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

CHIABRANDO GA; RIDANO MAGALI E; SANCHEZ CECILIA; PAZ MC; BARCELONA P; SUBIRADA CALDARONE PAULA

Congreso; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

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 withthe development of many neurodegenerative diseases. Cytoplasmicaccumulation and aggregation of p62, an adaptor protein involved inthe incorporation of ubiquitinated proteins into the autophagosome,seems to be a key event in neuronal dysfunction. In this work weanalysed in a mouse model of oxygen induced retinopathy (OIR):a) changes in autophagy flux in the retinal layers; and b) if pharmacologicalmodulation of autophagy could prevent neuronal alterations.For this purpose, C57/BL6 mice were exposed to 75% O2from postnatal day (P)7 to 12, and then they were brought to roomair (RA). Age-matched mice maintained in RA were used as control.Animals were sacrificed at P17 and P26. We observed at the innerretinal layers altered autophagy flux with increased levels of p62 atthe neovascularization peak (P17). As a valid strategy to modulatep62, P12 mice were intraocularly injected with Spautin-1 (a specificautophagy inhibitor). Western blot of neural retinas and immunofluorescencestaining showed that Spautin-1 decreased p62 levels andslightly increase LC3II, but did not modified detoxifying and stressproteins expression at P17. At the same time point electroretinogram(ERG) activity evidenced a decreased photoreceptor function.However, at P26 autophagy flux was restored, Glutamine synthaseincreased, ERG response improved and a minor number of TUNELpositive cells were observed. Structural and vascular modificationswere also analysed. The results suggest that in the outer nuclearlayer autophagy is preserved during hypoxia and constitutes a survivalmechanism. Whereas in the inner layers, where cells are severelyaffected by hypoxia, the inhibition of autophagy decreasedp62 levels and decreased neuronal death.