Background— Sudden cardiac arrest (CA) is one of the leading causes of death worldwide. We sought to evaluate the impact of hydrogen sulfide (H ₂ S) on the outcome after CA and cardiopulmonary resuscitation (CPR) in mouse. Methods and Results— Mice were subjected to 8 minutes of normothermic CA and resuscitated with chest compression and mechanical ventilation. Seven minutes after the onset of CA (1 minute before CPR), mice received sodium sulfide (Na ₂ S) (0.55 mg/kg IV) or vehicle 1 minute before CPR. There was no difference in the rate of return of spontaneous circulation, CPR time to return of spontaneous circulation, and left ventricular function at return of spontaneous circulation between groups. Administration of Na ₂ S 1 minute before CPR markedly improved survival rate at 24 hours after CPR (15/15) compared with vehicle (10/26; P =0.0001 versus Na ₂ S). Administration of Na ₂ S prevented CA/CPR-induced oxidative stress and ameliorated left ventricular and neurological dysfunction 24 hours after CPR. Delayed administration of Na ₂ S at 10 minutes after CPR did not improve outcomes after CA/CPR. Cardioprotective effects of Na ₂ S were confirmed in isolated-perfused mouse hearts subjected to global ischemia and reperfusion. Cardiomyocyte-specific overexpression of cystathionine γ-lyase (an enzyme that produces H ₂ S) markedly improved outcomes of CA/CPR. Na ₂ S increased phosphorylation of nitric oxide synthase 3 in left ventricle and brain cortex, increased serum nitrite/nitrate levels, and attenuated CA-induced mitochondrial injury and cell death. Nitric oxide synthase 3 deficiency abrogated the protective effects of Na ₂ S on the outcome of CA/CPR. Conclusions— These results suggest that administration of Na ₂ S at the time of CPR improves outcome after CA possibly via a nitric oxide synthase 3–dependent signaling pathway.

Anaphylactic shock is a sudden, life-threatening allergic reaction associated with severe hypotension. Platelet-activating factor (PAF) is implicated in the cardiovascular dysfunctions occurring in various shock syndromes, including anaphylaxis. Excessive production of the vasodilator NO causes inflammatory hypotension and shock, and it is generally accepted that transcriptionally regulated inducible iNOS is responsible for this. Nevertheless, the contribution of NO to PAF-induced shock or anaphylactic shock is still ambiguous. We studied PAF and anaphylactic shock in conscious mice. Surprisingly, hyperacute PAF shock depended entirely on NO, produced not by inducible iNOS, but by constitutive eNOS, rapidly activated via the PI3K pathway. Soluble guanylate cyclase (sGC) is generally regarded as the principal vasorelaxing mediator of NO. Nevertheless, although methylene blue partially prevented PAF shock, neither 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ) nor sGCα1 deficiency did. Also, in 2 different models of active systemic anaphylaxis, inhibition of NOS, PI3K, or Akt or eNOS deficiency provided complete protection. In contrast to the unsubstantiated paradigm that only excessive iNOS-derived NO underlies cardiovascular collapse in shock, our data strongly support the unexpected concept that eNOS-derived NO is the principal vasodilator in anaphylactic shock and define eNOS and/or PI3K or Akt as new potential targets for treating anaphylaxis.

Significance: Type I collagenopathies are a heterogenous group of connective tissue disorders, caused by genetic defects in type I collagen. Inherent to these disorders is a large clinical variability, of which the underlying molecular basis remains undefined. By systematically analyzing skeletal phenotypes in a large set of type I collagen zebrafish mutants, we show that zebrafish models are able to both genocopy and phenocopy different forms of human type I collagenopathies, arguing for a similar pathogenetic basis. This study illustrates the future potential of zebrafish as a tool to further dissect the molecular basis of phenotypic variability in human type I collagenopathies, to improve diagnostic strategies as well as promote the discovery of new targetable pathways for pharmacological intervention of these disorders.

The effects of nitric oxide (NO) in the cardiovascular system are attributed in part to cGMP synthesis by the α₁β₁ isoform of soluble guanylate cyclase (sGC). Because available sGC inhibitors are neither enzyme- nor isoform-specific, we generated knockout mice for the α₁ subunit (sGCα₁^−/− mice) in order to investigate the function of sGCα₁β₁ in the regulation of blood pressure and cardiac function. Blood pressure was evaluated, using both non-invasive and invasive haemodynamic techniques, in intact and gonadectomized male and female sGCα₁^−/− and wild-type (WT) mice. Cardiac function was assessed with a conductance catheter inserted in the left ventricle of male and female sGCα₁^−/− and WT mice. Male sGCα₁^−/− mice developed hypertension (147 ± 2 mmHg), whereas female sGCα₁^−/− mice did not (115 ± 2 mmHg). Orchidectomy and treatment with an androgen receptor antagonist prevented hypertension, while ovariectomy did not influence the phenotype. Chronic testosterone treatment increased blood pressure in ovariectomized sGCα₁^−/− mice but not in WT mice. The NO synthase inhibitor N^ω-nitro-L-arginine methyl ester hydrochloride raised blood pressure similarly in male and female WT and sGCα₁^−/− mice. The ability of NO donor compounds to reduce blood pressure was slightly attenuated in sGCα₁^−/− male and female mice as compared to WT mice. The direct sGC stimulator BAY 41-2272 reduced blood pressure only in WT mice. Increased cardiac contractility and arterial elastance as well as impaired ventricular relaxation were observed in both male and female sGCα₁^−/− mice. These findings demonstrate that sGCα₁β₁-derived cGMP signalling has gender-specific and testosterone-dependent cardiovascular effects and reveal that the effects of NO on systemic blood pressure do not require sGCα₁β₁.

Background—: Sudden cardiac arrest (CA) is a leading cause of death worldwide. Breathing nitric oxide (NO) reduces ischemia/reperfusion injury in animal models and in patients. The objective of this study was to learn whether inhaled NO improves outcomes after CA and cardiopulmonary resuscitation (CPR). Methods and Results—: Adult male mice were subjected to potassium-induced CA for 7.5 minutes whereupon CPR was performed with chest compression and mechanical ventilation. One hour after CPR, mice were extubated and breathed air alone or air supplemented with 40 ppm NO for 23 hours. Mice that were subjected to CA/CPR and breathed air exhibited a poor 10-day survival rate (4 of 13), depressed neurological and left ventricular function, and increased caspase-3 activation and inflammatory cytokine induction in the brain. Magnetic resonance imaging revealed brain regions with marked water diffusion abnormality 24 hours after CA/CPR in mice that breathed air. Breathing air supplemented with NO for 23 hours starting 1 hour after CPR attenuated neurological and left ventricular dysfunction 4 days after CA/CPR and markedly improved 10-day survival rate (11 of 13; P =0.003 versus mice breathing air). The protective effects of inhaled NO on the outcome after CA/CPR were associated with reduced water diffusion abnormality, caspase-3 activation, and cytokine induction in the brain and increased serum nitrate/nitrite levels. Deficiency of the α1 subunit of soluble guanylate cyclase, a primary target of NO, abrogated the ability of inhaled NO to improve outcomes after CA/CPR. Conclusions—: These results suggest that NO inhalation after CA and successful CPR improves outcome via soluble guanylate cyclase–dependent mechanisms.

Rationale:: The regulation of calcium (Ca ²⁺ ) homeostasis by β-adrenergic receptor (βAR) activation provides the essential underpinnings of sympathetic regulation of myocardial function, as well as a basis for understanding molecular events that result in hypertrophic signaling and heart failure. Sympathetic stimulation of the βAR not only induces protein phosphorylation but also activates nitric oxide–dependent signaling, which modulates cardiac contractility. Nonetheless, the role of nitric oxide in βAR-dependent regulation of Ca ²⁺ handling has not yet been explicated fully. Objective:: To elucidate the role of protein S-nitrosylation, a major transducer of nitric oxide bioactivity, on βAR-dependent alterations in cardiomyocyte Ca ²⁺ handling and hypertrophy. Methods and Results:: Using transgenic mice to titrate the levels of protein S-nitrosylation, we uncovered major roles for protein S-nitrosylation, in general, and for phospholamban and cardiac troponin C S-nitrosylation, in particular, in βAR-dependent regulation of Ca ²⁺ homeostasis. Notably, S-nitrosylation of phospholamban consequent upon βAR stimulation is necessary for the inhibitory pentamerization of phospholamban, which activates sarcoplasmic reticulum Ca ²⁺ -ATPase and increases cytosolic Ca ²⁺ transients. Coincident S-nitrosylation of cardiac troponin C decreases myocardial sensitivity to Ca ²⁺ . During chronic adrenergic stimulation, global reductions in cellular S-nitrosylation mitigate hypertrophic signaling resulting from Ca ²⁺ overload. Conclusions:: S-Nitrosylation operates in concert with phosphorylation to regulate many cardiac Ca ²⁺ -handling proteins, including phospholamban and cardiac troponin C, thereby playing an essential and previously unrecognized role in cardiac Ca ²⁺ homeostasis. Manipulation of the S-nitrosylation level may prove therapeutic in heart failure.