Reproposing Neutral Red as a Colorimetric Probe for Quantitative Assessment of Lysosomal Clearance in Neuroblastoma Cell Line

Abstract

AbstractWe report herein a method for investigating lysosome clearance function based on colorimetric analysis of neutral red (NR) that had accumulated in lysosomes of a neuroblastoma cell line. The NR in lysosome can be easily observed as red puncta under microscope and has a characteristic absorbance maximum at 525 nm. Clearance of NR from lysosomes can be monitored by observing red signal fading under a light microscope and can also be monitored by measuring its change in characteristic absorbance using a microplate reader. Clearance kinetics of NR in lysosomes were found to obey simplified one phase decay kinetics. By fitting the data, we were able to parameterize the rate constant (k) which was implemented in the lysosome clearance function. Notably, dys‐regulated lysosome induced by bafilomycin A1, had less k value, implying a lower lysosome clearance efficiency. Obviously, the cells with less k value were found to have been less capable of clearing amyloid beta out of the cells. These results substantiate that this method can be utilized as a new method for assessment of lysosome clearance function.