The Antifungal Agent Itraconazole Induces the Accumulation of High Mannose Glycoproteins in Macrophages

Bacterial lipopolysaccharide (LPS) is a key mediator in the development of Gram-negative septic shock, which is a major health problem. The effect of LPS on myeloid cells is mediated by a multicomplex receptor system in which CD14, a glycosylphosphatidylinositol-anchored glycoprotein, and Toll-like receptor 4 are the major players. We have found that incubation of macrophages with itraconazole (ICZ), an azole antifungal commonly used in humans, altered both the expression and glycosylation of CD14. This glycoprotein, which is endo H-resistant in untreated cells, becomes endo H-sensitive following ICZ treatment. The effect of ICZ on glycan processing was observed in all newly synthesized glycoproteins as indicated by incorporation of [2-H-3] mannose. In addition, cells treated with ICZ increased surface concanavalin A (ConA) binding, corroborating an increase in high mannose surface glycoproteins. Although the glycosylation pattern of CD14 was altered, this glycoprotein was delivered to the cell surface or was secreted. Moreover, it appeared functional as demonstrated by the release of LPS-induced tumor necrosis factor-alpha under conditions specific for a CD14-mediated activation process. The effect of ICZ on glycosylation was not dependent on inhibition of the cholesterol biosynthetic pathway and was specific for this drug because other azole antifungals, such as ketoconazole and econazole, did not alter glycan processing. These results suggest a possible secondary effect of ICZ that impacts the processing of glyconjugates and may alter cellular function and homeostasis.