ARG1 and Alzheimer disease: The results illustrated that circAPP knockdown downregulated the expression of the M1 marker CD16 and proinflammatory cytokines, including TNF-α, pro- and cleaved IL-1β, but upregulated the expression of the M2 marker Arg1 and the anti-inflammatory cytokine IL-10 in Aβ-treated BV-2 cells and the hippocampus of APP/PS1 mice (Fig. 1Q, S ~ V; Fig. 2A ~ E), indicating a modulatory role of circAPP in AD microglial polarization.