Abstract
Purpose:
Agonistic Autoantibodies (AABs) against G protein coupled receptors (GPCR) are found in several human diseases (e. g. Asthma, arterial hypertension). β2-adrenergic receptors (ß2-AR) are involved in the regulation of aqueous humor dynamics and were found on retinal blood vessels. Agonistic β2-adrenergic receptor autoantibodies (β2-AABs) were found in glaucoma suspects and glaucoma patients, yet not in normals. The aim of this study was to investigate retinal capillary flow and its potential correlation with β2-AAB activity in these groups.
Methods:
74 probands were included (25 normals, 21 OHTs, 10 pre-perimetric POAGs, 18 POAGs; Erlangen Glaucoma Registry, ISSN 2191-5008, CS-2011; NTC00494923). All patients underwent complete ophthalmological examinations including examinations with Octopus G1 program and measurements of retinal capillary flow by Heidelberg Retina Flowmetry. Serum probes of all patients were analyzed of β2-AABs using a bioassay (1). In this assay the alteration of the beating rate of spontaneously beating cultured neonatal rat cardiomyocytes, expressing GPCR, due to the applied serum level of AABs, is counted. Statistical analysis was done using non-parametric U-Test. The protocol was approved by the local Ethics Committee (3457).<br /> (1) Dragun D et al. (2005) Angiotensin II type 1-receptor activating antibodies in renal-allograft rejection. N Engl J Med 352: 558-569
Results:
(1) Retinal capillary flow was reduced in OHTs (246±59 [AU]) and glaucoma patients (pre-POAG: 238±49 [AU]; POAG: 247±62 [AU]). (2) Correlation analysis for all patients with β2-AAB positivity showed a significant correlation of retinal capillary flow with β2-AAB (p=0.014; R=0.349). (3) Subgroup analysis for patients with OHT, glaucoma patients with and without perimetric defects revealed no correlation of retinal capillary flow in patients with OHT (p=0.298). However a tendency could be observed in pre-POAG (p=0.144; R=0.497) up to a statistically significant correlation between retinal capillary flow and β2-AAB in POAG (p=0.012; R=0.578).
Conclusions:
The high percentage of β2-AAB positivity in glaucoma patients and glaucoma suspects suggests a potentially primary role for β2-AAB in glaucoma disease. The strong correlation of β2-AABs with retinal capillary flow in POAG as well as the trend in pre-POAG, suggest a potential influence of β2-AABs on retinal microcirculation.