EphB receptors modulate neuropathic pain via Ca2+/calpain/autophagy in spinal cord of mice.

Objectives: The EphB receptors play an important role in regulation of neuropathic pain. This study aimed to investigate the role of EphB receptors in the spinal cord of CCI mice. BACKGROUND: Previous studies have found that the EphB receptors were upregulated in the spinal cord of bone cancer pain rats, and activation or inhibition of EphB receptors regulated pain behaviors of rats. However, the specific mechanism involved is not clear.

Methods: Normal mice were injected with ephrinB2-Fc intrathecally to activate EphB receptors, and changes in pain behavior and spinal cord calpain activity were detected. Intrathecal injection of EphB2-Fc and AAV-shEphB2 in CCI mice inhibits EphBs, and changes in mouse behavior and spinal cord calpain activity are detected. Intraperitoneal injection of calpain inhibitor MDL-28170 was used to detect the effect of ephrinB2 Fc on mouse behavior. After inhibiting EphBs receptor and calpain activity in CCI mice, changes in spinal Ca²⁺- dependent p-ERK and p-CaMKII, autophagy, and inflammation related factors were detected.

Results: Spinal cord activation of EphBs induced pain hyperalgesia and calpain activation in normal mice, while inhibition of EphBs alleviated pain hyperalgesia and calpain activation in CCI mice. Intraperitoneal injection of calpain inhibitor MDL-28170 alleviated pain hypersensitivity induced by ephrinB2 Fc. Inhibiting calpain or EphBs suppressed the expression of spinal Ca²⁺- dependent p-ERK and p-CaMKII, promoted spinal autophagy, reduced the expression of pro-inflammatory factors IL-6, IL-1 β, TNF - α, and promotes IL-10 expression.

Conclusion: In summary, EphBs regulate neuropathic pain through neuroinflammation and autophagy by Ca²⁺/calpain/autophagy pathway.