Protective Role of Cynara cardunculus L. var. altilis Against Oxidative Stress and Corneal Dysfunction in High Glucose-Damaged Human Corneal Epithelial Cells.

Abstract

Background: The global increase in diabetes mellitus has been accompanied by a significant rise in related complications. Diabetic patients frequently experience ocular surface disorders and multiple studies have demonstrated that the diabetic corneal epithelium is characterized by increased cellular fragility and compromised barrier integrity. It has been demonstrated that the processes of oxidative stress and inflammation are pivotal in causing ocular tissue damage in diabetic patients. Numerous studies have explored the protective effects of various antioxidants, especially those sourced from plants. Cynara cardunculus L. var. altilis (DC.), a species widely integrated into the Mediterranean diet and commonly known as cultivated cardoon (CC), is particularly rich in bioactive phenolic compounds, recognized for their antioxidant effects.

Methods: The current work focuses on assessing the effect of CC leaf extracts on high glucose-treated human corneal epithelial cells (HCEpiCs). HCEpiCs were cultured for 24 h in a medium supplemented with glucose up to a concentration of 25 mM. Mannitol treatment was included to distinguish whether the observed effects were due to glucose metabolism or solely osmotic stress. To evaluate the effect of CC extracts, corneal cells were pre-incubated with the CC extract 10-20 μg/mL for 24 h before high glucose (HG) treatment. Cell viability, transepithelial electrical resistance, wound healing assay and reactive oxygen species (ROS) measurements were performed after HG treatment. To evaluate the levels of oxidative stress, the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), along with glutathione (GSH) levels were assayed. The mitogen-activated protein kinase ERK1/2/cytosolic phospholipases A₂ (cPLA₂)/cyclooxygenase-2 (COX-2) signaling pathway, triggering the inflammatory process, was evaluated by western blot analyses.

Results: Our findings indicate that CC extract (i) improved viability, reducing oxidative stress by lowering ROS production and enhancing SOD, CAT activities and GSH content in human corneal epithelial cells exposed to high glucose concentrations; (ii) maintained a high TEER and promoted corneal epithelial wound healing; and (iii) induced down-regulation of the ERK 1/2/cPLA₂/COX-2 signaling pathway involved in the inflammatory process and ROS production.

Conclusions: CC leaf extract could improve human corneal epithelial cell function suggesting its potential as a preventive agent against the development of chronic diabetic complications.