Oxidation of rat liver phospholipids: comparison of pathways in homogeneous solution, in liposomal suspension and in whole tissue homogenates

Evaluation of antioxidant status and oxidative stress markers in thermal sulfurous springs residents

Sulfurous springs have been traditionally used in medical treatment for different purposes. These beneficial effects of sulfurous water have been attributed to the presence of sulfurous compounds mainly in the form of hydrogen sulfide (H₂S). The purpose of the present study is to explore the effects of long-term exposure to sulfurous springs on oxidative stress and antioxidant biomarkers responses in individuals who lived nearby the sulfurous springs. The studied area was Al- Hammah sulfurous springs, which is located in the northern part of the Jordan Rift Valley and host many sulfurous springs. Residents in sulfurous springs area are continuously exposed to water and gases emission more than the overall population. We have found that the sulphate levels were 7 times higher in sulfurous springs water samples than control water samples. The majority of the volunteers involved in the present study were more than ten years long residence and lived in range distance between one to five kilometers (less than 3 miles) away from main sulfurous spring, and visited the sulfurous spring at least once a month. We did not find any noticeable symptoms in sulfur spring residents such as headaches, nausea, breathing problems. The total oxidative stress (TOS) and oxidative stress index (OSI) in sulfurous spring residents were lower than control individuals. The total antioxidant capacity (TAC) and total nitric oxide (NO_X) levels were higher in sulfurous spring residents compared to control group. Furthermore, we have highlighted that living nearby the sulfurous springs does not affect oxygen saturation levels (SPO₂) or heart pulse rate . These findings suggest that long-term exposure to sulfurous springs boost the antioxidant capacity and reduce oxidative stress levels in the human body. Hence, visiting sulfurous springs can act as natural remedies to diminish oxidative stress as they show promising potential in several-oxidative stress-related diseases treatment.

Identification of phenolic compounds in polyphenols-rich extract of Malaysian cocoa powder using the HPLC-UV-ESI-MS/MS and probing their antioxidant properties

The antioxidant components of cocoa powder, which is rich in polyphenols, were isolated using column chromatography and high performance liquid chromatography. Polyphenolic compounds were then characterized by high-performance liquid chromatography/Ultraviolet and electronspray ionization-tandem mass spectrometry (HPLC-UV-/ESI-MS-MS). As a result, five phenolic compounds were detected. In this study we also investigated scavenging or the total antioxidant capacity (%) of cocoa polyphenol (CP) fractionated from cocoa powder extract. 114.0 mg/g of gallic acid -equivalent phenolics and 94.3 mg/g catechin- equivalent flavonoids were quantified in this extract. Their free radical-scavenging activity was assessed by 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) assay, β-carotene bleaching test, and xanthine oxidase inhibitory activity (OX). Total antioxidant capacity (TAC) was further assessed against the myoglobin-induced oxidation of 6-hydroxy-2, 5, 7, 8-tetramethylchroman-2-carboxylic acid (ABTS) and expressed as Trolox equivalent. A high correlation between TAC and phenolic contents indicated that phenolic compounds from cocoa were a major contributor of antioxidant activity (0.967 ≤ r ≤ 1.00). CP extract had significantly (P < 0.05) potential antioxidant activities with various concentrations. These results suggest that Polyphenols-rich cocoa extract possess prominent medical properties and can be exploited as natural drug to treat free radical associated diseases.

Efficient assay for total antioxidant capacity in human plasma using a 96-well microplate

In the present study, we tried to establish an efficient assay for total antioxidant capacity (TAC) in human plasma using a 96-well microplate. TAC was assessed using lag time by antioxidants against the myoglobin-induced oxidation of 2,2'-azino-di(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) with hydrogen peroxide, and expressed as Trolox equivalent. The linearity of the calibration curve with Trolox was maintained with the Trolox concentration range from 2.5 µM to 25 µM (R² = 0.997). The assay was applied to the measurement of TAC in healthy human plasma. Coefficient of variation in intraday assay was 2.4%. Difference was not observed in interday assay. Plasma TAC of men ((569 ± 41) µM Trolox equivalent; n = 6) was higher than that of women ((430 ± 28) µM Trolox equivalent; n = 4). After the vegetable juice was drunk for 1 week, the increase in plasma TAC was observed in almost all the volunteers. In summary, we developed the efficient assay for plasma TAC using a 96-well microplate.

Role of phospholipase A2 activation and calcium in CYP2E1-dependent toxicity in HepG2 cells

Previous studies suggested a role for calcium in CYP2E1-dependent toxicity. The possible role of phospholipase A2 (PLA2) activation in this toxicity was investigated. HepG2 cells that overexpress CYP2E1 (E47 cells) exposed to arachidonic acid (AA) +Fe-NTA showed higher toxicity than control HepG2 cells not expressing CYP2E1 (C34 cells). This toxicity was inhibited by the PLA2 inhibitors aristolochic acid, quinacrine, and PTK. PLA2 activity assessed by release of preloaded [3H]AA after treatment with AA+Fe was higher in the CYP2E1 expressing HepG2 cells. This [3H]AA release was inhibited by PLA2 inhibitors, alpha-tocopherol, and by depleting Ca2+ from the cells (intracellular + extracellular sources), but not by removal of extracellular calcium alone. Toxicity was preceded by an increase in intracellular calcium caused by influx from the extracellular space, and this was prevented by PLA2 inhibitors. PLA2 inhibitors also blocked mitochondrial damage in the CYP2E1-expressing HepG2 cells exposed to AA+Fe. Ca2+ depletion and removal of extracellular calcium inhibited toxicity at early time periods, although a delayed toxicity was evident at later times in Ca2+-free medium. This later toxicity was also inhibited by PLA2 inhibitors. Analogous to PLA2 activity, Ca2+ depletion but not removal of extracellular calcium alone prevented the activation of calpain activity by AA+Fe. These results suggest that release of stored calcium by AA+Fe, induced by lipid peroxidation, can initially activate calpain and PLA2 activity, that PLA2 activation is critical for a subsequent increased influx of extracellular Ca2+, and that the combination of increased PLA2 and calpain activity, increased calcium and oxidative stress cause mitochondrial damage, that ultimately produces the rapid toxicity of AA+Fe in CYP2E1-expressing HepG2 cells.

Lipid oxidation in human low-density lipoprotein induced by metmyoglobin/H2O2: involvement of alpha-tocopheroxyl and phosphatidylcholine alkoxyl radicals

Metmyoglobin (metMb) and H(2)O(2) can oxidize low-density lipoprotein (LDL) in vitro, and oxidized LDL may be atherogenic. The role of alpha-tocopherol (alpha-TOH) in LDL oxidation by peroxidases such as metMb is unclear. Herein, we show that during metMb/H(2)O(2)-induced oxidation of native LDL, alpha-tocopheroxyl radical (alpha-TO(*)) and hydroperoxides and alcohols of cholesteryl esters [CE-O(O)H] and phosphatidylcholine [PC-O(O)H] accumulate concomitantly with alpha-TOH consumption. The ratio of accumulating CE-O(O)H to PC-O(O)H remains constant as long as alpha-TOH is present. Accumulation of CE-O(O)H is dependent on, and correlates with, LDL's alpha-TOH content, yet does not require preformed lipid hydroperoxides or H(2)O(2). This indicates that in native LDL alpha-TOH can act as a phase-transfer agent and alpha-TO(*) as a chain-transfer agent propagating LDL lipid peroxidation via tocopherol-mediated peroxidation (TMP). After alpha-TOH depletion, CE-O(O)H continues to accumulate, albeit at a slower rate than in the presence of alpha-TOH. This second phase of LDL oxidation is accompanied by depletion of PC-OOH, a rapid increase in the CE-O(O)H/PC-O(O)H ratio, formation of lipid-derived alkoxyl radicals and phosphatidylcholine hydroxides (PC-OH), and accumulation of a second organic radical, characterized by a broad singlet EPR signal. The latter persists for several hours at 37 degrees C. We conclude that metMb/H(2)O(2)-induced peroxidation of LDL lipids occurs initially via TMP. After alpha-TOH depletion, cholesteryl esters peroxidize at higher fractional rates than surface phospholipids, and this appears to be mediated at least in part via reactions involving alkoxyl radicals derived from the peroxidatic activity of metMb on PC-OOH.

Cucumber cotyledon lipoxygenase during postgerminative growth. Its expression and action on lipid bodies

In cucumber (Cucumis sativus), high lipoxygenase-1 (LOX-1) activity has been detected in the soluble fraction prepared from cotyledons of germinating seeds, and the involvement of this enzyme in lipid turnover has been suggested (K. Matsui, M. Irie, T. Kajiwara, A. Hatanaka [1992] Plant Sci 85: 23-32; I. Fuessner, C. Wasternack, H. Kindl, H. Kühn [1995] Proc Natl Acad Sci USA 92: 11849-11853). In this study we have investigated the expression of the gene lox-1, corresponding to the LOX-1 enzyme. LOX-1 expression is highly coordinated with that of a typical glyoxysomal enzyme, isocitrate lyase, during the postgerminative stage of cotyledon development. In contrast, although icl transcripts accumulated in tissue during in vitro senescence, no accumulation of lox-1 mRNA could be observed, suggesting that lox-1 plays a specialized role in fat mobilization. LOX-1 is also known to be a major lipid body protein. The partial peptide sequences of purified LOX-1 and lipid body LOX-1 entirely coincided with that deduced from the lox-1 cDNA sequence. The data strongly suggest that LOX-1 and lipid body LOX-1 are derived from a single gene and that LOX-1 can exist both in the cytosol and on the lipid bodies. We constructed an in vitro oxygenation system to address the mechanism of this dual localization and to investigate the action of LOX-1 on lipids in the lipid bodies. LOX-1 cannot act on the lipids in intact lipid bodies, although degradation of lipid body proteins, either during seedling growth or by treatment with trypsin, allows lipid bodies to become susceptible to LOX-1. We discuss the role of LOX-1 in fat mobilization and its mechanism of action.

1,2-Diacylglycerol hydroperoxides induce the generation and release of superoxide anion from human polymorphonuclear leukocytes

We examined the effect of 1-palmitoyl-2-linoleoylglycerol (PLG), PLG hydroxide (PLG-OH), and PLG hydroperoxide (PLG-OOH) on the release of superoxide anion from human PMNs monitored by the chemiluminescence generated by the superoxide anion-sensitive reagent, 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazin++ +-3-one (MCLA). PLG-OOH at low micromolar concentrations stimulated human PMNs whereas PLG and PLG-OH did not. 1,3-Dilinoleoylglycerol hydroperoxide, 1-palmitoyl-2-linoleoylphosphatidylcholine hydroperoxide, and linoleic acid hydroperoxide were much less efficient in stimulating human PMNs than PLG-OOH. The PKC inhibitors, chelerythrine chloride and staurosporine, inhibited the stimulation of PMNs. Possible pathophysiological role of 1,2-diacylglycerol hydroperoxides is discussed.