibrosis in the kidney. In addition, we found that the improvement of glomerular function by fisetin was mediated by reducing the production of reactive oxygen species (ROS), advanced glycosylation end products (AGEs) and inflammatory cytokines. Furthermore, fisetin treatment reduced accumulation of extracellular matrix (ECM) in the kidney by inhibiting the expression of vascular endothelial growth factor A (VEGFA), fibronectin and collagens, while enhancing matrix metalloproteinases 2 (MMP2) and MMP9, which was mainly mediated by inactivating transforming growth factor β (TGFβ)/SMAD family member 2/3 (Smad2/3) pathways. In both in vivo and in vitro experiments, we demonstrated that the therapeutic effects of fisetin on kidney fibrosis resulted from inhibiting CD36 expression. In conclusion, our results suggest that fisetin is a promising natural agent for the treatment of renal injury caused by diabetes and atherosclerosis. We reveal that fisetin is an inhibitor of CD36 for reducing the progression of kidney fibrosis, and fisetin-regulated CD36 may be a therapeutic target for the treatment of renal fibrosis.

Microarray Expression Profile of Myricetin-Treated THP-1 Macrophages Exhibits Alterations in Atherosclerosis-Related Regulator Molecules and LXR/RXR Pathway

Atherosclerosis is a chronic inflammation characterized by macrophage infiltration, lipid deposition, and arterial wall thickening. Prevention of atherosclerosis by nutraceuticals is gaining attention. Myricetin, a dietary flavonol, is claimed to possess anti-atherosclerosis properties. We studied myricetin's effect on the atherosclerosis-associated molecular mechanism. Cytotoxicity and proliferation testing to check the viability of myricetin-treated THP-1 macrophages and monocyte migration study in the presence and absence of myricetin was performed. The whole transcriptome analysis was conducted using the Affymetrix microarray platform. The Partek genomics suite for detecting differentially expressed genes (DEGs) and ingenuity pathway analysis was used to identify canonical pathways. Cytotoxicity assays exhibited no significant toxicity in THP-1 macrophages treated with different myricetin concentrations (10-200 μM). Genome-wide expression profiling revealed 58 DEGs (53 upregulated and 5 downregulated) in myricetin-treated THP-1 macrophages. Pathway analysis revealed inhibition of LXR/RXR activation and angiogenesis inhibition by thrombospondin-1 and activated phagocytosis in myricetin-treated THP-1 macrophages. The cytotoxicity assay shows myricetin as a safe phytochemical. In vitro and in silico pathway studies on THP-1 macrophages showed that they can inhibit THP-1 monocyte migration and alter the cholesterol efflux mediated via LXR/RXR signaling. Therefore, myricetin could help in the prevention of cell infiltration in atherosclerotic plaque with reduced risk of stroke or brain damage.

Role of CD36 in cancer progression, stemness, and targeting

CD36 is highly expressed in diverse tumor types and its expression correlates with advanced stages, poor prognosis, and reduced survival. In cancer cells, CD36: 1) increases fatty acid uptake, reprogramming lipid metabolism; 2) favors cancer cell proliferation, and 3) promotes epithelial-mesenchymal transition. Furthermore, CD36 expression correlates with the expression of cancer stem cell markers and CD36⁺ cancer cells display increased stemness functional properties, including clonogenicity, chemo- and radioresistance, and metastasis-initiating capability, suggesting CD36 is a marker of the cancer stem cell population. Thus, CD36 has been pointed as a potential therapeutic target in cancer. At present, at least three different types of molecules have been developed for reducing CD36-mediated functions: blocking monoclonal antibodies, small-molecule inhibitors, and compounds that knock-down CD36 expression. Herein, we review the role of CD36 in cancer progression, its participation in stemness control, as well as the efficacy of reported CD36 inhibitors in cancer cell cultures and animal models. Overall, the evidence compiled points that CD36 is a valid target for the development of new anti-cancer therapies.

Dietary Isorhamnetin Intake Is Inversely Associated with Coronary Artery Disease Occurrence in Polish Adults

The role of antioxidative agents in coronary artery disease (CAD) has been investigated, but the analysis of specific flavonols intake in Polish adults requires validated tools. The aim of this study was to estimate the dietary intake of flavonols in CAD patients by creating a food frequency questionnaire (FFQ) dedicated for this purpose in Polish adults. The FFQ included 140 products from 12 food groups. The study involved 103 adult respondents (43 CAD patients and 60 healthy controls). Mean daily intakes of total flavonols, quercetin, kaempferol, myricetin and isorhamnetin were calculated as absolute values and quartiles. Mean daily intakes of 12 main food categories and 27 subcategories were calculated as portions and quartiles. The validity test revealed high correlation for total flavonols, kaempferol, myricetin and isorhamnetin and moderate for quercetin. In the reproducibility analysis, the correlation was high for total flavonols, quercetin, kaempferol and myricetin, moderate for isorhamnetin and high for all 12 categories and 25 out of 27 subcategories of the tested food groups. The application of the FFQ in healthy adults and CAD patients revealed that dietary intakes of total flavonols and proportional intakes of kaempferol and isorhamnetin in Polish adults and CAD patients are higher than in most other European countries, while the proportional intakes of quercetin and myricetin are lower than in most European countries. The comparison between CAD patients and the healthy controls revealed significant differences in dietary isorhamnetin intake (p = 0.002). The results suggest that dietary isorhamnetin could have a potential role in CAD prevention.

Can Polyphenols Inhibit Ferroptosis?

Polyphenols, a diverse group of naturally occurring molecules commonly found in higher plants, have been heavily investigated over the last two decades due to their potent biological activities—among which the most important are their antioxidant, antimicrobial, anticancer, anti-inflammatory and neuroprotective activities. A common route of polyphenol intake in humans is through the diet. Since they are subjected to excessive metabolism in vivo it has been questioned whether their much-proven in vitro bioactivity could be translated to in vivo systems. Ferroptosis is a newly introduced, iron-dependent, regulated mode of oxidative cell death, characterized by increased lipid peroxidation and the accumulation of toxic lipid peroxides, which are considered to be toxic reactive oxygen species. There is a growing body of evidence that ferroptosis is involved in the development of almost all chronic diseases. Thus, ferroptosis is considered a new therapeutic target for offsetting many diseases, and researchers are putting great expectations on this field of research and medicine. The aim of this review is to critically analyse the potential of polyphenols to modulate ferroptosis and whether they can be considered promising compounds for the alleviation of chronic conditions.

Fisetin prevents oxidized low-density lipoproteins induced macrophage foam cell formation

ABSTRACT

Foam cell formation in an important event in atherosclerosis. Fisetin, a bioflavonoid, has long been identified to possess anti-inflammatory, anti-lipidemic and anti-cancerous properties, however its role as a lipid homeostasis regulator in macrophage specifically in presence of metabolic stressors such as oxLDL is not well understood. In this study we have investigated the role of fisetin in preventing oxLDL-induced macrophage FCF. U937-derived macrophages were stimulated with oxLDL with or without fisetin for varied time points and various parameters were assessed including cell viability by MTT assay, ROS by DCFDA assay, lipid accumulation by Oil Red O staining, and expression of NLRP3, Sterol regulatory element binding protein (SREBP)-1 and associated downstream proteins HMG CoA reductase (HMGCR) and fatty acid synthase (FAS) were assessed by RT-qPCR and immunoblotting. Functionality of FAS enzyme was determined using enzyme activity assay. Docking studies were performed to determine in-silico interaction between NLRP3 and fisetin. The results showed that fisetin, up to the dose of 10 µM did not alter cell viability but at the same dose could decrease the accumulation of lipids in macrophages and prevented FCF. Fisetin could also ameliorate and reduce oxLDL-induced upregulation of SREBP-1 and thereby expression of its downstream liposynthesis genes HMGCR and FAS and inhibited ROS-induced NLRP3 inflammasome activation. In conclusion, fisetin could inhibit foam cell formation by blocking oxLDL induced ROS formation and subsequent NLRP3 activation, thereby inhibiting SREBP-1 and its downstream genes including FAS and HMGCR.

Fisetin Alleviates Neointimal Hyperplasia via PPARγ/PON2 Antioxidative Pathway in SHR Rat Artery Injury Model

The phenotypic transformation of proliferation and migration in vascular smooth muscle cells (VSMCs) from media to intima is the basic pathology of neointimal hyperplasia after angioplasty in hypertensive patients. Angiotensin II (AngII) stimulates oxidative stress in VSMC, inducing VSMC proliferation and migration, which is a critical factor in both developments of hypertension and angioplasty-induced arterial restenosis. Fisetin, a plant flavonoid polyphenol, has been reported to be antioxidative and potent senolytic. It is unknown whether fisetin would inhibit neointimal hyperplasia. Therefore, we investigated the role of fisetin in neointimal formation in vitro and in vivo. The rat thoracic aortic smooth muscle cells (A10 cells) stimulated by AngII were used as the in vitro neointimal hyperplasia model, where AngII significantly induced the proliferation and migration in A10 cells. We found that fisetin could dose-dependently inhibit the effect of AngII via inducing the expression of an antioxidant, paraoxonase-2 (PON2), whose overexpression could inhibit the proliferation and migration of A10 cells and downexpression by siRNA had the opposite effect. Furthermore, we found the mechanism of fisetin's inducing PON2 expression involved PPARγ. Rosiglitazone, a PPARγ agonist, could increase PON2 expression in A10 cells, while the PPARγ inhibitor prevented the effect of fisetin on PON2. The in vivo neointimal hyperplasia model was established 2 weeks after the carotid artery balloon injury in SHR rats. Administration of fisetin (ip 3 mg/kg daily for 2 weeks) right after the injury significantly increased PON2 expression in the artery, inhibiting ROS production, and efficiently reduced carotid neointimal hyperplasia. These results indicate that fisetin increases the expression of antioxidant PON2 via activation of PPARγ, reducing oxidative stress, inhibiting VSMC proliferation and migration, and alleviates neointimal hyperplasia after intimal injury. PON2 may be a potential therapeutic target to reduce arterial remodeling after angioplasty in hypertensive patients.

Effects of phytochemicals on macrophage cholesterol efflux capacity: Impact on atherosclerosis

High-density lipoprotein cholesterol (HDL) is the major promoter of reverse cholesterol transport and efflux of excess cellular cholesterol. The functions of HDL, such as cholesterol efflux, are associated with cardiovascular disease rather than HDL levels. We have reviewed the evidence base on the major classes of phytochemicals, including polyphenols, alkaloids, carotenoids, phytosterols, and fatty acids, and their effects on macrophage cholesterol efflux and its major pathways. Phytochemicals show the potential to improve the efficiency of each of these pathways. The findings are mainly in preclinical studies, and more clinical research is warranted in this area to develop novel clinical applications.

Dynamic Role of Macrophage Sub Types for Development of Atherosclerosis and Potential Use of Herbal Immunomodulators as Imminent Therapeutic Strategy

Atherosclerosis, a major contributor to cardiovascular disease is a global alarm causing mortality worldwide. Being a progressive disease in the arteries, it mainly causes recruitment of monocytes to the inflammatory sites and subside pathological conditions. Monocyte-derived macrophage mainly acts in foam cell formation by engorging the LDL molecules, oxidizes it into Ox-LDL and leads to plaque deposit development. Macrophages in general differentiate, proliferate and undergo apoptosis at the inflammatory site. Frequently two subtypes of macrophages M1 and M2 has to act crucially in balancing the micro-environmental conditions of endothelial cells in arteries. The productions of proinflammatory mediators like IL-1, IL-6, TNF-α by M1 macrophage has atherogenic properties majorly produced during the early progression of atherosclerotic plaques. To counteract cytokine productions and M1-M2 balance, secondary metabolites (phytochemicals) from plants act as a therapeutic agent in alleviating atherosclerosis progression. This review summarizes the fundamental role of the macrophage in atherosclerotic lesion formation along with its plasticity characteristic as well as recent therapeutic strategies using herbal components and anti-inflammatory cytokines as potential immunomodulators.

Morin hydrate attenuates adenine-induced renal fibrosis via targeting cathepsin D signaling

Lysosomal proteases such as cathepsins B, D, L, and K can regulate the process of fibrosis in most of the organs. However, the role of cathepsin D (CATD) in kidney fibrosis and corresponding chronic kidney disease (CKD) is still unknown. We investigated whether CATD immunomodulation using morin hydrate (MH) can attenuate kidney fibrosis in CKD. Here, CKD was developed by an oral dosage of adenine (AD) in the mice model. Histopathological detection using H & E and Oil-Red-O staining revealed tissue deposition. An escalation in serum creatinine, albumin, and blood urea nitrogen (BUN) revealed a failure in kidney function. An increase in fibrosis was determined using protein analysis and mRNA analysis of MMP-9 and MMP-2 respectively. Both immunoblot analysis and histological analysis indicated that MH immunomudulated CATD expression in AD treated kidneys. With docking analysis, we found MH can bind with the catalytic core of CATD with binding efficiency of -6.83 kcal/mol. Further, MH prevented AD mediated fibrosis by reducing collagen fragmentation as evidenced by the decrease in MMP-2 (P < 0.05) and MMP-9 (P < 0.001) protein levels. MH lowered the levels of inflammation by reducing the AD enhanced expression of MCP-1 and COX-2 nearly threefold. MH treatment increased body weight, enhance kidney function, and improved survival by nearly 150% compared to AD treated mice. CATD inactivation by MH after AD treatment resulted in decreased ECM degradation, fibrosis, and inflammation which resulted in improved renal function and survival.

Oxylipin regulation by phenolic compounds from coffee beverage: Positive outcomes from a randomized controlled trial in healthy adults and macrophage derived foam cells

Oxylipins are considered biomarkers related to cardiovascular diseases (CVDs). They are generated in vivo via the oxygenation of polyunsaturated fatty acids as a result of oxidative stress and inflammation. Oxylipins are involved in vascular functions and are produced during foam cell formation in atherogenesis. Additionally, the consumption coffee is associated with the regulation on a particular oxylipin group, the F_2t-isoprostanes (F_2t-IsoPs). This function has been attributed to the chlorogenic acids (CGAs) from the coffee beverage. Considering the anti-inflammatory and antioxidant properties of CGAs, we evaluated the effects of two types of coffee that provided 787 mg CGAs/day (Coffee A) and 407 mg CGAs/day (Coffee B) by reducing 35 selected oxylipins in healthy subjects. Furthermore, we assessed the effect of CGAs on the cellular proatherogenic response in foam cells by using an oxidized LDL (oxLDL)-macrophage interaction model. After eight weeks of coffee consumption, the contents of 12 urine oxylipins were reduced. However, the effect of Coffee A showed a stronger decrease in IsoPs, dihomo-IsoPs, prostaglandins (PGs) and PG metabolites, probably due to its higher content of CGAs. Neither of the two coffees reduced the levels of oxLDL. Moreover, the in vitro oxylipin induction by oxLDL on foam cells was ameliorated by phenolic acids and CGAs, including the inhibition of IsoPs and PGs by caffeoylquinic and dicaffeoylquinic acids, respectively, while the phenolic acids maintained both antioxidant and anti-inflammatory activities. These findings suggest that coffee antioxidants are strong regulators of oxylipins related to CVDs. The clinical trial was registered on the International Clinical Trials Registry Platform, WHO primary registry (RPCEC00000168).

Fisetin ameliorates atherosclerosis by regulating PCSK9 and LOX-1 in apoE-/- mice

The purpose of the current study was to investigate the mechanism by which fisetin improves atherosclerosis (AS) by regulating lipid metabolism and senescence in apolipoprotein E-deficient (apoE^-/-) mice. An AS model was established by feeding apoE^-/- mice a high-fat diet. Mice were randomly divided into the model group (n=18), the fisetin group (n=18) and the atorvastatin group (n=18). The control group (n=18) was composed of wild-type C57BL/6 mice of the same age and genetic background. The fisetin and atorvastatin groups were respectively treated with aqueous solutions of fisetin (12.5 mg/kg) and atorvastatin (2 mg/kg) via oral gavage daily for 12 weeks. The pathological morphology, lipid accumulation, collagen deposition of the aortic sinus were observed, serum lipids, superoxide dismutase (SOD) and malondialdehyde (MDA) levels and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were measured in the peripheral blood serum. Additionally, the expressions of proprotein convertase subtilisin/kexin type 9 (PCSK9), lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), tumor suppressor protein p53 (p53), cyclin-dependent kinase inhibitor 1A (p21) and multiple tumor suppressor-1 (p16) were analyzed in the aorta. The results of the current study indicated that compared with the control group, a large area of AS plaque in the aortic sinus that contained a large amount of red-stained lipids and decreased collagen fiber content were found in the model group, which exhibited higher total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), oxidized low-density lipoprotein (ox-LDL) and MDA levels; higher ALT and AST activities, lower high-density lipoprotein cholesterol (HDL-C) and SOD levels and increased expression levels of PCSK9, LOX-1, p53, p21 and p16. Fisetin is a phytochemical and bioflavonoid that serves a potential role in chronic diseases including AS, obesity, diabetes and cancer due to its wide biological activities, such as regulating lipid metabolism and anti-aging, anti-oxidation and anti-inflammatory. Atorvastatin is recognized as a first-line treatment drug for AS; therefore it was used as a positive control in the current study. Following fisetin and atorvastatin treatment, both the AS plaque and the lipid accumulation in the aortic sinus were significantly reduced, and the expressions of PCSK9, LOX-1 and aging markers, including p53, p21 and p16 were downregulated.

Myricetin bioactive effects: moving from preclinical evidence to potential clinical applications

Several flavonoids have been recognized as nutraceuticals, and myricetin is a good example. Myricetin is commonly found in plants and their antimicrobial and antioxidant activities is well demonstrated. One of its beneficial biological effects is the neuroprotective activity, showing preclinical activities on Alzheimer, Parkinson, and Huntington diseases, and even in amyotrophic lateral sclerosis. Also, myricetin has revealed other biological activities, among them as antidiabetic, anticancer, immunomodulatory, cardiovascular, analgesic and antihypertensive. However, few clinical trials have been performed using myricetin as nutraceutical. Thus, this review provides new insights on myricetin preclinical pharmacological activities, and role in selected clinical trials.

Fisetin protects against cardiac cell death through reduction of ROS production and caspases activity

Myocardial infarction (MI) is a leading cause of death worldwide. Reperfusion is considered as an optimal therapy following cardiac ischemia. However, the promotion of a rapid elevation of O₂ levels in ischemic cells produces high amounts of reactive oxygen species (ROS) leading to myocardial tissue injury. This phenomenon is called ischemia reperfusion injury (IRI). We aimed at identifying new and effective compounds to treat MI and minimize IRI. We previously studied heart regeneration following myocardial injury in zebrafish and described each step of the regeneration process, from the day of injury until complete recovery, in terms of transcriptional responses. Here, we mined the data and performed a deep in silico analysis to identify drugs highly likely to induce cardiac regeneration. Fisetin was identified as the top candidate. We validated its effects in an in vitro model of MI/IRI in mammalian cardiac cells. Fisetin enhances viability of rat cardiomyocytes following hypoxia/starvation – reoxygenation. It inhibits apoptosis, decreases ROS generation and caspase activation and protects from DNA damage. Interestingly, fisetin also activates genes involved in cell proliferation. Fisetin is thus a highly promising candidate drug with clinical potential to protect from ischemic damage following MI and to overcome IRI.

Ameliorative Effects and Cellular Aspects of Phytoconstituents in Atherosclerosis

Atherosclerosis is a cardiovascular disease that involves vessels through the development of fatty streaks and plaques. Plant-based compounds can help treat or prevent atherosclerosis by affecting various factors that are involved in the disease. The present review discusses our current knowledge of the major cellular and molecular mechanisms of phytotherapeutics for the treatment of atherosclerosis. Numerous studies have evaluated the antiatherosclerotic activity of phytoconstituents to provide preliminary evidence of efficacy, but only a few studies have delineated the underlying molecular mechanisms. Plant-derived phytotherapeutics primarily targets abnormal levels of lipoproteins, endothelial dysfunction, smooth muscle cell migration, foam cell development, and atheromatous plaque formation. Nonetheless, the principal mechanisms that are responsible for their therapeutic actions remain unclear. Further pharmacological studies are needed to elucidate the underlying molecular mechanisms of the antiatherosclerotic response to these phytoconstituents.

Myricetin ameliorates atherosclerosis in the low-density-lipoprotein receptor knockout mice by suppression of cholesterol accumulation in macrophage foam cells

Background

Myricetin, a major flavonoid found in several foods including berries, grapes and wine, exhibited strong antioxidant potency, yet the effect on atherosclerosis is not fully understood. In this study, we examined the effect of myricetin on lipid accumulation in macrophage and atherosclerosis in atherosclerosis-prone low density lipoprotein receptor-deficient (Ldlr ^-/- ) mice.

Methods

Ldlr ^-/- mice were fed an atherogenic diet supplemented with myricetin (0.15% in the diet, v/v) for 8 weeks. Body weight, adipose tissue weight, food intake, serum biochemical parameters were measured. Atherosclerosis lesions and macrophages accumulaton in lesions were analyzed and quantified. Macrophages were exposed to 20 μM of myricetin before incubated with oxidized low-density lipoprotein (ox-LDL) (25μg/mL) or Dil-ox-LDL for the indicated time. Lipid uptake and foam cell formation were evaluated by flow cytometry and microscopy. The intracellular lipids were extracted and measured. mRNA expression and protein of cholesterol metabolism related receptors were analyzed.

Results

Myricetin administration reduced the weight, plasma lipid levels but not food intake in Ldlr ^-/- mice when fed an atherogenic diet. Myceritin-treated Ldlr ^-/- mice displayed significantly less atherosclerotic areas and macrophages in the cross sections of the aortic root. There were also less lipophilic areas in En face Oil red O staining of aorta from myceritin-treated Ldlr ^-/- mice. Myceritin treatment also markedly ameliorated ox-LDL-induced cholesterol accumulation in macrophages. The expression of CD36 were decreased in myricetin treated macrophages with ox-LDL incubation, while scavenger receptors class A (SR-A) and scavenger receptors class B (SR-BI) expression was not altered, indicating that these effect of myricetin were dependent on CD36 pathway.

Conclusions

Our findings indicated that myricetin suppressed cholesterol accumulation in macrophage foam cells by inhibition of CD36-mediated ox-LDL uptake, and suggested myricetin may have an important therapeutic function for atherosclerosis.

Lipoproteins modulate growth and P-glycoprotein expression in drug-resistant HER2-overexpressed breast cancer cells

BACKGROUND

Drug resistance remains as a challenge in the treatment of HER2-overexpressed breast cancer. Emerging evidence from clinical studies show relation of oxidized low density lipoprotein (LDL) and very low density lipoprotein (VLDL) level with drug resistance. However, the underlying molecular mechanisms for this effect remain unclear. Therefore, the aim of this study was to determine the effects of oxidized-LDL and VLDL in drug-resistant HER2-overexpressed breast cancer cells.

METHODS

An in vitro cell model for tamoxifen-resistant HER2 overexpressed UACC732 cells was created using the pulse method. Cells were exposed to oxidized LDL (oxLDL) and very low density lipoprotein (VLDL) separately. Effects on cell morphology was studied using phase contrast microscopic changes. Percentage of cell viability was measured using proliferation assay kit. Development of tamoxifen resistance was determined based on P-gp expression with flow cytometry. Further analysis includedcell death measurement with flow cytometry method.

RESULTS

UACC732 cells exposed to VLDL exhibited fibroblast-like morphology. This was further supported by proliferation assay, where the percentage of cell viability achieved more than 100% with 100 μg/ml of VLDL exposure, indicating cell proliferation. Findings also showed that VLDL caused reduction in expression of Pgp in resistant cells compared to resistant cells alone (p = 0.02).

CONCLUSION

Results of this study suggest that VLDL may play a role in growth of drug-resistant HER2-overexpressing cells. Lower expression of P-gp in presence of VLDL need to be investigated further.

Flavonoids and Their Biological Secrets

Flavonoids are tricyclic polyphenolic compounds naturally occurring in plants. Being nature’s antioxidants flavonoids have been shown to reduce the damages induced by oxidative stress in cells. Besides being an antioxidant, flavonols are demonstrated to have anti-infective properties, i.e., antiviral, antifungal, anti-angiogenic, anti-tumorigenic, and immunomodulatory bioproperties. Plants use them as one of their defense mechanisms against radiation-induced DNA damage and also for fungal infections. The use of flavonols for fabrication of new drugs has been underway with objectives to develop safer and effective therapeutic agents. This review covers 15 flavonols for their structure, biological properties, role in plant metabolisms, and current research focused on computational drug design using flavonols for searching drug leads.

Myricetin inhibits NLRP3 inflammasome activation via reduction of ROS-dependent ubiquitination of ASC and promotion of ROS-independent NLRP3 ubiquitination

Myricetin is a plant-derived flavonoid that exhibits diverse pharmacological properties. The NLRP3 (NLR family, pyrin domain-containing 3 protein) inflammasome is a cytosolic multiprotein complex that plays a critical role in the innate immune response and pathogenesis of multiple inflammatory disorders. The present study found that myricetin inhibited NLRP3 inflammasome assembly via promotion of reactive oxygen species (ROS)-independent ubiquitination of NLRP3 and reduction of ROS-dependent ubiquitination of ASC (apoptosis-associated speck-like protein containing a CARD), which disrupted the interaction between ASC and NLRP3 and inhibited ASC oligomerization. This effect was further confirmed in vivo using mouse models of lipopolysaccharide (LPS)-induced sepsis and alum-induced peritonitis. These results suggest the therapeutic value of myricetin by targeting NLRP3-driven inflammatory diseases.

Morin Prevents Granule Cell Dispersion and Neurotoxicity via Suppression of mTORC1 in a Kainic Acid-induced Seizure Model

An abnormal reorganization of the dentate gyrus and neurotoxic events are important phenotypes in the hippocampus of patients with temporal lobe epilepsy (TLE). The effects of morin, a bioflavonoid constituent of many herbs and fruits, on epileptic seizures have not yet been elucidated, though its beneficial effects, such as its anti-inflammatory and neuroprotective properties, are well-described in various neurodegenerative diseases. In the present study, we investigated whether treatment with morin hydrate (MH) can reduce the susceptibility to seizures, granule cell dispersion (GCD), mammalian target of rapamycin complex 1 (mTORC1) activity, and the increases in the levels of apoptotic molecules and inflammatory cytokines in the kainic acid (KA)-induced seizure mouse model. Our results showed that oral administration of MH could reduce susceptibility to seizures and lead to the inhibition of GCD and mTORC1 activity in the KA-treated hippocampus. Moreover, treatment with MH significantly reduced the increased levels of apoptotic signaling molecules and pro-inflammatory mediators in the KA-treated hippocampus compared with control mice, suggesting a neuroprotective role. Therefore, these results suggest that morin has a therapeutic potential against epilepsy through its abilities to inhibit GCD and neurotoxic events in the in vivo hippocampus.

Oxidative Stress in Cardiovascular Diseases: Involvement of Nrf2 Antioxidant Redox Signaling in Macrophage Foam Cells Formation

Oxidative stress is an important risk factor contributing to the pathogenesis of cardiovascular diseases. Oxidative stress that results from excessive reactive oxygen species (ROS) production accounts for impaired endothelial function, a process which promotes atherosclerotic lesion or fatty streaks formation (foam cells). Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor involved in cellular redox homeostasis. Upon exposure to oxidative stress, Nrf2 is dissociated from its inhibitor Keap-1 and translocated into the nucleus, where it results in the transcriptional activation of cell defense genes. Nrf2 has been demonstrated to be involved in the protection against foam cells formation by regulating the expression of antioxidant proteins (HO-1, Prxs, and GPx1), ATP-binding cassette (ABC) efflux transporters (ABCA1 and ABCG1) and scavenger receptors (scavenger receptor class B (CD36), scavenger receptor class A (SR-A) and lectin-type oxidized LDL receptor (LOX-1)). However, Nrf2 has also been reported to exhibit pro-atherogenic effects. A better understanding on the mechanism of Nrf2 in oxidative stress-induced cardiac injury, as well as the regulation of cholesterol uptake and efflux, are required before it can serve as a novel therapeutic target for cardiovascular diseases prevention and treatment.

Oxidative Stress in Cardiovascular Diseases: Involvement of Nrf2 Antioxidant Redox Signaling in Macrophage Foam Cells Formation

Oxidative stress is an important risk factor contributing to the pathogenesis of cardiovascular diseases. Oxidative stress that results from excessive reactive oxygen species (ROS) production accounts for impaired endothelial function, a process which promotes atherosclerotic lesion or fatty streaks formation (foam cells). Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor involved in cellular redox homeostasis. Upon exposure to oxidative stress, Nrf2 is dissociated from its inhibitor Keap-1 and translocated into the nucleus, where it results in the transcriptional activation of cell defense genes. Nrf2 has been demonstrated to be involved in the protection against foam cells formation by regulating the expression of antioxidant proteins (HO-1, Prxs, and GPx1), ATP-binding cassette (ABC) efflux transporters (ABCA1 and ABCG1) and scavenger receptors (scavenger receptor class B (CD36), scavenger receptor class A (SR-A) and lectin-type oxidized LDL receptor (LOX-1)). However, Nrf2 has also been reported to exhibit pro-atherogenic effects. A better understanding on the mechanism of Nrf2 in oxidative stress-induced cardiac injury, as well as the regulation of cholesterol uptake and efflux, are required before it can serve as a novel therapeutic target for cardiovascular diseases prevention and treatment.

Morin hydrate promotes inner ear neural stem cell survival and differentiation and protects cochlea against neuronal hearing loss

We aimed to investigate the effect of morin hydrate on neural stem cells (NSCs) isolated from mouse inner ear and its potential in protecting neuronal hearing loss. 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2‐H‐tetrazolium bromide (MTT) and bromodeoxyuridine incorporation assays were employed to assess the effect of morin hydrate on the viability and proliferation of in vitro NSC culture. The NSCs were then differentiated into neurons, in which neurosphere formation and differentiation were evaluated, followed by neurite outgrowth and neural excitability measurements in the subsequent in vitro neuronal network. Mechanotransduction of cochlea ex vivo culture and auditory brainstem responses threshold and distortion product optoacoustic emissions amplitude in mouse ototoxicity model were also measured following gentamicin treatment to investigate the protective role of morin hydrate against neuronal hearing loss. Morin hydrate improved viability and proliferation, neurosphere formation and neuronal differentiation of inner ear NSCs, and promoted in vitro neuronal network functions. In both ex vivo and in vivo ototoxicity models, morin hydrate prevented gentamicin‐induced neuronal hearing loss. Morin hydrate exhibited potent properties in promoting growth and differentiation of inner ear NSCs into functional neurons and protecting from gentamicin ototoxicity. Our study supports its clinical potential in treating neuronal hearing loss.

Myricetin: A Dietary Molecule with Diverse Biological Activities

Myricetin is a common plant-derived flavonoid and is well recognised for its nutraceuticals value. It is one of the key ingredients of various foods and beverages. The compound exhibits a wide range of activities that include strong anti-oxidant, anticancer, antidiabetic and anti-inflammatory activities. It displays several activities that are related to the central nervous system and numerous studies have suggested that the compound may be beneficial to protect against diseases such as Parkinson's and Alzheimer's. The use of myricetin as a preserving agent to extend the shelf life of foods containing oils and fats is attributed to the compound's ability to protect lipids against oxidation. A detailed search of existing literature revealed that there is currently no comprehensive review available on this important molecule. Hence, the present work includes the history, synthesis, pharmaceutical applications and toxicity studies of myricetin. This report also highlights structure-activity relationships and mechanisms of action for various biological activities.

Morin hydrate attenuates the acrylamide-induced imbalance in antioxidant enzymes in a murine model

Liver diseases are among the most serious health issues nowadays. Hepatocellular carcinoma, one of the most lethal types of cancer worldwide, can be caused by chemically-induced oxidative stress. In the present study, we aimed to evaluate the protective effects of morin hydrate (MH) against acrylamide (AA)-induced hepatotoxicity in male ICR mice. The mice were randomly allocated into 4 groups [the control, the group subcutaneously injected with AA alone (50 mg/kg body weight), the group subcutaneously injected with AA (50 mg/kg body weight) and MH (5 mg/kg body weight) and the group subcutaneously injected with AA (50 mg/kg body weight) and MH (15 mg/kg body weight) for 5 consecutive days]. Histopathological evaluations were performed and the levels of serum hepatic enzymes were analyzed to determine initial liver injury, and the mice in the AA-treated groups were compared with the mice receiving no treatment and with the mice administered MH in combination with AA. Furthermore, oxidative stress, hepatic inflammation and the levels of DNA damage-related markers were evaluated to determine the extent of liver damage induced by AA within a short-term period. The subcutaneous administration of AA induced severe hepatic injury, and combined treatment with AA and MH resulted in a significant improvement in all evaluated parameters. This recovery was most obvious in the group receiving AA and 15 mg/kg body weight dose of MH. The findings of our study demonstrated that MH protected mice from severe hepatic injury induced by AA. Moreover, MH is a natural polyphenolic compound, and thus it has potential for use in the treatment of severe liver diseases, in place of many synthetic drugs.

Eriodictyol Protects Endothelial Cells against Oxidative Stress-Induced Cell Death through Modulating ERK/Nrf2/ARE-Dependent Heme Oxygenase-1 Expression

The pathophysiology of cardiovascular diseases is complex and may involve oxidative stress-related pathways. Eriodictyol is a flavonoid present in citrus fruits that demonstrates anti-inflammatory, anti-cancer, neurotrophic, and antioxidant effects in a range of pathophysiological conditions including vascular diseases. Because oxidative stress plays a key role in the pathogenesis of cardiovascular disease, the present study was designed to verify whether eriodictyol has therapeutic potential. Upregulation of heme oxygenase-1 (HO-1), a phase II detoxifying enzyme, in endothelial cells is considered to be helpful in cardiovascular disease. In this study, human umbilical vein endothelial cells (HUVECs) treated with eriodictyol showed the upregulation of HO-1 through extracellular-regulated kinase (ERK)/nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathways. Further, eriodictyol treatment provided protection against hydrogen peroxide-provoked cell death. This protective effect was eliminated by treatment with a specific inhibitor of HO-1 and RNA interference-mediated knockdown of HO-1 expression. These data demonstrate that eriodictyol induces ERK/Nrf2/ARE-mediated HO-1 upregulation in human endothelial cells, which is directly associated with its vascular protection against oxidative stress-related endothelial injury, and propose that targeting the upregulation of HO-1 is a promising approach for therapeutic intervention in cardiovascular disease.

Antihyperlipidemic effect of fisetin, a bioflavonoid of strawberries, studied in streptozotocin-induced diabetic rats

Chronic hyperglycemia in diabetes is associated with profound changes in lipid and lipoprotein metabolism, with resultant alterations in particle distribution within lipoprotein classes. In the present study, an attempt has been made to explore the antihyperlipidemic effect of fisetin in streptozotocin-induced experimental diabetes in rats. Upon fisetin treatment to diabetic rats, the levels of blood glucose were significantly reduced with an improvement in plasma insulin. The increased levels of lipid contents in serum, hepatic, and renal tissues observed in diabetic rats were normalized upon fisetin administration. Also, the decreased levels of high-density lipoprotein cholesterol, and increased levels of low-density lipoprotein (LDL) and very LDL (VLDL) cholesterol in serum of diabetic rats were normalized. Oil Red O staining established a large number of intracellular lipid droplets accumulation in the diabetic rats. Fisetin treatment exacerbated the degree of lipid accumulation. The results of the present study exemplify the antihyperlipidemic property of the fisetin.

Antiartherosclerotic effects of plant flavonoids

Atherosclerosis is the process of hardening and narrowing the arteries. Atherosclerosis is generally associated with cardiovascular diseases such as strokes, heart attacks, and peripheral vascular diseases. Since the usage of the synthetic drug, statins, leads to various side effects, the plants flavonoids with antiartherosclerotic activity gained much attention and were proven to reduce the risk of atherosclerosis in vitro and in vivo based on different animal models. The flavonoids compounds also exhibit lipid lowering effects and anti-inflammatory and antiatherogenic properties. The future development of flavonoids-based drugs is believed to provide significant effects on atherosclerosis and its related diseases. This paper discusses the antiatherosclerotic effects of selected plant flavonoids such as quercetin, kaempferol, myricetin, rutin, naringenin, catechin, fisetin, and gossypetin.

Immunosuppressive effects of fisetin against dinitrofluorobenzene-induced atopic dermatitis-like symptoms in NC/Nga mice

Atopic dermatitis (AD) is a multifactorial chronic skin disorder that is increasing in prevalence globally. In NC/Nga mice, repetitive epicutaneous applications of 2-4-dinitrofluorobenzene (DNFB) induces AD-like clinical symptoms. Bioflanonol fisetin (3,7,3',4'-tetrahydroxyflavone) is a dietary component found in plants, fruits and vegetables. Fisetin has various physiological effects that include anti-oxidation, anti-angiogenesis, anti-carcinogenesis and anti-inflammation. In this study, we investigated whether fisetin relieves AD-like clinical symptoms induced by repeated DNFB treatment in NC/Nga mice. Fisetin significantly inhibited infiltration of inflammatory cells including eosinophils, mast cells and CD4(+) T and CD8(+) T cells, and suppressed the expressions of cytokines and chemokines associated with dermal infiltrates in AD-like skin lesions. Total serum immunoglobulin E (IgE) levels and the ratio of phospho-NF-κB p65 to total NF-κB p65 were markedly reduced by fisetin. Fisetin also reduced the production of interferon-gamma and interleukin-4 by activated CD4(+) T cells in a dose-dependent manner, whereas the anti-inflammatory cytokine, interleukin-10 was increased. These results implicate fisetin as a potential therapeutic for AD.

Fisetin: a dietary antioxidant for health promotion

SIGNIFICANCE

Diet-derived antioxidants are now being increasingly investigated for their health-promoting effects, including their role in the chemoprevention of cancer. In general, botanical antioxidants have received much attention, as they can be consumed for longer periods of time without any adverse effects. Flavonoids are a broadly distributed class of plant pigments that are regularly consumed in the human diet due to their abundance. One such flavonoid, fisetin (3,3',4',7-tetrahydroxyflavone), is found in various fruits and vegetables, such as strawberry, apple, persimmon, grape, onion, and cucumber.

RECENT ADVANCES

Several studies have demonstrated the effects of fisetin against numerous diseases. It is reported to have neurotrophic, anticarcinogenic, anti-inflammatory, and other health beneficial effects.

CRITICAL ISSUES

Although fisetin has been reported as an anticarcinogenic agent, further in-depth in vitro and in vivo studies are required to delineate the mechanistic basis of its observed effects. In this review article, we describe the multiple effects of fisetin with special emphasis on its anticancer activity as investigated in cell culture and animal models.

FUTURE DIRECTIONS

Additional research focused toward the identification of molecular targets could lead to the development of fisetin as a chemopreventive/chemotherapeutic agent against cancer and other diseases.