Endothelial cell‐specific inducible G2APOL1 risk variant induces hypertension and hypertensive kidney disease in uni‐nephrectomy and high‐salt mice model
Authors: Poudel Bibek , Vassalotti Allison , Wahba Joseph , Raman Archana , Wu Junnan , Susztak Katalin 
Published: May 2022

Hypertension affects 108 million in the United States, which is more common in African American (AA) population (54%). Several Genome‐Wide Association Studies (GWAS) showed a strong association between the apolipoprotein1 (apol1) gene and hypertension in AA adults. Nearly 45% of AAs carry a coding variant of the APOL1 gene either G1APOL1 or G2APOL1. The disease phenotypes associated with APOL1 RV are dependent on the cell type‐specific expression and toxicity of APOL1. Recently, we have reported that APOL1 is highly expressed in endothelial cells (EC) of the human kidneys using single‐cell analysis, single nuclei analysis, and in‐situ hybridization. People who carry G1 or G2 APOL1 RV have a high risk of chronic kidney disease and hypertensive kidney disease. However, the direct role of APOL1 in the development of hypertension and hypertensive kidney disease is clear. Therefore, the objective of the current study was to examine the role of endothelial‐specific inducible G2APOL1 risk variants in the development of hypertension and hypertensive kidney disease. To understand the role of APOL1 in endothelial cells, we generated mice with endothelial‐specific inducible expression of APOL1 (EC/G2‐APOL1) by crossing the TRE‐G2APOL1 mice with the Cdh5tTA animals. Cadherin 5 (VE‐cadherin or endothelial cadherin) is an endothelial‐specific gene, removal of doxycycline from the diet led to a significant expression of APOL1 in different vascular beds such as the lung, heart, and kidney, which was confirmed both by in situ hybridization and qRT‐PCR. After collecting the baseline data, we performed UNX surgery on both WT control and Cdh5tTA/TRE‐G2APOL1 five‐week‐old mice and kept them in 4% salt diet for 12 weeks after UNX surgery. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) (measured by tail‐cuff method) were significantly higher in Cdh5tTA/TRE‐G2APOL1 mice compared to control WT mice after 6 weeks of UNX surgery on a high salt diet. The significantly higher blood pressure in Cdh5tTA/TRE‐G2APOL1 mice was further associated with the increased urinary albumin/creatinine ratio and renal fibrosis. Interestingly, the blood pressure parameters SBP, DBP, and MAP were significantly reduced on STING, NLRP3, and gasdermin knock‐out mice on Cdh5tTA/TRE‐G2APOL1 background compared to Cdh5tTA/TRE‐G2APOL1 mice upon UNX‐surgery and 4% salt diet. Furthermore, the expression of the transcript of the mitochondrial gene including COX1, COX2, ATP6, and ND6 in the cytoplasm from kidney tissue obtained from Cdh5tTA/TRE‐G2APOL1 mice was significantly higher compared to control‐WT, which indicate that mitochondrial damage and leakage of the mitochondrial gene into the cytoplasm take place in the Cdh5tTA/TRE‐G2APOL1 mice upon UNX‐surgery and 4% salt‐diet. Therefore, EC specific apol1 gene induces mitochondrial damage, upregulates inflammasome and cGAS‐STING pathway to develop hypertension leading to hypertensive kidney disease. This project was supported by DK105821.