BACKGROUND Robust activation of glial cells has been reported to occur particularly during the pathogenesis of bone cancer pain (BCP). Researchers from our group and others have shown that histone deacetylases (HDACs) play a significant role in modulating glia-mediated immune responses; however, it still remains unclear whether HDACs are involved in the activation of glial cells during the development of BCP. METHODS BCP model was established by intra-tibia tumor cell inoculation (TCI). The expression levels and distribution sites of histone deacetylases (HDACs) in the spinal dorsal horn and dorsal root ganglia were evaluated by Western blot and immunofluorescent staining, respectively. Suberoylanilide hydroxamic acid (SAHA), a clinically used HDAC inhibitor, was then intraperitoneally and intrathecally injected to rescue the increased expression levels of HDAC1 and HDAC2. The analgesic effects of SAHA administration on BCP were then evaluated by measuring the paw withdrawal thresholds (PWTs). The effects of SAHA on activation of glial cells and expression of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) in the spinal dorsal horn and dorsal root ganglia of TCI rats were further evaluated by immunofluorescent staining and Western blot analysis. Subsequently, the effects of SAHA administration on tumor growth and cancer cell-induced bone destruction were analyzed by hematoxylin and eosin (HE) staining and micro-CT scanning. RESULTS TCI caused rapid and long-lasting increased expression of HDAC1/HDAC2 in glial cells of the spinal dorsal horn and dorsal root ganglia. Inhibiting HDACs by SAHA not only reversed TCI-induced upregulation of HDACs but also inhibited the activation of glial cells in the spinal dorsal horn and dorsal root ganglia, and relieved TCI-induced mechanical allodynia. Further, we found that SAHA administration could not prevent cancer infiltration or bone destruction in the tibia, which indicated that the analgesic effects of SAHA were not due to its anti-tumor effects. Moreover, we found that SAHA administration could inhibit GSK3β activity in the spinal dorsal horn and dorsal root ganglia, which might contributed to the relief of BCP. CONCLUSION Our findings suggest that HDAC1 and HDAC2 are involved in the glia-mediated neuroinflammation in the spinal dorsal horn and dorsal root ganglia underlying the pathogenesis of BCP, which indicated that inhibiting HDACs by SAHA might be a potential strategy for pain relief of BCP.

中文翻译：

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SAHA抑制组蛋白脱乙酰基酶可通过抑制脊髓背角和背根神经节中神经胶质细胞的活化来减轻大鼠的骨癌疼痛。

背景技术据报道，特别是在骨癌性疼痛（BCP）的发病机理期间，发生了神经胶质细胞的强烈活化。我们小组和其他小组的研究人员表明，组蛋白脱乙酰基酶（HDACs）在调节神经胶质介导的免疫反应中起着重要作用。然而，尚不清楚在BCP发生过程中HDAC是否参与神经胶质细胞的活化。方法通过胫骨内肿瘤细胞接种（TCI）建立BCP模型。分别通过蛋白质印迹和免疫荧光染色评估组蛋白脱乙酰酶（HDACs）在脊髓背角和背根神经节中的表达水平和分布部位。Suberoylanilide异羟肟酸（SAHA），临床上使用的HDAC抑制剂，然后经腹膜内和鞘内注射以拯救HDAC1和HDAC2表达水平的增加。然后通过测量爪退缩阈值（PWT）评估SAHA给药对BCP的镇痛作用。通过免疫荧光染色和Western印迹分析进一步评估了SAHA对TCI大鼠脊髓背角和背根神经节中神经胶质细胞活化和促炎细胞因子（TNF-α，IL-1β和IL-6）表达的影响。 。随后，通过苏木精和曙红（HE）染色以及显微CT扫描分析了SAHA给药对肿瘤生长和癌细胞诱导的骨破坏的影响。结果TCI导致脊髓背角和背根神经节神经胶质细胞中HDAC1 / HDAC2的表达迅速且持久地增加。SAHA抑制HDACs不仅可以逆转TCI诱导的HDACs上调，而且可以抑制脊髓背角和背根神经节中的神经胶质细胞活化，并减轻TCI诱导的机械性异常性疼痛。此外，我们发现SAHA的给药不能预防胫骨中的癌症浸润或骨破坏，这表明SAHA的镇痛作用不是由于其抗肿瘤作用。此外，我们发现SAHA给药可以抑制脊髓背角和背根神经节中的GSK3β活性，这可能有助于缓解BCP。结论我们的发现表明HDAC1和HDAC2参与了胶质细胞介导的BCP发病机理的脊髓背角和背根神经节的神经炎症，