IL-1β-induces NF-κB and upregulates microRNA-372 to inhibit spinal cord injury recovery.

Excessive inflammation including IL-1β-initiated signaling is among the earlies reactions that can cause neuronal damage following spinal cord injury (SCI). It has been suggested that microRNAs may participate in stem cell repair to facilitate functional recovery following SCI. In this study we have shown that in cultured human neural stem cells (hNSC), IL-1β reduced the expression of both KIF3B (kinesin family member 3B) and NOSIP (nitric oxide synthase-interacting protein), two key modulators for restricting inflammation and promoting neuronal regeneration. The induction of microRNA-372 (miR-372) by IL-1β is specifically responsible for the inhibition of KIF3B and NOSIP. The 3'-untranslated regions (UTRs) of both KIF3B and NOSIP contain targeting sequences to miR-372 that directly inhibit their expression. Moreover, we found that the expression of miR-372 was stimulated in hNSC by IL-1β through an NF-κB binding site at its promoter region. Finally, stable overexpression of miR-372 inhibitor in hNSC rescued the IL-1β-induced impairment as shown by significant improvements in tissue water content, myeloperoxidase activity, and behavioral assessments in SCI rats. These findings suggest a critical role of miR-372 in inflammatory signaling and pinpoint a novel target for the treatment of acute SCI. Our data demonstrate that IL-1β can impair the functional recovery of neural stem cell transplant therapy for spinal cord injury (SCI) treatment in rats. This effect is dependent on microRNA-372 (miR-372)-dependent gene repression of KIF3B and NOSIP. Therefore, specific knockdown of miR-372 may provide benefits for SCI treatments.