## 2 Results  
Effects of Selected Statins or M\(\beta\)CD on Cell Viability of Neuronal PC-12 Cells Overexpression Wild-Type or Mutated (Swedish Mutation) A\(\beta\)PP Gene  
Atorvastatin (50 \(\upmu\)M, ATR), simvastatin (50 \(\upmu\)M, SIM) or methyl-\(\beta\)-cyclodextrintrim (0.2 mM, M\(\beta\)CD) were used in one-day treatment (24 h) in PC-12 neuronal cells with _A\(\beta\)PP_-wt, _A\(\beta\)PP_-sw or mock-transfected cells. This experiment demonstrated higher susceptibility (lower cell viability) of _A\(\beta\)PP_-wt transfected cells to HMGER inhibitors, but not to M\(\beta\)CD when compared to non-treated control cells (\(p<0.001\), Figure 1A). Additionally, _A\(\beta\)PP_-sw gene rendered PC-12 neuronal cells highly vulnerable to any statin or M\(\beta\)CD (\(p<0.05\)-0.001, Figure 1A). To reverse the effects of ATR, SIM or M\(\beta\)CD, which caused cholesterol depletion, water soluble cholesterol (1 mM, Chol-PEG) was co-administered. The protective effect of Chol-PEG was hardly observed, it does evenly strengthen M\(\beta\)CD-induced loss in cell viability with regard to non-treated control cells (\(p<0.001\), Figure 1B). Figure 1: Effect of water-soluble cholesterol (Chol-PEG, 1 mM) on cell viability affected by mevalonate (MEV) pathway modulators (atorvastatin – ATR, simvastatin – SIM, 50 uM each) or cholesterol chelator methyl-\(\beta\)-cyclodextrintrim (M\(\beta\)CD, 0.2 mM). One day (24 h) treatment with **(A)** ATR or SIM (50 uM) or M\(\beta\)CD (0.2 mM) alone or **(B)** together with Chol-PEG. Bar charts show percentage (% control) cell viability measured by [3-(4,5-dimethylthiazol-2-yl)-2-5-diphenyltetrazolzolium bromide] (MTT) assay. Two-way ANOVA test followed by [PERSON]’s multiple comparisons was employed to analyze the data. **(A)** ATR, SIM or M\(\beta\)CD dose-dependently diminished fraction of viable cells. Except M\(\beta\)CD, neither _A\(\beta\)PP_-wt, nor Swedish mutation _A\(\beta\)PP_-sw gene affected ATR- or SIM-dependent effects on viable cells in comparison to empty-vector transfected cells. The results amounted to: \(p<0.0302\) for interaction, \(p<0.1409\) for genes, \(p<0.0001\) for ATR; \(p<0.0629\) for interaction, \(p<0.338\) for genes, \(p<0.0001\) for SIM; \(p<0.0343\) for interaction, \(p<0.0024\) for genes, \(p<0.0667\) for M\(\beta\)CD. **(B)** Adding Chol-PEG could not rescue ATR, or SIM, or M\(\beta\)CD diminished viable cells. Both _A\(\beta\)PP_-wt and Swedish mutation _A\(\beta\)PP_-sw genes affected Chol-PEG-dependent effects on viable cells in comparison to empty-vector transfected cells. The results amounted to: \(p=0.5034\) for interaction, \(p<0.0117\) for genes, \(p<0.0001\) for Chol-PEG. Error bars = S.E.M., and \({}^{*}p<0.05\), \({}^{**}p<0.01\), \({}^{***}p<0.001\) for comparison with non-treated control cells. The results are indicative of three independent experiments performed in eight replicates. Effect of Some Non-Sterol Isoprenoids on Cell Viability of Neuronal PC-12 Cells Overexpression Wild-Type or Mutated (Swedish Mutation) AgPP Gene Treated with Selected Statins or M\(\beta\)CD  
Statins inhibit HMGCR, the rate-limiting enzyme of the MEV pathway. As HMGCR inhibitors, statins limit MEV entry for several intermediary metabolic pathways, such as synthesis of non-sterol isoprenoids (geranylgeraniol, farnesol, dolichol, ubiquinol), as well as cholesterol. The effects of different non-sterol isoprenoids were tested herein (mevalonate - MEV 100 uM, geranylgeraniol - GGGH 10 uM, farnesol - FOH 10 uM, dolichol - DOH 0.1 ug/mL, ubiquinol - UBOH 10 ug/mL) vs. cholesterol as water soluble conjugate Chol-PEG (1 mM) in cell cultures challenged with statins or cholesterol chelator methyl-\(\beta\)-cyclodextrintrin (M\(\beta\)CD, Supplementary data 2). Metabolic inhibitors of selected enzymes in the MEV pathway were also monitored via the [3-(4,5-dimethylthiazol-2-yl)-2-5-diphenyltetrazolzolium bromide] (MTT) assay (Supplementary data 3). Initially, the cytoprotective effect of MEV pathway intermediates was evaluated.