HomeLarge Type Edition
HOME ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Services
Right arrow Download to citation manager
PubMed
Right arrow PubMed Citation
The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 63:1043-1052 (2008)
© 2008 The Gerontological Society of America

Hepatic Gene Expression Changes in an Experimental Model of Accelerated Senescence: The SAM-P8 Mouse

Laia Vilà, Núria Roglans, Marta Alegret, Antoni Camins, Mercè Pallàs, Rosa María Sánchez, Manuel Vázquez-Carrera and Juan Carlos Laguna

Pharmacology Unit, Department of Pharmacology and Therapeutic Chemistry, School of Pharmacy, University of Barcelona and IBUB (Institute of Biomedicine University of Barcelona), Spain.

Address correspondence to Juan Carlos Laguna, PhD, Unitat de Farmacologia, Facultat de Farmacia, Avda Diagonal 643, Barcelona 08028, Spain. E-mail: jclagunae{at}ub.edu


   Abstract
Top
 Abstract
Material and Methods
 Results
 Discussion
 References
 
The senescence-accelerated mouse (SAM) is an experimental model of aging, established through phenotypic selection from a common genetic pool of AKR/J mice. Here we use complementary DNA microarray, Western blot, and electrophoretic mobility shift assay to consider whether changes in liver gene expression observed in 5-month-old SAM-prone 8 (P8) mice, compared to SAM-R1 controls, are similar to those reported in aged rodents. Livers from SAM-P8 mice presented 88 differentially expressed transcripts, 59% of which were upregulated and 41% were downregulated. Of these, 14% were related to inflammatory/immunity processes, 10% were related to the xenobiotic metabolism (XM) and 3% to nervous system pathophysiology (NSP). Depressed expression and activity of genes related to XM, and altered expression of genes related to NSP, are similar to changes observed in aged rodents. Increased expression of heat shock protein 1 and Jun-B, reduced activity of activator protein 1 and absence of nuclear factor-{kappa}B activation indicate the lack of a strong liver inflammatory response in 5-month-old SAM-P8 mice.

Key Words: SAM mice • Liver • Inflammation • Xenobiotic metabolism

MEDICAL advances during the past century have increased the average life span for humans; as a consequence, the number of elderly people in western societies has been continuously growing, and it is estimated that by the year 2050, nearly 25% of Americans will be at least 65 years old (1). As the number of people reaching advanced age increases, there will be an associated need for increased medical care. Despite this situation, the molecular changes underlying the physiological decline associated with senescence are poorly defined.

With aging comes a decline in physiologic function in most organ systems (2). Work from different laboratories including our own has shown that humans and rodents share common phenotypical changes associated with liver senescence. These include increased plasma and liver tissue triglyceride content and decreased hepatic fatty acid oxidation (3–6). In addition to regulating lipid and carbohydrate metabolism, the liver plays a pivotal role in the breakdown of potentially toxic lipophilic endotoxins and xenotoxins, as well as in the production of many kinds of serum proteins implicated in the control of hormonal, inflammatory, and coagulation processes. Through these and other processes the liver influences entire body physiology in many ways, suggesting that the elucidation of the age-related changes in gene expression in the liver may lead to a better understanding (and thereby treatment) of physiological dysfunction in the elderly population.

The senescence-accelerated mouse (SAM) is an experimental model of aging, established through phenotypic selection (based on the degree of senescence, the life span, and the age-associated pathologic phenotypes) from a common genetic pool of AKR/J strain mice. The SAM-resistant (R) series (substrains SAM-R1, 4, and 5) exhibit normal aging characteristics, whereas the SAM-prone (P) series (substrains SAM-P1–3 and 6–11) display accelerated aging, including loss of skin glossiness, increased skin coarseness, hair loss, periophthalmic lesions, and increased lordokyphosis of the spine (7). SAM-P8 mice are characterized by both accelerated aging and neuronal dysfunctions (8), appearing from age 2 to 8 months, and severe liver pathology with fatty degeneration and inflammatory mononuclear cell infiltration at late age (10 months and older age) (9). The life span of SAM-P8 mice ranges from 10 to 17 months, whereas SAM-R1 mice live for 19–21 months and age normally with an increased propensity for nonthymic lymphoma, histiocytic sarcoma, and ovarian cyst.

In this study, we used Affymetrix GeneChips arrays to characterize differences between the liver gene expression patterns of 5-month-old SAM-P8 and SAM-R1 mice [before the appearance of severe liver pathology in the SAM-P8 mice strain (9)]. Our results indicate that, besides specific changes in lipid metabolism [as described in our previous article (6)], the livers of SAM-P8 mice show marked changes in the expression of genes related to inflammatory/immune processes, xenobiotic metabolism, and nervous system pathophysiology.


   MATERIAL AND METHODS
Top
 Abstract
 Material and Methods
Results
 Discussion
 References
 
Animals and Experimental Design
Five male SAM-P8 mice and SAM-R1 mice were provided by Harlan Interfauna Ibérica (Barcelona, Spain). All the mice were bred under standard conditions with free access to food and water. After 5 months, the mice were killed under pentobarbitone anesthesia. Animal handling and disposal were performed in accordance with the 5/1995 Act of July 21, of the Generalitat de Catalunya regional authority.

Sample Preparations
Blood samples were collected at the time of death in 5% EDTA tubes; plasma was obtained by centrifugation and stored at –80°C until needed. Mice livers were excised and perfused in 0.9% NaCl. Liver tissue (150 mg from each animal) was homogenized in a 150 mM NaCl, 1 mM dithiothreitol, 30 mM EDTA, 50 mM KH2PO4, pH 7.4, buffer to obtain the postnuclear supernatant fraction by centrifugation and stored at –80°C until needed. Liver tissue (10–100 mg) was immediately frozen in liquid N2 and stored at –80°C until used for total RNA extraction. Two additional liver samples (150 mg) were stored at –80°C for quantifying liver lipids and to obtain nuclear protein extracts. The nuclear extracts were isolated using the Helenius method (10). The protein concentration of each fraction was determined by the Bradford method (11).

Lipids, Glucose, and Insulin Determination
Plasma triglyceride, non-esterified fatty acids, total cholesterol, and glucose concentrations were measured using triglyceride L-type, NEFAC, Chol-H L-type, and glucose kit tests, respectively (Wako Chemicals GmbH; Neuss, West Germany). Plasma insulin concentration was determined with the Rat Insulin radioimmunoassay kit (RPA547; Amersham Biosciences Europe GmbH, Freiburg, Germany). Liver lipids were extracted and measured as described previously, using the homogenate fraction (12).

Hepatic fatty acid ß-oxidation activity was determined as described previously (13), using 30 µg of postnuclear supernatant of each sample.

Arrays
Six total RNA pools were prepared, three for SAM-P8 mice and three for SAM-R1 mice. Each pool was prepared with the same amount of RNA from two different SAM mice, with a total of six mice in each of two test groups (SAM-P8 and SAM-R1). The RNA pools were used to analyze gene expression profiles through microarray technology supplied by Progenika BioPharma S.A. (Derio, Spain). This company is part of the Spanish National Network on Genetic Hyperlipidemia, to which our research group also belongs. Briefly, complementary DNA (cDNA) was prepared by reverse transcription, and biotinylated RNA was prepared according to the Affymetrix protocol (Affymetrix Inc., Santa Clara, CA). Labeled cDNA was purified using the GeneChip Sample Cleanup Module from Affymetrix, fragmented, and hybridized to the Affymetrix Mouse Genome 430A 2.0 GeneChip array. All six hybridized arrays were considered of sufficient quality to be further analyzed, according to the presence of spike controls and the 3'/5' sequence ratio of the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH).

Array Data Processing and Analysis
GeneChip arrays were washed and scanned using a GeneArray Scanner, and scanned images were quantified according to Affymetrix standard procedures to obtain signal intensity for each gene in each array. Using the Affymetrix software GCOS 1.1, we calculated the mean intensity of each array, and the arrays were linearly scaled to an average expression level of 100. Signals were normalized by using GeneSpring 7.1 software by dividing each gene by the median of its measurements in all samples.

To identify the genes that were significantly different in SAM-P8 compared to SAM-R1 mice, we applied two methods based on different mathematical formulae: (i) a comparison algorithm using the GCOS 1.1 software (pairwise comparisons [nine9 in total] were performed, and only sequences that were overexpressed or repressed in at least 7 of the 9 comparisons were selected; and (ii) a parametric analysis of variance test, performed using GeneSpring 7.1 software, where only the changes with a p value ≤.05 were considered. As a result, two different lists of genes were obtained, and only the genes appearing on both lists were considered to be differentially expressed.

Real-Time Reverse Transcription–Polymerase Chain Reaction
To confirm the expression patterns of upregulated or downregulated genes, we chose several genes for further analysis by using relative quantitative real-time reverse transcription–polymerase chain reaction (RT–PCR) in a 96-well format. Complementary DNA from the same RNA samples used in microarray experiments was synthesized as described previously (14). RT–PCR was performed by using the Perkin-Elmer ABI Prism 7700 sequence detection system, using the TaqMan Universal PCR Master Mix, PCR primers, and TaqMan probes obtained from TaqMan Gene Expression Assays (Applied Biosystems, Foster City, CA). As an internal control, primers for GAPDH were amplified in parallel with the genes of interest. All the analyses were run in triplicate. Sequence detector software (S.D.S 1.9.1) was used for data analysis. A threshold cycle value (CT) was obtained for each amplification plot, and after normalization by the reference gene GAPDH, the relative expression ratio for each gene was calculated, based on the difference between the mean CT of a sample and the corresponding control situation.

Electrophoretic Mobility Shift Assays
Double-stranded oligonucleotide DNA sequences were the consensus binding site of the activator protein 1 (AP-1) response element (5'-CGCTTGATGAGTCAGCCGGAA-3') from Promega (Madison, WI) and the mouse constitutive activated receptor (mCAR) response element (5'-GACTCTGTACTTTCCTGACCTTGGCA-3'). Oligonucleotides were labeled, and electrophoretic mobility shift assays (EMSAs) were performed exactly as previously described (15). For supershift assays, antibodies were added before incubation with labeled probe for another 30 minutes at 4°C. Antibodies against c-Jun and octamer motif-1 transcription factor (Oct-1) were obtained from Santa Cruz Biotechnology (Santa Cruz, CA).

Western Blot Analysis
Liver total protein (30 µg, for heat shock protein 1 [HSP1]) or crude nuclear extract (for Jun-B) was subjected to 12% sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Proteins were then transferred to Immobilon polyvinylidene difluoride transfer membranes (Millipore, Bedford, MA) and blocked for 1 hour at room temperature with 5% nonfat milk solution in Tris-buffered saline–0.1% Tween 20. Membranes were then incubated with the primary polyclonal antibody raised against HSP1 (dilution 1:5000) and Jun-B (dilution 1:200) in TBS–0.1% Tween 20 with 5% nonfat milk at 4°C overnight. After several washes, they were incubated with horseradish peroxidase (HRP)-conjugated antirabbit immunoglobulin G (1:3000 dilution). Detection was achieved using the ECL chemiluminescence kit for HRP (Amersham Biosciences Europe). To confirm the uniformity of protein loading in each lane, the blots were incubated with β-actin protein. The size of detected proteins was estimated using protein molecular-mass standards (Invitrogen, Life Technologies, Carlsbad, CA). All antibodies (except HSP1 that was from R&D Systems, Minneapolis, MN) were obtained from Santa Cruz Biotechnology.

Statistical Analysis
The results are expressed as the mean of n values ± standard deviation. Plasma samples were assayed in duplicate. Significant differences were established by the unpaired t test, using the computer program GraphPad InStat (GraphPad Software V2.03). When the variance was not homogeneous, a nonparametric test was performed (Mann–Whitney U test). The level of statistical significance was set at p <.05.


   RESULTS
Top
 Abstract
 Material and Methods
 Results
Discussion
 References
 
Five month-old SAM-P8 mice were hypertriglyceridemic and had hepatic steatosis and a reduced capacity for hepatic fatty acid oxidation compared to control SAM-R1 mice [detailed results have been published in (6)]. Livers from 5-month-old SAM-P8 mice presented 88 differentially expressed transcripts vis-à-vis control SAM-R1 mice. Of these, 52 were upregulated (59%, Table 1), and 36 were downregulated (41%, Table 2). Twenty percent of differentially expressed transcripts had unknown functions. A significant proportion (26%) was related to lipid metabolism, with 10 genes upregulated (11%) and 13 genes downregulated (15%) in SAM-P8 mice; the validity and significance of these genes has been reported in a previous publication (6). In the present work, we report the real-time RT–PCR validation of several genes selected on the basis of their fold-change and biological relevance related to: (i) inflammatory/immune processes (14% differentially expressed transcripts), (ii) xenobiotic metabolism (10% differentially expressed transcripts), and (iii) nervous system pathophysiology (3% differentially expressed transcripts).


View this table:
[in this window]
[in a new window]

  		Table 1. Differentially Upregulated Genes in Livers of 5-Month-Old SAM-P8 Versus SAM-R1 Mice.

 

View this table:
[in this window]
[in a new window]

  		Table 2. Differentially Downregulated Genes in Livers of 5-Month-Old SAM-P8 Versus SAM-R1 Mice.

 
Genes Related to Inflammatory/Immune Processes
To confirm our results, five genes were selected for analysis by real-time RT–PCR on the basis of their fold-change and/or biological relevance. As shown in Figure 1, all of them showed similar changes in their specific messenger RNA (mRNA) content between the cDNA arrays and the RT-PCR assays. We determined also the content of HSP1 and Jun-B oncogene (Jun-B) proteins in hepatic samples from SAM-R1 and SAM-P8 mice. Both proteins are elevated (Figure 2) although, in the case of HSP1, the observed protein fold increase in SAM-P8 mice (1.35x vs SAM-R1 controls) was much lower than the corresponding increase in its mRNA levels (around 4x vs SAM-R1 controls).


Figure 01
View larger version (13K):
[in this window]
[in a new window]

  		Figure 1. Validation of differentially expressed genes in hepatic senescence-accelerated mouse-prone 8 (SAM-P8) samples compared to control SAM-resistant 1 (SAM-R1) samples. Comparison of results obtained by Affymetrix array (filled columns) and real-time polymerase chain reaction (Taqman) (open columns). Values are expressed as a percentage of increase or decrease in gene expression, compared to the corresponding control. Genes: HSP1 = heat shock protein 1; Jun-B oncogene; Tfpi2 = tissue factor pathway inhibitor 2; Tff3 = trefoil factor 3 intestinal; Trp53 = transformation-related protein 53 inducible nuclear protein 1

 

Figure 02
View larger version (14K):
[in this window]
[in a new window]

  		Figure 2. Relative levels of Jun-B (A) and heat shock protein 1 (HSP 1) (B) in hepatic samples from senescence-accelerated mouse-resistant 1 ( SAM-R1) (empty columns), and SAM-prone (SAM-P8) (filled bar) mice. Each bar represents the mean ± standard deviation of values from five animals. A (top), Representative Western blot showing the Jun B bands that correspond to three different SAM-R1 and SAM-P8 mice. The amount of protein loaded was confirmed by the Bradford method, and the uniformity of protein loading in each lane was assessed by incubation with β-tubulin

 
AP-1 is a transcription factor involved in immune and inflammatory processes. It is not a single protein, but a dimer composed of several combinations of proteins from the Jun, Fos, Maf, and ATF families of proteins. Among the Jun family of proteins, c-Jun is a common constituent of the AP-1 dimer and one of the most potent transcriptional activators, whereas Jun-B attenuates or even antagonizes AP-1 activity (16). We determined the AP-1 binding activity of liver nuclear extracts from SAM-R1 and SAM-P8 mice. Nuclear extracts from SAM-R1 mice incubated in the presence of an AP-1 response element oligonucleotide produced two specific bands that disappeared in the presence of an excess of unlabeled probe (Figure 3A); band I was supershifted in the presence of c-Jun antibody (see supershifted band IC in Figure 3A), confirming the involvement of AP-I at least in the formation of band I. Band I, the band with the highest binding intensity, and band II, were undetectable in gel-shift assays performed with liver nuclear extracts obtained from SAM-P8 mice (Figure 3B), indicating a possible antagonizing effect of the high hepatic levels of Jun-B on AP-1 binding activity in these animals. Furthermore, we assayed the binding activity of another nuclear factor related to inflammatory processes, nuclear factor {kappa}B (NF-{kappa}B). Liver nuclear extracts from SAM-R1 mice incubated in the presence of an NF-{kappa}B response oligonucleotide produced three specific bands that disappeared in the presence of an excess of unlabeled probe (Figure 4A). No significant change in the intensity of any of the three specific bands was detected in gel-shift assays performed with liver nuclear extracts from SAM-P8 mice (Figure 4B).


Figure 03
View larger version (35K):
[in this window]
[in a new window]

  		Figure 3. A, Electrophoretic mobility shift assay (EMSA) showing the binding of senescence-accelerated mouse-resistant 1 (SAM-R1) hepatic nuclear extracts (NE) to activator protein 1 (AP-1) oligonucleotide, forming at least two specific bands (bands I and II). Band I is supershifted (IC) in the presence of a c-Jun antibody. B, Representative EMSA autoradiograph showing the specific bands I and II formed with hepatic nuclear extracts from four SAM-R1 and four SAM-prone 8 (SAM-P8) mice

 

Figure 04
View larger version (40K):
[in this window]
[in a new window]

  		Figure 4. A, Electrophoretic mobility shift assay (EMSA) showing the binding of senescence-accelerated mouse-resistant 1 (SAM-R1) hepatic nuclear extracts (NE) to a nuclear factor {kappa}B (NF-{kappa}B) oligonucleotide, forming at least three specific bands (bands I, II, and III). B, Representative EMSA autoradiograph showing the specific bands I, II, and III formed with hepatic NE from four SAM-R1 and four SAM-prone 8 (SAM-P8) mice

 
Genes Related to Xenobiotic Metabolism
To confirm our results, two genes were selected for analysis by real-time PCR on the basis of their fold-change and/or biological relevance. As shown in Figure 5A, the genes showed similar changes in their specific mRNA content according to the cDNA arrays and the RT–PCR assays. D site albumin promoter binding protein (Dbp) is a proline and acidic amino acid-rich (PAR)-domain basic leucine zipper transcription factor that, among other known functions, controls the expression of CAR (17). We determined the CAR binding activity of liver nuclear extracts from SAM-R1 and SAM-P8 mice; nuclear extracts from SAM-R1 mice incubated in the presence of a CAR response element oligonucleotide produced two specific bands that disappeared in the presence of an excess of unlabeled probe (Figure 6A). Although the intensity of band I in gel-shift assays performed with liver nuclear extracts was the same for SAM-P8 and SAM-R1 mice (Figure 6B), the intensity of band II was significantly reduced in the SAM-P8 mice, in accordance with the reduced expression and binding activity of CAR.


Figure 05
View larger version (10K):
[in this window]
[in a new window]

  		Figure 5. A, Validation of two differentially expressed genes in hepatic senescence-accelerated mouse prone 8 (SAM-P8) samples compared to control SAM-resistant 1 (SAM-R1) samples. Comparison of results obtained by Affymetrix array (filled columns) and real-time polymerase chain reaction (PCR) (Taqman) (open columns). Values are expressed as a percentage of decrease in gene expression, compared to the corresponding control. Genes: mCAR = mouse constitutive androstane receptor; Dbp = D site albumin promoter binding protein. B, Validation of three differentially expressed genes in hepatic SAM-P8 mice samples compared to control SAM-R1 samples. Comparison of results obtained by Affymetrix array (filled columns) and real-time PCR (Taqman) (open columns). Values are expressed as percentage increase or decrease in gene expression, compared to the corresponding control. Genes: Arsa = Arylsulfatase A; Ndrl = N-myc downstream regulated gene 1; Psen2 = presenilin 2

 

Figure 06
View larger version (41K):
[in this window]
[in a new window]

  		Figure 6. A, Electrophoretic mobility shift assay (EMSA) showing the binding of senescence-accelerated mouse resistant 1 (SAM-R1) hepatic nuclear extracts (NE) to a constitutive androstane receptor (CAR) oligonucleotide, forming at least two specific bands (bands I and II). B, Representative EMSA autoradiography showing the specific bands I and II formed with hepatic NE from four SAM-R1 and four SAM-prone 8 (SAM-P8) mice

 
Genes Related to Nervous System Pathophysiology
To confirm our results, three genes were selected for analysis by real-time PCR on the basis of their fold-change and/or biological relevance. As shown in Figure 5B, all of them showed similar changes in their specific mRNA content between the cDNA arrays and the RT–PCR assays, although RT–PCR results for the presenilin 2 (Psen2) gene did not reach statistical significance.


   DISCUSSION
Top
 Abstract
 Material and Methods
 Results
 Discussion
References
 
The rare inbred mouse strain generated by breeding and selection and known as the SAM-P8, in which the features of senescence become apparent at 4 months of age, has been proposed as an appropriate model for studying the complex process of aging in gerontological research (18). Besides its role in orchestrating whole-body lipid and glucose metabolism, the liver is critical in the production of many plasma proteins involved in physiological processes and in the breakdown of potentially toxic lipophilic toxins. Aging profoundly affects these liver activities, contributing to the decline of healthy functioning of the whole organism. Triglyceride accretion and a deficit in hepatic fatty acid oxidation appear to be common phenotypic features of the aging process in mammals (including the SAM-P8 mouse). However, our previous work (6) has demonstrated that the molecular alteration responsible for these metabolic irregularities differs between "physiological" aging in rodents and in the SAM-P8 mouse. This study indicates that there are other differences in liver gene expression, as well as similarities, between the SAM-P8 mouse model and the normal aging process in rodents.

SAM-P8 mice show age-related memory deficits related to central nervous system neurodegeneration (8). Although we have studied hepatic samples, changes in the expression of genes related the nervous system pathophysiology in livers of SAM-P8 mice are consistent with an accelerated process of neurodegeneration in these animals. N-myc downstream-regulated gene 1 (Ndrg1) is localized in the cytoplasm of myelinating Schwann cells, and it is essential for maintenance of the myelin sheaths in peripheral nerves (19,20). Its increased expression in liver samples from SAM-P8 mice could be a reflection of an active process of nerve remodeling and regeneration as a result of increasing neurodegeneration and axonal loss (21). Among their functions, presenilin proteins, including Psen2, are essential for myelopoiesis (22) and for the maintenance of cortical structures and function (23). Furthermore, arylsulfatase A (Arsa) activity is also essential for myelin formation (24). Thus, the reduced expression of Psen2 and Arsa in SAM-P8 liver samples appears to indicate a neurodegenerative process taking place in these animals. Nevertheless, it must be borne in mind that it is not possible to directly correlate changes in gene expression from one tissue to another, as an increase has been reported in Psen2 in hippocampus and cerebral cortex of SAM-P8 mice (25).

Aging is associated, whether or not as a causative factor, with an increased production of oxidative products in body tissues (26), underlying the progressive increased prevalence of chronic inflammatory processes in mammals (27). The results obtained with liver samples from SAM-P8 mice indicate that, at least at 5 month of age, there is a robust anti-inflammatory response in liver tissue that keeps inflammation at bay. Tissue factor pathway inhibitor-2 (Tfpi2) and transformation-related protein 53/inducible nuclear protein 53 (Trp53) expression is increased in several pathophysiological situations, including cancer and inflammatory processes (28,29). Thus, their increased expression in livers from SAM-P8 mice, confirmed by the RT–PCR data, indicates that inflammation is taking place in the liver tissue of SAM-P8 mice. However, HSP1 (known also as HSP27) and Jun-B were also highly upregulated in the livers of SAM-P8 mice. HSPs are a group of proteins that accumulate in cells stressed by a variety of stimuli and pathophysiological situations, such as inflammation, ischemia, and cancer (30). Thus far, all age-related studies agree that HSP expression decreases with age and is linked to the pro-inflammatory status of the elderly population (30). The fact that livers of SAM-P8 had an increased expression of HSP1 indicates that, in these animals, a strong counter-anti-inflammatory response is taking place. The increased expression of Jun-B points in the same direction, as it is probably related to the observed reduced binding activity of the pro-inflammatory transcription factor AP-1 (16) in liver samples from SAM-P8 mice. Furthermore, the binding activity of NF-{kappa}B, a transcription factor mainly involved in the transduction of inflammatory signals (31), was unchanged in livers from SAM-P8 mice; NF-kB activity has been reported to be higher in the livers of aged rats (32) and mice (33). Thus, the overall picture indicates that 5-month-old SAM-P8 mouse livers cope with inflammatory processes by activating counter-regulatory measures. It is interesting to note that the expression of trefoil factor 3, intestinal (Tff3), a protein markedly increased during liver inflammatory processes and cancer progression (34), is reduced in the livers of SAM-P8 mice.

Aged mammals show a progressive impairment in the activity of liver-detoxifying enzymes, either by transcriptional or post-transcriptional mechanisms (35). CAR is one of the main transcription factors involved in controlling the expression of drug-metabolizing enzymes (36). Livers from SAM-P8 mice show a marked decrease in the expression and binding activity of CAR and in the expression of Dbp, a transcription factor controlling the expression of CAR. Such a decrease could imply a serious deterioration in the capacity of SAM-P8 mouse livers to metabolize toxic xenobiotics. This deterioration in xenobiotic metabolism could be one of the triggers of the early appearance of severe liver disease in this strain of mice (9), and also of the above-mentioned changes in the expression of pro- and anti-inflammatory factors. Indeed, PAR bZip triple knockout mice, including Dbp, are hypersensitive to the effect of xenobiotic compounds and show manifestations of early aging (17).

Summary
Our present and previously published (6) data obtained from the analysis of livers from 5-month-old SAM-P8 mice show similarities (liver xenobiotic metabolism, nervous system pathophysiology) and some dissimilarities (inflammation, lipid metabolism) with published information referring to changes observed in the livers of normally aged rodents.


   Acknowledgments
Top
 Abstract
 Material and Methods
 Results
 Discussion
 References
 
This work was supported by grants from Fundació Privada Catalana de Nutrició i Lípids (FPCNL), Ministerio de Ciencia y Tecnologia (MCYT; SAF2004-03045), Red de Grupos en Diabetes Mellitus (REDIMET), and Fondo Europeo de Desarrollo Regional (FEDER) funds. Laia Vila was supported by a Research and Teaching Grant from the University of Barcelona.

We have been nominated as a Consolidated Research Group by the Generalitat de Catalunya (SGR05-00833), with no financial aid whatsoever.


   Footnotes
Top
 Abstract
 Material and Methods
 Results
 Discussion
 References
 
Decision Editor: Huber R. Warner, PhD

Received October 25, 2007

Accepted May 28, 2008


   References
Top
 Abstract
 Material and Methods
 Results
 Discussion
 References
 

  1. Day JC. Population projections of the United States by age, sex, race and Hispanic origin: 1993–1950. Washington, DC: U.S. Department of Commerce Bureau of Census; 2003:25–1104.
  2. Zenilman ME. Surgery in the elderly. Curr Probl Surg. 1998;35:99-179.[Medline]
  3. Corti MC, Barbato GM, Baggio G. Lipoprotein alterations and atherosclerosis in the elderly. Curr Opin Lipidol. 1997;8:236-241.[Medline]
  4. Toth MJ, Tchernof A. Lipid metabolism in the elderly. Eur J Clin Nutr. 2000;54:S121-S125.[Medline]
  5. Sanguino E, Bejarano R, Alegret M, et al. Sexual dimorphism in lipid metabolic phenotype associated with old age in Sprague-Dawley rats. Exp Gerontol. 2004;39:1295-1306.[Medline]
  6. Vilà L, Roglans N, Alegret M, et al. Hypertriglyceridemia and hepatic steatosis in senescence accelerated mouse associate to changes in lipid-related gene expression. J Gerontol A Biol Sci Med Sci. 2007;62:1219-1227.[Abstract/Free Full Text]
  7. Takeda T, Hosokawa M, Takeshita S, et al. A new murine model of accelerated senescence. Mech Ageing Dev. 1981;17:183-194.[Medline]
  8. Butterfield DA, Poon HF. The senescence-accelerated prone mouse (SAMP-8): a model of age-related cognitive decline with relevance to alterations of the gene expression and protein abnormalities in Alzheimer's disease. Exp Gerontol. 2005;40:774-783.[Medline]
  9. Ye X, Meeker HC, Koxlowski PB, et al. Pathological changes in the liver of a senescence accelerated mouse strain (SAMP8): a mouse model for the study of liver diseases. Histol Histopathol. 2004;19:1141-1151.[Medline]
  10. Helenius M, Hänninen M, Lehtinen SK, Salminen A. Aging-induced up-regulation of nuclear binding activities of oxidative stress responsive NF{kappa}B transcription factor in mouse cardiac muscle. J Mol Cell Cardiol. 1996;28:487-498.[Medline]
  11. Bradford MM. A rapid sensitive method for the quantitation of microgram quantities of protein utilizing the principles of protein-dye binding. Anal Biochem. 1976;72:248-254.[Medline]
  12. Roglans N, Sanguino E, Peris C, et al. Atorvastatin treatment induced peroxisome proliferator-activated receptor {alpha} expression and decreased plasma nonesterified fatty acids and liver triglyceride in fructose-fed rats. J Pharmacol Exp Ther. 2002;302:232-239.[Abstract/Free Full Text]
  13. Lazarow PB. Assay of peroxisomal β-oxidation of fatty acids. Methods Enzymol. 1981;72:315-319.[Medline]
  14. Sanguino E, Ramón M, Michalik L, et al. Lack of hypotriglyceridemic effect of gemfibrozil and age-related changes in rat liver PPAR{alpha}. Biochem Pharmacol. 2004;67:157-166.[Medline]
  15. Sanguino E, Roglans N, Alegret M, Sánchez RM, Vázquez-Carrera M, Laguna JC. Prevention of age-related changes in rat cortex transcription factor activator protein-1 by hypolipidemic drugs. Biochem Pharmacol. 2005;68:1411-1421.
  16. Shaulian E, Karin M. AP-1 as a regulator of cell life and death. Nat Cell Biol. 2002;4:E141-E136.
  17. Gachon F, Olela FF, Schaad O, Descombes P, Schibler U. The circadian PAR-domain basic leucine zipper transcription factors DBP, TEF, and HLF modulate basal and inducible xenobiotic metabolism. Cell Metab. 2006;4:25-36.[Medline]
  18. Takeda K, Hosokawa M, Michalik L. Senescence-accelerated mouse (SAM): a novel murine model of senescence. Exp Gerontol. 1997;32:105-109.[Medline]
  19. Okuda T, Higashi Y, Kokame K, Tanaka C, Kondoh H, Miyauchi T. Ndrg-1-deficient mice exhibit a progressive demyelinating disorder of peripheral nerves. Mol Cell Biol. 2004;24:3949-3956.[Abstract/Free Full Text]
  20. Berger P, Sirkowski EE, Scherer SS, Suter U. Expression analysis of the N-Myc downstream-regulated gene 1 indicates that myelinating Schwann cells are the primary disease target in hereditary motor and sensory neuropathy. Neurobiol Dis. 2004;17:290-299.[Medline]
  21. Hirata K, Masuda K, Morikawa W, et al. N-myc downstream-regulated gene 1 expression in injured sciatic nerves. Glia. 2004;47:325-334.[Medline]
  22. Qyang Y, Chambers SM, Wang P, et al. Myeloproliferative disease in mice with reduced presenilin gene dosage: effect of gamma-secretase blockage. Biochemistry. 2004;43:5352-5359.[Medline]
  23. Feng R, Wang H, Wang J, Shrom D, Zeng X, Tsien JZ. Forebrain degeneration and ventricle enlargement caused by double knockout of Alzheimer's presenilin-1 and presenilin-2. Proc Natl Acad Sci U S A. 2004;101:8162-8167.[Abstract/Free Full Text]
  24. Yaghootfam A, Gielselmann V, Eckhardt M. Delay of myelin formation in arylsulphatase A-deficient mice. Eur J Neurosci. 2005;21:711-720.[Medline]
  25. Wei X, Zhang Y, Zhou J. Alzheimer's disease-related gene expression in the brain of senescence accelerated mouse. Neurosci Lett. 1999;268:139-142.[Medline]
  26. Beckman K, Ames BN. The free radical theory of aging matures. Physiol Rev. 1998;78:547-581.[Abstract/Free Full Text]
  27. Sarkar D, Fisher PB. Molecular mechanisms of aging-associated inflammation. Cancer Lett. 2006;236:13-23.[Medline]
  28. Chand HS, Foster DC, Kisiel W. Structure, function and biology of tissue factor pathway inhibitor-2. Thromb Haemost. 2005;94:1122-1130.[Medline]
  29. Tomasini R, Seux M, Nowak J, et al. TP53INP1 is a novel p73 target gene that induces cell cycle arrest and cell death by modulating p73 transcriptional activity. Oncogene. 2005;24:8093-8104.[Medline]
  30. Larbi A, Kempf J, Wistuba-Hamprecht K, Haug C, Pawalec G. The heat shock proteins in cellular aging: is zinc the missing link? Biogerontology. 2006;7:399-408.[Medline]
  31. Bowie A, O'Neill LAJ. Oxidative stress and nuclear factor-{kappa}B activation. A reassessment of the evidence in the light of recent discoveries. Biochem Pharmacol. 2000;59:13-23.[Medline]
  32. Supakar PC, Jung MH, Song CS, Chatterjee B, Roy AK. Nuclear factor {kappa}B functions as a negative regulator for the rat androgen receptor gene and NF-{kappa}B activity increases during the age-dependent desensitization of the liver. J Biol Chem. 1995;270:837-842.[Abstract/Free Full Text]
  33. Spencer NFL, Poynter ME, Im S-Y, Daynes RA. Constitutive activation of NF-{kappa}B in an animal model of aging. Int Immunol. 1997;9:1581-1588.[Abstract/Free Full Text]
  34. Okada H, Kimura MT, Tan D, et al. Frequent trefoil factor 3 (TFF3) overexpression and promoter hypomethylation in mouse and human hepatocellular carcinomas. Int J Oncol. 2005;26:369-377.[Medline]
  35. Wauthier V, Verbeeck RK, Calderon PB. The effect of ageing on cytochrome p459 enzymes: consequences for drug biotransformation in the elderly. Curr Med Chem. 2007;14:745-757.[Medline]
  36. Wang H, LeCluyse EL. Role of orphan nuclear receptors in the regulation of drug-metabolising enzymes. Clin Pharmacokinet. 2003;42:1331-1357.[Medline]




This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Services
Right arrow Download to citation manager
PubMed
Right arrow PubMed Citation

HOME ARCHIVE SEARCH TABLE OF CONTENTS