Age-related down regulation of hepatic cytochrome P1-450, P3-450, catalase and CuZn-superoxide dismutase RNA

Gene expression of drug metabolizing enzymes in adult and aged mouse liver: A modulation by immobilization stress

The role of stress in the regulation of enzymatic systems involved in the biotransformation of xenobiotics, as well as endogenous substrates in the liver was investigated using single immobilization stress as a model. Adult (3 months of age) and aged (26 months) C3H/a male mice were used. Cytochrome P450 1A1 and 1A2 (CYP1A1 and CYP1A2), glutathione S-transferase M1 (GSTM1), aryl hydrocarbon receptor (AHR), aryl hydrocarbon receptor nuclear translocator (ARNT) and catechol-O-methyltransferase (COMT) mRNA levels in the mouse liver were measured by a semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) method. Excluding CYP1A1, experiments revealed significant differences in the expression of these genes between adult- and aged-control animals. The influence of stress on the expression of genes studied was shown to be higher in adult mice than in aged ones. Our results clearly demonstrate the lack of response or even the attenuation of gene expression in aged animals that may play an important role in age-related pathologies and diseases.

Genomic profiling of short- and long-term caloric restriction effects in the liver of aging mice

We present genome-wide microarray expression analysis of 11,000 genes in an aging potentially mitotic tissue, the liver. This organ has a major impact on health and homeostasis during aging. The effects of life- and health-span-extending caloric restriction (CR) on gene expression among young and old mice and between long-term CR (LT-CR) and short-term CR (ST-CR) were examined. This experimental design allowed us to accurately distinguish the effects of aging from those of CR on gene expression. Aging was accompanied by changes in gene expression associated with increased inflammation, cellular stress, and fibrosis, and reduced capacity for apoptosis, xenobiotic metabolism, normal cell-cycling, and DNA replication. LT-CR and just 4 weeks of ST-CR reversed the majority of these changes. LT-CR produced in young mice a pattern of gene expression that is a subset of the changes found in old LT-CR mice. It is possible that the early changes in gene expression, which extend into old age, are key to the life- and health-span-extending effects of CR. Further, ST-CR substantially shifted the "normo-aging" genomic profile of old control mice toward the "slow-aging" profile associated with LT-CR. Therefore, many of the genomic effects of CR are established rapidly. Thus, expression profiling should prove useful in quickly identifying CR- mimetic drugs and treatments.

Effects of calorie restriction and aging on the expression of antioxidant enzymes and ubiquitin in the liver of Emory mice

We studied the effect of age and calorie restriction on the expression of genes involved in antioxidant defenses in livers of young (4.5-6 months) and old (22 months) Emory mice fed a control (C) or restricted (R) diet. Specifically examined were catalase (CAT), glutathione peroxidase (Gpx), Cu/Zn and Mn superoxide dismutase (Cu/ZnSOD and MnSOD). As an indicator of oxidative damage to the tissues we measured lipid peroxidation. As indicators of oxidative stress we determined ubiquitin mRNA levels and endogenous high molecular weight (HMW) ubiquitin conjugates. Lower mRNA levels of ubiquitin (P < 0.05), CAT (P < 0.01) and Gpx (P < 0.01) were observed in tissues from young R versus C animals. The old C group had a lower CAT mRNA level (P < 0.0001) compared with young C. In the R group, age did not affect the CAT mRNA levels or Gpx mRNA levels; however, ubiquitin mRNA levels were higher (P < 0.05). No significant changes in Cu/Zn or MnSOD mRNA were observed with age or diet. Cu/ZnSOD protein levels were lower in the young R at 4.5 months (P < 0.05) than young C, and higher in the old R group versus old C (P < 0.05). CAT protein levels were higher in the old C versus old R (P < 0.05). Changes of HMW ubiquitin conjugates with age r diet were not significant. Of the four groups, the old R group showed the highest levels of lipid peroxidation.

IAP retrotransposons in the mouse liver as reporters of ageing

IAP are endogenous retrovirus-like elements present at a thousand copies in the murine genome. They can modulate the level of expression of the tagged genes into which they have inserted, and conversely their activity could be influenced by the level of activity of the genes and/or DNA sequences into which they are embedded. In this report, we have analysed by Northern blots the pattern of expression of the IAP-related transcripts in the organs of young and ageing mice. We show that IAP transcripts of unexpected size (namely 10 kb and 6 kb) are induced in the liver of ageing mice from all inbred and hybrid strains tested. These transcripts are not detected in young mice, and their intensity disclose variations depending on the strain, as those observed for the two canonical 7.2 and 5.4 kb IAP transcripts. It is suggested that these age-dependent IAP transcripts originate from unique sites within the mouse genome that are 'tagged' by an IAP sequence, which would be sensitive both to strain-dependent cellular factors acting at the level of all IAPs, and to an age-dependent liver-specific cellular factor and/or DNA state, responsible for the position-dependent effect. These age-dependent transcripts should allow the identification of putative genes or factors of 'senescence'.

Genotype effects on the antioxidant enzymes activity and mRNA expression in liver and kidney tissues of autoimmune-prone MRL/MpJ-lpr/lpr mice

Congeneic pairs of MRL/lpr and MRL/++ (+/+) mice differ in incidence of autoantibodies, lymphoproliferative disease and survival, characteristics that are linked to immunological abnormalities. MRL/lpr mice have a significantly shorter life span compared to +/+ mice. Because a weak antioxidant defense and an increased generation of free radicals are generally implicated in the severity of many autoimmune disease, the present study was undertaken to compare the influence of genotype on lipid composition, lipid peroxidation and expression of mRNA, and activity of antioxidant enzymes such as catalase (CAT), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in the livers and kidneys of these mice. The expression of SOD, GSH-Px and CAT mRNAs was significantly higher (P < 0.05) in the livers of +/+ mice, while in the kidneys only SOD expression was found significantly higher in +/+ mice when compared to MRL/lpr mice. Further, the activity of cytosolic SOD and GSH-Px was also found significantly higher (P < 0.001) in the livers of +/+ mice. Both livers and kidneys of MRL/lpr mice exhibited significantly higher levels of arachidonic acid (20:4(n-6)), significantly higher generation of thiobarbituric acid reactive substances (TBARS) and higher estimated peroxidation index than the +/+ mice. In addition, the MRL/lpr mice had higher levels of serum anti-cardiolipin antibodies. In summary, the results from the present study indicate that besides several immune-related abnormalities, the MRL/lpr mice may exhibit their inability to cope with oxidative stress due to a poor antioxidant defense system.(ABSTRACT TRUNCATED AT 250 WORDS)

Gene expression and aging

Considerable amount of data has accumulated during the past few years showing several changes in gene expression as a function of age. However, the basic mechanism of aging still remains poorly understood. In this review, we have mainly analysed the data pertaining to the hypothesis that aging is associated with genetic instability and have attempted further to highlight the gaps that need to be bridged in order to have a clear picture of the aging phenomenon. Extensive investigations employing new and novel approaches are needed in future to elucidate the intricately interwoven patterns of molecular control that underlie the various aspects of gene expression during aging.

Age-related variations of enzymatic defenses against free radicals and peroxides

Superoxide dismutase, glutathione peroxidase and catalase are the three main enzymatic systems of defense of the organism against free radicals and peroxides. A survey of the literature shows that no general tendency of evolution of these systems in aging emerges, even if some recent studies in humans demonstrate the existence of a concomitant decrease in most of the antioxidant enzymes in blood of the elderly. The study of the antioxidant systems and their interrelations in the elderly represents a large field of future investigations.

Effect of aging and other factors on monocyte aryl hydrocarbon hydroxylase activity

A measure of the activity of macrophage drug metabolizing enzymes through assay of peripheral monocytes was used to assess the hepatic enzymatic status and thereby evaluate age related changes in drug metabolism. Blood was obtained from elderly subjects (aged 74.8 +/- 5.2, mean +/- S.E., n = 16) and a young control group (aged 23.5 +/- 2.0, n = 27). Monocyte AHH activity was used as an index of liver drug metabolism, ALT activity as an index of liver function, monocyte media IL-1 and as an index of macrophage activation and serum IL-1 levels as a measure of endogenous pyrogenic activity. The medium collected from the cultured monocytes was also assessed for the presence of AHH inhibitory activity. Subjects provided information relating to their age, sex, alcohol consumption, cigarette smoking, recent infection, recent surgery, disease status and medications which could alter drug metabolism. Elderly patients were drawn both from independent seniors living at home and seniors visiting a geriatric day hospital and compared to a control group of young healthy volunteers. Using the experimental design AHH activity did not differ within experimental error between aged (0.832 +/- 0.32 nmol/mg prot. per h, n = 16) and young control subjects (0.452 +/- 0.17, n = 27). ALT activity did not differ between aged (2.83 I.U. +/- 0.46) and young (4.24 +/- 0.82). Monocyte AHH activity did not differ between males (0.45 +/- 0.14, n = 33) compared to females (0.65 +/- 0.18, n = 29), but was significantly higher in smokers (2.5 +/- 1.0, n = 5) compared to non-smokers (0.35 +/- 0.05, n = 52). Mild to moderate alcohol use showed no significant effect on AHH activity. There was no significant difference between the mean level of MCM inhibition of murine hepatocyte AHH between elderly (44.3 +/- 8.32%, n = 8) and control (31.5 +/- 6.21%, n = 15) subjects, but a larger proportion of the elderly population demonstrated such an effect. Serum IL-1 levels (range 0-55.9 pg/ml) were compared to MCM IL-1 and AHH inhibitory activity in the elderly and young group.

Sex-dependent differences in the effects of aging on antioxidant defense mechanisms of rat liver

Information about age-related factors that influence sensitivity to hepatotoxic injury is important to geriatric medicine and environmental health. The purpose of the present study was to determine whether age-associated changes occur in hepatic antioxidant defense mechanisms of male and female Fischer 344 rats. Liver homogenates and post-mitochondrial supernatant fractions from rats aged 4, 14, 24 and 29 months were analyzed for antioxidant enzyme activities and for vitamin E and malondialdehyde content. Age-associated changes in catalase and glutathione reductase activities were observed that could be described as sex-determined differences that disappeared in old age. Cytosolic superoxide dismutase and glutathione peroxidase activities displayed sex-dependent variations in activity but were unaffected by aging. Hepatic vitamin E concentrations were lower in male rats than in female malondialdehyde concentrations also were lower in males than in females; malondialdehyde content increased in old males and decreased in old females. The results indicate that age-associated changes in enzymatic and nonenzymatic antioxidant defense mechanisms of rat liver are sex-dependent. In addition, comparison with findings from other studies in rats suggests that the effects of aging may also depend on the strain of rat.

Aging alters hepatic expression of insulin receptor and c-jun mRNA in the mouse

The clear association between species and life span suggests that aging, like development, is genetically orchestrated. To explore this hypothesis, the expression of mRNA for a number of transcription regulatory and signal transduction proteins was investigated during aging of B10.RIII, C57BL/10 and B10.BR mice. mRNA for glucocorticoid receptor, CCAAT and enhancer binding protein, transcription factor Sp1 and RNA polymerase II elongation factor S-II were unchanged between 4 and 24 months of age in these mice. These factors are required for the normal transcription of many genes, perhaps explaining their steady rates of expression throughout life. Insulin-like growth factor I mRNA also remained unchanged. By contrast, mRNA for the insulin receptor and transcription factor c-jun changed significantly during aging. c-Jun mRNA decreased approximately 55% between 4 and 12 months of age and then increased by 24-25 months of age to levels approximately equal to those found in young mice. Insulin receptor mRNA increased approximately 30% by 24-25 months of age in all strains of mice. These results suggest that factors determining the steady state level of these mRNAs are altered in level or activity during aging. Assessing the causes and significance of these changes will require further study. However, our results demonstrate that alterations in the expression of specific regulatory genes occur during aging.