Association between 91 circulating inflammatory proteins and the risk of glaucoma: A Mendelian randomization study

Glaucoma is a leading cause of irreversible blindness worldwide, with its pathogenesis incompletely understood. Inflammation, as an important aspect of glaucoma, has attracted increasing attention. In this study, we performed a Mendelian randomization (MR) analysis to investigate the association between 91 circulating inflammatory proteins and glaucoma. First, a bidirectional MR was employed to screen for inflammatory proteins that potentially influence glaucoma risk, with the findings further confirmed by a replication sample MR. Then, a mediation analysis was employed to assess the mediating effects of glaucoma endophenotypes on glaucoma. Finally, we performed a subgroup MR to investigate the association between circulating proteins and glaucoma subtypes, including primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG). The bidirectional MR suggested 7 out of the 91 proteins were possibly related with glaucoma risk, with T-cell surface glycoprotein CD5 (CD5) (odds ratio (OR) = 0.87; 95% confidence interval (CI): 0.81-0.94; P = 2.46 × 10^-4) passing false discovery rate correction. This result was verified by the replication sample MR. The mediation analysis revealed that intraocular pressure (IOP) (β=-0.05; 95% CI: -0.02--0.09; P = 1.56 × 10^-3) was a mediator of CD5's protective effect on glaucoma. The subgroup MR indicated that CD5 conferred a protective causal effect specifically on POAG, not PACG. Moreover, IOP served as a mediator in the association between CD5 and POAG, explaining a proportion of 38.29% of CD5's protective effect against POAG. Our findings suggest a negative causal association between circulating CD5 and POAG risk, which is partially mediated by IOP. This indicates that targeted CD5 therapy may be beneficial to POAG eyes.