HEALTH POTENTIAL OF ALOE VERA AND POLYDEOXYRIBONUCLEOTIDE (PDRN) AGAINST OXIDATIVE STRESS INDUCED CORNEAL DAMAGE: AN IN VITRO MODEL OF FUCHS ENDOTHELIAL CORNEAL DYSTROPHY

Fuchs endothelial corneal dystrophy (FECD) is a bilateral, hereditary syndrome characterized by a progressive injury of the corneal endothelium caused by oxidative stress and inflammatory processes activation that worsens the prognosis of the disease, up to corneal transplantation in the affected patients. In particular, oxidative stress stimulates Reactive Oxygen Species (ROS) release, thus promoting cell damage and activation of cell death mechanisms (corneal endothelial cells (CECs) apoptosis). For this reason, antioxidant compounds might be considered as good candidates for the treatment of the corneal diseases characterized by oxidative stress. In this context, previous studies already demonstrated that also the use of adenosine A2A receptor (A2Ar) agonists might be useful in reducing oxidative stress and inflammation, as well as in modulating apoptosis. Therefore, the aim of this study was to evaluate the effects of i) an aloe extract with antioxidant properties and ii) a biological drug that acts through adenosine A2Ar, Polydeoxyribonucleotide (PDRN), in two “in vitro” models of FECD. Hydrogen peroxide (H2O2) was used at the concentration of 200 µM for 2 hours in human corneal endothelial cells (HCE) to induce an oxidative stress damage and the respective treatments were incubated for additional 24 hours. In the first set of experiments, H2O2 challenge significantly reduced cell viability and increased both ROS and malondialdehyde levels. The m-RNA expression and activity of the anti-oxidant transcription factor Nrf-2, as well as of Catalase and Superoxide dismutase (SOD) enzymes, were reduced following H2O2 stimulation whereas an enhanced expression of IL-1β, Tumor Necrosis Factor-α (TNF-α), IL-6, and cyclooxygenase 2 (COX-2) was observed. Furthermore, Bax, Caspase-3 and Caspase-8 were downregulated while Bcl-2 was up-regulated following H2O2 incubation. Aloe extract blunted the oxidative stress-induced inflammatory cascade triggered by H2O2 and modulated apoptosis. In the second set of experiments, H2O2 reduced cell viability and increased the expression of the pro-inflammatory markers NF-κB, IL-6, IL-1β and TNF-α; by contrast, the oxidant stimulus decreased the expression of the anti-inflammatory IL-10. Moreover, the pro-apoptotic molecules Bax, Caspase-3 and Caspase-8 were up-regulated with a consequent decrease of the anti-apoptotic Bcl-2. PDRN reverted H2O2 effects whereas the co-incubation with the A2Ar antagonist, ZM241385, abolished PDRN effects, indicating that A2Ar is involved in the PDRN mode of action. Taken together, these data suggest that Aloe Vera extract and PDRN were protective against H2O2-induced damage, potentially as a result of their antioxidant, anti-inflammatory and anti-apoptotic effects, thus indicating that eye drops containing Aloe Vera extract or PDRN might be used in the future as an adjunctive treatment for FECD.