Neurodegeneration Markers Galectin-3 and Apolipoprotein E Are Elevated in the Aqueous Humor of Eyes With Glaucoma

Abstract

Purpose: Galectin-3 (Gal-3) and apolipoprotein E (APOE) are markers of activated microglia in neurodegenerative diseases of the central nervous system, whose targeting is protective in mouse models of glaucoma. In this study, we examined levels of Gal-3 and APOE in human aqueous humor (AH) and defined their clinical associations with glaucoma.

Methods: We collected AH from 59 glaucoma patients and 15 controls at the start of planned ophthalmic surgery. Gal-3 and APOE levels were quantified by enzyme-linked immunosorbent assay. Total protein in AH was quantified by bicinchoninic acid assay. Significant associations between Gal-3, APOE, and clinical covariates were defined using univariate and multivariate linear regression models.

Results: Gal-3 and APOE levels were significantly elevated in the AH of glaucoma patients compared to controls (P = 0.004 and P < 0.001, respectively). Gal-3 and APOE were positively correlated across the entire cohort (r = 0.65, P = 6.2E-9). No association was observed between Gal-3 and total protein or APOE and total protein (P = 0.35 and P = 0.50, respectively), indicating that their levels were not increased in glaucomatous AH due to nonspecific protein accumulation. Multivariate linear regression modeling revealed significant associations between Gal-3 and maximum recorded intraocular pressure (P = 0.009) and between APOE and number of past ophthalmic surgeries (P = 0.031).

Conclusions: We demonstrate that Gal-3 and APOE are significantly elevated in the AH of eyes with glaucoma and are associated with a history of poorly controlled disease.

Translational relevance: Gal-3 and APOE in AH may inform clinical decision-making as quantifiable readouts of microglial activation in eyes with glaucoma.

Figure 1.

(A) Gal-3 and (B) APOE levels are elevated in the aqueous humor of patients with glaucoma. Significance was determined using the Kruskal-Wallis test and results are shown as mean ± standard error of the mean (SEM). **P < 0.01, ***P < 0.001.

Figure 2.

(A) There is moderate, positive association between Gal-3 and APOE across the entire cohort (r = 0.65, P = 6.2E-9). No association was observed between Gal-3 and total protein (r = 0.10, P = 0.35) (B) or APOE and total protein (r = 0.09, P = 0.50) (C). Individual circles depict individual participants, and dashed lines represent 95% confidence interval bands. Pearson's correlation coefficient r is reported.

Figure 3.

There is a significant association between Gal-3 and maximum intraocular pressure (max IOP) (A) and Gal-3 and number of past ophthalmic surgeries (B). Trending association was observed between Gal-3 and both preoperative IOP (C) and number of preoperative glaucoma medications (D). No association was observed between Gal-3 and HVF mean deviation (E) or optical coherence tomography RNFL thickness (F). Individual circles depict individual participants and dashed lines represent 95% confidence intervals bands. Green indicates significant association (A-B) (P < 0.05), yellow indicates association trending toward significance (C-D) (P < 0.1), and red indicates no significant association (E-F) (P ≥ 0.1). Pearson's correlation coefficient r is reported.

Figure 4.

There is a significant association between APOE and number of past ophthalmic surgeries (A) and APOE and maximum intraocular pressure (max IOP) (B). Trending association was observed between APOE and both number of preoperative glaucoma medications (C) and HVF mean deviation (D). No association was observed between APOE and preoperative IOP (E) or optical coherence tomography RNFL thickness (F). Individual circles depict individual participants and dashed lines represent 95% confidence intervals bands. Green indicates significant association (A-B) (P < 0.05), yellow indicates association trending toward significance (C-D) (P < 0.1), and red indicates no significant association (E-F) (P ≥ 0.1). Pearson's correlation coefficient r is reported.