Wijesinghe Printha, Whitmore Clayton A, Campbell Matthew, Li Charles, Tsuyuki Miranda, To Eleanor, Haynes Justin, Pham Wellington, Matsubara Joanne A
Department of Ophthalmology and Visual Sciences, Faculty of Medicine, Eye Care Centre, The University of British Columbia, Vancouver, BC, Canada.
Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States.
Front Neurosci. 2023 Mar 14;17:1107436. doi: 10.3389/fnins.2023.1107436. eCollection 2023.
Ergothioneine (Ergo) is a naturally occurring dietary antioxidant. Ergo uptake is dependent on the transporter, organic cation transporter novel-type 1 (OCTN1) distribution. OCTN1 is highly expressed in blood cells (myeloid lineage cells), brain and ocular tissues that are likely predisposed to oxidative stress. Ergo may protect the brain and eye against oxidative damage and inflammation, however, the underlying mechanism remains unclear. Amyloid beta (Aβ) clearance is a complex process mediated by various systems and cell types including vascular transport across the blood-brain barrier, glymphatic drainage, and engulfment and degradation by resident microglia and infiltrating innate immune cells. Impaired Aβ clearance is a major cause for Alzheimer's disease (AD). Here we investigated neuroretinas to explore the neuroprotective effect of Ergo in a transgenic AD mouse model.
Age-matched groups of Ergo-treated 5XFAD, non-treated 5XFAD, and C57BL/6J wildtype (WT controls) were used to assess Ergo transporter OCTN1 expression and Aβ load along with microglia/macrophage (IBA1) and astrocyte (GFAP) markers in wholemount neuroretinas ( = 26) and eye cross-sections ( = 18). Immunoreactivity was quantified by fluorescence or by semi-quantitative assessments.
OCTN1 immunoreactivity was significantly low in the eye cross-sections of Ergo-treated and non-treated 5XFAD vs. WT controls. Strong Aβ labeling, detected in the superficial layers in the wholemounts of Ergo-treated 5XFAD vs. non-treated 5XFAD reflects the existence of an effective Aβ clearance system. This was supported by imaging of cross-sections where Aβ immunoreactivity was significantly low in the neuroretina of Ergo-treated 5XFAD vs. non-treated 5XFAD. Moreover, semi-quantitative analysis in wholemounts identified a significantly reduced number of large Aβ deposits or plaques, and a significantly increased number of IBA1(+)ve blood-derived phagocytic macrophages in Ergo-treated 5XFAD vs. non-treated 5XFAD. In sum, enhanced Aβ clearance in Ergo-treated 5XFAD suggests that Ergo uptake may promote Aβ clearance possibly by blood-derived phagocytic macrophages and perivascular drainage.
麦角硫因（Ergo）是一种天然存在的膳食抗氧化剂。Ergo的摄取取决于转运蛋白——新型有机阳离子转运体1（OCTN1）的分布。OCTN1在血细胞（髓系谱系细胞）、大脑和眼组织中高表达，这些组织可能易受氧化应激影响。Ergo可能保护大脑和眼睛免受氧化损伤和炎症，但潜在机制仍不清楚。淀粉样β蛋白（Aβ）的清除是一个复杂的过程，由多种系统和细胞类型介导，包括穿过血脑屏障的血管运输、类淋巴引流以及常驻小胶质细胞和浸润的先天免疫细胞的吞噬和降解。Aβ清除受损是阿尔茨海默病（AD）的主要原因。在此，我们研究了神经视网膜，以探索Ergo在转基因AD小鼠模型中的神经保护作用。
使用年龄匹配的经Ergo处理的5XFAD组、未经处理的5XFAD组和C57BL/6J野生型（WT对照组），以评估Ergo转运体OCTN1的表达、Aβ负荷以及全层神经视网膜（n = 26）和眼横截面（n = 18）中的小胶质细胞/巨噬细胞（IBA1）和星形胶质细胞（GFAP）标志物。通过荧光或半定量评估对免疫反应性进行定量。
与WT对照组相比，经Ergo处理和未经处理的5XFAD的眼横截面中OCTN1免疫反应性显著降低。在经Ergo处理的5XFAD全层的表层中检测到的强烈Aβ标记与未经处理的5XFAD相比，反映了有效的Aβ清除系统的存在。这在横截面成像中得到了支持，其中与未经处理的5XFAD相比，经Ergo处理的5XFAD的神经视网膜中Aβ免疫反应性显著降低。此外，全层的半定量分析发现，与未经处理的5XFAD相比，经Ergo处理的5XFAD中大型Aβ沉积物或斑块的数量显著减少，IBA1（+）阳性血源性吞噬巨噬细胞的数量显著增加。总之，经Ergo处理的5XFAD中Aβ清除增强表明，Ergo摄取可能通过血源性吞噬巨噬细胞和血管周围引流促进Aβ清除。
