Inhibition of platelet aggregation by olive oil phenols via cAMP-phosphodiesterase

The aim of the present study was to confirm that olive oil phenols reduce human platelet aggregability and to verify the hypothesis that cAMP- and cGMP- phosphodiesterases (PDE) could be one of the targets of the biological effect. Four extracts from oils characterized by a high phenol content (HPE), and low phenol levels (LPE) were prepared and analyzed quali- and quantitatively by HPLC-UV and electrospray ionization–MS/MS. Human washed platelets stimulated with thrombin were used for the aggregation assay. Human platelet cAMP-PDE and recombinant PDE5A1 were used as enzyme source. Platelet aggregation and enzyme activity were assayed in the presence of HPE, LPE and individual phenols. The phenol content of HPE ranged between 250 and 500 mg/kg, whereas the LPE content was 46 mg/kg. The compounds identified were hydroxytyrosol (HT), tyrosol (TY), oleuropein aglycone (OleA) and the flavonoids quercetin (QU), luteolin (LU) and apigenin (AP). OleA was the most abundant phenol (range 23·3 to 37·7 %) and LU was the most abundant flavonoid in the extracts. Oil extracts inhibited platelet aggregation with an 50% inhibitory concentration interval of 1·23–11·2 μg/ml. The inhibitory effect of individual compounds (10 μm) including homovanillyl alcohol (HVA) followed this order: OleA>LU>HT = TY = QU = HVA, while AP was inactive. All the extracts inhibited cAMP-PDE, while no significant inhibition of PDE5A1 (50μg/ml) was observed. All the flavonoids and OleA inhibited cAMP-PDE, whereas HT, TY, HVA (100 μm) were inactive. Olive oil extracts and part of its phenolic constituents inhibit platelet aggregation; cAMP-PDE inhibition is one mechanism through which olive oil phenols inhibit platelet aggregation

Ellagitannins of the fruit rind of pomegranate (Punica granatum) antagonize in vitro the host inflammatory response mechanisms involved in the onset of malaria

<p>Abstract</p> <p>Background</p> <p>The sun-dried rind of the immature fruit of pomegranate (<it>Punica granatum</it>) is presently used as a herbal formulation (OMARIA, Orissa Malaria Research Indigenous Attempt) in Orissa, India, for the therapy and prophylaxis of malaria. The pathogenesis of cerebral malaria, a complication of the infection by <it>Plasmodium falciparum</it>, is an inflammatory cytokine-driven disease associated to an up-regulation and activity of metalloproteinase-9 and to the increase of TNF production. The <it>in vitro </it>anti-plasmodial activity of <it>Punica granatum (Pg) </it>was recently described. The aim of the present study was to explore whether the anti-malarial effect of OMARIA could also be sustained via other mechanisms among those associated to the host immune response.</p> <p>Methods</p> <p>From the methanolic extract of the fruit rind, a fraction enriched in tannins (<it>Pg</it>-FET) was prepared. MMP-9 secretion and expression were evaluated in THP-1 cells stimulated with haemozoin or TNF. The assays were conducted in the presence of the <it>Pg</it>-FET and its chemical constituents ellagic acid and punicalagin. The effect of urolithins, the ellagitannin metabolites formed by human intestinal microflora, was also investigated.</p> <p>Results</p> <p><it>Pg</it>-FET and its constituents inhibited the secretion of MMP-9 induced by haemozoin or TNF. The effect occurred at transcriptional level since MMP-9 mRNA levels were lower in the presence of the tested compounds. Urolithins as well inhibited MMP-9 secretion and expression. <it>Pg</it>-FET and pure compounds also inhibited MMP-9 promoter activity and NF-kB-driven transcription.</p> <p>Conclusions</p> <p>The beneficial effect of the fruit rind of <it>Punica granatum </it>for the treatment of malarial disease may be attributed to the anti-parasitic activity and the inhibition of the pro-inflammatory mechanisms involved in the onset of cerebral malaria.</p

In vitro studies on the mechanism of action of two compounds with antiplasmodial activity: ellagic acid and 3,4,5-Trimethoxyphenyl(6?-O-Galloyl)-β-D-glucopyranoside

To investigate the mechanism of action of two antiplasmodial compounds, ellagic acid and 3,4,5-trimethoxyphenyl (6′-O-galloyl)-β-D-glucopyranoside (TMPGG), we studied in vitro two metabolic reactions of intraerythrocytic parasites: the activity of recombinant plasmepsin II, one of the haemoglobin proteases, and the detoxification of haematin into β-haematin. Both compounds inhibited plasmepsin II activity, but at concentrations ten-fold higher than those needed for inhibiting parasite growth. Moreover, ellagic acid inhibited the formation of β-haematin, with an IC50 only 3-fold higher than that of chloroquine. These data suggest that the antiplasmodial activity of ellagic acid could be related to the inhibition of β-haematin formation, whereas plasmepsin II does not represent the main target of the two compounds

Inhibition of metalloproteinase-9 secretion and gene expression by artemisinin derivatives

Malaria remains one of the world's most common infectious diseases, being responsible for more deaths than any other communicable disease except tuberculosis. There is strong evidence that tumour necrosis factor α and interleukin-1β are important contributors to the systemic disease caused by the infection with Plasmodium falciparum. Circulating levels of TNFα are increased after infection, as a consequence of stimulation of monocyte-macrophages by infected red blood cells or parasite products, as shown in vitro for the malaria pigment haemozoin. TNFα in turn enhances the synthesis of metalloproteinase-9 in monocytes and macrophages. Metalloproteinase-9 acts on the extracellular matrix but also on non-traditional substrates, including precursors of inflammatory cytokines, which are proteolytically activated and contribute to the amplification of the inflammatory response. The aim of the present work was to establish whether artemisinin and its derivatives artemisone, artesunate and dihydroartemisinin possess immuno-modulatory properties. In particular, it is necessary to evaluate their effects on mRNA levels and secretion of MMP-9 by the human monocytic cell line (THP-1 cells) stimulated by hemozoin or TNFα. 5. μM of each derivative, although not artemisinin itself, induced significantly inhibited TNFα production. Artesunate, artemisone and DHA antagonized haemozoin-induced MMP-9 secretion by 25%, 24% and 50%, respectively. mRNA levels were also depressed by 14%, 20% and 27%, respectively, thus reflecting in part the effect observed on protein production. The derivatives significantly inhibited both TNFα-induced MMP-9 secretion and mRNA levels to a greater extent than haemozoin itself. Both haemozoin and TNFα increased NF-κB driven transcription by 11 and 7.7 fold, respectively. Artesunate, artemisone and DHA inhibited haemozoin-induced NF-κB driven transcription by 28%, 34%, and 49%, respectively. Similarly the derivatives, but not artemisinin, prevented TNFα-induced NF-κB driven transcription by 47-51%. The study indicates that artemisinins may attenuate the inflammatory potential of monocytes in vivo. Thus, in addition to direct anti-parasitic activities, the beneficial clinical effects of artemisinins for the treatment of malaria include the apparent ability to attenuate the inflammatory response, thus limiting the risk of progression to the more severe form of the disease, including the onset of cerebral malaria. © 2014 Elsevier B.V