RPE Messengers, Transcription and Photoreceptor Renewal

Project Summary / Abstract Despite their adverse environment, the question of how photoreceptor cells (PRC) and retinal pigment epithelial cells (RPECs) are functionally unchanged for decades in healthy eyes remains to be answered. Studies supported by this grant have defined the molecular cascade by which bioactive derivatives of the essential fatty acid family member docosahexaenoic acid (DHA) sustain the protection of PRCs and RPECs, including TXNRD1 and GPR120. We have shown that the synthesis of one DHA-derived mediator, Neuroprotectin D1 (NPD1), is activated at the onset of RPE homeostatic disruptions (also supported by this grant), and recently, we discovered a second set of mediators, elovanoids (ELVs), that are critical in the protection cascade. Mechanisms include gene clusters that promote homeostasis and maintenance of cell integrity. To explore these mechanisms, we propose three Specific Aims. Aim 1 will test the prediction that uptake and metabolism of DHA in rods and cones are impaired in AMD. The proposed experiments are supported by our findings in AMD retinas, especially in females, suggesting that failure in the pathway for ELV synthesis in rods leads to retinal degeneration. Aim 2 will test the prediction that ELV-N34 targets TXNRD1 and GPR120 to protect PRC and RPE integrity. Experiments in this aim will unravel regulated downstream signaling and are supported by our observations that GPR120, a G-protein receptor, is targeted by ELVs in the RPE and that ELVs target TXNRD1 at the initiation of ferroptosis and uncompensated oxidative stress in RPEC. Aim 3 will test the prediction that ELVs contribute to RPEC/PRC resiliency and integrity by epigenetic modulation of specific inflammatory and homeostatic pathways. In this aim, we will identify the specific gene clusters and proteins that modulate the integrity of PRC and RPE in response to ELVs. These studies will use control and AMD retinas as well as AdipoR1 global KO, MFRP (rd6), and single- cell genomics to define the signaling pathways that are required to sustain RPEC and PRC homeostasis and functional integrity promoted by the lipid mediators. The outcomes of this fundamental investigation will provide new information on the basic molecular and genetic signals and mechanisms required to sustain PRC function. Our studies of these relationships in disease models will provide information that will help us define fundamental mechanisms in the normal human retina that are dysfunctional in AMD. Results from our proposed studies will set the parameters and define avenues for future studies that may ultimately contribute to the development of new therapeutic strategies to slow n or delay the progression of AMD.