Metformin protects trabecular meshwork against oxidative injury via activating integrin/ROCK signals

Abstract

This study aimed to investigate the protective effect of metformin on trabecular meshwork (TM) and explore its molecular mechanisms in vivo and in vitro. Ocular hypertension (OHT) mouse models were induced with dexamethasone and further treated with metformin to determine the intraocular pressure (IOP)-lowering effect. Cultured human TM cells (HTMCs) were pre-stimulated with tert-butyl hydroperoxide (tBHP) to induce oxidative damage and then supplemented with metformin for another 24 hr. The expression of fibrotic markers and integrin/Rho-associated kinase (ROCK) signals, including α-smooth muscle actin (α-SMA), transforming growth factor-β (TGF-β), fibronectin, integrin beta 1, ROCK 1/2, AMP-activated protein kinase, myosin light chain 1, and F-actin were determined by western blotting and immunofluorescence. Reactive oxygen species (ROS) content was analysed using flow cytometry. Transmission electron microscopy was performed to observe microfilaments in HTMCs. It showed that metformin administration reduced the elevated IOP and alleviated the fibrotic activity of aqueous humour outflow in OHT models. Additionally, metformin rearranged the disordered cytoskeleton in the TM both in vivo and in vitro and significantly inhibited ROS production and activated integrin/ROCK signalling induced by tBHP in HTMCs. These results indicated that metformin reduced the elevated IOP in steroid-induced OHT mouse models and exerted its protective effects against oxidative injury by regulating cytoskeleton remodelling through the integrin/ROCK pathway. This study provides new insights into metformin use and preclinical evidence for the potential treatment of primary open-angle glaucoma.

Nutritional Factors: Benefits in Glaucoma and Ophthalmologic Pathologies

“…In the field of ophthalmology, metformin has been found to yield control of steroid-induced ocular hypertension in mouse models [ 32 ]. This outcome has been suggested to be associated with a metformin-dependent exertion of antioxidant effects on the trabecular meshwork cytoskeleton via the integrin/ROCK pathway [ 32 ].…”

Metformin prevents glucocorticoid-induced trabecular meshwork damage and intraocular pressure elevation via activating mitophagy

“…Our previous study demonstrated the therapeutic potential of MET against DEX-induced oxidative damage in the TM, both in vivo and in vitro [34]. In this study, we con rmed the preventive effect of MET against DEX-induced TM damage and the onset of OHT using the following evidence: 1) Signi cantly lowered IOP in MET + DEX mice than in PBS + DEX mice, and 2) ECM signals (α-SMA, bronectin) were blocked by MET in OHT mice or DEX-treated HTMC.…”

“…Human tissue collection was approved by the Eye Hospital of the Wenzhou Medical University (2022-129-K-98). The cell culture protocol was consistent with our previous study [34]. Brie y, HTMCs were cultured in DMEM/F12 medium (Cytiva, HyClone Laboratories, Logan, Utah, USA) containing 10% fetal bovine serum (FBS; BI, USA) at 37°C and 5% CO 2 .…”

“…ROS levels were measured according to our previous study [34]. Brie y, a 2′,7′-dichloro uorescein diacetate (DCFH-DA) probe (Beyotime Biotechnology, Shanghai, China) was diluted in serum-free DMEM/F12 medium, then incubated with the cells.…”

“…We previously demonstrated that MET has protective therapeutic potential against TM damages via attenuating oxidative damages [34]. However, despite the encouraging result that MET reduces IOP, it cannot explain its preventive effect in human beings against the onset of open-angle glaucoma (OAG) [35].…”