Detection of Alzheimer peptides and chemokines in the aqueous humor

PURPOSE. Alzheimer disease (AD) and age-related ocular diseases are characterized by inflammation and accumulation of insoluble proteins. We aimed to investigate the detectability and clinical relevance of a panel of AD-related markers, such as Alzheimer peptides and chemokines, in the aqueous humor (AH) samples taken from patients with cataract only, or cataract and 1 other ocular disease. METHODS. The AH samples were obtained during cataract surgery from patients with cataract only (n=162), cataract and glaucoma (n=21), cataract and exfoliation (PEX) (n=31), cataract and macular degeneration (n=36), and cataract and diabetic retinopathy (n=16). The AD peptides (A beta(1-42), A beta(1-40), A beta(1-38)) and chemokines (eotaxin, eotaxin 3, interleukin [IL]-8, inducible protein-10, monocyte chemotactic protein [MCP]-1, MCP-4, macrophage-derived chemokine, macrophage inflammatory protein-1 beta, thymus and activation-egulated chemokine) were quantified by using multiplex immunoassays. RESULTS. The levels of the AH peptides (A beta(1-38), A beta(1-40), A beta(1-42)) did not differ between disease groups. Independently of disease group, the A beta(1-38) levels correlated with A beta(1-40) and A beta(1-42) (p<0.001, n=277). Notably, the ratio A beta(1-42) to A beta(1-38) differed between PEX and macular degeneration (mean 95% confidence interval [CI] =8.12 [11.3-3.99] vs 2.23 [2.67-0.52], p=0.003). Among chemokines examined, only MCP-1 and IL-8 were detected in about 90% to 46% of all analyzed (n=266) samples. Higher levels of AH IL-8 were found in the glaucoma group than in cataract only (p=0.011). Independently of disease group, a correlation was observed between AH MCP-1 and IL-8 (rho=0.275, p<0.001, n=266) and between MCP-1 and A beta(1-40) (rho=0.239, p<0.001, n=266). CONCLUSIONS. Our findings highlight pathologic similarities between AD and eye diseases, and show the potential of modern technologies to detect AD biomarkers in age-related eye diseases.