Abstract：
Proinflammatory cytokines are crucial contributors to neuroinflammation in the development of chronic pain. Here, we identified il16, which encodes interleukin-16 (IL-16), as a differentially expressed gene in spinal dorsal horn of a complete Freund\'s Adjuvant (CFA) inflammatory pain model in mice by RNA sequencing. We further investigated whether and how IL-16 regulates pain transmission in the spinal cord and contributes to the development of inflammatory pain hypersensitivity. RNA sequencing and bioinformatics analysis revealed elevated IL-16 transcript levels in the spinal dorsal horn after CFA injection. This increase was further confirmed by qPCR, immunofluorescence, and western blotting. Knockdown of IL-16 by intrathecal injection of IL-16 siRNA not only attenuated CFA-induced mechanical and thermal pain hypersensitivity, but also inhibited enhanced c-fos expression and glial activation in the spinal dorsal horn in male mice injected with CFA. Moreover, exogenous IL-16 induced nociceptive responses and increased c-fos expression and glial activation in spinal dorsal horn. This effect was largely impaired when CD4, the binding receptor for IL-16, was inhibited. In addition, CD4 expression was upregulated in the spinal dorsal horn after CFA injection and CD4 was present in microglia and in contact with astrocytes and activated spinal neurons. Taken together, these results suggest that enhanced IL-16-CD4 signaling triggers pain and activates microglia and astrocytes in the spinal dorsal horn, thus contributing to inflammatory pain. IL-16 may serve as a promising target for the treatment of inflammatory pain.
摘要：
促炎细胞因子是慢性疼痛发展中神经炎症的关键贡献者。这里,我们鉴定了编码白细胞介素16（IL-16）的il16，通过RNA测序，作为完整的弗氏佐剂（CFA）炎性疼痛小鼠模型的脊髓背角差异表达基因。我们进一步研究了IL-16是否以及如何调节脊髓中的疼痛传递，并有助于炎症性疼痛超敏反应的发展。RNA测序和生物信息学分析显示，注射CFA后脊髓背角IL-16转录水平升高。qPCR进一步证实了这种增加，免疫荧光，和西方印迹。通过鞘内注射IL-16siRNA敲除IL-16不仅减轻了CFA诱导的机械和热痛超敏反应，同时也抑制注射CFA的雄性小鼠脊髓背角c-fos表达增强和胶质细胞活化。此外，外源性IL-16可诱导脊髓背角的伤害性反应，并增加c-fos表达和胶质细胞活化。当IL-16的结合受体CD4被抑制时，这种作用在很大程度上受到损害。此外,注射CFA后，CD4在脊髓背角的表达上调，CD4存在于小胶质细胞中，并与星形胶质细胞和活化的脊髓神经元接触。一起来看,这些结果表明，增强的IL-16-CD4信号触发疼痛并激活脊髓背角的小胶质细胞和星形胶质细胞，从而导致炎性疼痛。IL-16可以作为治疗炎性疼痛的有希望的靶标。
