Abstract
Induction of lysosomal exocytosis alleviates lysosomal storage of undigested metabolites in cell models of lysosomal disorders (LDs). However, whether this strategy affects other vesicular compartments, e.g., those involved in endocytosis, is unknown. This is important both to predict side effects and to use this strategy in combination with therapies that require endocytosis for intracellular delivery, such as lysosomal enzyme replacement therapy (ERT). We investigated this using δ-tocopherol as a model previously shown to induce lysosomal exocytosis and cell models of type A Niemann-Pick disease, a LD characterized by acid sphingomyelinase (ASM) deficiency and sphingomyelin storage. δ-Tocopherol and derivative CF3-T reduced net accumulation of fluid phase, ligands, and polymer particles via phagocytic, caveolae-, clathrin-, and cell adhesion molecule (CAM)-mediated pathways, yet the latter route was less affected due to receptor overexpression. In agreement, δ-tocopherol lowered uptake of recombinant ASM by deficient cells (known to occur via the clathrin pathway) and via targeting intercellular adhesion molecule-1 (associated to the CAM pathway). However, the net enzyme activity delivered and lysosomal storage attenuation were greater via the latter route. Data suggest stimulation of exocytosis by tocopherols is not specific of lysosomes and affects endocytic cargo. However, this effect was transient and became unnoticeable several hours after tocopherol removal. Therefore, induction of exocytosis in combination with therapies requiring endocytic uptake, such as ERT, may represent a new type of drug interaction, yet this strategy could be valuable if properly timed for minimal interference.
Footnotes
- Received February 11, 2019.
- Accepted May 15, 2019.
↵1 R.L.M. and J.A.R. contributed equally to this work.
This work was supported by the National Institutes of Health [Grant R01 HL98416]; Spanish Ministry of Economy and Competitiveness—MINECO/FEDER Project SEV-2014-0425, Spanish Ministry of Science, Innovation and University—MINECO/EXPLORA Project SAF2017-91909-EXP and MINECO/RETOS Project RTI2018-101034-B-I00, and CERCA Program of the Generalitat de Catalunya (awarded to S.M.); National Science Foundation Graduate Research Fellowship [DGE-0750616], University of Maryland Flagship Fellowship, and the National Institutes of Health Ruth L. Kirschstein Predoctoral Fellowship [F31-HL128121 (awarded to R.L.M.)]; Howard Hughes Medical Institute Fellowship Program under the University of Maryland Undergraduate Science Education Program (awarded to J.A.R.); and Intramural Research Program of the National Institutes of Health National Center for Advancing Translational Sciences (awarded to W.Z.).
↵This article has supplemental material available at jpet.aspetjournals.org.
- U.S. Government work not protected by U.S. copyright