Biomedical subjects

Ilya Pinchuk

Publications and source records attributed to Ilya Pinchuk.

13 recordsLinked to original sources

PubMed2006

Serum lipid oxidizibility in term premature rupture of the membranes.

OBJECTIVE: In our previous studies we have shown that the process of term labor is associated with oxidative stress, as indicated by increased susceptibility of maternal serum lipids to copper induced peroxidation. In order to continue evaluating the role of oxidative stress in the labor process, we next tested whether term premature rupture of the membranes (PROM) is also associated with increased susceptibility of maternal serum lipids to copper induced peroxidation. DESIGN: A controlled prospective study. SETTING: Tertiary care centre. POPULATION: 31 healthy women with term PROM and 19 healthy pregnant women with intact membranes. The women were matched for maternal and gestational age. METHODS: Venous blood was drawn from the women (up to 6h after rupture of the membranes and prior to labor in the PROM group), and the kinetics of copper-induced oxidation of serum lipids ex vivo were monitored spectroscopically at 37 degrees C by continuous recording of absorbance at 245 nm. RESULTS: The lag phase, reflecting resistance of serum lipids to oxidation, was similar in the PROM group when compared to the control group (43.7+/-3.2 versus 41.9+/-1.6 min, P=0.61). However, the maximal rate of oxidation (V(max)) and the maximal accumulation of absorbing products (OD(max)) were shorter in the PROM group when compared to the control group (5.14+/-0.26 versus 6.29+/-0.4010(-3) OD(245) nm/min, P=0.016; 0.61+/-0.03 versus 0.71+/-0.04 OD(245) nm, P=0.07). CONCLUSION: As opposed to term labor, term PROM is not associated with increased maternal systemic oxidative stress when compared to normal pregnant women. The role for oxidative stress in preterm PROM warrants further studies.

Adult↗

PubMed2005

Celecoxib and curcumin synergistically inhibit the growth of colorectal cancer cells.

PURPOSE: Multiple studies have indicated that cyclooxygenase-2 (COX-2) inhibitors may prevent colon cancer, which is one of the leading causes of cancer death in the western world. Recent studies, however, showed that their long-term use may be limited due to cardiovascular toxicity. This study aims to investigate whether curcumin potentiates the growth inhibitory effect of celecoxib, a specific COX-2 inhibitor, in human colon cancer cells. EXPERIMENTAL DESIGN: HT-29 and IEC-18-K-ras (expressing high levels of COX-2), Caco-2 (expressing low level of COX-2), and SW-480 (no expression of COX-2) cell lines were exposed to different concentrations of celecoxib (0-50 micromol/L), curcumin (0-20 micromol/L), and their combination. COX-2 activity was assessed by measuring prostaglandin E(2) production by enzyme-linked immunoassay. COX-2 mRNA levels were assessed by reverse transcription-PCR. RESULTS: Exposure to curcumin (10-15 micromol/L) and physiologic doses of celecoxib (5 micromol/L) resulted in a synergistic inhibitory effect on cell growth. Growth inhibition was associated with inhibition of proliferation and induction of apoptosis. Curcumin augmented celecoxib inhibition of prostaglandin E(2) synthesis. The drugs synergistically down-regulated COX-2 mRNA expression. Western blot analysis showed that the level of COX-1 was not altered by treatment with celecoxib, curcumin, or their combination. CONCLUSIONS: Curcumin potentiates the growth inhibitory effect of celecoxib by shifting the dose-response curve to the left. The synergistic growth inhibitory effect was mediated through a mechanism that probably involves inhibition of the COX-2 pathway and may involve other non-COX-2 pathways. This synergistic effect is clinically important because it can be achieved in the serum of patients receiving standard anti-inflammatory or antineoplastic dosages of celecoxib.

Analysis of Variance↗

PubMed2005

Oxidative stress in the fetal circulation does not depend on mode of delivery.

OBJECTIVE: We tested whether neonates are subject to oxidative stress by comparing the susceptibility of umbilical blood lipids with copper-induced peroxidation. STUDY DESIGN: Umbilical arterial and venous blood samples were drawn from 32 pregnant women who delivered by elective cesarean section (CS) and from 32 pregnant women who delivered by spontaneous vaginal delivery (SVD) in a tertiary care center. Oxidative stress was evaluated by spectrophotometric monitoring of copper-induced peroxidation of serum samples. RESULTS: The lag preceding lipid peroxidation in umbilical arterial blood was shorter than the lag in umbilical venous blood, irrespective of mode of delivery (14.0+/-1.8 vs 50.6+/-8.25 min, P=.0004 in SVD group; 17.7+/-1.6 vs 39.2+/-7.6 min, P=.006 in CS group). CONCLUSION: Umbilical arterial lipids are more susceptible to peroxidation than umbilical venous lipids, indicating high oxidative stress in the fetal circulation irrespective of mode of delivery.

Adult↗

PubMed2005

Kinetic studies of copper-induced oxidation of urate, ascorbate and their mixtures.

Urate and ascorbate are the major water-soluble low molecular weight antioxidants in serum. Much attention has been devoted to the effect of these antioxidants on lipoprotein peroxidation in vivo and on their effect on copper-induced peroxidation ex vivo. These studies revealed that urate inhibits ascorbate oxidation in vitro, whereas the effect of ascorbate on urate oxidation has not been systematically studied thus far. The present study addresses mechanistic aspects of the kinetics of copper-induced oxidation of both these antioxidants and their mutual effects in aqueous solutions. We found that: (i) ascorbate becomes oxidized much faster than urate. (ii) Urate inhibits the oxidation of ascorbate but, even in the presence of excess urate, ascorbate becomes oxidized much faster than urate. (iii) Ascorbate, as well as the products of its oxidation (and/or hydrolysis) inhibit the copper-induced oxidation of urate. All these results are consistent with the hypothesis that the rate of ascorbate oxidation is determined by the rate of reoxidation of reduced copper (Cu(I)) to Cu(II) by molecular oxygen, whereas the rate of urate oxidation is governed by the rate of oxidation of urate within a 2:1 urate/copper complex. We think that the mutual effects of urate and ascorbate on each other's oxidation are likely to enhance their inhibitory effect on lipid peroxidation in biologically relevant systems including membranes and lipoproteins.

Antioxidants↗

PubMed2004

Lipid peroxidation in the presence of albumin, inhibitory and prooxidative effects.

Oxidative modifications of LDL are involved in atherogenesis. Previously we have developed a simple assay to evaluate the susceptibility of lipids to copper-induced peroxidation in the relatively natural milieu of unfractionated serum in the presence of excess citrate. Based on our previous results we have proposed that the inducer of peroxidation in our optimized assay is a copper-citrate complex. Recent investigations indicate that under certain conditions a copper-albumin complex may induce peroxidation of ascorbate. Two different complexes may be formed in albumin-containing systems (e.g. serum) namely 1:1 and 2:1 copper-albumin complexes. The aim of the present work was to evaluate the possibility that at least one of these complexes may be responsible for the induction of peroxidation of lipids in lipidic systems containing copper and albumin, including our optimized assay. Towards this end, we have investigated the dependence of copper-induced peroxidation on the concentration of added albumin in lipidic systems in the absence and presence of citrate. In all the systems investigated in this study (PLPC liposomes, LDL, HDL and mixtures of HDL and LDL) we found that at low concentrations of free copper (e.g. in the presence of excess citrate) the 2:1 copper-albumin complex is redox-active and that this complex is the major contributor to the initiation of lipid peroxidation in these systems and in our optimized assay. The possible relevance of the induction of peroxidation in vivo by the latter complex has yet to be studied.

Citric Acid↗

PubMed2003

Peroxidation of liposomal palmitoyllinoleoylphosphatidylcholine (PLPC), effects of surface charge on the oxidizability and on the potency of antioxidants.

Peroxidation of membrane phospholipids is an important determinant of membrane function. Previously we studied the kinetics of peroxidation of the polyunsaturated fatty acid (PUFA) residues in model membranes (liposomes) made by sonication of palmitoyllinoleoylphosphatidylcholine (PLPC). Since most biomembranes are negatively-charged, we have now studied the effect of negative surface charge on the kinetics of peroxidation of liposomes made of PLPC and 9% of one of the negatively-charged phospholipids phosphatidylserine (PS) or phosphatidic acid (PA). Peroxidation was initiated by either CuCl2 or AAPH and continuously monitored spectrophotometrically. The following results were obtained: (i) The negative charge had only a slight effect on AAPH-induced peroxidation, but accelerated markedly copper-induced peroxidation of the liposomes, probably by increasing the binding of copper to the membrane surface. (ii) Ascorbic acid (AA) inhibited AAPH-induced but promoted copper-induced peroxidation in all the studied liposomes, probably by enhancing the production of free radicals upon reduction of Cu(II) to Cu(I). (iii) alpha-tocopherol (Toc) inhibited AAPH-induced peroxidation in all the studied liposomes, whereas the effect of tocopherol on copper-induced peroxidation varied from being pro-oxidative in PA-containing liposomes, to being extremely anti-oxidative in PS-containing liposomes, even at very low tocopherol concentrations. The significance of the latter unusual protective effect, which we attribute to recycling of tocopherol by a PS-Cu complex, requires further investigation.

Antioxidants↗

PubMed2003

Preeclampsia is associated with increased susceptibility of serum lipids to copper-induced peroxidation in vitro.

BACKGROUND: Several reports suggest preeclampsia to be associated with oxidative stress. In view of potential experimental artifacts in these studies, we tested the effect of preeclampsia on the oxidizibility of maternal serum lipids, using an optimized ex vivo method. METHODS: This prospective study included 28 pregnant women with preeclampsia and 28 women matched for maternal and gestational age with normal pregnancies. Venous blood was drawn from the consenting women. Serum levels of lipid peroxidation products and the kinetics of copper-induced oxidation ex vivo were monitored spectroscopically by continuous recording of absorbance at 245 nm. RESULTS: The initial optical density (OD) at 245 nm, attributed to preformed products of lipid peroxidation, was higher in the women with preeclampsia than in the controls (1.26 +/- 0.02 vs. 1.17 +/- 0.02 OD units; p = 0.01). The lag phase preceding oxidation, reflecting resistance of serum lipids to oxidation, was significantly shorter in the preeclampsia group than in the controls (47.4 +/- 2.3 vs. 57.6 +/- 4.0 min; p = 0.027). CONCLUSIONS: High levels of serum hydroperoxides and increased susceptibility of serum lipids to copper-induced peroxidation ex vivo indicate preeclampsia to be associated with high oxidative stress. The role of this high oxidizibility in the pathogenesis of preeclampsia has yet to be evaluated.

Adult↗

PubMed2003

Lipid oxidation kinetics in hemodialysis patients with and without history of myocardial infarction.

BACKGROUND: In lipid oxidation kinetics studies, prevalent cardiovascular disease has been associated with shortened lag phase, the length of time preceding the onset of oxidation. OBJECTIVES: To examine, in vitro, copper-induced lipid oxidation kinetics in unfractionated serum from hemodialysis patients and to determine differences in kinetic parameters between patients with and without a history of CVD. METHODS: Of the 76 patients enrolled in a study of oxidative stress in hemodialysis (44/76 with prevalent CVD, 53/76 males), 9 males with a history of myocardial infarction were selected and matched for age, diabetes and smoking status with 9 males from the non-CVD group. The kinetics of lipid oxidation was studied. Blood chemistry determinations including serum lipids, lipoproteins, hemostatic factors and serum malondialdehyde were obtained. Variables were compared using the t-test for independent samples with history of MI entered as the categorical variable. RESULTS: Tmax, the oxidation kinetic parameter defined as the time at which the rate of absorbing product accumulation was maximal, was significantly shorter in dialysis patients with a history of MI than in those without (115.2 +/- 38.5 vs. 162.7 +/- 48.9 minutes, P = 0.04). Further, Tmax and MDA were negatively correlated to one another (r = -0.47, P = 0.04). Odds ratios indicate that each 1 minute increase in Tmax was associated with a 3% decrease in odds that a subject had a history of MI. CONCLUSIONS: These findings indicate the presence of increased oxidative stress in hemodialysis patients with a history of MI.

Case-Control Studies↗

PubMed2002

Heat evolution of micelle formation, dependence of enthalpy, and heat capacity on the surfactant chain length and head group.

Micelle formation by many surfactants is endothermic at low temperatures but exothermic at high temperatures. In this respect, dissociation of micelles (demicellization) is similar to dissolving hydrocarbons in water. However, a remarkable difference between the two processes is that dissolving hydrocarbons is isocaloric at about 25 degrees C, almost independently of the hydrocarbon chain length, whereas the temperature (T*) at which demicellization of different surfactants is athermal varies over a relatively large range. We have investigated the temperature dependence of the heat of demicellization of three alkylglucosides with hydrocarbon chains of 7, 8, and 9 carbon atoms. At about 25 degrees C, the heat of demicellization of the three studied alkylglucosides varied within a relatively small range (DeltaH=-7.8+/-0.4 kJ/mol). The temperature dependence of DeltaH(demic) indicates that within the studied temperature range the heat capacity of demicellization (DeltaC(P,demic)) is about constant. The value of DeltaC(P,demic) exhibited an apparently linear dependence on the surfactant's chain length (DeltaC(P,demic)/n(CH(2))=47+/-7 kJ/mol K). Our interpretation of these results is that (i) the transfer of the head groups from micelles to water is exothermic and (ii) the temperature dependence of the heat associated with water-hydrocarbon interactions is only slightly affected by the head group. This implies that the deviation of the value of T* from 25 degrees C results from the contribution of the polar head to the overall heat of demicellization. Calorimetric studies of other series of amphiphiles will have to be conducted to test whether the latter conclusion is general.

Hot Temperature↗

PubMed2002

Copper-induced peroxidation of liposomal palmitoyllinoleoylphosphatidylcholine (PLPC), effect of antioxidants and its dependence on the oxidative stress.

In an attempt to deepen our understanding of the mechanisms responsible for lipoprotein peroxidation, we have studied the kinetics of copper-induced peroxidation of the polyunsaturated fatty acid residues in model membranes (small, unilamellar liposomes) composed of palmitoyllinoleoylphosphatidylcholine (PLPC). Liposomes were prepared by sonication and exposed to CuCl(2) in the absence or presence of naturally occurring reductants (ascorbic acid (AA) and/or alpha-tocopherol (Toc)) and/or a Cu(I) chelator (bathocuproinedisulfonic acid (BC) or neocuproine (NC)). The resultant oxidation process was monitored by recording the time-dependence of the absorbance at several wavelengths. The observed results reveal that copper-induced peroxidation of PLPC is very slow even at relatively high copper concentrations, but occurs rapidly in the presence of ascorbate, even at sub-micromolar copper concentrations. When added from an ethanolic solution, tocopherol had similar pro-oxidative effects, whereas when introduced into the liposomes by co-sonication tocopherol exhibited a marked antioxidative effect. Under the latter conditions, ascorbate inhibited peroxidation of the tocopherol-containing bilayers possibly by regeneration of tocopherol. Similarly, both ascorbate and tocopherol exhibit antioxidative potency when the PLPC liposomes are exposed to the high oxidative stress imposed by chelated copper, which is more redox-active than free copper. The biological significance of these results has yet to be evaluated.

Antioxidants↗

PubMed2002

The mechanism of action of antioxidants against lipoprotein peroxidation, evaluation based on kinetic experiments.

Peroxidation of blood lipoproteins is regarded as a key event in the development of atherosclerosis. Hence, attenuation of the oxidative modification of lipoproteins by natural and synthetic antioxidants in vivo is considered a possible way of prevention of cardiovascular disorders. The assessment of the susceptibility of lipoproteins to oxidation is commonly based on in vitro oxidation experiments. Monitoring of oxidation provides the kinetic profile characteristic for the given lipoprotein preparation. The kinetic profile of peroxidation is characterized by three major parameters: the lag preceding rapid oxidation, the maximal rate of oxidation (V(max)) and the maximal accumulation of oxidation products (OD(max)). Addition of antioxidants alters this pattern, affecting the kinetic parameters of oxidation. In particular, antioxidants may prolong the lag and/or decrease the V(max) and/or decrease the OD(max). Such specific variation of the set of kinetic parameters may provide important information on the mechanism of the inhibitory action of a given antioxidant (scavenging free radicals, metal-binding or other mechanisms). Numerous natural and synthetic compounds were reported to inhibit oxidation of lipoproteins. Based on the analysis of reported effects and theoretical considerations, we propose a simple protocol that relates the kinetic effects of a given antioxidant to the mechanism of its action.

Animals↗

PubMed2002

Oxygen availability as a possible limiting factor in LDL oxidation.

Kinetic studies of copper-induced LDL peroxidation commonly assume that the availability of molecular oxygen in the reaction media is not a limiting factor. The present study reveals that this assumption is valid only at low LDL concentrations. At high LDL concentrations, accumulation of oxidation products, as monitored spectroscopically under conditions of various oxygen concentrations in the medium, comes to a halt when the oxygen concentration in the solution, as measured by an oxygen electrode, decreases to near zero levels. Bubbling of the oxygen into the solution results in resumption of peroxidation. These results are important with respect to the ex vivo assaying of lipoprotein peroxidation because many previous studies have been conducted with LDL concentrations that corresponded to polyunsaturated fatty acid concentrations in access of the concentration of molecular oxygen. The possible pathophysiological significance of the results of this study has yet to be evaluated.

Copper↗

PubMed2002

Active labour is associated with increased oxidisibility of serum lipids ex vivo.

OBJECTIVE: As a first step towards evaluating the role of oxidative stress in the process of labour, we tested whether term labour is associated with increased oxidisibility of maternal serum lipids. DESIGN: A controlled prospective study. SETTING: Tertiary care centre. POPULATION: Twenty healthy women in active labour and 20 healthy pregnant women not in labour (controls) matched for maternal and gestational age. METHODS: Venous blood was drawn from women in both groups. Serum levels of lipid peroxidation products and the kinetics of copper-induced oxidation ex vivo were monitored spectroscopically at 37 degrees C by continuous recording of absorbance at 245 nm. MAIN OUTCOME MEASURES: Oxidative stress parameters. RESULTS: The initial optical density (OD) at 245 nm, attributed to preformed dienic hydroperoxides and 7-keto-cholesterol (main products of lipid peroxidation), was higher in the labouring group than in the controls (1.30 +/- 0.11 vs 1.18 +/- 0.09, OD 245 nm, respectively, P < 0.001). The lag phase, reflecting resistance of serum lipids to oxidation, was significantly shorter in the labouring group than in the controls (43.2 +/- 1.4 vs 56.2 +/- 4.7 min, respectively, P = 0.01). CONCLUSION: High levels of serum hydroperoxides and decreased resistance of serum lipids to copper-induced peroxidation ex vivo suggest labour to be associated with high oxidative stress. Whether oxidative stress is involved in initiating the labour process or is consequent awaits further studies.

Adult↗