ROS formation, mitochondrial potential and osmotic stability of the lamprey red blood cells: effect of adrenergic stimulation and hypoosmotic stress

Semi-anadromous animals experience salinity fluctuations during their life-span period. Alterations of environmental conditions induce stress response where catecholamines (CA) play a central role. Physiological stress and changes in external and internal osmolarity are frequently associated with increased production of reactive oxygen species (ROS). In this work, we studied the involvement of the cAMP/PKA pathway in mediating catecholamine-dependent effects on osmoregulatory responses, intracellular production of ROS, and mitochondrial membrane potential of the river lamprey (Lampetra fluviatilis, Linnaeus, 1758) red blood cells (RBCs). We also investigated the role of hypoosmotic shock in the process of ROS production and mitochondrial respiration of RBCs. For this, osmotic stability and the dynamics of the regulatory volume decrease (RVD) following hypoosmotic swelling, intracellular ROS levels, and changes in mitochondrial membrane potential were assessed in RBCs treated with epinephrine (Epi, 25 μM) and forskolin (Forsk, 20 μM). Epi and Forsk markedly reduced the osmotic stability of the lamprey RBCs whereas did not affect the dynamics of the RVD response in a hypoosmotic environment. Activation of PKA with Epi and Forsk increased ROS levels and decreased mitochondrial membrane potential of the lamprey RBCs. In contrast, upon hypoosmotic shock enhanced ROS production in RBCs was accompanied by increased mitochondrial membrane potential. Overall, a decrease in RBC osmotic stability and the enhancement of ROS formation induced by β-adrenergic stimulation raises concerns about stress-associated changes in RBC functions in agnathans. Increased ROS production in RBCs under hypoosmotic shock indicates that a decrease in blood osmolarity may be associated with oxidative damage of RBCs during lamprey migration.

Protein kinase A activity and NO are involved in the regulation of crucian carp (Carassius carassius) red blood cell osmotic fragility

Activation of the cAMP pathway by β-adrenergic stimulation and cGMP pathway by activation of guanylate cyclase substantially affects red blood cell (RBC) membrane properties in mammals. However, whether similar mechanisms are involved in RBC regulation of lower vertebrates, especially teleosts, is not elucidated yet. In this study, we evaluated the effects of adenylate cyclase activation by epinephrine and forskolin, guanylate cyclase activation by sodium nitroprusside, and the role of Na⁺/H⁺-exchanger in the changes of osmotic fragility and regulatory volume decrease (RVD) response in crucian carp RBCs. Western blot analysis of protein kinase A and protein kinase G substrate phosphorylation revealed that changes in osmotic fragility were regulated via the protein kinase A, but not protein kinase G signaling pathway. At the same time, the RVD response in crucian carp RBCs was not affected either by activation of adenylate or guanylate cyclase. Adenylate cyclase/protein kinase A activation significantly decreased RBC osmotic fragility, i.e., increased cell rigidity. Inhibition of Na⁺/H⁺-exchanger by amiloride had no effect on the epinephrine-mediated decrease of RBC osmotic fragility. NO donor SNP did not activate guanylate cyclase, however affected RBCs osmotic fragility by protein kinase G-independent mechanisms. Taken together, our data demonstrated that the cAMP/PKA signaling pathway and NO are involved in the regulation of crucian carp RBC osmotic fragility, but not in RVD response. The authors confirm that the study has no clinical trial.

The effects of Momordica balsamina methanolic extract on haematological function in streptozotocin-induced diabetic rats: Effects on selected markers

BACKGROUND

Chronic hyperglycaemia-induced haematological changes increase the risk of cardiovascular complications in diabetic patients. The administration of insulin injection as a bolus is accompanied with increased blood viscosity, which is not recommended for patients with congestive heart failure. Momordica balsamina methanolic extract (MB) has previously been shown to possess anti-hyperglycaemic and renal dysfunction ameliorative effects; however, the haematological effects of MB have not been shown. The current study therefore, investigated the short-term effects MB on selected haematological parameters in streptozotocin (STZ)-induced diabetic rats.

METHODS

Briefly, the air-dried Momordica balsamina leaves were sequentially extracted with methanol to yield a methanolic extract. STZ-induced diabetic rats were divided into untreated and treated groups with insulin (170 μg kg^-1 s.c.) and metformin (500 mg kg^-1 p.o.) MB (250 mg kg^-1 p.o.). MB was administered twice daily for the 5-week experimental period. Blood glucose concentration was monitored weekly. Animals were sacrificed terminally. Blood and kidneys were collected for haematological and biochemical analysis respectively.

RESULTS

Treatment with MB significantly decreased blood glucose concentration and improved erythropoietin secretion, thus significantly increasing red blood cell production in treated diabetic animals by comparison to untreated animals. MB also significantly improved haemoglobin concentrations and moderately increased erythrocyte indices specifically, mean corpuscular volume (MCV), mean corpuscular haemoglobin concentration (MCHC) and mean corpuscular haemoglobin (MCH) to no significance by comparison to untreated diabetic animals. MB treatment decreased the oxidative stress evoked by the induction of diabetes while improving the antioxidant status of treated animals by comparison to untreated animals respectively.

CONCLUSIONS

Administration of Momordica balsamina methanolic extract protects against some injurious haematological changes induced by hyperglycaemia, which may reduce the risks of cardiovascular complications.

Physical and Chemical Processes and the Morphofunctional Characteristics of Human Erythrocytes in Hyperglycaemia

Background: This study examines the effect of graduated hyperglycaemia on the state and oxygen-binding ability of hemoglobin, the correlation of phospholipid fractions and their metabolites in the membrane, the activity of proteolytic enzymes and the morphofunctional state of erythrocytes. Methods: Conformational changes in the molecule of hemoglobin were determined by Raman spectroscopy. The structure of the erythrocytes was analyzed using laser interference microscopy (LIM). To determine the activity of NADN-methemoglobinreductase, we used the P.G. Board method. The degree of glycosylation of the erythrocyte membranes was determined using a method previously described by Felkoren et al. Lipid extraction was performed using the Bligh and Dyer method. Detection of the phospholipids was performed using V. E. Vaskovsky method. Results: Conditions of hyperglycaemia are characterized by a low affinity of hemoglobin to oxygen, which is manifested as a parallel decrease in the content of hemoglobin oxyform and the growth of deoxyform, methemoglobin and membrane-bound hemoglobin. The degree of glycosylation of membrane proteins and hemoglobin is high. For example, in the case of hyperglycaemia, erythrocytic membranes reduce the content of all phospholipid fractions with a simultaneous increase in lysoforms, free fatty acids and the diacylglycerol (DAG). Step wise hyperglycaemia in incubation medium and human erythrocytes results in an increased content of peptide components and general trypsin-like activity in the cytosol, with a simultaneous decreased activity of μ-calpain and caspase 3. Conclusions: Metabolic disorders and damage of cell membranes during hyperglycaemia cause an increase in the population of echinocytes and spherocytes. The resulting disorders are accompanied with a high probability of intravascular haemolysis.