Vascular protection of salicin on IL-1β-induced endothelial inflammatory response and damages in retinal endothelial cells

Retinal endothelial cells (RECs) are involved in many ocular diseases such as age-related macular degeneration (AMD) and diabetic retinopathy. Salicin is the major ingredient of willow bark extract, and it has been shown to be a potent anti-inflammatory agent. We aim to explore whether salicin has a vascular protective effect in RECs. Our data indicate that the presence of salicin in RECs culture media ameliorates interleukin-1 beta (IL-1 beta)-induced cellular reactive oxygen species (ROS) production and NADPH oxidase 4 (NOX-4) expression. At the cellular level, salicin attenuates IL-1 beta-induced mitochondrial injury as revealed by its preservation on mitochondrial membrane potential (MMP). Furthermore, salicin inhibits IL-1 beta-induced production of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and monocyte chemoattractant protein-1 (MCP-1), vascular adhesion molecules such as intercellular cell adhesion molecule-1 (iCAM-1) and vascular cell adhesion molecule 1 (VCAM-1), and high-mobility group protein 1 (HMGB-1). On the other hand, salicin recovers IL-1 beta-induced reduction of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) release. The presence of salicin significantly reduces the IL-1 beta-induced release of lactate dehydrogenase (LDH), indicating that it mitigates cytokine caused cytotoxicity. Mechanistically, we show that salicin suppresses IL-1 beta-induced activation of the nuclear factor-kappa B (NF-kappa B) signaling as revealed by its suppression on nuclear p65 protein and transfected NF-kappa B promoter. Collectively, our study demonstrates by multiple facets of its mechanisms that salicin is a protective agent in retinal endothelial cells. These results imply its potential use in therapeutic usage of retinal disease.