Mechanical stiffness softening and cell adhesion are coordinately regulated by ERM dephosphorylation in KG-1 cells

A study of macrophage mechanical properties and functional modulation based on the Young's modulus of PLGA-PEG fibers

The immune response of macrophages plays an important role in defending against viral infection, tumor deterioration and repairing of contused tissue. Macrophage functional differentiation induced by nanodrugs is the leading edge of current research, but nanodrugs have toxic side effects, and the influence of their physical properties on macrophages is not clear. Here we create an alternative way to modulate macrophage function through PLGA-PEG fibers' Young's modulus. Previously, we revealed that by controlling the Young's modulus of the fibers from kPa to MPa, all the fibers entered murine macrophage cells (RWA 264.7) in a similar manner, and based on that, we found that macrophages' mechanical properties were affected by the fibers' Young's modulus, that is, hard fibers with a Young's modulus of ∼1 MPa increased the cell average Young's modulus, but did not affect the cell shape, while soft fibers with a Young's modulus of ∼100 kPa decreased the cell average Young's modulus and modulated the cell shape to a more spherical one. On the other hand, only the soft fibers induced proinflammatory cytokine secretion, indicating an M1 macrophage functional modulation by low Young's modulus fibers. This study explored the mechanical properties of the interactions between PLGA-PEG fibers and cells, in particular, when guiding the direction of the modulation of macrophage function, which is of great significance for the applications of material biology in the biomedical field.

Alpha-mangostin dephosphorylates ERM to induce adhesion and decrease surface stiffness in KG-1 cells

Surface stiffness is a unique indicator of various cellular states and events and needs to be tightly controlled. α-Mangostin, a natural compound with numerous bioactivities, reduces the mechanical stiffness of various cells; however, the mechanism by which it affects the actin cytoskeleton remains unclear. We aimed to elucidate the mechanism underlying α-mangostin activity on the surface stiffness of leukocytes. We treated spherical non-adherent myelomonocytic KG-1 cells with α-mangostin; it clearly reduced their surface stiffness and disrupted their microvilli. The α-mangostin-induced reduction in surface stiffness was inhibited by calyculin A, a protein phosphatase inhibitor. α-Mangostin also induced KG-1 cell adhesion to a fibronectin-coated surface. In KG-1 cells, a decrease in surface stiffness and the induction of cell adhesion are largely attributed to the dephosphorylation of ezrin/radixin/moesin proteins (ERMs); α-mangostin reduced the levels of phosphorylated ERMs. It further increased protein kinase C (PKC) activity. α-Mangostin-induced KG-1 cell adhesion and cell surface softness were inhibited by the PKC inhibitor GF109203X. The results of the present study suggest that α-mangostin decreases stiffness and induces adhesion of KG-1 cells via PKC activation and ERM dephosphorylation.