Abstract

We and other investigators obtained evidence that platelets stimulate endothelin-1 (ET-1) production at both message and protein levels in vascular endothelial cells (ECs), and that platelet-derived transforming growth factor-beta 1 (TGF-beta 1) is responsible for this stimulation. In the present study, we examined the effects of acidification or heat treatment, known to activate latent TGF-beta 1, on the platelet supernatant-induced ET-1 production in cultured porcine aortic ECs. Supernatant of platelets (6.0 x 10(8) platelets/ml) aggregated by adenosine diphosphate contained large amounts of TGF-beta 1, but were almost in a latent form, and the proportion of active TGF-beta 1 in the supernatant was increased markedly in the case of acidification or heat treatment. These treatments also significantly potentiated the supernatant-induced stimulation of prepro ET-1 mRNA expression and the ET-1 release in ECs. Purified TGF-beta 1 also enhanced ET-1 release, dose-dependently, but the enhancement declined at the higher concentrations. Thus, powerful stimulation of ET-1 production by platelet supernatant after acidification or heat treatment cannot be explained only by increments in active TGF-beta 1. The supernatant-induced stimulation of ET-1 synthesis was significantly inhibited by concomitant treatment of TGF-beta 1 neutralizing antibody, but this inhibition was incomplete even at a concentration that abolished TGF-beta 1-induced maximal stimulation. These results suggest that platelet-induced stimulation and subsequent acidification and heat treatment-induced potentiation on endothelial ET-1 production depend closely on release and activation of TGF-beta 1 derived from platelets.(ABSTRACT TRUNCATED AT 250 WORDS)