Anti-inflammatory and anti-apoptotic effects of N-acetylcysteine in diabetic rat corneal epithelium

AIM:To characterize the anti-inflammatory and antiapoptotic effects of N-acetylcysteine(NAC)in streptozotocin(STZ)-induced diabetic rat corneal epithelium and human corneal epithelial cells(HCECs)exposed to a high-glucose environment.METHODS:HCECs were incubated in 0,5,50 mmol/L glucose medium,or 50 mmol/L glucose medium with NAC for 24h.Diabetes was induced in rats by intraperitoneal injection of 65 mg/kg STZ and some of these rats were topically administered NAC to corneas with 3 mice per group.We characterized receptor for advanced glycation end-products(RAGE)expression using immunofluorescence,and interleukin(IL)-1βand cleaved caspase-3(CCAP-3)expression using immunohistochemistry.Circulating tumor necrosis factor(TNF)-αconcentration was measured by ELISA and cleaved poly-ADP ribose polymerase(PARP)concentration was quantified by Western blotting.Apoptotic cells were detected using TUNEL assay and annexin V and propidium iodide staining.RESULTS:Diabetic rats had higher expression of RAGE(2.46±0.13 fold),IL-1β,and CCAP-3 in apoptotic cells of their corneas than control rats.The expression of RAGE(1.83±0.11 fold),IL-1β,and CCAP-3,and the number of apoptotic cells,were reduced by topical NAC treatment.HCECs incubated in 50 mmol/L glucose medium showed high concentrations of TNF-α(310±2.00 pg/mL)and cleaved PARP(7.43±0.56 fold),and more extensive apoptosis than cells in 50 mmol/L glucose medium.However,the addition of NAC reduced the concentrations of TNF-α(153.67±2.31 pg/mL)and cleaved PARP(5.55±0.31 fold)and the number of apoptotic cells.CONCLUSION:NAC inhibits inflammation and apoptosis in the corneas of diabetic rats and HCECs maintained in a high-glucose environment.