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Biomedical subjects

W B Weglicki

Publications and source records attributed to W B Weglicki.

At least 37 records · Page 2Linked to original sources
PubMed1995

Protective effects of calcium channel blockers against free radical-impaired endothelial cell proliferation.

We have shown previously that the lipophilic calcium channel blockers exhibit membrane antioxidant activity. In the present study, when attached bovine aortic endothelial cells were exposed for 20 min to a low concentration of oxy-radicals generated from dihydroxyfumarate + Fe-ADP, no loss of glutathione or viability was detected; however, cell number, determined 48 hr later by the tetrazolium salt MTT assay, decreased to 45% of controls. Treatment of the cells for 1 hr with the calcium blockers (2-20 microM) prior to free radical exposure protected against the impaired cell growth in a concentration-dependent manner. The order of potency was nicardipine > or = nifedipine > or = verapamil > diltiazem, which appears to parallel their antioxidant potency. In addition, (+)-nicardipine, and its pharmacologically inactive isomer, (-)-nicardipine, were similarly effective. We conclude that it was the antioxidant activity of the calcium channel blockers that preserved the cell growth capacity against free-radical damage; such protective effects may contribute to their antiatherogenic effects.

Animals↗
PubMed1995

Phospholipid hydroperoxides are precursors of lipid alkoxyl radicals produced from anoxia/reoxygenated endothelial cells.

Endothelial cells have been shown to generate primary oxygen-centered free radicals (hydroxyl, superoxide anion) during post-anoxic reoxygenation, but little evidence is available concerning subsequent initiation of lipid peroxidative injury in this model. Electron spin resonance (ESR) spectroscopy with alpha-phenyl-N-tert-butylnitrone (PBN) spin trapping was used to monitor lipid peroxidation (LPO)-derived free radicals formed by cultured bovine aortic endothelial cell suspensions exposed (37 degrees C) to anoxia (A, 45 min, N2 gas) and reoxygenation (R, 15 min, 95% O2/5% CO2). In some studies, superoxide dismutase (SOD, 10 micrograms/ml) was introduced just prior to R to assess the effects of this primary free radical scavenger on LPO-derived free radical production. At various times, aliquots were removed and PBN was introduced to either the cell suspension aliquot (8 mM PBN final, 1 min), or to the corresponding cell-free filtrate (60 mM PBN final), prior to extraction with toluene and ESR spectroscopy. A LPO-derived alkoxyl radical adduct of PBN (PBN/RO., hyperfine splitting alpha N = 13.63 G and alpha H = 1.94-1.98 G) was observed during R using both trapping procedures, with maximal production at 4-5 min and a second minor peak at 10 min. SOD effectively reduced PBN/RO. production and improved viability of A/R cells. In parallel studies, lipid hydroperoxide production was assessed in lipid extracts of A/R cells by high-performance liquid chromatography. Their separation profiles revealed a peak of oxidized lipid occurring between phosphatidylethanolamine (PE) and phosphatidylcholine (PC) in samples taken at 4-5 min and 10 min of R. Resolubilizing cell lipid extracts in oxygen-free benzene containing cobalt (II) acetylacetonate and PBN led to alkoxyl radical production, but only in the oxidized lipid samples, confirming the presence of hydroperoxides. These results suggest that A/R leads to primary free radical induced-lipid peroxidative injury to endothelial cells, as indicated by alkoxyl radical production originating from oxidized membrane phospholipids.

Aerobiosis↗
PubMed1994

Cytokines, neuropeptides, and reperfusion injury during magnesium deficiency.

In summary, hypomagnesemia enhances reperfusion injury. We postulate that neurogenic inflammation, which occurs very early during hypomagnesemia, predisposes the myocardium to reperfusion injury by depleting endogenous antioxidants and recruiting inflammatory cells, which can participate in enhanced free radical production during postischemic reperfusion. Vitamin E supplements can prevent the occurrence of this enhanced injury possibly through the restoration of endogenous antioxidant defenses.

Animals↗
PubMed1994

Lipid peroxidation-derived free radical production and postischemic myocardial reperfusion injury.

ESR spin trapping techniques, which monitor LPO-derived secondary free radical production, provide a quantitative index of irreversible oxidative injury in in vivo and in vitro models of postischemic stress. Secondary radical detection, in conjunction with other indices of injury, also offers a powerful approach for assessing protection against reperfusion-mediated oxidative injury in the presence of anti-radical intervention (Fig. 11). Monitoring secondary radical production has allowed us to demonstrate (1) a direct relationship between ischemic duration and the subsequent postischemic production of alkoxyl radicals from heart tissue; (2) changes in total secondary radical levels directly parallel the severity of mechanical dysfunction and/or tissue injury in postischemic tissue models; (3) interventions that interrupt LPO-derived secondary radical production by different mechanisms also attenuate reperfusion-mediated functional and/or tissue injury; and (4) secondary radical detection provides a standard measure of injury independent of the oxidative stress model used (A-R cells; buffer- and blood-perfused tissues; and global or regional ischemia) or animal species employed (rat, hamster, swine, dog, and human models). The lack of species-specificity for this index suggests the potential for clinical application, especially in light of our recent report demonstrating detection of secondary alkoxyl and alkyl radicals during the postoperative period after human open heart surgery.

Animals↗
PubMed1994

Neurogenic peptides and the cardiomyopathy of magnesium-deficiency: effects of substance P-receptor inhibition.

Dietary deficiency of magnesium (Mg) in rodents results in cardiomyopathic lesion formation. In our rat model, these lesions develop after 3 weeks on the Mg-deficient diet; significant elevation of several cytokines, IL-1, IL-6 and TNF alpha also occurs. In probing the mechanisms of lesion formation, we obtained data supporting the participation of free radicals (Freedman AM et al.: Bioch Biophys Res Commun 1990; 170: 1102). Recently, we identified an early elevation of circulating substance P and proposed a role of neurogenic peptides during Mg-deficiency (Weglicki WB, Phillips TM: AM J Phys 1992;262:R734). The present study was designed to evaluate the contribution of neurogenic peptides to the pathogenesis of Mg-deficiency. In the blood, substance-P and calcitonin gene related peptide (CGRP) are elevated during the first week on the diet. During the second week, circulating histamine, PGE2 and TBAR-materials were elevated and red cell glutathione was reduced, all prior to the elevation of the inflammatory cytokines during the third week. When the rats were treated with the substance P-receptor blocker [CP-96,345], the levels of substance P and CGRP remained elevated; however, increases in histamine, PGE2, TBAR-materials, and the decrease in red cell glutathione were inhibited; also, the development of cardiac lesions was inhibited significantly. These data support a central role for neurogenic peptides, especially substance P, in the development of cardiomyopathic lesions during Mg-deficiency.

Animals↗
PubMed1994

Magnesium deficiency prolongs myocardial stunning in an open-chest swine model.

The effect of magnesium deficiency on postischemic myocardial dysfunction (myocardial stunning) in an open-chest swine model was studied. Twelve swine were assigned either to low magnesium diet or control diet. Myocardial stunning was assessed by measuring regional wall thickening by epicardial Doppler before and after brief occlusion (8 min) of the left anterior descending coronary artery. Serum magnesium levels decreased significantly in the experimental group only. Glutathione levels were 42.6% lower in the magnesium deficient swine than in controls. Stunning time was significantly prolonged from 32.8 +/- 3.1 min in the control group to 43.8 +/- 4.6 min in the hypomagnesemic swine. In conclusion, magnesium deficiency is associated with prolonged recovery from myocardial stunning.

Animal Feed↗
PubMed1994

Magnesium-deficiency potentiates free radical production associated with postischemic injury to rat hearts: vitamin E affords protection.

Preexisting magnesium deficiency may alter the susceptibility of rat hearts to postischemic oxidative injury (free radicals). This was examined in rats maintained for 3 weeks on a magnesium-deficient (Mg-D) diet with or without concurrent vitamin E treatment (1.2 mg/day, SC). Magnesium-sufficient (Mg-S) rats received the same diet supplemented with 100 mmol Mg/kg feed. Following sacrifice, isolated working hearts were subjected to 30-, 40-, or 60-min global ischemia and 30-min reperfusion. Postischemic production of free radicals was monitored using electron spin resonance (ESR) spectroscopy and spin trapping with alpha-phenyl-N-tert butylnitrone (PBN, 3 mM final); preischemic and postischemic effluent samples were collected and then extracted with toluene. PBN/alkoxyl adduct(s) (PBN/RO.; alpha H = 1.93 G, alpha N = 13.63 G) were the dominant signals detected in untreated Mg-S and Mg-D postischemic hearts, with comparably higher signal intensities observed for the Mg-D group following any ischemic duration. Time courses of postischemic PBN/RO. detection were biphasic for both groups (maxima: 2-4 and 8.5-12.5 min), and linear relationships between the extent of PBN/RO. production and the severity of both mechanical dysfunction and tissue injury were determined. Following each duration of ischemia, Mg-D hearts displayed greater levels of total PBN adduct production (1.7-2.0 times higher) and lower recovery of cardiac function (42-48% less) than Mg-S hearts. Pretreating Mg-D rats with vitamin E prior to imposing 40-min ischemia/reperfusion, led to a 49% reduction in total PBN/RO. production, a 55% lower LDH release and a 2.2-fold improvement in functional recovery, compared to untreated Mg-D hearts. These data suggest that magnesium deficiency predisposes postischemic hearts to enhanced oxidative injury and functional loss, and that antioxidants may offer significant protection against the pro-oxidant influence(s) of magnesium deficiency.

Animals↗
PubMed1994

Loss of red blood cell glutathione during Mg deficiency: prevention by vitamin E, D-propranolol, and chloroquine.

Mg deficiency results in loss of red blood cell glutathione and was thought to be due to decreased Mg-dependent synthesis. The effects of vitamin E, D-propranolol, and chloroquine on red blood cell glutathione levels in Mg-deficient rats were examined. Feeding the rats a Mg-deficient diet for 3 wk resulted in an approximately 80% decrease in serum Mg and a 55% loss of red blood cell glutathione; concomitantly, plasma thiobarbituric acid reactive (TBAR) materials rose 240%. All three drug treatments had no effect on the plasma Mg levels but significantly inhibited the rise in TBAR content and attenuated (60-80% effective) the loss of glutathione. Red blood cell ghost membranes from the Mg-deficient rats also exhibited 2.3-fold higher TBAR content, which was attenuated by vitamin E treatment. With isolated red blood cells from Mg-sufficient rats, loss of glutathione could be induced by a chemical oxyradical system. Direct protective effects were afforded by alpha-tocopherol and D-propranolol but not by chloroquine. The data suggest that 1) the loss of glutathione during Mg deficiency was due to increased oxidative degradation, 2) both vitamin E and D-propranolol protected by a membrane antiperoxidative action, and 3) chloroquine probably protected by diminishing prooxidant activity secondary to its inhibition of cytokine induction during Mg deficiency.

Animals↗
PubMed1994

Blockade of cardiac inflammation in Mg2+ deficiency by substance P receptor inhibition.

In previous work we reported the elevation of circulating inflammatory cytokines in rodents maintained on a Mg(2+)-deficient diet. Within the first week of Mg2+ deficiency, significant elevation of the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) occurs. The present study was designed to assess the effects of SP receptor blockade by CP-96,945 and its inactive enantiomer CP-96,344 on tissue cytokine levels and in vivo oxidative indexes. CP-96,345 had no significant effect on circulating levels of SP or CGRP; however, at the tissue level, a significant decrease (P < .01) in myocardial accumulation of SP occurred; the inactive enantiomer was only slightly effective. In addition, CP-96,345 significantly reduced (by 53%) the accumulation of tumor necrosis factor-alpha (TNF-alpha) (but not interleukin-1 and interleukin-6) within the lesions; the effect of the enantiomer was insignificant. We conclude that treatment with CP-96,345 inhibits SP and TNF-alpha tissue levels in cardiac lesions, indicating a linkage between this neuropeptide and TNF-alpha. Both SP and TNF-alpha can trigger free radical production; plasma thiobarbituric acid-reactive materials were elevated 2.5-fold and red blood cell reduced glutathione was reduced 55% during Mg2+ deficiency. In the presence of CP-96,345, both indexes of in vivo oxidation were significantly attenuated; the enantiomer was ineffective. These latter observations point to a neuropeptide/TNF-alpha/free radical-triggered mechanism that may be the major pathway of systemic oxidative injury inducing the cardiomyopathic lesions seen during Mg2+ deficiency.

Animals↗
PubMed1993

Inhibition of tumor necrosis factor-alpha by thalidomide in magnesium deficiency.

The effect of thalidomide on circulating cytokines and myocardial lesion formation was investigated in Mg-deficient rats. After two weeks on a Mg-deficient diet, rats show an increase in circulating levels of tumor necrosis factor-alpha and interleukin 1. Thalidomide (1 mg/day) caused a complete inhibition of the increase in circulating tumor necrosis factor-alpha levels, without having an effect on interleukin 1. However, a marked increase in cardiomyopathic lesion formation was observed in Mg-deficient animals treated with thalidomide; possible mechanisms for thalidomide's enhancement of myocardial injury are discussed.

Animals↗
PubMed1993

Protein oxidation in magnesium deficient rat brains and kidneys.

Magnesium deficiency produces a pro-oxidant systemic inflammation in rats. The purpose of these experiments was to determine if and when there is any oxidation of cellular proteins. We have found there is a significant increase in protein oxidation products, protein carbonyls, in both the brain and the kidney within 2 to 3 weeks on a magnesium deficient diet. These changes occur prior to any detectable changes in cellular glutathione, tissue damage or dysfunction. We conclude that oxidation of cellular proteins occur early in magnesium deficiency and may contribute to the tissue damage and loss of function observed in the later stages of the deficiency. This is the first demonstration of the time course of protein oxidation product development in magnesium deficient animals.

Animals↗
PubMed1993

Detection of alkoxyl and carbon-centered free radicals in coronary sinus blood from patients undergoing elective cardioplegia.

Confirmation of the involvement of free radicals in postischemic injury in human heart has been elusive. The present study was performed to determine the presence of free radicals in coronary sinus blood from patients undergoing elective open heart surgery and cardioplegia. Six patients who were scheduled for nonurgent elective open heart surgery were used in this study. Coronary sinus blood samples were withdrawn at 1, 3, 5, 10, 15, 20, and 25 min in post-cross-clamp and immediately mixed with isosmotic alpha-phenyl-tert-butylnitrone (PBN) and then centrifuged to obtain plasma. Plasma samples were extracted with toluene and analyzed using electron spin resonance (ESR) spectroscopy. We observed ESR spectra consistent with the formation of alkoxyl and carbon-centered radical adducts of PBN (aN = 13.6 G, a beta H = 1.9 G, and aN = 14.1 G, a beta H = 4.2 G) in six of six patients. We obtained complete free radical production time courses during reperfusion from five patients, and all demonstrated a biphasic profile with an initial burst from 5 to 10 min followed by a second maxima at 25 min. Total PBN-adduct production during reperfusion increased in patients subjected to longer aortic cross-clamp times (global ischemia). These data demonstrate that postcardioplegia free radical production is detectable in coronary sinus blood using an ex vivo spin-trapping technique and that the extent of formation may be related to the severity of ischemia.

Aged↗
PubMed1993

Reactions of captopril and epicaptopril with transition metal ions and hydroxyl radicals: an EPR spectroscopy study.

In the present study, using the technique of EPR spin trapping with DMPO a spin trap, we demonstrated formation of thiyl radicals from thiol-containing angiotensin converting enzyme (ACE) inhibitor captopril (CAP) and from its stereoisomer epicaptopril (EPICAP), a non-ACE inhibitor, in the process of .OH radical scavenging. Splitting constants of DMPO/thiyl radical adducts were identical for both thiols and were aN = 15.3 G, and aH = 16.2 G. Bimolecular rate constants for the reaction of CAP and EPICAP with .OH radicals were close to a diffusion-controlled rate (approximately 2 x 10(10) M-1s-1). Our data also show that both CAP and EPICAP reduce Fe(III) ions and that their respective thiyl radicals are formed in this reaction. In the presence of Fe(III), H2O2, and CAP, or EPICAP, .OH radicals were produced by a thiol-driven Fenton mechanism. Copper(II) ions were also reduced by these thiols, but no thiyl radicals could be detected in these reactions, and no .OH or other Fenton oxidants were observed in the presence of H2O2. Our data show direct evidence that thiol groups of CAP and EPICAP are involved in scavenging of .OH radicals. The direct .OH radical scavenging, together with the reductive "repair" of other sites of .OH radical attack, may contribute to the known protective effect of CAP against ischemia/reperfusion-induced arrhythmias. The formation of reactive thiyl radicals in the reactions of the studied compounds with .OH radicals and with Fe(III) ions may play a role in some of the known adverse effects of CAP.

Captopril↗
PubMed1993

Modulation of cytokines and myocardial lesions by vitamin E and chloroquine in a Mg-deficient rat model.

Antioxidant treatment with alpha-tocopherol did not affect the level of the "inflammatory cytokines" in Mg-deficient animals, although it diminished the extent of the myocardial lesions. In another group of Mg-deficient animals chloroquine treatment diminished significantly the levels of circulating cytokines (interleukin-1, interleukin-6, and tumor necrosis factor-alpha) and also resulted in a major decrease in myocardial lesions. These results raise the question of the role of these inflammatory cytokines in the formation of lesions in Mg-deficient myocardium. Because these cytokines are able to stimulate free radical production in various cell types, we postulate that Mg deficiency involves free radical mechanisms that can be amplified by inflammatory cytokines; whether these cytokines initiate lesion formation is unclear. Although our data do not confirm either possibility, we submit that these results implicate a role for the inflammatory cytokines in the cardiac pathology of Mg deficiency.

Animals↗
PubMed1992

Antioxidant drug mechanisms: transition metal-binding and vasodilation.

In our work evaluating the antioxidant properties of a number of cardiovascular drugs, we have emphasized the importance of lipophilicity as a property contributing to antioxidant potency. Thus, the dihydropyridine calcium channel blockers and propranolol, one of the most lipophilic beta-blockers, were found to exhibit the greatest potency in membrane and cellular models. Both beta-blockers and calcium channel blockers are classified as antihypertensive agents. We found that the specific chemical moieties of various drugs may participate in the antioxidant mechanism of action. While reviewing relevant work from the past literature, it became apparent that some of the chemical moieties of antihypertensive and vasodilator drugs may bind transition metals. Thus, this present review focuses on common properties of transition metal-interaction that are shared, to a greater or lesser degree, by a number of vasoactive drugs and chemical agents. Although this observation has been pursued by other investigators in the past, we submit that the potential relevance to the newer pharmacological agents needs to be explored further. In addition, new information regarding the role of transition metals and free radicals involving vascular cells focuses greater importance on transition metal-interaction as a potential mechanism in vasodilation. This review does not intend to be inclusive of all chemical structures capable of binding transition metals; only those that are clinically relevant will be considered in some detail. Potential mechanisms of metal-chelating actions leading to vasodilation are also discussed.

Animals↗
PubMed1992

Magnesium deficiency in vitro enhances free radical-induced intracellular oxidation and cytotoxicity in endothelial cells.

The effect of magnesium (Mg)-deficient culture on endothelial cell susceptibility to oxidative stress was examined. Bovine endothelial cells were cultured in either control sufficient (0.8 mM) or deficient (0.4 mM) levels of MgCl2. Oxygen radicals were produced extracellularly by the addition of dihydroxyfumarate and Fe(3+)-ADP. Isolated Mg-deficient endothelial cells produced 2- to 3-fold higher levels of thiobarbituric acid (TBA)-reactive materials when incubated with this free radical system. Additional studies were performed using digitized video microscopy and 2',7'-dichlorofluorescein diacetate (DCFDA) as an intracellular indicator for oxidative events at the single cell level. In response to the exogenous oxidative stress, endothelial cells exhibited a time-dependent increase in fluorescence, suggestive of intracellular lipid peroxidation. The increase in cellular fluorescence began within 1 min of free radical addition; the Mg-deficient cells exhibited a more rapid increase in fluorescence than that of Mg-sufficient cells. In separate experiments, cellular viability was assessed using the Trypan blue exclusion assay. Mg deficiency increased cytotoxicity of the added oxyradicals, but the loss of cellular viability began to occur only after 15 min of free radical exposure, lagging behind the detection of intracellular oxidation products. These results suggest that increased oxidative endothelial cell injury may contribute to vascular injury during Mg deficiency.

Adenosine Diphosphate↗
PubMed1992

Formation of superoxide in the reaction of photolytically altered nifedipine--a nitroso compound--with unsaturated membrane lipids.

Nifedipine, which is unstable at light, is photolytically converted to the corresponding 4-[2'-nitrosophenyl]-pyridine (NTP). We reported earlier that NTP react with unsaturated lipids in a pseudo Diels-Alder reaction, thus forming stable nitroxide radicals. In this paper we report that superoxide is being generated in the latter reaction. Superoxide formation was evidenced by SOD-inhibitable cytochrome c reduction in the reaction of NTP with egg phosphatidylcholine at molar ratio 1:1, and 1:3. In this reaction an ESR-observable nitroxide radical was formed. Maximum nitroxide formation was observed after 90 min; the addition of SOD (93 units/ml) increased the concentration of nitroxide. This effect of SOD was reversed by catalase, indicating involvement of hydrogen peroxide in this effect. The nitroxide radical formation appears to be metal-independent, since neither iron salts, nor an iron chelator, desferal, influenced the nitroxide formation. Although production of superoxide in our system was only observed at high concentrations of NTP and of unsaturated lipids, this reaction may be of potential cytotoxic significance due to redox cycling of the nitroxide/hydroxylamine couple in cellular systems.

Chelating Agents↗