Comparative studies on the mechanisms of paraquat and 1-methyl-4-phenylpyridine (MPP+) cytotoxicity

1-methyl-4-phenylpyridine (MPP+) is the putative toxic metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and is structurally similar to the herbicide paraquat (PQ++). We have therefore compared the effects of MPP+ and PQ++ on a well characterized experimental model, namely isolated rat hepatocytes. PQ++ generates reactive oxygen species within cells by redox cycling and its toxicity to hepatocytes was potentiated by pretreatment with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of glutathione reductase. In BCNU-treated cells, PQ++ caused GSH depletion, lipid peroxidation and cell death. These cytotoxic effects were prevented by the antioxidant N,N'-diphenyl-p-phenylenediamine (DPPD) and the iron-chelating agent desferrioxamine. MPP+ also caused GSH depletion in BCNU-treated hepatocytes but its cytotoxicity was not markedly affected by BCNU, nor was it accompanied by significant lipid peroxidation. DPPD and desferrioxamine also failed to prevent MPP+-induced cell death. We conclude that the production of active oxygen species is likely to play a major role in PQ++ cytotoxicity, while MPP+-induced cell damage may involve additional, more important toxic mechanisms.     

Turnera ulmifolia L. (Turneraceae): preliminary study of its antioxidant activity

Turnera ulmifolia L. is used in Brazilian folk medicine as an anti-inflammatory. Since this activity may be correlated with the presence of antioxidant compounds, a leaf extract was evaluated for its radical scavenging capacity (RSC). The in vitro RSC of a 50% hydroethanolic (HE) extract was evaluated by beta-carotene/linoleic acid coupled oxidation system for the inhibition of oxidation and the lipid peroxidation inhibition in rat brain homogenates, using thiobarbituric acid reactive substances (TBARS) and chemiluminescence (CL). Results indicated, through peroxidation suppression, that this extract exhibited greater antioxidative activity (77.4% +/- 10%) than alpha-tocopherol (58.4% +/- 3.7%). TBARS and CL inhibition was concentration-dependent and Q(1/2) values were 8.2 and 6.0 microg/mL for TBARS and CL, respectively. For alpha-tocopherol these values were 7.1 microg/mL (TBARS) and 9.8 microg/mL (CL). Phenolic compounds may be responsible for this antioxidant capacity.     

Protective effect of unsymmetrical dichalcogenide, a novel antioxidant agent, in vitro and an in vivo model of brain oxidative damage

Unsymmetrical dichalcogenides, a class of organoselenium compounds, were screened for antioxidant activity in rat brain homogenates in vitro. Unsymmetrical dichalcogenides (1-3) were tested against lipid peroxidation induced by sodium nitroprusside (SNP) or malonate, and reactive species (RS) production induced by sodium azide in rat brain homogenates. Compounds 1 (without a substituent at the phenyl group), 2 (chloro substituent at the phenyl group bounded to the sulfur atom) and 3 (chloro substituent at the phenyl group bounded to the selenium atom) protected against lipid peroxidation induced by SNP. The IC50 values followed the order 3<2<1. Lipid peroxidation induced by malonate was also reduced by dichalcogenides 1, 2 and 3. The IC50 values were 3相似文献   

Rabbit liver microsomal lipid peroxidation. The effect of lipid on the rate of peroxidation

Rat and rabbit liver microsomes catalyze an NADPH-cytochrome P-450 reductase-dependent peroxidation of endogenous lipid in the presence of the chelate, ADP-Fe3+. Although liver microsomes from both species contain comparable levels of NADPH-cytochrome P-450 reductase and cytochrome P-450, the rate of lipid peroxidation (assayed by malondialdehyde and lipid hydroperoxide formation) catalyzed by rabbit liver microsomes is only about 40% of that catalyzed by rat liver microsomes. Microsomal lipid peroxidation was reconstituted with liposomes made from extracted microsomal lipid and purified protease-solubilized NADPH-cytochrome P-450 reductase from both rat and rabbit liver microsomes. The results demonstrated that the lower rates of lipid peroxidation catalyzed by rabbit liver microsomes could not be attributed to the specific activity of the reductase. Microsomal lipid from rabbit liver was found to be much less susceptible to lipid peroxidation. This was due to the lower polyunsaturated fatty acid content rather than the presence of antioxidants in rabbit liver microsomal lipid. Gas-liquid chromatographic analysis of fatty acids lost during microsomal lipid peroxidation revealed that the degree of fatty acid unsaturation correlated well with rates of lipid peroxidation.     

Cinnamophilin as a novel antiperoxidative cytoprotectant and free radical scavenger

The antioxidant properties of cinnamophilin were evaluated by studying its ability to react with relevant reactive oxygen species, and its protective effect on cultured cells and biomacromolecules under oxidative stress. Cinnamophilin concentration-dependently suppressed non-enzymatic iron-induced lipid peroxidation in rat brain homogenates with an IC50 value of 8.0+/-0.7 microM and iron ion/ADP/ascorbate-initiated rat liver mitochondrial lipid peroxidation with an IC50 value of 17.7+/-0.2 microM. It also exerted an inhibitory activity on NADPH-dependent microsomal lipid peroxidation with an IC50 value of 3.4+/-0.1 microM without affecting microsomal electron transport of NADPH-cytochrome P-450 reductase. Both 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azo-bis(2-amidinopropane) dihydrochloride-derived peroxyl radical tests demonstrated that cinnamophilin possessed marked free radical scavenging capacity. Cinnamophilin significantly protected cultured rat aortic smooth muscle cells (A7r5) against alloxan/iron ion/H2O2-induced damage resulting in cytoplasmic membranous disturbance and mitochondrial potential decay. By the way, cinnamophilin inhibited copper-catalyzed oxidation of human low-density lipoprotein, as measured by fluorescence intensity and thiobarbituric acid-reactive substance formation in a concentration-dependent manner. On the other hand, it was reactive toward superoxide anions generated by the xanthine/xanthine oxidase system and the aortic segment from aged spontaneously hypertensive rat. Furthermore, cinnamophilin exerted a divergent effect on the respiratory burst of human neutrophil by different stimulators. Our results show that cinnamophilin acts as a novel antioxidant and cytoprotectant against oxidative damage.     

Involvement of Oxidative Stress in Paraquat-Induced Metallothionein Synthesis Under Glutathione Depletion

The inhibition of glutathione (GSH) synthesis by -buthionine-SR-sulfoximine (BSO) causes aggravation of hepatotoxicity of paraquat (PQ), an oxidative-stress inducing substance, in mice. On the other hand, synthesis of metallothionein (MT), a cysteine-rich protein having radical scavenging activity, is induced by PQ, and the induction by PQ is significantly enhanced by pretreatment of mice with BSO. The purpose of present study is to examine whether generation of reactive oxygens is involved in the induction of MT synthesis by PQ under inhibition of GSH synthesis. Administration of PQ to BSO-pretreated mice increased hepatic lipid peroxidation and frequency of DNA single strand breakage followed by manifestation of the liver injury and induction of MT synthesis. Both vitamin E and deferoxamine prevented MT induction as well as lipid peroxidation in the liver of mice caused by administration of BSO and PQ. In cultured colon 26 cells, both cytotoxicity and the increase in MT mRNA level caused by PQ were significantly enhanced by pretreatment with BSO. Facilitation of PQ-induced reactive oxygen generation was also observed by BSO treatment. These results suggest that reactive oxygens generated by PQ under inhibition of GSH synthesis may stimulate MT synthesis. GSH depletion markedly increased reactive oxygen generation induced by PQ, probably due to the reduced cellular capability to remove the radical species produced.     

Lipid Peroxidation and Antioxidant Systems in Rat Brain: Effect of Chronic Alcohol Consumption

The effect of chronic ethanol exposure, in a liquid diet, on lipid peroxidation and some antioxidant systems of rat brain was investigated. Chronic ethanol administration induced a greater susceptibility to iron/ascorbate-induced lipid peroxidation, estimated as thiobarbituric reactive substances (TBARS) production, in the microsomal fraction, but a lower lipid peroxidation in the total homogenate. Glutathione (GSH) levels as well as GSH peroxidase and GSH reductase were unaffected, while the activity of Cu-Zn superoxide dismutase was decreased and that of catalase increased. Lipid peroxidation experiments performed in the presence of some hydroxyl radical scavengers suggested that a greater OH^· generation may be responsible of the greater TBARS production in the microsomal fraction of ethanol treated rats; differently, in total homogenate of control and ethanol rats a relationship was found between the redox state of iron and TBARS production, suggesting that the lower lipid peroxidation in treated rats may depend on a different modulation of the iron redox state.     

Role of metal-induced reactive oxygen species generation in lung responses caused by residual oil fly ash

Inhalation of residual oil fly ash (ROFA) increases pulmonary morbidity in exposed workers. We examined the role of reactive oxygen species (ROS) in ROFA-induced lung injury. ROFA was collected from a precipitator at Boston Edison Co., Everett, MA, USA. ROFA (ROFA-total) was suspended in saline, incubated for 24 h at 37 degrees C, centrifuged, and separated into its soluble (ROFA-sol.) and insoluble (ROFA-insol.) fractions. Sprague-Dawley rats were intratracheally instilled with saline or ROFA-total or ROFA-sol. or ROFA-insol. (1 mg/100 g body wt.). Lung tissue and bronchoalveolar lavage cells were harvested at 4, 24, and 72 h after instillation. Chemiluminescence (CL) of recovered cells was measured as an index of ROS production, and tissue-lipid-peroxidation was assessed to determine oxidative injury. Significant amounts of Al, Fe, and Ni were present in ROFA-sol., whereas ROFA-insol. contained Fe, V, and Al. Using electron spin resonance (ESR), significantly more hydroxyl radicals were measured in ROFA-sol. as compared to ROFA-insol. None of the ROFA samples had an effect on CL or lipid peroxidation at 4 h. Treatment with ROFA-total and ROFA-insol. caused significant increases in both CL (at 24 h) and lipid peroxidation (at 24 and 72 h) when compared to saline control value. ROFA-sol. significantly reduced CL production at 72 h after treatment and had no effect on lipid peroxidation at any time point. In summary, ROFA, particularly its soluble fraction, generated a metal-dependent hydroxyl radical as measured by a cell-free ESR assay. However, cellular oxidant production and tissue injury were observed mostly with the ROFA-total and ROFA-insol. particulate forms. ROS generated by ROFA-sol. as measured by ESR appear not to play a major role in the lung injury caused after ROFA exposure.     

9,10-Phenanthraquinone in diesel exhaust particles downregulates Cu,Zn-SOD and HO-1 in human pulmonary epithelial cells: intracellular iron scavenger 1,10-phenanthroline affords protection against apoptosis

9,10-Phenanthraquinone (PQ), a major quinone contained in diesel exhaust particles and atmospheric PM(2.5), undergoes one-electron reduction by flavin enzymes such as NADPH-cytochrome P450 reductase, leading to production of reactive oxygen species in vitro. We have detected an ESR signal for superoxide (O(2)(-)) and hydroxyl radicals ((.)OH) by the spin trap method when PQ was mixed with P450 reductase, NADPH, and iron(III). When we examined the effects of PQ on A549 human pulmonary epithelial cells, PQ induced apoptosis with a LC(50) of approximately 7 microM. Formation of protein carbonyls was also detected in cells after treatment with PQ, suggesting that PQ induces oxidative damage. Iron chelators such as 1,10-phenanthroline (OP), desferrioxamine mesylate, and deferiprone respectively afforded protection against the toxic effects of PQ. Furthermore, treatment of A549 cells with 10-20 microM PQ for 12 h specifically down-regulated protein levels of Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and heme oxygenase-1 (HO-1) by more than 50%. Pretreatment of cells with OP (10 microM) markedly reduced the down-regulation of Cu,Zn-SOD and HO-1 and protein carbonyl formation in response to PQ. The inhibitor of Cu,Zn-SOD, diethyldithiocarbamate, enhanced the toxic effects of 5 microM PQ. The present findings suggest that PQ causes iron-mediated oxidative damage that is exacerbated by the concomitant down-regulation of Cu,Zn-SOD.     

Stimulation and inhibition of iron-dependent lipid peroxidation by desferrioxamine

Peroxidation of rat brain synaptosomes was assessed by the formation of thiobarbituric acid reactive products in either 50 mM potassium phosphate buffer (pH 7.4) or pH adjusted saline. In phosphate, addition of Fe2+ resulted in a dose-related increase in lipid peroxidation. In saline, stimulation of lipid peroxidation by Fe2+ was maximal at 30 uM, and was less at concentrations of 100 uM and above. Whereas desferrioxamine caused a dose-related inhibition of iron-dependent lipid peroxidation in phosphate, it stimulated lipid peroxidation with Fe2+ by as much as 7-fold in saline. The effects of desferrioxamine depended upon the oxidation state of iron, and the concentration of desferrioxamine and lipid. The results suggest that lipid and desferrioxamine compete for available iron. The data are consistent with the hypothesis that either phosphate or desferrioxamine may stimulate iron-dependent lipid peroxidation under certain circumstances by favoring formation of Fe2+/Fe3+ ratios.     

Plastoquinone: possible involvement in plant disease resistance

The plant Solanum nigrum treated with the pathogen Phytophthora infestans-derived elicitor responded by elevated reactive oxygen species (ROS) production, lipid peroxidation and lipoxygenase (EC 1.13.11.12) activity in comparison with control plants indicating that oxidative stress took place. We demonstrate that these events are accompanied by a significant increase in plastoquinone (PQ) level. It is postulated that PQ may be associated with mechanisms maintaining a tightly controlled balance between the accumulation of ROS and antioxidant activity that determines the full expression of effective defence.     

Inhibition of lipid peroxidation by prostaglandin oligomeric derivatives.

The inhibition of lipid peroxidation by oligomeric derivatives synthesized from prostaglandin E1 (PGE1) and PGB2 was studied using two rat models. In an in vitro model, the brain was exposed to decapitation-ischemia, the cortex was removed and homogenized, and the formation of thiobarbituric acid reactive substances (TBAR) was measured after exposing the homogenate to in vitro reoxygenation either in the presence or absence of oligomers. It was found that these oligomers could inhibit lipid peroxidation, and that their activities were higher than that of superoxide dismutase (SOD). In an in vivo administration model, either the oligomer or the vehicle was injected i.p. 30 min before decapitation. The brain was exposed to decapitation-ischemia, the cortex was homogenized and exposed to 'in vitro' reoxygenation, after which TBAR value was determined. Ester-type compounds had a greater activity than free-acid type compounds in inhibiting lipid peroxidation. A possible mechanism of the protective effect of these oligomers in ischemia/reperfusion injury may be to scavenge oxygen free radicals.     

Lipid peroxidation associated cardiolipin loss and membrane depolarization in rat brain mitochondria

Oxidative stress induced by Fe2+ (50 microM) and ascorbate (2 mM) in isolated rat brain mitochondria incubated in vitro leads to an enhanced lipid peroxidation, cardiolipin loss and an increased formation of protein carbonyls. These changes are associated with a loss of mitochondrial membrane potential (depolarization) and an impaired activity of electron transport chain (ETC) as measured by MTT reduction assay. Butylated hydroxytoluene (0.2 mM), an inhibitor of lipid peroxidation, can prevent significantly the loss of cardiolipin, the increased protein carbonyl formation and the decrease in mitochondrial membrane potential induced by Fe2+ and ascorbate, implying that the changes are secondary to membrane lipid peroxidation. However, iron-ascorbate induced impairment of mitochondrial ETC activity is apparently independent of lipid peroxidation process. The structural and functional derangement of mitochondria induced by oxidative stress as reported here may have implications in neuronal damage associated with brain aging and neurodegenerative disorders.     

2,2′-dithienyl diselenide,an organoselenium compound,elicits antioxidant action and inhibits monoamine oxidase activity in vitro

Context: Organoselenium compounds have been described as antioxidant and neuroprotective agents.

Objective: To evaluate the antioxidant action of 2,2′-dithienyl diselenide (DTDS) and its effects in brain monoamine oxidase (MAO) activity in vitro.

Materials and methods: Assays for reactive species (RS), lipid peroxidation, protein oxidation, MAO A and B activities in rat brain homogenate as well as mimetic dehydroascorbate reductase and glutathione S-transferase activities were performed using DTDS (μM range).

Results: DTDS was effective in decreasing the levels of RS as well as lipid peroxidation induced by malonate, sodium nitroprusside or FeCl₂/EDTA and protein carbonyl in the rat brain homogenate. DTDS elicited dehydroascorbate reductase-like and glutathione S-transferase-like activities. DTDS was effective in inhibiting both MAO-A and MAO-B activities.

Discussion: The results demonstrated that DTDS is an antioxidant agent with non-selective inhibitory effect on MAO activity.

Conclusion: DTDS is a promising molecule to be evaluated in experimental models of neurological diseases.     

The involvement of nitric oxide in maneb- and paraquat-induced oxidative stress in rat polymorphonuclear leukocytes

Oxidative stress plays a crucial role in the manifestations of maneb (MB) and paraquat (PQ)-induced toxicity including MB+PQ-induced Parkinson's disease (PD). Polymorphonuclear leukocytes (PMNs) actively participate in the oxidative stress-mediated inflammation and organ toxicity. The present study was undertaken to investigate the MB- and/or PQ-induced alterations in the indices of oxidative stress in rat PMNs. Animals were treated with or without MB and/or PQ in an exposure time dependent manner. In some sets of experiments, the animals were pre-treated with NOS inhibitors N(G)-nitro-L-arginine methyl ester (L-NAME) and aminoguanidine (AG) along with respective controls. A significant increase in myeloperoxidase (MPO), superoxide dismutase (SOD), nitric oxide, iNOS expression and lipid peroxidation (LPO) was observed in PMNs of MB- and/or PQ-treated animals, while catalase and glutathione S-transferase (GST) activities were attenuated. L-NAME and AG significantly reduced the augmented nitrite content, iNOS expression and MPO activity to control level in MB and PQ exposed animals. Although the augmented LPO was also reduced significantly in L-NAME and AG treated rat PMNs, the level was still higher as compared with controls. Alterations induced in SOD and GST activities were not affected by NOS inhibitors. The results thus suggest that MB and/or PQ induce iNOS-mediated nitric oxide production, which in turn increases MPO activity and lipid peroxidation, thereby oxidative stress.     

In vitro study of the antioxidant properties of non steroidal anti-inflammatory drugs by chemiluminescence and electron spin resonance (ESR)

Objectives. To determine the antioxidant activities of nonsteroidal anti-inflammatory drugs (NSAIDS), we examined by chemiluminescence (CL) and electron spin resonance (ESR) their scavenging properties towards lipid peroxides, hypochlorous acid and peroxynitrite.

Methods. The antioxidant properties of nimesulide (NIM), 4-hydroxynimesulide (4-HONIM), aceclofenac (ACLO), 4-hydroxyaceclofenac (4-HOA-CLO), diclofenac (DICLO) and indomethacin (INDO) were tested on four different reactive oxygen species (ROS) generating systems: (I) phorbol-myristate acetate (PMA)-activated neutrophils, (II) Fe²⁺/ascorbate-induced lipid peroxidation, (III) HOCl-induced light emission, (IV) the kinetics of ONOO^- decomposition followed by spectrophotometry. ROS production was monitored by luminol-enhanced CL or by ESR using two different spin traps.

Results. At 10 μM, ACLO, NIM, 4-HONIM, 4-HOA-CLO, and DICLO decreased luminol-enhanced CL generated by PMA-activated neutrophils. Inversely, INDO increased the luminol enhanced CL. Interestingly, hydroxylated metabolites were more potent antioxidants than the parent drugs. Furthermore, all drugs tested, excepted ACLO, lowered lipid peroxidation induced by Fe²⁺/ascorbate system. ACLO and DICLO, even at the highest concentration tested (100 μM), did not significantly lower HOCl induced CL, whereas the other drugs were potent scavengers. Finally, all the NSAIDS accelerated decomposition of ONOO^-, suggesting a potential capacity of the molecules to scavenge peroxynitrite.

Conclusion. The NSAIDs possess variable degrees of antioxidant activities, linked to their ability to react with HOCl, lipid peroxides or ONOO^-. These antioxidant activities could offer interesting targeted side-effects in the treatment of joint inflammatory diseases.     

The involvement of nitric oxide in maneb- and paraquat-induced oxidative stress in rat polymorphonuclear leukocytes

Oxidative stress plays a crucial role in the manifestations of maneb (MB) and paraquat (PQ)-induced toxicity including MB+PQ-induced Parkinson's disease (PD). Polymorphonuclear leukocytes (PMNs) actively participate in the oxidative stress-mediated inflammation and organ toxicity. The present study was undertaken to investigate the MB- and/or PQ-induced alterations in the indices of oxidative stress in rat PMNs. Animals were treated with or without MB and/or PQ in an exposure time dependent manner. In some sets of experiments, the animals were pre-treated with NOS inhibitors N^G-nitro-L-arginine methyl ester (L-NAME) and aminoguanidine (AG) along with respective controls. A significant increase in myeloperoxidase (MPO), superoxide dismutase (SOD), nitric oxide, iNOS expression and lipid peroxidation (LPO) was observed in PMNs of MB- and/or PQ-treated animals, while catalase and glutathione S-transferase (GST) activities were attenuated. L-NAME and AG significantly reduced the augmented nitrite content, iNOS expression and MPO activity to control level in MB and PQ exposed animals. Although the augmented LPO was also reduced significantly in L-NAME and AG treated rat PMNs, the level was still higher as compared with controls. Alterations induced in SOD and GST activities were not affected by NOS inhibitors. The results thus suggest that MB and/or PQ induce iNOS-mediated nitric oxide production, which in turn increases MPO activity and lipid peroxidation, thereby oxidative stress.     

Metalloporphyrins are potent inhibitors of lipid peroxidation

The objectives of these studies were to determine whether metalloporphyrins could inhibit lipid peroxidation, characterize factors that influence their potency and compare their potency to prototypical antioxidants. Lipid peroxidation was initiated with iron and ascorbate in rat brain homogenates and the formation of thiobarbituric acid reactive species was used as an index of lipid peroxidation. Metalloporphyrins were found to be a novel and potent class of lipid peroxidation inhibitors. Inhibition of lipid peroxidation by metalloporphyrins was dependent on the transition metal ligated to the porphyrin, indicating that metal centered redox chemistry was important to the mechanism of their antioxidant activities. Manganese porphyrins with the highest superoxide dismutase (SOD) activities, MnOBTM-4-PyP and MnTM-2-PyP (charges are omitted throughout text for clarity), were the most potent inhibitors of lipid peroxidation with calculated IC50s of 1.3 and 1.0 microM, respectively. These manganese porphyrins were 2 orders of magnitude more potent than either trolox (IC50 = 204 microM) or rutin (IC50 = 112 microM). The potencies of the manganese porphyrins were related not only to their redox potentials and SOD activities, but also to other factors that may contribute to their ability to act as electron acceptors. The broad array of antioxidant activities possessed by metalloporphyrins make them attractive therapeutic agents in disease states that involve the overproduction of reactive oxygen species.     

Paraquat toxicity is reduced by metal chelators in rice leaves

The possible mediatory role of transition metals in paraquat (PQ) toxicity in rice leaves was investigated. Metal chelators (2,2'-bipyridine, 8-hydroxylquinoline and 1,10-phenanthroline) reduced PQ toxicity in rice leaves. The reduction of PQ toxicity by 1,10-phenanthroline (PA) is closely associated with the decrease in lipid peroxidation and increase in activities of enzymes detoxifying active oxygen species. Our results support the notion that iron or copper plays a major role in PQ toxicity in detached rice leaves. Reduction of PQ toxicity by PA in detached rice leaves is most likely mediated through chelation of iron or copper and an increase in superoxide dismutase and glutathione reductase activities.     

Dual effect of heparin on Fe2+-induced cardiolipin peroxidation: implications for peroxidation of cytochrome c oxidase bound cardiolipin

The effect of heparin on peroxidation of cardiolipin (CL) initiated by ferrous iron was studied in vitro using detergent-solubilized CL, liposomal CL, or CL bound to isolated cytochrome c oxidase (CcO). Heparin increased both the rate and the extent of CL peroxidation for detergent-solubilized CL and for CcO-bound CL. The effect of heparin was time- and concentration-dependent as monitored by the formation of conjugated dienes or thiobarbituric acid reactive substances. The results showed great similarity between the effect of heparin and the effect of certain iron chelators, such as ADP, on phospholipid peroxidation. Heparin increased the peroxidation of CcO-bound CL only when tertiary butyl hydroperoxide was also present. The enzyme activity of the resulting CcO complex decreased 25 %, in part due to peroxidation of functionally important CL. In contrast to peroxidation of detergent-solubilized CL, peroxidation of liposomal CL was inhibited by heparin, suggesting that the effect of heparin and ferrous iron depends on their proximity to the acyl chains of CL.