Effect of bencyclane fumarate on intestinal ischaemia reperfusion injury

Background: Post‐ischaemic intestinal tissue damage appears to be due to the formation of oxygen radicals. Free radical‐initiated lipid peroxidation following intestinal ischaemia/reperfusion (I/R) may disrupt mucosal integrity. Indirectly, the radicals trigger the accumulation of neutrophils within the affected tissue, initiating inflammatory processes that lead to severe mucosal lesions. We have investigated the protective effect of bencyclane fumarate, a vasodilating Ca²⁺ channel blocker, which has been used for the treatment of peripheral arterial occlusive diseases, on intestinal ischaemia reperfusion (IR) injury in rats. Methods: Forty‐eight Wistar albino rats were divided into three groups: a sham‐operated group (no IR injury, n = 16), an ischaemic control group (IR, n = 16), and BF‐treated group (pretreatment 5 mg/kg bencyclane fumarate + IR, n = 16). A marker for lipid peroxidation, namely malondialdehyde; free radical scavengers, glutathione peroxidase, catalase and superoxide dismutase levels; an index of polymorphonuclear neutrophils, myeloperoxidase activity and mucosal damage were investigated. Results: Malondialdehyde levels, myeloperoxidase activity and the severity of mucosal damage were decreased in the BF group. In addition, in the BF group, glutathione peroxidase, catalase and superoxide dismutase levels were higher compared with the IR group. Conclusion: The pretreatment of rats with bencyclane fumarate before intestinal ischaemia attenuates the mucosal damage in intestinal IR injury, probably by altering lipid peroxidation, neutrophil accumulation and antioxidant activity.     

Lipid peroxidation and activity of antioxidant enzymes in muscle of the lower leg before and after arterial reconstruction

Reperfusion syndrome and lipid peroxidation due to toxic effects of free oxygen radicals might be one pathophysiological cause of the oedema that develops during the first week after a femoro-popliteal reconstruction. This paper reports the activity of the protecting antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase and catalase in gastrocnemic muscle before and after reperfusion of chronically ischaemic legs with comparison to activities in non-ischaemic muscle. Furthermore the susceptibility to lipid peroxidation in the muscle was measured as thiobarbituric acid reactive material (TBAR). The activities of CuZn SOD, Mn SOD and glutathione peroxidase were equal in normally perfused and chronically ischaemic muscle and there was no difference after reperfusion. Muscle catalase activity was low compared to activity of red blood cells and could not be reliably estimated. There was no difference in iron-stimulated lipid peroxidation of ischaemic and non-ischaemic muscle but in reliably estimated. There was no difference in iron-stimulated lipid peroxidation of ischaemic and non-ischaemic muscle but in muscle biopsied 10 min after reperfusion there was a significant increase in production of TBAR indicating an increased susceptibility for lipid peroxidation at this time. The finding is compatible with the occurrence of an oxidant insult on the muscle at reperfusion. Ischaemia--or reperfusion--induced reductions in activity of antioxidant enzymes are however not related to this reaction.     

Effect of pentoxifylline on experimentally induced lipid peroxidation in human spermatozoa

We demonstrated previously that pentoxifylline in millimolar concentrations can inhibit superoxide anion production by human spermatozoa. In the present study we have examined the effects of the same concentrations of pentoxifjrlline on experimentally induced lipid peroxidation, as measured by malondialdehyde formation in the thiobarbituric (TBA) assay. Under the experimental conditions used, preincubation of spermatozoa with pentoxifjdline led to a significant dose-dependent stimulation (p<0.005) of malondialdehyde production amounting to 10.77 ± 2.35%, 13.45 ±2.99% and 17.4 ± 1.99% (mean ± SEM) for 1.9, 3.7 and 11.2 mmol/l pentoxifylline, respectively. In the presence of 11.2 mmol/l pentoxifylline, an increase in iron-catalysed lipid peroxidation potential was detected in samples of spermatozoa from 29 infertile men, regardless of their initial levels of malondialdehyde. The results of this study indicate that pentoxifylline might further augment the ferrous ion-stimulated decomposition of pre-accumulation lipid hydroperoxides in the sperm plasma membrane and thus promote malondialdehyde generation in the TBA assay.
It is concluded that the stimulatory effect of pentoxifjdline on iron-induced lipid peroxidation may have an adverse effect on the quality of sperm suspensions prepared for in vitro fertilization, a possibility which should be investigated further.     

Chlamydia trachomatis and sperm lipid peroxidation in infertile men

Aim: To relate the presence of anti-Chlamydial trachomatis IgA in semen with sperm lipid membrane peroxidation and changes in seminal parameters. Methods: Semen samples of the male partners of 52 couples assessed for undiagnosed infertility were examined for the presence of IgA antibody against C. trachomatis. The level of sperm membrane lipid peroxidation was estimated by determining the malondialdehyde (MDA) formation. Results: Sperm membrane of infertile males with positive IgA antibodies against C. trachomatis showed a higher level of lipid peroxidation than that of infertile males with negative IgA antibody (P<0.05). There was a positive correlation (P< 0.01) between the level of C. trachomatis antibody and the magnitude of sperm membrane lipid peroxidation. All the other tested semen parameters were found to be similar in the two groups. Conclusion: The activation of immune system by C. trachomatis may promote lipid peroxidation of the sperm membrane. This could be the way by which C. trachomatis a     

Influence of preservation solutions on lipid peroxidation and mitochondrial respiration in rat kidneys

The role of hypothermic storage of rat kidneys on lipid peroxidation compared to its effect on mitochondrial respiratory parameters has been investigated. Rat kidneys were flushed with cold solutions of isotonic sodium chloride; Euro-Collins'; preservation solution containing histidine buffer, tryptophane, and alpha-ketoglutarate (HTK); or hypertonic citrate and then stored for 20 hr at 4 degrees C. After storage, the endogenous contents of malondialdehyde as well as the chemically (by Fe2+/ascorbic acid) and enzymatically (by Fe3+/ADP/NADPH) induced generation of malondialdehyde were measured in cortical homogenates and partly in mitochondria and microsomes by the thiobarbituric-acid reaction. Compared to the values measured in fresh, unstored kidneys, the levels of malondialdehyde were significantly higher in kidneys preserved in solutions of isotonic sodium chloride or HTK. This stimulating effect of the HTK solution on the generation of lipid peroxidation products could also be established when homogenate was incubated with this solution. Euro-Collins' and hypertonic citrate solution did not change the endogenous contents of malondialdehyde in kidneys during hypothermic storage. Both the chemically and enzymatically induced lipid peroxidation increased after hypothermic storage of kidneys in all solutions investigated. No direct relationship between the contents of malondialdehyde and respiratory mitochondrial parameters was detectable. The results demonstrate that the extent of lipid peroxidation does not correlate with preservation effectiveness.     

Effect of magnolol on in vitro mitochondrial lipid peroxidation and isolated cold-preserved warm-reperfused rat livers

BACKGROUND/AIM: A mechanism suggested to cause injury to preserved organs is the generation of oxygen free radicals. Lipid peroxidation is one of the biological damages caused by oxygen free radicals. It is our aim to investigate whether magnolol, a strong antioxidant, suppresses the generation of oxygen free radicals and improves the viability of cold-preserved warm-reperfused rat livers. MATERIALS AND METHODS: In vitro lipid peroxidation was induced in rat hepatic mitochondria with ADP and FeSO4. The inhibitory effect of magnolol on lipid peroxidation was measured with oxygen consumption and malondialdehyde (MDA) formation. Subsequently, we preserved and reperfused rat livers in preservation solutions that contained magnolol. The hepatic enzymes and liver MDA were measured to assess the protective effect of magnolol on isolated rat livers. RESULTS: In rat hepatic mitochondria, magnolol was 470 times more potent than alpha-tocopherol in inhibiting oxygen consumption and 340 times more potent than alpha-tocopherol in inhibiting MDA formation. Addition of magnolol to Ringer's lactate solution had a protective effect, in terms of MDA formation and leakage of hepatic enzymes, on warm-reperfused but not cold-stored liver tissue. Addition of magnolol to University of Wisconsin (UW) solution, a widely used preservation solution, did not modify the effect of this solution on isolated liver tissues. CONCLUSIONS: We conclude that magnolol is an effective antioxidant and suppresses lipid peroxidation in rat liver mitochondria and can be used as a rinsing solution in protecting transplanted organs from lipid peroxidation during reperfusion, especially for those organs not preserved with UW solution.     

Effect of dobutamine infusion on endotoxin-induced lipid peroxidation in awake sheep.

beta-agonists are known to not only increase oxygen delivery, but also attenuate the inflammatory response. We studied the effect of infusing the beta-agonist, dobutamine, on the oxidant-induced lung and liver tissue lipid peroxidation seen after endotoxemia. Twelve unanesthetized adult sheep with lung and soft tissue (prefemoral) lymph fistulae were given 5 micrograms/kg of Escherichia coli endotoxin intravenously. In six sheep, dobutamine 10 to 15 micrograms/kg/min was infused beginning 3 hours after endotoxin to increase oxygen delivery by 75% above baseline. Animals were killed at 6 hours, and lung and liver lipid peroxidation, measured as malondialdehyde, was obtained. Data were compared to six control sheep. Endotoxin alone produced increased lung and soft tissue vascular permeability as evidenced by a twofold increase in protein-rich lymph flow. Lung and liver malondialdehyde increased to 116 +/- 40 nmol/gm and 202 +/- 64 nmol/gm, respectively, compared to control values of 42 +/- 7 nmol/gm and 110 +/- 20 nmol/gm, respectively. Dobutamine infusion after endotoxin increased oxygen delivery by 75%, although changes in total oxygen consumption were not different from those seen with endotoxin alone. Lung and soft tissue lymph flow did not change with dobutamine. However, lung malondialdehyde was 41 +/- 17 nmol/gm, not different from controls. Liver malondialdehyde remained elevated at 164 +/- 26 nmol/gm. We conclude that dobutamine infusion prevents further oxidant-induced lung tissue lipid peroxidation but does not reverse the increased permeability already present. Liver lipid peroxidation was not decreased, suggesting the liver oxidant process may not be caused by the same mechanism as the lung lipid peroxidation.     

Interleukin-6 (IL-6) in seminal plasma of infertile men, and lipid peroxidation of their sperm

Concentrations of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in seminal fluid, as well as levels of sperm lipid membrane peroxidation, were investigated in fertile and infertile men. Semen samples, obtained by masturbation from 37 infertile and 14 fertile men, were examined for the presence of TNF-alpha and IL-6. The level of lipid peroxidation of the sperm membrane was measured by determining malondialdehyde (MDA) formation. The correlation between the IL-6 and the TNF-alpha concentrations in seminal plasma with the levels of lipid peroxidation of the sperm membranes was statistically evaluated. The IL-6 concentration in seminal plasma of infertile men was significantly higher than that of fertile men (p < .05). Similarly, the level of membrane lipid peroxidation was higher for the semen of infertile men than that of fertile men (p < .001). A significant positive correlation was found between IL-6 levels in seminal plasma and membrane sperm lipid peroxidation (p < .002), but not between this parameter and TNF-alpha levels in seminal plasma. These findings suggest a possible association between IL-6 seminal plasma levels and lipid peroxidation of sperm membrane. Stimulation of reactive species production by human sperm and leucocytes, induced by the high levels of IL-6, could explain these results.     

Reperfusion after cardioplegic cardiac arrest - effects on intracoronary leucocyte elastase release and oxygen free radical mediated lipid peroxidation

In experimental animal models reperfusion of ischaemic myocardium causes sequestration of leucocytes within the coronary circulation. Leucocytes contribute to postischaemic myocardial injury by releasing proteolytic enzymes and by generating oxygen free radicals. The aim of this study was to investigate whether leucocytes also contribute to myocardial injury following ischaemia and reperfusion associated with cardioplegic cardiac arrest. Therefore, we studied the release of the proteolytic enzyme elastase and oxygen free radical initiated myocardial lipid peroxidation in coronary sinus blood during reperfusion after cardioplegic cardiac arrest. The elastase-alpha-1-proteinase inhibitor complex and malondialdehyde (a byproduct of myocardial lipid peroxidation) were measured in arterial, central venous and coronary sinus blood samples in 19 patients undergoing elective coronary artery bypass grafting before aortic crossclamping and 1,5, 10 and 20 min after aortic declamping. Malondialdehyde concentrations did not increase significantly during the study period, whereas elastase concentrations showed a significant increase during cardiopulmonary bypass in arterial, central venous as well as coronary sinus blood. Neither elastase nor malondialhyde concentrations in coronary sinus blood differed significantly from arterial or central venous blood at any time point measured. Our data demonstrated increased elastase concentrations during cardiopulmonary bypass, but we did not find enhanced intracoronary elastase release or myocardial lipid peroxidation. Our data suggest that patients are sufficiently protected from leucocyte mediated ischaemia reperfusion injury during uncomplicated coronary artery bypass grafting with cardioplegic arrest.     

Halothane-induced lipid peroxidation and glucose-6-phosphatase inactivation in microsomes under hypoxic conditions

Halothane-induced lipid peroxidation was studied in microsomes from phenobarbital-pretreated male rats at defined steady state oxygen partial pressures (PO2). At PO2 less than 10 mmHg on addition of halothane to NADPH-reduced microsomes, significant increases in malondialdehyde (MDA) formation, oxygen uptake, and conjugated dienes were measured. At the maximum, near a PO2 of 1 mmHg, halothane induced the formation of about 0.75 nmol MDA X mg microsomal protein-1 X min-1; it also stimulated microsomal oxygen uptake twofold to threefold, and caused an almost threefold increase in conjugated diene absorption. Moreover, at this PO2 microsomal glucose-6-phosphatase lost about 70% of its activity. At PO2 greater than 10 mmHg, no significant effects of halothane on MDA formation, oxygen uptake, conjugated diene absorption, and glucose-6-phosphatase activity were observed; likewise under anaerobic conditions there was only a slight increase in conjugated dienes. The findings demonstrate that halothane induces microsomal lipid peroxidation at low PO2 and in the presence of particular cytochrome P-450 isoenzymes, and that the halothane-induced lipid peroxidation leads to severe microsomal lesions, as indicated by the loss of glucose-6-phosphatase activity.     

Halothane-dependent lipid peroxidation in human liver microsomes is catalyzed by cytochrome P4502A6 (CYP2A6)

BACKGROUND: Halothane is extensively (approximately 50%) metabolized in humans and undergoes both oxidative and reductive cytochrome P450-catalyzed hepatic biotransformation. Halothane is reduced under low oxygen tensions by CYP2A6 and CYP3A4 in human liver microsome to an unstable free radical, and then to the volatile metabolites chlorodifluoroethene (CDE) and chlorotrifluoroethane (CTE). The free radical is also thought to initiate lipid peroxidation. Halothane-dependent lipid peroxidation has been shown in animals in vitro and in vivo but has not been evaluated in humans. This investigation tested the hypothesis that halothane causes lipid peroxidation in human liver microsomes, identified P450 isoforms responsible for halothane-dependent lipid peroxidation, and tested the hypothesis that lipid peroxidation is prevented by inhibiting halothane reduction. METHODS: Halothane metabolism was determined using human liver microsomes or cDNA-expressed P450. Lipid peroxidation was quantified by malondialdehyde (MDA) formation using high-pressure liquid chromatography-ultraviolet analysis of the thiobarbituric acid-MDA adduct. CTE and CDE were determined by gas chromatography-mass spectrometry. RESULTS: Halothane caused MDA formation in human liver microsomes at rates much lower than in rat liver microsomes. Human liver microsomal MDA production exhibited biphasic enzyme kinetics, similar to CDE and CTE production. MDA production was inhibited by the CYP2A6 inhibitor methoxsalen but not by the CYP3A4 inhibitor troleandomycin. Halothane-dependent MDA production was catalyzed by cDNA-expressed CYP2A6 but not CYP3A4 or P450 reductase alone. CYP2A6-catalyzed MDA production was inhibited by methoxsalen or anti-CYP2A6 antibody. CONCLUSIONS: Halothane causes lipid peroxidation in human liver microsomes, which is catalyzed by CYP2A6, and inhibition of halothane reduction prevents halothane-dependent lipid peroxidation in vitro.     

Early postburn lipid peroxidation: effect of ibuprofen and allopurinol

We measured lipid peroxidation of plasma, lung, and liver in anaesthetized sheep after third-degree burns involving 30% of total body surface. Animals were resuscitated to baseline filling pressures with lactated Ringer's solution and killed 10 hours after burn. Six sheep were pretreated with ibuprofen (12.5 mg/kg) and five with allopurinol (50 mg/kg). We used conjugated dienes and malondialdehyde as measures of lipid peroxidation. Circulating conjugated dienes increased from a baseline of 0.48 +/- 0.06 to 0.64 +/- 0.05 after burn, while protein-rich burn tissue lymph flow increased up to eightfold. We also noted a significant increase in lung tissue malondialdehyde from 45 +/- 4 to 60 +/- 6 nmol/gm and liver malondialdehyde from 110 +/- 20 to 271 +/- 34 nmol/gm along with increased tissue neutrophil sequestration. Ibuprofen attenuated lung-tissue malondialdehyde but had no effect on lung inflammation, circulating lipid peroxides or burn edema, indicating that ibuprofen most likely decreased O2 radical release in lung tissue by the already-sequestered neutrophils. Allopurinol, possibly via xanthine oxidase inhibition, markedly attenuated burn QL and circulating lipid peroxides and prevented all pulmonary lipid peroxidation and inflammation, indicating that release of oxidant from burn tissue was in part responsible for local burn edema, as well as distant inflammation and oxidant release, the latter most likely from complement activation. Neither antioxidant decreased lipid peroxidation in the liver; this indicates that its mechanism of production was different from that seen in burn tissue, in plasma, or in the lung. An ischemic event resulting from a selective decrease in splanchnic blood flow may be the cause of the liver changes.     

The effects of the pretreatment of intravenous high dose methylprednisolone on Na+-K+/Mg+2 ATPase and lipid peroxidation and early ultrastructural findings following middle cerebral artery occlusion in the rat

Summary The sodium-potassium activated and magnesium dependent adenosine-5-triphosphatase (Na⁺-K⁺/Mg⁺² ATPase EC.3.6.1.3.) activity and lipid peroxidation and early ultrastructural findings were determined in rat brain at the acute stage of ischaemia produced by permanent unilateral occlusion of the middle cerebral artery (MCA). The effects of the pretreatment with intravenous high-dose methylprednisolone (MP) on these biochemical indices and ultrastructural findings were also evaluated in the same model. The rats were divided into four groups. In group I, 10 rats were used to determine Na⁺-K⁺/Mg⁺² ATPase activity and the extent of lipid peroxidation by measuring the malondialdehyde (MDA) content and normal ultrastructural findings. In group II on 20 rats, only subtemporal craniectomy was done in order to determine the effects of the surgical procedure on these indices and findings. This group was treated intravenously with saline solution before occlusion. In group III with MCA occlusion, saline solution was administered intravenously to 20 rats in the same amount of methylprednisolone used in group IV, ten minutes before the occlusion. In Group IV, a single high-dose (30 mg/kg) of methylprednisolone was administered intravenously, ten minutes before occlusion in 20 rats. After occlusion of the middle cerebral artery, Na⁺-K⁺/Mg⁺² ATPase activity was decreased promptly in the first ten minutes in the ischaemic hemisphere and remained at a lower level than the contralateral hemispheres in the same group and the normal levels in group I, during 120 minutes of ischaemia. A single dose methylprednisolone pretreatment prohibited the inactivation of Na⁺-K⁺/Mg⁺² ATPase. On the other hand, there was significant difference in malondialdehyde content between group I and group III. Malondialdehyde levels were significantly increased following ischaemia and a non-significant increase was observed in the contralateral hemisphere. Methylprednisolone treatment significantly decreased malondialdehyde content on the side of the ischaemic hemisphere. We conclude that there is a positive relationship between membrane-bound enzyme Na⁺-K⁺/Mg⁺² ATPase activity, malondialdehyde content and early ultrastructural changes in the treated group with MP.These data suggest that the pretreatment injection of high doses (30 mg/kg) methylprednisolone contribute to the protection of the brain from ischaemia with stabilization of the cell membrane by effecting the lipid peroxidation and the activation of Na⁺-K⁺/Mg⁺² ATPase.     

Halothane-dependent Lipid Peroxidation in Human Liver Microsomes Is Catalyzed by Cytochrome P4502A6 (CYP2A6)

Background: Halothane is extensively (approximately 50%) metabolized in humans and undergoes both oxidative and reductive cytochrome P450-catalyzed hepatic biotransformation. Halothane is reduced under low oxygen tensions by CYP2A6 and CYP3A4 in human liver microsome to an unstable free radical, and then to the volatile metabolites chlorodifluoroethene (CDE) and chlorotrifluoroethane (CTE). The free radical is also thought to initiate lipid peroxidation. Halothane-dependent lipid peroxidation has been shown in animals in vitro and in vivo but has not been evaluated in humans. This investigation tested the hypothesis that halothane causes lipid peroxidation in human liver microsomes, identified P450 isoforms responsible for halothane-dependent lipid peroxidation, and tested the hypothesis that lipid peroxidation is prevented by inhibiting halothane reduction.

Methods: Halothane metabolism was determined using human liver microsomes or cDNA-expressed P450. Lipid peroxidation was quantified by malondialdehyde (MDA) formation using high-pressure liquid chromatography-ultraviolet analysis of the thiobarbituric acid-MDA adduct. CTE and CDE were determined by gas chromatography-mass spectrometry.

Results: Halothane caused MDA formation in human liver microsomes at rates much lower than in rat liver microsomes. Human liver microsomal MDA production exhibited biphasic enzyme kinetics, similar to CDE and CTE production. MDA production was inhibited by the CYP2A6 inhibitor methoxsalen but not by the CYP3A4 inhibitor troleandomycin. Halothane-dependent MDA production was catalyzed by cDNA-expressed CYP2A6 but not CYP3A4 or P450 reductase alone. CYP2A6-catalyzed MDA production was inhibited by methoxsalen or anti-CYP2A6 antibody.     

Effect of 21-aminosteroid U-74006F on lipid peroxidation in subarachnoid clot

The present study was undertaken to investigate the effect of U-74006F on malondialdehyde (a by-product of lipid peroxidation) in subarachnoid clot. Eighteen cynomolgus monkeys were divided into three groups of six each. There were two U-74006F-treated groups, receiving doses of 0.3 or 1.0 mg/kg, and a placebo-treated group. Each monkey underwent baseline cerebral angiography followed by right-sided craniectomy and placement of subarachnoid clot around the middle cerebral artery (MCA). Treatment was administered intravenously every 8 hours for 6 days. Seven days after the experimental subarachnoid hemorrhage (SAH), angiography was repeated and the animals were killed. In the placebo-treated group, significant vasospasm occurred in the MCA on the side of the clot (p less than 0.01). After U-74006F treatment at both dosages, significantly less vasospasm developed in the clot-side MCA (p less than 0.01). The content of malondialdehyde was measured by both the thiobarbituric acid test and high-performance liquid chromatography (HPLC). Comparing the two methods, HPLC proved to be more accurate than the thiobarbituric acid test, especially for measurement of low concentrations of malondialdehyde. In the placebo-treated group, the malondialdehyde content was significantly increased in the Day 7 clot (p less than 0.05). In contrast, malondialdehyde content in freshly prepared clot was very low. In the 0.3-mg/kg U-74006F group, the malondialdehyde content of clot was significantly less at Day 7 compared to clot from the placebo-treated group (p less than 0.05). Although the malondialdehyde content of clot from the 1.0 mg/kg U-74006F-treated group was less than that of placebo, it was not significantly so. Malondialdehyde was not detected in the actual vessel wall of the MCA of any group. These results suggest that lipid peroxidation in subarachnoid clot may play a role in the pathogenesis of vasospasm and that the salutary effects of U-74006F in vasospasm may be mediated by a reduction of lipid peroxidation in SAH.     

The lung inflammatory response to thermal injury: relationship between physiologic and histologic changes

We studied the effect of a body burn on lung physiologic, biochemical, and histologic changes in a 2-day postburn period. A 15% of total-body-surface third-degree burn was produced in 24 adult sheep with lung and burn lymph fistulas. Eight sheep were killed at 12 hours and eight at 48 hours. At 12 hours we noted increased lung tissue lipid peroxidation, lung congestion, and neutrophil sequestration, in addition to a 30% decrease in lung compliance. Lung permeability and water content were not increased. Increased release of lipid peroxides and prostanoids were noted from burn tissue, as evidenced by increased plasma levels of malondialdehyde and conjugated dienes that remained elevated for about 8 hours and were decreased with wound removal. The lung inflammatory response was still present at 48 hours, the cells being primarily neutrophils. Nevertheless, the lipid peroxidation process, as measured by lung tissue malondialdehyde, had resolved. There was no evidence of burn tissue infection, measured by quantitative culture, to explain the persistent increase in lung inflammatory cells. Excision and closure of the burn wound at 3 hours postburn in eight sheep attenuated the lipid peroxidation and compliance changes but did not decrease the neutrophil sequestration. We conclude that burn injury results in a local wound oxidant release that leads to lipid peroxidation, both in wounds and in lung, as well as lung inflammation. The lipid peroxidation process may be attenuated by removal of the wound. The neutrophil sequestration is not altered, however, indicating this response occurs very early after injury, probably as a result of oxidant-initiated complement activation.     

The effects of chronic alpha-tocopherol administration on lipid peroxidation in an experimental model of acute spinal cord injury

Most of the numerous experimental studies to research pathophysiological changes following acute spinal cord injury suggest a two-step mechanism of damage to the spinal cord in which the primary (direct) or mechanical injury caused by the trauma initiates secondary (indirect) or progressive autodestructive injury of the cord. During recent years, free oxygen radical generation and lipid peroxidation have been considered to be responsible for secondary autodestructive injury.Alpha tocopherol occupies an important and unique position in the overall antioxidant defense. Alpha tocopherol-depleted animals are generally more susceptible to the adverse effects of environmental agents than are supplemented animals. This study was planned to study the effectiveness in counteracting this autodestructive process by supplementing alpha-tocopherol in rats maintained on a nutritionally adequate diet, and also to evaluate whether it will provide additional protection or not. Eighty healthy Wistar rats (treatment and controls) were included. The treatment group received 100 mg/kg alpha tocopherol each day, intraperitoneally for seven days. Using a standard acute spinal cord trauma model in Wistar rats trauma was applied, an malondialehyde (MDA) which is a lipid peroxidation product was measured in the traumatized spinal cord at various times following the trauma in order to indirectly evaluate the lipid peroxidation and generation of free oxygen radicals in a time sequence. Statistical analysis of the values demonstrated that malondialdehyde formation in the alpha-tocopherol administered group was significantly lower than in the control group. These findings indicate that longterm administration of alpha-tocopherol may be useful to decrease lipid peroxidation following acute spinal cord trauma.     

Early changes in plasma antioxidant and lipid peroxidation levels following coronary artery bypass surgery: a complex response

Objective: Total plasma antioxidant capacity (TPAC) quantitatively defines extracellular fluid antioxidant capacity, the mechanism of which is different from the intracellular mechanism. Patients undergoing surgery for congenital heart defects have suppressed TPAC in the early postoperative periods. Our aim was to study the early changes of TPAC following coronary artery bypass grafting (CABG), in relation to lipid peroxidation, and to identify clinical factors affecting these changes. Methods: We studied 28 consecutive patients undergoing routine uncomplicated CABG with cardiopulmonary bypass (CPB). Patients taking known antioxidants, such as captopril and allopurinol, and those receiving transfusion of blood or blood products at operation or during the first 72 postoperative hours were excluded. Serial blood samples were obtained for TPAC and lipid hydroperoxide concentration (LPX). Results: TPAC was suppressed for 72 h after the operation, while LPX exhibited a significant increase only 1 h post-operatively. TPAC time changes resulted from a simultaneous depression (50% of the baseline occurring approximately 6 h after the operation) and production (18% of the baseline occurring approximately 6 h after the operation) of plasma antioxidants. The earlier the peak of plasma antioxidant production the later and the less the plasma antioxidant depression. Plasma antioxidant depression was inversely related to LPX (r=−0.37, P=0.05 and r=−0.40, P=0.04 at 1 and 6 h respectively). Ejection fraction and operative myocardial ischaemic times significantly influenced plasma antioxidant depression. Conclusions: TPAC is suppressed for 72 h following CABG. TPAC depression may be involved in the mechanism of lipid peroxidation and is influenced by clinical factors known to be related to post CABG morbidity and mortality, like low ejection fraction and long ischaemic times.     

Heme metabolism and lipid peroxidation in rat kidney hexachlorobenzene-induced porphyria: A compartmentalized study of biochemical pathogenic mechanisms

In the present study, the effects of hexachlorobenzene (HCB) on lipid peroxidation and heme metabolism in the different constitutive suborgans of the kidney were determined. For this purpose, conjugated diene and malondialdehyde levels, as lipid peroxidation parameters, and porphyrin accumulation, uroporphyrinogen decarboxylase activity, and its inhibitor formation, as measures of heme metabolism, were determined in renal cortex, medulla, and papilla. Adult Wistar rats were treated with HCB during 1, 2, 3, or 4 weeks. A significant increase in cortical conjugated dienes was observed from the 1st week of treatment. The malondialdehyde levels rose by 47, 34, and 28% after 2, 3, and 4 weeks of intoxication, respectively. The porphyrin content showed a tenfold increase after 4 weeks of treatment, and the uroporphyrinogen decarboxylase activity was reduced by 26 and 58% with respect to control values after 3 and 4 weeks of treatment, respectively. The results demonstrate a direct correlation between the oxidative environment and the effect elicited by the drug on heme metabolism in the renal cortex. In contrast, in papilla and medulla, where the antioxidant systems were higher, HCB showed no porphyrinogenic effect.     

A small dose of hydrogen peroxide enhances tumor necrosis factor-alpha toxicity in inducing human vascular endothelial cell apoptosis: reversal with propofol

We designed the present study to test the hypothesis that oxygen free radicals can enhance tumor necrosis factor (TNF)-alpha cellular toxicity, which might be reversed by propofol, an anesthetic with antioxidant properties, in human vascular endothelial cell line ECV304. Cultured ECV304 were either not treated, treated with 10 muM of hydrogen peroxide (H2O2), treated with TNF-alpha (40 ng/mL) alone, TNF-alpha in the presence of 10 microM of H2O2 (H+T), or propofol plus H2O2 for 24 h. Cell viability was measured by lactate dehydrogenate (LDH) assay. Cell apoptosis was assessed by flow cytometry and terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick end-labeling. The antiapoptotic Bcl-2 and pro-apoptotic Bax protein expressions were measured by immunocytochemical analysis. Increases in apoptosis, Bax, lipid peroxidation product malondialdehyde, LDH, and decreases in Bcl-2, superoxide dismutase, and glutathione peroxidase were observed in TNF-alpha-treated cells. H2O2 10 microM did not cause significant lipid peroxidation (0.75 +/- 0.03 nmol/mg of malondialdehyde protein) as compared with control (0.70 +/- 0.04 nmol/mg of malondialdehyde protein) (P > 0.05) but further enhanced TNF-alpha-induced lipid peroxidation, upregulated Bax, and down-regulated Bcl-2 expression and enhanced TNF-alpha-induced cell apoptosis (P < 0.05). Propofol 50 microM attenuated TNF-alpha and H2O2-induced cell apoptosis, accompanied by decreases in malondialdehyde and LDH production and restoration of Bcl-2 expression. Propofol exerts protective effects against H2O2-enhanced TNF-alpha cell toxicity by reducing oxidative injury.