Certain carotenoids enhance the intracellular glutathione level in a murine cultured macrophage cell line by inducing glutamate-cysteine-ligase

Preventive Action of Beta-Carotene against the Indoxyl Sulfate-Induced Renal Dysfunction in Male Adult Zebrafish via Regulations of Mitochondrial Inflammatory and β-Carotene Oxygenase-2 Actions

Indoxyl sulfate (IS) is a metabolic byproduct of indole metabolism. IS readily interacts with the mitochondrial redox metabolism, leading to altered renal function. The β-carotene oxygenase-2 (BCO2) enzyme converts carotenoids to intermediate products. However, the role of β-carotene (BC) in IS-induced renal dysfunction in zebrafish and their modulatory action on BCO2 and mitochondrial inflammations have not been explored yet. Hence, the present study is designed to investigate the role of BC in the attenuation of IS-induced renal dysfunction via regulations of mitochondrial redox balance by BCO2 actions. Renal dysfunction was induced by exposure to IS (10 mg/L/hour/day) for 4 weeks. BC (50 and 100 mg/L/hour/day) and coenzyme Q10 (CoQ10; 20 mg/L/hour/day) were added before IS exposure. BC attenuated the IS-induced increase in blood urea nitrogen (BUN) and creatinine concentrations, adenosine triphosphate (ATP), and complex I activity levels, and the reduction of renal mitochondrial biomarkers, i.e., BCO2, superoxide dismutase-2 (SOD2), glutathione peroxidase-1 (GPX1), reduced and oxidized glutathione (GSH/GSSG) ratio, and carbonylated proteins. Moreover, renal histopathological changes were analyzed by the eosin and hematoxylin staining method. As a result, the administration of BC attenuated the IS-induced renal damage via the regulation of mitochondrial function.

Sulodexide Increases Glutathione Synthesis and Causes Pro-Reducing Shift in Glutathione-Redox State in HUVECs Exposed to Oxygen–Glucose Deprivation: Implication for Protection of Endothelium against Ischemic Injury

Sulodexide (SDX), a purified glycosaminoglycan mixture used to treat vascular diseases, has been reported to exert endothelial protective effects against ischemic injury. However, the mechanisms underlying these effects remain to be fully elucidated. The emerging evidence indicated that a relatively high intracellular concentration of reduced glutathione (GSH) and a maintenance of the redox environment participate in the endothelial cell survival during ischemia. Therefore, the aim of the present study was to examine the hypothesis that SDX alleviates oxygen–glucose deprivation (OGD)-induced human umbilical endothelial cells’ (HUVECs) injury, which serves as the in vitro model of ischemia, by affecting the redox state of the GSH: glutathione disulfide (GSSG) pool. The cellular GSH, GSSG and total glutathione (tGSH) concentrations were measured by colorimetric method and the redox potential (ΔEh) of the GSSG/2GSH couple was calculated, using the Nernst equation. Furthermore, the levels of the glutamate–cysteine ligase catalytic subunit (GCLc) and the glutathione synthetase (GSS) proteins, a key enzyme for de novo GSH synthesis, were determined using enzyme-linked immunoassay (ELISA). We demonstrated that the SDX treatment in OGD conditions significantly elevated the intracellular GSH, enhanced the GSH:GSSG ratio, shifting the redox potential to a more pro-reducing status. Furthermore, SDX increased the levels of both GCLc and GSS. The results show that SDX protects the human endothelial cells against ischemic stress by affecting the GSH levels and cellular redox state. These changes suggest that the reduction in the ischemia-induced vascular endothelial cell injury through repressing apoptosis and oxidative stress associated with SDX treatment may be due to an increase in GSH synthesis and modulation of the GSH redox system.

Antioxidant and Signal-Modulating Effects of Brown Seaweed-Derived Compounds against Oxidative Stress-Associated Pathology

The biological and therapeutic properties of seaweeds have already been well known. Several studies showed that among the various natural marine sources of antioxidants, seaweeds have become a potential source of antioxidants because of their bioactive compounds. Most of the metabolic diseases are caused by oxidative stress. It is very well known that antioxidants have a pivotal role in the treatment of those diseases. Recent researches have revealed the potential activity of seaweeds as complementary medicine, which have therapeutic properties for health and disease management. Among the seaweeds, brown seaweeds (Phaeophyta) and their derived bioactive substances showed excellent antioxidant properties than other seaweeds. This review focuses on brown seaweeds and their derived major bioactive compounds such as sulfated polysaccharide, polyphenol, carotenoid, and sterol antioxidant effects and molecular mechanisms in the case of the oxidative stress-originated disease. Antioxidants have a potential role in the modification of stress-induced signaling pathways along with the activation of the oxidative defensive pathways. This review would help to provide the basis for further studies to researchers on the potential antioxidant role in the field of medical health care and future drug development.

Retinol but not retinoic acid can enhance the glutathione level, in a manner similar to β-carotene, in a murine cultured macrophage cell line

SCOPE

We evaluated the potential of retinol and retinoic acid (RA) to enhance intracellular glutathione (GSH) levels in a murine cultured macrophage cell line, RAW264, to investigate whether the RA signaling pathway is involved in the β-carotene-induced GSH enhancement.

METHODS AND RESULTS

We examined GSH levels in RAW264 cells cultured in media supplemented with β-carotene and various inhibitors (ER50891 for RA receptor (RAR)α, CD2665 for RARβ/γ, or HX531 for all subtypes of retinoid X receptor (RXR)), to verify each inhibitor's activity against β-carotene, as well as in media supplemented with various stimulants (AM80 for RARα, CD2314 for RARβ, CD437 for RARγ, or SR11237 for RXR), to compare their activity with that of β-carotene. We also examined the GSH level and glutamate-cysteine-ligase (GCL) expression in RAW264 cells cultured in all-trans RA- or retinol-supplemented media. Enhanced GSH production was not inhibited by any tested antagonist, and, apart from β-carotene, no agonist induced GSH production. Retinol, but not all-trans RA, enhanced GSH synthesis and increased GCL expression, similar to that observed with β-carotene.

CONCLUSION

The RA signaling pathway may not be involved in the β-carotene-induced enhancement of GSH levels in RAW264 cells, whereas, like β-carotene, retinol can enhance the GSH level and GCL expression.

Dietary Carotenoid Roles in Redox Homeostasis and Human Health

Classic nutrition believed that healthy diets should simply provide sufficient antioxidant loads to organisms, to hamper free radical processes and avoid oxidative stress. Current redox biology was proven much more intricate. Carotenoids are bioactive compounds in the human diet with a multifaceted role in redox metabolism. This perspective discusses the participation of α/β-carotene, lutein, zeaxanthin, lycopene, β-cryptoxanthin, astaxanthin, and derivatives in redox homeostasis focusing on (i) their antioxidant/pro-oxidant activities, (ii) control of gene expression via Nrf2-Keap1 and NF-κB pathways, and (iii) their link with (sub)cellular redox circuits, as part of the "redox code" that orchestrates physiological processes and health in humans.

Hepatoprotective effects of rice-derived peptides against acetaminophen-induced damage in mice

Glutathione, the most abundant intracellular antioxidant, protects cells against reactive oxygen species induced oxidative stress and regulates intracellular redox status. We found that rice peptides increased intracellular glutathione levels in human hepatoblastoma HepG2 cells. Acetaminophen is a commonly used analgesic. However, an overdose of acetaminophen causes severe hepatotoxicity via depletion of hepatic glutathione. Here, we investigated the protective effects of rice peptides on acetaminophen-induced hepatotoxicity in mice. ICR mice were orally administered rice peptides (0, 100 or 500 mg/kg) for seven days, followed by the induction of hepatotoxicity via intraperitoneal injection of acetaminophen (700 mg/kg). Pretreatment with rice peptides significantly prevented increases in serum alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase levels and protected against hepatic glutathione depletion. The expression of γ-glutamylcysteine synthetase, a key regulatory enzyme in the synthesis of glutathione, was decreased by treatment with acetaminophen, albeit rice peptides treatment recovered its expression compared to that achieved treatment with acetaminophen. In addition, histopathological evaluation of the livers also revealed that rice peptides prevented acetaminophen-induced centrilobular necrosis. These results suggest that rice peptides increased intracellular glutathione levels and could protect against acetaminophen-induced hepatotoxicity in mice.

Quercetin affects glutathione levels and redox ratio in human aortic endothelial cells not through oxidation but formation and cellular export of quercetin-glutathione conjugates and upregulation of glutamate-cysteine ligase

Endothelial dysfunction due to vascular inflammation and oxidative stress critically contributes to the etiology of atherosclerosis. The intracellular redox environment plays a key role in regulating endothelial cell function and is intimately linked to cellular thiol status, including and foremost glutathione (GSH). In the present study we investigated whether and how the dietary flavonoid, quercetin, affects GSH status of human aortic endothelial cells (HAEC) and their response to oxidative stress. We found that treating cells with buthionine sulfoximine to deplete cellular GSH levels significantly reduced the capacity of quercetin to inhibit lipopolysaccharide (LPS)-induced oxidant production. Furthermore, incubation of HAEC with quercetin caused a transient decrease and then full recovery of cellular GSH concentrations. The initial decline in GSH was not accompanied by a corresponding increase in glutathione disulfide (GSSG). To the contrary, GSSG levels, which were less than 0.5% of GSH levels at baseline (0.26±0.01 vs. 64.7±1.9 nmol/mg protein, respectively), decreased by about 25% during incubation with quercetin. As a result, the GSH: GSSG ratio increased by about 70%, from 253±7 to 372±23. These quercetin-induced changes in GSH and GSSG levels were not affected by treating HAEC with 500 µM ascorbic acid phosphate for 24 h to increase intracellular ascorbate levels. Incubation of HAEC with quercetin also led to the appearance of extracellular quercetin-glutathione conjugates, which was paralleled by upregulation of the multidrug resistance protein 1 (MRP1). Furthermore, quercetin slightly but significantly increased mRNA and protein levels of glutamate-cysteine ligase (GCL) catalytic and modifier subunits. Taken together, our results suggest that quercetin causes loss of GSH in HAEC, not because of oxidation but due to formation and cellular export of quercetin-glutathione conjugates. Induction by quercetin of GCL subsequently restores GSH levels, thereby suppressing LPS-induced oxidant production.

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Glutathione mediates the antioxidant effects of quercetin in human aortic endothelial cells.

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Quercetin affects cellular levels of GSH and GSSG, resulting in an increased redox ratio.

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Quercetin forms conjugates with GSH, which are rapidly excreted from the cells.

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Quercetin induces glutamate-cysteine ligase and multidrug resistance protein 1 via Nrf2 activation.

Nitric oxide-eluting scaffolds and their interaction with smooth muscle cells in vitro

Fabrication of scaffolds loaded with nitric oxide (NO) donors (S-nitrosoglutathione, GSNO, and isosorbide mononitrate, ISMN) with suitable cell compatibility and optimized properties for tissue-engineering applications is reported using "in situ" technique. Based on FDA-approved polymer, solvent and dosage forms, this gentle process allowed the incorporation of the GSNO labile drug into scaffolds made of either poly(lactide-co-glycolide) (PLGA) or PLGA/poly(ɛ-caprolactone) (PCL) blend. During scaffolds manufacturing process including washing cycles, NO donors were leached from scaffolds. However, GSNO and ISMN concentrations in the last washing medium (10(-7) M and 10(-4) M, respectively) were in the range of cell suitability for tissue engineering. Further morphological analyses indicated that smoother surfaces with fewer but bigger pores (compatible with cell penetration and ingrowth) were obtained with PLGA in comparison with PLGA/PCL scaffolds. Among all tested matrices, only unloaded PLGA and GSNO-loaded PLGA/PCL exhibited intermediate cell anchorage, with mitochondrial activity close to the control and an increase in protein content, a prognostic for scaffold cell colonization, defining them as promising candidates. Deeper analyses of these two scaffolds looking at intracellular redox balance through reactive oxygen species production, glutathione, S-nitrosothiols, and nitrite ions content exhibited GSNO-loaded PLGA/PCL as the best of all tested 3D scaffolds for tissue engineering.