ABSTRACT
BACKGROUND: Caspase-3 is well recognized as the key caspase carrying out apoptosis in animal and human brain. To date, a few studies revealed the expression of caspase-3 protein in brains of normal persons and Alzheimer patients but data obtained from rodents exhibited much discrepancy.OBJECTIVE: To investigate the different expression patterns of caspase-3in rodent and monkey brain, and the different expression of caspase-3 in different brain regions and during aging in monkeys.DESIGN: Parallel comparison between means of single variable.SETTING: Institute of Hepatobiliary Surgery, Chinese PLA General Hospital and Department of Anatomy, the Chinese University of Hong Kong.MATERIALS: The experiment was carried out from August, 2003 to February, 2005 in Institute of Hepatobiliary Surgery, Chinese PLA General Hospital and Department of Anatomy, the Chinese University of Hong Kong. Sprague Dawley rats, ICR mice and senescence-accelerated mice (SAM) with ages ranging from postnatal 2, 12, 24 to 48 weeks(n=5 for each age group of different rodents) were included in the present study. All of these animals were supplied by Laboratory Animal Services Center, the hinese University of Hong Kong. Totally 8 rhesus monkeys aged 4 years (n=4) or 20 years (n=4) were selected from the Laboratory Animal Center in Chinese PLA General Hospital [SCXK-(Beijing)2003-002]. Both ro dents and monkeys were female and were raised under standard conditions without any experimental interventions. METHODS: ①Brain tissue samples were taken freshly from both rodents and monkeys and made into homogenate. The expression of caspase-3 pro tein in brains of both rodents and monkeys was investigated with im munoblot. ② The expression levels in monkey brains were exhibited quantitatively with the same method in three brain regions, such as the frontal cortex, hippocampus and cerebellar cortex, for the two age-groups. In vivo distribution patterns of caspase-3-immunoreactive cells were further presented in 3 brain regions of monkeys through immunohistochemistry. MAIN OUTCOME MEATURES: ①Detection of caspase-3 protein with immunoblot in the brain of rodents and monkeys; ② Distribution patterns of caspase-3-immunoreactive cells in 3 brain regions of monkeys. RESULTS: ① Result of detection with immunoblot: The same pattern of caspase-3 protein expression in brain of three kinds of 2-week-old rodents. But the expression was not seen in any other brains of older ages. Caspase 3 was expressed in a relatively high level inboth adult and aged monkey brains, and the amount did not attain to the level in 2-week-old rodents. Caspase-3 Was expressed in the pattern of zymogen (Mr 32 000). The ex pressions of caspase-3 in brains of monkey were not different in ages and brain regions. ②Result of Immunohistochemistry: It was showed that most neurons in the frontal cortex lack detectable caspase-3 immunoreactivity, whereas low to moderate caspase-3 immunostaining be found mainly in pyramidal cells in CA1, CA3 and CA4 subfields of hippocampus. And in the cerebellum, a small number of Purkinje cells were strongly stained in their cytosol and dendrites. Age-related expression pattern of caspase-3 were not found except that in the motor cortex of aged monkeys in which there were a limited number of large pyramidal cells in layer Ⅴ that were strongly stained with caspase-3 antibody.③ Immunoblot procedure revealed that the caspase-3 protein expressed in monkey brains is in the form of zymogen (Mr 32 000) and there is no significant difference in caspase-3 expression level as a function of either brain region or age of animals.CONCLUSION: Unlike rodents in which caspase-3 protein rapidly drops to an undetectable level since animals grow up, the primate expresses caspase-3 constitutively in brain until the late period of lifetime. But there are no significant brain region- or age-related differences in the protein levels in monkey brain.
