Abstract 159: Inhibition of Ace Does Not Prevent 20-hete-mediated Vascular Injury in Cyp4a12tg Mice

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20-hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P450-arachidonic acid metabolite in the microcirculation, increases smooth muscle contraction and proliferation, stimulates endothelial dysfunction and activation and promotes hypertension that is dependent, in part, on the renin angiotensin system (RAS). We showed that in cultured human microvascular endothelial cells, 20-HETE increases angiotensin converting enzyme (ACE) mRNA by 3.1-fold (± 0.16; p<0.05), ACE protein by 4.2-fold (±0.99; p<0.05) and cellular and extracellular ACE activity by 2.2-fold (±0.09; p<0.05) and 1.96-fold (±0.16; p<0.05), respectively. The contribution of ACE to vascular 20-HETE-mediated microvascular remodeling in hypertension was assessed using the Cyp4a12 transgenic mouse in which the expression of the Cyp4a12-20-HETE synthase is driven by a tetracyclin (doxycycline, DOX)-sensitive promoter. Treatment of Cyp4a12tg mice with DOX increased blood pressure (133±6 vs. 107±3 mmHg; p<0.05) and remodeling of renal resistance arteries (M/L, 0.15±0.01 vs. 0.07±0.01; p<0.05); these increases were abrogated by co-treatment with the 20-HETE antagonist, 20-HEDGE. Renal ACE protein expression was significantly higher in DOX-treated (1.6 ± 0.17 fold; p<0.05) as compared to untreated Cyp4a12tg mice; co-treatment with 20-HEDGE prevented the increase in ACE expression. Lisinopril treatment of Cyp4a12tg mice concurrently receiving DOX prevented the blood pressure increase (133±6 vs. 104±2 mmHg; p<0.05) but did not interfere with renal microvascular 20-HETE production (1.05±0.18 vs 1.09±0.30 ng/mg). Co-treatment with lisinopril and DOX attenuated but did not prevent remodeling of renal microvessels (M/L, 0.07±0.0 vs. 0.15±0.01 vs. 0.11±0.01; p<0.05 in water, DOX and DOX+Lisinopril, respectively). In contrast, co-treatment with 20-HEDGE prevented DOX-induced remodeling of resistance arteries of Cyp4a12tg mice. This study demonstrates that 20-HETE is a key determinant of microvascular remodeling in DOX-induced Cyp4a12tg hypertensive mice. 20-HETE’s mechanism only partially relies on activation of the RAS. Thus, the 20-HETE-driven microvascular remodeling does not fully depend on the upregulation of ACE and elevation of blood pressure.

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