Down-Regulation of NOX4 Expression in Dorsal Horn of Spinal Cord Could Alleviate Cancer-Induced Bone Pain in Rats by Reducing Oxidative Stress Response.

Introduction: Cancer-induced bone pain (CIBP) is very common in patients with advanced cancer. Recent studies have shown that reactive oxygen species (ROS) can sense and regulate pain response process through spinal cord mechanism, and play a role in CIBP. NADPH oxidase (NOX) is a group of protease complexes that produce ROS. In the current study, we investigated the expression of NOX4 in the spinal dorsal horn of rats with CIBP and its related role and molecular mechanism. Materials and Methods: A rat CIBP model was established by injecting Walker-256 cells into the tibia medullary cavity, and the expression of NOX4 in spinal dorsal horn was downregulated by injecting lentivirus into spinal cord. RT-PCR, Western blot and immunofluorescence staining were used to detect the expression of NOX4 in CIBP rats, cell localization and its effect on CIBP rats, and the effect of down-regulating the expression of NOX4 on the expression of H2O2, nitric oxide synthase nNO, antioxidant enzyme SOD, and the activity of neuro-receptor in spinal dorsal horn of rats. Results: In rats with CIBP, the expression of NOX4 was significantly increased, and immunofluorescence showed that NOX4 was mainly expressed in microglia in the dorsal horn of spinal cord. Down-regulating the expression of NOX4 in rats can reduce the level of H2O2 and nNO in dorsal horn tissue, and increase the expression of SOD to reduce the oxidative stress response. At the same time, down-regulating NOX4 can reduce the sensitivity of spinal cord and relieve the pain of bone cancer by inhibiting the expression of NMDAR and GABAA-gamma 2 in dorsal horn tissue. Conclusion: NOX4 is a promising therapeutic target in CIBP, and down-regulation of NOX4 expression can alleviate CIBP in rats by reducing oxidative stress and weakening spinal cord sensitization.