Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, 19 Qixiu Road, Nantong, 226001, People's Republic of China.
Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, People's Republic of China.
J Neuroinflammation. 2021 Sep 16;18(1):205. doi: 10.1186/s12974-021-02271-3.
Two activation states of reactive astrocytes termed A1 and A2 subtypes emerge at the lesion sites following spinal cord injury (SCI). A1 astrocytes are known to be neurotoxic that participate in neuropathogenesis, whereas A2 astrocytes have been assigned the neuroprotective activity. Heat shock transcription factor 1 (HSF1) plays roles in protecting cells from stress-induced apoptosis and in controlling inflammatory activation. It is unknown whether HSF1 is involved in suppressing the conversion of A1 astrocytes following SCI.
A contusion model of the rat spinal cord was established, and the correlations between HSF1 expression and onset of A1 and A2 astrocytes were assayed by Western blot and immunohistochemistry. 17-AAG, the agonist of HSF1, was employed to treat the primary cultured astrocytes following a challenge by an A1-astrocyte-conditioned medium (ACM) containing 3 ng/ml of IL-1α, 30 ng/ml of TNF-α, and 400 ng/ml of C1q for induction of the A1 subtype. The effects of 17-AAG on the phenotype conversion of astrocytes, as well as underlying signal pathways, were examined by Western blot or immunohistochemistry.
The protein levels of HSF1 were significantly increased at 4 days and 7 days following rat SCI, showing colocalization with astrocytes. Meanwhile, C3-positive A1 astrocytes were observed to accumulate at lesion sites with a peak at 1 day and 4 days. Distinctively, the S100A10-positive A2 subtype reached its peak at 4 days and 7 days. Incubation of the primary astrocytes with ACM markedly induced the conversion of the A1 phenotype, whereas an addition of 17-AAG significantly suppressed such inducible effects without conversion of the A2 subtype. Activation of HSF1 remarkably inhibited the activities of MAPKs and NFκB, which was responsible for the regulation of C3 expression. Administration of 17-AAG at the lesion sites of rats was able to reduce the accumulation of A1 astrocytes.
Collectively, these data reveal a novel mechanism of astrocyte phenotype conversion following SCI, and HSF1 plays key roles in suppressing excessive increase of neurotoxic A1 astrocytes.
在脊髓损伤（SCI）后，病变部位出现两种称为 A1 和 A2 亚型的反应性星形胶质细胞激活状态。已知 A1 星形胶质细胞具有神经毒性，参与神经发病机制，而 A2 星形胶质细胞具有神经保护活性。热休克转录因子 1（HSF1）在保护细胞免受应激诱导的细胞凋亡和控制炎症激活中发挥作用。尚不清楚 HSF1 是否参与抑制 SCI 后 A1 星形胶质细胞的转化。
建立大鼠脊髓挫伤模型，通过 Western blot 和免疫组织化学检测 HSF1 表达与 A1 和 A2 星形胶质细胞发生的相关性。用 17-AAG（HSF1 的激动剂）处理 A1 星形胶质细胞条件培养基（ACM）孵育的原代培养星形胶质细胞，ACM 中含有 3ng/ml 的 IL-1α、30ng/ml 的 TNF-α和 400ng/ml 的 C1q，以诱导 A1 亚型。通过 Western blot 或免疫组织化学检测 17-AAG 对星形胶质细胞表型转化及其潜在信号通路的影响。
大鼠 SCI 后 4 天和 7 天，HSF1 蛋白水平明显升高，与星形胶质细胞共定位。同时，病变部位 C3 阳性的 A1 星形胶质细胞在 1 天和 4 天达到高峰。明显地，S100A10 阳性的 A2 亚型在 4 天和 7 天达到高峰。原代星形胶质细胞用 ACM 孵育可明显诱导 A1 表型转化，而加入 17-AAG 可显著抑制这种诱导作用而不转化 A2 亚型。HSF1 的激活显著抑制了 MAPKs 和 NFκB 的活性，这是调节 C3 表达的原因。在大鼠病变部位给予 17-AAG 可减少 A1 星形胶质细胞的积累。
总之，这些数据揭示了 SCI 后星形胶质细胞表型转化的一种新机制，HSF1 在抑制神经毒性 A1 星形胶质细胞过度增加中起关键作用。
