Lipoxygenases and other stress response proteins in experimental models of Alzheimer’s disease. Searching for promising targets in neuroprotection

It is proposed that oxidative stress, amyloid β oligomers (AβO) and alterations of ceramide metabolism/level may play a crucial role in pathogenesis and in mechanism of Alzheimer’s disease (AD). This study focused on the expression of genes encoded lipoxygenases and other prooxidative/antioxidative enzymes and proteins in experimental models of AD. The study were carried out on in vivo model: FVB/APP+ transgenic (Tg) mice with London APP mutation (V7171), and control FVB/APP-mice; and in vitro model: PC12 cells transfected with human wild type APP (APPwt) or bearing double Swedish mutation (APPsw) and control PC12 cells transfected with empty vector. The PC12 cells were subjected also to additional stress evoked by ceramide. The effect of selected pharmacological compounds was investigated. Molecular biology and biochemical methods were applied. Our study carried out on Tg mice demonstrated alterations of gene expression and protein level for prooxidative enzymes such as 12- and 5-lipoxygeneses (12-LOX, 5-LOX) and nitric oxide synthase (NOS) in hippocampus and brain cortex. The anti-oxidative enzymes: SOD1 and SOD2 expression was not changed. However, mRNA and protein level of mitochondrial apoptosis inducing factor (AIF), crucial player in antioxidative defense and regulator of cells survival or death, was significantly upregulated, which may suggest its protective function in this conditions. Moreover, the transcription of subunits of all ETC complexes was not altered. The further analysis of molecular processes carried out on cell cultures indicated that ceramide induces AIF release from mitochondria and affects transcription of mitochondria sirtuins. Ceramide in APP transfected PC12 cells enhanced gene expression for BACE1 and subunits of secretase γ and significantly decreased cells viability. Agonist of S1P receptor, SEW 278 protects the cells against ceramide and Aβ toxicity. Our study suggest that 12-LOX and 5-LOX and S1P receptor 1 should be promising targets for improvement of AD therapy.