The siRNA was mixed with the in vivo jetPEI transfection reagent and incubated for 15 minutes at room temperature. The final concentration of siRNA was 3 µg siRNA of 0.36 µL jetPEI in 10 µL 5% glucose solution.

Our preliminary experiment indicated the activation of with-nolysine kinases 1 (WNK1) in bone cancer pain (BCP) rats. This study aimed to investigate the underlying mechanisms via which WNK1 contributed to BCP. A rat model of BCP was induced by Walker-256 tumor cell implantation. WNK1 expression and distribution in the lumbar spinal cord dorsal horn and dorsal root ganglion were examined. SPS1-related proline/alanine-rich kinase (SPAK), oxidative stress-responsive kinase 1 (OSR1), sodium-potassium-chloride cotransporter 1 (NKCC1), and potassium-chloride cotransporter 2 (KCC2) expression were assessed. Pain behaviors including mechanical allodynia and movement-evoked pain were measured. BCP rats exhibited significant mechanical allodynia, with increased WNK1 expression in the dorsal horn and dorsal root ganglion neurons, elevated SPAK/OSR1 and NKCC1 expression in the dorsal root ganglion, and decreased KCC2 expression in the dorsal horn. WNK1 knock-down by small interfering alleviated mechanical allodynia and movement-evoked pain, inhibited WNK1-SPAK/OSR1-NKCC1 activities, and restored KCC2 expression. In addition, closantel (a WNK1-SPAK/OSR1 inhibitor) improved pain behaviors, downregulated SPAK/OSR1 and NKCC1 expression, and upregulated KCC2 expression in BCP rats. Activation of WNK1-SPAK/OSR1 signaling contributed to BCP in rats by modulating NKCC1 and KCC2 expression. Therefore, suppression of WNK1-SPAK/OSR1 may serve as a potential target for BCP therapy. PERSPECTIVE: Our findings demonstrated that the WNK1-SPAK/OSR1 signaling contributed to BCP in rats via regulating NKCC1 and KCC2. Suppressing this pathway reduced pain behaviors. Based on these findings, the WNK1-SPAK/OSR1 signaling may be a potential target for BCP therapy.