The aim of the present study was to investigate the role of histatin 1 (Hst1) in human corneal epithelial cells (HCECs) exposed to ultraviolet (UV) radiation. Prior to UV irradiation for various durations, HCECs were pre-treated with different concentrations of Hst1 and the effect on cell apoptosis and cell viability were examined by flow cytometry, alamarBlue® and MTT assays to determine the optimal concentration of Hst1 and UV dose. Cells were then subjected to quantitative PCR, ELISA and western blot analysis to determine the expression of cell damage-associated genes. HCECs exposed to UV light for 1 h displayed decreased viability when compared to that of control cells, and a 3 h UV exposure markedly increased the apoptotic rate of HECEs, while apoptosis was inhibited by pre-treatment with Hst1. UV radiation downregulated expression of insulin-like growth factor (IGF)-1 and B-cell lymphoma 2 (Bcl-2), while it upregulated Bcl-2-associated X protein (Bax) expression. Hst1 protected HCECs against UV-induced damage by upregulating the expression of IGF-1 protein and increasing the Bcl-2/Bax ratio. In conclusion, Hst1 may prevent UV-induced damage to corneal epithelial tissue injury and promote its healing.

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Background. Immunological rejection is one of the problems in corneal transplantation. Recently, some research found out that soluble programmed death protein-1 (sPD-1) and soluble programmed death ligand protein-1 (sPD-L1) play a significant role in immunologic suppression. Objectives.To explore expression of sPD-1 and sPD-L1 in a penetrative corneal transplantation model and its relationship with transplant rejection. Material and methods.Autologous corneal transplantation rat models and allogeneic corneal transplantation rat models were used as the control group and the experimental group, respectively. Changes of the transplanted grafts were observed under a slit-lamp microscope. Hematoxylin-eosin (H&E) staining was applied to examine the histopathological features of the corneal grafts. Flow cytometry was used to analyze CD4 + CD25 + Treg in the serum and spleen. The sPD-1, sPD-L1, interleukin 10 (IL-10) and interleukin 4 (IL-4) levels in serum and the aqueous humor of the rats were detected using enzyme-linked immunosorbent assay (ELISA).Results. After the operation, no transplant rejection occurred in the control group. Flow cytometry results showed that expressions of CD4 + CD25 + Treg in serum in the experimental group were lower than those in the control group (p < 0.05). The ELISA results showed that after the operation, sPD-1 and sPD-L1 expression levels in serum in the experimental group were higher than in the control group (all p < 0.05). After the operation, lL-10 and IL-4 content in serum in the experimental group was lower than in the control group (all p < 0.05). The sPD-1/sPD-L1 ratio in the experimental group was higher than in the control group.Conclusions. Increases of sPD-1 content and decreases of CD4 + CD25 + Treg, IL-10 and IL-4 levels may be involved in corneal allograft rejection. Dynamic detection of the content of sPD-1 and sPD-L1 in serum and aqueous humor after the operation would help in understanding the local immune response in a clinical setting and predicting the occurrence of corneal graft rejection.