Kab Ryong Chae

Alterations in behavior, amyloid β-42, caspase-3, and Cox-2 in mutant PS2 transgenic mouse model of Alzheimer’s disease

Alzheimers disease (AD) occurs when neurons in the memory and cognition regions of the brain are accompanied by an accumulation of the long amyloid p‐proteins of the 39 to 43 amino acids derived from the amyloid precursor protein (APP) by cleavage with p‐and γ‐secretase. An increased production of Ap‐42 by mutation of PS2 genes promotes caspase expression and is associated with the Cox‐2 found in the brain of AD patients. To address this question in vivo, we expressed the human mutant PS2 (hPS2m) (N141I) as well as wild PS2 (hPS2w) as a control in transgenic (Tg) mice under control of the neuron‐specific enolase (NSE) promoter. Water maze tests were used to demonstrate the behavioral defect; dot blot, Western blot, and immunohistochemical analyses were performed on the brain with the hPS2, Ap‐42, caspase‐3, and Cox‐2 antibody. We concluded that 1) Tg mice showed a behavioral dysfunction in the water maze test, 2) levels of hPS2, Ap‐42, caspase‐3, and Cox‐2 expression were modulated in the brains of both Tg mice, 3) dense staining with antibody to hPS2, Ap‐42, caspase‐3, and Cox‐2 was visible in the brains of Tg mice compared with age‐matched control mice, and 4) distinguishable AD phenotypes between hPS2w‐and hPS2m‐Tg mice did not appear. These results suggest that an elevation of Ap‐42 by overexpression of hPS2 and mutation of hPS2m might induce the behavioral deficit and caspase‐3 and Cox‐2 induction, which could be useful in the therapeutic testing of compounds to have considerable clinical effects.—Hwang, D. Y., Chae, K. R., Kang, T. S., Hwang, J. H., Lim, C. H., Kang, H. K., Goo, J. S., Lee, M. R., Lim, H. J., Min, S. H., Cho, J. Y., Hong, J. T., Song, C. W., Paik, S. G., Cho, J. S., Kim, Y. K. Alterations in behavior, amyloid p‐42, caspase‐3, and Cox‐2 in mutant PS2 transgenic mouse model of Alzheimers disease. FASEB J. 16, 805–813 (2002)

Aberrant expressions of pathogenic phenotype in Alzheimer's diseased transgenic mice carrying NSE-controlled APPsw

Mutations in the APP gene lead to enhanced cleavage by the beta- and gamma-secretase, and increased Abeta formation, which are tightly associated with Alzheimers disease (AD)-like neuropathological changes. To examine whether depositions of Abeta by APP mutations are increased, and if this is associated with potential pathogenic phenotypes, the APPsw was expressed in a transgenic line under the control of the neuron-specific enolase (NSE) promoter. A behavioral dysfunction was shown at 12 months, and intensive staining bands, with APP and Abeta-42 antibodies, were visible in the brains of transgenic mice. Of the MAPK family, both JNK and p38 were activated in the brains of transgenic mice, whereas there was no significant activation of the ERK. In parallel, tau phosphorylation was also enhanced in the transgenic relative to the control mice. Moreover, the Cox-2 levels, from Western blot and immunostaining, were increased in the brains of the transgenic line. Furthermore, there were significant caspase-3- and TUNEL-stained nuclei in the transgenic line compared to the age-matched control mice. Thus, these results suggest that NSE-controlled APPsw transgenic mice appear to be a more relevant model in neuropathological phenotypes of AD, and thus could be useful in developing new therapeutic treatments for targeting the aberrant phenotypes that appear in these mice.

Role of dietary fat type in the development of adiposity from dietary obesity-susceptible Sprague–Dawley rats

The present study was designed to define how dietary fat type regulates body adiposity in dietary obesity-susceptible (DOS) Sprague-Dawley (SD) rats. Eighty-three SD rats received a purified diet containing 50 g maize oil (MO)/kg for 3 weeks and then thirty-nine of the rats, designated as the DOS rats, were allotted to diets containing 160 g MO (DOS-MO), beef tallow (DOS-BT) or fish oil (DOS-FO)/kg for 9 weeks. As a result of the experiment, the DOS-FO rats had significantly (P<0.05) reduced weight gain and abdominal and epididymal fat-pad mass than the DOS-MO and DOS-BT rats. Serum leptin level was also significantly (P<0.05) lower in the DOS-FO rats; however, hypothalamic leptin receptor (a and b) mRNA and neuropeptide Y expressions were not altered by dietary fat sources. A lower acetyl-CoA carboxylase mRNA expression in the liver was observed in the DOS-FO group, whereas hepatic peroxisome proliferator-activated receptor-gamma mRNA and protein expressions were markedly elevated in the DOS-FO group compared with those in the other groups. We did not observe differences in acetyl-CoA carboxylase and peroxisome proliferator-activated receptor-gamma expressions in epididymal fat of the DOS rats consuming MO, BT or FO. It is concluded from our present observations that dietary fat type, especially that rich in FO, plays a potential role in down-regulation of adiposity by altering hepatic lipogenic genes, rather than feeding behaviour, in the DOS-SD rats.

Differential expression of the tetracycline-controlled transactivator-driven human CYP1B1 gene in double-transgenic mice is due to androgens: application for detecting androgens and antiandrogens.

Differential expression of the tetracycline-controlled transactivator (tTA)-driven human cytochrome p450 (CYP) 1B1 gene was found in the livers of male mice, at high levels in neonates, but at low levels in adults. The goals of this study were to determine whether the differential expression of the tTA-driven human CYP1B1 (hCYP1B1) gene in neonates and adults was testosterone dependent and whether flutamide, a representative potent antiandrogen, led to the induction of hCYP1B1. This was tested by treating castrated transgenic mice with testosterone propionate and musk extracts. It was concluded that: (i). the levels of expression of both tTA and hCYP1B1 gradually declined, with clear changes being apparent between 2 and 4 weeks of age, (ii). castration of adult males resulted in the increased expressions of both tTA and hCYP1B1 to levels similar to those found in adult females, (iii). treatment of castrated male and adult female mice with testosterone propionate and musk extracts led to the restoration of the levels of expression of hCYP1B1 in the adult males, and (iv). treatment of adult males with flutamide caused an increase in the levels of expression of hCYP1B1 in the adult females, as indicated by the antiandrogenic activity. Thus, the differential expression of the tTA-driven hCYP1B1 gene in the transgenic mice was caused by androgen, and it is possible that castrated male and adult female mice expressing the tTA-controlled hCYP1B1 could be used as the basis for a strategy for the detection of androgens and antiandrogens.

The effects of long-duration, low-temperature ground transportation on physiological and biochemical indicators of stress in mice.

Transportation can cause stress to laboratory animals and alter physiological characteristics that may confound experimental results. The authors investigated stress-related effects of 3–4 h of transportation by truck in two strains of mice (C57BL/6, which are known to be aggressive, and ICR, which are less aggressive). Transported mice had sufficient space and access to water, though temperature in the truck was lower than what is usually recommended. Transportation affected the following parameters in both strains of mice: (i) serum corticosterone concentrations, (ii) expression of the chaperone proteins Hsp70 and Grp78 in various tissues and (iii) concentrations of serological enzymes that are associated with liver disease. These parameters also differed substantially between the two strains of mice.

PEN-2 overexpression induces γ-secretase protein and its activity with amyloid β-42 production

PEN-2 is a component of the γ-secretase complex, which is involved in the cleavage of the β-amyloid precursor protein. The aim of this study was to determine the mechanism by which PEN-2 overexpression regulates γ-secretase expression and the production of Aβ-42. In order to determine this, a hybrid gene harboring human PEN-2 was constructed, and used in the transfection of SK-N-MC human neuroepitheliomal cells. This cell line was also co-transfected with a combination of human mutant presenilin 2 (hPS2m) and APPsw. Our results indicated that (i) human PEN-2 overexpression induced an increase in γ-secretase activity and its proteins, including PS1-CTF, APH-1, and nicastrin, thus production of Aβ-42, (ii) co-transfection of human PEN-2 with both hPS2m and APPsw exerted no more profound effects on the induction of γ-secretase proteins and its activity than did transfection with hPEN-2 alone. Thus, PEN-2 overexpression may facilitate assembly into the more active γ-secretase complex, and may also induce an increase in activity, thus affecting Aβ-42 production.

Differential Effect of 7,12-Dimethylbenz[a]anthracene on Human and Mouse CYP1B1 from Livers of Castrated Transgenic Mice

Humanized transgenic mice coexpressing tetracycline-controlled transactivator (tTA) and human cytochrome P450 1B1 (CYP1B1) (hCYP1B1) have been created by this group. The aims of this study was to determine if 7,12-dimethylbenz[a]anthracene (DMBA) functions as testosterone or doxycycline in its ability to induce or reduce expression of hCYP1B1 or endogenous mouse CYP1B1 (mCYP1B1). This was tested in the livers by treating castrated transgenic males and hCYP1B1/luciferase-transfected cells with DMBA. Herein, DMBA-treated group exhibited (i) gradual reduction of hCYP1B1 expression at the transcript, protein, and activity levels but gradually induced its transcript level during DMBA release; (ii) gradual reduction of hCYP1B1 at the transcript and protein levels, as in the case of doxycycline or testosterone; (iii) gradual induction of mCYP1B1 expression at the transcript and protein levels but gradually reduced its transcript level during DMBA release. In parallel, DMBA-treated transfected cells exhibited gradual increase in luciferase activity in a time- and dose-dependent manner. Thus, castrated transgenic males or in vitro system could be useful as models for the detection of polycyclic aromatic hydrocarbons (PAHs) or environmental toxicants by measuring either hCYP1B1 or mCYP1B1 expressions.