Abstract 16868: Conditional Renal Tubule Specific Deletion of KDM6a Gene Causes Hypertension in Mice

Abstract

Objective: Aging-associated downregulation of Klotho is partly due to epigenetic upregulation of H3K27me3 in the kidney. The purpose of this study is to investigate the potential role of KDM6a, a demethylase of histone 3 lysine (K) 27 trimethylation (H3K27me3), in the regulation of blood pressure and explore the related molecular pathways that may influence the kidney function during aging. Methods and Results: Wild type and Ksp-Cre/KDM6a-floxed mice were divided into vehicle control and tamoxifen (10 mg/kg/mouse/7days) treated cohorts (WT mice: KDM6a floxed or Ksp-Cre only and Ksp-Cre/KDM6a -loxed mice). Blood pressure (BP) was measured by tail cuff method and confirmed by carotid artery cannulation at the end of study. Deletion of the KDM6a gene (KDM6a-cKO) significantly increased BP at day 7. BP remained elevated throughout the study. We found that the H3K27me3 level was significantly increased in the kidneys of KDM6a-cKO mice compared to control mice confirming that KDM6a is an important H3K27 demethylase in the control of methylation levels in the kidney. Elevation of BP was likely due to upregulation of the Na + :K + :2Cl - co-transporter (NKCC2) in the thick ascending limb of Henle's loop and NaCl co-transporter (NCC) in the distal convoluted tubule confirmed by qPCR and immunohistochemistry. Accordingly, we found that the urine sodium level was decreased in KDM6a-cKO mice compared to KDM6a-con mice. We showed that expression of aquaporin 2 (AQP2) was increased in the kidney of KDM6a-cKO mice, suggesting that AQP2 may also contribute to increased BP through modulation of body water homeostasis. Furthermore, we demonstrated that expression of Klotho was downregulated by 50%, which blocked FGFR1/Klotho/ERK signaling in the kidney of KDM6a-cKO mice. Notably, expression of aging markers including p53, p21, and p16 was significantly increased in the kidney of KDM6a-cKO mice, indicating that deletion of KDM6a in the renal tubule results in kidney aging. Conclusion: KDM6A is essential to the maintenance of normal kidney function and blood pressure. Renal-specific KDM6A knockout-induced hypertension is likely attributed to increased H3K27me3 levels and the resultant dowregulation of Klotho gene expression which impairs the FGFR1/Klotho/ERK signaling.