Comparison of catalase immunoreactivity in the hippocampus between young, adult and aged mice and rats

Abstract

Catalase (CAT) is an important antioxidant enzyme and is crucial in modulating synaptic plasticity in the brain. In this study, CAT expression as well as neuronal distribution was compared in the hippocampus among young, adult and aged mice and rats. Male ICR mice and Sprague Dawley rats were used at postnatal month (PM) 1, PM 6 and PM 24 as the young, adult and aged groups, respectively (n=14/group). CAT expression was examined by immunohistochemistry and western blot analysis. In addition, neuronal distribution was examined by NeuN immunohistochemistry. In the present study, the mean number of NeuN‑immunoreactive neurons was marginally decreased in mouse and rat hippocampi during aging, although this change was not identified to be significantly different. However, CAT immunoreactivity was significantly increased in pyramidal and granule neurons in the adult mouse and rat hippocampi and was significantly decreased in the aged mouse and rat hippocampi compared with that in the young animals. CAT protein levels in the hippocampus were also lowest in the aged mouse and rat hippocampus. These results indicate that CAT expression is significantly decreased in the hippocampi of aged animals and decreased CAT expression may be closely associated with aging.

Figure 1

NeuN immunohistochemistry in the hippocampus of the (A) mice and (B) rats in the young, adult and aged groups. The distribution pattern and numbers of NeuN-immunoreactive neurons are not significantly different among all of the groups. GCL, granule cell layer; ML, molecular layer; PL, polymorphic layer; SO, stratum oriens; SP, stratum pyramidale; SR, stratum radiatum; DG, dentate gyrus. Scale bar, 400 µm (a–c) and 100 µm (d–l). (m) Mean percentage of NeuN-immunoreactive neurons in the hippocampus (n=7 per group). The bars indicate the mean ± standard error of the mean.

Figure 2

CAT immunohistochemistryin the hippocampus of the (A) mice and (B) rats in the young, adult and aged groups. CAT immunoreactivity is highest in the adult group and lowest in the aged group. GCL, granule cell layer; ML, molecular layer; PL, polymorphic layer; SO, stratum oriens; SP, stratum pyramidale; SR, stratum radiatum; DG, dentate gyrus. Scale bar, 400 µm (a–c) and 100 µm (d–l). (m) ROD as % of CAT-immunoreactive structures in the hippocampus (n=7 per group). ^*P<0.05, compared with the young group and ^†P<0.05, compared with the adult group. The bars indicate the mean ± standard error of the mean. ROD, relative optical density.

Figure 3

Western blot analysis of catalase (~60 kDa) in the hippocampus of the young, adult and aged mice and rats. The ROD as percentage of the immunoblot band is presented (n=7 per group). ^*P<0.05, compared with the young group, ^†P<0.05, compared with the adult group. The bars indicate the mean ± standard error of the mean. ROD, relative optical density.