Attenuation of advanced atherosclerosis and aortic aneurysm in hph-1/apoE DKO mice by folic acid and DHFR overexpression.

INTRODUCTION

Atherosclerosis and aortic aneurysms often co-exist, attributed to common risk factors predisposing to development of these severe vascular disorders. The apoE null mice represent a classical model of atherosclerosis. It has been shown that endothelial nitric oxide synthase (eNOS) is modestly uncoupled in apoE null mice at baseline to contribute to oxidative stress.

METHODS

Notably, we have previously demonstrated marked activation of eNOS in its uncoupled state in angiotensin II (Ang II) infused hph-1 mice, which triggers formation of abdominal aortic aneurysm (AAA), representing the first evidence documenting a direct causal role of eNOS uncoupling in AAA formation that can be reversed by recoupling of eNOS with oral administration of folic acid (FA) or plasmid-mediated overexpression of dihydrofolate reductase (DHFR). In the present study, hph-1(hyperphenylalaninemia-1)/apoE double mutant mice were created in-house, and exposed to Ang II infusion (0.7 mg/kg/day) for 2 weeks alongside apoE null mice, during which formation of AAA was monitored by echo determination of abdominal aortic size on weekly basis and post-mortem inspection.

RESULTS

Indeed, although AAA formation was not significantly different between apoE and hph-1/apoE mice, there were significantly more atherosclerotic lesions formed in hph-1/apoE double mutant mice. These data indicate that AAA forms consequent to a certain extent of eNOS uncoupling activity. By contrast, worsened eNOS uncoupling activity is still associated with deteriorated atherogenesis in hph-1/apoE double mutant mice. In addition, oral FA administration or overexpression of DHFR substantially alleviated excessive atherosclerosis and AAA formation in apoE null mice and hph-1/apoE double mutant mice.

DISCUSSION: These findings seem to establish that targeting DHFR to fully restore eNOS function or to fully recouple eNOS into its native coupled state, can be employed as a novel and robust therapeutic strategy to alleviate advanced atherosclerosis.