Abstract Body: Introduction: Tetralogy of Fallot (TOF) is one of the most frequent congenital heart diseases. Current treatment of TOF relies on surgery to correct associated cardiac defects. Despite surgery in early infancy, long-term cardiac complications of TOF remain a major problem. Our search for pathomechanisms involved in TOF recently detected the up-regulated bublin coiled coil protein (BBLN) on heart specimens of patients with uncorrected TOF and cyanosis. Increased cardiac BBLN causes severe heart failure with cardiac enlargement and early mortality in transgenic mice.
Research Question and Aim: Because patients with corrected TOF not only have an increased heart failure risk, but are also prone to aortic and coronary artery disease, we asked whether BBLN exerts a role in atherosclerosis. Therefore, we investigated the impact of BBLN on symptoms of atherosclerosis.
Methods: The study used 8-9-month-old male and female apolipoprotein E-deficient (B6-Apoe^-/-) mice as a model of atherosclerosis. The relationship between BBLN and atherosclerosis was investigated by generation of transgenic B6-Apoe^-/-Tg(CMVBBLN) mice with increased expression of BBLN under control of the ubiquitous CMV promoter. The third study group were B6-Apoe^-/-Tg(CMV)miBbln mice with expression of miBbln, which targets endogenous Bbln by miRNA-mediated down-regulation. Atherosclerotic lesion area in the aorta was quantified by oil red O staining. Immunohistology localized BBLN in the atherosclerotic aorta. Immunoblot detection of proteins was applied to quantify aortic proteins.
Results: Our study found that 8-9-month-old B6-Apoe^-/-Tg(CMVBBLN) mice with 2.5 ± 0.5-fold elevated (n=4, mean ± s.d.) aortic BBLN levels had a significantly 282.5 ± 36.7 % increased atherosclerotic plaque area (n=4, mean ± s.d., p<0.0001, Dunnett test). Vice versa, the atherosclerotic plaque area of age-matched B6-Apoe^-/-Tg(CMV)miBbln mice was strongly reduced, i.e. the atherosclerotic lesion size was only 27.7 ± 19.9 % of the lesion size of B6-Apoe^-/- mice (mean ± s.d., n=4, p=0.0098, Dunnett Test).
Conclusion: The TOF-related BBLN is a previously unrecognized atherosclerosis-enhancing protein. Thus, up-regulation of BBLN could account for the enhanced CAD risk of TOF patients.