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Search Results: 1 - 10 of 462262 matches for " Constantinos A. Demopoulos "
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Evaluation of Sensory and in Vitro Cardio Protective Properties of Sardine (Sardina pilchardus): The Effect of Grilling and Brining  [PDF]
Constantina Nasopoulou, Evangelia Psani, Eleni Sioriki, Constantinos A. Demopoulos, Ioannis Zabetakis
Food and Nutrition Sciences (FNS) , 2013, DOI: 10.4236/fns.2013.49122

The aim of this study was to investigate the effect of grilling and brining on the sensory properties, the fillet fatty acid composition and the cardio-protective activity of sardine (Sardina pilchardus), studying the in vitro activity against Platelet-Activating-Factor (PAF) induced platelet aggregation. Sensory evaluation of grilled and brined sardine showed that grilled sardine had higher scores for the attributes: grilled fish, marine and fresh fish whereas brined sardine had higher scores for the attributes: salty, iodine, oily and bitter. Grilled sardine exhibited significantly increased fillet fatty acid content while the brined fish sample significantly decreased fatty acid levels. Polar lipids of all specimens (raw, grilled and brined) showed strong inhibitory activity against PAF action indicating that grilling and brining have not diminished the cardio-protective properties of sardine.

Structurally Diverse Metal Coordination Compounds, Bearing Imidodiphosphinate and Diphosphinoamine Ligands, as Potential Inhibitors of the Platelet Activating Factor
Alexandros B. Tsoupras,Maria Roulia,Eleftherios Ferentinos,Ioannis Stamatopoulos,Constantinos A. Demopoulos,Panayotis Kyritsis
Bioinorganic Chemistry and Applications , 2010, DOI: 10.1155/2010/731202
Abstract: Metal complexes bearing dichalcogenated imidodiphosphinate ligands (E = O, S, Se, Te), which act as (E,E) chelates, exhibit a remarkable variety of three-dimensional structures. A series of such complexes, namely, square-planar , tetrahedral , E = O, S, and octahedral , were tested as potential inhibitors of either the platelet activating factor (PAF)- or thrombin-induced aggregation in both washed rabbit platelets and rabbit platelet rich plasma. For comparison, square-planar , X = Cl, Br, the corresponding metal salts of all complexes and the ligand were also investigated. showed the highest anti-PAF activity but did not inhibit the thrombin-related pathway, whereas , with also a significant PAF inhibitory effect, exhibited the highest thrombin-related inhibition. and inhibited moderately both PAF and thrombin, being more effective towards PAF. This work shows that the PAF-inhibitory action depends on the structure of the complexes studied, with the bulkier being the most efficient and selective inhibitor. 1. Introduction Extensive research work over the last few years has revealed a remarkable structural variability of transition metal compounds bearing dichalcogenated imidodiphosphinate type of ligands, that is, , E = O, S, Se, Te; R, = various aryl or alkyl groups. These ligands have been shown to display great coordinating versatility, producing both single and multinuclear metal complexes, with a variety of bonding modes [1–3]. The coordinating flexibility of these (E,E) chelating ligands is attributed, mainly, to their large ( 4??) E E?bite, which would accommodate a range of coordination sphere geometries. For instance, it was recently shown that the [ P(Se)NP(Se) ligand affords both tetrahedral and square-planar complexes of Ni(II) [4], in agreement with an earlier observation on the analogous [Ph2P(S)NP(S)Ph2 ligand [5]. Moreover, the nature of the R and peripheral groups of the [R2P(S)NP(S) ligand has been shown to affect the geometry of the complexes formed upon its coordination to Ni(II) [6, 7]. In a more general sense, depending on the nature of the metal ion, the chalcogen E atom and the R peripheral group, complexes bearing the above type of ligands were shown to contain rather diverse coordination spheres [8]. Such structural differences are of significant importance, as they are expected to lead not only to different stereochemical characteristics, but also to varied electronic properties of the metal site, which, in turn, could potentially result in significant biological reactivity [9]. The aim of this work was to investigate a
Hydroxyl-platelet-activating factor exists in blood of healthy volunteers and periodontal patients
Smaragdi Antonopoulou,Alexandros Tsoupras,George Baltas,Helen Kotsifaki,Zacharias Mantzavinos,Constantinos A. Demopoulos
Mediators of Inflammation , 2003, DOI: 10.1080/09629350310001599666
Abstract: Periodontal diseases are localized chronic inflammatory conditions of the gingival and underlying bone and connective tissue. Platelet-activating factor (PAF), a potent inflammatory phospholipid mediator that has been previously detected in elevated levels in inflamed gingival tissues, in gingival crevicular fluid and in saliva, is implicated in periodontal disease. Our results from previous studies showed that the biologically active phospholipid detected in gingival crevicular fluid is a hydroxyl-PAF analogue. In this study, hydroxyl-PAF analogue was detected for the first time in human blood derived from patients with chronic periodontitis as well as from periodontally healthy volunteers. The hydroxyl-PAF analogue was purified by high-performance liquid chromatography, detected by biological assays and identified by electrospray analysis. In addition, the quantitative determination of PAF and hydroxyl-PAF analogue (expressed as PAF-like activity) showed a statistically significant increase in the ratio of hydroxyl-PAF analogue levels to PAF levels in periodontal patients, suggesting that this bioactive lipid may play a role in oral inflammation.
Fish polar lipids retard atherosclerosis in rabbits by down-regulating PAF biosynthesis and up-regulating PAF catabolism
Constantina Nasopoulou, Alexandros B Tsoupras, Haralabos C Karantonis, Constantinos A Demopoulos, Ioannis Zabetakis
Lipids in Health and Disease , 2011, DOI: 10.1186/1476-511x-10-213
Abstract: The specific activities of four PAF metabolic enzymes; in leukocytes, platelets and plasma, and PAF concentration; either in blood cells or plasma were determined. Samples were acquired at the beginning and at the end of a previously conducted study in male New Zealand white rabbits that were fed for 45 days with atherogenic diet supplemented (group-B, n = 6) or not (group-A, n = 6) with gilthead sea bream (Sparus aurata) polar lipids.The specific activity of PAF-Acetylhydrolase (PAF-AH); a catabolic enzyme of PAF, was decreased in rabbits' platelets of both A and B groups and in rabbits' leukocytes of group A (p < 0.05). On the other hand the specific activity of Lipoprotein-associated Phospholipase A2 (Lp-PLA2); the catabolic enzyme of PAF in plasma was increased in both A and B groups in both leukocytes and platelets (p < 0.05). PAF-cholinephosphotransferase (PAF-CPT); a biosynthetic enzyme of PAF showed increased specific activity only in rabbits' leukocytes of group A (p < 0.05). Neither of the two groups showed any change in Lyso-PAF-acetyltransferase (Lyso-PAF-AT) specific activity (p > 0.05). Free and bound PAF levels increased in group A while decreased in group B (p < 0.05).Gilthead sea bream (Sparus aurata) polar lipids modulate PAF metabolism upon atherosclerotic conditions in rabbits leading to lower PAF levels and activity in blood of rabbits with reduced early atherosclerotic lesions compared to control group.Platelet Activating Factor (PAF) [1] has been proposed as key factor in atherosclerosis development [2]. Dysregulation of PAF metabolism, lead to increased PAF-levels and triggers local inflammatory response onto the endothelium of arteries [2] with prominent role in atherogenesis [3,4].The biosynthesis of PAF is accomplished through two distinctive enzymatic pathways; the de novo pathway; catalyzed by a specific dithiothreitol-insensitive CDP-choline: 1-alkyl-2-acetyl-sn-glycerol cholinephosphotransferase (PAF-cholinephosphotransferase; PAF-CPT,
Evaluation of the in Vitro Anti-Atherogenic Properties of Lipid Fractions of Olive Pomace, Olive Pomace Enriched Fish Feed and Gilthead Sea Bream (Sparus aurata) Fed with Olive Pomace Enriched Fish Feed
Constantina Nasopoulou,Vassiliki Gogaki,Giorgos Stamatakis,Leonidas Papaharisis,Constantinos A. Demopoulos,Ioannis Zabetakis
Marine Drugs , 2013, DOI: 10.3390/md11103676
Abstract: Given the pivotal role of Platelet-Activating-Factor (PAF) in atherosclerosis and the cardio-protective role of PAF-inhibitors derived from olive pomace, the inclusion of olive pomace in fish feed has been studied for gilthead sea bream ( Sparus aurata). The aim of the current research was to elucidate the anti-atherogenic properties of specific HPLC lipid fractions obtained from olive pomace, olive pomace enriched fish feed and fish fed with the olive pomace enriched fish feed, by evaluating their in vitro biological activity against washed rabbit platelets. This in vitro study underlines that olive pomace inclusion in fish feed improves the nutritional value of both fish feed and fish possibly by enriching the marine lipid profile of gilthead sea bream ( Sparus aurata) with specific bioactive lipid compounds of plant origin.
Antithrombotic and Antiatherosclerotic Properties of Olive Oil and Olive Pomace Polar Extracts in Rabbits
Nektaria Tsantila,Haralabos C. Karantonis,Despina N. Perrea,Stamatios E. Theocharis,Dimitrios G. Iliopoulos,Smaragdi Antonopoulou,Constantinos A. Demopoulos
Mediators of Inflammation , 2007, DOI: 10.1155/2007/36204
Abstract: Olive oil polar lipid (OOPL) extract has been reported to inhibit atherosclerosis development on rabbits. Olive pomace polar lipid (PPL) extract inhibits PAF activity in vitro and the most potent antagonist has been identified as a glycerylether-sn-2-acetyl glycolipid with common structural characteristics with the respective potent antagonist of OOPL. The aim of this study was to investigate the effect of PPL on early atherosclerosis development on rabbits and to compare it with the antiatherosclerotic effect of OOPL. OOPL and PPL inhibition potency, towards both PAF action and PAF binding, was tested in vitro on washed rabbit platelets. Consequently, rabbits were divided into three groups (A, B, and C). All groups were fed atherogenic diet for 22 days. Atherogenic diets in groups B and C were enriched with OOPL and PPL, respectively. At the end of the experimental time, rabbits were euthanized and aortic samples were examined histopathologically. OOPL and PPL inhibited PAF-induced aggregation, as well as specific PAF binding, with PPL being more potent. Free and bound PAF levels and PAF-AH activity were significantly elevated at the end of the experimental time. Plasma total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides levels were also found increased. Groups B and C exhibited significantly increased values of EC50 compared to group A. Histopathological examination revealed that the development of early atherosclerosis lesions in groups B and C were significantly inhibited compared to group A. Significant differences were noted in the early atherosclerosis lesions between groups B and C, thus indicating that PPL exhibit its anti-atherosclerotic activity by blocking PAF receptor. Specific PAF antagonists with similar in vitro and in vivo bioactivity to those that have been previously reported in OOPL exist in PPL.
In vitro anti-inflammatory and anti-coagulant effects of antibiotics towards Platelet Activating Factor and thrombin
Alexandros B Tsoupras, Maria Chini, Nickolaos Tsogas, Athina Lioni, George Tsekes, Constantinos A Demopoulos, Marios C Lazanas
Journal of Inflammation , 2011, DOI: 10.1186/1476-9255-8-17
Abstract: We assessed the inhibitory effect of these drugs against PAF or thrombin induced aggregation on washed rabbit platelets (WRPs) or rabbit Platelet Reach Plasma (rPRP) by evaluating their IC50 values. We also studied their effect on Cholinephosphotransferase of PAF (PAF-CPT)/Lyso-PAF-Acetyltransferase (Lyso-PAF-AT) of rabbit leukocytes (RLs), as well as on rabbit plasma-PAF-AH, the key enzymes of both de novo/remodelling PAF biosynthesis and PAF degradation, respectively.Several antibiotics inhibited PAF-induced platelet aggregation of both WRPs and rPRP in a concentration-depended manner, with clarithromycin, azithromycin and amikacin exhibiting the higher inhibitory effect, while when combined they synergistically inhibited PAF. Higher concentrations of all antibiotics tested were needed in order to inhibit PAF induced aggregation of rPRP, but also to inhibit thrombin induced aggregation of WRPs. Concentrations of these drugs similar to their IC50 values against PAF activity in WRPs, inhibited also in vitro PAF-CPT and Lyso-PAF-AT activities of rabbit leukocytes, while only clarithromycin and azithromycin increased rabbit plasma-PAF-AH activity.These newly found properties of antibiotics used in sepsis suggest that apart from their general actions, these drugs may present additional beneficial anti-inflammatory and anti-coagulant effects against the onset and establishment of sepsis by inhibiting the PAF/PAF-receptor and/or the thrombin/protease-activated-receptor-1 systems, and/or by reducing PAF-levels through both PAF-biosynthesis inhibition and PAF-catabolism induction. These promising in vitro results need to be further studied and confirmed by in vivo tests, in order to optimize the efficacy of antibiotic treatment in sepsis.Platelet Activating Factor (PAF) is a phospholipid signalling molecule of inflammation and a significant mediator of the immune system [1,2]. PAF transmits outside-in signals to intracellular transduction systems in a variety of cell types
Platelet activating factor levels and metabolism in tangier disease: a case study
Vana Kolovou, Vasiliki D Papakonstantinou, George Stamatakis, Sophia N Verouti, Marianna N Xanthopoulou, Genovefa Kolovou, Constantinos A Demopoulos
Lipids in Health and Disease , 2012, DOI: 10.1186/1476-511x-11-89
Abstract: The EC50 value of PRP was measured by an aggregometer. The determination of the specific activity of PAF-CPT and Lyso-PAF-AT was made after in vitro enzymatic assay, chromatographic separation and measurement of the produced PAF in a biological assay with washed rabbit platelets. The determination of PAF-AH and Lp-PLA2 was made after an in vitro enzymatic assay from the decay of radioactive PAF.The TD patient had lower bound-PAF values in blood, decreased specific activity of PAF-CPT and Lyso-PAF-AT, increased specific activity of PAF-AH in platelets and leukocytes and Lp-PLA2 activity in plasma compared to healthy women. The EC50 of PAF and Thrombin were higher compared to healthy women.The increased Lp-PLA2 activity, as well as, the decreased activities of PAF-CPT and Lyso-PAF-AT, explain the decreased bound-PAF level in TD patient and the EC50 of PAF. However, total PAF is in a normal range and this probably can explain one of the reasons this TD patient has no CAD.
ATP-binding cassette transporter A1 gene polymorphisms and serum lipid levels in young Greek nurses
Vana Kolovou, Genovefa Kolovou, Apostolia Marvaki, Agathi Karakosta, Georgios Vasilopoulos, Antonia Kalogiani, Dimitrios Degiannis, Christina Marvaki, Constantinos A Demopoulos
Lipids in Health and Disease , 2011, DOI: 10.1186/1476-511x-10-56
Abstract: The study population consisted of 308 unrelated nurses who were genotyped and the ABCA1 polymorphisms were detected. Additionally, lipid profile [total cholesterol (TC), triglycerides (TGs), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C) and apolipoprotein (apo) A] was evaluated.There was no difference in the genotypic and allelic frequencies of the R219K polymorphism according to lipid profile. The R1587K genotypes differed significantly according to TC, LDL-C and TGs concentration (p = 0.023, p = 0.014 and p = 0.047, respectively). Particularly, significant difference in TC, LDL-C and TGs concentration was detected between RK and RR genotypes (p = 0.006, p = 0.004, p = 0.014, respectively). Women with RK genotype compared to RR genotype had higher concentration of TGs (134.25 mg/dl vs 108.89 mg/dl, p = 0.014, respectively), total cholesterol (207.41 mg/dl vs 187.69 mg/dl, p = 0.006, respectively), and LDL-C (110.6 mg/dl vs 96.9 mg/dl, p = 0.004, respectively).These findings suggest that the R1587K polymorphism of ABCA1 gene was associated with lipid profile of Greek nurses. Women with RK genotype had higher TGs, total and LDL-C concentration compared to RR genotype. These observations may be significant in assessing the risk of CAD since a 1% change in LDL-C is associated with a 1% change of cardiovascular events. Also, TGs concentration were documented to play a significant role in women. However, this needs to be confirmed by larger studies.The ATP-binding cassette transporter A1 (ABCA1) acts as a vehicle for cellular cholesterol which after crossing cell membrane bounds to acceptor molecule such as apolipoprotein (apo) A [1-3]. Thus, ABCA1 influences the initial steps in high density lipoprotein (HDL) formation and in reverse cholesterol transport. The ABCA1 protein belongs to ABC proteins family, which are ingredients of biological membranes and use ATP to transfer various particles such as lipids [1]. The ABCA1 prote
Characterization of Acetyl-CoA: Lyso-PAF Acetyltransferase of Human Mesangial Cells
Elizabeth Fragopoulou,Christos Iatrou,Constantinos Alexandros Demopoulos
Mediators of Inflammation , 2005, DOI: 10.1155/mi.2005.263
Abstract: Platelet activating factor (PAF) is a potent inflammatory mediator produced by various renal cells and it is implicated in renal pathology. The aim of this study is the characterization of remodeling lyso-PAF acetyltransferase, which is activated under inflammatory conditions, in human mesangial cell. Total membranes of mesangial cells were isolated and enzymatic activity and kinetic parameters were determined by trichloroacetic acid precipitation method. The effect of BSA, divalent cations, EDTA, and various chemicals on the activity of lyso-PAF acetyltransferase was also studied. Various detergents were also tested for the solubilization of the enzyme and only glycerol did not affect its activity. Partial purification of solubilized enzyme preparations of human kidney tissue and mesangial cells was performed on anion exchange column chromatography and native-PAGE electrophoresis and two active fractions were detected.
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