Novel fluorescein-based flow-cytometric method for detection of lipid peroxidation

Detection of lipid peroxidation in dog spermatozoa with the fluorescent dye C11-BODIPY581/591

C11-BODIPY^581/591 is a fluorescent probe that has been successfully used to evaluate lipid peroxidation in different species, but it has not been completely studied in the dog. Thus, the aim of the present study was to assess lipid peroxidation of dog spermatozoa using C11-BODIPY^581/591 and compare different positive controls of the technique. Twenty-four ejaculates were collected from 8 adult male dogs. Routine seminal characteristics were evaluated in raw semen. Lipid peroxidation evaluation was performed as described in other species. Samples were divided in three aliquots, exposed to UV radiation, incubated with hydrogen peroxide or left without treatment (control). Lipid peroxidation was significantly greater only in UV-exposed samples than in the control ones (91 ± 6% vs. 8.3 ± 3.5%, p ˂ .01). In conclusion, C11-BODIPY^581/591 is useful to evaluate lipid peroxidation of dog spermatozoa and UV radiation is a good promoter of membrane oxidation, so irradiated samples can be used as a positive control of this technique.

Effect of drying on oxidation of membrane lipids and expression of genes encoded by the Shiga toxin prophage in Escherichia coli

Drying processes do not eliminate pathogenic Escherichia coli in foods but induce sublethal injury, which may also induce the Shiga toxin (Stx) prophage. This study investigated the effect of drying on membrane lipid oxidation and stx expression in E. coli. Lipid peroxidation was probed with C₁₁-BODIPY^581/591; and stx expression was assayed by quantification of GFP in E. coli O104:H4 Δstx2a:gfp:amp^r. Treatment of E. coli with H₂O₂ oxidized the probe; probe oxidation was also observed after drying and rehydration. Lipid oxidation and the lethality of drying were reduced when cells were dried with trehalose under anaerobic condition; in addition, viability and probe oxidation differed between E. coli AW1.7 and E. coli AW1.7Δcfa. Desiccation tolerance thus relates to membrane lipid oxidation. Drying also resulted in expression of GFP in 5% of the population. Overexpression of gfp and recA after drying and rehydration suggested that the expression of Stx prophage was regulated by the SOS response. Overall, C₁₁-BODIPY^581/591 allowed investigation of lipid peroxidation in bacteria. Drying causes lipid oxidation, DNA damage and induction of genes encoded by the Stx prophage in E. coli.

Doxorubicin-polyglycerol-nanodiamond composites stimulate glioblastoma cell immunogenicity through activation of autophagy

Immunosuppression is a salient feature of GBM associated with the disease's grim prognosis and the limited success of anti-GBM immunotherapy. Stimulating immunogenicity of the GBM cells (GC) is a promising approach to subverting the GBM-associated immunosuppression. We had previously devised a drug composite based on polyglycerol-functionalized nanodiamonds bearing doxorubicin (Nano-DOX) and demonstrated that Nano-DOX effectively modulated GBM's immunosuppressive microenvironment through stimulating the immunogenicity of GC and initiated anti-GBM immune responses. The present study now explored the mechanism of Nano-DOX's immunostimulatory action. Nano-DOX was found to induce autophagy rather than apoptosis in GC and stimulated GC to emit antigens and damage-associated molecular patterns (DAMPs) that are potent adjuvants, which resulted in enhanced activation of dendritic cells (DC). Heightened autophagosome release was observed in Nano-DOX-treated GC but was shown not to be a major channel of antigen donation. Blocking autophagy in GC not only reduced Nano-DOX-stimulated GC antigen donation and DAMPs emission, but also efficiently attenuated DC activation stimulated by Nano-DOX-treated GC. Taken together, these findings suggest that activation of autophagy is a central mechanism whereby Nano-DOX stimulates GC's immunogenicity. Our work provides new insight on how nanotechnology can be applied to therapeutically modulate the GBM immune microenvironment by harnessing autophagy in the cancer cells. STATEMENT OF SIGNIFICANCE: Immunosuppression is a salient feature of GBM associated with the grim prognosis of the disease and the limited success of anti-GBM immunotherapy. We demonstrated that Doxorubicin-polyglycerol-nanodiamond composites could activate autophagy in GBM cells and thereby stimulate the immunogenecity of GBM cells. This discovery 1, sheds new light on how nanotechnology could be applied to therapeutically modulate the tumor immune microenvironment, and 2, provides a powerful tool for subverting the GBM's immunosuppressive microenvironment, which has great therapeutic potential for the treatment of GBM.

Plasmon-induced oxidative stress and macromolecular damage in pathogenic bacteria

Bacterial death during PACT would be consequence of macromolecular damage by large amounts of radicals produced after plasmon excitation of nanoparticles.

Interference of flavonoids with fluorescent intracellular probes: methodological implications in the evaluation of the oxidative burst by flow cytometry

The evaluation of oxidative burst is particularly relevant in many pathological and subclinical conditions. Flow cytometry provides quick and accurate measures of the reactive oxygen species production by leukocytes in most situations. However, spurious results, related to probes' efflux may be observed in several instances. Many factors affect the evaluation of the oxidative burst with fluorescent probes that require intracellular deacetylation and could be substrate of the multidrug resistance proteins (MDR). After discussing the implications of the efflux of fluorophores in the normalization strategies in flow cytometry assays, we have pointed out the possible interference of flavonoids with fluorescet probes' staining and signal. We have also reviewed the results from human intervention studies regarding the evaluation of oxidative burst with these probes. In vitro, at concentrations close to post-ingestion circulating levels, some flavonoids and their metabolites could interfere with probes' staining and fluorescence signal through different mechanisms, such as the inhibition of esterases, the modulation of the MDR-mediate efflux of probe and the inhibition of the oxidation of probe. These effects may explain the contrasting results obtained by human intervention studies. Finally, also inflammatory state or the use of drugs substrate of MDR proteins could affect the evaluation of the oxidative burst with intracellular probes.

A transgenic mouse model expressing exclusively human hemoglobin E: indications of a mild oxidative stress

Hemoglobin (Hb) E (β26 Glu→Lys) is the most common abnormal hemoglobin (Hb) variant in the world. Homozygotes for HbE are mildly thalassemic as a result of the alternate splice mutation and present with a benign clinical picture (microcytic and mildly anemic) with rare clinical symptoms. Given that the human red blood cell (RBC) contains both HbE and excess α-chains along with minor hemoglobins, the consequence of HbE alone on RBC pathophysiology has not been elucidated. This becomes critical for the highly morbid β(E)-thalassemia disease. We have generated transgenic mice exclusively expressing human HbE (HbEKO) that exhibit the known aberrant splicing of β(E) globin mRNA, but are essentially non-thalassemic as demonstrated by RBC α/β (human) globin chain synthesis. These mice exhibit hematological characteristics similar to presentations in human EE individuals: microcytic RBC with low MCV and MCH but normal MCHC; target RBC; mild anemia with low Hb, HCT and mildly elevated reticulocyte levels and decreased osmotic fragility, indicating altered RBC surface area to volume ratio. These alterations are correlated with a mild RBC oxidative stress indicated by enhanced membrane lipid peroxidation, elevated zinc protoporphyrin levels, and by small but significant changes in cardiac function. The C57 (background) mouse and full KO mouse models expressing HbE with the presence of HbS or HbA are used as controls. In select cases, the HbA full KO mouse model is compared but found to be limited due to its RBC thalassemic characteristics. Since the HbEKO mouse RBC lacks an abundance of excess α-chains that would approximate a mouse thalassemia (or a human thalassemia), the results indicate that the observed in vivo RBC mild oxidative stress arises, at least in part, from the molecular consequences of the HbE mutation.

Investigation of polymer electrolyte membrane chemical degradation and degradation mitigation using in situ fluorescence spectroscopy

A fluorescent molecular probe, 6-carboxy fluorescein, was used in conjunction with in situ fluorescence spectroscopy to facilitate real-time monitoring of degradation inducing reactive oxygen species within the polymer electrolyte membrane (PEM) of an operating PEM fuel cell. The key requirements of suitable molecular probes for in situ monitoring of ROS are presented. The utility of using free radical scavengers such as CeO(2) nanoparticles to mitigate reactive oxygen species induced PEM degradation was demonstrated. The addition of CeO(2) to uncatalyzed membranes resulted in close to 100% capture of ROS generated in situ within the PEM for a period of about 7 h and the incorporation of CeO(2) into the catalyzed membrane provided an eightfold reduction in ROS generation rate.

Methods for evaluating the potency and efficacy of antioxidants

PURPOSE OF REVIEW

The aim of this article is to present a brief panorama of the most widely used methods and of new analytical approaches for evaluating antioxidant capacity and to discuss them in terms of advantages and drawbacks.

RECENT FINDINGS

To date, many in-vitro tests are available from the chemical assay performed in a homogenous solution such as oxygen radical antioxidant capacity assay to more complex cell-based methods using exogenic probes to detect oxidation. In complement to these existing methods, novel approaches have recently been developed such as the conjugated autoxidizable triene assay implemented in emulsions and using tung oil as ultraviolet probe.

SUMMARY

The complexity and diverse range of research topics investigated have led to the development of a multitude of tests, but unfortunately none of them are universal. Thus, one of the major challenges is to know which method is best suited for a particular application.

Flow cytometric analysis of the oxidative status in human peripheral blood mononuclear cells of workers exposed to welding fumes

Flow cytometry is a simple analytical technique that identifies, counts, and characterizes cells. The oxidative status of cells is influenced by many exogenous sources, such as occupational exposure to welding fumes. This study evaluated flow cytometry as a method to determine the oxidative status of male welders (n = 15) occupationally exposed to welding fumes. Flow cytometric analysis of reactive oxygen species (ROS) was carried out in peripheral blood mononuclear cells (PBMC) by using the probe 2, 7-dichlorodihydrofluorescein diacetate (DCFH-DA). Lipid peroxidation was measured by the decrease of fluor-DHPE fluorescence and intracellular glutathione (GSH) levels by using mercury orange. All of the parameters were also observed under a confocal microscope. The oxidative stress ratio was calculated from the oxidative damage and the antioxidant capacity to give an accurate account of the cellular oxidative status. ROS and lipid peroxidation levels were elevated by approximately 87% and approximately 96%, respectively, and GSH levels lowered approximately 96% in PBMC of workers exposed to welding fumes compared with non-exposed controls. The oxidative stress ratio was significantly higher (p < 0.001) in the exposed group. Flow cytometry can be useful for the measurement of cellular oxidative stress in somatic cells of workers exposed to welding fumes and other occupational settings. Calculating an oxidative stress index may be useful in predicting disease outcomes and whether preventative control measures are efficient.

Swallow-tailed perylene derivative: a new tool for fluorescent imaging of lipid hydroperoxides

A swallow-tailed perylene derivative including a triphenylphosphine moiety was synthesized and applied to the detection and the live-cell imaging of lipid hydroperoxides. The novel probe, named Spy-LHP, reacted rapidly and quantitatively with lipid hydroperoxides to form the corresponding oxide, Spy-LHPOx, which emits extremely strong fluorescence (Phi approximately 1) in the visible range (lambda(em) = 535 nm, 574 nm). Spy-LHP was highly selective for lipid hydroperoxides, and the addition of other reactive oxygen species (ROS) including hydrogen peroxides, hydroxyl radical, superoxide anion, nitric oxide, peroxynitrite, and alkylperoxyl radical, caused no significant increase in the fluorescence intensity. The probe exhibited good localization to cellular membranes and was successfully applied to the confocal laser scanning microscopy (CLSM) imaging of lipid hydroperoxides in live J774A.1 cells, in which lipid peroxidation was proceeded by the stimulation of 2,2-azobis(2-amidinopropane)dihydrochloride (AAPH). These findings establish Spy-LHP as a promising new tool for investigating the physiology of lipid hydroperoxides.

Evaluation of the ability of antioxidants to counteract lipid oxidation: Existing methods, new trends and challenges

Oxidative degradation of lipids, especially that induced by reactive oxygen species (ROS), leads to quality deterioration of foods and cosmetics and could have harmful effects on health. Currently, a very promising way to overcome this is to use vegetable antioxidants for nutritional, therapeutic or food quality preservation purposes. A major challenge is to develop tools to assess the antioxidant capacity and real efficacy of these molecules. Many rapid in vitro tests are now available, but they are often performed in dissimilar conditions and different properties are thus frequently measured. The so-called 'direct' methods, which use oxidizable substrates, seem to be the only ones capable of measuring real antioxidant power. Some oxidizable substrates correspond to molecules or natural extracts exhibiting biological activity, such as lipids, proteins or nucleic acids, while others are model substrates that are not encountered in biological systems or foods. Only lipid oxidation and direct methods using lipid-like substrates will be discussed in this review. The main mechanisms of autoxidation and antioxidation are recapitulated, then the four components of a standard test (oxidizable substrate, medium, oxidation conditions and antioxidant) applied to a single antioxidant or complex mixtures are dealt with successively. The study is focused particularly on model lipids, but also on dietary and biological lipids isolated from their natural environment, including lipoproteins and phospholipidic membranes. Then the advantages and drawbacks of existing methods and new approaches are compared according to the context. Finally, recent trends based on the chemometric strategy are introduced as a highly promising prospect for harmonizing in vitro methods.

Induction and modulation of apoptosis in neonatal monocytes by polyunsaturated fatty acids

Polyunsaturated fatty acids (PUFAs), known modulators of the immune response, are the source of essential fatty acids in total parenteral nutrition-dependent patients. Critically ill infants on TPN have an increased incidence of sepsis, and lipid emulsions depress various immune functions. Recent studies have demonstrated that PUFAs induce apoptosis in various tissue cells in vitro and ex vivo. The susceptibility of neonatal monocytes, as major early effector cells in the host response to sepsis, to PUFA-mediated apoptosis and the mechanisms associated with PUFA-induced apoptosis were investigated. Both n-3 and n-6 PUFAs induced rapid, dose-dependent cell death in purified monocytes. Polyunsaturated fatty acids induced significant activation of upstream caspases 8 and 9 as well as caspase 3. The PUFA treatment resulted in a 4-fold increase in oxidative stress and a loss of monocyte mitochondrial potential compared with carrier controls (P < .05). The addition of cyclosporin, which blocks the development of mitochondrial transition pores, completely abolished the proapoptotic effects of PUFAs. Although Trolox (Sigma Aldrich) reduced PUFA-induced intracellular oxidative stress in neonatal monocytes, apoptosis was not blocked by this potent antioxidant. The data identify PUFAs as potent inducers of monocyte apoptosis, which can occur independently of the induction of oxidative stress, by using a mitochondrial dependent pathway. The TPN-dependent infant may be particularly sensitive to such PUFA effects, having a relatively poor capacity to both use and clear PUFAs.

Human and mouse hemoglobin association with the transgenic mouse erythrocyte membrane

Transgenic mouse models of hemoglobinopathies unravel pathophysiological mechanisms; yet the validity of the red blood cell (RBC) model of human hemoglobin (hHb) enveloped by a mouse (m) membrane has been questioned. Isoelectric focusing of hHb and mHb from transgenic mRBC shows a greater association of mHb to the mouse membrane compared to normal hHbA, supporting a species-specific Hb-mRBC membrane interaction. Enhanced hmutant Hb (HbE, HbS and HbC)-mRBC membrane affinities correlates with enhanced membrane lipid peroxidation and parallel those reported in hRBC, lending support to transgenic mRBC as models of hemoglobinopathies. Species-specific Hb-membrane interaction may be overridden by Hb charge and conformational alterations.

Fluorescence probes used for detection of reactive oxygen species

Endogenously produced pro-oxidant reactive species are essential to life, being involved in several biological functions. However, when overproduced (e.g. due to exogenous stimulation), or when the levels of antioxidants become severely depleted, these reactive species become highly harmful, causing oxidative stress through the oxidation of biomolecules, leading to cellular damage that may become irreversible and cause cell death. The scientific research in the field of reactive oxygen species (ROS) associated biological functions and/or deleterious effects is continuously requiring new sensitive and specific tools in order to enable a deeper insight on its action mechanisms. However, reactive species present some characteristics that make them difficult to detect, namely their very short lifetime and the variety of antioxidants existing in vivo, capable of capturing these reactive species. It is, therefore, essential to develop methodologies capable of overcoming this type of obstacles. Fluorescent probes are excellent sensors of ROS due to their high sensitivity, simplicity in data collection, and high spatial resolution in microscopic imaging techniques. Hence, the main goal of the present paper is to review the fluorescence methodologies that have been used for detecting ROS in biological and non-biological media.

Implications of oxidative stress in the cytotoxicity of Pseudomonas aeruginosa ExoU

ExoU PLA2-like activity has been shown to account for membrane lysis and acute death of infected cells. Translocation of effector proteins by the type III secretion systems depends on close contact between microbial and host cells. Our finding that both the ExoU-producing PA103 Pseudomonas aeruginosa and its mutant obtained by deletion of exoU adhered poorly to endothelial cells (EC) led to the hypothesis that, in some cells, the amount of injected toxin may not be enough to induce cell lysis but cells would suffer from a long-term effect of ExoU intoxication. To address this question, cells were exposed to both bacteria for 1 h and then treated with gentamicin-containing medium, to eliminate infecting microorganisms. After 24 h, the percentage of viable EC in PA103-infected cultures was significantly lower than in cultures exposed to the mutant, as determined by the MTT assay. Cell death was not likely to depend on the ExoU lytic activity since cell labeling with propidium iodide was similar in cultures infected with both bacterial strains. Bacterial cytotoxicity was significantly reduced by MAFP, a specific inhibitor of cPLA2 and iPLA2. Since the PLA2 activity on membrane phospholipids generates free fatty acid, including arachidonic acid (AA), we next compared the bacterial ability to release AA from infected EC. PA103 was shown to induce a potent AA release that was inhibited by MAFP. AA oxidation by oxygenases generates eicosanoids, known to induce both cell death and proliferation. However neither inhibitors of cyclooxygenases (ibuprofen) nor lipoxygenases (NDGA) reduced the ExoU toxicity. Since non-enzymatic oxidation of AA generates reactive radicals, we next investigated the PA103 ability to induce oxidative stress in infected cells. FACS analysis of cell labeling with the C-11 fluor probe and with anti-4-hydroxynonel antibody revealed a significant peroxidation of cell membrane lipids. These results, together with our finding that PA103-infected EC death was significantly attenuated by alpha-tocopherol, led to the conclusion that AA-induced oxidative stress may be another mechanism of cell damage in the course of infection by ExoU-producing P. aeruginosa.

Pseudomonas aeruginosa‐induced production of free radicals by IFNγ plus TNFα‐activated human endothelial cells: mechanism of host defense or of bacterial pathogenesis?

We have previously shown that human umbilical vein endothelial cells (HUVEC) can be activated by IFNgamma plus TNFalpha to kill intracellular (IC) Pseudomonas aeruginosa through production of reactive oxygen intermediate, but the cumulative effects of cytokine activation and bacterial infection on host cells has not been extensively addressed. In this study we investigated the fate of IFNgamma plus TNFalpha-activated HUVEC that have harboured IC bacteria for up to 24 h. At 10 h, the endothelial cell killing of P. aeruginosa isolates exceeded 90%. IC bacteria enhanced the expression of inducible nitric oxide synthase (iNOS) and induced overproduction of NO and superoxide by infected HUVEC. P. aeruginosa IC infection also induced a slight decrease in the cellular level of reduced glutathione (GSH). Overproduction of NO correlated with a marked peroxidation of plasma membrane lipids and decline in HUVEC viability. Treatment of cells with the antioxidant alpha-lipoic acid significantly increased the survival of infected cells. Our data suggest that with the failure of adequate scavenger mechanisms, oxidant radicals overproduced in response to bacterial infection were highly toxic to host cells. Therefore, instead of contributing to defence against infectious agents, the upregulation of free radicals production by endothelial cells in response to cytokine activation would be detrimental to the host.

Flow cytometric analysis of the oxidative status of normal and thalassemic red blood cells

BACKGROUND

The oxidative status of cells has been shown to modulate various cell functions and be involved in physiological and pathological conditions, including hereditary chronic anemias, such as thalassemia. It is maintained by the balance between oxidants, such as reactive oxygen species (ROS), and antioxidants, such as reduced glutathione (GSH).

METHODS

We studied peripheral RBC derived from normal and thalassemic donors. Flow cytometric methods were used to measure (1) generation of ROS; (2) the content of reduced GSH; and (3) peroxidation of membrane lipids as an indication of membrane damage.

RESULTS

ROS and lipid peroxidation were found to be higher, and GSH lower, in thalassemic RBC compared with normal RBC, both at baseline as well as following oxidative stress, such as exposure to hydrogen peroxide. To simulate a state of iron overload, normal RBC were exposed to extracellular ferric ammonium citrate or hemin, or their Hb was denatured by phenylhydrazine. All these treatments increased ROS and lipid peroxidation and decreased GSH. These effects were reversed by N-acetyl cysteine, a known ROS scavenger.

CONCLUSIONS

Flow cytometry can be useful for measuring oxidative stress and its effects on RBC in various diseases and for studying various chemical agents as antioxidants.

Assessment of membrane protection by traditional Chinese medicines using a flow cytometric technique: preliminary findings

In this preliminary study, we used a 'living cell' flow-cytometric approach to membrane protection by four traditional Chinese medicines (TCMs). Cells were incubated, separately, for 30 min with aqueous extracts (1.5% w/v) of lingzhi (Ganoderma lucidum), ginger (Zingiber officianale), ginseng (Panax ginseng), and green tea (Camellia sinensis). Membranes were labelled with a fluorescent probe, cells were then incubated with cumene hydroperoxide, and site-specific oxidation induced by iron/ascorbate. Oxidation of membrane lipids quenches fluorescence. Forward-scatter fluorescence was measured at timed intervals after initiation of oxidation. Results indicate that lingzhi and ginger contain antioxidant component(s) that act within the cell membrane and slow lipid peroxidation in situ. Results demonstrate also that this living cell model is a useful biomonitoring tool to help determine molecular aspects of putative health effects of TCMs.

Troglitazone-induced intracellular oxidative stress in rat hepatoma cells: a flow cytometric assessment

BACKGROUND

Troglitazone (TRO), a thiazolidinedione (TZD) peroxisome proliferator-activated receptor gamma agonist, was recently withdrawn from the market because of rare but serious hepatotoxicity. Previous studies investigating the cytotoxicity of TRO in cultured rat hepatocytes have conjectured about the role of oxidative stress in TRO-induced hepatotoxicity. Therefore, we investigated whether TRO induces oxidative stress and, if so, the portion of the TRO molecule responsible for the induction of oxidative stress.

METHODS

Novikoff rat hepatoma (N1S1) cells were incubated with TRO, troglitazone quinone (TQ), thiazolidinedione-phenoxyacetic acid (TD-PAA) or rosiglitazone (RSG). Membrane peroxidation, intracellular glutathione (GSH) content, and cellular viability were monitored simultaneously by multiparameter flow cytometry.

RESULTS

TRO and TQ increased membrane peroxidation, decreased intracellular GSH, and decreased cell viability in a concentration-dependent manner. In contrast, TD-PAA and RSG neither increased membrane peroxidation nor induced loss of cell viability. In addition, TRO caused a concentration-dependent increase in intracellular superoxide generation accompanied by a collapse in mitochondrial membrane potential.

CONCLUSION

Multiparameter flow cytometric evaluation of N1S1 cells indicated that the chromane ring of TRO, rather than the TZD moiety, may be responsible for oxidative stress and suggested that a direct effect on mitochondrial physiology may play a role in TRO-mediated hepatotoxicity.

C11-BODIPY(581/591), an oxidation-sensitive fluorescent lipid peroxidation probe: (micro)spectroscopic characterization and validation of methodology

C11-BODIPY(581/591) is a fluorescent radio-probe for indexing lipid peroxidation and antioxidant efficacy in model membrane systems and living cells, with excellent characteristics: (i) emission in the visible range of the electromagnetic spectrum, with good spectral separation of the nonoxidized (595 nm) and oxidized (520 nm) forms; (ii) has a high quantum yield and because of this, low labeling concentrations can be used, ensuring minimal perturbation of the membrane whilst retaining favorable signal to noise ratios; (iii) has a good photo-stability and displays very few fluorescence artifacts; (iv) is virtually insensitive to environmental changes, i.e., pH or solvent polarity; (v) is lipophilic and as such easily enters membranes; (vi) once oxidized, C11-BODIPY(581/591) remains lipophilic and does not spontaneously leave the lipid bilayer; (vii) C11-BODIPY(581/591) localizes in two distinct pools within the lipid bilayer, a shallow pool at 18 A and a deep pool at < 7.5 A from the center of the bilayer; (viii) is not cytotoxic to rat-1 fibroblasts up to 50 microM; (ix) is sensitive to a variety of oxy-radicals and peroxynitrite, but not to superoxide, nitric oxide, transition metal ions, and hydroperoxides per se; (x) its sensitivity to oxidation is comparable to that of endogenous fatty acyl moieties.

Flow cytometric determination of lipid peroxidation using fluoresceinated phosphoethanolamine

In conclusion, we describe the use of fluor-DHPE as a flow cytometric probe to assess lipid peroxidation in erythrocytes. The stability and nonexchangeability of this probe make it suitable for monitoring lipid peroxidation in a particular cell type via flow cytometry, which can be done in the presence of other cells. Application of the probe in erythrocytes from rats fed a vitamin E-deficient diet demonstrated a higher susceptibility to lipid peroxidation among these cells than among erythrocytes from rats fed a normal diet. The current flow cytometric lipid peroxidation detection method can be interfaced directly with several standard techniques that are available to measure specific blood cell populations via flow cytometry.

Estimation of lipid peroxidation of live cells using a fluorescent probe, diphenyl-1-pyrenylphosphine

Diphenyl-1-pyrenylphosphine (DPPP), which reacts with lipid hydroperoxides stoichiometrically to yield fluorescent product DPPP oxide, was used as a fluorescent probe for lipid peroxidation in live cells. DPPP was successfully incorporated into U937 cells. Incorporation of DPPP into the cell membrane was confirmed by fluorescence microscopy. Reaction of DPPP with hydroperoxides was examined by monitoring increase in fluorescence intensity of the cell. It was found that lipid-soluble hydroperoxides such as methyl linoleate hydroperoxide preferably react with DPPP, whereas hydrogen peroxide did not react with DPPP located in the membrane. Linear correlation between increase in fluorescence intensity and the amount of methyl linoleate hydroperoxide applied to the cell was observed. DPPP gave little effect on cell proliferation, cell viability or cell morphology for at least 3 d. DPPP oxide, fluorescent product of DPPP, was quite stable in the membrane of living cells for at least 2 d. Fluorescence of DPPP-labeled cells was measured after treating with diethylmaleate (DEM), or 2,2'-Azobis(2-amidinopropane) dihydrochloride (AAPH), or culturing with low serum content. These reagents and culture condition induced dose- and/or time-dependent increase in fluorescence. Addition of vitamin E effectively suppressed increase in fluorescence. When DPPP-labeled cells and DCFH-DA-labeled cells were treated with NO, H(2)O(2), AAPH, and DEM to compare the formation of hydoperoxides in the membrane and cytosol, distinct patterns of peroxide formation were observed. These results indicate that fluorescent probe DPPP is eligible for estimation of lipid peroxidation proceeding in the membrane of live cells, and use of this probe is especially advantageous in long-term peroxidation of the cell.

A fluorometric method for measurement of oxygen radical-scavenging activity of water-soluble antioxidants

The relative activities of the antioxidants Trolox, ascorbic acid, uric acid, quercetin, and rutin, and the activities of total antioxidants in serum samples were determined using a fluorometric assay based on the dye 6-carboxyfluoroscein (6C-Fl) as a fluorescent indicator; 2,2'-azobis-2-amidinopropane hydrochloride (AAPH) as a peroxyl radical generator; 6-hydroxy-2,5,7, 8-tetramethyl-1-chroman-2-carboxylic acid (Trolox) as a calibrator; and phosphate buffer (pH 7.0) as a solvent. Incubation of 6C-Fl in 0. 075 M phosphate buffer, in the presence of AAPH at 37 degrees C, resulted in loss of its fluorescence signal at 520 nm with excitation at 495 nm. The antioxidants Trolox, ascorbic acid, and uric acid provided protection of the fluorescence of 6C-Fl, and the relative antioxidant activities, determined by the net protection area under curve technique, were found to be 1:0.4:1, respectively. Trolox and ascorbic acid were used to validate this assay. A linear correlation of the net protection value with the concentration of serum, Trolox, ascorbic acid, and uric acid was demonstrated. Quercetin and rutin were shown to have strong antioxidant activities, nearly 10 times those of vitamin C. This assay is simple, reliable, and suitable for automation to handle many samples and requires few microliters of serum samples.

Probe-assisted flow cytometric analysis of erythrocyte membrane response to site-specific oxidant stress

BACKGROUND

Probe-assisted flow cytometry was used to monitor the response of membranes of living cells to oxidant stress in the presence and absence of antioxidants. Test conditions (fluorophore loading, oxidant concentration) were investigated and storage-related changes in erythrocyte response to oxidant stress explored.

METHODS

Erythrocytes were incubated with a lipophilic fluorescent probe and exposed to site-specific oxidant challenge, induced by cumene hydroperoxide, in the presence and absence of urate, ascorbate, or alpha tocopherol in physiological amounts. Fluorescence of labeled and treated erythrocytes was measured for 120 min using a Coulter EPICS Elite ESP flow cytometer.

RESULTS

Probe loading was dose and time dependent. Cumene hydroperoxide exhibited a potent and dose-dependent oxidant effect on erythrocyte membranes. Alpha tocopherol slowed, but did not prevent, membrane oxidation. Ascorbate appeared to have no effect on peroxidation initially, but then slowed and stopped propagation of membrane oxidation. The effect of urate was slight.

CONCLUSIONS

This technique can provide insight into oxidative processes at the cellular level. Results indicated that lipophilic alpha tocopherol was the most effective antioxidant in slowing membrane peroxidation, but ascorbate appears to stop chain propagation. This effect may be owing to vitamin C/E interaction. Further study is needed.

Myocardial protection with red wine extract

Cardioprotective action of red wine was studied by preperfusing isolated rat hearts with ethanol-free red wine extract for 15 min before subjecting them to 30 min of global ischemia followed by 2 h of reperfusion. Four other group of rats were studied under identical conditions, of which one served as control; one was treated with 10 microM trans-resveratrol (RVT), one of the major antioxidants found in red wines; another, with 0.07% ethanol; and another, with 0.07% ethanol plus 10 microM RVT. The results of our study demonstrated that both red wine extract and RVT were equally cardioprotective, as evidenced by their abilities to improve postischemic ventricular functions including developed pressure and aortic flow. Developed pressure values at 60 min after reperfusion were 81.8 +/- 1.2 and 68.8 +/- 4.1 mm Hg for the red wine extract and RVT groups, respectively, versus 49.7 +/- 2.7 mm Hg for the control group. These compounds also reduced myocardial infarct size compared with the control hearts (20.1 +/- 0.5% and 10.5 +/- 0.3% for red wine extract and RVT groups, respectively, vs. 29.9 +/- 3.1% for the control group). The ethanol-treated group displayed slightly better functional recovery, which deteriorated sharply toward the end of the reperfusion period, and the extent of infarction was comparable to that of the control group (31.5 +/- 0.9%). In the ethanol plus RVT group, postischemic contractile function was significantly better than control, and infarct size also was reduced to 20.9 +/- 0.7%. The amount of malonaldehyde formation in the postischemic myocardium was reduced by red wine extract and RVT, indicating a reduction of oxidative stress developed in the ischemic reperfused myocardium. In vitro studies revealed that red wine extract is a potent antioxidant as evidenced by its ability to scavenge peroxyl radical in vitro. Taken together, the results of our study indicate that red wines are cardioprotective by their ability to function as an in vivo antioxidant.

Myocardial protection by protykin, a novel extract of trans-resveratrol and emodin

Protykin is an all-natural, high potency standardized extract of trans-resveratrol (20%) and emodin (10%) derived from the dried rhizome of Polygonum cuspidatum. Previous studies have demonstrated free radical scavenging and anti-inflammatory activities of resveratrol. Since free radicals play a crucial role in the pathogenesis of myocardial ischemia/reperfusion injury, we examined whether Protykin could preserve the heart during ischemic arrest. Sprague-Dawley rats were divided into two groups: experimental group was gavaged Protykin (100 mg/kg body wt) dissolved in corn oil for three weeks, while the control group was gavaged corn oil alone. After three weeks, rats were sacrificed, isolated hearts perfused via working mode, were made globally ischemic for 30 min followed by 2 h of reperfusion. Left ventricular functions were continuously monitored and malonaldehyde (MDA) (presumptive marker for oxidative stress) formation were estimated. At the end of each experiment, myocardial infarct size was measured by TTC staining method. Peroxyl radical scavenging activity of Protykin was determined by examining its ability to remove peroxyl radical generated by 2,2'-azobis (2-amidinopropane) dihydrochloride, while hydroxy radical scavenging activity was tested with its ability to reduce 7-OH*-coumarin-3-carboxylic acid. The results of our study demonstrated that the Protykin group provided cardioprotection as evidenced by improved post-ischemic left ventricular functions (dp, dp/dt(max)) and aortic flow as compared to control group. This was further supported by the reduced infarct size in the Protykin group. Formation of MDA was also reduced by Protykin treatment. In vitro studies demonstrated that Protykin possessed potent peroxyl and hydroxyl radical scavenging activities. The results of this study indicate that Protykin can provide cardioprotection, presumably by virtue of its potent free radical scavenging activity.

Humic acid-mediated oxidative damages to human erythrocytes: a possible mechanism leading to anemia in Blackfoot disease

Humic acid (HA) has been proposed as a factor that causes Blackfoot disease, an endemic peripheral vascular disease prevailing in the southwest coast of Taiwan. However, the relationship between HA and anemia associated with Blackfoot disease remains unclear. In this study, we showed that HA imposed damages on human red blood cells (RBCs), which were manifested as reduction in deformability of RBCs and hemolysis. At concentrations ranging from 10 to 100 microg/ml, HA caused lipid peroxidation in a dose-dependent manner. Such changes were accompanied by a depletion of glutathione and a reduction in activities of the antioxidant enzymes including catalase, superoxide dismutase, and glucose-6-phosphate dehydrogenase. These results indicate that HA initiates oxidative stress on RBCs and results in their dysfunction. Consistent with our previous findings, the present study supports the notion that HA plays an important role in the pathogenesis of Blackfoot disease.

The red wine antioxidant resveratrol protects isolated rat hearts from ischemia reperfusion injury

The consumption of red wine has been reported to impart a greater benefit in the prevention of coronary heart disease than the consumption of other alcoholic beverages. This beneficial effect is increasingly being attributed to certain antioxidants comprising the polyphenol fraction of red wine such as transresveratrol. In the present study, we investigated the potential cardioprotective effects of resveratrol in the face of ischemia reperfusion (I/R) injury. Isolated perfused working rat hearts after stabilization were perfused with Krebs-Henseleit Bicarbonate buffer (KHB) either in the presence or absence of transresveratrol (RVT) at a concentration of 10 microM for 15 min prior to subjecting them to 30 min of global ischemia followed by 2 h of reperfusion. Left ventricular functions were monitored at various timepoints throughout the reperfusion period to assess the extent of postischemic recovery in comparison with baseline values. Coronary perfusate samples were also collected to determine malonaldehyde (MDA) levels. The results demonstrated that RVT exhibited significant myocardial protection. This was evidenced by improved recovery of post-ischemic ventricular function including developed pressure and aortic flow as compared to the control group (KHB). Values for developed pressure in the RVT-treated group were significantly higher than those in the control group throughout the reperfusion period (71.09+/-4.88 mm Hg vs. 58.47+/-3.88 mm Hg, 68.87+/-5.07 mm Hg vs. 49.74+/-2.65 mm Hg and 51.67+/-3.95 mm Hg vs. 30.50+/-4.80 mm Hg at reperfusion timepoints R-15, R-60, and R-120, respectively). From R-30 onwards, aortic flow was markedly higher in the RVT treated group as compared with the control group, the differences being most significant at R-90 (32.45+/-2.19 ml/min vs. 19.83+/-1.62 ml/min) and R-120 (27.15+/-2.27 ml/min vs. 14.10+/-1.69 ml/min). In contrast to the KHB treated group, the RVT-treated group displayed significant reduction in MDA formation especially in the immediate early reperfusion period (63.71+/-8.19 pM/ml vs. 130.86+/-4.76 pM/ml, 63.84+/-15.62 pM/ml vs. 156.99+/-18.93 pM/ml, 71.29+/-2.80 pM/ml vs. 129.5+/-10.30 pM/ml and 56.25+/-5.79 pM/ml vs. 127.99+/-3.50 pM/ml at timepoints R-1, R-3, R-5, and R-7, respectively) indicating a reduction in I/R injury related oxidative stress. Infarct size was markedly reduced in the RVT group when compared with the control group (10.57+/-0.35% vs. 36.27+/-5.28%). In vitro studies revealed RVT to be a potent scavenger of peroxyl radicals suggestive of a probable mechanism involved in the protective ability of RVT. The results of this study indicate that resveratrol possesses cardioprotective effects which may be attributed to its peroxyl radical scavenging activity.

Vitamin C: prospective functional markers for defining optimal nutritional status

Most species of plants and animals synthesize ascorbic acid, but human subjects cannot, making vitamin C an essential component of our diet. Relationships between vitamin C intake and status, and between status and health are not yet clear. There is evidence, however, that higher intake of vitamin C is associated with lower risk of disease, supporting the concept that optimal intake is needed for optimal vitamin C status, and that both factors are required for optimal health. Vitamin C has low toxicity in healthy subjects, but a clear definition of optimal status and the dietary intake required to meet and maintain this status is needed before a change in the current recommended intake can be considered. Available evidence suggests that intake of 200 mg vitamin C/d saturates tissues and maintains fasting plasma levels above the proposed threshold (50 mumol/l) for minimum risk of CHD. However, the issue of whether or not these levels produce 'optimal vitamin C status' awaits the clear and accepted definition of the term. This definition in turn awaits the development of reliable functional markers capable of assessing the effects of varying levels of vitamin C nutriture. In the present paper the relationship between intake and body stores of vitamin C and the role of vitamin C in human health are reviewed briefly. The requirements of a reliable functional marker of human vitamin C status are defined, three classes of functional markers (molecular, biochemical and physiological) are described, and possible candidate markers are examined.

Dynamics of reactive oxygen intermediate production in human glioma: n-6 essential fatty acid effects

BACKGROUND

Reactive oxygen intermediates (ROIs) are important signals controlling cell growth and cell death. Local essential fatty acid (EFA) deficiencies in tumour cells may limit tumour ROI generation. This deficiency may be rectified by the addition of exogenous EFA.

MATERIALS AND METHODS

The n-6 EFA effects on tumour ROIs were analysed in terms of kinetics, dose-response and individual cell type responses using flow cytometry of intracellular 2',7'-dichlorofluorescin oxidation. ROI formation in 30 gliomas and five paired samples of normal brain tissue, > 500 000 cells per specimen, was analysed every 10 s for 0-25 min.

RESULTS

Tumour cell basal ROI was lower than normal brain tissue ROI from the same subjects (P < 0.00002). Normal and tumour cell ROIs were stimulated by 4-40 micromol L-1 n-6 EFAs, arachidonic acid (AA) and gamma-linolenic acid (GLA). The stimulated ROI rate was exponential, with the maximum dependent on EFA concentration and tumour grade.

CONCLUSIONS

EFAs stimulated tumour cells more than normal cells (P < 0.0000017, n = 71) and increased ROIs in glial fibrillary acidic protein-positive cells in tumours. This indicated high sensitivity of glioma cell ROIs to n-6 EFAs.

Validation of the peroxidative indicators, cis-parinaric acid and parinaroyl-phospholipids, in a model system and cultured cardiac myocytes

cis-Parinaric acid is increasingly being used in eukaryotic cells as a very sensitive marker for the initial stages of lipid peroxidation. Despite the increased application of this probe, no extensive validation, especially in cellular systems, has been performed. cis-Parinaric acid can either be inserted freely into biomembranes or incorporated (bio)synthetically into lipids (parinaroyl-lipid). Therefore, a direct comparison was made between the peroxidative behaviour of the two parinaroyl probes and the endogenous polyunsaturated fatty acids arachidonic and linoleic acid, in both an artificial lipidic system and in cultured neonatal rat heart cells. Three different radical generating systems were used, i.e., hydrogen peroxide, cumene hydroperoxide and the thermo-labile 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH). The data demonstrate that the peroxidation rate of cis-parinaric acid is higher than that of the parinaroyl, arachidonoyl and linoleoyl lipids. The latter three displayed comparable peroxidation rates, showing that the peroxidative decay of parinaroyl-lipid is a good marker for the degradation of endogenous polyunsaturated fatty acids. Experimental results using the freely inserted cis-parinaric acid could potentially lead to an overestimation of the inflicted damage and should be interpreted with care. In addition, a comparison was made with the measurement of conjugated dienes and malon dialdehyde as thiobarbituric acid reactive substances. The results demonstrate that measurement of conjugated dienes and malon dialdehyde only provide information on peroxidative processes in vitro, but are not suitable for in-depth studies in cultured cells. In contrast, the use of the parinaroyl probes is a suitable, straightforward, sensitive and reproducible method for detecting the initial stages of lipid peroxidation in living cells.

Fluoresceinated phosphoethanolamine for flow-cytometric measurement of lipid peroxidation

A new lipophilic fluorescein probe (fluor-DHPE) has been identified that can assay lipid peroxidation in mammalian cells on a cell-by-cell or selected-cell-subpopulation basis by flow cytometry. Application of this approach requires that the fluorescent probe be nonexchangeable among cells. Fluorescein is an appropriate fluorophore, since its fluorescence matches the specifications of common flow cytometers and the compound loses its fluorescence upon reaction with peroxyl radicals. Upon examination of four lipophilic derivatives of fluorescein, fluor-DHPE was found to be the only probe that was nonexchangeable among labeled and unlabeled rat RBC for at least 24 h. The exposure of fluor-DHPE-labeled RBC to benzoyl peroxide followed by mixing the sample with RBC unexposed to peroxide led to a decrease in fluorescence. Furthermore, the flow cytometer could clearly select the subpopulation of cells undergoing lipid peroxidation from those cells that were not. Fluor-DHPE-labeled-RBC obtained from rats and exposed to cumene hydroperoxide also displayed a gradual decrease in fluorescence. This decrease was preventable by either regulation of the vitamin E content in the animal diet or in vitro supplementation of cells with vitamin E. We conclude that fluor-DHPE is a stable and nonexchangeable probe for monitoring lipid peroxidation in cell subpopulations by flow cytometry.

Detection of lipid peroxidation on erythrocytes using the excimer-forming property of a lipophilic BODIPY fluorescent dye

Lipophilic analogues of dipyrrometheneboron (BODIPY-FL) dyes, used for membrane studies, normally fluoresce in the green wavelength region (approximately 516 nm), but at high local concentration, they shift their emission to the red region (approximately 540-600 nm) via excimer formation. A two-wavelength-based method is described that utilizes the excimer-forming property of BODIPY-FL for the sensitive monitoring of membrane lipid peroxidation on erythrocytes (RBCs). Bodipy-FL- C3-EDA, a relatively water-soluble analogue of BODIPY-FL, loses its single fluorescence peak at 516 nm upon reaction with peroxyl radicals generated in aqueous phase by 2,2'-azobis(2-amidinopropane), AAPH, and the loss of fluorescence is prevented by the presence of the peroxyl radical scavenger, Trolox (a water-soluble analogue of vitamin E). Hexadecanoyl-BODIPY-FL (C16-BODIPY, a lipophilic analogue of BODIPY-FL) incorporated into RBC membranes, in addition to the peak at 516 nm, also forms excimer fluorescent peaks at 546 and 590 nm. The relative intensity of the emission peaks depends on the concentration of membrane-incorporated dye. Upon addition of cumene hydroperoxide (CH, 0-10 microM) or benzoyl peroxide (BP, 0-5 microM) to C16-BODIPY-labeled RBC suspensions, gradual changes in the fluorescent peaks occur, the 516 nm peak initially increases, then decreases, while the 546 and 590 nm excimer peaks continuously decrease, as measured by fluorometry or by flow cytometry. The data indicate that lipid peroxidation radicals reacting with C16-BODIPY localized on RBC membranes oxidize the dye and the resulting molecule cannot participate in the excimer formation; this oxidization leads to the observed changes in the fluorescent peaks. The ratio of the fluorescence levels at 590 and 516 nm is a measure of the excimer formation between fluorophores and can be used to monitor the onset of lipid peroxidation in RBCs.