Ambra1 haploinsufficiency results in metabolic alterations and exacerbates age‐associated retinal degeneration

Purpose: Retina is a highly complex and metabolically active tissue that sense the light. Persistent light‐induced stimuli lead to constant turnover of the damaged cellular structures by proteostatic mechanisms such as autophagy. During aging there is a gradual decrease of autophagy which compromises retinal homeostasis and visual function. AMBRA1 (autophagy and beclin‐1 regulator 1) is a key protein involved in the initiation phase of autophagy pathway. To further determine the importance of autophagy along aging, we will use Ambra1+/gt heterozygous mice, mimicking the decrease of autophagy during the aging process. Methods: We have used young (3 months), middle‐aged (12 months) and old (25 months) Ambra1+/+ and Ambra1+/gt mice for this study. Visual function was determined by electroretinographic recordings (ERGs) along aging. Eyes were enucleated for histological porpoises or retinas were isolated for biochemical procedures. Retinal morphology and cellular components were assessed by immunofluorescence techniques on retinal cryosections or flatmounts. mRNA and protein lysates were obtained from isolated retinas. Metabolomic analyses were conducted using mass spectrometry and bioinformatic analysis was performed. Results: Ambra1+/gt retinas display a reduced autophagic flux at young without changes in the retinal integrity and function. However, aged Ambra1+/gt animals show an exacerbated loss of visual function also evidenced by morphological changes as increased gliosis, reduced nuclear density and cone number. Interestingly, we observed increased bipolar cell protrusions that might indicate the loss of synapsis between retinal layers. Partial loss of autophagy results in increased damaged mitochondria evidenced by a reduction in the mitochondrial membrane potential (MMP) in young age, higher oxidative stress at middle‐aged and accumulation of mitochondrial mass in old Ambra1+/gt retinas. Finally, by metabolomics, we demonstrate marked metabolic alterations suggestive of defective oxidative metabolism in Ambra1+/gt animals at 1 year of age. Conclusions: Reduced autophagic response in Ambra1 haploinsufficient retinas leads to an exacerbated age‐associated declines in retinal function, metabolic alterations and accumulation of damaged mitochondria.