Endothelin-1 (ET-1), a potent vasoconstrictive peptide, is implicated in cyclosporin A (CyA) vasculopathy. Previously we have demonstrated, in an in vitro model of endothelial capillaries, that CyA inhibits the formation of the capillaries and, in high doses, disrupts the capillaries. This study addresses the role of ET-1 in CyA-induced endothelial dysfunction of the in vitro capillaries.

Endothelial cells (ECs) were cultured on a laminin-rich matrix, Matrigel, to form capillary-like networks. The ECs were treated with CyA either before capillary tube formation or after capillary tubes had formed. ppET-1 gene expression was studied by reverse transcriptase polymerase chain reaction. To determine if ET-1 was involved in the CyA-mediated disruption of the in vitro capillaries, ET-1 binding to the endothelial cells was blocked by ET-1 antibody and ET receptor antagonists. The effects of exogenous ET-1 were also studied. The results were quantified by counting the number of capillary networks, and the statistical significance was determined with ANOVA.

ppET-1 was expressed in ECs during capillary tube formation, but disappeared once capillary tubes had matured. The ppET-1 gene expression reappeared when the capillary tubes were exposed to CyA. Exogenous ET-1 partially reversed the inhibition of tube formation by cyclohexamide, allowing initiation of tube formation. CyA-mediated capillary dysfunction was completely prevented by an anti-ET-1 antibody and an ET-B receptor antagonist.

Endothelin-1 plays a significant role in CyA-induced endothelial dysfunction and may play a role in allograft vasculopathy. Blocking of ET-1 is a strategy to prevent endothelial dysfunction caused by CyA.