Qosa Hisham, LeVine Harry, Keller Jeffrey N, Kaddoumi Amal
Department of Basic Pharmaceutical Science, School of Pharmacy, University of Louisiana at Monroe, Monroe, LA, USA.
Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA.
Biochim Biophys Acta. 2014 Sep;1842(9):1806-15. doi: 10.1016/j.bbadis.2014.06.029. Epub 2014 Jul 2.
Senile amyloid plaques are one of the diagnostic hallmarks of Alzheimer's disease (AD). However, the severity of clinical symptoms of AD is weakly correlated with the plaque load. AD symptoms severity is reported to be more strongly correlated with the level of soluble amyloid-β (Aβ) assemblies. Formation of soluble Aβ assemblies is stimulated by monomeric Aβ accumulation in the brain, which has been related to its faulty cerebral clearance. Studies tend to focus on the neurotoxicity of specific Aβ species. There are relatively few studies investigating toxic effects of Aβ on the endothelial cells of the blood-brain barrier (BBB). We hypothesized that a soluble Aβ pool more closely resembling the in vivo situation composed of a mixture of Aβ40 monomer and Aβ42 oligomer would exert higher toxicity against hCMEC/D3 cells as an in vitro BBB model than either component alone. We observed that, in addition to a disruptive effect on the endothelial cells integrity due to enhancement of the paracellular permeability of the hCMEC/D3 monolayer, the Aβ mixture significantly decreased monomeric Aβ transport across the cell culture model. Consistent with its effect on Aβ transport, Aβ mixture treatment for 24h resulted in LRP1 down-regulation and RAGE up-regulation in hCMEC/D3 cells. The individual Aβ species separately failed to alter Aβ clearance or the cell-based BBB model integrity. Our study offers, for the first time, evidence that a mixture of soluble Aβ species, at nanomolar concentrations, disrupts endothelial cells integrity and its own transport across an in vitro model of the BBB.
老年淀粉样斑块是阿尔茨海默病（AD）的诊断标志之一。然而，AD临床症状的严重程度与斑块负荷的相关性较弱。据报道，AD症状的严重程度与可溶性淀粉样β蛋白（Aβ）聚集体的水平相关性更强。可溶性Aβ聚集体的形成是由大脑中单体Aβ的积累所刺激的，这与其脑清除功能缺陷有关。研究往往集中在特定Aβ种类的神经毒性上。相对较少有研究调查Aβ对血脑屏障（BBB）内皮细胞的毒性作用。我们假设，一种更类似于体内情况的可溶性Aβ池，由Aβ40单体和Aβ42寡聚体的混合物组成，作为体外BBB模型，对hCMEC/D3细胞的毒性将高于单独的任何一种成分。我们观察到，除了由于hCMEC/D3单层细胞旁通透性增强而对内皮细胞完整性产生破坏作用外，Aβ混合物还显著降低了单体Aβ跨细胞培养模型的转运。与其对Aβ转运的影响一致，Aβ混合物处理24小时导致hCMEC/D3细胞中低密度脂蛋白受体相关蛋白1（LRP1）下调和晚期糖基化终末产物受体（RAGE）上调。单独的Aβ种类未能改变Aβ清除或基于细胞的BBB模型完整性。我们的研究首次提供了证据，表明纳摩尔浓度的可溶性Aβ种类混合物会破坏内皮细胞完整性及其在体外BBB模型中的自身转运。
