Pharmacokinetics and pharmacodynamics of single dose of inhaled nebulized sodium nitrite in healthy and hemoglobin E/β-thalassemia subjects

Efficacy and safety of inhaled nitrite in addition to sildenafil in thalassemia patients with pulmonary hypertension: A 12-week randomized, double-blind placebo-controlled clinical trial

Pulmonary hypertension is a significant complication in thalassemia patients. Recent studies showed that inhaled nebulized nitrite could rapidly decrease pulmonary artery pressure. We conducted a multicenter, randomized, double-blind, placebo-controlled trial in thalassemia patients with symptomatic pulmonary hypertension diagnosed by right heart catheterization. Eleven patients were recruited; five were assigned to the nitrite group and six to the placebo group. Patients were treated with the optimal doses of sildenafil for pulmonary hypertension and randomly assigned into the placebo or nitrite groups. Patients in the nitrite group were given inhaled nebulized 30 mg sodium nitrite twice a day for 12 weeks. The clinical outcomes measured at week 12 were the changes in 6-min walk distance (6MWD), mean pulmonary artery pressure (MPAP), and N-terminal pro B-type natriuretic peptide. The MPAP estimated by echocardiography was significantly reduced from 33.6 ± 7.5 mmHg to 25.8 ± 6.0 mmHg (mean difference = 7.76 ± 3.69 mmHg, p = 0.009 by paired t-test). Furthermore, 6MWD was slightly increased from 382.0 ± 54.0 m to 432 ± 53.9 m (mean difference = 50.0 ± 42.8 m, p = 0.059 by paired t-test) in the nitrite group. At week 12, the nitrite group had lower MPAP than the placebo group (25.8 ± 6.0 vs. 45.7 ± 18.5 mmHg, p = 0.048 by unpaired t-test). No significant difference in 6MWD and N-terminal pro B-type natriuretic peptide between the two groups was observed at week 12. There was no hypotension or other significant adverse effects in the nitrite group.

Nitrous anhydrase activity of carbonic anhydrase II: cysteine is required for nitric oxide (NO) dependent phosphorylation of VASP in human platelets

The carbonic anhydrase (CA) family does not only catalyse the reversible hydration of CO₂ to bicarbonate, but it also possesses esterase and phosphatase activity. Recently, bovine CA II and human CA II have been reported to convert inorganic nitrite (O=N-O⁻) to nitric oxide (NO) and nitrous anhydride (N₂O₃). Given the ability of NO to mediate vasodilation and inhibit platelet aggregation, this CA II activity would represent a bioactivation of nitrite. There are contradictory reports in the literature and the physiological role of CA II nitrite bioactivation is still disputed. Here, we provide new experimental data in support of the nitrous anhydrase activity of CA II and the key role L-cysteine in the bioactivation of nitrite by CA II. Using washed human platelets and by measuring VASP phosphorylation we provide evidence that exogenous nitrite (10 µM) is bioactivated to NO in a manner strongly depending on L-cysteine (100 and 200 µM). The process is not inhibitable by acetazolamide, a potent CA inhibitor. The contradictory results of recently published studies in this area are thoroughly discussed.

Sodium nitrite detection in costal cartilage and vitreous humor - Case report of fatal poisoning with sodium nitrite

Medico-legal case reports very rarely describe sodium nitrite poisonings, but when they do most often they describe fatal suicide attempts. The case report presents a suicidal attempt with sodium nitrite of unknown provenance and the first attempt to detect nitrite ions in costal cartilage and vitreous humor samples. In February 2020, the corpse of a 23-year-old man was revealed in a student apartment. According to the prosecutor's office, the deceased had an incomplete IT (Information Technology) degree. The onsite inspection revealed the body on the bathroom floor, an opened container with sodium nitrite III in the bathroom cabinet, and a farewell letter in the apartment. The autopsy showed the hypoxia symptoms. The blood and urine of the deceased showed no trace of ethyl alcohol or psychoactive substances. Analyses showed the presence of nitrite ions in the blood (0.2 μg/ml) and urine (24.6 μg/ml) of the deceased. Additional analyses revealed nitrites presence in the gastric contents (2200 μg/ml), liver tissue (0.3 μg/g), kidney tissue (3.6 μg/g) and, for the first time, in costal cartilage (3.4 μg/g) and vitreous humor (57.7 μg/ml). The autopsy concluded that the cause of death was an acute cardio-respiratory failure in the course of suicidal sodium nitrite poisoning. The presented case indicates the need for collecting a wide range of samples for toxicological analyses. It also proves that both costal cartilage and vitreous humor may serve as an alternative forensic material in sodium nitrite poisonings.

Efficacy and safety of inhaled nebulized sodium nitrite in asthmatic patients

BACKGROUND

Nitrite is a physiologic nitric oxide (NO) derivative that can be bioactivated to NO. NO has been shown to attenuate airway inflammation and enhance the anti-inflammatory effect of corticosteroids in the animal model of asthma. Here, we aimed to investigate the efficacy and safety of inhaled sodium nitrite as add-on therapy with inhaled corticosteroid (ICS) in adult patients with persistent asthma.

METHODS

In protocol 1, 10 asthmatic patients were administered a single dose of nebulized 15-mg sodium nitrite to assess safety, effect on lung function, and pharmacokinetics of nitrite within 120 min. In protocol 2, 20 patients were randomly assigned to a nitrite (15 mg twice daily) group or a placebo group to assess the efficacy over 12 weeks. The primary outcome was the forced expiratory volume in 1 s (FEV₁). The secondary outcomes were other lung function parameters, unplanned asthma-related visits at the emergency department (ED) or outpatient department (OPD), admission days, asthma control test (ACT), and safety.

RESULTS

Nebulized sodium nitrite had neither acute adverse effect nor effect on lung function test within 120 min. No blood pressure change was seen. At week 12, FEV₁ increased in the nitrite group, whereas there was no change in the placebo group. There were 5 events of asthma exacerbation, 4 ED visits, and one unplanned OPD visit in the placebo group, but none of these was noted in the nitrite group. There was no change in ACT scores in both groups. No adverse event was reported during 12 weeks in the nitrite group. There was no change in methemoglobin levels and sputum inflammatory markers.

CONCLUSION

From our pilot trial, nebulized sodium nitrite is safe in asthmatic patients, and shows the potential to reduce asthma exacerbation compared with placebo.