Prolonged exposure to YC-1 induces apoptosis in adrenomedullary endothelial and chromaffin cells through a cGMP-independent mechanism

YC-1, a benzyl indazole derivative, is an NO-independent direct activator o f soluble guanylyl cyclase (sGC), which presents a synergistic action with NO in stimulating cGMP synthesis. These properties have served to suggest Y C-1 as an attractive therapeutic agent by permitting the reduction of nitro vasodilator dosage and regulating endogenous cGMP metabolism. Here we studi ed the effect of prolonged exposure of adrenomedullary endothelial and chro maffin cells to YC-1. We found that YC-1 increased cGMP in the two types of cells and this action was blocked by the sGC inhibitor 1H-[1,2,4]oxadiazol o[4,3-a]quinoxalin-1-one (ODQ). Cells underwent apoptotic death in associat ion with increased caspase-3-like activity, DNA fragmentation, cytoskeletal disorganization and changes in membrane permeability after prolonged incub ation with YC-1. Caspase-3-like protease activity and DNA fragments in the cytoplasm were increased in a dose-dependent manner by 16 h YC-1 treatment. The specific and cell permeable caspase-3-like protease inhibitor DEVD-CHO effectively inhibited YC-1-mediated caspase-3-like activation and DNA frag mentation. Moreover, YC-1 also induced cell shape changes accompanied by ac tin filament disorganization and alterations in membrane permeability. Cell s incubated for 24 h with YC-1 showed damaged membranes by binding to nucle ic acid of a dye excluded by the intact plasma membrane of live cells. YC-1 also induced a decrease in the intracellular non-specific esterase activit y, another indication of cell toxicity. Apoptotic phenomena were not preven ted by the presence of ODQ although it effectively inhibited the YC-1-elici ted cGMP increases. These findings indicate that YC-1 induces apoptosis by activating caspase-3-like protease through a mechanism independent of sGC a ctivation. (C) 2001 Elsevier Science Ltd. All rights reserved.