FOLLOWING HYPOXIC GRADIENT: DIFFERENT REGULATION OF AUTOPHAGY FLUX IN INNER AND OUTER NUCLEAR LAYERS

SUBIRADA CALDARONE, PV; PAZ, M.C.; RIDANO, ME; BARCELONA, P.F.; CHIABRANDO, G. A.; SANCHEZ, M.C.

Buenos Aires

Congreso; Reunión Conjunta de las Sociedades de Biociencias; 2017

Sociedades de Biociencias

In order to maintain homeostasis post mitotic cells, as neurons, require efficient degradation systems that eliminate cellular waste. In this sense, defective autophagy flux has been associated with the development of many neurodegenerative diseases. Cytoplasmic accumulation and aggregation of p62, an adaptor protein involved in the incorporation of ubiquitinated proteins into the autophagosome, seems to be a key event in neuronal dysfunction. In this work we analysed in a mouse model of oxygen induced retinopathy (OIR): a) changes in autophagy flux in the retinal layers; and b) if pharmacological modulation of autophagy could prevent neuronal alterations. For this purpose, C57/BL6 mice were exposed to 75% O2 from postnatal day (P)7 to 12, and then they were brought to room air (RA). Age-matched mice maintained in RA were used as control. Animals were sacrificed at P17 and P26. We observed at the inner retinal layers altered autophagy flux with increased levels of p62 at the neovascularization peak (P17). As a valid strategy to modulate p62, P12 mice were intraocularly injected with Spautin-1 (a specific autophagy inhibitor). Western blot of neural retinas and immunofluorescence staining showed that Spautin-1 decreased p62 levels and slightly increase LC3II, but did not modified detoxifying and stress proteins expression at P17. At the same time point electroretinogram (ERG) activity evidenced a decreased photoreceptor function. However, at P26 autophagy flux was restored, Glutamine synthase increased, ERG response improved and a minor number of TUNEL positive cells were observed. Structural and vascular modifications were also analysed. The results suggest that in the outer nuclear layer autophagy is preserved during hypoxia and constitutes a survival mechanism. Whereas in the inner layers, where cells are severely affected by hypoxia, the inhibition of autophagy decreased p62 levels and decreased neuronal death