Age affects ERK1/2 and NRF2 signaling in the regulation of GCLC expression

Does Nrf2 Play a Role of a Master Regulator of Mammalian Aging?

For a long time Nrf2 transcription factor has been attracting attention of researchers investigating phenomenon of aging. Numerous studies have investigated effects of Nrf2 on aging and cell senescence. Nrf2 is often considered as a key player in aging processes, however this needs to be proven. It should be noted that most studies were carried out on invertebrate model organisms, such as nematodes and fruit flies, but not on mammals. This paper briefly presents main mechanisms of mammalian aging and role of inflammation and oxidative stress in this process. The mechanisms of Nrf2 activity regulation, its involvement in aging and development of the senescence-associated secretory phenotype (SASP) are also discussed. Main part of this review is devoted to critical analysis of available experimental data on the role of Nrf2 in mammalian aging.

Lability of the Nrf2/Keap/ARE Cell Defense System in Different Models of Cell Aging and Age-Related Pathologies

The level of oxidative stress in an organism increases with age. Accumulation of damages resulting in the disruption of genome integrity can be the cause of many age-related diseases and appearance of phenotypic and physiological signs of aging. In this regard, the Nrf2 system, which regulates expression of numerous enzymes responsible for the antioxidant defense and detoxification, is of great interest. This review summarizes and analyzes the data on the age-related changes in the Nrf2 system in vivo and in vitro in various organs and tissues. Analysis of published data suggests that the capacity for Nrf2 activation (triggered by the increased level of oxidative stress) steadily declines with age. At the same time, changes in the Nrf2 activity under the stress-free conditions do not have such unambiguous directionality; in many studies, these changes were statistically insignificant, although it is commonly accepted that the level of oxidative stress steadily increases with aging. This review examines the role of cell regulatory systems limiting the ability of Nrf2 to respond to oxidative stress. Senescent cells are extremely susceptible to the oxidative damage due to the impaired Nrf2 signaling. Activation of the Nrf2 pathway is a promising target for new pharmacological or genetic therapeutic strategies. Suppressors of the Nrf2 expression, such as Keap1, GSK3, c-Myc, and Bach1, may contribute to the age-related impairments in the induction of Nrf2-regulated antioxidant genes. Understanding the mechanisms of regulatory cascades linking the programs responsible for the maintenance of homeostasis and cell response to the oxidative stress will contribute to the elucidation of molecular mechanisms underlying aging and longevity.

M2 macrophage-derived exosomes promote the c-KIT phenotype of vascular smooth muscle cells during vascular tissue repair after intravascular stent implantation

Rationale: For intravascular stent implantation to be successful, the processes of vascular tissue repair and therapy are considered to be critical. However, the mechanisms underlying the eventual fate of vascular smooth muscle cells (VSMCs) during vascular tissue repair remains elusive. In this study, we hypothesized that M2 macrophage-derived exosomes to mediate cell-to-cell crosstalk and induce dedifferentiation phenotypes in VSMCs. Methods: In vivo, 316L bare metal stents (BMS) were implanted from the left iliac artery into the abdominal aorta of 12-week-old male Sprague-Dawley (SD) rats for 7 and 28 days. Hematoxylin and eosin (HE) were used to stain the neointimal lesions. En-face immunofluorescence staining of smooth muscle 22 alpha (SM22α) and CD68 showed the rat aorta smooth muscle cells (RASMCs) and macrophages. Immunohistochemical staining of total galactose-specific lectin 3 (MAC-2) and total chitinase 3-like 3 (YM-1) showed the total macrophages and M2 macrophages. In vitro, exosomes derived from IL-4+IL-13-treated macrophages (M2Es) were isolated by ultracentrifugation and characterized based on their specific morphology. Ki-67 staining was conducted to assess the effects of the M2Es on the proliferation of RASMCs. An atomic force microscope (AFM) was used to detect the stiffness of the VSMCs. GW4869 was used to inhibit exosome release. RNA-seq was performed to determine the mRNA profiles of the RASMCs and M2Es-treated RASMCs. Quantitative real-time PCR (qRT-PCR) analysis was conducted to detect the expression levels of the mRNAs. Western blotting was used to detect the candidate protein expression levels. T-5224 was used to inhibit the DNA binding activity of AP-1 in RASMCs. Results: M2Es promote c-KIT expression and softening of nearby VSMCs, hence accelerating the vascular tissue repair process. VSMCs co-cultured in vitro with M2 macrophages presented an increased capacity for de-differentiation and softening, which was exosome dependent. In addition, the isolated M2Es helped to promote VSMC dedifferentiation and softening. Furthermore, the M2Es enhanced vascular tissue repair potency by upregulation of VSMCs c-KIT expression via activation of the c-Jun/activator protein 1 (AP-1) signaling pathway. Conclusions: The findings of this study emphasize the prominent role of M2Es during VSMC dedifferentiation and vascular tissue repair via activation of the c-Jun/AP-1 signaling pathway, which has a profound impact on the therapeutic strategies of coronary stenting techniques.

Kidney epithelium specific deletion of kelch-like ECH-associated protein 1 (Keap1) causes hydronephrosis in mice

Background

Transcription factor Nrf2 protects from experimental acute kidney injury (AKI) and is promising to limit progression in human chronic kidney disease (CKD) by upregulating multiple antioxidant genes. We recently demonstrated that deletion of Keap1, the endogenous inhibitor of Nrf2, in T lymphocytes significantly protects from AKI. In this study, we investigated the effect of Keap1 deletion on Nrf2 mediated antioxidant response in the renal tubular epithelial cells.

Methods

We deleted Keap1 exon 2 and 3 in the renal tubular epithelial cells by crossing Ksp-Cre mice with Keap1 floxed (Keap1^f/f) mice. Deletion of Keap1 gene in the kidney epithelial cells of Ksp-Keap1^-/- mice and its effect on Nrf2 target gene expression was performed using PCR and real-time PCR respectively. Histological evaluation was performed on H&E stained sections. Complete blood count, serum and urine analysis were performed to assess systemic effects of defective kidney development. Student’s T test was used to determine statistical difference between the groups.

Results

Ksp-Cre resulted in the deletion of Keap1 exon 2 and 3 and subsequent upregulation of Nrf2 target genes, Nqo1, Gclm and Gclc in the kidney epithelial cells of Ksp-Keap1^-/- mice at baseline. Renal epithelial cell specific deletion of Keap1 in Ksp-Keap1^-/- mice caused marked renal pelvic expansion and significant compression of medullary parenchyma consistent with hydronephrosis in both (3 month-old) males and females. Kidneys from 6 month-old Ksp-Keap1^-/- mice showed progressive hydronephrosis. Hematological, biochemical and urinary analysis showed significantly higher red blood cell count (p = 0.04), hemoglobin (p = 0.01), hematocrit (p = 0.02), mean cell volume (p = 0.02) and mean cell hemoglobin concentration (p = 0.003) in Ksp-Keap1^-/- mice in comparison to Keap1^f/f mice.

Conclusions

These unexpected findings demonstrate that Keap1 deletion in renal tubular epithelial cells results in an abnormal kidney development consistent with hydronephrosis and reveals a novel Keap1 mediated signaling pathway in renal development.

Impaired transcriptional activity of Nrf2 in age-related myocardial oxidative stress is reversible by moderate exercise training

Aging promotes accumulation of reactive oxygen/nitrogen species (ROS/RNS) in cardiomyocytes, which leads to contractile dysfunction and cardiac abnormalities. These changes may contribute to increased cardiovascular disease in the elderly. Inducible antioxidant pathways are regulated by nuclear erythroid 2 p45-related factor 2 (Nrf2) through antioxidant response cis-elements (AREs) and are impaired in the aging heart. Whereas acute exercise stress (AES) activates Nrf2 signaling and promotes myocardial antioxidant function in young mice (∼2 months), aging mouse (>23 months) hearts exhibit significant oxidative stress as compared to those of the young. The purpose of this study was to investigate age-dependent regulation of Nrf2-antioxidant mechanisms and redox homeostasis in mouse hearts and the impact of exercise. Old mice were highly susceptible to oxidative stress following high endurance exercise stress (EES), but demonstrated increased adaptive redox homeostasis after moderate exercise training (MET; 10m/min, for 45 min/day) for ∼6 weeks. Following EES, transcription and protein levels for most of the ARE-antioxidants were increased in young mice but their induction was blunted in aging mice. In contrast, 6-weeks of chronic MET promoted nuclear levels of Nrf2 along with its target antioxidants in the aging heart to near normal levels as seen in young mice. These observations suggest that enhancing Nrf2 function and endogenous cytoprotective mechanisms by MET, may combat age-induced ROS/RNS and protect the myocardium from oxidative stress diseases.

Nrf2-regulated phase II enzymes are induced by chronic ambient nanoparticle exposure in young mice with age-related impairments

Many xenobiotic detoxifying (phase II) enzymes are induced by sublethal doses of environmental toxicants. However, these adaptive mechanisms have not been studied in response to vehicular-derived airborne nano-sized particulate matter (nPM). Because aging is associated with increased susceptibility to environmental toxicants, we also examined the expression of Nrf2-regulated phase II genes in middle-aged mice and their inducibility by chronic nPM. The nPM from vehicular traffic was collected in urban Los Angeles and reaerosolized for exposure of C57BL/6J male mice (3 and 18 months old) for 150 h over 10 weeks. Brain (cerebellum), liver, and lung were assayed by RT-PCR and/or Western blots for the expression of phase II enzymes, glutamate cysteine ligase (catalytic GCLC, and modifier GCLM subunits), NAD(P)H:quinone oxidoreductase 1 (NQO1), heme oxygenase 1 (HO-1), and relevant transcription factors, NF-E2-related factor 2 (Nrf2), c-Myc, Bach1. Chronic nPM exposure induced GCLC, GCLM, HO-1, NQO1 mRNA, and protein similarly in cerebellum, liver, and lung of young mice. Middle-aged mice had elevated basal levels, but showed impaired further induction by nPM. Similarly, Nrf2 increased with age and was induced by nPM in young but not old. c-Myc showed the same age and induction profile while the age increase in Bach1 was further induced by nPM. Chronic exposure to nanoparticles induced Nrf2-regulated detoxifying enzymes in brain (cerebellum), liver, and lung of young adult mice, indicating a systemic impact of nPM. In contrast, middle-aged mice did not respond above their elevated basal levels except for Bach1. The lack of induction of phase II enzymes in aging mice may be a model for the vulnerability of elderly to air pollution.

Mechanism of the Nrf2/Keap1/ARE signaling system

Nrf2 regulates expression of genes containing antioxidant-respons(iv)e element (ARE) in their promoters and plays a pivotal role among all redox-sensitive transcription factors. Nrf2 is constitutively controlled by repressor protein Keap1, which acts as a molecular sensor of disturbances in cellular homeostasis. These molecular patterns are in close interconnection and function as parts of the integrated redox-sensitive signaling system Nrf2/Keap1/ARE. Depending on cellular redox balance, activity of this signaling system changes at the levels of transcription, translation, posttranslational modification, nuclear translocation of transcription factor, and its binding to ARE-driven gene promoters. This review summarizes current conceptions of Nrf2/Keap1/ARE induction and inactivation.

Impaired redox signaling and antioxidant gene expression in endothelial cells in diabetes: a role for mitochondria and the nuclear factor-E2-related factor 2-Kelch-like ECH-associated protein 1 defense pathway

Type 2 diabetes is an age-related disease associated with vascular pathologies, including severe blindness, renal failure, atherosclerosis, and stroke. Reactive oxygen species (ROS), especially mitochondrial ROS, play a key role in regulating the cellular redox status, and an overproduction of ROS may in part underlie the pathogenesis of diabetes and other age-related diseases. Cells have evolved endogenous defense mechanisms against sustained oxidative stress such as the redox-sensitive transcription factor nuclear factor E2-related factor 2 (Nrf2), which regulates antioxidant response element (ARE/electrophile response element)-mediated expression of detoxifying and antioxidant enzymes and the cystine/glutamate transporter involved in glutathione biosynthesis. We hypothesize that diminished Nrf2/ARE activity contributes to increased oxidative stress and mitochondrial dysfunction in the vasculature leading to endothelial dysfunction, insulin resistance, and abnormal angiogenesis observed in diabetes. Sustained hyperglycemia further exacerbates redox dysregulation, thereby providing a positive feedback loop for severe diabetic complications. This review focuses on the role that Nrf2/ARE-linked gene expression plays in regulating endothelial redox homeostasis in health and type 2 diabetes, highlighting recent evidence that Nrf2 may provide a therapeutic target for countering oxidative stress associated with vascular disease and aging.

Age-related changes in redox signaling and VSMC function

Epidemiological studies have shown that advancing age is associated with an increased prevalence of cardiovascular disease (CVD). Vascular smooth muscle cells (VSMC) comprise the major arterial cell population, and changes in VSMC behavior, function, and redox status with age contribute to alterations in vascular remodeling and cell signaling. Over two decades of work on aged animal models provide support for age-related changes in VSMC and/or arterial tissues. Enhanced production of reactive oxygen species (ROS) and insufficient removal by scavenging systems are hallmarks of vascular aging. VSMC proliferation and migration are core processes in vascular remodeling and influenced by growth factors and signaling networks. The intrinsic link between gene regulation and aging often relates directly to transcription factors and their regulatory actions. Modulation of growth factor signaling leads to up- or downregulation of transcription factors that control expression of genes associated with VSMC proliferation, inflammation, and ROS production. Four major signaling pathways related to the transcription factors, AP-1, NF-kappaB, FoxO, and Nrf2, will be reviewed. Knowledge of age-related changes in signaling pathways in VSMC that lead to alterations in cell behavior and function consistent with disease progression may help in efforts to attenuate age-related CVD, such as atherosclerosis.

Age-related toxicity of amyloid-beta associated with increased pERK and pCREB in primary hippocampal neurons: reversal by blueberry extract

Further clarification is needed to address the paradox that memory formation, aging and neurodegeneration all involve calcium influx, oxyradical production (ROS) and activation of certain signaling pathways. In aged rats and in APP/PS-1 mice, cognitive and hippocampal Ca(2+) dysregulation was reversed by food supplementation with a high antioxidant blueberry extract. Here, we studied whether neurons were an important target of blueberry extract and whether the mechanism involved altered ROS signaling through MAP kinase and cyclic-AMP response element binding protein (CREB), pathways known to be activated in response to amyloid-beta (Aβ). Primary hippocampal neurons were isolated and cultured from embryonic, middle-age or old-age (24 months) rats. Blueberry extract was found to be equally neuroprotective against Aβ neurotoxicity at all ages. Increases in Aβ toxicity with age were associated with age-related increases in immunoreactivity of neurons to pERK and an age-independent increase in pCREB. Treatment with blueberry extract strongly inhibited these increases in parallel with neuroprotection. Simultaneous labeling for ROS and for glutathione with dichlorofluorescein and monochlorobimane showed a mechanism of action of blueberry extract to involve transient ROS generation with an increase in the redox buffer glutathione. We conclude that the increased age-related susceptibility of old-age neurons to Aβ toxicity may be due to higher levels of activation of pERK and pCREB pathways that can be protected by blueberry extract through inhibition of both these pathways through an ROS stress response. These results suggest that the beneficial effects of blueberry extract may involve transient stress signaling and ROS protection that may translate into improved cognition in aging rats and APP/PS1 mice given blueberry extract.

Identification and characterization of an Nrf2-mediated ARE upstream of the rat glutamate cysteine ligase catalytic subunit gene (GCLC)

The antioxidant response element (ARE) is an essential component of upstream regulatory sequences present on genes for most phase II detoxification enzymes, including the glutamate cysteine ligase catalytic subunit (GCLC). NF-E2-related factor 2 (Nrf2) is a principal transcription factor that binds to the ARE and plays a key role in cellular responses to stress via the Keap1-Nrf2-ARE pathway. However, the ARE that mediates human GCLC gene expression has not been found in the rat. Thus, how the ARE-mediated Keap1-Nrf2-ARE pathway regulates glutathione homeostasis in the rat remains a puzzle. We have identified a putative ARE sequence approximately 4 kb upstream in the rat GCLC. We further defined the rat GCLC-ARE in the category with the most ARE characters, that is, this rat GCLC-ARE is a sequence-specific site that significantly enhances promoter activity in reporter genes. The rat GCLC-ARE is an Nrf2-mediated element to which binding has been demonstrated in nuclear extracts and induced by tert-butylhydroquinone. Given the central role that rat models play in toxicology and pathology, this first discovery of the rat GCLC-ARE enhancer similar to that found in the human gene has broad implications for the study of antioxidant defenses and their regulation in a number of different fields.

Targeting the Nrf2 pathway against cardiovascular disease

Nuclear factor E2-related factor 2 (Nrf2) is a transcription factor that controls the basal and inducible expression of a battery of antioxidant genes and other cytoprotective Phase II detoxifying enzymes. Nrf2 is ubiquitously expressed in the cardiovascular system. While several Nrf2 downstream genes have been implicated in protection against the pathogenesis of cardiovascular diseases, the precise role of Nrf2 in the cardiovascular system remains to be elucidated. Nevertheless, mounting evidence has revealed that Nrf2 is a critical regulator of cardiovascular homeostasis via the suppression of oxidative stress, a major causative factor for the development and progression of cardiovascular diseases. Therefore, Nrf2 promises to be an attractive therapeutic target for the treatment of cardiovascular disease. Herein, we review the current literature that suggests that Nrf2 is a valuable therapeutic target for cardiovascular disease, as well as experiments that illustrate the mechanisms of Nrf2 cardioprotection.

Vascular action of polyphenols

Dietary patterns are widely recognised as contributors to cardiovascular and cerebrovascular disease. Endothelial function, the elastic properties of large arteries and the magnitude and timing of wave reflections are important determinants of cardiovascular performance. Several epidemiological studies suggest that the regular consumption of foods and beverages rich in flavonoids is associated with a reduction in the risk of several pathological conditions ranging from hypertension to coronary heart disease, stroke and dementia. The impairment of endothelial function is directly related to ageing and an association between decreased cerebral perfusion and dementia has been shown to exist. Cerebral blood flow (CBF) must be maintained to ensure a constant delivery of oxygen and glucose as well as the removal of waste products. Increasing blood flow is one potential way for improving brain function and the prospect for increasing CBF with dietary polyphenols is extremely promising. The major polyphenols shown to have some of these effects in humans are primarily from cocoa, wine, grape seed, berries, tea, tomatoes (polyphenolics and nonpolyphenolics), soy and pomegranate. There has been a significant paradigm shift in polyphenol research during the last decade. This review summarises our current knowledge in this area and points the way for the development of new types of functional foods targeted to brain health through improving vascular health.

Age-related differences in insulin-like growth factor-1 receptor signaling regulates Akt/FOXO3a and ERK/Fos pathways in vascular smooth muscle cells

Advanced age is a major risk factor for atherosclerosis, but how aging per se influences pathogenesis is not clear. Insulin-like growth factor-1 receptor (IGF-1R) promotes aortic vascular smooth muscle cell (VSMC) growth, migration, and extracellular matrix formation, but how IGF-1R signaling changes with age in VSMC is not known. We previously found age-related differences in the activation of Akt/FOXO3a and ERK1/2 pathways in VSMC, but the upstream signaling remains unclear. Using explanted VSMC from Fischer 344/Brown Norway F1 hybrid rats shown to display age-related vascular pathology similar to humans, we compared IGF-1R expression in early passages of VSMC and found a constitutive activation of IGF-1R in VSMC from old compared to young rats, including IGF-1R expression and its tyrosine kinase activity. The link between IGF-1R activation and the Akt/FOXO3a and ERK pathways was confirmed through the induction of IGF-1R with IGF-1 in young cells and attenuation of IGF-1R with an inhibitor in old cells. The effects of three kinase inhibitors: AG1024, LY294002, and TCN, were compared in VSMC from old rats to differentiate IGF-1R from other upstream signaling that could also regulate the Akt/FOXO and ERK pathways. Genes for p27kip-1, catalase and MnSOD, which play important roles in the control of cell cycle arrest and stress resistance, were found to be FOXO3a-targets based on FOXO3a-siRNA treatment. Furthermore, IGF-1R signaling modulated these genes through activation of the Akt/FOXO3a pathway. Therefore, activation of IGF-1R signaling influences VSMC function in old rats and may contribute to the increased risk for atherosclerosis.

GSK-3beta down-regulates the transcription factor Nrf2 after oxidant damage: relevance to exposure of neuronal cells to oxidative stress

Oxidant injury activates the neuroprotective pathway represented by phosphatidylinositol 3 kinase (PI3K) and Akt. However, the final outcome of oxidant exposure is often associated with neuronal death. This study was aimed to identify the molecular mechanism responsible for loss of tolerance to an oxidative environment. In N2A neuroblasts, serum and H2O2 exhibited different kinetics of regulation for the Ser/Thr kinases Akt and glycogen synthase kinase 3beta (GSK-3beta) and for the transcription factor Nrf2, which governs redox homeostasis. Thus, H2O2 rapidly activated Akt, inhibited GSK-3beta, and directed the transcription factor Nrf2 to the nucleus, but after 4 h Akt was inactive, GSK-3beta was active and Nrf2 was more cytosolic than nuclear. Inhibition of the PI3K/Akt pathway by LY294002, impeded the short-term effect of H2O2 on nuclear translocation of Nrf2. GSK-3beta activation (inhibiting PI3K/Akt) or direct GSK-3beta inhibition in cerebellar granule neurons resulted in respective nuclear exclusion and nuclear accumulation of Nrf2. Moreover, in these neurons, nuclear accumulation of Nrf2 correlated with increased heme oxygenase-1 expression. Over-expression of the kinase active GSK-3beta (Delta9) mutant, induced Nrf2 cytoplasmic localization and inhibited Nrf2 transcriptional activity towards an antioxidant-response-element luciferase reporter. Moreover, GSK-3beta (Delta9) sensitized N2A neuroblasts to H2O2-induced oxidative stress and cell death. This study identifies GSK-3beta, a kinase known to participate in neurodegeneration, as a fundamental element in the down-regulation of the antioxidant cell defense elicited by Nrf2 after oxidant injury and provides a mechanism to explain the loss of oxidant tolerance that happens under persistent oxidant exposure such as those found in several neuropathologies.

Transcription factor Nrf2 activation by deltamethrin in PC12 cells: Involvement of ROS

Activation of transcription factor NF-E2-related factor 2 (Nrf2) is a key initiation step in the cellular protection against a broad range of chemical oxidative stresses. To gain insights into dopaminergic cell responses to pesticides, the present study was conducted to examine the effects of deltamethrin (DM), a prototype of widely used pyrithroid pesticides, on the activation and expression of Nrf2 in PC12 rat adrenal pheochromocytoma cells as a dopaminergic cell model. We found, for the first time, that DM enhanced cellular expression of Nrf2 at the transcriptional and protein levels and activated expression of Nrf2-regulated genes in these cells. In addition, DM exposure caused nuclear accumulation of Nrf2 in association with downstream activation of Nrf2-mediated oxidative response genes, such as heme oxygenase-l (HO-1) and gamma-glutamylcysteine synthetase catalytic heavy subunit (GCSh). Furthermore, when cells were pretreated with N-acetyl cysteine (NAC), a scavenger of reactive oxygen species (ROS), DM-induced Nrf2 signaling was suppressed. These results indicate that ROS is the mediator of nuclear Nrf2 accumulation. Taken together, these data clearly show that DM increases Nrf2 expression and activity and that ROS is one of the mediators of this process.

Modulation of antioxidant gene expression by 4-hydroxynonenal: atheroprotective role of the Nrf2/ARE transcription pathway

The aldehyde 4-hydroxy-2-nonenal (HNE) is an end-product of polyunsaturated fatty acid oxidation. HNE is involved in the pathogenesis of coronary artery disease and is present in oxidatively modified low density lipoproteins and in atherosclerotic plaques in humans. HNE enhances chronic inflammation within the vessel wall by activating macrophages, stimulates smooth muscle cell proliferation and fibrosis and contributes to endothelial cell dysfunction. Endogenous adaptive antioxidant pathways are activated in response to oxidative injury elicited by 4-HNE. The induction of antioxidant genes such as heme oxygenase-1 (HO-1) is co-ordinated by activation of mitogen-activated protein kinase pathways, leading to nuclear translocation of the transcription factor Nrf2 and subsequent transactivation of an antioxidant response element in the promoter regions of these genes. We here review the evidence that HNE activates Nrf2 and antioxidant gene expression in vascular and other cells types, highlighting the potential of targeting the Nrf2 as a therapeutic strategy for the prevention of vascular diseases characterised by oxidative injury and diminished antioxidant defence.

Down-regulation of manganese-superoxide dismutase through phosphorylation of FOXO3a by Akt in explanted vascular smooth muscle cells from old rats

Manganese-superoxide dismutase (MnSOD) is one of the major cellular antioxidant defense systems. To study the effect of age on the regulation of MnSOD in the vasculature, we compared MnSOD expression and its transcriptional regulation in explanted vascular smooth muscle cells (VSMC) isolated from old (24 months old) versus young (6 months old) rats and grown in a normal (5 mM) or high (12.5 and 25 mM) glucose or tumor necrosis factor alpha (5 ng/ml) environment to induce oxidative stress. Both MnSOD protein and activity were reduced in VSMC from old compared with young animals. FOXO3a, a member of the family of Forkhead transcription factors, interacted with the promoter of the rat MnSOD gene at a specific binding site. Inhibition of FOXO3a transcription with small interfering RNA led to a reduction in MnSOD gene expression. VSMC from old rats had increased phosphorylated FOXO3a at Ser(253), which paralleled the reduction of MnSOD protein. Treatment of VSMC with 5 nm insulin-like growth factor-1 induced phosphorylation of Akt and FOXO3a over time, repressing FOXO3a DNA binding and consequently MnSOD gene expression. Furthermore, Akt activity was selectively increased in VSMC from the old, supporting the hypothesis that increased age-related Akt activity might be responsible for the phosphorylation and inactivation of FOXO3a, which in turn down-regulates MnSOD transcription.