Dry eye disease (DED) is a common chronic ophthalmic disorder, and there is no effective treatment to cure it. It is urgent to find new antidry eye compounds. Here, the effects and underlying mechanisms of tilapia skin peptides (TSP) on DED were investigated. In vitro, human corneal epithelial cells (HCECs) were cultured in a hypertonic medium containing TSP for 12h. The MTT assay, calcein-AM/PI staining, reactive oxygen (ROS) analysis, and western blot were performed at the end of the experiments. In the in vivo model of DED, mice eyes were dropped with 0.3 benzalkonium chloride (BAC) and 0.1% TSP for 14 days. Mice were treated with BAC and TSP twice daily with a 10-hour time interval between treatments. After treatment, phenolic red cotton experiment, tear ferning test, and histology assay were carried out. In vitro, TSP significantly restored the cell viability of HCECs challenged by NaCl. In vivo, tear secretion function and tear fern-like crystal levels were considerably improved in the DED group after treatment with TSP. Mechanically, TSP impend the DED development by regulating Bax/Bcl-2 signal pathway, inhibiting iNOS and COX-2 protein expression, moderating ROS/Nrf2/HO-1 axis, inhibiting cell apoptosis in the corneal regions, increasing the number of conjunctival goblet cells, and arresting corneal epithelial thinning. In conclusion, TSP ameliorated DED-like disorder in BAC-induced DED mice and cell damage in NaCl-induced HCECs. TSP improved DED by suppressing apoptosis, inflammation, and oxidative stress. Consequently, this study reveals the beneficial activity of TSP in DED.

Tilapia skin is a great source of collagen. Here, we aimed to isolate and identify the peptides responsible for combating dry eye disease (DED) in tilapia skin peptides (TSP). In vitro cell DED model was used to screen anti-DED peptides from TSP via Sephadex G-25 chromatography, LC/MS/MS, and in silico methods. The anti-DED activity of the screened peptide was further verified in the mice DED model. TSP was divided into five fractions (TSP-I, TSP-II, TSP-III, TSP-IV, and TSP-V), and TSP-II exerted an effective effect for anti-DED. A total of 131 peptides were identified using LC/MS/MS in TSP-II, and NGGPSGPR (NGG) was screened as a potential anti-DED fragment in TSP-II via in silico methods. In vitro, NGG restored cell viability and inhibited the expression level of Cyclooxygenase-2 (COX-2) protein in Human corneal epithelial cells (HCECs) induced by NaCl. In vivo, NGG increased tear production, decreased tear ferning score, prevented corneal epithelial thinning, alleviated conjunctival goblet cell loss, and inhibited the apoptosis of corneal epithelial cells in DED mice. Overall, NGG, as an anti-DED peptide, was successfully identified from TSP, and it may be devoted to functional food ingredients or medicine for DED.