Activating transcription factor 6 is involved in the beneficial effects of growth hormone-releasing hormone antagonists in the corneal endothelium

The corneal endothelium maintains eye transparency through fluid regulation, and its dysfunction has been associated with impaired vision. This study is focused on the possible involvement of activating transcription factor 6 (ATF6) in the beneficial effects of Growth Hormone - Releasing Hormone antagonists (GHRHAnt) in corneal cells. ATF6 is a UPR sensor involved in barrier function, previously shown to exert anti-inflammatory activities. The aim of this study is to evaluate involvement of ATF6 in the effects of GHRHAnt in the corneal endothelium. MTT assay was used to measure the cell viability of ATF6 modulator. We demonstrated the efficient ATF6 manipulation by AA147 and Ceapin-A7, which are specific ATF6 modulators. Western blot analysis was used to detect the protein expression levels. FITC-dextran assay and DCFDA were utilized to measure paracellular permeability and reactive oxygen species generation, respectively. AA147 enhanced Grp94 and BiP expression, both being downstream ATF6 targets, whereas Ceapin-A7 exerted the opposite effects. Then, we investigated the possible involvement of ATF6 in the protective activities of GHRHAnt in the corneal endothelium. ATF6 activation enhanced the protective effects of GHRHAnt by reducing paracellular permeability and ROS generation, while ATF6 inhibition exerted the opposite effects. Our study suggests that ATF6 mediates - at least in part - the beneficial effects of GHRHAnt in the cornea.