Hemoglobin (Hb) is the main component of red blood cells, and the majority of alpha-synuclein in the blood is present inside them. In Parkinson’s disease and aging human brains, the levels of mitochondrial neuronal hemoglobin are significantly decreased in neurons where α-Syn has accumulated, suggesting a relationship between these two proteins. In the present study, we demonstrate that a complex comprising α-Syn and Hb exists in both peripheral RBCs and brain tissue in aging humans using Co-Immunoprecipitation and a newly established ELISA assay. The nHb^α−Syn levels in the mitochondrial fraction of the human striatum reduced in an age-dependent manner which was negatively correlated with the nHb^α−Syn complex levels in the cytoplasmic extraction. In contrast, no age-related alteration in the nHb^α−Syn complex was found in the above subcellular fractions of the human cerebellum. Furthermore, the nHb^α−Syn complex levels in RBCs increased with age, which agrees with the changes observed in the cytoplasm of the human striatum. Meanwhile, sequential window acquisition of all theoretical mass spectra-MS (SWATH-MS) was used to confirm the presence of the Hb^α−Syn complex in RBCs and also found that nHb^α−Syn levels increased notably in PD patients compared to healthy controls (HC). Receiver operating characteristic (ROC) curves indicated that Hb^α−Syn in PD patients was distinct from HC, with areas under the curve (AUCs) of 0.875. The above results suggest that the alteration in nHb^α−Syn levels in RBCs reflects those in select regions of the human brain, thereby providing a possibility of using Hb^α−Syn as a biomarker to diagnose PD.

血红蛋白（Hb）是红细胞的主要成分，血液中的大多数α-突触核蛋白都存在于其中。在帕金森氏病和人脑衰老中，线粒体神经元血红蛋白的水平在α-Syn积累的神经元中显着降低，表明这两种蛋白之间存在关联。在本研究中，我们证明了使用共免疫沉淀和新建立的ELISA分析方法，在老年人的外周血红细胞和脑组织中都存在包含α-Syn和Hb的复合物。人纹状体线粒体部分中的nHbα ^-Syn水平以年龄相关的方式降低，与nHbα ^-Syn负相关复杂水平的细胞质提取。相反，在人小脑的上述亚细胞部分中未发现nHbα ^-Syn复合物的年龄相关变化。此外，红细胞中的nHbα ^-Syn复合物水平随年龄增加而增加，这与人纹状体细胞质中观察到的变化一致。同时，所有理论质谱的连续窗口采集（SWATH-MS）用于确认红细胞中Hbα ^-Syn复合物的存在，并且还发现与健康对照相比，PD患者中的nHbα ^-Syn水平显着增加（HC）。接收器工作特性（ROC）曲线表明Hbα ^-SynPD患者的HC与HC有所不同，曲线下面积（AUC）为0.875。以上结果表明，RBC中nHbα ^-Syn水平的变化反映了人脑某些区域的变化，从而提供了使用Hbα ^-Syn作为生物标志物诊断PD的可能性。