The Actions and Mechanisms of P2X7R and p38 MAPK Activation in Mediating Bortezomib-Induced Neuropathic Pain

The proteasome inhibitor bortezomib (BTZ) is a potent first-line anticancer drug for multiple myeloma; nonetheless, it induced peripheral neuropathy. It has been suggested that many cytokines may play a role in mediating neuropathic pain, but the underlying molecular mechanism is not fully understood. Recent studies have shown that neuropathic pain is closely related to the purinergic ligand-gated ion channel 7 receptor (P2X7R), one of the P2X receptors, which is richly expressed in glial cells. P2X7-p38 pathway is correlated with microglia- and satellite glial cell- (SGC-) mediated neuropathic pain. However, the association of P2X7R and p38MAPK in mediating BTZ-induced neuropathic pain remains unclear. In this study, the relationship between P2X7R activation and p38 phosphorylation in the dorsal root ganglion (DRG) and spinal dorsal horn (SDH) in the development and maintenance of BTZ-induced neuropathic pain was elucidated. The results showed that BTZ increased mechanical thresholds in rats, accompanied with upregulation of P2X7R expression and p38MAPK phosphorylation, indicating that P2X7R and p38MAPK are key molecules in the development and maintenance of BTZ-induced neuropathic pain. Inhibiting p38MAPK phosphorylation with SB203580 resulted in downregulation of P2X7R expression levels. Inhibition of P2X7R with Brilliant Blue G (BBG) reversed neuropathic pain might decrease through the expression of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 via inhibiting p38MAPK phosphorylation. The P2X7R/p38MAPK signaling pathway in SGCs of DRG and microglia of SDH might be a potential pharmacological target behind this mechanism as an opportunity to relieve BTZ-induced neuropathic pain.