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Marc Labetoulle, Eva Hernandez, Oscar Haigh, Antoine Rousseau, Audrey Esclatine; Up-regulating autophagy with trehalose: a contribution to osmoprotective properties ?. Invest. Ophthalmol. Vis. Sci. 2019;60(9):267.
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© ARVO (1962-2015); The Authors (2016-present)
Osmoprotection is the mechanism by which cells of an organism protect themselves against osmotic stress. There are several osmoprotectors that are currently used in eye drops formulation with the aim of trying to reduce the consequence of hyperosmolarity, a hallmark of the dry eye disease. However, the mechanisms of osmoprotection are still poorly understood. In this in vitro study, we assessed the effect of trehalose, a non-reducing natural disaccharide used as osmoprotector in marketed eye drops, on the different steps of autophagy. Autophagy is a mechanism highly involved in the maintenance of the homeostasis of cells, by degrading and recycling cellular compounds and can be stimulated by different stresses, allowing the cell to adapt and survive under harsh environmental conditions.
Trehalose alone, or eye drops containing sodium hyaluronate alone (SH) alone (Hyabak, THEA, France) or in combination with trehalose (Thealose, THEA, France) were compared to control conditions activating autophagy (namely nutrient starvation) for the ability to upregulate the different autophagy steps in human epithelial cells in culture. For the purpose of the study, the cell line was tagged with LC3, a marker of the autophagic machinery fused with a green fluorescent protein (GFP) or a tandem of GFP and mRFP (red fluorescent protein). Thanks to the quenching of GFP in an acidic environment, it was possible to differentiate whether or not the activation of the autophagic flux was complete.
We observed that trehalose alone was able to induce a complete autophagic flux, as shown by an increase of the number of GFP-LC3 dots in immunofluorescent assays, and an accumulation of LC3-II (the lipidated form of LC3 associated with autophagosomes) by western blot. Induction of the autophagic flux was confirmed and characterized by using tandem-tagged LC3 and incubation with chloroquine (which is an inhibitor of autophagic degradation). Moreover, there was a synergistic effect of SH for the induction of autophagy when combined to trehalose, compared to any of the two components alone.
Autophagic flux is induced by trehalose, and this phenomenon is enhanced by the combination with sodium hyaluronate. This is likely related to the osmoprotective effects of trehalose, as hyperosmolarity is a stimulus for regulation processes to maintain epithelial cells homeostasis in dried out conditions.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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