The metabolic sensor AMPK is essential for the high metabolic program of Photoreceptors, but is surprisingly not required in RPE cells.

Abstract

Purpose : Recent evidence suggests that metabolic dysregulation may be a major contributing factor to diseases such as retinitis pigmentosa and age-related macular degeneration.5’ adenosine monophosphate-activated protein kinase (AMPK) is a critical energy sensor and metabolic regulator in a variety of tissues, however its role in regulation of metabolism the retina remains poorly understood.To better understand the role of AMPK in the retina we conditionally deleted AMPK either in the neurons of the retina or in the retinal pigment epithelium (RPE).

Methods : Electroretinography (ERG) was performed to assess retinal function, fundoscopy was used to assess retinal morphology, and SD-OCT was utilized to examine retinal morphology and outer nuclear layer (ONL) thickness in vivoon VMD2Cre;AMPKα1^fl/flα2^fl/flor Chx10Cre;AMPKα1^fl/flα2^fl/flmice on a BALB/c background. IHC and western blotting were used to examine protein expression; qRT-PCR was used to measure gene expression. All procedures were conducted in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Visual Research.

Results : Loss of AMPK in the neurons in the retina led to accelerated loss of retinal function by 2 months of age, however we did not find any measurable differences in ONL thickness until 8 months of age. Loss of function was associated with alterations in the metabolic ecosystem in the neuroretina at 4 months of age. By 12 months of age, we observed secondary loss of function of the RPE even though AMPK expression was not ablated in the RPE. This coincided with loss of RPE barriers as measured by ZO-1 staining. Interestingly, we have not observed any loss of retinal function with deletion of AMPK specifically in the RPE.

Conclusions : AMPK expression in the neurons of the retina is necessary for maintaining the metabolic ecosystem in the retina. Deletion of AMPK in the neuroretina results in loss of retinal function with secondary loss of RPE function. We do not observe loss of retinal cells until later ages, suggesting that the metabolic shift we observe is able to prevent cell death until later ages. AMPK is not necessary for RPE function under non-stressed conditions. These findings implicate AMPK as an ideal therapeutic target to maintain retinal metabolism in retinal degenerations.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.