Cardiovascular effects of modulators of soluble guanylyl cyclase activity

Soluble guanylyl cyclase (sGC) is one of the key enzymes of the nitric-oxide (NO)/cyclic 3',5'-guanosine monophosphate (cGMP) pathway. Located in virtually all mammalian cells, it controls the vessel tone, smooth muscle cell growth, platelet aggregation, and leukocyte adhesion. In vivo sGC activity is mainly regulated by NO which in turn is released from L-arginine by nitric oxide synthases. One of the main diseases of the cardiovascular system, endothelial dysfunction, leads to a diminished NO synthesis and thus increases vessel tone as well as the risk of thrombosis. The predominant therapeutic approach to this condition is a NO replacement therapy, as exemplified by organic nitrates, molsidomin, and other NO releasing substances. Recent advances in drug discovery provided a variety of other approaches to activate sGC, which may help to circumvent both the tolerance problem and some non-specific actions associated with NO donor drugs. Substances like BAY 41-2272 stimulate sGC in a heme-dependent fashion and synergize with NO, allowing to enhance the effects both of endogenous NO and of exogenous NO donors. On the other hand, heme-independent activators like BAY 58-2667 allow to activate sGC even if it is rendered unresponsive to NO due to oxidative stress or heme loss. Furthermore, a few substances have been described as specific inhibitors of sGC that allow to alleviate the effects of excess NO production as seen in shock. This review discusses the cardiovascular effects of heme-dependent and heme-independent activators as well as of inhibitors of sGC.