6533b7d6fe1ef96bd12670aa

RESEARCH PRODUCT

A non-canonical chemical feedback self-limits nitric oxide-cyclic GMP signaling in health and disease

subject

description

Endothelial nitric oxide (NO) stimulates the heme protein, soluble guanylyl cyclase (sGC) to form vasoprotective cyclic GMP (cGMP). In different disease states such as pulmonary hypertension, NO-cGMP signaling is pharmacologically augmented, yet the pathomechanisms leading to its dysregulation are incompletely understood. Here we show in pulmonary artery endothelial cells that endogenous NO or NO donor compounds acutely stimulate sGC activity, but chronically down-regulate both sGC protein and cGMP formation. Surprisingly, this endogenous feedback mechanism was independent of canonical cGMP signaling via cGMP-dependent protein kinase. It did not involve thiol-dependent modulation, a process relevant for sGC maturation, either. Rather tonic NO exposure led to inactivation and degradation of NO-sGC and without affecting NO-insensitive apo-sGC levels. Apo-sGC could be re-activated pharmacologically by the heme mimetic class of so-called sGC activators. Importantly, this non-canonical feedback was also observed in vivo. Specifically, it was induced by pathological high levels of NO in acute respiratory distress syndrome in which a similar self-limiting redox shift from NO-sensitive sGC to NO-insensitive apo-sGC occurred. Thus, our data establish a bimodal mechanism by which NO acutely stimulates sGC and chronically decreases sGC levels as part of a physiological and pathological self-limiting feedback. Of therapeutic importance in disease, our findings i) caution against any chronic use of classical NO donor drugs and ii) suggest that high NO-induced apo-sGC can be functionally fully recovered by sGC activator drugs to re-establish cGMP formation.