Her the association between SAP and toxic TTR aggregates might have functional consequences. We used the human neuroblastoma cell line IMR-32, which has been established as a model for studies of TTR toxicity, and WST-assay to measure cytotoxic effects. Cells in the medium without the addition of TTRs or SAP served as control and their viability was arbitrarily set at 100 , meaning no (i.e. 0 ) toxicity. All Tetracosactrin site toxicity data are shown as percentage change relative to control (for details of calculations, see Material and Methods). In the experiment, SAP was co-incubated with different concentrations of either TTR-A or TTR-D. After 12 h in culture, both mutants induced cell death in a dose-dependent manner with the maximum toxicity reached within the 5?0 mM range of TTR concentration. SAP atSAP and Aggregation-Induced Cell Death3 mM totally inhibited the toxic response of the neuroblastoma cell line IMR-32 to pre-fibrillar aggregates of either TTR-A or TTRD (Fig. 2A). Interestingly, this protective feature was unique to SAP since none of several other amyloid-associated molecules, i.e. hyaluronic acid, chondroitin sulfate A, B and C, or the pentraxin family member CRP, had any effect on the TTR-induced toxicity (Fig. S1). It has been reported that amyloid toxicity is dependent on free radical production, and increased 101043-37-2 levels of H2O2 and lipid peroxides have been shown to accumulate in cells exposed toseveral amyloidogenic peptides [36,37]. Antioxidants such as vitamin E or catalase, a potent scavenger of H2O2, have been shown previously to block both Ab- and TTR-induced toxic responses in the IMR-32 cell line [34]. We therefore tested whether SAP can rescue IMR-32 cells from the oxidative stress induced by increasing doses of H2O2 (0? mM). The cells that were exposed to 0.05 mM H2O2 showed some toxic responses measured after 24 h with WST-1 assay; this toxic effect reached its maximum at H2O2 concentrations between 1 and 5 mM. When catalase (1,000 U/ml) was added to IMR-32 cells in the presenceFigure 2. Effects of SAP on amyloidogenic aggregates. (A) The effect of SAP on TTR-induced toxicity. IMR-32 cells were incubated with the indicated concentrations of either TTR-A (m) or TTR-D ( ) for 12 h. Solid lines represent the toxic response when cells were incubated with the respective proteins, and dashed lines represent experiments with the addition of 3 mM SAP. One-way ANOVA with sequential Bonferroni post-hoc test revealed significant protective effects of SAP on cells in the presence of either TTR-A or TTR-D (P = 0.004 and P = 0.003, respectively) (B) The effect of SAP on H2O2-induced cytotoxicity. IMR-32 cells were treated with different concentrations of H2O2 (in the range 0? mM) without addition of ( ) or in the presence of 1,000 U/ml catalase (m) or 3 mM SAP ( ). Oxidative stress-induced toxicity in IMR-32 cells was significantly reduced by catalase treatment (P,0.001; one-way ANOVA, sequential Bonferroni post-hoc test) but not by SAP treatment (P = 0.4). Error bars indicate SD. doi:10.1371/journal.pone.0055766.gN NSAP and Aggregation-Induced Cell Deathof H2O2, oxidative damage was blocked and the cells remained as metabolically active as in the controls without H2O2, catalase, or SAP. Importantly, in contrast to the positive result obtained with catalase, we were unable to demonstrate that SAP could block H2O2-induced cell death, thus excluding SAP as an oxidative stress scavenger (Fig. 2B).against tubulin levels; represented by bars i.Her the association between SAP and toxic TTR aggregates might have functional consequences. We used the human neuroblastoma cell line IMR-32, which has been established as a model for studies of TTR toxicity, and WST-assay to measure cytotoxic effects. Cells in the medium without the addition of TTRs or SAP served as control and their viability was arbitrarily set at 100 , meaning no (i.e. 0 ) toxicity. All toxicity data are shown as percentage change relative to control (for details of calculations, see Material and Methods). In the experiment, SAP was co-incubated with different concentrations of either TTR-A or TTR-D. After 12 h in culture, both mutants induced cell death in a dose-dependent manner with the maximum toxicity reached within the 5?0 mM range of TTR concentration. SAP atSAP and Aggregation-Induced Cell Death3 mM totally inhibited the toxic response of the neuroblastoma cell line IMR-32 to pre-fibrillar aggregates of either TTR-A or TTRD (Fig. 2A). Interestingly, this protective feature was unique to SAP since none of several other amyloid-associated molecules, i.e. hyaluronic acid, chondroitin sulfate A, B and C, or the pentraxin family member CRP, had any effect on the TTR-induced toxicity (Fig. S1). It has been reported that amyloid toxicity is dependent on free radical production, and increased levels of H2O2 and lipid peroxides have been shown to accumulate in cells exposed toseveral amyloidogenic peptides [36,37]. Antioxidants such as vitamin E or catalase, a potent scavenger of H2O2, have been shown previously to block both Ab- and TTR-induced toxic responses in the IMR-32 cell line [34]. We therefore tested whether SAP can rescue IMR-32 cells from the oxidative stress induced by increasing doses of H2O2 (0? mM). The cells that were exposed to 0.05 mM H2O2 showed some toxic responses measured after 24 h with WST-1 assay; this toxic effect reached its maximum at H2O2 concentrations between 1 and 5 mM. When catalase (1,000 U/ml) was added to IMR-32 cells in the presenceFigure 2. Effects of SAP on amyloidogenic aggregates. (A) The effect of SAP on TTR-induced toxicity. IMR-32 cells were incubated with the indicated concentrations of either TTR-A (m) or TTR-D ( ) for 12 h. Solid lines represent the toxic response when cells were incubated with the respective proteins, and dashed lines represent experiments with the addition of 3 mM SAP. One-way ANOVA with sequential Bonferroni post-hoc test revealed significant protective effects of SAP on cells in the presence of either TTR-A or TTR-D (P = 0.004 and P = 0.003, respectively) (B) The effect of SAP on H2O2-induced cytotoxicity. IMR-32 cells were treated with different concentrations of H2O2 (in the range 0? mM) without addition of ( ) or in the presence of 1,000 U/ml catalase (m) or 3 mM SAP ( ). Oxidative stress-induced toxicity in IMR-32 cells was significantly reduced by catalase treatment (P,0.001; one-way ANOVA, sequential Bonferroni post-hoc test) but not by SAP treatment (P = 0.4). Error bars indicate SD. doi:10.1371/journal.pone.0055766.gN NSAP and Aggregation-Induced Cell Deathof H2O2, oxidative damage was blocked and the cells remained as metabolically active as in the controls without H2O2, catalase, or SAP. Importantly, in contrast to the positive result obtained with catalase, we were unable to demonstrate that SAP could block H2O2-induced cell death, thus excluding SAP as an oxidative stress scavenger (Fig. 2B).against tubulin levels; represented by bars i.
