Reprogramming of GM-CSF-dependent alveolar macrophages through GSK3 activity modulation.

Monocyte-derived macrophages recruited into inflamed tissues can acquire an array of functional states depending on the extracellular environment. Since the anti-inflammatory/pro-fibrotic macrophage profile is determined by MAFB, whose activity/protein levels are regulated by GSK3, we addressed the macrophage reprogramming potential of GSK3 modulation. GM-CSF-dependent (GM-MØ) and M-CSF-dependent monocyte-derived macrophages (M-MØ) exhibited distinct levels of inactive GSK3, and inhibiting GSK3 in GM-MØ led to the acquisition of transcriptional, phenotypic, and functional properties characteristic of M-MØ (enhanced expression of IL-10 and monocyte-recruiting factors, and higher efferocytosis). These reprogramming effects were also observed upon GSK3α/β knockdown and through GSK3 inhibition in ex vivo isolated human alveolar macrophages (AMØ). Notably, GSK3 downmodulation potentiated the transcriptional signature of interstitial macrophages (IMØ) while suppressing the AMØ-specific gene profile. Indeed, heightened levels of inactive GSK3 and MAFB-dependent proteins were observed in severe COVID-19 patients' lung macrophages, highlighting the GSK3-MAFB axis as a therapeutic target for macrophage reprogramming.