Uric acid directly induced macrophage M2 polarization and
strongly activated ITGAM and FAK signaling
We performed in vitro experiments to explore how uric acid functions on
macrophage. Since uric acid at high concentration causes tubular
damages(Johnson et al., 2018; Milanesi et al., 2019), we designed two in
vitro models: model1, using uric acid to stimulate Raw 264.7 macrophage;
and model 2, using uric acid to stimulate the co-culture environment of
Raw 264.7+proximal tubular cell TCMK1. Macrophages were collected after
24 hours and 48 hours of stimulation (Figure 4A ). The ITGAM
mRNA expression in model 1 quickly increased to peak after 24 hours, and
ITGAM in model 1 was higher or equal to that in model 2 at time points
of 24 and 48 hours, respectively (Figure 4B ). Although not
highly consistence in M2 polarization markers, two models both presented
obvious M2 polarization especially after 48 hours (Figure 4C ).
ITGAM and downstream FAK signaling were activated after 24 hours of uric
acid stimulation. As indicated by KEGG enrichment, we confirmed the
higher phosphorylation of FAK and Akt1, lower phosphorylation of GSK-3β,
and less degraded β-catenin (Figure 4D ). Evidence above
indicated that uric acid strongly activated ITGAM/FAK signaling in
macrophage and M2 polarization, regardless of existence of tubular
epithelial cells.