Bioactive IL-1a is Cytolytically Released from C. albicans-infected Oral Epithelial Cells

Objective: The purpose of this investigation was to study the Interleukin-1a (IL-1a) responses of oral epithelial cells to C. albicans infection and further define the role of this cytokine in regulating the mucosal inflammatory response to this pathogen. Methods: Epithelial cell lines (SCC4, SCC15, OKF6/TERT-1 and OKF6/TERT-2), primary gingival keratinocytes and gingival fibroblasts were used. Cells were cocultured with C. albicans for 2-24 h, and supernatants and lysates were analyzed for cytokines by ELISA. C. albicans SC5314, germination deficient mutants (efg1/cph1, ura3), and oral strains forming hyphae or pseudohyphae, were tested. Viability of epithelial cells was assessed by trypan blue exclusion. To assess the role of IL-1a in regulating other proinflammatory cytokine responses we tested the effect of neutralizing anti-IL-1a Ab or IL-1ra on the IL-8 and GM-CSF responses to: a) C. albicans or b) culture supernatants from the interaction of oral epithelial cells with C. albicans. Results: Infection of epithelial cells with C. albicans for 24 h resulted in significant release of IL-1a in culture supernatants (>20 fold). In kinetic experiments the viability of epithelial cells declined throughout the coculture period, paralleled by an increase in IL-1a in culture supernatants. Analysis of cell lysates and supernatants at different infectivity ratios, in conjunction with cell viability, revealed that >90% of the IL-1a generated in this system remains intracellular and is released following cell lysis. Yeast or pseudohyphal forms did not affect epithelial cell viability or IL-1a synthesis. Anti-IL-1a Ab or IL-1ra inhibited synthesis of IL-8 and GM-CSF by C. albicans-infected epithelial cells by >50%, and blocked >90% of the supernatant-induced IL-8 and GM-CSF in uninfected epithelial cells and gingival fibroblasts. Conclusions: IL-1a is cytolytically released by C. albicans-infected epithelial cells and regulates IL-8 and GM-CSF secretion by oral mucosal cells. Supported by NIDCR RO1 DE13986 and RO3 DE12668.