RESUMEN
Despite the unique and complex nature of cancer pain, the activation of different ion channels can be related to the initiation and maintenance of pain. The transient receptor potential vanilloid 4 (TRPV4) is a cation channel broadly expressed in sensory afferent neurons. This channel is activated by multiple stimuli to mediate pain perception associated with inflammatory and neuropathic pain. Here, we focused on summarizing the role of TRPV4 in cancer etiology and cancer-induced pain mechanisms. Many studies revealed that the administration of a TRPV4 antagonist and TRPV4 knockdown diminishes nociception in chemotherapy-induced peripheral neuropathy (CIPN). Although the evidence on TRPV4 channels' involvement in cancer pain is scarce, the expression of these receptors was reportedly enhanced in cancer-induced bone pain (CIBP), perineural, and orofacial cancer models following the inoculation of tumor cells to the bone marrow cavity, sciatic nerve, and tongue, respectively. Effective pain management is a continuous problem for patients diagnosed with cancer, and current guidelines fail to address a mechanism-based treatment. Therefore, examining new molecules with potential antinociceptive properties targeting TRPV4 modulation would be interesting. Identifying such agents could lead to the development of treatment strategies with improved pain-relieving effects and fewer adverse effects than the currently available analgesics.
RESUMEN
Objective: To investigate the analgesic mechanism of cinobufagin in rats with bone cancer pain. Methods: Female SD rats meeting the conditions of pain threshold were selected to construct cancer-induced bone pain (CIBP) model. On the 7th day after modeling, the sham group and the model group were administrated by saline, while the treatment groups were administrated with the low, medium and high concentrations of cinobufagin for consecutive 7 d. The pain behavior (mechanical withdrawal threshold and thermal pain threshold) was tested before modeling and after modeling, and single injection of cinobufagin after 0.5, 1, 2, 4, 6, 8 and 24 h at the first day. The expression of MAPKs protein was detected by Western Blotting, and the content of spinal cytokines (IL-1β, TNF-α, MCP-1) was detected by ELISA. Results: The mechanical pain threshold and thermal pain threshold were significantly decreased in the model group, compared with the sham group (P 0.05). Protein levels of MAPKs were increased in the model group, while the levels of JNK and p38 were decreased in the cinobufagin group (P 0.05). ELISA results showed that cinobufagin significantly decreased the content of cytokines in the spinal cord, when compared with the model group (P < 0.05). Conclusion: Cinobufagin can inhibit the expression of MAPKs proteins in the spinal cord of the rat model with bone cancer pain, ultimately decrease the content of IL-1β, TNF-α, and MCP-1 to alleviate the pain during the process of cancer pain.