HDAC3 promotes macrophage pyroptosis via regulating histone deacetylation in acute lung injury

Abstract Activated inflammation and pyroptosis in macrophage are closely associated with acute lung injury (ALI). Histone deacetylase 3 (HDAC3) serves as an important enzyme that could repress gene expression by mediating chromatin remodeling. Here, we aim to explore the role and potential molecular basis of HDAC3 in lipopolysaccharide (LPS)-induced ALI. We found that HDAC3 was highly expressed in lung tissues of LPS-treated mice and in LPS-induced macrophages. Lung tissues from macrophage HDAC3-deficient mice stimulated with LPS showed alleviative lung pathological injury and inflammatory response. HDAC3 silence by small interfering RNA (siRNA) significantly blocked the activation of cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway while HDAC3 overexpression by adenovirus transfection significantly promoted the activation of cGAS/STING pathway and aggravated pyroptosis in LPS-induced macrophage. However, HDAC3 silence or overexpression at baseline showed no effects on the level of mitochondrial DNA (mt-DNA) and the activation of cGAS/STING pathway. But HDAC3 at baseline could change the mRNA and protein levels of cGAS. Additionally, autophagy or proteasome inhibition in LPS-induced macrophages transfected with Hdac3 siRNA did not affect the protein level of cGAS. Mechanistically, cGAS was a direct target gene of miR-4767 in macrophage. LPS could recruit HDAC3 and H3K9Ac to the miR-4767 gene promoter, which repressed the expression of miR-4767 by decreasing histone acetylation of the miR-4767 gene promoter. To this end, intratracheal administration of liposomes loaded with Hdac3 siRNA prevented mice from LPS-induced lung injury and inflammation. Taken together, our findings demonstrated that HDAC3 played a pivotal role in mediating pyroptosis in macrophage and ALI by activating cGAS/STING pathway through decreasing histone acetylation of the miR-4767 gene promoter. Targeting HDAC3 in macrophage may provide a new therapeutic target for the prevention of LPS-induced ALI.