Proximal tubular‐specific over‐expression of the Cyp4a12‐20‐HETE synthase in male mice promotes salt‐sensitive hypertension

Abstract

20‐Hydroxyeicosatetraenoic acid (20‐HETE), the ω‐hydroxylation metabolite of arachidonic acid produced by cytochrome P450 (CYP) enzymes of the 4A and 4F gene families, has been linked to the regulation of blood pressure (BP) via actions on the renal microvasculature and tubules. In renal microvessels, 20‐HETE promotes vasoconstriction, endothelial dysfunction and vascular remodeling; all of which contribute to hypertension, whereas in renal tubules 20‐HETE inhibits sodium transport and contributes to lowering of BP. However, some studies suggested that 20‐HETE promotes sodium reabsorption by actions on proximal and distal tubule transport mechanisms. In order to assess the contribution of renal tubular 20‐HETE to hypertension, we generated transgenic mice with proximal tubule‐specific overexpression of the Cyp4a12‐20‐HETE synthase (PEPCK‐Cyp4a12 mice). 20‐HETE levels in kidney cortex of PEPCK‐4a12 males showed a 2.5‐fold increase compared to littermate WT (966.63 ± 209.63 vs. 248.87 ± 69.46 pg/mg protein; p<0.05). In females, renal cortical 20‐HETE levels were not different between PEPCK‐4a12 and corresponding littermate WT mice (120.88 ± 14.50 vs. 91.65 ± 11.08 pg/mg protein; p=0.99). The absence of a significant increase in 20‐HETE levels in female PEPCK‐4a12 mice was associated with a lack of increases in CYP4a12 mRNA and protein levels in the kidney cortex compared to littermate WT (mRNA: 1.57 ± 0.39 vs. 1.07 ± 0.18; p=0.644; protein: 0.416 ± 0.046 vs. 0.330 ± 0.013; p=0.631). In contrast, renal cortical Cyp4a12 mRNA and protein in male PEPCK‐4a12 mice significantly increased compared to WT (mRNA: 2.61 ± 0.52 vs. 1.01 ± 0.09; p=0.05; protein: 0.824 ± 0.10 vs. 0.295 ± 0.023; p<0001). Males PEPCK‐Cyp4a12 mice displayed elevated BP (142 ± 1.4 vs 111 ± 4 mmHg in WT, p<0.0001), whereas BP in females PEPCK‐Cyp4a12 mice was not significantly different from corresponding WT (118 ± 2 vs 117 ± 2 mmHg for WT; p=0.98). In male PEPCK‐4a12 mice, BP decreased when transitioned from a control salt (0.4%) to a low salt diet (0.075%) from 135 ± 4 to 120 ± 6 mmHg (p=0.10) and increased to 153 ± 5 mmHg (p<0.05) when placed on a high salt diet (4%). Female PEPCK‐4a12 mice did not show changes in BP on either low or high salt diet (120 ± 2, 123 ± 4, and 120 ± 3 mmHg on control, low and high salt diet, respectively). Urine volume (2.15 ± 0.18 vs. 3.17 ± 0.15 mL/day; p=0.02) and sodium excretion (5.75 ± 0.45 vs 8.65 ± 1.11 μmol/g BW/day; t‐test P=0.05; 2‐way ANOVA p=0.21) tend to be lower in PEPCK‐4a12 males compared to WT. In female PEPCK‐4a12 urine volume (1.53 ± 0.23 vs. 1.13 ± 0.20 ml/day; p=0.45) and sodium excretion (9.38 ± 1.15 vs. 7.73 ± 0.77 μmol/g BW/day; t‐test P=0.27; 2‐way ANOVA p=0.57) were not different compared to WT. In conclusion, the expression of Cyp4a12 driven by the PEPCK promoter is gender‐specific probably due to the X‐linked PEPCK. The salt‐sensitive hypertension seen in PEPCK‐4a12 male mice may be due to a potential anti‐natriuretic activity of 20‐HETE.Support or Funding InformationSupported by NIH grants PO1‐034300 and HL‐139793This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.