Checkpoint kinase 1 (Chk1) inhibition promotes motor function recovery through suppressing pyroptosis signalling and attenuating microglial polarization shift to M1 phenotype in spinal cord injury mice

Background and Purpose Microglial polarization shifts that induce inflammatory responses play a role in the occurrence and progression of spinal cord injury (SCI). We reported that checkpoint kinase 1 (Chk1) was involved in regulating SCI‐induced motor dysfunction. We aim now to determine whether the microglial polarization shift is involved in the action of Chk1 on SCI‐induced motor dysfunction. Experimental Approach The pathological SCI in vivo model was induced in mice through spinal cord contusion injury, while the in vitro model was established by exposing cultured murine BV2 cells to lipopolysaccharide (LPS). To analyse the expression levels of associated genes and proteins, we utilized quantitative real‐time polymerase chain reaction, western blotting and immunofluorescence staining. We employed the cell counting kit‐8, EdU assay and comet assay to evaluate microglia proliferation and DNA damage. Key Results Chk1 down‐regulation reversed the shift in microglial polarization and pyroptosis induced by SCI in vivo , improving motor dysfunction. Up‐regulation of Chk1 worsened the microglial polarization shift and pyroptosis, causing deterioration in motor function following SCI. In vitro , both γ ‐H2AX and Chk1 activation increased in BV2 cells in a dose‐ and time‐dependent manner in response to LPS. The selective Chk1 inhibitor SCH900776 or the DNA damage repair agonist AV‐153 showed that LPS‐induced microglial polarization shifted from M2 to M1 and this shift was linked to the suppression of pyroptosis signalling. Conclusions and Implications Our results demonstrate that the Chk1‐regulated shift in microglial polarization through pyroptosis signalling may be a promising drug target for future therapies for SCI‐induced motor dysfunction.