HIPK2 mediates M1 polarization of microglial cells via STAT3: A new mechanism of depression-related neuroinflammation

This study aimed to investigate the role of protein kinase HIPK2 in depression and its associated mechanism. The chronic unpredictable mild stress (CUSM) model was constructed to simulate mice with depression to detect the mouse behaviors. Moreover, by using mouse microglial cells BV2 as the model. After conditional knockdown of HIPK2, the depressive behavior disorder of mice was improved, meanwhile, neuroinflammation was alleviated, and the M1 cell proportion was reduced. Similar results were obtained after applying the HIPK2 inhibitor tBID or ASO-HIPK2 treatment. HIPK2 was overexpressed in BV2 cells, which promoted M1 polarization of cells, while tBID suppressed the effect of HIPK2 and reduced the M1 polarized level in BV2 cells. Pull-down assay results indicated that HIPK2 bound to STAT3 and promoted STAT3 phosphorylation. We found that HIPK2 can bind to STAT3 to promote its phosphorylation, which accelerates M1 polarization of microglial cells, aggravates the depressive neuroinflammation, and leads to abnormal behaviors. HIPK2 is promising as the new therapeutic target of depression.