Potentiation of antiaggregating effect of prostaglandins by alpha-tocopherol and quercetin

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.

Inhibition of platelet activation using vitamins

Some vitamins have beneficial effects on cardiovascular diseases, normalizing platelet function and preventing their excess activation. Anti-platelet vitamins can act directly through inhibitory biochemical pathways in platelets or indirectly by preventing damage to the endothelium or low-density lipoprotein from oxidation. As a rule, each vitamin alone is a weak inhibitor of platelet aggregation. However, in combination, they may act synergistically or enhance the effects of endogenous anti-platelet compounds, such as prostacyclin or nitric oxide, and appear to have a sufficient anti-thrombotic effect. This review will focus on vitamins, which inhibit platelet activation and the mechanisms of their action. The relationship between the vitamins that inhibit platelet aggregation and vascular diseases is examined.

Alterations in the extracellular catabolism of nucleotides and platelet aggregation induced by high-fat diet in rats: effects of α-tocopherol

The aim of this study was to assess whether α-tocopherol administration prevented alterations in the ectonucleotidase activities and platelet aggregation induced by high-fat diet in rats. Thus, we examined four groups of male rats which received standard diet, high-fat diet (HFD), α-tocopherol (α-Toc), and high-fat diet plus α-tocopherol. HFD was administered ad libitum and α-Toc by gavage using a dose of 50 mg/kg. After 3 months of treatment, animals were submitted to euthanasia, and blood samples were collected for biochemical assays. Results demonstrate that NTPDase, ectonucleotide pyrophosphatase/phosphodiesterase, and 5'-nucleotidase activities were significantly decreased in platelets of HFD group, while that adenosine deaminase (ADA) activity was significantly increased in this group in comparison to the other groups (P < 0.05). When rats that received HFD were treated with α-Toc, the activities of these enzymes were similar to the control, but ADA activity was significantly increased in relation to the control and α-Toc group (P < 0.05). HFD group showed an increased in platelet aggregation in comparison to the other groups, and treatment with α-Toc significantly reduced platelet aggregation in this group. These findings demonstrated that HFD alters platelet aggregation and purinergic signaling in the platelets and that treatment with α-Toc was capable of modulating the adenine nucleotide hydrolysis in this experimental condition.

Quercetin: potentials in the prevention and therapy of disease

PURPOSE OF REVIEW

Quercetin is discussed since several decades as a multipotent bioflavonoid with great potential for the prevention and treatment of disease. In the current review, we present the most recent findings on quercetin with regard to the pharmacology, the in-vitro and in-vivo effects in different cell systems and animal models, and the clinical effects in humans.

RECENT FINDINGS

Quercetin bioavailability has been underestimated in the past and can be improved by food matrix components or particular delivery forms. Among the biological effects of particular relevance, the antihypertensive effects of quercetin in humans and the improvement of endothelial function should be emphasized. Together with its antithrombotic and anti-inflammatory effects, the latter mainly mediated through the inhibition of cytokines and nitric oxide, quercetin is a candidate for preventing obesity-related diseases. Most exiting are the findings that quercetin enhances physical power by yet unclear mechanisms. The anti-infectious and immunomodulatory activities of quercetin might be related to this effect.

SUMMARY

Quercetin is a most promising compound for disease prevention and therapy; however, many of the effects still need confirmation by human intervention trials.

Prostaglandin E1 versus steroid in combination with hyperbaric oxygen therapy for idiopathic sudden sensorineural hearing loss

OBJECTIVE

We conducted a controlled retrospective analysis of patients with idiopathic sudden sensorineural hearing loss (ISSNHL) in order to investigate the effect of prostaglandin E1 (PGE1) plus hyperbaric oxygen (HBO) therapy in comparison with that of steroid plus HBO therapy.

METHODS

One hundred and ninety-six consecutive patients with ISSNHL (hearing levels > or ==40dB; time from the onset of hearing loss to the start of treatment < or ==30 days) were enrolled. Ninety-five patients underwent PGE1 plus HBO therapy (PG group) and 101 underwent steroid administration plus HBO therapy (steroid group). Hearing recovery was evaluated by grade assessment and by the improvement in hearing compared to the unaffected contralateral ear.

RESULTS

The hearing levels after treatment were 52.2+/-3.0 and 47.5+/-2.8dB, the hearing gains were 31.3+/-2.2 and 27.2+/-2.3dB, the cure rates were 28.4% and 28.7%, the recovery rates were 54.7% and 53.5%, and the hearing improvement rates were 48.4+/-5.1% and 53.9+/-4.2% in the PG and steroid groups, respectively. There were no significant differences between the two groups.

CONCLUSION

We concluded that PGE1 and a steroid are equally effective in the treatment of ISSNHL when used together with HBO therapy. PGE1 plus HBO therapy can be one of the potential alternative treatments for ISSNHL, particularly in steroid-intolerant patients such as those with severe diabetes mellitus, an active peptic ulcer, or viral hepatitis.

Lipoprotein-associated proteins involved in platelet signaling

Platelets and lipoproteins are both key elements in the development of atherosclerosis and thrombosis. Based on their density, five classes of lipoproteins have been identified which all influence platelets via distinct mechanisms. The activation of platelets starts with binding of apolipoproteins to different platelet receptors and is followed by the activation of signaling pathways resulting in activation or inhibition of platelet functions like aggregation or secretion. In addition to apolipoproteins, lipoproteins are also associated to a large amount of proteins, enzymes and lipids that also can induce platelet activation or inhibition. This review provides a summary of the activation of signaling pathways after platelet-lipoprotein interactions initiated by lipoprotein-associated proteins and lipids.

Quercetin reverses D-galactose induced neurotoxicity in mouse brain

We assessed the neuroprotective effects of quercetin-feeding at doses of 5 and 10 mg/(kg day) on Kunming mice injected daily with D-gal (50 mg/(kg day)) by behavioral tests. Quercetin-fed mice showed higher activity upon induction by new environmental stimuli, lower anxiety and higher novelty-seeking behavior in the open field tasks, and significantly improved learning and memory ability in step-through and Morris water Maze tests compared with D-gal-treated mice. We further investigated the mechanisms involved in the neuroprotective effects of quercetin on mouse brain. Quercetin significantly increased superoxide dismutase (SOD) activity and decreased the malondialdehyde (MDA) level. These results imply that quercetin can reverse oxidant impairment induced by D-gal in mouse brain. Neurotoxicity is also associated with Ca(2+) overload induced by oxidant stress. Quercetin could maintain the Ca(2+) homeostasis in the brain of D-gal-treated mice. Furthermore, we also examined the expression of growth-associated protein GAP43 mRNA in mouse brain by in situ hybridization. We found that quercetin dramatically elevated the GAP43 mRNA expression in the brain of D-gal-treated mice to regenerate normal function of neurons against the cellular injury caused by D-gal.

A prothrombin activator (Lopap) modulating inflammation, coagulation and cell survival mechanisms

A severe hemorrhagic syndrome produced by contact with Lonomia obliqua caterpillars has become epidemic in southern Brazil. A significant thrombin production with intense consumption of fibrinogen and high D-dimer production indicates a consumption coagulopathy and secondary fibrinolysis in patients. Lopap is a single-chain 69kDa serine protease isolated from the crude extract of L. obliqua bristles. Experiments in mice showed that the purified protein, similar to the crude extract, causes uncoagulable blood by fibrinogen depletion. In order to characterize the effects of Lopap on cells involved with hemostatic system, we performed experiments using human umbilical vein endothelial cells (HUVECs). Our results show that Lopap exerts a direct effect on endothelial cells by increasing the liberation of molecules involved in the regulation of vascular tone, inhibiting platelet activation and chemotaxis, apart from inducing the expression of cell adhesion molecules which participate in inflammatory responses. The release or new synthesis of mediators involved in coagulation as von Willebrand factor and tissue factor, or in fibrinolysis as tissue plasminogen activator, was not affected by Lopap. Also our results demonstrated that Lopap acts on cell survival of HUVECs, regulating the expression of molecules as NO and avoiding cell death.

Quercetin, but not rutin and quercitrin, prevention of H2O2-induced apoptosis via anti-oxidant activity and heme oxygenase 1 gene expression in macrophages

In the present study, we examine the protective mechanism of quercetin (QE) on oxidative stress-induced cytotoxic effect in RAW264.7 macrophages. Results of Western blotting show that QE but not its glycoside rutin (RUT) and quicitrin-induced HO-1 protein expression in a time- and dose-dependent manner, and HO-1 protein induced by QE was blocked by an addition of cycloheximide or actinomycin D. Induction of HO-1 gene expression by QE was accompanied by inducing ERKs, but not JNKs or p38, proteins phosphorylation. Addition of PD98059, but not SB203580 or SP600125, significantly attenuates QE-induced HO-1 protein and mRNA expression associated with blocking the expression of phosphorylated ERKs proteins. H(2)O(2) addition reduces the viability of cells by MTT assay, and appearance of DNA ladders, hypodiploid cells, and an increase in intracellular peroxide level was detected. Addition of QE, but not QI or RUT, significantly reduced the cytotoxic effect induced by H(2)O(2) associated with blocking the production of intracellular peroxide, DNA ladders, and hypodiploid cells. QE protection of cells from H(2)O(2)-induced apoptosis was significantly suppressed by adding HO inhibitor SnPP or ERKs inhibitor PD98059. Additionally, QE protects cells from H(2)O(2)-induced a decrease in the mitochondrial membrane potential and a release of cytochrome c from mitochondria to cytosol by DiOC6 and Western blotting assay, respectively. Activation of apoptotic proteins including the caspase 3, caspase 9, PARP, D4-GDI proteins was identified in H(2)O(2)-treated cells by Western blotting and enzyme activity assay, and that was significantly blocked by an addition of QE, but not RUT and QI. Furthermore, HO-1 catalytic metabolites carbon monoxide (CO), but not Fe(2+), Fe(3+), biliverdin or bilirubin, performed protective effect on cells from H(2)O(2)-induced cell death with an increase in HO-1 protein expression and ERKs protein phosphorylation. These data suggest that induction of HO-1 protein may participate in the protective mechanism of QE on oxidative stress (H(2)O(2))-induced apoptosis, and reduction of intracellular ROS production and mitochondria dysfunction with blocking apoptotic events were involved. Differential anti-apoptotic effect between QE and its glycosides RUT and QI via distinct HO-1 protein induction was also delineated.

The snake venom metalloproteases berythractivase and jararhagin activate endothelial cells

PIII snake venom metalloproteases (SVMPs) are metalloproteases structurally related to ADAMs (a disintegrin and metalloprotease human family of proteins). Berythractivase and jararhagin are PIII SVMPs with 69% homology that have different hemostatic properties. In order to clarify these differences and further characterize the biological effects of these proteins, we have analyzed the effect of both proteases on human umbilical-vein endothelial cell functions. We found that both proteins enhanced nitric oxide generation, prostacyclin production and interleukin-8 release. Berythractivase but not jararhagin increased the expression of decay accelerating factor. Jararhagin decreased cell viability in a concentration-dependent manner and induced cellular apoptosis, while berythractivase did not modulate cell survival. Our results show for the first time that, besides the known anti-aggregating or procoagulant effects of PIII SVMPs, these proteins trigger endothelial cell effector responses. Although structurally related, berythractivase and jararhagin induce a dissimilar generation and release of endothelial molecules that may account for their different hemorrhagic activity.