Role of ERK in Hydrogen Peroxide-Induced Cell Death of Human Glioma Cells

Loss of Kmt2c in vivo leads to EMT, mitochondrial dysfunction and improved response to lapatinib in breast cancer

Deep sequencing of human tumours has uncovered a previously unappreciated role for epigenetic regulators in tumorigenesis. H3K4 methyltransferase KMT2C/MLL3 is mutated in several solid malignancies, including more than 10% of breast tumours. To study the tumour suppressor role of KMT2C in breast cancer, we generated mouse models of Erbb2/Neu, Myc or PIK3CA-driven tumorigenesis, in which the Kmt2c locus is knocked out specifically in the luminal lineage of mouse mammary glands using the Cre recombinase. Kmt2c knock out mice develop tumours earlier, irrespective of the oncogene, assigning a bona fide tumour suppressor role for KMT2C in mammary tumorigenesis. Loss of Kmt2c induces extensive epigenetic and transcriptional changes, which lead to increased ERK1/2 activity, extracellular matrix re-organization, epithelial-to-mesenchymal transition and mitochondrial dysfunction, the latter associated with increased reactive oxygen species production. Loss of Kmt2c renders the Erbb2/Neu-driven tumours more responsive to lapatinib. Publicly available clinical datasets revealed an association of low Kmt2c gene expression and better long-term outcome. Collectively, our findings solidify the role of KMT2C as a tumour suppressor in breast cancer and identify dependencies that could be therapeutically amenable.

Therapeutic Potential of Berberine in the Treatment of Glioma: Insights into Its Regulatory Mechanisms

Glioma is known as one of the most common primary intracranial tumors accounting for four-fifths of malignant brain tumors. There are several biological pathways that play a synergistic, pathophysiological role in glioma, including apoptosis, autophagy, oxidative stress, and cell cycle arrest. According to previous rese arches, the drugs used in the treatment of glioma have been associated with significant limitations. Therefore, improved and/or new therapeutic platforms are required. In this regard, multiple flavonoids and alkaloids have been extensively studied in the treatment of glioma. Berberine is a protoberberine alkaloid with wide range of pharmacological activities, applicable to various pathological conditions. Few studies have reported beneficial roles of berberine in glioma. Berberine exerts its pharmacological functions in glioma by controlling different molecular and cellular pathways. We reviewed the existing knowledge supporting the use of berberine in the treatment of glioma and its effects on molecular and cellular mechanisms.

Neuroprotective effects of zonisamide on cerebral ischemia injury via inhibition of neuronal apoptosis

It is known that neuronal apoptosis contributes to pathology of cerebral ischemia injury. Zonisamide (ZNS) has shown anti-apoptosis effects in recent studies. The present study investigated whether the anti-apoptotic effect can account for the neuroprotective action of ZNS on cerebral ischemia. Neuronal cells were maintained under oxygen-glucose deprivation conditions to simulate cerebral ischemia and treated with ZNS simultaneously. The apoptosis of the cells and expression of apoptosis-related proteins were investigated by flow cytometry and western blot analysis, respectively. A cerebral ischemia mouse model was created via middle cerebral artery occlusion, and the mice were treated with ZNS. Neurological deficit scores and infarct volumes of the cerebral ischemia mice were measured. The apoptosis status of the neuronal cells was evaluated by TUNEL staining. In vitro, the ZNS treatment inhibited both the apoptosis of the neuronal cells and apoptosis-related protein expression (caspase-3, caspase-8, and calpain-1) induced by the oxygen-glucose deprivation. The anti-apoptosis effect of ZNS could occur through the blocking of reactive oxygen species. Moreover, ZNS treatment significantly ameliorated neurological deficits and reduced infarct volumes in the cerebral ischemia mice model. In this study, ZNS exerted neuroprotective effects by inhibition of apoptosis in neuronal cells in cerebral ischemia. Therefore, ZNS might be a promising therapy for cerebral ischemia.

SYPL1 Inhibits Apoptosis in Pancreatic Ductal Adenocarcinoma via Suppression of ROS-Induced ERK Activation

Synaptophysin-like 1 (SYPL1) is a neuroendocrine-related protein. The role of SYPL1 in pancreatic ductal adenocarcinoma (PDAC) and the underlying molecular mechanism remain unclarified. Here, after analyzing five datasets (GSE15471, GSE16515, GSE28735, TCGA, and PACA-AU) and 78 PDAC patients from Sun Yat-sen University Cancer Center, we demonstrated that SYPL1 was upregulated in PDAC and that a high level of SYPL1 indicated poor prognosis. Bioinformatics analysis implied that SYPL1 was related to cell proliferation and cell death. To validate these findings, gain-of-function and loss-of-function experiments were carried out, and we found that SYPL1 promoted cell proliferation in vitro and in vivo and that it protected cells from apoptosis. Mechanistic studies revealed that sustained extracellular-regulated protein kinase (ERK) activation was responsible for the cell death resulting from knockdown of SYPL1. In addition, bioinformatics analysis showed that the expression of SYPL1 positively correlated with antioxidant activity. Reactive oxygen species (ROS) were upregulated in cells with SYPL1 knockdown and vice versa. Upregulated ROS led to ERK activation and cell death. These results suggest that SYPL1 plays a vital role in PDAC and promotes cancer cell survival by suppressing ROS-induced ERK activation.

Potential implications of hydrogen peroxide in the pathogenesis and therapeutic strategies of gliomas

Glioma is the most common type of primary brain tumor, and it has a high mortality rate. Currently, there are only a few therapeutic approaches for gliomas, and their effects are unsatisfactory. Therefore, uncovering the pathogenesis and exploring more therapeutic strategies for the treatment of gliomas are urgently needed to overcome the ongoing challenges. Cellular redox imbalance has been shown to be associated with the initiation and progression of gliomas. Among reactive oxygen species (ROS), hydrogen peroxide (H₂O₂) is considered the most suitable for redox signaling and is a potential candidate as a key molecule that determines the fate of cancer cells. In this review, we discuss the potential cellular and molecular roles of H₂O₂ in gliomagenesis and explore the potential implications of H₂O₂ in radiotherapy and chemotherapy and in the ongoing challenges of current glioma treatment. Moreover, we evaluate H₂O₂ as a potential redox sensor and potential driver molecule of nanocatalytic therapeutic strategies for glioma treatment.

M1 macrophage mediated increased reactive oxygen species (ROS) influence wound healing via the MAPK signaling in vitro and in vivo

Thulium laser resection of the prostate (TmLRP), a major treatment for benign prostatic hyperplasia (BPH), has several postoperative complications that affect the patients' quality of life. The aim of this study was to investigate the effect of the M1 macrophage-secreted reactive oxygen species (ROS) on prostatic wound healing, and the role of MAPK signaling in this process. A co-culture model in vitro was established using macrophages and prostate epithelial or stromal cells. Cell proliferation, migration, apoptosis, MAPK pathway-related gene expression levels were evaluated by standard assays. In addition, an in vivo model of prostatectomy was established in beagles by subjecting them to TmLRP, and were either treated with N-acetyl-L-cysteine (NAC) and or placebo. Wound healing and re-epithelialization were analyzed histopathologically in both groups, in addition to macrophage polarization, oxidative stress levels and MAPK pathway-related proteins expressions. Intracellular ROS levels were significantly increased in the prostate epithelial and stromal cells following co-culture with M1-like macrophages and H₂O₂ exposure via MAPK activation, which affected their proliferation, migration and apoptosis, and delayed the wound healing process. The cellular functions and wound healing capacity of the prostate cells were restored by blocking or clearing the macrophage-secreted ROS. In the beagle model, increased ROS levels impaired cellular functions, and appropriate removing ROS accelerated the wound healing process.

The testosterone metabolite 3α-androstanediol inhibits oxidative stress-induced ERK phosphorylation and neurotoxicity in SH-SY5Y cells through an MKP3/DUSP6-dependent mechanism

Testosterone exerts neuroprotective effects on the brain, but the mechanisms by which these effects are exerted appear to be different in males and females. While in females they involve local conversion to estradiol, in males they may be androgen receptor-dependent, or mediated through metabolism to neurosteroids such as 5α-androstane-3α,17β-diol (3α-diol), which acts through different mechanisms than testosterone itself. Recently, we demonstrated that 3α-diol can protect neurons and neuronal-like cells against oxidative stress-induced neurotoxicity associated with prolonged phosphorylation of the extracellular signal-regulated kinase (ERK). The mechanism(s) responsible for these effects remain unknown. In the present study, we sought to determine whether the ERK-specific phosphatase, mitogen-activated protein kinase phosphatase 3/dual specificity phosphatase 6 (MKP3/DUSP6), is involved in the cytoprotective effects of 3α-diol in SH-SY5Y human female neuroblastoma cells. 3α-diol inhibited ERK phosphorylation and ameliorated cell death induced by the oxidative stressor hydrogen peroxide (H₂O₂). These protective effects were significantly reduced by pre-treatment with the MKP3/DUSP6 inhibitor BCI. In addition, H₂O₂ decreased expression of MKP3/DUSP6, and this was prevented by co-treatment with 3α-diol. These findings suggest that the protective effects of 3α-diol are mediated through regulation of ERK phosphorylation in neurotoxic conditions and indicate that these effects may be exerted through modulation of MKP3/DUSP6. Targeting the regulation of MKP3/DUSP6 may be beneficial in reducing toxicity under conditions of oxidative stress.

Chronic exposure of the RAW246.7 macrophage cell line to H2O2 leads to increased catalase expression

Altered cellular redox states have been associated with a variety of chronic diseases, especially those correlated with inflammation. One of the primary oxidants generated during the inflammatory response is hydrogen peroxide (H₂O₂). Macrophages in particular are thought to produce large amounts of H₂O₂, however they must somehow protect themselves from the potentially lethal concentrations they produce. To investigate how immune cells protect themselves from H₂O₂ observed in chronic inflammatory diseases, we established an adapted population of macrophages in culture by gradually increasing sub-lethal concentrations of H₂O₂ in the media to typically lethal concentrations over the course of more than a month. The resulting cells were tolerant to very high concentrations of H₂O₂. Further investigation revealed that the cells were able to rapidly neutralize the H₂O₂ added to their culture media due to a dramatic upregulation of catalase. Interestingly, T cells, which are also implicated in chronic inflammation, were unable to adapt to H₂O₂ under the same procedure, however when T cells were cultured in media from adapted macrophages, they were able to survive typically lethal concentrations of H₂O₂. These data support the hypothesis that macrophages are able to protect themselves and neighboring cells during states of chronic inflammation from the oxidizing environment they create.

Phosphorylation of human TRM9L integrates multiple stress-signaling pathways for tumor growth suppression

The human transfer RNA methyltransferase 9-like gene (TRM9L, also known as KIAA1456) encodes a negative regulator of tumor growth that is frequently silenced in many forms of cancer. While TRM9L can inhibit tumor cell growth in vivo, the molecular mechanisms underlying the tumor inhibition activity of TRM9L are unknown. We show that oxidative stress induces the rapid and dose-dependent phosphorylation of TRM9L within an intrinsically disordered domain that is necessary for tumor growth suppression. Multiple serine residues are hyperphosphorylated in response to oxidative stress. Using a chemical genetic approach, we identified a key serine residue in TRM9L that undergoes hyperphosphorylation downstream of the oxidative stress-activated MEK (mitogen-activated protein kinase kinase)-ERK (extracellular signal-regulated kinase)-RSK (ribosomal protein S6 kinase) signaling cascade. Moreover, we found that phosphorylated TRM9L interacts with the 14-3-3 family of proteins, providing a link between oxidative stress and downstream cellular events involved in cell cycle control and proliferation. Mutation of the serine residues required for TRM9L hyperphosphorylation and 14-3-3 binding abolished the tumor inhibition activity of TRM9L. Our results uncover TRM9L as a key downstream effector of the ERK signaling pathway and elucidate a phospho-signaling regulatory mechanism underlying the tumor inhibition activity of TRM9L.

Redox modulation of thimet oligopeptidase activity by hydrogen peroxide

Thimet oligopeptidase (EC 3.4.24.15, TOP) is a cytosolic mammalian zinc protease that can process a diversity of bioactive peptides. TOP has been pointed out as one of the main postproteasomal enzymes that process peptide antigens in the MHC class I presentation route. In the present study, we describe a fine regulation of TOP activity by hydrogen peroxide (H₂O₂). Cells from a human embryonic kidney cell line (HEK293) underwent an ischemia/reoxygenation-like condition known to increase H₂O₂ production. Immediately after reoxygenation, HEK293 cells exhibited a 32% increase in TOP activity, but no TOP activity was observed 2 h after reoxygenation. In another model, recombinant rat TOP (rTOP) was challenged by H₂O₂ produced by rat liver mitoplasts (RLMt) alone, and in combination with antimycin A, succinate, and antimycin A plus succinate. In these conditions, rTOP activity increased 17, 30, 32 and 38%, respectively. Determination of H₂O₂ concentration generated in reoxygenated cells and mitoplasts suggested a possible modulation of rTOP activity dependent on the concentration of H₂O₂. The measure of pure rTOP activity as a function of H₂O₂ concentration corroborated this hypothesis. The data fitted to an asymmetrical bell-shaped curve in which the optimal activating H₂O₂ concentration was 1.2 nM, and the maximal inhibition (75% about the control) was 1 μm. Contrary to the oxidation produced by aging associated with enzyme oligomerization and inhibition, H₂O₂ oxidation produced sulfenic acid and maintained rTOP in the monomeric form. Consistent with the involvement of rTOP in a signaling redox cascade, the H₂O₂-oxidized rTOP reacted with dimeric thioredoxin-1 (TRx-1) and remained covalently bound to one subunit of TRx-1.

ROS signalling in the biology of cancer

Increased reactive oxygen species (ROS) production has been detected in various cancers and has been shown to have several roles, for example, they can activate pro-tumourigenic signalling, enhance cell survival and proliferation, and drive DNA damage and genetic instability. Counterintuitively ROS can also promote anti-tumourigenic signalling, initiating oxidative stress-induced tumour cell death. Tumour cells express elevated levels of antioxidant proteins to detoxify elevated ROS levels, establish a redox balance, while maintaining pro-tumourigenic signalling and resistance to apoptosis. Tumour cells have an altered redox balance to that of their normal counterparts and this identifies ROS manipulation as a potential target for cancer therapies. This review discusses the generation and sources of ROS within tumour cells, the regulation of ROS by antioxidant defence systems, as well as the effect of elevated ROS production on their signalling targets in cancer. It also provides an insight into how pro- and anti-tumourigenic ROS signalling pathways could be manipulated in the treatment of cancer.

Protective effects of casein-derived peptide VLPVPQK against hydrogen peroxide–induced dysfunction and cellular oxidative damage in rat osteoblastic cells

Oxidative stress inhibits osteoblast differentiation and function that lead to the development of osteoporosis. Casein-derived peptide VLPVPQK (PEP), a potent antioxidant, was isolated from β-casein of buffalo milk. We used an in vitro oxidative stress model induced by hydrogen peroxide (H2O2) in rat osteoblastic cells to investigate the protective effects of PEP against H2O2-induced dysfunction and oxidative damage. Cells were pretreated with PEP (50–200 ng/mL) for 2, 7 or 21 days followed by 0.3 mM H2O2 treatment for 24 h and then markers of osteogenic development, oxidative damage and apoptosis were examined. PEP significantly increased the viability and differentiation markers of osteoblast cells such as alkaline phosphatase and calcium mineralization. Moreover, PEP suppressed the production of reactive oxygen species (ROS), lipid peroxidation and ameliorated H2O2-induced reduction in glutathione, superoxide dismutase and catalase activities. In addition, PEP partially inhibited caspase-9 and-3 activities and reduced propidium iodide–positive cells. Altogether, our results demonstrated that PEP could protect rat osteoblast against H2O2-induced dysfunction and oxidative damage by reduction of ROS production, lipid peroxidation and increased antioxidant enzyme activities. Thus, our data suggest that PEP might be a valuable protective agent against oxidative stress–related diseases such as osteoporosis.

Long lasting MDM2/Translocator protein modulator: a new strategy for irreversible apoptosis of human glioblastoma cells

The development of multi-target drugs and irreversible modulators of deregulated signalling proteins is the major challenge for improving glioblastoma multiforme (GBM) treatment. Reversible single-target drugs are not sufficient to sustain a therapeutic effect over time and may favour the activation of alternative signalling pathways and the onset of resistance phenomena. Thus, a multi-target compound that has a long-lasting mechanism of action might have a greater and longer life span of anti-proliferative activity. Recently, a dual-target indol-3ylglyoxyldipeptide derivative, designed to bind to the Translocator Protein (TSPO) and reactivate p53 function via dissociation from its physiological inhibitor, murine double minute 2 (MDM2), has been developed as a potent GBM pro-apoptotic agent. In this study, this derivative was chemically modified to irreversibly bind MDM2 and TSPO. The new compound elicited a TSPO-mediated mitochondrial membrane dissipation and restored p53 activity, triggering a long-lasting apoptosis of GBM cells. These effects were sustained over time, involved a stable activation of extracellular signal regulated kinases and were specifically observed in cancer cells, in which these protein kinases are deregulated. Dual-targeting and irreversible binding properties combined in the same molecule may represent a useful strategy to overcome the time-limited effects elicited by classical chemotherapies.

The protective mechanism of quercetin-3-O-β-D-glucuronopyranoside (QGC) in H2O2-induced injury of feline esophageal epithelial cells

Quercetin-3-O-β-D-glucuronopyranoside (QGC) is a flavonoid glucoside extracted from Rumex Aquaticus. Recent studies have shown that QGC exhibits anti-inflammatory, anti-oxidateve effect in vivo and cytoprotective effect in vitro. Reactive oxygen species (ROS), at low concentration, play role as a primary signal or second messenger, however, at high concentration, ROS are cytotoxic. In this study, we investigated the protective mechanism of QGC in H2O2-induced injury of Feline Esophageal Epithelial Cells. Primary-cultured feline esophagus cells were identified by an indirect immunofluorescent staining method using a cytokeratin monoclonal antibody. Cell viability was determined by the conventional MTT reduction assay. Western blot analysis was performed with specific antibodies to investigate the activation of MAPKs, NF-κB, and IκB-α, and the expression of COX-2. When the cells were exposed to 600 μM H2O2 medium for 24 h, cell viability decreased to 54 %. However, when cells were pretreated with 50-150 μM QGC for 12 h, the viability of cells exposed to H2O2 significantly increased in the dose dependent manner. QGC (50 μM, 12 h) also inhibited the expression of COX-2 induced by 10 μM H2O2 for 24 h. We found that treatment of H2O2 activated p38 MAPK and JNK, but not ERK. However QGC inhibited the H2O2-induced p38 MAPK and JNK phosphorylation. In addition, NF-κB was activated by H2O2 and translocated into the nucleus, but QGC inhibited the activation of NF-κB by blocking degradation of IκB. These data suggest that QGC reduces H2O2-induced COX-2 production by modulating the p38 MAPK, JNK, NF-κB signal pathway in feline esophageal epithelial cells.

Disulfiram anti-cancer efficacy without copper overload is enhanced by extracellular H2O2 generation: antagonism by tetrathiomolybdate

Highlights

Background

Cu/Zn superoxide dismutases (SODs) like the extracellular SOD3 and cytoplasmic SOD1 regulate cell proliferation by generating hydrogen peroxide (H₂O₂). This pro-oxidant inactivates essential cysteine residues in protein tyrosine phosphatases (PTP) helping receptor tyrosine kinase activation by growth factor signaling, and further promoting downstream MEK/ERK linked cell proliferation. Disulfiram (DSF), currently in clinical cancer trials is activated by copper chelation, being potentially capable of diminishing the copper dependent activation of MEK1/2 and SOD1/SOD3 and promoting reactive oxygen species (ROS) toxicity. However, copper (Cu) overload may occur when co-administered with DSF, resulting in toxicity and mutagenicity against normal tissue, through generation of the hydroxyl radical (•OH) by the Fenton reaction.

Purpose

To investigate: a) whether sub-toxic DSF efficacy can be increased without Cu overload against human melanoma cells with unequal BRAF(V600E) mutant status and Her2-overexpressing SKBR3 breast cancer cells, by increasing H₂O₂from exogenous SOD; b) to compare the anti-tumor efficacy of DSF with that of another clinically used copper chelator, tetrathiomolybdate (TTM)

Results

a) without copper supplementation, exogenous SOD potentiated sub-toxic DSF toxicity antagonized by sub-toxic TTM or by the anti-oxidant N-acetylcysteine; b) exogenous glucose oxidase, another H₂O₂ generator resembled exogenous SOD in potentiating sub-toxic DSF.

Conclusions

potentiation of sub-lethal DSF toxicity by extracellular H₂O₂ against the human tumor cell lines investigated, only requires basal Cu and increased ROS production, being unrelated to non-specific or TTM copper chelator sequestration.

Significance

These findings emphasize the relevance of extracellular H₂O₂ as a novel mechanism to improve disulfiram anticancer effects minimizing copper toxicity.

Temporal Analyses of the Response of Intervertebral Disc Cells and Mesenchymal Stem Cells to Nutrient Deprivation

Much emphasis has been placed recently on the repair of degenerate discs using implanted cells, such as disc cells or bone marrow derived mesenchymal stem cells (MSCs). This study examines the temporal response of bovine and human nucleus pulposus (NP) cells and MSCs cultured in monolayer following exposure to altered levels of glucose (0, 3.15, and 4.5 g/L) and foetal bovine serum (0, 10, and 20%) using an automated time-lapse imaging system. NP cells were also exposed to the cell death inducers, hydrogen peroxide and staurosporine, in comparison to serum starvation. We have demonstrated that human NP cells show an initial “shock” response to reduced nutrition (glucose). However, as time progresses, NP cells supplemented with serum recover with minimal evidence of cell death. Human NP cells show no evidence of proliferation in response to nutrient supplementation, whereas MSCs showed greater response to increased nutrition. When specifically inducing NP cell death with hydrogen peroxide and staurosporine, as expected, the cell number declined. These results support the concept that implanted NP cells or MSCs may be capable of survival in the nutrient-poor environment of the degenerate human disc, which has important clinical implications for the development of IVD cell therapies.

Carnosic acid protects normal mouse hepatocytes against H2 O2 -induced cytotoxicity via sirtuin 1-mediated signaling

AIM

Carnosic acid (CA) is well known for its antioxidant properties. The aim of this study was to examine the effects of CA on cytotoxicity under oxidative stress.

METHODS

Primary hepatocytes and AML12 cells were treated with: (i) 0.1 μM, 1 μM and 10 μM CA; (ii) 3 mM H2 O2 with or without 1 μM CA; or (iii) 3 mM H2 O2 with 1 μM CA and 0.04 μM sirtuin 1 (SIRT1) inhibitor EX527 or 10 μM mitogen-activated protein kinase (MAPK) inhibitor U0126. Cell viability, intracellular reactive oxygen species (ROS) and lactate dehydrogenase (LDH) leakage were determined. In addition, total protein levels of cleaved caspase 3, SIRT1, phosphorylated Nrf2, 5'-adenosine monophosphate-activated protein kinase (AMPK) and MAPKs were evaluated by western blot analysis and suspension array system.

RESULTS

First, although 10 μM CA produced cytotoxicity, CA at concentrations at or below 1 μM did not inhibit cell viability. Second, H2 O2 increased total cellular ROS and LDH leakage and decreased cell viability, whereas co-treatment with H2 O2 and 1 μM CA significantly inhibited these effects of H2 O2 . Third, CA at 1 μM increased protein levels of SIRT1. Pretreatment with EX527 or transfection of siRNA-targeting SIRT1 weakened the protective effects of CA against H2 O2 -induced cell death. Fourth, H2 O2 induced phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) in primary hepatocytes. U0126 inhibited oxidative damage induced by H2 O2 . Co-treatment with CA inhibited ERK1/2 activation induced by H2 O2 .

CONCLUSION

Our data indicate that CA protects against oxidative stress-induced cytotoxicity via SIRT1 by regulating subsequent downstream factors such as ERK1/2.

MAP kinases and the inflammatory signaling cascade as targets for the treatment of endometriosis?

INTRODUCTION

The pathogenesis of endometriosis, a common benign disease, remains ill-defined, although it is clear that chronic inflammation plays a crucial role through mitogen-activated protein kinase (MAPK) signaling pathways. All current medical therapies for endometriosis are antigonadotropic, and therefore have a contraceptive effect. A concerted research effort is hence warranted with the aim of delivering novel therapeutics that reduces disease symptoms without blocking ovulation.

AREAS COVERED

The authors review the complex pathogenic mechanisms of chronic inflammation in endometriosis and their relationships with MAPK pathways. The authors conducted a literature search of descriptive and functional targeted validation of MAPK in the pathogenesis of endometriosis. The effects of MAPK inhibitors, which constitute potential agents for future treatments, are also described.

EXPERT OPINION

Preliminary studies have highlighted a crucial role for MAPK in driving endometriosis-related inflammation. MAPK inhibitors exhibit potent activity in terms of controlling growth of endometriosis lesions both in vitro and in animal models. As MAPK inhibitors are known to have a multitude of undesirable side effects, their use in humans has to be approached with great care. Indeed, use of these drugs would probably be limited to short exposures prior to surgery in cases involving the most severe disease phenotypes.

p53 protein-mediated up-regulation of MAP kinase phosphatase 3 (MKP-3) contributes to the establishment of the cellular senescent phenotype through dephosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2)

Growth arrest is one of the essential features of cellular senescence. At present, the precise mechanisms responsible for the establishment of the senescence-associated arrested phenotype are still incompletely understood. Given that ERK1/2 is one of the major kinases controlling cell growth and proliferation, we examined the possible implication of ERK1/2. Exposure of normal rat epithelial cells to etoposide caused cellular senescence, as manifested by enlarged cell size, a flattened cell body, reduced cell proliferation, enhanced β-galactosidase activity, and elevated p53 and p21. Senescent cells displayed a blunted response to growth factor-induced cell proliferation, which was preceded by impaired ERK1/2 activation. Further analysis revealed that senescent cells expressed a significantly higher level of mitogen-activated protein phosphatase 3 (MKP-3, a cytosolic ERK1/2-targeted phosphatase), which was suppressed by blocking the transcriptional activity of the tumor suppressor p53 with pifithrin-α. Inhibition of MKP-3 activity with a specific inhibitor or siRNA enhanced basal ERK1/2 phosphorylation and promoted cell proliferation. Apart from its role in growth arrest, impairment of ERK1/2 also contributed to the resistance of senescent cells to oxidant-elicited cell injury. These results therefore indicate that p53-mediated up-regulation of MKP-3 contributes to the establishment of the senescent cellular phenotype through dephosphorylating ERK1/2. Impairment of ERK1/2 activation could be an important mechanism by which p53 controls cellular senescence.

Role of the ERK pathway for oxidant-induced parthanatos in human lymphocytes

Reactive oxygen species (ROS) are formed by myeloid cells as a defense strategy against microorganisms. ROS however also trigger poly(ADP-ribose) polymerase 1- (PARP-1) dependent cell death (parthanatos) in adjacent lymphocytes, which has been forwarded as a mechanism of immune escape in several forms of cancer. The present study assessed the role of mitogen-activated protein kinases (MAPKs), in particular the extracellular signal-regulated kinase (ERK), in ROS-induced signal transduction leading to lymphocyte parthanatos. We report that inhibitors of ERK1/2 phosphorylation upheld natural killer (NK) cell-mediated cytotoxicity under conditions of oxidative stress and rescued NK cells and CD8⁺ T lymphocytes from cell death induced by ROS-producing monocytes. ERK1/2 phosphorylation inhibition also protected lymphocytes from cell death induced by exogenous hydrogen peroxide (H₂O₂) and from ROS generated by xanthine oxidase or glucose oxidase. Phosphorylation of ERK1/2 was observed in lymphocytes shortly after exposure to ROS. ROS-generating myeloid cells and exogenous H₂O₂ triggered PARP 1-dependent accumulation of poly ADP-ribose (PAR), which was prevented by ERK pathway inhibitors. ERK1/2 phosphorylation was induced by ROS independently of PARP-1. Our findings are suggestive of a role for ERK1/2 in ROS-induced lymphocyte parthanatos, and that the ERK axis may provide a therapeutic target for the protection of lymphocytes against oxidative stress.

Modulation of Human Cardiac Progenitors via Hypoxia-ERK Circuit Improves their Functional Bioactivities

Recent accumulating studies have reported that hypoxic preconditioning during ex vivo expansion enhanced the self-renewal or differentiation of various stem cells and provide an important strategy for the adequate modulation of oxygen in culture conditions, which might increase the functional bioactivity of these cells for cardiac regeneration. In this study, we proposed a novel priming protocol to increase the functional bioactivity of cardiac progenitor cells (CPCs) for the treatment of cardiac regeneration. Firstly, patient-derived c-kit⁺ CPCs isolated from the atrium of human hearts by enzymatic digestion and secondly, pivotal target molecules identifi ed their differentiation into specific cell lineages. We observed that hCPCs, in response to hypoxia, strongly activated ERK phosphorylation in ex vivo culture conditioning. Interestingly, pre-treatment with an ERK inhibitor, U0126, significantly enhanced cellular proliferation and tubular formation capacities of CPCs. Furthermore, we observed that hCPCs efficiently maintained the expression of the c-kit, a typical stem cell marker of CPCs, under both hypoxic conditioning and ERK inhibition. We also show that hCPCs, after preconditioning of both hypoxic and ERK inhibition, are capable of differentiating into smooth muscle cells (SMCs) and cardiomyocytes (CMs), but not endothelial cells (ECs), as demonstrated by the strong expression of α-SMA, Nkx2.5, and cTnT, respectively. From our results, we conclude that the functional bioactivity of patient-derived hCPCs and their ability to differentiate into SMCs and CMs can be effi ciently increased under specifically defined culture conditions such as shortterm hypoxic preconditioning and ERK inhibition.

Endothelial nitric oxide synthase phosphorylation at Threonine 495 and mitochondrial reactive oxygen species formation in response to a high H₂O₂ concentration

BACKGROUND

Hydrogen peroxide (H₂O₂) is produced in vessels during ischemia/reperfusion and during inflammation, both leading to vascular dysfunction. We investigated cellular pathways involved in endothelial nitric oxide synthase (eNOS) phosphorylation at Threonine 495 (Thr(495)) in human umbilical vein endothelial cells (HUVECs) exposed to H₂O₂.

METHODS

HUVECs were exposed to 400 μM H₂O₂ for 30 min. Phosphorylation at Thr(495) was assessed by Western blotting and reactive oxygen species (ROS) monitored by flow cytometry. Protein kinase C (PKC) pathways were investigated by pretreatment with PKC-β inhibitor ruboxistaurin or pan-PKC inhibitor GF109203X. In addition, we investigated ROCK and ERK pathways by MEKK1/2 inhibitor U0126 and ROCK inhibitor Y27632.

RESULTS

H₂O₂ increased eNOS phosphorylation at Thr(495) (to 176% vs. control (100%), p < 0.001) along with increased mitochondrial ROS formation (from 19.7 to 45.3%, p < 0.01). This rise in phosphorylation could be prevented by U0126 and Y27632 in a dose-dependent manner, but did not result in lowered mitochondrial ROS formation. Conversely, addition of the antioxidant N-acetyl-L-cysteine only prevented mitochondrial ROS formation but did not prevent phosphorylation of eNOS Thr(495).

CONCLUSION

H₂O₂-mediated phosphorylation of eNOS Thr(495) is mediated by ROCK and ERK activity, but not by PKC, and is uncoupled from mitochondrial ROS signaling. Furthermore, ERK inhibition increased mitochondrial ROS formation.

Adult neural stem cells from the subventricular zone: a review of the neurosphere assay

The possibility of obtaining large numbers of cells with potential to become functional neurons implies a great advance in regenerative medicine. A source of cells for therapy is the subventricular zone (SVZ) where adult neural stem cells (NSCs) retain the ability to proliferate, self-renew, and differentiate into several mature cell types. The neurosphere assay, a method to isolate, maintain, and expand these cells has been extensively utilized by research groups to analyze the biological properties of aNSCs and to graft into injured brains from animal models. In this review we briefly describe the neurosphere assay and its limitations, the methods to optimize culture conditions, the identity and the morphology of aNSC-derived neurospheres (including new ultrastructural data). The controversy regarding the identity and "stemness" of cells within the neurosphere is revised. The fine morphology of neurospheres, described thoroughly, allows for phenotypical characterization of cells in the neurospheres and may reveal slight changes that indirectly inform about cell integrity, cell damage, or oncogenic transformation. Along this review we largely highlight the critical points that researchers have to keep in mind before extrapolating results or translating experimental transplantation of neurosphere-derived cells to the clinical setting.

Protective effects of andrographolide analogue AL-1 on ROS-induced RIN-mβ cell death by inducing ROS generation

Oxidative stress is considered to be a major factor contributing to pathogenesis and progression of many diseases. A novel andrographolide-lipoic acid conjugate (AL-1) could protect pancreatic β-cells from reactive oxygen species (ROS)-induced oxidative injury. However, its protective mechanism is still unclear. In this work, we used proteomics to identify AL-1-regulated proteins in β-cells and found that 13 of the 71 proteins regulated by AL-1 were closely associated with antioxidation. These differential proteins were mainly involved in the ERK1/2 and AKT1 signaling pathways. Functional investigation demonstrated that AL-1 exerted its protective effects on H₂O₂-induced cell death of β-cells by generating NADPH oxidase-dependent ROS to activate ERK1/2 and AKT1 signaling pathways. As a consequence, the expressions of antioxidant proteins including Trx1, Prx1 and Prx5, and anti-apoptotic proteins including PDCD6IP, prohibitin, galectin-1 and HSP were upregulated. AL-1 probably worked as a “vaccinum” to activate the cellular antioxidant system by inducing the generation of low concentration ROS which then reciprocally protected β-cells from oxidative damage caused by high-level ROS from H₂O₂. To the best of our knowledge, this is the first comprehensive proteomic analysis illustrating a novel molecular mechanism for the protective effects of antioxidants on β-cells from H₂O₂-induced cell death.

The Protective Effect of Eupatilin against Hydrogen Peroxide-Induced Injury Involving 5-Lipoxygenase in Feline Esophageal Epithelial Cells

In this study, we focused to identify whether eupatilin (5,7-dihydroxy-3',4',6-trimethoxyflavone), an extract from Artemisia argyi folium, prevents H₂O₂-induced injury of cultured feline esophageal epithelial cells. Cell viability was measured by the conventional MTT reduction assay. Western blot analysis was performed to investigate the expression of 5-lipoxygenase by H₂O₂ treatment in the absence and presence of inhibitors. When cells were exposed to 600 µM H₂O₂ for 24 hours, cell viability was decreased to 40%. However, when cells were pretreated with 25~150 µM eupatilin for 12 hours, viability was significantly restored in a concentration-dependent manner. H₂O₂-treated cells were shown to express 5-lipoxygenase, whereas the cells pretreated with eupatilin exhibited reduction in the expression of 5-lipoxygenase. The H₂O₂-induced increase of 5-lipoxygenase expression was prevented by SB202190, SP600125, or NAC. We further demonstrated that the level of leukotriene B₄ (LTB₄) was also reduced by eupatilin, SB202190, SP600125, NAC, or nordihydroguaiaretic acid (a lipoxygenase inhibitor) pretreatment. H₂O₂ induced the activation of p38MAPK and JNK, this activation was inhibited by eupatilin. These results indicate that eupatilin may reduce H₂O₂-induced cytotoxicity, and 5-lipoxygenase expression and LTB₄ production by controlling the p38 MAPK and JNK signaling pathways through antioxidative action in feline esophageal epithelial cells.

Mitogen-activated protein kinases in mammalian oxidative stress responses

All aerobic organisms are exposed to oxidative stress during their lifetime and are required to respond appropriately for maintenance of their survival and homeostasis. Sustained exposure to oxidative stress has devastating effects in organisms, and, not surprisingly, oxidative stress has been implicated in numerous human diseases. Therefore, an understanding of how mammals respond to oxidative stress is crucial both biologically and clinically. Intracellular signaling pathways, which are activated in response to excessive oxygen radicals, play essential roles in overcoming oxidative stress. The mitogen-activated protein kinase (MAPK) signaling pathways are involved in diverse physiological processes, and are critical for induction of oxidative stress responses. In this review, we will discuss the physiological roles of MAPKs in oxidative stress, the upstream signaling pathways leading to MAPK activation, their regulation, and the MAPK downstream substrates, with a focus on mammalian systems.

Redox control of GTPases: from molecular mechanisms to functional significance in health and disease

Small GTPases, including the proto-oncoprotein Ras and Rho GTPases, are involved in various cellular signaling events. Some of these small GTPases are redox sensitive, including Ras, Rho, Ran, Dexras1, and Rhes GTPases. Thus, the redox-mediated regulation of these GTPases often determines the course of their cellular signaling cascades. This article takes into consideration the application of Marcus theory to potential redox-based molecular mechanisms in the regulation of these redox-sensitive GTPases and the relevance of such mechanisms to a specific redox-sensitive motif. The discussion also takes into account various diseases, including cancers, heart, and neuronal disorders, that are often linked with the dysregulation of the redox signaling cascades associated with these redox-sensitive GTPases.

Oncogenic H-Ras, FK228, and exogenous H2O2 cooperatively activated the ERK pathway in selective induction of human urinary bladder cancer J82 cell death

More than 35% of human urinary bladder cancers involve oncogenic H-Ras activation. The goal of this study was to investigate the role of the ERK pathway in mediating apoptotic signals induced by oncogenic H-Ras, FK228 treatment, and exogenous H(2) O(2) treatment to increase Nox-1 elevation, leading to production of intracellular reactive oxygen species (ROS) for inducing apoptosis in human bladder cancer J82 cells. Our study revealed that FK228 combined with exogenous H(2)O(2) cooperatively induced activation of Mek1/2 and Erk1/2 to increase Nox-1 elevation, intracellular ROS production, caspase activation, and cell death. Expression of oncogenic H-Ras significantly increased these FK228- and exogenous H(2)O(2)-induced effects. Oncogenic H-Ras-increased cell susceptibility to FK228 could be alternately achieved by additional treatment with exogenous H(2)O(2). Hence, combined use of FK228 with ROS-generating agents may apply to therapeutic strategies to preferentially kill malignant cells with or without oncogenic H-Ras activation.

Oligonol a low molecular weight polyphenol of lychee fruit extract inhibits proliferation of influenza virus by blocking reactive oxygen species-dependent ERK phosphorylation

The emergence of resistance to anti-influenza drugs calls for the search for new antiviral molecules with different resistance profiles. Polyphenolic compounds are found in various plants and have antiviral and antioxidative properties. We tested the hypothesis that oligonol, a lychee fruit-derived low molecular weight polyphenol, possesses anti-influenza effects by inhibiting phosphorylation of extracellular-signal-regulated kinases (ERK). Real time PCR, plaque assay, and immunofluorescence techniques were used to study the effects of oligonol on proliferation of influenza virus. Oligonol inhibits influenza virus proliferation by blocking attachment of the virus to MDCK cells and by suppression of nuclear export of influenza virus ribonucleoprotein (RNP). Infection of MDCK cells with influenza virus leads to an increase in production of reactive oxygen species (ROS) and induction of a ROS-dependent ERK phosphorylation. Inhibition of ERK activation by a dominant negative mutant of ERK or N-acetyl-cysteine (NAC) leads to inhibition of influenza RNP nuclear export. Phorbol 12-myristate 13-acetate (PMA) induces ROS production, ERK phosphorylation and enhances influenza proliferation in MDCK cells. Oligonol and NAC inhibit PMA-induced ERK phosphorylation and ROS production. Our studies suggest that the underlying mechanism for the inhibitory effect of oligonol on influenza virus RNP nuclear export is blocking of ROS-dependent induction of ERK phosphorylation.

Reactive oxygen species in cancer

Elevated rates of reactive oxygen species (ROS) have been detected in almost all cancers, where they promote many aspects of tumour development and progression. However, tumour cells also express increased levels of antioxidant proteins to detoxify from ROS, suggesting that a delicate balance of intracellular ROS levels is required for cancer cell function. Further, the radical generated, the location of its generation, as well as the local concentration is important for the cellular functions of ROS in cancer. A challenge for novel therapeutic strategies will be the fine tuning of intracellular ROS signalling to effectively deprive cells from ROS-induced tumour promoting events, towards tipping the balance to ROS-induced apoptotic signalling. Alternatively, therapeutic antioxidants may prevent early events in tumour development, where ROS are important. However, to effectively target cancer cells specific ROS-sensing signalling pathways that mediate the diverse stress-regulated cellular functions need to be identified. This review discusses the generation of ROS within tumour cells, their detoxification, their cellular effects, as well as the major signalling cascades they utilize, but also provides an outlook on their modulation in therapeutics.

Hydrogen peroxide toxicity induces Ras signaling in human neuroblastoma SH-SY5Y cultured cells

It has been reported that overproduction of reactive oxygen species occurs after brain injury and mediates neuronal cells degeneration. In the present study, we examined the role of Ras signaling on hydrogen peroxide-induced neuronal cells degeneration in dopaminergic neuroblastoma SH-SY5Y cells. Hydrogen peroxide significantly reduced cell viability in SH-SY5Y cultured cells. An inhibitor of the enzyme that catalyzes the farnesylation of Ras proteins, FTI-277, and a competitive inhibitor of GTP-binding proteins, GDP-beta-S significantly decreased hydrogen peroxide-induced reduction in cell viability in SH-SY5Y cultured cells. The results of this study might indicate that a Ras-dependent signaling pathway plays a role in hydrogen peroxide-induced toxicity in neuronal cells.

TRAIL and interferon-alpha act synergistically to induce renal cell carcinoma apoptosis

PURPOSE

Despite modern targeted therapy metastatic renal cell carcinoma remains a deadly disease. Interferon-alpha (Calbiochem(R)) is currently used to treat this condition, mainly combined with the targeted anti-vascular endothelial growth factor antibody bevacizumab. TRAIL (Apo2 ligand/tumor necrosis factor related apoptosis inducing ligand) (Calbiochem) is a novel antineoplastic agent now in early phase clinical trials. Interferon-alpha and TRAIL can act synergistically to kill cancer cells but to our knowledge this has never been tested in the context of renal cell carcinoma. We hypothesized that TRAIL and interferon-alpha could synergistically induce apoptosis in renal cell carcinoma cells.

MATERIALS AND METHODS

We treated renal cell carcinoma cell lines with recombinant TRAIL and/or interferon-alpha. Viability and apoptosis were assessed by MTS assay, flow cytometry and Western blot. Synergy was confirmed by isobologram. Interferon-alpha induced changes in renal cell carcinoma cell signaling were assessed by Western blot, flow cytometry and enzyme-linked immunosorbent assay.

RESULTS

TRAIL and interferon-alpha acted synergistically to increase apoptotic cell death in renal cell carcinoma cells. Interferon-alpha treatment altered the ability of cells to activate extracellular signal-regulated kinase while inhibiting extracellular signal-regulated kinase with UO126 abrogated TRAIL and interferon-alpha apoptotic synergy. Interferon-alpha did not induce changes in TRAIL or death receptor expression, or change other known mediators of the intrinsic and extrinsic apoptotic cascade in the cells.

CONCLUSIONS

TRAIL plus interferon-alpha synergistically induces apoptosis in renal cell carcinoma cells, which is due at least in part to interferon-alpha mediated changes in extracellular signal-regulated kinase activation. TRAIL and interferon-alpha combination therapy may be a novel approach to advanced renal cell carcinoma that warrants further testing in vivo.

Glioma cell death: cell-cell interactions and signalling networks

The prognosis for patients with malignant gliomas is poor, but improvements may emerge from a better understanding of the pathophysiology of glioma signalling. Recent therapeutic developments have implicated lipid signalling in glioma cell death. Stress signalling in glioma cell death involves mitochondria and endoplasmic reticulum. Lipid mediators also signal via extrinsic pathways in glioma cell proliferation, migration and interaction with endothelial and microglial cells. Glioma cell death and tumour regression have been reported using polyunsaturated fatty acids in animal models, human ex vivo explants, glioma cell preparations and in clinical case reports involving intratumoral infusion. Cell death signalling was associated with generation of reactive oxygen intermediates and mitochondrial and other signalling pathways. In this review, evidence for mitochondrial responses to stress signals, including polyunsaturated fatty acids, peroxidizing agents and calcium is presented. Additionally, evidence for interaction of glioma cells with primary brain endothelial cells is described, modulating human glioma peroxidative signalling. Glioma responses to potential therapeutic agents should be analysed in systems reflecting tumour connectivity and CNS structural and functional integrity. Future insights may also be derived from studies of signalling in glioma-derived tumour stem cells.

Autophagy induced by valproic acid is associated with oxidative stress in glioma cell lines

Autophagy represents an alternative tumor-suppressing mechanism that overcomes the dramatic resistance of malignant gliomas to radiotherapy and proapoptotic-related chemotherapy. This study reports that valproic acid (VPA), a widely used anti-epilepsy drug, induces autophagy in glioma cells. Autophagy, crucial for VPA-induced cell death, is independent of apoptosis, even though apoptotic machinery is proficient. Oxidative stress induced by VPA occurs upstream of autophagy. Oxidative stress also activates the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway, whereas blocking this pathway inhibits autophagy and induces apoptosis. VPA-induced autophagy cannot be alleviated by inositol, suggesting a mechanism different from that for lithium. Moreover, VPA potentiates autophagic cell death, but not apoptosis, when combined with other autophagy inducers such as rapamycin, Ly294002, and temozolomide in glioma cells both in vitro and in vivo, which may warrant further investigation toward possible clinical application in patients with malignant gliomas.

Activation of ERK1/2 by protein kinase C-alpha in response to hydrogen peroxide-induced cell death in human gingival fibroblasts

Hydrogen peroxide (H(2)O(2)) increases protein tyrosine phosphorylation of numerous proteins in human gingival fibroblasts (HGFs). Two main proteins, with an apparent molecular weight of 44 and 42kDa, were phosphorylated after hydrogen peroxide stimulation of the human gingival fibroblasts. Further analysis identified these two proteins as ERK1/2. Maximum phosphorylation was detected at 10min post-H(2)O(2) treatment. Pretreatment with an MEK inhibitor, PD98059, inhibited H(2)O(2)-stimulated ERK1/2 phosphorylation in a dose-dependent manner. Treatment with H(2)O(2) also induced phosphorylation of protein kinase C-alpha (PKCalpha). Staurosporine, a PKC inhibitor, blocked ERK1/2 phosphorylation induced by H(2)O(2). In addition, H(2)O(2)-induced cell death was prevented by PD98059, SB203580, and calphostin C, which are MEK, p38 and PKC inhibitors, respectively. These results suggest that H(2)O(2) leads to the phosphorylation and activation of ERK1/2 in a PKC-dependent manner. These findings demonstrate that the MAPK signaling pathway plays an active role in mediating the H(2)O(2)-induced decrease in HGF cell viability and ATP depletion.

Silibinin inhibits glioma cell proliferation via Ca2+/ROS/MAPK-dependent mechanism in vitro and glioma tumor growth in vivo

Anticancer activity of silibinin, a flavonoid, has been demonstrated in various cancer cell types. However, the underlying mechanism and in vivo efficacy in glioma were not elucidated. The present study was undertaken to determine the effect of silibinin on glioma cell proliferation in vitro and to examine whether silibinin inhibits tumor growth in vivo. Silibinin resulted in inhibition of proliferation in a dose- and time-dependent manner, which was largely attributed to cell death. Silibinin induced a transient increase in intracellular Ca2+ followed by an increase in reactive oxygen species (ROS) generation. The silibinin-induced cell death was prevented by EGTA, calpain inhibitor and antioxidants (N-acetylcysteine and Trolox). Western blot analysis showed that silibinin also induced ROS-dependent activation of extracellular signal-regulated kinase, p38 kinase, and c-Jun N-terminal kinase. Inhibitors of these kinases prevented the silibinin-induced cell death. Silibinin caused caspase activation and the silibinin-induced cell death was prevented by caspase inhibitors. Glioma cell migration was also decreased by silibinin treatment. Oral administration of silibinin in animals with subcutaneous U87MG glioma cells reduced tumor volume. Subsequent tumor tissue analysis showed a decrease in Ki-67 positive cells, an increase in TUNEL-positive cells, and caspase activation. These results indicate that silibinin induces a caspase-dependent cell death via Ca2+/ROS/MAPK-mediated pathway in vitro and inhibits glioma growth in vivo. These data suggest that silibinin may serve as a potential therapeutic agent for malignant human gliomas.

HMG-CoA reductase inhibitors: do they have potential in the treatment of polycystic ovary syndrome?

Many women of reproductive age are affected by polycystic ovary syndrome (PCOS), a heterogeneous endocrinopathy characterized by androgen excess, chronic oligo-anovulation and/or polycystic ovarian morphology. In addition, PCOS is often associated with insulin resistance, systemic inflammation and oxidative stress, which, on one hand, lead to endothelial dysfunction and dyslipidaemia with subsequent cardiovascular sequelae and, on the other hand, to hyperplasia of the ovarian theca compartment with resultant hyperandrogenism and anovulation. Traditionally, HMG-CoA reductase inhibitors (statins) have been used to treat dyslipidaemia by blocking HMG-CoA reductase (the rate-limiting step in cholesterol biosynthesis); however, they also possess pleiotropic actions, resulting in antioxidant, anti-inflammatory and anti-proliferative effects. Statins offer a novel therapeutic approach to PCOS in that they address the dyslipidaemia associated with the syndrome, as well as hyperandrogenism or hyperandrogenaemia. These actions may be due to an inhibition of the effects of systemic inflammation and insulin resistance/hyperinsulinaemia. Evidence to date, both in vitro and in vivo, suggests that statins have potential in the treatment of PCOS; however, further clinical trials are needed before they can be considered a standard of care in the medical management of this common endocrinopathy.

Role of oxidative stress in pancreatic inflammation

Reactive oxygen and reactive nitrogen species (ROS/RNS) have been implicated in the pathogenesis of acute and chronic pancreatitis. Clinical and basic science studies have indicated that ROS/RNS formation processes are intimately linked to the development of the inflammatory disorders. The detrimental effects of highly reactive ROS/RNS are mediated by their direct actions on biomolecules (lipids, proteins, and nucleic acids) and activation of proinflammatory signal cascades, which subsequently lead to activation of immune responses. The present article summarizes the possible sources of ROS/RNS formation and the detailed signaling cascades implicated in the pathogenesis of pancreatic inflammation, as observed in acute and chronic pancreatitis. A therapeutic ROS/RNS-scavenging strategy has been advocated for decades; however, clinical studies examining such approaches have been inconsistent in their results. Emerging evidence indicates that pancreatitis-inducing ROS/RNS generation may be attenuated by targeting ROS/RNS-generating enzymes and upstream mediators.

Effect of dihydrotestosterone on mouse embryonic stem cells exposed to H2O2-induced oxidative stress

Oxidative stresses induced by reactive oxygen species (ROS) have been shown to be involved in several physiological and pathophysiological processes, such as cell proliferation and differentiation. Steroid hormones can protect cells against apoptosis or induce cell proliferation by several mechanisms. Among androgenic hormones, dihydrotestosterone (DHT) is generated by a 5alpha- reduction of testosterone. Unlike testosterone, DHT cannot be aromatized to estradiol, therefore DHT is considered a pure androgenic steroid. This study was conducted to examine the effect of DHT (10(-7) M) on H2O2 (10(-3) M) -induced injuries in mouse embryonic stem (ES) cells. H2O2 induced ROS generation and increased lipid peroxide formation and DNA fragmentation. These effects of H2O2 were inhibited by pretreatment with DHT. H2O2 also increased the phosphorylation of p38 MAPK, SAPK/JNK and nuclear factor kappa B (NF-kappaB), but DHT blocked these effects. Moreover, H2O2 decreased DNA synthesis and the levels of cell cycle regulatory proteins [cyclin D1, cyclin E, cyclin-dependent kinase (CDK) 2, and CDK 4]. These effects of H2O2 were inhibited by pretreatment with DHT. In conclusion, DHT may partially prevent H2O2-induced cell injury through inhibition of ROS and ROS-induced activation of p38 MAPK, SAPK/JNK and NF-kappaB in mouse ES cells.

Hydrogen peroxide enhances TRAIL-induced cell death through up-regulation of DR5 in human astrocytic cells

The central nervous system (CNS) is particularly vulnerable to reactive oxygen species (ROS), which have been implicated in the pathogenesis of various neurological disorders. The TNF superfamily of cytokines, especially tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), induces caspase-dependent cell death and is also implicated in various neurodegenerative diseases. In this study, we investigated the relationship between ROS and TRAIL-induced cell death. Exposure to hydrogen peroxide (H(2)O(2)) (100 microM) sensitized human astrocytic cells to TRAIL-induced cell death (up to 7-fold induction). To delineate the molecular mechanisms responsible for H(2)O(2)-induced sensitization, we examined expression of various genes (Caspase-8, Fas, FasL, DR4, DR5, DcR1, DcR2, TRAIL, TNFRp55) related to TRAIL-induced cell death. Treatment with H(2)O(2) significantly increased DR5 mRNA and protein expression in a time- and dose-dependent manner. H(2)O(2)-mediated cell death was blocked upon treatment with DR5:Fc protein, a TRAIL-specific antagonistic protein. These findings collectively suggest that oxidative stress sensitizes human astroglial cells to TRAIL-induced cell death through up-regulation of DR5 expression.

Statins in the treatment of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy affecting reproductive-aged women. The hyperandrogenemia associated with the syndrome is a result of excessive growth and steroidogenic activity of theca-interstitial tissues in response to various factors, including elevated gonadotropins, hyperinsulinemia, and oxidative stress. PCOS frequently coexists with other cardiovascular risk factors, such as dyslipidemia and systemic inflammation. Statins inhibit the synthesis of mevalonate, the key precursor to cholesterol biosynthesis, and reduce cardiovascular morbidity and mortality. Blockade of mevalonate production may also lead to decreased maturation of insulin receptors, inhibition of steroidogenesis (e.g., via limiting the amount of substrate: cholesterol), and alteration of signal transduction pathways that mediate cellular proliferation. The latter depend upon posttranslational modification of proteins (prenylation), a process mediated by mevalonate derivatives. Statins also have intrinsic antioxidant properties. Given the pleiotropic actions of statins, they are likely not only to improve the dyslipidemia associated with PCOS but may also exert other beneficial metabolic and endocrine effects.