Development of Robust 17(R),18(S)-Epoxyeicosatetraenoic Acid (17,18-EEQ) Analogues as Potential Clinical Antiarrhythmic Agents

17(R),18(S)-Epoxyeicosatetraenoic acid (EEQ) is a cytochrome P450 metabolite of eicosapentaenoic acid (EPA) and a powerful negative chronotrope with low nanomolar activity in a neonatal rat cardiomyocyte (NRCM) arrhythmia model. Prior studies identified oxamide 2b as a soluble epoxide hydrolase (sEH) stable replacement but unsuitable for in vivo applications due to limited oral bioavailability and metabolic stability. These ADME limitations have been addressed in an improved generation of negative chronotropes, e.g., 4 and 16, which were evaluated as potential clinical candidates.

Abstract 631: Cardiomyocyte-specific Cyp4a12a Overexpression Aggravates Maladaptive Cardiac Hypertrophy

Alterations in cytochrome P450 (CYP)-dependent formation of 20-hydroxyeicosatetraenoic acid (20-HETE) are associated with hypertension and end-organ damage. The cause-and-effect relationships are only partially understood and difficult to dissect due to the multiple and partially opposing roles of 20-HETE in different tissues. We established a Cre/loxP-system for tissue-specific overexpression of Cyp4a12a, a murine 20-HETE producing isoform. We used this system to test the hypothesis that enhanced formation of 20-HETE plays a detrimental role in cardiac hypertrophy. Floxed Cyp4a12a mice were crossed with alpha-MHC-Cre mice to generate animals with cardiomyocyte-specific Cyp4a12a overexpression (CYP) and wildtype littermates (WT). RT-PCR and immunohistochemistry confirmed Cyp4a12a overexpression in CYP compared to WT hearts. The animals (n=10-12 per group) were subjected to transverse aortic constriction (TAC). Eight weeks after TAC, the left ventricular mass-to-tibia length ratio (mg/mm) increased to 14.6±2.3 in male WT and to 12.6±2.3 in male CYP mice. Hypertrophy was lower in WT females (11.2±1.4) but not in CYP females (12.3±2.1), compared to their male counterparts. ANP and βMHC expression levels were higher in CYP than WT mice (2.6- and 2.2-fold in males, and 1.9- and 1.8-fold in females). The ejection fraction (%) was more severely impaired in the CYP than WT groups (male WT: 22.3±4.7 vs. CYP: 9.5±3.4; female WT: 21.8±11.7 vs. CYP: 15.5±4.8). Cyp4a12a overexpression also worsened TAC-induced end-diastolic posterior wall thinning (male WT: 1.05±0.17 vs. CYP: 0.80±0.12; female WT: 0.93±0.12 vs. CYP: 0.85±0.11mm), and dilation (male WT: 5.21±0.53 vs. TG: 5.83±0.53; female WT: 4.82±0.56 vs. CYP: 5.39±0.43mm). Moreover, the interventricular septal thickness was clearly reduced in male CYP compared to WT hearts after TAC. The lung weight was markedly higher in male CYP than WT mice (WT: 201.4±90.9 vs. CYP: 485.3±50.7 mg), but not different in female groups. These results demonstrate that cardiomyocyte-specific overexpression of Cyp4a12a/20-HETE aggravates pressure overload-induced maladaptive hypertrophy and promotes the development of dilated cardiomyopathy. The effects were more pronounced in males compared to females.