What is the clinical evidence from this study?

Study design: Other. Population: Aortic valve disease (n=21). Intervention: TNFα with or without BH4 or peg-SOD vs. Control. Primary outcome: Endothelial oxidative stress and calcification.

April 13, 2015Open Access

Endothelial-Derived Oxidative Stress Drives Myofibroblastic Activation and Calcification of the Aortic Valve

Key Result

TNFα-driven endothelial oxidative stress causes loss of endothelial protective function, chronic inflammation, and fibrogenic and osteogenic activation, which are mitigated differentially by BH4 and peg-SOD.

Structured PICO

Population

21 adults aged 65-90 years undergoing planned, non-elective valve replacement surgery for calcified aortic valves, alongside porcine in vitro and ex vivo models.

Intervention

TNFα treatment (30 ng/mL) alone or co-treated with tetrahydrobiopterin (BH4 10 μmol/L), apocynin (100 μmol/L), or peg-SOD (20U/mL) for up to 48 hours in cells and 21 days in ex vivo leaflets.

Comparator

Untreated controls or TNFα treatment alone.

Outcome

Endothelial oxidative stress (superoxide, H2O2), endothelial function (eNOS, VE-cadherin, NO secretion), inflammatory response (VCAM-1), and fibrogenic/osteogenic activation (collagen, αSMA, calcification).surrogate

TNFα-driven endothelial oxidative stress promotes aortic valve calcification and fibrosis, which can be mitigated by targeted antioxidants like BH4 and peg-SOD.

Limitations

Lack of direct experimental interrogation of mtROS as a propagator of AVD.

Abstract

AIMS: Oxidative stress is present in and contributes to calcification of the aortic valve, but the driving factors behind the initiation of valve oxidative stress are not well understood. We tested whether the valve endothelium acts as an initiator and propagator of oxidative stress in aortic valve disease. METHODS AND RESULTS: Calcified human aortic valves showed side-specific elevation of superoxide in the endothelium, co-localized with high VCAM1 expression, linking oxidative stress, inflammation, and valve degeneration. Treatment with inflammatory cytokine TNFα increased superoxide and oxidative stress and decreased eNOS and VE-cadherin acutely over 48 hours in aortic valve endothelial cells (VEC) and chronically over 21 days in ex vivo AV leaflets. Co-treatment of VEC with tetrahydrobiopterin (BH4) but not apocynin mitigated TNFα-driven VEC oxidative stress. Co-treatment of ex vivo AV leaflets with TNFα+BH4 or TNFα+peg-SOD rescued endothelial function and mitigated inflammatory responses. Both BH4 and peg-SOD rescued valve leaflets from the pro-osteogenic effects of TNFα treatment, but only peg-SOD was able to mitigate the fibrogenic effects, including increased collagen and αSMA expression. CONCLUSIONS: Aortic valve endothelial cells are a novel source of oxidative stress in aortic valve disease. TNFα-driven VEC oxidative stress causes loss of endothelial protective function, chronic inflammation, and fibrogenic and osteogenic activation, mitigated differentially by BH4 and peg-SOD. These mechanisms identify new targets for tailored antioxidant therapy focused on mitigation of oxidative stress and restoration of endothelial protection.

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