The effects of catalase and kisspeptin overexpression on amyloid peptide toxicity
Amyloid β (Aβ) is the major component of the senile plaques in Alzheimer’s disease (AD). The mechanism underlying cell death in AD includes oxidative stress, apoptosis, impaired mitochondrial function and receptor mediated effects. Compounds that specifically bind to Aβ are neuroprotective. Catalase is an antioxidant enzyme that specifically binds Aβ. Kisspeptin (KP) is a product of the KiSS-1 gene and contains an Aβ binding domain, which also interacts with Aβ. The localization of catalase, KP and Aβ in the AD brain plus the effects of catalase and KiSS-1 overexpression in neuronal cells were investigated in the present study. Tissue sections from the AD pons region were immunohistochemically stained to determine if catalase or KP colocalized with Aβ deposits. The immunohistochemistry results show that immunoreactive KP or immunoreactive catalase co-localizes with immunoreactive Aβ in AD pons sections. These results suggest that endogenous catalase and KP could play neuroprotective roles in AD. Catalase and KiSS-1 overexpressing gene models were created by stably transfecting human catalase and KiSS-1 constructs into SH-SY5Y cells and overexpression confirmed by RT-PCR, immunocytochemistry and Western blotting. The effects of Aβ and H2O2 on cell viability were determined by either MTT (3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) or trypan blue assay. Catalase overexpressing SH-SY5Y neurons showed a reduced susceptibility to Aβ and H2O2 toxicity compared to vector control cells. The catalase overexpression neuroprotection could by reduced by the catalase activity inhibitor 3-Amino-1,2,4-triazole and an inhibitor of catalase-Aβ interactions benzothiazole aniline-tetra (ethylene glycol). The KiSS-1 overexpressing SH-SY5Y neurons also showed a reduced susceptibility to Aβ and H2O2 toxicity compared to vector control cells. The KiSS-1 overexpression neuroprotection could by reduced by an anti-KP antibody, the oyxtocin antagonist atosiban and the cyclooxygenase inhibitor SC-560. In conclusion, both catalase and KP colocalize with Aβ in AD pons sections and overexpression of catalase or KiSS-1 is neuroprotective against Aβ toxicity.
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