Alterations in sensitivity to calcium and enzymatic hydrolysis of membranes from sickle cell disease and trait erythrocytes.
Normally, human erythrocytes display several responses to elevated intracellular calcium levels. These include a shape transition from discocyte to spherocyte, shedding of microvesicles into the extracellular fluid, and enhanced susceptibility to the hydrolytic action of secretory phospholipase A(2). These responses to elevated intracellular calcium were all blunted in erythrocytes containing hemoglobin S. The reduction of both the shape transition and the shedding of microvesicles were greater than the impairment of phospholipase susceptibility, and both correlated strongly with the intracellular content of hemoglobin S. In contrast to the response to elevated intracellular calcium, erythrocytes containing hemoglobin S displayed a 2.5-fold increase in basal susceptibility to phospholipase A(2) compared to control erythrocytes in the absence of ionophore. The effect was more prominent among samples from patients heterozygous for hemoglobin S than in samples from homozygous individuals. These results reveal additional abnormalities in the membranes of sickle cell erythrocytes beyond those described previously and demonstrate that red blood cells from both heterozygous and homozygous are affected. Furthermore, they suggest a possible means by which sickle cell disease and trait patients may display enhanced vulnerability to inflammatory stimuli.
Judd
Allan M
AM
Department of Physiology and Developmental Biology and Neuroscience Center, Brigham Young University, Provo, Utah 84602, USA.
Best
Katrina B
KB
Christensen
Kathrine
K
Rodgers
George M
GM
Bell
John D
JD
D000755:Anemia, Sickle Cell / Q000097:blood*; D002118:Calcium / Q000097:blood*; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D006451:Hemoglobin, Sickle / Q000032:analysis; D006801:Humans; D006868:Hydrolysis; D015759:Ionomycin / Q000494:pharmacology; D007700:Kinetics; D008027:Light; D010741:Phospholipases A / Q000378:metabolism*; D012542:Scattering, Radiation; D012805:Sickle Cell Trait / Q000097:blood*; D013050:Spectrometry, Fluorescence
D005227:Fatty Acids; D006451:Hemoglobin, Sickle; D015759:Ionomycin; D010741:Phospholipases A; D002118:Calcium