Platelet-activating factor-induced intracellular signaling and release of cytokines and prostaglandin E2 in immortalized human corneal epithelial cells.

PURPOSE AND METHODS

Immortalized human corneal epithelial (CEPI-17-CL4) cells were exposed to different concentrations of platelet-activating factor (PAF) and the mobilization of intracellular calcium (Ca(2+)) was studied using fluorometrics. Additionally, the production of the cytokines [interleukin-6 (IL-6), interleukin-8 (IL-8), granulocyte macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor-alpha (TNF-alpha)], and matrix metalloproteinase-1 (MMP-1) and prostaglandin E(2) (PGE(2)) from PAF-stimulated cells was also determined using ELISA assays.

RESULTS

While PAF, histamine, and bradykinin stimulated the mobilization of Ca(2+) in these cells, PAF was the least efficacious. Ca(2+) mobilization induced by PAF was inhibited by 2 PAF receptor antagonists, PCA-42481 and CV-6209 (both 10 microM), and by a phospholipase C inhibitor, U73122 (60% at 4 microM). PAF increased the production of PGE(2) (with maximum effect at 30 and 100 nM) and GM-CSF (maximum effect at 1 microM) in CEPI-17-CL4 cells. However, PAF did not stimulate the generation of IL-6, IL-8, TNF-alpha, and MMP-1 to any significant level and in a consistent manner. PAF increased the incorporation of [(3)H]-thymidine into CEPI-17-CL4 cells with a maximal effect at 30 nM.

CONCLUSIONS

These data indicate that functional PAF receptors are present on CEPI-17-CL4 cells that can activate mobilization of Ca(2+). Other consequences of PAF receptor activation in CEPI-17-CL4 cells are the generation of PGE(2) and certain proinflammatory cytokines such as GM-CSF, and increasing cell proliferation.