M2 polarization enhances silica nanoparticle uptake by macrophages

Abstract

While silica nanoparticles have enabled numerous industrial and medical applications, their toxicological safety requires further evaluation. Macrophages are the major cell population responsible for nanoparticle clearance in vivo. The prevailing macrophage phenotype largely depends on the local immune status of the host. Whereas M1-polarized macrophages are considered as pro-inflammatory macrophages involved in host defense, M2 macrophages exhibit anti-inflammatory and wound-healing properties, but also promote tumor growth. We employed different models of M1 and M2 polarization: granulocyte-macrophage colony-stimulating factor/lipopolysaccharide (LPS)/interferon (IFN)-γ was used to generate primary human M1 cells and macrophage colony-stimulating factor (M-CSF)/interleukin (IL)-10 to differentiate M2 monocyte-derived macrophages (MDM). PMA-differentiated THP-1 cells were polarized towards an M1 type by LPS/IFN-γ and towards M2 by IL-10. Uptake of fluorescent silica nanoparticles (Ø26 and 41 nm) and microparticles (Ø1.75 μm) was quantified. At the concentration used (50 μg/ml), silica nanoparticles did not influence cell viability as assessed by MTT assay. Nanoparticle uptake was enhanced in M2-polarized primary human MDM compared with M1 cells, as shown by flow cytometric and microscopic approaches. In contrast, the uptake of microparticles did not differ between M1 and M2 phenotypes. M2 polarization was also associated with increased nanoparticle uptake in the macrophage-like THP-1 cell line. In accordance, in vivo polarized M2-like primary human tumor-associated macrophages obtained from lung tumors took up more nanoparticles than M1-like alveolar macrophages isolated from the surrounding lung tissue. In summary, our data indicate that the M2 polarization of macrophages promotes nanoparticle internalization. Therefore, the phenotypical differences between macrophage subsets should be taken into consideration in future investigations on nanosafety, but might also open up therapeutic perspectives allowing to specifically target M2 polarized macrophages.

Intracellular disposition of chitosan nanoparticles in macrophages: intracellular uptake, exocytosis, and intercellular transport

“…Over different time intervals (2,4,6,8,12,24, and 36 h), the medium was removed and collected, and the cells were washed with cold PBS buffer (pH 8.0). The FIs of NPs retained in the cells were detected using a multimode microplate reader and a laser confocal microscope.…”

“…At different time points (2,4,6,8,12,24, and 36 h), the cells were fixed with paraformaldehyde and labeled with a Lyso Tracker Red DND-99, which was usually used to specifically label acidic compartment cells, eg, lysosomes and other acidic organelles. The location of NPs in the cells was observed using a laser confocal microscopy.…”

“…After pre-incubation of RAW 264.7 cells with FRET-CsNPs (250 μg/mL) for 2 h, the NP-containing medium was replaced with fresh medium, and this time point was set as the starting time (0 h). At various time points (2,4,6,8,12,24, and 36 h), the medium was removed. The FIs in the cells were detected by fluorescence spectrophotometry.…”

“…The endocytosis of NMs by macrophages has been well documented in the literature, [5][6][7][8][9] and it has been reported that NMs with high surface charge and large particle size are phagocytized more efficiently by macrophages. 6,7 The shape of NMs has a profound impact on their endocytosis by macrophages as spherical particles have 5,9 Besides the physicochemical properties of NMs, the macrophage phenotype also has a great impact on NM endocytosis.…”

Induction of Glucocorticoid-induced Leucine Zipper (GILZ) Contributes to Anti-inflammatory Effects of the Natural Product Curcumin in Macrophages

“…Determination of Cell Viability-To ensure that non-toxic concentrations of curcumin were used, the MTT colorimetric assay was performed as described previously (20,54). Absorbance measurements were carried out at 550 nm with 630 nm as the reference wavelength using a microplate reader (Tecan Sunrise).…”