Effects of soluble guanylate cyclase activation on heart transplantation in a rat model.

BACKGROUND: The nitric oxide (NO)/soluble guanylate cyclase (sGC)/cyclic guanosine monophosphate (cGMP) pathway is an important key mechanism to protect the heart from ischemia/reperfusion injury. However, this pathway is disrupted in several cardiovascular diseases as a result of decreased NO bioavailability and increased NO-insensitive forms of sGC. Cinaciguat preferentially activates these NO-insensitive, oxidized forms of sGC. METHODS: We assessed the hypothesis that targeting NO-unresponsive sGC would protect the graft against ischemia/reperfusion injury in a rat heart transplantation model. Before explantation, donor Lewis rats received methylcellulose (1%) vehicle or cinaciguat 10 mg/kg. The hearts were excised, stored in cold preservation solution, and heterotopically transplanted. We evaluated in vivo left ventricular function of the graft. RESULTS: After transplantation, decreased left ventricular systolic pressure (77 ± 3 mm Hg vs 123 ± 13 mm Hg, p < 0.05), dP/dt(max) (1,703 ± 162 mm Hg vs 3,350 ± 444 mm Hg, p < 0.05), and dP/dt(min) (995 ± 110 mm Hg vs 1,925 ± 332 mm Hg, p < 0.05) were significantly increased by cinaciguat. Coronary blood flow was significantly higher in the cinaciguat group compared with the control group. Additionally, cinaciguat increased adenosine triphosphate levels (1.9 ± 0.4 µmol/g vs 6.6 ± 0.8 µmol/g, p < 0.05) and improved energy charge potential. After transplantation, increased c-jun messenger RNA expression was downregulated, whereas superoxide dismutase-1 and cytochrome-c oxidase mRNA levels were upregulated by cinaciguat. Cinaciguat also significantly decreased myocardial DNA strand breaks induced by ischemia/reperfusion during transplantation and reduced death of cardiomyocytes in a cellular model of oxidative stress. CONCLUSIONS: By interacting with NO-unresponsive sGC, cinaciguat enhances the protective effects of the NO/cGMP pathway at different steps of signal transduction after global myocardial ischemia/reperfusion. Its clinical use as pre-conditioning agent could be a novel approach in cardiac surgery.

Nitric oxide- and heme-independent activation of soluble guanylate cyclase attenuates peroxynitrite-induced endothelial dysfunction in rat aorta.

Oxidative stress interferes with nitric oxide (NO)/soluble guanylate cyclase (sGC)/cyclic guanosine monophosphate (cGMP) signalling pathway through reduction of endogenous NO and formation of the strong intermediate oxidant peroxynitrite and leads to vascular dysfunction. We evaluated the effects of oral treatment with NO- and heme-independent sGC activator cinaciguat on peroxynitrite-induced vascular dysfunction in rat aorta. Sprague-Dawley rats were treated orally 2 times at an interval of 17 hours with vehicle or with cinaciguat (10 mg/kg). One hour after the last treatment, the animals were anesthetized, the thoracic aorta was removed, and the aortic segment preparations were incubated with and without the reactive oxidant peroxynitrite (200 µmol/L, 30 minutes). Endothelium-dependent (acetylcholine), -independent (sodium nitroprusside) vasorelaxations were investigated, and histopathological examination was performed. Incubation of aortic rings with peroxynitrite significantly attenuated the maximal endothelium-dependent relaxation (R (max)) to acetylcholine (peroxynitrite, 44.5% ± 5.9% vs control, 93.2% ± 2.0%, P < .05) and decreased pD(2) values (-logEC(50), EC(50) being the concentration of acetylcholine that elicited 50% of the maximal response) for the concentration-response curves as compared to control segments. Treatment of rats with cinaciguat significantly improved the decreased acetylcholine-induced vasorelaxation after exposure of aortic rings to peroxynitrite (cinaciguat + peroxynitrite, 67.1% ± 3.5% vs peroxynitrite, 44.5% ± 5.9%, P < .05). Incubation of aortic segments with peroxynitrite caused a significant shift of the sodium nitroprusside concentration-response curves to the right without any alterations in the R (max). Moreover, exposure of aortic rings to peroxynitrite resulted in increased nitro-oxidative stress and DNA breakage which were improved by cinaciguat. Treatment of rats with cinaciguat significantly increased intracellular cGMP levels in the aortic wall. Our results show under conditions of nitro-oxidative stress when signalling in the NO/sGC/cGMP pathway is impaired, acute activation of sGC by cinaciguat might be advantageous in the treatment of endothelial dysfunction in cardiovascular disease.