Zhang Haocong, Qin Xianyun, Yuan Hong, Xiang Liangbi, Yu Hailong
Department of Orthopaedics, The General Hospital of Northern Theater Command, Shenyang, Liaoning, China.
Department of Orthopaedics, The 945th Hospital of the Joint Logistic Support Force, Ya'an, Sichuan, China.
FASEB J. 2025 May 15;39(9):e70561. doi: 10.1096/fj.202403101R.
Neuronal inflammation and apoptosis aggravate the secondary injury after spinal cord injury (SCI). Cathepsin L (CTSL) is a lysosomal cysteine protease with effects on the regulation of inflammation, but its role in SCI remains unclear. The in vivo T10 mouse spinal cord contusion model was established. The results showed that CTSL expression was increased following SCI and then gradually decreased. Moreover, CTSL was mainly expressed in microglia. To detect the function of CTSL, after contusive injury, the mice were immediately injected with lentiviruses carrying CTSL shRNA. The results showed that CTSL depletion promoted functional recovery, accompanied by increased locomotor ability. CTSL deficiency reduced lesion cavity areas by inhibiting neuronal apoptosis and neuroinflammation. Indeed, CTSL deficiency decreased the secretion of TNF-α, IL-6, and MCP-1 and M1 microglia polarization in the spinal cord. CTSL depletion inhibited the expression and assembly of NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome. In vitro, CTSL expression was increased in LPS-treated BV2 cells. CTSL silencing repressed LPS-induced M1 polarization, as evidenced by the reduction in TNF-α, IL-6, and MCP-1 expression in the supernatant of BV2 cells. CTSL knockdown induced the downregulation of NLRP3 expression and activation. The inhibition role of CTSL knockdown in microglial inflammation and M1 polarization was reversed by NLRP3 agonist. Collectively, the study suggests that CTSL induces the microglia M1 polarization-mediated inflammation via promoting NLRP3 activation and thereby inhibits functional recovery after SCI.
神经元炎症和凋亡会加重脊髓损伤（SCI）后的继发性损伤。组织蛋白酶L（CTSL）是一种溶酶体半胱氨酸蛋白酶，对炎症调节有作用，但其在SCI中的作用仍不清楚。建立了体内T10小鼠脊髓挫伤模型。结果显示，SCI后CTSL表达增加，随后逐渐下降。此外，CTSL主要在小胶质细胞中表达。为检测CTSL的功能，在挫伤性损伤后，立即给小鼠注射携带CTSL shRNA的慢病毒。结果显示，CTSL缺失促进了功能恢复，伴有运动能力增强。CTSL缺乏通过抑制神经元凋亡和神经炎症减少了损伤腔面积。事实上，CTSL缺乏降低了脊髓中TNF-α、IL-６和MCP-1的分泌以及M1小胶质细胞极化。CTSL缺失抑制了NOD样受体热蛋白结构域相关蛋白3（NLRP3）炎性小体的表达和组装。在体外，LPS处理的BV2细胞中CTSL表达增加。CTSL沉默抑制了LPS诱导的M1极化，这由BV2细胞上清液中TNF-α、IL-6和MCP-1表达的降低所证明。CTSL敲低诱导了NLRP3表达和激活的下调。NLRP3激动剂逆转了CTSL敲低对小胶质细胞炎症和M1极化的抑制作用。总的来说，该研究表明CTSL通过促进NLRP3激活诱导小胶质细胞M1极化介导的炎症，从而抑制SCI后的功能恢复。
