Anti-inflammatory and anti-apoptotic effects of N-acetylcysteine in diabetic rat corneal epithelium
Authors:   Research Institute of Miso Eye Clinic, Gyeonggi-do 13640, Republic of Korea; Biomedical Research Center, Asan Institute for Life Science, Asan Medical Center, Seoul 05505, Republic of Korea, Hwang Sae-Byeok , Park Ji-Yun ,   Department of Ophthalmology, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea, Kang Soon-Suk ,   Biomedical Research Center, Asan Institute for Life Science, Asan Medical Center, Seoul 05505, Republic of Korea; Research Institute for Biomacromolecules, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea, Chung Ho Seok ,   Department of Ophthalmology, Dankook University Hospital, Dankook University College of Medicine, Cheonan 31116, Republic of Korea, Lee Hun ,   Biomedical Research Center, Asan Institute for Life Science, Asan Medical Center, Seoul 05505, Republic of Korea; Department of Ophthalmology, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea, Kim Jae Yong ,   Biomedical Research Center, Asan Institute for Life Science, Asan Medical Center, Seoul 05505, Republic of Korea; Department of Ophthalmology, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea, Tchah Hungwon ,   Biomedical Research Center, Asan Institute for Life Science, Asan Medical Center, Seoul 05505, Republic of Korea; Department of Ophthalmology, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea
Published: November 2021

AIM: To characterize the anti-inflammatory and anti-apoptotic 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)-1β and cleaved caspase-3 (CCAP-3) expression using immunohistochemistry. Circulating tumor necrosis factor (TNF)-α concentration 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.