Plasma endothelin-1 and endothelin-A receptor concentrations in patients with primary open-angle glaucoma

Endothelin-1 (ET-1) is a potent vasoconstrictor and is considered to have a key role in the regulation of ocular perfusion and glaucoma pathogenesis. High ET-1 and ETA-receptor levels are reported in patients with primary open-angle glaucoma (POAG). We compared the mean plasma ET-1 and ETA-receptor concentration of controls and patients with early and advanced POAG stage, and assessed the correlation with the retinal nerve fibre layer (RNFL) thickness. The study included a total of 75 participants, aged 45-83 years: 25 (controls), 22 (early glaucoma) and 28 (advanced glaucoma). The plasma concentration of ET-1 and ETA-receptor was determined by enzyme-linked immunosorbent assay. The RNFL thickness was evaluated with spectral-domain optical coherence tomography. The mean ET-1 concentration was lower in the control group (4.88 +/- 1.75 pg/mL) than in the early and advanced POAG group (6.33 +/- 2.38 and 6.34 +/- 1.56 pg/mL). Statistically significant difference was found between the mean ET-1 concentrations in controls and glaucoma patients (p = 0.029 - early glaucoma, p = 0.018 - advanced glaucoma), and no significant difference was observed between the two POAG groups (p = 0.998). The mean ETA-receptor concentration was highest in the control group (1209.28 +/- 314.48 pg/mL) and the differences between the three groups were significant. Significant relationship was found only between ET-1 and RNFL. This study demonstrated the role of ET-1 in glaucoma pathogenesis based on the observed significant high ET-1 and ETA-receptor plasma levels in POAG patients. A new therapeutical approach needs to be considered in some patients.