Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal.
Cell Death Dis. 2019 Nov 5;10(11):840. doi: 10.1038/s41419-019-2078-z.
Parkinson's disease (PD) is driven by dopaminergic neurodegeneration in the substantia nigra pars compacta (SN) and striatum. Although apoptosis is considered the main neurodegenerative mechanism, other cell death pathways may be involved. In this regard, necroptosis is a regulated form of cell death dependent on receptor interacting protein 3 (RIP3), a protein also implicated in apoptosis and inflammation independently of its pro-necroptotic activity. Here, we explored the role of RIP3 genetic deletion in in vivo and in vitro PD models. Firstly, wild-type (Wt) and RIP3 knockout (RIP3ko) mice were injected intraperitoneally with MPTP (40 mg/kg, i.p.), and sacrificed after either 6 or 30 days. RIP3ko protected from dopaminergic neurodegeneration in the SN of MPTP-injected mice, but this effect was independent of necroptosis. In keeping with this, necrostatin-1s (10 mg/kg/day, i.p.) did not afford full neuroprotection. Moreover, MPTP led to DNA fragmentation, caspase-3 activation, lipid peroxidation and BAX expression in Wt mice, in the absence of caspase-8 cleavage, suggesting intrinsic apoptosis. This was mimicked in primary cortical neuronal cultures exposed to the active MPTP metabolite. RIP3 deficiency in cultured cells and in mouse brain abrogated all phenotypes. Curiously, astrogliosis was increased in the striatum of MPTP-injected Wt mice and further exacerbated in RIP3ko mice. This was accompanied by absence of microgliosis and reposition of glial cell line-derived neurotrophic factor (GDNF) levels in the striata of MPTP-injected RIP3ko mice when compared to MPTP-injected Wt mice, which in turn showed a massive GDNF decrease. RIP3ko primary mixed glial cultures also presented decreased expression of inflammation-related genes upon inflammatory stimulation. These findings hint at possible undescribed non-necroptotic roles for RIP3 in inflammation and MPTP-driven cell death, which can contribute to PD progression.
帕金森病（PD）是由黑质致密部（SN）和纹状体中的多巴胺能神经退行性变引起的。尽管细胞凋亡被认为是主要的神经退行性机制，但其他细胞死亡途径也可能参与其中。在这方面，坏死性凋亡是一种依赖受体相互作用蛋白 3（RIP3）的受调控的细胞死亡形式，RIP3 蛋白也独立于其促坏死性凋亡活性而参与凋亡和炎症。在这里，我们探讨了 RIP3 基因缺失在体内和体外 PD 模型中的作用。首先，将野生型（Wt）和 RIP3 敲除（RIP3ko）小鼠腹膜内注射 MPTP（40mg/kg，ip），并在 6 或 30 天后处死。RIP3ko 可防止 MPTP 注射小鼠 SN 中的多巴胺能神经退行性变，但这种作用与坏死性凋亡无关。与此一致的是，坏死性凋亡抑制剂 1s（10mg/kg/天，ip）并不能提供完全的神经保护。此外，MPTP 导致 Wt 小鼠中 DNA 片段化、半胱天冬酶-3 激活、脂质过氧化和 BAX 表达，但没有半胱天冬酶-8 切割，提示存在内在凋亡。这在暴露于活性 MPTP 代谢物的原代皮质神经元培养物中得到了模拟。在培养细胞和小鼠脑中缺失 RIP3 可消除所有表型。有趣的是，MPTP 注射的 Wt 小鼠纹状体中的星形胶质细胞增生增加，而 RIP3ko 小鼠中的星形胶质细胞增生进一步加剧。与此相伴的是，MPTP 注射的 RIP3ko 小鼠纹状体中的小胶质细胞缺失和胶质细胞源性神经营养因子（GDNF）水平的重新定位，而 MPTP 注射的 Wt 小鼠则表现出大量 GDNF 减少。RIP3ko 原代混合神经胶质培养物在炎症刺激下也表现出炎症相关基因表达下调。这些发现暗示了 RIP3 在炎症和 MPTP 驱动的细胞死亡中可能存在未被描述的非坏死性凋亡作用，这可能有助于 PD 的进展。
