Cardiovascular and pharmacological implications of haem-deficient NO-unresponsive soluble guanylate cyclase knock-in mice

Abstract

Oxidative stress, a central mediator of cardiovascular disease, results in loss of the prosthetic haem group of soluble guanylate cyclase (sGC), preventing its activation by nitric oxide (NO). Here we introduce Apo-sGC mice expressing haem-free sGC. Apo-sGC mice are viable and develop hypertension. The haemodynamic effects of NO are abolished, but those of the sGC activator cinaciguat are enhanced in apo-sGC mice, suggesting that the effects of NO on smooth muscle relaxation, blood pressure regulation and inhibition of platelet aggregation require sGC activation by NO. Tumour necrosis factor (TNF)-induced hypotension and mortality are preserved in apo-sGC mice, indicating that pathways other than sGC signalling mediate the cardiovascular collapse in shock. Apo-sGC mice allow for differentiation between sGC-dependent and -independent NO effects and between haem-dependent and -independent sGC effects. Apo-sGC mice represent a unique experimental platform to study the in vivo consequences of sGC oxidation and the therapeutic potential of sGC activators.

Contemporary Approaches to Modulating the Nitric Oxide–cGMP Pathway in Cardiovascular Disease

“…Analogously, it can also be assumed that NOsGC activators will preferentially target the NOsGC in patients suffering from cardiovascular diseases as under these conditions the increased concentrations of ROS oxidizing the heme b in NOsGC, making the NOsGC more prone to lose its cofactor 104 . A recent study has generated mice lacking the prosthetic heme group of sGC and these mice are non-responsive to NO, hypertensive and are restored to normal blood pressure with cinaciguat but not the sGC stimulator, BAY 41-2272 105 proving the pathological significance of Apo-sGC and specificity of cinaciguat.…”

Decreased Soluble Guanylate Cyclase Contributes to Cardiac Dysfunction Induced by Chronic Doxorubicin Treatment in Mice

“…Since cardiac sGC expression was not altered by doxorubicin treatment, the observed decrease in activity likely results from post-translational modification of sGC. Oxidative modification of sGC, leading to loss of its prosthetic heme group and generation of NOinsensitive sGC, was previously reported in cardiovascular diseases associated with increased oxidative stress (2,4,26,42,48). In vivo administration of the radical scavenger, tempol, or targeting oxidized and heme-free sGC by adding the sGC activator, BAY 58-2667, ex vivo rescued the doxorubicinassociated decrease in cardiac sGC activity, suggesting that doxorubicin-induced oxidative modification of sGC represents an underlying mechanism for the reduction in activity.…”

“…It is conceivable that the oxidative stress associated with doxorubicin administration results in direct oxidative modification of sGC, potentially leading to loss of its prosthetic heme moiety (2,4,26,42,48) and decreased enzyme activity. To explore this possibility, we administered the radical scavenger tempol to WT mice before treatment with doxorubicin (20 mg/ kg, IP) or saline and evaluated cardiac sGC activity in the presence of DETA-NO.…”

Guanylyl cyclase can't stand the HETE

“…Preclinical models have also borne out a clear relationship between sGC activity, local vascular tone, and systemic blood pressure. This is best illustrated by the hypertensive phenotype in mice with genetic deletions of either sGC␣ 1 or sGC␤ 1 (3,8,9,17,19). Interestingly, the sGC␣ 1 and sGC␤ 1 null mice exhibit a strainand sex-specific rise in blood pressure (3,17), and this phenomenon has shed light on mechanisms critical to the vasoprotective functions of NO-sGC signaling, both in terms of endothelium-dependent dilatation and more global effects on neurohormonal axes.…”

“…This is best illustrated by the hypertensive phenotype in mice with genetic deletions of either sGC␣ 1 or sGC␤ 1 (3,8,9,17,19). Interestingly, the sGC␣ 1 and sGC␤ 1 null mice exhibit a strainand sex-specific rise in blood pressure (3,17), and this phenomenon has shed light on mechanisms critical to the vasoprotective functions of NO-sGC signaling, both in terms of endothelium-dependent dilatation and more global effects on neurohormonal axes. For example, the sex difference in response to sGC deletion dovetails well with studies revealing a marked increase in blood pressure in male endothelial NO synthase (eNOS)/cyclooxygenase-1 double knockout (KO) mice, which are unable to synthesize two principal endotheliumderived vasodilators, NO and prostacyclin (14).…”