Up-Regulation of CX3CL1 via STAT3 Contributes to SMIR-Induced Chronic Postsurgical Pain

Chronic postsurgical pain (CPSP) often occurs after surgery and has a strong impact on patients' daily lives. However, the underlying mechanism of CPSP remains unknown. Here, we used a skin/muscle incision and retraction (SMIR) model to investigate the role of CX3CL1 in SMIR-induced pain and its underlying mechanism. We found that up-regulation of CX3CL1 in the spinal dorsal horn contributed to SMIR-induced mechanical allodynia. The use of a CX3CL1-neutralizing antibody to block CX3CL1 attenuated mechanical allodynia induced by SMIR surgery. We also found that phospho-STAT3 co-localizes with CX3CL1 in spinal neurons after SMIR surgery and that this contributes to SMIR-induced mechanical allodynia. Intrathecal administration of the STAT3 inhibitor S3I-201 suppressed up-regulation of CX3CL1 at both the protein and mRNA levels after SMIR surgery. Chromatin immunoprecipitation further demonstrated that SMIR promotes the recruitment of STAT3 to the cx3cl1 gene promoter (- 1032/- 1022). These findings suggest that activation of STAT3 after SMIR mediates the up-regulation of CX3CL1, leading to mechanical allodynia, and that this upregulation may partly be due to the enhanced recruitment of STAT3 to the cx3cl1 gene promoter after SMIR.