Role of the membrane in the formation of heme degradation products in red blood cells

Abstract

Aims-Red blood cells (RBCs) have an extensive antioxidant system designed to eliminate the formation of reactive oxygen species (ROS). Nevertheless, RBC oxidant stress has been demonstrated by the formation of a fluorescent heme degradation product (ex.321 nm, em 465 nm) both in vitro and in vivo. We investigated the possibility that the observed heme degradation results from ROS generated on the membrane surface that are relatively inaccessible to the cellular antioxidants.Main Methods-Membrane and cytosol were separated by centrifugation and the fluorescence intensity and emission maximum was measured. The effect on the maximum emission of adding oxidized and reduced hemoglobin to the fluorescent product formed when hemin is degraded by H 2 O 2 was studied.Key findings-90% of the fluorescent heme degradation products in hemolysates are found on the membrane. Furthermore, these products are not transferred from the cytosol to the membrane and must, therefore, be formed on the membrane. We also showed that the elevated level of heme degradation in HbCC cells that is attributed to increased oxidative stress was found on the membrane.Significance-These results suggest that, although ROS generated in the cytosol are neutralized by antioxidant enzymes, H 2 O 2 generated by the membrane bound hemoglobin is not accessible to the cytostolic antioxidants and reacts to generate fluorescent heme degradation products. The formation of H 2 O 2 on the membrane surface can explain the release of ROS from the RBC to other tissues and ROS damage to the membrane that can alter red cell function and lead to the removal of RBCs from circulation by macrophages.

Stabilization of erythrocytes against oxidative and hypotonic stress by tannins isolated from sumac leaves (Rhus typhina L.) and grape seeds (Vitis vinifera L.)

“…The oxidative stress of erythrocytes accompanies many pathological conditions, such as sickle cell and iron deficiency anemias and thalassemia [8,29,30], as well as aging [17,31], hypoxia [9] and obesity [32]. An intensive search has been going on for natural antioxidants to treat diseases induced by RONS.…”

“…The damage of erythrocytes, for example by thermal injury-induced hemolysis, can also be accomplished by the activation of neutrophils [6]. On the other hand, in different pathological situations, erythrocytes are a potential source of RONS due to autoxidation of hemoglobin which leads to formation of superoxide anions and hydroperoxides [7][8][9]. Oxidative stress induces the loss of cell plasticity with impaired deformability, associated with changes in the cytoskeleton network and also suicidal death of erythrocytes, known as eryptosis [10][11][12], which leads to the elimination of erythrocytes and finally to anemia.…”

Erythrocytes Induce Proinflammatory Endothelial Activation in Hypoxia

“…The hypoxiainduced p65 translocation was inhibited in mice overexpressing the H 2 O 2 inhibitor catalase (28) ( Figure 6C, lanes 2 and 4), indicating that H 2 O 2 played a critical role in the response. In mice expressing endothelial-specific heterozygous mutations on Ser 32 and Ser 36 of the negative regulator of NF-kBa (IkBa 1/2 ) that block NF-kB activation (30), hypoxia did not cause nuclear p65 translocation ( Figure 6C, lanes 7 and 8), affirming that NFkB was activated in hypoxia. Further, in FLECs derived from IkBa 1/2 mice, HIF1a stabilization in hypoxia was absent ( Figure 6D), and the hypoxia-induced increase of E-selectin expression was markedly blunted ( Figures 6E, 6F, E6A, and E6B).…”

“…A mechanistic understanding of the erythrocyte effect was developed through a consideration of the role of Hb binding to erythrocyte membrane protein, band 3 (32). Although band 3 has multiple erythrocyte functions, including bicarbonatechloride exchange and cytoskeletal stability (33), the N-terminal cytoplasmic region of band 3 is the site for the competitive binding of deoxy-Hb and several glycolytic enzymes (22,31,34).…”

Which hemogram parameter is more cautionary in euthyroid patients with gestational diabetes mellitus

“…The metaanalysis, which states that 1% increase of RDW is associated with the 14% mortality increase in patients with Diabetes Mellitus, is the leading motive behind the research of these parameter (8). The reason of the increase of DM can not be enlightened completely, however it can be associated with oxidative stress and rapid erythrocyte elimination (9). Any significant relation in respect of RDW between patients with GDM and healthy pregnant women has not been found in the study of Erdogan et al (10).…”