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N. Boehm, S. Beck, U. Lossbrand, N. Pfeiffer, F. H. Grus; Analysis of Complement Proteins in Retina and Sera of Glaucoma Patients. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5221.
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Recently an alteration in expression of complement proteins C1q and C3 in the retina of ocular hypertension patients could be demonstrated. The present study sought to determine and compare the levels of all main proteins of the complement cascade in sera and retinas of primary open-angle glaucoma patients (POAG) and healthy subjects (CO), as well as the expression status of several heat shock proteins and structural proteins of the retina.
Sera of POAG patients (n=32) and CO subjects (n=32) as well as retina samples from POAG (n=6) and CO (n=6) donor eyes were used for protein analysis. For protein expression analysis we prepared antibody microarrays by spotting 40 different antibodies against all complement proteins (e.g. C1r/q, C3) and against e.g. heat shock protein 27, Myelin Basic Protein (MBP) or Glial Fibrillary Acidic Protein (GFAP) onto microarray-slides. Sample proteins were labeled with a fluorescence dye, followed by incubation on arrays (5 µg). The emitted fluorescence signals of captured proteins were digitized and spot intensities were compared using diverse statistical techniques such as ANOVA or multivariate analysis of discriminance.
In POAG serum samples 4 complement proteins (e.g. C3, C6) showed statistical significant increased expression levels in comparison to control subjects (P≤0.001). For heat shock and structural proteins we detected significant increased (HSP10, HSP60, HSP90; P≤0.002) but also decreased quantities (MBP, β-Tubulin; P≤0.01) in POAG. In retina samples of glaucoma patients we found e.g. 1.7 fold increased levels of HSP90 (CO: ME 16764±4204, POAG: ME 28769±9402; P≤0.01) and several other altered protein expression levels (C3, C5, Caspase 3, MBP; P≤0.003), also. Using discriminant analysis we detected a Mahalanobis distance of 79.55±17.52 (P<0.001) for POAG protein patterns in comparison to the CO group.
We could prove a significant increase in quantity of complement proteins in retinas as well as in sera of POAG subjects. Also, proteins functionally related to stress responses showed altered protein levels in POAG patients. Our findings indicate a correlation between the increase of complement proteins in sera with the amounts of deposited complement proteins in the retina of glaucoma patients. The results provide further hints for an activation of the complement cascade in the retina of glaucoma patients, which may form membrane attack complexes, resulting in retinal ganglion cell death.
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