Impact of specific functional groups in flavonoids on the modulation of platelet activation

Anti-hemostatic, antithrombotic, and chemical profiles of a curly-leaf variety of Petroselinum crispum (Apiaceae), a food and medicinal aromatic herb

Thrombosis is currently among the major causes of morbidity and mortality in the World. New prevention and therapy alternatives have been increasingly sought in medicinal plants. In this context, we have been investigating parsley, Petroselinum crispum (Mill.) Nym, an aromatic herb with two leaf varieties. We report here the in vitro, in vivo, and ex vivo anti-hemostatic and antithrombotic activities of a parsley curly-leaf variety. Aqueous extracts of aerial parts (PCC-AP), stems (PCC-S), and leaves (PCC-L) showed significant in vitro antiplatelet activity. PCC-AP extract exhibited the highest activity (IC50 2.92 mg/mL) when using ADP and collagen as agonists. All extracts also presented in vitro anticoagulant activity (APTT and PT) and anti-thrombogenic activity. PCC-S was the most active, with more significant interference in the factors of the intrinsic coagulation pathway. The oral administration of PCC-AP extract in rats caused a greater inhibitory activity in the deep vein thrombi (50%; 65 mg/kg) than in arterial thrombi formation (50%; 200 mg/kg), without cumulative effect after consecutive five-day administration. PCC-AP extract was safe in the induced bleeding time test. Its anti-aggregating profile was similar in ex vivo and in vitro conditions but was more effective in the extrinsic pathway when compared to in vitro results. Apiin and coumaric acid derivatives are the main compounds in PCC-AP according to the HPLC-DAD-ESI-MS/MS profile. We demonstrated for the first time that extracts from different parts of curly parsley have significant antiplatelet, anticoagulant, and antithrombotic activity without inducing hemorrhage, proving its potential as a source of antithrombotic compounds.

Plasma proteome profiling reveals molecular mechanisms underlying the effects of daily consumption of 'Bahia' and 'Cara Cara' orange juices

Orange juice is an important food source of bioactive compounds, mainly the flavanones hesperidin and narirutin. This study aimed to investigate the underlying molecular mechanisms of action of orange juice's health properties by analyzing changes in the plasma proteome of healthy Brazilian volunteers after consuming juices made from 'Bahia' (BOJ-source of flavanones) and 'Cara Cara' (CCOJ-source of flavanones and carotenoids) oranges cultivated in Brazil. We used an untargeted proteomic approach, with a particular emphasis on the juices' effects on blood coagulant activity. We identified 247 differentially expressed proteins, of which 170 significantly increased or decreased after BOJ consumption and 145 after CCOJ. These proteins are involved in 105 processes that can significantly regulate cell adhesion, cell signaling, cell metabolism, inflammation, or others. Bioinformatic analysis evidenced proteins with major cellular regulatory capacity (e.g., FN1 and GAPDH) and predicted transcription factors (TFs) (e.g., SP1 and CEBPA) and miRNAs (e.g., miR-1-3p and miR-615-3p) that could be involved in the regulation of differentially expressed proteins. In-silico docking analyses between flavanone metabolites and TFs evidenced the higher binding capacity of narirutin phase II metabolites with akt1 and p38, interactions that suggest how the expression of genes of differentially expressed proteins were activated or inhibited. Moreover, the study shed light on proteins of coagulation cascade that presented expression modulated by both juices, proposing the modulation of blood coagulant activity as a potential benefit of OJ (mainly CCOJ) consumption. Taken together, this study revealed that BOJ and CCOJ consumption affected plasma proteome in healthy individuals, suggesting potential molecular targets and mechanisms of OJ bioactive compounds in humans.

Structural and functional studies reveal the molecular basis of substrate promiscuity of a glycosyltransferase originating from a major agricultural pest

The two-spotted spider mite, Tetranychus urticae, is a major cosmopolitan pest that feeds on more than 1100 plant species. Its genome contains an unprecedentedly large number of genes involved in detoxifying and transporting xenobiotics, including 80 genes that code for UDP glycosyltransferases (UGTs). These enzymes were acquired via horizontal gene transfer from bacteria after loss in the Chelicerata lineage. UGTs are well-known for their role in phase II metabolism; however, their contribution to host adaptation and acaricide resistance in arthropods, such as T. urticae, is not yet resolved. TuUGT202A2 (Tetur22g00270) has been linked to the ability of this pest to adapt to tomato plants. Moreover, it was shown that this enzyme can glycosylate a wide range of flavonoids. To understand this relationship at the molecular level, structural, functional, and computational studies were performed. Structural studies provided specific snapshots of the enzyme in different catalytically relevant stages. The crystal structure of TuUGT202A2 in complex with UDP-glucose was obtained and site-directed mutagenesis paired with molecular dynamic simulations revealed a novel lid-like mechanism involved in the binding of the activated sugar donor. Two additional TuUGT202A2 crystal complexes, UDP-(S)-naringenin and UDP-naringin, demonstrated that this enzyme has a highly plastic and open-ended acceptor-binding site. Overall, this work reveals the molecular basis of substrate promiscuity of TuUGT202A2 and provides novel insights into the structural mechanism of UGTs catalysis.

Development of a Novel Apigenin Dosage form as a Substitute for the Modern Triple Antithrombotic Regimen

The simultaneous administration of three antiplatelet agents has been proposed as an efficient strategy for the secondary prevention of atherothrombotic events and is included in the European guidelines. However, this strategy presented an increased risk of bleeding; therefore, the identification of new antiplatelet agents, with improved efficacy and diminished side effects, is of great importance. In silico studies, UPLC/MS Q-TOF plasma stability, in vitro platelet aggregation experiments, and pharmacokinetic studies were exploited. In the present study, it has been predicted that the flavonoid apigenin could target different platelet activation pathways, including P2Y12, protease-activated receptor-1 (PAR-1), and cyclooxygenase 1 (COX-1). To enhance apigenin's potency, hybridization with docosahexaenoic acid (DHA) was performed, as fatty acids have illustrated potent efficacy against cardiovascular diseases (CVDs). The new molecular hybrid, termed 4'-DHA-apigenin, demonstrated enhanced inhibitory activity against platelet aggregation induced by thrombin receptor activator peptide-6 (TRAP-6), adenosine diphosphate (ADP), and arachidonic acid (AA), with respect to the parent apigenin. The 4'-DHA-apigenin hybrid illustrated an almost 2-fold enhanced inhibitory activity, with respect to apigenin, and an almost 3-fold enhanced inhibitory activity, with respect to DHA, for the ADP-induced platelet aggregation. Additionally, the hybrid presented a more than 12-fold enhanced inhibitory activity with respect to DHA for the TRAP-6 induced platelet aggregation. Furthermore, a 2-fold enhanced inhibitory activity was recorded for the 4'-DHA-apigenin hybrid for the AA-induced platelet aggregation with respect to apigenin. To surmount the reduced LC-MS based plasma stability, a novel dosage form in olive oil has been developed. The 4'-DHA-apigenin olive oil-based formulation presented an enhanced antiplatelet inhibitory effect in three activation pathways. To further explore the pharmacokinetic profile of 4'-DHA-apigenin in olive oil formulations, a UPLC/MS Q-TOF protocol has been established to quantify the serum levels of apigenin after oral administration to C57BL/6J wild type mice. The olive oil-based formulation of 4'-DHA-apigenin demonstrated an increase in apigenin bioavailability of 262 %. This study may offer a new therapeutic strategy tailored to improve the treatment of CVDs.

Structure-Activity Relationship Analysis of Rhosin, a RhoA GTPase Inhibitor, Reveals a New Class of Antiplatelet Agents

Current antiplatelet therapies have several clinical complications and are mostly irreversible in terms of suppressing platelet activity; hence, there is a need to develop improved therapeutic agents. Previous studies have implicated RhoA in platelet activation. Here, we further characterized the lead RhoA inhibitor, Rhosin/G04, in platelet function and present structure-activity relationship (SAR) analysis. A screening for Rhosin/G04 analogs in our chemical library by similarity and substructure searches revealed compounds that showed enhanced antiplatelet activity and suppressed RhoA activity and signaling. A screening for Rhosin/G04 analogs in our chemical library using similarity and substructure searches revealed compounds that showed enhanced antiplatelet activity and suppressed RhoA activity and signaling. SAR analysis revealed that the active compounds have a quinoline group optimally attached to the hydrazine at the 4-position and halogen substituents at the 7- or 8-position. Having indole, methylphenyl, or dichloro-phenyl substituents led to better potency. Rhosin/G04 contains a pair of enantiomers, and S-G04 is significantly more potent than R-G04 in inhibiting RhoA activation and platelet aggregation. Furthermore, the inhibitory effect is reversible, and S-G04 is capable of inhibiting diverse-agonist-stimulated platelet activation. This study identified a new generation of small-molecule RhoA inhibitors, including an enantiomer capable of broadly and reversibly modulating platelet activity.

Effects of Momordica charantia exosomes on platelet activation, adhesion, and aggregation

The platelets play a crucial role in the progression of multiple medical conditions, such as stroke and tumor metastasis, where antiplatelet therapy may be a boon for treating these diseases. In this study, we have attempted to study the effects of extracted Momordica charantia exosomes (MCEs) on platelet activation, adhesion, and aggregation. Adult platelets isolated from healthy individuals were dose-dependently treated with MCEs (0.1, 40, and 200 μg/ml). We performed flow cytometry to detect the expression of platelet activation protein marker-activated GP IIb/IIIa (PAC-1) and P-selectin (CD62P). Platelet adhesion was analyzed through fluorescence labeling assays. The effect of MCEs on platelet-mediated cell migration of HCT116 cells was observed by transwell. Furthermore, the MCAO model of Sprague-Dawley rats was used to observe the effect of MCEs (200, 400, and 800 μg/kg) on platelet aggregation and maximum thrombotic agglutination in vivo. The results showed that 200 μg/ml MCEs exerted the most pronounced effect on platelet activation, adhesion, and aggregation. Experiments on animals showed that MCEs significantly inhibited platelet aggregation and attenuated the maximum thrombus agglutination. We concluded that MCEs inhibited platelet activation, adhesion, aggregation, and platelet-mediated migration of HCT116 cells, indicating the potential role MCEs may play in the treatment of stroke and tumor metastasis.

An ethnopharmacological review on the therapeutical properties of flavonoids and their mechanisms of actions: A comprehensive review based on up to date knowledge

Flavonoids -a class of low molecular weight secondary metabolites- are ubiquitous and cornucopia throughout the plant kingdom. Structurally, the main structure consists of C6-C3-C6 rings with different substitution patterns so that many sub-classes are obtained, for example: flavonols, flavonolignans, flavonoid glycosides, flavans, anthocyanidins, aurones, anthocyanidins, flavones, neoflavonoids, chalcones, isoflavones, flavones and flavanones. Flavonoids are evaluated to have drug like nature since they possess different therapeutic activities, and can act as cardioprotective, antiviral, antidiabetic, anti-inflammatory, antibacterial, anticancer, and also work against Alzheimer's disease and others. However, information on the relationship between their structure and biological activity is scarce. Therefore, the present review tries to summarize all the therapeutic activities of flavonoids, their mechanisms of action and the structure activity relationship.

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Latest updated ethnopharmacological review of the therapeutic effects of flavonoids.

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Flavonoids are attracting attention because of their therapeutic properties.

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Flavonoids are valuable candidates for drug development against many dangerous diseases.

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This overview summarizes the most important therapeutic effect and mechanism of action of flavonoids.

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General knowledge about the structure activity relationship of flavonoids is summarized.

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Substitution of chemical groups in the structure of flavonoids can significantly change their biological and chemical properties.

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The chemical properties of the basic flavonoid structure should be considered in a drug-based structural program.

Phenolic Bioactives as Antiplatelet Aggregation Factors: The Pivotal Ingredients in Maintaining Cardiovascular Health

Cardiovascular diseases (CVD) are one of the main causes of mortality in the world. The development of these diseases has a specific factor-alteration in blood platelet activation. It has been shown that phenolic compounds have antiplatelet aggregation abilities and a positive impact in the management of CVD, exerting prominent antioxidant, anti-inflammatory, antitumor, cardioprotective, antihyperglycemic, and antimicrobial effects. Thus, this review is intended to address the antiplatelet activity of phenolic compounds with special emphasis in preventing CVD, along with the mechanisms of action through which they are able to prevent and treat CVD. In vitro and in vivo studies have shown beneficial effects of phenolic compound-rich plant extracts and isolated compounds against CVD, despite that the scientific literature available on the antiplatelet aggregation ability of phenolic compounds in vivo is scarce. Thus, despite the current advances, further studies are needed to confirm the cardioprotective potential of phenolic compounds towards their use alone or in combination with conventional drugs for effective therapeutic interventions.

Flavonoids as potential anti-platelet aggregation agents: from biochemistry to health promoting abilities

Cardiovascular ailments are the number one cause of mortalities throughout the globe with 17.9 million deaths per year. Platelet activation and aggregation play a crucial role in the pathogenesis of arterial diseases, including acute coronary syndrome, acute myocardial infarction, cerebrovascular transient ischemia, unstable angina, among others. Flavonoids-rich plant extracts are gaining interest for treating the heart-related problems due to safe nature of these herbal extracts. Consumption of plant-food-derived bioactives, particularly flavonoids, has shown antithrombotic, and cardiovascular protective effects due to its anti-platelet activity. Preclinical and clinical trials have proven that flavonoid-rich plant extracts are protective against the cardiac ailments through anti-platelet aggregation activity. This review aims to highlight the anti-platelet aggregation potential of flavonoids with a key emphasis on the therapeutic efficacy in humans. The mechanism of flavonoids in preventing and treating cardiovascular diseases is also highlighted based on preclinical and clinical experimental trials. Further studies are the need of time for exploring the exact molecular mechanism of flavonoids as anti-platelet aggregation agents for treating heart-related problems.

Astragalin Inhibits Cigarette Smoke-Induced Pulmonary Thrombosis and Alveolar Inflammation and Disrupts PAR Activation and Oxidative Stress-Responsive MAPK-Signaling

Epidemiological evidence shows that smoking causes a thrombophilic milieu that may play a role in the pathophysiology of chronic obstructive pulmonary disease (COPD) as well as pulmonary thromboembolism. The increased nicotine level induces a prothrombotic status and abnormal blood coagulation in smokers. Since several anticoagulants increase bleeding risk, alternative therapies need to be identified to protect against thrombosis without affecting hemostasis. Astragalin is a flavonoid present in persimmon leaves and green tea seeds and exhibits diverse activities of antioxidant and anti-inflammation. The current study investigated that astragalin attenuated smoking-induced pulmonary thrombosis and alveolar inflammation. In addition, it was explored that molecular links between thrombosis and inflammation entailed protease-activated receptor (PAR) activation and oxidative stress-responsive mitogen-activated protein kinase (MAPK)-signaling. BALB/c mice were orally administrated with 10-20 mg/kg astragalin and exposed to cigarette smoke for 8 weeks. For the in vitro study, 10 U/mL thrombin was added to alveolar epithelial A549 cells in the presence of 1-20 µM astragalin. The cigarette smoking-induced the expression of PAR-1 and PAR-2 in lung tissues, which was attenuated by the administration of ≥10 mg/kg astragalin. The oral supplementation of ≥10 mg/kg astragalin to cigarette smoke-challenged mice attenuated the protein induction of urokinase plasminogen activator, plasminogen activator inhibitor-1and tissue factor, and instead enhanced the induction of tissue plasminogen activator in lung tissues. The astragalin treatment alleviated cigarette smoke-induced lung emphysema and pulmonary thrombosis. Astragalin caused lymphocytosis and neutrophilia in bronchoalveolar lavage fluid due to cigarette smoke but curtailed infiltration of neutrophils and macrophages in airways. Furthermore, this compound retarded thrombin-induced activation of PAR proteins and expression of inflammatory mediators in alveolar cells. Treating astragalin interrupted PAR proteins-activated reactive oxygen species production and MAPK signaling leading to alveolar inflammation. Accordingly, astragalin may interrupt the smoking-induced oxidative stress-MAPK signaling-inflammation axis via disconnection between alveolar PAR activation and pulmonary thromboembolism.

A review of in vitro studies of the anti-platelet potential of citrus fruit flavonoids

The citrus plants of the Rutaceae, such as oranges, grapefruits and mandarins, are cultivated worldwide. Their fruits and their juices are rich sources of flavonoids: for example, hesperidin and narirutin in oranges, and narirutin and naringin in grapefruits. Although these flavonoids have been found to potentially modulate blood platelet activity, most studies have been performed in vitro; in addition, the body of evidence regarding antiplatelet activity is relatively weak and the exact mechanisms remain poorly understood. More importantly, the concentrations of flavonoids studied in vitro (i.e. 3.125-300 μM) with washed blood platelets did not always correspond with their physiological concentrations in vivo, i.e. in whole blood after oral administration, and citrus fruit flavonoids are also characterized by low bioavailability. Therefore, more detailed studies on the antiplatelet potential of citrus flavonoids are needed, especially in in vivo models.

Synthesis and pharmacological evaluation of acylhydroquinone derivatives as potent antiplatelet agents

Platelets are the smallest blood cells, and their activation (platelet cohesion or aggregation) at sites of vascular injury is essential for thrombus formation. Since the use of antiplatelet therapy is an unsolved problem, there are now focused and innovative efforts to develop novel antiplatelet compounds. In this context, we assessed the antiplatelet effect of an acylhydroquinone series, synthesized by Fries rearrangement under microwave irradiation, evaluating the effect of diverse acyl chain lengths, their chlorinated derivatives, and their dimethylated derivatives both in the aromatic ring and also the effect of the introduction of a bromine atom at the terminus of the acyl chain. Findings from a primary screening of cytotoxic activity on platelets by lactate dehydrogenase assay identified 19 non-toxic compounds from the 27 acylhydroquinones evaluated. A large number of them showed IC₅₀ values less than 10 µM acting against specific pathways of platelet aggregation. The highest activity was obtained with compound 38, it exhibited sub-micromolar IC₅₀ of 0.98 ± 0.40, 1.10 ± 0.26, 3.98 ± 0.46, 6.79 ± 3.02 and 42.01 ± 3.48 µM against convulxin-, collagen-, TRAP-6-, PMA- and arachidonic acid-induced platelet aggregation, respectively. It also inhibited P-selectin and granulophysin expression. We demonstrated that the antiplatelet mechanism of compound 38 was through a decrease in a central target in human platelet activation as in mitochondrial function, and this could modulate a lower response of platelets to activating agonists. The results of this study show that the chemical space around ortho-carbonyl hydroquinone moiety is a rich source of biologically active compounds, signaling that the acylhydroquinone scaffold has a promising role in antiplatelet drug research.

Catechin and epicatechin as an adjuvant in the therapy of hemostasis disorders induced by snake venoms

Snake toxins, such as phospholipases A₂ and proteases, are used as research tools to evaluate biological activities and to understand physiopathological processes of natural compounds better. In the present study, the phenolic compounds catechin and epicatechin were incubated with snake venoms to evaluate their inhibition against different substrates. Catechin and epicatechin exerted inhibitions between 20% and 95% on the activity of phospholipases A₂ present in the venom of Bothrops alternatus. In the hemolytic activity, catechin exerted inhibitions between 20% and 25% in all proportions evaluated on the B. jararacussu venom, whereas epicatechin inhibited 20% of the venom activity. Coagulation induced by B. atrox and B. jararacussu venoms was significantly inhibited by catechin and epicatechin, where the time for coagulation was two to three times higher after previous incubation of the venoms with the compounds. The most significant inhibitions for the proteolytic activity on casein were 17% and 27%, respectively, by both compounds. Catechin inhibited serine protease activity induced by B. atrox venom by 64% and epicatechin by 65%. Regarding B. atrox-induced thrombolysis, catechin exerted 40% inhibition and epicatechin around 30%. The fibrinogen proteolysis was completely inhibited by catechin acting on the B. atrox venom in the proportion of 1:1 and by epicatechin on B. jararacussu venom. Catechin and epicatechin showed promising inhibitory action on proteases and phospholipases A₂ . Therefore, these compounds can be explored as an adjuvant for serum therapy or pharmaceutical purposes, once they act on homologous enzymes that are present in humans.

Anti-platelet role of Korean ginseng and ginsenosides in cardiovascular diseases

Cardiovascular diseases prevail among modern societies and underdeveloped countries, and a high mortality rate has also been reported by the World Health Organization affecting millions of people worldwide. Hyperactive platelets are the major culprits in thrombotic disorders. A group of drugs is available to deal with such platelet-related disorders; however, sometimes, side effects and complications caused by these drugs outweigh their benefits. Ginseng and its nutraceuticals have been reported to reduce the impact of thrombotic conditions and improve cardiovascular health by antiplatelet mechanisms. This review provides (1) a comprehensive insight into the available pharmacological options from ginseng and ginsenosides (saponin and nonsaponin fractions) for platelet-originated cardiovascular disorders; (2) a discussion on the impact of specific functional groups on the modulation of platelet functions and how structural modifications among ginsenosides affect platelet activation, which may further provide a basis for drug design, optimization, and the development of ginsenoside scaffolds as pharmacological antiplatelet agents; (3) an insight into the synergistic effects of ginsenosides on platelet functions; and (4) a perspective on future research and the development of ginseng and ginsenosides as super nutraceuticals.

Effect of ultrapure lipopolysaccharides derived from diverse bacterial species on the modulation of platelet activation

Platelets are small circulating blood cells that play essential roles in the maintenance of haemostasis via blood clotting. However, they also play critical roles in the regulation of innate immune responses. Inflammatory receptors, specifically Toll-like receptor (TLR)-4, have been reported to modify platelet reactivity. A plethora of studies have reported controversial functions of TLR4 in the modulation of platelet function using various chemotypes and preparations of its ligand, lipopolysaccharide (LPS). The method of preparation of LPS may explain these discrepancies however this is not fully understood. Hence, to determine the impact of LPS on platelet activation, we used ultrapure preparations of LPS from Escherichia coli (LPS_EC), Salmonella minnesota (LPS_SM), and Rhodobacter sphaeroides (LPS_RS) and examined their actions under diverse experimental conditions in human platelets. LPS_EC did not affect platelet activation markers such as inside-out signalling to integrin α_IIbβ₃ or P-selectin exposure upon agonist-induced activation in platelet-rich plasma or whole blood whereas LPS_SM and LPS_RS inhibited platelet activation under specific conditions at supraphysiological concentrations. Overall, our data demonstrate that platelet activation is not largely influenced by any of the ultrapure LPS chemotypes used in this study on their own except under certain conditions.

Isorhapontigenin, a resveratrol analogue selectively inhibits ADP-stimulated platelet activation

Isorhapontigenin is a polyphenolic compound found in Chinese herbs and grapes. It is a methoxylated analogue of a stilbenoid, resveratrol, which is well-known for its various beneficial effects including anti-platelet activity. Isorhapontigenin possesses greater oral bioavailability than resveratrol and has also been identified to possess anti-cancer and anti-inflammatory properties. However, its effects on platelet function have not been reported previously. In this study, we report the effects of isorhapontigenin on the modulation of platelet function. Isorhapontigenin was found to selectively inhibit ADP-induced platelet aggregation with an IC₅₀ of 1.85 μM although it displayed marginal inhibition on platelet aggregation induced by other platelet agonists at 100 μM. However, resveratrol exhibited weaker inhibition on ADP-induced platelet aggregation (IC₅₀ > 100 μM) but inhibited collagen induced platelet aggregation at 50 μM and 100 μM. Isorhapontigenin also inhibited integrin αIIbβ3 mediated inside-out and outside-in signalling and dense granule secretion in ADP-induced platelet activation but interestingly, no effect was observed on α-granule secretion. Isorhapontigenin did not exert any cytotoxicity on platelets at the concentrations of up to 100 μM. Furthermore, it did not affect haemostasis in mice at the IC₅₀ concentration (1.85 μM). In addition, the mechanistic studies demonstrated that isorhapontigenin increased cAMP levels and VASP phosphorylation at Ser157 and decreased Akt phosphorylation. This suggests that isorhapontigenin may interfere with cAMP and PI3K signalling pathways that are associated with the P2Y₁₂ receptor. Molecular docking studies emphasised that isorhapontigenin has greater binding affinity to P2Y₁₂ receptor than resveratrol. Our results demonstrate that isorhapontigenin has selective inhibitory effects on ADP-stimulated platelet activation possibly via P2Y₁₂ receptor.

Synthetic Flavonoids as Novel Modulators of Platelet Function and Thrombosis

Cardiovascular diseases represent a major cause of mortality and morbidity in the world, and specifically, thrombotic conditions such as heart attacks and strokes are caused by unwarranted activation of platelets and subsequent formation of blood clots (thrombi) within the blood vessels during pathological circumstances. Therefore, platelets act as a primary therapeutic target to treat and prevent thrombotic conditions. Current treatments are limited due to intolerance, and they are associated with severe side effects such as bleeding complications. Hence, the development of novel therapeutic strategies for thrombotic diseases is an urgent priority. Flavonoids are naturally occurring plant-derived molecules that exert numerous beneficial effects in humans through modulating the functions of distinct cell types. However, naturally occurring flavonoids suffer from several issues such as poor solubility, lipophilicity, and bioavailability, which hinder their efficacy and potency. Despite these, flavonoids act as versatile templates for the design and synthesis of novel molecules for various therapeutic targets. Indeed, several synthetic flavonoids have recently been developed to improve their stability, bioavailability, and efficacy, including for the modulation of platelet function. Here, we provide insight into the actions of certain natural flavonoids along with the advantages of synthetic flavonoids in the modulation of platelet function, haemostasis, and thrombosis.

Beneficial Effects of Citrus Flavonoids on Cardiovascular and Metabolic Health

The prevalence of cardiovascular disease (CVD) is increasing over time. CVD is a comorbidity in diabetes and contributes to premature death. Citrus flavonoids possess several biological activities and have emerged as efficient therapeutics for the treatment of CVD. Citrus flavonoids scavenge free radicals, improve glucose tolerance and insulin sensitivity, modulate lipid metabolism and adipocyte differentiation, suppress inflammation and apoptosis, and improve endothelial dysfunction. The intake of citrus flavonoids has been associated with improved cardiovascular outcomes. Although citrus flavonoids exerted multiple beneficial effects, their mechanisms of action are not completely established. In this review, we summarized recent findings and advances in understanding the mechanisms underlying the protective effects of citrus flavonoids against oxidative stress, inflammation, diabetes, dyslipidemia, endothelial dysfunction, and atherosclerosis. Further studies and clinical trials to assess the efficacy and to explore the underlying mechanism(s) of action of citrus flavonoids are recommended.

The endogenous antimicrobial cathelicidin LL37 induces platelet activation and augments thrombus formation

Platelet-associated complications including thrombosis, thrombocytopenia, and hemorrhage are commonly observed during various inflammatory diseases such as sepsis, inflammatory bowel disease, and psoriasis. Despite the reported evidence on numerous mechanisms/molecules that may contribute to the dysfunction of platelets, the primary mechanisms that underpin platelet-associated complications during inflammatory diseases are not fully established. Here, we report the discovery of formyl peptide receptor 2, FPR2/ALX, in platelets and its primary role in the development of platelet-associated complications via ligation with its ligand, LL37. LL37 acts as a powerful endogenous antimicrobial peptide, but it also regulates innate immune responses. We demonstrate the impact of LL37 in the modulation of platelet reactivity, hemostasis, and thrombosis. LL37 activates a range of platelet functions, enhances thrombus formation, and shortens the tail bleeding time in mice. By utilizing a pharmacological inhibitor and Fpr2/3 (an ortholog of human FPR2/ALX)-deficient mice, the functional dependence of LL37 on FPR2/ALX was determined. Because the level of LL37 is increased in numerous inflammatory diseases, these results point toward a critical role for LL37 and FPR2/ALX in the development of platelet-related complications in such diseases. Hence, a better understanding of the clinical relevance of LL37 and FPR2/ALX in diverse pathophysiological settings will pave the way for the development of improved therapeutic strategies for a range of thromboinflammatory diseases.