Lipid hydroperoxides induce apoptosis in T cells displaying a HIV-associated glutathione peroxidase deficiency

Exercise Cuts Both Ways with ROS in Remodifying Innate and Adaptive Responses: Rewiring the Redox Mechanism of the Immune System during Exercise

Nearly all cellular functions depend on redox reactions, including those of immune cells. However, how redox reactions are rearranged to induce an immune response to the entry of pathogens into the host is a complex process. Understanding this scenario will facilitate identification of the roles of specific types of reactive oxygen species (ROS) in the immune system. Although the detrimental effect of ROS could support the innate immune system, the adaptive immune system also requires a low level of ROS in order to stimulate various molecular functions. The requirements and functions of ROS vary in different cells, including immune cells. Thus, it is difficult to understand the specific ROS types and their targeting functions. Incomplete transfer of electrons to a specific target, along with failure of the antioxidant response, could result in oxidative-damage-related diseases, and oxidative damage is a common phenomenon in most immune disorders. Exercise is a noninvasive means of regulating ROS levels and antioxidant responses. Several studies have shown that exercise alone boosts immune functions independent of redox reactions. Here, we summarize how ROS target various signaling pathways of the immune system and its functions, along with the possible role of exercise in interfering with immune system signaling.

Therapeutic Potential of Alpha-Lipoic Acid in Viral Infections, including COVID-19

Oxidative stress (OS), resulting from a disrupted balance between reactive oxygen species (ROS) and protective antioxidants, is thought to play an important pathogenetic role in several diseases, including viral infections. Alpha-lipoic acid (LA) is one of the most-studied and used natural compounds, as it is endowed with a well-defined antioxidant and immunomodulatory profile. Owing to these properties, LA has been tested in several chronic immunoinflammatory conditions, such as diabetic neuropathy and metabolic syndrome. In addition, a pharmacological antiviral profile of LA is emerging, that has attracted attention on the possible use of this compound for the cotreatment of several viral infections. Here, we will review the emerging literature on the potential use of LA in viral infections, including COVID-19.

Alterations in Serum Zinc and Polyunsaturated Fatty Acid Concentrations in Treatment-Naive HIV-Diagnosed Alcohol-Dependent Subjects with Liver Injury

Heavy alcohol drinking causes alterations in the metabolism of fatty acids and zinc that participate in inflammation and liver injury. HIV infection has been reported to cause dysregulated polyunsaturated fatty acid (PUFA) and zinc metabolism. In this pilot study, we examined the role of dysregulated PUFA metabolism and zinc deficiency in the liver injury occurring in heavy drinkers with early-stage HIV diagnosis. Fourteen heavy drinking alcohol-dependent (AD) patients [seven with treatment-naive HIV diagnosis (AD+HIV) and seven without HIV infection (AD)] participated in this study. Liver injury, serum zinc, PUFAs, viral load, CD4⁺ count, and drinking measures using lifetime drinking history (LTDH), and timeline follow-back past 90 days (TLFB90) were evaluated. Liver injury was also assessed in seven age- and gender-matched socially drinking HIV treatment-naive patients who served as disease controls. HIV viral load by itself did not show any correlation with liver injury. Liver enzymes were significantly elevated in both AD+HIV and AD patients, and AD+HIV patients had significantly higher alanine aminotransferase (ALT) levels than did AD patients, even with lower drinking. Serum zinc was significantly lower in AD+HIV patients. Only AD+HIV patients showed a significant elevation in linoleic acid (LA) and alpha-linoleic acid (ALA) levels. Serum zinc and ALT, LA and ALT, and ALA and ALT were significantly associated only in AD+HIV patients. The association between LA and ALT showed a higher effect than did the ALA and ALT association in the AD+HIV patients. Interestingly, AD+HIV subjects (who drank less), nevertheless, showed more liver injury compared with AD patients, who reported heavier drinking. We speculate that the underlying proinflammatory response resulting from zinc deficiency and an elevation in serum LA likely contributed to liver injury in AD+HIV patients, even with a comparatively lower degree of heavy drinking.

Ferulic Acid and Naturally Occurring Compounds Bearing a Feruloyl Moiety: A Review on Their Structures, Occurrence, and Potential Health Benefits

The ubiquitous compound 4-hydroxy-3-methoxycinnamic acid, also known as ferulic acid (FA), constitutes a bioactive ingredient of many foods that may offer beneficial effects against disorders related to oxidative stress, including cancer, diabetes, and neurodegenerative diseases. This review discusses the antioxidant properties of FA, establishing relationships to several biological activities already described for this natural product. Next, 387 naturally occurring compounds, all isolated from plants and published between 1990 and 2015, the structures of which bear 1 or more feruloyl moieties, are covered in this review along with their structural formulas, botanical sources, and bioactivities. The compounds' distribution, structural patterns, bioactivities, and perspectives on food research are also succinctly discussed.

Redox regulation of T-cell function: from molecular mechanisms to significance in human health and disease

Reactive oxygen species (ROS) are thought to have effects on T-cell function and proliferation. Low concentrations of ROS in T cells are a prerequisite for cell survival, and increased ROS accumulation can lead to apoptosis/necrosis. The cellular redox state of a T cell can also affect T-cell receptor signaling, skewing the immune response. Various T-cell subsets have different redox statuses, and this differential ROS susceptibility could modulate the outcome of an immune response in various disease states. Recent advances in T-cell redox signaling reveal that ROS modulate signaling cascades such as the mitogen-activated protein kinase, phosphoinositide 3-kinase (PI3K)/AKT, and JAK/STAT pathways. Also, tumor microenvironments, chronic T-cell stimulation leading to replicative senescence, gender, and age affect T-cell susceptibility to ROS, thereby contributing to diverse immune outcomes. Antioxidants such as glutathione, thioredoxin, superoxide dismutase, and catalase balance cellular oxidative stress. T-cell redox states are also regulated by expression of various vitamins and dietary compounds. Changes in T-cell redox regulation may affect the pathogenesis of various human diseases. Many strategies to control oxidative stress have been employed for various diseases, including the use of active antioxidants from dietary products and pharmacologic or genetic engineering of antioxidant genes in T cells. Here, we discuss the existence of a complex web of molecules/factors that exogenously or endogenously affect oxidants, and we relate these molecules to potential therapeutics.

Metabonomic analysis of HIV-infected biofluids

Monitoring the progression of HIV infection to full-blown acquired immune deficiency syndrome (AIDS) and assessing responses to treatment will benefit greatly from the identification of novel biological markers especially since existing clinical indicators of disease are not infallible. Nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) are powerful methodologies used in metabonomic analyses for an approximation of HIV-induced changes to the phenotype of an infected individual. Although early in its application to HIV/AIDS, (biofluid) metabonomics has already identified metabolic pathways influenced by both HIV and/or its treatment. To date, biofluid NMR and MS data show that the virus and highly active antiretroviral treatment (HAART) mainly influence carbohydrate and lipid metabolism, suggesting that infected individuals are susceptible to very specific metabolic complications. A number of well-defined biofluid metabonomic studies clearly distinguished HIV negative, positive and treatment experienced patient profiles from one another. While many of the virus or treatment affected metabolites have been identified, the metabonomics measurements were mostly qualitative. The identities of the molecules were not always validated neither were the statistical models used to distinguish between groups. Assigning particular metabolic changes to specific drug regimens using metabonomics also remains to be done. Studies exist where identified metabolites have been linked to various disease states suggesting great potential for the use of metabonomics in disease prognostics. This review therefore examines the field of metabonomics in the context of HIV/AIDS, comments on metabolites routinely detected as being affected by the pathogen or treatment, explains what existing data suggest and makes recommendations on future research.

Jacaric acid, a linolenic acid isomer with a conjugated triene system, has a strong antitumor effect in vitro and in vivo

In this study, we compared the cytotoxic effects of natural conjugated linolenic acids (CLnAs) on human adenocarcinoma cells (DLD-1) in vitro, with the goal of finding CLnA isomers with strong cytotoxic effects. The antitumor effect of the CLnA with the strongest cytotoxic effect was then examined in mice. The results showed that all CLnA isomers have strong cytotoxic effects on DLD-1 cells, with jacaric acid (JA) having the strongest effect. Examination of the mechanism of cell death showed that CLnAs induce apoptosis in DLD-1 cells via lipid peroxidation. The intracellular levels of incorporated CLnAs were measured to examine the reason for differences in cytotoxic effects. These results showed that JA was taken into cells efficiently. Collectively, these results suggest that the cytotoxic effect of CLnAs is dependent on intracellular incorporation and induction of apoptosis via lipid peroxidation. JA also had a strong preventive antitumor effect in vivo in nude mice into which DLD-1 cells were transplanted. These results suggest that JA can be used as a dietary constituent for prevention of cancer.

Mitochondrial abnormalities in Alzheimer's disease: possible targets for therapeutic intervention

Mitochondria from persons with Alzheimer's disease (AD) differ from those of age-matched control subjects. Differences in mitochondrial morphology and function are well documented, and are not brain-limited. Some of these differences are present during all stages of AD, and are even seen in individuals who are without AD symptoms and signs but who have an increased risk of developing AD. This chapter considers the status of mitochondria in AD subjects, the potential basis for AD subject mitochondrial perturbations, and the implications of these perturbations. Data from multiple lines of investigation, including epidemiologic, biochemical, molecular, and cytoplasmic hybrid studies, are reviewed. The possibility that mitochondria could potentially constitute a reasonable AD therapeutic target is discussed, as are several potential mitochondrial medicine treatment strategies.

The effect of raw soybean on oxidative status of digestive organs in mice

The present study was undertaken to specify the effect of raw soybean on oxidative status of digestive organs in mice. For this purpose, thirty male (C57BL/6J) mice were randomly divided into three groups and fed on different diets as follows: Group 1 was fed on control diet, Group 2 was fed on raw soybean diet and Group 3 was fed on raw soybean diet supplemented with 30 mg/kg cysteamine. After two weeks of feeding, duodenum, liver and pancreas samples were collected to measure oxidative and antioxidative parameters. The results show that ingestion of raw soybean markedly increased contents of superoxide anion and malondialdehyde (MDA) and activity of inducible nitric oxide synthase (iNOS), decreased activity of superoxide dismutase (SOD), T-AOC and content of reduced glutathione (GSH) in digestive organs of mice (P < 0.05). In the group fed with raw soybean diet supplemented with cysteamine, oxidative stress was mitigated. However, oxidative parameter levels were still higher than those of control diet-fed group. The present study indicates that ingestion of raw soybean could result in an imbalance between oxidant and antioxidant, and thus induce oxidative stress in digestive organs of mice.

Effects of different inspired oxygen fractions on lipid peroxidation during general anaesthesia for elective Caesarean section

BACKGROUND

During general anaesthesia (GA) for Caesarean section (CS), fetal oxygenation is increased by administering an inspired oxygen fraction (Fi(o(2))) of 1.0. However, it is unclear whether such high Fi(o(2)) will increase oxygen free radical activity.

METHODS

We randomized 39 ASA I-II parturients undergoing elective CS under GA to receive 30% (Gp 30), 50% (Gp 50), or 100% (Gp 100) oxygen with nitrous oxide and sevoflurane adjusted to provide equivalent minimum alveolar concentration. Baseline maternal arterial blood before preoxygenation and maternal arterial, umbilical arterial and venous blood at delivery were sampled for assays of the by-product of lipid peroxidation, isoprostane, and for measurement of blood gases and oxygen content.

RESULTS

Maternal and umbilical isoprostane concentrations were similar among the three groups at delivery, despite significantly increased maternal and fetal oxygenation in Gp 100. However, paired comparisons of maternal delivery vs baseline concentration of isoprostane showed an increase at delivery for all groups [Gp 30: mean 342 (sd 210) vs 154 (65) pg ml(-1), P=0.016; Gp 50: 284 (129) vs 156 (79) pg ml(-1), P=0.009; Gp 100: 332 (126) vs 158 (68) pg ml(-1), P<0.001]. The magnitude of increase was similar in all three groups and independent of the Fi(o(2)) or duration after induction.

CONCLUSIONS

GA for CS is associated with a marked increase in free radical activity in the mother and baby. The mechanism is unclear but it is independent of the inspired oxygen in the anaesthetic mixture. Therefore, when 100% oxygen is administered with sevoflurane for GA, fetal oxygenation can be increased, without inducing an increase in lipid peroxidation.

N-acetylcysteine does not prevent hepatorenal ischaemia-reperfusion injury in patients undergoing orthotopic liver transplantation

BACKGROUND

Glutathione (GSH) acts as a free radical scavenger that may be helpful in preventing reperfusion injury. N-acetylcysteine (NAC) replenishes GSH stores. The aims of this study were to evaluate the efficacy of NAC in improving liver graft performance and reducing the incidence of post-operative acute kidney injury (AKI).

METHODS

Our study was a randomized, double-blind, placebo-controlled trial of 100 patients; 50 received placebo and 50 received a loading dose of 140 mg/kg of intravenous (IV) NAC over 1 h followed by 70 mg/kg IV repeated every 4 h for a total of 12 doses. Both groups were followed up for 1 year post-orthotopic liver transplant (OLT). We recorded liver function tests, renal function tests, graft survival, patient survival, plasma GSH and duration of hospital and ICU stay. In addition to serum creatinine (SCr) levels, we analysed cystatin C and beta-trace as independent measures of glomerular filtration. All clinical data were recorded daily for the first week after the surgery, then on Days 14, 21, 30, 90 and 180 and at the end of the first year.

RESULTS

IV NAC did not affect survival, graft function or risk of AKI. However, GSH levels were highly variable with only 50% of patients receiving NAC exhibiting increased levels and fewer patients developed AKI when GSH levels were increased. Additional risk factors for AKI in the post-transplant period were female gender (P = 0.05), increased baseline serum bilirubin (P = 0.004) and increased baseline SCr levels (P = 0.02).

CONCLUSIONS

IV NAC was not effective in reducing renal or hepatic injury in the setting of liver transplantation. The dose and duration of NAC used, though higher than most renal protection studies, may have been ineffective for raising GSH levels in some patients.

Clearance of oxidatively damaged cells by macrophages: recognition of glycoprotein clusters by macrophage-surface nucleolin as early apoptotic cells

The mechanism of macrophage recognition of oxidatively damaged cells was investigated. Jurkat T cells exposed to various concentrations of H(2)O(2) were bound and phagocytosed by macrophages. The cells exposed to 0.1 mM H(2)O(2) were best bound. The cell-surface ligands recognized by macrophages were suggested to be sialylpolylactosaminyl sugar chains of a major sialoglycoprotein CD43 because 1) the cell binding was inhibited by oligosaccharides containing sialylpolylactosaminyl chains, and their inhibitory activity was destroyed by a polylactosamine-cleaving enzyme endo-beta-galactosidase, and by neuraminidase; 2) the oxidized Jurkat cells pretreated with either glycosidase or with anti-CD43 antibody were not bound. The macrophage receptor involved in the binding was suggested to be cell-surface nucleolin because 1) anti-nucleolin antibody inhibited the binding; 2) nucleolin-transfected HEK293 cells bound the oxidized cells; and 3) this binding was inhibited by anti-nucleolin antibody and by anti-CD43 antibody. CD43 on oxidized Jurkat cells tended to form clusters in good accordance with their susceptibility to the macrophage binding. CD43 clustering and the oxidized-cell binding to macrophages were prevented by a caspase inhibitor Z-VAD-fmk, suggesting that the oxidized and bound cells were undergoing apoptosis. Indeed, caspase-3 activity of Jurkat cells increased by the oxidation. These results suggest that moderately oxidized cells undergo apoptosis and are recognized by macrophages as early apoptotic cells.

Inhibitory effect of conjugated alpha-linolenic acid from bifidobacteria of intestinal origin on SW480 cancer cells

In this study, we assessed the ability of six strains of bifidobacteria (previously shown by us to possess the ability to convert linoleic acid to c9, t11-conjugated linoleic acid (CLA) to grow in the presence of alpha-linolenic acid and to generate conjugated isomers of the fatty acid substrate during fermentation for 42 h. The six strains of bifidobacteria were grown in modified MRS (mMRS) containing alpha-linolenic acid for 42 h at 37 degrees C, after which the fatty acid composition of the growth medium was assessed by gas liquid chromatography (GLC). Indeed, following fermentation of one of the strains, namely Bifidobacterium breve NCIMB 702258, in the presence of 0.41 mg/ml alpha-linolenic acid, 79.1% was converted to the conjugated isomer, C18:3 c9, t11, c15 conjugated alpha-linolenic acid (CALA). To examine the inhibitory effect of the fermented oils produced, SW480 colon cancer cells were cultured in the presence of the extracted fermented oil (10-50 microg/ml) for 5 days. The data indicate an inhibitory effect on cell growth (p <or= 0.001) of CALA, with cell numbers reduced by 85% at a concentration of 180 microM, compared with a reduction of only 50% with alpha-linolenic acid (p <or= 0.01).

Interaction of SIV/SHIV infection and morphine on plasma oxidant/antioxidant balance in macaque

A homeostatic balance exists between the cellular generation of oxidant species and endogenous antioxidants under normal physiological conditions. Human Immunodeficiency Virus (HIV) infection is known to affect this balance causing oxidative stress. However, the interaction of HIV infection with a substance abuse on cellular oxidant/antioxidant system is sparse. This study was designed in order to investigate the interactive effect of morphine abuse and Simian Immunodeficiency Virus/ Simian Human Immunodeficiency Virus (SIV/SHIV) infection on plasma oxidant/antioxidant balance in rhesus macaques. Six rhesus macaques adapted to morphine dependence (20 weeks) along with three controls were infected with mixture of SHIV(KU-1B), SHIV(89.6P), and SIV(17E-Fr). Plasma samples from morphine-dependent and control macaques were analyzed for an array of oxidative stress indices after 16 weeks of infection. Morphine-dependence significantly increased plasma malondialdehyde (MDA) and 8-isoprostane levels (8-fold and 2-fold), but these animals showed higher MDA and 8-isoprostane levels after viral infection (18-fold and 4-fold) which was directly correlated with increase in viral load and decline in CD4+ cells. Plasma glutathione (GSH) level depleted (55%) with morphine dependence that was further depleted (25%) by the infection. Activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were increased by 30% and 110%, respectively with morphine dependence, but that was decreased by the infection. Catalase (CAT) activity declined (25%) with morphine dependence that was further declined by infection. Our results clearly suggest that morphine interaction with SIV/SHIV infection causes higher oxidative tissue injury that might have implication in the pathogenesis of AIDS in morphine-dependent macaques.

Morphine-mediated deterioration of oxidative stress leads to rapid disease progression in SIV/SHIV-infected macaques

Oxidative stress is well documented in HIV infection, but the effect of concomitant substance abuse is largely unknown. We studied oxidative stress in our macaque model of morphine abuse and AIDS. In plasma, we found an approximately 50% decrease in catalase activity with morphine dependence that was exacerbated by infection in rapid progressors. Superoxide dismutase was decreased by a similar degree, but only in the presence of both morphine and viral infection. The loss of these antioxidant systems was coincident with significantly increased plasma malondialdehyde upon viral infection that displayed a synergistic increase in conjunction with morphine and rapid disease.

Cellular and molecular hemocyte responses of the Pacific oyster, Crassostrea gigas, following bacterial infection with Vibrio aestuarianus strain 01/32

The strategies used by bacterial pathogens to circumvent host defense mechanisms remain largely undefined in bivalve molluscs. In this study, we investigated experimentally the interactions between the Pacific oyster (Crassostrea gigas) immune system and Vibrio aestuarianus strain 01/32, a pathogenic bacterium originally isolated from moribund oysters. First, an antibiotic-resistant V. aestuarianus strain was used to demonstrate that only a limited number of bacterial cells was detected in the host circulatory system, suggesting that the bacteria may localize in some organs. Second, we examined the host defense responses to V. aestuarianus at the cellular and molecular levels, using flow-cytometry and real-time PCR techniques. We showed that hemocyte phagocytosis and adhesive capabilities were affected during the course of infection. Our results also uncovered a previously-undescribed mechanism used by a Vibrio in the initial stages of host interaction: deregulation of the hemocyte oxidative metabolism by enhancing the production of reactive oxygen species and down-regulating superoxide dismutase (Cg-EcSOD) gene expression. This deregulation may provide an opportunity to the pathogen by impairing hemocyte functions and survival. These findings provide new insights into the cellular and molecular bases of the host-pathogen interactions in C. gigas oyster.

Polyunsaturated but not Conjugated Linoleic Acid Supplementation of Leukemic U937 Cells Can Act as an Amplification Factor for Photofrin-mediated Photodynamic Therapy

Polyunsaturated fatty acids located in leukemia cell membranes are excellent targets for peroxidation. They can significantly enhance the effectiveness of Photofrin-mediated photodynamic therapy (PDT)-induced cell killing. In this study, the peroxidizability of conjugated fatty acid isomers (9c,11t-linoleic acid and 9c,11c-linoleic acid) and polyunsaturated fatty acids (PUFAs; linoleic acid, gamma-linolenic acid and arachidonic acid) with 2,2'-azo-bis(2-amidinpropane)dihydrochloride, soybean lipoxygenase and photomediated peroxidation are compared with each other. Peroxidation was determined using different methods: by means of gas chromatography to estimate the fatty acid (FA) consumption, by photometry for the level of FA peroxides or phospholipid peroxides and by definition of the content of malondialdehyde for thiobarbituric acid reactive substances (TBARS). The results suggest that the generation of oxidation products from individual FAs indicate a different formation rate of oxidation products. Radical FA peroxides were produced most by polyunsaturated arachidonic acid, followed by linoleic acid and gamma-linolenic acid, whereas conjugated FA isomers did not generate peroxides. Accordingly, the levels of lipid peroxides and TBARS were substantially increased after incorporation and oxidation of polyunsaturated FAs into U937 cells and could significantly enhance the effectiveness of Photofrin-PDT-induced cytotoxicity. The results showed that PUFA, but not conjugated FA supplementation of U937 cells, can act as a PDT amplification factor.

Old yellow enzyme interferes with Bax-induced NADPH loss and lipid peroxidation in yeast

The yeast transcriptional response to murine Bax expression was compared with the changes induced by H(2)O(2) treatment via microarray technology. Although most of the Bax-responsive genes were also triggered by H(2)O(2) treatment, OYE3, ICY2, MLS1 and BTN2 were validated to have a Bax-specific transcriptional response not shared with the oxidative stress trigger. In knockout experiments, only deletion of OYE3, coding for yeast Old yellow enzyme, attenuated the rate of Bax-induced growth arrest, cell death and NADPH decrease. Lipid peroxidation was completely absent in DeltaOYE3 expressing Bax. However, the absence of OYE3 sensitized yeast cells to H(2)O(2)-induced cell death, and increased the rate of NADPH decrease and lipid peroxidation. Our results clearly indicate that OYE3 interferes with Bax- and H(2)O(2)-induced lipid peroxidation and cell death in Saccharomyces cerevisiae.

Enhanced 15-HPETE production during oxidant stress induces apoptosis of endothelial cells

Oxidant stress plays an important role in the etiology of vascular diseases by increasing rates of endothelial cell apoptosis, but few data exist on the mechanisms involved. Using a unique model of oxidative stress based on selenium deficiency (-Se), the effects of altered eicosanoid production on bovine aortic endothelial cells (BAEC) apoptosis was evaluated. Oxidant stress significantly increased the immediate oxygenation product of arachidonic acid metabolized by the 15-lipoxygenase pathway, 15-hydroxyperoxyeicosatetraenoic acid (15-HPETE). Treatment of -Se BAEC with TNFalpha/cyclohexamide (CHX) exhibited elevated levels of apoptosis, which was significantly reduced by the addition of a specific 15-lipoxygenase inhibitor PD146176. Furthermore, the addition of 15-HPETE to PD146176-treated BAEC, partially restored TNF/CHX-induced apoptosis. Increased exposure to 15-HPETE induced apoptosis, as determined by internucleosomal DNA fragmentation, chromatin condensation, caspase-3 activation, and caspase-9 activation, which suggests mitochondrial dysfunction. The expression of Bcl-2 protein also was decreased in -Se BAEC. Addition of a caspase-9 inhibitor (LEHD-fmk) completely blocked 15-HPETE-induced chromatin condensation in -Se BAEC, suggesting that 15-HPETE-induced apoptosis is caspase-9 dependent. Increased apoptosis of BAEC as a result of oxidant stress and subsequent production of 15-HPETE may play a critical role in a variety of inflammatory based diseases.

The molecular mechanism of protecting cells against oxidative stress by 2-selenium-bridged β-cyclodextrin with glutathione peroxidase activity

Ultraviolet B (UVB) induces apoptosis and lipid peroxidation of NIH3T3 cells by producing reactive oxygen species (ROS). Glutathione peroxidase (GPX) is one of the most important antioxidant enzymes in organism and it can scavenge ROS. 2-selenium-bridged beta-cyclodextrin (2-SeCD) is a GPX mimic generated in our lab. Its GPX activity is 7.4 U/mumol, which is 7.5 times as much as that of ebselen. In this paper, we have established a cell damage system using UVB radiation. Using this system, we have determined antioxidant effect of 2-SeCD by comparison of malondialdehyde (MDA) and H(2)O(2) contents in NIH3T3 cells before and after UVB radiation. Experimental results indicate that 2-SeCD can inhibit lipid peroxidation and protect the cells from the damage generated by UVB radiation. To evaluate the molecular mechanism of this protection, we determined the effect of 2-SeCD on the expression of p53 and Bcl-2 in NIH3T3 cells. The results showed that 2-SeCD inhibits the increase of p53 expression level and the decrease of expression of Bcl-2 induced by UVB radiation. Thus, we have concluded that protection of NIH3T3 cells against oxidative stress by 2-SeCD was carried out by regulation of the expression of Bcl-2 and p53.

Cutting Edge: Novel Role of Lipoxygenases in the Inflammatory Response: Promotion of TNF mRNA Decay by 15-Hydroperoxyeicosatetraenoic Acid in a Monocytic Cell Line

The metabolism of arachidonic acid via the lipoxygenase and cyclooxygenase pathways generates metabolites that regulate the inflammatory response. Although products of lipoxygenase are classically proinflammatory, recently it has been demonstrated that lipoxins, 15-hydroperoxyeicosatetraenoic acid (15-HPETE) and 15-hydroxyeicosatetraenoic acid exhibit anti-inflammatory activity. We now demonstrate for the first time that 15-HPETE regulates the production of the proinflammatory cytokine TNF posttranscriptionally by promoting degradation of LPS-induced TNFmRNA in a human monocytic cell line, Mono Mac 6. 15-HPETE causes a significant increase in the rate of TNF but not G3PDHmRNA degradation in the presence of the transcription inhibitor, actinomycin D. The decay of TNFmRNA is accelerated 1.7-fold, and its half-life is decreased by 57%. In view of its chemical and physical properties, we propose that 15-HPETE may function by destabilizing TNFmRNA by interaction with a trans-activating protein bound to the AU-rich element of TNFmRNA.

Catalase Regulates Cell Growth in HL60 Human Promyelocytic Cells: Evidence for Growth Regulation by H2O2

Reactive oxygen species (ROS) including hydrogen peroxide (H(2)O(2)) are generated constitutively in mammalian cells. Because of its relatively long life and high permeability across membranes, H(2)O(2) is thought to be an important second messenger. Generation of H(2)O(2) is increased in response to external insults, including radiation. Catalase is located at the peroxisome and scavenges H(2)O(2). In this study, we investigated the role of catalase in cell growth using the H(2)O(2)-resistant variant HP100-1 of human promyelocytic HL60 cells. HP100-1 cells had an almost 10-fold higher activity of catalase than HL60 cells without differences in levels of glutathione peroxidase, manganese superoxide dismutase (MnSOD), and copper-zinc SOD (CuZnSOD). HP100-1 cells had higher proliferative activity than HL60 cells. Treatment with catalase or the introduction of catalase cDNA into HL60 cells stimulated cell growth. Exposure of HP100-1 cells to a catalase inhibitor resulted in suppression of cell growth with concomitant increased levels of intracellular H(2)O(2). Moreover, exogenously added H(2)O(2) or depletion of glutathione suppressed cell growth in HL60 cells. Extracellular signal regulated kinase 1/2 (ERK1/2) was constitutively phosphorylated in HP100-1 cells but not in HL60 cells. Inhibition of the ERK1/2 pathway suppressed the growth of HP100-1 cells, but inhibition of p38 mitogen-activated protein kinase (p38MAPK) did not affect growth. Moreover, inhibition of catalase blocked the phosphorylation of ERK1/2 but not of p38MAPK in HP100-1 cells. Thus our results suggest that catalase activates the growth of HL60 cells through dismutation of H(2)O(2), leading to activation of the ERK1/2 pathway; H(2)O(2) is an important regulator of growth in HL60 cells.

Synthesis of the conjugated trienes 5E,7E,9E,14Z,17Z-eicosapentaenoic acid and 5Z,7E,9E,14Z,17Z-eicosapentaenoic acid, and their induction of apoptosis in DLD-1 colorectal adenocarcinoma cells

During the course of our recent study on the anti-tumor effect of conjugated eicosapentaenoic acids (CEPA), we found that acid mixtures prepared by treating EPA with KOH in ethylene glycol induced potent apoptotic cell death in human tumor cells via membrane phospholipid peroxidation. Interestingly, the KOH-treated CEPA mixtures were more cytotoxic than EPA and CLA and had no effect on normal human fibroblast cells. To identify the specific cytotoxic FA in the CEPA mixture, we synthesized possible candidates for the active species. Here, we report the synthesis of (5E,7E,9E, 14Z, 17Z)-5,7,9,14,1 7-eicosapentaenoic acid (E-CEPA) and its 5-(Z) isomer (Z-CEPA), both of which are conjugated trienes that exist naturally in red algae (Ptilota filicina J. Agardh). E-CEPA and Z-CEPA were synthesized from methyl 5-oxopentanoate in six steps, using three types of Wittig reactions as the key steps. Next, we examined the cytotoxicity of E-CEPA and Z-CEPA in human tumor cells and confirmed their bioactivity. Both E-CEPA and Z-CEPA had a strong cytotoxic reaction in tumor cells, and this effect occurred through induction of apoptosis.

Differential effects of dietary fatty acids on the regulation of CYP2E1 and protein kinase C in human hepatoma HepG2 cells

We investigated the effects of different fatty acids (FAs) or with different degrees of unsaturation on cytochrome P450 2E1 (CYP2E1) induction and protein kinase C (PKC) activity in human hepatoma HepG2 cells. As the degree of unsaturation increased, the cell survival rate decreased for FAs with 18 carbons, but linolenic acid (LNA) or docosahexaenoic acid (DHA) groups were similar even through they have different degrees of unsaturation. Treatment with palmitic acid (PA), oleic acid (OA), linoleic acid (LA), LNA, and DHA resulted in respective cellular FA concentrations of C16:0 (43.1%), C18:1 (18.5%), C18:2 (7.4%), LNA (2.85%), and C22:6 (3.13%), which was highest for the FA that was used as the treatment, indicating that their incorporation within the cell is directly proportional to treatment. After 2 hours of cultivation, the lipid peroxide (LPO) in the DHA group increased 600% compared with control, and was much higher than in the groups treated with the other FAs, with LNA > LA > OA > PA. CYP2E1 induction increased with greater effect as the degree of unsaturation of OA, LA, and DHA increased. PA did not affect PKC activity, but DHA treatment increased PKC activity the most. The effects of LNA and LA were similar, but less than that of DHA, and that of OA was lower still, indicating that activity of PKC is proportional to the degree of unsaturation, and not the configuration of the FA. Increased plasma membrane concentrations of n-3 FA, such as DHA, might exert regulatory effects on PKC by increasing membrane fluidity, causing changes in CYP2E1, elevating levels of LPO, or producing oxidative stress.

Conjugated linoleic acid modulation of cell membrane in leukemia cells

This study compared the cellular uptake of pure conjugated linoleic acid isomers (CLA(9c,11t) and CLA(9c,11c)) to linoleic acid (LA) and their effects on polyunsaturated fatty acid (PUFA) synthesis, its metabolism into conjugated long chain fatty acids (FAs) by desaturation and chain-elongation as well as cell proliferation and the associated anticarcinogenic effects on various human leukemia cell lines (K562, REH, CCRF-CEM and U937 cells). Furthermore, selective effects of this individual isomers of CLA on desaturation steps involved in the biosynthesis of PUFAs associated with cell growth were investigated. CLA isomers supplemented in the culture medium was readily incorporated and esterified into phospholipids (PLs) in the four cell lines in a concentration- and time-dependent manner. The incorporation of the specific CLA isomers in PLs was similar to LA. All four incubating leukemia cells (40 microM CLA for 48 h) showed very high cellular CLA content in PLs (range: 32-63 g FA/100 g total phospholipid fatty acid) affected by the nature of CLA and the cell type. Supplementation with CLA or LA altered also cell membrane composition by n-6 PUFA synthesis. Accordingly, CLA metabolism interferes with LA metabolism. We were able to show that CLA isomers are converted by the leukemia cells of the same metabolic pathway into conjugated diene fatty acids (CDFAs) as LA into non-conjugated PUFAs. In this view, the gas chromatography-flame ionization detector detection of major CDFAs (CD-18:3, CD-20:2 and CD-20:3) in cell membrane of CLA-treated cultures resulted from successive Delta6-desaturation, elongation and Delta5-desaturation of CLA isomers. However, in comparison to LA, relatively lower amounts of elongation and/or desaturation metabolites were detected for CLA(9c,11t), and only minor amounts or trace CDFAs were observed for CLA(9c,11c). Furthermore, CLA(9c,11t) revealed only very low levels of CD-20:4 FA and no CLA(9c,11c)-conversion could be detected. The metabolization of CLA indicated that CLA(9c,11c)<CLA(9c,11t) were a poorer substrates in compared to LA for the Delta5,6-desaturation/elongation in REH, CCRF-CEM and U937 cells or for the Delta5-desaturation/elongation in the K562 cells. CLA(9c,11t) suppresses Delta6-desaturation in CCRF-CEM, REH, and U937 cells (43.5, 54.6 and 58.8% Delta6-inhibition, respectively) and as well Delta9-desaturation in all four cell lines (Delta9-inhibition; 47.1, 33.9, 29.8 and 25.9% for CCRF-CEM, REH, K562 and U937 cells, respectively). However, CLA(9c,11c) does not inhibit or only slightly affected these desaturations. CLA(9c,11t) isomer was found as an Delta6-desaturase inhibitor with a dose-dependent relationship between inhibition of Delta6-desaturase activity and decreases in cell growth. The growth inhibitory effects of CLA (with 30-120 microM) on leukemia cells were dependent upon the type and concentration of CLA isomers present. CLA-supplemented cells with low concentrations (<60 microM) were not sufficient to impair cell proliferation. Nevertheless, higher amounts of CLAs (>60 microM) had the CLA type dependent antiproliferative effects. Thus, the 9cis,11trans- and the 9cis,11cis-CLA isomers regulate cell growth and survival in different leukemia cell types through their existence alone and/or by their inhibitory effects of desaturase activity.

Conjugated eicosapentaenoic acid (EPA) inhibits transplanted tumor growth via membrane lipid peroxidation in nude mice

Both conjugated linoleic acid (CLA) and eicosapentaenoic acid (EPA) have an antitumor effect. Hence, we hypothesized that a combination of conjugated double bonds and an (n-3) highly unsaturated fatty acid would produce stronger bioactivity. To verify the antitumor effect of conjugated EPA (CEPA), we transplanted DLD-1 human colon tumor cells into nude mice, and compared the tumor growth between CEPA-fed mice and CLA- and EPA-fed mice. After tumor cell inoculation, mice were assigned to 1 of 4 groups (control, CLA, EPA, and CEPA) consisting of 10 mice each. The control group received only safflower oil fatty acids, whereas the remaining groups received a mixture of safflower oil fatty acids and 20 g/100 g of total fatty acids as CLA, EPA, or CEPA. Mice were fed once every 2 d for 4 wk at a dose of 50 mg/mouse at each feeding. After 4 wk, tumor growth in CEPA-fed mice was significantly suppressed, compared with that in CLA- (P < 0.005) and EPA-fed mice (P < 0.001). DNA fragmentation in the tumor tissues of the CEPA-fed mice occurred more frequently than in the CLA- (P < 0.001) and EPA-fed mice (P < 0.001), suggesting that CEPA induced apoptosis in the tumor tissues. To further investigate the mechanism, the level of oxidative stress in the tumor tissues was determined. The CEPA-fed mice showed significant lipid peroxidation, compared with the CLA- (P < 0.001) and EPA-fed mice (P < 0.001). Therefore, we verified that CEPA has a stronger in vivo antitumor effect than EPA and CLA, and that CEPA acts through induction of apoptosis via lipid peroxidation.

The Role of Oxygen-Free Radical in the Apoptosis of Enterocytes in Scalded Rats After Delayed Resuscitation

BACKGROUND

This study aimed to evaluate the relation between apoptosis of enterocytes and oxygen-free radical injury in scalded rats with delayed resuscitation as well as the role of antioxidants in the prevention of enterocyte apoptosis.

METHODS

For this study, 150 male Wistar rats were divided randomly into four groups representing early resuscitation (ER), delayed resuscitation (DR), N-acetylcysteine (NAC) treatment, and allopurinol (Allo) treatment. The animals were subjected to a 30% total body surface area, full-thickness scald. Fluid therapy was started 6 hours after the injury in the DR and treatment groups. Apoptosis of enterocytes was identified by DNA fragmentation (ap%), DNA agarose gel electrophoresis, and terminal deoxynucleotidyl transferace (TdT)-mediated dUPT-biotin nick end labeling (TUNEL). The contents of malondialdehyde (MDA), total sulfhydryl (TSH), and nonprotein sulfhydryl (NPSH) and the activity of xanthine oxidase in intestinal mucosa were determined after the burn in the four groups.

RESULTS

Apoptosis of enterocytes increased significantly in all the groups. The animals in the DR group showed an earlier and greater increase in ap% than the animals in the ER group. Similar results were seen for electrophoresis, TUNEL assay, and levels of MDA, xanthine oxidase (XO), TSH, and NPSH. Treatment with NAC was associated with a decrease in ap% and MDA, but not XO, as compared with the levels in the DR group, whereas treatment with Allo was associated with a decrease in MDA and XO, but not ap%. Delayed resuscitation was associated with significant decreases in TSH and NPSH, as compared with the levels in the ER group, whereas both the NAC and Allo groups had significantly higher levels of TSH and NPSH than the DR group.

CONCLUSIONS

Significant apoptosis of enterocytes was induced by oxidative stress in the intestinal mucosa after a burn in rats. The findings show that NAC blunted intestinal apoptosis induced by oxygen-free radical, which was generated in the process of ischemia-reperfusion injury after a burn because of delayed resuscitation.

Lipid Peroxidation during the Hypersensitive Response in Potato in the Absence of 9-Lipoxygenases

Hypersensitive cell death is an important defense reaction of plants to pathogen infection and is accompanied by lipid peroxidation processes. These may occur non-enzymatically by the action of reactive oxygen species or may be catalyzed by enzymes such as alpha-dioxygenases, lipoxygenases, or peroxidases. Correlative data showing increases in 9-lipoxygenase products in hyper-sensitively reacting cells have so far suggested that a large part of lipid peroxidation is mediated by a specific set of 9-lipoxygenases. To address the significance of 9-lipoxygenases for this type of pathogen response in potato, RNA interference constructs of a specific pathogen-induced potato 9-lipoxygenase were transferred to potato plants. Significantly reduced 9-lipoxygenase transcript levels were observed in transgenic plants after pathogen treatment. In addition, 9-lipoxygenase activity was hardly detectable, and levels of 9-lipoxygenase-derived oxylipins were reduced up to 12-fold after pathogen infection. In contrast to wild type plants, high levels of non-enzymatically as well as 13-lipoxygenase-derived oxylipins were present in 9-lipoxygenase-deficient plants. From this we conclude that during the normal hypersensitive response in potato, lipid peroxidation may occur as a controlled and directed process that is facilitated by the action of a specific 9-lipoxygenase. If 9-lipoxygenase-mediated formation of hydroperoxides is repressed, autoxidative lipid peroxidation processes and 13-lipoxygenase-mediated oxylipins synthesis become prominent. The unaltered timing and extent of necrosis formation suggests that the origin of lipid hydroperoxides does not influence pathogen-induced cell death in potato.

Appetizing rancidity of apoptotic cells for macrophages: oxidation, externalization, and recognition of phosphatidylserine

Programmed cell death (apoptosis) functions as a mechanism to eliminate unwanted or irreparably damaged cells ultimately leading to their orderly phagocytosis in the absence of calamitous inflammatory responses. Recent studies have demonstrated that the generation of free radical intermediates and subsequent oxidative stress are implicated as part of the apoptotic execution process. Oxidative stress may simply be an unavoidable yet trivial byproduct of the apoptotic machinery; alternatively, intermediates or products of oxidative stress may act as essential signals for the execution of the apoptotic program. This review is focused on the specific role of oxidative stress in apoptotic signaling, which is realized via phosphatidylserine-dependent pathways leading to recognition of apoptotic cells and their effective clearance. In particular, the mechanisms involved in selective phosphatidylserine oxidation in the plasma membrane during apoptosis and its association with disturbances of phospholipid asymmetry leading to phosphatidylserine externalization and recognition by macrophage receptors are at the center of our discussion. The putative importance of this oxidative phosphatidylserine signaling in lung physiology and disease are also discussed.

Phospholipid hydroperoxide glutathione peroxidase induces a delay in G1 of the cell cycle

Phospholipid hydroperoxide glutathione peroxidase (PhGPx) is an antioxidant enzyme that reduces cellular phospholipid hydroperoxides (PLOOHs) to alcohols. Cellular peroxide tone has been implicated in cell growth and differentiation. By reducing the PLOOH level in the cell membrane, PhGPx regulates the peroxide tone and thereby might be involved in cell growth. We hypothesized that overexpression of PhGPx in human breast cancer cells would decrease their growth rate. We stably transfected MCF-7 cells (Wt) with L-PhGPx and measured cell doubling time, plating efficiency, and cell cycle phase transit times. P-4 cells (8-fold increase in PhGPx activity) showed a 2-fold increase in doubling time; doubling time increased directly with PhGPx activity (r = 0.95). The higher the PhGPx activity, the lower the plating efficiency (r = -0.86). The profile of other antioxidant enzymes was unchanged. Overexpression of PhGPx lowered the steady-state level of PLOOH (by > 60%). Results from bromodeoxyuridine pulse-chase experiments and flow cytometry indicate that PhGPx induced a delay in MCF-7 proliferation that was primarily due to a slower progression from G1 to S. These results support the hypothesis that PhGPx plays a regulatory role in the progression of MCF-7 cells from G1 to S possibly by regulating the steady-state levels of PLOOH. These data suggest that PhGPx can lower the peroxide tone, which might change the cellular redox environment resulting in a delay in G1 transit. Thus, PhGPx could be an important factor in cell growth.

The caspase inhibitor IDN-6556 prevents caspase activation and apoptosis in sinusoidal endothelial cells during liver preservation injury

Cold ischemia (CI)-warm reperfusion (WR) liver injury remains a problem in liver transplantation. CI-WR initially causes sinusoidal endothelial cell (SEC) apoptosis through a caspase-dependent mechanism. We previously showed that the caspase inhibitor IDN-1965 prevents CI-WR-induced SEC apoptosis. However, this agent required to be administered to the donor, preservation solution, and recipient for efficacy. Here, we show that a second-generation caspase inhibitor, IDN-6556, effectively prevents CI-WR-induced SEC injury when added only to University of Wisconsin (UW) cold storage media. Rat livers were stored in UW solution for 24 hours at 4 degrees C and reperfused for 1 hour at 37 degrees C. Apoptosis was quantitated using terminal deoxynucleotide transferasemediated deoxyuridine triphosphate nick end labeling (TUNEL) assay and caspase 3 activation determined by biochemical measurement and immunohistochemical analysis. Pan-caspase inhibitors (IDN-8066, IDN-7503, IDN-7436, IDN-1965, and IDN-6556) were applied at preischemic, cold preservation, or reperfusion periods. TUNEL-positive SEC and caspase 3-like activity in the liver was increased by CI-WR. Three caspase inhibitors (IDN-8066, IDN-1965, and IDN-6556) effectively attenuated SEC apoptosis and caspase 3 activation. The most potent inhibitor, IDN-6556, reduced SEC apoptosis and caspase 3 activity by 55% and 94%, respectively. Prevention of SEC apoptosis by IDN-6556 was not reduced when this agent was administered only during the cold preservation period. When added to the preservation solution, the caspase inhibitor IDN-6556 appears to be a feasible therapeutic agent against ischemia-reperfusion injury in liver transplantation.

Global effects of xanthine oxidase stress on alveolar type II cells

OBJECTIVE: To delineate biochemical details of graded xanthine oxidase stress toward cultured alveolar type II cells, particularly oxidant-mediated damage of type II cell nucleic acid, protein, and lipid, as an in vitro model of distant ischemia-reperfusion lung injury. DESIGN: In vitro injury model using native rat and immortalized mouse alveolar type II cells and exogenous xanthine oxidase. SETTING: Research laboratory. Measurement: Cultured type II cells were subjected to xanthine oxidase-derived reactive oxygen stress at variable concentrations and incubation times. Reduction of type II cell double-stranded DNA, inhibition of de novo phosphatidyl choline synthesis, enhancement of lipid peroxidation, and suppression of mitochondrial redox capacity were analyzed in relation to high-intensity (xanthine oxidase, 25 munits/mL) oxidant stress. Alterations in type II cell cellular glutathione-related antioxidant repertoire were assessed at both high-intensity and low-intensity (xanthine oxidase, 1 munits/mL) oxidant stress. MAIN RESULTS: High-intensity xanthine oxidase stress significantly increased type II cell DNA strand breakage, inhibited de novo phosphatidyl choline synthesis, diminished mitochondrial integrity, and enhanced lipid peroxidation in the absence of overt cytolysis. This injury was modulated with addition of exogenous glutathione peroxidase, or catalase/superoxide dismutase, but not glutathione or N-acetylcysteine. Although aspects of the glutathione antioxidant repertoire were similarly diminished with high-intensity xanthine oxidase stress, low-dose (long duration) xanthine oxidase stress augmented the activities of type II cell glutathione peroxidase and gamma-glutamyl transferase (the rate-limiting enzyme in glutathione synthesis). CONCLUSION: High-intensity xanthine oxidase stress (in vitro model of in vivo ischemia-reperfusion) may overwhelm type II cell antioxidant defenses and mediate oxidant injury to nucleic acid, protein, and lipid in the absence of cell lysis. Immortalized murine type II cells seem to appropriately model xanthine oxidase-mediated nucleic acid and protein injury of native rat type II cells. Exogenous glutathione peroxidase reduces oxidant injury in this in vitro model. Depending on magnitude (and possibly duration) of the xanthine oxidase stress, type II cell glutathione antioxidant elements may be diminished or enhanced.

Fatty acid oxidation and signaling in apoptosis

It is well established that fatty acid metabolites of cyclooxygenase, lipoxygenase (LOX), and cytochrome P450 are implicated in essential aspects of cellular signaling including the induction of programmed cell death. Here we review the roles of enzymatic and non-enzymatic products of polyunsaturated fatty acids in controlling cell growth and apoptosis. Also, the spontaneous oxidation of polyunsaturated fatty acids yields reactive aldehydes and other products of lipid peroxidation that are potentially toxic to cells and may also signal apoptosis. Significant conflicting data in terms of the role of LOX enzymes are highlighted, prompting a re-evaluation of the relationship between LOX and prostate cancer cell survival. We include new data showing that LNCaP, PC3, and Du145 cells express much lower levels of 5-LOX mRNA and protein compared with normal prostate epithelial cells (NHP2) and primary prostate carcinoma cells (TP1). Although the 5-LOX activating protein inhibitor MK886 killed these cells, another 5-LOX inhibitor AA861 hardly showed any effect. These observations suggest that 5-LOX is unlikely to be a prostate cancer cell survival factor, implying that the mechanisms by which LOX inhibitors induce apoptosis are more complex than expected. This review also suggests several mechanisms involving peroxisome proliferator activated receptor activation, BCL proteins, thiol regulation, and mitochondrial and kinase signaling by which cell death may be produced in response to changes in non-esterified and non-protein bound fatty acid levels. Overall, this review provides a context within which the effects of fatty acids and fatty acid oxidation products on signal transduction pathways, particularly those involved in apoptosis, can be considered in terms of their overall importance relative to the much better studied protein or peptide signaling factors.

Lipoxygenase activity in altered gravity

Lipoxygenases are a family of enzymes which dioxygenate unsaturated fatty acids, thus initiating lipoperoxidation of membranes or the synthesis of signalling molecules, or inducing structural and metabolic changes in the cell. This activity is the basis for the critical role of lipoxygenases in a number of pathophysiological conditions, both in animals and plants. We review the effects of microgravity on the catalytic efficiency of purified soybean (Glycine max) lipoxygenase-1, as well as the modulation of the activity and expression of 5-lipoxygenase in human erythroleukemia K562 cells subjected to altered gravity. We also outline the molecular properties of the lipoxygenase family and discuss its possible involvement in space-related processes, such as apoptosis (programmed cell death) and immuno-depression. Finally, we discuss the modulation of cyclooxygenase activity and expression in K562 cells exposed to altered gravity, because cyclooxygenase catalyzes the oxidation of arachidonate through a pathway different from that catalyzed by lipoxygenase activity.

Evidence of oxidative stress following the viral infection of two lepidopteran insect cell lines

The infection of Spodoptera frugiperda Sf-9 (Sf-9) and Trichoplusia ni BTI-Tn-5B1-4 (Tn-5B1-4) insect cell lines with Autographa californica multiple nucleopolyhedrovirus (AcMNPV) resulted in increased levels of lipid hydroperoxides and protein carbonyls. In addition, the viral infection resulted in a significant decrease in the reduced glutathione to oxidized glutathione (2GSH/GSSG) ratio. These results are all consistent with an increased level of oxidative stress as a result of the viral infection. It was also observed that the oxidative damage corresponded to reduced cell viability, i.e., the results are consistent with the premise that oxidative damage contributes to cell death. Finally, the measured intracellular activities of most of the antioxidant enzymes, specifically manganese superoxide dismutase (MnSOD), ascorbate peroxidase (APOX), and catalase (CAT, not present in Sf-9 cells), did not significantly decrease following viral infection. In contrast, the measured activity of copper-zinc superoxide dismutase (CuZnSOD) decreased in the Sf-9 and Tn-5B1-4 cells following AcMNPV infection.

Ceramide in apoptosis signaling: relationship with oxidative stress

Ceramide is one of the major sphingosine-based lipid second messengers that is generated in response to various extracellular agents. However, while widespread attention has focused on ceramide as a second messenger involved in the induction of apoptosis, important issues with regard to the mechanisms of ceramide formation and mode of action remain to be addressed. Several lines of evidence suggest that ceramide and oxidative stress are intimately related in cell death induction. This review focuses on the putative relationships between oxidative stress and sphingolipid metabolism in the apoptotic process and discusses the potential mechanisms that connect and regulate the two phenomena.

Diclofenac induced in vivo nephrotoxicity may involve oxidative stress-mediated massive genomic DNA fragmentation and apoptotic cell death

Diclofenac (DCLF) is a nonsteroidal anti-inflammatory drug that is widely used for the treatment of osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, and acute muscle pain conditions. Toxic doses of DCLF can cause nephrotoxicity in humans and experimental animals. However, whether this DCLF-induced nephrotoxicity involves apoptotic cell death in addition to necrosis is unknown. The goals of this investigation were to determine whether DCLF-induced nephrotoxicity involves oxidative stress and apoptotic type genomic DNA fragmentation, and if so, whether DCLF-induced oxidative stress and DNA fragmentation cause apoptotic cell death in mouse kidneys. Male ICR mice (CD-1; 25-45 g), fed ad libitum, were administered nephrotoxic doses of DCLF (100, 200, 300 mg/Kg, po) and sacrificed 24 h later. Blood was collected to evaluate renal injury (BUN), lipid peroxidation (MDA: malondialdehyde levels), and superoxide dismutase (SOD) activity (a marker of oxidative stress). Kidney tissues were analyzed both quantitatively and qualitatively to determine the degree and type of DNA damage, and evaluated histopathologically for the presence of apoptotic characteristics in the nucleus of diverse types of kidney cells. Results show that diclofenac is a powerful nephrotoxicant (at 100, 200, and 300 mg/kg: 4.7-, 4.9-, and 5.0-fold increases in BUN compared to the control, respectively) and a strong inducer of oxidative stress (significant increase in MDA levels). Oxidative stress induced by DCLF was also coupled with massive kidney DNA fragmentation (100, 200, and 300 mg/kg: 3-, 8-, and 10-fold increases compared to control, respectively). A dose-dependent increase in MDA levels and SOD activity was also observed, which indicated a link between oxidative stress and nephrotoxicity. Qualitative analysis of DNA fragmentation by gel electrophoresis showed a DNA ladder indicative of Ca2+-Mg2+-endonuclease activation. Histopathological examination of kidney sections revealed numerous apoptotic nuclei across proximal and distal tubular cell linings. Collectively, these data for the first time suggest that DCLF-induced nephrotoxicity may involve production of reactive oxygen species leading to oxidative stress and massive genomic DNA fragmentation, and these two free radical mediated events may ultimately translate into apoptotic cell death of kidney cells in vivo, and reveal a DNA-active role for DCLF.

Aldehydic lipid peroxidation products derived from linoleic acid

Lipid peroxidation (LPO) processes observed in diseases connected with inflammation involve mainly linoleic acid. Its primary LPO products, 9-hydroperoxy-10,12-octadecadienoic acid (9-HPODE) and 13-hydroperoxy-9,11-octadecadienoic acid (13-HPODE), decompose in multistep degradation reactions. These reactions were investigated in model studies: decomposition of either 9-HPODE or 13-HPODE by Fe(2+) catalyzed air oxidation generates (with the exception of corresponding hydroxy and oxo derivatives) identical products in often nearly equal amounts, pointing to a common intermediate. Pairs of carbonyl compounds were recognized by reacting the oxidation mixtures with pentafluorobenzylhydroxylamine. Even if a pure lipid hydroperoxide is subjected to decomposition a great variety of products is generated, since primary products suffer further transformations. Therefore pure primarily decomposition products of HPODEs were exposed to stirring in air with or without addition of iron ions. Thus we observed that primary products containing the structural element R-CH=CH-CH=CH-CH=O add water and then they are cleaved by retroaldol reactions. 2,4-Decadienal is degraded in the absence of iron ions to 2-butenal, hexanal and 5-oxodecanal. Small amounts of buten-1,4-dial were also detected. Addition of m-chloroperbenzoic acid transforms 2,4-decadienal to 4-hydroxy-2-nonenal. 4,5-Epoxy-2-decenal, synthetically available by treatment of 2,4-decadienal with dimethyldioxirane, is hydrolyzed to 4,5-dihydroxy-2-decenal.

The growth inhibitory effect of conjugated linoleic acid on a human hepatoma cell line, HepG2, is induced by a change in fatty acid metabolism, but not the facilitation of lipid peroxidation in the cells

We investigated the growth inhibitory effect of conjugated linoleic acid (CLA) on HepG2 (human hepatoma cell line), exploring whether the inhibitory action occurs via lipid peroxidation in the cells. When the cells were incubated up to 72 h with 5-40 microM of CLA (a mixture of 9c,11t-18:2 and 10t,12c-18:2), cell proliferation was clearly inhibited in a dose and time dependent manner but such an inhibition was not confirmed with linoleic acid (LA). In order to evaluate the possible contribution of lipid peroxidation exerted by CLA to cell growth inhibition, alpha-tocopherol (5-20 microM) and BHT (1-10 microM) as potent antioxidants were added to the medium with CLA (20 microM), which did not restore cell growth at all. Furthermore, after 72 h incubation, the membranous phospholipid hydroperoxide formation in the CLA-supplemented cells was suppressed respectively to 25% and 50% of that in LA-supplemented cells and control cells. No difference was observed by a conventional lipid peroxide assay, the TBA test, between CLA-supplemented cells and LA-supplemented cells. Although the cellular lipid peroxidation was not stimulated, lipid contents (triacylglycerol, total cholesterol and free cholesterol) and fatty acid contents (palmitic acid, palmitoleic acid and stearic acid) markedly increased in CLA-supplemented cells compared with LA-supplemented and control cells. Moreover, supplementation with 20 microM LA and 20 microM arachidonic acid profoundly interfered with the inhibitory effect of CLA in HepG2. These results suggest that the growth inhibitory effect of CLA on HepG2 is due to changes in fatty acid metabolism but not to lipid peroxidation.

Reactive oxygen intermediates involved in cellular regulation

Reactive oxygen intermediates (ROIs) in low concentration, as released permanently by nonphagocytic cells, possess important functions in inter- and intracellular signalling. They lead to alterations in the phosphorylation pattern followed by gene activation, including the expression of proto-oncogenes. Redox-sensitive sites in membrane molecules may trigger adhesion and chemotaxis or open ion channels and activate transport processes across the cytoplasma membrane. ROIs shift the ratio of cyclic GMP to cyclic AMP giving signals to proliferation and differentiation processes. Senescence, apoptosis, and cell death can also be modulated by ROIs, depending on concentration and cell type.

Glutathione peroxidase and viral replication: implications for viral evolution and chemoprevention

It is likely that several of the biological effects of selenium are due to its effects on selenoprotein activity. While the effects of the anti-oxidant selenoprotein glutathione peroxidase (GPx) on inhibiting HIV activation have been well documented, it is clear that increased expression of this enzyme can stimulate the replication and subsequent appearance of cytopathic effects associated with an acutely spreading HIV infection. The effects of GPx on both phases of the viral life cycle are likely mediated via its influence on signaling molecules that use reactive oxygen species, and similar influences on signaling pathways may account for some of the anti-cancer effects of selenium. Similarly, selenium can alter mutagenesis rates in both viral genomes and the DNA of mammalian cells exposed to carcinogens. Comparisons between the effects of selenium and selenoproteins on viral infections and carcinogenesis may yield new insights into the mechanisms of action of this element.

Apoptosis and apoptosis-associated perturbations of peripheral blood lymphocytes during HIV infection: comparison between AIDS patients and asymptomatic long-term non-progressors

This study was designed to compare the degree of lymphocyte apoptosis and Fas-Fas ligand (FasL) expression in AIDS patients and long-term non-progressors (LTNPs) and correlate these parameters with apoptosis-associated perturbations in lymphocyte function. LTNPs had a lower frequency of apoptotic CD4+ and CD8+ T cells compared with subjects with AIDS. This correlated with a lower frequency of cells expressing Fas and FasL. The frequency of selected lymphocyte populations exhibiting a disrupted mitochondrial transmembrane potential (DeltaPsim) and increased superoxide generation was lower in LTNPs than in patients with AIDS; these abnormalities were associated with lower levels of caspase-1 activation in LTNPs. The results indicate a significantly reduced level of apoptosis and apoptosis-associated parameters in LTNPs than in patients developing AIDS. Based on these findings, a crucial role for mitochondria can be predicted in the process of lymphocyte apoptosis during the evolution of AIDS.

Role of glutathione S-transferases in oxidative stress-induced male germ cell apoptosis

Cellular apoptosis in a tissue may occur for the maintenance of proper ratio of cells or because of toxic effects of free radicals or other agents. Male germ cell apoptosis is pivotal in maintaining the proper functioning of the testis, but it is not clear how free radicals affect germ cells and what the defense mechanisms are that are used by these cells to combat the toxic effects of the products of oxidative stress. This study shows that male germ cells are susceptible to H(2)O(2)-induced stress and, upon exposure to H(2)O(2) in vitro, demonstrate a typical apoptotic phenotype that includes DNA fragmentation and formation of DNA ladders. Other changes include considerable accumulation of products of lipid peroxidation in the germ cells after exposure to H(2)O(2). Evidence is presented for the existence of multiple isoforms of glutathione S-transferases (GSTs) that possess both transferase and Se-independent peroxidase activity. Germ cell GST activity increases after H(2)O(2) exposure. If this increase in activity is inhibited with suitable inhibitors, the formation of products of lipid peroxidation is augmented, resulting in germ cell apoptosis. Also, when constitutive GST activity is inhibited, accumulation of products of lipid peroxidation occurs, resulting in increased cellular apoptosis. These data show that GSTs form a part of adaptive response of germ cells to oxidative stress and are important constituents in detoxifying the products of lipid peroxidation.

Melatonin attenuates acute renal failure and oxidative stress induced by mercuric chloride in rats

We evaluated the effect of melatonin (Mel), a potent scavenger of reactive oxygen species, in the course of HgCl(2)-induced acute renal failure. Rats received by gastric gavage 1 mg/kg of Mel (n = 21) or vehicle (n = 21), 30 min before the subcutaneous injection of HgCl(2) (2.5 mg/kg). Rats were killed at 24, 48, and 72 h, and plasma creatinine (S(cr)), renal histology, proliferative activity, apoptosis, and superoxide-producing cells were studied. We also determined the renal content of malondialdehyde (MDA) and glutathione (GSH) and the activities of glutathione peroxidase and catalase. Mel pretreatment (Mel plasma levels of 3.40 +/- 3.15 microgram/ml at the time of HgCl(2) injection) prevented the increment in S(cr) and reduced tubular necrosis from 41.0 +/- 10.5 to 4.2 +/- 5.1% of proximal tubules (P < 0.01). Apoptosis and postnecrotic proliferative activity were twice more intense in the group untreated with Mel. Increment in renal content of MDA and decrease in GSH resulting from HgCl(2) toxicity were prevented by Mel. Mel also induced an important reduction in superoxide-positive cells. In contrast to the beneficial effects of pretreatment with Mel, the administration of Mel in conjunction with HgCl(2) had no effect on the oxidative damage and did not prevent nephrotoxicity. We conclude that the beneficial effects of pharmacological doses of Mel are due to its antioxidant properties.