Avaliação dos efeitos biomecânicos e funcionais da exposição de macrófagos às lipoproteínas nativas e oxidadas

Abstract

Atherosclerosis is chronic inflammatory disease characterised by the formation of an atheromatous plaque that diminish the blood vessel lumen. The plaque can also rupture and block small vessels, leading to complications such as strokes and heart attacks. This process is triggered by the presence of oxidised LDL (oxLDL) in the tunica intima of blood vessels and the consequent macrophage recruitment. In these sites, macrophages capture and accumulate oxLDL in their cytoplasm, turning into foam cells. These cells produce proinflammatory cytokines that recruit more immune cells, stimulating the inflammatory process progression and plaque growth. Many studies try to elucidate the role of oxLDL accumulation in macrophage activation and foam cell formation. However, little is known about the biomechanical effects induced by oxLDL in macrophages, as well as their consequences for cell activation that are not directly related to the cholesterol accumulation in the cytoplasm of these cells. In non-professional phagocytic cells, oxLDL induces increased membrane rigidity and actin cytoskeleton alteration. These effects are partially reproducible by cholesterol depletion and membrane rafts disorganization, induced by the treatment with MβCD. Since membrane rafts are important domains to the recruitment, organization and activity of plasma membrane proteins, alterations in raft dynamics can lead to several effects in the cell. It was shown in nonprofessional phagocytic cells that raft disruption affects actin reorganization and integrin distribution in the cell surface, also affecting cell migration and membrane rigidity. However, little is known about the morphofunctional effects of raft disruption in professional phagocytic cells, such as macrophages. Therefore, the goal of this study is to analyse the morphological, mechanical and functional effects of oxLDL treatment that are consequences of raft disruption, in macrophages, in order to elucidate the contribution of rafts for the pathologic process of atherosclerosis. We observed that the treatment with oxLDL alteres raft conformation of bone marrow derived macrophages (BMDM). A similar effect was observed in the treatment with MβCD. The similarities between the treatments could also be observed in the actin cytoskeleton organization, cell morphology and integrin distribution. OxLDL-treated macrophages showed higher actin polimerization, diffuse integrin distribution and cell shrinkage similarly 12 with the observed in MβCD-treated macrophages. Both treatments also increased the physical interaction between the actin cytoskeleton and membrane rafts, indicating a similar action mechanism. The physical alterations induced by oxLDL and MβCD also lead to deficient migration in macrophages. These results indicate that oxLDL can induce physical alterations in macrophages due to raft desorganization. Those alterations can have implications in the macrophage retention in the atheromatous plaque, the formation of foam cells, and consequently, atherosclerosis progression.