Serum Deprivation via MAP Kinase Pathway Endothelin-1 Inhibits Apoptosis of Vascular Smooth Muscle Cells Induced by Nitric Oxide

Endothelin (ET)-1, an endothelium-derived vasoconstrictor and mitogen, acts as an antiapoptotic factor against serum deprivation–induced apoptosis of endothelial cells and fibroblasts but enhances apoptosis of some cancer cells. In the present study, we examined whether nitric oxide (NO) and ET-1 modulate apoptosis of rat vascular smooth muscle cells (VSMCs) via the mitogen-activated protein (MAP) kinase pathway. Both serum deprivation and NO donors (FK409 and SNAP) caused apoptosis of VSMCs, as demonstrated by TdT-mediated dUTP-biotin nick end-labeling, appearance of fragmented DNA, and induction of caspase-3 activity. ET-1 dose-dependently antagonized apoptosis induced by serum deprivation and NO donors. A selective ETA receptor antagonist (BQ123) and a nonselective ETA/B receptor antagonist (TAK044), but not a selective ETB receptor antagonist (BQ788), inhibited the antiapoptotic effect of ET-1, indicating that the antiapoptotic effect of ET-1 is mediated via the ETA receptor. ET-1 activated MAP kinase, whose effect was inhibited by FK409. Transfection with an unphosphorylated wild-type MAP kinase kinase-1 (MAPKK-1) or its constitutively activated mutant protected VSMCs against apoptosis induced by serum deprivation and NO donors. Inhibition of MAP kinase activity with PD98059, a specific inhibitor of MAPKK-1, or by transfection of a dominant-negative MAPKK-1 mutant antagonized the antiapoptotic effect of ET-1, suggesting the involvement of MAP kinase in the antiapoptotic effect. The potent inhibitory effect of ET-1 on apoptosis of VSMCs induced by serum deprivation and NO suggests that the counterbalance between the 2 endothelium-derived factors contributes to the process of vascular remodeling by determining VSMC survival and death, respectively, via a common MAP kinase pathway. (Arterioscler Thromb Vasc Biol. 2000;20:989-997.)