Ovocystatin Induced Changes in Expression of Alzheimer's Disease Relevant Proteins in APP/PS1 Transgenic Mice

Abstract

Background: Ovocystatin is marked by structural and biological similarities to human cystatin C, which plays an important role in the course of neurodegenerative diseases. Recently, it has been shown that ovocystatin might prevent aging-related cognitive impairment in rats and reduce memory decline in an APP/PS1 mice model. Thus, this study aimed to assess the effect of ovocystatin on histopathological changes in APP/PS1 mice. Materials and methods: Ovocystatin was administered intraperitoneally for four weeks (40 μg/mouse) to 35-weeks-old transgenic (AD, n = 14) and wild type (NCAR, n = 15) mice (stock B6C3-Tg(APPswe, PSEN1dE9)85Dbo/Mmjax). A histopathological evaluation comprised antibodies directed against β-amyloid (1:400, SIG-39320-1000, Covance) and Tau (1:4000, AHB0042, Invitrogen). Three regions of the hippocampus— the dentate gyrus (DG) and the cornu ammonis (CA1 and CA3)—were analyzed by immunohistochemistry in each animal. All differences are expressed as percentage relative to the control group. Results: The main results showed that the percentage of immunoreactive area of β-amyloid, tau protein deposits in APP/PS1+ovCYS was decreased in DG, CA1, and CA3 regions compared with the APP/PS1 control, respectively (p < 0.05). Conclusions: Ovocystatin caused significant changes in the expression pattern of all investigated proteins in hippocampal tissues both in APP/PS1 and NCAR mice.

Keywords: Alzheimer’s disease; chicken cystatin; cystatin C; mice; ovocystatin.

Figure 1

Immunoreactive area (percentage of the total area measured) of β-amyloid (a) and tau (b) burden in three hippocampal regions. (a) the burden of β-amyloid significantly decreased in the ovocystatin-treated transgenic group within all analyzed regions of the hippocampus, (b) deposits of misfolded tau protein significantly decreased in both non-carrier and transgenic ovocystatin-treated groups within all analysed hippocampal regions. NCAR—non-carrier group, NCAR+ovCYS—ovocystatin-treated non-carrier group, APP/PS1—transgenic group, APP/PS1+ovCYS—ovocystatin-treated transgenic group. Statistical significance of treated ovCYS versus untreated groups was indicated as * at p < 0.05, ** at p < 0.01, and *** at p < 0.001 within the respective hippocampal region.

Figure 2

Representative images of immunohistochemical reactions indicating β-amyloid (A,B) and TAU-5 (C,D) antigen expression were carried out on APP/PS1 + ovCYS group (A,C) and NCAR control (B,D) mouse brain. Nuclei are stained using hematoxylin. Magnification ×200 (A,B) and ×400 (C,D and insert).