Introduction:
Bicuspid aortic valve (BAV) is associated with an aortopathy that manifests as a dilatation of the proximal ascending aorta. The mechanisms of aneurysm formation in BAV patients are not completely understood. Our group established that medial smooth muscle cells (SMC) from aneurysmal BAV patients exhibit a weakened oxidative stress defense.
Hypothesis:
The weakened oxidative stress defense of medial SMCs in BAV patients leads to elevated oxidative stress in the proximal ascending aorta and decreases SMC viability.
Methods:
Aortic specimens were harvested from patients undergoing aortic valve and/or ascending aortic replacement due to aneurysm, or heart transplant, with IRB approval and informed patient consent. Levels of the superoxide anion-specific oxidation product 2-OH-E
+
was detected via HPLC in hydroethidine-exposed fresh human aortic specimens. Lipid peroxidation was quantified by ELISA-based detection of 8-iso-prostaglandin F2α. Superoxide anion (O
2
•-
) production and cell viability in primary SMC were detected using the cytochrome c reduction assay, and the MTT assay respectively.
Results:
Levels of O
2
•-
and lipid peroxidation were elevated in BAV specimens when compared with tricuspid aortic valve (TAV) specimens (8.7 ± 0.90 vs 6.1 ± 0.90 pmol/mg, and 610±32 vs 458±45 pg/mg, Fig A and B respectively). Elevated O
2
•-
production was detected in primary SMC
in vitro
when compared with SMC from TAV patients (13.2 ± 2.9 vs 6.7 ± 1.7 pmol/min/mg, Fig C). Addition of peroxide to primary SMC resulted in intracellular O
2
•-
-mediated cell death (Fig D).
Conclusions:
Our results indicate that accumulation of O
2
•-
in SMC is associated with increased oxidative stress and with increased cell death in the setting of BAV. Ongoing studies are focused on defining mechanisms of O
2
•-
generation and the impact on aortic wall biomechanics. Importantly, this could help to develop novel interventions for BAV patients who are at risk for aortic catastrophe.
RpoHII Activates Oxidative-Stress Defense Systems and Is Controlled by RpoE in the Singlet Oxygen-Dependent Response in Rhodobacter sphaeroides