Huang Meixiang, Tallon Carolyn, Zhu Xiaolei, Huizar Kaitlyn D J, Picciolini Silvia, Thomas Ajit G, Tenora Lukas, Liyanage Wathsala, Rodà Francesca, Gualerzi Alice, Kannan Rangaramanujam M, Bedoni Marzia, Rais Rana, Slusher Barbara S
Johns Hopkins Drug Discovery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Pharmaceutics. 2023 Sep 21;15(9):2364. doi: 10.3390/pharmaceutics15092364.
The progression of Alzheimer's disease (AD) correlates with the propagation of hyperphosphorylated tau (pTau) from the entorhinal cortex to the hippocampus and neocortex. Neutral sphingomyelinase2 (nSMase2) is critical in the biosynthesis of extracellular vesicles (EVs), which play a role in pTau propagation. We recently conjugated DPTIP, a potent nSMase2 inhibitor, to hydroxyl-PAMAM-dendrimer nanoparticles that can improve brain delivery. We showed that dendrimer-conjugated DPTIP (D-DPTIP) robustly inhibited the spread of pTau in an AAV-pTau propagation model. To further evaluate its efficacy, we tested D-DPTIP in the PS19 transgenic mouse model. Unexpectantly, D-DPTIP showed no beneficial effect. To understand this discrepancy, we assessed D-DPTIP's brain localization. Using immunofluorescence and fluorescence-activated cell-sorting, D-DPTIP was found to be primarily internalized by microglia, where it selectively inhibited microglial nSMase2 activity with no effect on other cell types. Furthermore, D-DPTIP inhibited microglia-derived EV release into plasma without affecting other brain-derived EVs. We hypothesize that microglial targeting allowed D-DPTIP to inhibit tau propagation in the AAV-hTau model, where microglial EVs play a central role in propagation. However, in PS19 mice, where tau propagation is independent of microglial EVs, it had a limited effect. Our findings confirm microglial targeting with hydroxyl-PAMAM dendrimers and highlight the importance of understanding cell-specific mechanisms when designing targeted AD therapies.
阿尔茨海默病（AD）的进展与过度磷酸化tau蛋白（pTau）从内嗅皮质向海马体和新皮质的传播相关。中性鞘磷脂酶2（nSMase2）在细胞外囊泡（EVs）的生物合成中起关键作用，而细胞外囊泡在pTau传播中发挥作用。我们最近将一种强效的nSMase2抑制剂DPTIP与能改善脑内递送的羟基化聚酰胺-胺树枝状聚合物纳米颗粒偶联。我们发现树枝状聚合物偶联的DPTIP（D-DPTIP）在AAV-pTau传播模型中能强力抑制pTau的扩散。为进一步评估其疗效，我们在PS19转基因小鼠模型中测试了D-DPTIP。出乎意料的是，D-DPTIP没有显示出有益效果。为了解这种差异，我们评估了D-DPTIP在脑内的定位。通过免疫荧光和荧光激活细胞分选，发现D-DPTIP主要被小胶质细胞内化，在小胶质细胞中它选择性地抑制小胶质细胞的nSMase2活性，而对其他细胞类型没有影响。此外，D-DPTIP抑制小胶质细胞衍生的EV释放到血浆中，而不影响其他脑源性EVs。我们推测，靶向小胶质细胞使D-DPTIP能够在AAV-hTau模型中抑制tau蛋白的传播，在该模型中，小胶质细胞EVs在传播中起核心作用。然而，在PS19小鼠中，tau蛋白的传播独立于小胶质细胞EVs，它的作用有限。我们的研究结果证实了用羟基化聚酰胺-胺树枝状聚合物靶向小胶质细胞，并强调了在设计靶向性AD治疗方法时了解细胞特异性机制的重要性。
