Decreased glutathione levels potentiate the apoptotic efficacy of selenium: possible involvement of p38 and JNK MAPKs—in vitro studies

Protective Effects and Mechanisms of Pourthiaea villosa (Thunb.) Decne. Extract on Hydrogen Peroxide-Induced Skin Aging in Human Dermal Fibroblasts

Skin aging is associated with increased reactive oxygen species (ROS) produced by human cells. These radicals are the main causes of skin aging, and skin cells have developed antioxidant enzymes for protection against ROS-induced damage. Antioxidants play critical roles to prevent ROS-induced aging symptoms. In this study, the antioxidant properties of Pourthiaea villosa (Thunb.) Decne. extract (PVDE) were studied. Human dermal fibroblast (HDF) cells were treated with PVDE to evaluate its antioxidant and antiaging activities and to investigate the underlying mechanisms. The identified compounds were polyols, and phenolic and flavonoid compounds from PVDE by UHPLC-LTQ-IT-MS/MS. PVDE exhibited significant antioxidant effects, as evaluated with reducing power, and ABTS and DPPH radical scavenging activity. Furthermore, PVDE treatment significantly increased antioxidant enzyme expressions and effectively blocked H₂O₂-induced matrix metalloproteinase activity through MAPK signaling pathways in HDFs. Therefore, these results showed that PVDE affords an advantage of being a functional natural material with antioxidant and antiaging effects for the skin.

Selenocompounds in Cancer Therapy: An Overview

In vitro and in vivo experimental models clearly demonstrate the efficacy of Se compounds as anticancer agents, contingent upon chemical structures and concentrations of test molecules, as well as on the experimental model under investigation that together influence cellular availability of compounds, their molecular dynamics and mechanism of action. The latter includes direct and indirect redox effects on cellular targets by the activation and altered compartmentalization of molecular oxygen, and the interaction with protein thiols and Se proteins. As such, Se compounds interfere with the redox homeostasis and signaling of cancer cells to produce anticancer effects that include alterations in key regulatory elements of energy metabolism and cell cycle checkpoints that ultimately influence differentiation, proliferation, senescence, and death pathways. Cys-containing proteins and Se proteins involved in the response to Se compounds as sensors and transducers of anticancer signals, i.e., the pharmacoproteome of Se compounds, are described and include critical elements in the different phases of cancer onset and progression from initiation and escape of immune surveillance to tumor growth, angiogenesis, and metastasis. The efficacy and mode of action on these compounds vary depending on the inorganic and organic form of Se used as either supplement or pharmacological agent. In this regard, differences in experimental/clinical protocols provide options for either chemoprevention or therapy in different human cancers.

Hexavalent chromium induces apoptosis in male somatic and spermatogonial stem cells via redox imbalance

Hexavalent chromium [Cr(VI)], an environmental toxicant, causes severe male reproductive abnormalities. However, the actual mechanisms of toxicity are not clearly understood and have not been studied in detail. The present in vitro study aimed to investigate the mechanism of reproductive toxicity of Cr(VI) in male somatic cells (mouse TM3 Leydig cells and TM4 Sertoli cells) and spermatogonial stem cells (SSCs) because damage to or dysfunction of these cells can directly affect spermatogenesis, resulting in male infertility. Cr(VI) by inducing oxidative stress was cytotoxic to both male somatic cells and SSCs in a dose-dependent manner, and induced mitochondria-dependent apoptosis. Although the mechanism of Cr(VI)-induced cytotoxicity was similar in both somatic cells, the differences in sensitivity of TM3 and TM4 cells to Cr(VI) could be attributed, at least in part, to cell-specific regulation of P-AKT1, P-ERK1/2, and P-P53 proteins. Cr(VI) affected the differentiation and self-renewal mechanisms of SSCs, disrupted steroidogenesis in TM3 cells, while in TM4 cells, the expression of tight junction signaling and cell receptor molecules was affected as well as the secretory functions were impaired. In conclusion, our results show that Cr(VI) is cytotoxic and impairs the physiological functions of male somatic cells and SSCs.

Impact of L-carnitine and Selenium Treatment on Testicular Apoptosis in Rats Exposed to 2.45 GHz Microwave Energy

OBJECTIVE

It has been suggested that electromagnetic radiation (EMR) by wireless devices (2.45 GHz) induces testicular apoptosis. We investigated if supplemental selenium (Se) and L-carnitine may reduce this adverse effect.

MATERIAL

Twelve-week old male Wistar albino rats were used in this study. Twenty-four rats were equally divided into four groups which were named as: sham group, EMR-only, EMR+L-carnitine (1.5 mg L-carnitine/kg/day) and EMR+Se (1.5 mg Se/kg/-every other day).

RESULTS

The level of Bcl-2, Bax, caspase-3 and -8 were compared and a significant difference was found between the sham and EMR-only groups (p < 0.05), and Bcl-2, Bax, caspase-3 and -8 expressions increased in the EMR-only group. The level of Bcl-2, Bax, tumour necrosis factor-alpha (TNF-α), caspase-3 and -8 were compared and a significant difference was found between the sham and EMR+L-carnitine groups (p < 0.05) and Bcl-2, Bax, TNF-α, caspase-3 and -8 expressions increased in the EMR+L-carnitine group. The level of Bcl-2, Bax, TNF-α, caspase-3 and -8 were compared and a significant difference was found between the sham and EMR+Se groups (p < 0.05) and Bcl-2, Bax, TNF-α, caspase-3 and -8 expressions increased in the EMR+Se group. When the expression of caspase-8 was compared, a significant difference was found between the EMR-only and EMR+Se groups (p < 0.05). Caspase-8 expression decreased in EMR+Se group compared with EMR-only group.

CONCLUSION

Electromagnetic radiation exposure resulted in testicular apoptosis in rats, mainly by the intrinsic pathways by down-regulated expression of caspase-8. Reduction in the activation of the intrinsic pathway of apoptosis was found higher with selenium administration compared with L-carnitine administration.

Protection of murine spermatogenesis against ionizing radiation-induced testicular injury by a green tea polyphenol

Epigallocatechin-3-gallate (EGCG), a bioactive polyphenol in green tea, exerts antiapoptotic activity and prevents tissue damage against different stimuli. Herein, we investigated the effects of EGCG treatment to simultaneously improve spermatogenesis following ionizing radiation (IR) (at a dose of 2 Gy). Mice were intraperitoneally injected with 50 mg/kg EGCG or vehicle control 3 days prior to the irradiation, and the treatment lasted intermittently for 24 days. Supplement with exogenous EGCG protected against short-term germ cell loss and attenuated IR-elicited testicular oxidative stress. Mechanistically, prosurvival effects of EGCG treatment upon IR stress were regulated, at least in part, via the mitogen-activated protein kinase/BCL2 family/caspase 3 pathway. Consistently, at post-IR Day 21, histological analyses revealed tubule damage, desquamation of germ cells, and impairment of caudal parameters in irradiated testis, which could be significantly improved by intermittent EGCG treatment. In addition, long-term EGCG application ameliorated the IR-induced blood-testicular barrier permeability and suppressed testicular steroidogenesis, thus exerting a stimulatory effect on the spermatogenic recovery. Collectively, EGCG appeared to efficiently prevent germ cells from radiation-induced cell death via multiple mechanisms. Employment of this bioactive polyphenol should be an attractive strategy to preserve fertility in males exposed to conventional radiation therapy and warrants further investigation.

Selenium compounds as therapeutic agents in cancer

BACKGROUND

With cancer cells encompassing consistently higher production of reactive oxygen species (ROS) and with an induced antioxidant defense to counteract the increased basal ROS production, tumors have a limited reserve capacity resulting in an increased vulnerability of some cancer cells to ROS. Based on this, oxidative stress has been recognized as a tumor-specific target for the rational design of new anticancer agents. Among redox modulating compounds, selenium compounds have gained substantial attention due to their promising chemotherapeutic potential.

SCOPE OF REVIEW

This review aims in summarizing and providing the recent developments of our understanding of the molecular mechanisms that underlie the potential anticancer effects of selenium compounds.

MAJOR CONCLUSIONS

It is well established that selenium at higher doses readily can turn into a prooxidant and thereby exert its potential anticancer properties. However, the biological activity of selenium compounds and the mechanism behind these effects are highly dependent on its speciation and the specific metabolic pathways of cells and tissues. Conversely, the chemical properties and the main molecular mechanisms of the most relevant inorganic and organic selenium compounds as well as selenium-based nanoparticles must be taken into account and are discussed herein.

GENERAL SIGNIFICANCE

Elucidating and deepening our mechanistic knowledge of selenium compounds will help in designing and optimizing compounds with more specific antitumor properties for possible future application of selenium compounds in the treatment of cancer. This article is part of a Special Issue entitled Redox regulation of differentiation and de-differentiation.

Serum Levels of Melatonin and Oxidative Stress Markers and Correlation between Them in Infertile Men

INTRODUCTION

Infertility is the problem of 15% of young couples in different societies. One of the factors that could affect fertility is oxidative stress. Therefore, the aim of the present study is to investigate the level of Melatonin, a free radical scavenger, and its correlation with oxidative biomarkers in infertile men.

METHODS

For this purpose, fertile and infertile men in 2 groups, 30 people in each group, were studied. The fertile men were selected from husbands of patients admitted to Alzahra obstetric and gynecology hospital, according to WHO standards. The infertile men were selected from patients referred to infertility ward. Blood sampling from the participants carried out at a specific time, sera collected and the levels of malondialdehyde, total antioxidant capacity and Melatonin were detected in the sera. The data were analyzed using t-test and Sperman's correlation method.

RESULTS

Melatonin level in the sera from fertile men were 522 (39.32) ng/L and in infertile men were 511.78 (34.6) ng/L. MDA level in fertile and infertile men were 2.26 (0.34) vs 2.99 (0.44) nmol/ml which was significantly different. The level of TAC in the sera from fertile men were significantly higher than in infertile men. The result obtained for correlation coefficient Spearman's test revealed a significant, strong and direct correlation between Melatonin and TAC and a significant and reverse correlation between melatonin and MDA.

CONCLUSION

It is concluded that melatonin could be involved in infertility. In other word, melatonin treatment and antioxidant-rich nutrition could help fertility by combating oxidative stress.

Selenate inhibits adipogenesis through induction of transforming growth factor-β1 (TGF-β1) signaling

Selenium is essential for many aspects of human health. While selenium is known to protect against cancer and cardiovascular diseases, the role of selenium in adipose development is unknown. Here we show that selenate at non-toxic concentration exhibits an anti-adipogenic function in vitro and ex vivo. In addition, selenate induced a morphological change of these cells from fibroblast-like to spindle cell shape. However, other forms of selenium, including selenite and methylseleninic acid, showed either toxic or no effect on adipogenesis and morphology change of preadipocytes. The effects of selenate on adipogenesis and cell morphology change were blunted by the treatment with SB431542, a specific inhibitor of transforming growth factor-β1 (TGF-β1) receptor, neutralization TGF-β1 by its antibody, and knockdown of TGF-β1 in preadipocytes, suggesting a requirement of TGF-β signaling for the anti-adipogenic function of selenate. Among tested forms of selenium, selenate appears to be an effective activator of TGF-β1 expression in preadipocytes. These results indicate that selenate is a novel dietary micromineral that activates TGF-β1 signaling in preadipocytes and modulates adipogenesis.

Selenium compounds, apoptosis and other types of cell death: an overview for cancer therapy

Selenium (Se) is an essential trace element involved in different physiological functions of the human body and plays a role in cancer prevention and treatment. Induction of apoptosis is considered an important cellular event that can account for the cancer preventive effects of Se. The mechanisms of Se-induced apoptosis are associated with the chemical forms of Se and their metabolism as well as the type of cancer studied. So, some selenocompounds, such as SeO₂ involve the activation of caspase-3 while sodium selenite induces apoptosis in the absence of the activation of caspases. Modulation of mitochondrial functions has been reported to play a key role in the regulation of apoptosis and also to be one of the targets of Se compounds. Other mechanisms for apoptosis induction are the modulation of glutathione and reactive oxygen species levels, which may function as intracellular messengers to regulate signaling pathways, or the regulation of kinase, among others. Emerging evidence indicates the overlaps between the apoptosis and other types of cell death such as autophagy. In this review we report different processes of cell death induced by Se compounds in cancer treatment and prevention.

Gender disparity in susceptibility to oxidative stress and apoptosis induced by autoantibodies specific to RLIP76 in vascular cells

AIM

Ral-binding protein 1 (RLIP76) is a cell surface protein that catalyzes the extrusion from the cell of reduced glutathione (GSH) conjugates. We recently demonstrated the presence of serum antibodies to RLIP76 (aaRLIP76) in patients with immune-mediated diseases characterized by vascular dysfunction. The aim of this work was to analyze the possible implication of gender in this issue, investigating the effects of aaRLIP76 in rat vascular smooth muscle cells and human endothelial cells from males and females.

RESULTS

We observed that, after aaRLIP76 treatment, vascular cells from females showed a significantly higher susceptibility to the disturbance of intracellular redox balance, in terms of H(2)O(2) and O(2)(*) production, 4-hydroxy-t-2,3-nonenal and GSH levels, C-Jun NH2 kinase signaling activation, and apoptosis in comparison with cells from males. Interestingly, under mild oxidative stress (H(2)O(2) 30 μm for 30 min), these sex-associated differences became significantly more pronounced. Experiments carried out in the presence of sex hormones in the culture medium clearly suggested that estrogens could significantly increase the susceptibility of cells from females to the effects of aaRLIP76, whereas cells from males appeared unaffected.

INNOVATION

These results open a new perspective in the gender-dependent pathogenic mechanisms of autoimmune diseases characterized by vascular dysfunction.

CONCLUSIONS

Altogether these results suggest that the impairment of RLIP76 by aaRLIP76 can play a role in the damage of vascular cells from females, contributing to the gender-associated pathogenesis of immune-mediated vascular diseases.

Promising effects of the 4HPR-BSO combination in neuroblastoma monolayers and spheroids

To enhance the efficacy of fenretinide (4HPR)-induced reactive oxygen species (ROS) in neuroblastoma, 4HPR was combined with buthionine sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, in neuroblastoma cell lines and spheroids, the latter being a three-dimensional tumor model. 4HPR exposure (2.5-10 μM, 24 h) resulted in ROS induction (114-633%) and increased GSH levels (68-120%). A GSH depletion of 80% of basal levels was observed in the presence of BSO (25-100 μM, 24 h). The 4HPR-BSO combination resulted in slightly increased ROS levels (1.1- to 1.3-fold) accompanied by an increase in cytotoxicity (110-150%) compared to 4HPR treatment alone. A correlation was observed between the ROS-inducing capacity of each cell line and the increase in cytotoxicity induced by 4HPR-BSO compared to 4HPR. No significant correlation between baseline antioxidant levels and sensitivity to 4HPR or BSO was observed. In spheroids, 4HPR-BSO induced a strong synergistic growth retardation and induction of apoptosis. Our data show that BSO increased the cytotoxic effects of 4HPR in neuroblastoma monolayers and spheroids in ROS-producing cell lines. This indicates that the 4HPR-BSO combination might be a promising new strategy in the treatment of neuroblastoma.

Glutaredoxin 2a, a mitochondrial isoform, plays a protective role in a human cell line under serum deprivation

The roles of mitochondrial glutaredoxin (Grx2a) under serum deprivation were assessed using the human stable HepG2 cell lines overexpressing or down-regulating Grx2a. The Grx2a-overexpressing stable cells displayed enhanced proliferation, decreased reactive oxygen species (ROS) and caspase-3 activity levels, and increased total GSH level, compared to the vector control cells. These characteristics of the overexpressing stable cells were reversed by down-regulating Grx2a in the same cell line. In the limited serum conditions, the Grx2a-overexpressing stable pcDNA3.0/HA-Grx2a cells exhibited higher cellular viabilities and total GSH level, and showed much lower enhancement in ROS and caspase-3 activity levels than the vector control pcDNA3.0/HA cells. However, the Grx2a-down-regulating stable cells gave rise to diminished cellular viabilities and further decreased total GSH level, and contained significantly higher ROS and caspase-3 activity levels, under serum deprivation than the vector control cells. These results suggest that Grx2a plays proliferative and anti-apoptotic roles under serum deprivation.

Disruption of redox homeostasis and induction of apoptosis by suppression of glutathione synthetase expression in a mammalian cell line

The stable HepG2 transfectants anti-sensing expression of the glutathione synthetase (GS) gene exhibited delayed cell growth and increased reactive oxygen species (ROS) level. After the treatment with hydrogen peroxide, the intracellular ROS level was much higher in the stable transfectants than in the vector control cells. However, the GSH levels decreased more significantly in the stable transfectants than in the vector control cells, in the presence of hydrogen peroxide. Hydrogen peroxide-induced apoptosis of the stable transfectants was notably higher than that of the vector control cells. The GS anti-sense RNAs rendered the HepG2 cells more sensitive to growth arrest caused by glucose deprivation. They also sensitized the HepG2 cells to cadmium chloride (Cd) and nitric oxide (NO)-generating sodium nitroprusside (SNP). In brief, the results confirm that GS plays an important role in the defense of the human hepatoma cells against oxidative stress by reducing apoptosis and maintaining redox homeostasis.

Selenium in the prevention of human cancers

Selenium is an essential element with remarkable chemical properties. The similarity to sulphur results in a number of chemical interactions mainly connected to thiols and redox processes. The element modulates cell growth; in low concentrations it is absolutely required for growth and an essential component of serum free growth media. However moderate to high concentrations potently inhibit cell growth. The inhibitory effects are tumour specific and selenium induces apoptosis in malignant cells at concentrations that do not affect the viability of normal cells. Depending on concentration and chemical form selenium may prevent or treat tumour disease. Selenium supplementation has been found to be of value in preventing hepatocellular cancer by hepatitis B, in reducing the incidence of liver cancer in general and in decreasing mortality of colorectal, lung and prostate cancer. This review focuses on the current knowledge of the preventive effects of selenium with special emphasis on major human tumours. The unique chemical properties along with metabolism and preventive mechanisms are also discussed.

Gaining insights into the Bcr-Abl activity-independent mechanisms of resistance to imatinib mesylate in KCL22 cells: a comparative proteomic approach

Imatinib mesylate is a potent inhibitor of Bcr-Abl tyrosine kinase, an oncoprotein that plays a key role in the development of chronic myeloid leukemia. Consequently, imatinib is used as front-line therapy for this disease. A major concern in imatinib treatment is the emergence of resistance to the drug. Here we used the imatinib-resistant KCL22R and imatinib-sensitive KCL22S cells in which none of the known resistance mechanisms has been detected and hence novel Bcr-Abl activity-independent mechanisms could be envisaged. We characterized proteins that were differentially expressed between the KCL22R and KCL22S cells. Using two-dimensional differential gel electrophoresis coupled with mass spectrometry and Western blot analysis we identified 51 differentially expressed proteins: 27 were over-expressed and 24 were under-expressed in KCL22R versus KCL22S cells. Several of these proteins are likely to be involved in such survival mechanisms as modulation of redox balance and activation of anti-apoptotic pathways mediated by NF-kappaB and Ras-MAPK signaling. The data reported may be useful for further studies on mechanisms of imatinib resistance and for the screening of biomarkers to develop new combinatorial therapeutic approaches.

ACh receptors link two signaling pathways to neuroprotection against glutamate-induced excitotoxicity in isolated RGCs

Previous studies have reported that activation of nicotinic acetylcholine (ACh) receptors (nAChRs) on cultured pig retinal ganglion cells (RGCs) has a neuroprotective effect against glutamate-induced excitotoxicity. However, the mechanism linking nAChRs to neuroprotection is unknown. Here, we tested the hypothesis that signaling cascades involving p38 mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) --> Akt are involved in linking activation of nAChRs to neuroprotection in isolated pig RGCs. In ELISA studies, regulation of phosphorylated p38 MAPK and Akt were analyzed after inducing excitotoxicity or neuroprotection in the presence and absence of specific inhibitors for p38 MAPK and PI3K. ELISA results demonstrated that ACh significantly increased phosphorylated Akt and decreased p38 MAPK. Glutamate increased phosphorylated p38 MAPK but had no significant effect on phosphorylated Akt. Other ELISA studies using p38 MAPK and PI3K inhibitors also supported the hypothesis that ACh up-regulated Bcl-2 levels downstream from PI3K and Akt, whereas glutamate down-regulated Bcl-2 levels downstream from p38 MAPK. RGC survival was subsequently assessed by culturing RGCs in conditions to induce excitotoxicity or neuroprotection in the presence or absence of specific inhibitors of p38 MAPK or PI3K. The p38 MAPK inhibitor significantly decreased the number of RGCs that died by glutamate-induced excitotoxicity but had no effect on the number of cells that survived because of ACh-induced neuroprotection. PI3K inhibitors significantly decreased cell survival caused by ACh-induced neuroprotection but had no effect on cell death caused by glutamate-induced excitotoxicity. These results demonstrate that glutamate mediates excitotoxicity through the p38 MAPK signaling pathway and that ACh provides neuroprotection by stimulating the PI3K --> Akt --> Bcl-2 signaling pathway and inhibiting the p38 MAPK --> Bcl-2 pathway.

Treatment of human cancer cells with selenite or tellurite in combination with auranofin enhances cell death due to redox shift

Selenium is an essential trace element incorporated as selenocysteine in 25 human selenoproteins. Among them are thioredoxin reductases (TrxR) and glutathione peroxidases, all central proteins in the regulation of the cellular thiol redox state. In this paper the effects of selenite and tellurite treatment in human cancer cells are reported and compared. Our results show that both selenite and tellurite, at relatively low concentrations, are able to increase the expression of mitochondrial and cytosolic TrxR in cisplatin-sensitive (2008) and -resistant (C13*) phenotypes. We further investigated the cellular effects induced by selenite or tellurite in combination with the specific TrxR inhibitor auranofin. Selenite pretreatment induced a dramatic increase in auranofin cytotoxicity in both resistant and sensitive cells. Investigation of TrxR activity and expression levels as well as the cellular redox state demonstrated the involvement of TrxR inhibition and redox changes in selenite and auranofin combined action.