Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
School of Biological Sciences, Nanyang Technological University, Singapore.
J Proteomics. 2014 Mar 17;99(100):54-67. doi: 10.1016/j.jprot.2014.01.011. Epub 2014 Jan 19.
Vascular dementia (VaD) is a leading cause of dementia in the elderly together with Alzheimer's disease with limited treatment options. Poor understanding of the pathophysiology underlying VaD is hindering the development of new therapies. Hence, to unravel its underlying molecular pathology, an iTRAQ-2D-LC-MS/MS strategy was used for quantitative analysis of pooled lysates from Brodmann area 21 of pathologically confirmed cases of VaD and matched non-neurological controls. A total of 144 differentially expressed proteins out of 2281 confidently identified proteins (false discovery rate=0.3%) were shortlisted for bioinformatics analysis. Western blot analysis of selected proteins using samples from individual patients (n=10 per group) showed statistically significant increases in the abundance of SOD1 and NCAM and reduced ATP5A in VaD. This suggested a state of hypometabolism and vascular insufficiency along with an inflammatory condition during VaD. Elevation of SOD1 and increasing trend for iron-storage proteins (FTL, FTH1) may be indicative of an oxidative imbalance that is accompanied by an aberrant iron metabolism. The synaptic proteins did not exhibit a generalized decrease in abundance (e.g. syntaxin) in the VaD subjects. This reported proteome offers a reference data set for future basic or translational studies on VaD.
Our study is the first quantitative clinical proteomic study where iTRAQ-2D-LC-MS/MS strategy has been used to identify the differential proteome in the VaD cortex by comparing VaD and matched control subjects. We generate testable hypothesis about the involvement of various proteins in the vascular and parenchymal events during the evolution of VaD that finally leads to malfunction and demise of brain cells. This study also establishes quantitative proteomics as a complementary approach and viable alternative to existing neurochemical, electron microscopic and neuroimaging techniques that are traditionally being used to understand the molecular pathology of VaD. Our study could inspire fellow researchers to initiate similar retrospective studies targeting various ethnicities, age-groups or sub-types of VaD using brain samples available from brain banks across the world. Meta-analysis of these studies in the future may be able to shortlist candidate proteins or pathways for rationale exploration of therapeutic targets or biomarkers for VaD.
血管性痴呆（VaD）是老年人中与阿尔茨海默病一起导致痴呆的主要原因，治疗选择有限。对 VaD 潜在病理生理学的理解不足阻碍了新疗法的发展。因此，为了揭示其潜在的分子病理学，我们使用 iTRAQ-2D-LC-MS/MS 策略对经病理证实的 VaD 患者和匹配的非神经对照组的 Brodmann 区 21 的混合裂解物进行定量分析。在 2281 个可置信鉴定蛋白中，有 144 个差异表达蛋白（错误发现率=0.3%）被列为生物信息学分析的候选蛋白。使用个体患者的样本（每组 10 例）对选定蛋白进行 Western blot 分析表明，在 VaD 中 SOD1 和 NCAM 的丰度增加，而 ATP5A 减少。这表明在 VaD 期间存在代谢低下和血管不足以及炎症状态。SOD1 的升高和铁储存蛋白（FTL、FTH1）的增加趋势可能表明氧化失衡伴随着异常的铁代谢。突触蛋白在 VaD 患者中没有表现出普遍的丰度降低（例如，突触素）。该报道的蛋白质组为未来 VaD 的基础或转化研究提供了参考数据集。
我们的研究是第一项使用 iTRAQ-2D-LC-MS/MS 策略的定量临床蛋白质组学研究，该策略用于通过比较 VaD 和匹配的对照组来鉴定 VaD 皮质中的差异蛋白质组。我们提出了各种蛋白质在 VaD 演变过程中参与血管和实质事件的可检验假设，这些事件最终导致脑细胞功能障碍和死亡。这项研究还将定量蛋白质组学确立为一种补充方法和可行的替代方案，可替代传统上用于理解 VaD 分子病理学的神经化学、电子显微镜和神经影像学技术。我们的研究可以启发其他研究人员使用世界各地脑库中的脑样本，针对各种族裔、年龄组或 VaD 亚型启动类似的回顾性研究。未来对这些研究进行荟萃分析可能能够为 VaD 的治疗靶点或生物标志物的合理探索选择候选蛋白或途径。
