Release of Interleukins 6 and 8 Induced by Zymosan and Mediated by MAP Kinase and NF-κB Signaling Pathways in Human Corneal Fibroblasts

Abstract

Zymosan is derived from the cell wall of yeast and induces immune responses associated with fungal infection. The effects of zymosan on the expression of proinflammatory cytokines, chemokines, and adhesion molecules and on the activity of signaling pathways were examined in cultured human corneal fibroblasts. Release of the proinflammatory cytokines interleukin (IL)-6, IL-1beta, and IL-12 and of the chemokines IL-8, IP-10, and RANTES was measured with enzyme-linked immunosorbent assays. Expression of intercellular adhesion molecule-1 (ICAM-1) and vascular adhesion molecule-1 (VCAM-1) was evaluated by immunoblot and immunofluorescence analyses. Phosphorylation of mitogen-activated protein kinases (MAPKs) and the NF-kappaB inhibitory protein IkappaB-alpha was assessed by immunoblot analysis. Subcellular localization of the p65 subunit of the transcription factor NF-kappaB was determined by immunofluorescence analysis. Zymosan induced the release of IL-6 and IL-8 from corneal fibroblasts without affecting either the release of IL-1beta, IL-12, IP-10, or RANTES or the expression of ICAM-1 or VCAM-1. Zymosan also activated the MAPKs ERK, p38, and JNK and induced the phosphorylation of IkappaB-alpha and the nuclear translocation of p65 in these cells. The zymosan-induced release of IL-6 and IL-8 was attenuated by inhibitors of ERK, p38, JNK, and NF-kappaB signaling. Zymosan induces the release of IL-6 and IL-8 from human corneal fibroblasts in a manner dependent on MAPK and NF-kappaB signaling pathways. Corneal fibroblasts may thus modulate the local immune response to fungal infection in the corneal stroma.