Overexpression of endothelin-1 and endothelin receptors in the pulmonary arteries of failed Fontan patients

Abstract

Background: Endothelin-1 (ET-1), a potent vasoconstrictor, is considered to be implicated in failing Fontan circulation, however the expressions of ET-1 and endothelin receptor type A (ET(A)R) and type B (ET(B)R) in the pulmonary arteries of failed Fontan patients were not elucidated.

Methods: Immunohistochemistry and quantitative real-time PCR were used to analyse the expression levels of ET-1 and its receptors in the pulmonary arteries of the autopsy lung tissues of the patients who died after the Fontan procedure (n=10). We divided these patients into 3 groups, failed Fontan (n=4), heart failure (n=3) and non-failed Fontan (n=3), and then compared those to the age-matched normal controls (n=4).

Results: The intra-acinar pulmonary arteries of failed Fontan patients showed significant medial hypertrophy. Computational optical density analyses of the immunostaining revealed that the expressions of ET-1, ET(A)R, and ET(B)R in the intra-acinar pulmonary arteries were significantly increased in the failed Fontan patients (P<0.05 vs. normal controls), however no significant difference was observed between the non-failed Fontan patients and the normal controls. Quantitative real-time PCR analyses confirmed that the mRNA expressions of ET-1, ET(A)R, and ET(B)R were significantly increased in the failed Fontan patients (P<0.05 vs. normal controls).

Conclusion: The overexpression of ET-1 and its receptors in the pulmonary arteries can cause pulmonary vasoconstriction and vascular remodelling, leading to failed Fontan circulation. This study suggests a histopathological rationale for the potential benefits of endothelin receptor antagonists in patients with failing Fontan circulation.