Liver Of Old Rats Research Articles

Ellagic acid reduces hepatic lipid contents through regulation of SIRT1 and AMPK in old rats

Objective Ellagic acid is used in traditional medicine for the treatment of lipid disorders. In this study, the effects of ellagic acid on key regulators of lipid metabolism, and histopathological alterations in aged liver were examined. Methods A total of 21 male Wistar rats were divided into three groups, including young control, old control, and old ellagic acid. After one month of treatment with ellagic acid, the expression levels of hepatic SIRT1, AMPK, SREBP-1c, PPAR-α, and phosphorylated AMPK (p-AMPK) were evaluated. The levels of several serum biochemical factors, and hepatic triglyceride, and cholesterol contents were assessed. Results Ellagic acid elevated the levels of SIRT1, p-AMPK, and PPAR-α and reduced SREBP-1c level in the liver of old rats. It decreased triglyceride and cholesterol contents in the aged liver and improved histopathological changes. Conclusions The results demonstrated that ellagic acid can exert protective effects against hepatic lipid metabolism disorders induced by ageing.

Effects of a high-carbohydrate high-fat diet on liver morphology in young and old rats

The liver is a complex metabolic organ that, through the regulation of energy metabolism, maintains the homeostasis of the whole organism.Aim: To establish the morphological changes in hepatocytes and the expression of endothelial vascular factor in a high-carbohydrate high-fat diet (HCHFD) depending on age.Material and Methods. A histological study of the liver was carried out in four groups of male Wistar rats: 1st group – 5-month-old animals on a standard diet; 2nd group – 5-month-old animals on HCHFD for 90 days (from 2 months of age); 3rd group – 18-month-old animals on a standard diet; 4th group – 18-month-old animals on HCHFD for 90 days (from 15 months of age). Using morphometric methods, the specific volumes (%) of unchanged and binuclear hepatocytes, sinusoidal capillaries, inflammatory infiltrates, and foci of fibrosis in the liver were determined. The expression of vascular endothelial growth factor (VEGF) in endothelial cells and hepatocytes was evaluated by immunohistochemical method. The concentration of cholesterol and triglycerides was determined by the enzymatic colorimetric method in the blood serum and in the liver.Results. A morphological study revealed a significant expansion of sinusoidal capillaries in groups 2 and 4. A statistically significant increase in the specific volume of hepatocytes with vacuolar inclusions, binuclear hepatocytes, fibrous foci and small inflammatory infiltrates was detected in the 4th group. VEGF expression increased in hepatocytes of groups 2 and 4. Biochemical study found an increase in the concentration of triglycerides in the rats’ liver of the 4th group. Thus, HCHFD, despite the pronounced signs of regeneration, increased age-related changes in the liver of old rats.

Age-related effects of fenofibrate on the hepatic expression of sirtuin 1, sirtuin 3, and lipid metabolism-related genes.

Sirtuin 1 (Sirt1) and sirtuin 3 (Sirt3) participate in the regulation of lipid metabolism. Our aim was to investigate the effects of the hypolipemic drug fenofibrate (FN) on hepatic Sirt1 and Sirt3 expression, in relation to the expression of lipid metabolism-related genes and in the context of aging. Young and old male Wistar rats were fed standard chow or supplemented with 0.1% or 0.5% FN for 30 days (n=7-10 in each group). In young rats, 0.1% FN did not affect Sirt1 expression, however, 0.5% FN decreased Sirt1 and both doses reduced Sirt3 protein levels. In old rats, 0.5% FN decreased hepatic Sirt1 mRNA and both doses reduced Sirt1 protein levels, but not Sirt3 expression. Although hepatic Pparα protein levels did not change, FN treatment of young rats induced Cpt1b expression, whereas Lcad, Acox1, Pmp70, and Hmgcs2 expression increased only after 0.1% FN, and Fas2 expression decreased after 0.5% FN. In the liver of old rats, both doses increased Cpt1b and Lcad expression. Only 0.1% FN increased Pmp70 and Hmgcs2 expression, and only 0.5% FN increased Acox1 and Fas2 mRNA levels. Treatment with fenofibrate at low or high doses may downregulate the expression of Sirt1 and Sirt3 proteins in the rat liver. The dosage of FN affects molecular changes, and aging alters the response to 0.5% FN.

Late-Onset Calorie Restriction Improves Lipid Metabolism and Aggravates Inflammation in the Liver of Old Wistar Rats.

Aging is a progressive process that could disturb metabolic homeostasis in the liver via ectopic lipid accumulation, oxidative stress, and deterioration of inflammatory response. Although calorie restriction (CR) is recognized as beneficial for life span and health span prolongation, it is still unclear how late-onset CR, characterized by late beginning and short duration, affects age-related processes. The aim of this study was to examine how late-onset CR-induced metabolic adjustments impact lipid status and inflammation in the liver of old rats. The experiments were conducted on aging male Wistar rats fed ad libitum (AL) or exposed to late-onset CR (60% of AL daily intake) from 21st to 24th month. The results showed that late-onset CR reduces body weight, visceral adipose tissue and liver mass, and triglyceride levels when compared to old animals on AL diet. The ameliorating effects of CR on lipid metabolism include increased activity of AMP-activated protein kinase, suppressed de novo fatty acid synthesis, stimulated β-oxidation, decreased lipotoxicity, and limited triglyceride synthesis and packaging in the liver. Restricted diet regime, however, does not improve expression of antioxidant enzymes, although it leads to progression of age-related inflammation in the liver, partially through lower corticosterone concentration and decreased activation of glucocorticoid receptor. In conclusion, late-onset CR is able to restore age-related imbalance of lipid metabolism in the liver, but has a negative impact on hepatic inflammatory status, implying that the type of diet for older individuals must be balanced and chosen carefully with appropriate duration and start point.

Effect of Metformin and tBHQ exercise and treatment on mitochondrial function in liver of old rats with obesity

Effect of Metformin and tBHQ exercise and treatment on mitochondrial function in liver of old rats with obesity

Aging Induces Hepatic Oxidative Stress and Nuclear Proteomic Remodeling in Liver from Wistar Rats.

Aging is a continuous, universal, and irreversible process that determines progressive loss of adaptability. The liver is a critical organ that supports digestion, metabolism, immunity, detoxification, vitamin storage, and hormone signaling. Nevertheless, the relationship between aging and the development of liver diseases remains elusive. In fact, although prolonged fasting in adult rodents and humans delays the onset of the disease and increases longevity, whether prolonged fasting could exert adverse effects in old organisms remains incompletely understood. In this work, we aimed to characterize the oxidative stress and nuclear proteome in the liver of 3-month- and 24-month-old male Wistar rats upon 36 h of fasting and its adaptation in response to 30 min of refeeding. To this end, we analyzed the hepatic lipid peroxidation levels (TBARS) and the expression levels of genes associated with fat metabolism and oxidative stress during aging. In addition, to gain a better insight into the molecular and cellular processes that characterize the liver of old rats, the hepatic nuclear proteome was also evaluated by isobaric tag quantitation (iTRAQ) mass spectrometry-based proteomics. In old rats, aging combined with prolonged fasting had great impact on lipid peroxidation in the liver that was associated with a marked downregulation of antioxidant genes (Sod2, Fmo3, and Cyp2C11) compared to young rats. Besides, our proteomic study revealed that RNA splicing is the hepatic nuclear biological process markedly affected by aging and this modification persists upon refeeding. Our results suggest that aged-induced changes in the nuclear proteome could affect processes associated with the adaptative response to refeeding after prolonged fasting, such as those involved in the defense against oxidative stress.

Aging is associated with increased TRB3, ER stress, and hepatic glucose production in the liver of rats.

TRB3, a mammalian homolog of Drosophila tribbles, plays an important role in multiple tissues and it has been implicated in stress response regulation and metabolic control. However, the role of hepatic TRB3 and its relationship with endoplasmic reticulum stress (ER stress) during aging has not been elucidated. Thus, the present study aimed to explore the association of aging with TRB3 and ER stress on the hepatic glucose production in Wistar rats. We found the TRB3 protein content to be higher in livers of old rats (27months) compared to young (3months) and middle-aged (17months) rats. The increased content of hepatic TRB3 of the old rats was associated with insulin resistance (decreased protein kinase B (Akt) and Forkhead Box O1 (FoxO1) phosphorylation) and increased enzymes of gluconeogenesis (phosphoenolpyruvate carboxykinase (PEPCK) and Glucose 6-phosphatase (G6Pase)). Moreover, aging was associated with activation of the endoplasmic reticulum stress pathway-related molecules, with an increase in phosphorylation of Inositol-requiring enzyme 1 (p-IRE1α), the protein kinase RNA-like endoplasmic reticulum kinase (p-PERK), eukaryotic translation initiation factor-α (p-eIF2α), binding immunoglobulin protein (BiP), and the C/EBP homologous protein (CHOP) contents in rats. These molecular changes resulted in increased liver glucose production in response to the pyruvate challenge and hyperglycemia of the old rats. In conclusion, our results suggested that, by interfering with insulin signaling in the liver, TRB3 was associated with ER stress and increased hepatic glucose production in aging rats.

Features of electron microscopic changes in the liver of rats aged 24-26 months under conditions of hyperhomocysteinemia

Disruption of the metabolism of the essential amino acid methionine causes the syndrome of hyperhomocysteinemia. This pathological condition is associated with the risk of developing a number of diseases, including chronic liver disease. The mechanisms of liver tissue damage in hyperhomocysteinemia remain poorly understood and require more detailed study. The aim of the study is to establish the features of submicroscopic changes in the liver structure of old rats with hyperhomocysteinemia. The experimental study was performed on 22 white nonlinear old (24-26 months) male rats, which were divided into a control group and an experimental group. A model of persistent hyperhomocysteinemia was created by administering to rats of experimental group of thiolactone homocysteine at a dose of 200 mg/kg body weight intragastrically for 60 days. The study of ultrastructural changes in the lungs of rats was performed using an electron microscope PEM-125K. At experimental hyperhomocysteinemia in a liver of old rats there are changes in all structural components. Mitochondrial destruction and edema were observed in the vascular endothelium. Organelles have an enlightened matrix, a reduced number of cristae. A significant content of destructively altered mitochondria in endothelial cells indicates a failure of adaptation mechanisms. Erythrocyte sludges are observed in the lumens of the sinusoids. The number of fat-accumulating cells decreases, which indicates their transformation into fibroblasts and leads to the growth of collagen fibers, expansion of the sinusoidal spaces and the development of stromal fibrosis.

Effect of high chronic intake of sucrose on liver metabolism in aging rats. Modulation by rutin and micronutrients.

High-sugar intake and senescence share common deleterious effects, in particular in liver, but combination of these two factors was little studied. Our aims were to examine the effect of a high-sucrose diet in liver of old rats and also the potential benefices of a polyphenol/micronutrient supplementation. Four groups of 22-month-old male rats fed during 5months with a diet containing either 13 or 62% sucrose, supplemented or not with rutin, vitamin E, A, D, selenium, and zinc were compared. We measured liver macronutrient composition, glycation/oxidative stress, enzyme activities (lipogenesis, β-oxidation, fructokinase), gene expression (enzymes and transcription factors), in vivo protein synthesis rates and plasma parameters. Sucrose induced an increase in plasma and liver lipid content, and a stimulation of liver protein synthesis rates. Gene expression was little changed by sucrose, with lower levels for LXR-α and LXR-β. Polyphenol/micronutrient supplementation tended to limit liver triglyceride infiltration through variations in fatty acid synthase, acyl coA oxidase, and possibly ATP-citrate lyase activities. In conclusion, despite differences in enzymatic regulations, and blunted responses of gene expression, high-sucrose diet was still able to induce a marked increase in liver lipid content in old animals. However, it probably attenuated the positive impact of polyphenol/micronutrients.

Effects of combined therapy with resveratrol, continuous and interval exercises on apoptosis, oxidative stress, and inflammatory biomarkers in the liver of old rats with non-alcoholic fatty liver disease

Context: Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disorder.Objective: Effects of combined therapy with resveratrol, interval and continuous exercises on oxidative stress, inflammation, and apoptosis in the liver of rats with NAFLD.Methods: NAFLD rats were organised in patient, saline, resveratrol (RSV), continuous exercise, interval exercise, continuous exercise + RSV, and interval exercise + RSV groups.Results: Resveratrol supplementation alone or in combination with interval and continuous training significantly decreased malondialdehyde and TNF-α level (p < .05), while the levels of catalase; superoxide dismutase and IL-10 were significantly increased (p < .05). Although RSV alone significantly decreased the percentage of apoptotic cells (17.12%), its combination with interval (10.74%), and continuous (14.85%) exercise training demonstrated higher anti-apoptotic activity (p < .05).Conclusions: Although resveratrol alone has an antioxidant, anti-apoptotic and anti-inflammatory properties, combined therapy with interval, and continuous training can be more effective to mitigate these abnormalities in NAFLD patients.

Dietary supplementation with acetyl-l-carnitine counteracts age-related alterations of mitochondrial biogenesis, dynamics and antioxidant defenses in brain of old rats

We previously reported the ability of dietary supplementation with acetyl-l-carnitine (ALCAR) to prevent age-related decreases of mitochondrial biogenesis in skeletal muscle and liver of old rats. Here, we investigate the effects of ALCAR supplementation in cerebral hemispheres and cerebellum of old rats by analyzing several parameters linked to mitochondrial biogenesis, mitochondrial dynamics and antioxidant defenses.We measured the level of the coactivators PGC-1α and PGC-1β and of the factors regulating mitochondrial biogenesis, finding an age-related decrease of PGC-1β, whereas PGC-1α level was unvaried. Twenty eight-month old rats supplemented with ALCAR for one and two months showed increased levels of both factors. Accordingly, the expression of the two transcription factors NRF-1 and TFAM followed the same trend of PGC-1β. The level of mtDNA, ND1 and the activity of citrate synthase, were decreased with aging and increased following ALCAR treatment. Furthermore, ALCAR counteracted the age-related increase of deleted mtDNA. We also analyzed the content of proteins involved in mitochondrial dynamics (Drp1, Fis1, OPA1 and MNF2) and found an age-dependent increase of MFN2 and of the long form of OPA1. ALCAR treatment restored the content of the two proteins to the level of the young rats. No changes with aging and ALCAR were observed for Drp1 and Fis1. ALCAR reduced total cellular levels of oxidized PRXs and counteracted the age-related decrease of PRX3 and SOD2.Overall, our findings indicate a systemic positive effect of ALCAR dietary treatment and a tissue specific regulation of mitochondrial homeostasis in brain of old rats. Moreover, it appears that ALCAR acts as a nutrient since in most cases its effects were almost completely abolished one month after treatment suspension. Dietary supplementation of old rats with this compound seems a valuable approach to prevent age-related mitochondrial dysfunction and might ultimately represent a strategy to delay age-associated negative consequences in mitochondrial homeostasis.

Rutin protects against aging-related metabolic dysfunction.

Aging is a complex process which is accompanied by multiple related chronic diseases. Among them, metabolic dysfunction is one of the most important aging-related disorders. In the present study, we aimed to investigate the effect of rutin on aging-related metabolic dysfunction. We found that the increase of fasting blood glucose, insulin levels, blood pressure and HOMA-IR in aged rats was significantly inhibited by rutin. In addition, rutin improved glucose and insulin tolerance in aged rats, as reflected by decreased glucose level in IPGTT and IPITT test. Rutin treatment notably increased Akt and IRS-1 phosphorylation in the livers of old rats. The increase of inflammatory markers, such as IL-1β and TNFα, was prevented by the rutin administration. Moreover, in circulation and livers of old rats, rutin treatment significantly decreased the content of TG. Rutin also inhibited the increase of serum AST and ALT levels. Furthermore, rutin treatment markedly inhibited aging-related mitochondrial dysfunction, ER stress, and oxidative stress, as evidenced by increased oxygen consumption rate and activities of Na(+)/K(+)-ATPase and Ca2(+)-ATPase, decreased expression of ATF3 and GRP78, decreased level of MDA, increased content of GSH and enhanced activity of SOD in aged rats. We show that the administration of rutin could effectively improve aging-related metabolic dysfunction. The amelioration of inflammation, lipid accumulation, mitochondrial dysfunction, ER stress, and oxidative stress may be involved in the effect of rutin on aging-related metabolic dysfunction. These findings provide novel insights into the potential use of rutin in the intervention of aging and its related metabolic diseases.

Ginger and alpha lipoic acid ameliorate age-related ultrastructural changes in rat liver

Because of the important role that oxidative stress is thought to play in the aging process, antioxidants could be candidates for preventing its related pathologies. We investigated the ameliorative effects of two antioxidant supplements, ginger and alpha lipoic acid (ALA), on hepatic ultrastructural alterations in old rats. Livers of young (4 months) and old (24 months) Wistar rats were studied using transmission electron microscopy. Livers of old rats showed sinusoidal collapse and congestion, endothelial thickening and defenestration, and inconsistent perisinusoidal extracellular matrix deposition. Aged hepatocytes were characterized by hypertrophy, cytoplasmic vacuolization and a significant increase in the volume densities of the nuclei, mitochondria and dense bodies. Lipofuscin accumulation and decreased microvilli in bile canaliculi and space of Disse also were observed. The adverse alterations were ameliorated significantly by both ginger and ALA supplementation; ALA was more effective than ginger. Ginger and ALA appear to be promising anti-aging agents based on their amelioration of ultrastructural alterations in livers of old rats.

Hepatic expression of redox factor‐1 and thioredoxin‐1: effects of aging and environmental heat stress

Aging is associated with reduced tolerance to physiological stressors such as hyperthermia. In animal models, heat stress is associated with increased oxidative DNA damage in the livers of old rats. In this study, we evaluated the expression of redox factor‐1 (Ref‐1), a DNA repair enzyme, and thioredoxin‐1 (Trx‐1), an antioxidant protein. We hypothesized that these proteins would be induced by heat stress in young animals, and that aging would attenuate this response. Young (6 mo) and old (24 mo) male Fischer 344 rats were exposed to a two‐heat stress protocol, and livers were harvested at several time points after the second heat stress. Ref‐1 and Trx‐1 were evaluated by immunoblot and immunohistochemistry. In young rats, Ref‐1 was induced immediately (0 h) after heat stress, and returned to control levels at 2h. We observed no heat‐induced elevation of Ref‐1 in old rats; however, Ref‐1 was increased ~2‐fold in old, compared to young rats at all time points. At 2h after heat stress, Trx‐1 was increased in old rats, but there was no change in young rats. In tissue sections, Trx‐1 was localized to Kupffer cells in both age groups. Also, we observed frequent ductular reactions in the old rats that were positive for both Ref‐1 and Trx‐1. The impairment in the induction of Ref‐1 suggests a mechanism for the increased oxidative DNA damage observed in old rats after heat stress. Furthermore, the observation of ductular reactions positive for both Ref‐1 and Trx‐1 demonstrates a proliferative cellular niche that develops with aging.

PSS238 - Strawberry Enriched Diet Counteracts Oxidative Stress in Plasma and Liver of Old Rats and Improves Mitochondrial Functionality

Vascular diseases such as atherosclerosis, stroke or myocardial infarction are a significant public health problem worldwide. Attempts to prevent vascular diseases often imply modifications and improvement of causative risk factors such as high blood pressure, obesity, an unfavorable profile of blood lipids or insulin resistance. In addition to numerous preventive and therapeutic drug regimens, there has been increased focus on identifying dietary compounds that may contribute to cardiovascular health in recent years. Food-derived bioactive peptides represent one such source of health-enhancing components. They can be released during gastrointestinal digestion or food processing from a multitude of plant and animal proteins, especially milk, soy or fish proteins. Biologically active peptides are considered to promote diverse activities, including opiate-like, mineral binding, immunomodulatory, antimicrobial, antioxidant, antithrombotic, hypocholesterolemic and antihypertensive actions. By modulating and improving physiological functions, bioactive peptides may provide new therapeutic applications for the prevention or treatment of chronic diseases. As components of functional foods or nutraceuticals with certain health claims, bioactive peptides are of commercial interest as well. The current review centers on bioactive peptides with properties relevant to cardiovascular health.

Acute exercise decreases PTP-1B protein level and improves insulin signaling in the liver of old rats

It is now commonly accepted that chronic inflammation associated with obesity during aging induces insulin resistance in the liver. In the present study, we investigated whether the improvement in insulin sensitivity and insulin signaling, mediated by acute exercise, could be associated with modulation of protein-tyrosine phosphatase 1B (PTP-1B) in the liver of old rats. Aging rats were subjected to swimming for two 1.5-h long bouts, separated by a 45 min rest period. Sixteen hours after the exercise, the rats were sacrificed and proteins from the insulin signaling pathway were analyzed by immunoblotting. Our results show that the fat mass was increased in old rats. The reduction in glucose disappearance rate (Kitt) observed in aged rats was restored 16 h after exercise. Aging increased the content of PTP-1B and attenuated insulin signaling in the liver of rats, a phenomenon that was reversed by exercise. Aging rats also increased the IRβ/PTP-1B and IRS-1/PTP-1B association in the liver when compared with young rats. Conversely, in the liver of exercised old rats, IRβ/PTP-1B and IRS-1/PTP-1B association was markedly decreased. Moreover, in the hepatic tissue of old rats, the insulin signalling was decreased and PEPCK and G6Pase levels were increased when compared with young rats. Interestingly, 16 h after acute exercise, the PEPCK and G6Pase protein level were decreased in the old exercised group. These results provide new insights into the mechanisms by which exercise restores insulin signalling in liver during aging.

Potential hepato-protective effect of α-tocopherol or simvastatin in aged rats

BackgroundThe effect of α-tocopherol or simvastatin treatment on antioxidant defense in liver of old rats was investigated. MethodsEndogenous thiobarbituric acid reactive substances (TBARS) and total nitrite/nitrate (NO2/NO3) levels as well as non-enzymatic glutathione (GSH) and enzymatic antioxidants [glutathione-S-transferase (GST), superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) activities] were determined in the livers of young (3 months), aged (22 months), α-tocopherol- or simvastatin-treated aged rats. Serum lipid profile and liver function parameters were also assessed in these 4 groups. ResultsBoth α-tocopherol and simvastatin almost equally restored the age-induced changes in liver TBARS and CAT activity, serum aspartate aminotransferase (GOT), alanine aminotransferase (GPT) and alkaline phosphatase (ALP). α-Tocopherol, but not simvastatin, tended to restore GST and GPX activities in livers of aged rats. Simvastatin, on the other hand, counteracted ageinduced increases in serum cholesterol, TG, LDL, total hepatic NO2/NO3 level, and preserved a normal liver function during aging. ConclusionThus, either drug may be beneficial, in spite of a mechanistic difference in the antioxidant effect of both of them, in alleviating age-induced liver injury.

Acetyl-l-Carnitine Activates the Peroxisome Proliferator-Activated Receptor-γ Coactivators PGC-1α/PGC-1β–Dependent Signaling Cascade of Mitochondrial Biogenesis and Decreases the Oxidized Peroxiredoxins Content in Old Rat Liver

The behavior of the peroxisome proliferator-activated receptor-γ coactivators PGC-1α/PGC-β-dependent mitochondrial biogenesis signaling pathway, as well as the level of some antioxidant enzymes and proteins involved in mitochondrial dynamics in the liver of old rats before and after 2 months of acetyl-L-carnitine (ALCAR) supplementation, was tested. The results reveal that ALCAR treatment is able to reverse the age-associated decline of PGC-1α, PGC-1β, nuclear respiratory factor 1 (NRF-1), mitochondrial transcription factor A (TFAM), nicotinamide adenine dinucleotide (NADH) dehydrogenase subunit 1 (ND1), and cytochrome c oxidase subunit IV (COX IV) protein levels, of mitochondrial DNA (mtDNA) content, and of citrate synthase activity. Moreover, it partially reverses the mitochondrial superoxide dismutase 2 (SOD2) decline and reduces the cellular content of oxidized peroxiredoxins. These data demonstrate that ALCAR treatment is able to promote in the old rat liver a new mitochondrial population that can contribute to the cellular oxidative stress reduction. Furthermore, a remarkable decline of Drp1 and of Mfn2 proteins is reported here for the first time, suggesting a reduced mitochondrial dynamics in aging liver with no effect of ALCAR treatment.

Identification of age‐specific Nrf2 binding to a novel antioxidant response element locus in the Gclc promoter: a compensatory means for the loss of glutathione synthetic capacity in the aging rat liver?

NFE2-related factor 2 (Nrf2) transcriptionally governs the cellular response to harmful electrophiles, xenobiotics, and reactive oxygen species. Its nuclear levels decline with age (Suh et al., 2004a), which in part explains the age-related loss of phase II detoxification. However, little work has yet characterized how age affects Nrf2 DNA binding or the role that alterations to the Nrf2 transcriptional apparatus plays in modulating Nrf2-mediated gene expression. In this study, we used immunoprecipitation assays to show that Nrf2 bound to the active antioxidant response element (ARE) of the catalytic subunit of glutamate cysteine ligase (GCLC) is significantly lower in hepatic chromatin from aged vs. young rats. Moreover, the activity at this ARE locus is diminished during aging because of the presence of Bach1 and the absence of CREB-binding protein (CBP), a transcriptional repressor and co-activator, respectively. Further analysis reveals that Nrf2 occupies an alternate ARE site located -2.2 kb downstream from the normally active ARE binding site in livers of old rats, indicating an age-specific adaptation to maintain gene expression. Our results, thus, show that the conversion of Nrf2 binding from an active ARE to an alternative ARE element is not adequate to maintain basal expression of hepatic Gclc in old rats, which provides a potential mechanism for the age-related loss of glutathione synthetic and other phase II enzymes.

Cellular stress response pathways and ageing: intricate molecular relationships.

Ageing is driven by the inexorable and stochastic accumulation of damage in biomolecules vital for proper cellular function. Although this process is fundamentally haphazard and uncontrollable, senescent decline and ageing is broadly influenced by genetic and extrinsic factors. Numerous gene mutations and treatments have been shown to extend the lifespan of diverse organisms ranging from the unicellular Saccharomyces cerevisiae to primates. It is becoming increasingly apparent that most such interventions ultimately interface with cellular stress response mechanisms, suggesting that longevity is intimately related to the ability of the organism to effectively cope with both intrinsic and extrinsic stress. Here, we survey the molecular mechanisms that link ageing to main stress response pathways, and mediate age-related changes in the effectiveness of the response to stress. We also discuss how each pathway contributes to modulate the ageing process. A better understanding of the dynamics and reciprocal interplay between stress responses and ageing is critical for the development of novel therapeutic strategies that exploit endogenous stress combat pathways against age-associated pathologies.