DOCK2 deficiency alleviates neuroinflammation and affords neuroprotection after spinal cord injury

Neuroinflammation-caused secondary injury is a key event after spinal cord injury (SCI). Dedicator of cytokinesis 2 (DOCK2) belonging to DOCK-A subfamily has a vital role in microglia polarization and neuroinflammation via mediating Rac activation. However, the role of DOCK2 in SCI is unclear. In the present study, SCI model in mice was established by an impactor at thoracic T10 level. DOCK2 expression was significantly increased in the spinal cord after SCI. After knocking down DOCK2 using a lentivirus-mediated method, SCI mice exhibited improved motor function recovery, as revealed by increased Basso Mouse Scale (BMS) score, angle of incline, and relatively coordinated footprint, and decreased damaged area in the spinal cord. DOCK2 deficiency reduced neuronal apoptosis in the spinal cord after injury. Besides, deficiency of DOCK2 suppressed neuroinflammation after SCI, demonstrated by the reduction in pro-inflammatory mediators including IFN-γ, IL-1β and IL-6 and the increase in IL-4, IL-10 and IL-13, anti-inflammatory factors. The CD86, iNOS and COX-2 were down-regulated in the spinal cord, whereas CD206, Arg-1 and TGF-β were up-regulated by DOCK2 deficiency. Rac activation was prevented by DOCK2 deficiency following SCI. In vitro experiments were conducted for further verification. Treatment of BV-2 microglia with lentivirus-mediated DOCK2 inhibited IFN-γ/LPS-induced pro-inflammatory microglia polarization but increased IL-4-induced anti-inflammatory microglia, through inhibiting Rac activation. In brief, our data reveal that DOCK2 deficiency improves functional recovery in mice after SCI, which is related to Rac activation.