A BIOPHYSICAL INVESTIGATION ON THE MANNOSE-BINDING LECTIN INTERACTION WITH NORMAL AND SICKLE CELL ANEMIA RED BLOOD CELLS

Mannose-binding lectin (MBL) is a calcium-dependent protein with important functions in the human innate immune system. Studies have also shown that individuals with sickle cell anemia (SCA) and MBL deficiency are more susceptible to vaso-occlusive crises, indicating a potential role of MBL on SCA red blood cells (RBCs). This study aimed to investigate the MBL interaction with HbA (normal) and SCA RBCs using advanced biophysical techniques: optical tweezers (OT) and atomic force microscopy (AFM). The OT and the AFM are complementary tools. While the OT provides the overall RBC elasticity, the AFM gives information on ultrastructural properties and punctual membrane stiffness. Herein, fluorescent cationic quantum dots (QDs) were also used to evaluate the membrane charges of SCA RBCs. Osmotic fragility tests were also performed to complement further the study of the MBL effects on RBC membrane in both populations. The results with QDs showed that the membrane of SCA RBCs is less negative than HbA RBCs, possibly due to reduced sialic acid content. The OT, osmotic fragility, and AFM assays corroborated each other, suggesting that MBL can modulate the biomechanics of both HbA e SCA RBC populations, decreasing their deformability, and also may have greater interaction with SCA RBCs. Under the in vitro conditions evaluated, we believe that in the body, MBL may be (i) helping to stabilize the membrane and cytoskeleton of SCA RBCs preventing their sickling, and (ii) by having greater interaction with SCA RBCs, MBL may act as an opsonizing (and activating) biomolecule helping to deplete these cells, preventing their accumulation and possible clot formation in the microvessels. Overall, we believe this study provided insights into the role of MBL on SCA RBCs, inciting further investigations to understand better its involvement in the SCA pathophysiology. This work was supported by CNPq, CAPES, and FACEPE. The authors also acknowledge the National Institute of Photonics (INFo).