C/EBP aggravates renal fibrosis in CKD through the NOX4-ROS-apoptosis pathway in tubular epithelial cells

Background: Chronic kidney disease (CKD) is a prevalent renal disorder with various risk factors. Emerging evidence indicates that the transcriptional factor CCAAT/enhancer binding protein alpha (C/EBP alpha) may be associated with renal fibrosis. However, the precise role of C/EBP alpha in CKD progression remains unexplored. Methods: We investigated the involvement of C/EBP alpha in CKD using two distinct mouse models induced by folic acid (FA) and unilateral ureteral obstruction (UUO). Additionally, we used RNA sequencing and KEGG analysis to identify potential downstream pathways governed by C/EBP alpha. Findings: Cebpa knockout significantly shielded mice from renal fibrosis and reduced reactive oxygen species (ROS) levels in both the FA and UUO models. Primary tubular epithelial cells (PTECs) lacking Cebpa exhibited reduced apoptosis and ROS accumulation following treatment with TGF-beta. RNA sequencing analysis suggested that apoptosis is among the primary pathways regulated by C/EBP alpha, and identified NADPH oxidoreductase 4 (NOX4) as a key protein upregulated upon C/EBP alpha induction (ICCB280). Treatment with L-Theanine, a potential NOX4 inhibitor, mitigated renal fibrosis and inflammation in both the FA and UUO mouse models. Interpretation: Our study unveils a role for C/EBP alpha in suppressing renal fibrosis, mitigating ROS accumulation, and reducing cell apoptosis. Furthermore, we investigate whether these protective effects are mediated by C/ EBP alpha's regulation of NOX4 expression. These findings present a promising therapeutic target for modulating ROS and apoptosis in renal tubular cells, potentially offering an approach to treating CKD and other fibrotic diseases.