Hemoglobin deoxygenation and methemoglobinemia prevent regulatory volume decrease in crucian carp (Carassius carassius) red blood cells

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.

Short communication: ROS production and mitochondrial membrane potential in hemocytes of marine bivalves, Mytilus galloprovincialis and Magallana gigas, under hypoosmotic stress

Bivalve mollusks that inhabit low-depth coastal and estuarine areas frequently experience osmotic stress that may be also associated with alterations of antioxidant enzyme activities and markers of oxidative stress. Mitochondria are a major source of reactive oxygen species (ROS) in eucaryotic cells. Overpoduction of ROS induces oxidative stress leading to a damage of intracellular compartments and cell death. In euryhaline bivalves, information concerning cellular ROS production upon osmotic stress and changes in mitochondrial membrane potential is scarce. The present study investigates osmotic stability and hemocytes` regulatory volume decrease (RVD) of Mediterranean mussel (Mytilus galloprovincialis) and the Pacific oyster (Magallana gigas). We also studied dynamic changes in intracellular ROS levels and mitochondrial membrane potential in hemocytes undergoing the RVD response following hypoosmotic swelling. Our data revealed that osmotic stability of mussel and oyster hemocytes did not significantly differ. Loss of environmental osmolarity from 460.0 ± 2.0 mOsm l-1 to 216.0 ± 4.0 mOsm l-1 resulted in an increase of hemocyte volume by 60% of the initial cellular volume in mussels and by 28% in oysters. After rapid hypoosmotic swelling hemocytes of both species demonstrated the RVD response. At the end of 60 min exposure to hypoosmotic environment, hemocyte volume significantly decreased in both species by 10-12% compared to the maximal hemocyte volume. Hypoosmotic shock induced an increase of mitochondrial membrane potential in hemocytes of mussels and oysters. In mussels, increased mitochondrial membrane potential was accompanied with decreased ROS levels in hemocytes, whereas oyster hemocytes showed enhanced ROS production.

Cellular osmoregulation of the ark clam (Anadara kagoshimensis) hemocytes to hyposmotic media

Many bivalve species are considered to be euryhaline organisms due to effective adaptation to fluctuations of environmental salinity. Cellular mechanisms responsible for tolerance to salinity changes remain unclear for bivalves despite this question being critically important for commercially cultured species frequently introduced into regions differing from natural habitat by salinity regime. In the present work laser diffraction method was used for the analysis of volume changes in hemoglobin-containing ark clam (Anadara kagoshimensis) hemocytes following hyposmotic stimulation. Hemocytes responded to hyposmotic shock (decrease of media osmolarity from 461 to 216 mОsm/L) by a rapid swelling up to 171.5 ± 15.2% of control level. At normal osmotic conditions (osmolarity 461 mOsm/L), hemocyte mean cellular volume (MCV) was 354.0 ± 24.4 fl and maximum MCV of hyposmotically swollen cells prior lysis was 555.5 ± 57.4 fl (at the osmolarity 194 mOsm/L). Ark clam hemocytes demonstrated volume recovery response following hyposmotic swelling. Regulatory volume decrease (RVD) reaction did not depend on hemoglobin confirmation status. Final MCV of swollen hemocytes at the end of experimental period of RVD in oxygenated and deoxygenated suspensions did not significantly differ.

IMPROVEMENT OF CARDIOVASCULAR FUNCTION HEALTH LEVEL BY REGULAR SPORTS

ABSTRACT Introduction Regular physical activity helps improve cardiovascular and cerebrovascular skills. How to evaluate the nervous tension of the cardiovascular and cerebrovascular vessels through sports is a hot topic. Objective The paper discusses the influence of regular participation in sports on people’s cardiovascular function and blood-related indicators. Methods We select 30 healthy older adults who regularly participate in sports, record their ECG changes, blood pressure, heart rate and other related cardiovascular function indicators, and analyze the blood function of the elderly. Detection of blood cell count (RBC), red blood cell volume (MCV) and hemoglobin (Hb), serum creatinine (Cr), blood glucose (BGS), triglycerides (TG), cholesterol (TC), low-density lipoprotein (LDL) and high-Density lipoprotein (HDL) is measured. Results Older adults who persist in exercise for a long time have better indicators than those who do not exercise. Conclusions Appropriate aerobic exercise can reduce the stiffness of blood vessels in the elderly. Exercise can help the elderly increase heart rate variability and improve the heart’s autonomic nerve function’s blood indicators, and body mass. Level of evidence II; Therapeutic studies - investigation of treatment results.

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.

Potential role of cytoplasmic protein binding to erythrocyte membrane in counteracting oxidative and metabolic stress

The ability of protein to reversibly bind with membrane components is considered to be one of the oldest mechanisms of cell response to external stimuli. Erythrocytes have a well-developed mechanism of an adaptive response involving sorption-desorption processes, e.g. interactions of key glycolytic enzymes and hemoglobin with band 3 protein. A few publications have shown that under oxidative stress, cytoplasmic enzymes such as catalase, glutathione peroxidase and рeroxiredoxin bind to the erythrocyte membrane. The present work is a continuation of research in this direction to determine the causes and consequences of the interaction of cytoplasmic proteins with the membrane under conditions of oxidative stress and different glucose content. Human erythrocytes were incubated for five hours at 20 °C in an oxidizing medium of AscH – 1 · 10–4 M, Cu2+– 5 · 10–6 M with different glucose content (0–8 mM). Dynamic changes in the accumulation of membrane-bound hemoglobin, the distribution of ligand forms of hemoglobin in the cytoplasmic and membrane-bound fractions, the activity of membrane-associated and cytoplasmic forms of Cu/Zn superoxide dismutase (SOD1) and catalase, H2O2 content in extracellular and intracellular media were recorded. It was shown that binding of catalase and SOD1 to the erythrocyte membrane is initiated by oxidative stress and is a physiological function aimed at complete inactivation of extracellular and H2O2 and protection against their entry into the cell. It was shown that under conditions of glucose depletion and oxidative loading, catalase and SOD1 bind to the erythrocyte membrane, leading to inactivation of these enzymes. Membrane-bound hemoglobin was higher in cells incubated under these conditions than in glucose experiments. Glucose introduced into the incubation medium in an amount 4–8 mM causes complete binding of SOD1 to the membrane of erythrocytes, by involving it in the processes of casein kinase stabilization and glycolytic fluxes regulation. With mild oxidation, the amount of hemoglobin bound to the membrane does not change, indicating the presence of certain binding sites for hemoglobin with membrane proteins. We show that the activity of membrane-bound SOD1 along with the content of ligand forms in the composition of membrane-bound hemoglobin are informative indicators of the metabolic and redox state of erythrocytes.