Background: Bortezomib is a frequently used chemotherapeutic drug for the treatment of multiple myeloma and other nonsolid malignancies. Accumulating evidence has demonstrated that bortezomib-induced persistent pain serves as the most frequent reason for treatment discontinuation.
Methods: The von Frey test was performed to evaluate neuropathic pain behavior, and real-time quantitative reverse transcription polymerase chain reaction, chromatin immunoprecipitation, western blot, immunohistochemistry, and small interfering RNA were performed to explore the molecular mechanisms in adult male Sprague-Dawley rats.
Results: We found that application of bortezomib significantly increased the expression of NALP1 protein and mRNA levels in spinal dorsal horn neurons, and intrathecal application of NALP1 siRNA attenuated the bortezomib-induced mechanical allodynia. In addition, bortezomib also decreased the SIRT1 expression, and treatment with SIRT1 activator resveratrol ameliorated the NALP1 upregulation and mechanical allodynia induced by bortezomib. Meanwhile, knockdown of SIRT1 using the SIRT1 siRNA induced the NALP1 upregulation in dorsal horn and mechanical allodynia in normal animal. These results suggested that reduction of SIRT1 induced the NALP1 upregulation in dorsal horn neurons, and participated in bortezomib-induced mechanical allodynia. Importantly, we found that the binding of SIRT1 and NALP1 promoter region did not change before and after bortezomib treatment, but SIRT1 downregulation increased p-STAT3 expression. Furthermore, the activation of STAT3 enhanced the recruitment of p-STAT3 to the Nalp1 gene promoter, which increased the acetylation of histone H3 and H4 in NALP1 promoter regions and epigenetically upregulated NALP1 expression in the rodents with bortezomib treatment.
Conclusion: These findings suggested a new epigenetic mechanism for NALP1 upregulation involving SIRT1 reduction and subsequent STAT3-mediated histone hyperacetylation in NALP1 promoter region in dorsal horn neurons, which contributed to the bortezomib-induced mechanical allodynia.
Keywords: Bortezomib; Mechanical allodynia; NALP1; SIRT1; STAT3.