Protective role of glutathione synthesis in response to oxidized low density lipoprotein in human vascular endothelial cells

The Effects of Chia Defatted Flour as a Nutritional Supplement in C57BL/6 Mice Fed a Low-Quality Diet

Today, consumption of diets rich in saturated fat and fructose, associated with a variety of metabolic deregulations, has increased. The aim of this study was to evaluate the effect of dietary supplementation with a residue of defatted chia seed on a diet with low nutritional quality. To do this, C57BL/6 male mice were fed with the Control (C), Low-Nutritional-Quality (LNQ), or supplemented-with-chia-defatted-flour (LNQ+C) diets. After 12 weeks, the glucose and lactate levels were determined in the serum, liver, and kidney, along with reactive oxygen species (ROS) levels, antioxidant enzyme activity, reduced glutathione (GSH), and protein oxidation (AOPP). The LNQ diet increased the glucose and lactate levels (+25% and +50% approx. in the liver, with respect to the control group) and generated oxidative stress by modifying the levels of ROS and the activity of antioxidant enzymes, causing oxidative damage to proteins (+12% in the liver, with respect to the control). Chia supplementation helped to restore the glucose to control levels and modulate the endogenous antioxidant system, resulting in a decrease in protein oxidation products with no differences compared to the control group. In conclusion, supplementation with chia showed beneficial effects on the general health of mice, even when fed a low-nutritional-quality diet.

The Impact of Genetic Polymorphisms in Glutamate-Cysteine Ligase, a Key Enzyme of Glutathione Biosynthesis, on Ischemic Stroke Risk and Brain Infarct Size

The purpose of this pilot study was to explore whether polymorphisms in genes encoding the catalytic (GCLC) and modifier (GCLM) subunits of glutamate-cysteine ligase, a rate-limiting enzyme in glutathione synthesis, play a role in the development of ischemic stroke (IS) and the extent of brain damage. A total of 1288 unrelated Russians, including 600 IS patients and 688 age- and sex-matched healthy subjects, were enrolled for the study. Nine common single nucleotide polymorphisms (SNPs) of the GCLC and GCLM genes were genotyped using the MassArray-4 system. SNP rs2301022 of GCLM was strongly associated with a decreased risk of ischemic stroke regardless of sex and age (OR = 0.39, 95%CI 0.24−0.62, p < 0.0001). Two common haplotypes of GCLM possessed protective effects against ischemic stroke risk (p < 0.01), but exclusively in nonsmoker patients. Infarct size was increased by polymorphisms rs636933 and rs761142 of GCLC. The mbmdr method enabled identifying epistatic interactions of GCLC and GCLM gene polymorphisms with known IS susceptibility genes that, along with environmental risk factors, jointly contribute to the disease risk and brain infarct size. Understanding the impact of genes and environmental factors on glutathione metabolism will allow the development of effective strategies for the treatment of ischemic stroke and disease prevention.

Knockdown of Long Noncoding RNA (lncRNA) AK094457 Relieved Angiotensin II Induced Vascular Endothelial Cell Injury

Background

Hypertension could induce many serious diseases, including damage to vascular endothelial cells. As a non-coding RNA, long noncoding RNA (lncRNA) has received much attention in scientific research and has a regulating efficacy on many critical life activities in human body. The level of lncRNA AK094457 is thought to be elevated in hypertensive rats. However, there is no research indicating the relationship between the level of lncRNA AK094457 and vascular endothelial injury.

Material/Methods

In our study, we used lentiviral to knockdown lncRNA AK094457, and the human umbilical vein endothelial cells (HUVECs) were stimulated by the Ang II to imitate the vascular endothelial cell damage caused by hypertension. The Cell Counting Kit-8 assays were used to detect the cells viability. Western blotting was performed to detect the endothelial nitric oxide synthase (eNOS), p-eNOS and endothelin-1 (ET-1). After that the production of the NO was monitored. At last, the reactive oxygen species (ROS) levels and apoptosis rates were detected in this study.

Results

According to the results, we found that knockdown lncRNA AK094457 could alleviate the decrease of vascular endothelial cell viability induced by angiotensin II (Ang II). The knockdown of lncRNA AK094457 also relieved the downregulation of eNOS and p-eNOS, and the decreasing of NO release. At the same time, the knockdown of lncRNA inhibited the levels of Ang II-induced proinflammatory cytokines (tumor necrosis factor [TNF]-α, interleukin [IL]-1, and IL-6) and cell adhesion molecules (vascular cell adhesion molecule 1 [VCAM-1], intercellular adhesion molecule 1 [ICAM-1], and monocyte chemoattractant protein-1 [MCP-1]). The levels of ROS and apoptosis rates also decreased after the knockdown of lncRNA AK094457.

Conclusions

All these results indicated that lncRNA AK094457 could promote Ang II-induced vascular endothelial cell injury. On the contrary, knockdown of lncRNA AK094457 could alleviate this damage.

Aldo-keto reductase 1B10 promotes development of cisplatin resistance in gastrointestinal cancer cells through down-regulating peroxisome proliferator-activated receptor-γ-dependent mechanism

Cisplatin (cis-diamminedichloroplatinum, CDDP) is one of the most effective chemotherapeutic drugs that are used for treatment of patients with gastrointestinal cancer cells, but its continuous administration often evokes the development of chemoresistance. In this study, we investigated alterations in antioxidant molecules and functions using a newly established CDDP-resistant variant of gastric cancer MKN45 cells, and found that aldo-keto reductase 1B10 (AKR1B10) is significantly up-regulated with acquisition of the CDDP resistance. In the nonresistant MKN45 cells, the sensitivity to cytotoxic effect of CDDP was decreased and increased by overexpression and silencing of AKR1B10, respectively. In addition, the AKR1B10 overexpression markedly suppressed accumulation and cytotoxicity of 4-hydroxy-2-nonenal that is produced during lipid peroxidation by CDDP treatment, suggesting that the enzyme acts as a crucial factor for facilitation of the CDDP resistance through inhibiting induction of oxidative stress by the drug. Transient exposure to CDDP and induction of the CDDP resistance decreased expression of peroxisome proliferator-activated receptor-γ (PPARγ) in MKN45 and colon cancer LoVo cells. Additionally, overexpression of PPARγ in the cells elevated the sensitivity to the CDDP toxicity, which was further augmented by concomitant treatment with a PPARγ ligand rosiglitazone. Intriguingly, overexpression of AKR1B10 in the cells resulted in a decrease in PPARγ expression, which was recovered by addition of an AKR1B10 inhibitor oleanolic acid, inferring that PPARγ is a downstream target of AKR1B10-dependent mechanism underlying the CDDP resistance. Combined treatment with the AKR1B10 inhibitor and PPARγ ligand elevated the CDDP sensitivity, which was almost the same level as that in the parental cells. These results suggest that combined treatment with the AKR1B10 inhibitor and PPARγ ligand is an effective adjuvant therapy for overcoming CDDP resistance of gastrointestinal cancer cells.

Role of Nrf2 in the pathogenesis of atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the vascular arterial walls. A number of studies have revealed the biological and genetic bases of atherosclerosis, and over 100 genes influence atherosclerosis development. Nrf2 plays an important role in oxidative stress response and drug metabolism, but the Nrf2 signaling pathway is closely associated with atherosclerosis development. During atherosclerosis progression, Nrf2 signaling modulates many physiological and pathophysiological processes, such as lipid homeostasis regulation, foam cell formation, macrophage polarization, redox regulation and inflammation. Interestingly, Nrf2 exhibits both pro- and anti-atherogenic effects in experimental animal models. These observations make the Nrf2 pathway a promising target to prevent atherosclerosis.

Antioxidant and anti-inflammatory effects of selenium in oral buccal mucosa and small intestinal mucosa during intestinal ischemia-reperfusion injury

Background

The aim of this study were to investigate whether selenium treatment attenuates lipid peroxidation and downregulates the NF-κB pathway in small intestinal mucosa and to examine whether the effect of selenium is also observed in oral buccal mucosa, during small intestinal IR injury.

Materials and methods

Eighteen rats were assigned into three groups: sham, IR, and IR + selenium. Saline or selenium was administered through a tail vein. 24 hours later, the superior mesenteric artery was exposed and clamped in the IR and IR + selenium groups. After ischemic and reperfusion period, animals were sacrificed and oral buccal mucosa and small intestinal mucosa were harvested.

Results

Glutathione peroxidase activity and cytoplasmic IκB-α expression was higher in the IR + selenium group than that in the IR group. A malondialdehyde level, cytoplasmic phosphorylated inhibitor κB-α, nuclear NF-κB p65 expressions, and NF-κB p65 DNA-binding activity were lower in the IR + selenium group than those in the IR group.

Conclusion

A selenium treatment may cause increased GPx activity, attenuated lipid peroxidation, and downregulated the NF-κB pathway during small intestinal IR injury. Furthermore, these therapeutic benefits of selenium can be observed in oral buccal mucosa as well as small intestinal mucosa.

Targeting the transcription factor Nrf2 to ameliorate oxidative stress and inflammation in chronic kidney disease

Oxidative stress and inflammation are mediators in the development and progression of chronic kidney disease (CKD) and its complications, and they are inseparably linked as each begets and amplifies the other. CKD-associated oxidative stress is due to increased production of reactive oxygen species (ROS) and diminished antioxidant capacity. The latter is largely caused by impaired activation of Nrf2, the transcription factor that regulates genes encoding antioxidant and detoxifying molecules. Protective effects of Nrf2 are evidenced by amelioration of oxidative stress, inflammation, and kidney disease in response to natural Nrf2 activators in animal models, while Nrf2 deletion amplifies these pathogenic pathways and leads to autoimmune nephritis. Given the role of impaired Nrf2 activity in CKD-induced oxidative stress and inflammation, interventions aimed at restoring Nrf2 may be effective in retarding CKD progression. Clinical trials of the potent Nrf2 activator bardoxolone methyl showed significant improvement in renal function in CKD patients with type 2 diabetes. However, due to unforeseen complications the BEACON trial, which was designed to investigate the effect of this drug on time to end-stage renal disease or cardiovascular death in patients with advanced CKD, was prematurely terminated. This article provides an overview of the role of impaired Nrf2 activity in the pathogenesis of CKD-associated oxidative stress and inflammation and the potential utility of targeting Nrf2 in the treatment of CKD.

Cardioprotective effects of a proanthocyanidin-rich fraction from Croton celtidifolius Baill: focus on atherosclerosis

Proanthocyanidins are the most abundant polyphenols in human diets. Epidemiological studies have pointed to proanthocyanidins as promising molecules that could prevent the development of several coronary syndromes by inhibiting the atherogenic process. The present study was designed to investigate the antiatherogenic effects of a proanthocyanidin-rich fraction (PRF) obtained from Croton celtidifolius Baill (Euphorbiaceae) barks. In isolated human LDL, PRF caused a concentration-dependent inhibition of Cu2+-induced oxidative modifications, evidenced by the increasing of the lag phase of lipid peroxidation and decreasing in the oxidation rate (Vmax), moreover, the protein moieties from LDL were protected against Cu2+-induced oxidation. In human umbilical vein endothelial cells (HUVECs), PRF reduced the ROS production stimulated by oxidized LDL. Herein, we demonstrate that oral treatment with PRF improved endothelium-dependent vasorelaxation in hypercholesterolemic LDL receptor knockout mice (LDLr-/-), however, the fraction did not modify plasma lipids and atherosclerotic lesion size in this experimental model. Finally, our results showed for the first time that PRF prevent isolated LDL oxidation, decrease oxidative stress in endothelial cells and improve endothelial function in mice.

Gain and loss of function for glutathione synthesis: impact on advanced atherosclerosis in apolipoprotein E-deficient mice

OBJECTIVE

Glutamate-cysteine ligase (GCL) is the rate-limiting step in glutathione synthesis. The enzyme is a heterodimer composed of a catalytic subunit, GCLC, and a modifier subunit, GCLM. We generated apolipoprotein E (apoE)-/- mice deficient in GCLM (apoE-/-/Gclm-/-) and transgenic mice that overexpress GCLC specifically in macrophages (apoE-/-/Gclc-Tg) to test the hypothesis that significantly altering the availability of glutathione has a measurable impact on both the initiation and progression of atherosclerosis.

METHODS AND RESULTS

Atherosclerotic plaque size and composition were measured in the innominate artery in chow-fed male and female mice at 20, 30, 40, and 50 weeks of age and in the aortic sinus at 40 and 50 weeks of age. The apoE-/-/Gclm-/- mice more rapidly developed complex lesions, whereas the apoE-/-/Gclc-Tg mice had reduced lesion development compared with the littermate apoE-/- control mice. Transplantation of bone marrow from the apoE-/-/Gclm-/- and apoE-/-/Gclc-Tg mice into apoE-/- mice with established lesions also stimulated or inhibited further lesion development at 30 weeks posttransplant.

CONCLUSION

Gain and loss of function in the capacity to synthesize glutathione especially in macrophages has reciprocal effects on the initiation and progression of atherosclerosis at multiple sites in apoE-/- mice.

(1)H NMR-based metabolomic profiling in mice infected with Mycobacterium tuberculosis

Tuberculosis (TB) is one of three major infectious diseases, and the control of TB is becoming more difficult because of the emergence of multidrug-resistant and extensively drug-resistant strains. In this study, we explored the (1)H NMR-based metabolomics of TB using an aerobic TB infection model. Global profiling was applied to characterize the responses of C57Bl/6 mice to an aerobic infection with virulent Mycobacterium tuberculosis (MTB). The metabolic changes in organs (i.e., the lung, the target organ of TB, and the spleen and liver, remote systemic organs) and in serum from control and MTB-infected rats were investigated to clarify the host-pathogen interactions in MTB-infected host systems. Principal components analysis (PCA) and orthogonal partial least-squares discriminant analysis (OPLS-DA) score plots showed distinct separation between control and MTB-infected rats for all tissue and serum samples. Several tissue and serum metabolites were changed in MTB-infected rats, as compared to control rats. The precursors of membrane phospholipids, phosphocholine, and phosphoethanolamine, as well as glycolysis, amino acid metabolism, nucleotide metabolism, and the antioxidative stress response were altered based on the presence of MTB infection. This study suggests that NMR-based global metabolite profiling of organ tissues and serum could provide insight into the metabolic changes in host infected aerobically with virulent Mycobacterium tuberculosis.

Contribution of impaired Nrf2-Keap1 pathway to oxidative stress and inflammation in chronic renal failure

Oxidative stress and inflammation are constant features and major mediators of progression of chronic kidney disease (CKD). Nuclear factor erythroid-2-related factor-2 (Nrf2) confers protection against tissue injury by orchestrating antioxidant and detoxification responses to oxidative and electrophilic stress. While sources of oxidative stress and inflammation in the remnant kidney have been extensively characterized, the effect of CKD on Nrf2 activation and expression of its downstream gene products is unknown and was investigated. Subgroups of male Sprague-Dawley rats were subjected to 5/6 nephrectomy or sham operation and observed for 6 or 12 wk. Kidneys were then harvested, and Nrf2 activity and its downstream target gene products (antioxidant and phase II enzymes) were assessed. In addition, key factors involved in promoting inflammation and oxidative stress were studied. In confirmation of earlier studies, rats with chronic renal failure exhibited increased lipid peroxidation, glutathione depletion, NF-κB activation, mononuclear cell infiltration, and upregulation of monocyte chemoattractant protein-1, NAD(P)H oxidase, cyclooxygenase-2, and 12-lipoxygenase in the remnant kidney pointing to oxidative stress and inflammation. Despite severe oxidative stress and inflammation, remnant kidney tissue Nrf2 activity (nuclear translocation) was mildly reduced at 6 wk and markedly reduced at 12 wk, whereas the Nrf2 repressor Keap1 was upregulated and the products of Nrf2 target genes [catalase, superoxide dismutase, glutathione peroxidase, heme oxygenase-1, NAD(P)H quinone oxidoreductase, and glutamate-cysteine ligase] were reduced or unchanged at 6 wk and significantly diminished at 12 wk. Thus oxidative stress and inflammation in the remnant kidney are compounded by conspicuous impairment of Nrf2 activation and consequent downregulation of the antioxidant enzymes.

Glutamate-cysteine ligase polymorphism, hypertension, and male sex are associated with cardiovascular events. Biochemical and genetic characterization of Italian subpopulation

BACKGROUND

Glutathione (GSH) is an important intravascular scavenger that protects endothelial cells from atherosclerosis. However, it is still unknown whether cardiovascular (CV) events are associated with metabolic and genetic factors, linked to GSH synthesis in an Italian subpopulation, and if a glutamate-cysteine ligase polymorphism within the catalytic subunit (GCLC) could affect blood and plasma GSH concentrations.

METHODS

One hundred subjects, with or without CV risk factors, were enrolled to evaluate plasma and erythrocyte redox status (GSH, homocysteine, cysteine, cysteinylglycine), antioxidant vitamins (alpha-tocopherol and ascorbate), malondialdehyde, a lipid peroxidation product, and the presence of the GCLC-129 C/T polymorphism; an experimental hyperhomocysteinemia after methionine-induced stimulation of transsulfuration pathway was performed in 91% of enrolled subjects. Clinical, biochemical, and genetic variables were correlated with the presence of CV events (myocardial infarction, transient ischemic attacks, and stroke).

RESULTS

By multiple logistic regression analysis, male sex (P = .027), hypertension (P = .001), and GCLC C/T genotype (P = .009) were the only variables associated with events. Plasma alpha-tocopherol content decreased postmethionine in the T allele subjects compared with wild type (P for time x group interaction = .001). Plasma-reduced GSH level was higher in C/T than in C/C genotype subjects at both time points (P for group = .03), whereas intracellular GSH concentration did not differ between the 2 genotype groups either at baseline or postmethionine.

CONCLUSIONS

GCLC T allele, together with hypertension and male sex, is associated with CV events in our study population. Moreover, after stimulation of transsulfuration, intracellular GSH content is preserved in T allele subjects, probably by increases in GSH turnover and export, and consumption of alpha-tocopherol.

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) transcriptional regulation by Oct-1 in human endothelial cells: implications for atherosclerosis

LOX-1, a receptor for ox-LDL (oxidized low-density lipoprotein), has recently been determined to play a critical role in the progression of atherosclerosis. LOX-1 expression (mRNA and protein) has been shown to be up-regulated by pro-atherogenic stimuli, such as ox-LDL and Ang II (angiotensin II). However, the molecular mechanisms of these up-regulations are unclear. In the present study, we explored LOX-1 transcriptional promoter activation in response to ox-LDL and Ang II. Under basal states, LOX-1 core promoter (LOX-1 -35/+36) was found to be sufficient for its basal activity in HCAECs (human coronary artery endothelial cells). More importantly, we found that ox-LDL (60 microg/ml for 24 h) induced LOX-1 promoter activity significantly and that a 105 bp fragment (between nt -1599 and -1494) was required for this activation. Within this 106 bp fragment, there is a potential binding motif for the transcription factor Oct-1 (octamer-1). By electrophoretic mobility-shift assay, we observed the activation of Oct-1 by ox-LDL. The critical role of Oct-1 in ox-LDL-induced LOX-1 promoter activation was further confirmed by mutagenesis assay. For comparison, we also examined LOX-1 promoter activation in response to Ang II (1 micromol/l for 24 h). Interestingly, another promoter region, between nt -2336 and -1990, was required for Ang II-induced LOX-1 promoter activation. In conclusion, the present study strongly suggests that ox-LDL, by activating Oct-1, induces LOX-1 promoter activation. Furthermore, this study suggests that while ox-LDL and Ang II both induce LOX-1 expression in HCAECs, the underlying mechanisms of promoter activation are different from each other.

Regulation of glutathione in inflammation and chronic lung diseases

Oxidant/antioxidant imbalance, a major cause of cell damage, is the hallmark for lung inflammation. Glutathione (GSH), a ubiquitous tripeptide thiol, is a vital intra- and extra-cellular protective antioxidant against oxidative stress, which plays a key role in the control of signaling and pro-inflammatory processes in the lungs. The rate-limiting enzyme in GSH synthesis is glutamylcysteine ligase (GCL). GSH is essential for development as GCL knock-out mouse died from apoptotic cell death. The promoter (5'-flanking) region of human GCL is regulated by activator protein-1 (AP-1) and antioxidant response element (ARE), and are modulated by oxidants, phenolic antioxidants, growth factors, inflammatory and anti-inflammatory agents in various cells. Recent evidences have indicated that Nrf2 protein, which binds to the erythroid transcription factor (NF-E2) binding sites, and its interaction with other oncoproteins such as c-Jun, Jun D, Fra1 and Maf play a key role in the regulation of GCL. Alterations in alveolar and lung GSH metabolism are widely recognized as a central feature of many chronic inflammatory lung diseases. Knowledge of the mechanisms of GSH regulation could lead to the pharmacological manipulation of the production and/or gene transfer of this important antioxidant in lung inflammation and injury. This article describes the role of AP-1 and ARE in the regulation of cellular GSH biosynthesis and assesses the potential protective and therapeutic role of glutathione in oxidant-induced lung injury and inflammation.

Induction of heme oxygenase 1 by moderately oxidized low-density lipoproteins in human vascular smooth muscle cells: role of mitogen-activated protein kinases and Nrf2

Oxidized low-density lipoproteins (LDL) play a central role in atherogenesis and induce expression of the antioxidant stress protein heme oxygenase 1 (HO-1). In the present study we investigated induction of HO-1 and adaptive increases in reduced glutathione (GSH) in human aortic smooth muscle cells (SMC) in response to moderately oxidized LDL (moxLDL, 100 microg protein/ml, 24 h), a species containing high levels of lipid hydroperoxides. Expression and activity of HO-1 and GSH levels were elevated to a greater extent by moxLDL than highly oxidized LDL but unaffected by native or acetylated LDL. Inhibitors of protein kinase C (PKC) or mitogen-activated protein kinases (MAPK) p38(MAPK) and MEK or c-jun-NH2-terminal kinase (JNK) significantly attenuated induction of HO-1. Phosphorylation of p38(MAPK), extracellular signal-regulated kinase (ERK1/2), or JNK and nuclear translocation of the transcription factor Nrf2 were enhanced following acute exposure of SMC to moxLDL (100 microg protein/ml, 1-2 h). Pretreatment of SMC with the antioxidant vitamin C (100 microM, 24 h) attenuated the induction of HO-1 by moxLDL. Native and oxidized LDL did not alter basal levels of intracellular ATP, mitochondrial dehydrogenase activity, or expression of the lectin-like oxidized LDL receptor (LOX-1) in SMC. These findings demonstrate for the first time that activation of PKC, p38(MAPK), JNK, ERK1/2, and Nrf2 by oxidized LDL in human SMC leads to HO-1 induction, constituting an adaptive response against oxidative injury that can be ameliorated by vitamin C.

Effects of L-mono Methyl-arginine, N-Acetyl-cysteine and Diphenyleniodonium on Free Radical Release in C6 Glial Cells Enriched in Hexacosenoic Acid

Previously, we have shown that C6 glial cells enriched in hexacosenoic acid (HA) incubated with oxidative stressors released higher amounts of nitric oxide (NO) products and superoxide (O2(-)), compared to native C6 cells. In the present study, we examined the effects of pretreatment with some of free radical release inhibitors. The aim was to determine the origin of the enhanced generation of NO and superoxide, and to test the possibility of preventing it. Pre-treatment with L-mono-methyl-arginine and N-acetyl-cysteine in oxidized low-density lipoprotein (ox-LDL) exposed HA cells, inhibited not only nitrite but also superoxide production suggesting that O2(-) anion could partially derive from inducible NO synthase. We also observed that ox-LDL treatment of HA cells reduced the intracellular glutathione levels and activated extracellular signal-related kinases. Since this signalling is related to neurotoxic effect, our data substantiate the role of the free radicals in X-linked adrenoleukodystrophy pathogenesis, as HA cells have been used as an in vitro model for this disease.

Glutathione, stress responses, and redox signaling in lung inflammation

Changes in the ratio of intracellular reduced and disulfide forms of glutathione (GSH/GSSG) can affect signaling pathways that participate in various physiological responses from cell proliferation to gene expression and apoptosis. It is also now known that many proteins have a highly conserved cysteine (sulfhydryl) sequence in their active/regulatory sites, which are primary targets of oxidative modifications and thus important components of redox signaling. However, the mechanism by which oxidants and GSH/protein-cysteine-thiols actually participate in redox signaling still remains to be elucidated. Initial studies involving the role of cysteine in various proteins have revealed that cysteine-SH may mediate redox signaling via reversible or irreversible oxidative modification to Cys-sulfenate or Cys-sulfinate and Cys-sulfonate species, respectively. Oxidative stress possibly via the modification of cysteine residues activates multiple stress kinase pathways and transcription factors nuclear factor-kappaB and activator protein-1, which differentially regulate the genes for proinflammatory cytokines as well as the protective antioxidant genes. Understanding the redox signaling mechanisms for differential gene regulation may allow for the development of novel pharmacological approaches that preferentially up-regulate key antioxidants genes, which, in turn, reduce or resolve inflammation and injury. This forum article features the current knowledge on the role of GSH in redox signaling, particularly the regulation of transcription factors and downstream signaling in lung inflammation.

Manipulation of antioxidant pathways in neonatal murine brain

To assess the role of brain antioxidant capacity in the pathogenesis of neonatal hypoxic-ischemic brain injury, we measured the activity of glutathione peroxidase (GPX) in both human-superoxide dismutase-1 (hSOD1) and human-GPX1 overexpressing transgenic (Tg) mice after neonatal hypoxia-ischemia (HI). We have previously shown that mice that overexpress the hSOD1 gene are more injured than their wild-type (WT) littermates after HI, and that H(2)O(2) accumulates in HI hSOD1-Tg hippocampus. We hypothesized that lower GPX activity is responsible for the accumulation of H(2)O(2). Therefore, increasing the activity of this enzyme through gene manipulation should be protective. We show that brains of hGPX1-Tg mice, in contrast to those of hSOD-Tg, have less injury after HI than WT littermates: hGPX1-Tg, median injury score = 8 (range, 0-24) versus WT, median injury score = 17 (range, 2-24), p < 0.01. GPX activity in hSOD1-Tg mice, 2 h and 24 h after HI, showed a delayed and bilateral decline in the cortex 24 h after HI (36.0 +/- 1.2 U/mg in naive hSOD1-Tg versus 29.1 +/- 1.7 U/mg in HI cortex and 29.2 +/- 2.0 for hypoxic cortex, p < 0.006). On the other hand, GPX activity in hGPX1-Tg after HI showed a significant increase by 24 h in the cortex ipsilateral to the injury (48.5 +/- 5.2 U/mg, compared with 37.2 +/- 1.5 U/mg in naive hGPX1-Tg cortex, p < 0.008). These findings support the hypothesis that the immature brain has limited GPX activity and is more susceptible to oxidative damage and may explain the paradoxical effect seen in ischemic neonatal brain when SOD1 is overexpressed.

Oxidative modulation of NF-κB signaling by oxidized low-density lipoprotein

Oxidized low-density lipoprotein (oxLDL) modifies macrophage inflammatory responses in the pathogenesis of atherosclerosis. In the present study, we focused on gamma-glutamylcysteine synthetase (gamma-GCS), a rate limiting enzyme of glutathione synthesis, and examined whether inflammatory stimulation of gamma-GCS gene in macrophages by lipopolysaccharide (LPS) is modified when the cells were exposed to oxLDL. We found that the nuclear factor-kappaB (NF-kappaB)-mediated induction of gamma-GCS by LPS (100 ng/ml) was suppressed by a 48-h pre-treatment with oxLDL (50 micro/ml), and this was due to a decrease in the DNA-binding activity of NF-kappaB. Furthermore, pre-treatment with oxLDL caused a carbonylation of NF-kappaB subunit p65. With alpha-tocopherol, the oxLDL-induced carbonylation of proteins decreased with a restoration of DNA-binding activity of NF-kappaB. Together, these indicate that oxidative modification of NF-kappaB suppresses LPS-induced expression of gamma-GCS gene in ox-LDL-treated cells, suggesting an implication of oxLDL-induced modulation of NF-kappaB signaling with atherosclerosis.

Polymorphism in glutamate-cysteine ligase modifier subunit gene is associated with impairment of nitric oxide-mediated coronary vasomotor function

BACKGROUND

The minor -588T allele of polymorphism -588C/T of a modifier subunit gene in glutamate-cysteine ligase (GCLM), a rate-limiting enzyme for glutathione (GSH) synthesis, was associated with lower plasma GSH levels and was a risk factor for myocardial infarction.

METHODS AND RESULTS

We examined effects of the -588C/T polymorphism on coronary arterial diameter and blood flow responses to intracoronary infusion of acetylcholine in 157 consecutive subjects who had normal coronary angiograms. In multivariate linear regression analysis with covariates including traditional risk factors, the minor -588T allele had an independent association with impaired dilation or enhanced constriction of epicardial coronary arteries in response to acetylcholine, and it was independently associated with blunted increase in coronary flow response to acetylcholine. In a subgroup of 59 consecutive subjects, constrictor responses of epicardial coronary diameter to intracoronary infusion of NG-monomethyl-l-arginine, reflecting the presence of coronary nitric oxide (NO) bioactivity, had an inverse and independent association with the -588T allele in multivariate analysis.

CONCLUSIONS

The -588T polymorphism of the GCLM gene causes a decrease in endothelial NO bioactivity, leading to impairment of endothelium-dependent vasomotor function in large and resistance coronary arteries. The GCL-GSH-NO axis may play a role in the defense system against coronary artery disease.

Induced expression of manganese superoxide dismutase by non-toxic concentrations of oxidized low-density lipoprotein (oxLDL) protects against oxLDL-mediated cytotoxicity

Oxidized low-density lipoprotein (oxLDL) affects macrophages and plays a critical role in the development of atherosclerosis. In the present paper, we demonstrate that high concentrations of oxLDL provoked apoptosis of human Mono-Mac-6 cells, which was blocked by diphenylene-iodonium (DPI), an inhibitor of flavin-containing enzymes, such as NADPH oxidase, suggesting the involvement of reactive oxygen species (ROS). Importantly, pre-treatment of cells with low concentrations of oxLDL prevented apoptosis in response to high concentrations of oxLDL by up-regulating manganese superoxide dismutase (MnSOD). DPI prevented expression of MnSOD by oxLDL, whereas inhibitors of cytochrome P450 (methoxalen) or xanthine oxidase (allopurinol) did not, thus pointing to a role of NADPH-oxidase-derived ROS in oxLDL-induced MnSOD expression. Transfection of cells with MnSOD antisense, but not scrambled antisense, oligonucleotides significantly attenuated oxLDL-mediated MnSOD expression and hindered cytoprotective effects of non-toxic oxLDL concentrations. Our findings suggest that up-regulation of MnSOD by low concentrations of oxLDL is critical for protection towards oxLDL-mediated cytotoxicity.

Induction of glutathione synthesis in macrophages by oxidized low-density lipoproteins is mediated by consensus antioxidant response elements

The uptake of oxidized low-density lipoproteins (oxLDL) by macrophages leading to conversion into foam cells is a seminal event in atherogenesis. Excessive accumulation of oxLDL can cause oxidative stress in foam cells leading to cell death and the progression and destabilization of atherosclerotic lesions. Oxidative stress induces a protective compensatory increase in the synthesis of the endogenous antioxidant glutathione (GSH). Glutamate-cysteine ligase (GCL) is the rate-limiting enzyme in GSH synthesis and is composed of a catalytic subunit (GCLC) and a modifier subunit (GCLM), which are products of separate genes. Treatment of RAW 264.7 mouse macrophages and mouse peritoneal macrophages with oxLDL (30 microg/mL) induces increased expression of both Gclc and Gclm in vitro. The increase in mRNA occurs in part via increased transcription as demonstrated with luciferase reporter constructs. The promoters for both GCLC and GCLM contain consensus antioxidant response elements (AREs). Electrophoretic mobility shift assays revealed induction of nuclear factor binding to these AREs after treatment of RAW 264.7 cells and mouse peritoneal macrophages with oxLDL. Nuclear factor binding to the AREs is diminished by a single base pair substitution in the core sequence. Site-directed mutagenesis of the AREs within the Gclc and Gclm promoters resulted in a decrease of oxLDL-induced luciferase activity. Supershift analyses revealed that oxLDL stimulates binding of the transcription factors Nrf1, Nrf2, and c-jun to the AREs. These data suggest that AREs play a direct role in mediating the induction of GSH synthesis by oxLDL and in protecting macrophages against oxidized lipid-induced oxidative stress.

Association of polymorphism in glutamate-cysteine ligase catalytic subunit gene with coronary vasomotor dysfunction and myocardial infarction

OBJECTIVES

The purpose of this study was to test the hypothesis that polymorphisms in the promoter region of the glutamate-cysteine ligase catalytic subunit (GCLC) gene may be associated with coronary endothelial vasomotor dysfunction and myocardial infarction (MI).

BACKGROUND

Glutamate-cysteine ligase is a rate-limiting enzyme for synthesis of glutathione (GSH) that plays a crucial role in the intracellular antioxidant defense systems. Oxidants transcriptionally upregulate the GCLC gene for GSH synthesis, providing a protective mechanism against oxidant-induced endothelial dysfunction or activation, which plays a pathogenetic role in cardiovascular diseases.

METHODS

The association of the possible polymorphisms with coronary arterial diameter responses to acetylcholine was determined in 62 male subjects. The frequency of polymorphisms was compared between 255 male patients with MI and 179 male control subjects.

RESULTS

We found a polymorphism (-129C/T) in which the T allele showed lower promoter activity (50% to 60% of the activity of the C allele) in response to H(2)O(2) in human endothelial cells. Endothelium-dependent dilation of coronary arteries was impaired in subjects with the -129T allele (n = 31), as compared with the age-matched subjects without the -129T allele (n = 31). The T allele was highly frequent in patients with MI as compared with control subjects, and it was a significant risk factor for MI, independent of traditional coronary risk factors (odds ratio [OR] 1.81, 95% confidence interval [CI] 1.08 to 3.03; p = 0.03).

CONCLUSIONS

The -129T polymorphism of the GCLC gene may suppress the GCLC gene induction response to an oxidant, and it is implicated in coronary endothelial vasomotor dysfunction and MI.

Post-transcriptional regulation of VEGF expression by oxidised LDL in human macrophages

BACKGROUND

Accumulation of oxidised low density lipoproteins (oxLDL) in macrophages and their subsequent transformation into lipid-filled foam cells is generally considered an early event in atherosclerosis. Vascular Endothelial Growth Factor (VEGF) may contribute to atherogenesis through increased vascular permeability, chemoattraction towards monocytes and intraplaque vessel formation. In this study we investigate the effect and regulation of VEGF expression in human macrophages stimulated with oxLDL.

MATERIALS AND METHODS

Vascular Endothelial Growth Factor mRNA and protein expression was assayed using RT-PCR and ELISA, respectively. The activity of mitogen-activated protein kinases (MAPKs) was investigated using Western blots.

RESULTS

In human monocyte-derived macrophages, oxLDL significantly increased VEGF mRNA expression and subsequent protein secretion in a concentration-dependent manner after 6 h and 18 h, respectively. Using an in vitro mRNA decay assay, we show that this oxLDL-induced VEGF expression partly is regulated through increased stability of the VEGF mRNA. Involvement of MAPKs has previously been implicated in the stabilisation of VEGF mRNA. Activity of the p38 MAPK, but not the c-jun-N-terminal kinase (JNK), increased in macrophages stimulated with oxLDL (50 micro g mL-1) for 5-15 min. Preincubation with SB202190 (20 micro M), a specific inhibitor of p38 MAPK, significantly decreased the oxLDL-induced VEGF mRNA expression by 40%. The prolonged half-life of VEGF mRNA, induced by oxLDL, was not inhibited by SB202190.

CONCLUSIONS

OxLDL increases VEGF expression and p38 MAPK activity in human macrophages. The increased VEGF mRNA expression by oxLDL is mediated through at least two intracellular pathways, one involving p38 MAPK and another that independently of p38 MAPK activity increases VEGF mRNA stability.

Stimulation by de novo-synthesized ceramide of phospholipase A(2)-dependent cholesterol esterification promoted by the uptake of oxidized low-density lipoprotein in macrophages

The involvement of cytosolic phospholipase A(2) (cPLA(2)) and ceramide in the accumulation of cholesteryl ester induced by the uptake of oxidized low-density lipoproteins (oxLDL) in macrophages was investigated. Uptake of oxLDL by [(3)H]oleic acid-labeled macrophages stimulated the formation of cholesteryl oleate, and this process was completely inhibited by a cPLA(2) inhibitor. Under the conditions, a time-dependent increase in ceramide was observed, while sphingomyelin levels were unaffected. The production of ceramide was completely inhibited by fumonisin B1, an inhibitor of the de novo synthesis of ceramide, and oxLDL-induced cholesteryl oleate formation was inhibited partially. Treatment of the cells with sphingomyelinase accelerated the formation of cholesteryl ester. Furthermore, sphingomyelinase or cell-permeable ceramide induced the release of oleic acid, and this was inhibited by a cPLA(2) inhibitor. These results suggest that activation of cPLA(2) is responsible for the formation of cholesteryl ester induced by the uptake of oxLDL in macrophages, and that de novo-synthesized ceramide is implicated, at least in part, in this process.

Polymorphism in the 5'-flanking region of human glutamate-cysteine ligase modifier subunit gene is associated with myocardial infarction

BACKGROUND

Human glutamate-cysteine ligase (GCL) is a rate-limiting enzyme for the synthesis of glutathione that plays a crucial role in antioxidant defense mechanisms in most mammalian cells, including vascular cells. Oxidants transcriptionally upregulate GCL genes for glutathione synthesis, providing a protective mechanism against oxidative stress-induced cellular dysfunction. This study examined the hypothesis that variation in the GCL genes may be associated with coronary artery disease in which oxidative stress plays a pathogenetic role.

METHODS AND RESULTS

We searched for the common variants in the 5'-flanking region of the GCL modifier subunit (GCLM) gene in patients with myocardial infarction (MI). We found a polymorphism (-588C/T) in which the T allele showed lower promoter activity (40% to 50% of C allele) in response to oxidants in the luciferase reporter gene assay. Allele frequencies were determined by polymerase chain reaction-based analysis of restriction fragment length polymorphism in 429 patients with MI and 428 control subjects (as defined by angiography) in Kumamoto Prefecture, Japan. The frequency of the T polymorphism was significantly higher in the MI group than in the control group (CT and TT genotypes: 31.5% in MI group versus 19.2% in control group; P<0.001). In multiple logistic regression analysis, the T polymorphism was a risk factor for MI independent of traditional coronary artery disease risk factors (odds ratio, 1.98; 95% confidence interval, 1.38 to 2.83; P<0.001).

CONCLUSIONS

These findings suggest that the -588T polymorphism of the GCLM gene may suppress GCLM gene induction in response to oxidants and that it is a genetic risk factor for MI.

Induction of glutathione synthesis by oxidized low-density lipoprotein and 1-palmitoyl-2-arachidonyl phosphatidylcholine: protection against quinone-mediated oxidative stress

Exposure of endothelial cells to oxidized low-density lipoprotein (oxLDL) leads to diverse cellular effects, including induction of the intracellular antioxidant GSH. It is not known whether lipid-or protein-derived oxidation products cause GSH induction and whether this involves increased activity of the key enzyme in its synthesis, glutamate-cysteine ligase (GCL). Furthermore, the effect of oxLDL exposure on the cell's ability to combat oxidative stress has not been previously examined. In the present study we found that, in bovine aortic endothelial cells, LDL or 1-palmitoyl-2-arachidonyl phosphatidylcholine oxidized by different reactive oxygen and nitrogen species induced GSH synthesis. However, prevention of GSH synthesis during exposure to oxLDL caused extensive cell death. The mediator causing GSH induction was shown to be a polar lipid and resulted in the increased activity of GCL as well as increased protein levels of the regulatory subunit of GCL. Pretreatment with both oxLDL and the polar lipid subfraction of the oxLDL protected cells against the toxicity of 2,3-dimethoxynaphthoquinone (DMNQ), a superoxide- and H(2)O(2)-forming compound. The potential of a low level of lipid peroxidation products to initiate cytoprotective pathways are discussed.

Paraquat-induced oxidative stress and dysfunction of the glutathione redox cycle in pulmonary microvascular endothelial cells

Oxidative stress and changes in the antioxidant defense system that include the glutathione redox cycle in cultured pulmonary microvascular endothelial cells after exposure to paraquat at 0.1 and 0.5 mM were examined as a function of time. Cell viability was substantially lost 72 h after exposure to 0.5 mM paraquat, but not 0.1 mM paraquat. Viability loss was accompanied by increased glutathione-protein mixed disulfide formation, as well as a loss in glyceraldehyde-3-phosphate dehydrogenase activity, indicating a low defense potential. At 4 h after exposure to paraquat at both doses, however, a marked loss in NADPH was found, together with a decrease in aconitase activity. With 0.5 mM paraquat, increased NADP(+) accompanied by NADPH loss diminished constantly after 48 h without recovery of lost NADPH, suggesting destruction of pyridine nucleotides under oxidative stress. NAD(+) decreased 72 h after exposure to 0.5 mM paraquat, but NADH was not influenced. 3-Aminobenzamide did not protect the loss in NADP(+) or NAD(+) and cell viability. Although oxidized glutathione did not increase by exposure to paraquat at both doses through a 96-h exposure period, reduced glutathione increased at 48 to 72 h, with an increase in glutathione disulfide reductase activities. In contrast, a marked loss in glutathione peroxidase activity was produced 48 h after exposure to 0.5 mM paraquat, preceding cell injury. Mercaptosuccinate, an inhibitor of glutathione peroxidase, distinctly hastened viability loss by paraquat. These results indicate that the reduced ability of the glutathione redox cycle, leading to high oxidative stress, is closely associated with paraquat-induced cytotoxicity.

Oral L-arginine administration attenuates postprandial endothelial dysfunction in young healthy males

BACKGROUND

Endothelial dysfunction is considered the earliest stage of atherosclerosis. Postprandial phase is associated with a transient impairment of endothelial function concomitantly with the triglyceride-rich lipoprotein increase. This phenomenon may be explained by the oxidative burden induced by triglyceride-rich lipoproteins, reducing nitric oxide bioavailability.

OBJECTIVE

To investigate the effect of a diet enriched with L-arginine, the substrate for nitric oxide synthesis on endothelial function in healthy volunteers.

METHODS

Endothelial function (expressed as flow-mediated vasodilation (FMV) of the brachial artery), total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, LDL-size, Lp (a) and reduced glutathione (GSH) were evaluated in seven healthy males (mean age 23 +/- 3 years) without cardiovascular risk factors. Measurements were made at baseline and 2, 4 and 6 h after a standardized oral fat load. L-arginine (6 g daily) was administered for 10 days. On the 11th day the oral fat load and the parameters examined previously at entry were repeated.

RESULTS

After the first oral fat load, FMV significantly decreased at 2 and 4 h, and overlapped with the basal levels at 6 h. After L-arginine treatment, FMV significantly decreased at 2 h and normalized after 4 and 6 h. Triglycerides increased at 2 and 4 h and decreased after 6 h in both sets of observations relating to before and after L-arginine administration. GSH dropped 2 h after the fat load, both before and after L-arginine. Before L-arginine, FMV exhibited a significant correlation with triglycerides (r= -0.426, P= 0.024) and GSH (r=0.48; P=0.009). After L-arginine, FMV was related to GSH (r=0.39; P=0.03) but not to triglycerides (r= -0.12; P=0.52).

CONCLUSION

Postprandial endothelial impairment is partly abolished by L-arginine administration. These data, which require confirmation, suggest the importance of dietary choice for atherosclerosis prevention even in young healthy subjects.

Requirement for GSH in recycling of ascorbic acid in endothelial cells

Ascorbic acid may be involved in the defense against oxidant stress in endothelial cells. Such a role requires that the cells effectively recycle the vitamin from its oxidized forms. In this work, we studied the ability of cultured bovine aortic endothelial cells (BAECs) to take up and reduce dehydroascorbic acid (DHA) to ascorbate, as well as the dependence of ascorbate recycling on intracellular GSH. BAECs took up and reduced DHA to ascorbate much more readily than they took up ascorbate. Although BAECs in culture did not contain ascorbate, ascorbate accumulated to concentrations of 2-3 mM in BAECs following incubation with 400 microM DHA. Extracellular ferricyanide oxidized intracellular ascorbate, which was recycled by the cells. Reduction of DHA, either when added to the cells or when generated in response to ferricyanide, caused significant decreases in intracellular GSH concentrations. Depletion of intracellular GSH with 1-chloro-2,4-dinitrobenzene, diethylmaleate, and diamide almost abolished the ability of the cells to reduce DHA to ascorbate. DHA reduction by thioredoxin reductase was evident in dialyzed cell extracts, but occurred at rates far lower than direct GSH reduction of DHA. These results suggest that maximal rates of DHA reduction, and thus recycling of ascorbate from DHA, are dependent upon GSH in these cells.

Alteration of antioxidants during the progression of heart disease in streptozotocin-induced diabetic rats

Involvement of oxidative stress is implicated in the progression of complication of diabetes mellitus. With respect to heart diseases, we have studied role of oxidative stress/antioxidants using rats treated with streptozotocin to induce diabetes (DM). Hemodynamic and echocardiographic measurements showed thickening of the wall and an increase in the internal dimension of the left ventricle (LV) in DM rats at 8th week. Decrease in diastolic posterior wall velocity and rate of LV pressure change, and increase in LV end diastolic pressures also proved cardiac dysfunction. These changes were further developed in DM rats after 12 weeks. Utilizing rat hearts at 8th and 12th weeks, the following estimations were performed. There was a decrease in the activity of Mn-superoxide dismutase (SOD), suggesting abnormal mitochondrial metabolism of reactive oxygen species. The level of glutathione (GSH) decreased concomitant with a decrease in the expression of gamma-glutamylcysteine synthetase (gamma-GCS). The expression of transforming growth factor-beta1 (TGF-beta1), known as a growth factor and a suppressor of GSH synthesis, elevated in DM rat hearts. Immunohistochemical estimation showed an increase in type IV collagen in DM hearts. Collectively, it was suggested a linkage between mitochondrial damage to generate reactive oxygen species and inactivation of Mn-SOD and elevation of the expression of TGF-beta1 to lead suppression of GSH synthesis and induction of fibrous change for the consequent cardiac dysfunction in DM.

Adaptive responses to peroxynitrite: increased glutathione levels and cystine uptake in vascular cells

We and others recently demonstrated increased glutathione levels, stimulated cystine uptake, and induced gamma-glutamylcysteinyl synthase (gamma-GCS) in vascular cells exposed to nitric oxide donors. Here we report the effects of peroxynitrite on glutathione levels and cystine uptake. Treatment of bovine aortic endothelial and smooth muscle cells with 3-morpholinosydnonimine (SIN-1), a peroxynitrite donor, resulted in transient depletion of glutathione followed by a prolonged increase beginning at 8-9 h. Concentration-dependent increases in glutathione of up to sixfold occurred 16-18 h after 0.05-2.5 mM SIN-1. Responses to SIN-1 were inhibited by copper-zinc superoxide dismutases and manganese(III)tetrakis(1-methyl-4-pyridyl)porphyrin pentachloride, providing evidence for peroxynitrite involvement. Because glutathione synthesis is regulated by amino acid availability, we also studied cystine uptake. SIN-1 treatment resulted in a prolonged increase in cystine uptake beginning at 6-9 h. Increases in cystine uptake after SIN-1 were blocked by inhibitors of protein and RNA synthesis, by extracellular glutamate but not by extracellular sodium. These studies suggest induction of the x(c)(-) pathway of amino acid uptake. A close correlation over time was observed for increases in cystine uptake and glutathione levels. In summary, vascular cells respond to chronic peroxynitrite exposure with adaptive increases in cellular glutathione and cystine transport.

Lysophosphatidylcholine induces apoptotic and non-apoptotic death in vascular smooth muscle cells: in comparison with oxidized LDL

Oxidized low-density lipoprotein (oxLDL) plays a key role in the development of atherogenesis, partly by causing injury to vascular cells. However, different preparations of LDL, methods of oxidation, and/or active components often produce cellular effects of various degrees. To explore the quantitative relationship between dose and level of oxidation of the oxLDL utilized, we employed combinations of different levels of oxidation and concentrations of oxLDL to induce cell death in cultured vascular smooth muscle cells (VSMC). We also examined the effect of lysophosphatidylcholine (lysoPC), a putative active component of oxLDL, on VSMCs by determining, in parallel with a cytotoxicity test (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay), DNA fragmentation ([3H]thymidine release), and flow cytometric analyses. We found that oxLDL caused cytotoxicity in an oxidative level- and dose-dependent manner, lysoPC also caused dose-dependent cytotoxicity with or without serum. Fragmentation of DNA was observed in both oxLDL- and lysoPC-treated VSMCs. Furthermore, lysoPC-induced DNA ladder was also demonstrated by gel electrophoresis at a concentration of 25 micromol/l or higher. Flow cytometric analysis yielded similar results for oxLDL- and lysoPC-treated VSMC; namely, an accumulation in the fraction of cells in G(0)/G(1) phase with a reciprocal change in S-phase fraction. Membrane phosphatidylserine exposure, detected by annexin V staining, provided additional evidence that lysoPC induced significant apoptosis in VSMC. Taken together, the degree of oxLDL-induced cytotoxicity/apoptosis of VSMC depended on combined effects of oxLDL concentration and oxidative level. Moreover, lysoPC also elicited a dose-dependent apoptosis in addition to cytotoxicity.

Mitogen-activated protein kinase, ERK1/2, is essential for the induction of vascular endothelial growth factor by ionizing radiation mediated by activator protein-1 in human glioblastoma cells

Vascular Endothelial Growth Factor (VEGF)/Vascular Permeability Factor plays an important role in angiogenesis and cell proliferation of cancer cells. Glioblastoma cells are most malignant and show resistance to radiation therapy inducing VEGF to cause angiogenesis and brain edema. In the present study, the regulatory mechanism of the expression of VEGF by ionizing radiation was studied in three human glioblastoma cells. Induction of VEGF mRNA by ionizing radiation was dependent on dose and incubation time. Activator protein-1 (AP-1) was activated by 10 Gy of ionizing radiation in 1 h in T98G glioblastoma cells on an electrophoretic mobility shift assay. We constructed chimeric genes containing various regions of the VEGF promoter gene and the coding region for chloramphenicol acetyltransferase (CAT) and transiently transfected them to T98G cells. CAT assay with the VEGF promoter gene containing an AP-1 site demonstrated that the promoter activity of the VEGF gene was enhanced by ionizing radiation. Immunological analysis of the activity of mitogen-activated protein kinase, ERK1/2, showed that this activity is up-regulated by ionizing radiation. These results suggest that ERK1/2 pathway is involved in the up-regulation of VEGF expression ionizing radiation mediated by AP-1, which may lead to further neovascularization and proliferation of glioblastoma cells resistant to radiation therapy.

Regulation of gamma-glutamylcysteine synthetase subunit gene expression: insights into transcriptional control of antioxidant defenses

Gamma-glutamylcysteine synthetase (GCS; also referred to as glutamate-cysteine ligase, GLCL) catalyzes the rate-limiting reaction in glutathione (GSH) biosynthesis. The GCS holoenzyme is composed of a catalytic and regulatory subunit, each encoded by a unique gene. In addition to some conditions which specifically upregulate the catalytic subunit gene, expression of both genes is increased in response to many Phase II enzyme inducers including oxidants, heavy metals, phenolic antioxidants and GSH-conjugating agents. Electrophile Response Elements (EpREs), located in 5'-flanking sequences of both the GCSh and GCSl subunit genes, are hypothesized to at least partially mediate gene induction following xenobiotic exposure. Recent experiments indicate that the bZip transcription factor Nrf2 participates in EpRE-mediated GCS subunit gene activation in combination with other bZip proteins. An AP-1-like binding sequence and an NF-kappaB site have also been implicated in regulation of the catalytic subunit gene following exposure to certain pro-oxidants. Potential signaling mechanisms mediating GCS gene induction by the diverse families of Phase II enzyme inducers include thiol modification of critical regulatory sensor protein(s) and the generation of the reactive oxygen species. This review summarizes recent progress in defining the molecular mechanisms operative in transcriptional control of the genes encoding the two GCS subunits, identifying areas of agreement and controversy. The mechanisms involved in GCS regulation might also be relevant to the transcriptional control of other components of the antioxidant defense battery.

In vitro study of the cytotoxicity of isolated oxidized lipid low-density lipoproteins fractions in human endothelial cells: relationship with the glutathione status and cell morphology

Toxic effects of oxidized lipid compounds contained in oxidized LDL to endothelial cells are involved in the pathogenesis of atherosclerosis. Glutathione (GSH) plays an important role in the redox status of the cell and in the protective effect against oxidant injuries. However, little is known about the respective effect of these different oxidized lipid compounds toward cytotoxicity and GSH status of the cell. In this report, we isolated by high-performance liquid chromatography oxidized lipid compounds from low-density lipoproteins (LDL) oxidized by copper and we examined their effects on cultured endothelial cells. Cytotoxicity and GSH status were determined after incubation of endothelial cells with crude LDL or isolated lipid fractions derived from cholesterol, phospholipids, or cholesteryl esters. Their effects on cell morphology were also assessed. Oxidized lipids coming from cholesteryl esters (hydroperoxides or short-chain polar derivatives) induced a slight but significant GSH depletion without inducing cytotoxicity. The same species coming from phospholipids induced a more pronounced GSH depletion and a cytotoxic effect which is only present for the more polar compounds (short-chain polar derivatives) and corresponding to a total GSH depletion. In contrast, fractions containing oxysterols had a larger cytotoxic effect than their effect on GSH depletion suggesting that their cytotoxic effects are mediated by a GSH-independent pathway. All together, these data suggest that LDL-associated oxidized lipids present in copper-oxidized LDL exert cytotoxicity by an additional or synergistic effect on GSH depletion, but also by another mechanism independent of the redox status of the cell.

Multi-faceted regulation of gamma-glutamylcysteine synthetase

Glutathione is an important antioxidant that is involved in numerous cellular activities. gamma-Glutamylcysteine synthetase (gammaGCS) is a key regulatory enzyme in the synthesis of glutathione. It is a heterodimeric zinc metalloprotein that belongs to a unique class of proteins that gain activity due to formation of a reversible disulfide bond. The two subunits of gammaGCS exhibit differential and coordinate transcription regulation. In addition, the subunits are regulated at the posttranscriptional and posttranslational levels. These various levels of regulation allow numerous stimuli to induce or inhibit activity.

Lung glutathione and oxidative stress: implications in cigarette smoke-induced airway disease

Glutathione (GSH), a ubiquitous tripeptide thiol, is a vital intra- and extracellular protective antioxidant in the lungs. The rate-limiting enzyme in GSH synthesis is gamma-glutamylcysteine synthetase (gamma-GCS). The promoter (5'-flanking) region of the human gamma-GCS heavy and light subunits are regulated by activator protein-1 and antioxidant response elements. Both GSH and gamma-GCS expression are modulated by oxidants, phenolic antioxidants, and inflammatory and anti-inflammatory agents in lung cells. gamma-GCS is regulated at both the transcriptional and posttranscriptional levels. GSH plays a key role in maintaining oxidant-induced lung epithelial cell function and also in the control of proinflammatory processes. Alterations in alveolar and lung GSH metabolism are widely recognized as a central feature of many inflammatory lung diseases including chronic obstructive pulmonary disease (COPD). Cigarette smoking, the major factor in the pathogenesis of COPD, increases GSH in the lung epithelial lining fluid of chronic smokers, whereas in acute smoking, the levels are depleted. These changes in GSH may result from altered gene expression of gamma-GCS in the lungs. The mechanism of regulation of GSH in the epithelial lining fluid in the lungs of smokers and patients with COPD is not known. Knowledge of the mechanisms of GSH regulation in the lungs could lead to the development of novel therapies based on the pharmacological or genetic manipulation of the production of this important antioxidant in lung inflammation and injury. This review outlines 1) the regulation of cellular GSH levels and gamma-GCS expression under oxidative stress and 2) the evidence for lung oxidant stress and the potential role of GSH in the pathogenesis of COPD.

Melatonin induces gamma-glutamylcysteine synthetase mediated by activator protein-1 in human vascular endothelial cells

In the present study, we show that melatonin induces the expression of gamma-glutamylcysteine synthetase (gamma-GCS), the rate-limiting enzyme of glutathione (GSH) synthesis, in ECV304 human vascular endothelial cells. One micromolar melatonin induced the expression of gamma-GCS mRNA followed by an increase in the concentration of GSH with a peak at 24 h. An electrophoretic mobility shift assay showed that melatonin stimulates the DNA-binding activity of activator protein-1 (AP-1) as well as retinoid Z receptor/retinoid receptor-related orphan receptor alpha (RZR/RORalpha). ECV304 cells transiently transfected with a plasmid containing the gamma-GCS promoter-luciferase construct showed increased luciferase activity when treated with melatonin. The melatonin-dependent luciferase activity was found in the gamma-GCS promoter containing AP-1 site. The luciferase activity mediated by AP-1 was repressed in the promoter containing RZR/RORalpha site. In addition, cell cycle analysis showed that melatonin increases the number of cells in the G0/G1 phase; however, treatment of the cells with buthionine sulfoximine, a specific inhibitor of gamma-GCS, abolished the effect of melatonin on the cell cycle, suggesting induction of cell arrest by melatonin requires GSH. As conclusion, induction of GSH synthesis by melatonin protects cells against oxidative stress and regulates cell proliferation.

Inflammation and the regulation of glutathione level in lung epithelial cells

Inflammation is a highly complex biochemical protective response to cellular injury. If this process is continuously unchecked, it leads to chronic inflammation, a hallmark of various inflammatory lung diseases. Reactive oxygen intermediates generated by immune cells recruited to the sites of inflammation are a major cause of cell damage. Glutathione (GSH), is a vital intra- and extracellular protective antioxidant in the lungs. The rate-limiting enzyme in GSH synthesis is gamma-glutamylcysteine synthetase (gamma-GCS). Both GSH and gamma-GCS expression are modulated by oxidants, phenolic antioxidants, inflammatory, and anti-inflammatory agents in lung cells. GSH plays a key role in regulating oxidant-induced lung epithelial cell function and also in the control of pro-inflammatory processes. Alterations in the alveolar and lung GSH metabolism are widely recognized as a central feature of many inflammatory lung diseases. Oxidative processes have a fundamental role in lung inflammation through redox-sensitive transcription factors such as NF-kappaB and AP-1, which regulated the genes for pro-inflammatory mediators and protective antioxidant genes such as gamma-GCS. The critical balance between the induction of pro-inflammatory mediators and antioxidant genes in response to oxidative stress at the site of inflammation is not known. Knowledge of the mechanisms of GSH regulation in lung inflammation could lead to the development of novel therapies based on the pharmacological manipulation of the production of this important antioxidant in lung inflammation and injury. This review describes the potential role of GSH for lung oxidant stress, inflammation and injury.