Microglial polarization and necroptosis in the spinal cord

Paclitaxel (PTX) is a widely used chemotherapeutic agent for the treatment of several types of tumors. However, PTX-induced peripheral neuropathy (PIPN) is a common adverse effect of long-term PTX use that significantly impairs quality of life. Necroptosis has been implicated in various neurodegenerative disorders, with necroptosis of dorsal root ganglion (DRG) neurons specifically being reported to contribute to the pathogenesis of PIPN. Therefore, the present study aims to investigate the effect of spinal neuronal necroptosis on PIPN, and to explore the potential role of microglia polarization on necroptosis. We established rat models of PIPN via quartic PTX administration on alternate days (accumulated dose: 8mg/kg). PTX caused evident neuronal necroptosis and upregulated the expression of receptor-interacting protein kinase (RIP3) and mixed lineage kinase domain-like protein (MLKL) in the spinal dorsal horn, and a necroptosis pathway inhibitor, necrostatin-1 (Nec-1), was able to inhibit these effects. The regulatory impact of microglial polarization on spinal necroptosis was elucidated by administering minocycline to specifically inhibit PTX-induced M1 polarization of spinal microglia caused by PTX. We observed a significant inhibitory effect of minocycline on PTX-induced necroptosis in spinal cord cells, as evidenced by the downregulation of RIP3 and MLKL expression, and suppression of TNF-α and IL-β production. Additionally, minocycline improved hyperalgesia symptoms in PIPN rats. Overall, this study provides evidence that PTX-induced polarization of spinal microglia contributes to RIP3/MLKL-regulated necroptosis, and is implicated in the development of PIPN. These findings suggest a potential novel therapeutic target for the prevention and treatment of neuropathic pain.

紫杉醇（Paclitaxel，PTX）是临床广泛应用于多种肿瘤治疗的化疗药物。然而，紫杉醇诱导的周围神经病变（Paclitaxel-induced peripheral neuropathy，PIPN）是长期使用PTX常见的不良反应，可显著损害患者的生活质量。细胞坏死性凋亡（Necroptosis）已被证实与多种神经退行性疾病的发病机制相关，其中背根神经节（Dorsal Root Ganglion，DRG）神经元的坏死性凋亡已被报道参与PIPN的发生发展。因此，本研究旨在探讨脊髓神经元坏死性凋亡在PIPN中的作用，并探索小胶质细胞极化（microglia polarization）在坏死性凋亡中的潜在调控功能。本研究通过隔日四次紫杉醇给药（累积剂量：8mg/kg）构建PIPN大鼠模型。PTX可诱导脊髓背角出现显著的神经元坏死性凋亡，并上调受体相互作用蛋白激酶3（Receptor-interacting protein kinase，RIP3）与混合谱系激酶结构域样蛋白（Mixed Lineage Kinase Domain-like protein，MLKL）的表达；坏死性凋亡通路抑制剂坏死素-1（Necrostatin-1，Nec-1）可抑制上述效应。为明确小胶质细胞极化对脊髓坏死性凋亡的调控作用，本研究给予米诺环素（minocycline）以特异性阻断PTX诱导的脊髓小胶质细胞M1型极化。结果显示，米诺环素可显著抑制PTX诱导的脊髓细胞坏死性凋亡，具体表现为RIP3与MLKL的表达下调，同时抑制肿瘤坏死因子-α（Tumor Necrosis Factor-α，TNF-α）与白细胞介素-1β（Interleukin-1β，IL-β）的生成。此外，米诺环素可改善PIPN大鼠的痛觉超敏症状。综上，本研究证实PTX诱导的脊髓小胶质细胞极化可通过调控RIP3/MLKL通路介导坏死性凋亡，进而参与PIPN的发生发展。上述研究结果为神经病理性疼痛的防治提供了潜在的新型治疗靶点。