Nitric oxide synthase inhibition impairs myocardial efficiency and ventriculo-arterial matching in acute ischemic heart failure

Efficacy of Vincamine treatment in a rat model of anterior ischemic optic neuropathy

Non-arteritic anterior ischemic optic neuropathy (NAION) is characterized by the progressive and irreversible death of retinal ganglion cells (RGCs) which is caused by the insufficient blood supply to the optic nerve (ON) head. At present, hormone therapy is used to reduce optic edema, followed by nerve nutrition therapy to protect the ON. However, no surgical or medical therapy has proven to be beneficial consistently in treating NAION. Vincamine is an alkaloid extracted from the Apocynaceae Vinca plant. Vincamine and its derivatives acting as cerebral vasodilators can easily cross the blood-brain barrier, improve the metabolism of ischemic tissue and protect the neuron. In this study, we aimed to investigate the potential neuroprotection of Vincamine in the photodynamic induced rat model of NAION (rAION), to evaluate its effects and possible mechanisms. We found that Vincamine can rescue RGC death and reduce the number of apoptotic cells. The protection of Vincamine might play through the PI3K/Akt/eNOS signaling pathway. Therefore, Vincamine can be an effective therapy method for NAION.

The effect of Riociguat on cardiovascular function and efficiency in healthy, juvenile pigs

INTRODUCTION

Riociguat is a soluble guanylate cyclase stimulator approved for the treatment of pulmonary hypertension. Its effect on cardiometabolic efficiency is unknown. A potential cardiac energy sparing effect of this drug could imply a positive prognostic effect, particularly in patients with right heart failure from pulmonary hypertension.

METHOD

We infused Riociguat in six healthy juvenile pigs and measured the integrated cardiovascular effect and myocardial oxygen consumption. To assess the interplay with NO-blockade on cardiac function and efficiency we also administered the NO-blocker L- NAME to the animals after Riociguat.

RESULTS AND DISCUSSION

Infusion of 100 µg/kg Riociguat gave modest systemic vasodilatation seen as a drop in coronary and systemic vascular resistance of 36% and 26%, respectively. Right and left ventriculoarterial coupling index (Ees/Ea), stroke work efficiency (SWeff), and the relationship between left ventricular myocardial oxygen consumption (MVO₂ ) and total mechanical work (pressure-volume area; PVA) were unaffected by Riociguat. In contrast, systemic and pulmonary vasoconstriction induced by L-NAME (15 mg/kg) shifted the Ees/Ea ratio toward reduced SWeff in both systemic and pulmonary circulation. However, there was no surplus oxygen consumption, that was measured by the MVO₂ /PVA relationship after L-NAME in Riociguat-treated pigs. This suggests that Riociguat can reduce the NO-related cardiometabolic inefficiency previously observed by blocking the NO pathway.

Cardiogenic Shock: Failure of Oxygen Delivery and Oxygen Utilization

Cardiogenic shock remains a highly lethal condition. Conventional therapy including revascularization and mechanical circulatory support aims to improve cardiac output and oxygen delivery, but increasing basic and clinical observations indicate wider circulatory and cellular abnormalities, particularly at the advanced stages of shock. Progressive cardiogenic shock is associated with microcirculatory and cellular abnormalities. Cardiogenic shock is initially characterized by a failure to maintain global oxygen delivery; however, progressive cardiogenic shock is associated with the release of pro-inflammatory cytokines, derangement of the regulation of regional blood flow, microcirculatory abnormalities, and cellular dysoxia. These abnormalities are analogous to septic shock and may not be reversed by increase in oxygen delivery, even to supranormal levels. Earlier mechanical circulatory support in cardiogenic shock may limit the development of microcirculatory and cellular abnormalities.

Reassessment of a suggested pharmacological approach to heart failure: L-arginine is only a marginal NO donor in pigs

OBJECTIVES

L-Arginine has been tested in various cardiovascular diseases, mainly to improve endothelial function through NO production. However, as the results have been partly unpredictable, we assessed the hemodynamic, energetic and metabolic effects of L-arginine to clarify any potential benefits in postischemic left ventricular (LV) dysfunction.

METHODS

LV dysfunction was induced by repetitive brief coronary occlusions in 12 anesthetized, open chest pigs. L-Arginine was subsequently infused (bolus 400 mg·kg and continuously for 1 hour, 250 mg·kg·h). Hemodynamic parameters, metabolites of L-arginine and myocardial energetics were assessed sequentially.

RESULTS

L-Arginine infusions caused a substantial rise in plasma L-arginine (3474 ± 358 μmole·L) accompanied by a 2-fold increase in plasma L-citrulline. No significant alterations in vascular resistance or LV contractility were observed from L-arginine. Mean arterial pressure dropped from 78 ± 11 to 72 ± 10 mm Hg (P = 0.019) and 70 ± 8 mm Hg (P = 0.003) after bolus and infusions, respectively. Myocardial oxygen consumption was unaltered, and myocardial creatine content was not increased after 90 minutes of L-arginine infusion.

CONCLUSION

L-Arginine infusion did not influence the energetic cost of myocardial contractility, and only minor hemodynamic changes were observed despite a demonstrable turnover of L-arginine. These findings question the use of L-arginine to promote therapeutic NO formation in the acute setting.

Health-related quality of life of survivors of penetrating trunk trauma in Johannesburg, South Africa

PURPOSE

To study how the health-related quality of life (HRQOL) of survivors of penetrating trunk trauma (PTT) changes from pre-morbid status to 6 months after hospital discharge and to determine differences in the HRQOL between subjects ventilated for short and prolonged periods of time. To determine how the HRQOL of PTT survivors compares with that of a healthy control group in order to identify limitations imposed by critical illness.

METHODS

Retrospective and observational prospective assessment of the quality of life (QoL) of PTT survivors with the Medical Outcomes Short Form-36 (SF-36) UK English version questionnaire. Cross-sectional assessment of the QoL of a healthy control group with the SF-36.

RESULTS

The physical component summary (PCS) score was significantly reduced for the short mechanical ventilation (MV) group (n = 13) at 1 and 3 months compared to pre-admission status (p = 0.00, respectively). The mental component summary (MCS) score was significantly reduced at 1, 3 and 6 months (p = 0.00, respectively). The PCS and MCS were significantly reduced for the long MV group (n = 29) at all three assessments compared to the pre-admission HRQOL (p = 0.00-0.01). The short MV group reported HRQOL comparable to that of the healthy group (n = 40) at 6 months after discharge. The long MV group had a significant reduction in the PCS at 1, 3 and 6 months compared to the healthy group (p = 0.00, respectively). The long MV group had significantly reduced PCS at 3 and 6 months compared to the short MV group (p = 0.01 and 0.00, respectively).

CONCLUSIONS

Subjects who had higher morbidity and prolonged MV suffered from reduced HRQOL related to physical health for up to 6 months after discharge.

Post-resuscitation NOS inhibition does not improve hemodynamic recovery of hypoxic newborn pigs

BACKGROUND

Significant improvement in myocardial recovery has been shown previously with interventions to decrease reactive oxygen species after ischemia/hypoxia. We investigated whether co-administration of N-acetylcysteine (NAC, a scavenger for reactive oxygen species) and N (G)-monomethyl-L: -arginine (L-NMMA, a non-selective nitric oxide synthase inhibitor) results in better hemodynamic recovery.

DESIGN

Controlled, block-randomized study.

SETTING

University research laboratory.

SUBJECT

Mixed breed piglets (1-4d, 1.6-2.4 kg).

INTERVENTIONS

Acutely instrumented piglets received normocapnic alveolar hypoxia (10-15% oxygen) for 2 h followed by reoxygenation with 100% oxygen (1 h) then 21% oxygen (3 h). After reoxygenation, hypoxic-reoxygenated piglets were given either saline (controls), NAC [30 mg/kg bolus + 20 mg/(kg h) infusion], NMMA [0.1 mg/kg bolus + 0.1 mg/(kg h) infusion] or NAC + L-NMMA via intravenous infusion in a blinded, randomized fashion (n = 8/group). Sham-operated piglets had no hypoxia-reoxygenation (n = 5).

MEASUREMENTS AND RESULTS

Both cardiac index and stroke volume of hypoxia-reoxygenation controls remained depressed during reoxygenation (vs. normoxic baseline, p < 0.05). Post-resuscitation treatment with L-NMMA alone did not improve systemic hemodynamic recovery, but caused pulmonary hypertension (vs. controls). In contrast, treating the piglets with either NAC or NAC + L-NMMA improved cardiac index and stroke volume, with no effect on heart rate and blood pressure (vs. controls). These treatments also decreased various oxidative stress markers in myocardial tissues (vs. controls). However, there was no significant difference between NAC- and NAC + L-NMMA groups in all examined parameters.

CONCLUSIONS

Post-resuscitation administration of NAC improved cardiac function and reduced oxidative stress in newborn pigs with hypoxia-reoxygenation insult. Low-dose, non-selective inhibitor of nitric oxide synthase activity did not provide any further beneficial effect.

Inhibition of endogenous nitric oxide synthase augments contractile response to adenylyl cyclase stimulation without altering mechanical efficiency in patients with idiopathic dilated cardiomyopathy

BACKGROUND

Increased nitric oxide (NO) in the failing heart attenuates the myocardial contractile response to beta-adrenergic receptor stimulation. However, the physiological effects of NO on the beta-adrenergic post-receptor signaling system are unknown. The objective of the present study was to examine the effects of cardiac NO synthase (NOS) inhibition on left ventricular (LV) hemodynamics and mechanoenergetics in response to adenylyl cyclase stimulation in human heart failure.

METHODS AND RESULTS

The study group comprised 13 patients with heart failure because of idiopathic cardiomyopathy (IDC). Emax was examined as an index of LV contractility, LV external work (EW), pressure-volume area (PVA), myocardial oxygen consumption (MVO2), and mechanical efficiency (EW/MVO2) with the use of conductance and coronary sinus thermodilution catheters before and during colforsin daropate infusion, and during concurrent infusion of colforsin daropate with the NOS inhibitor, NG-monomethyl-L-arginine (L-NMMA; 200 micromol). Colforsin daropate increased Emax by 53% and EW by 18%, and reduced PVA by 14%, without altering MVO2 or mechanical efficiency. The combination of colforsin daropate with L-NMMA further increased Emax by 26% and reduced PVA by 9%, without altering MVO2 or mechanical efficiency.

CONCLUSIONS

These findings suggest endogenous NO may modulate beta-adrenergic post-receptor pathways and preserve myocardial efficiency in patients with IDC.