Synergistic induction of eotaxin expression in human keratocytes by TNF-alpha and IL-4 or IL-13

PURPOSE. To investigate the effects of tumor necrosis factor (TNF)-alpha, i nterleukin (IL)-4, and IL-13 on expression of the chemokine eotaxin by cult ured human keratocytes. METHODS. Cultured human keratocytes were incubated with various combination s and concentrations of TNF-alpha, IL-4, and IL-13. The concentration of eo taxin in the culture supernatant was subsequently measured by enzyme-linked immunosorbent assay, and the amount of eotaxin mRNA in cell lysates was de termined by reverse transcription-polymerase chain reaction analysis, RESULTS. Keratocytes incubated in the absence of cytokines did not release detectable amounts of eotaxin into the culture medium. Whereas incubation o f keratocytes with TNF-alpha, IL-4, or IL-13 alone or with the combination of IL-4 and IL-13 had only a small effect on eotaxin release, exposure of t he cells to TNF-alpha in combination with either IL-4 or IL-13 resulted in a marked increase in eotaxin production that was both time and dose depende nt. The abundance of cotaxin mRNA in keratocytes was also increased in a sy nergistic manner by incubation of cells with TNF-alpha together with either IL-4 or IL-13. CONCLUSIONS. Stimulation of human keratocytes with the combination of TNF-a lpha and either IL-4 or IL-13 resulted in synergistic increases in both the abundance of eotaxin mRNA and the release of eotaxin protein. This cytokin e-induced increase in eotaxin production by keratocytes may contribute to e osinophil infiltration in inflammatory ocular diseases such as vernal kerat oconjunctivitis.