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

Inhaled sodium nitrite has been reported to decrease pulmonary artery pressure in hemoglobin E/ß-thalassemia (HbE/ß-thal) patients with pulmonary hypertension. This study investigated the pharmacokinetics and pharmacodynamics of inhaled nebulized sodium nitrite in 10 healthy subjects and 8 HbE/ß-thal patients with high estimated pulmonary artery pressure. Nitrite pharmacokinetics, fraction exhaled nitric oxide (FENO), estimated right ventricular systolic pressure (eRVSP) measured by echocardiography, and platelet activation were determined. Nebulized sodium nitrite at doses used in this study (37.5 and 75 mg for healthy subjects and 15 mg for HbE/ß-thal patients) was well tolerated and did not cause changes in methemoglobin levels and systemic blood pressure. Absorption of inhaled nitrite was rapid with the absolute bioavailability of 18%. In whole blood, nitrite exhibited the dose-independent pharmacokinetics with clearance (CL) of 1.5 l/h/kg, volume of distribution (Vd) of 1.3 l/kg and half-life (t1/2) of 0.6 h. CL and Vd of nitrite was higher in red blood cells (RBC) than whole blood and plasma. HbE/ß-thal patients had lower nitrite CL and longer t1/2 in RBC than healthy subjects. FENO increased immediately after inhalation. Following nitrite inhalation, eRVSP remained unchanged but platelet activation was suppressed as evidenced by inhibition of adenosine diphosphate (ADP)-induced P-selectin expression and increase in phosphorylated vasodilator-stimulated phosphoprotein (P-VASPSer239) in platelets. There were no changes in markers of oxidative and nitrosative stress after inhalation. Our results support further development of inhaled nebulized sodium nitrite for treatment of pulmonary hypertension in ß-thalassemia.

Abnormal red blood cell morphological changes in thalassaemia associated with iron overload and oxidative stress.

AIMS: Iron overload is a major factor contributing to the overall pathology of thalassaemia, which is primarily mediated by ineffective erythropoiesis and shorter mature red blood cell (RBC) survival. Iron accumulation in RBCs generates reactive oxygen species (ROS) that cause cellular damage such as lipid peroxidation and RBC membrane deformation. Abnormal RBCs in patients with thalassaemia are commonly known as microcytic hypochromic anaemia with poikilocytosis. However, iron and ROS accumulation in RBCs as related to RBC morphological changes in patients with thalassaemia has not been reported. METHODS: Twenty-one patients with thalassaemia, including HbH, HbH with Hb Constant Spring and ß-thalassaemia/HbE (splenectomy and non-splenectomy) genotypes, and five normal subjects were recruited. RBC morphology was analysed by light and scanning electron microscopy. Systemic and RBC iron status and oxidative stress were examined. RESULTS: Decreased normocytes were observed in the samples of patients with thalassaemia, with RBC morphological abnormality being related to the type of disease (α-thalassaemia or ß-thalassaemia) and splenic status. Target cells and crenated cells were mainly found in splenectomised patients with ß-thalassaemia/HbE, while target cells and teardrop cells were found in non-splenectomised patients. Patients with thalassaemia had high levels of serum ferritin, red cell ferritin and ROS in RBCs compared with normal subjects (p<0.05). Negative correlations between the amount of normocytes and serum ferritin (rs=-0.518, p=0.011), red cell ferritin (rs=-0.467, p=0.025) or ROS in RBCs (rs=-0.672, p<0.001) were observed. CONCLUSIONS: Iron overload and its consequent intracellular oxidative stress in RBCs were associated with reduce normocytes in patients with thalassaemia.