ERK phosphorylates p66shcA on Ser36 and subsequently regulates p27kip1 expression via the Akt-FOXO3a pathway: implication of p27kip1 in cell response to oxidative stress

Endoplasmic Reticulum-Mitochondria Contacts Modulate Reactive Oxygen Species-Mediated Signaling and Oxidative Stress in Brain Disorders: The Key Role of Sigma-1 Receptor

Significance: Mitochondria-Associated Membranes (MAMs) are highly dynamic endoplasmic reticulum (ER)-mitochondria contact sites that, due to the transfer of lipids and Ca2+ between these organelles, modulate several physiologic processes, such as ER stress response, mitochondrial bioenergetics and fission/fusion events, autophagy, and inflammation. In addition, these contacts are implicated in the modulation of the cellular redox status since several MAMs-resident proteins are involved in the generation of reactive oxygen species (ROS), which can act as both signaling mediators and deleterious molecules, depending on their intracellular levels. Recent Advances: In the past few years, structural and functional alterations of MAMs have been associated with the pathophysiology of several neurodegenerative diseases that are closely associated with the impairment of several MAMs-associated events, including perturbation of the redox state on the accumulation of high ROS levels. Critical Issues: Inter-organelle contacts must be tightly regulated to preserve cellular functioning by maintaining Ca2+ and protein homeostasis, lipid metabolism, mitochondrial dynamics and energy production, as well as ROS signaling. Simultaneously, these contacts should avoid mitochondrial Ca2+ overload, which might lead to energetic deficits and deleterious ROS accumulation, culminating in oxidative stress-induced activation of apoptotic cell death pathways, which are common features of many neurodegenerative diseases. Future Directions: Given that Sig-1R is an ER resident chaperone that is highly enriched at the MAMs and that controls ER to mitochondria Ca2+ flux, as well as oxidative and ER stress responses, its potential as a therapeutic target for neurodegenerative diseases such as Amyotrophic Lateral Sclerosis, Alzheimer, Parkinson, and Huntington diseases should be further explored. Antioxid. Redox Signal. 37, 758-780.

Parathyroid hormone-related protein inhibits nitrogen-containing bisphosphonate-induced apoptosis of human periodontal ligament fibroblasts by activating MKP1 phosphatase

Massive production of reactive oxygen species (ROS) in human periodontal ligament fibroblasts (HPdLFs) by nitrogen-containing bisphosphonates (BPs) is the main factor causing BP-related osteonecrosis of the jaw. Further, oxidative stress and apoptosis of fibroblasts induced by ROS are closely associated with the activation of MAPK. Parathyroid hormone-related protein (PTHrP) can block the activity of MAPK by regulating the levels of MAPK phosphatase 1 (MKP1). Therefore, it is speculated that PTHrP can inhibit the apoptosis of HPdLFs caused by nitrogen-containing BP via regulating the expression levels of MKP1. Herein, alendronate sodium salt trihydrate (nitrogen-containing BP, FOS) and HPdLFs were co-cultured for 24 h, 48 h, and 72 h, and the levels of ROS and apoptosis were determined, respectively. After 48 h co-culture, FOS significantly increased the levels of ROS and apoptosis, and high phosphorylation levels of p38, ERK1/2 and p66^Shc were found in this study. However, the inhibitors of p38 and ERK1/2 significantly reduced the apoptosis of HPdLFs. Interestingly, PTHrP pre-treatment significantly reduced the phosphorylation levels of p38, ERK1/2, and p66^Shc. More importantly, MKP1 inhibitor sanguinarine inhibited the dephosphorylation levels of p38, ERK1/2, and p66^Shc caused by PTHrP. Altogether, PTHrP can inhibit nitrogen-containing BP-induced apoptosis of HPdLFs by activating MKP1 phosphatase.

RAF-MEK-ERK pathway in cancer evolution and treatment

The RAF-MEK-ERK signaling cascade is a well-characterized MAPK pathway involved in cell proliferation and survival. The three-layered MAPK signaling cascade is initiated upon RTK and RAS activation. Three RAF isoforms ARAF, BRAF and CRAF, and their downstream MEK1/2 and ERK1/2 kinases constitute a coherently orchestrated signaling module that directs a range of physiological functions. Genetic alterations in this pathway are among the most prevalent in human cancers, which consist of numerous hot-spot mutations such as BRAF^V600E. Oncogenic mutations in this pathway often override otherwise tightly regulated checkpoints to open the door for uncontrolled cell growth and neoplasia. The crosstalk between the RAF-MEK-ERK axis and other signaling pathways further extends the proliferative potential of this pathway in human cancers. In this review, we summarize the molecular architecture and physiological functions of the RAF-MEK-ERK pathway with emphasis on its dysregulations in human cancers, as well as the efforts made to target the RAF-MEK-ERK module using small molecule inhibitors.

ER membranes associated with mitochondria: Possible therapeutic targets in heart-associated diseases

Cardiovascular system cell biology is tightly regulated and mitochondria play a relevant role in maintaining heart function. In recent decades, associations between such organelles and the sarco/endoplasmic reticulum (SR) have been raised great interest. Formally identified as mitochondria-associated SR membranes (MAMs), these structures regulate different cellular functions, including calcium management, lipid metabolism, autophagy, oxidative stress, and management of unfolded proteins. In this review, we highlight MAMs' alterations mainly in cardiomyocytes, linked with cardiovascular diseases, such as cardiac ischemia-reperfusion, heart failure, and dilated cardiomyopathy. We also describe proteins that are part of the MAMs' machinery, as the FUN14 domain containing 1 (FUNDC1), the sigma 1 receptor (Sig-1R) and others, which might be new molecular targets to preserve the function and structure of the heart in such diseases. Understanding the machinery of MAMs and its function demands our attention, as such knowledge might contribute to strengthen the role of these relative novel structures in heart diseases.

Diurnal oscillations of endogenous H2O2 sustained by p66Shc regulate circadian clocks

Redox balance, an essential feature of healthy physiological steady states, is regulated by circadian clocks, but whether or how endogenous redox signalling conversely regulates clockworks in mammals remains unknown. Here, we report circadian rhythms in the levels of endogenous H₂O₂ in mammalian cells and mouse livers. Using an unbiased method to screen for H₂O₂-sensitive transcription factors, we discovered that rhythmic redox control of CLOCK directly by endogenous H₂O₂ oscillations is required for proper intracellular clock function. Importantly, perturbations in the rhythm of H₂O₂ levels induced by the loss of p66^Shc, which oscillates rhythmically in the liver and suprachiasmatic nucleus (SCN) of mice, disturb the rhythmic redox control of CLOCK function, reprogram hepatic transcriptome oscillations, lengthen the circadian period in mice and modulate light-induced clock resetting. Our findings suggest that redox signalling rhythms are intrinsically coupled to the circadian system through reversible oxidative modification of CLOCK and constitute essential mechanistic timekeeping components in mammals.

Studying the ShcD and ERK interaction under acute oxidative stress conditions in melanoma cells

The newly identified melanoma-associated adaptor ShcD was found to translocate to the nucleus upon hydrogen peroxide treatment. Therefore, the aim of this study was to identify the ShcD network in melanoma cells under oxidative stress. LC-MS/MS and GFP-trap were performed to study the ShcD phosphorylation status during acute severe oxidative stress. ShcD was found to be phosphorylated at threonine-159 (Thr159) in response to 5 mM H₂O₂ treatment. The GPS 2.1 phosphorylation prediction program predicted that the Thr159Pro motif, housed in the N-terminus of the ShcD-CH2 domain, is a potential phosphorylation site for MAPKs (ERK, JNK or p38). Co-immunoprecipitation experiments revealed that ShcD mainly interacts with ERK in B16 and MM138 melanoma cells under both hydrogen peroxide-untreated and -treated conditions. Moreover, ShcD interacts with both phosphorylated and un-phosphorylated ERK, although the interaction between ShcD and phospho-ERK was primarily observed after H₂O₂ treatment. A MEK inhibitor (U0126) enhanced the interaction between ShcD and unphosphorylated ERK under oxidative stress conditions. Furthermore, Thr159 was mutated to either alanine (A) or glutamic acid (E) to study whether the threonine phosphorylation state influences the ShcD/ERK interaction. Introducing the T159E mutation obliterated the ShcD/ERK interaction. To identify the functional impact of the ShcD/ERK interaction on cell survival signalling under oxidative stress conditions, caspase 3/7 assays and 7AAD cell death assays were used. The ShcD/ERK interaction promoted anti-survival signalling upon exposure to hydrogen peroxide, while U0126 treatment reduced death signalling. Our data also showed that the death signalling initiated by the ShcD/ERK interaction was accompanied by p21 phosphorylation. In summary, these data identified ShcD, via its interaction with ERK, as a proapoptotic protein under oxidative stress conditions.

The Src homology and collagen A (ShcA) adaptor protein may participate in the pathogenesis of membranous lupus nephritis

The Src homology and collagen A (ShcA) adaptor protein that binds to tyrosine kinase receptors. ShcA plays a role in insulin signaling, stress resistance and energy metabolism. The 66-kDa Src homology 2 domain-containing protein (p66shc) belongs to the ShcA family and has been associated with reactive oxygen species (ROS); increased ROS is involved in the pathology of lupus nephritis (LN). However, whether ShcA can act as a biomarker for oxidative injury in LN is unknown. This study is aimed to investigate the ShcA expression in kidney tissues from patients presenting with LN and the association between ShcA expression and clinical parameters. Renal biopsy tissues were obtained from 62 LN, 20 primary membranous nephropathy (MN) and 10 other secondary MN patients. ShcA was measured by immunofluorescence. The expression of ShcA in the membranous lupus nephritis (class V) group showed a higher trend but there were no significant differences compared with pure mesangial disease (class II) and proliferative (Class III/IV) lupus nephritis. ShcA deposits were negative in primary and other secondary MN. ShcA might act as a new biomarker and a diagnostic tool to identify membranous lupus nephritis with other MN.

Mitochondria-associated membranes in aging and senescence: structure, function, and dynamics

Sites of close contact between mitochondria and the endoplasmic reticulum (ER) are known as mitochondria-associated membranes (MAM) or mitochondria-ER contacts (MERCs), and play an important role in both cell physiology and pathology. A growing body of evidence indicates that changes observed in the molecular composition of MAM and in the number of MERCs predisposes MAM to be considered a dynamic structure. Its involvement in processes such as lipid biosynthesis and trafficking, calcium homeostasis, reactive oxygen species production, and autophagy has been experimentally confirmed. Recently, MAM have also been studied in the context of different pathologies, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, type 2 diabetes mellitus and GM1-gangliosidosis. An underappreciated amount of data links MAM with aging or senescence processes. In the present review, we summarize the current knowledge of basic MAM biology, composition and action, and discuss the potential connections supporting the idea that MAM are significant players in longevity.

Anthocyanins Protect SK-N-SH Cells Against Acrolein-Induced Toxicity by Preserving the Cellular Redox State

In Alzheimer's disease (AD) and in mild cognitive impairment (MCI) patients, by-products of lipid peroxidation such as acrolein accumulated in vulnerable regions of the brain. We have previously shown that acrolein is a highly reactive and neurotoxic aldehyde and its toxicity involves the alteration of several redox-sensitive pathways. Recently, protein-conjugated acrolein in cerebrospinal fluid has been proposed as a biomarker to distinguish between MCI and AD. With growing evidence of the early involvement of oxidative stress in AD etiology, one would expect that a successful therapy should prevent brain oxidative damage. In this regard, several studies have demonstrated that polyphenol-rich extracts exert beneficial effect on cognitive impairment and oxidative stress. We have recently demonstrated the efficacy of an anthocyanin formulation (MAF14001) against amyloid-β-induced oxidative stress. The aim of this study is to investigate the neuroprotective effect of MAF14001 as a mixture of anthocyanins, a particular class of polyphenols, against acrolein-induced oxidative damage in SK-N-SH neuronal cells. Our results demonstrated that MAF14001, from 5μM, was able to efficiently protect SK-N-SH cells against acrolein-induced cell death. MAF14001 was able to lower reactive oxygen species and protein carbonyl levels induced by acrolein. Moreover, MAF1401 prevented glutathione depletion and positively modulated, in the presence of acrolein, some oxidative stress-sensitive pathways including the transcription factors NF-κB and Nrf2, the proteins γ-GCS and GSK3β, and the protein adaptator p66Shc. Along with its proven protective effect against amyloid-β toxicity, these results demonstrate that MAF14001 could target multiple mechanisms and could be a promising agent for AD prevention.

Parathyroid Hormone-Related Protein Protects Osteoblastic Cells From Oxidative Stress by Activation of MKP1 Phosphatase

Oxidative damage is an important contributor to the morphological and functional changes in osteoporotic bone. Aging increases the levels of reactive oxygen species (ROS) that cause oxidative stress and induce osteoblast apoptosis. ROS modify several signaling responses, including mitogen-activated protein kinase (MAPK) activation, related to cell survival. Both parathyroid hormone (PTH) and its bone counterpart, PTH-related protein (PTHrP), can regulate MAPK activation by modulating MAPK phosphatase-1 (MKP1). Thus, we hypothesized that PTHrP might protect osteoblasts from ROS-induced apoptosis by targeting MKP1. In osteoblastic MC3T3-E1 and MG-63 cells, H₂ O₂ triggered p38, JNK, ERK and p66^Shc phosphorylation, and cell apoptosis. Meanwhile, PTHrP (1-37) rapidly but transiently increased ERK and Akt phosphorylation without affecting p38, JNK, or p66^Shc activation. H₂ O₂ -induced p38 and ERK phosphorylation and apoptosis were both decreased by pre-treatment with specific kinase inhibitors or PTHrP (1-37) in both osteoblastic cell types. These dephosphorylating and prosurvival actions of PTHrP (1-37) were prevented by a phosphatase inhibitor cocktail, the phosphatase MKP1 inhibitor sanguinarine or a MKP1 siRNA. PTHrP (1-37) promptly enhanced MKP1 protein and gene expression and MKP1-dependent catalase activity in osteoblastic cells. Furthermore, exposure to PTHrP (1-37) adsorbed in an implanted hydroxyapatite-based ceramic into a tibial defect in aging rats increased MKP1 and catalase gene expression in the healing bone area. Our findings demonstrate that PTHrP counteracts the pro-apoptotic actions of ROS by a mechanism dependent on MKP1-induced dephosphorylation of MAPKs in osteoblasts. J. Cell. Physiol. 232: 785-796, 2017. © 2016 Wiley Periodicals, Inc.

Effects of Resveratrol on p66Shc phosphorylation in cultured prostate cells

There is increasing evidence that diet plays a crucial role in age-related diseases and cancer. Oxidative stress is a conceivable link between diet and diseases, thus food antioxidants, counteracting the damage caused by oxidation, are potential tools for fight age-related diseases and cancer. Resveratrol (RSV), a polyphenolic antioxidant from grapes, has gained enormous attention particularly because of its ability to induce growth arrest and apoptosis in cancer cells, and it has been proposed as both chemopreventive and therapeutic agent for cancer and other diseases. Even though the effects of RSV have been studied in prostate cancer cells and animal models, little is known about its effects on normal cells and tissues. To address this issue, we have investigated the effects of RSV on EPN cells, a human non-transformed prostate cell line, focusing on the relationship between RSV and p66Shc, a redox enzyme whose activities strikingly intersect those of RSV. p66Shc activity is regulated by phosphorylation of serine 36 (Ser36) and has been related to mitochondrial oxidative stress, apoptosis induction, regulation of cell proliferation and migration. Here we show that RSV inhibits adhesion, proliferation and migration of EPN cells, and that these effects are associated to induction of dose- and time-dependent p66Shc-Ser36 phosphorylation and ERK1/2 de-phosphorylation. Moreover, we found that RSV is able to activate also p52Shc, another member of the Shc protein family. These data show that RSV affects non-transformed prostate epithelial cells and suggest that Shc proteins may be key contributors of RSV effects on prostate cells.

ShcA Protects against Epithelial-Mesenchymal Transition through Compartmentalized Inhibition of TGF-β-Induced Smad Activation

Epithelial–mesenchymal transition (EMT) is a normal cell differentiation event during development and contributes pathologically to carcinoma and fibrosis progression. EMT often associates with increased transforming growth factor-β (TGF-β) signaling, and TGF-β drives EMT, in part through Smad-mediated reprogramming of gene expression. TGF-β also activates the Erk MAPK pathway through recruitment and Tyr phosphorylation of the adaptor protein ShcA by the activated TGF-β type I receptor. We found that ShcA protects the epithelial integrity of nontransformed cells against EMT by repressing TGF-β-induced, Smad-mediated gene expression. p52ShcA competed with Smad3 for TGF-β receptor binding, and down-regulation of ShcA expression enhanced autocrine TGF-β/Smad signaling and target gene expression, whereas increased p52ShcA expression resulted in decreased Smad3 binding to the TGF-β receptor, decreased Smad3 activation, and increased Erk MAPK and Akt signaling. Furthermore, p52ShcA sequestered TGF-β receptor complexes to caveolin-associated membrane compartments, and reducing ShcA expression enhanced the receptor localization in clathrin-associated membrane compartments that enable Smad activation. Consequently, silencing ShcA expression induced EMT, with increased cell migration, invasion, and dissemination, and increased stem cell generation and mammosphere formation, dependent upon autocrine TGF-β signaling. These findings position ShcA as a determinant of the epithelial phenotype by repressing TGF-β-induced Smad activation through differential partitioning of receptor complexes at the cell surface.

The adaptor protein ShcA protects epithelial cells from transitioning toward a mesenchymal phenotype by controlling partitioning of the TGF-β receptor and repressing downstream Smad2/3 activation.

TGF-β family proteins control cell differentiation and various cell functions. Increased TGF-β signaling, acting through heteromeric receptor complexes, contributes to carcinoma progression and fibrosis. TGF-β drives epithelial–mesenchymal transdifferentiation (EMT), which enables cell migration and invasion. Upon TGF-β binding, “type I” receptors activate, through phosphorylation, Smad2 and Smad3 that control target gene transcription. In EMT, Smad complexes activate the expression of EMT “master” transcription factors and cooperate with these to repress the epithelial phenotype and activate mesenchymal gene expression. TGF-β receptors also activate Erk MAPK signaling, involving association of the adaptor protein ShcA and Tyr phosphorylation of ShcA by type I receptors. We now show that the predominant ShcA isoform, p52ShcA, competes with Smad2/3 for binding to type I TGF-β receptors, thus repressing Smad2/3 activation in response to TGF-β and localizing the receptors to caveolar compartments. Consequently, decreased ShcA expression enhanced TGF-β receptor localization in clathrin compartments and autocrine Smad2/3 signaling, repressed the epithelial phenotype, and promoted EMT. The changes following decreased ShcA expression resulted in increased cell migration and invasion, as well as increased stem cell generation, dependent upon autocrine TGF-β signaling. These findings position ShcA as a determinant of the epithelial phenotype by repressing TGF-β-induced Smad activation through differential partitioning of receptor complexes at the cell surface.

Expression of FOXO3a and Correlation With Histopathologic Features in Retinoblastoma

Forkhead box (FOX) transcription factors are a class of highly conserved proteins, which serve critical cellular functions including cell cycle regulation. The downstream mechanisms of cell cycle regulation involve preservation of retinoblastoma protein function. Its deactivation by phosphorylation and translocation from nucleus to cytoplasm leads to cell proliferation. FOXO3a has been found to be dysregulated in few cancers. However, no study has been reported on role of FOXO3a in retinoblastoma. We assessed the expression of FOXO3a in sections of archived tissue blocks of enucleated/exenterated specimens of retinoblastoma by immunohistochemistry. The histopathologic features were reviewed and correlated with its expression. Effect of FOXO3a expression on survival was assessed. FOXO3a expression was assessed in 100 sections. Six samples did not contain any viable tissue. Retrospective data of 94 patients revealed that median age at presentation was 36 months with male:female ratio of 1.9:1. Fifty-one percent of patients were International Retinoblastoma Staging System stage 1. Of the 94 sections, 68 (72%) showed cytoplasmic expression. Choroidal invasion was associated with cytoplasmic FOXO3a (P=0.04). A trend was also noted in optic nerve cut end involvement (P=0.07). No other histopathologic features were found to be associated with FOXO3a expression. The overall survival and progression-free survival were not found to be affected by FOXO3a expression. Cytoplasmic expression of FOXO3a is frequently found in retinoblastoma and may be involved in pathogenesis. Activation by relocation of FOXO3a to nucleus may activate nonmutated retinoblastoma and may be a potential target of treatment in retinoblastoma.

The p66(Shc) redox adaptor protein is induced by saturated fatty acids and mediates lipotoxicity-induced apoptosis in pancreatic beta cells

AIMS/HYPOTHESIS

The role of the redox adaptor protein p66(Shc) as a potential mediator of saturated fatty acid (FA)-induced beta cell death was investigated.

METHODS

The effects of the FA palmitate on p66(Shc) expression were evaluated in human and murine islets and in rat insulin-secreting INS-1E cells. p66(Shc) expression was also measured in islets from mice fed a high-fat diet (HFD) and from human donors with different BMIs. Cell apoptosis was quantified by two independent assays. The role of p66(Shc) was investigated using pancreatic islets from p66 (Shc-/-) mice and in INS-1E cells with knockdown of p66(Shc) or overexpression of wild-type and phosphorylation-defective p66(Shc). Production of reactive oxygen species (ROS) was evaluated by the dihydroethidium oxidation method.

RESULTS

Palmitate induced a selective increase in p66(Shc) protein expression and phosphorylation on Ser(36) and augmented apoptosis in human and mouse islets and in INS-1E cells. Inhibiting the tumour suppressor protein p53 prevented both the palmitate-induced increase in p66(Shc) expression and beta cell apoptosis. Palmitate-induced apoptosis was abrogated in islets from p66 (Shc-/-) mice and following p66 (Shc) knockdown in INS-1E cells; by contrast, overexpression of p66(Shc), but not that of the phosphorylation-defective p66(Shc) mutant, enhanced palmitate-induced apoptosis. The pro-apoptotic effects of p66(Shc) were dependent upon its c-Jun N-terminal kinase-mediated phosphorylation on Ser(36) and associated with generation of ROS. p66(Shc) protein expression and function were also elevated in islets from HFD-fed mice and from obese/overweight cadaveric human donors.

CONCLUSIONS/INTERPRETATION

p53-dependent augmentation of p66(Shc) expression and function represents a key signalling response contributing to beta cell apoptosis under conditions of lipotoxicity.

Mitochondria-associated membranes: composition, molecular mechanisms, and physiopathological implications

SIGNIFICANCE

In all cells, the endoplasmic reticulum (ER) and mitochondria are physically connected to form junctions termed mitochondria-associated membranes (MAMs). This subcellular compartment is under intense investigation because it represents a "hot spot" for the intracellular signaling of important pathways, including the synthesis of cholesterol and phospholipids, calcium homeostasis, and reactive oxygen species (ROS) generation and activity.

RECENT ADVANCES

The advanced methods currently used to study this fascinating intracellular microdomain in detail have enabled the identification of the molecular composition of MAMs and their involvement within different physiopathological contexts.

CRITICAL ISSUES

Here, we review the knowledge regarding (i) MAMs composition in terms of protein composition, (ii) the relationship between MAMs and ROS, (iii) the involvement of MAMs in cell death programs with particular emphasis within the tumor context, (iv) the emerging role of MAMs during inflammation, and (v) the key role of MAMs alterations in selected neurological disorders.

FUTURE DIRECTIONS

Whether alterations in MAMs represent a response to the disease pathogenesis or directly contribute to the disease has not yet been unequivocally established. In any case, the signaling at the MAMs represents a promising pharmacological target for several important human diseases.

Smoking p66Shc knocked out mice develop respiratory bronchiolitis with fibrosis but not emphysema

The adaptor protein p66Shc regulates intracellular oxidant levels through the modulation of a forkhead-related transcription factor (FOXO3a). The genetic ablation of p66^Shc (p66^Shc–/–) renders mice resistant to oxidative stress and p53-dependent apoptosis. We investigated whether p66^Shc ablation in mice modifies lung cellular and molecular responses to cigarette smoke (CS) exposure. No differences between wild type (WT) and p66^Shc–/– mice were observed in terms of inflammation and oxidant burden after acute CS exposure; however,p66^Shc ablation modifies specific features of chronic inflammation induced by repeated exposure to CS. Unlike WT mice, p66^Shc–/– mice did not develop emphysema, showing protection toward oxidative damage to DNA and apoptosis as revealed by a trivial 8-hydroxyguanosine staining and faint TUNEL and caspase-3 positivity on alveolar epithelial cells. Unexpectedly, CS exposure in p66^Shc–/– mice resulted in respiratory bronchiolitis with fibrosis in surrounded alveoli. Respiratory bronchiolitis was characterized by peribronchiolar infiltrates of lymphocytes and histiocytes, accumulation of ageing pigmented macrophages within and around bronchioles, and peribronchiolar fibrosis. The blockage of apoptosis interferes with the macrophage “clearance” from alveolar spaces, favouring the accumulation of aging macrophages into alveoli and the progressive accumulation of iron pigment in long-lived senescent cells. The presence of areas of interstitial and alveolar fibrosis in peripheral parenchyma often accompanied the bronchiolar changes. Macrophages from smoking p66^Shc–/– mice elaborate M2 cytokines (i.e., IL-4 and IL-13) and enzymes (i.e., chitinase and arginase I), which can promote TGF-beta expression, collagen deposition, and fibrosis in the surrounding areas. We demonstrate here that resistance to oxidative stress and p53-dependent apoptosis can modify tissue responses to CS caused by chronic inflammation without influencing early inflammatory response to CS exposure.

Modelling the p53/p66Shc Aging Pathway in the Shortest Living Vertebrate Nothobranchius Furzeri

Oxidative stress induced by reactive oxygen species (ROS) increases during lifespan and is involved in aging processes. The p66Shc adaptor protein is a master regulator of oxidative stress response in mammals. Ablation of p66Shc enhances oxidative stress resistance both in vitro and in vivo. Most importantly, it has been demonstrated that its deletion retards aging in mice. Recently, new insights in the molecular mechanisms involving p66Shc and the p53 tumor suppressor genes were given: a specific p66Shc/p53 transcriptional regulation pathway was uncovered as determinant in oxidative stress response and, likely, in aging. p53, in a p66Shc-dependent manner, negatively downregulates the expression of 200 genes which are involved in the G2/M transition of mitotic cell cycle and are downregulated during physiological aging. p66Shc modulates the response of p53 by activating a p53 isoform (p44/p53, also named Delta40p53). Based on these latest results, several developments are expected in the future, as the generation of animal models to study aging and the evaluation of the use of the p53/p66Shc target genes as biomarkers in aging related diseases. The aim of this review is to investigate the conservation of the p66Shc and p53 role in oxidative stress between fish and mammals. We propose to approach this study trough a new model organism, the annual fish Nothobranchius furzeri, that has been demonstrated to develop typical signs of aging, like in mammals, including senescence, neurodegeneration, metabolic disorders and cancer.

Aβ induces PUMA activation: a new mechanism for Aβ-mediated neuronal apoptosis

p53 upregulated modulator of apoptosis (PUMA) is a promising tumor therapy target because it elicits apoptosis and profound sensitivity to radiation and chemotherapy. However, inhibition of PUMA may be beneficial for curbing excessive apoptosis associated with neurodegenerative disorders. Alzheimer's disease (AD) is a representative neurodegenerative disease in which amyloid-β (Aβ) deposition causes neurotoxicity. The regulation of PUMA during Aβ-induced neuronal apoptosis remains poorly understood. Here, we reported that PUMA expression was significantly increased in the hippocampus of transgenic mice models of AD and hippocampal neurons in response to Aβ. PUMA knockdown protected the neurons against Aβ-induced apoptosis. Furthermore, besides p53, PUMA transactivation was also regulated by forkhead box O3a through p53-independent manner following Aβ treatment. Notably, PUMA contributed to neuronal apoptosis through competitive binding of apoptosis repressor with caspase recruitment domain to activate caspase-8 that cleaved Bid into tBid to accelerate Bax mitochondrial translocation, revealing a novel pathway of Bax activation by PUMA to mediate Aβ-induced neuronal apoptosis. Together, we demonstrated that PUMA activation involved in Aβ-induced apoptosis, representing a drug target to antagonize AD progression.

Mechanisms in cardiac fibroblast growth: an obligate role for Skp2 and FOXO3a in ERK1/2 MAPK-dependent regulation of p27kip1

Cardiac fibroblast hyperplasia associated with enhanced matrix deposition is a major determinant of tissue remodeling in several disease states of the heart. However, mechanisms controlling cell cycle progression in cardiac fibroblasts remain unexplored. Identification of cell cycle regulatory elements in these cells is important to develop strategies to check adverse cardiac remodeling under pathological conditions. This study sought to probe the mechanisms underlying ERK1/2-mediated p27Kip1 regulation in mitogenically stimulated cardiac fibroblasts. Addition of 10% fetal calf serum to quiescent cultures of adult rat cardiac fibroblasts promoted ERK1/2 activation, as evidenced by its phosphorylation status. Reduction in [3H]thymidine incorporation into DNA increased population doubling time, flow cytometry, and Western blot analysis showing reduced levels of cyclins D and A, p27Kip1 induction, and retinoblastoma protein (Rb) hypophosphorylation in ERK1/2-inhibited cells indicated ERK1/2 dependence of G1-S transition in cardiac fibroblasts. Lack of p27Kip1 protein in serum-stimulated, ERK1/2-active cells was associated with increased levels of Skp2, an E3 ubiquitin ligase for p27Kip1, whose knockdown by RNA interference induced p27Kip1 expression. Further, forced expression of Skp2 in ERK1/2-inhibited cells downregulated p27Kip1. Transcriptional upregulation of p27Kip1 mRNA in ERK1/2-inhibited cells, demonstrated by real-time PCR, correlated with forkhead box O 3a (FOXO3a) transcription factor activation, shown by gel shift assay. FOXO3a knockdown attenuated p27Kip1 mRNA and protein expression in ERK1/2-inhibited cells. We provide evidence for the first time that, in cardiac fibroblasts, activated ERK1/2 regulates p27Kip1 expression transcriptionally and posttranslationally via FOXO3a- and Skp2-dependent mechanisms. Additionally, this study uncovers interesting interactions between critical cell cycle regulatory elements that are only beginning to be understood.

SHetA2 interference with mortalin binding to p66shc and p53 identified using drug-conjugated magnetic microspheres

SHetA2 is a small molecule flexible heteroarotinoid (Flex-Het) with promising cancer prevention and therapeutic activity. Extensive preclinical testing documented lack of SHetA2 toxicity at doses 25 to 150 fold above effective doses. Knowledge of the SHetA2 molecular target(s) that mediate(s) the mechanism of SHetA2 action is critical to appropriate design of clinical trials and improved analogs. The aim of this study was to develop a method to identify SHetA2 binding proteins in cancer cells. A known metabolite of SHetA2 that has a hydroxyl group available for attachment was synthesized and conjugated to a linker for attachment to a magnetic microsphere. SHetA2-conjugated magnetic microspheres and unconjugated magnetic microspheres were separately incubated with aliquots of a whole cell protein extract from the A2780 human ovarian cancer cell line. After washing away non-specifically bound proteins with the protein extraction buffer, SHetA2-binding proteins were eluted with an excess of free SHetA2. In two independent experiments, an SDS gel band of about 72 kDa was present at differential levels in wells of eluent from SHetA2-microspheres in comparison to wells of eluent from unconjugated microspheres. Mass spectrometry analysis of the bands (QStar) and straight eluents (Orbitrap) identified mortalin (HSPA9) to be present in the eluent from SHetA2-microspheres and not in eluent from unconjugated microspheres. Co-immunoprecipitation experiments demonstrated that SHetA2 interfered with mortalin binding to p53 and p66 Src homologous-collagen homologue (p66shc) inside cancer cells. Mortalin and SHetA2 conflictingly regulate the same molecules involved in mitochondria-mediated intrinsic apoptosis. The results validate the power of this protocol for revealing drug targets.

Arginase-II induces vascular smooth muscle cell senescence and apoptosis through p66Shc and p53 independently of its l-arginine ureahydrolase activity: implications for atherosclerotic plaque vulnerability

Background

Vascular smooth muscle cell (VSMC) senescence and apoptosis are involved in atherosclerotic plaque vulnerability. Arginase‐II (Arg‐II) has been shown to promote vascular dysfunction and plaque vulnerability phenotypes in mice through uncoupling of endothelial nitric oxide synthase and activation of macrophage inflammation. The function of Arg‐II in VSMCs with respect to plaque vulnerability is unknown. This study investigated the functions of Arg‐II in VSMCs linking to plaque vulnerability.

Methods and Results

In vitro studies were performed on VSMCs isolated from human umbilical veins, whereas in vivo studies were performed on atherosclerosis‐prone apolipoprotein E‐deficient (ApoE^−/−) mice. In nonsenescent VSMCs, overexpressing wild‐type Arg‐II or an l‐arginine ureahydrolase inactive Arg‐II mutant (H160F) caused similar effects on mitochondrial dysfunction, cell apoptosis, and senescence, which were abrogated by silencing p66Shc or p53. The activation of p66Shc but not p53 by Arg‐II was dependent on extracellular signal‐regulated kinases (ERKs) and sequential activation of 40S ribosomal protein S6 kinase 1 (S6K1)—c‐Jun N‐terminal kinases (JNKs). In senescent VSMCs, Arg‐II and S6K1, ERK‐p66Shc, and p53 signaling levels were increased. Silencing Arg‐II reduced all these signalings and cell senescence/apoptosis. Conversely, silencing p66Shc reduced ERK and S6K1 signaling and Arg‐II levels and cell senescence/apoptosis. Furthermore, genetic ablation of Arg‐II in ApoE^−/− mice reduced the aforementioned signaling and apoptotic VSMCs in the plaque of aortic roots.

Conclusions

Arg‐II, independently of its l‐arginine ureahydrolase activity, promotes mitochondrial dysfunction leading to VSMC senescence/apoptosis through complex positive crosstalk among S6K1‐JNK, ERK, p66Shc, and p53, contributing to atherosclerotic vulnerability phenotypes in mice.

Icariin delays homocysteine-induced endothelial cellular senescence involving activation of the PI3K/AKT-eNOS signaling pathway

CONTEXT

Homocysteine-induced endothelial cellular senescence may contribute to some cardiovascular disorders. Icariin (ICA), a flavonoid derived from Epimedium sagittatum Maxim. (Berberidaceae), has been reported to increase production of nitric oxide (NO) and reduce reactive oxygen species (ROS) levels in human umbilical vein endothelial cells (HUVECs).

OBJECTIVE

To observe the effects of ICA on homocysteine-induced senescence and the underlying mechanisms in HUVECs.

MATERIALS AND METHODS

ICA at concentrations of 0.1, 1, and 5 μM was added into homocysteine pretreated HUVECs. Cellular senescence was assayed by senescence-associated β-galactosidase (SA-β-gal) staining and cumulative population doublings (CPDs). ICA (5 μM) was given orally to homocysteine-treated rats, luminal surface of aortic artery of rats was subjected to SA-β-gal staining. Protein expression was measured by western blot.

RESULTS

Homocysteine significantly increased cellular senescence both in vitro and in vivo. After treatment by ICA, the percentage of SA-β-gal-positive cells, and the ROS level significantly decreased. The CPDs were partially restored. ICA also significantly reduced the mean density of SA-β-gal staining in vivo. We found that NO production and phosphorylation of AKT, ERK, and endothelial NO synthase (eNOS) were elevated by ICA in HUVECs. Furthermore, the increased level of NO production was fully abolished by the phosphatidylinositol-3-kinase (PI3K) inhibitor wortmannin. The mitogen-activated protein kinase (MEK) inhibitor PD98059, which can inhibit phosphorylation of ERK, did not show this ability.

DISCUSSION AND CONCLUSION

Our results indicate that ICA delays homocyteine-induced endothelial senescence in vitro and in vivo. Activation of PI3K/Akt-eNOS-dependent signaling pathway may be responsible for this efficacy of ICA.

The anti-angiogenic activities of glycyrrhizic acid in tumor progression

Glycyrrhizic acid (GA) is the bioactive compound of licorice and has been used as a herbal medicine because of its anti-viral, anti-cancer, and anti-inflammatory properties. This study was designed to investigate the effects of GA on tumor growth, angiogenesis, and the mechanisms underlying the anti-angiogenic activities of GA. We observed that GA inhibited tumor growth and angiogenesis in mice. GA decreased angiogenic activities, such as the migration, invasion, and tube formation of endothelial cells. We also demonstrated that GA reduced the production of reactive oxygen species and activation of ERK in endothelial cells. Our findings suggest that GA is a promising anti-angiogenic therapeutic agent that targets the ERK pathway. Considering that angiogenesis is highly stimulated in the majority of cancers, GA could offer a potent therapeutic agent for cancer.

Disrupted ATP synthase activity and mitochondrial hyperpolarisation-dependent oxidative stress is associated with p66Shc phosphorylation in fibroblasts of NARP patients

p66Shc is an adaptor protein involved in cell proliferation and differentiation that undergoes phosphorylation at Ser36 in response to oxidative stimuli, consequently inducing a burst of reactive oxygen species (ROS), mitochondrial disruption and apoptosis. Its role during several pathologies suggests that p66Shc mitochondrial signalling can perpetuate a primary mitochondrial defect, thus contributing to the pathophysiology of that condition. Here, we show that in the fibroblasts of neuropathy, ataxia and retinitis pigmentosa (NARP) patients, the p66Shc phosphorylation pathway is significantly induced in response to intracellular oxidative stress related to disrupted ATP synthase activity and mitochondrial membrane hyperpolarisation. We postulate that the increased phosphorylation of p66Shc at Ser36 is partially responsible for further increasing ROS production, resulting in oxidative damage of proteins. Oxidative stress and p66Shc phosphorylation at Ser36 may be mitigated by antioxidant administration or the use of a p66Shc phosphorylation inhibitor. This article is part of a Directed Issue entitled: Bioenergetic dysfunction, adaptation and therapy.

HIV gene expression deactivates redox-sensitive stress response program in mouse tubular cells both in vitro and in vivo

Human immunodeficiency virus (HIV)-1 has been reported to cause tubular cell injury both in in vivo and in vitro studies. In the present study, we evaluated the role of oxidative stress in the induction of apoptosis in HIV gene expressing mouse tubular cells in in vivo (Tg26, a transgenic mouse model of HIV-associated nephropathy) and in vitro (tubular cells were transduced with pNL4-3: ΔG/P-GFP, VSV.G psueudo typed virus) studies. Although Tg26 mice showed enhanced tubular cell reactive oxygen species (ROS) generation and apoptosis, renal tissue did not display a robust antioxidant response in the form of enhanced free radical scavenger (MnSOD/catalase) expression. Tg26 mice not only showed enhanced tubular cell expression of phospho-p66ShcA but also displayed nuclear Foxo3a translocation to the cytoplasm. These findings indicated deactivation of tubular cell Foxo3A-dependent redox-sensitive stress response program (RSSRP) in Tg26 mice. In in vitro studies, NL4-3 (pNL4-3: ΔG/P-GFP, VSV.G pseudotyped virus)-transduced mouse proximal tubular cells (NL4-3/MPTEC) displayed enhanced phosphorylation of p66ShcA. NL4-3/MPTECs also displayed greater (P < 0.01) ROS generation when compared with empty vector-transduced tubular cells; however, both diminution of p66ShcA and N-acetyl cysteine attenuated NL4-3-induced tubular cell ROS generation as well as apoptosis. In addition, both antioxidants and free radical scavengers partially inhibited HIV-induced tubular cell apoptosis. NL4-3/MPTEC displayed deactivation of RSSRP in the form of enhanced phosphorylation of Foxo3A and attenuated expression of superoxide dismutase (SOD) and catalase. Since both SOD and catalase were able to provide protection against HIV-1-induced tubular cell apoptosis, it suggests that HIV-1-induced proapoptotic effect may be a consequence of the deactivated RSSRP.

Novel role of p66Shc in ROS-dependent VEGF signaling and angiogenesis in endothelial cells

p66Shc, a longevity adaptor protein, is demonstrated as a key regulator of reactive oxygen species (ROS) metabolism involved in aging and cardiovascular diseases. Vascular endothelial growth factor (VEGF) stimulates endothelial cell (EC) migration and proliferation primarily through the VEGF receptor-2 (VEGFR2). We have shown that ROS derived from Rac1-dependent NADPH oxidase are involved in VEGFR2 autophosphorylation and angiogenic-related responses in ECs. However, a role of p66Shc in VEGF signaling and physiological responses in ECs is unknown. Here we show that VEGF promotes p66Shc phosphorylation at Ser36 through the JNK/ERK or PKC pathway as well as Rac1 binding to a nonphosphorylated form of p66Shc in ECs. Depletion of endogenous p66Shc with short interfering RNA inhibits VEGF-induced Rac1 activity and ROS production. Fractionation of caveolin-enriched lipid raft demonstrates that p66Shc plays a critical role in VEGFR2 phosphorylation in caveolae/lipid rafts as well as downstream p38MAP kinase activation. This in turn stimulates VEGF-induced EC migration, proliferation, and capillary-like tube formation. These studies uncover a novel role of p66Shc as a positive regulator for ROS-dependent VEGFR2 signaling linked to angiogenesis in ECs and suggest p66Shc as a potential therapeutic target for various angiogenesis-dependent diseases.

Hydrogen-rich saline prevents neointima formation after carotid balloon injury by suppressing ROS and the TNF-α/NF-κB pathway

BACKGROUND

Reactive oxygen species (ROS) play a pivotal role in neointima hyperplasia after balloon injury. Molecular hydrogen has emerged as a novel antioxidant and has been proven effective in treating many diseases.

OBJECTIVES

We aimed to determine the mechanism by which hydrogen affects neointima formation.

METHODS

We assessed the influence of a hydrogen-rich saline solution (HRSS) by daily injection in rats. Rats were euthanized to evaluate the neointima. ROS, malondialdehyde (MDA) and superoxide dismutase (SOD) and reduced glutathione (GSH), were detected in the injured artery. Macrophage infiltration and the production of inflammatory factors (i.e., IL-6, TNF-α and NF-κB) were also observed. The in vitro effects of hydrogen on vascular smooth muscle cell (VSMC) proliferation were also measured.

RESULTS

HRSS decreased the neointima area significantly. The neointima/media ratio was also reduced by HRSS. There was a decline in the number of PCNA-positive cells in the intima treated with HRSS. Meanwhile, HRSS ameliorated the ROS and MDA levels and increased SOD, reduced GSH levels in the injured carotid. In addition, the levels of inflammatory factors, such as IL-6, TNF-α and NF-κB p65, were attenuated by HRSS. In vitro studies also confirmed the anti-proliferative capability of the hydrogen solution and ROS generation in VSMCs induced by PDGF-BB.

CONCLUSION

HRSS may have a protective role in the prevention of neointima hyperplasia and restenosis after angioplasty. HRSS may partially exert its role by neutralizing the local ROS and suppressing the TNF-α/NF-κB pathway.

SOD3 decreases ischemic injury derived apoptosis through phosphorylation of Erk1/2, Akt, and FoxO3a

Background

Extracellular superoxide dismutase (SOD3), which dismutates superoxide anion to hydrogen peroxide, has been shown to reduce the free radical stress derived apoptosis in tissue injuries. Since both superoxide anion and hydrogen peroxide have a marked impact on signal transduction pathways and could potentially explain a number of apoptosis and survival -related phenomena in different pathological conditions, we clarified the impact of SOD3 on Akt and Erk1/2 cell survival pathways in rat hind limb injury model.

Methodology and Principal Findings

Based on our data, the hind limb ischemic rats treated with virally delivered sod3 have milder injury and less apoptosis than control animals that could be due to parallel activation of pro-proliferative and anti-apoptotic Erk1/2 and Akt pathways. The common downstream factor of both signaling pathways, the apoptosis related forkhead box protein O3a (FoxO3a), was phosphorylated and translocated to the cytoplasm in sod3 treated tissues and cell line. Additionally, we obtained increased mRNA production of elk-1, ets-1, and microRNA 21 (miR-21), whereas synthesis of bim mRNA was decreased in sod3 overexpressing tissues. We further showed that overexpression of sod3 modulated redox related gene expression by downregulating nox2 and inos when compared to injured control animals.

Conclusions and Significance

The study shows the complexity of SOD3-derived effects on tissue injury recovery that are not limited to the reduction of superoxide anion caused cellular stress but highlights the impact of SOD3 related signal transduction on tissue functions and suggests an important role for SOD3 in attenuating cell stress effects in different pathological conditions.

Applications of post-translational modifications of FoxO family proteins in biological functions

The functions of the FoxO family proteins, in particular their transcriptional activities, are modulated by post-translational modifications (PTMs), including phosphorylation, acetylation, ubiquitination, methylation and glycosylation. These PTMs occur in response to different cellular stresses, which in turn regulate the subcellular localization of FoxO family proteins, as well as their half-life, DNA binding, transcriptional activity and ability to interact with other cellular proteins. In this review, we summarize the role of PTMs of FoxO family proteins in linking their biological and functional relevance with various diseases.

FOXO3a inhibits TNF-α- and IL-1β-induced astrocyte proliferation:Implication for reactive astrogliosis

Reactive astrogliosis is one of the pathological hallmarks of neurodegenerative diseases. Inflammatory cytokines, such as TNF-α and IL-1β, have been shown to mediate the reactive astrogliosis in neurodegenerative diseases; however, the molecular mechanism remains unclear. In this study, we investigated the role of transcription factor FOXO3a on astrocyte proliferation, one primary aspect of severe reactive astrogliosis. Our results confirmed that TNF-α and IL-1β increased astrocyte proliferation, as determined by Ki67 and BrdU immunostaining. Furthermore, we found that cytokine-mediated astrocyte proliferation was accompanied by an increase of the phosphorylation and reduced nuclear expression of FOXO3a. Intracranial injection of TNF-α and IL-1β induced astrocyte proliferation and hypertrophy, which was associated with reduced nuclear expression of Foxo3a in astrocytes. To determine the function of FOXO3a in astrocyte proliferation, wild type FOXO3a was overexpressed with adenovirus, which subsequently upregulated p27Kip1 and Gadd45α, and significantly inhibited cytokine-induced astrocyte proliferation. In contrast, overexpression of dominant negative FOXO3a decreased p27Kip1, upregulated cyclin D1 and promoted astrocyte proliferation. Along the same line, astrocytes isolated from Foxo3a-null mice have higher proliferative potential. In response to intracranial injection of cytokines, Foxo3a-null mice manifested severe astrogliosis in vivo. In conclusion, FOXO3a is important in restraining astrocyte proliferation during proinflammatory cytokine stimulation and loss of function of FOXO3a may be responsible for the proliferation of astrocytes in the severe form of reactive astrogliosis. Understanding the key regulatory role of FOXO3a in reactive astrogliosis may provide a novel therapeutic target during neuroinflammation.

Up-regulation of p27(kip1) contributes to Nrf2-mediated protection against angiotensin II-induced cardiac hypertrophy

AIMS

Nuclear factor erythroid-2-related factor 2 (Nrf2) appears to be a negative regulator of maladaptive cardiac remodelling and dysfunction; however, a potential of the Nrf2-mediated cardiac protection in diverse pathological settings remains to be determined. This study was aimed to explore the role of Nrf2 in angiotensin II (Ang II)-induced cardiac hypertrophy.

METHODS AND RESULTS

Littermate wild-type (WT) and Nrf2 knockout (Nrf2(-/-)) mice were administered Ang II via osmotic mini-pumps for 2 weeks to induce cardiac hypertrophy. Elevation of blood pressure by the continuous Ang II infusion was comparable between WT and Nrf2(-/-) mice. Relative to WT mice, however, Nrf2(-/-) mice exhibited exaggerated myocardial oxidative stress with an impaired induction of a group of antioxidant genes and increased cardiac hypertrophy in response to the sustained Ang II stimulation. In cultured cardiomyocytes, adenoviral overexpression of Nrf2 shRNA enhanced Ang II-induced reactive oxygen species (ROS) production and protein synthesis, whereas adenoviral overexpression of Nrf2 exerted opposite effects. Moreover, Nrf2 deficiency exacerbated Ang II-induced down-regulation of p27(kip1) expression in the heart via a mechanism of post-transcriptional regulation. In contrast, adenoviral overexpression of Nrf2 increased p27(kip1) protein but not mRNA expression and reversed Ang II-induced down-regulation of p27(kip1) protein expression in cultured cardiomyocytes by suppressing ROS formation. Finally, the enhancement of Ang II-induced hypertrophic growth due to the Nrf2 deficiency was negated by overexpressing p27(kip1) in cultured cardiomyocytes.

CONCLUSION

The Nrf2-p27(kip1) pathway serves as a novel negative feedback mechanism in Ang II-induced pathogenesis of cardiac hypertrophy, independent of changes in blood pressure.

Resveratrol regulates p66Shc activation in HaCaT cells

Skin is exposed to both endogenous and environmental oxidant agents, leading to the harmful generation of reactive oxygen species. Particular interest has been pointed on plant antioxidants, such as resveratrol, because of their wide-ranging biological activity and clinical potential. Resveratrol exerts antioxidant, metabolism-regulating and pro-apoptotic/anti-cancer effects on a variety of experimental models and has been suggested to protect skin from ultraviolet-induced photodamaging and photoaging. In parallel, also the biological significance of p66Shc, a member of the Src Homologue and Collagene homologue family with redox activity, is getting further attention. Because of the striking intersection among the activities of resveratrol with those of p66Shc, we investigated whether resveratrol would activate p66Shc in human immortalised keratinocytes (HaCaT cells), a well known and largely used model for skin keratinocytes. HaCaT cells were treated with resveratrol (10-150 μm) for different times. The effect of resveratrol on the proliferation of HaCaT cells and the activation of ERK1/2, AKT, and p66Shc was investigated by cell counting, fluorescence-activated cell sorting, and western blot analysis of total or immunoprecipitated cell extracts. In HaCaT cells, resveratrol induces dose- and time-dependent growth arrest, p66Shc-Ser36 phosphorylation, ERK1/2 phosphorylation and AKT dephosphorylation. Finally, we showed that resveratrol-induced p66Shc-Ser36 phosphorylation is dependent on ERK1/2 activation. Interestingly, these resveratrol-induced molecular effects were associated with reduced adhesion and reversible growth arrest rather than cell death pathways. This is the first evidence linking resveratrol with p66Shc and suggests that p66Shc may contribute to the effect of resveratrol on cell proliferation and function in the outermost layer of the skin.

Cisplatin induces apoptosis through the ERK-p66shc pathway in renal proximal tubule cells

The extracellular signal-regulated kinase (ERK) has been shown to mediate cisplatin (CP)-induced toxicity to renal proximal tubule cells. Here, we demonstrate that ERK serves as the kinase that phosphorylates the pro-apoptotic p66shc protein at its Serine36 residue in CP-treated renal proximal tubule cells. Pharmacologic or dominant-negative inhibition of ERK mitigates cisplatin-induced Ser36 phosphorylation of p66shc. Overexpression of p66shc exacerbates while its knockdown or mutation of the Serine36 site to alanine ameliorates CP-induced nephrotoxicity in vitro. Since p66shc is Serine36 phosphorylated in the kidneys of mice after treatment with CP, a similar mechanism might exist in vivo.

Synaptic activity and nuclear calcium signaling protect hippocampal neurons from death signal-associated nuclear translocation of FoxO3a induced by extrasynaptic N-methyl-D-aspartate receptors

Synaptic activity and the generation of nuclear calcium signals promote neuronal survival through a transcription-dependent process that is not fully understood. Here we show that one mechanism of activity-induced acquired neuroprotection involves the Forkhead transcription factor, FoxO3a, which is known to induce genomic death responses upon translocation from the cytosol to the nucleus. Depletion of endogenous FoxO3a using RNA interference renders hippocampal neurons more resistant to excitotoxic cell death. Using a FoxO3a-green fluorescent protein (GFP) fusion protein to monitor in real time the localization of FoxO3a in hippocampal neurons, we found that several cell death inducing stimuli, including the stimulation of extrasynaptic N-methyl-D-aspartate receptors, growth factor withdrawal, and oxygen-glucose deprivation, caused a swift translocation of FoxO3a-GFP from the cytosol to the cell nucleus. This translocation was inhibited in hippocampal neurons that had undergone prolonged periods of synaptic activity before exposure to cell death-inducing conditions. The activity-dependent protection from death signal-induced FoxO3a-GFP nuclear translocation required synaptic N-methyl-D-aspartate receptor activation and was dependent on nuclear calcium signaling and calcium/calmodulin-dependent protein kinase IV. The modulation of nucleo-cytoplasmic shuttling of FoxO3a may represent one mechanism through which nuclear calcium-induced genomic responses affect cell death processes.

High Erk activity suppresses expression of the cell cycle inhibitor p27Kip1 in colorectal cancer cells

The molecular heterogeneity of human cancer cells at the level of signaling protein activities remains poorly understood. Using a panel of 64 colorectal (CRC) cancer cell lines the activity status of the MAP kinases Erk1 and Erk2 was investigated. Erk1/2 activity varied greatly within the CRC cell line panel and was not detectably associated with the speed of cell growth in 10 CRC lines analyzed. As expected, mutations in K-Ras or B-Raf were often, albeit not always, linked to high Erk1/2 activity. The phosphorylation of several known Erk1/2 targets investigated did not generally reflect Erk1/2 activity in the 10 CRC lines analyzed. However, the reduction of Erk1/2 activity with MEK inhibitors generally abolished cell growth but only led to an increase of cellular p27Kip1 levels in CRC cells with high Erk1/2 activity levels. The results indicate that high Erk1/2 activation is utilized by some CRC lines to override the cell cycle brake p27Kip1, while others presumably rely on different mechanisms in order to inactivate this important cell cycle brake. Such detailed knowledge of the molecular diversity of cancer cell signaling mechanisms may eventually help to develop molecularly targeted, patient-specific therapeutic strategies and treatments.

The Role of p66shc in Oxidative Stress and Apoptosis

p66shcis a gene that regulates the level of reactive oxygen species (ROS), apoptosis induction, and lifespan in mammals. Miceknocked out forp66shchave a lifespan~30% longeranddemonstrate an enhanced resistance to oxidative stress and age-related pathologies such as hypercholesterolemia, ischemia, and hyperglycemia. In this respect, p66shc is a promising pharmacological target for the treatment of age-related diseases. In this review, an attempt has been made to survey and put to a critical analysis data concerning the involvement of p66shс in the different signaling pathways that regulate oxidative stress and apoptosis.

The PI3K/Akt/FOXO3a/p27Kip1 signaling contributes to anti-inflammatory drug-suppressed proliferation of human osteoblasts

Akt has been reported to suppress p27(Kip1) promoter activity through Forkhead box O (FOXO) in different kinds of cells. Previous studies indicated that anti-inflammatory drugs up-regulated p27(Kip1), and this effect might play an important role in anti-inflammatory drug-induced cell cycle arrest of human osteoblasts (hOBs). In this study, we hypothesized that these drugs might increase p27(Kip1) expression in hOBs by altering the Akt/FOXO signaling. We tested this hypothesis by examining the influences of three anti-inflammatory drugs on the levels and/or activities of Akt, FOXO and p27(Kip1) as well as the relationship between these factors and proliferation of hOBs. We tested the effects of indomethacin (10(-5) and 10(-4)M), celecoxib (10(-6) and 10(-5)M), and dexamethasone (10(-7) and 10(-6)M) using PI3K inhibitor, LY294002 (10(-5)M) as the basis of comparison. The three drugs suppressed the canonical level of phosphorylated Akt in hOBs. This was accompanied by elevated FOXO3a level and increased promoter activity, mRNA expression and protein level of p27(Kip1). Furthermore, the anti-inflammatory drugs suppressed the EGF-induced increases in proliferation, phosphorylation, and nucleus translocation of Akt. Simultaneously, they suppressed EGF-induced decreases of FOXO3a nucleus accumulation and p27(Kip1) mRNA expression. On the other hand, FOXO silencing significantly attenuated the drug-induced up-regulation of p27(Kip1) and suppression of proliferation in hOBs. To the best of our knowledge, this study represents the first to demonstrate that Akt/FOXO3a/p27(Kip1) pathway contributes to suppression of hOB proliferation by anti-inflammatory drugs. We suggest that anti-inflammatory drugs suppress hOB proliferation, at least partly, through inactivating Akt, activating FOXO3a, and eventually up-regulating p27(Kip1) expression.

Endothelin-1 induces p66Shc activation through EGF receptor transactivation: Role of beta(1)Pix/Galpha(i3) interaction

Endothelin-1 (ET-1) is a vasoconstrictor peptide known to be a potent mitogen for glomerular mesangial cells. We have shown that ET-1 stimulates the adaptor protein p66Shc through Rac/Cdc42 guanine nucleotide exchange factor beta(1)Pix. In this study, we demonstrate that ET-1-induced serine phosphorylation of p66Shc is mediated through Galpha(i3). Pertussis toxin treatment of cells induced a significant decrease in the interaction between beta(1)Pix and ET(A)-R, and an increase in the binding of Galpha(i3) and G(beta1) to beta(1)Pix. Activation of heterotrimeric G proteins by AlF(4)(-) resulted in an increase of Galpha(i3) binding to beta(1)Pix, which was significantly disrupted in cells expressing beta(1)Pix dimerization deficient mutant, beta(1)PixDelta (602-611). In cells expressing beta(1)PixDelta (602-611), ET-1-induced p66Shc activation was also significantly decreased. Specific inhibition of EGF receptor by AG1478 blocked ET-1-induced p66Shc activation and the binding of p66Shc and Galpha(i3) to beta(1)Pix. Inhibition of Erk1/2 blocked p66Shc activation induced by ET-1. Altogether, our results indicate that ET-1 activates p66Shc through EGF receptor transactivation, leading to the activation of Galpha(i3), beta(1)Pix and Erk1/2.

Something old, something new, something borrowed; how the thermoacidophilic archaeon Sulfolobus solfataricus responds to oxidative stress

To avoid molecular damage of biomolecules due to oxidation, all cells have evolved constitutive and responsive systems to mitigate and repair chemical modifications. Archaea have adapted to some of the most extreme environments known to support life, including highly oxidizing conditions. However, in comparison to bacteria and eukaryotes, relatively little is known about the biology and biochemistry of archaea in response to changing conditions and repair of oxidative damage. In this study transcriptome, proteome, and chemical reactivity analyses of hydrogen peroxide (H(2)O(2)) induced oxidative stress in Sulfolobus solfataricus (P2) were conducted. Microarray analysis of mRNA expression showed that 102 transcripts were regulated by at least 1.5 fold, 30 minutes after exposure to 30 microM H(2)O(2). Parallel proteomic analyses using two-dimensional differential gel electrophoresis (2D-DIGE), monitored more than 800 proteins 30 and 105 minutes after exposure and found that 18 had significant changes in abundance. A recently characterized ferritin-like antioxidant protein, DPSL, was the most highly regulated species of mRNA and protein, in addition to being post-translationally modified. As expected, a number of antioxidant related mRNAs and proteins were differentially regulated. Three of these, DPSL, superoxide dismutase, and peroxiredoxin were shown to interact and likely form a novel supramolecular complex for mitigating oxidative damage. A scheme for the ability of this complex to perform multi-step reactions is presented. Despite the central role played by DPSL, cells maintained a lower level of protection after disruption of the dpsl gene, indicating a level of redundancy in the oxidative stress pathways of S. solfataricus. This work provides the first "omics" scale assessment of the oxidative stress response for an archeal organism and together with a network analysis using data from previous studies on bacteria and eukaryotes reveals evolutionarily conserved pathways where complex and overlapping defense mechanisms protect against oxygen toxicity.

Mammalian sterile 20-like kinase 3 (MST3) mediates oxidative-stress-induced cell death by modulating JNK activation

MST3 (mammalian sterile 20-like kinase 3) is a sterile 20 kinase reported to have a role in Fas-ligation- and staurosporine-induced cell death by unknown mechanism(s). We found that MST3-deficient cells are resistant to H2O2, which was reversed by reconstituting recombinant MST3. H2O2-induced JNK (c-Jun N-terminal kinase) activation was greatly enhanced in shMST3 cells (a cell line treated with short hairpin RNA against MST3). Suppression of JNK activity by the inhibitor SP600125 or by dominant-negative JNK2 re-sensitized cells to H2O2. Furthermore, c-Jun Ser-63 phosphorylation was augmented in shMST3 cells, whereas JunAA (dominant-negative c-Jun) reduced H2O2 resistance, implicating an AP-1 (activator protein 1) pathway in H2O2-induced survival signalling. Total cytoprotective HO-1 (haem oxygenase 1) expression, which was attenuated by JunAA, was induced up to 5-fold higher in shMST3 cells compared with controls. Zinc protoporphyrin IX, a potent inhibitor of HO reversed the H2O2-resistance of shMST3 cells. Our results reveal that H2O2-induced MST3-mediated cell death involves suppressing both a JNK survival pathway and up-regulation of HO-1.

Inhibition of p66ShcA longevity gene rescues podocytes from HIV-1-induced oxidative stress and apoptosis

Glomerular visceral epithelial cells (podocytes) play a critical role in the pathogenesis of human immunodeficiency virus (HIV)-associated nephropathy. A key question concerns the mechanism(s) by which the HIV-1 genome alters the phenotype of the highly specialized, terminally differentiated podocytes. Here, using an in vitro system of conditionally immortalized differentiated human podocytes (CIDHPs), we document a pivotal role for the p66ShcA protein in HIV-1-induced reactive oxygen species generation and CIDHP apoptosis. CIDHP transfected with truncated HIV-1 construct (NL4-3) exhibit increased reactive oxygen species metabolism, DNA strand breaks, and a 5-fold increase in apoptosis, whereas the opposite was true for NL4-3/CIDHP co-transfected with mu-36p66ShcA (micro-36) dominant negative expression vector or isoform-specific p66-small interfering RNA. Phosphorylation at Ser-36 of the wild type p66ShcA protein, required for p66ShcA redox function and inhibition of the potent stress response regulator Foxo3a, was unchanged in micro-36/NL4-3/CIDHP but increased in NL4-3/CIDHP. Acute knockdown of Foxo3a by small interfering RNA induced a 50% increase in micro-36/NL4-3/CIDHP apoptosis, indicating that Foxo3a-dependent responses promote the survival phenotype in micro-36 cells. We conclude that inhibition of p66ShcA redox activity prevents generation of HIV-1 stress signals and activation of the CIDHP apoptosis program.

Peripheral nerve injury induces down-regulation of Foxo3a and p27kip1 in rat dorsal root ganglia

FOXO3a, as a forkhead transcription factor, can control cell cycle through transcriptionally down-regulating p27(kip1) level, which is a key regulator of the mammalian cell cycle and a good candidate to regulate multiple aspects of neurogenesis. To elucidate their expression and function in nervous system lesion and repair, we performed an acute sciatic nerve crush model and studied differential expressions of Foxo3a and p27(kip1) in lumbar dorsal root ganglia. Temporally, Foxo3a protein level was reduced 1 day after injury, and following Foxo3a down-regulation, p27(kip1) mRNA and protein levels were also decreased after injury. Spatially, decreased levels of Foxo3a and p27(kip1) were predominant in neurons and glial cells, which were regenerating axons and largely proliferated after injury, respectively. Together with previous reports, we hypothesized decreased levels of Foxo3a and p27(kip1) in lumbar dorsal root ganglia were implicated in axonal regeneration and the proliferation of glial cells after sciatic nerve injury.

Regulation of Akt/FOXO3a/GSK-3beta/AR signaling network by isoflavone in prostate cancer cells

We have previously shown that genistein could inhibit Akt activation and down-regulate AR (androgen receptor) and PSA (prostate-specific antigen) expression in prostate cancer (PCa) cells. However, pure genistein showed increased lymph node metastasis in an animal model, but such an adverse effect was not seen with isoflavone, suggesting that further mechanistic studies are needed for elucidating the role of isoflavone in PCa. It is known that FOXO3a and GSK-3beta, targets of Akt, regulate cell proliferation and apoptosis. Moreover, FOXO3a, GSK-3beta, and Src are AR regulators and regulate transactivation of AR, mediating the development and progression of PCa. Therefore, we investigated the molecular effects of isoflavone on the Akt/FOXO3a/GSK-3beta/AR signaling network in hormone-sensitive LNCaP and hormone-insensitive C4-2B PCa cells. We found that isoflavone inhibited the phosphorylation of Akt and FOXO3a, regulated the phosphorylation of Src, and increased the expression of GSK-3beta, leading to the down-regulation of AR and its target gene PSA. We also found that isoflavone inhibited AR nuclear translocation and promoted FOXO3a translocation to the nucleus. By electrophoretic mobility shift assay and chromatin immunoprecipitation assay, we found that isoflavone inhibited FOXO3a binding to the promoter of AR and increased FOXO3a binding to the p27(KIP1) promoter, resulting in the alteration of AR and p27(KIP1) expression, the inhibition of cell proliferation, and the induction of apoptosis in both androgen-sensitive and -insensitive PCa cells. These results suggest that isoflavone-induced inhibition of cell proliferation and induction of apoptosis are partly mediated through the regulation of the Akt/FOXO3a/GSK-3beta/AR signaling network. In conclusion, our data suggest that isoflavone could be useful for the prevention and/or treatment of PCa.