Relationship between PI3K/mTOR/RhoA pathway-regulated cytoskeletal rearrangements and phagocytic capacity of macrophages

Abstract

The objective of this study was to investigate the relationship between PI3K/mTOR/RhoA signaling regulated cytoskeletal rearrangements and phagocytic capacity of macrophages. RAW264.7 macrophages were divided into four groups; blank control, negative control, PI3K-RNAi, and mTOR-RNAi. The cytoskeletal changes in the macrophages were observed. Furthermore, the phagocytic capacity of macrophages against Escherichia coli is reported as mean fluorescence intensity (MFI) and percent phagocytosis. Transfection yielded 82.1 and 81.5% gene-silencing efficiencies against PI3K and mTOR, respectively. The PI3K-RNAi group had lower mRNA and protein expression levels of PI3K, mTOR, and RhoA than the blank and negative control groups (Po0.01). The mTOR-RNAi group had lower mRNA and protein levels of mTOR and RhoA than the blank and the negative control groups (Po0.01). Macrophages in the PI3K-RNAi group exhibited stiff and inflexible morphology with short, disorganized filopodia and reduced number of stress fibers. Macrophages in the mTOR-RNAi group displayed pronounced cellular deformations with long, dense filopodia and an increased number of stress fibers. The PI3K-RNAi group exhibited lower MFI and percent phagocytosis than blank and negative control groups, whereas the mTOR-RNAi group displayed higher MFI and percent phagocytosis than the blank and negative controls (Po0.01). Before and after transfection, the mRNA and protein levels of PI3K were both positively correlated with mTOR and RhoA (Po0.05), but the mRNA and protein levels of mTOR were negatively correlated with those of RhoA (Po0.05). Changes in the phagocytic capacity of macrophages were associated with cytoskeletal rearrangements and were regulated by the PI3K/mTOR/RhoA signaling pathway.

MiR-155 enhances phagocytosis of alveolar macrophages through the mTORC2/RhoA pathway

“…After silencing mTOR expression, the expression level of RhoA and p-RhoA in macrophages was up-regulated, and phagocytosis was enhanced. [12] However, the specific mechanism of mTOR/RhoA causing phagocytic dysfunction remains unknown. More and more evidence shows that mTORC2 and GTPase jointly mediate actin polymerization and play an important role in actin cytoskeleton recombination.…”

“…[11] Studies have confirmed that the change in the phagocytotic rate of macrophages is related to cytoskeleton rearrangement. [12] Mammalian rapamycin target protein (mTOR) is an evolutionarily conserved serine/ threonine kinase of the phosphatidylinositol-3 kinase family. There are 2 known complexes, mTORC1, and mTORC2, with unique structures and functions.…”

Therapeutic Properties of Flavonoids in Treatment of Cancer through Autophagic Modulation: A Systematic Review

“…The activation of PI3K, stimulates AKT, leading to the activation of mTOR. (17) mTOR has two protein complexes, mTORC1 and mTORC2, with mTORC1 being one of the main regulators of autophagy, since, when activated, it suppresses autophagy and, when inactivated, stimulates autophagy. (18) In this sense, flavonoids have shown ways to inactivate this pathway, thus stimulating autophagy.…”

Anti-Inflammatory Activity of Extracts and Pure Compounds Derived from Plants via Modulation of Signaling Pathways, Especially PI3K/AKT in Macrophages

“…Actin polymerizations promote formation of filopodia, the structure that enables movement to the inflammation site. The study investigated gene silencing against PI3K and mTOR in macrophages indicates that PI3K ablation group exhibited short disorganized filopodia, whereas mTOR ablation group show long, dense ones [ 190 ]. AKT2 is also essential for tumor-associated macrophages chemotaxis [ 191 ].…”