Therapeutic Effects and Molecular Mechanisms of KD025 in Intraocular Pressure Regulation.

Aim: To quantitatively evaluate the IOP-lowering efficacy of topical KD025 in normotensive and steroid-induced ocular hypertensive rat models, and to elucidate its mechanisms concerning TM cytoskeletal remodeling, fibrotic modulation, and cell behavior using primary human TM cells.

Methods: Normotensive and steroid-induced (dexamethasone) ocular hypertensive Sprague-Dawley rats received topical KD025; IOP was monitored using rebound tonometry. TM morphology was assessed by H&E staining. In primary human TM cells, functional effects (wound healing) and the expression of α-smooth muscle actin (α-SMA), fibronectin (FN), F-actin, and myocilin (a steroid-response marker) were analyzed via immunofluorescence and Western blotting following KD025 and/or dexamethasone treatment.

Results: KD025 significantly reduced IOP in normotensive rats, with peak effects at 6 h post-administration (though no clear dose-dependency was observed between 10-25 µM). In steroid-induced hypertensive rats, 20 µM KD025 achieved significantly greater IOP reduction versus vehicle (p < 0.01). Histological analysis suggested potential TM structural relaxation. In vitro, KD025 significantly inhibited TM cell migration and downregulated dexamethasone-induced α-SMA expression. Paradoxically, and differing from typical pan-ROCK inhibitor effects, KD025 treatment increased total cellular FN protein (p < 0.01 vs DEX alone) and further exacerbated dexamethasone-induced F-actin protein levels (p < 0.05 vs DEX alone).

Conclusions: KD025 demonstrates effective IOP-lowering capabilities in rodent models. Its mechanism likely involves modulating TM cell contractility (via α-SMA reduction) and inhibiting cell migration. The unexpected findings on fibronectin and F-actin suggest that selective ROCK2 inhibition by KD025 induces complex and distinct effects on TM extracellular matrix dynamics and cytoskeletal organization compared to non-selective ROCK inhibitors. These results highlight ROCK2 as a promising therapeutic target for glaucoma, though its distinct cellular actions warrant further investigation.