Journals of Gerontology Series A: Biological Sciences and Medical Sciences Large Type Edition
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Wang, J.
Right arrow Articles by Higuchi, K.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Wang, J.
Right arrow Articles by Higuchi, K.
The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 55:B432-B439 (2000)
© 2000 The Gerontological Society of America

Wild Type ApoA-II Gene Does Not Rescue Senescence-Accelerated Mouse (SAMP1) From Short Life Span and Accelerated Mortality

Jing Wanga,b,c, Takatoshi Matsushitab, Kumiko Kogishib, Chen Xiab, Akira Ohtab, Takuya Chibab,c, Akihiro Nakamurac, Hisatoshi Kondod, Masayuki Moric, Masanori Hosokawab and Keiichi Higuchic

a Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, Canada
b Field of Regeneration Control, Institute for Frontier Medical Science, Kyoto University, Kyoto, Japan
c Department of Aging Angiology, Research Center on Aging and Adaptation, Shinshu University School of Medicine, Matsumoto, Japan
d Atomic Bomb Disease Institute, Nagasaki University School of Medicine, Nagasaki, Japan

Keiichi Higuchi, Department of Aging Angiology, Research Center on Aging and Adaptation, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan E-mail: khiguchi{at}sch.md.shinshu-u.ac.jp.

Decision Editor: Jay Roberts, PhD


   Abstract
Top
 Abstract
Materials and Methods
 Results
 Discussion
 References
 
Biochemical and genetic data suggest that the Apoa2c allele of the apolipoprotein A-II gene causes severe senile amyloidosis (AApoAII) in SAMP1, a mouse model for accelerated senescence. We analyzed the effects of replacement of Apoa2c in SAMP1 mice with non-amyloidogenic Apoa2b on amyloidosis, lipoprotein metabolism, and progression of senescence using a congenic strain, P1.R1-Apoa2b, which has the Apoa2b chromosome region of SAMR1 in the genome of SAMP1. Age-associated amyloid deposition was not observed, but plasma concentrations of apoA-II protein and HDL-cholesterol decreased with age in P1.R1-Apoa2b. P1.R1-Apoa2b showed lower scores of senescence than did SAMP1. However, the life span and mortality rate doubling time were similar in P1.R1-Apoa2b and SAMP1. These results suggest that replacement of Apoa2c with non-amyloidogenic Apoa2b does not rescue SAMP1 mice from a short life span and accelerated mortality.

SENESCENCE-accelerated mouse (SAM) strains provide a unique model system for studying the aging process in higher organisms. SAM strains include the senescence-prone SAMP series and senescence-resistant SAMR series (1)(2)(3). SAMP strains have a markedly shorter life span, and they show early signs of aging. Analysis of aging dynamics, based on survival curves and senescence scores, suggests that the aging pattern in SAMP is one of accelerated senescence after normal development. Analysis with the Gompertz function shows that SAMP strains have the same initial mortality rate (IMR) as SAMR strains but a shorter mortality rate doubling time (MRDT), presumably due to genes that accelerate the rate of senescence (4). Molecular genetic characterization of SAM strains revealed that they might be a group of related inbred strains developed by some accidental outbreeding between the AKR/J strain and an unknown strain (5)(6). SAMP1, a strain in the SAMP series, has accelerated the progression of many age-associated degenerative diseases such as senile amyloidosis, impaired immune response, hyperinflation of the lungs, and hearing impairment (2)(3). Senile amyloidosis is one of the most characteristic age-associated disorders (7).

Amyloidosis is a disorder of protein structure in which normally soluble proteins are deposited in tissues as abnormally polymerized insoluble amyloid fibrils (8)(9)(10)(11)(12). In humans, a wide variety of precursor proteins can form amyloid fibrils, e.g., amyloid A protein (AA) in secondary amyloidosis, amyloid ß protein (Aß) in Alzheimer's disease, prion protein (PrPSc) in Prion diseases, immunoglobulin light chains (AL) in amyloidosis of AL type, and transthyretin (ATTR) in familial amyloid polyneuropathy and senile systemic amyloidosis (13)(14)(15)(16). In mice, two amyloid proteins have been known to deposit systemically. AA protein deposits are associated with infections and inflammation. ApoA-II, an apolipoprotein in serum high-density lipoprotein (HDL) is a precursor of murine senile amyloid fibrils [AApoAII; (17)]. Three variants of apoA-II protein (types A, B, and C) with different amino acid substitutions at four positions are present among inbred strains of mice (18). Previously, we found that SAMP1 had the Apoa2c allele coding type C apoA-II protein and that early deposition of AApoAII in SAMP1 is linked to Apoa2c in the genetic linkage analyses (19)(20)(21). Amyloid deposition such as of amylin and Aß is toxic to tissues (22)(23). We developed a congenic strain of mice (R1.P1-Apoa2c), which had the amyloidogenic Apoa2c transferred from SAMP1 on the genetic background of SAMR1 (24)(25) to study the effects of Apoa2c on the life span and progression of senescence. We found that the transferred Apoa2c region induces severe senile amyloid deposition throughout the body. The concentration of apoA-II was low in plasma of R1.P1-Apoa2c, and both apoA-II and HDL concentrations decreased rapidly with age. The life span was about 20% shorter in the congenic strain. The Gompertz function showed a higher IMR but the same MRDT as that of SAMR1 (25). We assumed that replacement of Apoa2c in SAMP1 with Apoa2b would reduce the susceptibility to amyloidosis and thus lengthen the life span. Thus, we developed another kind of congenic strain, P1.R1-Apoa2b (26), and analyzed the effects of Apoa2b on amyloidosis, age-related changes in lipoprotein metabolism, and progression of senescence. Unexpectedly, the replacement of the Apoa2c chromosome region with non-amyloidogenic Apoa2b did not extend the life span of SAMP1.


   Materials and Methods
Top
 Abstract
 Materials and Methods
Results
 Discussion
 References
 
Animals
The congenic strain, P1.R1-Apoa2b was produced by 12 generations of backcrosses between recipient SAMP1 and the offspring having the Apoa2b allele of donor SAMR1. The identity of the genetic background of P1.R1-Apoa2b and SAMP1 was confirmed using endogenous provirus and microsatellite markers. Localization of the proximal and distal end of the transferred chromosomal region (between D1Mit33 and D1Mit16, and Apoa2 and Mpmv-29, respectively) revealed that only a small region less than 8 centimorgans surrounding the apoA-II gene was transferred (26). P1.R1-Apoa2b and SAMP1 were maintained by sister and brother mating. All mice were raised under conventional conditions at 24 ± 2°C under a 12-h light/12-h dark cycle with free access to a commercial diet (CE-2, Nihon CLEA, Tokyo, Japan) containing 4% fat and tap water. We used 355 female P1.R1-Apoa2b and 159 female SAMP1 mice. Animals at around 2 months of age were housed 5 to 10 in each cage (20 cm wide x 30 cm high x 10 cm deep) according to strain, without regrouping, until they died. The degree of senescence in each mouse was evaluated every 2 months. Mice were inspected daily, and those that died were necropsied. Tissues of the whole body were fixed in 10% neutral buffered formalin, embedded in paraffin, and sliced into 4 µm sections that were stained with hematoxylin and eosin or used for immunohistochemical demonstration of amyloid proteins. Animal studies were conducted in accordance with the guidelines for the use of laboratory animals of Kyoto University and Shinshu University School of Medicine.

Detection of Amyloid Deposition
Amyloid deposition was identified according to evidence of green birefringence in the Congo-red-stained sections under polarizing microscopy (7)(27). Amyloid fibril proteins, AApoAII, and AA, were immunohistochemically identified by the avidin-biotinylated horseradish peroxidase complex method with specific antiserum (7). The intensity of AApoAII and AA deposition was determined semiquantatively using amyloid index, a geometric parameter. Amyloid index is the average degree of amyloid deposition graded 0 (no deposition), 1 (slight), 2 (moderate), 3 (severe), and 4 (most severe) in five major organs (liver, spleen, skin, heart, stomach) in sections stained immunohistochemically. Two observers (who had no information about the tissue examined) independently graded and averaged the amyloid index for each mouse.

Induction of AA Amyloidosis
Two-month-old female P1.R1-Apoa2b, SAMP1, and C57BL/6J were used for the induction of AA amyloidosis, according to the method of Hoshii and colleagues (28). In brief, a mixture of Freund's complete adjuvant and Mycobacterium butyricum was injected intraperitoneally into each mouse, and the second injection of the same mixture was performed subcutaneously one week later. Mice were killed 3 weeks after the second injection, and the liver, spleen, skin, heart, and stomach obtained from each mouse were fixed in 10% neutral buffered formalin.

Lipoprotein Quantitation
Mice were killed after 16 hours of fasting. Plasma was isolated by centrifugation of blood containing 0.5 M EDTA at the concentration of 15 µl/ml, at 10,000 rpm for 10 min at 4°C. HDL cholesterol was estimated according to a modified heparin-manganese precipitation procedure (HDL cholesterol C-Test Wako, Wako Pure Chemical Industries, Osaka, Japan). Plasma concentrations of total cholesterol were determined using enzymatic procedures employing colorimetric end points (cholesterol C-Test Wako).

Concentrations of apoA-I and apoA-II were determined by a quantitative immunoblotting method. Plasma aliquots (10 nl) were subjected to 15 to 25% gradient SDS-polyacrylamide gel electrophoresis at 15 mA for 2.5 hours. After electrophoresis, proteins were electrophoretically transferred to a polyvinylidene difluoride (PVDF) membrane (BioRad Laboratories, Richmond, CA) using a semi-dry apparatus (Nihon Eido, Tokyo, Japan) at 150 mA for 2 hours. The blot was then incubated with primary antibody solution, either with monospecific rabbit anti-mouse apoA-I or apoA-II antisera (diluted 1:4000) in 1% skim milk in phosphate-buffered saline (PBS) containing 0.1% Tween-20 (T-PBS) for 1 hour at room temperature with gentle shaking. Blots were washed in T-PBS and incubated for 1 hour with horseradish peroxidase-conjugated anti-rabbit IgG (Daiichi Pure Chemicals, Tokyo, Japan) solution in T-PBS (1:800). Apolipoproteins were detected by the ECL chemiluminescence method (Amersham, Buckinghamshire, England) and quantitated using a video densitometeric image analyzer (Luzex 3U, Nikon, Tokyo, Japan).

The age-specific mortality rate was calculated for each 25-day period throughout the life of each strain population and analyzed by the Gompertz-Makeham equation (29)(30).

Evaluation of the Degree of Senescence
The degree of senescence was evaluated by observing 11 categories of behavioral activity and gross appearance considered to be associated with the aging process: reactivity, passivity, loss of hair and of glossiness, skin coarseness, skin ulcers, periophthalmic lesions, cataracts, corneal ulcers, corneal opacity, and lordokyphosis of the spine. Each category was graded 0 to 4 according to the degree of change, the senescence score for each mouse being the sum of the grades of each category (31). Because the senescence score increased irreversibly and universally with advancing age in all strains of mice tested, and there was a statistically significant reverse correlation between the remaining life span and the total score, this score appears valid for evaluation of the degree of senescence (32). Grading was done at a fixed time, from 2 PM to 4 PM, by two independent observers who were not told the strain or age of the mice examined.

Statistical Analysis
All data are presented as the means ± SD. A Statview software package (Abacus Concepts, Berkeley, CA) was used to analyze the data. Because the amyloid index and senescence scores are nonlinear indexes, two strains were compared with the nonparametric Mann-Whitney U test. The correlation between amyloid index and age was analyzed with Spearman's rank test (33). Survival curves were estimated by the Kaplan-Meier test (34) and were compared with the Wilcoxon test (33). The two strains were compared at the 10th decile with Student's t test. The effects of age and apoA-II type on lipoprotein metabolism were analyzed by two-way analysis of variance (ANOVA).


   Results
Top
 Abstract
 Materials and Methods
 Results
Discussion
 References
 
Amyloid Deposition
We selected 28 P1.R1-Apoa2b and 22 SAMP1 mice without advanced postmortem changes for pathological examination. We obtained the amyloid index as shown in Fig. 1. In SAMP1, age-associated and severe AApoAII deposits were observed in all tissues examined except for brain parenchyma. A significant correlation was observed between age and amyloid index for AApoAII in SAMP1 ( , Spearman's rank test), whereas in P1.R1-Apoa2b, no AApoAII was observed except in two mice aged 315 and 574 days. The incidence of AApoAII deposition was significantly lower ( p < .0001, Fisher's exact test) in P1.R1-Apoa2b than noted in SAMP1 (Table 1 ). These findings suggested that Apoa2b in the transferred region prevented the severe AApoAII amyloidosis that occurred in SAMP1.



View larger version (17K):
[in this window]
[in a new window]
  		Figure 1. AApoAII, A, and AA, B, deposition in the apoA-II congenic strains. Amyloid index was calculated using five tissues each from 28 P1.R1-Apoa2b (•) and 22 SAMP1 ({circ}) after staining with anti-apoA-II, A, and anti-mouse AA, B, antiserum (7).

 

View this table:
[in this window]
[in a new window]
  		Table 1. Pathological Findings in the ApoA-II Congenic Strain

 
AA-amyloid deposits were observed in the spleen, liver, small intestine, kidney, heart, tongue, and stomach of 22 (78.5%) P1.R1-Apoa2b and 8 (36.3%) SAMP1 mice. Depositions of both AApoAII and AA were noted in 8 SAMP1 mice. The incidence of AA amyloidosis was significantly higher in P1.R1-Apoa2b ( p = .0037 Fisher's exact test; see Table 1 ). The amyloid index of AA amyloidosis was significantly higher in P1.R1-Apoa2b ( p < .0001, Mann-Whitney U test). In contrast to AApoAII, a significant correlation was not obtained between the amyloid index for AA and age in either P1.R1-Apoa2b ( , Spearman's rank test) or SAMP1 ( ) mice.

Other Pathological Findings
The primary pathological findings in addition to amyloidosis were inflammatory changes (mainly pneumonia and abscess), tumors (malignant lymphoma and lung tumors), and contracted kidney (Table 1 ). The incidence of inflammations and tumors was not significantly different in the two strains. Autopsy revealed various inflammatory lesions: skin ulcer (7 mice), abscesses in the liver, kidney, skin, heart and tail (16 mice), and pneumonia (6 mice) in mice which had AA deposition. The cause of abscess was not clear but may have been small wounds caused by self-infliction and fighting. Lower incidence of contracted kidneys was suggested in P1.R1-Apoa2b but was not significant ( , Fisher's exact test). Severe AApoAII or AA depositions were observed in the kidneys of all P1.R1-Apoa2b and SAMP1 mice with contracted kidneys. AApoAII deposits were mainly in the papillae and parenchymal tissues of the kidney. In the five P1.R1-Apoa2b mice with contracted kidneys, AA deposits were produced mainly in the glomerulus. Other pathological findings that might have caused death were massive coagulation necrosis in the liver (one P1.R1-Apoa2b mouse), meteorism (one P1.R1-Apoa2b mouse), colitis (one P1.R1-Apoa2b mouse), pyelonephritis (one SAMP1 mouse), and interstitial nephritis (three SAMP1 mice).

Induction of AA Amyloidosis in the Congenic Strains
To examine whether the Apoa2c gene might have inhibitory effects on AA amyloidosis, we induced AA by injection of Mycobacterium butyricum with Freund's complete adjuvant (Table 2 ). Amyloid deposits positively reacting with anti-mouse AA antibody were seen in the spleen in four C57BL/6J and P1.R1-Apoa2b mice. By contrast, no AA amyloid deposits were observed in SAMP1.


View this table:
[in this window]
[in a new window]
  		Table 2. AA Amyloid Deposition in Each Group of Mice

 
Age-associated Changes in Lipoproteins
Age-associated changes in the plasma concentrations of apoA-II (Fig. 2), apoA-I (Fig. 3), total cholesterol (Fig. 4), and HDL cholesterol (Fig. 5) were determined. ANOVA with the Statview system was used to examine the correlation between the age-associated changes and the allele of the apoA-II gene. The effects of the apoA-II allele (strain) and age were highly significant, but the interaction between strain and age was not significant for apoA-II ([, p < .0001; age: , p < .0001; Strain x Age: ); total cholesterol (strain: , p < .0001; Age: , p < .0001; Strain x Age: ); and HDL cholesterol (strain: , p < .0001; age: , p < .0001; Strain x Age: ). These results indicated that the plasma concentrations of apoA-II, total cholesterol, and HDL cholesterol were higher in P1.R1-Apoa2b than they were in SAMP1 at all ages, but that they decreased in an age-associated manner in both P1.R1-Apoa2b and SAMP1. These results suggest that the apoA-II allele controls the concentrations of apoA-II and cholesterol, but does not play an important role in the age-associated change in lipoprotein metabolism. Age-associated changes in plasma apoA-I were slightly different but similar to those in apoA-II. The effects of strain (), age (, p < .0001), and interaction between the two () were significant for plasma concentrations of apoA-I. Plasma concentrations of apoA-I were higher in P1.R1-Apoa2b than in SAMP1 at all ages except for 12 months ( p < .0001 at 3 and 6 months, at 9 months and at 12 months by Tukey's procedure).



View larger version (26K):
[in this window]
[in a new window]
  		Figure 2. Age-associated changes in plasma concentrations of apoA-II in the apoA-II congenic strains. Four or five mice were used for each age point (3, 6, 9, and 12 months old). Bars represent means ± SD.

 


View larger version (29K):
[in this window]
[in a new window]
  		Figure 3. Age-associated changes in plasma concentrations of apoA-I in the apoA-II congenic strains. Four or five mice were used for each age point (3, 6, 9, and 12 months old). Bars represent means ± SD.

 


View larger version (28K):
[in this window]
[in a new window]
  		Figure 4. Age-associated changes in plasma concentrations of total cholesterol in the apoA-II congenic strains. Four or five mice were used for each age point (3, 6, 9, and 12 months old). Bars represent means ± SD.

 


View larger version (29K):
[in this window]
[in a new window]
  		Figure 5. Age-associated changes in plasma concentrations of high-density lipoprotein (HDL) cholesterol in the apoA-II congenic strains. Four or five mice were used for each age point (3, 6, 9, and 12 months old). Bars represent means ± SD.

 
Survival Curves and Longevity
The survival curve of the congenic P1.R1-Apoa2b strain was compared with that of the recipient SAMP1 strain (Fig. 6). The Wilcoxon test analysis revealed no significant differences in survival curves of the two strains (). The age at 50% survival in P1.R1-Apoa2b (231 days, 95% confidence interval [CI], 224 to 238) was similar to that (236 days, 95% confidence interval, 211 to 271) in SAMP1. In addition, the mean life span of the last one-tenth to survive in P1.R1-Apoa2b (385 ± 44 days) did not differ significantly from that in SAMP1 (374 ± 51 days) (, Student's t test).



View larger version (17K):
[in this window]
[in a new window]
  		Figure 6. Survival curves A, and Gompertz functions, B of the apoA-II congenic strains. Subjects were 355 female P1.R1-Apoa2b(•) and 159 female SAMP1({circ}).

 
Then we compared the simple linear regression of age-specific mortality rates (after log10 transformation) in relation to chronological age of each strain (Fig. 6). We applied a simple working model of the Gompertz equation: m(t) = A10{alpha}t, where m(t) is the age-specific mortality rate (%/day) and {alpha} is the rate constant for the age-related increase of mortality, corresponding to the slope of the regression line. Because mortality rates strayed off the linear regression and converged toward common values after the age of 300 days in both strains, we used the mortality rate in the 0–300 day range for the Gompertz equation (mt in P1.R1-Apoa2b and in SAMP1). Linear regression was obvious and significant in this range in both strains (, p < .0001 for P1.R1-Apoa2b and , p < .0001 for SAMP1). The results revealed no significant differences () in the slopes of the regression lines of the two strains (95% CI of {alpha} is .0053 to .0075 in P1.R1-Apoa2b, and .0049 to .0089 in SAMP1). We calculated the mortality rate doubling time in reference to {alpha}; . Division by 365 gave MRDT per year. There was no significant difference in MRDT between the two strains (.13 year, in P1.R1-Apoa2b and .12 year in SAMP1). The initial mortality rate (IMR; %/day), which was calculated as an intercept of and converted to /year (.13/year, 95% CI; .09/year to .20/year in P1.R1-Apoa2b and .11/year, 95% CI; .05/year to .23/year in SAMP1), was not significantly different (). These findings suggested that the life span of P1.R1-Apoa2b was not lengthened and that the accelerated mortality of the SAMP1 strain was not improved.

Senescence Score
We compared the degree of senescence between the two strains (Fig. 7). The senescence score began to increase from 3 months of age and continued to increase with age both in P1.R1-Apoa2b and SAMP1. P1.R1-Apoa2b showed significantly lower scores than did SAMP1 in age groups of 51-100 days ( , Mann-Whitney U test), 101–200 days ( ), and 201–300 days ( p < .0001), and nonsignificant scores in age groups of 301–400 days ( ). Nominal significance level calculated from the total significant level, .05, for multiple comparison was .0009.



View larger version (21K):
[in this window]
[in a new window]
  		Figure 7. Age-related changes of the senescence scores in the apoA-II congenic strains. The degree of senescence for each mouse was recorded by the graded scores (31) every 100 days throughout the life of P1.R1-Apoa2b (closed bars) and SAMP1 (open bars). The value is a median of mice in each age group. Numbers over the columns indicate the number of mice examined. There was a significant difference in scores between the two strains until death, except for the scores after 300 days.

 

   Discussion
Top
 Abstract
 Materials and Methods
 Results
 Discussion
References
 
We used several parameters to analyze the progress of senescence in the apoA-II congenic strain of SAMP1. Unexpectedly, the life span of P1.R1-Apoa2b was not lengthened. When we assumed that the hazard function of P1.R1-Apoa2b and SAMP1 was proportional, the power of this study to detect a significant decrease in the survival of P1.R1-Apoa2b greater than 0.1 at the median survival time of SAMP1 (that means the hazard ratio is 1.32) was relatively high, 0.84 (significant level, p < .05) (35). The Gompertz mortality model has been used to describe senescence of populations, and age-related increase of mortality rate is used to calculate MRDT, which is considered to be a fundamental measure of the rate of senescence (30). The transferred Apoa2b region did not change the MRDT and IMR significantly. The survival curve of P1.R1-Apoa2b was significantly different from that of SAMR1 reported previously [ p < .0001, Wilcoxon test; (25)]. The 95% CI of 50% survival of P1.R1-Apoa2b did not overlap with that of SAMR1 (527–583 days). Although MRDT of P1.R1-Apoa2b was significantly shorter than that of SAMR1 (.344 year, ), IMR was not significantly different from that of SAMR1 (.07/year, ). These results suggest that our analysis has sufficient statistical power at least to reveal the difference between aging dynamics of SAMP1 and SAMR1. Two explanations are possible: (i) Genetic factors other than the apoA-II gene responsible for the short life span and accelerated mortality of SAMP1 might be strong enough to mask the effect of prevention of amyloid deposition, and (ii) AA amyloidosis may, to some extent, shorten the life span of P1.R1-Apoa2b. Interestingly, AA deposition was significantly severer in P1.R1-Apoa2b than in SAMP1 although the incidence of inflammation was similar. The results of induction experiments showed AA deposits only in the spleen from control C57BL/6J and P1.R1-Apoa2b, which supported this observation. From these findings, we hypothesized that the amyloidogenic Apoa2c may inhibit the deposition of AA. The mechanism of inhibition is unclear: There might be competition between the two amyloid proteins in binding to a common molecule that modulates the amyloid fibril formation (36).

The grading system used here was developed in our laboratory for evaluation of the degree of senescence in mice and has been used for selection and maintenance of the phenotype of SAMP strains (31). This system was designed to satisfy the following criteria: (i) appropriate for longitudinal studies of individual mice; (ii) easy to apply; (iii) results expressed numerically and analyzed statistically; and (iv) objective and reproducible graded score (1)(32). Lower scores in P1.R1-Apoa2b suggest that the Apoa2b gene might retard general senescence. Compared with SAMR1 (25), the senescence score of P1.R1-Apoa2b was higher even at the age of 51–100 days ( p < .0001, Mann-Whitney U test). This finding is not consistent with the previously observed absence of difference between SAMP1 and SAMR1 before 6 months of age (4)(32). The reason is not clear, but the high incidence of inflammation or uncertain difference in experimental conditions may be the cause.

Human studies on the genetic regulation of HDL metabolism are confounded by genetic heterogeneity, environmental influences, aging, and other factors (37). In mice, there is evidence that variations in the apoA-II structure and expression have a dramatic effect on HDL levels and size (24)(38)(39)(40). At the age of 3 months, the levels of apoA-II and HDL in SAMP1 were only about 50% of those in the SAMR1 strain, and decreased rapidly with age; in the SAMR1 strain, however, those levels did not decrease until the age of 17 months (21). Age-related acceleration of apoA-II turnover and decrease in apoA-II synthesis was observed in SAMP1 (41)(42). Thus, we have tried to elucidate the complex relation among lipoprotein metabolism, aging, and amyloidosis. We previously reported the age-associated rapid decrease in lipoprotein concentrations in R1.P1-Apoa2c mice with accelerated senile amyloidosis (25). In this study, AApoAII amyloid deposition was almost completely prevented in P1.R1-Apoa2b; concentrations of lipoproteins were high compared to SAMR1 at the age of 3 months, but they decreased rapidly with age as in SAMP1. These findings suggested that both AApoAII deposition and aging might induce the age-associated decrease in lipoproteins. However there is a possibility that rapid decrease of apoA-II from a younger age might induce amyloid deposition in the Apoa2c strains. Recently, we revealed the critical roles of Apoa2b on lipoprotein metabolism and prevention of AApoAII amyloidosis by adenovirus-mediated overexpression of Apoa2b (43). Further studies should be done to elucidate this complex relationship.

The incidence of contracted kidney, a characteristic pathological finding in SAMP1 (3), was significantly higher in R1.P1-Apoa2c than in SAMR1 (25). Here, the lower incidence of contracted kidney in P1.R1-Apoa2b was not significant but suggestive. These findings suggested that amyloidosis may play some role in the manifestation of contracted kidney.

Although our congenic mice should be a good model for the analysis of apoA-II function, small transferred regions around Apoa2 (less than 1% of total genome) in R1.P1-Apoa2c and P1.R1-Apoa2b still contain many genes besides Apoa2 (26). Thus, we could not exclude the possibility that other genes in the differential regions might play important roles in amyloidosis, lipoprotein metabolism, and the aging progress in the congenic strains.

Because we tested here approximately 30 hypotheses to elucidate the role of apoA-II, we should consider the results carefully when p values were greater than .002 (.05/30). However, our studies provided new evidence supporting that (i) the occurrence of amyloidosis is affected by the genotype of Apoa2 for the most part, (ii) the genotype of Apoa2 does not modulate age-related acceleration of the mortality rate in mice, and (iii) the occurrence of amyloidosis would influence the lipoprotein levels in mice, but they would decrease with the aging process. We need to examine further the genetic factors responsible for the accelerated senescence of SAMP1.


   Acknowledgments
 
This work was supported in part by a grant from the Ministry of Health and Welfare of Japan and Grant-in-Aid for Scientific Research (C) (09670224) and Priority Areas (09276209) from the Ministry of Education, Science, Sports and Culture, Japan.

We thank Dr. T. Takeda from the SAM Research Council for pathological examination of the tissues. Gratitude is also extended to E. Deguchi, K. Yasuoka, and Y. Kishimoto for the close care of the SAMP1 and congenic mice.

Received May 25, 1999

Accepted February 17, 2000


   References
Top
 Abstract
 Materials and Methods
 Results
 Discussion
 References
 

  1. Takeda T, Hosokawa M, Takeshita S, et al. 1981. A new murine model of accelerated senescence. Mech Ageing Dev. 17:183-194. [Medline]
  2. Takeda T, Hosokawa M, Higuchi K, 1991. Senescence-accelerated mouse (SAM): a novel murine model of accelerated senescence. J Am Geriatr Soc. 39:911-919. [Medline]
  3. Takeda T, Higuchi K, Hosokawa M, 1998. Senescence-Accelerated Mouse (SAM): with special reference to development and pathological phenotypes. ILAR J. 38:109-117.
  4. Higuchi K, 1997. Genetic characterization of Senescence-Accelerated Mouse (SAM). Exp Gerontol. 32:129-138. [Medline]
  5. Kitado H, Higuchi K, Takeda T, 1994. Molecular genetic characterization of Senescence-Accelerated Mouse (SAM). J Gerontol Biol Sci. 49:B247-254.
  6. Xia C, Higuchi K, Shimizu M, et al. 1999. Genetic typing of the Senescence-Accelerated Mouse (SAM) strains with microsatellite markers. Mamm Genome. 10:235-238. [Medline]
  7. Higuchi K, Matsumura A, Honma A, et al. 1983. Systemic senile amyloid in senescence accelerated mice: a unique fibril protein demonstrated in tissue from various organs by the unlabeled immunoperoxidase method. Lab Invest. 48:231-240. [Medline]
  8. Glenner GG, 1980. Amyloid deposits and amyloidosis. The ß-fibrilloses. Part I. N Engl J Med. 302:1283-1292. [Medline]
  9. Jarrett JT, Lansbury PJ, 1993. Seeding "one-dimensional crystallization" of amyloid: a pathogenic mechanism in Alzheimer's disease and scrapie?. Cell. 73:1055-1058. [Medline]
  10. Cohen AS, Jones LA, 1994. Advances in amyloidosis. Curr Opin Rheumatol. 6:55-67. [Medline]
  11. Kelly JT, Lansbury PT, Jr 1994. A chemical approach to elucidate the mechanism of transthyretin and ß-protein amyloid fibril formation. Amyloid. 1:186-205.
  12. Westermark P, 1998. The pathogenesis of amyloidosis: understanding general principles. Am J Pathol. 152:1125-1127. [Medline]
  13. Cohen AS, Jones LA, 1993. Proteins of the systemic amyloidosis. Curr Opin Rheumatol. 5:62-76. [Medline]
  14. Prusiner SB, 1997. Prion diseases and the BSE crisis. Science. 278:245-251. [Abstract/Free Full Text]
  15. Wetzel R, 1997. Domain stability in immunoglobulin light chain deposition disorders. Adv Protein Chem. 50:183-242. [Medline]
  16. Harper JD, Wong SS, Lieber CM, Lansbury PT, Jr 1997. Observation of metastable Aß amyloid protofibrils by atomic force microscopy. Chem Biol. 4:119-125. [Medline]
  17. Higuchi K, Yonezu T, Kogishi K, et al. 1986. Purification and characterization of a senile amyloid-related antigenic substance (apoSASSAM) from mouse serum. apoSASSAM is an apoA-II apolipoprotein of mouse high density lipoproteins. J Biol Chem. 261:12834-12840. [Abstract/Free Full Text]
  18. Higuchi K, Kitagawa K, Naiki H, Hanada K, Hosokawa M, Takeda T, 1991. Polymorphism of apolipoprotein A-II (apoA-II) among inbred strains of mice: relationship between the molecular type of apoA-II and mouse senile amyloidosis. Biochem J. 249:427-433.
  19. Higuchi K, Naiki H, Kitagawa K, Hosokawa M, Takeda T, 1991. Mouse senile amyloidosis: ASSAM amyloidosis in mice presents universally as a systemic age-associated amyloidosis. Virchows Arch B: Cell Pathol. 60:231-239. [Medline]
  20. Naiki H, Higuchi K, Shimada A, Takeda T, Nakakuki K, 1993. Genetic analysis of murine senile amyloidosis. Lab Invest 68:332-337. [Medline]
  21. Higuchi K, Naiki H, Kitagawa K, et al. 1995. Apolipoprotein A-II gene and development of amyloidosis and senescence in a congenic strain of mice carrying amyloidogenic ApoA-II. Lab Invest. 72:75-82. [Medline]
  22. Lorenzo A, Razzaboni B, Weir GC, Yankner BA, 1994. Pancreatic islet cell toxicity of amylin associated with type-2 diabetes mellitus. Nature. 368:756-760. [Medline]
  23. Lorenzo A, Yankner BA, 1996. Amyloid fibril toxicity in Alzheimer's disease and diabetes. Ann NY Acad Sci. 777:89-95. [Medline]
  24. Higuchi K, Kitado H, Kitagawa K, Kogishi K, Naiki H, Takeda T, 1993. Development of congenic strains of mice carrying amyloidogenic apolipoprotein A-II (Apoa2C): Apoa2C reduces the plasma level and size of high density lipoprotein. FEBS Lett. 317:207-210. [Medline]
  25. Higuchi K, Wang J, Kitagawa K, et al. 1996. Accelerated senile amyloidosis induced by amyloidogenic apoA-II gene shortens the life span of mice but does not accelerate the rate of senescence. J Gerontol Biol Sci. 51A:B295-B302. [Abstract]
  26. Wang J, Kitagawa K, Kitado H, et al. 1997. Regulation of the metabolism of plasma lipoproteins by apolipoprotein A-II. Biochim Biophys Acta. 1345:248-258. [Medline]
  27. Takeshita S, Hosokawa M, Irino M, et al. 1982. Spontaneous age-associated amyloidosis in Senescence-Accelerated Mouse (SAM). Mech Ageing Dev. 20:13-23. [Medline]
  28. Hoshii Y, Kawano H, Cui D, et al. 1997. Amyloid A protein amyloidosis induced in apolipoprotein-E-deficient mice. Am J Pathol. 151:911-917. [Abstract]
  29. Gompertz B, 1852. On the nature of the function expressive of the law of human mortality, and on a new mode of determining the value of life contingencies. Philos Trans R Soc London. 115:513-585.
  30. Finch CE, 1990. Longevity, Senescence, and the Genome The University of Chicago Press, Chicago.
  31. Hosokawa M, Kasai R, Higuchi K, et al. 1984. Grading score system: a method for evaluation of the degree of senescence in senescence accelerated mouse (SAM). Mech Ageing Dev. 26:91-102. [Medline]
  32. Hosokawa M, 1994. Grading score system; a method of evaluation of the degree of senescence in Senescence-accelerated Mouse (SAM). Takeda T, , ed.The SAM Model of Senescence 23-28. Excerpta Medica, Amsterdam.
  33. Steel RGD, Torrie JH, 1980. Principles and Procedures of Statistics: a Biometrical Approach McGraw Hill;, New York.
  34. Kaplan EL, Meier P, 1958. Nonparametric estimation from incomplete observation. J Am Stat Assoc. 53:457-481.
  35. Shoenfeld DA, 1981. The asymptotic properties of comparative test for comparing survival distributions. Biometrika. 68:316-319. [Abstract/Free Full Text]
  36. Togashi S, Lim SK, Kawano H, et al. 1997. Serum amyloid P component enhances induction of murine amyloidosis. Lab Invest. 77:525-531. [Medline]
  37. Mehrabian M, Lusis AJ, 1992. Genetic markers for studies of atherosclerosis and related risk factors. Lusis AJ, Rotter JI, Sparkes RS, , ed.Molecular Genetic of Coronary Artery Disease: Candidate Genes and Processes in Atherosclerosis 363-418. Skarger AG, Basel, Switzerland.
  38. Doolittle MH, LeBoeuf RC, Warden CH, Bee LM, Lusis AJ, 1990. A polymorphism affecting apolipoprotein A-II translational efficiency determines high density lipoprotein size and composition. J Biol Chem. 265:10380-10388.
  39. Lusis AJ, Taylor BA, Wangenstein RW, LeBoeuf RC, 1983. Genetic control of lipid transport in mice: II. Genes controlling structure of high density lipoproteins. J Biol Chem. 258:5071-5078. [Abstract/Free Full Text]
  40. Castellani LW, Navab M, Lenten BJV, et al. 1997. Overexpression of apolipoprotein A-II in transgenic mice converts high density lipoproteins to proinflammatory particles. J Clin Invest. 100:464-474. [Medline]
  41. Naiki H, Higuchi K, Yonezu T, Hosokawa M, Takeda T, 1988. Metabolism of senile amyloid precursor and amyloidogenesis: age-related acceleration of apolipoprotein A-II clearance in the senescence accelerated mouse. Am J Pathol 130:579-587. [Abstract]
  42. Kitagawa K, Naiki H, Takeda T, Higuch K, 1994. Age-associated decrease in the mRNA levels and the rate of synthesis of apoA-II in murine senile amyloidosis. Lab Invest. 70:565-571. [Medline]
  43. Chiba T, Kogishi K, Wang J, Xia C, et al. 1999. Mouse senile amyloid deposition is suppressed by adenovirus-mediated overexpression of amyloid-resistant apolipoprotein A-II. Am J Pathol. 155:1319-1326. [Abstract/Free Full Text]




This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Wang, J.
Right arrow Articles by Higuchi, K.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Wang, J.
Right arrow Articles by Higuchi, K.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
All GSA journals The Gerontologist
Journals of Gerontology Series B: Psychological Sciences and Social Sciences