Effects of salidroside on trabecular meshwork cell extracellular matrix expression and mouse intraocular pressure

Abstract

PURPOSE. Excessive accumulation of extracellular matrix (ECM) in the trabecular meshwork (TM) reduces aqueous humor outflow, which likely contributes to elevation of IOP in primary open-angle glaucoma (POAG). Salidroside, a phenolic glycoside isolated from Rhodiola rosea is reported to prevent profibrotic responses by inhibiting Smad signaling pathway activated by TGF-β in liver, lung, and kidney tissues. We tested if salidroside can (1) inhibit TGF-β2- induced ECM expression in cultured human TM cells, and (2) lower TGF-β2-induced ocular hypertension in the mouse. METHODS. Cultured human TM cells stimulated with 5 ng/mL TGF-β2 for 48 hours were treated with salidroside for 24 hours. The expressions of fibronectin (FN), collagen type IV (COL-IV), and laminin (LN) were evaluated by quantitative PCR, Western blot, and immunocytochemistry. BALB/cJ mice were injected intravitreally with an adenoviral vector encoding a bioactive mutant of TGF-β2 (Ad.hTGF-β2226/228) in one eye to induce ocular hypertension, with the uninjected contralateral or Ad.Empty-injected eyes serving as controls. Mice were treated with a daily intraperitoneal injection of 40 mg/kg salidroside. Conscious mouse IOP values were measured using a TonoLab rebound tonometer. RESULTS. In cultured human TM cells, treatment with TGF-β2 increased expressions of FN, COL-IV, and LN, as assessed by quantitative PCR, Western blotting, and immunocytochemistry, all of which were significantly and completely ameliorated by 30 lM salidroside. Daily intraperitoneal injections of salidroside (40 mg/kg), starting either at day 0 (same day as Ad.hTGF-β2226/228 injection) or at day 14, significantly lowered TGF-β2-induced ocular hypertension in the mouse. In contrast, salidroside did not affect IOP of control eyes. CONCLUSIONS. These results demonstrated that salidroside is capable of minimizing TGF-β2- induced ECM expression in cultured human TM cells. It also reduced TGF-β2-induced ocular hypertension in the mouse. These findings indicate that this phenolic glycoside may be useful as a novel treatment for POAG.