Protective Effects of Theaflavins and Epigallocatechin Gallate against ZnO-NP-Induced Cell Apoptosis In Vitro

Zinc oxide nanoparticles (ZnO-NPs) are commonly used in various commercial applications, causing toxic effects on organisms and destroying biodiversity, but information about their protective approaches remains unknown. This study aims to evaluate the protective effects of theaflavins (TFs) and epigallocatechin gallate (EGCG) against ZnO-NP-induced cytotoxicity in rat tracheal epithelial (RTE) cells. Herein, RTE cells were exposed to 100 μg/L ZnO-NPs for 12 h, then treated with 0, 10, 100, and 1000 μg/L TFs or EGCG for another 12 h; subsequently, oxidative stress, inflammation, and apoptosis analyses were conducted. Relative to the control groups, TFs and EGCG treatment significantly inhibited the levels of reactive oxygen species and malondialdehyde content. Exposure to 1000 μg/L TFs or EGCG treatment downregulated cytochrome C gene expression levels by 59.10% and 77.27%; Caspase 3 gene expression by 50.03% and 60.01%; Caspase 8 gene expression by 45.11% and 55.57%; and Caspase 9 gene expression by 51.33% and 66.67%, respectively. Meanwhile, interleukin 1β and interleukin 6, tumor necrosis factor-α, and the other inflammatory chemokines such as C-C motif chemokine 2 and C-X-C motif chemokine 8 expression were all gradually rescued after the addition of TFs or EGCG. These results imply that TFs or EGCG possibly ameliorated ZnO-NPs-induced toxicity through antiapoptotic, antioxidant, and anti-inflammatory effects. This study provides novel approaches which mitigate the emerging nanoparticle pollutant toxicity in organisms, which may potentially slow down the destruction of biodiversity.