#4904 EPAC1- MEDIATED CAMP SIGNALLING PROMOTES CELLULAR ENERGY ADAPTATIONS IN PODOCYTES TO PROTECT FROM GLOMERULONEPHRITIS
Authors: Abbad Lilia , Detrait Maximin , Kavvadas Panagiotis , Melis Lisa , Hadji Sabrina , Bergonnier Dorian , Lezoualch Frank , Chatziantoniou Christos 
Published: June 2023

Abstract

Background and Aims
Many efforts are made to identify new therapeutic targets to slow down, prevent or even reverse Chronic Kidney Disease (CKD) progression. One of the therapeutic approaches is activating the renoprotective cAMP pathway, especially by stimulation of its downstream effector, the protein kinase A (PKA). PKA was considered as the unique cAMP effector, however, the exchange factor directly activated by cAMP 1 (EPAC1) has been recently identified as a novel, PKA-independent, mediator of cAMP signalling. EPAC1 is a guanidine exchange factor that promotes the exchange of GDP for GTP regulating important cellular functions. Epac1 activation exerts a renoprotective effect during acute kidney injury, via maintenance of epithelial adhesion and protection from oxidative stress. However, the role of EPAC1 in CKD remains poorly understood. Here we aim to determine the role of EPAC1 in CKD progression.

Method
Nephrotoxic serum glomerulonephritis (NTS-GN) is induced in genetically modified mice with total and conditional EPAC1 deletion. Then isolated glomeruli from mice with conditional EPAC1 deletion in podocytes are analysed by RNA-sequencing. The main metabolic energy pathways are studied in podocytes in vitro under oxidative stress exposure in the presence or absence of an EPAC1 agonist.

Results
Following the induction of NTS-GN, mice with genetic deletion of EPAC1 show aggravated renal disease, characterized by increased proteinuria, glomerular damage, tissue inflammation and fibrosis compared to wild-type mice. Conversely, pharmacological activation of EPAC1, with the agonist 8-pCPT-2-OMe-cAMP, delays NTS-GN progression. Since in human and wild type mouse kidney tissues we observe EPAC1 expression in podocytes, mice with conditional deletion of EPAC1 in podocytes (Nphs2Cre:epac) are generated. Similar to the whole-body knockout, mice with EPAC1 deletion in podocytes show increased renal damage and worsened disease progression compared to control mice. RNA-sequencing analysis of glomeruli isolated from these mice show that gene expression of proteins linked to the pathway of glycolysis are abolished in early stage of NTS-GN (day 4). These data suggest that EPAC1-mediated activation of glycolysis in podocytes is essential to limit GN progression. This is substantiated by the in vitro experiments in podocytes, in which EPAC1 activation under oxidative stress promotes glycolysis with cellular energy production independently from mitochondrial respiration. The EPAC1-mediated glycolysis protected podocytes by increasing cell viability, decreasing LDH release and activating the AKT pathway.

Conclusion
Our results suggest a protective role of podocytes-derived EPAC1 against the development of GN through cellular energetic adaptations based on metabolic switch to glycolysis. Activating the cAMP-EPAC1 signalling axis could represent a therapeutic option to delay the development of CKD. Further investigations are needed to define its relevance in human CKD.