Differential regulation of ENA-78 and GCP-2 gene expression in human corneal keratocytes and epithelial cells.

PURPOSE To determine whether interleukin (IL)-1alpha- and tumor necrosis factor (TNF)-alpha-stimulated human corneal epithelial cells (HCECs) and human corneal keratocytes (HCKs) produce the alpha-chemokines epithelial cell-derived neutrophil attractant (ENA)-78 and granulocyte chemotactic protein (GCP)-2. METHODS Cultures of HCECs and HCKs were stimulated with either human recombinant IL-1alpha or TNF-alpha. At selected times after stimulation, culture supernatants were harvested and assayed for ENA-78 and GCP-2 by enzyme-linked immunosorbent assay. RNA was extracted from cell cultures to measure steady state levels of intracellular ENA-78 and GCP-2 pre-mRNA and mRNA by the reverse transcription-polymerase chain reaction. RESULTS Exposure of HCECs to either IL-1alpha or TNF-alpha stimulated a more than 4.5-fold increase in ENA-78 RNA and protein synthesis without stimulating a significant increase in either GCP-2 RNA synthesis or protein production. Exposure of HCK to IL-1alpha stimulated a 10-fold increase in ENA-78 and GCP-2 RNA synthesis and a more than 300-fold increase in ENA-78 and GCP-2 protein production. In contrast, exposure of keratocytes to TNF-alpha significantly enhanced ENA-78 RNA synthesis, resulting in a more than 68-fold increase in ENA-78 protein synthesis without significantly enhancing either GCP-2 gene expression or protein secretion. CONCLUSIONS ENA-78 gene expression is significantly enhanced in both HCECs and HCKs in response to either IL-1alpha or TNF-alpha stimulation. In contrast, GCP-2 synthesis is only inducible in IL-1alpha-stimulated HCKs. The results suggest that GCP-2 gene expression is more tightly regulated in diseased or injured corneal tissue than is ENA-78 gene expression.