Biochemical characterization of sirtuin 6 in the brain and its involvement in oxidative stress response

Neuronal UBE3A substrates hold therapeutic potential for Angelman syndrome

Emerging therapies for Angelman syndrome, a severe neurodevelopmental disorder, are focused on restoring UBE3A gene expression in the brain. Further therapeutic opportunities may arise from a better understanding of how UBE3A gene products-both long and short isoforms of the ubiquitin ligase E3A (UBE3A)-function in neurons. Great strides have been made recently toward identifying ubiquitin substrates of UBE3A in vitro and in heterologous expression systems. From this work, a particularly close relationship between UBE3A and subunits of the 19S regulatory particle of the proteasome has become evident. We propose that further research cognizant of isoform-specific UBE3A functional roles will be instrumental in elucidating key UBE3A/substrate relationships within distinct neuronal compartments, lending to the discovery of novel therapeutic targets and valuable clinical biomarkers for the treatment of Angelman syndrome.

The DNA repair protein DNA-PKcs modulates synaptic plasticity via PSD-95 phosphorylation and stability

The key DNA repair enzyme DNA-PKcs has several and important cellular functions. Loss of DNA-PKcs activity in mice has revealed essential roles in immune and nervous systems. In humans, DNA-PKcs is a critical factor for brain development and function since mutation of the prkdc gene causes severe neurological deficits such as microcephaly and seizures, predicting yet unknown roles of DNA-PKcs in neurons. Here we show that DNA-PKcs modulates synaptic plasticity. We demonstrate that DNA-PKcs localizes at synapses and phosphorylates PSD-95 at newly identified residues controlling PSD-95 protein stability. DNA-PKcs -/- mice are characterized by impaired Long-Term Potentiation (LTP), changes in neuronal morphology, and reduced levels of postsynaptic proteins. A PSD-95 mutant that is constitutively phosphorylated rescues LTP impairment when over-expressed in DNA-PKcs -/- mice. Our study identifies an emergent physiological function of DNA-PKcs in regulating neuronal plasticity, beyond genome stability.

In silico screening of small molecule modulators and their binding studies against human sirtuin-6 protein

Sirtuin-6 (SIRT6), class III family of deacetylase regulates several biological functions, including transcriptional repression, telomere maintenance, and DNA repair. It is unique among sirtuin family members with diverse enzymatic functions: mono-ADP-ribosylase, deacetylase and defatty-acylase. The studies so far implicated SIRT6 role in lifespan extension, tumor suppression, and is considered as an attractive drug target for aging-related disease. In this study, we have carried out in silico screening for human SIRT6 modulators using NCI Diversity Set III library, molecular dynamic (MD) simulations to analyze the protein-ligand interaction, and validated their binding-affinity (Kd) using MicroScale Thermophoresis. This study yielded two novel compounds, ((3Z)-3-((4-(dimethylamino)phenyl)methylidene)-5-(5,6,7,8-tetrahydronaphthalen-2-yl)furan-2-one and 5-phenyl-2-(5-phenyl-2,3-dihydro-1,3-benzoxazol-2-yl)-2,3-dihydro-1,3-benzoxazole showing high-affinity interaction for SIRT6. The structural analysis from MD simulation suggests both compounds might act as substrate-analogs or mimic the nicotinamide binding. On considering the uniqueness of SIRT6 substrate binding acyl channel among sirtuin family member, binding of both compounds to the above site suggesting their specificity for SIRT6 isoform. Therefore, it may form the basis for the development of potential modulators for human SIRT6.Communicated by Ramaswamy H. Sarma.

Ginsenoside Rc Modulates SIRT6-NRF2 Interaction to Alleviate Alcoholic Liver Disease

Alcoholic liver disease (ALD) is a serious worldwide health problem. Ginsenoside Rc is a major active ingredient isolated from Panax ginseng, whose pharmacological effects counteract oxidative stress, inflammation, and lipid accumulation. However, it is still unclear whether ginsenoside Rc might exert beneficial effects on alcohol-induced liver injury. To this aim, mice primary hepatocytes (MPHs) were challenged with alcohol to test ginsenoside Rc's effects on their intracellular alcohol metabolism. C57BL/6J mice or SIRT6alb-/- mice were chronically fed a diet with added alcohol or given a single gavage of alcohol with or without ginsenoside Rc. Analyses of alcohol metabolism, oxidative stress, inflammation, lipid metabolism, and RNaseq expression were conducted to explore potential targets exploited by ginsenoside Rc to protect against ALD. Our results showed that ginsenoside Rc attenuated alcohol-induced liver injury by regulating oxidative stress, inflammation, and lipid accumulation both in vivo and in vitro. Ginsenoside Rc did increase the deacetylase activity of SIRT6, thereby lowering acetylated NRF2 levels, which elevated NRF2's stability, and subsequently exerting an antioxidant effect. In keeping with this, the hepatic knockout of SIRT6 almost abolished the hepatoprotective effects of ginsenoside Rc against ALD. Therefore, our results suggest that ginsenoside Rc attenuated hepatocytes' damage and oxidative stress in ALD by up-regulating the SIRT6/NRF2 pathway. Hence, ginsenoside Rc may be a promising drug to treat or relieve ALD.

Sirtuins functions in central nervous system cells under neurological disorders

The sirtuins (SIRTs), a class of NAD+ -dependent deacylases, contain seven SIRT family members in mammals, from SIRT1 to SIRT7. Extensive studies have revealed that SIRT proteins regulate virous cell functions. Central nervous system (CNS) decline resulted in progressive cognitive impairment, social and physical abilities dysfunction. Therefore, it is of vital importance to have a better understanding of potential target to promote homeostasis of CNS. SIRTs have merged as the underlying regulating factors of the process of neurological disorders. In this review, we profile multiple functions of SIRT proteins in different cells during brain function and under CNS injury.

Sirtuins and cognition: implications for learning and memory in neurological disorders

Sirtuins are an evolutionarily conserved family of regulatory proteins that function in an NAD+ -dependent manner. The mammalian family of sirtuins is composed of seven histone deacetylase and ADP-ribosyltransferase proteins (SIRT1-SIRT7) that are found throughout the different cellular compartments of the cell. Sirtuins in the brain have received considerable attention in cognition due to their role in a plethora of metabolic and age-related diseases and their ability to induce neuroprotection. More recently, sirtuins have been shown to play a role in normal physiological cognitive function, and aberrant sirtuin function is seen in pathological cellular states. Sirtuins are believed to play a role in cognition through enhancing synaptic plasticity, influencing epigenetic regulation, and playing key roles in molecular pathways involved with oxidative stress affecting mitochondrial function. This review aims to discuss recent advances in the understanding of the role of mammalian sirtuins in cognitive function and the therapeutic potential of targeting sirtuins to ameliorate cognitive deficits in neurological disorders.

Histone Deacetylases and Their Isoform-Specific Inhibitors in Ischemic Stroke

Cerebral ischemia is the second leading cause of death in the world and multimodal stroke therapy is needed. The ischemic stroke generally reduces the gene expression due to suppression of acetylation of histones H3 and H4. Histone deacetylases inhibitors have been shown to be effective in protecting the brain from ischemic damage. Histone deacetylases inhibitors induce neurogenesis and angiogenesis in damaged brain areas promoting functional recovery after cerebral ischemia. However, the role of different histone deacetylases isoforms in the survival and death of brain cells after stroke is still controversial. This review aims to analyze the data on the neuroprotective activity of nonspecific and selective histone deacetylase inhibitors in ischemic stroke.

Sirtuins-Mediated System-Level Regulation of Mammalian Tissues at the Interface between Metabolism and Cell Cycle: A Systematic Review

Sirtuins are a family of highly conserved NAD+-dependent proteins and this dependency links Sirtuins directly to metabolism. Sirtuins' activity has been shown to extend the lifespan of several organisms and mainly through the post-translational modification of their many target proteins, with deacetylation being the most common modification. The seven mammalian Sirtuins, SIRT1 through SIRT7, have been implicated in regulating physiological responses to metabolism and stress by acting as nutrient sensors, linking environmental and nutrient signals to mammalian metabolic homeostasis. Furthermore, mammalian Sirtuins have been implicated in playing major roles in mammalian pathophysiological conditions such as inflammation, obesity and cancer. Mammalian Sirtuins are expressed heterogeneously among different organs and tissues, and the same holds true for their substrates. Thus, the function of mammalian Sirtuins together with their substrates is expected to vary among tissues. Any therapy depending on Sirtuins could therefore have different local as well as systemic effects. Here, an introduction to processes relevant for the actions of Sirtuins, such as metabolism and cell cycle, will be followed by reasoning on the system-level function of Sirtuins and their substrates in different mammalian tissues. Their involvement in the healthy metabolism and metabolic disorders will be reviewed and critically discussed.

Emerging roles of SIRT6 in human diseases and its modulators

The biological functions of sirtuin 6 (SIRT6; e.g., deacetylation, defatty-acylation, and mono-ADP-ribosylation) play a pivotal role in regulating lifespan and several fundamental processes controlling aging such as DNA repair, gene expression, and telomeric maintenance. Over the past decades, the aberration of SIRT6 has been extensively observed in diverse life-threatening human diseases. In this comprehensive review, we summarize the critical roles of SIRT6 in the onset and progression of human diseases including cancer, inflammation, diabetes, steatohepatitis, arthritis, cardiovascular diseases, neurodegenerative diseases, viral infections, renal and corneal injuries, as well as the elucidation of the related signaling pathways. Moreover, we discuss the advances in the development of small molecule SIRT6 modulators including activators and inhibitors as well as their pharmacological profiles toward potential therapeutics for SIRT6-mediated diseases.

Sirtuin 6 is a regulator of dendrite morphogenesis in rat hippocampal neurons

Sirtuin 6 (SIRT6), a member of the Sirtuin family, acts as nicotinamide adenine dinucleotide (NAD)-dependent protein deacetylase, mono-adenosine diphosphate (ADP)-ribosyltransferase, and fatty acid deacylase, and plays critical roles in inflammation, aging, glycolysis, and DNA repair. Accumulating evidence has suggested that SIRT6 is involved in brain functions such as neuronal differentiation, neurogenesis, and learning and memory. However, the precise molecular roles of SIRT6 during neuronal circuit formation are not yet well understood. In this study, we tried to elucidate molecular roles of SIRT6 on neurite development by using primary-cultured hippocampal neurons. We observed that SIRT6 was abundantly localized in the nucleus, and its expression was markedly increased during neurite outgrowth and synaptogenesis. By using shRNA-mediated SIRT6-knockdown, we show that both dendritic length and the number of dendrite branches were significantly reduced in the SIRT6-knockdown neurons. Microarray and subsequent gene ontology analysis revealed that reducing SIRT6 caused the downregulation of immediate early genes (IEGs) and alteration of several biological processes including MAPK (ERK1/2) signaling. We found that nuclear accumulation of phosphorylated ERK1/2 was significantly reduced in SIRT6-knockdown neurons. Overexpression of SIRT6 promoted dendritic length and branching, but the mutants lacking deacetylase activity had no significant effect on the dendritic morphology. Collectively, the presented findings reveal a role of SIRT6 in dendrite morphogenesis, and suggest that SIRT6 may act as an important regulator of ERK1/2 signaling pathway that mediates IEG expression, which leads to dendritic development.

Localization and Expression of Sirtuins 1, 2, 6 and Plasticity-Related Proteins in the Recovery Period after a Photothrombotic Stroke in Mice

Sirtuins, class III histone deacetylases, are involved in the regulation of tissue repair processes and brain functions after a stroke. The ability of some isoforms of sirtuins to circulate between the nucleus and cytoplasm may have various pathophysiological effects on the cells. In present work, we focused on the role of non-mitochondrial sirtuins SIRT1, SIRT2, and SIRT6 in the restoration of brain cells following ischemic stroke. Here, using a photothrombotic stroke (PTS) model in mice, we studied whether local stroke affects the level and intracellular localization of SIRT1, SIRT2, and SIRT6 in neurons and astrocytes of the intact cerebral cortex adjacent to the ischemic ipsilateral hemisphere and in the analogous region of the contralateral hemisphere at different time points during the recovery period after a stroke. We evaluated the co-localization of sirtuins with growth-associated protein-43 (GAP-43), the presynaptic marker synaptophysin (SYN) and acetylated α-tubulin (Ac-α-Tub), that are associated with brain plasticity and are known to be involved in brain repair after a stroke. The results show that during the recovery period, an increase in SIRT1 and SIRT2 levels occurred. The increase of SIRT1 level was associated with an increase in synaptic plasticity proteins, whereas the increase of SIRT2 level was associated with an acetylated of α-tubulin, that can reduce the mobility of neurites. SIRT6 co-localized with GAP-43, but not with SYN. Moreover, we showed that SIRT1, SIRT2, and SIRT6 are not involved in the PTS-induced apoptosis of penumbra cells. Taken together, our results suggest that sirtuins functions differ depending on cell type, intracellular localization, specificity of sirtuins isoforms to different substrates and nature of post-translational modifications of enzymes.

The effect of baicalein-loaded Y-shaped miktoarm copolymer on spatial memory and hippocampal expression of DHCR24, SELADIN and SIRT6 genes in rat model of Alzheimer

In the present study, we successfully synthesized nanocarriers (NCs) based on Y-shaped miktoarm copolymers, Poly Ethylene Glycol-Lysine-(Poly Caprolactone)₂ (PEG-Lys-PCL₂), which were loaded by baicalein (B) through the nanoprecipitation process to assess their in-vitro and in-vivo properties. We applied various methods and measurements including proton nuclear magnetic resonance (HNMR), dynamic light scattering (DLS), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), MTT assay, hemolysis test, lethal dose, real-time PCR, and Morris water maze. The results of DLS indicated that the size and zeta potential of the obtained NCs and B-loaded NCs were acceptable. Also, in-vivo and in-vitro biocompatibility examinations proved that miktoarm-based NCs were safe, and all rats treated with miktoarm-based NCs did not exhibit any remarkable weight loss during the experiment. The results of the Morris water maze (in-vivo test) revealed that the normal saline-treated group, as well as B-miktoarm + Scopolamine (M + B + S) and B-miktoarm-Tween80 + Scopolamine (M + B + T + S) pretreatment groups, spent more time in the target quadrant. Thus, this experiment showed that pretreatment of rats with M + B + S and M + B + T + S had the most effects on spatial memory. According to quantitative PCR analysis, we hypothesized that, in comparison with other experimental groups, pretreatment of rats with M + B + T + S could be more effective in preventing cholinergic dysfunction, brain oxidative stress and cognitive deficits which cause by Scopolamine HBr. This outcome may be partially due to the upregulation of DHCR24, SELADIN, and SIRT6 in entire of the hippocampal region of normal saline-treated and M + B + T + S pretreatment groups. These results may be because mimicking the cell membrane structure would be an excellent feature for miktoarm, and partial coating of Tween-80 can play a critical role for PEG-Lys-PCL₂-based NCs in crossing the brain cell membrane, and they can easily be uptaken by the cells. Eventually, all of the obtained data confirmed that PEG-Lys-PCL₂ miktoarm star copolymers are suitable for delivering therapeutic agents to the brain for the treatment of Alzheimer's disease (AD). Also, it seems that baicalein should be taken into account as a potent compound for the treatment of AD.

Sirtuins and SIRT6 in Carcinogenesis and in Diet

Sirtuins are a highly conserved family of nicotinamide adenine dinucleotide (NAD)-dependent protein lysine modifying enzymes. They are key regulators for a wide variety of cellular and physiological processes such as cell proliferation, differentiation, DNA damage and stress response, genome stability, cell survival, metabolism, energy homeostasis, organ development and aging. Aging is one of the major risk factors of cancer, as many of the physiological mechanisms and pathologies associated with the aging process also contribute to tumor initiation, growth and/or metastasis. This review focuses on one the mammalian sirtuins, SIRT6, which has emerged as an important regulator of longevity and appears to have multiple biochemical functions that interfere with tumor development and may be useful in cancer prevention and for site-specific treatment. The recent evidence of the role of SIRT6 in carcinogenesis is also discussed, focusing on the potential use of SIRT6 modulators in cancer nanomedicine.

Understanding Epigenetics in the Neurodegeneration of Alzheimer's Disease: SAMP8 Mouse Model

Epigenetics is emerging as the missing link among genetic inheritance, environmental influences, and body and brain health status. In the brain, specific changes in nucleic acids or their associated proteins in neurons and glial cells might imprint differential patterns of gene activation that will favor either cognitive enhancement or cognitive loss for more than one generation. Furthermore, derangement of age-related epigenetic signaling is appearing as a significant risk factor for illnesses of aging, including neurodegeneration and Alzheimer’s disease (AD). In addition, better knowledge of epigenetic mechanisms might provide hints and clues in the triggering and progression of AD. Intense research in experimental models suggests that molecular interventions for modulating epigenetic mechanisms might have therapeutic applications to promote cognitive maintenance through an advanced age. The SAMP8 mouse is a senescence model with AD traits in which the study of epigenetic alterations may unveil epigenetic therapies against the AD.

Nicotine promotes neuron survival and partially protects from Parkinson's disease by suppressing SIRT6

Parkinson’s disease is characterized by progressive death of dopaminergic neurons, leading to motor and cognitive dysfunction. Epidemiological studies consistently show that the use of tobacco reduces the risk of Parkinson’s. We report that nicotine reduces the abundance of SIRT6 in neuronal culture and brain tissue. We find that reduction of SIRT6 is partly responsible for neuroprotection afforded by nicotine. Additionally, SIRT6 abundance is greater in Parkinson’s patient brains, and decreased in the brains of tobacco users. We also identify SNPs that promote SIRT6 expression and simultaneously associate with an increased risk of Parkinson’s. Furthermore, brain-specific SIRT6 knockout mice are protected from MPTP-induced Parkinson’s, while SIRT6 overexpressing mice develop more severe pathology. Our data suggest that SIRT6 plays a pathogenic and pro-inflammatory role in Parkinson’s and that nicotine can provide neuroprotection by accelerating its degradation. Inhibition of SIRT6 may be a promising strategy to ameliorate Parkinson’s and neurodegeneration.

The NAD+-Dependent Family of Sirtuins in Cerebral Ischemia and Preconditioning

SIGNIFICANCE

Sirtuins are an evolutionarily conserved family of NAD+-dependent lysine deacylases and ADP ribosylases. Their requirement for NAD+ as a cosubstrate allows them to act as metabolic sensors that couple changes in the energy status of the cell to changes in cellular physiological processes. NAD+ levels are affected by several NAD+-producing and NAD+-consuming pathways as well as by cellular respiration. Thus their intracellular levels are highly dynamic and are misregulated in a spectrum of metabolic disorders including cerebral ischemia. This, in turn, compromises several NAD+-dependent processes that may ultimately lead to cell death. Recent Advances: A number of efforts have been made to replenish NAD+ in cerebral ischemic injuries as well as to understand the functions of one its important mediators, the sirtuin family of proteins through the use of pharmacological modulators or genetic manipulation approaches either before or after the insult. Critical Issues and Future Directions: The results of these studies have regarded the sirtuins as promising therapeutic targets for cerebral ischemia. Yet, additional efforts are needed to understand the role of some of the less characterized members and to address the sex-specific effects observed with some members. Sirtuins also exhibit cell-type-specific expression in the brain as well as distinct subcellular and regional localizations. As such, they are involved in diverse and sometimes opposing cellular processes that can either promote neuroprotection or further contribute to the injury; which also stresses the need for the development and use of sirtuin-specific pharmacological modulators. Antioxid. Redox Signal. 28, 691-710.

Emerging Roles of Sirtuins in Ischemic Stroke

Ischemic stroke is one of the leading causes of death worldwide. It is characterized by a sudden disruption of blood flow to the brain causing cell death and damage, which will lead to neurological impairments. In the current state, only one drug is approved to be used in clinical setting and new therapies that confer ischemic neuroprotection are desperately needed. Several targets and pathways have been indicated to be neuroprotective in ischemic stroke, among which the sirtuin family of nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases has emerged as important modulators of several processes in the normal physiology and pathological conditions such as stroke. Recent studies have identified some members of the sirtuin family are able to ameliorate the devastating consequences of ischemic stroke by conferring neuroprotection by means of reducing neuronal cell death, oxidative stress, and neuroinflammation whereas some sirtuins are found to be detrimental in the pathophysiology of ischemic stroke. This review summarizes implications of sirtuins in ischemic stroke and the experimental evidences that demonstrate the potential of sirtuin modulators as neuroprotective therapy for ischemic stroke.

Metabolic Stress Induces Cognitive Disturbances and Inflammation in Aged Mice: Protective Role of Resveratrol

Inflammation and oxidative stress (OS) are key points in age progression. Both processes impact negatively in cognition and in brain functions. Resveratrol (RV) has been postulated as a potent antioxidant natural compound, with rejuvenating properties. Inducing a metabolic stress by high-fat (HF) diet in aged C56/BL6 (24 months) led to cognitive disturbances compared with control age mated and with young mice. These changes were prevented by RV. Molecular determinations demonstrated a significant increase in some inflammatory parameters (TNF-α, Cxcl10, IL-1, IL-6, and Ccl3) in old mice, but slight changes in OS machinery. RV mainly induced the recovery of the metabolically stressed animals. The study of key markers involved in senescence and rejuvenation (mitochondrial biogenesis and Sirt1-AMPK-PGC1-α) demonstrated that RV is also able to modulate the changes in these cellular metabolic pathways. Moreover, changes of epigenetic marks (methylation and acetylation) that are depending on OS were demonstrated. On the whole, results showed the importance of integrative role of different cellular mechanisms in the deleterious effects of age in cognition and the beneficial role of RV. The work presented in this study showed a wide range of processes modified in old age and by metabolic stress, weighting the importance of each one and the role of RV as a possible strategy for fighting against.

Epigenetic mechanisms underlying cognitive impairment and Alzheimer disease hallmarks in 5XFAD mice

5XFAD is an early-onset mouse transgenic model of Alzheimer disease (AD). Up to now there are no studies that focus on the epigenetic changes produced as a result of Aβ-42 accumulation and the possible involvement in the different expression of related AD-genes. Under several behavioral and cognition test, we found impairment in memory and psychoemotional changes in female 5XFAD mice in reference to wild type that worsens with age. Cognitive changes correlated with alterations on protein level analysis and gene expression of markers related with tau aberrant phosphorylation, amyloidogenic pathway (APP, BACE1), Oxidative Stress (iNOS, Aldh2) and inflammation (astrogliosis, TNF-α and IL-6); no changes were found in non-amyloidogenic pathway indicators such as ADAM10. Epigenetics changes as higher CpG methylation and transcriptional changes in DNA methyltransferases (DNMTs) family were found. Dnmt1 increases in younger 5XFAD and Dnmt3a and b high levels in the oldest transgenic mice. Similar pattern was found with histone methyltransferases such as Jarid1a andG9a. Histone deacetylase 2 (Hdac2) or Sirt6, both related with cognition and memory, presented a similar pattern. Taken together, these hallmarks presented by the 5XFAD model prompted its use in assessing different potential therapeutic interventions based on epigenetic targets after earlier amyloid deposition.

Autophagy induction by SIRT6 is involved in oxidative stress-induced neuronal damage

SIRT6 is a NAD⁺-dependent histone deacetylase and has been implicated in the regulation of genomic stability, DNA repair, metabolic homeostasis and several diseases. The effect of SIRT6 in cerebral ischemia and oxygen/glucose deprivation (OGD) has been reported, however the role of SIRT6 in oxidative stress damage remains unclear. Here we used SH-SY5Y neuronal cells and found that overexpression of SIRT6 led to decreased cell viability and increased necrotic cell death and reactive oxygen species (ROS) production under oxidative stress. Mechanistic study revealed that SIRT6 induced autophagy via attenuation of AKT signaling and treatment with autophagy inhibitor 3-MA or knockdown of autophagy-related protein Atg5 rescued H₂O₂-induced neuronal injury. Conversely, SIRT6 inhibition suppressed autophagy and reduced oxidative stress-induced neuronal damage. These results suggest that SIRT6 might be a potential therapeutic target for neuroprotection.

The Response to Oxidative DNA Damage in Neurons: Mechanisms and Disease

There is a growing body of evidence indicating that the mechanisms that control genome stability are of key importance in the development and function of the nervous system. The major threat for neurons is oxidative DNA damage, which is repaired by the base excision repair (BER) pathway. Functional mutations of enzymes that are involved in the processing of single-strand breaks (SSB) that are generated during BER have been causally associated with syndromes that present important neurological alterations and cognitive decline. In this review, the plasticity of BER during neurogenesis and the importance of an efficient BER for correct brain function will be specifically addressed paying particular attention to the brain region and neuron-selectivity in SSB repair-associated neurological syndromes and age-related neurodegenerative diseases.