Ascorbate and alpha-tocopherol prevent apoptosis induced by serum removal independent of Bcl-2

An AlphaFold Structure Analysis of COQ2 as Key a Component of the Coenzyme Q Synthesis Complex

Coenzyme Q (CoQ) is a lipidic compound that is widely distributed in nature, with crucial functions in metabolism, protection against oxidative damage and ferroptosis and other processes. CoQ biosynthesis is a conserved and complex pathway involving several proteins. COQ2 is a member of the UbiA family of transmembrane prenyltransferases that catalyzes the condensation of the head and tail precursors of CoQ, which is a key step in the process, because its product is the first intermediate that will be modified in the head by the next components of the synthesis process. Mutations in this protein have been linked to primary CoQ deficiency in humans, a rare disease predominantly affecting organs with a high energy demand. The reaction catalyzed by COQ2 and its mechanism are still unknown. Here, we aimed at clarifying the COQ2 reaction by exploring possible substrate binding sites using a strategy based on homology, comprising the identification of available ligand-bound homologs with solved structures in the Protein Data Bank (PDB) and their subsequent structural superposition in the AlphaFold predicted model for COQ2. The results highlight some residues located on the central cavity or the matrix loops that may be involved in substrate interaction, some of which are mutated in primary CoQ deficiency patients. Furthermore, we analyze the structural modifications introduced by the pathogenic mutations found in humans. These findings shed new light on the understanding of COQ2's function and, thus, CoQ's biosynthesis and the pathogenicity of primary CoQ deficiency.

Coenzyme Q-related compounds to maintain healthy mitochondria during aging

Mitochondrial dysfunction is one of the main factors that affects aging progression and many age-related diseases. Accumulation of dysfunctional mitochondria can be driven by unbalanced mito/autophagy or by decrease in mitochondrial biosynthesis and turnover. Coenzyme Q is an essential component of the mitochondrial electron transport chain and a key factor in the protection of membrane and mitochondrial DNA against oxidation. Coenzyme Q levels decay during aging and this can be considered an accelerating factor in mitochondrial dysfunction and aging progression. Supplementation with coenzyme Q is successful for some tissues and organs but not for others. For this reason, the role of coenzyme Q in systemic aging is a complex picture that needs different strategies depending on the organ considered the main objective to be addressed. In this chapter we focus on the different effects of coenzyme Q and related compounds and the probable strategies to induce endogenous synthesis to maintain healthy aging.

Coenzyme Q homeostasis in aging: Response to non-genetic interventions

Coenzyme Q (CoQ) is a key component for many essential metabolic and antioxidant activities in cells in mitochondria and cell membranes. Mitochondrial dysfunction is one of the hallmarks of aging and age-related diseases. Deprivation of CoQ during aging can be the cause or the consequence of this mitochondrial dysfunction. In any case, it seems clear that aging-associated CoQ deprivation accelerates mitochondrial dysfunction in these diseases. Non-genetic prolongevity interventions, including CoQ dietary supplementation, can increase CoQ levels in mitochondria and cell membranes improving mitochondrial activity and delaying cell and tissue deterioration by oxidative damage. In this review, we discuss the importance of CoQ deprivation in aging and age-related diseases and the effect of prolongevity interventions on CoQ levels and synthesis and CoQ-dependent antioxidant activities.

Extracellular pH and lung infections in cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive disease caused by CFTR mutations. It is characterized by high NaCl concentration in sweat and the production of a thick and sticky mucus, occluding secretory ducts, intestine and airways, accompanied by chronic inflammation and infections of the lungs. This causes a progressive and lethal decline in lung function. Therefore, finding the mechanisms driving the high susceptibility to lung infections has been a key issue. For decades the prevalent hypothesis was that a reduced airway surface liquid (ASL) volume and composition, and the consequent increased mucus concentration (dehydration), create an environment favoring infections. However, a few years ago, in a pig model of CF, the Na⁺/K⁺ concentrations and the ASL volume were found intact. Immediately a different hypothesis arose, postulating a reduced ASL pH as the cause for the increased susceptibility to infections, due to a diminished bicarbonate secretion through CFTR. Noteworthy, a recent report found normal ASL pH values in CF children and in cultured primary airway cells, challenging the ASL pH hypothesis. On the other hand, recent evidences revitalized the hypothesis of a reduced ASL secretion. Thus, the role of the ASL pH in the CF is still a controversial matter. In this review we discuss the basis that sustain the role of CFTR in modulating the extracellular pH, and the recent results sustaining the different points of view. Finding the mechanisms of CFTR signaling that determine the susceptibility to infections is crucial to understand the pathophysiology of CF and related lung diseases.

The benefits of hypothermic machine perfusion are enhanced with Vasosol and α-tocopherol in rodent donation after cardiac death livers

The use of hypothermic machine perfusion (HMP) has recently been used to show an improvement in both standard and extended criteria donor liver grafts but creating a more dynamic preservation environment that can be supplemented with a variety of additives to aid in cold temperature metabolism and vasodilatation. Increasing the benefits of HMP, we explore the use of α-tocopherol in reducing inflammatory markers and apoptotic pathways to reduce the incidence of preservation injury. We explored the use of a donation after cardiac death (DCD) rodent model to test the additive benefits of α-tocopherol in HMP. The addition of α-tocopherol reduced the level of alanine aminotransferase (ALT) over the course of reperfusion as well, reduced the levels of inflammatory cytokines within a 90 minute reperfusion biopsy. Further benefit was seen with α-tocopherol through the reduction of the level of caspase 3/7 in the circulation, shown to be a result of the reduction of the levels of Cytochrome C mRNA. Liver perfusion with Vasosol® and HMP could benefit further from the addition of α-tocopherol to existing formulations of Vasosol®.

Neuronal vulnerability of stroke-prone spontaneously hypertensive rats to ischemia and its prevention with antioxidants such as vitamin E

Stroke-prone spontaneously hypertensive rats (SHRSP/Izm) develop severe hypertension, and more than 95% of them die of cerebral stroke. Hypoxic stimulation followed by oxygen reperfusion induces neuronal damage in both normotensive Wistar Kyoto/Izm (WKY/Izm) and SHRSP/Izm rats, and the percentage of neurons that undergo apoptosis during hypoxia-reperfusion is markedly higher in SHRSP/Izm rats than in WKY/Izm rats. The biochemical characteristics of the SHRSP/Izm rats, unlike those of WKY/Izm rats, might act as a factor in the stroke proneness of SHRSP/Izm rats. In the hippocampus, the formation of hydroxyl radicals and the cerebral blood flow-independent formation of nitric oxide (NO) were strongly increased after reperfusion in SHRSP/Izm rats, and the neuronal expression of the thioredoxin and Bcl-2 genes was significantly decreased in the SHRSP/Izm rats compared with the WKY/Izm rats. On the other hand, the effects of antioxidants against neuronal death associated with cerebral ischemia-reperfusion were stronger in the SHRSP/Izm rats, in which the addition of vitamin E or ebselen almost completely inhibited neuronal death. Namely, the addition of 100 microg/ml of vitamin E under hypoxia/reoxygenation (H/R) conditions completely inhibited WKY and SHRSP/Izm neuronal death. Vitamin E exerts a marked inhibitory effect against neuronal damage via its incorporation into mitochondrial membranes, where it captures reactive oxygen and free radicals. The susceptibility of neurons to apoptosis in SHRSP/Izm rats is partly due to an insufficiency of mitochondrial redox regulation and apoptosis-inhibitory proteins. In this review, we describe the neuronal vulnerability of SHRSP/Izm rats induced by cerebral ischemia and the effects of antioxidants such as vitamin E.

Effects of combined treatment with vitamins C and E on passive avoidance learning and memory in diabetic rats

Learning and memory deficits occur in diabetes mellitus. Although the pathogenesis of cognitive impairment in diabetes has not been fully elucidated, factors such as metabolic impairments, vascular complications and oxidative stress are thought to play possible roles. Here we investigated the effect of chronic treatment with vitamin C (50mg/kg, p.o), vitamin E (100mg/kg, p.o) and both together on passive avoidance learning (PAL) and memory in male Wistar control and diabetic rats. Treatments were begun at the onset of hyperglycemia. Passive avoidance learning was assessed 30 days later. Retention was tested 24h after training. At the end, animals were weighed and blood samples were drawn for plasma glucose measurement. Diabetes caused impairment in acquisition and retrieval processes of PAL and memory. The combination of vitamin C and E improved learning and memory in controls and reversed learning and memory deficits in diabetic rats. Combined treatment also affected the body weight and plasma glucose level of diabetic treated animals compared to untreated diabetic animals. Hypoglycemic effects and antioxidant properties of the vitamins may be involved in the nootropic effect of such treatment. These results show that combined treatment with vitamins C and E improved PAL and memory of control rats. In addition, combined vitamins administration to rats for 30 days from onset of diabetes alleviated the negative influence of diabetes on learning and memory. Therefore, combined vitamins treatment may provide a new potential alternative for prevention of impaired cognitive functions associated with diabetes and may warrant further clinical study.

Cell apoptosis induced by delta-elemene in colorectal adenocarcinoma cells via a mitochondrial-mediated pathway

The chemical compound delta-elemene, isolated from the Chinese herbal medicine plant Curcuma Wenyujin, has been known to exert antitumor activity. In this study we demonstrated that apoptotic cell death induced by delta-elemene in DLD-1 cells was concentration-and time-dependent, and had little inhibition of the normal human liver cell line WRL-68. Apoptosis was further confirmed and quantified by DNA fragmentation ELISA, Annexin V (AnV) binding of externalized phosphatidylserine and the mitochondrial probe JC-1 using flow cytometry. The rapid increase in intracellular reactive oxygen species (ROS) levels was involved in the mechanism of cell death. Western blot analysis demonstrated that delta-elemene activated the caspase-signaling pathway, leading to the proteolysis conversion of pro-caspase-3 to activate caspase-3, and the subsequent cleavage of the caspase substrate PARP. In the process of the induction of apoptotic cell death, Bax translocated into mitochondria, a reduction in Deltapsim was observed and a release of cytochrome c and apoptosis inducing factor (AIF) from mitochondria into the cytosol occurred, indicating that cell death induced by delta-elemene was through a mitochondrial-mediated pathway.

Beta-catenin regulates vitamin C biosynthesis and cell survival in murine liver

Because the Wnt/beta-catenin pathway plays multiple roles in liver pathobiology, it is critical to identify gene targets that mediate such diverse effects. Here we report a novel role of beta-catenin in controlling ascorbic acid biosynthesis in murine liver through regulation of expression of regucalcin or senescence marker protein 30 and L-gulonolactone oxidase. Reverse transcription-PCR, Western blotting, and immunohistochemistry demonstrate decreased regucalcin expression in beta-catenin-null livers and greater expression in beta-catenin overexpressing transgenic livers, HepG2 hepatoma cells (contain constitutively active beta-catenin), regenerating livers, and in hepatocellular cancer tissues that exhibit beta-catenin activation. Interestingly, coprecipitation and immunofluorescence studies also demonstrate an association of beta-catenin and regucalcin. Luciferase reporter and chromatin immunoprecipitation assays verified a functional TCF-4-binding site located between -163 and -157 (CTTTGCA) on the regucalcin promoter to be critical for regulation by beta-catenin. Significantly lower serum ascorbate levels were observed in beta-catenin knock-out mice secondary to decreased expression of regucalcin and also of L-gulonolactone oxidase, the penultimate and last (also rate-limiting) steps in the synthesis of ascorbic acid, respectively. These mice also show enhanced basal hepatocyte apoptosis. To test if ascorbate deficiency secondary to beta-catenin loss and regucalcin decrease was contributing to apoptosis, beta-catenin-null hepatocytes or regucalcin small interfering RNA-transfected HepG2 cells were cultured, which exhibited significant apoptosis that was alleviated by the addition of ascorbic acid. Thus, through regucalcin and L-gulonolactone oxidase expression, beta-catenin regulates vitamin C biosynthesis in murine liver, which in turn may be one of the mechanisms contributing to the role of beta-catenin in cell survival.

ReviewPart of the Series: From Dietary Antioxidants to Regulators in Cellular Signalling and Gene ExpressionReview: When is an antioxidant not an antioxidant? A review of novel actions and reactions of vitamin C

Vitamin C (or ascorbic acid) is regarded as the most important water-soluble antioxidant in human plasma and mammalian cells which have mechanisms to recycle and accumulate it against a concentration gradient, suggesting that the vitamin might also have important intracellular functions. In this review we summarize evidence from human trials that have attempted an association between vitamin C supplementation and an effect on biomarkers of oxidative DNA damage. Most studies reviewed herein showed either a vitamin C-mediated reduction in oxidative DNA damage or a null effect, whereas only a few studies showed an increase in specific base lesions. We also address the possible beneficial effects of vitamin C supplementation for the prevention of cancer and cardiovascular disease. Finally, we discuss the contribution of cell culture studies to our understanding of the mode of action of vitamin C and we review recent evidence that vitamin C is able to modulate gene expression and cellular function, with a particular interest in cell differentiation.

Bcl-2 family proteins as regulators of oxidative stress

The Bcl-2 family of proteins includes pro- and anti-apoptotic factors acting at mitochondrial and microsomal membranes. An impressive body of published studies, using genetic and physical reconstitution experiments in model organisms and cell lines, supports a view of Bcl-2 proteins as the critical arbiters of apoptotic cell death decisions in most circumstances (excepting CD95 death receptor signaling in Type I cells). Evasion of apoptosis is one of the hallmarks of cancer [Hanahan D, Weinberg RA. The hallmarks of cancer. Cell 2000;100:57-70], relevant to tumorigenesis as well as resistance to cytotoxic drugs, and deregulation of Bcl-2 proteins is observed in many cancers [Manion MK, Hockenbery DM. Targeting BCL-2-related proteins in cancer therapy. Cancer Biol Ther. 2003;2:S105-14; Olejniczak ET, Van Sant C, Anderson MG, Wang G, Tahir SK, Sauter G, et al. Integrative genomic analysis of small-cell lung carcinoma reveals correlates of sensitivity to bcl-2 antagonists and uncovers novel chromosomal gains. Mol Cancer Res. 2007;5:331-9]. The rekindled interest in aerobic glycolysis as a cancer trait raises interesting questions as to how metabolic changes in cancer cells are integrated with other essential alterations in cancer, e.g. promotion of angiogenesis and unbridled growth signals. Apoptosis induced by multiple different signals involves loss of mitochondrial homeostasis, in particular, outer mitochondrial membrane integrity, releasing cytochrome c and other proteins from the intermembrane space. This integrative process, controlled by Bcl-2 family proteins, is also influenced by the metabolic state of the cell. In this review, we consider the role of reactive oxygen species, a metabolic by-product, in the mitochondrial pathway of apoptosis, and the relationships between Bcl-2 functions and oxidative stress.

Bcl-2 family proteins as regulators of oxidative stress

The Bcl-2 family of proteins includes pro- and anti-apoptotic factors acting at mitochondrial and microsomal membranes. An impressive body of published studies, using genetic and physical reconstitution experiments in model organisms and cell lines, supports a view of Bcl-2 proteins as the critical arbiters of apoptotic cell death decisions in most circumstances (excepting CD95 death receptor signaling in Type I cells). Evasion of apoptosis is one of the hallmarks of cancer [Hanahan D, Weinberg RA. The hallmarks of cancer. Cell 2000;100:57-70], relevant to tumorigenesis as well as resistance to cytotoxic drugs, and deregulation of Bcl-2 proteins is observed in many cancers [Manion MK, Hockenbery DM. Targeting BCL-2-related proteins in cancer therapy. Cancer Biol Ther. 2003;2:S105-14; Olejniczak ET, Van Sant C, Anderson MG, Wang G, Tahir SK, Sauter G, et al. Integrative genomic analysis of small-cell lung carcinoma reveals correlates of sensitivity to bcl-2 antagonists and uncovers novel chromosomal gains. Mol Cancer Res. 2007;5:331-9]. The rekindled interest in aerobic glycolysis as a cancer trait raises interesting questions as to how metabolic changes in cancer cells are integrated with other essential alterations in cancer, e.g. promotion of angiogenesis and unbridled growth signals. Apoptosis induced by multiple different signals involves loss of mitochondrial homeostasis, in particular, outer mitochondrial membrane integrity, releasing cytochrome c and other proteins from the intermembrane space. This integrative process, controlled by Bcl-2 family proteins, is also influenced by the metabolic state of the cell. In this review, we consider the role of reactive oxygen species, a metabolic by-product, in the mitochondrial pathway of apoptosis, and the relationships between Bcl-2 functions and oxidative stress.

Vitamin E succinate induces ceramide-mediated apoptosis in head and neck squamous cell carcinoma in vitro and in vivo

PURPOSE

Vitamin E succinate (alpha-TOS) inhibits the growth of cancer cells without unacceptable side effects. Therefore, the mechanisms associated with the anticancer action of alpha-TOS, including ceramide-mediated apoptosis, were investigated using head and neck squamous cell carcinoma (HNSCC) in vitro and in vivo.

EXPERIMENTAL DESIGN

Five different human HNSCC cell lines (JHU-011, JHU-013, JHU-019, JHU-022, and JHU-029) were treated with alpha-TOS, and its effects on cell proliferation, cell cycle progression, ceramide-mediated apoptosis, and ceramide metabolism were evaluated. The anticancer effect of alpha-TOS was also examined on JHU-022 solid tumor xenograft growth in immunodeficient mice.

RESULTS

Alpha-TOS inhibited the growth of all the HNSCC cell lines in vitro in a dose- and time-dependent manner. Thus, JHU-013 and JHU-022 cell lines were more sensitive to alpha-TOS than the other cell lines. Cellular levels of ceramide, sphingomyelinase activity, caspase-3, and p53 were elevated with increasing time of exposure to alpha-TOS. The degradation of poly(ADP-ribose) polymerase protein in JHU-022 cells treated with alpha-TOS provided evidence for apoptosis. The amounts of nuclear factor kappaB, Bcl-2, and Bcl-X(L) proteins were reduced in the cells treated with alpha-TOS for 6 hours. The levels of caspase-9, murine double minute-2, and IkappaB-alpha proteins were unchanged after alpha-TOS treatment. I.p. administration of alpha-TOS slowed tumor growth in immunodeficient mice.

CONCLUSIONS

Alpha-TOS showed promising anticancer effects to inhibit HNSCC growth and viability in vivo and in vitro. The induction of enzymes involved in ceramide metabolism by alpha-TOS suggests that ceramide-mediated apoptosis may expand therapeutic strategies in the treatment of carcinoma.

Topical isoflavones provide effective photoprotection to skin

BACKGROUND/PURPOSE

Isoflavones, one main group of phytoestrogens, have antioxidative and photoprotective effects in cellular and mouse studies. The aim of this study is to obtain a more comprehensive understanding of the isoflavone-mediated photoprotection with the pig skin model, a more human-resembling model.

METHODS

The pig skin was treated with five well-known isoflavone compounds (genistein, equol, daidzein, biochanin A, and formononetin) and one antioxidant combination solution of 15% vitamin C and 1% vitamin E and 0.5% ferulic acid (CEF) daily for 4 days. Skin was irradiated with solar-simulated UV irradiation, 1 to 5 minimal erythema dose (MED) at 1-MED intervals. Evaluation was carried out 24 h later by colorimeter-measured erythema and sunburn cell numbers.

RESULTS

Topical application of 0.5% solutions of three individual phytoestrogens - genistein, daidzein, biochanin A - are better than similar solutions of equol or formononetin in protecting pig skin from solar-simulated ultraviolet (SSUV)-induced photodamage, as measured by sunburn cell formation and/or erythema. However, the protection was less than that provided by a topical combination antioxidant standard containing 15% L-ascorbic acid, 1%alpha-tocopherol, and 0.5% ferulic acid.

CONCLUSION

Isoflavones provide effective photoprotection and are good candidate ingredients for protection against ultraviolet (UV) photodamage.

Low serum alpha-tocopherol and selenium are associated with accelerated apoptosis in severe sepsis

During sepsis, a severe systemic disorder, micronutrients often are decreased. Apoptosis is regarded as an important mechanism in the development of often significant immunosuppression in the course of the disease. This study aimed to investigate alpha-tocopherol and selenium in reference to apoptosis in patients with sepsis. 16 patients were enrolled as soon as they fulfilled the criteria of severe sepsis. 10 intensive care patients without sepsis and 11 healthy volunteers served as controls. alpha-Tocopherol, selenium and nucleosomes were measured in serum. Phosphatidylserine externalization and Bcl-2 expression were analyzed in T-cells by flow cytometry. Serum alpha-tocopherol and selenium were decreased in severe sepsis but not in non-septic critically ill patients (p < 0.05). Conversely, markers of apoptosis were increased in sepsis but not in critically ill control patients: Nucleosomes were found to be elevated 3 fold in serum (p < 0.05) and phosphatidylserine was externalized on an expanded subpopulation of T-cells (p < 0.05) while Bcl-2 was expressed at lower levels (p < 0.05). The decrease of micronutrients correlated with markers of accelerated apoptosis. Accelerated apoptosis in sepsis is associated with low alpha-tocopherol and selenium. The results support the investigation of micronutrient supplementation strategies in severe sepsis.

In vitro models of acute and long-term continuous infection of human respiratory epithelial cells with Chlamydophila pneumoniae have opposing effects on host cell apoptosis

Persistent infection with the obligate intracellular pathogen Chlamydophila pneumoniae has been implicated in the pathogenesis of many chronic diseases, but its mechanism remains unclear. Many pathogens have been found to modulate cellular apoptosis in order to survive and multiply. Chlamydial species were shown to both induce and inhibit host cell apoptosis depending on the experimental conditions. We utilized in vitro models of acute and long-term continuous (LTC) infection with the same cell line (HEp-2) and chlamydial isolate (TW-183) used in both models. Host cell apoptosis in infected and uninfected cells was assessed by fluorescence microscopy and flow cytometry. While acute infection induced apoptosis 72 h post-infection, LTC-infected cells had low rates of apoptosis and showed resistance to different exogenous inducers of apoptosis (sorbitol, serum withdrawal, hydrogen peroxide) when compared to uninfected cells. Chronicity of infection appears to be a critical factor in the modulation of host cell apoptosis by C. pneumoniae. Induction of apoptosis may help to propagate the infection, while inhibition of apoptosis could help protect the organism in chronic infection.

The importance of plasma membrane coenzyme Q in aging and stress responses

The plasma membrane of eukaryotic cells is the limit to interact with the environment. This position implies receiving stress signals that affects its components such as phospholipids. Inserted inside these components is coenzyme Q that is a redox compound acting as antioxidant. Coenzyme Q is reduced by diverse dehydrogenase enzymes mainly NADH-cytochrome b(5) reductase and NAD(P)H:quinone reductase 1. Reduced coenzyme Q can prevent lipid peroxidation chain reaction by itself or by reducing other antioxidants such as alpha-tocopherol and ascorbate. The group formed by antioxidants and the enzymes able to reduce coenzyme Q constitutes a plasma membrane redox system that is regulated by conditions that induce oxidative stress. Growth factor removal, ethidium bromide-induced rho degrees cells, and vitamin E deficiency are some of the conditions where both coenzyme Q and its reductases are increased in the plasma membrane. This antioxidant system in the plasma membrane has been observed to participate in the healthy aging induced by calorie restriction. Furthermore, coenzyme Q regulates the release of ceramide from sphingomyelin, which is concentrated in the plasma membrane. This results from the non-competitive inhibition of the neutral sphingomyelinase by coenzyme Q particularly by its reduced form. Coenzyme Q in the plasma membrane is then the center of a complex antioxidant system preventing the accumulation of oxidative damage and regulating the externally initiated ceramide signaling pathway.

Attenuated Leishmanial sphingolipid induces apoptosis in A375 human melanoma cell via both caspase-dependent and -independent pathways

A fraction of attenuated Leishmanial lipid (ALL) rich in sphingolipids, previously shown to have apoptosis inducing activity in mouse melanoma (B16F10) and human melanoma (A375) cells, was resolved to isolate the bioactive sphingolipid. The mechanism of apoptosis induction by this bioactive attenuated Leishmanial sphingolipid (ALSL) was studied in A375 cells. Apoptosis induced by ALSL in A375 cells was found to be dose and time-dependent. Exposure of cells to ALSL resulted in a rapid increase in reactive oxygen species generation. Pretreatment of cells with the antioxidant N-acetyl-cystein reduced ROS generation and attenuated apoptosis induced by ALSL. Again, ALSL sensitization resulted in the activation of caspase-3 and -9 but not caspase-8. However, inhibitors of these caspases could not protect the cells completely from ALSL-induced apoptosis. N-acetyl-cystein pretreatment was again found to attenuate the activation of caspase-3 and -9. ALSL treatment also resulted in the alteration of mitochondrial membrane potential, and release of pro-apoptotic factors such as cytochrome c and apoptosis inducing factor (AIF) from mitochondria. Furthermore, c-Jun N-terminal kinase was activated that resulted in apoptosis of A375 cells, whereas p38 MAPK was activated to counteract the stress generated in cells in response to ALSL treatment. Taken together, our results indicate that ALSL-induced apoptosis of A375 cells is mediated by both mitochondrial caspase-dependent and -independent pathways and it involves ROS and JNK activation in the mitogen-activated protein kinase cascade.

Development of standardized cell culture conditions for tumor cells with potential clinical application

BACKGROUND

Tumor cell lines have enormous value for the study of different aspects of cancer biology and have also recently gained great importance in autologous cell-based anti-tumor therapies. However, the use of these cells is still limited because in vitro growth is hampered by suboptimal culture conditions and current media contain fetal bovine serum (FBS), which poses serious safety concerns regarding clinical application.

METHODS

To address this drawback, we aimed to develop a strategy for optimization of the culture medium for human medullary thyroid carcinoma (MTC) cell lines as a model system. We combined the general cell screening system (GCSS), which continuously measured the growth behavior of cells in a 96-well plate format, with statistically based experimental designs.

RESULTS

The results obtained clearly demonstrated that, just by changing the composition of the basal medium, a significantly enhanced growth rate could be observed, and by subsequent addition of several substances a serum-free cell culture medium could be developed. This medium allowed the propagation of two MTC cell lines comparable with conventionally used serum-supplemented medium.

DISCUSSION

We present a fast and easy way to screen for substances that are essential for tumor cell growth in vitro. Furthermore, these tumor cells can be adapted to culture conditions that allow the use of the cells in safe cell-based therapies. This is of utmost importance because of increasing regulatory requirements.

Glaucomatous outflow pathway and oxidative stress

Oxidative free radicals and reactive oxygen species (ROS) are able to affect the cellularity of the human trabecular meshwork (HTM). These findings suggest that intraocular pressure increase, which characterises most glaucomas, is related to oxidative degenerative processes affecting the HTM and specifically its endothelial cells. Much evidence indicates that in this region ROS play a fundamental pathogenic role by reducing local antioxidant activities, inducing outflow resistance and exacerbating the activities of superoxide dismutase and glutathione peroxidase in glaucomatous eyes. Furthermore, hydrogen peroxide induces rearrangement of HTM cells and compromises their integrity. Glaucomatous subjects might have a genetic predisposition rendering them more susceptible to ROS-induced damage. A fairly significant correlation between oxidative DNA damage in the HTM and intraocular pressure increase and visual field defects in glaucomatous patients has been demonstrated. Thus, oxidative stress may play a significant role during glaucoma course initially damaging HTM cells, then contributing to the alteration of the homeostasis between NO and endothelins, and finally through its possible involvement in ganglional cell death. On the whole, these findings support the hypothesis that oxidative damage is an important step in the pathogenesis of primary open-angle glaucoma, and might be a relevant target for both prevention and therapy.

Pro-oxidative vs antioxidative properties of ascorbic acid in chromium(VI)-induced damage: an in vivo and in vitro approach

The effect of antioxidant ascorbic acid (vitamin C) pretreatment on chromium(VI)-induced damage was investigated using the yeast Saccharomyces cerevisiae as a model organism. The objective of this study was to pretreat yeast cells with the antioxidant ascorbic acid in an effort to increase cell tolerance against reactive chromium intermediates and reactive oxygen species formed during chromium(VI) reduction. Intracellular oxidation was estimated using the fluorescence indicators dihidro-2,7-dichlorofluorescein, dihydroethidium and dihydrorhodamine 123. The role of ascorbic acid pretreatment on chromium(VI) toxicity was determined by measuring mitotic gene conversion, reverse mutations, 8-OHdG, hydroxyl radical, superoxide anion and chromium(V) formation. The chromium content in the biomass was determined by flame atomic absorption spectrometry. In the absence of chromium, ascorbic acid effectively protected the cells against endogenous reactive oxygen species formed during normal cellular metabolism. In vitro measurements employing EPR and the results of supercoiled DNA cleavage revealed that the pro-oxidative action of ascorbic acid during Cr(VI) reduction was concentration-dependent and that harmful hydroxyl radical and Cr(V) had formed following Cr(VI) reduction. However, the in vivo results highlighted the important role of increased cytosol reduction capacity related to modification of Cr(V) formation, increased chromium accumulation, better scavenging ability of superoxide anions and hydrogen peroxide, and consequently decreased cytotoxicity and genotoxicity in ascorbic acid pretreated cells. Ascorbic acid influenced Cr(VI) toxicity both as a reducing agent, by decreasing Cr(V) persistence, and as an antioxidant, by decreasing intracellular superoxide anion and hydrogen peroxide formation and by quenching free radicals formed during Cr(VI) to Cr(III) reduction. Increased 8-OHdG and decreased reduced glutathione in ascorbic acid-treated cells might induce an endogenous antioxidant defense system and thus increase cell tolerance against subsequent Cr-induced stress.

Comparative study on in vitro effects of homocysteine thiolactone and homocysteine on HUVEC cells: evidence for a stronger proapoptotic and proinflammative homocysteine thiolactone

Hyperhomocysteinemia is an independent risk factor for the development of atherosclerosis. However the underlying mechanisms responsible for endothelial cell injury with increased plasma concentration of homocysteine or homocysteine derivatives remains still incompletely elucidated. In this study, we investigated the ability of homocysteine (Hcy) and homocysteine thiolactone (HcyT) to induce cell death and IL-8 secretion in primary human umbilical vein endothelial cells (HUVEC). Hcy and HcyT were both cytotoxic and capable of promoting cell death, as measured by caspase-3 activation and DNA fragmentation. ELISA assays clearly demonstrated that Hcy and HcyT strongly activated IL-8 release. Furthermore, our results showed that HcyT was much more efficient than Hcy in activating caspase-3 or in inducing IL-8 secretion. The use of antioxidants such as vitamin C and vitamin E strongly but not completely reduced programmed cell death and chemokine release suggesting that other pathways different than reactive oxygen species are also involved. This study suggests that Homocysteine derivatives like HcyT might possess stronger cytotoxicity and pro-inflammatory properties and that Hcy derivatives levels should therefore be more taken into account during diagnostics.

Regulation by the cAMP cascade of oxygen free radical balance in mammalian cells

A study is presented of the effect of the cAMP cascade on oxygen metabolism in mammalian cell cultures. Serum-starvation of the cell cultures resulted in depression of the forward NADH-ubiquinone oxidoreductase activity of complex I, decreased content of glutathione, and enhancement of the cellular level of H2O2. Depressed transcription of cytosolic Cu/Zn-SOD 1, mitochondrial glutathione peroxidase and catalase was also observed. Activation of the cAMP cascade reversed the depression of the activity of complex I and the accumulation of H2O2. The effect of cAMP involved the cAMP-dependent protein kinase.

Vitamins E and C pretreatment prevents ovariectomy-induced memory deficits in water maze

We investigated whether the pretreatment with vitamins E (alpha-tocopherol) and C (ascorbic acid) would act on ovariectomy-induced memory deficits in Morris water maze tasks. Adult female Wistar rats were divided into three groups: (1) naive (control), (2) sham (submitted to surgery without removal of ovaries) and (3) ovariectomized. Thirty days after surgery, they were trained in the Morris water maze in order to verify ovariectomy effects both on reference and working memory tasks. Results show that ovariectomized rats presented impairment in spatial navigation in the acquisition phase, as well as in the time spent in target quadrant and in the latency to cross over the location of the platform in test session, when compared to naive and sham groups (controls), in the reference memory task. Ovariectomy did not affect performance in the working memory task. Confirming our hypothesis, ovariectomized rats pretreated for 30 days with vitamins E and C had those impairments prevented. We conclude that ovariectomy significantly impairs spatial reference learning/memory and that pretreatment with vitamins E and C prevents such effect. Assuming this experimental memory impairment might mimic, at least in part, the cognitive deficit sometimes present in the human condition of lack of reproductive hormones, our findings lend support to a novel therapeutic strategy, based on vitamins E and C, to cognitive impairments in post-menopausal women.

Cell death induced by ent-11α-hydroxy-15-oxo-kaur-16-en-19-oic-acid in anaplastic thyroid carcinoma cells is via a mitochondrial-mediated pathway

The chemical compound ent-11alpha-hydroxy-15-oxo-kaur-16-en-19-oic-acid (5F), isolated from the Chinese herbal medicine plant Pteris semipinnata L, has been known to exert antitumor activity. However, the molecular mechanism of the action is not understood. In this study we demonstrated that apoptotic cell death induced by 5F in FRO cells was concentration- and time-dependent. The rapid increase in intracellular reactive oxygen species (ROS) levels was involved in the mechanism of cell death. c-Jun N-terminal kinase (JNK) activation and G2 block were related to cell death induced by 5F. Extracellular signal-related kinase (ERK) and p38 were also activated, but as survival signals in response to 5F treatment to counteract the induction of cell death. In the process of the induction of apoptotic cell death, Bax translocated into mitochondria, a reduction in Delta psi(m) was observed and a release of cytochrome c and apoptosis inducing factor (AIF) from mitochondria into the cytosol occurred, indicating that cell death induced by 5F was through a mitochondrial-mediated pathway.

Ascorbic acid and alpha-tocopherol as potent modulators of apoptosis on arsenic induced toxicity in rats

Apoptosis or programmed cell death (PCD) is a genetically regulated cellular, physiological and biochemical suicidal mechanism that plays a crucial role in the development and defense of homeostasis, in which the cell participates in its own demise via a cascade of molecular interactions. PCD can be modulated by various stimuli including infectious agents or drugs. Arsenic is one among inducible toxic agent that triggers apoptosis via free radical generation. Since the generation of free radicals during the metabolism of arsenic is thought to be involved in arsenic toxicosis, understanding the deleterious effects caused by the ROS that attack the vital molecules like DNA has become important. The present work was conducted to evaluate the regulatory effect exerted by Vitamin C and Vitamin E upon the apoptotic process, which can be assessed by the presence of cells with apoptosis associated DNA breaks and characterize the role of TNF-alpha and caspase-3 in rats intoxicated with arsenic. Male albino rats of wistar strain (120-150 g) were used in this study and are further divided into seven groups. We observed that ascorbate and alpha-tocopherol selectively altered the extent of DNA damage by reducing TNF-alpha level and inhibiting the activation of caspase cascade, from these observations it is strongly believed that the present vitamins supplementation perspective, though observed in animal model, will have sustainable curative value among the already afflicted populations, neutralizing impact on freshly emerging arsenicosis scenario and possible proactive protection to those potentially susceptible to arsenicals exposure.

Functional dichotomy: glutathione and vitamin E in homeostasis relevant to primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is a complex chronic neurological disease that can result in blindness. The goal of understanding the aetiology of POAG is to be able to target effective treatment to individuals who will eventually go blind without it. Epidemiological studies of POAG have not specifically addressed the possibility that nutrition may play a role in the development of POAG. A handful of papers have considered that nutrition may have an impact on POAG patients. POAG is not believed to be a 'vitamin-deficiency disease'. The concept of 'vitamin-deficiency diseases' and the recommended daily allowances have not kept pace with the growing understanding of the cellular and molecular functions of vitamins and other micronutrients. The aetiology of POAG remains a mystery. Discoveries in cell physiology can be assimilated from the literature and applied to known homeostatic mechanisms of the eye. In this way the possible roles of nutritional components involved in the aetiology of POAG can be described. The mechanisms may be subject to many influences in ways that have yet to be defined. Two distinct changes in the trabecular meshwork can be identified: trabecular meshwork changes that cause intra-ocular pressure to increase and trabecular meshwork changes that are directly correlated to optic nerve atrophy. Compelling evidence suggests that collagen trabecular meshwork extracellular matrix (ECM) remodelling is correlated to increased intraocular pressure in POAG. Elastin trabecular meshwork ECM remodelling is correlated to POAG optic nerve atrophy. There appear to be two different pathways of ECM remodelling and apoptosis induction in POAG. The pathway for collagen remodelling and apoptosis induction seems to be exogenously influenced by water-soluble antioxidants, for example, glutathione. The pathway for elastin remodelling and apoptosis induction seems to be influenced by endogenous lipid-soluble antioxidants, for example, vitamin E. Roles can be defined for antioxidants in the two different pathways of ECM remodelling and apoptosis induction. This suggests that antioxidants are important in maintaining cellular homeostasis relevant to the aetiology of POAG.

Cellular Events Involved in Butyric Acid-Induced T Cell Apoptosis

We have previously demonstrated that butyric acid induces cytotoxicity and apoptosis of murine thymocytes, splenic T cells, and human Jurkat T cells. Therefore, to determine the apoptotic signaling pathway induced by butyric acid, we investigated the contribution of reactive oxygen species (ROS), mitochondria, ceramide, and mitogen-activated protein kinases in butyric acid-induced human Jurkat cell apoptosis. After exposure of cells to butyric acid, a pronounced accumulation of ROS was seen. Pretreatment of cells with the antioxidant N-acetyl-cysteine or 3-aminobenzamide attenuated butyric acid-induced apoptosis through a reduction of ROS generation. Cytochrome c, apoptosis-inducing factor, and second mitochondria-derived activator of caspases protein release from mitochondria into the cytosol were detected shortly after butyric acid treatment. Exposure of cells to butyric acid resulted in an increase in cellular ceramide in a time-dependent fashion. In addition, butyric acid-induced apoptosis was inhibited by DL-threo-dihidrosphingosine, a potent inhibitor of sphingosine kinase. Using anti-extracellular signal-regulated kinase (ERK), anti-c-Jun N-terminal kinase (JNK), and anti-p38 phosphospecific Abs, we showed a decrease in ERK, but not in JNK and p38 phosphorylation after treatment of cells with butyric acid. Pretreatment of cells with the JNK inhibitor SP600125 attenuated the effect of butyric acid on apoptosis, whereas no effect was seen with the p38 inhibitor SB202190 or the ERK inhibitor PD98059. Taken together, our results indicate that butyric acid-induced T cell apoptosis is mediated by ceramide production, ROS synthesis in mitochondria, and JNK activation in the mitogen-activated protein kinase cascade. Finally, these results were further substantiated by the expression profile of butyric acid-treated Jurkat cells obtained by means of cDNA array.

Antioxidant response induced by serum withdrawal protects HL-60 cells against inhibition of NAD(P)H:quinone oxidoreductase 1

We have previously shown that inhibition of NAD(P)H:quinone acceptor oxidoreductase 1 with dicoumarol decreases growth and viability of HL-60 cells in the absence of serum. Here we demonstrate that culturing HL-60 cells in serum-free medium in the presence of dicoumarol results in a significant potentiation of apoptosis. However, when cells were preincubated for 24 h without serum before they were treated with dicoumarol, the effect of the inhibitor on cell growth and death was much lower. We have investigated cellular changes induced in HL-60 cells by removal of serum that could account for protection against the effects of dicoumarol. Serum removal induced significant increases of NAD(P)H:quinone acceptor oxidoreductase 1, particularly at 32 h after serum withdrawal. Total amounts of ubiquinone in cells were unchanged but, its reduction state paralleled the observed increase in quinone reductase activity. Levels of the antiapoptotic protein Bcl-2 were also significantly increased after serum removal. Our results indicate that removal of serum evokes an antioxidant protective response that make HL-60 cells less sensitive to cell death induced by inhibition of NAD(P)H:quinone acceptor oxidoreductase 1 with dicoumarol.

N-Acetylcysteine, vitamin C and vitamin E diminish homocysteine thiolactone-induced apoptosis in human promyeloid HL-60 cells

We showed previously that homocysteine thiolactone (HcyT) is a potent inducer of apoptosis in HL-60 cells. In the present study, the role of some radical scavengers (N-acetylcysteine, vitamin C, vitamin E and folate) on the reduction of HcyT-induced apoptosis was investigated. Preincubation of HcyT-treated HL-60 cells with vitamin C (Vit C; 100 micro mol/L) or vitamin E (Vit E; 100 micro mol/L) for 2 h significantly reduced the proportion of apoptotic cells with hypodiploid DNA contents or with membrane phosphatidylserine exposure, and attenuated the apoptotic DNA fragmentation. Preincubation of cells with N-acetylcysteine (NAC; 5 mmol/L) for 2 h significantly reduced HcyT-promoted apoptosis measured by membrane phosphatidylserine exposure only. The reduction of HcyT-induced apoptosis by NAC, Vit C or Vit E occurred simultaneously with a significant decrease in intracellular H(2)O(2) levels and reduced caspase-3 enzymatic activity. In contrast, folate had no H(2)O(2) scavenging capacity and did not suppress caspase-3 activity 6 h after HcyT treatment, although folate exhibited antioxidant behavior toward superoxide anions, hydroxyl radicals and peroxynitrite. Preincubation of cells with folate (10 micro mol/L) for 3 d did not affect the extent of HcyT-promoted apoptotic damage. Taken together, our findings suggest that antioxidant pretreatment with NAC, Vit C or Vit E exerts more beneficial effects than folate on reducing apoptotic cell damage induced by homocysteine thiolactone.

Phosphatidylserine peroxidation/externalization during staurosporine-induced apoptosis in HL-60 cells

Although oxidative stress is commonly associated with apoptosis, its specific role in the execution of the apoptotic program has yet to be described. We hypothesized that catalytic redox interactions between negatively charged phosphatidylserine (PS) and positively charged cytochrome c released into the cytosol, along with the production of reactive oxygen species (ROS), results in pronounced oxidation and externalization of PS, and subsequent recognition of apoptotic cells by macrophages. By using staurosporine, a protein kinase inhibitor that does not act as a prooxidant, we were able to induce apoptosis in HL-60 cells without triggering the confounding effects of non-specific oxidation reactions. Through this approach, we demonstrated for the first time that PS underwent a statistically significant and pronounced oxidation at an early stage (2 h) of non-oxidant-induced apoptosis while the most abundant phospholipid, phosphatidylcholine, did not. Glutathione (GSH), the most abundant cytosolic thiol, also remained unoxidized at this time point. Furthermore, PS oxidation and the appearance of cytochrome c in the cytosol were concurrent; PS externalization was followed by phagocytosis of apoptotic cells. These findings are compatible with our proposed roles for oxidative PS-dependent signaling during apoptosis and phagocytosis.

Chlamydia trachomatis-induced apoptosis occurs in uninfected McCoy cells late in the developmental cycle and is regulated by the intracellular redox state

Infections with the obligate intracellular bacterium Chlamydia trachomatis are characterized by avoidance of fusion between chlamydia-containing endosomes and lysosomes, bacterial persistence and development of post-infectious sequelae. In this report we show that C. trachomatis induces apoptosis in McCoy and HeLa cells. Apoptosis was monitored by three different techniques; enzyme-linked immunoassay (EIA) of fragmented nucleosomes, terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) and flow cytometry of propidium iodide-stained cells. Apoptosis occurred in uninfected cells, was induced late in the chlamydial developmental cycle, beyond 24 h post-infection and was dependent on bacterial protein synthesis. Apoptosis was not significantly increased in infected, inclusion-containing cells. Treatment of cells with the antioxidants ascorbic acid (10 microM) and alpha-tocopherol (10 microM) reduced the degree of apoptosis. These results suggest that host cells infected with C. trachomatis generate proapoptotic stimuli that induce apoptosis in uninfected, neighbouring cells and that the redox state of the cell is a regulator in chlamydia-induced apoptosis.

Vitamin E and genome stability

Free radicals and reactive oxygen species (ROS) which are generated continuously cause mutagenic alterations resulting in cancer, aging and abnormalities in the nervous system. Accumulating evidence indicates that Vitamin E, the most potent lipid peroxyl radical scavenger, may reduce free radical induced chromosomal damages through inhibition of free radical formation, and activation of endonuclease that can be triggered by intracellular oxidative stress, and by increasing the rate of removal of damaged DNA. Although some studies suggest a potential usefulness of Vitamin E in the prevention of mutagenic effects caused by genotoxic free radicals, other studies report no effects. Thus the data are not conclusive enough to be used as a basis to change the current recommended dietary allowances (RDA). Future research should address molecular mechanisms underlying the protective effects of Vitamin E and develop appropriate biologically relevant biomarkers of DNA damage to further help in determining the dietary levels of Vitamin E needed to protect the genetic pool from internally and externally induced DNA damages.

Neutral magnesium-dependent sphingomyelinase from liver plasma membrane: purification and inhibition by ubiquinol

Plasma membranes isolated from pig liver contained almost no acid sphingomyelinase but significant neutral magnesium-dependent sphingomyelinase that was activated by phosphatidylserine. We report here the purification to apparent homogeneity of neutral sphingomyelinase of about 87 kDa from liver plasma membranes. The purified enzyme strictly required magnesium and had a neutral optimal pH. In contrast with neutral sphingomyelinase purified from other sources (such as brain), the enzyme purified from from liver plasma membrane was not inhibited by GSH and, strikingly, it was not activated by phosphatidylserine. Liver sphingomyelinase was inhibited by several lipophilic antioxidants in a dose-dependent way. Ubiquinol-10 was more effective than alpha-tocopherol, alpha-tocopherylquinone, alpha-tocopherylquinone, and ubiquinone-10, and inhibition was noncompetitive. Differential inhibition of neutral sphingomyelinase by antioxidants did not correlate with different levels of protection against lipid peroxidation. The purified sphingomyelinase was not inhibited significantly by ubiquinone-10 and ubiquinol- 10, but ubiquinol-0 and ubiquinone-0 inhibited by 30 and 60% respectively. Our results demonstrate a direct inhibitory effect of ubiquinol on the plasma membrane n-SMase and support the participation of this molecule in the regulation of ceramide-mediated signaling.

Dual role of plasma membrane electron transport systems in defense

Because oxidative stress is one of the main sources of severe cellular damage, cells have different defense weapons against reactive oxygen species. Ubiquitous plasma membrane redox systems play a role in defense against oxidative stress damage. On the other hand, a tightly controlled and localized production of reactive oxygen species by a plasma membrane NADPH oxidase can be used as a potent microbicidal weapon. This dual, prooxidant and antioxidant role of plasma membrane electron transport systems in defense is studied and discussed.

The in vitro cytotoxicity of ascorbate depends on the culture medium used to perform the assay and involves hydrogen peroxide

Reports about the effects of ascorbate (vitamin C) on cultured cells are confusing and conflicting. Some authors show inhibition of cell death by ascorbate, whereas others demonstrate that ascorbate is cytotoxic. In this report, using three different cell types and two different culture media (Dulbecco's modified Eagle's medium and RPMI 1640), we show that the toxicity of ascorbate is due to ascorbate-mediated production of H2O2, to an extent that varies with the medium used to culture the cells. For example, 1 mM ascorbate generates 161 +/- 39 microM H2O2 in Dulbecco's modified Eagle's medium and induces apoptosis in 50% of HL60 cells, whereas in RPMI 1640 only 83 +/- 17 microM H2O2 is produced and no apoptosis is detected. Apoptosis is prevented by catalase, and direct addition of H2O2 at the above concentration to the cells has similar effects to ascorbate. These results show that ascorbate itself is not toxic to the cell lines used and that effects of ascorbate in vivo cannot be predicted from studies on cultured cells. The ability of ascorbate to interact with different cell culture media to produce H2O2 at different rates could account for many or all of the conflicting results obtained using ascorbate in cultured cell assays.

Carboxyfullerenes protect human keratinocytes from ultraviolet-B-induced apoptosis

Carboxyfullerene, a water-soluble carboxylic acid derivative of a fullerene, which acts as a free-radical scavenger, was investigated as a protective agent against ultraviolet-light-induced damage in human keratinocytes. First, we demonstrate that carboxyfullerene is not cytotoxic for these cells. In addition, this compound significantly reduces the ultraviolet-B-induced inhibition of keratinocyte proliferation and protects keratinocytes from apoptosis caused by ultraviolet B irradiation in a time- and dose-dependent fashion. Furthermore, the percentage of cells with depolarized mitochondria is significantly lower in ultraviolet-B-irradiated keratinocytes pretreated with carboxyfullerene than in cells provided with diluent alone. Carboxyfullerene also protects human keratinocytes from apoptosis induced by exposure to deoxy-D-ribose, a sugar that causes cell death through a pathway involving oxidative stress. On the other hand, ultraviolet B downregulates bcl-2 levels in human keratinocytes, and carboxyfullerene fails to prevent this effect. These results suggest that carboxy- fullerene protects human keratinocytes from ultraviolet B damage possibly via a mechanism interfering with the generation of reactive oxygen species from depolarized mitochondria without the involvement of bcl-2.

Mitochondrial cytochrome c release and caspase-3-like protease activation during indomethacin-induced apoptosis in rat gastric mucosal cells

Indomethacin (IND), a nonsteroidal anti-inflammatory drug, has been known to cause gastric mucosal injury as a side effect. Using a rat gastric mucosal cell line, RGM1, we determined whether apoptosis is involved in IND-mediated gastropathy, and whether caspase activation and mitochondrial cytochrome c release play an important role in producing apoptosis of IND-treated RGM1 cells in the presence of serum. IND caused caspase-3-like protease activation followed by apoptosis in a dose- and time-dependent manner. Caspase-1-like protease activity did not change during IND-induced apoptosis. IND also increased mitochondrial cytochrome c release in a time-dependent fashion. Mitochondrial cytochrome c efflux occurred just before or at the same time as caspase-3-like protease activation, and preceded the increase in apoptotic cell numbers. Z-VAD-FMK, a caspase inhibitor, inhibited both the increase in caspase-3-like protease activity and apoptosis in IND-treated RGM1 cells but did not affect caspase-1-like protease activity or mitochondrial cytochrome c release. These observations suggest that the apoptosis of gastric mucosal cells could be involved in IND-induced gastropathy, that cytochrome c is released from mitochondria into the cytosol during the early phase of IND-mediated apoptosis, and that subsequent activation of caspase-3-like protease, but not caspase-1-like protease, is required for the execution of apoptosis.

Conditions that affect acquisition of developmental competence by mouse oocytes in vitro: FSH, insulin, glucose and ascorbic acid

The simplest unit required for the support of oocyte growth and development is the oocyte-granulosa cell complex. Therefore, a culture system was established that utilizes these complexes to assess mechanisms promoting nuclear, cytoplasmic and genomic maturation in mammalian oocytes. Deletion of serum from the culture, results in increased apoptosis in oocyte-associated granulosa cells (OAGCs), however, addition of ascorbic acid (0.5 mM) significantly reduced the level of apoptosis in the OAGCs, although no improvement of oocyte developmental competence was detected. The effects of reducing glucose during oocyte growth were studied since, under some culture conditions, glucose has deleterious effects on early preimplantation development. Reducing the glucose concentration to 1 mM resulted in the production of oocytes with greatly reduced developmental competence. Deleterious effects of FSH plus insulin during oocyte growth in vitro on preimplantation development are reviewed and discussed in terms of the communication of oocytes with inappropriately developing granulosa cells. Evidence that oocytes promote the appropriate differentiation of OAGCs in intact follicles in vivo is also discussed. It is hypothesized that oocytes control the differentiation of these cells, in order to promote intercellular signaling essential for the acquisition of competence to undergo normal embryogenesis.

Docosahexaenoic acid and vitamin E can reduce human monocytic U937 cell apoptosis induced by tumor necrosis factor

The effects of polyunsaturated fatty acids and vitamin E on tumor necrosis factor (TNF)-induced apoptosis of human monocytic U937 cells was explored to assess to what extent these nutrients could attenuate apoptosis. Preincubation of U937 cells with arachidonic acid for 24 h did not affect TNF-induced apoptosis. Eicosapentaenoic acid slightly but significantly reduced the proportion of apoptotic cells only when apoptosis was induced by TNF without cycloheximide (CHI). In contrast, preincubation with docosahexaenoic acid (DHA) greatly (40 approximately 70%) attenuated apoptosis induced by stimulation with either TNF or TNF + CHI for 3 h. The inhibition of apoptosis was accompanied by enrichment of DHA in membrane phospholipids, indicating that DHA probably exerted its inhibitory activity after being incorporated into the phospholipids. Vitamin E also played a role as a partial inhibitor of apoptosis 3 h after TNF addition. This vitamin could further reduce the apoptosis of DHA-treated cells, and such an additive effect was obvious when apoptosis was induced at a low frequency. Longer-range stimulation of U937 cells with TNF showed that inhibition of apoptosis by preincubating cells with either DHA or vitamin E was not significant 9 h after TNF addition, but that preincubation with both DHA and vitamin E could reduce the proportion of apoptotic cells even at this time point. Our findings suggested that ingestion of nutrients such as DHA and vitamin E might exert beneficial effects on organ dysfunction associated with various TNF-related diseases.

Coenzyme Q protects cells against serum withdrawal-induced apoptosis by inhibition of ceramide release and caspase-3 activation

Coenzyme Q10 (CoQ10) is a component of the antioxidant machinery that protects cell membranes from oxidative damage and decreases apoptosis in leukemic cells cultured in serum-depleted media. Serum deprivation induced apoptosis in CEM-C7H2 (CEM) and to a lesser extent in CEM-9F3, a subline overexpressing Bcl-2. Addition of CoQ10 to serum-free media decreased apoptosis in both cell lines. Serum withdrawal induced an early increase of neutral-sphingomyelinase activity, release of ceramide, and activation of caspase-3 in both cell lines, but this effect was more pronounced in CEM cells. CoQ10 prevented activation of this cascade of events. Lipids extracted from serum-depleted cultures activated caspase-3 independently of the presence of mitochondria in cell-free in vitro assays. Activation of caspase-3 by lipid extracts or ceramide was prevented by okadaic acid, indicating the implication of a phosphatase in this process. Our results support the hypothesis that plasma membrane CoQ10 regulate the initiation phase of serum withdrawal-induced apoptosis by preventing oxidative damage and thus avoiding activation of downstream effectors as neutral-sphingomyelinase and subsequent ceramide release and caspase activation pathways.

Plasma membrane redox system in the control of stress-induced apoptosis

The plasma membrane of animal cells contains an electron transport system based on coenzyme Q (CoQ) reductases. Cytochrome b5 reductase is NADH-specific and reduces CoQ through a one-electron reaction mechanism. DT-diaphorase also reduces CoQ, although through a two-electron reaction mechanism using both NADH and NADPH, which may be particularly important under oxidative stress conditions. Because reduced CoQ protects membranes against peroxidations, and also maintains the reduced forms of exogenous antioxidants such as alpha-tocopherol and ascorbate, this molecule can be considered a central component of the plasma membrane antioxidant system. Stress-induced apoptosis is mediated by the activation of plasma membrane-bound neutral sphingomyelinase, which releases ceramide to the cytosol. Ceramide-dependent caspase activation is part of the apoptosis pathway. The reduced components of the plasma membrane antioxidant system, mainly CoQ, prevent both lipid peroxidation and sphingomyelinase activation. This results in the prevention of ceramide accumulation and caspase 3 activation and, as consequence, apoptosis is inhibited. We propose the hypothesis that antioxidant protective function of the plasma membrane redox system can be enough to protect cells against the externally induced mild oxidative stress. If this system is overwhelmed, intracellular mechanisms of protection are required to avoid activation of the apoptosis pathway.

Plasma membrane NADH-oxidoreductase system: a critical review of the structural and functional data

The observation in the early 1970s that ferricyanide can replace transferrin as a growth factor highlighted the major role plasma membrane proteins can play within a mammalian cell. Ferricyanide, being impermeant to the cell, was assumed to act at the level of the plasma membrane. Since that time, several enzymes isolated from the plasma membrane have been described, which, using NADH as the intracellular electron donor, are capable of reducing ferricyanide. However, their exact modes of action, and their physiological substrates and functions have not been solved to date. Numerous hypotheses have been proposed for the role of such redox enzymes within the plasma membrane. Examples include the regulation of cell signaling, cell growth, apoptosis, proton pumping, and ion channels. All of these roles may be a result of the function of these enzymes as cellular redox sensors. The emergence of many diverse roles for ferricyanide utilizing redox enzymes present in the plasma membrane might also, in part, be due to the numerous redox enzymes present within the membrane; the poor molecular characterization of the enzymes may be the reason for some of the diverging results reported in the literature as various researchers may be working on different enzymes. Here we review the diverse proposals given for structure and function to the plasma membrane NADH-oxidoreductase system(s) with a specific focus on those enzyme activities which can couple ferricyanide and NADH. Although they are still ill-defined enzymes, evidence is rising that they are of utmost significance for cellular regulation.

Anti-oxidative capacity in patients with ataxia telangiectasia

Highly reactive oxygen species (ROS) are involved in T-cell activation and in the defense against environmental pathogens. An imbalance of ROS generation and detoxifying scavenger enzymes could contribute to the increased susceptibility to cancer and infections in ataxia telangiectasia. We studied oxidative status, i.e. plasma total antioxidant capacity (TEAC), retinol, alpha-tocopherol, ubiquinol, and the number of activated T cells in 10 patients with ataxia telangiectasia (AT) compared to age-matched healthy controls. As expected, patients showed significantly increased levels of activated human leukocyte antigen-DR and CD45RO expressing T cells. TEAC levels as well as the exogenous antioxidants retinol and alpha-tocopherol were significantly reduced in patients. In addition, patients showed slightly reduced plasma levels of the endogenous ROS scavenger enzyme ubiquinol (Q10). Although no correlation between number of activated T-cells and antioxidant capacity could be demonstrated, an increase in ROS and a diminished reactive oxygen scavenger capacity may be involved in the disease process of patients with AT.

Importance of glucose-6-phosphate dehydrogenase activity in cell death

The intracellular redox potential plays an important role in cell survival. The principal intracellular reductant NADPH is mainly produced by the pentose phosphate pathway by glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme, and by 6-phosphogluconate dehydrogenase. Considering the importance of NADPH, we hypothesized that G6PDH plays a critical role in cell death. Our results show that 1) G6PDH inhibitors potentiated H2O2-induced cell death; 2) overexpression of G6PDH increased resistance to H2O2-induced cell death; 3) serum deprivation, a stimulator of cell death, was associated with decreased G6PDH activity and resulted in elevated reactive oxygen species (ROS); 4) additions of substrates for G6PDH to serum-deprived cells almost completely abrogated the serum deprivation-induced rise in ROS; 5) consequences of G6PDH inhibition included a significant increase in apoptosis, loss of protein thiols, and degradation of G6PDH; and 6) G6PDH inhibition caused changes in mitogen-activated protein kinase phosphorylation that were similar to the changes seen with H2O2. We conclude that G6PDH plays a critical role in cell death by affecting the redox potential.