Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
Cell Biol Int. 2022 Feb;46(2):323-330. doi: 10.1002/cbin.11718. Epub 2021 Nov 9.
Epithelial-mesenchymal transition (EMT) occurs when polarised epithelial cells change to a mesenchymal phenotype. EMT plays a role in several chronic conditions, including ocular diseases with retinal pigment epithelium (RPE) EMT associated with retinal diseases such as diabetic retinopathy (DR). Here, EMT results in breakdown of the blood-retinal barrier (BRB) leading to sub-retinal fluid deposition and retinal detachment. Previous studies have shown that blocking connexin43 (Cx43) hemichannels can protect against RPE BRB breakdown, but the underlying mechanism is unknown. To determine whether open Cx43 hemichannels may enable EMT of RPE cells and thus result in BRB breakdown, ARPE-19 cells were either challenged with high glucose plus the inflammatory cytokines IL-1β and TNF-α (HG + Cyt) to simulate DR or treated with the Cx43 hemichannel blocker tonabersat alongside the HG + Cyt challenge. HG + Cyt induced a morphological change in RPE cells to a fibroblastic phenotype with a corresponding decrease in epithelial zonular occludens-1 and an increase in the fibroblastic marker α-SMA. The HG + Cyt challenge also induced loss of transepithelial electrical resistance while increasing dye passage between RPE cells. All of these changes were significantly reduced with tonabersat treatment, which also prevented HG + Cyt-induced transforming growth factor-β2 (TGF-β2) release. In conclusion, Cx43 hemichannel block with tonabersat attenuated both TGF-β2 release and RPE EMT under disease-mimicking conditions, offering the potential to ameliorate the progression of EMT-associated retinal diseases.
上皮-间充质转化 (EMT) 发生在极化的上皮细胞转变为间充质表型时。EMT 在几种慢性疾病中起作用，包括与视网膜疾病相关的眼部疾病，如糖尿病视网膜病变 (DR) 中的视网膜色素上皮 (RPE) EMT。在这里，EMT 导致血视网膜屏障 (BRB) 破裂，导致视网膜下液沉积和视网膜脱离。先前的研究表明，阻断连接蛋白 43 (Cx43) 半通道可以防止 RPE BRB 破裂，但潜在机制尚不清楚。为了确定开放的 Cx43 半通道是否可能使 RPE 细胞发生 EMT，从而导致 BRB 破裂，ARPE-19 细胞要么受到高葡萄糖加炎症细胞因子 IL-1β 和 TNF-α (HG + Cyt) 的挑战，以模拟 DR，要么与 HG + Cyt 一起接受 Cx43 半通道阻滞剂 tonabersat 治疗。HG + Cyt 诱导 RPE 细胞发生形态变化，向成纤维细胞表型转变，上皮带Occludens-1 相应减少，成纤维细胞标志物 α-SMA 增加。HG + Cyt 挑战还诱导上皮细胞间电阻丧失，同时增加 RPE 细胞之间染料的通透性。所有这些变化在用 tonabersat 治疗后均显著减少，同时还阻止了 HG + Cyt 诱导的转化生长因子-β2 (TGF-β2) 释放。总之，用 tonabersat 阻断 Cx43 半通道可减轻疾病模拟条件下的 TGF-β2 释放和 RPE EMT，为改善 EMT 相关视网膜疾病的进展提供了潜力。
