Human corneal epithelial cell functional responses to inflammatory agents and their antagonists

PURPOSE. TO investigate the epithelial nature of primary and SV40 virus-imm ortalized human corneal epithelial (CEPI) cells and to study a variety of f unctional responses to some key inflammatory agents (bradykinin [BK], hista mine, and platelet-activating factor [PAF]) and their antagonists in these cells. METHODS. Primary CEPI (P-CEPI) and clone 4 of the SV40 virus-immortalized ( CEPI-17-CL4) cells were analyzed for their interaction with several monoclo nal antibodies selective for various cytokeratins to define their immunocyt ochemical characteristics and phenotypic traits. Both cell types were teste d for their ability to respond to BK, histamine, and PAF and their antagoni sts, using the production of [H-3]inositol phosphates ([H-3]IPs) as an inde x of receptor activation. The ability of BK, PAF, and histamine to stimulat e cytokine release and the induction of mRNA for matrix metalloproteinase-1 (MMP-1) were also studied using enzyme-linked immunosorbent assay and reve rse transcriptase-polymerase chain reaction techniques, respectively. RESULTS. P-CEPI and CEPI-17-CL4 cells were both shown to possess the epithe lial cell cytokeratins labeled with AE1 and AE3 antibodies. The potencies ( EC(50)s) of BK, histamine, and PAF were similar for stimulating [H-3]IPs pr oduction in P-CEPI and CEPI-17-CL4 cells: BK = 2.27 to 2.99 nM, PAF = 17.1 to 18.26 nM, and histamine = 1.65 to 5.74 mu M (all n = 3 to 6). Both cell types also responded similarly to receptor-selective antagonists for BK, PA F, and histamine (Hoe-140: K-i = 10.1 to 11.9 nM; PCA-4248: K-i = 315 to 42 1 nM; triprolidine: K-i = 0.8 to 4.76 nM; all n = 5 to 10). Histamine (100 mu M) and interleukin-1 alpha (IL-1 alpha, 10 ng/ml) significantly stimulat ed IL-6 and granulocyte macrophage colony-stimulating factor release, and h istamine, BK, and PAF stimulated the mRNA for MMP-1 in these cells. CONCLUSIONS. These studies have shown that the primary and immortalized hum an corneal epithelial cells express functional BK (a B-2 subtype), histamin e (an H-1 subtype), and PAF receptors and exhibit very similar immunocytoch emical, signal transduction, and pharmacological properties. Therefore, the CEPI-17-CL4 cells (currently at passage 220) appear to provide a useful re presentative in vitro model system to study the physiological and pathologi c aspects of the human corneal epithelium.