Neuroprotectin D1 induces dephosphorylation of Bcl-xL in a PP2A-dependent manner during oxidative stress and promotes retinal pigment epithelial cell survival

Eicosanoid signaling in neuroinflammation associated with Alzheimer's disease

Alzheimer's disease (AD) is a prevalent neurodegenerative condition affecting a substantial portion of the global population. It is marked by a complex interplay of factors, including the accumulation of amyloid plaques and tau tangles within the brain, leading to neuroinflammation and neuronal damage. Recent studies have underscored the role of free lipids and their derivatives in the initiation and progression of AD. Eicosanoids, metabolites of polyunsaturated fatty acids like arachidonic acid (AA), emerge as key players in this scenario. Remarkably, eicosanoids can either promote or inhibit the development of AD, and this multifaceted role is determined by how eicosanoid signaling influences the immune responses within the brain. However, the precise molecular mechanisms dictating the dual role of eicosanoids in AD remain elusive. In this comprehensive review, we explore the intricate involvement of eicosanoids in neuronal function and dysfunction. Furthermore, we assess the therapeutic potential of targeting eicosanoid signaling pathways as a viable strategy for mitigating or halting the progression of AD.

Biotransformation of docosahexaenoic acid into 10R,17S-dihydroxydocosahexaenoic acid as protectin DX 10-epimer by serial reactions of arachidonate 8R- and 15S-lipoxygenases

Protectins, 10,17-dihydroxydocosahexaenoic acids (10,17-DiHDHAs), are belonged to specialized pro-resolving mediators (SPMs). Protectins are generated by polymorphonuclear leukocytes in humans and resolve inflammation and infection in trace amounts. However, the quantitative production of protectin DX 10-epimer (10-epi-PDX, 10R,17S-4Z,7Z,11E,13Z,15E,19Z-DiHDHA) has been not attempted to date. In this study, 10-epi-PDX was quantitatively produced from docosahexaenoic acid (DHA) by serial whole-cell biotransformation of Escherichia coli expressing arachidonate (ARA) 8R-lipoxygenase (8R-LOX) from the coral Plexaura homomalla and E. coli expressing ARA 15S-LOX from the bacterium Archangium violaceum. The optimal bioconversion conditions to produce 10R-hydroxydocosahexaenoic acid (10R-HDHA) and 10-epi-PDX were pH 8.0, 30 °C, 2.0 mM DHA, and 4.0 g/L cells; and pH 8.5, 20 °C, 1.4 mM 10R-HDHA, and 1.0 g/L cells, respectively. Under these optimized conditions, 2.0 mM (657 mg/L) DHA was converted into 1.2 mM (433 mg/L) 10-epi-PDX via 1.4 mM (482 mg/L) 10R-HDHA by the serial whole-cell biotransformation within 90 min, with a molar conversion of 60% and volumetric productivity of 0.8 mM/h (288 mg/L/h). To the best of our knowledge, this is the first quantitative production of 10-epi-PDX. Our results contribute to the efficient biocatalytic synthesis of SPMs.

Lipid mediators in glaucoma: Unraveling their diverse roles and untapped therapeutic potential

Glaucoma is a complex neurodegenerative disease characterized by optic nerve damage and visual field loss, and remains a leading cause of irreversible blindness. Elevated intraocular pressure (IOP) is a critical risk factor that requires effective management. Emerging research underscores dual roles of bioactive lipid mediators in both IOP regulation, and the modulation of neurodegeneration and neuroinflammation in glaucoma. Bioactive lipids, encompassing eicosanoids, specialized pro-resolving mediators (SPMs), sphingolipids, and endocannabinoids, have emerged as crucial players in these processes, orchestrating inflammation and diverse effects on aqueous humor dynamics and tissue remodeling. Perturbations in these lipid mediators contribute to retinal ganglion cell loss, vascular dysfunction, oxidative stress, and neuroinflammation. Glaucoma management primarily targets IOP reduction via pharmacological agents and surgical interventions, with prostaglandin analogues at the forefront. Intriguingly, additional lipid mediators offer promise in attenuating inflammation and providing neuroprotection. Here we explore these pathways to shed light on their intricate roles, and to unveil novel therapeutic avenues for glaucoma management.

Novel lipid mediator 7S,14R-docosahexaenoic acid: biogenesis and harnessing mesenchymal stem cells to ameliorate diabetic mellitus and retinal pericyte loss

Introduction: Stem cells can be used to treat diabetic mellitus and complications. ω3-docosahexaenoic acid (DHA) derived lipid mediators are inflammation-resolving and protective. This study found novel DHA-derived 7S,14R-dihydroxy-4Z,8E,10Z,12E,16Z,19Z-docosahexaenoic acid (7S,14R-diHDHA), a maresin-1 stereoisomer biosynthesized by leukocytes and related enzymes. Moreover, 7S,14R-diHDHA can enhance mesenchymal stem cell (MSC) functions in the amelioration of diabetic mellitus and retinal pericyte loss in diabetic db/db mice. Methods: MSCs treated with 7S,14R-diHDHA were delivered into db/db mice i.v. every 5 days for 35 days. Results: Blood glucose levels in diabetic mice were lowered by 7S,14R-diHDHA-treated MSCs compared to control and untreated MSC groups, accompanied by improved glucose tolerance and higher blood insulin levels. 7S,14R-diHDHA-treated MSCs increased insulin+ β-cell ratio and decreased glucogan+ α-cell ratio in islets, as well as reduced macrophages in pancreas. 7S,14R-diHDHA induced MSC functions in promoting MIN6 β-cell viability and insulin secretion. 7S,14R-diHDHA induced MSC paracrine functions by increasing the generation of hepatocyte growth factor and vascular endothelial growth factor. Furthermore, 7S,14R-diHDHA enhanced MSC functions to ameliorate diabetes-caused pericyte loss in diabetic retinopathy by increasing their density in retina in db/db mice. Discussion: Our findings provide a novel strategy for improving therapy for diabetes and diabetic retinopathy using 7S,14R-diHDHA-primed MSCs.

Regulation and role of the PP2A-B56 holoenzyme family in cancer

Protein phosphatase 2A (PP2A) inactivation is common in cancer, leading to sustained activation of pro-survival and growth-promoting pathways. PP2A consists of a scaffolding A-subunit, a catalytic C-subunit, and a regulatory B-subunit. The functional complexity of PP2A holoenzymes arises mainly through the vast repertoire of regulatory B-subunits, which determine both their substrate specificity and their subcellular localization. Therefore, a major challenge for developing more effective therapeutic strategies for cancer is to identify the specific PP2A complexes to be targeted. Of note, the development of small molecules specifically directed at PP2A-B56α has opened new therapeutic avenues in both solid and hematological tumors. Here, we focus on the B56/PR61 family of PP2A regulatory subunits, which have a central role in directing PP2A tumor suppressor activity. We provide an overview of the mechanisms controlling the formation and regulation of these complexes, the pathways they control, and the mechanisms underlying their deregulation in cancer.

Enzymatic Formation of Protectin Dx and Its Production by Whole-Cell Reaction Using Recombinant Lipoxygenases

In the human body, docosahexaenoic acid (DHA) contained in fish oil is converted to trace amounts of specialized pro-resolving mediators (SPMs) as the principal bioactive metabolites for their pharmacological effects. Protectin Dx (PDX), an SPM, is an important medicinal compound with biological activities such as modulation of endogenous antioxidant systems, inflammation pro-resolving action, and inhibition of influenza virus replication. Although it can be biotechnologically synthesized from DHA, it has not yet been produced quantitatively. Here, we found that 15S-lipoxygenase from Burkholderia thailandensis (BT 15SLOX) converted 10S-hydroxydocosahexaenoic acid (10S-HDHA) to PDX using enzymatic reactions, which was confirmed by LC-MS/MS and NMR analyses. Thus, whole-cell reactions of Escherichia coli cells expressing BT 15SLOX were performed in flasks to produce PDX from lipase-treated DHA-enriched fish oil along with E. coli cells expressing Mus musculus (mouse) 8S-lipoxygenase (MO 8SLOX) that converted DHA to 10S-HDHA. First, 1 mM DHA (DHA-enriched fish oil hydrolysate, DFOH) was obtained from 455 mg/L DHA-enriched fish oil by lipase for 1 h. Second, E. coli cells expressing MO 8SLOX converted 1 mM DHA in DFOH to 0.43 mM 10S-HDHA for 6 h. Finally, E. coli cells expressing BT 15SLOX converted 0.43 mM 10S-HDHA in MO 8SLOX-treated DFOH to 0.30 mM (108 mg/L) PDX for 5 h. Consequently, DHA-enriched fish oil at 455 mg/L was converted to 108 mg/L PDX after a total of 12 h (conversion yield: 24% (w/w); productivity: 4.5 mg/L/h). This study is the first report on the quantitative production of PDX via biotechnological approaches.

PUMA overexpression dissociates thioredoxin from ASK1 to activate the JNK/BCL-2/BCL-XL pathway augmenting apoptosis in ovarian cancer

ASK1-JNK signaling promotes mitochondrial dysfunction-mediated apoptosis, but the bridge between JNK and apoptosis is not fully understood. PUMA induces apoptosis through BAX/BAK. Our previous study suggests a therapeutic potential of PUMA for ovarian cancer. However, whether and how PUMA activates ASK1 remains unclear. Here, we found for the first time that PUMA activated ASK1 by dissociating thioredoxin (TRX) from ASK1, however, it neither interacted with ASK1 nor TRX. Furthermore, PUMA overexpression caused ROS release from mitochondrial. H₂O₂ significantly impaired the interaction of ASK1 with TRX, whereas ROS scavenger NAC effectively abrogated the H₂O₂ effect, partly rescued PUMA-interfered interaction of ASK1 with TRX, and also abolished ASK1 phosphorylation. Interestingly, PUMA could not impair the association of ASK1 with TRX-C32S or TRX-C35S, two TRX mutants which are no longer oxidized in response to ROS. We further showed that PUMA activated ASK1-JNK axis to phosphorylate BCL-2 and BCL-XL, further augmenting apoptosis of ovarian cancer cells. In vivo, PUMA adenovirus combined with paclitaxel significantly inhibited intrinsically cisplatin-resistant ovarian cancer growth, and caused phosphorylation of BCL-2 and BCL-XL. Our results from human ovarian cancer TMA chips also revealed a positive correlation between PUMA expression and the phosphorylation of BCL-2 and BCL-XL. More importantly, all patients had no distal metastasis, implying a possibly clinical significance. Collectively, our results reveal a new pro-apoptotic signal amplification mechanism for PUMA by which PUMA overexpression first induces ROS-mediated dissociation of TRX from ASK1, and then causes JNK activation-triggering BCL-2/BCL-XL phosphorylation, ultimately augmenting apoptosis in ovarian cancer.

Identification of Resolvin D1 and Protectin D1 as Potential Therapeutic Agents for Treating Kidney Stones

Intrarenal calcium oxalate (CaOx) crystals induce renal tubular epithelial cell (TEC) inflammatory and oxidative injury. This study is aimed at exploring potential therapeutic lipid components in kidney stones because lipids are involved in the development of several diseases and indicate the risk of kidney stones. Serum specimens were collected from 35 kidney stone patients and 35 normal controls. The lipid components in serum were measured, and differences were analyzed. The documented biological importance was comprehensively reviewed to identify lipids that differed significantly between the two groups to find potential agents associated with kidney stones. CaOx nephrocalcinosis mouse model was established to examine the therapeutic effects of specific lipids on CaOx deposition and CaOx-induced oxidative renal injury. Several lipids with significantly different levels were present in the serum of patients with stones and normal controls. Resolvin D1 (RvD1) (4.93-fold change, P < 0.001) and protectin D1 (PD1) (5.06-fold change, P < 0.001) were significantly decreased in the serum of patients with kidney stones, and an integrative review suggested that these factors might be associated with inflammatory responses, which is a crucial mechanism associated with stone damage. The administration of RvD1 and PD1 significantly inhibited kidney CaOx deposition and suppressed CaOx-induced renal tubular cell inflammatory injury and necrosis in a CaOx nephrocalcinosis mouse model. Furthermore, RvD1 and PD1 facilitated the expression of the oxidative indicator superoxide dismutase 2 (SOD2), inhibited NADPH oxidase 2 (NOX2) expression, and diminished intracellular reactive oxygen species (ROS) levels. This study preliminarily elucidated the role of lipids in kidney stones. The inhibitory effects of RvD1 and PD1 on oxidative damage induced by CaOx deposition provide a promising perspective for kidney stone treatment strategies.

A New CYP2E1 Inhibitor, 12-Imidazolyl-1-dodecanol, Represents a Potential Treatment for Hepatocellular Carcinoma

Cytochrome P450 2E1 (CYP2E1) is a key target protein in the development of alcoholic and nonalcoholic fatty liver disease (FLD). The pathophysiological correlate is the massive production of reactive oxygen species. The role of CYP2E1 in the development of hepatocellular carcinoma (HCC), the final complication of FLD, remains controversial. Specifically, CYP2E1 has not yet been defined as a molecular target for HCC therapy. In addition, a CYP2E1-specific drug has not been developed. We have already shown that our newly developed CYP2E1 inhibitor 12-imidazolyl-1-dodecanol (I-ol) was therapeutically effective against alcoholic and nonalcoholic steatohepatitis. In this study, we investigated the effect of I-ol on HCC tumorigenesis and whether I-ol could serve as a possible treatment option for terminal-stage FLD. I-ol exerted a very highly significant antitumour effect against hepatocellular HepG2 cells. Cell viability was reduced in a dose-dependent manner, with only the highest doses causing a cytotoxic effect associated with caspase 3/7 activation. Comparable results were obtained for the model colorectal adenocarcinoma cell line, DLD-1, whose tumorigenesis is also associated with CYP2E1. Transcriptome analyses showed a clear effect of I-ol on apoptosis and cell-cycle regulation, with the increased expression of p27Kip1 being particularly noticeable. These observations were confirmed at the protein level for HepG2 and DLD-1 cells grafted on a chorioallantoic membrane. Cell-cycle analysis showed a complete loss of proliferating cells with a simultaneous increase in S-phase arrest beginning at a threshold dose of 30 μM. I-ol also reduced xenograft tumour growth in nude mice. This antitumour effect was not associated with tumour cachexia. I-ol was not toxic to healthy tissues or organs. This study demonstrates for the first time the therapeutic effect of the specific CYP2E1 inhibitor I-ol on the tumorigenesis of HCC. Our findings imply that I-ol can potentially be applied therapeutically on patients at the final stage of FLD.

NPD1 rapidly targets mitochondria-mediated apoptosis after acute injection protecting brain against ischemic injury

Mitochondria-related cell death pathways play a major role in ischemic brain injury. Thus, mitochondrial "protective" molecules could be considered for new therapeutic regimens. We recently reported that acute administration of docosahexaenoic acid (DHA) triglyceride lipid emulsion, immediately after hypoxic-ischemic (HI) insult, markedly attenuated brain infarct size. This was associated with an early change of DHA-derived specialized pro-resolving mediator (SPM) profiles. Specifically, DHA treatment induced a 50% increase of neuroprotectin D1 (NPD1) levels in ischemic brain. Based on these findings, we questioned if direct administration of NPD1 after HI injury also affords neuroprotection, and if so, by what mechanisms. Using HI insult to mimic ischemic stroke in neonatal mice, we observed that acute intraperitoneal injection of NPD1 immediately after HI injury prevented the expansion of the ischemic core by ~40% and improved coordination and motor abilities compared to the control group. At 7 days after HI injury, NPD1 treatment decreased ipsilateral hemisphere atrophy and preserved motor functions in wire-holding and bridge-crossing tests compared to control littermates. Brain mitochondria, isolated at 4 h after reperfusion from mice treated with NPD1, showed an increase in the capacity to buffer calcium after HI injury, as result of the preservation of mitochondrial membranes. Further, NPD1 induced a reduction of mitochondrial BAX translocation and oligomerization, attenuated cytochrome C release and decreased AIF nuclear translocation. To confirm whether NPD1 acts as BAX inhibitor, we evaluated NPD1 action co-administrated with a pro-apoptotic agent, staurosporine, using mouse embryonic fibroblasts as in vitro model of apoptosis. NPD1 exposure markedly decreased mitochondria-mediated apoptosis, blocking BAX translocation from cytosol to mitochondria and subsequently reducing caspase-3 activation. Our findings provide novel evidence that the neuroprotective action of NPD1 is elicited rapidly in the first few hours after ischemic injury and is associated with both preserved mitochondrial membrane structure and reduced BAX mitochondrial translocation and activation.

Increased Antioxidant Capacity and Pro-Homeostatic Lipid Mediators in Ocular Hypertension-A Human Experimental Model

The main risk factor for primary open-angle glaucoma (POAG) is increased intraocular pressure (IOP). It is of interest that about half of the patients have an IOP within the normal range (normal-tension glaucoma, NTG). Additionally, there is a group of patients with a high IOP but no glaucomatous neurodegeneration (ocular hypertension, OHT). Therefore, risk factors other than IOP are involved in the pathogenesis of glaucoma. Since the retina has a very high oxygen-demand, decreased autoregulation and a fluctuating oxygen supply to the retina have been linked to glaucomatous neurodegeneration. To assess the significance of these mechanisms, we have utilized a human experimental model, in which we stress participants with a fluctuating oxygen supply. Levels of oxidative stress molecules, antioxidants, and lipid mediators were measured in the plasma. Patients with NTG, OHT, and control subjects were found to have similar levels of oxidative stress markers. In contrast, patients with OHT had a higher level of total antioxidant capacity (TAC) and pro-homeostatic lipid mediators. Thus, we suggest that OHT patients manage fluctuating oxygen levels more efficiently and, thus, are less susceptible to glaucomatous neurodegenerations, due to enhanced systemic antioxidant protection.

Dual Switch Mechanism of Erythropoietin as an Antiapoptotic and Pro-Angiogenic Determinant in the Retina

Constant or intense light degenerates the retina and retinal pigment epithelial cells. Light generates reactive oxygen species and nitric oxide leading to initial reactions of retinal degeneration. Apoptosis is the primary mechanism of abnormal death of photoreceptors, retinal ganglion cells, or retinal pigment epithelium (RPE) in degenerative retinal diseases, including diabetic retinopathy and age-related macular degeneration. The current study evaluated the function of erythropoietin (EPO) on angiogenesis and apoptosis in the retina and RPE under oxidative stress. We determined the pro-angiogenic and antiapoptotic mechanism of EPO under stress conditions using a conditional EPO knockdown model using siRNA, EPO addition, proteomics, immunocytochemistry, and bioinformatic analysis. Our studies verified that EPO protected retinal cells from light-, hypoxia-, hyperoxia-, and hydrogen peroxide-induced apoptosis through caspase inhibition, whereas up-regulated angiogenic reactions through vascular endothelial growth factor (VEGF) and angiotensin pathway. We demonstrated that the EPO expression in the retina and subsequent serine/threonine/tyrosine kinase phosphorylations might be linked to oxidative stress response tightly to determining angiogenesis and apoptosis. Neuroprotective roles of EPO may involve the balance between antiapoptotic and pro-angiogenic signaling molecules, including BCL-xL, c-FOS, caspase-3, nitric oxide, angiotensin, and VEGF receptor. Our data indicate a new therapeutic application of EPO toward retinal degeneration based on the dual roles in apoptosis and angiogenesis at the molecular level under oxidative stress.

Proresolving Lipid Mediators: Endogenous Modulators of Oxidative Stress

Specialized proresolving mediators (SPMs) are a novel class of endogenous lipids, derived by ω-6 and ω-3 essential polyunsaturated fatty acids such as arachidonic acid (AA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) that trigger and orchestrate the resolution of inflammation, which is the series of cellular and molecular events that leads to spontaneous regression of inflammatory processes and restoring of tissue homeostasis. These lipids are emerging as highly effective therapeutic agents that exert their immunoregulatory activity by activating the proresolving pathway, as reported by a consistent bulk of evidences gathered in the last two decades since their discovery. The production of reactive oxygen (ROS) and nitrogen (RNS) species by immune cells plays indeed an important role in the inflammatory mechanisms of host defence, and it is now clear that oxidative stress, viewed as an imbalance between such species and their elimination, can lead to many chronic inflammatory diseases. This review, the first of its kind, is aimed at exploring the manifold effects of SPMs on modulation of reactive species production, along with the mechanisms through which they either inhibit molecular signalling pathways that are activated by oxidative stress or induce the expression of endogenous antioxidant systems. Furthermore, the possible role of SPMs in oxidative stress-mediated chronic disorders is also summarized, suggesting not only that their anti-inflammatory and proresolving properties are strictly associated with their antioxidant role but also that these endogenous lipids might be exploited in the treatment of several pathologies in which uncontrolled production of ROS and RNS or impairment of the antioxidant machinery represents a main pathogenetic mechanism.

Molecular genetic mechanisms of influence of laser radiation with 577 nm wavelength in a microimpulse mode on the condition of the retina

THE AIM OF THE STUDY

was to investigate the molecular genetic mechanisms of the influence of laser radiation with 577 nm wavelength in a microimpulse mode on the retina in the experimental conditions after the intravitreal injection of VEGF.

MATERIALS AND METHODS

The study was performed on 4-5 week-old male mice of the line C57BL/6J. The animals were divided into 4 groups of 5 mice in each group, one eye was excremental, the contralateral eye remained intact. In the first group, intravitreal injection of PBS was performed; in the second group, intravitreal injection of 50 ng/ml of recombinant VEGF₁₆₅ in 2 μL of phosphate-buffered saline (PBS) was performed; in the third and fourth groups, a day after the intravitreal injection of recombinant VEGF₁₆₅, laser radiation with wavelength 577 nm was applied in the micropulse and continuous modes, respectively. Tissue samples (neuroepithelium, pigment epithelium) for the microarray transcription analysis in the animals from group 1 and 2 were taken 2 days after the injection of PBS and VEGF, in the animals from group 3 and 4 - a day after the retina was exposed to laser radiation.

RESULTS AND CONCLUSION

Molecular genetic mechanisms of the influence of laser radiation with wavelength 577 nm in a microimpulse mode on the retina in experimental conditions were studied and the genes that significantly changed the level of expression (the genes that take part in the regulation of neoangiogenesis, structural cell functions, processes of cells proliferation, transcription, differentiation, transmembrane transport, signaling, synaptic transmission, etc.) were identified.

Regulation of the phosphoprotein phosphatase 2A system and its modulation during oxidative stress: A potential therapeutic target?

Phosphoprotein phosphatases are of growing interest in the pathophysiology of many diseases and are often the neglected partner of protein kinases. One family member, PP2A, accounts for dephosphorylation of ~55-70% of all serine/threonine phosphosites. Interestingly, dysregulation of kinase signalling is a hallmark of many diseases in which an increase in oxidative stress is also noted. With this in mind, we assess the evidence to support oxidative stress-mediated regulation of the PP2A system In this article, we first present an overview of the PP2A system before providing an analysis of the regulation of PP2A by endogenous inhibitors, post translational modification, and miRNA. Next, a detailed critique of data implicating reactive oxygen species, ischaemia, ischaemia-reperfusion, and hypoxia in regulating the PP2A holoenzyme and associated regulators is presented. Finally, the pharmacological targeting of PP2A, its endogenous inhibitors, and enzymes responsible for its post-translational modification are covered. There is extensive evidence that oxidative stress modulates multiple components of the PP2A system, however, most of the data pertains to the catalytic subunit of PP2A. Irrespective of the underlying aetiology, free radical-mediated attenuation of PP2A activity is an emerging theme. However, in many instances, a dichotomy exists, which requires clarification and mechanistic insight. Nevertheless, this raises the possibility that pharmacological activation of PP2A, either through small molecule activators of PP2A or CIP2A/SET antagonists may be beneficial in modulating the cellular response to oxidative stress. A better understanding of which, will have wide ranging implications for cancer, heart disease and inflammatory conditions.

Protein Phosphatases-A Touchy Enemy in the Battle Against Glioblastomas: A Review

Glioblastoma (GBM) is the most common malignant tumor arising from brain parenchyma. Although many efforts have been made to develop therapies for GBM, the prognosis still remains poor, mainly because of the difficulty in total resection of the tumor mass from brain tissue and the resistance of the residual tumor against standard chemoradiotherapy. Therefore, novel adjuvant therapies are urgently needed. Recent genome-wide analyses of GBM cases have clarified molecular signaling mechanisms underlying GBM biology. However, results of clinical trials targeting phosphorylation-mediated signaling have been unsatisfactory to date. Protein phosphatases are enzymes that antagonize phosphorylation signaling by dephosphorylating phosphorylated signaling molecules. Recently, the critical roles of phosphatases in the regulation of oncogenic signaling in malignant tumor cells have been reported, and tumorigenic roles of deregulated phosphatases have been demonstrated in GBM. However, a detailed mechanism underlying phosphatase-mediated signaling transduction in the regulation of GBM has not been elucidated, and such information is necessary to apply phosphatases as a therapeutic target for GBM. This review highlights and summarizes the phosphatases that have crucial roles in the regulation of oncogenic signaling in GBM cells.

Nutritional Regulators of Bcl-xL in the Brain

B-cell lymphoma-extra large (Bcl-xL) is an anti-apoptotic Bcl-2 protein found in the mitochondrial membrane. Bcl-xL is reported to support normal brain development and protects neurons against toxic stimulation during pathological process via its roles in regulation of mitochondrial functions. Despite promising evidence showing neuroprotective properties of Bcl-xL, commonly applied molecular approaches such as genetic manipulation may not be readily applicable for human subjects. Therefore, findings at the bench may be slow to be translated into treatments for disease. Currently, there is no FDA approved application that specifically targets Bcl-xL and treats brain-associated pathology in humans. In this review, we will discuss naturally occurring nutrients that may exhibit regulatory effects on Bcl-xL expression or activity, thus potentially providing affordable, readily-applicable, easy, and safe strategies to protect the brain.

The impact of phosphatases on proliferative and survival signaling in cancer

The dynamic and stringent coordination of kinase and phosphatase activity controls a myriad of physiologic processes. Aberrations that disrupt the balance of this interplay represent the basis of numerous diseases. For a variety of reasons, early work in this area portrayed kinases as the dominant actors in these signaling events with phosphatases playing a secondary role. In oncology, these efforts led to breakthroughs that have dramatically altered the course of certain diseases and directed vast resources toward the development of additional kinase-targeted therapies. Yet, more recent scientific efforts have demonstrated a prominent and sometimes driving role for phosphatases across numerous malignancies. This maturation of the phosphatase field has brought with it the promise of further therapeutic advances in the field of oncology. In this review, we discuss the role of phosphatases in the regulation of cellular proliferation and survival signaling using the examples of the MAPK and PI3K/AKT pathways, c-Myc and the apoptosis machinery. Emphasis is placed on instances where these signaling networks are perturbed by dysregulation of specific phosphatases to favor growth and persistence of human cancer.

Improvement of Storage Medium for Cultured Human Retinal Pigment Epithelial Cells Using Factorial Design

Storage of human retinal pigment epithelium (hRPE) can contribute to the advancement of cell-based RPE replacement therapies. The present study aimed to improve the quality of stored hRPE cultures by identifying storage medium additives that, alone or in combination, contribute to enhancing cell viability while preserving morphology and phenotype. hRPE cells were cultured in the presence of the silk protein sericin until pigmentation. Cells were then stored for 10 days in storage medium plus sericin and either one of 46 different additives. Individual effects of each additive on cell viability were assessed using epifluorescence microscopy. Factorial design identified promising additive combinations by extrapolating their individual effects. Supplementing the storage medium with sericin combined with adenosine, L-ascorbic acid and allopurinol resulted in the highest cell viability (98.6 ± 0.5%) after storage for three days, as measured by epifluorescence microscopy. Flow cytometry validated the findings. Proteomics identified 61 upregulated and 65 downregulated proteins in this storage group compared to the unstored control. Transmission electron microscopy demonstrated the presence of melanosomes after storage in the optimized medium. We conclude that the combination of adenosine, L-ascorbic acid, allopurinol and sericin in minimal essential medium preserves RPE pigmentation while maintaining cell viability during storage.

Retinal Pigment Epithelium and Photoreceptor Preconditioning Protection Requires Docosanoid Signaling

Omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) are necessary for functional cell integrity. Preconditioning (PC), as we define it, is an acquired protection or resilience by a cell, tissue, or organ to a lethal stimulus enabled by a previous sublethal stressor or stimulus. In this study, we provide evidence that the omega-3 fatty acid docosahexaenoic acid (DHA) and its derivatives, the docosanoids 17-hydroxy docosahexaenoic acid (17-HDHA) and neuroprotectin D1 (NPD1), facilitate cell survival in both in vitro and in vivo models of retinal PC. We also demonstrate that PC requires the enzyme 15-lipoxygenase-1 (15-LOX-1), which synthesizes 17-HDHA and NPD1, and that this is specific to docosanoid signaling despite the concomitant release of the omega-6 arachidonic acid and eicosanoid synthesis. These findings advocate that DHA and docosanoids are protective enablers of PC in photoreceptor and retinal pigment epithelial cells.

Molecular mechanisms of signaling via the docosanoid neuroprotectin D1 for cellular homeostasis and neuroprotection

Docosahexaenoic acid, enriched in the brain and retina, generates docosanoids in response to disruptions of cellular homeostasis. Docosanoids include neuroprotectin D1 (NPD1), which is decreased in the CA1 hippocampal area of patients with early-stage Alzheimer's disease (AD). We summarize here how NPD1 elicits neuroprotection by up-regulating c-REL, a nuclear factor (NF)-κB subtype that, in turn, enhances expression of BIRC3 (baculoviral inhibitor of apoptosis repeat-containing protein 3) in the retina and in experimental stroke, leading to neuroprotection. Elucidating the mechanisms of action of docosanoids will contribute to managing diseases, including stroke, AD, age-related macular degeneration, traumatic brain injury, Parkinson's disease, and other neurodegenerations.

Elovanoids are novel cell-specific lipid mediators necessary for neuroprotective signaling for photoreceptor cell integrity

Docosahexaenoic acid (DHA, 22:6 n-3) is abundant in the retina and is enzymatically converted into pro-homeostatic docosanoids. The DHA- or eicosapentaenoic acid (EPA)-derived 26 carbon fatty acid is a substrate of elongase ELOVL4, which is expressed in photoreceptor cells and generates very long chain (≥C28) polyunsaturated fatty acids including n-3 (VLC-PUFAs,n-3). While ELOVL4 mutations are linked to vision loss and neuronal dysfunctions, the roles of VLC-PUFAs remain unknown. Here we report a novel class of lipid mediators biosynthesized in human retinal pigment epithelial (RPE) cells that are oxygenated derivatives of VLC-PUFAs,n-3; we termed these mediators elovanoids (ELV). ELVs have structures reminiscent of docosanoids but with different physicochemical properties and alternatively-regulated biosynthetic pathways. The structures, stereochemistry, and bioactivity of ELVs were determined using synthetic materials produced by stereo-controlled chemical synthesis. ELVs enhance expression of pro-survival proteins in cells undergoing uncompensated oxidative stress. Our findings unveil a novel autocrine/paracrine pro-homeostatic RPE cell signaling that aims to sustain photoreceptor cell integrity and reveal potential therapeutic targets for retinal degenerations.

Bcl-xL deamidation and cancer: Charting the fame trajectories of legitimate child and hidden siblings

Bcl-2 family proteins control programmed cell death through a complex network of interactions within and outside of this family, that are modulated by post-translational modifications (PTM). Bcl-x_L, an anti-apoptotic member of this family, is overexpressed in a number of cancers, plays an important role in tumorigenesis and is correlated with drug resistance. Bcl-x_L is susceptible to a number of different PTMs. Here, we focus on deamidation. We will first provide an overview of protein deamidation. We will then review how the apoptotic and autophagic functions of Bcl-x_L are modified by this PTM, and how this impacts on its oncogenic properties. Possible therapeutic outcomes will also be discussed. Finally, we will highlight how the specific case of Bcl-x_L deamidation provides groundings to revisit some concepts related to protein deamidation in general.

Autophagy and KRT8/keratin 8 protect degeneration of retinal pigment epithelium under oxidative stress

Contribution of autophagy and regulation of related proteins to the degeneration of retinal pigment epithelium (RPE) in age-related macular degeneration (AMD) remain unknown. We report that upregulation of KRT8 (keratin 8) as well as its phosphorylation are accompanied with autophagy and attenuated with the inhibition of autophagy in RPE cells under oxidative stress. KRT8 appears to have a dual role in RPE pathophysiology. While increased expression of KRT8 following autophagy provides a cytoprotective role in RPE, phosphorylation of KRT8 induces pathologic epithelial-mesenchymal transition (EMT) of RPE cells under oxidative stress, which is mediated by MAPK1/ERK2 (mitogen-activated protein kinase 1) and MAPK3/ERK1. Inhibition of autophagy further promotes EMT, which can be reversed by inhibition of MAPK. Thus, regulated enhancement of autophagy with concurrent increased expression of KRT8 and the inhibition of KRT8 phosphorylation serve to inhibit oxidative stress-induced EMT of RPE cells as well as to prevent cell death, suggesting that pharmacological manipulation of KRT8 upregulation through autophagy with combined inhibition of the MAPK1/3 pathway may be attractive therapeutic strategies for the treatment of AMD.

Pro-Resolving Lipid Mediators Improve Neuronal Survival and Increase Aβ42 Phagocytosis

Inflammation in the brain is a prominent feature in Alzheimer's disease (AD). Recent studies suggest that chronic inflammation can be a consequence of failure to resolve the inflammation. Resolution of inflammation is mediated by a family of lipid mediators (LMs), and the levels of these specialized pro-resolving mediators (SPMs) are reduced in the hippocampus of those with AD. In the present study, we combined analysis of LMs in the entorhinal cortex (ENT) from AD patients with in vitro analysis of their direct effects on neurons and microglia. We probed ENT, an area affected early in AD pathogenesis, by liquid chromatography-tandem mass spectrometry (LC-MS-MS), and found that the levels of the SPMs maresin 1 (MaR1), protectin D1 (PD1), and resolvin (Rv) D5, were lower in ENT of AD patients as compared to age-matched controls, while levels of the pro-inflammatory prostaglandin D2 (PGD2) were higher in AD. In vitro studies showed that lipoxin A4 (LXA4), MaR1, resolvin D1 (RvD1), and protectin DX (PDX) exerted neuroprotective activity, and that MaR1 and RvD1 down-regulated β-amyloid (Aβ)42-induced inflammation in human microglia. MaR1 exerted a stimulatory effect on microglial uptake of Aβ42. Our findings give further evidence for a disturbance of the resolution pathway in AD, and indicate that stimulating this pathway is a promising treatment strategy for AD.

Regulation of Bcl-xL-ATP Synthase Interaction by Mitochondrial Cyclin B1-Cyclin-Dependent Kinase-1 Determines Neuronal Survival

The survival of postmitotic neurons needs continuous degradation of cyclin B1, a mitotic protein accumulated aberrantly in the damaged brain areas of Alzheimer's disease and stroked patients. Degradation of cyclin B1 takes place in the proteasome after ubiquitylation by the anaphase-promoting complex/cyclosome (APC/C)-cadherin 1 (Cdh1), an E3 ubiquitin ligase that is highly active in neurons. However, during excitotoxic damage-a hallmark of neurological disorders-APC/C-Cdh1 is inactivated, causing cyclin B1 stabilization and neuronal death through an unknown mechanism. Here, we show that an excitotoxic stimulus in rat cortical neurons in primary culture promotes cyclin B1 accumulation in the mitochondria, in which it binds to, and activates, cyclin-dependent kinase-1 (Cdk1). The cyclin B1-Cdk1 complex in the mitochondria phosphorylates the anti-apoptotic protein B-cell lymphoma extra-large (Bcl-xL), leading to its dissociation from the β subunit of F1Fo-ATP synthase. The subsequent inhibition of ATP synthase activity causes complex I oxidative damage, mitochondrial inner membrane depolarization, and apoptotic neuronal death. These results unveil a previously unrecognized role for mitochondrial cyclin B1 in the oxidative damage associated with neurological disorders.

The Docosanoid Neuroprotectin D1 Induces TH-Positive Neuronal Survival in a Cellular Model of Parkinson's Disease

Parkinson's disease (PD) does not manifest clinically until 80 % of striatal dopamine is reduced, thus most neuronal damage takes place before the patient presents clinical symptoms. Therefore, it is important to develop preventive strategies for this disease. In the experimental models of PD, 1-methyl-4-phenylpyridinium ion (MPP+) and rotenone induce toxicity in dopaminergic neurons. Neuroprotectin D1 (NPD1) displays neuroprotection in cells undergoing proteotoxic and oxidative stress. In the present report, we established an in vitro model using a primary neuronal culture from mesencephalic embryonic mouse tissue in which 17-20 % of neurons were TH-positive when differentiated in vitro. NPD1 (100 nM) rescued cells from apoptosis induced by MPP+ and rotenone, and the dendritic arbor of surviving neurons was examined using Sholl analysis. Rotenone, as well as MPP+ and its precursor 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), severely promoted retraction of dendritic arbor distal segments, thus decreasing the maximum branch order reached. On average, NPD1 counteracted the effects of MPP+ on the dendritic arborization, but failed to do so in the rotenone-treated neurons. However, rotenone did decrease the Sholl intersection number from radii 25 to 125 µm, and NPD1 did restore the pattern to control levels. Similarly, NPD1 partially reverted the dendrite retraction caused by MPP+ and MPTP. These results suggest that the apoptosis occurring in mesencephalic TH-positive neurons is not a direct consequence of mitochondrial dysfunction alone and that NPD1 signaling may be counteracting this damage. These findings lay the groundwork for the use of the in vitro model developed for future studies and for the search of specific molecular events that NPD1 targets to prevent early neurodegeneration in PD.

Protectins and maresins: New pro-resolving families of mediators in acute inflammation and resolution bioactive metabolome

Acute inflammatory responses are protective, yet without timely resolution can lead to chronic inflammation and organ fibrosis. A systems approach to investigate self-limited (self-resolving) inflammatory exudates in mice and structural elucidation uncovered novel resolution phase mediators in vivo that stimulate endogenous resolution mechanisms in inflammation. Resolving inflammatory exudates and human leukocytes utilize DHA and other n-3 EFA to produce three structurally distinct families of potent di- and trihydroxy-containing products, with several stereospecific potent mediators in each family. Given their potent and stereoselective picogram actions, specific members of these new families of mediators from the DHA metabolome were named D-series resolvins (Resolvin D1 to Resolvin D6), protectins (including protectin D1-neuroprotectin D1), and maresins (MaR1 and MaR2). In this review, we focus on a) biosynthesis of protectins and maresins as anti-inflammatory-pro-resolving mediators; b) their complete stereochemical assignments and actions in vivo in disease models. Each pathway involves the biosynthesis of epoxide-containing intermediates produced from hydroperoxy-containing precursors from human leukocytes and within exudates. Also, aspirin triggers an endogenous DHA metabolome that biosynthesizes potent products in inflammatory exudates and human leukocytes, namely aspirin-triggered Neuroprotectin D1/Protectin D1 [AT-(NPD1/PD1)]. Identification and structural elucidation of these new families of bioactive mediators in resolution has opened the possibility of diverse patho-physiologic actions in several processes including infection, inflammatory pain, tissue regeneration, neuroprotection-neurodegenerative disorders, wound healing, and others. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance".

Black Soybean Seed Coat Extract Prevents Hydrogen Peroxide-Mediated Cell Death via Extracellular Signal-Related Kinase Signalling in HepG2 Cells

Oxidative stress reduces cell viability and contributes to disease processes. Flavonoids including anthocyanins and proanthocyanidins reportedly induce intracellular antioxidant defence systems. Thus, in this study, we examined the antioxidant effects of a commercial extract from black soybean seed coats (BE), which are rich in anthocyanin and proanthocyanidin, and investigated the associated intracellular mechanisms in HepG2 cells. HepG2 cells treated with hydrogen peroxide (HPO) showed 60% viability, whereas pretreatment with BE-containing media for 2 h ameliorated HPO-mediated cell death by up to 90%. Pretreatment with BE for 2 h partially blocked HPO-mediated activation of ERK in HepG2 cells, and that for 1 h led to a 20% increase in intracellular total protein phosphatase (PP) activity, which is known to deactivate protein kinases. These results indicate that BE prevents HPO-mediated cell damage by inhibiting ERK signalling, potentially via PPs.

Protein phosphatase 6 controls BCR-induced apoptosis of WEHI-231 cells by regulating ubiquitination of Bcl-xL

Crosslinking BCR in the immature B cell line WEHI-231 causes apoptosis. We found that Bcl-xL was degraded by polyubiquitination upon BCR crosslinking and in this study explored the mechanism that controls the degradation of Bcl-xL. Ser(62) of Bcl-xL was phosphorylated by JNK to trigger polyubiquitination, and this was opposed by serine/threonine protein phosphatase 6 (PP6) that physically associated with Bcl-xL. We show BCR crosslinking decreased PP6 activity to allow Ser(62) phosphorylation of Bcl-xL. CD40 crosslinking rescues BCR-induced apoptosis, and we found PP6 associated with CD40 and PP6 activation in response to CD40. Our data suggest that PP6 activity is regulated to control apoptosis by modulating Ser(62) phosphorylation of Bcl-xL, which results in its polyubiquitination and degradation.

Antioxidants Improve the Viability of Stored Adult Retinal Pigment Epithelial-19 Cultures

Introduction

There is increasing evidence that retinal pigment epithelium (RPE) can be used to treat age-related macular degeneration, one of the leading causes of blindness worldwide. However, the best way to store RPE to enable worldwide distribution is unknown. We investigated the effects of supplementing our previously published storage method with seven additives, attempting to improve the number of viable adult retinal pigment epithelial (ARPE)-19 cells after storage.

Materials and methods

ARPE-19 cells were cultured on multiwell plates before being stored for 1 week at 16 °C. Unsupplemented Minimal Essential Medium (MEM) (control) and a total of seven individual additives (DADLE ([d-Ala², d-Leu⁵]-encephalin), capsazepine, docosahexaenoic acid (DHA), resveratrol, quercetin, simvastatin and sulforaphane) at three to four concentrations in MEM were tested. The individual effect of each additive on cell viability was analyzed with a microplate fluorometer. Cell phenotype was investigated by both microplate fluorometer and epifluorescence microscopy, and morphology by scanning electron microscopy.

Results

Supplementation of the storage medium with DADLE, capsazepine, DHA or resveratrol significantly increased the number of viable cells by 86.1% ± 41.9%, 67.9% ± 24.7%, 36.5% ± 10.3% and 21.1% ± 6.4%, respectively, compared to cells stored in unsupplemented MEM. DHA and resveratrol significantly reduced caspase-3 expression, while expression of RPE65 was maintained across groups.

Conclusion

The number of viable ARPE-19 cells can be increased by the addition of DADLE, capsazepine, DHA or resveratrol to the storage medium without perturbing apoptosis or differentiation.

Electronic supplementary material

The online version of this article (doi:10.1007/s40123-014-0024-9) contains supplementary material, which is available to authorized users.

Docosahexaenoic acid and tetracyclines as promising neuroprotective compounds with poly(ADP-ribose) polymerase inhibitory activities for oxidative/genotoxic stress treatment

The human genome is exposed to oxidative/genotoxic stress by several endogenous and exogenous compounds. These events evoke DNA damage and activate poly(ADP-ribose) polymerase-1 (PARP-1), the key enzyme involved in DNA repair. The massive stress and over-activation of this DNA-bound enzyme can be responsible for an energy crisis and neuronal death. The last data indicated that product of PARP-1, i.e. poly(ADP-ribose) (PAR), acts as a signalling molecule and plays a significant role in nucleus-mitochondria cross-talk. PAR translocated to the mitochondria can be involved in mitochondrial permeability, the release of an apoptosis-inducing factor (AIF). Its translocation into the nucleus leads to chromatin condensation, fragmentation and cell death. The exact mechanism of this novel death pathway has not yet fully been understood. In this study the relationship between AIF and PARP/PAR in death signalling in the neuronal cell line (HT22) subjected to oxidative/genotoxic stress evoked by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was explored. The neuroprotective influence of docosahexaenoic acid (DHA), major dietary ω-3 long-chain polyunsaturated fatty acids as well as the action of tetracyclines, the novel suppressors of PARP-1, were examined. The effect of these all compounds was compared with specific PARP-1 inhibitors. The oxidative/genotoxic stress evoked by MNNG enhanced the level of PAR in a time-dependent manner with a concomitant significant decrease in the mitochondrial AIF protein level. Moreover, the down-regulation of the anti-apoptotic proteins (Bcl-2 and Bcl-xL) and the up-regulation of the Bax pro-apoptotic protein were presented. In these conditions massive HT22 cell death was observed. Both PARP-1 inhibitors: 3-aminobenzamide (3-AB) and PJ 34, tetracycline: doxocycline and minocycline, as well as DHA protected the cells against PAR formation and AIF translocation. Moreover, all of these compounds enhanced Bcl-xL gene expression and protected the cells against MNNG-induced death. Our data show that both DHA and tetracyclines offer a novel neuroprotective strategy for oxidative/genotoxic stress treatment.

The docosanoid neuroprotectin D1 induces homeostatic regulation of neuroinflammation and cell survival

The onset of neurodegenerations and nervous system injury both trigger cell signaling perturbations that lead to damage of neuronal circuits and synapic connections, as well as protective signaling that aims to halt disease onset. Here we review recent findings that support the role of the docosanoid mediator neuroprotectin D1 (NPD1) as an early response or sentinel during the initial phase of nervous system damage. NPD1 is derived from docosahexaenoic acid that is selectively concentrated and retained in the nervous system. The protein misfolding triggers the biosynthesis of NPD1 which in turn downregulates pathways that lead to cell death and changes the outcome to cell survival. Proteotoxic stress as a result of protein misfolding is a widespread event in many neurodegenerative diseases. Therefore, mechanisms and mediators such as NPD1 that curtail consequences of these events are of interest as leads in the search for novel preventive and or therapeutic approaches.

Age-related susceptibility to apoptosis in human retinal pigment epithelial cells is triggered by disruption of p53-Mdm2 association

PURPOSE

Relatively little is known about the contribution of p53/Mdm2 pathway in apoptosis of retinal pigment epithelial (RPE) cells or its possible link to dysfunction of aging RPE or to related blinding disorders such as age-related macular degeneration (AMD).

METHODS

Age-associated changes in p53 activation were evaluated in primary RPE cultures from human donor eyes of various ages. Apoptosis was evaluated by activation of caspases and DNA fragmentation. Gene-specific small interfering RNA was used to knock down expression of p53.

RESULTS

We observed that the basal rate of p53-dependent apoptosis increased in an age-dependent manner in human RPE. The age-dependent increase in apoptosis was linked to alterations in several aspects of the p53 pathway. p53 phosphorylation Ser15 was increased through the stimulation of ATM-Ser1981. p53 acetylation Lys379 was increased through the inhibition of SIRT1/2. These two posttranslational modifications of p53 blocked the sequestration of p53 by Mdm2, thus resulting in an increase in free p53 and of p53 stimulation of apoptosis through increased expression of PUMA (p53 upregulated modulator of apoptosis) and activation of caspase-3. Aged RPE also had reduced expression of antiapoptotic Bcl-2, which contributed to the increase in apoptosis. Of particular interest in these studies was that pharmacologic treatments to block p53 phosphorylation, acetylation, or expression were able to protect RPE cells from apoptosis.

CONCLUSIONS

Our studies suggest that aging in the RPE leads to alterations of specific checkpoints in the apoptotic pathway, which may represent important molecular targets for the treatment of RPE-related aging disorders such as AMD.

Neuroinflammation and proteostasis are modulated by endogenously biosynthesized neuroprotectin D1

Neurodegenerative diseases encompass complex cell signaling disturbances that initially damage neuronal circuits and synapses. Due to multiple protective mechanisms enacted to counteract the onset of neurodegenerative diseases, there is often a prolonged period without noticeable impairments during their initiation. Since severe cognitive deficit or vision loss takes place after that period there is an opportunity to harness endogenous protective mechanisms as potential therapeutic approaches. The activation of the biosynthesis of the docosanoid mediator neuroprotectin D1 (NPD1) is an early response to the upsurge of protein misfolding and other neuroinflammatory events. This overview discusses the potent neuroprotective and inflammation-modulating bioactivity of NPD1. This lipid mediator represents an early response to neurodegenerations, aiming to restore homeostasis.

The B55α-containing PP2A holoenzyme dephosphorylates FOXO1 in islet β-cells under oxidative stress

The FOXO1 (forkhead box O1) transcription factor influences many key cellular processes, including those important in metabolism, proliferation and cell death. Reversible phosphorylation of FOXO1 at Thr(24) and Ser(256) regulates its subcellular localization, with phosphorylation promoting cytoplasmic localization, whereas dephosphorylation triggers nuclear import and transcriptional activation. In the present study, we used biochemical and molecular approaches to isolate and link the serine/threonine PP2A (protein phosphatase 2A) holoenzyme containing the B55α regulatory subunit, with nuclear import of FOXO1 in pancreatic islet β-cells under oxidative stress, a condition associated with cellular dysfunction in Type 2 diabetes. The mechanism of FOXO1 dephosphorylation and nuclear translocation was investigated in pancreatic islet INS-1 and βTC-3 cell lines subjected to oxidative stress. A combined chemical cross-linking and MS strategy revealed the association of FOXO1 with a PP2A holoenzyme composed of the catalytic C, structural A and B55α regulatory subunits. Knockdown of B55α in INS-1 cells reduced FOXO1 dephosphorylation, inhibited FOXO1 nuclear translocation and attenuated oxidative stress-induced cell death. Furthermore, both B55α and nuclear FOXO1 levels were increased under hyperglycaemic conditions in db/db mouse islets, an animal model of type 2 diabetes. We conclude that B55α-containing PP2A is a key regulator of FOXO1 activity in vivo.

Ataxin-1 poly(Q)-induced proteotoxic stress and apoptosis are attenuated in neural cells by docosahexaenoic acid-derived neuroprotectin D1

Neurodegenerative diseases share two common features: enhanced oxidative stress and cellular inability to scavenge structurally damaged abnormal proteins. Pathogenesis of polyglutamine (poly(Q)) diseases involves increased protein misfolding, along with ubiquitin and chaperon protein-containing nuclear aggregates. In spinocerebellar ataxia, the brain and retina undergo degeneration. Neuroprotectin D1 (NPD1) is made on-demand in the nervous system and retinal pigment epithelial (RPE) cells in response to oxidative stress, which activates prosurvival signaling via regulation of gene expression and other processes. We hypothesized that protein misfolding-induced proteotoxic stress triggers NPD1 synthesis. We used ARPE-19 cells as a cellular model to assess stress due to ataxin-1 82Q protein expression and determine whether NPD1 prevents apoptosis. Ectopic ataxin-1 expression induced RPE cell apoptosis, which was abrogated by 100 nm docosahexaenoic acid, 10 ng/ml pigment epithelium-derived factor, or NPD1. Similarly, NPD1 was protective in neurons and primary human RPE cells. Furthermore, when ataxin-1 82Q was expressed in 15-lipoxygenase-1-deficient cells, apoptosis was greatly enhanced, and only NPD1 (50 nm) rescued cells from death. NPD1 reduced misfolded ataxin-1-induced accumulation of proapoptotic Bax in the cytoplasm, suggesting that NPD1 acts by preventing proapoptotic signaling pathways from occurring. Finally, NPD1 signaling interfered with ataxin-1/capicua repression of gene expression and decreased phosphorylated ataxin-1 in an Akt-independent manner, suggesting that NPD1 signaling modulates formation or stabilization of ataxin-1 complexes. These data suggest that 1) NPD1 synthesis is an early response induced by proteotoxic stress due to abnormally folded ataxin-1, and 2) NPD1 promotes cell survival through modulating stabilization of ataxin-1 functional complexes and pro-/antiapoptotic and inflammatory pathways.

Docosahexaenoic acid signalolipidomics in nutrition: significance in aging, neuroinflammation, macular degeneration, Alzheimer's, and other neurodegenerative diseases

Essential polyunsaturated fatty acids (PUFAs) are critical nutritional lipids that must be obtained from the diet to sustain homeostasis. Omega-3 and -6 PUFAs are key components of biomembranes and play important roles in cell integrity, development, maintenance, and function. The essential omega-3 fatty acid family member docosahexaenoic acid (DHA) is avidly retained and uniquely concentrated in the nervous system, particularly in photoreceptors and synaptic membranes. DHA plays a key role in vision, neuroprotection, successful aging, memory, and other functions. In addition, DHA displays anti-inflammatory and inflammatory resolving properties in contrast to the proinflammatory actions of several members of the omega-6 PUFAs family. This review discusses DHA signalolipidomics, comprising the cellular/tissue organization of DHA uptake, its distribution among cellular compartments, the organization and function of membrane domains rich in DHA-containing phospholipids, and the cellular and molecular events revealed by the uncovering of signaling pathways regulated by DHA and docosanoids, the DHA-derived bioactive lipids, which include neuroprotectin D1 (NPD1), a novel DHA-derived stereoselective mediator. NPD1 synthesis agonists include neurotrophins and oxidative stress; NPD1 elicits potent anti-inflammatory actions and prohomeostatic bioactivity, is anti-angiogenic, promotes corneal nerve regeneration, and induces cell survival. In the context of DHA signalolipidomics, this review highlights aging and the evolving studies on the significance of DHA in Alzheimer's disease, macular degeneration, Parkinson's disease, and other brain disorders. DHA signalolipidomics in the nervous system offers emerging targets for pharmaceutical intervention and clinical translation.

Endogenous signaling by omega-3 docosahexaenoic acid-derived mediators sustains homeostatic synaptic and circuitry integrity

The harmony and function of the complex brain circuits and synapses are sustained mainly by excitatory and inhibitory neurotransmission, neurotrophins, gene regulation, and factors, many of which are incompletely understood. A common feature of brain circuit components, such as dendrites, synaptic membranes, and other membranes of the nervous system, is that they are richly endowed in docosahexaenoic acid (DHA), the main member of the omega-3 essential fatty acid family. DHA is avidly retained and concentrated in the nervous system and known to play a role in neuroprotection, memory, and vision. Only recently has it become apparent why the surprisingly rapid increases in free (unesterified) DHA pool size take place at the onset of seizures or brain injury. This phenomenon began to be clarified by the discovery of neuroprotectin D1 (NPD1), the first-uncovered bioactive docosanoid formed from free DHA through 15-lipoxygenase-1 (15-LOX-1). NPD1 synthesis includes, as agonists, oxidative stress and neurotrophins. The evolving concept is that DHA-derived docosanoids set in motion endogenous signaling to sustain homeostatic synaptic and circuit integrity. NPD1 is anti-inflammatory, displays inflammatory resolving activities, and induces cell survival, which is in contrast to the pro-inflammatory actions of the many of omega-6 fatty acid family members. We highlight here studies relevant to the ability of DHA to sustain neuronal function and protect synapses and circuits in the context of DHA signalolipidomics. DHA signalolipidomics comprises the integration of the cellular/tissue mechanism of DHA uptake, its distribution among cellular compartments, the organization and function of membrane domains containing DHA phospholipids, and the precise cellular and molecular events revealed by the uncovering of signaling pathways regulated by docosanoids endowed with prohomeostatic and cell survival bioactivity. Therefore, this approach offers emerging targets for prevention, pharmaceutical intervention, and clinical translation involving DHA-mediated signaling.

The role of Bcl-xL in mouse RPE cell survival

PURPOSE. Retinal pigment epithelial (RPE) cell survival plays a critical role in normal physiology and in retinal diseases, such as age-related macular degeneration (AMD) and proliferative vitreoretinopathy (PVR). We have previously demonstrated that Bcl-x(L) is an important cell survival protein in human RPE (hRPE) cells. Herein, we determined the role of Bcl-x(L) as a survival protein in mouse RPE (mRPE) cells. METHODS. Survival factor gene expression and Bcl-x(L) protein distribution were determined using qRT-PCR and immunohistochemistry, respectively. Cultured mRPE cells were transfected with two modified 2'-O-methoxyethoxy antisense oligonucleotides (ASOs): Bcl-x(L)-mismatched control and Bcl-x(L)-specific. Bcl-x(L) protein levels were analyzed using Western blot. To determine the effects of survival factor regulation in mRPE cells, cultured cells were treated for 24 hours with mouse TNF-α, human IL-1β, and human TNF-α. RESULTS. Bcl-x(L) was the most highly expressed survival factor in both mouse eyecup and cultured mRPE cells, whereas Bax was the most highly expressed antisurvival factor. Bcl-x(L) was expressed in the RPE layer, and the distribution among the retinal layers was similar to that observed in human eyecups. IL-1β and TNF-α had minimal effect on Bcl-x(L) and Bax expression and strongly upregulated Traf-1. Transfection with Bcl-x(L)-specific ASO resulted in markedly diminished Bcl-x(L) gene expression, Bcl-x(L) protein levels, and cell number. CONCLUSIONS. Bcl-x(L) is the most highly expressed survival gene in mRPE cells and is essential for mRPE cell survival. Our data suggest that mouse tissue is an appropriate model for investigations of RPE survival factor genes.

Inhibition of Mdm2 sensitizes human retinal pigment epithelial cells to apoptosis

PURPOSE

Because recent studies indicate that blocking the interaction between p53 and Mdm2 results in the nongenotoxic activation of p53, the authors sought to investigate whether the inhibition of p53-Mdm2 binding activates p53 and sensitizes human retinal epithelial cells to apoptosis.

METHODS

Apoptosis was evaluated by the activation of caspases and DNA fragmentation assays. The Mdm2 antagonist Nutlin-3 was used to dissociate p53 from Mdm2 and, thus, to increase p53 activity. Knockdown of p53 expression was accomplished by using p53 siRNA.

RESULTS

ARPE-19 and primary RPE cells expressed high levels of the antiapoptotic proteins Bcl-2 and Bcl-xL. Exposure of these cells to camptothecin (CPT) or TNF-α/ cycloheximide (CHX) failed to induce apoptosis. In contrast, treatment with the Mdm2 antagonist Nutlin-3 in the absence of CPT or TNF-α/CHX increased apoptosis. Activation of p53 in response to Nutlin-3 also increased levels of Noxa, p53-upregulated modulator of apoptosis (PUMA), and Siva-1, decreased expression of Bcl-2 and Bcl-xL, and simultaneously increased caspases-9 and -3 activities and DNA fragmentation. Knockdown of p53 decreased the basal expression of p21Cip1 and Bcl-2, inhibited the Nutlin-3-induced upregulation of Siva-1 and PUMA expression, and consequently inhibited caspase-3 activation.

CONCLUSIONS

These results indicate that the normally available pool of intracellular p53 is predominantly engaged in the regulation of cell cycle checkpoints by p21Cip1 and does not trigger apoptosis in response to DNA-damaging agents. However, the blockage of p53 binding to Mdm2 frees a pool of p53 that is sufficient, even in the absence of DNA-damaging agents, to increase the expression of proapoptotic targets and to override the resistance of RPE cells to apoptosis.

Beneficial effect of docosahexaenoic acid on cholestatic liver injury in rats

Bile duct obstruction and subsequent cholestasis are associated with hepatocellular injury, cholangiocyte proliferation, stellate cell activation, Kupffer cell activation, oxidative stress, inflammation and fibrosis. Docosahexaenoic acid (DHA) is an essential polyunsaturated fatty acid that has been shown to possess health beneficial effects, including hepatoprotection. However, the molecular mechanism of DHA-mediated hepatoprotection is not fully understood. In the present study, we report the protective effect of DHA on cholestatic liver injury. Cholestasis was produced by bile duct ligation (BDL) in male Sprague-Dawley rats for 3 weeks. Daily administration of DHA was started 2 weeks before injury and lasted for 5 weeks. In comparison with the control group, the BDL group showed hepatic damage as evidenced by histological changes and elevation in serum biochemicals, ductular reaction, fibrosis, inflammation and oxidative stress. These pathophysiological changes were attenuated by chronic DHA supplementation. DHA alleviated BDL-induced transforming growth factor beta-1 (TGF-β1), intereukin-1beta, connective tissue growth factor and collagen expression. The anti-fibrotic effect of DHA was accompanied by reductions in α-smooth muscle actin-positive matrix-producing cells and Smad 2/3 activity critical to the fibrogenic potential of TGF-β1. DHA also attenuated BDL-induced leukocyte accumulation and nuclear factor-κB (NF-κB) activation. Further studies demonstrated an inhibitory effect of DHA on redox-sensitive intracellular signaling molecule extracellular signal-regulated kinase (ERK). Taken together, the hepatoprotective, anti-inflammatory and anti-fibrotic effects of DHA seem to be multifactorial. The beneficial effects of chronic DHA supplementation are associated with anti-oxidative and anti-inflammatory potential as well as down-regulation of NF-κB and transforming growth factor beta/Smad signaling probably via interference with ERK activation.

Neuroprotectin D1 induces neuronal survival and downregulation of amyloidogenic processing in Alzheimer's disease cellular models

The mediator neuroprotectin D1 (NPD1) is an enzymatic derivative of the omega-3 essential fatty acid docosahexaenoic acid. NPD1 stereoselectively and specifically binds to human retinal pigment epithelium (RPE) cells and neutrophils. In turn, this lipid mediator induces dephosphorylation of Bcl-x(L) in a PP2A-dependent manner and induces PI3K/Akt and mTOR/p70S6K pathways leading to RPE cell survival during oxidative stress-induced apoptosis. As a proof of principle of its systemic in vivo bioactivity, NPD1 attenuates laser-induced choroidal neovascularization in mice. Using human neural cells transfected with amyloid precursor protein (APP)sw (Swedish double mutation APP695sw, K595N, M596L), NPD1 was shown to regulate secretase-mediated production of Aβ peptide, downregulates pro-inflammatory gene expression, and promotes cell survival. In human neural cells overexpressing beta-amyloid precursor protein (βAPP), the lipid mediator suppressed Aβ42 shedding by downregulating β-secretase (BACE1) while activating the α-secretase (ADAM10), thus shifting the βAPP cleavage from the noxious amyloidogenic pathway into a non-amyloidogenic, neurotrophic pathway. Furthermore, downregulation of Aβ42 peptide release by NPD1 may be dependent upon PPARγ activation. In conclusion, NPD1 exhibits anti-inflammatory, anti-amyloidogenic, and anti-apoptotic bioactivities in human neural cells in part via PPARγ signaling and through the targeting of α- and β-secretase systems.

Docosahexaenoic acid-derived neuroprotectin D1 induces neuronal survival via secretase- and PPARγ-mediated mechanisms in Alzheimer's disease models

Neuroprotectin D1 (NPD1) is a stereoselective mediator derived from the omega-3 essential fatty acid docosahexaenoic acid (DHA) with potent inflammatory resolving and neuroprotective bioactivity. NPD1 reduces Aβ42 peptide release from aging human brain cells and is severely depleted in Alzheimer's disease (AD) brain. Here we further characterize the mechanism of NPD1's neurogenic actions using 3xTg-AD mouse models and human neuronal-glial (HNG) cells in primary culture, either challenged with Aβ42 oligomeric peptide, or transfected with beta amyloid precursor protein (βAPP)(sw) (Swedish double mutation APP695(sw), K595N-M596L). We also show that NPD1 downregulates Aβ42-triggered expression of the pro-inflammatory enzyme cyclooxygenase-2 (COX-2) and of B-94 (a TNF-α-inducible pro-inflammatory element) and apoptosis in HNG cells. Moreover, NPD1 suppresses Aβ42 peptide shedding by down-regulating β-secretase-1 (BACE1) while activating the α-secretase ADAM10 and up-regulating sAPPα, thus shifting the cleavage of βAPP holoenzyme from an amyloidogenic into the non-amyloidogenic pathway. Use of the thiazolidinedione peroxisome proliferator-activated receptor gamma (PPARγ) agonist rosiglitazone, the irreversible PPARγ antagonist GW9662, and overexpressing PPARγ suggests that the NPD1-mediated down-regulation of BACE1 and Aβ42 peptide release is PPARγ-dependent. In conclusion, NPD1 bioactivity potently down regulates inflammatory signaling, amyloidogenic APP cleavage and apoptosis, underscoring the potential of this lipid mediator to rescue human brain cells in early stages of neurodegenerations.

Regulation of DNA fragmentation: the role of caspases and phosphorylation

DNA fragmentation is a hallmark of apoptosis that is induced by apoptotic stimuli in various cell types. Apoptotic signal pathways, which eventually cause DNA fragmentation, are largely mediated by the family of cysteinyl aspartate-specific protease caspases. Caspases mediate apoptotic signal transduction by cleavage of apoptosis-implicated proteins and the caspases themselves. In the process of caspase activation, reversible protein phosphorylation plays an important role. The activation of various proteins is regulated by phosphorylation and dephosphorylation, both upstream and downstream of caspase activation. Many kinases/phosphatases are involved in the control of cell survival and death, including the mitogen-activated protein kinase signal transduction pathways. Reversible protein phosphorylation is involved in the widespread regulation of cellular signal transduction and apoptotic processes. Therefore, phosphatase/kinase inhibitors are commonly used as apoptosis inducers/inhibitors. Whether protein phosphorylation induces apoptosis depends on many factors, such as the type of phosphorylated protein, the degree of activation and the influence of other proteins. Phosphorylation signaling pathways are intricately interrelated; it was previously shown that either induction or inhibition of phosphorylation causes cell death. Determination of the relationship between protein and phosphorylation helps to reveal how apoptosis is regulated. Here we discuss DNA fragmentation and protein phosphorylation, focusing on caspase and serine/threonine protein phosphatase activation.