Reduction in band 3 protein of red cells in sickle cell anaemia

Signaling-biophysical modeling unravels mechanistic control of red blood cell phagocytosis by macrophages in sickle cell disease

Red blood cell (RBC) aging manifests through progressive changes in cell morphology, rigidity, and expression of membrane proteins. To maintain the quality of circulating blood, splenic macrophages detect the biochemical signals and biophysical changes of RBCs and selectively clear them through erythrophagocytosis. In sickle cell disease (SCD), RBCs display alterations affecting their interaction with macrophages, leading to aberrant phagocytosis that may cause life-threatening spleen sequestration crises. To illuminate the mechanistic control of RBC engulfment by macrophages in SCD, we integrate a system biology model of RBC-macrophage signaling interactions with a biophysical model of macrophage engulfment, as well as in vitro phagocytosis experiments using the spleen-on-a-chip technology. Our modeling framework accurately predicts the phagocytosis dynamics of RBCs under different disease conditions, reveals patterns distinguishing normal and sickle RBCs, and identifies molecular targets including Src homology 2 domain-containing protein tyrosine phosphatase-1 (SHP1) and cluster of differentiation 47 (CD47)/signal regulatory protein α (SIRPα) as therapeutic targets to facilitate the controlled clearance of sickle RBCs in the spleen.

Alterations in band 3 protein and anion exchange in red blood cells of renal failure patients

The precise nature of band 3 protein and its involvement in oxalate exchange in the red blood cells (RBCs) of renal failure patients has not been studied in detail. Therefore, here we studied the oxalate exchange and binding by band 3 protein in RBCs of humans with conditions of acute and chronic renal failure (ARF and CRF). The RBCs of ARF and CRF patients exhibited abnormal red cell morphology and an increased resistance to osmotic hemolysis. Further, an increase in the cholesterol content and decrease in the activities of Na(+)-K(+)-, Ca(2+)-, and Mg(2+)-ATPases of membranes were observed in the RBCs of ARF and CRF patients. A decrease in the oxalate flux was observed in the RBCs of ARF and CRF patients. The oxalate-binding activities of the RBC membranes were significantly lower in ARF (20 pmoles/mg protein) and CRF (5.3 pmoles/mg protein) patients as compared to that in the normal subjects (36 pmoles/mg protein). DEAE-cellulose and Sephadex G-200 column chromatography purification profiles revealed a distinctive shift in oxalate-binding activity of band 3 protein of RBCs of ARF and CRF patients as compared to that of the normal subjects. It was also observed from the binding studies with a fluorescent dye, eosin-5-maleimide, which specifically binds to band 3 protein, that the RBCs of ARF and CRF patients exhibited only 53 and 32% of abundance of band 3 protein, respectively, as compared to that in the RBCs of the normal subjects, thus revealing a decrease in the band 3 protein content in ARF and CRF patients. These results for the first time showed a decrease in the oxalate exchange in RBCs of patients with ARF and CRF, which was also concomitant with the low levels of abundance of band 3 protein.

Increased activity of 5' nucleotidase in serum of patients with sickle cell anaemia

Fifty-nine patients with homozygous sickle cell anaemia, 17 heterozygous individuals and 22 controls were investigated in respect to serum (S) 5'nucleotidase (5'NT, EC 3.1.3.5). The patients showed a significantly higher mean value of S-5'NT compared to the controls. However, this rise was heterogeneous as it occurred only among a subgroup of patients. The heterozygous individuals were not different from either the patients or the controls generating a situation which puts the heterozygous individuals in an intermediate position between the patients and the controls. S-5'NT showed significant correlation with S-bilirubin, S-aspartate aminotransferase, S-alanine aminotransferase and especially S-gammaglutamyl transferase. However, it was not correlated with S-alkaline phosphatase, which is another marker for hepatobiliary disease. These results suggest that the liver involvement in a subgroup of patients with sickle cell anaemia is a mixture of hepatocyte damage and the biliary tree involvement.

Increased membrane activity of glyceraldehyde 3-phosphate dehydrogenase in erythrocytes of patients with homozygous sickle cell anaemia

Membrane-bound glyceraldehyde 3-phosphate dehydrogenase activity was measured in erythrocytes from 43 patients with sickle cell anaemia, 24 heterozygous and 27 controls. A significant increase of the activity was found among the patients but no such difference was observed between the heterozygous and the control individuals. The patients showed nearly non Gaussian distribution of the enzyme activity and were subgrouped on the basis of these results, subgroup I had normal values and subgroup II showed markedly increased activities. The patients in subgroup II had significantly lower blood haemoglobin concentrations and significantly higher lactate dehydrogenase activities in serum than subgroup I. The subgroups did not differ in blood reticulocyte counts, serum bilirubin, serum iron concentrations or band 3 protein content of erythrocyte membranes.