Ysosomes, photo-oxidation of AO (Gurr, Poole, UK) was employed as described earlier [23]. AO is a metachromatic dye that, when excited by blue light, emits red fluorescence when highly concentrated inside lysosomes and green fluorescence when diluted in the cytosol [26]. Cells seeded on coverslips were incubated with AO (2 mg/ml) for 15 min at 37uC, washed with phosphate buffered saline (PBS), and placed on the stand of a Nikon Eclipse E600 laser scanning confocal microscope. AO was excited using a 488 nm light from a 100-mW diode laser, and loss of 
lysosomal proton gradient was followed by capturing laser scanning micrographs every 330 ms in a channel defined by bandpass filters for 495?55 nm. Green fluorescence intensity in 
pre-defined areas was subsequently analyzed using Volocity (PerkinElmer, Waltham, MA, USA) and plotted. The loss of lysosomal integrity was determined as the lag time from the start of blue laser irradiation until the rupture of lysosomes induced an increase of green fluorescence in the cytosol (Figure 3E).Viability analysisAfter treatment, cell cultures were morphologically examined in a phase contrast microscope and viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT; Calbiochem, San Diego, CA, USA) reduction assay. Cells were incubated with 0.25 mg/ml MTT for 2h at 37uC. The MTT solution was then removed and the formazan product dissolved in DMSO. The absorbance was measured at 550 nm. In addition, the amount of surviving and thus attached cells was determined using crystal FCCP violet staining. Cells were fixed in 4 paraformaldehyde for 20 min, followed by 0.04 crystal violet staining for 20 min at room temperature. The plates were washed thoroughly by dipping in H2O and subsequently air-dried. Samples were then solubilized in 1 Sodium dodecyl sulfate (SDS) before absorbance was measured at 550 nm. Caspase-3-like activity was analyzed using the substrate Ac-DEVD-AMC (Becton, Dickinson and Company, Franklin Lakes, NJ) according to the manufacturer’s instructions. Fluorescence was correlated to NHS-Biotin protein content.Statistical analysisAll experiments were repeated at least three times and the results are presented as the means and standard deviations of independent samples. Data were statistically evaluated using a nonparametric Kruskal-Wallis test, followed by Mann-Whitney U test for comparison of two groups. P values #0.05 were considered to be significant and marked with an asterisk in figures.Lipid measurementsUnesterified cholesterol content was measured in cell lysates using the Amplex Red Cholesterol Assay Kit (Invitrogen, Paisley, UK), as described by the manufacturer. Cholesterol amount was correlated to protein content. Sphingomyelin content was analyzed according to a previously described method [28].Supporting InformationFigure S1 Viability of human fibroblasts after MSDH 1326631 exposureImmunocytochemistryCells were prepared for immuno-cytochemistry as described elsewhere [20]. Antibodies against LAMP-2 (Southern Biotech, Birmingham, AL, USA), followed by antibodies conjugated to Alexa Fluor (Molecular Probes), were used. To visualize unesterified cholesterol, cells were stained with filipin (125 mg/ml; SigmaAldrich) for 1 h at room temperature. Cover slips were washed and mounted using Prolong gold (Invitrogen). Cells were examined using a Nikon Eclipse E600 laser scanning confocal microscope (Nikon, Tokyo, Japan) together with the EZC1 3.7 software (Nikon Instruments.Ysosomes, photo-oxidation of AO (Gurr, Poole, UK) was employed as described earlier [23]. AO is a metachromatic dye that, when excited by blue light, emits red fluorescence when highly concentrated inside lysosomes and green fluorescence when diluted in the cytosol [26]. Cells seeded on coverslips were incubated with AO (2 mg/ml) for 15 min at 37uC, washed with phosphate buffered saline (PBS), and placed on the stand of a Nikon Eclipse E600 laser scanning confocal microscope. AO was excited using a 488 nm light from a 100-mW diode laser, and loss of lysosomal proton gradient was followed by capturing laser scanning micrographs every 330 ms in a channel defined by bandpass filters for 495?55 nm. Green fluorescence intensity in pre-defined areas was subsequently analyzed using Volocity (PerkinElmer, Waltham, MA, USA) and plotted. The loss of lysosomal integrity was determined as the lag time from the start of blue laser irradiation until the rupture of lysosomes induced an increase of green fluorescence in the cytosol (Figure 3E).Viability analysisAfter treatment, cell cultures were morphologically examined in a phase contrast microscope and viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT; Calbiochem, San Diego, CA, USA) reduction assay. Cells were incubated with 0.25 mg/ml MTT for 2h at 37uC. The MTT solution was then removed and the formazan product dissolved in DMSO. The absorbance was measured at 550 nm. In addition, the amount of surviving and thus attached cells was determined using crystal violet staining. Cells were fixed in 4 paraformaldehyde for 20 min, followed by 0.04 crystal violet staining for 20 min at room temperature. The plates were washed thoroughly by dipping in H2O and subsequently air-dried. Samples were then solubilized in 1 Sodium dodecyl sulfate (SDS) before absorbance was measured at 550 nm. Caspase-3-like activity was analyzed using the substrate Ac-DEVD-AMC (Becton, Dickinson and Company, Franklin Lakes, NJ) according to the manufacturer’s instructions. Fluorescence was correlated to protein content.Statistical analysisAll experiments were repeated at least three times and the results are presented as the means and standard deviations of independent samples. Data were statistically evaluated using a nonparametric Kruskal-Wallis test, followed by Mann-Whitney U test for comparison of two groups. P values #0.05 were considered to be significant and marked with an asterisk in figures.Lipid measurementsUnesterified cholesterol content was measured in cell lysates using the Amplex Red Cholesterol Assay Kit (Invitrogen, Paisley, UK), as described by the manufacturer. Cholesterol amount was correlated to protein content. Sphingomyelin content was analyzed according to a previously described method [28].Supporting InformationFigure S1 Viability of human fibroblasts after MSDH 1326631 exposureImmunocytochemistryCells were prepared for immuno-cytochemistry as described elsewhere [20]. Antibodies against LAMP-2 (Southern Biotech, Birmingham, AL, USA), followed by antibodies conjugated to Alexa Fluor (Molecular Probes), were used. To visualize unesterified cholesterol, cells were stained with filipin (125 mg/ml; SigmaAldrich) for 1 h at room temperature. Cover slips were washed and mounted using Prolong gold (Invitrogen). Cells were examined using a Nikon Eclipse E600 laser scanning confocal microscope (Nikon, Tokyo, Japan) together with the EZC1 3.7 software (Nikon Instruments.
