Figure 4
Both R-(−)-apomorphine and raloxifene protect cells from p-tau cytotoxicity. (a) and (b) Viability curves of SH-SY5Y cells treated with varying concentrations of p-tau and (a) R-(−)-apomorphine or (b) raloxifene. P-tau (without pre-aggregation) and compounds were added together to cells. Cell viability was quantified by FDA and PI differential staining 24 h later. The red dash lines indicate 50% viability, with which LD50 was derived. (c) Estimation of EC50 of R-(−)-apomorphine. SH-SY5Y cells were treated with 0.8-µM p-tau in the presence of 0–17 µM of R-(−)-apomorphine. Cellular viability was characterized as above and plotted against the compound concentration. Trend lines in panels (a)–(c) were obtained with the dose response curve fitting function of the software Origin (Origin Pro 8, OriginLab Corporation, Northampton, MA, USA). (d) Representative images of apoptotic cells after treatment of p-tau. SH-SY5Y cells were treated with 0.6 µM of p-tau for 12 h before harvesting for annexin V and PI staining. Under this sub-lethal dose of p-tau, apoptotic and live cells were easily detectable, allowing for the assessment of the effect of R-(−)-apomorphine. The white arrow shows a live cell with normal morphology. (e) R-(−)-apomorphine curtails the pro-apoptotic activity of p-tau. The percentage of apoptotic SH-SY5Y cells was quantified by annexin V and PI double staining of cells receiving 12 h of the indicated treatment under each column in the graph. Error bars are standard deviations; n = 3. Apo, R-(−)-apomorphine; Ann, annexin-V; PI, propidium iodide.
