Unveiling the roles of HIPK2 in atherosclerosis: Insights into the β-catenin/STAT1 signaling cascade and the involvement of SENP1

Abstract

Atherosclerosis is a disorder of lipid metabolism, but its pathogenesis has not yet been fully elucidated. This study aimed to clarify the roles of homeodomain interacting protein kinase 2 (HIPK2) in atherosclerosis. Atherosclerotic model was constructed by feeding apolipoprotein E knockout (ApoE^-/-) mice with a high-fat diet. Human THP-1 macrophages and mouse RAW 264.7 macrophages were stimulated with IFN-γ to establish an in vitro model. We showed an upregulation of HIPK2 in the aorta of atherosclerotic mice. HIPK2 knockdown reduced macrophage infiltration, M1 polarization, and attenuates atherosclerosis development. Downregulation of HIPK2 in macrophages led to a significant suppression in the expression of pro-inflammatory factors, which was accompanied by an enhancement in the phosphorylation and degradation of β-catenin, as well as the activation of the signal transducer and activator of transcription 1 (STAT1) signaling pathway. Silencing of HIPK2 alone in THP-1 macrophages resulted in anti-inflammatory effects and suppression of M1 macrophage polarization. However, simultaneous silencing of HIPK2 and β-catenin (CTNNB1) reversed these effects, counteracting the outcomes observed with HIPK2 silencing alone. We validated that small ubiquitin-like modifier (SUMO)-specific peptidase 1 (SENP1) regulated HIPK2 function by affecting the SUMOylation of HIPK2 at the K32 site. SENP1 knockdown promoted HIPK2 SUMOylation, impairing its protein stability. In the rescue experiments, IFN-γ-induced inflammation and M1 polarization were resumed upon restoration of HIPK2 expression in SENP1-silenced macrophages. Our work demonstrated that HIPK2 accelerated the progression of atherosclerosis by regulating β-catenin/STAT1 signaling cascade to promote macrophage infiltration and M1 polarization. HIPK2 was regulated by SENP1-mediated de-SUMOylation.