Epigallocatechin-3-Gallate Protects Trabecular Meshwork Cells from Endoplasmic Reticulum Stress

Abstract

Primary open-angle glaucoma (POAG) is the most common form of glaucoma, for which elevated intraocular pressure (IOP) is a major risk factor. IOP is mainly regulated by dynamic balance of aqueous humor (AH) production and outflow via the conventional trabecular meshwork/Schlemm’s canal (TM/SC) pathway. Dysfunctions of TM cells due to endoplasmic reticulum (ER) stress have been demonstrated to increase the resistance of AH outflow, resulting in IOP elevation. Epigallocatechin-3-gallate (EGCG), the most abundant polyphenolic component in green tea, has been shown to alleviate ER stress in several diseases while its potential roles in alleviating ER stress in TM cells have not been determined. In this study, we investigate the mitigation of tunicamycin-induced ER stress in TM cells by EGCG. MTT assay was used to measure the cell viability of human TM (HTM) cells and primary porcine TM (PTM) cells. ER stress levels in both HTM cells and primary PTM cells were detected by quantitative real-time PCR. The primary PTM cells isolated from porcine TM tissues were characterized by immunostaining. We found that 40 μM and 80 μM EGCG pretreatment substantially promoted HTM cell survival under 3 μM tunicamycin-induced ER stress. Pretreatment of 40 μM EGCG markedly reduced the expression of ER stress markers ATF4, HSPA5, and DDIT3, evoked by 3 μM tunicamycin in HTM cells. Furthermore, 40 μM EGCG pretreatment significantly decreased the expressions of ATF4, HSPA5, and DDIT3 at the mRNA level induced by 3 μM tunicamycin and improved cell viability in primary PTM cells. Our results show that EGCG is capable of protecting TM cells from ER stress. EGCG provides a promising therapeutic option for POAG treatment.

Epigallocatechin-3-Gallate Reduces Cd-Induced Developmental Toxicity of Bodysize in Caenorhabditis elegans via the PEK-1/eIF-2α/ATF-4 Pathway

“…PERK (PEK-1 in C. elegans), the second ER stress sensor, is an ER transmembrane protein [27]. In a cellular model, EGCG inhibited the expression of the ER stress marker ATF4 in trabecular meshwork cells treated with Tm [39], suppressed the increase in p-PERK/p-eIF-2α/ATF-4 expression levels in Caco-2 cells treated with Tm and thapsigargin [40], and decreased the expression of p-PERK in high-glucose-induced podocytes [41]. Our study shows that RNAi targeting pek-1 abolishes the inhibitory effect of EGCG on Cd-induced ER stress in the nematode head (Figure 5A,B).…”

Potential therapeutic effects of green tea (Camellia sinensis) in eye diseases, a review

“…In an in vivo study, the therapeutic potential of EGCG was investigated on ER stress markers and HTM cell viability. Results indicate the efficacy of EGCG in treating primary open-angle glaucoma [ 90 ].…”

“… [ 87 ] in-vitro human trabecular meshwork (HTM) cell primary open-angle glaucoma EGCG (10, 20, 40, and 80 μM) EGCG can shield TM cells from endoplasmic reticulum stress, indicating that it has the potential as a therapeutic choice for treating POAG. [ 90 ] in-vivo rat uveitis GTE (550 mg/kg) GTE is a powerful anti-inflammatory agent that effectively combats endotoxin-induced uveitis (EIU) inflammation, indicating its potential usefulness in treating acute uveitis. [ 97 ] in-vivo murine autoimmune uveitis GTE (137.5 mg/kg and 275 mg/kg GTE suspension, 96.25 mg/kg and 192.5 mg/kg EGCG suspension in 0.1 mL distilled water) Relief from intraocular inflammation can be achieved by suppressing the expression of pro-inflammatory genes associated with Th17 cells.…”