Akt1 protects against inflammatory microglial activation through maintenance of membrane asymmetry and modulation of cysteine protease activity

The Latest Evidence of Erythropoietin in the Treatment of Glaucoma

Erythropoietin (EPO) is a circulating hormone conventionally considered to be responsible for erythropoiesis. In addition to facilitating red blood cell production, EPO has pluripotent potential, such as for cognition improvement, neurogenesis, and anti-fibrotic, anti-apoptotic, anti-oxidative, and anti-inflammatory effects. In human retinal tissues, EPO receptors (EPORs) are expressed in the photoreceptor cells, retinal pigment epithelium, and retinal ganglion cell layer. Studies have suggested its potential therapeutic effects in many neurodegenerative diseases, including glaucoma. In this review, we discuss the correlation between glaucoma and EPO, physiology and potential neuroprotective function of the EPO/EPOR system, and latest evidence for the treatment of glaucoma with EPO.

Chlorhexidine as a Keap1-Nrf2 inhibitor: a new target for an old drug for Parkinson's disease therapy

Oxidative stress plays a vital role in the pathophysiology of most neurodegenerative diseases such as Parkinson's disease (PD). The Keap1-Nrf2-ARE pathway, one of the internal defense mechanisms, curbs the reactive oxygen species (ROS) generated in the cellular environment. The pathway leads to the expression of antioxidant genes such as HO-1, GCLC, and NQO1, which act as cellular redox switches and protect the cellular environment. Keap1, the negative regulator of Nrf2, is a potential therapeutic target for treating age-related neurodegenerative diseases. Tecfidera (Dimethyl fumarate), used in the intervention for relapsing multiple sclerosis, is the only commercial drug known to regulate the Nrf2 function. Here, we have identified a repurposing drug, chlorhexidine (LBP125), through ligand-based pharmacophore development and screening against the DrugBank, as a potential inhibitor of the β-propeller domain of Keap1 (Keap1-DC). Chlorhexidine, an antimicrobial agent, is widely used as a mouthwash, skin cleanser, and intervening bacterial infection during childbirth. The biochemical assay confirmed a significant binding affinity of 30 µM and competitively inhibited the Nrf2 peptide interaction. Moreover, chlorhexidine also exerts cytoprotection in a neurotoxic cell model of PD through Keap1-Nrf2 disruption leading to nuclear translocation of Nrf2 and expression of downstream genes, HO-1, and NQO1. Hence, the chemical scaffold of chlorhexidine is a potential lead to develop new chemical libraries with drug-like properties for treating PD. Communicated by Ramaswamy H. Sarma.

Molecular and cellular pathways contributing to brain aging

Aging is the leading risk factor for several age-associated diseases such as neurodegenerative diseases. Understanding the biology of aging mechanisms is essential to the pursuit of brain health. In this regard, brain aging is defined by a gradual decrease in neurophysiological functions, impaired adaptive neuroplasticity, dysregulation of neuronal Ca2+ homeostasis, neuroinflammation, and oxidatively modified molecules and organelles. Numerous pathways lead to brain aging, including increased oxidative stress, inflammation, disturbances in energy metabolism such as deregulated autophagy, mitochondrial dysfunction, and IGF-1, mTOR, ROS, AMPK, SIRTs, and p53 as central modulators of the metabolic control, connecting aging to the pathways, which lead to neurodegenerative disorders. Also, calorie restriction (CR), physical exercise, and mental activities can extend lifespan and increase nervous system resistance to age-associated neurodegenerative diseases. The neuroprotective effect of CR involves increased protection against ROS generation, maintenance of cellular Ca2+ homeostasis, and inhibition of apoptosis. The recent evidence about the modem molecular and cellular methods in neurobiology to brain aging is exhibiting a significant potential in brain cells for adaptation to aging and resistance to neurodegenerative disorders.

Alzheimer's Disease and Protein Kinases

Alzheimer's disease (AD) is the most common neurodegenerative disorder and accounts for more than 60-80% of all cases of dementia. Loss of pyramidal neurons, extracellular amyloid beta (Abeta) accumulated senile plaques, and neurofibrillary tangles that contain hyperphosphorylated tau constitute the main pathological alterations in AD.Synaptic dysfunction and extrasynaptic N-methyl-D-aspartate receptor (NMDAR) hyperactivation contributes to excitotoxicity in patients with AD. Amyloid precursor protein (APP) and Abeta promoted neurodegeneration develop through the activation of protein kinase signaling cascade in AD. Furthermore, ultimate neuronal death in AD is under control of protein kinases-related signaling pathways. In this chapter, critical check-points within the cross-talk between neuron and protein kinases have been defined regarding the initiation and progression of AD. In this context, amyloid cascade hypothesis, neuroinflammation, oxidative stress, granulovacuolar degeneration, loss of Wnt signaling, Abeta-related synaptic alterations, prolonged calcium ions overload and NMDAR-related synaptotoxicity, damage signals hypothesis and type-3 diabetes are discussed briefly.In addition to clinical perspective of AD pathology, recommendations that might be effective in the treatment of AD patients have been reviewed.

Reduced Apoptotic Injury by Phenothiazine in Ischemic Stroke through the NOX-Akt/PKC Pathway

Phenothiazine treatment has been shown to reduce post-stroke ischemic injury, though the underlying mechanism remains unclear. This study sought to confirm the neuroprotective effects of phenothiazines and to explore the role of the NOX (nicotinamide adenine dinucleotide phosphate oxidase)/Akt/PKC (protein kinase C) pathway in cerebral apoptosis. Sprague-Dawley rats underwent middle cerebral artery occlusion (MCAO) for 2 h and were randomly divided into 3 different cohorts: (1) saline, (2) 8 mg/kg chlorpromazine and promethazine (C+P), and (3) 8 mg/kg C+P as well as apocynin (NOX inhibitor). Brain infarct volumes were examined, and cell death/NOX activity was determined by assays. Western blotting was used to assess protein expression of kinase C-δ (PKC-δ), phosphorylated Akt (p-Akt), Bax, Bcl-XL, and uncleaved/cleaved caspase-3. Both C+P and C+P/NOX inhibitor administration yielded a significant reduction in infarct volumes and cell death, while the C+P/NOX inhibitor did not confer further reduction. In both treatment groups, anti-apoptotic Bcl-XL protein expression generally increased, while pro-apoptotic Bax and caspase-3 proteins generally decreased. PKC protein expression was decreased in both treatment groups, demonstrating a further decrease by C+P/NOX inhibitor at 6 and 24 h of reperfusion. The present study confirms C+P-mediated neuroprotection and suggests that the NOX/Akt/PKC pathway is a potential target for efficacious therapy following ischemic stroke.

Intranasal administration of tetrabromobisphenol A bis(2-hydroxyethyl ether) induces neurobehavioral changes in neonatal Sprague Dawley rats

Tetrabromobisphenol A (TBBPA) and its derivatives are now being highly concerned due to their emerging environmental occurrence and deleterious effects on non-target organisms. Considering the potential neurotoxicity of TBBPA derivatives which has been demonstrated in vitro, what could happen in vivo is worthy of being studied. Tetrabromobisphenol A bis(2-hydroxyethyl ether) (TBBPA-BHEE), a representative TBBPA derivative, was selected for a 21-day exposure experiment on neonatal Sprague Dawley (SD) rats through intranasal administration. The neurobehavioral, histopathological changes, and differentially expressed genes based on RNA microarray were investigated to evaluate the neurological effects of this chemical. The results indicated that TBBPA-BHEE exposure significantly compromised the motor co-ordination performance and the locomotor activities (p<0.05). The neurobehavioral phenotype could be attributed to the obvious histopathological changes in both cerebrum and cerebellum, such as neural cell swelling, microglial activation and proliferation. A total of 911 genes were up-regulated, whereas 433 genes were down-regulated. Gene set enrichment analysis showed multiple signaling pathways, including ubiquitin-mediated proteolysis and wingless-int (Wnt) signaling pathway etc. were involved due to TBBPA-BHEE exposure. The gene ontology enrichment analysis showed the basic cellular function and the neurological processes like synaptic transmission were influenced. The toxicological effects of TBBPA-BHEE observed in this study suggested the potential neuronal threaten from unintended exposure, which would be of great value in the biosafety evaluation of TBBPA derivatives.

Neuregulin-1 protects mouse cerebellum against oxidative stress and neuroinflammation

Cerebellum undergoes degenerative changes in neurodegenerative diseases. Two main factors including oxidative stress and neuroinflammation mediate neurodegeneration. Neuregulin-1 (Nrg1) has been implicated in many neurodegenerative diseases, while the underlying mechanisms are unknown. We hypothesized that Nrg1 prevents oxidative stress and neuroinflammation in neurodegeneration. We found a positive correlation between Nrg1 protein levels and ErbB4 and ErbB2 receptor phosphorylation in microarrays of normal human cerebellar tissue. In addition, Nrg1 was also co-localized with pErbB4 and pErbB2. Primary mouse cerebellar granule neurons (CGNs) were treated with H₂O₂ or LPS combined with recombinant Nrg1β (rNrg1β). Western blot analysis and immunofluorescence revealed that H₂O₂ and LPS-induced neuronal toxicity down-regulated the activation of ErbB receptors and Akt1, and the ratio of Bcl2/Bax, which was reversed by rNrg1β. In vivo studies showed that LPS-induced neuroinflammation in mouse cerebellum down-regulated pErbB4, pErbB2, pAkt1/Akt1 and Bcl2/Bax levels, whereas rNrg1β treatment reversed the changes. Immunohistochemistry and Western blot analysis showed that rNrg1β alleviates neuroinflammation by reducing the number of microglial cells and astrocytes and the expression of IL1β. Our results indicate that Nrg1 protects against oxidative stress and neuroinflammation in mouse cerebellum, suggesting potential therapeutic application in neuroinflammation associated with neurodegenerative diseases.

Phenothiazines Enhance Mild Hypothermia-induced Neuroprotection via PI3K/Akt Regulation in Experimental Stroke

Physical hypothermia has long been considered a promising neuroprotective treatment of ischemic stroke, but the treatment's various complications along with the impractical duration and depth of therapy significantly narrow its clinical scope. In the present study, the model of reversible right middle cerebral artery occlusion (MCAO) for 2 h was used. We combined hypothermia (33-35 °C for 1 h) with phenothiazine neuroleptics (chlorpromazine & promethazine) as additive neuroprotectants, with the aim of augmenting its efficacy while only using mild temperatures. We also investigated its therapeutic effects on the Phosphatidylinositol 3 kinase/Protein kinase B (PI3K/Akt) apoptotic pathway. The combination treatment achieved reduction in ischemic rat temperatures in the rectum, cortex and striatum significantly (P < 0.01) faster than hypothermia alone, accompanied by more obvious (P < 0.01) reduction of brain infarct volume and neurological deficits. The combination treatment remarkably (P < 0.05) increased expression of p-Akt and anti-apoptotic proteins (Bcl-2 and Bcl-xL), while reduced expression of pro-apoptotic proteins (AIF and Bax). Finally, the treatment's neuroprotective effects were blocked by a p-Akt inhibitor. By combining hypothermia with phenothiazines, we significantly enhanced the neuroprotective effects of mild hypothermia. This study also sheds light on the possible molecular mechanism for these effects which involves the PI3K/Akt signaling and apoptotic pathway.

FOXO Signaling Pathways as Therapeutic Targets in Cancer

Many transcription factors play a key role in cellular differentiation and the delineation of cell phenotype. Transcription factors are regulated by phosphorylation, ubiquitination, acetylation/deacetylation and interactions between two or more proteins controlling multiple signaling pathways. These pathways regulate different physiological processes and pathological events, such as cancer and other diseases. The Forkhead box O (FOXO) is one subfamily of the fork head transcription factor family with important roles in cell fate decisions and this subfamily is also suggested to play a pivotal functional role as a tumor suppressor in a wide range of cancers. During apoptosis, FOXOs are involved in mitochondria-dependent and -independent processes triggering the expression of death receptor ligands like Fas ligand, TNF apoptosis ligand and Bcl‑X_L, bNIP3, Bim from Bcl-2 family members. Different types of growth factors like insulin play a vital role in the regulation of FOXOs. The most important pathway interacting with FOXO in different types of cancers is the PI3K/AKT pathway. Some other important pathways such as the Ras-MEK-ERK, IKK and AMPK pathways are also associated with FOXOs in tumorigenesis. Therapeutically targeting the FOXO signaling pathway(s) could lead to the discovery and development of efficacious agents against some cancers, but this requires an enhanced understanding and knowledge of FOXO transcription factors and their regulation and functioning. This review focused on the current understanding of cell biology of FOXO transcription factors which relates to their potential role as targets for the treatment and prevention of human cancers. We also discuss drugs which are currently being used for cancer treatment along with their target pathways and also point out some potential drawbacks of those drugs, which further signifies the need for development of new drug strategies in the field of cancer treatment.

Neuroketotherapeutics: A modern review of a century-old therapy

Neuroketotherapeutics represent a class of bioenergetic medicine therapies that feature the induction of ketosis. These therapies include medium-chain triglyceride supplements, ketone esters, fasting, strenuous exercise, the modified Atkins diet, and the classic ketogenic diet. Extended experience reveals persons with epilepsy, especially pediatric epilepsy, benefit from ketogenic diets although the mechanisms that underlie its effects remain unclear. Data indicate ketotherapeutics enhance mitochondrial respiration, promote neuronal long-term potentiation, increase BDNF expression, increase GPR signaling, attenuate oxidative stress, reduce inflammation, and alter protein post-translational modifications via lysine acetylation and β-hydroxybutyrylation. These properties have further downstream implications involving Akt, PLCγ, CREB, Sirtuin, and mTORC pathways. Further studies of neuroketotherapeutics will enhance our understanding of ketone body molecular biology, and reveal novel central nervous system therapeutic applications.

Salidroside attenuates colistin-induced neurotoxicity in RSC96 Schwann cells through PI3K/Akt pathway

Neurotoxicity is a key dose-limiting factor for colistin therapy. This study aimed to investigate the protective effect of Salidroside on colistin-induced neurotoxicity in RSC96 Schwann cells and the underlying mechanisms. After Salidroside (12.5, 25, 50 μg/mL) treatment for 2 h, the cells were cultured with 250 μg/mL colistin for 24 h. In order to investigate the role of phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway, the cells were pre-treated with LY294002 (12.5 μmol/L, a specific inhibitor of PI3K phosphorylation) for 1 h before Salidroside (50 μg/mL) treatment, then were co-cultured with colistin (250 μg/mL) for 24 h. The results showed that colistin treatment could induce apoptotic cell death which was associated with oxidative stress injury. Salidroside could reduce colistin-induced neurotoxicity, decrease the effect of colistin on the reduced expression levels of p-Akt and Bcl-2, and increased the expresion of Bax, release of Cyt c, and activation of caspase-3. However, the protective effect of Salidroside against colistin-induced apoptosis was partly abolished by LY294002. These findings suggest that Salidroside could attenuate colistin-induced neurotoxicity in RSC96 Schwann cells via the PI3K/Akt pathway.

Targeting PRAS40 for multiple diseases

Proline-rich Akt substrate 40kDa (PRAS40) bridges cell signaling between protein kinase B (Akt) and the mammalian target of rapamycin complex 1 (mTORC1). Both Akt and mTORC1 can phosphorylate PRAS40. As a negative regulator of mTORC1, PRAS40 prevents the binding of mTOR to its substrates. The phosphorylation of PRAS40 results in its dissociation from mTORC1 and enhanced mTOR activation. PRAS40 in conjunction with mTORC1 has been closely associated with programmed cell death and is implicated in diabetes mellitus (DM), cardiovascular diseases, cancer, and neurological diseases. Thus, targeting PRAS40 might hold great promise for innovative therapeutic strategies for these diseases.

The neuroprotective effect of Klotho is mediated via regulation of members of the redox system

Generation of reactive oxygen species (ROS), leading to oxidative damage and neuronal cell death, plays an important role in the pathogenesis of neurodegenerative disorders, including Alzheimer disease. The present study aimed to examine the mechanism by which the anti-aging protein Klotho exerts neuroprotective effects against neuronal damage associated with neurodegeneration and oxidative stress. Pretreatment of rat primary hippocampal neurons and mouse hippocampal neuronal cell line HT22 with recombinant Klotho protected these cells from glutamate and oligomeric amyloid β (oAβ)-induced cytotoxicity. In addition, primary hippocampal neurons obtained from Klotho-overexpressing mouse embryos were more resistant to both cytotoxic insults, glutamate and oAβ, compared with neurons from wild-type littermates. An antioxidative stress array analysis of neurons treated with Klotho revealed that Klotho significantly enhances the expression of the thioredoxin/peroxiredoxin (Trx/Prx) system with the greatest effect on the induction of Prx-2, an antioxidant enzyme, whose increase was confirmed at the mRNA and protein levels. Klotho-induced phosphorylation of the PI3K/Akt pathway, a pathway important in apoptosis and longevity, was associated with sustained inhibitory phosphorylation of the transcription factor forkhead box O3a (FoxO3a) and was essential for the induction of Prx-2. Down-regulation of Prx-2 expression using a lentivirus harboring shRNA almost completely abolished the ability of Klotho to rescue neurons from glutamate-induced death and significantly, but not completely, inhibited cell death mediated by oAβ, suggesting that Prx-2 is a key modulator of neuroprotection. Thus, our results demonstrate, for the first time, the neuroprotective role of Klotho and reveal a novel mechanism underlying this effect.

Shedding new light on neurodegenerative diseases through the mammalian target of rapamycin

Neurodegenerative disorders affect a significant portion of the world's population leading to either disability or death for almost 30 million individuals worldwide. One novel therapeutic target that may offer promise for multiple disease entities that involve Alzheimer's disease, Parkinson's disease, epilepsy, trauma, stroke, and tumors of the nervous system is the mammalian target of rapamycin (mTOR). mTOR signaling is dependent upon the mTORC1 and mTORC2 complexes that are composed of mTOR and several regulatory proteins including the tuberous sclerosis complex (TSC1, hamartin/TSC2, tuberin). Through a number of integrated cell signaling pathways that involve those of mTORC1 and mTORC2 as well as more novel signaling tied to cytokines, Wnt, and forkhead, mTOR can foster stem cellular proliferation, tissue repair and longevity, and synaptic growth by modulating mechanisms that foster both apoptosis and autophagy. Yet, mTOR through its proliferative capacity may sometimes be detrimental to central nervous system recovery and even promote tumorigenesis. Further knowledge of mTOR and the critical pathways governed by this serine/threonine protein kinase can bring new light for neurodegeneration and other related diseases that currently require new and robust treatments.

Oxidant stress and signal transduction in the nervous system with the PI 3-K, Akt, and mTOR cascade

Oxidative stress impacts multiple systems of the body and can lead to some of the most devastating consequences in the nervous system especially during aging. Both acute and chronic neurodegenerative disorders such as diabetes mellitus, cerebral ischemia, trauma, Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and tuberous sclerosis through programmed cell death pathways of apoptosis and autophagy can be the result of oxidant stress. Novel therapeutic avenues that focus upon the phosphoinositide 3-kinase (PI 3-K), Akt (protein kinase B), and the mammalian target of rapamycin (mTOR) cascade and related pathways offer exciting prospects to address the onset and potential reversal of neurodegenerative disorders. Effective clinical translation of these pathways into robust therapeutic strategies requires intimate knowledge of the complexity of these pathways and the ability of this cascade to influence biological outcome that can vary among disorders of the nervous system.

Erythropoietin: new directions for the nervous system

New treatment strategies with erythropoietin (EPO) offer exciting opportunities to prevent the onset and progression of neurodegenerative disorders that currently lack effective therapy and can progress to devastating disability in patients. EPO and its receptor are present in multiple systems of the body and can impact disease progression in the nervous, vascular, and immune systems that ultimately affect disorders such as Alzheimer's disease, Parkinson's disease, retinal injury, stroke, and demyelinating disease. EPO relies upon wingless signaling with Wnt1 and an intimate relationship with the pathways of phosphoinositide 3-kinase (PI 3-K), protein kinase B (Akt), and mammalian target of rapamycin (mTOR). Modulation of these pathways by EPO can govern the apoptotic cascade to control β-catenin, glycogen synthase kinase-3β, mitochondrial permeability, cytochrome c release, and caspase activation. Yet, EPO and each of these downstream pathways require precise biological modulation to avert complications associated with the vascular system, tumorigenesis, and progression of nervous system disorders. Further understanding of the intimate and complex relationship of EPO and the signaling pathways of Wnt, PI 3-K, Akt, and mTOR are critical for the effective clinical translation of these cell pathways into robust treatments for neurodegenerative disorders.

Salidroside protects PC12 cells from MPP⁺-induced apoptosis via activation of the PI3K/Akt pathway

Oxidative stress plays an important role in the pathogenesis of Parkinson's disease (PD). Salidroside (SAL), a phenylpropanoid glycoside isolated from Rhodiola rosea L., can exert potent antioxidant properties. In this study, we investigated the protective effects, and the possible mechanism of action, of SAL against 1-methyl-4-phenylpyridinium (MPP(+))-induced cell damage in rat adrenal pheochromocytoma PC12 cells. Pretreatment of PC12 cells with SAL significantly reduced the ability of MPP(+) to induce apoptosis in a dose and time-dependent manner. SAL significantly and dose-dependently inhibited MPP(+)-induced chromatin condensation and MPP(+)-induced release of lactate dehydrogenase by PC12 cells. SAL enhanced Akt phosphorylation in PC12 cells, and the protective effects of SAL against MPP(+)-induced apoptosis were abolished by LY294002, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K) phosphorylation. These findings suggest that SAL prevents MPP(+)-induced apoptosis in PC12 cells, at least in part through activation of the PI3K/Akt pathway.

Wnt1 inducible signaling pathway protein 1 (WISP1) blocks neurodegeneration through phosphoinositide 3 kinase/Akt1 and apoptotic mitochondrial signaling involving Bad, Bax, Bim, and Bcl-xL

Wnt1 inducible signaling pathway protein 1 (WISP1) is a member of the CCN family of proteins that determine cell growth, cell differentiation, immune system activation, and cell survival in tissues ranging from the cardiovascular-pulmonary system to the reproductive system. Yet, little is known of the role of WISP1 as a neuroprotective entity in the nervous system. Here we demonstrate that WISP1 is present in primary hippocampal neurons during oxidant stress with oxygen-glucose deprivation (OGD). WISP1 expression is significantly enhanced during OGD exposure by the cysteine-rich glycosylated protein Wnt1. Similar to the neuroprotective capabilities known for Wnt1 and its signaling pathways, WISP1 averts neuronal cell injury and apoptotic degeneration during oxidative stress exposure. WISP1 requires activation of phosphoinositide 3-kinase (PI 3-K) and Akt1 pathways to promote neuronal cell survival, since blockade of these pathways abrogates cellular protection. Furthermore, WISP1 through PI 3-K and Akt1 phosphorylates Bad and GSK-3β, minimizes expression of the Bim/Bax complex while increasing the expression of Bclx(L)/Bax complex, and prevents mitochondrial membrane permeability, cytochrome c release, and caspase 3 activation in the presence of oxidant stress. These studies provide novel considerations for the development of WISP1 as an effective and robust therapeutic target not only for neurodegenerative disorders, but also for disease entities throughout the body.

EPO relies upon novel signaling of Wnt1 that requires Akt1, FoxO3a, GSK-3β, and β-catenin to foster vascular integrity during experimental diabetes

Multiple complications can ensue in the cardiovascular, renal, and nervous systems during diabetes mellitus (DM). Given that endothelial cells (ECs) are susceptible targets to elevated serum D-glucose, identification of novel cellular mechanisms that can protect ECs may foster the development of unique strategies for the prevention and treatment of DM complications. Erythropoietin (EPO) represents one of these novel strategies but the dependence of EPO upon Wnt1 and its downstream signaling in a clinically relevant model of DM with elevated D-glucose has not been elucidated. Here we show that EPO can not only maintain the integrity of EC membranes, but also prevent apoptotic nuclear DNA degradation and the externalization of membrane phosphatidylserine (PS) residues during elevated D-glucose over a 48-hour period. EPO modulates the expression of Wnt1 and utilizes Wnt1 to confer EC protection during elevated D-glucose exposure, since application of a Wnt1 neutralizing antibody, treatment with the Wnt1 antagonist DKK-1, or gene silencing of Wnt1 with Wnt1 siRNA transfection abrogates the protective capability of EPO. EPO through a novel Wnt1 dependent mechanism controls the post-translational phosphorylation of the "pro-apoptotic" forkhead member FoxO3a and blocks the trafficking of FoxO3a to the cell nucleus to prevent apoptotic demise. EPO also employs the activation of protein kinase B (Akt1) to foster phosphorylation of GSK-3β that appears required for EPO vascular protection. Through this inhibition of GSK-3β, EPO maintains β-catenin activity, allows the translocation of β-catenin from the EC cytoplasm to the nucleus through a Wnt1 pathway, and requires β-catenin for protection against elevated D-glucose since gene silencing of β-catenin eliminates the ability of EPO as well as Wnt1 to increase EC survival. Subsequently, we show that EPO requires modulation of both Wnt1 and FoxO3a to oversee mitochondrial membrane depolarization, cytochrome c release, and caspase activation during elevated D-glucose. Our studies identify critical elements of the protective cascade for EPO that rely upon modulation of Wnt1, Akt1, FoxO3a, GSK-3β, β-catenin, and mitochondrial apoptotic pathways for the development of new strategies against DM vascular complications.

AKT/GSK3 signaling pathway and schizophrenia

Schizophrenia is a prevalent complex trait disorder manifested by severe neurocognitive dysfunctions and lifelong disability. During the past few years several studies have provided direct evidence for the involvement of different signaling pathways in schizophrenia. In this review, we mainly focus on AKT/GSK3 signaling pathway in schizophrenia. The original study on the involvement of this pathway in schizophrenia was published by Emamian et al. in 2004. This study reported convergent evidence for a decrease in AKT1 protein levels and levels of phosphorylation of GSK-3β in the peripheral lymphocytes and brains of individuals with schizophrenia; a significant association between schizophrenia and an AKT1 haplotype; and a greater sensitivity to the sensorimotor gating-disruptive effect of amphetamine, conferred by AKT1 deficiency. It also showed that haloperidol can induce a stepwise increase in regulatory phosphorylation of AKT1 in the brains of treated mice that could compensate for the impaired function of this signaling pathway in schizophrenia. Following this study, several independent studies were published that not only confirmed the association of this signaling pathway with schizophrenia across different populations, but also shed light on the mechanisms by which AKT/GSK3 pathway may contribute to the development of this complex disorder. In this review, following an introduction on the role of AKT in human diseases and its functions in neuronal and non-neuronal cells, a review on the results of studies published on AKT/GSK3 signaling pathway in schizophrenia after the original 2004 paper will be provided. A brief review on other signaling pathways involved in schizophrenia and the possible connections with AKT/GSK3 signaling pathway will be discussed. Moreover, some possible molecular mechanisms acting through this pathway will be discussed besides the mechanisms by which they may contribute to the pathogenesis of schizophrenia. Finally, different transcription factors related to schizophrenia will be reviewed to see how hypo-activity of AKT signaling pathway may impact such transcriptional mechanisms.

Erythropoietin employs cell longevity pathways of SIRT1 to foster endothelial vascular integrity during oxidant stress

Given the cytoprotective ability of erythropoietin (EPO) in cerebral microvascular endothelial cells (ECs) and the invaluable role of ECs in the central nervous system, it is imperative to elucidate the cellular pathways for EPO to protect ECs against brain injury. Here we illustrate that EPO relies upon the modulation of SIRT1 (silent mating type information regulator 2 homolog 1) in cerebral microvascular ECs to foster cytoprotection during oxygen-glucose deprivation (OGD). SIRT1 activation which results in the inhibition of apoptotic early membrane phosphatidylserine (PS) externalization and subsequent DNA degradation during OGD becomes a necessary component for EPO protection in ECs, since inhibition of SIRT1 activity or diminishing its expression by gene silencing abrogates cell survival supported by EPO during OGD. Furthermore, EPO promotes the subcellular trafficking of SIRT1 to the nucleus which is necessary for EPO to foster vascular protection. EPO through SIRT1 averts apoptosis through activation of protein kinase B (Akt1) and the phosphorylation and cytoplasmic retention of the forkhead transcription factor FoxO3a. SIRT1 through EPO activation also utilizes mitochondrial pathways to prevent mitochondrial depolarization, cytochrome c release, and Bad, caspase 1, and caspase 3 activation. Our work identifies novel pathways for EPO in the vascular system that can govern the activity of SIRT1 to prevent apoptotic injury through Akt1, FoxO3a phosphorylation and trafficking, mitochondrial membrane permeability, Bad activation, and caspase 1 and 3 activities in ECs during oxidant stress.

Erythropoietin and Wnt1 govern pathways of mTOR, Apaf-1, and XIAP in inflammatory microglia

Inflammatory microglia modulate a host of cellular processes in the central nervous system that include neuronal survival, metabolic fluxes, foreign body exclusion, and cellular regeneration. Elucidation of the pathways that oversee microglial survival and integrity may offer new avenues for the treatment of neurodegenerative disorders. Here we demonstrate that erythropoietin (EPO), an emerging strategy for immune system modulation, prevents microglial early and late apoptotic injury during oxidant stress through Wnt1, a cysteine-rich glycosylated protein that modulates cellular development and survival. Loss of Wnt1 through blockade of Wnt1 signaling or through the gene silencing of Wnt1 eliminates the protective capacity of EPO. Furthermore, endogenous Wnt1 in microglia is vital to preserve microglial survival since loss of Wnt1 alone increases microglial injury during oxidative stress. Cellular protection by EPO and Wnt1 intersects at the level of protein kinase B (Akt1), the mammalian target of rapamycin (mTOR), and p70S6K, which are necessary to foster cytoprotection for microglia. Downstream from these pathways, EPO and Wnt1 control "anti-apoptotic" pathways of microglia through the modulation of mitochondrial membrane permeability, the release of cytochrome c, and the expression of apoptotic protease activating factor-1 (Apaf-1) and X-linked inhibitor of apoptosis protein (XIAP). These studies offer new insights for the development of innovative therapeutic strategies for neurodegenerative disorders that focus upon inflammatory microglia and novel signal transduction pathways.

The Phosphatidylinositol 3-Kinase/mTor Pathway as a Therapeutic Target for Brain Aging and Neurodegeneration

Many pathological conditions are associated with phosphatidylinositol 3-kinase (PI3K) dysfunction, providing an incentive for the study of the effects of PI3K modulation in different aspects of diabetes, cancer, and aging. The PI3K/AKT/mTOR pathway is a key transducer of brain metabolic and mitogenic signals involved in neuronal proliferation, differentiation, and survival. In several models of neurodegenerative diseases associated with aging, the PI3K/AKT pathway has been found to be dysregulated, suggesting that two or more initiating events may trigger disease formation in an age-related manner. The search for chemical compounds able to modulate the activity of the PI3K/AKT/mTOR pathway is emerging as a potential therapeutic strategy for the treatment and/or prevention of some metabolic defects associated with brain aging. In the current review, we summarize some of the critical actions of PI3K in brain function as well as the evidence of its involvement in aging and Alzheimer's disease.

Novel avenues of drug discovery and biomarkers for diabetes mellitus

Globally, developed nations spend a significant amount of their resources on health care initiatives that poorly translate into increased population life expectancy. As an example, the United States devotes 16% of its gross domestic product to health care, the highest level in the world, but falls behind other nations that enjoy greater individual life expectancy. These observations point to the need for pioneering avenues of drug discovery to increase life span with controlled costs. In particular, innovative drug development for metabolic disorders such as diabetes mellitus becomes increasingly critical given that the number of diabetic people will increase exponentially over the next 20 years. This article discusses the elucidation and targeting of novel cellular pathways that are intimately tied to oxidative stress in diabetes mellitus for new treatment strategies. Pathways that involve wingless, β-nicotinamide adenine dinucleotide (NAD(+)) precursors, and cytokines govern complex biological pathways that determine both cell survival and longevity during diabetes mellitus and its complications. Furthermore, the role of these entities as biomarkers for disease can further enhance their utility irrespective of their treatment potential. Greater understanding of the intricacies of these unique cellular mechanisms will shape future drug discovery for diabetes mellitus to provide focused clinical care with limited or absent long-term complications.

Therapeutic promise and principles: metabotropic glutamate receptors

For a number of disease entities, oxidative stress becomes a significant factor in the etiology and progression of cell dysfunction and injury. Therapeutic strategies that can identify novel signal transduction pathways to ameliorate the toxic effects of oxidative stress may lead to new avenues of treatment for a spectrum of disorders that include diabetes, Alzheimer's disease, Parkinson's disease and immune system dysfunction. In this respect, metabotropic glutamate receptors (mGluRs) may offer exciting prospects for several disorders since these receptors can limit or prevent apoptotic cell injury as well as impact upon cellular development and function. Yet the role of mGluRs is complex in nature and may require specific mGluR modulation for a particular disease entity to maximize clinical efficacy and limit potential disability. Here we discuss the potential clinical translation of mGluRs and highlight the role of novel signal transduction pathways in the metabotropic glutamate system that may be vital for the clinical utility of mGluRs.

A fork in the path: Developing therapeutic inroads with FoxO proteins

Advances in clinical care for disorders involving any system of the body necessitates novel therapeutic strategies that can focus upon the modulation of cellular proliferation, metabolism, inflammation and longevity. In this respect, members of the mammalian forkhead transcription factors of the O class (FoxOs) that include FoxO1, FoxO3, FoxO4 and FoxO6 are increasingly being recognized as exciting prospects for multiple disorders. These transcription factors govern development, proliferation, survival and longevity during multiple cellular environments that can involve oxidative stress. Furthermore, these transcription factors are closely integrated with several novel signal transduction pathways, such as erythropoietin and Wnt proteins, that may influence the ability of FoxOs to act as a “double-edge sword” to sometimes promote cell survival, but at other times lead to cell injury. Here we discuss the fascinating but complex role of FoxOs during cellular injury and oxidative stress, progenitor cell development, fertility, angiogenesis, cardiovascular function, cellular metabolism and diabetes, cell longevity, immune surveillance and cancer.

Wnt1 neuroprotection translates into improved neurological function during oxidant stress and cerebral ischemia through AKT1 and mitochondrial apoptotic pathways

Although essential for the development of the nervous system, Wnt1 also has been associated with neurodegenerative disease and cognitive loss during periods of oxidative stress. Here we show that endogenous expression of Wnt1 is suppressed during oxidative stress in both in vitro and in vivo experimental models. Loss of endogenous Wnt1 signaling directly correlates with neuronal demise and increased functional deficit, illustrating that endogenous neuronal Wnt1 offers a vital level of intrinsic cellular protection against oxidative stress. Furthermore, transient overexpression of Wnt1 or application of exogenous Wnt1 recombinant protein is necessary to preserve neurological function and rescue neurons from apoptotic membrane phosphatidylserine externalization and genomic DNA degradation, since blockade of Wnt1 signaling with a Wnt1 antibody or dickkopf related protein 1 abrogates neuronal protection by Wnt1. Wnt1 ultimately relies upon the activation of Akt1, the modulation of mitochondrial membrane permeability, and the release of cytochrome c to control the apoptotic cascade, since inhibition of Wnt1 signaling, the phosphatidylinositol 3-kinase pathway, or Akt1 activity abrogates the ability of Wnt1 to block these apoptotic components. Our work identifies Wnt1 and its downstream signaling as cellular targets with high clinical potential for novel treatment strategies for multiple disorders precipitated by oxidative stress.

Mammalian target of rapamycin: hitting the bull's-eye for neurological disorders

The mammalian target of rapamycin (mTOR) and its associated cell signaling pathways have garnered significant attention for their roles in cell biology and oncology. Interestingly,the explosion of information in this field has linked mTOR to neurological diseases with promising initial studies. mTOR, a 289 kDa serine/threonine protein kinase, plays an important role in cell growth and proliferation and is activated through phosphorylation in response to growth factors, mitogens and hormones. Growth factors, amino acids, cellular nutrients and oxygen deficiency can downregulate mTOR activity. The function of mTOR signaling is mediated primarily through two mTOR complexes: mTORC1 and mTORC2. mTORC1 initiates cap-dependent protein translation, a rate-limiting step of protein synthesis, through the phosphorylation of the targets eukaryotic initiation factor 4E-binding protein 1 (4EBP1) and p70 ribosomal S6 kinase (p70S6K). In contrast, mTORC2 regulates development of the cytoskeleton and also controls cell survival. Although closely tied to tumorigenesis, mTOR and the downstream signaling pathways are significantly involved in the central nervous system (CNS) with synaptic plasticity, memory retention, neuroendocrine regulation associated with food intake and puberty and modulation of neuronal repair following injury. The signaling pathways of mTOR also are believed to be a significant component in a number of neurological diseases, such as Alzheimer disease, Parkinson disease and Huntington disease, tuberous sclerosis, neurofibromatosis, fragile X syndrome, epilepsy, traumatic brain injury and ischemic stroke. Here we describe the role of mTOR in the CNS and illustrate the potential for new strategies directed against neurological disorders.

Early apoptotic vascular signaling is determined by Sirt1 through nuclear shuttling, forkhead trafficking, bad, and mitochondrial caspase activation

Complications of diabetes mellitus (DM) weigh heavily upon the endothelium that ultimately affect multiple organ systems. These concerns call for innovative treatment strategies that employ molecular pathways responsible for cell survival and longevity. Here we show in a clinically relevant model of DM with elevated D-glucose that endothelial cell (EC) SIRT1 is vital for the prevention of early membrane apoptotic phosphatidylserine externalization and subsequent DNA degradation supported by studies with modulation of SIRT1 activity and gene knockdown of SIRT1. Furthermore, during elevated D-glucose exposure, we show that SIRT1 is sequestered in the cytoplasm of ECs, but specific activation of SIRT1 shuttles the protein to the nucleus to allow for cytoprotection. The ability of SIRT1 to avert apoptosis employs the activation of protein kinase B (Akt1), the post-translational phosphorylation of the forkhead member FoxO3a, the blocked trafficking of FoxO3a to the nucleus, and the inhibition of FoxO3a to initiate a "pro-apoptotic" program as shown by complimentary gene knockdown studies of FoxO3a. Vascular apoptotic oversight by SIRT1 extends to the direct modulation of mitochondrial membrane permeability, cytochrome c release, Bad activation, and caspase 1 and 3 activation, since inhibition of SIRT1 activity and gene knockdown of SIRT1 significantly accentuate cascade progression while SIRT1 activation abrogates these apoptotic elements. Our work identifies vascular SIRT1 and its control over early apoptotic membrane signaling, Akt1 activation, post-translational modification and trafficking of FoxO3a, mitochondrial permeability, Bad activation, and rapid caspase induction as new avenues for the treatment of vascular complications during DM.

Diabetes mellitus: channeling care through cellular discovery

Diabetes mellitus (DM) impacts a significant portion of the world's population and care for this disorder places an economic burden on the gross domestic product for any particular country. Furthermore, both Type 1 and Type 2 DM are becoming increasingly prevalent and there is increased incidence of impaired glucose tolerance in the young. The complications of DM are protean and can involve multiple systems throughout the body that are susceptible to the detrimental effects of oxidative stress and apoptotic cell injury. For these reasons, innovative strategies are necessary for the implementation of new treatments for DM that are generated through the further understanding of cellular pathways that govern the pathological consequences of DM. In particular, both the precursor for the coenzyme beta-nicotinamide adenine dinucleotide (NAD(+)), nicotinamide, and the growth factor erythropoietin offer novel platforms for drug discovery that involve cellular metabolic homeostasis and inflammatory cell control. Interestingly, these agents and their tightly associated pathways that consist of cell cycle regulation, protein kinase B, forkhead transcription factors, and Wnt signaling also function in a broader sense as biomarkers for disease onset and progression.

FOXO3a governs early and late apoptotic endothelial programs during elevated glucose through mitochondrial and caspase signaling

Mechanisms that preserve endothelial cell (EC) integrity remain elusive, but are critical for new strategies directed against endocrine disorders such as diabetes mellitus (DM). Here we demonstrate in primary cerebral ECs with a clinically relevant model of elevated d-glucose that Akt1 and the post-translational modification and subcellular trafficking of the forkhead transcription factor FoxO3a are critical for early apoptotic membrane signaling and subsequent degradation of nuclear DNA. FoxO3a also directly governs apoptotic mitochondrial signal transduction pathways, since gene knockdown of FoxO3a prevents mitochondrial membrane depolarization as well as the release of cytochrome c. Control of this apoptotic cascade extends to the rapid and progressive activation of caspases. The presence of FoxO3a is necessary for cleaved (active) caspase 1 and 3 expression, since loss of FoxO3a abrogates the induction of caspase activity. Our work identifies Akt1, FoxO3a and closely aligned pathways as key therapeutic targets during impaired glucose tolerance and DM.

Inflammatory neurodegeneration and mechanisms of microglial killing of neurons

Inflammatory neurodegeneration contributes to a wide variety of brain pathologies. A number of mechanisms by which inflammatory-activated microglia and astrocytes kill neurons have been identified in culture. These include: (1) acute activation of the phagocyte NADPH oxidase (PHOX) found in microglia, (2) expression of the inducible nitric oxide synthase (iNOS) in glia, and (3) microglial phagocytosis of neurons. Activation of PHOX (by cytokines, beta-amyloid, prion protein, lipopolysaccharide, ATP, or arachidonate) causes microglial proliferation and inflammatory activation; thus, PHOX is a key regulator of inflammation. However, activation of PHOX alone causes little or no death, but when combined with iNOS expression results in apparent apoptosis via peroxynitrite production. Nitric oxide (NO) from iNOS expression also strongly synergizes with hypoxia to induce neuronal death because NO inhibits cytochrome oxidase in competition with oxygen, resulting in glutamate release and excitotoxicity. Finally, microglial phagocytosis of these stressed neurons may contribute to their loss.

FoxO3a governs early microglial proliferation and employs mitochondrial depolarization with caspase 3, 8, and 9 cleavage during oxidant induced apoptosis

Microglia of the central nervous system have a dual role in the ability to influence the survival of neighboring cells. During inflammatory cell activation, microglia can lead to the disposal of toxic cellular products and permit tissue regeneration, but microglia also may lead to cellular destruction with phagocytic removal. For these reasons, it is essential to elucidate not only the underlying pathways that control microglial activation and proliferation, but also the factors that determine microglial survival. In this regard, we investigated in the EOC 2 microglial cell line with an oxygen-glucose deprivation (OGD) injury model of oxidative stress the role of the "O" class forkhead transcription factor FoxO3a that in some scenarios is closely linked to immune system function. We demonstrate that FoxO3a is a necessary element in the control of early and late apoptotic injury programs that involve membrane phosphatidylserine externalization and nuclear DNA degradation, since transient knockdown of FoxO3a in microglia preserves cellular survival 24 hours following OGD exposure. However, prior to the onset of apoptotic injury, FoxO3a facilitates the activation and proliferation of microglia as early as 3 hours following OGD exposure that occurs in conjunction with the trafficking of the unphosphorylated and active post-translational form of FoxO3a from the cytoplasm to the cell nucleus. FoxO3a also can modulate apoptotic mitochondrial signal transduction pathways in microglia, since transient knockdown of FoxO3a prevents mitochondrial membrane depolarization as well as the release of cytochrome c during OGD. Control of this apoptotic cascade also extends to progressive caspase activation as early as 1 hour following OGD exposure. The presence of FoxO3a is necessary for the expression of cleaved (active) caspase 3, 8, and 9, since loss of FoxO3a abrogates the induction of caspase activity. Interestingly, elimination of FoxO3a reduced caspase 9 activity to a lesser extent than that noted with caspase 3 and 8 activities, suggesting that FoxO3a in relation to caspase 9 may be more reliant upon other signal transduction pathways potentially independent from caspase 3 and 8.

Oxidative stress: Biomarkers and novel therapeutic pathways

Oxidative stress significantly impacts multiple cellular pathways that can lead to the initiation and progression of varied disorders throughout the body. It therefore becomes imperative to elucidate the components and function of novel therapeutic strategies against oxidative stress to further clinical diagnosis and care. In particular, both the growth factor and cytokine erythropoietin (EPO) and members of the mammalian forkhead transcription factors of the O class (FoxOs) may offer the greatest promise for new treatment regimens since these agents and the cellular pathways they oversee cover a range of critical functions that directly influence progenitor cell development, cell survival and degeneration, metabolism, immune function, and cancer cell invasion. Furthermore, both EPO and FoxOs function not only as therapeutic targets, but also as biomarkers of disease onset and progression, since their cellular pathways are closely linked and overlap with several unique signal transduction pathways. However, biological outcome with EPO and FoxOs may sometimes be both unexpected and undesirable that can raise caution for these agents and warrant further investigations. Here we present the exciting as well as complicated role EPO and FoxOs possess to uncover the benefits as well as the risks of these agents for cell biology and clinical care in processes that range from stem cell development to uncontrolled cellular proliferation.

New strategies for Alzheimer's disease and cognitive impairment

Approximately five million people suffer with Alzheimer's disease (AD) and more than twenty-four million people are diagnosed with AD, pre-senile dementia, and other disorders of cognitive loss worldwide. Furthermore, the annual cost per patient with AD can approach $200,000 with an annual population aggregate cost of $100 billion. Yet, complete therapeutic prevention or reversal of neurovascular injury during AD and cognitive loss is not achievable despite the current understanding of the cellular pathways that modulate nervous system injury during these disorders. As a result, identification of novel therapeutic targets for the treatment of neurovascular injury would be extremely beneficial to reduce or eliminate disability from diseases that lead to cognitive loss or impairment. Here we describe the capacity of intrinsic cellular mechanisms for the novel pathways of erythropoietin and forkhead transcription factors that may offer not only new strategies for disorders such as AD and cognitive loss, but also function as biomarkers for disease onset and progression.

Erythropoietin, forkhead proteins, and oxidative injury: biomarkers and biology

Oxidative stress significantly impacts multiple cellular pathways that can lead to the initiation and progression of varied disorders throughout the body. It therefore becomes imperative to elucidate the components and function of novel therapeutic strategies against oxidative stress to further clinical diagnosis and care. In particular, both the growth factor and cytokine erythropoietin (EPO), and members of the mammalian forkhead transcription factors of the O class (FoxOs), may offer the greatest promise for new treatment regimens, since these agents and the cellular pathways they oversee cover a range of critical functions that directly influence progenitor cell development, cell survival and degeneration, metabolism, immune function, and cancer cell invasion. Furthermore, both EPO and FoxOs function not only as therapeutic targets, but also as biomarkers of disease onset and progression, since their cellular pathways are closely linked and overlap with several unique signal transduction pathways. Yet, EPO and FoxOs may sometimes have unexpected and undesirable effects that can raise caution for these agents and warrant further investigations. Here we present the exciting as well as the complex role that EPO and FoxOs possess to uncover the benefits as well as the risks of these agents for cell biology and clinical care in processes that range from stem cell development to uncontrolled cellular proliferation.

The vitamin nicotinamide: translating nutrition into clinical care

Nicotinamide, the amide form of vitamin B(3) (niacin), is changed to its mononucleotide compound with the enzyme nicotinic acide/nicotinamide adenylyltransferase, and participates in the cellular energy metabolism that directly impacts normal physiology. However, nicotinamide also influences oxidative stress and modulates multiple pathways tied to both cellular survival and death. During disorders that include immune system dysfunction, diabetes, and aging-related diseases, nicotinamide is a robust cytoprotectant that blocks cellular inflammatory cell activation, early apoptotic phosphatidylserine exposure, and late nuclear DNA degradation. Nicotinamide relies upon unique cellular pathways that involve forkhead transcription factors, sirtuins, protein kinase B (Akt), Bad, caspases, and poly (ADP-ribose) polymerase that may offer a fine line with determining cellular longevity, cell survival, and unwanted cancer progression. If one is cognizant of the these considerations, it becomes evident that nicotinamide holds great potential for multiple disease entities, but the development of new therapeutic strategies rests heavily upon the elucidation of the novel cellular pathways that nicotinamide closely governs.

A "FOXO" in sight: targeting Foxo proteins from conception to cancer

The successful treatment for multiple disease entities can rest heavily upon the ability to elucidate the intricate relationships that govern cellular proliferation, metabolism, survival, and inflammation. Here we discuss the therapeutic potential of the mammalian forkhead transcription factors predominantly in the O class, FoxO1, FoxO3, FoxO4, and FoxO6, which play a significant role during normal cellular function as well as during progressive disease. These transcription factors are integrated with several signal transduction pathways, such as Wnt proteins, that can regulate a broad array of cellular process that include stem cell proliferation, aging, and malignancy. FoxO transcription factors are attractive considerations for strategies directed against human cancer in light of their pro-apoptotic effects and ability to lead to cell cycle arrest. Yet, FoxO proteins can be associated with infertility, cellular degeneration, and unchecked cellular proliferation. As our knowledge continues to develop for this novel family of proteins, potential clinical applications for the FoxO family should heighten our ability to limit disease progression without clinical compromise.

Enhanced tolerance against early and late apoptotic oxidative stress in mammalian neurons through nicotinamidase and sirtuin mediated pathways

Focus upon therapeutic strategies that intersect between pathways that govern cellular metabolism and cellular survival may offer the greatest impact for the treatment of a number of neurodegenerative and metabolic disorders, such as diabetes mellitus. In this regard, we investigated the role of a Drosophila nicotinamidase (DN) in mammalian SH-SY5Y neuronal cells during oxidative stress. We demonstrate that during free radical exposure to nitric oxide generators DN neuronal expression significantly increased cell survival and blocked cellular membrane injury. Furthermore, DN neuronal expression prevented both apoptotic late DNA degradation and early phosphatidylserine exposure that may serve to modulate inflammatory cell activation in vivo. Nicotinamidase activity that limited nicotinamide cellular concentrations appeared to be necessary for DN neuroprotection, since application of progressive nicotinamide concentrations could abrogate the benefits of DN expression during oxidative stress. Pathways that involved sirtuin activation and SIRT1 were suggested to be vital, at least in part, for DN to confer protection through a series of studies. First, application of resveratrol increased cell survival during oxidative stress either alone or in conjunction with the expression of DN to a similar degree, suggesting that DN may rely upon SIRT1 activation to foster neuronal protection. Second, the overexpression of either SIRT1 or DN in neurons prevented apoptotic injury specifically in neurons expressing these proteins during oxidative stress, advancing the premise that DN and SIRT1 may employ similar pathways for neuronal protection. Third, inhibition of sirtuin activity with sirtinol was detrimental to neuronal survival during oxidative stress and prevented neuronal protection during overexpression of DN or SIRT1, further supporting that SIRT1 activity may be necessary for DN neuroprotection during oxidative stress. Implementation of further work to elucidate the cellular mechanisms that govern nicotinamidase activity in mammalian cells may offer novel avenues for the treatment of disorders tied to oxidative stress and cellular metabolic dysfunction.

The "O" class: crafting clinical care with FoxO transcription factors

Forkhead Transcription Factors: Vital Elements in Biology and Medicine provides a unique platform for the presentation of novel work and new insights into the vital role that forkhead transcription factors play in both cellular physiology as well as clinical medicine. Internationally recognized investigators provide their insights and perspectives for a number of forkhead genes and proteins that may have the greatest impact for the development of new strategies for a broad array of disorders that can involve aging, cancer, cardiac function, neurovascular integrity, fertility, stem cell differentiation, cellular metabolism, and immune system regulation. Yet, the work clearly sets a precedent for the necessity to understand the cellular and molecular function of forkhead proteins since this family of transcription factors can limit as well as foster disease progression depending upon the cellular environment. With this in mind, our concluding chapter for Forkhead Transcription Factors: Vital Elements in Biology andMedicine offers to highlight both the diversity and complexity of the forkhead transcription family by focusing upon the mammalian forkhead transcription factors of the O class (FoxOs) that include FoxO1, FoxO3, FoxO4, and FoxO6. FoxO proteins are increasingly considered to represent unique cellular targets that can control numerous processes such as angiogenesis, cardiovascular development, vascular tone, oxidative stress, stem cell proliferation, fertility, and immune surveillance. Furthermore, FoxO transcription factors are exciting considerations for disorders such as cancer in light of their pro-apoptotic and inhibitory cell cycle effects as well as diabetes mellitus given the close association FoxOs hold with cellular metabolism. In addition, these transcription factors are closely integrated with several novel signal transduction pathways, such as erythropoietin and Wnt proteins, that may influence the ability of FoxOs to lead to cell survival or cell injury. Further understanding of both the function and intricate nature of the forkhead transcription factor family, and in particular the FoxO proteins, should allow selective regulation of cellular development or cellular demise for the generation of successful future clinical strategies and patient well-being.

Clever cancer strategies with FoxO transcription factors

Given that cancer and related disorders affect a wide spectrum of the world's population, and in most cases are progressive in nature, it is essential that future care must overcome the present limitations of existing therapies in the absence of toxic side effects. Mammalian forkhead transcription factors of the O class (FoxOs) may fill this niche since these proteins are increasingly considered to represent unique cellular targets directed against human cancer in light of their pro-apoptotic effects and ability to lead to cell cycle arrest. Yet, FoxOs also can significantly affect normal cell survival and longevity, requiring new treatments for neoplastic growth to modulate novel pathways that integrate cell proliferation, metabolism, inflammation and survival. In this respect, members of the FoxO family are extremely compelling to consider since these transcription factors have emerged as versatile proteins that can control angiogenesis, stem cell proliferation, cell adhesion and autoimmune disease. Further elucidation of FoxO protein function during neoplastic growth should continue to lay the foundation for the successful translation of these transcription factors into novel and robust clinical therapies for cancer.

Erythropoietin with retrobulbar administration protects retinal ganglion cells from acute elevated intraocular pressure in rats

OBJECTIVE

The aim of this study was to clarify whether erythropoietin (EPO) with a retrobulbar administration could protect retinal ganglion cells (RGCs) from acute elevated intraocular pressure (IOP).

METHODS

The anterior chamber of the right eye was cannulated, and the IOP was raised to 70 mm Hg for a duration of up to 60 min. One thousand (1000) units of recombinant erythropoietin (rhEPO) or vehicle solution was administered a retrobulbar injection immediately after the onset of the acute elevated IOP. After 1 week, RGCs were labeled with a commercially available retrograde tracer applied to the superior colliculi. Densities of surviving RGCs were estimated by counting retrograde-tracer-labeled cells in whole-mounted retinas. The ultrastructural changes of RGCs were observed by transmission electron microscope. Immunocytochemistry was used to detect EPO and erythropoietin receptor (EPOR) expression in the RGCs layer.

RESULTS

The acute elevated IOP could result in the loss of RGCs. The number of surviving RGCs per square millimeter in the eyes of the acute elevated IOP + rhEPO retrobulbar injection group was significantly higher than that in the eyes of the acute elevated IOP and acute elevated IOP + vehicle solution retrobulbar injection groups (P < 0.05). The number of the organelles in the RGCs plasm decreased, but some intact mitochondrian still existed in the RGCs plasm in the eyes of the acute elevated IOP + rhEPO retrobulbar injection group. The densities of EPO and EPOR expression of the RGCs layer in the eyes of the acute elevated IOP + rhEPO retrobulbar injection group were significantly higher than that in the eyes of the acute elevated IOP and acute elevated IOP + vehicle solution retrobulbar injection groups (P < 0.01).

CONCLUSION

EPO with a retrobulbar administration could protect RGCs from acute elevated IOP.

Erythropoietin: elucidating new cellular targets that broaden therapeutic strategies

Given that erythropoietin (EPO) is no longer believed to have exclusive biological activity in the hematopoietic system, EPO is now considered to have applicability in a variety of nervous system disorders that can overlap with vascular disease, metabolic impairments, and immune system function. As a result, EPO may offer efficacy for a broad number of disorders that involve Alzheimer's disease, cardiac insufficiency, stroke, trauma, and diabetic complications. During a number of clinical conditions, EPO is robust and can prevent metabolic compromise, neuronal and vascular degeneration, and inflammatory cell activation. Yet, use of EPO is not without its considerations especially in light of frequent concerns that may compromise clinical care. Recent work has elucidated a number of novel cellular pathways governed by EPO that can open new avenues to avert deleterious effects of this agent and offer previously unrecognized perspectives for therapeutic strategies. Obtaining greater insight into the role of EPO in the nervous system and elucidating its unique cellular pathways may provide greater cellular viability not only in the nervous system but also throughout the body.

Erythropoietin and oxidative stress

Unmitigated oxidative stress can lead to diminished cellular longevity, accelerated aging, and accumulated toxic effects for an organism. Current investigations further suggest the significant disadvantages that can occur with cellular oxidative stress that can lead to clinical disability in a number of disorders, such as myocardial infarction, dementia, stroke, and diabetes. New therapeutic strategies are therefore sought that can be directed toward ameliorating the toxic effects of oxidative stress. Here we discuss the exciting potential of the growth factor and cytokine erythropoietin for the treatment of diseases such as cardiac ischemia, vascular injury, neurodegeneration, and diabetes through the modulation of cellular oxidative stress. Erythropoietin controls a variety of signal transduction pathways during oxidative stress that can involve Janus-tyrosine kinase 2, protein kinase B, signal transducer and activator of transcription pathways, Wnt proteins, mammalian forkhead transcription factors, caspases, and nuclear factor kappaB. Yet, the biological effects of erythropoietin may not always be beneficial and may be poor tolerated in a number of clinical scenarios, necessitating further basic and clinical investigations that emphasize the elucidation of the signal transduction pathways controlled by erythropoietin to direct both successful and safe clinical care.

Triple play: promoting neurovascular longevity with nicotinamide, WNT, and erythropoietin in diabetes mellitus

Oxidative stress is a principal pathway for the dysfunction and ultimate destruction of cells in the neuronal and vascular systems for several disease entities, not promoting the ravages of oxidative stress to any less of a degree than diabetes mellitus. Diabetes mellitus is increasing in incidence as a result of changes in human behavior that relate to diet and daily exercise and is predicted to affect almost 400 million individuals worldwide in another two decades. Furthermore, both type 1 and type 2 diabetes mellitus can lead to significant disability in the nervous and cardiovascular systems, such as cognitive loss and cardiac insufficiency. As a result, innovative strategies that directly target oxidative stress to preserve neuronal and vascular longevity could offer viable therapeutic options to diabetic patients in addition to more conventional treatments that are designed to control serum glucose levels. Here we discuss the novel application of nicotinamide, Wnt signaling, and erythropoietin that modulate cellular oxidative stress and offer significant promise for the prevention of diabetic complications in the nervous and vascular systems. Essential to this process is the precise focus upon diverse as well as common cellular pathways governed by nicotinamide, Wnt signaling, and erythropoietin to outline not only the potential benefits, but also the challenges and possible detriments of these therapies. In this way, new avenues of investigation can hopefully bypass toxic complications, or at the very least, avoid contraindications that may limit care and offer both safe and robust clinical treatment for patients.

Raves and risks for erythropoietin

Global use of erythropoietin (EPO) continues to increase as a proven agent for the treatment of anemia. Yet, EPO is no longer believed to have exclusive biological activity in the hematopoietic system and is now considered applicable for a variety of disorders such as diabetes, Alzheimer's disease, and cardiovascular disease. Treatment with EPO is considered to be robust and can prevent metabolic compromise, neuronal and vascular degeneration, and inflammatory cell activation. On the converse side, observations that EPO administration is not without risk have fueled controversy. Here we present recent advances that have elucidated a number of novel cellular pathways governed by EPO to open new therapeutic avenues for this agent and avert its potential deleterious effects.

The Wnt signaling pathway: aging gracefully as a protectionist?

No longer considered to be exclusive to cellular developmental pathways, the Wnt family of secreted cysteine-rich glycosylated proteins has emerged as versatile targets for a variety of conditions that involve cardiovascular disease, aging, cancer, diabetes, neurodegeneration, and inflammation. In particular, modulation of Wnt signaling may fill a critical void for the treatment of disorders that impact upon both cellular survival and cellular longevity. Yet, in some scenarios, Wnt signaling can become the catalyst for disease development or promote cell senescence that can compromise clinical utility. This double edge sword in regards to the role of Wnt and its signaling pathways highlights the critical need to further elucidate the cellular mechanisms governed by Wnt in conjunction with the development of robust pharmacological ligands that may open new avenues for disease treatment. Here we discuss the influence of the Wnt pathway during cell survival, metabolism, and aging in order for one to gain a greater insight for the novel role of Wnt signaling as well as exemplify its unique cellular pathways that influence both normal physiology and disease.

"Sly as a FOXO": new paths with Forkhead signaling in the brain

The Forkhead transcription factor FOXO3a has emerged as a versatile target for diseases that impact upon neuronal survival, vascular integrity, immune function, and cellular metabolism. Enthusiasm is high to fill a critical treatment void through FOXO3a signaling for several neurodegenerative disorders that include aging, neuromuscular disease, systemic lupus erythematosus, stroke, and diabetic complications. Here we discuss the influence of FOXO3a upon cell survival and longevity, the intricate signal transduction pathways of FOXO3a, insights into present disease models, and the potential clinical translation of FOXO3a signaling into novel therapeutic strategies.