FLAG adenovirus

Primary open-angle glaucoma (POAG) is the second leading cause of irreversible blindness worldwide. Increased endothelin-1 (ET-1) is observed in the aqueous humor (AH) of POAG patients, resulting in increased outflow resistance of the AH. However, the underlying mechanisms remain elusive. Using established in vivo and in vitro POAG models, researchers demonstrate that the water channel aquaporin 1 (AQP1) is downregulated in trabecular meshwork (TM) cells upon exposure to ET-1, which results in a series of glaucomatous changes including actin fiber reorganization, collagen production, extracellular matrix deposition, and altered TM cell contractility. Ectopic expression of AQP1 can reverse ET-1-induced TM tissue remodeling, which requires the presence of β-catenin. More importantly, ET-1-induced AQP1 repression is mediated by the unfolded protein response transcription factor ATF4, which binds to the AQP1 promoter and negatively regulates AQP1 transcription. Therefore, these studies reveal a novel function of ATF4 in controlling the ET-1-induced TM remodeling process in POAG by inhibiting AQP1 transcription.

Here, researchers determined whether AQP1 reduction is responsible for ET-1-induced pathological changes in POAG. Knockdown of AQP1 in HTMCs with si-AQP1 resulted in collapse of actin arcs and formation of thick actin bundles (Figure 1A), altered intracellular and extracellular collagen (Figure 1B-E), and enhanced cellular contractility (Figure 1F), which mimicked the effects of ET-1 on HTMCs. Furthermore, ectopic expression of AQP1 by transfecting HTMCs with an adenoviral vector encoding full-length AQP1 significantly reversed ET-1-induced stress fiber reorganization (Figure 1A), collagen deposition (Figure 1B-E), and enhanced contractility (Figure 1F) in HTMCs compared with vector control (Ad-Flag). Thus, these results suggest that a decrease in AQP1 is required for ET-1-induced TM tissue remodelling in POAG.

Figure 1. AQP1 inhibits ET-1-induced F-actin reorganization, elevated contractility and collagen deposition in HTMCs. (Zhao Y, et al., 2020)