P2X7 receptor induces microglia polarization to the M1 phenotype in cancer-induced bone pain rat models

Background The transition from pro-inflammatory M1 phenotype to anti-inflammatory M2 phenotype presents a novel therapeutic strategy for chronic pain. Objective We investigated the role of microglia polarization in cancer-induced bone pain (CIBP), as well as the role of the P2X7 receptor in modulating M1 to M2 polarization. Methods Walker-256 breast cancer cells were administered into tibias of female rats to induce bone cancer–associated cancer. Results During bone cancer development, the P2X7 receptor and M1 microglia markers were upregulated. In contrast, inhibition of the P2X7 receptor by BBG, a blood-brain barrier-permeable P2X7R-specific antagonist, alleviated the pain and promoted microglia polarization toward the M2 phenotype, while suppressing the M1 phenotype in vivo and in vitro. Conclusion P2X7 receptor-mediated spinal microglia polarization is involved in alleviation of CIBP. Therefore, P2X7R is a potential option for CIBP treatment.