TLR4/NF-κB signaling activation in plantar tissue and dorsal root ganglion involves in the development of postoperative pain

Severe postoperative pain remains a clinical problem that impacts patient’s rehabilitation. The present work aims to investigate the role of Toll-like receptor-4 (TLR4) activation in wounded plantar tissue and dorsal root ganglion (DRG) in the genesis of postoperative pain and its underlying mechanisms. Postoperative pain was induced by plantar incision in rat hind paw. Plantar incision led to increased expression of TLR4 in ipsilateral L4/5 DRGs, which occurred after 2 hour and was persistent to the third day after surgery. Similar to the change in TLR4 expression, there was also significant increase in phosphorylated NF-κB p65 (p-p65) in DRGs after surgery. Immunofluorescence staining revealed that the increased expressions of TLR4 and p-p65 not only in neuronal cells, but also in satellite glial cells in DRG. Furthermore, the enhanced expressions of TLR4 and p-p65 were also detected in plantar tissues around the incision, which was observed starting at 2 hours and lasting until the third day after surg...